US3457070A - Electrophotography - Google Patents

Electrophotography Download PDF

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US3457070A
US3457070A US471606A US3457070DA US3457070A US 3457070 A US3457070 A US 3457070A US 471606 A US471606 A US 471606A US 3457070D A US3457070D A US 3457070DA US 3457070 A US3457070 A US 3457070A
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light
insulating layer
photosensitive
layer
latent image
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Yoshiyuki Watanabe
Koichi Kinoshita
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Matsuragawa Electric Co Ltd
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Matsuragawa Electric Co Ltd
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/14—Inert intermediate or cover layers for charge-receiving layers
    • G03G5/147—Cover layers
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/056—Electrographic processes using a charge pattern using internal polarisation
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/02—Charge-receiving layers
    • G03G5/024—Photoelectret layers

Definitions

  • the fourth involves the so-called persistent internal polarization process, wherein a latent image on a phosphor material induced by persistent internal polarization of such material exposed to light is utilized to effect copying.
  • the second system makes use of a phenomenon in which localized and selective irradiation by light induces transfer of electric charges from the photosensitive material to the recording plate when such photosensitive material is spaced from the recording plate by a narrow air gap of from about 2 to 10 microns in thickness. It is noteworthy that this narrow air gap operates as a specific type of resistance component, and that the transfer of electrical charges does not occur until the electric field intensity selectively impressed across this resistance attains a certain critical value; however, when such field intensity does reach this critical value, the migration of charges takes place with abrupt intensity. The process makes use of this phenomenon in an effort to obtain a higher resolution of the copy. Conversely, this phenomenon is obviously essential in this particular process to maintain a latent image induced on the recording plate. One of the major technical obstacles associated with this process is the necessity of maintaining such as critical narrow air gap between the photosensitive element and the recording plate.
  • the third system attempts to make use of the residual internal polarization.
  • the recording plate is made so that prolonged retention of residual internal polarization is possible by mixing a specially selected material in the recording plate; this enables retention of internal polarization of the recording plate that is induced by a rise of electric field intensity in areas selectively distributed over the recording plate, which is in turn induced by the selectively localized decrease of field intensity impressed over the photosensitive element at areas thereof exposed to light. Since this process makes use of the internal polarization, it differs substantially from the above-described two processes, and particularly does not require the narrow air gap of the second process. This process, therefore, is less difficult to practice as a practical matter.
  • the fourth process i.e., the so-called persistent internal polarization (PIP) process
  • PIP persistent internal polarization
  • the PIP process makes use of a phenomenon known as persistent internal polarization induced within the photosensitive element.
  • Still another object of this invention is to provide a novel photosensitive element using photoconductive materials of high sensitivity that heretofore have been unusable in the field of electrophotographic copying, as well as certain methods whereby to determine the operative characteristics of such photosensitive elements.
  • Still another object of the present invention is to provide certain control methods whereby light images are converted into electrophotographic latent images by using such a novel photosensitive element.
  • the present invention relates to the formation of a latent image, defined by electrical charge patterns corresponding to the light image, directly on a thin layer of material having high electrical insulation properties and comprising an integral portion of a photosensitive element.
  • the latent image may be developed by applying finely divided particles of any suitable dry developing material to the charge patterns and transferring the resulting visible image to another surface, such as the surface of a recording paper sheet. Use of a special recording paper is not required.
  • the latent image does not scatter or disappear even when the element containing such latent image is subsequently exposed to light.
  • FIGURE 4 graphically illustrates changes in relation to time of electrical charge potential on the surface of a photosensitive element used in this invention
  • FIGURE 5 diagrammatically illustrates means, and an operation, for developing the latent image on the photosensitive element by application of dry developer particles
  • FIGURE 6 diagrammatically illustrates means and operations for transferring the latent image to a sheet of paper and fixing it on the paper;
  • FIGURES 7, 8 and 9 are, respectively, a representation of an equivalent circuit and characteristic curves illustrating the operation of the photosensitive element embodying the invention.
  • FIGURES 12A and 12B are graphic illustrations of still another example of the relationship to time of electrical charge potential on the surface of a photosensitive element in this invention.
  • FIGURE 14 is a graphic illustration of another example of relative values of impressed voltage and illumination of light, for a photosensitive element intended for a particular use.
  • the thin insulating layer 3 is preferably a 12.5 micron thick layer of, for example, solid, transparent polyester syntheic resin material; the insulating layer 3 is laminated to one of the surfaces of the photosensitive layer 2 by a polyester synthetic resin adhesive transparent to light.
  • FIGURE 2 is a schematic view of an electrophotographic system embodying the present invention for inducing a latent image or charge pattern corresponding to a light image impressed on the element 1.
  • An electrode 5 of glass that is transparent to light and electrically conductive, such, for example, as NESA glass made by orning Glass Works of Corning, NY is di p h a conductive surface 5a in contact with the surface of the insulating layer 3 of the element 1.
  • a direct current (DC) supply source 6 impresses an electric potential across the transparent electrode 5 between its conductive surface 511 and the electrode 4 of element 1.
  • a switching means 7 is connected between the current source 6 and element 1 to connect or disconnect the electric current, and to change the polarity of the electric potential so impressed across the transparent electrode 5 and the electrode 4.
  • FIGURE 3 The manner in which a latent image is produced in the element 1 is graphically illustrated in FIGURE 3 in which the ordinate in the upper part of the figure is the electric potential impressed between the transparent electrode 5 and the electrode layer 4 of the element 1, and the ordinate in the lower part of the figure represents the light projected on element 1.
