Abstract: A bimodal electrophotographic apparatus and process which incorporates capabilities for making both positive and reversal copies. One surface of a layer of a zinc oxide coated paper, or the like, is given an initial electrostatic charge. The charged surface is then exposed to an image having light and dark areas for causing surface charge to dissipate, in varying degree depending on the amount of light striking the charged paper, in the exposure areas. A charged toner is applied to the zinc-oxide-coated paper by a magnetic brush. In the reversal mode, the brush has a bias potential. The brush is formed by an aggregation of magnetic toner particles clinging to the outside of a cylindrical sleeve while magnets inside the sleeve rotate. The toner collects on the paper to form an image depending upon where the charge is dissipated.

Abstract: A bimodal electrophotographic apparatus and process which incorporates capabilities for making both positive and reversal copies. One surface of a layer of a zinc oxide coated paper, or the like, is given an initial electrostatic charge. The charged surface is then exposed to an image having light and dark areas for causing surface charge to dissipate, in varying degree depending on the amount of light striking the charged paper, in the exposure areas. A charged toner is applied to the zinc-oxide-coated paper by a magnetic brush. In the reversal mode, the brush has a bias potential. The brush is formed by an aggregation of magnetic toner particles clinging to the outside of a cylindrical sleeve while magnets inside the sleeve rotate. The toner collects on the paper to form an image depending upon where the charge is dissipated.