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Publication numberUS3575500 A
Publication typeGrant
Publication dateApr 20, 1971
Filing dateMar 16, 1966
Priority dateApr 6, 1965
Also published asDE1522688A1
Publication numberUS 3575500 A, US 3575500A, US-A-3575500, US3575500 A, US3575500A
InventorsBrown Felix H, Schlein Herbert N
Original AssigneeRahn Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Pip machine
US 3575500 A
Images(3)
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Description  (OCR text may contain errors)

United States Patent Inventors Herbert N. Schlein Beverly, Mass; Felix H. Brown, Okemos, Mich. Appl. No' 534,697 Filed Mar. 16, 1966 Patented Apr. 20, I971 Assignee Rahn Corporation Continuation-impart of application Ser. No. 445,910, Apr. 6, 1965, now abandoned.

PIP MACHINE 42 Claims, 8 Drawing Figs.

US. Cl. 355/3 Int. (I 603g 5/00 FieIdotSear-ch 355/3,16; 96/ I [56] References Cited UNITED STATES PATENTS 3,199,086 8/1965 Kallmann 340/ I 73 3,268,331 8/1966 Harper 96/1 3,356,831 12/1967 Andrus SSS/3X Primary Examiner-John M. Horan Att0rney-Burns, Doane, Benedict, Swecker & Mathis ABSTRACT: A copying machine whose operation utilizes the phenomenon known as persistent internal polarization." An image is impressed by exposing to an electric field during or after light exposure a photoconductive insulative body constructed so as to be capable of recording a latent image by persistent internal polarization. Development may be done by toner, and the developed image may be transferred to paper, as in xerographic reproduction.

PATEN TEU APR 20 197i 3; 5 75; 500

sum 1 OF 3 I INVENTORS HERBERT N. SCHLEIN y I FELIX H. BROWN ATTORNEYS PATEN-TED mm :91: 3 575 500 sum 2 or 3 I N VENTORS HERBERT N. SCHLEIN By FELIX H. BROWN ATTORNEYS PATENTED men IBYI SHEEI 3' OF 3 ERBERT N. S E H. BROWN ATTORNEYS INVENTORS CHLEIN PIP mourns This is a continuation-in-part of application Ser. No. 445,910, filed Apr. 6, 1965.

This invention relates in general to image forming processes and more particularly to a machine and methods for forming and reproducing images.

A typical prior art method and machine which has been useful for image transfer or reproduction is known as xerography. This process comprises the steps of spraying electric charges on the surface of a photoconductor by means of corona discharge. Following the establishment of the charge on the surface of the photoconductive layer, the image to be reproduced is formed on the layer by means of selectively discharging the charges from the surface. This selective discharge, which must be accomplished within a few moments of the establishment of the charge, occurs when the layer is exposed to light. This light causes the exposed areas of the layer to become photoconductive, pennitting a substantial leakage of surface charges through the layer to ground. Since the unexposed areas of the layer remain nonconductive, the charges on the surface of the unexposed areas remain in place.

Following this selective discharge of surface charges, there is deposited on the surface an electroscopic powder that assumes the form of the image through electrostatic attraction and that can be readily transferred from the surface to a sheet of suitable material, such as paper, and fused thereto.

Apparatus utilizing the above image forming technique have a number of drawbacks in that the photoconductive layer is expensive to produce and requires special preparation. Further, as is well known, the corona discharge establishing the surface charge requires DC voltages in the order of 6l0 kilovolts. Still further, such machines require 200 watt power supplies. Additionally, because the charges utilized in such an electrophotographic process are surface charges, the machines are humidity sensitive. That is, high humidity conditions can cause the surface charges to leak off prematurely or prevent the establishment of adequate surface charges. Furthermore, these machines cannot produce multiple copies from a single exposure. Moreover, these machines as presently sold have difficulty in obtaining continuous tone gradations, and thus do not provide quality photographic reproductions. Additionally, such machines because of inherent limitations in the electrophotographic process cannot be used to produce color images by simultaneously applying at least two different colors to the charge pattern.

The present invention avoids the above difficulties and disadvantages as presently found in such prior art machines and processes by providing a device which is capable of quality, continuous tone reproductions without requiring high voltages or expensive and difficult-to-produce materials.

Further, the present invention is insensitive to humidity and has the additional capability of producing multiple copies from a single exposure or producing color images by the simultaneous application of at least two different colored toners.

Furthermore, the present invention provides a device wherein latent images can be stored or retained for extended periods of time without substantial deterioration of the image.

Moreover, the present invention requires very small power supplies for operation and typically needs and uses only about 2 l0 watts, which is about 100,000 times smaller than is required on the prior art devices.

Still further, the resolution of the images provided by the present invention may be varied to meet the requirements of the use as distinguished from prior art devices whose resolution is fixed.

These and other features of the present invention are accomplished in a machine which exploits the phenomena known as persistent internal polarization." This phenomena hereinafter called PIP exists in certain photoconductive insulators dispersed in selected dielectric media and is produced by placing the loaded dielectric in an electric field during or after light exposure whereby an internal polarization is created.

The machine of the present invention establishes a persistent internal polarization in a photoconductive insulative body, by the application of an external electric field, and forms an image on the surface of the body by the selective modification of the PIP in the bulk of the material and surface deposition of a toner attractable to the charged areas. Following deposition of the toner on the body in the form of the image, the toner is transferred, if desired, to a medium such as paper and fused thereto. It may also be fixed to the phosphor layer.

Although to the casual observer there appears to be identity between the electrostatic phenomenon previously described and the phenomenon known as PIP, there are significant external differences and the underlying physical mechanisms are fundamentally dissimilar and distinct.

These differences and distinctions are what give rise to the advantages of the present invention enumerated above. These differences and the attendant advantages thereof when' employed by the present invention are fully discussed and explained below especially when considered in conjunction with the following drawings, wherein:

FIG. I is a schematic cross-sectional view of the machine utilizing the invention;

FIG. 2 is a cross-sectional view of the material utilized in the invention;

FIG. 3 is a greatly magnified view of a portion of the material of FIG. 2 when placed in condition for an image to be produced thereon;

FIG. 4 portrays one scheme for producing an image of the body of FIG. 2;

FIG. 4A describes the application of a toner to the body of FIG. 4;

FIG. 5 discloses an additional method of producing an image in the body of FIG. 2; and

FIG. 5A shows a method of applying multiple colors to the body depicted in FIG. 5;

FIG. 6 is a schematic cross-sectional view of another embodiment utilizing the invention.

