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Publication numberUS3835355 A
Publication typeGrant
Publication dateSep 10, 1974
Filing dateAug 13, 1973
Priority dateAug 13, 1973
Publication numberUS 3835355 A, US 3835355A, US-A-3835355, US3835355 A, US3835355A
InventorsTsukada S
Original AssigneeCanon Kk
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Liquid discharging or charging device
US 3835355 A
Abstract
A liquid discharging or charging device comprises means for supplying discharging or charging liquid to the surface of a photosensitive medium in an electrophotographic copying apparatus. Means is provided to apply a reference potential to the supplied liquid. A blade bears against the surface of the photosensitive medium to remove the supplied discharging or charging liquid therefrom. Means is provided to supply lubricant liquid to the area of contact of the blade with the surface of the photosensitive medium. A container is provided for collecting therein the discharging or charging liquid removed by the blade.
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Description  (OCR text may contain errors)

Limited States Patent Tsukada T Sept. 10, 1974 LIQUID DISCHARGING 0R CHARGING 3,648,133 3/1972 Leiga 317/262 A DEVICE Primary Examiner-L. T. Hix [75] Inventor Syusel Tsukada Tokyo Japan Attorney, Agent, or FirmFitzpatrick, Cella, Harper [73] Assignee: Canon Kabushiki Kaisha, Tokyo, & Scinto Japan [22 Filed: Aug. 13, 1973 ABSTRACT [21] Appi NOJ 387,815 A liquid discharging or charging device comprises means for supplying discharging or charging liquid to the surface of a photosensitive medium in an electro- U-S. A photographic copying apparatus Means is provided to Ilt. a reference potential to the upplied A Field of Search 355/ 3 317/262 A blade bears against the surface of the photosensitive medium to remove the supplied discharging or charg- References Cited ing liquid therefrom. Means is provided to supply lu- UNITED STATES PATENTS bricant liquid to the area of contact of the blade with 2,904,431 9/1959 Moncrieff-Yeates 317/262 A the sulface 0f the photosensitive medium A Container 2,987,660 6/1961 Walkup 317/262 A is Provided for Collecting therein the discharging of 3,398,336 8/1968 Martel et al. 317/262 A charging liquid removed by the blade. 3,546,545 12/1970 Sato et al 317/262 A 3,549,962 12/1970 126111 317/262 A 41 Claims, 39 Drawing Figures PATENTEDSEPI 0:914

SHEET 01 0F 13 FIG.

FIG. 2

SHEET 02 HF 13 PAIENIE sEP 1 01914 FIG. 3

FIG. 4

sum UBUF 13 FIG. 5

FIG. 6

PATENTED SEP] 0 [974 PATENTEDSEPIOIBH 3.555.355 SHEET (:06 0F 13 PAIENTEUSEPIOIQH 3555.355

' SHEET 09 0F 13 FIG. I4B

PATENTEI] SEP 1 01974 SHEET 11 OF 13 PAIENTEU SEP] 0 1974 sum '12 or 13 FIG. I9

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a liquid discharging or charging device. More particularly, it relates to a liquid discharging or charging device of the type in which noninsulative liquid at a desired potential is used to discharge or charge the surface of a photosensitive medium in an electrophotographic copying apparatus, and to improvements in such device so as to the reduce the friction produced between the surface of the photosensitive medium and a resilient blade when the liquid used for the discharging or charging is removed from said surface by said resilient blade.

