Liquid discharge head

Abstract

To suppress cracking from occurring on a vibration plate.SOLUTION: A liquid discharge head 3 comprises: a vibration plate 35; a pressure chamber substrate 34 which is provided on a first surface SF1 side of the vibration plate 35 and has a pressure chamber CV; and a piezoelectric element PZ which is provided on a second surface SF2 side of the vibration plate 35, and which has a lower electrode Zd, a piezoelectric body layer Zm and an upper electrode Zu. The lower electrode Zd, the piezoelectric body layer Zm and the upper electrode Zu are provided on the second surface SF2 side of the vibration plate 35 in this order. The upper electrode Zu has an oxide of a predetermined element and includes a first area AR1 overlapping with both of the piezoelectric body layer Zm and the lower electrode Zd in plan view. The first area AR1 includes two second areas AR2 which are away from each other, and a third area AR3 positioned between the two second areas AR2, in a direction along an X-axis, which is a longitudinal direction of the pressure chamber CV. A rate of content of the oxide in the third area AR3 is higher than the rate of content of the oxide in each of the two second areas AR2.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a liquid ejection head. [Background technology]

[0002] A liquid ejection device that prints an image by ejecting liquid such as ink from a nozzle using a piezoelectric element is known. For example, the liquid ejection device has a liquid ejection head that ejects liquid filled in a pressure chamber from a nozzle by vibrating a vibration plate that constitutes a part of the pressure chamber using a piezoelectric element. Patent Document 1 discloses a liquid ejection head having a flow path forming substrate provided with a plurality of individual flow paths that include pressure generating chambers and are partitioned by partition walls, and a common flow path to which the plurality of individual flow paths communicate, and a vibration plate provided above the flow path forming substrate and constituting one surface of the individual flow paths. In the liquid ejection head described in Patent Document 1, in order to suppress the occurrence of cracks between the partition wall and the vibration plate, a groove portion filled with a resin material is provided between the tip of the partition wall on the common flow path side and the vibration plate, and the partition wall and the vibration plate are fixed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-143170 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the problem of cracks occurring in the diaphragm has been known for a long time. For this reason, it is desirable to suppress the occurrence of cracks in the diaphragm, without being limited to the methods of the conventional technology. [Means for solving the problem]

[0005] In order to solve the above problems, the liquid ejection head of the present invention comprises a vibration plate having a first surface and a second surface opposite to the first surface, a pressure chamber substrate provided on the first surface side of the vibration plate and having a pressure chamber filled with liquid, and a piezoelectric element provided on the second surface side of the vibration plate and having a first electrode, a piezoelectric layer, and a second electrode, wherein the first electrode, the piezoelectric layer, and the second electrode are provided, in this order, on the second surface side of the vibration plate along a first direction from the first surface to the second surface, the second electrode has an oxide of a predetermined element and includes a first region that overlaps both the piezoelectric layer and the first electrode in a planar view from the first direction, the first region includes two second regions that are separated from each other in a second direction that is the longitudinal direction of the pressure chamber, and a third region located between the two second regions, and the oxide content in the third region is higher than the oxide content in each of the two second regions. [Brief description of the drawings]

[0006] [Figure 1] 1 is an explanatory diagram for explaining an example of a liquid ejection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an exploded perspective view of the liquid ejection head. [Diagram 3] 3 is a cross-sectional view taken along line aa in FIG. 2. [Figure 4] FIG. 2 is a plan view of a plurality of piezoelectric elements. [Diagram 5] 5 is a cross-sectional view taken along the line bb in FIG. 4. [Figure 6] 5 is a cross-sectional view taken along line cc in FIG. 4. [Figure 7] FIG. 11 is an explanatory diagram for explaining the occurrence of cracks. [Figure 8] 5 is a diagram illustrating the relationship between the degree of oxidation of the upper electrode and the characteristic fluctuation and crack resistance of the piezoelectric element. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part are appropriately different from the actual ones. In addition, since the embodiments described below are preferred specific examples of the present invention, various technically preferable limitations are attached, but the scope of the present invention is not limited to these embodiments unless otherwise stated in the following description to the effect that the present invention is particularly limited.

[0008] [1. Embodiment] First, an overview of a liquid ejection device 1 according to this embodiment will be described with reference to Fig. 1. In this embodiment, it is assumed, as an example, that the liquid ejection device 1 is a serial printer.

[0009] FIG. 1 is an explanatory diagram for explaining an example of a liquid ejection device 1 according to an embodiment of the present invention. In the following, for convenience of explanation, an X-axis, a Y-axis, and a Z-axis that are perpendicular to each other will be appropriately used. In addition, in the following, one direction along the X-axis will be referred to as the X1 direction, and the direction opposite to the X1 direction will be referred to as the X2 direction. Similarly, one direction along the Y-axis will be referred to as the Y1 direction, and the direction opposite to the Y1 direction will be referred to as the Y2 direction. Furthermore, one direction along the Z-axis will be referred to as the Z1 direction, and the direction opposite to the Z1 direction will be referred to as the Z2 direction.

[0010] The liquid ejection device 1 in Fig. 1 is an inkjet printing device that ejects ink onto a medium PP. Note that ink is an example of a "liquid." The medium PP is typically printing paper, but a printing target made of any material, such as a resin film or fabric, can be used as the medium PP.

[0011] 1, a liquid container 14 for storing ink is installed in the liquid ejection device 1. As the liquid container 14, for example, a cartridge that is detachable from the liquid ejection device 1, a bag-shaped ink pack made of a flexible film, or an ink tank that can be refilled with ink can be used. The type of ink stored in the liquid container 14 is not particularly limited and can be any type.

[0012] The liquid ejection device 1 also has a control unit 2, a medium transport mechanism 71, a carriage transport mechanism 72, and a liquid ejection head 3. The control unit 2 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory, and performs overall control of each element of the liquid ejection device 1.

[0013] The medium transport mechanism 71 transports the medium PP in the Y2 direction along the Y axis under the control of the control unit 2. The carriage transport mechanism 72 reciprocates the liquid ejection head 3 along the X axis under the control of the control unit 2. The carriage transport mechanism 72 has, for example, a substantially box-shaped carriage 721 that houses the liquid ejection head 3, and an endless belt 722 to which the carriage 721 is fixed. Note that a configuration in which multiple liquid ejection heads 3 are mounted on the carriage 721 may also be employed. The liquid container 14 may also be stored in the carriage 721 together with the liquid ejection head 3.

[0014] The liquid ejection head 3 ejects ink onto the medium PP from a plurality of nozzles N shown in Fig. 2 (described later) under the control of the control unit 2. For example, the liquid ejection head 3 ejects ink supplied from a liquid container 14 onto the medium PP from a plurality of nozzles N. An image is formed on the surface of the medium PP by each liquid ejection head 3 ejecting ink onto the medium PP in parallel with the transport of the medium PP by the medium transport mechanism 71 and the repeated reciprocating movement of the carriage 721.

[0015] Next, the schematic structure of the liquid ejection head 3 will be described with reference to FIGS.

[0016] Fig. 2 is an exploded perspective view of the liquid ejection head 3. Fig. 3 is a cross-sectional view taken along line aa shown in Fig. 2. The aa cross section is parallel to the XZ plane and passes through an introduction port 364, which will be described later.

