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WO2001049500A1 - Dispositif et procede d'impression directe - Google Patents

Dispositif et procede d'impression directe Download PDF

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Publication number
WO2001049500A1
WO2001049500A1 PCT/SE2000/000010 SE0000010W WO0149500A1 WO 2001049500 A1 WO2001049500 A1 WO 2001049500A1 SE 0000010 W SE0000010 W SE 0000010W WO 0149500 A1 WO0149500 A1 WO 0149500A1
Authority
WO
WIPO (PCT)
Prior art keywords
apertures
printhead structure
toner particles
forming apparatus
image
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.)
Ceased
Application number
PCT/SE2000/000010
Other languages
English (en)
Inventor
Agneta Sandberg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Holdings Corp
Array Printers AB
Original Assignee
Matsushita Electric Industrial Co Ltd
Array Printers AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Matsushita Electric Industrial Co Ltd, Array Printers AB filed Critical Matsushita Electric Industrial Co Ltd
Priority to AU29519/00A priority Critical patent/AU2951900A/en
Priority to PCT/SE2000/000010 priority patent/WO2001049500A1/fr
Publication of WO2001049500A1 publication Critical patent/WO2001049500A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • 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]
    • 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

  • the invention relates to an image forming apparatus in which image information is converted into a pattern of electrostatic fields for modulating a transport of charged toner particles from a particle carrier toward a back electrode member.
  • the image forming apparatus includes a background voltage source for producing a background electric field which enables a transport of charged toner particles from said particle carrier towards said back electrode member, a printhead structure arranged in said background electric field, including a plurality of apertures and control electrodes arranged in conjunction to the apertures, said apertures being positioned along at least one row thereby defining a plurality of intermediate areas which are positioned between each two adjacent apertures.
  • the image forming apparatus also includes control voltage sources for supplying control potentials to said control electrodes in accordance with the image information to selectively permit or restrict the transport of charged toner particles from the particle carrier through the apertures, and an image receiving member caused to move in relation to the printhead structure for intercepting the transported charged particles in image configuration. Furthermore, the invention relates to a printhead structure for use in an image forming apparatus of the above-mentioned kind, and a method for manufacturing such a printhead structure.
  • U.S. Patent No. 5,036,341 discloses a direct electro- static printing device and a method to produce text and pictures with toner particles on an image receiving substrate directly from computer generated signals.
  • Such a device generally includes a printhead structure provided with a plurality of apertures through which toner particles are selectively transported from a particle source to an image receiving medium due to control in accordance with image information.
  • the apertures are normally arranged along two or more parallel rows extending generally perpendicular to the direction of travel of said image receiving member, i.e. at a right angle to the direction of motion of the image receiving medium.
  • a plurality of intermediate areas are defined in between each pair of two adjacent aperture in each row.
  • said rows are normally arranged slightly displaced in relation to each other (as seen in the direction along which said rows extend) .
  • the apertures in a first row will be aligned with the intermediate areas in the second row, and vice versa, when regarded along the direction of travel of the image receiving medium.
  • toner particles will be transported from the surface of said particle carrier, more precisely from areas on the particle carrier which correspond to the locations of the apertures of said rows.
  • a disadvantage related to the image forming apparatus of the above-mentioned type, in which the apertures are arranged in two or more rows relates to the fact that not only toner particles from locations on the particle carrier which correspond exactly to the apertures will be fed into the apertures, but also toner particles from around these locations (i.e. from the areas between such locations).
  • This means that the so-called "footprint" of the particle carrier - i.e. the area on particle carrier from which toner particles are fed - will be of greater width than the width of the corresponding apertures in the printhead structure.
  • toner particles being positioned on the particle carrier at locations corresponding to said intermediate areas of the first row will, to a certain extent, be fed into the apertures adjacent to the respective ntermediate area.
  • the row of apertures that the particle source "reaches first" will have a full supply of toner particles.
  • the second and further rows will have less toner particles available if there has been some printing done by the first row.
  • this is because the toner particle pick-up area of an aperture is somewhat larger than the aperture which causes the first row of apertures to "steal" toner particles from the second and further rows' supply.
