EP0307403B1 - Ink writing head with piezoelectrically excitable membrane - Google Patents

Ink writing head with piezoelectrically excitable membrane Download PDF

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Publication number
EP0307403B1
EP0307403B1 EP87903243A EP87903243A EP0307403B1 EP 0307403 B1 EP0307403 B1 EP 0307403B1 EP 87903243 A EP87903243 A EP 87903243A EP 87903243 A EP87903243 A EP 87903243A EP 0307403 B1 EP0307403 B1 EP 0307403B1
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EP
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Prior art keywords
membrane
ink
layer
writing head
channel
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EP87903243A
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German (de)
French (fr)
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EP0307403A1 (en
Inventor
Joachim Heinzl
Manfred Lehmann
Günter Elmar TRAUSCH
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Siemens AG
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Siemens AG
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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
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2/14201—Structure of print heads with piezoelectric elements
    • B41J2/14233—Structure of print heads with piezoelectric elements of film type, deformed by bending and disposed on a diaphragm
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B43/00—Machines, pumps, or pumping installations having flexible working members
    • F04B43/02—Machines, pumps, or pumping installations having flexible working members having plate-like flexible members, e.g. diaphragms
    • F04B43/04—Pumps having electric drive
    • F04B43/043—Micropumps
    • F04B43/046—Micropumps with piezoelectric drive

Definitions

  • the invention relates to an ink writing head and a method for producing an ink writing head according to the preamble of claims 1 and 13.
  • Piezoelectric drive elements in ink pens are generally known.
  • DE-A-21 64 614 describes an arrangement in writing mechanisms for writing with colored liquid on paper, in which a liquid located in an ink chamber is ejected from a writing nozzle via a piezoelectrically operated drive element.
  • the change in volume in the chamber is brought about by an electrically controlled piezoceramic which sits on a metal plate and which bulges into the chamber.
  • the piezo drive element used consists of a continuously polarized piezoceramic layer which is arranged on a metal plate, the metal plate serving as a counter electrode.
  • a suitable voltage pulse is applied, the piezoceramic contracts. Since the ceramic is attached to a metal plate, a bending moment affects this plate. As a result, the central part of the plate bulges into the liquid chamber.
  • the changes in length that can be generated directly piezoelectrically are negligibly small. They are also limited by the electric field strengths that can be applied to the ceramic without causing breakdowns or arcing. Furthermore, the field strengths created must not lead to a polarization reversal, they must also be switchable via appropriate control circuits.
  • the field strength should be less than 1 V / gm in the opposite direction to the polarization.
  • the distances between electrodes in air should also not be less than 1 pmN.
  • the direct change in length that can be achieved in this way is thus around 1%. or about 0.2 ⁇ m at 200 pm layer density, provided the ceramic is thoroughly active and not partially inactive through a burning skin.
  • the drive elements be they piezo tubes or piezo plates, are necessary for a whole range of functions.
  • the object of the invention is therefore to design an ink head of the type mentioned in such a way that it can be easily produced on the one hand in a galvanoplastic process and on the other hand it has a high degree of efficiency.
  • the membrane has a piezoelectrically excitable peripheral region and a piezoelectrically excitable central region, which are controlled in such a way that the membrane in its peripheral region is shortened by transverse contraction and lengthened in its central region to produce a membrane deflection, results in a particularly large one Stroke.
  • This stroke is the result of the exploitation of two effects, namely the exploitation of the transverse contraction in the ceramic itself and the curvature of the bond between adjacent layers, which expand differently.
  • the cross-contraction can increase the stroke of the membrane by reducing the layer thickness and increasing the length dimensions.
  • a particularly advantageous force effect results if the membrane regions are arranged concentrically with one another, so that they bulge out like warts when excited.
  • This wart-like bulge represents the smallest and most compact geometric shape, which starts from a flat layer and widens and closes a cavity. It is rotationally symmetrical about a surface normal and leaves the plane in a toroidal fillet which merges into a lenticular spherical section. The required state of curvature changes at the transition line.
  • the electrodes are accordingly arranged or the corresponding membrane regions are polarized and controlled via the electrodes in such a way that the peripheral region (circular ring) is shortened, but the central region is lengthened.
  • the edge of the membrane does not change its inclination when deflected, which is why it can be firmly clamped.
  • the bending line essentially corresponds to a deflection under internal pressure.
  • a plurality of membranes which can be activated individually and independently of one another are arranged on a common substrate surface, the control lines for the individual membrane regions leading over unpolarized regions of the substrate surface, so that no undesired piezoelectric effects occur when these control lines are activated.
  • a further piezoelectrically excitable layer can be arranged instead of the support layer, which is polarized in the opposite direction to the first piezoelectrically excitable layer. This almost doubles the stroke.
  • a particularly simple, reliably operating ink writing head can be formed in that each ink channel is assigned three membranes which are connected to one another via a pump channel for the writing liquid and form a static pump with two controllable locking slides and a variable cavity.
  • the first membrane area is connected on the one hand to the ink supply system via a supply channel, and on the other hand to the variable cavity and serves as an inlet valve.
  • the second membrane area is associated with the variable cavity and a third membrane area is located between the cavity and the ink channel as an outlet valve.
  • the pump channel connecting the membranes has separating webs in the region of the membranes designed as valves, which cooperate with the membrane surfaces in such a way that the pump channel opens after the membrane surfaces have been deflected via the separating webs and the pump channel in the region of the separating webs via the Membrane surfaces in the undeflected state of the membrane surfaces is interrupted.
  • the separating webs can be designed as continuous webs or as collar-shaped elevations with outlet openings or inlet openings in between.
  • the ink can be filtered considerably better, thus preventing the penetration of dirt into the ink channels.
  • the separator can be cleaned immediately with ultrasound and contaminations on the separator can be ground.
  • the transducer elements keep the ink channels closed as long as the transducer elements are not activated, a mechanical closure of the nozzles between the print head and paper is not necessary and the drive of such a closure can be dispensed with. This makes it possible to reduce the paper gap very much, so that the typeface is less affected by the dispersion of the airspeed and the direction of flight of the drops. Since the pressure on the nozzle can be applied statically, the flight speed can be increased. Crosstalk between the nozzles is eliminated since there is no flow connection when spraying.
  • the spray frequency is not limited by reflections in the channel and not by crosstalk from neighboring nozzles, but only by the eigenvalues of the individual transducer elements. An individual adjustment of the transducer elements can be omitted, since the transducer is coupled to the ink in a much more direct and uniform manner.
  • the ink supply system according to the invention is independent of static negative pressure, it becomes substantially less sensitive, which also means that the acceleration sensitivity of the ink writing head disappears.
  • Static pumping removes air bubbles from the ink channel. Empty channels can be filled electrically controlled.
  • the ink reservoir can be accommodated stationary in the printer without difficulty. Pressure waves from the moving supply hose have no effect on the drop formation.
  • the monitoring of the ink supply is no longer tied to the narrow limits of a static pressure in the reservoir.
  • the entire print head can be produced in a particularly simple manner using planar techniques.
  • the critical part, namely the piezoceramic, can be checked before the actual assembly.
  • a planar transducer made of piezoceramic consists of a piezoelectrically excitable layer 1 made of piezoceramic which is polarized in one direction and a support layer 2, for example made of Nikkel, which is firmly connected to this excitable layer.
  • This electrically controllable membrane thus formed is controlled via corresponding electrodes 3, 4, the support layer 2 serving as a continuous ground electrode and the actual control electrodes consisting of a peripheral control electrode 3 and a central control electrode 4.
  • These control electrodes 3 and 4 define membrane regions arranged concentrically to one another in the form of circular surfaces or circular ring surfaces.
  • the drive electrodes 3 and 4 are now designed according to the invention in connection with the piezoelectrically excitable layer 1 and the support layer 2, which serves as a ground electrode, in such a way that this ideal shape approximately results during the deflection.
  • the circular outer electrode 3 is arranged in the outer region of curvature of the membrane and is subjected to an electrical field such that the piezoelectric layer contracts in this region of curvature.
  • the inner electrode 4, which is arranged concentrically thereto, is in turn subjected to a field such that the central region of the piezoceramic layer 1 expands.
  • the ratio of the electrode areas to one another is now dimensioned such that the desired approximation of the course in FIG. 1a results. This results in an inclination in accordance with FIG. 1b with the associated curvature in FIG. 1c (right side in FIG. 1).
  • a static pump consisting of two controllable gate valves SE and SA and a variable cavity H can be formed.
  • three membrane areas for SE, H, SA are formed in a ceramic substrate.
  • a pump channel P is formed in a carrier layer T carrying the substrate 1 with its associated support layer 2. This pump channel P is connected to a fluid supply V (FIG. 4).
  • a transverse rib Q is formed in the pump channel in the area of the inlet valve SE, against which the membrane made of piezoceramic 1 and support layer 2 is applied in the unexcited state and thus closes the channel. In the excited state according to FIG. 2, the membrane lifts off in a wart-like manner and thus opens the channel P.
  • the pump channel can also be designed in a different way. It is also possible to replace the transverse ribs Q by walls of round inlet and outlet openings A which protrude into the pump channels. The membrane surface then lies in the unexcited state in a manner analogous to that on the transverse rib on this collar and thus closes the inlet or outlet.
  • an ink writing head can be constructed in which e.g. nine writing nozzles S1 to S9 are arranged. Each of these writing nozzles consists of an inlet valve SE, a variable cavity H and an outlet valve SA. The writing nozzles S1 to S9 are connected to the storage area V. In order to be able to form a write head with a larger number of nozzles, it is also possible to pack several substrates 1 with write nozzles one above the other.
  • the writing nozzles S1 to S9 are functionally completely separated from the ink supply V.
  • a mechanical closure of the nozzles between the write head and the paper arranged in front of it and the drive of this closure can thus be dispensed with, since the ink channels are closed by the outlet valves SA as long as these outlet valves SA are not actuated.
  • Crosstalk between the nozzles is eliminated, since the actual one Spraying process there is no flow connection.
  • the spraying processes are not limited by the reflection in the spray channel and not by the crosstalk from neighboring nozzles, but only by the eigenvalues of the individual writing nozzles S1 to S9.
  • Static pumping removes air bubbles from ink channel P and refills empty channels.
  • the ink write head according to the invention can be produced particularly simply using planar technology.
  • a substrate 1 consisting of piezoceramic with a thickness of approximately 200 ⁇ m is first polarized and tested. Then the piezoceramic 1 is metallized on both sides by vacuum evaporation or sputtering (e.g. 50 nm Ti and 500 nm Cu).
  • the support layer 2 is galvanically deposited over the entire surface.
  • the peripheral and central control electrodes 3 and 4 together with supply lines L e.g. 100 ⁇ m Ni
  • supply lines L e.g. 100 ⁇ m Ni
  • a thin intermediate layer Z e.g. 0.2 mm Al or Cu
  • Z e.g. 0.2 mm Al or Cu
  • It is vapor-deposited or sputtered and structured using photolithography and etching technology.
  • the channels P can be formed by electrodeposition of a metal layer W between a photoresist structure (e.g. 50 ⁇ m Ni). After a metallic conductive layer has been applied over the non-conductive photoresist, the support layer T is then galvanically deposited over the entire surface (e.g. 100 ⁇ m Ni). However, the channel walls W can also be produced together with the carrier layer T in one step. For this purpose, a structure K made of photoresite or metal (e.g. Cu) of the shape of the later channels and cavities is produced on the support layer 2. If photoresite is used, then its surface must be made conductive with another thin metal layer. If metal is used, the channel wall support layer metal can be electrodeposited directly on the structure K and the remaining exposed substrate surface 2 (e.g. 100 pm Ni), FIG. 11.
  • a photoresist structure e.g. 50 ⁇ m Ni
  • the support layer T is then galvanically deposited over the entire surface (e.g. 100 ⁇ m Ni).
  • the channel walls W can also be
  • the structure K made of photoresite or metal is then selectively removed from the overall structure and finally the crossbar Q is separated from the wart by removing the intermediate layer.
  • the etchable filler is then removed and the auxiliary layer (Z) is also removed so that the transverse ribs Q can detach from the support layer 2 when the substrate 1 bulges.
  • openings can be provided which are later closed again.
  • a further support layer SS can be applied outside the electrodes on the back of the ceramic layer 1. It is also possible to produce the lines L for the electrodes 3 and 4 (FIG. 10) simultaneously with the support layer, ie from the same material and with the same thickness.
  • the transverse rib Q it is also possible according to FIG. 12 to design the transverse rib in a circular manner, with the axis of the outlet nozzle A then having a direction perpendicular to the substrate surface 1. It is therefore possible to construct the ink writing head so that the outlet nozzles A are arranged on the end face of the substrate or in such a way that they are arranged on the substrate surface. Which is the more advantageous arrangement depends on the intended use. As also shown in FIG. 14, to increase the division view between the raster line RZ the ink writing head can be inclined at an angle to the raster line.

