EP1128232A1 - Dispositif d'impression électrostatique directe dans lequel la couche de particules de toner chargé présente sur la surface de support de toner est homogénéisée - Google Patents

Dispositif d'impression électrostatique directe dans lequel la couche de particules de toner chargé présente sur la surface de support de toner est homogénéisée Download PDF

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Publication number
EP1128232A1
EP1128232A1 EP00200631A EP00200631A EP1128232A1 EP 1128232 A1 EP1128232 A1 EP 1128232A1 EP 00200631 A EP00200631 A EP 00200631A EP 00200631 A EP00200631 A EP 00200631A EP 1128232 A1 EP1128232 A1 EP 1128232A1
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EP
European Patent Office
Prior art keywords
bearing surface
toner
toner bearing
conductive element
coupled
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.)
Withdrawn
Application number
EP00200631A
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German (de)
English (en)
Inventor
Desie Guido
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Agfa Gevaert NV
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Agfa Gevaert NV
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Agfa Gevaert NV filed Critical Agfa Gevaert NV
Priority to EP00200631A priority Critical patent/EP1128232A1/fr
Publication of EP1128232A1 publication Critical patent/EP1128232A1/fr
Withdrawn legal-status Critical Current

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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
    • G03G15/34—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 powder image is formed directly on the recording material, e.g. by using a liquid toner
    • G03G15/344—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 powder image is formed directly on the recording material, e.g. by using a liquid toner by selectively transferring the powder to the recording medium, e.g. by using a LED array
    • G03G15/346—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 powder image is formed directly on the recording material, e.g. by using a liquid toner by selectively transferring the powder to the recording medium, e.g. by using a LED array by modulating the powder through holes or a slit
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2217/00—Details of electrographic processes using patterns other than charge patterns
    • G03G2217/0008—Process where toner image is produced by controlling which part of the toner should move to the image- carrying member
    • G03G2217/0025—Process where toner image is produced by controlling which part of the toner should move to the image- carrying member where the toner starts moving from behind the electrode array, e.g. a mask of holes

