Patent ID: 6140022
Filing Date: 2000-10-31
Classification: B41C,B41M,Y10S

Abstract:
A method for obtaining a negative working lithographic printing plate comprising the steps of:(a) image-wise or information-wise exposing to IR light or heat an imaging element comprising on a flexible support, having thereon a cross-linked hydrophilic layer, an image forming layer including (1) an alkali soluble or swellable resin having a phenolic hydroxy group, (2) a latent Bronsted acid, (3) an infrared absorber, and (4) an amino cross-linking agent, wherein said infrared absorber is a dye or pigment selected from the group consisting of the croconate, cyanine. merocyanine, indolizine, pyrylium and metal dithiolene compounds;(b) heating said exposed imaging element to provide reduced solubility in the exposed areas;(c) developing said exposed and heated imaging element with an aqueous alkaline developing solution in order to remove the unexposed areas and thereby form a lithographic printing plate.