US3843885A - Method for charging electrophotographic material - Google Patents

Method for charging electrophotographic material Download PDF

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Publication number
US3843885A
US3843885A US00275400A US27540072A US3843885A US 3843885 A US3843885 A US 3843885A US 00275400 A US00275400 A US 00275400A US 27540072 A US27540072 A US 27540072A US 3843885 A US3843885 A US 3843885A
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United States
Prior art keywords
insulating layer
photoconductive insulating
corona
photoconductive
corona discharge
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Expired - Lifetime
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US00275400A
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English (en)
Inventor
M Sato
M Takimoto
T Komaki
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Fujifilm Holdings Corp
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Fuji Photo Film Co Ltd
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Application filed by Fuji Photo Film Co Ltd filed Critical Fuji Photo Film Co Ltd
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/02—Sensitising, i.e. laying-down a uniform charge

Definitions

  • corona ions with a desired polarity produced by a corona discharge unit are sprayed onto the surface of the photoconductive insulating layer while the surface of the photoconductive insulating layer is simultaneously exposed to corona ions with the opposite polarity produced by another corona discharge unit.
  • a conductive layer is temporarily produced on the surface of the photoconductive insulating layer so that the photoconductive insulating layer is charged or sensitized.
  • this method is not able to provide the charging for high-insulating electrophotographic material, such as polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, 'polyarnide, polyirnide,
  • a method for charging an electrophotographic material having a high-insulating base and a photoconductive insulating layer coated directly thereon, without a conductive layer therebetween, is disclosed in British Pat. No. 971,281 Specification.
  • light having a wavelength which penetrates the base and is absorbed into the photoconductive layer is irradiated onto the material from the base-side thereof so as to make the contacting portion, of the photoconductive insulating layer with thebase, temporarily conductive.
  • the charging is provided by corona discharge during the period when the temporary conductive layer exists.
  • the connector which contacts to the surface of photoconductive insulating layer tends to produce line-cuts thereon which produce line-scars in the developed image and accordingly a significant deterioration of image quality. Furthermore, since the connector is merely contacted onto the surface of photoconductive insulating layer, there is a non-uniformity of charging due to imperfections in the contactTIt is therefore necessary to more strongly press the connector onto the surface of photoconductive insulating layer in order to provide a better contact, so that sharper line-cuts are produced thereon. In addition, since it is necessary that lights penetrate theba se, it is impossible to use a non-transparent material such as veneer, plastics, concrete or the like.
  • an object of this invention is to provide a novel and effective charging method and apparatus for electrophotographic material consisting of a high-insulating base and a photoconductive insulating layer coated thereon with no conductive layer.
  • Another object of this invention is to provide a method and apparatus for charging electrophotographic material having a base of opaque or nontransparent material.
  • electrophotographic material which consists of a high-insulating base and a photoconductive insulating layer coated directly thereon, is uniformly exposed to light having a spectrum absorbable in the photoconductive insulating layer on the side of the surface of the photoconductive insulating layer.
  • corona ions, with a first polarity are emitted from a corona discharge unit and are sprayed onto the surface of the photoconductive insulating layer, while at least a portion of the photoconductive insulating layer is exposed to corona discharge ions with the opposite polarity.
  • a conductive layer is formed temporarily on the surface of the photoconductive insulating layer, so that it is possible to charge, or sensitize, the electrophotographic material.
  • this invention provides a novel method and apparatus toenable the charging of an electrophotographic material by uniformly exposing the surface of a photoconductive insulating layer to form a conductive layer on the surface. It is, therefore, possible that an electrophotographic material consisting of a high-insulating base and a photoconductive insulating layer coated thereon is charged without providing any special conductive layer. Accordingly, it is possible to obtain a good electrophotographic image with no line-scar because it is not necessary to ground the material. Further, it is possible to use, as an insulating base, opaque or non-transparent insulating material such as veneer, plastics, concrete, wall, floor or the like.
