EP0849645A1 - Appareil d'impression pour imprimer à grand format utilsant un appareil d'impression électrostatique direct - Google Patents

Appareil d'impression pour imprimer à grand format utilsant un appareil d'impression électrostatique direct Download PDF

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Publication number
EP0849645A1
EP0849645A1 EP97203821A EP97203821A EP0849645A1 EP 0849645 A1 EP0849645 A1 EP 0849645A1 EP 97203821 A EP97203821 A EP 97203821A EP 97203821 A EP97203821 A EP 97203821A EP 0849645 A1 EP0849645 A1 EP 0849645A1
Authority
EP
European Patent Office
Prior art keywords
toner
printing
width
substrate
delivery means
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Withdrawn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
EP97203821A
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German (de)
English (en)
Inventor
Guido Desie
Jacques Leonard
Hilbrand Van Den Wijngaert
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Agfa Gevaert NV
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Agfa Gevaert NV
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Filing date
Publication date
Application filed by Agfa Gevaert NV filed Critical Agfa Gevaert NV
Priority to EP97203821A priority Critical patent/EP0849645A1/fr
Publication of EP0849645A1 publication Critical patent/EP0849645A1/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Withdrawn legal-status Critical Current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
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0806—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller
    • 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
    • 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
    • G03G15/65—Apparatus which relate to the handling of copy material
    • G03G15/6588—Apparatus which relate to the handling of copy material characterised by the copy material, e.g. postcards, large copies, multi-layered materials, coloured sheet material
    • G03G15/6594—Apparatus which relate to the handling of copy material characterised by the copy material, e.g. postcards, large copies, multi-layered materials, coloured sheet material characterised by the format or the thickness, e.g. endless forms
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/00362—Apparatus for electrophotographic processes relating to the copy medium handling
    • G03G2215/00443—Copy medium
    • G03G2215/00451—Paper
    • G03G2215/00464—Non-standard format
    • G03G2215/00468—Large sized, e.g. technical plans
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/06—Developing structures, details
    • G03G2215/0634—Developing device
    • G03G2215/0636—Specific type of dry developer device
    • G03G2215/0648—Two or more donor members
    • 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 printing apparatus for large format printing with electrostatic printing means and more particularly with Direct Electrostatic Printing (DEP) printing means.
  • DEP Direct Electrostatic Printing
  • electrostatic printing is performed directly from a toner delivery means on a receiving member substrate 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 is an intermediate endless flexible belt (e.g. aluminium, polyimide etc.)
  • the image-wise deposited toner must be transferred onto another final substrate. If, however, the toner is deposited directly on the final receiving substrate, a possibility is fulfilled 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.
  • Direct electrostatic printing is also quite different from ionography where an electrostatic latent image is formed on a charge retentive surface either by image-wise applying charges (ions) on that surface, or by image-wise neutralising charges on a uniformly charged charge retentive surface by image-wise discharging the surface by applying charges of different polarity (ions of different polarity).
  • This latent image is then, as in classical electrophotography, developed by charged toner particles.
  • a DEP device is disclosed in, e.g., US 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 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 receiving member support 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 member substrate, interposed in the modulated particle stream.
  • the receiving member substrate is transported in a direction perpendicular to the printhead structure, to provide a line-by-line scan printing.
  • the shield electrode may face the toner delivery means and the control electrode may face the receiving member substrate.
  • a DC field is applied between the printhead structure and a single back electrode on the receiving member support.
  • the propulsion field is responsible for the attraction of toner to the receiving member substrate that is placed between the printhead structure and the back electrode.
  • the printing device as described in US 3,689,935 is very sensitive to changes in distances from the toner application module towards said shield electrode, leading to changes in image density. For that reason it is very difficult to construct a printer for large format printouts.
  • Multi-applicator module printing systems have been disclosed, but only with the construction of different application modules perpendicular in the printing direction, leading to the possibility of obtaining a single pass multi-colour printer.
  • Such descriptions have been given in e.g. US 5,132,708, US 5,283,594 and US 5,477,250.