Definitions

  • This invention relates to a method and an apparatus used in the process of electrostatic printing and more particularly in Direct Electrostatic Printing (DEP).
  • DEP Direct Electrostatic Printing
  • electrostatic printing on an image receiving substrate is performed by creating a flow of toner particles from a toner bearing surface to the image receiving substrate and image-wise modulating the flow of toner particles by means of an electronically addressable printhead structure.
  • the toner or developing material is deposited directly in an image-wise way on a receiving substrate, the latter not bearing any image-wise latent electrostatic image.
  • the substrate can be an intermediate endless flexible belt (e.g. aluminium, polyimide etc.).
  • the image-wise deposited toner must be transferred onto another final substrate.
  • the toner is deposited directly on the final receiving substrate, thus offering a possibility to create directly the image on the final receiving substrate, e.g. plain paper, transparency, etc.
  • This deposition step is followed by a final fusing step.
  • the method makes the method different from classical electrography, in which a latent electrostatic image on a charge retentive surface is developed by a suitable material to make the latent image visible. Further on, either the powder image is fused directly to said charge retentive surface, which then results in a direct electrographic print, or the powder image is subsequently transferred to the final substrate and then fused to that medium. The latter process results in an indirect electrographic print.
  • the final substrate may be a transparent medium, opaque polymeric film, paper, etc.
  • DEP is also markedly different from electrophotography in which an additional step and additional member is introduced to create the latent electrostatic image. More specifically, a photoconductor is used and a charging/exposure cycle is necessary.
  • a DEP device is disclosed in e.g. US-A-3 689 935 This document discloses an electrostatic line printer having a multi-layered particle modulator or printhead structure comprising :
  • Each control electrode is formed around one aperture and is isolated from each other control electrode.
  • Selected electric potentials are applied to each of the control electrodes while a fixed potential is applied to the shield electrode.
  • An overall applied propulsion field between a toner delivery means and a support for a toner receiving substrate projects charged toner particles through a row of apertures of the printhead structure.
  • the intensity of the particle stream is modulated according to the pattern of potentials applied to the control electrodes.
  • the modulated stream of charged particles impinges upon a receiving substrate, interposed in the modulated particle stream.
  • the receiving substrate is transported in a direction orthogonal to the printhead structure, to provide a line-by-line scan printing.
  • the shield electrode may face the toner delivery means and the control electrodes may face the receiving substrate.
  • a DC-field is applied between the printhead structure and a single back electrode on the receiving substrate. This propulsion field is responsible for the attraction of toner to the receiving substrate that is placed between the printhead structure and the back electrode.
  • banding visible as density fluctuations in parts of the printed image intended to show even density
  • white stripes absence of density
  • a DEP device i.e. a device for direct electrostatic printing that can print at high speed, high maximum density, a high degree of density resolution (i.e. for producing an image comprising a high amount of differentiated density levels) and high spatial resolution without banding and/or white stripes in the print direction.
  • a device for direct electrostatic printing comprising :
  • Fig. 1 shows schematically a "development zone" in a DEP-device.
  • Fig 2. shows schematically a first embodiment of a DEP-device, according to this invention, including a conductive element upstream the "development zone".
  • Fig 3 shows schematically a second embodiment of a DEP-device, according to this invention, including a conductive element upstream the "development zone".
  • Fig 4 shows a schematic exploded view of a third embodiment of a DEP-device, according to this invention, including a conductive element upstream the "development zone".
  • the "development zone” is the volume between the printhead structure (103) and the toner bearing surface (101), under the row(s) of printing apertures.
  • a non-limitative example of a development zone is given.
  • the array of printing apertures (105) has an extension in the printing direction, C and an extension perpendicular to the printing direction, defining the printing width, PW, of the device.
  • the plane A,A',A'' in figure 1 shows the plane in which the cross-sections of figure 2 and 3 are made.
  • the conductive element (102) used in a DEP device according to this invention can be made of any conductive material. It may be made of metal, e.g., stainless steel, copper, nickel, etc., it may be made of metal alloys, it may be a non-conductive material whereon a conductive layer is present, e.g., it may be a plastic sheets carrying a conductive layer, which conductive layer can be made, e.g., of metal, metal alloys, metal oxides and conductive organic polymers.
  • the conductive element (102) used in a DEP device according to this invention can be made as a single sheet of conductive material so that it forms one electrode extending over de printing width of the device and that the toner particles are made to oscillate between the toner bearing surface and the conductive member in a direction essentially perpendicular to the toner bearing surface.
  • the conductive element may also be construed as ,e.g., two sets of electrodes isolated from each other extending over the printing width and the AC-voltage source is then coupled to each of the sets in turn.
  • the sets of electrodes on the conductive member (102) are preferably construed as combs with the teeth of one comb being interposed between, but isolated from the teeth of the second comb.
  • a DEP-device incorporating a conductive member for homogenising the layer or stack of layers of toner particles on the toner bearing surface is shown. It comprises a charged toner bearing surface (101), carrying charged toner particles (106) and coupled to a DC-voltage source, DC1 (which may be earth potential). The toner bearing surface is further equipped to be moved in the direction of arrow A. Opposite to the toner bearing surface (101), a back electrode (108) is placed, this back electrode is coupled to a DC-voltage source, DC4.
  • the DC-voltage applied to the back electrode is different from the one applied to the toner bearing surface and so a DC-propulsion filed is created wherein the charged toner particles can move, as a flow of toner particles, from the toner bearing surface to the back electrode.
  • a printhead structure (103) is interposed, having an array of printing apertures (105) that are associated with control electrodes (104) coupled to a DC-voltage source, VS3, that is image-wise varied for selectively opening and closing said printing apertures.
  • An image receiving member (109) is passed between the printhead structure and the back electrode.
  • the toner particles (106) on said surface (101) are, due to the movement of the toner bearing surface, passed under a conductive element, E, (102), placed at a distance, d, from the toner bearing surface and coupled to an AC-voltage source AC2 so that an AC-field exist between said element, E, and the toner bearing surface (101).
  • the toner particles (106) are kind of shuffled and seemingly more evenly distributed.
