Lithographic process involving on press development

A presensitized lithographic plate which comprises a hydrophilic support and an image-forming layer containing an infrared absorbing agent, a radical polymerization initiator, an ethylenically unsaturated polymerizable compound and a binder polymer, said polymerization initiator being a salt of a sulfonium ion with an anion selected from the group consisting of (1) hydrogensulfate ion, (2) a sulfate ester ion, (3) a polymer having a carboxylate ion, (4) a polymer having a sulfonate ion, and (5) a polymer having an anion of —SO2—N−—R1 (wherein R1 is carboxyl, formyl, an aliphatic group, an aromatic group, a heterocyclic group, —O—R, —S—R, —CO—R, —O—CO—R or —CO—O—R, and wherein R is an aliphatic group, an aromatic group or a heterocyclic group), wherein the polymerizable compound is contained in microcapsules, which are dispersed in the image-forming layer, and the binder polymer is arranged outside the microcapsules.

A presensitized lithographic plate which comprises a hydrophilic support and an image-forming layer containing an infrared absorbing agent, a radical polymerization initiator, an ethylincially unsaturated polymerizable compound and a binder polymer, said polymerization initiator being a salt of an anion with a sulfonium ion which comprises a sulfur atom to which three aromatic groups are attached, at least one of the aromatic groups being substituted with an electron attractive group, wherein the polymerizable compound is contained in microcapsules, which are dispersed in the image-forming layer, and the binder polymer is arranged outside the microcapsules.