DEVELOPING METHOD FOR POSITIVE TYPE PHOTOSENSITIVE LITHOGRAPHIC PRINTING PLATE

摘要

PURPOSE:To make a developing soln. usable stably for a long period of time without exchaging by using the developing soln. consisting of potassium silicate of specific composition mainly in developing a titled printing plate contg. an o-quinone diazide as a photosensitive component. CONSTITUTION:In subjecting a positive type lithographic printing plate made by providing a photosensitive layer consisting of o-quinone diazide as a photosensitive component on an aluminum plate to image exposure thence to development with a developing soln., which consisting substantially of potassium silicate is used. A potassium hydroxide soln. is added to the developing soln., to adjust the molar ratio of SiO2/K2O in the developing soln. to 1.6-2 and the content of K2O in the developing soln. to 1.8-7.2wt%. Thereby, the developing soln. is made usable for a long period of time without exchanging and without causing clogging of spraying nozzles in the case of using an automtic developing machine of a system of spraying the developing soln. onto the surface of the photosensitive layer.