JP2010253884A - Liquid ejection method by ink-jet and ink-jet apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for ejecting liquid with high accuracy even in an ink-jet apparatus with a small opening of a nozzle. <P>SOLUTION: The method is provided for ejecting liquid by supplying driving pulses to an actuator of the ink-jet apparatus n-times [n is an integer of 2 or more] within one driving cycle, wherein a liquid drop before flying after pushed out of the nozzle by the driving pulse of the m-th time [m is an integer from 1 to (n-1)] is united with a liquid drop pushed out of the nozzle by the driving pulse of (m+1)th time, and the united liquid drop is allowed to fly by the driving pulse of n-th time to eject the liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for ejecting liquid by inkjet and an inkjet apparatus.

  An ink jet apparatus is an apparatus that performs printing by discharging a liquid contained in an ink jet head. An ink jet head mounted on an ink jet apparatus includes a pressure chamber that stores ink, a nozzle that communicates with the pressure chamber, and an actuator that applies pressure to the ink in the pressure chamber so that ink is ejected from the nozzle. Further, the ink jet apparatus includes drive signal supply means for supplying a drive signal to the actuator. In order to reduce the size of the head and the like, an actuator having a piezoelectric element is often used (for example, see Patent Document 1).

  In recent years, such ink jet apparatuses have been applied to the manufacture of electronic devices such as organic EL displays and liquid crystal panels. In order to manufacture an organic EL display or a liquid crystal panel with an inkjet apparatus, an ink containing an organic light emitting material or a functional liquid such as a liquid crystal material may be supplied to an inkjet head and printed on a prepared panel.

  When applying an inkjet apparatus to manufacture of an electronic device, high printing accuracy is calculated | required by an inkjet apparatus. For this reason, when applying an inkjet apparatus to manufacture of an electronic device, in order to raise printing accuracy, the inkjet head containing the nozzle which has a smaller opening part is used.

  Also, two or more droplets discharged from the same nozzle can be obtained by discharging two or more droplets from the nozzle and making the discharge rate of the droplets discharged later higher than the discharge rate of the droplets discharged first. A method has been proposed in which the two are combined during flight to form a single droplet before landing (see, for example, Patent Document 2). In such a method, the size of the ink dot on the recording medium can be adjusted by adjusting the number of droplets to be combined during the flight.

JP 2005-205285 A JP 2003-175601 A

  However, when printing is performed using an inkjet head having a nozzle with a small opening as described above, the liquid ejection accuracy may be reduced depending on the printing conditions. For example, when a high-viscosity liquid such as a solution containing a polymer organic EL material is discharged, or immediately after the start of discharge, the droplet discharge angle is not stable, and the straightness of the droplet is reduced, and printing of an inkjet device is performed. The accuracy may be reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides a method for discharging liquid with high accuracy from an inkjet head having a nozzle having a small opening.

  The present inventor has found that increasing the weight of the droplets flying from the nozzle improves the straightness of the flying droplets and improves the liquid ejection accuracy, thereby completing the present invention.

That is, the first of the present invention relates to a liquid discharge method described below.
[1] From an inkjet head having a pressure chamber containing a predetermined liquid, a nozzle communicating with the pressure chamber, and an actuator for applying pressure to the liquid in the pressure chamber, the actuator is driven within one drive cycle. A method of discharging the liquid by supplying a pulse n times [n is an integer equal to or greater than 2], the m-th driving [m being an integer from 1 to (n−1)]. A step of combining a droplet pushed out of the nozzle by a pulse and not flying with a droplet pushed out of the nozzle by the (m + 1) th driving pulse, and flying the united droplet by the nth driving pulse And a step of discharging the liquid.
[2] The ejection method according to [1], wherein T _m ≦ T _{m + 1} when the pulse period of the m-th drive pulse is T _m and the pulse period of the m + 1-th drive pulse is T _{m + 1.} .
[3] When the pulse voltage of the m-th drive pulse is V _m and the pulse voltage of the m + 1-th drive pulse is V _{m + 1} , V _m ≦ V _{m + 1} , [1] or [2] The discharge method described.
[4] The pulse period T of the drive pulse is 0.5Ta ≦ T ≦ 1.5Ta with respect to the natural vibration period Ta of the actuator, according to any one of [1] to [3]. Discharge method.
[5] The method further includes the step of supplying the actuator with a pulse having a waveform opposite in phase to the n-th drive pulse after the n-th drive pulse is supplied to the actuator. The discharge method according to any one of the above.

