US3928032A - Methods of and apparatus for reproducing images by transferring electrostatic charges - Google Patents

Methods of and apparatus for reproducing images by transferring electrostatic charges Download PDF

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Publication number
US3928032A
US3928032A US421041A US42104173A US3928032A US 3928032 A US3928032 A US 3928032A US 421041 A US421041 A US 421041A US 42104173 A US42104173 A US 42104173A US 3928032 A US3928032 A US 3928032A
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US
United States
Prior art keywords
paper
capacitance
drums
photoconductive
belt
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
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US421041A
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English (en)
Inventor
Pham Kim Quang
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Cellophane SA France
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Individual
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Filing date
Publication date
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Publication of US3928032A publication Critical patent/US3928032A/en
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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
    • G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
    • G03G15/18—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a charge pattern

Definitions

  • the two drums are connected through a circuit which contains an auxiliary capacitor that has a capacitance at least 100 times greater than the capacitance existing between the drums. Since the capacitance of this auxiliary capacitor is so high, it renders the capacitance existing between the two drums insignificant in relation to the total capacitance thereby, in essence, rendering the capacitance independent of both environmental conditions and incompatibility between the paper and photoconductive belt.
  • This invention relates to methods of and apparatus for transferring and permanently recording images and, more particularly, this invention relates to methods of and apparatus for reproducing documents by electrostatically transferring images of those documents to a dielectric surface, such as a sheet of paper.
  • the afore-described process is most conveniently accomplished by training the paper and the photoconductive belt about peripherally juxtaposed drums made of conductive material.
  • the drums are generally of the same diameter and are rotated at the same peripheral or tangential speed.
  • a potential difference is created between the drums by charging one drum and grounding the other so that as the photoconductive belt and paper come into line contact, the ionization threshold between the two is exceeded, causing transfer of the electrostatic charges.
  • photoconductive belt may be used in some instances, it is also a general practice to simply make the surface of the drum not carrying the paper photoconductive so that a photoconductive belt need not be used.
  • the drum that carries the photoconductive surface or has a photoconductive layer is charged by a coronacharging device to a value Q C V where C is the capacitance existing between the drums and V is the potential difference created between the drums.
  • the charge Q is limited by leakage resistance, but the value of V is variable because of variations in C, due to the aforementioned environmental variations and to imperfections in the compatibility between the photoconductive and dielectric surfaces. These variations manifest themselves by undesirable discharges which create distortion in line contact as the electrostatic charges are transferred from the photoconductive surface to the paper.
  • Another object of this invention is to provide new and improved methods of and apparatus for reproducing images, wherein the reproduction thereof is unaffected by environmental conditions, such as temperature and humidity.
  • Still another object of the instant invention is to provide new and improved methods of and apparatus for reproducing images, wherein the reproduction thereof is independent of the homogeneity or compatibility between a photoconductive surface carrying an array of charges conforming to the image and a dielectric surface receiving an array of charges.
  • a method Q? practicing the instant invention includes forming images of documents or the like on a photoconductive surface while advancing the photoconductive surface over a first electrode. The image is then transferred to an uncharged dielectric surface while the uncharged dielectric surface is in contact with a second electrode, juxtaposed with the first electrode, in order to bring the photoconductive surface and the uncharged surface into proximity with one another, to thereby transfer the image to the uncharged surface.
  • This transfer is effected by creating a potential difference between the electrodes by charging the first electrode with a corona-charging device while grounding the second electrode.
  • a cir- 3 cuit including an auxiliary capacitor is connected between the two electrodes to form a circuit parallel with the two electrodes.
  • This auxiliary capacitor has the capacitance which is substantially higher than the capacitance existing between the electrodes.
  • An apparatus for practicing the instant invention includes first and second electrode means for advancing a photoconductive surface and a dielectric surface respectively, wherein an image of electrostatic charges is formed on the photoconductive surface for transfer to the dielectric surface.
  • a corona-charging device is utilized to bring the first electrode to saturation potential and thereby create a potential difference between the first and second electrodes. Since a capacitance exists between the electrodes, a parallel capacitive circuit is connected between them.
  • This capacitive circuit includes an auxiliary capacitor having a capacitance which is substantially higher than the capacitance existing between the electrodes.
