EP0731394B1 - Vorrichtung zum direkten elektrostatischen Drucken mit aus einer magnetischer Bürste und Druckkopf bestehende Struktur mit spezieller Geometrie - Google Patents

Vorrichtung zum direkten elektrostatischen Drucken mit aus einer magnetischer Bürste und Druckkopf bestehende Struktur mit spezieller Geometrie Download PDF

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Publication number
EP0731394B1
EP0731394B1 EP19950200556 EP95200556A EP0731394B1 EP 0731394 B1 EP0731394 B1 EP 0731394B1 EP 19950200556 EP19950200556 EP 19950200556 EP 95200556 A EP95200556 A EP 95200556A EP 0731394 B1 EP0731394 B1 EP 0731394B1
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EP
European Patent Office
Prior art keywords
magnetic brush
apertures
magnetic
printhead structure
printing
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EP19950200556
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English (en)
French (fr)
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EP0731394A1 (de
Inventor
Guido Desie
Jacques Leonard
Frans Backeljauw
André Van Geyte
Serge Tavernier
Dirk Broddin
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Agfa Gevaert NV
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Agfa Gevaert NV
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Priority to DE1995602927 priority Critical patent/DE69502927T2/de
Priority to EP19950200556 priority patent/EP0731394B1/de
Priority to JP7953696A priority patent/JPH0999577A/ja
Publication of EP0731394A1 publication Critical patent/EP0731394A1/de
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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

