Patent ID: 9605355
Date: 2017-03-28
CPC Classifications: B29C,C25D

Claim:
1. A method for producing anodic porous alumina where an oxide layer having a plurality of pores is formed on an aluminum substrate surface, comprising: step (a) for immersing an aluminum substrate in an electrolyte containing two or more acids, wherein the two or more acids include oxalic acid and phosphoric acid; step (b) for applying a voltage on the aluminum substrate immersed in the electrolyte; step (c) for keeping the aluminum substrate immersed in the electrolyte while applying substantially no voltage on the aluminum substrate; and step (d) for alternately repeating steps (b) and (c), wherein the temperature of the electrolyte is at least 10° C. but lower than 25° C., and the phosphoric acid concentration (M) (mol/L) and time (T) (min.) for keeping the aluminum substrate immersed in the electrolyte are set to satisfy the formulas (1) and (2) below, and the time (T) indicates time (min.) per etching treatment on the aluminum substrate in the step (c),