US3930257A - Methods of and apparatus for electrostatic printing - Google Patents

Methods of and apparatus for electrostatic printing Download PDF

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Publication number
US3930257A
US3930257A US452346A US45234674A US3930257A US 3930257 A US3930257 A US 3930257A US 452346 A US452346 A US 452346A US 45234674 A US45234674 A US 45234674A US 3930257 A US3930257 A US 3930257A
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Prior art keywords
charges
potential
electrostatic
dielectric layer
paper
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Expired - Lifetime
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US452346A
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English (en)
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Pham Kim Quang
Rene Gasdoue
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Cellophane SA France
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Individual
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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
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/32—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the charge pattern is formed dotwise, e.g. by a thermal head
    • G03G15/321—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the charge pattern is formed dotwise, e.g. by a thermal head by charge transfer onto the recording material in accordance with the image
    • G03G15/325—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the charge pattern is formed dotwise, e.g. by a thermal head by charge transfer onto the recording material in accordance with the image using a stylus or a multi-styli array

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  • ABSTRACT Printed matter is recorded on dielectric paper by depositing an array of electrostatic charges on one surface of the paper at a potential level lower than the ionization potential and then raising the potential level of the charges higher than their ionization level according to a selected pattern with stylet-like electrodes.
  • the selected pattern causes a developer to adhere to the dielectric paper in accordance with the pattern, thereby making the pattern visible.
  • the present invention relates to electrostatic printing. More particularly, the present invention relates to methods of and apparatus for arranging electrostatic charges in a selected configuration on a sheet of paper or other dielectric material to be subsequently developed by a liquid or powder developer.
  • the potential difference between the electrodes must be between 400 and 500 volts, and often, depending on the nature of the insulating layer, support and spacing between the stylet and the dielectric sheet, the voltages may range from 600 to 1,000 volts. These high voltages require a good deal of electricity, and make it necessary to take certain precautions to ensure safety. In addition, the practical problems raised by utilizing this particular process are complicated due to the need for rapid switching devices.
  • the prior art suggests placing two additional electrodes on opposite sides of the mobile stylet electrodes. These two electrodes amid voltages having a sign opposite to that of the stylet thereby raise the potential level of the conductive support over which the paper passes.
  • this process it is possible to operate with slightly lower voltages, but obviously this approach is merely remedial and adds to the complexity of the printer.
  • the use of the additional two electrodes still requires using a support for the paper or dielectric material which is a good electrical conductor.
  • Still a further object of the instant invention is to provide new and improved methods of and apparatus for electrostatic printing wherein the dielectric layer which is printed upon may be composed of readily available, inexpensive paper having a conventional, readily available, dielectric surface.
  • the instant invention is directed to methods of and apparatus for electrostatic printing which include the concepts of advancing a strip of dielectric material past a charging station in order to distribute an array of electrostatic charges thereon, and then re-arranging the array of electrostatic charges to correspond to a selected image by advancing the dielectric material past an electrode means maintained at a potential level different from the potential level of the array. The resulting image is then developed by fixing it permanently on the dielectric material.
  • FIG. 2 is a schematic view of a second embodiment of the invention wherein electrostatic charges are placed directly on a strip of dielectric material without first utilizing a belt of insulating material as an intermediary to deposit the charges;
  • FIG. 3 is an enlarged cross-section of the type of paper being printed upon in accordance with the principles of the invention.
  • FIG. '1 there is shown one embodiment of a printer in accordance with the instant invention, wherein negative charges are deposited on a belt 1 1 of insulating material, such as polyester film, by a corona-charging device 12.
  • the belt 11 is trained around three rollers l3, l4 and 15, one of which is driven and all of which are positively engaged by the belt.
  • the belt is driven by the powered roller to travel in the direction of the arrow 16 so as to pass through a printing station, designated generally by the numeral 17.
  • a supply of dielectric paper 18 is dispensed from a supply reel 19 and passes over a roller 21 positioned opposite the roller 13, and a roller 22 positioned opposite the roller 14, so as to travel in a parallel direction with the belt 11 while in the printing station 17.
  • the paper 18 is positively driven by the rollers 21 and 22 at the same linear speed that the belt 11 is driven. This may be accomplished by any convenient means, such as gearing the rollers 21 and 13 together and the rollers 14 and 22 together so that these rollers each rotate at the same speed.
  • the electrostatic charges 10 are transferred in a selected manner so as to record intelligence on the paper 18 by raising the level of potential of the charges to their ionization level according to a selected pattern.
  • the charges so raised will, in effect, transfer to the paper 18 in the selected pattern to record intelligence on the paper in the form of letters, numbers and the like.
  • stylets 24 (only one of which is shown). These stylets are electrodes which are connected by leads 26 to a pole 27 of a low voltage generator 28.
  • the pole 27 is opposite in polarity from the charges 10 deposited by coronacharging device 12. In other words, if the charges 10 are negative, the pole 27 will be positive, and it the charges 10 are positive, then the pole 27 will be negative.
  • the generator 28 has another pole 30 which is grounded through lead 31, and is controlled by signals from a controller 32 impressed over a lead 34. Controller 32 lies outside the scope of the present invention, but may be assumed to be the type that is used to control the prior art electrostatic printers.
  • the stylet 24 Since the stylet 24 has an opposite polarity from the charges 10 due to the pole 27, when the charges 10 located opposite the stylet advance past the stylet, their level of potential is raised. If the potential level of the charges 10 are quite close to their ionization threshold, then the electric field at the tip of the stylet 24 will cause the charges to ionize if the potential level of the stylet, when added to the potential level of the charges, exceeds the ioniza- 4 tion threshold. This phenomenon may be expressed as follows:
  • V V s V no transfer of charge 10 from belt 11 to paper 18.
  • V V V V (results in a transfer of charges 10 from belt 11 to paper 18).
  • stylets 24 may be arranged in any manner which is convenient to cause transfer of the charges 10 from the belt 11 to the paper 18 according to a selected pattern of intelligence.
  • each electrode 24 may be connected to an associated generator by a suitable switching system of a conventional, well-known type. These aspects lie outside the scope of the present invention.
  • the intelligence recorded on the paper 18 is not yet visible.
  • the paper 18 is carried around a conductive roller 36 and passed between the conductive roller and a developing roller 37.
  • the developing roller 37 rotates through a bath 38 of liquid developer which is transferred to the paper 18 and fixed to the paper by a heater 39 before being accumulated on a take-up roll 40.
  • the conductive roller 36 serves to short-circuit the backside of the paper 18 so that charges deposited thereon are removed from the backside before the liquid developer 38 is deposited by the developing roller 37. Although the charges are removed from the backside of the paper 18, they remain on the front side of the paper so that the intelligence recorded on the front side of the paper is not confused by developer which is adhered to the paper due to charges on the back of the paper. Consequently, the background is not darkened, and print on the front of the paper is clearly developed.
  • One of the objects of this invention is to have the stylets 24 operate with a relatively low potential.
  • this potential is on the order of 50V.
  • this potential may be regulated to be as high or low as desired so long as, when added to the potential of the charges 10 on the belt 11, the ionization thresh old of the charges will be exceeded.
  • the paper 18 may be considered a dielectric system in which paper forming an insulating layer 45 is coated with a standard dielectric layer or coating 46 of, for example, butadiene-styrene pigmented with zinc sulfide.
  • the resin may be any other sufficiently dielectric polymer, such as one of the vinyl copolymers, acrylic resins, silicones, cellulose esters, etc.
  • titanium, zinc, tin oxide, silica and/or any other know pigment may be used.
  • the most suitable dielectric paper are those which have volume resistances equal to or in excess of l0 ohms/cm /cm. Since, in this process, the charges are not placed on the paper by passage of current between two electrodes, but rather by injection through the supporting paper or insulating layer 45, the paper 18 does not have to be a good conductor of electricity. Consequently, ordinary paper may be used.
  • the potential level developed at the tip of the stylet 24 is achieved by pulsing the stylet with pulses having a period of to 50 micro seconds at a level, as mentioned previously, of 50V; whereas, in the prior art, the pulses were for a period of a millisecond at a potential level of 600 to 1,000 V.
  • FIG. 2 An additional embodiment of the present invention is shown in FIG. 2 where the use of a belt of insulating material, such as the belt 11 of FIG. 1, is dispensed with.
  • a strip of dielectric paper 18 is advanced from a supply roll 19' around a first roller 21 and a second roller 22.
  • a printing station 17' is disposed between the first roller 21' and the second roller 22.
  • a corona-charging device 12 is positioned in the printing station 17' at a location just opposite the stylet 24'.
  • the corona-charging device 12 deposits charges on the paper 18 while the stylet 24' raises certain of these charges past their ionization level at selected locations across the paper 18 to thereby record intelligence on the paper 18'.
  • the stylet 24' is connected to a pole 27 on a low voltage generator 28 which is opposite in polarity to the polarity of the charges deposited on the paper 18 by the corona-charging device 12'.
  • the low voltage generator 28 is controlled in the same way as the low voltage generator of the FIG. 1 embodiment by using a controller 32. Downstream of the roller 22', a conductive roller 36' and development roller 37' cooperate with a heat-fixing device 39 to form an image on the paper 18' in the same way as done with the embodiment of FIG. 1.
  • the corona-charging device 12' may be placed at the back of the supporting layer of the dielectric paper 18' at a distance ranging from 10 to 100 mm. It has been found that a distance of to mm gives good results, and that it is not necessary to place the corona-charging device 12' exactly opposite the stylet 24.
  • the corona-charging device 12' may be shifted around, provided that no metallic portion thereof comes into contact with the back of the paper 18 in the zone located between the corona-charging device and the stylet 24.
  • the wires of the corona-charging device 12-12 are elevated to a potential of between 1,000 to 15,000 V.
  • a potential ofl ,000 to 6,000 V is used. It is found that potential must be increased as the distance between the corona 12 and the paper support 18 is increased. The value of this potential, of course, must be regulated as a function of this distance between the corona and the paper to produce an electric field which is less than the field necessary to reach the ionization potential, but is as close to the threshold of ionization potential as possible.
  • the voltage that must be applied to the stylet may be reduced to a range of 25 to V.
  • the external field may be created by applying an insulating sheet of a film, such as polyester film, which is uniformly charged to the backside of the dielectric support or paper.
  • This dielectric sheet may be uniformly charged beforehand by a corona-charging device, such as those disclosed.
  • tribo-electricity or, rather, friction-induced electricity.
  • a convenient tribo-electricity generating device which, for example, may be a nylon brush applied against the back of the supporting layer of the paper 18 and rotated at high speed in a direction opposite the advance of the paper 18.
  • Another approach within the spirit of this invention is to raise the value of the field of charges deposited on the dielectric paper to a level sufficient to produce a deposit of charges on the dielectric paper as soon as stylet 24' or 24 is brought close to the opposite surface of the paper.
  • the distance between the stylet and paper may be reduced, in this case, hundreds of millimeters.
  • the level of the field in the paper should be higher than the ionization threshold for the distance considered.
  • An apparatus for electrostatic printing on a strip of material wherein said material includes an insulating support layer with a dielectric layer thereupon, the dielectric layer having an interior surface and an exterior surface, said apparatus comprising:
  • stylet means for creating the charge image, said stylet means being located in said printing station, wherein said stylet means is brought to a predetermined level of potential substantially lower than that of the electrostatic charges and of opposite polarity, but high enough to cause ionization when added to the potential level of said charges to thereby transfer a charge image to the exterior surface of the dielectric layer;
  • the stylet means includes a plurality of electrodes, each of which is selectively pulsed to the predetermined level of potential by a low voltage generator.
  • a process of electrostatic printing on a strip of material wherein said material includes an insulating support layer with a dielectric layer thereupon, the dielectric layer having an interior surface and an exterior surface, comprising the steps of:

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
US452346A 1973-04-03 1974-03-18 Methods of and apparatus for electrostatic printing Expired - Lifetime US3930257A (en)

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FR7311867A FR2224790B1 (OSRAM) 1973-04-03 1973-04-03

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4137537A (en) * 1976-12-13 1979-01-30 Fujitsu Limited Electrostatic transfer process and apparatus for carrying out the same
US4446471A (en) * 1978-12-20 1984-05-01 Ricoh Company, Ltd. Electrostatic recording method and apparatus therefor
US6069641A (en) * 1997-02-27 2000-05-30 Hitachi, Ltd. Ion flow recording apparatus and liquid developing method
US20180033620A1 (en) * 2015-02-26 2018-02-01 Dynamic Solar Systems Ag Room temperature method for the production of electrotechnical thin layers, the use of same, and a thin layer heating system obtained in this manner
US10892160B2 (en) 2015-02-26 2021-01-12 Dynamic Solar Systems Ag Method for producing electrotechnical thin layers at room temperature, and electrotechnical thin layer
US11935976B2 (en) 2015-02-26 2024-03-19 Dynamic Solar Systems Ag Room temperature method for the production of electrotechnical thin layers, and a thin layer sequence obtained following said method

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3023731A (en) * 1957-06-06 1962-03-06 Haloid Co Electrostatic alphanumerical printer with image transfer mechanism
US3626422A (en) * 1969-07-28 1971-12-07 Varian Associates Electrographic-writing head having a preponderance of conductive portions engaging the recording medium
US3778841A (en) * 1972-08-09 1973-12-11 Xerox Corp Induction imaging system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3023731A (en) * 1957-06-06 1962-03-06 Haloid Co Electrostatic alphanumerical printer with image transfer mechanism
US3626422A (en) * 1969-07-28 1971-12-07 Varian Associates Electrographic-writing head having a preponderance of conductive portions engaging the recording medium
US3778841A (en) * 1972-08-09 1973-12-11 Xerox Corp Induction imaging system

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4137537A (en) * 1976-12-13 1979-01-30 Fujitsu Limited Electrostatic transfer process and apparatus for carrying out the same
US4446471A (en) * 1978-12-20 1984-05-01 Ricoh Company, Ltd. Electrostatic recording method and apparatus therefor
US6069641A (en) * 1997-02-27 2000-05-30 Hitachi, Ltd. Ion flow recording apparatus and liquid developing method
US20180033620A1 (en) * 2015-02-26 2018-02-01 Dynamic Solar Systems Ag Room temperature method for the production of electrotechnical thin layers, the use of same, and a thin layer heating system obtained in this manner
US10892160B2 (en) 2015-02-26 2021-01-12 Dynamic Solar Systems Ag Method for producing electrotechnical thin layers at room temperature, and electrotechnical thin layer
US11935976B2 (en) 2015-02-26 2024-03-19 Dynamic Solar Systems Ag Room temperature method for the production of electrotechnical thin layers, and a thin layer sequence obtained following said method

Also Published As

Publication number Publication date
FR2224790B1 (OSRAM) 1977-04-29
FR2224790A1 (OSRAM) 1974-10-31

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