Definitions

  • This invention relates to an apparatus used in the process of electrostatic printing and more particularly in Direct Electrostatic Printing (DEP).
  • 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 imagewise way on a receiving substrate, the latter not bearing any imagewise latent electrostatic image.
  • the substrate can be an intermediate endless flexible belt (e.g. aluminium, polyimide etc.).
  • the imagewise 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-P 3,689,935.
  • This document discloses an electrostatic line printer having a multi-layered particle modulator or printhead structure comprising :
  • 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 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 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. This 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.
  • a DEP device is well suited to print half-tone images.
  • the densities variations present in a half-tone image can be obtained by modulation of the voltage applied to the individual control electrodes.
  • large apertures are used for obtaining a high degree of density resolution (i.e. for producing an image comprising a high amount of differentiated density levels).
  • the overall printing density is rather low. This means that either the printing speed too is rather low, or that multiple overlapping rows of addressable apertures have to be implemented, yielding a complex printhead structure and printing device.
  • Printhead structures with enhanced density and/or spatial control have been described in the literature.
  • US-P 4,860,036 e.g. a printhead structure has been described consisting of at least 3 (preferentially 4 or more) rows of apertures which makes it possible to print images with a smooth page-wide density scale without white banding.
  • the main drawback of this kind of printhead structure deals with the toner particle application module, which has to be able to provide charged toner particles in the vicinity of all printing apertures with a nearly equal flux.
  • US-P 5,040,004 this problem has been tackled by the introduction of a moving belt which slides over an accurately positioned shoe that is placed at close distance from the printhead structure.
  • DEP system comprising a printhead structure comprising multiple rows of apertures and a toner application module with appropriate geometry and dimension so that images with excellent sharpness and density profiles can be obtained in a fast and reproducible way.
  • DEP Direct Electrostatic Printing
  • Fig. 1 is a schematic illustration of a possible embodiment of a DEP device according to the present invention.
  • Fig. 2 is a schematic illustration of the development zone.
  • Fig. 3 is a cross-section of fig 2 along the plane A-A'-A''.
  • a DEP device comprises a printhead structure with multiple rows of printing apertures. Since printing devices are preferably kept as small as possible, it is interesting to use, in any printing device, the smallest components possible. For that reason a magnetic brush with small diameter is preferably used in any electro(photo)graphic device. Magnetic brush assemblies with a small diameter of the outer sleeve are very interesting for their small size and low cost. However, it is very difficult to use a very small magnetic brush with a printhead structure that has multiple rows of apertures, needing a relatively wide development zone.
  • R fulfils the equation II : R ⁇ C 2 1.55B + 0.25
  • R fulfils the equation III : R ⁇ C 2 0.30B + 0.25
  • a magnetic brush fulfilling the equations above has a curvature, expressed as a radius, R, (mm) of a circle that best fits to said curvature of said magnetic brush (103) in the development zone (111), wherein R ⁇ 10 mm
  • the most important part is the part located in the development zone (111) with surface 112 in the development zone. It was found that the quality of the printing is largely determined by the number of magnetic poles per unit length of said magnetic brush in development zone 111 and thus under surface 112. Good printing quality can be obtained, when the number of magnetic poles (M) situated in that quarter of the core, immediately adjacent to said development zone 111, the middle of which is situated in the middle of the surface (112) of the sleeve (103b) in development zone 111, is related to the total number of magnetic poles (N) comprised in the magnetic brush. For good printing quality, it is preferred that M/N ⁇ 0.30.
  • At least 30 % of all magnetic poles present are located in that quarter of the core (103a) under the middle of the surface of the magnetic brush (112) delimiting the development zone 111.
  • the quarter of the core (103a) of the magnetic brush (103) immediatly underneath development zone 111 is denoted as 113 and the middle of this quarter by the point Y.
  • the middle of the surface (112) of the sleeve (103b) of the magnetic brush is denoted by the point X.
  • the number M is the number of magnetic poles present in the quarter of the core where X and Y coincide.
