Liquid discharge head

Abstract

To prevent occurrence of cracks in an actuator comprising a piezoelectric element and a vibration plate.SOLUTION: A liquid discharge head comprises a piezoelectric element, a vibration plate that is vibrated by driving of the piezoelectric element, and a pressure chamber substrate provided with a pressure chamber that applies pressure to liquid by vibration of the vibration plate. The pressure chamber substrate, the vibration plate, and the piezoelectric element are laminated in this order in a stacking direction. The vibration plate comprises a first layer containing silicon as a constituent element and a second layer provided on the first layer in the stacking direction and containing titanium oxide. The main state of titanium oxide contained in the second layer is any one of anatase structure, brookite structure, or amorphous state.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head. [Background technology]

[0002] A liquid ejection head used in a device such as a piezoelectric inkjet printer has a piezoelectric element and a diaphragm that vibrates when driven by the piezoelectric element. For example, Patent Document 1 discloses a diaphragm having an elastic film made of silicon dioxide and an insulating film made of zirconium oxide. Here, the elastic film is formed by thermally oxidizing one surface of a silicon single crystal substrate. The insulating film is formed by thermally oxidizing a layer of simple zirconium formed on the elastic film by a method such as sputtering. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-78407 Summary of the Invention [Problem to be solved by the invention]

[0004] The technique described in Patent Document 1 has the risk of causing cracks in the diaphragm and the like. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of the liquid ejection head according to the present invention comprises a piezoelectric element, a vibration plate that vibrates when driven by the piezoelectric element, and a pressure chamber substrate in which a pressure chamber is provided that applies pressure to a liquid by the vibration of the vibration plate, wherein the pressure chamber substrate, the vibration plate, and the piezoelectric element are stacked in this order in a stacking direction, the vibration plate has a first layer containing silicon as a constituent element, and a second layer that is provided on the first layer in the stacking direction and contains titanium oxide, and the titanium oxide contained in the second layer has a predominant state of either an anatase structure, a brookite structure, or amorphous. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a configuration diagram that schematically shows a liquid ejection device that includes a liquid ejection head according to a first embodiment. [Figure 2] FIG. 1 is an exploded perspective view of a liquid ejection head according to a first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is a plan view showing a vibration plate of the liquid ejection head according to the first embodiment. [Figure 5] 5 is a cross-sectional view taken along line VV in FIG. 4. [Figure 6] FIG. 10 is a diagram showing an example of the results of measuring the second layer by X-ray crystal structure analysis. [Figure 7] 5A to 5C are diagrams illustrating a method for manufacturing a liquid ejection head. [Figure 8] FIG. 10 is a cross-sectional view of a liquid ejection head according to a second embodiment. [Figure 9] FIG. 10 is a diagram showing the relationship between the state of the second layer and the evaluation in Examples 1 to 9 and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that 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. Furthermore, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited thereto.

[0008] In the following description, the mutually intersecting X-axis, Y-axis, and Z-axis will be used as appropriate. Furthermore, one direction along the X-axis will be referred to as the X1 direction, and the direction opposite to the X1 direction will be referred to as the X2 direction. Similarly, opposite directions along the Y-axis will be referred to as the Y1 direction and the Y2 direction. Furthermore, opposite directions along the Z-axis will be referred to as the Z1 direction and the Z2 direction. Furthermore, viewing in the direction along the Z-axis is referred to as "planar view."

[0009] Typically, the Z axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. 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. For example, they may intersect at an angle between 80° and 100°.

[0010] 1. First embodiment 1-1. Overall configuration of the liquid ejection device FIG. 1 is a schematic diagram illustrating a liquid ejection device 100 equipped with a liquid ejection head 26 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 12. The medium 12 is typically printing paper. However, the medium 12 is not limited to printing paper and may be a printing target made of any material, such as a resin film or fabric.

[0011] As shown in FIG. 1, the liquid ejection device 100 includes a liquid container 14, a control unit 20, a transport mechanism 22, a moving mechanism 24, and a liquid ejection head .

[0012] The liquid container 14 is a container that stores ink. Specific examples of the liquid container 14 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 14 is arbitrary.

[0013] The control unit 20 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.

[0014] The transport mechanism 22 transports the medium 12 in the Y2 direction under the control of the control unit 20. The movement mechanism 24 reciprocates the liquid ejection head 26 in the X1 and X2 directions under the control of the control unit 20. In the example shown in FIG. 1, the movement mechanism 24 has a substantially box-shaped transport body 242 called a carriage that houses the liquid ejection head 26, and a transport belt 244 to which the transport body 242 is fixed. Note that the number of liquid ejection heads 26 mounted on the transport body 242 is not limited to one, and may be multiple. In addition to the liquid ejection head 26, the aforementioned liquid container 14 may also be mounted on the transport body 242.

[0015] The liquid ejection head 26 ejects ink supplied from the liquid container 14 from each of a plurality of nozzles onto the medium 12 in the Z2 direction under the control of the control unit 20. This ejection is performed in parallel with the transport of the medium 12 by the transport mechanism 22 and the reciprocating movement of the liquid ejection head 26 by the movement mechanism 24, thereby forming an ink image on the surface of the medium 12.

[0016] 1-2. Overall configuration of liquid ejection head FIG. 2 is an exploded perspective view of the liquid ejection head 26 according to the first embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. As shown in FIG. 2, the liquid ejection head 26 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. Here, the elements associated with each nozzle N in the first row L1 of the liquid ejection head 26 and the elements associated with each nozzle N in the second row L2 are configured to be substantially symmetrical to each other in a direction along the X axis.

[0017] However, the positions of the multiple nozzles N in the first row L1 and the multiple nozzles N in the second row L2 in the direction along the Y axis may or may not match. In the following, a configuration in which the positions of the multiple nozzles N in the first row L1 and the multiple nozzles N in the second row L2 in the direction along the Y axis match is exemplified.

[0018] 2 and 3, the liquid ejection head 26 has a flow path substrate 32, a pressure chamber substrate 34, a nozzle plate 62, a vibration absorber 64, a diaphragm 36, a plurality of piezoelectric elements 44, a housing 48, a wiring board 46, and a drive circuit 50. The diaphragm 36 and the piezoelectric elements 44 constitute an actuator that applies pressure to ink in a pressure chamber C, which will be described later.

[0019] Here, the pressure chamber substrate 34, the vibration plate 36, the plurality of piezoelectric elements 44, the housing 48, and the sealing plate 57 are disposed in an area positioned further in the Z1 direction than the flow path substrate 32. On the other hand, the nozzle plate 62 and the vibration absorber 64 are disposed in an area positioned further in the Z2 direction than the flow path substrate 32. Each element of the liquid ejection head 26 is roughly a plate-like member that is elongated in the direction along the Y axis, and is joined to one another by, for example, an adhesive.