  • DEP Direct Electrostatic Printing
  • DEP Direct Electrostatic Printing
  • a printer with printing width PW, for printing a toner image on a substrate, said substrate having a width, WS, and a length, LS, comprising a DEP printing engine, having
  • Fig. 1 is a schematic perspective view of a possible configuration of a printer according to a first specific embodiment of the present invention.
  • Fig. 2 is a schematic lateral view of a possible configuration of a printer according to a first specific embodiment of the present invention.
  • Fig. 3 shows the projection in the plane of the image receiving substrate of the toner applicator means, in an other possible configuration of a printer according to a first specific embodiment of the present invention.
  • Fig. 4 is a schematic illustration of a possible configuration of a printer according to a second specific embodiment the present invention.
  • Fig. 5 is a schematic lateral view of a possible configuration of a printer according to a second specific embodiment of the present invention.
  • toner delivery means is used to designate those parts of a DEP printing engine comprising a surface carrying developer with charged toner particles and that is used for creating, in an electric field, a cloud or flow of charged toner particles from the surface carrying the developer in the direction of an image receiving substrate.
  • this flow originates from a layer of charged toner particles present on the surface of a charged toner conveyor " then this charged toner conveyer " is the toner delivery means "
  • this flow originates directly from a magnetic brush, then the magnetic brush is the toner delivery means " .
  • a printhead structure, with printing apertures is interposed for image-wise modulating said flow of toner particles.
  • toner applicator module is used for the module, comprised in a toner delivery means, that brings charged toner particles to an intermediate member with a surface, comprised in the same toner delivery means, from which a cloud of charged toner particles is generated, i.e. a toner applicator module is a part of the toner delivery means.
  • the toner delivery means comprises a charged toner conveyor (CTC), from the surface of which a cloud of charged toner particles is generated, said charged toner particles are brought to the CTC by a “toner applicator module”, e.g., a magnetic brush.
  • CTC charged toner conveyor
  • staggered configuration with respect the large substrate means that the toner delivery means or the toner applicator modules with a width (WTD) smaller than the printing width (PW) are spread over the printing width, essentially parallel with that printing width, so that an image can be printed over the total printing width and that not all the toner delivery means or toner applicator modules are located on a single line.
  • WTD width
  • PW printing width
  • the wording substrate " or image receiving element” can in this document mean a final image receiving element whereon the toner image is printed, as well as an intermediate image receiving member " used to accept a toner image and to transfer that image to a final image receiving member.
  • the width of the image receiving substrate (WS) is the dimension of that substrate that is essentially perpendicular to the direction of movement of the substrate in the printer.
  • the length of the image receiving substrate (WL) is the dimension of that substrate that is essentially parallel to the direction of movement of the substrate in the printer.
  • a large format printer (large means in this document a surface of at least 0.25 m 2 and an image width of at least 30 cm), using a DEP engine device and method, could be produced by using in said DEP engine either at least two, preferably at least three, toner applicator modules or at least two, preferably at least three, toner delivery means, which were staggered with respect to the large substrate.
  • the advantage of a staggered configuration of the toner applicator modules or the toner delivery means over the total width of a large substrate to be printed lays mainly in the printing speed, which can be made higher and in the possibility to have a rigidly positioned, well outlined printing engine.
  • a printer according to the present invention wherein at least two toner applicator modules or at least two toner delivery means are present can be constructed in such a way that any printing width, from 10 cm up to more than, e.g., 5 meter, can be realised. It is however preferred that the printing width (PW) of a printer according to the present invention is at least 40 cm, more preferably at least 60 cm and more preferably 120 cm.
  • a printhead structure having a width equal to or larger than the printing width (PW) is used in combination with a charged toner conveyor (CTC), also having a width equal to or larger than the printing width (PW).
  • CTC charged toner conveyor
  • To the surface of this CTC charged toner particles are applied from different staggered toner applicator means.
  • FIG 1 a schematic perspective view of a possible configuration of a large format printer to this first specific embodiment of this invention is shown.
