Liquid discharge head

Abstract

To provide a liquid discharge head in which the deformation amount of a piezoelectric element is prevented from dropping significantly.SOLUTION: The liquid discharge head includes: a piezoelectric element in which a piezoelectric layer, an upper electrode provided in the upper part of the piezoelectric layer, and a lower electrode provided in the lower part of the piezoelectric layer are provided; and a vibration plate vibrated by driving of the piezoelectric element. The orientation rate of the (100)-plane of the piezoelectric layer is at least 90% and the half band width of the peak in the (100)-plane obtained by performing an X-ray rocking curve measurement on the piezoelectric layer is 4° at a maximum.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a liquid ejection head.

Background Art

[0002] Conventionally, there has been a liquid ejection device including a piezoelectric element. In this liquid ejection device, liquid is ejected by utilizing the piezoelectric characteristics of the piezoelectric element that deforms when a voltage is applied. For the purpose of improving the piezoelectric characteristics of the piezoelectric element, attempts have been made to improve the orientation of the piezoelectric layer included in the piezoelectric element (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even when the initial piezoelectric characteristics are good, the displacement amount of the piezoelectric element may significantly decrease when a voltage is repeatedly applied to the piezoelectric element.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms. According to one form of the present disclosure, a liquid ejection head is provided. This liquid ejection head has a piezoelectric element provided with a piezoelectric layer, an upper electrode provided above the piezoelectric layer, and a lower electrode provided below the piezoelectric layer, and a diaphragm that vibrates when the piezoelectric element is driven. The orientation ratio of the (100) plane of the piezoelectric layer is 90% or more, and the full width at half maximum of the peak of the (100) plane obtained when the piezoelectric layer is measured by an X-ray rocking curve is 4° or less.

Brief Description of the Drawings

[0006]

Figure 1

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Figure 5

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Mode for Carrying Out the Invention

[0007] A. Embodiment: A1. Overall configuration of the liquid ejection device: FIG. 1 is a schematic diagram showing a schematic configuration of an inkjet liquid ejection apparatus 100 according to an embodiment. The liquid ejection apparatus 100 is an inkjet printing apparatus that performs printing by ejecting droplets of ink as a liquid onto a medium 12. As the medium 12, in addition to printing paper, a printing target made of any material such as a resin film or cloth can be adopted. In the following description, the X direction, Y direction, and Z direction that are orthogonal to each other are used. Also, when specifying a direction, the positive direction is denoted as "+", and the negative direction is denoted as "-", and positive and negative signs are used together in the direction notation. In the present embodiment, the X direction is the main scanning direction that is the moving direction of the liquid ejection head 26. The Y direction is the sub-scanning direction that is the medium feeding direction orthogonal to the main scanning direction. The -Z direction is the ink ejection direction.

[0008] The liquid ejection apparatus 100 includes a liquid ejection head 26, a head moving mechanism 20, a liquid storage unit 14, a conveyance mechanism 16, and a control unit 80.

[0009] The liquid storage unit 14 stores ink to be supplied to the liquid ejection head 26. As the liquid storage unit 14, a bag-shaped liquid pack formed of a flexible film, an ink tank capable of ink replenishment, a detachable ink cartridge, or the like can be used.

[0010] The liquid ejection head 26 has a plurality of nozzles N for ejecting ink. The plurality of nozzles N are arranged in the Y direction. The liquid ejection head 26 ejects the ink supplied from the liquid storage unit 14 toward the medium 12 from the plurality of nozzles N.

[0011] The head moving mechanism 20 includes a conveyance belt 21 and a carriage 22 that houses the liquid ejection head 26. The carriage 22 is connected to the conveyance belt 21 and is reciprocated in the X direction as the conveyance belt 21 is driven. The conveyance mechanism 16 conveys the medium 12 in the +Y direction.

[0012] The control unit 80 includes processing circuits such as one or more CPUs (Central Processing Units) and FPGAs (Field Programmable Gate Arrays), and a storage circuit such as a semiconductor memory, and controls the operation of the entire liquid ejection device 100. The control unit 80 is electrically connected to the conveyance mechanism 16, the head movement mechanism 20, and the liquid ejection head 26, and controls each part. By ejecting liquid from the nozzle N onto the medium 12 conveyed by the conveyance mechanism 16, an image is printed on the medium 12.

[0013] A2. Configuration of the liquid ejection head: FIG. 2 is an exploded perspective view of the liquid ejection head 26 according to the embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a plan view of the piezoelectric element 44. In FIG. 4, hatching is applied to the formation region of the upper electrode 445 other than the regions where the first conductive layer 451 and the second conductive layer 452 are formed. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4.

[0014] As shown in FIG. 2, the liquid ejection head 26 includes a nozzle plate 62, two vibration dampers 64, a flow path substrate 32, a pressure chamber substrate 34, a diaphragm 36, a sealing body 46, a housing portion 48, and a circuit board 50. The nozzle plate 62, the vibration dampers 64, the flow path substrate 32, the pressure chamber substrate 34, the diaphragm 36, and the sealing body 46 are plate-like members that are long in the Y direction. Each of the nozzle plate 62, the flow path substrate 32, the pressure chamber substrate 34, the diaphragm 36, and the sealing body 46 has a substantially line-symmetric structure with respect to the center line in the X direction. The planar sizes of the pressure chamber substrate 34, the diaphragm 36, and the sealing body 46 are smaller than the planar sizes of the flow path substrate 32 and the housing portion 48. During assembly, the nozzle plate 62, the two vibration dampers 64, the flow path substrate 32, the pressure chamber substrate 34, the diaphragm 36, the sealing body 46, and the housing portion 48 are laminated in this order and adhered to each other with, for example, an adhesive.

[0015] The nozzle plate 62 is a plate-shaped member in which a plurality of nozzles N are formed. The nozzle N is a through-hole having a substantially circular planar shape. The plurality of nozzles N are arranged along the Y direction. There are two rows in which the plurality of nozzles N are arranged, and the two rows are arranged side by side in the X direction. The two vibration absorbers 64 are flexible films and are arranged sandwiching the nozzle plate 62 in the X direction.

