US3647286A

US3647286A - Reproduction apparatus using photovoltaic material

Info

Publication number: US3647286A
Application number: US797729A
Authority: US
Inventors: John H Delorme Jr
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-02-10
Filing date: 1969-02-10
Publication date: 1972-03-07
Anticipated expiration: 1989-03-07
Also published as: FR2030959A5; DE1963882A1; CA933584A; GB1297144A; DE1963882B2

Abstract

Apparatus for the reproduction of visual images which uses a layer of photovoltaic material deposited on a substrate in such a way as to substantially increase the voltage produced when exposed to light according the pattern of an image to be reproduced so that no external charging voltage is required. The application of a toner to the material develops the image which may then be transferred to a copy sheet to reproduce the image. After discharge, either naturally by the passage of time or intentionally, the material may be exposed once again to permit the reproduction of a new image.

Description

l Umted States Patent [151 3,647,286

Delorme, Jr. 1 Mar. 7, 1972 [54] REPRODUCTION APPARATUS USING 2,990,280 6/1961 Giaimo ..355/1 7 X PHOTOVOLTAIC MATERIAL 3,185,051 5/1965 Goffe ..355/3 3,199,086 8/1965 Ka11mann.... 355/17 X [72] lnventor: John H. Delorme, Jr., 6826 North Wayne, 3 226 253 12/19 5 gobrechtw 1 7 0 X ChICag 60 6 3,254,998 6/ 1966 Schwertz ..355/ 17 [22] Filed: ML 10 1969 3,498,835 3/1970 Chiang ..1 17/107 X [21] App1.No.: 797,729 Primary ExaminerJohn M. l-loran Assistant Examiner-Monroe H. Hayes 52 us. Cl ..3ss/17, 96/1 Hersh and 1 III. [58] Field olSeareh ..355/3, 17;96/1, 1 A, 1 PC; l

' 117/106 R 07 .Apparatus for the reproduction of visual images which uses a layer of photovoltaic material deposited on a substrate in such 56] R f e Cited a way as to substantially increase the voltage produced .when

exposed to light according the pattern of an image to be UNITED STATES PATENTS reproduced so that no external charging voltage is required. The application of a toner to the material develops the image 2,453,763 11/1948 Smith ..117/106 X which may then be transferred to a copy She?t to reproduce 258L460 H1952 Vangeen'" ""117/106 the image. After discharge, either naturally by the passage of 2'624'652 H1953 i "355/17 X time or intentionally, the material may be exposed once again 2,654,853 10/ 1953 We1mer.... ..l 17/ 107 UX to permit the reproduction ofa new image 2,829,025 4/1958 Clemens ..355/3 X 7 2,860,221 Kohl ..1 17/107 2 Claims, 5 Drawing Figures REPRODUCTION APPARATUS USING PHOTOVOLTAIC MATERIAL BACKGROUND OF THE INVENTION development in recent years. The processes and apparatus in use to date have used photoconductive materials which are charged in an overall pattern by corona discharge from an electrostatic source. Thereafter the charge is destroyed or removed from portions exposed to light through or reflected from animage such as the original copyof a document to leave a latent electrostatic image can be transferred to a copy sheet brought into surface contact with the developed image by reversal of the electrostatic charge or by'providing a copy material having an adhesive coat.

Other approaches in this art. have involved the use of photosensitive materials which, while they do not require the surface of the material to be charged as by the use of a corona, but nevertheless still require the provision of a voltage source in order to produce latent electrostatic images when the material is imaged by selective radiation.

The necessity for a voltage source to charge a surface or produce selective polarization of the photosensitive material when it is exposed to light introduces an expense and structural complications in apparatus built for these purposes. Furthermore, it restricts the use of such apparatus to essentially stationary equipment thus precluding the use of electrostatic copying process in hand and other portable cameras.

Therefore it is an object of this invention to provide a novel electrostatic method of and apparatus for the reproduction of images which does not require a voltage source to charge or otherwise condition a photosensitive material and consequently is relatively simple in its construction and may be utilized in relatively portable systems.

