Method of manufacturing actuators, a method of measuring a thickness of an active layer of an actuator, a method of manufacturing a recording head, and a recording device

A method of manufacturing actuators for an inkjet head includes the step of measuring an absolute value of a coercive voltage of an active layer. The method further includes the step of sorting the actuators based at least on the coercive voltage. Each of the actuators includes a first electrode, a second electrode, an active layer positioned between the first electrode and the second electrode, and an inactive layer wherein the second electrode is positioned between the inactive layer and the active layer.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2007-309808, filed Nov. 30, 2007, the entire subject matter and disclosure of which incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The features herein relate to a method of manufacturing actuators, a method of measuring a thickness of an active layer of the actuator, a method of manufacturing a recording head, and a recording device.

2. Description of the Related Art

A known inkjet head provided in an inkjet printer, which ejects ink droplets onto a recording medium such as a recording sheet, includes a flow-path unit and a plurality of actuators. The flow-path unit has nozzles which eject ink droplets, and pressure chambers communicating with the nozzles. The actuators apply ejection energy to ink in the pressure chambers. An actuator applies a pressure to ink in a pressure chamber by changing the volume of the pressure chamber.

The actuators may vary in operating characteristics as a result of different manufacturing conditions (firing conditions, variation in materials, and the like). Thus, for the inkjet head having the plurality of actuators, it is desirable to sort actuators in accordance with operating characteristics, and to use actuators having equal operating characteristics. A known method of manufacturing actuators having piezoelectric layers includes a technique of sorting actuators in accordance with operating characteristics (displacement characteristics) which are estimated based on capacitances of the actuators.

However, the operating characteristics of the actuators are determined not only by the capacitances. The thickness of the active layer significantly affects the operating characteristic. Meanwhile, to measure the thickness of the active layer, an observation of a cross section of the actuator has to be performed.

SUMMARY OF THE INVENTION

According to one embodiment herein, a method of manufacturing actuators, each of the actuators comprising a first electrode, a second electrode, an active layer positioned between the first electrode and the second electrode, and an inactive layer wherein the second electrode is positioned between the inactive layer and the active layer, the method may comprise the steps of measuring an absolute value of a coercive voltage of the active layer, and sorting the actuators based at least on the coercive voltage.

According to another embodiment herein, a method of measuring a thickness of an active layer of an actuator, the actuator including a first electrode, a second electrode, the active layer positioned between the first electrode and the second electrode, and an inactive layer wherein the second electrode is positioned between the inactive layer and the active layer, the method may comprise the steps of measuring an absolute value of a coercive voltage of the active layer, and calculating an active-layer thickness by dividing the absolute value of a coercive voltage measured.

According to another embodiment herein, a method of manufacturing a recording head, the method comprising the steps of forming a flow-path unit including pressure chambers and forming an actuator including a first electrode, a second electrode, an active layer positioned between the first electrode and the second electrode, and an inactive layer wherein the second electrode is positioned between the inactive and the active layer. The method may further comprise the steps of measuring an absolute value of a coercive voltage of the active layer, sorting the actuators based at least on the coercive voltage, and assembling the sorted actuators with the flow-path unit.

Other objects, features and advantages will be apparent to those skilled in the art from the following detailed description and accompanying drawings.

DESCRIPTION OF THE EMBODIMENTS

Various embodiments, and their features and advantages, may be understood by referring toFIGS. 1-9, like numerals being used for corresponding parts in the various drawings.

Referring toFIG. 1, an inkjet printer101may be a color inkjet printer including a plurality of, e.g., four, inkjet heads1. The inkjet printer101may have a feed section11on the left side in the drawing, and a discharge section12on the right side in the drawing.

A sheet-conveying path may be positioned in the inkjet printer101. A sheet P may be conveyed from the feed section11to the discharge section12through the sheet-conveying path. A plurality of, e.g., two, feed rollers5aand5bmay be positioned directly downstream of the feed section11. The feed rollers5aand5bmay nip and convey the sheet P, so as to feed the sheet P from the feed section11toward the right side in the drawing. A conveyance mechanism13may be positioned in an intermediate portion of the sheet-conveying path. The conveyance mechanism13may include a plurality of, e.g., two, belt rollers6and7, an endless conveying belt8which is wound around the belt rollers6and7, and a platen15which is positioned in a region surrounded by the conveying belt8. The platen15may support the conveying belt8at a position opposing the inkjet head1, so as to prevent the conveying belt8from being bent downwardly. A nip roller4may be positioned at a position opposing the belt roller7. The nip roller4may press the sheet P, which is fed from the feed section11by the feed rollers5aand5b, to an outer peripheral surface8aof the conveying belt8.

