Liquid discharge head, liquid discharge device, and method of manufacturing liquid discharge head

Abstract

To provide a liquid discharge head excellent in discharge characteristics, and a liquid discharge device and a method of manufacturing the liquid discharge head.SOLUTION: In a liquid discharge head, a pressure chamber substrate in which a plurality of pressure chambers are provided, a vibration plate, a first common electrode which is provided commonly for the plurality of pressure chambers and to which a reference voltage that does not change over time is applied, a first thin film piezoelectric body, individual electrodes which are provided individually for the plurality of pressure chambers and to which a drive voltage that changes over time is applied, a second thin film piezoelectric body, and a second common electrode which is provided commonly for the plurality of pressure chambers and to which the reference voltage is applied are stacked in this order from a lower side to an upper side. A first orientation control layer for controlling an orientation of the first thin film piezoelectric body is provided between the first thin film piezoelectric body and the first common electrode. A second orientation control layer for controlling an orientation of the second thin film piezoelectric body is provided between the second thin film piezoelectric body and the individual electrodes.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head, a liquid ejection apparatus, and a method for manufacturing a liquid ejection head. [Background technology]

[0002] Liquid ejection devices equipped with a liquid ejection head that ejects liquid such as ink onto a medium such as printing paper have been proposed. Piezo inkjet printers are known as such liquid ejection devices. The piezoelectric method uses a piezoelectric element that vibrates a diaphragm that forms part of the wall of a pressure chamber. The vibration of the diaphragm caused by the piezoelectric element causes the liquid filled in the pressure chamber to be ejected from the nozzle.

[0003] The piezoelectric element of the liquid ejection head described in Patent Document 1 has a first common electrode, a thin-film lower piezoelectric layer, individual electrodes, a thin-film upper piezoelectric layer, and a second common electrode stacked in this order. In other words, the piezoelectric element has a configuration in which two thin-film piezoelectrics are stacked. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-256137 Summary of the Invention [Problem to be solved by the invention]

[0005] When thin-film piezoelectric elements are stacked as in Patent Document 1, the amount of displacement per unit voltage can be nearly doubled compared to when the thin-film piezoelectric element is a single layer. This makes it possible to improve ejection characteristics at the same voltage as a single layer, and to reduce costs by replacing components with those that have a lower rated voltage. However, as a result of further investigation by the inventors, it was found that more desirable effects can be obtained by setting the physical properties of the lower piezoelectric layer and the upper piezoelectric layer to appropriate values.

[0006] In the laminated piezoelectric element of Patent Document 1, the physical properties of each thin film piezoelectric element are easily affected by the substrate during the manufacturing process. The physical properties of each thin film piezoelectric element can be controlled to some extent by the composition of each thin film piezoelectric element, but among the physical properties, orientation is particularly affected by the substrate. For this reason, it has not been possible to sufficiently control orientation in conventional laminated piezoelectric elements. [Means for solving the problem]

[0007] A preferred embodiment of the present invention provides a liquid ejection head comprising: a pressure chamber substrate having a plurality of pressure chambers; a vibration plate; a first common electrode provided in common to the plurality of pressure chambers and to which a time-invariant reference voltage is applied; a first thin-film piezoelectric; individual electrodes provided individually for the plurality of pressure chambers and to which a time-variant drive voltage is applied; a second thin-film piezoelectric; and a second common electrode provided in common to the plurality of pressure chambers and to which the reference voltage is applied, stacked in this order from bottom to top; wherein a first orientation control layer for controlling the orientation of the first thin-film piezoelectric is provided between the first thin-film piezoelectric and the first common electrode, and a second orientation control layer for controlling the orientation of the second thin-film piezoelectric is provided between the second thin-film piezoelectric and the individual electrode.

[0008] A liquid ejection apparatus according to a preferred aspect of the present invention includes a liquid ejection head and a voltage application circuit for applying the reference voltage and the drive voltage.

[0009] A preferred embodiment of the present invention relates to a method for manufacturing a liquid ejection head, which includes the following steps in this order: a first step of forming a first common electrode on a vibration plate; a second step of depositing a first orientation control layer on the first common electrode; a third step of depositing a first thin-film piezoelectric on the first orientation control layer; a fourth step of forming individual electrodes on the first thin-film piezoelectric; a fifth step of patterning the individual electrodes, the first thin-film piezoelectric, and the first orientation control layer; a sixth step of forming a second orientation control layer on the individual electrodes; a seventh step of depositing a second thin-film piezoelectric on the second orientation control layer; an eighth step of patterning the second thin-film piezoelectric and the second orientation control layer; and a ninth step of forming a second common electrode to cover the second thin-film piezoelectric. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic view illustrating the configuration of a liquid ejection device according to a first embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the liquid ejection head shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view of a portion of the liquid ejection head shown in FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a portion of the liquid ejection head shown in FIG. [Figure 5] FIG. 4 is an enlarged cross-sectional view of a portion of the liquid ejection head shown in FIG. [Figure 6] 5 is a diagram showing a planar arrangement of the individual electrodes and the second common electrode in FIG. 4. FIG. [Figure 7] FIG. 3 is a diagram for explaining a driving voltage and a reference voltage. [Figure 8] 10 is a diagram illustrating an example of voltages applied to a first thin-film piezoelectric element and a second thin-film piezoelectric element. [Figure 9] 10 is a flow chart showing a method for manufacturing a piezoelectric element, which is part of a method for manufacturing a liquid ejection head. [Figure 10] 10A to 10C are diagrams for explaining a method for manufacturing the piezoelectric element shown in FIG. [Figure 11] 10A to 10C are diagrams for explaining a method for manufacturing the piezoelectric element shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The dimensions and scale of each part in the drawings may differ from the actual dimensions, and some parts are shown schematically to facilitate understanding. The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to limit the present invention. The term "equal" includes not only cases where the dimensions are strictly equal, but also cases where there is a difference within the measurement error range. Furthermore, the term "element α and element β are stacked" means that the elements α and β are aligned vertically, and does not necessarily mean that the elements α and β are in direct contact with each other.

[0012] The following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. One direction along the X-axis is referred to as the X1 direction, and the direction opposite to the X1 direction is referred to as the X2 direction. Opposite directions along the Y-axis are referred to as the Y1 direction and the Y2 direction. Opposite directions along the Z-axis are referred to as the Z1 direction and the Z2 direction. Viewing in a direction along the Z-axis is referred to as a "planar view." The Z-axis is typically a vertical axis. The Z1 direction is the upper side, and the Z2 direction is the lower side. However, the Z-axis does not have to be a vertical axis. Furthermore, the X-axis, Y-axis, and Z-axis are typically perpendicular to each other, but are not limited to this and may intersect at an angle between 80° and 100°, for example.

[0013] 1. Embodiment 1-1. Overall configuration of the liquid ejection device 100 FIG. 1 is a schematic diagram illustrating a configuration of a liquid ejection device 100 according to a first embodiment. The liquid ejection device 100 is an inkjet printing device that ejects ink, an example of a liquid, as droplets onto a medium M. The medium M is typically printing paper. However, the medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

[0014] 1, a liquid container 90 for storing ink is attached to the liquid ejection device 100. Specific examples of the liquid container 90 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. The type of ink stored in the liquid container 90 is arbitrary.

[0015] The liquid ejection device 100 has a control unit 91, a transport mechanism 92, a movement mechanism 93, and a liquid ejection head 1. The control unit 91 includes 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 elements 7, which will be described later, to eject ink from the nozzles. The voltage application circuit 910 applies a reference voltage VBS and a drive voltage Com, which will be described later, to the piezoelectric elements 7.

[0016] The transport mechanism 92 transports the medium M in the Y2 direction under the control of the control unit 91. The movement mechanism 93 reciprocates the liquid ejection head 1 in the X1 and X2 directions under the control of the control unit 91. In the example shown in FIG. 1, the movement mechanism 93 has a substantially box-shaped transport body 931 called a carriage that houses the liquid ejection head 1, and a transport belt 932 to which the transport body 931 is fixed. Note that the number of liquid ejection heads 1 mounted on the transport body 931 is not limited to one, and may be multiple. In addition to the liquid ejection head 1, a liquid container 90 may also be mounted on the transport body 931.

