Coating formulation for printing plate precursor, printing plate precursor, printing press, fabrication process of printing plate, and regeneration process of printing Plate

Abstract

Disclosed are a printing plate precursor, a fabrication process of the printing plate precursor, a fabrication process of a printing plate, a regeneration process of the printing plate, a printing press, and a coating formulation for the printing plate precursor. According to the present invention, a printing plate can be fabricated directly from digital data, and sufficient image quality can be obtained without a developing step, i.e., a developer. To permit repeated use of the precursor, the precursor has a surface, which contains a photocatalyst and is capable of showing hydrophilicity when exposed to activating light having energy higher than band gap energy of the photocatalyst. A coating formulation—which comprises fine particles of a thermoplastic resin having both a property that the particles unite to the surface when heated and a property that the particles decompose under action of the photocatalyst when exposed to activating light having energy higher than band gap energy of the photocatalyst—is applied as a hydrophobizing agent onto the surface. At least apart of the surface of the precursor is heated such that the fine particles applied on the part of the surface are fixed to form a hydrophobic image area. The fine particles applied on the remaining part of the surface with the image area formed thereon are then removed.

1 . A printing press comprising: 
 a plate cylinder for mounting thereon a printing plate precursor having a surface in which a photocatalyst is contained,    a plate cleaning unit for removing ink from said surface of said printing plate precursor,    a hydrophobizing agent coater for applying, onto said surface of said printing plate precursor, a coating formulation which comprises fine particles of a thermoplastic resin having both a property that said fine particles unite to said surface of said printing plate precursor when heated and a property that said fine particles decompose under action of said photocatalyst when exposed to activating light having energy higher than band gap energy of said photocatalyst,    an image area inscribing unit for heating at least a part of said surface of said printing plate precursor to form a hydrophobic image area,    a drier for drying said surface of said printing plate precursor, and    a regenerating unit for irradiating said activating light onto said surface of said printing plate precursor to erase said hydrophobic image area.    
   
   
       2 . A printing press according to  claim 1 , further comprising a hydrophobizing agent remover for removing said fine particles of said resin in said hydrophobizing agent applied on a part of said surface of said printing plate precursor, said part being other than said hydrophobic image area.  
   
   
       3 . A printing press according to  claim 1 , wherein said image area inscribing unit is a non-activating light irradiating unit for irradiating non-activating light, which has energy lower than said band gap energy of said photocatalyst, such that said fine particles of said resin are heated by said energy of said non-activated light to have said fine particles fixed on said surface of said printing plate precursor and to inscribe said image area.  
   
   
       4 . A printing press according to  claim 1 , wherein said photocatalyst is a titanium oxide photocatalyst.  
   
   
       5 . A process for fabricating a printing plate having a surface, which contains a photocatalyst and is capable of showing hydrophilicity when exposed to light having energy higher than band gap energy of said photocatalyst, to form a hydrophobic image area in at least a part of said surface of said printing plate precursor, which comprises: 
 a hydrophobizing agent coating step for applying a coating formulation, which comprises fine particles of a thermoplastic resin having both a property that said fine particles unite to said surface of said printing plate precursor when heated and a property that said fine particles decompose under action of said photocatalyst when exposed to said activating light, onto said surface of said printing plate precursor,    an image area inscribing step for heating at least said part of said surface of said printing plate precursor to form said hydrophobic image area, and    a hydrophobizing agent removing step for removing said fine particles of said resin applied on a part of said surface of said printing plate precursor, said part being other than said image area.    
   
   
       6 . A fabrication process according to  claim 5 , wherein said image area inscribing step comprises irradiating non-activating light, which has energy lower than said band gap energy of said photocatalyst, such that said fine particles of said resin are heated and melted into a film form by said energy of said non-activating light to make said fine particles unite to said surface of said printing plate precursor and to inscribe said image area.  
   
   
       7 . A fabrication process according to  claim 6 , wherein said image area inscribing step comprises irradiating an infrared ray to heat and melt said fine particles of said resin into a film form by energy of said infrared ray such that said fine particles unite to said surface of said printing plate precursor and said image area is inscribed.  
   
   
       8 . A fabrication process according to  claim 5 , wherein said hydrophobizing agent removing step comprises removing said fine particles of said resin from said surface of said printing plate precursor by adhesive force of ink and/or washing action of a fountain solution in an initial stage of beginning of a printing operation.  
   
   
       9 . A fabrication process according to  claim 5 , wherein said fine particles have an average particle size in a range of from 0.01 to 5 μm, a weight average molecular weight Mw of not higher than 400,000, a ratio of Mw to a number average molecular weight Mn, Mw/Mn, of not greater than  4 , and a glass transition temperature (Tg) in a range of from 20 to 180° C.  
   
   
       10 . A fabrication process according to  claim 5 , wherein said resin is at least one of acrylic resins, styrene resins, styrene-acrylic resins, urethane resins, phenolic resins, ethylene resins, vinyl resins, butadiene resins, polyacetal resins, polyethylene terephthalate resin, and polypropylene resin.  
   
   
       11 . A fabrication process according to  claim 5 , wherein said photocatalyst is a titanium oxide photocatalyst.  
   
   
       12 . A fabrication process according to  claim 5 , wherein said coating formulation is in a water-based form.  
   
   
       13 . A fabrication process according to  claim 5 , wherein said coating formulation is in a solvent-based form.  
   
   
       14 . A process for regenerating a printing plate having a surface and an image area formed on said surface, said surface containing a photocatalyst and being capable of showing hydrophilicity when exposed to activating light having energy higher than band gap energy of said photocatalyst, and said image are a comprising a thermoplastic resin having both a property that said fine particles unite to said surface of said printing plate to form said image area when heated and a property that said fine particles decompose under action of said photocatalyst when exposed to said activating light, which comprises: 
 an ink removing step for removing ink from said surface of said printing plate after completion of a printing operation, and    a regeneration step for irradiating said activating light onto said surface of said printing plate such that said image area is decomposed and removed and said surface of said printing plate is hydrophilized.    
   
   
       15 . A process for regenerating a printing plate having a surface and an image area formed on said surface, said surface containing a photocatalyst and being capable of showing hydrophilicity when exposed to activating light having energy higher than band gap energy of said photocatalyst, and said image area comprising fine particles of a thermoplastic resin having both a property that said fine particles unite to said surface of said printing plate to form said image area when heated and a property that said fine particles decompose under action of said photocatalyst when exposed to said activating light, which comprises: 
 an ink removing step for removing ink from said surface of said printing plate after completion of a printing operation, and    a regeneration step for hydrophilizing and regenerating said surface of said printing plate by performing a removing operation, which comprises irradiating said activating light onto said surface of said printing plate to decompose and remove said image area, and a washing step, which comprises washing said surface of said printing plate with a washing solution, either at the same time or repeatedly in an alternating manner.