Die, die manufacturing method, liquid droplet discharge head, and liquid droplet discharge apparatus

Abstract

The invention provides a tube core capable of suppressing generation of cracks, a method for manufacturing the tube core, a liquid droplet discharge head provided with the tube core, and a liquid droplet discharge apparatus. A die includes a piezoelectric actuator including a piezoelectric element and a hollow portion serving as a pressure chamber, and the piezoelectric element includes at least a piezoelectric film, a first electrode positioned above the piezoelectric film, and a second electrode positioned below the piezoelectric film. The second electrode also serves as a vibrating plate or has another vibrating plate below the second electrode, the hollow portion is located below the second electrode also serving as a vibrating plate or another vibrating plate, the main surface of the piezoelectric film is a (001) plane, the crystal orientation is aligned in the main surface out-of-plane direction and the main surface in-plane direction, and the crystal orientation is aligned in the main surface out-of-plane direction and the main surface in-plane direction. When the longitudinal direction of the hollow portion is defined as a first direction and the [100] direction of the piezoelectric film is defined as a second direction when viewed from the out-of-plane direction of the main surface of the piezoelectric film, an acute angle [theta] 1 formed by the first direction and the second direction is within the range of 30-60 degrees.

Description

Technical Field

[0001] The present invention relates to a tube die, a method for manufacturing a tube die, a liquid droplet discharge head, and a liquid droplet discharge device, and more particularly to a tube die and the like in which cracks are suppressed. Background Art

[0002] In the semiconductor field, a chip that integrates components, wiring, etc., such as a droplet ejection head chip, is called a "die". In a die having a piezoelectric actuator, a piezoelectric actuator having a piezoelectric element and an oval shape with a hollow portion (a portion that becomes a pressure chamber) in the long side direction and the short side direction is sometimes used. In addition, in the piezoelectric film of the piezoelectric element of the piezoelectric actuator, a piezoelectric film whose crystal orientation is aligned at least in the out-of-plane direction of the main surface is mostly used (for example, see patent documents 1 and 2), and a technology using a piezoelectric film whose crystal orientation is aligned not only in the out-of-plane direction of the main surface but also in the in-plane direction of the main surface is also disclosed (for example, see patent document 3).

[0003] However, the piezoelectric film whose crystal orientation is aligned not only in the out-of-plane direction of the principal surface but also in the in-plane direction of the principal surface has the advantage of excellent piezoelectric characteristics, but on the other hand, there is a problem that cracks are easily generated due to the application of voltage. The cracks generated in the piezoelectric film of the tube core reduce the performance of the device having the tube core. For example, in the case of a droplet discharge device having a tube core as a droplet discharge head chip, the cracks generated in the piezoelectric film reduce the discharge stability of the droplet discharge device.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2007-042983

[0005] Patent Document 2: Japanese Patent Application Publication No. 2003-179279

[0006] Patent Document 3: Japanese Patent Application Publication No. 2006-173646 Summary of the invention

[0007] The present invention has been made in view of the above-mentioned problems and circumstances, and aims to provide a die that suppresses the generation of cracks, a method for manufacturing the die, a liquid droplet ejection head having the die, and a liquid droplet ejection device.

[0008] In order to solve the above-mentioned problems, the inventors conducted research on the causes of the above-mentioned problems, and as a result, discovered the following and completed the present invention: in a tube core having a piezoelectric actuator including a piezoelectric element and a hollow portion serving as a pressure chamber, the generation of cracks can be suppressed by limiting the size of the acute angle formed by the

[100] direction of the piezoelectric film and the long side direction of the hollow portion or the direction in which the piezoelectric actuator is arranged to a certain range.

[0009] That is, the above-mentioned problems of the present invention are solved by the following means.

[0010] 1. A tube core having one or more piezoelectric actuators having a piezoelectric element and a hollow portion serving as a pressure chamber, characterized in that:

[0011] The piezoelectric element at least comprises a piezoelectric film, a first electrode located on the piezoelectric film, and a second electrode located under the piezoelectric film.

[0012] In the above-mentioned piezoelectric actuator, the above-mentioned second electrode also serves as a vibration plate, or a vibration plate is separately provided under the above-mentioned second electrode.

[0013] The hollow portion is located below the second electrode also serving as a vibration plate or the vibration plate provided separately.

[0014] The piezoelectric film has a main surface set as a (001) plane, and the crystal orientation of the piezoelectric film is aligned in the main surface out-of-plane direction and the main surface in-plane direction.

[0015] When the long side direction of the hollow portion when viewed out of the main surface of the piezoelectric film is set as a first direction and the

[100] direction of the piezoelectric film is set as a second direction, an acute angle θ1 formed by the first direction and the second direction is in the range of 30 to 60°.

[0016] 2. The tube core according to item 1, characterized in that:

[0017] The acute angle θ1 is within the range of 40 to 50 degrees.

[0018] 3. A tube core having a plurality of piezoelectric actuators each having a piezoelectric element and a hollow portion serving as a pressure chamber, characterized in that:

[0019] The piezoelectric element at least comprises a piezoelectric film, a first electrode located on the piezoelectric film, and a second electrode located under the piezoelectric film.

[0020] In the above-mentioned piezoelectric actuator, the above-mentioned second electrode also serves as a vibration plate, or a vibration plate is separately provided under the above-mentioned second electrode.

[0021] The hollow portion is located below the second electrode also serving as a vibration plate or the vibration plate provided separately.

[0022] The piezoelectric film has a main surface set as a (001) plane, and the crystal orientation of the piezoelectric film is aligned in the main surface out-of-plane direction and the main surface in-plane direction.

[0023] When the direction in which the plurality of piezoelectric actuators are arranged is set as a third direction and the

[100] direction of the piezoelectric film is set as a second direction, an acute angle θ2 formed by the third direction and the second direction is in the range of 30 to 60 degrees.

[0024] 4. The tube core according to item 3, characterized in that

[0025] The acute angle θ2 is within the range of 40 to 50 degrees.

[0026] 5. A tube core according to any one of items 1 to 4, characterized in that:

[0027] A distance between the first electrode and the second electrode in the piezoelectric element is in a range of 0.1 to 5 μm.

[0028] 6. A tube core according to any one of items 1 to 4, characterized in that:

[0029] The piezoelectric element includes a dielectric film between the piezoelectric film and the second electrode.

[0030] The crystal orientation of the dielectric film is aligned in the out-of-plane direction of the main surface and in the in-plane direction of the main surface.

[0031] The aligned out-of-plane crystal orientation of the piezoelectric film coincides with the aligned out-of-plane crystal orientation of the dielectric film, and the aligned in-plane crystal orientation of the piezoelectric film coincides with the aligned in-plane crystal orientation of the dielectric film.

[0032] 7. A tube core according to any one of items 1 to 4, characterized in that:

[0033] The first electrode is a multi-layer structure.

[0034] The crystal orientation of the bottom layer of the first electrode located closest to the piezoelectric film in the multilayer structure is aligned in the out-of-plane direction of the principal surface and in the in-plane direction of the principal surface.

[0035] The aligned out-of-plane crystal orientation of the piezoelectric film coincides with the aligned out-of-plane crystal orientation of the lowermost layer of the first electrode, and the aligned in-plane crystal orientation of the piezoelectric film does not coincide with the aligned in-plane crystal orientation of the lowermost layer of the first electrode.

