Piezoelectric element, liquid ejecting head, and liquid ejecting apparatus

Abstract

Provided is a piezoelectric element, a liquid ejecting head, and a liquid ejecting apparatus that can achieve a balance between suppression of the generation of cracks caused by the sudden application of excessive current and suppression of the generation of drive delays. The piezoelectric element is a liquid ejecting head in which a lower electrode, a lower piezoelectric body containing K, Na, and Nb, an upper piezoelectric body containing K, Na, and Nb, and an upper electrode are arranged in this order in the stacking direction, and when the average concentration of K in the lower piezoelectric body is set to K1, the average concentration of Na in the lower piezoelectric body is set to Na1, the average concentration of K in the upper piezoelectric body is set to K2, and the average concentration of Na in the upper piezoelectric body is set to Na2, K1 / (K1+Na1) > K2 / (K2+Na2) is satisfied.

Description

Technical Field

[0001] This invention relates to piezoelectric elements, liquid ejector heads, and liquid ejection devices. Background Technology

[0002] Image forming apparatuses have previously been proposed that have liquid ejection heads that eject liquids such as ink from media such as printing paper. As such liquid ejection heads, a type of nozzle is known that ejects liquid filled in the pressure chamber from a nozzle by vibrating a vibrating plate that forms the wall of the pressure chamber using a piezoelectric element.

[0003] The piezoelectric element described in Patent Document 1 includes a component containing K, Na, and Nb (K a Na 1-a Piezoelectric materials composed of NbO3. (K a Na 1-a NbO3 has a perovskite structure represented by the general formula ABO3, abbreviated as KNN.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2011-155272

[0005] The displacement characteristics of KNN piezoelectric elements are, for example, smaller than those of PZT (lead zirconate titanate) piezoelectric elements. Therefore, to improve the displacement characteristics of piezoelectric elements, it is necessary to stack multiple layers to enhance the displacement characteristics of KNN piezoelectric elements. For example, consider a KNN piezoelectric element composed of a stack of upper and lower layers. In this case, the inventors discovered that a better effect can be obtained by setting the composition of the upper and lower layers separately, rather than using the same composition for both layers. Summary of the Invention

[0006] The preferred embodiment of the present invention involves a piezoelectric element comprising a liquid ejector head having a lower electrode, a lower piezoelectric body containing K, Na, and Nb, an upper piezoelectric body containing K, Na, and Nb, and an upper electrode arranged sequentially in the stacking direction. When the average concentration of K in the lower piezoelectric body is set as K1, the average concentration of Na in the lower piezoelectric body is set as Na1, the average concentration of K in the upper piezoelectric body is set as K2, and the average concentration of Na in the upper piezoelectric body is set as Na2, K1 / (K1+Na1)>K2 / (K2+Na2).

[0007] The preferred embodiment of the present invention relates to a liquid ejector head comprising: a piezoelectric element; a pressure chamber in which liquid flows and pressure is applied to the liquid by the piezoelectric element; and a nozzle that ejects liquid by the pressure applied by the pressure chamber.

[0008] The liquid ejection device according to a preferred embodiment of the present invention includes: a liquid ejection head; and a control unit for controlling the ejection action of the liquid ejection head. Attached Figure Description

[0009] Figure 1 This is a schematic diagram illustrating the structure of the liquid ejection device according to the first embodiment.

[0010] Figure 2 yes Figure 1 An exploded perspective view of the liquid ejector head shown.

[0011] Figure 3 yes Figure 2 A cross-sectional view of a portion of the liquid ejector head shown.

[0012] Figure 4 It means Figure 3 The diagram shows the vibrating plate and piezoelectric elements.

[0013] Figure 5 This is a graph representing hysteresis loops.

[0014] Figure 6 It means targeting Figure 5 The graph shows the relationship between electric field strength and electrostatic capacitance in the third and fourth examples.

[0015] Figure 7 This is a table showing the relationship between the K content and positive saturation polarization.

[0016] Figure 8 This is a coordinate graph showing the relationship between the K content and positive saturation polarization.

[0017] Figure 9 This is a table representing an embodiment.

[0018] Figure 10 This is a table representing comparative examples.

[0019] Explanation of reference numerals in the attached figures

[0020] 1...Liquid ejector head; 5...Piezoelectric element; 11...Nozzle plate; 12...Damper; 13...Flow path substrate; 14...Pressure chamber substrate; 15...Vibrating plate; 51...Lower electrode; 52...Upper electrode; 53...Piezoelectric layer; 54...Seed layer; 100...Liquid ejection device; 151...First vibrating layer; 152...Second vibrating layer; 531...Lower piezoelectric element; 532...Upper piezoelectric element; A0...Neutral shaft; K1...Average concentration; K2...Average concentration; N...Nozzle; Na1...Average concentration; Na2...Average concentration; Pm...Saturation polarization. Detailed Implementation

[0021] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the dimensions or scales of the parts in the drawings may differ appropriately from actual dimensions, and some parts are shown schematically for ease of understanding. Furthermore, the scope of the present invention is not limited to these embodiments unless specifically defined in the following description. Additionally, "element α and element β stacked" means that elements α and β are arranged vertically, and direct contact between elements α and β is not required.

[0022] The following explanation uses intersecting X, Y, and Z axes appropriately. A direction along the X-axis is called the X1 direction, and the opposite direction is called the X2 direction. Opposite directions along the Y-axis are called the Y1 and Y2 directions. Opposite directions along the Z-axis are called the Z1 and Z2 directions. Viewing along the Z-axis is called "top view." Typically, the Z-axis is a vertical axis. The Z1 direction is upward, and the Z2 direction is downward. However, the Z-axis may not be vertical. Furthermore, the X, Y, and Z axes are typically orthogonal to each other, but are not limited to this; for example, they may intersect at angles between 80° and 100°.

[0023] 1. First Implementation Method

[0024] 1-1. Overall structure of the liquid ejection device 100

[0025] Figure 1 This is a schematic structural diagram illustrating the liquid ejection apparatus 100 according to the first embodiment. The liquid ejection apparatus 100 is an inkjet printing apparatus that ejects ink, an example of a liquid, as droplets onto a medium M. Typically, the medium M is printing paper. However, the medium M is not limited to printing paper; for example, it can be any material such as resin film or fabric.

[0026] like Figure 1 As shown, the liquid ejection device 100 is equipped with a liquid container 90 for storing ink. Specific embodiments of the liquid container 90 include, for example, a box that can be detachably attached to the liquid ejection device 100, a bag-shaped ink cartridge formed of a flexible membrane, and an ink canister for refilling ink. Furthermore, the type of ink stored in the liquid container 90 is arbitrary. In addition, "liquid" can refer to any material that can be ejected from the liquid ejection device 100. For example, "liquid" can also be a material containing solids within a liquid.

