Liquid ejecting head and recording apparatus

Abstract

The invention provides a liquid ejecting head and a recording apparatus. The piezoelectric actuator has a first active region and a second active region. The first active region is composed of a piezoelectric body polarized in the thickness direction, and overlaps a central portion of the pressure chamber in a plan view of the pressing surface. The second active region is formed of a piezoelectric body polarized in the thickness direction, is positioned closer to the pressing surface than the first active region, and overlaps a peripheral edge portion of the pressure chamber and a region outside the pressure chamber in a plan view of the pressing surface. In the liquid ejection control, the driver controls the intensity of a first electric field applied to the first active region and the intensity of a second electric field applied to the second active region such that one of extension and contraction occurs in the second active region in at least a part of a period during which the one of extension and contraction occurs in the first active region. The intensity of the first electric field is greater than that of the second electric field.

Description

[0001] This application is a divisional application of the invention patent application with application date of March 26, 2021, application number 202180021584.9, and invention name “Liquid ejection head and recording device”. Technical Field

[0002] The present disclosure relates to a liquid ejection head and a recording device having the same. Background Art

[0003] Piezoelectric actuators used in inkjet heads and the like are well known (for example, Patent Documents 1 and 2). For example, a single crystal piezoelectric actuator has a vibration plate covering the upper opening of a pressure chamber filled with liquid (ink) and a piezoelectric layer overlapping the vibration plate. The piezoelectric layer stretches or contracts in the direction along the surface, whereby the piezoelectric actuator produces flexural deformation like a bimetal. Thus, if pressure is applied to the pressure chamber, the liquid is ejected. For example, when a voltage is applied to the piezoelectric layer in an area overlapping with the center of the pressure chamber when viewed from above, the piezoelectric layer stretches or contracts in the direction along the surface. Patent Documents 1 and 2 disclose a structure in which a voltage is also applied to a portion of the vibration plate composed of a piezoelectric body that is located on the outer edge side of the pressure chamber when viewed from above. Patent Documents 3 and 4 disclose a technology for applying an electric field to a piezoelectric body for polarization treatment.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-182448

[0007] Patent Document 2: Japanese Patent Application Publication No. 2010-155386

[0008] Patent Document 3: Japanese Patent Application Publication No. 2006-158127

[0009] Patent Document 4: Japanese Patent Application Publication No. 2010-228144 Summary of the invention

[0010] A liquid ejection head according to one embodiment of the present disclosure includes a flow path member, a piezoelectric actuator, and a driver. The flow path member includes a pressurizing surface and a pressure chamber opened on the pressurizing surface. The piezoelectric actuator overlaps with the pressurizing surface. The driver drives the piezoelectric actuator. The piezoelectric actuator includes 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 is composed of a piezoelectric body polarized in the thickness direction, and overlaps with the central portion of the pressure chamber in a top view of the pressurizing surface. The second active region is composed of a piezoelectric body polarized in the thickness direction, and is located closer to the pressurizing surface than the first active region, and overlaps with the peripheral portion of the pressure chamber and the area outside the pressure chamber in a top view of the pressurizing surface. The driver controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction in a liquid ejection control for ejecting liquid. By this control, during at least a portion of a period in which the first active region is extended or contracted in a direction along the pressurizing surface, the second active region is extended or contracted in the direction along the pressurizing surface. In the liquid ejection control, the maximum value of the intensity of the first electric field is greater than the maximum value of the intensity of the second electric field.

[0011] A liquid ejection head according to one embodiment of the present disclosure includes a flow path member, a piezoelectric actuator, and a driver. The flow path member includes a pressurizing surface and a pressure chamber opened on the pressurizing surface. The piezoelectric actuator overlaps with the pressurizing surface. The driver drives the piezoelectric actuator. The piezoelectric actuator includes 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 is composed of a piezoelectric body polarized in the thickness direction, and overlaps with the central part of the pressure chamber in a top view of the pressurizing surface. The second active region is composed of a piezoelectric body polarized in the thickness direction, and is located closer to the pressurizing surface than the first active region, and overlaps with the peripheral part of the pressure chamber and the area outside the pressure chamber in a top view of the pressurizing surface. In the control of ejecting 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. Thus, during at least a portion of a period in which the first active region is extended or contracted in a direction along the pressurizing surface, the second active region is extended or contracted in the direction along the pressurizing surface. In a plan view of the pressurizing surface, an area of ​​a second portion of the second active region located outside the pressure chamber is larger than an area of ​​a first portion of the second active region overlapping the pressure chamber.

[0012] A liquid ejection head according to one embodiment of the present disclosure includes a flow path member, a piezoelectric actuator, and a driver. The flow path member includes a pressurized surface and a pressure chamber opened on the pressurized surface. The piezoelectric actuator overlaps with the pressurized surface. The driver drives the piezoelectric actuator. The piezoelectric actuator includes a first active region, a second active region, and an inactive region. The direction perpendicular to the pressurized surface is referred to as the thickness direction. In this case, the first active region is composed of a piezoelectric body polarized in the thickness direction, and overlaps with the central portion of the pressure chamber in a top view of the pressurized surface. The second active region is composed of a piezoelectric body polarized in the thickness direction, and is located closer to the pressurized surface than the first active region, and overlaps with the peripheral portion of the pressure chamber and the region outside the pressure chamber in a top view of the pressurized surface. The inactive region is composed of a piezoelectric body and is connected to the periphery of the first active region. The driver performs liquid ejection control and reorientation control. In the liquid ejection control, the driver controls the intensity of the electric field applied to the first active area in the thickness direction and the intensity of the electric field applied to the second active area in the thickness direction. Thus, in at least a portion of a period in which the first active area is extended or contracted in the direction along the pressurizing surface, the second active area is extended or contracted in the direction along the pressurizing surface. In the reorientation control, the driver applies an electric field in the thickness direction to the inactive area when the liquid ejection control is not performed.

[0013] A recording device according to one embodiment of the present disclosure includes a liquid ejection head and a control unit for controlling the liquid ejection head. The liquid ejection head includes a flow path member and a piezoelectric actuator. The flow path member includes a pressurizing surface and a pressure chamber opened on the pressurizing surface. The piezoelectric actuator overlaps the pressurizing surface. In addition, the piezoelectric actuator includes a first active region and a second active region. The direction perpendicular to the pressurizing surface is referred to as a thickness direction. In this case, the first active region is composed of a piezoelectric body polarized in the thickness direction and overlaps with the central part of the pressure chamber in a perspective view of the pressurizing surface from above. The second active region is composed of a piezoelectric body polarized in the thickness direction and is located closer to the pressurizing surface than the first active region. It overlaps with the peripheral part of the pressure chamber and the area outside the pressure chamber in a perspective view of the pressurizing surface from above. The control unit controls the intensity of a first electric field applied to the first active region in the thickness direction and the intensity of a second electric field applied to the second active region in the thickness direction in liquid ejection control for ejecting liquid. Thus, during at least a portion of a period in which the first active region is extended or contracted in a direction along the pressurizing surface, the second active region is extended or contracted in a direction along the pressurizing surface. In the liquid ejection control, the maximum value of the intensity of the first electric field is greater than the maximum value of the intensity of the second electric field.

[0014] A recording device according to one embodiment of the present disclosure includes a liquid ejection head and a control unit for controlling the liquid ejection head. The liquid ejection head includes a flow path member and a piezoelectric actuator. The flow path member includes a pressurizing surface and a pressure chamber opened on the pressurizing surface. The piezoelectric actuator overlaps with the pressurizing surface. In addition, the piezoelectric actuator includes a first active region and a second active region. The direction perpendicular to the pressurizing surface is referred to as a thickness direction. In this case, the first active region is composed of a piezoelectric body polarized in the thickness direction and overlaps with the central part of the pressure chamber in a perspective view of the pressurizing surface from above. The second active region is composed of a piezoelectric body polarized in the thickness direction and is located closer to the pressurizing surface than the first active region. It overlaps with the peripheral part of the pressure chamber and the area outside the pressure chamber in a perspective view of the pressurizing surface from above. In the control of ejecting liquid droplets, 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. Thus, during at least a portion of a period in which the first active region is extended or contracted in a direction along the pressurizing surface, the second active region is extended or contracted in the direction along the pressurizing surface. In a plan view of the pressurizing surface, an area of ​​the second active region that overlaps with the outer region is larger than an area of ​​the second active region that overlaps with the pressure chamber.

[0015] A recording device according to one embodiment of the present disclosure includes a liquid ejection head and a control unit for controlling the liquid ejection head. The liquid ejection head includes a flow path member and a piezoelectric actuator. The flow path member includes a pressurizing surface and a pressure chamber opened on the pressurizing surface. The piezoelectric actuator overlaps the pressurizing surface. In addition, the piezoelectric actuator includes a first active region, a second active region, and an inactive region. The direction perpendicular to the pressurizing surface is referred to as a thickness direction. In this case, the first active region is composed of a piezoelectric body polarized in the thickness direction, and overlaps with the central portion of the pressure chamber in a perspective view of the pressurizing surface from above. The second active region is composed of a piezoelectric body polarized in the thickness direction, and is located closer to the pressurizing surface than the first active region, and overlaps with the peripheral portion of the pressure chamber and the region outside the pressure chamber in a perspective view of the pressurizing surface from above. The inactive region is composed of a piezoelectric body and is connected to the periphery of the first active region. The control unit performs liquid ejection control and reorientation control. In the liquid ejection control, the control unit controls the intensity of the first electric field applied to the first active area in the thickness direction and the intensity of the second electric field applied to the second active area in the thickness direction. Thus, in at least a portion of a period in which the first active area is extended or contracted in the direction along the pressurizing surface, the second active area is extended or contracted in the direction along the pressurizing surface. In the reorientation control, the control unit applies an electric field in the thickness direction to the inactive area when the liquid ejection control is not performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A It is a side view of the recording device involved in the first embodiment.

[0017] Figure 1B It is a top view of the recording device involved in the first embodiment.

[0018] Figure 2 It is a plan view of a part of the liquid ejecting head according to the first embodiment.

[0019] Figure 3 yes Figure 2 Cross-sectional view at line III-III.

[0020] Figure 4 It is a plan view of the pressure chamber of the liquid ejecting head according to the first embodiment.

[0021] Figure 5 It is a cross-sectional view schematically showing the piezoelectric actuator and the upper portion of the flow path member of the liquid ejection head according to the first embodiment.

[0022] Figure 6This is a schematic cross-sectional view showing the polarization direction of the piezoelectric layer in the piezoelectric actuator according to the first embodiment.

[0023] Figure 7 This is an exploded perspective view of a part of the liquid ejecting head according to the first embodiment.

[0024] Figure 8 yes Figure 7 A magnified portion of the image.

[0025] Fig. 9 This is a plan view showing a part of the conductor layer of the liquid ejecting head according to the first embodiment in a simplified manner.

[0026] Fig.10 yes Fig. 9 Cross-sectional view at line XX.

[0027] Fig.11 This is a schematic cross-sectional view showing the potential when the liquid is ejected in the liquid ejection head according to the first embodiment.

[0028] Fig.12 This is a schematic cross-sectional view showing the potential during the polarization process in the liquid ejecting head according to the first embodiment.

[0029] Fig.13 It is a schematic cross-sectional view of a liquid ejecting head according to a second embodiment.

[0030] Fig.14 It is a schematic cross-sectional view of a liquid ejecting head according to a third embodiment.

[0031] Fig.15 It is a schematic cross-sectional view of a liquid ejecting head according to a fourth embodiment.

[0032] Fig.16 It is a schematic cross-sectional view of a liquid ejecting head according to a fifth embodiment.

[0033] Fig.17A It is a cross-sectional view showing the structure of a piezoelectric layer according to a modification.

[0034] Fig. 17B It is a cross-sectional view showing the structure of a piezoelectric layer according to another modification. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In addition, the following drawings are schematic. Therefore, details may be omitted. In addition, the dimension ratio may not be consistent with the actual dimension ratio. The dimension ratios of multiple drawings may not be consistent with each other. Sometimes, a specific dimension may be displayed larger than the actual size, and a specific shape may be exaggerated.

[0036] In the description of the second embodiment and thereafter, the parts different from the previously described embodiment are basically described. Matters not specifically mentioned may be the same as the previously described embodiment, or may be inferred from the previously described embodiment. In addition, in a plurality of embodiments, for structures corresponding to each other, even if the details are different, sometimes the same reference numerals are given to each other.

[0037] The “similarity” in the present disclosure includes similarity in mathematics, but is not limited thereto. Similarity in mathematics refers to a situation where a shape is consistent with other shapes when it is enlarged or reduced (or when such a proportional transformation is not performed). However, with reference to technical common sense and other reasonable considerations, a relationship close to the mathematical similarity holds and can also be considered similar. For example, an ellipse and an ellipse with an outer edge located at a fixed distance inside or outside the outer edge of the ellipse are not similar in mathematics because the ratio of the major diameter to the minor diameter is different between the two. However, the above-mentioned relationship can also be included in the similarity in the present disclosure.

[0038] In addition, the terms (e.g., "circle," "ellipse," or "rectangle") used in the present disclosure to represent various shapes include shapes represented by these terms in mathematics, but are not limited thereto. For example, an ellipse can be formed by only a curve that becomes convex toward the outside, as long as the long side direction and the short side direction that are substantially orthogonal to each other can be determined. In addition, for example, the corners of a rectangle may be chamfered.

[0039] <First embodiment>

[0040] (Overall structure of the printer)

[0041] FIG1(a) is a schematic side view of a color inkjet printer 1 (an example of a recording device, hereinafter sometimes simply referred to as a printer) including a liquid ejection head 2 (hereinafter sometimes simply referred to as a head) according to an embodiment of the present disclosure. FIG1(b) is a schematic top view of the printer 1 .

[0042] In addition, the head 2 or the printer 1 can set any direction as the vertical direction, but for convenience, the vertical direction of the paper surface of FIG. 1(a) is sometimes used as the vertical direction, and the terms such as upper surface or lower surface are used. In addition, the terms of top view or top perspective view refer to the situation of observing in the vertical direction of the paper surface of FIG. 1(a) unless otherwise specified.

[0043] The printer 1 conveys the printing paper P (an example of a recording medium) from the paper feed roller 80A to the recovery roller 80B, thereby moving the printing paper P relative to the head 2. The paper feed roller 80A and the recovery roller 80B and various rollers described later constitute a moving unit 85 that moves the printing paper P relative to the head 2. The control unit 88 controls the head 2 based on data such as images and characters, that is, print data, etc., to eject liquid toward the printing paper P, and droplets of liquid fall on the printing paper P, thereby performing printing or other recording on the printing paper P.

[0044] In this embodiment, the head 2 is fixed relative to the printer 1, and the printer 1 is a so-called line printer. As another embodiment of the recording device, a so-called serial printer can be cited, which alternately moves the head 2 in a direction intersecting the conveying direction of the printing paper P (for example, a substantially orthogonal direction) and ejects droplets and conveys the printing paper P.

[0045] In the printer 1, four flat head mounting frames 70 (hereinafter sometimes referred to as frames) are fixed substantially parallel to the printing paper P. Five holes (not shown) are provided in each frame 70, and five heads 2 are mounted in the respective holes. Five heads 2 mounted on one frame 70 constitute one head group 72. The printer 1 has four head groups 72, and a total of 20 heads 2 are mounted.

[0046] The portion of the head 2 mounted on the frame 70 that discharges liquid faces the printing paper P. The distance between the head 2 and the printing paper P is set to, for example, about 0.5 to 20 mm.

[0047] The 20 heads 2 may be directly connected to the control unit 88 or may be connected to the control unit 88 via a distribution unit that distributes print data. For example, the control unit 88 may send print data to one distribution unit, and the one distribution unit may distribute the print data to the 20 heads 2. In addition, 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 in the corresponding head group 72.

[0048] The head 2 has a long and thin strip shape in the direction from the front to the inside of FIG. 1 (a) and in the vertical direction of FIG. 1 (b). In one head group 72, three heads 2 are arranged along a direction intersecting the conveying direction of the printing paper P (for example, a substantially orthogonal direction), and the other two heads 2 are arranged one by one between the three heads 2 at positions offset along the conveying direction. To put it another way, in one head group 72, the heads 2 are arranged in a staggered manner. The heads 2 are arranged so that the range that can be printed by each head 2 is connected in the width direction of the printing paper P, that is, in the direction intersecting the conveying direction of the printing paper P, or the ends are repeated, thereby enabling gapless printing in the width direction of the printing paper P.

[0049] The four head groups 72 are arranged along the conveying direction of the printing paper P. Liquid (e.g., ink) is supplied to each head 2 from a liquid supply tank (not shown). The same color of ink is supplied to the heads 2 belonging to one head group 72, and four colors of ink can be printed using the four head groups 72. The colors of the ink ejected from each head group 72 are, for example, magenta (M), yellow (Y), cyan (C), and black (K). By making the above-mentioned ink fall on the printing paper P, a color image can be printed.

[0050] If the printing is in monochrome and the range that can be printed by one head 2 is to be printed, the number of heads 2 mounted on the printer 1 may be one. The number of heads 2 included in the head group 72 and the number of head groups 72 can be appropriately changed according to the object to be printed and the printing conditions. For example, in order to further perform multi-color printing, the number of head groups 72 may be increased. In addition, if a plurality of head groups 72 for printing in the same color are configured and print alternately in the conveying direction, the conveying speed can be increased even if heads 2 with the same performance are used. Thus, the printing area per unit time can be increased. In addition, a plurality of head groups 72 for printing in the same color may be prepared, and the configuration may be deviated in a direction intersecting the conveying direction, thereby improving the resolution in the width direction of the printing paper P.

