EP0458997B1 - Method of operating a thermal ink jet printer - Google Patents

Method of operating a thermal ink jet printer Download PDF

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Publication number
EP0458997B1
EP0458997B1 EP19900110284 EP90110284A EP0458997B1 EP 0458997 B1 EP0458997 B1 EP 0458997B1 EP 19900110284 EP19900110284 EP 19900110284 EP 90110284 A EP90110284 A EP 90110284A EP 0458997 B1 EP0458997 B1 EP 0458997B1
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EP
European Patent Office
Prior art keywords
ink
drop
channel
ejected
pulse
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.)
Expired - Lifetime
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EP19900110284
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German (de)
French (fr)
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EP0458997A1 (en
Inventor
Andreas Berchtold
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Eastman Kodak Co
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Siemens AG
Eastman Kodak Co
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Priority to DE59006710T priority Critical patent/DE59006710D1/en
Priority to EP19900110284 priority patent/EP0458997B1/en
Publication of EP0458997A1 publication Critical patent/EP0458997A1/en
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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
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
    • B41J2/04516—Control methods or devices therefor, e.g. driver circuits, control circuits preventing formation of satellite drops
    • 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
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
    • B41J2/04528—Control methods or devices therefor, e.g. driver circuits, control circuits aiming at warming up the head
    • 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
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
    • B41J2/0458—Control methods or devices therefor, e.g. driver circuits, control circuits controlling heads based on heating elements forming bubbles

Definitions

  • the invention relates to a method for operating an ink writing device working according to the thermal converter principle and a recording head for such a device according to the features of the patent claim.
  • Known ink heads that work according to the thermal converter principle (bubble jet principle) and are described, for example, in DE-OS 30 12 698, have a large number of individual nozzles from which defined individual droplets are ejected under the action of an electronic control.
  • a characteristic feature of this technology is that an electrical resistor designed as a heating element is located in a capillary filled with ink, in the vicinity of its opening. If a certain amount of thermal energy is supplied to this heating element by means of a short current pulse, extremely rapid heat transfer to the ink liquid (film boiling) first creates a rapidly expanding ink vapor bubble (bubble), which then collapses relatively quickly after the energy supply is lost by cooling the ink liquid .
  • the pressure wave generated by the ink vapor bubble in the interior of the capillaries causes an ink jet of limited mass to emerge from the nozzle opening onto the surface of a nearby recording medium.
  • An advantage of this bubble jet principle is that by utilizing the phase change liquid-gaseous-liquid of the ink liquid, the relatively large and rapid volume change necessary for ink ejection is obtained from a very small active transducer area (typically approx. 0.01 mm2) .
  • the small transducer areas when using modern manufacturing processes, such as high-precision photolithographic processes in layer technology, allow a relatively simple and inexpensive construction of ink writing heads which are distinguished by a high density of traces and small dimensions.
  • Such ink writing heads are therefore advantageously used in ink writing devices which operate according to the so-called drop-on-demand principle, i.e.
  • the structure of the characters and / or the graphic patterns is carried out by the controlled ejection of individual ink droplets which, with a corresponding relative movement between the recording medium and the writing head, build up the characters or patterns in a grid in a predetermined character matrix.
  • To generate an acceptable typeface it is necessary to eject spherical droplets of the same mass and speed at precisely defined points in time.
