Lithographic printing plate precursor

1. A positive-working lithographic printing plate precursor which comprises on a support having a hydrophilic surface or which is provided with a hydrophilic layer, a heat and/or light-sensitive coating including an infrared absorbing agent and an alkali soluble resin including a benzoxazine group, wherein the alkali soluble resin comprises a monomeric unit derived from the monomer according to the following structure (V):

wherein

R 3 to R 6 represent hydrogen, a halogen, an optionally substituted straight, branched or cyclic alkyl, aralkyl, hetero-aralkyl, (di)alkylamine, aryl, heteroaryl group, or a structural moiety comprising an ethylenically unsaturated polymerizable group and/or combinations thereof;

each of adjacent R 3 to R 5 may represent the necessary atoms to form one or more cyclic structure(s); and

with the proviso that at least one of R 3 to R 6 represents or comprises a structural moiety including an ethylenically unsaturated polymerizable group.

2. A printing plate precursor according to claim 1 wherein the ethylenically unsaturated polymerizable group is represented by:

wherein

X represents oxygen, sulfur or an optionally substituted nitrogen;

m represents 0, 1 or an integer greater than 1; and

R 7 represents hydrogen, an alkyl, an alkoxy, a carboxylic acid or an ester group; and

* represents the bond whereby the ethylenically unsaturated polymerizable group is attached to structure (V).

3. A printing plate precursor according to claim 1 wherein the alkali soluble resin comprises 0.5 to 10 mol % of the monomeric unit according to structure (V).

4. A printing plate precursor according to claim 1 wherein the alkali soluble resin further comprises a monomeric unit selected from an acrylate, a methacrylate, styrene, an acrylamide, a methacrylamide or a maleimide, or a monomeric unit including a sulphonamide group.

5. A printing plate precursor according to claim 1 wherein the alkali soluble resin further comprises a monomeric unit including a sulphonamide group represented by —NR j —SO 2 —, —SO 2 —NR k — wherein R j and R k each independently represent hydrogen, an optionally substituted alkyl, alkanoyl, alkenyl, alkynyl, cycloalkyl, heterocyclic, aryl, heteroaryl, aralkyl, heteroaralkyl group or combinations thereof.

6. A printing plate precursor according to claim 5 wherein the alkali soluble resin comprises 50 to 80 mol % of the monomeric unit including a sulphonamide group.

7. A printing plate precursor according to claim 2 wherein the alkali soluble resin comprises 0.5 to 10 mol % of the monomeric unit according to structure (V).

8. A printing plate precursor according to claim 2 wherein the alkali soluble resin further comprises a monomeric unit selected from an acrylate, a methacrylate, styrene, an acrylamide, a methacrylamide or a maleimide, or a monomeric unit including a sulphonamide group.

9. A printing plate precursor according to claim 2 wherein the alkali soluble resin further comprises a monomeric unit including a sulphonamide group represented by —NR j —SO 2 —, —SO 2 —NR k — wherein R j and R k each independently represent hydrogen, an optionally substituted alkyl, alkanoyl, alkenyl, alkynyl, cycloalkyl, heterocyclic, aryl, heteroaryl, aralkyl, heteroaralkyl group or combinations thereof.

10. A method for making a positive-working lithographic printing plate comprising the steps of:

imagewise exposing a heat-sensitive lithographic printing plate precursor according to claim 1 to heat and/or infrared light;

developing said imagewise exposed precursor with an aqueous alkaline developer so that the exposed areas are dissolved; and

baking the obtained plate.

11. A positive-working lithographic printing plate precursor which comprises on a support having a hydrophilic surface or which is provided with a hydrophilic layer, a heat and/or light-sensitive coating including an infrared absorbing agent and a compound including a benzoxazine group represented by one of the following structures:

wherein

Q and Q′ independently represent an optionally substituted alkylidene or hetero-alkylidene group, an optionally substituted nitrogen, an oxygen, a sulphone, a sulphoxide, a carbonyl, a thioether, a thiol or a phosphine oxide group;

R 10 represents hydrogen or an optionally substituted alkyl, alicyclic alkyl, aralkyl, aryl or heteroaryl group;

R 11 , R 12 and R 13 independently represent hydrogen, a halogen or an optionally substituted alkyl, alicyclic alkyl, aralkyl, aryl or heteroaryl group; and

n and n′ independently represent an integer comprised between 1 and 4, wherein the compound including a benzoxazine group is present in the coating in an amount comprised between 0.01 g/m 2 to 1 g/m 2 .

12. A method for making a positive-working lithographic printing plate comprising the steps of:

imagewise exposing a heat-sensitive lithographic printing plate precursor according to claim 11 to heat and/or infrared light;

developing said imagewise exposed precursor with an aqueous alkaline developer so that the exposed areas are dissolved; and

baking the obtained plate.