Provided is a method of producing a planographic printing plate, including: subjecting a planographic printing plate precursor, which has a support and a positive-working image recording layer, to image-wise exposure; and developing it using an alkaline aqueous solution which contains a specific compound and has a pH of from 8.5 to 10.8, in this order. The recording layer has: a lower layer containing a water-insoluble and alkali-soluble resin and an infrared ray absorbing agent; and an upper layer containing a water-insoluble and alkali-soluble polyurethane resin and a polyorganosiloxane. The specific compound is a nonionic or anionic surfactant, or at least one compound represented by Formula (1) or (2), wherein R.sup.11, R.sup.12, and R.sup.13 each represent an alkyl group; R.sup.14 represents an alkylene group; and R.sup.15 represents a single bond or a divalent linking group containing a hetero atom; and R.sup.21, R.sup.22, and R.sup.23 each represent an alkyl group. ##STR00001##

Provided is a method of producing a planographic printing plate, including: subjecting a planographic printing plate precursor, which has a support and a positive-working image recording layer, to image-wise exposure; and developing it using an alkaline aqueous solution which contains a specific compound and has a pH of from 8.5 to 10.8, in this order. The recording layer has: a lower layer containing a water-insoluble and alkali-soluble resin and an infrared ray absorbing agent; and an upper layer containing a water-insoluble and alkali-soluble polyurethane resin and a polyorganosiloxane. The specific compound is a nonionic or anionic surfactant, or at least one compound represented by Formula (1) or (2), wherein R.sup.11, R.sup.12, and R.sup.13 each represent an alkyl group; R.sup.14 represents an alkylene group; and R.sup.15 represents a single bond or a divalent linking group containing a hetero atom; and R.sup.21, R.sup.22, and R.sup.23 each represent an alkyl group. ##STR00001##

A negative type lithographic printing plate precursor includes a support having a hydrophilic surface; and an image recording layer, on the support, containing a polymerization initiator and a polymer compound having a structure represented by Formula 1 in a main chain and an ethylenically unsaturated bond. Further, a method of preparing a lithographic printing plate includes, in order, an exposure step of image-exposing the negative type lithographic printing plate precursor; and a development step of performing development by removing a non-exposed portion of the exposed negative type lithographic printing plate precursor using a developer. In Formula 1, R.sup.1 represents an (x+2)-valent aromatic hydrocarbon ring group, and x represents an integer of 1 to 4.

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An infrared-sensitive color developing composition develops colors in a high density with an infrared exposure and does not significantly discolor when aged. A lithographic printing plate precursor which has extremely excellent plate-inspecting properties and favorable storage stability and is capable of maintaining favorable color-developing properties is provided, as is a plate making method for a lithographic printing plate in which the lithographic printing plate precursor is used. A new compound that can be preferably used as an infrared-sensitive color developer is also provided. An infrared-sensitive color developing composition of the invention includes a compound represented by Formula (1) (Component A). In addition, the compound in the present invention is represented by Formula (1). ##STR00001##

Provided is a planographic printing plate precursor including: a support; and an image recording layer formed on the support, in which the content of fine particles per unit area in a region on a plate surface on the image recording layer side from an end portion of the planographic printing plate precursor to a portion inside the end portion by 5 mm is greater than the content of the fine particles per unit area in a region other than the region by an amount of 10 mg/m.sup.2 or greater, edge stains are not generated therein, and transferring of the image recording layer is prevented even in a case where planographic printing plate precursors are stored in a stacked state. Further, provided are a method of producing the same and a printing method using the same.

Disclosed is a waterless planographic printing plate precursor including at least a substrate, a heat sensitive layer and an ink repellent layer in this order, wherein the substrate has a white color layer or a white color surface, and wherein the heat sensitive layer includes at least (a) an infrared-absorbing dye having a maximum absorption wavelength of 700 to 1,000 nm, (b) a dye that changes color by proton acceptance, and (c) a proton-donating compound. The present invention provides a waterless planographic printing plate precursor capable of obtaining high contrast between the image area and the non-image area by exposure without the need for a special layer.

An on-press development type lithographic printing plate precursor including a support, and an image-recording layer on the support, in which the image-recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compound, and one or more compounds selected from the group consisting of a compound represented by Formula (1) and a compound represented by Formula (2) (in Formula (1) and (2), Ra.sub.1 and Ra.sub.2 represent an alkyl group, Rb.sub.1 and Rb.sub.3 represent an alkyl group, Rb.sub.2 and Rb.sub.4 represent an alkyl group, and EDG's each independently represent a hydrogen atom or an electron-donating group, provided that at least one of the four EDG's in Formula (1) represents an electron-donating group).

A positive-working lithographic printing plate precursor includes a coating optimized for producing a minimum extent of ablation when exposed to heat and/or light. The coating includes an infrared absorbing agent which contains a structural element according to Formula I:

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wherein A represents SR.sup.1 wherein R.sup.1 represents an optionally substituted alkyl, aralkyl, alkaryl, cycloalkyl, alkenyl, alkynyl, aryl, or heteroaryl group, and/or combinations thereof; and Q=CHRCHR, CRCR or CHRCHRCHR and R, R and R independently represent hydrogen, an alkyl, cycloalkyl, aralkyl, alkaryl, aryl or heteroaryl group, or R and R or R and R form together a cyclic structure.

A lithographic printing plate precursor has a support and an image-recording layer on the support. The image-recording layer contains an infrared absorber, a polymer A that has a weight-average molecular weight of more than 15,000 and 150,000 or less, and a polymerizable compound B that has a weight-average molecular weight of 1,000 or more and 15,000 or less, and the polymer A is a polymer represented by Formula (I):
A.sup.P-(B.sup.P).sub.nPFormula (I) In Formula (I), A.sup.P represents an nP-valent organic group having a hydrogen bonding group, B.sup.P represents a group having 2 or more Polymerizable groups, nP represents an integer of 2 or more, and weight-average molecular weight of A.sup.P/(molecular weight of B.sup.PnP) is 1 or less.

Provided is a planographic printing plate precursor including: a support; and an image recording layer formed on the support, in which a region on the plate surface on the image recording layer side from an end portion of the planographic printing plate precursor to a portion inside the end portion by 5 mm contains a polymer containing a functional group represented by the following Formula (A), and the content of the polymer per unit area in the region is greater than the content of the polymer per unit area in a region other than the above-described region by an amount of 10 mg/m.sup.2 or greater.
Si(X).sub.m(R.sup.3).sub.n(A)