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Patent US4238341A successfully refreshed from Google Patents.
US4238341A
Expired / Lapsed
US
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Composition of magnetic recording media
Assignee: Hitachi Ltd
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Filing: 1979-10-12
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Granted: 1980-12-09
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Expires: 1999-10-12
Abstract
Abstract A composition of magnetic recording media consisting of a ferromagnetic powder such as γ-Fe 2 O 3 , a binder and single crystal alumina as a reinforcing agent. Single crystal α-alumina is preferably used as said single crystal alumina and its amount is preferably from 1 to 20% by weight based on the magnetic powder.
Inventors
- 👤 Yoshiki Kato
- 👤 Heigo Ishihara
- 👤 Hajime Fukke
- 👤 Katsuyoshi Chiba
- 👤 Waichi Nagashiro
- 👤 Teruo Tsunoda
- 👤 Munehisa Mitsuya
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 11:44
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/708; G11B5/702; G11B5/7023; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/31504; Y10T428/31511; Y10T428/31855; Y10T428/31859; Y10T428/31877
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
74 words
A composition of magnetic recording medium consisting of a ferromagnetic powder, a binder, and single crystal alumina as a reinforcing agent in an amount of from 1 to 20 percent by weight on the basis of said ferromagnetic powder, said composition when coated on a disc exhibiting a greater sliding distance than a corresponding composition of said ferromagnetic powder, binder and same amount of polycrystalline alumina employed for grinding when coated on a disc.
Claim 2
Dependent Claim
74 words
A composition of magnetic recording medium consisting of a ferromagnetic powder, a binder, and single crystal alumina as a reinforcing agent in an amount of from 1 to 20 percent by weight on the basis of said ferromagnetic powder, said composition when coated on a disc exhibiting a greater sliding distance than a corresponding composition of said ferromagnetic powder, binder and same amount of polycrystalline alumina employed for grinding when coated on a disc.
Claim 3
Dependent Claim
33 words
The composition of magnetic recording medium as defined in claim 1, wherein the amount of said single crystal alumina is from 2 to 20% by weight on the basis of said ferroomagnetic powder.
Claim 4
Dependent Claim
28 words
The composition of magnetic recording medium as defined in claim 1 or 2 wherein the grain size of said single crystal alumina is from 0.5 to 5 μm.
Claim 5
Dependent Claim
28 words
The composition of magnetic recording medium as defined in claim 1 or 2 wherein said binder consists of an epoxy resin, a phenol-formaldehyde resin and a vinyl resin.
Claim 6
Dependent Claim
19 words
The composition of magnetic recording medium as defined in claim 4 wherein said vinyl resin is a polyvinyl butyral.
Claim 7
Dependent Claim
11 words
A magnetic disc comprising the composition as defined in claim 1.
Claim 8
Dependent Claim
23 words
The magnetic disc as defined in claim 6, wherein the grain size of said single crystal alumina is from 0.5 to 5 μm.
Claim 9
Dependent Claim
23 words
The magnetic disc as defined in claim 6, wherein said binder consists of an epoxy resin, a phenol-formaldehyde resin and a vinyl resin.
Claim 10
Dependent Claim
15 words
The magnetic disc as defined in claim 8, wherein said vinyl resin is polyvinyl butyral.
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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) | 1983-12-09 | 1984-06-09 | 1984-12-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-12-09 | 1988-06-09 | 1988-12-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-12-09 | 1992-06-09 | 1992-12-09 | $7700.00 | Window Closed / Lapsed |