Lithographic printing plate precursor

1. A lithographic printing plate precursor comprising on a substrate, which has a hydrophilic surface or which is provided with a hydrophilic layer, a coating comprising a photopolymerisable layer comprising a polymerisable compound, a photoinitiator, and an adhesion promoting compound containing (i) at least one thiol group and (ii) at least one group selected from a phosphate group and a phosphonate group, which is capable of adhering to the substrate.

2. The printing plate precursor of claim 1 , wherein the adhesion promoting compound comprises at least two thiol groups.

3. The printing plate precursor of claim 1 , wherein the adhesion promoting compound is of Formula I:

wherein

m and p each independently represent 1, 2, or 3;

Y represents a z-valent core having 1 to 12 atoms;

z is the sum of m and p and z is 2, 3, 4, or 5;

X represents a phosphate or a phosphonate group; and

L1, L2, and L3 each independently represent a linking group.

4. The printing plate precursor of claim 3 , wherein L3 includes —(O—CH 2 —CH 2 )o-, wherein o is an integer between 1 and 15.

5. The printing plate precursor of claim 3 , wherein the z-valent core represents an optionally substituted carbon atom or an isocyanurate group.

6. The printing plate precursor of claim 1 , wherein the adhesion promoting compound has a molecular weight of at least 400 g/mol.

7. The printing plate precursor of claim 2 , wherein the adhesion promoting compound has a molecular weight of at least 400 g/mol.

8. The printing plate precursor of claim 3 , wherein the adhesion promoting compound has a molecular weight of at least 400 g/mol.

9. The printing plate precursor of claim 1 , wherein the adhesion promoting compound has a weight average molecular weight of not more than 5,000 g/mol.

10. The printing plate precursor of claim 2 , wherein the adhesion promoting compound has a weight average molecular weight of not more than 5,000 g/mol.

11. The printing plate precursor of claim 3 , wherein the adhesion promoting compound has a weight average molecular weight of not more than 5,000 g/mol.

12. The printing plate precursor of claim 1 , wherein the adhesion promoting compound is selected from:

wherein n is 1 to 15.

13. A method for making a printing plate precursor, the method comprising:

coating on a support (i) a photopolymerisable layer including a polymerisable compound, a photoinitiator, and an adhesion promoting compound as defined in claim 1 , and

drying the precursor.

14. A method for making a printing plate precursor, the method comprising:

coating on a support (i) a photopolymerisable layer including a polymerisable compound, a photoinitiator, and an adhesion promoting compound as defined in claim 12 , and

drying the precursor.

15. A method for making a printing plate, the method comprising:

image-wise exposing the printing plate precursor of claim 1 to heat and/or IR radiation whereby a lithographic image consisting of image areas and non-image areas is formed, and

developing the exposed precursor.

16. The method of claim 15 , wherein the precursor is developed by mounting the precursor on a plate cylinder of a lithographic printing press and rotating the plate cylinder while feeding dampening liquid and/or ink to the precursor.

17. The method of claim 15 , wherein the precursor is developed by applying a gum solution.

18. A method for making a printing plate, the method comprising:

image-wise exposing the printing plate precursor of claim 12 to heat and/or IR radiation whereby a lithographic image consisting of image areas and non-image areas is formed, and

developing the exposed precursor.

19. The method of claim 18 , wherein the precursor is developed by mounting the precursor on a plate cylinder of a lithographic printing press and rotating the plate cylinder while feeding dampening liquid and/or ink to the precursor.

20. The method of claim 18 , wherein the precursor is developed by applying a gum solution.