[0017] The liquid ejection head 1 ejects ink supplied from a liquid container 90 from each of a plurality of nozzles in the Z2 direction onto the medium M under the control of a control unit 91. This ejection is performed in parallel with the transport of the medium M by a transport mechanism 92 and the reciprocating movement of the liquid ejection head 1 by a movement mechanism 93, thereby forming an ink image on the surface of the medium M.

[0018] The liquid ejection device 100 includes a liquid ejection head 1, which will be described later, and a control unit 91. The control unit 91 includes a voltage application circuit 910 that causes ink to be ejected from the nozzles N. The liquid ejection device 100 includes a liquid ejection head 1 having the characteristics, which will be described later, and therefore can achieve improved ejection performance.

[0019] 1-2. Overall configuration of liquid ejection head FIG. 2 is an exploded perspective view of the liquid ejection head 1 shown in FIG. 1. FIG. 3 is a cross-sectional view of a portion of the liquid ejection head 1 shown in FIG. 2, taken along line III-III in FIG. 2. As shown in FIG. 2, the liquid ejection head 1 has a plurality of nozzles N arranged in a direction along the Y axis. In the example shown in FIG. 2, the plurality of nozzles N are divided into a first row L1 and a second row L2 arranged at intervals along the X axis. Each of the first row L1 and the second row L2 is a collection of a plurality of nozzles N linearly arranged in a direction along the Y axis. In the liquid ejection head 1, elements associated with each nozzle N in the first row L1 and elements associated with each nozzle N in the second row L2 are substantially symmetrical to each other in a direction along the X axis. In the following description, the elements associated with the first row L1 will be mainly described, and descriptions of elements associated with the second row L2 will be omitted as appropriate.

[0020] The positions of the nozzles N in the first row L1 and the nozzles N in the second row L2 along the Y axis may be the same or different. Also, elements related to each nozzle N in one of the first row L1 and the second row L2 may be omitted.

[0021] 2 and 3, the liquid ejection head 1 has a nozzle plate 11, a vibration absorber 12, a flow path substrate 13, a pressure chamber substrate 14, a diaphragm 15, a wiring substrate 16, a housing unit 17, and a drive circuit 20. The nozzle plate 11, the vibration absorber 12, the flow path substrate 13, the pressure chamber substrate 14, the diaphragm 15, the wiring substrate 16, and the housing unit 17 are each a plate-like member that is elongated in the direction along the Y axis. The nozzle plate 11, the flow path substrate 13, the pressure chamber substrate 14, the diaphragm 15, and the wiring substrate 16 are arranged in this order in the Z1 direction.

[0022] The nozzle plate 11 is a plate-like member in which a plurality of nozzles N are formed. Each of the plurality of nozzles N is a circular through-hole that allows ink to pass through. The nozzles N eject ink by vibration of the vibration plate 15. The nozzle plate 11 is bonded to the flow path substrate 13 with, for example, an adhesive.

[0023] The flow path substrate 13 is formed with flow paths for supplying ink to the multiple nozzles N. Specifically, the flow path substrate 13 is formed with a space Ra, multiple supply flow paths 131, multiple communication flow paths 132, and a supply liquid chamber 133. The space Ra is an elongated opening extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. Each of the supply flow paths 131 and the communication flow paths 132 is a through-hole formed for each nozzle N. The supply liquid chamber 133 is an elongated space extending in the direction along the Y axis across the multiple nozzles N, and connects the space Ra and the multiple supply flow paths 131 to each other. Each of the multiple communication flow paths 132 overlaps with one nozzle N corresponding to that communication flow path 132 in a plan view. A pressure chamber substrate 14 is bonded to the flow path substrate 13 with, for example, an adhesive.

[0024] A plurality of pressure chambers C are provided in the pressure chamber substrate 14. The plurality of pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in a direction along the X axis in a plan view. The pressure chamber C is a space located between the flow path substrate 13 and the vibration plate 15. The pressure chamber C communicates with the nozzle N via a communication flow path 132, and also communicates with the space Ra via a supply flow path 131 and a supply liquid chamber 133.

[0025] The nozzle plate 11, the flow path substrate 13, and the pressure chamber substrate 14 are each manufactured by processing a silicon single crystal substrate using, for example, dry etching, wet etching, etc. However, other known methods may also be used as appropriate to manufacture the nozzle plate 11, the flow path substrate 13, and the pressure chamber substrate 14.

[0026] A diaphragm 15 is disposed on the surface facing the Z1 direction of the pressure chamber substrate 14. The diaphragm 15 is a plate-like member that can vibrate elastically.

[0027] A plurality of piezoelectric elements 7 corresponding to the nozzles N are arranged on the surface of the vibration plate 15 facing the Z1 direction. Each piezoelectric element 7 has an elongated shape extending in the direction along the X axis in a plan view. The plurality of piezoelectric elements 7 correspond to a plurality of pressure chambers C and are arranged in the direction along the Y axis. The piezoelectric elements 7 deform when a voltage is applied. When the vibration plate 15 vibrates in conjunction with the deformation, the pressure in the pressure chambers C fluctuates, causing ink to be ejected from the nozzles N.

[0028] The housing 17 is a case for storing ink to be supplied to the multiple pressure chambers C. As shown in FIG. 3, a space Rb is formed in the housing 17. The space Rb in the housing 17 and the space Ra in the flow path substrate 13 are connected to each other. The space formed by the spaces Ra and Rb functions as a liquid storage chamber R, which is a reservoir that stores ink to be supplied to the multiple pressure chambers C. Ink is supplied to the liquid storage chamber R via an inlet 171 formed in the housing 17. The ink in the liquid storage chamber R is supplied to the pressure chambers C via the supply liquid chamber 133 and each supply flow path 131.

[0029] The vibration absorber 12 is a flexible film that forms the wall surface of the liquid storage chamber R. The vibration absorber 12 is a compliant substrate that absorbs pressure fluctuations of the ink inside the liquid storage chamber R.

[0030] The wiring board 16 is a plate-like member on which wiring is formed for electrically connecting the drive circuit 20 and the plurality of piezoelectric elements 7. The surface of the wiring board 16 facing the Z2 direction is joined to the diaphragm 15 via a plurality of conductive bumps 16B. On the other hand, the drive circuit 20 is mounted on the surface of the wiring board 16 facing the Z1 direction. 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 7.

[0031] 2, ends of external wiring 21 are joined to the surface of wiring board 16 facing the Z1 direction. External wiring 21 is formed of a connecting component such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable). Wiring board 16 is formed with a plurality of wirings 22 that electrically connects external wiring 21 to drive circuit 20, and a plurality of wirings 23 to which drive voltage Com output from drive circuit 20 and reference voltage VBS are supplied.

[0032] The wiring board 16 is not limited to a rigid board, and may be, for example, an FPC (Flexible Printed Circuits) or an FFC (Flexible Flat Cable). In this case, the wiring board 16 may also serve as the external wiring 21.

[0033] 1-3.Vibration plate 15 Figures 4 and 5 are enlarged cross-sectional views of a portion of the liquid ejection head 1 shown in Figure 3. The diaphragm 15 shown in Figures 4 and 5 vibrates in response to the vibration of the piezoelectric element 7. The diaphragm 15 has, for example, a first layer 151 and a second layer 152. The first layer 151 and the second layer 152 are stacked in this order from bottom to top, i.e., in the Z1 direction.

[0034] The first layer 151 is, for example, an elastic film made of silicon oxide (SiO2). The elastic film is formed, for example, by thermally oxidizing one surface of a silicon single crystal substrate. The second layer 152 is, for example, an insulating film made of zirconium oxide (ZrO2). The insulating film is formed, for example, by forming a zirconium layer by sputtering and then thermally oxidizing the layer. Zirconium oxide has excellent electrical insulation properties, mechanical strength, and toughness. Therefore, by including the second layer 152 containing zirconium oxide in the diaphragm 15, the characteristics of the diaphragm 15 can be improved.

[0035] Note that another layer such as a metal oxide may be interposed between the first layer 151 and the second layer 152. Also, part or all of the diaphragm 15 may be configured integrally with the pressure chamber substrate 14. Also, the diaphragm 15 may be configured as a layer of a single material. Also, the neutral axis A1 of the diaphragm 15 is shown in FIG.

