WO1995025011A1 - Ameliorations apportees a un appareil a impulsions de depot de gouttelettes - Google Patents

Ameliorations apportees a un appareil a impulsions de depot de gouttelettes Download PDF

Info

Publication number
WO1995025011A1
WO1995025011A1 PCT/GB1995/000562 GB9500562W WO9525011A1 WO 1995025011 A1 WO1995025011 A1 WO 1995025011A1 GB 9500562 W GB9500562 W GB 9500562W WO 9525011 A1 WO9525011 A1 WO 9525011A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage
channels
channel
pressure
electrode means
Prior art date
Application number
PCT/GB1995/000562
Other languages
English (en)
Inventor
Stephen Temple
Michael George Arnott
Original Assignee
Xaar Limited
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 Xaar Limited filed Critical Xaar Limited
Priority to KR1019960705109A priority Critical patent/KR100341175B1/ko
Priority to DE69505960T priority patent/DE69505960T2/de
Priority to EP95911395A priority patent/EP0751873B1/fr
Priority to CA002184076A priority patent/CA2184076C/fr
Priority to JP7523918A priority patent/JP2969570B2/ja
Publication of WO1995025011A1 publication Critical patent/WO1995025011A1/fr
Priority to US08/699,798 priority patent/US6123405A/en
Priority to HK98113826A priority patent/HK1013639A1/xx

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—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
    • B41J2/04525—Control methods or devices therefor, e.g. driver circuits, control circuits reducing occurrence of cross talk
    • 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
    • B41J2/04581—Control methods or devices therefor, e.g. driver circuits, control circuits controlling heads based on piezoelectric elements
    • 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
    • B41J2/04588—Control methods or devices therefor, e.g. driver circuits, control circuits using a specific waveform
    • 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
    • B41J2/04596—Non-ejecting pulses
    • 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
    • B41J2/055—Devices for absorbing or preventing back-pressure
    • 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
    • B41J2202/00—Embodiments of or processes related to ink-jet or thermal heads
    • B41J2202/01—Embodiments of or processes related to ink-jet heads
    • B41J2202/10—Finger type piezoelectric elements

