US5370928A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium
Assignee: Fujifilm Holdings Corp
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Filing: 1992-01-27
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Granted: 1994-12-06
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Expires: 2012-01-27
Abstract
Abstract A magnetic recording medium providing a high reproducing output and a high C/N over a wide recording frequency region is disclosed. The magnetic recording medium comprises a non-magnetic substrate and a lower magnetic layer, a non-magnetic intermediate layer and an upper magnetic layer on the substrate in this order so that the ratio of the non-magnetic intermediate layer thickness (t) to the upper magnetic layer thickness (d), i.e., (t/d), is within the range of 0.1/1 to 0.3/1.
Inventors
- 👤 Makoto Funabashi
- 👤 Naoto Abe
- 👤 Koji Sasazawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 14:23
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/66; G11B5/676; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/12; Y10T428/12465; Y10T428/12493; Y10T428/12771; Y10T428/12861; Y10T428/12931; Y10T428/26; Y10T428/263; Y10T428/264; Y10T428/265
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
113 words
A ferromagnetic metal thin film recording medium, comprising a non-magnetic substrate, a lower magnetic layer, a non-magnetic intermediate layer having a thickness of t, and an upper magnetic layer having a thickness of d, the lower magnetic layer, the non-magnetic intermediate layer and the upper magnetic layer being arranged in this order on the non-magnetic substrate, wherein t/d is between 0.1 to 0.3, the lower magnetic layer has a coercive force of at least 1,000 Oe, the upper magnetic layer has a coercive force of at least 250 Oe higher than the coercive force of the lower magnetic layer, and the upper magnetic layer has a thickness of from 300 to 1,200 Å.
Claim 2
Dependent Claim
113 words
A ferromagnetic metal thin film recording medium, comprising a non-magnetic substrate, a lower magnetic layer, a non-magnetic intermediate layer having a thickness of t, and an upper magnetic layer having a thickness of d, the lower magnetic layer, the non-magnetic intermediate layer and the upper magnetic layer being arranged in this order on the non-magnetic substrate, wherein t/d is between 0.1 to 0.3, the lower magnetic layer has a coercive force of at least 1,000 Oe, the upper magnetic layer has a coercive force of at least 250 Oe higher than the coercive force of the lower magnetic layer, and the upper magnetic layer has a thickness of from 300 to 1,200 Å.
Claim 3
Dependent Claim
21 words
The magnetic recording medium as claimed in claim 1, wherein the ferromagnetic metal thin film is formed by oblique vapor deposition.
Claim 4
Dependent Claim
21 words
The magnetic recording medium as claimed in claim 1, wherein the non-magnetic intermediate layer is a metal or metal oxide layer.
Claim 5
Dependent Claim
23 words
The magnetic recording medium as claimed in claim 3, wherein the metal in the non-magnetic intermediate layer is Cu, Ti, Au, or Al.
Claim 6
Dependent Claim
23 words
The magnetic recording medium as claimed in claim 1, wherein the upper magnetic layer has a thickness of from 600 to 1,000 Å.
Claim 7
Dependent Claim
23 words
The magnetic recording medium as claimed in claim 1, wherein the intermediate non-magnetic layer has a thickness of from 30 to 360 Å.
Claim 8
Dependent Claim
23 words
The magnetic recording medium as claimed in claim 1, wherein the intermediate non-magnetic layer has a thickness of from 60 to 250 Å.
Claim 9
Dependent Claim
23 words
The magnetic recording medium as claimed in claim 1, wherein the lower magnetic layer has a thickness of from 50 to 2,000 Å.
Claim 10
Dependent Claim
23 words
The magnetic recording medium as claimed in claim 1, wherein the lower magnetic layer has a thickness of from 500 to 2,000 Å.
Claim 11
Dependent Claim
27 words
The magnetic recording medium as claimed in claim 3, wherein the metal oxide in the non-magnetic intermediate layer is an oxide of Co, Ni, Si or Ti.
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) | 1997-12-05 | 1998-06-06 | 1998-12-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-12-05 | 2002-06-06 | 2002-12-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-12-05 | 2006-06-06 | 2006-12-06 | $7700.00 | Window Closed / Lapsed |