A second aspect of the present invention relates to the following ink jet apparatus.
[6] An ink jet head having a pressure chamber containing a predetermined liquid, a nozzle communicating with the pressure chamber, and an actuator for applying pressure to the liquid in the pressure chamber; and n within one drive cycle of the actuator. A drive signal supply means for supplying a drive signal having a drive pulse having a drive pulse of n times (n is an integer of 2 or more), wherein the drive signal is m-th [m is from 1 to (n−1 The liquid droplets pushed out from the nozzle by the drive pulse in the above-described manner and not flying are combined with the liquid droplet pushed out from the nozzle by the m + 1th drive pulse, and the n-th time An ink jet apparatus that is adjusted so that the combined droplets fly by driving pulses.

  According to the present invention, even when the opening of the nozzle is small, the weight of the droplet flying from the nozzle can be increased, the straightness of the flying droplet can be improved, and the printing accuracy of the inkjet apparatus can be improved. Can be improved.

Diagram showing liquid discharge angle Configuration diagram of ink jet apparatus according to Embodiment 1 The figure which shows the waveform of the drive signal which the drive signal supply means of Embodiment 1 forms The figure which shows the discharge method of Embodiment 1. The figure which shows the waveform of the drive signal which the drive supply means of Embodiment 2 forms.

1. Inkjet Device The inkjet device of the present invention includes an inkjet head and drive signal supply means. The ink jet apparatus of the present invention is characterized by the waveform of the drive signal supplied by the drive signal supply means as will be described later.

  The inkjet head is a member that discharges liquid in the inkjet apparatus. The ink jet head includes a plurality of pressure chambers that store ink, a plurality of nozzles that communicate with the pressure chambers, and a plurality of actuators that apply pressure to the liquid in each pressure chamber.

  The pressure chamber is a space for storing the liquid supplied from a liquid supply unit such as a reservoir. The pressure chamber is normally connected to the reservoir via a supply port.

  The liquid supplied to the pressure chamber is appropriately selected depending on the object to be printed. For example, when the object is an organic EL panel, the liquid supplied to the pressure chamber is a solution containing a hole injection material such as PEDOT: PSS or an organic light emitting material such as a light emitting material. When the object is a liquid crystal panel, the liquid supplied to the pressure chamber is a high-viscosity functional liquid such as a liquid crystal material.

In the present invention, the viscosity of the liquid supplied to the pressure chamber is preferably high. Specifically, the viscosity of the liquid supplied to the pressure chamber is preferably 1 to 40 mPas. In order to increase the viscosity of the liquid, the concentration of the solute may be increased or the viscosity of the solvent may be increased. The surface tension of the liquid supplied to the pressure chamber is, for example, 10 to 75 mN / m, and the density of the liquid supplied to the pressure chamber is, for example, 0.7 to 1.2 g / cm ³ . Examples of such a liquid include a solution containing 0.1 to 2 wt% of the polymer organic EL material. When the viscosity of the liquid supplied to the pressure chamber is high, before the droplet ejected from the nozzle by one driving pulse flies, it becomes easy to merge with the droplet ejected by the next pulse ( Later).

  The actuator is a mechanism for converting input energy into physical energy and applying pressure to the liquid in each pressure chamber. The actuator has, for example, a heater or a piezoelectric element.