[0017] 2 and 3, the liquid ejection head 3 includes a wiring board 20, a flow path board 33, a pressure chamber board 34, a vibration plate 35, a plurality of piezoelectric elements PZ, a case 36, a sealing plate 37, a nozzle board 38, and a vibration absorber 39. The wiring board 20 is a mounting component on which a plurality of wirings are formed for electrically connecting the control unit 2 and the piezoelectric elements PZ. For example, a flexible wiring board 20 such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably used. A drive signal and a reference voltage for driving the piezoelectric elements PZ are supplied to each piezoelectric element PZ from the wiring board 20.

[0018] Here, in an area located in the Z1 direction from the flow path substrate 33, a pressure chamber substrate 34, a vibration plate 35, a plurality of piezoelectric elements PZ, a case 36, and a sealing plate 37 are disposed. On the other hand, in an area located in the Z2 direction from the flow path substrate 33, a nozzle substrate 38 and a vibration absorber 39 are disposed. Also, the wiring substrate 20 is provided, for example, on the Z1 direction surface of the sealing plate 37. Each element of the liquid ejection head 3 is roughly a plate-like member that is elongated in the direction along the Y axis, and is joined to one another, for example, by an adhesive.

[0019] 2, the nozzle substrate 38 is a plate-like member on which a plurality of nozzles N are formed and arranged along the Y axis. Each nozzle N is a through hole through which ink passes. The flow path substrate 33, the pressure chamber substrate 34, and the nozzle substrate 38 are formed, for example, by processing a silicon single crystal substrate using a semiconductor manufacturing technique such as etching. However, the materials and manufacturing methods of each element of the liquid ejection head 3 are arbitrary.

[0020] The flow path substrate 33 is a plate-like member for forming a flow path of ink. As shown in FIG. 2 and FIG. 3, an opening 332, a plurality of supply flow paths 334, and a plurality of communication flow paths 336 are formed in the flow path substrate 33. The opening 332 is a through hole that is continuous across the plurality of nozzles N along the Y axis in a plan view from the direction along the Z axis. That is, the opening 332 is an elongated through hole that extends in the direction along the Y axis. The supply flow path 334 and the communication flow path 336 are through holes that are individually formed for each nozzle N. In addition, as shown in FIG. 3, a relay flow path 338 that spans the plurality of supply flow paths 334 is formed on the surface of the flow path substrate 33 in the Z2 direction. The relay flow path 338 is a flow path that communicates the opening 332 and the plurality of supply flow paths 334.

[0021] The pressure chamber substrate 34 is a plate-like member in which a plurality of pressure chambers CV corresponding to the plurality of nozzles N are formed. The pressure chambers CV are spaces called cavities for applying pressure to the ink filled in the pressure chambers CV. For example, the pressure chambers CV are spaces located between the flow path substrate 33 and the vibration plate 35 and partitioned by the partitions 342 of the pressure chamber substrate 34. The plurality of pressure chambers CV are arranged in a direction along the Y axis. Each pressure chamber CV is formed of a hole that opens on both sides of the pressure chamber substrate 34 and has an elongated shape extending in a direction along the X axis. That is, the direction along the X axis corresponds to the longitudinal direction of the pressure chambers CV. The direction along the X axis is an example of the "second direction". The end of each pressure chamber CV in the X2 direction communicates with the corresponding supply flow path 334 among the plurality of supply flow paths 334. On the other hand, the end of each pressure chamber CV in the X1 direction communicates with the corresponding communication flow path 336 among the plurality of communication flow paths 336.

[0022] A vibration plate 35 is provided on the surface of the pressure chamber substrate 34 opposite to the surface facing the flow channel substrate 33. The vibration plate 35 is an elastically deformable plate-like member. As shown in FIG. 3, the vibration plate 35 includes an insulating film 352 and an elastic film 351 laminated in a direction along the Z axis. In this specification, the expression "element A and element B are laminated" does not mean to limit the configuration in which element A and element B are in direct contact with each other. In other words, a configuration in which another element C is interposed between element A and element B is also included in the concept of "element A and element B are laminated." Similarly, the expression "element B is formed on the surface of element A" is not limited to a configuration in which element A and element B are in direct contact with each other. In other words, even if an element C is formed on the surface of element A and an element B is formed on the surface of element C, the concept of "element B is formed on the surface of element A" is included in the concept of "element B is formed on the surface of element A" as long as at least a part of element A and element B overlap in a plan view. The insulating film 352 is located on the opposite side to the pressure chamber substrate 34 as viewed from the elastic film 351. The elastic film 351 is made of, for example, silicon oxide. The insulating film 352 is made of, for example, zirconium oxide.

[0023] As can be understood from Figs. 2 and 3, the flow path substrate 33 and the vibration plate 35 face each other with a gap between them inside each pressure chamber CV. The vibration plate 35 forms part of the wall surface of the pressure chamber CV. For example, the vibration plate 35 has a first surface SF1 and a second surface SF2 opposite to the first surface SF1. The pressure chamber substrate 34 is provided on the first surface SF1 side of the vibration plate 35. In this case, the first surface SF1 of the vibration plate 35 forms part of the wall surface of the pressure chamber CV. As shown in Fig. 3, the ink stored in the liquid storage chamber RS ​​branches from the relay flow path 338 to each supply flow path 334 and is supplied to and filled in parallel into the multiple pressure chambers CV.

[0024] As shown in FIG. 2 and FIG. 3, a surface of the vibration plate 35 facing away from the pressure chamber substrate 34, that is, the second surface SF2, is provided with a plurality of piezoelectric elements PZ corresponding to the plurality of nozzles N. The nozzle N corresponding to the piezoelectric element PZ is a nozzle N communicating with the pressure chamber CV that partially or completely overlaps with the piezoelectric element PZ in a plan view in the Z2 direction. Each piezoelectric element PZ is an actuator that deforms when a drive signal is supplied, and has an elongated shape extending in the direction along the X axis. The plurality of piezoelectric elements PZ are arranged in the direction along the Y axis so as to correspond to the plurality of pressure chambers CV. When the drive signal is supplied to the piezoelectric element PZ, the vibration plate 35 vibrates in conjunction with the deformation of the piezoelectric element PZ, and the pressure in the pressure chamber CV fluctuates. When the pressure in the pressure chamber CV fluctuates, the ink filled in the pressure chamber CV passes through the communication flow path 336 and the nozzle N and is ejected. That is, the piezoelectric element PZ is a driving element that vibrates the vibration plate 35 to eject the ink in the pressure chamber CV from the nozzle N.

[0025] As shown in FIG. 3, the piezoelectric element PZ has a lower electrode Zd to which a drive signal is supplied, an upper electrode Zu to which a reference voltage is supplied, and a piezoelectric layer Zm provided between the lower electrode Zd and the upper electrode Zu. For example, the lower electrode Zd, the piezoelectric layer Zm, and the upper electrode Zu are provided in this order on the second surface SF2 side of the vibration plate 35 along the Z1 direction from the first surface SF1 to the second surface SF2. That is, the piezoelectric element PZ is generally configured by laminating the lower electrode Zd, the piezoelectric layer Zm, and the upper electrode Zu. A pressure chamber CV is provided in the Z2 direction of the piezoelectric element PZ. The Z1 direction is an example of the "first direction", and the Z2 direction is an example of the "third direction". One of the lower electrodes Zd is an example of the "first electrode", and the upper electrode Zu is an example of the "second electrode".

