| 摘要 |
PURPOSE:To enhance an adhesive property for a photosensitive image part and obtain a printing plate excellent in durability by electrolytically etching an aluminum plate in a specified electrolytic solution. CONSTITUTION:The surface of an aluminum plate of an aluminum alloy plate is previously degreased and washed to remove dusts and the like. Then the thus cleaned surface is electrolytically etched in an electrolytic solution containing about 3.5-35g/l, preferably 7-21g/l of hydrochloric acid and 0.01-20g/l, preferably 0.1-10g/l of a beta-dicarbonyl compound, usually at a current density of 20- 200A/dm<2>. By this etching, a grain suitable for use as a printing plate is obtained in which the diameters of pits are uniform, the pits are sufficiently close to each other and flat trapezoid parts are very little. Accordingly, a printing plate excellent in adhesive property for image parts and in durability is obtained.
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