Patent US4009111A successfully refreshed from Google Patents.
US4009111A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: Fujifilm Holdings Corp
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Filing: 1975-10-20
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Granted: 1977-02-22
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Expires: 1995-10-20
Abstract
Abstract A magnetic recording medium for high density recording comprising a support having thereon a magnetic recording layer comprising a ferromagnetic metal powder of the Fe-Co-Cr-B system and having a coercive force of about 700 to 1500 orsteds in the oriented direction of the magnetic substance and a residual magnetic flux density of about 1500 gauses or more, the residual magnetic flux density of which after storage for 160 hours under the conditions of a temperature of 60° C and 90%RH is 85% or more of the initial value thereof before storage under these conditions in a binder. The magnetic recording medium is especially suitable for high density recording, having sufficient sensitivity and excellent resistance.
Inventors
- 👤 Yasuo Tamai
- 👤 Masashi Aonuma
- 👤 Matsuaki Nakamura
- 👤 Hiroshi Agawa
- 👤 Goro Akashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 20:47
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/70621; B; B22; B22F; B22F9/00; B22F9/16; B22F9/18; B22F9/24; C; C22; C22C; C22C33/00; C22C33/02; C22C33/0257; C22C33/0278; C22C33/0285; G11B5/70615
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
178 words
A magnetic recording medium comprising a support having thereon a magnetic recording layer comprising a binder and a ferromagnetic alloy powder, said magnetic recording layer having a coercive force of about 700 to 1500 oersteds in the oriented direction of the ferromagnetic powder and a residual magnetic flux density of about 1500 gausses or higher, the residual magnetic flux density of which after storage for 160 hours in an atmosphere of 60° C and 90% RH is 85% or higher of the initial value thereof before said storage, and said ferromagnetic alloy powder comprising the reaction product of reducing a mixed solution containing Fe, Co and Cr ions with a borohydride compound reducing agent, said mixed solution containing metal ions ranging from 0.01 to 0.5 mole/liter in concentration, such that said ferromagnetic alloy powder comprises about 65 to 89% Fe, about 7 to 34% Co, and about 0.5 to 5% Cr, said percentages being by weight, and wherein the reducing in mixed solution to prepare said ferromagnetic alloy powder is conducted at -10° C to about 40° C.
Claim 2
Dependent Claim
178 words
A magnetic recording medium comprising a support having thereon a magnetic recording layer comprising a binder and a ferromagnetic alloy powder, said magnetic recording layer having a coercive force of about 700 to 1500 oersteds in the oriented direction of the ferromagnetic powder and a residual magnetic flux density of about 1500 gausses or higher, the residual magnetic flux density of which after storage for 160 hours in an atmosphere of 60° C and 90% RH is 85% or higher of the initial value thereof before said storage, and said ferromagnetic alloy powder comprising the reaction product of reducing a mixed solution containing Fe, Co and Cr ions with a borohydride compound reducing agent, said mixed solution containing metal ions ranging from 0.01 to 0.5 mole/liter in concentration, such that said ferromagnetic alloy powder comprises about 65 to 89% Fe, about 7 to 34% Co, and about 0.5 to 5% Cr, said percentages being by weight, and wherein the reducing in mixed solution to prepare said ferromagnetic alloy powder is conducted at -10° C to about 40° C.
Claim 3
Dependent Claim
27 words
The magnetic recording medium as claimed in claim 1, wherein the borohydride compound is in a solution having a hydroxide ion concentration of about 0.001N to 0.6N.
Claim 4
Dependent Claim
40 words
The magnetic recording medium as claimed in claim 1, wherein Br/Hc of the ferromagnetic metal powder is about 1.5 to 4.5, in which Hc is the coercive force in oersteds and Br is the residual magnetic flux density in gausses.
Claim 5
Dependent Claim
16 words
The magnetic recording medium as claimed in claim 3, wherein the Br/HC is 3.8 to 2.0.
Claim 6
Dependent Claim
28 words
The magnetic recording medium as claimed in claim 1, wherein the proportion of the respective metal components is within the range of the cross-hatched portion in FIG. 1.
Claim 7
Dependent Claim
21 words
A magnetic recording medium as claimed in claim 1, wherein the squareness ratio, Br/Bm, thereof is between about 0.80 and 0.85.
References Cited (Backward Citations)
US3943012A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-02-22 | 1980-08-23 | 1981-02-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-02-22 | 1984-08-23 | 1985-02-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-02-22 | 1988-08-23 | 1989-02-22 | $7700.00 | Window Closed / Lapsed |