Image formation method of planographic printing plate material

摘要

Disclosed is a method of forming an image on a light sensitive planographic printing plate material comprising a hydrophilic support and provided thereon, a light sensitive layer containing an addition polymerizable ethylenically unsaturated monomer, a photopolymerization initiator, a polymer binder, and a sensitizing dye having an absorption maximum in the wavelength regions of from 390 to 430 nm, the minimum laser exposure amount necessary to form an image on the material being from 1.0 to 100 muJ/cm², the method comprising the step of imagewise exposing the light sensitive planographic printing plate material to laser under a non-yellow safelight to form an image, the non-yellow safelight having an optical filter cutting out light with a wavelength of less than 440 nm, and satisfying the following expression: 0.800700<1.00.