Method for forming negative and positive images in electrophotographic process

DETAILED DESCRIPTION It is therefore a primary object of the present invention to provide an electrophotographic process in which negative images and positive images can be optionally formed only by electric controls by using an ordinary photosensitive material and a single developer.
Another object of the present invention is to provide an electrophotographic process in which not only a positive image-forming capacity but also a negative image-forming capacity is given to a conventional electrophotographic copying machine by selecting a developer and building an electric control circuit in the copying machine.
More specifically, in accordance with the present invention, there is provided an electrophotographic process which comprises developing an electrophotographic light-sensitive layer having an electrostatic charge image of a certain polarity with a one-component type magnetic developer where positive and negative frictional charge polarities are mingled, under development bias voltage conditions capable of developing the electrostatic charge image, the background or both, and bringing the light-sensitive layer having a developer layer formed thereon into contact with a transfer sheet under a transfer charge of the same polarity as that of the electrostatic charge image when a positive image is formed or under a transfer charge of a polarity reverse to that of the electrostatic charge image when a negative image is formed, to form an image on the transfer sheet.