| 摘要 |
PURPOSE:To prevent the reversal photographic fog due to a toner having an opposite polarity and prevent scattering of the toner into a device and a waste of the toner, by switching a DC developing bias in accordance with the surface potential of a non-image area. CONSTITUTION:A semiconductor laser 1 of 770-800nm and a photosensitive drum 3 where metallic phthalocyanine is applied are used. Consequently, the photosensitive drum 3 is charged electrostatically uniformly with about -500- -800V by a primary charger 4, and thereafter, the image is exposed to the photosensitive drum. The potential of a part VL to which the laser light is irradiated is lowered to -50--200V, and a negative toner is used to develop this part in a developing device to make the image in this part VL visible. A positive electric charge is given to the developed toner in a transfer position from the back of a transfer material by a transfer charger 8, and the negative toner on the photosensitive drum 3 is transferred to the transfer material. Since the potential on the photosensitive drum 3 is not uniform because of the bright part VL, a dark part VD, the presence or the absence of the transfer material, etc., the photosensitive drum 3 is charged uniformly again by pre-exposure and the primary charger 4 having a grid. |