Definitions

  • the present invention relates to pulsed droplet deposition apparatus, for example drop-on-demand-ink jet printing apparatus and, in the most important example, provides voltage waveforms for the control of such apparatus.
  • Ink jet printing apparatus having a multiplicity of closely spaced parallel ink channels and channel separating piezo-electricaliy displaceable wall actuators have been disclosed for example in US-A-4879568 (EP-B-0277703) and in EP-A-4887100 (EP-B-0278590). In such apparatus each channel is actuable by one or both of the displaceable side-walls.
  • an external connection is provided which relates to each channel and when a voltage difference is applied between the electrode corresponding to one channel and the electrodes of the neighbouring channels, the walls adjacent to the channel are displaced causing the volume of the centre channel, depending on the voltage sign, t expand or to contract and an ink drop to be ejected from the nozzle communicating with the channel.
  • One feature of the above printing apparatus having displaceable side-walls is that operation of every channel at the same time is excluded. Operation takes place by dividing the printhead into two groups of odd and even channels, which are operated alternately. Alternatively the printhead i divided into groups of three, four or more channels which are operated in rotation (EP-A-0376532).
  • the present invention seeks to reduce or eliminate one or both of the foregoing disadvantages.
  • the present invention consists in one aspect in a method of operating multichannel pulsed droplet deposition apparatus having droplet liquid channels each with a nozzle having a negative pressure wave reflection coefficient r, the method comprising ejecting a droplet from a selected channel by generating a defined pressure pulse therein and substantially cancelling residual pressure waves in said channel by generating a further pressure pulse after a delay of 2L/c where L is the length of the channel and c is the effective velocity of pressure waves therein.
  • the amplitude of said furiher pressure pulse being related to the amplitude of said defined pressure pulse by the factor r.
  • the method comprises ejecting a droplet from a selected channel by generating a negative pressure pulse of duration IVc followed by a positive pressure pulse of duration at least LJc with the duration of said positive pressure pulse preferably being 2L/c
  • the selected channel is bounded by a displaceable wall actuator, displacement of which generates said first and further pressure pulses, said actuator also bounding an adjacent non- selected channel, the selected and non-selected channels being in respective groups of channels which are actuated sequentially, the displacement of the actuator also generating a complementary first pressure pulse in the adjacent channel and a complementary further pulse in said adjacent channel which cancels residual pressure waves therein arising from the complementary first pressure pulse.
  • the present invention consists in a method of operating multichannel pulsed droplet deposition apparatus having droplet liquid channels separated by wall actuators displaceable on the application thereto of a voltage difference, each channel having electrode means associated with the wall actuators bounding that channel such that a voltage difference can be applied to a specified wall actuator by the application of different voltages to the respective electrode means of the two channels separated by the said wall actuator, the method comprising the actuation of a selected channel through the steps of applying in different time periods a first actuating voltage to the electrode means of the selected channel and a second actuating voltage of the same polarity to the electrode means of non-selected channels, thereby to cause an expansion and contraction of the droplet liquid volume of the selected channel to effect ejection of a droplet therefrom.
  • the channels are divided into at least two groups, the groups being sequentially enabled for actuation, adjacent channels being in different groups.
  • the present ivention consists in a method of operating multichannel pulsed droplet deposition apparatus having droplet liquid channels, the channels being divided into at least two groups, the groups being sequentially enabled for actuation, adjacent channels being in different groups, comprising the steps of actuating selected channels by the application thereto of an actuating pressure variation to effect droplet ejection therefrom, and ensure no pressure wave contribution to the droplet liquid in the channels of sequentially enabled groups of channels by the application of a correcting pressure variation.
  • the correcting pressure variation is delayed in time with respect to the actuating pressure variation by the interval 2LJc.
  • the present invention consists in a method of operating multichannel pulsed droplet deposition apparatus having droplet liquid channels of length L, having an effective velocity c of pressure waves therein, with a droplet ejection nozzle having a pressure wave reflection coefficient r, comprising the steps of actuating selected channels by the application thereto of an actuating pressure variation to effect droplet ejection therefrom, and cancelling residual waves by the application of a correcting pressure variation delayed in time by the interval 2L/c, wherein the correcting pressure variation varies in time in the same manner as the actuating pressure variation and is related in amplitude to the actuating pressure variation by a factor less than 1.
  • the present invention consists in a method of operating multichannel pulsed droplet deposition apparatus having droplet liquid channels separated by wall actuators displaceable on the application thereto of a voltage difference, each channel having electrode means associated with the wall actuators bounding that channel such that a voltage difference can be applied to a specified wall actuator by the application of different voltages to the respective electrode means of the two channels separated by the said wall actuator, the method comprising the actuation of a selected channel through the steps of applying an actuating voltage to the electrode means of the selected channel thereby to effect ejection of a droplet therefrom and the at least partial cancellation of residual pressure waves by applying a correcting voltage of the same polarity to the electrode means of non-selected channels.
  • the present invention consists in a driving circuit for a multi-channel pulsed droplet deposition apparatus having droplet liquid channels separated by wall actuators displaceable on the application thereto of a voltage difference, each channel having electrode means associated with the wall actuators bounding that channel such that a voltage difference can be applied to a specified wall actuator by the application of different voltages to the respective electrode means of the two channels separated by the said wall actuator, the driving circuit having terminals for respective connection with said electrode means and being adapted for actuation of a selected channel through the steps of applying in different time periods a first actuating voltage to the electrode means of the selected channel and a second actuating voltage of the same polarity to the electrode means of non-selected channels, thereby to cause an expansion and contraction of the droplet liquid volume of the selected channel to effect ejection of a droplet therefrom.
  • waveforms are suitable for the operation of multi-channel ink jet printheads having channel dividing wall actuators in which the channels are operated in groups.
  • the waveforms are arranged for application by a unipolar drive circuit, but maintain the advantages of driving the ink channels to eject drops by causing both expansion and contraction of ink channels during operation.
