FERRITE CARRIER CORE MATERIAL AND FERRITE CARRIER FOR ELECTROPHOTOGRAPHIC DEVELOPER, METHODS FOR MANUFACTURING THESE, AND ELECTROGRAPHIC DEVELOPER USING THE FERRITE CARRIER

摘要

It is an object of the present invention to provide a ferrite carrier core material and a ferrite carrier for an electrophotographic developer, which have an excellent charging property, hardly cause carrier scattering due to cracking and chipping of the core material, and have a prolonged life, and methods for manufacturing these, and an electrophotographic developer using the ferrite carrier. For this object, the ferrite carrier core material and a ferrite carrier for an electrophotographic developer, wherein (1) the ferrite composition contains 0.5 to 2.5% by weight of Sr, and the presence amount of Sr—Fe oxides satisfies a specific conditional expression, (2) the distribution in the number of the shape factor SF-2 is in a specific range, (3) the BET specific surface area is 0.15 to 0.30 m²/g, (4) the average particle diameter D₅₀ is 20 to 35 μm, and (5) the magnetization is 50 to 65 Am²/kg.