| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a ferrite carrier core material for an electrophotographic developer having an approximately spherical particle shape with minute projections and recesses on the surface, and thereby, in spite of a small particle diameter of the core material, having a larger BET specific surface area compared to conventional core material particles, and having excellent charging property and a long service life while preventing scattering of a carrier caused by breakage or chipping of the core material, and to provide a ferrite carrier and a method for producing the core material and the carrier, and an electrophotographic developer using the ferrite carrier. <P>SOLUTION: A ferrite carrier core material for an electrophotographic developer shows magnetization of 50 to 65 Am<SP POS="POST">2</SP>/kg by VSM (vibration sample magnetometer) measurement when a magnetic field of 1 K 1000/4π A/m is applied, and has a BET specific surface area of 0.12 to 0.30 m<SP POS="POST">2</SP>/g, an average particle diameter of 20 to 35 μm, and a distribution of a ratio of (boundary length)/(envelope length) by number satisfying the following conditions. The conditions are: particles in the range from 1.02 to less than 1.04 of the above ratio are included by 75% to 90% by number; and particles in the range from 1.04 to less than 1.06 are included by 20% by number or less. Methods for producing the carrier core material and the carrier, and an electrophotographic developer using the ferrite carrier are also disclosed. <P>COPYRIGHT: (C)2012,JPO&INPIT |