2. Description of the Prior Art The present Applicants have previously proposed an improved electrophotographic method in Japanese Patent Application No. 1482/1972. Such electrophotographic method has comprised using a photosensitive medium basically consisting of an insulative layer, a photoconductive layer and a conductive backing member; pre-charging the surface of the insulative surface of the photosensitive medium with a desired polarity by means of an electrode, a corona discharger or a liquid discharging or charging device, said polarity being positive or negative in dependence of N- or P-type photoconductivity of said photoconductive layer, thereby forming a charge opposite in polarity to the charge of the surface ofsaid insulative layer in the vicinity of the interface between the photoconductive layer and the insulative layer; then contacting the liquid with the charged surface of said insulative layer, said liquid being preset to satisfy the relation that (I) t/Ci-d, where is the resistivity of said liquid, Ci the electrostatic capacity ofsaid insulative layer, d the thickness of the layer of the liquid and t the discharging or charging time, said liquid being brought to a desired potential (including a grounded potential), and simultaneously therewith or immediately therebefore, applying an image light to the surface of said photosensitive medium to thereby vary the charged condition of the photosensitive medium in accordance with the lightand-dark pattern of an original image; subsequently removing the discharging or charging liquid; thereafter uniformly exposing the entire surface of the insulative layer to light to liberate the charge in the vicinity of an interface between the photoconductive layer and the insulative layer corresponding to the dark area of the original image, thereby forming an electrostatic copy image of high contrast on the surface of the photosensitive medium. Further, the formed electrostatic image is liquidor dry-developed by a developer chiefly composed of charged toner particles, whereafter the now visible image is transferred to paper or the like transfer medium by utilizing an internal or external field and, then, the transfer image is heated and fixed by an infrared ray lamp or like means to provide an electrophotographic copy image. On the other hand, after the image has been transferred, the surface of the aforesaid insulative layer is cleaned to remove any residual charged particles therefrom so that the photosensitive medium is ready for repeated use. Where a photosensitive medium in use comprises three layers, i.e. an insulative layer, a photoconductive layer and an insulative layer, or further includes a conductive layer, a discharging or charging liquid is used for said discharging or charging simultaneously with or immediately before the application of image light, the liquid being at a desired potential (including a grounded potential) and preset to satisfy the relation that (1: t(Cl C2)/Cl-C2'd, where d) is the resistivity of the liquid, C l and C2 the electrostatic capacities of said insulative layers, d the thickness of the layer of the liquid, and t the discharging or charging time, whereafter the subsequent steps similar to those described above may occur.

In such electrophotographic method, a liquid discharging or charging device is provided so that discharging or charging liquid at a desired potential is caused to exist on the surface of the photosensitive medium to thereby effect the discharging or charging action, whereafter the liquid remaining on such surface is removed by a blade or the like means disposed in contact with said surface. Such liquid discharging or charging device has suffered'from a problem that the liquid used for the discharging or charging is so poor in wettability with respect to the surface of the photosensitive medium or of the resilient blade that the liquid, which is to be removed by the blade, would not readily come into the area of contact between the blade and the photosensitive medium, thus resulting in their unsmooth relative movement. In other words, the blade would tend to take off the surface of the photosensitive medium or produce noises or vibrations, thus making the setting of the blade quite difficult.

With such liquid discharging or charging device, it has also been unavoidable that when the discharging or charging is being carried out with the discharging or charging liquid supplied into the clearance between the photosensitive medium and an adjacent member for the application of image light (the entire face of an optical fiber tube if such tube is used for the application of image light simultaneously with the discharging or charging), foreign materials such as fine particles of metal, dirt, dust, fiber, etc. suspended within the copying apparatus and fine particles of toner remaining on the surface of the photosensitive medium come to mingle to the liquid. Entry of such a mixture of liquid and foreign materials into said clearance has injured or damaged the surface of the photosensitive medium and/or the face of the adjacent member (optical fiber tube). Further, during the simultaneous application of image light and discharging or charging, the clearance between the photosensitive medium and the adjacent member (optical fiber tube) must be of the order of O to microns, which is wide enough to permit intrusion of said foreign materials into such clearance, and this has not only imparted injuries to the surfaces of the photosensitive medium and adjacent member (optical fiber tube) but also caused formation of stained copy images because those foreign materials are projected together upon the surface of the photosensitive medium during the image light application effected through the adjacent member (optical fiber tube).

After the surface of the photosensitive medium has been discharged or charged, the liquid used therefor must be removed by the blade, but the use of such blade alone might leave uncleaned portions on the surface of the photosensitive medium because of the presence of solid toner and dust or other foreign particles sticking to such portions, or such foreign materials themselves would contact an electrostatic latent image to partly disturb such image or injure the photosensitive medium or the blade. Also, it has been possible that the liquid leaks down from the opposite sides of the blade to adversely affect the subsequent steps such as overall exposure, development, etc.

SUMMARY or THE INVENTION It is another object of the present invention to provide an improved liquid discharging or charging device which supplies lubricant liquid between a blade and the photosensitive medium when discharging or charging liquid is removed by the blade after completion of the liquid discharging or charging, thereby providing a smooth relative movement between the blade and the photosensitive medium.

It is still another object of the present invention to provide an improved liquid discharging or charging device which remove fine particles of foreign materials that have intruded into the discharging or charging liquid supplied to the device.

It is yet another object of the present invention to provide an improved liquid dischargingor charging device which removes by sucking the discharging or charging liquid as it is wiped off the surface of the photosensitive medium by the blade after completion of the discharging or charging.