[0036] 8. A tube core according to any one of items 1 to 4, characterized in that:

[0037] The piezoelectric element includes a dielectric film between the piezoelectric film and the second electrode.

[0038] The first electrode is a multi-layer structure.

[0039] The piezoelectric film, the dielectric film, and the first electrode bottom layer of the multilayer structured first electrode located closest to the piezoelectric film all have a perovskite structure represented by ABO 3 .

[0040] 9. A tube core according to any one of items 1 to 4, characterized in that the above-mentioned piezoelectric film is a lead zirconate titanate film.

[0041] 10. A tube core according to any one of items 1 to 4, characterized in that:

[0042] The piezoelectric element includes a dielectric film between the piezoelectric film and the second electrode.

[0043] The dielectric film is a lead lanthanum titanate film.

[0044] The first electrode is a multi-layer structure.

[0045] The bottom layer of the first electrode of the multilayer structure, which is located closest to the piezoelectric film, is a strontium ruthenate film or a lanthanum nickelate film.

[0046] 11. A tube core according to any one of items 1 to 4, characterized in that:

[0047] The upper surface of the first electrode is covered with a protective film.

[0048] The protective film is a zirconium dioxide film, an aluminum oxide film, a hafnium oxide film, a yttrium oxide film or an aluminum nitride film.

[0049] 12. A method for manufacturing a tube core, using a Si substrate, characterized in that:

[0050] The manufacturing method of the tube core at least comprises:

[0051] A step of forming a stacked body including the die described in any one of items 1 to 4 on the above-mentioned Si substrate; and

[0052] a step of cutting the stack to individualize the dies,

[0053] When the vertical direction of the notch or orientation plane of the Si substrate is set as the fourth direction, and the cutting direction in the process of individualizing the die that forms the smallest angle with the fourth direction is set as the fifth direction, the acute angle θ3 formed by the fourth direction and the fifth direction is in the range of 0 to 15°.

[0054] 13. The method for manufacturing a tube core according to item 12, characterized in that:

[0055] The acute angle θ3 is within the range of 0 to 5°.

[0056] 14. A liquid droplet ejection head, comprising a tube core, characterized in that:

[0057] The above-mentioned tube core is the tube core described in any one of items 1 to 4.

[0058] 15. A liquid droplet discharge device, comprising a liquid droplet discharge head, characterized in that:

[0059] The liquid droplet ejection head is the liquid droplet ejection head described in Item 14.

[0060] According to the above means of the present invention, it is possible to provide a die that suppresses the generation of cracks, a method for manufacturing the die, a liquid droplet ejection head including the die, and a liquid droplet ejection device.

[0061] The discovery mechanism or action mechanism of the effect of the present invention is estimated as follows.

[0062] As a reason why cracks are easily generated in a piezoelectric film in a piezoelectric actuator using a piezoelectric film whose crystal orientation is aligned in the out-of-plane direction and in the in-plane direction of the principal surface, the inventors focused on the crystal structure of the piezoelectric film, the shape of the piezoelectric actuator, and the arrangement of the piezoelectric actuator.

[0063] Regarding the crystal structure of the piezoelectric film, the inventors have found that: in a piezoelectric film whose crystal structure is aligned in the in-plane direction of the principal surface, cracks are more likely to occur in the

[100] direction and the

[010] direction when the principal surface is set as the (001) plane, compared with a piezoelectric film whose crystal structure is not aligned in the in-plane direction of the principal surface. In addition, regarding the shape of the piezoelectric actuator, the inventors have found that: in the case where the hollow portion of the piezoelectric actuator has a long side direction and a short side direction such as an oval, rectangular, elliptical, rhombus, etc., cracks in the piezoelectric film are more likely to occur in the long side direction and the short side direction.

[0064] Based on these findings, in order to suppress the generation of cracks, one embodiment of the tube core of the present invention determines the acute angle θ1 formed by the long side direction of the hollow portion (first direction) and the

[100] direction (second direction) of the piezoelectric film within a range of 30 to 60 degrees. In the tube core in which the range of θ1 is determined in this way, there is a deviation between the direction in which cracks are likely to be generated from the perspective of the shape of the piezoelectric actuator and the direction in which cracks are likely to be generated from the perspective of the crystal structure of the piezoelectric film, thereby suppressing the generation of cracks.

[0065] In addition, regarding the arrangement of the piezoelectric actuators in the die, the inventors have found that cracks in the piezoelectric film are likely to occur in the direction in which the plurality of piezoelectric actuators are arranged.

[0066] Based on this discovery, in order to suppress the generation of cracks, one embodiment of the tube core of the present invention determines the acute angle θ2 formed by the arrangement direction (third direction) of the plurality of piezoelectric actuators and the

[100] direction (second direction) of the piezoelectric film within a range of 30 to 60 degrees. In the tube core in which the range of θ2 is determined in this way, there is a deviation between the direction in which cracks are likely to be generated from the perspective of the arrangement of the piezoelectric actuators and the direction in which cracks are likely to be generated from the perspective of the crystal structure of the piezoelectric film, thereby suppressing the generation of cracks.

[0067] According to such a discovery mechanism or action mechanism, a die or the like that suppresses the generation of cracks can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is a schematic top view of the tube core viewed from the bottom side (hollow part side).

[0069] Figure 2 It is a simplified cross-sectional view showing a portion of the tube core.

[0070] Figure 3 This is a diagram showing a layer structure of a piezoelectric actuator in a case where the second electrode also serves as a vibration plate.

[0071] Figure 4 This is a diagram showing a layer structure of a piezoelectric actuator in the case where a vibration plate is additionally provided below a second electrode.

[0072] Figure 5 These are electron microscope photographs of cracks generated in the

[100] direction (second direction) and the

[010] direction (in-plane perpendicular direction to the second direction) of the piezoelectric film.

[0073] Figure 6 This is an explanatory diagram regarding the acute angle θ1.

[0074] Figure 7 This is an explanatory diagram regarding the acute angle θ2.

[0075] Figure 8 This is an explanatory diagram regarding the acute angle θ3. DETAILED DESCRIPTION

[0076] As one embodiment, the tube core of the present invention has one or more piezoelectric actuators having a piezoelectric element and a hollow portion that serves as a pressure chamber, characterized in that the piezoelectric element has at least a piezoelectric film, a first electrode located on the piezoelectric film, and a second electrode located below the piezoelectric film. In the piezoelectric actuator, the second electrode also serves as a vibration plate, or a vibration plate is additionally provided below the second electrode. The hollow portion is located below the second electrode that also serves as a vibration plate or the additional vibration plate. The piezoelectric film has a principal surface set as a (001) surface, and the crystal orientation of the piezoelectric film is aligned in an out-of-plane direction and an in-plane direction of the principal surface. When the long side direction of the hollow portion when observed from an out-of-plane direction of the principal surface of the piezoelectric film is set as a first direction, and the

[100] direction of the piezoelectric film is set as a second direction, the acute angle θ1 formed by the first direction and the second direction is in the range of 30 to 60°.

