Liquid dispensing head and recording device

Abstract

To improve durability of a head by reducing stress generated in a piezoelectric element.SOLUTION: A piezoelectric actuator 13 has a first active region 53A and a second active region 53B. The first active region overlaps a center section of a pressure chamber 21. The second active region is positioned on a pressurizing surface side of the first active region and overlaps a peripheral edge section of the pressure chamber and a region outside the pressure chamber. By driving not only the first active region but also the second active region, displacement as the whole of the piezoelectric element can be increased. In the second active region, stress is easy to be increased in the vicinity of an outer edge of the pressure chamber. By making intensity of an electric field to be applied to the first active region larger than intensity of an electric field to be applied to the second active region, stress applied to the second active region is reduced and durability of a head can be improved.SELECTED DRAWING: Figure 11

Description

Technical Field

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

Background Art

[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 diaphragm that covers an upper opening of a pressure chamber filled with a liquid (ink), and a piezoelectric layer that overlaps the diaphragm. When the piezoelectric layer expands or contracts in a direction along the surface, the piezoelectric actuator undergoes a bending deformation like a bimetal. As a result, pressure is applied to the pressure chamber and the liquid is ejected. The piezoelectric layer is, for example, extended or contracted in a direction along the surface by applying a voltage in a region overlapping the central portion of the pressure chamber in a plan view. In Patent Documents 1 and 2, a configuration in which a voltage is also applied to a portion of the diaphragm made of a piezoelectric material that is located on the outer edge side of the pressure chamber in a plan view is disclosed. In Patent Documents 3 and 4, techniques for applying an electric field to a piezoelectric material to perform polarization treatment are disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0004] A liquid discharge head according to one aspect of the present disclosure comprises a flow channel member, a piezoelectric actuator, and a driver. The flow channel member has a pressurizing surface and a pressure chamber opening to the pressurizing surface. The piezoelectric actuator overlaps the pressurizing surface. The driver drives the piezoelectric actuator. The piezoelectric actuator has a first active region and a second active region. The direction perpendicular to the pressurizing surface is referred to as the thickness direction. In this case, the first active region consists of a piezoelectric body polarized in the thickness direction and overlaps the central part of the pressure chamber in a plan view of the pressurizing surface. The second active region consists of a piezoelectric body polarized in the thickness direction, is located closer to the pressurizing surface than the first active region, and overlaps the peripheral edge of the pressure chamber and the area outside the pressure chamber in a plan view of the pressurizing surface. In liquid discharge control for discharging 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. This control causes the second active region to undergo either extension or contraction in the direction along the pressure surface for at least a portion of the period during which the first active region undergoes either extension or contraction in the direction along the pressure surface. In the liquid discharge 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.

[0005] A liquid discharge head according to one aspect of the present disclosure includes a flow channel member, a piezoelectric actuator, and a driver. The flow channel member has a pressurizing surface and a pressure chamber opening to the pressurizing surface. The piezoelectric actuator overlaps the pressurizing surface. The driver drives the piezoelectric actuator. The piezoelectric actuator has a first active region and a second active region. The direction perpendicular to the pressurizing surface is referred to as the thickness direction. In this case, the first active region consists of a piezoelectric body polarized in the thickness direction and overlaps the central part of the pressure chamber in a plan view of the pressurizing surface. The second active region consists of a piezoelectric body polarized in the thickness direction and is located closer to the pressurizing surface than the first active region, and overlaps the peripheral edge of the pressure chamber and the area outside the pressure chamber in a plan view of the pressurizing surface. In controlling the discharge of liquid droplets, 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. As a result, during at least a portion of the period in which the first active region undergoes either extension or contraction in the direction along the pressure surface, the second active region undergoes either extension or contraction in the direction along the pressure surface. In a plan view of the pressure surface, the area of ​​the second portion of the second active region located outside the pressure chamber is larger than the area of ​​the first portion of the second active region overlapping the pressure chamber.

[0006] A liquid discharge head according to one aspect of the present disclosure comprises a flow channel member, a piezoelectric actuator, and a driver. The flow channel member has a pressurizing surface and a pressure chamber opening to the pressurizing surface. The piezoelectric actuator overlaps the pressurizing surface. The driver drives the piezoelectric actuator. The piezoelectric actuator has a first active region, a second active region, and an inactive region. The direction perpendicular to the pressurizing surface is referred to as the thickness direction. In this case, the first active region consists of a piezoelectric material polarized in the thickness direction and overlaps the central part of the pressure chamber in a plan view of the pressurizing surface. The second active region consists of a piezoelectric material polarized in the thickness direction and is located closer to the pressurizing surface than the first active region, and overlaps the peripheral edge of the pressure chamber and the area outside the pressure chamber in a plan view of the pressurizing surface. The inactive region consists of a piezoelectric material and is connected to the outer circumference of the first active region. The driver performs liquid discharge control and reorientation control. In the liquid discharge control, 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. As a result, the second active region undergoes either expansion or contraction in the direction along the pressure surface for at least a portion of the period during which the first active region undergoes either expansion or contraction in the direction along the pressure surface. In the reorientation control, the driver applies an electric field in the thickness direction to the inactive region when the liquid discharge control is not being performed.

[0007] A recording device according to one aspect of the present disclosure includes a liquid discharge head and a control unit for controlling the liquid discharge head. The liquid discharge head includes a flow channel member and a piezoelectric actuator. The flow channel member has a pressurizing surface and a pressure chamber opening to the pressurizing surface. The piezoelectric actuator overlaps the pressurizing surface. The piezoelectric actuator also has a first active region and a second active region. The direction perpendicular to the pressurizing surface is referred to as the thickness direction. In this case, the first active region consists of a piezoelectric body polarized in the thickness direction and overlaps the central part of the pressure chamber in a plan view of the pressurizing surface. The second active region consists of a piezoelectric body polarized in the thickness direction and is located closer to the pressurizing surface than the first active region, and overlaps the peripheral edge of the pressure chamber and the area outside the pressure chamber in a plan view of the pressurizing surface. In liquid discharge control for discharging 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. As a result, during at least a portion of the period in which the first active region undergoes either extension or contraction in the direction along the pressurized surface, the second active region undergoes either extension or contraction in the direction along the pressurized surface. In the liquid discharge 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.

[0008] A recording device according to one aspect of the present disclosure includes a liquid discharge head and a control unit for controlling the liquid discharge head. The liquid discharge head includes a flow channel member and a piezoelectric actuator. The flow channel member has a pressure surface and a pressure chamber opening to the pressure surface. The piezoelectric actuator overlaps the pressure surface. The piezoelectric actuator also has a first active region and a second active region. The direction perpendicular to the pressure surface is referred to as the thickness direction. In this case, the first active region consists of a piezoelectric body polarized in the thickness direction and overlaps the central part of the pressure chamber in a plan view of the pressure surface. The second active region consists of a piezoelectric body polarized in the thickness direction and is located closer to the pressure surface than the first active region, and overlaps the peripheral edge of the pressure chamber and the area outside the pressure chamber in a plan view of the pressure surface. In controlling the discharge of liquid droplets, the control unit 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. As a result, during at least a portion of the period in which the first active region undergoes either extension or contraction in the direction along the pressurizing surface, the second active region undergoes either extension or contraction in the direction along the pressurizing surface. In a planar view of the pressurizing surface, the area of ​​the second active region overlapping the outer region is greater than the area of ​​the second active region overlapping the pressure chamber.

[0009] A recording device according to one aspect of the present disclosure includes a liquid discharge head and a control unit for controlling the liquid discharge head. The liquid discharge head includes a flow channel member and a piezoelectric actuator. The flow channel member has a pressurizing surface and a pressure chamber opening to the pressurizing surface. The piezoelectric actuator overlaps the pressurizing surface. The piezoelectric actuator also has a first active region, a second active region, and an inactive region. The direction perpendicular to the pressurizing surface is referred to as the thickness direction. In this case, the first active region consists of a piezoelectric material polarized in the thickness direction and overlaps the central part of the pressure chamber in a plan view of the pressurizing surface. The second active region consists of a piezoelectric material polarized in the thickness direction and is located closer to the pressurizing surface than the first active region, and overlaps the peripheral edge of the pressure chamber and the area outside the pressure chamber in a plan view of the pressurizing surface. The inactive region consists of a piezoelectric material and is connected to the outer circumference of the first active region. The control unit performs liquid discharge control and reorientation control. In the liquid discharge control, the control unit 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. As a result, the second active region undergoes either expansion or contraction in the direction along the pressure surface for at least a portion of the period during which the first active region undergoes either expansion or 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 discharge control is not being performed. [Brief explanation of the drawing]

[0010] [Figure 1A] This is a side view of a recording device according to the first embodiment. [Figure 1B] This is a plan view of the recording device according to the first embodiment. [Figure 2] This is a plan view of a part of the liquid discharge head according to the first embodiment. [Figure 3] This is a cross-sectional view along line III-III in Figure 2. [Figure 4]It is a plan view of a pressure chamber of a liquid ejection head according to the first embodiment. [Figure 5] It is a cross-sectional view schematically showing an upper part of a piezoelectric actuator and a flow path member of a liquid ejection head according to the first embodiment. [Figure 6] It is a schematic cross-sectional view showing a polarization direction of a piezoelectric layer in a piezoelectric actuator according to the first embodiment. [Figure 7] It is an exploded perspective view of a part of a liquid ejection head according to the first embodiment. [Figure 8] It is a partially enlarged view of FIG. 7. [Figure 9] It is a plan view schematically showing a part of a conductor layer of a liquid ejection head according to the first embodiment. [Figure 10] It is a cross-sectional view taken along the line X-X of FIG. 9. [Figure 11] It is a schematic cross-sectional view showing a potential when discharging liquid in a liquid ejection head according to the first embodiment. [Figure 12] It is a schematic cross-sectional view showing a potential during polarization treatment in a liquid ejection head according to the first embodiment. [Figure 13] It is a schematic cross-sectional view of a liquid ejection head according to the second embodiment. [Figure 14] It is a schematic cross-sectional view of a liquid ejection head according to the third embodiment. [Figure 15] It is a schematic cross-sectional view of a liquid ejection head according to the fourth embodiment. [Figure 16] It is a schematic cross-sectional view of a liquid ejection head according to the fifth embodiment. [Figure 17A] It is a cross-sectional view showing a configuration of a piezoelectric layer according to a modification example. [Figure 17B] It is a cross-sectional view showing a configuration of a piezoelectric layer according to another modification example.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following drawings are schematic. Therefore, details may be omitted. Also, dimensional ratios do not necessarily match the actual ones. Dimensional ratios between multiple drawings do not necessarily match either. Specific dimensions may be shown larger than actual, and specific shapes may be exaggerated.

[0012] In the description of the embodiments after the second embodiment, basically, differences from the previously described embodiments will be described. For matters not particularly mentioned, they may be the same as those in the previously described embodiments or inferred from the previously described embodiments. Also, between multiple embodiments, for corresponding configurations, even if the details are different, they may be given the same reference numerals.

[0013] "Similar" in the present disclosure includes, but is not limited to, similarity in mathematics. Similarity in mathematics means that when one shape is enlarged or reduced (or when such a scale transformation is not performed), it becomes congruent with another shape. However, in light of common technical knowledge and the like, if a relationship close to this mathematical similarity can be reasonably considered to hold, it may be regarded as similar. For example, an ellipse and an ellipse having an outer edge located inside or outside at a certain distance from the outer edge of the ellipse have different ratios of the major axis to the minor axis between the two, so they are not similar in mathematics. However, such a relationship may also be included in the similarity in the present disclosure.

[0014] Also, terms indicating various shapes in the present 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 may be composed only of curves that are convex outward, and any shape that can specify a longitudinal direction and a lateral direction that are generally orthogonal to each other may be acceptable. Also, for example, a rectangle may have rounded corners.

[0015] <First Embodiment> (Overall Configuration of Printer) Figure 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 one embodiment of the present disclosure. Figure 1(b) is a schematic top view of the printer 1.

[0016] Note that while head 2 or printer 1 can be positioned vertically in any direction, for convenience, the vertical direction of the paper in Figure 1(a) is sometimes considered the vertical direction, and terms such as "top" or "bottom" are used accordingly. Furthermore, unless otherwise specified, the terms "planar view" or "planar perspective" refer to viewing in the vertical direction of the paper in Figure 1(a).

[0017] The printer 1 moves the printing paper P (an example of a recording medium) relative to the head 2 by transporting it from the paper feed roller 80A to the recovery roller 80B. The paper feed roller 80A, the recovery roller 80B, and various rollers described later constitute a moving section 85 that moves the printing paper P and the head 2 relative to each other. The control unit 88 controls the head 2 based on print data such as images and characters to eject liquid toward the printing paper P, causing droplets to land on the printing paper P and recording such as printing on the printing paper P.

[0018] In this embodiment, the head 2 is fixed to the printer 1, and the printer 1 is a so-called line printer. Another embodiment of the recording device is a so-called serial printer, in which the head 2 is moved in a direction intersecting (for example, approximately perpendicular to) the transport direction of the printing paper P while ejecting droplets, and the printing paper P is transported alternately.

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

[0020] The head 2 mounted on the frame 70 is positioned so that the part that ejects the 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 they may be connected to the control unit 88 via a distribution unit that distributes print data. For example, the control unit 88 may send print data to one distribution unit, and one distribution unit may distribute the print data to the 20 heads 2. Alternatively, for example, the control unit 88 may distribute print data to four distribution units corresponding to four head groups 72, and each distribution unit may distribute the print data to five heads 2 within the corresponding head group 72.

