US4908727A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Disk with substrate of alumina silicate resin glass
Assignee: TDK Corp
•
Filing: 1988-11-08
•
Granted: 1990-03-13
•
Expires: 2008-11-08
Abstract
Abstract A vertical recording system using a rigid disk medium with high recording density has a substrate made of alumina silicate resin glass and a vertical magnetic anisotropic film located on said substrate. Said anisotropic film has an easy axis of magnetization in the thickness direction of the film, and the hard axis of magnetization in the film plane. The maximum surface roughness R max of said disk is less than 50 Å, and a magnetic recording head which moves relative to the medium operates with said head contacted with the medium. A recording density higher than 200 KFRPI (kilo flux reversal per inch) is obtained by the present invention.
Inventors
- 👤 Joichiro Ezaki
- 👤 Kazumasa Fukuda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:22
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/74; G11B5/82; G11B5/62; G11B5/73; G11B5/739; G11B5/73911; G11B5/73921; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
50 words
A recording disk having a magnetization axis in the vertical direction comprising a rigid substrate made of alumina silicate resin glass ceramic, and a vertical magnetic anisotropic film coupled with said substrate, wherein the improvement comprises that maximum surface roughness R max of said substrate is less than 50 Å.
Claim 2
Dependent Claim
50 words
A recording disk having a magnetization axis in the vertical direction comprising a rigid substrate made of alumina silicate resin glass ceramic, and a vertical magnetic anisotropic film coupled with said substrate, wherein the improvement comprises that maximum surface roughness R max of said substrate is less than 50 Å.
Claim 3
Dependent Claim
17 words
A recording disk according to claim 1, wherein said vertical magnetic anisotropic film is made of Co-Cr.
Claim 4
Dependent Claim
22 words
A recording disk according to claim 1, wherein another magnetic film is provided between said substrate and said vertical magnetic anisotropic film.
Claim 5
Dependent Claim
17 words
A recording disk according to claim 3, wherein said vertical magnetic anisotropic film is made of Co-Cr.
References Cited (Backward Citations)
US4327387A
Cited
JPS5690427A
Cited
JPS5982626A
Cited
US4590119A
Cited
US4633351A
Cited
JPS6079518A
Cited
US4659606A
Cited
US4619856A
Cited
EP0180651A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-03-12 | 1993-09-11 | 1994-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-03-12 | 1997-09-11 | 1998-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-03-12 | 2001-09-11 | 2002-03-13 | $7700.00 | Window Closed / Lapsed |