US4515857A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium
Assignee: Fujifilm Holdings Corp
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Filing: 1982-05-06
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Granted: 1985-05-07
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Expires: 2002-05-06
Abstract
Abstract In a magnetic recording medium comprising a non-magnetic support and a magnetic recording layer coated thereon in which ferromagnetic particles are dispersed in a non-magnetic binder, the ferromagnetic particles are cubic particles of 0.3 or less micron and are subjected to an orientation treatment in the vertical direction to the recording surface, whereby the output and S/N ratio in a high density recording are increased.
Inventors
- 👤 Tatsuji Kitamoto
- 👤 Goro Akashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 11:16
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/84; G11B5/852; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/714; G11B5/842; G11B5/845; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/26; Y10T428/263; Y10T428/264; Y10T428/265
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
75 words
A magnetic recording medium having a high signal-to-noise ratio in high density recording and a low noise level in short wavelength recording and comprising a non-magnetic support and a magnetic recording layer coated directly thereon, the magnetic recording layer comprising ferromagnetic particles dispersed in a non-magnetic binder, wherein the ferromagnetic particles are cubic particles of at most 0.3 micron and are subjected to a magnetic orientation treatment in the vertical direction to the recording surface.
Claim 2
Dependent Claim
75 words
A magnetic recording medium having a high signal-to-noise ratio in high density recording and a low noise level in short wavelength recording and comprising a non-magnetic support and a magnetic recording layer coated directly thereon, the magnetic recording layer comprising ferromagnetic particles dispersed in a non-magnetic binder, wherein the ferromagnetic particles are cubic particles of at most 0.3 micron and are subjected to a magnetic orientation treatment in the vertical direction to the recording surface.
Claim 3
Dependent Claim
87 words
The magnetic recording medium of claim 1, wherein the ferromagnetic particles are selected from the group consisting of particles of γ-Fe 2 O 3 , Co-doped γ-Fe 2 O 3 , Fe 3 O 4 , Co-doped Fe 3 O 4 , Berthollide compounds of γ-Fe 2 O 3 and Fe 3 O 4 , Co-doped Berthollide compounds of γ-Fe 2 O 3 and Fe 3 O 4 , CrO 2 , Co-Ni-P alloys, Co-Ni-Fe alloys, Co-Ni-Fe-B alloys, Fe-Ni-Zn alloys, Fe-Mn-Zn alloys, Fe-Co-Ni-P alloys and Ni-Co alloys.
Claim 4
Dependent Claim
40 words
The magnetic recording medium of claim 1, wherein the ferromagnetic particles are prepared by boiling a solution of ferrous or ferric ion in a strong alkali to precipitate magnetite and drying at 200° C. in an inert gas or air.
Claim 5
Dependent Claim
51 words
The magnetic recording medium of claim 1, wherein the ferromagnetic particles are prepared by adding an alkali in an amount of at least equivalent to neutralization to ferrous ion, boiling with blowing air therein or adding an oxidizer thereto and then drying at 200° C. in an inert gas or air.
Claim 6
Dependent Claim
22 words
The magnetic recording medium of claim 3 or 4, wherein the iron oxide is reduced with hydrogen to obtain a metallic powder.
Claim 7
Dependent Claim
59 words
The magnetic recording medium of claim 1, wherein the ferromagnetic particles are prepared by subjecting to a heat treatment in an inert gas a metallic powder obtained by vaporizing and condensing iron, cobalt, nickel or alloys thereof in a low vacuum or by reducing a solution of a salt of iron, cobalt or nickel with sodium borohydride or hypophosphite.
Claim 8
Dependent Claim
36 words
The magnetic recording medium of claim 1, wherein the mixing ratio of the ferromagnetic particles and binder is 100 to 200 parts by weight of the binder to 100 parts by weight of the ferromagnetic particles.
Claim 9
Dependent Claim
20 words
The magnetic recording medium of claim 1, wherein the magnetic recording layer has a thickness of 0.1 to 10 microns.
Claim 10
Dependent Claim
26 words
The magnetic recording medium of claim 1, wherein the orientation treatment is carried out in a magnetic field in the vertical direction to the recording surface.
Claim 11
Dependent Claim
18 words
The magnetic recording medium of claim 9, wherein the magnetic field is a DC field or AC field.
Claim 12
Dependent Claim
20 words
The magnetic recording medium of claim 10, wherein the magnetic field has a field strength of 500 to 5,000 gauss.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-05-06 | 1988-11-05 | 1989-05-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-05-06 | 1992-11-05 | 1993-05-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-05-06 | 1996-11-05 | 1997-05-07 | $7700.00 | Window Closed / Lapsed |