[0022] The head 2 has an elongated shape, oriented from front to back in Figure 1(a) and vertically in Figure 1(b). Within one head group 72, three heads 2 are arranged along a direction intersecting the transport direction of the printing paper P (for example, a nearly perpendicular direction), while the other two heads 2 are positioned offset along the transport direction, one by one between the three heads 2. In other words, within one head group 72, the heads 2 are arranged in a staggered pattern. The heads 2 are arranged such that the printable area of ​​each head 2 connects in the width direction of the printing paper P, that is, in the direction intersecting the transport direction of the printing paper P, or their edges overlap, enabling gap-free printing in the width direction of the printing paper P.

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

[0024] The number of heads 2 installed in printer 1 is sufficient if printing is done in a single color and within the printable area of ​​one head 2. The number of heads 2 included in head group 72, and the number of head group 72, can be changed as appropriate depending on the object to be printed and the printing conditions. For example, the number of head group 72 can be increased to print in more colors. Also, by arranging multiple head group 72 that print in the same color and printing alternately in the transport direction, the transport speed can be increased even when using heads 2 with the same performance. This increases the printable area per unit of time. Alternatively, multiple head group 72 that print in the same color can be prepared and arranged offset 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. As a coating agent, for example, when using a recording medium that is not easily permeable to liquids, a coating agent that forms a liquid-receiving layer can be used to facilitate liquid fixation. Alternatively, as a coating agent, when using a recording medium that is easily permeable to liquids, a coating agent that forms a liquid penetration suppression layer can be used to prevent excessive liquid bleeding or mixing with other liquids that land adjacent to it. In addition to printing with the head 2, the coating agent may also be uniformly applied by a coating machine 76 controlled by the control unit 88.

[0026] Printer 1 prints on the printing paper P, which is the recording medium. The printing paper P is wound onto the paper feed roller 80A. The printing paper P is fed 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 the recovery roller 80B. When printing, the transport rollers 82C are rotated to transport the printing paper P at a constant speed, and the print is made by the head 2.

[0027] Next, we will explain the details of printer 1, in the order in which the printing paper P is transported. The printing paper P, fed from the paper feed roller 80A, passes between the two guide rollers 82A and then under the coating machine 76. The coating machine 76 applies the aforementioned 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 generally isolated from the outside, although it is connected to the outside in some areas, such as where the printing paper P enters and exits. The head chamber 74 is controlled by control factors such as temperature, humidity, and atmospheric pressure by the control unit 88, etc., as needed. Since the head chamber 74 is less affected by external disturbances compared to the outside where the printer 1 is installed, the range of fluctuations of the aforementioned control factors can be narrower than in the outside.

[0029] The head chamber 74 has five guide rollers 82B, and the printing paper P is transported over the guide rollers 82B. The five guide rollers 82B are arranged so that, when viewed from the side, their centers are convex in the direction in which the frame 70 is located. As a result, the printing paper P transported over the five guide rollers 82B is in an arc shape when viewed from the side, and tension is applied to the printing paper P so that the printing paper P between each guide roller 82B becomes flat. One frame 70 is placed between two guide rollers 82B. The angle at which the frame 70 is installed is slightly changed so that it is parallel to the printing paper P being transported below it.

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

[0031] Drying in the dryer 78 makes it less likely for overlapping sheets of printing paper P to stick together or for undried liquid to rub against each other in the recovery roller 80B. For high-speed printing, drying must also be done quickly. To speed up drying, the dryer 78 may use multiple drying methods sequentially, or multiple drying methods may be used in combination. Examples of drying methods used in such cases include blowing hot air, irradiating with infrared rays, or contact with a heated roller. When irradiating with infrared rays, infrared rays within a specific frequency range may be used to speed up drying while minimizing damage to the printing paper P. When the printing paper P is in contact with a heated roller, the time for heat transfer may be extended by transporting the printing paper P along the cylindrical surface of the roller. The transport range along the cylindrical surface of the roller should ideally be at least 1 / 4 of the roller's circumference, and even better, at least 1 / 2 of the roller's circumference. When printing with UV-curable inks, a UV irradiation light source may be placed in place of the dryer 78, or in addition to the dryer 78. The UV light source may be placed between each frame 70.

[0032] Printer 1 may be equipped with a cleaning unit for cleaning the head 2. The cleaning unit performs cleaning, for example, by wiping and / or capping. Wiping involves, for example, using a flexible wiper to rub the surface of the part where the liquid is ejected, for example, the ejection surface 11a (described later), to remove any liquid adhering to that surface. Cleaning by capping is performed, for example, as follows: First, a cap is placed over the part where the liquid is ejected, for example, the ejection surface 11a (this is called capping), so that the ejection surface 11a and the cap are almost sealed and a space is created. In this state, the liquid is ejected repeatedly to remove any liquid that has become more viscous than the standard state, foreign matter, etc., that has been clogging the ejection hole 3 (described later). Because it is capped, the liquid being cleaned is less likely to splash onto the printer 1, and the liquid is less likely to adhere to the transport mechanism such as the printing paper P and rollers. The ejection surface 11a after cleaning may be wiped further. Cleaning by wiping and / or capping may be performed manually by a person operating the wiper and / or cap attached to the printer 1, or it may be performed automatically by the control unit 88.

[0033] The recording medium may be other than printing paper P, such as a roll of cloth. Alternatively, instead of directly transporting the printing paper P, the printer 1 may transport the recording medium on a conveyor belt. In this way, sheet paper, cut cloth, wood, or tiles can be used as the recording medium. Furthermore, the print head 2 may be configured to eject a liquid containing conductive particles to print wiring patterns for electronic devices. Additionally, the print head 2 may eject a predetermined amount of liquid chemical agent or a liquid containing a chemical agent towards a reaction vessel, and a chemical mixture may be reacted to produce a chemical product.

[0034] Furthermore, the printer 1 may be fitted with a position sensor, a speed sensor, and / or a temperature sensor, and the control unit 88 may control each part of the printer 1 according to the state of each part of the printer 1 as determined from the information from each sensor. For example, if the temperature of the head 2, the temperature of the liquid in the liquid supply tank that supplies liquid to the head 2, and / or the pressure that the liquid in the liquid supply tank applies to the head 2 are affecting the discharge characteristics of the discharged liquid (e.g., discharge volume and / or discharge speed), the control unit 88 may change the drive signal for discharging the liquid according to this information.

[0035] (discharge surface) Figure 2 is a plan view showing a portion of the surface of the head 2 facing the printing paper P (discharge surface 11a). For convenience, this figure includes a Cartesian coordinate system consisting of the D1, D2, and D3 axes. The D1 axis is defined parallel to the direction of relative movement between the head 2 and the printing paper P. The relationship between the positive and negative signs of the D1 axis and the direction of travel of the printing paper P relative to the head 2 is not particularly relevant in this embodiment. The D2 axis is defined parallel to the discharge surface 11a and the printing paper P, and perpendicular to the D1 axis. The positive and negative signs of the D2 axis are also not particularly relevant. The D3 axis is defined perpendicular to the discharge surface 11a and the printing paper P. The -D3 side (the front side of the paper in Figure 2) is the direction from the head 2 to the printing paper P. Note that when simply referring to the D3 direction, it may refer to either the +D3 direction toward the +D3 side or the -D3 direction toward the -D3 side. As previously described, head 2 has a shape with the D2 direction as its longitudinal direction, and here, one end portion in that longitudinal direction is shown.

[0036] The ejection surface 11a is, for example, a plane that constitutes most of the surface of the head 2 facing the printing paper P. Furthermore, the ejection surface 11a is, for example, roughly rectangular with the D2 direction as its longitudinal direction. Multiple ejection holes 3 for ejecting ink droplets are opened on the ejection surface 11a. The multiple ejection holes 3 are arranged so that their positions differ from each other in a direction (D2 direction) perpendicular to the direction of relative movement between the head 2 and the printing paper P (D1 direction). Therefore, by ejecting ink droplets from the multiple ejection holes 3 while moving the head 2 and the printing paper P relative to each other using the moving unit 85, any two-dimensional image can be formed.

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

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

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

[0040] The head body 7 is generally a plate-shaped member, with one side of the plate being the discharge surface 11a described above. The thickness of the head body 7 is, for example, 0.5 mm to 2 mm. The head body 7 is a piezo-type head that discharges droplets by applying pressure to the liquid through the mechanical strain of a piezoelectric element. The head body 7 has a plurality of discharge elements 9, each containing a discharge hole 3. The plurality of discharge elements 9 and the configurations related to the plurality of discharge elements 9 (for example, the wiring connected to the plurality of discharge elements 9) may be basically the same as each other. The plurality of discharge elements 9 are arranged two-dimensionally along the discharge surface 11a.

[0041] From another perspective, the print head body 7 includes a roughly plate-shaped flow channel member 11 through which liquid (ink) flows, and a piezoelectric actuator 13 for applying pressure to the liquid within the flow channel member 11. Multiple ejection elements 9 are composed of the flow channel member 11 and the piezoelectric actuator 13. The ejection surface 11a is formed by the flow channel member 11. The surface of the flow channel member 11 opposite to the ejection surface 11a is referred to as the pressurized surface 11b.

[0042] The flow channel member 11 has a common flow channel 15 and a plurality of individual flow channels 17 (one is shown in Figure 3) each connected to the common flow channel 15. Each individual flow channel 17 has the discharge hole 3 described above, and also has a connecting flow channel 19, a pressure chamber 21, and a partial flow channel 23 in order from the common flow channel 15 to the discharge hole 3.

[0043] Multiple individual channels 17 and a common channel 15 are filled with liquid. As the volume of the multiple pressure chambers 21 changes and pressure is applied to the liquid, the liquid is sent from the multiple pressure chambers 21 to the multiple partial channels 23, and multiple droplets are discharged from the multiple discharge holes 3. In addition, the multiple pressure chambers 21 are replenished with liquid from the common channel 15 via multiple connecting channels 19. The piezoelectric actuator 13 (piezoelectric element 27) applies pressure to the liquid in the pressure chambers 21, for example, by causing a bending deformation toward the pressure chamber 21 side and / or by returning from a bent state toward the opposite side of the pressure chamber 21 to a flat state.

[0044] The flow channel member 11 is constructed by stacking, for example, multiple plates 25A to 25J (hereinafter, A to J may be omitted). Multiple holes (mainly through holes; recesses are also possible) are formed in the plates 25, which constitute multiple individual flow channels 17 and a common flow channel 15. The thickness of the multiple plates 25 and the number of stacks may be appropriately set according to the shape of the multiple individual flow channels 17 and the common flow channel 15. The multiple plates 25 may be formed from an appropriate material. For example, the multiple plates 25 are made of metal or resin. The thickness of the plates 25 is, for example, 10 μm or more and 300 μm or less. The plates 25 are fixed to each other by, for example, an adhesive (not shown) interposed between the plates 25.

[0045] (Flow channel shape) The specific shape and dimensions of each channel within the channel member 11 may be set as appropriate. In the illustrated example, they are as follows:

[0046] The common channel 15 extends in the longitudinal direction of the head 2 (the direction through the paper in Figure 3). While only one common channel 15 may be provided, multiple channels may be provided in parallel to each other, for example. The cross-sectional shape of the common channel 15 is rectangular.

[0047] Multiple individual channels 17 (or discharge elements 9 from another perspective) are arranged along the length of each common channel 15. Consequently, the multiple discharge holes 3 individually contained within the multiple individual channels 17 are also arranged along the common channel 15. In the arrangement of discharge holes 3 shown in Figure 2, for example, two rows of discharge holes 3 may be arranged on each side of one common channel 15. In total, 16 rows of discharge holes 3 may be arranged across four common channels 15.

[0048] The pressure chamber 21 opens, for example, to the pressurized surface 11b and is closed by the piezoelectric actuator 13. The pressure chamber 21 may also be closed by a plate 25. However, this can be considered a matter of whether the plate 25 that closes the pressure chamber 21 is considered as part of the flow path member 11 or as part of the piezoelectric actuator 13. In this disclosure, the layer (plate) above the pressure chamber 21 is considered as part of the piezoelectric actuator 13.

[0049] The shapes of the multiple pressure chambers 21 are, for example, identical to 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 extends along the pressurizing surface 11b with a constant thickness. However, the pressure chamber 21 may have parts with different thicknesses. The thin shape is, for example, a shape in which the thickness is smaller than any of the diameters in a plan view.

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

[0051] The planar shape of the pressure chamber 21 may be, for example, a shape having mutually orthogonal longitudinal and transverse directions (e.g., a rhombus or an ellipse), or it may be a shape in which such directions cannot be conceived (e.g., a circle). Furthermore, the relationship between the longitudinal and transverse directions and the arrangement of the multiple pressure chambers 21 is also arbitrary. In the description of this embodiment, as will be described later, a shape that is a combination of a circle and an ellipse will be taken as an example. From another viewpoint, a shape in which longitudinal and transverse directions can be conceived will be taken as an example. In the illustrated example, the left-right direction of the paper in Figure 3 is the longitudinal direction of the pressure chamber 21. This direction is, for example, the direction that intersects (e.g., orthogonal) the direction in which the common flow path 15 extends, and from another viewpoint, it is the transverse direction of the head body 7.