  • the surrounding ink liquid is heated up to evaporation by a suitable current pulse through the resistance heating element.
  • the resulting ink vapor bubble briefly generates a high pressure in the ink channel, which leads to the ejection of an ink droplet, hereinafter referred to as primary drop, from the nozzle opening.
  • primary drop an ink droplet
  • overpressure arises again, which can lead to the ejection of another droplet, the so-called micro-jet, especially at high speeds of the primary drop.
  • micro jets in bubble jet writing mechanisms can be suppressed by reducing the drop flight speed of the primary drop and thus the flow speeds in the ink channel as a whole.
  • the lowering of the flying speed of the primary drop requires a lowering of the working speed (spray frequency) of the entire ink writing device.
  • the invention is therefore based on the object of specifying measures for an ink writing device of the type mentioned at the outset with which these micro-jets can be safely prevented in a simple manner without impairing the printing speed.
  • the condensation of the ink vapor bubble can be delayed either by increased heat supply to the electrothermal transducer element or by reduced heat dissipation not according to the invention.
  • the increased supply of heat is achieved according to the invention by reheating the heating element by means of one or more current pulses of suitable duration but of the same amplitude. This subsequent heat supply is adjusted in terms of the time and the amount so that the collapse of the ink vapor bubble is only delayed, but not a new one is generated, which in turn would lead to the ejection of a further drop.
  • FIG. 1 shows a schematic representation of a print head structure as used in an ink printing device that works according to the so-called bubble jet principle.
  • the ink writing head 10 is built up in layers and the ink is supplied through an opening in the cover plate.
  • a series of ink channels 12 are formed on a substrate 11, for example made of silicon, by means of separating webs 13.
  • Each ink channel 12 ends on the side facing a recording medium (not shown here) in an outlet nozzle 14. All ink channels 12 are connected to an ink chamber 15 in the interior of the print head 10.
  • Each ink channel 12 is assigned an electrothermal transducer element in the form of a heating resistor 16, which can be contacted and controlled individually from the outside via contact connections 17, which run in the form of conductor tracks on the substrate 11.
  • a protective layer 18 covering the heating resistors 16 and the contact connections 17 serves to reduce interfering influences between the ink liquid 23 and the resistance or contact material.
  • a cover plate 19 above the substrate 11 and the channel structure 12 built thereon which is preferably consists of glass or a similar material and in which the ink chamber 15 is formed.
  • the ink is supplied to the ink chamber 15 via an opening 20 through which the ink liquid 23 is introduced into the ink chamber 15, for example via a line or via a channel 21, additional connecting and sealing devices 22 being provided.
  • the supply of ink liquid 23 into the ink chamber 15 can alternatively take place through an opening in the substrate 11.
  • the left half of FIG. 2 shows a current pulse 26 suitable for the control of the electrothermal transducer elements 16, which is characterized by its relative amplitude I / I max under the pulse duration T.
  • the pulse is applied to the transducer element 16. This begins to heat up and the ink liquid 23 is heated locally. Pressure begins to build up within the ink channel 12 and the ink vapor bubble 28 begins to develop. After approximately 6 ⁇ s, the pulse is switched off again, the ink vapor bubble continues to grow, and a primary drop 24 is expelled from the outlet nozzle 14.
  • the ink vapor bubble 28 condenses very quickly, in the ink channel 12 there is negative pressure when the vapor bubble collapses, through which ink liquid 23 is sucked out of the ink channel 12 and ink liquid 23 is withdrawn from the outlet nozzle 14.
  • the collision of these two liquid fronts from the ink channel and the nozzle again leads to excess pressure, which causes an additional, troublesome drop, the so-called "micro-jet" 25, to emerge from the nozzle 14.

