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 improve displacement properties and stability of displacement. The piezoelectric element is formed of 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 in this order. In each layer of the N layers of the upper piezoelectric body and the M layers of the lower piezoelectric body, the concentrations of K and Na respectively vary in a manner that has an extreme value in the interior of the layer. In each layer of the M layers, let the maximum value of the intensity of K be I1, the minimum value of the intensity of K be I2, the maximum value of the intensity of Na be I3, and the minimum value of the intensity of Na be I4. In each layer of the N layers, let the maximum value of the intensity of K be I5, the minimum value of the intensity of K be I6, the maximum value of the intensity of Na be I7, and the minimum value of the intensity of Na be I8. In a combination of a specific layer among the M layers and a specific layer among the N layers, (I5-I6) / (I1-I2) < 1.00 is satisfied, and (I7-I8) / (I3-I4) < 1.00 is satisfied.

Description

Technical Field

[0001] This invention relates to a piezoelectric element, a liquid ejector head, and a liquid ejection device. Background Technology

[0002] Previously, liquid ejection devices have been proposed that have liquid ejection heads that spray liquids such as ink onto media such as printing paper. As such liquid ejection heads, there are known heads that spray 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 Summary of the Invention

[0005] The displacement characteristics of KNN piezoelectric elements are smaller than those of PZT (lead zirconate titanate) piezoelectric elements, for example. 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 constructing a KNN piezoelectric element from a stack of two layers, an upper layer and a lower layer. In this case, the inventors have found that, compared to having the upper and lower layers of the same composition, setting the composition of the upper and lower layers separately yields a better effect.

[0006] The preferred embodiment of the present invention involves a piezoelectric element comprising a lower electrode, a lower piezoelectric body, an upper piezoelectric body, and an upper electrode arranged sequentially along a stacking direction. The lower piezoelectric body contains K, Na, and Nb and is composed of M (M≥1) layers. The upper piezoelectric body contains K, Na, and Nb and is composed of N (N≥1) layers. In each of the N-layer upper piezoelectric body and the M-layer lower piezoelectric body, the concentrations of K and Na vary along the stacking direction in such a way that they have extreme values ​​within the layer. In each of the M-layers, the intensity of K during SIMS measurement along the stacking direction is... The maximum value is I1, the minimum value of K intensity is I2, the maximum value of Na intensity is I3, and the minimum value of Na intensity is I4. In each of the N layers of the upper piezoelectric body, if the maximum value of K intensity is I5, the minimum value of K intensity is I6, the maximum value of Na intensity is I7, and the minimum value of Na intensity is I8 when performing SIMS measurement along the stacking direction, then in a specific combination of a specific layer in the M layer and a specific layer in the N layer, (I5-I6) / (I1-I2) < 1.00 and (I7-I8) / (I3-I4) < 1.00.

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

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

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

[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 is shown Figure 3 A diagram of the vibrating plate and piezoelectric elements.

[0013] Figure 5 yes Figure 4 A schematic diagram of the piezoelectric layer is shown.

[0014] Figure 6This is a diagram illustrating the SIMS data results of the first embodiment.

[0015] Figure 7 This is a diagram illustrating the SIMS data results of the second embodiment.

[0016] Figure 8 This is a graph illustrating the SIMS data results of the third embodiment.

[0017] Figure 9 This is a table showing the extreme values ​​of the lower piezoelectric element in the first embodiment.

[0018] Figure 10 This is a table showing the extreme values ​​of the upper piezoelectric element in the first embodiment.

[0019] Figure 11 This is a diagram showing (I5-I6) / (I1-I2) of the first embodiment.

[0020] Figure 12 This is a diagram showing (I7-I8) / (I3-I4) of the first embodiment.

[0021] Explanation of reference numerals in the attached figures

[0022] 1…Liquid ejector head, 5…Piezoelectric element, 11…Nozzle plate, 12…Vibration absorber, 13…Flow path substrate, 14…Pressure chamber substrate, 15…Vibrating plate, 51…Lower electrode, 52…Upper electrode, 53…Piezoelectric layer, 53a…Lower piezoelectric, 53b…Upper piezoelectric, 100…Liquid ejection device, 531…First layer, 532…Second layer, 533…Third layer, 534…Fourth layer, 535…Fifth layer, 536…Sixth layer, 537…Seventh layer, 538…Eighth layer, 539…Ninth layer, A1…Central shaft, C…Pressure chamber, I1…Maximum value, I2…Minimum value, I3…Maximum value, I4…Minimum value, I5…Maximum value, I6…Minimum value, I7…Maximum value, I8…Minimum value, N…Nozzle. Detailed Implementation

[0023] 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 slightly from actual dimensions, and some parts are shown schematically for ease of understanding. Furthermore, unless otherwise specified in the following description, the scope of the present invention is not limited to these embodiments. Additionally, the term "layering of elements α and β" simply means that elements α and β are arranged vertically, and whether elements α and β are in direct contact or not is not required.