[0026] In Figure 3, in order to avoid complicating the drawing, the wiring connected to the lower electrode Zd and supplying a drive signal to the lower electrode Zd, and the wiring connected to the upper electrode Zu and supplying a reference voltage to the upper electrode Zu are omitted.

[0027] 2 and 3, the case 36 is a structure manufactured by, for example, injection molding of a resin material, and is fixed to the surface of the flow path substrate 33 in the Z1 direction. As shown in FIG. 3, a storage section 362 and an inlet 364 are formed in the case 36. The storage section 362 is a recess having an outer shape corresponding to the opening 332 of the flow path substrate 33. The inlet 364 is a through hole communicating with the storage section 362. The space formed by the opening 332 of the flow path substrate 33 and the storage section 362 of the case 36 functions as a liquid storage chamber RS, which is a reservoir that stores ink to be supplied to the multiple pressure chambers CV. Ink supplied from the liquid container 14 and passing through the inlet 364 is stored in the liquid storage chamber RS.

[0028] The sealing plate 37 is a structure that protects the multiple piezoelectric elements PZ from the outside air and reinforces the mechanical strength of the pressure chamber substrate 34 and the vibration plate 35. The sealing plate 37 is fixed to the second surface SF2 of the vibration plate 35, for example, by an adhesive. As shown in FIG. 3, the sealing plate 37 has a recess on the surface facing the vibration plate 35. A sealed space 372 is formed by fixing the sealing plate 37 to the second surface SF2 of the vibration plate 35. The sealed space 372 contains the multiple piezoelectric elements PZ.

[0029] The vibration absorber 39 absorbs pressure fluctuations in the liquid storage chamber RS. That is, the vibration absorber 39 absorbs vibrations of the ink stored in the liquid storage chamber RS. For example, the vibration absorber 39 includes a flexible sheet member capable of elastic deformation. Specifically, the vibration absorber 39 is installed on the surface in the Z2 direction of the flow path substrate 33 so as to close the opening 332, the relay flow path 338, and the multiple supply flow paths 334 of the flow path substrate 33 and form the bottom surface of the liquid storage chamber RS.

[0030] Next, a specific configuration of each piezoelectric element PZ will be described with reference to FIGS.

[0031] Fig. 4 is a plan view of a plurality of piezoelectric elements PZ. Fig. 5 is a cross-sectional view taken along line bb in Fig. 4. Fig. 6 is a cross-sectional view taken along line cc in Fig. 4. In Fig. 4, the periphery of an element located behind any one element is also shown by a solid line for the sake of convenience.

[0032] As shown in FIGS. 4 to 6, the piezoelectric element PZ is generally formed by laminating a lower electrode Zd, a piezoelectric layer Zm, and an upper electrode Zu.

[0033] The lower electrode Zd is formed on the second surface SF2 of the vibration plate 35. The lower electrode Zd is an individual electrode formed for each piezoelectric element PZ. Specifically, a plurality of lower electrodes Zd extending in the direction along the X-axis are arranged in the direction along the Y-axis at intervals from each other. A drive signal for controlling the ejection of ink from the nozzle N corresponding to the piezoelectric element PZ is applied to the lower electrode Zd of each piezoelectric element PZ via the wiring board 20. For example, a wiring LW to which a drive signal is supplied is connected to the lower electrode Zd of each piezoelectric element PZ.

[0034] The piezoelectric layer Zm is formed on the surface of the lower electrode Zd. The piezoelectric layer Zm is a strip-shaped dielectric film extending in the direction along the Y axis so as to be continuous across the piezoelectric elements PZ. As shown in FIG. 4, in a plan view from the Z2 direction, a long notch G is formed in the direction along the X axis in an area of ​​the piezoelectric layer Zm corresponding to the gap between adjacent pressure chambers CV. The notch G is a through hole penetrating the piezoelectric layer Zm. According to the above configuration, each piezoelectric element PZ is deformed individually for each pressure chamber CV, so that the propagation of vibration between the piezoelectric elements PZ is suppressed. This makes it possible to control the ink ejection characteristics of each nozzle N with high precision. The ejection characteristics are, for example, the amount of ink ejected, the ink ejection speed, or the ink ejection direction.

[0035] The upper electrode Zu is formed on the surface of the piezoelectric layer Zm. Specifically, the upper electrode Zu is a strip-shaped common electrode that extends in the direction along the Y axis so as to be continuous across the plurality of piezoelectric elements PZ.

[0036] The piezoelectric layer Zm is deformed according to the voltage difference between the drive signal supplied to the lower electrode Zd and the reference voltage supplied to the upper electrode Zu. For example, the portion of the piezoelectric layer Zm sandwiched between the lower electrode Zd and the upper electrode Zu is deformed. This deformation causes the piezoelectric element PZ to bend the vibration plate 35. That is, the piezoelectric element PZ vibrates the vibration plate 35 according to the voltage difference between the drive signal applied to the lower electrode Zd and the reference voltage supplied to the upper electrode Zu. The piezoelectric element PZ is formed individually for each pressure chamber CV. Specifically, a plurality of piezoelectric elements PZ formed long in the direction along the X-axis are arranged in the direction along the Y-axis at intervals from each other. The direction along the X-axis corresponds to the direction intersecting the direction along the Y-axis along which the plurality of pressure chambers CV are arranged. In this embodiment, the width of the pressure chamber CV in the direction along the Y-axis is larger than the width of the piezoelectric element PZ in the direction along the Y-axis.

[0037] In this embodiment, a first conductor CD1 and a second conductor CD2 are formed on the surface of the upper electrode Zu. The first conductor CD1 is a strip-shaped conductive film extending in the direction along the Y axis along the edge of the upper electrode Zu on the X1 direction side. The second conductor CD2 is a strip-shaped conductive film extending in the direction along the Y axis along the edge of the upper electrode Zu on the X2 direction side. In this manner, the first conductor CD1 and the second conductor CD2 are stacked on the upper electrode Zu in the Z1 direction and are spaced apart from each other in the direction along the X axis. The first conductor CD1 and the second conductor CD2 are formed using a low-resistance conductive material such as gold (Au). By forming the first conductor CD1 and the second conductor CD2, the voltage drop of the reference voltage in the upper electrode Zu is suppressed.

[0038] The first conductor CD1 and the second conductor CD2 also function as weights for suppressing deformation of the diaphragm 35 and the piezoelectric element PZ. That is, the region of the diaphragm 35 between the first conductor CD1 and the second conductor CD2 is a vibration region ARv that actually vibrates in conjunction with the deformation of the piezoelectric element PZ. One of the first conductor CD1 and the second conductor CD2 is an example of a "first weight portion," and the other of the first conductor CD1 and the second conductor CD2 is an example of a "second weight portion."