[0052] In embodiments where the cross-sectional shape of the pressure chamber 21 parallel to the pressurizing surface 11b is not constant in the vertical direction, the description of the planar shape of the pressure chamber 21 in this disclosure may be applied, for example, to the planar shape of the pressurizing surface 11b (the opening surface of the pressure chamber 21). This is because the shape of the pressurizing surface 11b has a significant influence on the pressure received from the piezoelectric actuator 13 in the pressure chamber 21.

[0053] The partial flow path 23 extends from the pressure chamber 21 toward the discharge surface 11a. The shape of the partial flow path 23 is generally cylindrical. The partial flow path 23 may extend with an inclination in the vertical direction toward the discharge surface 11a from the pressure chamber 21 (as shown in the example), or it may extend without an inclination. Furthermore, the area of ​​the cross-section of the partial flow path 23 may differ depending on its vertical position. In a plan view, the partial flow path 23 is connected, for example, to the 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 into 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 shape of the longitudinal cross-section of the discharge hole 3 is tapered, with the diameter decreasing towards the discharge surface 11a side. However, the discharge hole 3 may be partially or entirely reverse-tapered.

[0055] The connecting channel 19 has, for example, a portion extending upward from the upper surface of the common channel 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 small cross-sectional area perpendicular to the flow direction and functions as a so-called constriction. In a plan view, the connection position of the connecting channel 19 to the pressure chamber 21 is, for example, the end of the lower surface of the pressure chamber 21 opposite to the partial channel 23 with respect to the center of the lower surface.

[0056] Regarding the arrangement of the multiple pressure chambers 21, the description of the arrangement of the multiple discharge holes 3, which was explained with reference to Figure 2, may be used as a reference. However, the arrangement of the multiple pressure chambers 21 and the arrangement of the multiple discharge holes 3 do not have to be different. For example, the arrangement of the multiple pressure chambers 21 and the arrangement of the multiple discharge holes 3 may be different by making the shapes of the multiple partial flow paths 23 different from each other. Furthermore, unlike the multiple discharge holes 3 shown in Figure 2, the multiple pressure chambers 21 may be uniformly distributed in both the D1 and D2 directions (the pitch between rows of pressure chambers 21 may be constant), or they may be arranged in fewer rows than the number of rows of discharge holes 5.

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

[0058] The planar shape of the pressure chamber 21 is, for example, the sum of a circular region C1 and regions R2 (one of which is hatched) that protrude from the circular region C1 in a predetermined direction (up and down direction on the paper). The outer edge of region R2 opposite to the circular region C1 (shown by a solid line) is a curve that bulges outward. The curvature of this curve (or the average value if it is not constant) is, for example, greater than the curvature of the circular region C1.

[0059] The planar shape of the pressure chamber 21 described above can be understood as the sum of the overlapping regions (areas enclosed by dotted lines) and non-overlapping regions (areas enclosed 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 considered as closed curves in a Venn diagram, the planar shape of the pressure chamber 21 corresponds to their union (or logical OR from another perspective).

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

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

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

[0063] In other words, the shape of the pressure chamber 21 described above is such that the majority (or even the entire) of its outer edge is composed of arcs. For example, the outer edge of the pressure chamber 21 is composed of arcs in a portion corresponding to an angle of 180° or more around the center of the pressure chamber 21.

[0064] In the following explanation, the terms "central portion" and "peripheral portion" of the pressure chamber 21 may be used. In Figure 4, the central portion 21a is indicated by the dashed line Ln1 at its outer edge. The central portion 21a is, for example, the region that includes the center O1 of the pressure chamber 21 in a plan view and is located away from the outer edge of the pressure chamber 21 towards the center O1. In Figure 4, the peripheral portion 21b is indicated by the dashed line Ln1 at its inner edge and by the solid line indicating the outer edge of the pressure chamber 21 at its outer edge. The peripheral portion 21b is, for example, the region that is in contact with the outer edge (basically its entire circumference) of the pressure chamber 21 in a plan view and is located away from the center of the pressure chamber 21.

[0065] The central portion 21a and the peripheral portion 21b can be defined in a manner in which the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b are separated from each other, or in a manner in which the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b coincide, or in a manner in which the outer edge portion of the central portion 21a and the inner edge portion of the peripheral portion 21b overlap each other. For convenience in describing the embodiment, the central portion 21a and the peripheral portion 21b are defined in a manner in which the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b coincide with each other.

[0066] In a plan view, the shape and dimensions of the central portion 21a and the peripheral portion 21b may be set as appropriate. For convenience, in the following description, the positions and dimensions of various parts or components (for example, various electrodes described later) may be explained in comparison with the positions and dimensions of the central portion 21a and the peripheral portion 21b. However, in actual products, the positions and dimensions of the central portion 21a and the peripheral portion 21b may be determined from the positions and dimensions of various parts or components. Therefore, the shapes and dimensions of the central portion 21a and the peripheral portion 21b may be determined by referring to the positions and dimensions of various parts or components described later.

[0067] Furthermore, in the following explanation, the region where the inner edge is defined by the outer edge of the pressure chamber 21 and the outer edge is defined by the dashed line Ln2 in Figure 4 may be referred to as the region 11e outside the pressure chamber 21. In other words, the region surrounding the pressure chamber 21 within the non-location region of the pressure chamber 21 (the region outside the pressure chamber 21 in a broad sense) may be referred to as the region 11e. The shape and dimensions of this region 11e may also be determined by referring to the positions and dimensions of various parts or members described later.

[0068] (Piezoelectric actuator) Returning to Figure 3, the piezoelectric actuator 13 is, for example, a roughly plate-shaped structure with an area spanning 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 channel member 11, and the second surface 13b is the surface on the flow channel member 11 side. The piezoelectric actuator 13 has a piezoelectric element 27 that applies pressure to the pressure chamber 21 for each discharge element 9 (for each pressure chamber 21). That is, the piezoelectric actuator 13 has multiple piezoelectric elements 27 at multiple positions along the first surface 13a.

[0069] The piezoelectric actuator 13 is constructed by laminating multiple layered members that extend along the second surface 13b. Specifically, for example, the piezoelectric actuator 13 has first piezoelectric layer 29A to fourth piezoelectric layer 29D (hereinafter sometimes simply referred to as piezoelectric layer 29) in order from the first surface 13a to the second surface 13b. The piezoelectric actuator 13 also has first conductor layer 31A to fifth conductor layer 31E (hereinafter sometimes simply referred to as conductor layer 31) in order from the first surface 13a to the second surface 13b at a position on or between the piezoelectric layer 29. Although not specifically shown, the piezoelectric actuator 13 may have an insulating layer (e.g., solder resist) covering the first conductor layer 31A.

[0070] Each piezoelectric layer 29 extends substantially without gaps across multiple pressure chambers 21 (or, from another perspective, multiple piezoelectric elements 27). The term "substantially" is used because, for example, through conductors (described later) for connecting conductor layers may penetrate the insulating layer (the same applies hereafter). Each conductor layer 31 has an appropriate planar shape, for example, including multiple electrodes provided corresponding to the multiple pressure chambers 21, as will be detailed later.

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

[0072] In Figure 5, the first piezoelectric layer 29A and the second piezoelectric layer 29B shown in Figure 3 are conceptualized as the main piezoelectric layer 51A (illustrated). Similarly, in Figure 5, the third piezoelectric layer 29C and the fourth piezoelectric layer 29D shown in Figure 3 are conceptualized as the secondary piezoelectric layer 51B (illustrated). Hereinafter, the main piezoelectric layer 51A and the secondary piezoelectric layer 51B will simply be referred to as the piezoelectric layer 51, and the two will not be distinguished.

[0073] The piezoelectric layer 51 has an active region 53 (53A and 53B) that is driven when a droplet is ejected, and an inactive region 55 (55A to 55C; see Figure 6 for 55C) that is not driven. The active region 53 is a region that is polarized and to which an electric field in the direction of polarization or the opposite direction is applied when a droplet is ejected. The inactive region 55 is an unpolarized region, and / or a region to which no electric field in either the direction of polarization or the opposite direction is applied when a droplet is ejected. A polarized region is, for example, a region in which the direction of spontaneous polarization has been aligned to some extent by a polarization treatment.

[0074] More specifically, the main piezoelectric layer 51A has a first active region 53A that overlaps with the central part 21a of the pressure chamber 21 in a plan view, and a first inactive region 55A adjacent to it on the outside. The secondary piezoelectric layer 51B has a second inactive region 55B that overlaps with the central part 21a of the pressure chamber 21 in a plan view, and a second active region 53B adjacent to it on the outside. From another viewpoint, the first inactive region 55A and the second active region 53B overlap with the peripheral part 21b of the pressure chamber 21 and the region 11e outside the pressure chamber 21 in a plan view.

[0075] The first active region 53A has its polarization direction in the thickness direction (D3 direction). When an electric field (or voltage, from another perspective; the same applies hereafter) 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 arrow in Figure 5. On the other hand, the second inactive region 55B does not contract. As a result, the entire first active region 53A and the second inactive region 55B undergo a bending deformation that is convex toward the pressure chamber 21, as shown by the arrows drawn at both ends of them, like a bimetal.

[0076] The second active region 53B has its 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 Figure 5. On the other hand, the first inactive region 55A does not contract. As a result, as shown in Figure 5, the entire second active region 53B and the first inactive region 55A undergo a bending deformation that becomes concave towards the pressure chamber 21, like a bimetal.

[0077] Here, the portions of the second active region 53B and the first inactive region 55A that are located outside the pressure chamber 21 (sometimes referred to as the second portion 53Bb for the second active region 53B) are constrained from deflection by being joined to the plate 25J. Therefore, as shown in Figure 5, when the second active region 53B and the first inactive region 55A undergo a deflection that causes them to become concave towards the pressure chamber 21, the portions of the second active region 53B and the first inactive region 55A that overlap the pressure chamber 21 (sometimes referred to as the first portion 53Ba for the second active region 53B) will deflect towards the pressure chamber 21 like a cantilever beam. Consequently, the first active region 53A and the second inactive region 55B are displaced towards the pressure chamber 21.

[0078] Therefore, by applying an electric field in the polarization direction to both the first active region 53A and the second active region 53B, the displacement of the center of the first active region 53A toward the pressure chamber 21 can be increased compared to the case where an electric field is applied only to the first active region 53A in the polarization direction. This makes it possible to increase the volume change when decreasing the volume of the pressure chamber 21. Similarly, when increasing the volume of the pressure chamber 21, an electric field may be applied to both the first active region 53A and the second active region 53B in the opposite direction to the polarization direction, causing the first active region 53A and the second active region 53B to extend in a direction along the surface. This increases the displacement of the center of the first active region 53A and thus increases the volume increase of the pressure chamber.

[0079] With respect to the bending rigidity 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 generally located at the boundary between the main piezoelectric layer 51A and the secondary piezoelectric layer 51B. The displacement between this boundary and the neutral plane is, for example, less than 1 / 4 of the thinner of the thicknesses of the main piezoelectric layer 51A and the secondary piezoelectric layer 51B.

[0080] (Planar shape of active and inactive 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 can be understood from the description below, in this embodiment, in the first active region 53A, the portion composed of the first piezoelectric layer 29A and the portion composed of the second piezoelectric layer 29B can have different planar shapes. In the following description, we will take as an example an embodiment in which the planar shape of the active region 53 (or inactive region 55) is generally constant in the thickness direction. In embodiments in which the planar shape of the active region 53 (or 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 planar perspective.

[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 in a planar perspective, for example. More specifically, for example, the former surrounds the latter all around. However, the former does not have to surround the latter all around. For example, the former may surround the latter in a range of 270° or more and less than 360° around its center.

[0082] In planar perspective, the first active region 53A (its outer edge portion) and the second active region 53B (its inner edge portion) may be separate from each other, adjacent to each other (as shown in the illustration), or overlapping. From another viewpoint, the first active region 53A and the second inactive region 55B adjacent to the inside of the second active region 53B may be identical in shape and dimensions (as shown in the illustration), or they may not be. Similarly, the first inactive region 55A adjacent to the outside of the first active region 53A and the second active region 53B may be identical in shape and size (as shown in the illustration), or they may not be.

[0083] In this embodiment, for convenience, the central portion 21a of the pressure chamber 21 is defined such 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. Also, as previously stated, in this embodiment, for convenience, the central portion 21a and the peripheral portion 21b are defined 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 with at least the outer edge of the peripheral portion 21b, and does not overlap with at least the center of the central portion 21a. As described above, the presence or absence of overlap between the outer edge portion of the first active region 53A and the inner edge portion of the second active region 53B is arbitrary. Therefore, the second active region 53B does not have to overlap the inner edge portion of the peripheral portion 21b, it may overlap the entire peripheral portion 21b without any excess or deficiency (as shown in the illustrated example), or it 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 Figure 4) may be set as appropriate. 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 it 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. Also, in planar perspective, the center of the first active region 53A and the center of the pressure chamber 21 may be roughly coincide (as shown in the example), or they may be offset.

[0085] The size of the first active region 53A in plan view may be set as appropriate. 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 or 50% or more, or 70% or less or 80% or less, and the above lower and upper limits may be combined as appropriate. As an example, 50% or more and 70% or less can be given. Also, for example, when comparing the diameters in the same direction or the equivalent diameters of circles in the first active region 53A and the pressure chamber 21, the diameter of the first active region 53A may be 0.6 times or more or 0.7 times or more, or 0.9 times or less, the above lower and upper limits may be combined as appropriate.

