US3887927A - Apparatus and process for producing latent electrostatic images - Google Patents

Apparatus and process for producing latent electrostatic images Download PDF

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Publication number
US3887927A
US3887927A US359593A US35959373A US3887927A US 3887927 A US3887927 A US 3887927A US 359593 A US359593 A US 359593A US 35959373 A US35959373 A US 35959373A US 3887927 A US3887927 A US 3887927A
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Prior art keywords
carrier member
original document
process according
dielectric
original
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US359593A
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English (en)
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Garbor Forgo
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Turlabor AG
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Turlabor AG
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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
    • G03G15/225—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 using contact-printing

Definitions

  • ABSTRACT Process and apparatus for producing a latent electrostatic image on a dielectric surface which corresponds to areas on a surface of a master (origi' nal) which are more electrically conductive than other areas on the said surface.
  • the process includes the steps of positioning a dielectric carrier member in contact with a surface of the master (original), provid ing an electrically conductive element on the free sur face of the carrier member, applying an electric field potential between the free surface of the master (original) and the conductive element, and thereafter removing the field potential and separating the master (original) and the carrier.
  • An electrostatic latent image which corresponds to the selected areas on the master (original) is retained on the carrier. Apparatus is disclosed for performing the described process.
  • This invention relates to a process and an apparatus for producing latent images and to the application of this process. More particularly, the invention relates to an electrographic process for producing latent electrostatic charge images and to an apparatus for carrying out this process. The invention also relates in particular to a process for reproducing one-sided originals. The duplicates produced from these originals can also be used as intermediate originals for other reproduction processes. The print obtained can reproduce writing, drawings, printing, etc.
  • Master copies can be reproduced by a number of different processes, for example by the hectography process using alcoholsoluble dyes, the helio process, electrophotographic processes, conventional photocopying processes, transfer copying processes using carbon paper and similar films and also specially prepared papers which are sensitive to pressure.
  • the object of the present invention is to provide a process for producing images which, with the simplest of means, enables any number of copies to be produced from a master (original) without any serious restrictions as to format.
  • Another object of the invention is to provide an apparatus for carrying out this process which is simple in structure and easy to handle.
  • the present invention relates to a process for producing latent electrostatic charge images which is distinguished by the fact that a charge image corresponding to a master (original) is produced on the basis of the differences in conductivity between the printed, written or drawn areas of the master (original) and its blank areas.
  • the invention also relates to an apparatus for carrying out this process which is characterised by a master (original) in contact with a dielectric carrier, an electrical field being associated with at least part of the master (original) and carrier in contact with one another.
  • FIG. I shows the production of a latent charge image in accordance with a first embodiment.
  • FIG. 2 shows the removal of the master (original) from the carrier.
  • FIG. 3 shows the charging of the carrier according to a second embodiment.
  • FIG. 4 shows the production of the charge image according to the second embodiment.
  • FIG. 5 shows the removal of the master (original).
  • FIG. 6 shows the development of the latent charge image.
  • FIG. 7 shows the fixing of the toner image.
  • FIG. 8 shows the charging of the carrier according to a third embodiment.
  • FIG. 9 shows the production of the charge image according to the third embodiment.
  • FIG. 10 shows the removal of the master (original).
  • FIG. 11 shows the production of the charge image according to a fourth embodiment.
  • FIG. I2 shows the production of a charge image according to a fifth embodiment.
  • an electrostatic charge image is initially produced on a carrier with a photoconductive layer, being rendered visible by a subsequent developing process.
  • a photoconductive layer arranged on the carrier is electrically charged in the dark and selectively discharged by exposure according to a pictorial or manuscript original. Exposed areas of the photoconductive layer become low in resistance so that a previously applied electrical charge is discharged, leaving an electrostatic charge image corresponding to the master (original).
  • This electrostatic charge image is subsequently developed by known methods, for example by dry development using a magnetic brush known per se and toner particles.
  • the electrostatic charge image corresponding to the master (original) is produced, according to the invention, by the direct effect of voltage upon the master (original) which rests on a dielectric carrier. Accordingly, there is no need for any lighting arrangement or for a photoconductive layer for producing the charge image used for reproduction.
  • a dielectric carrier for example a piece of writing paper with relatively good insulating properties, lies on a conductive base plate.
  • the paper can be additionally dried under heat, for example before it is used.
