| 摘要 |
PURPOSE:To prevent a latent image from being formed in an area other than an image area and excessive toner from sticking thereto by limiting an entire-surface exposure area in an electrophotographic copying device which forms an electrostatic latent image on a photoreceptor coated with an insulating layer by performing primary charging, simultaneous exposure and charging, and entire- surface exposure. CONSTITUTION:When primary charging t0-t1, simultaneous exposure and charging t2-t3, and entire-surface exposure t4-t5 are carried out, the dark part potential VD of image exposure rises and the light part potential VL is nearly unchanged. This latent image is developed to obtain a toner image. For copying on size reduction basis, the entire-surface exposure is carried out only at the original image projection area of the photoreceptor to suppress a rise in its potential VD', preventing toner from sticking thereto. In concrete terms, the driving range of a light emitting diode array 20 is limited and the exposure area of a cold cathode-ray discharge tube 25 is limited by a liquid-crystal plate 26 to limit the range of the entire-surface exposure to only the original projection area. |