  • the external magnetic field measured at the outer surface of said sleeve of said magnetic brush, and extending along the distance B, is peferably larger than 0.015 T (Tesla), more preferably more than 0.05 T, and most preferably more than 0.1 T. It is clear that if this magnetic field strength is chosen high enough, carrier loss can be minimized to a large extent. However, increasing the field strength also increases the cost of the apparatus. For that reason an optimum between the actual number of poles and the intrinsic field strength of the individual magnets has to be chosen.
  • the printhead structure is fabricated in such a way as to impose the smallest possible implication upon the size and cost of the magnetic brush used in the toner application module.
  • a magnetic brush with small curvature in the development zone combined with a printhead structure with many rows of apertures, each of said apertures having a rather large diameter.
  • the printhead structure used in a preferred embodiment of the present invention is made in such a way that reproducible printing is possible without clogging and with accurate control of printing density.
  • Such a printhead structure has been described in European patent application 94203764.9 filed on December 1994.
  • a non limitative example of a device for implementing a DEP method using toner particles according to the present invention comprises (fig 1):
  • a DEP method using toner particles according to the present invention using devices with different constructions of the printhead (106). It is, e.g. possible to implement a DEP method with a device having a printhead comprising only one electrode structure aswell as with a device having a printhead comprising more than two electrode structures.
  • the apertures in these printhead structures can have a constant diameter, or can have a broader entrance or exit diameter.
  • the back electrode (105) of this DEP device can also be made to cooperate with the printhead structure, said back electrode being constructed from different styli or wires that are galvanically isolated and connected to a voltage source as disclosed in e.g. US-P 4,568,955 and US-P 4,733,256.
  • the back electrode, cooperating with the printhead structure can also comprise one or more flexible PCB's (Printed Circuit Board).
  • V3 is selected, according to the modulation of the image forming signals, between the values V3 0 and V3 n , on a timebasis or gray-level basis.
  • Voltage V4 is applied to the back electrode behind the toner receiving member. In other embodiments of the present invention multiple voltages V2 0 to V2 n and/or V4 0 to V4 n can be used.
  • said toner delivery means 101 creates a layer of multi-component developer (e.g. a two-component developer, comprising carrier and toner particles wherein the toner particles are triboelectrically 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) on a magnetic brush 103, and the toner cloud 104 is directly extracted from said magnetic brush 103.
  • the toner is first applied to a conveyer belt and transported on this belt in the vicinity of the apertures.
  • a device is also operative with a mono-component developer or toner, which is transported in the vicinity of the apertures 107, via a conveyer for charged toner.
  • a conveyer can be a moving belt or a fixed belt.
  • the latter comprises an electrode structure generating a corresponding electrostatic travelling wave pattern for moving the toner particles.
  • the curvature of said belt has a maximum curvature, depending on the extension of the array of printing apertures measured in the direction of the movement of receiving substrate and the distance between said conveying belt and the printhead structure.
  • the magnetic brush 103 preferentially used in a DEP device according to an embodiment of the present invention is of the type with stationary core and rotating sleeve.
  • any type of known carrier particles and toner particles can successivefully be used. It is however preferred to use "soft" magnetic carrier particles.
  • Soft magnetic carrier particles useful in a DEP device according to the present invention are soft ferrite carrier particles. Such soft ferrite particles exhibit only a small amount of remanent behaviour, characterised in coercivity values ranging from about 3979 up to 19 894 A.m (50 up to 250 Oe).
  • Further very useful soft magnetic carrier particles, for use in a DEP device according to the present invention are composite carrier particles, comprising a resin binder and a mixture of two magnetites having a different particle size as described in EP-B 289 663.
  • the particle size of both magnetites will vary between 0.05 and 3 ⁇ m.
  • the carrier particles have preferably an average volume diameter (d v50 ) between 10 and 300 ⁇ m, preferably between 20 and 100 ⁇ m. More detailed descriptions of carrier particles, as mentioned above, can be found in European patent application 94201026.5, filed on April 14th, 1994, and titled "A method and device for direct electrostatic printing (DEP)".
  • ⁇ 20 fC preferably to 1 fC ⁇
  • the charge distribution is narrow, i.e. shows a distribution wherein the coefficient of variability ( ⁇ ), i.e. the ratio of the standard deviation to the average value, is equal to or lower than 0.33.
  • ⁇ coefficient of variability
  • the toner particles used in a device according to the present invention have an average volume diameter (d v50 ) between 1 and 20 ⁇ m, more preferably between 3 and 15 ⁇ m. More detailed descriptions of toner particles, as mentioned above, can be found in European patent application 94201026.5, filed on April 14th, 1994, and titled "A method and device for direct electrostatic printing (DEP)".