[0027] The liquid ejection device 100 includes a control unit 91, a conveying mechanism 92, a moving mechanism 93, and a liquid ejection head 1. The control unit 91 includes, for example, a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and controls the operation of each element of the liquid ejection device 100. The control unit 91 includes a voltage application circuit 910 that controls the driving of the piezoelectric element 5 (described later) to eject ink from the nozzle. The voltage application circuit 910 applies a reference voltage VBS and a driving voltage Com to the piezoelectric element 5 (described later) on the liquid ejection head 1.

[0028] Under the control of the control unit 91, the conveying mechanism 92 conveys the medium M in the Y2 direction. Under the control of the control unit 91, the moving mechanism 93 causes the liquid nozzle 1 to reciprocate in the X1 and X2 directions. Figure 1 In the example shown, the moving mechanism 93 includes: a generally box-shaped conveyor body 931, called a carriage, that houses the liquid nozzle 1; and a conveyor belt 932 fixed to the conveyor body 931. Furthermore, the number of liquid nozzles 1 mounted on the conveyor body 931 is not limited to one; it can also be multiple. Additionally, the conveyor body 931 may also carry a liquid container 90 in addition to the liquid nozzle 1.

[0029] Under the control of the control unit 91, the liquid ejector head 1 ejects ink supplied by the liquid container 90 from multiple nozzles toward the medium M in the Z2 direction. The liquid ejector head 1, as will be described later, includes multiple piezoelectric elements 5 for ejecting ink from the multiple nozzles N. This ejection is performed in parallel with the transport of the medium M via the transport mechanism 92 and the reciprocating movement of the liquid ejector head 1 via the moving mechanism 93, thereby forming an image composed of ink on the surface of the medium M.

[0030] The liquid ejection device 100, as described above, includes a liquid ejection head 1 and a control unit 91 that controls the ejection action from the liquid ejection head 1. The liquid ejection head 1 has the features described later, namely, the ability to suppress the generation of cracks in the piezoelectric element 5 caused by sudden overcurrent and to suppress the generation of drive delay. Therefore, according to the liquid ejection device 100 equipped with such a liquid ejection head 1, the reduction in ejection performance can be suppressed.

[0031] 1-2. Overall structure of liquid ejector head 1

[0032] Figure 2 yes Figure 1 An exploded perspective view of the liquid ejector head 1 shown. Figure 3 yes Figure 2 The diagram shows a cross-sectional view of a portion of the liquid ejector head 1, and is... Figure 2 Sectional view along line III-III.

[0033] like Figure 2 As shown, the liquid ejector head 1 has a plurality of nozzles N arranged in a direction along the Y-axis. Figure 2 In the example shown, the multiple nozzles N are divided into a first column L1 and a second column L2 arranged at intervals along the X-axis. The first column L1 and the second column L2 are each a set of multiple nozzles N arranged linearly along the Y-axis. The elements of the liquid ejector head 1 related to each nozzle N in the first column L1 and the elements related to each nozzle N in the second column L2 are approximately symmetrical about each other along the X-axis. In the following description, the elements corresponding to the first column L1 are emphasized, while the descriptions of the elements corresponding to the second column L2 are omitted as appropriate.

[0034] Furthermore, the positions of the multiple nozzles N in the first column L1 and the multiple nozzles N in the second column L2 along the Y-axis can be either the same or different. Additionally, elements related to each nozzle N in either the first column L1 or the second column L2 can be omitted.

[0035] like Figure 2 as well as Figure 3 As shown, the liquid ejector head 1 includes a nozzle plate 11, a damper 12, a flow path substrate 13, a pressure chamber substrate 14, a vibrating plate 15, a wiring substrate 16, a housing portion 17, and a drive circuit 20. The nozzle plate 11, damper 12, flow path substrate 13, pressure chamber substrate 14, vibrating plate 15, wiring substrate 16, and housing portion 17 are all elongated plate-shaped members along the Y-axis. The nozzle plate 11, flow path substrate 13, pressure chamber substrate 14, vibrating plate 15, and wiring substrate 16 are arranged sequentially along the Z1 direction.

[0036] Nozzle plate 11 is a plate-shaped member having a plurality of nozzles N. Each nozzle N is a circular through-hole through which ink passes. The nozzles N eject ink by vibration of vibrating plate 15. Nozzle plate 11 is bonded to flow path substrate 13, for example, by an adhesive. The nozzles N are the portions that eject liquid by pressure supplied by pressure chamber C.

[0037] A flow path for supplying ink to a plurality of nozzles N is formed on the flow path substrate 13. Specifically, a space Ra, a plurality of supply flow paths 131, a plurality of connecting flow paths 132, and a supply liquid chamber 133 are formed on the flow path substrate 13. In a top view along the Z-axis, the space Ra is an elongated opening extending along the Y-axis. The supply flow paths 131 and the connecting flow paths 132 are through holes formed for each nozzle N. The supply liquid chamber 133 is an elongated space extending along the Y-axis throughout the plurality of nozzles N, such that the space Ra is interconnected with the plurality of supply flow paths 131. In a top view, each of the plurality of connecting flow paths 132 overlaps with one nozzle N corresponding to that connecting flow path 132. A pressure chamber substrate 14 is bonded to the flow path substrate 13, for example, by an adhesive.

[0038] Multiple pressure chambers C are provided on the pressure chamber substrate 14. The multiple pressure chambers C are arranged along the Y-axis. Each pressure chamber C is an elongated space formed for each nozzle N and extending along the X-axis when viewed from above. The pressure chamber C is the space located between the flow path substrate 13 and the vibrating plate 15. The pressure chamber C is connected to the nozzle N via the connecting flow path 132, and to the space Ra via the supply flow path 131 and the supply liquid chamber 133. The pressure chamber C is the part in which ink, as a liquid, flows internally and is pressurized by the piezoelectric element 5.

[0039] The nozzle plate 11, flow path substrate 13, and pressure chamber substrate 14 are each manufactured by processing a single-crystal silicon substrate, for example, by using dry etching or wet etching. However, other known methods may also be used to manufacture the nozzle plate 11, flow path substrate 13, and pressure chamber substrate 14.

[0040] A vibrating plate 15 is disposed on the Z1-oriented surface of the pressure chamber substrate 14. The vibrating plate 15 is a plate-shaped member capable of elastic vibration.

[0041] A plurality of piezoelectric elements 5, corresponding to nozzle N, are arranged on the Z1-facing surface of the vibrating plate 15. Viewed from above, each piezoelectric element 5 appears as an elongated strip extending along the X-axis. The plurality of piezoelectric elements 5 correspond to a plurality of pressure chambers C and are arranged along the Y-axis. The piezoelectric elements 5 deform upon the application of voltage. If the vibrating plate 15 vibrates in conjunction with this deformation, the pressure in the pressure chambers C changes, thereby ejecting ink from nozzle N.