  • the starvation problem can be solved by means of suitable control of said control voltages, in particular by controlling the amount of toner particles being fed to the first row of apertures to a slightly lower amount (or during a slightly shorter time period) than would normally have been done. This is accomplished by changing the opening and closing times of the apertures and/or by changing the voltage potentials of the control electrodes during opening and closing.
  • An object of the invention is to provide an improved image forming apparatus including a printhead structure by means of which said starvation problem is solved, which in turn leads to an improved printing quality of the printhead structure.
  • Said object is accomplished by an image forming apparatus in which each said intermediate area comprises an inclining section sloping downwards in a direction from each of said adjacent apertures, towards a recessed section positioned in said intermediate area, i.e. according to subsequent claim 1.
  • toner particles can be prevented from being fed sideways from the intermediate areas to the apertures in the printhead structure. In this manner, a suffcient amount of toner particles will be available for use in a subsequent row.
  • Fig. 1 is a schematic view of an image forming apparatus in accordance with a preferred embodiment of the present invention
  • Fig. 2 is a schematic section view across a print station in an image forming apparatus, such as, for example, that shown in Fig. 1,
  • Fig. 3 is a schematic section view of the print zone, illustrating the positioning of a printhead structure in relation to a particle source and an image receiving member,
  • Fig. 4a is a partial view of a printhead structure of a type used in the image forming apparatus according to the invention, showing the surface of the printhead structure that is facing the toner delivery unit,
  • Fig. 4b is a partial view of said printhead structure, showing the surface of the printhead structure that is facing the intermediate transfer belt,
  • Fig.4c is a section view across a section line I-I in the printhead structure of Fig. 4a and across the corresponding section line II-II of Fig. 4b, and
  • Fig. 5 is a cross-sectional view showing in detail the function of the invention.
  • a background electric field is produced between a particle carrier and a back electrode to enable a transport of charged particles therebetween.
  • a printhead structure such as an electrode matrix provided with a plurality of selectable apertures, is interposed in the background electric field between the particle carrier and the back electrode and connected to a control unit which converts the image information into a pattern of electrostatic fields which, due to control in accordance with the image information, selectively open or close passages in the electrode matrix to permit or restrict the transport of charged particles from the particle carrier.
  • the modulated stream of charged particles allowed to pass through the opened apertures are thus exposed to the background electric field and propelled toward the back electrode.
  • the charged particles are deposited on the image receiving substrate to provide line-by line scan printing to form a visible image.
  • a printhead structure for use in direct electrostatic printing may take on many designs, such as a lattice of intersecting wires arranged in rows and columns, or an apertured substrate of electrically insulating material overlaid with a printed circuit of control electrodes arranged in conjunction with the apertures.
  • a printhead structure includes a flexible substrate of insulating material such as polyimide or the like, having a first surface facing the particle carrier, a second surface facing the back electrode and a plurality of apertures arranged through the substrate. The first surface is coated with an insulating layer and control electrodes are arranged between the first surface of the substrate and the insulating layer, in a configuration such that each control electrode surrounds a corresponding aperture.
  • the apertures are preferably aligned in one or several rows extending transversally across the width of the substrate, i.e. perpendicular to the motion direction of the image receiving substrate. According to such a method, each single aperture is utilized to address a specific dot position of the image in a transversal direction.
  • the transversal print addressability is limited by the density of apertures through the printhead structure. For instance, a print addressability of 300 dpi requires a printhead structure having 300 apertures per inch in a transversal direction.
  • a direct electrostatic printing device includes a dot deflection control (DDC) .
  • DDC dot deflection control
  • the invention is not limited to such an embodiment, but may be implemented without dot deflection control.
  • each single aperture is used to address several dot positions on an image receiving substrate by controlling not only the transport of toner particles through the aperture, but also their transport trajectory toward the image receiving substrate, and thereby the location of the obtained dot.
  • the DDC method increases the print addressability without requiring a larger number of apertures in the printhead structure.
  • a DDC method performing three deflection steps per print cycle, provides a print addressability of 600 dpi utilizing a printhead structure having only 200 apertures per inch.
