Electrostatic latent image developing white developer, image forming method, image forming apparatus, and process cartridge

Patent metadata

Field	Value
Publication number	US-10067438-B2
Application number	US-201515522306-A
Country	US
Kind code	B2
Filing date	Sep 29, 2015
Priority date	Oct 30, 2014
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

Provided is an electrostatic latent image developing white toner, including: a white toner including at least a binder resin, a white pigment, and a release agent; and a magnetic carrier including at least a core material, and a coating layer coating the core material and made of a coating resin and conductive particles, wherein Ra of the magnetic carrier is in a range of from 0.50 μm to 1.00 μm, and a bulk density of the magnetic carrier is in a range of from 2.08 g/cm3 to 2.24 g/cm3.

First claim

The invention claimed is:

1. An electrostatic latent image developing white developer, comprising:
a white toner comprising a binder resin, a white pigment, and a release agent; and
a magnetic carrier comprising a core material, and a coating layer coating the core material and made of a coating resin and conductive particles,
wherein Ra of the magnetic carrier ranges from 0.50 μm to 1.00 μm, and a bulk density of the magnetic carrier ranges from 2.08 g/cm 3 to 2.24 g/cm 3 ,
the white pigment is titanium oxide surface-treated with a polyol, and a content of the titanium oxide in the white toner is from 50 parts by mass to 80 parts by mass relative to 100 parts by mass of the binder resin, and
the binder resin comprises at least two polyester resins comprising a first polyester resin and a second polyester resin, the first polyester resin having a weight average molecular weight of from 6,000 to 14,000, and the second polyester resin having a weight average molecular weight of from 25,000 to 90,000.

2. The electrostatic latent image developing white developer according to claim 1 , wherein a ratio D/h of a volume average particle diameter D (μm) of the conductive particles in the coating layer of the magnetic carrier to an average thickness h (μm) of the coating layer satisfies: 0.50≤D/h≤1.10.

3. An image forming method, comprising:
forming an electrostatic latent image over an electrostatic latent image bearer;
developing the electrostatic latent image with a two-component developer to form a visible image;
transferring the visible image to a recording medium; and
fixing the transferred image transferred to the recording medium thereon,
wherein as the two-component developer, the electrostatic latent image developing white developer according to claim 2 is used solely or in combination with a developer using another color toner.

4. An image forming apparatus, comprising:
an electrostatic latent image bearer;
an electrostatic latent image forming unit configured to form an electrostatic latent image over the electrostatic latent image bearer;
a developing unit containing a two-component developer and configured to develop the electrostatic latent image with the two-component developer to form a visible image;
a transfer unit configured to transfer the visible image to a recording medium; and
a fixing unit configured to fix the transferred image transferred to the recording medium thereon, wherein the two-component developer comprises the electrostatic latent image developing white developer according to claim 2 and optionally a developer comprising another color toner.

5. A process cartridge, comprising:
an electrostatic latent image bearer; and
a developing unit containing a two-component developer and configured to develop an electrostatic latent image formed over the electrostatic latent image bearer with the two-component developer to form a visible image,
wherein the two-component developer is the electrostatic latent image developing white developer according to claim 2 .

6. An image forming method, comprising:
forming an electrostatic latent image over an electrostatic latent image bearer;
developing the electrostatic latent image with a two-component developer to form a visible image;
transferring the visible image to a recording medium; and
fixing the transferred image transferred to the recording medium thereon,
wherein as the two-component developer, the electrostatic latent image developing white developer according to claim 1 is used solely or in combination with a developer using another color toner.

7. An image forming apparatus, comprising:
an electrostatic latent image bearer;
an electrostatic latent image forming unit configured to form an electrostatic latent image over the electrostatic latent image bearer;
a developing unit containing a two-component developer and configured to develop the electrostatic latent image with the two-component developer to form a visible image;
a transfer unit configured to transfer the visible image to a recording medium; and
a fixing unit configured to fix the transferred image transferred to the recording medium thereon,
wherein the two-component developer comprises the electrostatic latent image developing white developer according to claim 1 and optionally a developer comprising another color toner.

8. A process cartridge, comprising; an electrostatic latent image bearer; and
a developing unit containing a two-component developer and configured to develop an electrostatic latent image formed over the electrostatic latent image bearer with the two-component developer to form a visible image,
wherein the two-component developer is the electrostatic latent image developing white developer according to claim 1 .

Assignees

• Murasawa Yoshihiro
• Tohmatsu Hiroshi
• Iwatsuki Hitoshi
• Takii Mariko
• Sakata Koichi
• Kishida Hiroyuki
• Tano Toyoaki
• Mashiko Kenichi
• Ricoh Co Ltd

Inventors

• Murasawa Yoshihiro
• Tohmatsu Hiroshi
• Iwatsuki Hitoshi
• Takii Mariko
• Sakata Koichi
• Kishida Hiroyuki
• Tano Toyoaki
• Mashiko Kenichi

Classifications

• G03G9/1075 Primary

  Structural characteristics of the carrier particles, e.g. shape or crystallographic structure · CPC title

• G03G9/08755

  Polyesters · CPC title

• G03G9/1139

  Inorganic components of coatings · CPC title

• G03G9/1131

  Coating methods; Structure of coatings · CPC title

• G03G9/0902

  Inorganic compounds · CPC title