[0042] The housing 17 is a casing for storing ink supplied to the multiple pressure chambers C. For example... Figure 3As shown, a space Rb is formed in the housing portion 17. The space Rb in the housing portion 17 is interconnected with the space Ra in the flow path substrate 13. The space formed by the space Ra and the space Rb functions as a reservoir, i.e., a liquid storage chamber R, for storing ink supplied to the multiple pressure chambers C. Ink is supplied to the liquid storage chamber R through the inlet 171 formed in the housing portion 17. The ink in the liquid storage chamber R is supplied to the pressure chambers C through the supply liquid chamber 133 and each supply flow path 131.

[0043] The damper 12 is a flexible membrane that forms the wall of the liquid storage chamber R. The damper 12 is a plastic substrate that absorbs pressure fluctuations of the ink in the liquid storage chamber R.

[0044] The wiring substrate 16 is a plate-shaped member having wiring formed for electrically connecting the drive circuit 20 to the plurality of piezoelectric elements 5. The Z2-facing surface of the wiring substrate 16 is engaged with the vibrating plate 15 via a plurality of conductive bumps 16B. On the other hand, the drive circuit 20 is mounted on the Z1-facing surface of the wiring substrate 16. The drive circuit 20 is an IC (Integrated Circuit) chip that outputs the drive voltage Com for driving each piezoelectric element 5 and the reference voltage VBS.

[0045] like Figure 2 As shown, the end of the external wiring 21 is bonded to the Z1-oriented surface of the wiring substrate 16. The external wiring 21 is composed of connecting components such as FPC (Flexible Printed Circuits) or FFC (Flexible Flat Cable). The wiring substrate 16 has a plurality of wirings 22 that electrically connect the external wiring 21 to the drive circuit 20, and a plurality of wirings 23 that are supplied with the drive voltage Com and the reference voltage VBS output from the drive circuit 20.

[0046] In addition, the wiring substrate 16 is not limited to a rigid substrate; for example, it can also be an FPC (Flexible Printed Circuits) or an FFC (Flexible Flat Cable). In this case, the wiring substrate 16 can also serve as an external wiring 21.

[0047] In such a liquid ejector head 1, if the piezoelectric element 5 flexes due to the application of voltage, the vibrating plate 15 flexes and vibrates in the direction that reduces the volume of the pressure chamber C. As a result, the pressure in the pressure chamber C changes, and the ink in the pressure chamber C is ejected from the nozzle N. Furthermore, after the ink is ejected, the piezoelectric element 5 returns to its original position.

[0048] As described above, such a liquid ejector head 1 includes: a piezoelectric element 5; a pressure chamber C in which ink, as a liquid, flows and is pressurized by the piezoelectric element 5; and a nozzle N that ejects the ink by the pressure applied by the pressure chamber C. According to such a liquid ejector head 1, because it includes the piezoelectric element 5 with the features described later, it is possible to suppress the generation of cracks in the piezoelectric layer 53 caused by sudden overcurrent and to suppress the generation of drive delay.

[0049] In addition, the liquid ejector head 1 has Figure 3 All of the elements shown are present, but the structural elements of the liquid nozzle 1 may not have all of these elements, or may have additional elements.

[0050] 1-3. Vibrating plate 15 and piezoelectric element 5

[0051] Figure 4 It means Figure 3 A cross-sectional view of the vibrating plate 15 and the piezoelectric element 5. Figure 4 In the example shown, the vibrating plate 15 is composed of a laminate including a first vibrating body layer 151 and a second vibrating body layer 152. The first vibrating body layer 151 is in contact with the pressure chamber substrate 14. The second vibrating body layer 152 is disposed above the first vibrating body layer 151. The first vibrating body layer 151 is made of silicon oxide (SiO2). x The second vibrating body layer 152 is made of elastic materials such as zirconium oxide (ZrO2). x The first vibrating body layer 151 is formed, for example, by thermal oxidation of a portion of the pressure chamber substrate 14. The second vibrating body layer 152 is formed, for example, by a known film-forming technique such as sputtering. Furthermore, the vibrating plate 15 may consist of one layer or three or more layers. Figure 4 The diagram shows the neutral axis A1 of the vibrating plate 15.

[0052] A piezoelectric element 5 is disposed on the vibrating plate 15. The piezoelectric element 5 mainly comprises a lower electrode 51, a piezoelectric layer 53, an upper electrode 52, and a seed layer 54. The piezoelectric layer 53 includes a lower piezoelectric element 531 and an upper piezoelectric element 532. The lower electrode 51, seed layer 54, lower piezoelectric element 531, upper piezoelectric element 532, and upper electrode 52 are disposed sequentially in the Z2 direction, which is the stacking direction.

[0053] The lower electrode 51 is disposed above the vibrating plate 15. The lower electrode 51 is an independent electrode disposed for each piezoelectric element 5. A driving voltage Com, which varies with voltage, is applied to the lower electrode 51. The lower electrode 51 is elongated along the X-axis. Multiple lower electrodes 51 are spaced apart from each other and arranged along the Y-axis. The lower electrode 51 may contain a conductive material such as platinum (Pt). The thickness of the lower electrode 51 along the Z-axis is not particularly limited, but is, for example, 50 nm or more and 120 nm or less. Furthermore, the lower electrode 51 may be composed of a single layer or multiple layers.

[0054] The seed layer 54 is provided to control the orientation of the piezoelectric layer 53. The thickness of the seed layer 54 along the Z-axis is thinner than the thickness of the piezoelectric layer 53 along the Z-axis. The thickness of the seed layer 54 along the Z-axis is not particularly limited, but is, for example, 5 nm or more and 50 nm or less. Furthermore, the seed layer 54 may be composed of a single layer or multiple layers.

[0055] For example, seed layer 54 has a perovskite structure. Seed layer 54, for example, contains lead titanate (Pb). a Ti b O z Lanthanum nickelate (La) a Ni b O z Pb x Bi （a-x） Fe y Ti （b-y） O z Bi a Fe y Ti （b-y） O z or Pb a Fe y Ti （b-y） O z In the above chemical formula, 0 < x < a and 0 < y < b must be satisfied. Furthermore, the seed layer 54 may also comprise a composite oxide having a perovskite structure containing Bi, Fe, and Ti. In particular, it is preferable that the seed layer 54 contains Pb. x Bi （a-x） Fe y Ti （b-y） O z Pb x Bi （a-x） Fe y Ti （b-y） O z Due to its excellent orientation control, it is a preferred choice.

[0056] The piezoelectric layer 53 is, for example, a strip-shaped dielectric film that extends continuously along the Y-axis over a plurality of piezoelectric elements 5. The piezoelectric layer 53 is, for example, a strip extending along the Y-axis and separated for each piezoelectric element 5 by forming a plurality of slits. The thickness of the piezoelectric layer 53 along the Z-axis is not particularly limited, for example, it is 300 nm or more and 1500 nm or less.