[0024] The following explanation will use intersecting X, Y, and Z axes as appropriate. One direction along the X-axis will be called the X1 direction, and the opposite direction will be called the X2 direction. Opposite directions along the Y-axis will be called the Y1 and Y2 directions. Opposite directions along the Z-axis will be called the Z1 and Z2 directions. Viewing along the Z-axis is referred to as "top-down view." The Z-axis is typically a vertical axis. The Z1 direction is upward, and the Z2 direction is downward. However, the Z-axis may not be vertical. Furthermore, while the X, Y, and Z axes are typically orthogonal, this is not a limitation; for example, they may intersect at angles between 80° and 100°.

[0025] 1. First Implementation Method

[0026] 1-1. Overall structure of the liquid ejection device 100

[0027] 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. The medium M is typically printing paper. It should be noted that the medium M is not limited to printing paper, and can also be any printing material such as resin film or cloth.

[0028] like Figure 1 As shown, a liquid container 90 is installed in the liquid dispensing device 100, and the liquid container 90 stores ink. Specific examples of the liquid container 90 include: a removable ink cartridge from the liquid dispensing device 100, a bag-shaped ink pouch formed of a flexible membrane, and an ink canister capable of being refilled. It should be noted that the type of ink stored in the liquid container 90 is arbitrary. Furthermore, "liquid" can refer to any material that can be dispensed from the liquid dispensing device 100. For example, "liquid" can be a material containing solids within a liquid.

[0029] The liquid ejection device 100 includes a control unit 91, a conveying mechanism 92, a moving mechanism 93, and a liquid ejection head 1. For example, the control unit 91 includes processing circuitry such as a CPU (Central Processing Unit) or FPGA (Field Programmable Gate Array) and storage circuitry such as semiconductor memory, controlling the operation of various elements 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) in the liquid ejection head 1.

[0030] The conveying mechanism 92, under the control of the control unit 91, conveys the medium M along the Y2 direction. The moving mechanism 93, under the control of the control unit 91, causes the liquid nozzle 1 to reciprocate along the X1 and X2 directions. Figure 1 In the example shown, the moving mechanism 93 has a generally box-shaped conveyor body 931, called a carriage, that houses the liquid nozzle 1, and a conveyor belt 932 for fixing the conveyor body 931. It should be noted that the number of liquid nozzles 1 mounted on the conveyor body 931 is not limited to one, and can be multiple. Furthermore, in addition to the liquid nozzles 1, a liquid container 90 may also be mounted on the conveyor body 931.

[0031] 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. By causing the ejection and conveying mechanism 92 to perform reciprocating movements of the liquid ejector head 1 in parallel with the conveying and moving mechanism 93 of the medium M, an image is formed on the surface of the medium M by the ink.

[0032] The liquid ejection device 100 includes a liquid ejection head 1 (described later) and a control unit 91, which controls the ejection action from the liquid ejection head 1. Because the liquid ejection device 100 has the liquid ejection head 1 with the features described later, the displacement capability and displacement stability of the piezoelectric element 5 are improved. Therefore, a liquid ejection device 100 with excellent ejection performance can be provided.

[0033] 1-2. Overall structure of liquid ejector head 1

[0034] Figure 2 yes Figure 1 An exploded perspective view of the liquid ejector head 1 shown. Figure 3 yes Figure 2 The cross-sectional view shown is of a portion of the liquid ejection head 1. Figure 2 Sectional view along line III-III.

[0035] like Figure 2 As shown, the liquid ejector head 1 has a plurality of nozzles N arranged in the direction along the Y-axis. Figure 2 In the example shown, the multiple nozzles N are respectively divided into a first column L1 and a second column L2 arranged with gaps between them along the X-axis. The first column L1 and the second column L2 are sets of multiple nozzles N arranged in a straight line along the Y-axis. The elements related to each nozzle N in the first column L1 and the elements related to each nozzle N in the second column L2 in the liquid nozzle head 1 are approximately symmetrical to each other along the X-axis. In the following description, the elements corresponding to the first column L1 will be described in detail, and the description of the elements corresponding to the second column L2 will be omitted as appropriate.

[0036] It should be noted that 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 the same or different. Furthermore, elements related to each nozzle N in either the first column L1 or the second column L2 can be omitted.

[0037] like Figure 2 and Figure 3 As shown, the liquid ejector head 1 includes: a nozzle plate 11, a vibration absorber 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, vibration absorber 12, flow path substrate 13, pressure chamber substrate 14, vibrating plate 15, wiring substrate 16, and housing portion 17 are all elongated plate-shaped components 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.

[0038] Nozzle plate 11 is a plate-shaped component 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 adhesive. The nozzles N are the portions that eject liquid by pressure applied in pressure chamber C.

