US3783283A - Corona charging device with semiconductive shield - Google Patents

Corona charging device with semiconductive shield Download PDF

Info

Publication number
US3783283A
US3783283A US00292285A US3783283DA US3783283A US 3783283 A US3783283 A US 3783283A US 00292285 A US00292285 A US 00292285A US 3783283D A US3783283D A US 3783283DA US 3783283 A US3783283 A US 3783283A
Authority
US
United States
Prior art keywords
shield
resistivity
photoconductive surface
improvement
semiconductive
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.)
Expired - Lifetime
Application number
US00292285A
Other languages
English (en)
Inventor
D Smith
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.)
Unisys Corp
Original Assignee
Sperry Rand 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 Sperry Rand Corp filed Critical Sperry Rand Corp
Application granted granted Critical
Publication of US3783283A publication Critical patent/US3783283A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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

Definitions

  • ABSTRACT A corona charging device, suitable for imparting an electrostatic charge to a photoconductive surface
  • the semiconductiv e shield results in a more efficient-charging device since less of the corona ion current flows to the shield.lt also permits charging of the photoconductive surface to a higher voltage than prior art devices without the occurrence of arcing, and if arcing does occur it takes place between the electrode and the shield rather than between the electrode and the photoconductive surface.
  • the corona charging device impart as high a uniform charge to the photoconductive surface as possible since this enables the charged areas to better attract toner during the developing step, thereby resulting in better contrast between light and dark areas on the finished copy.
  • Efforts to obtain ahigh uniform charge have resulted in many different corotron designs but these designs generally fall into two classes. Both classes include a corona discharge electrode positioned adjacent the surface to be charged, the electrode'bei ng maintained at a high voltage, and a grounded shield partially surrounding the electrode.
  • the shield is an insulator.
  • the grounded shield is a conductor.
  • Corotrons of both classes have distinct disadvantages.
  • the insulator shield being of higher resistivity cient.
  • Corotrons employing the conductive shield overcome the problem of destruction of the photoconductive surface, but this is accomplished at the expense of efficiency. Because of the low resistivity of the shield as compared to the photoconductive surface, up to 85 percent of the corona current flows to the shield and not to the photoconductive surface. Also,.because ofthe low resistivity of the shield, arcing from the discharge electrode to the shield occurs at lower voltages than if the shield were an insulator. This prevents operation of the discharge electrodeat a high enough voltage to obtain maximum charging of the photoconductive surface.
  • the discharge electrode may be operated at higher voltages than heretofor without arcing, and wherein arcing, if it does occur, takes place between the electrode and a shield partially surrounding the electrode.
  • a further object of the invention is to provide a corona discharging unit with a semiconductive shield.
  • a further object of the invention is to provide a corona charging unit which is more efficient in operation than the corona charging units now known.
  • a corona discharging unit includes a discharge electrode and a semiconductive shield partially surrounding the electrode.
  • a high voltage is applied to the electrode so that a corona discharge takes place.
  • the corona current flows through an opening in the shield to uniformly charge a photoconductive surface as relative movement takes place between the surface and the corona charging unit.
  • FIG. 1 is a diagrammatic view, partly in section, of a corona charging unit and a xerographic drum having a photoconductive surface;
  • FIG. 2 is a graph showing corotron current versus current to the photoconductive surface, for corotron units employing a conductive shield and semiconductive shield;
  • FIG. 3 is a graph showing corotron current versus voltage at the photoconductive drum surface, for corotron units employing a conductive shield and a semiconductive shield.
  • FIG. 1 shows a corotron or corona charging unit 10 disposed adjacent the surface of a conventional rotatable x erographic drum 12.
  • the drum has a photoconductive layer or surface 14 covering a supporting substrate 16.
  • the substrate 16 is made of a conductive material such as, for example, aluminum,and the substrate is connected to electrical ground.
  • the layer or surface 14 is made of any suitable photoconductive insulating material such as, for example, vitreous selenium. i
  • the corona charging unit comprises a discharge electrode means, illustrated as a single conductive wire 18, partially surrounded by shield 20.
  • the wire 18 is maintained equidistant from the photoconductive surface but in close proximity thereto, the wire extending transverse to the direction of movement of the photoconductive surface.
  • the shield extends parallel to the wire and has an elongated opening or slot so that corona current may flow from the wire, through the slot to the photoconductive surface.
  • the shield 20 is made of a semiconductive material.
  • semiconductive material as used in this description and the following claims means a material having a resistivity generally in the range 2O -lO ohm-cm.