[0051] Furthermore, in addition to printing colored ink, in order to perform surface treatment of printing paper P, liquids such as coating agents may be printed uniformly or patterned by the head 2. For example, when a material that is difficult for liquid to penetrate is used as a recording medium, a material that forms a liquid receiving layer that is easy for liquid to fix can be used as a coating agent. In addition, when a material that is easy for liquid to penetrate is used as a recording medium, a material that forms a liquid penetration inhibition layer is used as a coating agent so that the liquid does not ooze out too much or does not mix too much with other liquids that fall down adjacently. In addition to printing with the head 2, the coating agent may also be uniformly applied by a coating machine 76 controlled by a control unit 88.

[0052] The printer 1 prints on the printing paper P as a recording medium. The printing paper P is wound around the paper feed roller 80A, and the printing paper P fed from the paper feed roller 80A passes through the lower side of the head 2 mounted on the frame 70, passes between two conveying rollers 82C, and is finally collected by the collection roller 80B. When printing, the conveying roller 82C is rotated, so that the printing paper P is conveyed at a fixed speed and printed by the head 2.

[0053] Next, the printer 1 will be described in detail in the order in which the printing paper P is conveyed. The printing paper P fed from the paper feed roller 80A passes between two guide rollers 82A and then passes under the coater 76. The coater 76 coats the printing paper P with the coating agent described above.

[0054] Next, the printing paper P enters the head chamber 74 that accommodates the frame 70 on which the head 2 is mounted. The head chamber 74 is connected to the outside in a part such as the part where the printing paper P enters and exits, but is generally a space isolated from the outside. The head chamber 74 controls control factors such as temperature, humidity, and air pressure by the control unit 88 as needed. In the head chamber 74, the influence of interference can be reduced compared to the outside where the printer 1 is installed, so the range of variation of the above-mentioned control factors can be narrower than that of the outside.

[0055] Five guide rollers 82B are arranged in the head chamber 74, and the printing paper P is conveyed on the guide rollers 82B. When viewed from the side, the five guide rollers 82B are arranged so that the center becomes convex toward the direction where the frame 70 is arranged. As a result, the printing paper P conveyed on the five guide rollers 82B becomes an arc shape when viewed from the side, and by applying tension to the printing paper P, the printing paper P between the guide rollers 82B is stretched into a flat shape. One frame 70 is arranged between two guide rollers 82B. The setting angle of the frame 70 is slightly changed so as to be parallel to the printing paper P conveyed thereunder.

[0056] The printing paper P output from the head chamber 74 to the outside passes between the two conveying rollers 82C, passes through the dryer 78, passes between the two guide rollers 82D, and is recovered by the recovery roller 80B. The conveying speed of the printing paper P is set to 100 m / min, for example. Each roller can be controlled by the control unit 88 or manually operated by a person.

[0057] By drying with the dryer 78, it is difficult to cause the overlapping and wound printing paper P to adhere to each other or the undried liquid to rub in the recovery roller 80B. In order to print at high speed, it is necessary to dry quickly. In order to speed up the drying, in the dryer 78, drying can be carried out in sequence by multiple drying methods, or multiple drying methods can be used for drying at the same time. As the drying method adopted at this time, for example, there are blowing of warm air, irradiation of infrared rays, contact with the heated roller, etc. In the case of irradiating infrared rays, infrared rays in a specific frequency range can also be irradiated to reduce damage to the printing paper P and speed up drying. In the case of making the printing paper P contact with the heated roller, the printing paper P can also be conveyed along the cylindrical surface of the roller to extend the heat conduction time. The range of conveying along the cylindrical surface of the roller can be more than 1 / 4 of the cylindrical surface of the roller, and can also be more than 1 / 2 of the cylindrical surface of the roller. In the case of printing UV curing ink, etc., the dryer 78 can be replaced, or a UV irradiation light source can be additionally configured in the dryer 78. The UV irradiation light source can also be configured between each frame 70.

[0058] The printer 1 may also include a cleaning unit for cleaning the head 2. The cleaning unit performs cleaning by wiping and / or capping, for example. Wiping is performed by, for example, wiping the surface of the part where the liquid is ejected, such as the ejection surface 11a (described later), with a soft wiper, so as to remove the liquid attached to the surface. Cleaning by capping is performed, for example, in the following manner. First, the gap is covered (this operation is called capping) so that the part where the liquid is ejected, such as the ejection surface 11a, is covered, thereby forming a space by roughly sealing the ejection surface 11a and the gap. In this state, by repeatedly ejecting the liquid, liquid with a viscosity higher than the standard state, foreign matter, etc. that clogs the ejection hole 3 (described later) is removed. By capping, the liquid being cleaned is difficult to scatter to the printer 1, and the liquid is difficult to adhere to the conveying mechanism such as the printing paper P and rollers. The ejection surface 11a that has been cleaned may also be further wiped. Cleaning by wiping and / or capping may be performed by a person manually operating a wiper and / or cap installed in the printer 1 , or may be performed automatically by the control unit 88 .

[0059] The recording medium may be a roll of cloth or the like in addition to the printing paper P. In addition, the printer 1 may also carry a conveying belt instead of directly carrying the printing paper P, and place the recording medium on the conveying belt for carrying. In this way, a single sheet of processed paper, cut cloth, wood or tile, etc. may be used as a recording medium. Furthermore, a liquid containing conductive particles may be ejected from the head 2 to print wiring patterns of electronic devices, etc. In addition, a chemical agent or a liquid of a chemical agent containing a given amount of liquid may be ejected from the head 2 toward a reaction container, etc., to react, etc., to produce chemicals.

[0060] In addition, position sensors, speed sensors, and / or temperature sensors may be installed in the printer 1, and the control unit 88 controls each unit of the printer 1 based on the status of each unit of the printer 1 obtained from the information from each sensor. For example, in the case where the temperature of the head 2, the temperature of the liquid in the liquid supply tank that supplies the liquid to the head 2, and / or the pressure applied by the liquid in the liquid supply tank to the head 2 affect the ejection characteristics (for example, the ejection amount and / or the ejection speed) of the ejected liquid, the drive signal for ejecting the liquid may be changed based on this information.

[0061] (Spraying surface)

[0062] Figure 2 It is a top view showing a part of the surface (discharge surface 11a) of the head 2 facing the printing paper P. In this figure, for convenience, an orthogonal coordinate system consisting of the D1 axis, the D2 axis and the D3 axis is given. The D1 axis is defined as being parallel to the direction of relative movement of 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 limited in the description of this embodiment. The D2 axis is defined as being parallel to the discharge surface 11a and the printing paper P, and being orthogonal to the D1 axis. The positive and negative signs of the D2 axis are also not particularly limited. The D3 axis is defined as being orthogonal to the discharge surface 11a and the printing paper P. -D3 side ( Figure 2 The direction from the head 2 to the printing paper P is the direction near the front side of the paper surface. In addition, when it is simply referred to as the D3 direction, it can also be set to either the +D3 direction toward the +D3 side or the -D3 direction toward the -D3 side. As described above, the head 2 is shaped such that the D2 direction is the long side direction, and here, one end side portion of the long side direction is shown.

[0063] The ejection surface 11a is, for example, a plane constituting a large part of the surface of the head 2 facing the printing paper P. In addition, the ejection surface 11a is, for example, set to be a substantially rectangular shape with the D2 direction as the long side direction. A plurality of ejection holes 3 for ejecting ink droplets are opened on the ejection surface 11a. The plurality of ejection holes 3 are arranged so that the positions in the direction (D2 direction) orthogonal to the direction (D1 direction) of relative movement of the head 2 and the printing paper P are different from each other. Therefore, the head 2 and the printing paper P are relatively moved by the moving unit 85, and ink droplets are ejected from the plurality of ejection holes 3, thereby forming an arbitrary two-dimensional image.

[0064] More specifically, the plurality of ejection holes 3 are arranged in a plurality of rows (16 rows in the example shown in the figure). That is, the plurality of ejection holes 3 constitute a plurality of ejection hole rows 5. In the plurality of ejection hole rows 5, the positions of the plurality of ejection holes 3 in the D2 direction are different from each other. Thus, a plurality of ink dots arranged in the D2 direction at a pitch narrower than the pitch of the ejection holes 3 in each ejection hole row 5 can be formed on the printing paper P. However, the head 2 may also be a structure having only one row instead of the ejection hole row 5.

[0065] The plurality of ejection hole rows 5 are, for example, substantially parallel to each other and have the same length. In the example shown in the figure, the ejection hole row 5 is parallel to the direction (D2 direction) perpendicular to the direction of relative movement of the head 2 and the printing paper P. The ejection hole row 5 may be inclined relative to the D2 direction. In addition, in the example shown in the figure, the size of the gaps between the plurality of ejection hole rows 5 (intervals in the D1 direction) is not equal. This is due to, for example, the convenience of configuring the flow path inside the head 2. Of course, the size of the gaps between the ejection hole rows 5 may also be equal.

[0066] (Head body)

[0067] Figure 3 yes Figure 2 Cross-sectional view at III-III. Figure 3 The side below the paper surface is the printing paper P side. Here, the structure involved in one ejection hole 3 is mainly shown. In addition, the head body 7 including the ejection surface 11a in the head 2 (that is, only a part of the ejection surface 11a side) is shown here. In addition, the head body 7 can also be regarded as a liquid ejection head.

[0068] The head body 7 is a roughly plate-shaped member, and one side of the back side of the plate-shaped surface becomes the above-mentioned ejection surface 11a. The thickness of the head body 7 is, for example, not less than 0.5 mm and not more than 2 mm. The head body 7 is a piezoelectric head that applies pressure to the liquid by mechanical deformation of the piezoelectric element to eject droplets. The head body 7 has a plurality of ejection elements 9, each of which includes an ejection hole 3. The plurality of ejection elements 9 and structures related to the plurality of ejection elements 9 (for example, wiring connected to the plurality of ejection elements 9) can basically be set to the same structure as each other. The plurality of ejection elements 9 are arranged two-dimensionally along the ejection surface 11a.

[0069] In another viewpoint, the head body 7 includes: a substantially plate-shaped flow path member 11 forming a flow path for liquid (ink) to flow; and a piezoelectric actuator 13 for applying pressure to the liquid in the flow path member 11. The plurality of ejection elements 9 include the flow path member 11 and the piezoelectric actuator 13. The ejection surface 11a includes the flow path member 11. The surface of the flow path member 11 on the opposite side to the ejection surface 11a is referred to as a pressurizing surface 11b.

[0070] The flow path member 11 includes a common flow path 15 and a plurality of individual flow paths 17 ( Figure 3 1 is shown in the figure). Each individual flow path 17 has the above-mentioned ejection hole 3, and further has a connecting flow path 19, a pressure chamber 21, and a partial flow path 23 in order from the common flow path 15 to the ejection hole 3.

[0071] The plurality of individual flow paths 17 and the common flow path 15 are filled with liquid. Pressure is applied to the liquid by the volume change of the plurality of pressure chambers 21, so that the liquid is sent from the plurality of pressure chambers 21 to the plurality of partial flow paths 23, and a plurality of liquid droplets are ejected from the plurality of ejection holes 3. In addition, the liquid is replenished from the common flow path 15 to the plurality of pressure chambers 21 via the plurality of connecting flow paths 19. The piezoelectric actuator 13 (piezoelectric element 27) applies pressure to the liquid in the pressure chamber 21 by, for example, generating bending deformation toward the pressure chamber 21 side and / or by restoring to a flat state from a state bent toward the side opposite to the pressure chamber 21 side.

[0072] The flow path member 11 is constituted, for example, by stacking a plurality of plates 25A to 25J (hereinafter, A to J are sometimes omitted). A plurality of holes (mainly through holes. Concave portions may also be formed) constituting a plurality of individual flow paths 17 and a common flow path 15 are formed in the plate 25. The thickness and the number of stacking of the plurality of plates 25 may be appropriately set according to the shapes of the plurality of individual flow paths 17 and the common flow path 15, etc. The plurality of plates 25 may include appropriate materials. For example, the plurality of plates 25 include metal or resin. The thickness of the plate 25 is, for example, greater than 10 μm and less than 300 μm. The plates 25 are fixed to each other, for example, by an adhesive (not shown) sandwiched between the plates 25.

[0073] (Flow path shape)

[0074] The specific shape and size of each flow path in the flow path member 11 can be appropriately set. In the example shown in the figure, it is as follows.

[0075] The common flow path 15 is in the long side direction of the head 2 ( Figure 3 The common flow path 15 may be provided in only one direction, or may be provided in parallel with each other in a plurality of directions, for example. The cross-sectional shape of the common flow path 15 is set to be rectangular.

[0076] The plurality of individual flow paths 17 (or the ejection elements 9 in another viewpoint) are arranged along the longitudinal direction of each common flow path 15. Furthermore, the plurality of ejection holes 3 individually included in the plurality of individual flow paths 17 are also arranged along the common flow path 15. Figure 2 In the arrangement of the ejection holes 3 as shown, for example, two rows of ejection holes 3 may be arranged on both sides of one common flow path 15. Alternatively, 16 rows of ejection holes 3 may be arranged in four common flow paths 15 in total.

[0077] The pressure chamber 21 opens, for example, at the pressurizing surface 11b and is blocked by the piezoelectric actuator 13. Alternatively, the pressure chamber 21 may be blocked by the plate 25. This may also be considered as a question of whether the plate 25 blocking the pressure chamber 21 is considered as a part of the flow path member 11 or as a part of the piezoelectric actuator 13. In the description of the present disclosure, the layer (plate) on the upper side of the pressure chamber 21 is understood as a part of the piezoelectric actuator 13.

[0078] The shapes of the plurality of pressure chambers 21 are, for example, identical to each other. The shape of each pressure chamber 21 can be appropriately set. For example, the pressure chamber 21 is formed into a thin shape extending along the pressurizing surface 11b with a certain thickness. The pressure chamber 21 may also have portions with different thicknesses. The thin shape is, for example, a shape whose thickness is smaller than any diameter in a plan view.

[0079] In addition, the diameter is, for example, the length of a portion of a straight line that passes through the center of the top view figure and crosses the top view figure and is located in the top view figure. When viewed from above, when the center (or center, etc.) is called (for the top view figure, the center is called), unless otherwise specified, the center can be, for example, the centroid. The centroid is the center of gravity of the top view figure, and is the point where the first moment of the cross section with respect to any axis passing through the point is 0.

[0080] For example, the top view shape of the pressure chamber 21 may be a shape having a long side direction and a short side direction that are orthogonal to each other (e.g., a rhombus or an ellipse), or a shape that cannot conceptualize such directions (e.g., a circle). In addition, the relationship between the long side direction and the short side direction and the arrangement of the plurality of pressure chambers 21 is also arbitrary. In the description of this embodiment, as described later, a shape obtained by superimposing a circle and an ellipse is taken as an example. In other viewpoints, a shape that can conceptualize the long side direction and the short side direction is taken as an example. In the illustrated example, Figure 3 The left-right direction of the paper is the long side direction of the pressure chamber 21. This direction is, for example, a direction intersecting (for example, orthogonal) with the direction in which the common flow path 15 extends, and in other viewpoints, is the short side direction of the head body 7.

[0081] In addition, in a mode where the shape of the cross section of the pressure chamber 21 parallel to the pressurizing surface 11b is not constant in the vertical direction, the description of the top view shape of the pressure chamber 21 in the present disclosure can be applied to the top view shape of the pressurizing surface 11b (the opening surface of the pressure chamber 21), for example. This is because the shape of the pressure chamber 21 that has a large influence on the pressure received from the piezoelectric actuator 13 is the shape of the pressurizing surface 11b.

[0082] The partial flow path 23 extends from the pressure chamber 21 toward the ejection surface 11a. The shape of the partial flow path 23 is generally cylindrical. In addition, the partial flow path 23 may extend obliquely in the vertical direction from the pressure chamber 21 toward the ejection surface 11a (the example shown in the figure), or may extend without being inclined. In addition, the area of ​​the cross section of the partial flow path 23 may also be different depending on the vertical position. When viewed from above, the partial flow path 23 is connected to, for example, an end of the pressure chamber 21 in a given direction (for example, the long side direction of the pressure chamber 21 in a top view).

[0083] The ejection hole 3 is formed in a part of the bottom surface of the partial flow path 23 (the surface on the side opposite to the pressure chamber 21). The ejection hole 3 is, for example, located substantially in the center of the bottom surface of the partial flow path 23. The ejection hole 3 may be disposed eccentrically relative to the center of the bottom surface of the partial flow path 23. The ejection hole 3 has a longitudinal cross-sectional shape that is tapered with a smaller diameter as it approaches the ejection surface 11a. A part or all of the ejection hole 3 may also be in an inverted cone shape.

[0084] The connecting flow path 19 includes, for example, a portion extending upward from the upper surface of the common flow path 15, a portion extending from the portion in a direction along the plate 25, and a portion extending upward from the portion and connected to the lower surface of the pressure chamber 21. The cross-sectional area perpendicular to the flow direction of the portion along the plate 25 is reduced, and functions as a so-called throttle valve. When viewed from above, the connection position of the connecting flow path 19 to the pressure chamber 21 is set to, for example, an end portion of the lower surface of the pressure chamber 21 on the side opposite to the center of the lower surface and the partial flow path 23.

