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EP0963853B1 - Druckverfahren für eines Gerät zum direkten elektrostatischen Drucken, das eine Druckkopfanordnung erhaltet mit Ablenkelektroden und Mitteln zur elektrischen Steuerung dieser Ablenkelektroden - Google Patents

Druckverfahren für eines Gerät zum direkten elektrostatischen Drucken, das eine Druckkopfanordnung erhaltet mit Ablenkelektroden und Mitteln zur elektrischen Steuerung dieser Ablenkelektroden Download PDF

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Publication number
EP0963853B1
EP0963853B1 EP19990200480 EP99200480A EP0963853B1 EP 0963853 B1 EP0963853 B1 EP 0963853B1 EP 19990200480 EP19990200480 EP 19990200480 EP 99200480 A EP99200480 A EP 99200480A EP 0963853 B1 EP0963853 B1 EP 0963853B1
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EP
European Patent Office
Prior art keywords
printing
deflection electrodes
printhead structure
substrate
voltage
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EP19990200480
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English (en)
French (fr)
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EP0963853A1 (de
Inventor
Guido Desie
Hilbrand Van Den Wijngaert
François Backeljauw
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Agfa Gevaert NV
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Agfa Gevaert NV
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Priority to EP19990200480 priority Critical patent/EP0963853B1/de
Publication of EP0963853A1 publication Critical patent/EP0963853A1/de
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Publication of EP0963853B1 publication Critical patent/EP0963853B1/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/385—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material
    • B41J2/41—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material for electrostatic printing
    • B41J2/415—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material for electrostatic printing by passing charged particles through a hole or a slit
    • B41J2/4155—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material for electrostatic printing by passing charged particles through a hole or a slit for direct electrostatic printing [DEP]

Definitions

  • This invention relates to a recording method and an apparatus for use in the process of Direct Electrostatic Printing (DEP), in which an image is created upon a receiving substrate 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.
  • DEP Direct Electrostatic Printing
  • toner particles are deposited directly in an image-wise way on a receiving substrate, the latter not bearing any image-wise latent electrostatic image.
  • 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 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 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.
  • US-A-4 860 036 e.g. a printhead structure with at least 3 rows of printing apertures is disclosed in order to diminish the white zone between neighbouring printing apertures.
  • a DEP device having a printhead structure that comprises an insulating material with apertures and control electrodes, and extra apertures in between two of said neighbouring control electrodes.
  • a printhead structure lower density banding in the print direction is impossible.
  • the construction of said slit-printhead structure is not that easy.
  • a DEP device comprising a printhead structure, an ultrasonic vibration means, an image information generating means and a toner deflecting means.
  • Said toner deflecting means is a set of deflection electrodes (isolated from said control electrodes) positioned in between said image receptive member and said printhead structure. Between said two sets of deflection electrodes a varying electrical field is applied resulting to deformation of said toner flux towards said image receptive member.
  • said varying electrical field can be a pulsed voltage, a stepwise voltage as well as a saw-tooth voltage.
  • the printhead structure is rather complex since it comprises (if it is formed in a PCB-layout) three different conductor layers that have to be isolated from each other. If a simple printhead structure is used with only two planes with electrodes, a further set of deflection electrodes is placed between the printhead structure and the substrate to be printed.
  • a DEP device which comprises a layer of control electrodes in a control grid, a toner flying stabilisation grid and a set of deflection electrodes that can position a dot on the final receiver on one of different possible positions.
  • a DEP device and a method of printing have been described comprising at least a set of deflection electrodes and a controller for said deflection electrodes so that through one printing aperture three dots can be printed, in a straight, a left and a right position.
  • the number of control electrodes is lower than the addressability of the device. I.e. there are less control electrodes than dots printed.
  • This implementation can enhance the resolution of the printhead structure or diminish the complexity by reducing the number of control IC's that are essential for providing the image variation, but by using said deflection electrodes on a time-based scale to print three different dots on the receiving material in consecutive order, the maximum attainable printing speed is diminished by a factor of at least 3.
  • a DEP device and a method of printing have been described comprising at least a set of deflection electrodes and a controller for said deflection electrodes. On the control electrodes a changing voltage is applied with a period equal to the line time.
  • It is an object of the invention is to provide a DEP device, i.e. a device for direct electrostatic printing that can print at high speed with low clogging of the printing apertures and with high and constant maximum density with almost no white stripes parallel to the printing direction even in low density areas. It is an other object of the invention to provide a method for direct electrostatic printing with dry toner particles making it possible to print patches of even density with very low unevenness and almost no white striping parallel to the printing direction even in low density areas. Further objects and advantages of the invention will become clear from the detailed description herein after.