  • the abscissae represent time in each case.
  • an electric potential is applied across the transparent electrode 5 and the electrode layer 4 in such a manner that the polarity of electrode 5 is positive with respect to the layer 4.
  • the element 1 is not at this time exposed to light.
  • the surface of the insulating layer 3 of the element 1 at this time contains an electrical charge pattern forming a latent image which corresponds to the incident light image to which the element 1 was exposed during the period t to t
  • the latent image so formed demonstrates almost no attenuation even under a subsequent exposure to light, nor is there any diffusion of charges comprising such latent image.
  • FIGURE 4- graphically illustrates the changes of electrical potential in the element 1 with respect to time in this embodiment of the invention.
  • the symbols t t and t represent respectively the same time sequences described at t t and t in connection with FIGURE 3.
  • Curve a depicts changes in electrical charge potential on the upper surface of the element 1 during the interval t through 2
  • the broken line a connected to curve a indicates that continued impression of the electrical potential having the same polarity will not further increase the surface charge potential of the element 1.
  • Curve b represents the change on the surface electrical potential of the element 1 at areas where the incident light does not strike the element surface during the time interval represented by t through t
  • Curve 0 represents the changes in the surface electrical potential of the element 1 at areas where incident light strikes the element surface during the time interval t through tg.
  • carbon black impregnated styrene resin may be used as a negatively charged toner; and as a positively charged toner, a thermoplastic, methylated paraflinic resin, essentially composed by polymers of pinene, such as Piccopale resin manufactured by Pennsylvania Industrial Chemical Corp. of Clairton, Pa., impregnated with oil black, may be used. In either case, powdered iron may be used as carriers for the toner. Particularly because of the high potential difference between the areas charged and the areas substantially devoid of charges, the visible deposited image will have a fine resolution and will provide excellent reproduction of the latent image on the element.
  • the negatively charged toner will adhere to the areas that were not exposed to light, while the positively charged toner will adhere to the areas that were exposed to light.
  • This can be accomplished, for example, as shown in FIGURE 5, by placing the charged photosensitive element 1 with its charged surface facing down over a container 21 containing the toner particles admixed in a suitable carrier 22 that are moved by agitator 23 into contact with the element to form an image 24.
  • undesired particles can be removed by conventional means, as by blowing air.
  • the visible image can then be readily transferred to a sheet 25 of paper or the like by pressing the paper against the surface of the element 1 carrying the visible image to transfer the particles forming the image to the paper by light pressure applied by an electrode 26, preferably a roller electrode, electrically connected to backing electrode 4 of element 1.
  • the paper can then be passed to a processor 27 that sets the image on the paper, as by fusing it in the conventional manner by known means.
  • FIGURE 7 depicts an equivalent circuit, representing the light sensitive element 1 when an electric potential E is impressed on the element, in which Z represents the impedance component of the transparent insulating layer 3 comprising the surface of the element 1, and Z represents the impedance component of the light sensitive layer 2.
  • a DC field impressed on layers 2 and 3 from outside of the layers is essentially electrostatic in nature. Such DC field will be distributed according to the impedance present, because the light sensitive element of the present invention exhibits extremely high resistivity and current flow is'minimal.
  • the polyester resin film constituting the thin insulating layer 3 had a high unit area resistivity of approximately l.25 ohms per square centimeter and a dielectric constant of 3.1.
  • the light sensitive layer 2 exhibited, after having been stored in the dark for a prolonged period of time, a unit area resistivity of about 1x 10 ohms, which reduced to approximately 1X 10 ohms when exposed to light having intensity of 20 lux.
  • the dielectric constant of layer 2 determined by a method generally used, was 2.4 in the dark, which increased to as high as 30 or more when exposed to light having intensity of about 20 lux.
  • the layer functions essentially as a ca pacitive component
  • the light sensitive layer 2 in its unexposed state exhibits a very high resistance'
  • T the length of the time required to have the surface potential saturated to a specific value is shown as T, which in terms of the photosensitive element described in Example 1 was approximately 0.1 second.
  • the charging time is computed, assuming that pure capacitive components alone were involved, the results indicate that the saturation should be reached in much shorter time than the actual saturation time given above. The fact that it takes a longer period of time for saturation, coupled with the fact that the level of the electric potential of the unexposed element is not determined by the impedance and dielectric constant of the element 1, appears to suggest occurrence of unique potential changes within the light sensitive layer 2.
  • FIGURE 9 illustrates this change in terms of current flow.
  • the potential impressed in FIGURE 9 has the same polarity during the time intervals respectively designated as t to t and then beyond t During the time interval shown at t to t the polarity is reversed.
  • Excitation by light is performed during the interval shown as t to t
  • a decrease of current fiow commences immediately after the removal of excitation, and would follow the curve indicated by the broken line except for reversal of the polarity t
  • the polarity of the field is reversed at t there is an instantaneous substantial flow of current, which decreases rapidly and settles down to a flow of small amount.
  • the polarity is again reversed at i back to the original polarity, an instantaneous substantial flow of sudden current is again observed, which attenuates rapidly in a short period of time and reaches the value of the so-called dark current.
  • the residual effect of the light to which the CdS crystals of layer 2 may have been previously exposed is predominant, and the density of electrons within the conduction band or in the trap levels, which can easily liberate electrons into the conduction band, is quite high.
