JPH10215009A - Displacement control actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement control actuator whose constitution is simple, whose displacement amount is large, in which irregularities in a characteristic such as the displacement amount or the like are extremely small, and by which the displacement amount can be controlled with high accuracy. SOLUTION: In piezoelectric substrates 2a, 2b whose main faces are faced, whose thickness is 50μm, whose width is 1mm and whose length is 8mm and which are composed of rectangular lithium niobate (LiNbO3 ), their main faces are bonded directly in such a way that their polarization axes are directed in mutually opposite directions. Thereby, a piezoelectric element 2 is constituted. Electrodes 3a, 3b whose thickness is 0.2μm and which are composed of chromium-nickel are formed respectively on the two opposite main faces of the piezoelectric element 2, and a precision displacement control actuator which is composed of a bimorph-type mechanical-electric conversion element 1 is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement control actuator having a relatively large displacement while ensuring high reliability and capable of controlling the displacement with high accuracy.

[0002]

2. Description of the Related Art Conventional piezoelectric actuators include a linear displacement type and a bending displacement type. The linear displacement type includes a single plate type and a laminated type, and the bending displacement type includes a bimorph type. The linear displacement type, especially the laminated type, is difficult to obtain a large displacement due to its configuration, but can obtain a large force, and thus has been used as a fine actuator for precision equipment.
However, since a large number of piezoelectric bodies and electrodes are stacked, the actuator tends to be expensive. In addition, the bending displacement type bimorph type is configured by laminating the mechanical-electrical transducers and laminating the mechanical-electrical transducers and the metal plate. Since this actuator has a very large displacement and is inexpensive, it is used in many fields.

More specifically, as shown in FIG. 28, a bimorph-type actuator 50 using a piezoelectric effect is a bimorph-type actuator that uses piezoelectric ceramics 51a and 51b on which electrodes 52a and 52b are formed. It is formed by bonding with an adhesive 53 such as.

As shown in FIG. 29, the cantilever structure of the bimorph-type electromechanical transducer 50 is such that one end of the bimorph-type electromechanical transducer 50 is bonded to a fixing member 55 with a conductive adhesive 54 or the like. It is fixed. Bimorph type electro-mechanical transducers with a cantilever structure are used in applications where the resonance frequency varies at a low frequency away from the resonance frequency because they vary from one transducer to another, and the drive frequency is appropriately selected for each transducer. It is used in fields where it is possible.

As an example of using a piezoelectric ceramic for an optical deflector, a mirror is conventionally mounted on an actuator formed by stacking piezoelectric elements, and a voltage is applied to the actuator to change the direction of the mirror (VJFowler). & JS
chlafer.Proc. IEEE., VOL. 54 (1966), p. 1437).
However, since this optical deflector uses a laminated actuator, there is a disadvantage that the angle of deflection of light with respect to an applied voltage cannot be increased.

Further, another optical deflector (Japanese Patent Laid-Open No. 58-957)
No. 10), the mirror is rotated using a bimorph actuator. However, this optical deflector has a disadvantage that the structure becomes extremely complicated because a plurality of bimorph-type actuators and the rotating shaft of the mirror are mechanically connected.

Further, another optical deflector (Japanese Patent Laid-Open No. 58-189)
No. 618), the electrode of the piezoelectric element of the bimorph actuator is divided into a plurality of parts, and the number of electrodes to which a voltage is applied is controlled to control the amount of deformation of the piezoelectric element. However, this optical deflector has a disadvantage that the control of the deflection amount is complicated.

[0008]

However, in such a conventional precision displacement control actuator using piezoelectric ceramics, even if the driving frequency is set to a frequency much lower than the resonance frequency of the element, the breaking limit is 10%. At higher applied voltages, the relationship with displacement shows a large nonlinearity,
Because it is difficult to control the displacement strictly, and because the piezoelectric ceramic itself is manufactured by mixing and firing various raw materials, the dispersion of material constants is larger than that of a single crystal material. The problem is that the displacement amount of the displacement control actuator varies greatly.

In such a conventional actuator, an adhesive made of epoxy resin or the like is usually used for bonding the piezoelectric ceramic, and the Young's modulus of the piezoelectric ceramic is 5 × 10 ¹⁰ N / m ² or more. Young's modulus of the epoxy resin as compared to 15 × ^{10 10} N / m ² is 0.5 × ^{10 10} N / m ²
Because of the following, the distortion of the electromechanical transducer caused by the application of the driving voltage is absorbed by the epoxy resin or the like, and the displacement is reduced.

Furthermore, since it is difficult to adhere the piezoelectric ceramics with the thickness of the adhesive layer being uniform, there is also a problem that the characteristics of the electromechanical transducer, particularly the displacement and the resonance frequency, vary.

In addition, in order to stabilize the displacement of the rectangular bimorph type electromechanical transducer, it is necessary to stabilize its resonance frequency. In this case, it is necessary to stabilize the fixed state of the electromechanical transducer. However, in practice, the supporting portion such as a metal or the like is mechanically or caused by stress generated by a temperature change or the like. The part supported or fixed by the fixing member is displaced. For example, when the electromechanical transducer is fixed using an adhesive, the fixing position changes depending on the application range of the adhesive, and the resonance frequency of the electromechanical transducer varies. In addition, the fixed state of the electromechanical transducer fluctuates due to a change in the temperature of the adhesive, and it becomes difficult to maintain a stable fixed state.

