Apparatus for creating an electrostatic latent image by charge modulation

Claim 1

Electrostatic photocopy apparatus comprising, in combination: A. a photoconductive insulating member; B. a non-photoconductive insulating film; C. means mounting said member and said film for movement into and out of juxtaposition; D. a first corona charging unit for depositing a uniform electrostatic charge on the surface of said photoconductive member prior to its movement into juxtaposition with said film; E. an imaging station for projecting an optical image on said photoconductive member while in juxtaposition with said insulating film, whereby to produce a first electrostatic latent image on the surface of said photoconductive member; F. a second corona charging unit stationed beyond said imaging station in the direction of movement of said juxtaposed photoconductive member and insulating film, said second corona charging unit having 1 a grounded grid, and 2 corona charging wires excited from an AC source, 3 the deposition of charges being modulated by said first electrostatic latent image so as to deposit on the insulating film surface a charge pattern effective to create a zero electrostatic potential plane at the insulating film surface, and G. means beyond said second corona charging unit in the direction of movement of said juxtaposed photoconductive member and insulating film for rendering said charge pattern effective as a developable second electrostatic latent image corresponding to said first electrostatic latent image, said means including 1 a light source for flooding said photoconductive member, and 2 a development station located beyond said light source in the direction of movement of said juxtaposed photoconductive member and insulating film for depositing electroscopic toner particles on said exposed film surface to visibly develop said second electrostatic latent image.