US3834809A - Electrophotographic system - Google Patents

Electrophotographic system Download PDF

Info

Publication number
US3834809A
US3834809A US00382643A US38264373A US3834809A US 3834809 A US3834809 A US 3834809A US 00382643 A US00382643 A US 00382643A US 38264373 A US38264373 A US 38264373A US 3834809 A US3834809 A US 3834809A
Authority
US
United States
Prior art keywords
layer
electrode
image
insulating layer
photoconductive
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
US00382643A
Other languages
English (en)
Inventor
M Yoshizawa
M Ohnishi
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.)
Mitsubishi Electric Corp
Original Assignee
Mitsubishi Electric 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 Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Application granted granted Critical
Publication of US3834809A publication Critical patent/US3834809A/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
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20

Definitions

  • a photosensitive member is composed of an electrode layer, a photoconductive layer responsive to visible light and an ultraviolet photoconductive, electrically insulating layerv
  • the photoconductive layer is irradiated by visible light from an object to be reproduced simultaneously with the negative corona charging of the electrically insulating layer to form an electrostatic latent image on the latter.
  • a positive voltage is applied to the electrode layer. The application of this voltage can also be accomplished during dry development of the image.
  • the electrostatic image left on the insulating layer is erased by irradiation with ultraviolet radiation. It has been found that, as the photoconductive layer has a finite dark resistance, aleakage current flows through that layer to more or less charge the insulating layer with the same polarity as the-bright portion of the electrostatic image.
  • a photosensitive member includes a visible photoconductive layer having superposed thereon a thin layer of electrically high insulating material transmissive to visible light and photoconductive in the ultraviolet range.
  • the insulating layer is irradiated with visible light from an object to be reproduced and is simultaneously charged a predetermined This leads to a decrease in the ratio of a concentration of the recorded image onthe record medium to a concentration of the background on the medium. As a result, the intensity of the recorded image decreases due to the decrease in this so called signal-to-noise ratio. 4
  • an electrophotographic system comprising, in combination, a combined substrate and electrode member, a photoconductive layer, and an ultraviolet photoconductive, electrically high insulating layer disposed in the named order to form an electrophotographic sheet-like member, means for irradiating the photosensitive member with visible light from an object to be reproduced and simultaneously charging the insulating layer a predetennined polarity to form an electrostatic latent image corresponding in pattern to the object thereon, and means for developing the electrostatic latent image and fixing the developed image.
  • the present invention is further characterized in that there is provided means for applying to the combined substrate and electrode member a biasing voltage having a reverse polarity from the above note predetermined polarity during the simultaneous irradiation-with-light and charging.
  • a biasing voltage having its polarity reversed from the predetermined polarity may be additionally. applied to the combined substrate andelectrode member during the development of the electrostatic latent image.
  • the biasing voltage applied to the combined substrate and electrode member during the simultaneous irradiation-with-light and charging may be derived from the same biasing source as that applied to the member during the development of the electrostatic latent image.
  • FIG. 1 is a fragmental cross sectional viewof a photosensitive member disclosed in copending US. applicationSer. No. 305,827 as above cited;
  • FIG.2 is a schematic diagram useful in explaining the principles of the present invention.
  • FIG. 3 isa graph illustrating the relationship between a surface potential on the photoconductive,electrically high insulatinglayer shownin FIGS. 1 and 2 andabiasing-potential applied to the electrode shown .in 'FIGS. 1 and 2;
  • FIG. 4 isafront elevational-sectional viewnof one embodiment constructed in accordance with the electrophotographic system of the present inventionrand
  • FIG. 5 is a schematic side elevational viewas viewed in a direction parallel to thedirection of rotation ofthe photosensitive drum shown in FIG. '4.
  • FIG. 1 of the drawings is schematically illustrated a photosensitive .sheet-llike member.
  • the photosensitive memberl isgenerallydesignated by the reference numeral land comprises a combined substrate and electrode member l2,aphotoconductive, layer 1 1 and a layer '16 of'photoconductive, electrically high insulatingmaterial superposed on each other.
  • the photoconductive ilayer .14 is -fonned of a photoconductive material sensitive to the spectral range of visible radiation. For example, :the
  • layer 14 may be prepared by :mixing a cadmiumsulfide '(CdS) powder having added .thereto very small amounts of copper and chlorine with from :to 50 percent by volume of a binder selected from the group consisting of the vinyl, acrylic and cellulose systems.
  • a binder selected from the group consisting of the vinyl, acrylic and cellulose systems.
  • the material thus prepared is applied on the combined electrode and substrate member 12 in any suitable mannen
  • the layer 16v is composed of any suitable transparent, electrically high insulating material having photoconductive property within the spectral range of so ultraviolet radiation.
  • An example of the material of the layer 16 is polyvinyl carbazole containing about 0.2% by weight of picric acid and dissolved into a'solvent such as dioxan, tetrahydrofuran or the like.
  • the solution thus prepared is applied to the photoconductive 5 term C is negligiblysmall.
  • the insulating layer 16 has formed on the surface thereof .an electrostatic latent image including portions charged respectively positively and negatively with respect to ground potential in accordance with the bright and dark portions of the light image.
  • the second step is toirradiate the photoconductive, insulating layer 16 with suitably intense ultraviolet radiationto decreasethe internal impedanceofrthe layer-'16. This results in the erasure of theentire electrostatic la- :tent image remaining on the surface ofthe .insulatng layer "l6so that the photosensitivemember "'10 is ready :for the succeeding visible irradiation step.