[0039] A flow path for supplying ink to a plurality of nozzles N is formed on the flow path substrate 13. Specifically, the flow path substrate 13 has a space Ra, a plurality of supply flow paths 131, a plurality of connecting flow paths 132, and a supply liquid chamber 133. The space Ra is an elongated opening extending in the Y-axis direction when viewed from above in the Z-axis direction. 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 in the Y-axis direction among the plurality of nozzles N, connecting the space Ra and the plurality of supply flow paths 131 to each other. When viewed from above, each of the plurality of connecting flow paths 132 overlaps with a 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.

[0040] Multiple pressure chambers C are provided on the pressure chamber substrate 14. The multiple pressure chambers C are arranged in the direction along the Y-axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in the direction 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 is connected to the space Ra via the supply flow path 131 and the supply liquid chamber 133. The pressure chamber C is the part where liquid flows inside and pressure is applied to the liquid by the piezoelectric element 5.

[0041] The nozzle plate 11, flow path substrate 13, and pressure chamber substrate 14 are each manufactured by processing a silicon single crystal substrate using methods such as 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.

[0042] A vibrating plate 15 is disposed on the Z1-facing surface of the pressure chamber substrate 14. The vibrating plate 15 is a plate-shaped component capable of elastic vibration.

[0043] A plurality of piezoelectric elements 5, corresponding to nozzle N, are arranged on the Z1-facing surface of the vibrating plate 15. Each piezoelectric element 5, when viewed from above, is formed 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 when a voltage is applied. If the vibrating plate 15 vibrates with this deformation, the pressure in the pressure chambers C changes, thereby causing ink to be ejected from nozzle N.

[0044] The housing 17 is a housing for storing ink supplied to the multiple pressure chambers C. For example... Figure 3 As shown, a space Rb is formed in the housing portion 17. The space Rb of the housing portion 17 is interconnected with the space Ra of the flow path substrate 13. The space formed by the space Ra and the space Rb functions as a liquid storage chamber R, which is a reservoir for storing ink supplied to the plurality of 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.

[0045] The vibration absorber 12 is a flexible membrane that forms the wall of the liquid storage chamber R. The vibration absorber 12 is a malleable substrate that absorbs pressure fluctuations of the ink in the liquid storage chamber R.

[0046] The wiring substrate 16 is a plate-shaped component with wiring for electrically connecting the drive circuit 20 and the plurality of piezoelectric elements 5. The Z2-facing side of the wiring substrate 16 is bonded to 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 side of the wiring substrate 16. The drive circuit 20 is an IC (Integrated Circuit) chip that outputs a drive voltage Com and a reference voltage VBS for driving each piezoelectric element 5.

[0047] like Figure 2As shown, the end of the external wiring 21 is joined on the Z1-facing surface of the wiring substrate 16. For example, the external wiring 21 is composed of connecting components such as FPC (Flexible Printed Circuits) or FFC (Flexible Flat Cable). A plurality of wirings 22 and a plurality of wirings 23 are formed on the wiring substrate 16. The plurality of wirings 22 are electrically connected to the external wiring 21 and the drive circuit 20, and the plurality of wirings 23 are supplied with the drive voltage Com and the reference voltage VBS output from the drive circuit 20.

[0048] It should be noted that the wiring substrate 16 is not limited to a rigid substrate, and can be, for example, an FPC (Flexible Printed Circuits) or an FFC (Flexible Flat Cable). In this case, the wiring substrate 16 can also serve as external wiring 21.

[0049] In this liquid ejector head 1, if the piezoelectric element 5 flexes and deforms due to the application of voltage, the vibrating plate 15 flexes and deforms in the direction that reduces the volume of the pressure chamber C, i.e., vibrates. 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. It should be noted that after the ink is ejected, the piezoelectric element 5 returns to its original position.

[0050] The liquid ejector head 1 includes: a piezoelectric element 5; a pressure chamber C through 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 to the pressure chamber C. According to this liquid ejector head 1, due to the presence of the piezoelectric element 5 with the features described later, displacement characteristics and displacement stability can be improved. Therefore, a liquid ejector head 1 of excellent quality can be provided.

[0051] In addition, the liquid ejector head 1 has Figure 3 The structural elements shown are all of the elements shown, but the liquid nozzle 1 may not have all of these elements, and may further have additional elements.

[0052] 1-3. Vibrating plate 15 and piezoelectric element 5

[0053] Figure 4 It is shown 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). xThe second vibrating body layer 152 is made of elastic materials such as zirconium oxide (ZrO2). x The first vibrating body layer 151 is formed by, for example, thermal oxidation of a portion of the pressure chamber substrate 14. The second vibrating body layer 152 is formed by, for example, a known film-forming technique such as sputtering. It should be noted that the vibrating plate 15 may consist of one layer or three or more layers. Furthermore, Figure 4 The image shows the neutral axis A1 of the vibrating plate 15.

