| 摘要 |
PURPOSE:To contrive the improvement in durability by controlling the saturated magnetization of a cored ferrite and the particle distribution, selecting a specific copolymer as a composition of a copolymer for covering with a resin and controlling the resistivity. CONSTITUTION:As for the magnetic carrier particles, a surface of the magnetic particle is covered with the resin, and the main component of the cover with the resin is an acryl-styrene copolymer in which ethyl-methacrylate constitutes a copolymer with a non-substituted styrene monomer. The styrene contents in the copolymer are 15-25 wt.% and in the copolymer a dedecyl-methacrylate is incorporated whose dedecyl-methacrylate contents are preferably 0.1-2 wt.%. Also in the copolymer, 2-hydroxyethyl acrylate is incorporated and the contents are preferably <= 2wt.% and the resistivity is 8.5-220 X 10<7> OMEGA. Thus, the durabil ity is enhanced. |