  • an improved DDC method provides a simultaneous dot size and dot position control. This method utilizes the deflection electrodes to influence the convergence of the modulated stream of toner particles thus controlling the dot size.
  • Each aperture is surrounded by two deflection electrodes connected to respective deflection voltages Dl, D2, such that the electrostatic control field generated by the control electrode remains substantially symmetrical as long as both deflection voltages Dl, D2 have the same amplitude.
  • the amplitude of Dl and D2 are modulated to apply converging forces on toner particles as they are transported toward the image receiving medium, thus providing smaller dots.
  • the dot position is simultaneously controlled by modulating the amplitude difference between Dl and D2 to deflect the toner trajectory toward predetermined dot positions.
  • a printhead structure for use in DDC methods generally includes a flexible substrate of electrically insulating material such as polyimide or the like, having a first surface facing the particle carrier, a second surface facing the back electrode and a plurality of apertures arranged through the substrate.
  • the first surface is overlaid with a first printed circuit including the control electrodes and the second surface is overlaid with a second printed circuit including the deflection electrodes. Both printed circuits are coated with insulative layers. Utilizing such a method, 60 micrometer dots can be obtained with apertures having a diameter in the order of 160 micrometer.
  • the four print stations are arranged in relation to the intermediate image receiving member 1.
  • the image receiving member, preferably a transfer belt 1 is mounted over the driving roller 10.
  • the at least one support roller 11 is provided with a mechanism for maintaining the transfer belt 1 with a constant tension, while preventing transversal movement of the transfer belt 1.
  • the holding elements 12 are for accurately positioning the transfer belt 1 with respect to each print station.
  • the driving roller 10 is preferably a cylindrical metallic sleeve having a rotation axis extending perpendicular to the motion direction of the belt 1 and a rotation velocity adjusted to convey the belt 1 at a velocity of one addressable dot location per print cycle, to provide line by line scan printing.
  • the adjustable holding elements 12 are arranged for maintaining the surface of the belt at a predetermined gap distance from each print station.
  • the holding elements 12 are preferably cylindrical sleeves disposed perpendicularly to the belt motion in an arcuated configuration so as to slightly bend the belt 1 at least in the vicinity of each print station in order to, in combination with the belt tension, create a stabilization force component on the belt. That stabilization force component is opposite in direction and preferably larger in magnitude than an electrostatic attraction force component acting on the belt 1 due to interaction with the different electric potentials applied on the corresponding print station.
  • the transfer belt 1 is preferably an endless band of 30 to 200 microns thick composite material as a base.
  • the base composite material can suitably include thermoplastic polyamide resin or any other suitable material having a high thermal resistance, such as 260°C of glass transition point and 388°C of melting point, and stable mechanical properties under temperatures in the order of 250°C.
  • the composite material of the transfer belt has preferably a homogeneous concentration of filler material, such as carbon or the like, which provides a uniform electrical conductivity throughout the entire surface of the transfer belt 1.
  • the outer surface of the transfer belt 1 is preferably coated with a 5 to 30 microns thick coating layer made of electrically conductive polymer material having appropriate conductivity, thermal resistance, adhesion properties, release properties and surface smoothness .
  • the transfer belt 1 is conveyed past the four different print stations, whereas toner particles are deposited on the outer surface of the transfer belt and superposed to form a four color toner image.
  • Toner images are then preferably conveyed through a fuser unit 13 comprising a fixing holder 14 arranged transversally in direct contact with the inner surface of the transfer belt.
  • the fixing holder includes a heating element 15 preferably of a resistance type of e.g. molybdenium, maintained in contact with the inner surface of the transfer belt 1. As an electric current is passed through the heating element 15, the fixing holder 14 reaches a temperature required for melting the toner particles deposited on the outer surface of the transfer belt 1.
  • the fusing unit 13 further includes a pressure roller 16 arranged transversally across the width of the transfer belt 1 and facing the fixing holder 14.
  • An information carrier 2 such as a sheet of plain untreated paper or any other medium suitable for direct printing, is fed from a paper delivery unit 21 and conveyed between the pressure roller 16 and the transfer belt.
