Disclosed is a infrared radiation sensitive positive-working imageable element. The imageable element comprises: (a) a substrate, (b) an inner coating covering the substrate, and (c) an outer coating covering the inner coating. The inner coating comprises a repeating unit derived from a maleimide monomer and a (meth)acrylamide monomer, and a polymer hinder P that is soluble in an alkaline developing solution; and the outer coating comprises an infrared radiation absorbing compound and a polymer binder Q which is different from that in the inner coating. The imageable element is designed such that same is not only sensitive to radiation with a maximum wavelength of 700-1200 nm, but also has a good resistance to chemical solvents when used as a lithographic printing plate precursor, and same is not easily corroded and dissolved by printing chemicals during use, thus facilitating the prolonging of the service life of a lithographic printing plate.

Provided is an on-press development type lithographic printing plate precursor having a support and an image-recording layer on the support, in which the image-recording layer contains a compound A that has a partial structure satisfying Δd≥15.5 wherein δd is a value of a dispersion element in the Hansen solubility parameters, and a content of the partial structure satisfying Δd≥15.5 in the compound A is 50% by mass or more with respect to a total mass of the compound. Also provided is a method of preparing lithographic printing plate or a lithographic printing method using the lithographic printing plate precursor.

Provided is an on-press development type lithographic printing plate precursor having 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 a color-developing substance precursor, and in a case where the image-recording layer is exposed to an infrared laser having a wavelength of 830 nm at an energy density of 110 mJ/cm.sup.2, a loss of ethylenically unsaturated bonds in an exposed area in the image-recording layer is 10% to 40% of ethylenically unsaturated bonds in a non-exposed area in the image-recording layer. Also provided is a method for preparing a lithographic printing plate or a lithographic printing method using the on-press development type lithographic printing plate precursor.

A lithographic printing plate precursor has an infrared radiation-sensitive image-recording layer containing an IR absorber, and an ozone-blocking material of 1500 or less molecular weight and has structure (I), (II), or (III): ##STR00001##
wherein R is a hydrocarbon having 14-30 carbon atoms; m is 1 or 2; n is 1-6; the sum of m and n is >2 and <8; and A is a multivalent organic moiety free of R and OH groups and has a valence m+n; ##STR00002##
wherein R.sub.1 and R.sub.2 are alkyl groups of 14-22 carbon atoms, and o is 1-3;
R.sub.3C(═O)NR.sub.4R.sub.5   (III)
wherein R.sub.3 is an alkenyl with a C═C bond within a carbon-carbon chain of 16-30 carbons, and R.sub.4 and R.sub.5 are hydrogen or unsubstituted alkyls of 1-4 carbon atoms. Such ozone-blocking materials can be used to protect infrared radiation-sensitive dyes that may be degraded by ozone and thus improve imaging sensitivity.

A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound and a photoinitiator, and a toplayer provided above the photopolymerisable layer; characterized in that the toplayer includes a hydrophobic binder.

Provided are a lithographic printing plate precursor including a support, and an image recording layer on the support, in which the image recording layer contains an infrared absorbing agent, a polymerization initiator, and core-shell particles, a core portion of each core-shell particle contains a resin A containing a functional group A, and a shell portion of the core-shell particle contains a resin B containing a functional group B that is bondable to or interactable with the functional group A and a polymerizable group: a method of preparing a lithographic printing plate using the lithographic printing plate precursor; and a lithographic printing method carried out using the lithographic printing plate precursor.

Provided are a planographic printing plate precursor including a support and an image recording layer on the support, in which the image recording layer contains an organic particle containing a resin that has a constitutional unit A having a cation moiety and a constitutional unit B having an anion moiety; and a method of preparing a planographic printing plate using the planographic printing plate precursor.

Provided are a planographic printing plate precursor including a support, and an image recording layer on the support, in which the image recording layer contains an infrared absorbing agent, a polymerization initiator, and a core-shell particle, a core portion of the core-shell particle contains a resin A containing a functional group A, and a shell portion of the core-shell particle contains a resin B containing a functional group B that is bondable to or interactable with the functional group A and a dispersion group; a method of preparing a planographic printing plate using the planographic printing plate precursor; and a planographic printing method carried out using the planographic printing plate precursor.

The invention relates to an imageable coating layer, thermal negative-working lithography printing plate, and platemaking method. The coating layer includes constituents in parts by weight: a radically polymerizable compound 20-60 parts, a radiation-absorbing compound 0.5-12 parts, a free radical initiator 1-25 parts, a binding agent 10-70 parts, and a development accelerator 0.5-15 parts. The platemaking method includes the steps: S1, preparing a printing plate precursor that includes a substrate having a hydrophilic surface or is provided with a hydrophilic layer and imageable coating layer covering the substrate; S2, patternedly exposing the printing plate precursor, forming an exposed area and an unexposed area; and S3, removing the unexposed area via a development process. The employment of the imageable coating layer and the plate making method allows the implementation of a flexible development process of “on-press development” or “off-press development” and produces a printing plate provided with great printing performance.

A lithographic printing plate precursor is disclosed including a support and a coating comprising a photopolymerisable layer including a polymerisable compound, a photoinitiator, and an infrared absorbing compound including a long chain linear or branched alkyl group.