, Throughout the several drawings, like reference numbers will be used to designate like components.

With reference now to the drawing and more particularly to FIG. I thereof, there is shown in schematic form a machine for producing dry printed reproductions embodying the present invention. For purposes of clarity, all structural detail of the machine has been omitted from the FIG. and can be readily supplied by the utilization of prior art techniques.

In the specific embodiment of the machine being described, there is on the surface of a large conductive drum 20 secured a multiplicity of plates 21 which are composed of a material exhibiting the phenomenon known as PIP and whose features and characteristics are more fully described in conjunction with FIG. 2.

Referring now to FIG. 2 which shows a cross-sectional view of one of the plates 21, it being understood that certain features of the material composing the plate 21 have been greatly enlarged for purposes of this description, it is seen to comprise photoconductive insulator particles 22 dispersed in a matrix 23 secured to the surface of drum 20 by any convenient method. For example, if desired, the mixture could be deposited on a sleeve of conductive paper which is then placed on the drum. It is preferable, but not necessary, in order to achieve better charging and erasure characteristics and to lengthen the life of the plates, that there be on the upper surface 24 of the plates 21 an insulative layer 25.

Materials found suitable for use as the photoconductive insulators which exhibit PIP are commercially available.

Such substances are, by way of example only, activated (Zn:Cd)S phosphors, alkali halides, anthracene, chrysene, and other inorganic or organic photoconductors which exhibit a high resistance when not illuminated. Improved materials found to be particularly suited for use as the photoconductive insulators and their method of making are illustrated in the following examples:

EXAMPLE I 100 grams of pigmentary ZnS sold under the name Sachtolith, were mixed with 0.0196 grams of CuSO -5H and 180 ml. of acetone and agitated for 2% hours, following which the acetone was allowed to evaporate off. The resultant dry mixture was then agitated 1 hour, following which it was fired in a quartz tube at 1 150 C. for 2 hours in a flowing atmosphere consisting of 570 cc./min. of N and 30 cc./min. of gases comprising 4 parts of H 8, 2 parts of HCl, and 1 part of H The mixture was then allowed to cool to room temperature and washed with a 5 percent aqueous solution of KCN. Following this washing step the material was allowed to dry and was then ball-milled for 1 hour.

EXAMPLE II A composition of 90 grams of ZnS, grams of CdS, 0.008 grams of AgNO and 0.203 grams of MnSO, was prepared as in Example I with the mixture being washed in a 5 percent aqueous solution of NIL in place of the 5 percent solution of KCN.

EXAMPLE III A composition was prepared as in Example I with 0.008 grams of AgNO and 0203 grams of MnCl being added to the original mixture of ZnS following the procedure of Example I with the final wash being a 5 percent aqueous solution of NH as in Example II.

Matrices found particularly suitable for suspension of the phosphors are cyclieized rubber, cellulose nitrate, polyvinyl acetate, acrylonitrile-butadiene-styrene terpolymer. styrenated alltyds, and polyvinylidine chloride-acrylonitrile copolymers. Any material having a resistivity greater than l0 ohm-cm. will be useful to a greater or lesser degree.

In order to produce the plates 21, a photoconductive insulator, such as zinc cadmium sulfide (ZnCd)S, and a binder, such as polyvinyl chloride-acrylonitrile, are selected and the insulator dispersed in the binder by well-known methods, at a preferred ratio of 16 parts photoconductive insulator to 1 part binder. It has been found that this ratio can be as low as 2 to l and as high as 24 to 1. After dispersing of the photoconductive insulator in the hinder, the mixture is deposited on the drum 20 by any convenient means, preferably in a layer 0.05 to 0.5 millimeters in thickness. Following deposition of the mixture, the layer is segmented into six portions, preferably 8% inches by l3 inches, and an insulative cover or layer is placed over and between the portions 21. This layer 25 preferably comprises one of the previously mentioned binders which utilizes a different solvent in order to prevent dissolution of the surface of plates 21. For example, since we assumed that the binder of FIG. 2 comprised polyvinyl chloride-acrylonitrile polymer whose solvent is methyl ethyl lretone, then the insulative layer should be a material such as butadiene-styrene-acrylonitrile terpolymer whose solvent is toluene. In any event, it has been found that the matrix 23 and the insulative layer 25 should have a volume resistivity of at least 10 ohmem. when in their pure state.

Station A of FIG. 1 shows one method of placing a plate 21, designated 21a, in condition for the impressment of an image. Shown coupled with the layer 25 is a NESA tube 26 whose length is equal to that of plate 21. This tube 26 is preferably of glass and has an elongated ribbon filament 27. On the surface of the tube 26 is deposited a thin transparent coating 28 of tin oxide. The tube 26 is designed to irradiate the body 21a with light and simultaneously apply an electric field across the body 21. To avoid wear of the NESA coating 28 and the plates, the lamp 26 need not be in intimate contact with the insulative layer 25. It has been found that a slight airgap, just sufficient to avoid frictional wear of the materials, may be provided between the surface of layer 25 and NESA coating 28. Another method of avoiding wear is to coat the NESA layer with one of the matrices previously described. Using the above-described mixture for the plate 21, the voltage applied to it should produce a field strength in the order of 1,000 to 15,000 volts/cm. in the PIP layer while the incident light intensity is in the range of 0.2 to 4,500 foot-candles. A voltage differential of from 220 to 3,000 volts may be applied between the drum 20 and the NESA coating 28 to produce the desired field. The exposure time of plate 21a is dependent not only on the intensity of the lamp 26 but also on the strength of the applied field. To illustrate: with an applied field of 3,000 volts/cm, a light intensity of 2,000 foot-candles need only be incident on the plate for 0.2 seconds.

To illustrate the effect of the voltage and irradiation of the body 21, we now refer simultaneously to FIG. 3 and FIG. 6. A power source such as battery 29 is connected between drum 20, and coating 28 on tube 26. Although the FIG. shows the battery 29 connected with its negative terminal to the drum 20 and its positive terminal to the coating 28, it being understood that the battery polarity can be reversed whereby resultant PIP polarities would also be reversed. When the filament 27 of lamp 26 is energized by a power source (not shown) light emitted from the filament passes through the walls of the tube, the coating 28 and insulative layer 25 into body 21.

