Actuator, liquid ejection head, and printer

Abstract

The invention relates to an actuator, a liquid ejection head, and a printer. Provided is an actuator capable of suppressing an increase in the amount of displacement of a diaphragm from becoming small even if the applied voltage between a first electrode and a second electrode is increased. The actuator includes: a diaphragm; the first electrode is arranged above the vibration plate; a piezoelectric layer that is provided above the first electrode and contains a composite oxide having a perovskite-type structure; and a second electrode provided above the piezoelectric layer, the residual polarization of the piezoelectric layer being 0.535 times or less of the spontaneous polarization of the piezoelectric layer.

Description

Technical Field

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

[0002] An actuator including a diaphragm and a piezoelectric element is applied to, for example, a liquid ejection head of an inkjet printer.

[0003] For example, Patent Document 1 discloses a piezoelectric actuator including a diaphragm and a piezoelectric element. The piezoelectric element includes a piezoelectric thin film having a crystal structure in which the directions of spontaneous polarization are aligned in a certain direction.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-294844

[0005] In such a piezoelectric actuator, the larger the displacement amount of the diaphragm is, the smaller the increase amount of the displacement amount of the diaphragm with respect to the increase amount of the displacement amount of the piezoelectric thin film is. Therefore, there is a technical problem that the larger the voltage applied to the piezoelectric element is, the smaller the increase amount of the displacement amount of the diaphragm is. Summary of the Invention

[0006] One aspect of the actuator according to the present invention includes:

[0007] A diaphragm;

[0008] A first electrode provided above the diaphragm;

[0009] A piezoelectric layer provided above the first electrode and including a composite oxide having a perovskite structure; and

[0010] A second electrode provided above the piezoelectric layer,

[0011] The remanent polarization of the piezoelectric layer is 0.535 times or less of the spontaneous polarization of the piezoelectric layer.

[0012] One aspect of the liquid ejection head according to the present invention includes:

[0013] One aspect of the actuator; and

[0014] A flow path forming substrate having a pressure generating chamber formed therein, and the volume of the pressure generating chamber is changed by the actuator; and

[0015] A nozzle plate provided with nozzle holes communicating with the pressure generating chamber.

[0016] One aspect of the printer according to the present invention includes:

[0017] The liquid ejection head;

[0018] A conveyance mechanism that moves a recording medium relative to the liquid ejection head; and

[0019] A control unit that controls the liquid ejection head and the conveyance mechanism. Description of the Drawings

[0020] Figure 1 is a cross-sectional view schematically showing the actuator according to the present embodiment.

[0021] Figure 2 is the hysteresis curve of the actuator according to the present embodiment.

[0022] Figure 3 is a cross-sectional view schematically showing the manufacturing process of the actuator according to the present embodiment.

[0023] Figure 4 is a diagram for explaining the tensile stress generated in the piezoelectric layer of the actuator according to the present embodiment.

[0024] Figure 5 is an exploded perspective view schematically showing the liquid ejection head according to the present embodiment.

[0025] Figure 6 is a top view schematically showing the liquid ejection head according to the present embodiment.

[0026] Figure 7 is a cross-sectional view schematically showing the liquid ejection head according to the present embodiment.

[0027] Figure 8 is a perspective view schematically showing the printer according to the present embodiment.

[0028] Figure 9 is the hysteresis curve of Example 1.

[0029] Figure 10 is the hysteresis curve of Example 2.

[0030] Figure 11 is the hysteresis curve of Comparative Example 1.

[0031] Figure 12 is a coordinate diagram showing the relationship between the electric field generated in the piezoelectric layer and the displacement amount of the diaphragm in Examples 1 and 2 and Comparative Example 1.

[0032] Figure 13 is a table showing a summary of the experimental results of Examples 1 and 2 and Comparative Example 1.

[0033] Description of Reference Numerals

[0034] 10…Substrate; 12…Opening; 13…Partition wall; 14…First communication path; 15…Second communication path; 16…Third communication path; 17…Manifold; 18…Supply flow path; 20…Vibrating plate; 22…First layer; 24…Second layer; 30…Piezoelectric element; 32…First electrode; 34…Seed layer; 36…Piezoelectric layer; 36a…Crystal structure; 38…Second electrode; 100…Actuator; 200…Liquid ejection head; 202…Lead electrode; 203…Adhesive; 204…Connection wiring; 210…Nozzle plate; 212…Nozzle hole; 220…Protective substrate; 222, 224…Through hole; 226…Opening; 230…Circuit substrate; 240…Flexible substrate; 242…Sealing layer; 244…Fixing plate; 246…Through hole; 300…Printer; 310…Head unit; 312, 314…Cartridge; 316…Carriage; 320…Device main body; 330…Drive motor; 332…Timing belt; 340…Conveyor roller; 350…Printer controller. Detailed Description of the Embodiment

[0035] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the embodiments described below do not unduly limit the content of the present invention described in the claims. Further, the configurations described below are not limited to all being essential components of the present invention.

[0036] 1. Actuator

[0037] 1.1. Configuration

[0038] First, the actuator according to the present embodiment will be described with reference to the drawings. Figure 1 FIG. is a cross-sectional view schematically showing the actuator 100 according to the present embodiment.

[0039] As Figure 1 shown, the actuator 100 includes a vibrating plate 20 and a piezoelectric element 30. The actuator 100 is provided on the substrate 10.

[0040] The substrate 10 is, for example, a silicon substrate. In the illustrated example, an opening 12 is formed in the substrate 10. When the actuator 100 is applied to a liquid ejection head, the opening 12 serves as a pressure generating chamber that stores the liquid ejected from the liquid ejection head and applies pressure to the supplied liquid.

[0041] The diaphragm 20 is provided on the substrate 10. The diaphragm 20 is provided between the substrate 10 and the piezoelectric element 30. In the illustrated example, the diaphragm 20 closes the opening 12. The diaphragm 20 has, for example, a first layer 22 provided on the substrate 10 and a second layer 24 provided on the first layer 22. The first layer 22 is, for example, a silicon oxide layer. The second layer 24 is, for example, a zirconium oxide layer. The diaphragm 20 has flexibility. The diaphragm 20 deforms according to the deformation of the piezoelectric element 30.

