| 摘要 |
PURPOSE:To form an image of more colors than the number of developing devices by simple constitution, by applying a bias voltage of a different potential to plural developing devices through an applying path, respectively, and switching selectively its applying path by a switching means. CONSTITUTION:A blue toner and a red toner are supplied by the first developing device 4 and the second developing device 5, respectively, a colorless leuco dyestuff is contained in the blue toner, and a color developing agent is contained in the red toner. Also, a bias voltage of a different potential is applied to the first and the second developing devices 4, 5 through applying paths 7a, 7b by first and the second power sources 7, 8, respectively. Also, by operating a switching circuit 6, the first and the second developing devices 4, 5, the first and the second power sources 7, 8 and also an earth are switched and connected as a combination. In this way, development of red, blue and black can be executed, and development of more colors than the number of developing devices can be executed. |