  • FIG. 1 there is shown electrophotographic mate- .tial...l9,u 9r h s inre a- Ph t szq s us iye insula ing layer 11 is made of vacuum-deposited noncrystalline selenium, the mixture of photoconductive powder (e.g., zinc oxide, cadmium sulfide) and insulating resin and a, and a photoconductive organic material or the like. It is desirable that it exhibits a slow decay after the exposure light is turned off. When a photoconductive insulating material is subject to repeat cycles of charging and exposure, an effect known as fatigue sometimes occurs.
  • photoconductive powder e.g., zinc oxide, cadmium sulfide
  • High-insulating base 12 is made of well-drive paper, non-electrosensitive paper, polyethylene terephthalate, polypropylene, polycarbonate, polyamide, polyimide, polyvinyl chloride, diacetyl cellulose or polyacetyl cellulose, or it may be made of other nontransparent insulating material.
  • the photoconductive insulating layer is made of N-type semiconductor, e.g., by kneading together photoconductive zinc oxide powder and insulating resin, with reference to FIG. 2.
  • the electrophotographic material is exposed, on the side of the surface of photoconductive insulating layer 11, to the lights of a light source (not shown). The light is absorbable into the photoconductive insulating layer 11 to make it conductive.
  • Main corona discharge unit and sub-corona discharge unit 21 are arranged above the electrophotographic material 10 and having corona wires 22 and 23, respectively. Negative high voltage (e.g., 6 kV) is applied to the corona wire 22 of the main corona discharge unit 20 to emit negative corona ions onto the photoconductive insulating layer 11, and positive high voltage (e.g., 6 kV) is applied to the corona wire 23 of the sub-corona unit 21 to emit positive corona ions onto the photoconductive insulating layer 11.
  • Negative high voltage e.g., 6 kV
  • positive high voltage e.g., 6 kV
  • Fatigue is caused within the photoconductive insulating layer 11 by uniform exposure, so that there are relatively freely movable trapped electrons therein. These electrons are repulsed and driven away by the negative corona ions so that the trap centers are neutralized. Thus, the area R exposed to the negative corona discharge recovers from fatigue and is capable of being charged. On the other hand, the electrons in the area R, driven away by the negative corona ions, pass through the area outside the area R which has not recovered from fatigue and permits relatively free movement of electrons therein. These electrons are attracted by the positive corona ions emitted from the corona wire 23 for neutralization.
  • the area R is then expanded outwardly as a function of time so that the negative charging is provided over the large area.
  • a conductive layer is formed on the surface of the photoconductive insulating layer in accordance with the uniform exposure of the surface to lights and thus the electrophotographic material is charged. It is, therefore, possible to use electrophotographic material consisting of an opaque insulating base, such as veneer, plastics, concrete, wall or floor, and a photoconductive insulating layer directly coated thereon without the necessity of any special conductive layer.
  • FIG. 3 shows an example of electrophotographic apparatus for practicing the method of this invention, wherein (a) is the schematic front sectional view thereof and (b) is the schematic side sectional view thereof.
  • Main corona discharge unit 30 is composed of corona wire 31, shield case 32 and insulating supporter 33 for corona wire 31.
  • Sub-corona discharge unit 34 is composed of corona wire 35, shield case 36 and insulating supporter 37 for corona wire 35.
  • the corona wires 31 and 35 are positioned at right angles with respect to each other, the corona wire 31 being at a right angle to the forward direction of the electrophotographic material 10 and the corona wire 35 is parallel to the forward direction.
  • the electrophotographic material 10 Before the electrophotographic material 10 is exposed to corona discharge, it is uniformly exposed, on the side of the surface of the photoconductive insulating layer, to the lights from a light source 38. The light is absorbed by the photoconductive insulating layer to make the layer conductive.
  • a negative high voltage may be applied to the corona wire 31 of the main corona discharge unit 30 to produce corona discharge, while a positive high voltage may be applied to the corona wire 35 of the sub-corona discharge unit 34.
  • the po larity of high voltages applied to the corona wires may be opposite to the above case.
  • FIG. 4 is a schematic sectional view of another example of the apparatus according to this invention.
  • Electrophotographic material 10 is uniformly exposed to light from source 42 on the side of the surface of photoconductive insulating layer.
  • the layer is then exposed to positive corona ions produced by thesub-corona discharge unit 41 followed by exposure to negative corona ions produced by the main discharge unit 40 so as to become negatively charged.
  • the corona wire is made longer than the width of the material to uniformly charge the whole surface.
  • the corona discharge electrode it may be. possible to use, as the corona discharge electrode, a needle electrode or strip electrode instead of wire electrodes. It is necessary that the light source emit the lights in a spectrum which is absorbable by the photoconductive insulating layer.
  • the photoconductive insulating layer is made of zinc oxide, a tungsten light source may be used for pre-exposure.
