PURPOSE: To obtain images of good gradation reproducibility and good quality without producing any unpleasant feel through the use of a water-base developing solution by forming latent images at the interface of a kphotoconductive layer and a transparent insulation layer through the use of a photoreceptor provided with the transparent insulation layer and visualizing these with a water- base colloidal developing solution.

CONSTITUTION: A photoreceptor 1 is basically constituted by a substrate 2 comprising forming a metal plate such as of Al, Pb or other or a plate of metal compounds such as of SnO2 or other to cylindrical form, a photoconductive layer 3 of inorganic photoconductive material such as Se, CdS or other or organic photoconductive material such as phthalocyanine or other and a transparent insulation layer 4 composed of high polymer film of dielectric constants 2 to 4 of blank such as polytetrafluoroethylene or other. This photoreceptor 11 is subjected to primary charging and secondary charging of opposite polarity to form electrostatic latent images at the interface of the layers 3, 4. As a result, even if the surface of the photoreceptor 1 makes contact to a developing solution 16, latent images 15 will not be broken and the coloring agent particles 17 charged in water are attracted and deposited on the insulation layer 4, where visible images are obtained. Whereby, the images of good gradation characteristic and good quality may be obtained.