Traditionally, xerographic processes utilize toner charged to a single polarity (either positive or negative) in combination with an image-wise electrostatic field to develop a toner image. We present Reverse Charge Printing (RCP), a novel image development method and apparatus, whereby an image-wise charged toner layer along with a DC electrostatic field is used to produce a high quality toner image. The high resolution image-wise toner charging is accomplished by a wide beam ion source such that free mobile ions are introduced in the vicinity of an electrostatic latent image coated with a layer of developing material. The latent image causes the free mobile ions to flow in an image-wise stream corresponding to the latent image, which, in turn, leads to image-wise charging of the toner layer through ion bombardment, such that the toner layer itself becomes the latent image carrier. The latent image carrying toner layer is subsequently developed and transferred to a copy substrate to produce an output document. A liquid toner system embodiment of this process, Electro-Offset, is presented. This new electrostatic printing system can potentially enable an offset-like electrostatic printing system with characteristics such as very high resolution, high process speed as well as excellent extensibility to greater document width.
Chu-heng Liu, Weizhong Zhao, "Development with Image-wise Charged Toner Layer" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP15), 1999, pp 627 - 630, https://doi.org/10.2352/ISSN.2169-4451.1999.15.1.art00064_2