Planographic printing plate

1. A negative-type planographic printing plate having, disposed on a support, at least a recording layer comprising a radical-polymerizable negative-type image recording material on which an image can be recorded by irradiation with an infrared ray, the radical-polymerizable negative-type image recording material including an infrared ray absorbing agent comprising a cyanine dye in which at least one of substituents on nitrogen atoms at both terminal ends thereof is selected from the group consisting of the following substituents:

—C(═X)R 1 ;

—C(═X)R 2 R 3 ;

—CH═CR 4 R 5 ;

—C≡CR 6 ;

—CR 9 R 10 R 11 ; and

—Ar,

wherein X represents O or S; R 1 to R 6 each independently represent H or a hydrocarbon group having 20 or fewer carbon atoms which may have a substituent; R 7 to R 11 each independently represent a hydrocarbon group having 20 or fewer carbon atoms which may have a substituent; Ar represents an aromatic group which may have a substituent; and

wherein the radical-polymerizable negative-type image recording material further comprises a radical generating agent and a radical polymerizable compound.

2. The negative-type planographic printing plate of claim 1 , wherein the infrared ray absorbing agent comprises a cyanine dye represented by the following general formula (1):

wherein R a and R b may be the same as or different from each other and each independently represent a hydrogen atom or a monovalent substituent, and at least one of R a and R b represents a substituent selected from the group consisting of:

—C(═X)R 1 ;

—C(═X)NR 2 R 3 ;

—CH═CR 4 R 5 ;

—C≡CR 6 ;

—CHR 7 R 8 ;

—CR 9 R 10 R 11 ; and

—Ar,

wherein R 1 to R 6 each independently represent H or a hydrocarbon group having 20 or fewer carbon atoms which may have a substituent; R 7 to R 11 each independently represent a hydrocarbon group having 20 or fewer carbon atoms which may have a substituent; X represents O or S; Ar 1 and Ar 2 each independently represent an aromatic hydrocarbon group or a heterocyclic group which may have a substituent; Y 1 and Y 2 may be the same as or different from each other and each independently represent one selected from the group consisting of a sulfur atom, an oxygen atom, a selenium atom, a dialkylmethylene group having 12 or less carbon atoms, —CH═CH— and —NR Y1 —; Q represents a pentamethine group or a heptamethine group; and Z − represents a counter ion which is present when neutralization of an electric charge is required;

R Y1 represents H or a hydrocarbon group having 20 or fewer carbon atoms which may have a substituent.

3. The negative-type planographic printing plate of claim 1 , wherein the infrared ray absorbing agent is contained in an amount ranging from 0.01% by mass to 50% by mass based on a total solid content of the radical-polymerizable negative-type image recording material.

4. The negative-type planographic printing plate of claim 1 , wherein the infrared ray absorbing agent comprises at least one of an infrared ray absorbing dye and an infrared ray absorbing pigment, both of which have an absorption maximum in a wavelength range from 760 nm to 1200 nm.

5. The negative-type planographic printing plate of claim 1 , wherein the radical generating agent comprises at least one member selected from the group consisting of an onium salt, a triazine compound, a peroxide, an azo polymerization initiator, an azide compound, a quinone diazide compound, a metallocene compound and an organic borate compound.

6. The negative-type planographic printing plate of claim 1 , wherein the radical generating agent comprises an onium salt selected from the group consisting of a diazonium salt, an iodonium salt, a sulfonium salt, an ammonium salt and a pyridinium salt.

7. The negative-type planographic printing plate of claim 1 , wherein the radical generating agent comprises an onium salt selected from the group consisting of onium salts represented by the following general formulae (I) to (III):

Ar 11 —I + —Ar 12 (Z 11 ) −   General Formula(I)

Ar 21 —N + ≡N(Z 12 ) −   General Formula(II)

wherein, in general formula (I), Ar 11 and Ar 12 each independently represent an aryl group having 20 or fewer carbon atoms which may have a substituent; and (Z 11 ) − represents a counter ion selected from the group consisting of a halogen ion, a perchloric ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a carboxylate ion and a sulfonic acid ion,

wherein, in general formula (II), Ar 21 represents an aryl group having 20 or fewer carbon atoms which may have a substituent; and (Z 12 ) − represents a counter ion equivalent to (Z 11 ) − , and

wherein, in general formula (III), R 31 to R 33 may be the same as or different from one another and each independently represent a hydrocarbon group having 20 or fewer carbon atoms which may have a substituent; and (Z 13 ) − represents a counter ion equivalent to (Z 11 ) − .

8. The negative-type planographic printing plate of claim 1 , wherein the radical generating agent is contained in an amount ranging from 0.1% by mass to 50% by mass based on a total solid content of the radical-polymerizable negative-type image recording material.

9. The negative-type planographic printing plate of claim 1 , wherein the radical polymerizable compound has at least one ethylenically unsaturated double bond.

10. The negative-type planographic printing plate of claim 1 , wherein the radical polymerizable compound comprises at least one selected from the group consisting of an unsaturated carboxylic acids, unsaturated carboxylic acid esters and unsaturated carboxylic acid amides.

11. The negative-type planographic printing plate of claim 1 , wherein the radical-polymerizable negative-type image recording material further comprises a binder polymer.

12. The negative-type planographic printing plate of claim 11 , wherein the binder polymer is a linear organic polymer that is soluble or swellable in at least one of water and weak-alkaline water.

13. The negative-type planographic printing plate of claim 11 , wherein the binder polymer is contained in an amount ranging from 20% by mass to 95% by mass based on a total solid content of the radical-polymerizable negative-type image recording material.

14. The negative-type planographic printing plate of claim 1 , wherein the radical-polymerizable negative-type image recording material further comprises a coloring agent.

15. The negative-type planographic printing plate of claim 1 , wherein the radical-polymerizable negative-type image recording material further comprises a thermal polymerization inhibitor.

16. The negative-type planographic printing plate of claim 1 , wherein the radical-polymerizable negative-type image recording material further comprises at least one of a nonionic surfactant and an amphoteric surfactant.

17. The negative-type planographic printing plate of claim 1 , wherein the radical-polymerizable negative-type image recording material further comprises a plasticizer.