Patent ID: 7045266

Claim:
A lithographic printing original plate having a photosensitive layer on a substrate directly or on another layer provided thereon, said photosensitive layer being comprised of a crosslinked polymer having ink repellency, wherein the photosensitive layer is a water-insoluble photosensitive hydrophilic resin layer obtained by crosslinking a photosensitive composition consisting essentially of a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer and a light absorbing compound, wherein the photosensitive hydrophilic resin layer has a phase-separation structure comprised of a hydrophilic polymer phase comprised of a crosslinked hydrophilic polymer and a hydrophobic polymer phase comprised of a hydrophobic polymer, and wherein the photosensitive layer is changed from being ink-repellant to ink-receptive by irradiation with light whereby the plate is without need of developing the unexposed areas of the photosensitive layer with a fountain solution during printing.