Liquid ejection head and recording apparatus

Abstract

A piezoelectric actuator has a first active region and a second active region. The first active region comprises a piezoelectric body polarized in a thickness direction, and overlaps a central section of a pressure chamber in a plan view of a pressure application surface. The second active region comprises a piezoelectric body polarized in a thickness direction, is located closer to the pressure application surface than the first active region, and overlaps with a peripheral edge section of the pressure chamber and an outer region of the pressure chamber in a plan view of the pressure application surface. During liquid discharge control, a driver controls the intensity of a first electric field applied to the first active region and the intensity of a second electric field applied to the second active region such that the second active region produces either expansion or contraction during at least a portion of a period in which the first active region is produces either said expansion or contraction. The intensity of the first electric field is greater than the intensity of the second electric field.

Description

[Technical field]

[0001] The present disclosure relates to a liquid ejection head and a recording apparatus having the liquid ejection head. [Background technology]

[0002] Piezoelectric actuators used in inkjet heads and the like are known (for example, Patent Documents 1 and 2). For example, a unimorph type piezoelectric actuator has a vibration plate that covers the upper opening of a pressure chamber filled with liquid (ink), and a piezoelectric layer that overlaps the vibration plate. When the piezoelectric layer expands or contracts in a direction along the surface, the piezoelectric actuator is deformed by bending like a bimetal. This applies pressure to the pressure chamber and ejects liquid. For example, a voltage is applied to the piezoelectric layer in a region that overlaps the center of the pressure chamber in a plan view, causing the layer to expand or contract in a direction along the surface. Patent Documents 1 and 2 disclose a configuration in which a voltage is also applied to a portion of the vibration plate made of a piezoelectric material that is located on the outer edge side of the pressure chamber in a plan view. Patent Documents 3 and 4 disclose a technology in which an electric field is applied to a piezoelectric material to perform a polarization process. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-182448 A [Patent Document 2] JP 2010-155386 A [Patent Document 3] JP 2006-158127 A [Patent Document 4] JP 2010-228144 A Summary of the Invention

[0004] A liquid ejection head according to an aspect of the present disclosure includes a flow path member, a piezoelectric actuator, and a driver. The flow path member includes a pressure surface and a pressure chamber that opens to the pressure surface. The piezoelectric actuator overlaps the pressure surface. The driver drives the piezoelectric actuator. The piezoelectric actuator includes a first active region and a second active region. A direction perpendicular to the pressure surface is referred to as a thickness direction. In this case, the first active region is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber in a planar perspective of the pressure surface. The second active region is made of a piezoelectric body polarized in the thickness direction, is located closer to the pressure surface than the first active region, and overlaps a peripheral portion of the pressure chamber and an outer region of the pressure chamber in a planar perspective of the pressure surface. The driver controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction in a liquid ejection control for ejecting liquid. By this control, the second active region undergoes one of expansion and contraction in the direction along the pressure surface during at least a portion of a period in which the first active region undergoes one of expansion and contraction in the direction along the pressure surface. In the liquid ejection control, the maximum value of the strength of the first electric field is greater than the maximum value of the strength of the second electric field.

[0005] A liquid ejection head according to an aspect of the present disclosure includes a flow path member, a piezoelectric actuator, and a driver. The flow path member includes a pressure surface and a pressure chamber that opens to the pressure surface. The piezoelectric actuator overlaps the pressure surface. The driver drives the piezoelectric actuator. The piezoelectric actuator includes a first active region and a second active region. A direction perpendicular to the pressure surface is referred to as a thickness direction. In this case, the first active region is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber in a planar perspective view of the pressure surface. The second active region is made of a piezoelectric body polarized in the thickness direction and is located closer to the pressure surface than the first active region, and overlaps a peripheral portion of the pressure chamber and an outer region of the pressure chamber in a planar perspective view of the pressure surface. In controlling the ejection of droplets, the driver controls the strength of an electric field applied to the first active region in the thickness direction and the strength of an electric field applied to the second active region in the thickness direction. As a result, the second active region undergoes one of expansion and contraction in a direction along the pressure surface during at least a portion of a period in which the first active region undergoes one of expansion and contraction in a direction along the pressure surface. In a plan view perspective of the pressure surface, an area of ​​a second portion of the second active region located outside the pressure chamber is larger than an area of ​​a first portion of the second active region overlapping the pressure chamber.

[0006] A liquid ejection head according to an aspect of the present disclosure includes a flow path member, a piezoelectric actuator, and a driver. The flow path member includes a pressure surface and a pressure chamber that opens to the pressure surface. The piezoelectric actuator overlaps the pressure surface. The driver drives the piezoelectric actuator. The piezoelectric actuator includes a first active region, a second active region, and a non-active region. A direction perpendicular to the pressure surface is referred to as a thickness direction. In this case, the first active region is made of a piezoelectric body polarized in the thickness direction, and overlaps a center portion of the pressure chamber in a planar perspective of the pressure surface. The second active region is made of a piezoelectric body polarized in the thickness direction, is located closer to the pressure surface than the first active region, and overlaps a peripheral portion of the pressure chamber and an area outside the pressure chamber in a planar perspective of the pressure surface. The non-active region is made of a piezoelectric body and is connected to an outer periphery of the first active region. The driver executes liquid ejection control and reorientation control. In the liquid ejection control, the driver controls the strength of an electric field applied to the first active region in the thickness direction and the strength of an electric field applied to the second active region in the thickness direction, whereby the second active region undergoes one of elongation and contraction in the direction along the pressure surface during at least a portion of a period during which the first active region undergoes one of elongation and contraction in the direction along the pressure surface. In the reorientation control, the driver applies an electric field to the inactive region in the thickness direction when the liquid ejection control is not being performed.

[0007] A recording device according to an aspect of the present disclosure includes a liquid ejection head and a control unit that controls the liquid ejection head. The liquid ejection head includes a flow path member and a piezoelectric actuator. The flow path member includes a pressure surface and a pressure chamber that opens to the pressure surface. The piezoelectric actuator overlaps the pressure surface. The piezoelectric actuator includes a first active region and a second active region. A direction perpendicular to the pressure surface is referred to as a thickness direction. In this case, the first active region is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber in a planar perspective of the pressure surface. The second active region is made of a piezoelectric body polarized in the thickness direction, is located closer to the pressure surface than the first active region, and overlaps a peripheral portion of the pressure chamber and an outer region of the pressure chamber in a planar perspective of the pressure surface. The control unit controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction in a liquid ejection control for ejecting liquid. In the liquid ejection control, the maximum value of the strength of the first electric field is greater than the maximum value of the strength of the second electric field, and the second active region expands or contracts in a direction along the pressure surface during at least a portion of a period during which the first active region expands or contracts in a direction along the pressure surface.

[0008] A recording device according to an aspect of the present disclosure includes a liquid ejection head and a control unit that controls the liquid ejection head. The liquid ejection head includes a flow path member and a piezoelectric actuator. The flow path member includes a pressure surface and a pressure chamber that opens to the pressure surface. The piezoelectric actuator overlaps the pressure surface. The piezoelectric actuator includes a first active region and a second active region. A direction perpendicular to the pressure surface is referred to as a thickness direction. In this case, the first active region is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber in a planar perspective of the pressure surface. The second active region is made of a piezoelectric body polarized in the thickness direction, is located closer to the pressure surface than the first active region, and overlaps a peripheral portion of the pressure chamber and an outer region of the pressure chamber in a planar perspective of the pressure surface. In controlling the ejection of droplets, the control unit controls the strength of an electric field applied to the first active region in the thickness direction and the strength of an electric field applied to the second active region in the thickness direction. As a result, the second active region expands or contracts in a direction along the pressure surface during at least a portion of a period in which the first active region expands or contracts in a direction along the pressure surface. In a plan view perspective of the pressure surface, an area of ​​the second active region overlapping the outer region is larger than an area of ​​the second active region overlapping the pressure chamber.

[0009] A recording device according to an aspect of the present disclosure includes a liquid ejection head and a control unit that controls the liquid ejection head. The liquid ejection head includes a flow path member and a piezoelectric actuator. The flow path member includes a pressure surface and a pressure chamber that opens to the pressure surface. The piezoelectric actuator overlaps the pressure surface. The piezoelectric actuator includes a first active region, a second active region, and an inactive region. A direction perpendicular to the pressure surface is referred to as a thickness direction. In this case, the first active region is made of a piezoelectric body polarized in the thickness direction, and overlaps a center portion of the pressure chamber in a planar perspective of the pressure surface. The second active region is made of a piezoelectric body polarized in the thickness direction, is located closer to the pressure surface than the first active region, and overlaps a peripheral portion of the pressure chamber and an area outside the pressure chamber in a planar perspective of the pressure surface. The inactive region is made of a piezoelectric body and is connected to the outer periphery of the first active region. The control unit executes liquid ejection control and reorientation control. In the liquid ejection control, the control unit controls the strength of an electric field applied to the first active region in the thickness direction and the strength of an electric field applied to the second active region in the thickness direction, whereby the second active region undergoes one of elongation and contraction in the direction along the pressure surface during at least a portion of a period during which the first active region undergoes one of elongation and contraction in the direction along the pressure surface. In the reorientation control, the control unit applies an electric field along the thickness direction to the inactive region when the liquid ejection control is not being performed. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 2 is a side view of the recording apparatus according to the first embodiment. [Figure 1B] FIG. 1 is a plan view of a recording apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a plan view of a portion of the liquid ejection head according to the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4]2 is a plan view of a pressure chamber of the liquid ejection head according to the first embodiment. FIG. [Diagram 5] 2 is a cross-sectional view that illustrates a schematic view of an upper portion of a piezoelectric actuator and a flow path member of the liquid ejection head according to the first embodiment. [Figure 6] 1 is a schematic cross-sectional view showing the polarization direction of a piezoelectric layer in a piezoelectric actuator according to a first embodiment. [Figure 7] FIG. 2 is an exploded perspective view of a portion of the liquid ejection head according to the first embodiment. [Figure 8] FIG. 8 is a partially enlarged view of FIG. [Figure 9] 2 is a plan view showing, in a simplified form, a part of a conductor layer of the liquid ejection head according to the first embodiment. FIG. [Figure 10] 10 is a cross-sectional view taken along line XX in FIG. 9. [Figure 11] 3 is a schematic cross-sectional view showing a potential when liquid is ejected in the liquid ejection head according to the first embodiment. FIG. [Figure 12] 5A and 5B are schematic cross-sectional views showing potentials during polarization processing in the liquid ejection head according to the first embodiment. [Figure 13] FIG. 11 is a schematic cross-sectional view of a liquid ejection head according to a second embodiment. [Figure 14] FIG. 11 is a schematic cross-sectional view of a liquid ejection head according to a third embodiment. [Figure 15] FIG. 11 is a schematic cross-sectional view of a liquid ejection head according to a fourth embodiment. [Figure 16] FIG. 13 is a schematic cross-sectional view of a liquid ejection head according to a fifth embodiment. [Figure 17A] 13 is a cross-sectional view showing a configuration of a piezoelectric layer according to a modified example. FIG. [Figure 17B] FIG. 11 is a cross-sectional view showing a configuration of a piezoelectric layer according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The drawings are schematic. Therefore, details may be omitted. In addition, the dimensional ratios do not necessarily correspond to the actual ones. The dimensional ratios between the drawings do not necessarily correspond to each other. Certain dimensions may be shown larger than the actual ones, and certain shapes may be exaggerated.

[0012] In the explanation of the second and subsequent embodiments, differences from the previously described embodiments will be basically described. Matters that are not specifically mentioned may be the same as the previously described embodiments or may be inferred from the previously described embodiments. In addition, among multiple embodiments, the same reference numerals may be used for corresponding configurations even if the details are different.

[0013] In the present disclosure, "similarity" includes, but is not limited to, similarity in the mathematical sense. Similarity in the mathematical sense refers to a shape that becomes congruent with another shape when enlarged or reduced (or when no such scale conversion is performed). However, if a relationship close to this mathematical similarity is established in a reasonable manner in light of common technical knowledge, etc., it may be considered to be similar. For example, an ellipse and an ellipse having an outer edge located on the inside or outside of the outer edge of the ellipse at a certain distance from the outer edge of the ellipse are not similar in the mathematical sense because the ratio of the major axis to the minor axis is different between the two. However, such a relationship may also be included in similarity in the present disclosure.

[0014] In addition, the terms indicating various shapes in this disclosure (e.g., "circle", "ellipse" or "rectangle") include, but are not limited to, the shapes indicated by these terms in mathematics. For example, an ellipse is a shape that is composed only of curves that are convex outward, and can specify a long direction and a short direction that are approximately perpendicular to each other. For example, a rectangle may have chamfered corners.

[0015] First Embodiment (Overall printer configuration) Fig. 1(a) is a schematic side view of a color inkjet printer 1 (an example of a recording device, hereinafter sometimes simply referred to as a printer) including a liquid ejection head 2 (hereinafter sometimes simply referred to as a head) according to an embodiment of the present disclosure. Fig. 1(b) is a schematic plan view of the printer 1.

[0016] Although the head 2 or the printer 1 can be in any direction as the vertical direction, for convenience, the vertical direction of the paper in Fig. 1(a) is taken as the vertical direction, and terms such as top and bottom are used. Additionally, the terms plan view and plan perspective refer to the view from the vertical direction of the paper in Fig. 1(a) unless otherwise specified.

[0017] The printer 1 moves the print paper P (an example of a recording medium) relative to the head 2 by transporting the print paper P from the paper feed roller 80A to the recovery roller 80B. The paper feed roller 80A and the recovery roller 80B, as well as various rollers described below, constitute a moving unit 85 that moves the print paper P and the head 2 relatively. The control unit 88 controls the head 2 based on print data, which is data for images, characters, etc., to eject liquid toward the print paper P and cause droplets to land on the print paper P, thereby performing recording such as printing on the print paper P.

[0018] In this embodiment, the head 2 is fixed to the printer 1, which is a so-called line printer. Another embodiment of the recording device is a so-called serial printer, which alternates between ejecting droplets while moving the head 2 in a direction intersecting the transport direction of the print paper P (for example, a direction substantially perpendicular thereto) and transporting the print paper P.

[0019] Four flat head mounting frames 70 (hereinafter sometimes simply referred to as frames) are fixed to the printer 1 so as to be approximately parallel to the printing paper P. Each frame 70 is provided with five holes (not shown), and five heads 2 are mounted in each of the holes. The five heads 2 mounted on one frame 70 constitute one head group 72. The printer 1 has four head groups 72, and a total of 20 heads 2 are mounted.

[0020] The head 2 is mounted on the frame 70 so that the portion that ejects liquid faces the printing paper P. The distance between the head 2 and the printing paper P is, for example, about 0.5 to 20 mm.

[0021] The 20 heads 2 may be directly connected to the control unit 88, or may be connected to the control unit 88 via a distribution unit that distributes the print data. For example, the control unit 88 may send the print data to one distribution unit, and the one distribution unit may distribute the print data to the 20 heads 2. Also, for example, the control unit 88 may distribute the print data to four distribution units corresponding to the four head groups 72, and each distribution unit may distribute the print data to five heads 2 in the corresponding head group 72.

[0022] The heads 2 have an elongated shape that is long from the front to the back in FIG. 1(a) and vertically in FIG. 1(b). In one head group 72, three heads 2 are lined up in a direction intersecting (for example, a direction substantially perpendicular to) the transport direction of the print paper P, and the other two heads 2 are lined up one between each of the three heads 2 at positions shifted along the transport direction. In other words, in one head group 72, the heads 2 are arranged in a staggered pattern. The heads 2 are arranged so that the range that can be printed by each head 2 is connected in the width direction of the print paper P, i.e., in the direction intersecting the transport direction of the print paper P, or so that the ends overlap, making it possible to print without gaps in the width direction of the print paper P.

[0023] The four head groups 72 are arranged along the transport direction of the printing paper P. Each head 2 is supplied with liquid (e.g., ink) from a liquid supply tank (not shown). The heads 2 belonging to one head group 72 are supplied with ink of the same color, and the four head groups 72 can print with four colors of ink. The colors of ink ejected from each head group 72 are, for example, magenta (M), yellow (Y), cyan (C), and black (K). A color image can be printed by impacting such ink on the printing paper P.

[0024] The number of heads 2 mounted on the printer 1 may be one, so long as the printer 1 prints in a single color within a range that can be printed with one head 2. The number of heads 2 included in the head group 72 and the number of head groups 72 can be changed as appropriate depending on the object to be printed and the printing conditions. For example, the number of head groups 72 may be increased to print in more colors. In addition, by arranging multiple head groups 72 that print in the same color and printing alternately in the transport direction, the transport speed can be increased even if heads 2 with the same performance are used. This makes it possible to increase the printing area per unit time. In addition, multiple head groups 72 that print in the same color may be prepared and arranged at different positions in a direction intersecting the transport direction to increase the resolution in the width direction of the printing paper P.

[0025] Furthermore, in addition to printing colored inks, a liquid such as a coating agent may be printed uniformly or in a pattern by the head 2 to treat the surface of the printing paper P. For example, when a recording medium into which liquid does not easily penetrate is used, a coating agent that forms a liquid receiving layer so that the liquid can be easily fixed can be used. In addition, when a recording medium into which liquid easily penetrates is used, a coating agent that forms a liquid penetration suppressing layer can be used to prevent the liquid from bleeding too much or from mixing too much with another liquid that has landed next to it. In addition to printing the coating agent by the head 2, the coating agent may be uniformly applied by the applicator 76 controlled by the control unit 88.

[0026] The printer 1 prints on a recording medium, namely, printing paper P. The printing paper P is wound around a paper feed roller 80A, and the printing paper P sent out from the paper feed roller 80A passes under the head 2 mounted on the frame 70, then passes between two transport rollers 82C, and is finally collected by a collection roller 80B. When printing, the printing paper P is transported at a constant speed by rotating the transport roller 82C, and is printed on by the head 2.

[0027] Next, the printer 1 will be described in detail in the order in which the printing paper P is transported. The printing paper P sent out from the paper feed roller 80A passes between two guide rollers 82A, and then passes under the coater 76. The coater 76 applies the above-mentioned coating agent to the printing paper P.

[0028] The printing paper P then enters the head chamber 74, which houses the frame 70 on which the head 2 is mounted. The head chamber 74 is connected to the outside in some areas, such as the area where the printing paper P enters and exits, but is generally a space isolated from the outside. The control factors of the head chamber 74, such as temperature, humidity, and air pressure, are controlled by the control unit 88, etc., as necessary. The head chamber 74 is less susceptible to the effects of disturbances compared to the outside where the printer 1 is installed, so the range of variation of the above-mentioned control factors can be narrower than outside.

