TREATMENT OF PHOTOSENSITIVE LITHOGRAPHIC PRINTING PLATE

摘要

PURPOSE:To maintain stably the activity of a developing soln. with an inexpensive and simple method by detecting the area to be formed as the image part or non-image part after the development of a photosensitive lithographic printing plate prior to the development and adding the replenisher of the amt. predetermined according to the detected information. CONSTITUTION:The area to be formed as the image part or non-image part of the PS plate with which the reflectivity of the surface of the photosensitive layer to light is different in the exposed part and unexposed part is measured by an optical means. The amt. of the replenishment necessary per unit area of the non-image part of the PS plate is preliminarily determined by developing the PS plat having the specified area of the non-image part with a specified amt. of the developing soln., adding the replenisher thereto and measuring the amt. of the replenisher for restoring the activity of the developing son. prior to the development. The replenishment of the replenishing amt. corresponding to the area of the non-image part is made possible simply by making an electrical treatment such as the operation of a replenisher feed pump by as much as the time proportional to the area of, for example, the non-image part. The addition of the replenisher to the developing soln. during the development is made possible simply by making an electrical treatment so as to operate the replenisher feed pump at the same instant when the PS plate enters the developing zone.