Lithographic printing plate precursor and lithographic printing method

Abstract

A lithographic printing plate precursor comprising a support and an image recording layer capable of drawing an image by exposure with an infrared laser, wherein the image recording layer contains (A) an infrared absorbent and (B) an iodonium salt represented by the following formula (I): Ar 1 —I {circle around (+)} —Ar 2 Z {circle around (−)}   (1) wherein Ar 1 and Ar 2 each represents a benzene ring which may have a substituent, provided that two benzene rings are differing in the substituent from each other and a total of Hammett's σ values of substituents on at least one of the benzene rings is a negative value, and Z represents a counter anion.

1 . A lithographic printing plate precursor comprising a support and an image recording layer capable of drawing an image by exposure with an infrared laser, which allows for printing by loading the lithographic printing plate precursor on a printing press without passing through a development processing after recording an image or by recording an image after loading the lithographic printing plate precursor on a printing press, 
 wherein the image recording layer contains an infrared absorbent and an iodonium salt represented by the following formula (1):      Ar 1 —I {circle around (+)} —Ar 2 Z {circle around (−)}   (1)    wherein Ar 1  and Ar 2  each represents a benzene ring which may have a substituent, provided that two benzene rings are differing in the substituent from each other and a total of Hammett's σ values of substituents on at least one of the benzene rings is a negative value, and Z represents a counter anion.    
     
     
         2 . The lithographic printing plate precursor as claimed in  claim 1 , wherein the iodonium salt represented by the formula (1) is an iodonium salt represented by the following formula (1a):  
         Ar 1a —I {circle around (+)} —Ar 2a Z {circle around (−)}   (1a)  
       wherein Ar 1a  represents a benzene ring having a substituent, provided that a total of Hammett's σ values of substituents is a negative value, Ar 2a  represents a benzene ring having a substituent, provided that a total of Hammett's σ values of substituents is a positive value, and Z represents a counter anion.  
     
     
         3 . The lithographic printing plate precursor as claimed in  claim 1 , wherein in formula (1), a total of Hammett's σ values of substituents on the benzene ring of Ar 1  is 0 or less, and a total of Hammett's a values of substituents on the benzene ring of Ar 2  is 0 or less.  
     
     
         4 . A lithographic printing plate precursor comprising a support and an image recording layer capable of drawing an image by exposure with an infrared laser, which allows for printing by loading the lithographic printing plate precursor on a printing press without passing through a development processing after recording an image or by recording an image after loading the lithographic printing plate precursor on a printing press, 
 wherein the lithographic printing plate precursor further comprises a layer containing an infrared absorbent and an iodonium salt represented by the following formula (1):      Ar 1 —I {circle around (+)} —Ar 2 Z {circle around (−)}   (1)    wherein Ar 1  and Ar 2  each represents a benzene ring which may have a substituent, provided that two benzene rings are differing in the substituent from each other and a total of Hammett's σ values of substituents on at least one of the benzene rings is a negative value, and Z represents a counter anion.    
     
     
         5 . The lithographic printing plate precursor as claimed in  claim 4 , wherein the iodonium salt represented by the formula (1) is an iodonium salt represented by the following formula (1a):  
         Ar 1a —I {circle around (+)} —Ar 2a Z {circle around (−)}   (1a)  
       wherein Ar 1a  represents a benzene ring having a substituent, provided that a total of Hammett's σ values of substituents is a negative value, Ar 2a  represents a benzene ring having a substituent, provided that a total of Hammett's σ values of substituents is a positive value, and Z represents a counter anion.  
     
     
         6 . The lithographic printing plate precursor as claimed in  claim 1 , wherein the image recording layer further contains a radical-polymerizable compound.  
     
     
         7 . The lithographic printing plate precursor as claimed in  claim 4 , wherein the image recording layer contains a radical-polymerizable compound.  
     
     
         8 . The lithographic printing plate precursor as claimed in  claim 1 , wherein the image recording layer further contains a compound of changing in color under an action of a radical.  
     
     
         9 . The lithographic printing plate precursor as claimed in  claim 4 , wherein the layer containing the iodonium salt further contains a compound of changing in color under an action of a radical.  
     
     
         10 . The lithographic printing plate precursor as claimed in  claim 1 , wherein at least one of the infrared absorbent and the iodonium salt is enclosed in a microcapsule.  
     
     
         11 . The lithographic printing plate precursor as claimed in  claim 4 , wherein at least one of the infrared absorbent and the iodonium salt is enclosed in a microcapsule.  
     
     
         12 . A lithographic printing method comprising: 
 image-exposing the lithographic printing plate precursor claimed in  claim 1;     removing the image recording layer in an unexposed part of the image-exposed lithographic printing plate precursor so as to producing a printing plate; and    performing printing by using the produced printing plate.    
     
     
         13 . A printing method comprising: 
 image-exposing the lithographic printing plate precursor claimed in  claim 4;     removing the image recording layer in an unexposed part of the image-exposed lithographic printing plate precursor so as to producing a printing plate; and    performing printing by using the produced printing plate.