JP4039095B2 - Piezoelectric transducer and droplet ejection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric transducer and droplet ejection apparatus.
[0002]
[Prior art]
As an ink jet head used in an ink jet type printer, one using a piezoelectric transducer is known. In such an ink jet head, a plate-like member (piezoelectric material plate) made of a piezoelectric material is used for a wall portion that covers the ink liquid chamber. By applying a driving voltage to the piezoelectric material plate, the wall portion is deformed to change the ink pressure in the ink liquid chamber. As a result, ink is ejected from nozzles continuous with the ink liquid chamber.
[0003]
As a mode for driving and deforming such a piezoelectric material plate, there are usually a direct mode and a shear mode. In the direct mode, the direction of the driving electric field accompanying the application of the driving voltage is the direction along the polarization direction of the piezoelectric material plate, and the expansion / contraction deformation along the polarization direction of the piezoelectric material plate is used. In the shear mode, the direction of the driving electric field and the polarization direction of the piezoelectric material plate are substantially orthogonal to each other, and deformation in the shear direction of the piezoelectric material plate is used.
[0004]
[Problems to be solved by the invention]
Among these modes, particularly in the share mode, a configuration is adopted in which the polarization direction frequently changes so as to form a repeated pattern for each ink liquid chamber. For this reason, the polarization process tends to be complicated. In addition, in order to facilitate the polarization process, there may be a method in which electrodes used for polarization are formed in advance in the piezoelectric material plate. May cause crosstalk.
[0005]
The present invention aims at providing a polarization process is not complicated, yet beauty droplet ejecting apparatus Oyo piezoelectric transducer to availability and can adversely affect in performance.
[0006]
[Means for Solving the Problems]
The present invention provides a piezoelectric transducer having several positions double the operation portion piezoelectric material plate is deformed to a linear direction orthogonal to the surface, the interior of the piezoelectric material plate, at positions corresponding to the plurality of operation portions, the piezoelectric A plurality of sets of polarization electrodes for polarizing the piezoelectric material plate in the direction along the surface of the material plate and in the thickness direction, and a polarization voltage applied to the polarization electrode. A plurality of through-hole structures connected to each of the electrodes for polarization and drawn to the surface of the piezoelectric material plate, and on both surfaces of the piezoelectric material plate at positions corresponding to the plurality of operating portions. has possess a plurality of sets of drive electrodes facing each other across the polarization portion between the polarizing electrode, the opposing driving electrodes, a driving electric field in a direction crossing the direction of polarization of the polarized portion To apply The polarization electrodes are arranged symmetrically with respect to the central portion at the center and both ends of the operating portions, respectively, close to different surfaces of the two surfaces of the piezoelectric material plate, and the driving electrodes. Are arranged on both surfaces of the piezoelectric material plate corresponding to each other between the central polarization electrode and the polarization electrodes at both ends .
[0007]
According to this piezoelectric transducer, after the piezoelectric material plate is polarized by applying a voltage from the surface of the piezoelectric material plate to the polarization electrode through the through hole, the driving electrode can be formed. A piezoelectric transducer that does not complicate the process can be obtained.
[0008]
It is desirable that the opposing driving electrodes apply a driving electric field in a direction crossing the polarization direction of the polarization portion to deform the piezoelectric material plate in a shear mode.
[0009]
In this case, the polarization electrode is disposed at the center and both ends of each operation portion, close to a different surface of the piezoelectric material plate and symmetrically with respect to the center portion, and the drive electrode is disposed at the center. Since each of the piezoelectric material plates is disposed on both surfaces corresponding to each other between the polarization electrode and the polarization electrodes at both ends, each operation portion can be deformed symmetrically with respect to the center thereof.
[0010]
More preferably, the piezoelectric material plate is configured by laminating sheet-like materials, the polarization electrode is provided between the sheet-like materials, and the through-hole structure is located on the surface side of the polarization electrode. By providing the sheet-like material penetrating, the electrode for polarization is easily disposed in the piezoelectric material plate, and the electrode for polarization is easily pulled out to the surface by the through-hole structure.