  • a DEP device making use of the above mentioned marking toner 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 bilevel halftoning to render continuous tone images.
  • a DEP device is especially suited for rendering an image with a plurality of gray levels.
  • Gray level printing can be controlled by either an amplitude modulation of the voltage V3 applied on the control electrode 106a 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 gray levels. It is also possible to control the gray level printing by a combination of an amplitude modulation and a time modulation of the voltage V3, applied on the control electrode.
  • the carrier particles are of the carrier particles.
  • a macroscopic "soft" ferrite carrier consisting of a MgZn-ferrite with average particle size 50 ⁇ m, a magnetisation at saturation of 29A.m 2 .kg -1 (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 bispropoxylated bisphenol A, having an acid value of 18 and volume resistivity of 5.1 x 10 16 ohm.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 formula : (CH 3 ) 3 N + C 16 H 33 Br - was added in a quantity of 0.5 % with respect to the binder, as described in WO 94/027192. It was found that - by mixing with 5 % of said ammonium salt - the volume resistivity of the applied binder resin was lowered to 5x10 14 ⁇ .cm. This proves a high resistivity decreasing capacity (reduction factor : 100).
  • the solidified mass was pulverized and milled using an ALPINE Fliessbettarnastrahlmühle type 100AFG (tradename) and further classified using an ALPINE multiplex zig-zag classifier type 100MZR (tradename).
  • the average particle size was measured by Coulter Counter model Multisizer (tradename), was found to be 6.3 ⁇ m by number and 8.2 ⁇ m 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 said mixture of toner particles and colloidal silica in a 4 % ratio (w/w) with carrier particles.
  • the triboelectric charging of the toner-carrier mixture was performed by mixing said mixture in a standard tumbling set-up for 10 min.
  • the developer mixture was run in the development unit (magnetic brush) for 5 minutes, after which the toner was sampled and the tribo-electric properties were measured, according to a method as described in the above mentioned European application 94201026.5, filed on April 14, 1994 and published as EP-A- 0634862.
  • the average charge, q, of the toner particles was -7.1 fC.
  • a printhead structure 106 was made from a polyimide film of 50 ⁇ m thickness, double sided coated with a 17 ⁇ m thick copperfilm.
  • a ring shaped control electrode 106a was arranged around each aperture. Each of said control electrodes was individually addressable from a high voltage power supply.
  • a common shield electrode (106b) was present on the front side of the printhead structure, facing the toner delivery means.
  • the printhead structure 106 had six rows of apertures. The apertures had an aperture diameter of 200 ⁇ m. The width of the copper ring electrodes was 175 ⁇ m The rows of apertures were staggered to obtain an overall resolution of 79 dots per cm (200 dpi). The total extension of the array of said apertures in said printhead structure as defined above (C) was 3.25 mm.
  • the toner delivery means (101) The toner delivery means (101)
  • the toner delivery means 101 comprised a cylindrical, stationary core/rotating sleeve type magnetic brush (103) comprising two mixing rods and one metering roller. One rod was used to transport the developer through the unit, the other one to mix toner with developer.
  • the magnetic brush 103 was constituted of the so called magnetic roller, which in this case contained inside the roller assembly a stationary magnetic core, having nine magnetic poles with an open position (no magnetic poles present) to enable used developer to fall off from the magnetic roller (open position was one quarter of the perimeter and located at the position opposite to development zone 111).
  • the total number of magnetic poles N was 9.
  • the perimeter of the magnetic brush D was 66.0 mm
  • the magnetic roller contained also a sleeve, fitting around said stationary magnetic core, and giving to the magnetic brush an overall diameter of 21 mm.
  • the radius R (expressed in mm) of a circle that best fits to the curvature of said magnetic brush (103) in the development zone (111) was thus 10,5 mm.
  • a scraper blade was used to force developer to leave the magnetic roller.
  • a doctoring blade was used to meter a small amount of developer onto the surface of said magnetic brush.
  • the sleeve was rotating at 100 rpm, the internal elements rotating at such a speed as to conform to a good internal transport within the development unit.
  • the magnetic brush 103 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 distance B between the front side of the printhead structure 106 and the sleeve (reference surface) of the magnetic brush 103 was set at 350 ⁇ m.
  • the distance between the back electrode 105 and the back side of the printhead structure 106 i.e. control electrodes 106a
  • the back electrode 105 was connected to a high voltage power supply of +400 V.
  • To the sleeve of the magnetic brush an AC voltage of 600 V at 3.0 kHz was applied, without DC offset.