[0016] The flow path substrate 32 has two first openings 32a, a plurality of second openings 32b, and a plurality of third openings 32c. The planar shape of the first opening 32a is a rectangle elongated in the Y direction. The first opening 32a is formed along a side parallel to the Y direction of the flow path substrate 32. The plurality of second openings 32b are arranged in the Y direction. Similarly, the plurality of third openings 32c are arranged in the Y direction. There are two rows each of the second openings 32b and the third openings 32c. In the X direction, the first opening 32a, one row of the second openings 32b, one row of the third openings 32c, one row of the third openings 32c, one row of the second openings 32b, and the first opening 32a are formed side by side in this order. Further, the adjacent second opening 32b and the third opening 32c in the X direction are formed such that their positions in the Y direction are substantially the same.

[0017] A plurality of openings 34a are formed in the pressure chamber substrate 34. The planar shape of the opening 34a is a rectangle elongated in the X direction. The plurality of openings 34a are arranged in the Y direction. There are two rows in which the plurality of openings 34a are arranged, and the two rows are formed side by side in the X direction. Note that the opening 34a is formed at a position overlapping with the adjacent second opening 32b and third opening 32c formed in the flow path substrate 32 when viewed from the Z direction.

[0018] On the diaphragm 36, a piezoelectric element 44 is formed at a position overlapping with the opening 34a formed in the pressure chamber substrate 34 when viewed from the Z direction. The sealing body 46 reinforces the strength of the pressure chamber substrate 34 and the diaphragm 36 and protects the piezoelectric element 44. The sealing body 46 has a sealing body opening 46a and a sealing body recess 46b shown in FIG. 3. The planar shape of the sealing body opening 46a is a rectangle elongated in the Y direction. As shown in FIG. 3, the sealing body recess 46b is formed by being recessed from the surface of the sealing body 46 facing the piezoelectric element 44.

[0019] On the circuit board 50, a drive circuit (not shown) for driving the piezoelectric element 44 is mounted. The drive circuit is realized by an IC (Integrated Circuit) chip that outputs a drive signal and a reference voltage for driving the piezoelectric element 44. The drive circuit and the piezoelectric element 44 are electrically connected via the electrical wiring 51 shown in FIG. 3.

[0020] The housing portion 48 is a case for storing ink and has a frame shape. When laminated, the pressure chamber substrate 34, the diaphragm 36, and the sealing body 46 are arranged in the internal space of the housing portion 48. Through holes 48a are formed at each of both ends of the housing portion 48 in the X direction.

[0021] As shown in FIG. 3, spaces Rb extending in the Y direction are formed at both ends of the housing portion 48 in the X direction. The space Rb communicates with the through hole 48a. By connecting the flow path substrate 32 and the vibration absorber 64, a space Ra, a supply liquid chamber 26a, and a supply flow path 26b are formed. The space Ra is the internal space of the first opening 32a. The supply liquid chamber 26a is a space surrounded by a partition wall 32d separating the first opening 32a and the second opening 32b and the vibration absorber 64. The supply flow path 26b is the internal space of the second opening 32b. The space Ra communicates with the space Rb and the supply liquid chamber 26a, and the supply liquid chamber 26a communicates with the supply flow path 26b. By connecting the pressure chamber substrate 34 and the diaphragm 36, a pressure chamber C is formed. The pressure chamber C is a space surrounded by the opening 34a and the diaphragm 36. The pressure chamber C communicates with the supply flow path 26b. By connecting the flow path substrate 32 and the nozzle plate 62, a communication flow path 26c is formed. The communication flow path 26c is the internal space of the third opening 32c. The communication flow path 26c communicates with the pressure chamber C and the nozzle N.

[0022] The space Ra and the space Rb function as a liquid storage chamber for storing the ink supplied to the pressure chamber C. The space Rb communicates with a plurality of spaces Ra arranged in the Y direction, and the ink supplied through the through hole 48a is stored in the plurality of spaces Ra through the space Rb. The ink stored in the space Ra flows through the supply liquid chamber 26a and the supply flow path 26b and is supplied to the pressure chamber C.

[0023] In a plan view seen from the Z direction, piezoelectric elements 44 are arranged at positions overlapping each of the two pressure chambers C. A drive signal and a reference voltage are input from the circuit board 50 to the piezoelectric elements 44 via the electrical wiring 51. When the drive signal and the reference voltage are input and a voltage is applied, the piezoelectric elements 44 deform, and the diaphragm 36 vibrates in conjunction with the deformation of the piezoelectric elements 44, and the pressure in the pressure chamber C fluctuates, so that the ink is ejected from the nozzle N.

[0024] A3. Configuration of Piezoelectric Element: As shown in FIG. 5, the piezoelectric element 44 is formed by laminating a lower electrode 441, a piezoelectric layer 444, and an upper electrode 445 on the diaphragm 36 in this order. The upper electrode 445 is provided on the upper part of the piezoelectric layer 444. The lower electrode 441 is provided on the lower part of the piezoelectric layer 444. When viewed from the Z direction, the overlapping portion of the lower electrode 441, the piezoelectric layer 444, and the upper electrode 445 is the portion where the piezoelectric layer 444 deforms when a voltage is applied between the lower electrode 441 and the upper electrode 445.

[0025] The diaphragm 36 as the substrate has a silicon substrate 361 and an insulator layer 362. On the surface of the silicon substrate 361 located on the +Z direction side and in contact with the insulator layer 362, silicon dioxide is formed. The insulator layer 362 is made of zirconium oxide (ZrO 2 )). Note that the insulator layer 362 may be made of silicon nitride (SiN), hafnium oxide (HfOx), or the like. In this embodiment, the insulator layer 362 is an unoriented layer. Note that another layer such as a metal oxide may be interposed between the silicon substrate 361 and the insulator layer 362. The diaphragm 36 vibrates when the piezoelectric element 44 is driven.

