| 摘要 |
PROBLEM TO BE SOLVED: To prevent color mixtures of visible images formed on a photoreceptor and developers in respective developing devices and to obtain an image of high quality by applying a voltage having a reverse polarity to that of the electrostatic charge of toner used on the developing roller of a developing device in a separation state from a photoreceptor, to the developing roller. SOLUTION: A developing voltage producing means 14b in a high-voltage power source 13 is connected to a black developing roller 10 for executing a developing operation and a developing voltage having the same polarity as that of the electrostatic charge of the toner is applied to make an electrostatic latent image on the surface of the drum-like photoreceptor 1 visible. On the other hand, a reverse polarity set voltage producing means 15a in the high- voltage power source 13 is connected to a red developing roller 4 in a development inoperative position and a set voltage having the reverse polarity to that of the electrostatic charge of the toner is applied to attract/recover scattered red toner to the red developing roller 4. Thus, the voltage having the reverse polarity to that of the electrostatic charge of the toner used by the developing roller 4 of the developing device 3 in the separation state from the photoreceptor 1 is applied to the developing roller 4. |
