Piezoelectric element and liquid dispensing head

Abstract

To provide a piezoelectric element that is easy to use, and a liquid dispensing head that includes such 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 a first hydrogen absorption layer that absorbs hydrogen is located above or below the lower electrode in the stacking direction. Preferably, the first hydrogen absorption layer is provided between the lower electrode and the piezoelectric layer in the stacking direction.

Description

Technical Field

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

Background Art

[0002] Conventionally, 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 proposed. As the liquid ejection head, a head that discharges the liquid filled in the pressure chamber from the nozzle by vibrating a diaphragm constituting 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] <000​​​​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 vicinity of the interface and the center of each layer. Such compositional gradients may affect the displacement characteristics of the piezoelectric element.

[0007] Furthermore, through diligent research, the inventors 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. They also found that hydrogen tended to enter from the lower electrode side.

[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. [Means for solving the problem]

[0009] 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, and a first hydrogen absorption layer that absorbs hydrogen is located above or below the lower electrode in the stacking direction.

[0010] A liquid dispensing head according to a preferred embodiment of the present invention has a piezoelectric element. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram illustrating the configuration of an image forming apparatus according to the first embodiment. [Figure 2] Figure 1 is an exploded perspective view of the liquid dispensing head. [Figure 3] This is a cross-sectional view of a portion of the liquid dispensing head shown in Figure 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 flow of the manufacturing method of the piezoelectric element of FIG. 6. [Figure 9] It is a diagram schematically showing the piezoelectric element of the first modification example. [Figure 10] It is a diagram schematically showing the piezoelectric element of the second modification example. [Figure 11] It is a cross-sectional view of the piezoelectric element of the third modification example. [Figure 12] It is a diagram showing the measurement result of the secondary ion mass spectrometer of the piezoelectric element of the third modification example. [Figure 13] It is a diagram schematically showing the piezoelectric element of the fourth modification example.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the dimensions or scales of each part are 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 embodiments unless there is a description to specifically limit the present invention in the following description. 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 side by side in the vertical direction, and it does not matter whether element α and element β are in direct contact.

[0013] 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 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 necessarily 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 80° or more and 100° or less, for example.

[0014] The image forming apparatus 100 in FIG. 1 is an inkjet printing apparatus that discharges ink, which is an example of a liquid, onto a medium 90. The medium 90 is typically printing paper, but a printing object of any material such as a resin film or fabric can be used as the medium 90. As illustrated in FIG. 1, a liquid container 9 for storing ink is installed in the image forming apparatus 100. For example, a cartridge detachable from the image forming apparatus 100, a bag-shaped ink pack formed of a flexible film, or an ink tank capable of replenishing ink is used as the liquid container 9.

[0015] The image forming apparatus 100 includes a control unit 20, a medium conveyance mechanism 22, a moving mechanism 24, and a liquid discharge head 3. The control unit 20 includes 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 comprehensively controls each element of the image forming apparatus 100.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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 may be an integrated structure, or they may be separate structures joined together with an adhesive or the like.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 absorbs pressure fluctuations of the ink in the liquid storage chamber R.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 will be described later, as shown in Figure 6, the piezoelectric element 5 further comprises a first hydrogen absorption layer 54 and a second hydrogen absorption layer 55. Note that the piezoelectric layer 53, the first hydrogen absorption layer 54, and the second hydrogen absorption layer 55 are sometimes collectively referred to as the intermediate layer 50 located between the lower electrode 51 and the upper electrode 52.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] A voltage equivalent to the difference between the reference voltage applied to the upper electrode 52 and the drive signal 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.

[0040] 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.

[0041] 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).

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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 first hydrogen absorption layer 54, and a second hydrogen absorption layer 55. The lower electrode 51, the piezoelectric layer 53, and the upper electrode 52 are each composed of multiple layers. In this embodiment, the first hydrogen absorption layer 54 is placed between the lower electrode 51 and the piezoelectric layer 53. The second hydrogen absorption layer 55 is placed between the multiple layers that make up the piezoelectric layer 53. Therefore, the second hydrogen absorption layer 55 is located inside the piezoelectric layer 53.

[0046] The lower electrode 51 has a first electrode layer 511 and a second 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.

[0047] The second electrode layer 512 is positioned between the first electrode layer 511 and the first hydrogen absorption layer 54 and is in contact with them. The second electrode layer 512 contains, for example, iridium (Ir). The thickness of the second 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 second 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.

[0048] 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 second electrode layer 512 may be composed of any conductive material, and may be composed of materials other than those mentioned above.

[0049] The first hydrogen absorption layer 54 has the function of absorbing hydrogen present in each layer or between layers that constitute the piezoelectric element 5. In particular, the first hydrogen absorption layer 54 suitably absorbs hydrogen in the piezoelectric layer 53, hydrogen in the lower electrode 51, and hydrogen present at the interfaces of each layer below the piezoelectric layer 53.

[0050] In Figure 6, the interface between the first hydrogen absorption layer 54 and the piezoelectric layer 53 is clearly depicted, but it does not need to be clearly shown. For example, a portion of the first hydrogen absorption layer 54 may be embedded in, dispersed in, or integrated with the piezoelectric layer 53. Also, the composition within the first hydrogen absorption layer 54 may be constant or graded. Therefore, the composition of the first hydrogen absorption layer 54 may differ between the piezoelectric layer 53 side and the lower electrode 51 side. Furthermore, the thickness of the first hydrogen absorption layer 54 along the Z-axis is not particularly limited, but for example, it is between 2 nm and 20 nm. Also, the first hydrogen absorption layer 54 may be composed of multiple layers.

