US4753853A
Expired / Lapsed
US
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Double-layered magnetooptical recording medium
Assignee: Nikon Corp
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Filing: 1985-03-26
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Granted: 1988-06-28
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Expires: 2005-03-26
Abstract
Abstract A double-layered magnetooptical recording medium consists of two exchange-coupled layers that permit perpendicular magnetization, one layer having a low Curie point and a high coercive force and the other layer having a high Curie point and a low coercive force. The layer having low coercive force is made of a transition metal rich amporphous Gd U (Fe V Co 100-V ) 100-U alloy having the following compositional range, and the layer having high coercive force is made of a transition metal rich amorphous Tb W Fe 100-W alloy having the following compositional range: U=20-26 atomic %, V=50-80 atomic %, and W=27-33 atomic %.
Inventors
- 👤 Masatoshi Sato
- 👤 Hideki Akasaka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 13:53
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B11/10586; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/12; Y10T428/12493; Y10T428/12771; Y10T428/12861; Y10T428/12937; Y10T428/12951; Y10T428/12986
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
113 words
A double-layered magnetooptical recording medium comprising two exchange-coupled layers that permit perpendicular magnetization, one layer having a low Curie point and a high coercive force and the other layer having a high Curie point and a low coercive force, wherein said recording medium achieves a C/N ratio of 60 db or higher, and wherein said layer having low coercive force is made of a transition metal rich amorphous Gd X (Fe Y Co 100-Y ) 100-X alloy having the following compositional range, and said layer having high coercive force is made of a transitional metal rich amorphous Tb Z Fe 100-Z alloy having the following compositional range: X=20-26 atomic%, Y=50-80 atomic%, Z=18-26 atomic%.
Claim 2
Dependent Claim
113 words
A double-layered magnetooptical recording medium comprising two exchange-coupled layers that permit perpendicular magnetization, one layer having a low Curie point and a high coercive force and the other layer having a high Curie point and a low coercive force, wherein said recording medium achieves a C/N ratio of 60 db or higher, and wherein said layer having low coercive force is made of a transition metal rich amorphous Gd X (Fe Y Co 100-Y ) 100-X alloy having the following compositional range, and said layer having high coercive force is made of a transitional metal rich amorphous Tb Z Fe 100-Z alloy having the following compositional range: X=20-26 atomic%, Y=50-80 atomic%, Z=18-26 atomic%.
Claim 3
Dependent Claim
11 words
The recording medium of claim 1 wherein X=24, Y=70 and Z=24.
Claim 4
Dependent Claim
11 words
The recording medium of claim 1 wherein X=20, Y=60 and Z=22.
Claim 5
Dependent Claim
11 words
The recording medium of claim 1 wherein X=26, Y=75 and Z=26.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-06-28 | 1991-12-28 | 1992-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-06-28 | 1995-12-28 | 1996-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-06-28 | 1999-12-28 | 2000-06-28 | $7700.00 | Window Closed / Lapsed |