[0026] The lower electrode 441 is composed of a titanium (Ti) layer, a platinum (Pt) layer, and an iridium (Ir) layer. Note that the lower electrode 441 is not limited to a plurality of layers of a Ti layer, a Pt layer, and an Ir layer. For example, it may be a single layer of a metal material such as Ti, Pt, Ir, aluminum (Al), nickel (Ni), gold (Au), copper (Cu), ruthenium (Ru), etc., or a plurality of these metal materials may be laminated and formed. Note that a part of the metal constituting the lower electrode 441 may be oxidized.

[0027] The piezoelectric layer 444 is made of a composite oxide having piezoelectric characteristics that deform when a voltage is applied. The piezoelectric layer 444 contains at least two elements selected from the group consisting of Pb, K, Na, Zr, Ti, Nb, Ba, Bi, and Fe. Specifically, as the piezoelectric layer 444, for example, lead zirconate titanate (PZT), potassium sodium niobate ((K,Na)NbO 3), sodium bismuth titanate ((Bi,Na)TiO 3 ), barium bismuth iron titanate ((Bi,Ba)(Fe,Ti)O 3 ), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O 3 ), lead zirconium titanate niobate (Pb(Zr,Ti,Nb)O 3 ), lead magnesium zirconate titanate niobate (Pb(Zr,Ti)(Mg,Nb)O 3 ), lead magnesium niobate - lead titanate solid solution (Pb(Mg,Nb)O 3 -PbTiO 3 ), and mixed crystals of at least two crystals selected from the group consisting of these can be used. In the present embodiment, the piezoelectric layer 444 is configured to include lead zirconate titanate (PZT) having a perovskite structure.

[0028] The orientation ratio of the (100) plane of the piezoelectric layer 444 is 90% or more. The full width at half maximum of the peak of the (100) plane obtained when the piezoelectric layer 444 is measured by an X-ray rocking curve is 4° or less. Thereby, while improving the initial displacement amount of the piezoelectric layer 444, it is possible to suppress a decrease in the displacement amount even when voltage application is repeated.

[0029] The orientation ratio of the (100) plane is obtained using the peak intensities of the X-ray diffraction patterns of the non-oriented sample and the oriented sample to be measured, respectively. The range of 2θ of the X-ray diffraction pattern used is in the range from 10° to 50°. In the present embodiment, the piezoelectric layer 444 is used as the measurement object. The orientation ratio of the (100) plane is obtained by the following formula (1). Orientation ratio = ((ρ - ρ0) / (1 - ρ0)) × 100 ··· Formula (1) “ρ0” in formula (1) is obtained by the following formula (2). ρ0 = ΣI0(100) / ΣI0(hkl) ··· Formula (2) "ΣI0(hkl)" in Equation (2) is the sum of all diffraction intensities in the X-ray diffraction pattern of the non-oriented sample. "ΣI0(100)" in Equation (2) is the diffraction intensity of the (100) plane in the X-ray diffraction pattern of the non-oriented sample. "ρ" in Equation (1) is obtained by the following Equation (3). ρ = ΣI(100) / ΣI(hkl) ··· Equation (3) "ΣI(hkl)" in Equation (3) is the sum of all diffraction intensities in the X-ray diffraction pattern of the oriented sample. "ΣI(100)" in Equation (3) is the diffraction intensity of the (100) plane in the X-ray diffraction pattern of the oriented sample. Note that the peak intensity of the X-ray diffraction pattern of the non-oriented sample was determined using JCPDS Card No.: 06-0598.

[0030] In this embodiment, the apparatus used for measuring the X-ray diffraction pattern is D8 DISCOVER with GADDS manufactured by Bruker. The measurement conditions are: tube voltage: 50 kV, tube current: 100 mA, detector distance: 15 cm, collimator diameter: 0.1 mm, measurement time: 180 seconds. The two-dimensional data obtained by the measurement was converted into an X-ray diffraction intensity curve using the software attached to the apparatus with a 2θ range: 20° to 50°, χ range: -95° to -85°, step width: 0.02°, and intensity normalization method: Bin normalized.

[0031] The rocking curve half-width was determined by using an X-ray diffractometer to perform a scan in the tilt angle direction of the (100) plane. The apparatus used was the same as the one used for measuring the X-ray diffraction pattern.

[0032] The abundance ratio of carbon element to oxygen element inside the piezoelectric layer 444 is 0.20 or less, and more preferably 0.15 or less. Thereby, when a voltage is applied between the lower electrode 441 and the upper electrode 445, the leakage current flowing between the lower electrode 441 and the upper electrode 445 can be suppressed. Further, when different potentials are applied to two adjacent lower electrodes 441, the leakage current flowing between the two lower electrodes 441 can be suppressed. Therefore, heat generation and deterioration of piezoelectric performance in the piezoelectric element 44 can be suppressed.

[0033] In the following description, the "abundance ratio of carbon element to oxygen element" may be referred to as "abundance ratio (C / O)". Note that the carbon element contained in the piezoelectric layer 444 is considered to be the carbon element contained in the atmosphere or the carbon element contained in the solution used as a raw material, and is considered to be mixed in during the manufacturing process of the piezoelectric element 44.

[0034] In the present embodiment, the abundance ratio (C / O) is obtained by the following formula (4) using the respective abundance ratios [atom%] of the carbon element and the oxygen element measured by XPS (X-ray Photoelectron Spectroscopy). Abundance ratio (C / O) = abundance ratio of carbon element / abundance ratio of oxygen element ··· Formula (4)

[0035] In the present embodiment, the apparatus used for the XPS measurement is the X-ray photoelectron spectrometer "ESCALAB250" manufactured by Thermo Fisher Scientific. As the X-ray source, Al-Kα rays with a spot diameter of 500 μm were used, and the measurement was performed in a state where the electron gun was irradiated for charge correction. The Survey spectrum was measured at a step interval of 1 eV, a pass energy of 200 eV, and an integration time of 100 μs. The abundance ratios of the carbon element and the oxygen element were obtained from the obtained data.

