Piezoelectric element and liquid dispensing head

Abstract

To provide a piezoelectric element with excellent displacement characteristics and ease of use, and a liquid dispensing head equipped with such a piezoelectric element. [Solution] The piezoelectric element is a piezoelectric element in which a lower electrode, a piezoelectric layer made of a perovskite-type composite oxide, and an upper electrode are stacked in the stacking direction, and the upper electrode has an electrode layer and a hydrogen supply layer that supplies hydrogen to the piezoelectric layer or the electrode layer.

Description

Technical Field

[0001] The present invention relates to a piezoelectric element and a liquid ejection head.

Background Art

[0002] An image forming apparatus including a liquid ejection head that ejects a liquid such as ink onto a medium such as printing paper has been conventionally proposed. As the liquid ejection head, a head that discharges the liquid filled in the pressure chamber from the nozzle by vibrating a diaphragm that constitutes the wall surface of the pressure chamber with a piezoelectric element is known.

[0003] The piezoelectric element included in the liquid ejection head described in Patent Document 1 includes a pair of electrodes and a piezoelectric layer sandwiched between the pair of electrodes. The piezoelectric layer has a perovskite structure such as PZT.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The piezoelectric layer described in Patent Document 1 is composed of a plurality of layers formed by the sol-gel method. Each of the plurality of layers is formed by applying and drying a coating solution containing an organic compound to form a precursor film, and then firing the precursor film. By repeating the film formation and firing of the precursor film a plurality of times, a piezoelectric layer composed of a plurality of layers is formed.

[0006] It is known that in piezoelectric elements, compositional gradients occur within each layer depending on the crystallization temperature of the material. For example, if the piezoelectric layer is made of lead zirconate titanate, the difference in crystallization temperatures between lead titanate and lead zirconate causes titanium to segregate more readily at the interface where crystallization proceeds more quickly. As a result, the composition may differ between the interface and the center of each layer. Such compositional gradients may affect the displacement characteristics of the piezoelectric element.

[0007] Furthermore, as a result of diligent research, the inventors have discovered that the hysteresis characteristics change significantly depending on the hydrogen content of the piezoelectric layer. In particular, they found that even piezoelectric elements with equivalent compositional gradients exhibit different hysteresis characteristics depending on the hydrogen content.

[0008] When the hysteresis characteristics of a piezoelectric element change, differences in displacement occur for each piezoelectric element. Therefore, it is necessary to adjust for these differences by changing the driving voltage or waveform for each piezoelectric element. Consequently, this presents a problem in terms of usability.

[0009] Furthermore, the electrical resistance of the electrode layer may change depending on the hydrogen content of the electrode layer of the upper or lower electrode. If the electrical resistance differs for each piezoelectric element, it is necessary to adjust the difference by changing the driving voltage or waveform for each piezoelectric element. Therefore, there is a problem in terms of usability. [Means for solving the problem]

[0010] A piezoelectric element according to a preferred embodiment of the present invention is a piezoelectric element in which a lower electrode, a piezoelectric layer made of a perovskite-type composite oxide, and an upper electrode are stacked in a stacking direction, wherein the upper electrode has an electrode layer and a hydrogen supply layer that supplies hydrogen to the piezoelectric layer or the electrode layer.

[0011] A piezoelectric element according to a preferred embodiment of the present invention is a piezoelectric element in which a lower electrode, a piezoelectric layer made of a perovskite-type composite oxide, and an upper electrode are stacked in a stacking direction, wherein the lower electrode has an electrode layer and a hydrogen supply layer that supplies hydrogen to either the piezoelectric layer or the electrode layer.

[0012] The liquid ejection head according to a preferred embodiment of the present invention has a piezoelectric element.

Brief Description of Drawings

[0013] [Figure 1] It is a schematic diagram illustrating the configuration of an image forming apparatus according to the first embodiment. [Figure 2] It is an exploded perspective view of the liquid ejection head shown in FIG. 1. [Figure 3] It is a partial cross-sectional view of the liquid ejection head shown in FIG. 1. [Figure 4] It is a cross-sectional view of the piezoelectric element shown in FIG. 3. [Figure 5] It is a cross-sectional view of the piezoelectric element shown in FIG. 3. [Figure 6] It is a diagram schematically showing the piezoelectric element shown in FIG. 4. [Figure 7] It is a diagram showing the measurement result of the secondary ion mass spectrometer (SIMS) of the piezoelectric element shown in FIG. 6. [Figure 8] It is a diagram showing the measurement result of the secondary ion mass spectrometer of the piezoelectric element of another example. [Figure 9] It is a diagram showing the flow of the manufacturing method of the piezoelectric element of FIG. 6. [Figure 10] It is a diagram schematically showing the piezoelectric element of the first modification. [Figure 11] It is a diagram schematically showing the piezoelectric element of the second modification. [Figure 12] It is a diagram schematically showing the piezoelectric element of the third modification.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. Note that in the drawings, the dimensions or scales of each part may be appropriately different from the actual ones, and there are also parts schematically shown for easy understanding. Further, the scope of the present invention is not limited to these forms unless otherwise specified in the following description to limit the present invention. Also, "element β on element γ" is not limited to a configuration in which element γ and element β are in direct contact, and also includes a configuration in which element γ and element β are not in direct contact. "Element γ and element β are equal" means that element γ and element β may be substantially equal, including manufacturing errors and the like. Also, "element α and element β are laminated" means that element α and element β may be arranged in the vertical direction, and it does not matter whether element α and element β are in direct contact.

[0015] 1. First Embodiment 1-1. Overall Configuration of Image Forming Apparatus 100 FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus 100 according to the first embodiment. Hereinafter, for convenience of explanation, the X-axis, Y-axis, and Z-axis that are orthogonal to each other will be appropriately used for explanation. Also, one direction along the X-axis is denoted as the X1 direction, and the direction opposite to the X1 direction is denoted as the X2 direction. Similarly, one direction along the Y-axis is denoted as the Y1 direction, and the direction opposite to the Y1 direction is denoted as the Y2 direction. One direction along the Z-axis is denoted as the Z1 direction, and the direction opposite to the Z1 direction is denoted as the Z2 direction. Looking in the direction along the Z-axis is referred to as "plan view". Also, the "lamination direction" is the direction along the Z-axis. The Z-axis is typically a vertical axis. The Z2 direction is the upper side, and the Z1 direction is the lower side. However, the Z-axis does not have to be a vertical axis. Also, the X-axis, Y-axis, and Z-axis are typically orthogonal to each other, but are not limited thereto, and may intersect at an angle within a range of, for example, 80° or more and 100° or less.

[0016] The image forming apparatus 100 in Figure 1 is an inkjet printing apparatus that dispenses ink, which is an example of a liquid, onto a medium 90. The medium 90 is typically printing paper, but any material such as resin film or cloth can be used as the medium 90. As illustrated in Figure 1, the image forming apparatus 100 is equipped with a liquid container 9 for storing ink. For example, a cartridge that can be attached to the image forming apparatus 100, a bag-shaped ink pack made of flexible film, or an ink tank that can be refilled with ink can be used as the liquid container 9.

[0017] The image forming apparatus 100 comprises a control unit 20, a medium transport mechanism 22, a moving mechanism 24, and a liquid discharge head 3. The control unit 20 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or FPGA (Field Programmable Gate Array) and one or more storage circuits such as semiconductor memory, and comprehensively controls each element of the image forming apparatus 100.

[0018] The medium transport mechanism 22 transports the medium 90 in a direction along the Y-axis under the control of the control unit 20. The moving mechanism 24 reciprocates the liquid discharge head 3 along the X-axis under the control of the control unit 20. The moving mechanism 24 comprises a roughly box-shaped transport body 242 that houses the liquid discharge head 3 and a transport belt 244 to which the transport body 242 is fixed. A configuration in which multiple liquid discharge heads 3 are mounted on the transport body 242, or a configuration in which a liquid container 9 is mounted on the transport body 242 together with the liquid discharge head 3, may also be adopted.

[0019] The liquid ejection head 3 ejects ink supplied from the liquid container 9 onto the medium 90 from multiple nozzles under the control of the control unit 20. As the medium 90 is transported by the medium transport mechanism 22 and the transport body 242 moves back and forth repeatedly, each liquid ejection head 3 ejects ink onto the medium 90, forming an image on the surface of the medium 90.