Landscapes

  • Particle Formation And Scattering Control In Inkjet Printers (AREA)

Description

Die Erfindung betrifft ein Verfahren zum Betreiben einer nach dem Thermalwandler-Prinzip arbeitenden Tintenschreibeinrichtung sowie einen Aufzeichnungskopf für eine solche Einrichtung gemäß den Merkmalen des Patentansprüchs.The invention relates to a method for operating an ink writing device working according to the thermal converter principle and a recording head for such a device according to the features of the patent claim.

Ein Verfahren gemäß dem Oberbegriff des Anspruchs ist aus dem JP-A-63199652 bekannt.A method according to the preamble of the claim is known from JP-A-63199652.

Bekannte Tintenschreibköpfe, die nach dem Thermalwandler-Prinzip (Bubble-Jet-Prinzip) arbeiten und beispielsweise in der DE-OS 30 12 698 beschrieben werden, weisen eine Vielzahl von Einzeldüsen auf, aus denen unter Einwirkung einer elektronischen Steuerung definiert Einzeltröpfchen ausgestoßen werden. Charakteristisches Merkmal dieser Technologie ist, daß sich in einer mit Tinte gefüllten Kapillaren, und zwar in der Nähe ihrer Öffnung, ein als Heizelement ausgebildeter elektrischer Widerstand befindet. Wird diesem Heizelement bei Bedarf mittels eines kurzen Stromimpulses eine bestimmte Wärmeenergie zugeführt, entsteht durch äußerst schnelle Wärmeübertragung auf die Tintenflüssigkeit (Filmsieden) zuerst eine sich rasch expandierende Tintendampfblase (Bubble), die dann nach Wegfall der Energiezuführung durch Abkühlung der Tintenflüssigkeit relativ schnell in sich zusammenfällt. Die durch die Tintendampfblase im Inneren der Kapillaren entstehende Druckwelle läßt einen Tintenstrahl begrenzter Masse aus der Düsenöffnung auf die Oberfläche eines nahen Aufzeichnungsträgers austreten.Known ink heads that work according to the thermal converter principle (bubble jet principle) and are described, for example, in DE-OS 30 12 698, have a large number of individual nozzles from which defined individual droplets are ejected under the action of an electronic control. A characteristic feature of this technology is that an electrical resistor designed as a heating element is located in a capillary filled with ink, in the vicinity of its opening. If a certain amount of thermal energy is supplied to this heating element by means of a short current pulse, extremely rapid heat transfer to the ink liquid (film boiling) first creates a rapidly expanding ink vapor bubble (bubble), which then collapses relatively quickly after the energy supply is lost by cooling the ink liquid . The pressure wave generated by the ink vapor bubble in the interior of the capillaries causes an ink jet of limited mass to emerge from the nozzle opening onto the surface of a nearby recording medium.

Ein Vorteil dieses Bubble-Jet-Prinzips ist der, daß durch Ausnutzung des Phasenwechsels flüssig-gasförmig-flüssig der Tintenflüssigkeit die zum Tintenausstoß notwendige, relativ große und schnelle Volumenänderung aus einer sehr kleinen aktiven Wandlerfläche (typisch ca. 0,01 mm²) gewonnen wird. Die kleinen Wandlerflächen wiederum erlauben bei Anwendung moderner Herstellungsverfahren, wie hochpräzise photolithographische Verfahren in Schichttechnik, einen relativ einfachen und kostengünstigen Aufbau von Tintenschreibköpfen, die sich durch hohe Schreibspurendichte und geringe Abmessungen auszeichnen.An advantage of this bubble jet principle is that by utilizing the phase change liquid-gaseous-liquid of the ink liquid, the relatively large and rapid volume change necessary for ink ejection is obtained from a very small active transducer area (typically approx. 0.01 mm²) . The small transducer areas, in turn, when using modern manufacturing processes, such as high-precision photolithographic processes in layer technology, allow a relatively simple and inexpensive construction of ink writing heads which are distinguished by a high density of traces and small dimensions.

Solche Tintenschreibköpfe werden deshalb vorteilhaft in Tintenschreibeinrichtungen verwendet, die nach dem sogenannten Drop-on-Demand-Prinzip arbeiten, d.h. der Aufbau der Zeichen und/oder der graphischen Muster erfolgt durch den gesteuerten Ausstoß einzelner Tintentröpfchen, die bei einer entsprechenden Relativbewegung zwischen dem Aufzeichnungsträger und dem Schreibkopf die Zeichen oder Muster innerhalb einer vorgegebenen Zeichenmatrix rasterförmig aufbauen. Dabei ist zur Erzeugung eines akzeptablen Schriftbildes der Ausstoß von kugelförmigen Einzeltröpfchen gleicher Masse und Geschwindigkeit zu genau definierten Zeitpunkten erforderlich.Such ink writing heads are therefore advantageously used in ink writing devices which operate according to the so-called drop-on-demand principle, i.e. The structure of the characters and / or the graphic patterns is carried out by the controlled ejection of individual ink droplets which, with a corresponding relative movement between the recording medium and the writing head, build up the characters or patterns in a grid in a predetermined character matrix. To generate an acceptable typeface, it is necessary to eject spherical droplets of the same mass and speed at precisely defined points in time.