[0036] 1-4. Piezoelectric element 7 As shown in FIG. 3, the piezoelectric element 7 overlaps the pressure chamber C in a plan view. As shown in FIGS. 4 and 5, the piezoelectric element 7 is disposed on the vibration plate 15. The piezoelectric element 7 includes a first common electrode 71, a first orientation control layer 76, a first thin-film piezoelectric element 72, an individual electrode 73, a second orientation control layer 77, a second thin-film piezoelectric element 74, and a second common electrode 75. Of these, the first common electrode 71 and the second common electrode 75 are generally common to multiple piezoelectric elements 7. The first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 are separated by through holes H0 (described later) between the multiple piezoelectric elements 7 in a range that overlaps with the pressure chamber C in a plan view seen along the Z axis. However, they are connected in a range that does not overlap with the pressure chamber C, forming a continuous member. However, the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 do not have to be a continuous member. An individual electrode 73 is provided for each piezoelectric element 7. The pressure chamber substrate 14, diaphragm 15, first common electrode 71, first thin-film piezoelectric element 72, individual electrode 73, second thin-film piezoelectric element 74, and second common electrode 75 are laminated in this order from bottom to top. A first orientation control layer 76 is provided between the first thin-film piezoelectric element 72 and the first common electrode 71. A second orientation control layer 77 is provided between the second thin-film piezoelectric element 74 and the individual electrode 73. Other layers, such as layers for improving adhesion, may be appropriately interposed between the layers of the piezoelectric elements 7 or between the piezoelectric element 7 and the diaphragm 15.

[0037] 1-4a. First common electrode 71 The first common electrode 71 is provided in common to the multiple pressure chambers C. The first common electrode 71 is strip-shaped and extends in the direction along the Y axis so as to be continuous with the multiple pressure chambers C. A reference voltage VBS that does not change with time is applied to the first common electrode 71.

[0038] Examples of materials for the first common electrode 71 include metal materials or alloys such as platinum (Pt), iridium (Ir), aluminum (Al), nickel (Ni), gold (Au), and copper (Cu). The first common electrode 71 may be a single layer or multiple layers. For example, the first common electrode 71 has a layered structure in which a layer made of platinum is stacked on a layer made of iridium.

[0039] 1-4b. Individual electrode 73 The individual electrodes 73 are provided individually for the plurality of pressure chambers C. A driving voltage Com that changes with time is applied to the individual electrodes 73.

[0040] Examples of materials for the individual electrodes 73 include metal materials such as platinum, iridium, aluminum, nickel, gold, and copper, or alloys thereof. The individual electrodes 73 may be single-layered or multi-layered.

[0041] 1-4c.Second common electrode 75 The second common electrode 75 is provided in common to the multiple pressure chambers C. The second common electrode 75 is strip-shaped and extends in the direction along the Y axis so as to be continuous with the multiple pressure chambers C. A reference voltage VBS that does not change with time is applied to the second common electrode 75. Therefore, a common potential is applied to the first common electrode 71 and the second common electrode 75.

[0042] Examples of materials for the second common electrode 75 include metal materials such as platinum, iridium, aluminum, nickel, gold, and copper, or alloys thereof. The second common electrode 75 may be a single layer or multiple layers.

[0043] As shown in FIG. 5 , two conductors 781 and 782 are disposed on the second common electrode 75. Each of the conductors 781 and 782 is a strip-shaped conductive film extending in the direction along the Y-axis along the edge of the second common electrode 75 in the X1 or X2 direction. The conductors 781 and 782 are made of a conductive material with low electrical resistance, such as gold. The conductors 781 and 782 suppress a voltage drop in the reference voltage VBS at the second common electrode 75. The conductors 781 and 782 also function as weights that define the vibration region of the diaphragm 15. Note that the conductors 781 and 782 may be omitted.

[0044] FIG. 6 is a diagram showing the planar arrangement of the individual electrodes 73 and the second common electrode 75 of FIG. 4. As shown in FIG. 6, each individual electrode 73 is elongated and extends along the X-axis. The multiple individual electrodes 73 are spaced apart and aligned along the Y-axis. As shown in FIGS. 5 and 6, one end of each individual electrode 73 in the longitudinal direction along the X-axis is connected to an outgoing wiring 731 via a connection wiring 730. The outgoing wiring 731 is connected to wiring 70 extending along the Y-axis. The wiring 70 is electrically connected to the drive circuit 20 mounted on the wiring substrate 16 via the aforementioned multiple conductive bumps 16B. Although not shown in detail, the first common electrode 71, like the second common electrode 75, is electrically connected to the drive circuit 20 mounted on the wiring substrate 16 via the aforementioned multiple conductive bumps 16B.

[0045] The second common electrode 75 overlaps the individual electrodes 73 in a planar view. Although not shown in detail, the first common electrode 71 overlaps the individual electrodes 73 in a planar view. As described above, the second common electrode 75 is strip-shaped, e.g., rectangular, extending along the Y-axis. Lead wiring 750 is connected to the corners of the second common electrode 75. The lead wiring 750 is electrically connected to the drive circuit 20 mounted on the wiring substrate 16 via the conductive bumps 16B described above. Thus, the second common electrode 75 is electrically connected to the drive circuit 20. Meanwhile, the first common electrode 71 contacts the second common electrode 75 in a region that does not overlap with the pressure chambers C in a planar view along the Z-axis, as shown at the Y1-direction end and Y2-direction end in FIG. 4 and the X1-direction end in FIG. 5. This contact causes the first common electrode 71 to have the same potential as the second common electrode 75. In other words, the first common electrode 71 is electrically connected to the drive circuit 20 via the second common electrode 75. In this embodiment, the first common electrode 71 and the second common electrode 75 are in physical contact with each other, but other members may be interposed between them as long as they are electrically connected.

[0046] 7 is a diagram for explaining the drive voltage Com and the reference voltage VBS, in which the horizontal axis represents time and the vertical axis represents voltage [V].

[0047] A voltage is applied to the piezoelectric element 7 by the aforementioned voltage application circuit 910. Specifically, the voltage application circuit 910 applies a voltage to the first thin-film piezoelectric element 72 via the first common electrode 71 and the individual electrode 73, and the first thin-film piezoelectric element 72 deforms in response to the voltage applied between the first common electrode 71 and the individual electrode 73. Similarly, the voltage application circuit 910 applies a voltage to the second thin-film piezoelectric element 74 via the second common electrode 75 and the individual electrode 73, and the second thin-film piezoelectric element 74 deforms in response to the voltage applied between the second common electrode 75 and the individual electrode 73.

[0048] A driving voltage Com according to the amount of ink ejected is applied to the individual electrode 73. The driving voltage Com changes over time. The driving voltage Com includes a driving waveform WCom. The driving waveform WCom is repeated in a unit period Tu. The driving waveform WCom includes an intermediate voltage Ek, a maximum voltage En, and a minimum voltage Em. The maximum voltage En is the maximum value of the driving voltage Com. The minimum voltage Em is the minimum value of the driving voltage Com. The driving waveform WCom drops from the intermediate voltage Ek to the minimum voltage Em, maintains the minimum voltage Em, then rises from the minimum voltage Em to the maximum voltage En, maintains the maximum voltage En, and then drops to the intermediate voltage Ek. Note that the driving waveform WCom shown in FIG. 7 is an example, and the driving voltage Com may have other waveforms.

[0049] A constant reference voltage VBS is applied to each of the first common electrode 71 and the second common electrode 75, regardless of the amount of ink ejected. The reference voltage VBS is constant and does not change over time. In the illustrated example, the reference voltage VBS is a voltage value higher than the minimum voltage Em of the drive voltage Com, but is not limited to this. The reference voltage VBS may also be the GND potential, i.e., 0 V.

[0050] 8 shows an example of the applied voltage Ea applied to the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74. The applied voltage Ea shown in FIG. 8 is obtained by subtracting the reference voltage VBS from the drive voltage Com shown in FIG. 7 at each time.

[0051] By applying the drive voltage Com and the reference voltage VBS, a voltage corresponding to the difference between the drive voltage Com and the reference voltage VBS is applied to the first thin-film piezoelectric element 72 between the first common electrode 71 and the individual electrode 73, deforming the first thin-film piezoelectric element 72. Similarly, by applying the drive voltage Com and the reference voltage VBS, a voltage corresponding to the difference between the drive voltage Com and the reference voltage VBS is applied to the second thin-film piezoelectric element 74 between the second common electrode 75 and the individual electrode 73, deforming the second thin-film piezoelectric element 74.

