Patent ID: 6245481
Filing Date: 2001-06-12
Classification: B41C,G03F

Abstract:
A method of lithographically printing images on a receiving medium, comprising in order:(a) providing a lithographic plate comprising (i) a substrate; (ii) a photosensitive layer capable of hardening or solubilization upon exposure to an actinic radiation in ultraviolet and visible region, the non-hardened or solubilized areas of said photosensitive layer being soluble or dispersible in ink, and said photosensitive layer 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 sensitive mask layer which is substantially opaque to the actinic radiation, soluble or dispersible in ink (for waterless plate) or in ink and/or fountain solution (for wet plate), and capable of being removed or rendered transparent to the actinic radiation upon exposure to an infrared laser radiation;(b) imagewise exposing the plate with the infrared laser radiation to selectively remove or render transparent to the actinic radiation 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 or rendered transparent by the infrared laser radiation; and(d) on a printing press, contacting said exposed plate with ink (for waterless plate), or with ink and/or fountain solution (for wet plate) to remove the mask layer and develop the photosensitive layer, and to lithographically print images from said plate to the receiving medium.