PURPOSE: To obtain sufficient image density by setting a development bias voltage at least in a second and succeeding developing processes to the specific AC voltage in which a DC voltage overlaps with it.
CONSTITUTION: A first electrifier 2a, a first exposing means 3a, a first developing unit 4a, a second electrifier 2b, a second exposing means 3b, a second developing means 4b, a pretransfer corotron 5, a transfer corotron 6, a peeling corotron 7, a cleaner 8 and a light destaticization unit 9, all of which serve as an electrophotographic recording means, are disposed around a photosensitive drum 1 in that order in the direction of its rotation. The development bias voltage at least in the second and succeeding developing processes is the AC voltage in which the DC voltage overlaps it. The length of a time while this voltage changes from the voltage at which an electric field for the development of toner to the surface of the photosensitive drum 1 is maximum to the voltage at which the electric field for the development of the toner to the surface of the drum 1 is minimum is longer than the half of one period of an AC element.
NOAMI TSUNEO
SAIKAWA TAKESHI
AOSHIMA MIGAKU
EZURE HIRAKAZU