[0042] The piezoelectric element 30 is provided above the diaphragm 20. In the illustrated example, the piezoelectric element 30 is directly provided on the diaphragm 20. The piezoelectric element 30 includes, for example, a first electrode 32, a seed layer 34, a piezoelectric layer 36, and a second electrode 38.

[0043] In addition, in the description related to the present invention, for example, when the term "above" is used as "forming another specific member (hereinafter referred to as "B") "above" a specific member (hereinafter referred to as "A"), etc., the term "above" is used as a case including both the case of directly forming B on A and the case of forming B on A via other members.

[0044] The first electrode 32 is provided above the diaphragm 20. In the illustrated example, the first electrode 32 is directly provided on the diaphragm 20. The first electrode 32 is provided between the diaphragm 20 and the seed layer 34. The shape of the first electrode 32 is, for example, a layer shape. The thickness of the first electrode 32 is, for example, 3 nm or more and 300 nm or less. The first electrode 32 is, for example, a metal layer such as a platinum layer, an iridium layer, a titanium layer, a ruthenium layer, or a conductive oxide layer thereof. The first electrode 32 may also have a structure in which a plurality of the above-exemplified layers are laminated. The first electrode 32 may also be an electrode in which a platinum layer and an iridium layer are laminated from the side of the diaphragm 20. The first electrode 32 is an electrode for applying a voltage to the piezoelectric layer 36.

[0045] In addition, although not shown, in order to improve the adhesion between the diaphragm 20 and the first electrode 32, an adhesion layer may be provided between the diaphragm 20 and the first electrode 32. The adhesion layer is, for example, a titanium layer, a titanium oxide layer, or the like.

[0046] The seed layer 34 is provided on the first electrode 32. The seed layer 34 is provided between the first electrode 32 and the piezoelectric layer 36. In the illustrated example, the seed layer 34 is also provided on the diaphragm 20. The thickness of the seed layer 34 is, for example, 5 nm or more and 100 nm or less, preferably 10 nm or more and 50 nm or less.

[0047] The seed layer 34 is, for example, a composite oxide having a perovskite structure containing bismuth (Bi), iron (Fe), and titanium (Ti). The seed layer 34 may also be bismuth iron titanate (Bi(Fe,Ti)O 3: (BFT) layer. The seed layer 34 can also be a BFT layer doped with lead (Pb) or the like. When lead is added, the content of lead in the seed layer 34 is 0.1 mass% or less. Since the seed layer 34 has the same perovskite structure as the piezoelectric layer 36, the orientation, lattice constant, and crystal structure of the piezoelectric layer 36 can be easily controlled.

[0048] The piezoelectric layer 36 is disposed above the first electrode 32. In the illustrated example, the piezoelectric layer 36 is disposed on the first electrode 32 via the seed layer 34. The piezoelectric layer 36 is directly disposed on the seed layer 34. The piezoelectric layer 36 is disposed between the seed layer 34 and the second electrode 38. The piezoelectric layer 36 is formed by laminating a plurality of crystal layers, for example. The thickness of the piezoelectric layer 36 is, for example, 100 nm or more and 3 μm or less, preferably 200 nm or more and 2 μm or less.

[0049] The piezoelectric layer 36 contains a composite oxide having a perovskite structure. The piezoelectric layer 36 can also be composed of a composite oxide having a perovskite structure. The composite oxide can also be composed of a ferroelectric. A "ferroelectric" refers to a substance in which electric dipoles are aligned even without an external electric field, and the direction of the dipoles can be changed according to the electric field.

[0050] The piezoelectric layer 36 contains potassium (K), sodium (Na), and niobium (Nb), for example. The piezoelectric layer 36 is, for example, a sodium potassium niobate ((K,Na)NbO 3 : KNN) layer. The piezoelectric layer 36 can also be a KNN layer doped with an additive such as manganese (Mn). If the piezoelectric layer 36 is a KNN layer, an environmentally friendly lead-free piezoelectric layer 36 can be formed.

[0051] In addition, the piezoelectric layer 36 is not limited to the KNN layer. The piezoelectric layer 36 can also be a lead-based piezoelectric layer such as a lead zirconate titanate (Pb(Zr,Ti)O 3 : PZT) layer or a lead niobate zirconate titanate (Pb(Zr,Ti,Nb)O 3 : PZTN) layer. Alternatively, the piezoelectric layer 36 can also be a lead-free piezoelectric layer other than the KNN layer.

[0052] The lattice constant in the in-plane direction of the piezoelectric layer 36 is smaller than the lattice constant in the in-plane direction of the seed layer 34, for example. The "in-plane direction" refers to the direction orthogonal to the thickness direction of the substrate 10. When the material of the piezoelectric layer 36 is KNN, the lattice constant in the in-plane direction is the length in the a-axis direction.

[0053] A tensile stress is generated in the piezoelectric layer 36. The tensile stress in the piezoelectric layer 36 is, for example, 261 MPa or more and 1000 MPa or less. The tensile stress in the piezoelectric layer 36 is generated, for example, due to the difference in the lattice constant in the in-plane direction of the piezoelectric layer 36 and the lattice constant in the in-plane direction of the seed layer 34.

[0054] The second electrode 38 is provided above the piezoelectric layer 36. In the illustrated example, the second electrode 38 is directly provided on the piezoelectric layer 36. The shape of the second electrode 38 is, for example, a layer shape. The thickness of the second electrode 38 is, for example, 3 nm or more and 300 nm or less. The second electrode 38 is, for example, a metal layer such as a platinum layer, an iridium layer, a titanium layer, a ruthenium layer, or a conductive oxide layer thereof. The second electrode 38 may also have a structure in which a plurality of the above-exemplified layers are stacked. The second electrode 38 is an electrode for applying a voltage to the piezoelectric layer 36.

