JPS5734564A - Three-color electrophotographic copying method - Google Patents

Abstract

PURPOSE:To obtain a superior 3-color image by once original image exposure, by using a photoreceptor having 2 photoconductive layers different from each other in sensitivity to color lights A and B, and an original having 3-colors of A, B, and black as well as white, and conducting specified charging and exposure. CONSTITUTION:For example, in the case of A being red, and B being blue, a photoreceptor 1 having a photoconductive layer 12 insensitive to a red light and well sensitive to a blue light, such as an Se-Te alloy, and a photoconductive layer 13, such as a eutectic complex, well sensitive to a red light and poorly sensitive to a blue light on a conductive substrate 11 is illuminated with a red light LR and positively charged 2, and then oppositely charged 3. An original O having 3-colors of black N, red R, blue BL as well as white W is exposed to light to imagewise expose the receptor 1, and the parts of the receptor 1 corresponding to the red and blue parts of the original O are developed with toners Tr, Tb different from each other in charged polarity. The receptor 1 undergoes the following processing: uniform blue exposure, uniform positive charging 4, and reversal development with a positive black toner Tn on the black N corresponding part with its potential adjusted to almost zero, thus permitting this 3-color toner image having the same polarity to be transferred without any precharger, and a sharp 3-color copy without color mixing to be obtained.