Polymer for heat-sensitive lithographic printing plate precursor

1. A polymer comprising a phenolic monomeric unit of which the phenyl group is substituted by a group A, wherein group A has one of the following formulae:

wherein X and Y are independently selected from O and S,

wherein each R 1 and R 20 to R 23 is a terminal group independently selected from hydrogen, an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclic, aryl, heteroaryl, aralkyl or heteroaralkyl group, halogen, —SO 2 —NH—R 24 , —NH—SO 2 —R 27 , —CO—NR 24 —R 25 , —NR 24 —CO—R 27 , —NR 24 —CO—NR 25 —R 26 , —NR 24 —CS—NR 25 —R 26 , —NR 24 —CO—O—R 25 , —O—CO—NR 24 —R 25 , —O—CO—R 27 , —CO—O—R 24 , —CO—R 24 , —SO 3 —R 24 , —O—SO 2 —R 27 , —SO 2 —R 24 , —SO—R 27 , —P(═O)(—O—R 24 )(—O—R 25 ), —O—P(═O)(—O—R 24 )(—O—R 25 ), —NR 24 —R 25 , —O—R 24 , —S—R 24 —CN, —NO 2 , —N(—CO—R 24 )(—CO—R 25 ), —N-phthalimidyl, -M-N-phthalimidyl, and -M-R 24 ,

wherein M represents a divalent linking group containing 1 to 8 carbon atoms,

wherein R 24 to R 26 are independently selected from hydrogen and an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclic, aryl, heteroaryl, aralkyl or heteroaralkyl group,

wherein R 27 is selected from an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclic, aryl, heteroaryl, aralkyl and heteroaralkyl group,

wherein a and d are independently 0, 1, 2, 3 or 4,

wherein b and c are independently 0, 1, 2 or 3,

wherein E 3 is selected from O, S, NR 28 and R 29 -[L 15 ] i -C-[L 16 ] j -R 30 ,

wherein L, L 15 and L 16 are independently a linking group, wherein n, i and j independently are 0 or 1,

and wherein one of the groups selected from R 1 , R 20 , R 21 , R 22 , R 23 , R 28 , R 29 and R 30 represents the phenolic monomeric unit and the remaining groups represent a terminal group.

2. The polymer according to claim 1 , wherein said polymer comprising a phenolic monomeric unit is a novolac, resol or polyvinylphenol.

3. A heat-sensitive lithographic printing plate precursor comprising a support having a hydrophilic surface and an oleophilic coating provided on the hydrophilic surface, said coating comprising an infrared light absorbing agent and a polymer comprising a phenolic monomeric unit of which the phenyl group is substituted by a group A, wherein group A has one of the following formulae:

wherein X and Y are independently selected from O and S,

wherein each R 1 and R 20 to R 23 is a terminal group independently selected from hydrogen, an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclic, aryl, heteroaryl, aralkyl or heteroaralkyl group, halogen, —SO 2 —NH—R 24 , —NH—SO 2 —R 27 , —CO—NR 24 —R 25 , —NR 24 —CO—R 27 , —NR 24 —CO—NR 25 —R 26 , —NR 24 —CS—NR 25 —R 26 , —NR 24 —CO—O—R 25 , —O—CO—NR 24 —R 25 , —O—CO—R 27 , —CO—O—R 24 , —CO—R 24 , —SO 3 —R 24 , —O—SO 2 —R 27 , —SO 2 —R 24 , —SO—R 27 , —P(═O)(—O—R 24 )(—O—R 25 ), —O—P(═O)(—O—R 24 )(—O—R 25 ), —NR 24 —R 25 , —O—R 24 , —S—R 24 , —CN, —NO 2 , —N(—CO—R 24 )(—CO—R 25 ), —N-phthalimidyl, -M-N-phthalimidyl, and -M-R 24 ,

wherein M represents a divalent linking group containing 1 to 8 carbon atoms,

wherein R 24 to R 26 are independently selected from hydrogen and an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclic, aryl, heteroaryl, aralkyl or heteroaralkyl group,

wherein R 27 is selected from an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclic, aryl, heteroaryl, aralkyl and heteroaralkyl group,

wherein a and d are independently 0, 1, 2, 3 or 4,

wherein b and c are independently 0, 1, 2 or 3,

wherein E 3 is selected from O, S, NR 28 or R 29 -[L 15 ] i -C-[L 16 ] j -R 30 ,

wherein L, L 15 and L 16 are independently a linking group, wherein n, i and j independently are 0 or 1,

and wherein one of the groups selected from R 1 , R 20 , R 21 , R 22 , R 23 , R 28 , R 29 and R 30 represents the phenolic monomeric unit and the remaining groups represent a terminal group.

4. The lithographic printing plate precursor according to claim 3 , wherein said coating further comprises a dissolution inhibitor and wherein said precursor is a positive working lithographic printing plate precursor.

5. The lithographic printing plate precursor according to claim 4 , wherein said dissolution inhibitor is selected from the group consisting of

an organic compound which comprises at least one aromatic group and a hydrogen bonding site,

a polymer or surfactant comprising siloxane or perfluoroalkyl units, and mixtures thereof.

6. The heat-sensitive lithographic printing plate precursor according to claim 3 , wherein said coating further comprises a latent Brönsted acid and an acid-crosslinikable compound and wherein said precursor is a negative working lithographic printing plate precursor.

7. The polymer according to claim 3 , wherein said polymer comprising a phenolic monomeric unit is a novolac, resol or polyvinylphenol.

8. A method for increasing the chemical resistance of a coating of a positive working heat-sensitive lithographic printing plate precursor against printing liquids and press chemicals, the method comprising providing a coating comprising:

a polymer according to claim 1 ,

an infrared absorbing agent, and

a dissolution inhibitor.

9. A method for increasing the chemical resistance of a coating of a negative working heat-sensitive lithographic printing plate precursor against printing liquids and press chemicals, the method comprising providing a coating comprising:

a polymer according to claim 1 ,

a latent Brönsted acid, and

an acid-crosslinikable compound.