  • a DC current having a definite polarity to the sensitive layer 2
  • the conduction electrons readily drift toward the positive pole and thus form internal polarization.
  • the polarization of the sensitive layer 2 thus effected, as shown in FIGURE 10 is in the direction opposite to the polarity of the electric field externally applied, and the charge distribution within the sensitive layer 2 will be as shown in the figure.
  • the areas exposed to light during the time interval of f to t will now be discussed.
  • the polarization which has been induced during the time interval of t to I is completely depolarized by the incident light.
  • the impedance component Z of the sensitive layer 2 drops, and the dielectric constant increases as a result, which also increases the intensity of the field impressed on the insulating layer. This in turn induces a rise in the charge potential at the surface of the insulating layer.
  • the polarized carriers in the sensitive layer will become trapped according to the polarity of newly impressed field, and at the same time, there will be induced within the sensitive layer and the insulating layer certain internal charging, which occurs completely independently of the trapping of charged carriers.
  • the transparent electrode is removed from the light sensitive element.
  • the element 1 After the removal of the transparent electrode, it is not necessary for the element 1 to have any internal mechanism to retain the latent image induced on the surface of the insulating layer. Any subsequent exposure to light of the element will not affect the charge distribution on the surface 'of the element. The subsequent development operations can be handled in light. Furthermore, the latent image on element 1 will be retained semi-permanently, until such time as the element is again exposed to a new electric field. What is particularly noteworthy in the photosensitive element 1 is the fact that the charges of opposite polarity internally present in the element do not extend their influence externally because of the backing electrode 4 integrally comprising the sensitive element. The presence of the backing electrode additionally suggests a number of interesting technical possibilities.
  • the latent image defined by the charge pattern present on the surface of the insulating layer 3 interacts with the internal charges and shows hardly any attenuation.
  • the entire process as described above commencing with t to and thereafter can be repeated. Accordingly, even when charges are present on the surface of element 1, such charges will not affect in any way the subsequent formation of a fresh latent image on the element.
  • the element will be subjected to certain mechanical stimuli, but such stimuli do not extend their effect to the sensitive layer, and the effect will be limited to the thin insulating layer, which indicates that the possibility of fatigue or mechanical breakdown of the photosensitive layer is nil.
  • the charge distribution within the photosensitive layer of the element causes changes in the effective field distributed on the surface of the insulating layer and, without the provision of any air gap between the element and the transparent electrode or without special conditioning of the insulating layer, induces an electrostatic charge pattern forming a latent image of the pattern of incident light on the surface of the insulating layer.
  • the contacting of the transparent electrode and the photosensitive element does not require special skill or arrangement. It has been found that after the electrostatic charges have been induced according to the procedure described above, when the transparent electrode 5 and the electrode 4 laminated to the photosensitive element are short-circuited before removing the transparent electrode from the element, the latent image is destroyed. Such destruction of the image occurs as a result of a sudden drop of the surface potential of the element to zero level, and indicates that the electric charges present at the surface of the element are dispersed through the short-circuiting. In this case, the internal charge potential of the element which interacted to retain the equilibrium with the surface potential will also be destroyed.
  • the electric charges within the sensitive layer act as the retainer and controller of the charges distributed over the insulating layer surface, as indicated below.
  • the construction of the photosensitive element and the control method thereof in the present invention make possible the formation of a stable latent image while utilizing high sensitivity photoconductive materials which have not heretofore been used because their characteristics, manifested because they are highly sensitive to light, made them unfit for prior electrophotographic processes.
  • factors which contribute in latent image formation are the internal polarization and the charge distributions on the reverse side of the insulating layer or in the sensitive layer having a polarity which is the reverse of that of the charge pattern present on the surface of the insulating layer which defines the latent image.
  • the internal polarization contributes in inducing field distribution at the time the latent image is formed and in the image retention thereafter until and only until the transparent electrode is removed from the surface of the photosensitive element.
  • the internal polarization may disappear at any time after the removal of the transparent electrode, without in any way. affecting the latent image formed on the surface of the insulating layer.
  • the polarization need not be as deep in the trap level as would be necessitated when persistent internal polarization is desired, and this forms an important feature of the present invention as it eliminates the difficulties of selecting photosensitive materials suitable for the persistent internal polarization processes.
  • a material which exhibits persistent internal polarization effects would have a low photosensitivity and low impedance change characteristics except those resulting from the internal polarization effect.
  • materials of high photosensitivity and high impedance change characteristics may be used, thereby obtaining a very fast electrophotographic plate.
  • the use of materials which exhibits persistent internal polarization effects are not precluded from the present invention, as shown in the following example.
  • Example 2 ZnCds in powder form, silver (Ag) activated and having a grain size of about 5 microns, was molded into a thin layer 2 of about 50 micron thickness using cellulose acetate as the bonding agent.
  • an electrode 4 made from thin aluminum film, and on the obverse side an insulating layer made from 12.5 micron thick polyester resin film, were respectively laminated by suitable adhesive. This constituted the photosensitive element 1.
  • the transparent electrode 5 and the DC current source 6 were substantially the same as those of Example 1.
  • the element 1 was illuminated substantially uniformly over the entire surface by light during the time interval t to t while at the same time a voltage was impressed across the two electrodes such that the polarity of the potential was positive at the transparent electrode 5.
  • This step was taken to create an internal polarization of the entire surface of the element 1 in a single uniform direction, thereby preparing the plate for subsequent illumination by image. Thereafter, the polarity was reversed and during the time interval 1 to t the element was exposed to a light image.