[0086] The planar shape and dimensions of the second active region 53B (refer to the shape and dimensions of the annular region between the dashed-dot lines Ln1 and Ln2 shown in Figure 4) may be set as appropriate. 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 and / or outer edges of the annular shape may have irregularities or be polygonal (e.g., rectangular).

[0087] The shape of the inner and / or outer edges 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 illustration), or it 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 and outer edges of the second active region 53B. Also, in planar perspective, the center of the shape formed by the outer edge of the second active region 53B and the center of the pressure chamber 21 and / or the center of the first active region 53A may coincide approximately (as shown in the illustration), or they may be offset.

[0088] In an embodiment where the outer edge of the first active region 53A and the inner edge of the second active region 53B are offset when viewed from a plane, the distance between them may be set as appropriate. For example, the distance between them may be 10% or less or 5% or less of the diameter of the first active region 53A (e.g., minimum diameter, maximum diameter, or equivalent diameter of a circle). This upper limit may be applied to either an embodiment where the outer edge of the first active region 53A is located inside the inner edge of the second active region 53B, or an embodiment where the former is located outside the latter.

[0089] The distance from the outer edge of the second active region 53B to the outer edge of the pressure chamber 21 may be set as appropriate. For example, this distance may be 1 / 20 or more, 1 / 10 or more, or 1 / 5 or more of the diameter of the pressure chamber 21 (e.g., minimum diameter, maximum diameter, or equivalent diameter of a circle), or it may be 1 or less, 1 / 2 or less, 1 / 3 or less, or 1 / 5 or less, and the aforementioned lower and upper limits may be combined as appropriate as long as they do not contradict each other. For example, if the diameter of the pressure chamber 21 is 200 μm or more and 400 μm or less, then 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] The distance w1 (see Figure 4 for the symbol) from the outer edge of the pressure chamber 21 to the inner edge of the second active region 53B, and the distance w2 (see Figure 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. Distance w1 is, in other words, the width of the first portion 53Ba of the second active region 53B that overlaps with the pressure chamber 21. Distance w2 is, in other words, the width of the second portion 53Bb of the second active region 53B that is located outside the pressure chamber 21. Here, distances w1 and w2 are shown in a plan view, but distances w1 and w2 may also be compared in a cross section (longitudinal section) that passes through the center of the pressure chamber 21 and is perpendicular to the pressurized surface 11b, as shown in Figure 3.

[0091] In this embodiment, we take as an example the case in which distance w1 is shorter than distance w2. When distance w1 is shorter than distance w2, this may include not only the case in which distance w1 is shorter than distance w2 over the entire circumference of the second active region 53B, but also the case in which distance w1 is shorter than distance w2 over most of the circumferential direction of the second active region 53B. This is because the second active region 53B may have specific parts due to the shape of the pressure chamber 21 or the shape of the wiring for applying potential to the electrodes. For example, 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 distance w1 is shorter than distance w2, the ratio of distance w1 to distance w2 may be set as appropriate. For example, distance w1 may be 0.9 times or less, 0.8 times or less, or 0.7 times or less of distance w2.

[0092] In a planar perspective view, the area of ​​the first portion 53Ba, which overlaps the pressure chamber 21 within the second active region 53B, and the area of ​​the second portion 53Bb, which is located outside the pressure chamber 21 within the second active region 53B, may be larger than the other. In this embodiment, we will take as an example an example a configuration in which the area of ​​the first portion 53Ba is smaller than the area of ​​the second portion 53Bb. In this configuration, the ratio of the areas of the two may be set as appropriate. 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 the area of ​​the second portion 53Bb.

[0093] Furthermore, for example, when the first part 53Ba and the second part 53Bb are similar in shape, the latter is located outside the former, and therefore the latter has a longer circumferential length than the former. Consequently, even if distances w1 and w2 are equal, the area of ​​the first part 53Ba is smaller than the area of ​​the second part 53Bb. As can be understood from this, although not specifically illustrated, it is also possible that distance w1 is longer than distance w2, and the area of ​​the first part 53Ba is smaller than the area of ​​the second part 53Bb.

[0094] In commercially available products, differences in the areas of the first part 53Ba and the second part 53Bb, as well as differences in distances w1 and w2, may be measured as appropriate. For example, the electrode area and the displacement between the electrode and the pressure chamber 21 may be measured using X-ray CT (Computed Tomography) without disassembling the head body 7, and consequently, the areas of the first part 53Ba and the second part 53Bb, as well as distances w1 and w2, may be measured. Alternatively, for example, the head body 7 may be divided at multiple locations, and the cross-sections may be observed using an electron microscope to measure the electrode area and the displacement between the electrode and the pressure chamber 21, and consequently, the areas of the first part 53Ba and the second part 53Bb, as well as distances w1 and w2, may be measured.

[0095] The first inactive region 55A may be defined, for example, as the 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 view. 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, in a planar perspective view, the outer edge of the first active region 53A and the inner edge of the second active region 53B generally coincide, so the planar shape and dimensions of the first inactive region 55A are generally the same as those of the second active region 53B.

[0096] The second inactive region 55B may be defined, for example, as the 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 the 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) Returning to Figure 3, the material of the piezoelectric layer 29 may be, for example, a ferroelectric ceramic material. Examples of ceramic materials include lead zirconate titanate (PZT), NaNbO3, BaTiO3, (BiNa)TiO3, and BiNaNb5O. 15 Examples of such systems can be listed. However, the material of the piezoelectric layer 29 may be something other than a ceramic material. The material of the piezoelectric layer 29 may be a single crystal, a polycrystalline material, an inorganic material, an organic material, a ferroelectric material or not, or a pyroelectric material or not. The materials of multiple piezoelectric layers 29 may be the same as or different from each other.

[0098] The piezoelectric layer 29 is generally spread in a planar manner with a constant thickness; in other words, it is generally flat. Its area is generally equivalent to the area of ​​the piezoelectric actuator 13. The thickness of the piezoelectric layer 29 may be set as appropriate. Multiple piezoelectric layers 29 may have the same thickness (as shown in the illustration) or they may have different thicknesses. An example of a piezoelectric layer 29 thickness is 10 μm to 40 μm.

[0099] In the illustrated example, the thicknesses of the multiple piezoelectric layers 29 are identical. 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, respectively. Within the range in which this thickness relationship holds, the thicknesses of the multiple piezoelectric layers 29 may differ from one another. It should be noted that even if the thicknesses of two or more piezoelectric layers 29 being compared are said to be identical, errors may exist, and differences may also exist in the thickness of the conductor layer 31.

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

[0101] As shown by the dotted line, the piezoelectric actuator 13 has the first active region 53A, the second active region 53B, the first inactive region 55A, and the second inactive region 55B as described above. Furthermore, in the first piezoelectric layer 29A to the fourth piezoelectric layer 29D, the region outside the first inactive region 55A and the second active region 53B is referred to as the 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 (Figure 5), or these piezoelectric layers (29A and 29B) can be expanded together.

[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 this description of the embodiment, we will take as an example an embodiment 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 (Figure 5) or expanded together.

[0105] The polarization direction of the second active region 53B may be either the +D3 direction or the -D3 direction. Furthermore, 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 this description, we will take as an example the case where 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 region 55 (55A to 55C) may or may not be polarized. In the illustrated example, the first inactive region 55A is polarized, while the second inactive region 55B and the third inactive region 55C are not polarized.

[0107] The polarization direction of the first inactive region 55A is set to the thickness direction (D3 direction). The polarization direction of the first inactive region 55A may be either the +D3 direction or the -D3 direction, and the relationship with the polarization directions of the first active region 53A and the second active region 53B is also arbitrary. For example, the polarization direction of the first inactive region 55A may be the same as the polarization direction of the second active region 53B, or it may be the opposite. In describing this embodiment, we will take as an example the case in which the polarization direction of the first inactive region 55A is the same as the polarization direction of the second active region 53B.

[0108] (Conductor layer) Returning to Figure 3, the first conductor layer 31A is located on the upper 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 channel member 11 (plate 25J).

[0109] The material of the conductive layer 31 may be, for example, an appropriate metallic material. As metallic materials, for example, Ag-Pd alloys and Au alloys may be used. The materials of multiple conductive layers 31 may be the same as each other or may be different from each other. A single conductive layer 31 may be integrally constructed from one type of material, or it may be constructed by laminating different materials. The material of a single conductive layer 31 is the same at different positions in the planar direction. However, the material of some areas may be different from the material of other areas.

[0110] The conductive layer 31 is generally spread out in a planar manner with a constant thickness. The thickness of the conductive layer 31 may be set as appropriate. Furthermore, the thicknesses of multiple conductive layers 31 may be the same or different. The thickness of each layer is, for example, thinner than the thickness of the piezoelectric layer 29. An example of the thickness of the conductive layer 31 is that it may be between 0.5 μm and 3 μm.

[0111] (Shape of the conductor layer) Figures 7 and 8 are exploded perspective views of the piezoelectric actuator 13 and the upper part (plate 25J) of the flow path member 11. Figure 7 shows a portion of the head body 7 in plan view, which includes multiple piezoelectric elements 27. Figure 8 shows a region containing one piezoelectric element 27. For convenience, hatching is applied to the surface of the conductive layer 31 in these figures.

[0112] In these figures, the piezoelectric actuator 13 is shown as a plate-like member composed of two layers: each piezoelectric layer 29 and the conductor layer 31 overlapping its upper surface (the +D3 side), except for the fifth conductor layer 31E. This is for illustrative purposes only and does not mean that four such plate-like members are manufactured during the manufacturing process. For example, during the manufacturing process, each conductor layer 31 may be provided on the lower surface (the -D3 side) 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 composed of the first piezoelectric layer 29A) when droplets are ejected. The reorientation electrode 35 contributes to reducing the degradation of the characteristics of the piezoelectric actuator 13 by applying polarization treatment to the second inactive region 55B (part or most of it) when droplets are not being ejected.

[0114] In each piezoelectric element 27, the first electrode 33 and the reorientation electrode 35 are separated from each other, and potentials are applied to them separately. The distance between the first electrode 33 and the reorientation electrode 35 may be set as appropriate. For example, the distance between them may be made as short as possible without causing a short circuit.

[0115] (1st electrode) The first electrode 33 is a so-called individual electrode. That is, the multiple first electrodes 33 are separated from each other in terms of their shape and electrical properties. Furthermore, it is possible to assign different potentials to the multiple first electrodes 33.

[0116] The first electrode 33 includes, for example, an electrode body 33a that contributes to applying a voltage to the first active region 53A, and a lead-out portion 33b for connecting the electrode body 33a to an external signal line of the piezoelectric actuator 13. The external signal line is, for example, a wiring pattern on an FPC (flexible printed circuit board) facing the first surface 13a of the piezoelectric actuator 13, although not specifically shown in the figures. Note that only the electrode body 33a may be considered as the first electrode, and the lead-out portion 33b may be considered as wiring.

[0117] The planar shape and dimensions of the electrode body 33a are, for example, generally the same as those of the first active region 53A. Therefore, the previously described 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 previously described, the active region 53 is polarized and is the 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 composed of the first piezoelectric layer 29A coincides with or is located inside the outer edge of the electrode body 33a.

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

[0119] The specific shape, dimensions, and position of the lead-out portion 33b may be set as appropriate. For example, the lead-out portion 33b extends linearly from one end of the electrode body 33a in a predetermined direction (direction D1 in the illustrated example) to the same end in the predetermined direction. This 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-out portion 33b is, for example, approximately constant and smaller than the diameter of the electrode body 33a (for example, the minimum diameter). Unlike the illustrated example, the lead-out portion 33b may have a bent or curved portion. The end of the lead-out portion 33b opposite to the electrode body 33a may be wider than other parts. Furthermore, when viewed from above, the lead-out portion 33b may or may not be contained within the shape formed by the outer edge of the second active region 53B (as in the illustrated example).

[0120] (Reorientation electrode) The multiple reorientation electrodes 35 are separated from each other in terms of their shape and electrical properties. That is, the reorientation electrodes 35 are individual electrodes. However, as will be understood from the explanation below, the multiple reorientation electrodes 35 may be assigned the same potential to each other. Therefore, unlike the illustrated example, the first conductor layer 31A may have, for example, wiring connecting adjacent reorientation electrodes 35 to each other. Also, for example, the first conductor layer 31A may have electrodes (see fourth conductor layer 31D) that extend seamlessly into the first piezoelectric layer 29A except in the area where the first electrode 33 is placed, as reorientation electrodes.

[0121] The reorientation electrode 35 may, for example, apply voltage to substantially the entire second inactive region 55B in a plan view, or apply voltage to only a part of it (the inner edge, the central side, or the outer edge side), or apply 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 apply voltage to almost the entire first inactive region 55A, but not to the third inactive region 55C. That is, the reorientation electrode 35 is shaped to overlap the first inactive region 55A almost perfectly in a planar view. Therefore, the previously described 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 inactive region 55A, the reorientation electrode 35 is interrupted at the position of the lead-out portion 33b of the first electrode 33 and is formed in a C-shape. It should be noted that, similar to the annular shape, the C-shape referred to here is not limited to having a circular or elliptical inner and / or outer edge.