[0052] The horizontal axis in Figure 8 is time, and the vertical axis is voltage [V]. The applied voltage Ea includes a waveform WEa. The waveform WEa includes an intermediate voltage EK, a maximum voltage EN, and a minimum voltage EM. The maximum voltage EN is the difference between the maximum voltage En of the drive voltage Com and the reference voltage VBS. The minimum voltage EM is the difference between the minimum voltage Em of the drive voltage Com and the reference voltage VBS. Note that the waveform WEa shown in Figure 8 is an example and varies depending on the drive voltage Com and the reference voltage VBS.

[0053] Since the reference voltage VBS is constant, the voltage range RE of the applied voltage Ea and the voltage range RE of the drive voltage Com are equal.

[0054] 1-4d. First thin film piezoelectric element 72 and second thin film piezoelectric element 74 As described above, first thin-film piezoelectric element 72 is disposed between first common electrode 71 and individual electrode 73 , and deforms in response to the potential difference between first common electrode 71 and individual electrode 73 .

[0055] 4 and 5 is made of a composite oxide. A first orientation control layer 76 is disposed below the first thin-film piezoelectric element 72. The orientation of the first thin-film piezoelectric element 72 is controlled by the first orientation control layer 76.

[0056] The first thin-film piezoelectric element 72 includes an active portion and a non-active portion. The portion of the first thin-film piezoelectric element 72 that is located between the first common electrode 71 and the individual electrode 73 is the active portion, and the portion that is not located between the first common electrode 71 and the individual electrode 73 is the non-active portion.

[0057] As described above, the second thin-film piezoelectric element 74 is disposed between the second common electrode 75 and the individual electrode 73 , and is deformed in response to the potential difference between the second common electrode 75 and the individual electrode 73 .

[0058] Second thin-film piezoelectric element 74 is made of a composite oxide. Second orientation control layer 77 is disposed below second thin-film piezoelectric element 74. The orientation of second thin-film piezoelectric element 74 is controlled by second orientation control layer 77 below it.

[0059] 6, the second thin-film piezoelectric element 74 has a strip shape extending along the Y-axis. The second thin-film piezoelectric element 74 has through-holes H0 formed in regions corresponding in plan view to the gaps between adjacent pressure chambers C. The through-holes H0 separate the second thin-film piezoelectric element 74 into individual pressure chambers C. Although not shown in detail, the first thin-film piezoelectric element 72 also has through-holes similar to the through-holes H0 of the second thin-film piezoelectric element 74, and is separated into individual pressure chambers C.

[0060] 5, the second thin-film piezoelectric element 74 includes an active portion 741 and a non-active portion 742. The active portion 741 is a portion located between the individual electrode 73 and the second common electrode 75. The active portion 741 is located directly above the first thin-film piezoelectric element 72 and overlaps with the first thin-film piezoelectric element 72 in a planar view. The non-active portion 742 is a portion not located between the individual electrode 73 and the second common electrode 75. The non-active portion 742 extends outside the first thin-film piezoelectric element 72.

[0061] As described above, each of the first thin-film piezoelectric body 72 and the second thin-film piezoelectric body 74 is made of a composite oxide. Specifically, each of the first thin-film piezoelectric body 72 and the second thin-film piezoelectric body 74 is made of a piezoelectric material having a perovskite crystal structure.

[0062] Examples of the piezoelectric material include lead titanate (PbTiO), lead zirconate titanate (PZT: Pb(Zr,Ti)O), lead zirconate (PbZrO), lead lanthanum titanate ((Pb,La),TiO), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O), lead zirconium niobate titanate (Pb(Zr,Ti,Nb)O), and lead magnesium zirconium niobate titanate (Pb(Zr,Ti)(Mg,Nb)O). Among these, lead zirconate titanate (PZT) is preferably used as the material for the thin-film piezoelectric element. The thin-film piezoelectric element may contain small amounts of other elements, such as impurities. Each of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 may be a single layer or multiple layers.

[0063] The first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 may be made of the same material, but are preferably made of different materials. The desired physical properties of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 may differ depending on the type of piezoelectric element 7. For this reason, if the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 were made of the same material, the degree of freedom in design would be reduced, making it difficult to optimize the physical properties of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74. By using different materials for the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74, it is possible to design the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 to have optimal physical properties. This makes it possible to find the desired piezoelectric element 7.

[0064] From another perspective, it is preferable that the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 are made of the same material. If the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 are made of the same material, manufacturing is easy, and it is easy to design desired physical properties by simply controlling the film thickness, for example.

[0065] Each of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 is a thin film. Specifically, in this embodiment, a thin film has a thickness of at least 5 μm or less, and more preferably 2 μm or less. The thicknesses of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 may be the same or different.

[0066] During an expansion period T2 in which the voltage is reduced from the intermediate voltage EK to the minimum voltage EM in FIG. 8 to expand the pressure chamber C, the piezoelectric element 7 including the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 undergoes deformation such that the piezoelectric element 7 and the diaphragm 15 bend in the Z1 direction. That is, the piezoelectric element 7 deforms upward to expand the pressure chamber C. As a result, ink is taken into the pressure chamber C. Next, during a contraction period T1 in which the voltage is increased from the minimum voltage EM to the maximum voltage EN to contract the pressure chamber C, the piezoelectric element 7 and the diaphragm 15 deform so as to bend in the Z2 direction. That is, the piezoelectric element 7 deforms downward to contract the pressure chamber C. As a result, the ink in the pressure chamber C is ejected from the nozzle.

[0067] 1-4e. First alignment control layer 76 and second alignment control layer 77 4 and 5, the first orientation control layer 76 is provided between the first thin-film piezoelectric element 72 and the first common electrode 71. The second orientation control layer 77 is provided between the second thin-film piezoelectric element 74 and the individual electrode 73. The first orientation control layer 76 controls the orientation of the first thin-film piezoelectric element 72, and the second orientation control layer 77 controls the orientation of the second thin-film piezoelectric element 74.

[0068] Even in a structure having two layers, the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74, as in this embodiment, if displacement efficiency alone is considered, it is not necessary to provide two orientation control layers, the first orientation control layer 76 and the second orientation control layer 77, as in this embodiment. By providing an orientation control layer on only one of the thin-film piezoelectric elements and precisely controlling the orientation of that thin-film piezoelectric element, it is possible to significantly improve the displacement efficiency of that thin-film piezoelectric element. Sufficiently improving the displacement efficiency of just one thin-film piezoelectric element naturally improves the displacement efficiency of the entire piezoelectric element 7. However, this can have the adverse effect of shortening the life of the piezoelectric element 7. If an orientation control layer is provided on only one thin-film piezoelectric element, one thin-film piezoelectric element will have significantly greater displacement than the other, resulting in an imbalance in displacement efficiency. Since the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 are naturally an integral unit, since they constitute the same piezoelectric element 7. However, because they are an integral unit, strain due to an imbalance in displacement efficiency can accumulate internally, potentially causing component peeling. In contrast to this, in this embodiment, by providing an orientation control layer individually for each thin film piezoelectric, it is possible to optimize the orientation control of each thin film piezoelectric and also to prevent the displacement of only one thin film piezoelectric from being extremely biased, thereby achieving both displacement efficiency and a long lifespan.

[0069] The first orientation control layer 76 and the second orientation control layer 77 may be formed of the same material to reduce manufacturing costs. However, for the following reasons, it is more preferable that the first orientation control layer 76 and the second orientation control layer 77 be formed of different materials. By providing the first orientation control layer 76 and the second orientation control layer 77, the orientation of each of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 can be controlled. That is, the first orientation control layer 76 can preferentially orient the crystals of the first thin-film piezoelectric element 72 in a predetermined plane orientation and adjust the degree of orientation of the predetermined plane orientation. Similarly, the second orientation control layer 77 can preferentially orient the crystals of the second thin-film piezoelectric element 74 in a predetermined plane orientation and adjust the degree of orientation of the predetermined plane orientation. The first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 have different positions, properties, functions, etc., and therefore may have different preferred orientations. In this case, if first orientation control layer 76 and second orientation control layer 77 are made of different materials, the orientation of first thin-film piezoelectric element 72 and second thin-film piezoelectric element 74 can be controlled individually.