[0077] As one embodiment, the tube core of the present invention has multiple piezoelectric actuators having piezoelectric elements and a hollow portion that serves as a pressure chamber, characterized in that the piezoelectric element has at least a piezoelectric film, a first electrode located on the piezoelectric film, and a second electrode located below the piezoelectric film. In the piezoelectric actuator, the second electrode also serves as a vibration plate, or a vibration plate is additionally provided below the second electrode. The hollow portion is located below the second electrode that also serves as a vibration plate or the additional vibration plate. The piezoelectric film has a principal surface as a (001) surface, and the crystal orientation of the piezoelectric film is aligned in an out-of-plane direction and an in-plane direction of the principal surface. When the direction in which the multiple piezoelectric actuators are arranged is set as a third direction, and the

[100] direction of the piezoelectric film is set as a second direction, the acute angle θ2 formed by the third direction and the second direction is in the range of 30 to 60°.

[0078] These features are common or corresponding technical features in the following embodiments.

[0079] As an embodiment of the die of the present invention, from the viewpoint of being able to further suppress the occurrence of cracks, it is preferable that the acute angle θ1 is within a range of 40 to 50°.

[0080] As an embodiment of the die of the present invention, from the viewpoint of being able to further suppress the occurrence of cracks, it is preferable that the acute angle θ2 is within a range of 40 to 50 degrees.

[0081] As an embodiment of the die of the present invention, from the viewpoint of displacement generating force required of the piezoelectric element, it is preferable that a distance between the first electrode and the second electrode in the piezoelectric element is within a range of 0.1 to 5 μm.

[0082] As an embodiment of the tube core of the present invention, from the perspective of dielectric constant, it is preferred that the above-mentioned piezoelectric element has a dielectric film between the above-mentioned piezoelectric film and the above-mentioned second electrode, the crystal orientation of the above-mentioned dielectric film is aligned in the out-of-plane direction of the main surface and in the in-plane direction of the main surface, the aligned out-of-plane crystal orientation of the above-mentioned piezoelectric film is consistent with the aligned out-of-plane crystal orientation of the above-mentioned dielectric film, and the aligned in-plane crystal orientation of the above-mentioned piezoelectric film is also consistent with the aligned in-plane crystal orientation of the above-mentioned dielectric film.

[0083] As an embodiment of the tube core of the present invention, from the viewpoint of piezoelectric characteristics, it is preferred that the above-mentioned first electrode is a multi-layer structure, and the crystal orientation of the bottom layer of the first electrode of the multi-layer structure located closest to the above-mentioned piezoelectric film is aligned in the out-of-plane direction of the main surface and in the in-plane direction of the main surface, the aligned out-of-plane crystal orientation of the above-mentioned piezoelectric film is consistent with the aligned out-of-plane crystal orientation of the bottom layer of the above-mentioned first electrode, and the aligned in-plane crystal orientation of the above-mentioned piezoelectric film is inconsistent with the aligned in-plane crystal orientation of the bottom layer of the above-mentioned first electrode.

[0084] As an embodiment of the tube core of the present invention, from the viewpoint of piezoelectric characteristics, it is preferred that the piezoelectric element has a dielectric film between the piezoelectric film and the second electrode, the first electrode is a multi-layer structure, and the piezoelectric film, the dielectric film, and the bottom layer of the first electrode of the multi-layer structure located closest to the piezoelectric film all have a perovskite structure represented by ABO3.

[0085] As an embodiment of the tube core of the present invention, from the viewpoint of piezoelectric characteristics, it is preferable that the piezoelectric film is a lead zirconate titanate film.

[0086] As an embodiment of the tube core of the present invention, from the viewpoint of piezoelectric characteristics, it is preferred that the piezoelectric element has a dielectric film between the piezoelectric film and the second electrode, the dielectric film is a lead lanthanum titanate film, the first electrode is a multi-layer structure, and the bottom layer of the first electrode of the multi-layer structure located closest to the piezoelectric film is a strontium ruthenate film or a lanthanum nickelate film.

[0087] As an embodiment of the tube core of the present invention, from the viewpoint of piezoelectric characteristics, the upper surface of the above-mentioned first electrode is preferably covered with a protective film, and the above-mentioned protective film is a zirconium dioxide film, an aluminum oxide film, a hafnium oxide film, a yttrium oxide film or an aluminum nitride film.

[0088] The tube core manufacturing method of the present invention is a tube core manufacturing method using a Si substrate, characterized in that it comprises at least: a process of forming a stacked body including the tube core of the present invention on the above-mentioned Si substrate; and a process of cutting the above-mentioned stacked body to individualize the above-mentioned tube core, when the vertical direction of the notch or orientation plane of the above-mentioned Si substrate is set as the fourth direction, and the cutting direction in the process of individualizing the above-mentioned tube core that forms the smallest angle with the above-mentioned fourth direction is set as the fifth direction, the acute angle θ3 formed by the above-mentioned fourth direction and the above-mentioned fifth direction is in the range of 0 to 15°.

[0089] As an embodiment of the method for manufacturing a die of the present invention, from the viewpoint of making the acute angle θ1 or the acute angle θ2 within the range of 40 to 50 degrees, it is preferable that the acute angle θ3 is within the range of 0 to 5 degrees.

[0090] The liquid droplet ejection head of the present invention is characterized by comprising the die of the present invention.

[0091] The liquid droplet discharge device of the present invention is characterized by including the liquid droplet discharge head of the present invention.

[0092] Hereinafter, the present invention and its constituent elements, and forms / modes for carrying out the present invention will be described in detail. In addition, in the present application, "to" is used to mean that the numerical values ​​described before and after it are included as the lower limit and the upper limit.

[0093] <1. Overview of the die of the present invention>

[0094] As one embodiment, the tube core of the present invention has one or more piezoelectric actuators having a piezoelectric element and a hollow portion that serves as a pressure chamber, characterized in that the piezoelectric element has at least a piezoelectric film, a first electrode located on the piezoelectric film, and a second electrode located below the piezoelectric film. In the piezoelectric actuator, the second electrode also serves as a vibration plate, or a vibration plate is additionally provided below the second electrode. The hollow portion is located below the second electrode that also serves as a vibration plate or the additional vibration plate. The piezoelectric film has a principal surface set as a (001) surface, and the crystal orientation of the piezoelectric film is aligned in an out-of-plane direction and an in-plane direction of the principal surface. When the long side direction of the hollow portion when observed from an out-of-plane direction of the principal surface of the piezoelectric film is set as a first direction, and the

[100] direction of the piezoelectric film is set as a second direction, the acute angle θ1 formed by the first direction and the second direction is in the range of 30 to 60°.

[0095] In addition, as an embodiment, the tube core of the present invention has a plurality of piezoelectric actuators having piezoelectric elements and a hollow portion serving as a pressure chamber, characterized in that the piezoelectric element has at least a piezoelectric film, a first electrode located on the piezoelectric film, and a second electrode located below the piezoelectric film. In the piezoelectric actuator, the second electrode also serves as a vibration plate, or a vibration plate is additionally provided below the second electrode. The hollow portion is located below the second electrode also serving as a vibration plate or the additional vibration plate. The piezoelectric film has a principal surface as a (001) surface, and the crystal orientation of the piezoelectric film is aligned in an out-of-plane direction and an in-plane direction of the principal surface. When the direction in which the plurality of piezoelectric actuators are arranged is set as a third direction, and the

[100] direction of the piezoelectric film is set as a second direction, an acute angle θ2 formed by the third direction and the second direction is in the range of 30 to 60°.