[0124] Furthermore, the portion of the first piezoelectric layer 29A located outside the electrode body 33a in a plan view is not subjected to voltage during droplet ejection and therefore constitutes the first inactive region 55A. On the other hand, the inner edge of the reorienting electrode 35 is set outward from the outer edge of the electrode body 33a to prevent short-circuiting with the first electrode 33. Therefore, even though the reorienting electrode 35 generally overlaps the entire first inactive region 55A, the inner edge of the reorienting electrode 35 is located on the outer edge side of the portion of the first inactive region 55A that is composed of the first piezoelectric layer 29A.

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

[0126] (Second conductor layer) The second conductor layer 31B includes, 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 electrode 37 contributes to applying a voltage to the first active region 53A (more specifically, both the first piezoelectric layer 29A and the second piezoelectric layer 29B) when pressure is applied to the pressure chamber 21 to eject droplets. The plurality of wirings 39 contribute to applying a potential to the second electrode 37.

[0127] (2nd electrode) The multiple second electrodes 37 are separated from each other in terms of their shape. From another perspective, there are non-conducting regions between adjacent second electrodes 37. In other words, in terms of shape, the second electrodes 37 are individual electrodes. However, as previously described, unlike the multiple first electrodes 33, the multiple second electrodes 37 are connected to each other by multiple wirings 39 and are at the same potential.

[0128] The shape and dimensions of the second electrode 37 are, for example, generally the same as 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 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 point of view, when viewed from above, the second electrode 37 does not overlap with the re-orientation electrode 35. The description of 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, when viewed more precisely, in a planar perspective, the outer edge of the second electrode 37 may be located, in whole or in part, on the outer edge of the electrode body 33a, or between the outer edge of the electrode body 33a and the inner edge of the reorienting electrode 35, or on the inner edge of the reorienting electrode 35. In this disclosure, when we say 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 without excess or deficiency), it may include all of the above embodiments. Even when they coincide when viewed strictly, there may, of course, be errors 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 offset inward or outward relative to the outer edge of the electrode body 33a. From another perspective, as can be understood from the explanation described later, the region to which voltage is applied in the first piezoelectric layer 29A and the region to which voltage is applied in the second piezoelectric layer 29B may be different. From yet another perspective, assuming that the region to which voltage is applied is polarized, the first active region 53A may have different sizes in the portion composed of the first piezoelectric layer 29A and the portion composed of the second piezoelectric layer 29B.

[0131] (Wiring of the second conductor layer) The number, position, shape, and dimensions of the multiple wires 39 can be set as appropriate. For example, the wires 39 may connect adjacent second electrodes 37 in the D2 direction (as shown in the illustration), or they may connect adjacent second electrodes 37 in directions other than the D2 direction (the D1 direction or a direction inclined towards the D1 direction), or a combination of two or more of these connections may be realized. In the illustration, the wires 39 extend in a direction that intersects (more specifically, orthogonal to) the direction in which the lead-out portion 33b of the first electrode 33 extends. Consequently, the wires 39 and the lead-out portion 33b do not overlap.

[0132] Furthermore, for example, the wiring 39 may extend in a straight line (as shown in the illustration), or it may be bent or curved. Also, for example, the wiring 39 may have a substantially constant width along its length (as shown in the illustration), or its width may vary depending on its position along its length. The width of the wiring 39 is smaller than the diameter of the second electrode 37 in the width direction of the wiring 39, such that a gap is formed between the second electrodes 37 (so that the second electrodes 37 become individual electrodes in terms of shape). For example, the former may be 1 / 2, 1 / 3, or 1 / 4 of the latter.

[0133] (Third conductor layer) The third conductive layer 31C has, for example, a third electrode 41 provided for each pressure chamber 21 (piezoelectric element 27). The third electrode 41 contributes to applying a voltage to the first active region 53A (more specifically the portion composed of the second piezoelectric layer 29B) and 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 pressure is applied to the pressure chamber 21 to eject droplets. The third electrode 41, like the first electrode 33, is a so-called individual electrode. That is, the multiple third electrodes 41 are separated from each other in terms of their shape and electrical characteristics.

[0134] The planar shape and dimensions of the third electrode 41 are, for example, roughly the same as the planar shape and dimensions of the sum of the first electrode 33 and the reorientation electrode 35 (or, from another viewpoint, the sum of the first active region 53A and the second active region 53B). 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) with approximately no 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 and the shape and dimensions of the outer edge of the re-orientation electrode 35 may differ from each other. For example, when viewed from above, the outer edge of the re-orientation electrode 35 may be located inside or outside the outer edge of the third electrode 41. Also, for example, when viewed from above, 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 re-orientation electrode 35.

[0136] (Fourth 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 can be understood from the operation description described later, in this embodiment, the fourth conductor layer 31D does not contribute to applying voltage to the piezoelectric layer 29. The fourth conductor layer 31D may be omitted.

[0137] The shape, dimensions, and position of the fourth conductor layer 31D are set such that, for example, in a planar perspective view, it does not overlap with the electrodes to which voltage is applied to the piezoelectric layer 29. In this embodiment, the electrodes to which voltage is applied are the first electrode 33, the reorienting electrode 35, the second electrode 37, the third electrode 41, and the fourth electrode 45, which will be described later. As a result, the likelihood that the fourth conductor layer 31D will interfere with the application of voltage to the piezoelectric layer 29 by the electrodes is reduced.

[0138] However, the fourth conductor layer 31D may include a region that overlaps with a part of the electrodes. For example, if the reorienting 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 that overlaps with the third inactive region 55C), the fourth conductor layer 31D may include a region that overlaps with the region located outside. In this case, the fourth conductor layer 31D can contribute to the reorientation of the portion of the third inactive region 55C that is composed of 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 as appropriate. 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, except for the openings 43, the fourth conductor layer 31D is a solid, gapless layer that extends over the fourth piezoelectric layer 29D.

[0140] The planar shape and dimensions of the aperture 43 are, for example, generally the same as those of the third electrode 41 (or, from another viewpoint, the logical OR of the first active region 53A and the second active region 53B). When viewed from above, the aperture 43 overlaps the third electrode 41 with approximately no excess or deficiency. The description of the shape and dimensions of the outer edge of the second active region 53B may be used in conjunction with the description of the planar shape and dimensions of the aperture 43.

[0141] However, the opening 43 may be larger than the third electrode 41. This reduces the likelihood of overlap between the third electrode 41 (and other electrodes) and the fourth conductor layer 31D, for example. In addition, making the opening 43 larger may be consistent with the objective 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, which is larger than the third electrode 41, may or may not be similar to the shape of the third electrode 41 (or, from another perspective, the pressure chamber 21).

[0142] The planar shape (pattern) of the fourth conductor layer 31D can be various other than the shape in which the openings 43 are formed. For example, the planar shape of the fourth conductor layer 31D may consist of multiple linear patterns extending in appropriate directions, or it may be a mesh shape having openings other than the openings 43.

[0143] (Fifth 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 pressure is applied to the pressure chamber 21 to eject droplets. In addition, the fourth electrode 45 contributes to reducing the degradation of the characteristics of the piezoelectric actuator 13 by performing polarization treatment on the second inactive region 55B (part or most thereof) when 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 shape, the multiple fourth electrodes 45 are individual electrodes. However, unlike the multiple first electrodes 33, the multiple fourth electrodes 45 are assigned the same potential to each other. Specifically, in the illustrated example, the multiple fourth electrodes 45 are electrically connected to each other by a plate 25J made of metal. In contrast to this embodiment, the pressure surface 11b may be made insulating by making the plate 25J a resin plate, and the electrical connection of the multiple fourth electrodes 45 via the flow channel member 11 may be avoided.

[0145] The planar shape and dimensions of the fourth electrode 45 are, for example, generally the same as those of the reorientation electrode 35. From another perspective, the planar shape and dimensions of the fourth electrode 45 are generally the same as those of the region of the third electrode 41 that does not overlap with the electrode body 33a of the first electrode 33 (the outer peripheral region). From yet another perspective, the planar shape and dimensions of the fourth electrode 45 are generally the same as those of the second active region 53B. The description of the planar shape and dimensions of the second active region 53B may be applied to the description of 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 reorienting electrode 35) and the outer edge of the second electrode 37. More precisely, the inner edge of the fourth electrode 45, like the outer edge of the second electrode 37, may be located in whole or in part in planar perspective, either at the outer edge of the electrode body 33a, between the outer edge of the electrode body 33a and the inner edge of the reorienting electrode 35, or at the inner edge of the reorienting electrode 35. In this disclosure, when the inner edge of the fourth electrode 45 coincides with the outer edge of the electrode body 33a, it may include all of the above embodiments. The inner edge of the fourth electrode 45 may also be slightly offset inward or outward relative to the outer edge of the electrode body 33a and / or the outer edge of the second electrode 37.

[0147] In planar projection, 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 aperture 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 inward or outward relative to the outer edge of the fourth electrode 45. Also, similar to the relationship between the aperture 43 and the third electrode 41, the aperture 43 may be larger than the fourth electrode 45. Furthermore, the outer edge of the fourth electrode 45 may be offset inward or outward relative to the outer edge of the third electrode 41.

[0148] (Electrical connection of the conductor layer) As already mentioned, the first electrode 33 is an electrode to which a potential (drive signal) is individually applied to each piezoelectric element 27, and a potential is also applied to the lead portion 33b from an FPC (not shown) facing the first surface 13a of the piezoelectric actuator 13. For example, the end of the lead portion 33b opposite to 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 mentioned, the third electrode 41 is also an electrode to which a potential (drive signal) is individually applied to each piezoelectric element 27. However, in this embodiment, the third electrode 41 is given the same potential as the first electrode 33 of the piezoelectric element 27 to which it belongs. The application of the same potential can be achieved, for example, by electrically connecting the first electrode 33 and the third electrode 41 within the piezoelectric actuator 13.

[0150] The connection between the first electrode 33 and the third electrode 41 described above may be achieved by an appropriate conductor. For example, as shown in Figure 3, the first electrode 33 and the third electrode 41 may be connected by a through-conductor 47 that penetrates the first piezoelectric layer 29A and the second piezoelectric layer 29B. In Figure 8, the positions of the first electrode 33 and the third electrode 41 that are connected by the through-conductor 47 are connected by dotted lines. The connection position of the through-conductor 47 to the first electrode 33 may be, for example, the portion of the lead-out portion 33b that is located outside the pressure chamber 21 in a plan view (more specifically, for example, the portion located in the outer region 11e). The connection position of the through-conductor 47 to the third electrode 41 may be the position directly below the connection position of the through-conductor 47 to the lead-out portion 33b described above.

[0151] In addition, although not specifically shown, a through conductor that penetrates the first piezoelectric layer 29A and is connected to the first electrode 33, a through conductor that penetrates the second piezoelectric layer 29B and is connected to the third electrode 41, and layered wiring located between the first piezoelectric layer 29A and the second piezoelectric layer 29B and connecting the two through conductors may be provided. Furthermore, 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-out portion may be provided on the third electrode 41 that extends to a position that does not overlap with the re-orientation electrode 35 in a planar view, and a through conductor that is connected to the lead-out portion and exposed on the first surface 13a of the piezoelectric actuator 13 may be provided. 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 given a potential by being joined to an FPC (not shown) via a bump, similar to the first electrode 33. The joining position of the reorientation electrode 35 at this time may be at an appropriate position. For example, the joining position may be the part of the reorientation electrode 35 that is located on the opposite side of the lead portion 33b, with the electrode body 33a in between. And / or, for example, the joining position may be at a position that does not overlap with the pressure chamber 21 in a planar perspective view. This reduces the influence of the joining on the pressure in the pressure chamber 21, similar to the joining to the lead portion 33b.

[0153] In addition, although not specifically shown in the figures, for example, the reorientation electrode 35 may be provided with a lead-out portion extending away from the pressure chamber 21, and the FPC may be joined to this lead-out portion. Furthermore, it is not necessary for the multiple reorientation electrodes 35 to be individually potentialized from one another. Therefore, wiring connecting the multiple reorientation electrodes 35 to each other and a pad commonly connected to the multiple reorientation electrodes 35 may be provided, and the FPC may be joined to this pad.

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

[0155] As previously described, the multiple second electrodes 37 are connected by multiple wirings 39 and are given the same potential. Furthermore, although the fourth conductor layer 31D has multiple openings 43, it is essentially a single conductor pattern, and therefore naturally the same potential is applied to its entirety. In this embodiment, the multiple second electrodes 37 and the fourth conductor layer 31D are given the same potential. The multiple 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 that penetrates the piezoelectric layer 29. The configuration of the through-conductor may be set as appropriate. An example is shown below.

[0156] Figure 9 is an enlarged plan view of a portion of the second conductor layer 31B. This figure shows only two rows, each composed of multiple second electrodes 37 arranged in the D2 direction. For the sake of explanation, this figure assumes that each row contains four multiple second electrodes 37.

[0157] In each row, multiple second electrodes 37 are connected by multiple wires 39, as previously described. Furthermore, at both ends of each row, wires 39 are provided that extend outwards from the row (towards the -D2 side or the +D2 side). These wires 39 at both ends are connected to a common wire 49 that extends in a direction that intersects the multiple rows (in the D1 direction). In this way, the multiple rows are connected to each other. The common wire 49 is part of the second conductor layer 31B.

[0158] Figure 10 is a cross-sectional view along line XX in Figure 9.

