Liquid ejection head and actuator

Abstract

The present invention provides a liquid ejection head and actuator that suppress a decrease in ejection performance or durability. The liquid ejection head of the present invention comprises: a pressure chamber substrate having a plurality of pressure chambers arranged in a first direction; a vibration plate arranged in a second direction intersecting the first direction relative to the pressure chamber substrate; a first electrode arranged in the second direction relative to the vibration plate; a piezoelectric layer arranged in the second direction relative to the first electrode; and a second electrode arranged in the second direction relative to the first electrode. In the liquid ejection head, the piezoelectric layer comprises a first region that does not overlap with the first electrode in the first direction, and a second region that overlaps with the first electrode in the first direction. When the piezoelectric layer is analyzed by X-ray diffraction, the first region is preferentially oriented in the first plane direction, and the second region is preferentially oriented in the first plane direction.

Description

Technical Field

[0001] The present invention relates to a liquid ejection head and an actuator. Background Art

[0002] Conventionally, there has been proposed a liquid ejection head that uses a piezoelectric element to vibrate a vibration plate having a pressure chamber, thereby ejecting liquid filled in the pressure chamber from a nozzle.

[0003] The piezoelectric element described in Patent Document 1 includes a lower electrode, a piezoelectric thin film, and an upper electrode. A seed layer for aligning the piezoelectric thin film to a desired orientation is disposed on the lower electrode.

[0004] For example, in the case of a seed layer disposed on the lower electrode as in Patent Document 1, although the region of the piezoelectric layer overlapping with the lower electrode has the desired surface orientation due to the presence of the seed layer, the region of the piezoelectric layer not overlapping with the lower electrode becomes non-oriented due to the absence of the seed layer. Therefore, the surface orientation of the crystals is different in the region overlapping with the lower electrode and the region not overlapping with the lower electrode of the piezoelectric layer. When the surface orientations are different in the region overlapping with the lower electrode and the region not overlapping with the lower electrode of the piezoelectric layer, the physical properties such as the thermal expansion coefficient in these regions are different from each other. As a result, cracks may occur between these regions, thereby reducing the ejection performance or durability.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-238774 Summary of the Invention

[0006] In order to solve the above problems, a preferred embodiment of the present invention involves a liquid ejection head comprising: a pressure chamber substrate, which has a plurality of pressure chambers arranged in a first direction; a vibration plate, which is arranged in a second direction intersecting the first direction compared to the pressure chamber substrate; a first electrode, which is arranged in the second direction compared to the vibration plate; a piezoelectric layer, which is arranged in the second direction compared to the first electrode; and a second electrode, which is arranged in the second direction compared to the first electrode. In the liquid ejection head, the piezoelectric layer has a first region that does not overlap with the first electrode in the first direction, and a second region that overlaps with the first electrode in the first direction. When the piezoelectric layer is analyzed by X-ray diffraction, the first region is preferentially oriented to a first surface orientation, and the second region is preferentially oriented to the first surface orientation.

[0007] The actuator involved in a preferred embodiment of the present invention comprises: a pressure chamber substrate, which has a plurality of pressure chambers arranged in a first direction; a vibration plate, which is arranged in a second direction intersecting the first direction compared to the pressure chamber substrate; a first electrode, which is arranged in the second direction compared to the vibration plate; a piezoelectric layer, which is arranged in the second direction compared to the first electrode; and a second electrode, which is arranged in the second direction compared to the first electrode. In the actuator, the piezoelectric layer has a first region that does not overlap with the first electrode in the first direction, and a second region that overlaps with the first electrode in the first direction. When the piezoelectric layer is analyzed by X-ray diffraction, the first region is preferentially oriented in a first plane orientation, and the second region is preferentially oriented in the first plane orientation. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram illustrating the structure of the liquid ejecting device according to the first embodiment.

[0009] Figure 2 This is an exploded perspective view of the liquid ejection head.

[0010] Figure 3 A cross-sectional view of the liquid ejection head.

[0011] Figure 4 A top view showing a portion of the actuator.

[0012] Figure 5 for Figure 4 Cross-sectional view of line bb in.

[0013] Figure 6 It is a graph showing the results of XRD in the second region.

[0014] Figure 7 This is a graph showing the results of XRD in the first region.

[0015] Figure 8 It is a cross-sectional view showing a part of the actuator in the second embodiment.

[0016] Figure 9 It is a cross-sectional view showing a part of the actuator in a modified example.

[0017] Figure 10 It is a cross-sectional view showing a part of the actuator in a modified example. DETAILED DESCRIPTION

[0018] 1. First Implementation

[0019] 1-1. Overall Structure of Liquid Dispensing Device 100

[0020] Figure 1 1 is a structural diagram illustrating the liquid ejection device 100 according to the first embodiment. In the following, for convenience of description, the X-axis, Y-axis, and Z-axis, which are orthogonal to each other, are used as appropriate.

[0021] The liquid ejection device 100 of the first embodiment is an inkjet printing device that ejects ink as an example of liquid onto a medium 12. The medium 12 is typically printing paper, but a printing object made of any material such as a resin film or cloth can also be used as the medium 12. Figure 1 As shown, the liquid ejecting device 100 is provided with a liquid container 14 for storing ink. For example, an ink cartridge that can be attached to and detached from the liquid ejecting device 100, a bag-shaped ink pack formed of a flexible film, or an ink tank that can be refilled with ink can be used as the liquid container 14.