[0085] Regarding the arrangement of the plurality of pressure chambers 21, the arrangement may be generally carried out in the same manner as described in reference to Figure 2 The arrangement of the plurality of ejection holes 3 described above is described. The arrangement of the plurality of pressure chambers 21 may be different from the arrangement of the plurality of ejection holes 3. For example, by making the shapes of the plurality of partial flow paths 23 different from each other, the arrangement of the plurality of pressure chambers 21 may be different from the arrangement of the plurality of ejection holes 3. Figure 2 The plurality of ejection holes 3 shown may be uniformly distributed in both the D1 direction and the D2 direction (the pitch between rows of the pressure chambers 21 is set constant), or may be arranged in a smaller number of rows than the ejection hole rows 5 .

[0086] (Top view of the pressure chamber)

[0087] Figure 4 2 is a top view of the pressure chamber 21. In this figure, the pressure chamber 21 is shown by a solid line.

[0088] The top view shape of the pressure chamber 21 is, for example, a shape obtained by superimposing the region of the circle C1 and the region R2 protruding from the region of the circle C1 in a given direction (up and down direction on the paper) on both sides (one region R2 is shaded). The outer edge of the region R2 on the side opposite to the circle C1 (the outer edge shown by the solid line) is a curve bulging outward. The curvature of this curve (average value if not constant) is, for example, greater than the curvature of the circle C1.

[0089] The above-mentioned top view shape of the pressure chamber 21 can be understood as a shape obtained by superimposing the area where the circle C1 and the ellipse C2 overlap with each other (the area surrounded by the dotted line) and the area where they do not overlap with each other (the area surrounded by the solid line and the dotted line). That is, when the circle C1 and the ellipse C2 are regarded as closed curves in the bending diagram, the top view shape of the pressure chamber 21 is equivalent to a sum set (logical sum in other viewpoints).

[0090] More specifically, the center of the circle C1 coincides with the center of the ellipse C2 (see center O1). The major diameter rL of the ellipse C2 is longer than the radius r1 of the circle C1, and the minor diameter rS of the ellipse C2 is shorter than the radius r1 of the circle C1. Furthermore, the regions R2 on both end sides of the long side direction of the ellipse C2 are located outside the circle C1.

[0091] The curvature of the outer edge (the outer edge shown by the solid line) of the region R2 on the side opposite to the circle C1 may be constant. That is, the region R2 is not conceptualized as the two ends of an ellipse, but may be conceptualized as a part of a circle having a smaller radius than the circle C1.

[0092] Various dimensions of the above-mentioned shape (e.g., the relative lengths of the radius r1, the major diameter rL, and the minor diameter rS) can be appropriately set. An example is given below. The major diameter rL can be set to be greater than 1.2 times and less than 1.8 times the radius r1. The radius of curvature obtained by averaging the curvatures of the outer edge of the region R2 on the side opposite to the circle C1 can be set to be greater than 0.3 times and less than 0.6 times the radius r1.

[0093] In other words, the shape of the pressure chamber 21 described above is a shape in which most (or all) of its outer edge is formed by an arc. For example, the outer edge of the pressure chamber 21, which corresponds to a portion of the outer edge of the pressure chamber 21 that is 180° or more around the center of the pressure chamber 21, is formed by an arc.

[0094] In the following description, the terms "central portion" and "peripheral portion" of the pressure chamber 21 are sometimes used. Figure 4 In FIG. 1 , the outer edge of the central portion 21a is indicated by a two-dot chain line Ln1. The central portion 21a is, for example, a region that includes the center O1 of the pressure chamber 21 in a plan view and is separated from the outer edge of the pressure chamber 21 toward the center O1. Figure 4In FIG. 1 , the inner edge of the peripheral portion 21b is indicated by a two-dot chain line Ln1, and the outer edge is indicated by a solid line indicating the outer edge of the pressure chamber 21. The peripheral portion 21b is in contact with the outer edge (essentially the entire circumference) of the pressure chamber 21 when viewed from above, and is an area away from the center of the pressure chamber 21.

[0095] The central portion 21a and the peripheral portion 21b can be defined in a manner that the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b are separated from each other, can be defined in a manner that the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b are consistent with each other, or can be defined in a manner that the outer edge side portion of the central portion 21a and the inner edge side portion of the peripheral portion 21b overlap each other. In the description of the embodiment, for convenience, the central portion 21a and the peripheral portion 21b are defined in a manner that the outer edge of the central portion 21a and the inner edge of the peripheral portion 21b are consistent with each other.

[0096] When viewed from above, the shape and size of the central portion 21a and the peripheral portion 21b can be appropriately set. In the following description, for convenience, the position and size of various parts or components (such as various electrodes described later) described later are sometimes compared with the position and size of the central portion 21a and the peripheral portion 21b for description. Among them, in actual products, on the contrary, the position and size of the central portion 21a and the peripheral portion 21b can also be determined according to the position and size of various parts or components. Therefore, the shape and size of the central portion 21a and the peripheral portion 21b can refer to the position and size of various parts or components described later.

[0097] In the following description, the inner edge is sometimes defined by the outer edge of the pressure chamber 21, and the inner edge is sometimes defined by the outer edge of the pressure chamber 21. Figure 4 The area whose outer edge is defined by the double-dashed line Ln2 is referred to as the area 11e outside the pressure chamber 21. That is, in the non-arrangement area of ​​the pressure chamber 21 (the area outside the pressure chamber 21 in a broad sense), the area around the pressure chamber 21 is sometimes referred to as the area 11e outside. The shape and size of the area 11e can also refer to the positions and sizes of various parts or components described later.

[0098] (Piezoelectric Actuator)

[0099] return Figure 3The piezoelectric actuator 13 is, for example, a roughly plate-shaped device having a width extending over a plurality of 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 the present embodiment, the first surface 13a is the surface on the side opposite to the flow path member 11, and the second surface 13b is the surface on the flow path member 11 side. The piezoelectric actuator 13 has a piezoelectric element 27 that applies pressure to the pressure chamber 21 for each ejection element 9 (for each pressure chamber 21). That is, the piezoelectric actuator 13 has a plurality of piezoelectric elements 27 at a plurality of positions along the direction of the first surface 13a.

[0100] The piezoelectric actuator 13 is formed by stacking a plurality of layered members extending along the second surface 13b. Specifically, for example, the piezoelectric actuator 13 has a first piezoelectric layer 29A to a fourth piezoelectric layer 29D (hereinafter, sometimes referred to as the piezoelectric layer 29) in order from the first surface 13a side to the second surface 13b side. In addition, the piezoelectric actuator 13 has a first conductor layer 31A to a fifth conductor layer 31E (hereinafter, sometimes referred to as the conductor layer 31) in order from the first surface 13a side to the second surface 13b side on the surface of the piezoelectric layer 29 or between the piezoelectric layers 29. Although not specifically shown in the figure, the piezoelectric actuator 13 may also have an insulating layer (such as a solder resist) covering the first conductor layer 31A.

[0101] Each piezoelectric layer 29 extends substantially without gaps over a plurality of pressure chambers 21 (a plurality of piezoelectric elements 27 in another viewpoint). "Substantially" means, for example, that a through conductor (described later) that can also be used to connect the conductor layers penetrates an insulating layer, etc. (hereinafter, the same). Each conductor layer 31 includes, for example, a plurality of electrodes provided corresponding to the plurality of pressure chambers 21, etc., as described in detail later, and has an appropriate plan view shape.

[0102] (Overview of the operating principle of piezoelectric actuators)

[0103] Figure 5 2 is a cross-sectional view schematically showing the piezoelectric actuator 13 and the upper portion (plate 25J) of the flow path member 11. Figure 3 Different directions (with Figure 2 The cross section of the III-III line in different directions) is as follows, for example Figure 4 The VV line of FIG. 5 corresponds to the VV line of FIG. In this figure, the hatching indicating the cross section is omitted. In addition, as described later, this figure shows the state in which the piezoelectric actuator 13 is bent by applying an electric field to the first active region 53A and the second active region 53B. The piezoelectric actuator 13 has a nearly flat shape when no electric field is applied.

[0104] exist Figure 5 middle, Figure 3The first piezoelectric layer 29A and the second piezoelectric layer 29B shown are conceptualized (shown) as the main piezoelectric layer 51A. Figure 5 middle, Figure 3 The third piezoelectric layer 29C and the fourth piezoelectric layer 29D shown are conceptualized (not shown) as a sub-piezoelectric layer 51B. Hereinafter, the main piezoelectric layer 51A and the sub-piezoelectric layer 51B may be simply referred to as piezoelectric layers 51 without distinguishing between them.

[0105] The piezoelectric layer 51 includes active regions 53 (53A and 53B) that are driven when the droplets are ejected, and inactive regions 55 (55A to 55C. 55C refers to Figure 6 . ). The active region 53 is a region that is polarized and to which an electric field in the polarization direction or the opposite direction is applied when the droplets are ejected. The inactive region 55 is a region that is not polarized and / or to which no electric field in any direction of the polarization direction or the opposite direction is applied when the droplets are ejected. In addition, the polarized region is, for example, a region in which the direction of spontaneous polarization is aligned to some extent by polarization treatment.

[0106] More specifically, the main piezoelectric layer 51A includes: a first active region 53A overlapping with the central portion 21a of the pressure chamber 21 in a plan view; and a first inactive region 55A adjacent to the outer side thereof. The auxiliary piezoelectric layer 51B includes: a second inactive region 55B overlapping with the central portion 21a of the pressure chamber 21 in a plan view; and a second active region 53B adjacent to the outer side thereof. In another viewpoint, the first inactive region 55A and the second active region 53B overlap with the peripheral portion 21b of the pressure chamber 21 and the region 11e outside the pressure chamber 21 in a plan view.

[0107] The polarization direction of the first active region 53A is set to the thickness direction (D3 direction). Furthermore, if an electric field (voltage in other viewpoints, and the same applies below) is applied to the first active region 53A in the same direction as the polarization direction, the first active region 53A is Figure 5 As shown by the arrow in the figure, the first active region 53A and the second inactive region 55B contract in the direction along the surface. On the other hand, the second inactive region 55B does not contract. As a result, the first active region 53A and the second inactive region 55B as a whole are deformed to be convex toward the pressure chamber 21 side like a bimetal, as shown by the arrows drawn at both ends thereof.

[0108] The polarization direction of the second active region 53B is set to the thickness direction (D3 direction). Furthermore, if an electric field is applied to the second active region 53B in the same direction as the polarization direction, the second active region 53B is as follows: Figure 5As indicated by the arrow in FIG. 5 , the first inactive region 55A shrinks in the direction along the surface. On the other hand, the first inactive region 55A does not shrink. As a result, Figure 5 As shown, the second active region 53B and the first inactive region 55A as a whole are deformed to be concave toward the pressure chamber 21 like a bimetal.

[0109] Here, in the second active region 53B and the first inactive region 55A, the portion located outside the pressure chamber 21 (the second active region 53B is sometimes referred to as the second portion 53Bb) is joined to the plate 25J, thereby restraining its bending deformation. Figure 5 As shown in FIG. 1 , when the second active region 53B and the first inactive region 55A are deformed to be concave toward the pressure chamber 21, the portion of the second active region 53B and the first inactive region 55A that overlaps with the pressure chamber 21 (the second active region 53B is sometimes referred to as the first portion 53Ba) bends toward the pressure chamber 21 like a cantilever beam. Furthermore, the first active region 53A and the second inactive region 55B are displaced toward the pressure chamber 21.

[0110] Therefore, by applying an electric field in the polarization direction to the first active region 53A and applying an electric field in the polarization direction to the second active region 53B, the displacement of the center position of the first active region 53A toward the pressure chamber 21 side can be increased compared to the case where the electric field is applied only in the polarization direction to the first active region 53A. Thus, the volume change amount when the volume of the pressure chamber 21 is reduced can be increased. Similarly, when the volume of the pressure chamber 21 is increased, an electric field may be applied in the opposite direction of the polarization direction to the first active region 53A and an electric field may be applied in the opposite direction of the polarization direction to the second active region 53B so that the first active region 53A and the second active region 53B are extended in the direction along the surface. Thus, the displacement of the center position of the first active region 53A can be increased, and the increase in the volume of the pressure chamber can be increased.

[0111] Regarding the bending rigidity of the piezoelectric actuator 13, the neutral plane can be set to an appropriate position in the thickness direction. For example, the neutral plane is substantially located at the boundary between the main piezoelectric layer 51A and the auxiliary piezoelectric layer 51B. The deviation between the boundary and the neutral plane is, for example, less than 1 / 4 of the thickness of the thinner one of the thickness of the main piezoelectric layer 51A and the thickness of the auxiliary piezoelectric layer 51B.

[0112] (Top view of active and inactive regions)

[0113] Depending on the structure of the piezoelectric actuator, the top view shape of the active area 53 may sometimes be different in the thickness direction (D3 direction). For example, as can be understood from the description below, in the present embodiment, in the first active area 53A, the portion formed by the first piezoelectric layer 29A and the portion formed by the second piezoelectric layer 29B can be made to have different top view shapes from each other. In the following description, a method in which the top view shape of the active area 53 (or the inactive area 55) is substantially fixed in the thickness direction is taken as an example. In the method in which the top view shape of the active area 53 (or the inactive area 55) is not fixed in the thickness direction, the following description related to the top view shape can also be applied to the top view shape at any position in the thickness direction, for example, it can be applied to the top view shape with the smallest area in the top view perspective.

[0114] The first inactive region 55A and / or the second active region 53B surround the first active region 53A and / or the second inactive region 55B, for example, in a top view. More specifically, for example, the former surrounds the latter over the entire circumference. The former may not surround the latter over the entire circumference. For example, the former may surround the latter within a range of more than 270° and less than 360° around the center of the latter.

[0115] In a top view, the first active region 53A (the outer edge portion thereof) and the second active region 53B (the inner edge portion thereof) may be separated from each other, may be adjacent to each other (the example shown in the figure), or may overlap each other. In another viewpoint, the first active region 53A and the second inactive region 55B adjacent to the inner side of the second active region 53B may have the same shape and size (the example shown in the figure) or may not have such a shape and size. Similarly, the first inactive region 55A and the second active region 53B adjacent to the outer side of the first active region 53A may have the same shape and size (the example shown in the figure) or may not have such a shape and size.

[0116] In the description of the present embodiment, for convenience, the central portion 21a of the pressure chamber 21 is defined so that the outer edge of the first active region 53A coincides with the outer edge of the central portion 21a of the pressure chamber 21. In addition, as described above, in the description of the present embodiment, for convenience, the central portion 21a and the peripheral portion 21b are defined as being 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 side 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 side portion of the first active region 53A and the inner edge side portion of the second active region 53B is arbitrary. Therefore, the second active region 53B may not overlap with the inner edge side portion of the peripheral portion 21b, may not overlap with the entire peripheral portion 21b excessively or insufficiently (the example shown in the figure), or may overlap with the outer edge side portion of the central portion 21a in addition to the peripheral portion 21b.

[0117] The planar shape and size of the first active region 53A can be appropriately set (see Figure 4 The shape and size of the central portion 21a shown in the figure). The top view shape of the first active area 53A may be similar to the top view shape of the pressure chamber 21 (the example shown in the figure) or may be different. In short, the description related to the top view shape of the pressure chamber 21 can also be applied to the top view shape of the first active area 53A. In addition, in the top view perspective, the center of the first active area 53A and the center of the pressure chamber 21 may be substantially consistent (the example shown in the figure) or may be offset.

[0118] The size of the first active area 53A in a top view can be appropriately set. For example, in a top view perspective, the ratio of the area of ​​the first active area 53A to the area of ​​the pressure chamber 21 can be set to be greater than 40% or greater than 50%, and can also be set to be less than 70% or less than 80%. The above lower limit and upper limit can be appropriately combined. As an example, greater than 50% and less than 70% can be listed. In addition, for example, when the diameters in the same direction in the first active area 53A and the pressure chamber 21 are compared with each other or the equivalent circle diameters are compared with each other, the diameter of the first active area 53A can be set to be greater than 0.6 times or greater than 0.7 times the diameter of the pressure chamber 21, and can also be set to be less than 0.9 times. The above lower limit and upper limit can be appropriately combined.

[0119] The planar shape and size of the second active region 53B can be appropriately set (see Figure 4The shape and size of the annular region between the double-dashed line Ln1 and the double-dashed line Ln2 shown in FIG. 5A). For example, the top view 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 shape or an elliptical shape. For example, the inner edge and / or outer edge of the annular shape may have concave and convex shapes, or may be a polygon (e.g., a rectangular shape).

[0120] The shape of the inner edge and / or outer edge of the second active area 53B may be similar to or different from the top view shape of the pressure chamber 21 and / or the top view shape of the first active area 53A (example shown in the figure). In short, the description related to the top view shape of the pressure chamber 21 can be applied to the shape of the inner edge and outer edge of the second active area 53B. In addition, in the top view perspective, the center of the shape formed by the outer edge of the second active area 53B may be substantially consistent with the center of the pressure chamber 21 and / or the center of the first active area 53A (example shown in the figure) or may deviate.

[0121] In a manner in which the outer edge of the first active region 53A and the inner edge of the second active region 53B are offset from each other in a perspective plan view, the distance between the two can be appropriately set. For example, the distance between the two can be set to be less than 10% or less than 5% of the diameter (e.g., the minimum diameter, the maximum diameter, or the equivalent circle diameter) of the first active region 53A. This upper limit value can also be applied to either a manner in which the outer edge of the first active region 53A is located further inside than the inner edge of the second active region 53B or a manner in which the former is located further outside than the latter.