[0051] 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.

[0052] 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. Note that each layer constituting the piezoelectric layer 53 may be made of lead-free material. Examples of lead-free materials include bismuth ironate (BiFeO3), barium titanate (BaTiO3), and potassium sodium niobate ((K,Na)(NbO3)).

[0053] 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.

[0054] The first layer 531 is positioned between the first hydrogen absorption layer 54 and the second hydrogen absorption layer 55 and is in contact with them. The second hydrogen absorption layer 55 is positioned between the first layer 531 and the second layer 532 and is in contact with them.

[0055] The second hydrogen absorption layer 55 has the function of absorbing hydrogen present in each layer or between layers that constitute the piezoelectric element 5. In particular, the second hydrogen absorption layer 55 preferably absorbs hydrogen in the first layer 531 and the second layer 532.

[0056] In Figure 6, the interface between the second hydrogen absorption layer 55 and the second layer 532, and the interface between the second hydrogen absorption layer 55 and the first layer 531 are clearly depicted, but they do not necessarily have to be. For example, a portion of the second hydrogen absorption 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 second hydrogen absorption layer 55 may be constant or gradient. Therefore, the composition of the second hydrogen absorption layer 55 may differ on the second layer 532 side and the first layer 531 side. Furthermore, the thickness of the second hydrogen absorption layer 55 along the Z axis is not particularly limited, but for example, it is between 2 nm and 20 nm. In this embodiment, the film thickness D5 of the second hydrogen absorption layer 55 is thinner than the film thickness D4 of the first hydrogen absorption layer 54, but it may be greater than or equal to the film thickness D4 of the first hydrogen absorption layer 54. Also, the second hydrogen absorption layer 55 may be composed of multiple layers.

[0057] The upper electrode 52 is a structure in which the third electrode layer 521, the fourth electrode layer 522, the fifth electrode layer 523, and the third hydrogen absorption 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. The fourth electrode layer 522 is for example titanium oxide (TiO x The fourth electrode layer 522 contains iridium (Ir). The thickness of the fourth electrode layer 522 along the Z-axis is not particularly limited, but is, for example, 2 nm to 20 nm. The fifth electrode layer 523 contains iridium (Ir), for example. The thickness of the fifth electrode layer 523 along the Z-axis is not particularly limited, but is, for example, 5 nm to 50 nm.

[0058] The third hydrogen absorption layer 524 contains, for example, titanium (Ti). The thickness of the third hydrogen absorption layer 524 along the Z axis is not particularly limited, but is, for example, 5 nm to 20 nm. The third hydrogen absorption layer 524 has the function of absorbing hydrogen present in each layer or between layers constituting the piezoelectric element 5. In particular, the third hydrogen absorption layer 524 preferably absorbs hydrogen in the upper electrode 52. The composition of the third hydrogen absorption layer 524 may be constant or gradient within the layer. Furthermore, it may be formed from multiple layers.

[0059] 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 first hydrogen absorption layer 54 and the piezoelectric layer 53, but such an orientation control layer may be provided. Furthermore, the first hydrogen absorption layer 54 may also have the function of such an orientation control layer. Because the first hydrogen absorption 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 layers to a predetermined plane orientation, or adjusts the degree of orientation to a predetermined plane orientation.

[0060] Similarly, although an orientation control layer for controlling the orientation of the second layer 532 is not provided between the second hydrogen absorption layer 55 and the second layer 532, such an orientation control layer may be provided. The second hydrogen absorption layer 55 may have the function of such an orientation control layer. However, since the second hydrogen absorption 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.

[0061] 1-4. Hydrogen absorption layer As described above, the piezoelectric element 5 has a first hydrogen absorption layer 54. The first hydrogen absorption layer 54 is provided above the lower electrode 51 in the direction along the Z-axis, which is the stacking direction of the piezoelectric element 5, and has the function of absorbing hydrogen. With the piezoelectric element 5 having such a first hydrogen absorption layer 54, it is possible to absorb hydrogen present at the interface between the lower electrode 51 and other layers, hydrogen present in the piezoelectric layer 53, or hydrogen that may enter the piezoelectric layer 53.

[0062] The hysteresis characteristics of the piezoelectric element 5 change significantly depending on the hydrogen content of the piezoelectric layer 53 compared to the design stage. When the hysteresis characteristics change significantly, there is a risk that the difference in displacement between multiple piezoelectric elements 5 will become large. Therefore, in order 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.

[0063] Furthermore, when the piezoelectric element 5 has a piezoelectric layer 53 formed from multiple layers, the hydrogen content of the piezoelectric layer 53 tends to be higher than that at the design stage. As will be described later, the piezoelectric layer 53 is formed by repeatedly depositing and firing each of the multiple layers. It is thought that hydrogen enters the piezoelectric layer 53 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 occur among multiple piezoelectric elements 5 due to the hydrogen content of the piezoelectric layer 53.

[0064] As described above, the piezoelectric element 5 of this embodiment has a first hydrogen absorption layer 54 provided between the lower electrode 51 and the piezoelectric layer 53. Therefore, during the manufacturing and use of the piezoelectric element 5, it is possible to absorb hydrogen present in the piezoelectric layer 53 or hydrogen that may enter the piezoelectric layer 53. Therefore, it is possible to suppress a large change in the hysteresis characteristics of the piezoelectric element 5 compared to the design stage due to the hydrogen content of the piezoelectric layer 53. Therefore, it is possible to suppress a large difference in the amount of displacement due to changes in the hysteresis characteristics of 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. For this reason, the liquid discharge head 3 equipped with such piezoelectric elements 5 has excellent displacement characteristics and usability.