It is yet still another object of the present invention to providean improved. liquid discharging or charging device which employs a discharging or charging liquid having a refractive index of 1.3 or higher, thereby improving transmission of light information. from an optical fiber plate to the surface of the photosensitive medium.

present invention a slight amount of highly lubricant liquid is supplied to the area of contact between the surface of the photosensitive medium and the resilient blade to reduce the frictional coefficient therebetween and thereby ensure the blade to maintain a stable position for removing the discharging or charging liquid. Such highly lubricant liquid may desirably have a good wettability with respect to the surface of the photosensitive medium and of the blade, but may or may not have solubility to the discharging or charging liquid. Particularly, where the wet type development is employed, the lubricant-liquid should be insulative and desirably have no property which would affect the developing liquid if mingled with the latter.

As to the fine particles of foreign materials that have already intruded into the discharging or charging liquid, only the portion of the liquid which contains such foreign materials may be flushed and removed toprevent such foreign materials from intruding into the clearance between the surface of the photosensitive medium and'the adjacent member before discharging or charging liquid is supplied into such clearance. Alternatively, the liquid mingled with foreign materials may be sucked for removal with a portion of the liquid before it enters into the clearance. Further, any fine particles of foreign materials which tend to intrude into the space between the photosensitive medium and the blade may be sucked for removal by a suction nozzle To achieve these objects, in accordance with the provided near the area of contact between the blade and the photosensitive medium and, moreover, the liquid itself may be flowed down from the opposite sides of the blade to prevent intrusion of the foreign materials.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more fully apparent from the following detailed description of various embodiments thereof taken in conjunction with the accompanying drawings, in which:

FIG. '1 schematically illustrates an electrophot'ographic copying apparatus which incorporates an embodiment of a liquid discharging or charging device according to the present invention;

FIGS. 2 to 10 schematically illustrate various em bodiments of a liquid discharging or charging device according to the present invention;

FIG. 1 l is a schematic illustration of an electrophotographic copying apparatus which incorporates an embodiment of a liquid discharging or charging device according to the present invention;

FIGS. 12 to 15 schematically illustrate further embodiments of a liquid discharging or charging device according to the present invention;

FIG. 16' shows various forms of the suction nozzle shown in FIG. 15; and g FIGS. 17 to 21 schematically illustrate further embodiments of the discharging or charging device according to the present invention.

. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a photosensitive medium (drum) basically comprising an insulative layer, a photoconductive layer and a conductive backing layer is generally designated by reference numeral 1 and rotatable in the direction of an arrow. The outermost surface of the photosensitive drum may be uniformly charged by a primary charger 2. Thereafter, the said surface of the drum may be exposed to an image light through an optical fiber tube 3 while discharging or charging liquid from a tank 4 may be supplyed by a supply pump 5 into the clearance between the optical fiber tube and the photosensitive drum through a supply pipe 6 so as to form a layer of liquid 7 to which an appropriate potential may be applied, thus accomplishing the simultaneous application of image light and discharging or charging. The amount of the liquid once used for the simultaneous application of image light and discharging or charging may be removed from the surface of the photosensitive drum by means of a doctor blade 8, whereupon, in accordance with the present invention, a slight amount of lubricant liquid (which may also be insulative if required) may be supplied from a tank 9 through a supply nozzle 10 to the area of contact between the doctor blade and the surface of the photosensitive drum, thereby providing smooth relative movement between the drum surface and the doctor blade. Application of the voltage to the layer 7 of the discharging or charging liquid may be done with the front face of the optical fiber tube covered with a conductive covering, as shown, or with the liquid removing doctor blade pre-treated for conductivity, or with an electrode additionally provided. After the simultaneous application of image light and discharging or charging has been done, the photosensitive drum may undergo an overall exposure at overall exposure means 11 to provide thereon an electrostatic latent image of high contrast, which may then be developed at liquid developing means 12. The development may alternatively be done by dry type developing liquid squeezing corona discharger 13 for removal into the developing means. Thereafter, a transfer medium P may be separated from a stock pile on a transfer medium supply table 14 by a separator roll 15 and fed through a guide plate 16, a set of transport rolls 17 and a guide plate 18 to a transfer station T, where the developed image on the photosensitive drum surface may be transferred to the transfer medium by an image transfer corona discharger 19. After the image transer, the transfer medium P may be transported through a guide plate 20, a set of transport rolls 21 and a guide plate 22 into heating-fixing means 23, where the transfer image may be fixed. The image fixing may alternatively be accomplished by any other suitable techinque such as pressure-fixing, drying-fixing or the like.

