Ferrite particles, electrophotographic developer carrier core material, electrophotographic developer carrier, and electrophotographic developer

Patent metadata

Field	Value
Publication number	US-12422763-B2
Application number	US-202117915348-A
Country	US
Kind code	B2
Filing date	Mar 17, 2021
Priority date	Mar 31, 2020
Publication date	Sep 23, 2025
Grant date	Sep 23, 2025

Abstract

The present invention relates to a ferrite particle containing a crystal phase component containing a perovskite crystal represented by a compositional formula: RZrO 3 (provided that R represents an alkaline earth metal element), having a surface roughness Rz of 2.0 μm or more and 4.5 μm or less, and satisfying the following formulas: 6.5≤log H 1000 ≤8.5 and 0.80≤log H 1000 /log H 100 ≤1.00. The ferrite particle can be used as an electrophotographic developer carrier core material. In addition, an electrophotographic developer carrier and an electrophotographic developer can be obtained.

First claim

The invention claimed is:

1. A ferrite particle,
comprising a crystal phase component comprising a perovskite crystal represented by the compositional formula: RZrO 3 (provided that R represents an alkaline earth metal element),
having a surface roughness Rz of 2.0 μm or more and 4.5 μm or less, and
satisfying the following formulas:
6.5≤log H 1000 ≤8.5, and

0.80≤log H 1000 /log H 100 ≤1.00,

where log H 1000 : logarithmic value (log(Ω) of a resistance value H 1000 (Ω) of the ferrite particle when an applied voltage of 1,000 V is applied at a distance between electrodes of 2 mm in a high-temperature and high-humidity environment (30° C., relative humidity 80%), and
log H 100 : logarithmic value (log(Ω) of a resistance value H 100 (Ω) of the ferrite particle when an applied voltage of 100 V is applied at a distance between electrodes of 2 mm in the high-temperature and high-humidity environment (30° C., relative humidity 80%).

2. The ferrite particle according to claim 1 , wherein the surface roughness Rz is 2.5 μm or more and 4.2 μm or less.

3. The ferrite particle according to claim 1 , satisfying the following formulas:
6.7≤log H 1000 ≤8.2, and

0.85≤log H 1000 /log H 100 ≤1.00.

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

5. The ferrite particle according to claim 1 , comprising the crystal phase component comprising the perovskite crystal in an amount of 0.05% by mass or more and 4.00% by mass or less when a phase composition analysis of a crystal phase constituting the ferrite particle is performed by a Rietveld analysis of an X-ray diffraction pattern.

6. The ferrite particle according to claim 1 , wherein the ferrite particle is a spinel ferrite particle having a crystal phase component comprising a spinel crystal represented by the compositional formula: (MnO)x(MgO)y(Fe 2 O 3 )z (provided that 15≤x≤50, 2≤y≤35, 45≤z≤60, x+y+z=100 (mol %)) as a main composition.

7. An electrophotographic developer carrier core material, comprising the ferrite particle described in claim 1 .

8. An electrophotographic developer carrier, comprising the ferrite particle described in claim 1 and a resin coating layer provided on a surface of the ferrite particle.

9. An electrophotographic developer, comprising the electrophotographic developer carrier described in claim 8 and a toner.

10. The electrophotographic developer according to claim 9 , used as a replenishment developer.

Assignees

• Powdertech Co Ltd

Inventors

• Ishikawa Makoto
• Uemura Tetsuya

Classifications

• G03G9/1132

  Macromolecular components of coatings · CPC title

• C04B41/4535

  applied as a solution, emulsion, dispersion or suspension · CPC title

• C04B2235/3213

  Strontium oxides or oxide-forming salts thereof · CPC title

• C04B2235/663

  Oxidative annealing · CPC title

• C04B2235/6562

  Heating rate · CPC title