LITHOGRAPHIC DEVELOPING PROCESS USING AN ANIONIC MATERIAL TO COUPLE WITH UNEXPOSED DIAZO MATERIAL

摘要

ABSTRACTThe disclosure describes a process for removingunexposed diazo from a lithographic printing plate comprisinga silicated aluminum substrate having a hydrophilic, anionic,negatively charged surface and on and bonded to the substrate,a light sensitive, cationic, positively charged, water-solublediazo material which has been selectively exposed to actiniclight in an image area. The process comprises contacting theplate after exposure with a solution consisting essentially ofan anionic material in water in a quantity and for a timesufficient to couple the diazo with the anionic material anddissolve the coupled product from the non-image area therebyovercoming the bond between the diazo and the substrate leavinga clean, hydrophilic non-image area, and rinsing with water.