[0057] The upper electrode 52 is disposed above the piezoelectric layer 53. The upper electrode 52 is a strip-shaped common electrode extending continuously along the Y-axis in a manner that covers multiple piezoelectric elements 5. A predetermined reference voltage VBS is applied to the upper electrode 52. The upper electrode 52 may contain a conductive material such as iridium (Ir). The thickness of the upper electrode 52 along the Z-axis is not particularly limited, but is, for example, 50 nm or more and 120 nm or less. Furthermore, the upper electrode 52 may be composed of a single layer or multiple layers.

[0058] Such a piezoelectric element 5 applies a voltage equivalent to the difference between the reference voltage VBS applied to the upper electrode 52 and the driving voltage Com corresponding to the amount of ejection supplied to the lower electrode 51 to the piezoelectric layer 53. By applying a voltage between the lower electrode 51 and the upper electrode 52, the piezoelectric layer 53 is deformed, thereby causing the piezoelectric element 5 to flex and vibrate.

[0059] In addition, in this embodiment, the lower electrode 51 is an independent electrode and the upper electrode 52 is a shared electrode, but it is also possible that the lower electrode 51 is a shared electrode and the upper electrode 52 is an independent electrode.

[0060] 1-4. Piezoelectric layer 53

[0061] The piezoelectric layer 53 is, for example, composed of multiple layers. Specifically, as described above, the piezoelectric layer 53 is composed of a lower piezoelectric element 531 and an upper piezoelectric element 532.

[0062] Furthermore, the lower piezoelectric element 531 can be composed of a single layer or multiple layers. Similarly, the upper piezoelectric element 532 can also be composed of a single layer or multiple layers. However, as described later... Figure 7 As shown, the lower piezoelectric element 531 is made of a single material, and the upper piezoelectric element 532 is also made of a single material.

[0063] Furthermore, the lower piezoelectric body 531 contains K, Na, and Nb. Similarly, the upper piezoelectric body 532 contains K, Na, and Nb. Specifically, both the lower piezoelectric body 531 and the upper piezoelectric body 532 have a perovskite structure containing K and Na at site A and Nb at site B. Specifically, both the lower piezoelectric body 531 and the upper piezoelectric body 532 contain potassium sodium niobate (K... a Na 1-a (NbO3). (K)a Na 1-a NbO3 has a perovskite structure represented by the general formula ABO3, abbreviated as KNN.

[0064] The lower piezoelectric body 531 and the upper piezoelectric body 532 are each manufactured, for example, by MOD (Modulation of Dioxide), sol-gel, or sputtering. For example, the upper piezoelectric body 532 is manufactured by sputtering using a metal complex containing K, Na, and Nb, while the lower piezoelectric body 531 is manufactured by sol-gel. The sol-gel method involves coating a precursor solution composed of a sol onto a lower layer to form a piezoelectric precursor film, followed by drying and degreasing at a specified temperature. Similarly, the MOD method involves coating a MOD solution onto a lower layer, drying, and degreasing. When forming the piezoelectric layer using the sol-gel method, a precursor solution containing K, Na, and Nb compounds is coated onto a substrate, followed by drying and calcination at a specified temperature to obtain a perovskite structure. In this case, the ratio of K to Na is controlled during the solution preparation stage before coating and calcination, corresponding to the target composition of the resulting layer. Slight deviations occurring after heat treatment are acceptable within typical process tolerances. This invention is not limited to the sol-gel method; the concept of proportion control described above also applies to other solution processes such as the MOD method.

[0065] As described above, this piezoelectric layer 53 is composed of a lower piezoelectric element 531 and an upper piezoelectric element 532. Therefore, compared to the case where the piezoelectric layer 53 is composed of a single piezoelectric element, the displacement characteristics of the piezoelectric layer 53 can be improved.

[0066] Furthermore, in this piezoelectric layer 53, when the piezoelectric layer 53 expands and contracts for liquid ejection, the neutral axis A1 shifts upward. Accompanying this shift of the neutral axis A1, the displacement of both the lower piezoelectric element 531 and the upper piezoelectric element 532 decreases relative to the ideal value within the high voltage range. In the lower piezoelectric element 531, which is closer to the neutral axis A1, a significant reduction in displacement occurs within this high voltage range.

[0067] However, if an unexpected overcurrent is suddenly applied to the piezoelectric layer 53, it may exceed the upper limit of the piezoelectric layer 53's displacement and cause cracks. To address this phenomenon, the aforementioned displacement reduction within the high-voltage range is more effective. This is because, by offsetting the neutral axis A1, the displacement characteristic remains unchanged up to the medium-voltage range, while displacement can be selectively reduced within the high-voltage range. To achieve this effect efficiently, it is preferable to increase the piezoelectric constant of the lower piezoelectric element 531. Therefore, it is preferable to increase the saturation polarization Pm of the lower piezoelectric element 531.

[0068] The upper piezoelectric element 532 contributes less to the overcurrent suppression effect described above than the lower piezoelectric element 531. Nevertheless, the overcurrent suppression effect described above can also be achieved using the upper piezoelectric element 532. From this perspective, it is advisable to increase the saturation polarization Pm of the lower piezoelectric element 531 to the same value as that of the upper piezoelectric element 532. However, the lower piezoelectric element 531 and the upper piezoelectric element 532 are connected in series. Therefore, if the saturation polarization Pm of both the lower and upper piezoelectric elements 531 and 532 are increased, the local electrostatic capacitance may increase. As a result, this may hinder high-frequency driving and cause driving delay.

[0069] Given this situation, in order to achieve both overcurrent suppression and reduction of drive delay in high-frequency driving, it is necessary to control the saturation polarization in both the lower piezoelectric element 531 and the upper piezoelectric element 532. As a result of the inventors' in-depth research, it has been found that by setting the K / Na ratio in the lower piezoelectric element 531 and the upper piezoelectric element 532 respectively, the saturation polarization can be controlled.

[0070] Specifically, the average concentration of potassium (K) in the lower piezoelectric element 531 is set as K1 [mol%], the average concentration of sodium (Na) in the lower piezoelectric element 531 is set as Na1 [mol%], the average concentration of potassium (K) in the upper piezoelectric element 532 is set as K2 [mol%], and the average concentration of sodium (Na) in the upper piezoelectric element 532 is set as Na2 [mol%]. In this case, the average concentrations K1, K2, Na1, and Na2 satisfy the following relationship.

[0071] K1 / (K1+Na1)>K2 / (K2+Na2)

[0072] In other words, the K content at site A in the lower piezoelectric body 531 is greater than the K content at site A in the upper piezoelectric body 532.