[0122] The distance between the outer edge of the second active region 53B and the outer edge of the pressure chamber 21 can be appropriately set. For example, the distance can be set to be greater than 1 / 20, greater than 1 / 10, or greater than 1 / 5 of the diameter (e.g., the minimum diameter, the maximum diameter, or the equivalent diameter of a circle) of the pressure chamber 21, or can be set to be less than 1 time, less than 1 / 2, less than 1 / 3, or less than 1 / 5. The lower limit and the upper limit can be appropriately combined as long as they are not contradictory. For example, the diameter of the pressure chamber 21 is greater than 200 μm and less than 400 μm, and the distance from the outer edge of the pressure chamber 21 to the outer edge of the second active region 53B is greater than 50 μm and less than 200 μm.

[0123] The distance w1 from the outer edge of the pressure chamber 21 to the inner edge of the second active region 53B (reference numerals Figure 4 ) and a distance w2 from the outer edge of the pressure chamber 21 to the outer edge of the second active region 53B (reference numerals Figure 4) may be larger than the other. In other words, the distance w1 is the width of the first portion 53Ba of the second active region 53B that overlaps the pressure chamber 21. In other words, the distance w2 is the width of the second portion 53Bb of the second active region 53B that is located outside the pressure chamber 21. Here, the distances w1 and w2 are shown in a top view, but the distances w1 and w2 may also be as follows: Figure 3 Thus, comparison is made in a cross section (longitudinal cross section) that passes through the center of the pressure chamber 21 and is perpendicular to the pressurizing surface 11 b .

[0124] In the present embodiment, the method in which the distance w1 is shorter than the distance w2 is taken as an example. In the case where the distance w1 is shorter than the distance w2, for example, not only the method in which the distance w1 is shorter than the distance w2 throughout the entire circumference of the second active region 53B may be included, but also the method in which the distance w1 is shorter than the distance w2 in most of the circumferential direction of the second active region 53B may be included. This is because, due to the shape of the pressure chamber 21 or the shape of the wiring for imparting a potential to the electrode, a characteristic portion is sometimes provided in the second active region 53B. For example, the above-mentioned most of the circumferential direction may be set to an angle of 270° or more, 300° or more, or 330° or more around the center of the pressure chamber 21. In the method in which the distance w1 is shorter than the distance w2, the ratio of the distance w1 to the distance w2 may be appropriately set. For example, the distance w1 may be set to be less than 0.9 times, less than 0.8 times, or less than 0.7 times the distance w2.

[0125] In a top perspective view, either the area of ​​the first portion 53Ba overlapping the pressure chamber 21 in the second active region 53B or the area of ​​the second portion 53Bb located outside the pressure chamber 21 in the second active region 53B may be larger than the other. In the description of this embodiment, the area of ​​the first portion 53Ba is smaller than the area of ​​the second portion 53Bb. In this embodiment, the ratio of the areas of the two can be appropriately set. For example, the area of ​​the first portion 53Ba can be set to be less than 0.9 times, less than 0.8 times, or less than 0.7 times the area of ​​the second portion 53Bb.

[0126] In addition, for example, when the first portion 53Ba and the second portion 53Bb are similar in shape, since the latter is located outside the former, the circumferential length of the latter is longer than the circumferential length of the former. Therefore, for example, even if the distance w1 and the distance w2 are equal, the area of ​​the first portion 53Ba is smaller than the area of ​​the second portion 53Bb. It can be understood from this that, although not particularly shown in the figure, it is also possible to adopt a mode in which the distance w1 is longer than the distance w2 and the area of ​​the first portion 53Ba is smaller than the area of ​​the second portion 53Bb.

[0127] In the circulated product, the difference in the area of ​​the first part 53Ba and the second part 53Bb, the difference in the distance w1 and the distance w2, etc. can be appropriately measured. For example, X-ray CT (Computed Tomography) can be used to measure the electrode area and the deviation between the electrode and the pressure chamber 21 without disassembling the head body 7, and then the area of ​​the first part 53Ba and the second part 53Bb, and the distance w1 and the distance w2 can be measured. In addition, for example, the head body 7 can be cut at multiple locations and the cross section can be observed using an electron microscope to measure the electrode area and the deviation between the electrode and the pressure chamber 21, and then the area of ​​the first part 53Ba and the second part 53Bb, and the distance w1 and the distance w2 can be measured.

[0128] The first inactive region 55A can be defined as a region overlapping with the second active region 53B in a plan view, for example, in a region other than the first active region 53A in the main piezoelectric layer 51A. 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 the present embodiment, in a plan view, the outer edge of the first active region 53A roughly coincides with the inner edge of the second active region 53B, so the plan view shape and size of the first inactive region 55A are roughly the same as the plan view shape and size of the second active region 53B.

[0129] The second inactive region 55B can be defined as, for example, a region of the sub-piezoelectric layer 51B that overlaps with the pressure chamber 21 and is outside the second active region 53B. When the second active region 53B is annular, the second inactive region 55B is a region surrounded by the second active region 53B, and its outer edge is consistent with the inner edge of the second active region 53B.

[0130] (Piezoelectric layer)

[0131] return Figure 3 The material of the piezoelectric layer 29 can be, for example, a ceramic material having ferroelectricity. Examples of the ceramic material include lead zirconate titanate (PZT), NaNbO3, BaTiO3, (BiNa)TiO3, BiNaNb5O 15 Of course, it is also possible to set the material of the piezoelectric layer 29 to a material other than a ceramic material. The material of the piezoelectric layer 29 can be either a single crystal or a polycrystalline material, either an inorganic material or an organic material, and can be neither a ferroelectric nor a pyroelectric. The materials of the multiple piezoelectric layers 29 can be the same or different from each other.

[0132] The piezoelectric layer 29 is generally flat and has a fixed thickness. In other words, it is generally flat. Its width is generally the same as the width of the piezoelectric actuator 13. The thickness of the piezoelectric layer 29 can be appropriately set. The thicknesses of the plurality of piezoelectric layers 29 can be the same as each other (as shown in the example in the figure) or different from each other. If an example of the thickness of the piezoelectric layer 29 is given, it is greater than 10 μm and less than 40 μm.

[0133] In the example shown in the figure, the thicknesses of the plurality of piezoelectric layers 29 are the same as each other. In another viewpoint, the sum of the thickness of the third piezoelectric layer 29C and the thickness of the fourth piezoelectric layer 29D is thicker than the thickness of the first piezoelectric layer 29A and the thickness of the second piezoelectric layer 29B. Within the range in which this thickness relationship holds, the thicknesses of the plurality of piezoelectric layers 29 may be different from each other. In addition, even if the thicknesses of two or more piezoelectric layers 29 being compared are the same, there may of course be errors, and the thickness of the conductor layer 31 may also be different.

[0134] Figure 6 is a schematic cross-sectional view showing the polarization direction of the piezoelectric layer 29. Figure 5 Similarly, with Figure 4 The VV line corresponds to the VV line. In this figure, the white arrow indicates the polarization direction. In this figure, the hatching of the cross section is omitted.

[0135] As indicated by the dotted lines, the piezoelectric actuator 13 includes the first active region 53A, the second active region 53B, the first inactive region 55A, and the second inactive region 55B described above. In addition, in the first to fourth piezoelectric layers 29A to 29D, the region outside the first inactive region 55A and the second active region 53B is referred to as a third inactive region 55C.

[0136] 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 set to be 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 stretch these piezoelectric layers (29A and 29B) together.

[0137] In the first active region 53A, the polarization direction of the first piezoelectric layer 29A and the second piezoelectric layer 29B may be set to the +D3 direction or the -D3 direction. In the description of this embodiment, the polarization direction of the first piezoelectric layer 29A is set to the -D3 direction, and the polarization direction of the second piezoelectric layer 29B is set to the +D3 direction.

[0138] 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 set to be the same. Therefore, for example, in the second active region 53B, the same electric field is applied to the third piezoelectric layer 29C and the fourth piezoelectric layer 29D, thereby making it possible to contract these piezoelectric layers (29C and 29D) together ( Figure 5 ), or stretch them together.

[0139] The polarization direction of the second active region 53B may be either the +D3 direction or the -D3 direction. In addition, the polarization direction of the second active region 53B may be the same as any polarization direction of the first piezoelectric layer 29A and the second piezoelectric layer 29B in the first active region 53A. In the description of this embodiment, 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.

[0140] The inactive regions 55 (55A to 55C) may be polarized or not polarized. In the example shown in the figure, the first inactive region 55A is polarized, and the second inactive region 55B and the third inactive region 55C are not polarized.

[0141] 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 can 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 can be the same as the polarization direction of the second active region 53B, or it can be opposite. In the description of this embodiment, the polarization direction of the first inactive region 55A and the polarization direction of the second active region 53B are the same as an example.

[0142] (Conductor layer)

[0143] return 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 path member 11 (plate 25J).

[0144] The material of the conductor layer 31 can be set to, for example, an appropriate metal material. As the metal material, for example, an Ag-Pd alloy and an Au alloy can be used. The materials of the plurality of conductor layers 31 can be the same as or different from each other. One conductor layer 31 can be formed integrally with one material or can be formed by stacking different materials. The material of one conductor layer 31 is the same at different positions in the planar direction. However, the material of a part of the region can be different from the material of other regions.

[0145] The conductor layer 31 extends in a planar shape with a substantially constant thickness. The thickness of the conductor layer 31 can be appropriately set. In addition, the thicknesses of the plurality of conductor layers 31 can be the same as or different from each other. The thickness of each layer is, for example, thinner than the thickness of the piezoelectric layer 29. As an example of the thickness of the conductor layer 31, it can be set to be greater than 0.5 μm and less than 3 μm.

[0146] (Shape of the conductor layer)

[0147] Figure 7 and Figure 8 2 is an exploded perspective view of the piezoelectric actuator 13 and the upper portion (plate 25J) of the flow path member 11. Figure 7 , a part of the head body 7 in a plan view, that is, a region including a plurality of piezoelectric elements 27 is shown. Figure 8 , a region including one piezoelectric element 27 is shown. In these figures, the surface of the conductor layer 31 is shaded for convenience.

[0148] In these figures, the piezoelectric actuator 13 is decomposed into a plate-like member composed of two layers, each piezoelectric layer 29 and a conductor layer 31 superimposed on its upper surface (surface on the +D3 side), by removing the fifth conductor layer 31E. This is for the convenience of illustration and does not mean that the four plate-like members described above are made separately during the manufacturing process. For example, during the manufacturing process, each conductor layer 31 may also be provided on the lower surface (surface on the -D3 side) of the piezoelectric layer 29.

[0149] (First conductor layer)

[0150] The first conductor layer 31A includes, for example, a first electrode 33 and a reorientation electrode 35 for each pressure chamber 21 (piezoelectric element 27). The first electrode 33 helps to apply a voltage to the first active region 53A (more specifically, the portion thereof formed by the first piezoelectric layer 29A) when droplets are ejected. The reorientation electrode 35 helps to polarize the second inactive region 55B (a portion or most thereof) when droplets are not ejected, thereby reducing the degradation of the characteristics of the piezoelectric actuator 13.

[0151] In each piezoelectric element 27, the first electrode 33 and the reorientation electrode 35 are separated from each other and are independently given potentials. The distance between the first electrode 33 and the reorientation electrode 35 can be appropriately set. For example, the distance between the two can be minimized within a range that does not cause a short circuit.

[0152] (First electrode)

[0153] The first electrodes 33 are so-called individual electrodes. That is, the plurality of first electrodes 33 are separated from each other in terms of shape and also in terms of electrical properties. Furthermore, the plurality of first electrodes 33 can be given different potentials from each other.

[0154] The first electrode 33 includes, for example, an electrode body 33a that helps apply a voltage to the first active region 53A, and a lead portion 33b for connecting the electrode body 33a to a signal line outside the piezoelectric actuator 13. The external signal line is, for example, a wiring pattern of an FPC (flexible wiring board) that is opposed to the first surface 13a of the piezoelectric actuator 13, although not specifically shown. Alternatively, only the electrode body 33a may be regarded as the first electrode, and the lead portion 33b may be regarded as the wiring.

[0155] The top view shape and size of the electrode body 33a are, for example, substantially the same as the top view shape and size of the first active region 53A. Therefore, the description of the top view shape and size of the first active region 53A can be applied to the top view shape and size of the electrode body 33a. As described above, the active region 53 is polarized and is a region to which a voltage is applied when a droplet is ejected. Therefore, the outer edge of the portion of the first active region 53A formed by the first piezoelectric layer 29A is consistent with the outer edge of the electrode body 33a or is located on the inner side thereof.

[0156] The lead portion 33b extends from the electrode body 33a to the outside of the pressure chamber 21, for example, in a plan view. In addition, the portion of the lead portion 33b located outside the pressure chamber 21 (for example, the end portion on the opposite side to the electrode body 33a) is connected to an external signal line. Thus, the influence of the connection on the pressure imparted by the piezoelectric element 27 to the pressure chamber 21 can be reduced.

[0157] The specific shape, size, position, etc. of the lead portion 33b can be appropriately set. For example, the lead portion 33b extends linearly from the end of one side of a given direction (the D1 direction in the example shown in the figure) of the electrode body 33a to the one side of the given direction. The given direction can be set to an arbitrary direction. In the example shown in the figure, it is the long side direction of the electrode body 33a. In addition, the width of the lead portion 33b is, for example, approximately fixed and smaller than the diameter (for example, the minimum diameter) of the electrode body 33a. Unlike the example shown in the figure, the lead portion 33b may also have a tortuous or curved portion. In addition, the end of the lead portion 33b on the opposite side of the electrode body 33a may also be widened compared to other parts. In addition, the lead portion 33b may be accommodated in the shape formed by the outer edge of the second active area 53B (the example shown in the figure) or not when viewed from above.

[0158] (Reorienting Electrodes)

[0159] The plurality of reorientation electrodes 35 are separated from each other in terms of shape or electrical properties. That is, the reorientation electrodes 35 become individual electrodes. As will be understood from the following description, the plurality of reorientation electrodes 35 may be given the same potential. Therefore, unlike the example shown in the figure, the first conductor layer 31A may also have wiring that connects the adjacent reorientation electrodes 35 to each other. In addition, for example, the first conductor layer 31A may also have an electrode (see the fourth conductor layer 31D) that extends to the first piezoelectric layer 29A without a gap, as a reorientation electrode.

[0160] For example, when viewed from above, the reorientation electrode 35 can apply a voltage to substantially the entire second inactive region 55B, or can apply a voltage to only a portion (inner edge side, center side or outer edge side), or can apply a voltage not only to the second inactive region 55B but also to the third inactive region 55C.

[0161] In the example shown in the figure, reorientation electrode 35 is configured to apply a voltage to substantially the entire first inactive region 55A and not to apply a voltage to third inactive region 55C. That is, reorientation electrode 35 is configured to have a shape that does not substantially overlap first inactive region 55A excessively or insufficiently in a plan view. Therefore, the above-described description regarding the plan view shape and size of first inactive region 55A can be applied to the plan view shape and size of reorientation electrode 35.

[0162] Unlike the first inactive region 55A, the reorientation electrode 35 is interrupted at the position of the lead portion 33b of the first electrode 33 and formed into a C-shape. In addition, the C-shape here is the same as the ring shape, and the inner edge and / or outer edge are not limited to a circle or an ellipse.

[0163] In addition, the portion of the first piezoelectric layer 29A that is located outside the electrode body 33a in a plan view is not applied with a voltage during the ejection of droplets, and thus constitutes the first inactive region 55A. On the other hand, the inner edge of the reorientation electrode 35 is separated from the outer edge of the electrode body 33a to the outside so as not to be short-circuited with the first electrode 33. Therefore, even if the reorientation electrode 35 and the entire first inactive region 55A are substantially overlapped, the inner edge of the reorientation electrode 35 is located closer to the outer edge than the inner edge of the portion of the first inactive region 55A that is constituted by the first piezoelectric layer 29A.

[0164] In the embodiment where the top view shape of the reorientation electrode 35 (excluding the interrupted portion) is similar to the top view shape of the first active region 53A, the outer edge of the reorientation electrode 35 may be located inside or outside the outer edge of the first inactive region 55A (defined by the outer edge of the second active region 53B as described above), unlike the example shown in the figure. That is, the polarization treatment may not be performed on a portion of the outer edge side of the first inactive region 55A, or the polarization treatment may be performed on both the first inactive region 55A and the third inactive region 55C.

[0165] (Second conductor layer)

[0166] 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. The second electrode 37 helps apply a voltage to the first active region 53A (more specifically, both the first piezoelectric layer 29A and the second piezoelectric layer 29B) when a pressure is applied to the pressure chamber 21 to eject a droplet. The plurality of wirings 39 helps apply a potential to the second electrode 37.

[0167] (Second electrode)

[0168] The plurality of second electrodes 37 are separated from each other in terms of their shape. In other terms, the non-configuration region of the conductor is located between adjacent second electrodes 37. That is, in terms of shape, the second electrode 37 is a single electrode. However, as described above, the plurality of second electrodes 37 are connected to each other through the plurality of wirings 39, unlike the plurality of first electrodes 33, so that they have the same potential.

[0169] The shape and size of the second electrode 37 are set to be substantially the same as the shape and size of the electrode body 33a of the first electrode 33, for example. Moreover, when viewed from above, the second electrode 37 and the electrode body 33a are substantially overlapped with each other without excess or deficiency. In other words, when viewed from above, the outer edge of the second electrode 37 and the outer edge of the electrode body 33a are substantially consistent. In other viewpoints, when viewed from above, the second electrode 37 and the reorientation electrode 35 do not overlap. The description of the shape and size of the electrode body 33a (first active region 53A) when viewed from above and the description of the shape and size of the second electrode 37 can be appropriately applied to the shape and size of the second electrode 37.

