PHOTOSENSITIVE COMPOSITION AND PLANOGRAPHIC PRINTING PLATE MATERIAL AND IMAGE FORMING METHOD USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a planographic printing plate material which is capable of dealing with exposure by a semiconductor laser for radiating rays from visible to near IR regions, has excellent printing resistance and a good inking property and contributes to the decrease of loss paper at printing. SOLUTION: This photosensitive compsn. contains the following (A) and (B) spectrally sensitized to two different wavelengths as well as the compd. which induces a radical polymerizable monomer and a compd. which induces a decomposition reaction by an acid. (A) is a combination of a radical generator and sensitizing dyestuff A. (B) is a combination of a photo-acid generating agent and sensitizing dyestuff B. The layer of the photosensitive compsn. formed on a base in this image forming method is subjected imagewise to the decomposition reaction by the acid generated by the photo-acid generation reaction with the exposure light of the absorption wavelength region of the sensitizing dyestuff B to elute and develop the exposed parts and thereafter, the film is cured by the radical polymn. by the full-surface exposure of the absorption wavelength region of the sensitizing dyestuff A.