When the irradiation from the lamp 26 passes into the body 21, free charges, such as electrons 30 and holes 31, are generated in the body 21 by the absorption of photons. Since the generated charges are more free to move when the body is irradiated, the movement of these charges will hereafter be known as photomobility." These charges migrate to a barrier or trap under the influence of the applied electric field. The electrons drift toward the positive electrode and the holes drift toward the negative or ground electrode. When the light and the field are both shut off, the photomobility rapidly decays, despite the coulombic attraction of the oppositely charged holes and electrons. Because of the peculiar property, known as PIP, most of these charges remain trapped. This trapping of the free charges causes the body to become electrically polarized with a net field being observable at the surface of the body.

The charges will, through thermal effects, eventually recombine. Although the average half-life of polarization of the material as described is about 4 hours, half-lives of nearly 2,000 hours have been recorded.

Since the matrix in conjunction with the photoconductive insulator must prevent the recombination of the created free charges for prolonged periods, it must have the property of retaining the free charges in separation or in other words prevent their recombination.

Since it is necessary to create a uniform free charge in the body 21a, the lamp 26 must be made to pass over the entire surface of the body. This can be accomplished in any convenient manner such as by having the lamp 26 effectively roll across the surface of plate 21a. In order to prevent the light or radiation from the lamp from impinging upon adjacent plate 21b or from disturbing the charge created in segment 21a, baffles (not shown) can be suitably placed around the lamp 26.

In addition to the method described above wherein the light and field were applied simultaneously to the body, it has also been found that the light alone may be applied to the plate 214, followed in time by the application of the electric field alone. That is, the light and field are applied sequentially instead of simultaneously. This sequential method will be more fully described later in connection with FIG. 6.

Once the entire body 21a has been irradiated and a uniform charge created therein, the body is suitable for the impressment of an image. Such an image is created when the drum 20 revolves to carry plate 210 to the next station.

It will now be assumed that the segment 21b positioned at station B has already been conditioned at station A. Station B consists of any convenient means of selectively illuminating portions of body 21 to modify portions of the uniform free charge established in the body. The means of doing this utilized at station B may be any of a number of well-known optical reproduction systems, such as a flying spot or line scanner. For the sake of convenience, this type of apparatus is depicted as lens 33 in FIG. 1, it being understood that such flying spot scanners, for example, are considerably more complicated. Further, for the sake of illustrationonly, the item being copied is depicted as arrow 34.

One manner in which the image is impressed upon body 21 can be more fully understood if we now refer simultaneously to FIG. 4. The optical apparatus 33 traces the image 34 and impinges illumination on a selected portion of the body 21. If a positive reproduction is desired, the entire body 21 would be irradiated with the sole exception of those portions corresponding to the image 34. If a negative reproduction is desired, the opposite is true. The irradiation of the previously treated plate 21b caused certain of the free charges to "be weakened, destroyed, or extinguished. The light intensities applied are in the same order of magnitude as those applied at station A.

Another manner in which the image can be impressed utilizes a transparent electrode between lens 33 and body 21!) to create a reversed charge pattern in the irradiated portions. Preferably, but not necessarily, this electrode should be in contact with the surface. The effect of such an electrode is more fully illustrated and understood when considered in conjunction with FIG. 5 which depicts a power source 36 being placed across an electrode 37 and drum 20. The power source 36 is illustrated as a battery whose 'positivetermina'l is connected to drum 20 and whose negative terminal is connected to electrode 37 since it has been assumed that the plate 21b has been previously energized in the manner shown in FIG. 3.

When the electrode 37 is arranged as described above and a field is impressed on plate 21b, PIP is reversed in those areas on which the radiation, passing through the lens 33 and the electrode 37, impinges. This reversal of the internal field occursbecause the trapped charges become mobile under the influence of light and drift towards the oppositely charged electrodes under the influence of the applied electric field which is the reverse of the field previously applied to the body. The charges not so irradiated do not becomemobile and thus remain in position. Simultaneously, the radiation creates new charges which also drift under the influence of the applied field. In this manner, a reversed charge pattern or enhanced image, corresponding to the image being impressed,-iscreated in the body. It .is noted that reversal of the PIP is actually a two-step process involving a discharge of the initial PIP and creation of a PIP of the opposite polarity.

When this field reversal technique is used, the exposure time can be shortened by a'factor of 10. When the same light intensities as described in conjunction with station A are used, for example, assuming :a field of 3,000 volts/cm. and an intensity of 2,000 foot-candles, the exposure time is reduced to less than 0.01 seconds. Reduction of the light intensities increases the required exposure. To illustrate: assuming a field strength of 3,000 volts/cm. with the intensity reduced, by a factor of IO, to 200 foot-candles, the exposure time increases to 0.02 seconds.

Utilization of the electrode as depicted in FIG. 5 not only reduces the time of exposure and/or the intensities required, but it can also effectively double the range of the latent image impressed on the body 21b to result in image amplification or enhancement. This image enhancement isespecially made use of when black and white toners are used together 'in the production of a single print. If we assume that a positive image is to be produced then'by using black toner on the image and 'using white toner on the background greater contrast will -be background.

lmpressment of an image can also be achieved more expeditiously than with depolarization by light alone by the application of light and a reverse field sequentially instead of simultaneously. This sequential method will be more fully described later in connection with FIG. 6. I

Following the impressment of the image on the plate 211;, the drum 20 revolves to move the plate to station C where there is provided means for depositing a fusible toner on the surface of body 21. A trough-shaped hopper 41 is suspended over the entire length of 21c and has a toner 42 disposed in the trough. This toner is dispensed from hopper 41 through openings 44 provided in the bottom thereof in conjunction with a revolving paddle wheel 43 disposed in trough 41 to assure that the toner 42 is evenly dispensed and sifted over the entire surface of plate 210.

Toners suitable for use at this station are well known and may be readily purchased. Solid toners may be, for example, a powder of .nigrosine dye impregnated polystyrene, mixed with iron powder as a carrier.

It is, of course, necessary that the solid toner so dispensed be capable of acquiring a static charge by the triboelectric effect and thus have a charge opposite to the effective charge remaining in body 21c near the surface on which the toner is being dispersed in order that the toner will be attracted to and held only on the portions of body still retaining a charge. Such depositing of toners on the body 21 is more fully depicted with reference to FIGS. 4A and 5A.