Abstract

An ink writing head provided with ink ejection passages with their associated piezoelectric transducers, said passages being fed with a writing liquid via supply lines, comprises transducers with an electrically excitable membrane consisting of a first piezoelectrically excitable layer and a support layer suddenly attached to the latter. The piezoelectrically excitable layer has injectable regions which are broken down into a peripheral region and a central region. To produce the necessary projection of the membrane, the regions of the latter are excited in such a way that the peripheral region is shortened preferably by transverse contraction and the central region is elongated.

Description

Die Erfindung betrifft einen Tintenschreibkopf und ein Verfahren zum Herstellen eines Tintenschreibkopfes gemäß dem Oberbegriff der Patentansprüche 1 und 13.The invention relates to an ink writing head and a method for producing an ink writing head according to the preamble of claims 1 and 13.

Piezoelektrisch betriebene Antriebselemente in Tintenschreibern sind allgemein bekannt. So wird in der DE-A-21 64 614 eine Anordnung in Schreibwerken zum Schreiben mit farbiger Flüssigkeit auf Papier beschrieben, bei der über ein piezoelektrisch betriebenes Antriebselement eine in einer Tintenkammer befindliche Flüssigkeit aus einer Schreibdüse ausgestoßen wird. Die Volumenveränderung in der Kammer wird durch eine elektrisch angesteuerte Piezokeramik bewirkt, die auf einer Metallplatte sitzt und die sich in die Kammer hineinwölbt. Das verwendete Piezoantriebselement besteht aus einer durchgehend polarisierten Piezokeramikschicht, die auf einer Metallplatte angeordnet ist, wobei die Metallplatte als Gegenelektrode dient. Wenn ein geeigneter Spannungsimpuls angelegt wird, zieht sich die Piezokeramik zusammen. Da die Keramik auf einer Metallplatte befestigt ist, wirkt sich auf diese Platte ein Biegemoment aus. Das hat zur Folge, daß sich der Mittelteil der Platte in die Flüssigkeitskammer hineinwölbt.Piezoelectric drive elements in ink pens are generally known. DE-A-21 64 614 describes an arrangement in writing mechanisms for writing with colored liquid on paper, in which a liquid located in an ink chamber is ejected from a writing nozzle via a piezoelectrically operated drive element. The change in volume in the chamber is brought about by an electrically controlled piezoceramic which sits on a metal plate and which bulges into the chamber. The piezo drive element used consists of a continuously polarized piezoceramic layer which is arranged on a metal plate, the metal plate serving as a counter electrode. When a suitable voltage pulse is applied, the piezoceramic contracts. Since the ceramic is attached to a metal plate, a bending moment affects this plate. As a result, the central part of the plate bulges into the liquid chamber.