[0070] For example, when the first orientation control layer 76 preferentially orients the crystals of the first thin-film piezoelectric element 72 in the (100) plane, the piezoelectric characteristics of the piezoelectric element 7 can be improved compared to when the crystals are preferentially oriented in the (110) plane. Similarly, when the second orientation control layer 77 preferentially orients the crystals of the second thin-film piezoelectric element 74 in the (100) plane, the piezoelectric characteristics of the piezoelectric element 7 can be improved compared to when the crystals are preferentially oriented in the (110) plane. Therefore, the displacement efficiency of the piezoelectric element 7 can be increased.

[0071] The crystal orientation of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 can be determined by analyzing the X-ray diffraction intensity curves using X-ray diffraction (XRD). Preferential orientation in the (100) plane means that the peak intensity corresponding to the (100) plane is higher than the peak intensity corresponding to other directions, specifically the (110) plane. In particular, by orienting 50% or more, or even 80% or more, of the crystals of the thin-film piezoelectric element in the (100) plane, the displacement efficiency of the piezoelectric element 7 can be improved.

[0072] Furthermore, for example, the first orientation control layer 76 can adjust the degree of orientation of the crystals of the first thin-film piezoelectric 72 to the (100) plane. Similarly, the first orientation control layer 76 can adjust the degree of orientation of the crystals of the first thin-film piezoelectric 72 to the (100) plane. Therefore, by providing the first orientation control layer 76 that controls the orientation of the first thin-film piezoelectric 72 and the second orientation control layer 77 that controls the orientation of the second thin-film piezoelectric 74, it is possible to set the first thin-film piezoelectric 72 and the second thin-film piezoelectric 74 to their desired degrees of orientation. Therefore, it is possible to set optimal physical property values ​​for each of the first thin-film piezoelectric 72 and the second thin-film piezoelectric 74.

[0073] Each of the first orientation control layer 76 and the second orientation control layer 77 contains, for example, titanium (Ti) or a complex oxide having a perovskite structure. The complex oxide having a perovskite structure contains, for example, any of Ni (nickel), lanthanum (La), Bi (bismuth), lead (Pb), titanium (Ti), and iron (Fe) as a constituent element.

[0074] Specifically, for example, composite oxides having a perovskite structure include lead titanate (PbTiO3), lanthanum nickelate (LaNiO3), Pb x Bi (a-x) Fe y Ti (b-y) O z , and Pb x Fe y Ti (1-y) O z Each of the first orientation control layer 76 and the second orientation control layer 77 may be a single layer or multiple layers. Therefore, the first orientation control layer 76 and the second orientation control layer 77 may each be made of one type of material or multiple types of materials.

[0075] In addition, the aforementioned Pb x Bi (a-x) Fe y Ti (b-y) O zIn this case, a > x and b > y. Also, x / (a - x) preferably satisfies 0.04 < x / (a - x) < 1.40. Further, in order to orient it to the (100) plane, it is more preferable that x / (a - x) < 0.72. Also, it is preferable that b = 1, and it is preferable that 0.8 < (a / b) < 1.4. Also, z preferably satisfies 2.8 < z < 3.2.

[0076] Examples that satisfy these preferable ranges include, for example, a = 1.2, b = 1.0, x = 0.1, and y = 0.5.

[0077] Also, Pb x Fe y Ti (1-y) O z In this case, x satisfies the relationship 1.00 ≦ x < 2.00. In order to orient it to the (100) plane, it is preferable that x satisfies the relationship 1.00 ≦ x < 1.50. Also, y satisfies the relationship 0.10 ≦ y ≦ 0.90. In order to orient it to the (100) plane, it is preferable that 0.20 ≦ y ≦ 0.80. Also, z typically satisfies the relationship z = 3.00. However, z does not necessarily have to satisfy this relationship.

[0078] Incidentally, hereinafter, Pb x Bi (a-x) Fe y Ti (b-y) O z will be simply described as "PbBiFeTiO". Pb x Fe y Ti (1-y) O z will be simply described as "PbFeTiO".

[0079] For example, the second orientation control layer 77 preferably contains Bi, Fe, Ti, or Pb. In this case, specifically, the second orientation control layer 77 is, for example, PbBiFeTiO. PbBiFeTiO is superior to PbFeTiO, lanthanum nickelate, and titanium in terms of the performance of controlling the orientation of the second thin-film piezoelectric material 74. Therefore, for example, the degree of orientation of the second thin-film piezoelectric material 74 to the (100) plane can be increased. Therefore, the piezoelectric efficiency of the second thin-film piezoelectric material 74 can be increased.

[0080] Furthermore, the second orientation control layer 77 containing PbBiFeTiO has a self-orientation property, which is a property of self-orienting in a predetermined plane orientation. Therefore, when the second orientation control layer 77 is made of PbBiFeTiO, the second orientation control layer 77 is less susceptible to the plane orientation of the substrate underneath. Therefore, regardless of the plane orientation of the substrate, the second orientation control layer 77 self-orients in a predetermined plane orientation without being affected by the substrate. Therefore, under the influence of the plane orientation of the second orientation control layer 77, the second thin-film piezoelectric element 74 can be oriented in the same plane orientation as the second orientation control layer 77. Specifically, the second orientation control layer 77 is oriented in the (100) plane. The second orientation control layer 77 controls the orientation of the second thin-film piezoelectric element 74 to the (100) plane. Note that a layer without self-orientation would be oriented in a plane orientation other than the predetermined plane orientation under the influence of the plane orientation of the substrate.

[0081] 4, the second orientation control layer 77 includes a first portion 771 and a second portion 772. The first portion 771 is disposed directly above the individual electrode 73 and is in contact with the individual electrode 73. An active portion 741 of the second thin-film piezoelectric element 74 is provided on the first portion 771. The second portion 772 is disposed on the first common electrode 71 and is in contact with the first common electrode 71. The second portion 772 does not overlap with the individual electrode 73 in a plan view.

[0082] As described above, the base of the second orientation control layer 77 is not uniform but includes different portions. In other words, the second orientation control layer 77 is in contact with two or more different layers. Even if the base is not uniform, the second orientation control layer 77 has self-orientation properties, and thus the second orientation control layer 77 self-orients itself in a predetermined plane orientation without being affected by the base. Therefore, the second thin-film piezoelectric element 74 can be preferentially oriented in a predetermined plane orientation without being affected by a complex base.

[0083] As described above, the inactive portion 742 of the second thin-film piezoelectric element 74 extends to the outside of the first thin-film piezoelectric element 72. On this outside, a second portion 772 of the second orientation control layer 77 is provided between the second thin-film piezoelectric element 74 and the first common electrode 71. By providing a portion of the second orientation control layer 77 between the second thin-film piezoelectric element 74 and the first common electrode 71, it is possible to reduce the orientation difference within the second thin-film piezoelectric element 74 compared to when no second orientation control layer is provided.

[0084] If the second portion 772 were not provided, the orientation of the non-active portion would not be controlled by the second orientation control layer 77. In this case, the orientation of the active portion, whose orientation is controlled by the second orientation control layer 77, would be different from that of the non-active portion, whose orientation is not controlled by the second orientation control layer 77. In contrast, by providing the second portion 772, the orientation of the non-active portion is controlled by the second orientation control layer 77, just like the active portion. Therefore, the orientation difference between the non-active portion and the active portion can be reduced. By reducing the orientation difference within the second thin-film piezoelectric element 74, defects caused by displacement of the second thin-film piezoelectric element 74 due to the orientation difference can be reduced. By reducing the orientation difference within the second thin-film piezoelectric element 74, the stress in the second thin-film piezoelectric element 74 is dispersed and made uniform, making stress-induced fracture of the second thin-film piezoelectric element 74 less likely to occur. Therefore, cracks are less likely to occur in the second thin-film piezoelectric element 74, improving the reliability of the piezoelectric element 7.

[0085] Furthermore, for example, when second orientation control layer 77 contains Bi, Fe, Ti, and Pb, first orientation control layer 76 preferably also contains Bi, Fe, Ti, and Pb. Specifically, for example, first orientation control layer 76 is preferably PbBiFeTiO.