[0036] The abundance ratio (C / O) on the surface of the piezoelectric layer 444 on the lower electrode 441 side is 0.30 or less, preferably 0.25 or less. Thereby, a piezoelectric layer 444 with good crystallinity and orientation can be fabricated. The abundance ratio (C / O) on the surface of the piezoelectric layer 444 on the lower electrode 441 side was determined in the same manner as the abundance ratio (C / O) inside the piezoelectric layer 444.

[0037] The abundance ratio (C / O) inside the piezoelectric layer 444 is preferably lower than the abundance ratio (C / O) on the surface of the piezoelectric layer 444 on the lower electrode 441 side. Thereby, when a voltage is applied between the lower electrode 441 and the upper electrode 445, the leakage current flowing between the lower electrode 441 and the upper electrode 445 can be suppressed.

[0038] Here, as shown in FIG. 5, the inside of the piezoelectric layer 444 is an internal region Rin including the central position Pce in the stacking direction of the piezoelectric layer 444 located between the lower electrode 441 and the upper electrode 445. Further, the surface of the piezoelectric layer 444 on the lower electrode 441 side is a surface region Rsu including the interface between the piezoelectric layer 444 and the lower electrode 441.

[0039] The upper electrode 445 is made of Ir. Note that the upper electrode 445 is not limited to Ir, and for example, it may be a single layer of a metal material such as Pt, Al, Ni, Au, Cu, Ru, etc., or a plurality of these metal materials may be stacked to form it. Note that a part of the metal constituting the upper electrode 445 may be oxidized.

[0040] As shown in FIG. 4, the lower electrode 441 is formed for each pressure chamber C. The lower electrode 441 is drawn out in the +X direction and is individually electrically connected to the drive circuit via a first wiring 446 that conducts with the lower electrode 441. The first wiring 446 is formed of a conductive material having a lower resistance than the lower electrode 441. Specifically, the first wiring 446 is formed by laminating a conductive film of gold (Au) on the surface of a conductive film formed of, for example, nichrome (NiCr). On the other hand, the upper electrode 445 is formed so as to cover a plurality of pressure chambers C arranged in the Y direction. That is, the lower electrode 441 is individually provided for each of the plurality of pressure chambers C. In contrast, the upper electrode 445 is provided in common for the plurality of pressure chambers C. An individual drive voltage is applied to the lower electrode 441 for each pressure chamber C, and a common reference voltage is applied to the upper electrode 445 for the plurality of pressure chambers C arranged in the Y direction. Since an individual voltage is applied to the lower electrode 441 for each pressure chamber C, it is also called an individual electrode. Since a common voltage is applied to the upper electrode 445 for the pressure chambers C, it is also called a common electrode. The piezoelectric layer 444 is formed with a through hole 444a. The through hole 444a is an area where the piezoelectric layer 444 is not formed.

[0041] As shown in FIG. 4, a strip-shaped first conductive layer 451 and a second conductive layer 452 extending in the Y direction are formed on the upper electrode 445. The first conductive layer 451 and the second conductive layer 452 are electrically connected to the upper electrode 445. The first conductive layer 451 and the second conductive layer 452 are arranged to face each other in the X direction with the piezoelectric element 44 interposed therebetween. The first conductive layer 451 and the second conductive layer 452 are conductive patterns having a structure in which a conductive film of gold is laminated on the surface of a conductive film formed of, for example, nichrome. The first conductive layer 451 and the second conductive layer 452 also function as weights for suppressing the vibration of the diaphragm 36.

[0042] The structure of the piezoelectric element 44 is not limited to the above. As another embodiment of the piezoelectric element 44, an orientation control layer may be provided between the piezoelectric layer 444 and the lower electrode 441. The orientation control layer has a function of controlling the orientation of the piezoelectric layer 444. The orientation control layer can be formed, for example, to contain bismuth (Bi). In this embodiment, the orientation control layer 443 contains lead (Pb), bismuth (Bi), iron (Fe), and titanium (Ti). Specifically, the orientation control layer 443 is a composite oxide represented by ((Pb,Bi)(Fe,Ti)O x ). Further, the orientation control layer 443 may have a perovskite structure. As another embodiment, the orientation control layer 443 may contain Pb, Fe, and Ti and may not contain Bi. Alternatively, the orientation control layer 443 may contain Bi, Fe, and Ti and may not contain Pb. Also, the orientation control layer 443 may not have a perovskite structure. As another embodiment of the piezoelectric element 44, an amorphous layer may be further provided between the lower electrode 441 and the orientation control layer.

[0043] The abundance ratio (C / O) of the orientation control layer is 0.35 or less. Thereby, the orientation of the piezoelectric layer 444 can be improved. Since the orientation of the piezoelectric layer 444 tends to deteriorate when the content rate of the carbon element is high, it is preferable that the content rate of the carbon element is low.

[0044] FIG. 6 is a waveform diagram of a drive signal input to the lower electrode 441. One cycle of the drive signal includes a first section where the voltage is the reference voltage, a second section where the voltage decreases from the reference voltage to the minimum voltage and is maintained at the minimum voltage, a third section where the voltage increases from the minimum voltage to the maximum voltage and is maintained at the maximum voltage, and a fourth section where the voltage decreases from the maximum voltage to the reference voltage and is maintained at the reference voltage. When the piezoelectric element 44 is driven, a constant reference voltage is applied to the upper electrode 445.

[0045] When a minimum voltage is applied to the lower electrode 441, the piezoelectric layer 444 deforms, and the diaphragm 36 in contact with the piezoelectric element 44 deflects in the +Z direction, increasing the internal volume of the pressure chamber C. As a result, liquid is drawn from the space Ra into the pressure chamber C. Subsequently, when a maximum voltage is applied to the lower electrode 441, the piezoelectric layer 444 deforms, and the diaphragm 36 in contact with the piezoelectric element 44 deflects in the -Z direction, decreasing the internal volume of the pressure chamber C. As a result, liquid is ejected from the nozzle N. When a drive signal for one cycle is input to the lower electrode 441, liquid is ejected from the nozzle N once. For this reason, one cycle of the drive signal is also called one shot.

