Nozzle head and droplet application device

According to one embodiment, a nozzle head includes a nozzle plate, a piezoelectric element, an actuator plate, a fixing part, and a conductive part. The nozzle plate includes a plurality of nozzle holes. The piezoelectric element includes a plurality of first electrodes and a plurality of second electrodes provided alternately and a piezoelectric part provided between the plurality of first electrodes and the plurality of second electrodes. The piezoelectric element is provided for each of the plurality of nozzle holes. The actuator plate is provided on opposite side of the nozzle plate from a side to which the plurality of nozzle holes are opened. The fixing part is insulative and provided between each of a plurality of the piezoelectric elements and the actuator plate. The conductive part is conductive and provided between each of a plurality of the piezoelectric elements and the actuator plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-170706, filed on Sep. 12, 2018; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a nozzle head and a droplet application device.

BACKGROUND

A film formation device is used to manufacture e.g. printers and other printing devices, liquid crystal display devices, or semiconductor devices. In some devices such as the film formation device, a liquid material such as ink and film material is turned to droplets and discharged toward a target. In this case, in general, the viscosity of the droplet (liquid material) is made relatively low. For instance, the viscosity of the droplet is made less than 20 mPa·s.

However, in recent years, it has been desired to enable discharging of droplets having higher viscosity.

DETAILED DESCRIPTION

A nozzle head according to an embodiment comprises a nozzle plate, a piezoelectric element, an actuator plate, a fixing part, and a conductive part. The nozzle plate includes a plurality of nozzle holes capable of discharging droplets. The piezoelectric element includes a plurality of first electrodes and a plurality of second electrodes provided alternately and a piezoelectric part provided between the plurality of first electrodes and the plurality of second electrodes. The piezoelectric element is provided for each of the plurality of nozzle holes. The actuator plate is provided on opposite side of the nozzle plate from a side to which the plurality of nozzle holes are opened. The fixing part is insulative and provided between each of a plurality of the piezoelectric elements and the actuator plate. The conductive part is conductive and provided between each of a plurality of the piezoelectric elements and the actuator plate.

Embodiments will now be illustrated with reference to the drawings. In the drawings, the same elements are marked with the same reference numerals, and the detailed description thereof is omitted as appropriate.

FIG. 1is a schematic perspective view for illustrating a droplet application device1according to the embodiment.

Arrows X, Y, and Z inFIG. 1represent three directions orthogonal to each other. For instance, the vertical direction is the Z-axis direction, one direction in the horizontal plane is the X-axis direction, and the direction perpendicular to the Z-axis direction and the X-axis direction is the Y-axis direction.

FIG. 2is a schematic perspective view of a nozzle head2.

FIG. 3is a schematic sectional view taken along line A-A of the nozzle head2inFIG. 2.

FIG. 4is a schematic sectional view for illustrating an actuator plate25and a piezoelectric element26.FIG. 4is a schematic sectional view taken along line B-B of the actuator plate25and the piezoelectric element26inFIG. 3.

FIG. 5is a schematic perspective view for illustrating the piezoelectric element26.

As shown inFIG. 1, the droplet application device1is provided with a nozzle head2, a mounting part3, a supply part4, and a controller5.

As shown inFIGS. 2 and 3, the nozzle head2is a nozzle head of what is called the multi-nozzle type including a plurality of nozzle holes21a. The nozzle head2is also a nozzle head of the “piezoelectric type” that discharges droplets with the help of the bending displacement of the piezoelectric element26.

The nozzle head2is provided with a nozzle plate21, a flow channel plate22, a seal plate23, a diaphragm24, an actuator plate25, a piezoelectric element26, a fixing part27, and a conductive part28.

The nozzle plate21has a configuration extending in a prescribed direction. The nozzle plate21can be configured like e.g. a rectangular solid. The material of the nozzle plate21can be appropriately selected from e.g. resin, metal, and semiconductor material having corrosion resistance to the discharged liquid material. The nozzle plate21can be formed from e.g. stainless steel or nickel alloy.

In this specification, the “liquid material” is not limited to only liquid, but may be any material that is granulated when being discharged from the nozzle hole21a. For instance, the liquid material can be e.g. liquid or gel-like material. The “droplet” in this specification refers to a granulated liquid material.