[0020] The nozzle plate 62 is a plate-like member provided with a plurality of nozzles N. Each of the plurality of nozzles N is a through-hole that allows ink to pass through. The nozzle plate 62 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing techniques that employ processing techniques such as dry etching or wet etching. However, other known methods and materials may also be used as appropriate to manufacture the nozzle plate 62.

[0021] The flow path substrate 32 is provided with a space Ra, a plurality of supply flow paths 322, a plurality of communicating flow paths 324, and a supply liquid chamber 326 for each of the first row L1 and the second row L2. The space Ra is an elongated opening extending in the direction along the Y axis in a plan view taken along the Z axis. Each of the supply flow paths 322 and the communicating flow paths 324 is a through-hole provided for each nozzle N. The supply liquid chamber 326 is an elongated space extending in the direction along the Y axis across the plurality of nozzles N, and connects the space Ra and the plurality of supply flow paths 322 to each other. Each of the plurality of communicating flow paths 324 overlaps with one nozzle N corresponding to that communicating flow path 324 in a plan view.

[0022] The pressure chamber substrate 34 is a plate-like member in which a plurality of pressure chambers C are provided for each of the first row L1 and the second row L2. The pressure chambers C are spaces that apply pressure to ink by vibration of the diaphragm 36, and are also called cavities. The plurality of pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is provided for each nozzle N, and is an elongated space that extends in a direction along the X axis in a plan view. Like the nozzle plate 62 described above, the flow path substrate 32 and the pressure chamber substrate 34 are each manufactured by processing a silicon single crystal substrate using, for example, semiconductor manufacturing technology. However, other known methods and materials may also be used as appropriate to manufacture the flow path substrate 32 and the pressure chamber substrate 34.

[0023] The pressure chambers C are spaces located between the flow path substrate 32 and the vibration plate 36. A plurality of pressure chambers C are arranged in the direction along the Y axis in each of the first row L1 and the second row L2. The pressure chambers C are also in communication with the communication flow path 324 and the supply flow path 322. Therefore, the pressure chambers C are in communication with the nozzle N via the communication flow path 324, and are in communication with the space Ra via the supply flow path 322 and the supply liquid chamber 326.

[0024] A diaphragm 36 is disposed on the surface facing the Z2 direction of the pressure chamber substrate 34. The diaphragm 36 is a plate-like member that can elastically vibrate, and vibrates when driven by the piezoelectric element 44. The diaphragm 36 will be described in detail later.

[0025] On the surface of the vibration plate 36 facing the Z1 direction, a plurality of piezoelectric elements 44 corresponding to the nozzles N are arranged in each of the first row L1 and the second row L2. Each piezoelectric element 44 is a passive element that deforms when a drive signal is supplied. Each piezoelectric element 44 has an elongated shape extending in the direction along the X axis in a plan view. The plurality of piezoelectric elements 44 are arranged in the direction along the Y axis so as to correspond to the plurality of pressure chambers C. When the vibration plate 36 vibrates in conjunction with the deformation of the piezoelectric elements 44, the pressure in the pressure chambers C fluctuates, causing ink to be ejected from the nozzles N. The piezoelectric elements 44 will be described in detail later.

[0026] The housing 48 is a case for storing ink to be supplied to the multiple pressure chambers C. As shown in FIG. 3, the housing 48 of this embodiment is provided with a space Rb for each of the first row L1 and the second row L2. The space Rb of the housing 48 and the space Ra of the flow path substrate 32 are connected to each other. The space formed by the space Ra and the space Rb functions as a liquid storage chamber (reservoir) R that stores ink to be supplied to the multiple pressure chambers C. Ink is supplied to the liquid storage chamber R through an inlet 482 provided in the housing 48. The ink in the liquid storage chamber R is supplied to the pressure chambers C through the supply liquid chamber 326 and each supply flow path 322. The vibration absorber 64 is a flexible film (compliance substrate) that forms the wall surface of the liquid storage chamber R and absorbs pressure fluctuations of the ink in the liquid storage chamber R.

[0027] The wiring board 46 is a plate-like member provided with wiring for electrically connecting the drive circuit 50 and the plurality of piezoelectric elements 44. The surface of the wiring board 46 facing the Z2 direction is joined to the diaphragm 36 via a plurality of conductive bumps B. On the other hand, the drive circuit 50 is mounted on the surface of the wiring board 46 facing the Z1 direction. The drive circuit 50 is an IC (Integrated Circuit) chip that outputs drive signals and reference voltages for driving each of the piezoelectric elements 44.

[0028] Ends of external wiring 52 are joined to the surface of wiring board 46 facing the Z1 direction. External wiring 52 is formed of a connecting component such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable). Here, as shown in FIG. 2 , wiring board 46 is provided with a plurality of wirings 461 that electrically connects external wiring 52 and drive circuit 50, and a plurality of wirings 462 to which drive signals and reference voltages output from drive circuit 50 are supplied.

[0029] 1-3. Details of the diaphragm and piezoelectric element Fig. 4 is a plan view showing the vibration plate 36 of the liquid ejection head 26 in the first embodiment. Fig. 5 is a cross-sectional view taken along line VV in Fig. 4. In the liquid ejection head 26, as shown in Figs. 4 and 5, the pressure chamber substrate 34, the vibration plate 36, and the plurality of piezoelectric elements 44 are stacked in this order in the Z1 direction, which is the stacking direction.

[0030] As shown in Fig. 5, holes 341 that form pressure chambers C are provided in the pressure chamber substrate 34. Accordingly, wall-like partition portions 342 extending in the direction along the X-axis are provided in the pressure chamber substrate 34 between two adjacent holes 341. In Fig. 4, the planar shape of the holes 341 when formed by anisotropic etching on a silicon single crystal substrate with a (110) surface orientation is shown by dashed lines. Note that the planar shape of the holes 341 is not limited to the example shown in Fig. 4 and may be any shape.

[0031] As shown in Fig. 4, the piezoelectric element 44 overlaps the pressure chamber C in a plan view. As shown in Fig. 5, the piezoelectric element 44 has a first electrode 441, a piezoelectric layer 443, and a second electrode 442, which are stacked in this order in the Z1 direction. Note that the piezoelectric element 44 may have multiple layers in which electrodes and piezoelectric layers are alternately stacked, and may expand and contract toward the vibration plate 36. Furthermore, other layers, such as layers for improving adhesion, may be appropriately interposed between the layers of the piezoelectric element 44 or between the piezoelectric element 44 and the vibration plate 36.

[0032] The first electrodes 441 are individual electrodes spaced apart from one another and arranged for each piezoelectric element 44. Specifically, a plurality of first electrodes 441 extending in the direction along the X-axis are arranged in the direction along the Y-axis at intervals from one another. A drive signal for ejecting ink from the nozzle N corresponding to the piezoelectric element 44 is applied to the first electrode 441 of each piezoelectric element 44 via the drive circuit 50.

