Multicolor image-on-image forming machine using air breakdown charge and development (ABCD) Process
 A multicolor image-on-image reproduction machine includes a main assembly, a controller, a movable image bearing member having a path of movement, and a plurality of air breakdown charge and development (ABCD) imaging units mounted along the path of movement for forming color separation toner images. Each (ABCD) imaging unit includes a photoreceptor having a photoconductive surface forming a toner image separation development nip with the movable image bearing member; a toner supply apparatus for applying a layer of toner onto the photoconductive surface; a charging device for uniformly charging the photoconductive surface through the layer of toner; and an exposure device connected to the controller for image-wise exposing of the photoconductive surface and the layer of toner to form therein image areas and background areas of a desired color separation image. The multicolor image-on-image reproduction machine then includes a bias source for biasing the image bearing member at the toner image separation development nip to a potential sufficient to cause air breakdown selective recharging of the background areas of the layer of toner, thereby enabling the image areas of the layer of toner to be separated and developed as a color separation toner image onto the movable image bearing member, and the background areas thereof to remain on the photoreceptor. 
Xerox Corporation
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Chu-heng Weizhong
Liu Zhao