US4486496A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium
Assignee: Fujifilm Holdings Corp
•
Filing: 1982-05-26
•
Granted: 1984-12-04
•
Expires: 2002-05-26
Abstract
Abstract A magnetic recording medium which comprises a non-magnetic support having thereon a magnetic layer containing plate-shaped magnetic particles which have axes of easy magnetization perpendicular to their respective plate planes dispersed in a binder, the magnetic particles each having a multiple magnetic domain structure and having a particle diameter equal to or longer than the recorded effective shortest wavelength.
Inventors
- 👤 Shin-ichiro Dezawa
- 👤 Goro Akashi
- 👤 Tatsuji Kitamoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 07:16
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/714; G11B5/02; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
126 words
A magnetic recording medium which comprises (a) a non-magnetic support, (b) a magnetic layer containing plate-shaped magnetic particles having a mean particle size of 0.1 μm to 20 μm and a coercive force of 300 to 3,000 oersteads, and satisfying the following relationship K/2πM.sub.s.sup.2 ≧1 wherein K represents the magnetic anisotropy constant in the direction perpendicular to the individual plate-shaped magnetic particles' major plate plane, M s , represents saturation magnetization, and π is the ratio of circumference of a circle to its diameter, and which have axes of easy magnetization perpendicular to their plate planes dispersed in a binder, said plate-shaped magnetic particles each having a multiple magnetic domain structure and having a particle diameter equal to or longer than the recorded effective shortest wavelength.
Claim 2
Dependent Claim
126 words
A magnetic recording medium which comprises (a) a non-magnetic support, (b) a magnetic layer containing plate-shaped magnetic particles having a mean particle size of 0.1 μm to 20 μm and a coercive force of 300 to 3,000 oersteads, and satisfying the following relationship K/2πM.sub.s.sup.2 ≧1 wherein K represents the magnetic anisotropy constant in the direction perpendicular to the individual plate-shaped magnetic particles' major plate plane, M s , represents saturation magnetization, and π is the ratio of circumference of a circle to its diameter, and which have axes of easy magnetization perpendicular to their plate planes dispersed in a binder, said plate-shaped magnetic particles each having a multiple magnetic domain structure and having a particle diameter equal to or longer than the recorded effective shortest wavelength.
Claim 3
Dependent Claim
102 words
The magnetic recording medium described in claim 1, wherein said plate-shaped magnetic particles which have a multiple magnetic domain structure comprise hexagonal ferrites represented by the following general formulae: Mo.6Fe 2 O 3 , BaM 2 Fe 16 O 27 , Ba 2 M 2 Fe 12 O 22 , Ba 3 M 2 Fe 24 O 41 , wherein M represents a divalent metal ion and metals from Groups II, IV, V, and VIa of the Periodic Table and, wherein up to about 20 atm % of the barium ions or/and the iron ions may be replaced by other metal ions.
Claim 4
Dependent Claim
32 words
The magnetic recording medium described in claim 1 or claim 2, wherein said plate-shaped magnetic particles having multiple magnetic domain structures have a mean particle diameter of 0.5 μm to 10 μm.
Claim 5
Dependent Claim
28 words
A magnetic recording medium described in claim 1 wherein said plate-shaped magnetic particles have a ratio of diameter to thickness of from about the 2:1 to about 30:1.
Claim 6
Dependent Claim
25 words
The magnetic recording medium described in claim 1 wherein said plate-shaped magnetic particles have a ratio of diameter to thickness of from 4:1 to 30:1.
Claim 7
Dependent Claim
21 words
A magnetic recording medium as claimed in claim 1 wherein said particle diameter is longer than the recorded effective shortest wavelength.
References Cited (Backward Citations)
US3023166A
Cited
US3185775A
Cited
US3117065A
Cited
US4135016A
Cited
US4171408A
Cited
US4210946A
Cited
JPS5586103A
Cited
US4351010A
Cited
US4277809A
Cited
US4355072A
Cited
US4425401A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-12-04 | 1988-06-04 | 1988-12-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-12-04 | 1992-06-04 | 1992-12-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-12-04 | 1996-06-04 | 1996-12-04 | $7700.00 | Window Closed / Lapsed |