[0033] The first electrode 441 includes, for example, a layer made of iridium (Ir) and a layer made of titanium (Ti), which are stacked in this order in the Z1 direction. Iridium is an electrode material with excellent conductivity. Therefore, using iridium as a constituent material of the first electrode 441 can reduce the resistance of the first electrode 441. Furthermore, when forming the piezoelectric layer 443, the titanium island-shaped layers act as crystalline nuclei, controlling the orientation of the piezoelectric layer 443 and enhancing the crystallinity or orientation of the piezoelectric layer 443. Note that, instead of or in addition to the layer made of iridium, a layer made of another metal material may be provided. Examples of such another metal material include platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), and copper (Cu), and one of these may be used alone or two or more of these may be used in combination. Note that the electrode material used as a constituent material of the first electrode 441 is not limited to metal as long as it is conductive, and metal oxides may also be used.

[0034] The piezoelectric layer 443 has a strip shape extending in the direction along the Y-axis so as to be continuous across the plurality of piezoelectric elements 44. Although not shown, the piezoelectric layer 443 has through-holes extending in the direction along the X-axis that penetrate the piezoelectric layer 443 in regions that correspond in plan view to the gaps between adjacent pressure chambers C.

[0035] The piezoelectric layer 443 contains lead as a constituent element and is made of, for example, a piezoelectric material having a perovskite crystal structure represented by the general composition formula ABO3. Examples of such piezoelectric materials include lead titanate (PbTiO3), lead zirconate titanate (Pb(Zr,Ti)O3), lead zirconate (PbZrO3), lead lanthanum titanate ((Pb,La),TiO3), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O3), lead zirconium niobate titanate (Pb(Zr,Ti,Nb)O3), and lead magnesium zirconium niobate titanate (Pb(Zr,Ti)(Mg,Nb)O3). Among these, lead zirconate titanate is preferably used as the constituent material of the piezoelectric layer 443.

[0036] The second electrode 442 is a strip-shaped common electrode that extends in the direction along the Y-axis so as to be continuous across the plurality of piezoelectric elements 44. A predetermined reference voltage is applied to the second electrode 442.

[0037] The second electrode 442 is made of, for example, iridium (Ir). The material of the second electrode 442 is not limited to iridium, and may be, for example, a metal material such as platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), or copper (Cu). The second electrode 442 may be made of one of these metal materials alone, or may be made of a combination of two or more of these materials in a laminated form or the like. Alternatively, an oxide of these metal elements may be used.

[0038] In the example shown in FIG. 4 , a first conductor 55 and a second conductor 56 are provided on the surface of the second electrode 442. The first conductor 55 is a strip-shaped conductive film extending in the Y-axis direction along the edge of the second electrode 442 in the X1 direction. The second conductor 56 is a strip-shaped conductive film extending in the Y-axis direction along the edge of the second electrode 442 in the X2 direction. The first conductor 55 and the second conductor 56 are made of a low-resistance conductive material such as gold and are formed together as the same layer. The first conductor 55 and the second conductor 56 suppress a voltage drop of the reference voltage in the second electrode 442. The first conductor 55 and the second conductor 56 also function as weights that define the vibration region of the diaphragm 36. The first conductor 55 and the second conductor 56 may be provided as needed or may be omitted.

[0039] As described above, the liquid ejection head 26 has the piezoelectric layer 443, the vibration plate 36 that vibrates when driven by the piezoelectric layer 443, and the pressure chamber substrate 34 in which the pressure chambers C are provided that apply pressure to ink, which is an example of liquid, by the vibration of the vibration plate 36. The pressure chamber substrate 34, the vibration plate 36, and the piezoelectric layer 443 are layered in this order.

[0040] As shown in FIG. 5, the vibration plate 36 has a first layer 361, a second layer 362, and a third layer 363, which are stacked in this order in the Z1 direction. That is, the vibration plate 36 has the first layer 361, the second layer 362 arranged between the first layer 361 and the piezoelectric layer 443, and the third layer 363 arranged between the second layer 362 and the piezoelectric layer 443. Here, the first layer 361 is bonded to the pressure chamber substrate 34. The third layer 363 is bonded to the plurality of piezoelectric elements 44. The second layer 362 is interposed between the first layer 361 and the third layer 363. Note that, for convenience of explanation, FIG. 5 clearly illustrates the interfaces between the layers constituting the vibration plate 36, but the interfaces do not have to be clear. For example, the constituent materials of two adjacent layers may be mixed near the interface between the two layers.

[0041] The first layer 361 is a layer containing silicon (Si) as a constituent element. More specifically, the first layer 361 is an elastic film made of, for example, silicon oxide (SiO2). In addition to silicon oxide and its constituent elements, the first layer 361 may also contain small amounts of impurities such as zirconium (Zr), titanium (Ti), iron (Fe), chromium (Cr), or hafnium (Hf). Such impurities have the effect of softening the silicon oxide (SiO2).

[0042] In this way, the first layer 361 includes, for example, silicon oxide. Such a first layer 361 can be formed by thermal oxidation of a silicon single crystal substrate with better productivity than when formed by sputtering.

[0043] Silicon in first layer 361 may exist in the form of an oxide, or may exist in the form of an element, nitride, oxynitride, etc. The impurities in first layer 361 may be elements that are inevitably mixed in when first layer 361 is formed, or may be elements that are intentionally mixed in first layer 361.

[0044] The thickness T1 of the first layer 361 is determined according to the thickness T and width W of the vibration plate 36, and is not particularly limited, but is preferably in the range of 100 nm or more and 2000 nm or less, and more preferably in the range of 500 nm or more and 1500 nm or less.

[0045] The third layer 363 is disposed between the second layer 362 and the piezoelectric element 44 and is a layer containing zirconium (Zr) as a constituent element. In an embodiment using such a third layer 363, it is possible to suppress the diffusion of the piezoelectric material from the piezoelectric element 44 to the diaphragm 36. In addition, since a mixed layer can be easily formed from titanium and zirconium, it is possible to improve the adhesion within the diaphragm 36.

[0046] More specifically, the third layer 363 is an insulating film made of, for example, zirconium oxide (ZrO2). In addition to zirconium oxide and its constituent elements, the third layer 363 may contain small amounts of elements such as titanium (Ti), iron (Fe), chromium (Cr), or hafnium (Hf) as impurities. Such impurities have the effect of softening the zirconium oxide (ZrO2).