  • the prior illumination of the element was the only step which was materially different from those employed in Example 1.
  • the preexposure illumination lasted for 2 seconds, and the light image intensity at the time of the exposure of the element was 20 luxes.
  • FIGURE 12-A illustrates the changes in the surface potential at each step of the operation described
  • FIGURE 12-B illustrates the changes in the surface potential when the element was not exposed to light at the time the initial voltage was impressed across the element.
  • the potential difference G between the exposed and unexposed areas which determines the intensity of the latent image
  • FIG- URE 12-A which represents the operation in which the element was initially exposed to light when the field voltage was impressed.
  • a unique characteristic of this embodiment is the fact that the surface charge potential registered appears quite low even after the element is separated from the transparent electrode, if the element is not thereafter exposed to light.
  • the surface potential at the exposed areas of the element measured prior to such post-exposure illumination by light was found to be -200 volts, the same was measured at -400 volts after the element was so illuminated by light.
  • Example 1 An important difference between the processes of Example 1 and Example 2 involves charges at the boundary surface regions of the light sensitive crystals and bonding agent which are related to the changes in the intrinsic impedance of the light sensitive crystals.
  • Example 1 In case of Example 1, during the interval of t to t (FIGURES 3 and 4), the impedance of crystals present in the photosensitive layer unexposed to light is quite high, so that it is probable that, at the boundary surfaces of the light sensitive crystals, electric charges will build up which will correspond to the polarity of the externally applied electric field. On the other hand, during the interval of t to in the areas exposed to light, the resistivity of the light sensitive crystals greatly decreases, which indicates that such electrostatic charges would hardly build up at the surface regions of the crystals exposed to light.
  • Example 2 shows that in case of Example 1 wherein highly sensitive photoconductive crystals in particulate form are used, no charge build-up at the boundary surfaces of the photosensitive crystals where they are in contact with the bonding agent will occur in the areas exposed to light, and such charge build-up on the surface of the boundary regions will occur only in the areas unexposed to light during the time interval t to t
  • Example 2 the situation is different, and it is apparent that the rate of electron trap will become higher in the boundary surface regions because conduction electron density becomes higher there even at the areas exposed to light, and the boundary surface regions maintain a high resistivity and do not permit free migration of charged carriers at the surface of the crystals.
  • Example 2 in which phosphor crystals in powder form are used as the photosensitive material, the charge build-up may occur at the boundary surfaces of the photosensitive crystals where they are in contact with the bonding agent, irrespective of whether the crystals have been exposed to light.
  • the surface charges of the element are not counterbalanced merely by reverse charges and the internal polarization within the light sensitive crystals, but it should be clear from the foregoing discussion that it also involves the charges built up at the boundary surface regions of the light sensitive crystals and the bonding medium.
  • Such charges built up in the boundary surface regions have a reverse polarity with respect to the polarity of the internal polarization and operate to negate the internal polarization field induced within the crystals, and thus the total effect of such charges present at the boundary surface regions is detrimental to obtaining the optimum signal-to-noise ratio.
  • Example 1 using a highly photoconductivesubstance
  • Example 2 using a phosphor
  • the present invention does not rely solely upon the persistent internal polarization principles. Because the internal polarization principles fail to explain the relatively large fluctuation of the surface charge observed on the unexposed areas of the element when the element, after the removal of the transparent electrode, is illuminated by light, despite the fact that the areas not exposed to light during the time interval of t to t would have the least amount of photoconductive electrons and would have, accordingly, the least opportunity to form internal polarization, we believe that, as discussed above, the unexposed areas of the element described in Example 1 possess on the surface of the photoconductive crystals electric charges having such polarity as will be dictated by the externally applied electric field, which will disappear through recombination of electrons as a result of the lowering of the resistivity of the crystals induced by light to which the element is exposed after the removal of the transparent electrode.
  • Examples 3 and 4 are more symmetrical in construction than the element 1 used in Example 1, and they remove the disadvantages resulting from the asymmetrical construction utilized in Example 1.
  • Examples 3 and 4 also prove (as a result of insertion of another insulating layer, sandwiching the light sensitive layer) that the working principles of the element of the present invention do not depend on the transfer of charges carriers between the light sensitive layer and the electrical field externally applied for effective latent image formation, but that such formation of latent image on the surface of the insulating layer depends solely on the occurrences of certain phenomena, as described above, within the light sensitive layer, which distinguishes the invention from other dry electrophotographic methods with which the art is now familiar.
  • Example 3 The only difference in the construction of the light sensi- Example 1 is, as shown in FIGURE 13, that another insulating layer 10, having the material characteristics and dimensions equal to those of the insulating layer 3, was interposed between the sensitive layer 2 and the electrode 4, so the light sensitive layer 2 had an insulating layer on each side. Insulating layer was also integrally laminated to the element. Latent image formation was successfully carried out on this element 11 by the steps exactly as described in Example 1.
  • the photosensitivity of the element 11 was the same as the element described in Example 1, and an exposure for 0.1 second to a light image of luxes obtained a latent image of usable strength.
  • the exposure to light image, and the time sequency of field impression were the same as described in Example 1.
  • Example 1 When the voltage externally applied was 2,000 volts, as in Example 1, the charge potential of the element at the area exposed to light was 1,200 volts, whereas the charge potential at the unexposed areas was subsentially zero. While there was thus a slight drop in efficiency, this was compensated by an advantage not demonstrated by the element used in Example 1.