[0046] When the liquid ejection head 26 drives the piezoelectric element 44 in the initial state, the displacement amount of the diaphragm 36 is defined as the first displacement amount, and after driving 26 billion times from the initial state, when the displacement amount of the diaphragm 36 when the piezoelectric element 44 is driven is defined as the second displacement amount, the ratio of the second displacement amount to the first displacement amount is 95% or more. Thereby, a liquid ejection device 100 having good printing quality can be provided. Here, driving 26 billion times means inputting a drive signal of 26 billion cycles to the piezoelectric element 44. In the present embodiment, the initial state is a state in which a drive signal of 0.1 billion cycles is input to the piezoelectric element 44. In the present embodiment, the maximum voltage is 35V. The minimum voltage is -2.5V. The displacement amount is the displacement amount at the central position in a plan view of the diaphragm 36 when a maximum voltage is applied to the piezoelectric element 44, with the case where no voltage is applied to the piezoelectric element 44 as the reference position. As a measurement method, a method using a sensor having a light emitting element and a light receiving element can be used. Specifically, the sensor is installed outside the liquid ejection head 26, and the light emitting element is used to emit light toward the central position of the diaphragm 36 through the nozzle N, and the light receiving element receives the light reflected by the diaphragm 36. The displacement amount of the diaphragm 36 can be obtained using the time from when the light is emitted to when it is received. Note that the measurement method is not limited to the method using this sensor.

[0047] B. Other Embodiments: (B1) In the above-described embodiment, the lower electrode 441 is formed for each pressure chamber C, and the upper electrode 445 is provided in common for a plurality of pressure chambers C arranged in the Y direction. On the other hand, the lower electrode 441 may be provided in common for a plurality of pressure chambers C arranged in the Y direction, and the upper electrode 445 may be provided for each pressure chamber C. That is, the lower electrode 441 may function as a common electrode and the upper electrode 445 may function as an individual electrode.

[0048] (B2) In the above-described embodiment, the lower electrode 441 is formed by laminating a Ti layer, a Pt layer, and an Ir layer. And in order to be electrically connected to the drive circuit, the three layers of the Ti layer, the Pt layer, and the Ir layer are drawn out in the +X direction. On the other hand, only the Ir layer among the three layers may be drawn out in the +X direction, and the lower electrode 441 and the circuit board 50 may be electrically connected.

[0049] C. Examples and Comparative Examples: C1. Evaluation of the Rate of Change: Example 1, Example 2, and Comparative Examples 1 to 3 were fabricated. In the following description, Example 1, Example 2, and Comparative Examples 1 to 3 may be collectively referred to as samples. The samples were fabricated by sequentially laminating a lower electrode, an orientation control layer, a piezoelectric layer, and an upper electrode. Example 1 and Example 2 have different composition ratios of the piezoelectric layer. Example 1 and Comparative Example 1 have different fabrication methods of the orientation control layer. Comparative Example 1 and Comparative Examples 2 and 3 have different composition ratios of the piezoelectric layer.

[0050] The fabrication method of Example 1 will be described. First, a diaphragm was fabricated. Specifically, silicon dioxide was formed on the surface by thermally oxidizing a silicon substrate. Next, a Zr layer was formed by sputtering, and Zr was thermally oxidized to form a ZrO 2 layer as an insulator layer.

[0051] Next, the bottom electrode was formed. Specifically, a Ti layer and a Pt layer were sequentially deposited by sputtering. Next, an Ir layer was deposited by sputtering. Next, the Ti layer, Pt layer, and Ir layer were patterned using photolithography. Specifically, a resist was applied on the Ir layer, and after exposure, Ti, Pt, and Ir were ion milled. Next, the resist was removed by oxygen plasma ashing, and the substrate was cleaned.

[0052] Next, the orientation control layer was formed by a solution method. The specific formation method was as follows: First, a propionic acid solution of Bi, Fe, Ti, and Pb adjusted to a molar ratio of Bi:Pb:Fe:Ti = 110:10:50:50 was spin-coated onto the substrate. Next, drying and degreasing were performed at 350 °C using a hot plate. Next, heat treatment was performed at 650 °C for 3 minutes by RTA (Rapid thermal anneal).

[0053] Next, the piezoelectric layer was formed by a solution method. The specific formation method was as follows: First, an acetic acid solution of Pb, Zr, and Ti adjusted to a molar ratio of Pb:Zr:Ti = 118:52:48 was spin-coated onto the orientation control layer. Next, drying and degreasing were performed at 200 °C and 410 °C using a hot plate. Next, heat treatment was performed at 740 °C for 5 minutes by RTA. By repeating this process a plurality of times, a piezoelectric layer with a thickness of 1200 nm was fabricated.

[0054] Next, the top electrode was formed. Specifically, an Ir layer and a Ti layer were sequentially deposited by sputtering, and this deposition was repeated twice.

[0055] In Example 2, the molar ratio of the acetic acid solution for forming the piezoelectric layer is different from that in Example 1. Specifically, the molar ratio is Pb:Zr:Ti = 118:50:50. The fabrication methods of the other layers are the same as those in Example 1.

[0056] Comparative Example 1 is different from Example 1 in that the alignment control layer is formed by sputtering Ti. The manufacturing methods of the other layers are the same as those in Example 1. The materials and manufacturing methods of the alignment control layers in Comparative Example 2 and Comparative Example 3 are the same as those of the alignment control layer in Example 1. Also, the piezoelectric layers in Comparative Example 2 and Comparative Example 3 have a different molar ratio of the acetic acid solution for forming the piezoelectric layer from that in Comparative Example 1. Specifically, the molar ratio in Comparative Example 2 is Pb:Zr:Ti = 123:50:50. The molar ratio in Comparative Example 3 is Pb:Zr:Ti = 120:52:48.

[0057] The X-ray diffraction pattern of the sample was measured to obtain the orientation ratio of the piezoelectric layer. Also, the rocking curve measurement of the sample was performed to obtain the full width at half maximum of the peak of the (100) plane. The apparatus, measurement conditions, and calculation method used for the measurement of the orientation ratio and the full width at half maximum are the same as those described above.

