ON-PRESS DEVELOPMENT TYPE LITHOGRAPHIC PRINTING PLATE PRECURSOR, METHOD OF PREPARING LITHOGRAPHIC PRINTING PLATE, LITHOGRAPHIC PRINTING METHOD, AND COMPOUND

Abstract

There is provided an on-press development type lithographic printing plate precursor including a support, and an image-recording layer provided on the support, in which the image-recording layer contains (1) or (2). (1) a borate compound represented by Formula (1) and an electron-accepting polymerization initiator (2) a borate compound represented by Formula (1a) in Formula (1) and Formula (1a), R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group, and R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may each independently have a ring structure. Provided that at least one of R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is different from the other. M.sup.+ represents a cation. Ma.sup.+ represents an iodonium cation.

##STR00001##

Claims

1. An on-press development type lithographic printing plate precursor comprising: a support; and an image-recording layer provided on the support, wherein the image-recording layer contains (1) or (2), (1) a borate compound represented by Formula (1) and an electron-accepting polymerization initiator, ##STR00151## in Formula (1), R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group, and R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may each independently have a ring structure, provided that at least one of R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is different from the other, and M.sup.+ represents a cation, (2) a borate compound represented by Formula (Ia), ##STR00152## in Formula (1a), R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group, and R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may each independently have a ring structure, provided that at least one of R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is different from the other, Ma.sup.+ represents an iodonium cation.

2. The on-press development type lithographic printing plate precursor according to claim 1, wherein R.sup.1, R.sup.2, and R.sup.3 in Formula (1) or Formula (1a) are a phenyl group, and R.sup.4 is different from R.sup.1, R.sup.2, and R.sup.3.

3. The on-press development type lithographic printing plate precursor according to claim 1, wherein R.sup.1, R.sup.2, and R.sup.3 in Formula (1) or Formula (1a) are a phenyl group, and R.sup.4 is an aryl group having a substituent.

4. The on-press development type lithographic printing plate precursor according to claim 1, wherein M.sup.+ in Formula (1) is an inorganic cation.

5. The on-press development type lithographic printing plate precursor according to claim 1, wherein M.sup.+ in Formula (1) is at least one cation selected from the group consisting of an iodonium cation and an infrared-absorbing coloring agent cation.

6. The on-press development type lithographic printing plate precursor according to claim 3, wherein R.sup.1, R.sup.2, and R.sup.3 in Formula (1) or Formula (1a) are a phenyl group, R.sup.4 is an aryl group having a substituent, and a total number of carbon atoms and oxygen atoms in the substituent is 2 or more.

7. The on-press development type lithographic printing plate precursor according to claim 6, wherein the total number of carbon atoms and oxygen atoms in the substituent is 3 or more.

8. The on-press development type lithographic printing plate precursor according to claim 2, wherein R.sup.1, R.sup.2, and R.sup.3 in Formula (1) or Formula (1a) are a phenyl group substituted with an electron-withdrawing group, and R.sup.4 is a group different from R.sup.1, R.sup.2, and R.sup.3.

9. The on-press development type lithographic printing plate precursor according to claim 3, wherein the substituent of R.sup.4 in Formula (1) or Formula (1a) is at least one group selected from the group consisting of an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, and an amide group.

10. The on-press development type lithographic printing plate precursor according to claim 1, wherein the image-recording layer contains a color developing agent.

11. The on-press development type lithographic printing plate precursor according to claim 1, wherein the image-recording layer contains an infrared absorber.

12. The on-press development type lithographic printing plate precursor according to claim 1, wherein the electron-accepting polymerization initiator includes a compound represented by Formula (Ia) and at least one compound B selected from the group consisting of a compound represented by Formula (Ib) or a compound represented by Formula (Ic), ##STR00153## in Formulae (Ia) to (Ic), R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are each independently a substituted or unsubstituted alkyl group having 2 to 9 carbon atoms or a substituted or unsubstituted alkoxy group having 2 to 9 carbon atoms, at least one of R.sub.3 or R.sub.4 is different from R.sub.1 or R.sub.2, a difference between a total number of carbon atoms in R.sub.1 and R.sub.2 and a total number of carbon atoms in R.sub.3 and R.sub.4 is 0 to 4, a difference between the total number of carbon atoms in R.sub.1 and R.sub.2 and a total number of carbon atoms in R.sub.5 and R.sub.6 is 0 to 4, and X.sub.1, X.sub.2, and X.sub.3 are each independently a counteranion.

13. The on-press development type lithographic printing plate precursor according to claim 11, wherein the infrared absorber includes a compound represented by Formula (X), ##STR00154## in Formula (X), Ar.sub.11 and Ar.sub.12 each independently represent an atomic group necessary for forming a substituted or unsubstituted aromatic ring or for forming a substituted or unsubstituted heteroaromatic ring, R.sub.11 and R.sub.12 each independently represent a substituted or unsubstituted alkyl group, R.sub.13 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group, R.sub.14 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group, Y's each independently represent an oxygen atom, a sulfur atom, or a dialkylmethylene group represented by >C(R.sub.15R.sub.16), R.sub.15 and R.sub.16 each independently represent a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, A.sub.1 and A.sub.2 each independently represent a substituted or unsubstituted alkyl group or represent an atomic group including 2 or 3 carbon atoms, which is necessary for forming a substituted or unsubstituted 5- or 6-membered non-aromatic carbon ring by linking to each other, and Za represents a counterion that neutralizes charge.

14. The on-press development type lithographic printing plate precursor according to claim 11, wherein the infrared absorber includes a compound represented by Formula 1, ##STR00155## in Formula 1, R.sub.1 and R.sub.2 each independently represent a hydrogen atom or an alkyl group, R.sub.1 and R.sub.2 may be linked to each other to form a ring, R.sub.3 to R.sub.6 each independently represent a hydrogen atom or an alkyl group, R.sub.7 and R.sub.8 each independently represent an alkyl group or an aryl group, Y.sub.1 and Y.sub.2 each independently represent an oxygen atom, a sulfur atom, NR.sub.0, or a dialkylmethylene group, R.sub.0 represents a hydrogen atom, an alkyl group, or an aryl group, Ar.sub.1 and Ar.sub.2 each independently represent a group forming a benzene ring or a naphthalene ring which may have a group represented by Formula 2, A.sub.1 represents NR.sub.9R.sub.10, X.sub.1-L.sub.1 or a group represented by Formula 2, R.sub.9 and R.sub.10 each independently represent an alkyl group, an aryl group, an alkoxycarbonyl group, or an arylsulfonyl group, X.sub.1 represents an oxygen atom or a sulfur atom, L.sub.1 represents a hydrocarbon group, a heteroaryl group, or a group that undergoes bond cleavage from X.sub.1 by heat or exposure to infrared, Za represents a counterion that neutralizes charge, and at least one of Ar.sub.1 or Ar.sub.2 has a group represented by Formula 2,
XFormula 2 in Formula 2, X represents a halogen atom, C(O)X.sub.2R.sub.11, C(O)NR.sub.12R.sub.13, OC(O)R.sub.14, CN, SO.sub.2NR.sub.15R.sub.16, or a perfluoroalkyl group, X.sub.2 represents a single bond or an oxygen atom, R.sub.11 and R.sub.14 each independently represent an alkyl group or an aryl group, and R.sub.12, R.sub.13, R.sub.15, and R.sub.16 each independently represent a hydrogen atom, an alkyl group, or an aryl group.

15. The on-press development type lithographic printing plate precursor according to claim 11, wherein the infrared absorber includes a compound represented by Formula (P1), ##STR00156## in Formula (P1), R.sup.P1 represents a group represented by Formula (P2) or Formula (P3), R.sup.P2 and R.sup.P3 each independently represent a hydrogen atom or an alkyl group, R.sup.P2 and R.sup.P3 may be linked to each other to form a ring, Ar.sup.P1 and Ar.sup.P2 each independently represent a benzene ring or a naphthalene ring, Y.sup.P1 and Y.sup.P2 each independently represent an oxygen atom, a sulfur atom, NR.sup.P0, or a dialkylmethylene group, R.sup.P4 and R.sup.P5 each independently represent an alkyl group, R.sup.P6 to R.sup.P9 each independently represent a hydrogen atom or an alkyl group, R.sup.P0 represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counterion that neutralizes charge, ##STR00157## in Formula (P2) and Formula (P3), R.sup.P10 represents a monovalent organic group having an aryl group, R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20 each independently represent a hydrogen atom, an alkyl group, an aryl group, a hydroxy group, an alkoxy group, or a halogen atom, R.sup.P15 and R.sup.P16 each independently represent a hydrogen atom, an alkyl group, or an aryl group, at least two of R.sup.P11 to R.sup.P20 may be bonded to each other to form a ring structure, and * represents a single bond that is bonded to an oxygen atom in Formula (P1).

16. A method of preparing a lithographic printing plate, comprising: exposing the on-press development type lithographic printing plate precursor according to claim 1 in an imagewise manner; and supplying at least one selected from the group consisting of a printing ink and dampening water on a printer to remove an image-recording layer in a non-image area.

17. A compound represented by Formula (I), ##STR00158## in Formula (I), R represents a group in which a total number of carbon atoms and oxygen atoms is 2 or more, X represents a halogen atom, an alkyl group, or an alkoxy group, and a sum of Hammett values of R and X is 0.09 to 0.09, and M.sup.+ represents Li.sup.+, Na.sup.+, K.sup.+, an iodonium cation, or an infrared-absorbing coloring agent cation.

18. The compound according to claim 17, wherein R in Formula (I) represents an alkyl group having 2 or more and 4 or less carbon atoms, and X represents a halogen atom.

19. A compound represented by Formula (II), ##STR00159## in Formula (II), R represents an alkyl group having 2 or more carbon atoms or an alkoxy group in which a total number of carbon atoms and oxygen atoms is 2 or more, and M.sup.+ represents an iodonium cation or an infrared-absorbing coloring agent cation.

20. The compound according to claim 19, wherein R in Formula (II) is an alkyl group in which a total number of carbon atoms is 2 or more and 4 or less, or an alkoxy group in which the total number of carbon atoms and oxygen atoms is 2 or more and 4 or less.

21. A compound represented by B-7, B-25, B-26, B-29, or B-30. ##STR00160##

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0079] FIG. 1 is a schematic cross-sectional view of an embodiment of a support.

[0080] FIG. 2 is a schematic cross-sectional view of another embodiment of a support.

[0081] FIG. 3 is a schematic view of an anodization treatment device used for an anodization treatment in a manufacturing method of a support having an anodic oxide film.

[0082] FIG. 4 is a .sup.1H-NMR chart of the compound B-5.

[0083] FIG. 5 is a .sup.1H-NMR chart of the compound B-7.

[0084] FIG. 6 is a .sup.1H-NMR chart of the compound B-8.

[0085] FIG. 7 is a .sup.1H-NMR chart of the compound B-25.

[0086] FIG. 8 is a .sup.1H-NMR chart of the compound B-26.

[0087] FIG. 9 is a .sup.1H-NMR chart of the compound B-29.

[0088] FIG. 10 is a .sup.1H-NMR chart of the compound B-30.

[0089] FIG. 11 is a .sup.1H-NMR chart of the compound B-34.

[0090] FIG. 12 is a .sup.1H-NMR chart of the compound B-35.

[0091] FIG. 13 is a .sup.1H-NMR chart of the compound B-36.

[0092] FIG. 14 is a .sup.1H-NMR chart of the compound B-37.

[0093] FIG. 15 is a .sup.1H-NMR chart of the compound B-38.

[0094] FIG. 16 is a .sup.1H-NMR chart of the compound B-39.

[0095] FIG. 17 is a .sup.1H-NMR chart of the compound B-40.

[0096] FIG. 18 is a .sup.1H-NMR chart of the compound B-41.

[0097] FIG. 19 is a .sup.1H-NMR chart of the compound B-42.

[0098] FIG. 20 is a .sup.1H-NMR chart of the compound B-45.

[0099] FIG. 21 is a .sup.1H-NMR chart of the compound B-46.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0100] Hereinafter, the contents of the present disclosure will be described in detail. The description of configuration requirements below is made based on representative embodiments of the present disclosure in some cases, but the present disclosure is not limited to such embodiments.

[0101] In the present disclosure, a numerical range expressed using to includes numerical values listed before and after to as the lower limit value and the upper limit value.

[0102] In addition, in the present disclosure, in a case where there is no description regarding whether a group (atomic group) is substituted or unsubstituted, such a group includes both a group having no substituent and a group having a substituent. For example, alkyl group includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

[0103] In the present disclosure, (meth)acryl is a term used to explain a concept including both the acryl and methacryl, and (meth)acryloyl is a term used to explain a concept including both the acryloyl and methacryloyl.

[0104] The term step in the present disclosure means not only an independent step but also a step that cannot be clearly differentiated from other steps as long as the intended goal of the step is achieved.

[0105] In the present disclosure, % by mass and % by weight have the same meaning, and part(s) by mass and part(s) by weight have the same meaning.

[0106] In the present disclosure, unless otherwise specified, as each component contained in a composition or each structural unit contained in a polymer, one component or one structural unit may be used alone, or two or more components or two or more structural units may be used in combination.

[0107] In the present disclosure, in a case where there is a plurality of substances corresponding to each component in a composition, or in a case where there is a plurality of structural units corresponding to each structural unit in a polymer, unless otherwise specified, the amount of each component in the composition or the amount of each structural unit in the polymer means the total amount of the plurality of corresponding substances present in the composition or the total amount of the plurality of corresponding structural units present in the polymer.

[0108] In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.

[0109] In the present disclosure, unless otherwise specified, each of the weight-average molecular weight (Mw) and number-average molecular weight (Mn) is a molecular weight that is detected using a gel permeation chromatography (GPC) analysis device using TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (trade names, manufactured by Tosoh Corporation) as columns, tetrahydrofuran (THF) as a solvent, and a differential refractometer, and expressed in terms of polystyrene as a standard substance.

[0110] In the present disclosure, the term lithographic printing plate precursor refers not only to a lithographic printing plate precursor but also to a key plate precursor. The term lithographic printing plate refers not only to a lithographic printing plate prepared by performing operations such as exposure and development as necessary on a lithographic printing plate precursor but also to a key plate. The key plate precursor is not necessarily subjected to the operations such as exposure and development. The key plate refers to a lithographic printing plate precursor to be mounted on a plate cylinder that is not used, in a case where monochromatic or dichromatic printing is carried out on a part of paper during, for example, color newspaper printing.

[0111] In the present disclosure, * in a chemical structural formula represents a bonding position with other structures.

<On-Press Development Type Lithographic Printing Plate Precursor>

[0112] An on-press development type lithographic printing plate precursor according to the present disclosure (also simply referred to as a lithographic printing plate precursor) includes a support and an image-recording layer provided on the support, in which the image-recording layer contains (1) or (2). [0113] (1) a borate compound represented by Formula (1), and an electron-accepting polymerization initiator [0114] (2) a borate compound represented by Formula (Ia)

[0115] The lithographic printing plate precursor according to the present disclosure is preferably a negative tone lithographic printing plate precursor in which an exposed portion is polymerized by exposure to infrared.

[0116] The present inventors have found that it is difficult to obtain a lithographic printing plate precursor having excellent printing durability and suppressing property of development defect over time in the lithographic printing plate precursor in the related art as described in JP2020-069789A or JP2011-186367A.

[0117] Therefore, as a result of intensive studies, the present inventors have found that a lithographic printing plate precursor having excellent printing durability and suppressing property of development defect over time can be obtained by providing the image-recording layer having the above-described composition.

[0118] The detailed mechanism that brings about the aforementioned effect is unclear, but is assumed to be as below.

[0119] It is considered that a decrease in printing durability is due to one of the factors that the degree of curing of the exposed portion (image area) is low. The degree of curing of the exposed portion is affected by the amount of radicals generated by the reaction of the polymerization initiator such as the borate compound contained in the image-recording layer. Since the reaction of the polymerization initiator depends on the potential of the polymerization initiator, the amount of radicals generated can be adjusted by controlling the potential. The borate compound having an asymmetric structure represented by Formula (1) or Formula (1a) can perform more precise potential control than a borate compound having a symmetric structure, and can adjust the amount of radicals generated. As a result, it is presumed that the printing durability is improved.

[0120] It is considered that a decrease in suppressing property of development defect over time is due to one of the factors that a product formed by the reaction between the borate compound contained in the image-recording layer and another compound adheres to the non-image area.

[0121] Therefore, it is presumed that the reaction with another compound can be hindered by steric hindrance by using the borate compound having an asymmetric structure represented by Formula (1) or Formula (1a).

[0122] As a result, it is considered that the suppressing property of development defect over time is improved by suppressing the generation of a product that causes the ink to adhere to the non-image area.

[0123] From the above, the lithographic printing plate precursor according to the present disclosure has excellent printing durability and suppressing property of development defect over time.

[0124] Hereinafter, each of the configuration requirements in the lithographic printing plate precursor according to the present disclosure will be specifically described. In the present disclosure, unless otherwise specified, the image-recording layer includes the aspect of (1) and the aspect of (2).

[0125] Hereinafter, the aspect of (1) of the image-recording layer is also referred to as aspect A. Hereinafter, the aspect of (2) of the image-recording layer is also referred to as aspect B.

[0126] In addition, hereinafter, unless otherwise specified, the borate compound represented by Formula (1) and the borate compound represented by Formula (1a) are also collectively referred to as a specific borate compound.

(Image-Recording Layer)

[0127] The image-recording layer in the lithographic printing plate precursor according to the present disclosure is preferably a water-soluble or water-dispersible negative tone image-recording layer.

[0128] In addition, in the image-recording layer in the lithographic printing plate precursor according to the present disclosure, from the viewpoint of on-press developability, a non-exposed portion of the image-recording layer is preferably removable by at least any of dampening water or printing ink.

[0129] Hereinafter, each of the components to be contained in the image-recording layer will be specifically described.

Aspect A

[0130] The image-recording layer in aspect A contains a borate compound represented by Formula (1).

[0131] The borate compound represented by Formula (1) is used as an electron-donating polymerization initiator in the image-recording layer.

[0132] The specific borate compound is a compound that generates a polymerization initiation species such as a radical or a cation by light, heat, or energy of both.

##STR00015##

[0133] In Formula (1), R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group, and R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may each independently have a ring structure. Provided that at least one of R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is different from the other. M.sup.+ represents a cation.

[0134] Examples of the alkyl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4, which include those with 1 to 20 carbon atoms, include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, an s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group. The alkyl group described above may be linear or branched, or may have a ring structure.

[0135] In addition, the alkyl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4 may have a substituent. Examples of the substituent of the alkyl group include a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, a sulfonyl group, an amino group, an amide group, and a group obtained by combining these groups.

[0136] The alkyl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4 each independently preferably an unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, more preferably an unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms, and still more preferably an unsubstituted linear or branched alkyl group having 1 to 6 carbon atoms. Among these, from the viewpoint of suppressing development defect over time, an unsubstituted alkyl group having a branch is particularly preferable.

[0137] Examples of the aryl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4 include an aryl group having 6 to 20 carbon atoms, and examples thereof include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, an indenyl group, an acenaphthenyl group, and a fluorenyl group.

[0138] Examples of the substituent of the aryl group include the substituent of the above-described alkyl group.

[0139] The aryl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is each independently preferably a substituted or unsubstituted phenyl group.

[0140] Examples of the alkenyl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4 include an alkenyl group having 2 to 20 carbon atoms, and examples thereof include a vinyl group, a 1-propenyl group, a 1-butenyl group, a cinnamyl group, and a 2-chloro-1-etenyl group.

[0141] The alkenyl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4 may be linear, branched, or have a ring structure.

[0142] Examples of the substituent of the alkenyl group include the substituent of the above-described alkyl group.

[0143] The alkenyl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is each independently preferably an unsubstituted alkenyl group having 2 to 20 carbon atoms.

[0144] Examples of the alkynyl group represented by R.sup.1, R.sup.2, R.sup.3, or R.sup.4 include an alkynyl group having 2 to 20 carbon atoms, and examples thereof include an ethynyl group, a 1-propynyl group, a 1-butynyl group, a trimethylsilyl ethynyl group, and a phenyl ethynyl group. The alkynyl group may be linear or branched.

[0145] Among the above-described functional groups, R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are each independently preferably a substituted or unsubstituted aryl group.

[0146] By R.sup.1, R.sup.2, R.sup.3, and R.sup.4 being each independently a substituted or unsubstituted aryl group, the HOMO potential of the borate compound is lowered, and the film stability of the image-recording layer is improved. In this manner, the life of the lithographic printing plate can be extended.

[0147] In the present disclosure, at least one of R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is different from the other. Among these, it is preferable that R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are such that R.sup.1, R.sup.2, and R.sup.3 are the same and R.sup.4 is different from R.sup.1, R.sup.2, and R.sup.3. In this manner, a high-purity borate compound can be obtained. In addition, the generation of radicals can be suppressed, and side reactions are less likely to occur.

[0148] In the above case, it is more preferable that R.sup.1, R.sup.2, and R.sup.3 are a phenyl group.

[0149] In addition, it is also preferable that at least two of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are a phenyl group and at least one is a substituted aryl group.

[0150] Furthermore, it is more preferable that R.sup.1, R.sup.2, and R.sup.3 are a phenyl group and R.sup.4 is an aryl group having a substituent (that is, a substituted aryl group).

[0151] In a case where R.sup.1, R.sup.2, and R.sup.3 are a phenyl group and R.sup.4 is an aryl group having a substituent, the total number of carbon atoms and oxygen atoms in the substituent of the aryl group is preferably 2 or more and more preferably 3 or more. The upper limit thereof is, for example, 8 or less.

[0152] The compound represented by Formula (1) is preferably a compound represented by Formula (II).

##STR00016##

[0153] In Formula (II), R represents an alkyl group having 2 or more carbon atoms or an alkoxy group in which a total number of carbon atoms and oxygen atoms is 2 or more. M.sup.+ represents an iodonium cation or an infrared-absorbing coloring agent cation.

[0154] In Formula (II), the alkyl group represented by R preferably has 2 to 8 carbon atoms, more preferably has 2 to 6 carbon atoms, and still more preferably has 2 to 4 carbon atoms.

[0155] Examples of the above-described alkyl group include an ethyl group, a propyl group, an n-butyl group, a tert-butyl group, an isobutyl group, a sec-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a neopentyl group, and an isopropyl group.

[0156] The alkyl group described above may be linear or branched, or may have a ring structure.

[0157] In Formula (II), the alkoxy group of R preferably has a total number of carbon atoms and oxygen atoms of 2 to 4.

[0158] Examples of the above-described alkoxy group include a methoxy group, an n-propoxy group, an isopropoxy group, and an n-butoxy group.

[0159] The alkoxy group may be linear or branched.

[0160] In addition, in Formula (1), the phenyl group represented by R.sup.1, R.sup.2, or R.sup.3 is preferably a phenyl group substituted with an electron-withdrawing group.

[0161] Examples of the electron withdrawing group include a halogen atom and a fluoroalkyl group. Among these, a fluorine atom, a chlorine atom, and a fluoroalkyl group having 1 to 3 carbon atoms are preferable.

[0162] In Formula (1), the substituent contained in the aryl group represented by R.sup.4 is preferably an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, or an amide group, more preferably an alkyl group, an alkenyl group, or an alkoxy group, and still more preferably an alkyl group or an alkoxy group.

[0163] In the present disclosure, the compound represented by Formula (1) may be a compound represented by Formula (I).

##STR00017##

[0164] In Formula (I), R represents a group in which the total number of carbon atoms and oxygen atoms is 2 or more, X represents a halogen atom, an alkyl group, or an alkoxy group, and a sum of Hammett values of R and X is 0.09 to 0.09. M.sup.+ represents Li.sup.+, Na.sup.+, K.sup.+, an iodonium cation, or an infrared-absorbing coloring agent cation.

[0165] Examples of R in Formula (I) include an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, a sulfonyl group, an amide group, and a group obtained by combining these groups.

[0166] In Formula (I), examples of the halogen atom represented by X include a fluorine atom, a chlorine atom, and a bromine atom.

[0167] In Formula (I), the alkyl group and the alkoxy group represented by X are the same as the alkyl group and the alkoxy group in Formula (II), and the same applies to the preferred aspects thereof.

[0168] Among these, R in Formula (I) is preferably an alkyl group having 2 or more and 4 or less carbon atoms or an alkoxy group having 2 or more and 4 or less carbon atoms and oxygen atoms in total, and more preferably an alkyl group having 2 or more and 4 or less carbon atoms. In the above case, X is preferably a halogen atom. Here, the halogen atoms may be different halogen atoms from each other, but it is more preferable that all the halogen atoms are the same halogen atom.

[0169] In Formula (I), the sum of Hammett a values of the substituents (R and X) introduced into the aryl skeleton is preferably in a range of 0.2 to 0.2, and more preferably in a range of 0.09 to 0.09. In a case where the HOMO potential is within the above-described range, the HOMO potential can be adjusted to a desired range, and the balance between the film stability and the printing durability of the image-recording layer is excellent.

[0170] In the present disclosure, for the calculation of the total Hammett value of the substituents introduced into the aryl skeleton, the numerical values described in the reference Chemical Seminar 10 Hammett Side-Structure and Reactivity- (written by Naoki Inamoto, published by Maruzen Co., Ltd., June 1983) were used.

[0171] M.sup.+ in Formula (1) represents a cation. That is, M.sup.+ is a countercation of a boron anion. In the present disclosure, M.sup.+ is not particularly limited as long as it is a cation capable of neutralizing a boron anion, but from the viewpoint of suppressing contamination during development, at least one selected from the group consisting of an inorganic cation, an iodonium cation, and an infrared-absorbing coloring agent cation is preferable. The countercations may be used alone or in combination of two or more kinds thereof.

[0172] In Formula (I), M.sup.+ represents Li.sup.+, Na.sup.+, K.sup.+, an iodonium cation, or an infrared-absorbing coloring agent cation. In Formula (II), M.sup.+ represents an iodonium cation or an infrared-absorbing coloring agent cation.

[0173] The combination of two or more kinds of countercations is not particularly limited, but is preferably a combination of inorganic cations, a combination of iodonium cations, or a combination of infrared-absorbing coloring agent cations, and more preferably a combination of iodonium cations or a combination of infrared-absorbing coloring agent cations. In this manner, the suppressing property of the temporal development defect and the printing durability are further improved.

[0174] The iodonium cation may be a cationic moiety of an electron-accepting polymerization initiator described later, and the infrared-absorbing coloring agent cation may be a cationic moiety of an infrared absorber described later.

[0175] In the image-recording layer, the cationic moiety of the electron-donating polymerization initiator and the cationic moiety of the infrared absorber can be bonded to the anionic moiety of the borate compound represented by Formula (1) to form a salt.

[0176] Examples of the inorganic cation include a lithium cation, a sodium cation, a potassium cation, a calcium cation, and a magnesium cation. Among these, a sodium cation, a lithium cation, or a potassium cation is preferable, and a sodium cation is more preferable.

[0177] As the iodonium cation, a cationic moiety of an electron-accepting polymerization initiator described later can be used. Specific examples are shown in the following structural formulae. In the following structural formulae, Me represents a methyl group. The iodonium cation is not limited to the following specific examples.

##STR00018## ##STR00019##

[0178] As the infrared-absorbing coloring agent cation, a cationic moiety of an infrared absorber described later can be used. Specific examples are shown in the following structural formulae. In the following structural formulae, Me represents a methyl group, and Bu represents a butyl group. The infrared-absorbing coloring agent cation is not limited to the following specific examples.

##STR00020## ##STR00021##

[0179] From the viewpoint of chemical resistance and printing durability, the highest occupied molecular orbital (HOMO) of the specific borate compound is preferably 6.0 eV or more, more preferably 5.95 eV or more, and still more preferably 5.93 eV or more.

[0180] The upper limit of HOMO is preferably 5.00 eV or less and more preferably 5.40 eV or less. The range of the HOMO is still more preferably 5.93 eV to 5.70 eV.

[0181] In the present disclosure, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are calculated by the following methods.

[0182] First, the counteranion in the compound as a calculation object is ignored.

[0183] The structural optimization is carried out by DFT (B3LYP/6-31G(d)) using quantum chemical calculation software Gaussian 09.

[0184] The molecular orbital (MO) energy is calculated by DFT (B3LYP/6-31+G(d,p)/CPCM (solvent=methanol)) using the structure obtained by the structural optimization.

[0185] By the following formula, the MO energy Ebare (unit: hartree) obtained by the above-described MO energy calculation is converted into Escaled (unit: eV) used as the HOMO value and the LUMO value in the present disclosure.

[00001] $Escaled = 0.823168 27.2114 Ebare - 1.07634$

[0186] 27.2114 is simply a coefficient for converting hartree into eV, and 0.823168 and 1.07634 are adjustment coefficients. These are determined such that the calculated HOMO and LUMO of the compound as a calculation object match the measured values.

[0187] Preferred specific examples of the borate compound represented by Formula (1) (hereinafter, also referred to as a specific borate compound) are shown below, but the present disclosure is not limited thereto. In the following structural formulae, Me represents a methyl group.

##STR00022## ##STR00023## ##STR00024## ##STR00025## ##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030## ##STR00031## ##STR00032## ##STR00033## ##STR00034## ##STR00035## ##STR00036##

Aspect B

[0188] The image-recording layer in aspect B contains a borate compound represented by Formula (1a).

[0189] The borate compound represented by Formula (1a) is an aspect of the borate compound represented by Formula (1), and is used as an electron-donating polymerization initiator in the image-recording layer.

##STR00037##

[0190] In Formula (1a), R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group, and R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may each independently have a ring structure, Provided that at least one of R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is different from the other. Ma.sup.+ represents an iodonium cation.

[0191] In Formula (1a), R.sup.1, R.sup.2, R.sup.3, and R.sup.4 have the same meanings as R.sup.1, R.sup.2, R.sup.3, and R.sup.4 in Formula (1), and the same applies to the preferred aspects thereof.

[0192] In Formula (1a), Ma.sup.+ represents an iodonium cation. That is, the iodonium cation is a countercation of a boron anion. In the present disclosure, the iodonium cation is not particularly limited as long as it is a cation that can neutralize a boron anion. The iodonium cation may be contained alone or in combination of two or more kinds thereof.

[0193] Examples of the iodonium cation include those shown in the structural formulae described in the section of aspect A.

[0194] The preferred aspect of the highest occupied molecular orbital (HOMO) of the borate compound represented by Formula (1a) is the same as that of the borate compound represented by Formula (1). In addition, the calculation of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is also the same as the above-described method.

[0195] Hereinafter, preferred specific examples of the borate compound represented by Formula (1a) include B-18, B-19, B-31 to B-33, B-45, and B-46 described above, but the present disclosure is not limited thereto.

[0196] The image-recording layer may contain only one kind of specific borate compound, or may contain two or more kinds thereof. From the viewpoint of the color developability, the temporal color developability after exposure, the developability, and the property of suppressing the temporal development defect in the obtained lithographic printing plate, the content of the specific borate compound is preferably in a range of 0.01% by mass to 30% by mass, more preferably in a range of 0.05% by mass to 25% by mass, and still more preferably in a range of 0.1% by mass to 20% by mass with respect to the total mass of the image-recording layer, as the weight of the anion portion of the specific borate compound.

[0197] The specific borate compound may be a synthetic product.

[0198] In a case where the specific borate compound is prepared by synthesis, a borate compound having a different structure may be produced in addition to the target borate compound. In addition, the obtained borate compound may contain a small amount of impurities derived from a solvent, a catalyst, a raw material, and the like.

[0199] According to the studies of the present inventors, in the obtained borate compound, at least one of a borate compound having a structure different from the target borate compound or impurities is present, but the total content thereof is minute. Therefore, it has been confirmed that, even in a case where the borate compound obtained by synthesis is applied to the image-recording layer coating liquid without performing a special purification step such as removing impurities, the performance of the obtained lithographic printing plate precursor is not affected.

[0200] Therefore, the image-recording layer may contain at least one of a borate compound other than the specific borate compound or unavoidable impurities in manufacturing. The borate compound other than the specific borate compound and at least one of the unavoidable impurities in manufacturing include, for example, a raw material, a solvent, a catalyst, a by-product generated by a synthetic reaction, and a borate compound other than the specific borate compound.

<Electron-Accepting Polymerization Initiator>

[0201] The image-recording layer in aspect A of the present disclosure contains an electron-accepting polymerization initiator.

[0202] It is preferable that the image-recording layer in aspect B contains an electron-accepting polymerization initiator. The electron-accepting polymerization initiator contained in the image-recording layer in aspect B does not include the borate compound represented by Formula (1a).

[0203] The electron-accepting polymerization initiator is a compound that generates a polymerization initiation species such as a radical by accepting one electron through intermolecular electron transfer in a case where electrons of the infrared absorber are excited by exposure to infrared in one aspect.

[0204] In addition, the electron-accepting polymerization initiator used in the present disclosure is a compound that generates a polymerization initiation species such as a radical or a cation by either or both of light energy and heat energy, and can be appropriately selected from known thermal polymerization initiators, compounds having a bond that requires low bond dissociation energy, photopolymerization initiators, and the like.

[0205] The electron-accepting polymerization initiator is preferably a radical polymerization initiator and more preferably an onium salt compound.

[0206] In addition, as the electron-accepting polymerization initiator, an infrared-ray-sensitive polymerization initiator is preferable.

[0207] Examples of the electron-accepting radical polymerization initiator include (a) organic halide, (b) carbonyl compound, (c) azo compound, (d) organic peroxide, (e) metallocene compound, (f) azide compound, (g) hexaarylbiimidazole compound, (i) disulfone compound, (j) oxime ester compound, and (k) onium salt compound.

[0208] As (a) organic halide, for example, the compounds described in paragraphs 0022 and 0023 of JP2008-195018A are preferable.

[0209] As (b) carbonyl compound, for example, the compounds described in paragraph 0024 of JP2008-195018A are preferable.

[0210] As (c) azo compound, for example, the azo compounds described in JP1996-108621A (JP-H8-108621A) and the like can be used.

[0211] As (d) organic peroxide, for example, the compounds described in paragraph 0025 of JP2008-195018A are preferable.

[0212] As (e) metallocene compound, for example, the compounds described in paragraph 0026 of JP2008-195018A are preferable.

[0213] Examples of (f) azide compound can include compounds such as 2,6-bis(4-azidobenzylidene)-4-methylcyclohexanone.

[0214] As (g) hexaarylbiimidazole compound, for example, the compounds described in paragraph 0027 of JP2008-195018A are preferable.

[0215] Examples of (i) disulfone compound include the compounds described in JP1986-166544A (JP-S61-166544A) and JP2002-328465A.

[0216] As (j) oxime ester compound, for example, the compounds described in paragraphs 0028 to 0030 of JP2008-195018A are preferable.

[0217] Among the above electron-accepting polymerization initiators, from the viewpoint of curing properties, an oxime ester compound and an onium salt compound are preferable. Particularly, from the viewpoint of printing durability, an iodonium salt compound, a sulfonium salt compound, or an azinium salt compound is preferable, an iodonium salt compound or a sulfonium salt compound is more preferable, and an iodonium salt compound is particularly preferable.

[0218] Specific examples of these compounds will be shown below, but the present disclosure is not limited thereto.

[0219] As the iodonium salt compound, for example, a diaryliodonium salt compound is preferable. Particularly, an electron-donating group, for example, a diphenyl iodonium salt compound substituted with an electron-donating group such as an alkyl group or an alkoxyl group is more preferable. Furthermore, an asymmetric diphenyl iodonium salt compound is preferable. Specific examples thereof include diphenyliodonium=hexafluorophosphate, 4-methoxyphenyl-4-(2-methylpropyl)phenyliodonium=hexafluorophosphate, 4-(2-methylpropyl)phenyl-p-tolyliodonium=hexafluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyl iodonium=hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyl iodonium=tetrafluoroborate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyl iodonium=1-perfluorobutane sulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium=hexafluorophosphate, and bis(4-t-butylphenyl)iodonium=hexafluorophosphate.

[0220] As the sulfonium salt compound, for example, a triarylsulfonium salt compound is preferable. Particularly, a triarylsulfonium salt compound is preferable in which at least some of electron-withdrawing groups such as groups on an aromatic ring are substituted with halogen atoms, and a triarylsulfonium salt compound is more preferable in which the total number of halogen atoms as substituents on an aromatic ring is 4 or more. Specific examples thereof include triphenylsulfonium=hexafluorophosphate, triphenylsulfonium=benzoyl formate, bis(4-chlorophenyl)phenylsulfonium=benzoyl formate, bis(4-chlorophenyl)-4-methylphenylsulfonium=tetrafluoroborate, tris(4-chlorophenyl)sulfonium=3,5-bis(methoxycarbonyl)benzenesulfonate, tris(4-chlorophenyl)sulfonium=hexafluorophosphate, and tris(2,4-dichlorophenyl)sulfonium=hexafluorophosphate.

[0221] As a counteranion of the iodonium salt compound and the sulfonium salt compound, a sulfonamide anion or a sulfonimide anion is preferable, and a sulfonimide anion is more preferable.

[0222] As the sulfonamide anion, an aryl sulfonamide anion is preferable.

[0223] In addition, as the sulfonimide anion, a bisaryl sulfonimide anion is preferable.