[0170] Among them, when observing more strictly, in the perspective of the top view, part or all of the outer edge of the second electrode 37 may be located at the outer edge of the electrode body 33a, between the outer edge of the electrode body 33a and the inner edge of the reorientation electrode 35, or at the inner edge of the reorientation electrode 35. In the description of the present disclosure, when the outer edge of the second electrode 37 is consistent with the outer edge of the electrode body 33a (or the two electrodes do not overlap too much or too little), all of the above modes may be included. Even when they strictly appear to be consistent, there may of course be an error between the two (the same applies to other electrodes, etc.).

[0171] In addition, unlike the example shown in the figure, the outer edge of the second electrode 37 may be slightly deviated inward or outward relative to the outer edge of the electrode body 33a. In other viewpoints, it can be understood from the following description that the area to which the voltage is applied in the first piezoelectric layer 29A and the area to which the voltage is applied in the second piezoelectric layer 29B may also be different. In another viewpoint, the area to which the voltage is applied is polarized as a premise, but the first active area 53A may also have a width different between the portion composed of the first piezoelectric layer 29A and the portion composed of the second piezoelectric layer 29B.

[0172] (Wiring of the second conductor layer)

[0173] The number, position, shape, size, etc. of the plurality of wirings 39 can be appropriately set. For example, the wiring 39 can connect the second electrodes 37 adjacent to each other in the D2 direction (the example shown in the figure), can connect the second electrodes 37 adjacent to each other in directions other than the D2 direction (the D1 direction or the direction inclined to the D1 direction), or can realize a connection of two or more combinations of these connections. In the example shown in the figure, the wiring 39 extends in a direction that intersects (orthogonally to) the direction in which the lead portion 33b of the first electrode 33 extends. Furthermore, the wiring 39 does not overlap the lead portion 33b.

[0174] In addition, for example, the wiring 39 may extend in a straight line (the example shown in the figure), or may be zigzag or curved. In addition, for example, the wiring 39 may have a substantially constant width throughout its length direction (the example shown in the figure), or the width may vary depending on the position in the length direction. The width of the wiring 39 is smaller than the diameter of the second electrode 37 in the width direction of the wiring 37 so that a gap is formed between the second electrodes 37 (the second electrode 37 becomes a separate electrode in terms of shape). For example, the former may be set to less than 1 / 2, less than 1 / 3, or less than 1 / 4 of the latter.

[0175] (Third conductor layer)

[0176] The third conductor layer 31C includes, for example, a third electrode 41 provided for each pressure chamber 21 (piezoelectric element 27). The third electrode 41, for example, helps apply a voltage to the first active region 53A (more specifically, the portion thereof formed by the second piezoelectric layer 29B) and helps apply 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 is a so-called single electrode, similarly to the first electrode 33. That is, the plurality of third electrodes 41 are separated from each other in terms of their shape and also in terms of electrical properties.

[0177] The top view shape and size of the third electrode 41 are set to be substantially the same as the top view shape and size of the structure obtained by superimposing the first electrode 33 and the reorientation electrode 35 (in other viewpoints, the region obtained by superimposing the first active region 53A and the second active region 53B). In addition, when viewed from above, the third electrode 41 does not overlap 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) in a substantially excessive or insufficient manner. The description regarding the shape and size of the outer edge of the second active region 53B can be applied to the top view shape and size of the third electrode 41.

[0178] The shape and size of the third electrode 41 in a plan view and the shape and size of the outer edge of the reorientation electrode 35 may be different from each other. For example, in a plan view, the outer edge of the reorientation electrode 35 may be located inside or outside the outer edge of the third electrode 41. In addition, for example, the third electrode 41 may have a slit extending along the outer edge of the electrode body 33a between the electrode body 33a and the reorientation electrode 35 in a plan view.

[0179] (Fourth conductor layer)

[0180] 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. Therefore, as can be understood from the description of the operation described later, in this embodiment, the fourth conductor layer 31D does not contribute to applying a voltage to the piezoelectric layer 29. Of course, the fourth conductor layer 31D may be omitted.

[0181] The shape, size, and position of the fourth conductor layer 31D are set, for example, so as not to overlap with the electrodes for applying voltage to the piezoelectric layer 29 in a plan view. The electrodes for applying voltage are the first electrode 33, the reorientation electrode 35, the second electrode 37, and the third electrode 41 described above, and the fourth electrode 45 described later in this embodiment. Thus, the fourth conductor layer 31D can reduce the possibility of hindering the application of voltage to the piezoelectric layer 29 through the above-mentioned electrodes.

[0182] The fourth conductor layer 31D may include a region overlapping with a portion of the above-mentioned electrodes. For example, when the reorientation electrode 35 has a region located outside the outer edge of the third electrode 41 and the outer edge of the fourth electrode 45 (a region overlapping with the third inactive region 55C), the fourth conductor layer 31D may include a region overlapping with the above-mentioned 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 composed of the first piezoelectric layer 29A to the third piezoelectric layer 29C.

[0183] The shape and size of the fourth conductor layer 31D can be set appropriately. In the example shown in the figure, the fourth conductor layer 31D is set to a shape in which an opening 43 is formed for each pressure chamber 21 (piezoelectric element 27). In other words, the fourth conductor layer 31D is a flat surface extending without a gap on the fourth piezoelectric layer 29D if the opening 43 is removed.

[0184] The top view shape and size of the opening 43 are set to be substantially the same as the top view shape and size of the third electrode 41 (the logical sum of the first active region 53A and the second active region 53B in other viewpoints). In addition, when viewed from above, the opening 43 does not overlap the third electrode 41 excessively or insufficiently. The description of the shape and size of the outer edge of the second active region 53B can be applied to the top view shape and size of the opening 43.

[0185] The opening 43 may be larger than the third electrode 41. Thus, for example, the possibility of overlapping the third electrode 41 (and other electrodes) and the fourth conductor layer 31D can be reduced. In addition, the enlargement of the opening 43 may also be consistent with the purpose of equalizing the structural characteristics of the portion on the first surface 13a side and the portion on the second surface 13b side. The shape of the opening 43, which is larger than the third electrode 41, may be similar to the shape of the third electrode 41 (pressure chamber 21 in other viewpoints), or may not be similar.

[0186] The top view shape (pattern) of the fourth conductor layer 31D may be various shapes other than the shape having the openings 43. For example, the top view shape of the fourth conductor layer 31D may include a plurality of linear patterns extending in appropriate directions, or may be a mesh shape having openings other than the openings 43.

[0187] (Fifth conductor layer)

[0188] The fifth conductor layer 31E includes, for example, a fourth electrode 45 provided for each pressure chamber 21 (piezoelectric element 27). The fourth electrode 45, for example, helps to apply a voltage to the second active region 53B (more specifically, both the third piezoelectric layer 29C and the fourth piezoelectric layer 29D) when a pressure is applied to the pressure chamber 21 to eject a droplet. In addition, the fourth electrode 45, for example, helps to polarize the second inactive region 55B (a part or most of it) when no droplet is ejected, thereby reducing the deterioration of the characteristics of the piezoelectric actuator 13.

[0189] The plurality of fourth electrodes 45 are separated from each other from the perspective of their shapes. Therefore, from the perspective of shape, the plurality of fourth electrodes 45 are separate electrodes. Among them, the plurality of fourth electrodes 45 are different from the plurality of first electrodes 33 and are given the same potential as each other. Specifically, in the example shown in the figure, the plurality of fourth electrodes 45 are electrically connected to each other through the plate 25J made of metal. In addition, unlike the present embodiment, the plate 25J may be made into a resin plate or the like so that the pressurized surface 11b is insulated, and the electrical connection of the plurality of fourth electrodes 45 via the flow path member 11 is not performed.

[0190] The top view shape and size of the fourth electrode 45 are set to be substantially the same as the top view shape and size of the reorientation electrode 35, for example. In another viewpoint, the top view shape and size of the fourth electrode 45 are set to be substantially the same as the top view shape and size of the region (region on the outer peripheral side) of the third electrode 41 that does not overlap with the electrode body 33a of the first electrode 33. In another viewpoint, the top view shape and size of the fourth electrode 45 are set to be substantially the same as the top view shape and size of the second active region 53B. The description related to the top view shape and size of the second active region 53B can be applied to the top view shape and size of the fourth electrode 45.

[0191] In a top view, the inner edge of the fourth electrode 45 is substantially consistent with the outer edge of the electrode body 33a (the inner edge of the reorientation electrode 35) and the outer edge of the second electrode 37. The inner edge of the fourth electrode 45 is similar to the outer edge of the second electrode 37. When more strictly observed, in a top view, part or all of it may be located at the outer edge of the electrode body 33a, between the outer edge of the electrode body 33a and the inner edge of the reorientation electrode 35, or at the inner edge of the reorientation electrode 35. In the description of the present disclosure, when the inner edge of the fourth electrode 45 is consistent with the outer edge of the electrode body 33a, all of the above modes may be included. In addition, the inner edge of the fourth electrode 45 may deviate inwardly or outwardly relative to the outer edge of the electrode body 33a and / or the outer edge of the second electrode 37.

[0192] In a top perspective view, the outer edge of the fourth electrode 45 is substantially consistent with, for example, the outer edge of the reorientation electrode 35, the outer edge of the third electrode 41, and the edge of the opening 43. However, similar to the relationship between the reorientation electrode 35 and the third electrode 41, the outer edge of the reorientation electrode 35 may be located inside or outside relative to the outer edge of the fourth electrode 45. In addition, similar to the relationship between the opening 43 and the third electrode 41, the opening 43 may be larger than the fourth electrode 45. In addition, the outer edge of the fourth electrode 45 may also deviate to the inside or outside relative to the outer edge of the third electrode 41.

[0193] (Electrical connection of conductor layer)

[0194] As described above, the first electrode 33 is an electrode to which a potential (driving signal) is applied individually to each piezoelectric element 27, and a potential is applied to the lead portion 33b from the FPC (not shown) facing the first surface 13a of the piezoelectric actuator 13. For example, the end of the lead portion 33b on the opposite side to the electrode body 33a is bonded to the wiring pattern of the FPC via a bump (not shown). The bump is formed, for example, by solder (including lead-free solder).

[0195] As described above, the third electrode 41 is an electrode to which a potential (driving signal) is individually assigned for each piezoelectric element 27. In this embodiment, the third electrode 41 is assigned the same potential as the first electrode 33 of the piezoelectric element 27 to which it belongs. The assignment of the same potential can be achieved, for example, by electrically connecting the first electrode 33 and the third electrode 41 in the piezoelectric actuator 13.

[0196] The connection between the first electrode 33 and the third electrode 41 can be achieved by a suitable conductor. Figure 3 As shown in FIG. 4A and FIG. 4B , the first electrode 33 and the third electrode 41 can be connected by a through conductor 47 that penetrates the first piezoelectric layer 29A and the second piezoelectric layer 29B. Figure 8 In the figure, the positions of the first electrode 33 and the third electrode 41 connected by the through conductor 47 are connected by a dotted line. The connection position of the through conductor 47 with respect to the first electrode 33 can be set, for example, to a portion of the lead portion 33b located outside the pressure chamber 21 in a plan view (more specifically, for example, a portion of the outer region 11e). In addition, the connection position of the through conductor 47 with respect to the third electrode 41 can be set to a position directly below the connection position of the through conductor 47 with respect to the lead portion 33b.

[0197] Although not particularly shown in the figure, for example, 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 a layered wiring that is located between the first piezoelectric layer 29A and the second piezoelectric layer 29B and connects the two through conductors may be provided. In addition, in a mode in which the potential of the third electrode 41 is set to a potential different from that of the first electrode 33, for example, a lead portion that extends to a position that does not overlap with the reorientation electrode 35 in a top perspective view may be provided on the third electrode 41, and a through conductor that is connected to the lead portion and exposed on the first surface 13a of the piezoelectric actuator 13 may be provided. Furthermore, the through conductor or the pad overlapping thereon may be joined to a wiring pattern of an FPC that is not shown.

[0198] The reorientation electrode 35, for example, can be set to be given a potential by being joined to an FPC (not shown) via a bump, similarly to the first electrode 33. At this time, the joining position of the reorientation electrode 35 can be set to an appropriate position. For example, in the reorientation electrode 35, a portion that is located on the opposite side of the lead-out portion 33b and clamps the electrode body 33a can be set as the joining position. And / or, for example, the joining position can be set to a position that does not overlap with the pressure chamber 21 in a top perspective view. Thereby, as with the joining of the lead-out portion 33b, the influence of the joining on the pressure of the pressure chamber 21 can be reduced.

[0199] Although not particularly shown in the figure, for example, a lead portion extending in a direction away from the pressure chamber 21 may be provided on the reorientation electrode 35, and the FPC may be bonded to the lead portion. In addition, it is not necessary to individually apply potentials to the plurality of reorientation electrodes 35. Therefore, wiring that connects the plurality of reorientation electrodes 35 to each other and a pad commonly connected to the plurality of reorientation electrodes 35 may be provided, and the FPC may be bonded to the pad.

[0200] As described above, in the present embodiment, the plurality of fourth electrodes 45 are electrically connected to each other through the plate 25J made of metal and are given the same potential. The plate 25J may be given a reference potential, for example. 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 the FPC not shown to which the piezoelectric actuator 13 is connected), or may be connected to both. In the latter case, it may be directly connected to both or connected to the other via one. The structure for connection is arbitrary.

[0201] As described above, the plurality of second electrodes 37 are connected by the plurality of wirings 39 and are given the same potential. In addition, although the fourth conductor layer 31D forms a plurality of openings 43, it is basically a conductor pattern, so of course the same potential is given to the entirety. In addition, in the present embodiment, the plurality of second electrodes 37 and the fourth conductor layer 31D are given the same potential. The plurality of second electrodes 37 and the fourth conductor layer 31D can be electrically connected to an FPC (not shown) that is opposite to the first surface 13a of the piezoelectric actuator 13, for example, by providing a through conductor that penetrates the piezoelectric layer 29. The structure of the through conductor can be appropriately set. An example is shown below.

[0202] Fig. 9 31B is an enlarged top view of a portion of the second conductor layer 31B. In this figure, only two rows consisting of a plurality of second electrodes 37 arranged in the D2 direction are shown. In addition, in this figure, for the sake of convenience of explanation, it is assumed that the number of the plurality of second electrodes 37 included in one row is four.

[0203] In each row, the plurality of second electrodes 37 are connected by the plurality of wirings 39 as described above. Furthermore, wirings 39 extending to the outside of the row (-D2 side or +D2 side) are provided at both ends of each row. The wirings 39 at both ends are connected to the common wiring 49 extending in the direction (D1 direction) intersecting the plurality of rows. Thus, the plurality of rows are connected to each other. The common wiring 49 is a part of the second conductor layer 31B.

[0204] Fig.10 yes Fig. 9 Cross-sectional view at line XX.

[0205] like Fig. 9 and Fig.10 As shown in FIG. 1 , a through conductor 57 is provided at a position overlapping with the common wiring 49 in a plan view. Specifically, Fig.10 As shown in FIG. 1 , 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 and the fourth conductor layer 31D. Furthermore, the plurality of second electrodes 37 and the fourth conductor layer 31D are set to the same potential.

[0206] In addition, a through conductor 57 penetrating the first piezoelectric layer 29A is also provided. Thus, the FPC (not shown) facing the first surface 13a of the piezoelectric actuator 13 can be electrically connected to the plurality of second electrodes 37 and the fourth conductor layer 31D. Specifically, for example, a pad 59 is provided on the through conductor 57 penetrating the first piezoelectric layer 29A, and the pad 59 and the signal line (not shown) of the FPC are bonded via a bump (not shown).

[0207] like Fig. 9 As shown by the dotted line in FIG. 1 , a plurality of through conductors 57 may be provided along the common wiring 49, for example. Thus, the potential of the electrodes set to the same potential is stabilized. Of course, it is also possible to provide the through conductor 57 at only one place. The through conductor 57 located above the common wiring 49 and the through conductor 57 located below the common wiring 49 may overlap or may not overlap each other in a top perspective view.

[0208] Although not particularly shown, a through conductor 57 penetrating the fourth piezoelectric layer 29D may be provided. The through conductor 57 may electrically connect the plate 25J (the fourth electrode 45 in another viewpoint) and the second electrode 37 and the fourth conductor layer 31D.

[0209] (Potential given to the conductor layer)

[0210] Fig.11 2 is a schematic cross-sectional view showing the potential applied to the conductor layer 31 when the droplets are ejected. Fig.12 2 is a schematic cross-sectional view showing a potential applied to the conductive layer 31 when the first inactive region 55A is polarized. Figure 5 Similarly, with Figure 4 In these figures, hatching indicating a cross section is omitted. The arrow portion shown in the cross section of the piezoelectric layer 29 indicates the direction of the voltage (electric field) at a given time point in the cycle of ejecting droplets.

[0211] In these figures, a driver 61 is shown that supplies power to the piezoelectric actuator 13 to drive the piezoelectric actuator 13. However, the structure of the driver 61 shown here is a structure shown for the convenience of easy understanding of the potential given to the conductor layer 31. Therefore, the actual structure of the driver 61 may be different from the structure shown in the figure.

[0212] The driver 61 is composed of, for example, an IC (Integrated Circuit). The driver 61 can be mounted on the head 2, for example, by being mounted on an FPC (not shown) or the like that is opposite to the first surface 13a of the piezoelectric actuator 13. The driver 61 may not be mounted on the head 2. The sharing of functions between the driver 61 and the control unit 88 may be appropriately set. For example, part or all of the actions of the driver 61 described below may also be performed by the control unit 88. It is of course possible to set the driver 61 with a hardware structure that makes it difficult to conceptualize the control unit 88 alone. The driver 61 and the control unit 88 as a whole may also be understood as a control unit.

