ORIGINAL PLATE FOR PLANOGRAPHIC PRINTING PLATE

摘要

PROBLEM TO BE SOLVED: To provide a positive type original plate for planographic printing plate for an IR laser for direct plate making with recording layers excellent in sensitivity and development latitude in image formation, ensuring suppressed occurrence of defects due to a flaw in an image area and capable of forming a good image. SOLUTION: The original plate is obtained by disposing at least two positive type recording layers containing a water-insoluble and alkali-soluble resin and an IR absorbent and having solubility in an alkaline aqueous solution increased by exposure with infrared laser light on a base and the coating weight of the upper positive type recording layer is in the range of 0.05-0.45 g/m2. Preferably the upper positive type recording layer is one of the plurality of recording layers situated at a part nearest the surface.