[0096] In the present invention, a “piezoelectric element” refers to an element having a first electrode and a second electrode that is not electrically connected to the first electrode, with a piezoelectric body being sandwiched between the first electrode and the second electrode.

[0097] In the present invention, a "piezoelectric actuator" refers to an element having a piezoelectric element, wherein a voltage is applied between a first electrode and a second electrode to change the shape of the piezoelectric element, and the displacement obtained is used. A diaphragm structure in which a vibration plate is bonded to a piezoelectric element is also included in a piezoelectric actuator.

[0098] Figure 1 FIG. 1 is a schematic top view of a tube core 10 according to an embodiment of the present invention, viewed from the bottom (hollow portion side). Figure 1 When the tube core 10 is viewed from the bottom (hollow portion side) as described above, the pressure chamber member 60 and the hollow portion 50 of the piezoelectric actuator 20 are seen as the main structures. Figure 1 In the illustrated die 10 , the hollow portions 50 of the piezoelectric actuators 20 are arranged in two rows.

[0099] Figure 2 is an embodiment of the tube core of the present invention, showing a simplified cross-sectional view of a portion of the tube core 10, which is equivalent to Figure 1 The A-A section. Figure 2 , as a part of the tube core 10, a range in which five piezoelectric actuators 20 are arranged is shown. Figure 2 The illustrated piezoelectric actuator 20 is composed of a piezoelectric element 30 , a vibration plate 40 located below the piezoelectric element 30 , a hollow portion 50 located below the vibration plate 40 , and a pressure chamber member 60 forming the hollow portion 50 .

[0100] The piezoelectric actuator of the present invention is characterized in that the second electrode also serves as a vibration plate, or a vibration plate is provided separately below the second electrode. The piezoelectric actuator in which the second electrode also serves as a vibration plate is, for example, Figure 3 The layer structure shown. Figure 3 The piezoelectric actuator 20 shown in the figure includes a piezoelectric element 30 having a first electrode 31, a piezoelectric film 32, and a second electrode 33 also serving as a vibration plate, and a hollow portion 50 located below the piezoelectric element 30. In addition, the piezoelectric actuator in the case of having a vibration plate under the second electrode is, for example, Figure 4 The layer structure shown. Figure 4 The illustrated piezoelectric actuator 20 includes a piezoelectric element 30 having a first electrode 31 , a piezoelectric film 32 , and a second electrode 33 , a vibration plate 40 located below the piezoelectric element 30 , and a hollow portion 50 located below the vibration plate 40 .

[0101] The present invention is characterized in that the crystal orientation of the piezoelectric film 32 is aligned in the out-of-plane direction of the principal surface (hereinafter, also referred to as the "out-of-plane direction") and the in-plane direction of the principal surface (hereinafter, also referred to as the "in-plane direction"). Here, the "principal surface" in the present invention refers to the surface with the largest surface area.

[0102] In addition, in the present invention, the Miller Index is used to indicate the "crystal plane" and "crystal orientation" of the crystal constituting the piezoelectric film 32. A crystal is a collection of unit cells, and a unit cell is formed by a collection of planes composed of atoms. The plane composed of these atoms is called a "crystal plane". In addition, a crystal is formed by arranging crystal planes in parallel and at equal intervals, and the arrangement direction of the crystal planes (the perpendicular direction relative to the crystal planes) is called a "crystal orientation". The crystal planes are indicated as (100) planes, (110) planes, etc. using the plane indices in the Miller Index. In addition, the crystal orientation is indicated as the

[100] direction, etc. using the direction index (orientation index) in the Miller Index.

[0103] As a reference for the Miller index in the present invention, the main surface of the piezoelectric film 32 is set to the (001) plane. That is, the normal direction of the (001) plane, that is, the out-of-plane direction, is the

[001] direction, and the direction parallel to the main surface of the piezoelectric film 32, that is, the in-plane direction, the direction perpendicular to the (100) plane or the (010) plane is the

[100] direction or the

[010] direction, respectively. The

[100] direction and the

[010] direction of the piezoelectric film 32 are not distinguished due to the rotational symmetry of the crystal.

[0104] In the present invention, whether the crystal orientations are aligned in the out-of-plane direction of the principal surface and the in-plane direction of the principal surface can be confirmed by, for example, XRD (X-ray diffraction) measurement.

[0105] The piezoelectric actuator 20 of the present invention has a hollow portion 50 that has a shape having a long side direction and a short side direction, such as an oval, a rectangle, an ellipse, a rhombus, etc. when observed from the outside of the main surface of the piezoelectric film 32. The present invention suppresses the occurrence of cracks in the piezoelectric film 32 in the piezoelectric actuator 20 having a hollow portion 50 of such a shape.

[0106] <2. Acute angles θ1, θ2>

[0107] One embodiment of the tube core of the present invention is characterized in that, when the long side direction of the hollow portion 50 when viewed from the outward direction of the main surface of the piezoelectric film 32 is set as a first direction, and the

[100] direction of the piezoelectric film 32 is set as a second direction, the acute angle θ1 formed by the first direction and the second direction is in the range of 30 to 60 degrees. In addition, one embodiment of the tube core of the present invention is characterized in that, when the direction in which the plurality of piezoelectric actuators 20 are arranged is set as a third direction, and the

[100] direction of the piezoelectric film 32 is set as the second direction, the acute angle θ2 formed by the third direction and the second direction is in the range of 30 to 60 degrees.

[0108] As described above, the present inventors have found that cracks in the piezoelectric film 32 are likely to occur in the long and short directions of the hollow portion 50 of the piezoelectric actuator 20, that is, cracks in the piezoelectric film 32 are likely to occur in the first direction and in the in-plane perpendicular direction of the first direction. Figure 1 In the figure, the vertical direction is the first direction. Figure 2 , the depth direction of the figure is the first direction.

[0109] In addition, as described above, the present inventors have found that cracks in the piezoelectric film 32 are likely to occur in the direction in which the plurality of piezoelectric actuators 20 are arranged, that is, cracks in the piezoelectric film 32 are likely to occur in the third direction. In addition, in the die, when the plurality of piezoelectric actuators are arranged in two or more directions in the longitudinal and lateral directions, the direction in which the piezoelectric actuators are arranged at a closer interval is set as the third direction. Figure 1 as well as Figure 2 In the figure, the horizontal direction is the third direction.

[0110] Furthermore, as described above, the inventors have discovered that, in a piezoelectric film 32 whose crystal structure is aligned in the in-plane direction, cracks are easily generated in the

[100] direction and the

[010] direction of the piezoelectric film 32, that is, cracks are easily generated in the piezoelectric film 32 in the second direction and in the in-plane perpendicular direction to the second direction. Figure 5 The electron microscope photographs are taken to observe cracks generated in the

[100] direction (second direction) and the

[010] direction (in-plane perpendicular direction to the second direction) of the piezoelectric film 32. In the piezoelectric film 32 whose crystal structure is aligned in the in-plane direction, cracks are easily generated. Figure 5Cracks as shown.