  • the signal-to-noise ratio of the latent image was considerably improved compared with Example 1, which indicates elimination of the .socalled noise factor due to the highly unsymmetrical structure of the element or of the low energy input appearing as latent image. Particularly, the fact that noises due to unsymmetrical nature of the element are essentially eliminated has an important practical significance.
  • Example 4 In this example, the same photosentive element 11 described in Example 3 and shown in FIGURE 13 was used. As shown in FIGURE 14, the steps up to t starting from t were the same as those employed in Example 1. During the time interval to t without illuminating the element with a light image, the electric field was removed, the transparent electrode 5 temporarily separated from the element 11 and the transparent electrode 5 was again contacted with element 11.
  • the latent image produced in each of Examples 2 to 4, inclusive can be developed into a visible image and transferred to a sheet of paper, or the like, by the means and methods discussed above in connection with Example 1.
  • the characteristics of the photosensitive materials used are an important feature of the invention.
  • photosensitive material in powder form is bonded together in a thin layer by electrically insulating adhesive, and either one or both surfaces of the layer is covered with thin layer of electrically insulating material, a sudden change of resistance will occur when an electric field impressed across such element is reversed. This effect is more pronounced when an activating material is present in the photosensitive material to activate its light sensitivity.
  • the selected bonding agent should have a specific volume resistivity of at least 10 ohm-centimeters and be transparent to the incident light used.
  • the thickness of the sensitive layer should also be considered in selecting the bonding agent for desired strength and mechanical flexibility of the layer, as well as for the absorption of incident light.
  • a suitable insulating layer material which should be transparent to the incident light and which should allow most of the field to be impressed upon the sensitive layer when the sensitive layer is unexposed and most of the field to be impressed upon the insulating layer when the sensitive layer is exposed to light, is selected and bonded to the sensitive layer by a suitable adhesive transparent to the incident light and having high electrical resistance.
  • Such insulating layer may be bonded to one side of the sensitive layer, in which case the opposite side of the sensitive layer should be bonded by a suitable adhesive to an electrically conductive electrode, or such insulating layer may be bonded to both sides of the sensitive layer, in which case the backing electrode should be bonded to one of the outside surfaces of such insulating layers sandwiching the sensitive layer.
  • the insulating layer should preferably be selected from a group of materials having a volume resistivity of ohm-cm. or more and also having surface resistivity of 10 ohm-cm. or more.
  • the surface-to-surface resistance per unit area of such insulating layer should be 10 ohms per square centimeter or more, and dielectric constant thereof should be such that when considered in terms of the dielectric constant of the sensitive layer, in a perfect darkness and having no prior history of exposure to light, the intensity of electric field impressed to the insulating layer in that condition should be at least equal to or less than that of the field which would be distributed to the sensitive layer.
  • Another consideration relating to the se lection of the insulating layer material is that when the dielectric constant of the photosensitive layer is increased as a result either of sudden increase of conduction electrons within the sensitive layer or at the trap levels induced by exposure to light, the electric field impressed upon the insulating layer should be markedly greater than that impressed upon the sensitive layer.
  • the light sensitive material made into a thin layer, as a whole, and the insulating layer should satisfy the following requirements: First, as the rate of light absorption determines the sensitivity of the layer, light absorption should be high, but a layer excessively thick with respect to the incident light requires that a higher external voltage be impressed on the element, and such excess thickness also operates detrimentally to the formation of charge on the surface of the element; accordingly, the sensitive layer should not be thicker than necessary. Secondly, the insulating layer should be selected so that the impedance and dielectric constant thereof maintain discrete relationship to the impedance and dielectric constant of the sensitive layer. This is essential in obtaining an element of high efficiency.
  • a method of forming an electrostatic latent image comprising varying electric charges on an insulating surface comprises providing an element made up of a thin electrically insulating transparent layer that is bonded to a thin layer comprising finely divided particles of a material that develops electrical conductivity when exposed to light, which particles are bonded into such thin layer by a solid bonding agent that is electrically non-conductive but transparent to light, which thin layer of particles is in inductive proximity to another electrode on the side thereof opposite the side to which said insulating layer is bonded, positioning a removable light-transparent electrically conductive electrode in contact with said insulating transparent layer, impressing a direct current voltage across said transparent electrode and said other electrode, than reversing the polarity of said direct current voltage While substantially simultaneously illuminating through said transparent electrode the surface of said transparent insulating layer with a light image, extinguishing said illumination by said light image, ceasing impression of said direct current voltage and removing said transparent electrode from said surface of said transparent insulating layer while not permitting light to illuminate
