| 摘要 |
PURPOSE:To obtain magnetic particles used for electrophotographic developer, high in tap density and good in magnetic transportability, and giving a good developed image even in high-speed development, by dispersing the fine magnetic particles having coercive force not below a specified value into a binder. CONSTITUTION:The fine magnetic powder is used contg. an acicular magnetite, acicular gamma-Fe2O3, Co-contg. gamma-Fe2O3, or the like having >=300 Oe coercive force. A binder is prepared contg. >=30wt% brittle resin having <=1.9kg.cm/cm<3> Izod impact strength, such as styrene-acrylic resin. 150-250pts.wt. of said magnetic powder are added to 100pts.wt. of this binder, kneaded, then pulverized, and classified to obtain the intended magnetic particles for use in electrophotographic magnetic particles. The obtd. magnetic particles has >=1,050g/cm<3> tap density, and superior magnetic transportability, and they are favorably used for high speed development of an electrostatic latent image. |
