| 摘要 |
PROBLEM TO BE SOLVED: To obtain a finishing liquid for a planographic printing plate which ameliorates the ink contamination arising at the time of repetition of shutdown and reprinting and utilizes a silver complex salt diffusion transfer method using aluminum sheet as a base by applying the finishing liquid containing phosphoric acid ions at a specific ratio or above at the time of plate making processing of the plate consisting of the aluminum sheet as the base. SOLUTION: The phosphoric acid ions form a hydrophilicity impartation protective layer of aluminum phosphate insoluble in water while dissolving anodically oxidized silver to impart hydrophilicity to the plate surface and to protect the surface. Then, the occurrence of the contamination even after reprinting after the shutdown of printing may be suppressed. The phosphoric acid ions of >=0.25 mol/liter are necessary in order to impart this function to the finishing liquid. The phosphate of a supply source for the phosphoric acid ions includes salts, such as sodium, potassium, ammonium and calcium. Above all, the ammonium phosphate exhibits an extremely high effect to the contamination. Amines may be used as the counter-cation of the phosphoric acid ions for the finishing liquid. |
