Resin composition

1. A resin composition comprising:

(A) an alkali-soluble resin;

(B) an infrared absorbing agent having a maximum absorption wavelength in the range of 760 nm to 1200 nm; and

(C) a thiol compound,

wherein a solubility of the resin composition in an alkaline aqueous solution is changed by exposure with an infrared laser beam.

2. A resin composition according to claim 1 , further comprising:

(D) a compound that is thermally decomposable and substantially reduces a solubility of the alkali-soluble resin in an undecomposed state.

3. A resin composition according to claim 2 , wherein the compound that is thermally decomposable and substantially reduces a solubility of the alkali-soluble resin in an undecomposed state is a compound selected from a group consisting of onium salts, o-quinonediazide compounds, and alkyl sulfonate esters.

4. A resin composition according to claim 1 , wherein the thiol compound can tautomerize as shown by the following general formula (1):

wherein X represents a trivalent atom or atomic group.

5. A resin composition according to claim 4 , wherein X in general formula (1) is a nitrogen atom or a methine group.

6. A resin composition according to claim 1 , wherein the thiol compound is an aliphatic hydrocarbon having an SH group on a side chain or at a terminal.

7. A resin composition according to claim 1 , wherein the thiol compound is a cyclic hydrocarbon substituted by an SH group or a heterocyclic compound substituted by an SH group.

8. A resin composition according to claim 7 , wherein the cyclic hydrocarbon substituted by an SH group is a compound represented by the following general formula:

wherein in the general formula, R 1 through R 5 each independently represent a hydrogen atom, an alkyl group, a halogen atom, an alkoxy group, or a mercapto group.

9. A resin composition according to claim 7 , wherein the heterocyclic compound substituted by an SH group has two nitrogen atoms in the heterocyclic compound and is represented by the following general formula:

wherein in the general formula, R represents a hydrogen atom or an alkyl group.

10. A resin composition according to claim 7 , wherein the heterocyclic compound substituted by an SH group has three nitrogen atoms in the heterocyclic compound and is represented by at least one of the following general formulae:

wherein in the general formulae, R 1 through R 6 each independently represent a hydrogen atom, an alkyl group, an aryl group, an amino group, or a mercapto group, at least one of R 1 and R 3 represents a mercapto group, and at least one of R 4 and R 6 represents a mercapto group.

11. A resin composition according to claim 7 , wherein the heterocyclic compound substituted by an SH group has four nitrogen atoms in the heterocyclic compound and is represented by the following general formula:

wherein in the general formula, R represent an alkyl group or an aryl group, and when R represents an aryl group, R may represent an aryl group that has a substituent selected from the group consisting of a hydroxyl group, a carbamoyl group, and a carboxyl group.

12. A resin composition according to claim 7 , wherein the heterocyclic compound substituted by an SH group is a compound represented by the following general formula:

wherein in general formula, R represents an alkyl group, an amino group, an alkylthio group, or a mercapto group.

13. A resin composition according to claim 7 , wherein the heterocyclic compound substituted by an SH group is a compound represented by the following general formula:

wherein in general formula, R 1 and R 2 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a carbamoyl group, a nitro group, or a sulfonate group, and Z represents —NH—, an oxygen atom, or a sulfur atom.

14. A resin composition according to claim 7 , wherein the heterocyclic compound substituted by an SH group is a compound represented by the following general formula:

wherein in the general formula, R 1 and R 2 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a carbamoyl group, a nitro group, or a sulfonate group, and Z represents an oxygen atom or a sulfur atom.

15. A resin composition according to claim 7 , wherein the heterocyclic compound substituted by an SH group is a compound represented by the following formula:

wherein in the general formula, R 1 through R 3 each independently represent a hydrogen atom, an alkyl group, a haloalkyl group, a hydroxyl group, an amino group, a nitroso group, or a mercapto group.

16. A resin composition according to claim 1 , wherein the thiol compound is a compound obtained by substituting an SH group for a substituent on a cyclic hydrocarbon.

17. A resin composition according to claim 1 , wherein the thiol compound is contained in an amount of 0.2 to 20% by mass based on a total solids content of the resin composition.

18. A resin composition according to claim 1 , wherein the resin composition is a resin composition for a positive-type planographic printing plate precursor.

19. A positive-type image recording layer containing a resin composition according to claim 1 .

20. A positive-type image recording layer according to claim 19 , wherein the thiol compound can tautomerize as shown by the following general formula (1):

wherein X represents a trivalent atom or atomic group.

21. A negative-type image recording layer containing a resin composition according to claim 1 .