Die Längenänderungen, die man direkt piezoelektrisch erzeugen kann, sind verschwindend klein. Sie sind außerdem begrenzt durch die elektrischen Feldstärken, die man an der Keramik anlegen darf, ohne daß dies zu Durch- oder Überschlägen führt. Weiters dürfen die angelegten Feldstärken nicht zu einer Umpolarisation führen, sie müssen außerdem über entsprechende Ansteuerschaltkreise schaltbar sein.The changes in length that can be generated directly piezoelectrically are negligibly small. They are also limited by the electric field strengths that can be applied to the ceramic without causing breakdowns or arcing. Furthermore, the field strengths created must not lead to a polarization reversal, they must also be switchable via appropriate control circuits.

Es ist deshalb üblich, eine Spannung von ca. 200 V nicht zu Es ist deshalb üblich, eine Spannung von ca. 200 V nicht zu überschreiten. Die Feldstärke sollte dabei kleiner sein als ein 1 V/gm in Gegenrichtung zur Polarisation. Die Abstände zwischen Elektroden an Luft sollten außerdem nicht kleiner als 1 pmN sein. Die direkte Längenänderung, die auf diese Weise erzielbar ist, ist damit rund 1 %. oder etwa 0,2 um bei 200 pm Schichtdichte, vorausgesetzt die Keramik ist durch und durch aktiv und nicht etwa durch eine Brennhaut teilweise inaktiv. Beim Tintendruck sind die Antriebselemente, seien es nun Piezoröhrchen oder Piezoplättchen, für eine ganze Reihe von Funktionen notwendig. Sie sollen steuerbar kleineTintenmengen beschleunigen, als Tropfen ausstoßen und Tinte aus einem Reservoir nachfördern. Sie sollen aber auch, wenn möglich, die Ausstoßöffnungen verschließen, um das Auslaufen und das Austrocknen der Tinte zu verhindern. Schließlich sollen mit derartigen Elementen die Tintenkanäle und die Austrittsöffnungen gereinigt und entlüftet werden können.It is therefore common not to apply a voltage of approx. 200 V. It is therefore common not to exceed a voltage of approx. 200 V. The field strength should be less than 1 V / gm in the opposite direction to the polarization. The distances between electrodes in air should also not be less than 1 pmN. The direct change in length that can be achieved in this way is thus around 1%. or about 0.2 µm at 200 pm layer density, provided the ceramic is thoroughly active and not partially inactive through a burning skin. When it comes to ink printing, the drive elements, be they piezo tubes or piezo plates, are necessary for a whole range of functions. They are designed to accelerate small amounts of ink in a controllable manner, to eject them as drops and to supply ink from a reservoir. You should also, if possible, close the discharge openings to prevent the ink from leaking and drying out. Finally, the ink channels and the outlet openings should be able to be cleaned and vented with such elements.

Bei den bekannten Antriebselementen mit akustischer Tropfenbildung wird nur ein Teil dieser Funktionen voll erfüllt. Schallwellen im Tintenkanal können zwar schnellfliegende Tropfen formen, aber statischer Druck zur Beseitigung von Hindernissen im Kanal kann nicht erzeugt werden. Lufteinschlüsse im Tintenkanal begrenzen die Ausbreitung der Druckwellen im Kanal und leergelaufene Kanäle lassen sich nur durch einen Eingriff von außen wieder füllen. Der Verschluß der Austrittsöffnungen kann bei akustischer Tropfenbildung ebenfalls nur mechanisch von außen erfolgen.In the known drive elements with acoustic drop formation, only some of these functions are fully fulfilled. Sound waves in the ink channel can form fast-flying drops, but static pressure to remove obstacles in the channel cannot be generated. Air pockets in the ink channel limit the spread of the pressure waves in the channel and empty channels can only be refilled by external intervention. In the case of acoustic drop formation, the exit openings can also only be closed mechanically from the outside.

Aufgabe der Erfindung ist es deshalb, einen Tintenkopf der eingangs genannten Art so auszugestalten, daß er einerseits einfach im galvanoplastischen Verfahren hergestellt werden kann und daß er andererseits einen hohen Wirkungsgrad aufweist.The object of the invention is therefore to design an ink head of the type mentioned in such a way that it can be easily produced on the one hand in a galvanoplastic process and on the other hand it has a high degree of efficiency.

Diese Aufgabe wird bei einer Vorrichtung der eingangs genannten Art gemäß dem kennzeichnenden Teil des ersten Patentanspruches gelöst.This object is achieved in a device of the type mentioned at the outset according to the characterizing part of the first claim.

Vorteilhafte Ausführungsformen der Erfindung sind in den Unteransprüchen gekennzeichnet.Advantageous embodiments of the invention are characterized in the subclaims.

Dadurch, daß die Membran einen piezoelektrisch anregbaren peripheren Bereich und einen piezoelektrisch anregbaren zentralen Bereich aufweist, die derart angesteuert werden, daß zum Erzeugen einer Membranauslenkung die Membran in ihrem peripheren Bereich durch Querkontraktion verkürzt und in ihrem zentralen Bereich verlängert wird, ergibt sich ein besonders großer Hub. Dieser Hub ist das Ergebnis der Ausnutzung von zwei Wirkungen, nämlich der Ausnutzung der Querkontraktion in der Keramik selbst und die Krümmung des Verbundes benachbarter Schichten, die sich unterschiedlich ausdehnen. Durch die Querkontraktion läßt sich der Hub der Membran durch Verringerung der Schichtdicken und Vergrößerung der Längenabmessungen steigern.The fact that the membrane has a piezoelectrically excitable peripheral region and a piezoelectrically excitable central region, which are controlled in such a way that the membrane in its peripheral region is shortened by transverse contraction and lengthened in its central region to produce a membrane deflection, results in a particularly large one Stroke. This stroke is the result of the exploitation of two effects, namely the exploitation of the transverse contraction in the ceramic itself and the curvature of the bond between adjacent layers, which expand differently. The cross-contraction can increase the stroke of the membrane by reducing the layer thickness and increasing the length dimensions.