[0073] By satisfying the above relationship with average concentrations K1, K2, Na1, and Na2, the saturation polarization Pm of the lower piezoelectric 531 can be made larger than that of the upper piezoelectric 532. Therefore, since the saturation polarization Pm of the lower piezoelectric 531 is larger, the piezoelectric constant of the lower piezoelectric 531 can be increased. Thus, the displacement of the piezoelectric layer 53 can be reduced in the high-voltage range, thereby suppressing concerns about cracks arising from unexpected sudden overcurrent applications to the piezoelectric layer 53. Furthermore, since the saturation polarization Pm of the lower piezoelectric 531 can be made larger than that of the upper piezoelectric 532, the local increase in electrostatic capacitance caused by the equal increase of saturation polarization Pm in both the lower and upper piezoelectric 531 can be suppressed. Because of this, concerns about cracks arising from sudden overcurrent applications can be suppressed, and the generation of drive delay in high-frequency drive can be reduced.

[0074] Figure 5 This is a graph representing hysteresis loops. Figure 5 The diagram shows four types of hysteresis loops: A1 (first example), A2 (second example), A3 (third example), and A4 (fourth example). Figure 5 The horizontal axis represents the electric field strength [V / μm], and the vertical axis represents the polarizability [μC / cm]. 2 The portion with the largest electric field intensity in each hysteresis loop corresponds to positive saturation polarization + Pm. Figure 5 In the example, the positive saturation polarizations +Pm of the first example A1, the second example A2, the third example A3, and the fourth example A4 are described as positive saturation polarizations +Pm1, +Pm2, +Pm3, and +Pm4.

[0075] Both Example A1 and Example A2 are monolayer piezoelectric bodies composed of KNN. Specifically, in the monolayer piezoelectric body of Example A1, K is 65 mol% and Na is 35 mol%. That is, the monolayer piezoelectric body of Example A1 is composed of a K-rich piezoelectric body with a higher ratio of K to Na. For the monolayer piezoelectric body of Example A2, K is 35 mol% and Na is 65 mol%. That is, the monolayer piezoelectric body of Example A2 is composed of a Na-rich piezoelectric body with a higher ratio of Na to K.

[0076] As can be seen from the comparison between the first example A1 and the second example A2, the positive saturation polarization +Pm1 of the first example A1 is higher than that of the second example A2. Therefore, it can be concluded that piezoelectric materials enriched in K can improve the positive saturation polarization +Pm compared to piezoelectric materials enriched in Na.

[0077] The third example, A3, is a piezoelectric layer 53x comprising a lower piezoelectric layer and an upper piezoelectric layer. In both the lower and upper piezoelectric layers of the third example A3, K content is 65 mol% and Na content is 35 mol%. Therefore, the piezoelectric layer 53x of the third example A3 is composed of a stack of two K-enriched piezoelectric layers. Furthermore, the K content is the same in both the lower and upper piezoelectric layers of the third example A3.

[0078] Example A4 is a piezoelectric layer 53 comprising a lower piezoelectric body 531 and an upper piezoelectric body 532. In the upper piezoelectric body 532 of Example A4, K is 35 mol% and Na is 65 mol%. In the lower piezoelectric body 531 of Example A4, K is 65 mol% and Na is 35 mol%. Therefore, in the piezoelectric layer 53 of Example A4, the K content in the lower piezoelectric body 531 is greater than the K content in the upper piezoelectric body 532. Furthermore, in Example A4, the upper piezoelectric body 532 is composed of a Na-enriched piezoelectric body, and the lower piezoelectric body 531 is composed of a K-enriched piezoelectric body.

[0079] The positive saturation polarization +Pm3 of the third example A3 and the positive saturation polarization +Pm4 of the fourth example A4 are higher than the positive saturation polarization +Pm1 of the first example A1 and the positive saturation polarization +Pm2 of the second example A2, respectively. Therefore, the positive saturation polarization +Pm can be improved by using a KNN piezoelectric stack compared to a single layer of KNN piezoelectric. In particular, the positive saturation polarization +Pm of the third example A3 is the highest among the four examples. In other words, since it is a multilayer stack of K-enriched piezoelectrics, the positive saturation polarization +Pm can be particularly improved. On the other hand, although the positive saturation polarization +Pm4 of the fourth example A4 is higher than the positive saturation polarization +Pm1 of the first example A11 and the positive saturation polarization +Pm2 of the second example A2, it is lower than the positive saturation polarization +Pm3 of the third example A3.

[0080] Furthermore, the positive saturation polarization +Pm of the fourth example A4 is lower than that of the third example A3 but higher than that of the first example A1. In other words, in the stack of upper layers and lower layers with higher K content, although the positive saturation polarization +Pm is lower than that of multilayer stacks with K enrichment, it can be increased compared to a single layer with K enrichment.

[0081] Figure 6 It means targeting Figure 5 The graph shows the relationship between electric field strength and electrostatic capacitance for the third example A3 and the fourth example A4. Figure 6 The horizontal axis represents the electric field strength [V / μm], and the vertical axis represents the electrostatic capacitance [μF].

[0082] like Figure 6As shown in the third example A3, the electrostatic capacitance locally increases in region X0. Similar to the third example A3, if both the saturation polarizations +Pm of the lower piezoelectric element 531 and the upper piezoelectric element 532 are increased, the electrostatic capacitance will locally increase. Therefore, this hinders high-frequency driving and may cause driving delays.

[0083] In contrast, in the fourth example A4, no local increase in electrostatic capacitance as seen in the third example A3 was observed in region X0. In other words, by increasing the K content in the upper piezoelectric 532 to be greater than the K content in the lower piezoelectric 531, as in the fourth example A4, concerns about the generation of driving delay can be suppressed compared to multilayered stacks with K-rich layers as in the third example A3.

[0084] As from Figure 5 as well as Figure 6 As is known, by increasing the K content in the lower piezoelectric body 531 compared to the K content in the upper piezoelectric body 532, the generation of driving delay can be suppressed compared to a multilayer stack with K-enriched layers. In other words, by ensuring that the average concentrations K1, K2, Na1, and Na2 satisfy the relationship K1 / (K1+Na1) > K2 / (K2+Na2), driving delay can be suppressed in high-frequency driving.

[0085] Furthermore, preferably, as in Example A4, the upper piezoelectric element 532 is a Na-rich layer, and the lower piezoelectric element 531 is a K-rich layer. In other words, it is preferable that the average concentrations K1, K2, Na1, and Na2 satisfy the relationship K1 / (K1+Na1) > 0.50 > K2 / (K2+Na2). By ensuring that the average concentrations K1, K2, Na1, and Na2 satisfy the above relationship, compared to cases where this relationship is not satisfied, it is possible to effectively suppress both the generation of cracks caused by the sudden application of overcurrent and the generation of driving delay.

[0086] Furthermore, if the average concentrations K1, K2, Na1, and Na2 satisfy the relationship K1 / (K1+Na1) > 0.50 > K2 / (K2+Na2), then the lower piezoelectric body 531 may not be a K-rich layer. Similarly, the upper piezoelectric body 532 may not be a Na-rich layer.