[0054] A piezoelectric element 5 is provided on the vibrating plate 15. The piezoelectric element 5 mainly includes a lower electrode 51, a piezoelectric layer 53, an upper electrode 52, and a sheet layer 54. The piezoelectric layer 53 includes a lower piezoelectric body 53a and an upper piezoelectric body 53b. The lower electrode 51, the sheet layer 54, the lower piezoelectric body 53a, the upper piezoelectric body 53b, and the upper electrode 52 are arranged sequentially along the Z1 direction, which is the stacking direction.

[0055] The lower electrode 51 is disposed above the vibrating plate 15. The lower electrode 51 is an independent electrode provided 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 arranged along the Y-axis with spacing between them. The lower electrode 51 comprises a conductive material such as platinum (Pt). The thickness of the lower electrode 51 along the Z-axis is not particularly limited, for example, it is 50 nm or more and 120 nm or less. Furthermore, the lower electrode 51 can be composed of a single layer or multiple layers.

[0056] The sheet layer 54 is provided to control the orientation of the piezoelectric layer 53. The thickness of the sheet layer 54 along the Z-axis is thinner than the thickness of the piezoelectric layer 53 along the Z-axis. The thickness of the sheet layer 54 along the Z-axis is not particularly limited, for example, it is 5 nm or more and 50 nm or less. Furthermore, the sheet layer 54 can be composed of a single layer or multiple layers.

[0057] For example, sheet layer 54 has a perovskite structure. Sheet layer 54 contains, for example, 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 sheet layer 54 may contain a composite oxide having a perovskite structure containing Bi, Fe, and Ti. In particular, the sheet layer 54 preferably 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 It exhibits excellent orientation control and is therefore a preferred choice.

[0058] The piezoelectric layer 53 is, for example, a continuous strip of dielectric film extending along the Y-axis across a plurality of piezoelectric elements 5. The piezoelectric layer 53 is, for example, a strip extending along the Y-axis, separated from each piezoelectric element 5 by forming a plurality of notches. The thickness of the piezoelectric layer 53 along the Z-axis is not particularly limited, for example, being 300 nm or more and 1500 nm or less.

[0059] The piezoelectric layer 53 includes a lower piezoelectric layer 53a and an upper piezoelectric layer 53b. The lower piezoelectric layer 53a includes M layers of piezoelectric elements. The upper piezoelectric layer 53b includes N layers of piezoelectric elements. M and N are integers greater than or equal to 1.

[0060] It should be noted that the lower piezoelectric body 53a can be composed of one layer or multiple layers. Similarly, the upper piezoelectric body 53b can also be composed of one layer or multiple layers. It should be noted that "one layer" here refers to a layer formed by a single film-forming process.

[0061] 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 contains a conductive material such as iridium (Ir). The thickness of the upper electrode 52 along the Z-axis is not particularly limited, for example, it is 50 nm or more and 120 nm or less. Furthermore, the upper electrode 52 can be composed of a single layer or multiple layers.

[0062] In this piezoelectric element 5, a voltage is applied to the piezoelectric layer 53, which is equivalent to the difference between the reference voltage VBS and the driving voltage Com. The reference voltage VBS is applied to the upper electrode 52, and the driving voltage Com is supplied to the lower electrode 51 and corresponds to the ejection amount. 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.

[0063] It should be noted that in this embodiment, the lower electrode 51 is an independent electrode and the upper electrode 52 is a common electrode, but the lower electrode 51 can also be a common electrode and the upper electrode 52 can be an independent electrode.

[0064] 1-4. Piezoelectric layer 53

[0065] Figure 5 yes Figure 4 A schematic diagram of the piezoelectric layer 53 is shown. Figure 5 In the example shown, the lower piezoelectric element 53a and the upper piezoelectric element 53b of the piezoelectric layer 53 are each composed of, for example, multiple layers. As described above, the lower piezoelectric element 53a includes M layers of piezoelectric elements, and the upper piezoelectric element 53b includes N layers of piezoelectric elements. Figure 5 In the example, M is 3 and N is 6. Therefore, in Figure 5 In the example, the lower piezoelectric body 53a is composed of a three-layer stack consisting of a first layer 531, a second layer 532, and a third layer 533. The upper piezoelectric body 53b is composed of a six-layer stack consisting of a fourth layer 534, a fifth layer 535, a sixth layer 536, a seventh layer 537, an eighth layer 538, and a ninth layer 539.

[0066] Each layer of the lower piezoelectric body 53a contains K, Na, and Nb. Similarly, each layer of the upper piezoelectric body 53b also contains K, Na, and Nb. Specifically, the lower piezoelectric body 53a and the upper piezoelectric body 53b have perovskite structures containing K and Na at site A and Nb at site B, respectively. Specifically, the lower piezoelectric body 53a and the upper piezoelectric body 53b each 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.