Eine besonders vorteilhafte Kraftwirkung ergibt sich, wenn man die Membranbereiche konzentrisch zueinander anordnet, sodaß sie sich bei der Anregung warzenartig auswölben. Diese warzenartige Auswölbung stellt die kleinste und kompaktestegeometrische Form dar, die von einer ebenen Schicht ausgeht und einen Hohlraum erweitert und schließt. Sie ist rotationssymmetrisch um eine Flächennormale und verläßt die Ebene in einer torusförmigen Hohlkehle, die in einen linsenförmigen Kugelabschnitt übergeht. An der Übergangslinie ändert sich der benötigte Krümmungszustand. Entsprechend sind die Elektroden so angeordnet bzw. die entsprechenden Membranbereiche so polarisiert und über die Elektroden angesteuert, daß sich der periphere Bereich (Kreisring) verkürzt, derzentrale Bereich dagegen verlängert. Der Rand der Membran verändert bei Auslenkung seine Neigung nicht, weswegen er fest eingespannt werden kann. Die Biegelinie entspricht im wesentlichen einer Auslenkung unter Innendruck. Bei einer weiteren vorteilhaften Ausführungsform der Erfindung sind mehrere einzeln unabhängig voneinander aktivierbare Membranen auf einer gemeinsamen Substratfläche angeordnet, wobei die Ansteuerleitungen für die einzelnen Membranbereiche über unpolarisierte Bereiche der Substratflächeführen, damit bei derAnsteuerung über diese Ansteuerleitungen keine unerwünschten piezoelektrischen Effekte auftreten.A particularly advantageous force effect results if the membrane regions are arranged concentrically with one another, so that they bulge out like warts when excited. This wart-like bulge represents the smallest and most compact geometric shape, which starts from a flat layer and widens and closes a cavity. It is rotationally symmetrical about a surface normal and leaves the plane in a toroidal fillet which merges into a lenticular spherical section. The required state of curvature changes at the transition line. The electrodes are accordingly arranged or the corresponding membrane regions are polarized and controlled via the electrodes in such a way that the peripheral region (circular ring) is shortened, but the central region is lengthened. The edge of the membrane does not change its inclination when deflected, which is why it can be firmly clamped. The bending line essentially corresponds to a deflection under internal pressure. In a further advantageous embodiment of the invention, a plurality of membranes which can be activated individually and independently of one another are arranged on a common substrate surface, the control lines for the individual membrane regions leading over unpolarized regions of the substrate surface, so that no undesired piezoelectric effects occur when these control lines are activated.

Um den Hub noch weiter zu vergrößern, kann anstelle der Stützschicht eine weitere piezoelektrisch anregbare Schicht angeordnet sein, die jeweils in entgegengesetzter Richtung zur ersten piezoelektrisch anregbaren Schicht polarisiert ist. Damit ergibt sich nahezu eine Verdoppelung des Hubes.In order to increase the stroke even further, a further piezoelectrically excitable layer can be arranged instead of the support layer, which is polarized in the opposite direction to the first piezoelectrically excitable layer. This almost doubles the stroke.

Einen besonders einfachen betriebssicher arbeitenden Tintenschreibkopf kann man dadurch bilden, daß jedem Tintenkanal drei über einen Pumpkanal für die Schreibflüssigkeit miteinander verbundene Membranen zugeordnet sind, die eine statische Pumpe mit zwei steuerbaren Sperrschiebern und einen veränderlichen Hohlraum bilden. Der erste Membranbereich steht einerseits über einen Versorgungskanal mit dem Tintenversorgungssystem, andererseits mit dem veränderlichen Hohlraum in Verbindung und dient als Einlaßventil. Der zweite Membranbereich ist dem veränderlichen Hohlraumzugeordnet und ein dritter Membranbereich ist zwischen dem Hohlraum und dem Tintenkanal als Auslaßventil angeordnet. Bei einer vorteilhaften Ausführungsform der Erfindung weist der die Membranen verbindende Pumpkanal im Bereich der als Ventile ausgebildeten Membranen Trennstege auf, die mit den Membranflächen derart zusammenwirken, daß sich der Pumpkanal nach Auslenken der Membranflächen über die Trennstege öffnet und der Pumpkanal im Bereich der Trennstege über die Membranflächen im nichtausgelenkten Zustand der Membranflächen unterbrochen ist.A particularly simple, reliably operating ink writing head can be formed in that each ink channel is assigned three membranes which are connected to one another via a pump channel for the writing liquid and form a static pump with two controllable locking slides and a variable cavity. The first membrane area is connected on the one hand to the ink supply system via a supply channel, and on the other hand to the variable cavity and serves as an inlet valve. The second membrane area is associated with the variable cavity and a third membrane area is located between the cavity and the ink channel as an outlet valve. In an advantageous embodiment of the invention, the pump channel connecting the membranes has separating webs in the region of the membranes designed as valves, which cooperate with the membrane surfaces in such a way that the pump channel opens after the membrane surfaces have been deflected via the separating webs and the pump channel in the region of the separating webs via the Membrane surfaces in the undeflected state of the membrane surfaces is interrupted.

Die Trennstege können dabei als durchgehende Stege ausgebildet sein oder auch als kragenförmige Erhebungen mit dazwischenliegenden Austrittsöffnungen bzw. Einlaßöffnungen.The separating webs can be designed as continuous webs or as collar-shaped elevations with outlet openings or inlet openings in between.

Da bei dem erfindungsgemäßen Tintenschreibkopf Tinte mit niedriger Viskosität verwendet werden kann, kann die Tinte erheblich besser gefiltert werden, womit das Eindringen von Schmutz in die Tintenkanäle vermieden wird. Zusätzlich ist es möglich, zu Reinigungszwecken den Durchlaßquerschnitt elektrisch zu erweitern und die Pumprichtung umzukehren. Außerdem läßt sich der Trennsteg unmittelbar mit Ultraschall reinigen und es lassen sich Verunreinigungen an dem Trennsteg zermahlen.Since low viscosity ink can be used in the ink writing head according to the invention, the ink can be filtered considerably better, thus preventing the penetration of dirt into the ink channels. In addition, it is possible to extend the passage cross-section electrically for cleaning purposes and to reverse the pumping direction. In addition, the separator can be cleaned immediately with ultrasound and contaminations on the separator can be ground.

Da die Wandlerelemente die Tintenkanäle verschlossen halten solange die Wandlerelemente nicht angesteuert werden, ist ein mechanischer Verschluß der Düsen zwischen Schreibkopf und Papier nicht notwendig und der Antrieb eines solchen Verschlusses kann entfallen. Damit ist es möglich, den Papierabstand sehr stark zu verringern, womit das Schriftbild weniger durch die Streuung der Fluggeschwindigkeit und der Flugrichtung der Tropfen beeinträchtigt wird. Da der Druck auf der Düse statisch aufgeprägt werden kann, läßt sich die Fluggeschwindigkeit erhöhen. Ein Übersprechen zwischen den Düsen entfällt, da beim Spritzen keine Fließverbindung besteht.Since the transducer elements keep the ink channels closed as long as the transducer elements are not activated, a mechanical closure of the nozzles between the print head and paper is not necessary and the drive of such a closure can be dispensed with. This makes it possible to reduce the paper gap very much, so that the typeface is less affected by the dispersion of the airspeed and the direction of flight of the drops. Since the pressure on the nozzle can be applied statically, the flight speed can be increased. Crosstalk between the nozzles is eliminated since there is no flow connection when spraying.

Die Spritzfrequenz ist nicht durch Reflexionen im Kanal und nicht durch das Übersprechen von Nachbardüsen begrenzt sondern nur durch die Eigenwerte der einzelnen Wandlerelemente. Ein individueller Abgleich der Wandlerelemente kann entfallen, da die Kopplung des Wandlers an die Tinte viel direkter und gleichmäßiger erfolgt.The spray frequency is not limited by reflections in the channel and not by crosstalk from neighboring nozzles, but only by the eigenvalues of the individual transducer elements. An individual adjustment of the transducer elements can be omitted, since the transducer is coupled to the ink in a much more direct and uniform manner.

Da das erfindungsgemäße Tintenversorgungssystem unabhängig ist von statischem Unterdruck, wird es wesentlicher unempfindlicher, womit auch die Beschleunigungsempfindlichkeit des Tintenschreibkopfes verschwindet.Since the ink supply system according to the invention is independent of static negative pressure, it becomes substantially less sensitive, which also means that the acceleration sensitivity of the ink writing head disappears.

Durch statisches Pumpen lassen sich Luftblasen aus dem Tintenkanal entfernen. Leere Kanäle lassen sich elektrisch gesteuert füllen.Static pumping removes air bubbles from the ink channel. Empty channels can be filled electrically controlled.

