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:
Feb. 20, 2001
Filed:
Apr. 29, 1999
Applicant:
Inventor:
Katsuhiko Yamaguchi, Sagamihara, JP;
Assignee:
Kabushiki Kaisha Ohara, , JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
C03C 1/004 ; C03C 1/014 ;
U.S. Cl.
CPC ...
C03C 1/004 ; C03C 1/014 ;
Abstract
A glass-ceramic substrate for a magnetic disk suitable for use as a contact recording type magnetic disk includes alpha-cristobalite (alpha-SiO,) and lithium disilicate (Li,O·2SiO,) as main crystal phases. The ratio of alpha-cristobalite/lithium disilicate is within a range from 0.20 to less than 0.25, a grain diameter of crystal grains is within a range from 0.1 &mgr;m to 1.0 &mgr;m, surface roughness (Ra) of the substrate after polishing is within a range from 2 Å to 9 Å.