US3650622A - Apparatus for control of bias potential in an electrophotographic copier - Google Patents

Apparatus for control of bias potential in an electrophotographic copier Download PDF

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Publication number
US3650622A
US3650622A US17394A US3650622DA US3650622A US 3650622 A US3650622 A US 3650622A US 17394 A US17394 A US 17394A US 3650622D A US3650622D A US 3650622DA US 3650622 A US3650622 A US 3650622A
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Prior art keywords
potential
conducting layer
layer
path
photoconductor
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US17394A
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English (en)
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Theodore H Morse
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Eastman Kodak Co
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Eastman Kodak Co
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
    • G03G15/0291—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices corona discharge devices, e.g. wires, pointed electrodes, means for cleaning the corona discharge device

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  • ABSTRACT An apparatus and method are disclosed for adjusting the potential difference between the conducting layer and ground at any preselected position on a photoconductive element that is continuous from exposure through development stations.
  • the charging and developing operation be carried out under optimum electrical conditions. That is, the state of charge achieved on the surface of a photoconductor element as well as the performance of the element during development and transfer operations dependsv upon the potential difference between the conducting layer contained, within the photoconductor element and ground. In most photoconductive elements the conducting layer is simply grounded to the apparatus or other convenient ground. In xerographic operations such as disclosed in L. E. Walkup U.S. Pat. No. 2,934,649 where a selenium photoconductive insulating layer is used on a conducting metal drum, the drums potential'is not normally adjustable between the operations of charging, exposing, development and transfer.
  • Giaimo'US. Pat. Nos. 2,815,449 and 2,922,883 describe charging processes utilizing two chargers mounted on oppositc sides of the photoconductive element. These latter two patents describe the use of photoconductive elements which do not contain a conducting layer.
  • FIG. 1 shows the schematic of an electrophotographic duplication apparatus embodying the present invention.
  • FIG. 2 is a cross section of a normal photoconductive element showing charge patterns which occur during electrophotographic use of the element when the conducting layer is not grounded.
  • FIG. 3 is the same as FIG. 2 with charge patterns produced by the method and apparatus of the present invention.
  • FIG. 1 A typical xerographic processing system with which the present invention may be utilized is shown in FIG. 1 in which the various system components are schematically illustrated.
  • FIG. 1 A general understanding of operation of the present invention can be derived from examination of such a system, the teachings of course being applicable to other xerographic systems employing these same principles.
  • a pattern of actinic radiation representing the copy to be reproduced is projected onto the charged surface of a photoconductive element toform an electrostatic charge pattern thereon.
  • the electrostatic charge pattern is developed with an oppositely charged developing material to form a toner image, corresponding to the electrostatic charge pattern, on the surface of the photoconductive element.
  • the developed image is then typically transferred onto a second surface where it may be fused by a variety of fusing devices, such as heaters and the like, whereby the image is caused to adhere to the second surface permanently.
  • the electrostatic charge pattern can be developed by liquid development techniques with or without the necessity of afusing station.
  • the toner image can be developed 'to a permanent'or semipermanent form on the surface of the photoconductor element.
  • FIG. 1 shows a schematic illustration of an electrophotographic duplicating device utilizing a photoconductor-containing web moved by a roller transport mechanism.
  • the photoconductor containing web 12 is introduced to the mechanism from a supply roll I4 and rewound onto pickup roll '16.
  • Photoconductor-containing web 12 is transported around the mechanism by means of transport rollers 18 and developing station rollers 20.
  • a high voltage corona charger 30 is stationed before exposing station 22 and a second high voltage charger 30 is located after the developing station 24.
  • Exposing station 22 consists typically of a supply reel 26 containing film to'be duplicated and a film takeup reel 28 with a light'source 25 and aperture control 27 for control of the exposure of the photoconductor-containing web.
  • the development station 24 typically comprises a vessel containing small particles of marking material suspended in an insulating liquid and preferably utilizes a development electrode 23.
  • the corona chargers when activated, are set to different polarities and, in the configuration shown, establish the proper potential difference between the conducting layer and ground to provide for optimum charging before exposing station 22 and optimum development at station 24. Adjustment'of the voltages employed as well as the location and general configuration of the particular mechanism used will provide a predictable level of potential difference. Such adjustment will not require extensive experimentation and therefore should be within the skill of the operator to perform.
  • FIG. 2 shows a typical charge pattern distribution in an element having a photoconductive layer and a conducting layer on a support where a single charger 33 is used, and no connection made between the conducting layer and the ground plane 35.
  • a negative charge is applied to the surface of the photoconductor-containing insulating layer which induces positive charges to move in the conducting layer to a position near the negative surface charge.
  • the resulting negative charge in other areas of the conducting layer induce positive charges in the ground plane 35, resulting in an undesirable potential difference between the conducting layer and ground 35.
  • FIG. 3 shows the charge patterns produced according to the present invention wherein the first charger 33 and the second charger 36 are operated at different polarities. In this manner the conducting layer will achieve electrical neutrality. However, it can be seen that the location of the second charger, being at a specific point. on the photoconductorcontaining web, will produce a gradation from electrical neutrality to a positive or negative value depending on the position sensed between the two chargers. This is contrary to the phenomenon occurring in the photoconductor-containing web shown in FIG. 2 where the charges will be induced from the ground plane nearest the conducting layer. The following are examples of the operation of the method and apparatus of the present invention.
