Patent ID: 10088764

Abstract:
A carrier core material includes, a main component, a material represented by a composition formula MnXMYFe3−(X+Y)O4 (where M is selected from Mg, Ti, Cu, Zn and Ni, 0<X, 0≤Y, 0<X+Y<1), in which 0.1 to 1.0 mol % of at least one of Sr element and Ca element is contained as the total amount by conversion to SrO or CaO and in which the frequency of a grain whose length RSm is equal or more than 8.0 μm among grains appearing on the surface of particles of the carrier core material is equal to or less than 2.0 number percent. In this way, the degradation of a carrier caused by long-term use such as the separation of a coating resin is significantly reduced, stable charging performance is maintained and the cracking or chipping of the particles is reduced.