| 摘要 |
PROBLEM TO BE SOLVED: To provide a ferrite carrier core material for an electrophotographic developer which has high strength, significantly suppresses generation of cracks or chips in particles even under influences of agitation stresses for a long time, and has extremely excellent adhesiveness with a coating resin, and also provide a ferrite carrier, and an electrophotographic developer using the ferrite carrier.SOLUTION: The ferrite carrier core material for an electrophotographic developer comprises ferrite particles containing Sr and having a shape factor SF-1 (circularity) of 110 to 120 and a shape factor SF-2 (circularity/roundness) of 110 to 130. Nonmagnetic fine particles are adhering to a surface and/or inner surfaces of vacancies of the ferrite particle; the amount of metal elements present in the nonmagnetic fine particles is 500 to 5000 ppm with respect to the ferrite particle; and the amount of Sr present in the nonmagnetic fine particles is 50 to 1000 ppm with respect to the ferrite particles. A ferrite carrier, production methods for the core material and for the ferrite carrier, and an electrophotographic developer using the ferrite carrier are also disclosed. |