[0055] 1.2. Hysteresis Curve

[0056] Figure 2 It is a diagram for explaining the hysteresis curve in the piezoelectric layer 36. Figure 2 The electric field E on the horizontal axis is the electric field generated in the piezoelectric layer 36 by applying a voltage between the first electrode 32 and the second electrode 38. Figure 2 The polarization amount P on the vertical axis is the amount of polarization generated in the piezoelectric layer 36 by the electric field E.

[0057] The remanent polarization Pr is the polarization amount P when the electric field E is 0 kV / cm. The spontaneous polarization Ps is the polarization amount excluding the component caused by the contribution of the dielectric constant when the ferroelectric constituting the piezoelectric layer 36 is completely polarized. Hereinafter, the intercept of the tangent line T of the hysteresis curve at the maximum electric field Emax, i.e., E = 0, is defined as the spontaneous polarization Ps. In addition, the maximum electric field Emax is the electric field generated in the piezoelectric layer 36 when the applied voltage between the first electrode 32 and the second electrode 38 is maximized.

[0058] The remanent polarization Pr is, for example, 12.2 μC / cm 2 Hereinafter, it is preferably 12.0 μC / cm 2 Hereinafter. The remanent polarization Pr is, for example, 0.8 μC / cm 2 Above, preferably 1.0 μC / cm 2 Above, more preferably 1.2 μC / cm 2 Above.

[0059] The spontaneous polarization Ps is greater than the remanent polarization Pr. The spontaneous polarization Ps is, for example, 23.2 μC / cm 2 Hereinafter, preferably 23.0 μC / cm 2 Hereinafter. The spontaneous polarization Ps is, for example, 5.0 μC / cm 2Above, preferably 7.0 μC / cm 2 , more preferably 8.0 μC / cm 2 .

[0060] The remanent polarization Pr is 0.535 times or less of the spontaneous polarization Ps, preferably 0.521 times or less. The remanent polarization Pr is, for example, 0.10 times or more of the spontaneous polarization Ps, preferably 0.122 times or more, and more preferably 0.15 times or more.

[0061] The increase rate of the displacement amount of the diaphragm 20 when the electric field E generated in the piezoelectric layer 36 is increased by 10% from 210 kV / cm is, for example, 0.94 times or more with respect to the decrease rate of the displacement amount of the diaphragm 20 when the electric field E is decreased by 10% from 210 kV / cm. In other words, the increase rate of the displacement amount of the diaphragm 20 when the electric field E is increased from 210 kV / cm to 231 kV / cm is 0.94 times or more with respect to the decrease rate of the displacement amount of the diaphragm 20 when the electric field E is decreased from 210 kV / cm to 189 kV / cm.

[0062] 1.3. Effects

[0063] The actuator 100 includes: a diaphragm 20; a first electrode 32 provided above the diaphragm 20; a piezoelectric layer 36 provided above the first electrode 32 and including a complex oxide having a perovskite structure; and a second electrode 38 provided above the piezoelectric layer 36. The remanent polarization Pr of the piezoelectric layer 36 is 0.535 times or less of the spontaneous polarization Ps of the piezoelectric layer 36. Therefore, in the actuator 100, as shown in the "Examples and Comparative Examples" described later, the linearity of the hysteresis curve can be improved. Thus, even if the applied voltage between the first electrode 32 and the second electrode 38 is increased, it is possible to suppress a decrease in the increase amount of the displacement amount of the diaphragm 20. Therefore, the design of the operating voltage becomes easy.

[0064] In the actuator 100, the remanent polarization Pr is 12.2 μC / cm 2 or less, and the spontaneous polarization Ps is 23.2 μC / cm 2 or less. Therefore, in the actuator 100, the remanent polarization Pr can be set to 0.535 times or less of the spontaneous polarization Ps.

[0065] In the actuator 100, the increase rate of the displacement amount of the diaphragm 20 when the electric field E generated in the piezoelectric layer 36 is increased by 10% from 210 kV / cm is 0.94 times or more with respect to the decrease rate of the displacement amount of the diaphragm 20 when the electric field E is decreased by 10% from 210 kV / cm. Therefore, in the actuator 100, the linearity of the hysteresis curve can be improved.

[0066] In the actuator 100, the tensile stress of the piezoelectric layer 36 is 261 MPa or more. Therefore, in the actuator 100, in the polarization generated in the piezoelectric layer 36, the component in the film thickness direction can be reduced. Thereby, the remanent polarization Pr can be reduced, and the linearity of the hysteresis curve can be improved.

[0067] In the actuator 100, a seed layer 34 is provided between the first electrode 32 and the piezoelectric layer 36, and the lattice constant in the in-plane direction of the piezoelectric layer 36 is smaller than the lattice constant in the in-plane direction of the seed layer 34. Therefore, in the actuator 100, tensile stress can be generated in the piezoelectric layer 36.

[0068] 2. Manufacturing method of actuator

[0069] Next, the manufacturing method of the actuator 100 according to the present embodiment will be described with reference to the drawings. Figure 3 It is a cross-sectional view schematically showing the manufacturing process of the actuator 100 according to the present embodiment.

[0070] As Figure 3 shown, a first layer 22 is formed on the substrate 10. Next, a second layer 24 is formed on the first layer 22. The first layer 22 is formed, for example, by thermally oxidizing the substrate 10 which is a silicon substrate. The second layer 24 is formed by forming a zirconium layer on the first layer 22 by a sputtering method or the like and thermally oxidizing the zirconium layer. Through this process, the diaphragm 20 having the first layer 22 and the second layer 24 can be formed.

[0071] Next, a first electrode 32 is formed on the diaphragm 20. The first electrode 32 is formed, for example, by a sputtering method or a vacuum evaporation method. Next, the first electrode 32 is patterned. The patterning is performed by, for example, photolithography and etching.

[0072] As Figure 1 shown, a seed layer 34 is formed on the first electrode 32. The seed layer 34 is formed by a chemical solution deposition (CSD) method such as a sol-gel method or a MOD (Metal Organic Deposition) method. Hereinafter, the formation method of the seed layer 34 which is a BFT layer will be described.