[0224] Specific examples of the sulfonamide anion or the sulfonimide anion will be shown below, but the present disclosure is not limited thereto. In the following specific examples, Ph represents a phenyl group, Me represents a methyl group, and Et represents an ethyl group.

##STR00038## ##STR00039## ##STR00040## ##STR00041##

[0225] The electron-accepting polymerization initiator preferably includes a compound A represented by Formula (Ia) and one or more compounds B selected from the group consisting of a compound represented by Formula (Ib) or a compound represented by Formula (Ic).

##STR00042##

[0226] In Formulae (Ia) to (Ic), R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are each independently a substituted or unsubstituted alkyl group having 2 to 9 carbon atoms or a substituted or unsubstituted alkoxy group having 2 to 9 carbon atoms, at least one of R.sub.3 or R.sub.4 is different from R.sub.1 or R.sub.2, a difference between a total number of carbon atoms in R.sub.1 and R.sub.2 and a total number of carbon atoms in R.sub.3 and R.sub.4 is 0 to 4 (that is, 0, 1, 2, 3, or 4), a difference between the total number of carbon atoms in R.sub.1 and R.sub.2 and a total number of carbon atoms in R.sub.5 and R.sub.6 is 0 to 4, and X.sub.1, X.sub.2, and X.sub.3 are the same or different anions.

[0227] R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are each independently preferably a substituted or unsubstituted alkyl group having 2 to 9 carbon atoms or a substituted or unsubstituted alkoxy group having 2 to 9 carbon atoms, more preferably a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms or a substituted or unsubstituted alkoxy group having 3 to 6 carbon atoms, and even more preferably a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms. The alkyl group and the alkoxy group all may be linear or branched, but are preferably branched.

[0228] Examples of the substituted or unsubstituted alkyl group include an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, a t-pentyl group, a sec-pentyl group, a neopentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a t-hexyl group, an n-heptyl group, an n-octyl group, an iso-octyl group, a 2-ethyl hexyl group, and an n-nonyl group.

[0229] Examples of the substituted or unsubstituted alkoxy group include an ethoxy group, a propoxy group, an iso-propoxy group, a t-butoxy group, an n-butoxy group, and an n-octyloxy group.

[0230] As X.sub.1, X.sub.2, and X.sub.3, ClO.sub.4.sup., PF.sub.6.sup., BF.sub.4.sup., SbF.sub.6.sup., CH.sub.3SO.sub.3.sup., CF.sub.3SO.sub.3.sup., C.sub.6H.sub.5SO.sub.3.sup., CH.sub.3C.sub.6H.sub.4SO.sub.3.sup., HOC.sub.6H.sub.4SO.sub.3.sup., ClC.sub.6H.sub.4SO.sub.3.sup., and a borate anion represented by the following formula (Id) are preferable.

B.sup.(R.sup.1)(R.sup.2)(R.sup.3)(R.sup.4)Formula (Id)

[0231] In Formula (Id), R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group (including a halogen-substituted aryl group), a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted heterocyclic group. Two or more of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may be linked to each other to form a substituted or unsubstituted heterocyclic ring containing a boron atom. The heterocyclic ring to be obtained has a maximum of 7 carbon atoms, nitrogen atoms, oxygen atoms, or nitrogen atoms.

[0232] Examples of the substituent in R.sup.1, R.sup.2, R.sup.3, and R.sup.4 include a chlorine atom, a fluorine atom, a nitro group, an alkyl group, an alkoxy group, and an acetoxy group.

[0233] All of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are preferably a substituted or unsubstituted aryl group, and more preferably an unsubstituted phenyl group.

[0234] It is preferable that at least one of X.sub.1, X.sub.2, or X.sub.3 is a tetraaryl borate anion including the same or different aryl groups, it is more preferable that one or more of X.sub.1, X.sub.2, and X.sub.3 are tetraphenyl borate anions, and it is even more preferable that each of X.sub.1, X.sub.2, and X.sub.3 is a tetraphenyl borate anion.

[0235] Examples of a preferable aspect include an aspect in which the compound B includes a compound represented by Formula (Ic), R.sub.1 is the same as R.sub.5, and R.sub.2 is the same as R.sub.6. In particular, it is preferable that R.sub.1 is the same as R.sub.2, and for example, both R.sub.1 and R.sub.2 are an iso-propyl group, an iso-butyl group, or a t-butyl group.

[0236] In addition, examples of another preferable aspect include an aspect in which the compound B includes a compound represented by Formula (Ib), R.sub.1 is the same as R.sub.2, and R.sub.3 is the same as R.sub.4. In this case, it is preferable that both R.sub.1 and R.sub.2 are an iso-propyl group, an iso-butyl group, or a t-butyl group. In addition, the difference in the number of carbon atoms between R.sub.1 and R.sub.3 is preferably 1 or 2.

[0237] The compound B may be a mixture of a compound represented by Formula (Ib) and a compound represented by Formula (Ic).

[0238] The compounds represented by Formulae (Ia) to (Ic) may be obtained from Sigma-Aldrich Co., LLC or the like, or may be synthesized by a known synthesis method using easily available starting materials.

[0239] The molar ratio between the compound A and the compound B is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

[0240] From the viewpoints of developability and printing durability of the lithographic printing plate to be obtained, the electron-accepting polymerization initiator may include a compound represented by Formula (II) described in paragraphs 0186 to 0197 of WO2022/019217A.

[0241] From the viewpoint of improving sensitivity and making it difficult for plate missing to occur, the lowest unoccupied molecular orbital (LUMO) of the electron-accepting polymerization initiator is preferably 3.00 eV or less, and more preferably 3.02 eV or less.

[0242] The lower limit of LUMO is preferably 3.80 eV or more and more preferably 3.60 eV or more.

[0243] One electron-accepting polymerization initiator may be used alone, or two or more electron-accepting polymerization initiators may be used in combination.

[0244] The content of the electron-accepting polymerization initiator with respect to the total mass of the image-recording layer is preferably 0.1% by mass to 50% by mass, more preferably 0.5% by mass to 30% by mass, and particularly preferably 0.8% by mass to 20% by mass.

[0245] It is preferable that the image-recording layer according to the present disclosure contains an infrared absorber.

[0246] The infrared absorber is not particularly limited, and examples thereof include pigments and dyes.

[0247] As the dye that is used as the infrared absorber, it is possible to use commercially available dyes and known dyes described in publications, for example, Dye Handbooks (edited by the Society of Synthetic Organic Chemistry, Japan, 1970). Specific examples thereof include dyes such as an azo dye, a metal complex azo dye, a pyrazolone azo dye, a naphthoquinone dye, an anthraquinone dye, a phthalocyanine dye, a carbonium dye, a quinoneimine dye, a methine dye, a cyanine dye, a squarylium colorant, a pyrylium salt, and a metal thiolate complex.

[0248] Among these dyes, for example, a cyanine colorant, a squarylium colorant, a pyrylium salt, a nickel thiolate complex, and an indolenine cyanine colorant are particularly preferable. Furthermore, for example, a cyanine colorant or an indolenine cyanine colorant is preferable. Among these, a cyanine colorant is particularly preferable.

[0249] The infrared absorber is preferably a cationic polymethine colorant having an oxygen or nitrogen atom at the meso-position. Preferred examples of the cationic polymethine colorant include a cyanine colorant, a pyrylium colorant, a thiopyrylium colorant, an azulenium colorant, and the like. From the viewpoint of ease of availability, solubility in a solvent during an introduction reaction, and the like, a cyanine colorant is preferable.

[0250] Specific examples of the cyanine colorant include the compounds described in paragraphs 0017 to 0019 of JP2001-133969A and the compounds described in paragraphs 0016 to 0021 of JP2002-023360A and paragraphs 0012 to 0037 of JP2002-040638A. As the cyanine colorant, for example, the compounds described in paragraphs 0034 to 0041 of JP2002-278057A and paragraphs 0080 to 0086 of JP2008-195018A are preferable, and the compounds described in paragraphs 0035 to 0043 of JP2007-90850A and the compounds described in paragraphs 0105 to 0113 of JP2012-206495A are particularly preferable.

[0251] In addition, the compounds described in paragraphs 0008 and 0009 of JP1993-5005A (JP-H05-5005A) and paragraphs 0022 to 0025 of JP2001-222101A can also be preferably used.

[0252] As pigments, the compounds described in paragraphs 0072 to 0076 of JP2008-195018A are preferable.

[0253] In addition, the infrared absorber preferably contains an infrared absorber that decomposes by infrared exposure (decomposition-type infrared absorber), and more preferably contains a decomposition-type color-developing infrared absorber.

[0254] Presumably, in a case where a decomposition-type infrared absorber is used as the infrared absorber, the infrared absorber or a decomposition product thereof may promote polymerization, and the decomposition product of the infrared absorber and the polymerizable compound may interact with each other, which may result in excellent printing durability.

[0255] The decomposition-type infrared absorber is preferably an infrared absorber that performs a function of forming color by absorbing infrared and decomposing by exposure to infrared.

[0256] Hereinafter, a color-forming compound formed as a result of infrared absorption and decomposition of the decomposition-type infrared absorber by exposure to infrared will also be called color forming substance of the decomposition-type infrared absorber.

[0257] In addition, it is preferable that the decomposition-type infrared absorber have a function of absorbing infrared by exposure to infrared and converting the absorbed infrared into heat.

[0258] The decomposition-type infrared absorber may be an infrared absorber that decomposes by absorbing at least a part of light in the infrared wavelength region (wavelength of 750 nm to 1 mm). The decomposition-type infrared absorber is preferably an infrared absorber having a maximal absorption wavelength in a wavelength region of 750 nm to 1,400 nm, and more preferably an infrared absorber having a maximal absorption wavelength in a wavelength region of 760 nm to 900 nm.

[0259] More specifically, the decomposition-type infrared absorber is preferably a compound that decomposes upon the exposure to infrared and generates a compound having maximal absorption wavelength in a wavelength region of 500 nm to 600 nm.

[0260] The decomposition-type infrared absorber is preferably an infrared absorber that decomposes by either or both of heat and electron migration resulting from exposure to infrared, and more preferably an infrared absorber that decomposes by electron migration resulting from exposure to infrared. Decomposes by electron migration mentioned herein means that electrons excited to the lowest unoccupied molecular orbital (LUMO) from the highest occupied molecular orbital (HOMO) of the decomposition-type infrared absorber by exposure to infrared rays move to electron accepting groups (for example, groups having potential close to LUMO) in a molecule by means of intramolecular electron migration and thus result in decomposition.

[0261] The infrared absorber preferably includes a compound represented by Formula 1.

##STR00043##

[0262] In Formula 1, R.sub.1 and R.sub.2 each independently represent a hydrogen atom or an alkyl group, R.sub.1 and R.sub.2 may be linked to each other to form a ring, R.sub.3 to R.sub.6 each independently represent a hydrogen atom or an alkyl group, R.sub.7 and R.sub.8 each independently represent an alkyl group or an aryl group, Y.sub.1 and Y.sub.2 each independently represent an oxygen atom, a sulfur atom, NR.sub.0, or a dialkylmethylene group, R.sub.0 represents a hydrogen atom, an alkyl group, or an aryl group, Ar.sub.1 and Ar.sub.2 each independently represent a group forming a benzene ring or a naphthalene ring which may have a group represented by Formula 2 that will be described later, A.sub.1 represents NR.sub.9R.sub.10, X.sub.1-L.sub.1 or a group represented by Formula 2 that will be described later, R.sub.9 and R.sub.10 each independently represent an alkyl group, an aryl group, an alkoxycarbonyl group, or an arylsulfonyl group, X.sub.1 represents an oxygen atom or a sulfur atom, L.sub.1 represents a hydrocarbon group, a heteroaryl group, or a group that undergoes bond cleavage from X.sub.1 by heat or exposure to infrared, Za represents a counterion that neutralizes charge, and at least one of Ar.sub.1 or Ar.sub.2 has a group represented by Formula 2.

##STR00044##

[0263] In Formula 2, X represents a halogen atom, C(O)X.sub.2R.sub.11, C(O)NR.sub.12R.sub.13, OC(O)R.sub.14, CN, SO.sub.2NR.sub.15R.sub.16, or a perfluoroalkyl group, X.sub.2 represents a single bond or an oxygen atom, R.sub.11 and R.sub.14 each independently represent an alkyl group or an aryl group, and R.sub.12, R.sub.13, R.sub.15, and R.sub.16 each independently represent a hydrogen atom, an alkyl group, or an aryl group.

[0264] Ar.sub.1 and Ar.sub.2 each independently represent a group forming a benzene ring or a naphthalene ring. The benzene ring and the naphthalene ring may have a substituent other than X. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, groups obtained by combining these, and the like. Among these, an alkyl group is preferable.

[0265] In Formula 1, at least one of Ar.sub.1 or Ar.sub.2 has a group represented by Formula 2. From the viewpoint of printing durability and visibility, it is preferable that both of Ar.sub.1 and Ar.sub.2 have a group represented by Formula 2.

[0266] X in Formula 2 represents a halogen atom, C(O)X.sub.2R.sub.11, C(O)NR.sub.12R.sub.13, OC(O)R.sub.14, CN, SO.sub.2NR.sub.15R.sub.16, or a perfluoroalkyl group. From the viewpoint of printing durability, visibility, and temporal stability, X is preferably a halogen atom, C(O)X.sub.2R.sub.11, C(O)NR.sub.12R.sub.13, OC(O)R.sub.14, CN, or SO.sub.2NR.sub.15R.sub.16, more preferably a halogen atom, C(O)OR.sub.II, C(O)NR.sub.12R.sub.13, or OC(O)R.sub.14, even more preferably a halogen atom, C(O)OR.sub.II or OC(O)R.sub.14, particularly preferably a fluorine atom, a chlorine atom, a bromine atom, or C(O)OR.sub.17, and most preferably a chlorine atom or a bromine atom.

[0267] X.sub.2 represents a single bond or an oxygen atom, and is preferably an oxygen atom.

[0268] R.sub.11 and R.sub.14 each independently represent an alkyl group or an aryl group, preferably each independently represent an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably each independently represent an alkyl group having 1 to 12 carbon atoms.

[0269] R.sub.12, R.sub.13, R.sub.15, and R.sub.16 each independently represent a hydrogen atom, an alkyl group, or an aryl group, preferably each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, more preferably each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and even more preferably each independently represent an alkyl group having 1 to 12 carbon atoms.

[0270] R.sub.17 represents an alkyl group or an aryl group, preferably represents an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably represents an alkyl group having 1 to 12 carbon atoms.

[0271] A.sub.1 represents NR.sub.9R.sub.10, X.sub.1-L.sub.1, or X. From the viewpoint of printing durability, visibility, and temporal stability, A.sub.1 is preferably NR.sub.9R.sub.10 or X.sub.1-L.sub.1, and more preferably NR.sub.18R.sub.19 or SR.sub.20.

[0272] Furthermore, from the viewpoint of plate missing suppressing property, GLV suitability, and printing durability, A.sub.1 is preferably X, more preferably a halogen atom, even more preferably a chlorine atom or a bromine atom, and particularly preferably a chlorine atom.

[0273] R.sub.9 and R.sub.10 each independently represent an alkyl group, an aryl group, an alkoxycarbonyl group, or an arylsulfonyl group, preferably each independently represent an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably each independently represent an alkyl group having 1 to 12 carbon atoms.

[0274] X.sub.1 represents an oxygen atom or a sulfur atom. In a case where L.sub.1 is a hydrocarbon group or a heteroaryl group, X.sub.1 is preferably a sulfur atom. L.sub.1 is preferably a group that undergoes bond cleavage from X.sub.1 by heat or exposure to infrared.

[0275] L.sub.1 represents a hydrocarbon group, a heteroaryl group, or a group that undergoes bond cleavage from X.sub.1 by heat or exposure to infrared. From the viewpoint of printing durability, L.sub.1 is preferably a hydrocarbon group or a heteroaryl group, more preferably an aryl group or a heteroaryl group, and even more preferably a heteroaryl group.

[0276] In addition, from the viewpoint of visibility and suppressing fading over time, L.sub.1 is preferably a group that undergoes bond cleavage from X.sub.1 by heat or exposure to infrared. The group that undergoes bond cleavage from X.sub.1 by heat or exposure to infrared will be described later.

[0277] R.sub.18 and R.sub.19 each independently represent an aryl group, preferably each independently represent an aryl group having 6 to 20 carbon atoms, and more preferably each independently represent a phenyl group.

[0278] R.sub.20 represents a hydrocarbon group or a heteroaryl group, preferably represents an aryl group or a heteroaryl group, and more preferably represents a heteroaryl group.

[0279] Preferred examples of the heteroaryl group represented by L.sub.1 and R.sub.20 include the following groups.

##STR00045##

[0280] The alkyl group represented by R.sub.1 to R.sub.10 and R.sub.0 is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and even more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group described above may be linear or branched, or may have a ring structure.

[0281] Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, an s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group.

[0282] Among these alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is particularly preferable.

[0283] The alkyl group may have a substituent. Examples of the substituent include an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and a group obtained by combining these groups.

[0284] The aryl group represented by R.sub.9, R.sub.10, R.sub.15, R.sub.19, and R.sub.0 is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and even more preferably an aryl group having 6 to 12 carbon atoms.

[0285] The aryl group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and groups obtained by combining these, and the like.

[0286] Specific examples of the aryl group include a phenyl group, a naphthyl group, a p-tolyl group, a p-chlorophenyl group, a p-fluorophenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, a p-methylthiophenyl group, a p-phenylthiophenyl group, and the like.

[0287] Among these aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, or a naphthyl group is preferable.

[0288] It is preferable that R.sub.1 and R.sub.2 be linked to each other to form a ring.

[0289] In a case where R.sub.1 and R.sub.2 are linked to each other to form a ring, the formed ring is preferably a 5- or a 6-membered ring and more preferably a 6-membered ring. In addition, the ring formed of R.sub.1 and R.sub.2 linked to each other is preferably a hydrocarbon ring which may have an ethylenically unsaturated bond.

[0290] Y.sub.1 and Y.sub.2 each independently represent an oxygen atom, a sulfur atom, NR.sub.0, or a dialkylmethylene group. Among these, NR.sub.0 or a dialkylmethylene group is preferable, and a dialkylmethylene group is more preferable.

[0291] R.sub.0 represents a hydrogen atom, an alkyl group, or an aryl group. R.sub.0 is preferably an alkyl group.

[0292] It is preferable that R.sub.7 and R.sub.8 be the same group.

[0293] R.sub.7 and R.sub.8 preferably each independently represent a linear alkyl group or an alkyl group having a sulfonate group on a terminal, and more preferably each independently represent a methyl group, an ethyl group, or a butyl group having a sulfonate group on a terminal.

[0294] The countercation of the aforementioned sulfonate group may be a cation on a nitrogen atom in Formula 1 or may be an alkali metal cation or an alkaline earth metal cation.

[0295] From the viewpoint of improving water solubility of the compound represented by Formula 1, R.sub.7 and R.sub.8 preferably each independently represent an alkyl group having an anion structure, more preferably each independently represent an alkyl group having a carboxylate group or a sulfonate group, and even more preferably each independently represent an alkyl group having a sulfonate group on a terminal.

[0296] From the viewpoint of increasing the maximum absorption wavelength of the compound represented by Formula 1 and from the viewpoint of visibility and printing durability of the lithographic printing plate, R.sub.7 and R.sub.8 preferably each independently represent an alkyl group having an aromatic ring, more preferably each independently represent an alkyl group having an aromatic ring on a terminal, and particularly preferably each independently represent a 2-phenylethyl group, a 2-naphthalenylethyl group, or a 2-(9-anthracenyl)ethyl group.

[0297] R.sub.3 to R.sub.6 each independently represent a hydrogen atom or an alkyl group, and preferably each independently represent a hydrogen atom.

[0298] In addition, from the viewpoint of temporal stability and printing durability, the compound represented by Formula 1 preferably has one or more halogen atoms, more preferably has one or more halogen atoms in at least one selected from the group consisting of A.sub.1, Ar.sub.1, and Ar.sub.2, and particularly preferably A.sub.1, Ar.sub.1, and Ar.sub.2 each have one or more halogen atoms.

[0299] Furthermore, from the viewpoint of temporal stability and printing durability, the compound represented by Formula 1 more preferably has two or more halogen atoms, still more preferably has three or more halogen atoms, and particularly preferably has three or more and six or fewer halogen atoms.

[0300] Preferred examples of the aforementioned halogen atoms include a chlorine atom and a bromine atom.

[0301] Furthermore, from the viewpoint of temporal stability and printing durability, the compound represented by Formula 1 preferably has a halogen atom in at least one of Ar.sub.1 or Ar.sub.2, more preferably has a chlorine atom or a bromine atom in at least one of Ar.sub.1 or Ar.sub.2, and particularly preferably has a bromine atom in at least one of Ar.sub.1 or Ar.sub.2.

[0302] Za represents a counterion that neutralizes charge. In a case where Za represents anionic species, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a perchlorate ion, a sulfonamide anion, a sulfonimide anion, and the like. In a case where Za represents cationic species, an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is preferable, a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is more preferable, a sodium ion, a potassium ion, or an ammonium ion is even more preferable, and a sodium ion, a potassium ion, or a trialkylammonium ion is particularly preferable.

[0303] As Za, among the above, from the viewpoint of printing durability and visibility, an organic anion having a carbon atom is preferable, a sulfonate ion, a carboxylate ion, a sulfonamide anion, or a sulfonimide anion is more preferable, a sulfonamide anion or a sulfonimide anion is even more preferable, and a sulfonimide anion is particularly preferable.

[0304] R.sub.1 to R.sub.8, R.sub.0, A.sub.1, Ar.sub.1, Ar.sub.2, Y.sub.1, and Y.sub.2 may have an anion structure or a cation structure. In a case where all of R.sub.1 to R.sub.8, R.sub.0, A.sub.1, Ar.sub.1, Ar.sub.2, Y.sub.1, and Y.sub.2 represent a group having neutral charge, Za represents a monovalent counteranion. However, for example, in a case where two or more among R.sub.1 to R.sub.8, R.sub.0, A.sub.1, Ar.sub.1, Ar.sub.2, Y.sub.1, and Y.sub.2 have an anion structure, Za can be a countercation.

[0305] In Formula 1, in a case where portions other than Za have neutral charge, Formula 1 may not have Za.

[0306] As the sulfonamide anion, an aryl sulfonamide anion is preferable.

[0307] In addition, as the sulfonimide anion, a bisaryl sulfonimide anion is preferable.

[0308] Specific examples of the sulfonamide anion or the sulfonimide anion will be shown below, but the present disclosure is not limited thereto. In the following specific examples, Ph represents a phenyl group, Me represents a methyl group, and Et represents an ethyl group.

##STR00046## ##STR00047## ##STR00048## ##STR00049##

[0309] From the viewpoint of visibility, the group that undergoes bond cleavage from X.sub.1 by heat or exposure to infrared is preferably a group represented by any of Formulas (1-1) to (1-7), and more preferably a group represented by any of Formulas (1-1) to (1-3).

##STR00050##

[0310] In Formulas (1-1) to (1-7), * represents a bonding site with X.sub.1 in Formula 1, R.sup.10 each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, OR.sup.14, NR.sup.15R.sup.16, or SR.sup.17, R.sup.11 each independently represent a hydrogen atom, an alkyl group, or an aryl group, R.sup.12 represents an aryl group, OR.sup.14, NR.sup.15R.sup.16, SR.sup.17, C(O)R.sup.18, OC(O)R.sup.18, or a halogen atom, R.sup.13 represents an aryl group, an alkenyl group, an alkoxy group, or an onium group, R.sup.14 to R.sup.17 each independently represent a hydrogen atom, an alkyl group, or an aryl group, R.sup.18 each independently represent an alkyl group, an aryl group, OR.sup.14, NR.sup.15R.sup.16, or SR.sup.17, and Z.sup.1 represents a counterion that neutralizes charge.

[0311] In a case where R.sup.10, R.sup.11, and R.sup.14 to R.sup.18 each represent an alkyl group, preferred aspects of the alkyl group are the same as preferred aspects of the alkyl group represented by R.sup.2 to R.sup.9 and R.sup.0.

[0312] The number of carbon atoms in the alkenyl group represented by R.sup.10 and R.sup.13 is preferably 1 to 30, more preferably 1 to 15, and even more preferably 1 to 10.

[0313] In a case where R.sup.10 to R.sup.18 each represent an aryl group, preferred aspects of the aryl group are the same as preferred aspects of the aryl group represented by R.sup.0.

[0314] From the viewpoint of visibility, R.sup.10 in Formula (1-1) is preferably an alkyl group, an alkenyl group, an aryl group, OR.sup.14, NR.sup.15R.sup.16, or SR.sup.17, more preferably an alkyl group, OR.sup.14, NR.sup.15R.sup.16, or SR.sup.17, even more preferably an alkyl group or OR.sup.14, and particularly preferably OR.sup.14.

[0315] In a case where R.sup.10 in Formula (1-1) is an alkyl group, the alkyl group is preferably an alkyl group having an arylthio group or an alkyloxycarbonyl group at the -position.

[0316] In a case where R.sup.10 in Formula (1-1) represents OR.sup.14, R.sup.14 is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, even more preferably an isopropyl group or a t-butyl group, and particularly preferably a t-butyl group.

[0317] From the viewpoint of visibility, R.sup.11 in Formula (1-2) is preferably a hydrogen atom.

[0318] In addition, from the viewpoint of visibility, R.sup.12 in Formula (1-2) is preferably C(O)OR.sup.14, OC(O)OR.sup.14, or a halogen atom, and more preferably C(O)OR.sup.14 or OC(O)OR.sup.14. In a case where R.sup.12 in Formula (1-2) is C(O)OR.sup.14 or OC(O)OR.sup.14, R.sup.14 is preferably an alkyl group.

[0319] From the viewpoint of visibility, R.sup.11 in Formula (1-3) preferably each independently represent a hydrogen atom or an alkyl group. It is more preferable that at least one of R.sup.11's in Formula (1-3) be an alkyl group.

[0320] The alkyl group represented by R.sup.11 is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably an alkyl group having 3 to 10 carbon atoms.

[0321] Furthermore, the alkyl group represented by R.sup.11 is preferably an alkyl group having a branch or a cycloalkyl group, more preferably a secondary or tertiary alkyl group or a cycloalkyl group, and even more preferably an isopropyl group, a cyclopentyl group, a cyclohexyl group, or a t-butyl group.

[0322] In addition, from the viewpoint of visibility, R.sup.13 in Formula (1-3) is preferably an aryl group, an alkoxy group, or an onium group, more preferably a p-dimethylaminophenyl group or a pyridinium group, and even more preferably a pyridinium group.

[0323] Examples of the onium group represented by R.sup.13 include a pyridinium group, an ammonium group, a sulfonium group, and the like. The onium group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a sulfo group, an alkyloxycarbonyl group, an aryloxycarbonyl group, groups obtained by combining these, and the like. Among these, an alkyl group, an aryl group, and groups obtained by combining these are preferable.

[0324] Among these, a pyridinium group is preferable, an N-alkyl-3-pyridinium group, an N-benzyl-3-pyridinium group, an N-(alkoxypolyalkyleneoxyalkyl)-3-pyridinium group, an N-alkoxycarbonylmethyl-3-pyridinium group, an N-alkyl-4-pyridinium group, an N-benzyl-4-pyridinium group, an N-(alkoxypolyalkyleneoxyalkyl)-4-pyridinium group, an N-alkoxycarbonylmethyl-4-pyridinium group, or an N-alkyl-3,5-dimethyl-4-pyridinium group is more preferable, an N-alkyl-3-pyridinium group or an N-alkyl-4-pyridinium group is even more preferable, an N-methyl-3-pyridinium group, an N-octyl-3-pyridinium group, an N-methyl-4-pyridinium group, or an N-octyl-4-pyridinium group is particularly preferable, and an N-octyl-3-pyridinium group or an N-octyl-4-pyridinium group is most preferable.

[0325] In a case where R.sup.13 is a pyridinium group, examples of the counteranion include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, a perchlorate ion, and the like. Among these, a p-toluenesulfonate ion or a hexafluorophosphate ion is preferable.

[0326] From the viewpoint of visibility, R.sup.10 in Formula (1-4) is preferably an alkyl group or an aryl group. It is more preferable that one of two R.sup.10's be an alkyl group and the other be an aryl group.

[0327] From the viewpoint of visibility, R.sup.10 in Formula (1-5) is preferably an alkyl group or an aryl group, more preferably an aryl group, and even more preferably a p-methylphenyl group.

[0328] From the viewpoint of visibility, R.sup.10 in Formula (1-6) preferably each independently represent an alkyl group or an aryl group, and more preferably each independently represent a methyl group or a phenyl group.

[0329] From the viewpoint of visibility, Z.sup.1 in Formula (1-7) may be a counterion that neutralizes charge, and may be included in Za in the entirety of the compound.

[0330] Z.sup.1 is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a p-toluenesulfonate ion or a hexafluorophosphate ion.

[0331] The group that undergoes bond cleavage from X.sub.1 by heat or exposure to infrared is particularly preferably a group represented by Formula (1-8).

##STR00051##

[0332] In Formula (1-8), * represents a bonding site with X.sub.1 in formula 1, R.sup.19 and R.sup.20 each independently represent an alkyl group, and Za represents a counterion that neutralizes charge.

[0333] In Formula (1-8), the bonding position of a pyridinium ring and a hydrocarbon group having R.sup.20 is preferably the 3-position or 4-position of the pyridinium ring, and more preferably the 4-position of the pyridinium ring.

[0334] The alkyl group represented by R.sup.19 and R.sup.20 may be linear or branched, or may have a ring structure.

[0335] Furthermore, the above alkyl group may have a substituent, and preferred examples of the substituent include an alkoxy group and a terminal alkoxypolyalkyleneoxy group.

[0336] R.sup.19 is preferably an alkyl group having 1 to 12 carbon atoms, more preferably a linear alkyl group having 1 to 12 carbon atoms, even more preferably a linear alkyl group having 1 to 8 carbon atoms, and particularly preferably a methyl group or an n-octyl group. R.sup.20 is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 8 carbon atoms, even more preferably an isopropyl group or a t-butyl group, and particularly preferably an isopropyl group.

[0337] Za may be a counterion that neutralizes charge, and may be included in Za in the entirety of the compound.

[0338] Za is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a p-toluenesulfonate ion or a hexafluorophosphate ion.

[0339] From the viewpoint of improving visibility of exposed portions, the decomposition-type infrared absorber is preferably a cyanine colorant having a group that decomposes by exposure to infrared (specifically, R.sup.1 in Formulas 1-1 to 1-7).

[0340] From the viewpoint of improving visibility of exposed portions, the decomposition-type infrared absorber is more preferably a compound represented by Formula 1-1.

##STR00052##

[0341] In Formula 1-1, R.sup.1 represents a group that is represented by any of Formula 2-1 to Formula 4-1, R.sup.11 to R.sup.18 each independently represent a hydrogen atom, a halogen atom, R.sup.a, OR.sup.b, SR.sup.c, or NR.sup.dR.sup.e, R.sup.a to R.sup.e each independently represent a hydrocarbon group, A.sub.1, A.sub.2, and a plurality of R.sub.1 to R.sub.18 may be linked to each other to form a monocyclic or polycyclic ring, A.sub.1 and A.sub.2 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, n.sub.11 and n.sub.12 each independently represent an integer of 0 to 5, the sum of n.sub.11 and n.sub.12 is 2 or more, n.sub.13 and n.sub.14 each independently represent 0 or 1, L represents an oxygen atom, a sulfur atom, or NR.sup.10, R.sup.10 represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counterion that neutralizes charge.

##STR00053##

[0342] In Formula 2-1 to Formula 4-1, R.sup.20, R.sup.30, R.sup.41, and R.sup.42 each independently represent an alkyl group or an aryl group, Zb represents a counterion that neutralizes charge, and a wavy line represents a bonding site with a group represented by L in Formula 1-1.

[0343] In a case where the compound represented by Formula 1-1 is exposed to infrared, the R.sup.1-L bond is cleaved, L turns into O, S, or NR.sup.10, and the compound is discolored.

[0344] In Formula 1-1, R.sup.1 represents a group represented by any of Formula 2-1 to Formula 4-1.

[0345] Hereinafter, each of the group represented by Formula 2-1, the group represented by Formula 3-1, and the group represented by Formula 4-1 will be described.

[0346] In Formula 2-1, R.sup.20 represents an alkyl group or an aryl group, and the portion of the wavy line represents a bonding site with the group represented by L in Formula 1-1.

[0347] As the alkyl group represented by R.sup.20, an alkyl group having a carbon number of 1 to 30 is preferable, an alkyl group having a carbon number of 1 to 15 is more preferable, and an alkyl group having a carbon number of 1 to 10 is even more preferable.

[0348] The alkyl group described above may be linear or branched, or may have a ring structure.

[0349] The aryl group represented by R.sup.20 is preferably an aryl group having a carbon number of 6 to 30, more preferably an aryl group having a carbon number of 6 to 20, and even more preferably an aryl group having a carbon number of 6 to 12.

[0350] From the viewpoint of visibility, R.sup.20 is preferably an alkyl group.

[0351] From the viewpoint of decomposition properties and visibility, the alkyl group represented by R.sup.20 is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group.

[0352] Furthermore, from the viewpoint of decomposition properties and visibility, the alkyl group represented by R.sup.20 is preferably an alkyl group having a carbon number of 1 to 8, more preferably a branched alkyl group having a carbon number of 3 to 10, even more preferably a branched alkyl group having a carbon number of 3 to 6, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0353] Specific examples of the group represented by Formula 2-1 will be shown below. However, the present disclosure is not limited thereto. In the following structural formulas, .circle-solid. represents a bonding site with the group represented by L in Formula 1-1.

##STR00054##

[0354] In Formula 3-1, R.sup.30 represents an alkyl group or an aryl group, and the portion of the wavy line represents a bonding site with the group represented by L in Formula 1-1.

[0355] The alkyl group and aryl group represented by R.sup.30 are the same as the alkyl group and aryl group represented by R.sup.20 in Formula 2-1, and the preferred aspects thereof are also the same.

[0356] From the viewpoint of decomposition properties and visibility, the alkyl group represented by R.sup.30 is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group.

[0357] Furthermore, from the viewpoint of decomposition properties and visibility, the alkyl group represented by R.sup.30 is preferably an alkyl group having a carbon number of 1 to 8, more preferably a branched alkyl group having a carbon number of 3 to 10, even more preferably a branched alkyl group having a carbon number of 3 to 6, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0358] In addition, from the viewpoint of decomposition properties and visibility, the alkyl group represented by R.sup.30 is preferably a substituted alkyl group, more preferably a fluoro-substituted alkyl group, even more preferably a perfluoroalkyl group, and particularly preferably a trifluoromethyl group.

[0359] From the viewpoint of decomposition properties and visibility, the aryl group represented by R.sup.30 is preferably a substituted aryl group. Examples of the substituent include an alkyl group (preferably an alkyl group having a carbon number of 1 to 4), an alkoxy group (preferably an alkoxy group having a carbon number of 1 to 4), and the like.

[0360] Specific examples of the group represented by Formula 3-1 will be shown below. However, the present disclosure is not limited thereto. In the following structural formulas, .circle-solid. represents a bonding site with the group represented by L in Formula 1-1.

##STR00055##

[0361] In Formula 4-1, R.sup.41 and R.sup.42 each independently represent an alkyl group or an aryl group, Zb represents a counterion that neutralizes charge, and the portion of the wavy line represents a bonding site with the group represented by L in Formula 1-1.

[0362] The alkyl group and aryl group represented by R.sup.41 or R.sup.42 are the same as the alkyl group and aryl group represented by R.sup.20 in Formula 2-1, and preferred aspects thereof are also the same.

[0363] From the viewpoint of decomposition properties and visibility, R.sup.41 is preferably an alkyl group.

[0364] From the viewpoint of decomposition properties and visibility, R.sup.42 is preferably an alkyl group.

[0365] From the viewpoint of decomposition properties and visibility, the alkyl group represented by R.sup.41 is preferably an alkyl group having a carbon number of 1 to 8, more preferably an alkyl group having a carbon number of 1 to 4, and particularly preferably a methyl group.

[0366] From the viewpoint of decomposition properties and visibility, the alkyl group represented by R.sup.42 is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group.

[0367] Furthermore, from the viewpoint of decomposition properties and visibility, the alkyl group represented by R.sup.42 is preferably an alkyl group having a carbon number of 1 to 8, more preferably a branched alkyl group having a carbon number of 3 to 10, even more preferably a branched alkyl group having a carbon number of 3 to 6, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0368] Zb in Formula 4-1 may be a counterion that neutralizes charge, and may be included in Za in Formula 1-1 in the entirety of the compound.

[0369] Zb is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a tetrafluoroborate ion or a hexafluorophosphate ion.

[0370] Specific examples of the group represented by Formula 4-1 will be shown below. However, the present disclosure is not limited thereto. In the following structural formulas, .circle-solid. represents a bonding site with the group represented by L in Formula 1-1.

##STR00056##

[0371] L in Formula 1-1 is preferably an oxygen atom or NR.sup.10, and particularly preferably an oxygen atom.

[0372] In addition, R.sup.10 in NR.sup.10 is preferably an alkyl group. The alkyl group represented by R.sup.10 is preferably an alkyl group having a carbon number of 1 to 10. The alkyl group represented by R.sup.10 may be linear or branched, or may have a ring structure.

