LIQUID CRYSTAL MASK
Original Publication Date: 1980-Feb-29
Included in the Prior Art Database: 2004-Apr-02
Xerox Disclosure Journal
In an electrophotographic printing machine, it is frequently necessary to discharge selected portions of the charged photoreceptor so as to minimize the amount of developer material utilized. The portions discharged generally are. outside of the image areas. For example, the charge between successive images as well as the side marginal regions extending outwardly from the images should be discharged. In addition, it is frequently desirable to erase any residual charge remaining on the photoreceptor prior to cleaning. In order to optimize transfer, it may also be desirable to reduce the charge level causing the toner particles to adhere to the photoreceptor. All of the foregoing may be achieved by illuminating the charged photoreceptor. Hereinbefore, several light sources have been utilized to achieve the foregoing. Each light source has at its light waves shaped so as to illuminate a selected portion of the photoreceptor. In lieu of the foregoing, a single light source may be used in conjunction with a liquid crystal plate. Selective excitation of the liquid crystal plate causes portions thereof to become opaque with the remaining portions thereof remaining transparent. Thus, the light rays transmitted through the liquid crystal plate may be shaped to illuminated, selected portions of the photoreceptor. In this way, the edges or inter-image areas may be readily discharged. Alternatively, the transfer area or the entire photoreceptor surface may be illuminated prior to cleaning.