[0073] For example, a precursor solution is prepared by dissolving or dispersing a metal complex containing bismuth, a metal complex containing iron, and a metal complex containing tantalum in an organic solvent. As the metal complex containing bismuth, for example, bismuth 2-ethylhexanoate, bismuth acetate, etc. can be cited. As the metal complex containing iron, for example, iron 2-ethylhexanoate, iron acetate, iron(III) acetylacetonate, etc. can be cited. As the metal complex containing tantalum, for example, pentaethoxytantalum, etc. can be cited. In addition, two or more metal complexes can be used in combination. For example, as the metal complex containing bismuth, bismuth 2-ethylhexanoate and bismuth acetate can be used in combination.

[0074] As the organic solvent for preparing the precursor solution, for example, propanol, butanol, pentanol, hexanol, octanol, ethylene glycol, propylene glycol, octane, decane, cyclohexane, xylene, toluene, tetrahydrofuran, acetic acid, octanoic acid, 2-n-butoxyethanol, n-octane, etc., or a mixed solvent thereof, etc. can be cited. The precursor solution may also contain an additive that stabilizes the dispersion of each metal complex. As such an additive, for example, 2-ethylhexanoic acid or diethanolamine, etc. can be cited.

[0075] Next, the prepared precursor solution is coated on the first electrode 32 and the vibrating plate 20 using a spin coating method or the like to form a precursor layer. Next, the precursor layer is heated and dried at, for example, 130°C or higher and 250°C or lower for a certain period of time, and further, the dried precursor layer is heated and held at, for example, 300°C or higher and 450°C or lower for a certain period of time to perform debinding. Next, the debound precursor layer is crystallized by firing at, for example, 550°C or higher and 800°C or lower.

[0076] The heating device for drying and debinding the precursor layer is, for example, a hot plate. The heating device used in the firing of the precursor layer is, for example, a lamp annealing device.

[0077] Through the above steps, the seed layer 34 can be formed.

[0078] Next, a piezoelectric layer 36 is formed on the seed layer 34. The piezoelectric layer 36 is formed, for example, by the same chemical solution deposition method as the seed layer 34. Hereinafter, the formation method of the piezoelectric layer 36 as a KNN layer doped with manganese will be described.

[0079] For example, a precursor solution is prepared by dissolving or dispersing a metal complex containing potassium, a metal complex containing sodium, a metal complex containing niobium, and a metal complex containing manganese in an organic solvent.

[0080] Examples of metal complexes containing potassium include potassium 2-ethylhexanoate, potassium acetate, etc. Examples of metal complexes containing sodium include sodium 2-ethylhexanoate, sodium acetate, etc. Examples of metal complexes containing niobium include niobium 2-ethylhexanoate, pentaethoxyniobium, pentabutoxyniobium, etc. Examples of metal complexes containing manganese include manganese 2-ethylhexanoate, etc. In addition, two or more metal complexes can be used in combination. As the solvent, for example, the above-mentioned materials cited for forming the seed layer 34 are used.

[0081] Next, the prepared precursor solution is coated on the first electrode 32 using a spin coating method or the like to form a precursor layer. Next, the precursor layer is heated and dried at, for example, 130°C or higher and 250°C or lower for a certain period of time. Further, the dried precursor layer is heated and held at, for example, 300°C or higher and 450°C or lower for a certain period of time to perform degreasing. Next, the degreased precursor layer is fired at, for example, 550°C or higher and 800°C or lower to crystallize it and form a crystal layer. The heating device for the precursor layer uses, for example, the above-mentioned device cited for forming the seed layer 34.

[0082] Next, the crystal layer is cooled. Specifically, the crystal layer is cooled at a rate of 3.0°C / second or higher, preferably 5.0°C / second or higher. By cooling the crystal layer at such a rate, as Figure 4 shown, a tensile stress can be generated in the crystal structure 36a of the crystal layer.

[0083] For example, when the crystal layer is slowly cooled at 0.3°C / second, since the heat of the crystal layer is sufficiently transferred to the substrate and then cooled, the substrate also shrinks together with the crystal layer. Therefore, it is difficult to generate a tensile stress in the crystal layer.

[0084] On the other hand, when the crystal layer is rapidly cooled, since the heat of the crystal layer is cooled before being sufficiently transferred to the substrate, the crystal layer selectively shrinks. Therefore, the crystal layer is stretched in the in-plane direction by the substrate, and a tensile stress F is generated. When the tensile stress F is large, the remanent polarization Pr becomes smaller and the linearity of the hysteresis curve becomes higher. The cooling of the crystal layer can be performed, for example, by air cooling or water cooling based on circulating cooling water. In addition, Figure 4 is a diagram for explaining the tensile stress F generated in the crystal structure 36a, and the crystal structure 36a is simplified and shown.

[0085] The series of processes from the coating of the above-mentioned precursor solution to the firing of the precursor layer are repeated multiple times. Thereby, a piezoelectric layer 36 including a plurality of crystal layers can be formed. The number of crystal layers constituting the piezoelectric layer 36 is, for example, 5 or more and 20 or less, preferably 10 or more and 15 or less.

[0086] Through the above processes, the piezoelectric layer 36 can be formed.

[0087] In addition, the method for forming the piezoelectric layer 36 and the seed layer 34 is not limited to the chemical solution deposition method, and may also be a Physical Vapor Deposition (PVD) method. As the physical vapor deposition method, for example, a sputtering method or a laser ablation method can be cited.

[0088] Next, a second electrode 38 is formed on the piezoelectric layer 36. The second electrode 38 is formed, for example, by a sputtering method or a vacuum evaporation method. Next, the second electrode 38, the piezoelectric layer 36, and the seed layer 34 are patterned. The patterning is performed, for example, by photolithography and etching. By patterning the second electrode 38, the piezoelectric layer 36, and the seed layer 34 together, shortening of the manufacturing process can be achieved. In addition, the second electrode 38, the piezoelectric layer 36, and the seed layer 34 may also be patterned in different processes.

