US3354464A - Method of electrostatic printing of multiple copies - Google Patents

Method of electrostatic printing of multiple copies Download PDF

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Publication number
US3354464A
US3354464A US338345A US33834564A US3354464A US 3354464 A US3354464 A US 3354464A US 338345 A US338345 A US 338345A US 33834564 A US33834564 A US 33834564A US 3354464 A US3354464 A US 3354464A
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United States
Prior art keywords
sheets
sheet
sheaf
electrodes
image
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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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US338345A
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English (en)
Inventor
Tsukatani Kenmi
Nagamine Masaaki
Hamada Yuji
Takagi Kiyoshi
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Fujitsu Ltd
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Fujitsu Ltd
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/02—Charge-receiving layers
    • G03G5/0202—Dielectric layers for electrography
    • 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
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/02—Charge-receiving layers
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/10—Bases for charge-receiving or other layers

Definitions

  • FIG. 3 shows schematically and in section a portion of v a different sheet material prepared and used in accordance with the invention
  • FIG. 4 illustrates schematically an electrostatic printing apparatus according to the invention
  • FIG. 4a shows on a larger scale a sheaf of sheets being simultaneously imprinted in the apparatus
  • FIG. 5 is a planar development of type faces embodied in the apparatus of FIG. 4;
  • FIG. 6 shows schematically the arrangement of selector electrodes also forming part of the apparatus shown in FIG. 4.
  • the sheet material that is to receive the imprint consists of dielectric material having an extremely high insulation resistance (specific resistance) such as, for example, polystyrene.
  • the sheet may consist entirely of such material, or the high-resistance material may constitute a thin coating on a base of electrically conductive material.
  • the recording sheet is placed between two electrodes of which one has a front face constituting the type or other pattern to be reproduced. A high voltage is then impressed between the two electrodes to produce an electric field through the recording sheet. While this is being done, the sheet may be at standstill, or it may be advanced relative to the two electrodes, or vice versa.
  • the electric field causes an electric charge to occur at the highly resistive surface of the sheet on an area corresponding to the configuration of the pattern electrode.
  • an electrostatic latent image of the pattern is produced with an electric polarity and charge density depending upon the applied voltage.
  • the sheet is removed from the electrodes and subjected to a developing process which converts the latent electrostatic image to a visible and permanent image. This is done by contacting the sheet surface with powdered dielectric coloring material that electrostatically adheres to the charge areas and thereafter is fixed thereto, for example by a heat treatment if the powder contains thermoplastic constituents. .
  • various methods based upon the above-described principle are known, the applicable developing process for converting the latent image to a permanent printed image being substantially in accordance with those employed in xerography.
  • a recording or reproducing method of this kind serves to produce only one copy at a time, but fails if an attempt is made to pile several sheets upon each other for simultaneously impressing them electrostatically with latent images.
  • This will be understood from the fact that, when a plurality of sheets are placed upon each other and simultaneously subjected to the electrostatic field between the electrodes, a latent image formed by an electrostatic charge will appear on both sides of each sheet (with the exception of the one adjacent to the backing electrode).
  • the two charged images on each sheet have mutually opposed electric polarities and therefore tend to interfere with each other so as to cause partial or substantially complete neutralization. It has been found that when a sheaf of recording sheets, thus simultaneously subjected to an electrostatic printing field, is subsequently divided into individual sheets, the developing process fails to produce clear images due to the above-mentioned electric charge troubles and discharge phenomena.
  • FIG. 1 Shown in FIG. 1 is a pattern electrode 1 and a counter or backing electrode 2. A sheaf of three recording sheets 3 is located between the electrodes. The contact surface of the pattern electrode 1 forms a type face indicating a letter, numeral, code or other pattern to be reproduced on the recording sheets.
  • Each recording sheet was 1 inch wide and 0.5 mil thick, consisting of polyethylene terephthalate.
  • the three individual sheets 31, 3-2, 3-3 were jointly displaceable between the electrodes for repeating the electrostatic operation, but were kept stationary with respect to the electrodes during the interval in which a signal voltage was applied betweeen the pattern electrode 1 and the counter electrode 2.
  • a voltage of 1500 v. was supplied from a source 7 of direct voltage under control by a control device schematically shown at 8.
  • Still another object of our invention in conjunction with those mentioned above, is to permit using electrostatic record sheets which, with respect to appearance and use, are similar to ordinary paper.
  • each individual sheet comprises a paper base which is coated at least on one side with a layer of dielectric recording material.
  • the dielectric recording material has a specific resistance higher than ohm-cm. and a finely distributed surface irregularity or roughness whose roughness depth is between 2 and microns.
  • the back surface of the paper base sheet with a relatively high electric conductance, namely a specific resistance of 10 to 10 ohm-cm.
