Patent ID: 7157209

Claim:
A process for manufacturing an aluminum support for a planographic printing plate material having a negative working image formation layer which is a photopolymerizable image formation layer comprising a photopolymerizable composition, the process comprising the steps of: (a) electrolytically surface-roughening an aluminum plate; and, thereafter, (b) anodizing the surface-roughened aluminum plate, wherein the step (a) contains: (i) a first stage which surface-roughens the aluminum plate employing a sine-wave alternating current in a first electrolyte solution containing hydrochloric acid as a main component; and, thereafter (ii) a second stage which surface-roughens the aluminum plate employing a controlled sine-wave alternating current using a thyristor so that a current flow starts at a phase angle of 60 to 120 degree of an alternating current cycle, in a second electrolyte solution containing hydrochloric acid as a main component.