Ferrite particle, carrier core material for electrophotographic developer, carrier for electrophotographic developer, and electrophotographic developer

Patent metadata

Field	Value
Publication number	US-12455516-B2
Application number	US-202118022961-A
Country	US
Kind code	B2
Filing date	Aug 24, 2021
Priority date	Aug 24, 2020
Publication date	Oct 28, 2025
Grant date	Oct 28, 2025

Abstract

The present invention relates to a ferrite particle containing a crystal phase component containing a perovskite-type crystal represented by a composition formula of RZrO3 (wherein R is an alkaline earth metal element), and a Mg content of 0.45 mass % or less. The present invention also relates to a carrier core material for an electrophotographic developer, containing the ferrite particle; a carrier for an electrophotographic developer, containing the ferrite particle and a resin coating layer provided on a surface of the ferrite particle; and an electrophotographic developer containing the carrier for an electrophotographic developer and a toner.

First claim

The invention claimed is:

1. A ferrite particle comprising:
a crystal phase component containing a perovskite-type crystal represented by a composition formula of RZrO 3 (wherein R is an alkaline earth metal element),
a Mg content of 0.45 mass % or less, and
wherein the crystal phase component containing the perovskite-type crystal is contained in an amount of 0.05 mass % or more and 4.00 mass % or less when a phase composition analysis on a crystal phase constituting the ferrite particle is performed by Rietveld analysis of an X-ray diffraction pattern.

2. The ferrite particle according to claim 1 , wherein
R is at least one element selected from the group consisting of Sr, Ca, and Ba.

3. The ferrite particle according to claim 1 , having a Cl concentration measured by an elution method of 30 ppm or less.

4. The ferrite particle according to claim 1 , wherein
the ferrite particle is a spinel-type ferrite particle containing Mn, and satisfying the following formula when a Mn content in the ferrite particle is denoted x (mass %) and a Fe content in the ferrite particle is denoted y (mass %):
0.30 y≤x≤ 0.60 y.

5. The ferrite particle according to claim 1 , comprising substantially no Ti.

6. A carrier core material for an electrophotographic developer, comprising:
the ferrite particle described in claim 1 .

7. A carrier for an electrophotographic developer, comprising:
the ferrite particle described in claim 1 ; and
a resin coating layer provided on a surface of the ferrite particle.

8. An electrophotographic developer comprising:
the carrier for an electrophotographic developer described in claim 7 ; and
a toner.

9. The electrophotographic developer according to claim 8 , which is used as a replenishing developer.

Assignees

• Powdertech Co Ltd

Inventors

• Ishikawa Makoto
• Uemura Tetsuya

Classifications

• C01G25/02

  Oxides · CPC title

• H01F1/407

  Diluted non-magnetic ions in a magnetic cation-sublattice, e.g. perovskites, La1-x(Ba,Sr)xMnO3 · CPC title

• C04B35/2658

  Other ferrites containing manganese or zinc, e.g. Mn-Zn ferrites · CPC title

• C04B2235/6584

  at an oxygen percentage below that of air · CPC title

• C04B2235/6565

  Cooling rate · CPC title