When a conveying motor19(seeFIG. 6) rotates the belt roller6, the conveying belt8may travel. Hence, the conveying belt8may convey the sheet P, which is pressed to the outer peripheral surface8aby the nip roller4, toward the discharge section12while the conveying belt8adhesively holds the sheet P. A low-adhesive silicone resin layer may be formed on the surface of the conveying belt8.

A separation mechanism14may be positioned directly downstream of the conveying belt8. The separation mechanism14may separate the sheet P, which adheres on the outer peripheral surface8aof the conveying belt8, from the outer peripheral surface8a, and guide the sheet P to the discharge section12positioned on the right side in the drawing.

The plurality of inkjet heads1corresponding to a plurality of color inks, e.g., magenta, yellow, cyan, black, may be arranged and fixed in a conveying direction. The plurality of inkjet heads1may respectively have head bodies2at lower ends thereof. The head bodies2each may have a rectangular-parallelepiped shape elongated in a direction orthogonal to the conveying direction. Bottom surfaces of the head bodies2may function as ink ejection surfaces2a, which opposes the outer peripheral surface8a. When the sheet P conveyed by the conveying belt8passes through an area directly below the plurality of head bodies2, the color inks may be respectively ejected from the ink ejection surfaces2aonto an upper surface, i.e., a print surface of the sheet P. Hence, a desired color image may be formed on the print surface of the sheet P.

Referring toFIG. 2, the head body2may constitute the inkjet head1when the head body2is assembled with a driver IC51(seeFIG. 6) which generates driving signals to drive a reservoir unit (not shown) for supplying ink, and an actuator unit21. A plurality of, e.g., four, actuator units21may be positioned on an upper surface9aof a flow-path unit9in the head body2. The actuator unit21may have a trapezoidal flat surface. The actuator unit21may be made of a ferroelectric material of lead zirconate titanate (PZT) ceramics.

Referring toFIG. 3, an ink flow path containing the pressure chambers110and other components may be formed inside the flow-path unit9. Each actuator unit21may include a plurality of actuators respectively corresponding to the pressure chambers110. The actuator unit21may apply ejection energy selectively to ink in the pressure chambers110when the actuator unit21is driven by the driver IC51.

Referring back toFIG. 2, the flow-path unit9may have a rectangular-parallelepiped shape. A plurality of, e.g., ten in total, ink supply ports105bmay be formed in the upper surface9aof the flow-path unit9. The ink supply ports105bmay correspond to ink ejection paths (not shown) of the reservoir unit. Referring toFIGS. 2 and 3, manifold flow paths105and sub-manifold flow paths105amay be formed in the flow-path unit9. The manifold flow paths105may communicate with the ink supply ports105b. The sub-manifold flow paths105amay be split from the manifold flow paths105. The ink ejection surface2amay be formed on a lower surface of the flow-path unit9. A plurality of nozzles108may be arranged in a matrix in the ink ejection surface2a. Similarly to the nozzles108, the pressure chambers110may be arranged in a matrix in a fixing surface of the flow-path unit9, on which the actuator units21are fixed.

The array of the pressure chambers110may be arranged at regular intervals in a longitudinal direction of the flow-path unit9. The array of the pressure chamber110may comprise sixteen rows arranged in parallel to a short-side direction of the flow-path unit9. The number of pressure chambers110contained in each row may gradually decrease from a long side toward a short side of the actuator unit21, so as to be consistent with an external shape, e.g., trapezoidal shape, of the actuator unit21. The nozzles108may be arranged in a similar manner to the pressure chambers110.

Referring toFIG. 4, the flow-path unit9may include a plurality of, e.g., nine, plates122to130made of a metal material such as stainless steel. The plates122to130may have rectangular flat surfaces elongated in a main-scanning direction.

Through holes formed in the plates122to130may be connected by positioning and stacking the plates122to130, and hence, multiple individual ink-flow paths132may be formed. The individual ink-flow paths132may extend from the manifold flow paths105to the sub-manifold flow paths105a. Then, the individual ink-flow paths132may extend from outlet ports of the sub-manifold flow paths105a, through the pressure chambers110, to the nozzles108.