  • At the-first step offorming an electrostatic'latent image athoseportions of the photoconductive layer 'l4'no't irradiated with visible radiation have resistanceswhose magnitudes are finite rather than :infinitely great and accordingly leakage currents flow' tlierethrough. These flows of leakage current impart to the insulating layer 16 electric charges identical in polarity tothose result ing from the bright portions of the light image although the magnitudes of the changes are small.
  • This means thatacorresponding-image transferred to and recorded on a record medium has its concentration decreased with respect to a concentration of the background on the record medium. Therefore the recorded image has a decreased signal-to-noise ratio.
  • the arrangement illustrated comprises the photosensitive member of FIG. 1 including the photoconductive layer 14 formed, by way of example, of an N type semiconductive material.
  • the arrangement further comprises a negatively charging device generally designated by the reference numeral and including a length of very thin metallic wire 22 and a pair of grounded electrodes 24 disposed in opposite relationship whereby the length of wire 22 is located centrally therebetween.
  • the length of wire 22 is connected to a source 26 of negative corona voltage to be applied with a negative corona voltage a corona discharge occurs between the length of wire and the grounded electrodes 24-.
  • the corona discharge uniformly charges the surface of the insulating layer 16 with the negative polarity.
  • the combined substrate and electrode member 12 is connected to ground through a source 28 fof biasing voltage unlike what isdisclosed in the cited US. application.
  • the source 28 applies a biasing voltage V to the electrode member 12.
  • FIG. 3 illustrates a surface potential V, on the insulating layer 16 in ordinate plotted against the biasing voltage V in abscissa with the potential and voltage expressed in volts.
  • a solid line 0 describes surface potential on the insulating layer 16 after the layer has been negatively charged by the chargingdevice 20 withoutirradiation by visible radiation.
  • Another solid line b describes a surface potential on a similarly charged portionof the insulating layer l6 which has beenirradiated by visible light on the order of 30 luxes.
  • the solid-linen can represent a surface potential'on-that portion of the insulating layer 16 corresponding to a dark portion of a visiblelight image of an object tobe reproduced while the solid line b can represent a surface potential on that portion of the insulating layer 16 corresponding to a bright portion-of the light image.
  • the bright and dark portion of the insulating layer 16 are at surface potentials as shown at points B andA in FTG. 3 respectively.
  • a difference between the surface potentials on the bright and dark portions of the insulating layer 16 is called a contrast voltage and designated by AV hereinafter;
  • contrast voltage is at most about 200 volts for a null biasing voltage.
  • the contrast voltage is increased'through the negative charging, inthe presence of the biasing voltage according to the-principles of the present invention.
  • the present invention exhibits two results; the contrast voltage increases and a recorded image obtained by the dry development has an improved signal-to-noise ratio.
  • FIG. 4 there is illustrated one embodiment of the present invention as viewed in a direction perpendicular to the axis of rotation of a rotary photosensitive drum.
  • the arrangement illustrated includes a rotary photosensitive drum in the form of a hollow cylinder generally designated by the reference numeral 10.
  • the drum 10 has a cylindrical surface including an inner electrode layer 12, an intermediate photoconductive layer 14 and an outer insulating layer 16 corresponding to the components l2, l4 and 16 shown in FIG. 1.
  • the electrode layer 12 includes a plurality of electrode segments 12a, 12b, 12n extending longitudinally of the drum 10 with predetermined longitudinal gaps formed therebetween.
  • the photoconductive and insulating layers 14 and 16 respectively can be successively formed on the electrode layer 12, as above described in conjunction with FIG. 1 to complete the photosensitive drum 10.
  • gaps between the adjacent electrode segments are too broad, those portions of the photosensitive layer 14 disposed on the gap have formed thereon no electrostatic latent image resulting in the formation of a recorded image includes stripe-shaped blurs. This leads to a decrease in the quality of the recorded image. On the contrary, if the gaps are too narrow then those portions of the photoconductive layer 14 located above the gaps decrease in resistance and accordingly the electrode layer 12 fails to function as a segmented electrode.
  • the gaps between the electrode segments must be selected to be a width such that the quality of the recorded image is prevented from appreciably decreasing while the electrode layer is enabled to function as a segmented electrode.
  • the optimum width of the gaps depends upon the required quality of the recorded image, the resistivity and thickness of the photoconductive layer 12 etc. It has been found that, with satisfactory results, the gaps are preferably in the order of from 30 to 150 microns with the photoconductive layer 14 formed by applying a cadmium sulfide powder mixed with from 5 to 50% by volume of an organic resin such as acrylic resin in a thickness of about microns to the electric layer 12.
  • the gap may be approximately equal to the spacing between the characters, that may amount to several milimeters. In other words, the gap can be suitably determined for the particular application.
  • the adjacent electrode segments may electrically floated from the ground potential.
  • the latter may be applied with graded potentials. For example, if a potential of 1,000 volts is applied to the electrodes segment 12c, potentials of 500 volts may be applied to the adjacent electrode segments 12b and 12d while the electrode segments 12a and 12e (not shown) may be at a null potential.
  • a visible light image of an object to be reproduced is focussed on the photoconductive layer 14 of the rotating drum by a lens 32 before it has been transmitted through a negative corona discharging device substantially transmissive to a visible light beam from the object 30.
  • the device 20 negatively charges the insulating layer 16 of the rotating drum 10 and a brush 34a connected to a biasing source 28 engages only that electrode segment such as the electrode segment 12a overlain by the negatively charge portion of the insulating layer 16.
  • a positive biasing voltage from the source 28 is applied to that electrode segment 12a.
  • the negative corona voltage and the positive biasing voltage are applied in superposed relationship across the photosensitive drum 10 to form on the insulating layer 16 an electrostatic latent image corresponding in pattern to the object 30 with the contrast thereof improved due to an increase in the V in the equation (3) by the voltage V
  • the biasing voltage V goes to zero and thereafter that portion having formed thereon the electrostatic latent image enters a dry development unit 36.
