Negative working, heat-sensitive lithographic printing plate precursor

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

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

(b) an image-recording layer comprising hydrophobic thermoplastic polymer particles, an infrared light absorbing dye and an additional dye according to Formula I:

wherein

Q represents an optionally substituted mono-, tri- or penta-methine chain;

Z and Z′ independently represent O, NR′, S or CH═CH wherein R′ is an optionally substituted alkyl or (hetero)aryl group;

X and X′ independently represent hydrogen, halogen, O—CH 3 , an optionally substituted alkyl or (hetero)aryl group, or a condensed benzene ring;

L and L′ represent a linking group; and

G and G′ represent an acid group or salt thereof; and

wherein the additional dye according to Formula I has a most bathochromic light absorption peak at a wavelength between 451 and 750 nm.

2. The heat-sensitive negative working lithographic printing plate precursor according to claim 1 , wherein the acidic groups, G and G′ in Formula I are selected from the group consisting of:

(a) a substituted sulphonamido acid group;

(b) a carboxylic acid group;

(c) a sulphonic acid group;

(d) a dithiosulphonic acid group;

(e) a sulphuric acid group;

(f) a phosphoric acid group; and

(g) a phosphonic acid group.

3. The heat-sensitive negative working lithographic printing plate precursor according to claim 1 , wherein the linking groups L and L′ in Formula I are —(CH 2 ) q —, wherein q is an integer ranging from 1 to 5.

4. The heat-sensitive negative working lithographic printing plate precursor according to claim 2 , wherein the linking groups L and L′ in Formula I are —(CH 2 ) q —, wherein q is an integer ranging from 1 to 5.

5. The heat-sensitive negative working lithographic printing plate precursor according to claim 1 , wherein the sum of the amounts of the infrared light absorbing dye and the additional dye, without taking into account optional counter ions, is more than 0.70 mg per m 2 of the total surface of the particles, wherein the surface is measured by Hydrodynamic Fractionation.

6. The heat-sensitive negative working lithographic printing plate precursor according to claim 1 , wherein the sum of the amounts of the infrared light absorbing dye and the additional dye, without taking into account optional counter ions, is more than 0.80 mg per m 2 , wherein the surface is measured by Hydrodynamic Fractionation.

7. The heat-sensitive negative working lithographic printing plate precursor according to claim 1 , wherein the average particle diameter of the hydrophobic thermoplastic particles, measured by photon correlation spectroscopy, is from 25 nm to 55 nm.

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

(a) providing a printing plate precursor according to claim 1 ;

(b) exposing said printing plate precursor to infrared light; and

(c) developing said exposed printing plate precursor with a gum solution.

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

(a) providing a printing plate precursor according to claim 5 ;

(b) exposing said printing plate precursor to infrared light; and

(c) developing said exposed printing plate precursor with a gum solution.

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

(a) providing a printing plate precursor according to claim 1 ;

(b) exposing said printing plate precursor to infrared light; and

(c) developing said exposed printing plate precursor with an alkaline aqueous solution.

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

(a) providing a printing plate precursor according to claim 6 ;

(b) exposing said printing plate precursor to infrared light; and

(c) developing said exposed printing plate precursor with an alkaline aqueous solution.

12. A heat-sensitive negative-working lithographic printing plate precursor comprising:

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

(b) an image-recording layer comprising hydrophobic thermoplastic polymer particles, an infrared light absorbing dye and an additional dye according to any of Formulae II to V:

wherein

Z and Z′ independently represent 0, NR′, S or CH═CH wherein R′ is an optionally substituted alkyl or (hetero)aryl group;

X and X′ independently represent hydrogen, halogen, O—CH 3 , an optionally substituted alkyl or (hetero)aryl group, or a condensed benzene ring;

L and L′ represent a linking group; and

G and G′ represent an acid group or salt thereof; and

wherein R m , R 1 and R 2 independently represent H, alkyl or aryl.

13. The heat-sensitive negative working lithographic printing plate precursor according to claim 12 , wherein the acidic groups, G and G′ in Formulae II to V are selected from the group consisting of:

(a) a substituted sulphonamido acid group;

(b) a carboxylic acid group;

(c) a sulphonic acid group;

(d) a dithiosulphonic acid group;

(e) a sulphuric acid group;

(f) a phosphoric acid group; and

(g) a phosphonic acid group.

14. The heat-sensitive negative working lithographic printing plate precursor according to claim 12 , wherein the linking groups L and L′ in Formulae II to V are —(CH 2 ) q —, wherein q is an integer ranging from 1 to 5.

15. The heat-sensitive negative working lithographic printing plate precursor according to claim 13 , wherein said linking groups L and L′ in Formulae II to V are —(CH 2 ) q —, wherein q is an integer ranging from 1 to 5.

16. A heat-sensitive negative-working lithographic printing plate precursor comprising:

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

(b) an image-recording layer comprising hydrophobic thermoplastic polymer particles, an infrared light absorbing dye and an additional dye; according to Formulae VI or VII:

wherein

p and p′ are integers ranging from 0 to 3;

X and X′ independently represent hydrogen, halogen, O—CH 3 , an optionally substituted alkyl or (hetero)aryl group, or a condensed benzene ring; and

M + is a monovalent positive counter ion.

17. The heat-sensitive negative working lithographic printing plate precursor according to claim 16 , wherein the sum of the amounts of the infrared light absorbing dye and the additional dye, without taking into account optional counter ions, is more than 0.70 mg per m 2 of the total surface of the particles, wherein the surface is measured by Hydrodynamic Fractionation.

18. The heat-sensitive negative working lithographic printing plate precursor according to claim 16 , wherein the sum of the amounts of the infrared light absorbing dye and the additional dye, without taking into account optional counter ions, is more than 0.80 mg per m 2 , wherein the surface is measured by Hydrodynamic Fractionation.

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

(a) providing a printing plate precursor according to claim 17 ;

(b) exposing said printing plate precursor to infrared light; and

(c) developing said exposed printing plate precursor with a gum solution.

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

(a) providing a printing plate precursor according to claim 18 ;

(b) exposing said printing plate precursor to infrared light; and

(c) developing said exposed printing plate precursor with an alkaline aqueous solution.

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

(a) providing a printing plate precursor according to claim 16 ;

(b) exposing said printing plate precursor to infrared light; and

(c) developing said exposed printing plate precursor with an alkaline aqueous solution.