[0058] Figure 7 is a diagram showing the orientation ratio, full width at half maximum, change rate, and ratio of Example 1, Example 2, and Comparative Examples 1 to 3. The orientation ratios of Example 1 and Example 2 are 90% or more, while the orientation ratios of Comparative Examples 1 to 3 are less than 90%. The full width at half maximum of Example 1 and Example 2 is 4° or less, while the full width at half maximum of Comparative Examples 1 to 3 is greater than 4°. Thus, Comparative Examples 1 to 3 had a smaller orientation ratio and a larger full width at half maximum than Example 1 and Example 2.

[0059] An endurance test was performed by applying a drive signal of 25 billion cycles to the sample. The "change rate [%]" shown in Figure 7 was calculated by the following formula (5). Change rate [%] = (displacement amount (250) / displacement amount (0.1) - 1) × 100 ··· Formula (5) The "ratio [%]" shown in Figure 7 was calculated by the following formula (6). Ratio [%] = displacement amount (250) / displacement amount (0.1) × 100 ··· Formula (6) In Formula (5) and Formula (6), the "displacement amount (250)" is the displacement amount [nm] at the 25 billionth shot. The "displacement amount (0.1)" is the displacement amount [nm] at the 0.1 billionth shot. The input drive signal is the same as the drive signal described above. The method for measuring the displacement amount is the same as above.

[0060] As shown in FIG. 7, in Example 1 and Example 2, the change rate is -5% or more, and the ratio is 95% or more. On the other hand, in Comparative Example 1 to Comparative Example 3, the change rate is less than -5%, and the ratio is less than 95%. Thus, it was confirmed that when the crystallinity of the piezoelectric layer is good, the decrease in the displacement amount of the piezoelectric element can be reduced.

[0061] FIG. 8 is a diagram showing the relationship between the number of shots and the displacement amount in Example 1, Example 2, and Comparative Example 1. FIG. 9 is a diagram showing the relationship between the number of shots and the change rate in Example 1, Example 2, and Comparative Example 1. In FIGS. 8 and 9, the measured values at 0.1 billion shots, 30 billion shots, 60 billion shots, 130 billion shots, and 260 billion shots are plotted.

[0062] When used in a liquid ejection head, it is preferable that the piezoelectric element has a large initial displacement amount and a small decrease in the displacement amount due to use deterioration. As shown in FIG. 9, in both Example 1 and Example 2, the decrease in the change rate is smaller than the decrease in the change rate of Comparative Example 1. On the other hand, in Comparative Example 1, although the initial displacement amount is large as shown in FIG. 8, the displacement amount at the 26 billionth shot is significantly reduced with respect to the initial displacement amount as shown in FIG. 9. In Comparative Example 1 to Comparative Example 3, the composition ratio of lead zirconate titanate (PZT) is different from that of Example 1 or Example 2 as a representative, but due to other factors such as the firing temperature during piezoelectric body manufacturing and the thickness of each member, etc., if the conditions of the half-value width and the degree of orientation of the rocking curve are the same as those in Comparative Example 1 to 3, the change rate is also similar.

[0063] C2. Evaluation of crystallinity: FIG. 10 is a diagram showing the composition ratio of the piezoelectric layer, the abundance ratio (C / O) of the surface on the lower electrode side, and the evaluation results of crystallinity for Examples 1 to 11 and Comparative Examples 2 to 4. In the following description, Examples 1 to 11 and Comparative Examples 2 to 4 may be collectively referred to as samples.

[0064] The "composition ratio" in FIG. 10 indicates the molar ratio of the acetic acid solution for forming the piezoelectric layer. "C" in FIG. 10 indicates the abundance ratio of the carbon element on the surface of the lower electrode side of the piezoelectric layer determined by XPS. "O" in FIG. 10 indicates the abundance ratio of the oxygen element on the surface of the lower electrode side of the piezoelectric layer determined by XPS. "C / O" in FIG. 10 indicates the abundance ratio of the carbon element to the oxygen element on the surface of the lower electrode side of the piezoelectric layer. The apparatus, measurement conditions, and calculation method used for measuring "C", "O", and "C / O" in FIG. 10 are the same as those described above.

[0065] Example 1 and Example 2 are the same samples as Example 1 and Example 2 described above, respectively. Examples 3 to 11 were prepared by changing at least one of the molar ratio of the acetic acid solution for forming the piezoelectric layer, the production method of the alignment control layer, and the composition ratio of the alignment control layer so that it would not be the same as either Example 1 or Example 2. The materials and production methods of the alignment control layers of Comparative Examples 2 to 4 are the same as those of the alignment control layer of Example 1.

[0066] The "crystallinity" shown in FIG. 10 is the evaluation result of crystallinity, which is "〇", "△", "×" in order from the better crystallinity of each sample.

[0067] As shown in FIG. 10, it can be seen that when the abundance ratio (C / O) of the surface on the lower electrode side is 0.30 or less, the crystallinity is good, and when the abundance ratio (C / O) is 0.25 or less, the crystallinity is even better.

[0068] C3. Evaluation of leakage current: FIG. 11 is a diagram showing the abundance ratio (C / O) inside the piezoelectric layer of Examples 1 to 11 and Comparative Examples 2 to 4, and the evaluation results of leakage current. "C" in FIG. 11 indicates the abundance ratio of carbon element in the piezoelectric layer determined by XPS. "O" in FIG. 11 indicates the abundance ratio of oxygen element in the piezoelectric layer determined by XPS. "C / O" in FIG. 11 indicates the abundance ratio of carbon element to oxygen element inside the piezoelectric layer. The apparatus, measurement conditions, and calculation method used for the measurement of "C", "O", and "C / O" in FIG. 11 are the same as those described above.