[0029] Five guide rollers 82B are arranged in the head chamber 74, and the printing paper P is transported over the guide rollers 82B. The five guide rollers 82B are arranged so that the center is convex in the direction in which the frame 70 is arranged when viewed from the side. As a result, the printing paper P transported over the five guide rollers 82B has an arc shape when viewed from the side, and by applying tension to the printing paper P, the printing paper P between the guide rollers 82B is stretched so that it is flat. One frame 70 is arranged between two guide rollers 82B. The angle at which the frame 70 is installed is changed little by little so that it is parallel to the printing paper P transported underneath it.

[0030] The printing paper P that has left the head chamber 74 passes between two transport rollers 82C, through the dryer 78, between two guide rollers 82D, and is collected by the collection roller 80B. The transport speed of the printing paper P is set to, for example, 100 m / min. Each roller may be controlled by the control unit 88, or may be manually operated by a person.

[0031] By drying with the dryer 78, the printing paper P that is wound up overlapping on the collection roller 80B is less likely to stick to each other, and the undried liquid is less likely to rub against each other. In order to print at high speed, drying must also be performed quickly. To speed up drying, the dryer 78 may use multiple drying methods in sequence, or multiple drying methods may be used in combination. Drying methods used in such cases include, for example, blowing hot air, irradiating infrared rays, and contacting a heated roller. When irradiating infrared rays, infrared rays of a specific frequency range may be applied so that the printing paper P can be dried quickly while minimizing damage to the printing paper P. When the printing paper P is brought into contact with a heated roller, the time for heat to be transmitted may be increased by conveying the printing paper P along the cylindrical surface of the roller. The range of conveyance along the cylindrical surface of the roller is preferably 1 / 4 or more of the circumference of the cylindrical surface of the roller, and more preferably 1 / 2 or more of the circumference of the cylindrical surface of the roller. When printing with UV curable ink or the like, a UV irradiation light source may be arranged instead of the dryer 78 or in addition to the dryer 78. A UV irradiation source may be disposed between each of the frames 70 .

[0032] The printer 1 may include a cleaning unit that cleans the head 2. The cleaning unit performs cleaning by, for example, wiping and / or capping. Wiping is performed by, for example, rubbing the surface of the part where the liquid is discharged, for example, the discharge surface 11a (described later), with a flexible wiper to remove the liquid adhering to the surface. Cleaning with capping is performed, for example, as follows. First, a cap is placed over the part where the liquid is discharged, for example, the discharge surface 11a (this is called capping), so that the discharge surface 11a and the cap are substantially sealed to create a space. In this state, liquid is repeatedly discharged to remove liquid that has become clogged in the discharge hole 3 (described later) and has a higher viscosity than in a standard state, foreign matter, etc. The capping makes it difficult for the liquid during cleaning to splash on the printer 1, and the liquid is difficult to adhere to the print paper P or the transport mechanism such as the roller. The discharge surface 11a after cleaning may be further wiped. Cleaning by wiping and / or capping may be performed manually by a person using a wiper and / or a cap attached to the printer 1, or may be performed automatically by the control unit 88.

[0033] The recording medium may be a roll of cloth in addition to the printing paper P. Also, instead of directly transporting the printing paper P, the printer 1 may transport a transport belt and place the recording medium on the transport belt and transport it. In this way, sheets of paper, cut pieces of cloth, wood, tiles, etc. can be used as recording media. Furthermore, a liquid containing conductive particles may be ejected from the head 2 to print wiring patterns for electronic devices, etc. Furthermore, a chemical agent may be produced by ejecting a predetermined amount of liquid chemical agent or liquid containing a chemical agent from the head 2 toward a reaction vessel or the like and causing a reaction.

[0034] Furthermore, a position sensor, a speed sensor, and / or a temperature sensor may be attached to the printer 1, and the control unit 88 may control each part of the printer 1 according to the state of each part of the printer 1 determined from information from each sensor. For example, in cases where the temperature of the head 2, the temperature of the liquid in the liquid supply tank that supplies the liquid to the head 2, and / or the pressure that the liquid in the liquid supply tank applies to the head 2 affect the ejection characteristics of the ejected liquid (e.g., the ejection amount and / or the ejection speed), the drive signal for ejecting the liquid may be changed according to such information.

[0035] (discharge surface) FIG. 2 is a plan view showing a part of the surface (discharge surface 11a) of the head 2 facing the print paper P. For convenience, an orthogonal coordinate system consisting of the D1 axis, the D2 axis, and the D3 axis is attached to this figure. The D1 axis is defined parallel to the direction of relative movement between the head 2 and the print paper P. The relationship between the positive and negative of the D1 axis and the traveling direction of the print paper P relative to the head 2 is not particularly important in the description of this embodiment. The D2 axis is defined parallel to the discharge surface 11a and the print paper P and perpendicular to the D1 axis. The positive and negative of the D2 axis are also not particularly important. The D3 axis is defined perpendicular to the discharge surface 11a and the print paper P. The -D3 side (the front side of the paper in FIG. 2) is the direction from the head 2 to the print paper P. Note that when simply referring to the D3 direction, it may mean either the +D3 direction toward the +D3 side or the -D3 direction toward the -D3 side. As described above, head 2 has a shape whose longitudinal direction is in the D2 direction, and here, one end side portion in the longitudinal direction is shown.

[0036] The ejection surface 11a is, for example, a flat surface that constitutes most of the surface of the head 2 that faces the printing paper P. The ejection surface 11a is, for example, approximately rectangular with the D2 direction as the longitudinal direction. The ejection surface 11a has a plurality of ejection holes 3 that eject ink droplets. The ejection holes 3 are arranged at different positions in a direction (D2 direction) perpendicular to the direction (D1 direction) of relative movement between the head 2 and the printing paper P. Therefore, any two-dimensional image can be formed by ejecting ink droplets from the plurality of ejection holes 3 while moving the head 2 and the printing paper P relatively by the moving unit 85.

[0037] More specifically, the multiple ejection holes 3 are arranged in multiple rows (16 rows in the illustrated example). That is, the multiple ejection holes 3 form multiple ejection hole rows 5. The positions of the multiple ejection holes 3 in the direction D2 are different from one another in the multiple ejection hole rows 5. This makes it possible to form multiple dots on the printing paper P aligned in the direction D2 at a pitch narrower than the pitch of the ejection holes 3 in each ejection hole row 5. However, the head 2 may be configured to have only one ejection hole row 5.

[0038] The multiple ejection hole rows 5 are, for example, roughly parallel to each other and have the same length. In the illustrated example, the ejection hole rows 5 are parallel to a direction (direction D2) perpendicular to the direction of relative movement between the head 2 and the printing paper P. However, the ejection hole rows 5 may be inclined with respect to the direction D2. Also, in the illustrated example, the sizes of the gaps (intervals in direction D1) between the multiple ejection hole rows 5 are not uniform. This is due to, for example, the convenience of the arrangement of the flow paths inside the head 2. Of course, the sizes of the gaps between the ejection hole rows 5 may be uniform.

[0039] (Head body) Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. The lower side of Fig. 3 is the printing paper P side. Here, the configuration relating to one ejection hole 3 is mainly shown. Also shown here is the head body 7 including the ejection surface 11a of the head 2 (i.e., only a part of the ejection surface 11a side). The head body 7 may be regarded as a liquid ejection head.

[0040] The head body 7 is a generally plate-shaped member, and one of the front and back sides of the plate serves as the ejection surface 11a described above. The thickness of the head body 7 is, for example, 0.5 mm or more and 2 mm or less. The head body 7 is a piezoelectric head that applies pressure to liquid by mechanical distortion of a piezoelectric element to eject droplets. The head body 7 has a plurality of ejection elements 9, each of which includes an ejection hole 3. The plurality of ejection elements 9 and the configurations related to the plurality of ejection elements 9 (for example, wiring connected to the plurality of ejection elements 9) may basically be configured similarly to each other. The plurality of ejection elements 9 are two-dimensionally arranged along the ejection surface 11a.

[0041] From another perspective, the head body 7 has a generally plate-shaped flow path member 11 in which a flow path through which liquid (ink) flows is formed, and a piezoelectric actuator 13 for applying pressure to the liquid in the flow path member 11. The multiple ejection elements 9 are formed by the flow path member 11 and the piezoelectric actuator 13. The ejection surface 11a is formed by the flow path member 11. The surface of the flow path member 11 opposite to the ejection surface 11a is referred to as a pressure surface 11b.

[0042] The flow path member 11 has a common flow path 15 and a plurality of individual flow paths 17 (only one is shown in FIG. 3) each connected to the common flow path 15. Each individual flow path 17 has the above-mentioned discharge hole 3, and further has, in this order from the common flow path 15 to the discharge hole 3, a connecting flow path 19, a pressure chamber 21, and a partial flow path 23.

[0043] The individual flow paths 17 and the common flow path 15 are filled with liquid. When the volumes of the pressure chambers 21 change and pressure is applied to the liquid, the liquid is sent from the pressure chambers 21 to the partial flow paths 23 and a plurality of droplets are ejected from the ejection holes 3. In addition, the pressure chambers 21 are replenished with liquid from the common flow path 15 via the connecting flow paths 19. The piezoelectric actuator 13 (piezoelectric element 27) applies pressure to the liquid in the pressure chambers 21, for example, by causing bending deformation towards the pressure chamber 21 side and / or by returning to a flat state from a bent state towards the opposite side to the pressure chamber 21 side.

[0044] The flow path member 11 is configured, for example, by stacking a plurality of plates 25A to 25J (hereinafter, A to J may be omitted). A plurality of holes (mainly through holes, but may also be recesses) that constitute the plurality of individual flow paths 17 and the common flow path 15 are formed in the plate 25. The thickness and the number of layers of the plurality of plates 25 may be appropriately set according to the shapes of the plurality of individual flow paths 17 and the common flow path 15, etc. The plurality of plates 25 may be formed of an appropriate material. For example, the plurality of plates 25 are formed of metal or resin. The thickness of the plate 25 is, for example, 10 μm or more and 300 μm or less. The plates 25 are fixed to each other, for example, by an adhesive (not shown) interposed between the plates 25.

[0045] (Flow path shape) The specific shape and dimensions of each flow path in the flow path member 11 may be set appropriately. In the illustrated example, they are as follows.

[0046] The common flow path 15 extends in the longitudinal direction of the head 2 (the direction penetrating the paper surface in FIG. 3). Only one common flow path 15 may be provided, but for example, a plurality of common flow paths 15 are provided in parallel to each other. The cross-sectional shape of the common flow path 15 is rectangular.

[0047] The individual flow paths 17 (ejection elements 9 from another perspective) are arranged in the length direction of each common flow path 15. Moreover, the ejection holes 3 individually included in the individual flow paths 17 are also arranged along the common flow path 15. In the arrangement of the ejection holes 3 as shown in Fig. 2, for example, two rows of ejection holes 3 may be arranged on each side of one common flow path 15. Then, a total of 16 rows of ejection holes 3 may be arranged in four common flow paths 15.

[0048] The pressure chamber 21 is open to, for example, the pressure surface 11b, and is blocked by the piezoelectric actuator 13. The pressure chamber 21 may be blocked by a plate 25. However, this can also be considered as a question of whether the plate 25 blocking the pressure chamber 21 should be regarded as part of the flow path member 11, or as part of the piezoelectric actuator 13. In the description of the present disclosure, the layer (plate) above the pressure chamber 21 is regarded as part of the piezoelectric actuator 13.

[0049] The shapes of the multiple pressure chambers 21 are, for example, the same as each other. The shape of each pressure chamber 21 may be set as appropriate. For example, the pressure chamber 21 is formed in a thin shape that spreads with a constant thickness along the pressure surface 11b. However, the pressure chamber 21 may have portions with different thicknesses. The thin shape is, for example, a shape whose thickness is smaller than any diameter in a plan view.

[0050] The diameter is, for example, the length of a part of a line that passes through the center of a plane figure and crosses the plane figure, the part being located within the plane figure. When referring to the center (or middle, etc.) in a planar view (when referring to the center of a plane figure), the center may be, for example, the centroid, unless otherwise specified. The centroid is the center of gravity of a plane figure, and is the point at which the first moment of area with respect to any axis passing through that point is zero.

[0051] The planar shape of the pressure chamber 21 may be, for example, a shape having a longitudinal direction and a lateral direction perpendicular to each other (for example, a diamond or ellipse), or a shape in which such directions cannot be conceived (for example, a circle). The relationship between the longitudinal direction and the lateral direction and the arrangement of the multiple pressure chambers 21 is also arbitrary. In the description of this embodiment, as described later, a shape obtained by combining a circle and an ellipse is taken as an example. From another perspective, a shape in which the longitudinal direction and the lateral direction can be conceived is taken as an example. In the illustrated example, the left-right direction of the paper in FIG. 3 is the longitudinal direction of the pressure chamber 21. This direction is, for example, a direction intersecting (for example, perpendicular) the direction in which the common flow path 15 extends, and from another perspective, it is the lateral direction of the head main body 7.

[0052] In addition, in a mode in which the shape of a cross section of the pressure chamber 21 parallel to the pressure application surface 11b is not constant in the up-down direction, the explanation of the planar shape of the pressure chamber 21 in this disclosure may be applied to, for example, the planar shape of the pressure application surface 11b (opening surface of the pressure chamber 21). This is because the shape of the pressure chamber 21 that has the greatest effect on the pressure received from the piezoelectric actuator 13 is the shape of the pressure application surface 11b.

[0053] The partial flow paths 23 extend from the pressure chamber 21 toward the ejection surface 11a. The partial flow paths 23 are generally cylindrical in shape. The partial flow paths 23 may extend from the pressure chamber 21 toward the ejection surface 11a at an incline in the vertical direction (as shown in the example), or may extend without inclination. The partial flow paths 23 may have different cross-sectional areas depending on the vertical positions. In a plan view, the partial flow paths 23 are connected to, for example, an end of the pressure chamber 21 in a predetermined direction (for example, the longitudinal direction of the pressure chamber 21 in a plan view).

[0054] The discharge hole 3 opens in a part of the bottom surface of the partial flow path 23 (the surface opposite to the pressure chamber 21). The discharge hole 3 is located, for example, approximately in the center of the bottom surface of the partial flow path 23. However, the discharge hole 3 may be provided eccentrically with respect to the center of the bottom surface of the partial flow path 23. The vertical cross section of the discharge hole 3 is tapered so that the diameter becomes smaller toward the discharge surface 11a side. However, the discharge hole 3 may be partially or entirely reverse tapered.

[0055] The connection flow path 19 has, for example, a portion extending upward from the upper surface of the common flow path 15, a portion extending from that portion in a direction along the plate 25, and a portion extending upward from that portion and connected to the lower surface of the pressure chamber 21. The portion along the plate 25 has a reduced cross-sectional area perpendicular to the flow direction, and functions as a so-called throttle. In a plan view, the connection position of the connection flow path 19 to the pressure chamber 21 is, for example, an end of the lower surface of the pressure chamber 21 on the opposite side to the partial flow paths 23 with respect to the center of the lower surface.

[0056] The arrangement of the pressure chambers 21 may be generally similar to the arrangement of the discharge holes 3 described with reference to FIG. 2. However, the arrangement of the pressure chambers 21 may be different from the arrangement of the discharge holes 3. For example, the shapes of the partial flow paths 23 may be different from each other, so that the arrangement of the pressure chambers 21 may be different from the arrangement of the discharge holes 3. For example, unlike the discharge holes 3 shown in FIG. 2, the pressure chambers 21 may be uniformly distributed in both the D1 direction and the D2 direction (the pitch between the rows of the pressure chambers 21 may be constant) or may be arranged in a number of rows less than the number of the discharge hole rows 5.

[0057] (Planar shape of pressure chamber) 4 is a plan view of the pressure chamber 21. In this figure, the pressure chamber 21 is indicated by a solid line.

[0058] The planar shape of the pressure chamber 21 is, for example, a shape obtained by adding together a circular region C1 and a region R2 (one of the regions R2 is hatched) that protrudes from the circular region C1 on both sides in a predetermined direction (the vertical direction on the paper). The outer edge of the region R2 on the opposite side to the circular region C1 (the outer edge shown by the solid line) is a curve that bulges outward. The curvature of this curve (the average value if not constant) is, for example, larger than the curvature of the circular region C1.

[0059] The planar shape of the pressure chamber 21 can be considered as a shape obtained by adding together the overlapping area (area surrounded by dotted lines) and non-overlapping area (area surrounded by solid and dotted lines) of the circle C1 and the ellipse C2. In other words, when the circle C1 and the ellipse C2 are regarded as closed curves in a Venn diagram, the planar shape of the pressure chamber 21 corresponds to a union (or, from another point of view, a logical sum).

[0060] More specifically, the center of the circle C1 and the center of the ellipse C2 are aligned (see center O1). The major axis rL of the ellipse C2 is longer than the radius r1 of the circle C1, and the minor axis rS of the ellipse C2 is shorter than the radius r1 of the circle C1. Regions R2 on both ends of the ellipse C2 in the longitudinal direction are located outside the circle C1.

[0061] However, the outer edge of region R2 opposite to circle C1 (the outer edge shown by the solid line) may have a constant curvature. In other words, region R2 may have a shape that is not conceptualized as both ends of an ellipse, but rather as a part of a circle with a radius smaller than that of circle C1.

[0062] Various dimensions of such a shape (e.g., the relative lengths of the radius r1, major axis rL, and minor axis rS) may be set appropriately. An example is given below. The major axis rL may be set to 1.2 to 1.8 times the radius r1. The radius of curvature calculated from the average of the curvatures of the outer edge of region R2 opposite to circle C1 may be set to 0.3 to 0.6 times the radius r1.

[0063] The shape of the pressure chamber 21 described above is, in other words, a shape in which most of (or the entirety of) its outer edge is configured by a circular arc. For example, a portion of the outer edge of the pressure chamber 21 that corresponds to an angle of 180° or more around the center of the pressure chamber 21 is configured by a circular arc.

[0064] In the following description, the terms "central portion" and "peripheral portion" of the pressure chamber 21 may be used. The central portion 21a has its outer edge indicated by a two-dot chain line Ln1 in Fig. 4. The central portion 21a is, for example, a region that includes the center O1 of the pressure chamber 21 and is spaced away from the outer edge of the pressure chamber 21 toward the center O1 in a plan view. The peripheral portion 21b has its inner edge indicated by a two-dot chain line Ln1 in Fig. 4, and its outer edge indicated by a solid line indicating the outer edge of the pressure chamber 21. The peripheral portion 21b is, for example, a region that is in contact with the outer edge of the pressure chamber 21 (basically the entire circumference) and is spaced away from the center of the pressure chamber 21 in a plan view.

[0065] The central portion 21a and the peripheral portion 21b can be defined in such a manner that the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b are separated from each other, or in such a manner that the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b are aligned, or in such a manner that the outer edge side portion of the central portion 21a and the inner edge side portion of the peripheral portion 21b overlap each other. In the description of the embodiment, for convenience, the central portion 21a and the peripheral portion 21b are defined in such a manner that the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b are aligned with each other.