[0012] Even in an optical deflector using a mechanical-electrical transducer, a high driving voltage is required to obtain a large deflection angle or a deflection angle of the optical deflector due to the characteristics of the mechanical-electrical transducer described above. However, there was also a problem of large variations.

The present invention has been made in order to solve the above-mentioned problems of the above-mentioned conventional apparatus, and has a simple configuration, a large displacement, and extremely small variation in characteristics such as the displacement. An object of the present invention is to provide a displacement control actuator capable of controlling a displacement amount with high accuracy.

[0014]

To achieve the above object, according to the present invention, there is provided a piezoelectric substrate having at least two piezoelectric substrates having opposed first and second main surfaces. Supports a mechanical-electrical transducer having a piezoelectric element joined by using direct bonding, and an electrode formed on the second main surface of each of the piezoelectric elements, and supports the mechanical-electrical transducer. A displacement control actuator including a support.

According to a second aspect of the present invention, the first main surfaces of the two piezoelectric substrates are arranged so that the constituent atoms of the two piezoelectric substrates are at least one selected from the group consisting of oxygen and hydroxyl groups. The displacement control actuator according to claim 1, wherein the displacement control actuators are directly joined to each other by being connected to each other via a wire.

With such a structure, a stronger connection can be obtained, and the loss at the interface between the substrates can be minimized.
A large displacement can be secured.

According to a third aspect of the present invention, there is provided the displacement control actuator according to the first aspect, wherein the two piezoelectric substrates are joined so that the directions of the polarization axes are opposite to each other.

With such a configuration, for example, since each piezoelectric substrate effectively excites flexural vibration, a large displacement can be obtained.

According to a fourth aspect of the present invention, there is provided a buffer layer formed on one of the two piezoelectric substrates,
2. The displacement control actuator according to claim 1, wherein the other piezoelectric substrate of the two piezoelectric substrates is directly bonded.

With such a configuration, for example, it is possible to disregard the variation in the bonding surface condition, or to enable bonding of materials that are difficult to bond.

According to a fifth aspect of the present invention, there is provided the displacement control actuator according to the first aspect, wherein one end of the electromechanical transducer is supported by a support.

With such a configuration, for example, it is possible to improve the efficiency of taking out the displacement amount.

According to a sixth aspect of the present invention, when the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of 3m group, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes, The angle between the main surface of the piezoelectric substrate and the Y axis is +12.
2. The displacement control actuator according to claim 1, wherein a line that is perpendicular to an axis of 9 ° to + 152 ° and that includes the X axis and that connects a center of gravity of the piezoelectric substrate and the center of the support unit is perpendicular to the X axis. It is.

With such a configuration, for example, it is possible to secure a large displacement while suppressing variation in the displacement.

According to a seventh aspect of the present invention, when the piezoelectric substrate is made of a single crystal piezoelectric material having a crystal structure of 3m group, and the crystal axes of the single crystal piezoelectric material are X, Y, and Z axes, The angle between the main surface of the piezoelectric substrate and the Y axis is −26.
2. The displacement control actuator according to claim 1, wherein a line that is perpendicular to an axis of ° to + 26 °, includes the X axis, and connects a center of gravity of the piezoelectric substrate and the center of the support unit is parallel to the X axis. It is.

With such a configuration, for example, it is possible to secure a large displacement while suppressing variations in the displacement.

The present invention according to claim 8, wherein the piezoelectric substrate is made of a single crystal piezoelectric material having a crystal structure of group 32, and the crystal axes of the single crystal piezoelectric material are X, Y, and Z axes. 2. The piezoelectric substrate according to claim 1, wherein a main surface of the piezoelectric substrate is perpendicular to the X axis, and a line connecting a center of gravity of the piezoelectric substrate and a center of the supporting portion makes an angle of + 52 ° to + 86 ° with the Z axis. It is a displacement control actuator.

With such a configuration, for example, it is possible to secure a large displacement while suppressing variation in the displacement.

According to a ninth aspect of the present invention, when the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of Group 32, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes, The angle between the main surface of the piezoelectric substrate and the X axis is −26.
2. The displacement control actuator according to claim 1, wherein a line that is perpendicular to an axis of ° to + 26 °, includes the Y axis, and connects a center of gravity of the piezoelectric substrate and the center of the support unit is parallel to the Y axis. It is.

With such a configuration, for example, it is possible to secure a large displacement while suppressing variation in the displacement.

According to a tenth aspect of the present invention, when the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of Group 32, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes, The angle between the main surface of the piezoelectric substrate and the X axis is +82.
2. The displacement control actuator according to claim 1, wherein a line that is perpendicular to an axis of ° to + 98 ° and that includes the Z axis and that connects a center of gravity of the piezoelectric substrate and the center of the support unit is perpendicular to the Z axis. It is.

With such a configuration, for example, it is possible to secure a large displacement while suppressing variation in the displacement.