[0067] The lower piezoelectric body 53a and the upper piezoelectric body 53b are respectively formed by film deposition processes such as MOD (Metal-Organic Decomposition), sol-gel method, or sputtering. For example, the lower piezoelectric body 53a is formed by sol-gel method, and the upper piezoelectric body 53b is formed by sputtering using metal complexes containing K, Na, and Nb. The sol-gel method refers to a method in which a precursor solution composed of sol is coated onto a lower layer to form a piezoelectric precursor film, and then dried and degreased at a predetermined temperature. Similarly, the MOD method refers to a method in which an MOD solution is coated onto a lower layer and then dried and degreased.

[0068] exist Figures 6-8In the piezoelectric layer 53 shown in the first to third embodiments, the first layer 531 to the third layer 533 constituting the lower piezoelectric body 53a are formed by repeated film formation three times using the sol-gel method, and the fourth layer 534 to the ninth layer 539 are formed by repeated film formation six times using the sputtering method.

[0069] As described above, the piezoelectric layer 53 is composed of a lower piezoelectric body 53a and an upper piezoelectric body 53b. Therefore, compared with the case where the piezoelectric layer 53 is composed of either the lower piezoelectric body 53a or the upper piezoelectric body 53b, the displacement characteristics of the piezoelectric layer 53 can be improved.

[0070] Figure 6 This is a diagram illustrating the SIMS data results of the first embodiment. Figure 7 This is a diagram illustrating the SIMS data results of the second embodiment. Figure 8 This is a diagram illustrating the SIMS data results of the third embodiment. The first, second, and third embodiments each have [data / data / processes]. Figure 5 The piezoelectric layer 53 is composed of 9 layers.

[0071] Figures 6 to 9 These are the results of SIMS measurements performed along the stacking direction. SIMS is short for Secondary Ion Mass Spectrometry. In the SIMS measurements of each embodiment, Cs+ ions with an acceleration energy of 15 keV and a current of 10 nA, used as the primary ion beam, were irradiated onto the sample surface to detect negative secondary ions. During the measurement, a high-resolution mode was used to eliminate the influence of interfering ions. To prevent charge up buildup that occurs when measuring insulators, an Au coating was formed on the sample surface before electron beam irradiation.

[0072] The horizontal axis of each graph represents depth, and the vertical axis represents secondary ion intensity. It should be noted that in the SIMS data results for each graph, cluster ions bound to oxygen were detected to improve the generation efficiency of secondary ions during elemental measurements. Furthermore, the SIMS data results for each graph were obtained by performing SIMS measurements while drilling from the upper electrode 52 to the lower electrode 51. Therefore, the depth [nm] of the ninth layer 539 in the piezoelectric layer 53 is shallower than the depth [nm] of the first layer 531. Among the multiple layers of the piezoelectric layer 53, the ninth layer 539 is closest to a depth of 0 [nm]. Additionally, "1E+" on the vertical axis is an exponentiation of 10. For example, "1E+7" represents "1 × 10^7". Therefore, the ninth layer 539 in the piezoelectric layer 53 is the uppermost layer, and the first layer 531 is the lowermost layer.

[0073] like Figures 6-8As shown, in each embodiment, the amount of niobium (Nb) present in the piezoelectric layer 53 is substantially constant. On the other hand, the amounts of potassium (K) and sodium (Na) at site A differ in the piezoelectric layer 53.

[0074] Specifically, in each of the upper piezoelectric body 53b of the N layer and the lower piezoelectric body 53a of the M layer, the average concentrations of K and Na vary along the stacking direction in such a way that they have extreme values ​​within the layer. That is, in each of the upper piezoelectric body 53b of the N layer and the lower piezoelectric body 53a of the M layer, the composition of K and Na fluctuates between the top and bottom.

[0075] The lower piezoelectric body 53a has each layer with the maximum value I1 of K intensity, the minimum value I2 of K intensity, the maximum value I3 of Na intensity, and the minimum value I4 of Na intensity as extreme values. The upper piezoelectric body 53b has each layer with the maximum value I5 of K intensity, the minimum value I6 of K intensity, the maximum value I7 of Na intensity, and the minimum value I8 of Na intensity.

[0076] Figures 6-8 For example, in the second layer 532 of the lower piezoelectric element 53a, the extreme values ​​of K (maximum value I1), K (minimum value I2), Na (maximum value I3), and Na (minimum value I4) are shown. It should be noted that the first layer 531 and the third layer 533 also have the same maximum value of K (I1), minimum value of K (I2), maximum value of Na (I3), and minimum value of Na (I4), respectively. Furthermore, Figures 6-8 For example, in the seventh layer 537 of the upper piezoelectric body 53b, the extreme values ​​of K (maximum value I5), K (minimum value I6), Na (maximum value I7), and Na (minimum value I8) are shown. It should be noted that the fourth layer 534, fifth layer 535, sixth layer 536, eighth layer 538, and ninth layer 539 also have the same maximum value of K (I5), minimum value of K (I6), maximum value of Na (I7), and minimum value of Na (I8).