[0065] Furthermore, the first hydrogen absorption layer 54 is located below the piezoelectric layer 53, rather than above it. It is believed that hydrogen often enters the piezoelectric layer 53 from the lower electrode 51 side during manufacturing. Therefore, by providing the first hydrogen absorption layer 54 between the lower electrode 51 and the piezoelectric layer 53, it is possible to reduce the difference in hysteresis characteristics due to differences in hydrogen content among the multiple piezoelectric elements 5. In addition, by providing the first hydrogen absorption layer 54 between the lower electrode 51 and the piezoelectric layer 53, it is possible to position the first hydrogen absorption layer 54 closer to the piezoelectric layer 53 compared to when it is provided below the lower electrode 51. As a result, hydrogen that may enter the piezoelectric layer 53 can be absorbed efficiently.

[0066] The first hydrogen absorption layer 54 is composed of a material capable of absorbing hydrogen. Specifically, the first hydrogen absorption layer 54 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. When the first hydrogen absorption layer 54 absorbs hydrogen, hydrogen penetrates into the gaps in the crystal lattice of the hydrogen storage material. The hydrogen storage material includes metals such as magnesium (Mg), vanadium (V), lanthanum (La), and titanium (Ti), alloys containing such metals, or compounds. The first hydrogen absorption layer 54 is composed of, for example, titanium or lead titanate (PbTiO3). Alternatively, the first hydrogen absorption layer 54 may be composed of, for example, a composite oxide containing bismuth (Bi), iron (Fe), titanium (Ti), and lead (Pb).

[0067] Furthermore, the second hydrogen absorption layer 55 and the third hydrogen absorption layer 524 each similarly contain a hydrogen storage material that can combine with hydrogen to form a hydride.

[0068] 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 second electrode layer 512 is iridium. The first hydrogen absorption layer 54 contains titanium. The material of each layer of the piezoelectric layer 53 is lead zirconate titanate (PZT). The second hydrogen absorption layer 55 contains titanium. The material of the third electrode layer 521 is iridium oxide, the material of the fourth electrode layer 522 is titanium oxide, the material of the fifth electrode layer 523 is iridium, and the material of the third hydrogen absorption layer 524 is titanium.

[0069] 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.

[0070] The vertical axis of Figure 7 shows the hydrogen concentration [atoms / cc]. This hydrogen concentration was determined 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.

[0071] As can be seen from Figure 7, the hydrogen content of the first layer 531 is lower than that of the second layer 532. The first layer 531 is stacked above the first hydrogen absorption layer 54 and is in direct contact with the first hydrogen absorption layer 54. The second layer 532 is stacked above the first layer 531. Therefore, the first layer 531 is located closer to the first hydrogen absorption layer 54 than the second layer 532. Consequently, the function of the first hydrogen absorption layer 54 makes it possible to reduce the hydrogen content of the first layer 531 to that of the second layer 532.

[0072] Furthermore, the hydrogen content of the first layer 531 may be greater than or equal to the hydrogen content of the second layer 532.

[0073] Furthermore, as can be seen from Figure 7, the hydrogen content of the first hydrogen absorption layer 54 is greater than that of the first layer 531. Because the first hydrogen absorption layer 54 absorbs hydrogen, the hydrogen content of the first layer 531 can be reduced. With the provision of such a first hydrogen absorption layer 54, the intrusion of hydrogen into the piezoelectric layer 53, including the first layer 531, can be suppressed both after the manufacture of the piezoelectric element 5 and during use. In addition, by suppressing the increase in the hydrogen content of the first layer 531 due to the first hydrogen absorption layer 54, the increase in the hydrogen content of each of the second layers 532 to the sixth layer 536 on the first layer 531 can be suppressed.

[0074] Furthermore, the first hydrogen absorption layer 54 is provided on the lower electrode 51. Preferably, the first hydrogen absorption layer 54 is also provided on the portion of the diaphragm 33 shown in Figure 4 where the lower electrode 51 is not provided above, in addition to above the lower electrode 51. With the first hydrogen absorption layer 54 provided in this way, the entire lower surface of the first layer 531 is in contact with the first hydrogen absorption layer 54. Therefore, compared to a configuration where only a part of the lower surface of the first layer 531 is in contact with the first hydrogen absorption layer 54, the function of the first hydrogen absorption layer 54 can suppress the increase in the hydrogen content of the first layer 531.

[0075] Furthermore, the hydrogen content of the first hydrogen absorption layer 54 may be less than or equal to the hydrogen content of the first layer 531.

[0076] Furthermore, the first hydrogen absorption layer 54 has higher hydrogen absorption capacity than the lower electrode 51. High hydrogen absorption capacity indicates that it readily combines with hydrogen to form a hydride. Therefore, the lower electrode 51 is less likely to undergo hydrogenation than the first hydrogen absorption layer 54. For example, both the first hydrogen absorption layer 54 and the lower electrode 51 contain metals. However, the first hydrogen absorption layer 54 has excellent hydrogen absorption properties and is provided separately from the lower electrode 51. In other words, the lower electrode 51 contains metals, similar to the first hydrogen absorption layer 54, but does not need to be a hydrogen storage material. The lower electrode 51 may also contain a hydrogen storage material. Even in that case, the first hydrogen absorption layer 54 has superior hydrogen absorption properties compared to the lower electrode 51. By providing such a first hydrogen absorption layer 54 to reduce the hydrogen content of the piezoelectric layer 53, the effect of suppressing the decrease in hysteresis characteristics in the aforementioned multiple piezoelectric elements 5 is achieved.

