US 3925571 A
In a method for producing a charge carrier plate or foil having a non-conducting selenium layer for xerography, the selenium is deposited onto a carrier plate by evaporation in vacuum with a deposition rate of about 0.5 microns per minute.
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Description (OCR text may contain errors)
United States Patent Esser et a1. Dec. 9, 1975 METHOD OF MAKING A SELENIUM 2,962,376 11/1960 Schaffert 96/15 CHARGE CARRIER PLATE 3,226,253 12/1965 Gobrecht H 117/201 I 3,234,020 2/1966 Stockdale 96/115 1 Inventors: Karl Esser, Stem; John E. Segam, 3,467,548 9/1969 Straughan 117/106 R Gunzenhausen, both of Germany 3,598,644 8/1971 Goffe et a] 4 96/15  Assignee: International Standard Electric 5 et 961m ork 117/216 Corporatmm New York 3,652,330 3/1972 Anderson 117/201 22 Filed: Feb 1 1974 3,709,683 [/1973 Cuiffini et a1 96/15 3,775,109 11/1973 Ohta et a1 96/15 21 A 1. N 438,831 1 pp 0 FOREIGN PATENTS OR APPLICATIONS 912,837 12/1962 U 't d K' d 96/18  Foreign Application Priority Data m e mg 0m Feb. 8, 1973 Germany 2306157 Primary Examiner cameron K. Weiffenbach Attorney, Agent, or F1'rm.lohn T, OHalloran;  US. Cl. 427/76; 427/122; 427/248; Menom Lombardi, JR; Vincent lngrassia 427/372; 427/427; 96/15  Int. C13. B44D 1/18 581 Field 61 Search 96/15; 117/201, 216, 215, [5-7] ABSHLCT 11 427/76 122v 248, 372, 427 In a method for producing a charge carrier plate or foil having a non-conducting selenium layer for xerog-  References Cited raphy, the selenium is deposited onto a carrier plate UNITED STATES PATENTS by evaporation in vacuum with a deposition rate of about 0.5 microns per minute. 2,739,079 3/1956 Keck H 117/201 2,753,278 7/1956 Bixby et a], .4 117/106 R 7 Claims, N0 Drawings METHOD OF MAKING A SELENIUM CHARGE CARRIER PLATE BACKGROUND OF THE INVENTION The present invention relates to a process of preparing a selenium charge carrier plate or foil wherein a non-conductive layer of selenium is evaporated onto a metal foil.
According to the known xerographic processes, an image can be produced in that an image plate or drum coated with a photoconductive selenium layer, is charged to an electric potential and, by exposure, there is formed a charge distribution corresponding to the image pattern. The image is made visible by means of a non-conductive electroscopic powder. This powder image is then transferred to a paper tape, and fixed thereon.
As a support member for the photoconductive selenium layer, it is also known to use, instead of an image plate or drum, a flexible, tape-type metal foil. This reduces the size of the known electro-photographic copying machines operating according to this process.
As a rule, the selenium layer is deposited by evaporating the selenium under vacuum, and by condensing the vapor on the cold metal surface of the image plate or drum or foil respectively. The temperature of this cold surface is usually kept below 50 C. In order to subject as much of the surface a possible to evaporation during the time unit, evaporation speed has up to now always been kept at a high deposition rate.
The inventive process is particularly suitable for charge carrier foils.
However, care must be taken to provide sufficient adhesion of the selenium layer which is relatively brittle, because the carrier foil is led in the copying machine around transport rollers and is bent in accordance with the diameter thereof. For this purpose, there is provided an intermediate layer which does not impair the electrical and imaging properties of the selenium layer. This is accomplished by spraying a conductive layer of lacquer onto the metal foil in a dust-free room, which layer serves as the intermediate layer. This layer of lacquer consists of polyvinylacetal as the base material, to which there is added a portion of lampblack for increasing the conductivity, and which also contains ethyl acetal and methanol as non-conductive solvents. Since the surroundings are dust free, the surface of the layer of lacquer is very plane. This layer is preferably deposited onto the metal foil in a thickness of l to 2 microns, and has a conductivity of about 1.5 siemens when containing a lampblack component of about Thereafter, the coated foil is tempered, i.e. is held in a heat furnace at a temperature of 150 C for a period of about 8 hours. Prior to this tempering heating process and the subsequent cooling, the layer of lacquer is polished by the application of pressure, in order to further improve the smooth surface finish.
SUMMARY OF THE INVENTION It is an object of the present invention to improve the electrophotographic imaging quality of the selenium layer, especially with respect to its richness in contrast.
According to a broad aspect of the invention, there is provided an improved method of preparing a selenium charge carrier plate wherein a non-conducting layer of selenium is evaporated onto a metal substrate wherein the improvement comprises evaporating said selenium at a deposition rate of approximately 0.5 microns per minute.
The above and other objects of the invention will be better understood from the following detailed description.
DESCRIPTION OF THE PREFERRED EMBODIMENT The selenium is evaporated onto a metal surface of a layer support member to a thickness of about 60 microns under a pressure not exceeding about 10- torr (mm Hg) at a deposition rate of about 0.5 microns per minute. The temperature of the metal backing member during the evaporation process is kept constant at about 60 C. For avoiding crystallization of the selenium layer, approximately 0.5 per cent by weight of arsenic is added to the layer of selenium during evaporation of the selenium.
'By the reduction of the deposition rate, it is possible to achieve substantially higher electric charge potentials, as well as considerably improved properties with respect to the dark discharge of the selenium layer.
It is to be understood that the foregoing description of specific examples of this invention is made by way of example only and is not to be considered as a limiation on its scope.
1. An improved method of preparing a selenium charge carrier foil for use in a copying machine wherein a non-conducting layer of selenium is evaporated onto a metal substrate wherein the improvement comprises:
spraying a layer of conductive lacquer onto a flexible charge carrier metal foil; and
evaporating a non-conducting layer of selenium onto said layer of conductive lacquer at a deposition rate of approximately 0.5 microns per minute.
2. An improved method of preparing a selenium charge carrier foil according to claim I, wherein said selenium is evaporated under a pressure less than 10 torr (mm Hg).
3. An improved method of preparing a selenium charge carrier foil according to claim 1, wherein said metal substrate is kept at a temperature of substantially 60C during evaporation.
4. An improved method of preparing a selenium charge carrier foil according to claim 1, wherein said selenium layer is approximately 60 microns thick.
5. An improved method of preparing a selenium charge carrier foil according to claim 1, wherein said layer of conducting lacquer consists of polyvinylacetal as a base material containing the additive lampblack for increasing conductivity.
6. An improved method of preparing a selenium charge carrier foil according to claim 1, wherein said metal foil has a thickness of l to 2 microns.
7. An improved method of preparing a selenium charge carrier foil according to claim 6, further including the step of tempering the coated foil.