  • the printer uses a DEP printing engine comprising a toner delivery means (100) wherein three toner applicator modules (103a, b and c) in a staggered configuration deliver charged toner particles to the surface of a single CTC (104), having a width equal to or larger than the printing width (PW).
  • a DEP printing engine comprising a toner delivery means (100) wherein three toner applicator modules (103a, b and c) in a staggered configuration deliver charged toner particles to the surface of a single CTC (104), having a width equal to or larger than the printing width (PW).
  • PW printing width
  • the arrow A shows the direction of movement of the substrate.
  • the toner applicator means (103a, b and c) are preferably placed in a slight overlap so that on the surface of the CTC (104) an even and uninterrupted layer of toner particles is created.
  • the printhead structure used in the configuration of a first specific embodiment of the present invention, described immediately above, can be a flat printhead structure comprising non-staggered sets of rows of printing apertures and the CTC can be constructed so as to have a flat surface (such a CTC has, e.g., been disclosed in US 5,136,311) under the set of rows of apertures.
  • the printhead structure can be curved around the CTC so that over the complete width of the printhead structure a constant distance towards the CTC is obtained, whereby the risk of banding in the image is minimised.
  • An other way to minimise banding with a flat (not bent over the CTC) printhead structure is to adapt the diameter of the CTC to the distance between this CTC and this printhead structure and to the extension of the rows of printing apertures according to the formula (I): R ⁇ C 2 4.25B + 0.25 wherein
  • the staggered toner applicator means are magnetic brush assemblies applying charged toner particles towards the CTC.
  • the alignment between neighbouring magnetic brush assemblies is such that no visible banding (due to a varying toner layer thickness upon the surface of the CTC) is obtained.
  • the printhead structure does not have to be a printhead structure, having a width equal to or larger than the printing width (PW) of the printer. It is possible in the configuration of a first specific embodiment of the invention shown in figure 1, to use multiple printhead structures, each with one set of rows of printing apertures, that are spread out over the width of the substrate to be printed in a staggered configuration, this gives in fact a modular printhead structure. When several smaller printhead structures are staggered, also the sets of rows of printing apertures are staggered.
  • the advantage of using multiple printhead structures lays mainly in the fact that smaller printhead structures are more easily produced than larger ones, that the printing apertures in smaller printhead structures are more easily kept at a constant distance from the toner delivery means, in this case a CTC, and that in a modular printhead structure defects can more easily and economically be repaired, simply by replacing the defect module.
  • the sets of rows of printing apertures are also staggered, and thus are the distances of the various sets of rows of printing apertures to the surface of the single CTC not equal and the risk of banding in the image exists.
  • the banding can be avoided by using a CTC that is essentially flat under the printing apertures (such a CTC can, e.g., be an adaptation of the CTC disclosed in US 5,136,311).
  • the banding can also be avoided, when using a cylindrical CTC, by adapting the diameter of the CTC to the distance between the various sets of printing apertures.
  • Such a CTC has a curvature, R, in the development zone, fulfilling the equation : R ⁇ C 2 4.25B + 0.25 wherein
  • the DEP printing engine comprises :
  • V1, V2, V3, V4 and V5 indicate the different voltages applied to the different parts of the DEP printing engine, thus creating the necessary electrical fields for the operation of the device. Further on the role of the different voltages, which is in essence equal for all embodiments of the present invention is described.
  • a more complex set of five toner applicator modules (e.g., five magnetic brush assemblies) is used to bring charged toner particles to the CTC.
  • Three of toner applicator means (103a, b and c) are positioned in a staggered configuration, without overlap, so as to obtain an homogeneous toner density upon the charged toner conveyor.
  • Two extra toner applicator modules (103d and e) are staggered with respect to the first set of three toner applicator modules, with a certain overlap, so that charged toner particles are applied to the centre of the charged toner conveyor from two separate toner applicator modules.
  • toner applicator module 103d overlaps for 50 % with both toner module 103a and 103b and toner applicator module 103e overlaps 50 % with both toner module 103b and 103c. It was found that this arrangement results in an even better homogeneity of the charged toner layer thickness upon the charged toner conveyor.