The present invention according to claim 11, wherein the piezoelectric substrate is made of a single crystal piezoelectric material having a crystal structure of 4 mm group, and the crystal axes of the single crystal piezoelectric material are X, Y, and Z axes. The angle between the main surface of the piezoelectric substrate and the Y axis is +22.
2. The displacement control actuator according to claim 1, wherein a line that is perpendicular to an axis of ° to + 41 ° and that includes the X axis and that connects a center of gravity of the piezoelectric substrate and the center of the support unit is perpendicular to the X axis. It is.

With such a configuration, for example, it is possible to secure a large displacement while suppressing the variation in the displacement.

According to a twelfth aspect of the present invention, when the piezoelectric substrate is made of a single crystal piezoelectric material having a crystal structure of 4 mm group, and the crystal axes of the single crystal piezoelectric material are X, Y, and Z axes, The angle between the main surface of the piezoelectric substrate and the Z axis is +49.
2. The displacement control actuator according to claim 1, wherein a line that is perpendicular to an axis of ° to + 68 ° and that includes the Y axis and that connects a center of gravity of the piezoelectric substrate and the center of the support unit is perpendicular to the Y axis. It is.

With such a configuration, for example, it is possible to secure a large displacement while suppressing variation in the displacement.

According to a thirteenth aspect of the present invention, when the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of 4 mm group, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes, 2. The displacement control actuator according to claim 1, wherein a main surface of the piezoelectric substrate is perpendicular to the Z axis.

With such a configuration, for example, it is possible to secure a large displacement while suppressing the variation in the displacement.

According to a fourteenth aspect of the present invention, when the piezoelectric substrate is made of a single crystal piezoelectric material having a crystal structure of 6 mm group, and the crystal axes of the single crystal piezoelectric material are X, Y, and Z axes, The angle between the main surface of the piezoelectric substrate and the Y axis is +23.
2. The displacement control actuator according to claim 1, wherein a line that is perpendicular to an axis of ° to + 51 ° and that includes the X axis and that connects a center of gravity of the piezoelectric substrate and the center of the support unit is perpendicular to the X axis. It is.

With such a configuration, for example, it is possible to secure a large displacement while suppressing the variation in the displacement.

According to a fifteenth aspect of the present invention, when the piezoelectric substrate is made of a single crystal piezoelectric material having a crystal structure of 6 mm group, and the crystal axes of the single crystal piezoelectric material are X, Y, and Z axes, The angle between the main surface of the piezoelectric substrate and the Z axis is +46.
2. The displacement control actuator according to claim 1, wherein a line that is perpendicular to an axis of ° to + 66 ° and that includes the Y axis and that connects a center of gravity of the piezoelectric substrate and the center of the support unit is perpendicular to the Y axis. It is.

With such a configuration, for example, it is possible to secure a large displacement while suppressing variation in the displacement.

The present invention according to claim 16 is the first invention in which
A piezoelectric element in which the first main surfaces of at least two piezoelectric substrates having a second main surface and a second main surface are joined by using direct joining, and formed on the second main surface of each of the piezoelectric elements. -Electromechanical transducer having an electrode and
A displacement control actuator comprising a support for supporting an electric transducer, wherein the electromechanical transducer and the support are joined using direct joining.

According to a seventeenth aspect of the present invention, the piezoelectric substrate and the support constituting the electromechanical transducer are such that the constituent atoms of the piezoelectric substrate and the constituent atoms of the support are composed of oxygen and hydroxyl groups. 17. The displacement control actuator according to claim 16, wherein the displacement control actuator is directly joined by being mutually connected via at least one selected from the group.

With such a configuration, for example, a stronger connection can be obtained, a change in conditions at the joint surface is minimized, and a variation in displacement can be reduced under any environment.

The present invention according to claim 18 is the displacement control actuator according to claim 16, wherein the piezoelectric substrate and the support are made of the same material.

With such a configuration, for example, a change in the condition of the bonding surface can be made smaller, and the variation in the amount of displacement can be made smaller.

[0048] The present invention according to claim 19 is characterized in that:
A piezoelectric element in which the first main surfaces of at least two piezoelectric substrates having a second main surface and a second main surface are joined by using direct joining, and formed on the second main surface of each of the piezoelectric elements. -Electromechanical transducer having an electrode and
A support for supporting the electrical transducer, wherein the mechanical-electrical transducer and the support are joined using direct joining, and a reflector is attached to a free end of the mechanical-electrical transducer. The displacement control actuator.

The present invention according to claim 20 is the first invention in which
A piezoelectric element in which the first main surfaces of at least two piezoelectric substrates having a second main surface and a second main surface are joined by using direct joining, and formed on the second main surface of each of the piezoelectric elements. -Electromechanical transducer having an electrode and
A support for supporting the electrical transducer, wherein the mechanical-electrical transducer and the support are joined using direct joining, and the length of one piezoelectric substrate constituting the piezoelectric element is the other A displacement control actuator in which a reflection film is formed on a surface of a portion of the longer piezoelectric substrate that protrudes from a tip portion of the other piezoelectric substrate.

