Method for making lithographic printing plates.

摘要

Lithographic printing plates are prepared by: 1) providing a sensitized lithographic substrate (10) having a photochemical coating (12) thereon that has its solubïlity altered upon exposure to actinic radiation (for example an anodized aluminium substrate (10) coated with a UV sensitive diazo resin); 2) depositing on selected portions of the sensitized substrate a layer of non-silver halide material (14) that is opaque to the actinic radiation that will alter the solutility characteristics of the photochemical coating (this forms a so-called fugitive negative on the sensitized substrate and electrostatic or laser transfer techniques can be used for forming the fugitive negative); 3) exposing the sensitized substrate to actinic radiation to alter the solubility characteristics of the uncovered portions of the photochemical coating; and 4) dissolving away the soluble portions of the photochemical coating. If desired the non-silver halide fugitive negative can be removed after exposing the sensitized substrate.