[0069] "Leakage current" in FIG. 11 is an evaluation result obtained by evaluating the current value of the current flowing between two lower electrodes corresponding to two adjacent pressure chambers 34a when a voltage used for actually driving the piezoelectric element is applied between the lower electrode and the upper electrode. Based on the current values, all samples were divided into three groups, and were marked as "〇", "△", and "×" in ascending order of the leakage current. Here, since the lower electrodes are individual electrodes, the leakage current was evaluated between the lower electrodes. However, when the lower electrodes are common electrodes and the upper electrodes are individual electrodes, the evaluation can also be performed between the upper electrodes, and the same tendency is obtained in that case.

[0070] As shown in FIG. 11, it can be seen that when the abundance ratio (C / O) inside the piezoelectric layer is 0.30 or less, the leakage current is small, and when the abundance ratio (C / O) is 0.25 or less, the leakage current is even smaller. Further, as can be seen by comparing FIG. 10 and FIG. 11, in Examples 10 and 11 where the abundance ratio (C / O) inside the piezoelectric layer is equal to or greater than the abundance ratio (C / O) on the surface of the lower electrode side of the piezoelectric layer, the leakage current is smaller than that of samples where the abundance ratio (C / O) inside the piezoelectric layer is smaller than the abundance ratio (C / O) on the surface of the lower electrode side of the piezoelectric layer. Therefore, it can be seen that when the abundance ratio (C / O) inside the piezoelectric layer is smaller than the abundance ratio (C / O) on the surface of the lower electrode side of the piezoelectric layer, the leakage current can be suppressed.

[0071] C4. Evaluation of the orientation control layer: Eight samples were fabricated by sequentially laminating a lower electrode, an alignment control layer, a piezoelectric layer, and an upper electrode. In each sample, the piezoelectric layer was lead zirconate titanate (PZT). As a result of determining the abundance ratio (C / O) of the alignment control layer for each sample in the same manner as described above, the abundance ratio (C / O) was in the range of 0.21 or more and 0.31 or less. When the abundance ratio (C / O) of the alignment control layer is 0.35 or less, the orientation of the piezoelectric layer can be improved.

[0072] According to the embodiment described above, the liquid ejection head 26 includes a piezoelectric element 44 having a piezoelectric layer 444, an upper electrode 445, and a lower electrode 441, and a diaphragm 36. The orientation ratio of the (100) plane of the piezoelectric layer 444 is 90% or more, and the rocking curve half-value width of the peak of the (100) plane obtained when the piezoelectric layer 444 is measured by an X-ray rocking curve is 4° or less. Therefore, it is possible to provide a piezoelectric element 44 in which the initial displacement amount of the piezoelectric layer 444 is good and the decrease in the displacement amount is suppressed even when voltage application is repeated.

[0073] In addition, the abundance ratio (C / O), which is the abundance ratio of the carbon element to the oxygen element inside the piezoelectric layer 444, is 0.20 or less. Therefore, it is possible to suppress the leakage current flowing between the lower electrode 441 and the upper electrode 445 when a voltage is applied between the lower electrode 441 and the upper electrode 445. Further, the abundance ratio (C / O) inside the piezoelectric layer 444 is 0.15 or less. Therefore, the leakage current can be further suppressed.

[0074] In addition, the abundance ratio (C / O) on the surface of the piezoelectric layer 444 on the lower electrode 441 side is 0.30 or less. Therefore, the orientation of the piezoelectric layer 444 can be further improved. Further, the abundance ratio (C / O) on the surface of the piezoelectric layer 444 on the lower electrode 441 side is 0.25 or less. Therefore, the orientation of the piezoelectric layer 444 can be further improved.

[0075] Further, the abundance ratio (C / O) inside the piezoelectric layer 444 is lower than the abundance ratio (C / O) on the surface of the piezoelectric layer 444 on the lower electrode 441 side. Therefore, when a voltage is applied between the lower electrode 441 and the upper electrode 445, the leakage current flowing between the lower electrode 441 and the upper electrode 445 can be suppressed.

[0076] Further, the piezoelectric element 44 further has an orientation control layer between the piezoelectric layer 444 and the lower electrode 441. Therefore, the orientation of the piezoelectric layer 444 can be further improved. Further, the abundance ratio (C / O) of the orientation control layer is 0.35 or less. Therefore, the orientation of the piezoelectric layer 444 can be further improved.

[0077] Further, in the liquid ejection head 26, when the displacement amount of the diaphragm 36 when the piezoelectric element 44 is driven in the initial state is defined as the first displacement amount, and the displacement amount of the diaphragm 36 when the piezoelectric element 44 is driven after being driven 26 billion times from the initial state is defined as the second displacement amount, the ratio of the second displacement amount to the first displacement amount is 95% or more. Therefore, even when the liquid ejection head 26 is used for a long period of time, a liquid ejection head 26 having good ejection performance can be provided.

[0078] D. Other forms: The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the gist thereof. For example, the technical features of the embodiments corresponding to the technical features in each form described in the summary of the invention can be appropriately replaced or combined in order to solve some or all of the above-described problems or to achieve some or all of the above-described effects. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

[0079] (1) According to one embodiment of the present disclosure, a liquid ejection head is provided. This liquid ejection head includes a piezoelectric element provided with a piezoelectric layer, an upper electrode provided on the upper part of the piezoelectric layer, and a lower electrode provided on the lower part of the piezoelectric layer, and a diaphragm that vibrates when the piezoelectric element is driven. The orientation ratio of the (100) plane of the piezoelectric layer is 90% or more, and the full width at half maximum of the peak of the (100) plane obtained when the piezoelectric layer is measured by an X-ray rocking curve is 4° or less. According to this embodiment, it is possible to provide a piezoelectric element with a good initial displacement amount of the piezoelectric layer and suppressed reduction in the displacement amount even when voltage application is repeated.

[0080] (2) In the liquid ejection head of the above embodiment, the piezoelectric layer may contain Pb, Zr, and Ti.

[0081] (3) In the liquid ejection head of the above embodiment, the abundance ratio of the carbon element to the oxygen element inside the piezoelectric layer may be 0.20 or less. According to this embodiment, it is possible to suppress the leakage current flowing between the lower electrode and the upper electrode when a voltage is applied between the lower electrode and the upper electrode.