[0066] In a plan view, the shapes and dimensions of the central portion 21a and the peripheral portion 21b may be set as appropriate. In the following description, for convenience, the positions and dimensions of various parts or members (e.g., various electrodes described later) may be described in comparison with the positions and dimensions of the central portion 21a and the peripheral portion 21b. However, in an actual product, the positions and dimensions of the central portion 21a and the peripheral portion 21b may be determined from the positions and dimensions of the various parts or members. Therefore, the positions and dimensions of the various parts or members described later may be referenced for the shapes and dimensions of the central portion 21a and the peripheral portion 21b.

[0067] In the following description, the region whose inner edge is defined by the outer edge of the pressure chamber 21 and whose outer edge is defined by the two-dot chain line Ln2 in Fig. 4 may be referred to as the outer region 11e of the pressure chamber 21. In other words, of the non-arrangement region of the pressure chamber 21 (the region outside the pressure chamber 21 in a broad sense), the region around the pressure chamber 21 may be referred to as the outer region 11e. The shape and dimensions of this region 11e may also refer to the positions and dimensions of various parts or members described later.

[0068] (Piezoelectric Actuator) Returning to FIG. 3, the piezoelectric actuator 13 is, for example, generally plate-shaped with an area spanning the multiple pressure chambers 21. The piezoelectric actuator 13 has a first surface 13a and a second surface 13b as the front and back surfaces of the plate shape. In this embodiment, the first surface 13a is the surface opposite to the flow path member 11, and the second surface 13b is the surface on the flow path member 11 side. The piezoelectric actuator 13 has a piezoelectric element 27 for each ejection element 9 (for each pressure chamber 21) that applies pressure to the pressure chamber 21. That is, the piezoelectric actuator 13 has multiple piezoelectric elements 27 at multiple positions in a direction along the first surface 13a.

[0069] The piezoelectric actuator 13 is configured by laminating a plurality of layer members extending along the second surface 13b. Specifically, for example, the piezoelectric actuator 13 has a first piezoelectric layer 29A to a fourth piezoelectric layer 29D (hereinafter, sometimes simply referred to as piezoelectric layers 29) in order from the first surface 13a side to the second surface 13b side. Furthermore, the piezoelectric actuator 13 has a first conductor layer 31A to a fifth conductor layer 31E (hereinafter, sometimes simply referred to as conductor layers 31) on or between the above-mentioned piezoelectric layers 29 in order from the first surface 13a side to the second surface 13b side. Although not particularly shown, the piezoelectric actuator 13 may have an insulating layer (for example, a solder resist) covering the first conductor layer 31A.

[0070] Each piezoelectric layer 29 spreads substantially without gaps across the multiple pressure chambers 21 (from another point of view, the multiple piezoelectric elements 27). The reason for "substantially" is that, for example, a through conductor (described later) for connecting the conductor layers may penetrate the insulating layer (the same applies below). Each conductor layer 31 has an appropriate planar shape, for example, including multiple electrodes provided corresponding to the multiple pressure chambers 21, as described in detail later.

[0071] (Overview of the operating principle of piezoelectric actuators) 5 is a cross-sectional view showing a schematic view of the piezoelectric actuator 13 and the upper part (plate 25J) of the flow path member 11. This figure shows a cross section in a direction different from that of FIG. 3 (a direction different from line III-III of FIG. 2), for example, and corresponds to line VV of FIG. 4. In this figure, hatching indicating a cross section is omitted. In addition, as described later, this figure shows a state in which the piezoelectric actuator 13 is bent by applying an electric field to the first active region 53A and the second active region 53B, and when no electric field is applied, the piezoelectric actuator 13 has a substantially flat shape.

[0072] In Fig. 5, the first piezoelectric layer 29A and the second piezoelectric layer 29B shown in Fig. 3 are conceptualized (illustrated) as a main piezoelectric layer 51A. Similarly, in Fig. 5, the third piezoelectric layer 29C and the fourth piezoelectric layer 29D shown in Fig. 3 are conceptualized (illustrated) as a sub-piezoelectric layer 51B. Hereinafter, the main piezoelectric layer 51A and the sub-piezoelectric layer 51B will be simply referred to as piezoelectric layers 51, and there may be cases where no distinction is made between the two.

[0073] The piezoelectric layer 51 has active regions 53 (53A and 53B) that are driven when droplets are ejected, and inactive regions 55 (55A to 55C; see FIG. 6 for 55C) that are not driven. The active regions 53 are polarized, and an electric field in the polarization direction or the opposite direction is applied when droplets are ejected. The inactive regions 55 are non-polarized regions, and / or regions to which no electric field in either the polarization direction or the opposite direction is applied when droplets are ejected. Note that a polarized region is, for example, a region in which the direction of spontaneous polarization has been aligned to a certain degree by a polarization process.

[0074] More specifically, the main piezoelectric layer 51A has a first active region 53A overlapping the central portion 21a of the pressure chamber 21 in a planar perspective view, and a first inactive region 55A adjacent to the outside of the first active region 53A. The sub-piezoelectric layer 51B has a second inactive region 55B overlapping the central portion 21a of the pressure chamber 21 in a planar perspective view, and a second active region 53B adjacent to the outside of the first active region 53B. From another perspective, the first inactive region 55A and the second active region 53B overlap the peripheral portion 21b of the pressure chamber 21 and the region 11e outside the pressure chamber 21 in a planar perspective view.

[0075] The first active region 53A has a polarization direction in the thickness direction (direction D3). When an electric field (or voltage in another sense; the same applies below) is applied to the first active region 53A in the same direction as the polarization direction, the first active region 53A contracts in the direction along the surface, as shown by the arrows in FIG. 5. On the other hand, the second inactive region 55B does not contract. As a result, the first active region 53A and the second inactive region 55B as a whole undergo bending deformation that convexly faces the pressure chamber 21 side like a bimetal, as shown by the arrows drawn at both ends of the first active region 53A and the second inactive region 55B.

[0076] The second active region 53B has a polarization direction in the thickness direction (D3 direction). When an electric field is applied to the second active region 53B in the same direction as the polarization direction, the second active region 53B contracts in the direction along the surface as shown by the arrow in Fig. 5. On the other hand, the first inactive region 55A does not contract. As a result, as shown in Fig. 5, the second active region 53B and the first inactive region 55A as a whole undergo bending deformation that becomes concave toward the pressure chamber 21 like a bimetal.

[0077] Here, the bending deformation of the second active region 53B and the first inactive region 55A located outside the pressure chamber 21 (sometimes referred to as the second portion 53Bb for the second active region 53B) is restricted by being bonded to the plate 25J. Therefore, as shown in FIG. 5, when the second active region 53B and the first inactive region 55A are bent and concave toward the pressure chamber 21, the portion of the second active region 53B and the first inactive region 55A overlapping with the pressure chamber 21 (sometimes referred to as the first portion 53Ba for the second active region 53B) bends toward the pressure chamber 21 like a cantilever. As a result, the first active region 53A and the second inactive region 55B are displaced toward the pressure chamber 21.

[0078] Therefore, by applying an electric field to the first active region 53A in the polarization direction and applying an electric field to the second active region 53B in the polarization direction, the displacement of the center position of the first active region 53A toward the pressure chamber 21 can be made larger than when an electric field is applied only to the first active region 53A in the polarization direction. This makes it possible to increase the amount of volume change when the volume of the pressure chamber 21 is decreased. Similarly, when the volume of the pressure chamber 21 is increased, an electric field may be applied to the first active region 53A in the direction opposite to the polarization direction and an electric field may be applied to the second active region 53B in the direction opposite to the polarization direction, so that the first active region 53A and the second active region 53B are extended in the direction along the surface. This increases the displacement of the center position of the first active region 53A, and increases the amount of increase in the volume of the pressure chamber.

[0079] Regarding the bending stiffness of the piezoelectric actuator 13, the neutral plane may be located at an appropriate position in the thickness direction. For example, the neutral plane is located approximately at the boundary between the main piezoelectric layer 51A and the sub-piezoelectric layer 51B. The deviation between the boundary and the neutral plane is, for example, less than ¼ of the thinner of the thicknesses of the main piezoelectric layer 51A and the sub-piezoelectric layer 51B.

[0080] (Planar shapes of active and non-active regions) Depending on the structure of the piezoelectric actuator, the planar shape of the active region 53 may differ in the thickness direction (D3 direction). For example, as will be understood from the description below, in this embodiment, in the first active region 53A, the part formed by the first piezoelectric layer 29A and the part formed by the second piezoelectric layer 29B can have different planar shapes. In the following description, an example is taken in which the planar shape of the active region 53 (or the inactive region 55) is approximately constant in the thickness direction. In an example in which the planar shape of the active region 53 (or the inactive region 55) is not constant in the thickness direction, the following description of the planar shape may be applied to the planar shape at any position in the thickness direction, for example, to the planar shape with the smallest area in a planar perspective view.

[0081] The first inactive region 55A and / or the second active region 53B surround the first active region 53A and / or the second inactive region 55B, for example, in a planar perspective view. More specifically, for example, the former surrounds the latter over the entire circumference. However, the former does not have to surround the latter over the entire circumference. For example, the former may surround the latter within a range of 270° or more and less than 360° around its center.

[0082] In a planar perspective view, the first active region 53A (its outer edge side portion) and the second active region 53B (its inner edge side portion) may be separated from each other, may be adjacent to each other (illustrated example), or may overlap each other. From another perspective, the first active region 53A and the second inactive region 55B adjacent to the inside of the second active region 53B may be the same shape and size as each other (illustrated example), or may not be the same. Similarly, the first inactive region 55A adjacent to the outside of the first active region 53A and the second active region 53B may be the same shape and size as each other (illustrated example), or may not be the same.

[0083] In the description of this embodiment, for convenience, the central portion 21a of the pressure chamber 21 is defined so that the outer edge of the first active region 53A coincides with the outer edge of the central portion 21a of the pressure chamber 21. As described above, in the description of this embodiment, for convenience, the central portion 21a and the peripheral portion 21b are defined so as to be adjacent to each other. Therefore, the first active region 53A does not overlap with the peripheral portion 21b of the pressure chamber 21. The second active region 53B overlaps at least the outer edge side of the peripheral portion 21b, and does not overlap at least the center of the central portion 21a. As described above, the outer edge side portion of the first active region 53A and the inner edge side portion of the second active region 53B may or may not overlap each other. Therefore, the second active region 53B may not overlap the inner edge portion of the peripheral portion 21b, may overlap the entire peripheral portion 21b without any excess or deficiency (example shown), or may overlap the outer edge portion of the central portion 21a in addition to the peripheral portion 21b.

[0084] The planar shape and dimensions of the first active region 53A (see the shape and dimensions of the central portion 21a shown in FIG. 4) may be set appropriately. The planar shape of the first active region 53A may be similar to the planar shape of the pressure chamber 21 (as shown in the example), or may not be similar. In any case, the explanation regarding the planar shape of the pressure chamber 21 may be applied to the planar shape of the first active region 53A. In addition, in a planar perspective view, the center of the first active region 53A and the center of the pressure chamber 21 may roughly coincide (as shown in the example), or may be misaligned.

[0085] The size of the first active region 53A in plan view may be set appropriately. For example, in plan view, the ratio of the area of ​​the first active region 53A to the area of ​​the pressure chamber 21 may be 40% or more, 50% or more, or 70% or less, or 80% or less, and the above lower limit and upper limit may be combined appropriately. As an example, 50% or more and 70% or less may be mentioned. Also, for example, when comparing the diameters in the same direction of the first active region 53A and the pressure chamber 21 or the circle equivalent diameters, the diameter of the first active region 53A may be 0.6 times or more, 0.7 times or more, or 0.9 times or less, of the diameter of the pressure chamber 21, and the above lower limit and upper limit may be combined appropriately.

[0086] The planar shape and dimensions of the second active region 53B (see the shape and dimensions of the annular region between the two-dot chain line Ln1 and the two-dot chain line Ln2 shown in FIG. 4) may be set appropriately. For example, the planar shape of the second active region 53B is an annular region surrounding the first active region 53A. The annular shape here is not limited to a circular or elliptical shape. For example, the inner edge and / or outer edge of the annular shape may have irregularities or may be a polygon (e.g., a rectangle).

[0087] The shape of the inner edge and / or the outer edge of the second active region 53B may be similar to, for example, the planar shape of the pressure chamber 21 and / or the planar shape of the first active region 53A (as shown in the example), or may not be similar. In any case, the description of the planar shape of the pressure chamber 21 may be applied to the shape of the inner edge and the outer edge of the second active region 53B. In addition, in a planar perspective view, the center of the shape formed by the outer edge of the second active region 53B may roughly coincide with the center of the pressure chamber 21 and / or the center of the first active region 53A (as shown in the example), or may be deviated from the center.

[0088] In a mode in which the outer edge of the first active region 53A and the inner edge of the second active region 53B are misaligned when viewed from above, the distance between them may be set appropriately. For example, the distance between them may be set to 10% or less or 5% or less of the diameter (e.g., the minimum diameter, the maximum diameter, or the circle-equivalent diameter) of the first active region 53A. This upper limit value may be applied to both a mode in which the outer edge of the first active region 53A is located inside the inner edge of the second active region 53B and a mode in which the former is located outside the latter.

[0089] The distance of the outer edge of the second active region 53B from the outer edge of the pressure chamber 21 may be set appropriately. For example, the distance may be 1 / 20 or more, 1 / 10 or more, or 1 / 5 or more of the diameter of the pressure chamber 21 (for example, the minimum diameter, the maximum diameter, or the circle equivalent diameter), or may be 1 or less, 1 / 2 or less, 1 / 3 or less, or 1 / 5 or less, and the above lower limit and upper limit may be combined appropriately as long as there is no contradiction. As an example, the diameter of the pressure chamber 21 is 200 μm or more and 400 μm or less, and the distance from the outer edge of the pressure chamber 21 to the outer edge of the second active region 53B is 50 μm or more and 200 μm or less.

[0090] Either the distance w1 (see FIG. 4 for the symbol) from the outer edge of the pressure chamber 21 to the inner edge of the second active region 53B or the distance w2 (see FIG. 4 for the symbol) from the outer edge of the pressure chamber 21 to the outer edge of the second active region 53B may be greater than the other. In other words, the distance w1 is the width of the first portion 53Ba of the second active region 53B that overlaps with the pressure chamber 21. In other words, the distance w2 is the width of the second portion 53Bb of the second active region 53B that is located outside the pressure chamber 21. Here, the distances w1 and w2 are shown in a plan view, but the distances w1 and w2 may be compared in a cross section (longitudinal cross section) that passes through the center of the pressure chamber 21 and is perpendicular to the pressure surface 11b as shown in FIG. 3.

[0091] In this embodiment, the embodiment in which the distance w1 is shorter than the distance w2 is taken as an example. The case in which the distance w1 is shorter than the distance w2 may include, for example, not only the embodiment in which the distance w1 is shorter than the distance w2 over the entire circumference of the second active region 53B, but also the embodiment in which the distance w1 is shorter than the distance w2 over most of the circumferential direction of the second active region 53B. This is because a specific portion may be provided in the second active region 53B due to the shape of the pressure chamber 21 or the shape of the wiring for applying a potential to the electrode. For example, the most of the circumferential direction may be in the range of 270° or more, 300° or more, or 330° or more in terms of angle around the center of the pressure chamber 21. In the embodiment in which the distance w1 is shorter than the distance w2, the ratio of the distance w1 to the distance w2 may be appropriately set. For example, the distance w1 may be 0.9 times or less, 0.8 times or less, or 0.7 times or less of the distance w2.

[0092] In a planar perspective view, the area of ​​the first portion 53Ba of the second active region 53B overlapping the pressure chamber 21 and the area of ​​the second portion 53Bb of the second active region 53B located outside the pressure chamber 21 may be larger than the other. In the description of this embodiment, an example is taken in which the area of ​​the first portion 53Ba is smaller than the area of ​​the second portion 53Bb. In this example, the ratio between the areas may be set appropriately. For example, the area of ​​the first portion 53Ba may be 0.9 times or less, 0.8 times or less, or 0.7 times or less of the area of ​​the second portion 53Bb.

[0093] For example, when the first portion 53Ba and the second portion 53Bb are similar in shape, the latter is located on the outside of the former, and therefore the latter has a longer circumferential length than the former. Therefore, even if the distance w1 and the distance w2 are equal, the area of ​​the first portion 53Ba is smaller than the area of ​​the second portion 53Bb. As can be understood from this, although not shown, it is also possible to adopt an embodiment in which the distance w1 is longer than the distance w2 and the area of ​​the first portion 53Ba is smaller than the area of ​​the second portion 53Bb.

[0094] In distributed products, the difference in area between the first portion 53Ba and the second portion 53Bb, and the difference in distance w1 and distance w2, etc. may be measured as appropriate. For example, the electrode area and the deviation between the electrode and the pressure chamber 21, etc. may be measured using X-ray CT (Computed Tomography) without disassembling the head main body 7, and the areas of the first portion 53Ba and the second portion 53Bb, and the distances w1 and w2 may be measured. Also, for example, the head main body 7 may be cut at multiple positions, and the cross sections may be observed using an electron microscope to measure the electrode area and the deviation between the electrode and the pressure chamber 21, etc., and the areas of the first portion 53Ba and the second portion 53Bb, and the distances w1 and w2 may be measured.

[0095] The first inactive region 55A may be defined as, for example, a region of the main piezoelectric layer 51A other than the first active region 53A that overlaps with the second active region 53B in a planar perspective. Therefore, the inner edge of the first inactive region 55A coincides with the outer edge of the first active region 53A, and the outer edge of the first inactive region 55A coincides with the outer edge of the second active region 53B. In this embodiment, the outer edge of the first active region 53A and the inner edge of the second active region 53B generally coincide with each other in a planar perspective, so that the planar shape and dimensions of the first inactive region 55A are generally the same as the planar shape and dimensions of the second active region 53B.

[0096] The second inactive region 55B may be defined as, for example, a region of the sub-piezoelectric layer 51B that overlaps with the pressure chamber 21 and is a region other than the second active region 53B. When the second active region 53B is annular, the second inactive region 55B is a region surrounded by the second active region 53B, and its outer edge coincides with the inner edge of the second active region 53B.

[0097] (Piezoelectric layer) 3, the material of the piezoelectric layer 29 may be, for example, a ceramic material having ferroelectricity. Examples of the ceramic material include lead zirconate titanate (PZT)-based, NaNbO3-based, BaTiO3-based, (BiNa)TiO3-based, BiNaNb5O 15 Examples of the material of the piezoelectric layer 29 include ceramic-based materials. However, the material of the piezoelectric layer 29 may be a material other than a ceramic material. The material of the piezoelectric layer 29 may be a single crystal or a polycrystal, an inorganic material or an organic material, and may or may not be a ferroelectric material, or a pyroelectric material. The materials of the multiple piezoelectric layers 29 may be the same as each other or different from each other.