  • a print was made with the same printhead configuration and magnetic brush as described in example 1, but the distance of said magnetic brush towards said printhead structure was set to 500 ⁇ m.
  • comparative example 1 the same magnetic brush as described in example 1 was used, but for the printhead structure, an eight-rowed-array of printing apertures was used (same aperture diameter, copper-ring diameter and staggering).
  • the extension of said array of printing apertures as defined above was 4.55 mm.
  • the distance of said magnetic brush towards said printhead structure was set to 350 ⁇ m.
  • example 3 the same magnetic brush as described in example 1 was used, but for the printhead structure, a four-rowed-array of printing apertures was used (same aperture diameter, copper-ring diameter and staggering).
  • the extension of said array of printing apertures as defined above was 1.95 mm.
  • the distance of said magnetic brush towards said printhead structure was set to 500 ⁇ m.
  • example 4 the same magnetic brush as described in example 1 was used, but for the printhead structure, a compact design was chosen.
  • the printhead structure was formed of 2 rows of apertures, said apertures having a square form of 200 by 200 ⁇ m, a square copper electrode of 50 ⁇ m around each aperture, said 2 rows of apertures isolated from each other by a 100 ⁇ m broad isolation zone.
  • This printhead structure had a resolution of 50 dots per cm (127 dpi) and was fabricated using the technique of plasma etching.
  • the extension of said array of printing apertures in said printhead structure was only 0.4 mm.
  • the distance of said magnetic brush towards said printhead structure was set to 350 ⁇ m.
  • a printhead structure having a four-rowed-array of printing apertures was used (200 ⁇ m aperture diameter, copper-ring diameter of 550 ⁇ m and staggered to obtain an overall resolution of 50 dots per cm (127 dpi)).
  • the extension of said array of printing apertures as defined above was 1.95 mm.
  • the magnetic brush used consisted of 6 magnetic poles divided over half of the perimeter of an internal drum on the side facing the apertured printhead, and had a sleeve with outer diameter of 63 mm and a surface roughness of 3.5 ⁇ m (Ra).
  • the distance of said magnetic brush towards said printhead structure was set to 400 ⁇ m.
  • example 6 the same magnetic brush as described in example 5 was used.
  • the printhead structure used was one with eight rows of printing apertures with the same design parameters as described in example 5 but with an extension of said array of printing apertures of 4.55 mm.
  • the distance of the magnetic brush towards said printhead structure was 400 ⁇ m.
  • the magnetic brush consisted of only 3 magnetic poles divided over half of the perimeter of an internal drum on the side facing the printhead structure, and had a sleeve with outer diameter of 63 mm and a surface roughness of 3.5 ⁇ m (Ra).
  • the distance of said magnetic brush towards said printhead structure was set to 400 ⁇ m. Printing examples with good quality could not be obtained by this magnetic brush.
  • example 7 the same printhead structure as described in example 6 was used, but the magnetic brush consisted of 14 magnetic poles divided over two thirds of the perimeter of an internal drum on the side facing the apertured printhead, and had a sleeve with outer diameter of 63 mm and a surface roughness of 3.5 ⁇ m (Ra).
  • the distance of said magnetic brush towards said printhead structure was set to 400 ⁇ m. Printing examples with good quality could be obtained by this magnetic brush.
  • the magnetic field strength at the surface of said brush was smaller, but as the number of poles is much higher, no problem of carrier loss was observed.
  • a printhead structure was used, having 8 rows of printing apertures, each aperture having a diameter of 300 ⁇ m, and a copper electrode ring with a width of 200 ⁇ m. Each row of apertures was further separated from each other by an additional isolating zone of 200 ⁇ m.
  • As printhead substrate a 125 ⁇ m thick PI-foil was used.
  • the 8 rows of printing apertures were staggered to obtain an overall printing resolution of 39 dots per cm (100 dpi).
  • the extension of said array of printing apertures in said printhead structure was 6.30 mm.
  • the magnetic brush as described in example 7 was used. The magnetic brush was placed at 400 ⁇ m from said printhead structure.
  • example 9 the same experiment was performed as in example 8, but with the magnetic brush placed at 700 ⁇ m from said printhead structure.
  • the magnetic brush consisted of 15 magnetic poles divided over 60% of the perimeter of an internal drum on the side facing the apertured printhead, and had a sleeve with outer diameter of 42 mm and a surface roughness of 3.0 ⁇ m (Ra).
  • the distance of said magnetic brush towards said printhead structure was set to 500 ⁇ m.
  • Example R B C N/D M/N T E1 10.5 0.35 3.25 0.136 0.33 0.045 E2 10.5 0.50 3.25 0.136 0.33 0.045 CE1 10.5 0.35 4.55 0.136 0.33 0.045 E3 10.5 0.50 1.95 0.136 0.33 0.045 E4 10.5 0.35 0.40 0.136 0.33 0.045 E5 31.5 0.40 1.95 0.032 0.50 0.050 E6 31.5 0.40 4.55 0.032 0.50 0.050 CE2 31.5 0.40 4.55 0.015 0.33 0.040 E7 31.5 0.40 4.55 0.071 0.36 0.020 E8 31.5 0.40 6.30 0.071 0.36 0.020 E9 31.5 0.70 6.30 0.071 0.36 0.020 E10 21 0.50 4.55 0.114 0.40 0.100