  • a method of electrophotography which comprises providing an element composed of a photosensitive material in particulate form bonded into a film not more than 200 microns thick by means of a high polymer bonding agent having a specific volume resisitivity of at least 10 ohm-centimeters and transparent to light thereby providing a photosensitive layer, a thin insulating layer not more than 50 microns thick composed of a material selected from a group of materials being transparent to light and possessing a highly insulating property and having a specific volume resistivity of at least 10 ohm-centimeters and a specific surface resistivity of at least 10 ohms per square centimeter, said thin insulating layer having a surface-to-surface resistivity per unit area of at least 10 ohms per square centimeter and being bonded to said photosensitive layer and a electrode composed of an electrically conductive material bonded to the surface of said photosensitive layer opposite said insulating film, disposing a removable transparent electrode in surface-to-surface contact
  • a method of electrophotography which comprises providing an element composed of a photosensitive material in particulate form bonded into a film not more than 200 microns thick by means of a high polymer bonding agent having a specific volume resistivity of at least ohm-centimeters and transparent to light thereby providing a photosensitive layer, a thin insulating layer having not more than 50 microns in thickness of a material selected from a group of materials being transparent to light and possessing highly insulating property and having a specific volume resistivity of at least 10 ohms per square centimeter, said thin insulating layer having a surface-to-surface resistivity per unit area of at least 10 ohms per square centimeter and being bonded to said photosensitive layer, said materials of said photosensitive layer and said thin insulating layer being selected such that the consumption of electricity by an electric field externally impressed upon said two layers in said photosensitive layer at the time said photosensitive layer is illuminated by light falling thereon is not greater than the consumption of electricity by said field so impressed externally
  • a method of electrophotography which comprises providing an element composed of a photoconductive or phosphor material in particulate form bonded into a film not more than 200 microns thick by means of a high polymer bonding agent having a specific volume resistivity of at least 10 ohm-centimeters and transparent to light thereby providing a photosensitive layer, a first thin insulating layer not more than 50 microns thick composed of a material selected from a group of materials being transparent to light and possessing highly insulatmg property and having a specific volume resistivity of at least 10 ohm-centimeters and a specific surface resistivity of at least 10 ohms per square centimeter prepared such that the surface-to-surface resistivity of said layer is at least 10 ohms per square centimeter and being bonded to said photosensitive layer, a second thin insulating layer composed of a material selected from a group of materials possessing highly insulating property and having a specific volume resistivity of at least 10 ohm-centimeter
  • the method of forming an electrostatic latent image embodying varying electric charges on a surface composed of insulating material which comprises providing an element made up of a thin electrically insulating layer directly bonded through its entire area to a photosensitive layer, subjecting said element to an electric field between an electrode on the same side of said element as said insulating layer and an electrode on the side of said element opposite said insulating layer to deposit charges of a first polarity on the element, thereafter illuminating the element with a light image while subjecting the element to an electric field between an electrode on the same side of said element as said insulating layer and an electrode on the side of said element opposite said insulating layer to deposit on the element charges of a polarity opposite to the first polarity, stopping the illumination of the element with the image and removing the electric field without shortcircuiting the said electrodes between which the lastmentioned field was created, said latent image being characterized by not being erased by subsequent exposure to ambient light.
  • the method of forming an electrostatic latent image embodying varying electric charges on a surface composed of insulating material which comprises providing an element made up of a thin electrically insulating layer directly bonded through its entire area to a photosensitive layer, subjecting said element to an electric field between an electrode on the same side of said element as said insulating layer and an electrode on the side of said element opposite said insulating layer to deposit charges of a first polarity on the element, thereafter illuminating the element with a light image while subjecting the element to an electric field between an electrode on the same side of said element as said insulating layer and an electrode on the side of said element opposite said insulating layer to deposit on the element charges of a polarity opposite to the first polarity, stopping the illumination of the element with the image, removing the electric field without short-circuiting the said electrodes between which the last-mentioned field was created and thereafter subjecting said element to substantially uniform illumination thereby enhancing said latent image, said latent image being characterized by not being erased by subsequent exposure
