US5217804A
Expired / Lapsed
US
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Magnetic particles
Assignee: Eastman Kodak Co
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Filing: 1990-11-06
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Granted: 1993-06-08
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Expires: 2010-11-06
Abstract
Abstract Magnetic particles are cobalt surface treated gamma iron oxide (Fe2O3) having a specific area of at least 30 m2/g and a powder coercivity greater than about 450 Oe, the particles being coated with from about 10 to about 50% by weight of a material having a refractive index less than about the refractive index of a binder for the particles.
Inventors
- 👤 Robert O. James
- 👤 Sidney J. Bertucci
- 👤 George L. Oltean
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 19:38
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70657; G11B5/712; Y; Y10; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/29; Y10T428/2982; Y10T428/2991; Y10T428/2993; Y10T428/2998; Y10T428/31504; Y10T428/31507; Y10T428/3154; Y10T428/31544; Y10T428/31551; Y10T428/31591; Y10T428/31598; Y10T428/31609; Y10T428/31786; Y10T428/31797; Y10T428/31855; Y10T428/3188; Y10T428/31884; Y10T428/31891; Y10T428/31971
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
82 words
Magnetic particles in a binder to form a transparent magnetic layer comprising a cobalt surface treated gamma iron oxide core having a specific surface area of at least 30 m 2 /g and exhibiting a powder coercivity of greater than 450 Oe, the core surrounded by a shell, the shell comprising from 10 to 50 percent by weight of the total weight of the particle and being of a material having a refractive index less than the refractive index of the binder.
Claim 2
Dependent Claim
82 words
Magnetic particles in a binder to form a transparent magnetic layer comprising a cobalt surface treated gamma iron oxide core having a specific surface area of at least 30 m 2 /g and exhibiting a powder coercivity of greater than 450 Oe, the core surrounded by a shell, the shell comprising from 10 to 50 percent by weight of the total weight of the particle and being of a material having a refractive index less than the refractive index of the binder.
Claim 3
Dependent Claim
20 words
The particles of claim 1 wherein the specific surface area of the core is at least 40 m 2 /g.
Claim 4
Dependent Claim
20 words
The particles of claim 1 wherein the powder coercivity of the core is from about 650 to about 850 Oe.
Claim 5
Dependent Claim
21 words
The particles of claim 1 wherein the shell comprises from about 20 to about 45 percent by weight of the particle.
Claim 6
Dependent Claim
25 words
The particles of claim 1 wherein the shell material is selected from the group consisting of silica, magnesium fluoride, calcium, fluoride and fluorinated hydrocarbon resins.
Claim 7
Dependent Claim
11 words
The particles of claim 5 wherein the shell material is silica.
Claim 8
Dependent Claim
14 words
The particles of claim 5 wherein the shell material is a fluorinated hydrocarbon resin.
Claim 9
Dependent Claim
11 words
The particles of claim 7 wherein the shell material is polytetrafluoroethylene.
Claim 10
Dependent Claim
11 words
The particles of claim 1 wherein the shell material contains voids.
Claim 11
Dependent Claim
24 words
The particles of claim 1 wherein the refractive indices of the shell and the binder are less than the refractive index of the core.
Claim 12
Dependent Claim
74 words
Magnetic particles comprising a cobalt surface treated gamma iron oxide core having a specific surface area of at least 30 m 2 /g and exhibiting a powder coercivity of greater than 450 Oe, the core surrounded by a shell, the shell comprising from 10 to 50 percent by weight of the total weight of the particles of a material selected from the group consisting of silica, magnesium fluoride, calcium fluoride and fluorinated hydrocarbon resins.
Claim 13
Dependent Claim
74 words
Magnetic particles comprising a cobalt surface treated gamma iron oxide core having a specific surface area of at least 30 m 2 /g and exhibiting a powder coercivity of greater than 450 Oe, the core surrounded by a shell, the shell comprising from 10 to 50 percent by weight of the total weight of the particles of a material selected from the group consisting of silica, magnesium fluoride, calcium fluoride and fluorinated hydrocarbon resins.
Claim 14
Dependent Claim
20 words
The particles of claim 1 wherein the binder is gelatin, a cellulose ester, a polyurethane, a polyester or a polycarbonate.
References Cited (Backward Citations)
CA686172A
Cited
US3782947A
Cited
US4279945A
Cited
US4302523A
Cited
JPS5583207A
Cited
JPS5583209A
Cited
US4321303A
Cited
US4336310A
Cited
US4280918A
Cited
JPS58164706A
Cited
US4438156A
Cited
JPS60216510A
Cited
US4956220A
Cited
US4874668A
Cited
US4990276A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-06-07 | 1996-12-07 | 1997-06-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-06-07 | 2000-12-07 | 2001-06-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-06-07 | 2004-12-07 | 2005-06-08 | $7700.00 | Window Closed / Lapsed |