The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 10, 1985
Filed:
Mar. 01, 1984
Applicant:
Inventors:
Koichi Yoshida, Shizuoka, JP;
Yoshio Hirayama, Shizuoka, JP;
Yasuo Oka, Shizuoka, JP;
Takashi Kajiyama, Shizuoka, JP;
Kunihiko Hotta, Shizuoka, JP;
Assignee:
Nippon Light Metal Company Limited, Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
B21C / ;
U.S. Cl.
CPC ...
148 315 ; 428629 ; 148-6 ;
Abstract
An aluminum substrate for magnetic recording media such as magnetic disks, etc., is composed of an aluminum alloy plate containing 2 to 6% by weight magnesium and impurities in only limited amounts and having on the surface an anodic oxidation film with thickness more than 3 .mu.m formed by a chromic acid process. In the thus-anodized aluminum substrate, the occurrence of black spot defects is greatly reduced and the formation of cracks upon heating the substrate to high temperatures is prevented in spite of the thicker anodic oxidation film.