[0373] Among the alkyl groups, a methyl group or a cyclohexyl group is preferable.

[0374] In a case where R.sup.10 in NR.sup.10 represents an aryl group, the aryl group is preferably an aryl group having a carbon number of 6 to 30, more preferably an aryl group having a carbon number of 6 to 20, and even more preferably an aryl group having a carbon number of 6 to 12. These aryl groups may have a substituent.

[0375] In Formula 1-1, R.sup.11 to R.sup.18 preferably each independently represent a hydrogen atom, R.sup.a, OR.sup.b, SR.sup.c, or NR.sup.dR.sup.e.

[0376] The hydrocarbon group represented by R.sup.a to R.sup.e is preferably a hydrocarbon group having a carbon number of 1 to 30, more preferably a hydrocarbon group having a carbon number of 1 to 15, and even more preferably a hydrocarbon group having a carbon number of 1 to 10.

[0377] The hydrocarbon group may be linear or branched or may have a ring structure.

[0378] As the hydrocarbon group, an alkyl group is particularly preferable.

[0379] The aforementioned alkyl group is preferably an alkyl group having a carbon number of 1 to 30, more preferably an alkyl group having a carbon number of 1 to 15, and even more preferably an alkyl group having a carbon number of 1 to 10.

[0380] The alkyl group described above may be linear or branched, or may have a ring structure.

[0381] Specific examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, an s-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group.

[0382] Among these alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is preferable.

[0383] The alkyl group described above may have a substituent.

[0384] Examples of the substituent include an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, groups obtained by combining these, and the like.

[0385] R.sup.11 to R.sup.14 in Formula 1-1 preferably each independently represent a hydrogen atom or R.sup.a (that is, a hydrocarbon group), more preferably each independently represent a hydrogen atom or an alkyl group, and even more preferably each independently represent a hydrogen atom except in the cases described below.

[0386] Particularly, each of R.sup.11 and R.sup.13 bonded to the carbon atom that is bonded to the carbon atom to which L is bonded is preferably an alkyl group. It is more preferable that R.sup.11 and R.sup.13 be linked to each other to form a ring. The ring to be formed in this way may be a monocyclic or polycyclic ring. Specifically, examples of the ring to be formed include a monocyclic ring such as a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring, or a cyclohexadiene ring, and a polycyclic ring such as an indene ring or an indole ring.

[0387] Furthermore, it is preferable that R.sup.12 bonded to the carbon atom to which A.sub.1.sup.+ is bonded be linked to R.sup.15 or R.sup.16 (preferably R.sup.16) to form a ring, and R.sup.14 bonded to the carbon atom to which A.sub.2 is bonded be linked to R.sup.17 or R.sup.18 (preferably R.sup.18) to form a ring.

[0388] In Formula 1-1, n.sub.13 is preferably 1, and R.sup.16 is preferably R.sup.a (that is, a hydrocarbon group).

[0389] Furthermore, it is preferable that R.sup.16 be linked to R.sup.12 bonded to the carbon atom, to which A.sub.1.sup.+ is bonded, to form a ring. As the ring to be formed, an indolium ring, a pyrylium ring, a thiopyrylium ring, a benzoxazoline ring, or a benzimidazoline ring is preferable, and an indolium ring is more preferable from the viewpoint of improving visibility of exposed portions. These rings may further have a substituent.

[0390] In Formula 1-1, n.sub.14 is preferably 1, and R.sup.18 is preferably R.sup.a (that is, a hydrocarbon group).

[0391] In addition, it is preferable that R.sup.18 be linked to R.sup.14 bonded to the carbon atom, to which A.sub.2 is bonded, to form a ring. As the ring to be formed, an indole ring, a pyran ring, a thiopyran ring, a benzoxazole ring, or a benzimidazole ring is preferable, and an indole ring is more preferable from the viewpoint of improving visibility of exposed portions. These rings may further have a substituent.

[0392] It is preferable that R.sup.16 and R.sup.18 in Formula 1-1 be the same group. In a case where R.sup.16 and R.sup.18 each form a ring, it is preferable that the formed rings have the same structure except for A.sub.1.sup.+ and A.sub.2.

[0393] It is preferable that R.sup.15 and R.sup.17 in Formula 1-1 be the same group. In addition, R.sup.15 and R.sup.17 are preferably R.sup.a (that is, a hydrocarbon group), more preferably an alkyl group, and even more preferably a substituted alkyl group.

[0394] From the viewpoint of improving water solubility, R.sup.15 and R.sup.17 in the compound represented by Formula 1-1 are preferably a substituted alkyl group.

[0395] Examples of the substituted alkyl group represented by R.sup.15 or R.sup.17 include a group represented by any of Formula (a1) to Formula (a4).

##STR00057##

[0396] In Formula (a1) to Formula (a4), R.sup.W0 represents an alkylene group having a carbon number of 2 to 6, W represents a single bond or an oxygen atom, and n.sub.W1 represents an integer of 1 to 45, R.sup.W1 represents an alkyl group having a carbon number of 1 to 12 or C(O)R.sup.W5, R.sup.W5 represents an alkyl group having a carbon number of 1 to 12, R.sup.W2 to R.sup.W4 each independently represent a single bond or an alkylene group having a carbon number of 1 to 12, and M represents a hydrogen atom, a sodium atom, a potassium atom, or an onium group.

[0397] Specific examples of the alkylene group represented by R.sup.W0 in Formula (a1) include an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group, an n-hexyl group, an isohexyl group, and the like. Among these, an ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferable, and an n-propylene group is particularly preferable.

[0398] n.sub.W1 is preferably 1 to 10, more preferably 1 to 5, and particularly preferably 1 to 3.

[0399] Specific examples of the alkyl group represented by R.sup.W1 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, an n-octyl group, an n-dodecyl group, and the like. Among these, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, or a tert-butyl group is preferable, a methyl group or an ethyl group is more preferable, and a methyl group is particularly preferable.

[0400] The alkyl group represented by R.sup.W5 is the same as the alkyl group represented by R.sup.W1. Preferred aspects of the alkyl group represented by R.sup.W5 are the same as preferred aspects of the alkyl group represented by R.sup.W1.

[0401] Specific examples of the group represented by Formula (a1) will be shown below. However, the present disclosure is not limited thereto. In the following structural formulas, Me represents a methyl group, Et represents an ethyl group, and * represents a bonding site.

##STR00058## ##STR00059##

[0402] Specific examples of the alkylene group represented by R.sup.W2 to R.sup.W4 in Formula (a2) to Formula (a4) include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group, an n-hexyl group, an isohexyl group, an n-octylene group, an n-dodecylene group, and the like. Among these, an ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferable, and an ethylene group or an n-propylene group is particularly preferable.

[0403] In Formula (a3), two Ms may be the same as or different from each other.

[0404] Examples of the onium group represented by M in Formula (a2) to Formula (a4) include an ammonium group, an iodonium group, a phosphonium group, a sulfonium group, and the like.

[0405] All of CO.sub.2M in Formula (a2), PO.sub.3M.sub.2 in Formula (a2), and SO.sub.3M in Formula (a4) may have an anion structure from which M is dissociated. The countercation of the anion structure may be A.sub.1.sup.+ or a cation that can be contained in R.sup.1-L in Formula 1-1.

[0406] Among the groups represented by Formula (a1) to Formula (a4), the group represented by Formula (a1), Formula (a2), or Formula (a4) is preferable.

[0407] n.sub.11 and n.sub.12 in Formula 1-1 are preferably the same as each other, and preferably both represent an integer of 1 to 5, more preferably both represent an integer of 1 to 3, even more preferably both represent 1 or 2, and particularly preferably both represent 2.

[0408] A.sub.1 and A.sub.2 in Formula 1-1 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom. Among these, a nitrogen atom is preferable.

[0409] A.sub.1 and A.sub.2 in Formula 1-1 are preferably the same atoms.

[0410] Za in Formula 1-1 represents a counterion that neutralizes charge.

[0411] In a case where all of R.sup.11 to R.sup.18 and R.sup.1-L are groups having a neutral charge, Za is a monovalent counteranion. Here, R.sup.11 to R.sup.18 and R.sup.1-L may have an anion structure or a cation structure. For example, in a case where two or more among R.sup.11 to R.sup.18 and R.sup.1-L have an anion structure, Za can also be a countercation.

[0412] In a case where the cyanine colorant represented by Formula 1-1 has such a structure that the overall charge of the compound is neutral except for Za, Za is unnecessary.

[0413] In a case where Za is a counteranion, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, a perchlorate ion, and the like. Among these, a tetrafluoroborate ion is preferable.

[0414] In a case where Za is a countercation, examples thereof include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, a sulfonium ion, and the like. Among these, a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is preferable, and a sodium ion, a potassium ion, or an ammonium ion is more preferable.

[0415] From the viewpoint of improving visibility of exposed portions, the decomposition-type infrared absorber is more preferably a compound represented by Formula 1-2 (that is, a cyanine colorant).

##STR00060##

[0416] In Formula 1-2, R.sup.1 represents a group that is represented by any of Formula 2-1 to Formula 4-1, R.sup.19 to R.sup.22 each independently represent a hydrogen atom, a halogen atom, R.sup.a, OR.sup.b, CN, SR.sup.c, or NR.sup.dR.sup.e, R.sup.23 and R.sup.24 each independently represent a hydrogen atom or R.sup.a, R.sup.a to R.sup.e each independently represent a hydrocarbon group, R.sup.19 and R.sup.20, R.sup.21 and R.sup.22, or R.sup.23 and R.sup.24 may be linked to each other to form a monocyclic or polycyclic ring, L represents an oxygen atom, a sulfur atom, or NR.sup.10, R.sup.10 represents a hydrogen atom, an alkyl group, or an aryl group, R.sup.d1 to R.sup.d4, W.sup.1, and W.sup.2 each independently represent an alkyl group which may have a substituent, and Za represents a counterion that neutralizes charge.

[0417] R.sup.1 in Formula 1-2 has the same definition as R.sup.1 in Formula 1-1, and preferred aspects thereof are also the same.

[0418] In Formula 1-2, R.sup.19 to R.sup.22 preferably each independently represent a hydrogen atom, a halogen atom, R.sup.a, OR.sup.b, or CN.

[0419] More specifically, R.sup.19 and R.sup.21 are preferably a hydrogen atom or R.sup.a.

[0420] In addition, R.sup.20 and R.sup.22 are preferably a hydrogen atom, R.sup.a, OR.sup.b, or CN.

[0421] R.sup.a represented by R.sup.19 to R.sup.22 is preferably an alkyl group or an alkenyl group.

[0422] In a case where all of R.sup.19 to R.sup.22 are R.sup.a, it is preferable that R.sup.19 and R.sup.20 and R.sup.21 and R.sup.22 be linked to each other to form a monocyclic or polycyclic ring.

[0423] Examples of the ring formed of R.sup.19 and R.sup.20 or R.sup.21 and R.sup.22 linked to each other include a benzene ring, a naphthalene ring, and the like.

[0424] R.sup.23 and R.sup.24 in Formula 1-2 are preferably linked to each other to form a monocyclic or polycyclic ring.

[0425] The ring formed of R.sup.23 and R.sup.24 linked to each other may be a monocyclic or polycyclic ring. Specifically, examples of the ring to be formed include a monocyclic ring such as a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring, or a cyclohexadiene ring, and a polycyclic ring such as an indene ring.

[0426] R.sup.d1 to R.sup.d4 in Formula 1-2 are preferably an unsubstituted alkyl group. In addition, all of R.sup.d1 to R.sup.d4 are preferably the same group.

[0427] Examples of the unsubstituted alkyl group include unsubstituted alkyl groups having a carbon number of 1 to 4. Among these, a methyl group is preferable.

[0428] From the viewpoint of improving water solubility of the compound represented by Formula 1-2, W.sup.1 and W.sup.2 in Formula 1-2 preferably each independently represent a substituted alkyl group.

[0429] Examples of the substituted alkyl group represented by W.sup.1 and W.sup.2 include a group represented by any of Formula (a1) to Formula (a4) in Formula 1-1, and preferred aspects thereof are also the same.

[0430] From the viewpoint of on-press developability, W.sup.1 and W.sup.2 preferably each independently represent an alkyl group having a substituent. The alkyl group preferably has at least OCH.sub.2CH.sub.2, a sulfo group, a salt of a sulfo group, a carboxy group, or a salt of a carboxy group, as the substituent.

[0431] Za represents a counterion that neutralizes charge in the molecule.

[0432] In a case where all of R.sup.19 to R.sup.22, R.sup.23 and R.sup.24, R.sup.d1 to R.sup.d4, W.sup.1, W.sup.2, and R.sup.1-L are groups having a neutral charge, Za is a monovalent counteranion. Here, R.sup.19 to R.sup.22, R.sup.23 and R.sup.24, R.sup.d1 to R.sup.d4, W.sup.1, W.sup.2, and R.sup.1-L may have an anion structure or a cation structure. For example, in a case where two or more among R.sup.19 to R.sup.22, R.sup.23 and R.sup.24, R.sup.d1 to R.sup.d4, W.sup.1, W.sup.2, and R.sup.1-L have an anion structure, Za can be a countercation.

[0433] In a case where the compound represented by Formula 1-2 has such a structure that the overall charge of the compound is neutral except for Za, Za is unnecessary.

[0434] Examples of the case where Za is a counteranion are the same as such examples of Za in Formula 1-1, and preferred aspects thereof are also the same. Furthermore, examples of the case where Za is a countercation are the same as such examples of Za in Formula 1-1, and preferred aspects thereof are also the same.

[0435] From the viewpoint of decomposition properties and visibility, the cyanine dye as a decomposition-type infrared absorber is even more preferably a compound represented by any of Formula 1-3 to Formula 1-7.

[0436] Particularly, from the viewpoint of decomposition properties and visibility, the cyanine dye is preferably a compound represented by any of Formula 1-3, Formula 1-5, and Formula 1-6.

##STR00061##

[0437] In Formula 1-3 to Formula 1-7, R.sup.1 represents a group that is represented by any of Formula 2-1 to Formula 4-1, R.sup.19 to R.sup.22 each independently represent a hydrogen atom, a halogen atom, R.sup.a, OR.sup.b, CN, SR.sup.c, or NR.sup.dR.sup.e, R.sup.25 and R.sup.26 each independently represent a hydrogen atom, a halogen atom, or R.sup.a, R.sup.a to R.sup.e each independently represent a hydrocarbon group, R.sup.19 and R.sup.20, R.sup.21 and R.sup.22, or R.sup.25 and R.sup.26 may be linked to each other to form a monocyclic or polycyclic ring, L represents an oxygen atom, a sulfur atom, or NR.sup.10 R.sup.10 represents a hydrogen atom, an alkyl group, or an aryl group, R.sup.d1 to R.sup.d4, W.sup.1, and W.sup.2 each independently represent an alkyl group which may have a substituent, and Za represents a counterion that neutralizes charge.

[0438] R.sup.1, R.sup.19 to R.sup.22, R.sup.d1 to R.sup.d4, W.sup.1, W.sup.2, and L in Formula 1-3 to Formula 1-7 have the same definitions as R.sup.1, R.sup.19 to R.sup.22, R.sup.d1 to R.sup.d4, W.sup.1, W.sup.2, and L in Formula 1-2, and preferred aspects thereof are also the same.

[0439] R.sup.25 and R.sup.26 in Formula 1-7 preferably each independently represent a hydrogen atom or an alkyl group, more preferably each independently represent an alkyl group, and particularly preferably each independently represent a methyl group.

[0440] Specific examples of the cyanine dye as a decomposition-type infrared absorber will be shown below. However, the present disclosure is not limited thereto.

##STR00062## ##STR00063##

[0441] In addition, from the viewpoint of color developability, the infrared absorber preferably includes a compound represented by Formula (X) as a decomposition-type infrared absorber.

##STR00064##

[0442] In Formula (X), Ar.sub.11 and Ar.sub.2 each independently represent an atomic group necessary for forming a substituted or unsubstituted aromatic ring or for forming a substituted or unsubstituted heteroaromatic ring, R.sub.11 and R.sub.12 each independently represent a substituted or unsubstituted alkyl group, Rn represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group, R.sub.14 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group, Y's each independently represent an oxygen atom, a sulfur atom, or a dialkylmethylene group represented by >C(R.sub.15R.sub.16), R.sub.15 and R.sub.16 each independently represent a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, A.sub.1 and A.sub.2 each independently represent a substituted or unsubstituted alkyl group or represent an atomic group including 2 or 3 carbon atoms, which is necessary for forming a substituted or unsubstituted 5- or 6-membered non-aromatic carbon ring by linking to each other, and Za represents a counterion that neutralizes charge.

[0443] Ar.sub.11 and Ar.sub.12 each independently represent an atomic group necessary for forming a substituted or unsubstituted aromatic ring or a substituted or unsubstituted heteroaromatic ring, and examples of a substituent of the aromatic ring or the heteroaromatic ring include an alkyl group, an alkoxy group, a halogen atom, a cyano group, a COOR group, a SO.sub.3R group, or a SO.sub.2R group (R represents a substituted or unsubstituted alkyl group), and an alkyl group or a halogen atom is preferable.

[0444] In addition, Ar.sub.11 and Ar.sub.12 are preferably an atomic group necessary for forming a substituted or unsubstituted aromatic ring, and more preferably an atomic group necessary for forming a substituted or unsubstituted benzene ring or naphthalene ring.

[0445] Y's each independently preferably represent a dialkylmethylene group represented by >C(R.sub.15R.sub.16), and more preferably a dialkylmethylene group represented by >C(R.sub.15R.sub.16) in which R.sub.15 and R.sub.16 are the same. In this case, it is preferable that R.sub.15 and R.sub.16 each independently represent a substituted or unsubstituted alkyl group having 1 or 2 carbon atoms.

[0446] The above-described Y, in particular, is represented by >C(R.sub.15R.sub.16), and is preferably a dialkylmethylene group in which R.sub.15 and R.sub.16 are a methyl group.

[0447] R.sub.11 and R.sub.12 described above each independently preferably represent a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms. In addition, R.sub.11 and R.sub.12 may include an ether bond or an ester bond in the middle of a carbon chain of a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms.

[0448] R.sub.13 is preferably a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, and more preferably a haloalkyl group in which one or more of hydrogen atoms of an alkyl group having 1 to 12 carbon atoms are substituted with a halogen atom. In this case, preferred examples of the halogen atom include a chlorine atom and a bromine atom.

[0449] Among these, R.sub.11 and R.sub.12 each independently preferably represent a perfluoroalkyl group.

[0450] R.sub.14 is preferably a hydrogen atom or an unsubstituted alkyl group having 1 or 8 carbon atoms.

[0451] It is preferable that A.sub.1 and A.sub.2 each independently represent a substituted or unsubstituted alkyl group, or an atomic group bonded to each other and includes 2 or 3 carbon atoms, which is necessary for forming a cyclopentene ring or a cyclohexene ring.

[0452] In a case where Za is a counteranion, an anion containing a halogen atom or an anion containing a boron atom is preferable. Specific examples of Za include CLO.sub.4.sup., PF.sub.6.sup., BF.sub.4.sup., SbF.sub.6.sup., CH.sub.3SO.sub.3.sup., CF.sub.3SO.sub.3.sup., C.sub.6H.sub.5SO.sub.3.sup., CH.sub.3C.sub.6H.sub.5SO.sub.3.sup., HOC.sub.6H.sub.5SO.sub.3.sup., ClC.sub.6H.sub.5SO.sub.3.sup., CH.sub.3C.sub.6H.sub.5SO.sub.3.sup., and a tetraarylborate anion (for example, a tetraphenylborate anion).

[0453] In a case where Za is a countercation, examples thereof include an alkali metal ion, an alkaline earth metal ion, a tertiary ammonium ion, a quaternary ammonium ion, and an onium ion (an iodonium ion, a sulfonium ion, a phosphonium ion, and the like).

[0454] Specific examples of the compound represented by Formula (X) will be shown below. However, the present disclosure is not limited thereto. Ph represents a phenyl group.

##STR00065##

[0455] In addition, it is preferable that the decomposition-type infrared absorber contains a compound represented by Formula (P1).

##STR00066##

[0456] In Formula (P1), R.sup.P1 represents a group represented by Formula (P2) or Formula (P3), R.sup.P2 and R.sup.P3 each independently represent a hydrogen atom or an alkyl group, R.sup.P2 and R.sup.P3 may be linked to each other to form a ring, Ar.sup.P1 and Ar.sup.P2 each independently represent a benzene ring or a naphthalene ring, Y.sup.P1 and Y.sup.P2 each independently represent an oxygen atom, a sulfur atom, NR.sup.P0, or a dialkylmethylene group, R.sup.P4 and R.sup.P5 each independently represent an alkyl group, R.sup.P6 to R.sup.P9 each independently represent a hydrogen atom or an alkyl group, R.sup.P0 represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counterion that neutralizes charge.

##STR00067##

[0457] In Formula (P2) and Formula (P3), R.sup.P10 represents a monovalent organic group having an aryl group, R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20 each independently represent a hydrogen atom, an alkyl group, an aryl group, a hydroxy group, an alkoxy group, or a halogen atom, R.sup.P15 and R.sup.P16 each independently represent a hydrogen atom, an alkyl group, or an aryl group, at least two of R.sup.P11 to R.sup.P20 may be bonded to each other to form a ring structure, and * represents a single bond that is bonded to an oxygen atom in Formula (P1).

[0458] The compound represented by Formula (P1) has a characteristic of decomposing by heat or infrared energy to generate a color forming substance having high visibility. In the present specification, the color forming means that the coloring is stronger after heating or exposure to infrared than before heating or exposure to infrared, or the absorption is shifted to a shorter wavelength and absorption in the visible light region is exhibited. That is, the compound represented by Formula (P1) is a compound that is decomposed by heat or exposure to infrared, and has an increased absorption in the visible light region or has an absorption in the visible light region due to a shift of the absorption to a short wavelength side, as compared with the absorption before heating or exposure to infrared. The compound represented by Formula (P1) is preferably a compound that is decomposed by heat or exposure to infrared to generate a compound having a maximum absorption wavelength at 500 nm to 600 nm.

[0459] From the viewpoint of visibility, printing durability, synthetic suitability, and raw material supply suitability, R.sup.P1 is preferably a group represented by Formula (P2).

[0460] From the viewpoint of visibility, printing durability, on-press developability, and on-press developability after aging, the aryl group in R.sup.P10 is preferably an aryl group having 6 to 30 carbon atoms (also referred to as number of carbon atoms), more preferably an aryl group having 6 to 20 carbon atoms, and still more preferably an aryl group having 6 to 12 carbon atoms. In addition, from the viewpoint of visibility, printing durability, on-press developability, and on-press developability after aging, the aryl group as R.sup.P10 is preferably an aryl group having one or more substituents on an aromatic ring, more preferably a phenyl group having one or more substituents on an aromatic ring, still more preferably a phenyl group having one or more alkyl groups on an aromatic ring, and particularly preferably an alkylphenyl group. From the viewpoint of visibility, printing durability, on-press developability, and on-press developability after aging, R.sup.P10 is preferably a group having one or more substituents on an aromatic ring of an arylalkyl group, more preferably a group having one or more substituents on an aromatic ring of a benzyl group, still more preferably a benzyl group having one or more substituents (substituted benzyl group), and particularly preferably a benzyl group having an alkyl group on a benzene ring.

[0461] In addition, from the viewpoint of visibility, printing durability, on-press developability, and on-press developability after aging, R.sup.P10 is preferably a group represented by Formula (P4).

##STR00068##

[0462] In Formula (P4), X.sup.P2 represents a single bond or an alkylene group, and Ar.sup.P3 represents an aryl group.

[0463] From the viewpoint of visibility, printing durability, and synthetic suitability, X.sup.P2 is preferably an alkylene group, more preferably an alkylene group having 1 to 6 carbon atoms, still more preferably an alkylene group having 1 to 3 carbon atoms, particularly preferably an alkylene group having 1 or 2 carbon atoms, and most preferably a methylene group.

[0464] From the viewpoint of visibility, printing durability, and synthetic suitability, Ar.sup.P3 is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and still more preferably an aryl group having 6 to 12 carbon atoms.

[0465] The aryl group may have a substituent, and preferably has one or more substituents. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and groups obtained by combining these, and the like.

[0466] Specific examples thereof include a phenyl group, a naphthyl group, a p-tolyl group, a p-ethylphenyl group, a p-t-butylphenyl group, a p-chlorophenyl group, a p-fluorophenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, a p-methylthiophenyl group, a p-phenylthiophenyl group, a p-phenylphenyl group, an o-tolyl group, an o-ethylphenyl group, an o-tBu phenyl group, an o-chlorophenyl group, an o-fluorophenyl group, an o-methoxyphenyl group, an o-dimethylaminophenyl group, an o-methylthiophenyl group, and an o-phenylthiophenyl group.

[0467] In addition, from the viewpoint of visibility, printing durability, on-press developability, and on-press developability after aging, Ar.sup.P3 is preferably an aryl group having one or more substituents on an aromatic ring, more preferably a phenyl group (substituted phenyl group) having one or more substituents on an aromatic ring, still more preferably an alkylphenyl group, particularly preferably a phenyl group having a branched alkyl group, and most preferably a t-butylphenyl group.

[0468] In addition, from the viewpoint of visibility, printing durability, on-press developability, and on-press developability after aging, the alkylphenyl group is preferably a p-alkylphenyl group.

[0469] R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20 represent a hydrogen atom, an alkyl group, an aryl group, a hydroxy group, an alkoxy group, or a halogen atom, and may be the same group or different groups. In addition, a plurality of R.sup.P11's to R.sup.P14's and R.sup.P17's to R.sup.P20's may be linked to each other to form a ring.

[0470] The alkyl group in R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20 may be linear, branched, or have a ring structure.

[0471] Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, an s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group.

[0472] Among these alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is preferable.

[0473] The alkyl group in R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20 may have a substituent. Examples of the substituent include an aryl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and a group obtained by combining these groups.

[0474] The aryl group in R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20 is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and still more preferably an aryl group having 6 to 12 carbon atoms.

[0475] The above-described aryl group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and groups obtained by combining these, and the like.

[0476] Specific examples thereof include a phenyl group, a naphthyl group, a p-tolyl group, a p-chlorophenyl group, a p-fluorophenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, a p-methylthiophenyl group, and a p-phenylthiophenyl group.

[0477] Among these aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, or a naphthyl group is preferable.

[0478] From the viewpoint of visibility and printing durability, R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20 are each independently preferably a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom, and particularly preferably a hydrogen atom.

[0479] R.sup.P15 and R.sup.P16 represent a hydrogen atom, an alkyl group, or an aryl group, and may be the same group or different groups.

[0480] From the viewpoint of visibility, printing durability, and synthetic suitability, R.sup.P15 is preferably a hydrogen atom.

[0481] From the viewpoint of visibility and printing durability, R.sup.P16 is preferably an alkyl group or an aryl group, more preferably an alkyl group, still more preferably a branched alkyl group, and particularly preferably a t-butyl group.

[0482] From the viewpoint of visibility and printing durability, preferred examples of the branched alkyl group in R.sup.P16 include an isopropyl group, a t-butyl group, an isobutyl group, a cyclopentyl group, and a cyclohexyl group, and from the viewpoint of visibility and printing durability, preferred examples of the aryl group in R.sup.P16 include a phenyl group.

[0483] The alkyl group represented by R.sup.P15 and R.sup.P16 is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and still more preferably an alkyl group having 1 to 6 carbon atoms.

[0484] The alkyl group represented by R.sup.P15 and R.sup.P16 may be linear or branched, or may have a ring structure.

[0485] Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, an s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group.

[0486] Among the alkyl groups, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group, an isobutyl group, a cyclopentyl group, or a cyclohexyl group is preferable.

[0487] The alkyl group in R.sup.P15 and R.sup.P16 may have a substituent. Examples of the substituent include an aryl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and a group obtained by combining these groups.

[0488] Preferred aspects of the aryl group in R.sup.P15 and R.sup.P16 are the same as the preferred aspects of the aryl group in R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20.

[0489] Preferred aspects of the alkyl group in R.sup.P2, R.sup.P3, R.sup.P6, R.sup.P7, R.sup.P8, R.sup.P9, and R.sup.P0 are the same as the preferred aspects of the alkyl group in R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20.

[0490] Preferred aspects of the aryl group in R.sup.P0 are the same as the preferred aspects of the aryl group in R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20.

[0491] It is preferable that R.sup.P2 and R.sup.P3 are linked to each other to form a ring.

[0492] In a case where R.sup.P2 and R.sup.P3 are linked to each other to form a ring, a 5-membered ring or a 6-membered ring is preferable, and a 5-membered ring is particularly preferable.

[0493] Y.sup.P1 and Y.sup.P2 each independently represent an oxygen atom, a sulfur atom, NR.sup.P0, or a dialkylmethylene group, and NR.sup.P0 or a dialkylmethylene group is preferable and a dialkylmethylene group is more preferable.

[0494] R.sup.P0 represents a hydrogen atom, an alkyl group, or an aryl group and preferably an alkyl group.

[0495] The alkyl group represented by R.sup.P4 or R.sup.P5 is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and still more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group represented by R.sup.P4 and R.sup.P5 may be linear or branched, or may have a ring structure.

[0496] Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, an s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group.

[0497] The alkyl group in R.sup.P4 or R.sup.P5 may have a substituent. Examples of the substituent include an aryl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and a group obtained by combining these groups.

[0498] Among the alkyl groups in R.sup.P4 or R.sup.P5, a methyl group, an ethyl group, a propyl group, or a butyl group is preferable.

[0499] As the substituent on the alkyl group, a methoxy group, a phenoxy group, a phenyl group, or a naphthyl group is preferable.

[0500] From the viewpoint of solubility and developability, the alkyl group in R.sup.P4 or R.sup.P5 is particularly preferably an ethyl group or a propyl group having a substituent (for example, a substituent of Dye-12 described later).

[0501] In addition, it is preferable that R.sup.P4 and R.sup.P5 are the same group.

[0502] R.sup.P6 to R.sup.P9 each independently represent a hydrogen atom or an alkyl group, and a hydrogen atom is preferable.

[0503] Ar.sup.P1 and Ar.sup.P2 each independently represent a group that forms a benzene ring or a naphthalene ring. The benzene ring and the naphthalene ring may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, a phosphonic acid group, groups obtained by combining these, and the like. As the substituent, an alkyl group or an alkoxy group is preferable.

[0504] Further, from the viewpoints of increasing the maximum absorption wavelength of the compound represented by Formula (P1) and improving the color developability and the printing durability of the lithographic printing plate, Ar.sup.P1 and Ar.sup.P2 each independently represent preferably a naphthalene ring or a group that forms a benzene ring containing an alkyl group or an alkoxy group as a substituent, more preferably a naphthalene ring or a group that forms a benzene ring containing an alkoxy group as a substituent, and particularly preferably a group that forms a benzene ring containing a methoxy group as a substituent.

[0505] In Formula (P1), it is preferable that Ar.sup.P1 or Ar.sup.P2 is a group that forms a group represented by the following formula.

##STR00069##

[0506] In the formulae, R.sup.P21's each independently represent an alkyl group having 1 to 12 carbon atoms, an alkoxy group, an aryloxy group, an amino group, an alkoxythio group, or a halogen atom, nP3 represents an integer of 1 to 4, a plurality of R.sup.P21's may be bonded to each other to form a ring, and * represents a bonding site.

[0507] Za represents a counterion for neutralizing the electric charge. The counterion may be one counterion or two or more counterions depending on the neutralizing valence, and may have two or more counterions of the same or different kinds. Here, in a case where the compound represented by Formula (P1) has a corresponding ionic substituent in the structure and charge neutralization is not required, Za is unnecessary. In a case of indicating an anionic species, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, and a perchlorate ion, and a tetrafluoroborate ion, a hexafluorophosphate ion, or a p-toluenesulfonate ion is preferable. In a case of indicating a cationic species, examples thereof include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, and a sulfonium ion. Among these, a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is preferable, and a sodium ion, a potassium ion, or an ammonium ion is more preferable.

[0508] R.sup.P2 to R.sup.P9, R.sup.P0, Ar.sup.P1, Ar.sup.P2, Y.sup.P1 and Y.sup.P2 may have an anionic structure or a cationic structure, and Za is a monovalent counteranion as long as all of R.sup.P2 to R.sup.P9, R.sup.P0, Ar.sup.P1, Ar.sup.P2, Y.sup.P1 and Y.sup.P2 are electrically neutral groups, but for example, in a case where R.sup.P2 to R.sup.P9, R.sup.P0, Ar.sup.P1, Ar.sup.P2, Y.sup.P1, and Y.sup.P2 have two or more anionic structures, Za may also be a countercation.

[0509] From the viewpoint of visibility, printing durability, on-press developability, and on-press developability after aging, the compound represented by Formula (P1) is preferably a compound represented by Formula (P5) or Formula (P6), more preferably a compound represented by Formula (P7) or Formula (P8), and particularly preferably a compound represented by Formula (P9).

##STR00070##

[0510] In Formula (P5) and Formula (P6), R.sup.P4 and R.sup.P5 each independently represent an alkyl group, R.sup.P10 represents a monovalent organic group having an aryl group, R.sup.P11 to R.sup.P14 and R.sup.P17 to R.sup.P20 each independently represent a hydrogen atom, an alkyl group, an aryl group, a hydroxy group, an alkoxy group, or a halogen atom, R.sup.P15 and R.sup.P16 each independently represent a hydrogen atom, an alkyl group, or an aryl group, at least two of R.sup.P11 to R.sup.P20 may be bonded to each other to form a ring structure, R.sup.P21's each independently represent an alkyl group having 1 to 12 carbon atoms, an alkoxy group, an aryloxy group, an amino group, an alkoxythio group, or a halogen atom, and Za represents a counterion that neutralizes charge.

##STR00071##

[0511] In Formula (P7) and Formula (P8), X.sup.P2 represents a single bond or an alkylene group, Ar.sup.P3 represents an aryl group, R.sup.4 and R.sup.5 each independently represent an alkyl group, R.sup.P15 and R.sup.P16 each independently represent a hydrogen atom, an alkyl group, or an aryl group, R.sup.P15 and R.sup.P16 may be bonded to each other to form a ring structure, R.sup.P21's each independently represent an alkyl group having 1 to 12 carbon atoms, an alkoxy group, an aryloxy group, an amino group, an alkoxythio group, or a halogen atom, and Za represents a counterion that neutralizes charge.

##STR00072##

[0512] In Formula (P9), Ar.sup.P4 represents an aryl group, R.sup.P4 and R.sup.P5 each independently represent an alkyl group, R.sup.P21's each independently represent an alkyl group having 1 to 12 carbon atoms, an alkoxy group, an aryloxy group, an amino group, an alkoxythio group, or a halogen atom, R.sup.P22 represents a hydrogen atom, an alkyl group, or an aryl group, R.sup.P23's each independently represent a hydrogen atom or an alkyl group, and Za represents a counterion that neutralizes charge.

[0513] Preferred aspects of R.sup.P4, R.sup.P5, R.sup.P11 to R.sup.P20, and Za in Formulae (P5) to (P9) are the same as the preferred aspects of R.sup.P4, R.sup.P5, R.sup.P11 to R.sup.P20, and Za in Formulae (P1) to (P3), respectively. Preferred aspects of R.sup.P21 in Formulae (P5) to (P9) are the same as the above-described preferred aspects of R.sup.P21, respectively.

[0514] Preferred aspects of X.sup.P2 and Ar.sup.P3 in Formula (P7) and Formula (P8) are the same as the preferred aspects of X.sup.P2 and Ar.sup.P3 in Formula (P4), respectively.

[0515] Ar.sup.P4 in Formula (P9) is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and still more preferably an aryl group having 6 to 12 carbon atoms.

[0516] The above-described aryl group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, and a group obtained by combining these groups.

[0517] Among these, an alkyl group is preferable as the substituent.

[0518] Specific examples of Ar.sup.P4 in Formula (P9) include a phenyl group, a naphthyl group, a p-tolyl group, a p-ethylphenyl group, a p-t-butylphenyl group, a p-fluorophenyl group, and a p-methoxyphenyl group.

[0519] Among these, as Ar.sup.P4, from the viewpoint of visibility, printing durability, on-press developability, and on-press developability after aging, a phenyl group, a p-methoxyphenyl group, a p-tBu phenyl group, or a naphthyl group is preferable, a phenyl group, a p-methoxyphenyl group, or a p-t-butylphenyl group is more preferable, and a p-t-butylphenyl group is particularly preferable.

[0520] R.sup.P22 in Formula (P9) is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, and may be cleaved by an oxygen atom or the like.

[0521] From the viewpoints of visibility, printing durability, and synthetic suitability, the number of carbon atoms in the alkyl group is more preferably 1 to 6, still more preferably 3 to 5, and particularly preferably 3 or 4.

[0522] From the viewpoint of manufacturing suitability, R.sup.P23 in Formula (P9) is preferably a hydrogen atom.

[0523] Hereinafter, preferred specific examples of the compound represented by Formula (P1) are shown below, but the present disclosure is not limited thereto. In the following structural formulae, Me represents a methyl group, and Ts.sup.O represents a tosylate anion.