  • the pressure roller 16 rotates with applied pressure to the heated surface of the fixing holder 14 whereby the melted toner particles are fused on the information carrier 2 to form a permanent image.
  • the transfer belt is brought in contact with a cleaning element 17, such as for example a replaceable scraper blade of fibrous material extending across the width of the transfer belt 1 for removing all untransferred toner particles from the outer surface.
  • a print station in an image forming apparatus in accordance with the present invention includes a particle delivery unit 3 preferably having a replaceable or refillable container 30 for holding toner particles, the container 30 having front and back walls (not shown) , a pair of side walls and a bottom wall having an elongated opening 31 extending from the front wall to the back wall and provided with a toner feeding element 32 disposed to continuously supply toner particles to a developer sleeve 33 through a particle charging member 34.
  • the particle charging member 34 is preferably formed of a supply brush or a roller made of or coated with a fibrous, resilient material.
  • the supply brush is brought into mechanical contact with the peripheral surface of the developer sleeve 33 for charging particles by contact charge exchange due to triboelectrification of the toner particles through frictional interaction between the fibrous material on the supply brush and any suitable coating material of the developer sleeve.
  • the developer sleeve 33 is preferably made of metal coated with a conductive material, and preferably has a substantially cylindrical shape and a rotation axis extending parallel to the elongated opening 31 of the particle container 30. Charged toner particles are held to the surface of the developer sleeve 33 by electrostatic forces essentially proportional to (Q/D) 2 , where Q is the particle charge and D is the distance between the particle charge center and the boundary of the developer sleeve 33.
  • the charge unit may additionally include a charging voltage source (not shown) , which supply an electric field to induce or inject charge to the toner particles.
  • a charging voltage source not shown
  • the method can be performed using any other suitable charge unit, such as a conventional charge injection unit, a charge induction unit or a corona charging unit, without departing from the scope of the present invention.
  • a metering element 35 is positioned proximate to the developer sleeve 33 to adjust the concentration of toner particles on the peripheral surface of the developer sleeve 33, to form a relatively thin, uniform particle layer thereon.
  • the metering element 35 may be formed of a flexible or rigid, insulating or metallic blade, roller or any other member suitable for providing a uniform particle layer thickness.
  • the metering element 35 may also be connected to a metering voltage source (not shown) which influence the triboelectrification of the particle layer to ensure a uniform particle charge density on the surface of the developer sleeve.
  • the developer sleeve 33 is arranged in relation with a positioning device 40 for accurately supporting and maintaining the printhead structure 5 in a predetermined position with respect to the peripheral surface of the developer sleeve 33.
  • the positioning device 40 is formed of a frame 41 having a front portion, a back portion and two transversally extending side rulers 42, 43 disposed on each side of the developer sleeve 33 parallel with the rotation axis thereof.
  • the first side ruler 42 positioned at an upstream side of the developer sleeve 33 with respect to its rotation direction, is provided with fastening means 44 to secure the printhead structure 5 along a transversal fastening axis extending across the entire width of the printhead structure 5.
  • the second side ruler 43 positioned at a downstream side of the developer sleeve 33, is provided with a support element 45, or pivot, for supporting the printhead structure 5 in a predetermined position with respect to the peripheral surface of the developer sleeve 33.
  • the support element 45 and the fastening axis are so positioned with respect to one another, that the printhead structure 5 is maintained in an arcuated shape along at least a part of its longitudinal extension. That arcuated shape has a curvature radius determined by the relative positions of the support element 45 and the fastening axis and dimensioned to maintain a part of the printhead structure 5 curved around a corresponding part of the peripheral surface of the developer sleeve 33.
  • the support element 45 is arranged in contact with the printhead structure 5 at a fixed support location on its longitudinal axis so as to allow a slight variation of the printhead structure 5 position in both longitudinal and transversal direction about that fixed support location, in order to accommodate a possible excentricity or any other undesired variations of the developer sleeve 33. That is, the support element 45 is arranged to make the printhead structure 5 pivotable about a fixed point to ensure that the distance between the printhead structure 5 and the peripheral surface of the developer sleeve 33 remains constant along the whole transverse direction at every moment of the print process, regardless of undesired mechanical imperfections of the developer sleeve 33.
