Lithographic printing plate precursor

1. A lithographic printing plate precursor comprising a support and a coating comprising:

a polymerizable compound;

an infrared absorbing compound;

a borate compound according to Formula I:

wherein R b 1 , R b 2 , R b 3 and R b 4 are independently an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heteroaryl group; and M + is an alkali metal cation selected from Li + , Na + or K + or is an optionally substituted ammonium ion; and

a photoinitiator, wherein the photoinitiator is a tribromomethyl aryl sulfone, wherein the aryl group of the tribromomethyl aryl sulfone is substituted by at least one electron-donating group in an ortho or para position.

2. The lithographic printing plate precursor of claim 1 , wherein M + is an optionally substituted ammonium ion according to Formula II:

wherein

R n 1 , R n 2 and R n 3 are independently an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, an optionally substituted heteroaryl group, or a halogen.

3. The lithographic printing plate precursor of claim 1 , wherein R b 1 , R b 2 , R b 3 and R b 4 are independently an optionally substituted aryl group or an optionally substituted heteroaryl group.

4. The lithographic printing plate precursor of claim 1 , wherein the borate compound is present in the coating in an amount between 0.05% and 30% by weight.

5. The lithographic printing plate precursor of claim 1 , wherein the infrared absorbing compound has a chemical structure according to Formula III:

wherein

Ar 1 and Ar 2 are independently optionally substituted aryl groups,

W 1 and W 2 are independently a sulphur atom or a —CM 10 M 11 group, wherein M 10 and M 11 are independently an optionally substituted aliphatic hydrocarbon group, an optionally substituted heteroaryl group or an optionally substituted aryl group, or wherein M 10 and M 11 together comprise the necessary atoms to form a cyclic structure,

M 1 and M 2 together comprise the necessary atoms to form an optionally substituted cyclic structure,

M 3 and M 4 independently are optionally substituted aliphatic hydrocarbon groups,

M 5 , M 6 , M 7 and M 8 independently are hydrogen, halogen, or an optionally substituted aliphatic hydrocarbon group,

M 9 is a halogen, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, an optionally substituted heteroaryl group, —NR 1 R 2 , —NR 1 —CO—R 6 , —NR 1 —SO 2 —R 4 or —NR 1 —SO—R 5 ; wherein

R 1 and R 2 independently are hydrogen, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heteroaryl group;

R 4 and R 6 independently are —OR 7 , —NR 8 R 9 or —CF 3 ; wherein R 7 is an optionally substituted aryl group, an optionally substituted heteroaryl group, or an optionally substituted aliphatic hydrocarbon group and R 8 and R 9 independently are hydrogen, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group or an optionally substituted heteroaryl group, or R 8 and R 9 together comprise the atoms of a cyclic structure;

R 5 is hydrogen, an optionally substituted aliphatic hydrocarbon group, SO 3 —, —COOR 10 , an optionally substituted aryl group, or an optionally substituted heteroaryl group; wherein R 10 is an optionally substituted aryl group, an optionally substituted heteroaryl group, or an aliphatic hydrocarbon group; and

the infrared absorbing compound optionally comprises one or more counter ions such that the infrared absorbing compound is electrically neutral.

6. A method for making a printing plate including the steps of

a. image-wise exposing the lithographic printing plate precursor of claim 1 to heat and/or IR radiation to produce a lithographic image consisting of image areas and non-image areas; and

b. developing the exposed precursor.

7. The method of claim 6 , wherein the image-wise exposing step induces a colour change in the image areas.

8. The method of claim 6 , 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.

9. The method of claim 6 , wherein the precursor is developed by applying a gum solution to the precursor.