  • the waveforms incorporate reflection suppressing pulses which are applied in the printhead after a period of 2 LJc following the application of the drop ejecting pulse.
  • One particular advantage of the waveforms in the type of printhead referred to is that suppression of the reflected pressure waves occurs in the neighbouring channels as opposed to the channels from which a drop has just been ejected.
  • the waveform applied to the wall actuators comprises step voltage changes at periodic intervals L/c of the channel.
  • the waveform is completed after five intervals LJc : in another embodiment the waveform is completed after four intervals.
  • a portion of the waveform in selected periodic intervals may be applied to the wall actuators adjacent to channels not selected for firing and the remaining portion may be applied to the wall actuators adjacent to channels selected for actuation in accordance with print data provided to the group designated for printing.
  • the waveform applied to the wall actuators in causing the walls both to expand and contract the volume of said selected channels, generates both positive and negative acoustic pressure waves.
  • the positive wave in the second period may be selected in magnitude to control the ejection velocity of the drop.
  • the negative pressure wave in the third period may be selected in magnitude to control drop break-off.
  • voltage waveform is selected in the last two periods thereof to suppress residual acoustic pressure waves in the head, by generating voltage magnitudes which generate pressure waves to substantially cancel the residual acoustic energy after drop ejection in the said selected channel.
  • the voltage magnitudes are selected in relation to the nozzle reflection coefficient (r).
  • the voltage magnitudes for cancellation are applied two acoustic periods LJc (ie. one characteristic time Tc) after the period of generation of acoustic pressure waves generated to effect drop ejection or drop break-up.
  • the voltage waveform may be selected to suppress residual acoustic waves in neighbouring channels adjacent the channel selected for drop ejection.
  • Figure 1 illustrates an exploded view in perspective of one form of ink jet printhead incorporating piezo-electric wall actuators operating in shear mode and comprising a printhead base, a cover and a nozzle plate;
  • Figure 2 illustrates the printhead of Figure 1 in perspective after assembly
  • Figure 3 illustrates a drive circuit connected via connection tracks to the printhead to which are applied a drive voltage waveform, timing signals and print data for the selection of ink channels, so that on application of the waveform, drops are ejected from the channels selected;
  • Figure 4(a) illustrates one form of voltage pattern which on application to a channel generates pressure waves in the channel to eject a drop and subsequently cancels the residual pressure waves in the channel;
  • Figure 4(b) illustrates the corresponding pressure magnitudes in the actuated channel and in a neighbouring channel;
  • Figure 4(c) illustrates how the voltage pattern of Figure 4(a) can be resolved into an actuating voltage pattern (shown in full line) which generates pressure waves in the channel to eject a drop and a correcting voltage pattern (shown in dotted line) which cancels the residual pressure waves in the channel;
  • Figure 5(a) illustrates one unipolar waveform in which first voltage signals are continuously applied to non firing lines and second voltage signals are applied to the lines in channels selected for firing.
  • the waveform is self cancelling by applying cancelling pulses two periods LJc (one characteristic time Tc) following the firing pulses;
  • Figure 5(b) shows the corresponding right going pressure waves (the being adopted in this description that a right going pressure is incident in the nozzle) in the fired channels and in channels which are adjacent to the fired channels. The pressures in non fired channels and channels adjacent to them are negligible and are not shown;
  • Figure 6(a) shows an alternative voltage waveform that may be used in the non-fired and fired lines in place of the voltage signal used in Figure 5(a);
  • Figure 6(b) shows the corresponding right going pressure waves in fired and in adjacent non-fired lines
  • Figure 6(c) shows the difference voltage arising across a wall as a result of the application to the lines on either side of the waveforms shown in Figure 6(a), resolved into an actuating voltage pattern (shown in full line) which generates pressure waves in the channel to eject a drop and a correcting voltage pattern (shown in dotted line) which cancels the residual pressure waves in the channel;
  • Figure 7(a) shows a further alternative voltage waveform that may be used in the non-fired and fired lines in place of the voltage signals above;
  • Figure 7(b) shows the corresponding right going pressure waves in the fired and the adjacent non-fired lines
  • Figures 8 and 9 show still further alternative voltage waveforms that may be used in the non-fired and fired lines in place of the voltage signals of Figure 7(a);
  • Figure 10 is a diagram on which are superimposed for comparison purposes, the voltage difference signals arising from application to the fired and non-fired lines of the waveforms shown in Figure 7(a), Figure 8 and
  • Figure 11 is a diagram similar to Figure 7(a) illustrating a further modification to the invention.
  • Figure 1 shows an exploded view in perspective of a typical ink jet printhead 8 incorporating piezo-electric wall actuators operating in shear mode. It comprises a base 10 of piezo electric material mounted on a base 12 of which only a section showing connection tracks 14 is illustrated. A cover 16, which is bonded during assembly to the base 10 is shown above its assembled location. A nozzle plate 17 is also shown adjacent the printhead base.
  • a multiplicity of parallel grooves 18 are formed in the base 10 extending into the layer of piezo-electric material.
  • the grooves are formed for example as described in US-A-5016028 (EP-A-364136) and comprise a forward part in which the grooves are comparatively deep to provide ink channels 20 separated by opposing actuator walls 22.
  • the grooves in the rearward part are comparatively shallow to provide locations for connection tracks.
  • metallized plating is deposited in the forward part providing electrodes 26 on the opposing faces of the ink channels 20 where it extends approximately one half of the channel height from the tops of the walls and in the rearward part is deposited providing connection tracks 24 connected to the electrodes in each channel 20.
  • the tops of the walls are kept free of plating metal so that the track 24 and the electrodes 26 form isolated actuating electrodes for each channel.
  • the base 10 After the deposition of metallized plating and coating of the base 10 with a passivant layer for electrical isolation of the electrode parts from the ink, the base 10 is mounted as shown in Figure 1 on the circuit board 12 and bonded wire connections are made connecting the connection tracks 24 on the base part 10 to the connection tracks 14 on the circuit board 12.
  • the ink jet printhead 8 is illustrated after assembly in Figure 2.
  • the cover 16 is secured by bonding to the tops of the actuator walls 22 thereby forming a multiplicity of closed channels 20 having access at one end to the window 27 in the cover 16 which provides a manifold 28 for the supply of replenishment ink.
  • the nozzle plate 17 is attached by bonding at the other end of the ink channels.
  • the nozzles 30 are shown in locations in the nozzle plate communicating to each channel formed by UV excimer laser ablation.
  • the printhead is operated by delivering ink from an ink cartridge via the ink manifold 28, from where it is drawn into the ink channels to the nozzles 30 by capillary suction.
  • the drive circuit 32 connected to the printhead is illustrated in Figure 3.
