EP0363325A1 - Method for propelling droplets of a conductive liquid - Google Patents

Method for propelling droplets of a conductive liquid Download PDF

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Publication number
EP0363325A1
EP0363325A1 EP89810741A EP89810741A EP0363325A1 EP 0363325 A1 EP0363325 A1 EP 0363325A1 EP 89810741 A EP89810741 A EP 89810741A EP 89810741 A EP89810741 A EP 89810741A EP 0363325 A1 EP0363325 A1 EP 0363325A1
Authority
EP
European Patent Office
Prior art keywords
liquid
current
voltage
electrode
fact
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.)
Withdrawn
Application number
EP89810741A
Other languages
German (de)
English (en)
French (fr)
Inventor
Jacques Vermot-Gaud
Didier Joyeux
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Battelle Memorial Institute Inc
Original Assignee
Battelle Memorial Institute Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Battelle Memorial Institute Inc filed Critical Battelle Memorial Institute Inc
Publication of EP0363325A1 publication Critical patent/EP0363325A1/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—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
    • B41J2/14016—Structure of bubble jet print heads
    • B41J2/14088—Structure of heating means
    • B41J2/14096—Current flowing through the ink

Definitions

  • the present invention relates to a method for propelling droplets of an electrically conductive liquid, according to which the end of a first electrode whose cross-section is ap­proximately of the order of size of that of the droplets in dis­posed in this liquid, this end being flush with an insulated support surrounded by the said liquid a second electrode, a surface of which is substantially greater than that of the said end of the first electrode, is disposed in this liquid in con­tact with it, and these two electrodes are connected to the ter­minals of a pulse generator to cause resistive heating of the liquid in the immediate proximity of the said end, suitable for vaporising a quantity of the said liquid capable of producing a force able to propel a droplet of this liquid.
  • the present invention has as a subject a me­thod for propelling droplets of an electrically conductive liq­uid according to Claim 1.
  • the device illustrated in Figure 1 corresponds to that which is described and illustrated in European Patent Specifica­tion No. B1 0,106,802, which may be advantageously referred to for further details.
  • This device comprises a first electrode 1 formed by a thin wire of a metal which is a good conductor of electricity and is corrosion resistant, bonded onto an insulat­ing support 2. The end of this electrode 1 is flush with the surface of this support 2.
  • a membrane 3, which may be metallic, is pierced by an opening 4, disposed co-axially with the elec­trode 1, and serving for the projection of droplets of a liquid 5, which fills the space between the membrane 3 and the insulat­ing support 2, this space forming the reservoir for the liquid.
  • a second electrode 6, whose surface in contact with the liquid is appreciably greater than that of the end of the electrode 1, is disposed somewhere in the volume of liquid 5.
  • tests have been carried out with a mem­brane 3 40 ⁇ m to 50 ⁇ m thick, the opening 4 having a diameter of 80 ⁇ m to 100 ⁇ m, the membrane 3 being 40 ⁇ m from the support 2, and the electrode 1 being formed by a wire of stainless steel or platinum 20 ⁇ m to 25 ⁇ m diameter. Copper is also of interest as a metal for the electrode, in particular in regard to its re­sistance to electro-erosion. Other dimensions and different ma­terials have been used and also the electrode 1 has been placed at a positive or negative polarity, thus changing the direction of the current.
  • the con­ductive ink behaves as an electrolyte
  • the polarity of the electrode 1 is positive, it receives oxygen and is thus subject­ed to a high risk of corrosion.
  • the elec­trode 1 becomes the cathode, and it receives hydrogen or metal.
  • the superheating phase obtained on account of an increase in current is that which influences to the greatest extent the result obtained.
  • this current is strongly dependent on the level of ionisation, such that the corresponding energy may be very variable. Consequently, the formation and the dimension of the droplets may also vary in the same proportions, which constitutes an important disadvantage in this method of projection of droplets, consistency obviously be­ing a quality factor, in particular in the context of a printing process.
  • the inven­tion has an object, by limiting the current and as a conse­quence the energy during this second phase of the process of projection of droplets, so as to stabilise the formation of the droplets, reduce their size and maintain consistency of size.
  • Figure 4 illustrates the circuit of the electrical pulse generator used to produce the short voltage pulses of a duration of 5 to 10 microseconds and at a voltage preferably between 400 and 600 volts.
  • the resistivity of the ink is chosen preferably between 400 and 800 ohm-cm. Below this limit, the electroche­mical current would be increased and as a consequence the pro­duction of gas bubbles, while above this limit, the voltage of the electrical pulses would be increased.
  • this circuit comprises a step-up transformer TR in which the ratio between the secondary S400 and the primary P10 is here 40, that is, 400 turns for the secondary and 10 for the primary.
  • the primary P10 of this transformer is supplied with pulses by a generator G, which delivers pulses of the desired duration, here of 5 to 10 ⁇ s, to the base of a field effect transistor T1.
  • the supply circuit for the primary P10 of the transformer TR has three diodes in series, D1, D2, D3, with a resistance R1200 and a ca­pacitor C2 ⁇ F. These diodes in series with the resistance R1200 produce a polarisation of about 1.5V stored in the capacitor C2 ⁇ F.
  • the capacitor C2 ⁇ F discharges with a cur­rent of opposite direction directed in the direction of the ar­row CD, which passes through the resistance R120 and repolarises the transformer TR for the next pulse from the generator G.
  • a current limit­ing circuit is associated with the secondary S400.
  • the part of this circuit comprising a resistance R1M in series with a resistance R5K in parallel with a Zener diode is connected to the base of a transistor T2.