Ink, which is supplied from the reservoir unit to the inside of the flow-path unit9through the ink supply port105b, may flow in the manifold flow path105and may be split into the sub-manifold flow paths105a. The ink in the sub-manifold flow paths105amay flow into the individual ink-flow paths132, and may reach the nozzles108through the apertures112, which function as ink-limiting holes, and through the pressure chambers110.

Referring toFIG. 5, the actuator unit21may include three piezoelectric sheets (piezoelectric layers)141to143. Individual electrodes135may be positioned on the piezoelectric sheet141at positions corresponding to the pressure chambers110. Each individual electrode135may include an electrode portion and an extending portion. The electrode portion may be positioned at a position corresponding to a pressure chamber110. The extending portion may extend to the outside of a region corresponding to the pressure chamber110. A land136may be formed on the extending portion. A common electrode134may be positioned between the piezoelectric sheet141, which is a top layer, and the piezoelectric sheet142positioned below the piezoelectric sheet141. The common electrode134may extend over an entire plane between the piezoelectric sheets141and142.

A ground potential may be equally applied to regions of the common electrode134corresponding to the pressure chambers110. The individual electrodes135may be electrically connected with the driver IC51. Driving signals from the driver IC51may be selectively input to the individual electrodes135. A portion positioned between the individual electrode135and the pressure chamber110in the actuator unit21may serve as an individual actuator. A plurality of actuators may be formed by a number corresponding to the number of pressure chambers110.

The piezoelectric sheet141may be polarized in a thickness direction thereof. A portion of the piezoelectric sheet141corresponding to the individual electrode135may serve as an active portion which is bent by a piezoelectric effect. When the individual electrode135has a potential different from the potential of the common electrode134, an electric field may be applied to the active portion in a polarization direction. The active portion may be expanded in the thickness direction and contracted in a surface direction when the polarization direction corresponds to the direction of an electric-field direction. At this time, a displacement in the surface direction may be larger than the displacement in the thickness direction. As described above, the actuator unit21may be a so-called unimorph-type actuator, in which the upper piezoelectric sheet141spaced from the pressure chamber110serves as an active layer including the active portion, and in which the lower a plurality of, e.g., two, piezoelectric sheets142and143proximate to the pressure chamber110serve as inactive layers.

The piezoelectric sheets141to143may be positioned on an upper surface of the cavity plate122. The cavity plate122may partition the pressure chambers110. If a deformation of the electric-field applied portion of the piezoelectric sheet141is not consistent with deformations of corresponding portions of the piezoelectric sheets142and143, the piezoelectric sheets141to143may be entirely deformed to bulge inward of the pressure chamber110. Hence, a pressure (ejection energy) may be applied to ink in the pressure chamber110, causing a pressure wave to be generated in the pressure chamber110. The generated pressure wave may propagate from the pressure chamber110to the nozzle108. Thus, the nozzle108may eject an ink droplet.

The driver IC51may output a driving signal so as to preliminarily apply a predetermined potential to the individual electrode135again, to temporarily apply a ground potential to the individual electrode135every ejection request, and then to apply the predetermined potential to the individual electrode135at a given timing. Accordingly, the pressure of the ink in the pressure chamber110may decrease when the potential of the individual electrode135becomes the ground potential, and the ink may be sucked from the sub-manifold flow path105ato the individual ink-flow path132. Then, the pressure of the ink in the pressure chamber110may increase when the potential of the individual electrode135becomes the predetermined potential again, and the nozzle108may eject an ink droplet. Namely, a rectangular-wave pulse may be applied to the individual electrode135. The pulse width of the rectangular-wave pulse may be an acoustic length (AL) representing a time length in which a pressure wave propagates from an outlet port of the sub-manifold flow path105ato a tip end of the nozzle108in the pressure chamber110. When the pressure of the ink in the pressure chamber110is reversed from a negative pressure to a positive pressure, both pressures may be added. Hence, the nozzle108may eject an ink droplet with a high pressure.

Referring toFIG. 6, the control unit16may include an operating-characteristic-parameter storage portion65, a print data storage portion63, a head control portion64, and a conveying-motor control portion66.