[0047] As described above, the third layer 363 contains, for example, zirconium oxide. Such a third layer 363 can be obtained, for example, by forming a layer of simple zirconium by sputtering or the like and then thermally oxidizing the layer. This makes it easy to form the third layer 363 to a desired thickness. Furthermore, since zirconium oxide has excellent electrical insulation properties, mechanical strength, and toughness, the characteristics of the diaphragm 36 can be improved by including zirconium oxide in the third layer 363. Furthermore, for example, when the piezoelectric layer 443 is made of lead zirconate titanate, the third layer 363 contains zirconium oxide, which has the advantage of making it easier to form the piezoelectric layer 443 with a high (100) orientation.

[0048] The zirconium in the third layer 363 may exist in the form of an oxide, or may exist in the form of an element, a nitride, an oxynitride, or the like. The impurities in the third layer 363 may be elements that are inevitably mixed in when the third layer 363 is formed, or may be elements that are intentionally mixed in the third layer 363. For example, the impurities are impurities contained in a zirconium target used when the third layer 363 is formed by a sputtering method.

[0049] The thickness T3 of the third layer 363 is determined according to the thickness T and width W of the diaphragm 36, and is not particularly limited, but is within the range of 100 nm to 2000 nm, for example.

[0050] The second layer 362 is interposed between the first layer 361 and the third layer 363. This prevents contact between the first layer 361 and the third layer 363. This reduces the reduction of silicon oxide in the first layer 361 by zirconium in the third layer 363 compared to a configuration in which the first layer 361 and the third layer 363 are in contact with each other.

[0051] The second layer 362 is disposed on the first layer 361 in the stacking direction and contains titanium oxide. Titanium is a metal element that is more difficult to oxidize than zirconium. In other words, titanium is a metal element with a higher oxide formation free energy than zirconium. Because the second layer 362 contains titanium as a constituent element, reduction of silicon oxide contained in the first layer 361 can be reduced compared to a configuration in which the metal element contained in the second layer 362 is more easily oxidized than zirconium. This reduces the diffusion of elemental silicon generated by the reduction from the first layer 361 to the second layer 362, thereby reducing the generation of voids between the first layer 361 and the third layer 363 due to the diffusion. As a result, adhesion between the first layer 361 and the third layer 363 can be increased compared to a configuration without the second layer 362.

[0052] Titanium oxide, an oxide of titanium, is easily moved by heat. Therefore, when second layer 362 contains titanium oxide, the adhesive strength between first layer 361 and second layer 362 and between first layer 361 and third layer 363 and second layer 362 can be increased due to the anchor effect or chemical bond of titanium oxide.

[0053] Moreover, titanium easily forms oxides with silicon or zirconium, so that if second layer 362 contains titanium oxide, the adhesion between first layer 361 and second layer 362 can be increased, and if titanium forms an oxide with zirconium, the adhesion between first layer 361 and third layer 363 can be increased.

[0054] The second layer 362 containing titanium oxide is obtained by forming a layer of titanium by sputtering or the like, and then thermally oxidizing the layer. Therefore, when forming the second layer 362, the second layer 362 can be easily formed to a desired thickness.

[0055] Here, the titanium oxide contained in second layer 362 has a predominant structure of either an anatase structure, a brookite structure, or an amorphous structure. This makes it possible to suppress the occurrence of cracks in the actuator formed by piezoelectric element 44 and diaphragm 36, compared to an embodiment in which the titanium oxide contained in second layer 362 has a predominant structure of rutile.

[0056] The tensile stress of the anatase structure, brookite structure, and amorphous structure is smaller than that of the rutile structure. Therefore, when the titanium oxide contained in the second layer 362 has a predominant state of either the anatase structure, the brookite structure, or the amorphous structure, the tensile stress of the second layer 362 in the actuator is reduced. This increases the margin up to the critical stress when the second layer 362 deforms, making the second layer 362 less likely to break. As a result, the occurrence of cracks in the diaphragm 36 can be suppressed. Note that the "predominant state" refers to a state in which the titanium oxide content is 34% or more, more preferably a state in which the titanium oxide content is 50% or more.

[0057] It is more preferable that the titanium oxide contained in the second layer 362 has a predominant structure of either an anatase structure or a brookite structure. When the titanium oxide contained in the second layer 362 has a predominant structure of either an anatase structure or a brookite structure, the stability of the actuator can be improved compared to an embodiment in which the titanium oxide is predominantly amorphous by making the anatase structure or the brookite structure, which are more stable than amorphous, predominant in the second layer 362. Furthermore, by making the anatase structure or the brookite structure, which have lower tensile stress than amorphous, predominant in the second layer 362, the occurrence of cracks in the actuator can be suppressed compared to an embodiment in which the titanium oxide is predominantly amorphous.

[0058] For example, when second layer 362 is obtained by forming a layer of elemental titanium by sputtering or the like and then thermally oxidizing the layer, the predominant state of titanium oxide contained in second layer 362 can be determined by adjusting at least one of the thickness of the layer, the baking temperature and the baking time of the thermal oxidation. The predominant state of titanium oxide contained in second layer 362 can be measured, for example, by X-ray crystal structure analysis.

[0059] Fig. 6 is a diagram showing an example of the results of measuring second layer 362 by X-ray crystal structure analysis. Fig. 6 shows an example of the results of measuring second layer 362 made of titanium oxide and having a thickness of 600 nm by X-ray crystal structure analysis. In Fig. 6, the measurement results of second layer 362 obtained by baking at 650°C for 180 seconds are shown by a solid line, and the measurement results of second layer 362 obtained by baking at 500°C for 180 seconds are shown by a dotted line.

[0060] In the second layer 362 obtained by firing at 650° for 180 seconds, as shown by the solid line in the figure, a peak of the brookite structure (201) appears at the position where 2θ is α2, and a peak of the rutile structure (200) does not appear at the position where 2θ is α3, but a peak of the rutile structure (101) appears slightly at the position where 2θ is α1.

[0061] In the second layer 362 obtained by firing at 600°C for 180 seconds, as shown by the dashed lines in the figure, a peak of the brookite structure (131) appears at the position where 2θ is β1, and a peak of the brookite structure (220) appears at the position where 2θ is β2. Here, the peak at the position where 2θ is β2 is significantly larger than the peak of the brookite structure obtained by firing at 650°C for 180 seconds. Moreover, no peak of the rutile structure appears at the positions where 2θ is α1 and α3.

[0062] As can be seen from the results shown in Figure 6, the main state of titanium oxide contained in second layer 362 can be adjusted by changing the firing time. Note that when the firing temperature is 900°C or higher, titanium oxide transitions to a rutile structure. Therefore, it is preferable that the firing temperature be less than 900°C.

[0063] When the titanium oxide contained in the second layer 362 is primarily amorphous, X-ray crystal structure analysis of the second layer 362 reveals no peaks in the range of 2θ between 20° and 50° and γ between -95° and -85°. In this case, the titanium oxide contained in the second layer 362 is primarily amorphous, so defects due to crystallization of the second layer 362 do not occur. This prevents fracture due to stress concentration at weak points in the crystals of the second layer 362. Furthermore, while the tensile stress of the second layer 362 is greater than in a configuration in which the second layer 362 has a primarily anatase structure, the absence of defects due to crystallization of the second layer 362 increases the limit stress that the second layer 362 can withstand.