##STR00073## ##STR00074## ##STR00075## ##STR00076## ##STR00077## ##STR00078## ##STR00079## ##STR00080## ##STR00081## ##STR00082## ##STR00083## ##STR00084##

##STR00085## ##STR00086## ##STR00087## ##STR00088##

[0524] As the infrared absorber that decomposes by exposure to infrared, those described in JP2008-544322A or WO2016/027886A can also be suitably used.

[0525] In addition, as the cyanine colorant which is a decomposition-type infrared absorber, the infrared absorbing compounds described in WO2019/219560A can be suitably used.

[0526] The infrared absorber may be used alone or in combination of two or more kinds thereof. In one aspect, it is preferable that the image-recording layer contains two or more kinds of infrared absorbers. By using two or more kinds of infrared absorbers in combination, the suppressing property of development defect over time and the printing durability are further improved. In addition, as the infrared absorber, a pigment and a dye may be used in combination.

[0527] The total content of the infrared absorber in the image-recording layer with respect to the total mass of the image-recording layer is preferably 0.1% by mass to 10.0% by mass and more preferably 0.5% by mass to 5.0% by mass.

[Relationship Between Specific Borate Compound (Electron-Donating Polymerization Initiator), Electron-Accepting Polymerization Initiator, and Infrared Absorber]

[0528] It is preferable that the image-recording layer according to the present disclosure contains the specific borate compound and the electron-accepting polymerization initiator, and further contains an infrared absorber.

[0529] In a case where the image-recording layer contains the specific borate compound, the electron-accepting polymerization initiator, and the infrared absorber, it is preferable that the HOMO of the specific borate compound is 6.0 eV or more and the LUMO of the electron-accepting polymerization initiator is 3.0 eV or less.

[0530] More preferred aspects of the HOMO of the specific borate compound and the LUMO of the electron-accepting polymerization initiator are as described above.

[0531] In the image-recording layer according to the present disclosure, it is presumed that the specific borate compound, at least one of the infrared absorber, and the electron-accepting polymerization initiator are exchanging energy, for example, as described in the following chemical formulae.

[0532] Accordingly, it is considered that in a case where HOMO of the specific borate compound is 6.0 eV or more and LUMO of the electron-accepting polymerization initiator is 3.0 eV or less, radicals may be more efficiently generated, which may facilitate further improvement of chemical resistance and printing durability.

##STR00089##

[0533] From the viewpoint of printing durability and chemical resistance, the value of at least one HOMO of the infrared absorberHOMO of the specific borate compound is preferably 1.0 eV or less, more preferably 0.70 eV or less, and particularly preferably 0.60 eV or less. In addition, from the same viewpoint, the value of at least one HOMO of the infrared absorberHOMO of the specific borate compound is preferably 0.200 eV or more and more preferably 0.100 eV or more.

[0534] The negative value means that the HOMO of the specific borate compound is higher than the HOMO of at least one of the infrared absorbers.

[0535] In addition, from the viewpoint of printing durability and chemical resistance, the value of LUMO of the electron-accepting polymerization initiatorat least one LUMO of the infrared absorber is preferably 1.00 eV or less and more preferably 0.700 eV or less.

[0536] In addition, from the same viewpoint, the value of LUMO of the electron-accepting polymerization initiatorat least one LUMO of the infrared absorber is preferably 0.200 eV or more and more preferably 0.100 eV or more.

[0537] In addition, from the same viewpoint, the value of LUMO of the electron-accepting polymerization initiatorat least one LUMO of the infrared absorber is preferably 1.00 eV to 0.200 eV and more preferably 0.700 eV to 0.100 eV The negative value means that at least one LUMO of the infrared absorber is higher than the LUMO of the electron-accepting polymerization initiator.

[0538] The image-recording layer preferably contains a color developing agent, and more preferably contains an acid color developing agent.

[0539] Color developing agent used in the present disclosure means a compound that forms or removes color by a stimulus such as light or acid and thus changes the color of the image-recording layer. Furthermore, acid color developing agent means a compound that forms or removes color by being heated in a state of accepting an electron accepting compound (for example, a proton of an acid or the like) and thus changes the color of the image-recording layer. The acid color developing agent is particularly preferably a colorless compound which has a partial skeleton such as lactone, lactam, sultone, spiropyran, an ester, or an amide and allows such a partial skeleton to rapidly open the ring or to be cleaved when coming into contact with an electron-accepting compound.

[0540] Examples of such an acid color developing agent include phthalides such as 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide (referred to as crystal violet lactone), 3,3-bis(4-dimethylaminophenyl)phthalide, 3-(4-dimethylaminophenyl)-3-(4-diethylamino-2-methylphenyl)-6-dimethylaminophthalide, 3-(4-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3-(4-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, and 3-(4-dimethylaminophenyl)-3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide,

[0541] 3,3-bis[1,1-bis(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide, 3,3-bis[1-(4-dimethylaminophenyl)-1-(4-methoxyphenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1-(4-pyrrolidinophenyl)-1-(4-methoxyphenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3-[1,1-di(1-ethyl-2-methylindol-3-yl)ethylene-2-yl]-3-(4-diethylaminophenyl)phthalide, 3-[1,1-di(1-ethyl-2-methylindol-3-yl)ethylene-2-yl]-3-(4-N-ethyl-N-phenylaminophenyl)phthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)-phthalide, 3,3-bis(1-n-octyl-2-methylindol-3-yl)-phthalide, and 3-(2-methyl-4-diethylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)-phthalide,

[0542] 4,4-bis-dimethylaminobenzhydrinbenzylether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenyl leucoauramine, rhodamine-B-anilinolactam, rhodamine-(4-nitroanilino)lactam, rhodamine-B-(4-chloroanilino)lactam, 3,7-bis(diethylamino)-10-benzoylphenoxazine, benzoyl leucomethylene blue, and 4-nitrobenzoyl methylene blue,

[0543] fluorans such as 3,6-dimethoxyfluoran, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6,7-dimethylfluoran, 3-N-cyclohexyl-N-n-butylamino-7-methylfluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-di-n-hexylaminofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-(2-fluorophenylamino)fluoran, 3-diethylamino-7-(2-chlorophenylamino)fluoran, 3-diethylamino-7-(3-chlorophenylamino)fluoran, 3-diethylamino-7-(2,3-dichlorophenylamino)fluoran, 3-diethylamino-7-(3-trifluoromethylphenylamino)fluoran, 3-di-n-butylamino-7-(2-fluorophenylamino)fluoran, 3-di-n-butylamino-7-(2chlorophenylamino)fluoran, 3-N-isopentyl-N-ethylamino-7-(2-chlorophenylamino)fluoran,

[0544] 3-N-n-hexyl-N-ethylamino-7-(2-chlorophenylamino)fluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-di-n-butylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methoxy-7-anilinofluoran, 3-di-n-butylamino-6-ethoxy-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-morpholino-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di-n-pentylamino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-methylamino-6-methyl-7-anilinofluoran, 3-N-n-propyl-N-methylamino-6-methyl-7-anilinofluoran, 3-N-n-propyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-n-butyl-N-methylamino-6-methyl-7-anilinofluoran, 3-N-n-butyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-isobutyl-N-methylamino-6-methyl-7-anilinofluoran, 3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-isopentyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-n-hexyl-N-methylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-N-n-propylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-N-n-butylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-N-n-hexylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-N-n-octylamino-6-methyl-7-anilinofluoran,

[0545] 3-N-(2-methoxyethyl)-N-methylamino-6-methyl-7-anilinofluoran, 3-N-(2-methoxyethyl)-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-(2-methoxyethyl)-N-isobutylamino-6-methyl-7-anilinofluoran, 3-N-(2-ethoxyethyl)-N-methylamino-6-methyl-7-anilinofluoran, 3-N-(2-ethoxyethyl)-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-(3-methoxypropyl)-N-methylamino-6-methyl-7-anilinofluoran, 3-N-(3-methoxypropyl)-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-(3-ethoxypropyl)-N-methylamino-6-methyl-7-anilinofluoran, 3-N-(3-ethoxypropyl)-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-(2-tetrahydrofurfuryl)-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-(4-methylphenyl)-N-ethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-ethyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(3-methylphenylamino)fluoran, 3-diethylamino-6-methyl-7-(2,6-dimethylphenylamino)fluoran, 3-di-n-butylamino-6-methyl-7-(2,6-dimethylphenylamino)fluoran, 3-di-n-butylamino-7-(2,6-dimethylphenylamino)fluoran, 2,2-bis[4-(3-N-cyclohexyl-N-methylamino-6-methylfluoran)-7-ylaminophenyl]propane, 3-[4-(4-phenylaminophenyl)aminophenyl]amino-6-methyl-7-chlorofluoran, and 3-[4(dimethylaminophenyl)]amino-5,7-dimethylfluoran,

[0546] phthalides such as 3-(2-methyl-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-n-propoxycarbonylamino-4-di-n-propylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-methylamino-4-di-n-propylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-methyl-4-di-n-hexylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)-4,7-diazaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(1-n-octyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-octyl-2-methylindol-3-yl)-4 or 7-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4 or 7-azaphthalide, 3-(2-hexyloxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4 or 7-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-phenylindol-3-yl)-4 or 7-azaphthalide, 3-(2-butoxy-4-diethylaminophenyl)-3-(1-ethyl-2-phenylindol-3-yl)-4 or 7-azaphthalide, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(3-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran-3,6-bis(dimethylamino)fluorene-9-spiro-3-(6-dimethylamino)phthalide, and 3,6-bis(diethylamino)fluorene-9-spiro-3-(6-dimethylamino)phthalide,

[0547] 2-anilino-6-(N-ethyl-N-isopentyl)amino-3-methylspiro[isobenzofuran-1(3H),9-(9H)xanthen-3-one, 2-anilino-6-(N-ethyl-N-(4-methylphenyl))amino-3-methylspiro[isobenzofuran-1(3H),9-(9H)xanthen]-3-one, 3-N,N-dibenzylamino-6-N,N-diethylaminospiro[isobenzofuran-1(3H),9-(9H)xanthen]-3-one, 2-(N-methyl-N-phenyl)amino-6-(N-ethyl-N-(4-methylphenyl))aminospiro[isobenzofuran-1(3H),9-(9H)xanthen]-3-one, and the like.

[0548] Particularly, from the viewpoint of color developability, the color developing agent used in the present disclosure is preferably at least one kind of compound selected from the group consisting of a spiropyran compound, a spirooxazine compound, a spirolactone compound, and a spirolactam compound.

[0549] From the viewpoint of visibility, the hue of the colorant after color forming is preferably green, blue, or black.

[0550] From the viewpoint of color developability and visibility of exposed portions, the acid color developing agent is preferably a leuco colorant.

[0551] The leuco colorant is not particularly limited as long as it has a leuco structure. The leuco colorant preferably has a spiro structure, and more preferably has a spirolactone ring structure.

[0552] From the viewpoint of color developability and visibility of exposed portions, the leuco colorant is preferably a leuco colorant having a phthalide structure or a fluoran structure.

[0553] Furthermore, from the viewpoint of color developability and visibility of exposed portions, the leuco colorant having a phthalide structure or a fluoran structure is preferably a compound represented by any of Formula (Le-1) to Formula (Le-3), and more preferably a compound represented by Formula (Le-2).

##STR00090##

[0554] In Formula (Le-1) to Formula (Le-3), ERG's each independently represent an electron-donating group, X.sub.1 to X.sub.4 each independently represent a hydrogen atom, a halogen atom, or dialkylanilino group, X.sub.5 to X.sub.10 each independently represent a hydrogen atom, a halogen atom, or a monovalent organic group, Y.sub.1 and Y.sub.2 each independently represent C or N, X.sub.1 does not exist in a case where Y.sub.1 is N, X.sub.4 does not exist in a case where Y.sub.2 is N, Ra.sub.1 represents a hydrogen atom, an alkyl group, or an alkoxy group, and Rb.sub.1 to Rb.sub.4 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

[0555] From the viewpoint of color developability and visibility of exposed portions, the electron-donating group represented by ERG in Formula (Le-1) to Formula (Le-3) is preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkyl monoarylamino group, a monoalkyl monoheteroaryl amino group, a diarylamino group, a diheteroaryl amino group, a monoaryl monoheteroaryl amino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkyl monoarylamino group, a monoalkyl monoheteroaryl amino group, a diarylamino group, a diheteroarylamino group, a monoaryl monoheteroarylamino group, an alkoxy group, or an aryloxy group, even more preferably a monoalkyl monoarylamino group, a diarylamino group, a diheteroarylamino group, or a monoaryl monoheteroarylamino group, and particularly preferably a monoalkyl monoarylamino group.

[0556] From the viewpoints of color developability and visibility of exposed portions, the electron-donating group represented by ERG is preferably a disubstituted amino group having an aryl group that has a substituent on at least one ortho position or a heteroaryl group that has a substituent on at least one ortho position, more preferably a disubstituted amino group having a phenyl group having a substituent on at least one ortho position and an electron-donating group at a para position, even more preferably an amino group having a phenyl group having a substituent on at least one ortho position and an electron-donating group at a para position, and an aryl group or a heteroaryl group, and particularly preferably an amino group having a phenyl group having a substituent on at least one ortho position and an electron-donating group at a para position, and an aryl group having an electron-donating group or a heteroaryl group having an electron-donating group.

[0557] In the present disclosure, in a case where a bonding position of an aryl group or a heteroaryl group with other structures is defined as position 1, the ortho position in the aryl group or heteroaryl group other than a phenyl group is called a bonding position (for example, position 2 or the like) adjacent to the position 1.

[0558] Furthermore, from the viewpoints of color developability and visibility of exposed portions, the electron-donating group that the aryl group or heteroaryl group has is preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkyl monoarylamino group, a monoalkyl monoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoaryl monoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, and particularly preferably an alkoxy group.

[0559] From the viewpoints of color developability and visibility of exposed portions, X.sub.1 to X.sub.4 in Formula (Le-1) to Formula (Le-3) each independently are preferably a hydrogen atom or a chlorine atom, and more preferably each independently represent a hydrogen atom.

[0560] From the viewpoints of color developability and visibility of exposed portions, X.sub.5 to X.sub.10 in Formula (Le-2) or Formula (Le-3) each independently are preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkyl monoarylamino group, a monoalkyl monoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoaryl monoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, or a cyano group, more preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, or an aryloxy group, even more preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group, and particularly preferably a hydrogen atom.

[0561] From the viewpoints of color developability and visibility of exposed portions, it is preferable that at least one of Y.sub.1 or Y.sub.2 in Formula (Le-1) to Formula (Le-3) be C, and it is more preferable that both of Y.sub.1 and Y.sub.2 be C.

[0562] From the viewpoints of color developability and visibility of exposed portions, Ra.sub.1 in Formula (Le-1) to Formula (Le-3) is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group.

[0563] From the viewpoints of color developability and visibility of exposed portions, Rb.sub.1 to Rb.sub.4 in Formula (Le-1) to Formula (Le-3) preferably each independently represent a hydrogen atom or an alkyl group, more preferably each independently represent an alkyl group, and particularly preferably each independently represent a methyl group.

[0564] In addition, from the viewpoints of color developability and visibility of exposed portions, the leuco colorant having a phthalide structure or a fluoran structure is more preferably a compound represented by any of Formula (Le-4) to Formula (Le-6), and even more preferably a compound represented by Formula (Le-5).

##STR00091##

[0565] In Formula (Le-4) to Formula (Le-6), ERG's each independently represent an electron-donating group, X.sub.1 to X.sub.4 each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group, Y.sub.1 and Y.sub.2 each independently represent C or N, X.sub.1 does not exist in a case where Y.sub.1 is N, X.sub.4 does not exist in a case where Y.sub.2 is N, Ra.sub.1 represents a hydrogen atom, an alkyl group, or an alkoxy group, and Rb.sub.1 to Rb.sub.4 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

[0566] ERG, X.sub.1 to X.sub.4, Y.sub.1, Y.sub.2, Ra.sub.1, and Rb.sub.1 to Rb.sub.4 in Formula (Le-4) to Formula (Le-6) have the same definitions as ERG, X.sub.1 to X.sub.4, Y.sub.1, Y.sub.2, Ra.sub.1, and Rb.sub.1 to Rb.sub.4 in Formula (Le-1) to Formula (Le-3) respectively, and preferred aspects thereof are also the same.

[0567] Furthermore, from the viewpoints of color developability and visibility of exposed portions, the leuco colorant having a phthalide structure or a fluoran structure is even more preferably a compound represented by any of Formula (Le-7) to Formula (Le-9), and particularly preferably a compound represented by Formula (Le-8).

##STR00092##

[0568] In Formula (Le-7) to Formula (Le-9), X.sub.1 to X.sub.4 each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group, Y.sub.1 and Y.sub.2 each independently represent C or N, X.sub.1 does not exist in a case where Y.sub.1 is N, X.sub.4 does not exist in a case where Y.sub.2 is N, Ra.sub.1 to Ra.sub.4 each independently represent a hydrogen atom, an alkyl group, or an alkoxy group, Rb.sub.1 to Rb.sub.4 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group, and Rc.sub.1 and Rc.sub.2 each independently represent an aryl group or a heteroaryl group.

[0569] X.sub.1 to X.sub.4, Y.sub.1, and Y.sub.2 in Formula (Le-7) to Formula (Le-9) have the same definition as X.sub.1 to X.sub.4, Y.sub.1, and Y.sub.2 in Formula (Le-1) to Formula (Le-3) respectively, and preferred aspects thereof are also the same.

[0570] From the viewpoints of color developability and visibility of exposed portions, Ra.sub.1 to Ra.sub.4 in Formula (Le-7) or Formula (Le-9) each independently are preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably represent a methoxy group.

[0571] From the viewpoints of color developability and visibility of exposed portions, Rb.sub.1 to Rb.sub.4 in Formula (Le-7) to Formula (Le-9) each independently are preferably a hydrogen atom, an alkyl group, or an aryl group substituted with an alkoxy group, more preferably an alkyl group, and particularly preferably a methyl group.

[0572] From the viewpoints of color developability and visibility of exposed portions, Rc.sub.1 and Rc.sub.2 in Formula (Le-8) each independently are preferably a phenyl group or an alkylphenyl group, and more preferably a phenyl group.

[0573] From the viewpoints of color developability and visibility of exposed portions, Rc.sub.1 and Rc.sub.2 in Formula (Le-8) each independently are preferably an aryl group having a substituent on at least one ortho position or a heteroaryl group having a substituent on at least one ortho position, more preferably an aryl group having a substituent on at least one ortho position, even more preferably a phenyl group having a substituent on at least one ortho position, and particularly preferably a phenyl group having a substituent on at least one ortho position and having an electron-donating group at the para position. Examples of the substituent in Rc.sub.1 and Rc.sub.2 include substituents that will be described later.

[0574] In Formula (Le-8), from the viewpoints of color developability and visibility of exposed portions, it is preferable that X.sub.1 to X.sub.4 are a hydrogen atom, and Y.sub.1 and Y.sub.2 are C.

[0575] Furthermore, from the viewpoints of color developability and visibility of exposed portions, in Formula (Le-8), Rb.sub.1 and Rb.sub.2 each independently are preferably an alkyl group or an aryl group substituted with an alkoxy group.

[0576] Moreover, from the viewpoints of color developability and visibility of exposed portions, in Formula (Le-8), Rb.sub.1 and Rb.sub.2 each independently are preferably an aryl group or a heteroaryl group, more preferably an aryl group, even more preferably an aryl group having an electron-donating group, and particularly preferably a phenyl group having an electron-donating group at the para position.

[0577] From the viewpoints of color developability and visibility of exposed portions, the electron-donating group in Rb.sub.1, Rb.sub.2, Rc.sub.1, and Rc.sub.2 is preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkyl monoarylamino group, a monoalkyl monoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoaryl monoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, and particularly preferably an alkoxy group.

[0578] In addition, from the viewpoints of the color developability and the visibility of the exposed portion, it is also preferable that the acid color developing agent includes one or more compounds selected from the group consisting of a compound represented by Formula (Le-10) and a compound represented by Formula (Z-4).

[0579] That is, it is preferable that the image-recording layer in the lithographic printing plate precursor according to the present disclosure further contains one or more compounds selected from the group consisting of a compound represented by Formula (Le-10) and a compound represented by Formula (Z-4).

##STR00093##

[0580] In Formula (Le-10), Ar.sub.1's each independently represent an aryl group or a heteroaryl group, and Ar.sub.2's each independently represent an aryl group having a substituent on at least one ortho position or a heteroaryl group having a substituent on at least one ortho position.

[0581] Ar.sub.1 in Formula (Le-10) has the same definition as Rb.sub.1 and Rb.sub.2 in Formula (Le-7) to Formula (Le-9), and preferred aspects thereof are also the same.

[0582] Ar.sub.2 in Formula (Le-10) has the same definition as Rc.sub.1 and Rc.sub.2 in Formula (Le-7) to Formula (Le-9), and preferred aspects thereof are also the same.

[0583] The alkyl group in Formula (Le-1) to Formula (Le-9) may be linear or branched or may have a ring structure.

[0584] The carbon number of the alkyl group in Formula (Le-1) to Formula (Le-9) is preferably 1 to 20, more preferably 1 to 8, even more preferably 1 to 4, and particularly preferably 1 or 2.

[0585] The carbon number of the aryl group in Formula (Le-1) to Formula (Le-10) is preferably 6 to 20, more preferably 6 to 10, and particularly preferably 6 to 8.

[0586] Specific examples of the aryl group in Formula (Le-1) to Formula (Le-10) include a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, and the like which may have a substituent.

[0587] Specific examples of the heteroaryl group in Formula (Le-1) to Formula (Le-10) include a furyl group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, a thiophenyl group, and the like which may have a substituent.

[0588] Each of the groups in Formula (Le-1) to Formula (Le-10), such as a monovalent organic group, an alkyl group, an aryl group, a heteroaryl group, a dialkylanilino group, an alkylamino group, and an alkoxy group, may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a heteroaryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkyl monoarylamino group, a monoalkyl monoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoaryl monoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, a cyano group, and the like. In addition, these substituents may be further substituted with these substituents.

##STR00094##

[0589] In Formula (Z-4), Rza.sub.1 represents a hydrogen atom, an alkyl group, or an alkoxy group, Rzb.sub.1 to Rzb.sub.4 each independently represent a hydrogen atom, an alkyl group, or an aryl group, Rzb.sub.1 and Rzb.sub.2, and Rzb.sub.3 and Rzb.sub.4 may be linked to each other to form a ring structure, X represents O or NR, R represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group, and Y.sub.1 and Y.sub.2 each independently represent CH or N.

[0590] Rza.sub.1 in Formula (Z-4) is preferably an alkyl group or an alkoxy group.

[0591] Rzb.sub.1 and Rzb.sub.2 in Formula (Z-4) are each independently preferably an alkyl group.

[0592] Rzb.sub.3 and Rzb.sub.4 in Formula (Z-4) each independently represent a hydrogen atom, an alkyl group, or an aryl group, and it is preferable that one of them represents an aryl group.

[0593] X in Formula (Z-4) is preferably O, and Y.sub.1 and Y.sub.2 are preferably CH.

[0594] The alkyl group in Formula (Z-4) may be linear or branched or may have a ring structure.

[0595] The number of carbon atoms in the alkyl group in Formula (Z-4) is preferably 1 to 20, more preferably 1 to 8, and even more preferably 1 to 5.

[0596] The number of carbon atoms in the aryl group in Formula (Z-4) is preferably 6 to 20, more preferably 6 to 10, and particularly preferably 6 to 8.

[0597] Each of the groups such as the alkyl group and the aryl group in Formula (Z-4) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkyl monoarylamino group, a diarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a cyano group, and the like. In addition, these substituents may be further substituted with these substituents.

[0598] Examples of the leuco colorant having the phthalide structure or the fluoran structure that are suitably used include the following compounds. In addition, Me represents a methyl group.

##STR00095## ##STR00096## ##STR00097## ##STR00098## ##STR00099##

[0599] As the color developing agent, a commercially available product can be used, and examples thereof include ETAC, RED500, RED520, CVL, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, BLUE220, H-3035, BLUE203, ATP, H-1046, and H-2114 (all manufactured by Fukui Yamada Chemical Co., Ltd.), ORANGE-DCF, Vermilion-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF, and TH-107 (all manufactured by HODOGAYA CHEMICAL Co., LTD.), ODB, ODB-2, ODB-4, ODB-250, ODB-BlackXV, Blue-63, Blue-502, GN-169, GN-2, Green-118, Red-40, and Red-8 (all manufactured by Yamamoto Chemicals, Inc.), and Crystal Violet Lactone (manufactured by Tokyo Chemical Industry Co., Ltd.), and the like. Among these commercially available products, ETAC, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63, GN-169, and crystal violet lactone are preferable because these products form a film having excellent visible light absorbance.

[0600] Each of these color developing agents may be used alone. Alternatively, two or more components can be used in combination.

[0601] The content of the color developing agent with respect to the total mass of the image-recording layer is preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass.

[0602] It is also preferable that the image-recording layer contain a polymerizable compound.

[0603] In the present disclosure, a polymerizable compound refers to a compound having a polymerizable group.

[0604] The polymerizable group is not particularly limited, may be a known polymerizable group, and is preferably an ethylenically unsaturated group. In addition, the polymerizable group may be a radically polymerizable group or a cationically polymerizable group, and is preferably a radically polymerizable group.

[0605] Examples of the radically polymerizable group include a (meth)acryloyl group, an allyl group, a vinylphenyl group, a vinyl group, and the like. From the viewpoint of reactivity, a (meth)acryloyl group is preferable.

[0606] The molecular weight of the polymerizable compound (weight-average molecular weight in a case where the polymerizable compound has molecular weight distribution) is preferably 50 or more and less than 2,500.

[0607] The polymerizable compound may be, for example, a radically polymerizable compound or a cationically polymerizable compound. As the polymerizable compound, an addition polymerizable compound having at least one ethylenically unsaturated bond (ethylenically unsaturated compound) is preferable.

[0608] The ethylenically unsaturated compound is preferably a compound having at least one terminal ethylenically unsaturated bond, and more preferably a compound having two or more terminal ethylenically unsaturated bonds. The chemical form of the polymerizable compound is, for example, a monomer, a prepolymer which is in other words a dimer, a trimer, or an oligomer, a mixture of these, or the like.

[0609] Particularly, from the viewpoint of printing durability, the polymerizable compound preferably includes a polymerizable compound having functionalities of 3 or more, more preferably includes a polymerizable compound having functionalities of 7 or more, and even more preferably includes a polymerizable compound having functionalities of 10 or more. Particularly, from the viewpoint of printing durability of the lithographic printing plate to be obtained, the polymerizable compound preferably includes an ethylenically unsaturated compound having functionalities of 3 or more (preferably having functionalities of 7 or more and more preferably having functionalities of 10 or more), and more preferably includes a (meth)acrylate compound having functionalities of 3 or more (preferably having functionalities of 7 or more and more preferably having functionalities of 10 or more).

[0610] From the viewpoint of on-press developability and contamination suppressing property, the aforementioned polymerizable compound preferably includes a polymerizable compound having functionalities of 2 or less, more preferably includes a difunctional polymerizable compound, and particularly preferably includes a difunctional (meth)acrylate compound.

[0611] From the viewpoints of printing durability, on-press developability, and contamination suppressing property, the content of the polymerizable compound having functionalities of 2 or less (preferably a difunctional polymerizable compound) with respect to the total mass of polymerizable compounds in the image-recording layer is preferably 5% by mass to 100% by mass, more preferably 10% by mass to 100% by mass, and even more preferably 15% by mass to 100% by mass.

[0612] In addition, it is preferable that the polymerizable compound includes a polymer BB. The polymer BB has a structural unit (Bb1) represented by Formula (BI).

##STR00100##

[0613] In Formula (BI), R.sup.B11 and R.sup.B12 each independently represent a hydrogen atom or an alkyl group, R.sup.B13 represents a hydrogen atom or a monovalent substituent, L.sup.B11 and L.sup.B12 each independently represent a single bond or a divalent linking group, and Rh represents a substituent containing two or more silicon atoms.

[0614] Examples of the alkyl group represented by R.sup.B11 and R.sup.B12 include a linear alkyl group having 1 to 18 carbon atoms, and a branched or cyclic alkyl group having 3 to 18 carbon atoms. Specific examples of the alkyl group described above include a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a tert-butyl group, a cyclohexyl group, and the like.

[0615] It is preferable that R.sup.B11 and R.sup.B12 are both hydrogen atoms.

[0616] Examples of the monovalent substituent represented by R.sup.B13 include an alkyl group, an alkenyl group, and an aryl group. The alkyl group, the alkenyl group, and the aryl group are the same as the alkyl group, the alkenyl group, and the aryl group represented by R.sup.1, R.sup.2, and R.sup.3, respectively, and preferred aspects thereof are also the same.

[0617] R.sup.6 is preferably a hydrogen atom or a methyl group.

[0618] Examples of the divalent linking group represented by L.sup.B11 include C(O)O (so-called ester bond) and C(O)NH.

[0619] The divalent linking group represented by L.sup.B11 is preferably C(O)O, which is an ester bond.

[0620] The divalent linking group represented by L.sup.B12 is not particularly limited as long as it is a group capable of linking L.sup.B11 and Rh. Examples of the divalent linking group represented by L.sup.B12 include an alkylene group. The alkylene group is preferably an alkylene group having 2 to 10 carbon atoms, and more preferably an alkylene group having 4 to 8 carbon atoms.

[0621] The substituent containing two or more silicon atoms, which is represented by Rh, is not particularly limited as long as the atomic group constituting the substituent contains two or more silicon atoms. From the viewpoint of on-press developability, it is preferable that the substituent having two or more silicon atoms includes the silicon atom as a silicon-oxygen bond (SiO bond). The substituent having two or more silicon atoms preferably has two or more silicon-oxygen bonds, more preferably has three or more silicon-oxygen bonds, and even more preferably has 3 to 12 silicon-oxygen bonds. The substituent including two or more silicon atoms preferably includes a silicon-oxygen bond as a polysiloxane structure.

[0622] In addition, from the viewpoint of on-press developability, the substituent containing two or more silicon atoms preferably has a branched structure, and more preferably has a branched structure branched around a silicon atom.

[0623] Specifically, the substituent containing two or more silicon atoms is preferably a group containing two or more structures represented by Formula (BIa).

##STR00101##

[0624] In Formula (BIa), * represents a bonding position, and R.sup.b11, R.sup.b12, and R.sup.b13 each independently represent an alkyl group, an alkenyl group, an aryl group, or an alkylene aryl group.

[0625] Examples of the alkyl group represented by R.sup.b11, R.sup.b12, and R.sup.b13 include a linear alkyl group having 1 to 18 carbon atoms, and a branched or cyclic alkyl group having 3 to 18 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a tert-butyl group, and a cyclohexyl group.

[0626] Examples of the alkenyl group represented by R.sup.b11, R.sup.b12, and R.sup.b13 include an alkenyl group having 2 to 12 carbon atoms. Specific examples of the alkenyl group include a vinyl group, a 1-propenyl group, a 1-butenyl group, a 1-methyl-1-propenyl group, a 1-cyclopentenyl group, and a 1-cyclohexenyl group.

[0627] Examples of the aryl group represented by R.sup.b11, R.sup.b12, and R.sup.b13 include an aryl group having 6 to 12 carbon atoms. Specific examples of the aryl group include a phenyl group, an -methylphenyl group, and a naphthyl group.

[0628] Examples of the alkylene aryl group represented by R.sup.b11, R.sup.b12, and R.sup.b13 include an alkylene aryl group having 7 to 30 carbon atoms.

[0629] In Formula (BIa), it is preferable that R.sup.b11, R.sup.b12, and R.sup.b13 are each independently an alkyl group, it is more preferable that R.sup.b11, R.sup.b12, and R.sup.b13 are all the same alkyl group, it is still more preferable that R.sup.b11, R.sup.b12, and R.sup.b13 are all alkyl groups having 1 to 4 carbon atoms, and it is particularly preferable that R.sup.b11, R.sup.b12, and R.sup.b13 are all methyl groups.

[0630] The substituent containing two or more silicon atoms is preferably a group containing three or more structures represented by Formula (BIa), and more preferably a group containing three to six structures represented by Formula (BIa).

[0631] The substituent containing two or more silicon atoms is preferably a group represented by Formula (Ba2).

##STR00102##

[0632] In Formula (Ba2), * represents a bonding position, and R.sup.b1, R.sup.b2, and R.sup.b3 each independently represent an alkyl group, an alkenyl group, an aryl group, or an alkylene aryl group.

[0633] Examples of the alkyl group represented by R.sup.b1, R.sup.b2, and R.sup.b3 include a linear alkyl group having 1 to 18 carbon atoms, and a branched or cyclic alkyl group having 3 to 18 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a tert-butyl group, and a cyclohexyl group.

[0634] Examples of the alkenyl group represented by R.sup.b1, R.sup.b2, and R.sup.b3 include an alkenyl group having 2 to 12 carbon atoms. Specific examples of the alkenyl group include a vinyl group, a 1-propenyl group, a 1-butenyl group, a 1-methyl-1-propenyl group, a 1-cyclopentenyl group, and a 1-cyclohexenyl group.

[0635] Examples of the aryl group represented by R.sup.b1, R.sup.b2, and R.sup.b3 include an aryl group having 6 to 12 carbon atoms. Specific examples of the aryl group include a phenyl group, an -methylphenyl group, and a naphthyl group.

[0636] Examples of the alkylene aryl group represented by R.sup.b1, R.sup.b2, and R.sup.b3 include an alkylene aryl group having 7 to 30 carbon atoms.

[0637] In Formula (Ba2), it is preferable that R.sup.b1, R.sup.b2, and R.sup.b3 are each independently an alkyl group, it is more preferable that R.sup.b1, R.sup.b2, and R.sup.b3 are all the same alkyl group, it is still more preferable that R.sup.b1, R.sup.b2, and R.sup.b3 are all alkyl groups having 1 to 4 carbon atoms, and it is particularly preferable that R.sup.b1, R.sup.b2, and R.sup.b3 are all methyl groups.

[0638] Specific examples of the structural unit (Bb1) represented by Formula (BI) include monomers represented by K-1 to K-12. Specific examples of the monomer unit forming the structural unit having a substituent containing two or more silicon atoms in the side chain are not limited thereto.

[0639] In the following structures, n is an integer of 2 to 1,000.

##STR00103## ##STR00104##

[0640] From the viewpoint of obtaining more excellent on-press developability, the polymerizable BB is preferably a copolymer containing a structural unit having a substituent including two or more silicon atoms on the side chain and a structural unit having a hydrophilic group on the side chain.

[0641] The structural unit having a hydrophilic group on the side chain in the polymerizable BB is preferably a structural unit represented by Formula (a4).

##STR00105##

[0642] In Formula (Ba4), R.sup.B7 and R.sup.B8 each independently represent a hydrogen atom or an alkyl group, R.sup.B9 represents a hydrogen atom or a monovalent substituent, L.sup.B2 represents C(O)Oor C(O)NH, L.sup.B2 and L.sup.B3 represent a single bond or a divalent linking group, and X.sup.B represents a hydrophilic group.

[0643] In the alkyl group represented by R.sup.B7 and R.sup.B8, R.sup.B7 and R.sup.B8 each independently represent a hydrogen atom or an alkyl group.

[0644] Examples of the alkyl group represented by R.sup.B7 and R.sup.B8 include a linear alkyl group having 1 to 18 carbon atoms, and a branched or cyclic alkyl group having 3 to 18 carbon atoms. Specific examples of the alkyl group described above include a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a tert-butyl group, a cyclohexyl group, and the like.

[0645] It is preferable that R.sup.B7 and R.sup.B8 are both hydrogen atoms.

[0646] Examples of the monovalent substituent represented by R.sup.B9 include an alkyl group, an alkenyl group, and an aryl group. The alkyl group, the alkenyl group, and the aryl group are the same as the alkyl group, the alkenyl group, and the aryl group represented by R.sup.B11, R.sup.B12, and R.sup.B13, respectively, and preferred aspects thereof are also the same.

[0647] R.sup.B9 is preferably a hydrogen atom or a methyl group.

[0648] The divalent linking group represented by L.sup.B3 is not particularly limited as long as it is a group capable of linking L.sup.B2 and X.sup.B. Examples of the divalent linking group represented by L.sup.B3 include an alkylene group. The alkylene group is preferably an alkylene group having 2 to 10 carbon atoms, and more preferably an alkylene group having 4 to 8 carbon atoms.

[0649] Examples of the hydrophilic group represented by X.sup.B include a hydroxyl group, a phosphoric acid group, a polyalkyleneoxy group, and a group consisting of a combination of two or more thereof. Here, examples of the polyalkyleneoxy group include a polyethyleneoxy group, a polypropyleneoxy group, a polybutyleneoxy group, and a group obtained by combining these groups.

[0650] Specific examples of the monomer unit for forming the structural unit having a hydrophilic group in a side chain include monomers represented by H-1 to H-40. Specific examples of the monomer unit forming the structural unit having a hydrophilic group in a side chain are not limited thereto.

[0651] In the following structures, n and m are each independently an integer of 2 to 100.

[0652] In the following structures, the description of random means that a plurality of polyalkyleneoxy groups are randomly arranged.