  • connection tracks 14 In one form it is an external circuit connected to the connection tracks 14, but in an alternate form (not shown) an integrated circuit chip may be mounted on the printhead.
  • the drive circuit 32 is operated by applying by a data link 34 the print data 35 defining print locations in each print line as the printhead is scanned over a print surface 36 and at the same time applying an actuating voltage waveform 38 via the signal link 37.
  • the present invention relates particularly to printheads of the type described in US-A-4879568 (EP-B-0277703) and US-A-4887100
  • printheads of the type in which ink channels are divided by laterally displaceable wall actuators and in which each ink channels is actuable by displacing the two wall actuators which bound it on either side.
  • the laterally displaceable wall actuators are actuated by the application of a voltage difference between electrodes located on or adjacent to the walls, so that there may in some constructions be two external electrodes per wall, requiring two external connections for actuation.
  • connection it is usually convenient for connections to be made between the wall electrodes internally to provide one electrode per channel: when a voltage waveform is applied to the electrode corresponding to a channel and a datum voltage is applied to the electrodes of the neighbouring channel, the applied fields in the walls adjacent the channel then effect displacements of each wall causing the volume and pressure in the ink in each channel to be either increased or decreased. Regardless of whether the connections are made internally or externally of the printhead it is then convenient to describe the actuating signal as being applied in relation to a selected channel to effect drop ejection from that channel.
  • a second feature as indicated in the above patent specifications and related patent specifications is that only selected ink channels can be operated at one time and conveniently the channels may be operated in groups.
  • the printhead may be divided into two groups of odd and even channels which are actuated alternately.
  • the channels may be divided into three or four or more groups actuated in rotation.
  • the frequency at which drops may be ejected from one channel is determined by the replenishment time, that is the time following drop ejection that is required to restore the meniscus of ink in the nozzle. If a second waveform to effect drop ejection is applied to the channel following a first waveform before the ink meniscus has come to rest or is completely restored to the nozzle exit, so that replenishment of the channel following the first waveform is incomplete, then the drop generated via the second waveform is found to have a different volume and different velocity from the first drop.
  • printers having displaceable wall actuators by dividing the channels into groups actuated in rotation at first sight might appear to be at a disadvantage, because the speed of operation is reduced by two, three or four or more times depending on the number of groups.
  • ink replenishment time in each channel that controls print rate and there is usually time for drop ejection to take place before replenishment is complete in the first channel
  • this apparent disadvantage of operation in groups is found not to arise in practice: and therefore the advantages of printheads having displaceable wall actuators, which are high channel density, efficient and low voltage operation and low cost of manufacture are obtained with no serious cost in terms of performance or frequency of operation.
  • the present invention is described by reference to actuation of a printhead having displaceable wall actuators by applying voltage waveforms to the electrodes of channels divided into three groups. That is to say the printhead comprises ink channels divided into three groups a, b, and c. It is generally found with the waveforms described that after actuating selected channels of the group a, there is time to actuate channels with the same waveform from groups b and c before replenishment is complete in group a, when a further waveform may then be applied to a.
  • a typical ink channel 20 containing ink and terminated by a nozzle 30 has been recognised in the prior art (e.g. US-A-4743924 or US-A- 4752790) as behaving as an acoustic wave guide in which longitudinal pressure waves are generated.
  • the channel in the above cited art is characterised by an open end at the termination connected to the ink supply and by an acoustically closed end at the nozzle.
  • the pressure waves traverse the channel by 2 L and return to the starting point, but have inverted sign after the characteristic time Tc.
  • a cancelling wave is generated which suppresses or completely cancels the initial drop ejecting pressure pulse by applying a voltage waveform of the same form, but opposite in sign to the original drop ejecting waveform after a time equal to an even multiple of the characteristic time Tc (i.e. 2Tc, 4Tc, 6Tc etc. which equals 4 L/c, 8 L7c, 12 LJc etc.).
  • Tc characteristic time
  • Such a voltage pulse is referred to as reflection suppressing or self cancelling.
  • Current ink jet printheads typically print at the resolutions, delivering ink volumes and employing nozzle sizes of magnitudes approximately as follows: Resolution Drop Volume Nozzle size dpmm pl Diameter ⁇ m
  • nozzle terminations for nozzles of the above dimensions and with typical inks are generally acoustically open terminations. Accordingly the acoustic wave guide, represented by each channel has a negative reflection coefficient at the nozzle end.
  • Ink supply end RM -1 Nozzle end -0.2 ⁇ R M ⁇ -0.7
  • R N will vary depending upon the nozzle geometry and ink characteristics.
  • a unit pressure pulse in one period L c followed by a pressure pulse of magnitude -R M R N of the same duration applied after a delay of 2 IJc i.e. after one internally reflected characteristic period Tc
  • This shorter period for cancellation conveniently reduces the total period for the generation of a voltage waveform to effect drop ejection and then to suppress or cancel the residual pressure waves.
  • 2 LJc is the resonance period of a channel, and may include some allowance for the inertance of the channel terminations.
  • each period L/c generate right and left going waves which in turn reflect from the terminations, and add further pressure waves.
  • the applied pressure waves and the reflected waves are added in successive periods, the magnitudes of the total right and left going waves may be obtained, and these are shown in the third and fourth rows of Table I.
  • the cancelling voltage pulse +r in the third period is then seen to cause complete cancellation of both the right going and left going pressure waves in the fourth period. Since r is negative, the cancelling pressure pulse is opposite in sign to the initial pulse.
  • FIG. 4(a) A typical voltage waveform for drop ejection is illustrated in Figure 4(a). This is a voltage waveform of the draw release type first described initially in US-A-4161670 in connection with tubular actuators, wherein a voltage pulse is applied in the channel to be actuated first to expand the ink tube and to draw back ink in the nozzle termination and then a voltage of opposite polarity is applied causing the ink tube to contract and a pressure pulse to be generated causing ink drop ejection.
  • the waveform includes both the draw - release waveform above and further incorporates reflected pressure wave suppression in accordance with one aspect of the present invention.
  • This waveform consists of voltage pulses applied in successive periods corresponding to one acoustic period L/c of the channel of magnitudes -1, 1+r, 1, r(1+r) and r(1+r) where r is negative.
  • the voltage waveform thus lasts five acoustic periods.
