| 摘要 |
PROBLEM TO BE SOLVED: To provide magnetic particle powders for magnetic toner having a sufficient black color degree, excellent in electric characteristics, compatible with a vinyl aromatic resin, acrylic resin or copolymer resin thereof, and having good their dispersibility in a magnetic toner resin. SOLUTION: The magnetic particle powder consists of black magnetic iron oxide particles having 0.1 to 0.3 μm mean particle diameter. Each particle has a surface layer consisting of fine spinel iron oxide particles formed on the surface of a black spinel iron oxide particle as the core particle. The FeO content in the near-surface layer with the thickness corresponding to 3.5% of the radius of the particle from the surface of the surface layer is 8 to 14 wt.% of the amount of Fe included in the near-surface layer. Further, the particle surface of the black magnetic iron oxide particle is covered with an organic compound having hydrophobic groups. |
