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 and polyalkyleneimine. At this time the powdery metal oxide is provided with high hydrophobic property by the organo-polysiloxane and also provided effectively with positive electrostatic chargeability by the polyalkyleneimne which is strongly bonded through the organo-polysiloxane having high physical adhesion, to the surface of the powdery metal oxide that is at the same time provided with hydrophobic property by the organo- polysiloxane. Preferably, the electrophotographic developer which features in containing the powdery metal oxide having a ≥60% hydrophobicity determined by the transmissivity method, particularly that containing alumina or titania as the metal oxide, is provided.
NAKAMURA AKIHIRO
MUROTA MASAMICHI