  • corresponding pressures in the neighbouring lines assuming that the actuator walls are comparatively rigid compared with the compliance of the ink in the channels are of opposite sign and of value approximately one half of these values. If the compliance of the actuated walls is significant compared with that of the ink then a corresponding pressure ratio between the pressure in the actuated and non-actuated channels may be calculated as a function of the compliance ratio between the actuator wall and the ink.
  • Figure 5(a) illustrates the unipolar voltage waveforms applied to fired and unfired channels of groups a, b and c, these being shown in three periods a, b, c corresponding to the operation successively of channels in each group.
  • the voltage waveform to eject a drop and to cancel the residual acoustic waves lasts a period of 5 LJc in each group, so that for three groups a, b and c the frequency of printing each line of printed dots is (15I.-/C). This will be seen evidently to be the maximum print speed for operation, although blank periods may be inserted in a drop-on-demand printer to reduce the rate of output for variable speed applications.
  • the operating frequency may be 10 kHz. As already stated, this period is also usually dictated by replenishment time.
  • the normal operation of the printhead for a non-firing channel involves the application of no voltage in periods 1 , 4 and 5 of the five periods of IJc when a voltage waveform is applied in each group. However, a positive voltage pulse of (1+r) and 1 is applied in periods 2 and 3 of the voltage waveform for a non-firing channel. Thus voltage excursions are applied to all lines of a printhead even when no channels are activated. However, since it is the differential voltage between channels that causes drop ejection and the same voltage is applied to all non-firing lines, no pressures are generated.
  • the voltage applied to fire a channel is illustrated in the period allocated for the operation of each group a, b c etc., by reference to the voltage waveform for firing channels in the corresponding period.
  • a positive voltage of magnitude 1 is applied in the first period and a voltage r(r + 1) is applied in periods 4 and 5, while the voltage magnitude in the fired lines is zero in periods 2 and 3.
  • the voltages in the other groups b and c in the period correspond to those of neighbouring non-firing lines.
  • the sign convention in this example is that the positive voltage applied to a channel relative to the voltage in the neighbouring lines causes the ink channel to expand.
  • FIG. 6(a) A further voltage waveform, which suppresses residual acoustic waves is illustrated in Figure 6(a).
  • This waveform also lasts a period of five acoustic periods 5LJc
  • the waveform shown in Figure 6(a) similarly includes a waveform applied to non-firing lines and a second waveform which is applied to a fired channel in the time designated for the group corresponding to the fired channels.
  • the voltage waveform differs in that the voltage magnitude has values 1, 1 instead of (I + r), 1 in the non-fired lines.
  • the waveform in periods 4 and 5 is now r, r(1 + r) instead of r(1 + r), r(1 + r ) in the fired lines.
  • the voltage difference waveform applied to the wall actuator of a selected channel again takes the form of an actuating voltage difference waveform followed after a delay 2LJc by a correcting voltage difference waveform reduced in amplitude by the factor -0.3. This is shown in Figure 6(c).
  • FIG. 7 A further form of unipolar voltage waveform is illustrated in Figure 7.
  • This waveform lasts 4 periods of IJc in each group, so that the frequency of operation may be increased to c/12L, which is 20% faster.
  • it has pressure waves 3,-3 in periods 2 and 3, so that the pressure reversal in this case is now -6 instead of -4.4 in the waveform of Figure 5.
  • Figure 7(a) shows the unipolar voltages applied to the fired channel and adjacent non-fired channel whilst Figure 7(b) shows the right going pressure waves, that is to say the pressure waves incident upon the nozzle.
  • the nozzle reflection coefficient is not exactly constant. Although broadly constant when the ink meniscus is external to the nozzle it falls progressively in magnitude to more negative values when the ink meniscus retracts into the nozzle, and in particular takes lower values following drop ejection. Therefore although the above voltage waveforms provide clear guidance to the timing and magnitudes of voltage pulses to effect cancellation, and may in appropriate circumstances be usable directly.
  • the values used may also be measured or verified experimentally.
  • a drop ejection signal in response to a subsequent waveform generally results in drop ejection at reduced velocity. This is more particularly the case for the four period waveform described by reference to Figure 7.
  • Drop ejection velocity from the succeeding group (such as group b) is then increased by application of either a + ve pressure applied to the next - to - last pulse or a - ve pressure pulse applied to the last pulse period.
  • a + ve pressure applied to the next - to - last pulse or a - ve pressure pulse applied to the last pulse period There are accordingly a range of pulse magnitudes of the combined pulses in the two periods that create a pressure signal of the phase appropriate to effect correction or cancellation of the drop velocity variation.
  • there is one that also effects cancellation in the alternate pressure wave phase it is generally not deleterious but is sometimes useful to leave some energy in the alternate phase to modify performance of the printhead in some other respect.
  • Figure 8 shows a firing waveform in firing lines, that may be compared to the voltage waveform in Figure 7(a).
  • Each waveform has a total period of 4L/c.
  • the firing line voltage has an initial pulse 81 that withdraws ink into the nozzle.
  • the following firing pulse 82 is then applied to the non-fired lines in the active group and to all the lines in the inactive group in period two.
  • the waveform of Figure 8 follows the waveform in 7(a).
  • a cancelling pulse 83 is also applied in period four of the fired lines, whose magnitude is derived experimentally (by normalising the velocity of drops in the succeeding group).
  • This pulse has a value somewhat greater than the corresponding pulse magnitude in Figure 7(a) due to the absence in Figures 8 of a cancelling pulse in period three of the non-fired lines.
  • Such a pulse 83 may always be found to effect cancellation of the residual pressure wave contribution to drop velocity in the succeeding phase.
  • Figure 9 illustrates the other extreme where the cancellation pulse 93 in period three of the non-fired lines is present to a greater degree than employed in Figure 7(a). In the extreme its magnitude can be made so great that the pulse contribution 94 in period four, instead of compromising a positive pulse in the fired lines, becomes negative so that instead the pulse is applied to the non-fired lines.
  • a typical combination of pulses 93 and 94 in the third and fourth pulse periods in the non-fired lines is illustrated in Figure 9. The pulse magnitudes are determined experimentally by observing the drop velocity in the succeeding group and restoring its value to normal.
  • the waveform in Figure 9 illustrates the alternative extreme to that in
  • a method of correction found to be effective to allow for velocity variation due to a print pattern or print density variation is to vary the pulse width of the initial withdrawal pulse in the fired lines as shown in Figure 11 by reference to 106.
  • Pulse width 106 is narrowed when a higher density of line neighbours are selected and is restored to its normalised width when a single line without near neighbours is fired. It will, therefore, be evident that a number of different actuation waveforms may be selected to achieve different performance on criteria required for different applications of the printhead.