[0022] like Figure 1 As shown, the liquid ejection device 100 includes a control unit 20, a conveying mechanism 22, a moving mechanism 24, and a liquid ejection head 26. The control unit 20 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and one or more storage circuits such as semiconductor memories, and comprehensively controls the various components of the liquid ejection device 100. The conveying mechanism 22 conveys the medium 12 along the Y-axis under the control of the control unit 20.

[0023] The moving mechanism 24 reciprocates the liquid ejecting head 26 along the X-axis under the control of the control unit 20. The moving mechanism 24 includes a substantially box-shaped transport body 242 that accommodates the liquid ejecting head 26, and a conveyor belt 244 that secures the transport body 242. Alternatively, a structure in which a plurality of liquid ejecting heads 26 are mounted on the transport body 242, or a structure in which the liquid container 14 and the liquid ejecting head 26 are mounted on the transport body 242, may be employed.

[0024] The liquid ejection head 26 ejects ink supplied from the liquid container 14 onto the medium 12 from a plurality of nozzles under the control of the control unit 20. Each liquid ejection head 26 ejects ink onto the medium 12 in parallel with the transport of the medium 12 by the transport mechanism 22 and the reciprocating motion of the transport body 242, thereby forming an image on the surface of the medium 12.

[0025] 1-2. Overall Structure of the Liquid Ejection Head 26

[0026] Figure 2It is an exploded perspective view of the liquid ejection head 26. Figure 3 for Figure 2 Cross-sectional view of line aa in . Figure 3 The cross section shown in the figure is a cross section parallel to the XZ plane. The Z axis is the axis along the direction of ink ejection implemented by the liquid ejection head 26. In addition, a direction along the X axis is marked as the X1 direction, and the direction opposite to the X1 direction is marked as the X2 direction. Similarly, a direction along the Y axis is marked as the Y1 direction, and the direction opposite to the Y1 direction is marked as the Y2 direction. A direction along the Z axis is marked as the Z1 direction, and the direction opposite to the Z1 direction is marked as the Z2 direction. In addition, hereinafter, the situation of observing in the Z1 direction or the Z2 direction is referred to as "top view". In addition, for example, the Y1 direction is equivalent to the "first direction". The Z2 direction is equivalent to the "second direction" intersecting with the first direction. In addition, the Y2 direction can also be understood as the "first direction".

[0027] like Figure 2 As shown, the liquid ejection head 26 includes a plurality of nozzles N arranged along the Y axis. The plurality of nozzles N in the first embodiment are divided into a first row La and a second row Lb, which are arranged in parallel with each other at intervals along the X axis. The first row La and the second row Lb are each a set of the plurality of nozzles N arranged in the Y1 direction. Figure 3 The illustrated liquid ejection head 26 has a structure in which elements associated with the nozzles N in the first row La and elements associated with the nozzles N in the second row Lb are arranged substantially symmetrically. Therefore, in the following description, the elements corresponding to the first row La will be emphasized, and the description of elements corresponding to the second row Lb will be omitted as appropriate.

[0028] like Figure 2 as well as Figure 3 As shown, the liquid ejection head 26 includes a nozzle plate 41, a vibration absorber 42, a flow path substrate 31, a pressure chamber substrate 32, a vibration plate 33, a plurality of piezoelectric elements 34, a sealing member 35, a housing 36, and a wiring substrate 51. The nozzle plate 41, the vibration absorber 42, the flow path substrate 31, the pressure chamber substrate 32, the vibration plate 33, the sealing member 35, and the housing 36 are each elongated members extending in the Y1 direction. The nozzle plate 41, the flow path substrate 31, the pressure chamber substrate 32, the vibration plate 33, and the piezoelectric elements 34 are arranged in this order in the Z2 direction. Furthermore, the liquid ejection head 26 includes an actuator 30. The actuator 30 includes a pressure chamber substrate 32, a vibration plate 33, and a plurality of piezoelectric elements 34.

[0029] The nozzle plate 41 is a plate-shaped member having a plurality of nozzles N for ejecting ink. While each of the nozzles N is generally a circular through-hole for ejecting ink, ink can also be ejected through holes that are not circular. The nozzle plate 41 is manufactured, for example, by processing a single crystal silicon (Si) substrate using semiconductor manufacturing techniques such as photolithography and etching. However, any known material or manufacturing method can be used to manufacture the nozzle plate 41.

[0030] In the flow channel substrate 31, a space Ra, a plurality of supply flow channels 312, a plurality of connecting flow channels 314 and a relay liquid chamber 316 are formed. The space Ra is an opening formed in the shape of an elongated strip extending in the Y1 direction. The supply flow channel 312 and the connecting flow channel 314 are through-holes formed for each nozzle N, respectively. The relay liquid chamber 316 is a space formed in the shape of an elongated strip extending in the Y1 direction across the plurality of nozzles N, and the relay liquid chamber 316 connects the space Ra with the plurality of supply flow channels 312. The plurality of connecting flow channels 314 overlap with a nozzle N corresponding to the connecting flow channel 314 when viewed from above. The flow channel substrate 31 is manufactured, for example, by processing a single crystal substrate of silicon using semiconductor manufacturing technology.