[0098] The piezoelectric layer 29 spreads in a plane with a substantially constant thickness, in other words, is substantially flat. Its area is substantially equal to the area of ​​the piezoelectric actuator 13. The thickness of the piezoelectric layer 29 may be set appropriately. The thicknesses of the multiple piezoelectric layers 29 may be the same as each other (example shown in the figure) or may be different from each other. An example of the thickness of the piezoelectric layer 29 is 10 μm or more and 40 μm or less.

[0099] In the illustrated example, the thicknesses of the piezoelectric layers 29 are the same. From another perspective, the sum of the thicknesses of the third piezoelectric layer 29C and the fourth piezoelectric layer 29D is greater than the thicknesses of the first piezoelectric layer 29A and the second piezoelectric layer 29B. Within a range in which this thickness relationship holds, the thicknesses of the piezoelectric layers 29 may be different from one another. Note that even if the thicknesses of two or more piezoelectric layers 29 compared with one another are the same, there may of course be an error, and there may also be a difference in the thickness of the conductor layer 31.

[0100] Fig. 6 is a schematic cross-sectional view showing the polarization direction of the piezoelectric layer 29. This figure corresponds to the line VV in Fig. 4, similar to Fig. 5. In this figure, the outline arrows indicate the polarization direction. In this figure, hatching indicating a cross section is omitted.

[0101] As indicated by dotted lines, the piezoelectric actuator 13 has the already-described first active region 53A, second active region 53B, first inactive region 55A and second inactive region 55B. In the first piezoelectric layer 29A to fourth piezoelectric layer 29D, the region outside the first inactive region 55A and second active region 53B is referred to as a third inactive region 55C.

[0102] In the first active region 53A, the polarization direction of the first piezoelectric layer 29A and the polarization direction of the second piezoelectric layer 29B are opposite to each other. Therefore, in the first active region 53A, by applying electric fields in opposite directions to the first piezoelectric layer 29A and the second piezoelectric layer 29B, these piezoelectric layers (29A and 29B) can be contracted together (FIG. 5) or expanded together (29A and 29B).

[0103] In the first active region 53A, the polarization direction of the first piezoelectric layer 29A and the second piezoelectric layer 29B may be either the +D3 direction or the -D3 direction. In the description of this embodiment, an example is taken in which the polarization direction of the first piezoelectric layer 29A is the -D3 direction and the polarization direction of the second piezoelectric layer 29B is the +D3 direction.

[0104] In the second active region 53B, the polarization direction of the third piezoelectric layer 29C and the polarization direction of the fourth piezoelectric layer 29D are the same. Therefore, for example, in the second active region 53B, by applying the same electric field to both the third piezoelectric layer 29C and the fourth piezoelectric layer 29D, these piezoelectric layers (29C and 29D) can be contracted together (FIG. 5) or expanded together.

[0105] The polarization direction of the second active region 53B may be either the +D3 direction or the -D3 direction. The polarization direction of the second active region 53B may be the same as the polarization direction of either the first piezoelectric layer 29A or the second piezoelectric layer 29B in the first active region 53A. In the description of this embodiment, an example is taken in which the polarization direction of the second active region 53B is the same as the polarization direction of the first piezoelectric layer 29A in the first active region 53A.

[0106] The inactive regions 55 (55A to 55C) may be polarized or may not be polarized. In the illustrated example, the first inactive region 55A is polarized, and the second inactive region 55B and the third inactive region 55C are not polarized.

[0107] The polarization direction of the first non-active region 55A is the thickness direction (D3 direction). The polarization direction of the first non-active region 55A may be either the +D3 direction or the -D3 direction, and the relationship with the polarization direction of the first active region 53A and the second active region 53B is also arbitrary. For example, the polarization direction of the first non-active region 55A may be the same as the polarization direction of the second active region 53B, or may be opposite. In the description of this embodiment, an example is taken in which the polarization direction of the first non-active region 55A is the same as the polarization direction of the second active region 53B.

[0108] (Conductor layer) Returning to FIG. 3, the first conductor layer 31A is located on the top surface of the first piezoelectric layer 29A. The second conductor layer 31B is located between the first piezoelectric layer 29A and the second piezoelectric layer 29B. The third conductor layer 31C is located between the second piezoelectric layer 29B and the third piezoelectric layer 29C. The fourth conductor layer 31D is located between the third piezoelectric layer 29C and the fourth piezoelectric layer 29D. The fifth conductor layer 31E is located between the fourth piezoelectric layer 29D and the flow path member 11 (plate 25J).

[0109] The material of the conductor layer 31 may be, for example, an appropriate metal material. For example, an Ag-Pd alloy and an Au alloy may be used as the metal material. The materials of the multiple conductor layers 31 may be the same as each other or different from each other. One conductor layer 31 may be integrally formed of one type of material, or may be formed by laminating different materials. The material of one conductor layer 31 is the same at different positions in the planar direction. However, the material of some regions may be different from the material of other regions.

[0110] The conductor layer 31 spreads in a planar shape with a generally constant thickness. The thickness of the conductor layer 31 may be set appropriately. The thicknesses of the multiple conductor layers 31 may be the same as each other or may be different from each other. The thickness of each layer is set to be thinner than the thickness of the piezoelectric layer 29, for example. As an example, the thickness of the conductor layer 31 may be set to be 0.5 μm or more and 3 μm or less.

[0111] (Shape of conductor layer) 7 and 8 are exploded perspective views of the piezoelectric actuator 13 and the upper portion (plate 25J) of the flow path member 11. Fig. 7 shows a partial region of the head body 7 in a plan view, which includes a plurality of piezoelectric elements 27. Fig. 8 shows a region including one piezoelectric element 27. In these figures, the surface of the conductor layer 31 is hatched for the sake of convenience.

[0112] In these figures, the piezoelectric actuator 13 is shown decomposed into plate-like members each consisting of a piezoelectric layer 29 and a conductor layer 31 overlapping the upper surface (+D3 surface) of the piezoelectric layer 29, except for the fifth conductor layer 31E. This is for convenience of illustration, and does not mean that each of these four plate-like members is produced in the manufacturing process. For example, in the manufacturing process, each conductor layer 31 may be provided on the lower surface (-D3 surface) of the piezoelectric layer 29.

[0113] (First conductor layer) The first conductor layer 31A has, for example, a first electrode 33 and a reorientation electrode 35 for each pressure chamber 21 (piezoelectric element 27). The first electrode 33 contributes to applying a voltage to the first active region 53A (more specifically, the portion thereof constituted by the first piezoelectric layer 29A) when droplets are ejected. The reorientation electrode 35 contributes to reducing deterioration of the characteristics of the piezoelectric actuator 13 by performing a polarization process on the second inactive region 55B (a part or most of it) when droplets are not ejected.

[0114] In each piezoelectric element 27, the first electrode 33 and the reorientation electrode 35 are separated from each other, and a potential is applied to each of them separately. The distance between the first electrode 33 and the reorientation electrode 35 may be set appropriately. For example, the distance between them may be set as short as possible within a range where a short circuit does not occur.

[0115] (1st electrode) The first electrodes 33 are so-called individual electrodes. That is, the first electrodes 33 are separated from one another in terms of shape and electrical properties. The first electrodes 33 can be applied with different electric potentials.

[0116] The first electrode 33 has, for example, an electrode body 33a that contributes to applying a voltage to the first active region 53A, and an extraction portion 33b for connecting the electrode body 33a to an external signal line of the piezoelectric actuator 13. Although not particularly shown, the external signal line is, for example, a wiring pattern of an FPC (flexible printed circuit) facing the first surface 13a of the piezoelectric actuator 13. Note that only the electrode body 33a may be regarded as the first electrode, and the extraction portion 33b may be regarded as wiring.

[0117] The planar shape and dimensions of the electrode body 33a are, for example, approximately the same as those of the first active region 53A. Therefore, the above-mentioned explanation of the planar shape and dimensions of the first active region 53A may be applied to the planar shape and dimensions of the electrode body 33a. As mentioned above, the active region 53 is polarized, and is a region to which a voltage is applied when a droplet is ejected. Therefore, the outer edge of the portion of the first active region 53A that is formed by the first piezoelectric layer 29A coincides with or is located inside the outer edge of the electrode body 33a.

[0118] For example, in a planar perspective view, the lead-out portion 33b extends from the electrode body 33a to the outside of the pressure chamber 21. Then, a portion of the lead-out portion 33b located outside the pressure chamber 21 (for example, an end opposite the electrode body 33a) is joined to an external signal line. This reduces the effect of this joining on the application of pressure to the pressure chamber 21 by the piezoelectric element 27.

[0119] The specific shape, dimensions, position, etc. of the lead portion 33b may be set appropriately. For example, the lead portion 33b extends linearly from one end of the electrode body 33a in a predetermined direction (direction D1 in the illustrated example) to the one side in the predetermined direction. The predetermined direction may be any direction. In the illustrated example, it is the longitudinal direction of the electrode body 33a. The width of the lead portion 33b is, for example, approximately constant and is smaller than the diameter (for example, the minimum diameter) of the electrode body 33a. Unlike the illustrated example, the lead portion 33b may have a bent or curved portion. The end of the lead portion 33b opposite to the electrode body 33a may be wider than the other portions. The lead portion 33b may be contained within the shape formed by the outer edge of the second active region 53B when viewed from above (the illustrated example), or may not be contained therein.

[0120] (Reorientation electrode) The reorientation electrodes 35 are separated from each other in terms of shape and electrical properties. That is, the reorientation electrodes 35 are individual electrodes. However, as will be understood from the description below, the same potential may be applied to the reorientation electrodes 35. Therefore, unlike the illustrated example, the first conductor layer 31A may have, for example, wiring that connects adjacent reorientation electrodes 35. Also, for example, the first conductor layer 31A may have, as a reorientation electrode, an electrode (see the fourth conductor layer 31D) that spreads over the first piezoelectric layer 29A without gaps except for the arrangement region of the first electrode 33.

[0121] The reorientation electrode 35 may be capable of applying a voltage to substantially the entire second inactive region 55B in a planar view, or may be capable of applying a voltage to only a portion of the second inactive region 55B (the inner edge side, the central side, or the outer edge side), or may be capable of applying a voltage not only to the second inactive region 55B but also to the third inactive region 55C.

[0122] In the illustrated example, the reorientation electrode 35 is configured to be able to apply a voltage to almost the entire first inactive region 55A, and not to apply a voltage to the third inactive region 55C. That is, the reorientation electrode 35 is shaped to overlap the first inactive region 55A almost exactly in plan view. Therefore, the above description of the planar shape and dimensions of the first inactive region 55A may be applied to the planar shape and dimensions of the reorientation electrode 35.

[0123] However, unlike the first non-active region 55A, the reorientation electrode 35 is interrupted at the position of the drawn-out portion 33b of the first electrode 33 and is formed in a C-shape. Note that, like the ring shape, the C-shape here is not limited to one in which the inner edge and / or outer edge is circular or elliptical.

[0124] Furthermore, a portion of the first piezoelectric layer 29A located outside the electrode body 33a in a plan view constitutes a first inactive region 55A because no voltage is applied to the portion when droplets are ejected. On the other hand, the inner edge of the reorientation electrode 35 is spaced outward from the outer edge of the electrode body 33a so as not to short-circuit with the first electrode 33. Therefore, even though the reorientation electrode 35 overlaps almost the entire first inactive region 55A, the inner edge of the reorientation electrode 35 is located on the outer edge side of the inner edge of the portion of the first inactive region 55A that is constituted by the first piezoelectric layer 29A.

[0125] In a mode in which the planar shape of the reorientation electrode 35 (excluding the interrupted portion) is similar to the planar shape of the first active region 53A, the outer edge of the reorientation electrode 35 may be located inside or outside the outer edge of the first non-active region 55A (defined by the outer edge of the second active region 53B as described above), unlike the illustrated example. That is, a part of the first non-active region 55A on the outer edge side may not be subjected to polarization treatment, or polarization treatment may be applied to the third non-active region 55C in addition to the first non-active region 55A.

[0126] (Second conductor layer) The second conductor layer 31B has, for example, a second electrode 37 provided for each pressure chamber 21 (piezoelectric element 27) and a plurality of wirings 39 connecting the plurality of second electrodes 37 to each other. The second electrodes 37 contribute to applying a voltage to the first active regions 53A (more specifically, to both the first piezoelectric layer 29A and the second piezoelectric layer 29B) when pressure is applied to the pressure chambers 21 to eject droplets. The plurality of wirings 39 contribute to applying a potential to the second electrodes 37.

[0127] (2nd electrode) The second electrodes 37 are separated from one another in terms of their shapes. From another perspective, a non-conductor area is located between adjacent second electrodes 37. That is, from the perspective of their shapes, the second electrodes 37 are individual electrodes. However, as described above, unlike the first electrodes 33, the second electrodes 37 are connected to one another by the wirings 39 and are at the same potential.

[0128] The shape and dimensions of the second electrode 37 are, for example, generally similar to those of the electrode body 33a of the first electrode 33. When viewed from above, the second electrode 37 and the electrode body 33a overlap with each other without any excess or deficiency. In other words, when viewed from above, the outer edge of the second electrode 37 generally coincides with the outer edge of the electrode body 33a. From another perspective, when viewed from above, the second electrode 37 does not overlap with the reorientation electrode 35. The explanation regarding the planar shape and dimensions of the electrode body 33a (first active region 53A) may be appropriately applied to the shape and dimensions of the second electrode 37.

[0129] However, more precisely, in planar perspective, a part or the whole of the outer edge of the second electrode 37 may be located at the outer edge of the electrode body 33a, may be located between the outer edge of the electrode body 33a and the inner edge of the reorientation electrode 35, or may be located at the inner edge of the reorientation electrode 35. In the description of the present disclosure, when it is said that the outer edge of the second electrode 37 coincides with the outer edge of the electrode body 33a (or that the two electrodes overlap exactly), all of the above aspects may be included. Even when they strictly coincide, it goes without saying that there may be an error between them (the same applies to other electrodes, etc.).

[0130] Unlike the illustrated example, the outer edge of the second electrode 37 may be slightly shifted inward or outward with respect to the outer edge of the electrode body 33a. From another perspective, as will be understood from the description below, the region to which a voltage is applied in the first piezoelectric layer 29A and the region to which a voltage is applied in the second piezoelectric layer 29B may be different. From yet another perspective, on the premise that the region to which a voltage is applied is polarized, the area of ​​the first active region 53A may be different between the portion formed by the first piezoelectric layer 29A and the portion formed by the second piezoelectric layer 29B.

[0131] (Second conductor layer wiring) The number, position, shape, size, etc. of the multiple wirings 39 may be set appropriately. For example, the wirings 39 may connect the second electrodes 37 adjacent to each other in the D2 direction (the illustrated example), may connect the second electrodes 37 adjacent to each other in a direction other than the D2 direction (the D1 direction or a direction inclined toward the D1 direction), or may realize a combination of two or more of these connections. In the illustrated example, the wirings 39 extend in a direction intersecting (more specifically, perpendicular to) the direction in which the drawn-out portion 33b of the first electrode 33 extends. In addition, the wirings 39 and the drawn-out portion 33b do not overlap each other.

[0132] Also, for example, the wiring 39 may extend linearly (as in the illustrated example) or may be bent or curved. Also, for example, the wiring 39 may have a substantially constant width over its length (as in the illustrated example) or the width may vary depending on the position in the length direction. The width of the wiring 39 is smaller than the diameter of the second electrodes 37 in the width direction of the wiring 37 so that gaps are formed between the second electrodes 37 (so that the second electrodes 37 are individual electrodes in terms of shape). For example, the former may be 1 / 2 or less, 1 / 3 or less, or 1 / 4 or less of the latter.

[0133] (Third conductor layer) The third conductor layer 31C has, for example, a third electrode 41 provided for each pressure chamber 21 (piezoelectric element 27). For example, when pressure is applied to the pressure chamber 21 to eject a droplet, the third electrode 41 contributes to applying a voltage to the first active region 53A (more specifically, the portion thereof constituted by the second piezoelectric layer 29B) and also contributes to applying a voltage to the second active region 53B (more specifically, both the third piezoelectric layer 29C and the fourth piezoelectric layer 29D). The third electrode 41 is a so-called individual electrode, similar to the first electrode 33. That is, the multiple third electrodes 41 are separated from each other in terms of shape and electrical properties.

[0134] The planar shape and dimensions of the third electrode 41 are, for example, approximately the same as the planar shape and dimensions of the first electrode 33 and the reorientation electrode 35 combined (from another point of view, the first active region 53A and the second active region 53B combined). When viewed from above, the third electrode 41 overlaps the first electrode 33, the reorientation electrode 35, and the gap between these electrodes (33 and 35) (with respect to the first active region 53A and the second active region 53B) without any excess or deficiency. The description of the shape and dimensions of the outer edge of the second active region 53B may be applied to the planar shape and dimensions of the third electrode 41.

[0135] The planar shape and dimensions of the third electrode 41 may be different from the shape and dimensions of the outer edge of the reorientation electrode 35. For example, when viewed from above, the outer edge of the reorientation electrode 35 may be located inside or outside the outer edge of the third electrode 41. Also, for example, the third electrode 41 may have a slit extending along the outer edge of the electrode body 33a between the electrode body 33a and the reorientation electrode 35 when viewed from above.

[0136] (4th conductor layer) The fourth conductor layer 31D contributes to equalizing the structural characteristics of the portion on the first surface 13a side and the portion on the second surface 13b side in the piezoelectric actuator 13, for example. Therefore, as will be understood from the description of the operation described later, in this embodiment, the fourth conductor layer 31D does not contribute to applying a voltage to the piezoelectric layer 29. The fourth conductor layer 31D may be omitted.

[0137] The shape, size and position of the fourth conductor layer 31D are set so as not to overlap with electrodes that apply a voltage to the piezoelectric layer 29 in a planar perspective view, for example. In this embodiment, the electrodes that apply a voltage are the already-described first electrode 33, reorientation electrode 35, second electrode 37 and third electrode 41, as well as a fourth electrode 45 described below. This reduces the likelihood that the fourth conductor layer 31D will interfere with the application of a voltage to the piezoelectric layer 29 by the above-mentioned electrodes.

[0138] However, the fourth conductor layer 31D may include a region overlapping with a part of the above-mentioned electrodes. For example, in the case where the reorientation electrode 35 has a region located outside the outer edge of the third electrode 41 and the outer edge of the fourth electrode 45 (a region overlapping with the third inactive region 55C), the fourth conductor layer 31D may include a region overlapping with the above-mentioned outer region. In this case, the fourth conductor layer 31D can contribute to the reorientation of a portion of the third inactive region 55C that is constituted by the first piezoelectric layer 29A to the third piezoelectric layer 29C.

[0139] The shape and dimensions of the fourth conductor layer 31D may be set appropriately. In the illustrated example, the fourth conductor layer 31D has a shape in which an opening 43 is formed for each pressure chamber 21 (piezoelectric element 27). In other words, the fourth conductor layer 31D is a solid shape that spreads without gaps on the fourth piezoelectric layer 29D except for the openings 43.