[0111] Figure 6 This is an illustration of the acute angle θ1. Figure 6 As shown, in the present invention, the acute angle formed by the long side direction (first direction) of the hollow portion and the

[100] direction (second direction) of the piezoelectric film when viewed from the main surface out of the plane of the piezoelectric film is defined as acute angle θ1.

[0112] One embodiment of the tube core of the present invention is characterized in that the acute angle θ1 is in the range of 30 to 60 degrees. As a result, a deviation can be generated between the direction in which cracks are likely to occur from the perspective of the shape of the piezoelectric actuator and the direction in which cracks are likely to occur from the perspective of the crystal structure of the piezoelectric film, thereby suppressing the generation of cracks. In addition, from the perspective of further suppressing the generation of cracks, it is preferred that the acute angle θ1 is in the range of 40 to 50 degrees.

[0113] Figure 7 This is an illustration of the acute angle θ2. Figure 7 As shown, in the present invention, the acute angle formed by the direction in which the plurality of piezoelectric actuators are arranged (the third direction) and the

[100] direction (the second direction) of the piezoelectric film is defined as acute angle θ2.

[0114] One embodiment of the tube core of the present invention is characterized in that the acute angle θ2 is within the range of 30 to 60 degrees. As a result, a deviation can be generated between the direction in which cracks are likely to occur from the perspective of the arrangement of the piezoelectric actuator and the direction in which cracks are likely to occur from the perspective of the crystal structure of the piezoelectric film, thereby suppressing the generation of cracks. In addition, from the perspective of further suppressing the generation of cracks, it is preferred that the acute angle θ2 is within the range of 40 to 50 degrees.

[0115] Furthermore, for the tube core of the present invention, it is more preferred that both the acute angle θ1 and the acute angle θ2 are within the range of 30 to 60°, and it is particularly preferred that both the acute angle θ1 and the acute angle θ2 are within the range of 40 to 50°.

[0116] In the present invention, the

[100] direction (second direction) of the piezoelectric film 32 can be determined from a diffraction pattern obtained by in-plane measurement using an X-ray diffraction (XRD) method.

[0117] <3. Structure of the die>

[0118] The tube core 10 of the present invention is used as Figures 1 to 3As described above, there is one or more piezoelectric actuators 20 having a piezoelectric element 30 and a hollow portion 50 serving as a pressure chamber. The piezoelectric element 30 at least has a piezoelectric film 32, a first electrode 31 located on the piezoelectric film 32, and a second electrode 33 located below the piezoelectric film 32. In the piezoelectric actuator, the second electrode 33 also serves as a vibration plate, or a vibration plate 40 is separately provided below the second electrode 33. The hollow portion 50 is provided below the second electrode 33 also serving as a vibration plate or the separately provided vibration plate 40.

[0119] From the viewpoint of the displacement generating force required of the piezoelectric element, the distance between the first electrode and the second electrode in the piezoelectric element of the present invention is preferably in the range of 0.1 to 5 μm.

[0120] The material of the piezoelectric film is not particularly limited as long as it is a piezoelectric body, but it is preferable that the crystal structure is a perovskite structure.

[0121] "Perovskite structure" refers to a crystal structure identical to perovskite (perovskite CaTiO3). Typically, the composition of the perovskite crystal structure is represented by ABX3, in which A, B and X exist as structural ions of A cations, B cations and X anions. In addition, B cation-deficient perovskite compounds, A cation-deficient perovskite compounds and X anion-deficient perovskite compounds are also defined as compounds having a perovskite crystal structure in the present invention. In the perovskite structure, it is preferred that X of ABX3 is oxygen (O) and is represented by ABO3.

[0122] Examples of piezoelectric films made of a piezoelectric material having a perovskite structure represented by ABO3 include lead zirconate titanate (PZT: Pb(Zr, Ti)O3) film, lead titanate (PbTiO3) film, lead zirconate (PbZrO3) film, lead lanthanum titanate (PLT: (Pb, La)TiO3) film, and barium titanate (BaTiO3) film.

[0123] Among these, lead zirconate titanate films are preferred from the viewpoint of piezoelectric properties, and specifically, Pb X (Zr Y , Ti 1－Y )O3[1.0≤X≤1.2, 0.4≤Y≤0.6]. In the lead zirconate titanate film, Y is preferably in the range of 0.50 to 0.58, and is particularly preferably 0.52 from the viewpoint of piezoelectric characteristics.

[0124] The lead zirconate titanate film is preferably a non-stoichiometric composition. X (Zr Y , Ti1－Y )O3[1.0≤X≤1.2, 0.4≤Y≤0.6] represents the composition, preferably X>1.

[0125] The materials of the first electrode and the second electrode are not particularly limited, and can be Cr, Ni, Cu, Pt, Ir, Ti, Ir-Ti alloy, LaNiO3, SRO (SrRuO3), STO (SrTiO3), etc. The first electrode and the second electrode may each be a multilayer structure composed of two or more electrodes.

[0126] At least one of the first electrode and the second electrode preferably comprises a Pt electrode, and the principal surface of the Pt electrode is preferably a (001) plane, and the crystal orientation is aligned in the in-plane direction and the out-of-plane direction. When one of the first electrode and the second electrode comprises a Pt electrode, the other is preferably a Cu electrode.

[0127] In addition, it is preferred that the first electrode or the second electrode is a multilayer structure composed of a plurality of different electrodes. In particular, it is preferred that the first electrode is a multilayer structure, and the crystal orientation of the bottom layer of the first electrode located closest to the piezoelectric film of the multilayer structure is aligned in the out-of-plane direction and the in-plane direction. Furthermore, from the perspective of piezoelectric properties, it is preferred that the aligned out-of-plane crystal orientation of the piezoelectric film is consistent with the aligned out-of-plane crystal orientation of the bottom layer of the first electrode, and the aligned in-plane crystal orientation of the piezoelectric film is inconsistent with the aligned in-plane crystal orientation of the bottom layer of the first electrode.

[0128] In the present invention, whether the out-of-plane crystal orientation of a certain layer matches or does not match the out-of-plane crystal orientation of another layer can be confirmed based on a diffraction pattern obtained by in-plane measurement using an X-ray diffraction (XRD) method.

[0129] In the present invention, whether the in-plane crystal orientation of a certain layer matches or does not match the in-plane crystal orientation of another layer can be confirmed based on a diffraction pattern obtained by in-plane measurement using an X-ray diffraction (XRD) method.

[0130] When the first electrode has a multi-layer structure, the bottom layer of the first electrode of the multi-layer structure, which is located closest to the piezoelectric film, preferably has a perovskite structure represented by ABO3, and from the viewpoint of piezoelectric properties, it is preferably, for example, a strontium ruthenate (SrRuO3) film or a lanthanum nickelate (LaNiO3) film.

[0131] In the piezoelectric actuator of the present invention, the second electrode also serves as a vibration plate, or a vibration plate is separately provided below the second electrode. The material of the separately provided vibration plate can be the same as that of the second electrode.

[0132] From the viewpoint of dielectric constant, the piezoelectric element of the present invention preferably has a dielectric film between the piezoelectric film and the second electrode. The dielectric film is not particularly limited as long as it is a film made of a dielectric, but preferably has a lower dielectric constant than the piezoelectric film.