Das Tintenreservoir kann ohne Schwierigkeiten stationär im Drucker untergebracht werden. Druckwellen aus dem bewegten Versorgungsschlauch wirken sich nicht auf die Tropfenbildung aus.The ink reservoir can be accommodated stationary in the printer without difficulty. Pressure waves from the moving supply hose have no effect on the drop formation.

Die Überwachung des Tintenvorrates ist nicht mehr an die engen Grenzen eines statischen Druckes im Vorratsgefäß gebunden.The monitoring of the ink supply is no longer tied to the narrow limits of a static pressure in the reservoir.

Der gesamte Schreibkopf läßt sich in besonders einfacher Weise in planaren Techniken herstellen. Der kritische Teil, nämlich die Piezokeramik, kann vor dem eigentlichen Aufbau geprüft werden.The entire print head can be produced in a particularly simple manner using planar techniques. The critical part, namely the piezoceramic, can be checked before the actual assembly.

Ausführungsformen der Erfindung sind in den Zeichnungen dargestellt und werden im folgenden beispielsweise näher beschrieben. Es zeigen

  • Fig. 1 eine schematische Vergleichsdarstellung zwischen der Verformung einer Membranplatteunter Innendruck und einer Membranplatte mit aufgeprägter Wölbung,
  • Fig. 2 eine erfindungsgemäße Membran im ausgelenkten Zustand,
  • Fig. 3 eine erfindungsgemäße Membran im unerregten Zustand,
  • Fig. 4 eine statische Pumpe aus drei miteinander verbundenen Membranen in Draufsicht,
  • Fig. 5 eine statische Pumpe gemäß Fig. 4 im Querschnitt,
  • Fig. 6 bis Fig. 11 schematische Darstellungen des Schichtaufbaues des erfindungsgemäßen Tintenschreibkopfes,
  • Fig. 12 eine schematische Schnittdarstellung eines Wandlerelementes mit kragenförmigen Trennstegen,
  • Fig. 13 eine schematische Darstellung des erfindungsgemäßen Tintenschreibkopfes und
  • Fig. 14 eine schematische Darstellung der Schrägstellung des Tintenschreibkopfes in einer Zeilendruckeinrichtung.
Embodiments of the invention are shown in the drawings and are described in more detail below, for example. Show it
  • 1 is a schematic comparison illustration between the deformation of a membrane plate under internal pressure and a membrane plate with an embossed curvature,
  • 2 a membrane according to the invention in the deflected state,
  • 3 shows a membrane according to the invention in the unexcited state,
  • 4 shows a static pump from three interconnected membranes in plan view,
  • 5 shows a static pump according to FIG. 4 in cross section,
  • 6 to 11 are schematic representations of the layer structure of the ink writing head according to the invention,
  • 12 shows a schematic sectional illustration of a transducer element with collar-shaped separating webs,
  • Fig. 13 is a schematic representation of the ink writing head according to the invention and
  • Fig. 14 is a schematic representation of the inclination of the ink writing head in a line printing device.

Ein planarer Wandler aus Piezokeramik, wie er in den Fig. 2 und 3 dargestellt ist, besteht aus einer piezoelektrisch anregbaren durchgehend in eine Richtung polarisierten Schicht 1 aus piezokeramik und einer fest mit dieser anregbaren Schicht verbundenen Stützschicht 2, z.B. aus Nikkel. Diese so gebildete elektrisch ansteuerbare Membran wird über entsprechende Elektroden 3, 4 angesteuert, wobei die Stützschicht 2 als durchgehende Massenelektrode dient und die eigentlichen Ansteuerelektroden aus einer peripheren Ansteuerelektrode 3 und einer zentralen Ansteuerelektrode 4 bestehen. Diese Ansteuerelektroden 3 und 4 definieren konzentrisch zueinander angeordnete Membranbereiche in Form von Kreisflächen bzw. Kreisringflächen. Steuert man nun eine derartig aufgebaute Membran so an, daß sich zwischen den Elektroden 3 und 4 der polarisierten Piezokeramik 1 und der gemeinsamen Gegenelektrode 2 elektrische Felder unterschiedlicher Richtung ausbilden, so wölbt sich die Membran in der in der Fig. 2 dargestellten Richtung aus, wenn es durch die Kreisringelektrode 3 zu einer Kontraktion der Piezokeramikschicht 1 im Bereich der Ringelektrode 3 kommt und im Bereich der Elektrode 4 zu einer Dehnung der Piezokeramikschicht 1.A planar transducer made of piezoceramic, as shown in FIGS. 2 and 3, consists of a piezoelectrically excitable layer 1 made of piezoceramic which is polarized in one direction and a support layer 2, for example made of Nikkel, which is firmly connected to this excitable layer. This electrically controllable membrane thus formed is controlled via corresponding electrodes 3, 4, the support layer 2 serving as a continuous ground electrode and the actual control electrodes consisting of a peripheral control electrode 3 and a central control electrode 4. These control electrodes 3 and 4 define membrane regions arranged concentrically to one another in the form of circular surfaces or circular ring surfaces. Now you control one membrane constructed in such a way that between the electrodes 3 and 4 of the polarized piezoceramic 1 and the common counterelectrode 2 electric fields of different directions form, the membrane bulges in the direction shown in FIG. 2 when it passes through the circular electrode 3 there is a contraction of the piezoceramic layer 1 in the area of the ring electrode 3 and an expansion of the piezoceramic layer 1 in the area of the electrode 4.

Dies wird im folgenden anhand der Fig. 1 näher erläutert.This is explained in more detail below with reference to FIG. 1.

Die kleinste und kompakteste geometrische Form, die von einer ebenen Schicht ausgeht, nur schwache Krümmungen benötigt, und einen Hohlraum erweitert und schließt, ist eine Warze oder eine domartige Auswölbung. Eine derartige Form ist rotationssymmetrisch um eine Flächennormale und verläßt die Ebene in einer torusförmigen Hohlkehle, die in einen linsenförmige Kugelabschnitt übergeht.The smallest and most compact geometric shape, starting from a flat layer, requiring only slight curvatures, and expanding and closing a cavity, is a wart or a dome-like bulge. Such a shape is rotationally symmetrical about a surface normal and leaves the plane in a toroidal fillet which merges into a lenticular spherical section.

Eine derartige Idealform kann man nun dadurch erzeugen, daß man eine ebene elastische Membran einem gleichmäßigen Innendruck aussetzt. Damit ergibt sich die auf der linken Seite der Fig. 1a dargestellte Form mit dem in der Fig. 1b dargestellten Neigungsverlauf und einem Krümmungsverlauf gemäß Fig. 1c, wobei die Abszisse dem Radius der Membranfläche zugeordnet ist.Such an ideal shape can now be created by exposing a flat elastic membrane to a uniform internal pressure. This results in the shape shown on the left-hand side of FIG. 1a with the inclination curve shown in FIG. 1b and a curve curve according to FIG. 1c, the abscissa being assigned to the radius of the membrane surface.

Um diese ideale Warzenform zu erreichen, sind nun erfindungsgemäß die Ansteuerelektroden 3 und 4 in Verbindung mit der piezoelektrisch anregbaren Schicht 1 und der Stützschicht 2, die als Masseelektrode dient, so ausgebildet, daß sich näherungsweise diese Idealform bei der Auslenkung ergibt.In order to achieve this ideal wart shape, the drive electrodes 3 and 4 are now designed according to the invention in connection with the piezoelectrically excitable layer 1 and the support layer 2, which serves as a ground electrode, in such a way that this ideal shape approximately results during the deflection.

