Single pass digital printer with black, white and 2-color capability

摘要

Method and apparatus for printing toner images in black and at least two highlighting colors in a single pass of the imaging surface through the processing areas of the printing apparatus. Imaging and development techniques of color photography and tri-level xerography are combined to produce images with black and two colors wherein the two highlighting colors are developed with only one color toner. A single imaging step forms a four level charge pattern on a charge retentive surface followed by development of two of the image levels using tri-level imaging techniques. Uniform exposure of the imaging surface, similar to that used to color photography techniques precedes development of the last image. The uniform exposure modifies the last developed image level and the background charge level allowing development of the last image with a single toner.