| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for making a planographic printing plate free from edge stain even in printing repeated many times and with the lapse of time and suitable particularly for newspaper printing. SOLUTION: In the planographic printing plate obtained by subjecting the surface of an aluminum substrate to surface roughening treatment, anodic oxidation and treatment with at least one compound selected from a silicate, phosphonic acid and polyvinylphosphonic acid and disposing a layer containing a polyurethane resin having a substituent with an acidic hydrogen atom on the substrate, notched parts are present along the resin layer side angulate parts of at least two opposite edges, the resin layer side surfaces of the notched parts are flat or convex and have 5-45 deg. angle to the resin layer surface of the substrate, the height of each sag in the notched parts is 30-100 μm and the resin layer is present even on the notched parts. |