  • the development unit 13 selected ones of the electrode segments 12a, 12b, 1211 are again supplied the biasingvoltages V from the source 20 by having brushes 34b contacted thereby while the latent image is developed with toner particles disposed therein in the well known manner.
  • the biasing voltage V has a magnitude preselected so as to meet the requirements that a surface potential on the insulating layer 16 is positive or null on the portions thereof corresponding to the dark portion of the light image and negative on that the portions corresponding to the bright portion.
  • This measure is particularly effective for preventing the insulating layer 16 from being somewhat charged resulting from a leakage current flowing through the photoconductive layer and also decreasing a concentration of the background on the associated record medium as previously described. Therefore the resulting recorded image has a much improved signal-to-noise ratio.
  • the development unit 36 is shown in FIG. 4 as including a grounded electrode 38 disposed in opposite relationship with the photosensitive drum 10.
  • the grounded electrode 38 serves to effectively apply the biasing voltage V,, to the insulating layer 16. If desired, the electrode 38 may be supplied with a voltage suitable for the development of the latent image.
  • the present invention is not restricted to the application of the biasing voltage to the single electrode segment.
  • the biasing voltage V may be simultaneously applied to a plurality of adjacent electrode segments whose circumferential length is somewhat longer than the effective charging width provided by the corona charging device 20 with the width of the brush 34a correspondingly widened.
  • biasing source 28 is utilized in common with the simultaneous irradiation-with-light and negative charging and the development, it is to be understood that a separate biasing source may be additionally provided for the development phase. Alternatively, the biasing voltage may continue to be applied to the electrode segments for a time interval extending from the simultaneous irradiation-with-light and negative charging to the development step.
  • the drum 10 with the developed image is moved past an ultraviolet lamp 40a serving to decrease the resistance of the photoconductive high insulating layer 16 to thereby erase the electrostatic image left thereon. At that time, the'biasing voltage is not applied to the associated electrode segments and therefore the surface potential on the drum 10 becomes substantially null.
  • the rotating drum 10 reaches a transfer section including a supply roll 40 and a transferring roll 44.
  • the transferring roll 44 is operated to transfer the developed image from the drum to a dielectric coated tape from the supply roll 42 in the manner well known in the art.
  • the tape with the transferred image enters a fixation unit 48 where it is fixed by heating after which a cutter 50 cuts the tape to a predetermined length. At that time, the reproduction of the object has been completed.
  • the photosensitive layer thereof is successively irradiated by a ultraviolet lamp 40b so that any residual electrostatic image is completely erased. Then the drum 10 is cleaned by a cleaning unit 52. Thus the photosensitive drum 10 is ready for a succeeding operation.
  • FIG. 5 shows the photosensitive drum 10 as viewed in a direction parallel to the axis of rotation thereof.
  • the drum 10 has one side on which the photoconductive and insulating layers 14 and 16 respectively are not disposed in order to expose the end portions of the electrode segments 12a, l2b, 12c,
  • the brushes 34a and 34b are arranged to be directly contacted by those end portions of the electrode mension or width of a light beam to about three times of the effective charging width provided by the negative corona charging device although it is not particularly restricted. Since the conditions under which the light beam from the object irradiates the photosensitive drum is predetermined, a change in width of the electrode segments permits a variation in the quantity of charge on the insulating layer of the drum, resulting in a wide variety of controls of the electrophotographic recording characteristics and particularly of the charging characteristics. It has been also found that the gaps between the adjacent electrode segments are preferably tilted at angles formed between the direction of rotational axis of the drum and the direction of the diagonal of the corona charging device. However only for purposes of illustration, the gaps have been described as extending perpendicularly to the direction of rotation of the drum.
  • the present invention provides an electrophotographic system in which simultaneous irradiation-with-light and charging and the development is effected while the electrode involved is provided with a voltage having a polarity reversed from that of the charging voltage. This causes not only an increase in contrast voltage but also an improvement in the signalto-noise ratio during development.
  • the present invention has been described in conjunction with a few preferred embodiments thereof it is to be understood that numerous changes and modification may be resorted to without departing from the spirit and scope of the invention.
  • the electrode segments disposed on the cylindrical surface may be disposed on one end side of the photosensitive drum.
  • the photoconductive layer may be formed of a P type semiconductive material in place of an N type material with the polarity of the charging and biasing voltage accordingly varied.
  • selenium or selenium-tellurium compound of P type conductivity may be used to form the photoconductive layer.
  • An electrophotographic system comprising, in
  • a photosensitive member comprised of a combined substrate and electrode layer, a photoconductive layer and an ultraviolet photoconductive, electrically high insulating layer disposed in the recited order to form an electrophotograph sheet-like member, means operatively positioned for irradiating said photosensitive member with visible light from an object to be reproduced and simultaneously charging said insulating layer with a predetermined polarity to form an electrostatic latent image corresponding in pattern to the object thereon, and means operatively positioned for developing and fixing the electrostatic latent image, wherein means are provided for applying to said combined substrate and electrode layer a biasing voltage having its polarity reversed from said predetermined polarity simultaneously with the irradiation-with-visible light and charging.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Photoreceptors In Electrophotography (AREA)
US00382643A 1972-08-04 1973-07-26 Electrophotographic system Expired - Lifetime US3834809A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP47078150A JPS4936337A (en]) 1972-08-04 1972-08-04