[0089] Next, the lower surface of the substrate 10 is patterned to form an opening 12. The patterning is performed, for example, by photolithography and etching. In addition, before performing the patterning, the lower surface of the substrate 10 may be ground and polished.

[0090] Through the above processes, the actuator 100 can be manufactured.

[0091] 3. Liquid ejection head

[0092] Next, the liquid ejection head according to the present embodiment will be described with reference to the drawings. Figure 5 FIG. is an exploded perspective view schematically showing the liquid ejection head 200 according to the present embodiment. Figure 6 FIG. is a top view schematically showing the liquid ejection head 200 according to the present embodiment. Figure 7 FIG. is a schematic cross-sectional view taken along line VII-VII of the liquid ejection head 200 according to the present embodiment. In addition, in Figure 6 FIG., as three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis are illustrated. In addition, in Figures 5 to 7 FIG. and Figure 5 FIG., the piezoelectric element 30 is schematically illustrated in a simplified manner. Figure 7 In

[0093] As Figures 5 to 7 shown, the liquid ejection head 200 includes, for example, the actuator 100, a nozzle plate 210, a protective substrate 220, a circuit substrate 230, and a flexible substrate 240. In addition, for convenience, the illustration of the circuit substrate 230 is omitted in Figure 6 FIG.

[0094] An opening 12 serving as a pressure generating chamber is formed in the substrate 10 of the actuator 100. The opening 12 is partitioned by a plurality of partition walls 13. The volume of the opening 12 changes by displacing the diaphragm 20 through the piezoelectric element 30.

[0095] A first communication path 14 and a second communication path 15 are formed in the substrate 10. In the illustrated example, the first communication path 14 and the second communication path 15 are formed at the +X-axis direction end of the opening 12. The first communication path 14 is configured such that the opening area becomes smaller by narrowing the +X-axis direction end of the opening 12 in the Y-axis direction. The width of the second communication path 15 in the Y-axis direction is, for example, the same as the width of the opening 12 in the Y-axis direction. A third communication path 16 communicating with the plurality of second communication paths 15 is formed in the +X-axis direction of the second communication path 15. The third communication path 16 forms a part of the manifold 17. The manifold 17 becomes a common liquid chamber for each opening 12. Thus, the opening 12 and a supply flow path 18 including the first communication path 14, the second communication path 15, and the third communication path 16 are formed in the substrate 10. The substrate 10 is a flow path forming substrate. The supply flow path 18 communicates with the opening 12 and supplies liquid to the opening 12.

[0096] The nozzle plate 210 is provided on one surface of the substrate 10. The material of the nozzle plate 210 is, for example, SUS (Steel Use Stainless). The nozzle plate 210 is joined to the substrate 10 by, for example, an adhesive or a hot melt film. The substrate 10 is provided between the nozzle plate 210 and the diaphragm 20. A plurality of nozzle holes 212 are formed along the Y-axis in the nozzle plate 210. The nozzle holes 212 communicate with the opening 12 and eject liquid.

[0097] In the liquid ejecting head 200, the diaphragm 20 and the first electrode 32 are displaced due to the deformation of the piezoelectric layer 36 having electromechanical conversion characteristics. For example, a plurality of piezoelectric elements 30 are provided. The number of the piezoelectric elements 30 is not particularly limited.

[0098] The first electrode 32 is configured as a separate electrode independent for each opening 12. The size of the first electrode 32 in the Y-axis direction is, for example, smaller than the size of the opening 12 in the Y-axis direction. The size of the first electrode 32 in the X-axis direction is, for example, larger than the size of the opening 12 in the X-axis direction. In the X-axis direction, both ends of the first electrode 32 are located at positions sandwiching both ends of the opening 12. The -X-axis direction end of the first electrode 32 is connected to the lead electrode 202.

[0099] The size of the piezoelectric layer 36 in the Y-axis direction is, for example, larger than the size of the first electrode 32 in the Y-axis direction. The size of the piezoelectric layer 36 in the X-axis direction is, for example, larger than the size of the opening 12 in the X-axis direction. The +X-axis end of the first electrode 32 is, for example, located between the +X-axis end of the piezoelectric layer 36 and the +X-axis end of the opening 12. The +X-axis end of the first electrode 32 is covered by the piezoelectric layer 36. The -X-axis end of the piezoelectric layer 36 is, for example, located between the -X-axis side end of the first electrode 32 and the -X-axis end of the opening 12. The -X-axis side end of the first electrode 32 is not covered by the piezoelectric layer 36.

[0100] The second electrode 38 is, for example, continuously provided on the piezoelectric layer 36 and the diaphragm 20. In the illustrated example, the second electrode 38 is configured as a common electrode shared by the plurality of piezoelectric elements 30.

[0101] The protective substrate 220 is joined to the diaphragm 20 by an adhesive 203. A through-hole 222 is provided in the protective substrate 220. In the illustrated example, the through-hole 222 penetrates the protective substrate 220 in the Z-axis direction and communicates with the third communication path 16. The through-hole 222 and the third communication path 16 constitute a manifold 17 that serves as a common liquid chamber for the respective openings 12. Further, a through-hole 224 that penetrates the protective substrate 220 in the Z-axis direction is formed in the protective substrate 220. The end of the lead electrode 202 is located in the through-hole 224.

[0102] An opening 226 is formed in the protective substrate 220. The opening 226 is a space for not obstructing the driving of the piezoelectric element 30. The opening 226 may be sealed or may not be sealed.

[0103] The circuit board 230 is provided on the protective substrate 220. The circuit board 230 includes a semiconductor integrated circuit (IC) for driving the piezoelectric element 30. The circuit board 230 is electrically connected to the lead electrode 202 via a connection wiring 204.

[0104] The flexible substrate 240 is provided on the protective substrate 220. The flexible substrate 240 has a sealing layer 242 provided on the protective substrate 220 and a fixing plate 244 provided on the sealing layer 242. The sealing layer 242 is a layer for sealing the manifold 17. The sealing layer 242 has, for example, flexibility. A through-hole 246 is formed in the fixing plate 244. The through-hole 246 penetrates the fixing plate 244 in the Z-axis direction. When viewed from the Z-axis direction, the through-hole 246 is provided at a position overlapping the manifold 17.