[0011]
[0012]
[0013]
[0014]
[0015]
According to the present invention, in the droplet ejecting apparatus, the piezoelectric transducer is used continuously over a plurality of liquid chambers, and the plurality of the piezoelectric material plates are deformed by applying deformation of the piezoelectric material plate by applying a voltage to the driving electrode. The liquid in the liquid chamber can be ejected by selectively changing the volume of the liquid chamber. When the electrode for polarization is provided at the center and both ends of the operating part, the electrode for polarization at both ends is arranged so as to correspond to the partition wall between the liquid chambers, and the liquid chamber is formed by applying a voltage to the drive electrode. The piezoelectric material plate can be deformed symmetrically with respect to the portion of the piezoelectric material plate corresponding to the center of the piezoelectric material plate.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
-First embodiment-
Hereinafter, a first embodiment in which a piezoelectric transducer, a manufacturing method thereof, and a droplet ejecting apparatus of the present invention are applied to an inkjet head will be described with reference to FIGS.
[0017]
As shown in FIG. 1, the ink jet head 200 includes a piezoelectric transducer 103 and a liquid chamber forming unit 220. The liquid chamber forming unit 220 includes a liquid chamber plate 6, a spacer plate 7, and a nozzle plate having nozzles 8. 9.
[0018]
The liquid chamber 5 for containing ink is formed by covering the upper and lower sides of the opening formed in the liquid chamber plate 6 with the piezoelectric transducer 103 and the spacer plate 7 and, as shown in FIG. 4, has a plurality of rows and a plurality of columns. They are arranged in a plane and are separated from adjacent liquid chambers 5 by a partition wall 51. One end of the liquid chamber 5 in the length direction communicates with the nozzle 8 of the nozzle plate 9 through a communication hole 71 formed in the spacer plate 7, and the other end communicates with an ink supply source (not shown). The liquid chamber 5 is, for example, 0.375 mm in width (left-right direction in the figure) and 2.000 mm in length (direction orthogonal to the paper surface in the figure), and at a pitch (50 DPI) of 0.508 mm in the left-right direction in the figure. Is formed.
[0019]
The piezoelectric transducer 103 includes a piezoelectric material plate 31 made of a lead zirconate titanate (PZT) ceramic material. Furthermore, the piezoelectric material plate 31 is configured by laminating a plurality of sheet-like piezoelectric ceramic layers 1a to 1f, and the first driving is performed on the surface (lower surface in FIG. 1) of the piezoelectric material plate 31 on the liquid chamber 5 side. A second driving electrode 3 is formed on the surface of the electrode 2 and the surface opposite to the liquid chamber 5 (upper surface in FIG. 1). The first drive electrode 2 extends along the entire lower surface of the piezoelectric material plate 31 and is provided in common in each liquid chamber 5. The second driving electrode 3 is provided corresponding to each liquid chamber 5 and formed in a shape substantially corresponding to the shape of each liquid chamber 5. The thickness of one layer of the piezoelectric ceramic layers 1a to 1d is 0.015 mm. The first and second driving electrodes 2 and 3 are made of an Ag—Pd metal material and have a thickness of about 0.002 mm.
[0020]
Between the uppermost sheet-like material 1e and the second sheet-like material 1a of the piezoelectric material plate 31, a first polarizing electrode 11 is provided with a lowermost sheet-like material 1f and a sheet-like material 1d thereon. The second polarization electrode 12 is disposed between the first polarization electrode 11 and the first polarization electrode 11 above the center of each liquid chamber 5, and the second polarization electrode 12 is formed between the partition walls 51 between the liquid chambers. Corresponding to each above. Both the electrodes 11 and 12 are located at a distance from each other in the direction along the surface of the piezoelectric material plate 31 and in the thickness direction. By applying a voltage for polarization to both electrodes 11, 12, the piezoelectric material plate 31 is polarized in the direction in which both electrodes 11, 12 oppose (arrow A). That is, the piezoelectric material plate 31 is polarized in the direction from the central portion of each liquid chamber 5 toward the partition walls 51 on both sides, that is, symmetrically with respect to the central portion. Each polarization direction has a component along the upper and lower surfaces of the piezoelectric material plate 31, that is, a surface direction component, and is inclined with respect to the thickness direction. The first drive electrode 2 and the second drive electrode 3 are opposed to each other so as to sandwich the two polarized portions corresponding to the liquid chambers 5 from above and below. Therefore, the portion corresponding to each liquid chamber 5 of the piezoelectric material plate 31 constitutes a portion that is deformed, that is, an operation portion as will be described later.
