Patent US4132827A successfully refreshed from Google Patents.
US4132827A
Expired / Lapsed
US
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Magnetic recording substance
Assignee: Fujifilm Holdings Corp
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Filing: 1977-01-18
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Granted: 1979-01-02
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Expires: 1997-01-18
Abstract
Abstract In a magnetic recording substance comprising a non-magnetic support and a magnetic recording layer provided on the support, carbon black having a surface area of at least 700 m 2 /g and an oil absorption of at least 300 ml (DBP)/100 g is contained in the magnetic layer thereby lowering the surface electric resistance without deteriorating the characteristics of the magnetic recording layer.
Inventors
- 👤 Yoshito Mukaida
- 👤 Masaaki Fujiyama
- 👤 Shigeo Komine
- 👤 Masaaki Igarashi
- 👤 Nobutaka Yamaguchi
- 👤 Shinobu Iida
- 👤 Akira Kasuga
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 06:27
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/708; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/30
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
56 words
A magnetic recording medium comprising a non-magnetic support and a magnetic recording layer provided thereon containing at least 0.5% by weight based on the magnetic material in the magnetic recording layer of carbon black having a surface area of at least 700 m 2 /g and oil absorption of at least 300 ml (dibutyl phthalate)/100 g.
Claim 2
Dependent Claim
56 words
A magnetic recording medium comprising a non-magnetic support and a magnetic recording layer provided thereon containing at least 0.5% by weight based on the magnetic material in the magnetic recording layer of carbon black having a surface area of at least 700 m 2 /g and oil absorption of at least 300 ml (dibutyl phthalate)/100 g.
Claim 3
Dependent Claim
27 words
The magnetic recording medium of claim 1, wherein the non-magnetic support is of a material selected from the group consisting of polyesters, polyolefins, cellulose derivatives and polycarbonates.
Claim 4
Dependent Claim
34 words
The magnetic recording medium of claim 1, wherein said carbon black has a surface area of at least 900 m 2 /g and an oil absorption of at least 400 ml (dibutyl phthalate)/100 g.
Claim 5
Dependent Claim
19 words
The magnetic recording medium of claim 1, wherein the amount of carbon black is at least 1% by weight.
Claim 6
Dependent Claim
19 words
The magnetic recording medium of claim 1, wherein the carbon black has a particle size of about 20 mμ.
Claim 7
Dependent Claim
20 words
The magnetic recording medium of claim 1, wherein the thickness of said magnetic recording layer is from 0.5 to 10μ.
Claim 8
Dependent Claim
19 words
The magnetic recording medium of claim 1, wherein the magnetic recording layer comprises a ferromagnetic fine powder and binder.
Claim 9
Dependent Claim
89 words
The magnetic recording medium of claim 7, wherein the ferromagnetic fine powder 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 10
Dependent Claim
22 words
The magnetic recording medium of claim 3, wherein the ratio of binder to ferromagnetic fine powder is 10 to 400 parts/300 parts.
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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) | 1982-01-01 | 1982-07-03 | 1983-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-01-01 | 1986-07-03 | 1987-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-01-01 | 1990-07-03 | 1991-01-02 | $7700.00 | Window Closed / Lapsed |