Patent ID: 7867691
Filing Date: 2011-01-11
Classification: G03D,G03F

Abstract:
1. A process for preparing a lithographic plate for offset printing, comprising: (a) selecting a plate having a hydrophilic substrate and an overlying non-diazo based, photopolymerizable, solvent soluble oleophilic coating, which coating is partially polymerized, radiation sensitive, and further polymerizes where exposed to radiation in a particular wavelength range; (b) imagewise exposing the plate to radiation in said particular wavelength range, thereby producing a pattern of highly polymerized oleophilic regions and partially polymerized oleophilic regions; (c) exposing the entire coating to a high pressure stream of water at elevated temperature, whereby the water mechanically and completely removes only the partially polymerized regions to the substrate without dissolution of any of the coating, thereby directly producing a printing plate having an image pattern of highly polymerized, oleophilic regions of said coating and hydrophilic regions of said substrate, wherein the plate is continuously conveyed longitudinally in a process direction beneath a fixed nozzle frame that spans the width of the plate; and a nozzle that discharges water at a temperature in the range of about 90-115 deg. F. at a nozzle pressure above about 1000 psi is reciprocated within the frame across the width of the plate as the plate is conveyed, said nozzle having a spray pattern that at a given moment impinges the plate over a subarea of the entire coated area of the plate and rasters said subarea across the width of the plate until all of the plate surface has been exposed to the high pressure stream of water.