  • the front and back portions of the positioning device 40 are provided with securing members 46 on which the toner delivery unit 3 is mounted in a fixed position to provide a constant distance between the rotation axis of the developer sleeve 33 and a transversal axis of the printhead structure 5.
  • the securing members 46 are arranged at the front and back ends of the developer sleeve 33 to accurately space the developer sleeve 33 from the corresponding holding element 12 of the transfer belt 1 facing the actual print station.
  • the securing members 46 are preferably dimensioned to provide and maintain a parallel relation between the rotation axis of the developer sleeve 33 and a central transversal axis of the corresponding holding member 12.
  • a printhead structure 5 in an image forming apparatus in accordance with the present invention comprises a substrate 50 of flexible, electrically insulating material such as polyimide or the like, having a predetermined thickness, a first surface facing the developer sleeve, a second surface facing the transfer belt, a transversal axis 51 extending parallel to the rotation axis of the developer sleeve 33 (cf. Fig. 3) across the whole print area, and a plurality of apertures 52 arranged through the substrate 50 from the first to the second surface thereof.
  • the first surface of the substrate is coated with a first cover layer 501 of electrically insulating material, such as for example parylene.
  • a first printed circuit comprising a plurality of control electrodes 53 disposed in conjunction with the apertures, and, in some embodiments, shield electrode structures (not shown) arranged in conjunction with the control electrodes 53, is arranged between the substrate 50 and the first cover layer 501.
  • the second surface of the substrate is coated with a second cover layer 502 of electrically insulating material, such as for example parylene.
  • a second printed circuit including a plurality of deflection electrodes 54, is arranged between the substrate 50 and the second cover layer 502.
  • the printhead structure 5 further includes a layer of antistatic material (not shown) , preferably a semiconductive material, such as silicium oxide or the like, arranged on at least a part of the second cover layer 502, facing the transfer belt 1.
  • the printhead structure 5 is brought in cooperation with a control unit (not shown) comprising variable control voltage sources connected to the control electrodes 53 to supply control potentials which control the amount of toner particles to be transported through the corresponding aperture 52 during each print sequence.
  • the control unit further comprises deflection voltage sources (not shown) connected to the deflection electrodes 54 to supply deflection voltage pulses which controls the convergence and the trajectory path of the toner particles allowed to pass through the corresponding apertures 52.
  • the control unit in some embodiments, even includes a shield voltage source (not shown) connected to the shield electrodes to supply a shield potential which electrostatically screens adjacent control electrodes 53 from one another, preventing electrical interaction therebetween.
  • the substrate 50 is a flexible sheet of polyimide having a thickness on the order of about 50 microns.
  • the first and second printed circuits are copper circuits of approximately 8-9 microns thickness etched onto the first and second surface of the substrate 50, respectively, using conventional etching techniques.
  • the first and second cover layers 501, 502 are 5 to 10 microns thick parylene laminated onto the substrate 50 using vacuum deposition techniques .
  • the apertures 52 are made through the printhead structure 5 using conventional laser micromachining methods.
  • the apertures are generally rectangular as shown in Figs. 4a and 4b.
  • the invention is not limited to apertures of this shape, but can be implemented with apertures of other shapes, for example circular or square.
  • the length and width of the aperture may vary, but are of the magnitude 100 microns.
  • the apertures 52 have preferably a constant shape along their central axis, for example cylindrical apertures, it may be advantageous in some embodiments to provide apertures whose shape varies continuously or stepwise along the central axis, for example conical apertures.
  • the printhead structure 5 is dimensioned to perform 600 dpi printing utilizing three deflection sequences in each print cycle, i.e. three dot locations are addressable through each aperture 52 of the printhead structure during each print cycle. Accordingly, one aperture 52 is provided for every third dot location in a transverse direction, that is, 200 equally spaced apertures per inch aligned parallel to the transversal axis 51 of the printhead structure 5.