  • the extension of the set of toner delivery means gives the printing width (PW) of the printer.
  • the toner applicator modules in the first specific embodiment of the invention can be magnetic brush assemblies, using either a multi-component developer, comprising magnetic carrier particles and non-magnetic toner particles or a mono-component magnetic developer.
  • the applicator modules can also be applicators for non-magnetic mono-component developer.
  • the toner applicator modules are magnetic brush assemblies
  • the toner applicator modules (103) are magnetic brushes and some or each of the staggered magnetic brush configurations are constructed such as to comprise two separate magnetic brush assemblies, namely a pushing and a pulling magnetic brush assembly.
  • push-pull magnetic brushes are meant two different magnetic brushes depositing a layer of toner particles upon the charged toner conveyor from a multi-component developer (e.g. a two-component developer, comprising carrier and toner particles wherein the toner particles are tribo-electrically charged by the contact with carrier particles or 1.5 component developers, wherein the toner particles get tribo-electrically charged not only by contact with carrier particles, but also by contact between the toner particles themselves).
  • the first of the two different magnetic brushes is a pushing magnetic brush, used to jump charged toner particles to the CTC and being connected to a DC-source with the same polarity as the toner particles.
  • the second of the two magnetic brushes is a pulling magnetic brush, used to remove toner particles from the CTC and connected to a DC-source with a polarity opposite to the polarity of the toner particles.
  • a second separate CTC charged toner conveyor
  • an alternating electric field is applied between the two charged toner conveyors so that the charged toner is propelled between the two roller structures of the CTC's yielding a more uniform distribution of charged toner particles upon the first charged toner conveyor in the neighbourhood of the apertures in the printhead structure.
  • a printer is provided, with printing width (PW), for printing a toner image on a substrate comprising a DEP printing engine, having
  • Figure 4 shows a schematic perspective view of a possible configuration of a printer according to a second specific embodiment of the present invention.
  • a single printhead structure (106) having a width equal to or larger than the printing width (PW) of the printer, comprises multiple staggered sets of rows of printing apertures (107a, b and c), each of the staggered sets of rows of printing apertures having a width (WR) smaller that the printing width (PW).
  • WR width
  • charged toner particles are image-wise deposited on to the image receiving member (109), having a width (WS) and a length (LS) and that for clarity, is shown as a transparent substrate.
  • the arrow A shows the direction of movement of the image receiving member.
  • Figure 5 shows a more detailed lateral view of the configuration of a printer according to the second specific embodiment of this invention, shown in figure 4.
  • the DEP device comprises :
  • V2, V3, V4 and V5 indicate the different voltages applied to the different parts of the DEP device, thus creating the necessary electrical fields for the operation of the device. Further on the role of the different voltages, which is in essence equal for all embodiments of the present invention is described.
  • the developer used can be a mono-component magnetic developer or a multi-component developer comprising magnetic carrier particles and non-magnetic toner particles.
  • the toner delivery means (100a, b and c), shown in figure 4, comprise CTC's on which a layer of toner particles are deposited by toner applicator modules, as described under the first specific embodiment of the invention, and the cloud of toner particles (111) is created between the CTC's and the set of rows of printing apertures associated with each CTC.
  • the magnetic brush assemblies make contact over their magnetic hairs with the printhead structure that was stretched over a rigid four-bar frame as described in EP-A 712 056.
  • FIGS. 2 and 5 each schematically illustrating a printer according to the present invention, show printers wherein the substrate (109) to be printed is a web. It is evident that a printer, comprising staggered toner applicator modules or toner delivery means, capable to print on sheet material is within the scope of the present invention.
  • the DEP devices use a printhead structure wherein both a shield electrode and control electrodes, also DEP devices wherein a printhead structure comprising no shield electrode and only control electrodes are useful in the present invention.
  • the printing width (PW) is shown to be smaller than the width (WS) of the substrate to be printed.
  • a printer according to the present invention can have a printing width smaller than, equal to or larger than the width of the substrate to be printed.