[0031] The pressure chamber substrate 32 includes a plurality of pressure chambers C1, which serve as spaces in which ink is placed. The plurality of pressure chambers C1 are arranged one-to-one with respect to the plurality of nozzles N. The pressure chamber substrate 32 includes a wall surface 320 that forms a pressure chamber C1 corresponding to each nozzle N. Although not shown, a protective film is disposed on the wall surface 320 of the pressure chamber substrate 32 to protect the pressure chamber substrate 32 and the vibration plate 33 from contact with the ink.

[0032] The vibration plate 33 is arranged closer to the Z2 direction than the pressure chamber substrate 32. The vibration plate 33 can be elastically deformed. Figure 2 as well as Figure 3 In the illustrated example, the pressure chamber substrate 32 and the vibration plate 33 are formed of different members, but the pressure chamber substrate 32 and a portion of the vibration plate 33 may be formed of the same substrate.

[0033] Multiple piezoelectric elements 34 are arranged closer to the vibration plate 33 in the Z2 direction. Multiple piezoelectric elements 34 are provided for each pressure chamber C1. The piezoelectric elements 34 are long, passive elements extending in the X1 direction when viewed from above. The piezoelectric elements 34 are also driven elements that are driven by the application of a drive signal. The actuator 30, which includes the pressure chamber substrate 32, vibration plate 33, and piezoelectric elements 34, will be described in detail later.

[0034] The housing 36 is a casing for storing ink supplied to the multiple pressure chambers C1 and is formed, for example, by injection molding of a resin material. A space Rb and a supply port 361 are formed in the housing 36. The supply port 361 is a conduit through which ink is supplied from the liquid container 14 and communicates with the space Rb. The space Rb of the housing 36 communicates with the space Ra of the flow path substrate 31. The space formed by the spaces Ra and Rb functions as a liquid storage chamber R, which stores the ink supplied to the multiple pressure chambers C1. Ink supplied from the liquid container 14 and passing through the supply port 361 is stored in the liquid storage chamber R. The ink stored in the liquid storage chamber R branches from the relay liquid chamber 316 to each supply channel 312, thereby being supplied and filled in parallel with the multiple pressure chambers C1. The vibration absorber 42 is a flexible film forming the wall of the liquid storage chamber R and absorbs pressure fluctuations of the ink within the liquid storage chamber R.

[0035] The sealing body 35 is a structure that protects the multiple piezoelectric elements 34 and reinforces the mechanical strength of the pressure chamber substrate 32 and the vibration plate 33. The sealing body 35 is fixed to the surface of the vibration plate 33 by, for example, an adhesive. The multiple piezoelectric elements 34 are housed on the inner side of a recess formed on the opposite surface of the sealing body 35 that is opposite to the vibration plate 33. In addition, a wiring substrate 51 is bonded to the surface of the vibration plate 33. The wiring substrate 51 is a mounting component formed with multiple wirings for electrically connecting the control unit 20 and the liquid ejection head 26. It is preferable to use a flexible wiring substrate 51 such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable). The driving signal and reference voltage for driving the piezoelectric element 34 are supplied to each piezoelectric element 34 from the wiring substrate 51.

[0036] 1-3. Actuator 30

[0037] Figure 4 2 is a plan view showing a portion of the actuator 30 . Figure 5 for, Figure 4 Cross-sectional view of line bb in. Figure 4 as well as Figure 5 The actuator 30 shown in FIG has a pressure chamber substrate 32, a vibration plate 33, a plurality of piezoelectric elements 34, a first wiring 37, a second wiring 38, and a seed layer 39. Figure 4 , for convenience, a dot is marked on the second electrode 342.

[0038] like Figure 4As shown in FIG. 1 , the pressure chamber C1 of the pressure chamber substrate 32 is a long strip of space extending in the X1 direction when viewed from above. A plurality of pressure chambers C1 are arranged in the Y1 direction. The pressure chamber substrate 32 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology. The shape of the pressure chamber C1 when viewed from above is not limited to Figure 4 The quadrilateral shown may also be a parallelogram, for example.

[0039] The vibration plate 33 forms the pressure chamber C1 together with the pressure chamber substrate 32. In addition, the portion of the vibration plate 33 corresponding to the pressure chamber C1 is vibrated by the driving of the piezoelectric element 34. Figure 5 In the illustrated example, the vibration plate 33 includes a first layer 331 and a second layer 332. The first layer 331 is in contact with the pressure chamber substrate 32. The second layer 332 is arranged closer to the first layer 331 in the Z2 direction. The second layer 332 is arranged between the first layer 331 and the first electrode 341, and is in contact with both.

[0040] The material of the first layer 331 is, for example, silicon oxide (SiO2). The first layer 331 is formed, for example, by thermally oxidizing one surface of a single-crystal silicon substrate. Furthermore, the material of the first layer 331 is not limited to silicon oxide and may be other elastic materials such as silicon (Si).

[0041] The second layer 332 is preferably non-conductive, and particularly preferably contains any one of Zr (zirconium), Ti (titanium) or Si (silicon). That is, the end of the vibration plate 33 in the Z2 direction preferably contains any one of Zr, Ti, and Si. In this embodiment, the second layer 332 of the vibration plate 33 contains Zr. Specifically, the material of the second layer 332 is zirconium oxide (ZrO2). In addition, the material of the second layer 332 can also be other insulating materials such as silicon nitride (SiN). The second layer 332 is formed, for example, by sputtering and thermal oxidation. In addition, the second layer 332 is a non-oriented layer. However, it is not particularly limited to being non-oriented.

