Patent US4519931A successfully refreshed from Google Patents.
US4519931A
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US
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Magnetic fluid
Assignee: Panasonic Holdings Corp
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Filing: 1982-07-26
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Granted: 1985-05-28
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Expires: 2002-07-26
Abstract
Abstract This invention provides a magnetic fluid which is diversified in hue and stable in the electric fields. The magnetic fluid of this invention is composed of a dispersion of ferromagnetic particles dispersed by a surfactant, and a colorant having the same charge as the dispersing medium in said dispersing medium. The dyes effective for use in this invention are the nonionic azo dyes, anthrquinone dyes and metal-containing dyes, and the pigments useful in this invention are the organic or inorganic pigments treated so as to have an isoelectric point in the dispersing medium. A magnetic fluid having black color or other desired hues can be obtained by properly selecting the dye and/or pigment. The magnetic fluid of this invention exhibits its excellent properties particularly when used as a recording material.
Inventors
- 👤 Mamoru Soga
- 👤 Keiichi Yubakami
- 👤 Nobuo Sonoda
- 👤 Wataru Shimotsuma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 11:21
CPC Classifications
B; B82; B82Y; B82Y15/00; H; H01; H01F; H01F1/00; H01F1/44; Y; Y10; Y10T; Y10T428/00; Y10T428/12; Y10T428/12465; Y10T428/29; Y10T428/2982
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
71 words
A magnetic fluid suitable for use in image recording under the action of magnetic or electric force, comprising fine ferromagnetic particles dispersed in a liquid dispersing medium with the aid of a surfactant, and a suitable colorant dispersed or dissolved in said liquid dispersing medium, having the same charge as the liquid dispersing medium, said fluid being substantially free from colorant aggregation or separation in an electric field of 1 KV/mm.
Claim 2
Dependent Claim
71 words
A magnetic fluid suitable for use in image recording under the action of magnetic or electric force, comprising fine ferromagnetic particles dispersed in a liquid dispersing medium with the aid of a surfactant, and a suitable colorant dispersed or dissolved in said liquid dispersing medium, having the same charge as the liquid dispersing medium, said fluid being substantially free from colorant aggregation or separation in an electric field of 1 KV/mm.
Claim 3
Dependent Claim
27 words
The magnetic fluid according to claim 1, wherein said colorant contains at least one of the azo, anthraquinone and metal-containing dyes soluble in the liquid dispersing medium.
Claim 4
Dependent Claim
29 words
The magnetic fluid according to claim 1, wherein said colorant contains at least one of the organic or inorganic pigments which can be dispersed in said liquid dispersing medium.
Claim 5
Dependent Claim
28 words
The magnetic fluid according to any one of claims 1 to 3, wherein said dispersing medium contains at least one of liquid paraffin, liquid ether and liquid ester.
Claim 6
Dependent Claim
27 words
The magnetic fluid according to any one of claims 1 to 3, wherein the fine ferromagnetic particles contain at least one of cobalt, nickel, iron and ferrite.
Claim 7
Dependent Claim
16 words
The magnetic fluid according to claim 5, wherein said ferromagnetic particles are composed of Mn-Zn ferrite.
Claim 8
Dependent Claim
22 words
The magnetic fluid according to claim 1, wherein said fine ferromagnetic particles have a particle size of about 50 to 200 angstroms.
Claim 9
Dependent Claim
73 words
A magnetic fluid suitable for use in image recording under the action of magnetic or electric force, consisting essentially of fine ferromagnetic particles dispersed in a liquid dispersing medium with the aid of a surfactant, and a suitable colorant dispersed or dissolved in said liquid dispersing medium, having the same charge as the liquid dispersing medium, said fluid being substantially free from colorant aggregation or separation in an electric field of 1 KV/mm.
Claim 10
Dependent Claim
73 words
A magnetic fluid suitable for use in image recording under the action of magnetic or electric force, consisting essentially of fine ferromagnetic particles dispersed in a liquid dispersing medium with the aid of a surfactant, and a suitable colorant dispersed or dissolved in said liquid dispersing medium, having the same charge as the liquid dispersing medium, said fluid being substantially free from colorant aggregation or separation in an electric field of 1 KV/mm.
Claim 11
Dependent Claim
26 words
The magnetic fluid according to claim 8, wherein said colorant is at least one of azo, anthraquinone and metal-containing dyes soluble in said liquid dispersing medium.
Claim 12
Dependent Claim
28 words
The magnetic fluid according to claim 8, wherein said colorant is at least one of organic and inorganic pigments which can be dispersed in said liquid dispersing medium.
Claim 13
Dependent Claim
22 words
The magnetic fluid according to claim 8, wherein said fine ferromagnetic particles have a particle size of about 50 to 200 angstroms.
Claim 14
Dependent Claim
16 words
The magnetic fluid according to claim 8, wherein said ferromagnetic particles are composed of Mn-Zn ferrite.
Claim 15
Dependent Claim
46 words
The magnetic fluid of claim 9, wherein said dye is selected from the group consisting of 1,4-diaminoanthraquinone, 1,4-diaminoanthraquinone whose amino is substituted with an n-octylamino or n-dodecylamino group, Solvent Black 3 (C.I. 26,150), C.I. Direct Blue 76 (C.I. 24,411) and C.I. Direct Blue 98 (C.I. 23,155).
Claim 16
Dependent Claim
41 words
The magnetic fluid of claim 10, wherein said pigment is selected from the group consisting of C.I. Vat Blue 20 (C.I. 59,800), C.I. Acid Blue 45 (C.I. 63,010), C.I. Vat Blue 4 (C.I. 69,800), ultramarine blue, Prussian blue and cobalt blue.
References Cited (Backward Citations)
US4125667A
Cited
US4020236A
Cited
US4145300A
Cited
US4116906A
Cited
US4296176A
Cited
US4285801A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-05-27 | 1988-11-26 | 1989-05-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-05-27 | 1992-11-26 | 1993-05-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-05-27 | 1996-11-26 | 1997-05-28 | $7700.00 | Window Closed / Lapsed |