  • a carbon impregnated plastic material sold by the Dupont Company under the name Alathane" has been found to be admirably suited for use in the shield 20, but other semiconductive materials may be used.
  • the semiconductive material should have as high a resistivity as possible for maximum operating efficiency but the resistivity must be less than. that of the material in the photoconductive insulating surface 14 so that if arcing does occur, it takes place between the wire 18 and the shield.
  • the shield is grounded and the wire 18 is connected to the positive side of a source 22 of DC potential.
  • Applicants invention may be incorporated in corona charging devices having various well known structural features hence applicants invention is illustrated schematically in FIG. 1.
  • Typical prior art corona charging devices are illustrated in Walkup US. Pat. No. 2,777,957 and Vyverberg US. Pat. No. 2,836,725, but it will be understood thatapplicants invention is not limited to use in corona charging devices having the specific structural features shown in these patents.
  • a typical prior art corona charging device operates as follows.
  • the source 22 applies a high DC voltage in the range of 4,500 to 5,000 volts to the electrode or wire 18 thus causing a corona to be generated along the surface of the wire.
  • the positive ions emitted from the wire tend to drift along a path toward ground, this path being influenced in well known fashion by such factors as the spacing between the electrode 18 and shield 20' as compared to the spacing between the electrode and the photoconductive surface 14, and the relative resistivities of the materials in the shield and photoconductive surface.
  • the shield is made of a conductive material, Le, a material having a resistivity of less than ohm-cm.
  • Le a material having a resistivity of less than ohm-cm.
  • about 85 percent of the ions move to the shield and perform no usefulfunction.
  • the remaining ions move toward substrate 16 and are deposited on the photoconductive surface which typically has a dark resistivity on the order of" l 0 l 4ohm-cm.
  • the photoconductive surface 14 may be moved relative to the electrode 18 or the electrode may be moved relative to the surface 14 so that a substantially uniform charge may be deposited over the photoconductive surface.
  • FIG. 2 is a graph showing current flow I, to the photoconductive surface for increasing values of total charging current I
  • the line 24 represents values obtained when a semiconductive shield is used and the line 26 represents values obtained when a conductive shield is used. For any given value of charging current l use of a semiconductive rather than a conductive shield results in greater charging current to the photoconductive surface.
  • the semiconductive shield not only increases the efficiency of a corona charging device but also permits the photoconductive surface 14 to be charged to a higher voltage.
  • This higher voltage is desirable in electrophotography because upon subsequent exposure to a light image the portion of the photoconductive surface which is not exposed to light remains at a higher voltage and thus is better able to attract the developer material. This produces a darker copy of a copy with greater contrast, as is well known in the art.
  • One of'the problems in charging the photoconductor surface to a higher voltage is that of arcing. If the shield is made of conductive material there is a tendency for arcing to occur between the electrode 18 and the shield as electrode voltage is increased, With a conductive shield there is a low resistance current path to ground through the shield so with the spacings generally used in prior art devices the electrode is operated at a potential of about 5,000 volts to reduce the possibility of arcmg.
  • the semiconductor material used in the shield should have as high a resistivity as possible to reduce the possibility of arcing, but its resistivity must be sufficiently less than that of the material in the photoconductive surface 14 so thatif arcing does occur it takes place between the electrode and shield and not between the electrode and the photoconductive surface.
  • a corona charging device wherein relative movement between a photoconductive surface and an elongated corona discharge electrode means in close .proximity thereto takes place as a high voltage is apto said surface andextending transverse to said move-' ment, the improvement comprising an elongated shield of semiconductive material partially surrounding said electrode means and extending parallel thereto, said shield having an elongated slit extending transverse to the direction of said relative movement to permit the flow of corona current from said electrode means to said photoconductive surface.
  • said shield is made of a material having a resistivity in the range of to l0 ohm-cm.
  • said photoconductive surface is composed of a material having a dark resistivity of approximately l0ohm-cm., said shield comprising a material having a resistivity in the range of approximately 10 to l0 ohm-cm.
  • said photoconductive surface is comprised of a photoconductive material disposed in a layer over a conductive substrate, said semiconductive shield and said substrate being connected to ground potential, and said electrode means is connected to a source of unidirectional voltage.
  • said semiconductive shield is composed of a material having a resistivity in the range of 10 to lO ohm-cm., and said photoconductive material has a dark resistivity greater than the resistivity of said shield material.
  • Patent No. 3,7 3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated January 1, 1971;