After the image transfer, the photosensitive drum may be cleaned for reuse by a cleaning blade 24.

FIG. 2 shows, in perspective view, another embodiment of the liquid discharging or charging device according to the present invention. In the figure, a photosensitive medium 25 and an optical fiber plate 26 are arranged with a clearance therebetween so that the clearance may be filled with discharging, or charging liquid supplied through a supply pipe 27, which liquid may then be brought to a suitable potential. The liquid once used for the discharging or charging may be removed from the surface of the photosensitive medium by means of a doctor blade 28, whereupon an amount of lubricant liquid may be supplied through a lubricant liquid supply pipe 29 to the area of contact between the blade 28 and the surface of the photosensitive medium. To permit smooth collection of the discharging or charging liquid into a receptacle 30, there is provided an air flow nozzle 31 at each side of the blade 28 so that such liquid may be directed thereby toward the center of the blade and flow down along guide grooves 28a formed therein as shown and into the receptacle 30. Where the lubricant liquid is not soluble to the dis charging or charging liquid, the difference in specific gravity between the two liquids may be utilized to separate these two liquids from each other so that they can be reused for discharging or charging and lubrication, respectively.

FIG. 3 shows, in perspective view, a further embodiment of the liquid discharging or charging device according to the present invention, wherein an amount of discharging or charging liquid may be supplied into the clearance between a photosensitive medium 32 and an optical fiber tube 33 through a supply pipe 34 and then brought to a suitable potential.

Once used for its purpose, the amount of discharging or charging liquid may be removed by means of a blade 35 which is downwardly inclined with respect to the horizontal. Lubricant liquid may be supplied through a supply pipe 36 to an upper edge portion of the blade 35 so as to smooth lubrication for the area of contact between the blade and the surface of the photosensitive medium. The mixture of the discharging or charging liquid thus removed by the blade and the lubricant liquid may be forced by an air flow forming nozzle 37 to flow down the inclined surface of the blade. Obliquely downwardly of the blade 28, the mixture of the two liquids may be sucked into a liquid collecting pipe 38 by a suction pump '39 and collected into a liquid receptacle 40 therebelow. Where the two liquids thus collected are insoluble to each other and have a great difference in specific gravity, they may be separated from each other due to such difference, whereafter the lighter liquid, e.g., lubricant liquid and the heavier liquid, e.g., discharging or charging liquid may be recirculated for reuse into their respective supply pipe 36 and 34 by pumps, 41 and 42, respectively. A back plate 43 is attached to the blade 35 to prevent any overflow of the liquids therefrom.

FIG. 4 illustrates means for simultaneous application I of image light and discharging or charging to the photosensitive medium from therebelow. In the figure, the photosensitive medium is designated by 44 and partly bathed in a pool of discharging or charging liquid within a tank 45, which liquid is at a suitable potential. The bottom wall of the tank has a portion 46 which is transparent to light so as to permit application of image light to the photosensitive medium surface through a projection lens 47 and simultaneously therewith, permit the same surface to be discharged or charged by the liquid. After the discharging or charging, the surface of the photosensitive medium may have such liquid removed therefrom by a blade 48. In the shown arrangement, the tank 45 contains therewithin an ordinary non-lubricant discharging or charging liquid and further a lubricant liquid which is soluble to the former liquid, thereby aiding in smooth operation of the blade.

Referring to FIG. 5, there is shown a further embodiment of the present invention in which an amount of discharging or charging liquid may be supplied into the clearance between a photosensitive medium 49 and an optical fiber tube 50 through a supply pipe 51 and brought to a desired potential to effect discharging or charging, whereafter the liquid may be removed by a blade 52 which is provided with a radius of curvature as shown. In this instance, lubn'cant liquid is only supplied to the curve 52a through a supply pipe 53 in order that such liquid may be distributed throughout the area of contact between the blade and the surface of the photosensitive medium. The blade provided with such a radius of curvature tends to experience a take-off phenomenon, but this can be obviated by the action of the lubricant liquid. The liquid removed by the blade and collected in a receptacle 54 is a mixture of discharging or charging liquid and lubricant liquid, but such mixture may be separated into the two liquids which in turn may be recirculated for reuse by a discharging or charging liquid pump 55 and a lubricant liquid pump 56, respectively.