[0077] Furthermore, in the first, second, and third embodiments, the degree of tilt, i.e., the range of variation, of the K and Na composition in a specific layer of the M layer of the lower piezoelectric body 53a is greater than the degree of tilt, i.e., the range of variation, of the K and Na composition in a specific layer of the N layer of the upper piezoelectric body 53b. It should be noted that composition tilt can be understood as fluctuation. That is, in the first, second, and third embodiments, in the combination of a specific layer in the M layer of the lower piezoelectric body 53a and a specific layer in the N layer of the upper piezoelectric body 53b, (I5-I6) / (I1-I2) < 1.00 and (I7-I8) / (I3-I4) < 1.00 are satisfied.

[0078] In this embodiment, as shown in the first embodiment, the average concentration of K in the lower piezoelectric body 53a is preferably substantially equal to the average concentration of K in the upper piezoelectric body 53b. "Substantially equal" here means that the average concentration of K in the upper piezoelectric body 53b is greater than 0.8 and less than 1.2 relative to the average concentration of K in the lower piezoelectric body 53a. Furthermore, as shown in the first embodiment, the average concentration of Na in the lower piezoelectric body 53a is preferably substantially equal to the average concentration of Na in the upper piezoelectric body 53b. This means that the average concentration of Na in the upper piezoelectric body 53b is greater than 0.8 and less than 1.2 relative to the average concentration of Na in the lower piezoelectric body 53a. This is because if there is a significant difference in the macroscopic concentration ratio of K to Na in the lower piezoelectric body 53a and the upper piezoelectric body 53b, the properties of the lower piezoelectric body 53a and the upper piezoelectric body 53b will differ too much, which may adversely affect durability and ejection characteristics.

[0079] Here, KNN is a solid solution of potassium niobate (KNbO3) and sodium niobate (NaNbO3). NaNbO3 crystallizes more readily than KNbO3. The lower piezoelectric body 53a forms earlier than the upper piezoelectric body 53b. Therefore, by promoting the crystallization of the lower piezoelectric body 53a beforehand, its orientation is improved, making it easier for the orientation of the upper piezoelectric body 53b formed on top of it to be uniform. This results in improved displacement characteristics of both the lower and upper piezoelectric bodies 53a. Therefore, it is preferable for the lower piezoelectric body 53a to contain a higher amount of NaNbO3. However, as mentioned above, the difference in the macroscopic concentration ratio of K to Na between the upper and lower piezoelectric bodies 53a cannot be too large. Therefore, it is not preferable to simply increase the total amount of Na in the lower piezoelectric body 53a (while decreasing the total amount of K). Considering these aspects, in the lower piezoelectric body 53a, the degree of inclination of the Na composition is increased, and a portion with a higher Na content, i.e., NaNbO3, is locally formed. This allows for the formation of a NaNbO3-rich portion in the lower piezoelectric body 53a, thus promoting the crystallization of the lower piezoelectric body 53a that forms the film first, and consequently improving the orientation of both the lower piezoelectric body 53a and the upper piezoelectric body 53b. It should be noted that increasing the degree of inclination of Na at site A also increases the degree of inclination of K at site A.

[0080] On the other hand, increasing the tilt of the K and Na components means that the ideal K / Na ratio within the piezoelectric body deviates. Considering displacement stability, a smaller tilt of the components is preferable. Since the orientation of the upper piezoelectric body 53b can be easily aligned by the lower piezoelectric body 53a, there is no need to increase the tilt of the components in the upper piezoelectric body 53b. Considering displacement stability, a small tilt of the components is preferred.

[0081] This indicates that, in a combination of a specific layer in layer M and a specific layer in layer N, satisfying (I5-I6) / (I1-I2) < 1.00 and (I7-I8) / (I3-I4) < 1.00 can improve displacement performance and displacement stability. Here, "specific layer" refers to a single layer.

[0082] Figure 9 This is a table showing the extreme values ​​of the lower piezoelectric element 53a in the first embodiment. Figure 10 This is a table showing the extreme values ​​of the upper piezoelectric element 53b in the first embodiment.

[0083] Figure 9 In the middle section, as extreme values ​​in each layer of the lower piezoelectric body 53a, the maximum value I1 of K intensity, the minimum value I2 of K intensity, the maximum value I3 of Na intensity, and the minimum value I4 of Na intensity are shown. Furthermore, Figure 9 The diagram shows the degree of inclination of K in each layer of the lower piezoelectric body 53a (I1-I2) and the degree of inclination of Na (I3-I4). Similarly, in Figure 10 In the diagram, the maximum value I5 of the K intensity, the minimum value I6 of the K intensity, the maximum value I7 of the Na intensity, and the minimum value I8 of the Na intensity are shown as extreme values ​​in each layer of the upper piezoelectric body 53b. Furthermore, Figure 10 The diagram shows the degree of inclination of K in each layer of the lower piezoelectric body 53a (I5-I6) and the degree of inclination of Na (I7-I8).