[0020] The image forming apparatus 100 is a serial head system in which the liquid ejection head 3 moves back and forth on the medium 90. However, the image forming apparatus 100 may also be a line head system in which the liquid ejection head 3 is fixed.

[0021] 1-2. Overall configuration of liquid dispensing head 3 Figure 2 is an exploded perspective view of the liquid ejection head 3 shown in Figure 1. Figure 3 is a cross-sectional view of a part of the liquid ejection head 3 shown in Figure 1, and is the cross-sectional view along line aa in Figure 2. The cross-section shown in Figure 3 is parallel to the XZ plane. The Z axis is the axis along the direction of ink ejection by the liquid ejection head 3.

[0022] As illustrated in Figure 2, the liquid discharge head 3 comprises a plurality of nozzles N arranged along the Y-axis. The plurality of nozzles N in the first embodiment are divided into a first row La and a second row Lb, which are spaced apart from each other and arranged side by side along the X-axis. Each of the first row La and the second row Lb is a collection of a plurality of nozzles N arranged linearly along the Y-axis. The liquid discharge head 3 has a structure in which the elements associated with each nozzle N in the first row La and the elements associated with each nozzle N in the second row Lb are arranged substantially symmetrically. In the following description, the elements corresponding to the first row La will be described in detail, and the descriptions of the elements corresponding to the second row Lb will be omitted as appropriate.

[0023] As illustrated in Figures 2 and 3, the liquid discharge head 3 comprises a flow path forming substrate 31, a pressure chamber substrate 32, a diaphragm 33, a nozzle plate 37, a vibration absorber 38, a plurality of piezoelectric elements 5, a sealant 35, a housing portion 36, and a wiring board 40. Each of the flow path forming substrate 31, pressure chamber substrate 32, diaphragm 33, nozzle plate 37, vibration absorber 38, sealant 35, and housing portion 36 is a long, plate-shaped member along the Y-axis. Furthermore, the nozzle plate 37, flow path forming substrate 31, pressure chamber substrate 32, diaphragm 33, and sealant 35 are arranged in this order in the Z2 direction.

[0024] The nozzle plate 37 is a plate-shaped member on which a plurality of nozzles N are formed. Each of the plurality of nozzles N is a circular through-hole for ejecting ink. The nozzle plate 37 is joined to the surface of the flow path forming substrate 31 in the Z1 direction, for example, by adhesive.

[0025] The channel-forming substrate 31 forms channels through which the ink flows. Specifically, the channel-forming substrate 31 has a space Ra, an intermediate liquid chamber Rb, a plurality of supply channels 312, and a plurality of communication channels 314. Space Ra is an elongated opening formed along the Y-axis. Each of the supply channels 312 and communication channels 314 is a through-hole formed for each nozzle N. Each communication channel 314 overlaps a corresponding nozzle N in a plan view from the Z1 direction. The intermediate liquid chamber Rb is an elongated space formed along the Y-axis across multiple nozzles N, and connects space Ra and the plurality of supply channels 312 to each other. A pressure chamber substrate 32 is bonded to the Z2 direction surface of the channel-forming substrate 31 with adhesive.

[0026] Multiple pressure chambers C1 are formed in the pressure chamber substrate 32. Ink ejected from the nozzle N is stored in the pressure chamber C1. The pressure chamber C1 is located between the nozzle plate 37 and the diaphragm 33 and is a space formed by the inner wall surface 32a of the pressure chamber substrate 32. A pressure chamber C1 is formed for each nozzle N. The pressure chamber C1 is an elongated space and extends in the X1 direction. Multiple pressure chambers C1 are arranged along the Y axis. Each pressure chamber C1 communicates with the communication channel 314 and the supply channel 312. Therefore, the pressure chamber C1 communicates with the nozzle N via the communication channel 314 and with the space Ra via the supply channel 312 and the intermediate liquid chamber Rb.

[0027] The nozzle plate 37, the channel-forming substrate 31, and the pressure chamber substrate 32 are manufactured by processing a silicon (Si) single crystal substrate using semiconductor manufacturing technologies such as photolithography and etching. However, known materials and manufacturing methods can be arbitrarily used for the manufacture of the nozzle plate 37, the channel-forming substrate 31, and the pressure chamber substrate 32.

[0028] The diaphragm 33 is connected to the surface of the pressure chamber substrate 32 opposite to the flow path forming substrate 31. The diaphragm 33 is positioned on the pressure chamber C1 and is elastically deformable. The diaphragm 33 is a plate-like member formed in a long rectangular shape along the Y-axis in a plan view. The diaphragm 33 and the pressure chamber C1 may be an integrated structure, or they may be separate structures joined together with an adhesive or the like.

[0029] A piezoelectric element 5 is formed on the surface of the diaphragm 33 opposite to the pressure chamber C1. A piezoelectric element 5 is provided for each pressure chamber C1. The piezoelectric element 5 is elongated in shape along the X-axis in a plan view. The piezoelectric element 5 is a driving element that is driven when a driving signal is applied, and it applies pressure to the ink in the pressure chamber C1.

[0030] The seal 35 is bonded to the diaphragm 33, for example, by adhesive. The seal 35 is a structure that protects the multiple piezoelectric elements 5 and reinforces the mechanical strength of the pressure chamber substrate 32 and the diaphragm 33. A recess is formed in the seal 35 on the surface facing the diaphragm 33. The multiple piezoelectric elements 5 are housed inside this recess. The seal 35 also has a space 353 through which the wiring board 40 is inserted.

[0031] The housing portion 36 is joined to the flow channel forming substrate 31, for example, by adhesive. The housing portion 36 is a case for storing ink supplied to a plurality of pressure chambers C1. The housing portion 36 is formed, for example, by injection molding of a resin material. The housing portion 36 has a space Rc, a supply port 361, and a space 362. The supply port 361 is a conduit through which ink is supplied from the liquid container 9 and communicates with space Rc. Space Rc communicates with space Ra of the flow channel forming substrate 31. The space composed of space Rc and space Ra functions as a liquid storage chamber R for storing ink supplied to the plurality of pressure chambers C1. Ink supplied from the liquid container 9 and passing through the supply port 361 is stored in the liquid storage chamber R. The ink stored in the liquid storage chamber R branches from the relay liquid chamber Rb to each supply flow channel 312 and is supplied in parallel to the plurality of pressure chambers C1. Also, space 362 overlaps with space 353 of the sealing body 35 in a plan view. The wiring board 40 is inserted through spaces 353 and 362.

[0032] The wiring board 40 is connected to the diaphragm 33. The wiring board 40 is a mounted component on which multiple wires are formed for electrically connecting the control unit 20 and the liquid discharge head 3. For example, a flexible substrate such as an FPC (Flexible Printed Circuit) or FFC (Flexible Flat Cable) is preferably used for the wiring board 40. A drive signal and a reference voltage for driving the piezoelectric elements 5 are supplied from the wiring board 40 to each piezoelectric element 5.

[0033] Furthermore, a vibration absorber 38 is bonded to the Z1-direction surface of the channel-forming substrate 31, for example, by an adhesive. The vibration absorber 38 is a flexible film that constitutes the wall surface of the space Ra and supplies pressure fluctuations to the ink in the liquid storage chamber R.

[0034] In this liquid ejection head 3, when the piezoelectric element 5 is deflected and deformed by the application of voltage, the diaphragm 33 deflects and deforms, i.e., vibrates, in a direction that reduces the volume of the pressure chamber C1. As a result, the pressure in the pressure chamber C1 changes, and the ink in the pressure chamber C1 is ejected from the nozzle N. After the ink is ejected, the piezoelectric element 5 returns to its original position.

[0035] Furthermore, although the liquid discharge head 3 includes all the elements shown in Figure 3, the components of the liquid discharge head 3 do not necessarily have to include all of these elements, and may also include additional elements.

[0036] 1-3. Piezoelectric element 5 Figures 4 and 5 are cross-sectional views showing the piezoelectric element 5 in Figure 3. The cross-section shown in Figure 4 is parallel to the YZ plane. The cross-section shown in Figure 5 is parallel to the XZ plane.

[0037] As shown in Figures 4 and 5, the piezoelectric element 5 mainly comprises a lower electrode 51, a piezoelectric layer 53, and an upper electrode 52. The lower electrode 51, the piezoelectric layer 53, and the upper electrode 52 are stacked in a direction along the Z-axis, which is the stacking direction. Furthermore, as shown in Figure 6, the piezoelectric element 5 further comprises a hydrogen supply layer 54 and a fifth hydrogen supply layer 55. As will be described later, as shown in Figure 6, the upper electrode 52 has a hydrogen supply layer 50a. Note that the piezoelectric layer 53, the hydrogen supply layer 54, and the fifth hydrogen supply layer 55 are sometimes collectively referred to as the intermediate layer 50 located between the lower electrode 51 and the upper electrode 52.