  The actuator having a piezoelectric element is a piezoelectric actuator having a piezoelectric element and an electrode for applying a voltage to the piezoelectric element, and is preferably a flexural vibration type actuator. In this case, the actuator changes the pressure in the pressure chamber by reducing or expanding the pressure chamber, and pushes out a droplet from the opening of the nozzle or fills the pressure chamber with liquid. On the other hand, an actuator having a heater vaporizes the liquid in the pressure chamber, and applies pressure to the liquid by a change in volume of bubbles generated at that time.

  The nozzle is a tube that communicates with the pressure chamber and has an opening. Liquid is discharged from the opening of the nozzle. The diameter of the opening of the nozzle of the present invention is preferably 10 to 100 μm.

  The drive signal supply means is connected to the actuator and supplies a drive signal to the actuator. The drive signal supply means may have a drive signal generation circuit and a selection circuit. The drive signal generation circuit outputs a drive signal to the selection circuit in response to an instruction of a drive control signal input from the outside. The selection circuit selects a predetermined drive signal from among the plurality of drive signals output from the drive signal generation circuit based on the information of the drive signal to be selected, and supplies the selected drive signal to the actuator.

  When manufacturing an organic EL panel using the inkjet device of the present invention, an organic EL panel manufacturing device including the inkjet device is prepared, and a “drive control signal” is sent from a main control unit that controls the organic EL panel manufacturing device. And “information of drive signal to be selected” may be output.

  The inkjet apparatus of the present invention is characterized in that the drive signal supplied by the drive signal supply means has two or more drive pulses within one drive cycle (see FIG. 3). Here, “one drive cycle” means the time during which the actuator operates in order to print one dot pattern from the opening of the nozzle. The “driving pulse” means a pulse having a pulse voltage equal to or higher than a minimum voltage for driving the actuator so as to pressurize and pressurize the pressure chamber and ejecting liquid from the nozzle. Details of the drive signal supplied by the drive signal supply means will be described in the following ejection method.

2. Liquid Discharge Method The liquid discharge method of the present invention is characterized in that liquid is discharged from an ink jet head using the above-described ink jet apparatus.

The discharge method of the present invention is
First step: coalescing droplets extruded from the nozzle by each of n driving pulses (n is an integer of 2 or more);
Second step: The step of causing the liquid droplets combined in the first step to fly and discharging the liquid is included (see FIG. 4).

  Specifically, in the first step, the drive signal supply means supplies a drive signal having n drive pulses within one drive cycle to the actuator. Here, n means an integer of 2 or more. That is, one discharge of liquid is realized by a plurality of drive pulses. For this purpose, the (m + 1) th driving pulse is supplied before the droplet ejected from the nozzle by the mth driving pulse flies. Thereby, the droplet pushed out from the nozzle by the m-th driving pulse merges with the droplet pushed out from the nozzle by the m + 1-th driving pulse before flight. Here, m represents an integer from 1 to (n-1), and if n = 2, the coalescence is only once; if n = 3 or more, the coalescence is (n-1) times. repeat.

  The intensity (for example, pulse voltage) of each drive pulse is preferably higher than the minimum intensity at which droplets can be ejected from the nozzle. This is because the amount of droplets that are pushed out from the nozzle by each drive pulse is set to a sufficient amount to sufficiently increase the amount of droplets after merging. The minimum intensity at which droplets can be ejected from the nozzle needs to be adjusted according to the viscosity of the liquid, the pressure chamber, the nozzle shape, and the like.

  In order to realize the combination of the droplets, the “pulse voltage” of the drive signal, the “pulse period” of the drive signal, and the like may be set appropriately. “Pulse voltage” means a potential difference between the start point of the falling portion where the pushing operation starts and the end point of the falling portion where the pushing operation ends (see FIG. 3). Further, the “pulse voltage” may be a potential difference between the end point of the rising portion where the pulling operation ends and the end point of the falling portion where the pushing operation ends (see FIG. 3). The pulse period means the time between the start point of the potential maintaining part and the end point of the falling part of the drive pulse (see FIG. 3).