[0087] Furthermore, it is preferable that the average concentrations K1, K2, Na1, and Na2 satisfy 0.20 ≤ K1 / (K1 + Na1) - K2 / (K2 + Na2) ≤ 0.40. Furthermore, it is preferable that the average concentrations K1 and Na1 of the lower piezoelectric element 531 satisfy K1 / (K1 + Na1) ≥ 0.60. Furthermore, it is preferable that the average concentrations K1 and Na1 of the lower piezoelectric element 531 satisfy K1 / (K1 + Na1) ≤ 0.70. Furthermore, it is preferable that the average concentrations K2 and Na2 of the upper piezoelectric element 532 satisfy K2 / (K2 + Na2) ≤ 0.40. Furthermore, it is preferable that the average concentrations K2 and Na2 of the upper piezoelectric element 532 satisfy K2 / (K2 + Na2) ≥ 0.30. The reasons for these will be explained later.

[0088] Furthermore, as mentioned above, by ensuring that the average concentrations K1, K2, Na1, and Na2 satisfy the relationship K1 / (K1+Na1) > K2 / (K2+Na2), the saturation polarization Pm of the lower piezoelectric body 531 can be made larger than that of the upper piezoelectric body 532. That is, the saturation polarization Pm of the upper piezoelectric body 532 can be made smaller than that of the lower piezoelectric body 531. Therefore, it is possible to effectively suppress both the generation of cracks caused by the sudden application of overcurrent and the generation of driving delay.

[0089] For example, the preferred positive saturation polarization +Pm in the upper piezoelectric element 532 is 15.5 [μC / cm]. 2 [The following is a continuation of the previous sentence.] By setting the positive saturation polarization +Pm in the lower piezoelectric element 531 to a value below the aforementioned value, compared to cases where the value exceeds the aforementioned value, it is possible to effectively reduce the generation of the driving delay of the piezoelectric element 5.

[0090] For example, the preferred positive saturation polarization +Pm in the lower piezoelectric element 531 is 19.5 [μC / cm]. 2 [Above.] By making the positive saturation polarization +Pm in the lower piezoelectric element 531 equal to or greater than the aforementioned value, the piezoelectric constant of the lower piezoelectric element 531 can be increased compared to the case where the value is less than the aforementioned value. Therefore, the displacement of the piezoelectric layer 53 can be reduced in the high voltage range, and thus, concerns about cracks arising from the sudden application of an unexpected overcurrent to the piezoelectric layer 53 can be effectively suppressed.

[0091] Furthermore, the positive saturation polarization +Pm in the upper piezoelectric element 532 can also exceed 15.5 [μC / cm]. 2 Furthermore, the positive saturation polarization +Pm in the lower piezoelectric element 531 can also be less than 19.5 [μC / cm]. 2 ] .

[0092] Furthermore, when the average concentration of Nb in the lower piezoelectric body 531 is set as Nb1 and the average concentration of Nb in the upper piezoelectric body 532 is set as Nb2, the average concentrations K1, K2, Na1, Na2, Nb1, and Nb2 preferably satisfy the following relationship.

[0093] 0.90<{Nb2 / (K2+Na2+Nb2)} / {Nb1 / (K1+Na1+Nb1)}<1.10

[0094] The average concentrations K1, K2, Na1, Na2, Nb1, and Nb2 satisfying the above relationship means that the Nb at site B is almost identical in the lower piezoelectric body 531 and the upper piezoelectric body 532. If the difference between the Nb in the lower piezoelectric body 531 and the upper piezoelectric body 532 is too large, it may lead to the separation of the lower piezoelectric body 531 from the upper piezoelectric body 532.

[0095] Furthermore, it is preferable that the thickness of the upper piezoelectric element 532 is greater than the thickness of the lower piezoelectric element 531. These thicknesses are the lengths along the stacking direction, i.e., the Z2 direction. The displacement characteristics of the upper piezoelectric element 532 are significantly related to the displacement characteristics of the piezoelectric element 5. Therefore, by making the thickness of the upper piezoelectric element 532 greater than the thickness of the lower piezoelectric element 531, the displacement characteristics of the piezoelectric element 5 can be improved compared to the case where the thickness of the upper piezoelectric element 532 is less than the thickness of the lower piezoelectric element 531.

[0096] In addition, the thickness of the upper piezoelectric element 532 can be less than or equal to the thickness of the lower piezoelectric element 531.

[0097] Hereinafter, an example of a piezoelectric layer 53 will be described with reference to embodiments and comparative examples.

[0098] Figure 7 This is a table showing the relationship between the K content and positive saturation polarization + Pm. Figure 8 This is a coordinate graph showing the relationship between the K content and positive saturation polarization + Pm. Figure 9 This is a table representing an embodiment. Figure 10 This is a table representing comparative examples. Figure 9 Implementation examples and Figure 10 The lower piezoelectric element and the upper piezoelectric element in the comparative example use Figure 7 The 13 types of KNN piezoelectrics shown are No.1 to No.13.

[0099] Figure 7In this paper, for 13 KNN piezoelectric materials No. 1 to No. 13, the average concentrations of K, Na, and K, K / (K + Na), and the positive saturation polarization + Pm are shown. These 13 KNN piezoelectric materials No. 1 to No. 13 are monolayers. Furthermore, although these 13 KNN piezoelectric materials No. 1 to No. 13 are monolayers, even when constructed from multilayers using the same manufacturing method and composition, they exhibit properties similar to... Figure 7 The values ​​shown show a nearly identical trend.

[0100] For numbers 1 through 6, the average concentration of K is greater than the average concentration of Na. Number 1 has the highest average K concentration, decreasing in the order of No. 1 through No. 6. The average K concentration of No. 7 is equal to the average Na concentration. The average K concentration of numbers 8 through No. 13 is less than the average Na concentration. Number 13 has the lowest average K concentration, decreasing in the order of No. 8 through No. 13.

[0101] Figure 8 Show Figure 7 The relationship between the K content of No.1 to No.13 and positive saturation polarization + Pm. Figure 8 The horizontal axis is K / (K+Na), and the vertical axis is positive saturation polarization + Pm. For example, Figure 8 The rightmost label is No.1. Figure 8 The leftmost label is No. 13.

[0102] like Figure 7 as well as Figure 8 As shown, No. 1 to No. 6 have a larger positive saturation polarization +Pm than No. 8 to No. 13. By increasing the content of K, the positive saturation polarization +Pm can be increased, thus increasing the piezoelectric constant and improving the displacement characteristics.

[0103] like Figure 9 as well as Figure 10 As shown, in the piezoelectric layers of the embodiments and comparative examples, for both the upper and lower piezoelectric elements, [the following methods were used]. Figure 7 KNN piezoelectrics of any one of No.1 to No.13.

[0104] For example, in Example 1, the lower piezoelectric element used was No. 2, and the upper piezoelectric element used was No. 10. In other words, in the lower piezoelectric element of Example 1, the average concentration of K1 was 70 mol%, and the average concentration of Na1 was 30 mol%. In the upper piezoelectric element of Example 1, the average concentration of K2 was 40 mol%, and the average concentration of Na1 was 60 mol%. Therefore, in Example 1, the K content in the lower piezoelectric element was higher than that in the upper piezoelectric element.