##STR00106## ##STR00107## ##STR00108## ##STR00109## ##STR00110##

[0653] The polymer BB may contain one kind of the structural unit having a substituent including two or more silicon atoms on the side chain, or may contain two or more kinds thereof.

[0654] In the polymer BB, the content of the structural unit having a substituent containing two or more silicon atoms in a side chain may be 100% by mass, and is preferably 15% by mass to 70% by mass, more preferably 20% by mass to 60% by mass, and still more preferably 25% by mass to 50% by mass, with respect to the mass of the polymer BB.

[0655] In addition, the polymer BB may contain only one type of structural unit having a hydrophilic group in a side chain or may contain two or more types of structural units having a hydrophilic group in a side chain.

[0656] In the polymer BB, the content of the structural unit having a hydrophilic group in the side chain is preferably 30% by mass to 85% by mass, more preferably 40% by mass to 80% by mass, and still more preferably 50% by mass to 75% by mass with respect to the mass of the polymer BB.

[0657] The polymer BB may further include other structural units.

[0658] Examples of the other structural unit include a structural unit having a carboxylic acid group in the side chain. Examples of the structural unit having a carboxylic acid group in the side chain include (meth)acrylic acid, itaconic acid, an itaconic acid derivative, and the like. It is preferable that the structural unit having a carboxylic acid group in the side chain is included as a structural unit different from the above-mentioned structural unit having a hydrophilic group in the side chain.

[0659] Examples of the other structural units include alkyl (meth)acrylate (the number of carbon atoms in the alkyl group is 1 to 24), a styrene derivative, maleic acid anhydride, maleimide anhydride, (meth)acrylonitrile, a vinyl ether derivative, an alkyl (meth)acrylamide derivative, and the like.

[0660] In the polymer BB, the content of the other structural units is preferably 0% by mass to 20% by mass with respect to the mass of the polymer BB.

[0661] From the viewpoint of obtaining an image-recording layer having excellent surface state, the weight-average molecular weight of the polymer BB is preferably 5,000 to 100,000 and more preferably 8,000 to 60,000.

[0662] Specific examples of the polymer BB include BP-1 to BP-10 shown below. Specific examples of the polymer BB are not limited thereto.

##STR00111## ##STR00112## ##STR00113##

[0663] The content of the polymer BB is preferably 0.001% by mass to 0.1% by mass and more preferably 0.002% by mass to 0.01% by mass with respect to the total mass of the coating liquid for an image-recording layer.

(Oligomer)

[0664] As the polymerizable compound to be incorporated into in the image-recording layer, a polymerizable compound which is an oligomer (hereinafter, also simply called oligomer) is preferable.

[0665] In the present disclosure, an oligomer represents a polymerizable compound which has a molecular weight (weight-average molecular weight in a case where the compound has molecular weight distribution) of 600 or more and 15,000 or less and at least one polymerizable group.

[0666] From the viewpoints of excellent chemical resistance and excellent printing durability, the molecular weight of the oligomer is preferably 1,000 or more and 15,000 or less.

[0667] In addition, from the viewpoint of improving printing durability, the number of polymerizable groups in one molecule of the oligomer is preferably 2 or more, more preferably 3 or more, even more preferably 6 or more, and particularly preferably 10 or more.

[0668] The upper limit value of the number of the polymerizable groups in the oligomer is not particularly limited, but the number of polymerizable groups is preferably 20 or less.

[0669] From the viewpoints of printing durability and on-press developability, an oligomer having 7 or more polymerizable groups and a molecular weight of 1,000 or more and 15,000 or less is preferable, and an oligomer having 7 or more and 20 or less polymerizable groups and a molecular weight of 1,000 or more and 15,000 or less is more preferable.

[0670] The oligomer may contain a polymer component which is likely to be generated in the process of manufacturing the oligomer.

[0671] From the viewpoints of printing durability, visibility, and on-press developability, the oligomer preferably has at least one selected from the group consisting of a compound having a urethane bond, a compound having an ester bond, and a compound having an epoxy residue, and more preferably has a compound having a urethane bond.

[0672] In the present disclosure, an epoxy residue refers to a structure formed of an epoxy group and for example, means a structure similar to a structure obtained by the reaction between an acid group (carboxylic acid group or the like) and an epoxy group.

[0673] As the compound having a urethane bond, which is an example of the oligomer, for example, a compound having at least a group represented by Formula (Ac-1) or Formula (Ac-2) is preferable, and a compound having at least a group represented by Formula (Ac-1) is more preferable.

##STR00114##

[0674] In Formula (Ac-1) and Formula (Ac-2), L.sup.1 to L.sup.4 each independently represent a divalent hydrocarbon group having a carbon number of 2 to 20, and the portion of the wavy line represents a bonding position with other structures.

[0675] L.sup.1 to L.sup.4 preferably each independently represent an alkylene group having a carbon number of 2 to 20, more preferably each independently represent an alkylene group having a carbon number of 2 to 10, and even more preferably each independently represent an alkylene group having a carbon number of 4 to 8. The alkylene group may have a branched structure or a ring structure. The alkylene group is preferably a linear alkylene group.

[0676] The portion of the wavy line in Formula (Ac-1) or Formula (Ac-2) is preferably each independently directly bonded to the portion of the wavy line in a group represented by Formula (Ae-1) or Formula (Ae-2).

##STR00115##

[0677] In Formula (Ae-1) and Formula (Ae-2), R each independently represent an acryloyloxy group or a methacryloyloxy group, and the portion of the wavy line represents a bonding position with portion of the wavy line in Formula (Ac-1) and Formula (Ac-2).

[0678] As the compound having a urethane bond, a compound may also be used which is prepared by obtaining polyurethane by a reaction between a polyisocyanate compound and a polyol compound and introducing a polymerizable group into the obtained polyurethane by a polymer reaction.

[0679] For example, the compound having a urethane bond may be obtained by reacting a polyol compound having an acid group with a polyisocyanate compound to obtain a polyurethane oligomer and reacting the obtained polyurethane oligomer with a compound having an epoxy group and a polymerizable group.

[0680] The number of polymerizable groups in the compound having an ester bond, which is an example of oligomer, is preferably 3 or more, and more preferably 6 or more.

[0681] As the compound having an epoxy residue, which is an example of oligomer, a compound containing a hydroxy group is preferable.

[0682] The number of polymerizable groups in the compound having an epoxy residue is preferably 2 to 6, and more preferably 2 or 3.

[0683] The compound having an epoxy residue can be obtained, for example, by reacting a compound having an epoxy group with an acrylic acid.

[0684] Specific examples of oligomers will be shown as follows, but the oligomer used in the present disclosure is not limited thereto.

[0685] As the oligomer, commercially available products may also be used. Examples thereof include UA-510H, UA-306H, UA-306I, and UA-306T (all manufactured by KYOEISHA CHEMICAL Co., Ltd.), UV-1700B, UV-6300B, and UV7620EA (all manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.), U-15HA (manufactured by SHIN-NAKAMURA CHEMICAL Co., Ltd.), EBECRYL450, EBECRYL657, EBECRYL885, EBECRYL800, EBECRYL3416, and EBECRYL860 (all manufactured by DAICEL-ALLNEX LTD.), and the like. However, the oligomer is not limited to these.

[0686] From the viewpoints of improving chemical resistance and printing durability and further suppressing the residues of on-press development, the content of the oligomer with respect to the total mass of polymerizable compounds in the image-recording layer is preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

(Low-Molecular-Weight Polymerizable Compound)

[0687] The polymerizable compound may further include a polymerizable compound other than the oligomer described above.

[0688] From the viewpoint of chemical resistance, the polymerizable compound other than the oligomer is preferably a low-molecular-weight polymerizable compound. The low-molecular-weight polymerizable compound may take a chemical form such as a monomer, a dimer, a trimer, or a mixture of these.

[0689] From the viewpoint of chemical resistance, the low-molecular-weight polymerizable compound is preferably at least one polymerizable compound selected from the group consisting of a polymerizable compound having three or more ethylenically unsaturated groups and a polymerizable compound having an isocyanuric ring structure.

[0690] In the present disclosure, a low-molecular-weight polymerizable compound refers to a polymerizable compound having a molecular weight (weight-average molecular weight in a case where the compound has molecular weight distribution) of 50 or more and less than 600.

[0691] From the viewpoints of excellent chemical resistance, excellent printing durability, and excellently suppressing the residues of on-press development, the molecular weight of the low-molecular-weight polymerizable compound is preferably 100 or more and less than 600, more preferably 300 or more and less than 600, and even more preferably 400 or more and less than 600.

[0692] In a case where the polymerizable compound includes a low-molecular-weight polymerizable compound as the polymerizable compound other than the oligomer, from the viewpoints of chemical resistance and printing durability and suppressing the residues of on-press development, the ratio (oligomer/low-molecular-weight polymerizable compound) of the oligomer to the low-molecular-weight polymerizable compound (total amount in a case where the polymerizable compound includes two or more low-molecular-weight polymerizable compounds) based on mass is preferably 10/1 to 1/10, more preferably 10/1 to 3/7, and even more preferably 10/1 to 7/3.

[0693] As the low-molecular-weight polymerizable compound, the polymerizable compounds described in paragraphs 0082 to 0086 of WO2019/013268A can also be suitably used.

[0694] The details of how to use the polymerizable compound, such as the structure of the compound, whether the compound is used alone or used in combination with other compounds, and the additive amount of the compound, can be optionally set.

[0695] Particularly, from the viewpoint of printing durability, the image-recording layer preferably contains two or more polymerizable compounds.

[0696] The content of the polymerizable compound (total content of polymerizable compounds in a case where the image-recording layer contains two or more polymerizable compounds) with respect to the total mass of the image-recording layer is preferably 5% by mass to 75% by mass, more preferably 10% by mass to 70% by mass, and even more preferably 15% by mass to 60% by mass.

[0697] It is also preferable that the image-recording layer contains particles.

[0698] The particles may be organic particles or inorganic particles. From the viewpoint of printing durability, the image-recording layer preferably contains organic particles, and more preferably contains polymer particles.

[0699] As inorganic particles, known inorganic particles can be used, and metal oxide particles such as silica particles and titania particles can be suitably used.

[0700] The polymer particles are preferably selected from the group consisting of thermoplastic resin particles, thermal reactive resin particles, polymer particles having a polymerizable group, microcapsules encapsulating a hydrophobic compound, and a microgel (for example, crosslinked polymer particles). Among these, polymer particles having a polymerizable group or a microgel are preferable. In a particularly preferable embodiment, the polymer particles have at least one ethylenically unsaturated polymerizable group. The presence of such polymer particles brings about effects of improving the printing durability of an exposed portion and improving the on-press developability of a non-exposed portion.

[0701] From the viewpoints of printing durability and on-press developability, the polymer particles are preferably thermoplastic resin particles.

[0702] The thermoplastic resin particles are preferably the thermoplastic polymer particles described in Research Disclosure No. 33303 published in January 1992, JP1997-123387A (JP-H09-123387A), JP1997-131850A (JP-H09-131850A), JP1997-171249A (JP-H09-171249A), JP1997-171250A (JP-H09-171250A), EP931647B, and the like.

[0703] Specific examples of polymers constituting the thermoplastic resin particles include homopolymers or copolymers of monomers of ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinylcarbazole, acrylate or methacrylate having a polyalkylene structure, and the like, or mixtures of these. Preferred examples thereof can include polystyrene, copolymers having styrene and acrylonitrile, or polymethyl methacrylate. The average particle diameter of the thermoplastic resin particle is preferably 0.01 m to 3.0 m.

[0704] Examples of the thermal reactive resin particles include polymer particles having a thermal reactive group. The thermal reactive polymer particles form a hydrophobilized region through crosslinking by a thermal reaction and the accompanying change in functional groups.

[0705] The thermal reactive group in the polymer particles having a thermal reactive group may be a functional group that causes any reaction as long as chemical bonds are formed, and is preferably a polymerizable group. Preferred examples thereof include an ethylenically unsaturated group that causes a radical polymerization reaction (for example, an acryloyl group, a methacryloyl group, a vinyl group, an allyl group, and the like), a cationically polymerizable group (for example, a vinyl group, a vinyloxy group, an epoxy group, an oxetanyl group, and the like), an isocyanato group or a blocked isocyanato group that causes an addition reaction, an epoxy group, a vinyloxy group, an active hydrogen atom-containing functional group that is a reaction partner thereof (for example, an amino group, a hydroxy group, a carboxy group, and the like), a carboxy group that causes a condensation reaction, a hydroxy group or an amino group that is a reaction partner of the carboxy group, an acid anhydride that causes a ring-opening addition reaction, an amino group or a hydroxy group which is a reaction partner of the acid anhydride, and the like.

[0706] Examples of the microcapsules include microcapsules encapsulating at least some of the constituent components of the image-recording layer as described in JP2001-277740A and JP2001-277742A. The constituent components of the image-recording layer can also be contained in the exterior of the microcapsules. In a preferred aspect, the image-recording layer containing microcapsules is constituted such that hydrophobic constituent components are encapsulated in the microcapsules and hydrophilic constituent components are contained in the exterior of the microcapsules.

[0707] The microgel (for example, crosslinked polymer particles) can contain some of the constituent components of the image-recording layer, in at least one of the surface or the interior of the microgel. From the viewpoints of sensitivity of the lithographic printing plate precursor to be obtained and printing durability of the lithographic printing plate to be obtained, a reactive microgel having a radically polymerizable group on the surface thereof is particularly preferable.

[0708] In order to encapsulate the constituent components of the image-recording layer in microcapsules or microgels, known methods can be used.

[0709] From the viewpoints of printing durability, antifouling property, and storage stability of the lithographic printing plate to be obtained, the polymer particles are preferably polymer particles which are obtained by a reaction of a polyvalent isocyanate compound that is an adduct of a polyhydric phenol compound having two or more hydroxy groups in a molecule and isophorone diisocyanate with a compound having active hydrogen.

[0710] The polyhydric phenol compound is preferably a compound having a plurality of benzene rings having a phenolic hydroxy group.

[0711] The compound having active hydrogen is preferably a polyol compound or a polyamine compound, more preferably a polyol compound, and even more preferably at least one compound selected from the group consisting of propylene glycol, glycerin, and trimethylolpropane.

[0712] Preferred examples of the resin particles obtained by the reaction of a polyvalent isocyanate compound that is an adduct of a polyhydric phenol compound having two or more hydroxy groups in a molecule and isophorone diisocyanate, with a compound having active hydrogen include the polymer particles described in paragraphs 0032 to 0095 of JP2012-206495A.

[0713] Furthermore, from the viewpoint of printing durability and solvent resistance of the lithographic printing plate to be obtained, the polymer particles preferably have a hydrophobic main chain and include both i) structural unit having a pendant cyano group directly bonded to the hydrophobic main chain and ii) structural unit having a pendant group including a hydrophilic polyalkylene oxide segment.

[0714] Preferred examples of the hydrophobic main chain include an acrylic resin chain.

[0715] Preferred examples of the pendant cyano group include [CH.sub.2CH(CN] or [CH.sub.2C(CH.sub.3)(CN)].

[0716] In addition, the structural unit having the pendant cyano group can be easily derived from an ethylenically unsaturated monomer, for example, acrylonitrile or methacrylonitrile, or a combination of these.

[0717] Furthermore, as an alkylene oxide in the hydrophilic polyalkylene oxide segment, ethylene oxide or a propylene oxide is preferable, and ethylene oxide is more preferable.

[0718] The number of repeating alkylene oxide structures in the hydrophilic polyalkylene oxide segment is preferably 10 to 100, more preferably 25 to 75, and even more preferably 40 to 50.

[0719] As the resin particles having a hydrophobic main chain and including both i) structural unit having the pendant cyano group directly bonded to the hydrophobic main chain and ii) structural unit having a pendant group including the hydrophilic polyalkylene oxide segment, for example, the particles described in paragraphs 0039 to 0068 of JP2008-503365A are preferable.

[0720] From the viewpoints of printing durability and on-press developability, the polymer particles preferably have a hydrophilic group.

[0721] The hydrophilic group is not particularly limited as long as it has a hydrophilic structure, and examples thereof include an acid group such as a carboxy group, a hydroxy group, an amino group, a cyano group, a polyalkylene oxide structure, and the like.

[0722] Among these, from the viewpoints of on-press developability and printing durability, a polyalkylene oxide structure is preferable, and a polyethylene oxide structure, a polypropylene oxide structure, or a poly(ethylene oxide/propylene oxide) structure is more preferable.

[0723] In addition, from the viewpoints of on-press developability and suppressing the residues of development during on-press development, the polyalkylene oxide structure preferably has a polypropylene oxide structure, and more preferably has a polyethylene oxide structure and a polypropylene oxide structure.

[0724] From the viewpoints of printing durability, receptivity, and on-press developability, the hydrophilic group preferably has a structural unit having a cyano group, or a group represented by Formula Z, more preferably has a structural unit represented by Formula (AN) or a group represented by Formula Z, and particularly preferably has a group represented by Formula Z.

*-Q-WYFormula Z

[0725] In Formula Z, Q represents a divalent linking group, W represents a divalent group having a hydrophilic structure or a divalent group having a hydrophobic structure, and Y represents a monovalent group having a hydrophilic structure or a monovalent group having a hydrophobic structure, either W or Y has a hydrophilic structure, and * represents a bonding site with another structure.

##STR00116##

[0726] In Formula (AN), R.sup.AN represents a hydrogen atom or a methyl group.

[0727] From the viewpoint of printing durability, the polymer contained in the polymer particles preferably has a structural unit formed of a compound having a cyano group.

[0728] Generally, it is preferable that a cyano group is introduced as a structural unit having a cyano group into a resin by using a compound (for example, monomer) having a cyano group. Examples of the compound having a cyano group include acrylonitrile compounds and suitable examples thereof include (meth)acrylonitrile.

[0729] The structural unit having a cyano group is preferably a structural unit formed of an acrylonitrile compound, and more preferably a structural unit formed of (meth)acrylonitrile, that is, a structural unit represented by Formula (AN).

[0730] In a case where the polymer includes a polymer having a structural unit having a cyano group, from the viewpoint of printing durability, the content of the structural unit having a cyano group which is preferably a structural unit represented by Formula (AN) in the polymer having the structural unit having a cyano group with respect to the total mass of the polymer having the structural unit having a cyano group is preferably 5% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, and particularly preferably 30% by mass to 60% by mass.

[0731] In addition, from the viewpoints of printing durability, receptivity, and on-press developability, the polymer particles preferably include polymer particles having a group represented by Formula Z.

[0732] Q in Formula Z is preferably a divalent linking group having 1 to 20 carbon atoms, and more preferably a divalent linking group having 1 to 10 carbon atoms.

[0733] In addition, Q in Formula Z is preferably an alkylene group, an arylene group, an ester bond, an amide bond, or a group formed by combining two or more of these, and more preferably a phenylene group, an ester bond, or an amide bond.

[0734] The divalent group having a hydrophilic structure represented by W in Formula Z is preferably a polyalkyleneoxy group or a group in which CH.sub.2CH.sub.2NR.sup.W is bonded to one terminal of a polyalkyleneoxy group. R.sup.W represents a hydrogen atom or an alkyl group. The divalent group having a hydrophobic structure represented by W in Formula Z is preferably R.sup.WA, OR.sup.WAO, R.sup.WNR.sup.WANR.sup.W, OC(O)R.sup.WAO, or OC(O)R.sup.WAO. R.sup.WA's each independently represent a linear, branched, or cyclic alkylene group having a carbon number of 6 to 120, a haloalkylene group having a carbon number of 6 to 120, an arylene group having a carbon number of 6 to 120, an alkarylene group having a carbon number of 6 to 120 (that is, divalent group formed by removing one hydrogen atom from an alkylaryl group), or an aralkylene group having a carbon number of 6 to 120.

[0735] The monovalent group having a hydrophilic structure represented by Y in Formula Z is preferably OH, C(O)OH, a polyalkyleneoxy group having a hydrogen atom or an alkyl group on a terminal, or a group in which CH.sub.2CH.sub.2N(R.sup.W) is bonded to one terminal of a polyalkyleneoxy group having a hydrogen atom or an alkyl group on the other terminal.

[0736] The monovalent group having a hydrophobic structure represented by Y in Formula Z is preferably a linear, branched, or cyclic alkyl group having 6 to 120 carbon atoms, a haloalkyl group having 6 to 120 carbon atoms, an aryl group having 6 to 120 carbon atoms, an alkaryl group (alkylaryl group) having 7 to 120 carbon atoms, an aralkyl group having 7 to 120 carbon atoms, OR.sup.WB, C(O)OR.sup.WB, or OC(O)R.sup.WB. R.sup.WB represents an alkyl group having 6 to 20 carbon atoms.

[0737] From the viewpoints of printing durability, receptivity, and on-press developability, in the polymer particles having a group represented by formula Z, W is preferably a divalent group having a hydrophilic structure, and it is more preferable that Q is a phenylene group, an ester bond, or an amide bond, W is a polyalkyleneoxy group, and Y is a polyalkyleneoxy group having a hydrogen atom or an alkyl group on a terminal.

[0738] From the viewpoints of printing durability and on-press developability, the polymer particles preferably include polymer particles having a polymerizable group, and more preferably include polymer particles having a polymerizable group on the particle surface.

[0739] Furthermore, from the viewpoint of printing durability, the polymer particles preferably include polymer particles having a hydrophilic group and a polymerizable group.

[0740] The polymerizable group may be a cationically polymerizable group or a radically polymerizable group and, from the viewpoint of reactivity, is preferably a radically polymerizable group.

[0741] The polymerizable group is not particularly limited as long as it is a polymerizable group, but from the viewpoint of reactivity, is preferably an ethylenically unsaturated group, more preferably a vinylphenyl group (styryl group), a (meth)acryloxy group, or a (meth)acrylamide group, and particularly preferably a (meth)acryloxy group.

[0742] In addition, the polymer in the polymer particles having a polymerizable group preferably has a structural unit having a polymerizable group.

[0743] The polymerizable group may be introduced into the surface of the polymer particles by a polymer reaction.

[0744] In addition, from the viewpoints of printing durability and on-press developability, the image-recording layer preferably contains, as the polymer particles, addition polymerization-type resin particles having a dispersible group which more preferably includes a group represented by Formula Z.

[0745] Furthermore, from the viewpoint of printing durability, receptivity, on-press developability, and suppression of the occurrence of development residues during on-press development, the polymer particles preferably contain a resin having a urea bond, more preferably contain a resin having a structure obtained by reacting at least an isocyanate compound represented by Formula (Iso) with water, and particularly preferably contain a resin that has a structure obtained by reacting at least an isocyanate compound represented by Formula (Iso) with water and has a polyethylene oxide structure and a polypropylene oxide structure as polyoxyalkylene structures. Furthermore, the particles containing the resin having a urea bond are preferably a microgel.

##STR00117##

[0746] In Formula (Iso), n represents an integer of 0 to 10.

[0747] An example of the reaction between the isocyanate compound represented by Formula (Iso) and water is the reaction shown below. In the following example, a 4,4-isomer in which n=0 is used.

[0748] As shown below, in a case where the isocyanate compound represented by Formula (Iso) is reacted with water, the isocyanate group is partially hydrolyzed by water and generates an amino group. The generated amino group reacts with the isocyanate group and generates a urea bond, and a dimer is consequently formed. Furthermore, the following reaction is repeated to form a resin having a urea bond.

[0749] In the following reaction, by adding a compound (for example, compound having active hydrogen) such as an alcohol compound or an amine compound reactive with an isocyanate group, it is possible to introduce the structure of an alcohol compound, an amine compound, or the like to the resin having a urea bond.

[0750] As the compound having active hydrogen, for example, the compounds described above regarding the microgel are preferable.

##STR00118##

[0751] The resin having a urea bond preferably has an ethylenically unsaturated group, and more preferably has a group represented by Formula (PETA).

##STR00119##

[0752] In Formula (PETA), the portion of the wavy line represents a binding position with other structures.

[0753] From the viewpoints of printing durability and on-press developability, the image-recording layer preferably contains thermoplastic resin particles.

[0754] The thermoplastic resin contained in the thermoplastic resin particles is not particularly limited, and examples thereof include polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polymethyl (meth)acrylate, polyethyl (meth)acrylate, polybutyl (meth)acrylate, polyacrylonitrile, polyvinyl acetate, copolymers of these, and the like. The thermoplastic resin may be in the state of latex.

[0755] The thermoplastic resin according to the present disclosure is preferably a thermoplastic resin which melts or softens by heat generated in an exposure step that will be described later and thus forms a part or the entirety of a hydrophobic film forming the recording layer.

[0756] From the viewpoints of ink receptivity and printing durability, the thermoplastic resin preferably contains a resin A having a structural unit formed of an aromatic vinyl compound and a structural unit having a cyano group.

[0757] The resin A contained in the thermoplastic resin preferably has a structural unit formed of an aromatic vinyl compound.

[0758] The aromatic vinyl compound may have a structure composed of an aromatic ring and a vinyl group bonded thereto. Examples of the compound include a styrene compound, a vinylnaphthalene compound, and the like. Among these, a styrene compound is preferable, and styrene is more preferable.

[0759] Examples of the styrene compound include styrene, p-methylstyrene, p-methoxystyrene, -methylstyrene, p-methyl--methylstyrene, -methylstyrene, p-methoxy--methylstyrene, and the like. Among these, for example, styrene is preferable.

[0760] Examples of the vinylnaphthalene compound include 1-vinylnaphthalene, methyl-1-vinylnaphthalene, -methyl-1-vinylnaphthalene, 4-methyl-1-vinylnaphthalene, 4-methoxy-1-vinylnaphthalene, and the like. Among these, for example, 1-vinylnaphthalene is preferable.

[0761] In addition, preferred examples of the structural unit formed of an aromatic vinyl compound include a structural unit represented by Formula A1.

##STR00120##

[0762] In Formula A1, R.sup.A1 and R.sup.A2 each independently represent a hydrogen atom or an alkyl group, Ar represents an aromatic ring group, R.sup.A3 represents a substituent, and n represents an integer of 0 or greater and equal to or less than the maximum number of substituents of Ar.

[0763] In Formula A1, R.sup.A1 and R.sup.A2 preferably each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably each independently represent a hydrogen atom or a methyl group, and even more preferably both represent a hydrogen atom.

[0764] In Formula A1, Ar is preferably a benzene ring or a naphthalene ring, and more preferably a benzene ring.

[0765] In Formula A1, R.sup.A3 is preferably an alkyl group or an alkoxy group, more preferably an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and even more preferably a methyl group or a methoxy group.

[0766] In a case where there is a plurality of R.sup.A3's in Formula A1, the plurality of R.sup.A3's may be the same as or different from each other.

[0767] In Formula A1, n is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0768] In the resin A contained in the thermoplastic resin, from the viewpoint of ink receptivity, the content of the structural unit formed of an aromatic vinyl compound is preferably higher than the content of the cyano group-containing structural unit that will be described later. The content of the structural unit formed of an aromatic vinyl compound with respect to the total mass of the thermoplastic resin is more preferably 15% by mass to 85% by mass, and even more preferably 30% by mass to 70% by mass.

[0769] The resin A contained in the thermoplastic resin particles preferably has a cyano group-containing structural unit.

[0770] Generally, it is preferable that a cyano group be introduced as a cyano group-containing structural unit into the resin A by using a cyano group-containing compound (for example, monomer). Examples of the compound having a cyano group include acrylonitrile compounds and suitable examples thereof include (meth)acrylonitrile.

[0771] The cyano group-containing structural unit is preferably a structural unit formed of an acrylonitrile compound, and more preferably a structural unit formed of (meth)acrylonitrile.

[0772] As the structural unit formed of a cyano group-containing compound, for example, a structural unit represented by Formula B1 is preferable.

##STR00121##

[0773] In Formula B1, R.sup.B1 represents a hydrogen atom or an alkyl group.

[0774] In Formula B1, R.sup.B1 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

[0775] From the viewpoint of ink receptivity, the content of the cyano group-containing structural unit in the resin A is preferably less than the content of the structural unit formed of an aromatic vinyl compound described above. The content of the cyano group-containing structural unit with respect to the total mass of the resin A is preferably 55% by mass to 90% by mass, and more preferably 60% by mass to 85% by mass.

[0776] In a case where the resin A included in the thermoplastic resin has the structural unit formed of an aromatic vinyl compound and the cyano group-containing structural unit, the content ratio between the structural unit formed of an aromatic vinyl compound and the cyano group-containing structural unit (that is, structural unit formed of aromatic vinyl compound:cyano group-containing structural unit) is preferably 5:5 to 9:1 and more preferably 6:4 to 8:2 based on mass.

[0777] From the viewpoint of printing durability and chemical resistance, the resin A contained in the thermoplastic resin particles preferably further has a structural unit formed of an N-vinyl heterocyclic compound.

[0778] Examples of the N-vinyl heterocyclic compound include N-vinylpyrrolidone, N-vinylcarbazole, N-vinylpyrrole, N-vinylphenothiazine, N-vinylsuccinic acid imide, N-vinylphthalimide, N-vinylcaprolactam, and N-vinylimidazole. Among these, N-vinylpyrrolidone is preferable.

[0779] Preferred examples of the structural unit formed of an N-vinyl heterocyclic compound include a structural unit represented by Formula C1.

##STR00122##

[0780] In Formula C1, Ar.sup.N represents a nitrogen atom-containing heterocyclic structure, and the nitrogen atom in Ar.sup.N is bonded to the carbon atom represented by *.

[0781] In Formula C1, the heterocyclic structure represented by Ar.sup.N is preferably a pyrrolidone ring, a carbazole ring, a pyrrole ring, a phenothiazine ring, a succinimide ring, a phthalimide ring, a caprolactam ring, or an imidazole ring, and more preferably a pyrrolidone ring.

[0782] Furthermore, the heterocyclic structure represented by Ar.sup.N may have a known substituent.

[0783] In the resin A, the content of the structural unit formed of an N-vinyl heterocyclic compound with respect to the total mass of the resin A is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 40% by mass.

[0784] The resin A contained in the thermoplastic resin particles may contain an acidic group-containing structural unit. From the viewpoint of on-press developability and ink receptivity, it is preferable that the resin A does not contain an acidic group-containing structural unit.

[0785] Specifically, in the thermoplastic resin, the content of the acidic group-containing structural unit is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The lower limit of the content is not particularly limited, and may be 0% by mass.

[0786] The acid value of the thermoplastic resin is preferably 160 mg KOH/g or less, more preferably 80 mg KOH/g or less, and even more preferably 40 mg KOH/g or less. The lower limit of the acid value is not particularly limited, and may be 0 mg KOH/g.

[0787] In the present disclosure, the acid value is determined by the measurement method based on JIS K0070: 1992.

[0788] From the viewpoint of ink receptivity, the resin A contained in the thermoplastic resin particles may contain a hydrophobic group-containing structural unit.

[0789] Examples of the hydrophobic group include an alkyl group, an aryl group, an aralkyl group, and the like.

[0790] As the hydrophobic group-containing structural unit, a structural unit formed of an alkyl (meth)acrylate compound, an aryl (meth)acrylate compound, or an aralkyl (meth)acrylate compound is preferable, and a structural unit formed of an alkyl (meth)acrylate compound is more preferable.

[0791] The alkyl group in the alkyl (meth)acrylate compound preferably has 1 to 10 carbon atoms. The alkyl group may be linear or branched or may have a cyclic structure. Examples of the alkyl (meth)acrylate compound include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and the like.

[0792] The aryl group in the aryl (meth)acrylate compound preferably has 6 to 20 carbon atoms. The aryl group is more preferably a phenyl group. The aryl group may further have a known substituent. Preferred examples of the aryl (meth)acrylate compound include phenyl (meth)acrylate.

[0793] The alkyl group in the aralkyl (meth)acrylate compound preferably has 1 to 10 carbon atoms. The alkyl group may be linear or branched or may have a cyclic structure. The aryl group in the aralkyl (meth)acrylate compound preferably has 6 to 20 carbon atoms. The aryl group is more preferably a phenyl group. Preferred examples of the aralkyl (meth)acrylate compound include benzyl (meth)acrylate.

[0794] In the resin A contained in the thermoplastic resin particles, the content of the hydrophobic group-containing structural unit with respect to the total mass of the resin A is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass.

[0795] From the viewpoints of printing durability and on-press developability, the thermoplastic resin contained in the thermoplastic resin particles preferably has a hydrophilic group.

[0796] The hydrophilic group is not particularly limited as long as it has a hydrophilic structure, and examples thereof include an acid group such as a carboxy group, a hydroxy group, an amino group, a cyano group, a polyalkylene oxide structure, and the like.

[0797] From the viewpoints of printing durability and on-press developability, the hydrophilic group is preferably a group having a polyalkylene oxide structure, a group having a polyester structure, or a sulfonic acid group, more preferably a group having a polyalkylene oxide structure or a sulfonic acid group, and even more preferably a group having a polyalkylene oxide structure.

[0798] From the viewpoint of on-press developability, the polyalkylene oxide structure is preferably a polyethylene oxide structure, a polypropylene oxide structure, or a poly(ethylene oxide/propylene oxide) structure.

[0799] In addition, from the viewpoint of on-press developability, among the hydrophilic groups, as a polyalkylene oxide structure, groups having a polypropylene oxide structure are preferable, and groups having a polyethylene oxide structure and a polypropylene oxide structure are more preferable.

[0800] From the viewpoint of on-press developability, the number of alkylene oxide structures in the polyalkylene oxide structure is preferably 2 or more, more preferably 5 or more, even more preferably 5 to 200, and particularly preferably 8 to 150.

[0801] From the viewpoint of on-press developability, the hydrophilic group is preferably a group represented by Formula Z.

[0802] From the viewpoint of improving printing durability, chemical resistance, and on-press developability, the resin A contained in the thermoplastic resin particles preferably has a hydrophilic group-containing structural unit.

[0803] Examples of the hydrophilic group include OH, CN, CONR.sup.1R.sup.2, NR.sup.2COR.sup.1 (R.sup.1 and R.sup.2 each independently represent a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group, R.sup.1 and R.sup.2 may be bonded to each other to form a ring), NR.sup.3R.sup.4, N.sup.+R.sup.3R.sup.4R.sup.5X.sup. (R.sup.3 to R.sup.5 each independently represent an alkyl group of 1 to 8 carbon atoms, and X.sup. represents a counteranion), a group represented by Formula PO, a hydrophilic group that the thermoplastic resin contained in the thermoplastic resin particles preferably has, and the like.

[0804] Among these hydrophilic groups, CONR.sup.1R.sup.2 or a group represented by Formula PO is preferable, and a group represented by Formula PO is more preferable.

##STR00123##

[0805] In Formula PO, L.sup.P each independently represent an alkylene group, R.sup.P represents a hydrogen atom or an alkyl group, and n represents an integer of 1 to 100.

[0806] In Formula PO, L.sup.P preferably each independently represent an ethylene group, a 1-methylethylene group, or a 2-methylethylene group, and more preferably each independently represent an ethylene group.

[0807] In Formula PO, R.sup.P is preferably a hydrogen atom or an alkyl group having a carbon number of 1 to 18, more preferably a hydrogen atom or an alkyl group having a carbon number of 1 to 10, even more preferably a hydrogen atom or an alkyl group having a carbon number of 1 to 4, and particularly preferably a hydrogen atom or a methyl group.

[0808] In Formula PO, n is preferably an integer of 1 to 10, and more preferably an integer of 1 to 4.

[0809] In the resin A, the content of the hydrophilic group-containing structural unit with respect to the total mass of the resin A is preferably 5% by mass to 60% by mass, and more preferably 10% by mass to 30% by mass.

[0810] The resin A contained in the thermoplastic resin particles may further contain other structural units. The resin can contain, as those other structural units, structural units other than the structural units described above without particular limitations. Examples thereof include structural units formed of an acrylamide compound, a vinyl ether compound, and the like.

[0811] Examples of the acrylamide compound include (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, N-butyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-hydroxypropyl (meth)acrylamide, N-hydroxybutyl (meth)acrylamide, and the like.

[0812] Examples of the vinyl ether compound include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxypolyethylene glycol vinyl ether, and the like.

[0813] In the thermoplastic resin, the content of those other structural units with respect to the total mass of the thermoplastic resin is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass.

[0814] From the viewpoints of printing durability and ink receptivity, the glass transition temperature (Tg) of the thermoplastic resin is preferably 60 C. to 150 C., more preferably 80 C. to 140 C., and even more preferably 90 C. to 130 C.

[0815] In a case where the thermoplastic resin particles contain two kinds of thermoplastic resins, the value obtained by the FOX equation that will be described later is referred to as the glass transition temperature of the thermoplastic resin.

[0816] In the present disclosure, the glass transition temperature of a resin can be measured by differential scanning calorimetry (DSC).

[0817] Specifically, the glass transition temperature is measured according to the method described in JIS K 7121 (1987) or JIS K 6240 (2011). As the glass transition temperature in the present specification, an extrapolated glass transition initiation temperature (hereinafter, may be referred to as Tig) is used.

[0818] The method of measuring the glass transition temperature will be described in more detail.

[0819] In a case of determining the glass transition temperature, the device is kept at a temperature approximately 50 C. lower than the expected Tg of the resin until the device stabilizes. Then, the resin is heated at a heating rate of 20 C./min to a temperature approximately 30 C. higher than the temperature at which the glass transition ends, and a differential thermal analysis (DTA) curve or a DSC curve is created.

