Patent ID: 8087354
Filing Date: 2012-01-03
Classification: B41C,G03F

Abstract:
1. A method of lithographically printing images on a receiving medium, comprising in order: (a) providing a lithographic plate comprising (i) a substrate, and (ii) a photosensitive layer comprising a free radical polymerizable monomer, a free radical initiator, a sensitizing dye, and a material selected from the group consisting of a visible, dye, a latent dye, and a dispersed pigment; said photosensitive layer being soluble or dispersible in ink and/or fountain solution and capable of hardening upon exposure to a radiation having a wavelength selected from 200 to 1200 nm; (b) imagewise exposing said plate with said laser to cause hardening of said photosensitive layer in the exposed areas, with the non-exposed areas of said photosensitive layer remaining non-hardened; (c) overall contacting said exposed plate with a discoloring agent to change the color of the photosensitive layer primarily or only in the non-hardened areas, with less or no color change in the hardened areas; wherein said discoloring agent is capable of changing the color of the photosensitive layer in the non-hardened areas and is incapable or having reduced capability of changing the color of the photosensitive layer in the hardened areas; wherein said contacting step is carried out off press; and wherein said discoloring agent is a solution and said plate after contacted with said discoloring agent is further dried with forced air or heat (d) developing said discolored plate with ink and/or fountain solution on a lithographic press to remove the photosensitive layer in the non-hardened areas; and (e) lithographically printing images from said plate to the receiving medium.