[0077] As described above, the piezoelectric element 5 has a second hydrogen absorption layer 55. The second hydrogen absorption layer 55 is provided above the first layer 531 in the direction along the Z-axis, which is the stacking direction of the piezoelectric element 5, and has the function of absorbing hydrogen. By providing such a second hydrogen absorption layer 55, the hydrogen content of the piezoelectric layer 53 can be reduced more than when the second hydrogen absorption layer 55 is not provided.

[0078] The second hydrogen absorption layer 55 may be omitted as appropriate.

[0079] Furthermore, the hydrogen content of the second layer 532 of the piezoelectric layer 53 is lower than that of the third layer 533. The second layer 532 is stacked above the second hydrogen absorption layer 55 and is in contact with the second hydrogen absorption layer 55. The third layer 533 is stacked above the second layer 532. Therefore, the second layer 532 is positioned closer to the second hydrogen absorption layer 55 than the third layer 533. Thus, the hydrogen absorption function of the second hydrogen absorption layer 55 makes it possible to reduce the hydrogen content of the second layer 532.

[0080] Furthermore, as can be seen from Figure 7, the hydrogen content of the second hydrogen absorption layer 55 is lower than that of the first hydrogen absorption layer 54. By providing the second hydrogen absorption layer 55, the hydrogen content of the piezoelectric layer 53 can be reduced more effectively than when the second hydrogen absorption layer 55 is not provided. Even if the first hydrogen absorption layer 54 alone is not able to absorb all the hydrogen, the presence of the second hydrogen absorption layer 55 can more effectively suppress the increase in hydrogen content in the central part of the piezoelectric layer 53. Therefore, the deterioration of the displacement characteristics of the piezoelectric element 5 can be effectively suppressed.

[0081] Even when the first hydrogen absorption layer 54 is provided alone, it is considered that it can sufficiently absorb hydrogen. In addition, there is a significant intrusion of hydrogen from the piezoelectric layer 53 on the lower electrode 51 side. For these reasons, it is considered that the hydrogen content of the second hydrogen absorption layer 55 will be lower than that of the first hydrogen absorption layer 54.

[0082] Furthermore, the hydrogen content of the second hydrogen absorption layer 55 may be greater than or equal to the hydrogen content of the first hydrogen absorption layer 54.

[0083] In this embodiment, along the Z-axis, the film thickness D5 of the second hydrogen absorption layer 55 is thinner than the film thickness D4 of the first hydrogen absorption layer 54. Therefore, film thickness D4 is thicker than film thickness D5. Because film thickness D4 is thicker than film thickness D5, the penetration of hydrogen from the lower electrode 51 side into the piezoelectric layer 53 by the first hydrogen absorption layer 54 can be suppressed compared to the case where it is thinner.

[0084] Furthermore, the film thickness D5 of the second hydrogen absorption layer 55 may be greater than or equal to the film thickness D4 of the first hydrogen absorption layer 54.

[0085] Furthermore, as shown in Figure 7, when the peak hydrogen values ​​at the positions of the first hydrogen absorption layer 54 and the second hydrogen absorption layer 55 are measured using SIMS, it is preferable that the peak value at the position of the second hydrogen absorption layer 55 is between 0.3 and 0.5 relative to the peak value at the position of the first hydrogen absorption layer 54. In the example in Figure 7, the peak value at the position of the second hydrogen absorption layer 55 is between 0.3 and 0.5 relative to the peak value at the position of the first hydrogen absorption layer 54. Note that due to SIMS measurement errors and interfacial effects, the peak position may shift relative to the depth where the first hydrogen absorption layer 54 and the second hydrogen absorption layer 55 are located. In this case, the hydrogen peak observed near the depth where the first hydrogen absorption layer 54 and the second hydrogen absorption layer 55 are located will be considered as the peak value in the first hydrogen absorption layer 54 and the second hydrogen absorption layer 55.

[0086] Because the peak value is above the lower limit mentioned above, the second hydrogen absorption layer 55 can sufficiently absorb the hydrogen that was not absorbed by the first hydrogen absorption layer 54, compared to the case where the peak value is below the lower limit.

[0087] Because the relationship between peak values ​​is below the upper limit mentioned above, it is not necessary to excessively increase the film thickness D5 of the second hydrogen absorption layer 55, for example, compared to the case where the upper limit is exceeded. Therefore, the presence of the second hydrogen absorption layer 55 can suppress the risk of a decrease in the displacement amount of the piezoelectric layer 53.

[0088] Furthermore, from the viewpoint of demonstrating the effect significantly, the peak value at the position of the second hydrogen absorption layer 55 relative to the peak value at the position of the first hydrogen absorption layer 54 is more preferably 0.30 or more and 0.46 or less.

[0089] As shown in Figure 7, the variation in the average value of the hydrogen content in the central part of the piezoelectric element 5 in the stacking direction is preferably 24% or less. The central part is the layer located in the center of the piezoelectric layer 53 in the stacking direction and is not in contact with any layers other than the piezoelectric layer 53. In the example of Figure 6, the central part is the third layer 533 and the fourth layer 534. These layers are not in contact with the second hydrogen absorption layer 55 and the upper electrode 52, which are layers other than the piezoelectric layer 53.

[0090] In the example shown in Figure 7, the variation is 24% or less. By keeping the variation below 24%, it is possible to suppress the steepness of the slope of the hysteresis curve, which shows the relationship between the voltage and polarization of the piezoelectric layer 53, compared to the case where the variation exceeds 24%. Furthermore, it is possible to suppress changes in the shape of the hysteresis curve over time from the design stage. Therefore, a decrease in the displacement characteristics of the piezoelectric element 5 can be suppressed. Note that the variation relative to the average value of the hydrogen content in the central region may exceed 24%.

