| 摘要 |
PURPOSE:To obtain the titled printing plate with excellent printing durability and small point reproducibility in addition to a wider exposure latitude by a method wherein a base made of an iron material coated with a film of chrome series and a photosensitive component containng a o-quinone diazide compound are used. CONSTITUTION:The surface of an iron or steel material is provided with a layer comprising iron atoms, chrome atoms and oxygen atoms. The percentage of the iron atoms in the layer is increased in a part closer to the iron material, while its surface is composed of chrome and oxidized chrome. In addition, diffusion cracks, holes are provided in the layer, which is coated with a mixture of a base having crystalline chrome exposed on its surface and a compound having an o- quinone diazide radical in order to obtain printing durability of more than 250,000 sheets and a 2% area ratio of small point reproducibility, with a wider exposure latitude. The photosensitive lithographic plate thus obtained will not produce rust even if it is left unused for a week. |