  • the first object of the invention is realised by providing a device for direct electrostatic printing with an addressability, AD, in dots per cm, comprising
  • Figure la shows schematically the first face of a first possible embodiment of a printhead structure useful in a method for Direct Electrostatic Printing and in a DEP device according to of the present invention.
  • Figure 1b shows schematically the second face of a first possible embodiment of a printhead structure useful in a method for Direct Electrostatic Printing and in a DEP device according to of the present invention.
  • Figure 1c shows a cross section through a row of printing apertures in a printhead structure according said first possible embodiment of this invention.
  • Figure 2a shows schematically the first face of a second possible embodiment of a printhead structure useful in a method for Direct Electrostatic Printing and in a DEP device according to of the present invention.
  • Figure 2b shows schematically the second face of a second possible embodiment of a printhead structure useful in a method for Direct Electrostatic Printing and in a DEP device according to of the present invention.
  • Figure 2c shows a cross section through a row of printing apertures in a printhead structure according said first possible embodiment of this invention.
  • Figure 3 shows a DEP device comprising a printhead structure according to the first possible embodiment of a printhead structure useful in a method for Direct Electrostatic Printing and in a DEP device according to of the present invention.
  • Line time the time for printing one pixel dot.
  • maximum density is achieved in that one pixel dot.
  • the line time, LT is 8 ms.
  • WRT Write time
  • Addressability the number of dots printed per unit of length (25.4 dots per inch (dpi) equal 1 dot per cm) that are addressed.
  • a DEP device having a number of control electrodes equal to the addressability have one control electrode for each dot to be addressed.
  • One dot can be written via one printing aperture controlled by one control electrode or by more than one printing aperture when these printing apertures are controlled by one control electrode. The latter system has been described in detail in e.g. EP-A-754 557.
  • Printing element In this document, one or more printing apertures together with the part of a single control electrode near to that printing aperture(s) is designated by the wording "printing element". E.g., referring to figure la of this text, printing aperture 107 and conductor C1 of control electrode 106a together form a printing element 116.
  • Adjacent printing elements are printing elements that are adjacent in a row of printing elements. These can, but must not, be printing elements arranged in the printhead structure to print adjacent dots on the image receiving member.
  • toner particles are moved in a continuous flow in an electric field from a surface bearing toner particles to a substrate and a printhead structure with printing apertures associated with control electrode is positioned in that flow.
  • a printhead structure with printing apertures associated with control electrode is positioned in that flow.
  • a printhead structure is provided on an insulating material with printing apertures through said insulating material and control electrodes in one plane (e.g. on one face of the insulating material) associated with printing apertures and by providing further electrodes in the vicinity of the printing apertures in the same plane.
  • These further electrodes are, in US-A-5,774,159, equipped to be coupled to a voltage source for providing a varying voltage with a frequency, f, so that f x LT is exactly 1.00.
  • LT when the varying voltage is applied to the deflection electrodes, the flow of toner particles through the printing aperture moves from one side to the other side of said printing aperture in a direction perpendicular to the printing direction.
  • the teachings of this disclosure do make it possible to avoid the occurrence of white stripes in the higher density regions, but as shown in figure 10 of that disclosure, in the lower density areas the white stripes are not avoided.
  • the voltage source coupled to the deflection electrodes provided a varying voltage with a frequency, f, so that f x LT > 1.00 to the deflection electrodes, the occurrence of white stripes in lower densities could also be diminished and even avoided.
  • the voltage source coupled to the deflection electrodes provides these electrodes with a varying voltage with a frequency, f, so hat f x LT ⁇ 2.00. Even more preferably the frequency is chosen so that f x LT ⁇ 4.00.
  • the frequency, f, of said varying voltage is equal to or larger than 125 Hz.
  • a printhead structure for use in a DEP device according to this invention has preferably a number of printing elements per cm that is equal to the addressability, AD of the printer.
  • a printhead structure for use in a DEP device incorporates preferably at least two sets of deflection electrodes, more preferably it incorporates exactly two sets of deflection electrodes.
  • the at least two, or exactly two, sets of deflection electrodes are preferably arranged so as to have, near two adjacent printing elements , at least two deflection electrodes from different sets. More preferably, in a printhead structure of this invention, two sets of deflection electrodes are arranged so as to have two deflection electrodes from different sets extending to or passing between two adjacent printing elements .
  • a printhead structure according be used in a DEP device of the present invention can be implemented by providing on an insulating material, with a first and a second face, control electrodes on said first face associated with printing apertures and by providing further deflection electrodes in the vicinity of the printing elements on the same first face.
  • a printhead structure comprises a sheet of insulating material having a first and a second face and printing apertures through said insulating material and control electrodes associated with said printing apertures on said first face, and at least two sets of deflection electrodes on said second face of said insulating material near to said printing apertures, so that said printhead structure contains two planes with electrodes.
