| 摘要 |
PURPOSE:To enhance water retention, adhesion to a photosensitive layer and durability to repeated printing of a base for a planographic plate, by a method wherein bottom parts of grain of the base are shaped into acute-angular shapes by using an abrasive having an acute-angular shape with a radius of a tip part of not more than 20mum, and the specific gravity of the abrasive is specified so as to ensure deep graining. CONSTITUTION:An abrasive is used which has an acute-angular shape with a radius of a tip part of not more than 20mu and a specific gravity of not less than 2.5, and retains the acute-angular shape even when being broken. The particle size of the abrasive is about #20-#600. A device for jetting an abrasive slurry against the surface of a base comprises a nozzle connected to a high- pressure liquid supplying part and a jetting port making contact with an abrasive slurry supplying part. The nozzle and the port are so arranged that a flow of a high-pressure liquid jetted from the nozzle and a flow of the slurry jetted from the jetting port join each other. It is necessary that the liquid be jetted from the nozzle at a velocity of 31-140m/sec. After mechanical graining is finished, chemical etching or electrochemical surface roughening is conducted. |