Publications (1)

Publication Number Publication Date
US3834809A true US3834809A (en) 1974-09-10

Family

ID=13653865

Family Applications (1)

Application Number Title Priority Date Filing Date
US00382643A Expired - Lifetime US3834809A (en) 1972-08-04 1973-07-26 Electrophotographic system

Country Status (4)

Country Link
US (1) US3834809A (en])
JP (1) JPS4936337A (en])
DE (1) DE2339458C3 (en])
GB (1) GB1405201A (en])

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3941280A (en) * 1974-02-13 1976-03-02 Xerox Corporation Apparatus for controlling developer efficiency
US4088483A (en) * 1974-02-13 1978-05-09 Minolta Camera Kabushiki Kaisha Electrophotographic plate with charge transport overlayer
US4119373A (en) * 1976-03-08 1978-10-10 Minnesota Mining And Manufacturing Company Electrographic apparatus and method for using arsenic selenide as the photoconductor
US4131462A (en) * 1976-02-17 1978-12-26 Honeywell Inc. Element for thermoplastic recording
FR2441201A1 (fr) * 1978-11-09 1980-06-06 Savin Corp Procede et appareil de copie electrophotographique ayant une excellente resolution
US4362797A (en) * 1977-11-22 1982-12-07 Olympus Optical Company Limited Electrophotographc process to release trapped charges by charging and ultraviolet exposure
US4433038A (en) * 1980-11-12 1984-02-21 Olympus Optical Company Ltd. Electrophotographic copying process involving simultaneous charging and imaging
US4442191A (en) * 1980-11-12 1984-04-10 Olympus Optical Company Ltd. Electrophotographic copying process for producing a plurality of copies
US5202722A (en) * 1991-04-17 1993-04-13 Brother Kogyo Kabushiki Kaisha Image-forming system
US5214478A (en) * 1990-10-25 1993-05-25 Brother Kogyo Kabushiki Kaisha Image recording apparatus provided with a selective power applying device
US6624413B1 (en) 2002-11-12 2003-09-23 Qc Electronics, Inc. Corona treatment apparatus with segmented electrode