[0021]
The first drive electrode 2 and the second drive electrode 3 may be divided and provided only corresponding to each polarization portion. However, as described above, all the first drive electrodes 2 are provided. It is preferable in manufacturing that the second driving electrode 3 is continuously formed for each unit to which a voltage is applied simultaneously, that is, for each liquid chamber.
[0022]
Next, the operation of ejecting droplets will be described with reference to FIGS. As shown in FIG. 1, first, ink is filled into the liquid chamber 5. At this time, both the first drive electrode 2 and the second drive electrode 3 are connected to the ground GND (0 V). Next, as shown in FIG. 2, a positive drive voltage (for example, a voltage applied to the second drive electrode 3 of the liquid chamber 5 in which droplets are to be ejected while the first drive electrode 2 is connected to the ground GND. 20V-30V) is applied. At this time, since the direction of the electric field E generated between the first drive electrode 2 and the second drive electrode 3 and the polarization direction A of the piezoelectric material plate 31 are substantially orthogonal, the liquid chamber 5 corresponding two polarization portions are deformed in shear-over mode. That is, each of the polarized portions is deformed into a parallelogram shape symmetrically with the upper portion of the partition wall 51 as an approximately fulcrum and sandwiching the center of the liquid chamber 5, thereby forming the second drive electrode 3. The region of the material plate 31 moves so as to swell upward in the direction perpendicular to the surface direction of the piezoelectric material plate 31, that is, in FIG. 2, and the volume of the liquid chamber 5 increases. This state is maintained for a one-way propagation time T in the liquid chamber 5 of the pressure wave generated at this time. As the volume increases, ink is supplied to the liquid chamber 5 from an ink supply source (not shown). The one-way propagation time T is a time required for the pressure wave in the liquid chamber 5 to propagate in the longitudinal direction of the liquid chamber 5 (in the direction perpendicular to the paper surface in the figure), and the length of the liquid chamber 5 T = L / a is determined by L and the speed of sound a in the ink inside the liquid chamber 5.
[0023]
According to the pressure wave propagation theory, the pressure in the liquid chamber 5 reverses and changes to a positive pressure after approximately T time from the application of the voltage, and the first driving electrode 2 is moved in accordance with this timing. When the potential of the second drive electrode 3 is returned to the ground GND (0 V) while being connected to the ground GND, the shape of the piezoelectric material plate 31 returns to the state before deformation similar to FIG. Pressure is applied. At that time, the pressure turned positive and the pressure generated by returning the piezoelectric material plate 31 to the state before deformation are added together, and a relatively high pressure is generated in the vicinity of the nozzle 8 communicating with the liquid chamber 5. As shown in FIG. 3, the ink in the liquid chamber 5 is ejected from the nozzle 8 as ink droplets 10.
[0024]
Next, with reference to FIGS. 5 to 9, a method for manufacturing the inkjet head will be described.
[0025]
As shown in FIG. 5, six ceramic material green sheets 1a to 1f constituting the piezoelectric material plate 31 are laminated, and between the outermost green sheets 1e and 1f and the inner green sheets 1a and 1d. Are formed with a first polarization electrode 11 and a second polarization electrode 12, respectively.
[0026]
Specifically, as shown in FIG. 6, a conductive paste material is used for the first polarization electrode 11 at the position corresponding to the central portion of each liquid chamber 5 on the second green sheet 1a from the top. Then, it is formed by screen printing or vapor deposition of a conductive material. Further, in the uppermost green sheet 1e, through holes for drawing out the first polarization electrodes 11 to the upper surface of the piezoelectric material plate 31 through the through-hole structure 11a correspond to the respective polarization electrodes 11. The through-holes are filled with a conductive paste material. When the green sheet 1e is laminated on the green sheet 1a, each through-hole structure 11a is connected to each first polarization electrode 11.
[0027]
As shown in FIG. 7, the second polarizing electrode 12 is removed from the lowermost green sheet 1f as shown in FIG. It is formed by printing or vapor deposition. Further, a through-hole structure 12a is formed in the green sheet 1f, and the second polarization electrode 12 is drawn out to the lower surface of the green sheet 1f. The through-hole structure 12b is formed by filling a through-hole previously formed in the green sheet 1f with a conductive paste material when the polarization electrode 12 is formed on the green sheet 1f. Each of the polarization electrodes 11 and 12 is made of an Ag-Pd metal material and has a thickness of about 0.002 mm.
