Method and apparatus of creating two-color images in a single pass

Abstract

Two-color images are created in a single pass by forming an electrostatic image having three levels of electrostatic potential, low, intermediate and high. Toner of a first color is applied to the image in the presence of an electric field urging the toner toward one of the levels of potential. A second toner is applied to the electrostatic image having a second color, but of the same polarity as the first toner, in the presence of a second electric field urging the second toner both toward the areas that have been toned by the first toner and toward one of the other levels of potential. If the first toner is of a dark color and is used for text and the second color is the light color used for highlighting, a quality two-color image can be made in a single pass using toners of the same polarity.

Dependencies are inferred from the claim text.