Phosphor Type Photoconductive Coatings for Continuous Tone Electro-Optical Photography

摘要

Electrophotography is a pictorial process whereby images are obtained through the medium of supplying a photoconductive surface with electrons in the dark and discharging this photoconductive surface preferentially on exposure to light. The image is fixed by dusting the surface of such a plate with electrostatically charged particles which attach themselves preferentially to the surface depending on the nature of the charges remaining on the plate, and then removing powder in image form either by electrostatics or by offset means. It has been found that electro-optical photographs can be made using commercially available phosphors as the sensitive surface. Phosphors most suitable for the application are the sulfide family, primarily of the zinc, cadmium, sulfide types. The chief drawback to the use of phosphors of these chemical families for the photoconductive sensitive surface is that the photographic speed obtained through use of such materials is extremely low, being of the order of 1 A.S.A. or less. Deductive investigation has indicated that a phosphor-like material composed substantially of properly treated cadmium sulfide will exhibit speeds markedly greater than that of the zinc-sulfide types. (Author)