[0028]
The green sheets 1a, 1e, and 1f on which the polarization electrodes 11 and 12 and the extraction electrode 11b are formed are stacked with the other green sheets 1b, 1c, and 1d having no electrodes interposed therebetween, fired, and integrated. . Next, as shown in FIG. 8, lead electrodes 11b for connecting the plurality of through-hole structures 11a to each other are formed on the upper surface of the piezoelectric material plate 31, and the through-hole structures 12b are formed on the lower surface of the piezoelectric material plate 31. An extraction electrode (not shown) connected to is formed. These lead electrodes can be formed on the upper surface of the uppermost green sheet 1e and the lower surface of the lowermost green sheet 1f before the green sheets are laminated.
[0029]
Then, the piezoelectric transducer is immersed in an oil bath (not shown) filled with insulating oil such as silicon oil at about 130 ° C., and the second polarization electrode 12 is passed through the lowermost extraction electrode and through-hole structure 12a. Is connected to the ground GND (0 V), and a positive polarization voltage is applied to the first polarization electrode 11 through the uppermost lead electrode 11b and the through-hole structure 11a. An electric field of about 2.5 kV / mm is generated between the second polarization electrode 12 and a direction oblique to the surface direction and thickness direction of the piezoelectric material plate. As a result, as shown in FIG. 5, the piezoelectric material plate 31 is polarized in a direction (arrow A) according to the electric field direction.
[0030]
Thereafter, as shown in FIG. 9, electrode layers 3 </ b> A and 2 </ b> A are formed on the upper and lower surfaces of the piezoelectric material plate 31 so as to overlap the extraction electrodes by screen printing or vapor deposition. Then, as shown in FIG. 10, the electrode layer 3 </ b> A is divided together with the extraction electrode 11 b with a laser or the like to form the second driving electrode 3. That is, by removing the electrode layer 3 </ b> A at a position corresponding to the partition wall 51 between the liquid chambers 5, the driving electrode 3 is separated for each liquid chamber 5. The electrode layer 2 </ b> A may also be divided for each liquid chamber 5, but without division, the electrode layer 2 </ b> A is used as it is as the first driving electrode 2, and the first electrode 2 is made continuous over the entire liquid chamber 5. It is preferable to keep it.
[0031]
At this time, the driving electrodes 2 and 3 may remain connected to the polarization electrodes 12 and 11 via the through-hole structures 12a and 11a, respectively, but the electrode layers 2A and 3A are connected to the through-hole structures 11a and 12b. May be electrically separated by removal at the periphery. In the former case, the internal electrode 11 has the same potential as the second electrode 3, and the internal electrode 12 has the same potential as the first electrode 2.
[0032]
Note that the extraction electrodes on the upper and lower surfaces of the piezoelectric material plate 31 may be removed by polishing or the like before the electrode layers 3A and 2A are formed. The individual electrodes 3 may be formed only at positions corresponding to the liquid chambers 5. However, as described above, the electrode layer 3A is formed over the entire upper surface of the piezoelectric material plate 31 and separated by each liquid chamber 5, whereby the cutting operation of the extraction electrode 11b can be performed simultaneously.
[0033]
The piezoelectric transducer 103 formed as described above and the liquid chamber unit 220 including the liquid chamber plate 6, the spacer plate 7 and the nozzle plate 9 which are laminated in advance, and the second driving electrode 3 and the polarization portion are the liquid chamber 5. The inkjet head 200 is manufactured by bonding so as to correspond to the above.
[0034]
-Second Embodiment-
The second embodiment of the present invention will be described below with reference to FIGS. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the piezoelectric transducer 104 of this embodiment, as shown in FIG. 12, the second polarization electrode 112 connected to the ground GND at the time of polarization is formed in a ring shape so as to surround each liquid chamber 5. Accordingly, the green sheet 1f is provided with a through-hole structure 112b for each electrode 112, and all electrodes 112 are routed through the through-hole structure 112b by an extraction electrode (not shown) formed on the lower surface of the green sheet 1f. Connected to each other. The manufacturing method including the polarization method is almost the same as that of the first embodiment, and the deformation operation is also the same.