[0140] The planar shape and dimensions of the opening 43 are generally similar to those of the third electrode 41 (from another point of view, the logical sum of the first active region 53A and the second active region 53B), for example. When viewed from a plan view, the opening 43 overlaps the third electrode 41 with almost no overlap. The description of the shape and dimensions of the outer edge of the second active region 53B may be used for the planar shape and dimensions of the opening 43.

[0141] However, the opening 43 may be larger than the third electrode 41. This can reduce the likelihood that the third electrode 41 (and other electrodes) overlaps with the fourth conductor layer 31D, for example. In addition, making the opening 43 larger may be consistent with the purpose of equalizing the structural characteristics of the portion on the first surface 13a side and the portion on the second surface 13b side. The shape of the opening 43 larger than the third electrode 41 may or may not be similar to the shape of the third electrode 41 (or the pressure chamber 21 from another perspective).

[0142] The fourth conductor layer 31D may have various planar shapes (patterns) other than the shape in which the opening 43 is formed. For example, the planar shape of the fourth conductor layer 31D may be configured to include a plurality of linear patterns extending in an appropriate direction, or may be a mesh shape having openings other than the opening 43.

[0143] (5th conductor layer) The fifth conductor layer 31E has, for example, a fourth electrode 45 provided for each pressure chamber 21 (piezoelectric element 27). The fourth electrode 45 contributes to applying a voltage to the second active region 53B (more specifically, both the third piezoelectric layer 29C and the fourth piezoelectric layer 29D) when, for example, pressure is applied to the pressure chamber 21 to eject droplets. In addition, the fourth electrode 45 contributes to reducing deterioration of the characteristics of the piezoelectric actuator 13 by performing a polarization process on the second inactive region 55B (a part or most of it) when, for example, droplets are not being ejected.

[0144] The multiple fourth electrodes 45 are separated from each other in terms of their shape. Therefore, in terms of their shape, the multiple fourth electrodes 45 are individual electrodes. However, unlike the multiple first electrodes 33, the multiple fourth electrodes 45 are given the same potential. Specifically, in the illustrated example, the multiple fourth electrodes 45 are electrically connected to each other by a plate 25J made of metal. Unlike this embodiment, the plate 25J may be made a resin plate to make the pressurizing surface 11b insulating, so that the multiple fourth electrodes 45 are not electrically connected via the flow path member 11.

[0145] The planar shape and dimensions of the fourth electrode 45 are, for example, generally similar to the planar shape and dimensions of the reorientation electrode 35. From another perspective, the planar shape and dimensions of the fourth electrode 45 are generally similar to the planar shape and dimensions of a region (region on the outer periphery) of the third electrode 41 that does not overlap with the electrode body 33a of the first electrode 33. From yet another perspective, the planar shape and dimensions of the fourth electrode 45 are generally similar to the planar shape and dimensions of the second active region 53B. The explanation regarding the planar shape and dimensions of the second active region 53B may be applied to the planar shape and dimensions of the fourth electrode 45.

[0146] In planar perspective, the inner edge of the fourth electrode 45 generally coincides with the outer edge of the electrode body 33a (the inner edge of the reorientation electrode 35) and the outer edge of the second electrode 37. In a more strict view, the inner edge of the fourth electrode 45 may be located partly or entirely on the outer edge of the electrode body 33a, or may be located between the outer edge of the electrode body 33a and the inner edge of the reorientation electrode 35, or may be located on the inner edge of the reorientation electrode 35, in planar perspective, similar to the outer edge of the second electrode 37. In the description of the present disclosure, when the inner edge of the fourth electrode 45 coincides with the outer edge of the electrode body 33a, this may include all of the above aspects. Note that the inner edge of the fourth electrode 45 may be slightly shifted inward or outward with respect to the outer edge of the electrode body 33a and / or the outer edge of the second electrode 37.

[0147] In a planar perspective view, the outer edge of the fourth electrode 45 generally coincides with, for example, the outer edge of the reorientation electrode 35, the outer edge of the third electrode 41, and the edge of the opening 43. However, similar to the relationship between the reorientation electrode 35 and the third electrode 41, the outer edge of the reorientation electrode 35 may be located inside or outside the outer edge of the fourth electrode 45. Also, similar to the relationship between the opening 43 and the third electrode 41, the opening 43 may be larger than the fourth electrode 45. Also, the outer edge of the fourth electrode 45 may be shifted inside or outside the outer edge of the third electrode 41.

[0148] (Electrical connection of conductor layers) As already described, the first electrode 33 is an electrode to which an electric potential (driving signal) is individually applied for each piezoelectric element 27, and an electric potential is applied to the lead-out portion 33b from an FPC (not shown) that faces the first surface 13a of the piezoelectric actuator 13. For example, the end of the lead-out portion 33b opposite the electrode body 33a is joined to the wiring pattern of the FPC by a bump (not shown). The bump is made of, for example, solder (including lead-free solder).

[0149] As already described, the third electrode 41 is also an electrode to which a potential (drive signal) is individually applied for each piezoelectric element 27. However, in this embodiment, the third electrode 41 is applied with the same potential as the first electrode 33 of the piezoelectric element 27 to which it belongs. The application of the same potential may be achieved, for example, by electrically connecting the first electrode 33 and the third electrode 41 in the piezoelectric actuator 13.

[0150] The connection between the first electrode 33 and the third electrode 41 may be realized by an appropriate conductor. For example, as shown in FIG. 3, the first electrode 33 and the third electrode 41 may be connected by a through conductor 47 penetrating the first piezoelectric layer 29A and the second piezoelectric layer 29B. In FIG. 8, the positions of the first electrode 33 and the third electrode 41 that are connected by the through conductor 47 are connected by a dotted line. The connection position of the through conductor 47 to the first electrode 33 may be, for example, a portion of the drawn portion 33b that is located outside the pressure chamber 21 in a planar perspective view (more specifically, a portion that is located in the outer region 11e, for example). The connection position of the through conductor 47 to the third electrode 41 may be a position directly below the connection position of the through conductor 47 to the drawn portion 33b.

[0151] In addition, although not shown, for example, a through conductor penetrating the first piezoelectric layer 29A and connected to the first electrode 33, a through conductor penetrating the second piezoelectric layer 29B and connected to the third electrode 41, and a layered wiring located between the first piezoelectric layer 29A and the second piezoelectric layer 29B and connecting the two through conductors may be provided. In an embodiment in which the potential of the third electrode 41 is different from the potential of the first electrode 33, for example, a lead portion extending to a position not overlapping with the reorientation electrode 35 in a planar perspective may be provided in the third electrode 41, and a through conductor connected to the lead portion and exposed to the first surface 13a of the piezoelectric actuator 13 may be provided. Then, the through conductor or a pad overlapping thereon may be joined to a wiring pattern of an FPC (not shown).

[0152] The reorientation electrode 35 may be bonded to an FPC (not shown) via a bump, for example, in the same manner as the first electrode 33, so that a potential is applied to the reorientation electrode 35. In this case, the bonding position of the reorientation electrode 35 may be an appropriate position. For example, the bonding position may be a portion of the reorientation electrode 35 located on the opposite side of the electrode body 33a from the drawn-out portion 33b. And / or, for example, the bonding position may be a position that does not overlap the pressure chamber 21 in a planar perspective view. This reduces the effect of the bonding on the pressure of the pressure chamber 21, as with the bonding to the drawn-out portion 33b.

[0153] In addition, although not shown, for example, the reorientation electrode 35 may be provided with an extension extending in a direction away from the pressure chamber 21, and an FPC may be bonded to the extension. Also, the reorientation electrodes 35 do not need to be applied with potentials separately from one another. Therefore, wiring connecting the reorientation electrodes 35 to one another and a pad commonly connected to the reorientation electrodes 35 may be provided, and an FPC may be bonded to the pad.

[0154] As described above, in this embodiment, the multiple fourth electrodes 45 are electrically connected to each other by the plate 25J made of metal, and the same potential is applied to them. For example, the plate 25J may be applied with a reference potential. In this case, the plate 25J may be connected to only one of the frame ground and the signal ground (for example, a reference potential portion of an FPC (not shown) connected to the piezoelectric actuator 13), or may be connected to both. In the latter case, the plate 25J may be directly connected to both, or may be connected to the other via one. The configuration for the connection is arbitrary.

[0155] As described above, the second electrodes 37 are connected by the wirings 39, and the same potential is applied to each of them. Although the fourth conductor layer 31D has the openings 43, it is basically one conductor pattern, and therefore the same potential is naturally applied to the entire fourth conductor layer 31D. In this embodiment, the second electrodes 37 and the fourth conductor layer 31D are applied with the same potential. The second electrodes 37 and the fourth conductor layer 31D may be electrically connected to an FPC (not shown) facing the first surface 13a of the piezoelectric actuator 13, for example, by providing a through conductor penetrating the piezoelectric layer 29. The configuration of the through conductor may be set appropriately. An example is shown below.

[0156] 9 is an enlarged plan view of a portion of the second conductor layer 31B. In this figure, only two rows are shown, each row being configured by arranging a plurality of second electrodes 37 in the D2 direction. For ease of explanation, this figure assumes that one row includes four second electrodes 37.

[0157] In each row, the second electrodes 37 are connected by the wirings 39 as described above. Furthermore, at both ends of each row, wirings 39 are provided that extend outside the row (to the -D2 side or +D2 side). The wirings 39 at both ends are connected to a common wiring 49 that extends in a direction (D1 direction) intersecting the rows. This connects the rows to each other. The common wiring 49 is part of the second conductor layer 31B.

[0158] FIG. 10 is a cross-sectional view taken along line XX in FIG.

[0159] 9 and 10, a through conductor 57 that penetrates the piezoelectric layer 29 is provided at a position that overlaps with the common wiring 49 in a planar perspective. Specifically, as shown in Fig. 10, a through conductor 57 that penetrates the second piezoelectric layer 29B and the third piezoelectric layer 29C is provided. This connects the common wiring 49 and the fourth conductor layer 31D. Furthermore, the multiple second electrodes 37 and the fourth conductor layer 31D are at the same potential.

[0160] Also provided is a through conductor 57 that penetrates the first piezoelectric layer 29A. This allows an FPC (not shown) that faces the first surface 13a of the piezoelectric actuator 13 to be electrically connected to the second electrodes 37 and the fourth conductor layer 31D. Specifically, for example, a pad 59 is provided on the through conductor 57 that penetrates the first piezoelectric layer 29A, and this pad 59 and a signal line (not shown) of the FPC are joined by a bump (not shown).

[0161] 9, a plurality of through conductors 57 may be provided along the common wiring 49, for example. This stabilizes the potential of the electrodes that are at the same potential. Of course, the through conductor 57 may be provided at only one location. The through conductor 57 located above the common wiring 49 and the through conductor 57 located below the common wiring 49 may or may not overlap each other in a planar perspective view.

[0162] Although not particularly shown, a through conductor 57 may be provided penetrating the fourth piezoelectric layer 29D. The through conductor 57 may electrically connect the plate 25J (the fourth electrode 45 from another point of view) to the second electrode 37 and the fourth conductor layer 31D.

[0163] (electric potential applied to the conductor layer) Fig. 11 is a schematic cross-sectional view showing the potential applied to the conductor layer 31 when droplets are ejected. Fig. 12 is a schematic cross-sectional view showing the potential applied to the conductor layer 31 when a polarization process is performed on the first inactive region 55A. These figures correspond to the line VV in Fig. 4, as in Fig. 5, for example. In these figures, hatching indicating a cross section is omitted. The arrows shown in the cross section of the piezoelectric layer 29 indicate the direction of the voltage (electric field) at a given point in time in the cycle of ejecting droplets.

[0164] These figures show a driver 61 that supplies power to the piezoelectric actuator 13 to drive the piezoelectric actuator 13. However, the configuration of the driver 61 shown here is for the sake of convenience in illustrating the potential applied to the conductor layer 31. Therefore, the actual configuration of the driver 61 may differ from the configuration shown in the figures.

[0165] The driver 61 is configured by, for example, an IC (Integrated Circuit). The driver 61 may be mounted on the head 2, for example, by being mounted on an FPC (not shown) facing the first surface 13a of the piezoelectric actuator 13. However, the driver 61 does not have to be mounted on the head 2. The division of roles between the driver 61 and the control unit 88 may be appropriately set. For example, a part or all of the operation of the driver 61 described below may be executed by the control unit 88. The driver 61 may be provided in a hardware configuration that is difficult to conceptualize separately from the control unit 88. The driver 61 and the control unit 88 may be regarded as a control unit as a whole.

[0166] The driver 61 has, for example, a first signal source 63 capable of outputting power for ejecting droplets, a second signal source 65 capable of outputting power for polarization processing, and a switch unit 67 for controlling the connection between these signal sources and the piezoelectric actuator 13. The switch unit 67 is provided to clearly show which of the power for ejecting droplets and the power for polarization processing is applied to the piezoelectric actuator 13. In reality, the switch unit 67 may not be provided, and the power for ejecting droplets and the power for polarization processing may be selectively output by the operation of the first signal source 63 and the second signal source 65. Also, the first signal source 63 and the second signal source 65 may be partially shared.

[0167] 11 and 12 show a reference potential section 69 as a signal ground and / or a frame ground. The connection between the conductor layer 31 to which the reference potential is applied and the reference potential section 69 may or may not be via the driver 61. The illustrated configuration related to the connection of the reference potential section 69 is merely for the sake of convenience in showing the potential difference between the conductor layers 31 in an easily understandable manner.

[0168] (Liquid discharge control) As described with reference to Fig. 5, when ejecting droplets, the first signal source 63 applies a voltage (electric field) in the same direction (or opposite direction) as the polarization direction to the first active region 53A and the second active region 53B. As described with reference to Fig. 6, in this embodiment, in the first active region 53A, the polarization direction of the first piezoelectric layer 29A and the polarization direction of the second piezoelectric layer 29B are opposite to each other, and the polarization direction of the second active region 53B is the same as the polarization direction of the portion of the first active region 53A constituted by the first piezoelectric layer 29A. Therefore, as shown by arrows y1 and y2 in Figure 11, the driver 61 (first signal source 63) applies a potential to the conductor layer 31 so that in the first active region 53A, the voltage applied to the first piezoelectric layer 29A and the voltage applied to the second piezoelectric layer 29B are in opposite directions, and the voltage applied to the second active region 53B is in the same direction as the voltage applied to the portion of the first active region 53A formed by the first piezoelectric layer 29A.

[0169] More specifically, in the illustrated example, a reference potential is applied to the second electrode 37 and the fourth electrode 45. A potential higher than the reference potential (from another point of view, a potential with a positive polarity) is applied to the first electrode 33 and the third electrode 41. As a result, a voltage is applied between the first electrode 33 and the second electrode 37 (a portion of the first active region 53A constituted by the first piezoelectric layer 29A) in a direction from the former to the latter. A voltage is applied between the second electrode 37 and a region of the third electrode 41 overlapping with the second electrode 37 (a portion of the first active region 53A constituted by the second piezoelectric layer 29B) in a direction from the latter to the former. A voltage is applied between the region of the third electrode 41 overlapping with the fourth electrode 45 and the fourth electrode 45 in a direction from the former to the latter.

[0170] Although the above describes a case where a voltage is applied in the same direction as the polarization direction, it is possible to apply a voltage in the opposite direction to the polarization direction by applying a potential lower than the reference potential (from another point of view, a potential with a negative polarity) to the first electrode 33 and the third electrode 41. Also, the above description is based on the polarization direction shown in Fig. 6, but when the polarization direction is opposite to that in Fig. 6, the magnitude (positive and negative) of the above potential will be reversed.

[0171] In the above description, the second electrode 37 and the fourth electrode 45 are applied with a reference potential. However, a potential other than the reference potential may be applied to the second electrode 37 and the fourth electrode 45 while the fourth electrode 45 is not electrically connected to the metal plate 25J (see, for example, the embodiment described later). For example, a potential different from the potentials of the first electrode 33 and the third electrode 41 and higher or lower than the reference potential may be applied to the second electrode 37 and the fourth electrode 45. In addition, it is necessary to change the configuration of the conductor layer 31 and the arrangement of the through conductors so that potentials can be applied individually to the second electrode 37 and the fourth electrode 45. However, the reference potential may be applied to the first electrode 33 and the third electrode 41, and a potential higher or lower than the reference potential may be applied to the second electrode 37 and the fourth electrode 45. Therefore, in a broader conceptualization of this embodiment, the same potential (first potential) is applied to the first electrode 33 and the third electrode 41, and the same potential (second potential) is applied to the second electrode 37 and the fourth electrode 45, and the difference between the two potentials forms an electric field (first electric field) applied to the first active region 53A and an electric field (second electric field) applied to the second active region 53B.

[0172] In other embodiments, a voltage may be applied to the first active region 53A and the second active region 53B in the same direction as the polarization direction. For example, the first electrode 33 and the third electrode 41 may not be connected to each other, and the potentials of the first electrode 33 and the third electrode 41 may be different from each other and both may be higher (or lower) than the potential of the second electrode 37. Also, for example, the potentials of the second electrode 37 and the fourth electrode 45 may be different from each other and both may be lower (or higher) than the potential of the third electrode 41.

[0173] When applying a voltage for ejecting droplets, the reorientation electrode 35 and the fourth conductor layer 31D may be, for example, given a reference potential or may be in an electrically floating state (a state in which no potential is actively applied). In the example of Fig. 11, the reorientation electrode 35 is in an electrically floating state. In addition, in this embodiment, the fourth conductor layer 31D is connected to the second electrode 37 as described above, and therefore is given a reference potential.

[0174] Various known methods or applications of various known methods may be adopted as the method of driving the piezoelectric element 27 when applying pressure to the pressure chamber 21. A representative driving method is the so-called pull-hit type. When the pull-hit type is adopted, the operation of the driver 61 is, for example, as follows.

[0175] The driver 61 applies a potential higher than the reference potential (from another point of view, the same potential as the potential of the second electrode 37 and the fourth electrode 45; the same applies below) to the first electrode 33 and the third electrode 41 before ejecting the droplets. As a result, the piezoelectric element 27 is in a state in which bending deformation occurs toward the pressure chamber 21 side. When the timing for ejecting the droplets arrives, the driver 61 applies the reference potential to the first electrode 33 and the third electrode 41. As a result, the piezoelectric element 27 begins to return to a flat state, and the volume of the pressure chamber 21 begins to increase. From another point of view, the piezoelectric element 27 begins to vibrate at the natural frequency. After that, the volume of the pressure chamber 21 becomes maximum and then decreases again. As the volume decreases, the pressure of the pressure chamber 21 increases. Then, at the timing when the pressure becomes approximately maximum, a potential higher than the reference potential is applied to the first electrode 33 and the third electrode 41. As a result, the first applied vibration and the second applied vibration overlap each other, and a greater pressure is applied inside the pressure chamber 21. In this manner, the driver 61 inputs, to the first electrode 33 and the third electrode 41, a pulsed drive signal that is at a low potential for a certain period of time, based on a potential higher than the potentials of the second electrode 37 and the fourth electrode 45.