[0133] The dielectric film preferably has a perovskite structure represented by ABO3 in its crystal structure, and preferably is a lanthanum lead titanate film. As dielectric films having a perovskite structure represented by ABO3 in its crystal structure, lead titanate (PbTiO3) film, lanthanum lead titanate (PLT: (Pb, La)TiO3) film, barium titanate (BaTiO3) film, etc. are listed. Among these, it is preferred to contain lead, and the lanthanum lead titanate film is particularly preferred in terms of dielectric constant.

[0134] From the perspective of dielectric constant, it is preferred that the crystal orientation of the dielectric film is aligned in the out-of-plane direction of the principal surface and in the in-plane direction of the principal surface. In addition, it is more preferred that the aligned out-of-plane crystal orientation of the piezoelectric film is consistent with the aligned out-of-plane crystal orientation of the dielectric film, and the aligned in-plane crystal orientation of the piezoelectric film is also consistent with the aligned in-plane crystal orientation of the dielectric film.

[0135] The RMS (root mean square) value of the surface roughness of the second electrode side of the dielectric film is preferably 5.0 nm or less. It is more preferably 2.0 nm or less, and further preferably 1.6 nm or less. This improves reliability during long-term driving, adhesion of the film, and the like.

[0136] The RMS value of the surface roughness can be measured using, for example, an atomic force microscope (Dimension Icon manufactured by Bruker Corporation).

[0137] From the perspective of piezoelectric properties, the piezoelectric element of the present invention preferably has a dielectric film between the piezoelectric film and the above-mentioned second electrode. When the first electrode has a multi-layer structure, the piezoelectric film, the dielectric film, and the bottom layer of the first electrode of the multi-layer structure located closest to the piezoelectric film all have a perovskite structure represented by ABO3.

[0138] In addition, the upper surface of the first electrode of the piezoelectric element of the present invention is preferably covered with a protective film. From the perspective of piezoelectric properties, the protective film is preferably a zirconium dioxide (ZrO2) film, an aluminum oxide (Al2O3) film, a hafnium oxide (HfO2) film, a yttrium oxide (Y2O3) film or an aluminum nitride (AlN) film. In addition, a protective film made of a photosensitive polyimide resin or the like may be further provided on the protective film.

[0139] <4. Method for manufacturing a tube core>

[0140] The manufacturing method of the tube core of the present invention is not particularly limited. As an example of the manufacturing method, the manufacturing method is described below, and the manufacturing method at least includes: a process of forming a stacked body including the tube core on a Si substrate (a stacked body forming process); and a process of cutting the stacked body to individualize the tube core (a tube core individualization process).

[0141] In the stack formation process, the layers constituting the tube core are formed and stacked on the Si substrate by a known method such as sputtering. At this time, in the case of forming a layer in which the crystal orientation is aligned in the out-of-plane direction of the main surface and the in-plane direction of the main surface, it is necessary to make the crystal epitaxially grow. "Epitaxial growth" means that the crystal grows in a certain orientation according to the regularity of the atomic arrangement of the crystal of the underlying layer.

[0142] Each layer is patterned as necessary. In addition, as the Si substrate, not only a Si layer but also a commercially available substrate on which a first electrode and the like are already formed can be used, and necessary layers such as a piezoelectric film can be stacked thereon.

[0143] The crystal orientation of the Si substrate is aligned in the in-plane direction and the out-of-plane direction, and preferably has a notch or an orientation flat surface indicating the crystal orientation.

[0144] The stacked body formed on the Si substrate may be a stacked body that obtains only one tube core after individualization, or a stacked body in which the tube cores are arranged on a plane in a manner to obtain a plurality of tube cores. Generally, as long as there is no problem with the size of the Si substrate, the stacked body is formed in a manner to obtain a plurality of tube cores.

[0145] In addition, a pressure chamber member is stacked under the second electrode also serving as a vibration plate or a separately provided vibration plate to form a hollow portion serving as a pressure chamber. An ink blocking film or a seed layer may be formed between the vibration plate and the pressure chamber member.

[0146] In the die individualization process, the stacked body is cut to individualize the dies. At this time, when the perpendicular direction of the notch or the orientation plane of the Si substrate is set as the fourth direction, and the cutting direction in the die individualization process that forms the smallest angle with the fourth direction is set as the fifth direction, the acute angle θ3 formed by the fourth direction and the fifth direction is preferably in the range of 0 to 15°, more preferably in the range of 0 to 5°, and particularly preferably 0°.

[0147] Here, "a vertical direction of the notch or the orientation flat" refers to a direction from the center of the notch or the orientation flat toward the center of the Si substrate.

[0148] Figure 8 It is an explanatory diagram regarding the fourth direction, the fifth direction, and the acute angle θ3 formed by the fourth direction and the fifth direction. Figure 871 and a cut line (dashed line) of the stacked body along the contours of the 18 dies 10. Figure 8 As shown, when the Si substrate 70 has the notch 71, the fourth direction is the perpendicular direction to the notch 71. In addition, the cutting direction that forms the smallest angle with the fourth direction among the cutting directions is set as the fifth direction.

[0149] In addition, Figure 8 In the figure, for the convenience of illustration, the acute angle θ3 is shown as 15°, but the smaller the acute angle θ3, the better. Specifically, as described above, the acute angle θ3 is preferably in the range of 0 to 15°, more preferably in the range of 0 to 5°, and particularly preferably 0°.

[0150] The acute angle θ3 is small, so that the vertical direction (fourth direction) of the notch or the orientation plane represents the

[100] direction of the Si substrate, and there is a deviation of about 45° between the

[100] direction of the Si substrate and the

[100] direction of the piezoelectric film (second direction), and when the cutting direction (fifth direction) is perpendicular or parallel to the long side direction (first direction) of the hollow portion, the acute angle θ1 formed by the first direction and the second direction is close to 45°, thereby suppressing the generation of cracks. Alternatively, the vertical direction (fourth direction) of the notch or the orientation plane represents the

[100] direction of the Si substrate, and there is a deviation of about 45° between the

[100] direction of the Si substrate and the

[100] direction of the piezoelectric film (second direction), and when the cutting direction (fifth direction) is perpendicular or parallel to the direction in which a plurality of piezoelectric actuators are arranged (third direction), the acute angle θ2 formed by the third direction and the second direction is close to 45°, thereby suppressing the generation of cracks.

[0151] The

[100] direction of the Si substrate can also be determined from the diffraction pattern measured by the XRD method. By setting the notch or the orientation plane as a reference, the cutting direction for manufacturing the tube core of the present invention can be easily determined.

[0152] In addition, regarding the

[100] direction and the

[010] direction of the Si substrate, since Si is a cubic crystal phase and has rotational symmetry, no distinction is made.

[0153] <5. Purpose of the tube core>

[0154] The die of the present invention can be used for a liquid droplet ejection head or a liquid droplet ejection device including the liquid droplet ejection head by being combined with a nozzle plate or the like as a liquid droplet ejection head chip, for example.

[0155] The droplet ejection head and the droplet ejection device including the die of the present invention suppress the occurrence of cracks in the piezoelectric film and thus have excellent ejection stability.

[0156] In addition to the above, the die of the present invention can also be used for p-MUT (piezoelectric micromachined ultrasonic transducer), microphone, speaker, etc.

