EP0067623A2 - Procédé et dispositif d'images électrophotographiques - Google Patents

Procédé et dispositif d'images électrophotographiques Download PDF

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Publication number
EP0067623A2
EP0067623A2 EP82302847A EP82302847A EP0067623A2 EP 0067623 A2 EP0067623 A2 EP 0067623A2 EP 82302847 A EP82302847 A EP 82302847A EP 82302847 A EP82302847 A EP 82302847A EP 0067623 A2 EP0067623 A2 EP 0067623A2
Authority
EP
European Patent Office
Prior art keywords
photoreceptor
layer
photosensitive layer
electrically insulating
corotron
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP82302847A
Other languages
German (de)
English (en)
Other versions
EP0067623A3 (en
EP0067623B1 (fr
Inventor
Heinz W. Pinsler
Brian E. Springett
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xerox Corp
Original Assignee
Xerox Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Xerox Corp filed Critical Xerox Corp
Publication of EP0067623A2 publication Critical patent/EP0067623A2/fr
Publication of EP0067623A3 publication Critical patent/EP0067623A3/en
Application granted granted Critical
Publication of EP0067623B1 publication Critical patent/EP0067623B1/fr
Expired legal-status Critical Current

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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
    • 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
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/226—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 where the image is formed on a dielectric layer covering the photoconductive layer