Specifically, it is preferable to adjust so that V _m ≦ V _{m + 1} when the pulse voltage of the _mth drive pulse is V _m and the pulse voltage of the (m + 1) th drive pulse is V _{m + 1.} . By gradually increasing the pulse voltage, the droplets ejected from the nozzle by the m-th driving pulse are easily incorporated into the droplets ejected by the m + 1-th driving pulse before flying (see FIG. 4). As described above, all the pulse voltages may be equal to or higher than the minimum voltage at which droplets can be ejected from the nozzle. Further, it is preferable that the upper limit of the pulse voltage is appropriately adjusted according to the breakdown limit strength of the actuator.

Next, it is preferable to adjust so that T _m ≦ T _{m + 1} when the pulse cycle of the m-th drive pulse is T _m and the pulse cycle of the m + 1-th drive pulse is T _{m + 1} . That is, it is preferable to gradually increase the pulse period of the drive pulse. By gradually lengthening the pulse cycle, a sufficient amount of liquid can be replenished (filled) into the pressure chamber after the liquid droplet has been pushed out from the nozzle by the mth drive pulse, and the nozzle is driven by the m + 1th drive pulse. Since the appropriate amount of liquid extruded from the nozzle becomes a sufficient amount, it is easy to merge with the droplet extruded from the nozzle by the m-th driving pulse.

  Furthermore, it is preferable that the pulse period T of the drive pulse is 0.5Ta ≦ T ≦ 1.5Ta, where Ta is the natural vibration period of the actuator. This is because the drive pulse is supplied in synchronization with the resonance period of the liquid surface of the droplet extruded from the nozzle. As a result, the liquid droplets extruded from the nozzle are stabilized, and are easily merged with the liquid droplets extruded from the nozzle by the next drive pulse. When the pulse period T is out of the above range, the droplets are not pushed out from the nozzles, or the pushed-out droplets fall apart. The natural vibration period Ta of the actuator is usually 1 to 50 μsec.

  Further, when the voltage change time of the driving pulse is Tc, it is preferable that V / α ≦ Tc ≦ 0.5T. Here, α means the limit gradient (V / μs) that the actuator can follow. The voltage change time of the drive pulse means the time between the start point of the rising portion and the end point of the rising portion and the time between the start point of the falling portion and the end point of the falling portion (see FIG. 3). . When Tc is V / α or more, the drive of the actuator follows the waveform of the drive pulse. This facilitates control of the amount of liquid to be discharged. On the other hand, if Tc is 0.5T or more, a sufficient pulse voltage cannot be obtained, and it becomes difficult to discharge the liquid.

  Furthermore, the length Ti of the interval (potential maintaining unit) from the end of the supply of the mth drive pulse to the start of the supply of the (m + 1) th pulse is 0 of the mth pulse period (Tm). It is preferably 5 times or less (see FIG. 3). Further, the ratio between the length Ti of the potential maintaining portion and the pulse width Tp of the drive pulse within one pulse period is preferably 1: 1 to 1: 3 (see FIG. 3).

  As described above, in the first step, the droplets ejected from the nozzle by the m-th driving pulse fly by adjusting the pulse period and pulse voltage of each of the n driving pulses in the driving signal. Previously, it can be merged with the droplets extruded from the nozzle by the (m + 1) th drive pulse. The amount of droplets after coalescence is larger than the amount of droplets pushed out from the nozzle by each drive pulse. For example, the amount of the combined droplets obtained in the first step can be 2 to 20 pl.

  In the second step, the liquid droplets obtained by coalescence in the first step are ejected from the nozzles after the nth driving pulse is supplied, and the liquid is ejected. In order to cause the droplet to fly from the nozzle after the nth drive pulse is supplied, the supply of the drive pulse may be stopped without supplying the drive pulse after the nth drive pulse is supplied.

  As described above, the amount of the combined droplets obtained in the first step is larger than the amount of droplets pushed out from the nozzle by each drive pulse. Therefore, the weight of the droplet flying from the nozzle also increases. In this way, in the second step, a droplet with increased weight can be ejected from the nozzle; in particular, even when the nozzle opening is small and it is difficult to enlarge the droplet to be ejected, The droplets flying from the nozzle can be enlarged.