The present invention described in claim 21 is the first aspect of the present invention.
A piezoelectric element in which the first main surfaces of at least two piezoelectric substrates having a second main surface and a second main surface are joined by using direct joining, and formed on the second main surface of each of the piezoelectric elements. -Electromechanical transducer having an electrode and
A displacement support in which the electromechanical transducer and the support are joined using direct joining, and a reflective film is formed on the surface of the piezoelectric substrate. Actuator.

According to a twenty-second aspect of the present invention, the piezoelectric substrate and the support constituting the electromechanical transducer are such that the constituent atoms of the piezoelectric substrate and the constituent atoms of the support are oxygen and hydroxyl groups. 22. The displacement control actuator according to claim 19, 20 or 21, wherein the displacement control actuator is directly joined by being mutually connected via at least one selected from the group.

With such a configuration, for example, a stronger connection can be obtained, a change in conditions at the joint surface is minimized, and a variation in displacement can be reduced under any environment.

The present invention according to claim 23, wherein the buffer layer formed on the piezoelectric substrate and the support are directly bonded to each other, or the buffer layer formed on the support and the piezoelectric substrate And 16 are directly joined.
20. A displacement control actuator according to claim 19, 20, or 21.

With such a configuration, for example, it is possible to disregard the variation in the state of the bonding surface or to make it possible to bond materials that are difficult to bond.

The present invention according to claim 24 is the displacement control actuator according to claim 19, 20 or 21, wherein the piezoelectric substrate and the support are made of the same material.

With such a configuration, for example, a change in the condition of the bonding surface can be made smaller, and the variation in the displacement can be made smaller.

According to a twenty-fifth aspect of the present invention, there is provided the displacement control actuator according to the twenty-first aspect, wherein all or a part of the electrode also serves as a reflection film.

With such a configuration, for example, the structure can be simplified.

With the above configuration, for example, with a simple configuration,
It is possible to provide a displacement control actuator that has a large displacement amount, has extremely small variation in characteristics such as the displacement amount, and can control the displacement amount with high accuracy.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to embodiments. <First Embodiment> FIG. 1 is a perspective view showing a mechanical-electrical converter used for a precision displacement control actuator according to a first embodiment of the present invention. As shown in FIG. 1, rectangular lithium niobate (LiNbO ₃ ) having two opposing main surfaces and having a thickness of 50 μm, a width of 1 mm, and a length of 8 mm.
The main surfaces of the piezoelectric substrates 2a and 2b are directly joined to each other, and thus the piezoelectric element 2 is formed. Here, the piezoelectric substrates 2a and 2b are joined so that the directions of the polarization axes are opposite to each other. On two opposing main surfaces of the piezoelectric element 2, electrodes 3a and 3b made of chromium-nickel with a thickness of 0.2 μm are formed, respectively. Thereby, the bimorph type electromechanical transducer 1 is configured.

The following describes a machine having the above-described configuration.
An example of a method for manufacturing an electric transducer will be described.

FIGS. 2A to 2C show the state of the interface of the piezoelectric substrate at each stage of direct bonding in the method of manufacturing the electromechanical transducer used in the precision displacement control actuator according to the first embodiment of the present invention. FIG. FIG.
In (c), L ₁ , L ₂ , and L ₃ indicate the distances between the piezoelectric substrates.

First, two L substrates which are the piezoelectric substrates 2a and 2b
Both surfaces of the iNbO ₃ substrate were mirror-polished. Next, these piezoelectric substrates 2a and 2b are mixed with a mixed solution of ammonia, hydrogen peroxide and water (ammonia water: hydrogen peroxide solution: water = 1: 1: 1).
6 (volume ratio)), the piezoelectric substrate 2a,
2b was subjected to a hydrophilic treatment. As shown in FIG.
The surfaces of the piezoelectric substrates 2a and 2b washed with the mixed liquid were terminated with hydroxyl groups (-OH groups) and became hydrophilic. FIG.
(A) has shown the state before joining.

Next, as shown in FIG. 2B, two piezoelectric substrates (LiNbO ₃ ) 2a
b were joined so that the directions of the polarization axes were opposite to each other (L ₁ > L ₂ ). Thereby, dehydration occurs, and the piezoelectric substrate (LiNbO ₃ ) 2a and the piezoelectric substrate (LiNbO ₃ )
2b was attracted and joined by attractive forces such as -OH polymerization and hydrogen bonding.

Next, the piezoelectric substrates (LiNbO ₃ ) 2a and 2b bonded as described above were subjected to a heat treatment at a temperature of 450 ° C. As a result, as shown in FIG.
The constituent atoms of the piezoelectric substrate (LiNbO ₃ ) 2a and the constituent atoms of the piezoelectric substrate (LiNbO ₃ ) 2b are covalently bonded via oxygen (O) (L ₂ > L ₃ ), and the piezoelectric substrates 2a and 2b Was firmly joined directly at the atomic level. That is, a bonding state in which an adhesive layer such as an adhesive did not exist at the bonding interface was obtained. Alternatively, a piezoelectric substrate (LiNb
O ₃ ) 2 a and the constituent atoms of the piezoelectric substrate (LiNbO ₃ ) 2 b are covalently bonded via a hydroxyl group, and the piezoelectric substrates 2 a and 2 b may be firmly and directly joined at the atomic level. .

