A color transfer copying process for forming a colored image corresponding to an original by repeating prescribed times the procedures of projecting a reflected ray image from the original to be copied on a photosensitive material uniformly charged by a charging electrode through a filter to form an electrostatic latent image on the photosensitive material, converting the latent image to a toner image by using a powdery developer containing a coloring toner and transferring electrostatically the toner image onto a transfer sheet, while using selectively blue, green and red filters. Said process is characterized in that an electrode is disposed in the vicinity of a transfer passage for the transfer paper so that it acts on the transfer paper after completion of the transfer operation and said electrode is energized in regular sequence with the same frequency as that of the transfer operations or as that of the transfer operations exclusive of the final transfer operation to neutralize or diminish the retention charge of the coloring toner transferred onto the transfer paper at the transfer operation. It is made possible at the subsequent transfer operation to transfer and superpose a predetermined quantity of the coloring toner of the coloring toner image on the photosensitive material onto the transfer paper even in areas overlapped with the coloring toner image formed at the preceding transfer operation. A direct current having a polarity reverse to that of the transfer electrode for transferring the toner image to the transfer paper is applied to said charge-removing electrode.

An image forming apparatus according to the present invention comprises a photosensitive drum which is characterized by a charge generating layer and a charge transport layer. The drum is charged by means of a main charger. At this time, electric charge is produced and held in the charge generating layer. A light-beam bearing image information is applied to the charge generating layer of the drum through the charge transmission layer, by an exposure system. Thereupon, an electrostatic latent image corresponding to the image information is formed on the surface of the drum. The latent image is developed by means of a developing unit using a toner. Thus, a toner image is formed on the drum surface, from which it is transferred to the surface of a paper sheet by a transfer charger. The developing unit also serves to remove, simultaneously with the development of the electrostatic latent image, those toner particles remaining on the drum surface after the transfer by the transfer charger. The image forming apparatus is particularly characterized in that the light beam, applied by the exposure system, is also guided through the charge transport layer of the photosensitive drum to those regions of the charge generating layer shaded by the residual toner particles, thereby preventing white spots from being formed on a solid black image.

The invention is an electrophotographic imaging process comprising forming a first electrostatic latent image on an imaging surface of an electrophotographic imaging member comprising an electrophotographic insulating layer and an electrically conductive layer, developing said first electrostatic latent image with a conductive two-component developer having a conductivity between about 10.sup.-10 ohms-cm.sup.-1 and about 10.sup.-14 ohms-cm.sup.-1 in a development zone between said imaging surface and an electrically conductive developer applicator to form a toner image corresponding to said first electrostatic latent image, transferring most of said toner image to a receiving member with a residual toner image remaining on said imaging surface forming a second electrostatic latent image on said imaging surface bearing said residual toner image, and simultaneously developing said second electrostatic latent image and removing said residual toner image by contacting said electrophotographic imaging surface in said development zone with conductive two-component developer while simultaneously maintaining the minimum distance between said electrically conductive layer and said electrically conductive developer applicator in said development zone, supplying an electrical bias to said electrically conductive layer, and supplying an electrical bias to said conductive developer applicator.

A method and apparatus for transferring a latent electrical image from a photosensitive image receptor to a dielectric or insulating image receptor where the photosensitive image receptor comprises a conductive base, a photoconductive layer arranged on it and on top of it a protective layer of transparent, insulating and non-photoconductive material. The protective layer surface is charged in the dark to a specific first potential; the photoconductive layer is image-exposed thereafter; the insulating image receptor is placed on the protective layer and a second, lower potential applied on the free surface of the insulating image receptor; and the insulating image receptor is separated from the protective layer of the photosensitive image receptor.

In transferring a toner image carried on a toner image carrier onto a transfer medium, a uniform charge is imparted to the surface of the toner image carrier while a charge of the same polarity as the uniform charge is imparted to the surface of the transfer medium, whereafter a toner image is transferred from the surface of the toner image carrier to the surface of the transfer medium.