LASER RESPONSIVE LITHOGRAPHIC PRINTING PLATE ORIGINAL PLATE

摘要

PURPOSE: To obtain a laser responsive lithographic printing plate original plate in which ink can be efficiently repelled without impairing laser response by forming an ink repellent layer as a hydrophilic swelled layer in a lithographic printing plate obtained by laminating at least a laser responsive layer and the ink repellent layer in this order on a board. CONSTITUTION: In a lithographic printing plate obtained by laminating at least a laser responsive layer and an ink repellent layer in this order on a board, a hydrophilic swelled layer is used as the repellent layer. The swelled layer is formed to have a phase isolation structure formed of at least two layers of the phase containing at least hydrophilic polymer as a main ingredient and the phase containing hydrophobic polymer as a main ingredient. The laser responsive layer and the swelled layer causes a destructive absorption to response to an active light ray due to the emission of a laser. Thus, the responsive layer is formed of at least binder resin and thermal absorbent having absorption in a laser emitting wavelength band.