[0082] (4) In the liquid ejection head of the above embodiment, the abundance ratio may be 0.15 or less. According to this embodiment, it is possible to further suppress the leakage current flowing between the lower electrode and the upper electrode when a voltage is applied between the lower electrode and the upper electrode.

[0083] (5) In the liquid ejection head of the above embodiment, the abundance ratio of the carbon element to the oxygen element on the surface of the piezoelectric layer on the lower electrode side may be 0.30 or less. According to this embodiment, it is possible to improve the orientation of the piezoelectric layer.

[0084] (6) In the liquid ejection head of the above embodiment, the abundance ratio on the surface of the piezoelectric layer on the lower electrode side may be 0.25 or less. According to this embodiment, it is possible to further improve the orientation of the piezoelectric layer.

[0085] (7) In the liquid ejection head of the above-described embodiment, the abundance ratio of carbon element to oxygen element inside the piezoelectric layer may be lower than the abundance ratio on the surface of the piezoelectric layer on the lower electrode side. According to this embodiment, when a voltage is applied between the lower electrode and the upper electrode, the leakage current flowing between the lower electrode and the upper electrode can be suppressed.

[0086] (8) In the liquid ejection head of the above-described embodiment, an alignment control layer for controlling the alignment of the piezoelectric layer may be further provided between the piezoelectric layer and the lower electrode. According to this embodiment, the alignment property of the piezoelectric layer can be improved.

[0087] (9) In the liquid ejection head of the above-described embodiment, the abundance ratio of carbon element to oxygen element in the alignment control layer may be 0.35 or less. According to this embodiment, the alignment property of the piezoelectric layer can be further improved.

[0088] (10) In the liquid ejection head of the above-described embodiment, the alignment control layer may contain Bi.

[0089] (11) In the liquid ejection head of the above-described embodiment, when the displacement amount of the diaphragm when the piezoelectric element is driven in the initial state is defined as the first displacement amount, and the displacement amount of the diaphragm when the piezoelectric element is driven after being driven 26 billion times from the initial state is defined as the second displacement amount, the ratio of the second displacement amount to the first displacement amount may be 95% or more. According to this embodiment, even when the liquid ejection head is used for a long period of time, a liquid ejection head having good ejection performance can be provided.

Explanation of Reference Numerals

[0090] 12... Medium, 14... Liquid storage section, 16... Conveying mechanism, 20... Head movement mechanism, 21... Conveyor belt, 22... Carriage, 26... Liquid ejection head, 26a... Supply liquid chamber, 26b... Supply flow path, 26c... Communication flow path, 32... Flow path substrate, 32a... First opening, 32b... Second opening, 32c... Third opening, 32d... Partition wall, 34... Pressure chamber substrate, 34a... Opening, 36... Diaphragm, 44... Piezoelectric element, 46... Sealing body, 46a... Sealing body opening, 46b... Sealing body recess, 48... Housing section, 48a... Through hole, 50... Circuit board, 51... Electrical wiring, 62... Nozzle plate, 64... Vibration absorber, 80... Control unit, 100... Liquid ejection device, 361... Silicon substrate, 362... Insulator layer, 441... Lower electrode, 444... Piezoelectric layer, 444a... Through hole, 445... Upper electrode, 446... First wiring, 451... First conductive layer, 452... Second conductive layer, C... Pressure chamber, N... Nozzle, Pce... Central position, Ra... Space, Rb... Space, Rin... Inner region, Rsu... Surface region

Claims

1. A liquid ejection head, a piezoelectric element including a piezoelectric layer, an upper electrode provided on an upper portion of the piezoelectric layer, and a lower electrode provided on a lower portion of the piezoelectric layer; a vibration plate that vibrates when the piezoelectric element is driven, the (100) plane of the piezoelectric layer has an orientation rate of 90% or more; A liquid ejection head, wherein the half-width of a peak of a (100) plane obtained by X-ray rocking curve measurement of the piezoelectric layer is 4° or less.

2. 2. The liquid ejection head according to claim 1, The liquid ejection head, wherein the piezoelectric layer contains Pb, Zr, and Ti.

3. 3. The liquid ejection head according to claim 1, A liquid ejection head, wherein an abundance ratio of carbon elements to oxygen elements within the piezoelectric layer is 0.20 or less.

4. 4. The liquid ejection head according to claim 3, The liquid ejection head, wherein the abundance ratio within the piezoelectric layer is 0.15 or less.

5. 3. The liquid ejection head according to claim 1, A liquid ejection head, wherein the abundance ratio of carbon elements to oxygen elements on the surface of the piezoelectric layer facing the lower electrode is 0.30 or less.

6. 6. The liquid ejection head according to claim 5, The liquid ejection head, wherein the abundance ratio on the surface of the piezoelectric layer facing the lower electrode is 0.25 or less.

7. 3. The liquid ejection head according to claim 1, A liquid ejection head, wherein an abundance ratio of carbon elements to oxygen elements inside the piezoelectric layer is lower than the abundance ratio on a surface of the piezoelectric layer on the side of the lower electrode.

8. 3. The liquid ejection head according to claim 1, The liquid ejection head further comprises an orientation control layer between the piezoelectric layer and the lower electrode for controlling the orientation of the piezoelectric layer.

9. 9. The liquid ejection head according to claim 8, A liquid ejection head, wherein the abundance ratio of carbon elements to oxygen elements in the orientation control layer is 0.35 or less.

10. 10. The liquid ejection head according to claim 9, The liquid ejection head, wherein the orientation control layer contains Bi.

11. 3. The liquid ejection head according to claim 1, A liquid ejection head, wherein a first displacement amount is a displacement amount of the vibration plate when the piezoelectric element is driven in an initial state, and a second displacement amount is a displacement amount of the vibration plate when the piezoelectric element is driven after being driven 26 billion times from the initial state, and the ratio of the second displacement amount to the first displacement amount is 95% or more.

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