[0176] The driver 61 changes the amplitude of the pulsed driving signal and / or the number of driving signals depending on the size of the dot to be formed on the recording medium, for example, so that the ejected droplets are made larger or two or more droplets are ejected for one dot.

[0177] As can be understood from the above description, when droplets are discharged, the change in voltage applied to the first active region 53A is the same as the change in voltage applied to the second active region 53B. Therefore, the period during which the first active region 53A expands is the same as the period during which the second active region 53B expands, and the period during which the first active region 53A contracts is the same as the period during which the second active region 53B contracts. In other words, the period during which the first active region 53A contracts or expands is the same as the period during which the second active region 53B contracts or expands. In higher conceptualization, the period during which the first active region 53A expands or contracts is at least partially overlapped with the period during which the second active region 53B contracts or contracts.

[0178] As can be understood from the explanation of the push-pull type, the period during which one of contraction and expansion occurs is not limited to the period during which a voltage is actively applied to the first active region 53A and the second active region 53B. For example, the period during which one of contraction and expansion occurs may be a period during which the potentials of the first electrode 33 and the third electrode 41 are set to the reference potential when the timing for ejecting a droplet arrives. This period can be considered as a period during which no voltage is applied to the first active region 53A and the second active region 53B. However, in any case, it can be said that the driver 61 controls the intensity of the electric field applied to the first active region 53A and the intensity of the electric field applied to the second active region 53B in the liquid ejection control so that the second active region 53B expands or contracts during at least a part of the period during which the first active region 53A expands or contracts.

[0179] It is also possible to shift the period during which a voltage is applied between the first active region 53A and the second active region 53B. For example, the piezoelectric actuator is configured so that a potential can be applied individually to the multiple fourth electrodes 45. For example, in the above-mentioned example of the push-pull type, before the droplet is discharged, the same potential as that of the third electrode 41 may be applied to the fourth electrode 45 to not utilize the contraction of the second active region 53B, and when the potential of the third electrode 41 is returned to a potential higher than the reference potential, the reference potential may be applied to the fourth electrode to utilize the contraction of the second active region 53B. Conversely, before the droplet is discharged, the contraction of the second active region 53B may be utilized. Depending on the amount of droplet discharged (the size of the dot formed on the recording medium according to the image data), the use or non-use of the contraction of the second active region 53B may be changed. Note that in any of these modes, it can be said that the period during which the first active region 53A causes one of the expansion and contraction and the period during which the second active region 53B causes one of the expansion and contraction at least partially overlap each other.

[0180] The second electrode 37 and the fourth electrode 45 are applied with the same potential (reference potential). Therefore, the potential difference between the third electrode 41 and the second electrode 37 is the same as the potential difference between the third electrode 41 and the fourth electrode 45. In other words, the voltage applied to the part of the first active region 53A that is constituted by the second piezoelectric layer 29B is the same as the voltage applied to the second active region 53B. On the other hand, the former voltage is applied to the thickness of one piezoelectric layer 29 (29B), whereas the latter voltage is applied to the thickness of two piezoelectric layers (29C and 29D). Therefore, the intensity of the electric field formed by the former voltage is stronger than the intensity of the electric field formed by the latter voltage. The same can be said about the part of the first active region 53A that is constituted by the first piezoelectric layer 29A and the second active region 53B. From another perspective, when liquid is ejected, the intensity of the electric field in the first active region 53A (or, from another perspective, the amount of change therein) is greater than the intensity of the electric field in the second active region 53B.

[0181] In this embodiment, in the liquid ejection control, the electric field applied to the first active region 53A and the electric field applied to the second active region 53B both rise or fall. In a mode in which both electric fields do not change in the same way, unlike this embodiment, the maximum values ​​of the electric field intensity applied to the first active region 53A and the electric field intensity applied to the second active region 53B may be compared. Also, for example, in the push-pull type, depending on the specific driving waveform, the electric field that keeps the piezoelectric element 27 in a state of being deflected toward the pressure chamber 21 just before the ejection timing arrives is not an electric field during ejection, but may be referred to as the maximum value of the electric field applied to the active region 53 in the liquid ejection control. In a mode in which the electric field applied to the first active region 53A and the electric field applied to the second active region 53B are controlled separately, the maximum values ​​of the electric field intensity compared with each other may be those at different times.

[0182] (Reorientation Control) When the first inactive region 55A is repeatedly subjected to stress in a direction along the surface due to bending deformation of the piezoelectric element 27, movement of the domain walls (domain switching) occurs. As a result, the displacement of the piezoelectric element 27 decreases. Therefore, by performing a polarization process on the first inactive region 55A and keeping the polarization of the first inactive region 55A constant, the decrease in displacement can be reduced.

[0183] The polarization process by the reorientation electrode 35 may be performed at an appropriate time when droplets are not being ejected. For example, the polarization process may be performed when printing is not being performed, triggered by a user's operation on the printer 1. That is, the polarization process may be performed at any time. Also, for example, the control unit 88 may count the number of prints and perform the polarization process when a predetermined number of prints have been completed. When the printer 1 is shipped, the first inactive area 55A may be in a state where no polarization process has been performed, or in a state where a polarization similar to that achieved by the polarization process by the reorientation electrode 35 has been generated.

[0184] As described with reference to Fig. 6, in this embodiment, the first inactive region 55A is polarized in the thickness direction. In the polarization process, as shown by the arrow in Fig. 12, the driver 61 (second signal source 65) applies a voltage (DC voltage) in the same direction as the polarization direction of the first inactive region 55A. The voltage at this time may be, for example, a voltage that forms an electric field with a strength exceeding the coercive electric field of the first inactive region 55A, and may be a voltage equal to or greater than the voltage at which the polarization is saturated.

[0185] In order to apply the voltage as described above, in the illustrated example, the reorientation electrode 35 is applied with a potential higher than the reference potential (from another point of view, a potential with a positive polarity). The third electrode 41 is in an electrically floating state. The fourth electrode 45 is applied with a reference potential. As a result, an electric field is formed between the reorientation electrode 35 and the fourth electrode 45. The third electrode 41 interposed therebetween is in an electrically floating state, and therefore is unlikely to hinder the formation of the electric field. The electric field is then applied to the first inactive region 55A and the second active region 53B.

[0186] In the above, it is assumed that the polarization direction is downward as shown in Fig. 6. In an embodiment in which the polarization direction is the opposite direction, a potential lower than the reference potential (in other words, a potential with a negative polarity) may be applied to the reorientation electrode 35. Also, the fourth electrode 45 (in other words, the electrode that forms an electric field together with the reorientation electrode 35) may not be electrically connected to the metal plate 25J, and a potential other than the reference potential may be applied to the electrode. In this case, the potential applied to the reorientation electrode 35 may be the reference potential or a potential other than the reference potential.

[0187] When applying a voltage for polarization treatment, the first electrode 33, the second electrode 37, and the fourth conductor layer 31D may be given, for example, a reference potential or may be in an electrically floating state. In this embodiment, as described above, the first electrode 33 is electrically connected to the third electrode 41, and therefore is in an electrically floating state. In addition, the second electrode 37 and the fourth conductor layer 31D are given a reference potential.

[0188] The method of manufacturing the head body 7 may be similar to various known methods or applications of various known methods. For example, the piezoelectric actuator 13 may be produced by arranging the conductor layer 31 and a conductive paste that will become the through conductor on a ceramic green sheet that will become the piezoelectric layer 29, and then stacking and firing the ceramic green sheets. The flow path member 11 may be produced by bonding, with an adhesive, a plurality of plates 25 in which through holes that will become the flow paths are formed by etching or the like. Then, the head body 7 may be produced by joining the piezoelectric actuator 13 and the flow path member 11 with an adhesive.

[0189] The polarization treatment of the active region 53 may be performed, for example, at an appropriate time after the sintering of the piezoelectric actuator 13 (for example, after the piezoelectric actuator 13 and the flow path member 11 are bonded together). In the polarization treatment, for example, a DC voltage is applied to the first electrode 33, the second electrode 37, the third electrode 41, and the fourth electrode 45 so that an electric field indicated by arrows y1 and y2 in Fig. 11 is applied. The voltage at this time may be, for example, a voltage that forms an electric field having a strength exceeding the coercive electric field of the active region 53, and may be a voltage equal to or greater than the voltage at which the polarization becomes saturated.

[0190] As described above, in this embodiment, the liquid ejection head 2 has a flow path member 11, a piezoelectric actuator 13, and a driver 61. The flow path member 11 has a pressure surface 11b and a pressure chamber 21 that opens to the pressure surface 11b. The piezoelectric actuator 13 overlaps the pressure surface 11b. The driver 61 drives the piezoelectric actuator 13. The piezoelectric actuator 13 has a first active region 53A and a second active region 53B. When the direction perpendicular to the pressure surface 11b (direction D3) is referred to as the thickness direction, the first active region 53A is made of a piezoelectric body polarized in the thickness direction, and overlaps with the center portion 21a of the pressure chamber 21 in a planar perspective view of the pressure surface 11b. The second active region 53B is made of a piezoelectric body polarized in the thickness direction, and is located closer to the pressure surface 11b than the first active region 53A, and overlaps with the peripheral portion 21b of the pressure chamber 21 and the region 11e outside the pressure chamber 21 in a planar perspective view of the pressure surface 11b. In liquid ejection control, the driver 61 controls the intensity of a first electric field (arrow y1 in FIG. 11) applied in the thickness direction to the first active region 53A and the intensity of a second electric field (arrow y2 in FIG. 11) applied in the thickness direction to the second active region 53B so that the second active region 53B causes one of expansion and contraction in the direction along the pressure surface 11b during at least a part of a period during which the first active region 53A causes one of expansion and contraction in the direction along the pressure surface 11b. In liquid ejection control, the maximum value of the intensity of the first electric field is greater than the maximum value of the intensity of the second electric field.

[0191] Therefore, for example, by driving not only the first active region 53A but also the second active region 53B, the displacement of the piezoelectric element 27 as a whole can be increased. Since the deformation of the second active region 53B in the region overlapping with the region 11e outside the pressure chamber 21 is restricted by the flow path member 11, the stress is likely to be large near the outer edge of the pressure chamber 21. However, by making the strength of the electric field applied to the first active region 53A larger than that applied to the second active region 53B, the stress applied to the second active region 53B can be reduced while maintaining the above-mentioned effect of increasing the displacement of the piezoelectric element 27 as a whole. By reducing the stress applied to the second active region 53B, the durability of the head 2 can be improved.

[0192] In this embodiment, the head 2 has three or more electrodes (33, 37, 41, and 45). The three or more electrodes are located at different positions in the thickness direction, and each of them applies at least one of a first electric field to the first active region 53A and a second electric field to the second active region 53B. The distance in the thickness direction between two electrodes that are adjacent to each other among the three or more positions in the thickness direction of the three or more electrodes and apply the first electric field (at least one of the distance between 33 and 37 and the distance between 37 and 41) is defined as a first distance. The distance in the thickness direction between two electrodes that are adjacent to each other among the three or more positions and apply the second electric field (the distance between 41 and 45) is defined as a second distance. In this case, the first distance is shorter than the second distance.

[0193] Therefore, for example, even if the voltage (potential difference) forming the first electric field applied to the first active region 53A and the voltage (potential difference) forming the second electric field applied to the second active region 53B are the same, the intensity of the first electric field is stronger than the intensity of the second electric field. For this reason, it is easy to make the intensity of the first electric field stronger than the intensity of the second electric field.

[0194] In addition, in this embodiment, in addition to the above-mentioned relationship in distance between the electrodes being satisfied, in liquid ejection control, the maximum potential difference between the two electrodes (potential difference between 33 and 37 and / or potential difference between 37 and 41) that apply a first electric field to the first active region 53A is the same as the maximum potential difference between the two electrodes (41 and 45) that apply a second electric field to the second active region 53B.

[0195] In this case, for example, one of the two electrodes that apply the first electric field and one of the two electrodes that apply the second electric field can be connected (or integrated into one electrode), and the other of the two electrodes that apply the first electric field and the other of the two electrodes that apply the second electric field can be connected. As a result, with a simple configuration, the strength of the first electric field can be made stronger than the strength of the second electric field.

[0196] In this embodiment, the piezoelectric actuator includes a first piezoelectric layer 29A to a fourth piezoelectric layer 29D, a first electrode 33, a second electrode 37, a third electrode 41, and a fourth electrode 45. The side of the piezoelectric actuator 13 opposite to the flow path member 11 (+D3 side) is referred to as the first side, and the side of the piezoelectric actuator 13 facing the flow path member 11 (-D3 side) is referred to as the second side. At this time, the first piezoelectric layer 29A to the fourth piezoelectric layer 29D are laminated in order from the first side to the second side. The first electrode 33 overlaps the first side surface of the first piezoelectric layer 29A, and overlaps the central portion 21a of the pressure chamber 21 in a planar perspective. The second electrode 37 overlaps the second side surface of the first piezoelectric layer 29A, and overlaps the central portion 21a in a planar perspective. The third electrode 41 overlaps the second side surface of the second piezoelectric layer 29B, and overlaps the central portion 21a, the peripheral portion 21b of the pressure chamber 21, and the outer region 11e of the pressure chamber 21 in a planar perspective. The fourth electrode 45 overlaps the second side surface of the fourth piezoelectric layer 29D, and overlaps the peripheral portion 21b and the outer region 11e in a planar perspective. The first active region 53A has a region sandwiched between the first electrode 33 and the second electrode 37 in the first piezoelectric layer 29A, and a region sandwiched between the second electrode 37 and a portion overlapping the central portion 21a of the third electrode 41 in the second piezoelectric layer 29B. The second active region 53B has a region sandwiched between the fourth electrode 45 and a portion overlapping the peripheral portion 21b and the outer region 11e of the third electrode 41 in the third piezoelectric layer 29C and the fourth piezoelectric layer 29D.

[0197] In this case, for example, with a simple configuration, the first electric field applied to the first active region 53A can be made larger than the second electric field applied to the second active region 53B. For example, in the first active region 53A, a voltage is applied to the two piezoelectric layers 29 (29A and 29B) by three electrodes (33, 37, and 41) at different positions in the thickness direction, and in the second active region 53B, a voltage is applied to the two piezoelectric layers 29 (29C and 29D) by two electrodes. Therefore, it is easy to realize a configuration in which the distance between the two electrodes that apply a voltage to the first active region 53A is shorter than the distance between the two electrodes that apply a voltage to the second active region 53B. Due to the effect of this distance relationship, the voltage applied to the first active region 53A (29A and 29B) and the voltage applied to the second active region 53B (29C and 29D) can be made the same, so that, for example, an increase in potential can be suppressed and the configuration can be simplified. Furthermore, since the third electrode 41 is used to apply a voltage to both the first active region 53A and the second active region 53B, the number of electrodes (the number of conductor layers 31) can be reduced.

[0198] In this embodiment, the portion of the first piezoelectric layer 29A constituting the first active region 53A and the portion of the second piezoelectric layer 29B constituting the first active region 53A are polarized in the opposite directions. The portions of the third piezoelectric layer 29C and the fourth piezoelectric layer 29D constituting the second active region 53B are polarized in the same direction as the polarization direction of the portion of the first piezoelectric layer 29A constituting the first active region 53A. In liquid ejection control, the first electrode 33 and the third electrode 41 are set to the same potential, and the second electrode 37 and the fourth electrode 45 are set to the same potential, and a first electric field is applied to the first active region 53A and a second electric field is applied to the second active region 53B due to the potential difference between the potentials of the first electrode 33 and the third electrode 41 and the potentials of the second electrode 37 and the fourth electrode 45.

[0199] In this case, for example, an electric field can be applied in the polarization direction (or the opposite direction) of each of three regions (the portion of the first active region 53A constituted by the first piezoelectric layer 29A, the portion of the first active region 53A constituted by the second piezoelectric layer 29B, and the second active region 53B) with only two types of potentials. This simplifies the configuration of the piezoelectric actuator 13 and the driver 61.

[0200] In this embodiment, the sum of the thickness of the third piezoelectric layer 29C and the thickness of the fourth piezoelectric layer 29D is greater than each of the thicknesses of the first piezoelectric layer 29A and the second piezoelectric layer 29B.

[0201] In this case, from another point of view, the distance between the first electrode 33 and the second electrode 37 and the distance between the second electrode 37 and the third electrode 41 are each shorter than the distance between the third electrode 41 and the fourth electrode 45. As a result, for example, the electric field applied to the portion of the first active region 53A constituted by the first piezoelectric layer 29A and the electric field applied to the portion of the first active region 53A constituted by the second piezoelectric layer 29B can each be made larger than the electric field applied to the second active region 53B.

[0202] In addition, in this embodiment, the piezoelectric actuator 13 overlaps the second side (-D3 side) surface of the third piezoelectric layer 29C and has a conductor pattern (fourth conductor layer 31D) located outside the second active region 53B in a planar perspective view.

[0203] Here, in this embodiment, as described above, three electrodes (33, 37, and 41) are arranged for applying a voltage to the first active region 53A, and two electrodes (41 and 45) are arranged for applying a voltage to the second active region 53B (however, the third electrode 41 is shared). Therefore, in the piezoelectric actuator 13, the volume of the conductor on the first side (+D3 side) is likely to be larger than the volume of the conductor on the second side. However, by providing the fourth conductor layer 31D, it is easy to make the volume of the conductor (from another point of view, the ratio of the conductor to the piezoelectric body) equal on the +D3 side and the -D3 side. As a result, for example, the probability of unintended bending deformation caused by contraction during firing and / or expansion and contraction due to temperature changes during use is reduced.

[0204] In addition, in this embodiment, in a planar perspective view of the pressure surface 11b, the area of ​​the second portion 53Bb of the second active region 53B that is located outside the pressure chamber is larger than the area of ​​the first portion 53Ba of the second active region 53B that overlaps with the pressure chamber 21.

[0205] When the outer edge of the second active region 53B (from another point of view, the outer edge of the second portion 53Bb) approaches the outer edge of the pressure chamber 21, stress concentration is likely to occur near the outer edge of the pressure chamber 21. However, since the area of ​​the second portion 53Bb is larger than the area of ​​the first portion 53Ba, it is easy to move the outer edge of the second active region 53B away from the outer edge of the pressure chamber 21. In turn, the above-mentioned stress concentration can be alleviated. As a result, for example, the probability that deterioration occurs in the bond between the piezoelectric actuator 13 and the flow path member 11 around the pressure chamber 21 can be reduced. In addition, as described above, the strength of the first electric field applied to the first active region 53A is made larger than the strength of the second electric field applied to the second active region 53B (the second electric field is made relatively smaller), so that the stress applied to the second active region 53B can be reduced. As a result, for example, the effect of alleviating the stress concentration near the outer edge of the pressure chamber 21 described above is improved.

[0206] In this embodiment, in plan view of the pressure surface 11b, a portion of the outer edge of the pressure chamber 21 that corresponds to an angle of 180° or more around the center of the pressure chamber 21 is formed by a circular arc.