[0213] The driver 61 includes, for example, a first signal source 63 capable of outputting power for ejecting droplets, a second signal source 65 capable of outputting power for polarization, and a switch section 67 for controlling the connection between these signal sources and the piezoelectric actuator 13. The switch section 67 is a member for easily understanding the diagram of the power for ejecting droplets and the power for polarization to be given to the piezoelectric actuator 13. In fact, the switch section 67 may not be provided, and the power for ejecting droplets and the power for polarization may be selectively output through the operation of the first signal source 63 and the second signal source 65. In addition, the first signal source 63 and the second signal source 65 may share a part.

[0214] exist Fig.11 and Fig.12 , a reference potential portion 69 serving as a signal ground and / or a frame ground is shown. The conductor layer 31 to which the reference potential is assigned and the reference potential portion 69 may be connected via the driver 61 or not. The illustrated structure of the connection of the reference potential portion 69 is merely for convenience in easily understanding the structure of the potential difference between the conductor layers 31.

[0215] (Liquid spray control)

[0216] As reference Figure 5 As described above, when ejecting droplets, the first signal source 63 applies a voltage (electric field) in the same direction as (or in the opposite direction to) the polarization direction to the first active region 53A and the second active region 53B. Figure 6 As described above, in the present 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 formed by the first piezoelectric layer 29A. Fig.11As indicated by arrows y1 and y2, the driver 61 (first signal source 63) applies a potential to the conductor layer 31 so that in the first active area 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 area 53B is in the same direction as the voltage applied to the portion of the first active area 53A consisting of the first piezoelectric layer 29A.

[0217] More specifically, in the example shown in the figure, a reference potential is given to the second electrode 37 and the fourth electrode 45. A potential higher than the reference potential (a potential with a positive polarity in other viewpoints) is given to the first electrode 33 and the third electrode 41. As a result, a voltage is applied from the former to the latter between the first electrode 33 and the second electrode 37 (the portion of the first active region 53A formed by the first piezoelectric layer 29A). A voltage is applied from the latter to the former 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 formed by the second piezoelectric layer 29B). A voltage is applied from the latter to the former between the region of the third electrode 41 that overlaps with the fourth electrode 45 and the fourth electrode 45.

[0218] In the above description, the case where a voltage is applied in the same direction as the polarization direction is described. However, by giving a potential lower than the reference potential (a potential with a negative polarity in other viewpoints) to the first electrode 33 and the third electrode 41, a voltage can be applied in the opposite direction to the polarization direction. Figure 6 The polarization direction shown in the figure is assumed, but in the polarization direction Figure 6 In the case of the opposite direction, the height (positive and negative) of the above-mentioned potential is set to be opposite.

[0219] In the above description, the reference potential is assumed to be given to the second electrode 37 and the fourth electrode 45. However, it is also possible to give a potential other than the reference potential to the second electrode 37 and the fourth electrode 45 without electrically connecting the fourth electrode 45 to the metal plate 25J (for example, refer to the embodiment described later). For example, a potential different from the potential of the first electrode 33 and the third electrode 41 and higher or lower than the reference potential may be given to the second electrode 37 and the fourth electrode 45. In addition, although it is necessary to change the structure of the conductor layer 31 and the arrangement of the through conductors so that the second electrode 37 and the fourth electrode 45 can be given a potential independently, it is also possible to give the reference potential to the first electrode 33 and the third electrode 41 and give the second electrode 37 and the fourth electrode 45 a potential higher or lower than the reference potential in contrast to the above. Therefore, if the present embodiment is conceptualized in a higher level, the same potential (first potential) can be given to the first electrode 33 and the third electrode 41, and the same potential (second potential) can be given to the second electrode 37 and the fourth electrode 45, and 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 are formed based on the difference between the two potentials.

[0220] In a manner other than the above, it is of course possible to apply a voltage in the same direction as the polarization direction to the first active region 53A and the second active region 53B. For example, the first electrode 33 and the third electrode 41 may not be connected to each other, and the potential of the first electrode 33 and the potential of 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. In addition, for example, the potential of the second electrode 37 and the potential of 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.

[0221] When a voltage is applied to eject droplets, the reorientation electrode 35 and the fourth conductor layer 31 may be given a reference potential, or may be set to an electrically suspended state (positively speaking, a state where no potential is given). Fig.11 In the example of , the reorientation electrode 35 is set to be in an electrically floating state. In addition, in this embodiment, the fourth conductor layer 31D is connected to the second electrode 37 as described above, and thus is given a reference potential.

[0222] As a driving method of the piezoelectric element 27 when applying pressure to the pressure chamber 21, various known methods or structures applying various known methods can be adopted. As a typical driving method, the so-called traction method can be cited. The operation of the driver 61 when the traction method is adopted is as follows, for example.

[0223] The driver 61 preliminarily applies a potential higher than the reference potential (the same potential as the potential of the second electrode 37 and the fourth electrode 45 in other viewpoints. The same applies hereinafter) to the first electrode 33 and the third electrode 41 before the droplet is ejected. As a result, the piezoelectric element 27 is set to a state in which flexural deformation occurs on the pressure chamber 21 side. When the timing for ejecting the droplet 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 then the volume of the pressure chamber 21 begins to increase. In other viewpoints, the piezoelectric element 27 begins to vibrate at the natural frequency. Then, the volume of the pressure chamber 21 becomes maximum and decreases again. As the volume decreases, the pressure in the pressure chamber 21 increases. Moreover, at the timing when the pressure becomes approximately maximum, a potential higher than the reference potential is applied to the first electrode 33 and the third electrode 41. As a result, the vibration applied initially and the vibration applied next overlap, and a greater pressure is applied to the pressure chamber 21. In this way, the driver 61 uses a potential higher than the potentials of the second electrode 37 and the fourth electrode 45 as a reference, and inputs a pulse-shaped driving signal having a low potential for a fixed period to the first electrode 33 and the third electrode 41 .

[0224] The driver 61 changes the amplitude of the pulsed driving signal and / or the number of driving signals, for example, according to the size of the ink dot to be formed on the recording medium, thereby making the ejected droplets larger or ejecting two or more droplets for one ink dot.

[0225] As can be understood from the description so far, when ejecting droplets, the change in the voltage applied to the first active area 53A and the change in the voltage applied to the second active area 53B are the same. Therefore, the period during which the first active area 53A is extended is the same as the period during which the second active area 53B is extended, and the period during which the first active area 53A is contracted is the same as the period during which the second active area 53B is contracted. In other words, the period during which the first active area 53A is contracted and extended is the same as the period during which the second active area 53B is contracted and extended. In terms of a higher level concept, at least a portion of the period during which the first active area 53A is extended and contracted and the period during which the second active area 53B is extended and contracted overlap.

[0226] It can be understood from the description of the traction type that the period during which the so-called contraction and extension mentioned here occur is not limited to the period during which a voltage is actively applied to the first active area 53A and the second active area 53B. For example, the period during which the contraction and extension occur may also be the period during which the potential of the first electrode 33 and the third electrode 41 is set to a reference potential when the timing of ejecting droplets arrives. This period can be understood as a period during which no voltage is applied to the first active area 53A and the second active area 53B. In summary, it can be said that the driver 61 controls the intensity of the electric field applied to the first active area 53A and the intensity of the electric field applied to the second active area 53B in the liquid ejection control, so that the second active area 53B produces the extension and contraction during at least a part of the period during which the extension and contraction occur in the first active area 53A.

[0227] It is also possible to stagger the periods of applying voltage between the first active area 53A and the second active area 53B. For example, a potential can be individually given to a plurality of fourth electrodes 45 to form a piezoelectric actuator. Moreover, for example, in the above-mentioned traction type example, before the ejection of the droplet, the fourth electrode 45 can be given the same potential as the third electrode 41 without utilizing the contraction of the second active area 53B, and when the potential of the third electrode 41 is restored to a potential higher than the reference potential, the fourth electrode is given a reference potential to utilize the contraction of the second active area 53B. Conversely, the contraction of the second active area 53B can also be utilized before the ejection of the droplet. It is also possible to change the use of the contraction of the second active area 53B according to the ejection amount of the droplet (the size of the ink dot formed on the recording medium according to the image data). In addition, in any of these modes, it can be said that at least a part of the period during which the first active area 53A is stretched and contracted and the period during which the second active area 53B is stretched and contracted overlap each other.

[0228] The second electrode 37 and the fourth electrode 45 are given 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 the piezoelectric body 29 (29B) of one layer, while the latter voltage is applied to the thickness of the piezoelectric layer (29C and 29D) of two layers. Therefore, the intensity of the electric field formed by the former voltage is stronger than the intensity of the electric field formed by the latter voltage. The same situation can also exist for the portion of the first active region 53A composed of the first piezoelectric layer 29A and the second active region 53B. In other viewpoints, when the liquid is ejected, the intensity of the electric field in the first active region 53A (the amount of change in other viewpoints) becomes larger than the intensity of the electric field in the second active region 53B.

[0229] In the present embodiment, in the liquid ejection control, the electric field applied to the first active area 53A and the electric field applied to the second active area 53B rise or fall together. Unlike the present embodiment, in a method in which the two electric fields do not change together in the same manner, the intensity of the electric field applied to the first active area 53A and the intensity of the electric field applied to the second active area 53B can be compared with each other, for example, at the maximum value. In addition, for example, in the traction type, although it is also based on its specific driving waveform, the electric field that maintains the state of bending the piezoelectric element 27 to the pressure chamber 21 side before the ejection timing arrives is not the electric field during ejection, but can be referred to as the maximum value of the electric field applied to the active area 53 in the liquid ejection control. In a method in which the electric field applied to the first active area 53A and the electric field applied to the second active area 53B are controlled separately, the maximum values ​​of the intensity of the electric fields to be compared with each other can be values ​​at different time points.

[0230] (Reorientation Control)

[0231] 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, the domain wall moves (domain switching). As a result, the displacement of the piezoelectric element 27 is reduced. Therefore, by performing polarization treatment on the first inactive region 55A, the polarization of the first inactive region 55A is fixedly maintained, thereby reducing the reduction of the displacement.

[0232] The polarization process based on the reorientation electrode 35 can be performed at an appropriate time when droplets are not ejected. For example, the polarization process can be performed when printing is not performed, using the user's operation on the printer 1 as a trigger. In other words, the polarization process can be performed at any time. In addition, for example, the control unit 88 can also count the number of printings and perform the polarization process at the end of a given number of printings. When the printer 1 is shipped, the first inactive area 55A can be in a state where the polarization process is not performed, or in a state where the same polarization as the polarization achieved by the polarization process based on the reorientation electrode 35 is generated.

[0233] As reference Figure 6 As described above, in this embodiment, the first inactive region 55A is polarized in the thickness direction. Fig.12 As shown by the arrow in FIG. 1 , 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 can be set to a voltage that forms an electric field with an intensity exceeding the coercive electric field of the first inactive region 55A, or a voltage that is higher than the voltage at which the polarization becomes saturated.

[0234] As described above, in order to apply a voltage, in the example shown in the figure, the reorientation electrode 35 is given a potential higher than the reference potential (a potential with a positive polarity in other viewpoints). The third electrode 41 is in an electrically suspended state. The fourth electrode 45 is given a reference potential. As a result, an electric field is formed between the reorientation electrode 35 and the fourth electrode 45. The third electrode 41 sandwiched therebetween is set in an electrically suspended state, so it is unlikely to become an obstacle to the formation of the above-mentioned electric field. In addition, the above-mentioned electric field is applied to the first inactive region 55A and the second active region 53B.

[0235] In the above, the polarization direction is Figure 6 In the case where the polarization direction is the opposite direction, a potential lower than the reference potential (a potential with a negative polarity in other viewpoints) may be given to the reorientation electrode 35. In addition, the fourth electrode 45 (in other words, an 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 given to the electrode. In this case, the potential given to the reorientation electrode 35 may be either the reference potential or a potential other than the reference potential.

[0236] When a voltage for polarization is applied, the first electrode 33, the second electrode 37, and the fourth conductor layer 31D may be given a reference potential, or may be in an electrically suspended state. In this embodiment, as described above, the first electrode 33 is electrically connected to the third electrode 41, and thus is in an electrically suspended state. In addition, the second electrode 37 and the fourth conductor layer 31D are given a reference potential.

[0237] The manufacturing method of the head body 7 can be the same as various known methods or a method applying various known methods. For example, the piezoelectric actuator 13 can be manufactured by configuring a conductive paste that becomes a conductor layer 31 and a through conductor on a ceramic green sheet that becomes a piezoelectric body layer 29, and then stacking and firing the ceramic green sheets. The flow path member 11 can be manufactured by bonding a plurality of plates 25 that have through holes formed as flow paths by etching or the like, using an adhesive. Furthermore, the piezoelectric actuator 13 and the flow path member 11 can be bonded with an adhesive to manufacture the head body 7.

[0238] The polarization treatment of the active region 53 can be performed, for example, at an appropriate time after the firing of the piezoelectric actuator 13 (for example, after the piezoelectric actuator 13 and the flow path member 11 are joined). In the polarization treatment, for example, a DC voltage is applied to the first electrode 33, the second electrode 37, the third electrode 41, and the fourth electrode 45 so that the voltage applied to the active region 53 is Fig.11 The voltage at this time can be set to a voltage that forms an electric field with a strength exceeding the coercive electric field of the active region 53 or a voltage that is higher than the voltage at which polarization reaches a saturation state.

[0239] As described above, in the present embodiment, the liquid ejection head 2 has a flow path member 11, a piezoelectric actuator 13, and a driver 61. The flow path member 11 has a pressurizing surface 11b and a pressure chamber 21 opened on 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 area 53A and a second active area 53B. When the direction (D3 direction) perpendicular to the pressurizing surface 11b is called the thickness direction, the first active area 53A is composed of a piezoelectric body polarized in the thickness direction, and overlaps with the central portion 21a of the pressure chamber 21 in a top perspective view of the pressurizing surface 11b. The second active region 53B is composed of a piezoelectric body polarized in the thickness direction, and is located closer to the pressurizing surface 11b than the first active region 53A, and overlaps with the peripheral portion 21b of the pressure chamber 21 and the region 11e outside the pressure chamber 21 in a plan view of the pressurizing surface 11b. The actuator 61 controls the first electric field ( Fig.11 The intensity of the arrow portion y1) and the second electric field ( Fig.11The intensity of the arrow portion y2) is adjusted so that the second active area 53B is extended and contracted in the direction along the pressurizing surface 11b for at least a portion of the period during which the first active area 53A is extended and contracted in the direction along the pressurizing surface 11b. In the liquid ejection control, the maximum value of the intensity of the first electric field is greater than the maximum value of the intensity of the second electric field.

[0240] Therefore, for example, by driving not only the first active region 53A but also the second active region 53B, the displacement of the piezoelectric element 27 as a whole can be increased. Since the second active region 53B restricts the deformation of the region overlapping the region 11e outside the pressure chamber 21 by the flow path member 11, the stress is likely to increase near the outer edge of the pressure chamber 21. However, by making the intensity of the electric field applied to the first active region 53A larger than the intensity of the electric field applied to the second active region 53B, the above-mentioned effect of increasing the displacement of the piezoelectric element 27 as a whole can be maintained, while the stress applied to the second active region 53B can be reduced. By reducing the stress applied to the second active region 53B, the aging resistance of the head 2 can be improved.

[0241] In addition, in the present embodiment, the head 2 has three or more electrodes (33, 37, 41, and 45). The positions of the three or more electrodes in the thickness direction are different from each other, and at least one of the application of the first electric field to the first active area 53A and the application of the second electric field to the second active area 53B is performed respectively. At the positions adjacent to each other among the three or more positions in the thickness direction of the three or more electrodes, the distance in the thickness direction of the two electrodes applying the first electric field (at least one of the distance between 33 and 37 and the distance between 37 and 41) is set as the first distance. At the positions adjacent to each other among the three or more positions, the distance in the thickness direction of the two electrodes applying the second electric field (the distance between 41 and 45) is set as the second distance. At this time, the first distance is shorter than the second distance.

[0242] Therefore, for example, even if the voltage (potential difference) for forming the first electric field applied to the first active region 53A and the voltage (potential difference) for forming the second electric field applied to the second active region 53B are set to be the same, the intensity of the first electric field is stronger than the intensity of the second electric field. For the reasons described above, it is easy to make the intensity of the first electric field stronger than the intensity of the second electric field.

[0243] In addition, in the present embodiment, the above-mentioned relationship between the distances between the electrodes holds true, and in liquid ejection control, the maximum value of the potential difference between the above-mentioned two electrodes for applying the first electric field to the first active area 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 above-mentioned two electrodes (41 and 45) for applying the second electric field to the second active area 53B.

[0244] In this case, for example, one of the two electrodes applying the first electric field and one of the two electrodes applying the second electric field can be connected (or integrated into one electrode), and the other of the two electrodes applying the first electric field and the other of the two electrodes applying the second electric field can be connected. As a result, the intensity of the first electric field can be made stronger than the intensity of the second electric field with a simple structure.

