# US 8,465,898 B2 · Ferrite carrier core material and ferrite carrier for electrophotographic developer, and electrophotographic developer using the ferrite carrier

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- Number: US 8,465,898 B2
- Document ID: US8465898B2
- Status: Granted
- Kind: B2
- Application number: 13/161,697
- Filed: 2011-06-16
- Published: 2012-01-05
- Granted: 2013-06-18
- Earliest claimed: 2010-06-30
- Assignees: Powdertech Co., Ltd.
- Applicants: Toru Iwata; Koji Aga
- Inventors: Toru Iwata; Koji Aga
- Web page: https://patentgrep.com/patent/US8465898B2

## CPC

- G03G 9/1085: {with non-ferrous metal oxide, e.g. MgO-Fe2O3}
- G03G 9/1075: {Structural characteristics of the carrier particles, e.g. shape or crystallographic structure}
- G03G 9/1133: {obtained by reactions only involving carbon-to-carbon unsaturated bonds}
- G03G 9/1139: {Inorganic components of coatings}
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

There are provided a ferrite carrier core material for an electrophotographic developer, which contain 10 to 30% by weight of Mn, 1.0 to 3.0% by weight of Mg, 0.3 to 1.5% by weight of Ti and 40 to 60% by weight of Fe, a ferrite carrier for an electrophotographic developer obtained by coating the ferrite core material, and an electrophotographic developer using the ferrite carrier.

## Claims

### Claim 1

A ferrite carrier core material for an electrophotographic developer, comprising 13 to 27% by weight of Mn, 1.0 to 3.0% by weight of Mg, 0.3 to 1.5% by weight of Ti and 42 to 58% by weight of Fe.

### Claim 2 (depends on 1)

The ferrite carrier core material for an electrophotographic developer according to claim 1, wherein the ferrite carrier core material has a magnetization of 45 to 70 Am2/kg at an impressed magnetic field of 0.5 K·1000/4π A/m.

### Claim 3 (depends on 1)

The ferrite carrier core material for an electrophotographic developer according to claim 1, wherein the ferrite carrier core material has a volume resistance of 1×106 to 1×1010Ω at a 2 mm-Gap applied voltage of 50 V.

### Claim 4 (depends on 1)

The ferrite carrier core material for an electrophotographic developer according to claim 1, wherein the ferrite carrier core material has a BET specific surface area of 0.060 to 0.170 m2/g.

### Claim 5 (depends on 1)

The ferrite carrier core material for an electrophotographic developer according to claim 1, wherein the ferrite carrier core material has a ratio of a charge amount in a low-temperature and low-humidity environment to a charge amount in a high-temperature and high-humidity environment of 0.85 to 1.15.

### Claim 6 (depends on 1)

The ferrite carrier core material for an electrophotographic developer according to claim 1, comprising 0.1 to 1.0% of Sr.

### Claim 7 (depends on 1)

The ferrite carrier core material for an electrophotographic developer according to claim 1, wherein the ferrite carrier core material has an oxide film formed on a surface thereof.

### Claim 8 (depends on 1)

A ferrite carrier for an electrophotographic developer, being obtained by coating a surface of a ferrite carrier core material according to claim 1 with a resin.

### Claim 9 (depends on 8)

An electrophotographic developer, comprising a ferrite carrier according to claim 8 and a toner.

### Claim 10 (depends on 9)

The electrophotographic developer according to claim 9, being used as a refill developer.