Patent US4423453A successfully refreshed from Google Patents.
US4423453A
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Magnetic recording medium
Assignee: TDK Corp
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Filing: 1981-07-13
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Granted: 1983-12-27
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Expires: 2001-07-13
Abstract
Abstract A magnetic recording medium having two coated magnetic layers of a first magnetic layer and a second magnetic layer on a non-magnetic substrate. The first magnetic layer has a coercive force of 400 to 590 Oe and a thickness of 2.1 to 2.8μ and said second magnetic layer has a coercive force of 590 to 800 Oe and a thickness of at least 2.1μ.
Inventors
- 👤 Hiroshi Kawahara
- 👤 Hitoshi Azegami
- 👤 Eiji Horigome
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 13:14
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/716; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
70 words
In a magnetic recording medium having two coated magnetic layers of a first magnetic layer and a second magnetic layer on a non-magnetic substrate, an improvement characterized in that said first magnetic layer has a coercive force of 400 to 590 Oe and a thickness of 2.1 to 2.8μ and said second magnetic layer has a coercive force of 590 to 800 Oe and a thickness of at least 2.1μ.
Claim 2
Dependent Claim
70 words
In a magnetic recording medium having two coated magnetic layers of a first magnetic layer and a second magnetic layer on a non-magnetic substrate, an improvement characterized in that said first magnetic layer has a coercive force of 400 to 590 Oe and a thickness of 2.1 to 2.8μ and said second magnetic layer has a coercive force of 590 to 800 Oe and a thickness of at least 2.1μ.
Claim 3
Dependent Claim
26 words
The magnetic recording medium according to claim 1 wherein said first magnetic layer has a content of a magnetic powder of at least 81.8% by weight.
References Cited (Backward Citations)
US3328195A
Cited
US4075384A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-12-26 | 1987-06-27 | 1987-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-12-26 | 1991-06-27 | 1991-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-12-26 | 1995-06-27 | 1995-12-27 | $7700.00 | Window Closed / Lapsed |