SILICATE-CONTAINING DEVELOPING COMPOSITION AND PROCESSING METHOD FOR LITHOGRAPHIC PRINTING PLATE

摘要

PROBLEM TO BE SOLVED: To obtain an aq. alkaline silicate-contg. developing compsn. useful to develop a positive or negative working lithographic printing plate. SOLUTION: This alkaline developing compsn. for processing a lithographic printing plate has at least pH12 and contains at least 42g SiO2 based on 1,000g of this compsn. and such an amt. of an alkali metallic silicate as to regulate the weight ratio of SiO2 to M2 O (M is the alkali metal) to 0.55-0.925. The lithographic printing plate may be any of positive and negative working lithographic printing plates and includes a negative working heat sensitive plate.