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US4439796A
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Magnetic recording medium
Assignee: Fujifilm Holdings Corp
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Filing: 1981-12-09
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Granted: 1984-03-27
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Expires: 2001-12-09
Abstract
Abstract A magnetic recording medium is described having formed on a non-magnetic base at least two magnetic layers, each of the magnetic layers comprising ferromagnetic particles dispersed in a binder, wherein the ferromagnetic particles in the outermost magnetic layer are substantially cubic particles and have a side length of 0.3μ or less, and the ferromagnetic particles in an underlying magnetic layer are acicular particles.
Inventors
- 👤 Tatsuji Kitamoto
- 👤 Goro Akashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 01:17
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/716; G11B5/714; Y; Y10; Y10T; Y10T428/00; Y10T428/12; Y10T428/12014; Y10T428/12028; Y10T428/12049
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
56 words
A magnetic recording medium having formed on a non-magnetic base at least two magnetic layers, each comprising ferromagnetic particles dispersed in a binder, wherein the ferromagnetic particles in the outermost magnetic layer are substantially cubic particles having a side length of 0.3μ or less, and the ferromagnetic particles in an underlying magnetic layer are acicular particles.
Claim 2
Dependent Claim
56 words
A magnetic recording medium having formed on a non-magnetic base at least two magnetic layers, each comprising ferromagnetic particles dispersed in a binder, wherein the ferromagnetic particles in the outermost magnetic layer are substantially cubic particles having a side length of 0.3μ or less, and the ferromagnetic particles in an underlying magnetic layer are acicular particles.
Claim 3
Dependent Claim
33 words
A magnetic recording medium as in claim 1, wherein the acicular particles have a length to width ratio of 3/1 or more and are oriented in a direction parallel to the magnetic surface.
Claim 4
Dependent Claim
21 words
A magnetic recording medium as in claim 1 or 2, wherein the outermost magnetic layer has a thickness 3μ or less.
Claim 5
Dependent Claim
21 words
A magnetic recording medium as in claim 3, wherein the outermost magnetic layer has a thickness from about 0.5 to 2μ.
Claim 6
Dependent Claim
43 words
A magnetic recording medium as in claim 1 or 2, wherein the substantially cubic particles consist essentially of barium ferrite particles that are hexagonal and have crystalline magnetic anisotropy along the C-axis and are oriented in a direction normal to the magnetic surface.
References Cited (Backward Citations)
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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) | 1987-03-27 | 1987-09-26 | 1988-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-03-27 | 1991-09-26 | 1992-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-03-27 | 1995-09-26 | 1996-03-27 | $7700.00 | Window Closed / Lapsed |