  When the weight of the droplet flying from the nozzle is large, the droplet ejection accuracy can be improved. “Improving droplet ejection accuracy” means, for example, improving the straightness of droplets flying from a nozzle.

Table 1 shows a case where a liquid having a viscosity of 1 to 40 mPas, a surface tension of 10 to 75 mN / m, and a density of 0.7 to 1.2 g / cm ³ is discharged by the discharge method of the present invention, and a conventional discharge. Comparison results for the “diameter”, “volume”, and “ejection angle range” of the ejected droplets with the case of ejecting by the method (method in which the drive signal has only one drive pulse within one drive cycle) Indicated. Here, as shown in FIG. 1, the discharge angle means an angle α representing a deviation between the central axis X of the nozzle 101 and the droplet D10 discharged from the nozzle 101. Therefore, the smaller the discharge angle range, the higher the discharge accuracy.

  As shown in Table 1, it can be seen that in the ejection method of the present invention, the diameter and volume of the ejected droplets are larger than the droplets ejected by the conventional ejection method. According to the discharge method of the present invention, it can be seen that the discharge angle range (8.7 mrad) can be reduced to half or less of the discharge angle range (22 mrad) of the conventional discharge method. This supports that the discharge by the discharge method of the present invention can be stabilized.

  Further, the present invention may include a step of supplying an auxiliary pulse having a waveform opposite in phase to the drive pulse applied in the first step and the second step after the second step (see Embodiment 2). . The meniscus can be stabilized by applying an auxiliary pulse having an opposite phase after the last drive pulse.

  Hereinafter, a liquid discharge method using the ink jet apparatus and the ink jet head of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 2 shows a schematic configuration of a main part of an ink jet recording apparatus that realizes the liquid ejection method of the present invention. As shown in FIG. 2, the ink jet recording apparatus 10 includes an ink jet head 100 and drive signal supply means 150 that supplies a drive signal to the ink jet head 100.

  As shown in FIG. 2, the inkjet head 100 is configured by laminating a nozzle plate 103 on which nozzles 101 are formed and a partition wall 109 that partitions the pressure chamber 105 and the reservoir 107. An actuator 110 is stacked on the partition wall 109. The nozzle plate 103 is, for example, a polyimide plate having a thickness of 20 μm, and the partition wall 109 is, for example, a stainless steel laminate plate having a thickness of 480 μm or a laminate plate of stainless steel and photosensitive glass. The pressure chamber 105 contains the liquid 120 supplied from the reservoir 107.

  The actuator 110 includes a vibration plate 111 that covers the pressure chamber 105, a thin film piezoelectric element 113 that vibrates the vibration plate 111, and an individual electrode 115 that are sequentially stacked. The actuator 110 uses the piezoelectric effect of the piezoelectric element 113 and is a so-called piezoelectric actuator. The diaphragm 111 is a chromium plate having a thickness of 2 μm, for example, and functions as a common electrode for applying a voltage to the piezoelectric element 113 together with the individual electrode 115.

  The piezoelectric element 113 is, for example, PZT (lead zirconate titanate) having a thickness of 0.5 μm to 5 μm. The individual electrode 115 is a platinum plate having a thickness of 0.1 μm, for example, and the entire thickness of the actuator 110 is, for example, about 5 μm.

  The drive signal supply unit 150 includes a drive signal generation circuit 151 and a selection circuit 153. The drive signal generation circuit 151 outputs a drive signal corresponding to the instruction of the drive control signal output from the main control unit to the selection circuit 153. The drive signal is selected by the selection circuit 153 and supplied to the actuator 110.