[0064] Since the film stress of titanium oxide with a rutile structure is 900 MPa, the film stress of the second layer 362 should be less than 900 MPa, but preferably 700 MPa or less, and more preferably -300 MPa to -100 MPa. By keeping the film stress of the second layer 362 within this range, the tensile stress applied to the film disposed on the second layer 362 in the stacking direction can be reduced. As a result, cracks or breakage of the piezoelectric element 44 can be reduced. Another advantage is that the diaphragm 36 tends to have a convex shape toward the pressure chamber C, which makes it easier to achieve stable vibration of the diaphragm 36.

[0065] The second layer 362 preferably contains lead. In this case, the adhesion between the second layer 362 and the piezoelectric layer 443 can be improved. Furthermore, diffusing lead into the titanium oxide crystals can reduce the tensile stress of the second layer 362. Furthermore, the lead penetrates into the gaps between the titanium oxide crystals, widening the gaps between the crystals, thereby reducing the tensile stress of the second layer 362.

[0066] In addition to the titanium oxide, the second layer 362 may contain small amounts of elements such as titanium (Ti), silicon (Si), iron (Fe), chromium (Cr), or hafnium (Hf) as impurities. For example, the impurities are elements contained in the first layer 361 or the third layer 363. The impurities exist in the second layer 362 in the form of oxides together with the metal elements. Such impurities have the effect of reducing the diffusion of silicon from the first layer 361 to the second layer 362, or reducing the diffusion of silicon from the first layer 361 to the second layer 362 to the third layer 363 even if silicon diffuses from the first layer 361 to the second layer 362. The impurities in the second layer 362 may be elements that are inevitably mixed in during the formation of the second layer 362, or may be elements that are intentionally mixed in the second layer 362.

[0067] From this perspective, when the second layer 362 and the third layer 363 each contain impurities, the risk of cracks, etc. in the diaphragm 36 can be reduced by making the second layer 362 and the third layer 363 softer than when they do not.

[0068] Here, the impurity content in the second layer 362 is preferably higher than the impurity content in the third layer 363. In other words, it is preferable that the impurity concentration peak in the thickness direction of the laminate including the second layer 362 and the third layer 363 is located in the second layer 362. In this case, the formation of gaps at the interface between the second layer 362 and the third layer 363 or in the third layer 363 is prevented or reduced. In contrast, if the concentration peak is located in the third layer 363, the crystal structure in the third layer 363 will be distorted by the impurities. As a result, gaps will be formed at the interface between the second layer 362 and the third layer 363 or in the third layer 363, which may increase the risk of cracking the diaphragm 36.

[0069] The thickness T2 of the second layer 362 is determined according to the thickness T and width W of the diaphragm 36 and is not particularly limited, but in the case where the diaphragm 36 has the first layer 361, the second layer 362, and the third layer 363 as in this embodiment, it is preferable that the thickness T2 be thinner than each of the thickness T1 of the first layer 361 and the thickness T3 of the third layer 363. In this case, there is an advantage that the characteristics of the diaphragm 36 can be easily optimized.

[0070] When diaphragm 36 has first layer 361, second layer 362, and third layer 363, thickness T2 of second layer 362 may be thicker than thickness T3 of third layer 363. When third layer 363 has high rigidity, controlling the film thickness of the second layer makes it possible to control the stress of diaphragm 36 as a whole while ensuring a suitable film thickness for the diaphragm.

[0071] Specifically, the thickness T2 of the second layer 362 is preferably in the range of 200 nm to 600 nm, and more preferably in the range of 250 nm to 400 nm. When the thickness T2 is in this range, the second layer 362 can preferably exhibit the effect of increasing the adhesion between the first layer 361 and the third layer 363.

[0072] On the other hand, if thickness T2 is too thin, depending on the conditions of the heat treatment during manufacturing, elemental silicon diffused from first layer 361 to second layer 362 may reach third layer 363. On the other hand, if thickness T2 is too thick, the heat treatment during manufacturing of second layer 362 may not be performed sufficiently, or the thermal oxidation may take a long time, which may adversely affect other layers.

[0073] Furthermore, when diaphragm 36 has first layer 361, second layer 362, and third layer 363 as in this embodiment, thickness T2 of second layer 362, when combined with thickness T3 of third layer 363, is preferably 400 nm to 1300 nm, more preferably 500 nm to 700 nm. That is, the sum of thickness T2 and thickness T3 is preferably 400 nm to 1300 nm, more preferably 500 nm to 700 nm. This makes it easy to keep thickness T2 within the aforementioned preferred range.

[0074] 1-4. Manufacturing method of liquid ejection head 7 is a diagram illustrating a method for manufacturing a liquid ejection head. Hereinafter, the steps for manufacturing a laminate including the pressure chamber substrate 34, the vibration plate 36, and the piezoelectric element 44 of the liquid ejection head 26 will be described representatively with reference to FIG.

[0075] 7, the method for manufacturing the liquid ejection head 26 includes a substrate preparation step S10, a diaphragm formation step S20, a piezoelectric element formation step S30, and a pressure chamber formation step S40. Here, the diaphragm formation step S20 includes a first layer formation step S21, a second layer formation step S22, and a third layer formation step S23. Each step will be described below in order.

[0076] The substrate preparation step S10 is a step of preparing a substrate to become the pressure chamber substrate 34. The substrate is, for example, a silicon single crystal substrate.

[0077] The diaphragm forming process S20 is a process for forming the diaphragm 36 described above, and is performed after the substrate preparing process S10. In the diaphragm forming process S20, a first layer forming process S21, a second layer forming process S22, and a third layer forming process S23 are performed in this order.

[0078] The first layer forming step S21 is a step of forming the above-mentioned first layer 361. In the first layer forming step S21, for example, one surface of the silicon single crystal substrate prepared in the substrate preparing step S10 is thermally oxidized to form the first layer 361 made of silicon oxide (SiO2).

[0079] The second layer forming step S22 is a step of forming the second layer 362 described above. In the second layer forming step S22, for example, a titanium layer is formed on the first layer 361 by a sputtering method, and the layer is thermally oxidized to form the second layer 362 made of titanium oxide. Note that the method of forming the second layer 362 is not limited to using thermal oxidation, and for example, a CVD method or an atomic layer deposition (ALD) method may also be used. Furthermore, the thermal oxidation in the second layer forming step S22 may be performed simultaneously with the thermal oxidation in the third layer forming step S23 described below.

