Electrophotographic printing machine

An electrophotographic printing machine comprising:

• photoreceptor means including a transparent base having a transparent electrically conductive layer laminated thereon and a photoconductive layer laminated on said electrically conductive layer, the photoconductive layer being moved relative to developer holding means;
• developer holding means for holding a dielectric developer and applying the dielectric developer in contact with the photoconductive layer, the developer holding means being in contact with the photoreceptor means, the developer holding means being electrically conductive;
• and
• voltage application means for applying voltage across the developer holding means and the transparent electrically conductive layer,
• wherein in forming an image corresponding to an exposure pattern on the surface of the photoreceptor means, charging and developing processes are carried out almost at the same time by conducting an exposing process corresponding to an image by the exposure means while charging the surface of the photoreceptor means by applying a voltage across the developer holding means and the transparent electrically conductive layer, and
• the exposure means is set in such a manner that an exposing energy thereof is represented by an equation:
• V.sub.L .gtoreq.V.sub.D -V.sub.D1,
• where V.sub.D1 designates the surface electric potential of the photoreceptor means that is exerted when the surface of the photoreceptor means, originally having a surface electric potential of virtually zero V, passes by a portion in which the charging and developing processes are carried out;
• V.sub.D designates the saturation value of the surface electric potential of the photoreceptor means that is attained after the surface of the photoreceptor means has successfully passed by the portion;
• and V.sub.L designates the lowered surface electric potential of the photoreceptor means that is to be reached by an exposure.

An electrophotographic printing machine comprising:

• a rotative photoreceptor drum having an optically transparent cylindrical base, an optically transparent electrically conductive layer and a photoconductive layer, the photoreceptor drum being constituted of the transparent cylindrical base whereon the transparent electrically conductive layer and the photoconductive layer are formed in this order;
• a toner holder for holding an electrically conductive and magnetic toner by a magnetic force and applying the electrically conductive and magnetic toner to be in contact with the photoconductive layer;
• a power supply for applying voltage across the electrically conductive and magnetic toner and the transparent electrically conductive layer;
• exposure unit, installed inside the photoreceptor drum, for exposing the photoconductive layer at a contact portion to the the electrically conductive and magnetic toner by applying a light onto the photoconductive layer through the transparent base and the transparent electrically conductive layer;
• a dielectric belt which moves in contact with the photoconductive layer of the photoreceptor drum, with at least one surface in contact with the photoconductive layer being dielectric;
• a transfer roller for transferring a visible image formed on the photoconductive layer onto the dielectric belt while pressing the dielectric belt toward the photoconductive layer of the photoreceptor drum;
• a heating device for melting the toner of the visible image that has transferred onto the dielectric belt by heat treatment;
• and
• a pressing roller for pressing the superposed portion of the dielectric belt and a copying material toward the heating device, the pressing roller being placed face to face with the heating device,
• wherein the exposure unit is set in such a manner that an exposing energy thereof is represented by an equation:
• V.sub.L .gtoreq.V.sub.D -V.sub.D1,
• where V.sub.D1 designates the surface electric potential of the photoreceptor drum that is exerted when the surface of the photoreceptor drum, originally having a surface electric potential of virtually zero V, passes by the area in contact with the electrically conductive and magnetic toner;
• V.sub.D designates the saturation value of the surface electric potential of the photoreceptor drum that is attained after the surface of the photoreceptor drum has successively passed by the area in contact with the electrically conductive and magnetic toner;
• and V.sub.L designates the lowered surface electric potential of the photoreceptor drum that is to be reached by an exposure.