US4613545A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: Sony Corp
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Filing: 1983-07-01
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Granted: 1986-09-23
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Expires: 2003-07-01
Abstract
Abstract PCT No. PCT/JP83/00211 Sec. 371 Date Mar. 1, 1984 Sec. 102(e) Date Mar. 1, 1984 PCT Filed Jul. 1, 1983 PCT Pub. No. WO84/00241 PCT Pub. Date Jan. 19, 1984.A magnetic recording medium has on a nonmagnetic support, a magnetic layer consisting mainly of an acicular magnetic powder and a binder. The medium has excellent magnetic characteristics required for short-wave recording and has an excellent durability. For this purpose, the medium contains a ferromagnetic metal powder which has a coercive force of not less than 1,000 Oe and a specific surface area as determined by the BET method, of not less that 45 m2/g. The medium contains in the binder not less than 50% by weight of a resin which has a high dispersibility owing to the introduction of at least one polar group selected from the group consisting of polar groups having the general formulas of: <IMAGE> (wherein M is hydrogen, lithium, sodium or potassium; and M1 and M2 are hydrogen, lithium, sodium, potassium or alky groups).
Inventors
- 👤 Ryoji Chubachi
- 👤 Nobuyuki Nihei
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 15:57
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/702; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/31504; Y10T428/31551; Y10T428/31609; Y10T428/31786; Y10T428/31855; Y10T428/31935
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
155 words
A magnetic recording medium having on a nonmagnetic support a magnetic layer measuring from 0.5 to 6 microns and consisting mainly of an acicular ferromagnetic metal powder and a binder, characterized in that said acicular ferromagnetic metal powder has a coercive force of not less than 1,000 Oe, a specific surface area as determined by the BET method, of not less than 45 m 2 /g, an axial ratio of not less than 7, and said binder contains not less than 50% by weight of a resin having a molecular weight not in excess of 50,000 and containing at least one polar group selected from the group consisting of polar groups having the general formulas: ##STR5## (wherein M is hydrogen, lithium, sodium or potassium; and M 1 and M 2 are hydrogen, lithium, sodium, potassium or alkyl groups), the weight ratio of feromagnetic metal powder to binder being in the range of 5 to 12.
Claim 2
Dependent Claim
155 words
A magnetic recording medium having on a nonmagnetic support a magnetic layer measuring from 0.5 to 6 microns and consisting mainly of an acicular ferromagnetic metal powder and a binder, characterized in that said acicular ferromagnetic metal powder has a coercive force of not less than 1,000 Oe, a specific surface area as determined by the BET method, of not less than 45 m 2 /g, an axial ratio of not less than 7, and said binder contains not less than 50% by weight of a resin having a molecular weight not in excess of 50,000 and containing at least one polar group selected from the group consisting of polar groups having the general formulas: ##STR5## (wherein M is hydrogen, lithium, sodium or potassium; and M 1 and M 2 are hydrogen, lithium, sodium, potassium or alkyl groups), the weight ratio of feromagnetic metal powder to binder being in the range of 5 to 12.
Claim 3
Dependent Claim
24 words
A magnetic recording medium according to claim 1, characterized in that said acicular metal powder has a coercive force of 1,000 to 2,000 Oe.
Claim 4
Dependent Claim
25 words
A magnetic recording medium according to claim 1, characterized in that said acicular ferromagnetic metal powder has the coercive force of 1,100 to 1,500 Oe.
Claim 5
Dependent Claim
25 words
A magnetic recording medium according to claim 1, characterized in that an axial ratio of said acicular ferromagnetic metal powder is not less than 10.
Claim 6
Dependent Claim
30 words
A magnetic recording medium according to claim 1, characterized in that said alkyl group is a saturated, straight or branched chain aliphatic hydrocarbon group having up to 23 carbon atoms.
Claim 7
Dependent Claim
25 words
A magnetic recording medium according to claim 1, characterized in that the molecular weight of said resin having the polar group is 2,000 to 50,000.
Claim 8
Dependent Claim
28 words
A magnetic recording medium according to claim 1, characterized in that said resin having the polar group has a molecular weight of 200 to 50,000 per polar group.
Claim 9
Dependent Claim
28 words
A magnetic recording medium according to claim 1, characterized in that a main chain of said resin having the polar group is polyester, polyurethane or vinyl chloride-based copolymer.
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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) | 1989-09-22 | 1990-03-24 | 1990-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-09-22 | 1994-03-24 | 1994-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-09-22 | 1998-03-24 | 1998-09-23 | $7700.00 | Window Closed / Lapsed |