[0245] In addition, in the present embodiment, the piezoelectric actuator includes the first piezoelectric layer 29A to the fourth piezoelectric layer 29D, the first electrode 33, the second electrode 37, the third electrode 41, and the fourth electrode 45. The side of the piezoelectric actuator 13 opposite to the flow path member 11 (+D3 side) is referred to as the first side, and the flow path member 11 side (-D3 side) of the piezoelectric actuator 13 is referred to as the second side. At this time, 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 with the surface of the first side of the first piezoelectric layer 29A, and overlaps with the central portion 21a of the pressure chamber 21 in a plan view. The second electrode 37 overlaps with the surface of the second side of the first piezoelectric layer 29A, and overlaps with the central portion 21a in a plan view. The third electrode 41 overlaps with the surface of the second side of the second piezoelectric layer 29B, and overlaps with the central portion 21a, the peripheral portion 21b of the pressure chamber 21, and the region 11e outside the pressure chamber 21 in a plan perspective view. The fourth electrode 45 overlaps with the surface of the second side of the fourth piezoelectric layer 29D, and overlaps with the peripheral portion 21b and the region 11e outside the pressure chamber 21 in a plan perspective view. The first active region 53A includes: a region of the first piezoelectric layer 29A sandwiched by the first electrode 33 and the second electrode 37; and a region of the second piezoelectric layer 29B sandwiched by the second electrode 37 and a portion of the third electrode 41 overlapping with the central portion 21a. The second active region 53B includes a region of the third piezoelectric layer 29C and the fourth piezoelectric layer 29D that overlaps with the peripheral portion 21b of the third electrode 41 and the region 11e outside the pressure chamber 21, and a region sandwiched by the fourth electrode 45.

[0246] In this case, for example, with a simple structure, the first electric field applied to the first active region 53A can be made larger than the second electric field applied to the second active region 53B. For example, in the first active region 53A, a voltage is applied to the two piezoelectric layers 29 (29A and 29B) by three electrodes (33, 37, and 41) at different positions in the thickness direction, and in the second active region 53B, a voltage is applied to the two piezoelectric layers 29 (29C and 29D) by two electrodes. Therefore, it is easy to realize a structure in which the distance between the two electrodes for applying a voltage to the first active region 53A is shorter than the distance between the two electrodes for applying a voltage to the second active region 53B. Due to the effect brought about by the relationship of the distance, the voltage applied to the first active region 53A (29A and 29B each) and the voltage applied to the second active region 53B (29C and 29D) can be made the same, so that, for example, the increase in potential can be suppressed and the structure can be simplified. In addition, the third electrode 41 serves both as a voltage application device for the first active region 53A and a voltage application device for the second active region 53B, and thus the number of electrodes (the number of conductive layers 31 ) can be reduced.

[0247] In addition, in the present embodiment, the portion of the first piezoelectric layer 29A constituting the first active region 53A and the portion of the second piezoelectric layer 29B constituting the first active region 53A are polarized in opposite directions to each other. The portion of the third piezoelectric layer 29C and the fourth piezoelectric layer 29D constituting the second active region 53B is polarized in the same direction as the polarization direction of the portion of the first piezoelectric layer 29A constituting the first active region 53A. In liquid ejection control, the first electrode 33 and the third electrode 41 are set to the same potential, and the second electrode 37 and the fourth electrode 45 are set to the same potential, and the first electric field is applied to the first active region 53A and the second electric field is applied to the second active region 53B according to the potential difference between the potential of the first electrode 33 and the third electrode 41 and the potential of the second electrode 37 and the fourth electrode 45.

[0248] In this case, for example, only two potentials can be used to apply an electric field in the polarization direction (or the opposite direction) of each region to three regions (the portion of the first active region 53A formed by the first piezoelectric layer 29A, the portion of the first active region 53A formed by the second piezoelectric layer 29B, and the second active region 53B). Therefore, the structures of the piezoelectric actuator 13 and the driver 61 are simplified.

[0249] In addition, in the present embodiment, the total thickness of the third piezoelectric layer 29C and the fourth piezoelectric layer 29D is thicker than the thickness of the first piezoelectric layer 29A and the thickness of the second piezoelectric layer 29B.

[0250] In this case, from another viewpoint, 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 respectively 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 formed by the first piezoelectric layer 29A and the electric field applied to the portion of the first active region 53A formed by the second piezoelectric layer 29B are easily made larger than the electric field applied to the second active region 53B.

[0251] In the present embodiment, the piezoelectric actuator 13 includes a conductor pattern (fourth conductor layer 31D) overlapping with the second side (− D3 side) surface of the third piezoelectric layer 29C and located outside the second active region 53B in a plan perspective view.

[0252] Here, in this embodiment, as described above, three electrodes (33, 37, and 41) are configured to realize the application of voltage to the first active region 53A, and two electrodes (41 and 45) are configured to realize the application of voltage to the second active region 53B (wherein the third electrode 41 is shared). Therefore, in the piezoelectric actuator 13, the volume of the conductor on the first side (+D3 side) is likely to be larger than the volume of the conductor on the second side. However, by providing the fourth conductor layer 31D, it is easy to make the volume of the conductor (the proportion of the conductor in the piezoelectric body from other viewpoints) on the +D3 side and the -D3 side equal. As a result, for example, the possibility of the occurrence of unwanted flexural deformation caused by shrinkage during firing and / or expansion and contraction due to temperature changes during use can be reduced.

[0253] In the present embodiment, in a plan perspective view of the pressurizing surface 11 b , the area of ​​the second portion 53Bb located outside the pressure chamber in the second active region 53B is larger than the area of ​​the first portion 53Ba overlapping the pressure chamber 21 in the second active region 53B.

[0254] If the outer edge of the second active region 53B (in other viewpoints, the outer edge of the second portion 53Bb) is close to the outer edge of the pressure chamber 21, stress concentration is likely to occur near the outer edge of the pressure chamber 21. However, the area of ​​the second portion 53Bb is larger than the area of ​​the first portion 53Ba, so that the outer edge of the second active region 53B is easily separated from the outer edge of the pressure chamber 21. In addition, the above-mentioned stress concentration can be alleviated. As a result, for example, the possibility of deterioration of the bonding between the piezoelectric actuator 13 and the flow path member 11 around the pressure chamber 21 can be reduced. In addition, as described above, by making the intensity of the first electric field applied to the first active region 53A larger than the intensity of the second electric field applied to the second active region 53B (relatively reducing the second electric field), 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 described above is improved.

[0255] In the present embodiment, a 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 in a plan view of the pressurizing surface 11 b is formed by an arc.

[0256] In this case, the stress is evenly dispersed by the arc when viewed from above. That is, the possibility of particularly high stress is reduced. As a result, for example, the above-mentioned stress relaxation effect is improved. In particular, when the top view shape of the pressure chamber 21 is circular ( Figure 4 In the case where the pressure chamber 21 is composed only of the circle C1, the above-mentioned effect is improved.

[0257] In the present embodiment, in the cross section that passes through the center of the pressure chamber 21 and is perpendicular to the pressurizing surface 11 b , the width w2 of the second portion 53Bb is larger than the width w1 of the first portion 53Ba.

[0258] The outer edge of the second active region 53B can be separated from the outer edge of the pressure chamber 21. Therefore, the stress concentration described in the explanation of the effect of the second portion 53Bb being larger than the first portion 53Ba can be alleviated. If the area of ​​the second portion 53Bb is larger than the area of ​​the first portion 53Ba, and the width w2 is larger than the width w1, the effect of alleviating stress concentration is further improved.

[0259] In addition, in the present embodiment, the piezoelectric actuator 13 has an inactive region (first inactive region 55A). The first inactive region 55A is formed of a piezoelectric body and is connected to the outer periphery of the first active region 53A. The driver 61 performs the reorientation control ( Fig.12 ). In the re-orientation control, the actuator 61 applies an electric field in the thickness direction to the first inactive region 55A when the droplet discharge control is not being performed.

[0260] Therefore, for example, as described above, the possibility of displacement reduction caused by domain switching in the first inactive region 55A can be reduced by polarization treatment. The first inactive region 55A is a portion that is subjected to both stress of the first active region 53A and stress of the second active region 53B, and domain switching is likely to occur. By performing the polarization treatment of the first inactive region 55A as described above, the displacement reduction can be effectively reduced. Moreover, as described above, by making the intensity of the first electric field applied to the first active region 53A larger than the intensity of the second electric field applied to the second active region 53B (relatively reducing the second electric field), the stress applied to the second active region 53B can be reduced. Furthermore, the stress applied from the second active region 53B to the first inactive region 55A can be reduced. As a result, the possibility of domain switching in the first inactive region 55A can be reduced, and the frequency of polarization treatment on the first inactive region 55A can be reduced.

[0261] In addition, in the present 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 with the opposite side (+D3 side) of the pressurization surface 11b relative to the inactive area (first inactive area 55A). The third electrode 41 is located between the first inactive area 55A and the second active area 53B. The fourth electrode 45 overlaps with the pressurization surface 11b side (-D3 side) relative to the second active area 53B. The driver 61 applies a voltage to the third electrode 41 and the fourth electrode 45 in the liquid ejection control, thereby applying an electric field to the second active area 53B. In addition, the driver 61 applies a voltage to the reorientation electrode 35 and one of the third electrode 41 and the fourth electrode 45 (the fourth electrode 45 in the present embodiment) in the reorientation control, thereby applying an electric field to the first inactive area 55A.

[0262] In this case, the fourth electrode 45 (or the third electrode 41 ) is used in common for applying an electric field for ejecting droplets and applying an electric field for polarization processing. That is, the structure of the piezoelectric actuator 13 can be simplified.

[0263] In addition, in the present embodiment, in addition to the above-mentioned structure, the piezoelectric actuator 13 further includes an upper electrode (second electrode 37). The second electrode 37 is located on the opposite side (+D3 side) of the pressurizing surface 11b than the intermediate electrode (third electrode 41), and is opposed to the third electrode 41 by sandwiching at least a portion of the first active area 53A. In the liquid ejection control, the driver 61 applies a voltage to the second electrode 37 and the third electrode 41, thereby applying an electric field to the UDI first active area 53A. In addition, in the reorientation control, the driver 61 does not give a potential to the third electrode 41, but applies a voltage to the reorientation electrode 35 and the fourth electrode 45, thereby applying an electric field to the inactive area (first inactive area 55A).

[0264] 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 ejecting droplets. As a result, the structure of the piezoelectric actuator 13 can be simplified. On the other hand, in the polarization process, the third electrode 41 is in an electrically suspended state, so it is difficult to become an obstacle to the application of the electric field by the reorientation electrode 35 and the fourth electrode 45. The polarization process is performed by the reorientation electrode 35 and the fourth electrode 45, thereby performing not only the polarization process of the first inactive region 55A but also the polarization process of the second active region 53B. As a result, it is possible to reduce 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.

[0265] In addition, in the present embodiment, the piezoelectric actuator includes the first piezoelectric layer 29A to the fourth piezoelectric layer 29D, the first electrode 33, the second electrode 37, the third electrode 41, and the fourth electrode 45 as described above, thereby constituting the first active region 53A and the second active region 53B. Furthermore, the inactive region (the first inactive region 55A) includes a region of the first piezoelectric layer 29A and the second piezoelectric layer 29B sandwiched between the reorientation electrode 35 and the fourth electrode 45.

[0266] In this case, for example, as described above, 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 structure. Furthermore, the stress applied to the second active region 53B can be reduced with a simple structure, and the stress applied from the second active region 53B to the first inactive region 55A can be reduced.

[0267] <Second embodiment>

[0268] Fig.13 is a schematic cross-sectional view showing a head portion 207 according to the second embodiment, which is different from that of the first embodiment. Fig.12 Corresponding. That is, Fig.13 The potential applied to the conductive layer 31 when the first inactive region 55A is polarized is shown.

[0269] In the polarization process of the first embodiment, an electric field is 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 is applied to the first inactive region 55A by the reorientation electrode 35 and the third electrode 41. More specifically, in the example shown in the figure, a potential higher than the reference potential (a potential with a positive polarity in other viewpoints) is applied to the reorientation electrode 35. The third electrode 41 is applied with the reference potential.

[0270] In the above, the premise is that the polarization direction is Figure 6 In the embodiment in which the polarization direction is the opposite direction, a potential lower than the reference potential (a potential with a negative polarity in other viewpoints) may be given to the reorientation electrode 35. A potential other than the reference potential may also be given to the third electrode 41. In this case, the potential given to the reorientation electrode 35 may be either the reference potential or a potential other than the reference potential.

[0271] As described above, when a voltage for polarization is applied, the first electrode 33, the second electrode 37, the fourth electrode 45, and the fourth conductor layer 31D may be given a reference potential or may be electrically suspended. In this embodiment, as described above, the first electrode 33 is electrically connected to the third electrode 41, and thus is given a reference potential. The second electrode 37, the fourth electrode 45, and the fourth conductor layer 31D are given a reference potential.

[0272] <Third Embodiment>

[0273] Fig.14 is a schematic cross-sectional view showing a head portion 307 according to the third embodiment, which is different from that of the first embodiment. Fig.11 correspond.

[0274] In the first embodiment, the fifth conductor layer 31E (fourth electrode 45) is connected to the flow path member 11 (plate 25J) and is also exposed in the pressure chamber 21. On the other hand, in this embodiment, the insulating layer 30 is sandwiched between the fifth conductor layer 31E and the flow path member 11. In other viewpoints, the insulating layer 30 is sandwiched between the second active area 53B and the flow path member 11. The insulating layer 30 can be understood as a part of the piezoelectric actuator 13, a part of the flow path member 11, or a separate member from these. Fig.14 In FIG. 1 , the insulating layer 30 is shown with a reference numeral as a member separate from the piezoelectric actuator 13 and the flow path member 11 .

[0275] The insulating layer 30 may be made of either an inorganic material or an organic material. The inorganic material may be either a piezoelectric material or a non-piezoelectric material. The piezoelectric material may be the same as or different from the material of the piezoelectric layer 29, and may or may not be a material fired together with the piezoelectric layer 29. As an inorganic material other than a piezoelectric material, for example, SiO2 can be cited. In addition, as an organic material, resin can be cited. The insulating layer 30 composed of a material other than a piezoelectric material formed by firing can be formed on the lower surface of the piezoelectric actuator 13 by an appropriate thin film formation method such as CVD (chemical vapor deposition), for example, or can be adhered to the piezoelectric actuator 13 or the flow path member 11 by an adhesive.

[0276] The insulating layer 30, for example, extends substantially without gaps with a fixed thickness throughout the area where the plurality of pressure chambers 21 are arranged, similarly to the piezoelectric layer 29. However, when the insulating layer 30 is relatively thin, the insulating layer 30 cannot be arranged only directly below and around the second active area 53B (fourth electrode 45). The thickness of the insulating layer 30 can be appropriately set. For example, the thickness of the insulating layer 30 can be thinner than the thickness of the piezoelectric layer 29 (example shown in the figure), can be equal to it, or can be thicker. The thickness of the insulating layer 30 can be appropriately set, for example, taking into account the effects (strength and / or insulation) described later and / or the influence on the position of the neutral plane of the piezoelectric actuator 13.

[0277] The plurality of fourth electrodes 45 can be connected to each other through wiring included in the fifth conductor layer 31E, similarly to the plurality of second electrodes 37. In addition, unlike the embodiment, the plurality of fourth electrodes 45 can also be individually connected to a plurality of signal lines of an FPC (not shown) that is opposite to the first surface 13a of the piezoelectric actuator 13 via wiring and through conductors.

[0278] As described above, the head portion 307 includes the insulating layer 30 between the second active region 53B and the flow path member 11 .

[0279] In this case, for example, stress applied from the flow path member 11 to the second active region 53B is relieved by the insulating layer 30. For example, the deformation of the portion of the second active region 53B overlapping with the region 11e outside the pressure chamber 21 is constrained by the flow path member 11, and the stress in the position overlapping with the outer edge of the pressure chamber 21 is likely to increase. This stress is relieved. In addition, the insulating layer 30 covers the electrode (fourth electrode 45) that applies a 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 path member 11. In addition, the fourth electrode 45 does not come into contact with the liquid in the pressure chamber 21. As a result, for example, although it also depends on the type of liquid, the possibility of corrosion occurring in the fourth electrode 45 can be reduced.

[0280] <Fourth embodiment>

[0281] Fig.15 is a schematic cross-sectional view showing a head portion 407 according to a fourth embodiment, which is different from that of the first embodiment. Fig.11 correspond.

[0282] In the piezoelectric actuator 413 of the present embodiment, the fifth conductor layer 31E of the first embodiment is not provided. In addition, the fourth conductor layer 31D has a fourth electrode 445 which is equivalent to the fourth electrode 45 of the first embodiment. The second active region 53B is formed by the overlapping portion of the third electrode 41 and the fourth electrode 445 in the third piezoelectric layer 29C, and is not formed by the fourth piezoelectric layer 29D. In the present embodiment, as in the third embodiment, an insulating layer (the fourth piezoelectric layer 29D in the present embodiment) may be interposed between the second active region 53B and the flow path member 11.

[0283] The shape of the fourth electrode 445 can be set to an appropriate shape as long as it overlaps with the second active region 53B. For example, the shape of the fourth electrode 445 can be set to a shape obtained by superimposing the shapes of the fourth electrode 45 of the first embodiment and the fourth conductor layer 31D of the first embodiment. In other words, the fourth conductor layer 31D of the present embodiment can be set to a shape in which the outer edge of the opening 43 is substantially consistent with the outer edge of the electrode body 33a and / or the outer edge of the second electrode 37 in the fourth conductor layer 31D of the first embodiment. In addition, for example, the shape of the fourth electrode 445 can be set to be the same as the shape of the fourth electrode 45 of the first embodiment. In this case, for example, a plurality of fourth electrodes 445 can be connected to each other through a plurality of wirings included in the fourth conductor layer 31D, as with the second electrode 37. In addition, the plurality of fourth electrodes 445 can be individually given potentials, or can be connected to appropriate wirings and through conductors.

[0284] The potential applied to the fourth electrode 445 when the liquid is ejected and the polarization treatment is performed is, for example, the same as that of the fourth electrode 45 of the first embodiment. In this case, in the example shown in the figure, the distance between the electrodes in the first active region 53A is substantially equal to the distance between the electrodes in the second active region 53B, so the intensity of the electric field applied to the first active region 53A is substantially equal to the intensity of the electric field applied to the second active region 53B.

