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:
May. 28, 2002
Filed:
Aug. 04, 1999
Katsuhiko Yamaguchi, Sagamihara, JP;
Naoyuki Goto, Sagamihara, JP;
Kabushiki Kaisha Ohara, Kanagawa-ken, JP;
Abstract
A glass-ceramic substrate for a magnetic information storage medium having a super flat surface comprises, as a predominant phase or phases, at least one crystal phase selected from the group consisting of lithium disilicate (Li O.2SiO , having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.57 Å and 3.62 Å), quartz (SiO , having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.33 Å to 3.41 Å), quartz solid solution (SiO solid solution, having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.33 Å to 3.41 Å), cristobalite (SiO , having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 4.04 Å to 4.14 Å) and cristobalite solid solution (SiO solid solution, having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 4.04 Å to 4.14 Å), has a coefficient of thermal expansion within a range from +62×10− /° C. to +130×10 /° C. in a temperature range from −50° C. to +70° C., has Young's modulus within a range from 80 GPa to 150 GPa, has Vickers hardness within a range from 4.5 GPa to 15.0 GPa, has a specific gravity within a range from 2.2 to 2.8, has a surface roughness (Ra) after polishing within a range from 3 Å to 9 Å and contains Al O in the amount of 2% to less than 10%.