The Curie point of LiNbO ₃ is 1210 ° C., and the characteristics are degraded by a temperature history close to this, so that the heat treatment temperature is desirably equal to or lower than the Curie point.

By the way, the bonding that occurs directly between the interfaces without the intervention of an adhesive layer such as an adhesive by bringing the mirror-polished surfaces of the members to be bonded into contact with each other after the surface treatment is performed is called "direct bonding". Generally, by performing the heat treatment, a strong bond at the atomic level, such as a covalent bond or an ionic bond, becomes a bond due to intermolecular force.

Next, the directly bonded piezoelectric substrate (LiNb
O ₃ ) 2a, 2b, that is, chromium-nickel was vapor-deposited on two opposite main surfaces of the piezoelectric element 2 by a vacuum vapor deposition method to form electrodes 3a, 3b (see FIG. 1).

Finally, a bimorph type electromechanical transducer 1 was manufactured by cutting into a strip having a predetermined size using a dicing saw.

As shown in FIG. 3, it is also possible to directly join a buffer layer 46 made of a silicon oxide thin film or the like to one of the piezoelectric substrates, and then directly join the piezoelectric substrate to the other piezoelectric substrate again. That is, a buffer layer 46 made of a silicon oxide thin film having a thickness of 0.1 μm is directly joined to one main surface of the piezoelectric substrate 2a, and the buffer layer 46 and another piezoelectric substrate 2b are subjected to a hydrophilic treatment. Are superimposed and subjected to a heat treatment, whereby the constituent atoms of the piezoelectric substrate 2b and the constituent atoms of the buffer layer 46 are joined via an oxygen or hydroxyl group.

Even if the joint surface has undulations or irregularities, or foreign matter such as dust adheres to the joint surface, the buffer layer 46 absorbs the irregularities and the like, so that direct joining can be easily performed. it can.

Also, when joining a material in which oxygen and hydroxyl groups are hardly formed on the surface by the hydrophilic treatment, the joining can be easily performed by directly joining the buffer layer 46. In this case, the buffer layer 46 may be bonded to only one side of the surface to be bonded, or may be bonded to both surfaces.

As a material of the buffer layer, for example, silicon nitride, metal silicide, or the like can be used in addition to silicon oxide.

In the above embodiment, the buffer layer 46
Has been described directly to one of the piezoelectric substrates. However, the present invention is not limited to this. For example, the buffer layer 46 is formed on one of the piezoelectric substrates by using a film forming technique, and the buffer layer on the piezoelectric substrate is Of course, a configuration in which the above-mentioned piezoelectric substrate is directly bonded may be used. As a result, even in the case of a combination of piezoelectric substrates that are difficult to be directly bonded, direct bonding can be performed through the buffer layer, and there is an additional effect that the range of selection of the material of the piezoelectric substrate is widened. <Second Embodiment> FIG. 4 is a perspective view showing a precision displacement control actuator according to a second embodiment of the present invention, and FIG. 5 is a sectional view thereof. As shown in FIGS. 4 and 5, a piezoelectric substrate 2 made of rectangular LiNbO ₃ having a thickness of 50 μm, a width of 1 mm, and a length of 8 mm having two main surfaces facing each other.
The main surfaces of a and 2b are directly joined to each other, thereby forming the electromechanical transducer 1. here,
The piezoelectric substrates 2a and 2b are joined so that the directions of the polarization axes are opposite to each other. Machine - One end of the electrical transducer 1, the support 4a made of LiNbO _3, and is fixed in a state of being sandwiched 4b. Here, the electromechanical transducer 1 is directly joined to the supports 4a, 4b.
In this case, for example, as shown in FIG. 27, the junction between the electromechanical transducer 1 and the supports 4a and 4b may be a direct junction via a buffer layer made of a silicon oxide thin film or the like.
Electrodes 3a, 3b made of chromium-nickel having a thickness of 0.2 μm are provided on two opposing main surfaces of the electromechanical transducer 1.
The electrodes 3a and 3b are also formed continuously on the supports 4a and 4b in order to facilitate electrode extraction. Thus, the precision displacement control actuator 100 is configured.

The precision displacement control actuator 1 shown in FIG.
No. 00, a drive signal is applied between the electrodes 3a and 3b of the electromechanical transducer 1 made of LiNbO ₃ or the like, but the piezoelectric substrates 2a and 2b are joined so that the directions of the polarization axes are opposite to each other. Therefore, a strain that tends to expand or a strain that tends to shrink occurs in the piezoelectric substrate 2a,
Distortion opposite to that of the piezoelectric substrate 2a occurs on the piezoelectric substrate 2b. Therefore, the electromechanical transducer 1 excites flexural vibration with reference to the ends supported by the supports 4a and 4b (see FIG. 6).