  FIG. 3 shows the waveform of the drive signal supplied to the actuator 110 by the drive signal supply means 150 of the first embodiment. As shown in FIG. 3, in the present embodiment, the drive signal P has a first drive pulse P1 and a second drive pulse P2. The first drive pulse P1 and the second drive pulse P2 are pulses that drive the actuator 110 so that the pressure chamber 105 is once depressurized and pressurized, and liquid is ejected.

  The first drive pulse P1 includes a potential maintaining part P11 that maintains the reference potential Vm, a rising part P12, a peak hold part P13, and a falling part P14. The rising portion P12 is a potential for driving the actuator 110 so as to depressurize the inside of the pressure chamber 105, and the falling portion P14 is a potential for driving the actuator 110 so as to pressurize the inside of the pressure chamber 105.

  The second drive pulse P2 includes a potential maintaining part P21 that maintains the reference potential Vm, a rising part P22, a peak hold part P23, and a falling part P24. The rising portion P22 is a potential for driving the actuator 110 so as to reduce the pressure in the pressure chamber 105, and the falling portion P24 is a potential for driving the actuator 110 so as to pressurize the pressure chamber 105.

  As shown in FIG. 3, the pulse period T1 of the first drive pulse is shorter than the pulse period T2 of the second drive pulse P2.

When the natural vibration period of the actuator is Ta, the pulse periods T (T1 and T2) of the first drive pulse P1 and the second drive pulse P2 both satisfy the following conditions.
0.5Ta ≦ T ≦ 1.5Ta

  Further, the length Ti (interval between the first drive pulse P1 and the second drive pulse P2) of the potential maintaining portion P21 of the second drive pulse P2 is 0.5 times or less of the pulse period T1. The ratio between the length Ti of the potential maintaining part P21 and the pulse width Tp of the second drive pulse P2 is 1: 1 to 1: 3.

  Further, the voltage change time Tc of the drive pulse is V / α or more and 0.5T or less. α means the limit gradient (V / μs) that the actuator can follow. The voltage change time of the drive pulse is the time between the start point of the rising part (P12, P22) and the end point of the rising part, and between the start point of the falling part (P14, P24) and the end point of the falling part. Means time.

  As shown in FIG. 3, the pulse voltage V1 of the first drive pulse P1 is smaller than the pulse voltage V2 of the second drive pulse P2. Further, the pulse voltages V of the first drive pulse P1 and the second drive pulse P2 are both equal to or higher than the discharge minimum voltage.

  Next, a method for supplying the drive signal described above to the actuator and discharging the liquid will be described. As shown in FIG. 4, the liquid discharge method is as follows: 1) a first step (FIGS. 4A1 to 4A5) for forming a combined droplet D10; and 2) causing the combined droplet D10 to fly and discharging the liquid. It has a second step (FIG. 4B1, FIG. 4B2). Hereinafter, the relationship between the drive signal and the liquid behavior will be described in the first step and the second step.

1) First Step FIG. 4A1 shows the behavior of the liquid 120 near the opening of the nozzle 101 at the time of the potential maintaining part P11 of the first drive pulse P1. As shown in FIG. 4A1, the liquid 120 is stationary at the time of the potential maintaining part P11 of the first drive pulse P1.

  FIG. 4A2 shows the behavior of the liquid 120 near the opening of the nozzle 101 at the time of the peak hold part P13 of the first drive pulse P1. As shown in FIG. 4A2, in the peak hold portion P13, the pressure 120 is reduced by the rising portion P12 before the peak hold portion P13, so that the liquid 120 at the opening of the nozzle 101 is contained in the pressure chamber 105. Has been drawn into. In addition, when the pressure chamber 105 is depressurized, the predetermined liquid 120 is supplied from the reservoir 107 into the pressure chamber 105.

  FIG. 4A3 shows the behavior of the liquid 120 near the opening of the nozzle 101 at the time of the potential maintaining part P21 of the second drive pulse P2. As shown in FIG. 4A3, at the time of the potential maintaining portion P21, the liquid 120 is pushed out from the opening portion of the nozzle 101 by pressurizing the inside of the pressure chamber 105 by the falling portion P14 of the first drive pulse P1. A droplet D1 is formed.