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

[0160] Furthermore, a through-conductor 57 is provided that penetrates the first piezoelectric layer 29A. This allows for the electrical connection of an FPC (not shown) facing the first surface 13a of the piezoelectric actuator 13 with a plurality of second electrodes 37 and a 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] As shown by the dotted line in Figure 9, multiple through conductors 57 may be provided, for example, along the common wiring 49. This stabilizes the potential of electrodes that are at the same potential. Of course, the through conductor 57 may be provided in 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 in a planar perspective view.

[0162] Although not specifically shown in the figures, a through-conductor 57 may be provided that penetrates the fourth piezoelectric layer 29D. This through-conductor 57 may electrically connect the plate 25J (or, in other words, the fourth electrode 45) to the second electrode 37 and the fourth conductor layer 31D.

[0163] (Potential applied to the conductive layer) Figure 11 is a schematic cross-sectional view showing the potential applied to the conductive layer 31 when droplets are ejected. Figure 12 is a schematic cross-sectional view showing the potential applied to the conductive layer 31 when polarization treatment is performed on the first inactive region 55A. These figures correspond to the VV line in Figure 4, for example, as in Figure 5. In these figures, hatching to indicate cross-sections has been omitted. The arrows shown within the cross-section of the piezoelectric layer 29 indicate the direction of the voltage (electric field) at a predetermined point in time within the droplet ejection cycle.

[0164] These figures show a driver 61 that supplies power to the piezoelectric actuator 13 and drives it. However, the configuration of the driver 61 shown here is for convenience in illustrating the potential applied to the conductor layer 31 in an easy-to-understand manner. Therefore, the actual configuration of the driver 61 may differ from the configuration shown.

[0165] The driver 61 is composed of, 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 set as appropriate. For example, some or all of the operations of the driver 61 described below may be performed by the control unit 88. The driver 61 may be provided in a hardware configuration that makes it difficult to conceive of it separately from the control unit 88. The driver 61 and the control unit 88 as a whole may be considered as a control unit.

[0166] The driver 61 includes, for example, a first signal source 63 capable of outputting power for droplet ejection, a second signal source 65 capable of outputting power for polarization processing, and a switch unit 67 that controls the connection between these signal sources and the piezoelectric actuator 13. The switch unit 67 is intended to clearly illustrate whether power for droplet ejection or power for polarization processing is supplied to the piezoelectric actuator 13. In practice, the switch unit 67 may not be provided, and power for droplet ejection and 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] Figures 11 and 12 show a reference potential section 69 serving as the signal ground and / or 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 for the connection of the reference potential section 69 is merely for convenience to clearly show the potential difference between the conductor layers 31, etc.

[0168] (Liquid dispensing control) As explained with reference to Figure 5, when dispensing droplets, the first signal source 63 applies a voltage (electric field) to the first active region 53A and the second active region 53B in the same direction (or opposite direction) to the polarization direction. As explained with reference to Figure 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 that is composed of 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 such 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 that is composed of the first piezoelectric layer 29A.

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

[0170] The above explanation described the case where a voltage is applied in the same direction as the polarization direction. However, by applying a potential lower than the reference potential (or, from another perspective, a negative potential) to the first electrode 33 and the third electrode 41, a voltage can be applied in the opposite direction to the polarization direction. Furthermore, the above explanation assumed the polarization direction shown in Figure 6. However, if the polarization direction is opposite to that shown in Figure 6, the high and low (positive and negative) potentials will be reversed.

[0171] In the above description, it was assumed that a reference potential is applied to the second electrode 37 and the fourth electrode 45. However, a potential other than the reference potential may be applied to the second electrode 37 and the fourth electrode 45 while keeping the fourth electrode 45 from being electrically connected to the metal plate 25J (see, for example, the embodiment described later). For example, a potential different from that 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. Furthermore, although it is necessary to change the configuration of the conductor layer 31 and the arrangement of the through conductors so that a potential can be applied to the second electrode 37 and the fourth electrode 45 individually, conversely, a 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, to broaden the conceptual framework of this embodiment, it can be said that 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 addition to the above, 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 a voltage is applied for droplet ejection, the reorientation electrode 35 and the fourth conductor layer 31D may, for example, have a reference potential applied to them, or they may be in an electrically floating state (a state in which no potential is actively applied). In the example in Figure 11, the reorientation electrode 35 is in an electrically floating state. Also, in this embodiment, as described above, the fourth conductor layer 31D is connected to the second electrode 37 and therefore has a reference potential applied to it.

[0174] As for the driving method of the piezoelectric element 27 when applying pressure to the pressure chamber 21, various known methods or applications of various known methods may be employed. A typical driving method is the so-called pull-and-drive method. When the pull-and-drive method is employed, the operation of the driver 61 is as follows, for example.

[0175] The driver 61 pre-applies a potential higher than the reference potential (or, from another perspective, the same potential as the second electrode 37 and the fourth electrode 45; the same applies hereinafter) to the first electrode 33 and the third electrode 41 before droplet ejection. As a result, the piezoelectric element 27 is in a state of deflection deformation toward the pressure chamber 21. When the timing for droplet ejection 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 consequently, the volume of the pressure chamber 21 begins to increase. From another perspective, the piezoelectric element 27 begins to vibrate at its natural frequency. Subsequently, the volume of the pressure chamber 21 reaches its maximum and then decreases again. As the volume decreases, the pressure in the pressure chamber 21 increases. Then, at the timing when the pressure is approximately at its 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 vibration applied and the subsequent vibration overlap, applying a greater pressure to the pressure chamber 21. In this way, the driver 61 inputs a pulsed drive signal to the first electrode 33 and the third electrode 41 that is at a low potential for a certain period of time, with a potential higher than the potential of the second electrode 37 and the fourth electrode 45 as the reference.

[0176] The driver 61, for example, changes the amplitude of the pulsed drive signal and / or the number of drive signals depending on the size of the dot to be formed on the recording medium. This results in larger droplets being ejected, or two or more droplets being ejected for a single dot.

[0177] As can be understood from the above explanation, when a droplet is ejected, 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 extends and the period during which the second active region 53B extends are the same, and the period during which the first active region 53A contracts and the period during which the second active region 53B contracts are the same. In other words, the period during which the first active region 53A undergoes either contraction or extension is the same as the period during which the second active region 53B undergoes either contraction or extension. To put it in broader terms, the period during which the first active region 53A undergoes either contraction or extension and the period during which the second active region 53B undergoes either contraction or extension overlap in at least part.

[0178] As can be understood from the explanation of the pull-and-run method, the period during which either contraction or expansion occurs is not limited to the period during which voltage is actively applied to the first active region 53A and the second active region 53B. For example, the period during which either contraction or expansion occurs may be the period during which the potentials of the first electrode 33 and the third electrode 41 are set to a reference potential when the timing for droplet discharge arrives. This period can be considered as the period during which no voltage is applied to the first active region 53A and the second active region 53B. However, in any case, the driver 61 controls the strength of the electric field applied to the first active region 53A and the electric field applied to the second active region 53B in liquid discharge control such that the second active region 53B experiences either contraction or expansion during at least a portion of the period during which the first active region 53A experiences either contraction or expansion.

[0179] It is also possible to stagger the periods during which voltage is applied between the first active region 53A and the second active region 53B. For example, the piezoelectric actuator can be configured so that potential can be applied individually to multiple fourth electrodes 45. Then, for example, in the above example of the pull-shot type, before droplet ejection, the fourth electrode 45 may be given the same potential as the third electrode 41, and the contraction of the second active region 53B may not be utilized. When returning the potential of the third electrode 41 to a potential higher than the reference potential, the reference potential may be applied to the fourth electrode, and the contraction of the second active region 53B may be utilized. Conversely, the contraction of the second active region 53B may be utilized before droplet ejection. Depending on the amount of droplet ejection (the size of the dots 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. In all of these embodiments, it can be said that at least a portion of the period during which the first active region 53A undergoes either extension or contraction and the period during which the second active region 53B undergoes either extension or contraction overlap.

[0180] The second electrode 37 and the fourth electrode 45 are supplied 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 portion of the first active region 53A composed of 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), while the latter voltage is applied to the thickness of two piezoelectric layers (29C and 29D). Therefore, the strength of the electric field formed by the former voltage is stronger than the strength of the electric field formed by the latter voltage. The same applies to the portion of the first active region 53A composed of the first piezoelectric layer 29A and the second active region 53B. From another perspective, when the liquid is discharged, the electric field strength (or, from another perspective, the amount of change thereof) in the first active region 53A is greater than the electric field strength in the second active region 53B.

[0181] In this embodiment, during liquid discharge control, the electric field applied to the first active region 53A and the electric field applied to the second active region 53B both increase or decrease. In an embodiment different from this one, where both electric fields do not change in the same way, the strength of the electric field applied to the first active region 53A and the strength of the electric field applied to the second active region 53B may be compared, for example, by their maximum values. Also, for example, in a pull-type system, depending on the specific drive waveform, the electric field that maintains the piezoelectric element 27 in a state of being bent toward the pressure chamber 21 just before the discharge timing arrives is not the electric field during discharge, but may be referenced as the maximum value of the electric field applied to the active region 53 during liquid discharge control. In an embodiment where 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 strengths that are compared with each other may be at different points in time.

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

[0183] Polarization by the reorientation electrode 35 may be performed at an appropriate time when no droplets are being ejected. For example, polarization may be performed when printing is not taking place, triggered by user operation on the printer 1. In other words, polarization may be performed at any time. Alternatively, for example, the control unit 88 may count the number of prints and perform polarization when a predetermined number of prints have been completed. When the printer 1 is shipped, the first inactive region 55A may be in a state where polarization has not been performed, or it may be in a state where polarization similar to that achieved by polarization by the reorientation electrode 35 has occurred.

[0184] As explained with reference to Figure 6, in this embodiment, the first inactive region 55A is polarized in the thickness direction. During the polarization process, as indicated by the arrows in Figure 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 an intensity exceeding the coercive electric field of the first inactive region 55A, and a voltage that is greater than or equal to the voltage at which the polarization reaches a saturation state.

[0185] In order to apply the voltage as described above, in the illustrated example, the reorienting electrode 35 is given a potential higher than the reference potential (or, from another perspective, a potential with positive polarity). The third electrode 41 is in an electrically floating state. The fourth electrode 45 is given the reference potential. As a result, an electric field is formed between the reorienting electrode 35 and the fourth electrode 45. The third electrode 41, which is interposed between them, is in an electrically floating state and therefore does not easily interfere with 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] The above assumes a configuration in which the polarization direction is downward, as shown in Figure 6. In a configuration in which the polarization direction is reversed, a potential lower than the reference potential (or, from another perspective, a negative polarity potential) may be applied to the reorientation electrode 35. Alternatively, the fourth electrode 45 (in other words, the electrode that forms an electric field 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 this 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 a voltage for polarization is applied, the first electrode 33, the second electrode 37, and the fourth conductive layer 31D may, for example, have a reference potential applied to them, or they 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 is therefore in an electrically floating state. The second electrode 37 and the fourth conductive layer 31D are also provided with a reference potential.

[0188] The manufacturing method for the head body 7 may be the same as various known methods or methods that apply various known methods. For example, the piezoelectric actuator 13 may be manufactured by placing a conductive layer 31 and a conductive paste that will become a through-conductor on a ceramic green sheet that will become a piezoelectric layer 29, and then laminating and firing the ceramic green sheets. The flow channel member 11 may be manufactured by bonding together a plurality of plates 25, each having through-holes that will become flow channels formed by etching or the like, with an adhesive. The head body 7 may then be manufactured by joining the piezoelectric actuator 13 and the flow channel member 11 with an adhesive.

[0189] Polarization of the active region 53 may be performed, for example, at an appropriate time after firing of the piezoelectric actuator 13 (for example, after joining the piezoelectric actuator 13 to the flow channel member 11). In the polarization process, 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 the electric fields indicated by arrows y1 and y2 in Figure 11 are applied. The voltage at this time may be, for example, a voltage that forms an electric field with an intensity exceeding the coercive field of the active region 53, and a voltage that is greater than or equal to the voltage at which the polarization reaches a saturation state.

[0190] As described above, in this embodiment, the liquid discharge head 2 includes a flow path member 11, a piezoelectric actuator 13, and a driver 61. The flow path member 11 has a pressurizing surface 11b and a pressure chamber 21 that opens into the pressurizing surface 11b. The piezoelectric actuator 13 overlaps the pressurizing 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 pressurizing surface 11b (D3 direction) is referred to as the thickness direction, the first active region 53A consists of a piezoelectric material polarized in the thickness direction and overlaps the central part 21a of the pressure chamber 21 in a planar view of the pressurizing surface 11b. The second active region 53B is made of a piezoelectric material polarized in the thickness direction, is located on the pressure surface 11b side of the first active region 53A, and overlaps with the peripheral edge 21b of the pressure chamber 21 and the region 11e outside the pressure chamber 21 in a planar view of the pressure surface 11b. In liquid discharge control, the driver 61 controls the intensity of the first electric field (arrow y1 in Figure 11) applied to the first active region 53A in the thickness direction and the intensity of the second electric field (arrow y2 in Figure 11) applied to the second active region 53B in the thickness direction, so that the second active region 53B undergoes either expansion or contraction in the direction along the pressure surface 11b for at least a portion of the period during which the first active region 53A undergoes either expansion or contraction in the direction along the pressure surface 11b. In liquid discharge 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 overall displacement of the piezoelectric element 27 can be increased. In the second active region 53B, the deformation of the region overlapping with the outer region 11e of the pressure chamber 21 is restricted by the flow channel member 11, so stress tends to be high 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 greater than the strength of the electric field 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 overall displacement of the piezoelectric element 27. By reducing the stress applied to the second active region 53B, the durability of the head 2 can be improved.