These and other objects are achieved by the use of a photovoltaic material deposited on a substrate in such a way that repetitive faults or discontinuities appear therein, providing means for exposing the surface to transmitted or reflected light from an imageto be reproduced and then developing and transferring the latent electrostatic image formed on the surface of the material.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and advantages of this invention will hereinafter appear and, for purposes of illustration but not of limitation, embodiments of the invention are described and shown in the accompanying drawings in which:

.FIG. 1 is a diagrammatic illustration-showing how suitable photovoltaic material may be deposited on substrate for use in the invention;

FIG. 2 is a diagrammatic illustration of apparatus embodying the invention effective to carry out one of the steps thereof;

FIG. 3 is a diagrammatic illustration of apparatus embodying the invention effective to carry out another of the steps thereof;

FIG. 4 is an illustration of the manner in which still another step of the invention may be carried out; and

FIG. 5 is an illustration of the reproduction of an image using the method and apparatus of the invention.

Photovoltaic materials are those which generate an electromotive force where their surface is exposed to illumination. This phenomenon has been known for some time. However, the voltages generated have been, until relatively recently, quite small so that the use of such materials has been limited. The low values of voltage available has been due in large part to the method of fabricating such surfaces. However it is now known that if a material capable of photovoltaic activity is deposited on a substrate when the substrate is in a plane maintained at an angle with a line passing through a source of the material in an evaporator the available voltage can be increased significantly. Descriptions of techniques and analyses of the result of the method of photovoltaic material are to be found in the following articles: High Photovoltages in Cadmium Sulfide Films by Brandhorst et al.; NASA Technical Note D-3447, Acquisition No. N66-23455, April, 1966; Unusual Photovoltages in Evaporated Layers of Germanium by Kallmann et al.; ACTA Physica Polonica, Vol. 25, pp. 67l-678, 1964, High Photovoltages in Silicon and Silicon Carbide Films and Their Origin from a Trap-Induced Space Charge by Brandhorst et al.; Journal of Applied Physics, Vol. 35, No. 7, pp. 1997-2003, July, 1964.

A summary of the contents of these publications teaches the deposition of a suitable material such as germanium, silicon, silicon carbide, cadmium sulfide, and others may take place when a source of suitable material is provided in a crucible to be heated in a vacuum and disposed beneath a substrate material. A metallic shield is interposed between the source and the substrate to control material.

This is illustrated in FIG. 1 wherein a crucible 2 holding a source of suitable material is disposed beneath a metallic shield 4 having an opening 6 therein. A substrate 8, which may be of a metallic or conducting material, is maintained so that its centerline I0 is at an angle 6 to a line 12 extending perpendicularly through the crucible 2. The above-cited articles present values for the vacuum which should be maintained and show a range of 10 to I0 torr. The thickness of the deposited layer may vary from 0.5 to 50 microns, and it may have a resistivity greater than l0 ohm/cm. The angle between the plane of the substrate and a line through the crucible will vary depending on the material used and may vary from l0 to 60". It should be noted that in order to achieve voltages higher than those of the band gap of the material the deposition should not take place at right angles. This is because, in accordance with one theory of explanation, deposition at an angle results in the material being deposited with repetitive stacking faults" or as though it were a large number of individual crystals rather than one single crystal.

In addition to the materials noted above and in the referenced articles a wide variety of materials capable of photovoltaic activity may be used. These would include ZnS, ZnSe, ZnTe, CdSe, CdTc, Sb, SbS, SbTe, Se, Bi, BiS, and BiTe.

A process and apparatus for the reproduction of images using photovoltaic materials is illustrated in FIGS. 2 through 4. These illustrations are diagrammatic, for it is clear that a large number of variations in the particular apparatus used are possible and the particular ones selected are well within the choice of designers working within this field.

In FIG. 2 a layer 14 of photovoltaic material has been deposited on the substrate 8 in accordance with the process described so as to constitute an exposure plate which may be positioned by any desirable means suitably spaced from an original the image of which is to be reproduced. The original 16 may'take the form of a document bearing text material, photographs, drawings, or the like. It should be understood that it is considered within the scope of invention disclosed the original may be a three-dimensional object so that the process and apparatus may be used in what are considered devices of the class of cameras.