[0042] By including any of Zr, Ti, and Si in the Z2-direction end portion of the vibration plate 33, the mechanical strength of the vibration plate 33 can be improved while ensuring the required deformation corresponding to the vibration of the piezoelectric element 34, compared to a case where none of these elements are included. Therefore, the occurrence of cracks in the vibration plate 33 can be further suppressed.

[0043] In addition, another layer such as a metal oxide may be present between the first layer 331 and the second layer 332. It may also be a plurality of layers that are the same as or different from the first layer 331 or the second layer 332. In addition, the vibration plate 33 may not be a multi-layer but a single layer. Figure 5In the illustrated example, the thickness of the second layer 332 is thinner than that of the first layer 331 , but the thicknesses of the first layer 331 and the second layer 332 may be different from or equal to each other.

[0044] like Figure 5 As shown, the piezoelectric element 34 generally includes a first electrode 341, a piezoelectric layer 343, and a second electrode 342 in this order from the vibration plate 33. The stacking direction of the first electrode 341, the piezoelectric layer 343, and the second electrode 342 is the Z2 direction.

[0045] The first electrode 341 is positioned closer to the vibration plate 33 in the Z2 direction and in contact with the vibration plate 33. The first electrode 341 is strip-shaped and extends in the X1 direction. Multiple first electrodes 341 are arranged in the Y1 direction with spacing therebetween. The first electrodes 341 are separate, independent electrodes formed for each piezoelectric element 3.

[0046] The first electrode 341 includes a conductive material such as a metal. The first electrode 341 preferably includes any one of aluminum (Al), platinum (Pt) or iridium (Ir). By including any one of them, the first electrode 34 can be given elasticity that suppresses the generation of cracks in the piezoelectric layer 343 while allowing the deformation of the piezoelectric layer 343, compared to the case where any one of them is not included. In addition, for example, the first electrode 341 can have a stack of a Pt layer and an Ir layer. By having a Pt layer, a first electrode 341 that can allow deformation of the piezoelectric layer 343 can be provided. In addition, by having an Ir layer, the diffusion of components contained in the piezoelectric layer 343 can be suppressed. Therefore, changes in the composition of the piezoelectric layer 343 are suppressed.

[0047] like Figure 4 As shown in FIG. 1 , a first wiring 37 is electrically connected to the first electrode 341. The first wiring 37 is mounted on Figure 3 A drive circuit (not shown) on the wiring substrate 51 is wired with a drive signal, and the first wiring 37 supplies the drive signal to the first electrode 341. The first wiring 37 is formed of a conductive material having a lower resistance than the first electrode 341. The first wiring 37 is a conductive pattern having a structure in which a conductive film of gold (Au) is laminated on the surface of a conductive film formed of, for example, nickel-chromium alloy (NiCr).

[0048] like Figure 5 As shown in FIG. 3 , the piezoelectric layer 343 is arranged closer to the first electrode 341 in the Z2 direction. Figure 4As shown, the piezoelectric layer 343 is a strip of dielectric film that extends continuously in the Y1 direction across multiple piezoelectric elements 34. A notch G is formed along the X-axis in the piezoelectric layer 343 in the region corresponding to the gap between adjacent pressure chambers C1. The notch G is an opening that penetrates the piezoelectric layer 343. The notch G allows each piezoelectric element 34 to deform independently for each pressure chamber C1, thereby suppressing the propagation of vibration between the piezoelectric elements 34. Alternatively, a bottomed hole formed by removing a portion of the thickness of the piezoelectric layer 343 may be formed as the notch G.

[0049] like Figure 5 As shown, when viewed cross-sectionally in the X1 direction, the piezoelectric layer 343 includes a first region A1 and a second region A2. The first region A1 is the region that does not overlap with the first electrode 341 when viewed from above. The second region A2 is the region that overlaps with the first electrode 341 when viewed from above. To put it another way, the position of the first region A1 in the Y1 direction is different from that of the first electrode 341. The position of the second region A2 in the Y1 direction is the same as that of the first electrode 341.

[0050] like Figure 5 As shown in FIG. 3 , the second electrode 342 is arranged closer to the piezoelectric layer 343 in the Z2 direction and is in contact with the piezoelectric layer 343. Figure 4 as well as Figure 5 As shown, the second electrode 342 is a common electrode in the form of a strip extending in the Y1 direction in a continuous manner across a plurality of piezoelectric elements 34. A predetermined reference voltage is applied to the second electrode 342. The reference voltage is a fixed voltage, for example, set to a voltage higher than the ground voltage. A voltage corresponding to the difference between the reference voltage applied to the second electrode 342 and the drive signal supplied to the first electrode 341 is applied to the piezoelectric layer 343. In addition, a ground voltage may also be applied to the second electrode 342. In addition, the second electrode 342 is formed of a conductive material such as aluminum (Al), platinum (Pt) or iridium (Ir).

