Method for making a lithographic printing plate

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

providing a heat-sensitive printing plate precursor including on a support, having a hydrophilic surface or which is provided with a hydrophilic layer, a heat-sensitive coating;

image-wise exposing the precursor with heat and/or light; and

developing the exposed precursor with an aqueous alkaline, silicate based developing solution including lithium ions at a concentration of at least 0.05% wt and a salt of an aliphatic carboxylic acid; wherein

a molar ratio of the salt of the aliphatic carboxylic acid to the lithium ions is >1; and

the salt of the aliphatic carboxylic acid comprises 8 to 12 carbon atoms.

2. A method according to claim 1 , wherein the concentration of the lithium ions is at least 0.1% wt.

3. A method according to claim 1 , wherein the molar ratio of the salt of the aliphatic carboxylic acid to the lithium ions is greater than 1.

4. A method according to claim 2 , wherein the molar ratio of the salt of the aliphatic carboxylic acid to the lithium ions is greater than 1.

5. A method according to claim 1 , wherein the developing solution includes an image dissolution inhibiting agent.

6. A method according to claim 5 , wherein the image dissolution inhibiting agent is selected from:

(a) polyglycols with the following structure:

R a O—(CH 2 —CHR b —O) n —R c

wherein

R a represents hydrogen, an optionally substituted alkyl group including 1 to 30 carbon atoms, —COR t , or an optionally substituted aryl or aralkyl group;

R b represents hydrogen, methyl, ethyl, and/or mixtures thereof;

R c represents hydrogen, an alkyl group, —COR d , —NR d R e , —CH 2 COOH, or —CH 2 COO − M + ; and

M + represents NH 4 + , Na + , or K + and R d , R e , and R t independently represent hydrogen, an optionally substituted alkyl group including 1 to 30 carbon atoms, an optionally substituted aryl group or aralkyl group;

(b) polycondensation products of one or more alkylene groups and/or one or more polyoxyalkylene groups with an alkylene diamine, an alkylene triamine, an alkylene polyamine, or an alkylene imine group;

(c) cationic surfactants including primary, secondary, tertiary, or quaternary ammonium salts, phosphonium salts, or sulfonium salts.

7. A method according to claim 1 , wherein the heat-sensitive coating comprises at least two layers including:

a first layer including a water-insoluble and alkali soluble resin which exhibits an increased solubility upon exposure to heat and/or light; and

a second layer, which is located between the support and the first layer, including a water-insoluble and alkali soluble resin.

8. A method according to claim 7 , wherein the second layer includes a sulphonamide binder.

9. A method according to claim 8 , wherein the sulfonamide binder is represented by:

wherein

R 9 represents hydrogen or a hydrocarbon group including up to 12 carbon atoms;

X 1 represents a single bond or a divalent linking group;

Y 4 is a bivalent sulphonamide group; and

Z 1 represents a terminal group.

10. A method according to claim 2 , wherein the heat-sensitive coating comprises at least two layers including:

a first layer including a water-insoluble and alkali soluble resin which exhibits an increased solubility upon exposure to heat and/or light; and

a second layer, which is located between the support and the first layer, including a water-insoluble and alkali soluble resin.

11. A method according to claim 10 , wherein the developing solution includes an image dissolution inhibiting agent.

12. A method according to claim 4 , wherein the heat-sensitive coating comprises at least two layers including:

a first layer including a water-insoluble and alkali soluble resin which exhibits an increased solubility upon exposure to heat and/or light; and

a second layer, which is located between the support and the first layer, including a water-insoluble and alkali soluble resin.

13. A method according to claim 12 , wherein the developing solution includes an image dissolution inhibiting agent.

14. A method according to claim 1 , wherein the heat-sensitive coating comprises at least two layers including:

a first layer including a water-insoluble and alkali soluble resin which exhibits an increased solubility upon exposure to heat and/or light; and

a second layer, which is located between the support and the first layer, including a water-insoluble and alkali soluble resin.

15. A method according to claim 14 , wherein the second layer includes a sulphonamide binder.

16. A method according to claim 15 , wherein the sulfonamide binder is represented by:

wherein

R 9 represents hydrogen or a hydrocarbon group including up to 2 carbon atoms;

X 1 represents a single bond or a divalent linking group;

Y 4 is a bivalent sulphonamide group; and

Z 1 represents a terminal group.

17. A method according to claim 14 , wherein the developing solution includes an image dissolution inhibiting agent.

18. A method according to claim 17 , wherein the image dissolution inhibiting agent is selected from:

(a) polyglycols with the following structure:

R a O—(CH 2 —CHR b —O) n —R c

wherein

R a represents hydrogen, an optionally substituted alkyl group including 1 to 30 carbon atoms, —COR t , or an optionally substituted aryl or aralkyl group;

R b represents hydrogen, methyl, ethyl, and/or mixtures thereof;

R c represents hydrogen, an alkyl group, —COR d , —NR d R e , —CH 2 COOH, or —CH 2 COO − M + ; and

wherein M+ represents NH 4 +, Na+, or K+ and R d , R e , and R t independently represent hydrogen, an optionally substituted alkyl group including 1 to 30 carbon atoms, or an optionally substituted aryl group or aralkyl group;

(b) polycondensation products of one or more alkylene groups and/or one or more polyoxyalkylene groups with an alkylene diamine, an alkylene triamine, an alkylene polyamine, or an alkylene imine group;

(c) cationic surfactants including primary, secondary, tertiary, or quaternary ammonium salts, phosphonium salts, or sulfonium salts.

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

providing a heat-sensitive printing plate precursor including on a support, having a hydrophilic surface or which is provided with a hydrophilic layer, a heat-sensitive coating;

image-wise exposing the precursor with heat and/or light; and

developing the exposed precursor with an aqueous alkaline, silicate based developing solution including lithium ions at a concentration of at least 0.05% wt and a salt of an aliphatic carboxylic acid; wherein

a molar ratio of the salt of the aliphatic carboxylic acid to the lithium ions is ≧1;

the developing solution includes an image dissolution inhibiting agent;

the image dissolution inhibiting agent is selected from:

(a) polyglycols with the following structure:

R a O—(CH 2 —CHR b —O) n —R c

wherein

R a represents hydrogen, an optionally substituted alkyl group including 1 to 30 carbon atoms, —COR t , or an optionally substituted aryl or aralkyl group;

R b represents hydrogen, methyl, ethyl, and/or mixtures thereof;

R c represents hydrogen, an alkyl group, —COR d , —NR d R e , —CH 2 COOH, or —CH 2 COO − M + ; and

M + represents NH 4 + , Na + ,or K + and R d , R e and R t independently represent hydrogen, an optionally substituted alkyl group including 1 to 30 carbon atoms, an optionally substituted aryl group or aralkyl group;

(b) polycondensation products of one or more alkylene groups and/or one or more polyoxyalkylene groups with an alkylene diamine, an alkylene triamine, an alkylene polyamine, or an alkylene imine group;

(c) cationic surfactants including primary, secondary, tertiary, or quaternary ammonium salts, phosphonium salts, or sulfonium salts; and

the image dissolution inhibiting agent is the polycondensation product of the one or more alkylene groups and/or the one or more polyoxyalkylene groups with an alkylene diamine, an alkylene triamine, an alkylene polyamine, or an alkylene imine group.