Abstract: An electrographic copying machine has a photoreceptor drum which moves so that a photosensitive layer on its surface is successively charged, exposed, developed and charge-removed. The photosensitive layer is made of an amorphous material. The drum surface is charged by a charger before a latent image is formed thereon through exposure. A voltage generator is provided which supplies the charger with a voltage to charge the drum surface. It takes time for the potential of the charged drum surface at the developing section to reach a predetermined potential from a potential higher than the predetermined potential due to a rise characteristic of the surface potential. A controller is provided which corrects an output voltage value of the voltage generator to a voltage value necessary for the drum surface to be charged at the predetermined potential in a predetermined number of charging operations performed until the surface potential reaches the predetermined potential.

Abstract: In a copying processing performed several times from the depression of a copy button of a copying machine until the surface potential of the photoreceptor drum is stabilized, a voltage sufficiently high for correcting the rise characteristic of the photosensitive layer on the drum surface is applied to a charger. A main circuit having a controlling portion to realize this corrects the output voltage of the high-voltage generating circuit which applies a high voltage to the charger to a voltage value necessary for the drum surface to be charged at a stable potential level. The main circuit charges the drum surface at the stable potential level necessary for development from copying of the first sheet.

Abstract: More than 100,000 pieces of copy are obtained, in an electrophotographic process using an amorphous silicon photosensitive material, by maintaining the atmosphere for the photosensitive material and effecting the developing and polishing of the surface of the photosensitive material in a manner such that X, the degree of surface oxidation of the amorphous silicon photosensitive material (SiO/SiC), and Y, the amount of deposition of discharge products (mol/cm.sup.2), satisfy the relationships (1) and (2);0.4.ltoreq.x.ltoreq.1.25 (1)Y.ltoreq.2.2.times.10.sup.-9.exp(-2.0 x) (2)By this method, image flow is prevented without permitting the life of the photosensitive material to decrease, and an image can be stably formed for extended periods of time.

Abstract: Disclosed is a two-component type developer comprising a toner and a coated magnetic carrier wherein said toner has an electroconductivity lower than 3.5.times.10.sup.-10 S/cm and the coating of said magnetic carrier consists of a silicone resin having as its component unit a basic nitrogen atom-containing organic group bonded to a silicone atom (N-containing silicone resin).Such developer is capable of forming images having a high image density and a high image quality, particularly as a white developer or a color developer if developing is carried out even under ordinary conditions, since the toner has its charge quantity maintained in an appropriate range in the developing step.

Abstract: A two-component type developer comprising an electroscopic fixable toner containing, as the coloring pigment, carbon black having a coloring power of 100 to 120 and a magnetic carrier is sued for developing electrostatic latent images formed on a photosensitive plate in correspondence to an imitation original and an original, and the image density of the toner image corresponding to the imitation original is detected and the toner concentration in the developer is controlled based on the detected image density. According to this development process, the toner concentration in the developer can be maintained within an optimum range based on the optical density of the toner image formed on the photosensitive plate in correspondence to the imitation original.