An image forming apparatus includes a photoreceptor, and a developing unit arranged in the vicinity of the photoreceptor. At an upstream side from the developing unit, a precharger is provided in a manner that the same is brought into contact with a surface of the photoreceptor. A developing bias voltage is applied to a developing sleeve, and a charging voltage is applied to the precharger. After the photoreceptor is charged by the precharger, the surface of the photoreceptor is brought into contact with a magnetic brush formed by a developing agent in which an insulative toner and a semiconductive magnetic carrier is mixed, whereby the photoreceptor is charged again by the developing bias voltage through the semiconductive magnetic carrier.

This invention relates to a charging system for charging a body to be electrified, comprising a body to be electrified, and a charging member which can be applied with voltage to brush the surface of said body to be electrified and charge it. Wherein the surface of the body to be electrified exhibits a contact angle of 90.degree. or more for water.

An imagewise exposure device exposes the inner surface of a rotating photoreceptor. A developer layer is provided around the surface of a first developing roller to which a DC voltage, the polarity of which is the same as that of charge given to the insulating toner of the developer, is applied. The developer layer on the first developing roller contacts the outer surface of the photoreceptor, corresponding to the inner surface exposed, so that a toner layer is formed on the outer surface of the photoreceptor. A toner image is formed when a developer layer provided around a second developing roller contacts the outer surface of the photoreceptor on which the toner layer is formed, wherein a DC voltage having polarity reverse to that of the first developing roller is applied to the second developing roller.

An electrophotographic apparatus includes a photoconductor drum, also known as an electrostatic latent image holding member, with a magnet placed therein. An electrostatic latent image is formed on the magnetic drum. Then, the drum is brought into contact with a magnetic developer, or toner, in a developer reservoir to have the magnetic developer attached to the photoconductor drum surface by a magnetic force. A removing roller, having an AC voltage applied thereto, is passed in close vicinity of the magnetic drum with the resultant development of images because toner remains at image areas only. In the electrophotographic apparatus, the photoconductor drum, the removing roller or both include two magnetic poles. A device for increasing friction force of the surface of the photoconductor drum, of the removing roller or both may also be provided.

An electrophotographic printing machine is provided with a photoreceptor drum including a cylindrical transparent support having a transparent electrically conductive layer and a photoconductive layer laminated on a surface thereof and a dielectric belt having wound around the photoreceptor drum. A toner image is formed on a surface of a dielectric belt through a process of exposing the photoconductive layer by applying voltage across the toner to be applied to the surface of the dielectric belt and the transparent electrically conductive layer. Then, the toner image is transported up to a position apart from the photoreceptor drum where a copying material is superposed onto the toner image so as to apply heat and pressure thereto, whereby transfer and fusing processes of the toner image are carried out simultaneously to the copying material. As a result, a turbulence in the toner image is reduced, thereby providing high quality images.