Bei den bekannten Bubble-Jet-Schreibköpfen wird durch einen geeigneten Stromimpuls durch das Widerstands-Heizelement die umgebende Tintenflüssigkeit bis zur Verdampfung erwärmt. Die dabei entstehende Tintendampfblase erzeugt im Tintenkanal kurzzeitig einen hohen Druck, der zum Ausstoß eines Tintentröpfchens, in folgendem als Primärtropfen bezeichnet, aus der Düsenöffnung führt. Während des Zusammenfallens der Dampfblase herrscht Unterdruck, der Flüssigkeit aus dem Tintenkanal ansaugt und zum Zurückziehen der Tintenflüssigkeit in der Austrittsdüse führt. Treffen nun die beiden Flüssigkeitsfronten aus Tintenkanal und Austrittsdüse zusammen, so entsteht wiederum Überdruck, der besonders bei hoher Geschwindigkeit des Primärtropfens zum Ausstoß eines weiteren Tröpfchens, dem sogenannten Micro-Jet führen kann. Diese ungewollt zusätzlich ausgestoßenen Tröpfchen beeinträchtigen das Schriftbild, weil damit auf Rasterpunkte des Matrixgitters unterschiedliche Tintenmassen aufgebracht werden.In the known bubble jet writing heads, the surrounding ink liquid is heated up to evaporation by a suitable current pulse through the resistance heating element. The resulting ink vapor bubble briefly generates a high pressure in the ink channel, which leads to the ejection of an ink droplet, hereinafter referred to as primary drop, from the nozzle opening. During the collapse of the vapor bubble, there is negative pressure which draws liquid from the ink channel and leads to the withdrawal of the ink liquid in the outlet nozzle. If the two liquid fronts from the ink channel and the outlet nozzle now meet, overpressure arises again, which can lead to the ejection of another droplet, the so-called micro-jet, especially at high speeds of the primary drop. These unintentionally ejected droplets adversely affect the typeface because different ink masses are applied to grid points of the matrix grid.

Die Bildung dieser Micro-Jets bei Bubble-Jet-Schreibwerken kann dadurch unterdrückt werden, daß die Tropfenfluggeschwindigkeit des Primärtropfens und damit die Strömungsgeschwindigkeiten im Tintenkanal insgesamt verringert werden. Die Senkung der Flugeschwindigkeit des Primärtropfens bedingt aber eine Verringerung der Arbeitsgeschwindigkeit (Spritzfrequenz) der gesamten Tintenschreibeinrichtung.The formation of these micro jets in bubble jet writing mechanisms can be suppressed by reducing the drop flight speed of the primary drop and thus the flow speeds in the ink channel as a whole. However, the lowering of the flying speed of the primary drop requires a lowering of the working speed (spray frequency) of the entire ink writing device.

Der Erfindung liegt deshalb die Aufgabe zugrunde, Maßnahmen für eine Tintenschreibeinrichtung der eingangs genannten Art anzugeben, mit denen diese Micro-Jets auf einfache Weise sicher verhindert werden können, ohne daß dabei eine Beeinträchtigung der Druckgeschwindigkeit auftritt.The invention is therefore based on the object of specifying measures for an ink writing device of the type mentioned at the outset with which these micro-jets can be safely prevented in a simple manner without impairing the printing speed.

Diese Aufgabe wird gemäß den Merkmalen des Patentanspruchs gelöst.This object is achieved according to the features of the patent claim.

Die Bildung zusätzlicher Tropfen wird verhindert, indem der Überdruck abgebaut wird, der beim Zusammenfallen der Dampfblase entsteht. Dies kann erreicht werden durch eine Verzögerung der Kondensation der Dampfblase, wodurch die Strömungsgeschwindigkeit gesenkt wird, mit der die Flüssigkeitsfronten aus der Austrittsdüse und dem Tintenkanal aufeinandertreffen. Dies hat den Vorteil, daß die Geschwindigkeit des Primärtropfens davon unbeeinflußt bleibt.The formation of additional drops is prevented by reducing the excess pressure which arises when the vapor bubble collapses. This can be achieved by delaying the condensation of the vapor bubble, thereby reducing the flow rate at which the liquid fronts from the exit nozzle and the ink channel meet. This has the advantage that the speed of the primary drop remains unaffected.

Den größten Einfluß auf die Kondensation der Tintendampfblase hat die Wärme, die während dieses Vorgangs zu- oder abgeführt wird. Daher kann die Kondensation der Tintendampfblase entweder durch vermehrte Wärmezufuhr zu dem elektrothermischen Wandlerelement oder durch nicht erfindungsgemäße verringerte Wärmeabfuhr verzögert werden.The heat that is added or removed during this process has the greatest influence on the condensation of the ink vapor bubble. Therefore, the condensation of the ink vapor bubble can be delayed either by increased heat supply to the electrothermal transducer element or by reduced heat dissipation not according to the invention.