[0035]
As described above, in the inkjet head 200 of each embodiment, the first polarization electrodes 11 corresponding to the liquid chambers 5 are connected to each other by the extraction electrode 11b, and the first polarization electrode 11 and the second polarization electrode 11 are connected to each other. The polarization electrodes 12 and 112 are used to polarize the piezoelectric material plate 31. For this reason, it is possible to simultaneously polarize the liquid chambers without requiring a complicated operation. Then, after the piezoelectric material plate 31 is polarized, the extraction electrode 11b that has mutually connected the polarization electrodes 11 is cut. Therefore, when the piezoelectric transducer 103 is driven, a drive electric field leaks to the adjacent polarization electrode, and the like. It is possible to eliminate that the driving of the liquid chamber 5 affects other liquid chambers (crosstalk). Further, the electrode layers 2A and 3A are formed on the upper and lower surfaces of the piezoelectric material plate 31, and at least one of the electrode layers 3A is divided to form individual drive electrodes. At the same time, the extraction electrode 11b is cut as described above. Work man-hours can be reduced.
[0036]
In the above embodiment, the formation of the lead electrode, but the formation of electrode layer 2A or the electrode layer 3A Ru have a separate step, it may be used an electrode layer 2A or the electrode layer 3A as the lead electrode. In this case, it is not necessary to form the electrode layer of the first electrode 2 or the second electrode 3 again separately from the formation of the extraction electrode, so that the number of steps can be reduced. However, it is necessary to select the shape of the electrode layer 2A or the electrode layer 3A so that an electric field necessary for polarization can be obtained and the appropriate first electrode 2 and second electrode 3 can be formed by division.
[0037]
Then, as described above, since the polarization is inclined with respect to the surface direction and the thickness direction of the piezoelectric material plate 31, the polarization electrodes 11 and 12 are disposed near both surfaces of the piezoelectric material plate 31. Polarization can be performed by opposingly arranging in the inclined direction so as not to overlap each other in the thickness direction. Then, by arranging the driving electrodes 2 and 3 to face both surfaces of the piezoelectric material plate, an electric field substantially orthogonal to the inclined polarization direction can be applied, and the driving electrodes 2 and 3 can be efficiently deformed with a small number of electrodes.
[0038]
The direction of the direct current for polarization applied to the first polarization electrode 11 and the second polarization electrode 12 is reversed to reverse the polarization direction, or the positions of the drive electrodes 2 and 3 are turned upside down. By reversing the direction of the driving voltage, the piezoelectric material plate 31 can be deformed to reduce the volume of the liquid chamber 5 and ink can be ejected.
Further, in each of the above embodiments, the piezoelectric material plate is driven in the shear mode, but it can be driven in the direct mode depending on the arrangement of the electrodes. That is, in FIG. 1, the first driving electrode 2 is provided only at a position corresponding to the upper surface of the partition wall 51 of the first liquid chamber plate 6, and the width of the second electrode 3 is reduced, thereby driving electric field. The crossing angle between and polarization becomes smaller and operates in direct mode.
[0039]
-Inkjet printer-
Hereinafter, with reference to FIG. 13, an ink jet printer equipped with the droplet ejecting apparatus of the present invention will be described. FIG. 13 is a perspective view showing a main part of the ink jet printer.
[0040]
A platen 110 shown in FIG. 13 is rotatably attached to a frame 113 by a shaft 112 and is driven by a motor 114. A paper 111 is set on the platen 110, and the inkjet head 200 is provided so as to face the platen 110. The inkjet head 200 is placed on the carriage 118 together with the ink supply device 116. The carriage 118 is slidably supported by two guide rods 120 disposed in parallel to the axis of the platen 110, and a timing belt 124 wound around a pair of pulleys 122 is coupled thereto. Then, one pulley 122 is rotated by the motor 123 and the timing belt 124 is sent to move along the platen 110 to the carriage 118.
[0041]
The droplet ejecting apparatus of the present invention is not limited to application to an ink jet printer, and can be applied to various printing apparatuses and various coating apparatuses.