  • E, (102) After passing that element, E, (102) the toner particles that have been redistributed settle again on the toner bearing surface and are transported in the development zone (107),from where the toner particles are moved to back electrode (and thus to the image receiving member) through the printing apertures that are opened and closed in accordance with image data.
  • the conductive element (102) extends at least over the printing width, PW, defined by the extension of the array of printing apertures perpendicular to the print direction.
  • the DEP-device as shown in figure 2 operates without the presence of an AC-field in the "development zone", making the charged toner particles oscillate between the toner bearing surface and the printhead structure.
  • DEP-devices operating with an AC-field in the "development zone” have been disclosed, e.g., in US-A-4 491 855. It was showed now during experimentation, surprisingly, that banding was not avoided by having an AC-field in the "development zone", making the charged toner particles oscillate between the toner bearing surface and the printhead structure as in US-A-4 491 855, but that banding could be avoided by having the AC-field upstream of the "development zone".
  • the conductive element, E, (102) is showed as being flat, while the toner bearing surface is curved.
  • this embodiment does greatly diminish the banding, it was found that the influence of the AC-field created between said conductive member and the toner bearing surface was enhanced when the conductive member followed the shape of the toner bearing surface.
  • Such a DEP device which is a preferred embodiment of this invention, is shown in figure 3, for a curved toner bearing surface. It comprises a charged toner bearing surface (101), having a curvature defined by radius R1, carrying charged toner particles (106) and coupled to a DC-voltage source, DC1 (which may be earth potential) and to an AC-voltage source, AC1, for creating an AC-field in the development zone.
  • the toner bearing surface is further equipped to be moved in the direction of arrow A.
  • a back electrode (108) is placed, this back electrode is coupled to a DC-voltage source, DC4.
  • the DC-voltage applied to the back electrode is different from the one applied to the toner bearing surface and so a DC-propulsion field is created wherein the charged toner particles can move, as a flow of toner particles, from the toner bearing surface to the back electrode.
  • a printhead structure (103) is interposed, having an array of printing apertures (105) that are associated with control electrodes (104) coupled to a voltage source, VS3, that is image-wise varied for selectively opening and closing said printing apertures.
  • the voltage source VS3 can be a DC-voltage source or it can be an AC-voltage source as disclosed in, e.g., EP-A-911 706, or it can be arranged for applying a DC-biased, AC-voltage to the control electrodes.
  • An image receiving member (109) is passed between the printhead structure and the back electrode.
  • the toner particles (106) on said surface (101) are, due to the movement of the toner bearing surface in the direction of arrow A, passed under a conductive element, E, (102) that is coupled to an AC-voltage source AC2 so that an AC-field exist between said element, E, and the toner bearing surface (101).
  • the element, E, (102) is a bow of a circle, that is concentric with the circle defining the curvature of the toner bearing surface.
  • the radius, R2, the circle defining the bow of the conductive element (102) is larger than radius Rl defining the curvature of the toner bearing surface, i.e. R2 - R1 define the gap, d, between the conductive element and the toner bearing surface.
  • the toner particles settle again on the toner bearing surface and are transported in the development zone (107),from where the toner particles are moved to back electrode (and thus to the image receiving member) through the printing apertures that are opened and closed in accordance with image data.
  • the curved conductive element is constructed so as not to have points that might influence the uniformity of the AC-field, therefore in figure 3 the ends of the conductive element (102a) are flattened.
  • FIG 4 a schematic exploded view of a very preferred embodiment of the invention is shown.
  • the toner bearing surface is further equipped to be moved in the direction of arrow A.
  • a conductive element (102) Near that surface a conductive element (102), following the curvature of the toner bearing surface is shown.
  • the conductive element (102) is not a continuous conductive layer, but comprises two sets (102b) of electrodes constructed as combs with the teeth of one comb being interposed between, but isolated from the teeth of the second comb and extending at least over the printing width, PW.
  • the AC-voltage source AC2
  • AC2 is consecutively coupled to each of the sets of the conductive element.
  • the AC-field between the conductive element and the toner bearing surface also changes in a direction parallel to the printing direction (or to the toner bearing surface), so that the toner particles do not only oscillate from the toner bearing surface to the conductive element, but oscillate also parallel to the toner bearing surface. This brings about a very thorough shuffling of the toner particles in two dimensions, thus homogenising that layer almost completely.
  • the AC-voltage source coupled to the conductive element, E is preferably arranged to provide an AC-voltage with peak to peak voltage between 100 and 1500 and a frequency between 1 kHz and 7 kHz, with the gap, d, between said conductive element and said toner bearing surface having a value between 50 and 150 ⁇ m., more preferably said AC-voltage has a peak to peak value between 500 and 1000 V, and a frequency between 2 and 4 kHz.
  • the conductive element, 102 is not a continuous conductive layer, but comprise at least two sets of electrodes (102b), it is preferred that the consecutive coupling of the AC-voltage to the separate sets, proceeds with a speed so that during one line time, the field AC2 switches at least 1 time between the one set and the other of the electrodes (102b), for very good shuffling of the toner particles it is preferred that the field AC2 switches at least 5 times between the even and the uneven electrodes (102b). If the distance between said conductive element, E, and said toner bearing surface, 101, is kept low, i.e.
  • a conductive element as described in this invention can be added to any DEP device known in the art. It can, e.g., with the same beneficial effect be added in a DEP device wherein the toner bearing surface bringing charged toner particles to the development zone is the surface of the exit roller of a cassette with non-magnetic mono-component developer.
  • the Charged Toner Conveyor can be in the form of a belt or in the form of a cylinder.
  • DEP devices as disclosed in, e.g., EP-A-911 706 and in European Application 99203305, filed on October 8, 1999, wherein the control electrodes are coupled to an AC-voltage source to a open and close the printing apertures they control, a conductive element as per this invention can be beneficially included.
  • Typical surface coatings which are well known to those skilled in the art of carrier design, can be applied to the surface of said conductive element, so that not only a shuffling action is imposed upon said charged toner particles, but also additional charging and/or charge limitation is regulated by means of additional frictional contacts between said charged toner particles and said electrode member.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
EP00200631A 2000-02-23 2000-02-23 Dispositif d'impression électrostatique directe dans lequel la couche de particules de toner chargé présente sur la surface de support de toner est homogénéisée Withdrawn EP1128232A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP00200631A EP1128232A1 (fr) 2000-02-23 2000-02-23 Dispositif d'impression électrostatique directe dans lequel la couche de particules de toner chargé présente sur la surface de support de toner est homogénéisée

