| 摘要 |
PROBLEM TO BE SOLVED: To provide magnetic particle powders for magnetic toner which has excellent fluidity and electrification performance and which can stably maintain the fluidity and the charge amount. SOLUTION: The magnetic particle powder for a magnetic toner 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 Fe amount in the near-surface layer. Further, fine particles selected from oxides of Al, Si, Zr and Ti are deposited by 0.25 to 10 wt.% calculated as oxides to the black magnetic iron oxide particle powder on the surface of the black magnetic iron oxide particles. |