  • the apertures 52 are generally aligned in one or several rows, preferably in two parallel rows each comprising 100 apertures per inch.
  • the aperture pitch i.e. the distance between the central axes of two neighbouring apertures of a same row is 0,01 inch or about 254 microns.
  • the aperture rows are preferably positioned on each side of the transversal axis 51 of the printhead structure 5 and transversally shifted with respect to each other such that all apertures are equally spaced in a transverse direction.
  • the distance between the aperture rows is preferably chosen to correspond to a whole number of dot locations.
  • the apertures 52 are arranged along two generally parallel rows extending generally perpendicular to the direction of travel of said image receiving member, i.e. at a right angle to the direction of travel of the image receiving medium.
  • a plurality of intermediate areas 55 are defined between each pair of two adjacent apertures 52 in each row.
  • the rows are arranged slightly displaced in relation to each other as seen in the direction along which said rows extend.
  • the apertures in a first row will be aligned with the intermediate areas in the second row, and vice versa, when regarded along the direction of travel of the image receiving medium.
  • the first printed circuit comprises the control electrodes 53 each of which are formed so as to surround the periphery of a corresponding aperture 52, and a connector preferably extending in the longitudinal direction, connecting to a corresponding control voltage source (not shown in Figs. 4a, 4b, 4c) .
  • the control electrodes 53 may take on various shape for continuously or partly surrounding the apertures 52, preferably shapes having symmetry about the central axis of the apertures.
  • the second printed circuit comprises the plurality of deflection electrodes 54, each of which is divided into two semicircular or crescent shaped deflection segments 541, 542 spaced around a predetermined portion of the circumference of a corresponding aperture 52.
  • the deflection segments 541, 542 are arranged symmetrically about the central axis of the aperture 52 on each side of a deflection axis 543 extending through the center of the aperture 52 at a predetermined deflection angle d to the longitudinal direction.
  • the deflection axis 543 is dimensioned in accordance with the number of deflection sequences to be performed in each print cycle in order to neutralize the effects of the belt motion during the print cycle, to obtain transversally aligned dot positions on the transfer belt.
  • each deflection electrode 54 has a upstream segment 541 and a downstream segment 542, all upstream segments 541 being connected to a first deflection voltage source Dl, and all downstream segments 542 being connected to a second deflection voltage source D2.
  • an image forming apparatus in accordance with the present invention preferably further includes a cleaning unit (not shown in the drawings) which is used to prevent toner contamination. Due to undesired variations in the charge and mass distribution of the toner material, some of the toner particles released from the developer sleeve 33 do not reach sufficient momentum during a print sequence to be deposited onto the transfer belt 1 and contribute to image formation. Some toner particles having a charge polarity opposite to the intended, so called wrong signed toner, may be repelled back to the printhead structure 5 after passage through the apertures under influence of the background field, and adhere on the printhead structure 5 in the area surrounding the apertures 52.
  • Some particles may be deviated during transport and agglomerate on the apertures walls, obstructing the aperture 52. Residual toner particles have to be removed periodically during an appropriate cleaning cycle, for example after a predetermined number of image formation cycles or due to control in accordance with a sensor measuring the amount of residual toner.
  • the so-called "starvation” problem may occur if the amount of toner particles intended to be transported to the apertures of the second row is not sufficient, due to the fact that during operation of the image forming apparatus, not only toner particles from locations on the particle carrier which correspond to the apertures will be fed into the apertures, but also toner particles from outside these locations. As explained above, this means that the "footprint" in the surface of the particle particle carrier will be of greater width than the width of the corresponding apertures. In this manner, the amount of toner particles intended for the apertures of the second row will be insufficient. This situation may in turn lead to a deterioration of the print quality of the image forming apparatus.
  • each respective intermediate area 55 which is formed between a pair of adjacent apertures 52 includes inclining sections 56 sloping downwards from the surface of the first cover layer 501 (as regarded in a direction from each said aperture 52) .
  • the inclining section 56 extends in a direction from an aperture 52 towards a recessed section 57 positioned generally in the centre area of said intermediate area 55.