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
  • Magnetic Brush Developing In Electrophotography (AREA)

Claims (9)

  1. Vorrichtung für elektronischen Direktdruck, die folgendes umfaßt:
    eine Rückelektrode (105) und
    eine Druckkopfkonstruktion (106), zwischen denen das aufnehmende Substrat (109) befördert wird,
    ein Array aus Drucköffnungen (107) in der Druckkopfkonstruktion (106), durch das ein Teilchenfluß von einer Steuerelektrode (106a) elektrisch moduliert werden kann,
    ein eine Magnetbürste (103) umfassendes Tonerzuliefermittel (101) mit Tonerteilchen und magnetisch anziehbaren Trägerteilchen, wobei die Referenzoberfläche der Magnetbürste in einem Abstand B in mm von der Vorderseite der Druckkopfkonstruktion (106b), die der Magnetbürste zugewandt ist, angeordnet ist, dadurch gekennzeichnet, daß
    (i) ein Magnetfeld über die Entfernung B gebildet wird
    (ii) die Magnetbürste in der Entwicklungszone eine Krümmung aufweist, die der Gleichung genügt R ≥ C2 4,25B + 0,25 wobei die Krümmung R der Magnetbürste in der Entwicklungszone als der Radius in mm eines Kreises ausgedrückt wird, der so am besten zu der Krümmung der Magnetbürste in der Entwicklungszone paßt, und C die Dehnung in mm des Arrays von Drucköffnungen (107) in Richtung der Bewegung des aufnehmenden Substrats (109) ist, gemessen von der Mitte der Öffnungen in der ersten Reihe bis zur Mitte der Öffnungen in der letzten Reihe.
  2. Vorrichtung nach Anspruch 1, bei der der Radius R der Gleichung II genügt: R ≥ C2 1,55B + 0,25
  3. Vorrichtung nach Anspruch 1, bei der der Radius R der Gleichung III genügt: R ≥ C2 0,30B + 0,25
  4. Vorrichtung nach einem der Ansprüche 1 bis 3, bei der die Magnetbürste durch die folgende Beziehung gekennzeichnet ist:
       N ≥ 0,02 D, wobei N die (auf die nächsthöhere ganze Zahl gerundete) Anzahl der Magnetpole in der Magnetbürste und D die Länge des Umfangs der Magnetbürste in mm bezeichnet.
  5. Vorrichtung nach einem der vorhergehenden Ansprüche, bei der die Anzahl M von Magnetpolen in demjenigen Viertel (113) des Umfangs des Kerns (103a) der Magnetbürste (103), dessen Mitte sich in der Mitte der Oberfläche (112) der Hülse (103b) der Magnetbürste in der Entwicklungszone (111) befindet, zu der Gesamtzahl N von in der Magnetbürste vorliegenden Magnetpolen in Beziehung steht durch M/N ≥ 0,3.
  6. Vorrichtung nach einem der vorhergehenden Ansprüche, bei der an der Oberfläche (112) der Magnetbürste ein Magnetfeld von mindestens 0,02 T vorliegt.
  7. Vorrichtung nach einem der vorhergehenden Ansprüche, bei der die Magnetbürste zylindrisch ist und einen Radius von R > 10 mm aufweist.
  8. Vorrichtung nach einem der vorhergehenden Ansprüche, bei der die Drucköffnungen (107) quadratisch sind.
  9. Vorrichtung nach einem der vorhergehenden Ansprüche, bei der die Tonerteilchen eine durchschnittliche Ladung |q| mit einem Absolutwert aufweisen, die der Gleichung: 1 fC ≤ |q| ≤ 20 fC genügt.
EP19950200556 1995-03-07 1995-03-07 Vorrichtung zum direkten elektrostatischen Drucken mit aus einer magnetischer Bürste und Druckkopf bestehende Struktur mit spezieller Geometrie Expired - Lifetime EP0731394B1 (de)

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Application Number Priority Date Filing Date Title
DE1995602927 DE69502927T2 (de) 1995-03-07 1995-03-07 Vorrichtung zum direkten elektrostatischen Drucken mit aus einer magnetischer Bürste und Druckkopf bestehende Struktur mit spezieller Geometrie
EP19950200556 EP0731394B1 (de) 1995-03-07 1995-03-07 Vorrichtung zum direkten elektrostatischen Drucken mit aus einer magnetischer Bürste und Druckkopf bestehende Struktur mit spezieller Geometrie
JP7953696A JPH0999577A (ja) 1995-03-07 1996-03-06 特別なジオメトリーを有するプリントヘッド構造及び磁気ブラシを含む直接静電印刷ｄｅｐのための装置

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Application Number Priority Date Filing Date Title
EP19950200556 EP0731394B1 (de) 1995-03-07 1995-03-07 Vorrichtung zum direkten elektrostatischen Drucken mit aus einer magnetischer Bürste und Druckkopf bestehende Struktur mit spezieller Geometrie

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EP0731394A1 EP0731394A1 (de) 1996-09-11
EP0731394B1 true EP0731394B1 (de) 1998-06-10

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EP19950200556 Expired - Lifetime EP0731394B1 (de) 1995-03-07 1995-03-07 Vorrichtung zum direkten elektrostatischen Drucken mit aus einer magnetischer Bürste und Druckkopf bestehende Struktur mit spezieller Geometrie

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EP (1) EP0731394B1 (de)
JP (1) JPH0999577A (de)
DE (1) DE69502927T2 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6102523A (en) * 1996-12-19 2000-08-15 Agfa-Gevaert Printer for large format printing using a direct electrostatic printing (DEP) engine
US6074112A (en) * 1996-12-19 2000-06-13 Agfa-Gevaert Printer for large format printing

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58100153A (ja) * 1981-12-10 1983-06-14 Canon Inc 画像記録装置
JPS60140279A (ja) * 1983-12-27 1985-07-25 Hitachi Ltd 画像記録装置
US5327169A (en) * 1992-08-05 1994-07-05 Xerox Corporation Masked magnetic brush direct writing for high speed and color printing

Also Published As

Publication number Publication date
DE69502927T2 (de) 1999-01-21
DE69502927D1 (de) 1998-07-16
EP0731394A1 (de) 1996-09-11
JPH0999577A (ja) 1997-04-15

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