In this embodiment, LiNb having stable piezoelectric characteristics is used.
Since the piezoelectric substrates 2a and 2b made of O ₃ are used,
The linearity of the displacement with respect to the applied voltage is also excellent. Specifically, it shows linearity up to 85% or more of the breaking limit (see FIG. 19). As a result, a precise displacement control actuator having high controllability can be realized. In addition, the linearity of a conventional electromechanical transducer using a piezoelectric ceramic substrate is limited to 10% of a breaking limit (see FIG. 20). Furthermore, LiNbO with small material variation
_{Since the three} piezoelectric substrates 2a and 2b are used, the variation of the displacement amount of the precision displacement control actuator is small.

On the other hand, in the case of a conventional electromechanical transducer manufactured by bonding a piezoelectric ceramic substrate, an adhesive softer than the piezoelectric substrate is interposed between the piezoelectric substrates. When a drive signal is applied, the strain generated in each piezoelectric substrate is absorbed by the adhesive, and the effective strain effective for bending is reduced. For this reason, the amplitude of the flexural vibration excited by the electromechanical transducer becomes small.

However, since the electromechanical transducer 1 of this embodiment is manufactured by directly joining the piezoelectric substrates 2a and 2b, there is no adhesive layer such as an adhesive between the piezoelectric substrates 2a and 2b. do not do. That is, when a drive signal is applied to generate strain in the piezoelectric substrates 2a and 2b, there is no one that absorbs the strain, and thus the vibration is converted to flexural vibration without loss. As a result, a precise displacement control actuator having a large displacement can be realized.

Further, since the adhesive layer is not interposed between the piezoelectric substrates 2a and 2b, the vibration characteristics of the electromechanical transducer 1 do not change due to a temperature change.

Further, since the bonding state of the piezoelectric substrates 2a and 2b becomes uniform, the variation of the resonance frequency and the displacement of the electromechanical transducer 1 becomes extremely small.

On the other hand, the thickness direction of the LiNbO ₃ substrate is Y ′
When the axial direction and the longitudinal direction are set in the Z′-axis direction, compressive stress and tensile stress act in the Z′-axis direction, and electric charges are generated in the Y′-axis direction. In this case, the amount of generated electric charge largely depends on the piezoelectric constant d ₂₃ ′. Also, this piezoelectric constant d
The size of ₂₃ 'greatly changes depending on the direction of the Y' axis and the Z 'axis with respect to the crystal axis. That is, the displacement amount of the precision displacement control actuator greatly changes depending on the directions of the Y ′ axis and the Z ′ axis. When the Y ′ axis and the Z ′ axis are appropriately set and the cut angle is selected so that the absolute value of the piezoelectric constant d ₂₃ ′ becomes the largest, a precision displacement control actuator having the largest displacement can be obtained. . FIG.
4 shows the relationship between the crystal axis of the iNbO ₃ substrate and the cut angle. In FIG. 7, the X axis, the Y axis, and the Z axis indicate the directions of the crystal axes of LiNbO ₃ , and the X ′ axis (= X axis), the Y ′ axis, and the Z ′ axis have the Y axis at an angle θ 3 shows the orthogonal axis when rotated only by an angle. That is, the X 'axis (= X axis), the Y' axis,
The Z ′ axis indicates the cutting direction of the LiNbO ₃ substrate. When the direction of each axis is set as shown in FIG.
When the thickness direction of the bO ₃ substrate is set in the X′-axis direction and the longitudinal direction is set in the Y′-axis direction, the piezoelectric constant d ₁₂ ′ greatly affects the displacement of the precision displacement control actuator.

The thickness direction of the LiNbO ₃ substrate is represented by X ′.
When the axial direction and the longitudinal direction are set in the Z′-axis direction, the piezoelectric constant d ₁₃ ′ greatly affects the displacement amount of the precision displacement control actuator.

The thickness direction of the LiNbO ₃ substrate is Y ′
When the axial direction and the longitudinal direction are set to the X′-axis direction, the piezoelectric constant d ₂₁ ′ greatly affects the displacement amount of the precision displacement control actuator.

The thickness direction of the LiNbO ₃ substrate is Y ′
When the axial direction and the longitudinal direction are set in the Z′-axis direction, the piezoelectric constant d ₂₃ ′ greatly affects the displacement amount of the precision displacement control actuator.

The thickness direction of the LiNbO ₃ substrate is Z ′.
When the axis direction and the longitudinal direction are set to the X 'axis direction,
The piezoelectric constant d ₃₁ ′ greatly affects the displacement of the precision displacement control actuator.

The thickness direction of the LiNbO ₃ substrate is Z ′.
When the axial direction and the longitudinal direction are set to the Y′-axis direction, the piezoelectric constant d ₃₂ ′ greatly affects the displacement amount of the precision displacement control actuator.

FIG. 8 shows the relationship between the cut angle of the LiNbO ₃ substrate and the piezoelectric constant. As shown in FIG. 8, when the cut angle is 140 °, the piezoelectric constant d ₂₃ ′ has the largest value. The experimental results when a precision displacement control actuator was manufactured by actually changing the cut angle are shown in Table 1 below and FIG.
Shown in

[0088]

[Table 1]

As shown in the above (Table 1), it was confirmed that the Y-cut 140 ° substrate having the largest piezoelectric constant provided the precision displacement control actuator having the Z′-axis direction as the longitudinal direction and the largest displacement amount was obtained. Was done.