Definitions

  • This invention relates to an electrophotographic imaging process and apparatus and, more particularly, to a process and apparatus for uniformly charging a photosensitive member which is overcoated with an electrically insulating layer.
  • a process includes providing a photoreceptor comprising a conductive substrate, a photosensitive layer, and an electrically insulating layer over the photosensitive layer; electrically charging the photoreceptor; and exposing the photoreceptor to an imagewise pattern of electromagnetic radiation to which said photosensitive layer is sensitive whereby an electrostatic latent image is formed in said photosensitive layer.
  • photoreceptors having protective, electrically insulating coatings over the photosensitive layers include U.S. 3,895,943 and U.S. 3,904,409 to Hanada wherein the electrically insulating overcoating is utilized in conjunction with persistent internal polarization and contains the problem of charge build-up on the surface of the electrically insulating layer.
  • U.S. 3,895,943 and U.S. 3,904,409 to Hanada wherein the electrically insulating overcoating is utilized in conjunction with persistent internal polarization and contains the problem of charge build-up on the surface of the electrically insulating layer.
  • Small variations in the operation of the DC corotrons particularly utilized in the prior art to provide the sequential charging steps make the condition of zero voltage on the electrically insulating layer nearly impossible with ordinary equipment.
  • the present invention is intended to provide an apparatus and process wherein an electric field is provided in a single charging step across the photosensitive layer of a photoconductive member having an electrically insulating protective layer over the photosensitive layer, which step eliminates or prevents the build-up of electrical charge on the surface of the electrically insulating layer.
  • the process of the invention is characterised in that the charging is carried out by means of an AC corotron, the corotron having a shield bias voltage adjusted so as to provide substantially no voltage across the electrically insulating layer.
  • the process and apparatus of the invention enable the use of a photoreceptor containing an electrically insulating protective layer over the photosensitive layer wherein charge build-up on the electrically insulating layer is prevented.
  • the process is simplified in that it requires a reduced number of charging units to establish an electric field across the photosensitive layer.
  • the charged photoreceptor is exposed to an imagewise pattern of electromagnetic radiation to which the photosensitive layer is sensitive to provide a latent electrostatic image entirely within the photosensitive layer.
  • the latent image is developed by electroscopic materials applied to the electrically insulating overcoating, which image is then transferred to an image receiving sheet thereby allowing erasure of the electrostatic latent image by flood exposure of the photosensitive layer and reuse of the photoreceptor.
  • An important feature in the present invention is the presence of a rectifying layer at the interface of the photosensitive layer and the electrically conductive substrate.
  • a rectifying contact which injects positive charges into the photoconductive layer and blocks negative charges. If negative charges are deposited on the top of the photoreceptor, positive charges are injected from the interface into the photoconducting layer. They travel through the photoconducting layer to the interface between the photoconducting layer and the insulating layer where they are trapped. If the surface charge on top of the photoreceptor is positive, the negative counter charge remains at the conductive substrate because of the blocking nature of the interface.
  • the interface would have to be injecting for electronics and blocking for positive charges.
  • the preferred operating mode depends on the photoreceptor materials used. For example, in the case of the utilization of a selenium alloy photosensitive layer, positive charges are injected into the photosensitive layer during periods of negative charge on the surface of the electrically insulating layer. Because of the rectifying properties of the photosensitive layer, no negative charge is injected during those periods when the charge on the surface of the electrically insulating layer is positive. In such instance, a positive voltage is established across the photosensitive layer. With the proper adjustment of bias voltage on the shield of the AC corotron, the total current influx integrated over the time of exposure to charge can be made zero on the surface of the electrically insulating layer. Such condition also eliminates charge build-up due to the polarization of the overcoating since the net total charge deposited by the AC corotron is of such polarity to counteract the overcoating polarization.
  • a single corotron replaces three corotrons required in the prior art in order to properly provide an electrical field across the photoreceptor only and to eliminate residual charge on the electrically insulating, protective overcoating on the photosensitive layer.
  • the AC corotron is operated in the frequency range of from about 50 Hz to about 1000 Hz in the process of this invention.
  • the frequency is in the range of from about 50 Hz to about 400 Hz.
  • photoreceptor 1 comprising a conductive substrate 3 supporting a photosensitive layer 5.
  • An electrically insulating layer 7 resides on photosensitive layer 5 to provide protection from wear and contamination due to the repeated toning, transferring and cleaning which occurs in each imaging cycle and retards crystallization in the event a Se alloy is used.
  • FIG 2 there is shown the intermediate charge condition of the photoreceptor during the charging step in the process of this invention.
  • photoreceptor I is shown receiving, at the surface of the electrically insulating layer 7, both positive and negative charges, which are provided by an AC corotron.
  • the charged designations indicating positive and negative charges contained within circles indicate a transitory condition or charges in motion while those charge designations, both positive and negative, without circles indicate stable charges which remain in the photoreceptor until further processing occurs.
  • both positive and negative charges on the surface of electrically insulating layer 7 which are alternately supplied by an AC corotron.
  • Figure 2 indicates the segment of a photoreceptor, during the charging step, said segment is considered to be extremely small at any particular point in time during the charging step in the process of this invention.
  • Figure 2 illustrates the condition for purposes of illustration only.
  • the photoreceptor is illustrated in its charged condition - wherein there are stable negative charges residing at the interface of electrically conductive layer 3 and photosensitive layer 5 while equal charges of opposite polarity reside at the interface of photosensitive layer 5 and electrically insulating layer 7. These charges provide an electrical field across the photosensitive layer with no charge residing on the surface of electrically insulating layer 7.
  • the thus charged photosensitive layer is ready for imagewise light exposure to establish a latent image therein as is illustrated in Figure 4.
  • Light rays 9 are shown impinging on the surface of electrically insulating layer 7 which is transparent to said electromagnetic radiation allowing charge carriers to be created in the photosensitive material thereby eliminating the equal amounts of charge residing at the interfaces of said layer.
  • the photosensitive layer 5 may be exposed from either side as is known in the prior art when providing a transparent conductive substrate 3 or, more commonly, a transparent electrically insulating layer 7. Apparatus convenient for the purpose of the user is constructed utilizing the principals of the process of this invention in either case.
