# US 8,771,914 B2 · Toner for developing latent electrostatic image, two-component developer, image forming method and image forming apparatus

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,771,914 B2
- Document ID: US8771914B2
- Status: Granted
- Kind: B2
- Application number: 12/049,686
- Filed: 2008-03-17
- Published: 2008-09-25
- Granted: 2014-07-08
- Earliest claimed: 2007-03-23
- Assignees: Ricoh Company, Ltd.
- Applicants: Akihiro Kotsugai; Hiroshi Yamashita
- Inventors: Akihiro Kotsugai; Hiroshi Yamashita
- Web page: https://patentgrep.com/patent/US8771914B2

## CPC

- G03G 13/16: of a toner pattern, e.g. a powder pattern
- G03G 9/0806: {whereby chemical synthesis of at least one of the toner components takes place}
- G03G 9/0819: {characterised by the dimensions of the particles}
- G03G 9/0825: {characterised by their structure; characterised by non-homogenuous distribution of components (microcapsular toners G03G9/093)}
- G03G 9/0827: {characterised by their shape, e.g. degree of sphericity}
- G03G 9/08711: {with esters of acrylic or methacrylic acid}
- G03G 9/08793: {Crosslinked polymers}
- G03G 9/08795: {characterised by their chemical properties, e.g. acidity, molecular weight, sensitivity to reactants}
- G03G 9/08797: {characterised by their physical properties, e.g. viscosity, solubility, melting temperature, softening temperature, glass transition temperature}
- G03G 2215/0119: Linear arrangement adjacent plural transfer points
- G03G 2215/0607: two-component
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

The present invention provides a toner which, despite its spherical shape, makes it possible to prevent an external additive from being embedded in the toner easily or by a load generating low stress, reduce variation in image density, maintain cleaning ability and transfer ability throughout its long-term use and obtain excellent image quality, and further, provides a two-component developer, an image forming method and an image forming apparatus with the use of the toner. There is a toner including: base particles including a colorant and a resin, and hard fine particles, wherein the base particles and the hard fine particles are mixed together, and protruding portions formed of fine organic resin particles which are different in composition from a resin contained as a main component in the base particles are provided on surfaces of the base particles.

## Claims

### Claim 1

A toner for developing latent electrostatic images, comprising:
base particles including a colorant and a resin, and
hard fine particles,
wherein the hard fine particles exist on a surface of the base particles,
protruding portions formed of fine organic resin particles which are different in composition from a resin contained as a main component in the base particles are provided on surfaces of the base particles,
the main component in the base particles is a polyester resin and the fine organic resin particles are vinyl series resin,
wherein the toner is obtained by forming a liquid droplet by dispersing an oil phase, which is produced by dissolving or dispersing a toner material including polyester resin in an organic medium, in an aqueous medium comprising fine organic resin particles forming the protruding portions,
wherein a volume average diameter of the toner Dv is 2 μm to 7 μm, and a primary diameter of the fine organic resin particle is 520 nm to 710 nm.

### Claim 2 (depends on 1)

The toner for developing latent electrostatic images according to claim 1, wherein the fine organic resin particles have a diameter which is equal to or less than ⅕ the average particle diameter of the toner and have hemispherical convex portions.

### Claim 3 (depends on 1)

A two-component developer comprising:
the toner as claimed in claim 1, and
a carrier composed of magnetic particles.

### Claim 4 (depends on 1)

An image forming method comprising:
forming a toner image by developing a latent electrostatic image on an electrostatic image-bearing member with a developer,
bringing a transfer unit into contact with a surface of the electrostatic image-bearing member via a transfer material, and
electrostatically transferring the toner image onto the transfer material,
wherein the developer is a two-component developer containing the toner as claimed in claim 1, and a carrier composed of magnetic particles.

### Claim 5 (depends on 1)

The toner according to claim 1, wherein the primary diameter of the fine organic resin particle is 520 nm to 710 nm.

### Claim 6 (depends on 1)

The toner according to claim 1, wherein protrusion-forming fine resin particles comprise styrene-butyl acrylate.

### Claim 7 (depends on 6)

The toner according to claim 6, wherein protrusion-forming fine resin particles further comprise fine resin particles which are different from styrene-butyl acrylate.