Zu diesem Zweck ist die kreisförmige Außenelektrode 3 im äußeren Krümmungsbereich der Membran angeordnet und wird mit einem derartigen elektrischen Feld beaufschlagt, daß sich die piezoelektrische Schicht in diesem Krümmungsbereich zusammenzieht. Die konzentrisch dazu angeordnete Innenelektrode 4 wiederum wird mit einem derartigen Feld beaufschlagt, daß sich der zentrale Bereich der Piezokeramikschicht 1 ausdehnt. Damit werden zwei Effekte gleichzeitig ausgenutzt, nämlich die Querkontraktion der Keramik selbst und die Krümmung des Verbundes benachbarter Schichten, die sich unterschiedlich ausdehnen. Der Krümmungsradius, bis zu dem sich ebene Schichten derartig erwölben lassen liegt etwa bei 0,1 m bis 0,4 m je nachdem wie dünn man die Schichten fertigen kann. Das Verhältnis der Elektrodenflächen zueinander ist nun so dimensioniert, daß sich die gewünschte Näherung des Verlaufes in Fig. 1a ergibt. Dies ergibt eine Neigung gemäß Fig. 1b mit zugehöriger Krümmung Fig. 1c (rechte Seite Fig. 1).For this purpose, the circular outer electrode 3 is arranged in the outer region of curvature of the membrane and is subjected to an electrical field such that the piezoelectric layer contracts in this region of curvature. The inner electrode 4, which is arranged concentrically thereto, is in turn subjected to a field such that the central region of the piezoceramic layer 1 expands. Two effects are thus exploited simultaneously, namely the transverse contraction of the ceramic itself and the curvature of the bond between adjacent layers, which expand differently. The radius of curvature up to which flat layers can be arched in this way is approximately 0.1 m to 0.4 m, depending on how thin the layers can be made. The ratio of the electrode areas to one another is now dimensioned such that the desired approximation of the course in FIG. 1a results. This results in an inclination in accordance with FIG. 1b with the associated curvature in FIG. 1c (right side in FIG. 1).

Wie in den Fig. 2 bis 5 dargestellt, läßt sich mit einem derartigen planaren Wandler aus Piezokeramik eine statische Pumpe bestehend aus zwei steuerbaren Sperrschiebern SE und SA und einem veränderlichen Hohlraum H ausbilden. Zu diesem Zwecke sind in einem Keramiksubstrat drei Membranbereiche für SE, H, SA ausgebildet. In einer das Substrat 1 mit seiner zugehörigen Stützschicht 2 tragenden Trägerschicht T ist ein Pumpkanal P ausgebildet. Dieser Pumpkanal P steht mit einem Fluidvorrat V (Fig. 4) in Verbindung. In dem Pumpkanal ist im Bereich des Einlaßventiles SE eine Querrippe Q ausgeformt, an die sich im unerregten Zustand die Membran aus Piezokeramik 1 und Stützschicht 2 anlegt und damit den Kanal verschließt. Im angeregten Zustand entsprechend der Fig. 2 hebt sich die Membran warzenförmig ab und öffnet damit den Kanal P.As shown in FIGS. 2 to 5, with such a planar converter made of piezoceramic, a static pump consisting of two controllable gate valves SE and SA and a variable cavity H can be formed. For this purpose, three membrane areas for SE, H, SA are formed in a ceramic substrate. A pump channel P is formed in a carrier layer T carrying the substrate 1 with its associated support layer 2. This pump channel P is connected to a fluid supply V (FIG. 4). A transverse rib Q is formed in the pump channel in the area of the inlet valve SE, against which the membrane made of piezoceramic 1 and support layer 2 is applied in the unexcited state and thus closes the channel. In the excited state according to FIG. 2, the membrane lifts off in a wart-like manner and thus opens the channel P.

Derselbe Aufbau, wie beim Einlaßventil SE mit der Querrippe Q, ergibt sich beim Auslaßventil SA mit der dortigen Querrippe Q. Zwischen dem Einlaßventil SE und dem Auslaßventil SA befindet sich der als eigentliche Pumpe H dienende Membranbereich, der entsprechend den Membranen der Einlaßventile SE und SA aufgebaut ist. Eine derartig aufgebaute Pumpe, wie in den Fig. 4 und 5, läßt sich nun in vorteilhafter Weise z.B. über einen Dreiphasendrehstrom ansteuern und zwar dadurch, daß mit einer ersten Phase in einem Pumpschritt zunächst das Einlaßventil SE geöffnet wird, daß durch Auslenkung der Membran H Fluid aus dem Vorrat V angesaugt wird und daß dann nach Schließen des Einlaßventiles SE und nach Öffnen des Auslaßventiles SA (3. Phase) durch Betätigung der eigentlichen Pumpmembran H Fluid aus dem Auslaßbereich A ausgestoßen wird.The same structure as for the inlet valve SE with the transverse rib Q results in the outlet valve SA with the transverse rib Q there. Between the inlet valve SE and the outlet valve SA there is the membrane area serving as the actual pump H, which corresponds to the membranes of the inlet valves SE and SA is constructed. A pump constructed in this way, as in FIGS. 4 and 5, can now be advantageously used e.g. Control via a three-phase three-phase current, namely that the inlet valve SE is first opened with a first phase in a pumping step, that fluid is drawn in from the reservoir V by deflecting the membrane H and then after closing the inlet valve SE and opening the outlet valve SA (3rd phase) by actuating the actual pump membrane H fluid is ejected from the outlet area A.

Je nach Verwendungszweck läßt sich der Pumpkanal auch in anderer Weise ausbilden. So ist es auch möglich, durch kragenförmig ausgeformte Wände runder Einund Auslaßöffnungen A, die in die Pumpkanäle ragen die Querrippen Q zu ersetzen. Die Membranfläche legt sich dann im unerregten Zustand in analoger Weise wie auf die Querrippe auf diesen Kragen auf und verschließt so den Einoder Auslaß.Depending on the intended use, the pump channel can also be designed in a different way. It is also possible to replace the transverse ribs Q by walls of round inlet and outlet openings A which protrude into the pump channels. The membrane surface then lies in the unexcited state in a manner analogous to that on the transverse rib on this collar and thus closes the inlet or outlet.

Für eine derartige statische Pumpe sind nun vielerlei Anordnungen möglich. So kann entsprechend der Fig. 13 damit ein Tintenschreibkopf aufgebaut werden, bei dem auf einem einzigen Substrat 1 z.B. neun Schreibdüsen S1 bis S9 angeordnet sind. Jede dieser Schreibdüsen besteht aus einem Einlaßventil SE, einem veränderlichen Hohlraum H und einem Auslaßventil SA. Die Schreibdüsen S1 bis S9 stehen dabei mit dem Vorratsbereich V in Verbindung. Um einen Schreibkopf mit einer größeren Anzahl von Düsen bilden zu können, ist es auch möglich, mehrere Substrate 1 mit Schreibdüsen übereinander zu packen.Various arrangements are now possible for such a static pump. Thus, according to FIG. 13, an ink writing head can be constructed in which e.g. nine writing nozzles S1 to S9 are arranged. Each of these writing nozzles consists of an inlet valve SE, a variable cavity H and an outlet valve SA. The writing nozzles S1 to S9 are connected to the storage area V. In order to be able to form a write head with a larger number of nozzles, it is also possible to pack several substrates 1 with write nozzles one above the other.