[0038] As shown in Figures 4 and 5, the lower electrodes 51 are provided above the diaphragm 33. The lower electrodes 51 are individual electrodes provided for each piezoelectric element 5. A drive signal with fluctuating voltage is applied to the lower electrodes 51. The lower electrodes 51 are elongated along the X-axis. Multiple lower electrodes 51 are arranged along the Y-axis with spacing between them. The lower electrodes 51 contain a conductive material.

[0039] The piezoelectric layer 53 is provided above the lower electrode 51. The piezoelectric layer 53 is, for example, a strip-shaped dielectric film that is continuous along the Y-axis across multiple piezoelectric elements 5. The piezoelectric layer 53 is, for example, a strip extending along the Y-axis and is separated for each piezoelectric element 5 by the formation of multiple notches. The piezoelectric layer 53 is made of a perovskite-type composite oxide.

[0040] The upper electrode 52 is provided above the piezoelectric layer 53. The upper electrode 52 is a strip-shaped common electrode that extends along the Y-axis so as to be continuous across multiple piezoelectric elements 5. A predetermined reference voltage is applied to the upper electrode 52. The upper electrode 52 contains a conductive material.

[0041] A voltage equivalent to the difference between the reference voltage applied to the upper electrode 52 and the drive voltage corresponding to the discharge amount supplied to the lower electrode 51 is applied to the piezoelectric layer 53. The piezoelectric layer 53 deforms as a result of the voltage applied between the lower electrode 51 and the upper electrode 52, causing the piezoelectric element 5 to bend and deform, i.e., vibrate.

[0042] The diaphragm 33 vibrates when driven by the piezoelectric element 5. In the illustrated example, the diaphragm 33 is composed of a laminate including a first vibrating body layer 331 and a second vibrating body layer 332. The first vibrating body layer 331 is in contact with the pressure chamber substrate 32. The second vibrating body layer 332 is positioned above the first vibrating body layer 331. The first vibrating body layer 331 is made of silicon oxide (SiO₂). x The second vibrating body layer 332 is made of an elastic material such as zirconium oxide (ZrO). x It is formed of an insulating material such as ). The first vibrating body layer 331 is formed, for example, by thermal oxidation of a part of the pressure chamber substrate 32. The second vibrating body layer 332 is formed, for example, by known film deposition techniques such as sputtering. The diaphragm 33 may consist of one layer or three or more layers.

[0043] Figure 4 illustrates the neutral axis A1 of the diaphragm 33. The neutral axis A1 is the position where the compressive force and contractile force are balanced, and where the stress in the axial direction along the X-Y plane of the diaphragm 33 is 0 (zero).

[0044] As shown in Figure 5, two conductors 381 and 382 are arranged on the upper electrode 52. Each of the conductors 381 and 382 is a strip-shaped conductive film positioned along the edge of the upper electrode 52 in the X1 or X2 direction and extending in the direction along the Y axis. Conductors 381 and 382 are made of electrically low-resistance conductive materials such as gold. Conductors 381 and 382 suppress the voltage drop of the reference voltage at the upper electrode 52. Conductors 381 and 382 also function as weights that define the vibration region of the diaphragm 33. Conductors 381 and 382 may be omitted.

[0045] Furthermore, a connecting wire 380 is connected to one end of the lower electrode 51 in the longitudinal direction along the X-axis. The lower electrode 51 is electrically connected to the wiring board 40 via the connecting wire 380. The upper electrode 52 is electrically connected to the aforementioned wiring board 40 via wiring etc., which is not shown in the figure.

[0046] Furthermore, in this embodiment, the lower electrode 51 is an individual electrode and the upper electrode 52 is a common electrode, but the lower electrode 51 may be a common electrode and the upper electrode 52 may be an individual electrode.

[0047] Figure 6 is a schematic diagram of the piezoelectric element 5 shown in Figure 4. As described above, the piezoelectric element 5 has a lower electrode 51, a piezoelectric layer 53, an upper electrode 52, a hydrogen supply layer 54, and a fifth hydrogen supply layer 55. The lower electrode 51, the piezoelectric layer 53, and the upper electrode 52 are each composed of multiple layers. The hydrogen supply layer 54 is located between the lower electrode 51 and the piezoelectric layer 53. The fifth hydrogen supply layer 55 is located inside the piezoelectric layer 53. The upper electrode 52 also has a hydrogen supply layer 50a. The hydrogen supply layer 50a has a first hydrogen supply layer 522 and a second hydrogen supply layer 524.

[0048] The lower electrode 51 has a first electrode layer 511 and an electrode layer 512. The first electrode layer 511 is positioned above the diaphragm 33 and is in contact with the diaphragm 33. The first electrode layer 511 contains, for example, platinum (Pt). The thickness of the first electrode layer 511 along the Z axis is not particularly limited, but is, for example, 50 nm to 120 nm.

[0049] The electrode layer 512 is positioned between the first electrode layer 511 and the hydrogen supply layer 54 and is in contact with them. The electrode layer 512 contains, for example, iridium (Ir). The thickness of the electrode layer 512 along the Z axis is not particularly limited, but is, for example, 5 nm or more and 50 nm or less. In this embodiment, the thickness of the electrode layer 512 is thinner than the thickness of the first electrode layer 511, but it may be greater than or equal to the thickness of the first electrode layer 511.

[0050] In this embodiment, the lower electrode 51 is composed of two layers, but it may be composed of one layer or three or more layers. Furthermore, the first electrode layer 511 and the electrode layer 512 may be composed of any conductive material, and may be composed of materials other than those mentioned above.

[0051] The hydrogen supply layer 54 has the function of supplying hydrogen to the electrode layer 523 or the piezoelectric layer 53. In Figure 6, the interface between the hydrogen supply layer 54 and the piezoelectric layer 53 is clearly shown, but it does not have to be clearly shown. For example, a part of the hydrogen supply layer 54 may be embedded in the piezoelectric layer 53, dispersed, or integrated with it. Also, the composition within the layer of the hydrogen supply layer 54 may be constant or gradient. Therefore, the composition of the hydrogen supply layer 54 may differ between the piezoelectric layer 53 side and the lower electrode 51 side. Furthermore, the thickness of the hydrogen supply layer 54 along the Z axis is not particularly limited, but for example, it is between 2 nm and 20 nm. Also, the hydrogen supply layer 54 may be composed of multiple layers.

[0052] The piezoelectric layer 53 is a laminate in which the first layer 531, the second layer 532, the third layer 533, the fourth layer 534, the fifth layer 535, and the sixth layer 536 are stacked in this order. The number of layers in the piezoelectric layer 53 is not limited to six, and may be five or fewer, or seven or more. However, by having multiple layers rather than a single layer, it is possible to form a piezoelectric layer 53 with excellent piezoelectric properties.

[0053] Each layer constituting the piezoelectric layer 53 is made of a perovskite-type composite oxide. More specifically, each layer includes, for example, lead titanate (PbTiO3), lead zirconate titanate (PZT:Pb(Zr,Ti)O3), lead zirconate (PbZrO3), lead lanthanum titanate ((Pb,La),TiO3), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O3), lead zirconium niobate titanate (Pb(Zr,Ti,Nb)O3), lead zirconium magnesium niobate titanate (Pb(Zr,Ti)(Mg,Nb)O3), etc. In addition, each layer constituting the piezoelectric layer 53 may be made of a lead-free material. Examples of lead-free materials include bismuth ironate (BiFeO3), barium titanate (BaTiO3), and potassium sodium niobate (KNN:(K,Na)(NbO3)).

[0054] Furthermore, the thickness of each layer of the piezoelectric layer 53 is not particularly limited, but for example, it is between 90 nm and 250 nm.

[0055] The first layer 531 is located between the hydrogen supply layer 54 and the fifth hydrogen supply layer 55 and is in contact with them. The fifth hydrogen supply layer 55 is located between the first layer 531 and the second layer 532 and is in contact with them.

[0056] The fifth hydrogen supply layer 55 has the function of supplying hydrogen to the piezoelectric layer 53. In particular, the fifth hydrogen supply layer 55 suitably supplies hydrogen to the first layer 531 and the second layer 532.

