| 摘要 |
PURPOSE: To eliminate image repulsion or breakdown of a drum caused by electric leakage to a pin hole by specifying a maximum bias voltage against the electric resistance of a toner transfer roller. CONSTITUTION: Toner image is electrostatically transferred en bloc onto transfer material while making the transfer material pass by between an image carrier and a superimposed toner image in two colors or more and a transfer means, and impressing on the transfer means a bias voltage supplied from a constant current source. An example is now given as the maximum bias voltage impressed on the transfer roller is set to XKV or lower in a use environment of the transfer roller, especially when an electrical resistance value is 10XΩin an environment at a temperature of 20 deg.C and a humidity of 50%RH. Thus, the photoreceptor drum can be protected from breakdown by preventing generation of leakage in adjacent conductors and further leakage into pin holes, in a floating state of the transfer roller from the time when power supply is switched on until the time when the transfer roller comes into press-contact with the photoreceptor drum. |