  • the electrodes 1 and 6 of Figure 1 are connected respectively to the points a and b of the circuit of Figure 4, in such a way that the electrode 1 is negative with respect to the ink and the current I goes from the ink towards the electrode 1 in the direction of the arrow of Figure 4. This enables electrochemical corrosion of the elec­trode 1 to be avoided.
  • the Zener diode the polaris­ing voltage e o of the transistor T2 is maintained constant. Its emitter is thus at a potential e ′ o corresponding to the voltage e o less the voltage of the transistor, which is here 0.2V.
  • Another solution giving a less precise result but one which may be sufficient, would consist of using a series impedance, for example a resistance equal to the resistance of the elec­trode 1.
  • the circuit of Figure 4 was tested with success by limiting the value of the current I o to 30 mA. Accordingly comparative tests with and without current limitation were carried out. On the one hand, the energy of the phase 2 of superheating produc­ting the projection of the droplets was measured and the diameter of the droplets obtained was also measured. The tests were carried out with a device comprising an electrode 1 ot 12 ⁇ m diameter, of platimun, and having an opening 4 of 80 ⁇ m diameter and 40 ⁇ m length. The table below indicates the results ob­tained in the two cases. Superheating Energy (microjoules) Dimension of droplets ( ⁇ m) With current limitation 30 100 - 120 Without current limitation 30 - 80 100 - 200
  • the instability of the process of projection intervenes and is inherent in this process as long as the energy of the super-­heating phase of the liquid vapour is not limited. It hus fol­lows that in the context of the droplet propulsion process de­scribed, this limitation is a determining element for consisten­cy, inherent in the fact that only the superheating phase of the liquid vapour is capable of producing sufficient energy to project the droplets, but that the current in this medium in the vapour phase is extremely variable from one moment to another, generating energy levels liable to vary in an approximate ratio of 1 to 3.
  • an intermedi­ate energy storage element such as a capacitor or an inductance may be used.
  • a circuit enabling the energy delivered to be limited or defined by means of a capacitor C is illustrated in Figure 5.
  • a resistance R is chosen so that the capacitor C is charged slowly to a selected voltage V greater than the ionisation volt­age V o . While the transistor T conducts, the capacitor C dis­charges into the conductive liquid to be propelled between the electrodes 1 and 6, at a current level I, until the moment when the voltage becomes less than the ionisation voltage V o . At that moment, the transistor T ceases to conduct and the current I is interrupted.
  • the energy delivered is thus equal to 1/2 C (V2 - V 2 o )
  • Figure 6 illustrates the case of a circuit using an in­ductance L to limit the energy delivered. It is to be noted how­ever that this second solution is more difficult and more expen­sive than the preceding, as it requires a very great inductance L of the order of 100 mhenry while the circuit of Figure 5 only requires a very small capacitor C of the order of 100 picofarad.
  • the transistor T is then cut-off, causing at the point A of the circuit an increase in voltage sufficient to re-establish the current across the vaporised liquid because of the ionisation.
  • the discharge current of the inductance L continues until all the stored energy disappears. The energy supplied thus corresponds to: - 1/2 L I2.
  • the membrane will comprise seve­ral openings 4 side by side, and the insulating support several electrodes 1.
  • the ink is equipotential with respect to the electrodes 1 and 6.
  • the membrane 5 is electrically conductive, being for example formed by a sheet of copper which also serves as a counter-electrode 6.
  • This arrangement enables interference between neighbouring propelling devices to be avoided, which are spaced in this example at 250 ⁇ m from axis to axis, and in particular it enables obstruction of the passage of current in the case of formation of bubbles on an electrode 1 to be avoided.
  • the insu­lating support 2 the electrodes 1 to 1n, and the membrane 3 with the openings 4 disposed opposite the electrodes 1 to 1 n .
  • a high voltage source HT with the primary P10 and the secondary S400 of the transformer TR supplying the high voltage pulses of ⁇ 400 volts.
  • Each electrode 1 to 1 n is associated with a selector comprising a selection transistor TS1 to TS n whose base is selectively polarised by the logic of the printer (not shown) by voltage signals E1 to E n .
  • These transistors are provided with current limitation by virtue of the resistance of 220 ohms for example, placed in series with the emitter. The current is thus limited to (E i - V be ) / 220 (5 -1) / 220 ⁇ 18mA (V be : base-emitter voltage of the transistor).
  • the selectors thus play a double role, actual selection and limitation of current, and therefore of energy.
  • the ink and the membrane 3 must be at a positive potential with respect to the electrodes 1 to 1n to ensure that the direc­tion of the current is such that it enters these electrodes from the ink in such a manner that the potential of ⁇ 400 volts is applied to the membrane 3 while the electrode selectors are con­ nected to a 0 V reference potential.
  • each electrode 1 to 1n is ener­gised by the secondary S400 of an independent transformer sup­plying a pulse of ⁇ 400 volts to the electrode.
  • the reference point of each secondary is connected to a 0 volt potential, as is the membrane 3 which plays the role of counter-electrode.
  • Each pulse carries the potential of the electrode or the electrodes selected at -HT ( ⁇ 400 volts) to ensure the direction of the current from the ink to the electrode, the counter elec­trode being at the 0 volt potential.
  • the selection transistors TS1 to TS n are arranged in series with the primary P10 of each transformer.
  • the base of each tran­sistor is selectively polarised by the logic of the printer by voltage signals E1 to E n .
  • These transistors are provided with current limitation by virtue of the resistance of 1.5 ohms in series with the emitter. In this way, the current at the secon­dary S400 and as a consequence that on the electrode is likewise limited.
  • the leakage self-inductance of the transformers also produces a dynamic limitation of the electrode current.