[0057] In Figure 6, the interface between the fifth hydrogen supply layer 55 and the second layer 532, and the interface between the fifth hydrogen supply layer 55 and the first layer 531 are clearly indicated, but they do not necessarily have to be. For example, a portion of the fifth hydrogen supply layer 55 may be embedded in, dispersed in, or integrated with the first layer 531 or the second layer 532. Also, the composition within the fifth hydrogen supply layer 55 may be constant or gradient. Therefore, the composition of the fifth hydrogen supply layer 55 may differ on the second layer 532 side and the first layer 531 side. Furthermore, the thickness of the fifth hydrogen supply layer 55 along the Z axis is not particularly limited, but for example, it is between 2 nm and 20 nm.

[0058] The upper electrode 52 is a structure in which a third electrode layer 521, a first hydrogen supply layer 522, an electrode layer 523, and a second hydrogen supply layer 524 are stacked in this order. The third electrode layer 521 is positioned above the piezoelectric layer 53 and is in contact with the sixth layer 536 of the piezoelectric layer 53. The third electrode layer 521 is made of, for example, iridium oxide (IrO x ) is included. The thickness of the third electrode layer 521 along the Z axis is not particularly limited, but for example, it is 5 nm or more and 20 nm or less.

[0059] The first hydrogen supply layer 522 is, for example, titanium oxide (TiO x) is included. The film thickness D1 of the first hydrogen supply layer 522 along the Z axis is not particularly limited, but for example, it is 2 nm or more and 20 nm or less. The first hydrogen supply layer 522 has the function of supplying hydrogen to the electrode layer 523 or piezoelectric layer 53 of the upper electrode 52. The composition of the first hydrogen supply layer 522 may be constant or gradient within the layer. The first hydrogen supply layer 522 may also be formed of multiple layers.

[0060] The electrode layer 523 contains, for example, iridium (Ir). The thickness of the electrode layer 523 along the Z axis is not particularly limited, but is, for example, 5 nm or more and 50 nm or less.

[0061] The second hydrogen supply layer 524 contains, for example, titanium (Ti). The film thickness D2 of the second hydrogen supply layer 524 along the Z axis is not particularly limited, but is, for example, 5 nm or more and 20 nm or less. The second hydrogen supply layer 524 has the function of supplying hydrogen to the electrode layer 523 or piezoelectric layer 53 of the upper electrode 52. The composition of the second hydrogen supply layer 524 may be constant or gradient within the layer. Furthermore, the second hydrogen supply layer 524 may be formed of multiple layers.

[0062] In the example shown in Figure 6, an orientation control layer for controlling the orientation of the piezoelectric layer 53 is not provided between the hydrogen supply layer 54 and the piezoelectric layer 53, but such an orientation control layer may be provided. Furthermore, the hydrogen supply layer 54 may also have the function of such an orientation control layer. Because the hydrogen supply layer 54 has the function of such an orientation control layer, there is no need to provide a separate orientation control layer, thus simplifying manufacturing. The orientation control layer, for example, preferentially orients the crystals in the upper layer to a predetermined plane orientation, or adjusts the degree of orientation to a predetermined plane orientation.

[0063] Similarly, although an orientation control layer for controlling the orientation of the second layer 532 is not provided between the fifth hydrogen supply layer 55 and the second layer 532, such an orientation control layer may be provided. The fifth hydrogen supply layer 55 may have the function of such an orientation control layer. However, since the fifth hydrogen supply layer 55 has the function of such an orientation control layer, there is no need to provide a separate orientation control layer, making manufacturing easier.

[0064] Furthermore, as shown in Figure 5, a packing layer 6 is arranged on the upper surface of the piezoelectric layer 53. Specifically, the packing layer 6 is arranged on one end of the piezoelectric layer 53 along the X-axis. A portion of the upper surface of the piezoelectric layer 53 is not covered by the upper electrode 52 and is exposed. The packing layer 6 is arranged to fill, i.e., to fill, this exposed portion. The packing layer 6 includes, for example, aluminum oxide (AlOx) and ceramics such as silicon nitride. Note that the packing layer 6 may be omitted as appropriate.

[0065] 1-4. Hydrogen supply layer As described above, the piezoelectric element 5 has a hydrogen supply layer 54. The hydrogen supply layer 54 supplies hydrogen to either the electrode layer 512 or the piezoelectric layer 53 of the lower electrode 51. The hydrogen supply layer 54 is located above the lower electrode 51 and below the piezoelectric layer 53. By having such a hydrogen supply layer 54, the hydrogen content of the electrode layer 512 or the piezoelectric layer 53 can be adjusted. In particular, in this embodiment, the hydrogen supply layer 54 has the function of supplying hydrogen to both the electrode layer 512 and the piezoelectric layer 53.

[0066] The hydrogen supply layer 54 has the function of supplying hydrogen to the piezoelectric layer 53, which reduces the difference in hydrogen content of the piezoelectric layer 53 for each piezoelectric element 5. Therefore, it is possible to reduce the difference in hysteresis characteristics in the piezoelectric element 5.

[0067] The hysteresis characteristics of the piezoelectric element 5 may change significantly depending on the hydrogen content of the piezoelectric layer 53 compared to the design stage. If the hysteresis characteristics change significantly, the difference in displacement between multiple piezoelectric elements 5 may become large. To reduce the difference in displacement between multiple piezoelectric elements 5, it is necessary to change the drive voltage and waveform for each piezoelectric element 5. Adjusting the difference in displacement between multiple piezoelectric elements 5 in this way is time-consuming and inconvenient.

[0068] Furthermore, when the piezoelectric element 5 has a piezoelectric layer 53 formed from multiple layers, the hydrogen content of the piezoelectric layer 53 is more likely to change compared to the design stage. As will be described later, the piezoelectric layer 53 is formed by repeatedly depositing and firing each of the multiple layers multiple times. It is thought that the hydrogen content of the piezoelectric layer 53 changes during this manufacturing process. Moreover, not only when the composition in the piezoelectric layer 53 is constant, but also when there is a compositional gradient in the piezoelectric layer 53, differences in displacement will occur among multiple piezoelectric elements 5 due to the hydrogen content of the piezoelectric layer 53.

[0069] As described above, the piezoelectric element 5 of this embodiment has a hydrogen supply layer 54 provided above the lower electrode 51 and below the piezoelectric layer 53. Therefore, for example, hydrogen can be supplied to the piezoelectric layer 53 during the manufacturing of the piezoelectric element 5. This reduces the difference in hydrogen content of the piezoelectric layer 53 among multiple piezoelectric elements 5. Consequently, it is possible to suppress large differences in displacement due to changes in hysteresis characteristics among multiple piezoelectric elements 5. Therefore, it is possible to eliminate the need to change the driving voltage and waveform for each piezoelectric element 5, thereby suppressing deterioration in usability.

[0070] Furthermore, as mentioned above, the hydrogen supply layer 54 has the function of supplying hydrogen to the electrode layer 512. By adjusting the amount of hydrogen in the electrode layer 512 by the hydrogen supply layer 54, the electrode layer 512 can be reduced, and thus the electrical resistance of the electrode layer 512 can be lowered. In addition, by adjusting the amount of hydrogen in the electrode layer 512, the difference in electrical resistance of the electrode layer 512 among multiple piezoelectric elements 5 can be reduced. Therefore, it is not necessary to change the driving voltage and waveform for each piezoelectric element 5, and deterioration in usability can be suppressed.

[0071] Thus, the hydrogen supply layer 54 allows for adjustment of the hydrogen content of the electrode layer 523 or the piezoelectric layer 53. Therefore, the liquid discharge head 3 having the piezoelectric element 5 equipped with such a hydrogen supply layer 54 offers excellent displacement characteristics and ease of use.

[0072] The hydrogen supply layer 54 is composed of a material capable of releasing hydrogen. Specifically, the hydrogen supply layer 50a includes a hydrogen storage material that can combine with hydrogen to form a hydride. The hydrogen storage material absorbs or releases hydrogen depending on temperature or pressure. The hydrogen storage material includes metals such as magnesium (Mg), vanadium (V), lanthanum (La), and titanium (Ti), alloys containing such metals, or compounds. The hydrogen supply layer 54 is composed of, for example, titanium or lead titanate (PbTiO3). Alternatively, the hydrogen supply layer 54 may be composed of, for example, a composite oxide containing bismuth (Bi), iron (Fe), titanium (Ti), and lead (Pb).