Referring first to FIG. 4A, there is shown a toner 45 deposited on the surface of a plate 21c which has been treated as shown in FIG. 4 where the production of the negative of the image 34 has been produced. The toner 45 would be selected to have a weakly positive charge in order that it be attracted to andheld on the portions of plate 21 overlying that portion of the body in which-the PIP remains.

In FIG. 5A two toners 46 and 47 have been deposited on the surface of plate 21E to produce multicolored copies or to take advantage of the amplified image stored in the plate. In this instance toner 46 would have a weakly negative charge and toner 47 a weakly positive charge so that each would be attracted to a separate area of predetermined polarity. Thus,

toner 46 would be retained on the portions where reversal of the charge sign has occurred and toner 47 would adhere on the surface overlying the original charge sign. Such toners may be dispensed by a single hopper or by dual hoppers. When using a single hopper .to dispense such dual toners, the attractions between the toners 46 and 47 must be significantly less than the attraction between the toner and the charge pattern existing in body 21.

This depositing of dual toners can be used for the production of colored copies or for image enhancement. Assuming that black and white or positive reproductions are to be made, then ablack toner would be used to reproduce the image and a white toner would be used to enhance the contrast or suppress the background.

Following the depositing of the toner on body 21c, the drum will revolveandcarry the plate 21 to station D where the toner 48 is transferred to a suitable medium such as a paper sheet 49. In order to assure intimate contact between the toner 48 and the sheet 49, a roller is positioned adjacent to drum 20 such that the paper 49 is pressed tightly against the upper 'surface of plate 21d. In order to ensure that that toner is picked up by paper 49, his preferable that a voltage differential be provided between drum 20 and roller 50. It has *been found that a voltage difference of 1.5 kilovolts between the drum 20 and roller 50 is quite satisfactory to ensure transfer of the toner to the paper. Whereas field strength is the determinant'factor in imaging and erasing of the PIP layer, the determinant factor in toner transfer is the voltage differential. When a solid toner is used, the toner following its transferto the'paper must be fixed onto the paper in a separate-process well known to the prior artsuch as fusion.

It has been found that almost complete transfer ofthe toner from the plate to the paper can be achieved when the 'paper used has a machine calendared finish coated to a thickness of about 2 lbs/3,000 sq. ft. with a well-known polymer such as polyvinyl acetate emulsion. It has further been found that other material such as a polyacrylate emulsion and cyclicized rubber can be used and that when such a coated paper is used very little or no additional treatment of the paper is necessary in order to fix the toner thereto.

The continued rotation of drum 20 now conveys plate 21 to station E where any free charge remaining in the body Zle is eliminated by recombination effects. This elimination may be accomplished, for example, by flooding plate 2lle withradiation such as from a photoflood or infrared lamp 51. This elimination occurs once again because of photomobility. In this instance because no field is imposed on the body the charges will freely recombine.

The drum then presents the plate 21 to station F where any residual toner is removed by the action of brush 52 positioned so as to remove any particles of toner still adhering to the plate 21f. After passage of plate 21 through section F, it is once again presented to station A and the cycle previously described repeated.

To provide a rough indication of the preferred thicknesses of the various elements described in connection with the above embodiment, it is noted that the PIP layer may be from 0.0005 to 0.003 inch thick, the insulative layer may be from 0.0005 to 0.0015 inch thick and the transfer sheet about 0.003 inch thick.

It should be understood, however, that it is possible to eliminate the NESA coated lamp and use a standard incandescent photoflood having a conductive transparent material such as acrylic resin sold under the trade name LOIOL, which is both transparent and conductive, interposed between the lamp and the plate 21a. This material could be in the form of a belt or web continuously passing between the lamp and the body 21. However, to assure that the charges are created within the body 21, it is preferable that the belt be in contact with the surface of body 21.

Altemately, in some applications it may be desirable to use a conductive layer directly in contact with the PIP material composed of a photoconductive insulator 22 and a dielectric 23. This conductive layer would replace the insulating layer 25. When such a conductive layer is used, it is necessary that its volume resistivity be in the order of ohm-cm. less than the volume resistivity of the underlying PIP body and that the layer be removed before application of the toner to the PIP body.

Other variations and improvements in the machine may also be made. For example, stations E and F could be combined with station A so that station A could be used as an erasing step in which the previous history of the plate would be eradicated by use of light alone, field alone, or light and field simultaneously or sequentially as previously described. Such a use ensures a unifonnly conditioned plate without quenching, dark conditioning or the like. Further, station A could be used as a dark polarization station to provide erasure when the exposure was made with an oppositely oriented field. Such dark polarization would require a field strength in the PIP layer of 3,000 volts/cm. applied for 5 seconds. The insulative layer can also be applied to the NESA electrode in stations A and B.

As earlier noted and as shown in FIG. 6, station A need not be a single element such as a NESA tube providing both the irradiation andelectrical field, but may be composed of two separate elements, namely, an irradiation source 27' for irradiation and an electrode 23' located between source 27' and station B to provide the electrical field. Surprisingly, however, in such a sequential polarization embodiment, use of an electrode 28' in contact with the insulative layer 25 has not proven completely satisfactory. The resultant toner pattern on the transfer sheet 49 has displayed a substantial overall darkening with only a density differential in the toner pattern to indicate the PIP image impressed at station A. It has been found, however, that use of a sequential polarization embodiment having an electrode 28' slightly raised from the surface of the insulative layer 25 results in a toner pattern on the transfer sheet 49 comparable to that achieved by use of the NESA tube 26 providing a simultaneous irradiation and electrical field. Therefore, while the pertinent parameters of such separate elements may otherwise correspond to those of their functional equivalents in the NESA tube 26, the electrode 28' should preferably be spaced apart from the insulative layer 25, and may be, for example, a biased metal roller supported on the insulative layer 25 by thin, insulative shoulders, and not otherwise in contact therewith. One advantage of a sequential polarization embodiment using separate elements is that the conductive material is no longer interposed between the insulative layer 25 and the irradiation source 27'; as a result, the choice of a conductive material for electrode 28 is no longer limited by the requirement that it be transparent to the irradiation. Another advantage is that the difficulties involved in producing a smooth and regular curvature for a NESA tube are avoided, and a more uniform electrical field can be easily obtained. A NESA tube generally utilizes only a thin conductive coating 28 which, because of its proximity to the insulative layer 25, eventually becomes scratched during operation of the machine by the continual rubbing thereon of high spots on the insulative layer 25. On the other hand, electrode 28, although easily formed of any thickness and smoothness desired, is separated from the insulative layer 25 by from 0.01 to 0.05 millimeters so that no scratching thereof is possible and a more lasting, uniform electrical field provided.

