Patent US4699840A successfully refreshed from Google Patents.
US4699840A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: Victor Company of Japan Ltd
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Filing: 1985-09-27
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Granted: 1987-10-13
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Expires: 2005-09-27
Abstract
Abstract A magnetic recording medium has a magnetic layer which is made of a magnetic material constituted by a mixture of hexagonal system ferrite magnetic particles and acicular ferromagnetic particles.
Inventors
- 👤 Tsutomu Yashiro
- 👤 Mutsumu Kurihara
- 👤 Hiroshi Togashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:07
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/29; Y10T428/2982; Y10T428/2991
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
148 words
A magnetic recording medium comprising; a recording medium base; and a magnetic layer formed on said recording medium base, said magnetic layer being made of a magnetic material, said magnetic material being constituted by such a mixture of hexagonal system ferrite magnetic particles and acicular ferromagnetic particles that a weight percent occupied by said hexagonal system ferrite magnetic particles within said mixture is selected in a range of 2 to 60, said hexagonal system ferrite magnetic particles having an average particle diameter less than or equal to 0.2 μm and a coercive force in a range of more than 300 Oe and less than 600 Oe, said acicular ferromagnetic particles having an aspect ratio greater than or equal to, a magnetic saturation greater than or equal to 70 emu/g, and a BET specific surface area in a range of 20 m 2 /g to 60 m 2 /g.
Claim 2
Dependent Claim
148 words
A magnetic recording medium comprising; a recording medium base; and a magnetic layer formed on said recording medium base, said magnetic layer being made of a magnetic material, said magnetic material being constituted by such a mixture of hexagonal system ferrite magnetic particles and acicular ferromagnetic particles that a weight percent occupied by said hexagonal system ferrite magnetic particles within said mixture is selected in a range of 2 to 60, said hexagonal system ferrite magnetic particles having an average particle diameter less than or equal to 0.2 μm and a coercive force in a range of more than 300 Oe and less than 600 Oe, said acicular ferromagnetic particles having an aspect ratio greater than or equal to, a magnetic saturation greater than or equal to 70 emu/g, and a BET specific surface area in a range of 20 m 2 /g to 60 m 2 /g.
Claim 3
Dependent Claim
29 words
A magnetic recording medium as claimed in claim 1 in which a weight percent occupied by said hexagonal system ferrite magnetic particles within said mixture is selected to 10.
Claim 4
Dependent Claim
28 words
A magnetic recording medium as claimed in claim 1 in which said hexagonal system ferrite magnetic particles have a magnetic saturation greater than or equal to 50 emu/g.
Claim 5
Dependent Claim
30 words
A magnetic recording medium as claimed in claim 1 in which said hexagonal system ferrite magnetic particles have a coercive force in a range of 450 Oe to 580 Oe.
Claim 6
Dependent Claim
34 words
A magnetic recording medium as claimed in claim 1 in which said hexagonal system ferrite magnetic particles are MO(Fe 2 O 3 ) 6 , where M is one of Ba, Sr, and Ca.
Claim 7
Dependent Claim
47 words
A magnetic recording medium as claimed in claim 1 in which said acicular ferromagnetic particles is selected out of a group of γ-Fe 2 O 3 , Co adsorbed γ-Fe 2 O 3 , Fe 3 O 4 , CrO 2 , Fe, Co, and alloy particles.
References Cited (Backward Citations)
US4239637A
Cited
US4442159A
Cited
JPS57212623A
Cited
US4425401A
Cited
JPS58203625A
Cited
US4565726A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-10-12 | 1991-04-13 | 1991-10-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-10-12 | 1995-04-13 | 1995-10-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-10-12 | 1999-04-13 | 1999-10-13 | $7700.00 | Window Closed / Lapsed |