FIGS. 6(a) and (b) show, in schematic view and perspective view, an embodiment of the present invention which employs a projection lens 58 as an optical system for projecting therethrough an image light upon a photosensitive medium 57 and in which discharging liquid may be supplied from a tank 59 through a supply pipe 60 to a conductive roller 61 which is at a suitable potential, so that the liquid may be applied to the surface of the photosensitive medium by the roller, thereby accomplishing simultaneous application of image light and discharging or charging. Supply means for supplying the discharging or charging liquid by such applicator system may take various forms as will hereinafter be described in connection with FIGS. 7 to 10.

Referring to FIG. 7, there is shown one form of such liquid discharging or charging device. Abody of discharging or charging liquid 62 is contained within a liquid supply box 63, into which a liquid applicator member 64 formed of liquid absorbent material such as fabric, sponge, felt or the like extends and is dipped in the liquid. Because of the capillary effect of such applicator member, the discharging or charging liquid may be applied to the surface of the photosensitive medium to form a thin layer of such liquid thereon. The liquid supply box 63 may have a portion forming a keep plate member for urging the liquid applicator member against the surface of the photosensitive medium. The keep plate serves to provide a wider area of contact of the liquid applicator member with the surface of the photosensitive medium to thereby ensure stable formation of a liquid layer.

A desired voltage must be applied to the layer of discharging or charging liquid to thereby discharging or charging the surface of the photosensitive medium. The voltage application may be satisfactorily accomplished by directly short-circuiting to the liquid applicator member, or by forming a liquid removing blade 66 of a conductive material as disclosed hereinafter and short-circuiting to such blade, or by using thesev in combination. The discharging or charging liquid layer brought to a desired potential may take such a form on the surface of the photosensitive medium as indicated at 67 and at the same time, the image light from an original to be copied may be projected through a projection lens 68 to form on the surface of the photosensitive medium a latent image charged in accordance with the light-and-dark pattern of the original image. After this process has been completed, the'discharging or charging liquid may be collected by means of a liquid removing and collecting blade 66. The blade 66 is oriented in the direction counter to the direction of movement of the photosensitive medium and biased about a pivot 69 to bear against the surface of the photosensitive medium so that the liquid can flow down the upper surface of the blade and collected in a liquid collection box 70. The blade is held by a blade holder member 71. The discharging or charging liquid collected in the liquid collection box 70 may be recirculated for reuse into the liquid supply box 63 by a pump 72, but it is imperative at this stage that such liquid be passed through a filter 73 for purification because the liquid may often contain therein admixtures such as toner particles or other foreign materials.

FIG. 8 schematically shows another embodiment of a liquid discharging or charging device according to the present invention. There is a tank 74 for discharging or charging liquid, in which is dipped a liquid absorbent member 75 formed of felt, flannel, suede, sponge or like material so that the liquid may be absorbed in the member 75 due to the capillary effect thereof and applied in a predetermined layer thickness on the surface of the photosensitive medium by means of a discharging or charging liquid applicator roller 76 formed of conductive material such as rubber of .I IS 60 hardness. The liquid thus applied may be brought to a desired potential (including a grounded potential), which may be applied through the applicator roller, thereby forming a predetermined thickness of liquid layer on the area of the photosensitive surface which is exposed to an image light. In the exposure station, the exposure to an image light may be effected through a projection lens 77 simultaneously withthe discharging or charging effected by the liquid layer.

FIG. 9 schematically illustrates still a further embodiment of the present invention. A discharging or charging liquid supply tank 78 contains therewithina body of liquid 89 in which a supply roller 80 is dipped to absorb the liquid, so that the supply roller supplies the liquid to an applicator roller 81 which is in contact with the photosensitive medium surface so as to form a thin layer of such liquid on the surface portion of the photosensitive medium. The application of the potential to the discharging or charging liquid may be accomplished by forming the applicator roller of a conductive material and applying a desired potential thereto. The voltage may be discharged through a thin layer of liquid formed on the surface of the photosensitive medium and simultaneously therewith, an image light may be applied through a lens 82 to the photosensitive medium.

FIG. 10 schematically illustrates still another em- .bodiment of the device according-to the present invention. A tank 83 contains therewithin discharging or charging liquid, which may be delivered through a supplypipe 84 by a pump 85 and applied to the surface of the photosensitive medium through a nozzle port 86. In this instance, a great deal of developing liquid would tend to adhere to the surface of the photosensitive medium and therefore, a blade 87 for adjusting the thickness of liquid layer is provided to provide a predetermined thickness of thin liquid layer on the surface of the photosensitive medium, such liquid layer being moved to an exposure station. The adjust blade is formed of a conductive material so that any desired potential may be applied to such liquid layer through the adjust blade. Simultaneously with the discharging or charging effected by the liquid, an image light may be applied to the photosensitive medium through a lens 88.