The operating-characteristic-parameter storage portion65may store an operating characteristic parameter which represents a displacement6of the actuator unit21when a voltage is applied between the individual electrodes135and the common electrode134. The operating characteristic parameter may be calculated when the actuator unit21is manufactured. The inkjet head1may include the plurality of, e.g., four, actuator units21, and the plurality of, e.g., four, actuator units21having substantially equal operating characteristic parameters. Hence, the operating-characteristic-parameter storage portion65may store a single operating characteristic parameter.

The print data storage portion63may store print data which is transferred from a host computer (not shown). The print data may contain image data which relates to an image to be formed on a sheet P. The head control portion64may control the inkjet head1by outputting a control signal to the driver IC51so as to form an image on a sheet P, which is conveyed by the conveyance mechanism13, in accordance with the print data stored in the print data storage portion63.

The conveying-motor control portion66may control a driving speed of the conveying motor19so as to drive the conveying belt8at a predetermined speed pattern (containing an acceleration pattern, a constant-speed pattern, and a deceleration pattern).

The head control portion64may control ejection of an ink droplet from the nozzle108of the inkjet head1so as to print an image, which relates to the image data contained in the print data stored in the print data storage portion63, onto the conveyed sheet P. At this time, the head control portion64may control the driver IC51so that the volume of the ink droplet to be ejected from the nozzle108becomes a predetermined amount, in accordance with the operating characteristic parameter stored in the operating-characteristic-parameter storage portion65. In particular, a waveform pattern may be generated, such that a pulse width of a driving signal decreases as a displacement of the actuator unit21indicated by the operating characteristic parameter increases. Accordingly, variation in ink ejection characteristics of nozzles108may be reduced in inkjet heads1including the actuator units21having different operating characteristic parameters.

Referring toFIG. 7, the method of manufacturing the inkjet head1may include a flow-path-unit forming step, an actuator forming step, an actuator-thickness measuring step, a capacitance measuring step, a coercive-voltage-and-coercive-field measuring step, an active-layer-thickness calculating step, a dielectric-constant calculating step, an operating-characteristic-parameter calculating step, a sorting step, and an assembly step.

In the flow-path-unit forming step, the plates122to130may be positioned, stacked, and bonded, thereby forming the flow-path unit9. In the actuator forming step, a conductive pattern later serving as the common electrode134may be printed on a surface of a green sheet later serving as the piezoelectric sheet141. Green sheets later serving as the piezoelectric sheets142and143may be stacked in that order on the former green sheet such that the conductive pattern later serving as the common electrode134is interposed between the former green sheet and the two latter green sheets. Thereby forming a green-sheet stack may be constituted. After the green-sheet stack is fired, a conductive pattern containing the plurality of individual electrodes135may be printed on another surface of the piezoelectric sheet141, and the stack is fired again, thereby forming the actuator unit21.

In the actuator-thickness measuring step, an actuator thickness t0may be measured. The actuator thickness t0may be a total thickness of the actuator unit21formed in the actuator forming step. In this embodiment, in the capacitance measuring step, a total capacitance between all the individual electrodes135and the common electrode134of the actuator unit21may be measured, and the measured total capacitance may be divided by the number of the individual electrodes135, thereby calculating an average of capacitances C of the individual electrodes135. For sampling, individual capacitances of a predetermined number of individual electrodes135at predetermined positions may be measured for every actuator unit21, and an average of the individual capacitances may be used as a capacitance C.

In the coercive-voltage-and-coercive-field measuring step, a coercive field E0of the piezoelectric sheet141, which is the active layer of the actuator unit21, may be previously obtained. A coercive field may be an electric field generated when the polarization of a ferroelectric, such as the piezoelectric sheet141, is reversed. The coercive field may be one of parameters representing an electrical property of a ferroelectric material. In the coercive-voltage-and-coercive-field measuring step, the piezoelectric sheet141may be used for measurement of the coercive field E0of the piezoelectric sheet141. However, in this embodiment, a coercive field E0of a measurement sample may be measured. The measurement sample may be selected from a single lot of actuator units21formed in the actuator forming step with the same material under the same firing condition. The actuator units21formed with the same material under the same firing condition may exhibit substantially similar coercive fields E0.

