JPS5740273A - Copying method for tricolor electrophotography - Google Patents

Abstract

PURPOSE:To obtain a tricolor picture having a good quality, which is enough in density and gradation, and has no color mixture from the visible viewpoint, by setting the developing bias potential to a prescribed value, and forming a color mixed picture of a prescribed color toner. CONSTITUTION:A sensitive body 1 which is provided with two photoconductive layers whose sentivity is different depending on a color of exposure is charged positive by a charger 20, and after that, is charged negative by a charger 22, and is irradiated by an original optical image. Subsequently, electrostatic latent images corresponding to each red and blue picture are brought to a developing treatment by red and blue toners whose polarity is different, of developing devices 23, 24. After that, it is uniformly irradiated by a blue light illuminating device 5, and subsequently is developed and treated by a black toner of a developing device 26 under the developing bias potential being an intermediate value of the surface potential of the sensitive body 1 of a black picture corresponding part, and the surface potential of the sensitive body 1 of a white picture corresponding part. In this way, it is possible to form a color mixed picture of blue and black toners, which is enough in density, good in reproducibility of a low density part, too, and satisfactory in gradation. Accordingly, when a black mixed image is formed by use of a purplish black toner, a tricolor picture of a good quality, having substantially no color mixture is obtained.