Electrostatic multicolor composite printing method and apparatus

Abstract

A printing method and apparatus in which an elongate substrate such as a strip of paper, fabric, synthetic resin sheeting, foil or the like is imprinted with a plurality of patterns in different colors to achieve a composite multicolored image. The apparatus has multiple independent stations through which the substrate is passed, each station having a master sleeve with an image in semipermanent fixed primary toner formed thereon. The image is transferred to the substrate directly from the sleeve or by way of an intermediate transfer roll or blanket as in offset printing. The master sleeve is charged in light, the toned parts retaining charge by virtue of being dielectric in character, the now charged image is toned with a suitable pigmented secondary toner and this double toned image is pressed against the passing substrate or brought very close to it either directly or through the transfer medium. Through the aid of an electrical field established between the substrate and the sleeve or transfer medium the toner is transferred to the substrate and the sleeve and medium circulate back to pass through the same process of charge, tone and transfer. The transferred images on the substrate are fixed between or during movement through stations. Information on image density may be fed back to the same or previous stations for change in the bias field conditions or other parameters.