| 摘要 |
PURPOSE:To simplify a graining process, by a method wherein a surface of an Al plate is provided with oblong form press-recessed parts in a density not lower than a specified value so that the recessed parts partially overlap with each other to form a wavy pattern, and specified minute recessed parts are provided thereon by electrochemical etching. CONSTITUTION:The surface of the Al plate is provided with the oblong form press-recessed parts in a density of not lower than 200 pieces/mm.<2> so that the recessed parts overlap with each other to form a wavy pattern, and then the minute recessed parts with an average pitch of 1-10mum are provided thereon by electrochemical etching. Roughening of the surface of the Al plate is conducted by, e.g., a pressure roll the surface of which is previously roughened, whereby the surface of the Al plate is provided with the oblong press-recessed parts in a high density so that fringe parts partially overlap with each other to form a wavy pattern. The shape and the density of the oblong recesed parts are associated with adaptability for a planographic printing plate, and they are adjusted to within respective predetermined ranges. The density of the oblong press-recessed parts is preferably not lower than 200 pieces/mm.<2>, desirably, 1,000-10,000 pieces/mm.<2>. |