  • a document 11 to be reproduced which, in the illustrated embodiment, is advanced from a supply reel 12 to a take-up reel 13. If the document happens to be a negative, light may be passed therethrough, as shown by the arrows l4-l4. If the document is a print, then light will be reflected therefrom in a conventional manner. In any case, light either passed through or reflected from the document is focused by lens 16 to produce an image of the document on a photoconductive surface 17.
  • the photoconductive surface is a belt trained around a pair of drums l8 and 19.
  • the photoconductive surface may utilize any one of a number of photoconductive materials.
  • the belt may be in the strip of either paper or aluminum covered with a standard photoconductive layer having a base of zinc oxide, polyvinyl carbazole, cadium sulfide, or any other known photoconductive substance.
  • the drum [8 may provide a photoconductive surface in lieu of the belt by coating the drum with one of the afore-mentioned photoconductive substances or another known photoconductive substance.
  • the photoconductive belt 17 is initially charged upstream of the area of image impingement by a corona-charging device 2] which distributes an array of electrostatic charges 22-22 on the belt.
  • the charges 22-22 are advanced downstream through the image impinged on the belt 17, they are rearranged according to the density of light patterns on the belt. Since the light patterns are arranged according to the focused image, the charges 22-22 will arrange themselves according to the focused image. In other words, if the document being reproduced is a negative, then more of the particles will congregate in the relatively light areas or relatively illuminated areas than in the less illuminated areas. Consequently, when the image is finally fixed, the light areas will appear dark and the dark areas will appear light.
  • the charge is transferred to a strip of paper 26 which is being advanced from a supply reel 27 to a take-up reel 28 around a metallic drum 29.
  • the paper 26 is preferably dielectric paper which is, initially at least, uncharged.
  • the drum 29 has the same diameter as the drum l8 and is rotated in the opposite direction at the same peripheral or tangential speed as the drum 18. This counter-rotation is accomplished in some conventional manner by using, for example, a conventional gear train.
  • the drums are juxtaposed in close proximity to one another with a gap 31 therebetween, which is just wide enough to accommodate both the photoconductive belt 17 and the strip of paper 26. As the photoconductive belt 17 and the paper 26 traverse the narrowest portion of the gap 31, they come into virtual contact with one another, allowing the charges 22-22 to transfer from the photoconductive belt to the paper, as will be explained hereinafter.
  • the drum 18 is charged by a corona-charging device 32 which, in the illustrated embodiment, is a pointed metal probe which is spaced a distance of a few millimeters to two centimeters from the drum 18.
  • the corona-charging device 32 may be powered by a voltage supply 33 which energizes both the corona-charging device 32 and the corona-charging device 21 through a conventional controller 34.
  • the coronacharging device 32 by being brought to a potential of 5,000 to 30,000 volts, can induce a potential of between 200 to 3,000 volts in the drum l8. It should be kept in mind that, instead of using a pointed probe such as the device 32, a wire placed parallel to the drum 18 can also be used.
  • the drum 29 is grounded by a lead 37.
  • the potential difference thus created between the drums l8, and 29 causes the electrostatic charges 22-22 to transfer from the photoconductive belt 17 to the paper 26 as the paper and photoconductive belt come into virtual contact in the gap 31.
  • This contact is generally line contact so that the charges 22-22 will register in successive lines on the paper 26.
  • the successive lines ultitpately create an image of electrostatic charges on the paper 26.
  • the paper passes over a developer 38 which, in the illustrated embodiment, includes a roller 39 that engages the paper and distributes a toner 41 onto the paper.
  • the toner 41 of course, distributes itself across the paper in accordance with the density of the electrostatic charges 2222.
  • a heater 32 dries the toner and adheres the toner to the paper before the paper is stored on take-up reel 28.
  • This circuit 45 includes a large capacitance illustrated by the capacitor 46.
  • the capacitor 46 will have a capacitance which is at least 100 times that of the capacitance occurring at gap 31.
  • the capacitance at gap 31 will be in the order of I pico farads, while the value of the capacitor 46 will generally be between 10,000 and l00,000 pico farads or, rather, from to 100 nano farads. Consequently, the variations in the capacitor 31 due to atmospheric conditions and lack of homogeneity between the paper 26 and the photoconductive belt 17 will be inconsequential in relation to the total capacitance existing between the drums l8 and 29. This is because the total capacitance is orders of magnitude greater than any variation in capacitance caused by these conditions.
  • the paper 26 can be of ordinary quality. Although it is perhaps desirable to make the paper of dielectric material, even paper which has conductive properties may be used.
  • the paper may be coated with a layer of dielectric resin of any nature. For example, it may have a base of vinyl polymers, silicones, polystyrenes or styrene-butadiene copolymers.
  • pigments may be used to improve the appearance of the paper, such pigments being zinc sulfide, silica, titanium oxide, zinc oxide or other known materials.
  • a method of reproducing an image on an uncharged surface comprising the steps of:
  • first and second capacitors are cyclindrical drums of conductive material and wherein the drums are rotated at the same tangential speed and are separated by a gap which is just wide enough to accommodate the photoconductive surface and uncharged surface in virtual contact with one another in order to transfer the image of electrostatic charges.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
US421041A 1972-12-08 1973-12-03 Methods of and apparatus for reproducing images by transferring electrostatic charges Expired - Lifetime US3928032A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7243711A FR2210302A5 (xx) 1972-12-08 1972-12-08

