US3977985A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium comprising cobalt or cobalt alloy coated particles of spicular magnetite
Assignee: TDK Corp
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Filing: 1974-12-13
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Granted: 1976-08-31
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Expires: 1994-12-13
Abstract
Abstract A magnetic recording medium is disclosed as comprising powdered magnetic particles upon which there is deposited a ferro-magnetic metal or alloy such as cobalt or a cobalt alloy. Each magnetic particle is a spiculate magnetite and the deposite of cobalt or a cobalt alloy is in the range of 0.5 wt.% to 30 wt.%. The particles are heat treated in either a reducing or inert atmosphere to a sufficient temperature to improve the magnetic characteristics of the particles including their coercive force, Br/ rho and Bm/ rho . A layer of the recording medium is disposed on a support layer of polyester to form a magnetic tape.
Inventors
- 👤 Shinji Umeki
- 👤 Fujio Shibata
- 👤 Kazuo Takada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 22:10
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/712; B; B22; B22F; B22F1/00; B22F1/18; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; G11B5/70684; G11B5/70689
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
105 words
A magnetic recording medium comprising a layer of magnetic material disposed on a support layer wherein said layer of magnetic material comprises corpuscular magnetic core particles of spicular magnetite, with a coating of a material selected from the group consisting of cobalt and an alloy of cobalt wherein the amount of cobalt in said coating is in the range of from 4 to 10 wt% and is formed by heating a deposit selected from said group, said layered particles being heat treated to a temperature greater than 100°C, to effect said layered particles having a coercive force in the range of 490 to 900 Oe.
Claim 2
Dependent Claim
105 words
A magnetic recording medium comprising a layer of magnetic material disposed on a support layer wherein said layer of magnetic material comprises corpuscular magnetic core particles of spicular magnetite, with a coating of a material selected from the group consisting of cobalt and an alloy of cobalt wherein the amount of cobalt in said coating is in the range of from 4 to 10 wt% and is formed by heating a deposit selected from said group, said layered particles being heat treated to a temperature greater than 100°C, to effect said layered particles having a coercive force in the range of 490 to 900 Oe.
Claim 3
Dependent Claim
19 words
A magnetic recording medium as in claim 1, wherein said support layer comprises an extended strip of a polyester.
Claim 4
Dependent Claim
34 words
A magnetic recording medium as in claim 1, wherein said layer of magnetic material is mixed with other constituents to form a magnetic paint which is applied as a layer on said support layer.
Claim 5
Dependent Claim
26 words
A magnetic recording medium as in claim 1, wherein said layered particles are heat treated in an inert gas at a temperature between 100°C and 600°C.
Claim 6
Dependent Claim
26 words
A magnetic recording medium as in claim 1, wherein said layered particles are heat treated in a reductive gas at a temperature between 100°C and 300°C.
Claim 7
Dependent Claim
21 words
A magnetic recording medium as in claim 1, wherein said magnetic core particles have a mean length of approximately 0.5 microns.
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) | 1979-08-31 | 1980-03-01 | 1980-08-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-31 | 1984-03-01 | 1984-08-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-31 | 1988-03-01 | 1988-08-31 | $7700.00 | Window Closed / Lapsed |