Die erhöhte Wärmezufuhr wird erfindungsgemäß durch ein Nachheizen des Heizelementes mittels eines oder mehrerer Stromimpulse geeigneter Dauer aber gleicher Amplitude erreicht. Diese nachträgliche Wärmezufuhr wird bezüglich des Zeitpunktes und der Menge so abgestimmt, das das Zusammenfallen der Tintendampfblase lediglich verzögert, nicht aber eine neue erzeugt wird, die ihrerseits zum Ausstoß eines weiteren Tropfens führen würde.The increased supply of heat is achieved according to the invention by reheating the heating element by means of one or more current pulses of suitable duration but of the same amplitude. This subsequent heat supply is adjusted in terms of the time and the amount so that the collapse of the ink vapor bubble is only delayed, but not a new one is generated, which in turn would lead to the ejection of a further drop.

Die Erfindung wird in folgendem anhand eines Ausführungsbeispiels erläutert, wozu auf die Darstellungen verwiesen wird.The invention is explained below using an exemplary embodiment, for which reference is made to the illustrations.

Dort zeigen

Fig. 1
in Prinzipdarstellung den Aufbau eines Tintenschreibkopfes,
Fig. 2
die Dampfblasenerzeugung nach einem Stand der Technik und
Fig. 3
die Dampfblasenerzeugung nach der Erfindung.
Show there
Fig. 1
in principle the structure of an ink writing head,
Fig. 2
the vapor bubble generation according to a prior art and
Fig. 3
the vapor bubble generation according to the invention.

Die Fig. 1 zeigt in Prinzipdarstellung einen Schreibkopfaufbau, wie er in einer nach dem sogenannten Bubble-Jet-Prinzip arbeitenden Tintendruckeinrichtung Verwendung findet. Der Tintenschreibkopf 10 ist dabei schichtweise aufgebaut und die Tintenzufuhr erfolgt durch eine Öffnung in der Abdeckplatte. Auf einem Substrat 11, z.B. aus Silizium, sind eine Reihe von Tintenkanälen 12 mittels Trennstegen 13 ausgebildet. Jeder Tintenkanal 12 endet an der einem hier nicht dargestellten Aufzeichnungsträger zugewandten Seite in eine Austrittsdüse 14. Sämtliche Tintenkanäle 12 stehen mit einer Tintenkammer 15 im Innern des Druckkopfes 10 in Verbindung. Jedem Tintenkanal 12 ist ein elektrothermisches Wandlerelement in Form eines Heizwiderstandes 16 zugeordnet, der über Kontaktanschlüsse 17, die in Form von Leiterbahnen auf dem Substrat 11 verlaufen, von außen kontaktierbar und individuell ansteuerbar sind. Eine die Heizwiderstände 16 und die Kontaktanschlüsse 17 überdeckende Schutzschicht 18 dient zur Reduzierung störender Einflüsse zwischen der Tintenflüssigkeit 23 und dem Widerstands- bzw. Kontaktmaterial. Über dem Substrat 11 und der darauf aufgebauten Kanalstruktur 12 befindet sich eine Abdeckplatte 19, die vorzugsweise aus Glas oder einem ähnlichen Material besteht und in der die Tintenkammer 15 ausgeformt ist. Die Tintenzufuhr in die Tintenkammer 15 erfolgt über eine Öffnung 20, über die die Tintenflüssigkeit 23, z.B. über eine Leitung oder über einen Kanal 21, in die Tintenkammer 15 eingeführt wird, wobei zusätzliche Verbindungsund Abdichtungseinrichtungen 22 vorgesehen sind.1 shows a schematic representation of a print head structure as used in an ink printing device that works according to the so-called bubble jet principle. The ink writing head 10 is built up in layers and the ink is supplied through an opening in the cover plate. A series of ink channels 12 are formed on a substrate 11, for example made of silicon, by means of separating webs 13. Each ink channel 12 ends on the side facing a recording medium (not shown here) in an outlet nozzle 14. All ink channels 12 are connected to an ink chamber 15 in the interior of the print head 10. Each ink channel 12 is assigned an electrothermal transducer element in the form of a heating resistor 16, which can be contacted and controlled individually from the outside via contact connections 17, which run in the form of conductor tracks on the substrate 11. A protective layer 18 covering the heating resistors 16 and the contact connections 17 serves to reduce interfering influences between the ink liquid 23 and the resistance or contact material. There is a cover plate 19 above the substrate 11 and the channel structure 12 built thereon, which is preferably consists of glass or a similar material and in which the ink chamber 15 is formed. The ink is supplied to the ink chamber 15 via an opening 20 through which the ink liquid 23 is introduced into the ink chamber 15, for example via a line or via a channel 21, additional connecting and sealing devices 22 being provided.