[0192] Furthermore, in this embodiment, the head 2 has three or more electrodes (33, 37, 41, and 45). These three or more electrodes are positioned at different locations in the thickness direction, and each performs at least one of applying a first electric field to a first active region 53A and applying a second electric field to a 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 and to which the first electric field is applied (at least one of the distance between 33 and 37 and the distance between 37 and 41) is defined as the first distance. The distance in the thickness direction between two electrodes that are adjacent to each other among the three or more positions and to which the second electric field is applied (the distance between 41 and 45) is defined as the 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 strength of the first electric field will be stronger than the strength of the second electric field. For this reason, it is easy to make the strength of the first electric field stronger than the strength of the second electric field.

[0194] Furthermore, in this embodiment, in addition to the above-described relationship between the electrodes' distances being met, in liquid discharge control, the maximum value of the potential difference between the two electrodes to which the first electric field is applied to the first active region 53A (the potential difference between 33 and 37 and / or the potential difference between 37 and 41) is the same as the maximum value of the potential difference between the two electrodes to which the second electric field is applied to the second active region 53B (41 and 45).

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

[0196] In this embodiment, the piezoelectric actuator has a first piezoelectric layer 29A to a fourth piezoelectric layer 29D, as well as 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 channel member 11 (+D3 side) is referred to as the first side, and the side of the piezoelectric actuator 13 facing the flow channel member 11 (-D3 side) is referred to as the second side. In this case, the first piezoelectric layer 29A to the fourth piezoelectric layer 29D are stacked 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 part 21a of the pressure chamber 21 in a plan view. The second electrode 37 overlaps the second side surface of the first piezoelectric layer 29A and overlaps the central part 21a in a plan view. The third electrode 41 overlaps the second side surface of the second piezoelectric layer 29B and, in plan view, overlaps the central portion 21a, the peripheral portion 21b of the pressure chamber 21, and the outer region 11e of the pressure chamber 21. The fourth electrode 45 overlaps the second side surface of the fourth piezoelectric layer 29D and, in plan view, overlaps the peripheral portion 21b and the outer region 11e. 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 the portion of the second piezoelectric layer 29B that overlaps the central portion 21a of the third electrode 41. The second active region 53B has a region sandwiched between the portion of the third piezoelectric layer 29C and the fourth piezoelectric layer 29D that overlaps the peripheral portion 21b and the outer region 11e of the third electrode 41, and the fourth electrode 45.

[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 two piezoelectric layers 29 (29A and 29B) by three electrodes (33, 37, and 41) whose positions in the thickness direction are different from each other, and in the second active region 53B, a voltage is applied to 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 voltage to the first active region 53A is shorter than the distance between the two electrodes that apply voltage to the second active region 53B. Due to the effect of this distance relationship, the voltage applied to the first active region 53A (each of 29A and 29B) and the voltage applied to the second active region 53B (both 29C and 29D) can be made the same, so for example, the increase in potential can be suppressed and the configuration can be simplified. Furthermore, since the third electrode 41 is used for both applying voltage to the first active region 53A and applying voltage to the second active region 53B, the number of electrodes (number of conductor layers 31) can be reduced.

[0198] Furthermore, in this embodiment, the portion of the first piezoelectric layer 29A that constitutes the first active region 53A and the portion of the second piezoelectric layer 29B that constitutes the first active region 53A are polarized in opposite directions. The portions of the third piezoelectric layer 29C and the fourth piezoelectric layer 29D that constitute the second active region 53B are polarized in the same direction as the polarization of the portion of the first piezoelectric layer 29A that constitutes the first active region 53A. In liquid discharge control, the first electrode 33 and the third electrode 41 are at the same potential, and the second electrode 37 and the fourth electrode 45 are at the same potential. 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 is used to apply a first electric field to the first active region 53A and a second electric field to the second active region 53B.

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

[0200] Furthermore, in this embodiment, 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, respectively.

[0201] In this case, from another perspective, 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 composed of the first piezoelectric layer 29A, and the electric field applied to the portion of the first active region 53A composed of the second piezoelectric layer 29B, are each more likely to be larger than the electric field applied to the second active region 53B.

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

[0203] In this embodiment, as described above, three electrodes (33, 37, and 41) are arranged for the application of voltage to the first active region 53A, and two electrodes (41 and 45) are arranged for the application of 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) tends to be larger than the volume of the conductor on the second side. However, the provision of the fourth conductor layer 31D makes it easier to make the volume of the conductor (or, from another viewpoint, the proportion of the conductor that occupies the piezoelectric body) equal on the +D3 side and the -D3 side. As a result, for example, the likelihood of unintended bending deformation occurring due to shrinkage during firing and / or expansion and contraction due to temperature changes during use is reduced.

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

[0205] As the outer edge of the second active region 53B (or, from another perspective, 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, because the area of ​​the second portion 53Bb is larger than the area of ​​the first portion 53Ba, it is easier to keep the outer edge of the second active region 53B away from the outer edge of the pressure chamber 21. Consequently, the above-mentioned stress concentration can be alleviated. As a result, for example, the probability of deterioration occurring in the joint between the piezoelectric actuator 13 and the flow path member 11 around the pressure chamber 21 can be reduced. In addition, as previously described, by making the strength of the first electric field applied to the first active region 53A greater than the strength of the second electric field applied to the second active region 53B (making the second electric field relatively smaller), the stress applied to the second active region 53B can be reduced. As a result, for example, the effect of alleviating stress concentration near the outer edge of the pressure chamber 21 as described above is improved.

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

[0207] In this case, the stress is evenly distributed by the circular arc in a plan view. That is, the probability of stress becoming particularly high is reduced. As a result, for example, the stress relaxation effect described above is improved. In particular, the above effect is improved when the planar shape of the pressure chamber 21 is circular (when the pressure chamber 21 is composed only of the circular C1 in Figure 4).

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

[0209] In this case, the outer edge of the second active region 53B can be moved away from the outer edge of the pressure chamber 21. Therefore, the stress concentration described in the explanation of the effect of having a larger area in the second portion 53Bb than in the first portion 53Ba is relieved. 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 stress concentration relief is further improved.

[0210] Furthermore, 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 material and is connected to the outer circumference of the first active region 53A. The driver 61 performs reorientation control (Figure 12). In reorientation control, the driver 61 applies an electric field in the thickness direction to the first inactive region 55A when droplet ejection control is not being performed.

[0211] Therefore, as previously described, the probability of a decrease in displacement due to domain switching in the first inactive region 55A can be reduced by polarization treatment. The first inactive region 55A is a region that receives stress from both the first active region 53A and the second active region 53B, and is prone to domain switching. By performing polarization treatment on the first inactive region 55A, the decrease in displacement can be efficiently reduced. In addition, as previously described, by making the strength of the first electric field applied to the first active region 53A greater than the strength of the second electric field applied to the second active region 53B (making the second electric field relatively smaller), the stress applied to the second active region 53B can be reduced. Consequently, the stress applied from the second active region 53B to the first inactive region 55A can be reduced. As a result, the probability of domain switching occurring in the first inactive region 55A can be reduced, and the frequency of applying polarization treatment to the first inactive 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) from the pressurizing 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 pressurizing surface 11b side (-D3 side). In liquid discharge control, the driver 61 applies an electric field to the second active region 53B by applying 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 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 for both applying an electric field for droplet ejection and for polarization. In other words, the configuration of the piezoelectric actuator 13 is simplified.

[0214] In addition to the above configuration, in this embodiment, the piezoelectric actuator 13 also has an upper electrode (second electrode 37). The second electrode 37 is located on the opposite side (+D3 side) from the pressurizing surface 11b than the intermediate electrode (third electrode 41), and faces the third electrode 41 with at least a portion of the first active region 53A in between. In liquid discharge control, the driver 61 applies an electric field to the first active region 53A by applying 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 voltage to the reorientation electrode 35 and the fourth electrode 45 without applying 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 the control of droplet ejection. 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 electrically suspended, so it does not interfere with the application of electric fields by the reorientation electrode 35 and the fourth electrode 45. By performing the polarization process with the reorientation electrode 35 and the fourth electrode 45, polarization is performed not only on the first inactive 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 inactive region 55A but also the degradation of characteristics caused by domain switching in the second active region 53B can be reduced.

[0216] Furthermore, in this embodiment, as described above, the piezoelectric actuator has a first piezoelectric layer 29A to a fourth piezoelectric layer 29D, and a first electrode 33, a second electrode 37, a third electrode 41, and a fourth electrode 45, which constitute the first active region 53A and the second active region 53B. The inactive region (first inactive region 55A) has a region sandwiched between the re-orienting electrode 35 and the fourth electrode 45 in the first piezoelectric layer 29A and the second piezoelectric layer 29B.

[0217] In this case, for example, as previously described, 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 with a simple configuration. Consequently, the stress applied to the second active region 53B can be reduced with a simple configuration, and the stress applied from the second active region 53B to the first inactive region 55A can be reduced.

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

[0219] In the polarization process of the first embodiment, an electric field was applied to the first inactive region 55A by the reorientation electrode 35 and the fourth electrode 45. In the polarization process of the second embodiment, an electric field was applied to the first inactive region 55A by the reorientation electrode 35 and the third electrode 41. More specifically, in the illustrated example, the reorientation electrode 35 is given a potential higher than the reference potential (in other words, a potential with positive polarity). The third electrode 41 is given the reference potential.

[0220] The above assumes a configuration in which the polarization direction is downward, as shown in Figure 6. In a configuration in which the polarization direction is reversed, a potential lower than the reference potential (or, from another viewpoint, a potential with 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 a voltage for polarization is applied as described above, the first electrode 33, the second electrode 37, the fourth electrode 45, and the fourth conductor layer 31D may, for example, have a reference potential applied to them, or they may be in an electrically floating state. In this embodiment, as previously described, the first electrode 33 is electrically connected to the third electrode 41, and therefore has a reference potential applied to it. The second electrode 37, the fourth electrode 45, and the fourth conductor layer 31D have a reference potential applied to them.

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

[0223] In the first embodiment, the fifth conductor layer 31E (fourth electrode 45) was in contact with the flow channel member 11 (plate 25J) and exposed within the pressure chamber 21. In contrast, in this embodiment, an insulating layer 30 is interposed between the fifth conductor layer 31E and the flow channel member 11. From another viewpoint, an insulating layer 30 is interposed between the second active region 53B and the flow channel member 11. The insulating layer 30 may be considered as part of the piezoelectric actuator 13, as part of the flow channel member 11, or as a separate component from these. In Figure 14, the insulating layer 30 is indicated by reference numerals as a separate component from the piezoelectric actuator 13 and the flow channel member 11.

[0224] The insulating layer 30 may be made of an inorganic material or an organic material. The inorganic material may be a piezoelectric material or not. The piezoelectric material may be the same as or different from the material of the piezoelectric layer 29, and may be fired together with the piezoelectric layer 29 or not. 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, which is 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 it may be bonded to the piezoelectric actuator 13 or the flow channel member 11 with an adhesive.

[0225] The insulating layer 30, for example, similar to the piezoelectric layer 29, extends substantially without gaps over the region where the multiple pressure chambers 21 are arranged with a constant thickness. However, if the insulating layer 30 is relatively thin, it is not impossible to place the insulating layer 30 only directly below and around the second active region 53B (fourth electrode 45). The thickness of the insulating layer 30 may be set as appropriate. For example, the thickness of the insulating layer 30 may be thinner than the thickness of the piezoelectric layer 29 (as shown in the illustration), the same, or thicker. The thickness of the insulating layer 30 may be set as appropriate, taking into consideration, for example, the effects described later (strength and / or insulating properties), and / or the effect on the neutral plane position of the piezoelectric actuator 13.

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

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

[0228] In this case, for example, the stress applied from the flow channel member 11 to the second active region 53B is relieved by the insulating layer 30. For example, in the second active region 53B, the deformation of the portion overlapping with the outer region 11e of the pressure chamber 21 is constrained by the flow channel member 11, and the stress tends to be high at the position overlapping with the outer edge of the pressure chamber 21. This stress is relieved. In addition, the insulating layer 30 covers the electrode (fourth electrode 45) that applies voltage in the thickness direction to the second active region 53B. As a result, for example, the fourth electrode 45 can be insulated from the metal flow channel member 11. Also, the fourth electrode 45 will no longer come into contact with the liquid in the pressure chamber 21. As a result, for example, depending on the type of liquid, the probability of corrosion occurring on the fourth electrode 45 is reduced.

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

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

[0231] The shape of the fourth electrode 445 may be any shape as long as it overlaps with the second active region 53B. For example, the shape of the fourth electrode 445 may be a combination of 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 shaped such that the outer edge of the opening 43 in the fourth conductor layer 31D of the first embodiment roughly coincides with the outer edge of the electrode body 33a and / or the outer edge of the second electrode 37. Alternatively, 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, 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. Furthermore, multiple fourth electrodes 445 may be connected to appropriate wirings and through conductors so that they can be individually given potential.

[0232] The potential applied to the fourth electrode 445 when the liquid is ejected and when polarization 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, since 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, the strength of the electric field applied to the first active region 53A and the strength of the electric field applied to the second active region 53B are approximately equal.

