| 摘要 |
PROBLEM TO BE SOLVED: To obviate generation of gas in a plate surface protection solution even in continuously processing a large number of photosensitive lithographic printing plates. and provide fine ink application, plate wear, and ink fouling preventive property in a non-image portion by allowing plate surface liquid for a lithographic printing plate to contain citric acid and ethylene diamine tetraacetate. SOLUTION: Lithographic printing plate surface protection liquid used in a desensitizing process immediately after the photosensitive lithographic printing plate contains citric acid and ethylene diamine tetraacetate. Using citric acid as an additive acid shows an intensive pH buffer property and maintains acid dissociation, and further restrains ions of calcium and magnesium and prevent the occurrence of precipitation of an organic polymer dispersedly dissolved in plate surface protection liquid. By adding ethylene diamlne tetraacetate to plate surface protection liquid using citric acid, an ink application property can significantly be improved, which shows a state meaning a small sheets of waste paper until the image portion of printed matter leads to a normal printing density after the initiation of printing. |
