| 摘要 |
PURPOSE:To provide a color copying machine by which the excellent image of a 2nd color is obtained without disturbing the toner image of a 1st color and which has no color mixture by the 2nd color. CONSTITUTION:At the time of developing with the 2nd color, developing bias voltage consisting of the pulse voltage VPULS of a period TA(within 100muse) and the DC voltage VDC of a period TB in one cycle is repeatedly impressed in a state where frequency is <=5kHz. VPULS is set to be larger than the potential VD of a non-image part so that developing potential may be high, and VDC is set to be smaller than the potential VT and VD of the toner layer of the 1st color and larger than the potential VL of an image part so that sufficient developing potential may be obtained. A potential difference between VDC and VT is set to <=500V. A developing gap is set to 100-300mum. An overshoot part may be included in the fall part of VPULS and also chopping wave voltage may be impressed instead of VPULS. It is difficult to receive the effect of the developing potential of the 2nd color the attractive force of the toner of the 1st color already developed. Then, the toner of the 2nd color showing specified moving characteristic is selected at a developing gap. |