[0233] In this embodiment as well, similar to the first embodiment, the strength of the electric field applied to the first active region 53A may be stronger than the strength of the electric field applied to the second active region 53B. There are various ways to achieve such a relationship of electric field strength. For example, while the potential applied to the electrodes is the same as in the first embodiment, the thickness of the third piezoelectric layer 29C may be made thicker than the thickness of the first piezoelectric layer 29A and the thickness of the second piezoelectric layer 29B, respectively. Alternatively, for example, the second electrode 37 and the fourth electrode 445 may be disconnected so that separate potentials can be applied to each of them, and the potential difference between the third electrode 41 and the second electrode 37 may be made greater 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 channel member 11. Therefore, for example, the same effects as those described in the third embodiment are achieved.

[0235] <Fifth Embodiment> Figure 16 is a schematic cross-sectional view showing the head 507 according to the fifth embodiment, and corresponds to Figure 11 of the first embodiment. In this figure, as in Figure 6, the polarization direction is also indicated by a white 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 this 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 this configuration, various combinations of polarization direction, electrode structure, and potential are possible to realize the operation of the first active region 53A and the second active region 53B as described with reference to Figure 5. Examples shown are as follows:

[0238] Similar to the first embodiment, the piezoelectric actuator 513 has, in order from the top to the bottom, a first electrode 33 (and a re-orienting 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 channel member 11 by the insulating layer 30, and can be subjected to potentials 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 discharge control, a reference potential is applied to the third electrode 41 located between the two. The first electrode 33 and the fourth electrode 45 are applied to potentials with the same polarity as the reference potential. As a result, both the first active region 53A and the second active region 53B 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, making it possible to apply different potentials to the first electrode 33 and the fourth electrode 45. Therefore, in this embodiment as well, 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 illustrated example, the first electrode 33 and the fourth electrode 45 may be connected to each other and have the same potential applied to them.

[0241] (Variation of piezoelectric layer) Figure 17A is a cross-sectional view showing the configuration of the piezoelectric layer 29 according to a modified example, and is an enlarged view of region XVII in Figure 10.

[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 re-orienting electrode 35. The groove 29v extends, for example, along the outer edge of the first electrode 33, surrounding the first electrode 33. In other words, the groove 29v extends in an annular shape. However, the groove 29v may be interrupted in some parts. For example, the groove 29v may not be provided at a position opposite to the electrode body 33a with respect to the lead-out portion 33b.

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

[0244] The groove 29v may be formed by an appropriate method. For example, it may be formed by laser processing on the ceramic green sheet that will become the first piezoelectric layer 29A, or on the first piezoelectric layer 29A after firing.

[0245] By providing the groove 29v in this manner, for example, the likelihood of the metal material constituting the first electrode 33 and the reorientation electrode 35 moving to the region between these electrodes (causing migration) is reduced. As a result, the likelihood of a short circuit between the first electrode 33 and the reorientation electrode 35 can be reduced. From another perspective, in a plan view, the distance between the first electrode 33 and the reorientation electrode 35 is shortened, making it easier to apply polarization treatment to the portion of the first inactive region 55A adjacent to the first active region 53A. Consequently, the effect of maintaining the characteristics of the piezoelectric actuator by polarization treatment is improved. Note that the migration refers to electromigration and / or electrochemical migration.

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

[0247] An insulator 32 may be placed in the groove 29v described above. The insulator 32 is made of a material that has a lower probability of causing migration of the electrode material compared to the material of the first piezoelectric layer 29A. For example, the insulator 32 may be made of resin. The resin may be placed in the groove 29v by an appropriate method such as CVD.

[0248] The arrangement of the insulator 32 can improve the effect of reducing the likelihood of migration, for example. Furthermore, while reducing the likelihood of migration, it is possible to reduce the likelihood of a decrease in the strength of the piezoelectric actuator due to the groove 29v.

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

[0250] The technology relating to this disclosure is not limited to the embodiments described above and may be implemented in various forms.

[0251] For example, the first inactive region does not need to be polarized. That is, the head does not need to have a configuration for polarization. In liquid discharge control, a control other than the control that causes the second active region to extend or contract (referred to as the first control) may be performed for at least a portion of the period during which the first active region extends or contracts. For example, a control that causes the second active region to extend or contract (referred to as the second control) may be performed for at least a portion of the period during which the first active region extends or contracts. Then, the first control may be performed when discharging large droplets, and the second control may be performed when discharging small droplets. The head may be a device for circulating liquid.

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

[0253] 1...Printer (recording device), 2...Liquid ejection head, 7...Head body (liquid ejection head), 11...Flow channel member, 11b...Pressurized surface, 11e...Outer region (relative to the pressure chamber), 13...Piezoelectric actuator, 21...Pressure chamber, 21a...Central part (of the pressure chamber), 21b...Peripheral part (of the pressure chamber), 53A...First active region, 53B...Second active region, 53Ba...First part (of the second active region), 53Bb...Second part (of the second active region), 55A...First inactive region, 61...Driver.

Claims

1. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. The piezoelectric actuator has a plurality of first active region electrodes stacked on each other in the thickness direction for applying an electric field to the first active region, and a plurality of second active region electrodes stacked on each other in the thickness direction for applying an electric field to the second active region, The electrode closest to the pressure surface among the first active region electrodes and the electrode furthest away from the pressure surface among the second active region electrodes are located in the same layer and are electrically connected to form a shared electrode. Liquid dispensing head.

2. The electrode in the first active region electrode that faces the multi-purpose electrode and the electrode in the second active region electrode that faces the multi-purpose electrode are electrically connected. The liquid dispensing head according to claim 1.

3. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. A piezoelectric element located on the opposite side of the pressure surface from the second active region and connected to the outer circumference of the first active region constitutes an inactive region over the thickness of the first active region. Liquid dispensing head.

4. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. The piezoelectric element located on the pressurized side relative to the first active region and inside the second active region is inactive over the thickness of the second active region. Liquid dispensing head.

5. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. The aforementioned liquid discharge control involves waiting in a standby state, discharging the liquid, and then returning to the standby state. The first deformation that occurs in the second active region during liquid discharge control is either an extension beyond the standby state or a contraction beyond the standby state. Liquid dispensing head.

6. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. The liquid discharge control is such that the timing of the transition of the first active region to the first deformed state coincides with the timing of the transition of the second active region to the first deformed state. Liquid dispensing head.

7. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. The device has three or more electrodes, each positioned at different locations in the thickness direction, and each electrode applies at least one of the first electric field and the second electric field. The distance in the thickness direction between two electrodes to which the first electric field is applied, which are adjacent to each other among the three or more positions in the thickness direction of the three or more electrodes, is shorter than the distance in the thickness direction between two electrodes to which the second electric field is applied, which are adjacent to each other among the three or more positions. Liquid dispensing head.

8. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. In the liquid discharge control described above, the maximum value of the potential difference between the two electrodes to which the first electric field is applied is the same as the maximum value of the potential difference between the two electrodes to which the second electric field is applied. Liquid dispensing head.

9. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. When the piezoelectric actuator is described as having a first side on the side opposite to the flow channel member and a second side on the side of the piezoelectric actuator facing the flow channel member, A first piezoelectric layer and a second piezoelectric layer are stacked in order from the first side to the second side, The first electrode overlaps the first side surface of the first piezoelectric layer and overlaps the central part in a planar perspective view, The second electrode overlaps the second side surface of the first piezoelectric layer and overlaps the central part in a planar perspective view, It has a third electrode that overlaps the second side surface of the second piezoelectric layer and overlaps the central portion, the peripheral portion, and the outer region in a planar perspective view, The first active region is, The region sandwiched between the first electrode and the second electrode in the first piezoelectric layer, The second piezoelectric layer has a region sandwiched between the second electrode and the portion of the third electrode that overlaps the central part, The second active region is located on the second side of the portion of the third electrode that overlaps with the peripheral edge and the outer region. Liquid dispensing head.

10. A third piezoelectric layer and a fourth piezoelectric layer are stacked sequentially from the second piezoelectric layer toward the second side, The fourth electrode overlaps the second side surface of the fourth piezoelectric layer and overlaps the peripheral edge and the outer region in a planar perspective view, The aforementioned second active region is, The third and fourth piezoelectric layers have a region sandwiched between the portion of the third electrode that overlaps with the peripheral edge and the outer region, and the fourth electrode. The liquid dispensing head according to claim 9.

11. The portion of the first piezoelectric layer constituting the first active region and the portion of the second piezoelectric layer constituting the first active region are polarized in opposite directions. The portions of the third and fourth piezoelectric layers that constitute the second active region are polarized in the same direction as the polarization direction of the portion of the first piezoelectric layer that constitutes the first active region. In the liquid discharge control described above, the first electrode and the third electrode are at the same potential, the second electrode and the fourth electrode are at the same potential, and the first electric field and the second electric field are applied by the potential difference between the potentials of the first electrode and the third electrode and the potentials of the second electrode and the fourth electrode. The liquid dispensing head according to claim 10.

12. The sum of the thicknesses of the third piezoelectric layer and the fourth piezoelectric layer is greater than the thickness of the first piezoelectric layer and the thickness of the second piezoelectric layer, respectively. The liquid dispensing head according to claim 10 or 11.

13. The piezoelectric actuator has a conductive pattern that overlaps the second side surface of the third piezoelectric layer and is located outside the second active region in a planar perspective view. A liquid dispensing head according to any one of claims 10 to 12.

14. The piezoelectric actuator is It consists of a piezoelectric material and has an inactive region connected to the outer periphery of the first active region, A fourth electrode overlaps the second side surface of the second active region and overlaps the peripheral and outer regions in plan view, The first piezoelectric layer has a re-orienting electrode that overlaps the first side surface and overlaps the peripheral edge and the outer region in a planar perspective view, The driver performs reorientation control by applying an electric field in the thickness direction to the inactive region when the liquid discharge control is not being performed. The inactive region has a region in the first and second piezoelectric layers sandwiched between the reorienting electrode and the fourth electrode. A liquid dispensing head according to any one of claims 9 to 13.

15. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. In a cross-section passing through the center of the pressure chamber and perpendicular to the pressurizing surface, the width of the second portion of the second active region located outside the pressure chamber is greater than the width of the first portion of the second active region overlapping the pressure chamber. Liquid dispensing head.

16. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. The piezoelectric actuator is made of a piezoelectric material and has an inactive region connected to the outer periphery of the first active region. The driver performs reorientation control by applying an electric field in the thickness direction to the inactive region when the liquid discharge control is not being performed. Liquid dispensing head.

17. The piezoelectric actuator is A reorientation electrode that overlaps the inactive region on the side opposite to the pressurized surface, An intermediate electrode located between the inactive region and the second active region, It has a lower electrode that overlaps the second active region on the pressurized surface side, The aforementioned driver In the liquid discharge control described above, an electric field is applied to the second active region by applying a voltage to the intermediate electrode and the lower electrode. In the reorientation control described above, an electric field is applied to the inactive 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. The liquid dispensing head according to claim 16.

18. The piezoelectric actuator has an upper electrode located on the opposite side of the pressure surface from the intermediate electrode, and facing the intermediate electrode with at least a portion of the first active region in between. The aforementioned driver In the liquid discharge control described above, an electric field is applied to the first active region by applying a voltage to the upper electrode and the intermediate electrode. In the reorientation control described above, an electric field is applied to the inactive region by applying a voltage to the reorientation electrode and the lower electrode without applying a potential to the intermediate electrode. The liquid dispensing head according to claim 17.

19. A flow channel member having a pressurizing surface and a pressure chamber opening to the pressurizing surface, A piezoelectric actuator overlapping the aforementioned pressurizing surface, A driver for driving the piezoelectric actuator, It has, When the direction perpendicular to the pressing surface is referred to as the thickness direction, the piezoelectric actuator It consists of a piezoelectric material polarized in the thickness direction, and has a first active region that overlaps with the central part of the pressure chamber in a planar view of the pressurized surface, A piezoelectric material polarized in the thickness direction, a second active region located on the pressure surface side of the first active region, and overlapping the inner peripheral edge and the outer region of the pressure chamber in a plan view of the pressure surface, It has an insulating layer located between the second active region and the flow channel member, The driver controls the strength of the first electric field applied to the first active region in the thickness direction and the strength of the second electric field applied to the second active region in the thickness direction, such that the second active region undergoes the first deformation for at least a portion of the period during which the first active region undergoes the first deformation, by changing the applied electric field. In the liquid discharge control described above, 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 dispensing head.

20. The insulating layer is thinner than the piezoelectric layer that constitutes the first active region. A liquid dispensing head according to any one of claims 1 to 19.

21. The insulating layer is thinner than the piezoelectric layer that constitutes the second active region. A liquid dispensing head according to any one of claims 1 to 20.

22. In a planar view of the pressurized surface, the area of ​​the second portion of the second active region located outside the pressure chamber is larger than the area of ​​the first portion of the second active region overlapping the pressure chamber. A liquid dispensing head according to any one of claims 1 to 21.

23. In a plan view of the pressurized surface, the portion of the outer edge of the pressure chamber corresponding to an angle of 180° or more around the center of the pressure chamber is formed by an arc. A liquid dispensing head according to any one of claims 1 to 22.

24. A liquid dispensing head according to any one of claims 1 to 23, A control unit for controlling the liquid discharge head, It has Recording device.

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