Method for preparation of lithographic printing plate and lithographic printing plate prepared thereby

Abstract

A method for the preparation of a lithographic printing plate comprises exposing imagewise a lithographic printing plate precursor comprising a support having provided thereon a light-sensitive layer containing fine anatase-type titanium oxide grains and a complex composed of an organo-metallic polymer and an organic polymer containing at least one member selected from the group consisting of an amido bond, a urethane bond, a ureido bond and a hydroxy group to an ultraviolet ray to render a surface of the light-sensitive layer hydrophilic in the exposed area. A lithographic printing plate prepared according to the method is also disclosed.

What is claimed is:  
     
       1. A method for the preparation of a lithographic printing plate comprises exposing imagewise a lithographic printing plate precursor comprising a support having provided thereon a light-sensitive layer containing fine anatase titanium oxide grains and a complex composed of an organo-metallic polymer and an organic polymer containing at least one member selected from the group consisting of an amido bond, a urethane bond, a ureido bond and a hydroxy group to an ultraviolet ray to render a surface of the light-sensitive layer hydrophilic in the exposed area. 
     
     
       2. The method for the preparation of a lithographic printing plate as claimed in  claim 1 , wherein the organo-metallic polymer is a polymer formed by a hydrolysis polymerization condensation reaction of at least one organo-metallic compound represented by the following formula (I): 
       
         
           (R o ) n M(Y) x-n    (1)  
         
       
       wherein R o  represents a hydrogen atoms, a hydrocarbon group or a heterocyclic group; Y represents a reactive group; M represents a metallic atom having from 3 to 6 valences; x represents a valence of the metallic atom M; and n represents 0, 1, 2, 3 or 4, provided that the balance of x-n is not less than 2. 
     
     
       3. The method for the prepartion of a lithographic printing plate as claimed in  claim 1 , wherein a surface of the light-sensitive layer in the area unexposed with the ultra-violet ray has a contact angle with water of 20 degrees or more and the surface of the light-sensitive layer in the area exposed with the ultraviolet ray has a contact angle with water of 10 degrees or less. 
     
     
       4. The method for the preparation of a lithographic printing plate as claimed in  claim 1 , wherein the imagewise exposure is conducted using an ultraviolet laser beam. 
     
     
       5. The method for the preparation of a lithographic printing plate as claimed in  claim 1 , wherein an average particle size of the anatase titanium oxide grains is from 5 to 500 nm. 
     
     
       6. The method for the preparation of a lithographic printing plate as claimed in  claim 1 , wherein the light-sensitive layer contains the anatase titanium oxide grains in a range from 30 to 95% by weight. 
     
     
       7. The method for the preparation of a lithographic printing plate as claimed in  claim 1 , wherein the organic polymer is an amide resin having an —N(R 10 )CO— or —N(R 10 )SO 2 — bond wherein R 10  represents a hydrogen atom, a hydrocarbon group or a heterocyclic group, a ureido resin having an —NHCONH— bond or a urethane resin having an —NHCOO— bond. 
     
     
       8. The method for the preparation of a lithographic printing plate as claimed in  claim 1 , wherein the organic polymer is a polymer containing a repeating unit represented by the following formula (II):                    
       wherein Z 1  represents —CO— or —CS—; R 20  represents a hydrogen atom, a hydrocarbon group or a heterocyclic group; rrepresents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, r 1 s may be the same or different; and p represents an integer of 2 or 3. 
     
     
       9. The method for the preparation of a lithographic printing plate as claimed in  claim 1 , wherein a weight ratio of the organo-metallic polymer/organic polymer is from 10/90 to 90/10. 
     
     
       10. A method for the preparation of a lithographic printing plate which comprises after conducting printing using the lithographic printing plate prepared according to the method as claimed in  claim 1 , removing printing ink from the lithographic printing plate, subjecting the surface of the light-sensitive layer of the lithographic printing plate to heat treatment to turn the hydrophilic property in the exposed area to the inherent hydrophobic property, thereby reproducing the lithographic printing plate precursor, and repeating the method as claimed in  claim 1 . 
     
     
       11. A lithographic printing plate prepared according to the method as claimed in  claim 1 .