[0086] As a result, the first orientation control layer 76 and the second orientation control layer 77 are less susceptible to the influence of the plane orientation of the underlying layer, and it is easier to orient the first thin-film piezoelectric 72 and the second thin-film piezoelectric 74 in a predetermined plane orientation. This makes it possible to suppress a decrease in the degree of orientation of the predetermined plane orientation due to the influence of the underlying layer. Specifically, for example, the degree of orientation of both the first thin-film piezoelectric 72 and the second thin-film piezoelectric 74 in the (110) plane can be increased. This increases the piezoelectric efficiency of the second thin-film piezoelectric 74. This increases the amount of displacement per unit voltage, improving the ejection characteristics even at low voltages.

[0087] Furthermore, since the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 are made of the same material, the piezoelectric element 7 is easy to manufacture and it is easy to control the degrees of orientation of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74. For example, having the first orientation control layer 76 and the second orientation control layer 77 made of the same material is effective when it is desired to set the degree of orientation of the second thin-film piezoelectric element 74 to be approximately the same as that of the first thin-film piezoelectric element 72.

[0088] Furthermore, for example, when the second orientation control layer 77 contains Bi, Fe, Ti, and Pb, it is preferable that the first orientation control layer 76 contains Ti and Pb but does not contain Bi or Fe. Specifically, for example, the first orientation control layer 76 is the aforementioned PbTiOx.

[0089] When the first orientation control layer 76 is made of PbTiOx, the first thin-film piezoelectric 72 is preferably made of a material containing lead, such as PZT. In this case, for example, in manufacturing the first orientation control layer 76, the first thin-film piezoelectric 72 is formed on a layer made of single-crystal titanium. As a result, the single-crystal titanium reacts with components such as lead contained in the first thin-film piezoelectric 72 to form PbTiOx, which serves as a nucleus for crystal growth of the first thin-film piezoelectric 72. At this time, the PbTiOx acts as a crystal nucleus and orients the first thin-film piezoelectric 72 in a predetermined plane orientation, specifically, the (100) plane. In this case, the finally completed first orientation control layer 76 is made of PbTiOx. Note that the first orientation control layer 76 made of PbTiOx has the function of controlling the orientation of the first thin-film piezoelectric 72, but is considered not to have self-orientation properties.

[0090] The base of the first orientation control layer 76 has a structure that is less complicated than the base of the second orientation control layer 77. Therefore, from the viewpoint of ease of manufacture, it is preferable that the first orientation control layer 76 be a layer containing PbTiOx. Furthermore, in a layer containing PbTiOx, the components are less likely to diffuse into the first thin-film piezoelectric element 72 than in a layer containing lanthanum nickelate. Therefore, the piezoelectric properties of the first thin-film piezoelectric element 72 are less likely to deteriorate due to this diffusion.

[0091] Furthermore, for example, when the second orientation control layer 77 contains Bi, Fe, Ti, and Pb, it is preferable that the first orientation control layer 76 contains Ti but does not contain Bi, Fe, or Pb. Specifically, for example, it is preferable that the first orientation control layer 76 is a layer made of Ti as described above.

[0092] As described above, first orientation control layer 76 containing lead titanate is formed by forming first thin-film piezoelectric element 72 on a layer made of Ti. From this perspective, first orientation control layer 76 preferably includes a layer made of titanium. Furthermore, when Ti in first orientation control layer 76 acts as a crystalline nucleus to orient first thin-film piezoelectric element 72 in a predetermined plane orientation, the finally completed first orientation control layer 76 may include a layer made of PbTiOx and a layer made of Ti.

[0093] It is to be noted that first orientation control layer 76 made of Ti has the function of controlling the orientation of first thin-film piezoelectric element 72, but is not considered to have self-orientation. First orientation control layer 76 made of Ti is made of single crystal Ti.

[0094] Furthermore, for example, if it is desired to make the degree of orientation of a predetermined plane orientation of the second thin-film piezoelectric 74 higher than the degree of orientation of a predetermined plane orientation of the first thin-film piezoelectric 72, when the second orientation control layer 77 contains Bi, Fe, Ti, and Pb, it is preferable that the first orientation control layer 76 contains a layer composed of Ti or a layer composed of PbTiOx.

[0095] Furthermore, for example, it is preferable that second orientation control layer 77 contains Ti and Pb but does not contain Bi or Fe. Specifically, it is preferable that second orientation control layer 77 contains PbTiOx. A layer containing PbTiOx is less likely to have its components diffuse into second thin-film piezoelectric element 74 than a layer containing lanthanum nickelate. Therefore, the piezoelectric properties of second thin-film piezoelectric element 74 are less likely to deteriorate due to this diffusion.

[0096] Furthermore, when second orientation control layer 77 contains Ti and Pb but does not contain Bi or Fe, first orientation control layer 76 also preferably contains Ti and Pb but does not contain Bi or Fe. Specifically, first orientation control layer 76 is preferably PbTiOx, like second orientation control layer 77. This makes it less likely that the piezoelectric properties of first thin-film piezoelectric element 72 and second thin-film piezoelectric element 74 will be degraded due to the influence of diffusion of the aforementioned components.

[0097] Furthermore, since the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 are made of the same material, the piezoelectric element 7 is easy to manufacture and it is easy to control the degrees of orientation of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74. For example, the fact that the first orientation control layer 76 and the second orientation control layer 77 are made of the same material is effective when it is desired to set the degree of orientation of the second thin-film piezoelectric element 74 to be approximately the same as that of the first thin-film piezoelectric element 72.

[0098] Furthermore, when the second orientation control layer 77 contains Ti and Pb but does not contain Bi or Fe, it is preferable that the first orientation control layer 76 contains Ti but does not contain Bi, Fe, or Pb. Specifically, for example, the first orientation control layer 76 is preferably a layer made of Ti as described above. As described above, the first orientation control layer 76 containing PbTiOx is formed by forming the first thin-film piezoelectric 72 on a layer made of Ti. From this perspective, it is preferable that the first orientation control layer 76 includes a layer made of Ti. Furthermore, when the Ti of the first orientation control layer 76 acts as a crystal nucleus to orient the first thin-film piezoelectric 72 in a predetermined plane orientation, the finally completed first orientation control layer 76 may include a layer made of PbTiOx and a layer made of titanium.

[0099] Furthermore, when the second orientation control layer 77 contains Ti and Pb but does not contain Bi or Fe, the first orientation control layer 76 preferably contains Bi, Fe, Ti, and Pb. Specifically, the first orientation control layer 76 is preferably PbBiFeTiO. PbBiFeTiO is more likely to increase the degree of orientation of the first thin-film piezoelectric 72 than PbFeTiO, lanthanum nickelate, and PbTiOx. Therefore, for example, the degree of orientation of the first thin-film piezoelectric 72 to the (100) plane can be increased.

[0100] Furthermore, if it is desired to make the degree of crystal orientation of the first thin-film piezoelectric 72 higher than that of the second thin-film piezoelectric 74, it is preferable that the first orientation control layer 76 contains Bi, Fe, Ti, and Pb when the second orientation control layer 77 contains Ti and Pb but does not contain Bi or Fe.

[0101] As described above, by appropriately selecting the materials of the first orientation control layer 76 and the second orientation control layer 77, the piezoelectric properties of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 can be set to the desired properties.

[0102] Furthermore, the thickness D76 of the first orientation control layer 76 is thinner than the thickness D72 of the first thin-film piezoelectric 72, and the thickness D77 of the second orientation control layer 77 is thinner than the thickness D74 of the second thin-film piezoelectric 74. Each thickness is an average length along the Z axis. There are no particular limitations on either the thickness D76 or the thickness D77, but they are within the range of 20 nm to 200 nm, for example.

