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:
Oct. 22, 1996
Filed:
May. 16, 1995
Applicant:
Inventors:
Naoyuki Goto, Sagamihara, JP;
Katsuhiko Yamaguchi, Sagamihara, JP;
Assignee:
Kabushiki Kaisya Ohara, , JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
C03B / ;
U.S. Cl.
CPC ...
65 331 ; 65 338 ; 65111 ; 501-5 ; 501-7 ; 501 10 ; 4286 / ; 4286 / ;
Abstract
A magnetic disk substrate is made of a glass-ceramic having crystal phases of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and alpha-quartz (SiO.sub.2). The crystal phase of alpha-quartz is formed of grown crystal grains each having a globular grain structure made of aggregated particles. Each globular grain has a size within a range from 0.3 .mu.m to 3 .mu.m. Surface roughness (Ra) of a polished surface of the magnetic disk substrate is within a range from 15 .ANG. to 50 .ANG. which is an optimum range of surface roughness for the magnetic disk.