Patent ID: 6906019

Claim:
An aqueous pre-treatment liquid for use in preparation of an offset printing plate having a porous recording surface, for use with direct inkjet CTP, said pre-treatment liquid consisting of: an ion donor, selected from the group of an inorganic acid and a polyvalent metallic salt, and at least one of: a polymer swelling reagent, selected from the group of N-methyl pyrrolidone, organic esters, ketones and cyclic ethers, and a coalescence reagent, selected from the group of butyl glycol and glycol ethers, such that when said pre-treatment liquid is applied to said printing plate, it becomes physically localized in the porous recording surface, said ion donor binds chemically to the inkjet drops, and said at least one of a polymer swelling reagent and a coalescence reagent diffuses within the CTP liquid, thereby providing mechanical stability to each of the inkjet drops and enabling the formation of a stable dot shape, having good film properties and very good adhesion to said pre-treated recording surface, resulting in smaller dot size and subsequent improved image quality.