FERRITE CARRIER CORE MATERIAL FOR ELECTROPHOTOGRAPHIC DEVELOPERS, FERRITE CARRIER, AND MANUFACTURING PROCESSES FOR BOTH, AND ELECTROPHOTOGRAPHIC DEVELOPERS USING THE FERRITE CARRIER

摘要

The purpose of the present invention is to provide: a ferrite carrier core material for electrophotographic developers which have excellent electrification properties and which are less susceptible to carrier scattering caused by the fracture and/or chipping of core material and thus exhibit a long service life; a ferrite carrier; processes for producing both; and electrophotographic developers using the ferrite carrier. In order to achieve the purpose, employed are a ferrite carrier core material for electrophotographic developers and a ferrite carrier therefor, said core material having the characteristics: (1) the ferrite has a composition which contains 0.5 to 2.5wt% of Sr and in which the quantity of present Sr-Fe oxides satisfies a specific conditional expression; (2) the shape factor SF-2 has a specific frequency distribution; (3) the BET specific surface area is 0.15 to 0.30m2/g; (4) the median particle diameter (D50) is 20 to 35µm; and (5) the magnetization is 50 to 65Am2/kg. Also employed are manufacturing processes for both, and so on.