  • the back surface of the thin dielectric recording sheet is coated with material of relatively good electric conductivity and placed between the electrodes, across which a voltage is impressed, an external electrical field or electrostatic latent image cannot form the back surface of the conducting coating but appears only on the opposite surface.
  • several such sheets, each having the back surface coated with electrically conducting material of 10 to 10 ohm-cm. specific resistance are sandwiched between the electrodes, the applied voltage causes an electric field to extend through the entire sheaf, and after the electrodes are removed, the external electric field due to the electrostatic latent images does not appear on the back surfaces but occurs only on the opposite, dielectric surfaces.
  • the backing layer of 10 to 10 ohm-cm. resistance acts somewhat as a dielectric material, but also approaches the effect of a metal backing with respect to the electrostatic condition.
  • the thickness of the backing layer of electrical conductivity is limited by the definition or clarity desired of the electrostatic latent image in each sheet. That is, it has been found that in practice the conducting backing layer is limited in thickness to a maximum of about 0.05 mm.
  • Sufficient electric conductivity can be provided on one surface by absorption of water by the polar group in a molecule of a surface-activating agent coated on one side of the highly resistant sheet.
  • a surface layer of electric conductivity is provided by water absorption of the polar group generated by such chemical treatment as saponification, performed on one side of the highly resistant sheet consisting of synthetic resin.
  • Electric conductivity is provided by coating an organic semiconductor solution upon the sheet to form a film thereon.
  • Electric surface conductivity is provided by depositing in vacuum a semiconductor substance, such as selenium, or a semiconductor compound upon the highly insulating sheet.
  • a film of high insulation resistance is formed on sheet material previously treated with an antistatic reagent.
  • the base layer in the individual recording sheets is made of ordinary paper which is coated on one side with polystyrene or other suitable dielectric material having the above-mentioned surface roughness of fine distribution in comparison with the images to be recorded.
  • the back of the paper is preferably rendered more conductive, for example by one of the above-mentioned methods, so that it has a specific resistance of 10 to 10 ohm-cm.
  • Each of the individual sheets Zl, 32 and 33 in the sheaf between the pattern electrode 1 and counter electrode 2 of FIG. 1 consists essentially of a base layer b and a recording layer a as schematically shown in FIG. 2.
  • the recording layer a consists of highly insulating material having a specific resistance above 10 ohm-cm, such as polystyrene or the other plastic or plastics mentioned hereinafter.
  • the base layer b consists of paper. After a voltage is applied between the two electrodes, a latent image consisting of an electrostatic charge is produced on each of the three sheets. Thereafter the sheaf is separated, and the individual sheets are developed to produce a visible image in accordance with the above-mentioned known electrophotographic developing process.
  • the recording layer a of high insulating resistance is provided with fine surface irregularities which are uniformly distributed over the entire surface area and have a roughness depth between 2 and 20 microns.
  • the plastic surface coatings with the surface irregularities face the pattern electrode 1.
  • the sheaf comprises sheets of the present invention, of the aforeclescribed type, a clear print is obtained on each individual sheet after developing the latent image.
  • the paper used for the base layer [1 may also have the same irregularities from the outset so that these irregularities appear on the coated surface after the plastic coating is applied to one side-of the paper.
  • the paper used for the sheets may also have a smooth surface obtained by finishing processes such as sizing, filling or calendering, and only the coated thin film of plastic or other high-resistance material may be given the desired surface roughness. It has been found that it is not essential whether or not the back surface of the paper is smooth or uneven, this being of no effect upon the clearness of the electrostatic latent image. It has further been found by experimentation that the finer the distribution of the surface irregularities on the recording side, the better will be the definition of the image, and that the practically applicable depth of the irregularities is in the abovementioned range between 2 and 20 microns.
  • a variation in specific resistance of the paper used as base material does not impair the characteristics of the sheet with respect to the electrical charges, even if the rec-ording-sheets are left exposed to air having a relative humidity of approximately 20% to 75%.
  • it is advisable to further improve the sheets by forming an electrically conductive layer of film, not on the back surface of the paper, but between the base paper 12 and the recording layer a to thus provide an intermediate zone, as shown at c in FIG. 2, whose specific resistance is limited to a value of 'to' 10 ohms.
  • This intermediate layer can be produced for example by any of the above-described methods.
  • the upper limit of thickness for the paper base in practice is about 50 microns.
  • the definition and clearness of the resulting image decreases when the thickness is increased beyond this limit.
  • the charge density of the electrostatic latent image depends upon the intensity of the electric field applied to each recording medium.
  • the paper base I) of the sheet may be coated with a thin film of high-resistance material on only one side as described, or such a thin coating may be provided on both sides of the paper, at least one coated side then possessing the required unevenness or roughness at the surface that is to receive the image.
  • the back surface is rendered more conductive by one of the methods described in the foregoing.