[0103] The thickness D77 of the second orientation control layer 77 may be thicker than the thickness D76 of the first orientation control layer 76, for example. This configuration has the following advantages. In the manufacturing process of the piezoelectric element 7, as described below, the first orientation control layer 76 is also patterned when the first thin-film piezoelectric element 72 is etched, as shown in FIG. 10( e). At this time, due to an error in etching time or the like, etching may be performed to the extent that the first orientation control layer 76 is penetrated, potentially resulting in the first common electrode 71 being removed. However, since the first thin-film piezoelectric element 72 is relatively thin, the etching time is not short, and this is unlikely to occur. On the other hand, as shown in FIG. 11( c), the second orientation control layer 77 is patterned when the second thin-film piezoelectric element 74 is etched. Similarly, due to an error in etching time or the like, etching may be performed to the extent that the second orientation control layer 77 is penetrated, potentially resulting in the first common electrode 71 being removed. Here, the second thin-film piezoelectric element 74 is thicker than the first thin-film piezoelectric element 72. Therefore, it takes longer to etch the second thin-film piezoelectric element 74 than the first thin-film piezoelectric element 72, and therefore the possibility of etching errors increases. Therefore, the possibility of over-etching the second orientation control layer 77 and etching away the first common electrode 71 is higher than that of the first orientation control layer 76. By contrast, by making the second orientation control layer 77 thicker, the risk of such etching away the first common electrode 71 is reduced. During use, the orientation control layer functions to reduce the dielectric constant between each electrode and each thin-film piezoelectric element, so it is preferable that the orientation control layer be thinner if possible. Therefore, the first orientation control layer 76, which is inherently less likely to etch away the first common electrode 71, is made thinner than the second orientation control layer 77.

[0104] From another perspective, the thickness D77 of the second orientation control layer 77 may be thinner than the thickness D76 of the first orientation control layer 76. This configuration has the following advantages. Each of the first orientation control layer 76 and the second orientation control layer 77 is affected, at least in part, by the unevenness of the respective substrates. In particular, the first orientation control layer 76 is closer to the diaphragm 15 than the second orientation control layer 77 and is therefore more susceptible to the unevenness of the diaphragm 15 and the influence of elements (such as Zr) contained in the diaphragm 15. To suppress this influence, it is preferable that the thickness D76 of the first orientation control layer 76 be thicker. On the other hand, the second orientation control layer 77 is farther from the diaphragm 15 than the first orientation control layer 76, so this influence does not need to be taken into consideration as much. In addition, as described above, an unnecessarily thick orientation control layer causes a decrease in the dielectric constant. Therefore, it is preferable that the second orientation control layer 77, which is less affected by the unevenness and the influence of elements (such as Zr), be thinner than the first orientation control layer 76.

[0105] The thicknesses of the first orientation control layer 76 and the second orientation control layer 77 may be the same.

[0106] 1-5. Manufacturing method of piezoelectric element 7 9 is a flow chart showing a method for manufacturing the piezoelectric element 7, which is part of the method for manufacturing the liquid ejection head 1. As shown in Fig. 9, the method for manufacturing the piezoelectric element 7, which is part of the method for manufacturing the liquid ejection head 1, includes a first step S1, a second step S2, a third step S3, a fourth step S4, a fifth step S5, a sixth step S6, a seventh step S7, an eighth step S8, and a ninth step S9. These steps are performed in this order.

[0107] 10 and 11 are diagrams illustrating a method for manufacturing the piezoelectric element 7 shown in FIG. 10(a) is a diagram illustrating a first step S1. In the first step S1, a first common electrode 71 is formed on the vibration plate 15. The first common electrode 71 is formed by a known film formation technique such as vapor deposition or sputtering, or a known processing technique using photolithography, etching, or the like.

[0108] 10(b) is a diagram illustrating the second step S2. In the second step S2, a first orientation control layer 76 is formed on the first common electrode 71. The first orientation control layer 76 is formed by a known film formation technique such as evaporation or sputtering.

[0109] 10(c) is a diagram illustrating the third step S3. In the third step S3, the first thin-film piezoelectric 72 is formed on the first orientation control layer 76. The first thin-film piezoelectric 72 is formed, for example, by forming a precursor layer of the first thin-film piezoelectric 72 by a sol-gel method and then firing and crystallizing the precursor layer. The first thin-film piezoelectric 72 may also be formed by a sputtering method. However, by using the sol-gel method, it is possible to preferably form the first thin-film piezoelectric 72 having a thickness of 2 μm or less, or even 1 μm or less.

[0110] 10(d) is a diagram illustrating the fourth step S4. In the fourth step S4, the individual electrodes 73 are formed on the first thin-film piezoelectric elements 72. The first common electrode 71 is formed by a known film formation technique such as vapor deposition or sputtering.

[0111] 10(e) is a diagram for explaining the fifth step S5. In the fifth step S5, the individual electrodes 73, the first thin-film piezoelectric element 72, and the first orientation control layer 76 are patterned. These patterning processes are performed by a known processing technique such as etching.

[0112] 11(a) is a diagram illustrating the sixth step S6. In the sixth step S6, a second alignment control layer 77 is formed on the individual electrodes 73. The second alignment control layer 77 is formed by a known film formation technique such as vapor deposition or sputtering. The second alignment control layer 77 has a portion formed on the first common electrode 71 in addition to a portion formed on the individual electrodes 73.

[0113] 11(b) is a diagram illustrating the seventh step S7. In the seventh step S7, the second thin-film piezoelectric 74 is formed on the second orientation control layer 77. The second thin-film piezoelectric 74 is formed, for example, by forming a precursor layer of the second thin-film piezoelectric 74 by a sol-gel method, and then firing and crystallizing the precursor layer. The second thin-film piezoelectric 74 may also be formed by a sputtering method. However, by using the sol-gel method, the second thin-film piezoelectric 74 can be suitably formed to a thickness of 2 μm or less, or even 1 μm or less.

[0114] FIG. 11(c) is a diagram illustrating the eighth step S8. In the eighth step S8, the second thin-film piezoelectric element 74 and the second orientation control layer 77 are patterned. This patterning is performed by a known processing technique using etching or the like. In this etching, the active portion 741 and the non-active portion 742 are etched to different depths. Furthermore, in this etching, a first portion 771 and a second portion 772 of the second orientation control layer 77 are formed.

[0115] 11(d) is a diagram illustrating the ninth step S9. In the ninth step S9, the second common electrode 75 is formed so as to cover the second thin-film piezoelectric element 74. For example, the second common electrode 75 is formed by a known film formation technique such as vapor deposition or sputtering, or a known processing technique using photolithography, etching, or the like.

[0116] The piezoelectric element 7 of the liquid ejection head 1 is manufactured by the above method. This method allows the piezoelectric element 7 to be manufactured simply and with high precision. Furthermore, this method allows the first thin-film piezoelectric element 72 to be formed on the first orientation control layer 76, and thereby the orientation of the first thin-film piezoelectric element 72 is controlled by the first orientation control layer 76, and the second thin-film piezoelectric element 74 to be formed on the second orientation control layer 77, and thereby the orientation of the second thin-film piezoelectric element 74 is controlled by the second orientation control layer 77. Therefore, the physical properties of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 can be adjusted to desired values, and a piezoelectric element 7 having desired piezoelectric characteristics can be obtained.

[0117] Furthermore, in the sixth step S6 described above, the second orientation control layer 77 is formed not only on the individual electrodes 73 but also on the first common electrode 71. This reduces the orientation difference within the second thin-film piezoelectric element 74. Specifically, this reduces the orientation difference between the active portion 741 and the non-active portion 742. This makes it less likely for stress fracture to occur in the second thin-film piezoelectric element 74, making it less likely for cracks to occur in the second thin-film piezoelectric element 74 and improving the reliability of the piezoelectric element 7.

[0118] The following configuration may also be used. The second thin-film piezoelectric element 74 is farther from the neutral axis A1 than the first thin-film piezoelectric element 72. This increases the strain on the second thin-film piezoelectric element 74, potentially causing significant damage to the second thin-film piezoelectric element 74. On the other hand, the distance from the neutral axis A1 of the first thin-film piezoelectric element 72 is not greater than that of the second thin-film piezoelectric element 74. This reduces the strain on the first thin-film piezoelectric element 72 compared to the second thin-film piezoelectric element 74. Therefore, the second thin-film piezoelectric element 74 can be made relatively thin to minimize damage, while the first thin-film piezoelectric element 72, which is less susceptible to damage, can be made relatively thick, thereby improving the ejection characteristics as much as possible. In this way, the thickness of the first thin-film piezoelectric element 72 may be greater than that of the second thin-film piezoelectric element 74.

