Magnetic carrier, two-component developer and image forming method

摘要

A magnetic carrier constituting a two-component developer for use in an electrophotographic image forming method is formed of a carrier core comprising a first resin and magnetic fine particles dispersed in the first resin, and a second resin surface-coating the carrier core. (a) The magnetic carrier has a true specific gravity of 2.5-4.5, a magnetization sigma 1000 as measured in a magnetic field of 1000x(103/4 pi )xA/m (1000 oersted) of 15-60 Am2/kg (emu/g), a residual magnetization sigma r of 0.1-20 Am2/kg (emu/g) and a resistivity of 5x1011-5x1015 ohm.cm. (b) The first resin has a polymer chain including a methylene unit (-CH2-). (c) The second resin has at least a fluoro-alkyl unit, a methylene unit (-CH2-) and an ester unit. (d) The carrier core is surface-coated with (i) a mixture of the second resin and a coupling agent having at least an amino group and a methylene unit, or (ii) a coupling agent having at least an amino group and a methylene unit, and then with the second resin.