Coating composition and method for preparing radiation sensitive plate useful in lithographic printing and the like

Abstract

The invention relates to new radiation sensitive coating compositions and coating product which are radiation sensitive in the infrared region closed to the infrared, comprising two layers, the first layer comprising a hiding polymer and one or more infrared absorbing material which absorbs in the desired wavelength and a second layer coated on the first layer comprising one or more copolymer which is able to coat and make the polymer of the first layer insoluble in the conventional developer of positive plates, and when applied to an appropriate substrate is useful as off-set lithographic printing plates, for color proofing films and photoresist. The invention also refers to a printing or imaging process.

1 . A radiation sensitive coating composition, wherein said composition creates two superposing coating layers.  
     
     
         2 . A radiation sensitive coating composition according to  claim 1 , wherein the layers comprise: 
 a) a first layer containing a binding polymer and one or more infrared-absorbing compound;    b) a second layer containing one or more polymer for coating and protecting the binding polymer making it insoluble in the conventional positive plate developer.    
     
     
         3 . A coating composition according to  claim 2 , wherein the binding polymer is a first polymer which is a condensation product of phenol, o-chlorophenol, o-, m- or p-cresol, p-hydroxy benzoic acid, 2-naphthol or other aromatic monohydroxy monomer with an aldehyde such as formaldehyde, acetaldehyde, fural, benzaldehyde, or any other aliphatic or aromatic aldehyde.  
     
     
         4 . A coating composition according to  claim 2 , wherein the binding polymer has a molecular weight in the range from 2,000 to 80,000, more preferably in the range of 4,000 to 40,000 and most preferably in the range of 7,000 to 20,000.  
     
     
         5 . A coating composition according to  claim 2 , wherein the other polymers are added to the binding polymer for improving the plate performance.  
     
     
         6 . A coating composition according to  claim 5 , wherein said other polymer is a butylated melamine formaldehyde resin.  
     
     
         7 . A coating composition according to  claim 5 , wherein said other polymer is a butylated urea formaldehyde resin.  
     
     
         8 . A coating composition according to  claim 5 , wherein said other polymer is a copolymer of vinyl pirrolidone/vinyl acetate.  
     
     
         9 . A coating composition according to  claim 2 , wherein the infrared-absorbing compounds are dyes able to absorb radiation from 750 to 1200 nm.  
     
     
         10 . A coating composition according to  claim 9 , wherein said composition may contain one or more infrared-absorbing dye.  
     
     
         11 . A coating composition according to  claim 10 , wherein said composition may contain an infrared-absorbing dye at 830 nm and another infrared-absorbing dye at 1064 nm, allowing the composition to work on distinct infrared-emitting devices.  
     
     
         12 . A coating composition according to  claim 9 , wherein the infrared absorbers are preferably comprised of dyes from classes including pyridyl, quinolinyl, benzoxazolyl, thiazolyl, benzothiazolyl, oxazolyl and selenazolyl.  
     
     
         13 . A coating composition according to  claim 2 , wherein the layer coating and insolubilizing the binding polymer contains another polymer.  
     
     
         14 . A coating composition according to  claim 10 , wherein the polymer coating and insolubilizing the binding polymer is a polymeric amine.  
     
     
         15 . A coating composition according to  claim 10 , wherein the polymer coating and insolubilizing the binding polymer is a cellulose butyrate acetate.  
     
     
         16 . A coating composition according to  claim 10 , wherein the polymer coating and insolubilizing the binding polymer is a cellulose propionate acetate.  
     
     
         17 . A coating composition according to  claim 10 , wherein the polymer coating and insolubilizing the binding polymer is a methylated melamine formaldehyde.  
     
     
         18 . A coating composition according to  claim 10 , wherein the polymer coating and insolubilizing the binding polymer is a butylated urea formaldehyde.  
     
     
         19 . A coating composition according to  claim 6 , wherein the polymer coating and insolubilizing the binding polymer is a polyethylene glycol.  
     
     
         20 . A coating composition according to any of the preceding claims, wherein said composition is applied onto a graphic printing plate and said plate does not need a heat treatment prior to development.  
     
     
         21 . A coating composition according to any of the preceding claims, wherein said composition is applied onto a lithographic printing plate and said plate is subjected to a heat curing step after development.  
     
     
         22 . A coating composition according to any of the preceding claims, wherein said composition is dissolved in a suitable solvent system.  
     
     
         23 . A coating composition according to any of the preceding claims, wherein the first layer provides a coating having a dry weight in the range from 0.5 to 2.0 g/m2, preferably from 0.7 to 1.4 g/m2.  
     
     
         24 . A coating composition according to any of the preceding claims, wherein the second layer provides a coating having a dry weight in the range from 5 to 200 mg/m2, preferably from 10 to 100 mg/m2.  
     
     
         25 . A coating composition according to any of the preceding claims, wherein said composition is applied in order to provide a radiation sensitive coating between 750 and 1200 nn on an textured and anodized aluminum substrate or on a polyester substrate.  
     
     
         26 . A coating composition wherein said composition is as described in the specification and examples.  
     
     
         27 . A coating composition according to any of the preceding claims, wherein said composition comprises:  
       
         
           
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   (a) a first layer comprising: 
                 
                 
                 
                 
               
                     
                   phenolic polymer 
                    85-99% 
                 
                     
                   infrared absorber 
                   0.5 to 10% 
                 
                     
                   (b) a second layer comprising: 
                 
                     
                   a binding insolubilizing compound 
                     5 to 200 mg/m2. 
                 
                     
                     
                 
                     
                     
                 
             
                
                
               
               
                
               
            
             
                
                
                
                
                
                
               
            
           
         
       
     
     
         28 . A coating composition according to  claim 5 , wherein said other polymer associated to the binding polymer in the first layer comprises from 0.5 to 20% relative to the binding polymer weight.  
     
     
         29 . The use of radiation sensitive composition according to any of  claims 1  to  28 , wherein said composition is used for coating substrates, particularly lithographic printing plates, and as color proofing films or photoresist.  
     
     
         30 . A lithographic printing plate, wherein said plate comprises a coating prepared from a composition as defined in any of claims  1 - 28 .  
     
     
         31 . A printing or imaging process wherein said process comprises the use of a composition as defined in any of claims  1 - 28  for applying a coating onto a support and for imaging from a support coated with said composition.  
     
     
         32 . A printing or imaging process wherein said process is as described in the specification and examples.  
     
     
         33 . A radiation sensitive coating product wherein said product comprises two superposing layers.  
     
     
         34 . A product according to  claim 33 , wherein the layers comprise: 
 a) a first layer containing a binding polymer and one or more infrared-absorbing compound;    b) a second layer containing one or more polymer for coating and protecting the binding polymer making it insoluble in the conventional positive plate developer.    
     
     
         35 . A product according to claims  33  and 34, wherein said product comprises a radiation sensitive composition as defined is any of  claims 3  to  28 .  
     
     
         36 . radiation sensitive coating wherein said coating comprises two superposing layers.  
     
     
         37 . A coating according to  claim 36 , wherein the layers comprise: 
 a) a first layer containing a binding polymer and one or more infrared-absorbing compound;    b) a second layer containing one or more polymer for coating and protecting the binding polymer making it insoluble in the conventional positive plate developer.    
     
     
         38 . A coating according to  claim 36  or  37 , wherein said coating is made from a radiation sensitive composition as defined in any of  claims 3  to  28 .