# US 2013/0157183 A1 · Developer for electrophotography, image forming apparatus and process cartridge

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- Number: US 2013/0157183 A1
- Document ID: US20130157183A1
- Status: Published application
- Kind: A1
- Application number: 13/679,057
- Filed: 2012-11-16
- Published: 2013-06-20
- Earliest claimed: 2011-12-20
- Assignees: Ricoh Company, Ltd.
- Inventors: Hideyuki Santo; Masahide Yamada; Kazumi Suzuki; Shinya Nakayama; Atsushi Yamamoto; Tatsuya Morita; Shingo Sakashita; Yukiko Nakajima; Keiji Makabe; Daiki Yamashita
- Web page: https://patentgrep.com/patent/US20130157183A1

## CPC

- G03G 9/0832: {Metals}
- G03G 9/08797: {characterised by their physical properties, e.g. viscosity, solubility, melting temperature, softening temperature, glass transition temperature}
- G03G 9/108: {Ferrite carrier, e.g. magnetite}
- G03G 9/1087: {Specified elemental magnetic metal or alloy, e.g. alnico comprising iron, nickel, cobalt, and aluminum, or permalloy comprising iron and nickel}
- G03G 9/10882: {Binder is obtained by reactions only involving carbon-carbon unsaturated bonds}
- G03G 9/10884: {Binder is obtained other than by reactions only involving carbon-carbon unsaturated bonds}
- G03G 9/1131: {Coating methods; Structure of coatings}
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

A developer, including a toner including a binder resin comprising a crystalline resin; and a colorant, and a resin carrier comprising a resin; a magnetic particulate material having a magnetic anisotropy, dispersed in the resin, and having a saturated magnetization of from 16 to 30 emu/g, a coercive force of from 15 to 40 kA/m and an average particle diameter not less than 15 μm and less than 100 μm.

## Claims

### Claim 1

A developer, comprising:
a toner comprising:
a binder resin comprising a crystalline resin; and
a colorant, and
a resin carrier comprising:
a resin;
a magnetic particulate material having a magnetic anisotropy, dispersed in the resin, and
having a saturated magnetization of from 16 to 30 emu/g, a coercive force of from 15 to 40 kA/m and an average particle diameter not less than 15 μm and less than 100 μm.

### Claim 2 (depends on 1)

The developer of claim 1, wherein the binder resin comprises the crystalline resin in an amount not less than 50% by weight.

### Claim 3 (depends on 1)

The developer of claim 1, wherein the toner is prepared by dispersing or emulsifying at least the binder resin and the colorant in an aqueous medium.

### Claim 4 (depends on 2)

The developer of claim 2, wherein the crystalline resin is at least a resin selected from the group consisting of a polyester resin, a polyurethane resin, a polyurea resin, a polyamide resin and a polyether resins.

### Claim 5 (depends on 2)

The developer of claim 2, wherein the crystalline resin comprises at least one of a urethane skeleton and a urea skeleton.

### Claim 6 (depends on 2)

The developer of claim 2, wherein the crystalline resin comprises a crystalline resin (A) and a crystalline resin (B) having a weight-average molecular weight (Mw) different from each other.

### Claim 7 (depends on 1)

The developer of claim 1, wherein the toner satisfies the following relationships:
45≦Ta≦70, and 0.8≦Tb/Ta≦1.55
wherein Ta (° C.) is the maximum peak temperature of heat of melting the toner measured by a differential scanning calorimeter, and Tb (° C.) is a softening point of the toner measured by an elevated flow tester; and
1.0×103≦G′(Ta+20)≦5.0×106 and 1.0×103≦G″(Ta+20)≦5.0×106
wherein G′(Ta+20) (Pa·s) is the storage elastic modulus of the toner at the temperature of (Ta +20)° C., and G″(Ta+20) (Pa·s) is the loss elastic modulus of the toner at the temperature of (Ta +20)° C.

### Claim 8 (depends on 1)

The developer of claim 1, wherein the resin carrier comprises the resin and the magnetic particulate material in a weight ratio (binder resin/magnetic particulate material) of from 65/35 to 80/20.

### Claim 9 (depends on 1)

The developer of claim 1, wherein the resin carrier is a rare earth-iron-nitrogen magnet powder.

### Claim 10 (depends on 1)

The developer of claim 1, wherein the resin carrier is prepared by melt-kneading the magnetic particulate material in the resin and then leaving the resultant resin powder for 10 sec or longer in a magnetic flux density of 2 T (tesla) or higher.

### Claim 11 (depends on 1)

An image forming apparatus, comprising:
a latent image bearer;
a charger configured to charge the surface of the latent image bearer;
an irradiator configured to irradiate the surface of the latent image bearer to form an electrostatic latent image thereon;
an image developer configured to develop the electrostatic latent image with the developer according to claim 1 to form a toner image;
a transfer configured to transfer the toner image onto a transfer paper; and
a fixer configured to fix the toner image on the transfer paper at a linear speed of 200 mm/s.