Developer composition for PS plates for use in making lithographic printing plate and method of plate-making

摘要

A developer composition which comprises an aromatic compound having hydroxyl groups at the 1- and 3-positions thereof and free of any electron attractive group or a salt thereof, an alkaline agent and water. The developer composition can effectively be used, as a developer, in a method for making lithographic printing plates which comprises the steps of: exposing, to light, a presensitized plate for use in making a lithographic printing plate provided with a water-insoluble image-forming layer formed on a substrate and developing the plate to remove non-image portions. Lithographic printing plates manufactured according to the method provide printed matter free of background contamination. If the pH value of the developer is controlled to not less than 12, both positive- working and negative-working presensitized plate can be treated therewith. Moreover, if the developer composition is employed, the working efficiency is greatly improved since it is not necessary to previously provide two kinds of developer compositions and two kinds of developing machines. Besides, initial cost can be saved and the space for installing such machines are also greatly reduced.