| 摘要 |
PURPOSE:To provide a 2-color electrophotographic method good in resolution, and capable of selecting a color except black easily, by charging a photoreceptor to be exposed 3 times of positive, negative, and positive corona discharges, and exposing it uniformly, to optical image corresponding to a black image, and uniformly, following said charging steps using a conductive screen. CONSTITUTION:An original 2 consists of black (A), red (B), and white (C), and a negative charge reverse to charging in polarity is induced on the back side of an insulating layer 11 by primary charging. While secondary reverse-polarity charging is executed, a photoreceptor 1 is exposed to an optical image from the original 2 to retain resistance in the part corresponding to black (A). Then, while charging the same polarity as the secondary charge is carried on, resistance of the photoconductive layer of the photoreceptor 1 in the part corresponding to white (C) is lowered by illumination through a filter 3 intercepting only red light, resistance of the photoconductive layer 41 of a photoconductive screen 4 is lowered, an action in the part corresponding to black similar to that in the part corresponding to black (A) is exerted, and potential of the photoreceptor 1 surface goes further to a negative side. After that, its surface is uniformly exposed, resulting in occurrence of positive surface potential in the part corresponding to black (A), maintenance of negative surface potential, though small in the absolute value in the part corresponding to red (B), and maintenance of almost zero in the part corresponding to white (C). |
