PLANOGRAPHIC PRINTING PLATE FOR SCANNING TYPE EXPOSURE

摘要

PURPOSE:To provide the planographic printing plate by a silver salt diffusion transfer method which is free from degradation in plate wear and has a good preservability in a direct plate making method of a semiconductor laser diode scanning system. CONSTITUTION:This planographic printing plate for scanning type exposure is constituted by successively applying at least one undercoating layers, silver halide emulsion layer and physical development nuclei on a base. These silver halide emulsion layers contain sensitizing coloring matter having the max. spectral sensitivity in a long wavelength region of >=700nm. A developing agent of the amt. at which the exposed silver halide can be developed in an alkaline activating bath is incorporated into the constituting elements. The amt. of dihydroxybenzenes of such plate is in a 0.0045 to 0.0125mol/m<2> range and the finish coating liquid contains <=0.0036mol/m<2> dihydroxybenzenes and is so applied that the content thereof is 2/3, more preferably 1/3 the entire part. The remaining dihydroxybenzenes are incorporated into the undercoating layer.