  • the printhead structure can comprise two sets of deflection electrodes arranged in such a way that the deflection electrodes are symmetrically positioned (i.e. the centre of each printing element is located in the middle of the deflection electrodes belonging to each set) with respect to the printing apertures.
  • a printhead structure according to this invention is implemented with the control electrodes on a first face of the insulating material and at least two sets of deflection electrodes on the other side, it is advantageous to provide deflection electrodes with a thickness between 5 and 200 ⁇ m, even more advantageous to provide deflection electrodes with a thickness between 10 and 100 ⁇ m, both limits included.
  • FIG. la 1b and 1c the first and second face of a first embodiment of a printhead structure according to this invention is shown.
  • the printhead structure comprises an insulating material and conductors in only two planes.
  • Figure la shows the control electrodes (106a) on the first face of the insulating material, rectangular printing apertures (107) with three conductors, C1 around the apertures, C2 coupled to a voltage source (DC3) that in accordance with image-data changes the electric field in the printing aperture and a conductor C3, the conductor C1 and the printing aperture 107 associated with each of them, form printing element (116).
  • a printhead structure with such a configuration of the control electrodes has been described in European Application 97204014, filed on December 18, 1997.
  • Figure 1b shows the second face of the insulating material (106c) with a shield electrode is shown in a form so as to be useful as deflection electrode (further on such shield electrode will be termed 'deflection electrode').
  • 'deflection electrode' shows two sets of deflection electrodes, each of said sets formed as a comb.
  • the first set looks like first comb (106b1), the teeth of which extend to the row of printing elements (116) and the second set as a second comb (106b2), the teeth of which extend also to the row of printing elements.
  • the teeth of the comb are basically parallel with the printing direction.
  • the teeth of the first comb alternate with the teeth of the second comb, and on one side of each printing element (a side basically perpendicular to the printing direction extending to conductor C2) a tooth of the first comb is present and on the other side a tooth of the second comb.
  • two deflection electrodes, one of each set are present between two adjacent printing elements.
  • only one deflection electrode can be present, within the rows, two deflection electrodes, one of each set, are present between two adjacent printing apertures.
  • the centre of each printing aperture which coincides in this embodiment with the centre of the printing element, is located in the middle between the tooth of the first comb and the tooth of the second comb surrounding it.
  • the first comb is coupled to a voltage source (AC5) for providing a varying voltage on said first set of deflection electrodes (i.e. said first comb) and the second comb to a voltage source (AC5) for providing a varying voltage on said second set of deflection electrodes (i.e. said second comb).
  • a cross-section through the printing apertures and the electrodes is shown.
  • On one face of the insulating material control electrodes (106a) are present around each of the printing apertures (107)on the other face deflection electrodes are present between two printing apertures two deflection electrodes are present, one (106b1)of the first set and one (106b2) of the second set.
  • an alternating unit consisting of an aperture (107), deflection electrode one (106b1) and deflection electrode two (106b2) is present.
  • the teeth of the first comb alternate with the teeth of the second comb, this is not necessary so, a printhead structure wherein these teeth do not alternate regularly is within the scope of this invention as long as between two printing apertures at least two deflection electrodes from different sets are present.
  • a printhead structure according to a second implementation of the first embodiment of the present invention, is shown.
  • the printhead structure is construed as the one shown in figures la, 1b and lc, except that now two parallel rows of staggered printing elements are present each of them coupled to a voltage source (DC3) that in accordance with image-data changes the electric field in the printing aperture on the first side of the insulating material as shown in figure 2a.
  • DC3 voltage source
  • two sets of deflection electrodes 106b1, 106b2 are formed on the second side of the insulating material (106c) in the form of two combs the teeth of which are not rectilinear.
  • each printing element is located in the middle between the tooth of the first comb and the tooth of the second comb surrounding it.
  • figure 2c a cross-section through the printing apertures and the electrodes on one row is shown.
  • On one face of the insulating material control electrodes (106a) are present around each of the printing apertures (107) on the other face deflection electrodes are present between two printing apertures two deflection electrodes are present, one (106b1) of the first set and one (106b2) of the second set.
  • an alternating unit consisting of an aperture (107), deflection electrode one (106b1) and deflection electrode two (106b2) is present.
  • the insulating material, used for producing a printhead structure, according to the present invention can be glass, ceramic, plastic, etc.
  • said insulating material is a plastic material, and can be a polyimide, a polyester (e.g. polyethylelene terephthalate, polyethylene naphthalate, etc.), polyolefines, an epoxy resin, an organosilicon resin, rubber, etc.