  • intermediate layers may be placed between the conductive layer 3 and photosensitive layer 5 to enhance the charge injecting nature of the interface. Such materials are well known in the prior art and are chosen with regard for the type of photosensitive material utilized in layer 5.
  • adhesive layers may also be applied to the surfaces of photosensitive layer 5 in order to adhere the electrically insulating protective layer thereto, as well as providing adhesion of the photosensitive material to the conductive substrate as injection layer.
  • Typical electrically insulating layers include organic, as well as inorganic, materials.
  • a particularly preferred material is polyethylene terephthalate available commercially under the Tradename Mylar from the E.I. du Pont de Nemours & Company, Inc.. Such material is preferred because of its availability and ease of handling, as well as its electrical properties.
  • Other materials which can be typically utilized as protective layers include polyester, polyvinylchloride, polypropylene, polyvinylidenec- hloride, polycarbonate, polystyrene, polyamide, polyfluoroethylene, polyethylene, polyimide, polyvinylfluoride, polyvinylidene fluoride, poly- vinylidenechloride, polyurethane, etc..
  • Photosensitive materials utilized in the process of this invention are typically those which provide a rectifying boundary at the conductive substrate.
  • Typical photosensitive materials include selenium, selenium alloys such as selenium-tellurium alloys, selenium-arsenic alloys containing various dopants, such as cadmium sulfide, cadmium selenide, cadmium sulfoselenide, zinc oxide, zinc sulfide and zinc selenide.
  • said photosensitive materials may be dispersed in suitable binder materials as is well known in the art. Any suitable photosensitive material is included within the scope of this invention, such as a composite layer leaving fine photoconductive material in contact with the electrically insulating layer and relatively coarse photoconductive particles contacting the base.
  • Each portion of the composite layer is desirably dispersed in a suitable binder.
  • a suitable binder Such a photoreceptor is more fully described in U.S. Patent 3,801,317 to Tanada et al..
  • additional layers may be incorporated into the imaging member to aid in the various desired properties.
  • materials can be utilized at the interface between the photosensitive layer and the electrically conductive layer which promote charge injection of one polarity and suppress charge injection of another.
  • Such materials include trigonal Se, gold, Te-alloys and carbon.
  • the AC corotron utilized in the process of this invention is provided with a voltage bias on the shield thereof.
  • the bias voltage to the shield is adjusted so as to provide the desired zero voltage on the surface of the electrically insulating layer.
  • This voltage bias is typically determined empirically as it is highly dependent upon numerous operational factors such as distance between the corotron and the surface being charged, the amount of voltage desired to be utilized on the corotron wire and the nature of the surface being charged.
  • Figure 5 a schematic of a xerographic apparatus indicating the major operations of the xerographic process.
  • xerographic apparatus comprising a photoreceptor 13 having the configuration of the photoreceptor illustrated in Figure 1.
  • photoreceptor 13 is in the form of a typical xerographic rotary drum mounted upon a grounded support 15.
  • corotron 17 is utilized to charge photoreceptor 13 through power supply 19, either directly coupled to the wire or to the wire via a capacitance.
  • a variable power supply 21 is utilized to supply a bias voltage to the shield of corotron 17 as indicated in Figure 5.
  • a probe 23 is inserted subsequent to the charging operation to monitor the amount of charge on the photoreceptor.
  • the charged photoreceptor is then rotated past a typical slit scanning optical system 25 whereby the charged photoreceptor is exposed to a pattern of electromagnetic radiation to which the photosensitive material is sensitive.
  • the exposed photoreceptor is then rotated past the developing station 27 whereby the electrostatic latent image in the photosensitive layer is developed. After development, the image is transferred as shown at transfer station 29 with the aid of transfer corotron 31.
  • the photoreceptor 13 is prepared for further use by erase lamp 33 which collapses the remaining field in the photoreceptor followed by removal of residual toner material at cleaning station 35.
  • a probe 37 is inserted in the cycle after the erase lamp 33 to determine the amount of charge remaining in the photoreceptor. Since the erase lamp collapses the field remaining across the photosensitive layer, any voltage detected by probe 37 must represent charge residing on the electrically insulating layer.
  • Power supply 21 is adjusted so as to provide a proper bias voltage to the shield of corotron 17 which results in a zero net charge on the insulating layer as indicated by probe 37.
  • the bias voltage to the shield is made more negative.
  • the bias voltage to the shield is made more positive.
  • a photoreceptor comprising an electrically conductive substrate having coated thereon a 3 micron thick trigonal selenium injecting layer over which is coated a 60 micron thick selenium-arsenic alloy doped with chlorine. Over the photosensitive layer there is applied a 12 micron thick coating of an electrically insulating polyurethane layer. At a surface speed of about 51 cm./sec. the photoreceptor is rotated past a double wire corotron 13.5 cm in length and operated at 60 Hz. The corotron shield is biased to a negative 30 volts, while the corotron wire has 16,000 volts AC peak to peak applied thereto. A field condition of +80 volts was measured at probe 23 subsequent to charging. It was established that this voltage is completely across the photosensitive layer by the fact that no voltage was detected at probe 37 subsequent to the erase lamp. Any voltage detected by probe 37 would indicate a voltage across the overcoating since there would be no field left in the photosensitive layer.
  • Example I The procedure of Example I is repeated with the exception that the photoreceptor is moved past a double wire corotron which is the same as that of Example I except that the length was 12 cm. A positive voltage of 350 volts is measured at probe 23 while the shield voltage is held at +400 volts and the voltage applied to the corotron wires was 16,000 volts peak to peak. Again, there is no voltage measured at probe 37, indicating that the entire field of +350 volts existed across the photosensitive layer of the photoreceptor and no voltage was left residing on the surface of the electrically insulating polyurethane layer.
  • a single wire corotron 20 cm in length is utilized in the process of Example I to establish a field of 500 volts which is measured at probe 23 after exposure to the AC corotron having a shield bias of +520 volts and 16,000 volts peak to peak applied to the wire. Again, no voltage was detected by probe 37 subsequent to exposure to the erase lamp.
  • the insulating protective layer may vary in thickness from a few microns to in excess of 20 microns and the 60 micron photosensitive layer may vary in thickness from approximately 5 microns to 80 microns so that operation with a large range of electroscopic image development materials may be accommodated.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Discharging, Photosensitive Material Shape In Electrophotography (AREA)
EP19820302847 1981-06-03 1982-06-02 Procédé et dispositif d'images électrophotographiques Expired EP0067623B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US27016981A 1981-06-03 1981-06-03
US270169 1981-06-03