Bei einem derartigen Tintenschreibkopf sind die Schreibdüsen S1 bis S9 funktionell vollständig von der Tintenversorgung V getrennt. Damit kann ein mechanischer Verschluß der Düsen zwischen Schreibkopf und dem davor angeordneten Papier und der Antrieb dieses Verschlusses entfallen, da die Tintenkanäle durch die Auslaßventile SA geschlossen sind, solange diese Auslaßventile SA nicht angesteuert werden. Ein Übersprechen zwischen den Düsen entfällt, da beim eigentlichen Spritzvorgang keine Fließverbindung besteht. Die Spritzvorgänge werden dabeinicht durch die Reflektion im Spritzkanal und nicht durch das Übersprechen von Nachbardüsen begrenzt, sondern nur durch die Eigenwerte der einzelnen Schreibdüsen S1 bis S9. Durch statisches Pumpen lassen sich Luftblasen aus dem Tintenkanal P entfernen und leere Kanäle wieder füllen.In the case of such an ink writing head, the writing nozzles S1 to S9 are functionally completely separated from the ink supply V. A mechanical closure of the nozzles between the write head and the paper arranged in front of it and the drive of this closure can thus be dispensed with, since the ink channels are closed by the outlet valves SA as long as these outlet valves SA are not actuated. Crosstalk between the nozzles is eliminated, since the actual one Spraying process there is no flow connection. The spraying processes are not limited by the reflection in the spray channel and not by the crosstalk from neighboring nozzles, but only by the eigenvalues of the individual writing nozzles S1 to S9. Static pumping removes air bubbles from ink channel P and refills empty channels.

Wie in den Fig. 6 bi 10 dargestellt, läßt sich der erfindungsgemäße Tintenshreibkopf besonders einfach in planarer Technik herstellen. Zu diesem Zwecke wird gemäß Fig. 6 ein aus Piezokeramik bestehendes Substrat 1 von einer Stärke von etwa 200 um zunächst polarisiert und ge prüft. Dann wird die Piezokeramik 1 beidseitig durch Vakuumbedampfen oder Sputtern metallisiert (z.B. 50 nm Ti und 500 nm Cu). Die Stützschicht 2 wird ganzflächig galvanisch abgeschieden. Gleichzeitig können auf der gegenüberliegenden Seite der Keramik 1 mit Hilfe einer Fotoresistmarkierung die peripheren und zentralen Ansteuerelektroden 3 und 4 samt Zuleitungen L erzeugt werden (z.B. 100 um Ni).As shown in FIGS. 6 to 10, the ink write head according to the invention can be produced particularly simply using planar technology. For this purpose, according to FIG. 6, a substrate 1 consisting of piezoceramic with a thickness of approximately 200 μm is first polarized and tested. Then the piezoceramic 1 is metallized on both sides by vacuum evaporation or sputtering (e.g. 50 nm Ti and 500 nm Cu). The support layer 2 is galvanically deposited over the entire surface. At the same time, the peripheral and central control electrodes 3 and 4 together with supply lines L (e.g. 100 μm Ni) can be produced on the opposite side of the ceramic 1 with the aid of a photoresist marking.

Damit später die Warze vom Steg Q getrennt werden kann bedarf es in diesem Bereich einer zum übrigen Aufbau selektiv ätzbaren, dünnen Zwischenschicht Z (z.B. 0,2 mm AI oder Cu). Sie wird aufgedampft oder gesputtert und fotolithographisch-ätztechnisch strukturiert.So that the wart can later be separated from the web Q, a thin intermediate layer Z (e.g. 0.2 mm Al or Cu) that is selectively etchable to the rest of the structure is required in this area. It is vapor-deposited or sputtered and structured using photolithography and etching technology.

Die Ausformung der Kanäle P kann durch galvanische Abscheidung einer Metallschicht W zwischen einer Fotore siststruktur erfolgen (z.B. 50 um Ni). Nach Aufbringen einer metallischen Leitschicht über den nichtleitenden Fotoresist wird dann galvanisch die Trägerschicht T ganzflächig abgeschieden (z.B. 100 um Ni). Die Kanalwände W können aber auch mit derTrägerschichtTin einem Schritt zusammen erzeugt werden. Dazu wird auf der Stützschicht 2 eine Struktur K aus Fotoresit oder Metall (z.B. Cu) von der Gestalt der späteren Kanäle und Hohlräume erzeugt. Verwendet man Fotoresit so muß anschließend seine Oberfläche mit einer weiteren dünnen Metallschicht leitfähig gemacht werden. Bei Verwendung von Metall kann auf der Struktur K und der restlichen freiliegenden Substratfläche 2 direkt das Kanalwand-Trägerschicht Metall galvanisch abgeschieden werden (z.B. 100 pm Ni), FIG 11.The channels P can be formed by electrodeposition of a metal layer W between a photoresist structure (e.g. 50 μm Ni). After a metallic conductive layer has been applied over the non-conductive photoresist, the support layer T is then galvanically deposited over the entire surface (e.g. 100 μm Ni). However, the channel walls W can also be produced together with the carrier layer T in one step. For this purpose, a structure K made of photoresite or metal (e.g. Cu) of the shape of the later channels and cavities is produced on the support layer 2. If photoresite is used, then its surface must be made conductive with another thin metal layer. If metal is used, the channel wall support layer metal can be electrodeposited directly on the structure K and the remaining exposed substrate surface 2 (e.g. 100 pm Ni), FIG. 11.

Die Struktur K aus Fotoresit oder Metall wird dann selektiv zum Gesamtaufbau herausgelöst und abschließend der Quersteg Q durch Herauslösen der Zwischenschicht von der Warze getrennt.The structure K made of photoresite or metal is then selectively removed from the overall structure and finally the crossbar Q is separated from the wart by removing the intermediate layer.

Es ist aber auch möglich, zunächst auf den dünnen Hilfsschichten (ALU) die Wände der Kanalstruktur (W) zu strukturieren und in die so gebildeten Kanäle P einen ätzbaren Füllstoff einzufüllen. Nach Aufbringen der Trägerschicht T wird dann der ätzbare Füllstoff entfernt und die Hilfsschicht (Z) ebenfalls entfernt, damit sich die Querrippen Q beim Hochwölben des Substrates 1 von der Stützschicht 2 lösen können.However, it is also possible to first structure the walls of the channel structure (W) on the thin auxiliary layers (ALU) and to fill an etchable filler into the channels P thus formed. After the carrier layer T has been applied, the etchable filler is then removed and the auxiliary layer (Z) is also removed so that the transverse ribs Q can detach from the support layer 2 when the substrate 1 bulges.

Zur Erleichterung der ätztechnischen Entfernung der Hilfsschichten bzw. der die Kanäle strukturierenden Werkstoffe können Öffnungen vorgesehen sein, die später wieder geschlossen werden.To facilitate the etching removal of the auxiliary layers or the materials structuring the channels, openings can be provided which are later closed again.

Um ein Verlaufen des Verbundes bei Temperaturänderungen zu verhindern, kann außerhalb der Elektroden auf der Rückseite der Keramikschicht 1 eine weitere Stützschicht SS aufgebracht werden. Es ist auch möglich, die Leitungen L für die Elektroden 3 und 4 (Fig. 10) gleichzeitig mit der Stützschicht also aus dem gleichen Material und in gleicher Dicke zu erzeugen.In order to prevent the composite from running when the temperature changes, a further support layer SS can be applied outside the electrodes on the back of the ceramic layer 1. It is also possible to produce the lines L for the electrodes 3 and 4 (FIG. 10) simultaneously with the support layer, ie from the same material and with the same thickness.