Referring toFIG. 8, the polarization-voltage hysteresis characteristic of the measurement sample may be measured. In particular, a voltage in a waveform of continuous triangular waves may be applied between an individual electrode135and a common electrode134of the measurement sample. Note that V0and −V0, which are peak voltage values in the waveform pattern, may completely polarize the measurement sample.

Referring toFIG. 9, when the voltage in the waveform pattern is applied to the measurement sample, application of the voltage may be started from a state in which the measurement sample is not polarized. The degree of polarization of the measurement sample may increase as the applied voltage increases. When the applied voltage further increases and reaches V1, the measurement sample may be completely polarized.

After the measurement sample is completely polarized, the applied voltage may decrease. As the applied voltage decreases, the degree of polarization of the measurement sample may decrease. However, even when the applied voltage becomes zero, the polarization of the measurement sample does not become zero because a remnant polarization remains in the measurement sample. When the applied voltage further decreases and becomes −V1, the polarization of the measurement sample may become zero. When the applied voltage further decreases, reversal of the polarization may be started. When the applied voltage becomes −V0, the measurement sample may be completely polarized again. Although the degree of polarization of the measurement sample decreases as the applied voltage increases, even when the applied voltage becomes zero, the polarization of the measurement sample does not become zero because a remnant polarization remains in the measurement sample. When the applied voltage further increases and becomes V1, the polarization of the measurement sample may become zero again. An absolute value of the applied voltage V1or −V1when the polarization becomes zero may be assumed as a coercive voltage V of the measurement sample. An active-layer thickness t1of the measurement sample may be measured, and the coercive voltage V may be divided by the measured thickness t1, thereby calculating a coercive field E0. Note that the active-layer thickness t1may be measured by cutting the measurement sample along the thickness direction, and by observing a cross section of the measurement sample with an electron microscope.

In the coercive-voltage-and-coercive-field measuring step, a coercive voltage V of the active layer of the actuator unit21as an object to be sorted, namely, a coercive voltage V of the piezoelectric sheet141, may be measured. Similarly to the above-described measurement sample, a polarization-voltage hysteresis characteristic of the piezoelectric sheet141may be measured. In particular, a voltage in the form of triangular waves shown inFIG. 8may be applied between an individual electrode135and a common electrode134, so as to measure the polarization-voltage hysteresis characteristic of the piezoelectric sheet141. Then, an absolute value of the applied voltage V1or −V1when the polarization becomes zero obtained from the measured polarization-voltage hysteresis characteristic may be determined as a coercive voltage V of the piezoelectric sheet141.

Referring back toFIG. 7, in the active-layer-thickness calculating step, an active-layer thickness t1, which is a thickness of the piezoelectric sheet141, namely, a thickness of the active layer, may be calculated as follows:
t1=V/E0

In the dielectric-constant calculating step, a dielectric constant ∈ of the piezoelectric sheet141, namely, a dielectric constant ∈ of the active layer, may be calculated based on the capacitance C measured in the capacitance measuring step, the active-layer thickness t1calculated in the active-layer-thickness calculating step, and an electrode area S, which is a surface area of an individual electrode135. It is assumed that the electrode area S may be a design value of the individual electrode135. The capacitance C may be expressed as follows:
C=∈·S/t1(∈=∈0·∈′)
where ∈ is a dielectric constant of the piezoelectric sheet141, ∈0is a dielectric constant of vacuum, and ∈′ is a relative dielectric constant. Hence, the dielectric constant ∈ may be calculated as follows:
∈=C·t1/S

In the operating-characteristic-parameter calculating step, an operating characteristic parameter may be calculated based on the actuator thickness t0measured in the actuator-thickness measuring step, the capacitance C measured in the capacitance measuring step, the active-layer thickness t1calculated in the active-layer-thickness calculating step, and the dielectric constant ∈ calculated in the dielectric-constant calculating step. As described above, the operating characteristic parameter may represent a displacement δ of the actuator unit21when a voltage is applied between an individual electrode135and a common electrode134. The displacement δ may be expressed as follows by using the values obtained through the actual measurement and analysis:
δ=f(t1,t0,∈)
The displacement δ may be calculated as the operating characteristic parameter based on the above expression.

