Photopolymerizable composition

Abstract

A composition that is photopolymerizable upon absorption of light and/or heat, the composition including a binder, a polymerizable compound, a sensitizer, and a photoinitiator, characterized in that the composition includes, with respect to its non-volatile compounds, at least about 0.01 wt. % of a polythiol compound and has a very high sensitivity and hardness.

What is claimed is: 
     
         1 . A lithographic printing plate precursor comprising:
 a photopolymerizable composition, the composition including a binder, a polymerizable compound, a sensitizer, a photoinitiator, and a polythiol compound; wherein   the composition includes, with respect to its total solid weight, at least about 0.01 wt. % of the polythiol compound;   the polythiol compound an oligomer, polymer, or copolymer;   the oligomer, polymer, or copolymer includes at least six SH-groups per molecule; and   the thiol groups of the polythiol compound may also be present in their tautomeric thione form.   
     
     
         2 . The lithographic printing plate precursor according to  claim 1 , wherein the oligomer, polymer, or copolymer has a molecular weight of at least 500. 
     
     
         3 . The lithographic printing plate precursor according to  claim 1 , wherein the SH group is linked to the oligomer, polymer, or copolymer chain as shown in formula (V): 
       
         
           
           
               
               
           
         
         wherein 
         L 5  means a linking group; 
         R 12 , R 13  mutually independent mean H or a non-metal atom substituent; and 
         t means an integer from 2 to 10,000. 
       
     
     
         4 . The lithographic printing plate precursor according to  claim 1 , wherein the oligomer, polymer, or copolymer includes monomeric units of formula (VI): 
       
         
           
           
               
               
           
         
         wherein 
         D 1  means SiR 14 , CH, or CR 14 ; 
         B 1  means O if D 1  means SiR 14 ; 
         B 1  means CH 2  or CH-alkyl if D 1  means CH or CR 14 ; 
         R 14  means a substituted or unsubstituted alkyl chain with 1 to 12 carbon atoms; 
         R 15  means a substituted or unsubstituted alkylene group or an alkyl chain containing acyloxy, ether, carbonate, thioether, hydroxy, phenyl, heterocylic, amino, thiol, sulphonyl, amido, glycerol monoether, urethane, or urea functions; and 
         u means an integer from 2 to 10,000. 
       
     
     
         5 . The lithographic printing plate precursor according to  claim 1 , wherein the polymer has a hyperbranched structure and includes at least 6 thiol groups per molecule. 
     
     
         6 . The lithographic printing plate precursor according to  claim 1 , further comprising an additional sulfur containing compound as a chain transfer agent. 
     
     
         7 . The lithographic printing plate precursor according to  claim 1 , wherein a minimum exposure for image formation, measured on a surface of the plate, is about 100 μJ/cm 2  or less. 
     
     
         8 . A method of making a lithographic printing plate comprising the steps of:
 providing a photopolymer printing plate precursor as defined in  claim 1 ;   exposing the printing plate precursor with a laser having an emission wavelength in the range from about 300 nm to about 600 nm;   heating the plate to a temperature, when measured at a rear surface of the plate, of about 90° C. to about 150° C., for a time between 10 seconds and 1 minute; and   processing the printing plate precursor in an aqueous alkaline developer.