Some desirable factors of the discharging or charging liquid formed as a thin layer in each of the abovedescribed various embodiments will now be discussed.

1. Where ethanol of d) 10 0 cm'is employed as the i discharging or charging liquid, it is assumed that the liquid layer formed on the surface of the photosensitive medium has a thickness of 1 micron. With respect to an area of one square centimeter in such thin layer, it is assumed that the charge flows from one side a of the square to the oppsoed side b and thence to the earth. Then, the liquid in the thin layer has an apparent electrical resistance of 10 which is sufficient to attain a discharging or charging effect.

2. As the liquid which is usable with the present invention, i.e. which isrelatively' low in electrical resistance and can be applied as a thin layer, any of the following materials has been found to be successful: methyl alcohol, ethyl alcohol, propyl alcohol, mixture of alcohol and water, mixture of propyl alcohol and kerosene, gasoline cyclohexane, mixture of water and interfacial activator, etc.

3. Where there is a requirement for a liquid which is quick to vaporize, safety means must be provided against the vaporization of such liquid and such liquid should desirably have a vapor pressure of 30 mmHg or higher. For example, methyl alcohol has a vapor pressure of 92 to 98 mmHg and is highly preferable.

4. Where a blade is required to remove the liquid, the removal would be made readier if the liquid has a lower viscosity to some extent. For example, isopropyl alcohol has a viscosity of 2.2 cp and well meets this requirement. Methyl or ethyl alcohol kerosene is also low in viscosity. Experiments have shown that viscosities up to the order of 50 cp permit ready removal of the liquid but any higher viscosity encounters difficulties. However, viscosity is not the only factor which limits the readiness of liquid removal, but the wettability of the liquid with respect to the liquid removal means is also a factor.

5. In order that a thin and uniform layer of liquid may be applied as shown in FIGS. 7 to 10, the liquid must have a good wettability with respect to the surface of the photosensitive medium. Although the surface tension does not directly represent the wettability, it seems to be much correlated with the latter. Our experiments have shown that a surface tension lower than 30 dyne/cm enables substantially uniform application of the liquid. The thickness of the liquid layer could be considerably precisely controlled to about microns or less.

As has been fully described in connection with FIGS. 7 to 10, the present applicator system reduces the amount of the liquid to be supplied to the surface of the photosensitive medium during the liquid discharging or charging, thus simplifying the removal and collection of the liquid to a great extent. Further, this eliminates the possibility that the liquid once used for discharging or charging may leak to invade the overall exposure station and/or the developing station, which in turn means a very high utility of the system.

After the simultaneous application of image liqht and discharging or charging has been completed with a'thin layer of discharging or charging liquid formed as described above, the liquid layer may be removed by a blade 89 while a lubricant liquid may be supplied through a supply pipe 90 to the area of the blade which is in contact with the surface of the photosensitive medium. The two liquids so removed may be absorbed by a liquid absorbent member 91 such as fabric, blotting paper or the like atached to the surface of the blade, and then directed downwardly into a collector 92. The two liquids collected in the collector 92 may of course be separated for reuse. In the embodiment shown in FIG. 6, alcohol was employed as the discharging or charging liquid and a layer of such liquid with a thickness of 5 microns could be formed on the surface of the photosensitive medium by means of the conductive roller 61 while kerosene as the lubricant liquid was used at the rate of about 0.1 cc per second, thus resulting in very good discharging or charging effect as well as very good liquid removal effect of the blade.

In any of the various embodiments described above in conjunction with the drawings, a success could be attained by using a lubricant liquid such as fatty hydrocarbon solvent kerosene, cyclohexane, aromatic hydrocarbon, benzene, toluene, xylene, silicone liquid, hydrocarbon chloride, hydrocarbon fluoride, or the carrier liquid for the developing solution.

As has been described hitherto with respect to a liquid discharging or charging device of the present invention, the friction between the discharging or charging liquid removing blade and the photosensitive medium may be reduced by using a lubricant liquid therebetween, thus eliminating the vibrations or take-off" phenomenon of the blade and facilitating the blade setting. This also eliminates the irregular removal of the said liquid resulting from the vibrations of the blade which would in turn lead to irregular formation and development of a a resultant latent image. Further, the use of an insulative liquid as the lubricant liquid prevents the developing characteristic from being affected even if such liquid should enter the developing device. This effect is particularly conspicuous when the carrier liquid for the developing solution is used for the lubrication.

