Patent US4789591A successfully refreshed from Google Patents.
US4789591A
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Magnetic recording medium
Assignee: Konica Minolta Inc
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Filing: 1987-03-10
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Granted: 1988-12-06
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Expires: 2007-03-10
Abstract
Abstract A magnetic recording medium comprising a support and a magnetic layer on said support. Said magnetic layer is a unitary magnetic layer comprising iron oxide powder having cobalt adsorbed on the surface thereof. The average grain size of said powder is not more than 0.5μ, the ratio of the major axis to the minor axis (acicular ratio) of said powder is from 1.3 to 4.5 and the coercive force of said powder is from 500 to 800 Oe.
Inventors
- 👤 Issei Nakamura
- 👤 Kenji Itozawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:58
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70647; G11B5/714; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/29; Y10T428/2982; Y10T428/2991; Y10T428/31504; Y10T428/31551; Y10T428/31609; Y10T428/31627; Y10T428/3163; Y10T428/31721; Y10T428/31855; Y10T428/31935
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
88 words
A magnetic recording medium having improved thermal stability comprising a support and a magnetic layer on said support, said magnetic layer being a unitary magnetic layer comprising iron oxide powder having cobalt adsorbed on the surface thereof, the average grain size of said iron oxide powder being not more than 0.5μ, the ratio of the major axis to the minor axis (acicular ratio) of said iron oxide powder being from 1.3 to 4.5 and the coercive force of said iron oxide powder being from 550 to 800 Oe.
Claim 2
Dependent Claim
88 words
A magnetic recording medium having improved thermal stability comprising a support and a magnetic layer on said support, said magnetic layer being a unitary magnetic layer comprising iron oxide powder having cobalt adsorbed on the surface thereof, the average grain size of said iron oxide powder being not more than 0.5μ, the ratio of the major axis to the minor axis (acicular ratio) of said iron oxide powder being from 1.3 to 4.5 and the coercive force of said iron oxide powder being from 550 to 800 Oe.
Claim 3
Dependent Claim
26 words
The magnetic recording medium according to claim 1, wherein said average grain size of said cobalt-adsorbed iron oxide powder is between 0.05 micron to 0.5 micron.
Claim 4
Dependent Claim
26 words
The magnetic recording medium according to claim 1, wherein said average grain size of said cobalt-adsorbed iron oxide powder is between 0.1 micron to 0.3 micron.
Claim 5
Dependent Claim
24 words
The magnetic recording medium according to claim 1, wherein said support is selected from the group consisting of polymeric resins, non-magnetic metals and ceramics.
Claim 6
Dependent Claim
32 words
The magnetic recording medium according to claim 4, wherein said polymeric resin is selected from the group consisting of polyesters, polyolfins, cellulose derivatives, and plastics selected from polycarbonate, polyvinylchloride, polyimide and nylon.
Claim 7
Dependent Claim
23 words
The magnetic recording medium according to claim 4, wherein said support is a non-magnetic metal support of aluminium, zinc or an alloy thereof.
Claim 8
Dependent Claim
24 words
The magnetic recording medium according to claim 4, wherein said support is in the form of film or sheet, card, disc or cylindrical drum.
Claim 9
Dependent Claim
30 words
The magnetic recording medium according to claim 7, wherein the proportion of the cobalt adsorbed is 0.5 to 30% by weight relative to 100% by weight of said iron oxide.
Claim 10
Dependent Claim
30 words
The magnetic recording medium according to claim 7, wherein the proportion of the cobalt adsorbed is 2.5 to 30% by weight relative to 100% by weight of said iron oxide.
Claim 11
Dependent Claim
15 words
The magnetic recording medium according to claim 1, wherein said magnetic layer contains a binder.
Claim 12
Dependent Claim
39 words
The magnetic recording medium according to claim 10, wherein said binder is contained in said magnetic layer at a proportion of 5 to 400 parts by weight relative to 100 parts by weight of of said iron oxide powder.
Claim 13
Dependent Claim
39 words
The magnetic recording medium according to claim 10, wherein said binder is contained in said magnetic layer at a proportion of 10 to 100 parts by weight relative to 100 parts by weight of of said iron oxide powder.
Claim 14
Dependent Claim
33 words
The magnetic recording medium according to claim 10, wherein said binder is selected from the group consisting of thermoplastic resins, thermosetting resins, radiation curable resins, reactive resins, electron-irradiation-setting resins and any mixture thereof.
Claim 15
Dependent Claim
52 words
The magnetic recording medium according to claim 9, wherein said magnetic layer also contains a binder in an amount of between 10 and 100 parts by weight per 100 parts by weight of said ferromagnetic powder and wherein said average grain size of said powder is between 0.05 micron and 0.5 micron.
Claim 16
Dependent Claim
55 words
The magnetic recording medium according to claim 14, wherein said binder is selected from the group consisting of thermoplastic resins, thermosetting resins, radiation curable resins, reactive resins, electron-irradiation-setting resins and mixtures thereof and wherein said support is a polymeric material selected from the group consisting of polyesters, polyolefins, cellulose derivatives, polycarbonate, polyvinylchloride, polyimide and nylon.
Claim 17
Dependent Claim
25 words
The magnetic recording medium according to claim 15, wherein said average grain size of said iron oxide powder is between 0.1 micron to 0.3 micron.
Claim 18
Dependent Claim
39 words
The magnetic recording medium according to claim 15, wherein said support is a non-magnetic metal support of aluminum, zinc or an alloy thereof and wherein said average grain size of said powder is between 0.1 micron to 0.3 micron.
Claim 19
Dependent Claim
35 words
The magnetic recording medium according to claim 1, wherein said cobalt was adsorbed on the surface of said iron oxide powder after said iron oxide was formed as particles which comprise said iron oxide powder.
Claim 20
Dependent Claim
24 words
The magnetic recording medium according to claim 1, wherein said iron oxide is γ-Fe 2 O 3 having cobalt adsorbed on the surface thereof.
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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) | 1991-12-06 | 1992-06-06 | 1992-12-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-06 | 1996-06-06 | 1996-12-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-06 | 2000-06-06 | 2000-12-06 | $7700.00 | Window Closed / Lapsed |