Die Zufuhr von Tintenflüssigkeit 23 in die Tintenkammer 15 kann auch alternativ durch eine Öffnung im Substrat 11 erfolgen.The supply of ink liquid 23 into the ink chamber 15 can alternatively take place through an opening in the substrate 11.

Die linke Hälfte der Fig. 2 zeigt einen für die Ansteuerung der elektrothermischen Wandlerelemente 16 geeigneten Stromimpuls 26, der durch seine relative Amplitude I/Imax unter der Impulsdauer T charakterisiert ist. Die rechte Hälfte der Fig. 2 zeigt zeitabhängig die verschiedenen Stadien des Tröpfchenausstoßes mit anschließender Kondensation der Tintendampfblase 28. Zum Zeitpunkt t=0 wird der Impuls an das Wandlerelement 16 angelegt. Dieses beginnt sich zu erwärmen, und die Tintenflüssigkeit 23 wird lokal erhitzt. Innerhalb des Tintenkanals 12 beginnt sich ein Druck aufzubauen und die Tintendampfblase 28 beginnt sich zu entwickeln. Nach ca. 6 µs wird der Impuls wieder abgeschaltet, die Tintendampfblase wächst weiter, und es wird ein Primärtropfen 24 aus der Austrittsdüse 14 ausgestoßen. Die Tintendampfblase 28 kondensiert sehr rasch, im Tintenkanal 12 herrscht beim Zusammenfallen der Dampfblase Unterdruck, durch den Tintenflüssigkeit 23 aus dem Tintenkanal 12 nachgesaugt und Tintenflüssigkeit 23 aus der Austrittsdüse 14 zurückgezogen wird. Das Aufeinandertreffen dieser beiden Flüssigkeitsfronten aus dem Tintenkanal und der Düse führt wieder zu einem Überdruck, der einen zusätzlichen, störenden Tropfen, den sogenannten "Micro-Jet" 25, aus der Düse 14 austreten läßt.The left half of FIG. 2 shows a current pulse 26 suitable for the control of the electrothermal transducer elements 16, which is characterized by its relative amplitude I / I max under the pulse duration T. The right half of FIG. 2 shows the various stages of the droplet ejection with subsequent condensation of the ink vapor bubble 28 at time t = 0. The pulse is applied to the transducer element 16. This begins to heat up and the ink liquid 23 is heated locally. Pressure begins to build up within the ink channel 12 and the ink vapor bubble 28 begins to develop. After approximately 6 μs, the pulse is switched off again, the ink vapor bubble continues to grow, and a primary drop 24 is expelled from the outlet nozzle 14. The ink vapor bubble 28 condenses very quickly, in the ink channel 12 there is negative pressure when the vapor bubble collapses, through which ink liquid 23 is sucked out of the ink channel 12 and ink liquid 23 is withdrawn from the outlet nozzle 14. The collision of these two liquid fronts from the ink channel and the nozzle again leads to excess pressure, which causes an additional, troublesome drop, the so-called "micro-jet" 25, to emerge from the nozzle 14.

Anhand der Fig. 3 wird erläutert, wie gemäß der Erfindung diese zusätzlichen aus der Austrittsdüse austretenden Tintentröpfchen 25 vermieden werden können. Im Unterschied zur Fig. 1 wird dabei die Kondensation der Dampfblase verzögert, wodurch die Strömungsgeschwindigkeiten im Tintenkanal 12 gesenkt werden, mit denen die Flüssigkeitsfronten aus der Düse und demjenigen Teil des Tintenkanals 12, der mit dem Tintenreservoir verbunden ist, aufeinandertreffen. Die Geschwindigkeit, mit der der Primärtropfen 24 die Austrittsdüse 14 verläßt, bleibt dabei unbeeinflußt. Die Verzögerung der Kondensation der Tintendampfblase 28 wird durch erhöhte Wärmezufuhr an das Wandlerelement 16 erreicht. Hierzu dient ein Nachheizimpuls 27, der kurz vor dem endgültigen Zusammenfallen der Tintendampfblase an das Heizelement angelegt wird. Bei einem typischen Anwendungsfall mit einem den Primärtropfen 24 auslösenden Heizimpuls 26 von ca. 6 µs Impulsdauer und einer relativen Amplitude I/I max = 1