  • a printer comprises either a DEP printing engine as described in the first specific embodiment of the invention or as described in the second specific embodiment of the invention, integrated in a moving shuttle, said shuttle having, preferably, a printing width (swath width SWS) of at least 30 cm, more preferably larger than 40 cm, so that a large format image is written in separate image bands (swaths) .
  • the shuttle comprising a DEP printing engine, is travelling over the image receiving member in a first direction, preferably a direction that is essentially parallel to the width of the substrate to be printed, thus perpendicular to the length of the substrate.
  • the third specific embodiment of the invention encompasses a printer for large format printing, wherein a large substrate is movable in one direction and a shuttle comprising a DEP printing engine is movable in a second direction, the second direction being different from the first direction, the DEP printing engine comprising a printhead structure (106) comprising printing apertures (107) and control electrodes (106''), and a toner delivery means (100) and wherein the toner delivery means comprises at least two toner applicator modules (103), positioned in a staggered configuration.
  • the invention further encompasses a printer for large format printing, wherein a large substrate is movable in one direction and a shuttle comprising a DEP printing engine is movable in a second direction, the second direction being different from the first direction, the DEP printing engine comprising a printhead structure (106) comprising printing apertures (107) and control electrodes (106''), and a toner delivery means (100) and wherein the printhead structure (106), comprises at least two staggered sets of rows of printing apertures and each of the staggered sets of rows of printing apertures is combined with a toner delivery means (100).
  • a large substrate is preferably movable in one direction, and a shuttle is movable in a second direction, the second direction being essentially perpendicular to the first direction.
  • the shuttle comprising DEP devices as describe above, is arranged so that the width (WTD) of the staggered toner delivery means or toner applicator modules is essentially perpendicular to the width of the substrate to be printed and parallel to the direction of movement of the shuttle.
  • the third specific embodiment of the invention provides a printer with a shuttle comprising a printing engine with rather large printing width.
  • the shuttle in the third specific embodiment of the invention has a printing width (i.e. the swath width of the shuttle, SWS) of at least 40 cm, preferably 60 cm and more preferably 120 cm.
  • the shuttle comprising a wide DEP printing engine according to this invention, moves preferably in a direction essentially perpendicular to the movement of a large paper web so that images of very large dimension (e.g. > 5 meter width) can be obtained with a very fast printing speed (e.g. > 500 m2/hour) while keeping the shuttling speed fairly low.
  • both types of DEP engine as described in the first and second specific embodiment of the invention can be incorporated in said shuttle. And thus two kinds of printers belong also to this invention :
  • the back electrode (105) of DEP devices can also be made to co-operate with the printhead structure, the back electrode being constructed from different styli or wires that are galvanically insulated and connected to a voltage source as disclosed in e.g. US 4,568,955 and US 4,733,256.
  • the back electrode, co-operating with the printhead structure can also comprise one or more flexible PCB's (Printed Circuit Board).
  • the back electrode can be a page-wide back electrode or it can be various smaller back electrodes spread out over the total width of the large substrate to be printed.
  • the back electrode can shuttle with the engine or can be an electrode having a width equal to the maximum width of the printable substrates and being positioned in a steady position.
  • a DEP printing engine in a printer can also operate without a back electrode.
  • a conductive layer is present and an electrical field, creating a flow of charged toner particles, is applied between the conductive layer and the toner delivery means, such a DEP device has been disclosed in European Application 96202228, field on August 8, 1996.
  • Any DEP printing engine makes it possible to image-wise deposit toner particles by applying various electrical fields between the different parts of such a DEP device. Reverting to figure 2, between the printhead structure (106) and the charged toner conveyor (104), as well as between the charged toner conveyor and the magnetic brush assembly (103) as well as between the control electrode around the printing apertures (107) and the back electrode (105) behind the toner receiving member (109) as well as on the single electrode surface or between the plural electrode surfaces of the printhead structure (106) different electrical fields are applied.
  • a device useful for a DEP method, shown in fig 2.
