| 摘要 |
PURPOSE:To substantially obviate the generation of stains in shadow parts on a printing machine and to make it possible to obtain stable printed matter having high quality by specifying a relation between a base subjected to surface roughening and the surface roughness after development of a photosensitive layer formed on the surface thereof. CONSTITUTION:The surface roughness Ra of the base surface of the photosensitive planographic printing plate formed by providing the surface of the base subjected to the surface roughening with the photosensitive layer and the difference DELTARa between the surface roughness Ra of this base surface and the surface roughness TRa of the photosensitive layer after development are so set as to satisfy equation, where units are both mum. An aluminum sheet or the like is more preferable as this base. The aluminum sheet having about 0.1 to 0.6mm thickness is subjected to a sand dressing treatment by an electrochemical sand dressing method, etc., and is then etched by an alkali, etc. The conditions for application of the photosensitive layer are controlled according to the surface roughness of the base surface subjected to surface roughening. The base surface is respectively so treated that the surface roughness Ra of the base surface attains 0.2 to 1.5mum (10muR stylus) and is further preferably 0.4 to 1.2mum. |