[0084] Figure 11 This is a diagram showing (I5-I6) / (I1-I2) of the first embodiment. Figure 12 This is a diagram showing (I7-I8) / (I3-I4) of the first embodiment. Figure 11 In the figure, (I5-I6) / (I1-I2) related to K in the combination of a specific layer of the lower piezoelectric body 53a and a specific layer of the upper piezoelectric body 53b is shown. Figure 12 In the figure, (I7-I8) / (I3-I4) related to Na in the combination of a specific layer of the lower piezoelectric body 53a and a specific layer of the upper piezoelectric body 53b is shown.

[0085] like Figure 11 and Figure 12 As shown, in the first embodiment, in all combinations of any layer in layer M and any layer in layer N, (I5-I6) / (I1-I2) < 1.00 and (I7-I8) / (I3-I4) < 1.00 are satisfied. In this way, by satisfying the above relationships in all combinations, the displacement performance and displacement stability can be significantly improved.

[0086] It should be noted that the same tendency to achieve the above-described effect was also found in the second and third embodiments. Furthermore, it is not necessary for (I5-I6) / (I1-I2) < 1.00 and (I7-I8) / (I3-I4) < 1.00 to be satisfied in all combinations of any layer in layer M and any layer in layer N. The above relationship only needs to be satisfied in specific combinations of specific layers in layer M and specific layers in layer N. Therefore, for example, if the above relationship is satisfied in the combination of the first layer 531 and the ninth layer 539, then the above relationship may not be satisfied in the combination of the first layer 531 and the fourth to eighth layers 534 and 538.

[0087] Furthermore, in the first embodiment, in the combination of a specific layer in layer M and a specific layer in layer N, (I5-I6) / (I1-I2) ≤ 0.67 and (I7-I8) / (I3-I4) ≤ 0.67 are satisfied. By satisfying this relationship, the displacement performance and displacement stability can be further improved compared to when it is not satisfied. Moreover, by satisfying the above relationship in all combinations, the displacement performance and displacement stability can be further improved.

[0088] Furthermore, in the first embodiment, in the combination of a specific layer in layer M and a specific layer in layer N, (I5-I6) / (I1-I2) ≤ 0.56 and (I7-I8) / (I3-I4) ≤ 0.33 are satisfied. The first embodiment also satisfies this formula by the following: in the combination of the second and fourth layers, (I5-I6) / (I1-I2) is the largest, with a value of 0.56; in the combination of the second and fifth layers, (I7-I8) / (I3-I4) is the largest, with a value of 0.33. By satisfying this relationship, displacement performance and displacement stability can be improved compared to when it is not satisfied. Moreover, by satisfying the above relationship in all combinations, displacement performance and displacement stability can be improved particularly effectively.

[0089] Furthermore, in the combination of a specific layer in layer M and a specific layer in layer N, it is preferable that I3 > I7. That is, the maximum value I3 of the Na intensity in a specific layer of the lower piezoelectric body 53a is preferably greater than the maximum value I7 of the Na intensity in a specific layer of the upper piezoelectric body 53b. By increasing the Na content in the lower piezoelectric body 53a, the crystallization of the lower piezoelectric body 53a can be promoted, thereby improving the orientation of both the upper piezoelectric body 53b and the lower piezoelectric body 53a.

[0090] Furthermore, in all combinations of any layer in layer M and any layer in layer N, it is preferable that I3 > I7. By satisfying I3 > I7 in all combinations of layers, the orientation of the upper piezoelectric body 53b and the lower piezoelectric body 53a can be improved particularly effectively.

[0091] Furthermore, M ≥ 2 is preferred. That is, the lower piezoelectric body 53a may consist of one layer, but preferably consists of two or more layers. Additionally, in each of the M layers of the lower piezoelectric body 53a, when performing SIMS measurements along the stacking direction, the intensity of K is preferably I1 at the layer boundaries and I2 inside the layers. Here, displacement of the piezoelectric layer 53 may cause microcracks to form in the piezoelectric layer 53. These microcracks originate from strain generated inside the layer due to the layer boundaries. Increasing the average concentration of K can reduce the generation of these microcracks. Therefore, by increasing the intensity of K at and near the layer boundaries, the generation of this strain can be suppressed, thereby suppressing microcracks.

[0092] Furthermore, it is preferable that N > M. That is, the upper piezoelectric body 53b has more layers than the lower piezoelectric body 53a. The upper piezoelectric body 53b is significantly related to the displacement characteristics of the piezoelectric element 5. Therefore, by making N > M, it is easy to make the thickness of the upper piezoelectric body 53b greater than the thickness of the lower piezoelectric body 53a. By making the thickness of the upper piezoelectric body 53b greater than the thickness of the lower piezoelectric body 53a, the displacement characteristics of the piezoelectric element 5 can be improved compared to when it is thinner. In addition, since the lower piezoelectric body 53a is a piezoelectric body used to promote the crystallinity of the upper piezoelectric body 53b, the number of layers of the lower piezoelectric body 53a can be less than that of the upper piezoelectric body 53b.