[0820] The extrapolated glass transition initiation temperature (Tig), that is, the glass transition temperature Tg in the present specification is determined as a temperature at an intersection point between a straight line that is obtained by extending the baseline of a low temperature side in the DTA curve or the DSC curve to a high temperature side and a tangent line that is drawn at a point where the slope of the curve of a portion in which the glass transition changes stepwisely is maximum.

[0821] In a case where the thermoplastic resin particles contain two kinds of thermoplastic resins, Tg of the thermoplastic resin particles is determined as follows.

[0822] In a case where Tg1 (K) represents Tg of a first thermoplastic resin, W1 represents the mass ratio of the first thermoplastic resin to the total mass of thermoplastic resin components in the thermoplastic resin particles, Tg2 (K) represents Tg of a second thermoplastic resin, and W2 represents the mass ratio of the second resin to the total mass of thermoplastic resin components in the thermoplastic resin particles, Tg0 (K) of the thermoplastic resin particles can be estimated according to the following FOX equation.

[00002] $FOX equation : 1 / Tg 0 = (W 1 / Tg 1) + (W 2 / Tg 2)$

[0823] In addition, in a case where the thermoplastic resin particles contain three kinds of resins or in a case where three kinds of thermoplastic resin particles each containing different types of thermoplastic resins are contained in a pretreatment liquid, similarly to the case described above, in a case where Tgn (K) represents Tg of nth resin and Wn represents the mass ratio of the nth resin to the total mass of resin components in the thermoplastic resin particles, Tg0 (K) of the thermoplastic resin particles can be estimated according to the following equation.

[00003] $FOX equation : 1 / Tg 0 = (W 1 / Tg 1) + (W 2 / Tg 2) + (W 3 / Tg 3) .Math. + (Wn / Tgn)$

[0824] In the present disclosure, Tg is a value measured by a differential scanning calorimetry (DSC). As the differential scanning calorimeter (DSC), for example, EXSTAR 6220 manufactured by SII NanoTechnology Inc. can be used.

[0825] From the viewpoint of printing durability, the arithmetic mean particle diameter of the thermoplastic resin particles is preferably 1 nm or more and 200 nm or less, more preferably 3 nm or more and less than 80 nm, and even more preferably 10 nm or more and 49 nm or less.

[0826] Unless otherwise specified, the arithmetic mean particle diameter of the thermoplastic resin particles in the present disclosure refers to a value measured by a dynamic light scattering method (DLS). The measurement of the arithmetic mean particle diameter of the thermoplastic resin particles by DLS is carried out using Brookhaven BI-90 (manufactured by Brookhaven Instrument Company) according to the manual of the instrument.

[0827] The weight-average molecular weight of the thermoplastic resin contained in the thermoplastic resin particles is preferably 3,000 to 300,000, and more preferably 5,000 to 100,000.

[0828] The manufacturing method of the thermoplastic resin contained in the thermoplastic resin particles is not particularly limited, and the thermoplastic resin can be manufactured by known methods.

[0829] For example, the polymer is obtained by polymerizing a styrene compound, an acrylonitrile compound, and at least one kind of optional compound selected from the group consisting of the aforementioned N-vinyl heterocyclic compound, a compound used for forming the aforementioned ethylenically unsaturated group-containing structural unit, a compound used for forming the aforementioned acidic group-containing structural unit, a compound used for forming the aforementioned hydrophobic group-containing structural unit, and a compound used for forming the aforementioned other structural units by known methods.

[0830] Specific examples of the thermoplastic resin contained in the thermoplastic resin particles will be shown as follows, but the thermoplastic resin used in the present disclosure is not limited thereto.

##STR00124## ##STR00125##

[0831] The content ratio of the structural units in the above specific examples can be appropriately changed according to the preferred range of the content of each of the structural units described above.

[0832] Furthermore, the weight-average molecular weight of each of the compounds shown in the above specific examples can be appropriately changed according to the preferred range of the weight-average molecular weight of the thermoplastic resin described above.

[0833] The average particle diameter of the particles is preferably 0.01 m to 3.0 m, more preferably 0.03 m to 2.0 m, and even more preferably 0.10 m to 1.0 m. In a case where the average particle diameter is in this range, excellent resolution and excellent temporal stability are obtained.

[0834] The average primary particle diameter of the particles in the present disclosure is obtained by measuring with a light scattering method or by imaging an electron micrograph of the particles, measuring the particle diameter of a total of 5,000 particles in the photograph, and calculating the average value thereof. For non-spherical particles, the value of particle diameter of spherical particles having the same area as the area of the particles on the photograph is adopted as the particle diameter.

[0835] Unless otherwise specified, the average particle diameter in the present disclosure means a volume average particle diameter.

[0836] The image-recording layer may contain only one kind of particles, particularly, one kind of polymer particles or two or more kinds of polymer particles.

[0837] From the viewpoints of on-press developability and printing durability, the content of particles, particularly, the content of polymer particles in the image-recording layer with respect to the total mass of the image-recording layer is preferably 5% by mass to 90% by mass, more preferably 10% by mass to 90% by mass, even more preferably 20% by mass to 90% by mass, and particularly preferably 50% by mass to 90% by mass.

[0838] In addition, from the viewpoints of on-press developability and printing durability, the content of the polymer particles in the image-recording layer with respect to the total mass of components having a molecular weight of 3,000 or more in the image-recording layer is preferably 20% by mass to 100% by mass, more preferably 35% by mass to 100% by mass, even more preferably 50% by mass to 100% by mass, and particularly preferably 80% by mass to 100% by mass.

[0839] The image-recording layer may contain a binder polymer. As the binder polymer, binder polymers that can be used in an image-recording layer of on-press development type lithographic printing plate precursors can be used. Specifically, as the binder polymer, the binder polymer described in paragraphs 0288 to 0317 of WO2022/019217A can be suitably used.

[0840] In the image-recording layer, one kind of binder polymer may be used alone or two or more kinds thereof may be used in combination.

[0841] The content of the binder polymer to be contained in the image-recording layer can be optionally set, and the content of the binder polymer with respect to the total mass of the image-recording layer is preferably 1% by mass to 90% by mass and more preferably 5% by mass to 80% by mass.

[0842] In a case where the image-recording layer of the present disclosure contains other binder polymers, the content of those other binder polymers with respect to the total mass of the aforementioned thermoplastic resin particles and those other binder polymers is preferably more than 0% by mass and 99% by mass or less, more preferably 20% by mass to 95% by mass, and even more preferably 40% by mass to 90% by mass.

[0843] It is also preferable that the image-recording layer contains an oil agent.

[0844] In the present disclosure, an oil agent refers to a hydrophobic compound that is in a liquid state at 80 C. and is not mixed with water and separates in a case where the compound is mixed with water of the same mass.

[0845] In a case where two or more oil agents are used, the oil agents may include a compound having a melting point of 80 C. or higher as long as the two or more oil agents are in a liquid state at 80 C. in a mixed state.

[0846] In addition, from the viewpoint of on-press developability and dampening water turbidity suppressing property, the oil agent is preferably a compound having a molecular weight less than 1,000, more preferably a compound having a molecular weight of 200 to 800, and particularly preferably a compound having a molecular weight of 300 to 500.

[0847] Furthermore, from the viewpoint of on-press developability and dampening water turbidity suppressing property, the oil agent is preferably a compound having a boiling point of 200 C. or higher at 1 atm, more preferably a compound having a boiling point of 250 C. or higher at 1 atm, even more preferably a compound having a boiling point of 300 C. or higher at 1 atm, and particularly preferably a compound having a boiling point of 400 C. or higher and 500 C. or lower at 1 atm.

[0848] In the present disclosure, unless otherwise specified, boiling point means a boiling point at 1 atm.

[0849] In addition, from the viewpoint of on-press developability and dampening water turbidity suppressing property, the melting point of the oil agent at 1 atm is preferably 50 C. or lower, more preferably 30 C. or lower, and particularly preferably 200 C. or higher and 25 C. or lower.

[0850] In the present disclosure, unless otherwise specified, melting point means a melting point at 1 atm.

[0851] Examples of the oil agent include a phosphoric acid ester compound, an aromatic hydrocarbon compound, a glyceride compound, a fatty acid compound, an aromatic ester compound, and the like.

[0852] Among the above, from the viewpoints of printing durability, receptivity, on-press developability, and dampening water turbidity suppressing property, at least one compound selected from the group consisting of a phosphoric acid ester compound, an aromatic hydrocarbon compound, a glyceride compound, and an aromatic ester compound is preferable, at least one compound selected from the group consisting of a phosphoric acid ester compound, an aromatic hydrocarbon compound, and a glyceride compound is more preferable, at least one compound selected from the group consisting of a phosphoric acid ester compound and an aromatic hydrocarbon compound is even more preferable, and a phosphoric acid ester compound is particularly preferable.

[0853] As the phosphoric acid ester compound, from the viewpoints of printing durability, receptivity, on-press developability, and dampening water turbidity suppressing property, a phosphoric acid triester compound is preferable, a phosphoric acid triaryl ester compound is more preferable, tricresyl phosphate is even more preferable, and a mixture of two or more isomers among three kinds of ortho, meta, and para isomers of tricresyl phosphate is particularly preferable.

[0854] As the aromatic hydrocarbon compound, from the viewpoint of on-press developability and dampening water turbidity suppressing property, a compound having two or more aromatic rings is preferable, and a compound having two or more unfused benzene rings is more preferable.

[0855] As the glyceride compound, from the viewpoint of on-press developability and dampening water turbidity suppressing property, a triglyceride compound is preferable, a fatty oil is more preferable, and a fatty oil which is a liquid at 25 C., such as castor oil, is particularly preferable.

[0856] As the fatty acid compound, from the viewpoint of on-press developability and dampening water turbidity suppressing property, an unsaturated fatty acid is preferable, an unsaturated fatty acid having a carbon number of 8 to 30 is more preferable, and an unsaturated fatty acid having a carbon number of 12 to 24 is particularly preferable.

[0857] As the aromatic ester compound, from the viewpoint of on-press developability and dampening water turbidity suppressing property, an aromatic diester compound is preferable, and an aromatic diester compound having an aliphatic ring is more preferable.

[0858] As the aliphatic ester compound, from the viewpoint of on-press developability and dampening water turbidity suppressing property, an aliphatic ester compound having a branched alkyl group is preferable, and an aliphatic ester compound having a branched alkyl group and a carbon number of 10 to 24 is more preferable.

[0859] From the viewpoints of printing durability, receptivity, on-press developability, and dampening water turbidity suppressing property, the oil agent preferably includes an oil agent having a phosphorus atom, and is more preferably an oil agent having a phosphorus atom.

[0860] In addition, from the viewpoint of on-press developability and dampening water turbidity suppressing property, the oil agent preferably includes an oil agent having an aromatic ring, more preferably includes an oil agent having two or more aromatic rings, and particularly preferably includes an oil agent having two or more unfused benzene rings.

[0861] From the viewpoints of printing durability, receptivity, on-press developability, and dampening water turbidity suppressing property, a ClogP value of the oil agent is preferably 5.0 or more, more preferably 5.50 or more, even more preferably 5.50 or more and 10.0 or less, and particularly preferably 5.60 or more and 7.00 or less.

[0862] The ClogP value is a value obtained by calculating the common logarithm log P of the 1-octanol/water partition coefficient P. For calculating the ClogP value, known methods and software can be used. In the present disclosure, unless otherwise specified, the ClogP program incorporated into ChemBioDraw Ultra 12.0 from CambridgeSoft is used.

[0863] Specific examples of the oil agent include tricresyl phosphate, dimethyl(1-phenylethyl) benzene, 2,4-diphenyl-4-methyl-1-pentene, dicyclohexylphthalate, castor oil, -linolenic acid, tri(2-ethylhexyl) phosphate, and the like.

[0864] One oil agent may be used alone, or two or more oil agents may be used in combination. From the viewpoint of on-press developability and dampening water turbidity suppressing property, it is preferable that the image-recording layer contain two or more oil agents having different structures.

[0865] The content of the oil agent with respect to the total mass of the image-recording layer is preferably 0.0001% by mass to 10.0% by mass, more preferably 0.0002% by mass to 1.0% by mass, even more preferably 0.0005% by mass to 0.5% by mass, and particularly preferably 0.001% by mass to 0.05% by mass.

[0866] The image-recording layer may contain a chain transfer agent. As the chain transfer agent, a chain transfer agent used for an image-recording layer of an on-press development type lithographic printing plate precursor can be used. Specifically, as the chain transfer agent, the chain transfer agents described in paragraphs 0388 to 0393 of WO2022/019217A can be suitably used.

[0867] The chain transfer agent may be used alone or in combination of two or more kinds thereof.

[0868] The content of the chain transfer agent with respect to the total mass of the image-recording layer is preferably 0.01% by mass to 50% by mass, more preferably 0.05% by mass to 40% by mass, and even more preferably 0.1% by mass to 30% by mass.

[0869] In order to improve the ink receptivity, the image-recording layer may contain an oil sensitizing agent. As the oil sensitizing agent, an oil sensitizing agent used for an image-recording layer of an on-press development type lithographic printing plate precursor can be used. Specifically, as the oil sensitizing agent, the oil sensitizing agents described in paragraphs 0395 to 0404 of WO2022/019217A can be suitably used.

[0870] The content of the oil sensitizing agent with respect to the total mass of the image-recording layer is preferably 1% by mass to 40.0% by mass, more preferably 2% by mass to 25.0% by mass, and even more preferably 3% by mass to 20.0% by mass.

[0871] The image-recording layer may contain only one oil sensitizing agent, or two or more oil sensitizing agents may be used in combination.

[0872] One of the preferred aspects of the image-recording layer used in the present disclosure is an aspect in which the image-recording layer contains two or more compounds as an oil sensitizing agent.

[0873] Specifically, from the viewpoint of satisfying both the on-press developability and receptivity, the image-recording layer used in the present disclosure preferably uses all the phosphonium compound, the nitrogen-containing low-molecular-weight compound, and the ammonium group-containing polymer as an oil sensitizing agent, and more preferably uses all the phosphonium compound, the quaternary ammonium salts, and the ammonium group-containing polymer as an oil sensitizing agent.

[0874] The image-recording layer preferably further contains a development accelerator.

[0875] The value of polarity element as an SP value of the development accelerator is preferably 6.0 to 26.0, more preferably 6.2 to 24.0, even more preferably 6.3 to 23.5, and particularly preferably 6.4 to 22.0.

[0876] In the present disclosure, as the value of polarity element as an SP value (solubility parameter, unit: (cal/cm.sup.3).sup.1/2), the value of polarity element p in the Hansen solubility parameters is used. The Hansen solubility parameters are obtained by dividing the solubility parameters introduced by Hildebrand into three components, a dispersion element d, a polarity element p, and a hydrogen bond element h, and expressing the parameters in a three-dimensional space. In the present disclosure, the polarity element p is used.

[0877] p [cal/cm.sup.3] is a dipole-dipole force element in the Hansen solubility parameters, V [cal/cm.sup.3] is a molar volume, and [D] is a dipole moment. As p, the following expression simplified by Hansen and Beerbower is generally used.

[00004] $_{p} = \frac{37.4}{V^{1 / 2}}$

[0878] The development accelerator is preferably a hydrophilic polymer compound or a hydrophilic low-molecular-weight compound.

[0879] In the present disclosure, hydrophilic means that the value of polarity element as an SP value is 6.0 to 26.0, the hydrophilic polymer compound refers to a compound having a molecular weight (weight-average molecular weight in a case where the compound has molecular weight distribution) of 3,000 or more, and the hydrophilic low-molecular-weight compound refers to a compound having a molecular weight (weight-average molecular weight in a case where the compound has molecular weight distribution) of less than 3,000.

[0880] Examples of the hydrophilic polymer compound include a cellulose compound and the like. Among these, a cellulose compound is preferable.

[0881] Examples of the cellulose compound include cellulose or a compound obtained by modifying at least a part of cellulose (that is, modified cellulose compound). Among these, a modified cellulose compound is preferable.

[0882] Preferred examples of the modified cellulose compound include a compound which is obtained by substituting at least some of hydroxy groups of cellulose with at least one kind of group selected from the group consisting of an alkyl group and a hydroxyalkyl group.

[0883] The degree of substitution of the compound, which is obtained by substituting at least some of hydroxy groups of cellulose with at least one kind of group selected from the group consisting of an alkyl group and a hydroxyalkyl group, is preferably 0.1 to 6.0, and more preferably 1 to 4.

[0884] As the modified cellulose compound, an alkyl cellulose compound or a hydroxyalkyl cellulose compound is preferable, and a hydroxyalkyl cellulose compound is more preferable.

[0885] Preferred examples of the alkyl cellulose compound include methyl cellulose.

[0886] Preferred examples of the hydroxyalkyl cellulose compound include hydroxypropyl cellulose.

[0887] The molecular weight of the hydrophilic polymer compound (provided that, weight-average molecular weight in a case where the compound has molecular weight distribution) is preferably 3,000 to 5,000,000, and more preferably 5,000 to 200,000.

[0888] Examples of the hydrophilic low-molecular-weight compound include a glycol compound, a polyol compound, an organic amine compound, an organic sulfonic acid compound, an organic sulfamine compound, an organic sulfuric acid compound, an organic phosphonic acid compound, an organic carboxylic acid compound, a betaine compound, and the like. Among these, a polyol compound, an organic sulfonic acid compound, or a betaine compound is preferable.

[0889] Examples of the glycol compound include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol, and ether or ester derivatives of these compounds.

[0890] Examples of the polyol compound include glycerin, pentaerythritol, tris(2-hydroxyethyl) isocyanurate, and the like.

[0891] Examples of the organic amine compound include triethanolamine, diethanolamine, monoethanolamine, salts of these, and the like.

[0892] Examples of the organic sulfonic acid compound include alkyl sulfonic acid, toluene sulfonic acid, benzene sulfonic acid, salts of these, and the like. Among these, for example, alkyl sulfonic acid having an alkyl group having 1 to 10 carbon atoms is preferable.

[0893] Examples of the organic sulfamine compound include alkylsulfamic acid, salts thereof, and the like.

[0894] Examples of the organic sulfuric acid compound include alkyl sulfate, alkyl ether sulfuric acid, salts of these, and the like.

[0895] Examples of the organic phosphonic acid compound include phenylphosphonic acid, salts thereof, and the like.

[0896] Examples of the organic carboxylic acid compound include tartaric acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid, salts of these, and the like.

[0897] Examples of the betaine compound include a phosphobetaine compound, a sulfobetaine compound, a carboxybetaine compound, and the like. Among these, for example, trimethylglycine is preferable.

[0898] The molecular weight of the hydrophilic low-molecular-weight compound (provided that, weight-average molecular weight in a case where the compound has molecular weight distribution) is preferably 100 or more and less than 3,000, and more preferably 300 to 2,500.

[0899] The development accelerator is preferably a compound having a cyclic structure. The cyclic structure is not particularly limited. Examples thereof include a glucose ring in which at least some of hydroxy groups may be substituted, an isocyanuric ring, an aromatic ring which may have a heteroatom, an aliphatic ring which may have a heteroatom, and the like. Among these, for example, a glucose ring or an isocyanuric ring is preferable.

[0900] Examples of the compound having a glucose ring include the aforementioned cellulose compound.

[0901] Examples of the compound having an isocyanuric ring include the aforementioned tris(2-hydroxyethyl) isocyanurate and the like.

[0902] Examples of the compound having an aromatic ring include the toluene sulfonic acid and benzene sulfonic acid described above, and the like.

[0903] Examples of the compound having an aliphatic ring include a compound which is the aforementioned alkyl sulfate and has an alkyl group having a ring structure, and the like.

[0904] The compound having a cyclic structure preferably has a hydroxy group.

[0905] Preferred examples of the compound having a hydroxy group and a cyclic structure include the aforementioned cellulose compound and the aforementioned tris(2-hydroxyethyl) isocyanurate.

[0906] The development accelerator is preferably an onium salt compound.

[0907] Examples of the onium salt compound include an ammonium compound, a sulfonium compound, and the like. Among these, an ammonium compound is preferable.

[0908] Examples of the development accelerator which is an onium salt compound include trimethylglycine and the like.

[0909] The value of polarity element as an SP value of the onium salt compound in the electron-accepting polymerization initiator is not in a range of 6.0 to 26.0. This onium salt compound is not included in the development accelerator.

[0910] The image-recording layer may contain only one kind of development accelerator, or two or more kinds of development accelerators may be used in combination.

[0911] In the present disclosure, one of the preferred aspects of the image-recording layer is an aspect in which the image-recording layer contains two or more kinds of compounds as the development accelerator.

[0912] Specifically, from the viewpoint of on-press developability and receptivity, the image-recording layer preferably contains, as a development accelerator, the polyol compound and the betaine compound described above, the betaine compound and the organic sulfonic acid compound described above, or the polyol compound and the organic sulfonic acid compound described above.

[0913] The content of the development accelerator with respect to the total mass of the image-recording layer is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, and even more preferably 1% by mass or more and 10% by mass or less.

[0914] From the viewpoint of promoting on-press developability, improving the coating surface, and the like, it is preferable that the image-recording layer contains a surfactant. Examples of the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and fluorine-based surfactants. The surfactants may be used alone or in combination of two or more thereof.

[0915] The nonionic surfactant used in the present disclosure is not particularly limited, and any known nonionic surfactant in the related art can be used. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene-polystyryl phenyl ethers, polyoxyethylene-polyoxypropylene alkyl ethers, partial fatty acid esters of glycerol, partial fatty acid esters of sorbitan, partial fatty acid esters of pentaerythritol, monoesters of fatty acids with propylene glycol, partial fatty acid esters of sucrose, partial fatty acid esters of polyoxyethylene sorbitan, partial fatty acid esters of polyoxyethylene-sorbitol, polyethylene glycol fatty acid esters, partial fatty acid esters of polyglycerol, polyoxyethylated castor oils, partial fatty acid esters of polyoxyethylene glycerol, fatty acid diethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides, polyethylene glycol, and copolymers of polyethylene glycol and polypropylene glycol.

[0916] The anionic surfactant used in the present disclosure is not particularly limited, and any known anionic surfactant in the related art can be used. Examples of the anionic surfactant include fatty acid salts, abietic acid salts, hydroxyalkanesulfonates, alkanesulfonates, dialkylsulfosuccinates, linear alkylbenzenesulfonates, branched alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylphenoxypolyoxyethylene propylsulfonates, polyoxyethylene alkylsulfophenyl ether salts, N-methyl-N-oleyltaurine sodium salts, N-alkylsulfosuccinic acid monoamide disodium salts, petroleum sulfonates, sulfonated tallow oils, sulfuric acid ester salts of fatty acid alkyl esters, alkylsulfuric acid ester salts, polyoxyethylene alkyl ether sulfuric acid ester salts, fatty acid monoglyceride sulfuric acid ester salts, polyoxyethylene alkylphenyl ether sulfuric acid ester salts, polyoxyethylene styrylphenyl ether sulfuric acid ester salts, alkyl phosphate salts, polyoxyethylene alkyl ether phosphate salts, polyoxyethylene alkylphenyl ether phosphate salts, partially saponified products of a styrene/maleic anhydride copolymer, partially saponified products of an olefin/maleic anhydride copolymer, and naphthalene sulfonate/formalin condensates.

[0917] The cationic surfactant used in the present disclosure is not particularly limited, and any known cationic surfactant in the related art can be used. Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.

[0918] The amphoteric surfactant used in the present disclosure is not particularly limited, and any known amphoteric surfactant in the related art can be used. Examples of the amphoteric surfactant include carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfuric acid esters, and imidazolines.

[0919] Among the above-mentioned surfactants, those described as polyoxyethylene can also be read as polyoxyalkylene such as polyoxymethylene, polyoxypropylene, or polyoxybutylene, and those surfactants can also be used in the present disclosure.

[0920] Further preferred examples of the surfactant include a fluorine-based surfactant containing a perfluoroalkyl group in a molecule. Examples of such a fluorine-based surfactant include anionic types such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl phosphates; amphoteric types such as perfluoroalkyl betaines; cationic types such as perfluoroalkyl trimethylammonium salts; and nonionic types such as perfluoroalkyl amine oxides, perfluoroalkyl ethylene oxide adducts, oligomers containing a perfluoroalkyl group and a hydrophilic group, oligomers containing a perfluoroalkyl group and a lipophilic group, oligomers containing a perfluoroalkyl group, a hydrophilic group, and a lipophilic group, and urethanes containing a perfluoroalkyl group and a lipophilic group. In addition, suitable examples thereof also include the fluorine-based surfactants described in JP1987-170950A (JP-S62-170950A), JP1987-226143A (JP-S62-226143A), and JP1985-168144A (JP-S60-168144A).

[0921] In addition to the above-mentioned surfactants, other surfactants can be added, such as amphoteric surfactants as described in JP1984-121044A (JP-S59-121044A) and JP1992-013149A (JP-H04-013149A); siloxane-based compounds as described in EP950517A; fluorine-containing monomer copolymers as described in JP1999-288093A (JP-H11-288093A); and fluorine-based surfactants as described in JP1987-170950A (JP-S62-170950A), in order to broaden the stability of the treatment for the development conditions of the present disclosure or to improve the coating properties, within a range that does not impair the effects of the present disclosure.

[0922] Specific examples of the amphoteric surfactant include alkyl di(aminoethyl)glycine, alkyl polyaminoethyl glycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine, and N-tetradecyl-N,N-betaine type amphoteric surfactant (for example, trade name AMOGEN K, manufactured by DKS Co., Ltd.). A block copolymer of dimethylsiloxane and polyalkylene oxide is preferable as the siloxane-based compound, and specific examples thereof include polyalkylene oxide-modified silicones such as DBE-224, DBE-621, DBE-712, DBP-732, and DBP-534 manufactured by Chisso Corporation, and Tego Glide 100 manufactured by Tego GmbH (Germany).

[0923] Specific examples of commercially available surfactants include the following.

[0924] DOWSIL, XIAMETER, and SYLGARD are registered trademarks. In the following, the description that DOWSIL, XIAMETER, and SYLGARD are registered trademarks will be omitted.

[0925] Examples of products manufactured by Dow Toray Co., Ltd. include DOWSIL BY 16-205, DOWSIL BY 16-849 Fluid, DOWSIL FZ-3710 Fluid, DOWSIL FZ-3760, DOWSIL FZ-3785, DOWSIL SF 8417 Fluid, DOWSILBY 16-891, DOWSILFZ-3789, DOWSILBY 16-839 Fluid, DOWSIL SF 8411 Fluid, DOWSIL SF 8413 Fluid, DOWSIL SF 8421 Fluid, DOWSIL BY 16-880 Fluid, DOWSIL BY 16-201, DOWSIL SF 8427 Fluid, DOWSIL SF 8428 Fluid, DOWSIL 580 WAX, DOWSIL BY 16-606, DOWSIL BY 16-846 Fluid, XIAMETER OFX-0203 Fluid, XIAMETER OFX-0230 Fluid, DOWSIL SF 8416 Fluid, DOWSIL SF 8419 Fluid, DOWSIL 501W Additive, DOWSIL FZ-2110, DOWSIL FZ-2123, DOWSIL L-7001, SYLGARD OFX-0309 Fluid, XIAMETER OFX-5211 Fluid, DOWSIL SF 8410 Fluid, DOWSIL SH 3746 Fluid, DOWSIL SH 8400 Fluid, DOWSIL SH 8700 Fluid, DOWSIL SH 510 Fluid (100 cSt, 500 cSt), DOWSIL SH 550 Fluid, DOWSIL SH 710 Fluid, and DOWSIL FS 1265 Fluid.

[0926] Examples of the product manufactured by Shin-Etsu Chemical Co., Ltd. include KP series of KP-124, KP-109, KP-110, KP-121, KP-118, KP-341, KP-112, KP-125, KP-101, KP-106, KP-120, KP-105, KP-104, KP-611, KP-626, KP-327, KP-323, KP-322, KP-625, KP-623, KP-624, KP-620, and KP-651.

[0927] KP-652, KP-650, KP-310, KP-306, KP-301, KP-621, KP-369, KP-368, KP-126, and the like, KF series, and FL series such as KF-868, KF-865, KF-864, KF-859, KF-393, KF-860, KF-880, KF-8004, KF-8002, KF-8005, KF-867, KF-8021, KF-869, KF-861, KF-877, KF-101, KF-1001, KF-102, KF-1002, KF-1005, KF-2001, KF-2004, KF-99, KF-9901, PAM-E, KF-8010, KF-8012, KF-8008, KF-105, KF-6000, KF-6001, KF-6002, KF-6003, KF-6123, KF-9701, KF-2012, KF-857, KF-862, KF-858, KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-644, KF-6020, KF-6204, KF-6011, KF-6012, KF-6015, KF-6017, KF-410, FL-5, FL-100-100cs, FL-100-450cs, FL-100-1,000cs, FL-100-10,000cs, KF-412, KF-413, KF-414, KF-415, KF-4003, KF-4701, KF-4917, KF-7235B, KF-3935, KF-50-100cs, KF-50-300cs, KF-50-1,000cs, KF-50-3,000cs, KF-53, KF-54, and KF-6004.

[0928] Examples of products of BYK-Chemie GmbH include BYK-300, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313, BYK-315 N, BYK-320, BYK-322, BYK-323, BYK-325 N, BYK-326*, BYK-327*, BYK-330, BYK-331, BYK-333, BYK-342, BYK-345/346, BYK-347, BYK-348, BYK-349, BYK-370, BYK-375, BYK-377, BYK-378, BYK-3450*, BYK-3451*, BYK-3455, BYK-3456*, BYK-3760*, BYK-UV 3500, BYK-UV 3505*, BYK-UV 3510, BYK-UV 3530, BYK-UV 3535*, BYK-UV 3570, BYK-UV 3575*, BYK-UV 3576, BYK-350, BYK-354, BYK-355/356 acrylic copolymer, BYK-358 N/361 N, BYK-381 acrylic copolymer, BYK-392 acrylic copolymer, BYK-394 acrylic copolymer, BYK-3441 acrylic copolymer, BYK-399, BYK-3440*, BYK-3550, BYK-3560*, BYK-3565*, BYK-3566*, BYK-SILCLEAN 3700, BYK-SILCLEAN 3701*, BYK-SILCLEAN 3720, and BYK-DYNWET 800 N.

[0929] As other components, a polymerization inhibitor, a higher fatty acid derivative, a plasticizer, inorganic particles, an inorganic lamellar compound, and the like can be incorporated into the image-recording layer. Specifically, the description in paragraphs 0121 to 0159 of JP2008-284817A can be referred to.

<<Formation of Image-Recording Layer>>

[0930] The image-recording layer in the lithographic printing plate precursor according to the present disclosure can be formed, for example, by preparing a coating liquid by dispersing or dissolving the necessary components described above in a known solvent, coating a support with the coating liquid by a known method such as bar coating, and drying the coating liquid, as described in paragraphs 0142 and 0143 of JP2008-195018A. The coating amount (provided that, solid content) of the image-recording layer after coating and drying varies with uses, but is preferably 0.3 g/m.sup.2 to 3.0 g/m.sup.2. In a case where the coating amount is in this range, excellent sensitivity and excellent film characteristics of the image-recording layer are obtained. As the solvent, known solvents can be used. Specific examples thereof include water, acetone, methyl ethyl ketone (2-butanone), cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3-methoxy-1-propanol, methoxy methoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, -butyrolactone, methyl lactate, ethyl lactate, and the like. Only one solvent may be used, or two or more solvents may be used in combination. The concentration of solid contents in the coating liquid is preferably 1% by mass to 50% by mass.

[0931] The coating amount (provided that, solid content) of the image-recording layer after coating and drying varies with uses. However, from the viewpoint of obtaining excellent sensitivity and excellent film forming characteristics of the image-recording layer, the coating amount is preferably 0.3 g/m.sup.2 to 3.0 g/m.sup.2.

[0932] The film thickness of the image-recording layer in the lithographic printing plate precursor according to the present disclosure is preferably 0.1 m to 3.0 m, and more preferably 0.3 m to 2.0 m.

[0933] In the present disclosure, the film thickness of each layer in the lithographic printing plate precursor is checked by preparing a slice by cutting the lithographic printing plate precursor in a direction perpendicular to the surface of the precursor and observing the cross section of the slice with a scanning electron microscope (SEM).

(Support)

[0934] The lithographic printing plate precursor according to the present disclosure has a support.

[0935] The support to be used can be appropriately selected from known supports for a lithographic printing plate precursor.

[0936] As the support, a support having a hydrophilic surface is preferable.

[0937] As the support in the present disclosure, an aluminum plate is preferable which has been roughened using a known method and has undergone an anodization treatment. That is, the support in the present disclosure preferably has an aluminum plate and an aluminum anodic oxide film disposed on the aluminum plate.

[0938] In addition, it is preferable that the support has an aluminum plate and an anodic oxide film of aluminum disposed on the aluminum plate, the anodic oxide film is at a position closer to a side of the image-recording layer than the aluminum plate and has micropores extending in a depth direction from the surface of the anodic oxide film on the side of the image-recording layer, and the average diameter of the micropores within the surface of the anodic oxide film is more than 10 nm and 100 nm or less.

[0939] Furthermore, it is preferable that the micropores are each configured with a large diameter portion that extends to a position at a depth of 10 nm to 1,000 nm from the surface of the anodic oxide film and a small diameter portion that is in communication with a bottom portion of the large diameter portion and extends to a position at a depth of 20 nm to 2,000 nm from a communicate position, an average diameter of the large diameter portion within the surface of the anodic oxide film is preferably 15 nm to 100 nm, and an average diameter of the small diameter portion at the communicate position is preferably 13 nm or less.

[0940] FIG. 1 is a schematic cross-sectional view of an embodiment of an aluminum support 12a.

[0941] The aluminum support 12a has a laminated structure in which an aluminum plate 18 and an anodic oxide film 20a of aluminum (hereinafter, also simply called anodic oxide film 20a) are laminated in this order. The anodic oxide film 20a in the aluminum support 12a is positioned such that the anodic oxide film 20a is closer to the image-recording layer side than the aluminum plate 18. That is, it is preferable that the lithographic printing plate precursor according to the present disclosure have at least an anodic oxide film, an image-recording layer, and a water-soluble resin layer in this order on an aluminum plate.

Anodic Oxide Film

[0942] Hereinafter, preferred aspects of the anodic oxide film 20a will be described.

[0943] The anodic oxide film 20a is a film prepared on a surface of the aluminum plate 18 by an anodization treatment. This film has substantially uniformly distributed ultrafine micropores 22a approximately perpendicular to the surface of the film. The micropores 22a extend from a surface of the anodic oxide film 20a on the image-recording layer side (that is, a surface of the anodic oxide film 20a opposite to the aluminum plate 18) along the thickness direction (that is, toward the aluminum plate 18).

[0944] The average diameter (that is, average opening diameter) of the micropores 22a on the surface of the anodic oxide film 20a is preferably more than 10 nm and 100 nm or less. Particularly, from the viewpoint of balance between printing durability, antifouling properties, and image visibility, the average diameter of the micropores 22a is more preferably 15 nm to 60 nm, even more preferably 20 nm to 50 nm, and particularly preferably 25 nm to 40 nm. The internal diameter of the pores may be larger or smaller than the pore diameter within the surface layer.

[0945] In a case where the average diameter is more than 10 nm, printing durability and image visibility are excellent. In addition, in a case where the average diameter is 100 nm or less, printing durability is excellent.

[0946] The average diameter of the micropores 22a is a value determined by observing the surface of the anodic oxide film 20a with a field emission scanning electron microscope (FE-SEM) at 150,000 magnification (N=4), measuring the size (provided that, diameter) of 50 micropores existing in a range of 400 nm600 nm in the obtained 4 images, and averaging the measured sizes.

[0947] In a case where the shape of the micropores 22a is not circular, the equivalent circular diameter is used. Equivalent circular diameter is a diameter determined on an assumption that the opening portion is in the form of a circle having the same projected area as the projected area of the opening portion.

[0948] The shape of the micropores 22a is not particularly limited. In FIG. 1, the micropores 22a have a substantially straight tubular shape (that is, provided that cylindrical shape). However, the micropores 22a may have a conical shape that tapers along the depth direction (thickness direction). In addition, the shape of the bottom portion of the micropores 22a is not particularly limited, and may be a curved (convex) or flat surface shape.

[0949] In the support, the micropores may be each composed of a large diameter portion that extends to a position at a certain depth from the surface of the anodic oxide film and a small diameter portion that is in communication with a bottom portion of the large diameter portion and extends to a position at a certain depth from the communicate position.

[0950] For example, as shown in FIG. 2, an aspect may be adopted in which an aluminum support 12b includes an aluminum plate 18 and an anodic oxide film 20b having micropores 22b each composed of a large diameter portion 24 and a small diameter portion 26. For example, the micropores 22b in the anodic oxide film 20b are each composed of the large diameter portion 24 that extends to a position at a depth of 10 nm to 1,000 nm (depth D: see FIG. 2) from the surface of the anodic oxide film and the small diameter portion 26 that is in communication with the bottom portion of the large diameter portion 24 and further extends from the communicate position to a position at a depth of 20 nm to 2,000 nm. Specifically, for example, it is possible to use the aspect described in paragraphs 0107 to 0114 of JP2019-162855A.