[0039] By providing the first conductor CD1 and the second conductor CD2, the range of the vibration region ARv in the direction along the X-axis can be easily set to a targeted range, for example, the range of the design value. For example, the range of the vibration region ARv in the direction along the X-axis is between the edge of the first conductor CD1 on the X2 direction side and the edge of the second conductor CD2 on the X1 direction side. The range of the vibration region ARv in the direction along the Y-axis is between the edge of the pressure chamber CV on the Y1 direction side and the edge of the pressure chamber CV on the Y2 direction side. Therefore, as can be understood from FIG. 4, a plurality of vibration regions ARv long in the direction along the X-axis are arranged in the direction along the Y-axis at intervals from each other. The vibration region ARv of the vibration plate 35 has a tendency that cracks are easily generated along the long side of the vibration region ARv. In this way, cracks can be generated in the vibration plate 35.

[0040] According to the study by the inventors of the present application, it was found that cracks tend to occur particularly easily near the center of the vibration region ARv in the longitudinal direction of the pressure chamber CV. The vicinity of the center of the vibration region ARv in the longitudinal direction of the pressure chamber CV includes the position of the center LC of the vibration region ARv in the longitudinal direction of the pressure chamber CV. The position of the center LC of the vibration region ARv corresponds to the center position between the first conductor CD1 and the second conductor CD2 in the longitudinal direction of the pressure chamber CV. Hereinafter, the center between the first conductor CD1 and the second conductor CD2 may be referred to as the center LC between the first conductor CD1 and the second conductor CD2 using the same reference symbol as the center LC of the vibration region ARv.

[0041] In this embodiment, the occurrence of cracks is suppressed in the vicinity of the center of the vibration region ARv in the longitudinal direction of the pressure chamber CV, thereby suppressing the occurrence of cracks in the vibration plate 35. For example, in this embodiment, the occurrence of cracks in the vibration plate 35 is suppressed by adjusting the position and amount of deflection of the vibration plate 35. Details will be described in FIG. 8, but when the deflection of the vibration plate 35 in the Z2 direction is large, cracks are less likely to occur compared to when the deflection of the vibration plate 35 in the Z2 direction is small. The position and amount of deflection of the vibration plate 35 are adjusted, for example, by adjusting the degree of oxidation of the upper electrode Zu. For example, when the degree of oxidation of the upper electrode Zu is large, the deflection of the vibration plate 35 in the Z2 direction is larger than when the degree of oxidation of the upper electrode Zu is small.

[0042] For example, the upper electrode Zu has an oxide of a predetermined element. In this embodiment, the predetermined element is assumed to be iridium (Ir). That is, in this embodiment, the upper electrode Zu has an oxide of iridium. Also, as shown in FIG. 4 to FIG. 6, the upper electrode Zu includes a first region AR1 that overlaps with both the piezoelectric layer Zm and the lower electrode Zd in a plan view from the Z1 direction. The first region AR1 includes two second regions AR2 that are separated from each other in a direction along the X-axis that is the longitudinal direction of the pressure chamber CV, and a third region AR3 located between the two second regions AR2. The oxide content in the third region AR3 is higher than the oxide content in each of the two second regions AR2.

[0043] In the following, a portion of the vibration plate 35 that overlaps with a region of the upper electrode Zu in a plan view from the Z1 direction is also referred to as a portion corresponding to the region. For example, a portion of the vibration plate 35 that overlaps with the third region AR3 in a plan view from the Z1 direction is also referred to as a portion corresponding to the third region AR3. In addition, in the following, a portion of the piezoelectric element PZ that overlaps with a region of the upper electrode Zu in a plan view from the Z1 direction is also referred to as a region of the piezoelectric element PZ using the symbol of the region. For example, a portion of the piezoelectric element PZ that overlaps with the third region AR3 in a plan view from the Z1 direction is also referred to as the third region AR3 of the piezoelectric element PZ. Note that when the first region AR1, the second region AR2, or the third region AR3 is simply referred to, it means the first region AR1, the second region AR2, or the third region AR3 of the upper electrode Zu.

[0044] As described above, the oxide content in the third region AR3 is higher than the oxide content in each of the two second regions AR2. Therefore, in the third region AR3, the interface between the piezoelectric layer Zm and the upper electrode Zu becomes uniform compared to the second region AR2, and the residual strain caused by the generation of crystals that become the nuclei of polarization inversion is large. As a result, in this embodiment, the piezoelectric element PZ bends so that the third region AR3 of the piezoelectric element PZ is located in the Z2 direction more than the second region AR2 of the piezoelectric element PZ. As a result, in this embodiment, the vibration plate 35 bends so that the part corresponding to the third region AR3 is located in the Z2 direction more than the part corresponding to the second region AR2. In this embodiment, the part of the vibration plate 35 corresponding to the third region AR3 includes the vicinity of the center of the vibration region ARv. Therefore, in this embodiment, it is possible to suppress the occurrence of cracks near the center of the vibration region ARv in the longitudinal direction of the pressure chamber CV.

[0045] In this embodiment, for example, in the direction along the X-axis, the width War3 of the third region AR3 is smaller than the sum of the widths War2a and War2b of the two second regions AR2, "War2a+War2b". The width War3 of the third region AR3 should be as small as possible if cracks do not occur. Since cracks spread from the center LC of the vibrating region ARv, it is necessary to oxidize only the center LC of the vibrating region ARv, but considering the bending of the diaphragm 35, it is better for the third region AR3 to have a certain width.

[0046] For example, when focusing on the width Warv of the vibration region ARv in the direction along the X-axis, the width War3 of the third region AR3 is preferably less than half the width Warv of the vibration region ARv. For example, the range of the third region AR3 in the direction along the X-axis is preferably within a range of ±“0.25*Warv” from the center LC of the vibration region ARv. More preferably, the range of the third region AR3 in the direction along the X-axis is within a range of ±“0.05*Warv” from the center LC of the vibration region ARv. The above-mentioned “0.25*Warv” indicates 25% of the width Warv of the vibration region ARv, that is, 25% of the distance between the first conductor CD1 and the second conductor CD2. Also, the above-mentioned “0.05*Warv” indicates 5% of the width Warv of the vibration region ARv, that is, 5% of the distance between the first conductor CD1 and the second conductor CD2.

[0047] 4 and other figures illustrate a case where the range of the third region AR3 in the direction along the X-axis is within a range of ±0.25*Warv from the center LC of the vibration region ARv. In this case, the width War3 of the third region AR3 is half the width Warv of the vibration region ARv. In addition, in a plan view from the Z1 direction, the position of the center LC of the vibration region ARv is located within the third region AR3.

[0048] In addition, in the two second regions AR2 sandwiching the third region AR3 in the direction along the X-axis, the oxide content is lower than that in the third region AR3. Therefore, in the second region AR2, the interface between the piezoelectric layer Zm and the upper electrode Zu is not uniform, and the generation of crystals that become the nuclei of polarization inversion becomes dispersed, so that the residual strain generated is small. As a result, in the second region AR2 of the piezoelectric element PZ, the deformation of the shape can be suppressed compared to the third region AR3 of the piezoelectric element PZ. As a result, in this embodiment, the deflection of the part of the vibration plate 35 corresponding to the second region AR2 can be maintained in a small state. Also, as shown in FIG. 5, the second region AR2 of the piezoelectric element PZ generates a stress F that pulls the third region AR3 of the piezoelectric element PZ. As a result, in this embodiment, a stress that pulls the third region AR3 of the piezoelectric element PZ in the Z1 direction is generated, and the characteristic fluctuation of the piezoelectric element PZ can be appropriately suppressed. The characteristic fluctuation of the piezoelectric element PZ is, for example, a fluctuation in the ejection characteristics.