  • a master (original) printed on one side only for example is placed with its blank side on this piece of writing paper.
  • the image to be reproduced, either in the form of typescript or printing, is thus situated on that side of the master (original) remote from the dielectric carrier. It can be in the form of, for example, a sheet of paper that has been typed on one side.
  • An electrode for example in the form of a knife edge or roller, is guided over the typed side of the master (original).
  • This electrode is connected to one pole of a high-voltage source whose other pole is connected to the base plate. It has been found that the conductivity of the master (original) is higher where it has been printed or typed than where it is blank.
  • the dielectric carrier i.e. for example to the writing paper underneath the master (original), or by polarisation produced by the field applied, an electrostatic charge image corresponding to the master (original) is formed on the dielectric carrier.
  • the dielectric carrier supporting the latent charge image can be delivered to a conventional developing unit.
  • the charge image thus developed can then be fixed in a subsequent fixing process.
  • the papers coated with a so-called dielectric film of the kind commonly used in electrography, such as for example Kanzaki K-2l M and Varian Statos paper, represent particularly suitable carrier materials.
  • the charge image is produced by the varying exposure to light of the photoconductive layer corresponding to the exposed master (original).
  • the charge image is produced in the absence of exposure, or without optical reproduction of the master (original) on the charge carrier, for example the sheet of paper referred to above. Instead the difference in conductivity between written or printed areas and blank areas of the master (original) is used to produce the charge image.
  • the process according to the invention is thus particularly suitable for one-sided masters (originals) in whose case the printing ink should show adequate conductivity whilst the carrier material of the master (original) should not show excessively high conductivity.
  • the master (original) and the carrier on which the reproduction is formed are in contact with one another during production of the electrostatic charge image. Accordingly, this reproduction process eliminates the need to use optical systems, illuminating systems and photoconductive layers. Accordingly, it represents an extremely economical reproduction process.
  • the masters can consist, for example, of extracts from newspapers, sheets of typescript, sheets of manuscript written in pencil, ink, with ballpoint or felt pens, drawings in Indian ink, etc.
  • An insulating layer on a metal, preferably earthed substrate, can be used as the carrier for the latent electrostatic charge image.
  • the insulating layer can be in the form of for example a thin plastics film, although it is preferably in the form of a dielectrically coated paper with a resistivity of the order of l0 to 10 ohms/cm. Coated papers of this kind are commonly used in electrostatic reproduction apparatus. One of their sides is weakly conductive whilst the other carries a known dielectric layer. It is also possible to arrange a dielectric layer on both sides, so that it is possible to obtain an image on both sides of this carrier material by the process according to the invention. It is also possible to use thin Mylar films, for example 12 to 17 p.
  • the master (original) should preferably have a resistivity of less than 10' ohms/cm in its printed areas.
  • the ratio between the resistivity of the blank areas and the resistivity of the printed areas of the master (original) should be substantially of the order of IO l.
  • the printing ink should show adequate specific conductivity, for example of the order of 10 ohms cm. Suitable printing inks also include pencil graphite, ink for felt pens, newsprint etc.
  • An electrostatic dc. voltage field is applied between the surface of the master (original) and the base plate under the carrier for the electrostatic charge image.
  • This can be done in different ways, for example by means of a high-voltage corona discharge which charges the upper side of the master (original) or by using an electrode in the form of a sliding roller which is connected to a dc. voltage source and which is rolled over the top of the master (original) under light pressure.
  • a blade-like electrode can also be passed over the surface of the master (original).
  • the voltage required for producing the charge image is of the order of about 300 to 400 volts down to the breakdown voltage of the dielectric layer used. Accordingly, the upper limit is substantially in the range from I000 to 2000 volts.
  • the electrical field is best only briefly applied, for example for no longer than about 1 to 2 seconds. However, useful electrostatic charge images can also be obtained with a much shorter application of the electrical field.
  • the original is lifted off its support; this can be done with or without the assistance of a conductive roller connected to a suitable potential, for example the earth potential.
  • the latent electrostatic charge image formed on the dielectric layer can be developed by any of the developing processes known from electrography. Accordingly, it is possible to use either liquid developers or dry developers with subsequent fixing. It is also possible, however, to transfer the electrostatic charge image to a second carrier film by a so-called charge-transfer process.
  • the charged toner particles must have a suitable polarity. This should be opposite to the polarity of the charge applied.
  • the dielectric layer can be charged with opposite polarity either immediately before production of the electrostatic charge image or immediately thereafter, thus preventing the undesirable deposition of toner particles on those areas that are to remain white.
  • the image can be fixed by any of the known processes, for example by applying heat, by means of radiation or by passing a stream of hot air over it, etc.
