# US 11,029,618 B2 · Carrier, electrophotographic developer and production method of carrier

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- Number: US 11,029,618 B2
- Document ID: US11029618B2
- Status: Granted
- Kind: B2
- Application number: 16/059,405
- Filed: 2018-08-09
- Published: 2019-02-14
- Granted: 2021-06-08
- Earliest claimed: 2017-08-09
- Assignees: Powdertech Co., Ltd.
- Applicants: Powdertech Co., Ltd.
- Inventors: Aya Sakuta; Makoto Ishikawa; Hiroki Sawamoto; Tetsuya Uemura
- Web page: https://patentgrep.com/patent/US11029618B2

## CPC

- G03G 9/1134: {containing fluorine atoms}
- G03G 9/1131: {Coating methods; Structure of coatings}
- G03G 9/1135: {obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds}
- G03G 9/1138: {Non-macromolecular organic components of coatings}
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

There is provided a carrier including a magnetic core material having a surface coated with a surfactant-containing resin mixture of an elemental fluorine-containing resin and a polyimide resin. The carrier has an elution amount of an eluted material into water in an elution test ranging from 180 ppm to 3,500 ppm.

## Claims

### Claim 1

A carrier comprising:
(i) a magnetic core material having a surface; and
(ii) a resin coat layer coating the core material surface, wherein the resin coat layer comprises a mixture of:
(a) an elemental fluorine-containing resin;
(b) a polyimide (PI) resin having an imide bond in the main chain; and
(c) a surfactant;
wherein:
the surfactant has an elution amount of from 180 ppm to 3,500 ppm, remaining in water in an elution test comprising mixing the carrier into the water, filtering the carrier from the water, and measuring a weight of eluted material remaining after being removed from the water and dried, and
a mass ratio of the polyimide (PI) resin to the elemental fluorine-containing resin in the resin coat layer of 1/10 or more.

### Claim 2 (depends on 1)

The carrier according to claim 1,
wherein the elemental fluorine-containing resin is a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or a combination thereof.

### Claim 3 (depends on 1)

The carrier according to claim 1,
wherein the surfactant is a nonionic surfactant.

### Claim 4 (depends on 1)

The carrier according to claim 1, wherein the magnetic core material comprises an aggregate of individual ferrite particles.

### Claim 5 (depends on 1)

A two component electrophotographic developer comprising a toner and the of claim 1.

### Claim 6 (depends on 1)

A method for producing the carrier of claim 1, the method comprising:
preparing a resin layer-forming liquid including an elemental fluorine-containing resin and a polyimide resin dispersed together with a surfactant in a dispersion medium; and
coating the surface of the magnetic core material with the resin layer-forming liquid to obtain the carrier.

### Claim 7 (depends on 6)

The method according to claim 6,
wherein assuming a total amount of the elemental fluorine-containing resin and the polyimide resin is 100 parts by mass relative to the resin layer-forming liquid, a surfactant is added in an amount of 1.0 to 50 parts by mass.

### Claim 8 (depends on 1)

The carrier of claim 1, wherein the eluted material remaining in water in an elution test is in an amount ranging from 200 ppm to 800 ppm.

### Claim 9 (depends on 1)

The carrier of claim 1, wherein the magnetic core material comprises a ferrite represented by formula:
(MnO)x(MgO)y(Fe2O3),
wherein:
x is from 35 to 45 mol %, and
y is from 5 to 15 mol %,
wherein part of (MnO) and/or (MgO) may be substituted by one or more oxides selected from SrO, Li2O, CaO, TiO, CuO, ZnO, NiO, Bi2O3, or ZrO2.

### Claim 10 (depends on 9)

The carrier of claim 9, wherein the oxide substitution amount is from 0.35 to 5.0 mol %.

### Claim 11 (depends on 1)

The carrier of claim 1, wherein the amount of resin coat of the magnetic core material is 0.01% to 10% by mass relative to the magnetic core material.

### Claim 12 (depends on 1)

The carrier of claim 1, wherein the amount of surfactant in the resin coat layer is 2 to 40 parts by mass of 100 parts by mass of elemental fluorine-containing resin and PI resin.

### Claim 13 (depends on 1)

The carrier of claim 1, wherein the polyimide resin having an imide bond in the main chain is not a polyamide-imide resin.

### Claim 14 (depends on 1)

The carrier of claim 1, wherein the resin coat layer further comprises a charge control agent, an electrical conductor, or a combination thereof.

### Claim 15 (depends on 14)

The carrier of claim 14, wherein the charge control agent is a silane.

### Claim 16 (depends on 15)

The carrier of claim 15, wherein the silane is an aminosilane or a fluorine-based silane.

### Claim 17 (depends on 14)

The carrier of claim 14, wherein the electrical conductor is electroconductive carbon, titanium oxide, or tin oxide.