Abstract
This paper introduces a group of printing technologies which make surface charge image by ion projection. Histories and achievements of the following three major technologies are described : 1) Ionography process which use individual AC discharger for each dot;heavy duty high speed printing is its specialty utilizing toughness of dielectric imaging drum that enables simultaneous image transferring/fixing with pressure roller, 2) Ion flow process which use a common corona discharger and individual ion control apertures;its specialty is continuous tone reproduction at each dot, 3) Retention process which use photoconductor screen for ion controlling;its specialty is high speed duplication utilizing image memory function of the screen. The reasons why the three technologies have not been popularized are also mentioned. One of the major reasons must be related with the history that digital printing technologies have defeated analog printing technologies by using strong tools of mass storage image memories and advanced digital half toning methods.