  • a method according to claim 11 including the additional step of developing the latent image by the application of a toner thereto.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Photoreceptors In Electrophotography (AREA)
US471606A 1964-07-25 1965-07-13 Electrophotography Expired - Lifetime US3457070A (en)

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NL (1) NL6509608A (de)

Cited By (37)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3597072A (en) * 1968-10-03 1971-08-03 Owens Illinois Inc Electrode configuration for electrophotography
US3653064A (en) * 1968-02-25 1972-03-28 Canon Kk Electrostatic image-forming apparatus and process
US3655369A (en) * 1967-09-05 1972-04-11 Katsuragawa Denki Kk Persistent internal polarization process in electrophotography
US3681777A (en) * 1970-08-28 1972-08-01 Xerox Corp Recording apparatus
US3718462A (en) * 1969-06-03 1973-02-27 Xerox Corp Manifold electrification process
US3720513A (en) * 1969-08-21 1973-03-13 Xerox Corp Migration imaging method involving solvent wash-away of unmigrated particles
US3775104A (en) * 1970-12-29 1973-11-27 Mita Industrial Co Ltd Electrophotographic process using corona discharge current of an asymmetrical wave form
US3795011A (en) * 1968-04-10 1974-02-26 Ricoh Kk Electrostatic printing device
US3807998A (en) * 1969-12-17 1974-04-30 Katsuragawa Denki Kk Method of colour electrophotography
US3816115A (en) * 1970-06-26 1974-06-11 Xerox Corp Method for forming a plurality of electrostatic latent images on an electrophotographic plate
US3837849A (en) * 1973-02-20 1974-09-24 Xerox Corp Multilayered variable speed photoreceptor and method of using same
US3849129A (en) * 1970-10-27 1974-11-19 Katsuragawa Denki Kk ELECTROPHOTOGRAPHIC ELEMENT CONTAINING Se-Te ALLOY LAYERS
US3849128A (en) * 1967-12-30 1974-11-19 Canon Kk Process for producing a drum photosensitive member for electrophotography
US3894870A (en) * 1970-05-29 1975-07-15 Katsuragawa Denki Kk Photosensitive elements for use in electrophotography
US3932877A (en) * 1973-07-04 1976-01-13 Mitsubishi Denki Kabushiki Kaisha Electrophotographic recording system with plate cleaning
US3941591A (en) * 1969-01-22 1976-03-02 Canon Kabushiki Kaisha Electrophotographic photoconductive member employing a chalcogen alloy and a crystallization inhibiting element
US3948657A (en) * 1968-11-07 1976-04-06 Canon Kabushiki Kaisha Photosensitive matter for electrophotography and method of the production thereof
US3976483A (en) * 1970-01-02 1976-08-24 Xerox Corporation Erasing process
US4052208A (en) * 1973-05-04 1977-10-04 Martinelli Michael A Image recording medium employing photoconductive granules and a heat disintegrable layer
US4052206A (en) * 1974-11-07 1977-10-04 Hitachi, Ltd. Electrophotography
US4063943A (en) * 1976-08-23 1977-12-20 Xerox Corporation Electrostatographic imaging method
US4071361A (en) * 1965-01-09 1978-01-31 Canon Kabushiki Kaisha Electrophotographic process and apparatus
US4086088A (en) * 1976-03-25 1978-04-25 Addressograph Multigraph Corporation Imaging methods for use with charged particle modulator device
US4170475A (en) * 1977-05-12 1979-10-09 Coulter Information Systems, Inc. High speed electrophotographic method
US4233612A (en) * 1974-07-10 1980-11-11 Canon Kabushiki Kaisha Image information electrostatic recording device
US4255505A (en) * 1969-11-11 1981-03-10 Canon Kabushiki Kaisha Electrophotographic process using layered element containing p-type or n-type materials, with multiple charging steps and blanket irradiation
US4275134A (en) * 1974-07-30 1981-06-23 Canon Kabushiki Kaisha Electrophotographic method for reproducing a multicolor image
US4288514A (en) * 1969-07-28 1981-09-08 Canon Kabushiki Kaisha Method for controlling image formation in electrophotography by pre-exposure step
JPS5642866B1 (de) * 1970-10-29 1981-10-07
US4298669A (en) * 1966-02-23 1981-11-03 Canon Kabushiki Kaisha Electrophotographic process and apparatus
US4331753A (en) * 1978-11-27 1982-05-25 Minnesota Mining And Manufacturing Company Method for providing an electrical charge pattern on the insulative layer of an insulative layer-photoconductive layer-conductive layer structure
US4352875A (en) * 1980-02-05 1982-10-05 Canon Kabushiki Kaisha Voltage distribution difference electrophotographic process
US4391512A (en) * 1979-01-06 1983-07-05 Canon Kabushiki Kaisha Developing device using magnetic developer
US4444859A (en) * 1981-05-30 1984-04-24 Olympus Optical Company Limited Electrophotographic process and photosensitive member for use in said process
US4606949A (en) * 1983-07-18 1986-08-19 Canon Kabushiki Kaisha Coating method
US4621919A (en) * 1983-07-13 1986-11-11 Canon Kabushiki Kaisha Metal drum and image holding member using the same
US20120261181A1 (en) * 2009-05-22 2012-10-18 Koichi Izawa Electromagnetic shielding method and electromagnetic shielding film

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1797608C2 (de) * 1965-07-12 1980-04-24 Canon K.K., Tokio Elektrophotographisches Verfahren zum Erzeugen eines Ladungsbildes auf einer isolierenden Schicht
US4155640A (en) * 1977-05-12 1979-05-22 Coulter Systems Corporation High speed electrophotographic imaging system
DE59705891D1 (de) * 1996-03-29 2002-01-31 Oce Printing Systems Gmbh Elektrofotografisches druckverfahren zum bedrucken eines trägers

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US2853383A (en) * 1953-10-02 1958-09-23 Paul H Keck Method and apparatus for amplifying photoelectric currents
US2901348A (en) * 1953-03-17 1959-08-25 Haloid Xerox Inc Radiation sensitive photoconductive member
US2912592A (en) * 1954-10-07 1959-11-10 Horizons Inc Memory device
US3196011A (en) * 1962-05-08 1965-07-20 Xerox Corp Electrostatic frosting
US3268331A (en) * 1962-05-24 1966-08-23 Itek Corp Persistent internal polarization systems