<<Method of Producing Support>>

[0951] As a manufacturing method of the support used in the present disclosure, for example, a manufacturing method is preferable in which the following steps are sequentially performed. [0952] Roughening treatment step: step of performing roughening treatment on aluminum plate [0953] Anodization treatment step: step of subjecting aluminum plate having undergone roughening treatment to anodic oxidation [0954] Pore widening treatment step: step of bringing aluminum plate having anodic oxide film obtained by anodization treatment step into contact with aqueous acid solution or aqueous alkali solution such that diameter of micropores in anodic oxide film increases

[0955] Hereinafter, the procedure of each step will be specifically described.

<<Roughening Treatment Step>>

[0956] The roughening treatment step is a step of performing a roughening treatment including an electrochemical roughening treatment on the surface of the aluminum plate. This step is preferably performed before the anodization treatment step which will be described later. However, in a case where the surface of the aluminum plate already has a preferable shape, the roughening treatment step may not be performed. This step can be carried out by the method described in paragraphs 0086 to 0101 of JP2019-162855A.

<<Anodization Treatment Step>>

[0957] The procedure of the anodization treatment step is not particularly limited as long as the aforementioned micropores can be obtained. Examples thereof include known methods.

[0958] In the anodization treatment step, an aqueous solution of sulfuric acid, phosphoric acid, oxalic acid, or the like can be used as an electrolytic cell. For example, the concentration of sulfuric acid is 100 g/L to 300 g/L.

[0959] The conditions of the anodization treatment are appropriately set depending on the electrolytic solution used. For example, the liquid temperature is 5 C. to 70 C. (preferably 10 C. to 60 C.), the current density is 0.5 A/dm.sup.2 to 60 A/dm.sup.2 (preferably 1 A/dm.sup.2 to 60 A/dm.sup.2), the voltage is 1 V to 100 V (preferably 5 V to 50 V), the electrolysis time is 1 second to 100 seconds (preferably 5 seconds to 60 seconds), and the film amount is 0.1 g/m.sup.2 to 5 g/m.sup.2 (preferably 0.2 g/m.sup.2 to 3 g/m.sup.2).

<<Pore Widening Treatment>>

[0960] The pore widening treatment is a treatment of enlarging the diameter of micropores (that is, the pore diameter) present in the anodic oxide film formed by the aforementioned anodization treatment step (that is, the pore diameter enlarging treatment).

[0961] The pore widening treatment can be carried out by bringing the aluminum plate obtained by the aforementioned anodization treatment step into contact with an aqueous acid solution or an aqueous alkali solution. The contact method is not particularly limited, and examples thereof include a dipping method and a spraying method.

[0962] As necessary, the support may have a backcoat layer on the side opposite to the image-recording layer, the backcoat layer containing the organic polymer compound described in JP1993-045885A (JP-H5-45885A) or the alkoxy compound of silicon described in JP1994-035174A (JP-H6-35174A).

[0963] The lithographic printing plate precursor according to the present disclosure preferably has an undercoat layer (also called interlayer in some cases) between the image-recording layer and the support. The undercoat layer enhances the adhesiveness between the support and the image-recording layer in an exposed portion, and enables the image-recording layer to be easily peeled from the support in a non-exposed portion. Therefore, the undercoat layer inhibits the deterioration of printing durability and contributes to the improvement of developability. In addition, in the case of exposure to infrared laser, the undercoat layer functions as a heat insulating layer and thus brings about an effect of preventing sensitivity reduction resulting from the diffusion of heat generated by exposure to the support.

[0964] Examples of compounds that are used in the undercoat layer include polymers having adsorbent groups that can be adsorbed onto the surface of the support and hydrophilic groups. In order to improve adhesiveness to the image-recording layer, it is preferable that polymers having adsorbent groups and hydrophilic groups further have crosslinkable groups. The compounds that are used in the undercoat layer may be low-molecular-weight compounds or polymers. As necessary, as the compounds that are used in the undercoat layer, two or more compounds may be used by being mixed together.

[0965] In a case where the compound used in the undercoat layer is a polymer, a copolymer of a monomer having an adsorbent group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group is preferable.

[0966] As the adsorbent group that can be adsorbed onto the surface of the support, a phenolic hydroxy group, a carboxy group, PO.sub.3H.sub.2, OPO.sub.3H.sub.2, CONHSO.sub.2, SO.sub.2NHSO.sub.2, and COCH.sub.2COCH.sub.3 are preferable. As the hydrophilic groups, a sulfo group or salts thereof and salts of a carboxy group are preferable. As the crosslinking groups, an acryl group, a methacryl group, an acrylamide group, a methacrylamide group, an allyl group, and the like are preferable.

[0967] The polymer may have a crosslinking group introduced by the formation of a salt of a polar substituent of the polymer and a compound that has a substituent having charge opposite to that of the polar substituent and an ethylenically unsaturated bond, or may be further copolymerized with monomers other than the monomers described above and preferably with hydrophilic monomers.

[0968] Specifically, for example, silane coupling agents having addition polymerizable ethylenic double bond reactive groups described in JP1998-282679A (JP-H10-282679A) and phosphorus compounds having ethylenic double bond reactive groups described in JP1990-304441A (JP-H02-304441A) are suitable. The low-molecular-weight compounds or polymer compounds having crosslinking groups (preferably ethylenically unsaturated bonding groups), functional groups that interact with the surface of the support, and hydrophilic groups described in JP2005-238816A, JP2005-125749A, JP2006-239867A, and JP2006-215263A are also preferably used.

[0969] For example, the high-molecular-weight polymers having adsorbent groups that can be adsorbed onto the surface of the support, hydrophilic groups, and crosslinkable groups described in JP2005-125749A and JP2006-188038A are more preferable.

[0970] The content of ethylenically unsaturated bonding group in the polymer used in the undercoat layer is preferably 0.1 mmol to 10.0 mmol per gram of the polymer, and more preferably 0.2 mmol to 5.5 mmol per gram of the polymer.

[0971] The weight-average molecular weight (Mw) of the polymer used in the undercoat layer is preferably 5,000 or more and more preferably 10,000 to 300,000.

[0972] In order to prevent contamination with the passage of time, the undercoat layer may contain, in addition to the compounds for the undercoat layer described above, a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, a compound having an amino group or a functional group capable of inhibiting polymerization and a group that interacts with the surface of the support (for example, 1,4-diazabicyclo[2.2.2]octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, hydroxyethyl ethylenediaminetriacetic acid, dihydroxyethyl ethylenediaminediacetic acid, hydroxyethyl iminodiacetic acid, and the like), and the like.

[0973] The undercoat layer is formed by known coating methods. The coating amount (provided that, solid content) of the undercoat layer is preferably 0.1 mg/m.sup.2 to 100 mg/m.sup.2 and more preferably 1 mg/m.sup.2 to 30 mg/m.sup.2.

[0974] The lithographic printing plate precursor according to the present disclosure may have an outermost layer (also called protective layer or overcoat layer in some cases) on a surface of the image-recording layer that is opposite to the support side.

[0975] It is preferable that the lithographic printing plate precursor according to the present disclosure have a support, an image-recording layer, and an outermost layer in this order.

[0976] The outermost layer may have a function of suppressing the reaction inhibiting image formation by blocking oxygen, a function of preventing the damage of the image-recording layer, and a function of preventing ablation during exposure to high-illuminance lasers.

[0977] As the outermost layer, a well-known outermost layer (protective layer or overcoat layer) in an on-press development type lithographic printing plate precursor can be used. Specifically, as the outermost layer, the outermost layer described in paragraphs 0444 to 0462 of WO2022/019217A can be suitably used.

[0978] The lithographic printing plate precursor according to the present disclosure may have other layers in addition to those mentioned above.

[0979] Known layers can be adopted as those other layers without particular limitations. For example, as necessary, a backcoat layer may be provided on a surface of the support that is opposite to the image-recording layer side.

(Method of Preparing Lithographic Printing Plate and Lithographic Printing Method)

[0980] It is possible to prepare a lithographic printing plate by performing image exposure and a development treatment on the lithographic printing plate precursor according to the present disclosure.

[0981] The method of preparing a lithographic printing plate according to the present disclosure preferably includes a step of exposing the on-press development type lithographic printing plate precursor according to the present disclosure in an imagewise manner (hereinafter, this step will be also called exposure step) and a step of removing the image-recording layer in a non-image area by supplying at least one material selected from the group consisting of a printing ink and dampening water on a printer (hereinafter, this step will be also called on-press development step).

[0982] The lithographic printing method according to the present disclosure preferably includes a step of exposing the on-press development type lithographic printing plate precursor according to the present disclosure in an imagewise manner (that is, exposure step), a step of removing the image-recording layer in a non-image area on a printer by supplying at least one material selected from the group consisting of a printing ink and dampening water such that a lithographic printing plate is prepared (that is, on-press development step), and a step of performing printing using the obtained lithographic printing plate (that is, printing step).

[0983] The method of preparing a lithographic printing plate according to the present disclosure preferably includes a step of exposing an on-press development type lithographic printing plate precursor to an infrared laser in an imagewise manner and a step of removing an image-recording layer in a non-image area by supplying at least one material selected from the group consisting of printing ink and dampening water on a printer, in which the on-press development type lithographic printing plate precursor preferably has a support and an image-recording layer on the support, the image-recording layer preferably contains an infrared absorber capable of donating electrons to the aforementioned initiator and a color forming substance precursor, and in a case where the image-recording layer is exposed to an infrared laser with a wavelength of 830 nm at an energy density of 110 mJ/cm.sup.2, a brightness change L of the image-recording layer before and after the exposure is preferably 3.0 or more.

[0984] Furthermore, the method of preparing a lithographic printing plate according to the present disclosure preferably includes a step of exposing an on-press development type lithographic printing plate precursor to an infrared laser in an imagewise manner and a step of removing an image-recording layer in a non-image area by supplying at least one material selected from the group consisting of printing ink or dampening water on a printer, in which the on-press development type lithographic printing plate precursor has a support and an image-recording layer on the support, the image-recording layer preferably contains an initiator, an infrared absorber, and a color forming substance precursor, and the image-recording layer preferably satisfies Expression L.

2.0L1L0Expression L

[0985] In Expression L, L1 represents visibility of the image-recording layer, L0 represents the visibility of the image-recording layer from which the aforementioned color forming substance precursor has been removed.

[0986] Furthermore, regarding the lithographic printing method according to the present disclosure, for example, it is preferable that each of the above aspects include an aspect in which the lithographic printing method further includes the printing step described above.

[0987] Hereinafter, regarding the method of preparing a lithographic printing plate according to the present disclosure and the lithographic printing method according to the present disclosure, preferred aspects of each step will be described in order. Note that the lithographic printing plate precursor according to the present disclosure can also be developed using a developer.

[0988] Hereinafter, the exposure step and the on-press development step in the method of preparing a lithographic printing plate will be described. The exposure step in the method of preparing a lithographic printing plate according to the present disclosure is the same step as the exposure step in the lithographic printing method according to the present disclosure. Furthermore, the on-press development step in the method of preparing a lithographic printing plate according to the present disclosure is the same step as the on-press development step in the lithographic printing method according to the present disclosure.

[0989] The method of preparing a lithographic printing plate according to the present disclosure preferably includes an exposure step of exposing the lithographic printing plate precursor according to the present disclosure in an imagewise manner such that an exposed portion and a non-exposed portion are formed. The lithographic printing plate precursor according to the present disclosure is preferably exposed to a laser through a transparent original picture having a linear image, a halftone dot image, or the like or exposed in an imagewise manner by laser light scanning according to digital data, or the like.

[0990] The wavelength of a light source to be used is preferably 750 nm to 1,400 nm. As the light source having a wavelength of 750 nm to 1,400 nm, a solid-state laser or a semiconductor laser that radiates infrared rays is suitable. In a case where an infrared laser is used, the output is preferably 100 mW or higher, the exposure time per pixel is preferably 20 microseconds or less, and the amount of irradiation energy is preferably 10 mJ/cm.sup.2 to 300 mJ/cm.sup.2. In addition, in order to shorten the exposure time, a multibeam laser device is preferably used. The exposure mechanism may be any of an inner surface drum method, an external surface drum method, a flat head method, or the like.

[0991] The image exposure can be carried out by a common method using a platesetter or the like. In the case of on-press development, image exposure may be carried out on a printer after the lithographic printing plate precursor is mounted on the printer.

<On-Press Development Step>

[0992] The method of preparing a lithographic printing plate according to the present disclosure preferably includes an on-press development step of removing the image-recording layer in a non-image area by supplying at least one selected from the group consisting of printing ink and dampening water on a printer.

[0993] Hereinafter, the on-press development method will be described.

[On-Press Development Method]

[0994] In the on-press development method, the lithographic printing plate precursor having undergone image exposure is preferably supplied with an oil-based ink and an aqueous component on a printer such that the image-recording layer in a non-image area is removed and a lithographic printing plate is prepared.

[0995] That is, in a case where the lithographic printing plate precursor is subjected to image exposure and then mounted as it is on a printer without being subjected to any development treatment, or the lithographic printing plate precursor is mounted on a printer and then subjected to image exposure on the printer, and then an oil-based ink and an aqueous component are supplied to perform printing, at the initial stage in the middle of printing, in a non-image area, by either or both of the supplied oil-based ink and the aqueous component, a non-cured image-recording layer is dissolved or dispersed to remove, and the hydrophilic surface is exposed in the non-image area. Meanwhile, the image-recording layer cured by exposure forms an oil-based ink-receiving area having a lipophilic surface in the exposed portion. What is supplied first to the precursor surface may be any of the oil-based ink or the aqueous component. However, in view of preventing the plate from being contaminated by the components of the image-recording layer from which aqueous components are removed, it is preferable that the oil-based ink be supplied first. In the manner described above, the lithographic printing plate precursor is subjected to on-press development on a printer and used as it is for printing a number of sheets. As the oil-based ink and the aqueous component, ordinary printing ink and ordinary dampening water for lithographic printing are suitably used.

[0996] As the laser used for performing image exposure on the lithographic printing plate precursor according to the present disclosure, a light source having a wavelength of 300 nm to 450 nm or 750 nm to 1,400 nm is preferably used. A light source of 300 nm to 450 nm is preferable for a lithographic printing plate precursor including an image-recording layer containing sensitizing dye having maximum absorption in such a wavelength range. As the light source of 750 nm to 1,400 nm, those described above are preferably used. As the light source of 300 nm to 450 nm, a semiconductor laser is suitable.

[0997] The lithographic printing method according to the present disclosure includes a printing step of printing a recording medium by supplying a printing ink to the lithographic printing plate.

[0998] The printing ink is not particularly limited, and various known inks can be used as desired. In addition, preferred examples of the printing ink include oil-based ink or ultraviolet-curable ink (that is, UV ink).

[0999] In the printing step, as necessary, dampening water may be supplied.

[1000] Furthermore, the printing step may be successively carried out after the on-press development step without stopping the printer.

[1001] The recording medium is not particularly limited, and a known recording medium can be used as desired.

[1002] In the method of preparing a lithographic printing plate from the lithographic printing plate precursor according to the present disclosure and in the lithographic printing method according to the present disclosure, as necessary, the entire surface of the lithographic printing plate precursor may be heated before exposure, in the middle of exposure, or during a period of time from exposure to development. In a case where the lithographic printing plate precursor is heated as above, an image-forming reaction in the image-recording layer is accelerated, which can result in advantages such as improvement of sensitivity and printing durability, stabilization of sensitivity, and the like. Heating before development is preferably carried out under a mild condition of 150 C. or lower. In a case where this aspect is adopted, it is possible to prevent problems such as curing of a non-image area. For heating after development, it is preferable to use an extremely severe condition which is preferably in a range of 100 C. to 500 C. In a case where this aspect is adopted, a sufficient image-strengthening action is obtained, and it is possible to inhibit problems such as the deterioration of the support or the thermal decomposition of the image area.

[1003] All of the compounds represented by Formula (I) and Formula (II) are novel compounds, and can be suitably used as an electron-donating polymerization initiator.

[1004] Details and preferred aspects of the compound represented by Formula (I) and the compound represented by Formula (II) as the novel compounds are the same as the matters described in the description of the borate compound represented by Formula (1) or the borate compound represented by Formula (Ia) described above.

[1005] Among these, examples of the suitable novel compounds include compounds represented by B-7, B-25, B-26, B-29, or B-30.

##STR00126##

EXAMPLES

[1006] Hereinafter, the present disclosure will be described in detail with reference to examples, but the present disclosure is not limited thereto. In the present examples, unless otherwise specified, % and part mean % by mass and part by mass respectively. Unless otherwise described, the molecular weight of a high-molecular-weight compound is a weight-average molecular weight (Mw), and the ratio of repeating structural units of a polymer compound is expressed as molar percentage. In addition, the weight-average molecular weight (Mw) is a polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC).

[1007] Hereinafter, a synthesis example of the borate compound represented by Formula (1) will be shown. The structure identification of each compound was performed by a nuclear magnetic resonance (NMR) method.

Example 1-1: Synthesis of Compound B-2

[1008] To 1.2 g of magnesium, 22 g of tetrahydrofuran and 0.01 g of iodine were added, and magnesium was activated while stirring. 1-Bromo-4-tert-butylbenzene 8.1 g was added thereto to prepare a Grignard reagent. 7.8 g of a trifluoroborane-diethyl ether complex (46%) was diluted with 22 g of toluene. 10 mL of a phenylmagnesium bromide-diethyl ether solution (3 M), 3.5 mL of p-methoxyphenylmagnesium bromide (1 M), and 3.5 mL of p-methylphenylmagnesium bromide (1 M) were added thereto. Thereafter, the mixture was stirred at room temperature for 30 minutes, and the above-described Grignard reagent was added thereto.

[1009] After confirming the completion of the reaction, the mixture was added to a saturated sodium carbonate aqueous solution, the solvent was distill off from a tetrahydrofuran (THF) layer, and the residue was dissolved in toluene to obtain 2 g of a white solid.

Examples 1-2 to 1-20: Synthesis of Compounds B-3 to B-5, B-7 to B-17, B-20, B-21, B-24, B-26, B-29, and B-30

[1010] Each compound was synthesized in the same manner as in Example 1-1, except that the p-isopropylphenylboronic acid was changed to a boronic acid corresponding to each compound.

Example 1-21: Synthesis of Compound B-25

[1011] 5 g of p-tert-butylphenylboronic acid, 7.5 g of methyl orthoformate, and 0.4 g of concentrated hydrochloric acid were added thereto, and the mixture was stirred at room temperature, and methanol and methyl formate, which are reaction by-products, were distilled off.

[1012] 50 mL of p-fluorophenylmagnesium bromide (1 M) was added thereto, and the temperature was raised to 60 C. After confirming the completion of the reaction, the mixture was added to a saturated sodium carbonate aqueous solution, the solvent was distilled off from a THF layer, and the residue was dissolved in toluene to obtain 3 g of a white solid.

Examples 1-22 and 1-23: Synthesis of Compounds B-27 and B-28

[1013] Compounds B-27 and B-28 were synthesized by the same method as in Example 1-21, except that the corresponding bromide and the iodonium salt were changed in Example 1-21.

Example 1-24: Synthesis of Compound B-34

[1014] To 1.2 g of magnesium, 22 g of tetrahydrofuran and 0.01 g of iodine were added, and magnesium was activated while stirring. 1-Bromo-4-tert-butylbenzene 8.1 g was added thereto to prepare a Grignard reagent. 7.8 g of a trifluoroborane-diethyl ether complex (46%) was diluted with 22 g of toluene. 29 mL of a phenylmagnesium bromide-diethyl ether solution (3 M) was added thereto, and the mixture was stirred at room temperature for 30 minutes, and the above-described Grignard reagent was added thereto. After confirming the completion of the reaction, the mixture was added to a saturated sodium carbonate aqueous solution, the solvent was distilled off from a THF layer, and the residue was dissolved in toluene to obtain 4.5 g of a white solid. 1 g of the white solid and 1 g of the following infrared absorber (IR-3) were dissolved in 8 mL of acetone, and the solution was added to 24 mL of methanol. After filtering the obtained crystals, the crystals were washed with methanol to obtain 1 g of a compound B-31.

Examples 1-25 to 1-34: Synthesis of Compounds B-35 to B-44

[1015] Compounds B-35 to B-44 were synthesized by the same method as in Example 1-24, except that the corresponding borate compound and the infrared absorber described later were used in Example 1-24.

[1016] For the borate compounds other than those described above, the reaction was performed using the corresponding boronic acid compound and the magnesium bromide compound as raw materials to obtain a target compound, with reference to the above-described method.

[1017] Hereinafter, a synthesis example of the compound represented by Formula (1a) will be shown. The structure identification of each compound was performed by a nuclear magnetic resonance (NMR) method.

Example 2-1: Synthesis of Compound B-19

[1018] To 1.2 g of magnesium, 22 g of tetrahydrofuran and 0.01 g of iodine were added, and magnesium was activated while stirring.

[1019] 1-Bromo-4-tert-butylbenzene 8.1 g was added thereto to prepare a Grignard reagent.

[1020] 3.9 g of a trimethoxyborane-diethyl ether complex (46%) was diluted with 22 g of toluene, and 29 mL of a phenylmagnesium bromide-diethyl ether solution (3 M) was added thereto. After stirring at room temperature for 30 minutes, the above-described Grignard reagent was added thereto.

[1021] After confirming the completion of the reaction, the mixture was added to a saturated sodium carbonate aqueous solution, and 20 g of Bis(4-tert-butylphenyl)iodonium hexafluorophosphate was further added thereto. Then, the solvent was distilled off from the THF layer, and the residue was dissolved in methanol to obtain 5 g of a white solid.

Example 2-2: Synthesis of Compound B-18

[1022] Compound B-18 was synthesized in the same manner as in Example 2-1, except that the corresponding bromide and the iodonium salt were changed in Example 2-1.

Example 2-3: Synthesis of Compound B-45

[1023] Compound B-45 was synthesized in the same manner as in Example 2-1, except that Bis(4-tert-butylphenyl)iodonium hexafluorophosphate was changed to (4-octoxyphenyl)-(2,4,6-trimethoxyphenyl)iodonium 4-methylbenzenesulfonate in Example 2-1.

Example 2-4: Synthesis of Compound B-46

[1024] Compound B-46 was synthesized in the same manner as in Example 2-1, except that 1-bromo-4-tert-butylbenzene was changed to 1-bromo-4-methylbenzene in Example 2-1.

[1025] For the borate compounds other than those described above, the reaction was performed using the corresponding bromide and the iodonium salt as raw materials to obtain a target compound, with reference to the above-described method.

Examples 3-1 to 3-52, Examples 4-1 to 4-11, and Comparative Examples 1-1 to 1-4 and 2-1

(a) Alkaline Etching Treatment

[1026] An aqueous solution of caustic soda having a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass was sprayed onto the aluminum plate at a temperature of 70 C., thereby performing an etching treatment. Then, rinsing was performed by means of spraying. The amount of dissolved aluminum within the surface to be subjected to the electrochemical roughening treatment later was 5 g/m.sup.2.

(b) Desmutting Treatment Using Aqueous Acidic Solution (First Desmutting Treatment)

[1027] Next, a desmutting treatment was performed using an acidic aqueous solution. In the desmutting treatment, a 150 g/L aqueous sulfuric acid solution was used as the aqueous acidic solution. The liquid temperature was 30 C. The desmutting treatment was performed for 3 seconds by spraying the acidic aqueous solution onto the aluminum plate. Then, a water washing treatment was performed.

[1028] Next, an electrochemical roughening treatment was performed using alternating current and an electrolytic solution having a hydrochloric acid concentration of 14 g/L, an aluminum ion concentration of 13 g/L, and a sulfuric acid concentration of 3 g/L. The liquid temperature of the electrolytic solution was 30 C. The aluminum ion concentration was adjusted by adding aluminum chloride.

[1029] The waveform of the alternating current was a sine wave in which positive and negative waveforms are symmetrical, the frequency was 50 Hz, the ratio of the anodic reaction time and the cathodic reaction time in one cycle of the alternating current was 1:1, and the current density was 75 A/dm.sup.2 in terms of the peak current value of the alternating current waveform. In addition, the quantity of electricity was 450 C/dm.sup.2 which was the total quantity of electricity used for the aluminum plate to have an anodic reaction, and the electrolysis treatment was performed 4 times by conducting electricity of 112.5 C/dm.sup.2 for 4 seconds at each treatment session. A carbon electrode was used as the counter electrode of the aluminum plate. Then, a water washing treatment was performed.

(d) Alkaline Etching Treatment

[1030] An aqueous solution of caustic soda having a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass was sprayed onto the aluminum plate having undergone the electrochemical roughening treatment at a temperature of 45 C., thereby performing an etching treatment. The amount of dissolved aluminum within the surface having undergone the electrochemical roughening treatment was 0.2 g/m.sup.2. Then, a water washing treatment was performed.

(e) Desmutting Treatment Using Aqueous Acidic Solution

[1031] Next, a desmutting treatment was performed using an acidic aqueous solution. Specifically, the desmutting treatment was performed for 3 seconds by spraying the aqueous acidic solution onto the aluminum plate. In the desmutting treatment, an aqueous solution having a sulfuric acid concentration of 170 g/L and an aluminum ion concentration of 5 g/L was used as aqueous acidic solution. The liquid temperature was 30 C.

(f) First-Stage Anodization Treatment

[1032] By using an anodization treatment device 610 for direct current electrolysis having the structure shown in FIG. 3, a first-stage anodization treatment (also called first anodization treatment) was performed. Specifically, the first anodization treatment was performed under the conditions described in the column of First anodization treatment shown in the following Table 1, thereby forming an anodic oxide film having a predetermined film amount.

[1033] Hereinafter, the anodization treatment device 610 shown in FIG. 3 will be described.

[1034] In the anodization treatment device 610 shown in FIG. 3, an aluminum plate 616 is transported as indicated by the arrow in FIG. 3. In a power supply tank 612 storing an electrolytic solution 618, the aluminum plate 616 is positively (+) charged by a power supply electrode 620. Further, the aluminum plate 616 is transported upward by a roller 622 in the power supply tank 612, redirected downward by a nip roller 624, transported toward an electrolytic treatment tank 614 in which an electrolytic solution 626 is stored, and redirected to the horizontal direction by a roller 628. Next, the aluminum plate 616 is negatively () charged by an electrolysis electrode 630 so that an anodic oxide film is formed on the surface thereof, and the aluminum plate 616 coming out of the electrolytic treatment tank 614 is transported to the next step. In the anodization treatment device 610, the roller 622, the nip roller 624, and the roller 628 constitute a direction change unit. Furthermore, in the inter-tank portion between the power supply tank 612 and the electrolytic treatment tank 614, the aluminum plate 616 is transported in a ridge shape and an inverted U shape by the rollers 622, 624, and 628. The power supply electrode 620 and the electrolysis electrode 630 are connected to a direct current power source 634.

(g) Pore Widening Treatment

[1035] Under the conditions shown in the following Table 1, the aluminum plate having undergone the above anodization treatment was immersed in an aqueous solution of caustic soda at a temperature of 40 C. and having a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass, thereby performing a pore widening treatment. Then, rinsing was performed by means of spraying.

(h) Second Anodization Treatment

[1036] By using the anodization treatment device 610 for direct current electrolysis having the structure shown in FIG. 3, a second-stage anodization treatment (also called second anodization treatment) was performed. Specifically, the second anodization treatment was performed under the conditions described in the column of Second anodization treatment shown in the following Table 1, thereby forming an anodic oxide film having a predetermined film amount.

[1037] By the above method, a support was prepared.

[1038] For the obtained support, Table 2 shows the brightness L* of the micropores within the surface of the anodic oxide film in the L*a*b* color system, the average diameter and depth of the large diameter portion of the micropores within the surface of the oxide film, the average diameter (nm) and depth of the small diameter portion of the micropores at a communicate position, the depth (nm) of the large diameter portion and the small diameter portion, the micropore density, and the thicknesses of the anodic oxide film (also called film thicknesses) from the bottom portion of the small diameter portion to the surface of the aluminum plate.

[1039] In Table 1, film amount (AD) in the column of the first anodization treatment and film amount (AD) in the column of second anodization treatment represent the amount of film obtained by each treatment. As electrolytic solutions, the aqueous solutions containing the components in Table 1 were used.

TABLE-US-00001 TABLE 1 First anodization treatment Concentration Current Film Kind of Component of component Temperature density Time amount liquid of liquid (g/L) ( C.) (A/dm.sup.2) (s) (g/m.sup.2) Support Phosphate H.sub.3PO.sub.4 15 35 4.5 12 1 Pore widening treatment Temperature Time Component of liquid ( C.) (s) NaOH 5%/Al 0.5% 40 C. 3 s Second anodization treatment Concentration Current Film Kind of Component of component Temperature density Time amount liquid of liquid (g/L) ( C.) (A/dm.sup.2) (s) (g/m.sup.2) Sulfuric H.sub.2SO.sub.4/Al 170/5 50 15 10.5 1.4 acid

TABLE-US-00002 TABLE 2 Large diameter portion Average Small diameter portion diameter of Average Micropore Average bottom diameter at density Film diameter portion Depth communicate Depth (number/ thickness Brightness (nm) (nm) Shape (nm) position (nm) Shape (nm) m.sup.2) (nm) L* Support 35 35 Straight 100 10 Straight 570 320 1,000 80 tubular tubular shape shape

[1040] In Example 3-47, the following support B was used.

[1041] The following treatment was performed on an aluminum plate (aluminum alloy plate) having a thickness of 0.3 mm and a material 1S to produce a support 1. A rinsing treatment was performed between all the treatment steps. After the rinsing treatment, water was drained using a nip roller.

Alkaline etching treatment (1)

[1042] An aqueous solution of caustic soda having a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass was sprayed onto the aluminum plate at a temperature of 70 C., thereby performing an etching treatment. Then, rinsing was performed by means of spraying. The amount of dissolved aluminum within the surface to be subjected to the electrochemical roughening treatment later was 5 g/m.sup.2.

Desmutting Treatment (1) Using Acidic Aqueous Solution

[1043] Next, a desmutting treatment was performed using an acidic aqueous solution. Specifically, the desmutting treatment was performed for 3 seconds by spraying the aqueous acidic solution onto the aluminum plate. In the desmutting treatment, a 150 g/L aqueous sulfuric acid solution was used as the aqueous acidic solution. The liquid temperature was 30 C.

Hydrochloric Acid Electrolytic Treatment

[1044] Next, a hydrochloric acid electrolytic treatment was performed using an alternating current with an electrolytic solution having a hydrochloric acid concentration of 13 g/L, an aluminum ion concentration of 15 g/L, and a sulfuric acid concentration of 1.0 g/L. The liquid temperature of the electrolytic solution was 25 C. The aluminum ion concentration was adjusted by adding aluminum chloride.

[1045] The waveform of the alternating current was a sine wave in which the positive and negative waveforms were symmetrical, the frequency was 50 Hz, the ratio between the anodic reaction time and the cathodic reaction time in one cycle of the alternating current was 1:1, and the current density was 35 A/dm.sup.2 in terms of the peak current value of the alternating current waveform. Further, the sum of the electricity quantity for the anodic reaction of the aluminum plate was 320 C/dm.sup.2, and the electrolytic treatment was performed four times at energization intervals of 2.5 seconds for each electric quantity of 80 C/dm.sup.2. A carbon electrode was used as the counter electrode of the aluminum plate. Then, a water washing treatment was performed.

Alkaline Etching Treatment (2)

[1046] An aqueous solution of caustic soda having a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass was sprayed onto the aluminum plate after the hydrochloric acid electrolysis treatment at a temperature of 45 C. to perform an etching treatment. The amount of aluminum dissolved in the surface subjected to the hydrochloric acid electrolytic treatment was 0.1 g/m.sup.2. Then, a water washing treatment was performed.

Desmutting Treatment (2) Using Acidic Aqueous Solution

[1047] Next, a desmutting treatment was performed using an acidic aqueous solution. Specifically, the desmutting treatment was performed for 3 seconds by spraying the aqueous acidic solution onto the aluminum plate. In the desmutting treatment, an aqueous solution having a sulfuric acid concentration of 170 g/L and an aluminum ion concentration of 5 g/L was used as aqueous acidic solution. The liquid temperature was 35 C.

First-Stage Anodization Treatment

[1048] By using the anodization treatment device for direct current electrolysis having the structure shown in FIG. 3, a first-stage anodization treatment was performed. By using a 170 g/L aqueous sulfuric acid solution as an electrolytic solution, an anodization treatment was performed under the conditions of a liquid temperature of 40 C. and a current density of 20 A/dm.sup.2, thereby forming an anodic oxide film having a film amount of 0.3 g/m.sup.2.

Pore Widening Treatment

[1049] The aluminum plate having undergone the anodization treatment was immersed in an aqueous solution of caustic soda having a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass for 5 seconds at 40 C., thereby performing a pore widening treatment. Then, rinsing was performed by means of spraying.

Second-Stage Anodization Treatment

[1050] By using the anodization treatment device for direct current electrolysis having the structure shown in FIG. 3, a second-stage anodization treatment was performed. By using a 170 g/L aqueous sulfuric acid solution as an electrolytic solution, an anodization treatment was performed under the conditions of a liquid temperature of 50 C. and a current density of 13 A/dm.sup.2, thereby forming an anodic oxide film having a film amount of 3.5 g/m.sup.2.

Silicate Treatment

[1051] The aluminum plate having undergone the second anodization treatment was immersed in a No. 3 sodium silicate aqueous solution having a concentration of 5% by mass and a liquid temperature of 65 C. for 12 seconds, thereby obtaining a support B. The amount of Si attached to the support B was 21 mg/m.sup.2.

[1052] The obtained support was coated with the undercoat layer coating liquid A or B having the following composition such that the dry coating amount was 0.1 g/m.sup.2. In this way, an undercoat layer was formed.

Undercoat Layer Coating Liquid A

[1053] The undercoat layer coating liquid A was prepared by mixing the following compositional components. [1054] Compound for undercoat layer (following U-1, 11% aqueous solution): 0.0788 parts [1055] Hydroxyethyl diiminodiacetic acid: 0.0280 parts [1056] Sodium ethylenediaminetetraacetate tetrahydrate: 0.0499 parts [1057] Surfactant (EMALEX (registered trademark) 710, NUION EMULSION Co., Ltd.): 0.0016 parts [1058] Preservative (BIOHOPE L, manufactured by KI Chemical Industry Co., LTD.): 0.0015 parts [1059] Water: 2.8701 parts

Undercoat Layer Coating Liquid B

[1060] The undercoat layer coating liquid B was prepared by mixing the following compositional components. [1061] Compound for undercoat layer (following U-1, 11% aqueous solution): 0.0788 parts [1062] Sodium gluconate: 0.0700 parts [1063] Surfactant (EMALEX (registered trademark) 710, NUION EMULSION Co., Ltd.): 0.0016 parts [1064] Preservative (BIOHOPE L, manufactured by KI Chemical Industry Co., LTD.): 0.0015 parts [1065] Water: 2.870 parts

##STR00127##

[1066] In Examples 3-3, 3-4, 3-8 to 3-38, 3-40 to 3-52, 4-1 to 4-11, and Comparative Examples 1-1 to 1-4 and 2-1, the image-recording layer coating liquid was bar-coated on the undercoat layer, and dried in an oven at 120 C. for 40 seconds to form an image-recording layer having a dry coating amount of 1.0 g/m.sup.2.

[1067] In the examples other than those described above, the image-recording layer coating liquid was bar-coated on the support, and dried in an oven at 120 C. for 40 seconds to form an image-recording layer having a dry coating amount of 1.0 g/m.sup.2.

Image-Recording Layer Coating Liquid

[1068] The image-recording layer coating liquid was prepared by mixing the following compositional components. [1069] Electron-donating polymerization initiators listed in Tables 3 to 9: amounts listed in Tables 3 to 9 [1070] Infrared absorbing agents listed in Tables 3 to 9: amounts listed in Tables 3 to 9. [1071] Electron-accepting polymerization initiators listed in Tables 3 to 9: amounts listed in Tables 3 to 9 [1072] Polymerizable compounds listed in Tables 3 to 9: amounts listed in Tables 3 to 9. [1073] Polymer particles described in Tables 3 to 9: amount described in Tables 3 to 9 [1074] Binder polymers listed in Tables 3 to 9: amounts listed in Tables 3 to 9 [1075] Color developing agent described in Tables 3 to 9: amount described in Tables 3 to 8 [1076] Phenothiazine: amount described in Tables 3 to 9 [1077] Oily agent (tricresyl phosphate (triphenyl phosphate)): amount described in Tables 3 to 9 [1078] Surfactant described in Table 4: amount described in Table 4 [1079] Anionic surfactant (A-1): 0.0162 parts [1080] Fluorine-based surfactant (W-1): 0.0042 parts [1081] 2-Butanone: 5.3155 parts [1082] 1-Methoxy-2-propanol: 2.8825 parts [1083] Methanol: 2.3391 parts

[1084] The electron-donating polymerization initiator (that is, the specific borate compound or the comparative compound) described in Tables 3 to 9 is as follows in detail.

