Black magnetic iron oxide particles, magnetic carrier for electrophotographic developer and two-component developer

Patent metadata

Field	Value
Publication number	US-9285698-B2
Application number	US-48431809-A
Country	US
Kind code	B2
Filing date	Jun 15, 2009
Priority date	Jun 17, 2008
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

Black magnetic iron oxide particles having an average particle diameter of 0.05 to 2.0 μm and an electric resistance value at an applied voltage of 100 V of not less than 1×10 8 Ω·cm. Also a magnetic carrier for electrophotographic developer having spherical magnetic composite particles obtained by dispersing black magnetic iron oxide particles in a binder resin. The magnetic carrier has an electric resistance value R 100 at an applied voltage of 100 V of 1×10 8 to 1×10 14 Ω·cm, and an electric resistance value R 300 at an applied voltage of 300 V which satisfies the relationship represented by the formula:

0.1≦ R 300/ R 100≦1.

First claim

What is claimed is:

1. Black magnetic iron oxide particles which comprise core particles and a surface layer formed on the respective core particles and which have an average particle diameter of 0.05 to 2.0 μm and an electric resistance value RM 100 at an applied voltage of 100 V of not less than 1×10 8 Ω·cm.

2. Black magnetic iron oxide particles according to claim 1 , wherein the black magnetic iron oxide particles comprise core particles and a surface layer formed on the respective core particles the surface layer comprises one or more elements selected from the group consisting of Al, Mg, Mn, Zn, Ni, Cu, Ti and Si, and the elements are present in an amount of 0.3 to 4.5% by weight in the surface layer.

3. Black magnetic iron oxide particles according to claim 1 , wherein the black magnetic iron oxide particles have a water absorption Ma0.9 of not more than 15 mg/g.

4. Black magnetic iron oxide particles according to claim 1 , wherein the black magnetic iron oxide particles have an electric resistance value RM 10 at an applied voltage of 10 V which satisfies the relationship represented by the formula:
0.5≦ RM 100/ RM 10≦1.

5. A magnetic carrier for electrophotographic developer comprising spherical magnetic composite particles obtained by dispersing black magnetic iron oxide particles as defined in claim 1 in a binder resin, wherein the magnetic carrier has an electric resistance value R 100 at an applied voltage of 100 V of 1×10 8 to 1×10 14 Ω·cm, and an electric resistance value R 300 at an applied voltage of 300 V which satisfies the relationship represented by the formula:
0.1≦ R 300/ R 100≦1,

wherein the total content of the magnetic iron oxide particles in the spherical magnetic composite particles is 80 to 99% by weight based on the weight of the spherical magnetic composite particles.

6. A magnetic carrier for electrophotographic developer according to claim 5 , wherein the binder resin is a phenol resin.

7. A magnetic carrier for electrophotographic developer according to claim 5 , wherein a surface coating layer mainly comprising a resin is formed on a surface of the respective spherical magnetic composite particles.

8. A two-component electrophotographic developer comprising the magnetic carrier for electrophotographic developer as defined in claim 5 .

9. A magnetic carrier for electrophotographic developer according to claim 5 , having a saturation magnetization value of 40 to 100 Am 2 /kg when applying an external magnetic field of 795.8 kA/m (10 kOe).

10. A magnetic carrier for electrophotographic developer according to claim 5 , having a saturation magnetization value of 71.3 to 100 Am 2 /kg when applying an external magnetic field of 795.8 kA/m (10 kOe).

11. A magnetic carrier for electrophotographic developer according to claim 5 , wherein a total content of the magnetic iron oxide particles in the spherical magnetic composite particles is 85 to 99% by weight based on the weight of the spherical magnetic composite particles.

Assignees

• Uemoto Shinji
• Misawa Hiromitsu
• Iwai Ryo
• Uchida Naoki
• Aoki Koso
• Fujita Kazuya
• Kinoshita Kaori
• Takama Kazushi
• Kurita Eiichi
• Toda Kogyo Corp

Inventors

• Uemoto Shinji
• Misawa Hiromitsu
• Iwai Ryo
• Uchida Naoki
• Aoki Koso
• Fujita Kazuya
• Kinoshita Kaori
• Takama Kazushi
• Kurita Eiichi

Classifications

• G03G9/107 Primary

  having magnetic components · CPC title

• G03G9/113

  having coatings applied thereto · CPC title

• G03G9/1135 Primary

  obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds · CPC title

• G03G9/1136

  containing silicon atoms · CPC title

• G03G9/108 Primary

  Ferrite carrier, e.g. magnetite · CPC title