[0049] 6, the vibration region ARv of the vibration plate 35 includes a first portion V1 and a second portion V2 in the short-side direction of the piezoelectric element PZ. The first portion V1 is a region that overlaps with the piezoelectric layer Zm in a plan view from the Z1 direction, and the second portion V2 is a region that is located outside the piezoelectric layer Zm in a plan view from the Z1 direction. The second portion V2 corresponds to an arm-shaped portion that elastically supports the first portion V1.

[0050] 6 is a portion along the long side of the vibration region ARv, and corresponds to an edge of a connection between the vibration plate 35 and the partition wall 342 of the pressure chamber substrate 34. Hereinafter, the vicinity of the center of the specific portion Pc of the vibration region ARv in the direction along the X-axis, which is the longitudinal direction of the pressure chamber CV, may be simply referred to as the vicinity of the center of the specific portion Pc. In this embodiment, as described above, by making the oxide content in the third region AR3 higher than the oxide content in the second region AR2, it is possible to suppress the occurrence of cracks in the specific portion Pc of the vibration region ARv, particularly in the vicinity of the center of the specific portion Pc.

[0051] In addition, the oxidation degree of the portion of the upper electrode Zu between the first regions AR1 adjacent to each other in the direction along the Y axis is not particularly limited. For example, the portion of the upper electrode Zu between the first regions AR1 adjacent to each other in the direction along the Y axis may have the same oxidation degree as the first region AR1, or may have a different oxidation degree from the first region AR1. Specifically, the portion of the upper electrode Zu between the second regions AR2 adjacent to each other in the direction along the Y axis may have the same oxidation degree as the second region AR2, and the portion of the upper electrode Zu between the third regions AR3 adjacent to each other in the direction along the Y axis may have the same oxidation degree as the third region AR3. Alternatively, the portion of the upper electrode Zu between the first regions AR1 adjacent to each other in the direction along the Y axis may have a common oxidation degree in the entire portion. The common oxidation degree may be the same oxidation degree as one of the second region AR2 and the third region AR3.

[0052] The method of making the second region AR2 and the third region AR3 different in oxidation degree is not particularly limited. For example, the second region AR2 and the third region AR3 may be made different in oxidation degree by forming an iridium film in multiple stages. Alternatively, the second region AR2 and the third region AR3 may be made different in oxidation degree by repeating annealing. Alternatively, the second region AR2 and the third region AR3 may be made different in oxidation degree by laser annealing.

[0053] Next, the occurrence of cracks will be described with reference to FIG.

[0054] FIG. 7 is an explanatory diagram for explaining the occurrence of cracks. "0V applied" in FIG. 7 shows a schematic state of the vibration plate 35 seen from the X2 direction when the voltage between the upper electrode Zu and the lower electrode Zd is maintained at 0V. Also, "driving" in FIG. 7 shows a schematic state of the vibration plate 35 seen from the X2 direction when the piezoelectric element PZ is driven so as to contract the volume of the pressure chamber CV. The state in which the voltage between the upper electrode Zu and the lower electrode Zd is maintained at 0V corresponds to a state in which the piezoelectric element PZ is not driven. Note that the state in which the piezoelectric element PZ is not driven may be a state in which one or both of the upper electrode Zu and the lower electrode Zd are in high impedance.

[0055] 7, when the voltage between the upper electrode Zu and the lower electrode Zd is maintained at 0V, the difference in the direction along the Z axis between the position of the vibration plate 35 and the upper surface SFu of the partition wall 342 of the pressure chamber substrate 34 may be referred to as the deflection amount DF of the vibration plate 35. Furthermore, in this embodiment, unless otherwise specified, it is assumed that the vibration plate 35 deflects in the Z2 direction when the piezoelectric element PZ is not driven.

[0056] As shown in "During Driving" in FIG. 7, the vicinity of the specific portion Pc of the vibration plate 35, i.e., the end portion in the Y1 direction and the end portion in the Y2 direction of the vibration plate 35, are pushed up in the Z1 direction by the force Fu from the ink in the Z2 direction when the piezoelectric element PZ is driven. This generates high stress starting from the specific portion Pc of the vibration plate 35. As a result, cracks are generated in the specific portion Pc of the vibration plate 35. Also, although not shown in FIG. 7, when the vibration plate 35 deforms in the Z1 direction so as to expand the volume of the pressure chamber CV, if the vibration plate 35 is located in the Z1 direction above the upper surface SFu of the partition wall 342 of the pressure chamber substrate 34, stress is generated in the specific portion Pc of the vibration plate 35.

[0057] In addition, when the deflection amount DF of the vibration plate 35 is small, the vibration plate 35 is more likely to be located in the Z1 direction from the upper surface SFu of the partition wall 342 of the pressure chamber substrate 34 when the piezoelectric element PZ is driven, compared to when the deflection amount DF of the vibration plate 35 is large. In other words, when the deflection amount DF of the vibration plate 35 is large, the vibration plate 35 is prevented from being located in the Z1 direction from the upper surface SFu of the partition wall 342 of the pressure chamber substrate 34 when the piezoelectric element PZ is driven, compared to when the deflection amount DF of the vibration plate 35 is small. In addition, as described above, cracks are likely to occur near the center of the vibration region ARv in the direction along the X-axis, which is the longitudinal direction of the pressure chamber CV. Therefore, in this embodiment, as described above, the upper electrode Zu is oxidized so that the deflection amount DF near the center of the vibration region ARv is large.

[0058] Next, with reference to FIG. 8, the relationship between the degree of oxidation of the upper electrode Zu and the characteristic fluctuation and crack resistance of the piezoelectric element PZ will be described.

[0059] FIG. 8 is an explanatory diagram for explaining the relationship between the degree of oxidation of the upper electrode Zu and the characteristic fluctuation and crack resistance of the piezoelectric element PZ. The "Type explanatory diagram" of FIG. 8 shows an overview of three types TP1, TPe1, and TPe2 having different degrees of oxidation of the upper electrode Zu. The "Y-direction deflection image" of FIG. 8 shows a schematic state of the vibration plate 35 seen from the X2 direction when the piezoelectric element PZ is driven. The "Y-direction deflection image" of FIG. 8 shows a schematic state of the center LC of the vibration area ARv. The "X-direction deflection image" of FIG. 8 shows a schematic state of the vibration plate 35 seen from the Y2 direction when the voltage between the upper electrode Zu and the lower electrode Zd is maintained at 0V.

[0060] As shown in the "Type Explanatory Diagram" of FIG. 8, in type TP1 corresponding to this embodiment, the oxide content in the third region AR3 is higher than the oxide content in the second region AR2. For example, the third region AR3 is in a completely or almost completely oxidized state, and the second region AR2 is in an insufficiently oxidized state. Here, the almost completely oxidized state of the third region AR3 means, for example, that the oxide content in the third region AR3 is 90% or more. Moreover, the insufficiently oxidized state of the second region AR2 means, for example, that the oxide content in the second region AR2 is 50% or less. However, the almost completely oxidized state and the insufficiently oxidized state are not limited to the above examples.

