1. US6011944 - Printhead structure for improved dot size control in direct electrostatic image recording devices

A printhead structure for a direct electrostatic printing device selectively conveys a stream of charged toner particles from a particle source directly onto an image receiving substrate. The printhead structure includes an electrode plate having openings which surround the apertures. A voltage applied to the electrode plate causes a converging electric field to applied to the toner particles passing through the apertures. The converging electric field causes the toner particles to converge toward respective central axes of the apertures to thereby focus the stream of toner particles. The focusing of the toner particles considerably reduces the dot sizes on the printed image. The use of the printhead structure results in increased print resolution and improved image quality.