Regardless of the form of the original 16 it will include relatively dark areas and relatively light areas indicated by reference numerals l8 and 20, respectively. Visible light may be provided by sources 22 which when activated will provide a source of light to be reflected from the original I6. The reflected light is focused by a suitable optical system, including lenses and represented diagrammatically by the lens at that a corresponding area 26 on the surface of the layer 14 will develop little or no voltage while the relatively light areas will reflect greater light and the corresponding area 28 on the surface of layer 14 will develop greater voltages. As may be seen in the referenced articles the voltages developed are negative; i.e., the voltage at the surface which is that portion of the layer closest to the material source during formation of the layer are negative with respect to the material adjacent the substrate. Thus in the embodiment of FIG. 2 the areas 26 will be positive with respect to areas 28.

By further reference to the articles cited, if the light is removed a certain amount of time will be required for the generated voltages to be discharged for they will decay exponentially over a period of at least on the order of ten seconds or more.

During this period where the voltage appears on the surface of the layer 14 that latent electrostatic image of the original that has been created may be developed to present a visible image that can be transferred or otherwise caused to be printed on suitable copy paper.

The developing phase is effected by the apparatus of FIG. 3 showing a source 32 of charged electroscopic or toner material from which the surface of the layer 14 is dusted or coated. If it is desired to produce a positive image the toner material selected will be positively charged so that upon its application to the surface it will be attracted to the negatively charged portions of the surface. Alternatively if a negative is desired a negatively charged toner would be used.

In order to reproduce the image on a copy sheet for use, such a sheet 34 coated with adhesive material may be brought into contact the now developed surface of the layer 14 to transfer the image formed by the toner pattern to the copy sheet. HO. 5 illustrates a copy of an original appearing on a copy sheet 34.

As has been set out above it is contemplated that a large number of variations in the specific apparatus are using those elements well known in the art of electrostatic copying. For instance, the surface 14 could be formed on a drum shaped substrate and rotate from exposure to developing and then to printing positions. Other variations in the apparatus include depositing the photovoltaic material on a conductive web substrate and move it to exposing, and developing positions to produce a negative which could be severed from the web and used in other equipment as a master.

Thus it will be understood that any number of changes may be made in the details of construction, arrangement, and operation without departing from the spirit of the invention, especially as defined in the following claims.

What I claim and desire to secure by Letters Patent of the United States is:

1. Apparatus for reproducing visual images comprising: a substrate; a layer of photovoltaic material on said substrate having repetitive stacking faults therein; means for projecting an image to be reproduced onto said material to expose said material to a light pattern of the image thereby to produce a voltage pattern on said material conforming to the image; and means for applying a developing substance to said material whereby said substance assumes a pattern conforming to the voltage pattern.

UNITED STATES PATENT OFFICE v p CERTIFICATE CORRECTION Patent No. 3,647,286 Dated March 7, 1972' Inventor(s) John H. DeLorme, 'Jr I I 7 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Columh 1, line 17, after "image" insert --which can be developed by a suitable pigment powderor toner. The

toneron the developed image-.

Signed and sealed this 22nd day of August 1972.

" (SEAL) Auoest;

EDWARD M FLETCHER JR ROBERT GOTTSCHALK Attest ins Off icer Commissioner. of Pat ent s FORM PO-1050 (10-69) co 0375-p5 u.s. GOVERNMENT PRINTING orncz: was 0-366-334 UNITED STATES PATENT FFTQE v CERTIFICATE OF CORREQTION Patent No. 3,647,286 Dated March 7, 1972 Inventor(s) John H. DeLorme, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 17, after "image" insert --which can be developed by a suitable pigment powderor toner. The

toner on the developed image-.

Signed and sealed this 22nd day of August 1972.

(SEAL) At t eSt: I

EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK N Commissioner, of Patents:

Attesting Officer FORM PO-105O (10-69) co c 60375-1369 2' u.5 GOVERNMENT PRINTING OFFICE: I969 0-366-334

Claims

2. The apparatus of claim 1 including means for transferring the image formed by the developing substance to a copy material.