# US 12,204,280 B2 · Carrier, xerographic developer, and carrier production method

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- Number: US 12,204,280 B2
- Document ID: US12204280B2
- Status: Granted
- Kind: B2
- Application number: 17/430,440
- Filed: 2020-02-13
- Published: 2022-01-20
- Granted: 2025-01-21
- Earliest claimed: 2019-02-13
- Assignees: Powdertech Co., Ltd.
- Applicants: Powdertech Co., Ltd.
- Inventors: Aya Sakuta; Makoto Ishikawa; Hiroki Sawamoto; Tetsuya Uemura
- Web page: https://patentgrep.com/patent/US12204280B2

## CPC

- G03G 9/1134: {containing fluorine atoms}
- G03G 9/0819: {characterised by the dimensions of the particles}
- G03G 9/1075: {Structural characteristics of the carrier particles, e.g. shape or crystallographic structure}
- G03G 9/108: {Ferrite carrier, e.g. magnetite}
- G03G 9/1131: {Coating methods; Structure of coatings}
- G03G 9/1135: {obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds}
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

The present invention relates to a carrier including: a magnetic core material; and a resin coating layer coating a surface of the magnetic core material, in which the resin coating layer contains a binder resin, and fluorine element-containing resin particles dispersed in the binder resin, the resin coating layer has a coefficient of variation of a film thickness of 25% or less, and the resin coating layer has an average value of the number of the fluorine element-containing resin particles being 3 particles/μm2 or more and 350 particles/μm2 or less per unit area in a cross section of the resin coating layer, and has a coefficient of variation thereof being 20% or less.

## Claims

### Claim 1

A carrier comprising: a magnetic core material; and a resin coating layer coating a surface of the magnetic core material,
wherein the resin coating layer comprises a binder resin, and fluorine element-containing resin particles dispersed in the binder resin,
the resin coating layer has a thickness of 0.5 μm or more and 2.0 μm or less,
the resin coating layer has a coefficient of variation of the thickness of 25% or less, and the resin coating layer has an average value of the number of the fluorine element-containing resin particles being 3 particles/μm2 or more and 350 particles/μm2 or less per unit area in a cross section of the resin coating layer, and has a coefficient of variation of the average value of the number of the fluorine element-containing resin particles being 20% or less, wherein the fluorine element-containing resin particles have a volume average particle diameter (D50) of 0.05 μm or more and 0.40 μm or less, the fluorine element-containing resin particles consist of a tetrafluoroethylene-hexafluoropropylene (FEP) copolymer, the binder resin is a polyimide (PI) resin or a polyamide imide (PAI) resin, and the magnetic core material is formed of a ferrite particle.

### Claim 2 (depends on 1)

The carrier according to claim 1, wherein a surface coverage of the magnetic core material by the resin coating layer is 60% or more and 95% or less.

### Claim 3 (depends on 1)

The carrier according to claim 1, wherein the resin coating layer has a mass ratio of a content of the fluorine element-containing resin particles to a content of the binder resin being 9:1 to 2:8.

### Claim 4 (depends on 1)

The carrier according to claim 1, wherein the binder resin is a polyimide resin.

### Claim 5 (depends on 1)

A developer for electrophotography, comprising: the carrier described in claim 1; and a positively chargeable toner, wherein the carrier imparts a positive chargeability to the toner.