Abstract

Les canaux d'encre selectionnés d'une imprimante à jet d'encre déposant des gouttelettes à la demande sont soumis à un élargissement et à une contraction, les gouttelettes d'encre étant éjectées par application de tensions unipolaires, d'abord aux canaux sélectionnés et ensuite aux canaux non sélectionnés. D'autres tensions unipolaires, retardées en temps de 2 L/c et réglées selon un coefficient de réflexion d'ondes de pression r de l'ajutage, effectuent une annulation rapide des ondes de pression résiduelle de façon à ce que des canaux adjacents soient prêts à être actionnés avec un minimum de retard.
PCT/GB1995/000562 1994-03-16 1995-03-16 Ameliorations apportees a un appareil a impulsions de depot de gouttelettes WO1995025011A1 (fr)

Priority Applications (7)

Application Number Priority Date Filing Date Title
KR1019960705109A KR100341175B1 (ko) 1994-03-16 1995-03-16 개선된펄스소적(droplet)증착장치
DE69505960T DE69505960T2 (de) 1994-03-16 1995-03-16 Verbesserungen an einer gepulsten tröpfchen-niederschlagsvorrichtung
EP95911395A EP0751873B1 (fr) 1994-03-16 1995-03-16 Ameliorations apportees a un appareil a impulsions de depot de gouttelettes
CA002184076A CA2184076C (fr) 1994-03-16 1995-03-16 Ameliorations apportees a un appareil a impulsions de depot de gouttelettes
JP7523918A JP2969570B2 (ja) 1994-03-16 1995-03-16 パルス小滴溶着装置の改良
US08/699,798 US6123405A (en) 1994-03-16 1996-08-19 Method of operating a multi-channel printhead using negative and positive pressure wave reflection coefficient and a driving circuit therefor
HK98113826A HK1013639A1 (en) 1994-03-16 1998-12-17 Improvements relating to pulsed droplet deposition apparatus

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SG9608012A SG93789A1 (en) 1994-03-16 1994-03-16 Improvements relating to pulsed droplet deposition apparatus
GB9405137A GB9405137D0 (en) 1994-03-16 1994-03-16 Improvements relating to pulsed droplet deposition apparatus
GB9405137.2 1994-03-16

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US08/699,798 Continuation US6123405A (en) 1994-03-16 1996-08-19 Method of operating a multi-channel printhead using negative and positive pressure wave reflection coefficient and a driving circuit therefor

Publications (1)

Publication Number Publication Date
WO1995025011A1 true WO1995025011A1 (fr) 1995-09-21

Family

ID=28043418

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1995/000562 WO1995025011A1 (fr) 1994-03-16 1995-03-16 Ameliorations apportees a un appareil a impulsions de depot de gouttelettes

Country Status (8)

Country Link
EP (1) EP0751873B1 (fr)
JP (1) JP2969570B2 (fr)
CA (1) CA2184076C (fr)
DE (1) DE69505960T2 (fr)
GB (1) GB9405137D0 (fr)
HK (1) HK1013639A1 (fr)
SG (1) SG93789A1 (fr)
WO (1) WO1995025011A1 (fr)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997018952A1 (fr) * 1995-11-23 1997-05-29 Xaar Technology Limited Fonctionnement d'un appareil de depot de gouttelettes pulsees
EP0835757A2 (fr) * 1996-10-08 1998-04-15 Pelikan Produktions Ag Procédé d'actionnement des éléments piézoélectrique dans une tête d'impression d'un générateur de gouttes
WO1998051504A1 (fr) 1997-05-15 1998-11-19 Xaar Technology Limited Fonctionnement d'un appareil a depot de gouttelettes
WO1999012738A1 (fr) 1997-09-08 1999-03-18 Xaar Technology Limited Impression multi-teintes par jet d'encre goutte a la demande
WO1999041084A1 (fr) 1998-02-12 1999-08-19 Xaar Technology Limited Procede de mise en service d'un dispositif servant a deposer une gouttelette
EP0899103A3 (fr) * 1997-08-19 2000-03-01 Brother Kogyo Kabushiki Kaisha Appareil à jet d'encre et dispositif d'enregistrement à jet d'encre
WO2000011971A2 (fr) 1998-08-26 2000-03-09 Fuisz Technologies Ltd. Boisson et composition pour boisson a teneur renforcee en vitamines et en fibres
EP0988973A1 (fr) * 1998-09-21 2000-03-29 Eastman Kodak Company Appareil d'imagerie capable d'empêcher l'éjection involontaire d'une goutellette d'encre satellite et procédé d'assemblage de l'appareil
WO2000044565A1 (fr) 1999-02-01 2000-08-03 Xaar Technology Limited Appareil de depot de goutelettes
EP1108541A1 (fr) * 1998-07-29 2001-06-20 NEC Corporation Tete d'enregistrement a jet d'encre et enregistreur a jet d'encre
EP1213145A2 (fr) 1996-03-15 2002-06-12 Xaar Technology Limited Fonctionnement d'un appareil de dépot de gouttelettes
US6655798B2 (en) 1998-11-20 2003-12-02 Xaar Technology Limited Methods of inkjet printing
EP2184168A1 (fr) * 2008-11-07 2010-05-12 Konica Minolta IJ Technologies, Inc. Appareil d'enregistrement à jet d'encre
EP2275263A1 (fr) * 2009-06-29 2011-01-19 Konica Minolta IJ Technologies, Inc. Appareil d'enregistrement à jet d'encre et procédé de commande de tête d'enregistrement par jet d'encre
EP2275264A1 (fr) * 2009-06-29 2011-01-19 Konica Minolta IJ Technologies, Inc. Appareil d'enregistrement à jet d'encre
EP2528739A1 (fr) * 2010-01-29 2012-12-05 Hewlett Packard Development Company, L.P. Réduction de la diaphonie dans une tête d'impression piézoélectrique
EP2899027A1 (fr) * 2014-01-27 2015-07-29 Hewlett-Packard Industrial Printing Ltd. Commander une tête d'impression
WO2018002630A1 (fr) * 2016-06-30 2018-01-04 Xaar Technology Limited Appareil de dépôt de gouttelettes