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP00200631A EP1128232A1 (fr) 2000-02-23 2000-02-23 Dispositif d'impression électrostatique directe dans lequel la couche de particules de toner chargé présente sur la surface de support de toner est homogénéisée

Publications (1)

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EP1128232A1 true EP1128232A1 (fr) 2001-08-29

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EP00200631A Withdrawn EP1128232A1 (fr) 2000-02-23 2000-02-23 Dispositif d'impression électrostatique directe dans lequel la couche de particules de toner chargé présente sur la surface de support de toner est homogénéisée

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61138268A (ja) * 1984-12-11 1986-06-25 Olympus Optical Co Ltd 現像装置
US4743926A (en) * 1986-12-29 1988-05-10 Xerox Corporation Direct electrostatic printing apparatus and toner/developer delivery system therefor
US5541716A (en) * 1995-06-26 1996-07-30 Schmidlin; Fred W. Electrostatic toner conditioning and transport system
EP0911706A1 (fr) * 1997-10-20 1999-04-28 Agfa-Gevaert N.V. Dispositif d'impression électrostatique directe avec une structure d'une tête d'impression conventionelle et un circuit de couplage AC à l'électrode de commande

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61138268A (ja) * 1984-12-11 1986-06-25 Olympus Optical Co Ltd 現像装置
US4743926A (en) * 1986-12-29 1988-05-10 Xerox Corporation Direct electrostatic printing apparatus and toner/developer delivery system therefor
US5541716A (en) * 1995-06-26 1996-07-30 Schmidlin; Fred W. Electrostatic toner conditioning and transport system
EP0911706A1 (fr) * 1997-10-20 1999-04-28 Agfa-Gevaert N.V. Dispositif d'impression électrostatique directe avec une structure d'une tête d'impression conventionelle et un circuit de couplage AC à l'électrode de commande

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 010, no. 334 (P - 515) 13 November 1986 (1986-11-13) *

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