Publications (3)

Publication Number Publication Date
EP0067623A2 true EP0067623A2 (fr) 1982-12-22
EP0067623A3 EP0067623A3 (en) 1983-08-31
EP0067623B1 EP0067623B1 (fr) 1985-09-25

Family

ID=23030198

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19820302847 Expired EP0067623B1 (fr) 1981-06-03 1982-06-02 Procédé et dispositif d'images électrophotographiques

Country Status (4)

Country Link
EP (1) EP0067623B1 (fr)
JP (1) JPS57200060A (fr)
CA (1) CA1176694A (fr)
DE (1) DE3266508D1 (fr)

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5030532A (fr) * 1973-07-04 1975-03-26
JPS5264936A (en) * 1975-11-25 1977-05-28 Canon Inc Apparatus for electronic photography
JPS6040024B2 (ja) * 1976-09-17 1985-09-09 キヤノン株式会社 静電潜像安定化方法
JPS607269B2 (ja) * 1979-04-03 1985-02-23 キヤノン株式会社 電子写真方法
US4254199A (en) * 1980-03-10 1981-03-03 Xerox Corporation Electrophotographic imaging method having a double charging sequence

Also Published As

Publication number Publication date
EP0067623A3 (en) 1983-08-31
DE3266508D1 (en) 1985-10-31
EP0067623B1 (fr) 1985-09-25
JPS57200060A (en) 1982-12-08
CA1176694A (fr) 1984-10-23

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