Patent US4734831A successfully refreshed from Google Patents.
US4367263A
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Magnetic recording medium
Assignee: TDK Corp
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Filing: 1981-06-17
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Granted: 1983-01-04
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Expires: 2001-06-17
Abstract
Abstract A magnetic recording medium comprises a first magnetic layer containing magnetite or a cobalt doped magnetite which is coated on a non-magnetic substrate; and a second magnetic layer coating a cobalt doped γ-Fe 2 O 3 which is coated on said first magnetic layer. The magnetic recording medium has a high recording sensitivity, a high dynamic range, a less output fluctuation and especially superior sensitivity in low frequency band and superior maximum output level without a deterioration of transfer characteristics.
Inventors
- 👤 Hiroshi Kawahara
- 👤 Tadashi Nishimura
- 👤 Masatsugu Funakoshi
- 👤 Masaharu Nishimatsu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 04:22
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/716; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/26; Y10T428/263; Y10T428/264; Y10T428/265
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
126 words
A magnetic recording medium which comprises: a first magnetic layer containing magnetite, a cobalt doped γ-Fe 2 O 3 ; γ-Fe 2 O 3 or a cobalt doped magnetite, which is coated on a non-magnetic substrate and a second magnetic layer containing a cobalt doped γ-Fe 2 O 3 , which is coated on said first magnetic layer, wherein said first magnetic layer has a thickness of 3.0 to 6.0 microns and a coercive force of 400-560 Oe, and wherein said second magnetic layer has a thickness of 1.5 to 3.0 microns and a coercive force of 590 to 800 Oe, and wherein the residual magnetic flux density is greater than y, wherein Y=1.60X+556 (gauss) and X represents the coercive force of the first magnetic layer.
Claim 2
Dependent Claim
126 words
A magnetic recording medium which comprises: a first magnetic layer containing magnetite, a cobalt doped γ-Fe 2 O 3 ; γ-Fe 2 O 3 or a cobalt doped magnetite, which is coated on a non-magnetic substrate and a second magnetic layer containing a cobalt doped γ-Fe 2 O 3 , which is coated on said first magnetic layer, wherein said first magnetic layer has a thickness of 3.0 to 6.0 microns and a coercive force of 400-560 Oe, and wherein said second magnetic layer has a thickness of 1.5 to 3.0 microns and a coercive force of 590 to 800 Oe, and wherein the residual magnetic flux density is greater than y, wherein Y=1.60X+556 (gauss) and X represents the coercive force of the first magnetic layer.
References Cited (Backward Citations)
US4265931A
Cited
US4075384A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-01-03 | 1986-07-05 | 1987-01-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-01-03 | 1990-07-05 | 1991-01-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-01-03 | 1994-07-05 | 1995-01-04 | $7700.00 | Window Closed / Lapsed |