  • EXAMPLE 1 A 35 mm. photoconductor-containing web comprising a polyester support having coated thereon a cuprous iodide conducting layer, a barrier layer, and an'unsensitized photoconductor-containing insulating layer, was suspended between two insulating posts to provide electrical isolation from ground. Two corona chargers were placed facing the photoconductor-containing surface of the web and a distance of 3 feet from each other. An electrometer probe was positioned above the photoconductor-containing web surface, midway between the corona chargers so that the potential of the conducting layer could be measured.
  • the conducting layer could be made to assume a negative polarity of several hundred volts by adjusting the intensity ofthe first charger.
  • the second charger was then energized positively and its intensity gradually increased.
  • the conducting layer potential was observed to rise steadily form its negative value as the corona intensity was increased.
  • a second-charger setting was reached at which the conducting layer reached zero potential, when the second charger potential was increased further the conducting layer potential could be rendered positive.
  • a maximum positive conducting layer potential of approximately 200 volts was achieved by this method.
  • EXAMPLE 2 Utilizing the same setup as described in Example 1 the second or positive corona charger was moved so that it faced the edge of the photoconductor-containing web. The edge of the cuprous iodide layer was then exposed to the output of the charger. With this setup the intensity required to produce a conducting layer potential of zero was less than required when the charge was facing the photoconductor-containing surface. It was also possible to achieve a positive conducting layer potential of 400 volts.
  • Example 3 Using the isolated photoconductor-containing web, electrometer probe, and chargers as described in the previous examples, a chart recorder was connected to record the electrometer readings as a function to time. The two chargers were energized and adjusted to bring the conducting layer potential to zero. The chargers were then allowed to operate for a 5-minute period without adjustment. The chart record indicated a maximum deviation of volts from zero during EXAMPLE 4 Using a roller transport mechanism as shown in FIG. I, the second charger was added over the photoconductive surface at a point following the development station 24. With the first charger 30 adjusted to apply a 1000-volt potential to the photoconductor surface, the second charger was set to adjust the conducting layer potential to zero at the development station.
  • the photoconductor-containing belt or web was moved at 1 foot per second while charging, exposure and development were carried out without the second charger energized.
  • the developed elements had a high level of background toning indicating that the conducting layer was rising to a potential of the same polarity as the image charge.
  • the second charger was energized, bringing the potential of the conducting layer to zero.
  • the developed elements which resulted from this change had greatly reduced background densities compared to the single charger run.
  • the present invention permits adjustment of the bias for the development station in addition to facilitating the photoconductive surface charging whether the conducting layer is or is not exposed. Both ofthese operations can then be performed without physical contact with the conducting layer. For example, it is possible to position one charger next to the edge of the photoconductor-containing web shielding the surface of the photoconductor, if necessary. In this manner the second charger can be located from a position relatively near to the first charger to a point anywhere along the front or rear of the belt or web for example to the position shown after the development station.
  • the mechanism of the process appears to involve the exchange of charge carriers in the conducting layer between the two charger sites as hereinbefore described.
  • the associated currents which will be produced in a moving web will cause a potential gradient to exist in the conducting layer in the region between the two chargers.
  • the magnitude of the potential gradient is directly proportional to the conducting layer resistivity and the intensities of the corona chargers. If the currents induced by these two sources are balanced, the point on the conducting layer which ismidway between the two chargers will be at zero potential. An increase of reduction of either charger output will change the potential distribution along the conducting layer and move the point of zero potential.
  • the most successful and preferred photoconductor-containing webs or belts or supports are organic photoconductor-containing elements.
  • This description covers a very broad class of materials which are characterized by their ability to act as insulators until exposed to light. The same prerequisite is necessary for organometallic photoconductive materials which are normally dispersed in a resinous material.
  • Useful photoconductors of both types are described in Goldman and Johnson U.S. Patent application Ser. No. 650,664 filed July 3, 1967, U.S. Pat. No. 3,472,839 and Johnson application Ser. No. 755,711 filed Aug. 27, 1968.
  • organic amine photoconductors which are useful photoconductor-containing elements such as used herein.
  • Such compound include aryl amine compounds such as those described in Fox U.S. Pat. No. 3,240,597 issued Mar. 15, 1966 and the like as well as U.S. Pat. No. 3,180,730 issued Apr. 27, 1965 and Fox U.S. Pat. No. 3,265,496 issued Aug. 9, 1966, as well as U.S. No. 3,274,000 and French Pat. No. 1,383,461 likewise U.S. application Ser. No. 627,857, now U.S. Pat. No. 3,542,544 filed Apr. 3, 1967 discloses useful photoconductors.
  • Such photoconductors may, if desired, be used with or without sensitizers depending on the choice of the designer.
  • Typical sensitizing addenda for improving speed and/or spectral response as well as other desired electrophotographic characteristics are disclosed in U.S. Pat. Nos. 3,250,615, 3,141,770 and 2,987,395.
  • an electrophotographic copier including means for advancing along a predetermined path an electrophotographic developing means for applying an electrical potential to the conductive backing of the recording element to establish an optimum potential in the backing at any preselected position along said path.
  • said applying means comprises a second corona discharge source for directing ions of a polarity opposite said first potential at the recording element, and means for varying the discharge intensity of said second corona discharge source.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
US17394A 1970-03-09 1970-03-09 Apparatus for control of bias potential in an electrophotographic copier Expired - Lifetime US3650622A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3750624A (en) * 1970-07-21 1973-08-07 Fuji Photo Film Co Ltd Apparatus for developing electrophotographic continuous web material
US3783827A (en) * 1970-12-30 1974-01-08 Fuji Photo Film Co Ltd Liquid development apparatus for electrophotography
US3804659A (en) * 1970-12-10 1974-04-16 Fuji Photo Film Co Ltd Electrophotographic reversal development process for enhancing the quality of the developed image
US3807854A (en) * 1972-02-07 1974-04-30 Minolta Camera Kk Drive mechanism for photsensitive web in an image transfer type electrophotographic copier
US3972611A (en) * 1970-03-18 1976-08-03 Canon Kabushiki Kaisha Apparatus for transferring images produced by liquid developer
US4045217A (en) * 1974-12-24 1977-08-30 Ricoh Company, Ltd. Developing process for electrophotography
WO1980002466A1 (en) * 1979-05-10 1980-11-13 Eltra Corp Electrophotographic apparatus providing output from a typesetter

