PURPOSE: To promote the edge effect so as to obtain a high picture density and a desired developing characteristic, by applying an electrostatic charge of a prescribed polarity to the toner carrier and toner at the surface of the carrier and applying the charge having a reverse polarity in succession, to electrostatically charge the toner and the toner carrier with the reverse polarity.
CONSTITUTION: Plural minute electrodes 4 are scattered on the surface of an inductive layer 3 at the outer peripheral surface of a conductive base body 2. A negative voltage of 500V is impressed across the layer thickness adjusting member 8 of toner 7 and the electrode 4 and the toner on the surface are charged with the negative polarity, and then, positive electric charge is injected by means of a conductive brush electrostatically charged with negative voltage of 200V. However, the electrode 4 is hardly electrostatically charged with the charge to electrostatically charge only the toner with the positive polarity. At the developing position, the toner is transferred and attached to a photosensitive body 13 and the toner adhesion to the ground is prevented by the bias effect of the electrode 4 charged with the negative polarity. Furthermore, by the edge effect of the electrode 4 under a floating condition, a high picture density and a desired developing characteristic is obtained even for original of line-drawn picture.
KANEKO TOSHIO
SUGANO FUCHIO
YASUDA WATARU