[0105] 4. Printer

[0106] Next, the printer according to the present embodiment will be described with reference to the drawings.Figure 8 is a perspective view schematically showing a printer 300 according to this embodiment.

[0107] The printer 300 is an inkjet printer. As Figure 8 shown, the printer 300 includes a head unit 310. The head unit 310 has, for example, a liquid ejection head 200. The number of the liquid ejection heads 200 is not particularly limited. The cassette 312 and 314 that constitute the supply unit are detachably provided on the head unit 310. A carriage 316 on which the head unit 310 is mounted is axially movably provided on a carriage shaft 322 mounted on the apparatus main body 320, and ejects the liquid supplied from the liquid supply unit.

[0108] Here, the liquid means a material in a liquid phase state as long as it is a material, and liquid state materials such as sols and gels are also included in the liquid. In addition, not only is it included in the liquid as a state of matter, but substances in which particles of functional materials including solid substances such as pigments or metal particles are dissolved, dispersed, or mixed in a solvent are also included in the liquid. Representative examples of the liquid include ink, liquid crystal emulsifier, etc. Ink means general water-based ink, oil-based ink, and ink including various liquid compositions such as gel ink and hot melt ink.

[0109] In the printer 300, the driving force of the driving motor 330 is transmitted to the carriage 316 via a plurality of gears (not shown) and a timing belt 332. Thus, the carriage 316 on which the head unit 310 is mounted moves along the carriage shaft 322. On the other hand, a conveying roller 340 as a conveying mechanism is provided in the apparatus main body 320, and the conveying roller 340 relatively moves a sheet S such as paper as a recording medium relative to the liquid ejection head 200. The conveying mechanism for conveying the sheet S is not limited to the conveying roller, and may be a belt, a drum, or the like.

[0110] The printer 300 includes a printer controller 350 as a control unit that controls the liquid ejection head 200 and the conveying roller 340. The printer controller 350 is electrically connected to a circuit board 230 of the liquid ejection head 200. The printer controller 350 includes, for example, a RAM (Random Access Memory) that temporarily stores various data, a ROM (Read Only Memory) that stores a control program and the like, a CPU (Central Processing Unit), and a drive signal generation circuit that generates a drive signal for supplying to the liquid ejection head 200.

[0111] 5. Examples and Comparative Examples

[0112] 5.1. Preparation of Specimens

[0113] 5.1.1. Example 1

[0114] The surface of the single crystal silicon substrate was thermally oxidized to form a SiO layer with a thickness of 1460 nm. 2 Next, a Zr film with a thickness of 400 nm was formed by DC (Direct Current) sputtering, and a ZrO layer was formed by heat treatment at 850°C. 2 Thus, a layer including SiO 2 layer and ZrO 2 Layer of vibration plate.

[0115] Next, as the first electrode, a Ti layer, a Pt layer, and an Ir layer were formed by DC sputtering to have thicknesses of 20 nm, 80 nm, and 5 nm, respectively.

[0116] Next, a seed layer was formed. Specifically, a BFT precursor solution was prepared using bismuth acetate, ferric acetate, and tetraisopropyl titanate so as to have a molar ratio of Bi / Fe / Ti=110 / 50 / 50. The precursor solution was formed into a film with a thickness of 20 nm by spin coating, and lamp annealing was performed at 650°C in an oxygen atmosphere for 3 minutes to obtain a BFT crystal layer.

[0117] Next, a piezoelectric layer was formed. Specifically, a precursor solution of KNN was prepared using potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate so as to have a molar ratio of K / Na / Nb=52 / 52 / 100. In addition, a solution containing manganese 2-ethylhexanoate in a manner containing 0.2 wt% MnO as an additive was used. Such a precursor solution was formed into a film with a thickness of 70 nm by spin coating, and lamp annealing was performed at 700°C in an oxygen atmosphere for 3 minutes to obtain a KNN crystalline layer. Thereafter, the KNN crystalline layer was cooled at 5°C / second using air cooling and water cooling based on circulating cooling water. The above process was repeated 12 times to form a piezoelectric layer with a thickness of 840 nm.

[0118] Next, as a second electrode, a Pt layer was formed to a thickness of 50 nm by a DC sputtering method.

[0119] Next, the second electrode, the piezoelectric layer, and the seed layer were patterned by ion milling to produce a piezoelectric element.

[0120] Next, the back side of the single crystal silicon substrate was ground and polished to a thickness of about 400 μm. Next, a chromium oxide layer with a thickness of 60 nm and a chromium layer with a thickness of 100 nm were formed on the polished surface. Next, the chromium oxide layer and the chromium layer were patterned by wet etching. Furthermore, the single crystal silicon substrate was patterned by wet etching to form an opening.

[0121] Through the above, the actuator of Example 1 was formed.

[0122] 5.1.2. Example 2

[0123] By thermally oxidizing the surface of a single-crystalline silicon substrate, a SiO layer with a thickness of 1870 nm was formed 2 as a diaphragm. Next, as the first electrode, a Pt layer with a thickness of 200 nm was formed by DC sputtering.

[0124] Next, using a KNN target formulated to have a molar ratio of K / Na / Nb = 35 / 65 / 100, a piezoelectric layer with a thickness of 1000 nm was formed by RF sputtering.

[0125] Next, as the second electrode, a Pt layer with a thickness of 100 nm was formed by DC sputtering.

[0126] The subsequent processes were the same as those in Example 1.

[0127] Through the above, the actuator of Example 2 was formed.

[0128] 5.1.3. Comparative Example 1

[0129] By thermally oxidizing the surface of a single-crystalline silicon substrate, a SiO layer with a thickness of 1460 nm was formed 2 layer. Next, a Zr film with a thickness of 400 nm was formed by DC sputtering, and a ZrO layer was formed by heat treatment at 850 °C 2 layer. Thus, a diaphragm including a SiO layer and a ZrO layer was formed. 2 layer and ZrO 2 layer.