[0285] In this embodiment, as in the first embodiment, the intensity of the electric field applied to the first active region 53A can be made stronger than the intensity of the electric field applied to the second active region 53B. There are many methods for achieving the above-mentioned relationship between the intensity of the electric field. For example, the potential given to the electrode can be the same as in the first embodiment, and the thickness of the third piezoelectric layer 29C can be made thicker than the thickness of the first piezoelectric layer 29A and the thickness of the second piezoelectric layer 29B. In addition, for example, the second electrode 37 and the fourth electrode 445 can be set to be non-connected, and separate potentials can be given to each other, so that the potential difference between the third electrode 41 and the second electrode 37 is greater than the potential difference between the third electrode 41 and the fourth electrode 45.

[0286] As described above, the head 407 includes an insulating layer (fourth piezoelectric layer 29D) between the second active region 53B and the flow path member 11 similarly to the third embodiment. Therefore, for example, the same effects as those described in the third embodiment can be achieved.

[0287] <Fifth Embodiment>

[0288] Fig.16 2 is a schematic cross-sectional view showing a head portion 507 according to the fifth embodiment, and Fig.11 In this figure, and Figure 6 Similarly, the polarization direction is also indicated by the white arrow.

[0289] In the first embodiment, the first active region 53A is formed by two layers of piezoelectric layers 29, and the second active region 53B is formed by two layers of piezoelectric layers 29. In the piezoelectric actuator 513 of this embodiment, the first active region 53A is formed by one layer of the fifth piezoelectric layer 29E, and the second active region 53B is formed by one layer of the sixth piezoelectric layer 29F.

[0290] In the above structure, reference Figure 5 There are many possible combinations of the operations, polarization directions, electrode structures, and potentials of the first active region 53A and the second active region 53B described above. In the example shown in the figure, they are as follows.

[0291] The piezoelectric actuator 513 includes the first electrode 33 (and the reorientation electrode 35), the third electrode 41, and the fourth electrode 45 in order from the upper surface side to the lower surface side, as in the first embodiment. The first active region 53A includes a region of the fifth piezoelectric layer 29E sandwiched by the first electrode 33 and the third electrode 41. The second active region 53B includes a region of the sixth piezoelectric layer 29F sandwiched by the third electrode 41 and the fourth electrode 45. The fourth electrode 45 is insulated from the flow path member 11 by the insulating layer 30, and can be given a potential other than the reference potential.

[0292] The polarization directions of the first active region 53A and the second active region 53B are set to be opposite to each other. During the liquid ejection control, a reference potential is given to the third electrode 41 located between the two. A potential having the same polarity as the reference potential is given to the first electrode 33 and the fourth electrode 45. As a result, the first active region 53A and the second active region 53B are both contracted or both extended.

[0293] The driver 561 includes a signal source 63A for applying a potential to the first electrode 33 and a signal source 63B for applying a potential to the fourth electrode 45, and can apply different potentials to the first electrode 33 and the fourth electrode 45. Therefore, in this embodiment, as in the first embodiment, the electric field applied to the first active region 53A can be larger than the electric field applied to the second active region 53B. Unlike the example shown in the figure, the first electrode 33 and the fourth electrode 45 may be connected to each other and applied with the same potential.

[0294] (Modification of Piezoelectric Layer)

[0295] Fig.17A is a cross-sectional view showing the structure of the piezoelectric layer 29 according to a modified example. Fig.10 Magnified view of region XVII.

[0296] A groove 29v located between the first electrode 33 and the reorientation electrode 35 may be provided on the upper surface of the first piezoelectric layer 29A. The groove 29v extends, for example, along the outer edge of the first electrode 33 to surround the first electrode 33. In other words, the groove 29v extends in a ring shape. The groove 29v may be interrupted at a part. For example, the groove 29v may not be provided at a position on the opposite side of the electrode body 33a relative to the lead-out portion 33b.

[0297] The width of the groove 29v can be appropriately set within a range below the size of the gap between the first electrode 33 and the reorientation electrode 35. The width of the groove 29v can be fixed regardless of the position of the groove 29v in the longitudinal direction, or it can be changed according to the position of the groove 29v in the longitudinal direction. The depth of the groove 29v can be appropriately set within a range less than the thickness of the first piezoelectric layer 29A. For example, the depth of the groove 29v can be less than 1 / 2 of the thickness of the first piezoelectric layer 29A, or it can be more than 1 / 2. In addition, the depth of the groove 29v can also be set to be equal to the thickness of the first piezoelectric layer 29A.

[0298] The groove 29 v can be formed by an appropriate method, for example, by laser processing a ceramic green sheet to be the first piezoelectric layer 29A or the first piezoelectric layer 29A after firing.

[0299] Thus, if the groove 29v is provided, for example, the possibility of the metal material constituting the first electrode 33 and the reorientation electrode 35 moving in the region between these electrodes (causing migration) can be reduced. As a result, the possibility of the first electrode 33 and the reorientation electrode 35 being short-circuited can be reduced. From another perspective, it is easy to shorten the distance between the first electrode 33 and the reorientation electrode 35 when viewed from above, and it is easy to perform polarization treatment on the portion of the first inactive region 55A adjacent to the first active region 53A. Furthermore, the effect of maintaining the characteristics of the piezoelectric actuator based on the polarization treatment is improved. In addition, the migration is electromigration and / or electrochemical migration.

[0300] Fig. 17B is a cross-sectional view showing the structure of the piezoelectric layer 29 according to another modification example, and Fig.17A Same picture.

[0301] An insulator 32 may be disposed in the groove 29v. The insulator 32 may be formed of a material that is less likely to cause migration of the electrode material than the material of the first piezoelectric layer 29A. For example, the insulator 32 may be formed of a resin. The resin may be disposed in the groove 29v by an appropriate method such as CVD.

[0302] For example, the effect of reducing the possibility of migration can be improved by arranging the insulator 32. In addition, for example, the effect of reducing the possibility of migration can be obtained, and the possibility of reduction in the strength of the piezoelectric actuator due to the groove 29v can be reduced.

[0303] In the above embodiments, the third electrode 41 is an example of an intermediate electrode, and the fourth electrode 45 or 445 is an example of a lower electrode.

[0304] The technology involved in the present disclosure is not limited to the above-mentioned embodiments, and can be implemented in various forms.

[0305] For example, the first inactive area may not be subjected to polarization treatment. That is, a structure for polarization treatment may not be provided in the head. In the liquid ejection control, a control other than the control (set as the first control) in which the second active area elongates and contracts during at least a portion of the period in which the first active area elongates and contracts may be performed. For example, a control (set as the second control) in which the second active area elongates and contracts during at least a portion of the period in which the first active area elongates and contracts may be performed. Furthermore, the first control may be performed when ejecting large droplets, and the second control may be performed when ejecting small droplets. The head may also circulate the liquid.

[0306] According to the embodiments involved in the present disclosure, various concepts can be extracted. For example, in a top perspective view of the pressurized surface, the concept of a liquid ejection head can be extracted in which the area of ​​the second part of the second active area located outside the pressure chamber is larger than the area of ​​the first part of the second active area overlapping the pressure chamber. In addition, the piezoelectric actuator has an inactive area (composed of a piezoelectric body) connected to the periphery of the first active area, and the driver can extract the concept of a liquid ejection head that performs reorientation control of applying an electric field in the thickness direction to the inactive area when liquid ejection control is not performed. In the liquid ejection heads involved in these concepts, unlike the embodiments, the maximum value of the intensity of the electric field (first electric field) applied to the first active area and the maximum value of the intensity of the electric field (second electric field) applied to the second active area can be equal to each other, or the latter can be larger than the former.

[0307] -Explanation of symbols-

[0308] 1…printer (recording device), 2…liquid ejection head, 7…head body (liquid ejection head), 11…flow path member, 11b…pressurizing surface, 11e…outside area (for pressure chamber), 13…piezoelectric actuator, 21…pressure chamber, 21a…central portion (of pressure chamber), 21b…peripheral portion (of pressure chamber), 53A…first active area, 53B…second active area, 53Ba…first portion (of second active area), 53Bb…second portion (of second active area), 55A…first inactive area, 61…driver.

Claims

1. A liquid spraying head, comprising: A flow path member having a pressurizing surface and a pressure chamber opening on the pressurizing surface; a piezoelectric actuator overlapping the pressurizing surface; as well as a driver for driving the piezoelectric actuator, The piezoelectric actuator has, when a direction perpendicular to the pressurizing surface is referred to as a thickness direction: A first active region is formed of a piezoelectric body polarized in the thickness direction and overlaps with a central portion of the pressure chamber in a plan view of the pressurizing surface; A second active region, composed of a piezoelectric body polarized in the thickness direction, is located closer to the pressurizing surface than the first active region, and overlaps with the inner peripheral edge of the pressure chamber and the outer region of the pressure chamber in a plan perspective view of the pressurizing surface; as well as an insulating layer, located between the second active region and the flow path member, When the driver calls one of the extension and contraction in the direction along the pressurizing surface a first deformation and the other a second deformation, in liquid ejection control for ejecting liquid, the intensity of the first electric field applied to the first active area in the thickness direction and the intensity of the second electric field applied to the second active area in the thickness direction are controlled by changing the applied electric field, so that the second active area produces the first deformation in at least a part of the period when the first active area produces the first deformation.

2. The liquid ejection head according to claim 1, wherein: The insulating layer is thinner than the piezoelectric layer constituting the first active region.

3. The liquid ejection head according to claim 1, wherein: The insulating layer is thinner than the piezoelectric layer constituting the second active region.

4. The liquid ejection head according to any one of claims 1 to 3, wherein The piezoelectric actuator comprises: 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 pressurizing surface among the first active region electrodes and the electrode closest to the side opposite to the pressurizing surface among the second active region electrodes are located in the same layer and are electrically connected to constitute a shared electrode.

5. The liquid ejection head according to claim 4, wherein: An electrode of the first active region electrode that faces the shared electrode and an electrode of the second active region electrode that faces the shared electrode are electrically connected.

6. The liquid ejection head according to claim 1, wherein: The piezoelectric body located on the side opposite to the pressurizing surface with respect to the second active region and connected to the outer periphery of the first active region serves as an inactive region throughout the thickness of the first active region.

7. The liquid ejection head according to claim 1, wherein: The piezoelectric body located on the pressurizing surface side with respect to the first active region and inside the second active region serves as an inactive region throughout the thickness of the second active region.

8. The liquid ejection head according to claim 1, wherein: The liquid ejection control is in a standby state, and returns to the standby state after ejection. The first deformation of the second active region generated during the liquid ejection control is an extension compared to the standby state or a contraction compared to the standby state.

9. The liquid ejection head according to claim 1, wherein: In the liquid discharge control, a timing at which the first active region transitions to the state undergoing the first deformation coincides with a timing at which the second active region transitions to the state undergoing the first deformation.

10. The liquid ejection head according to claim 1, wherein having: three or more electrodes, which are located at different positions in the thickness direction and respectively perform at least one of application of the first electric field and application of the second electric field, The distance in the thickness direction between two electrodes that are adjacent to each other among three or more positions in the thickness direction of the three or more electrodes and that apply the first electric field is shorter than the distance in the thickness direction between two electrodes that are adjacent to each other among the three or more positions and that apply the second electric field.

11. The liquid ejection head according to claim 1, wherein: In the liquid ejection control, 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.

12. The liquid ejection head according to claim 1, wherein When the side of the piezoelectric actuator opposite to the flow path member is referred to as a first side, and the flow path member side of the piezoelectric actuator is referred to as a second side, the piezoelectric actuator has: A first piezoelectric layer and a second piezoelectric layer are stacked in order from the first side to the second side; a first electrode overlapping the surface of the first piezoelectric layer on the first side and overlapping the central portion in a plan view; a second electrode overlapping the surface of the second side of the first piezoelectric layer and overlapping the central portion in a plan perspective view; as well as a third electrode overlapping the second side surface of the second piezoelectric layer and overlapping the central portion, the peripheral portion, and the outer region in a plan perspective view; The first active region has: A region of the first piezoelectric layer sandwiched between the first electrode and the second electrode; and A region of the second piezoelectric layer sandwiched between the second electrode and the third electrode overlapping the central portion. The second active region is arranged on the second side of a portion of the third electrode that overlaps with the peripheral portion and the outer region.

13. The liquid ejection head according to claim 12, wherein: The liquid ejection head has: a third piezoelectric layer and a fourth piezoelectric layer stacked in order from the second piezoelectric layer toward the second side; as well as a fourth electrode overlapping the second side surface of the fourth piezoelectric layer and overlapping the peripheral portion and the outer region in a plan perspective view, The second active region includes a region of the third piezoelectric layer and the fourth piezoelectric layer that is sandwiched between a portion of the third electrode that overlaps with the peripheral portion and the outer region and the fourth electrode.

14. The liquid ejection head according to claim 13, wherein: A portion of the first piezoelectric layer constituting the first active region and a portion of the second piezoelectric layer constituting the first active region are polarized in opposite directions to each other. The portions of the third piezoelectric layer and the fourth piezoelectric layer that constitute the second active region are polarized in the same direction as the direction in which the portions of the first piezoelectric layer that constitute the first active region are polarized. In the liquid ejection control, the first electrode and the third electrode are set to the same potential, the second electrode and the fourth electrode are set to the same potential, and the first electric field and the second electric field are applied according to the potential difference between the potential of the first electrode and the third electrode and the potential of the second electrode and the fourth electrode.

15. The liquid ejection head according to claim 13, wherein: The sum of the thickness of the third piezoelectric layer and the thickness of the fourth piezoelectric layer is thicker than the thickness of the first piezoelectric layer and the thickness of the second piezoelectric layer, respectively.

16. The liquid ejection head according to claim 13, wherein: The piezoelectric actuator includes a conductor pattern that overlaps with the second surface of the third piezoelectric layer and is located outside the second active region in a plan view.

17. The liquid ejection head according to claim 1, wherein: In a plan perspective view of the pressurizing surface, an area of ​​a second portion of the second active region located outside the pressure chamber is larger than an area of ​​a first portion of the second active region overlapping the pressure chamber.

18. The liquid ejection head according to claim 1, wherein In a plan view of the pressurizing surface, a 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.

19. The liquid ejection head according to claim 1, wherein: In a cross section passing through the center of the pressure chamber and perpendicular to the pressurizing surface, a second portion of the second active region located outside the pressure chamber has a width greater than a first portion of the second active region overlapping the pressure chamber.

20. The liquid ejection head according to claim 1, wherein The piezoelectric actuator has an inactive region which is formed of a piezoelectric body and is connected to the periphery of the first active region. The driver performs reorientation control for applying an electric field in the thickness direction to the inactive region when the liquid ejection control is not performed.

21. The liquid ejection head according to claim 20, wherein: The piezoelectric actuator has: reorienting the electrode to overlap a side opposite the pressurized surface relative to the inactive region; an intermediate electrode, located between the inactive region and the second active region; as well as a lower electrode overlapping the pressurizing surface side with respect to the second active region, The drive, In the liquid ejection control, 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, 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.

22. The liquid ejection head according to claim 21, wherein The piezoelectric actuator includes an upper electrode located on the opposite side of the pressurizing surface from the intermediate electrode and facing the intermediate electrode with at least a portion of the first active region interposed therebetween. The drive, In the liquid ejection control, 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, no potential is given to the intermediate electrode, but a voltage is applied to the reorientation electrode and the lower electrode, thereby applying an electric field to the inactive region.

23. The liquid ejection head according to claim 12, wherein: The piezoelectric actuator has: an inactive region, which is composed of a piezoelectric body and is connected to the periphery of the first active region; a fourth electrode overlapping the surface of the second side of the second active region and overlapping the peripheral portion and the outer region in a plan perspective view; as well as a reorientation electrode overlapping with the first side surface of the first piezoelectric layer and overlapping with the peripheral portion and the outer region in a plan perspective view, The driver performs reorientation control of applying an electric field in the thickness direction to the inactive area when the liquid ejection control is not performed. The inactive region includes a region of the first piezoelectric layer and the second piezoelectric layer that is sandwiched between the reorientation electrode and the fourth electrode.

24. The liquid ejection head according to claim 1, wherein In the liquid ejection control, the maximum value of the intensity of the first electric field is greater than the maximum value of the intensity of the second electric field.

25. A recording device comprising: Liquid sprays out of the head; and A control unit controls the liquid ejection head, The liquid ejection head has: A flow path member having a pressurizing surface and a pressure chamber opening on the pressurizing surface; as well as a piezoelectric actuator overlapping the pressurizing surface, The piezoelectric actuator has, when a direction perpendicular to the pressurizing surface is referred to as a thickness direction: A first active region is formed of a piezoelectric body polarized in the thickness direction and overlaps with a central portion of the pressure chamber in a plan view of the pressurizing surface; A second active region, composed of a piezoelectric body polarized in the thickness direction, is located closer to the pressurizing surface than the first active region, and overlaps with the inner peripheral edge of the pressure chamber and the outer region of the pressure chamber in a plan perspective view of the pressurizing surface; as well as an insulating layer, located between the second active region and the flow path member, When the control unit calls one of the extension and contraction in the direction along the pressurizing surface a first deformation and the other a second deformation, in liquid ejection control for ejecting liquid, the intensity of the first electric field applied to the first active area in the thickness direction and the intensity of the second electric field applied to the second active area in the thickness direction are controlled by changing the applied electric field, so that the second active area produces the first deformation in at least a part of the period when the first active area produces the first deformation.

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