[0080] The third layer forming step S23 is a step of forming the aforementioned third layer 363. In the third layer forming step S23, for example, a zirconium layer is formed on the second layer 362 by a sputtering method, and the layer is thermally oxidized to form the third layer 363 made of zirconium oxide.

[0081] The piezoelectric element forming step S30 is a step of forming the above-mentioned plurality of piezoelectric elements 44, and is performed after the third layer forming step S23. In the piezoelectric element forming step S30, a first electrode 441, a piezoelectric layer 443, and a second electrode 442 are formed in this order on the third layer 363.

[0082] Each of the first electrode 441 and the second electrode 442 is formed by a known film formation technique such as sputtering, and a known processing technique using photolithography, etching, etc. The piezoelectric layer 443 is formed by, for example, forming a precursor layer of a piezoelectric material by a sol-gel method, and baking and crystallizing the precursor layer.

[0083] After the piezoelectric element 44 is formed, if necessary, one of the two surfaces of the substrate after the formation, other than the surface on which the piezoelectric element 44 is formed, is ground by CMP (chemical mechanical polishing) or the like to flatten that surface or adjust the thickness of the substrate.

[0084] The pressure chamber forming step S40 is a step of forming the pressure chambers C described above, and is performed after the piezoelectric element forming step S30. In the pressure chamber forming step S40, for example, holes 341 that form the pressure chambers C are formed by anisotropically etching one of the two surfaces of the silicon single crystal substrate after the piezoelectric elements 44 have been formed, the surface other than the surface on which the piezoelectric elements 44 are formed. As a result of the formation of the holes 341, the pressure chamber substrate 34 is obtained. At this time, for example, an aqueous potassium hydroxide solution (KOH) or the like is used as an etchant for the anisotropic etching. At this time, the first layer 361 functions as a stopping layer that stops the anisotropic etching.

[0085] After the pressure chamber forming step S40, steps such as joining the flow path substrate 32 to the pressure chamber substrate 34 with adhesive are appropriately carried out, thereby obtaining the liquid ejection head 26.

[0086] 2. Second embodiment A second embodiment of the present invention will be described below. In the following exemplary embodiment, for elements whose actions or functions are similar to those of the first embodiment, the reference numerals used in the description of the first embodiment will be used, and detailed descriptions of each element will be omitted as appropriate.

[0087] 8 is a cross-sectional view of a liquid ejection head 26A according to the second embodiment. The liquid ejection head 26A is configured similarly to the liquid ejection head 26 of the first embodiment, except that it includes a vibration plate 36A instead of the vibration plate 36 of the first embodiment. The vibration plate 36A is configured similarly to the vibration plate 36 of the first embodiment, except that the third layer 363 of the first embodiment is omitted. However, the thicknesses of the layers that make up the vibration plate 36A are adjusted as appropriate.

[0088] Here, the piezoelectric element 44 contacts the second layer 362 in the stacking direction. This has the advantage that a layer with high rigidity, such as a zirconia layer, is not interposed between the piezoelectric element 44 and the second layer 362, making it easier to reduce stress in the vibration plate 36A.

[0089] When diaphragm 36A does not have third layer 363 as in this embodiment, thickness T2 of second layer 362 is determined according to thickness T and width W of diaphragm 36, and is not particularly limited, but is preferably within a range of 600 nm to 700 nm. By having thickness T2 within this range, the necessary thickness T of diaphragm 36A can be suitably ensured even without third layer 363.

[0090] According to the second embodiment described above, it is also possible to prevent cracks from occurring in the actuator formed by the piezoelectric element 44 and the vibration plate 36A.

[0091] 3. Working Example Specific examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0092] A. Diaphragm manufacturing A-1. Example 1 First, one surface of a silicon single crystal substrate with a surface orientation (110) was thermally oxidized to form a first layer made of silicon oxide and having a thickness of 1500 nm.

[0093] Next, a film made of titanium was formed on the first layer by sputtering, and the film was thermally oxidized and baked at 500°C to form a second layer made of titanium oxide and having a thickness of 200 nm.

[0094] Subsequently, a film made of zirconium was formed on the second layer by sputtering, and the film was thermally oxidized at 900° C. to form a third layer made of zirconium oxide and having a thickness of 650 nm.

[0095] Thereafter, the other surface of the silicon single crystal substrate was anisotropically etched using an aqueous potassium hydroxide (KOH) solution or the like as an etching solution, thereby forming a recess having the first layer as its bottom.

[0096] In this way, a diaphragm consisting of the first, second and third layers was manufactured.

[0097] Here, X-ray crystal structure analysis was performed after the first and second layers were formed on the diaphragm. When the second layer of the diaphragm was measured using X-ray crystal structure analysis, the measurement data showed a peak in the 2θ range of 37.33 to 37.68, and the main states of the titanium oxide in the second layer were anatase and brookite structures. Furthermore, when the film stress of the second layer was measured, it was found to be -100 MPa to -300 MPa.

[0098] The film stress was calculated by measuring the amount of warping of the diaphragm on which the first and second layers were formed relative to the diaphragm on which the first layer was formed. More specifically, the diaphragm on which the first layer was formed and the diaphragm on which the first and second layers were formed were irradiated with laser light, the radius of curvature of each substrate surface was measured, and the film stress of the diaphragm on which the first and second layers were formed was calculated from the amount of change in the radius of curvature. When the film stress of the second layer was measured, it was found to be -100 MPa to -300 MPa.

[0099] A-2. Example 2 A diaphragm was manufactured in the same manner as in Example 1, except that the firing temperature when forming the second layer was set to 550°C.

[0100] The second layer of the resulting diaphragm was measured by X-ray crystal structure analysis, and the measurement data showed a peak in the 2θ range of 36.95 to 37.30, indicating that the main states of the titanium oxide in the second layer were anatase and brookite structures. Furthermore, when the film stress of the second layer was measured, it was found to be 0 MPa to 100 MPa.

[0101] A-3. Example 3 A diaphragm was manufactured in the same manner as in Example 1, except that the firing temperature when forming the second layer was set to 600°C.

[0102] The second layer of the resulting diaphragm was measured by X-ray crystal structure analysis, and the measurement data showed no peaks in the range of 2θ between 20° and 50° and γ between -95° and -85°, indicating that the titanium oxide in the second layer was primarily amorphous. Furthermore, the film stress of the second layer was measured and found to be 400 MPa to 600 MPa.

[0103] A-4. Example 4 A diaphragm was manufactured in the same manner as in Example 1, except that the thickness of the second layer was set to 400 nm.

[0104] The second layer of the resulting diaphragm was measured by X-ray crystal structure analysis, and the measurement data showed a peak in the 2θ range of 38.01 to 38.24, indicating that the main states of the titanium oxide in the second layer were anatase and brookite structures. Furthermore, when the film stress of the second layer was measured, it was found to be 0 MPa to 100 MPa.

