US4425400A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium
Assignee: Fujifilm Holdings Corp
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Filing: 1982-03-31
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Granted: 1984-01-10
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Expires: 2002-03-31
Abstract
Abstract In a magnetic recording medium comprising a magnetic recording layer on the surface of a non-magnetic support member, an abrasive having a Mohs' hardness of at least 6 and needle-shaped α-Fe 2 O 3 are incorporated in the magnetic layer, thus improving the coating durability and decreasing the head abrasion, jitter and noise.
Inventors
- 👤 Nobutaka Yamaguchi
- 👤 Masaaki Fujiyana
- 👤 Nobuo Tsuji
- 👤 Norio Nasu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 08:21
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/708; G11B5/7085; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/31504; Y10T428/31652; Y10T428/31663; Y10T428/31678
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
72 words
A magnetic recording medium comprising a magnetic recording layer on the surface of a non-magnetic support, the magnetic recording layer comprising a ferromagnetic substance, 0.5-15 wt % based on the weight of the ferromagnetic substance of an abrasive having a Mohs' hardness of at least 6 and 5-30 wt % based on the weight of the ferromagnetic substance of acicular α-Fe 2 O 3 having a length of 1.5 to 0.1 micron.
Claim 2
Dependent Claim
72 words
A magnetic recording medium comprising a magnetic recording layer on the surface of a non-magnetic support, the magnetic recording layer comprising a ferromagnetic substance, 0.5-15 wt % based on the weight of the ferromagnetic substance of an abrasive having a Mohs' hardness of at least 6 and 5-30 wt % based on the weight of the ferromagnetic substance of acicular α-Fe 2 O 3 having a length of 1.5 to 0.1 micron.
Claim 3
Dependent Claim
88 words
The magnetic recording medium of claim 1, wherein the ferromagnetic substance is selected from the group consisting of fine powders 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 abrasive having a Mohs' hardness of at least 6 is selected from the group consisting of fused alumina, silicon carbide, chromium oxide, corundum, synthetic corundum, diamond, synthetic diamond, garnet and emery.
Claim 5
Dependent Claim
25 words
The magnetic recording medium of claim 1, wherein the acicular α-Fe 2 O 3 has an acicular ratio (long axis/short axis) of 15/1 to 3/1.
Claim 6
Dependent Claim
27 words
The magnetic recording medium of claim 1, wherein the thickness (short axis) of the acicular α-Fe 2 O 3 is smaller than that of the ferromagnetic substance.
Claim 7
Dependent Claim
24 words
The magnetic recording medium of claim 5, wherein the acicular α-Fe 2 O 3 /ferromagnetic substance ratio (short axis ratio) is 1 to 0.3.
Claim 8
Dependent Claim
20 words
The magnetic recording medium of claim 1, wherein the magnetic recording layer further contains a fatty acid and silicone oil.
References Cited (Backward Citations)
US4275115A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-01-09 | 1987-07-11 | 1988-01-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-01-09 | 1991-07-11 | 1992-01-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-01-09 | 1995-07-11 | 1996-01-10 | $7700.00 | Window Closed / Lapsed |