A copolymer includes (i) a plurality of ethylenic moieties A having a structure according to the following formula:

##STR00001## wherein R2 and R3 independently represent hydrogen, a halogen or an optionally substituted linear, branched or cyclic alk(en)yl group, or an optionally substituted aromatic or heteroaromatic group, and (ii) a plurality of acetal moieties B having a structure according to the following formula:

##STR00002## wherein L represents a divalent linking group; x=0 or 1 and R1 represents an optionally substituted aromatic or heteroaromatic group including at least one hydroxyl group and optionally one or more additional substituent(s), and at least one electron withdrawing group in ortho or para position relative to the at least one hydroxyl group.

A negative-working lithographic printing plate precursor includes a support and a coating containing a photopolymerizable layer including a polymerizable compound including: a free radical polymerizable group, and at least one moiety having a structure according to Formula (I): ##STR00001## wherein n represents an integer equal to 0 or 1; L.sup.1 represents a divalent linking group; and * denotes the linking positions to the rest of the structure, with the proviso that the carbonyl groups in Formula (I) are bonded to a carbon atom.

A copolymer includes (i) a plurality of ethylenic moieties A having a structure according to the following formula: ##STR00001##
wherein R.sup.2 and R.sup.3 independently represent hydrogen, a halogen, or an optionally substituted linear, branched, or cyclic alk(en)yl group, or an optionally substituted aromatic or heteroaromatic, and (ii) a plurality of acetal moieties B having a structure according to the following formula: ##STR00002##
wherein L represents a divalent linking group; x=0 or 1; and R.sup.1 represents an optionally substituted aromatic or heteroaromatic group including at least one hydroxyl group. Use of these polymers in the coating of lithographic printing plates provides a good abrasion resistance while the balance between the ink acceptance, arising from the ethylenic moieties, and the solubility in an alkaline developer, arising form the acetal moieties, can be controlled efficiently.

There is provided a photosensitive resin composition which enables production of a lithographic printing plate precursor having a non-image portion which has good solubility in an alkali aqueous solution and which enables production of a lithographic printing plate having excellent printing durability, excellent chemical resistance, and, in particular, excellent printing durability at the time of using a low quality print material, a lithographic printing plate precursor obtained by using the photosensitive resin composition, and a method for producing a lithographic printing plate.

The photosensitive resin composition contains a polymer compound having a linking group represented by Formula A-1 in the main chain; and an infrared absorbing material. In Formula A-1, R.sup.1 and R.sup.2 each independently represent a hydrogen atom or a monovalent organic group, and X.sup.1 is a specific linking group.

##STR00001##

There is provided a photosensitive resin composition which enables production of a lithographic printing plate precursor having a non-image portion which has good solubility in an alkali aqueous solution and which enables production of a lithographic printing plate having excellent printing durability and excellent chemical resistance, a lithographic printing plate precursor obtained by using the photosensitive resin composition, and a method for producing a lithographic printing plate.

The photosensitive resin composition contains a polymer compound having a constitutional unit represented by the following Formula A-1 as a constitutional unit A and at least one constitutional unit among constitutional units represented by the following Formulas B-1 to B-6 as a constitutional unit B in the main chain, and an infrared absorbing material.

##STR00001##

A negative-working lithographic printing plate precursor has a negative-working infrared radiation-sensitive image-recording layer that has a) two or more free radically polymerizable components; b) an initiator composition capable of generating free radicals; and c) one or more infrared radiation absorbing cyanine dyes. The a) two or more free radically polymerizable components comprise a combination of a urethane (meth)acrylate and a polyester (meth)acrylate, which together, comprise 75-100 weight % of all free radically polymerizable components. The weight ratio of the urethane (meth)acrylates to the polyester (meth)acrylates is from 90:10 to and including 35:65. The urethane (meth)acrylates comprise one or more urethane linkages and at least 4 acrylate or methacrylate ester groups. Each of the one or more polyester (meth)acrylates is free of a urethane linkage and is represented following structure (I). These precursors are less sensitive to ambient ozone and can be infrared radiation imaged and developed on-press during lithographic printing.

A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound, a photoinitiator and an asymmetrically substituted infrared absorbing compound.

A lithographic printing plate precursor is disclosed including a support and a coating comprising a photopolymerisable layer including a polymerisable compound and a photoinitiator, characterized in that the coating comprises a hydrophilic adhesion promoting copolymer including at least one monomeric unit according to Formula I and at least one monomeric unit according to Formula II; and at least one group and/or moiety including a phosphor atom. ##STR00001##

A positive-working lithographic printing plate precursor including a support and an image-recording layer formed on the support and consisting of a positive-working photosensitive resin composition, in which the positive-working photosensitive resin composition contains a compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule, an alkali-soluble resin, and an infrared absorber, and the electron-withdrawing group excludes a sulfonyl group; and a method of preparing a lithographic printing plate using the positive-working lithographic printing plate precursor.