  • Insulating material useful in the present invention, has an elasticity modulus between 0.1 and 10 GPa, both limits included, preferably between 2 and 8 GPa and most preferably between 4 and 6 Gpa.
  • the insulating material has a thickness between 25 and 1000 ⁇ m, preferably between 50 and 200 ⁇ m.
  • the voltage source coupled to the deflection electrodes provides varying voltages varying on a time scale and thus the toner flux passing an aperture is, during the line time moved from left to right so that an elliptic dot would be formed through a circular-shaped aperture, said long side of said elliptic dot being positioned essentially perpendicular to said printing direction.
  • the voltage source for providing the varying voltage, that is coupled to the deflection electrodes may be equipped to provide a varying voltage with different shapes.
  • Various shapes of varying voltage signals can be used in the present invention: e.g. pulsed signals, stepwise signals, saw-tooth signals, sinusoidal signals , etc., as long as the signal has a frequency, f, fulfilling one of the conditions above.
  • the varying voltage is preferably synchronous with the line time, i.e. the application of the varying voltage to the sets of deflection electrodes starts when the printing starts, i.e. at the beginning of the line time, and ends when the printing ends, i.e. at the end of the line time.
  • the product f x LT is preferably chosen so that it is an integer value.
  • said product of f x LT should not be too close to an integer value because otherwise moiré effect at a low (i.e. visible) frequency can occur.
  • each set of deflection electrodes is coupled to a voltage source that applies a varying voltage to said set of deflection electrodes, i.e. set one is coupled to a voltage source providing a varying voltage, AC5 and the second set to a voltage source providing a varying voltage, AC6.
  • the frequencies and the peak-to-peak voltage of ACS and AC6 are equal.
  • the voltage signals, AC5 and AC6 are 180 ° out of phase so that the peak-to-peak voltage is in this case the sum of the peak-to-peak voltages of both signals, then the effect on the avoidance of lower density banding in the print direction is maximised.
  • the sum of the peak-to-peak voltages of AC5 and AC6 i.e. AC5 + AC6 is equal to or larger than 300 V.
  • a printhead structure having at least two sets of deflection electrodes and the coupling of those deflection electrodes can be used in any DEP device known in the art, e.g. in devices as described in EP-A-795 802, EP-A-780 740, EP-A-740 224, EP-A-731 394, EP-A-712 055, US-A-5 606 402, US-A-5 523 777, GB-A-2 108 432, US-A-4 743 926. It can also be used in a method for direct electrostatic printing operating without back electrode, as disclosed in EP-A-823 676. Also in a method and device for direct electrostatic printing wherein the toner bearing surface is the sleeve of a magnetic brush with a rotating core, as described in EP-A-827 046 a printhead structure according to this invention can be useful.
  • the invention thus includes a device for direct electrostatic printing with an addressability, AD, in dots per cm, comprising
  • two sets of deflection electrodes are arranged in said printhead structure so as to have two deflection electrodes from different sets extending or passing between two adjacent printing elements .
  • Said means for coupling an image receiving substrate (108) to a second electric potential (DC4) can be a back electrode placed directly behind the image receiving substrate. In this case, the substrate can be in contact with the back electrode or so close to the back electrode that both the back electrode and the image receiving substrate assume essentially the same electric potential.
  • Said means for coupling an image receiving substrate (108) to a second electric potential (DC4) can also be a conductive layer present, on the image receiving substrate, that is coupled to a voltage source.
  • Such DEP devices and methods have been described in e.g. EP-A-823 676 or European Application 98201302 filed on April 22 1998.
  • the DEP device shown comprises means for delivering toner particles with a container (101) for non magnetic mono component developer, a roller (112) having a surface on which toner particles are applied by means of a feeding roller (111) made of porous foamed polymers, a developer mixing blade (114) mixing and transporting said non-magnetic mono-component developer towards said feeding roller, a doctor blade (113) regulating the thickness of the charged toner particles upon the surface of said roller (112), i.e. on the toner bearing surface.
  • Said roller (112) bearing said charged toner particles rotates in a direction depicted by arrow B.
  • a device for applying a DC voltage is connected to the sleeve of said roller (112) and applies voltage DC1 to said sleeve and a device for applying an AC-field is connected to the sleeve of said roller and applies AC-field AC1 to said sleeve (the toner bearing surface).
  • the device further comprises a back electrode (105) connected to a DC voltage source applying a voltage DC4 to the electrode.
  • An image receiving substrate (108) is passed by means for moving (115) the substrate in the direction of arrow A between a printhead structure according to this invention and the back electrode by conveying means (115).
  • the difference between DC4 and DC1 applies a DC propulsion field wherein a flow of toner particles (104) is created from the sleeve of the roller bearing charged toner particles to the image receiving substrate on the back electrode.
