Multicolor image-on-image forming machine using reverse charge printing (RCP) process
 A multicolor image reproduction machine includes a main assembly having an image bearing member, a controller, and a bias source for biasing the image bearing member. It also includes a plurality of color separation toner image forming units each having a photoreceptor including a photoconductive surface forming a toner image separation development nip with the image bearing member. Each imaging unit also includes a toner supply apparatus for applying a layer of toner of a particular color onto the photoconductive surface; a first charging device for uniformly charging the photoconductive surface; an exposure device connected to the controller for image-wise exposing the photoconductive surface and the layer of toner to form therein image areas and background areas of a desired image; and a second charging device connected to the controller for selectively reversing charge in the background areas of the desired image, so as to enable subsequent separation of the background areas from the image areas. The multicolor image reproduction machine further includes a separation development assembly for separating and developing the image areas of the desired image from the layer of toner and onto the image bearing member of the main assembly to form a multicolor toner image. 
Xerox Corporation
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additional inventional inventional
Weizhong Chu-heng
Zhao Liu