[0119] The following configuration may also be used. The greater the Young's modulus of each thin-film piezoelectric element, the greater the generated force. Therefore, even in a structure in which multiple thin-film piezoelectric elements are stacked, as in this embodiment, it is preferable to increase the Young's modulus of each of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 in order to increase the displacement of the piezoelectric element 7 and improve the ejection characteristics as much as possible. However, increasing the Young's modulus of the second thin-film piezoelectric element 74 may have adverse effects. In manufacturing the piezoelectric element 7, each layer is formed from bottom to top. After the second thin-film piezoelectric element 74 is formed, the second common electrode 75 and various wiring lines are formed on top of it. This formation involves processing such as etching. The etching process used to form the second common electrode 75 and various wiring lines may affect the second thin-film piezoelectric element 74, potentially causing damage during film formation. This damage during film formation is more pronounced as the Young's modulus increases, i.e., the film becomes harder. In view of this, from the viewpoint of ejection characteristics, it is better for the second thin-film piezoelectric element 74 to have a larger Young's modulus; however, when film formation damage is taken into consideration, it is difficult to make the Young's modulus of the second thin-film piezoelectric element 74 that large. On the other hand, the first thin-film piezoelectric element 72 is less affected by film formation damage. Therefore, in this embodiment, since the Young's modulus of the second thin-film piezoelectric element 74 cannot be made large, the Young's modulus of the first thin-film piezoelectric element 72 is made large to compensate for this, thereby ensuring the ejection characteristics of the piezoelectric element 7 as a whole. In this way, the Young's modulus of the first thin-film piezoelectric element 72 may be made larger than the Young's modulus of the second thin-film piezoelectric element 74.

[0120] From another perspective, the following configuration may also be used. Provided that the possibility of the above-described film damage is not a consideration, the Young's modulus of the first thin-film piezoelectric element 72 may be smaller than that of the second thin-film piezoelectric element 74. Even if the generated forces of the first thin-film piezoelectric element 72 and the second thin-film piezoelectric element 74 are the same, the moment increases with distance from the neutral axis A1, thereby contributing significantly to the ejection characteristics. Therefore, from the perspective of maximizing the ejection characteristics, it is preferable to increase the Young's modulus of the second thin-film piezoelectric element 74. On the other hand, although the contribution of the first thin-film piezoelectric element 72 is small, it is also preferable to increase the Young's modulus of the first thin-film piezoelectric element 72 to maximize the ejection efficiency. However, increasing the Young's modulus of the first thin-film piezoelectric element 72, like the second thin-film piezoelectric element 74, may adversely affect the ejection characteristics, especially during high-frequency driving. When ejecting ink continuously, if the next ejection is performed while residual vibrations remain inside the pressure chamber C from the previous ejection, the residual vibrations may cause deviations in the characteristics of the next ejection. If the first thin-film piezoelectric element 72 has a small Young's modulus, its flexibility allows it to smoothly absorb the pressure of residual vibrations. This makes it less likely that deviations in characteristics will occur due to successive ejections. However, if the first thin-film piezoelectric element 72 has a large Young's modulus, it will not be able to sufficiently absorb the pressure of residual vibrations from the previous ejection. This could result in deviations in characteristics. Naturally, this pressure absorption of residual vibrations is more effective in areas where residual vibrations are occurring, i.e., areas closer to pressure chamber C. Therefore, reducing the Young's modulus of the first thin-film piezoelectric element 72 located closer to pressure chamber C leads to effective suppression of residual vibrations. From this perspective, it is also effective to make the Young's modulus of the first thin-film piezoelectric element 72 smaller than that of the second thin-film piezoelectric element 74.

[0121] 2. Variations The above-described exemplary embodiment may be modified in various ways. Specific modifications that may be applied to the above-described exemplary embodiment are exemplified below.

[0122] The "liquid ejection head" may be a circulation type head having a so-called circulation flow path.

[0123] A "liquid ejection device" can be employed in various devices such as facsimile machines and copiers, as well as devices dedicated to printing. The uses of a liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. A liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. A liquid ejection device that ejects a solution of an organic substance related to a living organism is used as a manufacturing device for manufacturing biochips, for example.

[0124] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments. Furthermore, the configuration of each part of the present invention can be replaced with any configuration that exhibits the same function as the above-described embodiments, and any configuration can be added. [Explanation of symbols]

[0125] 1...liquid ejection head, 7...piezoelectric element, 15...vibration plate, 20...driving circuit, 71...first common electrode, 72...first thin film piezoelectric, 73...individual electrode, 74...second thin film piezoelectric, 75...second common electrode, 76...first orientation control layer, 77...second orientation control layer, 100...liquid ejection device, 910...voltage application circuit, A1...neutral axis, C...pressure chamber, Com...driving voltage, D76...thickness, D77...thickness, N...nozzle, VBS...reference voltage.

Claims

1. a pressure chamber substrate provided with a plurality of pressure chambers; A diaphragm and a first common electrode provided in common to the plurality of pressure chambers and to which a reference voltage that does not change with time is applied; a first thin film piezoelectric body; individual electrodes provided individually for the plurality of pressure chambers, to which a driving voltage that varies with time is applied; a second thin film piezoelectric body; a second common electrode provided in common to the plurality of pressure chambers and to which the reference voltage is applied, and a first orientation control layer for controlling the orientation of the first thin-film piezoelectric material is provided between the first thin-film piezoelectric material and the first common electrode; A liquid ejection head, characterized in that a second orientation control layer for controlling the orientation of the second thin film piezoelectric element is provided between the second thin film piezoelectric element and the individual electrode.

2. the second thin-film piezoelectric element extends to the outside of the first thin-film piezoelectric element, 2. The liquid ejection head according to claim 1, wherein the second orientation control layer is provided on the outer side between the second thin-film piezoelectric element and the first common electrode.

3. 3. The liquid ejection head according to claim 1, wherein the first thin-film piezoelectric element and the second thin-film piezoelectric element are made of different materials.

4. 3. The liquid ejection head according to claim 1, wherein the first thin-film piezoelectric element and the second thin-film piezoelectric element are made of the same material.

5. 3. The liquid ejection head according to claim 1, wherein the second orientation control layer contains Bi, Fe, Ti, and Pb.

6. 6. The liquid ejection head according to claim 5, wherein the first orientation control layer contains Ti and Pb, but does not contain Bi and Fe.

7. 6. The liquid ejection head according to claim 5, wherein the first orientation control layer contains Ti, but does not contain Bi, Fe, or Pb.

8. 6. The liquid ejection head according to claim 5, wherein the first orientation control layer contains Bi, Fe, Ti, and Pb.

9. 3. The liquid ejection head according to claim 1, wherein the second orientation control layer contains Ti and Pb, but does not contain Bi and Fe.

10. 10. The liquid ejection head according to claim 9, wherein the first orientation control layer contains Ti and Pb, but does not contain Bi and Fe.

11. 10. The liquid ejection head according to claim 9, wherein the first orientation control layer contains Ti, but does not contain Bi, Fe, or Pb.

12. 10. The liquid ejection head according to claim 9, wherein the first orientation control layer contains Bi, Fe, Ti, and Pb.

13. 3. The liquid ejection head according to claim 1, wherein the first alignment control layer and the second alignment control layer are formed of different materials.

14. 3. The liquid ejection head according to claim 1, wherein the first alignment control layer and the second alignment control layer are formed of the same material.

15. 3. The liquid ejection head according to claim 1, wherein the second alignment control layer is thicker than the first alignment control layer.

16. 3. The liquid ejection head according to claim 1, wherein the second alignment control layer is thinner than the first alignment control layer.

17. the first orientation control layer has a property of not self-orienting in a predetermined plane orientation, 3. The liquid ejection head according to claim 1, wherein the second alignment control layer has a property of self-aligning in a predetermined plane direction.

18. The liquid ejection head according to claim 1; a voltage application circuit for applying the reference voltage and the drive voltage;

19. A method for manufacturing a liquid ejection head, comprising: a first step of forming a first common electrode on a diaphragm; a second step of depositing a first alignment control layer on the first common electrode; a third step of depositing a first thin-film piezoelectric material on the first orientation control layer; a fourth step of forming individual electrodes on the first thin film piezoelectric element; a fifth step of patterning the individual electrodes, the first thin-film piezoelectric element, and the first orientation control layer; a sixth step of forming a second alignment control layer on the individual electrodes; a seventh step of depositing a second thin-film piezoelectric material on the second orientation control layer; an eighth step of patterning the second thin-film piezoelectric element and the second orientation control layer; and a ninth step of forming a second common electrode so as to cover the second thin-film piezoelectric element.

20. 20. The method for manufacturing a liquid ejection head according to claim 19, wherein in the sixth step, the second alignment control layer is also formed on the first common electrode.

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