Developer for photopolymerizable presensitized plate for use in making lithographic printing plate and method for preparing lithographic printing plate

Abstract

A developer for a photopolymerizable presensitized plate for use in making a lithographic printing plate characterized in that it comprises an alkali silicate and a nonionic compound represented by the following general formula (I), it has a molar ratio: SiO2/M2O (wherein M represents an alkali metal or an ammonium group) ranging from 0.75 to 4.0, a pH value ranging from 11.5 to 12.8 and a conductivity ranging from 3 to 30 mS/cm: A—W  (I) wherein A represents a hydrophobic organic group whose logP as determined for A—H is not less than 1.5 and W represents a nonionic hydrophilic organic group whose logP as determined for W—H is less than 1.0; a method for preparing a lithographic printing plate comprising the steps of imagewise exposing, to light, a presensitized plate for use in making a lithographic printing plate, which comprises a substrate provided thereon with a photopolymerizable light-sensitive layer containing a compound having at least one addition-polymerizable ethylenically unsaturated double bond and a photopolymerization initiator; and then developing the exposed presensitized plate using the above developer. The developers and the method for making a lithographic printing plate according to the present invention can prevent scumming during printing and simultaneously attain sufficient printing durability without impairment of image-forming performance, and the developer can dissolve or disperse stably for a long period of time the compounds which are not soluble in the developer, and therefore the running performance of the developer can be excellent and stabilized.

Dependencies are inferred from the claim text.