| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a black magnetic iron oxide particle powder for a magnetic toner, which has sufficient blackness and is excellent in dispersibility and electric characteristics and also to provide a production process for the iron oxide particle powder. SOLUTION: Each of the particles of this black magnetic iron oxide particle powder comprises a black spinel-type iron oxide particle used as a core particle and a surface layer which is formed on the surface of the core particle and consists of fine spinel-type iron oxide particles, wherein in the surface layer, more specifically, a layer (surfacevicinity layer) is formed in close vicinity to the surface of the surface layer and this surface-vicinity layer has a thickness equivalent to 3.5% of the particle radius of each of the particles of the black magnetic iron oxide particle powder, from the surface of the surface layer and a 8-14 wt.% FeO content on the basis of the total Fe content in the surface- vicinity layer. The particles of the objective black magnetic iron oxide particle powder has a 0.1-0.3μm average particle diameter.</p> |
