PURPOSE: To obtain excellent flowability and to reduce secular changes of an electrophotographic developer, and also to make it hardly influenced by environment by using organo-polysiloxane having an epoxy group as a substituent together with polyalkyleneimine.
CONSTITUTION: A powdery metal oxide is surface treated by concurrently using organo-polysiloxane having an epoxy group as a substituent and polyalkyleneimine. At this time the surface of the powdery metal oxide is provided effectively with positive electrostatic chargeability by the polyalkyleneimine which is firmly fixed through the organo-polysiloxane having high physical adhesion, on the surface of the powdery metal oxide by allowing to react the epoxy group in the organo-polysiloxane with the amino group in the polyalkyleneimne. At the same time the surface of this powdery metal oxide is provided with hydrophobic property by the organo-polysiloxane. At this time, the electrophotographic developer which contains particularly the powdery metal oxide having a ≥60% hydrophobicity determined by the transmissivity method and alumina or titania as the metal oxide, is provided.
NAKAMURA AKIHIRO
MUROTA MASAMICHI