[0061] In the first comparative example, Type TPe1, which is compared with this embodiment, the entire upper electrode Zu is completely or almost completely oxidized, whereas in the second comparative example, Type TPe2, which is compared with this embodiment, the entire upper electrode Zu is insufficiently oxidized.

[0062] In type TP1, as shown in the "Type explanatory diagram" and "X-direction deflection image diagram", the deflection amount DF1b of the vibration plate 35 corresponding to the second region AR2 is small, and the deflection amount DF1a of the vibration plate 35 corresponding to the third region AR3 is large. Here, although not shown in FIG. 8, as described in FIG. 4 to FIG. 6, the vibration plate 35 is deflected by the deformation of the piezoelectric element PZ, so when the vibration plate 35 is deflected, the piezoelectric element PZ is also deflected. Therefore, in this embodiment, the piezoelectric element PZ is convex toward the Z2 direction opposite to the Z1 direction. And, the portion of the third region AR3 of the piezoelectric element PZ located most in the Z2 direction is located in the Z2 direction further than the portion of the second region AR2 of the piezoelectric element PZ located most in the Z2 direction. That is, the third region AR3 of the piezoelectric element PZ includes the portion of the first region AR1 of the piezoelectric element PZ located most in the Z2 direction.

[0063] In addition, in type TP1, as shown in the "Y-direction deflection image" of FIG. 8, when the piezoelectric element PZ is driven, the position of the vibration plate 35 in the direction along the Z axis at the center LC of the vibration area ARv changes between position Hz1 and position Lz1. For example, in type TP1, the change in the position of the vibration plate 35 in the direction along the Z axis at the center LC of the vibration area ARv is larger than that of type TPe2. When the change in the position of the vibration plate 35 in the direction along the Z axis is large, that is, when the change in the position of the piezoelectric element PZ in the direction along the Z axis is large, the characteristic fluctuation of the piezoelectric element PZ tends to become large. However, in type TP1, as shown in the "Y-direction deflection image" of FIG. 8, the deflection of the second area AR2 of the piezoelectric element PZ is small, so the characteristic fluctuation of the piezoelectric element PZ is suppressed from becoming large. 5, the second region AR2 of the piezoelectric element PZ generates a stress F that pulls the third region AR3 of the piezoelectric element PZ, so that the characteristic fluctuation of the piezoelectric element PZ is appropriately suppressed. As a result, the characteristic fluctuation of the piezoelectric element PZ is small in the type TP1.

[0064] In type TP1, the deflection amount DF1a of the vibration plate 35 in the portion where cracks are likely to occur, i.e., the portion corresponding to the third region AR3, is large, so that the occurrence of cracks is suppressed. For example, the position Hz1 of the vibration plate 35 when the piezoelectric element PZ is driven so as to expand the volume of the pressure chamber CV is a position in the Z2 direction from the upper surface SFu of the partition wall 342 of the pressure chamber substrate 34. Therefore, in type TP1, the occurrence of a force in the Z1 direction in the specific portion Pc of the vibration plate 35 is suppressed. As a result, the occurrence of cracks is suppressed in type TP1. Therefore, type TP1 has high crack resistance.

[0065] In type TPe1, as shown in the "Type explanatory diagram" and "X-direction deflection image", the deflection amount DFe1 of the diaphragm 35 is larger overall than that of type TPe2. In type TPe1, as shown in the "Y-direction deflection image" of FIG. 8, when the piezoelectric element PZ is driven, the position of the diaphragm 35 in the direction along the Z axis at the center LC of the vibration area ARv changes between positions Hz1 and Lz1, similar to type TP1. For example, in type TPe1, the change in the position of the diaphragm 35 in the direction along the Z axis at the center LC of the vibration area ARv is larger than that of type TPe2. In type TPe1, the change in the position of the diaphragm 35 in the direction along the Z axis is also larger in the part of the diaphragm 35 corresponding to the second area AR2 than that of type TPe2. For this reason, the characteristic fluctuation of the piezoelectric element PZ is large in type TPe1. Furthermore, in type TPe1, the occurrence of cracks is suppressed because the amount of deflection DFe1 of the diaphragm 35 is large. Therefore, type TPe1 has high crack resistance, similar to type TP1.

[0066] In type TPe2, as shown in the "Type explanatory diagram" and "X-direction deflection image", the deflection amount DFe2 of the diaphragm 35 is smaller overall than that of type TPe1. In addition, in type TPe2, as shown in the "Y-direction deflection image" of FIG. 8, when the piezoelectric element PZ is driven, the position of the diaphragm 35 in the direction along the Z axis at the center LC of the vibration area ARv changes between position Hz2 and position Lz2. For example, in type TPe2, the change in the position of the diaphragm 35 in the direction along the Z axis at the center LC of the vibration area ARv is smaller than that of type TPe1. In type TPe2, the change in the position of the diaphragm 35 in the direction along the Z axis is also smaller than that of type TPe1 in the part of the diaphragm 35 corresponding to the second area AR2. For this reason, the characteristic fluctuation of the piezoelectric element PZ is small in type TPe2. Furthermore, in type TPe2, the deflection amount DFe2 of the diaphragm 35 at the center LC of the vibration region ARv is small, so that cracks are likely to occur. For example, the position Hz2 of the diaphragm 35 when the piezoelectric element PZ is driven so as to expand the volume of the pressure chamber CV is a position in the Z1 direction from the upper surface SFu of the partition wall 342 of the pressure chamber substrate 34. Therefore, in type TPe2, a force in the Z1 direction is generated in the specific portion Pc of the diaphragm 35. As a result, in type TPe2, cracks are likely to occur in the specific portion Pc. Thus, type TPe2 has low crack resistance.

[0067] In this way, in type TPe1, the characteristic fluctuation of the piezoelectric element PZ becomes large, and in type TPe2, cracks are likely to occur. In contrast, in type TP1 corresponding to this embodiment, it is possible to suppress the occurrence of cracks while suppressing the increase in the characteristic fluctuation of the piezoelectric element PZ.

[0068] As described above, in this embodiment, the liquid ejection head 3 includes a vibration plate 35 having a first surface SF1 and a second surface SF2 opposite to the first surface SF1, a pressure chamber substrate 34 provided on the first surface SF1 side of the vibration plate 35 and having a pressure chamber CV filled with liquid, and a piezoelectric element PZ provided on the second surface SF2 side of the vibration plate 35 and having a lower electrode Zd, a piezoelectric layer Zm, and an upper electrode Zu. The lower electrode Zd, the piezoelectric layer Zm, and the upper electrode Zu are provided in this order on the second surface SF2 side of the vibration plate 35 along the Z1 direction from the first surface SF1 to the second surface SF2. The upper electrode Zu includes an oxide of a predetermined element and includes a first region AR1 that overlaps with both the piezoelectric layer Zm and the lower electrode Zd in a plan view from the Z1 direction. The first region AR1 includes two second regions AR2 that are separated from each other in the direction along the X-axis, which is the longitudinal direction of the pressure chamber CV, and a third region AR3 located between the two second regions AR2. The oxide content in the third region AR3 is higher than the oxide content in each of the two second regions AR2. The above-mentioned predetermined element is, for example, iridium.

