| 摘要 |
PURPOSE:To obtain a sharp 2-color toner image without color mixing, by executing the first and the second developments using reversal development characteristics, and performing the second development by applying bias voltage same in polarity as the charge forming an electrostatic image on a developing roll. CONSTITUTION:A photosensitive drum 1 rotating in the arrow direction is uniformly positively charged with a corona charger 2. An electrostatic latent image is formed by negative exposure to imagewise light 3, and developed with the first developer 5 in a developing device 4. The unexposed area on the drum 1 is negatively exposed to imagewise light 6 to form an electrostatic image, and it is developed with the second developer 8 in a developing device 7. Both developing devices 7, 4 have reversal developing functions, the developer 8 consists of positively charged toner and magnetic carrier, and attached to the surface of a magnetic roll 7b to which positive bias voltage is applied with a bias voltage source 7a, the first toner 5a is scraped down by mildly rubbing the drum 1 surface, and not mixed with the second developer 8, and hence, a sharp image is obtained. |