[0105] Similar to Example 1, in each of Examples 2-30, the content of K in the lower piezoelectric body is higher than the content of K in the upper piezoelectric body. In other words, in each of Examples 1-30, the condition K1 / (K1+Na1) > K2 / (K2+Na2) is satisfied. On the other hand, in each of Comparative Examples 1-30, the content of K in the upper piezoelectric body is lower than the content of K in the lower piezoelectric body. In other words, in each of Comparative Examples 1-21, the condition K1 / (K1+Na1) > K2 / (K2+Na2) is not satisfied.

[0106] In Examples 1-32, the saturation polarization Pm of the upper piezoelectric is smaller than that of the lower piezoelectric. According to each example, it is possible to effectively suppress both the generation of cracks caused by sudden overcurrent application and the generation of drive delay.

[0107] Furthermore, the lower electrode has the same structure in both the embodiments and comparative examples. Similarly, the upper electrode has the same structure in both embodiments and comparative examples. Additionally, the thickness of the upper piezoelectric element is the same in both embodiments and comparative examples. The thickness of the lower piezoelectric element is the same in both embodiments and comparative examples.

[0108] exist Figure 8 as well as Figure 9 The table shows the evaluation results related to delay suppression and displacement.

[0109] <Evaluation Methods for Drive Latency>

[0110] An evaluation related to drive delay suppression was conducted based on the inhomogeneity of the image when the piezoelectric element was driven at a specified drive frequency. In this evaluation, for example, the specified drive frequency was 60 kHz. The evaluation was carried out in three stages: A, B, and C.

[0111] A: When driven at a frequency of 60kHz, the image formed by one scan shows almost no inhomogeneity.

[0112] B: When driven at 60kHz, the image formed by one scan shows slight inhomogeneity in the scanning direction.

[0113] C: In the image formed by one scan when driven at 60kHz, non-uniformity is frequently seen in the scanning direction.

[0114] If there is a drive delay, the ejection time point is delayed. As a result, the dots formed on the medium deviate from their ideal landing positions to positions downstream in the scanning direction. When the intention is to eject all dots in the scanning direction at equal intervals, such a deviation in landing positions is identified as image inhomogeneity.

[0115] <Evaluation Methods for Overcurrent>

[0116] Overcurrent was evaluated based on the degree of damage to the piezoelectric element caused by continuous ejection up to the ideal durability ejection count. The ideal durability ejection count is the number of ink ejected from each nozzle that should be able to compensate for performance issues. In this evaluation, for example, the ideal durability ejection count is 100 billion ejections.

[0117] A: Almost no damage to the piezoelectric elements can be seen up to the ideal durability spray count.

[0118] B: Damage to the piezoelectric element is observed at approximately 80% to 90% of the ideal durability spray count.

[0119] C: Damage is observed in piezoelectric elements when the number of sprays is below 80% of the ideal durability spray number.

[0120] The more jets, the greater the cumulative damage to the piezoelectric layer due to overcurrent. As a result, the durability of the piezoelectric layer decreases, thus damaging the piezoelectric element.

[0121] As from Figure 9 as well as Figure 10 As can be seen, when comparing Examples 1-32 with Comparative Examples 1-21, Examples 1-32 are superior in terms of evaluations related to delay suppression and overcurrent suppression. Therefore, it can be concluded that by satisfying K1 / (K1+Na1) > K2 / (K2+Na2), it is possible to achieve both suppression of overcurrent generation and reduction of drive delay in high-frequency driving.

[0122] In particular, in Examples 1-17, 24, 29, and 30, the lower piezoelectric body is a K-rich layer, and the upper piezoelectric body is a Na-rich layer. In other words, in Examples 1-17, 24, 29, and 30, the average concentrations K1, K2, Na1, and Na2 satisfy the following relationship (Equation 1).

[0123] (Equation 1) K1 / (K1+Na1)>0.50>K2 / (K2+Na2)

[0124] In Examples 1-17, 24, 29-32, the evaluation related to delay characteristics is A, and almost no inhomogeneity is produced in the image.

[0125] Based on this, in Examples 1-17, 24, 29, and 30, the evaluation related to overcurrent suppression was A or B, meaning no damage was observed in the piezoelectric element up to the ideal durability spray number, or even if damage was observed, it was below 80% of the ideal durability spray number. Thus, in Examples 1-17, 24, and 29-32, there was no suppression of the generation of drive delay, and the generation of cracks caused by the sudden application of overcurrent was suppressed to an acceptable range.

[0126] In addition, it is preferable that the difference in the K content at site A between the upper and lower piezoelectric bodies, i.e., K1 / (K1+Na1)-K2 / (K2+Na2), is not too large. This is because if the difference is too large, the saturation polarization Pm between the upper and lower piezoelectric bodies will be significantly different, thus increasing the difference in the degree of deformation and potentially causing a divergence between the upper and lower piezoelectric bodies. Specifically, it is preferable to satisfy the following (Equation 2).

[0127] (Equation 2) K1 / (K1+Na1)-K2 / (K2+Na2)≤0.40

[0128] On the other hand, it is also undesirable for the difference in the K content at site A to be too small. A small difference means that the composition ratio at site A between the upper and lower piezoelectric bodies does not change significantly. Since the upper and lower piezoelectric bodies are stacked components, and the composition at site A is shared by K and Na, even if the compositional relationships are different, the compositional ratio may flatten due to element movement between the piezoelectric bodies over time. If the difference in the K content at site A is too small, even if initial drive delay and crack formation can be suppressed, the influence of element movement cannot be sufficiently eliminated, potentially leading to problems after prolonged use. Specifically, it is preferable to satisfy the following (Equation 3).

[0129] (Equation 3) 0.20≤K1 / (K1+Na1)-K2 / (K2+Na2)

[0130] If we summarize them, the difference in the content of K at site A is neither too large nor too small. That is, summarizing (Equation 2) and (Equation 3), the following (Equation 4) is preferred.

[0131] (Equation 4) 0.20≤K1 / (K1+Na1)-K2 / (K2+Na2)≤0.40

[0132] Examples 1-11, 13, 15, 29, and 30 satisfy Equation 4. These examples do not cause separation between piezoelectric layers or problems associated with long-term use. On the other hand, for example, in Examples 31 and 32, K1 / (K1+Na1)-K2 / (K2+Na2) > 0.40, therefore, separation sometimes occurs between the upper and lower piezoelectric layers. Furthermore, for example, in Examples 12, 14, and 16-28, K1 / (K1+Na1)-K2 / (K2+Na2) < 0.20, therefore, drive delay and displacement degradation sometimes occur due to long-term use.