[0073] Furthermore, the hydrogen supply layer 50a and the fifth hydrogen supply layer 55 also similarly contain hydrogen storage materials that can combine with hydrogen to form hydrides.

[0074] Figure 7 shows the measurement results of a secondary ion mass spectrometer (SIMS) for the piezoelectric element 5 of this embodiment. In Figure 7, the material of the first electrode layer 511 is platinum, and the material of the electrode layer 512 is iridium. The hydrogen supply layer 54 contains titanium. The material of each layer of the piezoelectric layer 53 is lead zirconate titanate (PZT). The fifth hydrogen supply layer 55 contains titanium. The material of the third electrode layer 521 is iridium oxide, and the material of the electrode layer 523 is iridium. The material of the first hydrogen supply layer 522 is titanium oxide, and the material of the second hydrogen supply layer 524 is titanium.

[0075] The horizontal axis in Figure 7 represents depth [nm]. Since the analysis was performed in the Z1 direction from the upper electrode 52, the shallower depths are on the upper electrode 52 side, and the deeper depths are on the lower electrode 51 side.

[0076] The vertical axis of Figure 7 shows the hydrogen concentration [atoms / cc]. This hydrogen concentration was quantified using standard samples doped with the target element at known concentrations. Titanium and zirconium are shown in terms of ionic intensity. While Figure 7 shows clear line segments along the interfaces of each layer, the exact location of the interfaces may vary slightly depending on the interpretation. Note that "E" represents a power of 10. For example, 1E+20 is 1 × 10⁻¹⁰. 20 This represents 1E+19, which is 1 × 10 19 It represents.

[0077] As can be seen from Figure 7, the hydrogen content of the first layer 531 of the piezoelectric layer 53 is greater than that of the second layer 532. The first layer 531 is located closer to the hydrogen supply layer 54 than the second layer 532. Therefore, the first layer 531 can absorb hydrogen more easily than the second layer 532. Consequently, the hydrogen content of the first layer 531 is greater than that of the second layer 532.

[0078] Furthermore, this embodiment includes a fifth hydrogen supply layer 55. The fifth hydrogen supply layer 55 is positioned between the first layer 531 and the second layer 532. By providing the fifth hydrogen supply layer 55 in addition to the hydrogen supply layer 54, it is possible to suppress an excessive decrease in the hydrogen content of the second layer 532, and furthermore, in the hydrogen content of each of the multiple layers from the third layer 533 onward.

[0079] Furthermore, the hydrogen content of the first layer 531 may be less than or equal to the hydrogen content of the second layer 532.

[0080] Furthermore, as can be seen from Figure 7, the hydrogen content of the hydrogen supply layer 54 is greater than the hydrogen content of the piezoelectric layer 53. In this embodiment, the hydrogen content of the hydrogen supply layer 54 is greater than the hydrogen content of each layer of the piezoelectric layer 53, and even greater than the total hydrogen content of all layers of the piezoelectric layer 53.

[0081] As mentioned above, the hydrogen supply layer 54 is made of hydrogen storage material and stores a large amount of hydrogen. Therefore, the hydrogen supply layer 54 can supply the stored hydrogen to other layers. With such a hydrogen supply layer 54 provided, hydrogen can be supplied to the piezoelectric layer 53 or the electrode layer 512. Thus, as mentioned above, the difference in displacement or electrical resistance among the multiple piezoelectric elements 5 can be reduced.

[0082] Furthermore, as mentioned above, the upper electrode 52 shown in Figure 6 has a hydrogen supply layer 50a. The hydrogen supply layer 50a supplies hydrogen to the piezoelectric layer 53 or the electrode layer 523. By having such a hydrogen supply layer 50a, the hydrogen content of the electrode layer 523 or the piezoelectric layer 53 can be adjusted. In particular, in this embodiment, the hydrogen supply layer 50a has the function of supplying hydrogen to both the electrode layer 523 and the piezoelectric layer 53.

[0083] The hydrogen supply layer 50a has the function of supplying hydrogen to the piezoelectric layer 53, which reduces the difference in hydrogen content of the piezoelectric layer 53 for each piezoelectric element 5. Therefore, it is possible to reduce the difference in hysteresis characteristics in the piezoelectric element 5.

[0084] The hydrogen supply layer 50a can supply hydrogen to the piezoelectric layer 53 during the manufacturing and use of the piezoelectric element 5. Therefore, differences in the hydrogen content of the piezoelectric layer 53 among multiple piezoelectric elements 5 can be reduced. Consequently, large differences in displacement due to changes in hysteresis characteristics among multiple piezoelectric elements 5 can be suppressed. Thus, there is no need to change the drive voltage and waveform for each piezoelectric element 5, and deterioration in usability can be suppressed.

[0085] Furthermore, as mentioned above, the hydrogen supply layer 50a has the function of supplying hydrogen to the electrode layer 523. By adjusting the amount of hydrogen in the electrode layer 523 by the hydrogen supply layer 50a, the electrode layer 523 can be reduced, and thus the electrical resistance of the electrode layer 523 can be lowered. In addition, by adjusting the amount of hydrogen in the electrode layer 523, the difference in electrical resistance of the electrode layer 523 among multiple piezoelectric elements 5 can be reduced. Therefore, it is not necessary to change the driving voltage and waveform for each piezoelectric element 5, and deterioration in usability can be suppressed.

[0086] Thus, the hydrogen supply layer 50a allows for adjustment of the hydrogen content of the electrode layer 523 or the piezoelectric layer 53. Therefore, the liquid discharge head 3 having the piezoelectric element 5 equipped with such a hydrogen supply layer 50a offers excellent displacement characteristics and ease of use.

[0087] Furthermore, as described above, the hydrogen supply layer 50a has a first hydrogen supply layer 522 and a second hydrogen supply layer 524. The first hydrogen supply layer 522 and the second hydrogen supply layer 524 are arranged so as to sandwich the electrode layer 523 in the direction along the Z axis, which is the stacking direction. Each of the first hydrogen supply layer 522 and the second hydrogen supply layer 524 is made of a hydrogen storage material.

[0088] Since the electrode layer 523 is provided between the first hydrogen supply layer 522 and the second hydrogen supply layer 524, hydrogen can be supplied to the electrode layer 523 from both sides.

[0089] Furthermore, a third electrode layer 521, different from the electrode layer 523, is provided below the first hydrogen supply layer 522. The third electrode layer 521 is in contact with the first hydrogen supply layer 522. Therefore, the electrical resistance of the third electrode layer 521 can also be suitably reduced.

[0090] Furthermore, as can be seen from Figure 7, the hydrogen content of the sixth layer 536 is greater than that of the fifth layer 535. Note that the "first upper layer" in claim 3 corresponds to the sixth layer 536, and the "second upper layer" in claim 3 corresponds to the fifth layer 535. The sixth layer 536, which corresponds to the "first upper layer" in claim 3, is the layer of the piezoelectric layer 53 closest to the hydrogen supply layer 50a. The fifth layer 535, which corresponds to the "second upper layer" in claim 3, is a layer that is in contact with the sixth layer 536 and is located below the sixth layer 536, and is the layer of the piezoelectric layer 53 closest to the hydrogen supply layer 50a after the sixth layer 536. Also, the piezoelectric layer 53 does not have to be six layers. For example, if the piezoelectric layer 53 has seven or more layers, an additional layer is interposed between the fifth layer 535 and the fourth layer 534.

[0091] The sixth layer 536 is located closer to the hydrogen supply layer 50a than the fifth layer 535. Therefore, the sixth layer 536 can absorb hydrogen more easily than the fifth layer 535. Consequently, the hydrogen content of the sixth layer 536 is higher than that of the fifth layer 535.

[0092] Furthermore, the second hydrogen supply layer 524 is positioned above the first hydrogen supply layer 522. The film thickness D2 of the second hydrogen supply layer 524 is preferably thicker than the film thickness D1 of the first hydrogen supply layer 522.

[0093] The second hydrogen supply layer 524 is deposited after the first hydrogen supply layer 522. By making the film thickness D2 thicker than the film thickness D1, it is easier to make the hydrogen content of the second hydrogen supply layer 524 higher than that of the first hydrogen supply layer 522. Therefore, even if the electrode layer 523 is oxidized during the deposition of the electrode layer 523 or the first hydrogen supply layer 522, the electrode layer 523 can be efficiently reduced in the subsequent deposition process of the second hydrogen supply layer 524.