[0091] Furthermore, as shown in Figure 7, the hydrogen content of the third layer 533 and the fourth layer 534, which are the central parts of the piezoelectric layer 53, is suppressed in the same way as the hydrogen content of the first layer 531. Specifically, the average hydrogen content of each layer in the central part of the piezoelectric layer 53 is preferably less than 1E+20 [atoms / cc], and more preferably less than 1E+19 [atoms / cc]. 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 This represents the performance of the piezoelectric element 5, where the range of the piezoelectric layer 53 that is farther from the neutral axis A1, as shown in Figure 4, is greater. The third layer 533 and the fourth layer 534 are further from the neutral axis A1 than the first layer 531. By reducing the hydrogen content of the third layer 533 and the fourth layer 534, which are farther from the neutral axis A1, the deterioration of the displacement characteristics of the piezoelectric element 5 can be suppressed.

[0092] As described above, the upper electrode 52 has a third hydrogen absorption layer 524. The third hydrogen absorption layer 524 is provided on the upper electrode 52 side relative to the piezoelectric layer 53 and is located at the topmost layer of the upper electrode 52. The third hydrogen absorption layer 524 has the function of absorbing hydrogen. By providing such a third hydrogen absorption layer 524, it is possible to suppress the intrusion of hydrogen into the piezoelectric layer 53 from the upper electrode 52 side compared to when it is not provided. In addition, it is possible to reduce the hydrogen content of each of the third electrode layers 521 to the fifth electrode layers 523.

[0093] Furthermore, the aforementioned fourth electrode layer 522 may also function as a hydrogen absorption layer. By having the fourth electrode layer 522 function as a hydrogen absorption layer, the intrusion of hydrogen into the piezoelectric layer 53 from the upper electrode 52 side can be more effectively suppressed. In addition, the hydrogen content of each of the third electrode layers 521 to the fifth electrode layer 523 can be further reduced. In this embodiment, the material of the third hydrogen absorption layer 524 is titanium, and the material of the fourth electrode layer 522 is titanium oxide. However, the third hydrogen absorption layer 524 and the fourth electrode layer 522 may be made of the same material or different materials.

[0094] 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). The use of PZT in the piezoelectric layer is particularly effective in suppressing changes in the hysteresis characteristics of the piezoelectric element 5 caused by the provision of the first hydrogen absorption layer 54. Moreover, when the piezoelectric layer 53 is composed of multiple layers, the effects of providing the first hydrogen absorption layer 54 can be particularly pronounced.

[0095] Furthermore, it is particularly preferable that each of the first hydrogen absorption layer 54, the second hydrogen absorption layer 55, and the third hydrogen absorption layer 524 contains titanium. Moreover, it is preferable that each of these layers is made of titanium. Titanium has excellent hydrogen absorption performance. Therefore, by including titanium in these layers, more hydrogen that might penetrate the piezoelectric layer 53 can be absorbed compared to when titanium is not included.

[0096] 1-5. Manufacturing method of piezoelectric element 5 Figure 8 shows the flow of the manufacturing method for the piezoelectric element 5 shown in Figure 6. As shown in Figure 8, 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.

[0097] 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 a second 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 second 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.

[0098] The intermediate layer formation step S12 includes the formation of a first hydrogen absorption layer 54, a piezoelectric layer 53, and a second hydrogen absorption layer. 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 first hydrogen absorption layer 54 and the first layer 531 are formed.

[0099] 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 second hydrogen absorption layer 55 and the second layer 532 are formed.

[0100] When forming the second hydrogen absorption layer 55, there is a risk that moisture may remain on the surface of the first layer 531 during the formation of the second hydrogen absorption layer 55. For this reason, it is preferable to perform a heating step to remove surface moisture during the formation of the second hydrogen absorption layer 55. This reduces the amount of moisture remaining on the surface of the first layer 531. As a result, the amount of hydrogen absorbed by the second hydrogen absorption layer 55 is reduced during its formation, allowing the second hydrogen absorption layer 55 to absorb hydrogen sufficiently after formation.

[0101] 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 first hydrogen absorption layer 54, the second hydrogen absorption layer 55, and the piezoelectric layer 53 are calcined together.

[0102] When each layer of the piezoelectric layer 53 is formed using a sol-gel, the shape and crystallinity of the lower layer affect the shape and crystallinity of the upper layer. In this embodiment, the hydrogen content of the second layer 532 is smaller than that of the third layer 533. Therefore, it is possible to suppress the influence of the shape and crystallinity of the second layer 532 on the third layer 533, which is the middle layer of the piezoelectric layer 53, when the third layer 533 is formed using a sol-gel.

[0103] 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, a fourth electrode layer 522, a fifth electrode layer 523, and a third hydrogen absorption 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 fourth electrode layer 522 containing a metal oxide is formed on the third electrode layer 521 by sputtering, vapor deposition, or CVD, followed by firing.

[0104] Next, a fifth electrode layer 523 is formed on the fourth electrode layer 522 by depositing a layer containing a conductive material such as iridium using sputtering, vapor deposition, or CVD. Then, a third hydrogen absorption layer 524 is formed on the fifth 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.

[0105] 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.