[0051] As described above, the first electrode 341 is individually disposed for each of the multiple pressure chambers C1, whereas the second electrode 342 is commonly disposed for each of the multiple pressure chambers C1. Therefore, the piezoelectric layer 343 can be protected by the second electrode 342. Therefore, while a separate protective layer is required to protect the piezoelectric layer 343 when the second electrode 342 is individually disposed, this is not necessary in this embodiment.

[0052] Furthermore, the second electrode 342 is arranged so as to cover the periphery of the surface of the piezoelectric layer 343 in the Z2 direction. In other words, the second electrode 342 covers the piezoelectric layer 343. Therefore, compared to a case where the piezoelectric layer 343 is not covered by the second electrode 342, the piezoelectric layer 343 and the like can be protected. Therefore, for example, degradation of the piezoelectric layer 343 due to hydrogen reduction can be prevented.

[0053] Alternatively, a conductive oxide such as lanthanum nickelate (LNO) may be disposed on the first electrode 341 or the second electrode 342. Alternatively, a layer of titanium or the like may be disposed on the first electrode 341 or the second electrode 342 within a range that does not impair the conductivity of the electrodes.

[0054] like Figure 4 As shown in FIG. 1 , a second wiring 38 electrically connected to the second electrode 342 is arranged closer to the second electrode 342 in the X1 direction. Figure 3 The wiring substrate 51 shown is supplied with a reference voltage not shown. Figure 4 As shown, the second wiring 38 includes a first conductive layer 381 in the strip shape extending in the Y1 direction, and a second conductive layer 382 in the strip shape extending in the Y1 direction. The first conductive layer 381 and the second conductive layer 382 are arranged with a predetermined spacing in the X1 direction. The second wiring 38 also functions as a weight to suppress the vibration of the vibration plate 33. The second wiring 38 is a conductive pattern having a structure in which a gold conductive film is laminated on the surface of a conductive film formed of a nickel-chromium alloy, for example.

[0055] In the piezoelectric element 34, a voltage is applied between the first electrode 341 and the second electrode 342, causing the piezoelectric layer 343 to deform. This deformation causes the piezoelectric element 34 to bend the vibration plate 33. The vibration of the vibration plate 33 causes the pressure in the pressure chamber C1 to change, thereby causing the ink in the pressure chamber C1 to move out of the chamber. Figure 3 The air is ejected from the nozzle N shown.

[0056] like Figure 5 As shown, the seed layer 39 is arranged between the first electrode 341 and the piezoelectric layer 343. In addition, the seed layer 39 is in contact with the first electrode 341, the vibration plate 33 and the piezoelectric layer 343. The seed layer 39 includes a crystalline structure that serves as a seed of the piezoelectric layer 343. The seed layer 39 is an orientation control layer for controlling the orientation of the crystals of the piezoelectric layer 343. The presence of the seed layer 39 can improve the orientation of the piezoelectric layer 343. Therefore, the displacement force of the piezoelectric element 34 can be increased. As a result, the ejection performance of the liquid ejection head 26 can be improved.

[0057] As described above, the actuator 30 included in the liquid ejection head 26 includes a pressure chamber substrate 32, a vibration plate 33, a first electrode 341, a piezoelectric layer 343, and a second electrode 342. The pressure chamber substrate 32 includes a plurality of pressure chambers C1 arranged in the Y1 direction. Furthermore, the piezoelectric layer 343 includes a first region A1 that does not overlap with the first electrode 341 in the Y1 direction, and a second region A2 that overlaps with the first electrode 341 in the Y1 direction.

[0058] When the piezoelectric layer 343 involved is analyzed in the Z1 direction by X-ray diffraction (XRD), the first region A1 and the second region A2 are preferentially oriented to the first surface orientation, respectively. That is, the first region A1 and the second region A2 are preferentially oriented to the same crystal surface orientation as each other. Therefore, the orientation of the surface orientation between the first region A1 and the second region A2 is not excessively different. Therefore, the difference in physical properties such as Young's modulus and thermal expansion coefficient caused by the difference in the surface orientation of the crystals in the first region A1 and the second region A2 of the piezoelectric layer 343 is suppressed. Therefore, the possibility of cracks between the first region A1 and the second region A2 due to the difference in physical properties is suppressed. Therefore, the decline in ejection performance or durability can be suppressed.

[0059] In this embodiment, the first plane orientation is the (100) plane. That is, the first region A1 and the second region A2 are preferentially oriented toward the (100) plane. Therefore, compared to cases where the first region A1 and the second region A2 are preferentially oriented toward other crystalline plane orientations, the ejection characteristics of the piezoelectric element 34 of this embodiment can be improved. Alternatively, the first plane orientation may be a (111) plane, etc., in addition to the (100) plane.

[0060] Furthermore, the Lotgering factor, which indicates the degree of orientation toward the first plane orientation when analyzing the piezoelectric layer 343 in the Z1 direction by X-ray diffraction, is preferably greater than or equal to 0.6 and less than or equal to 1.0 in each of the first region A1 and the second region A2. When the Lotgering factor is within the specified range, the difference in physical properties caused by the difference in the plane orientation of the crystals in the first region A1 and the second region A2 can be suppressed compared to when it is outside the specified range. Therefore, the possibility of cracks forming between the first region A1 and the second region A2 is further suppressed.