[0094] Note that film thickness D2 may be less than or equal to film thickness D1.

[0095] Furthermore, as mentioned above, the piezoelectric layer 53 is composed of a perovskite-type composite oxide, and is preferably composed of lead zirconate titanate (PZT). When the piezoelectric layer is made of PZT, it is particularly effective to provide a hydrogen supply layer 50a or a hydrogen supply layer 54.

[0096] Furthermore, as mentioned above, the piezoelectric layer 53 is composed of a perovskite-type composite oxide, and is preferably composed of potassium sodium niobate (KNN). When the piezoelectric layer is KNN, it is particularly effective to provide a hydrogen supply layer 50a or a hydrogen supply layer 54.

[0097] Furthermore, it is particularly preferable that the second hydrogen supply layer 524, the first hydrogen supply layer 522, the hydrogen supply layer 54, and the fifth hydrogen supply layer 55 each contain titanium. Titanium has excellent hydrogen supply performance. Therefore, by including titanium in these layers, the hydrogen supply function can be suitably performed compared to when it does not contain titanium.

[0098] Furthermore, in this embodiment, a hydrogen supply layer 54 is provided below the piezoelectric layer 53, and a hydrogen supply layer 50a is provided above the piezoelectric layer 53. Therefore, compared to the case where either the hydrogen supply layer 50a or the hydrogen supply layer 54 is provided, it is possible to particularly effectively suppress the large difference in displacement due to changes in the hysteresis characteristics of the multiple piezoelectric elements 5. Thus, it is not necessary to change the driving voltage and waveform for each piezoelectric element 5, and deterioration in usability can be suppressed.

[0099] Furthermore, in this embodiment, the hydrogen supply layer 54 is in contact with the electrode layer 512, and the hydrogen supply layer 50a is in contact with the electrode layer 523. This reduces the difference in electrical resistance between the electrodes of the multiple piezoelectric elements 5. Therefore, it is not necessary to change the driving voltage and waveform for each piezoelectric element 5, thus preventing deterioration in usability.

[0100] Figure 8 shows the measurement results of a secondary ion mass spectrometer for another example of piezoelectric element 5. The layer configuration of piezoelectric element 5 in the analysis results of Figure 8 is the same as the layer configuration of piezoelectric element 5 in the analysis results of Figure 7. The manufacturing temperature of piezoelectric element 5 in the analysis results of Figure 8 is slightly different from the manufacturing temperature of piezoelectric element 5 in the analysis results of Figure 7.

[0101] In Figure 8, the hydrogen content of the first layer 531 of the piezoelectric layer 53 is greater than that of the second layer 532. Furthermore, the hydrogen content of the hydrogen supply layer 54 is greater than that of the piezoelectric layer 53. Specifically, the hydrogen content of the hydrogen supply layer 54 is greater than the hydrogen content of each layer of the piezoelectric layer 53, and even greater than the total hydrogen content of all layers of the piezoelectric layer 53 combined. In addition, the hydrogen content of the sixth layer 536 of the piezoelectric layer 53 is greater than that of the fifth layer 535.

[0102] 1-5. Manufacturing method of piezoelectric element 5 Figure 9 shows the flow of the manufacturing method for the piezoelectric element 5 shown in Figure 6. As shown in Figure 9, the manufacturing method for the piezoelectric element 5 includes a lower electrode formation step S11, an intermediate layer formation step S12, and an upper electrode formation step S13. These steps are performed in this order.

[0103] In the lower electrode formation step S11, the lower electrode 51 is formed. The lower electrode formation step S11 includes the formation of a first electrode layer 511 and the formation of an electrode layer 512. Specifically, first, for example, the first electrode layer 511 is formed by depositing a layer containing a conductive material such as platinum on the diaphragm 33 using sputtering, vapor deposition, or CVD (Chemical Vapor Deposition). Next, for example, the electrode layer 512 is formed by depositing a layer containing a conductive material such as iridium on the first electrode layer 511 using sputtering, vapor deposition, or CVD.

[0104] The intermediate layer formation step S12 includes the formation of a hydrogen supply layer 54, a piezoelectric layer 53, and a fifth hydrogen supply layer 55. Specifically, first, a layer containing a hydrogen storage material such as titanium is formed on the lower electrode 51 using sputtering, vapor deposition, or CVD. Next, a first layer precursor made of a perovskite-type composite oxide such as PZT is formed on the layer containing the hydrogen storage material using the sol-gel method. Then, the layer containing the hydrogen storage material and the first layer precursor are fired. As a result, the hydrogen supply layer 54 and the first layer 531 are formed.

[0105] Next, another layer containing a hydrogen storage material such as titanium is deposited on the first layer 531 using sputtering, vapor deposition, or CVD. Then, a second layer precursor made of a perovskite-type composite oxide such as PZT is deposited on the other layer containing the hydrogen storage material using the sol-gel method. Next, the other layer containing the hydrogen storage material and the second layer precursor are fired. As a result, the fifth hydrogen supply layer 55 and the second layer 532 are formed.

[0106] Next, a third layer precursor made of a perovskite-type composite oxide such as PZT is deposited on the second layer 532 using the sol-gel method, and then the third layer precursor is calcined. This forms the third layer 533. The fourth layer 534, fifth layer 535, and sixth layer 536 are formed by the same method. After the formation of the sixth layer 536, the hydrogen supply layer 54, the fifth hydrogen supply layer 55, and the piezoelectric layer 53 are calcined together.

[0107] When each layer of the piezoelectric layer 53 is formed using a sol-gel method, the shape and crystallinity of the lower layer affect the shape and crystallinity of the upper layer. For example, when the first layer 531 of the piezoelectric layer 53 is made of KNN, the orientation of the first layer 531 deposited by the sol-gel method improves. Therefore, when layers are stacked on top of the first layer 531, the overall orientation of the piezoelectric layer 53 can be improved.

[0108] In the upper electrode formation step S13, the upper electrode 52 is formed. The upper electrode formation step S13 includes the formation of a third electrode layer 521, the formation of a first hydrogen supply layer 522, the formation of an electrode layer 523, and the formation of a second hydrogen supply layer 524. Specifically, for example, a third electrode layer 521 containing a metal oxide is formed on the sixth layer 536 by sputtering, vapor deposition, or CVD, followed by firing. Next, a first hydrogen supply layer 522 containing a metal oxide is formed on the third electrode layer 521 by sputtering, vapor deposition, or CVD, followed by firing.

[0109] Next, an electrode layer 523 is formed on the first hydrogen supply layer 522 by depositing a layer containing a conductive material such as iridium using sputtering, vapor deposition, or CVD. Then, a second hydrogen supply layer 524 is formed on the electrode layer 523 by depositing a layer containing a hydrogen storage material such as titanium using sputtering, vapor deposition, or CVD. The piezoelectric element 5 is thus manufactured.

[0110] Furthermore, in the manufacturing method of the piezoelectric element 5, a packing layer 6 is formed between the formation of the third electrode layer 521, the first hydrogen supply layer 522, and the electrode layer 523, and the formation of the second hydrogen supply layer 524. The packing layer 6 is mainly formed on the exposed portion of the upper surface of the piezoelectric layer 53 where the third electrode layer 521, the first hydrogen supply layer 522, and the electrode layer 523 are not provided. The packing layer 6 is formed by depositing a ceramic material using sputtering, vapor deposition, or CVD. As shown in Figure 5, parts of the third electrode layer 521, the first hydrogen supply layer 522, and the electrode layer 523 are located below the packing layer 6. Part of the second hydrogen supply layer 524 is located above the packing layer 6.

[0111] 2. Variations The embodiments illustrated above can be modified in various ways. Specific examples of modifications that can be applied to the aforementioned embodiments are given below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate, to the extent that they do not contradict each other.

[0112] 2-1. First variation Figure 10 is a schematic diagram of the piezoelectric element 5A of the first modified example. As shown in Figure 10, the piezoelectric element 5A of the first modified example further has an orientation control layer 56. The orientation control layer 56 is provided between the lower electrode 51 and the piezoelectric layer 53. In this embodiment, the orientation control layer 56 is positioned between the hydrogen supply layer 54 and the piezoelectric layer 53 and is in contact with them. The hydrogen supply layer 50a supplies hydrogen to the orientation control layer 56.