However, the nozzle head2according to this embodiment can discharge a liquid material of high viscosity that is difficult to discharge by a commonly-used nozzle head. For instance, the nozzle head2according to this embodiment can discharge droplets having a viscosity of 20 mPa·s or more.

The viscosity of the droplet discharged by the nozzle head2can be set to e.g. 20 mPa·s or more.

The nozzle plate21includes a plurality of liquid chambers21b. The plurality of liquid chambers21bcan be provided at e.g. an equal pitch. The plurality of liquid chambers21bare opened to one end surface of the nozzle plate21. A taper part21aais provided at the other end of the liquid chamber21b(the bottom surface of the liquid chamber21b). The cross-sectional dimension of the taper part21aain the direction orthogonal to its central axis gradually decreases toward the nozzle hole21aside. The angle of the taper part21aacan be set to 30° or more and 150° or less.

The nozzle plate21further includes a plurality of nozzle holes21acapable of discharging droplets. One end of the nozzle hole21ais connected to the taper part21aa. The other end of the nozzle hole21ais opened to the end surface of the nozzle plate21on the opposite side from the flow channel plate22side. That is, the liquid chamber21band the nozzle hole21aare connected through the taper part21aa.

The nozzle hole21aand the liquid chamber21bcan be shaped like e.g. a circular cylinder. The diameter of the nozzle hole21acan be set to e.g. approximately 20-50 μm. The diameter of the liquid chamber21bcan be set to e.g. approximately 250-600 μm.

The flow channel plate22is provided on the end surface of the nozzle plate21on the side to which the plurality of liquid chambers21bare opened. The flow channel plate22has a configuration extending in a prescribed direction. The flow channel plate22can be configured like e.g. a rectangular solid. The planar shape and the planar dimension of the flow channel plate22can be made identical to the planar shape and the planar dimension of the nozzle plate21. The flow channel plate22is provided with a hole22apenetrating in the thickness direction. The hole22ais provided at a position opposed to the plurality of liquid chambers21b. The hole22aserves as a flow channel when the liquid material supplied from the supply part4flows into the plurality of liquid chambers21b. In this example, the plurality of liquid chambers21bare connected to one hole22a(flow channel). However, each of the plurality of liquid chambers21bmay be connected to a dedicated hole22a(flow channel).

The material of the flow channel plate22can be made e.g. identical to the material of the nozzle plate21.

The flow channel plate22is not necessarily needed, but the flow channel may be provided in the nozzle plate21.

The seal plate23is provided in a plurality between the nozzle plate21and the actuator plate25. The seal plate23has a configuration extending in a prescribed direction. The seal plate23can be configured like e.g. a rectangular solid. The planar shape and the planar dimension of the seal plate23can be made identical to the planar shape and the planar dimension of the nozzle plate21. The seal plate23is provided with a plurality of holes23apenetrating in the thickness direction. Each of the plurality of holes23ais provided at a position opposed to the liquid chamber21b. The hole23ais provided to transmit the pressure wave caused by the bending displacement of the piezoelectric element26to the liquid material in the liquid chamber21b. The material of the seal plate23can be made e.g. identical to the material of the nozzle plate21.

Here, as shown inFIG. 3, the nozzle plate21is fixed to the actuator plate25with a fastening member such as a screw. The nozzle plate21and the actuator plate25have a configuration extending in the prescribed direction. Thus, if the neighborhoods of their end parts are fixed with a fastening member, at least one of the nozzle plate21and the actuator plate25may be subjected to deflection or warpage. If at least one of the nozzle plate21and the actuator plate25is subjected to deflection or warpage, the adjacent liquid chambers21bmay be connected through an interstice. Then, mutual interference may occur between the adjacent piezoelectric elements26or between the adjacent liquid chambers21b.

Thus, the nozzle head2according to this embodiment is provided with a plurality of seal plates23. The thickness of the seal plate23is thinner than the thickness of the nozzle plate21. Preferably, the thickness of the seal plate23is set to e.g. 0.1 mm or less. A plurality of seal plates23having a thin thickness thus provided can generate an interstice between the seal plates23when at least one of the nozzle plate21and the actuator plate25is subjected to deflection or warpage. That is, a large interstice generated by deflection or warpage can be dispersed into a plurality of small interstices by forming an interstice between the seal plates23. The small interstice has a larger flow channel resistance than the large interstice. This can suppress mutual interference between the adjacent piezoelectric elements26or between the adjacent liquid chambers21b.

