Development of electrostatic images

Abstract

Abstract Improved development of electrostatic images having features such as broad solid fill, continuous tone or low contrast is obtained by a two step process involving overdevelopment followed by selective cleaning. The overdevelopment is accomplished through the use of a development electrode that is either grounded or is biased to a polarity opposite to the polarity of the electrostatic image so as to enhance the deposition of toner onto the electrostatic image by creating an erected, unidirectional development field. This development field places toner uniformly on solid areas, proportionally on gray areas, in large amounts on low contrast image areas and also generally on background areas. The thus overdeveloped image is removed from the development field thereby establishing a bi-directional imaging clearing field that is directed toward desired image areas and away from background areas. A selective cleaning system such as a cascade of electrostatically attractive particles, is passed over the overdeveloped image in the presence of the image clearing field to selectively remove toner from background areas without equally removing toner from the image areas.

Inventors

• 👤 R Berlier
• 👤 R Ritchie

Bibliographic Details