[0130] Next, as the first electrode, Ti layers, Pt layers, Ir layers, and Ti layers with thicknesses of 20 nm, 80 nm, 5 nm, and 4 nm were respectively formed by DC sputtering.

[0131] Next, a piezoelectric layer was formed. Specifically, a precursor solution of PZT was prepared using lead acetate, zirconium butoxide, and titanium tetraisopropoxide so that the molar ratio of Pb / Zr / Ti = 118 / 52 / 48. This precursor solution was formed into a film by spin coating, and lamp annealing was performed at 737 °C for 5 minutes in a nitrogen atmosphere to obtain a PZT crystalline film. The above process was repeated 6 times to form a piezoelectric layer with a thickness of 1200 nm.

[0132] Next, the second electrode was formed. Specifically, Ir layers and Ti layers with thicknesses of 5 nm and 4 nm were respectively formed by DC sputtering. Next, lamp annealing was performed at 740 °C for 8 minutes in a nitrogen atmosphere to respectively form Ir layers and Ti layers with thicknesses of 6 nm and 25 nm.

[0133] The subsequent processes were the same as those in Example 1.

[0134] Through the above, the actuator of Comparative Example 1 was formed.

[0135] 5.2. Experimental Method

[0136] 5.2.1. Spontaneous Polarization and Remnant Polarization

[0137] As the measuring device, a ferroelectric tester FCE manufactured by Toyo Technica Co., Ltd. and a voltage amplifier F10A manufactured by Toyo Technica Co., Ltd. were used. A triangular wave with a frequency of 66 Hz and an electric field of 290 kV / cm was applied to the piezoelectric layer with an area of 97680 μm when viewed from above, and a hysteresis curve was obtained. The spontaneous polarization and remnant polarization were calculated by fitting using the modified Miller model obtained by modifying the model by Miller. The modified Miller model is shown by the following equations (1) to (3). 2 Moreover, in Equations (1) to (3), P is the polarization amount, Ps is the spontaneous polarization, Pr is the remnant polarization, V is the voltage, Vc is the coercive voltage, Vm is the maximum applied voltage, and Pm is the polarization amount when Vm is applied.

[0138] [Mathematical formula 1]

[0139]

[0140] In addition, in Equations (1) to (3), P is the polarization amount, Ps is the spontaneous polarization, Pr is the remnant polarization, V is the voltage, Vc is the coercive voltage, Vm is the maximum applied voltage, and Pm is the polarization amount when Vm is applied.

[0141] 5.2.2. Displacement Amount

[0142] As the measuring device for the displacement amount of the diaphragm, an arbitrary waveform generator AFG3022C manufactured by Tektronix, a voltage amplifier HSA4011 manufactured by NF Circuit Design Co., Ltd., an oscilloscope HDO4024 manufactured by Teledyne Lecroy, and a laser displacement meter NLV-2500 manufactured by Polytec were used. A square wave with a voltage width of 5 V to 35 V output from the arbitrary waveform generator and amplified 10 times by the voltage amplifier was applied to the piezoelectric layer having the same area as above. Then, the displacement amount of the diaphragm was detected by the laser displacement meter, and the displacement amount was converted into a voltage and taken into the oscilloscope. In Examples 1 and 2 and Comparative Example 1, the lowest voltage was adjusted so that the displacement amount became maximum. The reduction rate of the displacement amount when the electric field was reduced by 10% and the increase rate of the displacement amount when the electric field was increased by 10% were respectively evaluated with 210 kV / cm as the center, and the value obtained by dividing the latter by the former was used as an evaluation index for the linearity of the hysteresis curve (hereinafter also referred to as "linearity"). In this index, it can be said that the closer to 1, the higher the linearity.

[0143] 5.2.3. Tensile Stress

[0144] Using a thin film stress measurement device FLX-2908 (manufactured by KLA-Tencor Corporation), the tensile stress of the piezoelectric layers in Examples 1 and 2 and Comparative Example 1 was determined from the warpage amount of the laminated specimens.

[0145] Specifically, on the entire surface of a silicon substrate with a diameter of 150 mm, except for a range of 1 mm from the periphery, as described in the above "Fabrication of Specimens", each layer was laminated and the warpage amounts of the laminated specimens before and after forming the piezoelectric layer were measured. Specifically, regarding the warpage amount, the shape of a range except for a range of 10 mm from the periphery on a straight line including the center of the laminated specimen was measured. In the cases of Examples 1 and 2 and Comparative Example 1, since the center had a concave shape, the height difference in the direction perpendicular to the specimen surface between the two ends of the straight line and the center became the warpage amount.

[0146] When the warpage amount was much shorter than 130 mm, which was the range where the shape was measured, the stress of the piezoelectric layer was determined by the following formula (4).

[0147] [Mathematical formula 2]

[0148]

[0149] In addition, in formula (4), σ is the tensile stress, E S is the Young's modulus of the substrate, v is the Poisson's ratio of the substrate, L is the length of the measurement range, t S is the thickness of the substrate, t F is the thickness of the piezoelectric layer, z B is the warpage amount of the laminated specimen before forming the piezoelectric layer, z A is the warpage amount of the laminated specimen after forming the piezoelectric layer.

[0150] 5.2.4. Lattice constant

[0151] In Example 1 and Comparative Example 1, the lattice constants of the piezoelectric layer and the base layer were measured. The base layer is the layer directly below the piezoelectric layer, which is the BFT layer in Example 1 and the Pt layer in Comparative Example 1. Using a thin film X-ray diffraction device (D8 Discover, manufactured by Bruker AXS), the X-ray diffraction peaks of the crystal were obtained by the usual 2θ-ω method using Cu-Kα rays, and the lattice constants were determined according to the Bragg formula.

[0152] 5.3. Experimental results

[0153] Figure 9 is the hysteresis curve of Example 1. Figure 10 is the hysteresis curve of Example 2. Figure 11is the hysteresis curve of Comparative Example 1. In Figures 9 to 11 the measured values are shown by thick lines, and the fitting data are shown by thin lines.