Publications (1)

Publication Number Publication Date
US3928032A true US3928032A (en) 1975-12-23

Family

ID=9108395

Family Applications (1)

Application Number Title Priority Date Filing Date
US421041A Expired - Lifetime US3928032A (en) 1972-12-08 1973-12-03 Methods of and apparatus for reproducing images by transferring electrostatic charges

Country Status (15)

Country Link
US (1) US3928032A (xx)
JP (1) JPS5431813B2 (xx)
AT (1) AT345094B (xx)
BE (1) BE808375A (xx)
CA (1) CA1004284A (xx)
CH (1) CH578196A5 (xx)
DE (1) DE2360843A1 (xx)
DK (1) DK134206B (xx)
ES (1) ES421300A1 (xx)
FR (1) FR2210302A5 (xx)
GB (1) GB1433840A (xx)
IT (1) IT1000207B (xx)
NL (1) NL7316595A (xx)
SE (1) SE386749B (xx)
ZA (1) ZA739322B (xx)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3055006A (en) * 1961-01-24 1962-09-18 Ibm High density, erasable optical image recorder
US3057275A (en) * 1958-10-29 1962-10-09 Xerox Corp Image keeping
US3281857A (en) * 1962-01-12 1966-10-25 Xerox Corp Xerographic transfer platen
US3322538A (en) * 1962-11-30 1967-05-30 Gen Electric Electrophotographic process
US3394002A (en) * 1964-10-21 1968-07-23 Xerox Corp Charge transfer with liquid layers

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3057275A (en) * 1958-10-29 1962-10-09 Xerox Corp Image keeping
US3055006A (en) * 1961-01-24 1962-09-18 Ibm High density, erasable optical image recorder
US3281857A (en) * 1962-01-12 1966-10-25 Xerox Corp Xerographic transfer platen
US3322538A (en) * 1962-11-30 1967-05-30 Gen Electric Electrophotographic process
US3394002A (en) * 1964-10-21 1968-07-23 Xerox Corp Charge transfer with liquid layers

Also Published As

Publication number Publication date
IT1000207B (it) 1976-03-30
ATA1025273A (de) 1977-12-15
CH578196A5 (xx) 1976-07-30
ES421300A1 (es) 1976-05-01
AU6336073A (en) 1975-06-12
JPS5431813B2 (xx) 1979-10-09
AT345094B (de) 1978-08-25
FR2210302A5 (xx) 1974-07-05
DK134206B (da) 1976-09-27
CA1004284A (en) 1977-01-25
NL7316595A (xx) 1974-06-11
GB1433840A (en) 1976-04-28
ZA739322B (en) 1974-10-30
DE2360843A1 (de) 1974-06-12
DK134206C (xx) 1977-02-28
JPS506347A (xx) 1975-01-23
SE386749B (sv) 1976-08-16
BE808375A (fr) 1974-06-07

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