The number of seal plates23can be appropriately changed depending on e.g. the deformation amount of the nozzle plate21. For instance, the deformation amount of the nozzle plate21is denoted by S (μm), and the number of seal plates23is denoted by N. Then, it is preferable to satisfy S/N≤10.

The diaphragm24is provided on the opposite side of the plurality of seal plates23from the flow channel plate22side. The diaphragm24covers the plurality of holes23aprovided in the seal plates23. The diaphragm24may be provided, one for each hole23a. The material and the thickness of the diaphragm24are not particularly limited as long as it can be bent by the piezoelectric element26. The material of the diaphragm24can be e.g. polyethylene terephthalate. The thickness of the diaphragm24can be set to e.g. approximately 10 μm.

The actuator plate25is provided on the opposite side of the nozzle plate21from the side to which the plurality of nozzle holes21aare opened.

As shown inFIG. 4, the actuator plate25includes a base part25aand a support part25b. The base part25aand the support part25bcan be formed integrally.

The base part25ais provided on the opposite side of the plurality of seal plates23from the flow channel plate22side. In this case, the base part25acan be provided so as to cover the diaphragm24. The base part25ahas a configuration extending in a prescribed direction. The planar shape and the planar dimension of the base part25acan be made identical to the planar shape and the planar dimension of the nozzle plate21. The base part25ais provided with a plurality of holes25aapenetrating in the thickness direction. Each of the plurality of holes25aais provided at a position opposed to the liquid chamber21b. One end part of the piezoelectric element is inserted into the hole25aa. One end part of the piezoelectric element26is in contact with the diaphragm24.

The support part25bis provided on the longitudinal side of the base part25a. The support part25bis shaped like a plate and extends in the arranging direction of the plurality of holes25aa. The support part25bcan be made generally perpendicular to the surface of the base part25aon the seal plate23side.

The material of the actuator plate25(the base part25aand the support part25b) can be made e.g. identical to the material of the nozzle plate21.

The piezoelectric element26can be shaped like e.g. a rectangular solid. The piezoelectric element26is provided in a plurality on the opposite side of the diaphragm24from the seal plates23side. The end part of the piezoelectric element26inserted into the hole25aais in contact with the diaphragm24. The piezoelectric element26is provided, one for each of the liquid chambers21b. In this case, preferably, the piezoelectric element26is provided in the central axis direction of the liquid chamber21b. For instance, the piezoelectric element26can be provided directly above the liquid chamber21b. That is, preferably, the central axis of the nozzle hole21a, the central axis of the liquid chamber21b, and the central axis of the piezoelectric element26are placed on one straight line. The piezoelectric element26provided in such a position facilitates transmitting the pressure wave caused by the bending displacement of the piezoelectric element26to the liquid material in the liquid chamber21b.

As shown inFIGS. 4 and 5, the piezoelectric element26is provided with a plurality of electrodes26a(corresponding to an example of first electrodes), a plurality of piezoelectric parts26b, and a plurality of electrodes26c(corresponding to an example of second electrodes). The plurality of electrodes26aand the plurality of electrodes26ccan be provided generally parallel to the support part25b. One electrode26cis opposed to one electrode26a. The plurality of electrodes26aand the plurality of electrodes26care provided alternately. The plurality of electrodes26aare electrically connected to each other. For instance, the end parts of the plurality of electrodes26aon the opposite side from the diaphragm24side are electrically connected through a connection part26aa. The plurality of electrodes26care electrically connected to each other. For instance, the end parts of the plurality of electrodes26con the diaphragm24side are electrically connected through a connection part26ca.

Each of the plurality of piezoelectric parts26bis provided at least between the electrode26aand the electrode26c.

The cross-sectional area of the piezoelectric element26in the direction orthogonal to the central axis of the liquid chamber21bcan be made comparable to or less than the cross-sectional area of the liquid chamber21bin the direction orthogonal to the central axis.

Preferably, the extrusion amount is set to e.g. 0.06×10−3mm3or more when the viscosity of the droplet is 20 mPa·s. In this case, the extrusion amount is the product of the cross-sectional area of the piezoelectric element26in the direction orthogonal to the central axis of the liquid chamber21band the displacement amount of the piezoelectric element26.

The relationship between the viscosity of the droplet and the extrusion amount will be described later in detail.