  • the image produced can also be transferred to papers, textiles, metals or any other suitable substrates.
  • the master original
  • the master original
  • the master original
  • the process described above can be repeated with the same dielectric layer so that it is also possible to obtain overprints with the same colour or in several process stages with different colours of the copy.
  • a dielectric carrier 2 for example in the form of a paper provided with a dielectric film 3, of the kind commonly used in electrography, lies on a conductive base plate I.
  • the master (original) 4 with its image 5 to be reproduced lies on the dielectric carrier 2.
  • FIGS. 1 and 2 have not been drawn to scale, instead the structure of the image has been greatly exaggerated in the interests of clarity.
  • a roller 6 is designed to be guided over the image side of the master (original) 4 in the direction of the arrow 7.
  • the roller 6 either consists wholly of conductive material or at least its cylindrical surface is conductive.
  • An electrical voltage of for example 900 volts is applied through a line 8 to the roller 6 or to its conductive surface, the roller 6 being connected for example to the negative pole 9 of a voltage source (not shown in FIG. 1) whilst the base plate 1 is connected through a line 10 to the positive pole 11 of the voltage source.
  • the base plate 1 is preferably connected to earth as well through the line 10.
  • the arrangement illustrated in FIG. I produces a negative latent charge image corresponding to the image 5 after the roller has travelled over the master (original) 4 on the dielectric carrier 2. If a positive charge image is required, the polarity of the lines 8 and 10 has to be changed. In this way, it is possible to obtain the correct polarity of the charge image, depending upon the polarity of the toner used for development.
  • FIG. 2 diagrammatically illustrates removal of the master (original) 4 from the dielectric carrier 2, for which purpose the two lines 8 and 10 are separated from the voltage source, but connected to one another.
  • the latent charge image corresponding to the image 5 is situated on the dielectric layer 3.
  • the surface of the dielectric carrier 2 (cf. FIG. 3) is positively charged by means of a conventional corona unit 12. This is done for example by moving the corona unit 12 in the direction of the arrow 13. It would of course also be possible to use a stationary corona unit 12, in which case the base plate 1 together with the dielectric carrier 2 would be moved relative to the corona unit. i.e. against the direction of the arrow 13.
  • the master (original) 4 with its image 5 facing upwards is placed on the dielectric carrier 2 and rolled over by the roller 6 in the manner already described with reference to FIG. 1.
  • the roller 6 is connected through the line 8 to the negative pole of a high-voltage source 14 whose positive pole is connected through the line I0 to the base plate 1 and to earth.
  • the master (original) 4 is removed similarly to FIG. 2, the roller 6 being conductively connected to earth through the line 8.
  • FIG. 6 diagrammatically illustrates the development of the charge image produced on the dielectric carrier by means of a magnetic brush 15 which is moved over the dielectric carrier 2 in the direction of the arrow 16.
  • FIG. 7 diagrammatically illustrates the fixing of the toner image by means of a heat-radiation source 17 which is moved over the dielectric carrier 2 in the direction of the arrow 18.
  • the surface of the dielectric carrier 2 is initially positively charged by means of the corona unit 12.
  • the master (original) 4 is initially placed with its image 5 facing upwards on the dielectric carrier 2.
  • a negative corona unit 19 is then moved over the master (original) 4 in the direction of the arrow 20. Due to the electrical field produced in this case by the corona unit 19 rather than by a roller 6, a latent charge image corresponding to the image 5 is again produced on the surface of the dielectric carrier 2.
  • the master (original) 4 is removed in the manner already described with a roller 6 connected to earth.
  • a master (original) 4 wrapped around a roller 6 is rolled over a dielectric carrier 2 charged in accordance with FIG. 3.
  • the roller 6 is connected through the line 8 to one pole of the voltage source 14 whose other pole is connected to the base plate 1 and, preferably, to earth as well.
  • the electrical field between the roller 6 and the base plate 1 is used to produce a latent charge image from that part of the master (original) 4 in contact with the dielectric carrier Development and fixing are again carried out for example as already described with reference to FIGS. 6 and 7.
  • the master (original) 4 is placed on a dielectric carrier 2 charged in accordance with FIG. 3 and covered on its image side by a counter-electrode 21.
  • the counterelectrode 21 is connected through a line 22 to an output terminal of a dc. voltage impulse source 23 whose other terminal is connected to the base plate I and, preferably to earth.
  • One or several short impulses of, for example, O.l to 1 second in duration are sufficient to produce a latent charge image corresponding to the image 5 of the master (original) 4 on the dielectric carrier 2.
  • the charge image is mirror-inverted in relation to the master. This can be desirable for example in cases where an intermediate original" is to be produced from the charge image for further copying processes.
  • the charge image produced in accordance with any of the embodiments described above or modifications thereof can either be developed on the carrier 2 itself by a known method, for example dry by means of a magnetic brush containing toner material or wet by a process known from electrography and optionally fixed, or alternatively it can be transferred in a charge image transfer process to another carrier and then developed and fixed.
