| 摘要 |
PURPOSE:To prevent a high original density part from the reduction of image density by setting up a developing bias voltage to be impressed during developing operation so that it is gradually reduced every development in accordance with the reduction of the potential of an electrostatic latent image formed on a photosensitive body. CONSTITUTION:An original platen 5 is moved from the left end side in the right direction, the electrostatic latent images of an original are successively formed on respective photosensitive drums 7c, 7y, 7m and the drums 7c, 7y, 7m complete respective development by three rotations, two rotations and one rotation respectively until the original platen 5 is completely carried up to the right end side. In this case, the absolute value of the developing bias voltage is gradually reduced in the order of the 1st, 2nd and 3rd development to keep the potential difference from that of the electrostatic latent image almost at a constant value. Even if the developing operation is continued up to the 3rd times, a developer temporarily adhering to the surface of the electrostatic latent image can be prevented from being peeled off by the developing bias voltage, so that the reduction of the image density in a high original density part can be suppressed and the image quality can be improved. |