  • the AC-field - AC1 - on the sleeve of the toner roller (112) makes the flow (104)of toner particles denser than when no AC-field would be present.
  • a printhead structure (106) is placed in said flow (104) of toner particles, said printhead structure having an insulating material (106c) carrying control electrodes (106a) and deflection electrodes (106b1 and 106b2).
  • a DC-source (DC3) is connected to the control electrodes and the voltage applied by this DC-source is image-wise modulated in order to modulate the toner flow image wise in the vicinity of the control electrodes.
  • the voltage (V3) applied by the DC source, DC3, can be varied between a value totally blocking the passage of the toner particles, and a value leaving the toner flow pass totally unimpeded.
  • the control electrodes in said printhead structure are placed at a distance, d, in ⁇ m from the toner bearing surface, a spacer (110) keeps the distance d constant during operation of the device.
  • the printhead structure (106) is placed at a distance, d B , form the image receiving member.
  • the device comprises further means (109) for fixing the toner particles to the image receiving substrate.
  • the distance d B is calculated from the surface of the printhead structure to the surface of the imaging member.
  • the back electrode (105) of a DEP device can also be made to cooperate with the printhead structure according to this invention, 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-A- 4, 568 ,955 and US-A-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 present invention incorporates also a method for Direct Electrostatic Printing using a DEP device incorporating a printhead structure according to this invention. It thus includes a method for direct electrostatic printing with an addressability AD in dots per cm, on an image receiving substrate comprising the steps of :
  • Preferably said frequency, f, is chosen so that f x LT ⁇ 2.00 and more preferably so that f x LT ⁇ 4.00.
  • a printhead structure for use in a DEP device according to this invention has preferably a number of printing elements per cm that is equal to the addressability, AD of the printer.
  • a printhead structure used in the method according to this invention incorporates preferably at least two sets of deflection electrodes, more preferably it incorporates two sets of deflection electrodes.
  • the at least two, or exactly two, sets of deflection electrode are preferably arranged so as to have, near two adjacent printing elements , at least two deflection electrodes from different sets. More preferably, in a printhead structure of this invention, two sets of deflection electrodes are arranged so as to have two deflection electrodes from different sets extending or passing between two adjacent printing elements .
  • the time of application of the potentials by voltage source DC3 may be image-wise modulated while applying a constant potential (i.e. time modulation of the image signal or pulse-width-modulation),or the potential itself may be image-wise modulation at a constant line-time (amplitude modulation) or the amplitude modulation can be combined with a time modulation, the latter combination allowing for the printing of a large number of grey levels.
  • a constant potential i.e. time modulation of the image signal or pulse-width-modulation
  • the potential itself may be image-wise modulation at a constant line-time (amplitude modulation) or the amplitude modulation can be combined with a time modulation, the latter combination allowing for the printing of a large number of grey levels.
  • WRT write time
  • the write time (WRT) for low density areas is smaller than the total line time (LT).
  • the line time (LT) is divided into several smaller time units (called sublines (SL).
  • V 30 voltage allowing maximum density to be printed
  • V3n blocking voltage giving minimum density
  • the printing aperture is kept closed (a closing potential is applied to the printing element) during the first 4 ms of the line time, then the printing aperture is opened (an opening potential is applied to the printing element) for 2 ms and is closed for the remaining 4 ms of the line time.
  • the combination of the method of this invention with the method of EP-A-851 316 is performed by not positioning the write time, when it is smaller than the line time, for every pixel and line at a fixed position within the total line time, but by have it randomly positioned within the line time.
  • the step of sending a print signal for image-wise applying electric potentials to said printing elements can be performed by sending a print signal within a line time, to said printing elements, said print signal comprising elements necessitating a write time shorter than said line time, and by positioning said write time, shorter than said line time, randomly over said line time.
  • said write time, shorter than said line time is divided in portions and said print signal is adapted to send said portion in a random way during said line time.
  • the printing quality especially with respect to the lower density was visually evaluated on a scale from 1 to 10, wherein 1 is bad, 5 is acceptable and 10 is very good.
  • the line time LT was set to 8 ms and when two sets of deflection electrodes were present each of said sets was coupled to a voltage source delivering a varying voltage both voltages (AC5 and AC6) having the same frequency and being out of phase by 180 ° so that the peak voltage applied to the deflection electrodes, Vp, equals AC5 + AC6.
  • the printhead structure The printhead structure.
  • a printhead structure (106) was made from a polyimide film of 50 ⁇ m thickness (106c), double sided coated with a 5 ⁇ m thick copper film.
  • the printhead structure (106) had one row of printing apertures.