  • the recessed section 57 presents a surface extending generally parallel to the surface of the first cover layer 501.
  • Fig. 5 is an enlarged cross-sectional view showing an aperture 52 and two corresponding inclining sections 56 being positioned underneath the developer sleeve 33. Shown in Fig. 5 are also two schematical arrows, which indicate that toner particles from locations on the developer sleeve 33 which correspond to the intermediate areas 55 will "bounce" in the direction towards the centre of said intermediate areas 55, i.e. said toner particles will not be fed into the aperture 52. This means that essentially only toner particles from a section 58 of the developer sleeve 33 which corresponds to the position of the aperture 52 will be fed into said aperture 52. In this manner, the starvation problem can be solved.
  • the printhead structure including the inclining sections 56 and the recessed section 57 is suitably manufactured by laser cutting. More precisely, the depth dl (i.e. the distance between the two parallel surfaces being defined of the recessed section 57 is not more than approximately 30-40 ⁇ m, preferably about 25 urn. Furthermore, the distance d2 from the inner wall of the aperture 52 to the recessed section 57 is approximately 30 ⁇ m.
  • the image forming apparatus according to the invention can be used without the above-mentioned deflection electrodes 54 and the corresponding deflection voltage sources.

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

Abstract

L'invention concerne un appareil imageur dans lequel des données d'image sont converties en un motif de champs électrostatiques destinés à moduler le transport de particules de toner chargées d'un support à un élément électrode arrière. L'appareil imageur comprend une source de tension de fond destinée à produire un champ électrique de fond qui permet le transport de particules de toner chargées du support jusqu'à l'élément électrode arrière; une structure tête d'impression placée dans ce champ électrique de fond et comportant plusieurs ouvertures et des électrodes de commande disposées à proximité des ouvertures; ces ouvertures étant positionnées le long d'au moins une rangée définissant ainsi plusieurs zones intermédiaires qui sont positionnées respectivement entre deux ouvertures adjacentes ; des sources de tension de commande destinées à fournir des potentiels de commande à ces électrodes de commande conformément aux données d'image pour permettre sélectivement ou réduire le transport des particules de toner chargées du support par les ouvertures; et un élément recevant l'image et amené à se déplacer en relation avec la structure tête d'impression pour intercepter les particules chargées transportées dans une configuration d'image. L'invention est caractérisée en ce que cette zone intermédiaire comprend une section inclinée vers le bas dans une direction de chacune de ces ouvertures adjacentes, vers une section en retrait placée dans cette zone intermédiaire.
PCT/SE2000/000010 2000-01-05 2000-01-05 Dispositif et procede d'impression directe Ceased WO2001049500A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU29519/00A AU2951900A (en) 2000-01-05 2000-01-05 Direct printing device and method
PCT/SE2000/000010 WO2001049500A1 (fr) 2000-01-05 2000-01-05 Dispositif et procede d'impression directe

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE2000/000010 WO2001049500A1 (fr) 2000-01-05 2000-01-05 Dispositif et procede d'impression directe

Publications (1)

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WO2001049500A1 true WO2001049500A1 (fr) 2001-07-12

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0753412A1 (fr) * 1995-07-06 1997-01-15 Hewlett-Packard Company Imprimante de projection de toner avec structure d'électrodes de commande améliorée
EP0860289A1 (fr) * 1997-02-21 1998-08-26 Sharp Kabushiki Kaisha Appareil de formation d'images
WO1999044831A2 (fr) * 1998-03-04 1999-09-10 Array Printers Ab Structure de tete d'impression dans un dispositif d'enregistrement d'images

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0753412A1 (fr) * 1995-07-06 1997-01-15 Hewlett-Packard Company Imprimante de projection de toner avec structure d'électrodes de commande améliorée
EP0860289A1 (fr) * 1997-02-21 1998-08-26 Sharp Kabushiki Kaisha Appareil de formation d'images
WO1999044831A2 (fr) * 1998-03-04 1999-09-10 Array Printers Ab Structure de tete d'impression dans un dispositif d'enregistrement d'images

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