The material of the plurality of electrodes26aand the material of the plurality of electrodes26ccan be e.g. a conductive material such as copper alloy. The material of the plurality of piezoelectric parts26bcan be e.g. a piezoelectric ceramic such as lead zirconate titanate. The piezoelectric element26can be formed by integrally firing a plurality of electrodes26a, a plurality of piezoelectric parts26b, and a plurality of electrodes26c. In the piezoelectric element26provided with the plurality of electrodes26a, the plurality of piezoelectric parts26b, and the plurality of electrodes26c, the number of positions generating the electric field can be increased by the number of pairs of the electrodes26aand the electrodes26c. Thus, compared with the piezoelectric element including one electrode26a, one piezoelectric part26b, and one electrode26c, equal or larger displacement can be obtained even when the application voltage is lowered.

The number of the plurality of electrodes26ccan be made equal to the number of the plurality of electrodes26a. In this case, preferably, the number of the plurality of electrodes26ais set to an odd number. Preferably, the number of the plurality of electrodes26cis set to an odd number. Then, the number of the plurality of electrodes26aand the number of the plurality of electrodes26care odd. In this case, the electrode26acan be provided on the surface (one side surface) of the piezoelectric element26crossing the surface on the diaphragm24side, and the electrode26ccan be provided on the surface (the other side surface) opposed to the surface provided with the electrode26a. This facilitates electrically connecting the plurality of electrodes26aand the plurality of electrodes26cto e.g. an external power supply. In the case illustrated inFIG. 4, the plurality of electrodes26ccan be used as signal electrodes (positive electrodes) and electrically connected to e.g. the controller5. Alternatively, the plurality of electrodes26ccan be used as ground electrodes and electrically connected to e.g. the support part25bof the actuator plate25.

The piezoelectric element26is mechanically connected to the support part25bof the actuator plate25. That is, the piezoelectric element26is electrically and mechanically connected to the support part25bof the actuator plate25. In this case, the piezoelectric element26may be electrically and mechanically connected to the support part25busing a conductive adhesive. However, the distance between the electrode26aand the electrode26cis e.g. approximately 100 μm. Thus, when the piezoelectric element26is pressed to the support part25bvia the conductive adhesive, part of the conductive adhesive may extend around to the surface (side surface) of the piezoelectric element26crossing the surface on the support part25bside. The end part of the electrode26ais exposed to the surface of the piezoelectric element26crossing the surface on the support part25bside. Thus, the electrode26cand the electrode26amay make a short circuit through the conductive adhesive. In this case, decreasing the amount of conductive adhesive may result in failing to achieve a sufficient bonding strength.

Thus, the nozzle head2according to this embodiment is provided with a fixing part27and a conductive part28.

As shown inFIG. 4, the fixing part27is provided between each of a plurality of piezoelectric elements26and the support part25b(actuator plate25). The fixing part27is provided near the end part of the piezoelectric element26on the opposite side from the base part25aside (nozzle plate21side). In this case, the support part25bcan be provided with a protrusion25ba, and the fixing part27can be provided on the top surface of the protrusion25ba. This can align the position of the fixing part27, i.e., the fixing position of the plurality of piezoelectric elements26. Furthermore, the end part of the piezoelectric element26on the opposite side from the base part25aside can be caused to overhang from the protrusion25ba. The piezoelectric element26is fixed to the support part25bthrough the fixing part27. The fixing part27is insulative. The fixing part27can be formed by e.g. curing an insulative adhesive. The adhesive can be e.g. thermosetting adhesive, ultraviolet-curable adhesive, or room temperature-curable adhesive. In the case of using a thermosetting adhesive, preferably, its curing temperature is half or less of the Curie point of the material of the piezoelectric part26b. Use of an insulative adhesive can avoid short circuit between the electrode26cand the electrode26aeven if part of the adhesive extends around to the surface of the piezoelectric element26crossing the surface on the support part25bside when the piezoelectric element26is pressed to the support part25b. Thus, the adhesive can be used in an amount necessary for obtaining a sufficient bonding strength.