  • Each of said control electrodes had conductive paths in a direction parallel to the printing direction over 10 mm and was connected over 2 MQ resistors to a HV 507 (trade name) high voltage switching IC, commercially available through Supertex, USA, that was powered from a high voltage power amplifier.
  • the printing apertures were rectangular shaped with dimensions of 200 by 100 ⁇ m.
  • the dimension of the central part (C1) of the rectangular shaped copper control electrodes was 320 by 300 ⁇ m, the line width of the extending segments was 100 ⁇ m.
  • the apertures were spaced at a 500 ⁇ m pitch.
  • a double set of deflection electrodes (106b1 and 106b2) was arranged in between each set of neighbouring apertures.
  • Said deflection electrodes had a line width of 70 ⁇ m and were isolated from each other by a free zone of 70 ⁇ m. The centre of said free zone was located in the middle between two neighbouring printing apertures so that both sets of deflection electrodes were available in a symmetrical order with respect to the printing apertures.
  • Said printhead structure was fabricated in the following way. First of all the control electrode pattern and deflection electrode pattern was etched by conventional copper etching techniques. The apertures were made by a step and repeat focused excimer laser 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, commercially available from Griffin Chemie, was applied over the control electrode and deflection electrode side of said printhead structure.
  • the toner delivery means The toner delivery means
  • the toner delivery means was a commercially available toner cartridge comprising non magnetic mono component developer, the COLOR LASER TONER CARTRIDGE MAGENTA (M3760GIA), for the COLOR LASER WRITER (Trade names of Apple Computer, USA).
  • the toner bearing surface is the surface of an aluminium roller (112), whereon tone particles are applied by a feeding roller (111) The toner particles carried a negative charge.
  • the printhead structure mounted in a PVC-frame, was bent with frictional contact over the surface of the roller of the toner delivery means.
  • a 50 ⁇ m (this is distance d) thick polyurethane coating was used as self-regulating spacer means (110).
  • a back electrode was present behind the paper whereon the printing proceeded, the distance between the back electrode (105) and the back side of the printhead structure (d B ) was set to 1000 ⁇ m and the paper travelled at 300 cm/min.
  • the back electrode was connected to a high voltage power supply, applying a voltage DC4 of + 1000 V to the back electrode.
  • a sinusoidally changing AC voltage AC1 with 400 V peak to peak and a frequency of 3 kHz was applied and a DC-offset (DC1) of -50 V.
  • the DC-propulsion field i.e. the potential difference between DC4 and DC1, was 1050 V.
  • an (image-wise-selected) voltage was applied selected from 0 V (printing a pixel of maximum density) or -280 V (printing a pixel of minimum density).
  • a sinusoidally changing AC voltage (AC5) with 250 V peak to peak and a frequency of 500 Hz was applied
  • AC6 sinusoidally changing AC voltage
  • Said frequency was adjusted so that it was synchronised with said first AC-voltage applied to said first set of deflection electrodes but 180° out of phase: i.e. the voltage applied to said first set of deflection electrodes gained a maximum value (.e.g. +250 V) at the moment that the voltage applied tot said second set of deflection electrodes gained a minimum value (e.g. -250V) was applied.
  • the maximum peak voltage difference between on the sets of deflection electrodes was 500 V, this is Vp.
  • Grey scale images of a human face and control wedges from maximum to minimum density were printed during several minutes after which the image quality was observed in terms of lower density stripes in the printing direction in regions of higher image density.
  • the results of the evaluation of the printing quality are given in table 1.
  • deflection electrodes in different layers (multilayer structure) and enhancing the deflection voltage in ratio proportional to the isolation power. It is also possible to combine the concept of deflection electrodes with other concepts for elimination of lower density stripes as multiple printhead structures, multiple apertures per control electrode, multipass printing, sliding contact between the toner particle source and the printhead structure, etc..