In the sorting step, actuator units21may be sorted based on operating characteristic parameters calculated for the actuator units21in the operating-characteristic-parameter calculating step. In the assembly step, four actuator units21, which have operating characteristic parameter sorted into a single category in the sorting step, may be assembled with the flow-path unit9formed in the flow-path-unit forming step. Further, required electric components (including a chip on film (COF) with a driver IC51(seeFIG. 6) mounted and a control board, which are connected to each actuator unit21), ink-supply components, a protection cover, and other components may be assembled. Thus, manufacturing of the inkjet head1may be completed.

In this embodiment described above, the active-layer thickness t1, which is the thickness of the piezoelectric sheet141, namely, the thickness of the active layer, may be calculated based on the coercive voltage V (actually measured value) and the coercive field E0(previously obtained value) of the piezoelectric sheet141. Also, the dielectric constant ∈ may be calculated based on the capacitance C (actually measured value), the active-layer thickness t1, and the electrode area S (previously determined value). Then, the operating characteristic parameter may be calculated by using the active-layer thickness t1, the actuator thickness t0, and the dielectric constant ∈. As described above, because the operating characteristic parameter is calculated by using the active-layer thickness t1, the actuator thickness t0, and the dielectric constant C, which significantly affect the displacement of the actuator unit21, an accurate operating characteristic parameter of the actuator unit21may be easily obtained. At this time, because the active-layer thickness t1is calculated by using the coercive voltage V of the active layer, the actuator unit21may be not damaged. In addition, because the plurality of actuator units21, which have the operating characteristic parameters sorted into the single category, may be assembled in the inkjet head1, ink ejection characteristics of the nozzles of the inkjet head1may be equalized.

Further, because the actually measured values of the capacitance C and actuator thickness t0are used, a further accurate operating characteristic parameter may be calculated.

Because the driver IC51is controlled so that an ink droplet is ejected from a nozzle108by a predetermined volume, based on the operating characteristic parameter of the actuator unit21stored in the operating-characteristic-parameter storage portion65, variation in ink ejection characteristics of the nozzles108may be reduced in the inkjet heads1including the actuator units21having different operating characteristic parameters.

Although embodiments have been described in detail herein, the scope of this patent is not limited thereto. It will be appreciated by those of ordinary skill in the relevant art that various modifications may be made without departing from the scope of the invention. Accordingly, the embodiments disclosed herein are exemplary, and are not limiting. It is to be understood that the scope of the invention is to be determined by the claims.

As an example modification, in the above-described embodiment, although the dielectric constant ∈ is calculated based on the capacitance C measured in the capacitance measuring step, the active-layer thickness t1calculated by using the actually measured coercive voltage V, and the electrode area S of the design value, it is not limited thereto. A dielectric constant ∈ may be calculated by using a previously determined capacitance C, or by using an electrode area S of an actually measured value.

Furthermore, in the above-described embodiment, although the displacement δ of the actuator unit21is calculated by using the calculated active-layer thickness t1, the actuator thickness t0measured in the actuator-thickness measuring step, and the calculated dielectric constant ∈, it is not limited thereto. An electrode area S may be calculated by using an actually measured capacitance C, a calculated active-layer thickness t1, and a previously determined dielectric constant ∈. Also, a displacement δ may be calculated by using the active-layer thickness t1, the actuator thickness t0, and the calculated electrode area S. In particular, the capacitance C may be derived as follows:
C=∈·S/t1,
then, the electrode area S may be calculated as follows:
S=C·t1/∈,
and finally, the displacement δ may be calculated as follows by using the values obtained through the actual measurement and analysis:
δ=f′(t1,t0,S)

At this time, a displacement δ may be calculated by using previously determined dielectric constant ∈ and electrode area S. In particular, the active-layer thickness t1is obtained as follows:
t1=∈·S/C
and then, the displacement δ may be calculated as follows by using the values obtained through the actual measurement and analysis:
δ=f″(t1,t0)
Alternatively, a previously determined actuator thickness to may be used. Still alternatively, an operating characteristic parameter may be calculated as follows by using an actually measured coercive voltage V:
δ=f′″(V)

Furthermore, in the above-described embodiment, although the piezoelectric sheet141is positioned between the plurality of individual electrodes135and the common electrode134to form the actuator unit21including the plurality of actuators, it is not limited thereto. A piezoelectric sheet may be positioned between a single individual electrode and a single common electrode to form each actuator.

Furthermore, in the above-described embodiment, although the present invention is applied to the inkjet head1for ejecting ink droplets, it is not limited thereto. The present invention may be widely applied to recording heads having actuators.