# US 10,503,091 B2 · Carrier for electrostatic image development and electrostatic image developer

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- Number: US 10,503,091 B2
- Document ID: US10503091B2
- Status: Granted
- Kind: B2
- Application number: 16/120,457
- Filed: 2018-09-04
- Published: 2019-09-19
- Granted: 2019-12-10
- Earliest claimed: 2018-03-13
- Assignees: Fuji Xerox Co., Ltd.
- Applicants: Fuji Xerox Co., Ltd.
- Inventors: Yosuke Tsurumi; Moegi Iguchi; Shintaro Anno; Toshiaki Hasegawa
- Web page: https://patentgrep.com/patent/US10503091B2

## CPC

- G03G 9/1075: {Structural characteristics of the carrier particles, e.g. shape or crystallographic structure}
- G03G 9/0819: {characterised by the dimensions of the particles}
- G03G 9/0827: {characterised by their shape, e.g. degree of sphericity}
- 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

A carrier for electrostatic image development includes: resin-coated magnetic particles each including a magnetic particle and a resin layer that covers the magnetic particle; and strontium titanate particles composed of primary particles having an average circularity of 0.82 to 0.94 and an 84% cumulative circularity of more than 0.92.

## Claims

### Claim 1

A carrier for electrostatic image development, the carrier comprising:
resin-coated magnetic particles each including a magnetic particle and a resin layer that covers the magnetic particle; and
strontium titanate particles,
wherein the strontium titanate particles are composed of primary particles having an average circularity of 0.82 to 0.94 and an 84% cumulative circularity of more than 0.92,
wherein the strontium titanate particles in which a half width of a (110) peak obtained by an X-ray diffraction method is 0.2° to 2.0°,
wherein the strontium titanate particles have an average primary particle diameter of 15 nm to 60 nm.

### Claim 2 (depends on 1)

The carrier for electrostatic image development according to claim 1, wherein the strontium titanate particles contain a dopant.

### Claim 3 (depends on 1)

The carrier for electrostatic image development according to claim 1, wherein the amount of the strontium titanate particles with respect to the mass of the resin-coated magnetic particles is 0.02% by mass to 0.08% by mass.

### Claim 4 (depends on 1)

The carrier for electrostatic image development according to claim 1, wherein the ratio of exposed surfaces of the magnetic particles on the surfaces of the resin-coated magnetic particles is 2% to 20%.

### Claim 5 (depends on 1)

The carrier for electrostatic image development according to claim 1, wherein the magnetic particles are ferrite particles.

### Claim 6 (depends on 5)

The carrier for electrostatic image development according to claim 5, wherein the ferrite particles contain at least one selected from calcium oxide and strontium oxide, and the total content of a calcium element and a strontium element in the ferrite particles is 0.1% by mass to 2.0% by mass.

### Claim 7 (depends on 1)

An electrostatic image developer comprising:
a toner for electrostatic image development; and
the carrier for electrostatic image development according to claim 1.