| 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 of particles even under influences of agitation stresses for a long time, and has superior strength, a little scattering amount and good fluidity, 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 100 to 107 and a shape factor SF-2 (circularity/roundness) of 100 to 113. 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 is 1 to 500 ppm with respect to the ferrite particle. A ferrite carrier, production methods of the core material and the ferrite carrier, and an electrophotographic developer using the ferrite carrier are also disclosed. |