The conductive part28is provided between each of a plurality of piezoelectric elements26and the support part25b(actuator plate25). The conductive part28is provided near the end part of the piezoelectric element26on the opposite side from the base part25aside (nozzle plate21side). In this case, the conductive part28can be provided around the protrusion25ba. This can align the position of the conductive part28, i.e., the conducting position of the plurality of piezoelectric elements26. The piezoelectric element26is electrically connected to the support part25bthrough the conductive part28. The conductive part28is conductive. The conductive part28can be formed by e.g. curing a conductive adhesive. The conductive adhesive can be e.g. an adhesive containing a filler made of carbon or metal, or a silver paste. As described above, the piezoelectric element26is connected by the fixing part27. Thus, the conductive part28only needs to provide conduction between the piezoelectric element26and the support part25b. Accordingly, the amount of conductive adhesive can be made smaller than in the case of providing bonding and conduction using a conductive adhesive. This can suppress that part of the conductive adhesive extends around to the surface of the piezoelectric element26crossing the surface on the support part25bside when the piezoelectric element26is pressed to the support part25b.

The conductive part28can be appropriately changed as long as it provides conduction between the piezoelectric element26and the support part25b. For instance, the conductive part28may be e.g. a leaf spring or coil spring made of metal. The conductive part28may be e.g. a wiring connecting the piezoelectric element26and the support part25b.

FIGS. 6A to 6Care schematic process sectional views for illustrating the formation of the fixing part27and the conductive part28.

As shown inFIG. 6A, a diaphragm24is bonded to the end surface of the base part25aon the opposite side from the protruding side of the support part25b. For instance, the diaphragm24can be cemented to the end surface of the base part25a.

Next, as shown inFIG. 6B, one end part of the piezoelectric element26is inserted into the hole25aa. In this case, one end part of the piezoelectric element26is brought into contact with the diaphragm24.

Subsequently, an insulative adhesive is supplied between the top surface of the protrusion25baand the piezoelectric element26.

Subsequently, the piezoelectric element26is pressed to the support part25bwith a jig200. The insulative adhesive is cured in this state.

The fixing part27can be formed in the foregoing manner.

Next, as shown inFIG. 6C, a conductive adhesive is supplied around the protrusion25ba. Then, the conductive adhesive is cured to form a conductive part28.

The adhesive for forming the fixing part27and the adhesive for forming the conductive part28can be supplied from e.g. a dispenser.

In the case where the conductive part28is e.g. a leaf spring, the conductive part28is bonded to the support part25b. Subsequently, the piezoelectric element26may be inserted into the hole25aa, and the fixing part27may be formed. Alternatively, after forming the fixing part27, the conductive part28may be sandwiched between the piezoelectric element26and the support part25b.

Next, returning toFIG. 1, the mounting part3, the supply part4, and the controller5are described.

The mounting part3mounts a target100and moves the target100in a prescribed direction. The mounting part3illustrated inFIG. 1moves the target100in the X-axis direction. In this case, the mounting part3can be e.g. a uniaxial robot or conveyor. Alternatively, the mounting part3can move the target100in at least one of the X-axis direction and the Y-axis direction. In this case, the mounting part3can be e.g. an X-Y table. Alternatively, the mounting part3can move the target100in at least one of the X-axis direction, the Y-axis direction, and the Z-axis direction. In this case, the mounting part3can be e.g. a triaxial robot.

In the illustrated example, the target100moves below the nozzle head2. However, the nozzle head2may move above the target100.

The mounting part3can be provided with a holding part31as needed. The holding part31can be provided on e.g. the mounting surface for mounting the target100. The holding part31can hold e.g. the end part of the target100. For instance, the holding part31can be e.g. a mechanical chuck. Depending on the configuration and material of the target100, the holding part thus provided can be e.g. a vacuum chuck or electrostatic chuck.

The supply part4is connected to the nozzle head2(the hole22aof the flow channel plate22) through a piping43. The supply part4supplies a liquid material to the liquid chamber21bof the nozzle plate21.

The supply part4can be provided with a tank41and an open-close valve42.

The tank41stores a liquid material. For instance, the tank41can be provided above the nozzle head2. The tank41provided above the nozzle head2can supply the liquid material to the liquid chamber21bof the nozzle plate21with the help of potential energy. In this case, a moving part can be provided to move the position of the tank41in the Z-axis direction.

Alternatively, the liquid material can be supplied from the tank41to the liquid chamber21bof the nozzle plate21by providing a pump or supplying a gas into the tank41.

One port of the open-close valve42is connected to the tank41through a piping43. The other port of the open-close valve42is connected to the hole22aof the flow channel plate22through a piping43. The open-close valve42switches between the states of supplying and not supplying the liquid material. In addition, e.g. a control valve can be provided to control the pressure and flow rate of the liquid material.

