Planographic printing plate precursor

1 . A planographic printing plate precursor including a recording layer capable of forming an image upon irradiation with infrared rays, wherein the recording layer comprisng:

(A) an alkali-soluble resin having, in a main chain, a structural unit containing at least one type of bond selected from an amide bond, an urea bond, an urethane bond and an ester bond, and having at least one type of acid group selected from a phenolic hydroxyl group, a sulfonamide group and an active imide group; and

(B) an infrared absorbing agent.

2 . The planographic printing plate precursor according to claim 1 , wherein the at least one type of bond is represented by one of formulae (1) to (4):

wherein R 1 to R 4 each independently represents a hydrogen atom, an alkyl group or a carbonyl group, and when any one of R 1 to R 4 is a carbonyl group, the any one of R 1 to R 4 may be bonded to another functional group in the resin to form a cyclic imide structure.

3 . The planographic printing plate precursor according to claim 2 , wherein R 1 to R 4 each represents a hydrogen atom.

4 . The planographic printing plate precursor according to claim 2 , wherein the at least one type of bond represented by one of formulae (1) to (3) is a bond containing a nitrogen atom.

5 . The planographic printing plate precursor according to claim 1 , wherein a content of the at least one type of bond contained in alkali-soluble resin (A) is 0.5 to 10 meq/g (equivalent (unit: mmol) of the specific bond contained per 1 g of the resin).

6 . The planographic printing plate precursor according to claim 1 , wherein the acid group is a phenolic hydroxyl group.

7 . The planographic printing plate precursor according to claim 1 , wherein the alkali-soluble resin (A) further comprises a carboxyl group.

8 . The planographic printing plate precursor according to claim 1 , wherein, in the alkali-soluble resin (A), a content of all alkali soluble groups, including the acid group, is 1.0 to 10 meq/g.

9 . The planographic printing plate precursor according to claim 1 , wherein atoms constituting the main chain of alkali-soluble resin (A) form an aromatic ring structure containing a phenylene skeleton and/or alicyclic structure.

10 . The planographic printing plate precursor according to claim 1 , wherein the recording layer further comprises a development inhibitor (C) which reduces alkali solubility of alkali-soluble resin (A) but which, upon irradiation with infrared rays, loses its ability to reduce alkali solubility.

11 . A planographic printing plate precursor including a recording layer, wherein the recording layer comprising:

(A) an alkali-soluble resin having, in a main chain, a structural unit containing at least one type of bond selected from an amide bond, urea bond and an urethane bond, and having at least one type of acid group selected from a phenolic hydroxyl group, a sulfonamide group and an active imide group; and

(B) an infrared absorbing agent,

wherein atoms constituting the main chain of alkali-soluble resin (A) form an aromatic ring structure containing a phenylene skeleton and/or an alicyclic structure.

12 . A planographic printing plate precursor according to claim 11 , wherein the at least one type of bond is represented by one of formulae (1) to (3) blow:

wherein R 1 to R 4 each independently represents a hydrogen atom, an alkyl group or a carbonyl group, and when any one of R 1 to R 4 is a carbonyl group, the any one of R 1 to R 4 may be bonded to another functional group in the resin to form a cyclic imide structure.

13 . The planographic printing plate precursor according to claim 12 , wherein the acid group is a phenolic hydroxyl group.

14 . The planographic printing plate precursor according to claim 12 , wherein the alkali-soluble resin (A) further comprises a carboxyl group.

15 . The planographic printing plate precursor according to claim 11 , wherein the recording layer further comprises a development inhibitor (C) which reduces alkali solubility of alkali-soluble resin (A) but which, upon irradiation with infrared rays, loses an ability to reduce alkali solubility.

16 . A planographic printing plate precursor having a recording layer, wherein the recording layer comprising:

a lower layer containing a first alkali-soluble resin; and

an upper layer containing a second alkali-soluble resin, and a substance acting on the second alkali-soluble resin to reduce alkali solubility thereof,

wherein the first alkali-soluble resin has, in a main chain, a structural unit containing at least one type of bond selected from an amide bond, an urea bond and an urethane bond, and simultaneously has at least one type of acid group selected from a phenolic hydroxyl group, a sulfonamide group and an active imide group, and wherein the substance reducing the alkali solubility of the second alkali-soluble resin, upon irradiation with infrared rays, loses an ability to reduce alkali solubility of the second alkali-soluble resin.

17 . The planographic printing plate precursor according to claim 16 , wherein at least one of the upper layer and the lower layer includes an infrared absorbing agent.

18 . The planographic printing plate precursor according to claim 16 , wherein the at least one type of bond is represented by one of formulae (1) to (4) below:

wherein R 1 to R 4 each independently represents a hydrogen atom, an alkyl group or a carbonyl group, and when any one of R 1 to R 4 is a carbonyl group, the any one of R 1 to R 4 may be bonded to another functional group in the resin to form a cyclic imide structure.

19 . The planographic printing plate precursor according to claim 18 , wherein the acid group is a phenolic hydroxyl group.

20 . The planographic printing plate precursor according to claim 18 , wherein the alkali-soluble resin (A) further comprises a carboxyl group.