US4820581A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium
Assignee: Fujifilm Holdings Corp
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Filing: 1985-11-15
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Granted: 1989-04-11
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Expires: 2005-11-15
Abstract
Abstract A magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on said support, in which said magnetic recording layer comprises: a ferromagnetic metal powder having a specific surface area of not less than 40 m 2 /g and an abrasive having a Mohs' scale of hardness of not less than 6, both being dispersed in a binder containing a polycarbonate-polyurethane.
Inventors
- 👤 Shinji Saito
- 👤 Hiroshi Ogawa
- 👤 Akihiro Matsufuji
- 👤 Yasuo Tamai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:29
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/714; G11B5/702; G11B5/7021; G11B5/7022; G11B5/708; G11B5/7085; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/31504; Y10T428/31507; Y10T428/31551; Y10T428/31786
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
75 words
A magnetic recording medium comprising a non-magnetic support and a magnetic recording layer provided on said support, in which said magnetic recording layer comprises: a ferromagnetic metal alloy powder having a specific surface are of not less than 40 m 2 /g and an abrasive having a Mohs' scale of hardness of not less than 6, both being dispersed in a binder containing a polycarbonate-polyurethane having a weight average molecular weight of 5,000 to 200,000.
Claim 2
Dependent Claim
75 words
A magnetic recording medium comprising a non-magnetic support and a magnetic recording layer provided on said support, in which said magnetic recording layer comprises: a ferromagnetic metal alloy powder having a specific surface are of not less than 40 m 2 /g and an abrasive having a Mohs' scale of hardness of not less than 6, both being dispersed in a binder containing a polycarbonate-polyurethane having a weight average molecular weight of 5,000 to 200,000.
Claim 3
Dependent Claim
33 words
The magnetic recording medium as claimed in claim 1, wherein said binder contains said polycarbonate-polyurethane in an amount of at least 10 % by weight based on the total weight of the binder.
Claim 4
Dependent Claim
20 words
The magnetic recording medium as claimed in claim 1, wherein said binder further contains a vinyl chloride/vinyl acetate/maleic anhydride copolymer.
Claim 5
Dependent Claim
35 words
The magnetic recording medium as claimed in claim 1, wherein said abrasive is selected from the group consisting of α-Fe 2 O 3 , SiC, α-Al 2 O 3 and Cr 2 O 3 .
Claim 6
Dependent Claim
42 words
The magnetic recording medium as claimed in claim 4, wherein said abrasive is contained in said magnetic recording layer in an amount ranging from 0.1 to 20 parts by weight based on 100 parts by weight of the ferromagnetic metal alloy powder.
Claim 7
Dependent Claim
36 words
The magnetic recording medium as claimed in any claim of claims 1 to 4, wherein said nonmagnetic support has a center line average height of lower than 0.1 μm at a cut-off value of 0.25 mm.
Claim 8
Dependent Claim
36 words
The magnetic recording medium as claimed in any claim of claims 1 to 4, wherein said nonmagnetic support has a center line average height of lower than 0.02 μm at a cut-off value of 0.25 mm.
Claim 9
Dependent Claim
22 words
The magnetic recording medium as claimed in claim 1, wherein said polycarbonate-polyurethane has a repeating unit derived from an aromatic polyhydric alcohol.
Claim 10
Dependent Claim
17 words
The magnetic recording medium as claimed in claim 8, wherein said aromatic polyhydric alcohol is bisphenol A.
Claim 11
Dependent Claim
76 words
The magnetic recording medium as claimed in claim 2, wherein said ferromagnetic metal alloy powder is an Fe--Zn--Ni alloy powder, said abrasive is contained in said magnetic recording layer in an amount ranging from 0.1 to 20 parts by weight based on 100 parts by weight of the said ferromagnetic metal alloy powder and wherein said nonmagnetic support has a ceter line average height of lower than 0.1 um at a cut-off value of 0.25 mm.
Claim 12
Dependent Claim
60 words
The magnetic recording medium as claimed in claim 10 wherein said binder contains said polycarbonate-polyurethane in an amount of at least 30% by weight based on the total weight of the binder and wherein said abrasive is selected from the group consisting of α-Fe 2 O 3 , SiC, α- Al 2 O 3 and Cr 2 O 3 .
Claim 13
Dependent Claim
75 words
A magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on said support, in which said magnetic recording layer comprises: a magnetic powder consisting of a ferromagnetic metal alloy powder of not less than 40 m 2 /g and an abrasive having a Mohs' scale of hardness of not less than 6, both being dispersed in a binder containing a polycarbonate-polyurethane having a weight average molecular weight of 5,000 to 200,000.
Claim 14
Dependent Claim
75 words
A magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on said support, in which said magnetic recording layer comprises: a magnetic powder consisting of a ferromagnetic metal alloy powder of not less than 40 m 2 /g and an abrasive having a Mohs' scale of hardness of not less than 6, both being dispersed in a binder containing a polycarbonate-polyurethane having a weight average molecular weight of 5,000 to 200,000.
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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) | 1992-04-10 | 1992-10-10 | 1993-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-04-10 | 1996-10-10 | 1997-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-04-10 | 2000-10-10 | 2001-04-11 | $7700.00 | Window Closed / Lapsed |