TWO-COLOR MULTIPLE DEVELOPING METHOD

摘要

PURPOSE: To reduce the contamination of a second developing with a first toner by making a second developing bias gentle in the a change from a flying voltage to a return voltage and, long in the change time. CONSTITUTION: The developing bias impressed on the second developing device 6 consists of the alternate biases having the flying voltage Vmax whose duration is T1 and the return voltage Vmin whose duration is T2 in one cycle. The voltage Vmax is the peak value of the voltage for moving the second toner 19 in a direction that it is advanced to a photoreceptive drum 1 from the developing device 6. The voltage Vmin is the peak value of the voltage for moving the toner 19 in a direction that it is advanced to the developing device 6 from the drum 1. Then, the time T(1-2) required for shifting the bias to the voltage Vmin from the voltage Vmax and the time T(2-1) required for shifting the bias to the voltage Vmax from the voltage Vmin are defined as T(1-2)>T(2-1).