| 摘要 |
PROBLEM TO BE SOLVED: To prevent an environment contaminating substance from arising, provide a favorable image quality, and improve the plate wear by a method wherein for a printing original plate in order to manufacture an offset printing plate by forming an image by an ink jet method, the surface roughness of an image forming surface is within a specified range by a JIS indication. SOLUTION: As a method to form a hydrophilic image forming layer on the surface of aluminum, after performing a degreasing treatment of the aluminum surface, by treating the aluminum surface by a mechanical treatment such as a ball grinding, a chemical treatment by an acid such as sulfuric acid, and an electrochemical treatment such as electrolysis, a grain application is performed on the metal surface, and a water holding property is imparted on the metal surface, and by this method, a hydrophilic image forming layer wherein the surface roughness is within a range of 0.2-1.0μm by a central line average roughness conforming to JIS B0601, can be formed. In addition, in order to increase the strength at the time of printing and at the time of handling, or in order to increase the printing resistance by improving the fixing property of a solid ink, after performing the grain application, it is required to electrochemically treat the surface with an acid such as sulfuric acid, and apply an anodizing treatment to form a film of aluminum oxide.
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