Landscapes

  • Particle Formation And Scattering Control In Inkjet Printers (AREA)
  • Ink Jet (AREA)
EP89810741A 1988-10-05 1989-09-28 Method for propelling droplets of a conductive liquid Withdrawn EP0363325A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH3705/88 1988-10-05
CH3705/88A CH677755A5 (enrdf_load_stackoverflow) 1988-10-05 1988-10-05

Publications (1)

Publication Number Publication Date
EP0363325A1 true EP0363325A1 (en) 1990-04-11

Family

ID=4261749

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89810741A Withdrawn EP0363325A1 (en) 1988-10-05 1989-09-28 Method for propelling droplets of a conductive liquid

Country Status (4)

Country Link
US (1) US5001496A (enrdf_load_stackoverflow)
EP (1) EP0363325A1 (enrdf_load_stackoverflow)
JP (1) JPH02150358A (enrdf_load_stackoverflow)
CH (1) CH677755A5 (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0753410A3 (en) * 1995-06-28 1997-06-25 Riso Kagaku Corp Inkjet device and conductive liquid
US5801730A (en) * 1995-12-14 1998-09-01 Nec Corporation Ink jet print head having a projecting ejection electrode

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2783226B2 (ja) * 1995-12-06 1998-08-06 日本電気株式会社 インクジェット式ヘッド装置
KR100205747B1 (ko) * 1996-07-04 1999-07-01 윤종용 잉크젯프린터의 분사장치 및 분사방법
EP1199163B1 (en) * 1999-05-31 2008-04-02 FUJIFILM Corporation Lithographic method and lithographic device, plate making method and plate making device, and ink jet printing method and printing device
KR20050060288A (ko) * 2003-12-16 2005-06-22 삼성전자주식회사 잉크젯 프린트헤드

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4126867A (en) * 1977-08-29 1978-11-21 Silonics, Inc. Ink jet printer driving circuit
EP0106802A1 (fr) * 1982-10-08 1984-04-25 Battelle Memorial Institute Dispositif pour projeter des gouttelettes d'un liquide électriquement conducteur
US4746937A (en) * 1985-06-10 1988-05-24 Ing. C. Olivetti & C., S.P.A. Control apparatus for an on-demand ink jet printing element

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1129356B (it) * 1980-10-31 1986-06-04 Olivetti Ing C Spa Dispositivo di stampa a getto selettivo di inchiostro
IT1144294B (it) * 1981-07-10 1986-10-29 Olivetti & Co Spa Dispositivo di stampa getto selettivo d inchiostro

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4126867A (en) * 1977-08-29 1978-11-21 Silonics, Inc. Ink jet printer driving circuit
EP0106802A1 (fr) * 1982-10-08 1984-04-25 Battelle Memorial Institute Dispositif pour projeter des gouttelettes d'un liquide électriquement conducteur
US4746937A (en) * 1985-06-10 1988-05-24 Ing. C. Olivetti & C., S.P.A. Control apparatus for an on-demand ink jet printing element

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0753410A3 (en) * 1995-06-28 1997-06-25 Riso Kagaku Corp Inkjet device and conductive liquid
US5801730A (en) * 1995-12-14 1998-09-01 Nec Corporation Ink jet print head having a projecting ejection electrode

Also Published As

Publication number Publication date
JPH02150358A (ja) 1990-06-08
US5001496A (en) 1991-03-19
CH677755A5 (enrdf_load_stackoverflow) 1991-06-28

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