Similarly, as earlier noted and as shown in FIG. 6, station E need not apply both irradiation and electrical field simultaneously, but may, in order to avoid the requirement of transparency for electrode 37, utilize a sequential polarization technique. In this instance, as described immediately above with respect to station A, it is preferred that the electrode be slightly raised above the insulative layer.

If multiple copies of the same image are desired, all the stations except stations C, D, and F should be deactivated. Thus, a number of copies of the same image can be produced from one single exposure. This multiple copy feature is accomplished only because the application and removal of the toner at stations C and D does not appreciably adversely affect the free charge created in the body. In other words, recombination does not occur when the toner is applied or removed.

Furthermore, since the voltage used at station D in the transfer step does not generate enough dark depolarization to override the impressed PIP image, the quality of the transferred image is unaffected. However, since this transfer step may generate static electricity that remains on insulating layer 25 it is advisable that an additional grounding element be provided at station F so that copy quality is not interfered with. In such a case, any convenient means of grounding insulating layer 25 may be used. One such grounding means could be, for example, a metallic strip that brushes across layer 25.

When multiple copies are being produced from a single PIP latent image, removal of any electrostatic charge buildup on the insulative layer 25 may be further facilitated by introduction of a radioisotope emitting low energy, highly charged particles in the direction of the insulative layer 25. An emitter of weak alpha particles such as a polonium static eliminator is preferred over other emitters, such as .beta emitters, because the alpha particle combines a high ionization activity with a low range of penetration. As shown in FIG. 6, the alpha source 57 should be placed between stations D and F, preferably between stations E and F, and directed towards the corresponding portions of the insulative layer 25. Suitable baffles or shields (not shown) should be located about the alpha source to protect other portions of the insulative layer 25 from random radiation. The presence of highly charged alpha particles in the region about the insulative layer 25 facilitates discharging of the electrostatic charge into the air. The remaining electrostatic charge buildup may be discharged and grounded by means of a grounded conductive metal roller 58 contacting the insulative layer 25 between the alpha source 57 and station F.

While the alpha source 57 and the grounded roller 58 contacting the insulative layer 25 assist in the discharge of electrostatic charges which build up on the insulative layer 25, the time required for complete discharge is in fact so long, sometimes taking several hours, that it is desirable to prevent the buildup in the first instance. It is believed that this electrostatic charge buildup originates at station D, due to the electric field existing between the insulative layer 25 and the drum 50 as a result of the transfer voltage bias applied to cause transfer of the toner 48 onto the transfer paper 49. This electrostatic buildup may be minimized by use of the modifications in station D indicated in FIG. 6. In this modified station D, one or more positioning rollers (not shown) direct the front face of the transfer paper 49 against the toner 48 borne by the insulative layer 25. An appropriately biased transfer electrode 59, such as a wire or metal transfer roller, is located a small distance behind the rear face of the transfer paper 49. This biased transfer electrode 59 may be fixed in position either by attachment to the frame or, as shown in FIG. 6, by thin insulative shoulders 60 which ride on the nonimage bearing segments of the insulative layer 25. As the biased transfer electrode does not actually contact the transfer sheet, toner transfer is achieved with less disturbance of the toner and a significant reduction in the buildup of interfering to the biased transfer electrode 59 raised 0.025 millimeters above the rear face of the transfer sheet results in a comparable transfer to that achieved by applying a transfer voltage of 1.5 kilovolts.

it has been found that the number of copies that may be produced in this manner is limited only by the materials used. That is to say, the thermal decay qualities of the phosphor and the sensitivity of the toner have a direct bearing on the number of copies obtainable and the use of long life phosphors and more sensitive toners than those described increased significantly the number of copies that may be obtained.

While operation of the above-described mechanical embodiments of the invention to produce multiple copies from a single PlP latent image has resulted in satisfactory toner transfer in the later copies, the toner density on later transfer sheets has been found to ofien be significantly lower than the toner density on the original transfer sheets. Although the reason for this decay in quality in the later copies is not known with any certainty, it is believed to be related to a lowering of the toner mobility or transferability resulting from decay of the PIP latent image. in any case, it has been found that constant density multiple copies may be made from a single PlP latent image by gradually raising, for succeeding copies, the transfer voltage bias between the insulative layer 25 and the drum 50 (as shown in FIG. 1) or the biased transfer electrode 59 (as shown in FIG. 6). For example, five copies have essentially equal toner density were obtained by applying a 590-volt transfer bias between the insulative layer 25 and the biased transfer electrode 59 (as shown in H6. 6) for the first and second copies, a 670volt bias for the third and fourth copies, and a 760-volt bias for the fifth copy. Use of the higher voltages for production of the initial copies would cause an unnecessary buildup of the electrostatic charge on the surface of the insulative layer 25, and it is therefore desirable to provide means for roughly adjusting the transfer voltage for each successive copy of a single lPlP latent image in order to utilize the minimum transfer voltage necessary on such copy to achieve the same toner density as on preceding copies of the image.

It is also noted that utilization of the reverse field effect described in conjunction with FIG. 5 and FIG. 5A may be used to control the gradation of toning from a black through white with varying intermediate shades of gray. Such control is achieved by changing the field strength from a maximum to a lower voltage, so as to provide either continuous tone reproductions or very high contrast black and white copies.

Portions of the invention may also be utilized outside of the described machine. For example, the described phosphors could be coated onto sheets of paper which could then be irradiated by light or an electric field or both, simultaneously or sequentially, as described above in conjunction with station A. The uniformly charged coated sheet would then be exposed to the imaging radiation as explained in conjunction with station B above. Following the impressment of the image the toner would be applied directly to the sheet and, in the case of a fusible toner, fused thereto. if a liquid toner were used, the fusing step would be omitted. One such liquid toner is carbon black suspended in an organic liquid, such as kerosene,

.petroleum ether or Freon, and others are commercially available.

Electrophotographic printing receptor sheets suitable for the above were made by mixing the photoconductive insulator, prepared as described in Example l, at a ratio of 16 to l with a styrenated alkyd sold as DeSoto E 90-01 at 90 percent solids in toluene. This mixture was ball-milled for 2% hours after which it was coated on conductive paper at a weight of from S to 25 pounds per 3,000 sq. ft., especially satisfactory results being obtained at a weight of about 14 lbs. per 3,000 sq. ft.