The controller5can be provided with a computation part such as CPU (central processing unit) and a storage part such as a memory. The controller5controls the operation of each element provided in the droplet application device1based on the control program and data stored in the storage part. The control program for simply controlling the operation of each element can be based on known techniques. Thus, the detailed description thereof is omitted.

The dimension and shape of the target100are not particularly limited. For instance, the target may be a flat plate, and the application surface may be a generally flat surface. The application surface may be a curve surface, or may include irregularities or step differences. The material of the target100is not also particularly limited. The material of the target100may be any material to which the droplet can be attached.

The liquid material is not particularly limited as long as it can be discharged as droplets from the nozzle head2. The liquid material can be e.g. ink, a film material used to form e.g. a resist film or color filter, thermosetting resin, ultraviolet-curable resin, liquid crystal material, electroluminescence material, and biological material. However, the liquid material is not limited to the foregoing examples.

The nozzle head2according to this embodiment can discharge droplets having a viscosity of 20 mPa·s or more, although it can discharge droplets having a viscosity less than 20 mPa·s.

For instance, the piezoelectric element26includes a plurality of electrodes26a, a plurality of piezoelectric parts26b, and a plurality of electrodes26c. That is, the piezoelectric element26is a piezoelectric element having a stacked structure. Thus, compared with the piezoelectric element including one electrode26a, one piezoelectric part26b, and one electrode26c, equal or larger displacement can be obtained even when the application voltage is lowered. As a result, even a liquid material having a viscosity of 20 mPa·s or more can be easily discharged from the nozzle hole21a.

In this case, if the piezoelectric element26having a stacked structure is fixed to the support part25busing a conductive adhesive, part of the conductive adhesive may extend around to the side surface of the piezoelectric element26. Thus, the electrode26cand the electrode26amay make a short circuit. However, in the nozzle head2according to this embodiment, the piezoelectric element26is fixed to the support part25bby the insulative fixing part27. The piezoelectric element26is electrically connected to the support part25bby the conductive part28having electrical conductivity. This can suppress the occurrence of e.g. short circuit even in the case of using the piezoelectric element26having a stacked structure.

In the piezoelectric element26having a stacked structure, a prescribed amount of droplets can be easily discharged even when the droplet has a viscosity of 20 mPa·s or more.

FIG. 7is a graph for illustrating the relationship between the viscosity of the droplet and the extrusion amount.

FIG. 7shows the case of using the piezoelectric element26having a stacked structure.

When the viscosity of the droplet is high, the extrusion amount needs to be increased. In the piezoelectric element26according to this embodiment, the following formula is easily satisfied as shown inFIG. 7.
Y≥9E−05X2.1572

Here, X (mPa·s) is the viscosity of the droplet, and Y (mm3) is the extrusion amount.

As described above, the extrusion amount is the product of the cross-sectional area of the piezoelectric element26in the direction orthogonal to the central axis of the liquid chamber21band the displacement amount of the piezoelectric element26.

As seen fromFIG. 7, in the piezoelectric element26according to this embodiment, a prescribed amount of droplets can be easily discharged even when the liquid material has a viscosity of 20 mPa·s or more.

As seen fromFIG. 7, the extrusion amount needs to be increased to discharge droplets having a viscosity of 20 mPa·s or more. When the extrusion amount is increased, mutual interference is more likely to occur between the adjacent liquid chambers21b. The nozzle head2according to this embodiment is provided with a plurality of seal plates23. This can suppress mutual interference between the adjacent liquid chambers21beven when the extrusion amount is increased.

The storage part of the controller5can store data concerning the relationship between the viscosity of the droplet and the extrusion amount. The controller5can compute the extrusion amount from the inputted viscosity of the droplet and the data stored in the storage part. Based on the computed extrusion amount, the controller5can compute the displacement amount, and in addition, e.g. application voltage and application time.

For instance, the controller5can compute e.g. application voltage and application time so as to satisfy Y≥9E−05X2.1572.

Then, the controller5can control the displacement amount of the piezoelectric element26based on e.g. the computed application voltage and application time so as to discharge droplets appropriately.

That is, the controller5can control at least one of the applied voltage and the application time of the voltage for each of a plurality of piezoelectric elements26provided in the nozzle head2. The controller5can control at least one of the voltage and the application time of the voltage so as to satisfy Y≥9E−05X2.1572.