  FIG. 4A4 shows the behavior of the liquid 120 near the opening of the nozzle 101 at the time of the peak hold part P23 of the second drive pulse P2. As shown in FIG. 4A4, at the time of the peak hold portion P23, the pressure 120 is decompressed by the rising portion P22 before the peak hold portion P23, so that the liquid 120 at the opening of the nozzle 101 becomes the pressure chamber 105. It is drawn in. Further, when the pressure chamber is depressurized, the predetermined liquid 120 is supplied from the reservoir 107 into the pressure chamber 105. As described above, in the present embodiment, since the pulse period T2 of the second drive pulse P2 is longer than the pulse period T1 of the first drive pulse, a time for supplying the liquid 120 into the pressure chamber 105 is secured, The liquid 120 reduced by the formation of the droplet D1 can be supplied into the pressure chamber 105. On the other hand, the droplet D1 does not fly.

  FIG. 4A5 shows the behavior of the liquid 120 near the opening of the nozzle 101 at the time of the potential maintaining part P3 after the second drive pulse P2. As shown in FIG. 4A5, at the time of the potential maintaining portion P3, the liquid 120 is pushed out from the opening portion of the nozzle 101 by pressurizing the inside of the pressure chamber 105 by the falling portion P24 of the second drive pulse P2. A droplet D2 is formed. As described above, in the present embodiment, since the pulse voltage V2 of the second drive pulse P2 is higher than the pulse voltage V1 of the first drive pulse, the speed at which the droplet D2 is pushed out is higher than the speed at which the droplet D1 is pushed out. fast. As a result, the droplet D2 can be combined with the droplet D1 that is not flying to form the combined droplet D10. As described above, in the first step, the droplet D10 formed by the first drive pulse P1 and the droplet D2 formed by the second drive pulse P2 are combined before the flight, so that the droplet D10 having a large weight is obtained. Form.

2) About the second step In the second step, as shown in FIGS. 4B1 and 4B2, by stopping the drive pulse after the second drive pulse P2, the droplet D10 flies from the opening of the nozzle 101, Liquid is discharged.

  As described above, in the present embodiment, since the droplets pushed out by the two drive pulses are combined before the droplets fly from the nozzle, the weight of the droplets increases. This improves the liquid ejection accuracy.

[Embodiment 2]
In the second embodiment, a mode including a step of applying an auxiliary pulse to a piezoelectric element in order to suppress meniscus vibration after discharging a liquid will be described.

  The ink jet apparatus of the second embodiment is the same as the ink jet apparatus of the first embodiment except that the waveform of the drive signal supplied by the drive signal supply means is different. Therefore, in the second embodiment, the waveform of the drive signal supplied by the drive signal forming unit will be described.

  FIG. 5 shows a drive signal formed by the drive signal forming means of the second embodiment. As shown in FIG. 5, the drive signal P in the second embodiment has a first drive pulse P1, a second drive pulse P2, a first auxiliary pulse Ph1, and a second auxiliary pulse Ph2. The first drive pulse P1 and the second drive pulse P2 are the same as those in the first embodiment.

  The first auxiliary pulse Ph1 is a pulse having a waveform opposite in phase to the second drive pulse P2, and is a signal for canceling the residual vibration caused by the drive pulse. The first auxiliary pulse Ph1 includes a potential maintaining unit Ph11, a falling unit Ph12, a peak hold unit Ph13, and a rising unit Ph14. The pulse voltage Vh1 of the first auxiliary pulse Ph1 is preferably smaller than the pulse voltage V2 of the second drive pulse P2 and larger than the pulse voltage Vh2 of the second auxiliary pulse Ph2.

  Here, the pulse voltage Vh1 of the first auxiliary pulse Ph1 means a potential difference between the start point of the rising portion Ph14 and the end point of the rising portion Ph14. The potential difference Vh0 between the start point of the falling part Ph11 and the end point of the falling part Ph11 may be zero. That is, the first auxiliary pulse Ph1 may not include the potential maintaining unit Ph11 and the falling unit Ph12.