[0061] The Lotgering factor is more preferably 0.8 or more and 1.0 or less in each of the first region A1 and the second region A2. Furthermore, the maximum value of the Lotgering factor is 1.0. When the Lotgering factor is within the range, the piezoelectric properties of the piezoelectric layer 343 can be improved compared to when it is outside the range, and the difference in physical properties caused by the difference in the plane orientation of the crystals in the first region A1 and the second region A2 can be suppressed.

[0062] The material of the piezoelectric layer 343 is preferably a composite oxide having a perovskite structure represented by the general formula ABO3. Therefore, compared to a case where the piezoelectric layer 343 is formed of a material other than this composite oxide, superior piezoelectric properties can be exhibited by applying a voltage between the first electrode 341 and the second electrode 342. Consequently, ejection characteristics can be improved.

[0063] The piezoelectric layer 343 preferably contains at least lead (Pb), zirconium (Zr), and titanium (Ti) even in the composite oxide. By including these, it is possible to exhibit excellent piezoelectric properties by applying a voltage between the first electrode 341 and the second electrode 342, compared to a case where they are not included. Preferred materials for the piezoelectric layer 343 include, for example, piezoelectric materials such as lead zirconate titanate (Pb(Zr, Ti)O3) or lead magnesium niobate / lead titanate solid solution (Pb(Mg, Nb)O3-PbTiO3). In addition, the piezoelectric layer 343 may also be a material that does not contain lead, such as potassium sodium niobate ((KNa)NbO3) or sodium bismuth titanate ((Bi, Na)TiO3).

[0064] The piezoelectric layer 343 has an average crystal grain size of 2.0 μm or less in the first region A1 and an average crystal grain size of 2.0 μm or less in the second region A2. Furthermore, the average crystal grain size in each of the first region A1 and the second region A2 is preferably 5.0 nm or greater. By setting the average crystal grain size in each of the first region A1 and the second region A2 to 2.0 μm or less, the generation of cracks in the piezoelectric layer 343 can be suppressed compared to a case where the average crystal grain size exceeds 2.0 μm.

[0065] Furthermore, as previously described, the liquid ejection head 26 includes a seed layer 39 for controlling the orientation of the piezoelectric layer 343. The seed layer 39 is located between the piezoelectric layer 343 and the vibration plate 33 and corresponds to both the first region A1 and the second region A2. The presence of the seed layer 39 allows each of the first region A1 and the second region A2 to be preferentially oriented toward the first plane orientation. In other words, the first region A1 and the second region A2 can be preferentially oriented toward the same crystal plane orientation.

[0066] Furthermore, in this embodiment, the seed layer 39 is configured to cover the periphery of the surface of the first electrode 341 in the Z1 direction. To put it another way, the seed layer 39 overlaps with the first electrode 341 when viewed from above, and the area of the seed layer 39 when viewed from above is larger than the area of the first electrode 341 when viewed from above. By configuring the seed layer 39 to cover the periphery of the surface of the first electrode 341 in the Z1 direction, the unevenness of the upper surface of the first electrode 341 can be mitigated compared to a case where the seed layer 39 is not configured to cover the first electrode 341. Therefore, the possibility of cracks forming in the piezoelectric layer 343 due to the influence of these unevenness can be suppressed.

[0067] Furthermore, the thickness of the portion of the seed layer 39 corresponding to the first region A1 is relatively thick compared to the thickness of the portion of the seed layer 39 corresponding to the second region A2. Therefore, the surface 390 of the seed layer 39 in the Z2 direction can be made flat or nearly flat. This reduces the possibility of cracks forming in the piezoelectric layer 343 due to the height difference of the first electrode 341.

[0068] Although the seed layer 39 may include any material as long as it has the function of serving as an orientation control layer, it is preferably a composite oxide containing titanium (Ti) or having a perovskite structure. In particular, the seed layer 39 preferably includes a composite oxide having a perovskite structure, more preferably any one of bismuth (Bi), lead (Pb), iron (Fe) or titanium (Ti). By including any one of them, the orientation characteristics of the piezoelectric layer 343 can be improved compared to a case where any one of them is not included. In particular, when the piezoelectric layer 343 includes at least Pb, Zr and Ti, by making the seed layer 39 include any one of Bi, Pb, Fe or Ti, it is easy to preferentially orient the first region A1 and the second region A2 to the same crystal plane orientation. In addition, since the constituent elements of the piezoelectric layer 343 and the seed layer 39 are closer when the piezoelectric layer 343 includes at least Pb, Zr and Ti, the diffusion of impurities in the manufacturing process between the piezoelectric layer 343 and the seed layer 39 can also be reduced.

[0069] Figure 6 3 is a diagram showing the results of XRD in the second region A2 of the piezoelectric layer 343 in this embodiment. Figure 7 : is a graph showing the results of XRD in the first region A1 of the piezoelectric layer 343 in this embodiment. Here, the results are shown when the material of the seed layer 39 is a composite oxide having a perovskite structure containing Bi, Pb, Fe, and Ti.

[0070] Specifically, the actuator 30 including the seed layer 39 containing Bi, Pb, Fe, and Ti was formed in the following manner, and the piezoelectric layer 343 was analyzed by XRD.