[0069] Thus, in this embodiment, the oxide content in the third region AR3 located between two second regions AR2 separated from each other in the direction along the X-axis is higher than the oxide content in each of the two second regions AR2. As a result, in this embodiment, the deflection of the portion of the vibration plate 35 where cracks are likely to occur, i.e., the portion corresponding to the third region AR3, can be increased, so that the occurrence of cracks can be suppressed. Also, in this embodiment, the deflection of the second region AR2 of the piezoelectric element PZ is small, so that the characteristic fluctuation of the piezoelectric element PZ can be suppressed from increasing. That is, in this embodiment, the occurrence of cracks can be suppressed while suppressing the characteristic fluctuation of the piezoelectric element PZ from increasing.

[0070] In addition, in this embodiment, in the direction along the X-axis, the width War3 of the third region AR3 is smaller than the sum of the widths War2a and War2b of the two second regions AR2, "War2a+War2b". That is, in this embodiment, the width War3 of the third region AR3 of the piezoelectric element PZ is smaller than the sum of the widths War2a and War2b of the two second regions AR2 of the piezoelectric element PZ. The third region AR3 of the piezoelectric element PZ is more easily deformed in shape than the second region AR2 of the piezoelectric element PZ. Therefore, in this embodiment, the piezoelectric element PZ is formed so that the part that is easily deformed is narrow. As a result, in this embodiment, it is possible to suppress the characteristic fluctuation of the piezoelectric element PZ from becoming large.

[0071] In addition, in this embodiment, the first conductor CD1 and the second conductor CD2 are stacked on the upper electrode Zu in the Z1 direction, and are arranged apart from each other in the direction along the X axis, and further include the upper electrode Zu. In a plan view from the Z1 direction, one of the two second regions AR2 includes a region overlapping with the first conductor CD1, and the other of the two second regions AR2 includes a region overlapping with the second conductor CD2. In this embodiment, the electrical resistance of the upper electrode Zu can be reduced by providing the first conductor CD1 and the second conductor CD2. In this embodiment, the region between the first conductor CD1 and the second conductor CD2 of the diaphragm 35 corresponds to the vibration region ARv that actually vibrates in conjunction with the deformation of the piezoelectric element PZ. Therefore, in this embodiment, the range of the vibration region ARv in the direction along the X axis can be easily set to a desired range, for example, a range of a design value. In addition, in this embodiment, even when the first conductor CD1 and the second conductor CD2 are provided, the occurrence of cracks can be suppressed near the center of the vibration region ARv in the longitudinal direction of the pressure chamber CV, thereby suppressing the occurrence of cracks.

[0072] In this embodiment, the width War3 of the third region AR3 along the X-axis is equal to or less than half the length between the first conductor CD1 and the second conductor CD2 along the X-axis. In plan view from the Z1 direction, the position of the center LC between the first conductor CD1 and the second conductor CD2 along the X-axis is located within the third region AR3. Even in this case, the piezoelectric element PZ is formed so that the portion that is easily deformed is narrowed, so that the characteristic fluctuation of the piezoelectric element PZ can be suppressed from becoming large.

[0073] In addition, in this embodiment, the oxide content in each of the two second regions AR2 is 50% or less. As a result, in this embodiment, the shape deformation in the second region AR2 of the piezoelectric element PZ can be suppressed, and the deflection of the second region AR2 of the piezoelectric element PZ can be maintained small. As a result, in this embodiment, it is possible to suppress the characteristic fluctuation of the piezoelectric element PZ from becoming large.

[0074] In addition, in this embodiment, the oxide content in the third region AR3 is 90% or more. As a result, in this embodiment, the vibration plate 35 can be deflected so that the portion corresponding to the third region AR3 is located in the Z2 direction further than the portion corresponding to the second region AR2. As a result, in this embodiment, it is possible to suppress the occurrence of cracks near the center of the vibration region ARv in the longitudinal direction of the pressure chamber CV. Therefore, in this embodiment, it is possible to suppress the occurrence of cracks.

[0075] In addition, in this embodiment, the piezoelectric element PZ is convex toward the Z2 direction, which is the opposite direction to the Z1 direction, in a non-driven state. The portion of the piezoelectric element PZ that is located most in the Z2 direction in the portion overlapping with the third region AR3 in a plan view from the Z1 direction is located in the Z2 direction further than the portions located most in the Z2 direction in the two portions that overlap with the two second regions AR2 in a plan view from the Z1 direction. Thus, in this embodiment, the piezoelectric element PZ is convex toward the Z2 direction in a non-driven state. Therefore, in this embodiment, when the piezoelectric element PZ vibrates the vibration plate 35, it is possible to suppress the vibration plate 35 from becoming convex in the Z1 direction, that is, to suppress a portion of the vibration plate 35 from being located in the Z1 direction beyond the upper surface SFu of the partition wall 342 of the pressure chamber substrate 34. As a result, in this embodiment, it is possible to suppress the occurrence of cracks.

[0076] [2. Modifications] Each of the above embodiments may be modified in various ways. Specific modified embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples may be appropriately combined within a range that does not contradict each other. In the modified examples exemplified below, the elements whose actions and functions are equivalent to those of the embodiment will be appropriately omitted by using the symbols referenced in the above explanation.

[0077] [First Modification] In the above-mentioned embodiment, the first conductor CD1 and the second conductor CD2 are provided on the upper electrode Zu, but the present invention is not limited to such an embodiment. For example, the first conductor CD1 and the second conductor CD2 may not be provided on the upper electrode Zu. That is, the first conductor CD1 and the second conductor CD2 may be omitted. In this case, the range of the vibration region ARv in the direction along the X-axis is the range between the edge of the pressure chamber CV on the X1 direction side and the edge of the pressure chamber CV on the X2 direction side, that is, the range in which the piezoelectric layer Zm vibrates. As described above, in this modified example, the same effects as those of the above-mentioned embodiment can be obtained, except for the effects obtained by the first conductor CD1 and the second conductor CD2.

[0078] [Second modified example] In the above-mentioned embodiment and modified example, the lower electrode Zd is an individual electrode and the upper electrode Zu is a common electrode, but the present invention is not limited to such an embodiment. For example, the lower electrode Zd may be a common electrode that is continuous across multiple piezoelectric elements PZ, and the upper electrode Zu may be an individual electrode for each piezoelectric element PZ. Even in this case, each upper electrode Zu is formed so that the oxide content in the third region AR3 is higher than the oxide content in each of the two second regions AR2. As described above, the same effects as those of the above-mentioned embodiment can be obtained in this modified example.

[0079] [Third Modification] In the above-mentioned embodiment and modification, the case where the upper electrode Zu has an oxide of iridium is exemplified, but the present invention is not limited to such an embodiment. The oxide of the upper electrode Zu is not particularly limited as long as it is an oxide having electrical conductivity. For example, the upper electrode Zu may have lithium nickel oxide (LNO), strontium ruthenate (SrRuO3), or lanthanum nickel oxide (LaNiO3). The upper electrode Zu may have a plurality of types of oxides. As described above, the same effect as the above-mentioned embodiment can be obtained in this modification.