Landscapes

  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)

Claims (14)

  1. Einrichtung für den elektrostatischen Direktdruck mit einer Adressierbarkeit AD in Punkten pro cm, die folgendes umfaßt:
    ein Mittel zum Zuliefern von geladenen Tonerteilchen, wobei das Mittel eine Tonerteilchen tragende Oberfläche (112) aufweist, die an ein Mittel zum Anlegen eines ersten elektrischen Potentials (DC1) an die Oberfläche angekoppelt ist,
    ein Mittel zum Ankoppeln eines bildaufnehmenden Substrats (108) an ein von dem ersten unterschiedliches zweites elektrisches Potential (DC4), wobei die elektrische Potentialdifferenz (|DC4-DC1|) zwischen der Oberfläche und dem Substrat ein elektrisches Feld PF erzeugt, wobei ein Strom der geladenen Tonerteilchen (104) zu dem Substrat erzeugt wird,
    ein Mittel (115) zum Bewegen des Substrats in einer Druckrichtung (Pfeil A), um eine Zeilenzeit LT zu erhalten,
    eine Druckkopfkonstruktion (106), die zwischen der tonertragenden Oberfläche (112) und dem bildaufnehmenden Substrat (108) plaziert wurde, wobei zwischen der tonertragenden Oberfläche und der Druckkopfkonstruktion ein Spalt d bleibt und zwischen der Druckkopfkonstruktion und dem bildaufnehmenden Substrat ein Spalt dB bleibt,
    wobei die Druckkopfkonstruktion folgendes aufweist:
       eine Folie aus isolierendem Material (106c) mit einer ersten und einer zweiten Seite, eine Anzahl von Druckelementen (116), die mindestens eine Reihe auf dem Substrat bilden, wobei jedes der Druckelemente mindestens eine Drucköffnung (107) durch das isolierende Substrat enthält, und mindestens zwei Sätze von Ablenkelektroden (106b1, 106b2)
    eine Spannungsquelle DC3, die an die Druckelemente angekoppelt ist, zum bildmäßigen Anlegen von elektrischen Potentialen (V3) an die Druckelemente zum gezielten Öffnen und Schließen der Drucköffnungen gemäß Bilddaten und
    eine an jede der mindestens zwei Sätze von Ablenkelektroden angekoppelte Spannungsquelle zum Anlegen einer veränderlichen Spannung (AC5, AC6) mit einer Frequenz f, so daß f x LT > 1,00, an die Ablenkelektroden.
  2. Einrichtung nach Anspruch 1, dadurch gekennzeichnet, daß zwei Sätze von Ablenkelektroden in der Druckkopfkonstruktion vorliegen und derart in der Druckkopfkonstruktion angeordnet werden, daß sich mindestens zwei Ablenkelektroden unterschiedlicher Sätze zwischen zwei benachbarten Druckelementen befinden.
  3. Einrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß Steuerelektroden auf der ersten Seite des isolierenden Materials in der Druckkopfkonstruktion vorliegen und die Sätze von Ablenkelektroden auf der zweiten Seite des isolierenden Materials vorliegen.
  4. Einrichtung nach Anspruch 3, dadurch gekennzeichnet, daß die Ablenkelektroden eine Stärke zwischen 1 und 200 µm aufweisen.
  5. Einrichtung nach Anspruch 3, dadurch gekennzeichnet, daß die Ablenkelektroden eine Stärke zwischen 5 und 200 µm aufweisen.
  6. Einrichtung nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die an die Ablenkelektroden angekoppelte Spannungsquelle eine veränderliche Spannung (AC5, AC6) mit einer Frequenz f anlegt, so daß f x LT > 2,00.
  7. Einrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die an die Ablenkelektroden angekoppelte Spannungsquelle dafür ausgestattet wurde, eine veränderliche Spannung mit einem Spitze-Spitze-Spannungswert gleich groß wie oder größer als 300 V zu liefern.
  8. Einrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Entfernung dB in einem Verhältnis R1 zu der elektrischen Potentialdifferenz (|DC4-DC1|) in Beziehung steht, so daß
    (|DC4-DC1|)/dB ≤ 1,5 V/µm.
  9. Einrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Ablenkelektroden an eine Spannungsquelle angekoppelt werden, die dafür ausgestattet wurde, den Ablenkelektroden eine veränderliche Spannung mit einer Spitze-Spitze-Spannung Vp zu liefern, so daß Vp/R1 > 250 µm.
  10. Verfahren für den elektrostatischen Direktdruck mit einer Adressierbarkeit AD in Punkten pro cm auf einem bildaufnehmenden Substrat, wobei das Verfahren die folgenden Schritte umfaßt :
    das Anlegen einer elektrischen Potentialdifferenz (|DC4-DC1|) zwischen einer geladene Tonerteilchen tragenden Oberfläche und dem bildaufnehmenden Substrat, um einen Strom geladener Tonerteilchen von dieser Oberfläche zu dem Substrat zu erzeugen,
    das Plazieren, in dem Strom geladener Tonerteilchen, einer Druckkopfkonstruktion, die folgendes aufweist:
    ein isolierendes Substrat (106c) mit einer ersten und einer zweiten Seite und
    eine Anzahl von Druckelementen (116), die mindestens eine Reihe von Druckelementen auf dem Substrat bilden, wobei jedes der Druckelemente mindestens eine Drucköffnung (107) durch das isolierende Substrat enthält, und mindestens zwei Sätze von Ablenkelektroden (106b1, 106b2)
    das Bewegen des Substrats der Druckkopfkonstruktion gegenüber in einer Druckrichtung A, so daß eine Zeilenzeit von LT erhalten wird,
    das Senden eines Drucksignals zu einer Spannungsquelle DC3 zum bildmäßigen Anlegen von elektrischen Potentialen (V3) an die Druckelemente zum gezielten Öffnen und Schließen der Drucköffnungen gemäß Bilddaten und
    das Ankoppeln der Ablenkelektroden an eine Spannungsquelle zum Anlegen einer veränderlichen Spannung (AC5, AC6) mit einer Frequenz f, so daß f x LT > 1,00, an die Ablenkelektroden.