[0071] First, a silicon dioxide film is formed as the first layer 331 on a silicon substrate serving as the pressure chamber substrate 32. Next, a zirconium film is formed by sputtering, and this zirconium film is thermally oxidized to form a zirconium oxide film as the second layer 332. Subsequently, a stack consisting of titanium, platinum, and iridium layers is formed on the second layer 332 by sputtering. Next, a plurality of first electrodes 341 are formed from this stack by photolithography and dry etching.

[0072] Next, a solution of Bi:Ti:Fe:Ti=110:10:50:50 is applied to the first electrode 341 by spin coating so as to cover it. Thereafter, the seed layer 39 is formed by drying it at 350°C and heat treating it at 740°C for five minutes. Next, a solution of Pb:Zr:Ti=1.18:53:48 is applied to the seed layer 39 by spin coating. Thereafter, the piezoelectric layer 343 is formed by drying it at 200°C and 410°C and heat treating it at 740°C for five minutes. Next, the second electrode 342 composed of a layer of iridium and a layer of titanium is formed on the piezoelectric layer 343 by sputtering. In the above manner, the actuator 30 is formed.

[0073] The piezoelectric layer 343 of the actuator 30 formed as described above was analyzed by XRD using D8 DISCOVER with GADDS manufactured by Bruker.

[0074] like Figure 6 as well as Figure 7 As shown, it can be seen that in this embodiment, the (100) plane is preferentially oriented in both the first region A1 and the second region A2. This can reduce cracks between the first region A1 and the second region A2, thereby suppressing a decrease in ejection performance or durability.

[0075] 2. Second Implementation

[0076] In the following examples, elements having the same functions as those in the first embodiment will be assigned the same reference numerals as those used in the first embodiment, and detailed descriptions thereof will be omitted as appropriate.

[0077] Figure 8 2 is a cross-sectional view showing an actuator 30A in the second embodiment, and is similar to that in the first embodiment. Figure 5In this embodiment, an actuator 30A is used instead of the actuator 30 of the first embodiment. Hereinafter, regarding the actuator 30A, matters different from the actuator 30 of the first embodiment will be described, and descriptions of the same matters will be omitted as appropriate.

[0078] Figure 8 The illustrated actuator 30A does not include the seed layer 39 of the first embodiment. The vibration plate 33A of the actuator 30A includes a first layer 331 and a second layer 332A. The second layer 332A functions as an orientation control layer that controls the crystal orientation of the piezoelectric layer 343. For example, the second layer 332A is preferentially oriented in the same first plane orientation as the piezoelectric layer 343.

[0079] Even in the actuator 30A, as in the first embodiment, when the piezoelectric layer 343 is analyzed in the Z1 direction by XRD, the first region A1 and the second region A2 are preferentially oriented in the first plane orientation. Therefore, differences in physical properties such as Young's modulus and thermal expansion coefficient caused by the difference in plane orientation of crystals in the first region A1 and the second region A2 of the piezoelectric layer 343 are suppressed. Consequently, the possibility of cracks forming between the first region A1 and the second region A2 due to this difference in physical properties is suppressed. Consequently, a decrease in ejection performance or durability can be suppressed.

[0080] 2. Modification

[0081] The embodiments illustrated above can be modified in various ways. Specific modified methods applicable to the aforementioned embodiments are exemplified below. Two or more methods arbitrarily selected from the following examples can be appropriately combined within a range that is not contradictory to each other. In addition, the following modified examples related to the first embodiment can also be applied to the second embodiment within a range that is not contradictory.

[0082] Although the first electrode 341 of the piezoelectric element 34 is configured as an independent electrode and the second electrode 342 as a common electrode in the first embodiment, the first electrode 341 may be configured as a common electrode and the second electrode 342 as an independent electrode. However, even in this case, the first electrode 341, which serves as the common electrode, includes an area that does not overlap with the piezoelectric layer 343. In this case, this embodiment is preferably applicable. Alternatively, both the first electrode 341 and the second electrode 342 may be configured as independent electrodes.

[0083] Figure 9 , which is a cross-sectional view showing a portion of the actuator 30 in a modified example. In the first embodiment, the surface 390 of the seed layer 39 in the Z2 direction is a flat surface. However, as Figure 9As shown, the surface 390 of the seed layer 39 in the Z2 direction may have unevenness corresponding to the height difference of the first electrode 341 .

[0084] Figure 10 , which is a cross-sectional view showing a portion of the actuator 30 in a modified example. In the first embodiment, the seed layer 39 is common to the first region A1 and the second region A2. Figure 10 As shown, the seed layer 39 may also include a first portion 391 corresponding to the first region A1 and a second portion 392 corresponding to the second region A2. The first portion 391 and the second portion 392 are made of different materials. In addition, the first region A1 and the second region A2 are preferentially oriented in the same first plane orientation.

[0085] Although the first embodiment illustrates a serial liquid ejecting device 100 in which the conveying body 242 carrying the liquid ejecting head 26 moves back and forth, the present invention can also be applied to a row-type liquid ejecting device in which a plurality of nozzles N are distributed across the entire width of the medium 12.

[0086] The liquid ejection device 100 illustrated in the first embodiment can be used in various devices such as fax machines or copiers in addition to devices specifically used for printing. The use of the liquid ejection device of the present invention is not limited to printing. For example, a liquid ejection device that ejects a solution of a color material can also be used as a manufacturing device for forming a color filter for a display device such as a liquid crystal display panel. In addition, a liquid ejection device that ejects a solution of a conductive material can be used as a manufacturing device for forming wiring or electrodes of a wiring substrate. In addition, a liquid ejection device that ejects a solution of an organic substance related to a living body can be used as a manufacturing device for manufacturing a biochip, for example.