Thus, to use a sheet such as described above, the machine need not be as complex as that described wherein the photoconductive insulators were used in plate fonn. Basically, only station A, B, C and, if a solid toner were used, a fusing station would be required.

Still further improvements may be readily achieved by one skilled in the art. Accordingly, it is understood that, although certain specific materials and a specific method of applying and utilizing these materials are described in the foregoing specification, these materials and methods may be changed to conform to other conditions that may be encountered. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of this invention within the art.

We claim:

1. A copying machine comprising:

an image storage means, said storage means comprising a first conductive member and a medium supported thereon capable of being polarized by the application of radiation and electrical field;

means at a first station for uniformly irradiating said storage means and for applying to an exposed surface of said medium a second conductive member having a resistivity of at least 10 ohm-cm. less than said medium through which a first uniform directional electric field is applied to said storage means to internally uniformly polarize said storage means;

means at a second station for subjecting said storage means to a radiatiop image consisting of patterns of radiation and nonradiation to selectively discharge polarized areas of said storage means and for thereafter removing said second conductive member from said surface;

means at a third station for dispensing a charged toner on the surface of said storage means, said toner being maintained on said surface by interaction with the underlying areas of a predetermined polarity in said storage means;

means at a fourth station for transferring said toner from said surface to a body suitable for permanent retention of said toner; and

means for transporting said storage means past each of the enumerated stations in the order named.

2. The copying machine of claim 1 wherein said means at said first station applies said second conductive member to said surface prior to irradiating said storage means and said second conductive member is transparent to said radiation.

- 3. A copying machine comprising:

an image storage means, said storage means comprising a first conductive member and a medium supported thereon capable of being polarized by the application of radiation and electrical field;

first means for uniformly irradiating said storage means and for applying a first uniform directional electric field to said storage means to internally uniformly polarize said storage means comprising a first power source, a second conductive member in substantially parallel relationship to an opposed portion of said first conductive member with said medium between said first and second conductive members, and means connecting said first and second conductive members across said first power source;

second means for subjecting said storage means to a radiation image consisting of patterns of radiation and nonradiation to selectively discharge polarized areas of said storage means;

third means for dispensing a charged toner on the surface of said storage means, said toner being maintained on said surface by interaction with the underlying areas of a predetermined polarity in said storage means;

fourth means for transferring said toner from said surface to a body suitable for permanent retention of said toner; and means for transporting said storage means past each of the enumerated means.

4. The copying machine of claim 3 wherein said first means uniformly irradiates said storage means and applies said first uniform directional electric field to said storage means concurrently, said second conductive member being transparent to said radiation.

5. The copying machine of claim 4 wherein said first means comprises an electric light having a length equal to the width of said storage means and a conductive coating on the surface thereof transparent to said radiation.

6. The device of claim 5 wherein said electric light further has a transparent insulating layer on the surface of said transparent coating.

7. The device of claim 6 wherein said insulating layer is cyclicized rubber, cellulose nitrate, polyvinyl acetate, acrylonitrile-butadiene-styrene terpolymer, oxidized polystyrene, styrenated alkyd or polyvinylidine chlorideacrylonitrile copolymer.

8. The copying machine of claim 3 wherein said second conductive member is nontransparent to the irradiation and said first means uniformly irradiates said storage means and applies said first uniform directional electric field to said storage means sequentially.

9. The copying machine of claim 8 wherein said second conductive member is slightly raised above the exposed surface of said storage means.

10. The copying machine of claim 3 wherein said second means for subjecting said storage means to a radiation image further applies a second uniform directional electric field to said storage means, said second electric field having an opposite polarity to said first electric field to selectively reverse the polarity of areas of said storage means corresponding to said radiation pattern.

11. The copying machine of claim 10 wherein said second means comprises a third conductive member in substantially parallel relationship to an opposed portion of said first conductive member with said medium between said first and third conductive members and a second power source coupled to said first and third conductive members so as to provide a polarity opposite to said first electric field.

12. The copying machine of claim 10 wherein said second means applies said second electric field to said storage means concurrently with the subjecting of said storage means to said radiation image, whereby subjecting said storage means to said radiation image in the presence of said electric field causes a discharge and reversal of polarity in areas of said storage means corresponding to said radiation pattern.

13. The copying machine of claim 10 wherein said second means applies said second electric field to said storage means subsequent to subjecting said storage means to said radiation image, whereby application of said second electric field to said storage means causes said polarization discharged areas of said storage means to reversely polarize.

14. The copying machine of claim 10 wherein said third means dispenses two toners, one of said toners being attracted to and held on the underlying surface of the remaining of said initially polarized areas of said storage means and the other of said toners being attached to and held on the underlying surface of the reversely polarized areas of said storage means.

15. ln combination, a paper sheet and a copying machine comprising:

an image storage means, said storage means comprising a first conductive member and a medium supported thereon capable of being polarized by the application of radiation and electrical field;

first means for uniformly irradiating said storage means and for applying a first uniform directional electric field to said storage means to internally uniformly polarize said storage means;

second means for subjecting said storage means to a radiation image consisting of patterns of radiation and nonradiation to selectively discharge polarized areas of said storage means;

third means for dispensing a charged toner on the surface of said storage means. said toner being maintained on said surface by interaction with the underlying areas of a predetermined polarity in said storage means;

fourth means for placing said paper sheet onto the surface of said storage means for transferring said toner from said surface to said paper sheet for permanent retention of said toner said paper sheet having a machine calendared finish coated to a thickness of about 2 lbs. per 3,000 sq. ft. with an adhesive polymer; and

means for transporting said storage means past each of the enumerated means.

16. The copying machine of claim 15 wherein said transferring means comprises means for placing a paper sheet on the surface of said storage means, said paper sheet having a machine calendared finish coated to a thickness of about 2 lbs. per 3,000 sq. ft. with a polyvinyl acetate.

17. The copying machine of claim 15 wherein said transferring means comprises means for placing a paper sheet on the surface of said storage means, said paper sheet having a machine calendared finish coated to a thickness of about 2 lbs. per 3,000 sq. ft. with cyclicized rubber.