[0207] In this case, the stress is evenly distributed by the arc in plan view. In other words, the likelihood of the stress becoming specifically high is reduced. As a result, for example, the above-mentioned effect of stress relaxation is improved. In particular, when the planar shape of the pressure chamber 21 is circular (when the pressure chamber 21 is formed only by the circle C1 in FIG. 4), the above-mentioned effect is improved.

[0208] In this embodiment, in a cross section passing through the center of the pressure chamber 21 and perpendicular to the pressure surface 11b, the width w2 of the second portion 53Bb is larger than the width w1 of the first portion 53Ba.

[0209] In this case, the outer edge of the second active region 53B can be spaced away from the outer edge of the pressure chamber 21. This alleviates the stress concentration described in the description of the effect of the area of ​​the second portion 53Bb being larger than the area of ​​the first portion 53Ba. If the area of ​​the second portion 53Bb is larger than the area of ​​the first portion 53Ba and the width w2 is larger than the width w1, the effect of alleviating the stress concentration is further improved.

[0210] In this embodiment, the piezoelectric actuator 13 has an inactive region (first inactive region 55A). The first inactive region 55A is made of a piezoelectric body and is connected to the outer periphery of the first active region 53A. The driver 61 executes reorientation control (FIG. 12). In the reorientation control, the driver 61 applies an electric field in the thickness direction to the first inactive region 55A when the droplet discharge control is not being performed.

[0211] Therefore, for example, as described above, the probability of occurrence of a decrease in displacement due to domain switching in the first non-active region 55A can be reduced by the polarization treatment. The first non-active region 55A is a portion that receives both the stress of the first active region 53A and the stress of the second active region 53B, and domain switching is likely to occur. By performing such a polarization treatment on the first non-active region 55A, the decrease in displacement can be efficiently reduced. In addition, as described above, the stress applied to the second active region 53B can be reduced by making the strength of the first electric field applied to the first active region 53A larger than the strength of the second electric field applied to the second active region 53B (making the second electric field relatively smaller). In turn, the stress applied from the second active region 53B to the first non-active region 55A can be reduced. As a result, the probability of occurrence of domain switching in the first non-active region 55A can be reduced, and the frequency of performing the polarization treatment on the first non-active region 55A can be reduced.

[0212] In this embodiment, the piezoelectric actuator 13 has a reorientation electrode 35, an intermediate electrode (third electrode 41), and a lower electrode (fourth electrode 45). The reorientation electrode 35 overlaps the inactive region (first inactive region 55A) on the opposite side (+D3 side) of the pressure surface 11b. The third electrode 41 is located between the first inactive region 55A and the second active region 53B. The fourth electrode 45 overlaps the second active region 53B on the pressure surface 11b side (-D3 side). In liquid ejection control, the driver 61 applies an electric field to the second active region 53B by applying a voltage to the third electrode 41 and the fourth electrode 45. In reorientation control, the driver 61 applies an electric field to the first inactive region 55A by applying a voltage to the reorientation electrode 35 and one of the third electrode 41 and the fourth electrode 45 (the fourth electrode 45 in this embodiment).

[0213] In this case, the fourth electrode 45 (or the third electrode 41) is used both to apply an electric field for ejecting droplets and to apply an electric field for polarization processing, thus simplifying the configuration of the piezoelectric actuator 13.

[0214] In addition to the above configuration, in this embodiment, the piezoelectric actuator 13 has an upper electrode (second electrode 37). The second electrode 37 is located on the opposite side (+D3 side) of the pressure surface 11b from the intermediate electrode (third electrode 41), and faces the third electrode 41 across at least a part of the first active region 53A. In liquid ejection control, the driver 61 applies an electric field to the first active region 53A by applying a voltage to the second electrode 37 and the third electrode 41. In reorientation control, the driver 61 applies an electric field to the inactive region (first inactive region 55A) by applying a voltage to the reorientation electrode 35 and the fourth electrode 45 without applying a potential to the third electrode 41.

[0215] In this case, for example, the third electrode 41 is used to apply an electric field to both the first active region 53A and the second active region 53B in controlling the ejection of droplets. As a result, the configuration of the piezoelectric actuator 13 is simplified. On the other hand, in the polarization process, the third electrode 41 is in an electrically floating state, so that it is unlikely to hinder the application of an electric field by the reorientation electrode 35 and the fourth electrode 45. By performing the polarization process by the reorientation electrode 35 and the fourth electrode 45, the polarization process is performed not only on the first non-active region 55A but also on the second active region 53B. As a result, not only the degradation of characteristics caused by domain switching in the first non-active region 55A but also the degradation of characteristics caused by domain switching in the second active region 53B can be reduced.

[0216] In this embodiment, as described above, the piezoelectric actuator has the first piezoelectric layer 29A to the fourth piezoelectric layer 29D, the first electrode 33, the second electrode 37, the third electrode 41 and the fourth electrode 45, thereby constituting the first active region 53A and the second active region 53B. The inactive region (first inactive region 55A) has a region in the first piezoelectric layer 29A and the second piezoelectric layer 29B that is sandwiched between the reorientation electrode 35 and the fourth electrode 45.

[0217] In this case, for example, as described above, with a simple configuration, the electric field applied to the first active region 53A can be made larger than the electric field applied to the second active region 53B. Furthermore, with a simple configuration, the stress applied to the second active region 53B can be reduced, and the stress applied from the second active region 53B to the first inactive region 55A can be reduced.

[0218] <Second embodiment> Fig. 13 is a schematic cross-sectional view showing a head 207 according to the second embodiment and corresponds to Fig. 12 of the first embodiment. That is, Fig. 13 shows the potential applied to the conductor layer 31 when a polarization process is performed on the first inactive region 55A.

[0219] In the polarization process of the first embodiment, an electric field is applied to the first non-active area 55A by the reorientation electrode 35 and the fourth electrode 45. In the polarization process of the second embodiment, an electric field is applied to the first non-active area 55A by the reorientation electrode 35 and the third electrode 41. More specifically, in the illustrated example, a potential higher than a reference potential (a potential with a positive polarity in another respect) is applied to the reorientation electrode 35. The third electrode 41 is applied with the reference potential.

[0220] In the above, it is assumed that the polarization direction is downward as shown in Fig. 6. In an embodiment in which the polarization direction is the opposite direction, a potential lower than the reference potential (from another point of view, a potential with a negative polarity) may be applied to the reorientation electrode 35. A potential other than the reference potential may be applied to the third electrode 41. In this case, the potential applied to the reorientation electrode 35 may be the reference potential or a potential other than the reference potential.

[0221] When applying a voltage for polarization as described above, the first electrode 33, the second electrode 37, the fourth electrode 45, and the fourth conductor layer 31D may be given, for example, a reference potential or may be in an electrically floating state. In this embodiment, as described above, the first electrode 33 is electrically connected to the third electrode 41, and thus a reference potential is given to the first electrode 33. The second electrode 37, the fourth electrode 45, and the fourth conductor layer 31D are given a reference potential.

[0222] <Third embodiment> FIG. 14 is a schematic cross-sectional view showing a head 307 according to the third embodiment, and corresponds to FIG. 11 of the first embodiment.

[0223] In the first embodiment, the fifth conductor layer 31E (fourth electrode 45) is in contact with the flow path member 11 (plate 25J) and is exposed in the pressure chamber 21. On the other hand, in the present embodiment, the insulating layer 30 is interposed between the fifth conductor layer 31E and the flow path member 11. From another point of view, the insulating layer 30 is interposed between the second active region 53B and the flow path member 11. The insulating layer 30 may be regarded as a part of the piezoelectric actuator 13, may be regarded as a part of the flow path member 11, or may be regarded as a member separate from these. In FIG. 14, the insulating layer 30 is indicated by a reference symbol as a member separate from the piezoelectric actuator 13 and the flow path member 11.

[0224] The insulating layer 30 may be an inorganic material or an organic material. The inorganic material may be a piezoelectric material or may not be a piezoelectric material. The piezoelectric material may be the same as or different from the material of the piezoelectric layer 29, and may or may not be fired together with the piezoelectric layer 29. An example of an inorganic material that is not a piezoelectric material is SiO2. An example of an organic material is a resin. The insulating layer 30 made of a material other than a piezoelectric material formed by firing may be formed on the lower surface of the piezoelectric actuator 13 by an appropriate thin film formation method such as CVD (chemical vapor deposition), or may be attached to the piezoelectric actuator 13 or the flow path member 11 by an adhesive.

[0225] The insulating layer 30, for example, like the piezoelectric layer 29, has a constant thickness and spreads substantially without gaps over the region in which the multiple pressure chambers 21 are arranged. However, when the insulating layer 30 is relatively thin, it is not impossible to arrange the insulating layer 30 only directly under and around the second active region 53B (fourth electrode 45). The thickness of the insulating layer 30 may be set appropriately. For example, the thickness of the insulating layer 30 may be thinner than the thickness of the piezoelectric layer 29 (in the illustrated example), may be equal to the thickness of the piezoelectric layer 29, or may be thicker. The thickness of the insulating layer 30 may be set appropriately, for example, in consideration of the effects (strength and / or insulation properties) described later and / or the influence on the position of the neutral plane of the piezoelectric actuator 13.

[0226] The multiple fourth electrodes 45 may be connected to each other by the wiring included in the fifth conductor layer 31E, similar to the multiple second electrodes 37. Also, unlike the embodiment, the multiple fourth electrodes 45 may be individually connected to multiple signal lines of an FPC (not shown) facing the first surface 13a of the piezoelectric actuator 13 via the wiring and the through conductors.

[0227] As described above, the head 307 has the insulating layer 30 between the second active region 53B and the flow path member 11.

[0228] In this case, for example, the stress applied from the flow path member 11 to the second active region 53B is alleviated by the insulating layer 30. For example, the deformation of the portion of the second active region 53B overlapping with the region 11e outside the pressure chamber 21 is restrained by the flow path member 11, and the stress at the position overlapping with the outer edge of the pressure chamber 21 is likely to be high. This stress is alleviated. In addition, the insulating layer 30 covers the electrode (fourth electrode 45) that applies a voltage to the second active region 53B in the thickness direction. As a result, for example, the fourth electrode 45 can be insulated from the metal flow path member 11. In addition, the fourth electrode 45 does not come into contact with the liquid in the pressure chamber 21. As a result, for example, depending on the type of liquid, the likelihood of corrosion occurring in the fourth electrode 45 is reduced.

[0229] <Fourth embodiment> FIG. 15 is a schematic cross-sectional view showing a head 407 according to the fourth embodiment, and corresponds to FIG. 11 of the first embodiment.

[0230] In the piezoelectric actuator 413 of this embodiment, the fifth conductor layer 31E in the first embodiment is not provided. The fourth conductor layer 31D has a fourth electrode 445 corresponding to the fourth electrode 45 in the first embodiment. The second active region 53B is formed by a portion of the third piezoelectric layer 29C where the third electrode 41 and the fourth electrode 445 overlap, and is not formed by the fourth piezoelectric layer 29D. This embodiment can also be said to be an aspect in which an insulating layer (the fourth piezoelectric layer 29D in this embodiment) is interposed between the second active region 53B and the flow path member 11, similar to the third embodiment.

[0231] The shape of the fourth electrode 445 may be an appropriate shape as long as it overlaps with the second active region 53B. For example, the shape of the fourth electrode 445 may be a shape obtained by adding the shape of the fourth electrode 45 of the first embodiment and the shape of the fourth conductor layer 31D of the first embodiment. In other words, the fourth conductor layer 31D of this embodiment may be a shape in which the outer edge of the opening 43 in the fourth conductor layer 31D of the first embodiment is generally aligned with the outer edge of the electrode body 33a and / or the outer edge of the second electrode 37. Also, for example, the shape of the fourth electrode 445 may be the same as the shape of the fourth electrode 45 of the first embodiment. In this case, for example, the multiple fourth electrodes 445 may be connected to each other by multiple wirings included in the fourth conductor layer 31D, similar to the second electrode 37. Also, the multiple fourth electrodes 445 may be connected to appropriate wirings and through conductors so that a potential can be applied individually.

[0232] The potential applied to the fourth electrode 445 when the liquid is ejected and when the polarization process is performed is, for example, the same as that of the fourth electrode 45 in the first embodiment. In this case, in the illustrated example, the distance between the electrodes in the first active region 53A and the distance between the electrodes in the second active region 53B are approximately equal, so that the intensity of the electric field applied to the first active region 53A and the intensity of the electric field applied to the second active region 53B are approximately equal.

[0233] In this embodiment, as in the first embodiment, the intensity of the electric field applied to the first active region 53A may be stronger than the intensity of the electric field applied to the second active region 53B. There are various methods for realizing such a relationship in the intensity of the electric fields. For example, the potential applied to the electrodes may be the same as in the first embodiment, and the thickness of the third piezoelectric layer 29C may be thicker than the thickness of the first piezoelectric layer 29A and the thickness of the second piezoelectric layer 29B. Also, for example, the second electrode 37 and the fourth electrode 445 may be disconnected so that different potentials can be applied to them, and the potential difference between the third electrode 41 and the second electrode 37 may be larger than the potential difference between the third electrode 41 and the fourth electrode 45.

[0234] As described above, the head 407, like the third embodiment, has an insulating layer (fourth piezoelectric layer 29D) between the second active region 53B and the flow path member 11. Therefore, for example, the same effects as those described in the third embodiment are achieved.

[0235] <Fifth embodiment> Fig. 16 is a schematic cross-sectional view showing a head 507 according to the fifth embodiment, and corresponds to Fig. 11 of the first embodiment. In this figure, similar to Fig. 6, the polarization direction is also indicated by the outlined arrow.

[0236] In the first embodiment, the first active region 53A is composed of two piezoelectric layers 29, and the second active region 53B is composed of two piezoelectric layers 29. In the piezoelectric actuator 513 of the present embodiment, the first active region 53A is composed of one fifth piezoelectric layer 29E, and the second active region 53B is composed of one sixth piezoelectric layer 29F.

[0237] In such a configuration, various combinations of polarization directions, electrode structures, and potentials are possible to realize the operations of the first active region 53A and the second active region 53B described with reference to Fig. 5. In the illustrated example, they are as follows.

[0238] As in the first embodiment, the piezoelectric actuator 513 has, from the upper surface side to the lower surface side, a first electrode 33 (and a reorientation electrode 35), a third electrode 41, and a fourth electrode 45. The first active region 53A has a region of the fifth piezoelectric layer 29E sandwiched between the first electrode 33 and the third electrode 41. The second active region 53B has a region of the sixth piezoelectric layer 29F sandwiched between the third electrode 41 and the fourth electrode 45. The fourth electrode 45 is insulated from the flow path member 11 by the insulating layer 30, and can be given a potential other than the reference potential.

[0239] The polarization directions of the first active region 53A and the second active region 53B are opposite to each other. In liquid ejection control, a reference potential is applied to the third electrode 41 located between the two. A potential having the same polarity with respect to the reference potential is applied to the first electrode 33 and the fourth electrode 45. This causes both the first active region 53A and the second active region 53B to contract or expand.

[0240] The driver 561 has a signal source 63A that applies a potential to the first electrode 33 and a signal source 63B that applies a potential to the fourth electrode 45, and is capable of applying different potentials to the first electrode 33 and the fourth electrode 45. Therefore, in this embodiment as well, as in the first embodiment, the electric field applied to the first active region 53A can be made larger than the electric field applied to the second active region 53B. Unlike the example shown in the figure, the first electrode 33 and the fourth electrode 45 may be connected to each other and applied with the same potential.

[0241] (Modification of Piezoelectric Layer) FIG. 17A is a cross-sectional view showing the configuration of a piezoelectric layer 29 according to a modified example, and is an enlarged view of region XVII in FIG.

[0242] A groove 29v may be provided on the upper surface of the first piezoelectric layer 29A, located between the first electrode 33 and the reorientation electrode 35. The groove 29v extends, for example, along the outer edge of the first electrode 33 so as to surround the first electrode 33. In other words, the groove 29v extends in a ring shape. However, the groove 29v may be interrupted in part. For example, the groove 29v may not be provided at a position on the opposite side of the lead-out portion 33b from the electrode body 33a.

[0243] The width of the groove 29v may be set appropriately within a range equal to or smaller than the size of the gap between the first electrode 33 and the reorientation electrode 35. The width of the groove 29v may be constant regardless of the position in the longitudinal direction of the groove 29v, or may vary depending on the position in the longitudinal direction of the groove 29v. The depth of the groove 29v may be set appropriately within a range equal to or smaller than the thickness of the first piezoelectric layer 29A. For example, the depth of the groove 29v may be less than ½ of the thickness of the first piezoelectric layer 29A, or may be ½ or more. The depth of the groove 29v may also be equal to the thickness of the first piezoelectric layer 29A.

[0244] The grooves 29v may be formed by any suitable method, for example, by laser processing the ceramic green sheet that will become the first piezoelectric layer 29A, or the first piezoelectric layer 29A after firing.

[0245] Providing the groove 29v in this manner reduces the likelihood that, for example, the metal material constituting the first electrode 33 and the reorientation electrode 35 will move (migrate) into the region between these electrodes. As a result, it is possible to reduce the likelihood that the first electrode 33 and the reorientation electrode 35 will short-circuit. From another perspective, by shortening the distance between the first electrode 33 and the reorientation electrode 35 in a plan view, it becomes easier to perform a polarization process on the portion of the first inactive region 55A adjacent to the first active region 53A. As a result, the effect of maintaining the characteristics of the piezoelectric actuator by the polarization process is improved. The migration is electromigration and / or electrochemical migration.

[0246] FIG. 17B is a cross-sectional view showing the configuration of a piezoelectric layer 29 according to another modified example, and is a view similar to FIG. 17A.

[0247] An insulator 32 may be disposed in the groove 29v. The insulator 32 is made of a material that is less likely to cause migration of the electrode material than the material of the first piezoelectric layer 29A. For example, the insulator 32 may be made of a resin. The resin may be disposed in the groove 29v by a suitable method such as CVD.

[0248] By disposing the insulator 32, for example, it is possible to improve the effect of reducing the probability of migration occurring. In addition, for example, while obtaining the effect of reducing the probability of migration occurring, it is possible to reduce the probability of the strength of the piezoelectric actuator decreasing due to the groove 29v.

[0249] In the above embodiment, the third electrode 41 is an example of an intermediate electrode, and the fourth electrode 45 or 445 is an example of a lower electrode.

[0250] The technology according to the present disclosure is not limited to the above-described embodiment and may be implemented in various forms.

[0251] For example, the first inactive region may not be subjected to polarization processing. In other words, the head may not be provided with a configuration for polarization processing. In the liquid ejection control, a control other than the control (referred to as the first control) in which the second active region causes one of elongation and contraction during at least a portion of the period in which the first active region causes one of elongation and contraction may be performed. For example, a control (referred to as the second control) in which the second active region causes the other of elongation and contraction during at least a portion of the period in which the first active region causes one of elongation and contraction may be performed. The first control may be performed when ejecting large droplets, and the second control may be performed when ejecting small droplets. The head may circulate the liquid.

