Processless Development of Printing Plate

Abstract

On-press development of an imaged printing plate on a plate cylinder, in which ink is applied by an ink form roll, a blanket roll is in contact with the plate, a rubber roll is opposed to the blanket roll, and printable media passes between the blanket roll and the rubber roll. The plate comprises a substrate carrying an imaged coating and nonimage areas. The respective cohesive and adhesive properties of the nonimage and image areas to the applied ink, substrate, blanket roll and printable medium, and the ink to the roll are such that the blanket roll pulls the ink from the plate and the ink pulls the nonimage areas from the substrate as undissolved particles that are transferred by the blanket with the ink to the printable media.

1 . A process for developing a lithographic plate, comprising:
 (a) selecting an imaged plate having
 (i) a substrate with a grained, anodized, hydrophilic surface; 
 (ii) a negative working, organic, polymerizable coating in which all active components for polymerization are insoluble in any of the group of fluids consisting of water, fountain solution and ink; 
 (iii) wherein said coating is non-ionically bonded to the substrate and has been imaged by polymerization in areas exposed to radiation, such that the cohesion of the unimaged areas of the coating exceeds the adhesion of the unimaged areas of the coating to the substrate; and 
   (b) subjecting the entire coating to mechanical forces while the coating is in contact with one of said fluids, which forces disrupt and remove only the unimaged areas of the coating from the substrate surface in the form of particulate material and without dispersing the unimaged areas of the coating into the fluid at the substrate surface.   
     
     
         2 . The process of  claim 1 , wherein the mechanical forces are selected from the group consisting of compression, tension, impulse, and piercing. 
     
     
         3 . The process of  claim 1 , wherein the mechanical forces are provided by pushing against the coating. 
     
     
         4 . The process of  claim 1 , wherein the plate includes a top coat of a water soluble oxygen barrier and after imaging the topcoat is washed off with water before subjecting the entire coating to mechanical forces according to step (b). 
     
     
         5 . The process of  claim 1 , wherein the mechanical forces are provided by pressurized water spray. 
     
     
         6 . The process of  claim 1 , wherein the mechanical forces are provided by rotating brushes in the presence of water. 
     
     
         7 . A process for preparing a lithographic plate for offset printing, comprising the sequence of:
 (a) selecting a plate having an anodized, hydrophilic substrate and an overlying oleophilic, radiation polymerizable, non-aqueous organic coating non-ionically adhered to the substrate, wherein the cohesion of the coating to itself is greater than the adhesion of the coating to the substrate;   (b) imagewise exposing the plate to radiation, thereby producing a pattern of highly polymerized oleophilic imaged areas and unimaged oleophilic areas; and   (c) mechanically impinging the entire coating in a water environment supplied by a source of water, with sufficient energy to disrupt and dislodge the unimaged areas from the substrate and thereby remove the unimaged areas from the substrate in the form of discrete solid particles.   
     
     
         8 . The process of  claim 7 , wherein the step of mechanically impinging in step (c) is not performed by the source of water itself. 
     
     
         9 . The process of  claim 8 , wherein the discrete solid particles are removed substantially by the water source after being dislodged from the substrate. 
     
     
         10 . The process of  claim 7 , wherein between steps (b) and (c), the entire imagewise exposed plate is exposed to elevated temperature in the range of between about 175 to 250 degrees F. for a time period in the range of 5 to 15 seconds. 
     
     
         11 . The process of  claim 7 , wherein step (c) is performed with a high-pressure water spray. 
     
     
         12 . The process of  claim 7 , wherein step (c) is performed with a rotating brush. 
     
     
         13 . A process for preparing a lithographic plate for offset printing, comprising the sequence of:
 (a) selecting a plate having an anodized, hydrophilic substrate and an overlying oleophilic, radiation polymerizable, non-aqueous organic coating non-ionically adhered to the substrate, wherein the cohesion of the coating to itself is greater than the adhesion of the coating to the substrate and the coating is not dispersible in any of the group of fluids consisting of water, fountain solution and ink;   (b) imagewise exposing the plate to radiation, thereby producing a pattern of highly polymerized oleophilic imaged areas and unimaged oleophilic areas; and   (c) mechanically impinging the entire coating in a water environment with sufficient force to disrupt and dislodge the unimaged areas from the surface of the substrate and thereby remove the unimaged areas in the form of discrete solid particles.   
     
     
         14 . The process of  claim 13 , wherein between steps (b) and (c), the entire imagewise exposed plate is exposed to elevated temperature in the range of between about 175 to 250 degrees F. for a time period in the range of 5 to 15 seconds. 
     
     
         15 . The process of  claim 13 , wherein step (c) is performed with a high-pressure water spray. 
     
     
         16 . The process of  claim 13 , wherein step (c) is performed with a rotating brush.