DE1804014A1 - Semi-conductor arrangement for electro photography - Google Patents

Abstract

Electro-photographic recording material comprises an insulator layer, a p-semiconductor, a n-semiconductor and a metal electrode. The insulator is charged by an alternating current corona discharge, surface is imagewise exposed and discharged with corona electrode of opposite polarity or alternating current, when surface charge disappears in light parts and remains in dark parts. The latent image is then fast to light and can be developed by known methods in light.

Description

Method and arrangement for generating latent, electrostatic Charge images for electrophotographic purposes The known methods of generation of latent, electrostatic charge images for electrophotographic purposes use photo semiconductors, which behave practically like insulators in the dark, but become electrically conductive when exposed to light.

The discovery is based on the knowledge that with the help of a the well-known photogenerator similar semiconductor arrangement electrophotrgraphic, can generate latent charge images that are no longer photosensitive after their generation are, and gives as a new process for the generation of latent, electrostatic charge images For electrophotographic purposes according to the invention that an arrangement is used which consists of a layer sequence of insulator - p-semiconductor -n-semiconductor - metal electrode, or Isolatcr - n-semiconductor -p-semiconductor - metal electrode, that consists of the insulator surface of this arrangement initially averages a direct current corona discharge evenly is charged, that the surface is then darkened imagewise and that during polarized opposite to the image-wise darkening with a polarity opposite to the discharge polarity Corona discharge or an alternating current discharge is discharged imagewise.

The principle of the invention is outlined in the drawing. On the Metal electrode 1 is a layer made of an n-semiconductor (or p-semiconductor) 2. This is followed by a layer made of a p-semiconductor (or n-semiconductor) 3 and finally an insulator layer 4.

Such a sequence of layers can be z. B. produce that if a metal electrode (e.g. cadmium electrode) is vaporized with selenium, the whole thing tempered below the melting point with selenium until the selenium in the p-conducting, crystalline State has passed and there is an n-type metal selenide layer (Cadmium selenide layer) formed between the metal (cadmium) and selenium layers Has. Finally the exposed selenium surface is covered with an insulating layer from an epoxy resin 'covered a polyester or a polyurethane.

The above indicated use of crystalline selenium in an array for carrying out the method according to the invention should not be confused with Use of amorphous, glassy selenium in the known electrophotographic processes.

The properties of both selenium modifications are completely different from each other. Crystalline selenium is a p-semiconductor even in the dark, while amorphous Selenium only shows a certain conductivity when exposed to light.

One proceeds to the generation of the latent charge image according to the invention Proceed as follows: The insulator surface is with the help of a: corona electrode evenly charged. This can be compared to the known processes happen.

Men charges positively. if the p-semiconductor is on the insulator layer is negative if the n-semiconductor is arranged there. The opposite pole of the high voltage source lies on the metal electrode.

Then a positive image, which consists of a light-dark structure, projected onto the isolator surface.

While the image exists, a corona electrode is passed over it the insulator surface, with the discharge polarity opposite to the charge polarity or an AC discharge is used. The surface charge disappears at the bright spots of the superimposed on the discharge, on the insulator surface projected image and remains in the dark places.

The resulting, latent charge image is after switching off the discharge light-resistant and can be developed according to the known methods of electrophotography and transmitted.

The electrophotographic effect of the present invention can thus be interpreted that the insulating layer initially plays the role of the dielectric of a capacitor takes over. On the semiconductor side, the charge is dissociated from Defects, but not embodied by free charge carriers.

The discharge of the capacitor is only possible if one is on both Side of the dielectric neutralizes the charge at the same time. On the one hand - the neutralization is effected by the photogenerator in the places where there is light through the Insulator layer falls into the pn-U path; on the other On the other hand, the neutralization takes place via the discharge of the corona.

The discharge corona remains ineffective in the dark places, there no charge carriers from the phctogenerator are available here. Changes in the latent charge image are therefore only possible if the exposure results in a discharge X is overlaid.

Claims (1)

Claim Method and arrangement for generating latent, electrostatic Charge images for electrophotographic purposes, d u e h e k e n n -z e i c h n e t that an arrangement is used which consists of a sequence of layers: insulator - p-semiconductors - n-semiconductors - metal electrodes or insulators -n-semiconductors - p-semiconductors - Metal electrode, that consists of the insulator surface of this arrangement initially by means of a direct current corona discharge that the surface is charged evenly is then darkened image-wise, and that during the image-wise darkening with a corona discharge with opposite polarity to the discharge polarity or an alternating current discharge is discharged image-wise.