[0106] 2-1. First variation Figure 9 is a schematic diagram of the piezoelectric element 5A of the first modified example. As shown in Figure 9, the first hydrogen absorption layer 54A of the piezoelectric element 5A of the first modified example consists of multiple layers with different constituent elements. Specifically, the first hydrogen absorption layer 54A includes a first absorption layer 541 and a second absorption layer 542. The first absorption layer 541 is made of titanium, for example. The second absorption layer 542 is made of lead zirconate (PbZrO3) or lead titanate (PbTiO3), for example.

[0107] Since the first hydrogen absorption layer 54A is composed of multiple layers, the penetration of hydrogen into the piezoelectric layer 53 can be suppressed more effectively compared to a single layer.

[0108] Furthermore, the first absorption layer 541 and the second absorption layer 542 may have different or the same hydrogen absorption performance, i.e., the amount of hydrogen absorbed. The second absorption layer 542 may also function as the orientation control layer described above.

[0109] In the first embodiment and the first modified example, a portion of the lower electrode 51 may be considered as part of the first hydrogen absorption layer 54, and in this case as well, the first hydrogen absorption layer 54 may be considered to consist of multiple layers. For example, the second electrode layer 512 of the lower electrode 51 may be considered as part of the first hydrogen absorption layer 54. Furthermore, the first hydrogen absorption layer 54 may also function as an electrode.

[0110] 2-2. Second variation Figure 10 is a schematic diagram showing the piezoelectric element 5B of the second modified example. As shown in Figure 10, the first hydrogen absorption layer 54B of the second modified example is provided below the lower electrode 51 in the direction along the Z-axis, which is the stacking direction. The first hydrogen absorption layer 54B is positioned between the diaphragm 33 and the lower electrode 51 and is in contact with them.

[0111] By positioning the first hydrogen absorption layer 54B below the lower electrode 51, it is possible to suppress the intrusion of hydrogen into the piezoelectric layer 53 from the diaphragm 33 side.

[0112] 2-3. Third Variation Figure 11 is a cross-sectional view of the piezoelectric element 5 of the third modified example. As shown in Figure 11, a protective film 6 is placed on the upper surface of the piezoelectric layer 53. Specifically, the protective film 6 is placed 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 protective film 6 is placed on this exposed portion. The protective film 6 includes, for example, ceramics such as aluminum oxide (AlOx) and silicon nitride.

[0113] The protective film 6 is provided on the exposed portion of the piezoelectric layer 53, thereby suppressing hydrogen from entering the piezoelectric layer 53. In addition, a portion of the protective film 6 is sandwiched between the upper electrodes 52. Specifically, the third electrode layer 521, the fourth electrode layer 522, and the fifth electrode layer 523 are arranged below the protective film 6. The third hydrogen absorption layer 524 is arranged above the protective film 6. A portion of the third hydrogen absorption layer 524 is provided on the third hydrogen absorption layer 524, so that the third hydrogen absorption layer 524 can absorb hydrogen in the protective film 6, thereby suppressing hydrogen in the protective film 6 from entering the piezoelectric layer 53.

[0114] The third hydrogen absorption layer 524 may be located below the protective film 6. Furthermore, while the third hydrogen absorption layer 524 is provided on a portion of the upper surface of the protective film 6, it may also be provided on the entire upper surface of the protective film 6.

[0115] Furthermore, if a protective film 6 is provided, in the manufacturing method of the piezoelectric element 5, the protective film 6 is formed between the formation of the third electrode layer 521, the fourth electrode layer 522, and the fifth electrode layer 523, and the formation of the third hydrogen absorption layer 524. The protective film 6 is mainly formed on the exposed portion of the upper surface of the piezoelectric layer 53 where the third electrode layer 521, the fourth electrode layer 522, and the fifth electrode layer 523 are not provided. The protective film 6 is formed by depositing a ceramic material using sputtering, vapor deposition, or CVD.

[0116] Figure 12 shows a third modified example of a piezoelectric element secondary ion mass spectrometer. As can be seen from Figure 12, in this modified example, as in the first embodiment, the hydrogen content of the first layer 531 is smaller than that of the second layer 532. Also, the hydrogen content of the first hydrogen absorption layer 54 is larger than that of the first layer 531. Furthermore, the hydrogen content of the second hydrogen absorption layer 55 is smaller than that of the first hydrogen absorption layer 54.

[0117] Furthermore, in the example shown in Figure 12, the peak value at the position of the second hydrogen absorption layer 55 is 0.3 or more and 0.5 or less relative to the peak value at the position of the first hydrogen absorption layer 54. Also, in the example shown in Figure 12, the variation in the average value of the hydrogen content at the central part in the stacking direction of the piezoelectric element 5 is preferably 24% or less.

[0118] 2-4. Fourth Variation Figure 13 is a schematic diagram of the piezoelectric element 5C of the fourth modified example. As shown in Figure 13, the piezoelectric element 5C of the fourth modified example has a hydrogen barrier layer 56 at the top layer in the stacking direction that suppresses the intrusion of hydrogen. The hydrogen barrier layer 56 includes, for example, ceramics such as aluminum oxide (AlOx) and silicon nitride. By providing the hydrogen barrier layer 56, it is possible to suppress the intrusion of external hydrogen into the piezoelectric layer 53 compared to when it is not provided.

[0119] 2-5. Other variations The "liquid dispensing head" may be a circulating type head having a so-called circulation channel.

[0120] "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.

[0121] 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.

[0122] 3. Addendum From the above embodiments or modifications, for example, the following embodiments can be understood.

[0123] 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, and a first hydrogen absorption layer that absorbs hydrogen is located above or below the lower electrode in the stacking direction.