[0042]
【The invention's effect】
According to the present invention, since the external electrode can be formed after the piezoelectric material plate is polarized by applying a voltage from the surface of the piezoelectric material plate to the internal electrode through the through hole, the polarization process is complicated. In addition, a piezoelectric transducer and a liquid droplet ejecting apparatus without crosstalk can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an ink jet head according to a first embodiment of the present invention, and corresponds to a cross section taken along line XX in FIG.
FIG. 2 is a cross-sectional view illustrating the operating state of the ink jet head according to the first embodiment.
FIG. 3 is a cross-sectional view illustrating an operating state of the ink jet head according to the first embodiment.
FIG. 4 is a plan view for explaining an arrangement state of liquid chambers of the ink jet head according to the first embodiment.
FIG. 5 is a cross-sectional view showing a manufacturing process of the piezoelectric transducer of the ink jet head according to the first embodiment.
FIG. 6 is a diagram showing a manufacturing process of the piezoelectric transducer of the first embodiment, and is a plan view of one green sheet.
FIG. 7 is a diagram showing a manufacturing process of the piezoelectric transducer of the first embodiment, and is another plan view of another green sheet.
FIG. 8 is a cross-sectional view showing a manufacturing process of the piezoelectric transducer of the first embodiment.
FIG. 9 is a cross-sectional view showing a manufacturing process of the piezoelectric transducer of the first embodiment.
FIG. 10 is a cross-sectional view showing a manufacturing process of the piezoelectric transducer of the first embodiment.
FIG. 11 is a cross-sectional view showing the ink jet head according to the second embodiment.
FIG. 12 is a diagram showing a manufacturing process of the piezoelectric transducer of the ink jet head according to the second embodiment, and is a plan view of one green sheet.
FIG. 13 is a perspective view showing a main part of the ink jet printer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric material board 1a-1f Green sheet (sheet-like material)
2 First driving electrode 3 Second driving electrode 5 Liquid chamber 11 Polarizing electrode 11a Through-hole structure 11b Lead electrode 12 Polarizing electrode 12b Through-hole structure

Claims (4)

In the piezoelectric transducer with several locations double the operation portion piezoelectric material plate is deformed to a linear direction orthogonal to the plane,
Inside the piezoelectric material plate, at positions corresponding to the plurality of operating portions, the piezoelectric material plate is positioned with a gap in the direction along the surface of the piezoelectric material plate and in the thickness direction, A plurality of sets of electrodes for polarization; and
In order to apply a voltage for polarization to the electrode for polarization, a plurality of through-hole structures connected to the electrodes for polarization and drawn to the surface of the piezoelectric material plate;
Wherein both surfaces of the piezoelectric material plate, at positions corresponding to the plurality of operation portions, which have a plurality of sets of driving electrodes opposite to each other with respect to the polarization portion between the polarizing electrodes,
The opposing driving electrode applies a driving electric field in a direction crossing the polarization direction of the polarization part,
The polarizing electrode is disposed symmetrically with respect to the central portion at the center and both ends of each of the operating portions, close to different surfaces of the two surfaces of the piezoelectric material plate, respectively.
The piezoelectric transducer according to claim 1, wherein the driving electrode is disposed on both surfaces of the piezoelectric material plate corresponding to the gap between the central polarizing electrode and the polarizing electrodes at both ends . The piezoelectric material plate is configured by laminating sheet-like materials, and the polarization electrode is provided between the sheet-like materials,
2. The transducer according to claim 1 , wherein the through-hole structure is provided so as to penetrate a sheet-like material positioned on the surface side of the polarization electrode.   The piezoelectric transducer according to claim 1 is used continuously over a plurality of liquid chambers, and selectively deforms the volumes of the plurality of liquid chambers using deformation of the piezoelectric material plate by applying a voltage to the driving electrodes. A liquid droplet ejecting apparatus, wherein the liquid is ejected by changing the liquid in the liquid chamber. The piezoelectric transducer according to claim 2 is used continuously over a plurality of liquid chambers, the polarization electrodes at both ends are arranged so as to correspond to the partition walls between the liquid chambers, and voltage is applied to the drive electrodes. Accordingly, the piezoelectric material plate is deformed symmetrically with respect to the portion of the piezoelectric material plate corresponding to the center of the liquid chamber, and a liquid is ejected selectively from the plurality of liquid chambers.

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