| 摘要 |
PROBLEM TO BE SOLVED: To prevent the adjustment of image density from being applied for the other image quality and to obtain a two-color image with high quality when the image density is adjusted by changing the electrifying potential of a photoreceptor by an electrifier as much as identical amount to the change amount of a developing bias voltage by interlocking with it when the developing bias voltage applied on a reversal developing device has been changed. SOLUTION: The photoreceptor 1 is uniformly electrified by the electrifier 2 and an electrostatic latent image consisting of the combination of a high potential part, a medium potential part and a low potential part is formed at the photoreceptor 1 by a laser beam 3a emitted from an optical device 3. At the high potential part, positively electrifiable toner whose polarity is reverse to the photoreceptor 1 is normally developed by a normal developing device 4. At the low potential part, negatively electrifiable toner whose polarity is identical to the photoreceptor 1 is reversely developed by the reversal developing device 5. Then, when the developing bias voltage applied on the developing device 5 has been changed, the electrifying potential of the photoreceptor 1 by the electrifier 2 is changed as much as the identical amount to the change amount of the developing bias voltage by interlocking with it. |