[0105] A-5. Example 5 A diaphragm was manufactured in the same manner as in Example 1 described above, except that the thickness of the second layer was set to 400 nm and the firing temperature when forming the second layer was set to 550° C. That is, a diaphragm was manufactured in the same manner as in Example 2 described above, except that the thickness of the second layer was set to 400 nm.

[0106] The second layer of the resulting diaphragm was measured by X-ray crystal structure analysis, and the measurement data showed a peak in the 2θ range of 37.38 to 37.75, indicating that the main states of the titanium oxide in the second layer were anatase and brookite structures. Furthermore, when the film stress of the second layer was measured, it was found to be 0 MPa to 100 MPa.

[0107] A-6. Example 6 A diaphragm was manufactured in the same manner as in Example 1 described above, except that the thickness of the second layer was set to 400 nm and the firing temperature when forming the second layer was set to 600° C. That is, a diaphragm was manufactured in the same manner as in Example 3 described above, except that the thickness of the second layer was set to 400 nm.

[0108] The second layer of the resulting diaphragm was analyzed by X-ray crystal structure analysis, and the measurement data showed a peak in the 2θ range of 37.04 to 37.26, indicating that the main structures of the titanium oxide in the second layer were anatase and brookite. Furthermore, the film stress of the second layer was measured and found to be 200 MPa to 300 MPa.

[0109] A-7. Example 7 A diaphragm was manufactured in the same manner as in Example 1, except that the thickness of the second layer was set to 600 nm.

[0110] The second layer of the resulting diaphragm was measured by X-ray crystal structure analysis, and the measurement data showed a peak in the 2θ range of 38.20 to 38.45, indicating that the main states of the titanium oxide in the second layer were anatase and brookite structures. Furthermore, the film stress of the second layer was measured and found to be 100 MPa to 200 MPa.

[0111] A-8. Example 8 A diaphragm was manufactured in the same manner as in Example 1 described above, except that the thickness of the second layer was set to 600 nm and the firing temperature when forming the second layer was set to 550° C. That is, a diaphragm was manufactured in the same manner as in Example 2 described above, except that the thickness of the second layer was set to 600 nm.

[0112] The second layer of the resulting diaphragm was measured by X-ray crystal structure analysis, and the measurement data showed a peak in the 2θ range of 37.54 to 38.11, indicating that the main states of the titanium oxide in the second layer were anatase and brookite structures. Furthermore, when the film stress of the second layer was measured, it was found to be 100 MPa to 200 MPa.

[0113] A-9. Example 9 A diaphragm was manufactured in the same manner as in Example 1 described above, except that the thickness of the second layer was set to 600 nm and the firing temperature when forming the second layer was set to 600° C. That is, a diaphragm was manufactured in the same manner as in Example 3 described above, except that the thickness of the second layer was set to 600 nm.

[0114] The second layer of the resulting diaphragm was analyzed by X-ray crystal structure analysis, and the measurement data showed a peak in the 2θ range of 37.25 to 37.57, indicating that the main structures of the titanium oxide in the second layer were anatase and brookite. Furthermore, the film stress of the second layer was measured and found to be 200 MPa to 400 MPa.

[0115] A-10. Comparative example A diaphragm was manufactured in the same manner as in Example 1, except that the thickness of the second layer was set to 40 nm and the firing temperature when forming the second layer was set to 900°C.

[0116] The second layer of the resulting diaphragm was measured by X-ray crystal structure analysis, and the measurement data showed a peak in the 2θ range of 39.12 to 39.28, indicating that the main state of the titanium oxide in the second layer was the rutile structure. Furthermore, when the film stress of the second layer was measured, it was found to be 900 MPa.

[0117] B. Evaluation The diaphragm characteristics of each example and comparative example were evaluated according to the following criteria. The evaluation results are shown in FIG. 9 together with the respective conditions. P: The membrane stress of the second layer is less than 700 MPa. F: The membrane stress of the second layer is 700 MPa or more.

[0118] Fig. 9 shows the relationship between the state of the second layer and the evaluation for Examples 1-9 and the comparative example. As shown in Fig. 9, the film stress of the second layer was less than 700 MPa in Examples 1-9, whereas the film stress of the second layer was 700 MPa or more in the comparative example. Therefore, cracks in the diaphragm can be suppressed in Examples 1-9 compared to the comparative example.

[0119] 4. Variations Each of the above-mentioned exemplary embodiments can be modified in various ways. Specific modified embodiments that can be applied to each of the above-mentioned embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be appropriately combined within the scope of not contradicting each other.

[0120] 4-1. Variation 1 In each of the above-described embodiments, the liquid ejection head 26, 26A has a plurality of piezoelectric elements 44 including a piezoelectric layer 443. Here, the plurality of piezoelectric elements 44 have a plurality of first electrodes 441 provided individually for the plurality of piezoelectric elements, and a second electrode 442 provided in common for the plurality of piezoelectric elements 44. The plurality of first electrodes 441 are disposed between the piezoelectric layer 443 and the vibration plate 36.

[0121] In this way, in each of the above-described embodiments, a configuration is exemplified in which the first electrode 441 is an individual electrode and the second electrode 442 is a common electrode, but the first electrode 441 may be a common electrode that is continuous across multiple piezoelectric elements 44, and the second electrode 442 may be an individual electrode for each piezoelectric element 44. Also, both the first electrode 441 and the second electrode 442 may be individual electrodes.

[0122] 4-2. Variation 2 In each of the above-described embodiments, a serial type liquid ejection device 100 is exemplified, in which a transport body 242 carrying a liquid ejection head 26 is moved back and forth, but the present invention can also be applied to a line type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium 12.

[0123] 4-3. Variation 3 The liquid ejection device 100 exemplified in each of the above embodiments can be employed in various devices such as facsimile machines and copiers, as well as devices dedicated to printing. However, 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 is used as a manufacturing device for forming color filters for liquid crystal display devices. Furthermore, 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.

[0124] 5. Summary of this disclosure A summary of this disclosure is provided below.

[0125] (Appendix 1) A first aspect, which is a preferred example of a liquid ejection head of the present disclosure, comprises a piezoelectric element, a vibration plate that vibrates when driven by the piezoelectric element, and a pressure chamber substrate in which a pressure chamber is provided that applies pressure to a liquid by vibration of the vibration plate, wherein the pressure chamber substrate, the vibration plate, and the piezoelectric element are stacked in this order in a stacking direction, the vibration plate has a first layer containing silicon as a constituent element, and a second layer that is provided on the first layer in the stacking direction and contains titanium oxide, and the titanium oxide contained in the second layer has a predominant state of either an anatase structure, a brookite structure, or amorphous.

