EP0708379A2
Expired / Lapsed
EP
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Magnetic carrier for electrophotography
Assignee: Toda Kogyo Corp
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Filing: 1995-10-04
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Granted: —
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Expires: 2015-10-04
Abstract
Abstract Spherical composite particles for use as a magnetic carrier for electrophotography have a number average particle diameter of from 1 to 1000 µm and comprise ferromagnetic iron compound particles, non-magnetic metal oxide particles and a phenol-based resin as a binder resin, the total amount of said ferromagnetic iron compound particles and said non-magnetic metal oxide particles being from 80 to 99 wt% and the ratio of the number-average particle diameter of said non-magnetic metal oxide particles and the number-average particle diameter of said ferromagnetic iron compound particles being more than 1.0:1.
Inventors
- 👤 Toshiyuki Hakata
- 👤 Hiroomi Kakihara
- 👤 Masaaki Fukugauchi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 07:55
CPC Classifications
G; G03; G03G; G03G9/00; G03G9/08; G03G9/10; G03G9/113; G03G9/1132; G03G9/1133; G03G9/107; G03G9/1075; G03G9/108; G03G9/1085; G03G9/1088; G03G9/10882; G03G9/10884; G03G9/1137; G03G9/1139
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
93 words
Spherical composite particles suitable for use as a magnetic carrier for electrophotography, which particles have a number-average particle diameter of from 1 to 1000 µm and comprise ferromagnetic iron compound particles, non-magnetic metal oxide particles and a phenol-based resin as a binder resin, the total amount of said ferromagnetic iron compound particles and said non-magnetic metal oxide particles being from 80 to 99 wt% and the ratio of the number-average particle diameter of said non-magnetic metal oxide particles and the number-average particle diameter of said ferromagnetic iron compound particles being more than 1.0:1.
Claim 2
Dependent Claim
39 words
Particles according to claim 1, wherein said number-average particle diameter of said ferromagnetic iron compound particles is from 0.02 to 5 µm and said number-average particle diameter of said non-magnetic metal oxide particles is from 0.05 to 10 µm.
Claim 3
Dependent Claim
41 words
Particles according to claim 1 or 2, wherein said non-magnetic metal oxide particles are present in an amount of from 5 to 70 wt% based on the total amount of said ferromagnetic iron compound particles and said non-magnetic metal oxide particles.
Claim 4
Dependent Claim
43 words
Particles according to any one of the preceding claims, which have a saturation magnetization of from 20 to 90 Am/kg (20 to 90 emu/g), a true specific gravity of from 2.5 to 5.2 and an electric resistance of from 10¹⁰ to 10¹⁴ Ωcm.
Claim 5
Dependent Claim
18 words
Particles according to any one of the preceding claims, which have a sphericity of from 1.0 to 1.4.
Claim 6
Dependent Claim
20 words
Particles according to any one of the preceding claims, which have a bulk density of not more than 2.5 g/cm³.
Claim 7
Dependent Claim
51 words
Particles according to any one of the preceding claims, wherein said ferromagnetic iron compound particles are selected from ferromagnetic iron oxide particles, spinel ferrite particles containing at least one metal other than iron, magnetoplumbite ferrite particles and fine iron or iron alloy particles having an oxide film on the surfaces thereof.
Claim 8
Dependent Claim
38 words
Particles according to any one of the preceding claims, wherein said non-magnetic metal oxide particles are selected from titanium oxide particles, silica particles, alumina particles, zinc oxide particles, magnesium oxide particles, hematite particles, goethite particles and ilmenite particles.
Claim 9
Dependent Claim
29 words
Particles according to any one of the preceding claims, wherein said ferromagnetic iron compound particles and said non-magnetic metal oxide particles have been subjected to a lipophilic surface treatment.
Claim 10
Dependent Claim
40 words
Particles according to any one of the preceding claims, wherein a surface layer of a thermoplastic resin and/or a thermoset resin coats core particles comprising said ferromagnetic iron compound particles, said non-magnetic metal oxide particles and said phenol-based binder resin.
Claim 11
Dependent Claim
31 words
Particles according to claim 10, wherein said coating layer is present in an amount of from 0.1 to 50 parts by weight per 100 parts by weight of said core particles.
Claim 12
Dependent Claim
17 words
Particles according to claim 10 or 11, wherein said coating layer contains fine non-magnetic metal oxide particles.
Claim 13
Dependent Claim
90 words
Particles according to claim 12, wherein said coating layer is present in an amount of from 0.2 to 50 parts by weight per 100 parts by weight of said core particles, said fine non-magnetic metal oxide particles are present in said coating layer in an amount of from 0.1 to 10 parts by weight per 100 parts by weight of said core particles and the amount of said resin in said coating layer is from 0.1 to 50.0 parts by weight per 100 parts by weight of said core particles.
Claim 14
Dependent Claim
37 words
Particles according to claim 12 or 13 wherein said fine non-magnetic metal oxide particles are selected from titanium oxide particles, silica particles, alumina particles, zinc oxide particles, magnesium oxide particles, hematite particles, goethite particles and ilmenite particles.
Claim 15
Dependent Claim
28 words
Particles according to any one of claims 12 to 14, wherein the average particle diameter of said fine non-magnetic metal oxide particles is not more than 1 µm.
Claim 16
Dependent Claim
21 words
A developer for electrophotography comprising a toner and, as a carrier, particles as defined in any one of the preceding claims.
References Cited (Backward Citations)
JPS4713954A
Cited
JPS57660A
Cited
JPH02220068A
Cited
JPH04100850A
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JPH04124677A
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JPH05273789A
Cited
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