| 摘要 |
PURPOSE:To carry out sharp 2-color recording on a photosensitive drum without mixing of 2-color toners, by conducting formation of the first latent image and its development, and then, formation of the second latent image and its development. CONSTITUTION:Photosensitive drum 5 is charged to potential VS with charger 7, and positively exposed with exposing means 12, forming a latent image with potential VL of its exposed areas controlled to about 1/2 of VS. This image is developed positively with black toner 20 charged negatively in first developing device 13. Then, drum 5 is negatively exposed so as to render the potential of the exposed areas nearly zero V. The latent image is reversely developed with red toner having positive charge in second developing device 15. At that time, developing bias voltage VDB2 is kept somewhat lower than potential VL. Such a structure permits a black and red toner image to be formed on drum 5, and sharp 2-color recording becomes available on drum 5 without mixing of the 2-color toners. |