[0252] Various concepts can be extracted from the embodiments of the present disclosure. For example, the concept of a liquid ejection head can be extracted in which, in a planar perspective view of the pressure surface, the area of ​​a second portion of the second active region located outside the pressure chamber is larger than the area of ​​a first portion of the second active region overlapping the pressure chamber. Also, the concept of a liquid ejection head can be extracted in which a piezoelectric actuator has an inactive region (made of a piezoelectric body) connected to the outer periphery of the first active region, and a driver performs reorientation control to apply an electric field in the thickness direction to the inactive region when liquid ejection control is not being performed. In liquid ejection heads according to these concepts, unlike the embodiments, the maximum value of the intensity of the electric field (first electric field) applied to the first active region and the maximum value of the intensity of the electric field (second electric field) applied to the second active region may be equal to each other, or the latter may be larger than the former. [Explanation of symbols]

[0253] 1...printer (recording device), 2...liquid ejection head, 7...head main body (liquid ejection head), 11...flow path member, 11b...pressure surface, 11e...outer region (relative to pressure chamber), 13...piezoelectric actuator, 21...pressure chamber, 21a...central portion (of pressure chamber), 21b...peripheral portion (of pressure chamber), 53A...first active region, 53B...second active region, 53Ba...first portion (of second active region), 53Bb...second portion (of second active region), 55A...first inactive region, 61...driver.

Claims

1. a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface; A driver that drives the piezoelectric actuator; It has When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping an inner peripheral portion of the pressure chamber and an outer region of the pressure chamber when viewed from above on the pressure application surface; a non-active region made of a piezoelectric material, located on the opposite side of the second active region from the pressure application surface, connected to the outer periphery of the first active region, and extending through a thickness of the first active region; when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the driver controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation by changing the applied electric field, In the liquid ejection control, the maximum value of the intensity of the first electric field is greater than the maximum value of the intensity of the second electric field. Liquid ejection head.

2. A flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface; A driver that drives the piezoelectric actuator; It has When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the driver controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, The position of the thickness direction is different from each other, and the three or more electrodes each apply at least one of the first electric field and the second electric field, a distance in the thickness direction between two electrodes that are adjacent to each other among three or more positions in the thickness direction of the three or more electrodes and that apply the first electric field is shorter than a distance in the thickness direction between two electrodes that are adjacent to each other among the three or more positions and that apply the second electric field. Liquid ejection head.

3. In the liquid ejection control, a maximum value of a potential difference between the two electrodes to which the first electric field is applied is equal to a maximum value of a potential difference between the two electrodes to which the second electric field is applied. The liquid ejection head according to claim 2 .

4. When the side of the piezoelectric actuator opposite to the flow path member is referred to as a first side and the side of the piezoelectric actuator facing the flow path member is referred to as a second side, a first piezoelectric layer, a second piezoelectric layer, a third piezoelectric layer, and a fourth piezoelectric layer, which are laminated in this order from the first side to the second side; a first electrode overlapping the first side surface of the first piezoelectric layer and overlapping the central portion in a plan view; a second electrode overlapping the second surface of the first piezoelectric layer and overlapping the central portion in a plan view; a third electrode overlapping the second surface of the second piezoelectric layer and overlapping the central portion, the peripheral portion, and the outer region in a planar perspective view; a fourth electrode overlapping the second side surface of the fourth piezoelectric layer and overlapping the peripheral portion and the outer region in a planar perspective view, The first active region is a region of the first piezoelectric layer sandwiched between the first electrode and the second electrode; a region of the second piezoelectric layer that is sandwiched between the second electrode and a portion of the third electrode that overlaps with the central portion, The second active region is The third and fourth piezoelectric layers have a region sandwiched between a portion overlapping the peripheral portion and the outer region of the third electrode and the fourth electrode.

4. The liquid ejection head according to claim 1.

5. a portion of the first piezoelectric layer constituting the first active region and a portion of the second piezoelectric layer constituting the first active region are polarized in opposite directions to each other, a portion of the third and fourth piezoelectric layers constituting the second active region is polarized in the same direction as a portion of the first piezoelectric layer constituting the first active region, In the liquid ejection control, the first electrode and the third electrode are set to the same potential, the second electrode and the fourth electrode are set to the same potential, and the first electric field and the second electric field are applied by a potential difference between the potentials of the first electrode and the third electrode and the potentials of the second electrode and the fourth electrode.

5. The liquid ejection head according to claim 4.

6. The sum of the thickness of the third piezoelectric layer and the thickness of the fourth piezoelectric layer is greater than each of the thickness of the first piezoelectric layer and the thickness of the second piezoelectric layer.

6. The liquid ejection head according to claim 4 or 5.

7. A flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface; A driver that drives the piezoelectric actuator; It has When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the driver controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, When the side of the piezoelectric actuator opposite to the flow path member is referred to as a first side and the side of the piezoelectric actuator facing the flow path member is referred to as a second side, a first piezoelectric layer, a second piezoelectric layer, a third piezoelectric layer, and a fourth piezoelectric layer, which are laminated in this order from the first side to the second side; a first electrode overlapping the first side surface of the first piezoelectric layer and overlapping the central portion in a plan view; a second electrode overlapping the second surface of the first piezoelectric layer and overlapping the central portion in a plan view; a third electrode overlapping the second surface of the second piezoelectric layer and overlapping the central portion, the peripheral portion, and the outer region in a planar perspective view; a fourth electrode overlapping the second side surface of the fourth piezoelectric layer and overlapping the peripheral portion and the outer region in a planar perspective view, The first active region is a region of the first piezoelectric layer sandwiched between the first electrode and the second electrode; a region of the second piezoelectric layer that is sandwiched between the second electrode and a portion of the third electrode that overlaps with the central portion, The second active region is the third and fourth piezoelectric layers have a region sandwiched between a portion overlapping the peripheral portion and the outer region of the third electrode and the fourth electrode, The piezoelectric actuator has a conductor pattern that overlaps the second surface of the third piezoelectric layer and is positioned outside the second active region in a plan view. Liquid ejection head.

8. In a plan view perspective of the pressure surface, an area of ​​a second portion of the second active region located outside the pressure chamber is larger than an area of ​​a first portion of the second active region overlapping the pressure chamber. The liquid ejection head according to any one of claims 1 to 7.

9. In a plan view of the pressure application surface, a portion of the outer edge of the pressure chamber that corresponds to an angle of 180° or more around the center of the pressure chamber is configured as a circular arc.

9. The liquid ejection head according to claim 1.

10. In a cross section passing through the center of the pressure chamber and perpendicular to the pressure application surface, a width of a second portion of the second active region located outside the pressure chamber is larger than a width of a first portion of the second active region overlapping the pressure chamber. The liquid ejection head according to any one of claims 1 to 9.

11. A flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface; A driver that drives the piezoelectric actuator; It has When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the driver controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, An insulating layer is provided between the second active region and the flow path member. Liquid ejection head.

12. the piezoelectric actuator is made of a piezoelectric body and has a non-active region connected to an outer periphery of the first active region; The driver performs a reorientation control to apply an electric field in the thickness direction to the inactive region when the liquid ejection control is not performed. The liquid ejection head according to any one of claims 1 to 11.

13. A flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface; A driver that drives the piezoelectric actuator; It has When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the driver controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, the piezoelectric actuator is made of a piezoelectric body and has a non-active region connected to an outer periphery of the first active region; the driver performs a reorientation control to apply an electric field in the thickness direction to the inactive region when the liquid ejection control is not being performed; The piezoelectric actuator includes: a reorientation electrode overlying the non-active region on an opposite side to the pressure surface; an intermediate electrode located between the non-active region and the second active region; a lower electrode overlapping the second active region on the pressure surface side, The driver includes: In the liquid ejection control, a voltage is applied to the intermediate electrode and the lower electrode to apply an electric field to the second active region; In the reorientation control, an electric field is applied to the non-active region by applying a voltage to the reorientation electrode and the lower electrode, or by applying a voltage to the reorientation electrode and the intermediate electrode. Liquid ejection head.

14. the piezoelectric actuator has an upper electrode located on the opposite side of the intermediate electrode from the pressure surface and facing the intermediate electrode with at least a part of the first active region therebetween; The driver includes: In the liquid ejection control, a voltage is applied to the upper electrode and the intermediate electrode to apply an electric field to the first active region; In the reorientation control, an electric field is applied to the non-active region by applying a voltage to the reorientation electrode and the lower electrode without applying a potential to the intermediate electrode. The liquid ejection head according to claim 13.

15. A flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface; A driver that drives the piezoelectric actuator; It has When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the driver controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, When the side of the piezoelectric actuator opposite to the flow path member is referred to as a first side and the side of the piezoelectric actuator facing the flow path member is referred to as a second side, a first piezoelectric layer, a second piezoelectric layer, a third piezoelectric layer, and a fourth piezoelectric layer, which are laminated in this order from the first side to the second side; a first electrode overlapping the first side surface of the first piezoelectric layer and overlapping the central portion in a plan view; a second electrode overlapping the second surface of the first piezoelectric layer and overlapping the central portion in a plan view; a third electrode overlapping the second surface of the second piezoelectric layer and overlapping the central portion, the peripheral portion, and the outer region in a planar perspective view; a fourth electrode overlapping the second side surface of the fourth piezoelectric layer and overlapping the peripheral portion and the outer region in a planar perspective view, The first active region is a region of the first piezoelectric layer sandwiched between the first electrode and the second electrode; a region of the second piezoelectric layer that is sandwiched between the second electrode and a portion of the third electrode that overlaps with the central portion, The second active region is the third and fourth piezoelectric layers have a region sandwiched between a portion overlapping the peripheral portion and the outer region of the third electrode and the fourth electrode, The piezoelectric actuator includes: a non-active region made of a piezoelectric material and connected to the outer periphery of the first active region; a reorientation electrode overlying the first side surface of the first piezoelectric layer and overlying the peripheral portion and the outer region in a plan view, the driver performs a reorientation control to apply an electric field in the thickness direction to the inactive region when the liquid ejection control is not being performed; The inactive region includes a region of the first and second piezoelectric layers sandwiched between the reorientation electrode and the fourth electrode. Liquid ejection head.

16. a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface; A driver that drives the piezoelectric actuator; It has When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping an inner peripheral portion of the pressure chamber and an outer region of the pressure chamber in a plan view perspective of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, the driver controls the intensity of the electric field applied to the first active region in the thickness direction and the intensity of the electric field applied to the second active region in the thickness direction so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation by changing the applied electric field in controlling the ejection of droplets; In a plan view perspective of the pressure surface, an area of ​​a second portion of the second active region located outside the pressure chamber is larger than an area of ​​a first portion of the second active region overlapping the pressure chamber. Liquid ejection head.

17. a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface; A driver that drives the piezoelectric actuator; It has When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping an inner peripheral portion of the pressure chamber and an outer region of the pressure chamber when viewed from above on the pressure application surface; a non-active region made of a piezoelectric material and connected to the outer periphery of the first active region; When one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, a liquid ejection control for ejecting droplets, the liquid ejection control controlling an intensity of an electric field applied to the first active region in the thickness direction and an intensity of an electric field applied to the second active region in the thickness direction such that the second active region undergoes the first deformation during at least a portion of a period during which the first active region undergoes the first deformation by changing the applied electric field; and performing a reorientation control by applying an electric field in the thickness direction to the inactive region when the liquid ejection control is not being performed. Liquid ejection head.

18. A liquid ejection head; A control unit for controlling the liquid ejection head; It has The liquid ejection head includes: a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface, When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping an inner peripheral portion of the pressure chamber and an outer region of the pressure chamber when viewed from above on the pressure application surface; a non-active region made of a piezoelectric material, located on the opposite side of the second active region from the pressure application surface, connected to the outer periphery of the first active region, and extending through a thickness of the first active region; when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the control unit controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation by changing the applied electric field, In the liquid ejection control, the maximum value of the intensity of the first electric field is greater than the maximum value of the intensity of the second electric field. Recording device.

19. A liquid ejection head; A control unit for controlling the liquid ejection head; It has The liquid ejection head includes: a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface, When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping an inner peripheral portion of the pressure chamber and an outer region of the pressure chamber in a plan view perspective of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, the control unit controls, in a control of ejecting droplets, a strength of an electric field applied to the first active region in the thickness direction and a strength of an electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation by changing an applied electric field; In a planar perspective view of the pressure surface, an area of ​​the second active region overlapping the outer region is larger than an area of ​​the second active region overlapping the pressure chamber. Recording device.

20. A liquid ejection head; A control unit for controlling the liquid ejection head; It has The liquid ejection head includes: a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface, When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping an inner peripheral portion of the pressure chamber and an outer region of the pressure chamber when viewed from above on the pressure application surface; a non-active region made of a piezoelectric material and connected to the outer periphery of the first active region; When one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, a liquid ejection control for ejecting droplets, the liquid ejection control controlling an intensity of an electric field applied to the first active region in the thickness direction and an intensity of an electric field applied to the second active region in the thickness direction such that the second active region undergoes the first deformation during at least a portion of a period during which the first active region undergoes the first deformation by changing the applied electric field; and performing a reorientation control by applying an electric field along the thickness direction to the inactive region when the liquid ejection control is not being performed. Recording device.

21. A liquid ejection head; A control unit for controlling the liquid ejection head; It has The liquid ejection head includes: a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface, When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the control unit controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, The position of the thickness direction is different from each other, and the three or more electrodes each apply at least one of the first electric field and the second electric field, a distance in the thickness direction between two electrodes that are adjacent to each other among three or more positions in the thickness direction of the three or more electrodes and that apply the first electric field is shorter than a distance in the thickness direction between two electrodes that are adjacent to each other among the three or more positions and that apply the second electric field. Recording device.

22. A liquid ejection head; A control unit for controlling the liquid ejection head; It has The liquid ejection head includes: a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface, When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the control unit controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, When the side of the piezoelectric actuator opposite to the flow path member is referred to as a first side and the side of the piezoelectric actuator facing the flow path member is referred to as a second side, a first piezoelectric layer, a second piezoelectric layer, a third piezoelectric layer, and a fourth piezoelectric layer, which are laminated in this order from the first side to the second side; a first electrode overlapping the first side surface of the first piezoelectric layer and overlapping the central portion in a plan view; a second electrode overlapping the second surface of the first piezoelectric layer and overlapping the central portion in a plan view; a third electrode overlapping the second surface of the second piezoelectric layer and overlapping the central portion, the peripheral portion, and the outer region in a planar perspective view; a fourth electrode overlapping the second side surface of the fourth piezoelectric layer and overlapping the peripheral portion and the outer region in a planar perspective view, The first active region is a region of the first piezoelectric layer sandwiched between the first electrode and the second electrode; a region of the second piezoelectric layer that is sandwiched between the second electrode and a portion of the third electrode that overlaps with the central portion, The second active region is the third and fourth piezoelectric layers have a region sandwiched between a portion overlapping the peripheral portion and the outer region of the third electrode and the fourth electrode, The piezoelectric actuator has a conductor pattern that overlaps the second surface of the third piezoelectric layer and is positioned outside the second active region in a plan view. Recording device.

23. A liquid ejection head; A control unit for controlling the liquid ejection head; It has The liquid ejection head includes: a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface, When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the control unit controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, An insulating layer is provided between the second active region and the flow path member. Recording device.

24. A liquid ejection head; A control unit for controlling the liquid ejection head; It has The liquid ejection head includes: a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface, When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the control unit controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, the piezoelectric actuator is made of a piezoelectric body and has a non-active region connected to an outer periphery of the first active region; the control unit performs a reorientation control to apply an electric field in the thickness direction to the inactive region when the liquid ejection control is not being performed, The piezoelectric actuator includes: a reorientation electrode overlying the non-active region on an opposite side to the pressure surface; an intermediate electrode located between the non-active region and the second active region; a lower electrode overlapping the second active region on the pressure surface side, The control unit is In the liquid ejection control, a voltage is applied to the intermediate electrode and the lower electrode to apply an electric field to the second active region; In the reorientation control, an electric field is applied to the non-active region by applying a voltage to the reorientation electrode and the lower electrode, or by applying a voltage to the reorientation electrode and the intermediate electrode. Recording device.

25. A liquid ejection head; A control unit for controlling the liquid ejection head; It has The liquid ejection head includes: a flow path member having a pressure surface and a pressure chamber opening to the pressure surface; a piezoelectric actuator overlying the pressure surface, When the direction perpendicular to the pressure application surface is referred to as the thickness direction of the piezoelectric actuator, a first active region that is made of a piezoelectric body polarized in the thickness direction and overlaps a center portion of the pressure chamber when viewed from above on the pressure surface; a second active region made of a piezoelectric body polarized in the thickness direction, located closer to the pressure application surface than the first active region, and overlapping a periphery of the pressure chamber and an area outside the pressure chamber in a plan view of the pressure application surface, when one of the expansion and contraction in a direction along the pressure surface is referred to as a first deformation and the other is referred to as a second deformation, in liquid ejection control for ejecting liquid, the control unit controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction, so that the second active region causes the first deformation during at least a portion of a period during which the first active region causes the first deformation, In the liquid ejection control, a maximum value of the intensity of the first electric field is greater than a maximum value of the intensity of the second electric field, When the side of the piezoelectric actuator opposite to the flow path member is referred to as a first side and the side of the piezoelectric actuator facing the flow path member is referred to as a second side, a first piezoelectric layer, a second piezoelectric layer, a third piezoelectric layer, and a fourth piezoelectric layer, which are laminated in this order from the first side to the second side; a first electrode overlapping the first side surface of the first piezoelectric layer and overlapping the central portion in a plan view; a second electrode overlapping the second surface of the first piezoelectric layer and overlapping the central portion in a plan view; a third electrode overlapping the second surface of the second piezoelectric layer and overlapping the central portion, the peripheral portion, and the outer region in a planar perspective view; a fourth electrode overlapping the second side surface of the fourth piezoelectric layer and overlapping the peripheral portion and the outer region in a planar perspective view, The first active region is a region of the first piezoelectric layer sandwiched between the first electrode and the second electrode; a region of the second piezoelectric layer that is sandwiched between the second electrode and a portion of the third electrode that overlaps with the central portion, The second active region is the third and fourth piezoelectric layers have a region sandwiched between a portion overlapping the peripheral portion and the outer region of the third electrode and the fourth electrode, The piezoelectric actuator includes: a non-active region made of a piezoelectric material and connected to the outer periphery of the first active region; a reorientation electrode overlying the first side surface of the first piezoelectric layer and overlying the peripheral portion and the outer region in a plan view, the control unit performs a reorientation control to apply an electric field in the thickness direction to the inactive region when the liquid ejection control is not being performed, The inactive region includes a region of the first and second piezoelectric layers sandwiched between the reorientation electrode and the fourth electrode. Recording device.

Images