[0087] The actuator of the present invention is not limited to an actuator mounted on a liquid ejection head, but can also be applied to actuators mounted on other devices, such as ultrasonic devices such as ultrasonic transmitters, ultrasonic motors, pressure sensors, and pyroelectric sensors.

[0088] Explanation of symbols

[0089] 12…medium; 14…liquid container; 20…control unit; 22…transport mechanism; 24…moving mechanism; 26…liquid ejecting head; 30…actuator; 30A…actuator; 31…flow channel substrate; 32…pressure chamber substrate; 33…vibration plate; 33A…vibration plate; 34…piezoelectric element; 35…sealing member; 36…housing portion; 37…first wiring; 38…second wiring; 39…seed layer; 41…nozzle plate; 42…vibration absorber; 51…wiring substrate; 100…liquid ejecting device; 242…transport member; 244…conveyor belt; 31… 2…supply channel; 314…connecting channel; 316…relay liquid chamber; 320…wall surface; 331…first layer; 332…second layer; 332A…second layer; 341…first electrode; 342…second electrode; 343…piezoelectric layer; 361…supply port; 381…first conductive layer; 382…second conductive layer; A1…first region; A2…second region; C1…pressure chamber; D1…thickness; D2…thickness; G…cut; La…first column; Lb…second column; N…nozzle; R…liquid storage chamber; Ra…space; Rb…space.

Claims

1. A liquid ejection head, characterized in that: have: a pressure chamber substrate having a plurality of pressure chambers arranged in a first direction; a vibration plate arranged closer to the pressure chamber substrate in a second direction intersecting the first direction; a first electrode disposed closer to the second direction than the vibration plate; a piezoelectric layer disposed closer to the first electrode in the second direction; a second electrode disposed closer to the second direction than the first electrode; a seed layer located between the piezoelectric layer and the vibration plate and used to control the orientation of the piezoelectric layer; In the liquid ejection head, The piezoelectric layer includes a first region that does not overlap with the first electrode in the first direction, and a second region that overlaps with the first electrode in the first direction. When the piezoelectric layer is analyzed by X-ray diffraction, the first region is preferentially oriented in a first plane orientation, and the second region is preferentially oriented in the first plane orientation. The seed layer is arranged to correspond to both the first region and the second region. A portion of the seed layer corresponding to the first region is thicker than a portion of the seed layer corresponding to the second region.

2. The liquid ejection head according to claim 1, wherein The first plane orientation is (100) plane.

3. The liquid ejection head according to claim 1 or 2, wherein: The Lotgering factor indicating the degree of orientation in the first plane direction when the piezoelectric layer is analyzed by X-ray diffraction is 0.6 or more and 1.0 or less in each of the first region and the second region.

4. The liquid ejection head according to claim 3, wherein The Lotgering factor is 0.8 or more and 1.0 or less in the first region and the second region, respectively.

5. The liquid ejection head according to claim 1, wherein The piezoelectric layer is a composite oxide having a perovskite structure.

6. The liquid ejection head according to claim 1, wherein The piezoelectric layer includes at least Pb, Zr, and Ti.

7. The liquid ejection head according to claim 1, wherein The first electrode includes either Pt or Ir.

8. The liquid ejection head according to claim 1, wherein The end portion of the vibration plate in the second direction includes any one of Zr, Ti, and Si.

9. The liquid ejection head according to claim 1, wherein The piezoelectric layer has an average crystal grain size of 2.0 μm or less in the first region and an average crystal grain size of 2.0 μm or less in the second region.

10. The liquid ejection head according to claim 1, wherein The first electrode is individually arranged relative to the plurality of pressure chambers. The second electrode is commonly arranged with respect to the plurality of pressure chambers.

11. The liquid ejection head according to claim 1, wherein The second electrode is arranged so as to cover the periphery of the surface of the piezoelectric layer in the second direction.

12. The liquid ejection head according to claim 1, wherein The seed layer is arranged to cover the periphery of the surface of the first electrode in the second direction.

13. The liquid ejection head according to claim 1, wherein The seed layer includes any one of Bi, Pb, Fe or Ti.

14. An actuator, characterized in that: have: a pressure chamber substrate having a plurality of pressure chambers arranged in a first direction; a vibration plate arranged closer to the pressure chamber substrate in a second direction intersecting the first direction; a first electrode disposed closer to the second direction than the vibration plate; a piezoelectric layer disposed closer to the first electrode in the second direction; a second electrode disposed closer to the second direction than the first electrode; a seed layer located between the piezoelectric layer and the vibration plate and used to control the orientation of the piezoelectric layer; In the actuator, The piezoelectric layer includes a first region that does not overlap with the first electrode in the first direction, and a second region that overlaps with the first electrode in the first direction. When the piezoelectric layer is analyzed by X-ray diffraction, the first region is preferentially oriented in a first plane orientation, and the second region is preferentially oriented in the first plane orientation. The seed layer is arranged to correspond to both the first region and the second region. A portion of the seed layer corresponding to the first region is thicker than a portion of the seed layer corresponding to the second region.

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