PURPOSE: To increase the reproducibility of black by making only one layer of a sensitive element a light conductive layer having delay characteristic in the sensitive element which has 2 light conductive layers to form a picture composed of 3 colors corresponding to an original paper composed of color A (red), color B (blue) and black.

CONSTITUTION: Two light conductive layers 10 and 11 (one layer is composed of selenium and the other is composed of eutetic OPC) are laminated on a conductive base plate 9. The light conductive layer 11 is a light attenuation delayed light conductive layer which has the delay characteristic for holding charge for a constant period when blue light is exposed uniformly and prepared by mixing light conductive micropowder, resin, binder and an additive (for regulation of delay time). The sensitive element is charaged to plus primarily simultaneously with uniform red exposure and then charged to minus secondarily at a dark position. After a picture with 3 colors of red, blue and black is exposed on a white background, negatively charged red toner development, negative bias development by the positively charged blue toner and then black positive toner development after uniform blue exposure are performed.