  The second auxiliary pulse Ph2 is a signal for canceling the residual vibration newly generated by the first auxiliary pulse Ph1. Therefore, if no new residual vibration is generated by the first auxiliary pulse Ph1, the second drive pulse Ph2 may be omitted.

  The second auxiliary pulse Ph2 includes a rising portion Ph21, a peak hold portion Ph22, and a falling Ph23. The pulse period Th2 of the second auxiliary pulse Ph2 is preferably equal to or less than the natural vibration period Ta of the actuator. Further, the pulse voltage Vh2 of the second auxiliary pulse Ph2 is equal to or lower than the minimum discharge voltage.

  In the present invention, since a plurality of drive pulses are supplied within one drive cycle, the ratio of the drive pulse pulse cycle within one drive cycle is large. For this reason, after the last drive pulse is supplied, the residual vibration of the liquid may not stop until the next drive cycle starts. If the next driving cycle starts before the residual vibration of the liquid stops, the liquid may not be properly discharged in the next driving cycle. On the other hand, if a pulse having a waveform opposite in phase to the drive pulse is supplied to the actuator after the last drive pulse as in this embodiment, the residual vibration can be reliably stopped by the next drive cycle. For this reason, according to this Embodiment, a droplet can be discharged continuously and stably.

  According to the present invention, the liquid can be discharged with high accuracy, and therefore, the present invention can be applied to the manufacture of electronic devices such as an organic EL display and a liquid crystal panel.

DESCRIPTION OF SYMBOLS 10 Inkjet recording apparatus 100 Inkjet head 101 Nozzle 103 Nozzle plate 105 Pressure chamber 107 Reservoir 109 Partition wall 110 Actuator 111 Diaphragm 113 Piezoelectric element 115 Individual electrode 120 Liquid 150 Drive signal supply means 151 Drive signal generation circuit 153 Selection circuit

Claims (6)

From an inkjet head having a pressure chamber containing a predetermined liquid, a nozzle communicating with the pressure chamber, and an actuator for applying pressure to the liquid in the pressure chamber, a drive pulse is applied to the actuator within one drive cycle. A method in which the liquid is ejected by supplying the n times (n is an integer of 2 or more),
Liquid ejected from the nozzle by the m + 1th drive pulse and ejected from the nozzle by the mth drive pulse (m is an integer from 1 to (n-1)). A liquid ejection method comprising: a step of combining with a droplet; and a step of ejecting the liquid by flying the combined droplet by the nth driving pulse. 2. The ejection method according to claim ₁ , wherein T _m ≦ T _{m + 1} when a pulse period of the m-th drive pulse is T _m and a pulse period of the m + 1-th drive pulse is T _{m + 1} . a pulse voltage of the drive pulse of the m-th and V _m, a pulse voltage of m + 1 th of the driving pulse when the V _{m + 1,} is V _m ≦ V _{m + 1,} ejecting method according to claim 1.   The ejection method according to claim 1, wherein a pulse period T of the drive pulse is 0.5Ta ≦ T ≦ 1.5Ta with respect to a natural vibration period Ta of the actuator.   2. The ejection method according to claim 1, further comprising a step of supplying a pulse having a waveform opposite in phase to the n-th drive pulse to the actuator after the n-th drive pulse is supplied to the actuator. An ink jet head having a pressure chamber containing a predetermined liquid, a nozzle communicating with the pressure chamber, and an actuator for applying pressure to the liquid in the pressure chamber; and n times [n A drive signal supply means for supplying a drive signal having a drive pulse of
The drive signal is ejected from the nozzle by the m-th drive pulse [m is an integer from 1 to (n−1)], and a droplet that has not been ejected is ejected from the nozzle by the m + 1-th drive pulse. An ink jet apparatus that is united with a liquid ejected from the nozzle and adjusted so that the united liquid droplets fly by the n-th driving pulse.

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