| 摘要 |
PURPOSE:To preclude contamination and to obtain an image of high quality by increasing a repulsive electric field for toner from a developing device to the surface of an image carrier when the developing device moves to a development position and leaves the development position. CONSTITUTION:When the developing device moves to the development position and leaves the development position, the surface of the drum is held at Vd (-650V) through the electrostatic charging of a primary electrostatic charger 2 and the developing bias Vd is raised from -500V to -350V to generate a minus-directional potential difference on the drum surface; and the minus- directional potential difference on the drum surface is increased for minus toner, thereby preventing the toner from sticking. Namely, the repulsive electric field for toner from the developing device 4 to the surface of the photosensitive drum 1 is increased to prevent the toner from sticking on the surface of the photosensitive drum 1 from the developing device. Consequently, the sticking of the toner due to pressure to an image carrier and rubbing is precluded to prevent transfer paper from being stained, thereby obtaining an excellent image.
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