  11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß die Frequenz f so gewählt wird, daß f x LT ≥ 2,00.
  12. Verfahren nach Anspruch 10 oder 11, dadurch gekennzeichnet, daß vor dem Senden eines Drucksignals für jede zu druckende Zeile ein Druckelement, das eine kürzeste Schreibzeit WRTkurz aller Druckelemente in dieser Zeile erfordert, ermittelt wird, und dadurch, daß die Frequenz f so gewählt wird, daß
    1,00/ WRTkurz ≤ f ≤ 4000 Hz.
  13. Verfahren nach einem der Ansprüche 10 bis 12, dadurch gekennzeichnet, daß der Schritt, wobei ein Drucksignal zum bildmäßigen Anlegen elektrischer Potentiale an die Druckelemente gesandt wird, durchgeführt wird, indem innerhalb einer Zeilenzeit ein Drucksignal gesandt wird, wobei das Drucksignal Bildelementpunkte enthält, die eine Schreibzeit erfordern, die kürzer ist als die Zeilenzeit, und indem die Schreibzeit, die kürzer ist als die Zeilenzeit, regellos über die Zeilenzeit positioniert wird.
  14. Verfahren nach Anspruch 13, dadurch gekennzeichnet, daß vor dem Senden des Drucksignals die Schreibzeit, die kürzer ist als die Zeilenzeit, in Anteile aufgeteilt wird, und dadurch, daß das Drucksignal dafür angepaßt ist, den Anteil auf eine regellose Weise während der Zeilenzeit zu senden.
EP19990200480 1998-06-09 1999-02-18 Druckverfahren für eines Gerät zum direkten elektrostatischen Drucken, das eine Druckkopfanordnung erhaltet mit Ablenkelektroden und Mitteln zur elektrischen Steuerung dieser Ablenkelektroden Expired - Lifetime EP0963853B1 (de)

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EP98201965 1998-06-09
EP98201965 1998-06-09
EP19990200480 EP0963853B1 (de) 1998-06-09 1999-02-18 Druckverfahren für eines Gerät zum direkten elektrostatischen Drucken, das eine Druckkopfanordnung erhaltet mit Ablenkelektroden und Mitteln zur elektrischen Steuerung dieser Ablenkelektroden

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WO2001076880A1 (en) * 2000-04-07 2001-10-18 Array Ab Direct printing device and method

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3689935A (en) 1969-10-06 1972-09-05 Electroprint Inc Electrostatic line printer
US4860036A (en) 1988-07-29 1989-08-22 Xerox Corporation Direct electrostatic printer (DEP) and printhead structure therefor
JP2520500B2 (ja) * 1990-05-30 1996-07-31 三田工業株式会社 画像形成装置
JP3271816B2 (ja) 1993-03-09 2002-04-08 ブラザー工業株式会社 画像形成装置
JPH0740579A (ja) 1993-07-28 1995-02-10 Brother Ind Ltd 画像形成装置
US5606402A (en) * 1993-12-27 1997-02-25 Sharp Kabushiki Kaisha Electrostatic image former with improved toner control grid
JPH07304206A (ja) 1994-05-16 1995-11-21 Brother Ind Ltd 画像形成装置
SE503634C2 (sv) 1994-09-19 1996-07-22 Array Printers Ab Metod och anordning i en skrivare
DE69600779T2 (de) 1995-07-18 1999-05-27 Agfa-Gevaert N.V., Mortsel Druckkopfstruktur zur Verwendung in einem direkten elektrostatischen Druckgerät (DEP)
DE69522948T2 (de) 1995-12-18 2002-04-25 Agfa-Gevaert N.V., Mortsel Vorrichtung zum direkten elektrostatischen Drucken mit einer Druckkopfstruktur mit Schlitzöffnungen
US5847733A (en) * 1996-03-22 1998-12-08 Array Printers Ab Publ. Apparatus and method for increasing the coverage area of a control electrode during direct electrostatic printing
US5774159A (en) * 1996-09-13 1998-06-30 Array Printers Ab Direct printing method utilizing continuous deflection and a device for accomplishing the method

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