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3368894A (en) * 1963-11-05 1968-02-13 Australia Res Lab Multiple copy printing method and apparatus
US3456109A (en) * 1966-11-07 1969-07-15 Addressograph Multigraph Method and means for photoelectrostatic charging

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3368894A (en) * 1963-11-05 1968-02-13 Australia Res Lab Multiple copy printing method and apparatus
US3456109A (en) * 1966-11-07 1969-07-15 Addressograph Multigraph Method and means for photoelectrostatic charging

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3972611A (en) * 1970-03-18 1976-08-03 Canon Kabushiki Kaisha Apparatus for transferring images produced by liquid developer
US3750624A (en) * 1970-07-21 1973-08-07 Fuji Photo Film Co Ltd Apparatus for developing electrophotographic continuous web material
US3804659A (en) * 1970-12-10 1974-04-16 Fuji Photo Film Co Ltd Electrophotographic reversal development process for enhancing the quality of the developed image
US3783827A (en) * 1970-12-30 1974-01-08 Fuji Photo Film Co Ltd Liquid development apparatus for electrophotography
US3807854A (en) * 1972-02-07 1974-04-30 Minolta Camera Kk Drive mechanism for photsensitive web in an image transfer type electrophotographic copier
US4045217A (en) * 1974-12-24 1977-08-30 Ricoh Company, Ltd. Developing process for electrophotography
WO1980002466A1 (en) * 1979-05-10 1980-11-13 Eltra Corp Electrophotographic apparatus providing output from a typesetter
US4270859A (en) * 1979-05-10 1981-06-02 Eltra Corporation Electrophotographic apparatus for providing dry developed output from a typesetter

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DE2111158B2 (de) 1974-11-07
DE2111158A1 (de) 1971-09-30
FR2084218A5 (xx) 1971-12-17
DE2111158C3 (de) 1975-06-19

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