Anstelle der beschriebenen Querrippe Q ist es gemäß Fig. 12 auch möglich die Querrippe kreisförmig auszubilden, womit dann die Achse der Auslaßdüse A eine Richtung senkrecht zur Substratfläche 1 aufweist. Es ist also möglich, den Tintenschreibkop so aufzubauen, daß die Austrittsdüsen A stirnseitig am Substrat angeordnet sind oder derartig, daß sie an der Substratoberfläche angeordnet sind. Welches die vorteilhaftere Anordnung ist, hängt von dem Verwendungszweck ab. Wie außerdem in der Fig. 14 dargestellt, kann zur Erhöhung der Teilungssichte zwischen der Rasterzeile RZ der Tintenschreibkopf gegen die Raster zeile in einem Winkel geneigt sein.Instead of the transverse rib Q described, it is also possible according to FIG. 12 to design the transverse rib in a circular manner, with the axis of the outlet nozzle A then having a direction perpendicular to the substrate surface 1. It is therefore possible to construct the ink writing head so that the outlet nozzles A are arranged on the end face of the substrate or in such a way that they are arranged on the substrate surface. Which is the more advantageous arrangement depends on the intended use. As also shown in FIG. 14, to increase the division view between the raster line RZ the ink writing head can be inclined at an angle to the raster line.

Claims (19)

1. Ink writing head comprising ink ejection channels (P) and piezoelectric transducer elements (3, 4) allocated to the ink ejection channels (P), said transducer elements being supplied with writing fluid via supply lines (V), said transducer elements (3, 4) containing an electrically drivable membrane having a first piezoelectrically excitable layer (1) and a supporting layer (2) firmly joined to this excitable layer and the ink being ejected from the ink ejection channels (P) due to excursions of the membrane, characterized in that the piezoelectrically excitable layer (1) has a peripheral region (3) and a central region (4) which are driven in such a way for generating an excursion of the membrane needed for writing operation that the peripheral region (3) is shortened by transversal contraction and the central region (4) is lengthened by dilation.
2. Ink writing head according to Claim 1, characterized in that the piezoelectrically excitable layer (1), continuously polarized in one direction, has a through electrode (2) to earth on its one side and a first drive electrode (3), allocated to the peripheral region, and a second drive electrode (4), allocated to the central region, on its other side, the peripheral region and the central region being charged with different electrical fields for driving.
3. Ink writing head according to Claim 1, characterized in that the piezoelectrically excitable layer has a through electrode (2) to earth on its one side and a common drive electrode on its other side, the peripheral regions and the central region being differently polarized.
4. Ink writing head according to one of Claims 1 to 3, characterized in that the membrane regions (3, 4) of a membrane are arranged concentrically relative to one another and arc outwards in button-like fashion when driven.
5. Ink writing head according to one of Claims 1 to 4, characterized in that a plurality of membrane regions (3, 4) individually activatable independently of one another are arranged on a common substrate surface (1).
6. Ink writing head according to Claim 5, characterized in that the drive lines (L) for the individual membrane regions lead across unpolarized regions of the membrane surface.
7. Ink writing head according to one of Claims 1 to 6, characterized in that the supporting layer (2) is replaced by a further piezoelectrically excitable layer which is respectively polarized in a direction opposite the first piezoelectrically excitable layer.
8. Ink writing head according to one of Claims 1 to 7, characterized in that the membrane mechanically closes the ink channels in its non-activated condition.
9. Ink writing head according to one of Claims 1 to 8, characterized in that every ink channel has three membrane regions which are connected to one another via a pump channel (P) for the writing fluid allocated to it, said three membrane regions forming a static pump having two controllable rotary pistons (SE, SA) and a variable cavity (H), the first membrane region (SE) being connected on the one hand to the ink supply system (V) via a supply channel and on the other hand to the variable cavity (H) and arranged as an admission valve between the supply channel and the cavity, the second membrane region (PH) effecting the pump stroke with its variable cavity, and a third membrane region (SA) being arranged as outlet valve between the cavity (PH) and the outlet region (A) of the ink channel.
10. Ink writing head according to Claim 9, characterized in that the pump channel (P) connecting the membrane regions has parting webs (Q) in the region of the membrane surfaces fashioned as valves, said parting webs cooperating with the membrane surfaces such that, after outward arcing of the membrane surfaces, the pump channel opens via the parting webs and, in the non-deflected condition of the membrane surfaces, the pump channel is interrupted in the region of the parting webs (Q) via the membrane surfaces.
11. Ink writing head according to one of Claims 1 to 10, characterized in that a plurality of membrane surfaces are arranged over one another in the ink writing head.
12. Ink writing head according to one of Claims 1 to 11, characterized in that the ink writing head (TS) is inclined towards the scan lines in order to diminish the division between the scan lines (RZ).
13. Method of manufacturing an ink writing head according to one of Claims 1 to 12, characterized in that a thin layer of piezoceramic is used as substrate (1), the required structure of the ink head being galvanoplastically constructed thereon.
14. Method according to Claim 13, characterized in that the piezoceramic layer (1) is polarized before the galvanoplastic structuring.
15. Method according to one of Claims 13 or 14, characterized in that the piezoceramic (1) is metallized on both sides by vapour-deposition or sputtering, drive electrodes (3, 4) as well as the leads (Z) appertaining thereto are subsequently photolithographically-voltaically structured on the one side thereof, in that, simultaneously, the supporting layer (2) is electro-deposited on the other side of the piezoceramic and in that one or more thin auxiliary layers are then generated and structured on the supporting layer (2), the membrane being capable of being separated from the cross-rib (Q) in the channel structure (P) on the basis of the later dissolving-out of said auxiliary layers.
16. Method according to one of Claims 13 to 15, characterized in that the walls (W) of the channel structure (P) are electro-deposited over the supporting layer (2) and the thin auxiliary layers (Z) between photoresist structures, in that a thin metal layer is applied over the photoresist structures and over the channel wall layer, in that the carrier layer (T) is electro-deposited thereon surface-wide and in that the photoresist is selectively dissolved out.
17. Method according to one of Claims 13 to 15, characterized in that a structure (K) of photoresist or metal having the shape of the channels is generated over the supporting layer (2) and over the thin auxiliary layers (Z), in that, if the structure (K) is composed of photoresist, a thin metal film is applied thereover, in that the channel walls (W) and the carrier layer (T) are then electro-deposited in common over the supporting layer (2) and over the structure (K) as a topographic layer and in that, finally, the structure (K) is selectively dissolved out.
18. Method according to one of Claims 13 to 15, characterized in that the walls (W) of the channel structures for the acceptance of the writing fluid are structured on the thin auxiliary layers, in that the channels (P) formed in this way are then filled with an etchable filler and a cover layer (T) is applied to the channels (P) filled in this way and in that the filler is then removed.
19. Method according to one of Claims 16 or 17, characterized in that openings which are later closed are provided for facilitating the etched removal of the auxiliary layers or, respectively, of the materials which structure the channels (P).
EP87903243A 1986-05-30 1987-05-19 Ink writing head with piezoelectrically excitable membrane Expired - Lifetime EP0307403B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3618107 1986-05-30
DE19863618107 DE3618107A1 (en) 1986-05-30 1986-05-30 INK WRITING HEAD WITH PIEZOELECTRICALLY EXTENDABLE MEMBRANE

Publications (2)

Publication Number Publication Date
EP0307403A1 EP0307403A1 (en) 1989-03-22
EP0307403B1 true EP0307403B1 (en) 1990-08-01

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EP87903243A Expired - Lifetime EP0307403B1 (en) 1986-05-30 1987-05-19 Ink writing head with piezoelectrically excitable membrane

Country Status (5)

Country Link
US (1) US4888598A (en)
EP (1) EP0307403B1 (en)
JP (1) JPH01500891A (en)
DE (2) DE3618107A1 (en)
WO (1) WO1987007217A1 (en)

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Also Published As

Publication number Publication date
EP0307403A1 (en) 1989-03-22
DE3764094D1 (en) 1990-09-06
WO1987007217A1 (en) 1987-12-03
JPH01500891A (en) 1989-03-30
DE3618107A1 (en) 1987-12-03
US4888598A (en) 1989-12-19

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