Process for making lithographic printing plates

Claim 1

A process for making a lithographic printing plate, which comprises imagewise exposing to the radiation from a neon-helium laser or a light-emitting diode a photosensitive element comprising at least emulsion layer of silver halide containing 70 mol-% or more of silver chloride and surface layer containing physical development nuclei, said emulsion layer being spectrally sensitized with an anion- or betaine-type meso-substituted trimethine cyanine dye having at least one β-naphthothiazole nucelus represented by the general formula (I) ##STR12## where R 1 and R 2 each represents an alkyl group, an alkenyl group, an aryl group, or an aralkyl group, at least one of R 1 and R 2 is a group having a sulfo or carboxyl group; R 3 and R 4 each represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a hydroxyl group, an alkoxycarbonyl group, or a halogen atom, R 3 and R 4 may jointly form a benzene ring; R 5 represents an alkyl group, an aryl group, or an aralkyl group; Y 1 and Y 2 each represents a sulfur or selenium atom, provided that Y 1 and Y 2 are not simultaneously a selenium atom; X represents a cationic form of a hydrogen atom, an alkali metal atom, or an ammonium group; and m is 1 or 0, and developing the exposed element by the silver complex diffusion transfer process.