| 摘要 |
PURPOSE:To perform normal development in copying mode and reversal development in printing mode by a single developing device by using a photosensitive drum which has a photoconductive layer made of amorphous silicon, then changing charging polarity according to the copying and printing modes. CONSTITUTION:On the surface of a photosensitive drum 1 provided with a photoconductor layer which is made of amorphous silicon and has photosensitivity to positive and negative polarity charging, corona dischargers 2 and 3 which perform selective charging with the positive or negative polarity are provided. Further, an exposing device 4 for copying which irradiates the drum with an optical image corresponds to an image of an original 12, a light source 17 which irradiates the drum with a storage area corresponding to an image signal, and a liquid crystal optical shutter 16 are provided in combination to constitute an optical image scanner 5 for a printer. Then, normal development in copying mode and reversal development in printer mode are performed by a single developing device 6 by changing the polarities of charging, thereby reducing the size of the device. |