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4286032A (en) * 1978-04-27 1981-08-25 Canon Kabushiki Kaisha Electrophotographic process and apparatus therefor

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3288602A (en) * 1962-04-04 1966-11-29 Xerox Corp Xerographic plate and method
US3719481A (en) * 1970-03-07 1973-03-06 Xerox Corp Electrostatographic imaging process

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3288602A (en) * 1962-04-04 1966-11-29 Xerox Corp Xerographic plate and method
US3719481A (en) * 1970-03-07 1973-03-06 Xerox Corp Electrostatographic imaging process

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3941280A (en) * 1974-02-13 1976-03-02 Xerox Corporation Apparatus for controlling developer efficiency
US4088483A (en) * 1974-02-13 1978-05-09 Minolta Camera Kabushiki Kaisha Electrophotographic plate with charge transport overlayer
US4131462A (en) * 1976-02-17 1978-12-26 Honeywell Inc. Element for thermoplastic recording
US4119373A (en) * 1976-03-08 1978-10-10 Minnesota Mining And Manufacturing Company Electrographic apparatus and method for using arsenic selenide as the photoconductor
US4362797A (en) * 1977-11-22 1982-12-07 Olympus Optical Company Limited Electrophotographc process to release trapped charges by charging and ultraviolet exposure
FR2441201A1 (fr) * 1978-11-09 1980-06-06 Savin Corp Procede et appareil de copie electrophotographique ayant une excellente resolution
US4433038A (en) * 1980-11-12 1984-02-21 Olympus Optical Company Ltd. Electrophotographic copying process involving simultaneous charging and imaging
US4442191A (en) * 1980-11-12 1984-04-10 Olympus Optical Company Ltd. Electrophotographic copying process for producing a plurality of copies
US5214478A (en) * 1990-10-25 1993-05-25 Brother Kogyo Kabushiki Kaisha Image recording apparatus provided with a selective power applying device
US5202722A (en) * 1991-04-17 1993-04-13 Brother Kogyo Kabushiki Kaisha Image-forming system
US6624413B1 (en) 2002-11-12 2003-09-23 Qc Electronics, Inc. Corona treatment apparatus with segmented electrode

Also Published As

Publication number Publication date
DE2339458A1 (de) 1974-02-21
DE2339458C3 (de) 1980-07-03
GB1405201A (en) 1975-09-03
JPS4936337A (en]) 1974-04-04
DE2339458B2 (de) 1979-10-04

Similar Documents

Publication Publication Date Title
US3284224A (en) Controlled xerographic development
US3666363A (en) Electrophotographic process and apparatus
US3782818A (en) System for reducing background developer deposition in an electrostatic copier
US2892709A (en) Electrostatic printing
US3551146A (en) Induction imaging system
US3663219A (en) Electrophotographic process
US3639121A (en) Novel conducting lacquers for electrophotographic elements
US3834809A (en) Electrophotographic system
US3752572A (en) Apparatus for making electrographs
US3776627A (en) Electrophotographic apparatus using photosensitive member with electrically high insulating layer
US3615395A (en) Electrostatic and electrophotographic variable contrast image-forming methods
US3703376A (en) Induction imaging system
US3719481A (en) Electrostatographic imaging process
US3464818A (en) Method of photoelectric copying
US4334772A (en) Electrophotographic apparatus of retentive type
GB2065032A (en) Image recording method and apparatus
US3730709A (en) Method for electrophotography
US3932877A (en) Electrophotographic recording system with plate cleaning
DE3740158C2 (en])
US3890040A (en) Induction imaging apparatus
US3540885A (en) Reduction of fog formation in an electrophotographic light sensitive sheet
US3794418A (en) Imaging system
US3650622A (en) Apparatus for control of bias potential in an electrophotographic copier
US3797928A (en) Method and apparatus for electrophotography
US3666365A (en) Electrophotographic process and apparatus involving persistent internal polarization