18. A copying machine comprising:

an image storage means, said storage means comprising a first conductive member and a medium supported thereon capable of being polarized by the application of radiation and electrical field;

first means for uniformly irradiating said storage means and for applying a first uniform directional electric field to said storage means to internally uniformly polarize said storage means;

second means for subjecting said storage means to a radiation image consisting of patterns of radiation and nonradiation to selectively discharge polarized areas of said storage means;

third means for dispensing a charged toner on the surface of said storage means, said toner being maintained on said surface by interaction with the underlying areas of a predetermined polarity in said storage means;

fourth means for transferring said toner from said surface to a body suitable for permanent retention of said toner comprising means for positioning a front face of said body onto the surface of said storage means, an electrode slightly displaced from the other face of said body, and means for applying a direct bias voltage between said electrode and said storage means; and

means for transporting said storage means past each of the enumerated means.

19. The copying machine of claim 18 wherein said electrode is a conductive roller supported behind and apart from the rear face of said toner retaining body by thin insulative shoulders riding on said storage means.

20. The copying machine of claim 18 wherein said toner retaining body comprises a paper sheet and said fourth means further removes said paper sheet from said surface of said storage means.

21. The copying machine of claim 18 wherein means are provided for varying the applied direct bias voltage in accord with the number of identical copies desired.

22. A copying machine comprising:

an image storage means, said storage means comprising a first conductive member, a medium supported thereon capable of being polarized by the application of radiation and electrical field and an insulative layer supported on the surface of said medium in parallel opposition to the surface supported by said first conductive member;

first means for uniformly irradiating said storage means and for applying a first uniform directional electric field to said storage means to internally uniformly polarize said storage means;

second means for subjecting said storage means to a radiation image consisting of patterns of radiation and nonradiation to selectively discharge polarized areas of said storage means;

third means for dispensing a charged toner on the exposed surface of said insulative layer of said storage means, said toner being maintained on said surface by interaction with the underlying areas of a predetermined polarity in said storage means;

fourth means for transferring said toner from said surface to a body suitable for pennanent retention of said toner; means for transporting said storage means past each of the enumerated means; and

means for deactivating said first and second means and repetitively transporting said storage means past said third and fourth means.

23. The copying machine of claim 22 having means for discharging electrostatic charges accumulating on said insulative layer.

24. The copying machine of claim 23 wherein said discharge means comprises an alpha particle emitter.

25. A copying machine comprising:

an image storage means, said storage means comprising a first conductive member and a medium supported thereon capable of being polarized by the application of radiation and electrical field;

first means for uniformly irradiating said storage means and for applying a first uniform directional electric field to said storage means to internally uniformly polarize said storage means;

second means for subjecting said storage means to a radiation image consisting of patterns of radiation and nonradiation to selectively discharge polarized areas of said storage means;

third means for dispensing a charged toner on the surface of said storage means, said toner being maintained on said surface by interaction with the underlying areas of a predetermined polarity in said storage means;

fourth means for transferring said toner from said surface to a body suitable for permanent retention of said toner; means for transporting said storage means past each of the enumerated means; and

means for deactivating said first and second means and repetitively transporting said storage means past said third and fourth means.

26. The copying machine of claim 25 wherein said fourth means comprises an electrode, positioned on the opposite side of said-toner retaining body than said medium, for applying a voltage differential between said electrode and storage means and further having means for increasing said voltage differential for said repetitive transports of said storage means past said third, fourth and fifth means while said first and second means are deactivated.

27. A copying machine comprising latent image storage means, a first means for uniformly internally polarizing said storage means, a second means for impressing an image in said storage means by selectively discharging portions of said internal polarization, a third means for dispensing a toner on the surface of said storage means, a fourth means for transferring said toner to a retentive medium, a'fifth means for removing residual toner from the surface of said storage means; means for transporting said storage means past each of the enumerated means; and means for deactivating said first and said second means and repetitively transporting said storage means past said third, fourth and fifth means.

28. A copying machine comprising a latent image storage means, means for irradiating and applying a voltage to said storage means to internally uniformly polarize said storage means comprising an electric light having a length equal to said latent image storage means and having a transparent conductive coating on the surface thereof, means for impressing an image in said storage means by selectively discharging portions of said internal polarization, means for dispensing on the surface of said storage means a toner capable of being attracted to the field due to the polarization remaining in said storage means and means for transferring said toner to a medium suitable for the retention of said toner.

29. A machine of claim 28 wherein said latent image storage means comprises a medium capable of supporting internal polarization maintained between a conductive layer and an insulative layer, said medium being an insulative photoconductor dispersed in a binder having a volume resistivity greater than 10 ohm-cm.

30. A machine of claim 28 wherein said means for irradiating and applying a voltage comprises means for applying said voltage simultaneously with said irradiation.

31. A machine of claim 28 wherein said means for irradiating and applying a voltage comprises means for applying said voltage sequentially to said irradiation.

32. A copying machine comprising an image storage means, said storage means comprising a medium, capable of being internally polarized by the application of radiation and an electric field, having on a first surface an insulative layer and on a second surface in parallel opposition to said first surface a first conductive member, first means for uniformly irradiating said medium and for applying a uniform directional electric field to said medium to uniformly internally directionally polarize said medium, said field applying means having a power supply and a second conductive member being in substantially parallel relationship to said first conductive member with said medium and said insulative layer maintained therebetween, second means for applying a second unifonn directional field to said medium and for subjecting said medium to a selective radiation pattern in the presence of said second uniform directional field, said field applying means comprising said power supply being coupled to said conductors wherein said second field has a polarity opposite to said first field whereby application of 'said radiation pattern selectively reverses in the presence of said second field portions of said polarized medium, third means being provided for dispensing a charged toner on said insulative layer, said toner being maintained on the surface of said insulator overlying the remaining portions of said first polarization of said medium, fourth means for transferring said toner to a body suitable for permanent retention of said toner, fifth means for irradiating said medium to deplete all polarization in said medium, sixth means for removal of residual toner from the surface of said insulative layer, and means for transferring said storage means past said enumerated means.

33. The copying machine of claim 32 wherein the third means dispenses two toners, one of said toners being attracted to and held on the surface of said insulator overlying the remaining initially polarized portions of said medium and the other of said toners being attached to and held on the surface of said insulator overlying the portions of reversed polarization.