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
US00292285A 1972-09-26 1972-09-26 Corona charging device with semiconductive shield Expired - Lifetime US3783283A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US29228572A 1972-09-26 1972-09-26

Publications (1)

Publication Number Publication Date
US3783283A true US3783283A (en) 1974-01-01

Family

ID=23124022

Family Applications (1)

Application Number Title Priority Date Filing Date
US00292285A Expired - Lifetime US3783283A (en) 1972-09-26 1972-09-26 Corona charging device with semiconductive shield

Country Status (8)

Country Link
US (1) US3783283A (enrdf_load_stackoverflow)
JP (1) JPS4973139A (enrdf_load_stackoverflow)
BR (1) BR7307084D0 (enrdf_load_stackoverflow)
CA (1) CA996992A (enrdf_load_stackoverflow)
FR (1) FR2200651B1 (enrdf_load_stackoverflow)
GB (1) GB1395467A (enrdf_load_stackoverflow)
IT (1) IT993209B (enrdf_load_stackoverflow)
NL (1) NL151524B (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2658287A1 (de) * 1976-01-09 1977-07-14 Amcor Ltd Ionisierungsvorrichtung
US4110614A (en) * 1976-12-17 1978-08-29 Xerox Corporation Corona device
EP0016300A1 (en) * 1979-03-26 1980-10-01 International Business Machines Corporation Electrostatic copier
US4523082A (en) * 1983-05-05 1985-06-11 Sturdevant Eugene J Electrode shield device
US4836901A (en) * 1985-09-05 1989-06-06 Toyoda Gosei Co., Ltd. Corona discharge treating method and apparatus for resin moldings
US4910637A (en) * 1978-10-23 1990-03-20 Rinoud Hanna Modifying the discharge breakdown
US5587584A (en) * 1996-03-28 1996-12-24 Xerox Corporation Apparatus for charging a film on the internal surface of a drum
EP0878885A1 (en) * 1997-05-13 1998-11-18 Fuji Photo Film Co., Ltd. Web charging apparatus
US20070108984A1 (en) * 2003-11-12 2007-05-17 International Business Machines Corporation Ionization test for electrical verification

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52128138A (en) * 1976-04-20 1977-10-27 Canon Inc Method for removing insulating liquid
JPS5571575A (en) * 1978-11-24 1980-05-29 Matsushita Electric Ind Co Ltd Image recorder
JPS5859468A (ja) * 1982-07-12 1983-04-08 Sharp Corp コロナ帯電装置
US4762997A (en) * 1983-11-30 1988-08-09 Xerox Corporation Fluid jet assisted ion projection charging method

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3277298A (en) * 1964-10-05 1966-10-04 Formfoto Mfg Company Corona discharge device
US3611414A (en) * 1969-09-03 1971-10-05 Eastman Kodak Co Electrographic oscillograph
US3711710A (en) * 1969-11-07 1973-01-16 Australia Res Lab Method of and means for controlling corona emission