[0113] The crystal orientation of the piezoelectric layer 53 is easily affected by the substrate. The hydrogen supply layer 54 supplies hydrogen to the orientation control layer 56 and reduces it, thereby inhibiting the crystallization of the orientation control layer 56. Therefore, by providing the hydrogen supply layer 54, the orientation control layer 56 can be kept amorphous so that the crystal orientation of the lower electrode 51 does not affect the crystal orientation of the piezoelectric layer 53. Accordingly, the orientation control layer 56 is preferably an amorphous layer so that the crystal orientation of the lower electrode 51 does not affect the crystal orientation of the piezoelectric layer 53.

[0114] The orientation control layer 56 includes, for example, lead zirconate (PbZrO3), lead titanate (PbTiO3), or a composite oxide containing bismuth (Bi), iron (Fe), titanium (Ti), and lead (Pb). In Figure 10, the interfaces between the hydrogen supply layer 54, the orientation control layer 56, and the piezoelectric layer 53 are clearly shown, but they do not necessarily have to be clearly shown. For example, a part of the orientation control layer 56 may be embedded in the hydrogen supply layer 54 or the piezoelectric layer 53, dispersed, or integrated. Furthermore, the composition within the orientation control layer 56 may be constant or graded. Therefore, the composition of the orientation control layer 56 may differ between the piezoelectric layer 53 side and the lower electrode 51 side. The thickness of the orientation control layer 56 along the Z axis is not particularly limited, but for example, it is between 2 nm and 20 nm. Furthermore, the orientation control layer 56 may be composed of multiple layers.

[0115] 2-2. Second variation Figure 11 is a schematic diagram showing a piezoelectric element 5B of a second modified example. As shown in Figure 11, the piezoelectric element 5B of the second modified example has a hydrogen supply layer 50b. The hydrogen supply layer 50b has a third hydrogen supply layer 54B and a fourth hydrogen supply layer 57. The third hydrogen supply layer 54B has the same configuration as the hydrogen supply layer 54 of the first embodiment. The fourth hydrogen supply layer 57 is positioned below the lower electrode 51. The hydrogen supply layer 54 is made of a hydrogen storage material.

[0116] The third hydrogen supply layer 54B and the fourth hydrogen supply layer 57 sandwich the lower electrode 51, which includes the electrode layer 512. Therefore, hydrogen can be suitably supplied to the electrode layer 512 by the third hydrogen supply layer 54B and the fourth hydrogen supply layer 57.

[0117] 2-3. Third Variation Figure 12 is a schematic diagram showing a piezoelectric element 5C of the third modified example. As shown in Figure 12, the piezoelectric element 5C of the fourth modified example has a protective film 58 that suppresses the unintended ingress of hydrogen into the piezoelectric element 5. The protective film 58 includes, for example, ceramics such as aluminum oxide (AlOx) and silicon nitride. By providing the protective film 58, unintended compositional changes of the piezoelectric element 5 can be suppressed.

[0118] Furthermore, the hydrogen supply layer 50a is positioned below the protective film 58. Therefore, the hydrogen supply layer 50a is not provided on top of the protective film 58. Consequently, the risk of hydrogen being supplied to the protective film 58 and causing its reduction during manufacturing can be suppressed. In addition, the protective film 58 may be fired when it is formed. At this time, heating the hydrogen supply layer 50a together can promote the diffusion of hydrogen. Thus, hydrogen can be suitably supplied to the electrode layer 523 and the piezoelectric layer 53 by the hydrogen supply layer 50a.

[0119] 2-4. Other variations In the first embodiment, a hydrogen supply layer 54 is provided on the lower electrode 51 side of the piezoelectric layer 53, and a hydrogen supply layer 50a is provided on the upper electrode 52 side. That is, a "hydrogen supply layer" is provided on both the lower electrode 51 side and the upper electrode 52 side of the piezoelectric layer 53. However, the "hydrogen supply layer" only needs to be provided on either the lower electrode 51 side or the upper electrode 52 side of the piezoelectric layer 53.

[0120] The "liquid dispensing head" may be a circulating type head having a so-called circulation channel.

[0121] "Image forming apparatus" can be used not only in equipment dedicated to printing, but also in various other devices such as facsimile machines and photocopiers. The applications of image forming apparatus are not limited to printing. For example, an image forming apparatus that dispenses a colorant solution is used as a manufacturing apparatus to form color filters for display devices such as liquid crystal display panels. Also, an image forming apparatus that dispenses a conductive material solution is used as a manufacturing apparatus to form wiring and electrodes on a wiring board. Furthermore, an image forming apparatus that dispenses a solution of organic matter related to living organisms is used, for example, as a manufacturing apparatus to produce biochips.

[0122] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the embodiments described above. Furthermore, the configuration of each part of the present invention can be replaced with any configuration that performs a similar function to the embodiments described above, and any configuration can be added.

[0123] 3. Addendum From the above embodiments or modifications, for example, the following embodiments can be understood.

[0124] A piezoelectric element according to a first embodiment, which is a preferred example of the present disclosure, is a piezoelectric element in which a lower electrode, a piezoelectric layer made of a perovskite-type composite oxide, and an upper electrode are stacked in the stacking direction, wherein the upper electrode has an electrode layer and a hydrogen supply layer that supplies hydrogen to the piezoelectric layer or the electrode layer.

[0125] According to this first embodiment, the amount of hydrogen entering the electrode layer or piezoelectric layer can be adjusted by providing a hydrogen supply layer. Therefore, the effort of changing the driving voltage and waveform for each piezoelectric element is eliminated, resulting in superior ease of use.

[0126] In a piezoelectric element of the second embodiment, which is a preferred example of the first embodiment, the hydrogen supply layer is a layer that supplies hydrogen to the piezoelectric layer.

[0127] According to this second embodiment, the hysteresis characteristics can be adjusted by supplying hydrogen to the piezoelectric layer.

[0128] In a piezoelectric element of a third embodiment, which is a preferred example of the first or second embodiment, the piezoelectric layer comprises a plurality of layers including a first layer located below the hydrogen supply layer and a second layer located below the first layer, wherein the hydrogen content of the first layer is greater than the hydrogen content of the second layer.

[0129] According to this third embodiment, the first layer is located near the hydrogen supply layer, making it easier to incorporate hydrogen. For this reason, the hydrogen content of the first layer is greater than that of the second layer.

[0130] In a piezoelectric element of the fourth embodiment, which is a preferred example of the second or third embodiment, the hydrogen supply layer is a layer that supplies hydrogen to the electrode layer.

[0131] According to this fourth embodiment, the electrical resistance can be reduced by reducing the electrode layer.

[0132] In a piezoelectric element of the fifth embodiment, which is a preferred example of any of the first to fourth embodiments, the hydrogen supply layer has a first hydrogen supply layer and a second hydrogen supply layer, which are provided so as to sandwich the electrode layer in the stacking direction.

[0133] According to this fifth embodiment, hydrogen can be supplied to the electrode layer from both sides.

[0134] In the piezoelectric element of the sixth embodiment, which is a preferred example of any of the first to fifth embodiments, the second hydrogen supply layer is thicker than the first hydrogen supply layer.

[0135] According to this sixth embodiment, by making the second hydrogen supply layer thicker than the first hydrogen supply layer, if the electrode layer is oxidized during the deposition of the electrode layer or the second hydrogen supply layer, the amount of hydrogen in the film deposited in a subsequent step can be increased, thereby efficiently reducing the electrode layer.

[0136] A piezoelectric element according to a seventh embodiment, which is a preferred example of the present disclosure, is a piezoelectric element in which a lower electrode, a piezoelectric layer made of a perovskite-type composite oxide, and an upper electrode are stacked in the stacking direction, wherein the lower electrode has an electrode layer and a hydrogen supply layer that supplies hydrogen to either the piezoelectric layer or the electrode layer.

[0137] According to this seventh embodiment, the hydrogen supply layer allows for adjustment of the amount of hydrogen entering the electrode layer or piezoelectric layer. This eliminates the need to change the driving voltage and waveform for each piezoelectric element, resulting in superior ease of use.

[0138] In the piezoelectric element of the eighth embodiment, which is a preferred example of the seventh embodiment, the hydrogen supply layer supplies hydrogen to the piezoelectric layer.

[0139] According to the eighth aspect, the hysteresis characteristics can be adjusted by supplying hydrogen to the piezoelectric layer.

