| 摘要 |
PURPOSE:To improve water resistance, toner spent property and electrostatic chargeability by subjecting a core material contg. an acrylic resin consisting of a ferrite core material having a specific surface area and average grain size to a coating treatment with >=2wt.% resin. CONSTITUTION:The ferrite core material having the specific surface area S and average grain size (d) expressed by equation I and equation II is coated with the resin at >=2wt.% of the weight of the core material contg. the acrylic resin. The relation between the image quality and the carrier sticking is made into an adequate range and the fine ruggedness is increased in the surface of the core material when the surface area S and average grain size (d) are specified to the value expressed by formula I and formula II. The surface coating resin is impregnated into the bottom of the fine ruggedness, and has good adhesiveness to the core material. The acrylic resin has good adhesiveness to ferrite and allows sufficient coating on the surface ruggedness. The water resistance, toner spent property and the electrostatic chargeability are improved in such a manner. |