FIG. 10 shows the relationship between the cut angles of the precision displacement control actuator at this time. The precision displacement control actuator in which the Y axis is rotated 140 ° around the X axis as shown in FIG. 10, electrodes are provided on a plane perpendicular to the Y ′ axis, and the longitudinal direction is set in the Z ′ axis direction is the largest displacement. Amount indicated.

The crystal structure of LiNbO ₃ is trigonal 3
It is a member of the m group and has a symmetric structure three times around the Z axis. Therefore, there are several cut angles having the same piezoelectric constant. For example, as shown in FIG. 8, the piezoelectric constant d ₃₂ ′ at the cut angles of 50 ° and 230 ° and the cut angles of 140 ° and 32 °
The piezoelectric constant d ₂₃ ′ at 0 ° has the same value. This is clear when considering the symmetry of the crystal.

Further, at a cut angle near the optimum cut angle where the displacement amount becomes the largest, the dependence of the piezoelectric constant on the cut angle is small, and almost the same displacement amount can be obtained without strictly optimizing the cut angle. Rather than trying to optimize the cut angle strictly, the precision of the cut angle must be strictly specified, the processing cost must be increased due to the complexity of the process to suppress variation, and the unit price must be reduced due to the deterioration in yield. Increase is a problem.

On the other hand, in the present invention, one of the objectives is to use a material having a very small variation in piezoelectric constant, such as a single crystal material, and to develop a device having a small variation. Therefore, as a compromise between manufacturing and performance, in this specification, when the maximum value of the piezoelectric constant is 100%, the allowable range of the variation of the piezoelectric constant is 90% or more of the maximum value. .

Referring to the piezoelectric constant d ₂₃ ′, as shown in FIG. 8, the optimum cut angle is 140 °, but the cut angle at which the piezoelectric constant is 90% of the maximum value is 129 ° (in FIG. 8, The reference numeral 81 is assigned) and 152 ° (reference numeral 82 in FIG. 8). Therefore, the cut angle is 12
If the piezoelectric constant is within the range of 9 ° to 152 °, the piezoelectric constant becomes a value of 90 to 100% of the maximum value, and no problem occurs due to the deterioration of the displacement amount. When the thickness direction of the LiNbO ₃ substrate is set to the Y′-axis direction and the longitudinal direction is set to the X-axis direction, the amount of displacement of the precision displacement control actuator depends on the piezoelectric constant d ₂₁ ′. As shown in FIG. 8, the cut angle dependence of the piezoelectric constant d ₂₁ ′ is smaller than that of the piezoelectric constant d ₂₃ ′. However, in this case, if the cut angle is in the range of −26 ° to + 26 °, the piezoelectric constant becomes a value of 90 to 100% of the maximum value, and the cut angle dependence of the piezoelectric constant is very small. There is no problem due to variation in the amount.

Therefore, a precision displacement control actuator having a large displacement can be manufactured without finishing the cut angle with high precision, and the processing cost is reduced. If there is a difference between the cut angles of the two piezoelectric substrates, there is a problem that the charge generated by the pyroelectric effect of the piezoelectric substrates is not canceled out. Therefore, it is preferable that the difference between the cut angles of the two piezoelectric substrates is small. Since the cutoff angle dependence of the piezoelectric constant is not large,
The difference between the cut angles of the two piezoelectric substrates constituting the electromechanical transducer may be within 1 °.

Since the piezoelectric substrates 2a and 2b made of a LiNbO ₃ single crystal having stable piezoelectric characteristics are used, constants, especially piezoelectric constants, are applied to changes in electric charge applied to the substrates.
Since the elastic constant is constant, the linearity of the displacement with respect to the element applied voltage is excellent.

Specifically, 85% of the element breakdown voltage
The linearity has been shown above (see FIG. 19). As a result, it is possible to realize a precise displacement control actuator having high controllability in which the displacement amount can be controlled by controlling only the voltage. In addition, the linearity of a conventional electromechanical transducer using a piezoceramic substrate is less than the breaking limit of 10%.
%.

Further, since LiNbO ₃ is a single crystal, variations in piezoelectric constant, dielectric constant, elastic constant and the like are extremely small. In the case of piezoelectric ceramics, these material constants usually have a variation of about 20%. For this reason, the displacement amount and the resonance frequency of the precision displacement control actuator using the piezoelectric ceramic have a variation of about 20%. However, in the precision displacement control actuator of the present embodiment manufactured by directly bonding the LiNbO ₃ substrate, the displacement amount,
The variation in the resonance frequency was suppressed to 5% or less.

Piezoelectric ceramics change greatly with time and lack stability. For this reason, a precision displacement control actuator using a piezoelectric ceramic has a displacement amount of 10 to 10 with time.
There was a problem that it changed by about 15%. However, the precision displacement control actuator according to the present embodiment manufactured by directly bonding the LiNbO ₃ substrate was extremely stable, and the change with time was 2% or less.

The length, thickness and width of the electromechanical transducer 1 are determined in consideration of the driving frequency. Normally, as the drive frequency approaches the resonance frequency of the electromechanical transducer, the displacement of the precision displacement control actuator increases.

