PURPOSE: To prevent the staining of a non-image part without lowering printing durability, in preparing an original plate having an O-quinone diazide compound type photosensitive layer, by treating an anodic oxidation film in a dilute alkali solution with pH of 7.5W12 at 60W100°C.
CONSTITUTION: After an aluminum plate having a thickness of about 0.1W0.5mm is subjected to degreasing treatment and succeedingly subjected to sand dressing treatment according to a known method, the treated aluminum plate is subjected to anodic oxidation treatment in a solution with an electrolyte concn. of 1W 80wt% under such a treating condition that a solution temp. is 5W70°C, current density is 5W60A/dm2, voltage is 1W100V and an electrolytic time is 10secW 5min. The aluminum plate having an anodic oxidation film formed thereto is treated with a dilute alkali solution with a concn. of 5W5,000ppm for 5W120sec under such a treating condition that a pH is 7.5W12 and a temp is 60W100°C and, thereafter, an O-quinone azide compound-containing photosensitive layer is applied to the resulting aluminum plate. This photosensitive layer can use a resin soluble in an aqueous alkaline solution as a binder.
HASEGAWA KAZUYASU
MORITA AKIRA
MIYASHITA TERUO
NIPPON LIGHT METAL CO
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