| 摘要 |
<p>"Improvements in or relating to lithographic printing" In a method of manufacturing a lithographic printing plate a radiation sensitive plate comprising a grained substrate coated with a positive working radiation sensitive layer is exposed to actinic light through a continuous tone master, with no half tone screen between the plate and the light source. The layer comprises a naphthoquinone diazide ester and an alkali soluble resin in specified ratio, and the exposed plate is developed using a developer comprising an aqueous alkaline solution and a water miscible organic solvent, again in specified ratio. Plates produced by the method have an improved tonal range; the density range can be further extended by including in situ random spaced areas of opaque screening material on the surface of the layer such that the layer is struck by light which has passed through the screening material, optionally with a flash exposure before development.</p> |