[0154] Figure 12 is a coordinate diagram showing the relationship between the electric field generated in the piezoelectric layer and the displacement amount of the diaphragm in Examples 1 and 2 and Comparative Example 1. Figure 12 The vertical axis of

[0155] Figure 13 is a table showing an overview of the experimental results of Examples 1 and 2 and Comparative Example 1. Figure 13 The "spontaneous polarization" and "remnant polarization" in Figures 9 to 11 are the values read from

[0156] with the tolerance of "±0.2" added. "Remnant polarization / spontaneous polarization" shows the range considering the tolerance. Figure 13 As shown in

[0157] Examples 1 and 2 have a higher linearity compared to Comparative Example 1. It is known that by setting the remnant polarization to 0.535 times or less of the spontaneous polarization, the linearity can be made 0.94 times or more.

[0158] As shown in Figure 13 in Example 1, the lattice constant of the piezoelectric layer is smaller than that of the base layer. On the other hand, in Comparative Example 1, the lattice constant of the piezoelectric layer is larger than that of the base layer. In Example 1, a stronger tensile stress is generated in the piezoelectric layer compared to Comparative Example 1.

[0159] The above-described embodiments and modified examples are examples and are not limited thereto. For example, each embodiment and each modified example can be appropriately combined.

[0160] The present invention includes configurations that are substantially the same as those described in the embodiments, such as configurations having the same functions, methods, and results, or configurations having the same purposes and effects. In addition, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. In addition, the present invention includes configurations that can achieve the same functions and effects as those described in the embodiments or can achieve the same purposes. In addition, the present invention includes configurations in which well-known technologies are added to the configurations described in the embodiments.

[0161] The following can be derived from the above-described embodiments and modified examples.

[0162] One aspect of the actuator is

[0163] comprising:

[0164] a diaphragm;

[0165] a first electrode disposed above the diaphragm;

[0166] a piezoelectric layer disposed above the first electrode and comprising a complex oxide having a perovskite structure; and

[0167] a second electrode disposed above the piezoelectric layer,

[0168] the remanent polarization of the piezoelectric layer is 0.535 times or less of the spontaneous polarization of the piezoelectric layer.

[0169] According to this actuator, even if the applied voltage between the first electrode and the second electrode is increased, an increase in the displacement amount of the diaphragm can be suppressed from becoming small.

[0170] In one aspect of the actuator, it may also be that

[0171] the remanent polarization is 12.2 μC / cm 2 or less.

[0172] the spontaneous polarization is 23.2 μC / cm 2 or less.

[0173] According to this actuator, the remanent polarization can be set to 0.535 times or less of the spontaneous polarization.

[0174] In one aspect of the actuator, it may also be that

[0175] the increase rate of the displacement amount of the diaphragm when the electric field generated in the piezoelectric layer is increased by 10% from 210 kV / cm is 0.94 times or more relative to the decrease rate of the displacement amount of the diaphragm when the electric field is decreased by 10% from 210 kV / cm.

[0176] According to this actuator, the linearity of the hysteresis curve can be improved.

[0177] In one aspect of the actuator, it may also be that

[0178] the tensile stress of the piezoelectric layer is 261 MPa or more.

[0179] According to this actuator, the remanent polarization can be reduced and the linearity of the hysteresis curve can be improved.

[0180] In one aspect of the actuator, it may also be that,

[0181] a seed layer disposed between the first electrode and the piezoelectric layer,

[0182] the lattice constant in the in-plane direction of the piezoelectric layer is smaller than the lattice constant in the in-plane direction of the seed layer.

[0183] According to this actuator, tensile stress can be generated in the piezoelectric layer.

[0184] One aspect of the liquid ejection head includes:

[0185] one aspect of the actuator; and

[0186] a flow path forming substrate having a pressure generating chamber formed therein, the volume of the pressure generating chamber being changed by the actuator; and

[0187] a nozzle plate provided with nozzle holes communicating with the pressure generating chamber..

[0188] One aspect of the printer includes:

[0189] the liquid ejection head;

[0190] a conveyance mechanism that relatively moves a recording medium with respect to the liquid ejection head; and

[0191] a control unit that controls the liquid ejection head and the conveyance mechanism.

Claims

1. An actuator, characterized in that: Include: Vibration plate; A first electrode is disposed above the vibration plate; A piezoelectric layer, disposed above the first electrode, comprising a composite oxide of a perovskite structure; as well as A second electrode is provided above the piezoelectric layer, The remanent polarization of the piezoelectric layer is less than or equal to 0.535 times the spontaneous polarization of the piezoelectric layer.

2. The actuator according to claim 1, wherein: The remanent polarization is 12.2 μC / cm 2 the following, The spontaneous polarization is 23.2 μC / cm 2 the following.

3. The actuator according to claim 1, wherein: The increase rate of the displacement of the vibration plate when the electric field generated in the piezoelectric layer is increased by 10% from 210 kV / cm is 0.94 times or more relative to the decrease rate of the displacement of the vibration plate when the electric field is reduced by 10% from 210 kV / cm.

4. The actuator according to claim 1, wherein: The tensile stress of the piezoelectric layer is greater than or equal to 261 MPa.

5. The actuator according to claim 1, wherein: The actuator includes a seed layer disposed between the first electrode and the piezoelectric layer. The lattice constant of the piezoelectric layer in the in-plane direction is smaller than the lattice constant of the seed crystal layer in the in-plane direction.

6. A liquid ejection head, characterized in that: Include: An actuator according to any one of claims 1 to 5; A flow path forming substrate is formed with a pressure generating chamber, and the volume of the pressure generating chamber is changed by the actuator; as well as The nozzle plate is provided with a nozzle hole communicating with the pressure generating chamber.

7. A printer, characterized in that: Include: The liquid ejection head according to claim 6; a conveying mechanism for moving the recording medium relative to the liquid ejection head; and The control unit controls the liquid ejection head and the conveying mechanism.

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