[0157] Example

[0158] The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto. In the Examples, "parts" or "%" are used to indicate "parts by mass" or "mass %" unless otherwise specified.

[0159] Dies No. 1 to 3 (the present invention) and Die No. 4 (comparative example) were prepared, and the number of cracks generated in these dice was measured.

[0160] <Production of Die No.1>

[0161] For the Si substrate, an 8-inch Si substrate (manufactured by KRYSTAL) was used, which had a notch in the

[100] direction of the Si substrate in the vertical direction (fourth direction), and each layer was composed of SRO / Pt / ZrO2 / Si in the order. In this Si substrate, the Pt layer and the SRO layer are equivalent to the first electrode composed of the two layers of the Pt electrode and the SRO electrode. In addition, in this substrate, the ZrO2 layer is equivalent to the protective film (zirconium dioxide film) covering the upper surface of the first electrode. The crystal orientations of each layer of the substrate are aligned in the in-plane direction and the out-of-plane direction, and the main surface is the (001) plane.

[0162] A PZT film, which is a piezoelectric film, is formed on the SRO layer of the Si substrate by RF magnetron sputtering. The PZT ceramic target uses a lead composition (Pb) with an excess of 25% of Pb over the stoichiometric composition. 1.25 (Zr 0.52 、Ti 0.48 )O3). The PZT film is formed so that the acute angle formed by the

[100] direction of the Si layer and the

[100] direction of the PZT film becomes 45°. The

[100] direction of the PZT film is the second direction in the present invention.

[0163] The thickness of the PZT film and the sputtering conditions are as follows.

[0164] Thickness: 3.38 μm

[0165] RF power supply……3.0kW

[0166] Gas flow rate...Ar:O2=39.5:0.5sccm

[0167] Sputtering pressure……0.2Pa

[0168] Substrate set temperature……550℃

[0169] In the above-mentioned PZT film forming step, the PZT film is formed in two steps, and cleaning is performed between the first and second steps.

[0170] Next, a PLT film serving as a dielectric film is formed on the PZT film by RF magnetron sputtering. The PLT ceramic target uses a Pb composition (Pb) having an excess lead content of 25% greater than the stoichiometric composition of Pb:La = 0.9:0.1. 1.125 ,La 0.1 )TiO3) material.

[0171] The thickness of the PLT film and the sputtering conditions are as follows.

[0172] Thickness: 0.12 μm

[0173] RF power supply……2.0kW

[0174] Gas flow rate...Ar:O2=39.5:0.5sccm

[0175] Sputtering pressure……0.2Pa

[0176] Substrate set temperature……560℃

[0177] Next, a second electrode was formed on the dielectric film (PLT film) by sputtering using a Cu target. The thickness and sputtering conditions were as follows. The second electrode also served as a vibration plate in the piezoelectric actuator.

[0178] Thickness: 2.8 μm

[0179] DC power supply……1kW

[0180] Gas flow rate: Ar = 50 sccm

[0181] Sputtering pressure……0.15Pa

[0182] Substrate set temperature...Room temperature

[0183] Next, a photosensitive polyimide resin was applied onto the second electrode by spin coating, and was baked at 230° C. to be cured, thereby forming an ink blocking film with a thickness of 1 μm.

[0184] Next, a seed layer of 0.5 μm was formed on the ink blocking film by sputtering using a Ni target. The sputtering was performed for 15 minutes in an argon gas with a high frequency power of 500 W and a gas pressure of 1 Pa during sputtering.

[0185] Next, a hollow portion (the portion that becomes the pressure chamber) having an oval shape and a height of 150 μm, a length of 120 μm in the short side direction, and a length of 1250 μm in the long side direction was formed. Specifically, two layers of 80 μm thick dry film resist of ORDYLMP108 manufactured by Tokyo Ohka Co., Ltd. were stacked to form the hollow portion, and then a pressure chamber component made of Ni was deposited by Ni electroforming. Then, the dry film resist layer was removed, and the hollow portion was cleaned and dried to form the hollow portion.

[0186] At this time, the hollow portion was formed so that the acute angle θ1 formed by the long side direction (first direction) of the hollow portion and the

[100] direction (second direction) of the PZT film was 30°.

[0187] In addition, 400 hollow parts are formed in each tube core by arranging 200 piezoelectric actuators having hollow parts in 2 rows in one tube core. The direction in which the 200 piezoelectric actuators are arranged is the third direction, and here, the third direction is the in-plane perpendicular direction relative to the first direction. That is, in tube core No. 1, the acute angle θ2 formed by the direction in which the plurality of piezoelectric actuators are arranged (the third direction) and the

[100] direction (the second direction) of the piezoelectric film is 60°.

[0188] Next, an 8-inch glass support substrate was attached to the pressure chamber via a double-sided thermal release sheet manufactured by Nitto Denko Corporation.

[0189] Next, the Si layer is ground to a thickness of about 50 μm and completely removed by dry etching using SF 6 .

[0190] Next, an OMR resist manufactured by Tokyo Ohka Co., Ltd. is applied on the ZrO2 film, and the mask pattern is transferred and developed by exposure to form a resist mask. Next, the ZrO2 film and the first electrode thereunder in the area where the resist mask is not formed are dry-etched and removed using a mixed gas of argon, oxygen, and CHF3. After cleaning, the resist mask is stripped using a stripping solution.

[0191] Next, an OMR resist manufactured by Tokyo Ohka Co., Ltd. is applied, and the mask pattern is transferred by exposure and developed to form a resist mask. Next, the piezoelectric film (PZT film) and the dielectric film (PLT film) in the area where the resist mask is not formed are dry-etched and removed using a mixed gas of chlorine and bromine. After cleaning, the resist mask is stripped using a stripping solution.

[0192] Next, a photosensitive polyimide resin is applied on the protective film (ZrO2 film) by spin coating and patterned to further form a 1 μm protective film. The patterning is performed by transferring the mask pattern by exposure and developing. After patterning, it is cured by firing at 210°C.

[0193] Next, a die individualization process is performed. In the die individualization process, the stacked body is cut so that the acute angle θ3 formed by the vertical direction (fourth direction) of the notch of the Si substrate and the cutting direction (fifth direction) with the smallest angle with the fourth direction among the cutting directions becomes 15°.

[0194] Next, the support substrate was heated to a temperature higher than the temperature at which the thermal release sheet foamed, and the support substrate was removed, thereby obtaining die No. 1 having a plurality (400) of piezoelectric actuators.

[0195] <Production of Dies No. 2 to 4>

[0196] Except for changing the acute angle θ1, the acute angle θ2, and the acute angle θ3 as described in Table I, die Nos. 2 to 4 were manufactured in the same manner as die No. 1.

[0197] [Table 1]

[0198] θ1 θ2 θ3 Number of cracks Remark Die No.1 30° 60° 15° 3 The present invention Die No.2 40° 50° 5° 1 The present invention Die No.3 45° 45° 0° 1 The present invention Die No.4 20° 70° 25° 12 Comparative Example

[0199] <Evaluation of crack generation suppression>

[0200] A positive voltage of 40 V was applied to the first electrode of each piezoelectric actuator of the die for 1 minute. Afterwards, the surface of the piezoelectric film of all the piezoelectric actuators was observed, and the number of cracks generated in the piezoelectric film of every 400 piezoelectric actuators was measured. The results are shown in Table 1.

