Heat-sensitive positive-working lithographic printing plate precursor

1. A heat-sensitive positive-working lithographic printing plate precursor comprising:

a support having a hydrophilic surface or which is provided with a hydrophilic layer;

a heat-sensitive coating including an IR absorbing agent, a phenolic resin, and a first polymer; wherein

the first polymer is an alkaline soluble polymer including a monomeric unit having a structure according to Formula I or Formula II:

wherein:

* denotes binding sites of the monomeric unit in the polymer backbone;

R 1 is hydrogen or an alkyl group;

Z represents oxygen or —NR 2 —;

a and b independently are 0 or 1;

R 2 is hydrogen or an optionally substituted alkyl, alkenyl, or alkynyl group; and

Ar 1 and Ar 2 are an aromatic group with the proviso that at least one of Ar 1 and Ar 2 is an optionally substituted heteroaromatic group.

2. A precursor according to claim 1 , wherein the Ar 2 is an optionally substituted heteroaromatic group.

3. A precursor according to claim 1 , wherein the monomeric unit has a structure according to Formula I.

4. A precursor according to claim 1 , wherein the optionally substituted heteroaromatic group includes at least one nitrogen atom in the aromatic ring.

5. A precursor according to claim 1 , wherein the optionally substituted heteroaromatic group is selected from the group consisting of an optionally substituted furan, thiophene, pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, oxazole, isoxazole, thiazole, isothiazole, thiadiazole, oxadiazole, pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine or 1,2,3-triazine, benzofuran, benzothiophene, indole, indazole, benzoxazole, quinoline, quinazoline, benzimidazole, and benztriazole.

6. A precursor according to claim 1 , wherein the first polymer further includes other monomeric units selected from the group consisting of an optionally N-substituted (meth)acryl amide monomeric unit, an optionally N-substituted maleimide monomeric unit, an ester of a (meth)acrylic acid, polyoxyethylene (meth)acrylic acid ester, 2-hydroxy ethyl (meth)acrylate, an optionally substituted styrene, a styrene sulphonic acid, an o-, p- or m-vinyl benzoic acid, an optionally substituted vinyl pyridine, N-vinyl caprolactam, N-vinyl pyrrolidone, (meth)acrylic acid, itaconic acid, maleic acid, glycidyl (meth)acrylate, optionally hydrolysed vinyl acetate, and vinyl phosphonic acid.

7. A precursor according to claim 1 , wherein the first polymer includes a monomeric unit having a structure according to Formula I or Formula II, and the monomeric unit of the monomers N-benzyl (meth)acrylamide and (meth)acrylic acid.

8. A precursor according to claim 1 , wherein the monomeric unit having a structure according to Formula I or Formula II is present in the first polymer in an amount ranging between 10 mol % and 90 mol %.

9. A method for making a lithographic printing plate comprising the steps of:

providing a heat-sensitive lithographic printing plate precursor as defined in claim 1 ;

image-wise exposing the precursor with IR-radiation or heat; and

developing the image-wise exposed precursor.

10. A method for improving the chemical resistance of a heat-sensitive coating of a heat-sensitive lithographic printing plate precursor:

providing a heat-sensitive lithographic printing plate precursor including a support and a heat-sensitive coating including an alkaline soluble polymer, the alkaline soluble polymer including a monomeric unit having a structure according to Formula I or Formula II:

wherein:

* denotes binding sites of the monomeric unit in the polymer backbone;

R 1 is hydrogen or an alkyl group;

Z represents oxygen or —NR 2 —;

a and b independently are 0 or 1;

R 2 is hydrogen or an optionally substituted alkyl, alkenyl, or alkynyl group; and

Ar 1 and Ar 2 are an aromatic group with the proviso that at least one of Ar 1 and Ar 2 is an optionally substituted heteroaromatic group.