  • voltage V1 is applied to the sleeve of the charged toner conveyor 104, voltage V2 to the shield electrode 106', voltages V3 0 up to V3 n for the control electrode (106'').
  • the value of V3 is selected, according to the modulation of the image forming signals, between the values V3 0 and V3 n , on a time-basis or grey-level basis.
  • Voltage V4 is applied to the back electrode behind the toner receiving member. In other configurations of the present invention multiple voltages V2 0 to V2 n and/or V4 0 to V4 n can be used.
  • Voltage V5 is applied to the sleeve of the magnetic brush assemblies.
  • the printhead structure used in any embodiment of a DEP device according to the present invention can also be a mesh shaped structure as disclosed in, e.g., EP-A 390 847; it can comprise printing apertures in slit form as disclosed in, e.g., EP-A-780 740.
  • any printhead structure known in the art can be combined with a toner delivery means in DEP devices according to the present invention.
  • toner particles black, coloured or colourless, can be used in DEP devices according to the present invention. It is preferred to use toner particles as disclosed in European patent application EP-A 715 218, that is incorporated by reference.
  • a DEP device using the above mentioned marking particles can be addressed in a way that enables it to give black and white. It can thus be operated in a "binary way", useful for black and white text and graphics and useful for classical bi-level half-toning to render continuous tone images.
  • a DEP device is especially suited for rendering an image with a plurality of grey levels.
  • Grey level printing can be controlled by either an amplitude modulation of the voltage V3 applied on the control electrode 106'' or by a time modulation of V3. By changing the duty cycle of the time modulation at a specific frequency, it is possible to print accurately fine differences in grey levels. It is also possible to control the grey level printing by a combination of an amplitude modulation and a time modulation of the voltage V3, applied on the control electrode.
  • the DEP device The DEP device
  • a printhead structure (106) was made from a polyimide film of 50 ⁇ m thickness, double sided coated with a 17.5 ⁇ m thick copper film.
  • the printhead structure (106) had four rows of printing apertures.
  • a rectangular shaped control electrode (106'') was arranged around each aperture. Each of the control electrodes was individually addressable from a high voltage power supply.
  • a common shield electrode (106') was present on the front side of the printhead structure, facing the toner delivery means. Above the shield electrode a 200 ⁇ m thick plastic polyurethane member was present.
  • the printing apertures were rectangles of 400 by 150 ⁇ m.
  • the total width of the rectangular copper control electrodes was 600 by 250 ⁇ m, their internal aperture also being 400 by 150 ⁇ m.
  • the size of the aperture in the common shield electrode was 600 by 250 ⁇ m.
  • the total width of the printhead structure having four rows of printing apertures was 90 cm.
  • the printhead structure was fabricated in the following way. First of all the control electrode pattern was etched by conventional copper etching techniques. Then the shield electrode pattern was etched by conventional copper etching techniques. The polyurethane layer was laminated on top of the shield electrode layer.
  • the apertures were made by a step and repeat focused excimer laser burning making use of the control electrode patterns as focusing aid. After excimer burning the printhead structure was cleaned by a short isotropic plasma etching cleaning. Finally a thin coating of PLASTIK70, (trade name) commercially available from Griffin Chemie, was applied over the control electrode side of the printhead structure.
  • a charged toner conveyor of 90 cm width was used.
  • the charged toner conveyor was made of copper and had a diameter of 10 cm .
  • Charged toner particles were applied towards the charged toner conveyor from 3 different magnetic brush assemblies, each of them having a width of 30 cm.
  • These magnetic brush assemblies (103) were constituted of the so called magnetic roller, which in the case contained inside the roller assembly a fixed magnetic core, showing 9 magnetic poles of 50 mT (500 Gauss) magnetic field intensity.
  • the magnetic roller contained also a sleeve, fitting around the magnetic core, and giving to the magnetic brush assembly an overall diameter of 20 mm.
  • the sleeve was made of finely roughened stainless steel.
  • a scraper blade was used to force developer to leave the magnetic roller. And on the other side a doctoring blade was used to meter a small amount of developer onto the surface of the magnetic brush assembly.
