US4091158A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording members
Assignee: Fujifilm Holdings Corp
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Filing: 1976-04-12
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Granted: 1978-05-23
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Expires: 1996-04-12
Abstract
Abstract A magnetic recording member comprising a non-magnetic support and two or more magnetic layers provided on the non-magnetic support and composed mainly of a ferromagnetic fine powder and a binder. The upper layer of the magnetic layers has a dry thickness of about 0.3 to about 2.5 μm and the ferromagnetic fine powder contained in the upper layer is ferromagnetic iron oxide having an APP value of not more than about 1.0 and a coercive force of about 300 to about 500 Oe.
Inventors
- 👤 Akira Kasuga
- 👤 Goro Akashi
- 👤 Osamu Suzuki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 08:52
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/716; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942; Y10T428/2495; Y10T428/24967; Y10T428/24975; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/26; Y10T428/263; Y10T428/264; Y10T428/265
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
190 words
A magnetic recording medium comprising a non-magnetic support and upper and lower magnetic layers provided on said non-magnetic support, said magnetic layers comprising a ferromagnetic fine powder and a binder, wherein the uppermost layer of said magnetic layers has a dry thickness of about 0.3 to about 2.5 μm and said ferromagnetic fine powder contained in said uppermost layer is ferromagnetic iron oxide having an APP value of not more than 1.0 and a coercive force of about 330 to 450 Oe, and the ferromagnetic iron oxide of said upper layer having been heat treated in a gaseous phase under the following conditions to reduce its APP value to said value of not more than about 1.0; a temperature of 350° to 550° C, a pressure of 1 to 1.5 atmosphers and a treating time of 1 to 6 hours; and the lower magnetic layer has a dry thickness of about 3 to about 15 μm with said ferromagnetic fine powder contained in said lower layer being ferromagnetic iron oxide having an APP value of about 5 to about 10 and a coercive force of about 250 to 350 Oe.
Claim 2
Dependent Claim
190 words
A magnetic recording medium comprising a non-magnetic support and upper and lower magnetic layers provided on said non-magnetic support, said magnetic layers comprising a ferromagnetic fine powder and a binder, wherein the uppermost layer of said magnetic layers has a dry thickness of about 0.3 to about 2.5 μm and said ferromagnetic fine powder contained in said uppermost layer is ferromagnetic iron oxide having an APP value of not more than 1.0 and a coercive force of about 330 to 450 Oe, and the ferromagnetic iron oxide of said upper layer having been heat treated in a gaseous phase under the following conditions to reduce its APP value to said value of not more than about 1.0; a temperature of 350° to 550° C, a pressure of 1 to 1.5 atmosphers and a treating time of 1 to 6 hours; and the lower magnetic layer has a dry thickness of about 3 to about 15 μm with said ferromagnetic fine powder contained in said lower layer being ferromagnetic iron oxide having an APP value of about 5 to about 10 and a coercive force of about 250 to 350 Oe.
Claim 3
Dependent Claim
22 words
The magnetic recording medium according to claim 1, wherein the binder is a thermoplastic resin, a thermosetting resin, or a mixture thereof.
Claim 4
Dependent Claim
44 words
The magnetic recording medium according to claim 2, wherein the thermoplastic resin has a softening point of not more than about 150° C, an average molecular weight of about 10,000 to about 200,000, and a degree of polymerization of about 200 to about 2,000.
Claim 5
Dependent Claim
27 words
The magnetic recording medium according to claim 2, wherein the thermosetting resin has a molecular weight of not more than about 200,000 as the coating solution thereof.
Claim 6
Dependent Claim
26 words
The magnetic recording medium according to claim 1, wherein the ferromagnetic iron oxide is selected from the group consisting of maghemite, magnetite, and Berthollide compounds thereof.
Claim 7
Dependent Claim
25 words
The magnetic recording medium according to claim 1, wherein the magnetic layer further contains a dispersing agent, a lubricant, an abrasive, or an antistatic agent.
Claim 8
Dependent Claim
19 words
The magnetic recording medium of claim 1, wherein the binder of the lower magnetic layer is a thermosetting resin.
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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) | 1981-05-22 | 1981-11-21 | 1982-05-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-05-22 | 1985-11-21 | 1986-05-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-05-22 | 1989-11-21 | 1990-05-23 | $7700.00 | Window Closed / Lapsed |