  • the thin coating being of polystyrene, it may also comprise other synthetic plastics known as suitable for such dielectric purposes, for example polyethylene terephthalate, polytetrafiuorethylene or the like.
  • the apparatus comprises a rotary cylindrical electrode 11 which carries on its peripheral surface the code letters or other characters 12 to be transferred to the recording sheets.
  • the code characters 12, arranged as shown in FIG. 5, are formed by raised portions in the same manner as ordinary printing type faces, and the intermediate indented portions of the electrode surface are filled with material of high electric insulation resistance, such as polystyrol, so that the conducting type faces are flush with the cylindrical outer surface of the electrode.
  • the cylindrical electrode with its conductive type faces forms part of an electric circuit of the type shown in FIG. 1. According to FIG. 4, the rotary elec trode 11 and consequently all character units 12 are grounded.
  • the rotary electrode cooperates with a number of stationarily mounted selector electrodes 13 of electrically conductive material arranged as shown in FIG. 6.
  • 14 in FIG. 4 is a sheaf of recording sheets which are separately shown at 14-1, 14-2 and 14-3 in FIG. 4a.
  • Schematically indicated at 15 in FIG. 4 is a high-voltage driver circuit and at 16 a control stage.
  • the typeface electrode 11 rotates at constant speed in the direction indicated by the arrow, and the selector electrodes 13 register within the respective typeface characters on the rotary electrode 11 respectively, being radially spaced therefrom an amount sufficient to conveniently permit the insertion of a sheaf of recording sheets.
  • the selector electrodes are pressed toward the rotary electrode 11 with some amount of pressure for maintaining a good contact with the sheaf 14.
  • the sheaf of sheets is advanced between the electrodes in the downward direction as indicated by another arrow.
  • the control stage 16 actuates the high-voltage circuit 15 to apply a high voltage between the fixed selector electrode and the type-face electrode, for example 1500 v. or more depending upon the number of sheets in the sheaf.
  • a latent image consisting of an electrostatic charge is formed on the slightly rough surface of each recording sheet 14-1, 14-2, 14-3 facing toward the type-face electrode 11.
  • the operation is analogously repeated for different type-face characters and different lines of the recording sheets.
  • the advancing sheaf is separated into individual sheets on which a visible image is fixed by electrophotographic or xerographic development, causing powder material to adhere electrostatically to the latent image and to be subsequently fixed thereto such as by thermal treatment of thermoplastic coloring powder.
  • the electrostatic voltage to be applied between the two electrodes depends upon the number of sheets that form the sheaf, aside from the fact that the optimum voltage also varies with different sheet compositions and thicknesses.
  • Recording sheets used with the above-described apparatus according to FIGS. 4 to 6 were made of base paper 40 microns thick of the type employed for tracing paper and correspondingly having a dull and relatively rough finish. A film of polystyrene was coated on only one side of this paper to produce the recording layer of the desired degree of slight surface irregularity. The opposite, uncoated side of the paper was left in its original surface condition and consequently exhibited the same degree of surface roughness.
  • a voltage of about 2000 volts between the two electrodes was found satisfactory for simultaneously producing latent images on four sheets made of a base paper 38 microns thick, of the type used for carbon tissue paper, and coated with a toluene solution of polystyrene, so as to exhibit at the coated surface the fine irregularities of the paper.
  • the same irregularities caused by the fibers in the paper were permitted to remain on the opposite side.
  • any of the conventional developing methods was found applicable for obtaining a visible clear image on each of the four sheets.
  • the invention can also be used in cases where it is desired to print not only copies on paper but also upon a transparent sheet to be subsequently available for reproduction purposes such as for blueprinting.
  • a transparent recording sheet is incorporated into a sheaf otherwise consisting of paper base sheets of the present invention as described above.
  • Such a transparent sheet may consist of the above-mentioned dielectric synthetics known for electrostatic printing purposes, for example polyethylene terephthalate, polytetrafluorethylene or polystyrene.
  • the method of electric printing by electrostatically producing a latent image on insulating sheet material between backing electrode means and printing-face electrode means and thereafter developing a visible means by applying dielectric coloring substance to the image which comprises simultaneously placing a number of sheets as a sheaf between the two electrodes, each individual sheet comprising a paper base coated on one side with a layer of dielectric recording material of more than 10 ohmcm. specific resistance, said dielectric recording material having finely distributed surface irregularities of a roughness depth between 2 and 20 microns, applying voltage between the electrodes across the thickness of the sheaf whereby a latent electrostatic charge image is formed simultaneously on the coating of each sheet, and then separating the sheaf into individual sheets prior to developing the visible irnages thereon.
  • said sheets consist of a rough-surfaced paper base having on at least one side a synthetic plastic coating to serve as said recording material, said coating exhibiting substantially the surface roughness of said paper base with said roughness depth between 2 and 20 microns.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Photoreceptors In Electrophotography (AREA)
US338345A 1963-01-21 1964-01-17 Method of electrostatic printing of multiple copies Expired - Lifetime US3354464A (en)