##STR00128## ##STR00129## ##STR00130## ##STR00131## ##STR00132## ##STR00133## ##STR00134## ##STR00135## ##STR00136##

[Infrared Absorber]

[1085] IR-1 to IR-17: Compounds having the following structures

##STR00137## ##STR00138## ##STR00139## ##STR00140##

[Electron-Accepting Polymerization Initiator]

[1086] Int-1: compound having the following structure [1087] Int-2: compound having the following structure [1088] Int-3: compound having the following structure [1089] Int-4: compound having the following structure [1090] Int-5: compound having the following structure

##STR00141##

[Polymerizable Compound]

[1091] M-1: compound having the following structure [1092] M-2: Compound having the following structure [1093] M-3: dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer Company Inc) M-4: urethane acrylate (U-15HA, manufactured by Shin-Nakamura Chemical Co., Ltd.) [1094] M-5: Monomer synthesized by the following synthesis method

##STR00142##

[1095] A mixed solution of TAIKENATE D-160N (polyisocyanate trimethylolpropane adduct, manufactured by Mitsui Chemicals, Inc., 4.7 parts), ARONIX M-403 (manufactured by TOAGOSEI Co., Ltd., amount yielding the ratio of NCO value of TAKENATE D-160N:hydroxyl number of ARONIX M-403=1:1), t-butylbenzoquinone (0.02 parts), and methyl ethyl ketone (11.5 parts) was heated at 65 C. NEOSTAN U-600 (bismuth-based polycondensation catalyst, manufactured by NITTO KASEI Co., Ltd., 0.11 parts) was added to the reaction solution, and the reaction solution was heated at 65 C. for 4 hours. The reaction solution was cooled to room temperature (25 C.), and methyl ethyl ketone was added thereto, thereby synthesizing a urethane acrylate solution having a solid content of 50% by mass. By using recycling GPC (instrument: LC908-C60, column: JAIGEL-1H-40 and 2H-40 (manufactured by Japan Analytical Industry Co., Ltd.)) and tetrahydrofuran (THF) as an eluent, molecular weight fractionation of the urethane acrylate solution (M-5) was performed. The weight-average molecular weight was 20,000.

[Polymer Particles]

[1096] Microgel (polymer particles R-1): 2.640 parts [1097] Distilled water: 2.425 parts The microgel was prepared by the following method.

Preparation of Polyvalent Isocyanate Compound

[1098] Bismuth tris(2-ethylhexanoate) (NEOSTAN U-600, manufactured by NITTO KASEI CO., LTD., 0.043 parts) was added to an ethyl acetate (25.31 g) suspension solution of 17.78 parts (80 molar equivalents) of isophorone diisocyanate and 7.35 parts (20 molar equivalents) of the following polyhydric phenol compound (1), and the obtained solution was stirred. The reaction temperature was set to 50 C. at a point in time when heat release subsided, and the solution was stirred for 3 hours, thereby obtaining an ethyl acetate solution of the polyvalent isocyanate compound (1) (50% by mass).

##STR00143##

Preparation of Microgel

[1099] The following oil phase components and the water phase component were mixed with each other and emulsified at 12,000 rpm (revolution per minute) for 10 minutes using a homogenizer. The obtained emulsion was stirred at 45 C. for 4 hours, 5.20 g of a 10% by mass aqueous solution of 1,8-diazabicyclo[5.4.0]undec-7-ene-octylate (U-CAT SA102, manufactured by San-Apro Ltd.) was added thereto, and the solution was stirred at room temperature for 30 minutes and left to stand at 45 C. for 24 hours. Distilled water was added thereto such that the concentration of solid contents was adjusted to 20% by mass, thereby obtaining an aqueous dispersion of microgel. The average particle diameter thereof measured by a light scattering method was 0.20 m.

Oil-Phase Component

[1100] (Component 1) ethyl acetate: 12.0 parts [1101] (Component 2) an adduct obtained by addition of trimethylolpropane (6 molar equivalents), xylene diisocyanate (18 molar equivalents), and polyoxyethylene having one methylated terminal (1 molar equivalent, the number of repeating oxyethylene units: 90) (50% by mass ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.): 3.76 parts [1102] (Component 3) polyvalent isocyanate compound (1) (as 50% by mass ethyl acetate solution): 15.0 parts [1103] (Component 4) 65% by mass ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer Company Inc.): 11.54 parts [1104] (Component 5) 10% by mass ethyl acetate solution of sulfonate type surfactant (PIONIN A-41-C, manufactured by TAKEMOTO OIL & FAT Co., Ltd.): 4.42 parts

Water-Phase Component

[1105] Distilled water: 46.87 parts

Preparation of Oil-Phase Component

[1106] A polyfunctional isocyanate compound (PM-200: manufactured by Wanhua Chemical Group Co., Ltd.): 6.66 g, a 50% by mass ethyl acetate solution of TAKENATE (registered trademark) D-116N (adduct of trimethylolpropane (TMP)), m-xylylene diisocyanate (XDI), and polyethylene glycol monomethyl ether (EO90) (following structure) manufactured by Mitsui Chemicals, Inc.: 5.46 g, a 65% by mass ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer Company Inc.): 11.24 g, ethyl acetate: 14.47 g, and PIONIN (registered trademark) A-41-C manufactured by TAKEMOTO OIL & FAT Co., Ltd.: 0.45 g were mixed together and stirred at room temperature (25 C.) for 15 minutes, thereby obtaining an oil-phase component.

##STR00144##

Preparation of Water-Phase Component

[1107] As a water-phase component, 47.2 g of distilled water was prepared.

Microcapsule Forming Step

[1108] The oil-phase component and the water-phase component were mixed together, and the obtained mixture was emulsified at 12,000 rpm for 16 minutes by using a homogenizer, thereby obtaining an emulsion.

[1109] Distilled water (16.8 g) was added to the obtained emulsion, and the obtained liquid was stirred at room temperature for 10 minutes.

[1110] After stirring, the liquid was heated at 45 C., and stirred for 4 hours in a state of being kept at 45 C. such that ethyl acetate was distilled away from the liquid. Then, a 10% by mass aqueous solution of 5.12 g of 1,8-diazabicyclo[5.4.0]undeca-7-ene-octylate (U-CAT SA102, manufactured by San-Apro Ltd.) was added thereto, and the solution was stirred at room temperature for 30 minutes and left to stand at 45 C. for 24 hours. Distilled water was added thereto such that the concentration of solid contents was adjusted to 20% by mass, thereby obtaining an aqueous dispersion of polymer particles R-2. R-2 had a volume average particle diameter of 165 nm that was measured using a laser diffraction/scattering-type particle diameter distribution analyzer LA-920 (manufactured by HORIBA, Ltd.).

[1111] Dispersion unit: the following compound B-1 (n=45): 10.0 parts, 85.0 parts of distilled water, and 240.0 parts of n-propanol were added to a four-neck flask, and the mixture was heated and stirred at 70 C. in a nitrogen atmosphere.

[1112] Then, a mixture of the following compound A-1: 20.0 parts, the following compound A-2: 70.0 parts, and 0.7 parts of 2,2-azobisisobutyronitrile that were mixed together in advance was added dropwise for 2 hours to the four-neck flask.

[1113] After the dropwise addition ended, the reaction continued for 5 hours, then 0.5 parts of 2,2-azobisisobutyronitrile was added thereto, and the solution was heated to 80 C. The reaction was performed for a total of 19 hours by adding 0.4 parts of 2,2-azobisisobutyronitrile every 6 hours.

[1114] The reaction solution was left to cool to room temperature (25 C.), thereby obtaining a dispersion (solid content 23%) of polymer particles R-3.

##STR00145##

[1115] The polymer particles R-3 had a median diameter of 150 nm and a coefficient of variation of 23%.

[1116] Furthermore, the dispersibility of the polymer particles R-3 was checked by the method described above. As a result, the resin particles R-3 were found to be water-dispersible and organic solvent-dispersible particles.

[Binder Polymer]

[1117] P-1: Polyvinyl alcohol, S-LEC BX-5Z manufactured by SEKISUI CHEMICAL Co., Ltd. [1118] P-2: Polyvinyl alcohol, S-LEC BL10 manufactured by SEKISUI CHEMICAL CO., LTD. [1119] P-3: Resin synthesized by the following synthesis method

[1120] 1-Methoxy-2-propanol (78.0 parts) was weighed, put into a three-neck flask, and heated to 70 C. under a nitrogen stream. A mixed solution consisting of BLEMMER PME-100 (methoxydiethylene glycol monomethacrylate, manufactured by NOF CORPORATION.): 52.1 parts, methyl methacrylate: 21.8 parts, methacrylic acid: 14.2 parts, hexakis(3-mercaptopropionic acid)dipentaerythritol: 2.15 parts, V-601 (dimethyl 2,2-azobis(isobutyrate), manufactured by FUJIFILM Wako Pure Chemical Corporation): 0.38 parts, 1-methoxy-2-propanol: 54 parts was added dropwise to the reaction vessel for 2 hours and 30 minutes. After dropwise addition ended, the solution was heated to 80 C., and the reaction was continued for 2 more hours. A mixed solution consisting of V-601: 0.04 parts and 1-methoxy-2-propanol: 4 parts was added to the aforementioned mixed solution, the obtained mixed solution was heated to 90 C., and the reaction was continued for 2.5 hours. After the reaction ended, the reaction solution was cooled to room temperature.

[1121] 1-Methoxy-2-propanol: 137.2 parts, 4-hydroxytetramethylpiperidine-N-oxide: 0.24 parts, glycidyl methacrylate: 26.0 parts, and tetraethylammonium bromide: 3.0 parts were added to the reaction solution, and the reaction solution was well stirred and heated at 90 C.

[1122] After 18 hours, the reaction solution was cooled to room temperature (25 C.), and then 1-methoxy-2-propanol: 99.4 parts was added thereto for dilution.

[1123] The binder polymer P-3 obtained in this way had a concentration of solid contents of 23% by mass and a weight-average molecular weight of 35,000 measured by GPC and expressed in terms of polystyrene.

##STR00146##

[Color Developing Agent]

[1124] S-1: a compound having the following structure [1125] S-2: a compound having the following structure [1126] S-3: a compound having the following structure [1127] S-5: a compound having the following structure [1128] S-6: a compound having the following structure [1129] S-7: a compound having the following structure

##STR00147## ##STR00148##

[Surfactant]N

[1130] Anionic surfactant (A-1): the following compound [1131] Fluorine-based surfactant (W-1): the following compound [1132] Surfactant (W-2): following compound [1133] The surfactant (W-2) is a compound described in WO2024-117242A. [1134] Surfactant (W-3): MEGAFACE (registered trademark) EFS-241 (manufactured by DIC Corporation)

##STR00149##

[1135] The outermost layer coating liquid was bar-coated on the image-recording layer of each of Examples and each of Comparative Examples, and dried in an oven at 120 C. for 60 seconds to form an outermost layer having a dry coating amount of 0.41 g/m.sup.2.

[1136] After the above-described steps, the on-press development type lithographic printing plate precursor of each of Examples and each of Comparative Examples was obtained.

Outermost Layer Coating Liquid

[1137] The following components were dissolved or dispersed in deionized water, the solid content was adjusted to 20% by mass, thereby preparing an outermost layer coating liquid. [1138] Water-soluble polymer (polyvinyl alcohol, Mowiol 4-88 manufactured by KURARAY CO., LTD.): 250 parts by mass [1139] Hydrophobic polymer (aqueous polyvinylidene chloride dispersion, Diofan (registered trademark) A50 manufactured by Solvin S.A.): 250 parts by mass [1140] Surfactant (nonionic surfactant, Lutensol (registered trademark) A8 manufactured by BASF SE): 10 parts by mass [1141] Inorganic lamellar compound dispersion liquid shown below: amount described in Tables 3 to 9 [1142] Discoloring compound: type and amount described in Tables 3 to 9

[Inorganic Lamellar Compound Dispersion Liquid]

[1143] Synthetic mica (SOMASIF ME-100 manufactured by Co-op Chemical Co., Ltd., 6.4 parts) was added to 193.6 parts of deionized water and was dispersed using a homogenizer until the average particle diameter (the laser scattering method) reached 3 m. The aspect ratio of the obtained dispersed particles was 100 or more.

[Discoloring Compound]

[1144] wIR-1: compound represented by the following structure [1145] wIR-3: compound represented by the following structure

##STR00150##

[Suppressing Property of Development Defect Over Time]

[1146] The lithographic printing plate precursor of 62 cm40 cm was passed through a nip roller 50 times, and then 30 sheets of interleaving paper and 30 sheets of the lithographic printing plate precursor were alternately laminated, and a protective material (protective sheet: moisture content of 10% by mass) of 62 cm40 cm0.65 mm was further superimposed on the upper and lower surfaces, and the resultant was packaged with aluminum craft paper. The packaged article was left to stand in an environment of 50 C. for 20 days to produce a laminate. In all the laminates, the lithographic printing plate precursors were laminated with the support side facing down. The following evaluations were performed using a lithographic printing plate precursor which was in contact with a protective material at the uppermost portion of the obtained laminate through an interleaving paper.

[1147] The obtained lithographic printing plate precursor was exposed with Luxel (registered trademark) PLATESETTER T-6000III manufactured by FUJIFILM Corporation, equipped with an infrared semiconductor laser, under conditions of an outer drum rotation speed of 1,000 rpm, a laser output of 70%, and a resolution of 2,400 dpi (dot per inch). The exposure image included a solid image, a fine linear image (a test chart in which the thickness of the fine line (fine line-shaped image area in the non-image area) was changed at intervals of 2 m from 4 m to 30 m), and a 50% halftone dot chart of a 20 m dot FM screen.

[1148] The moisture content (equilibrium moisture content) of the protective material was measured by a measuring method according to JIS P 8202.

[1149] The obtained exposed precursor was mounted to the plate cylinder of a printer LITHRONE26 (manufactured by KOMORI Corporation) without performing a development treatment. On-press development was performed by supplying dampening water and ink according to a standard automatic printing start method of LITHRONE26 using dampening water in which the volume ratio of Ecolity-2 (manufactured by Fujifilm Corporation) to tap water was 2/98 and Values-G(N) BLACK INK (manufactured by DIC Graphics Corporation), and then printing was performed on 100 sheets of Tokubishi Art (manufactured by Mitsubishi Paper Mills, Ltd., ream weight: 76.5 kg) paper at a printing speed of 10,000 sheets per hour. The evaluation standard was as follows.

Evaluation Criteria

[1150] No contamination in non-image area: A [1151] Contamination in non-image area cannot be confirmed by visual observation, but can be confirmed by using a loupe: B [1152] Contamination in non-image area can be confirmed by visual observation: C [1153] Contamination of 30% or more in non-image area: D

[Printing Durability]

[1154] In Luxel PLATESETTER T-6000III manufactured by FUJIFILM Corporation that was equipped with an infrared semiconductor laser, the obtained lithographic printing plate precursor was exposed under the conditions of an outer drum rotation speed of 1,000 rpm, a laser output of 70%, and resolution of 2,400 dpi. The exposure image included a solid image and a 50% halftone dot chart of a 20 m dot frequency modulation (FM) screen.

[1155] The obtained exposed lithographic printing plate precursor was mounted to the plate cylinder of a printer LITHRONE26 (manufactured by KOMORI Corporation) without performing a development treatment. On-press development was performed by supplying dampening water and ink according to a standard automatic printing start method of LITHRONE26 using dampening water in which the volume ratio of Ecolity-2 (manufactured by Fujifilm Corporation) to tap water was 2/98 and Values-G(N) BLACK INK (manufactured by DIC Graphics Corporation), and then printing was performed on 100 sheets of Tokubishi Art (ream weight: 76.5 kg, manufactured by Mitsubishi Paper Mills, Ltd.) paper at a printing speed of 10,000 sheets per hour.

[1156] Printing was continued, and based on the number of printed sheets at a point in time when it was visually confirmed that the density of the solid image began to decrease, printing durability was evaluated. It can be said that the larger the number of sheets, the better the printing durability.

[Developability Over Time]

[1157] The obtained lithographic printing plate precursor was humidified for 1 hour in an environment at 25 C. and 80% RH. Thirty sheets of the lithographic printing plate precursors including interleaving paper interposed therebetween were laminated, and the obtained laminate was packaged with craft aluminum vapor-deposited paper. The gap was completely stopped up with a gummed tape to prevent outside air from entering and to make an airtight state. Then, the packaged laminate was left to stand for 4 days in a thermostatic chamber at a temperature set to 50 C. The laminate was taken out of the thermostatic chamber, cooled to room temperature (25 C.), and then the package was opened. By using the middle (15th) lithographic printing plate precursor, temporal on-press developability was evaluated based on the following evaluation standard. By using Magnus 800 Quantum manufactured by Kodak Japan Ltd. that was equipped with an infrared semiconductor laser, the lithographic printing plate precursor prepared as above was exposed under the conditions of output of 27 W, an outer drum rotation speed of 450 rpm, and a resolution of 2,400 dpi (dots per inch, 1 inch is equal to 2.54 cm) (irradiation energy equivalent to 110 mJ/cm.sup.2). The exposure image included a solid image and an amplitude modulation screen (AM screen) as a 50% halftone dot chart. The obtained exposed precursor was mounted on a Kikuban-sized cylinder of a printer SX-74 manufactured by Heidelberger Druckmaschinen AG without being developed. This printer was connected to a 100 L-capacity dampening water circulation tank having a non-woven fabric filter and a temperature control device. A circulation device was filled with dampening water (80 L) containing 2.0% dampening water S-Z1 (manufactured by FUJIFILM Corporation), and T&K UV OFS K-HS black GE-M (manufactured by T&K TOKA Co., Ltd.) was used as printing ink. The dampening water and ink were supplied by a standard automatic printing start method, and then printing was performed on 200 sheets of TOKUBISHI art paper (ream weight: 76.5 kg, manufactured by MITSUBISHI PAPER MILLS LIMITED.) at a printing speed of 10,000 sheets/hour. During the on-press development described above, the number of printing papers used until no ink was transferred to a non-image area was measured (hereinafter, also called number of sheets of on-press development). It can be said that the smaller the number of sheets of on-press development, the better the on-press developability. During the on-press development described above, the number of printing papers used until no ink was transferred to a non-image area was measured as the on-press developability. It can be said that the smaller the number of printing papers, the better the on-press developability.

[Visibility]

[1158] In Trendsetter 3244VX manufactured by Creo that was equipped with a water cooling-type 40 W infrared semiconductor laser, each of the obtained lithographic printing plate precursors was exposed under the conditions of an output of 11.5 W, an outer drum rotation speed of 220 rpm, and a resolution of 2,400 dots per inch (dpi, 1 inch=25.4 mm). The exposure was carried out in an environment of 25 C. and 50% RH.

[1159] Immediately after exposure, the color formation of the lithographic printing plate precursor was measured. The measurement was performed by the specular component excluded (that is, SCE) method by using a spectrocolorimeter CM2600d and operation software CM-S100W manufactured by Konica Minolta, Inc. The color developability is evaluated based on a difference L between the L* value of the exposed portion and the L* value of the unexposed portion using the L* value (that is, brightness) of the L*a*b* color system. It can be said that the larger the value of L, the better the color developability.

[Solvent Solubility]

[1160] The image-recording layer coating liquid obtained by mixing the compositional components and the amounts thereof described in Table 9 was stored at 25 C. for 3 days. Thereafter, the precipitate precipitated on the bottom surface was visually confirmed. The evaluation standard was as follows.

Evaluation Criteria

[1161] No precipitation: A [1162] 1 to 3 precipitates: B [1163] 4 or more precipitations: C

TABLE-US-00003 TABLE 3 Example Example Example Example Example Example Example Example 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 Undercoat layer A A A Image- Electron-accepting Kind Int-1 Int-1 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 recording polymerization Additive 60 60 109 109 100 109 109 109 layer initiator amount Infrared absorber Kind IR-11 IR-10 IR-9 IR-9 IR-9 IR-11 IR-4 IR-2 Additive 26 26 17.5 17.5 15 30 23 17.5 amount Electron-donating Kind B-4 B-4 B-3 B-5 B-6 B-7 B-9 B-11 polymerization Additive 50 50 20 80 25 25 25 50 initiator amount Polymerizable compound Kind M-1/ M-1/ M-4 M-4 M-4 M-4 M-4 M-4 M-2 M-2 Additive 250/250 250/250 212 212 300 300 300 212 amount Polymer particle Kind R-1 R-1 R-1 R-1 R-1 R-1 (solid amount) Additive 400 400 400 400 400 400 amount Binder polymer Kind P-1 P-2 Additive 150 150 amount Color developing Kind S-5 S-3 S-3 S-2 S-2 S-6 S-1 agent Additive 30 40 40 60 60 30 40 amount Phenothiazine Additive amount Oil agent Additive 45 12.5 12.5 8 12.5 12.5 12.5 amount Overcoat Discoloring Kind wIR-1 wIR-1 wIR-3 layer compound Additive 20 20 20 amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of A A B A C A A A development defect over time Printing durability 7.5 7.5 6.0 8.0 6.0 7.5 7.5 7.5 (10000 sheets) Example Example Example Example Example Example Example 3-9 3-10 3-11 3-44 3-45 3-46 3-47 Undercoat layer A A A A A A A Image- Electron-accepting Kind Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 recording polymerization Additive 109 109 109 30 30 30 109 layer initiator amount Infrared absorber Kind IR-2 IR-2 IR-2 IR-13 IR-14 IR-15 IR-9 Additive 17.5 17.5 17.5 30 30 50 17.5 amount Electron-donating Kind B-12 B-13 B-14 B-5 B-5 B-5 B-5 polymerization Additive 50 50 50 30 90 30 80 initiator amount Polymerizable compound Kind M-4 M-4 M-4 M-4 M-4 M-4 M-4 Additive 212 212 212 212 212 212 212 amount Polymer particle Kind R-1 R-1 R-1 R-1 R-1 R-1 R-1 (solid amount) Additive 400 400 400 400 400 400 400 amount Binder polymer Kind Additive amount Color developing Kind S-1 S-1 S-1 S-1 S-1 S-1 S-3 agent Additive 40 40 40 5 5 5 40 amount Phenothiazine Additive amount Oil agent Additive 12.5 12.5 12.5 12.5 12.5 12.5 12.5 amount Overcoat Discoloring Kind layer compound Additive amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of A A A A A A A development defect over time Printing durability 7.5 7.5 7.5 8 7.5 7.5 8.5 (10000 sheets)

TABLE-US-00004 TABLE 4 Example Example Example Example Example 3-48 3-49 3-50 3-51 3-52 Undercoat layer A A A A A Image-recording Electron-accepting Kind Int-3 Int-3 Int-3 layer polymerization initiator Additive 109 109 109 amount Infrared absorber Kind IR-2 IR-3 IR-2 IR-3 IR-2 IR-3 IR-16 IR-17 Additive 1.3 17.5 1.3 17.5 1.3 17.5 30 30 amount Electron-donating Kind B-5 B-5 B-5 B-47 B-48 polymerization initiator Additive 50 50 50 90 90 amount Polymerizable compound Kind M-5 M-5 M-5 M-5 M-5 Additive 212 212 212 212 212 amount Polymer particle Kind R-1 R-1 R-1 R-1 R-1 (solid amount) Additive 400 400 400 400 400 amount Binder polymer Kind Additive amount Color developing agent Kind S-1 S-1 S-1 S-1 S-1 Additive 40 40 20 40 40 amount Phenothiazine Additive 25 amount Surfactant Additive 12.5 12.5 5 10 10 amount Electron-accepting Kind W-1 W-2 W-3 W-3 W-3 polymerization initiator Additive 4.2 2.0 3.5 3.5 3.5 amount Overcoat layer Discoloring compound Kind Additive amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of development defect A A A C C over time Printing durability (10000 sheets) 8.0 8.0 8.0 6.0 6.0

TABLE-US-00005 TABLE 5 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple ple ple ple ple ple ple ple ple ple 3-12 3-13 3-14 3-15 3-16 3-17 3-18 3-19 3-20 3-21 Undercoat layer A A A A A A A A A A Image- Electron-accepting Kind Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 recording polymerization Additive 109 109 109 109 109 109 109 109 109 109 layer initiator amount Infrared absorber Kind IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 Additive 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 amount Electron-donating Kind B-15 B-16 B-17 B-18 B-19 B-20 B-21 B-22 B-23 B-24 polymerization Additive 50 50 50 50 50 50 50 50 50 50 initiator amount Polymerizable Kind M4 M-4 M-4 M-4 M-4 M-4 M-4 M-4 M-4 M-4 compound Additive 212 212 212 212 212 212 212 212 212 212 amount Polymer particle Kind R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 (solid amount) Additive 400 400 400 400 400 400 400 400 400 400 amount Binder polymer Kind Additive amount Color developing Kind S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 agent Additive 40 40 40 40 40 40 40 40 40 40 amount Phenothiazine Additive amount Oil agent Additive 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 amount Overcoat Discoloring compound Kind layer Additive amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of A A A B B B A C B A development defect over time Printing durability (10000 7.5 7.5 7.5 7.5 7.5 6.0 7.5 7.5 7.5 6.0 sheets) Compar- Compar- ative ative Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple ple ple ple ple ple ple ple ple ple 3-22 3-23 3-24 3-25 3-26 3-27 3-28 3-29 1-1 1-2 Undercoat layer A A A A A A A A A A Image- Electron-accepting Kind Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 recording polymerization Additive 109 109 109 109 109 109 109 109 109 109 layer initiator amount Infrared absorber Kind IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 Additive 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 amount Electron-donating Kind B-1 B-2 B-8 B-26 B-27 B-28 B-29 B-30 C-1 C-2 polymerization Additive 50 50 50 50 50 50 50 50 50 50 initiator amount Polymerizable Kind M-4 M-4 M-4 M-4 M-4 M-4 M-4 M-4 M-4 M-4 compound Additive 212 212 212 212 212 212 212 212 212 212 amount Polymer particle Kind R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 (solid amount) Additive 400 400 400 400 400 400 400 400 400 400 amount Binder polymer Kind Additive amount Color developing Kind S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 agent Additive 40 40 40 40 40 40 40 40 40 40 amount Phenothiazine Additive amount Oil agent Additive 12.5 12.5 12.5 12.5 12.5 12.5 12.5 125 12.5 12.5 amount Overcoat Discoloring compound Kind layer Additive amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of B B A A A B A A D D development defect over time Printing durability (10000 6.0 6.0 7.5 7.0 7.0 6.0 7.5 7.5 7 5.0 sheets)

TABLE-US-00006 TABLE 6 Example Example Example Example Example Example 3-30 3-31 3-32 3-33 3-34 3-35 Undercoat layer A A A A A A Image- Electron-accepting polymerization Kind Int-4/Int-5 Int-4/Int-5 recording initiator Additive amount 50/50 50/50 layer Infrared absorber Kind IR-2 IR-2 IR-2 IR-2 IR-2 IR-2 Additive amount 15 15 15 15 15 15 Electron-donating polymerization Kind B-18 B-31/B-32 B-6 B-33/B-19 B-45 B-46 initiator Additive amount 100 50/50 100 50/50 100 100 Polymerizable compound Kind M-3 M-3 M-3 M-3 M-3 M-3 Additive amount 300 300 300 300 300 300 Polymer particle Kind R-3 R-3 R-3 R-3 R-3 R-3 (solid amount) Additive amount 400 400 400 400 400 400 Binder polymer Kind Additive amount Color developing agent Kind S-2 S-2 S-2 S-2 S-2 S-2 Additive amount 40 40 40 40 40 40 Phenothiazine Additive amount 25 25 25 25 Oil agent Additive amount 5 5 5 5 5 5 Overcoat Discoloring compound Kind layer Additive amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of development defect over time A A B A A A Printing durability (10000 sheets) 8.0 8.0 7.0 8.5 8.0 8.0

TABLE-US-00007 TABLE 7 Example Example Example Example 3-36 3-37 3-38 3-39 Undercoat layer A B A Image-recording Electron-accepting polymerization Kind Int-3 Int-3 Int-3 layer initiator Additive amount 109 109 109 Infrared absorber Kind IR-2 IR-3 IR-2 IR-3 IR-2 IR-3 IR-2 IR-3 Additive amount 17.5 1.3 17.5 1.3 17.5 1.3 15 1.3 Electron-donating polymerization Kind B-6 B-3 B-18 B-10 initiator Additive amount 40 75 100 38 Polymerizable compound Kind M-5 M-4 M-4 M-4 Additive amount 212 600 212 100 Polymer particle Kind R-1 R-2 R-3 R-1 (solid amount) Additive amount 400 400 370 550 Binder polymer Kind P-3 P-1 Additive amount 40 70 Color developing agent Kind S-1 S-3 S-2 S-7 Additive amount 40 40 20 40 Phenothiazine Additive amount 25 Oil agent Additive amount 12.5 12.5 5 10 Overcoat layer Discoloring compound Kind Additive amount Inorganic lamellar compound dispersion liquid 50 Evaluation Suppressing property of development defect over B A A A time Printing durability (10000 sheets) 7.0 8.0 8 8

TABLE-US-00008 TABLE 8 Comparative Comparative Example Example Example Example Example Example 3-40 3-41 3-42 3-43 1-3 1-4 Undercoat layer A A A A A A Image- Electron-accepting Kind Int-3 Int-3 Int-4/Int-5 Int-3 Int-3 Int-3 recording polymerization initiator Additive 109 109 50/50 109 109 109 layer amount Infrared absorber Kind IR-2 IR-3 IR-9 IR-6 IR-12 IR-2 IR-2 Additive 17.5 13 17.5 15 26 17.5 17.5 amount Electron-donating Kind B-5 B-5 B-15 B-25 C-1 C-2 polymerization initiator Additive 40 40 50 100 10 50 amount Polymerizable compound Kind M-5 M-4 M-3 M-4 M-4 M-4 Additive 212 212 300 300 212 212 amount Polymer particle Kind R-1 R-1 R-3 R-1 R-1 R-1 (solid amount) Additive 400 400 400 400 400 400 amount Binder polymer Kind Additive amount Color developing agent Kind S-1 S-3 S-2 S-1 S-1 Additive 40 40 40 40 40 amount Phenothiazine Additive 25 amount Oil agent Additive 12.5 12.5 5 12.5 12.5 12.5 amount Overcoat Discoloring compound Kind layer Additive amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of development A A A A D D defect over time Printing durability (10000 sheets) 8.0 8.0 7.5 8.0 7.0 5.0 Develpoability over time (sheet) 40 40 30 20 30 80 Visibility (L) 12 11 12 9 6 15

TABLE-US-00009 TABLE 9 Example Example Example Example Example Example Example 4-1 4-2 4-3 4-4 4-5 4-6 4-7 Undercoat layer A A A A A A A Image- Electron-accepting Kind Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 Int-3 recording polymerization Additive 109 109 109 109 109 109 109 layer initiator amount Infrared absorber Kind Additive amount Electron-donating Kind B-34 B-35 B-36 B-37 B-38 B-39 B-40 polymerization Additive 60 60 60 60 60 60 60 initiator amount Polymerizable Kind M-4 M-4 M-4 M-4 M-4 M-4 M-4 compound Additive 212 212 212 212 212 212 212 amount Polymer particle Kind R-1 R-1 R-1 R-1 R-1 R-1 R-1 (solid amount) Additive 400 400 400 400 400 400 400 amount Binder polymer Kind Additive amount Color developing Kind S-3 S-3 S-3 S-3 S-3 S-3 S-3 agent Additive 40 40 40 40 40 40 40 amount Phenothiazine Additive amount Oil agent Additive 12.5 12.5 12.5 12.5 12.5 12.5 12.5 amount Overcoat Discoloring Kind layer compound Additive amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of A A A A A A A development defect over time Printing durability (10000 8.5 8.5 8.5 8.0 8.0 7.5 7.5 sheets) Solvent solubility A A A A A A A Comparative Example Example Example Example Example 4-8 4-9 4-10 4-11 2-1 Undercoat layer A A A A A Image- Electron-accepting Kind Int-3 Int-4/ Int-3 Int-4/ Int-3 recording polymerization Int-5 Int-5 layer initiator Additive 109 50/50 109 50/50 109 amount Infrared absorber Kind Additive amount Electron-donating Kind B-41 B-42 B-43 B-44 C-3 polymerization Additive 60 60 60 60 60 initiator amount Polymerizable Kind M-4 M-3 M-4 M-3 M-4 compound Additive 212 300 212 300 212 amount Polymer particle Kind R-1 R-3 R-1 R-3 R-1 (solid amount) Additive 400 400 400 400 400 amount Binder polymer Kind Additive amount Color developing Kind S-3 S-2 S-3 S-2 S-1 agent Additive 40 40 40 40 40 amount Phenothiazine Additive 25 25 amount Oil agent Additive 12.5 12.5 12.5 amount Overcoat Discoloring Kind layer compound Additive amount Inorganic lamellar compound dispersion liquid Evaluation Suppressing property of A A A B D development defect over time Printing durability (10000 7.0 7.0 7.0 6.0 7.0 sheets) Solvent solubility B B A A C

[1164] The value of L in Example 3-44 was 11.5, the value of L in Example 3-45 was 14, and the value of L in Example 3-46 was 14.

[1165] From the results described in Tables 3 to 9, it was found that the lithographic printing plate precursor according to the Examples had excellent suppressing property of development defect over time and printing durability as compared with the lithographic printing plate precursor according to the Comparative Examples.

[1166] Example 3-30 of Table 6 was an example in which the specific borate compound (B3-18) was used as the electron-donating polymerization initiator as in Example 3-15 of Table 5, and Example 3-32 of Table 6 was an example in which the specific borate compound (B3-6) was used as the electron-donating polymerization initiator as in Example 3-5 of Table 3.

[1167] In Examples 3-30 and 3-32, unlike in Examples 3-5 and 3-16, the suppressing property of development defect over time and the printing durability were improved in a case where two kinds of electron-accepting polymerization initiators were used in combination. From this, it was found that it was also preferable to use two or more kinds of electron-accepting polymerization initiators in combination.

[1168] In addition, as shown in Examples 3-31 and 3-33 of Table 6, it was found that the lithographic printing plate precursor had excellent suppressing property of development defect over time and printing durability even in a case where two kinds of specific borate compounds were used as the electron-donating polymerization initiator.

[1169] Example 3-36 of Table 7 was an example in which the specific borate compound (B-6) was used as the electron-donating polymerization initiator as in Example 3-5 of Table 3. In Example 3-36, unlike in Example 3-5, the suppressing property of development defect over time and the printing durability were improved in a case where two kinds of infrared absorptive initiators were used in combination.

[1170] From this, it was found that it was also preferable to use two or more kinds of infrared absorptive initiators in combination.

[1171] From the results described in Table 8, it was found that the suppressing property of development defect over time was improved not only by using the specific borate compound (asymmetric borate compound) as the electron-donating polymerization initiator, but also the developability over time and the visibility were improved.

[1172] It is presumed that this is because the HOMO potential changed to a preferred range by the asymmetry of the specific borate compound.

[1173] The electron-donating polymerization initiator used in Examples 4-1 to 4-11 of Table 9 was a specific borate compound in which an anionic moiety had an asymmetric structure and an infrared-absorbing coloring agent cation of a cationic moiety.

[1174] On the other hand, the electron-donating polymerization initiator used in Comparative Example 2-1 was a borate compound in which an anionic moiety had a symmetric structure and an infrared-absorbing coloring agent cation of a cationic moiety.

[1175] From the results described in Table 9, it was found that the specific borate compound in which the anionic moiety had an asymmetric structure and the infrared-absorbing coloring agent cation of a cationic moiety had excellent suppressing property of development defect over time and printing durability. In addition, it was found that not only the suppressing property of development defect over time and the printing durability were improved, but also the solvent solubility was improved.

EXPLANATION OF REFERENCES

[1176] 12a, 12b: aluminum support [1177] 14: undercoat layer [1178] 16: image-recording layer [1179] 18: aluminum plate [1180] 20a, 20b: anodic oxide film [1181] 22a, 22b: micropore [1182] 24: large diameter portion [1183] 26: small diameter portion [1184] D: depth of large diameter portion [1185] 610: anodization treatment device [1186] 612: power supply tank [1187] 614: electrolytic treatment tank [1188] 616: aluminum plate [1189] 618, 626: electrolytic solution [1190] 620: power supply electrode [1191] 622, 628: roller [1192] 624: nip roller [1193] 630: electrolysis electrode [1194] 632: cell wall [1195] 634: direct current power source

[1196] The disclosure of Japanese Patent Application No. 2023-114109 filed on Jul. 11, 2023 and the disclosure of Japanese Patent Application No. 2024-030659 filed on Feb. 29, 2024 are incorporated in the present specification by reference.

[1197] All documents, patent applications, and technical standards described in the present specification are incorporated herein by reference to the same extent as in a case of being specifically and individually noted that individual documents, patent applications, and technical standards are incorporated herein by reference.

ON-PRESS DEVELOPMENT TYPE LITHOGRAPHIC PRINTING PLATE PRECURSOR, METHOD OF PREPARING LITHOGRAPHIC PRINTING PLATE, LITHOGRAPHIC PRINTING METHOD, AND COMPOUND

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B41C1/1008

PERFORMING OPERATIONS; TRANSPORTING

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B41C2210/22

PERFORMING OPERATIONS; TRANSPORTING

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G03F7/12

PHYSICS

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G03F7/0045

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B41C2210/02

PERFORMING OPERATIONS; TRANSPORTING

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B41C1/10

PERFORMING OPERATIONS; TRANSPORTING

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G03F7/004

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G03F7/12

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Abstract

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