PURPOSE: To widen the tolerance width of a toner concn. by using a two- component type magnetic developer obtd. by mixing a magnetic carrier consisting of fine powder of iron bonded by an amine-modified resin and insulating toner having negative electric chargeability.
CONSTITUTION: The fine powder of iron is bonded by the amine-modified resin to form the magnetic carrier having 15W40μm average grain size. The fine powder of iron which has ≥80emu/g magnetization to 1kOe magnetic field and 0.2W2μm average grain size is used at this time. The fine powder of iron is incorporated into the carrier in a 50W80wt.% range of the total weight of the carrier. Such magnetic carrier is mixed with the insulating toner having the negative electric chargeability and 5W15μm average grain size to yield the two-component type magnetic developer. An electrostatic latent image is then developed by a developing method by a magnetic brush. Since the magnetic carrier of the small grain size is used, the tolerance width of the toner concn. is widened and the need for a mechanism to control the toner concn. is eliminated. Formation of a sharp image is thus permitted.
SARUWATARI NORIO
KO KATSUJI
KATAGIRI YOSHIMICHI
KAYAKAWA TAKAHIRO
TATEIWA YOSHIHIRO
NARISAWA TOSHIAKI