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
PL2446881T3 (pl) 2003-07-24 2014-08-29 Glaxosmithkline Llc Folie rozpuszczające się w jamie ustnej
JP2005041050A (ja) * 2003-07-25 2005-02-17 Toshiba Tec Corp インクジェットヘッドの駆動方法及びインクジェットヘッド記録装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4743924A (en) * 1985-05-02 1988-05-10 Ing. C. Olivetti & C., S.P.A. Control circuit for an ink jet printing element and a method of dimensioning and manufacture relating thereto
EP0376532A1 (fr) * 1988-12-30 1990-07-04 Am International Incorporated Appareil à déposition de gouttelettes

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59104950A (ja) * 1982-12-07 1984-06-18 Seiko Epson Corp インクジエツトヘツド駆動方法
GB8829567D0 (en) * 1988-12-19 1989-02-08 Am Int Method of operating pulsed droplet deposition apparatus
JPH07132590A (ja) * 1993-11-09 1995-05-23 Brother Ind Ltd インク噴射装置の駆動方法

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4743924A (en) * 1985-05-02 1988-05-10 Ing. C. Olivetti & C., S.P.A. Control circuit for an ink jet printing element and a method of dimensioning and manufacture relating thereto
EP0376532A1 (fr) * 1988-12-30 1990-07-04 Am International Incorporated Appareil à déposition de gouttelettes

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN *

Cited By (31)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6010202A (en) * 1995-11-23 2000-01-04 Xaar Technology Limited Operation of pulsed droplet deposition apparatus
CN1086636C (zh) * 1995-11-23 2002-06-26 萨尔技术有限公司 多通道脉冲式墨滴沉积设备及其操作方法
WO1997018952A1 (fr) * 1995-11-23 1997-05-29 Xaar Technology Limited Fonctionnement d'un appareil de depot de gouttelettes pulsees
EP1213145A2 (fr) 1996-03-15 2002-06-12 Xaar Technology Limited Fonctionnement d'un appareil de dépot de gouttelettes
US6286925B1 (en) 1996-10-08 2001-09-11 Pelikan Produktions Ag Method of controlling piezo elements in a printhead of a droplet generator
EP0835757A2 (fr) * 1996-10-08 1998-04-15 Pelikan Produktions Ag Procédé d'actionnement des éléments piézoélectrique dans une tête d'impression d'un générateur de gouttes
EP0835757A3 (fr) * 1996-10-08 1999-03-31 Pelikan Produktions Ag Procédé d'actionnement des éléments piézoélectrique dans une tête d'impression d'un générateur de gouttes
WO1998051504A1 (fr) 1997-05-15 1998-11-19 Xaar Technology Limited Fonctionnement d'un appareil a depot de gouttelettes
EP0899103A3 (fr) * 1997-08-19 2000-03-01 Brother Kogyo Kabushiki Kaisha Appareil à jet d'encre et dispositif d'enregistrement à jet d'encre
US6120120A (en) * 1997-08-19 2000-09-19 Brother Kogyo Kabushiki Kaisha Ink jet apparatus and ink jet recorder
WO1999012738A1 (fr) 1997-09-08 1999-03-18 Xaar Technology Limited Impression multi-teintes par jet d'encre goutte a la demande
WO1999041084A1 (fr) 1998-02-12 1999-08-19 Xaar Technology Limited Procede de mise en service d'un dispositif servant a deposer une gouttelette
EP1108541A4 (fr) * 1998-07-29 2001-10-24 Nec Corp Tete d'enregistrement a jet d'encre et enregistreur a jet d'encre
EP1108541A1 (fr) * 1998-07-29 2001-06-20 NEC Corporation Tete d'enregistrement a jet d'encre et enregistreur a jet d'encre
US6467865B1 (en) 1998-07-29 2002-10-22 Fuji Xerox Co., Ltd. Ink jet recording head and ink jet recorder
WO2000011971A2 (fr) 1998-08-26 2000-03-09 Fuisz Technologies Ltd. Boisson et composition pour boisson a teneur renforcee en vitamines et en fibres
EP0988973A1 (fr) * 1998-09-21 2000-03-29 Eastman Kodak Company Appareil d'imagerie capable d'empêcher l'éjection involontaire d'une goutellette d'encre satellite et procédé d'assemblage de l'appareil
US6655798B2 (en) 1998-11-20 2003-12-02 Xaar Technology Limited Methods of inkjet printing
WO2000044565A1 (fr) 1999-02-01 2000-08-03 Xaar Technology Limited Appareil de depot de goutelettes
EP2184168A1 (fr) * 2008-11-07 2010-05-12 Konica Minolta IJ Technologies, Inc. Appareil d'enregistrement à jet d'encre
US8231194B2 (en) 2008-11-07 2012-07-31 Konica Minolta Ij Technologies, Inc. Inkjet recording apparatus
EP2275264A1 (fr) * 2009-06-29 2011-01-19 Konica Minolta IJ Technologies, Inc. Appareil d'enregistrement à jet d'encre
EP2275263A1 (fr) * 2009-06-29 2011-01-19 Konica Minolta IJ Technologies, Inc. Appareil d'enregistrement à jet d'encre et procédé de commande de tête d'enregistrement par jet d'encre
US8246134B2 (en) 2009-06-29 2012-08-21 Konica Minolta Ij Technologies, Inc. Inkjet recording apparatus and drive method of inkjet recording head
EP2528739A1 (fr) * 2010-01-29 2012-12-05 Hewlett Packard Development Company, L.P. Réduction de la diaphonie dans une tête d'impression piézoélectrique
EP2528739A4 (fr) * 2010-01-29 2013-10-02 Hewlett Packard Development Co Réduction de la diaphonie dans une tête d'impression piézoélectrique
US8770692B2 (en) 2010-01-29 2014-07-08 Hewlett-Packard Development Company, L.P. Crosstalk reduction in piezo printhead
EP2899027A1 (fr) * 2014-01-27 2015-07-29 Hewlett-Packard Industrial Printing Ltd. Commander une tête d'impression
WO2018002630A1 (fr) * 2016-06-30 2018-01-04 Xaar Technology Limited Appareil de dépôt de gouttelettes
CN109414930A (zh) * 2016-06-30 2019-03-01 赛尔科技有限公司 液滴沉积装置
US10744764B2 (en) 2016-06-30 2020-08-18 Xaar Technology Limited Droplet deposition apparatus