[0080] [Fourth Variation] In the above-described embodiment and modified example, the liquid ejection device 1 is a serial printer, but the present invention is not limited to this embodiment. For example, the liquid ejection device 1 may be a so-called line printer in which the multiple nozzles N are provided in the liquid ejection head 3 so as to extend wider than the width of the medium PP. As described above, the modified example can also achieve the same effects as the above-described embodiment and modified example.

[0081] [Fifth Modification] The liquid ejection device 1 exemplified in the above-mentioned embodiment and modified example can be adopted in various devices such as facsimile machines and copy machines, in addition to devices dedicated to printing. However, the use of the liquid ejection device of the present invention is not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device that forms a color filter for a liquid crystal display device. Moreover, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device that forms wiring and electrodes of a wiring board. As described above, the same effects as those of the above-mentioned embodiment and modified example can be obtained in this modified example as well.

[0082] [3. Notes] From the above-described exemplary embodiments, for example, the following configurations can be understood.

[0083] A liquid ejection head according to aspect 1, which is a preferred aspect, comprises: a vibration plate having a first surface and a second surface opposite to the first surface; a pressure chamber substrate provided on the first surface side of the vibration plate and having a pressure chamber filled with liquid; and a piezoelectric element provided on the second surface side of the vibration plate, the piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode, the first electrode, the piezoelectric layer, and the second electrode being provided, in this order, on the second surface side of the vibration plate along a first direction from the first surface to the second surface, the second electrode having an oxide of a predetermined element and including a first region overlapping both the piezoelectric layer and the first electrode in a planar view from the first direction, the first region including two second regions that are separated from each other in a second direction that is the longitudinal direction of the pressure chamber, and a third region located between the two second regions, and the oxide content in the third region is higher than the oxide content in each of the two second regions. That is, in the first aspect, the content of the oxide in each of the two second regions is lower than the content of the oxide in the third region. According to the first aspect, it is possible to suppress the occurrence of cracks while suppressing the fluctuation in the characteristics of the piezoelectric element from becoming large.

[0084] In a liquid ejection head according to Aspect 2, which is a specific example of Aspect 1, the width of the third region in the second direction is smaller than the sum of the widths of the two second regions. That is, in Aspect 2, the sum of the widths of the two second regions in the second direction is larger than the width of the third region. According to the second aspect, it is possible to particularly prevent the characteristics of the piezoelectric element from fluctuating greatly.

[0085] The liquid ejection head according to aspect 3, which is a specific example of aspect 1 or 2, further includes a first weight portion and a second weight portion that are stacked on the second electrode in the first direction, are arranged apart from each other in the second direction, and press the second electrode, and when viewed in a planar view from the first direction, one of the two second regions includes an area that overlaps with the first weight portion, and the other of the two second regions includes an area that overlaps with the second weight portion. According to the third aspect, in particular, the occurrence of cracks can be suppressed.

[0086] In a liquid ejection head according to aspect 4, which is a specific example of aspect 3, the width of the third region in the second direction is less than half the length in the second direction between the first weight portion and the second weight portion, and when viewed in a plane from the first direction, the center position in the second direction between the first weight portion and the second weight portion is located within the third region. According to the fourth aspect, it is possible to particularly prevent the characteristics of the piezoelectric element from fluctuating greatly.

[0087] In a liquid ejection head according to Aspect 5, which is a specific example of any one of Aspects 1 to 4, the content of the oxide in each of the two second regions is 50% or less. Note that Aspect 5 may also be expressed as follows when focusing on the third region: The third region contains 50% or more of the specified element that is not oxidized. According to the fifth aspect, in particular, it is possible to prevent the characteristics of the piezoelectric element from fluctuating greatly.

[0088] In a liquid ejection head according to Aspect 6, which is a specific example of any one of Aspects 1 to 5, the content of the oxide in the third region is 90% or more. According to the sixth aspect, in particular, the occurrence of cracks can be suppressed.

[0089] In a liquid ejection head according to aspect 7, which is a specific example of any one of aspects 1 to 6, the piezoelectric element, when not driven, is convex toward a third direction opposite to the first direction, and the portion of the piezoelectric element that overlaps with the third region in a planar view from the first direction is located farthest in the third direction than the portions of the piezoelectric element that overlap with the two second regions in a planar view from the first direction that are located farthest in the third direction. That is, in aspect 7, the third region includes the portion of the first region that is located farthest in the third direction. According to the seventh aspect, in particular, the occurrence of cracks can be suppressed.

[0090] In the liquid ejection head according to Aspect 8, which is a specific example of any one of Aspects 1 to 7, the predetermined element is iridium. In the eighth aspect as well, the same effects as those of the above-mentioned aspects can be obtained. [Explanation of symbols]

[0091] 1...liquid ejection device, 14...liquid container, 2...control unit, 20...wiring board, 3...liquid ejection head, 33...flow path board, 34...pressure chamber board, 35...diaphragm, 36...case, 37...sealing plate, 38...nozzle board, 39...vibration absorber, 71...medium transport mechanism, 72...carriage transport mechanism, CV...pressure chamber, N...nozzle, PP...medium, PZ...piezoelectric element, RS...liquid storage chamber, Zd...lower electrode, Zm...piezoelectric layer, Zu...upper electrode.

Claims

1. a diaphragm having a first surface and a second surface opposite the first surface; a pressure chamber substrate provided on the first surface side of the vibration plate and having a pressure chamber filled with liquid; a piezoelectric element provided on the second surface side of the vibration plate, the piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode; Equipped with the first electrode, the piezoelectric layer, and the second electrode are provided in this order on the second surface side of the vibration plate along a first direction from the first surface to the second surface; the second electrode includes a first region that includes an oxide of a predetermined element and overlaps both the piezoelectric layer and the first electrode in a plan view from the first direction; the first region includes two second regions that are regions separated from each other in a second direction that is a longitudinal direction of the pressure chamber, and a third region located between the two second regions, The content of the oxide in the third region is higher than the content of the oxide in each of the two second regions. A liquid ejection head comprising:

2. In the second direction, a width of the third region is smaller than a sum of the widths of the two second regions. The liquid ejection head according to claim 1 .

3. a first weight portion and a second weight portion that are stacked on the second electrode in the first direction and spaced apart from each other in the second direction and press the second electrode, When viewed in a plan view from the first direction, one of the two second regions includes a region overlapping with the first weight portion, and the other of the two second regions includes a region overlapping with the second weight portion. The liquid ejection head according to claim 1 .

4. a width of the third region in the second direction is equal to or less than half a length between the first and second weight portions in the second direction, When viewed in a plan view from the first direction, a center position between the first weight portion and the second weight portion in the second direction is located within the third region. The liquid ejection head according to claim 3 .

5. The content of the oxide in each of the two second regions is 50% or less. The liquid ejection head according to claim 1 .

6. The content of the oxide in the third region is 90% or more. The liquid ejection head according to claim 1 .

7. When the piezoelectric element is not driven, the piezoelectric element has a convex shape in a third direction opposite to the first direction, a portion of the piezoelectric element overlapping with the third region in a plan view from the first direction that is furthest in the third direction is located in the third direction further than portions of two portions of the piezoelectric element overlapping with the two second regions in a plan view from the first direction that are furthest in the third direction; The liquid ejection head according to claim 1 .

8. The predetermined element is iridium. The liquid ejection head according to claim 1 .

Images