[0124] According to this first embodiment, hydrogen present at the interface between the lower electrode and other layers, hydrogen present in the piezoelectric layer, or hydrogen that may enter the piezoelectric layer can be absorbed. Therefore, changes in hysteresis characteristics due to an increase in the hydrogen content in the piezoelectric layer can be suppressed. Consequently, the risk of differences in displacement between piezoelectric elements can be suppressed. Therefore, it is not necessary to adjust for such differences by changing the driving voltage or waveform for each piezoelectric element, thereby improving ease of use.

[0125] In the piezoelectric element of the second embodiment, which is a preferred example of the first embodiment, the first hydrogen absorption layer is provided between the lower electrode and the piezoelectric layer in the stacking direction.

[0126] In this second embodiment, the first hydrogen absorption layer is positioned closer to the piezoelectric layer compared to the case where the first hydrogen absorption layer is positioned below the lower electrode. Therefore, hydrogen that might penetrate the piezoelectric layer can be absorbed efficiently.

[0127] In the piezoelectric element of the third embodiment, which is a preferred example of the second embodiment, the piezoelectric layer comprises a plurality of layers including a first layer laminated above the first hydrogen absorption layer and a second layer laminated above the first layer, wherein the hydrogen content of the first layer is smaller than the hydrogen content of the second layer.

[0128] According to this third embodiment, the first layer is located closer to the first hydrogen absorption layer than the second layer. Therefore, the hydrogen content of the first layer can be reduced by the function of the first hydrogen absorption layer.

[0129] In the piezoelectric element of the fourth embodiment, which is a preferred example of the third embodiment, the hydrogen content of the first hydrogen absorption layer is greater than the hydrogen content of the first layer.

[0130] According to this third embodiment, the hydrogen content of the first layer can be reduced because the first hydrogen absorption layer absorbs hydrogen.

[0131] In the piezoelectric element of the fifth embodiment, which is a preferred example of any of the first to fourth embodiments, the first hydrogen absorption layer consists of multiple layers with different constituent elements.

[0132] By being composed of multiple layers, the penetration of hydrogen into the piezoelectric layer can be more effectively suppressed.

[0133] In a piezoelectric element of the sixth embodiment, which is a preferred example of any of the first to fifth embodiments, the piezoelectric layer consists of a plurality of layers including a first layer laminated above the first hydrogen absorption layer, and has a second hydrogen absorption layer that absorbs hydrogen above the first layer in the lamination direction.

[0134] According to this sixth embodiment, the provision of the second hydrogen absorption layer makes it possible to further reduce the hydrogen content of the piezoelectric layer compared to the case where the second hydrogen absorption layer is not provided.

[0135] In the piezoelectric element of the seventh embodiment, which is a preferred example of the sixth embodiment, the piezoelectric layer comprises a plurality of layers including a second layer laminated above the second hydrogen absorption layer and a third layer laminated above the second layer, wherein the hydrogen content of the second layer is smaller than the hydrogen content of the third layer.

[0136] The function of the second hydrogen absorption layer allows for a reduction in the hydrogen content of the second layer.

[0137] In the piezoelectric element of the eighth embodiment, which is a preferred example of the sixth or seventh embodiment, the hydrogen content in the second hydrogen absorption layer is smaller than the hydrogen content in the first hydrogen absorption layer.

[0138] Since a large amount of hydrogen enters from the piezoelectric layer from the lower electrode side, the hydrogen content of the second hydrogen absorption layer is expected to be lower than that of the first hydrogen absorption layer. By providing both the first and second hydrogen absorption layers, the entry of hydrogen into the piezoelectric layer can be suppressed more effectively.

[0139] In the piezoelectric element of the ninth embodiment, which is a preferred example of any of the sixth to eighth embodiments, the thickness of the second hydrogen absorption layer is thinner than the thickness of the first hydrogen absorption layer in the stacking direction.

[0140] According to the ninth embodiment, by making the first hydrogen absorption layer thicker than the second hydrogen absorption layer, it is possible to suppress the entry of hydrogen into the piezoelectric layer from the lower electrode side compared to the case where the layers are thinner.

[0141] In the piezoelectric element of the 10th embodiment, which is a preferred example of any of the 6th to 9th embodiments, when the peak values ​​of hydrogen at the position of the first hydrogen absorption layer and the position of the second hydrogen absorption layer are measured with a secondary ion mass spectrometer, the peak value at the position of the second hydrogen absorption layer is 0.3 or more and 0.5 or less relative to the peak value at the position of the first hydrogen absorption layer.

[0142] According to the tenth embodiment, hydrogen can be sufficiently absorbed by the second hydrogen absorption layer, and the thickness of the piezoelectric element can be prevented from becoming excessively thick.

[0143] In the piezoelectric element of the 11th embodiment, which is a preferred example of any of the first to tenth embodiments, the first hydrogen absorption layer is provided below the lower electrode in the stacking direction.

[0144] According to the eleventh embodiment, by arranging the first hydrogen absorption layer below the lower electrode, it is possible to suppress the intrusion of hydrogen into the piezoelectric layer from the diaphragm side.

[0145] In the piezoelectric element according to the 12th embodiment, which is a preferred example of any of the 1st to 11th embodiments, the first hydrogen absorption layer has higher hydrogen absorption than the lower electrode.

[0146] The provision of this first hydrogen absorption layer has the effect of suppressing the decrease in hysteresis characteristics in multiple piezoelectric elements.

[0147] In the piezoelectric element according to the 13th embodiment, which is a preferred example of any of the 1st to 12th embodiments, the upper electrode has a third hydrogen absorption layer that absorbs hydrogen.

