| 摘要 |
PURPOSE:To prevent the deterioration in the quality of visible images when the repetitive number of the visible image formation is large, by increasing the potential of an electrostatic charger for modulation of an insulation drum which is process-controlled according to the mumber of the visible image formation. CONSTITUTION:The secondary latent image formed on an insulation drum with a screen drum by process control is retained by an electrostatic charger for modulation and visible images are formed reiteratively. The series resistance on the primary side of a high voltage transformer is short circuited successively by the selection of a corres ponding switch NC according to the number of copying sheets to be formed with the visible images, whereby the potential of the electrostatic charger for modulation of the insulation drum is decreased in the stage of transferring the 2nd sheet with respect to the potential in the stage of transferring the 1st sheet and is thereafter increased stepwise at every 10th sheet, 30th sheet, 50th sheet, 70th sheet and 90th sheet. The deterioration in the characteristic of the latent image on the insulation drum owing to a decrease in the potential according to the repetitive number of the visible image formation is compensated and even if the repetitive number of the visible image formation is compensated and even if the repetitive number of the visible image formation increases, the deterioration in the quality of the visible images is prevented. |
