Patent ID: 6383637
Filing Date: 2002-05-07
Classification: C01P,C09C,G03G,Y10S,Y10T

Abstract:
Black magnetic iron oxide particles having an average particle diameter of 0.1 to 0.3 &mgr;m, comprising:black spinel iron oxide particles as core particles; and a surface coating layer comprising fine spinel iron oxide particles formed on the surface of each core particle, wherein a surface layer portion has a depth of about 3.5% of a radius of the black magnetic iron oxide particle, the FeO content in the surface layer portion is 8 to 14% by weight based on the weight of Fe contained in the surface layer portion, and the FeO content in a central portion of black magnetic iron oxide particle as a remaining portion excluding the surface layer portion, is 27 to 34% by weight based on the weight of Fe contained in said central portion.