US3308233A (en) * 1963-09-09 1967-03-07 Xerox Corp Xerographic facsimile printer having light beam scanning and electrical charging with transparent conductive belt
US3347669A (en) * 1964-03-27 1967-10-17 Dick Co Ab Photoconductive copy system

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US2901348A (en) * 1953-03-17 1959-08-25 Haloid Xerox Inc Radiation sensitive photoconductive member
US2741959A (en) * 1953-04-10 1956-04-17 Haloid Co Electrophotography
US2853383A (en) * 1953-10-02 1958-09-23 Paul H Keck Method and apparatus for amplifying photoelectric currents
US2912592A (en) * 1954-10-07 1959-11-10 Horizons Inc Memory device
US3196011A (en) * 1962-05-08 1965-07-20 Xerox Corp Electrostatic frosting
US3268331A (en) * 1962-05-24 1966-08-23 Itek Corp Persistent internal polarization systems
US3308233A (en) * 1963-09-09 1967-03-07 Xerox Corp Xerographic facsimile printer having light beam scanning and electrical charging with transparent conductive belt
US3347669A (en) * 1964-03-27 1967-10-17 Dick Co Ab Photoconductive copy system

Cited By (38)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4071361A (en) * 1965-01-09 1978-01-31 Canon Kabushiki Kaisha Electrophotographic process and apparatus
US4298669A (en) * 1966-02-23 1981-11-03 Canon Kabushiki Kaisha Electrophotographic process and apparatus
US3655369A (en) * 1967-09-05 1972-04-11 Katsuragawa Denki Kk Persistent internal polarization process in electrophotography
US3849128A (en) * 1967-12-30 1974-11-19 Canon Kk Process for producing a drum photosensitive member for electrophotography
US3653064A (en) * 1968-02-25 1972-03-28 Canon Kk Electrostatic image-forming apparatus and process
US3795011A (en) * 1968-04-10 1974-02-26 Ricoh Kk Electrostatic printing device
US3597072A (en) * 1968-10-03 1971-08-03 Owens Illinois Inc Electrode configuration for electrophotography
US3948657A (en) * 1968-11-07 1976-04-06 Canon Kabushiki Kaisha Photosensitive matter for electrophotography and method of the production thereof
US3941591A (en) * 1969-01-22 1976-03-02 Canon Kabushiki Kaisha Electrophotographic photoconductive member employing a chalcogen alloy and a crystallization inhibiting element
US3718462A (en) * 1969-06-03 1973-02-27 Xerox Corp Manifold electrification process
US4288514A (en) * 1969-07-28 1981-09-08 Canon Kabushiki Kaisha Method for controlling image formation in electrophotography by pre-exposure step
US3720513A (en) * 1969-08-21 1973-03-13 Xerox Corp Migration imaging method involving solvent wash-away of unmigrated particles
US4255505A (en) * 1969-11-11 1981-03-10 Canon Kabushiki Kaisha Electrophotographic process using layered element containing p-type or n-type materials, with multiple charging steps and blanket irradiation
US3807998A (en) * 1969-12-17 1974-04-30 Katsuragawa Denki Kk Method of colour electrophotography
US3976483A (en) * 1970-01-02 1976-08-24 Xerox Corporation Erasing process
US3894870A (en) * 1970-05-29 1975-07-15 Katsuragawa Denki Kk Photosensitive elements for use in electrophotography
US3816115A (en) * 1970-06-26 1974-06-11 Xerox Corp Method for forming a plurality of electrostatic latent images on an electrophotographic plate
US3681777A (en) * 1970-08-28 1972-08-01 Xerox Corp Recording apparatus
US3849129A (en) * 1970-10-27 1974-11-19 Katsuragawa Denki Kk ELECTROPHOTOGRAPHIC ELEMENT CONTAINING Se-Te ALLOY LAYERS
JPS5642866B1 (de) * 1970-10-29 1981-10-07
US3775104A (en) * 1970-12-29 1973-11-27 Mita Industrial Co Ltd Electrophotographic process using corona discharge current of an asymmetrical wave form
US3837849A (en) * 1973-02-20 1974-09-24 Xerox Corp Multilayered variable speed photoreceptor and method of using same
US4052208A (en) * 1973-05-04 1977-10-04 Martinelli Michael A Image recording medium employing photoconductive granules and a heat disintegrable layer
US3932877A (en) * 1973-07-04 1976-01-13 Mitsubishi Denki Kabushiki Kaisha Electrophotographic recording system with plate cleaning
US4233612A (en) * 1974-07-10 1980-11-11 Canon Kabushiki Kaisha Image information electrostatic recording device
US4275134A (en) * 1974-07-30 1981-06-23 Canon Kabushiki Kaisha Electrophotographic method for reproducing a multicolor image
US4052206A (en) * 1974-11-07 1977-10-04 Hitachi, Ltd. Electrophotography
US4086088A (en) * 1976-03-25 1978-04-25 Addressograph Multigraph Corporation Imaging methods for use with charged particle modulator device
US4063943A (en) * 1976-08-23 1977-12-20 Xerox Corporation Electrostatographic imaging method
US4170475A (en) * 1977-05-12 1979-10-09 Coulter Information Systems, Inc. High speed electrophotographic method
US4331753A (en) * 1978-11-27 1982-05-25 Minnesota Mining And Manufacturing Company Method for providing an electrical charge pattern on the insulative layer of an insulative layer-photoconductive layer-conductive layer structure
US4391512A (en) * 1979-01-06 1983-07-05 Canon Kabushiki Kaisha Developing device using magnetic developer
US4352875A (en) * 1980-02-05 1982-10-05 Canon Kabushiki Kaisha Voltage distribution difference electrophotographic process
US4444859A (en) * 1981-05-30 1984-04-24 Olympus Optical Company Limited Electrophotographic process and photosensitive member for use in said process
US4621919A (en) * 1983-07-13 1986-11-11 Canon Kabushiki Kaisha Metal drum and image holding member using the same
US4606949A (en) * 1983-07-18 1986-08-19 Canon Kabushiki Kaisha Coating method
US20120261181A1 (en) * 2009-05-22 2012-10-18 Koichi Izawa Electromagnetic shielding method and electromagnetic shielding film
US8853562B2 (en) * 2009-05-22 2014-10-07 Sony Corporation Electromagnetic shielding method and electromagnetic shielding film

Also Published As

Publication number Publication date
FR1454439A (fr) 1966-02-11
DE1497164B2 (de) 1973-10-04
BE667299A (de) 1965-11-16
NL6509608A (de) 1966-01-26
DE1497164C3 (de) 1974-05-09
DE1497164A1 (de) 1969-04-17
GB1120123A (en) 1968-07-17

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