Canon Kabushiki Kaisha

Giichi Marushima

Shinkichi Takahashi

Hiroshi Tanaka

Umi Tosaka

Shusei Tsukada

Touru Takahashi

Takao Komiyu

A process and apparatus for forming an electrostatic image on a photosensitive plate having a conductive base, a photoconductive layer overlying the base and exhibiting p-type or n-type semiconductivity, and an insulative layer overlying the photoconductive layer. The photosensitive plate is characterized in having carrier charge of a polarity corresponding to the conductivity type of the photoconductive layer injectable from the conductive base into the photoconductive layer and bound in the region of the interface between the insulative and photoconductive layers. The conductive base is transparent to activating light and the insulative layer is opaque to the activating light. A first charge of a polarity opposite to the conductivity type of the photoconductive layer is applied onto the insulative layer to inject and bind carrier charge in the region of the interface between the insulative and photoconductive layers. Then, the photoconductive layer is exposed to a pattern of activating image light by projecting the image light through the transparent conductive base while a corona discharge is applied onto the insulative layer. Thereafter, the photoconductive layer is exposed to activating light through the transparent conductive base to discharge bound carrier charge remaining in the region of the interface and form a high constrast electrostatic image.

Electrophotographic process and apparatus

A process for forming an electrostatic image on a plate having a conductive base, a photoconductive layer exhibiting p-type or n-type semiconductivity and a covering insulative layer, said photosensitive plate being characterized in having carrier charge of a polarity corresponding to the conductivity type of said photoconductive layer injectable from said conductive base into said photoconductive layer and bound in the region of the interface between said insulative and photoconductive layers, wherein the covering insulative layer is initially charged with a polarity opposite to the conductivity type of said photoconductive layer to inject and bind charge carrier in the region of the interface between said insulative photoconductive layers, then the photoconductive layer is exposed to a pattern of image light, while a corona discharge of a polarity opposite to the first charge is applied onto the insulative layer, and then the photoconductive layer is exposed to activating light to discharge bound carrier charge remaining in the region of the interface between said insulating and photoconductive layers and form a high contrast electrostatic image.

An A.C. corona discharging device for use in the process in which discharge and exposure are accomplished contemporaneously has insulating members disposed so as to surround the discharge wire or electrode and define the opening for projecting the image of an original. The potential gradient is increased, the discharge efficiency is improved and the flow of useless current which heretofore traveled through the shielding electrode is not encountered.

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Komae, Japan

Giichi Marushima