[0148] According to the 13th embodiment, by providing a third hydrogen absorption layer on the upper electrode side with respect to the piezoelectric layer, the intrusion of hydrogen into the piezoelectric layer from the upper electrode side can be suppressed compared to the case where the third hydrogen absorption layer is not provided.

[0149] In the piezoelectric element according to the 14th embodiment, which is a preferred example of any of the 1st to 13th embodiments, the piezoelectric layer is composed of multiple layers, and the variation in the average value of the hydrogen content at the central part in the stacking direction of the piezoelectric layer is 24% or less.

[0150] By keeping this variation below 24%, it is possible to suppress changes in the shape of the hysteresis curve, which shows the relationship between the voltage and polarization of the piezoelectric material, from the time of design, compared to cases where the variation exceeds 24%.

[0151] In the piezoelectric element according to the 15th embodiment, which is a preferred example of any of the 1st to 14th embodiments, the piezoelectric layer is made of lead zirconate titanate.

[0152] When the piezoelectric layer is made of lead titanate, the first hydrogen absorption layer can be used to suppress changes in the hysteresis characteristics of the piezoelectric element.

[0153] 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 fifteen embodiments.

[0154] This allows us to provide a liquid dispensing head with excellent displacement characteristics and ease of use. [Explanation of Symbols]

[0155] 3...Liquid discharge head, 5...Piezoelectric element, 6...Protective film, 33...Diaphragm, 51...Lower electrode, 52...Upper electrode, 53...Piezoelectric layer, 54...First hydrogen absorption layer, 55...Second hydrogen absorption layer, 100...Image forming apparatus, 331...First vibrator layer, 332...Second vibrator layer, 511...First electrode layer, 512...Second electrode layer, 521...Third electrode layer, 522...Fourth electrode layer, 523...Fifth electrode layer, 524...Third hydrogen absorption layer, 531...First layer, 532...Second layer, 533...Third layer, 534...Fourth layer, 535...Fixed layer, 536...Sixth layer, 541...First absorption layer, 542...Second absorption layer, A1...Neutral axis, C1...Pressure chamber, D4...Film thickness, D5...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, In the stacking direction, above or below the lower electrode, there is a first hydrogen absorption layer that absorbs hydrogen. A piezoelectric element characterized by the following features.

2. In the piezoelectric element according to claim 1, The first hydrogen absorption layer is provided between the lower electrode and the piezoelectric layer in the stacking direction. A piezoelectric element characterized by the following features.

3. In the piezoelectric element according to claim 2, The piezoelectric layer comprises a plurality of layers, including a first layer laminated above the first hydrogen absorption layer and a second layer laminated above the first layer. The hydrogen content of the first layer is less than the hydrogen content of the second layer. A piezoelectric element characterized by the following features.

4. In the piezoelectric element according to claim 3, The hydrogen content of the first hydrogen absorption layer is greater than the hydrogen content of the first layer. A piezoelectric element characterized by the following features.

5. In the piezoelectric element according to claim 1, The first hydrogen absorption layer consists of multiple layers with different constituent elements. A piezoelectric element characterized by the following features.

6. In the piezoelectric element according to any one of claims 1 to 5, The piezoelectric layer consists of multiple layers, including a first layer stacked above the first hydrogen absorption layer. In the aforementioned stacking direction, a second hydrogen absorption layer that absorbs hydrogen is located above the first layer. A piezoelectric element characterized by the following features.

7. In the piezoelectric element according to claim 6, The piezoelectric layer comprises multiple layers, including a second layer laminated above the second hydrogen absorption layer and a third layer laminated above the second layer. The hydrogen content of the second layer is greater than the hydrogen content of the third layer. A piezoelectric element characterized by the following features.

8. In the piezoelectric element according to claim 6, The hydrogen content in the second hydrogen absorption layer is smaller than the hydrogen content in the first hydrogen absorption layer. A piezoelectric element characterized by the following features.

9. In the piezoelectric element according to claim 8, In the aforementioned lamination direction, the film thickness of the second hydrogen absorption layer is thinner than the film thickness of the first hydrogen absorption layer. A piezoelectric element characterized by the following features.

10. In the piezoelectric element according to claim 6, When the peak values ​​of hydrogen at the positions of the first hydrogen absorption layer and the second hydrogen absorption layer are measured using a secondary ion mass spectrometer, the peak value at the position of the second hydrogen absorption layer is 0.3 or more and 0.5 or less relative to the peak value at the position of the first hydrogen absorption layer. A piezoelectric element characterized by the following features.

11. In the piezoelectric element according to claim 1, The first hydrogen absorption layer is provided below the lower electrode in the stacking direction, A piezoelectric element characterized by the following features.

12. In the piezoelectric element according to any one of claims 1 to 5, The first hydrogen absorption layer has higher hydrogen absorption capacity than the lower electrode. A piezoelectric element characterized by the following features.

13. In the piezoelectric element according to any one of claims 1 to 5, The upper electrode has a third hydrogen absorption layer that absorbs hydrogen. A piezoelectric element characterized by the following features.

14. In the piezoelectric element according to claim 6, The piezoelectric layer is composed of multiple layers, The variation in the average value of the hydrogen content at the central part in the stacking direction of the piezoelectric layer is 24% or less. A piezoelectric element characterized by the following features.

15. In the piezoelectric element according to any one of claims 1 to 5, The piezoelectric layer is composed of lead zirconate titanate. A piezoelectric element characterized by the following features.

16. A piezoelectric element according to any one of claims 1 to 5, A liquid dispensing head characterized by the following features.

Images