The use ofa lubricant liquid which is insoluble to the discharging or charging liquid and greatly different in specific gravity therefrom provides easier separation of the two liquids in the receptacle to make them available for reuse.

While description has so far been made of the supply of the discharging or charging'liquid to the surface of the photosensitive medium and of the removal thereof from such surface, it has been unavoidable with the described liquid discharging or charging device that foreign materials such as fine particles of metal, dust, dirt, fiber, etc. suspended within the copying apparatus and the toner particles remaining on the surface of the photosensitive medium tend to mingle with the discharging or charging liquid as it is supplied into the clearance between the surface of the photosensitive medium and the adjacent member (e.g., the entire face of an optical fiber tube is such tube is used for the simultaneous application of image light and discharging or charging) to effect the discharging or charging. Also, entry of such foreign materials into said clearance would often impart damages to the surface of the photosensitive medium and/or of the adjacent member (optical fiber tube). Further, the simultaneous application of image light and discharging or charging has involved the necessity of providing a clearance of the order of 0 to microns between the surfaces of the photosensitive medium and the adjacent member (optical fiber tube), and entry of said foreign materials into such clearance would result not only in damages of the said surfaces but also contamination of the image formed on the surface of the photosensitive medium through the adjacent member (optical fiber tube) during the exposure. Therefore, it is necessary to prevent any discharging or charging liquid mingled with said foreign materials from passing into the aforesaid clearance.

In the described liquid discharging or charging device, the problem of foreign materials entering into the discharging or charging liquid might be solved by designing the entire electrophotographic copying apparatus as a highly hermetically sealed construction. In fact, however, a highly hermetically sealed construction would encounter difficulties in terms of repair of the copying apparatus and discharge of the heat produced within the apparatus, and would also involve a complex arrangement and higher cost. Moreover, it is nearly impossible to remove all the foreign particles which exist within the copying apparatus.

The present invention also provides a device for solving all the above-noted problems by employing a very simple means instead of any complex one. Briefly, this device is designed such that when discharging or charging liquid is brought into the clearance between the surfaces of the photosensitive medium and the adjacent member, only the amount of the liquid previously admixed with foreign particles may be removed so as to prevent such foreign particles in the liquid from entering into said clearance. In other words, it is designed such that the liquid with foreign particles is sucked and removed together with a portion of the liquid before it reaches the clearance. This will more fully be described in conjunction with the drawings.

FIGS. 11(a), (b) and (c) show, in schematic view, perspective view, and side elevation, a form of the copying apparatus incorporating the present invention. A drum 89 is rotatable in the direction of the arrow and supports thereover a photosensitive medium'comprising a conductive backing member (or insulative layer) 90, a photoconductive layer 91 and an insulative layer 92 closely disposed one upon another. The rotatable drum may take an alternative form such asendless belt or the like. The photosensitive medium may first be charged uniformly over the entire surface thereof by a primary charger 93, whereafter the surface of the photosensitive medium may be exposed to light information transmitted through an optical fiber tube 96 which comprises a cathode ray tube 94 provided with an optical fiber plate 95.

Simultaneously with this exposure, the surface of the photosensitive medium may be discharged or charged by the liquid discharging or charging device. The liquid discharging or charging device will now be described. The discharging or charging liquid may be supplied from a liquid reservoir and collector 97 by a pump 98 or charging liquid supply pipe '99, one or more liquid flow forming nozzles 103 may be provided adjacent the entrance to the clearance between the photosensitive medium and the optical fiber tube, with the nozzle ports being directed toward the opposite sides with respect to the direction of movement of the photosensiand through a liquid supply pipe 99 into the clearance between the photosensitive drum and the optical fiber plate. The supply rate of the discharging or charging liquid may be adjusted by a liquid level holding plate 100 which maintains a predetermined liquid level, as shown. Then, a suitable voltage (including a grounded potential) may be applied to the liquid 101, thus accomplishing the simultaneous application of image light and discharging or charging. The amount of the liquid used may thereafter be removed from the surface of the photosensitive medium by a doctor blade 102. Application of the suitable voltage to the discharging or charging liquid may be. carried out by one of various methods, e.g., by forming the liquidlevel holding plate 100 of a conductive material and applying a charge thereto, or by providing a thin conductive layer on the surface of the fiber plate adjacent the photosensitive drum and applying the voltage to such layer, or by pretreating the liquid removing doctor blade for conductivity and applying the voltage thereto, or by additionally providing an electrode for a voltage application.