  • the carrier 2 is of a suitable form, the toner image developed on the carrier 2 can also be transferred to another carrier in known manner by an image-transfer process and then fixed.
  • the electrical field required to carry the charge through the master (original) or to produce polarisation can be produced by a flat, arcuate, cylindrical, prismatic, stationary or moved electrode connected to different potentials.
  • the carrier and master (original) can also pass on top of one another for example between two conductive rollers which represent the two electrodes, in such a way that that part of the master (original) and carrier momentarily situated between the two rollers is always exposed to the electrical field.
  • the aforementioned electrical field can also by produced by charging the surfaces of the dielectric carrier or by corona effect on the master (original).
  • the varying conductivity of the master (original) referred to above can relate both to differences in surface conductivity and also to differences in volume conduc tivity or to both.
  • a one-step process for producing in the absence of intermediate masters a latent electrostatic charge image corresponding to selected areas on one of two surfaces of an uncoated original document having non-electrostatically produced indicia on said one surface thereof, said selected areas on said document being more conductive than other areas. comprising the steps of positioning a dielectric carrier member in contact with the other of the two surfaces of said original document, providing an electrically conductive element on the free surface of said carrier member, applying an electric field potential above at least 200 volts between the free surface of said original document and said conductive element, thereafter removing said field potential and separating said original document and said carrier member whereby a latent electrostatic image is retained on said carrier member.
  • said electrically conductive element is a first plate electrode, and including the step of positioning a second plate electrode in contact with the surface of the original document opposite its surface in contact with said dielectric carrier member, and wherein said electric field potential comprises at least one pulse and is applied between said first and second plate electrodes.
  • said separating step includes withdrawing the original document from the carrier member by maintaining at least a portion of the original document in contact with a conductive cylindrical electrode and moving said conductive cylindrical electrode relative to said dielectric carrier member while said conductive cylindrical electrode is maintained at at least substantially the same potential as said electrically conductive element.
  • said dielectric carrier member comprises paper having a dielectric coating on at least one surface thereof.
  • the process according to claim 1 further including the step of charging the dielectric carrier member with a corona discharge of a first polarity prior to positioning said dielectric carrier member in contact with said original document and applying said electric field potential between the free surface of said original document and conductive element by applying to said free surface of the original document a corona discharge of a polarity opposite to said first polarity to produce a latent electrostatic image on said carrier member.
  • the process according to claim 13 further including the step of: charging said carrier member prior to positioning said carrier member in contact with said original document.
  • said charging step comprises placing a charge on said carrier member of the opposite polarity to the polarity of the latent electrostatic image retained on said carrier member.
  • Apparatus for producing a latent electrostatic image corresponding to selected areas on one of two surfaces of an original document having non-electrostatically produced indicia being more electrically conductive than other areas thereon comprising means for contacting a dielectric carrier member with the other of the two surfaces of said original document, an electrically conductive element in contact with the free surface of said carrier member, means for applying an electric field potential between the free surface of said original document and said conductive element to produce a latent electrostatic image on said carrier member corresponding to the differences in conductivity between said selected and other areas on said one surface of the original document and means for separating said original document and carrier member whereby said latent electrostatic image is retained on said carrier member.
  • Apparatus according to claim 28 further comprising corona discharge means for charging at least one surface of said carrier member by conona discharge.
  • Apparatus according to claim 29 further comprising second corona discharge means for applying charges of a polarity opposite to the polarity of the charges produced by said first corona discharge means to the free surface of said original document while said original document is in contact with said dielectric carrier member.
  • Apparatus according to claim 28 wherein a second electrically conductive element is disposed in contact with said free surface of said carrier member, and said means for applying an electric field potential is arranged to apply said potential between said conductive elements.
  • Apparatus according to claim 31 wherein at least one of said electrically conductive elements is movable with respect to the other element.
  • Electrodes are at least temporarily connectable to said means for applying an electric field potential whereby different potentials are applicable thereto.
US359593A 1972-05-23 1973-05-11 Apparatus and process for producing latent electrostatic images Expired - Lifetime US3887927A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH758872A CH545494A (de) 1972-05-23 1972-05-23 Verfahren und Vorrichtung zur Erzeugung eines latenten elektrostatischen Ladungsbildes und Anwendung des Verfahrens

