Electrostatic image developer

Patent metadata

Field	Value
Publication number	US-9235153-B2
Application number	US-201214118277-A
Country	US
Kind code	B2
Filing date	May 18, 2012
Priority date	May 20, 2011
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

An electrostatic image developer having little change in charge amount, no generation of fog and excellent environmental stability under all of low temperature and low humidity environment, normal temperature and normal humidity environment, and high temperature and high humidity environment is provided. Disclosed is an electrostatic image developer comprising a colored resin particle containing a binder resin and a colorant, and an external additive, wherein the external additive contains an alumina fine particle in plate-like shape subjected to a hydrophobicity-imparting treatment having a number average primary particle diameter of 20 to 120 nm and an aspect ratio of 3 to 15, and a content of the alumina fine particle is in the range from 0.05 to 1 part by mass with respect to 100 parts by mass of the colored resin particle.

First claim

The invention claimed is:

1. An electrostatic image developer comprising a colored resin particle containing a binder resin and a colorant, and an external additive,
wherein the external additive contains an alumina fine particle in plate-like shape subjected to a hydrophobicity-imparting treatment having a number average primary particle diameter of 20 to 120 nm and an aspect ratio of 5.2to 15, and
a content of the alumina fine particle is in the range from 0.05 to 1 part by mass with respect to 100 parts by mass of the colored resin particle.

2. The electrostatic image developer according to claim 1 , wherein Dv90/Dv10 of the alumina fine particle is in the range from 1.5 to 3.0, wherein Dv10 represents a particle diameter at which a volume cumulative total from small particle diameter side of a particle size distribution is 10% and Dv90 represents a particle diameter at which the volume cumulative total from small particle diameter side of the particle size distribution is 90%.

3. The electrostatic image developer according to claim 1 , wherein the external additive contains a silica fine particle A having a number average primary particle diameter of 5 to 30 nm, and a content of the silica fine particle A is in the range from 0.1 to 2 parts by mass with respect to 100 parts by mass of the colored resin particle.

4. The electrostatic image developer according to claim 1 , wherein the external additive contains a silica fine particle B having a number average primary particle diameter of 35 to 80 nm, and a content of the silica fine particle B is in the range from 0.2 to 3 parts by mass with respect to 100 parts by mass of the colored resin particle.

5. The electrostatic image developer according to claim 1 , wherein the alumina fine particle is prepared by subjecting a boehmite particle obtainable by a hydrothermal reaction to firing and a hydrophobicity-imparting treatment.

6. The electrostatic image developer according to claim 5 , wherein the boehmite particle is prepared by adding a fatty acid salt to an aluminium hydroxide particle followed by a hydrothermal reaction.

Assignees

• Jin Hiromichi
• Chiba Takeru
• Iinuma Hidehiko
• Yamazaki Kenichi
• Zeon Corp
• Kanto Denka Kogyo Kk

Inventors

• Jin Hiromichi
• Chiba Takeru
• Iinuma Hidehiko
• Yamazaki Kenichi

Classifications

• G03G9/09725

  Silicon-oxides; Silicates · CPC title

• G03G9/09708 Primary

  Inorganic compounds · CPC title

• G03G9/08

  with toner particles · CPC title

• G03G9/097 Primary

  Plasticisers; Charge controlling agents · CPC title