Also Published As

Publication number Publication date
DE69505960T2 (de) 1999-04-08
EP0751873B1 (fr) 1998-11-11
CA2184076C (fr) 2005-08-09
GB9405137D0 (en) 1994-04-27
SG93789A1 (en) 2003-01-21
CA2184076A1 (fr) 1995-09-21
JP2969570B2 (ja) 1999-11-02
EP0751873A1 (fr) 1997-01-08
DE69505960D1 (de) 1998-12-17
JPH09505532A (ja) 1997-06-03
HK1013639A1 (en) 1999-09-03

Similar Documents

Publication Publication Date Title
US6123405A (en) Method of operating a multi-channel printhead using negative and positive pressure wave reflection coefficient and a driving circuit therefor
CA2184076C (fr) Ameliorations apportees a un appareil a impulsions de depot de gouttelettes
EP0049900B1 (fr) Appareil d'impression à jet d'encre
EP0737586B1 (fr) Appareil d'enregistrement à jet d'encre et procédé pour l'impression à jet d'encre
JP4247043B2 (ja) インクジェットヘッドの駆動装置
JP5309808B2 (ja) 液体吐出装置、及び、液体吐出装置の制御方法
US6402282B1 (en) Operation of droplet deposition apparatus
US20070008356A1 (en) Image reproducing/forming apparatus with print head operated under improved driving waveform
EP1213145A2 (fr) Fonctionnement d'un appareil de dépot de gouttelettes
JP2007062326A (ja) インクジェット式記録ヘッドの駆動方法
JP3770915B2 (ja) パルス化液滴デポジット装置の操作法
JP2000135800A (ja) オンデマンド型マルチノズルインクジェットヘッドの駆動方法
JP2785727B2 (ja) インクジェット式プリントヘッド及びその駆動方法
JP3986910B2 (ja) インクジェットヘッドの駆動方法およびその駆動方法を用いたインクジェット印刷装置
JP3525011B2 (ja) インクジェット記録ヘッドの駆動方法
JP5251562B2 (ja) 液体吐出装置、及び、液体吐出装置の制御方法
JP3069154B2 (ja) 液体噴射記録ヘッドの駆動方法
JP4678158B2 (ja) 液滴吐出ヘッドの駆動方法、液滴吐出ヘッド、及び液滴吐出装置
JP2006088484A (ja) 液滴吐出ヘッドの駆動方法、液滴吐出ヘッド及び液滴吐出装置
KR100341175B1 (ko) 개선된펄스소적(droplet)증착장치
JP4379963B2 (ja) オンデマンド型マルチノズルインクジェットヘッドの駆動方法
JP3648598B2 (ja) インク吐出制御方法およびインク吐出装置
US8702188B2 (en) Device and method for driving liquid-drop ejection head and image forming apparatus
JP2003260794A (ja) インクジェット画像形成装置及びインクジェット画像形成方法
JP3978752B2 (ja) インクジェットプリンタ、ならびにインクジェットプリンタ用記録ヘッドの駆動装置および方法

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): BR CA CN JP KR US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
121 Ep: the epo has been informed by wipo that ep was designated in this application
WWE Wipo information: entry into national phase

Ref document number: 1995911395

Country of ref document: EP

WWE Wipo information: entry into national phase

Ref document number: 08699798

Country of ref document: US

WWE Wipo information: entry into national phase

Ref document number: 2184076

Country of ref document: CA

WWE Wipo information: entry into national phase

Ref document number: 1019960705109

Country of ref document: KR

WWP Wipo information: published in national office

Ref document number: 1995911395

Country of ref document: EP

WWG Wipo information: grant in national office

Ref document number: 1995911395

Country of ref document: EP