  • This photoconductive insulating layer is photosensitive only to ultraviolet and near ultraviolet lightsand extremely absorbative to the spectral lights, so that only ultraviolet or near ultraviolet lights are available for exposure.
  • ultraviolet and near ultraviolet lights are absorbed in the surface of the photoconductive insulating layer, experiments show that the after effect on photoconductivity caused by the ultraviolet lights tends to continue for a relatively long period.
  • EXAMPLE I The electrophotographic material is made by kneading 100 parts photoconductive zinc oxide power (SaZeX No. 2000, Sakai Chemical Industry Co. Ltd.), 14 parts insulating resin (Styresol No. 4400, Japan Reichhold Chemical, Inc.) and 7 parts polyisocyanate compound (Desmodul L, Bayer A.G.), then painting the mixture onto a film of polyethylene terephthalate, of 150 thickness, to a thickness of about 7p. and then hardening the material in a constant temperature bath at 40C for 17 hours. After putting.
  • the electrophotographic material on a high-insulating plate (polymethylmethacrylate resin plate of mm thickness) in a dark place and exposing it uniformly on the side of the surface of the photoconductive insulating layer, to a tungsten lamp Lux sec (10,000 Lux X 20 sec), corona discharge units are arranged above the electrophotographic material as shown in FIG. 3.
  • a high-insulating plate polymethylmethacrylate resin plate of mm thickness
  • the distance between the corona wire and the surface to be charged is mm
  • the space between the corona wire and the shield case is 15 mm
  • the diameter of the wire is 0.05 mm
  • the length of the wire is 30 mm
  • the distance from the lower edge of the shield case to the surface to be charged is 8 mm
  • the material of the wire is tungsten.
  • the distance between the corona wire and the surface to be charged is 10 mm
  • the space between the corona wire and the shield case is 15 mm
  • the wire diameter is 0.05 mm
  • the wire length is 50 mm
  • the distance between the lower edge of the shield case and the surface to be charged is 2 mm
  • the wire material is tungsten.
  • EXAMPLE II The same electrophotographic material as in Example I is put on the similar insulating plate as in Example I and pre-exposed uniformly to the lights of 200,000 Lux' sec 10,000 Luxsec). Then, two needle corona discharge electrodes are arranged above the material at right angles to the surface to be charged. The distance between the corona discharge electrodes is 150 mm, the main corona discharge unit being posiwith an pq q ni x t q tioned above the center portion of the charged surface and the sub-corona discharge unit 34 being positioned above the edge portion of the charged surface.
  • the distance between the top of the main discharge unit electrode and the charged surface is 50 mm, and the distance-between the top of the sub-corona discharge unit electrode and the charged surface is 20 mm.
  • Applying 9 kV to the main corona discharge unit and +5 kV to the sub-corona discharge unit the electrophotographic material is moved below both electrodes at the speed of 30 mm/sec and the discharging is finished within 30 sec after the previous exposure, with the result that the center portion of the surface to be charged is charged to a l30 V surface potential.
  • EXAMPLE III The same material as in Example I is made zonal into a roll and transported at a speed of 30 mm/sec.
  • the light source and corona discharge units are arranged as shown in FIG. 4.
  • the light source consists of six tungsten lamps of 200 W arranged in double lines and provides an exposure quantity of 8000 Lux sec during the material passage.
  • a shielding plate is provided to prevent lights of the light source from leaking onto the charged area.
  • the electrophotographic material passes below the light source, then below the subcorona discharge unit 41 and then below the main corona discharge unit 40.
  • each corona discharge unit the corona wire is made of stainless steel with a 5 mm diameter, the distance between the shield case and the wire is 15 mm, and the distance between'the corona wire and the charged surface is 20 mm.
  • the distance between the first and the second corona discharge units is mm.
  • the length of each corona wire is 50 mm longer than the width of the electrophotographic material. Applying +9.5 kV to the corona wire of the first corona discharge unit 41 and 8.5 kV to the corona wire of the second corona discharge unit 40, the electrophotographic material is charged to a surface potential of V.
  • EXAMPLE IV The electrophotographic material is made by painting the same mixture as in Example I onto a veneer EXAMPLE V Using the same electrophotographic material as in Example I and charging it under the following conditions, measurements of the relation between exposure quantity and surface potential were made: The material was placed on the same insulating plate as in Example I, and two needle electrodes were arranged thereabove with a distanceof 80 mm between electrodes. The distance between the top of each needle electrode and the photoconductive insulating layer was 30 mm. The one needle electrode was applied with -5 kV and the other with a +5 kV, for a duration of 5 sec and 30 sec.
  • a method for charging to a first polarity electrophotographic material consisting of an insulating base and a photoconductive insulating layer directly coated thereon and including a semiconductor having majority carriers of said first polarity, said method comprising:

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Elimination Of Static Electricity (AREA)
  • Photoreceptors In Electrophotography (AREA)
US00275400A 1971-07-26 1972-07-26 Method for charging electrophotographic material Expired - Lifetime US3843885A (en)

Applications Claiming Priority (1)

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JP5583571A JPS5334492B1 (enrdf_load_stackoverflow) 1971-07-26 1971-07-26

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JP (1) JPS5334492B1 (enrdf_load_stackoverflow)
DE (1) DE2236716A1 (enrdf_load_stackoverflow)
GB (1) GB1379467A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4105321A (en) * 1976-10-27 1978-08-08 Xerox Corporation Illuminated charge control system for xerographic machines
US4248519A (en) * 1976-10-27 1981-02-03 Xerox Corporation Charge control system for xerographic machines
US4265998A (en) * 1979-11-13 1981-05-05 International Business Machines Corporation Electrophotographic photoreceptive background areas cleaned by backcharge process

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2955938A (en) * 1955-08-01 1960-10-11 Haloid Xerox Inc Xerography
US3676117A (en) * 1967-10-20 1972-07-11 Katsuragawa Denki Kk Method of electrophotography
US3715640A (en) * 1971-04-14 1973-02-06 Fuji Photo Film Co Ltd Corona charging process and apparatus in electrophotography

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2955938A (en) * 1955-08-01 1960-10-11 Haloid Xerox Inc Xerography
US3676117A (en) * 1967-10-20 1972-07-11 Katsuragawa Denki Kk Method of electrophotography
US3715640A (en) * 1971-04-14 1973-02-06 Fuji Photo Film Co Ltd Corona charging process and apparatus in electrophotography

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4105321A (en) * 1976-10-27 1978-08-08 Xerox Corporation Illuminated charge control system for xerographic machines
US4248519A (en) * 1976-10-27 1981-02-03 Xerox Corporation Charge control system for xerographic machines
US4265998A (en) * 1979-11-13 1981-05-05 International Business Machines Corporation Electrophotographic photoreceptive background areas cleaned by backcharge process

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Publication number Publication date
JPS5334492B1 (enrdf_load_stackoverflow) 1978-09-21
DE2236716A1 (de) 1973-02-08
GB1379467A (en) 1975-01-02

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