[0126] In the above-described embodiment, the titanium oxide contained in the second layer has a predominant structure of either anatase, brookite, or amorphous. This reduces the occurrence of cracks in an actuator composed of a piezoelectric element and a diaphragm, compared to an embodiment in which the titanium oxide contained in the second layer has a predominant structure of rutile. The tensile stress of each of the anatase, brookite, and amorphous structures is lower than that of the rutile structure. Therefore, by having the titanium oxide contained in the second layer have a predominant structure of either anatase, brookite, or amorphous, the tensile stress of the second layer, which is one of the causes of cracks in the actuator, is reduced. This increases the margin until the critical stress when the second layer deforms, making the second layer less susceptible to fracture. The term "predominant state" refers to a state in which the titanium oxide content is 34% or greater.

[0127] (Supplementary Note 2) In the second embodiment, which is a preferred example of the first embodiment, the titanium oxide contained in the second layer has a predominant structure of either an anatase structure or a brookite structure. In this embodiment, by having the anatase structure or the brookite structure, which are more stable than the amorphous structure, as the predominant structure, the stability of the actuator can be improved compared to an embodiment in which the amorphous structure is the predominant structure. Furthermore, by having the anatase structure or the brookite structure, which have a lower tensile stress than the amorphous structure, as the predominant structure, the occurrence of cracks in the actuator can be suppressed compared to an embodiment in which the amorphous structure is the predominant structure.

[0128] (Appendix 3) In the third embodiment, which is a preferred example of the first embodiment, when the second layer is measured by X-ray crystal structure analysis, the measurement data shows no peaks in the range of 2θ between 20° and 50° and γ between -95° and -85°. In the above embodiment, the titanium oxide contained in the second layer is primarily amorphous, so defects due to crystallization of the second layer do not occur. This prevents fracture due to stress concentration at weak points in the crystals of the second layer. Furthermore, although the tensile stress of the second layer is higher than in an embodiment in which the primary structure is anatase or the like, the absence of defects due to crystallization of the second layer allows the critical stress that the second layer can withstand to be increased.

[0129] (Note 4) In a fourth aspect, which is a preferred example of any of the first to third aspects, the film stress of the second layer is a tensile stress of 700 MPa or less. In the above aspect, the tensile stress applied to the film disposed on the second layer in the stacking direction can be suppressed. As a result, cracks or breakage of the piezoelectric element can be suppressed. Another advantage is that the diaphragm tends to have a convex shape toward the pressure chamber, making it easier to achieve stable vibration of the diaphragm.

[0130] (Supplementary Note 5) In a fifth aspect, which is a preferred example of any of the first to fourth aspects, the diaphragm further includes a third layer disposed between the second layer and the piezoelectric element and containing zirconia as a constituent element. In this aspect, diffusion of the piezoelectric material from the piezoelectric element to the diaphragm can be suppressed. In addition, since a mixed layer can be easily formed from titanium and zirconium, adhesion within the diaphragm can be improved.

[0131] (Supplementary Note 6) In a sixth aspect, which is a preferred example of any of the first to fourth aspects, the piezoelectric element contacts the second layer in the stacking direction. In this aspect, there is no layer, such as a zirconia layer, with high rigidity between the piezoelectric element and the second layer, which has the advantage of making it easier to reduce stress in the diaphragm.

[0132] Note that the configuration in which "the piezoelectric element is in contact with the second layer" includes not only a configuration in which the piezoelectric element is deposited directly on the second layer, but also a configuration in which the piezoelectric element is deposited via an orientation control layer that controls the orientation of the layers that make up the piezoelectric element between the piezoelectric element and the second layer.

[0133] (Appendix 7) In a seventh aspect, which is a preferred example of any of the first to sixth aspects, the piezoelectric element has a piezoelectric layer containing lead as a constituent element, and the second layer contains lead. In the above aspect, the interlayer adhesion between the second layer and the piezoelectric layer can be improved. Furthermore, by diffusing lead into the titanium oxide crystals, the tensile stress of the second layer can be reduced. Furthermore, the tensile stress of the second layer can be reduced by the lead entering the gaps between the titanium oxide crystals and widening the spaces between the crystals. [Explanation of symbols]

[0134] 12...medium, 14...liquid container, 20...control unit, 22...transport mechanism, 24...movement mechanism, 26...liquid ejection head, 26A...liquid ejection head, 32...flow path substrate, 34...pressure chamber substrate, 36...vibration plate, 36A...vibration plate, 44...piezoelectric element, 46...wiring substrate, 48...casing portion, 50...drive circuit, 52...external wiring, 55...first conductor, 56...second conductor, 57...sealing plate, 62...nozzle plate, 64...vibration absorber, 100...liquid ejection device, 242...transport body, 244...transport belt, 322...supply flow path, 324...communicating flow path, 326...supply liquid chamber, 341...hole, 342...partition wall portion, 361...first layer, 362...second layer, 363...third layer, 400 nm...thickness, 441...first electrode, 442...second electrode, 443...piezoelectric layer, 461...wiring, 462...wiring, 482...inlet, B...bump, C...pressure chamber, L1...first row, L2...second row, N...nozzle, R...liquid storage chamber, Ra...space, Rb...space, S10...substrate preparation process, S20...diaphragm formation process, S21...first layer formation process, S22...second layer formation process, S23...third layer formation process, S30...piezoelectric element formation process, S40...pressure chamber formation process, T...thickness, T1...thickness, T2...thickness, T3...thickness, W...width.

Claims

1. a piezoelectric element; a vibration plate that vibrates when driven by the piezoelectric element; a pressure chamber substrate provided with pressure chambers that apply pressure to liquid by vibration of the vibration plate; the pressure chamber substrate, the vibration plate, and the piezoelectric element are stacked in this order in a stacking direction, The diaphragm is a first layer containing silicon as a constituent element; a second layer provided on the first layer in the stacking direction and containing titanium oxide; the main state of titanium oxide contained in the second layer is any one of an anatase structure, a brookite structure, and an amorphous structure; A liquid ejection head characterized by:

2. The main state of titanium oxide contained in the second layer is either an anatase structure or a brookite structure. The liquid ejection head according to claim 1 .

3. When the second layer is measured by X-ray crystal structure analysis, the measurement data shows no peak in the range of 2θ being equal to or greater than 20° and equal to or less than 50°, and γ being equal to or greater than −95° and equal to or less than −85°. The liquid ejection head according to claim 1 .

4. The second layer has a tensile stress of 700 MPa or less. The liquid ejection head according to claim 1 .

5. the vibration plate further includes a third layer disposed between the second layer and the piezoelectric element and containing zirconia as a constituent element. The liquid ejection head according to claim 1 .

6. the piezoelectric element is in contact with the second layer in the stacking direction; The liquid ejection head according to claim 1 .

7. the piezoelectric element has a piezoelectric layer containing lead as a constituent element, the second layer comprises lead; The liquid ejection head according to claim 1 .

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