method of producing positive working printing plates from a bildaufzeichnungselement ofheat sensitive

摘要

PROBLEM TO BE SOLVED: To obtain a method for manufacturing a positive type printing plate from a thermal style sensitive image forming element. SOLUTION: In the method for manufacturing a lithographic printing plate comprising the steps of modifying a thermal style image-forming element having a first layer soluble in an alkali developing solution containing a polymer and a top layer without permeating alkali developing solution containing a compound for converting a light into a heat and an Si2 O disposed at the same side as the first layer as a silicate, chemically exposing the element in an image style, and developing the element exposed in the thermal style with the developing solution to dissolve the exposed area of the top layer and a first layer area disposed thereunder and to allow an unexposed area of the first layer to remain undissolved; the top layer contains an organic quaternary ammonium salt.