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3277298A (en) * 1964-10-05 1966-10-04 Formfoto Mfg Company Corona discharge device
US3611414A (en) * 1969-09-03 1971-10-05 Eastman Kodak Co Electrographic oscillograph
US3711710A (en) * 1969-11-07 1973-01-16 Australia Res Lab Method of and means for controlling corona emission

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2658287A1 (de) * 1976-01-09 1977-07-14 Amcor Ltd Ionisierungsvorrichtung
US4110614A (en) * 1976-12-17 1978-08-29 Xerox Corporation Corona device
US4910637A (en) * 1978-10-23 1990-03-20 Rinoud Hanna Modifying the discharge breakdown
EP0016300A1 (en) * 1979-03-26 1980-10-01 International Business Machines Corporation Electrostatic copier
US4523082A (en) * 1983-05-05 1985-06-11 Sturdevant Eugene J Electrode shield device
US4836901A (en) * 1985-09-05 1989-06-06 Toyoda Gosei Co., Ltd. Corona discharge treating method and apparatus for resin moldings
US5587584A (en) * 1996-03-28 1996-12-24 Xerox Corporation Apparatus for charging a film on the internal surface of a drum
EP0878885A1 (en) * 1997-05-13 1998-11-18 Fuji Photo Film Co., Ltd. Web charging apparatus
US6086675A (en) * 1997-05-13 2000-07-11 Fuji Photo Film Co., Ltd. Web charging apparatus
EP1465305A3 (en) * 1997-05-13 2005-03-30 Fuji Photo Film Co., Ltd. Web charging apparatus
EP1465306A3 (en) * 1997-05-13 2005-03-30 Fuji Photo Film Co., Ltd. Web charging apparatus
US20070108984A1 (en) * 2003-11-12 2007-05-17 International Business Machines Corporation Ionization test for electrical verification
US7808257B2 (en) 2003-11-12 2010-10-05 International Business Machines Corporation Ionization test for electrical verification

Also Published As

Publication number Publication date
FR2200651A1 (enrdf_load_stackoverflow) 1974-04-19
BR7307084D0 (pt) 1974-07-11
FR2200651B1 (enrdf_load_stackoverflow) 1976-11-19
NL151524B (nl) 1976-11-15
GB1395467A (en) 1975-05-29
DE2342471A1 (de) 1974-04-04
CA996992A (en) 1976-09-14
IT993209B (it) 1975-09-30
NL7313066A (enrdf_load_stackoverflow) 1974-03-28
DE2342471B2 (de) 1976-09-16
JPS4973139A (enrdf_load_stackoverflow) 1974-07-15

Similar Documents

Publication Publication Date Title
US2833648A (en) Transfer of electrostatic charge pattern
US3783283A (en) Corona charging device with semiconductive shield
US2951443A (en) Image reproduction
US3684364A (en) Lift off electrode
US3288602A (en) Xerographic plate and method
US3778841A (en) Induction imaging system
US3813549A (en) Self-healing electrode for uniform negative corona
US3937960A (en) Charging device for electrophotography
US3703376A (en) Induction imaging system
US3611074A (en) Corona discharge device
US3719481A (en) Electrostatographic imaging process
US3990394A (en) Control circuit used in development of electrostatic latent images and developing apparatus
JPS597973A (ja) 電子写真複写機の現像装置
US3772010A (en) Electrophotographic apparatus and method for imagewise charge generation and transfer
US3666364A (en) Electrophotographic apparatus
KR890004869B1 (ko) 전자사진인쇄에 있어서 토우너 화상의 형성방법
EP0004380B1 (en) Scorotron charging apparatus
US3412242A (en) Method of charging a zinc oxide photoconductive layer with a positive charge
US4282297A (en) Charge transfer imaging
US3122634A (en) Controlled charging in xerographic copying apparatus
US3813548A (en) Corona generating methods and apparatus therefor
US3543023A (en) Method of establishing an electrical charge on a conductive interlayer unconnected to a potential source
US4149796A (en) Electrophotographic apparatus comprising improved bias source for magnetic brush
US3794418A (en) Imaging system
US3783352A (en) Developing method for electrophotography