Three electrode system in the generation of electrostatic images
AssigneeDennison Manufacturing Company
InventorJeffrey J. Carrish
Life of this patent
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Abstract
Generation of charged particles by extracting them from a high density source provided by an electrical gas breakdown in an electrical field between two conducting electrodes separated by a solid insulator, subject to the influence of a third electrode. The ions are generated by a high frequency alternating potential between a "driver" electrode and a "control" electrode. The ions are employed in charging a dielectric member to form a latent electrostatic charge image. A "screen" electrode between the control electrode and dielectric member isolates the potential on the dielectric member from the ion generating means, and provides an electrostatic lensing action.
Claims16
An improved method for generating electrostatic images by means of an ion generating assembly of the type in which an alternating potential is applied between a "driver" electrode substantially in contact with one side of a solid dielectric member and a "control" electrode substantially in contact with an opposite side of the solid dielectric member, said control electrode having an edge surface disposed opposite said driver electrode to define an air region at the junction of the edge surface and the solid dielectric member, to induce ion producing electrical discharges in the air region between the solid dielectric member and the edge surface of the control electrode, and ions are extracted by an extraction potential V.sub.C between the control electrode and a further electrode member and these ions
- applied to a dielectric surface, in which the improvement comprises the steps of
- controlling the extraction of ions by
- providing an apertured "screen" electrode which is separated from the control electrode by an apertured solid dielectric member and which lies between the control electrode and the dielectric surface, and
- applying a "screen" voltage V.sub.S between the screen electrode and the further electrode member, wherein V.sub.S has a magnitude greater than or equal to zero and the same polarity as V.sub.C ;
- and
- forming an electrostatic image with the extracted ions.
Improved apparatus for generating electrostatic images of the type including a solid dielectric member, a "driver" electrode substantially in contact with one side of the solid dielectric member, a "control" electrode substantially in contact with an opposite side of the solid dielectric member, with an edge surface of said control electrode disposed opposite said driver electrode to define an air region at the junction of said edge surface and said solid dielectric member means for applying an alternating potential between said driver and control electrode of sufficient magnitude to induce ion producing electrical discharges in said air region between the solid dielectric member and the edge surface of the control electrode, and means for applying an ion extraction potential V.sub.C between the control electrode and a further electrode member to extract ions produced by the electrical discharges in said air region and apply these ions to a dielectric surface to form an electrostatic image thereon, in which the improvement comprises:
- a third electrode ("screen electrode");
- a solid dielectric layer separating said screen electrode from the control electrode and the solid dielectric member;
- and
- a source of "screen" voltage V.sub.S between the screen electrode and the further electrode member, wherein V.sub.S has a magnitude greater than or equal to zero and the same polarity as V.sub.C.
Dependencies are inferred from the claim text.