34. A copying machine comprising an image storage means, said storage means comprising a medium, capable of being polarized by the application of radiation and an electric field, maintained on a first conductive member, first means for uniformly irradiating said storage means and for applying a uniform directional electric field to said storage means to internally uniformly polarize said storage means, said field applying means consisting of a first power source and a second conductive member, transparent to the irradiation, maintained in substantially parallel relationship to said first conductive member with said storage means maintained between said first conductive member and said second conductive member, second means for subjecting said storage means to a radiation image consisting of patterns of radiation and nonradiation to selectively deplete areas of polarization contained in said storage means, third means for dispensing a charged toner on the surface of said storage means, said toner being maintained on said surface by interaction with the underlying polarized area of said storage means, fourth means for transferring said toner from said medium to a body suitable for permanent retention of said toner comprising a roller for placing a paper sheet on the surface of said storage means and for applying a voltage differential between said roller and said storage means, fifth means for irradiating said storage means to destroy the residual polarization in said storage means and for removing residual toner from said surface of said storage means and means for transporting said storage means past each of the enumerated means.

35. The copying machine of claim 34 wherein said transferring means comprises a roller for placing a paper sheet on the surface of said storage means, said paper sheet having a machine calendared finish coated to a thickness of about 2 lb. per 3,000 sq. ft., with an adhesive polymer.

as. The copying machine of claim 34 wherein said transferring means comprises a roller for placing a paper sheet on the surface of said storage means, said paper sheet having a machine calendared finish coated to a thicltness of about 2 lbs. per 3,000 sq. ft., with a polyvinyl acetate.

37. The device of claim 1% wherein said medium suitable for the retention of said toner comprises a paper sheet having a machine calendared finish coated to a thickness of about 2 lbs. per 3,000 sq. ft., with polyvinyl acetate.

38. A copying machine comprising means for transferring a latent image storage means through a first means for uniformly internally polarizing said storage means, a second means for impressing an image in said storage means by selectively discharging portions of said internal polarization, :1 third means for dispensing a toner on the surface of said storage means, a fourth means for transferring said toner to a retentive medium, a fifth means for removing residual toner from the surface of said storage means, and means for deactivating said first and said second means and repetitively transferring said storage means through said third, fourth and fifth means.

39. A copying machine comprising an image storage means, said storage means being a medium, capable of polarization by the application of radiation and an electric field, maintained on a first conductive member, first means for uniformly irradiating said storage means and for applying a uniform directional electric field to said storage means to internally uniformly polarize said storage means, said field applying means consisting of a power source and a second conductive member, transparent to the irradiation, maintained in substantially parallel relationship to said first conductive member with said storage means maintained between said first conductive member and said second conductive member, second means for applying a second uniform directional field to said medium and for subjecting said medium to a selective radiation pattern in the presence of said second uniform directional field, said second field applying means comprising said power supply coupled to said conductors such that said second field has a polarity opposite to said first field whereby application of said selective radiation pattern selectively reverses portions of said polarized medium, third means being provided for dispensing a charged toner on the surface of said storage means, said toner being maintained on said surface by interaction with the underlying initially polarized area of said storage means, fourth means for transferring said toner from said medium to a body suitable for permanent retention of said toner, fifth means for irradiating said storage means to destroy the polarization in said storage means, and for removing residual toner from said surface of said storage means, and means for transporting said storage means past each of the enumerated means.

40. A copying machine comprising means for transferring a latent image storage means through a first means for uniformly internally polarizing said storage means, through a second means for impressing an image in said storage means by selectively reversing portions of said internal polarization, through a third means for dispensing a toner on the surface of said storage means, through a fourth means for transferring said toner to a retentive medium, through a fifth means for removing residual toner form the surface of said storage means, and for repetitively transferring said storage means through said third, fourth, and fifth means.

41. A copying machine comprising an image storage means, said storage means comprising a medium, capable of being polarized by the application of radiation and an electric field, maintained on a first conductive member, first means for uniformly irradiating said storage means and for applying a uniform directional electric field to said storage means to internally uniformly polarize said storage means, said field applying means consisting of a first power source and a second conductive member having a resistivity of 10 ohm-cm. less than said medium, maintained in substantially parallel relationship to said first conductive member with said storage means maintained between said'first conductive member and said second conductive member, second ineans for subjecting said storage means to a radiation image consisting of patterns of radiation and nonradiation to selectively deplete areas of polarization contained in said storage means, third means for removing said second conductive layer, fourth means for dispensing a charged toner on the surface of said storage means, said toner being maintained on said surface by interaction with the underlying polarized area of said storage means, fifth means for transferring said toner from said medium to a body suitable for permanent retention of said toner, sixth means for irradiating said storage means to destroy the residual polarization in said storage means and for removing residual toner from said surface of said storage means and means for transporting said storage means past each of the enumerated means.

42. A copying machine comprising an image storage means, said storage means comprising a medium, capable of being polarized by the application of radiation and an electric field, maintained on a first conductive member, first means for uniformly irradiating said storage means and for applying a uniform directional electric field to said storage means to internally uniformly polarize said storage means, said field applying means consisting of a first power source and a second conductive member, transparent to the irradiation, maintained in substantially parallel relationship to said first conductive member with said storage means maintained between said first conductive member and said second conductive member, second means for subjecting said storage means to a radiation image consisting of patterns of radiation and nonradiation and to a second electric field, said second field having an opposite polarization to said first field, to

selectively reverse areas of polarization contained in said permanent retention of toner, fifth means for irradiating said storage means to destroy the residual polarization in said storage means and for removing residual toner from said surface of said storage means and means for transporting said storage means past each of the enumerated means.

Patent Citations
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US3199086 *Nov 25, 1960Aug 3, 1965Rahn CorpDevices exhibiting internal polarization and apparatus for and methods of utilizing the same
US3268331 *May 24, 1962Aug 23, 1966Itek CorpPersistent internal polarization systems
US3356831 *Dec 23, 1964Dec 5, 1967Xerox CorpXerographic fusing apparatus
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3776627 *Nov 13, 1972Dec 4, 1973Mitsubishi Electric CorpElectrophotographic apparatus using photosensitive member with electrically high insulating layer
US5312703 *Sep 12, 1990May 17, 1994Basf AktiengesellschaftReversible or irreversible production of an image
US5538824 *May 24, 1994Jul 23, 1996Basf AktiengesellschaftReversible or irreversible production of an image
DE2318839A1 *Apr 13, 1973Oct 18, 1973Canon KkElektrophotographische vorrichtung
Classifications
U.S. Classification399/232, 399/137
International ClassificationG03G15/056, G03G5/02, G03G5/024, G03G5/147
Cooperative ClassificationG03G15/056, G03G5/024, G03G5/147
European ClassificationG03G5/147, G03G5/024, G03G15/056