# US 5,350,656 A · Carrier and a production method thereof for developing an electrostatic image

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- Number: US 5,350,656 A
- Document ID: US5350656A
- Status: Granted
- Kind: A
- Application number: 07/669,932
- Filed: 1991-03-15
- Granted: 1994-09-27
- Earliest claimed: 1990-03-20
- Assignees: Konica Corporation
- Inventors: Shigenori Kouno; Ken Ohmura; Yoshiaki Koizumi; Kenji Tsujita
- Web page: https://patentgrep.com/patent/US5350656A

## CPC

- G03G 9/1131: {Coating methods; Structure of coatings}
- G03G 9/1132: {Macromolecular components of coatings}
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

There is disclosed an electrostatic image-developing carrier having a resin coat layer with an excellent mechanical strength. The carrier is prepared by repeatedly applying a mechanical impact force to the mixture of the core particle and the coating resin particle in a dry condition, wherein a molecular weight distribution chromatogram according to a gel permeation chromatography of a tetrahydro-furansoluble component in the resin coat layer has at least one peak or shoulder in a molecular weight range 1,000 to 20,000.

## Claims

### Claim 1

An electrostatic image-developing carrier comprising a ferrite core particle and a resin coat layer provided thereon by applying repeatedly a mechanical impact force to the mixture of the ferrite core particle and a single type of coating resin particle in a dry condition,
wherein the ferrite core particle and the coating resin particle are mixed at a temperature less than the glass transition point of the resin particles for time less than or equal to 20 minutes and
wherein the temperature of the resin layer-forming process is less than or equal to about 97.degree. C. and the stirring speed of the resin layer-forming process is 5.8 to 12.6 m/sec, and
wherein a molecular weight distribution chromatogram according to a gel permeation chromatography of a tetrahydrofuran-soluble component in the resin coat layer has at least one peak or shoulder in a molecular weight range of 1,000 to 20,000 and said peak or shoulder accounts for 5 to 65% of the area of the chromatogram.

### Claim 2 (depends on 1)

The carrier of claim 1, wherein the coating resin particle comprises a non-porous primary resin particle or a porous resin particle consisting of a primary resin particle.

### Claim 3 (depends on 2)

The carrier of claim 2, wherein the non-porous primary resin particle has a volume-average particle size of 0.001 to 1.0 .mu.m and a BET specific surface area of 40 to 6000 m.sup.2 /g.

### Claim 4 (depends on 2)

The carrier of claim 2, wherein the porous secondary resin particle has a volume-average particle size of 1.5 to 5.0 .mu.m and a BET specific surface area of 5 to 600 m.sup.2 /g.

### Claim 5 (depends on 1)

The carrier of claim 1, wherein the coating resin particle comprises at least one methacrylate monomer and at least one styrene monomer and acrylate monomer.

### Claim 6 (depends on 5)

The carrier of claim 5, wherein at least one of the methacrylate monomers is methyl methacrylate.

### Claim 7 (depends on 1)

The carrier of claim 1, wherein the resin coat layer is formed without melting of the core or coating particles.

### Claim 8 (depends on 1)

The carrier of claim 1, wherein the resin coat layer is formed at a temperature of 58.degree. to 97.degree. C.

### Claim 9 (depends on 1)

The electrostatic image-developing carrier of claim 1, wherein said single type of coating resin is a copolymer, wherein said coating resin comprises methyl methacrylate and methacrylate monomers and account for 30 to 90% by weight of said copolymer.

### Claim 10

A method of preparing an electrostatic image-developing carrier comprising a core particle and provided thereon a resin coat layer, comprising:
a mixing process in which the ferrite core particle and a single type of coating resin particle are mixed at a temperature less than the glass transition point of the resin particles for a time less than or equal to 20 minutes, and
a resin layer-forming process in which a mechanical impact force is repeatedly applied to the mixture of the core particle and a single type of coating resin particle in a dry condition to form the resin coat layer on the core particle, at a temperature of less than or equal to about 97.degree. C. and a stirring speed of 5.8 to 12.6 m/sec,
wherein a molecular weight distribution chromatogram according to gel permeation chromatography of a tetrahydrofuran-soluble component in the resin coat layer has at least one peak or shoulder in a molecular weight range of 1,000 to 20,000 and said peak or shoulder accounts for 5 to 65% of the area of the chromatogram.

### Claim 11 (depends on 10)

The method of claim 10, wherein a molecular chain of the coating resin is cut in the mixing process to form a lower molecular weight resin.

### Claim 12 (depends on 10)

The method of claim 10, wherein the layer-forming process occurs without melting of the core or coating particles.

### Claim 13 (depends on 10)

The method of claim 10, wherein the temperature of the resin layer-forming process is 58.degree. to 98.degree. C.

### Claim 14 (depends on 10)

The method of claim 10, wherein said single type of coating resin is a copolymer, wherein said coating resin comprises methyl methacrylate and methacrylate monomers and account for 30 to 90% by weight of said copolymer.