[0201] In the tube core No. 4 with an acute angle θ1 of 20°, the number of cracks was 12, whereas in the tube core No. 1 with an acute angle θ1 of 30°, the number of cracks was 3, which greatly suppressed the cracks. Furthermore, in the tube core No. 2 with an acute angle θ1 of 40° and the tube core No. 3 with an acute angle θ1 of 45°, the number of cracks was 1, which further greatly suppressed the cracks.

[0202] Similarly, in tube core No. 4 with an acute angle θ2 of 70°, the number of cracks was 12, whereas in tube core No. 1 with an acute angle θ2 of 60°, the number of cracks was 3, which significantly suppressed cracks. Furthermore, in tube core No. 2 with an acute angle θ2 of 50° and tube core No. 3 with an acute angle θ2 of 45°, the number of cracks was 1, which further significantly suppressed cracks.

[0203] In addition, if we focus on the die individualization process, the number of cracks in die No. 4 with an acute angle θ3 of 25° is 12, while the number of cracks in die No. 1 with an acute angle θ3 of 15° is 3, which greatly suppresses cracks. Furthermore, the number of cracks in die No. 2 with an acute angle θ3 of 5° and die No. 3 with an acute angle θ3 of 0° is 1, which further greatly suppresses cracks.

[0204] Industrial Applicability

[0205] The present invention can be used for a die in which generation of cracks is suppressed, a method for manufacturing the die, a liquid droplet ejection head including the die, and a liquid droplet ejection device.

[0206] Explanation of reference numerals: 10 ... tube core; 20 ... piezoelectric actuator; 30 ... piezoelectric element; 31 ... first electrode; 32 ... piezoelectric film; 33 ... second electrode; 40 ... vibration plate; 50 ... hollow portion; 60 ... pressure chamber member; 70 ... Si substrate; 71 ... notch.

Claims

1. A tube core having one or more piezoelectric actuators having a piezoelectric element and a hollow portion serving as a pressure chamber, characterized in that: The piezoelectric element includes at least a piezoelectric film, a first electrode located on the piezoelectric film, and a second electrode located under the piezoelectric film. In the piezoelectric actuator, the second electrode also serves as a vibration plate, or a vibration plate is separately provided under the second electrode. The hollow portion is located below the second electrode also serving as a vibration plate or the vibration plate provided separately. The piezoelectric film has a main surface as a (001) plane, and the crystal orientation of the piezoelectric film is aligned in an out-of-plane direction of the main surface and in an in-plane direction of the main surface. When the long side direction of the hollow portion when viewed from the out-of-plane direction of the main surface of the piezoelectric film is set as a first direction and the [100] direction of the piezoelectric film is set as a second direction, an acute angle θ1 formed by the first direction and the second direction is in the range of 30 to 60 degrees.

2. The tube core according to claim 1, characterized in that: The acute angle θ1 is in the range of 40 to 50 degrees.

3. A tube core having a plurality of piezoelectric actuators each having a piezoelectric element and a hollow portion serving as a pressure chamber, characterized in that: The piezoelectric element includes at least a piezoelectric film, a first electrode located on the piezoelectric film, and a second electrode located under the piezoelectric film. In the piezoelectric actuator, the second electrode also serves as a vibration plate, or a vibration plate is separately provided under the second electrode. The hollow portion is located below the second electrode also serving as a vibration plate or the vibration plate provided separately. The piezoelectric film has a main surface as a (001) plane, and the crystal orientation of the piezoelectric film is aligned in an out-of-plane direction of the main surface and in an in-plane direction of the main surface. When the direction in which the plurality of piezoelectric actuators are arranged is set as a third direction and the [100] direction of the piezoelectric film is set as a second direction, an acute angle θ2 formed by the third direction and the second direction is in a range of 30 to 60 degrees.

4. The tube core according to claim 3, characterized in that: The acute angle θ2 is in the range of 40 to 50 degrees.

5. The tube core according to any one of claims 1 to 4, characterized in that: A distance between the first electrode and the second electrode in the piezoelectric element is in a range of 0.1 to 5 μm.

6. The tube core according to any one of claims 1 to 4, characterized in that: The piezoelectric element includes a dielectric film between the piezoelectric film and the second electrode. The crystal orientation of the dielectric film is aligned in the out-of-plane direction of the main surface and in the in-plane direction of the main surface, The aligned out-of-plane crystal orientation of the piezoelectric film coincides with the aligned out-of-plane crystal orientation of the dielectric film, and the aligned in-plane crystal orientation of the piezoelectric film coincides with the aligned in-plane crystal orientation of the dielectric film.

7. The tube core according to any one of claims 1 to 4, characterized in that: The first electrode is a multi-layer structure, The crystal orientation of the bottom layer of the first electrode located closest to the piezoelectric film of the multilayer structure is aligned in the out-of-plane direction of the principal surface and in the in-plane direction of the principal surface. The aligned out-of-plane crystal orientation of the piezoelectric film is consistent with the aligned out-of-plane crystal orientation of the lowermost layer of the first electrode, and the aligned in-plane crystal orientation of the piezoelectric film is inconsistent with the aligned in-plane crystal orientation of the lowermost layer of the first electrode.

8. The tube core according to any one of claims 1 to 4, characterized in that: The piezoelectric element includes a dielectric film between the piezoelectric film and the second electrode. The first electrode is a multi-layer structure, The piezoelectric film, the dielectric film, and the first electrode bottom layer of the multilayer structure of the first electrode located closest to the piezoelectric film all have a perovskite structure represented by ABO3.

9. The tube core according to any one of claims 1 to 4, characterized in that: The piezoelectric film is a lead zirconate titanate film.

10. The tube core according to any one of claims 1 to 4, characterized in that: The piezoelectric element includes a dielectric film between the piezoelectric film and the second electrode. The dielectric film is a lanthanum lead titanate film, The first electrode is a multi-layer structure, The bottom layer of the first electrode of the multilayer structure, which is located closest to the piezoelectric film, is a strontium ruthenate film or a lanthanum nickelate film.

11. The tube core according to any one of claims 1 to 4, characterized in that: The upper surface of the first electrode is covered by a protective film, The protective film is a zirconium dioxide film, an aluminum oxide film, a hafnium oxide film, a yttrium oxide film or an aluminum nitride film.

12. A method for manufacturing a tube core, using a Si substrate, characterized in that: The manufacturing method of the tube core at least comprises: A step of forming a stacked body including the die according to any one of claims 1 to 4 on the Si substrate; and a step of cutting the stack to individualize the dies, When the vertical direction of the notch or orientation plane of the Si substrate is set as the fourth direction, and the cutting direction in the process of individualizing the tube core that forms the smallest angle with the fourth direction is set as the fifth direction, the acute angle θ3 formed by the fourth direction and the fifth direction is in the range of 0 to 15°.

13. The method for manufacturing a tube core according to claim 12, characterized in that: The acute angle θ3 is in the range of 0 to 5°.

14. A liquid droplet ejection head, comprising a tube core, characterized in that: The tube core is the tube core described in any one of claims 1 to 4.

15. A liquid droplet discharge device, comprising a liquid droplet discharge head, characterized in that: The liquid droplet ejection head is the liquid droplet ejection head described in claim 14.

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