  • the magnetic brush assemblies were connected to a high voltage power supply and the charged toner conveyor was connected to an AC power supply with a square wave oscillating field of 600 V at a frequency of 3.0 kHz with 0 V DC-offset.
  • the three magnetic brush assemblies were staggered in such a way that an homogeneous amount of charged toner particles could be applied towards the charged toner conveyor.
  • the alignment was tuned by translating the magnetic brush assemblies in a direction parallel towards the surface of the charged toner conveyor until visually no banding at all was observed.
  • a macroscopic "soft" ferrite carrier consisting of a MgZn-ferrite with average particle size 50 ⁇ m, a magnetisation at saturation of 36 ⁇ Tm 3 /kg (29 emu/g) was provided with a 1 ⁇ m thick acrylic coating. The material showed virtually no remanence.
  • the toner used for the experiment had the following composition : 97 parts of a co-polyester resin of fumaric acid and propoxylated bisphenol A, having an acid value of 18 and volume resistivity of 5.1 x 10 16 ⁇ .cm was melt-blended for 30 minutes at 110° C in a laboratory kneader with 3 parts of Cu-phthalocyanine pigment (Colour Index PB 15:3).
  • a resistivity decreasing substance - having the following structural formula : (CH 3 ) 3 N + C 16 H 33 Br - - was added in a quantity of 0.5 % with respect to the binder. It was found that - by mixing with 5 % of the ammonium salt - the volume resistivity of the applied binder resin was lowered to 5x10 14 ⁇ .cm.
  • the solidified mass was pulverised and milled using an ALPINE Fliessbettarnastrahlmühle type 100AFG (trade name) and further classified using an ALPINE multiplex zig-zag classifier type 100MZR (trade name).
  • the resulting particle size distribution of the separated toner measured by Coulter Counter model Multisizer (trade name), was found to be 6.3 ⁇ m average by number and 8.2 ⁇ m average by volume.
  • the toner particles were mixed with 0.5 % of hydrophobic colloidal silica particles (BET-value 130 m 2 /g).
  • An electrostatographic developer was prepared by mixing this mixture of toner particles and colloidal silica in a 4 % ratio (w/w) with carrier particles.
  • the tribo-electric charging of the toner-carrier mixture was performed by mixing this mixture in a standard tumbling set-up for 10 min.
  • the printhead structure was bent over the charged toner conveyor, making frictional contact over the polyurethane member with the charged toner particles on the surface of the CTC.
  • To the individual control electrodes an (image-wise) voltage V3 between 0 V and -300 V was applied.
  • the back electrode (105) was connected to a high voltage power supply of + 1500 V.
  • To the sleeve of the charged toner conveyor an AC voltage of 600 V at 3.0 kHz was applied, without DC offset.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
EP97203821A 1996-12-19 1997-12-05 Appareil d'impression pour imprimer à grand format utilsant un appareil d'impression électrostatique direct Withdrawn EP0849645A1 (fr)

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EP97203821A EP0849645A1 (fr) 1996-12-19 1997-12-05 Appareil d'impression pour imprimer à grand format utilsant un appareil d'impression électrostatique direct

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EP96203635 1996-12-19
EP96203635 1996-12-19
EP97203821A EP0849645A1 (fr) 1996-12-19 1997-12-05 Appareil d'impression pour imprimer à grand format utilsant un appareil d'impression électrostatique direct

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0952498A1 (fr) * 1998-04-22 1999-10-27 Agfa-Gevaert N.V. Procédé d'impression électrostatique directe pour la formation d'un motif résistant sur un substrat conducteur et utilisation dans la fabrication de circuits imprimés