[0093] Furthermore, it is preferable that N > 2M. By making N > 2M, the displacement property of the piezoelectric element 5 can be further improved. In addition, from the viewpoint that the lower piezoelectric body 53a is a piezoelectric body used to promote the crystallinity of the upper piezoelectric body 53b, it is also preferable that N > 2M.

[0094] It should be noted that N and M should both be 1 or higher, and N and M can be the same.

[0095] Furthermore, M=2 is preferred. That is, the lower piezoelectric element 53a is preferably composed of two layers. By making the lower piezoelectric element 53a composed of two layers, the displacement and displacement stability of the piezoelectric layer 53 can be improved particularly effectively.

[0096] 2. Variations

[0097] The above examples can be implemented in various ways. The following examples illustrate specific variations applicable to the aforementioned implementations. Any two or more methods selected from the following examples can be appropriately combined without contradiction.

[0098] "Liquid ejector head" can be a circulating head with a so-called circulating flow path.

[0099] Besides being used in printing equipment, liquid ejection devices can also be applied to various other devices such as fax machines and copiers. Their applications are not limited to printing. For example, liquid ejection devices that eject solutions of pigments are used in the manufacture of color filters for display devices such as liquid crystal display panels. Furthermore, liquid ejection devices that eject solutions of conductive materials are used in the manufacture of wiring and electrodes for wiring substrates. Additionally, liquid ejection devices that eject solutions of organic substances related to living organisms are used, for example, in the manufacture of biochips.

[0100] The piezoelectric elements involved in this invention are not limited to liquid ejector heads and liquid ejection devices; they can be any components that generate mechanical force by applying voltage or generate voltage by applying mechanical force, and have the function of converting voltage and mechanical force. Examples of 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, thermoelectric 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.

[0101] 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 arbitrary structures can also be added.

Claims

1. A piezoelectric element, characterized in that, The piezoelectric element is composed of a lower electrode, a lower piezoelectric body, an upper piezoelectric body, and an upper electrode arranged sequentially along the stacking direction. The lower piezoelectric body contains K, Na, and Nb and is composed of M layers, where M ≥ 1. The upper piezoelectric body contains K, Na, and Nb and is composed of N layers, where N ≥ 1. In each of the upper piezoelectric body (N layer) and the lower piezoelectric body (M layer), the concentrations of K and Na vary along the stacking direction in such a way that they have extreme values ​​within the layer. In each of the M layers, let the maximum value of K intensity during SIMS measurement along the stacking direction be I1, the minimum value of K intensity be I2, the maximum value of Na intensity be I3, and the minimum value of Na intensity be I4. In each of the N layers of the upper piezoelectric body, assuming the maximum value of K intensity is I5, the minimum value of K intensity is I6, the maximum value of Na intensity is I7, and the minimum value of Na intensity is I8 when performing SIMS measurements along the stacking direction, In a combination of a specific layer in layer M and a specific layer in layer N, the condition (I5-I6) / (I1-I2) < 1.00 is met. The condition (I7-I8) / (I3-I4) < 1.00 is satisfied.

2. The piezoelectric element according to claim 1, characterized in that, In a combination of a specific layer in layer M and a specific layer in layer N, the condition (I5-I6) / (I1-I2) ≤ 0.67 is met. The condition (I7-I8) / (I3-I4) ≤ 0.67 is satisfied.

3. The piezoelectric element according to claim 2, characterized in that, In a combination of a specific layer in layer M and a specific layer in layer N, the condition (I5-I6) / (I1-I2) ≤ 0.56 is met. The condition (I7-I8) / (I3-I4) ≤ 0.33 is satisfied.

4. The piezoelectric element according to claim 1, characterized in that, In a combination of a specific layer in layer M and a specific layer in layer N, I3 > I7.

5. The piezoelectric element according to claim 1, characterized in that, In all combinations of any layer in the M layers and any layer in the N layers, The condition (I5-I6) / (I1-I2) < 1.00 is met. The condition (I7-I8) / (I3-I4) < 1.00 is satisfied.

6. The piezoelectric element according to claim 1, characterized in that, M≥2， In each of the M layers of the lower piezoelectric body, when SIMS measurements are performed along the stacking direction, the intensity of K is I1 at the layer boundary and I2 inside the layer.

7. The piezoelectric element according to claim 1, characterized in that, N > M.

8. The piezoelectric element according to claim 7, characterized in that, N > 2M.

9. The piezoelectric element according to claim 1, characterized in that, M＝2。 10. The piezoelectric element according to claim 1, characterized in that, The average concentration of K in the lower piezoelectric element is substantially equal to the average concentration of K in the upper piezoelectric element. The average concentration of Na in the lower piezoelectric element is approximately equal to the average concentration of Na in the upper piezoelectric element.

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

12. A liquid ejection device, characterized in that, have: The liquid ejector head as claimed in claim 11; and The control unit controls the ejection action from the liquid nozzle.

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