In the construction of the liquid discharging or charging device described just above, foreign materials such as dust, dirt, fine particles of metal or the like sus pended in the interior of the copying apparatus and the toner particles remaining on the surface of the photosensitivemedium may intrude into the liquid during the discharging or charging. This may be avoided by providing a liquid flow forming nozzle 103, in addition to the liquid supply pipe, so that fresh discharging or charging liquid may be injected therethrough to cause the contaminated discharging or charging liquid to be carried away with the stream of the fresh liquid, thereby preventing entry of the contaminated liquid into the clearance between the photosensitive medium and the optical fiber plate. Reference numeral 104 designates a liquid flow forming pump.

This process will further be described with reference to FIGS. 11(b) and (c). In addition to the discharging tive medium in the manner as shown.

As a result, the liquid mingled with foreign materials may be removed before entering the clearance between the optical fiber tube and the photosensitive medium. The velocity at which fresh liquid is injected should desirably be higher than the velocity of the movement of the photosensitive medium relative to the optical fiber tube.

The contaminated liquid and the fresh liquid which has actually been used for the discharging or charging may thereafter be removed together by the blade 102 and collected in the liquid reservoir-collector 97. A filter 105 is disposed within the collector 97 to purify the contaminated liquid and thereby ensure fresh liquid to be supplied therefrom to the liquid supply pipe and to the liquid flow forming nozzle or nozzles, thus enabling repeated use of the liquid. The liquid flow forming nozzle need not be separate from butmay be common with the liquid supply pipe, whereas this latter case is not so preferable because it often permits entry of air into the clearance between the photosensitive medium and the optical fiber tube during the simultaneous application of image light and discharging or charging to thereby cause a failure of discharging or charging or disturbance to the formed image.

After the liquid discharging or charging, the photosensitive medium from which the discharging or charging liquid has been removed may then pass to an overall exposure process effected by an overall exposure device 107 which, if required, may have been dried by a blast drier device 106. A developing device 108 is shown to be of the wet type, but of course it may also be of the dry type using a magnetic brush or a fur brush. When developed, the photosensitive medium may further be rotated to reach a squeeze charger 109, which may squeeze and remove any residual liquid remaining on the developed surface. The liquid so removed by squeezing may be either recovered for reuse in the developing device 108 or dumped away. It will be noted that the use of the dry development would involve the use of a post-charger to enhance the transfer efficiency of the developing toner. The image thus developed on the photosensitive medium may be transferred onto a transfer medium 110, which has been fed to an image transfer station, by a transfer corona charger 111. The toner transferred may be fixed on the transfer medium by a fixing means 112 which may be of the heatingfixing type. After completion of the image transfer, the surface of the photosensitive medium may be cleaned by a cleaning device including a cleaning blade 113, thus becoming ready for reuse. In the described manner, the information from the cathode ray tube 94 may be copied on the transfer medium.

FIGS. 12(a), (b) and (c) illustrate, in schematic view, perspective view,'and side elevation, a further embodiment of the liquid discharging or charging device according to the present invention. Reference numeral 115 denotes a photosensitive medium movable in the direction of the arrow, 116 an optical fiber tube, and 117 a liquid level holding plate. Discharging or charging liquid may be supplied into the clearance be-

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4213168 *Jul 20, 1978Jul 15, 1980The United States Of America As Represented By The Secretary Of The Air ForceElectret charge technique
US5666607 *Jan 11, 1996Sep 9, 1997Hewlett-Packard CompanyWet contact charging for electrophotography
US5781833 *Dec 1, 1995Jul 14, 1998Xerox CorporationSealed liquid charging apparatus
US6600888 *Nov 2, 2001Jul 29, 2003Xerox CorporationLiquid charging method and apparatus
US8797502Jan 28, 2011Aug 5, 2014Nikon CorporationExposure apparatus, exposure method, and method for producing device with electricity removal device by adding additive to liquid
EP0918261A2 *Oct 27, 1998May 26, 1999Xerox CorporationControl of fluid carrier resistance and liquid concentration in an aquatron device
EP0918262A1 *Oct 28, 1998May 26, 1999Xerox CorporationControl of fluid carrier resistance and water concentration in an aquatron charging device
EP0929004A2 *Jan 4, 1999Jul 14, 1999Xerox CorporationCapture of paper moisture for aquatron replenishment
Classifications
U.S. Classification361/220, 361/225
International ClassificationG03G15/22, G03G15/02, G03G15/00
Cooperative ClassificationG03G15/226, G03G15/02, G03G15/0208
European ClassificationG03G15/02A, G03G15/22D, G03G15/02