Carrier core material and electrophotographic development carrier using same and electrophotographic developer

Abstract

A carrier core material includes ferrite particles, contains CaSiO3, and has a true density at least equal to 3.5 g/cm3 and at most equal to 4.5 g/cm3. A particle strength index calculated from formula (1) is preferably at most equal to 1.5% by volume. (1): Particle strength index=V2−V1 (In the formula, V1: cumulative value (% by volume) of particle size 22 μm or less in cumulative particle size distribution of carrier core material before crushing test, and V2: cumulative value (% by volume) of particle size 22 μm or less in cumulative particle size distribution of carrier core material after crushing test) Crushing test conditions: 30 g of carrier core material crushed using a sample mill for 60 seconds at a rotational speed of 14000 rpm.

Dependencies are inferred from the claim text.