| 摘要 |
PURPOSE:To improve the density of an image while gradation is maintained and to prevent the growing of the fine part of the image, as well, and simultaneously, the base fogging of a nonimage part. CONSTITUTION:A developing roller 1 whose surface has the formation of a conductive region surface 21 and an insulating region surface 22 by knurling processing, is arranged to be opposite to the surface of a photosensitive drum 3 on which an electrostatic latent image is formed, in the gap of 100mum. The insulating region surface 22 is rubbed by a toner supplying roller 8, holds the charge of a positive polarity, and forms a fine closed electric field between the insulating and conductive region surfaces 22 and 21, to carry negatively electrified toner 7. A biased DC pulse voltage is intermittently impressed on a developing part opposite to the developing roller 1 and the photosensitive drum 3, to execute reversal development. |