EP0984336A1 (fr) * 1998-09-08 2000-03-08 Agfa-Gevaert N.V. Appareil d'impression pour imprimer à grand format avec une seule unité centrale de contrôle et de surveillance de toner
US6246424B1 (en) 1998-11-16 2001-06-12 Agfa-Gevaert Device for large format printing comprising a single central conditioning unit for controlling and monitoring the condition of the developer

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JPS62164083A (ja) * 1986-01-16 1987-07-20 Canon Inc 画像表示装置
US4996556A (en) * 1989-08-03 1991-02-26 Xerox Corporation Large document copying system
JPH0511425A (ja) * 1991-07-08 1993-01-22 Brother Ind Ltd 画像形成装置
US5198841A (en) * 1989-12-08 1993-03-30 Minolta Camera Kabushiki Kaisha Electric printer
US5283594A (en) * 1990-12-18 1994-02-01 Brother Kogyo Kabushiki Kaisha Color image recording apparatus for recording a color image on a recording medium with color particles with a vibrating print head
EP0619188A2 (fr) * 1993-04-08 1994-10-12 Eastman Kodak Company Imprimante thermique pour l'impression ligne par ligne
US5477250A (en) * 1992-11-13 1995-12-19 Array Printers Ab Device employing multicolor toner particles for generating multicolor images
US5552862A (en) * 1994-08-18 1996-09-03 Fujitsu Limited Serial-type electrophotographic device and a method for adjusting printing based upon a detected humidity used therein
US5555078A (en) * 1994-05-18 1996-09-10 Fujitsu Limited Serial printer
EP0740224A1 (fr) * 1995-04-25 1996-10-30 Agfa-Gevaert N.V. Imprimante électrostatographique directe (DEP)
DE19540138C1 (de) * 1995-10-27 1996-12-05 Siemens Nixdorf Inf Syst Entwicklerstation mit mehreren nebeneinander angeordneten Entwicklerkammern

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JPS62164083A (ja) * 1986-01-16 1987-07-20 Canon Inc 画像表示装置
US4996556A (en) * 1989-08-03 1991-02-26 Xerox Corporation Large document copying system
US5198841A (en) * 1989-12-08 1993-03-30 Minolta Camera Kabushiki Kaisha Electric printer
US5283594A (en) * 1990-12-18 1994-02-01 Brother Kogyo Kabushiki Kaisha Color image recording apparatus for recording a color image on a recording medium with color particles with a vibrating print head
JPH0511425A (ja) * 1991-07-08 1993-01-22 Brother Ind Ltd 画像形成装置
US5477250A (en) * 1992-11-13 1995-12-19 Array Printers Ab Device employing multicolor toner particles for generating multicolor images
EP0619188A2 (fr) * 1993-04-08 1994-10-12 Eastman Kodak Company Imprimante thermique pour l'impression ligne par ligne
US5555078A (en) * 1994-05-18 1996-09-10 Fujitsu Limited Serial printer
US5552862A (en) * 1994-08-18 1996-09-03 Fujitsu Limited Serial-type electrophotographic device and a method for adjusting printing based upon a detected humidity used therein
EP0740224A1 (fr) * 1995-04-25 1996-10-30 Agfa-Gevaert N.V. Imprimante électrostatographique directe (DEP)
DE19540138C1 (de) * 1995-10-27 1996-12-05 Siemens Nixdorf Inf Syst Entwicklerstation mit mehreren nebeneinander angeordneten Entwicklerkammern

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PATENT ABSTRACTS OF JAPAN vol. 012, no. 002 (P - 652) 7 January 1988 (1988-01-07) *
PATENT ABSTRACTS OF JAPAN vol. 017, no. 273 (P - 1545) 26 May 1993 (1993-05-26) *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0952498A1 (fr) * 1998-04-22 1999-10-27 Agfa-Gevaert N.V. Procédé d'impression électrostatique directe pour la formation d'un motif résistant sur un substrat conducteur et utilisation dans la fabrication de circuits imprimés
EP0984336A1 (fr) * 1998-09-08 2000-03-08 Agfa-Gevaert N.V. Appareil d'impression pour imprimer à grand format avec une seule unité centrale de contrôle et de surveillance de toner
US6246424B1 (en) 1998-11-16 2001-06-12 Agfa-Gevaert Device for large format printing comprising a single central conditioning unit for controlling and monitoring the condition of the developer

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