PRODUCTION OF PLANOGRAPHIC PLATE BY USING INFRARED-SENSITIVE OR THERMOSENSITIVE IMAGE FORMING ELEMENT

摘要

PROBLEM TO BE SOLVED: To obtain a general method to obtain a negative planographic printing plate having high quality by using an image forming element which is substantially nonsensitive for room light. SOLUTION: This method to obtain a negative planographic printing plate includes the following processes. An image forming element having an IR- sensitive layer or thermosensitive layer which contains quinone diazide. water- insoluble alkali soluble or swellable resin and IR absorbent formed on a hydrophilic surface of a planographic printing plate base body is exposed to IR rays or heat according to an image or information. The image forming element is wholly exposed to UV rays so as to increase the solubility in the region which is not exposed to IR rays or heat according to the image or information. Then the image forming element exposed according to the image or information and further wholly exposed to UV rays is developed with an alkali developer to remove the region which is not exposed according to the image or information. Thus, a planographlc printing plate is formed.