Figure imgb0001
genügt ein Nachheizimpuls 27 gleicher Amplitude von ca. 3 µs Impulsdauer, der ca. nach 35 µs dem Hauptheizimpuls folgt. Dadurch wird eine Verzögerung der Kondensation der Dampfblase erreicht, ohne daß eine neue Dampfblase erzeugt wird, die ihrerseits zum Ausstoß eines weiteren Tropfens führen würde.3 explains how, according to the invention, these additional ink droplets 25 emerging from the outlet nozzle can be avoided. In contrast to FIG. 1, the condensation of the vapor bubble is delayed, as a result of which the flow velocities in the ink channel 12 are reduced, with which the liquid fronts from the nozzle and the nozzle Part of the ink channel 12, which is connected to the ink reservoir, meet. The speed at which the primary drop 24 leaves the outlet nozzle 14 remains unaffected. The delay in the condensation of the ink vapor bubble 28 is achieved by increased heat supply to the transducer element 16. A reheating pulse 27 is used for this purpose, which is applied to the heating element shortly before the ink vapor bubble finally collapses. In a typical application with a heating pulse 26 which triggers the primary drop 24 and has a pulse duration of approximately 6 μs and a relative amplitude I / I Max = 1
Figure imgb0001
 a reheating pulse 27 of the same amplitude of about 3 µs pulse duration is sufficient, which follows the main heating pulse after about 35 µs. This achieves a delay in the condensation of the vapor bubble without creating a new vapor bubble, which in turn would lead to the ejection of another drop.

Um die gewünschte Verzögerung beim Zusammenfallen der Dampfblase zu erreichen, ist es aber auch möglich, mehrere Nachheizimpulse gleicher Amplitude anzulegen.In order to achieve the desired delay in the collapse of the vapor bubble, it is also possible to apply several post-heating pulses of the same amplitude.

Claims (1)

  1. A method for operating an ink printer which operates according to the thermal converter principle, in which
    - ink (23) is heated in localized manner until it evaporates by means of current pulses (26) through electrothermal converter elements (16) located in ink channels (12) of an ink print head (10),
    - the resulting ink vapour bubble (28) in the ink channel (12) briefly causes a high pressure which causes a drop of ink (24) to be ejected from the outlet nozzles (14) at the end of the ink channels (12),
    - the underpressure prevailing upon the subsequent collapse of the ink vapour bubble (28) draws ink (23) out of the ink channel (12) and draws ink (23) back from the outlet nozzles (14), and
    - the overpressure occurring upon the meeting of the two liquid fronts in the ink channel (12) and in the outlet nozzle (14) is reduced such that the condensation of the ink vapour bubble (28) is delayed by an increased supply of heat to the converter element (16) and thereby once the ink drop (24) has been ejected no further, unwanted, ink drop (25) is ejected, and
    - the increased supply of heat to the converter element (16) takes place by at least one subsequent heating pulse (27) following the current pulse (26) triggering the evaporation,
    characterised in that the subsequent heating pulse has the same amplitude as the current pulse.
EP19900110284 1990-05-30 1990-05-30 Method of operating a thermal ink jet printer Expired - Lifetime EP0458997B1 (en)

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DE59006710T DE59006710D1 (en) 1990-05-30 1990-05-30 Method for operating an ink writing device according to the thermal converter principle.
EP19900110284 EP0458997B1 (en) 1990-05-30 1990-05-30 Method of operating a thermal ink jet printer

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Application Number Priority Date Filing Date Title
EP19900110284 EP0458997B1 (en) 1990-05-30 1990-05-30 Method of operating a thermal ink jet printer

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EP0458997B1 true EP0458997B1 (en) 1994-08-03

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US8449058B2 (en) * 2008-05-23 2013-05-28 Fujifilm Dimatix, Inc. Method and apparatus to provide variable drop size ejection with low tail mass drops

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4463359A (en) * 1979-04-02 1984-07-31 Canon Kabushiki Kaisha Droplet generating method and apparatus thereof
EP0112000A3 (en) * 1982-12-15 1985-04-03 Hewlett-Packard Company Thermal ink jet printer utilizing secondary ink vaporization
US4523200A (en) * 1982-12-27 1985-06-11 Exxon Research & Engineering Co. Method for operating an ink jet apparatus

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