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US3887927A true US3887927A (en) 1975-06-03

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US (1) US3887927A (de)
JP (1) JPS4943641A (de)
CA (1) CA1016989A (de)
CH (1) CH545494A (de)
DE (1) DE2317444C3 (de)
GB (1) GB1428817A (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0125081A1 (de) * 1983-04-28 1984-11-14 Xerox Corporation Verfahren und Vorrichtung zur Tonerübertragung

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1048590A (en) * 1974-10-25 1979-02-13 Oscar G. Hauser Electrostatographic method and apparatus

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2912586A (en) * 1957-11-01 1959-11-10 Haloid Xerox Inc Xerographic charging
US3194674A (en) * 1961-05-24 1965-07-13 Burroughs Corp Apparatus and method for duplicating messages which are electrostatically charged, developed and fixed on a master dielectric medium onto copy media capable of retainingelectrostatic charges
US3585061A (en) * 1968-07-29 1971-06-15 Eastman Kodak Co Electrostatic process for reproducing an image formed by discontinuous raised areas
US3703376A (en) * 1968-01-11 1972-11-21 Xerox Corp Induction imaging system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2912586A (en) * 1957-11-01 1959-11-10 Haloid Xerox Inc Xerographic charging
US3194674A (en) * 1961-05-24 1965-07-13 Burroughs Corp Apparatus and method for duplicating messages which are electrostatically charged, developed and fixed on a master dielectric medium onto copy media capable of retainingelectrostatic charges
US3703376A (en) * 1968-01-11 1972-11-21 Xerox Corp Induction imaging system
US3585061A (en) * 1968-07-29 1971-06-15 Eastman Kodak Co Electrostatic process for reproducing an image formed by discontinuous raised areas

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0125081A1 (de) * 1983-04-28 1984-11-14 Xerox Corporation Verfahren und Vorrichtung zur Tonerübertragung

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DE2317444B2 (de) 1977-10-06
GB1428817A (en) 1976-03-17
CH545494A (de) 1973-12-15
CA1016989A (en) 1977-09-06
JPS4943641A (de) 1974-04-24
DE2317444A1 (de) 1973-11-29
DE2317444C3 (de) 1978-05-24

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