Patent ID: 6245486
Filing Date: 2001-06-12
Classification: B41C,G03F

Abstract:
A method of imaging a lithographic plate, comprising in order:(a) providing a lithographic plate comprising in order: (i) a substrate; (ii) a photosensitive layer capable of hardening (negative-working) or solubilization (positive-working) upon exposure to an actinic radiation in ultraviolet and visible region and exhibiting an affinity or aversion substantially opposite to the affinity or aversion of said substrate to at least one printing liquid selected from the group consisting of ink and an abhesive fluid for ink; and (iii) an infrared laser ablatable mask layer which is substantially opaque to the actinic radiation and is capable of being removed upon exposure to an infrared laser radiation;(b) imagewise exposing the plate with the infrared laser radiation to selectively remove the exposed areas of the mask layer;(c) overall exposing the plate with the actinic radiation to cause hardening or solubilization of the photosensitive layer in the areas wherein the mask layer has been removed by the infrared laser radiation; and(d) further exposing the plate with the infrared laser radiation in, at least, part or all of the areas which have not been exposed with infrared laser radiation in step (b) to substantially remove the mask layer in said areas.