US4465735A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: Maxell Ltd
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Filing: 1982-09-23
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Granted: 1984-08-14
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Expires: 2002-09-23
Abstract
Abstract An improved magnetic recording medium suitable for high density recording is disclosed, which has a squareness ratio in the vertical direction of 0.6 or more and an orientation ratio (squareness ratio in the vertical direction/squareness ratio in the lengthwise direction) of 0.7 or more, prepared from acicular magnetic iron oxide particles having crystalline magnetic anisotropy and a ratio of Fe2+/Fe3+ of 0.05 or less uniformly cobalt-doped, the particles having preferably a particle size of 0.3 mu or less and an axial ratio of 6 to 10.
Inventors
- 👤 Fumio Togawa
- 👤 Shigeo Aoyama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 10:32
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70668; G11B5/70673; G11B5/70678; G11B5/70684; G11B5/70694; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/26; Y10T428/269; Y10T428/29; Y10T428/2982; Y10T428/2991; Y10T428/31504; Y10T428/31678
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
89 words
A magnetic recording medium comprising a magnetic layer superimposed on a support base, said magnetic layer comprising uniform acicular magnetic uniformly cobalt-doped iron oxide particles having crystalline magnetic anisotropy and a ratio of Fe 2+ /Fe 3+ of 0.05 or less in said cobalt-doped iron oxide particles, a squareness ratio in the vertical direction of 0.6 or more and an orientation ratio (squareness ratio in the vertical direction/squareness ratio in the lengthwise direction) of 0.7 or more so as to maintain sufficient vertical magnetic components in said magnetic layer.
Claim 2
Dependent Claim
89 words
A magnetic recording medium comprising a magnetic layer superimposed on a support base, said magnetic layer comprising uniform acicular magnetic uniformly cobalt-doped iron oxide particles having crystalline magnetic anisotropy and a ratio of Fe 2+ /Fe 3+ of 0.05 or less in said cobalt-doped iron oxide particles, a squareness ratio in the vertical direction of 0.6 or more and an orientation ratio (squareness ratio in the vertical direction/squareness ratio in the lengthwise direction) of 0.7 or more so as to maintain sufficient vertical magnetic components in said magnetic layer.
Claim 3
Dependent Claim
23 words
A magnetic recording medium according to claim 1, wherein said magnetic iron oxide particles have an average particle size of 0.3μ or less.
Claim 4
Dependent Claim
35 words
A magnetic recording medium according to claim 1, wherein said magnetic particles have a content of cobalt in the range of 3 to 15% by weight based on the total weight of said magnetic particles.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-08-14 | 1988-02-13 | 1988-08-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-08-14 | 1992-02-13 | 1992-08-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-08-14 | 1996-02-13 | 1996-08-14 | $7700.00 | Window Closed / Lapsed |