PHOTOSENSITIVE PLANOGRAPHIC PRINTING PLATE

摘要

PROBLEM TO BE SOLVED: To provide a positive type photosensitive planographic printing plate less liable to form an unnecessary image of an edge part on a printing plate, ensuring good image visibility after exposure and good plate inspectability after development and having high sensitivity. SOLUTION: The photosensitive planographic printing plate has a photosensitive layer containing a photo-acid generating agent, o-naphthoquinone diazide and a compound whose absorption is varied by an acid. The absorbance of the photosensitive layer freed of the o-naphthoquinone diazide at 400 nm increases by >=0.03 after exposure. The photosensitive planographic printing plate is preferably obtained by disposing a middle layer containing a high molecular compound containing (a) a unit which interacts with an alumina layer and (b) a unit which interacts with a layer formed by treatment for imparting hydrophilic property on an aluminum substrate subjected to anodic oxidation and treatment for imparting hydrophilic property and then disposing the photosensitive layer on the middle layer.