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GB (1) GB1057461A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3534383A (en) * 1964-12-14 1970-10-13 Fujitsu Ltd Method of electrostatic recording and electrostatic recording apparatus
US4276829A (en) * 1978-01-31 1981-07-07 Wu Chen Mechano-electrostatic charge-imaging method and apparatus
US4795676A (en) * 1985-12-18 1989-01-03 Oji Paper Co., Ltd. Electrostatic recording material

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3210185A (en) * 1961-03-22 1965-10-05 Rca Corp Simultaneous identical electrostatic image recording on multiple recording elements

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3084061A (en) * 1953-09-23 1963-04-02 Xerox Corp Method for formation of electro-static image

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3210185A (en) * 1961-03-22 1965-10-05 Rca Corp Simultaneous identical electrostatic image recording on multiple recording elements

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3534383A (en) * 1964-12-14 1970-10-13 Fujitsu Ltd Method of electrostatic recording and electrostatic recording apparatus
US4276829A (en) * 1978-01-31 1981-07-07 Wu Chen Mechano-electrostatic charge-imaging method and apparatus
US4795676A (en) * 1985-12-18 1989-01-03 Oji Paper Co., Ltd. Electrostatic recording material

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BE642781A (de) 1964-05-15
DE1259201B (de) 1968-01-18
GB1057461A (en) 1967-02-01

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