[0140] In a piezoelectric element of the ninth embodiment, which is a preferred example of the seventh or eighth embodiment, the piezoelectric layer comprises a plurality of layers including a first layer laminated above the hydrogen supply layer and a second layer laminated above the first layer, wherein the hydrogen content of the first layer is greater than the hydrogen content of the second layer.

[0141] According to the ninth embodiment, the first layer is located near the hydrogen supply layer, making it easier to incorporate hydrogen. For this reason, the hydrogen content of the first layer is greater than that of the second layer.

[0142] In the piezoelectric element of the 10th embodiment, which is a preferred example of any of the 7th to 9th embodiments, an orientation control layer is provided between the lower electrode and the piezoelectric layer in the stacking direction, and the hydrogen supply layer supplies hydrogen to the orientation control layer.

[0143] The crystal orientation of the piezoelectric layer is easily influenced by the substrate. By supplying hydrogen to the orientation control layer and reducing it, crystallization of the orientation control layer can be inhibited, and the orientation control layer can be kept amorphous so that the crystal orientation of the lower electrode does not affect the crystal orientation of the piezoelectric layer.

[0144] In the piezoelectric element of the 11th embodiment, which is a preferred example of any of the 7th to 10th embodiments, the orientation control layer is an amorphous layer.

[0145] According to the eleventh embodiment, the crystal orientation of the lower electrode can be prevented from affecting the crystal orientation of the piezoelectric layer.

[0146] In the piezoelectric element of the 12th embodiment, which is a preferred example of any of the 7th to 11th embodiments, the hydrogen supply layer supplies hydrogen to the electrode layer.

[0147] According to the twelfth embodiment, the electrical resistance can be reduced by reducing the electrode layer.

[0148] In the piezoelectric element of the 13th embodiment, which is a preferred example of any of the 7th to 12th embodiments, the hydrogen supply layer has a third hydrogen supply layer and a fourth hydrogen supply layer, which are provided so as to sandwich the electrode layer in the stacking direction.

[0149] According to the 13th embodiment, hydrogen can be supplied to the electrode layer from both sides of the electrode layer.

[0150] In the piezoelectric element of the 14th embodiment, which is a preferred example of any of the 7th to 13th embodiments, the piezoelectric layer consists of multiple layers, and the hydrogen content of the hydrogen supply layer is greater than the hydrogen content of the piezoelectric layer.

[0151] According to the 14th embodiment, the hydrogen supply layer that supplies hydrogen stores a large amount of hydrogen. Therefore, the hydrogen supply layer can supply the stored hydrogen to other layers.

[0152] In the piezoelectric element of the 15th embodiment, which is a preferred example of any of the first to sixth embodiments, a protective film is provided to protect the upper electrode, and the hydrogen supply layer is provided below the protective film in the stacking direction.

[0153] By not providing a hydrogen supply layer on top of the protective film, the risk of hydrogen being supplied to the protective film and causing its reduction can be suppressed.

[0154] In the piezoelectric element of the 16th embodiment, which is a preferred example of any of the 1st to 10th embodiments, the piezoelectric layer is made of lead zirconate titanate.

[0155] The provision of a hydrogen supply layer is particularly effective when the piezoelectric layer is made of lead zirconate titanate.

[0156] In the piezoelectric element of the 17th embodiment, which is a preferred example of any of the 1st to 13th embodiments, the piezoelectric layer is composed of potassium sodium niobate.

[0157] The provision of a hydrogen supply layer is particularly effective when the piezoelectric layer is made of potassium sodium niobate (KNN).

[0158] A preferred example of the liquid dispensing head of this disclosure has a piezoelectric element which is a preferred example of any of the first to seventeen embodiments.

[0159] This allows us to provide a liquid dispensing head with excellent displacement characteristics and ease of use. [Explanation of Symbols]

[0160] 3...Liquid discharge head, 5...Piezoelectric element, 50a...Hydrogen supply layer, 50b...Hydrogen supply layer, 51...Lower electrode, 52...Upper electrode, 53...Piezoelectric layer, 54...Hydrogen supply layer, 54B...Third hydrogen supply layer, 55...Fifth hydrogen supply layer, 56...Orientation control layer, 57...Fourth hydrogen supply layer, 58...Protective film, 100...Image forming apparatus, 331...First vibrator layer, 332...Second vibrator layer, 511...First electrode layer, 512...Electrode layer, 521...Third electrode layer, 522...First hydrogen supply layer, 523...Electrode layer, 524...Second hydrogen supply layer, 531...First layer, 532...Second layer, 533...Third layer, 534...Fourth layer, 535...Fifth layer (Second upper layer), 536...Sixth layer (First upper layer), A1...Neutral axis, C1...Pressure chamber, D1...Film thickness, D2...Film thickness, N...Nozzle.

Claims

1. A piezoelectric element comprising a lower electrode, a piezoelectric layer made of a perovskite-type composite oxide, and an upper electrode, stacked in the stacking direction, The upper electrode comprises an electrode layer and a hydrogen supply layer that supplies hydrogen to the piezoelectric layer or the electrode layer. A piezoelectric element characterized by the following features.

2. In the piezoelectric element according to claim 1, The hydrogen supply layer is a layer that supplies hydrogen to the piezoelectric layer. A piezoelectric element characterized by the following features.

3. In the piezoelectric element according to claim 2, The piezoelectric layer consists of multiple layers, including a first upper layer located below the hydrogen supply layer and a second upper layer located below the first upper layer. The hydrogen content of the first upper layer is greater than the hydrogen content of the second upper layer. A piezoelectric element characterized by the following features.

4. In the piezoelectric element according to claim 1, The hydrogen supply layer is a layer that supplies hydrogen to the electrode layer. A piezoelectric element characterized by the following features.

5. In the piezoelectric element according to claim 4, The hydrogen supply layer comprises a first hydrogen supply layer and a second hydrogen supply layer, which are provided so as to sandwich the electrode layer in the stacking direction. A piezoelectric element characterized by the following features.

6. In the piezoelectric element according to claim 5, The second hydrogen supply layer is thicker than the first hydrogen supply layer. A piezoelectric element characterized by the following features.

7. A piezoelectric element comprising a lower electrode, a piezoelectric layer made of a perovskite-type composite oxide, and an upper electrode, stacked in the stacking direction, The lower electrode has an electrode layer, The system includes a hydrogen supply layer that supplies hydrogen to either the piezoelectric layer or the electrode layer. A piezoelectric element characterized by the following features.

8. In the piezoelectric element according to claim 7, The hydrogen supply layer supplies hydrogen to the piezoelectric layer. A piezoelectric element characterized by the following features.

9. In the piezoelectric element according to claim 8, The piezoelectric layer consists of multiple layers, including a first layer stacked above the hydrogen supply layer and a second layer stacked above the first layer. The hydrogen content in the first layer is greater than the hydrogen content in the second layer. A piezoelectric element characterized by the following features.

10. In the piezoelectric element according to claim 7, In the aforementioned stacking direction, an orientation control layer is provided between the lower electrode and the piezoelectric layer. The hydrogen supply layer supplies hydrogen to the orientation control layer. A piezoelectric element characterized by the following features.

11. In the piezoelectric element according to claim 10, The orientation control layer is an amorphous layer. A piezoelectric element characterized by the following features.

12. In the piezoelectric element according to claim 7, The hydrogen supply layer supplies hydrogen to the electrode layer. A piezoelectric element characterized by the following features.

13. In the piezoelectric element according to claim 12, The hydrogen supply layer comprises a third hydrogen supply layer and a fourth hydrogen supply layer, which are provided so as to sandwich the electrode layer in the stacking direction. A piezoelectric element characterized by the following features.

14. In the piezoelectric element according to any one of claims 1 to 13, The piezoelectric layer consists of multiple layers, The hydrogen content of the hydrogen supply layer is greater than the hydrogen content of the piezoelectric layer. A piezoelectric element characterized by the following features.

15. In a piezoelectric element according to any one of claims 1 to 6, The upper electrode has a protective film that protects it, In the aforementioned stacking direction, the hydrogen supply layer is provided below the protective film. A piezoelectric element characterized by the following features.

16. In the piezoelectric element according to any one of claims 1 to 13, The piezoelectric layer is composed of lead zirconate titanate. A piezoelectric element characterized by the following features.

17. In the piezoelectric element according to any one of claims 1 to 13, The piezoelectric layer is composed of potassium sodium niobate. A piezoelectric element characterized by the following features.

18. Having the piezoelectric element according to claim 1 or claim 7, A liquid dispensing head characterized by the following features.

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