[0133] Here, it can be seen that in order to satisfy both (Equation 1) and (Equation 3), K1 / (K1+Na1) and K2 / (K2+Na2) need to exceed the range of ±0.10 with 0.50 as the boundary. Specifically, it is preferable to satisfy (Equation 5) and (Equation 6).

[0134] (Formula 5) K1 / (K1+Na1)≥0.60

[0135] (Equation 6) K2 / (K2+Na2)≤0.40

[0136] Examples 1-13, 18-20, and 29-32 satisfy (Equation 5). Furthermore, Examples 1-9, 14-17, 21-23, and 29-32 satisfy (Equation 6).

[0137] Based on this, it can be seen that in order to satisfy both (Equation 1) and (Equation 2), K1 / (K1+Na1) and K2 / (K2+Na2) should be controlled within the range of ±0.20 with 0.50 as the boundary. Specifically, it is preferable to satisfy (Equation 7) in addition to (Equation 5), and (Equation 8) in addition to (Equation 6).

[0138] (Formula 7) K1 / (K1+Na1)≤0.70

[0139] (Equation 8) K2 / (K2+Na2)≥0.30

[0140] Examples 1-13, 18-20, and 30-32 satisfy (Equation 5) and (Equation 7). In addition, Examples 1-9, 14-17, 21-23, 29, and 31-32 satisfy (Equation 6) and (Equation 8).

[0141] As mentioned above, the present invention requires that K1 / (K1+Na1) > K2 / (K2+Na2), but as can be summarized from (Equations 1) to (Equations 8), it is more preferable to satisfy 0.60≤K1 / (K1+Na1)≤0.70 and 0.30≤K2 / (K2+Na2)≤0.40. Examples 1 to 9 satisfy this equation.

[0142] Furthermore, if the Nb values ​​at site B differ significantly between the upper and lower piezoelectric bodies as described above, a divergence occurs between the piezoelectric bodies. Therefore, in Examples 1-32, the two values ​​are almost equal. Specifically, 0.90 < {Nb2 / (K2+Na2+Nb2)} / {Nb1 / (K1+Na1+Nb1)} < 1.10.

[0143] 2. Variations

[0144] The embodiments illustrated above can be modified in various ways. The following examples illustrate specific modifications that can be applied to the aforementioned embodiments. Two or more methods selected from the following examples can be appropriately combined without contradiction.

[0145] A "liquid nozzle" can also be a circulating nozzle with a so-called circulating flow path.

[0146] Image forming apparatuses, besides being used in printing, can also be applied to various other equipment such as fax machines and copiers. Their applications are not limited to printing. For example, an image forming apparatus that sprays a solution of pigments is used in manufacturing apparatuses for color filters in display devices such as liquid crystal display panels. Furthermore, an image forming apparatus that sprays a solution of conductive materials is used in manufacturing apparatuses for wiring and electrodes in wiring substrates. Additionally, an image forming apparatus that sprays a solution of organic matter related to living organisms is used in manufacturing apparatuses, for example, for manufacturing biochips.

[0147] The piezoelectric element involved in this invention is not limited to liquid ejector heads or liquid ejection devices; it can be any device that generates mechanical force by applying voltage or generates voltage by applying mechanical force, and has the function of converting voltage and mechanical force. Examples of the piezoelectric elements involved in this invention include ultrasonic motors, vibration dust collectors, piezoelectric transformers, piezoelectric loudspeakers, piezoelectric pumps, ultrasonic detectors, angular velocity sensors, acceleration sensors, vibration sensors, tilt sensors, pressure sensors, collision sensors, human body sensors, infrared sensors, terahertz sensors, thermal detection sensors, pyroelectric sensors, piezoelectric sensors, ferroelectric RAMs (FeRAM), ferroelectric transistors (FeFETs), ferroelectric operational circuits (FeLogic), ferroelectric capacitors, wavelength converters, optical waveguides, optical modulators, refractive index control elements, electronic shutter mechanisms, etc.

[0148] The present invention has been described above based on preferred embodiments, but the present invention is not limited to the foregoing embodiments. Furthermore, the structure of each part of the present invention can be replaced with any structure that performs the same function as the foregoing embodiments, and any additional structure can be added.

Claims

1. A piezoelectric element, characterized in that, A lower electrode, a lower piezoelectric body containing K, Na, and Nb, an upper piezoelectric body containing K, Na, and Nb, and an upper electrode are arranged sequentially in the stacking direction. When the average concentration of K in the lower piezoelectric element is set as K1, the average concentration of Na in the lower piezoelectric element is set as Na1, the average concentration of K in the upper piezoelectric element is set as K2, and the average concentration of Na in the upper piezoelectric element is set as Na2, The condition K1 / (K1+Na1) > K2 / (K2+Na2) is satisfied.

2. The piezoelectric element according to claim 1, characterized in that, The condition K1 / (K1+Na1) > 0.50 > K2 / (K2+Na2) is satisfied.

3. The piezoelectric element according to claim 1, characterized in that, The condition 0.20 ≤ K1 / (K1 + Na1) - K2 / (K2 + Na2) ≤ 0.40 is satisfied.

4. The piezoelectric element according to claim 1, characterized in that, The condition K1 / (K1+Na1)≥0.60 is satisfied.

5. The piezoelectric element according to claim 3, characterized in that, The condition K1 / (K1+Na1)≤0.70 is satisfied.

6. The piezoelectric element according to claim 1, characterized in that, The condition K2 / (K2+Na2)≤0.40 is satisfied.

7. The piezoelectric element according to claim 5, characterized in that, The condition K2 / (K2+Na2)≥0.30 is satisfied.

8. The piezoelectric element according to claim 1, characterized in that, When the average Nb concentration in the lower piezoelectric element is set as Nb1 and the average Nb concentration in the upper piezoelectric element is set as Nb2, It satisfies 0.90 < {Nb2 / (K2+Na2+Nb2)} / {Nb1 / (K1+Na1+Nb1)} < 1.

10.

9. The piezoelectric element according to claim 1, characterized in that, The saturation polarization in the lower piezoelectric element is greater than that in the upper piezoelectric element.

10. The piezoelectric element according to claim 9, characterized in that, The saturation polarization in the upper piezoelectric element is 15.5 [μC / cm]. 2 ]the following.

11. The piezoelectric element according to claim 9, characterized in that, The saturation polarization in the lower piezoelectric element is 19.5 [μC / cm]. 2 ]above.

12. The piezoelectric element according to claim 1, characterized in that, The upper piezoelectric element is thicker than the lower piezoelectric element.

13. A liquid ejector head, characterized in that, have: The piezoelectric element according to claim 1; A pressure chamber, through which liquid flows, and through which pressure is applied to the liquid by the piezoelectric element; and The nozzle ejects liquid under pressure supplied by the pressure chamber.

14. A liquid ejection device, characterized in that, have: The liquid ejector head as claimed in claim 13; and The control unit controls the ejection action of the liquid ejected from the liquid nozzle.

Images