The resonance frequency of the cantilever-structured electromechanical transducer 1 in which two LiNbO ₃ substrates having a thickness of 50 μm are directly bonded and the length from the tip to the support is set to 8 mm is 1.25 kHz. Met.

The resonance frequency of the electromechanical transducer 1 is determined by its length and thickness. In the case of a precision displacement control actuator using a conventional piezoelectric ceramic, the mechanical-electrical transducer is supported via an adhesive. It is difficult to control the application amount of the adhesive, and the dispersion is large such that the substantial length of the electromechanical transducer is shortened due to the protrusion of the adhesive.

Therefore, in the case of the conventional precision displacement control actuator using a small piezoelectric ceramic, the resonance frequency of the electromechanical transducer varies, and the displacement amount in the drive frequency region is varied. there were.

In the case of this embodiment, the support members 4a, 4a
Since b (see FIG. 5) is directly joined to the electromechanical transducer 1, variation in the length of the electromechanical transducer 1 is extremely small. As a result, the variation in the resonance frequency of the electromechanical transducer 1 becomes extremely small.

As can be seen from the measurement results of the displacement and the drive frequency in FIG. 9, when the drive frequency is 1 kHz or more,
Since the resonance frequency of the electromechanical transducer 1 is approached, the displacement amount is significantly increased. In other words, in the frequency region of 1 kHz or more, resonance tends to occur, and the frequency tends to be unstable, and it has been difficult to perform precise displacement control.

However, in the case of the present embodiment, since the direct connection is used for joining the electromechanical transducer 1 and joining the electromechanical transducer 1 and the support members 4a and 4b, the length and thickness thereof are reduced. The variability is extremely small. As a result, as described above, the variation in the resonance frequency is 5% or less, and the variation in the displacement near the resonance frequency is extremely small.

Therefore, in applications where a large displacement is required, a large displacement can be taken out by setting the driving frequency near the resonance frequency while suppressing the variation in the displacement.

In applications where a large displacement is not required, the resonance frequency is sufficiently separated from the drive frequency so that the resonance frequency is not affected in the drive frequency range, and variation in the displacement can be significantly reduced. . For this purpose, for example, the electromechanical transducer 1 may be designed such that the resonance frequency is at least 1.5 times the drive frequency.

The material of the piezoelectric substrates 2a and 2b may be a single crystal piezoelectric material that can be directly bonded, and may be LiNbO.
_{3 In} addition to lithium tantalate (LiTaO ₃ ), quartz, langaisato type piezoelectric crystal, lithium tetraborate (Li ₂ B ₄ O)
₇ ), potassium niobate (KNbO ₃ ), PZT piezoelectric single crystal, etc. can also be used. Examples of the langasite type piezoelectric crystal include La ₃ Ga ₅ SiO ₁₄ and La ₃ Ga _5.5
Nb _0.5 O ₁₄ , La ₃ Ga _5.5 Ta _0.5 O ₁₄ and the like.

The crystal structure of LiTaO ₃ is LiNbO ₃
It is a trigonal system 3m group, and its optimal cut angle is the same as that of LiNbO ₃ . Further, the crystal structure of quartz or a langasite-type piezoelectric crystal is a trigonal system group 32,
i ₂ B ₄ O ₇ is a tetragonal 4 mm group and includes KNbO ₃ and P
The ZT piezoelectric single crystal is a hexagonal 6 mm group.

FIGS. 11 to 13 show the relationship between the cut angle and the piezoelectric constant of a quartz substrate having a crystal structure of group 32, as shown in FIG.
To FIG. 23, Li ₂ B ₄ O ₇ having a 4 mm group crystal structure
24 to 26 show the relationship between the cut angle of the substrate and the piezoelectric constant.
6 shows the relationship between the cut angle and the piezoelectric constant of a KNbO ₃ substrate having a 6 mm group crystal structure.

FIG. 11 shows the relationship between the cut angle and the piezoelectric constant when the crystal substrate is rotated around the X axis as the rotation axis, and FIG. 12 shows the relationship between the cut angle and the piezoelectric constant when rotated around the Y axis as the rotation axis. FIG. 13 shows the relationship between the cut angle and the piezoelectric constant when rotating about the Z axis as the rotation axis.
Note that the same applies to the relationship between the cut angle of a substrate made of a langasite-type piezoelectric crystal and the piezoelectric constant. FIG. 21 shows the relationship between the cut angle and the piezoelectric constant of the 4 mm group Li ₂ B ₄ O ₇ substrate when rotated about the X axis as the rotation axis, and FIG. 22 shows the relationship between the cut angle when rotated about the Y axis as the rotation axis. Relationship with piezoelectric constant, Fig. 2
Numeral 3 indicates the relationship between the cut angle and the piezoelectric constant when rotating about the Z axis as the rotation axis.

FIG. 24 is a graph showing the relationship between the Xmm of the 6 mm KNbO ₃ substrate.
FIG. 25 shows the relationship between the cut angle and the piezoelectric constant when rotated about the axis as the rotation axis, FIG. 25 shows the relationship between the cut angle and the piezoelectric constant when rotated about the Y axis, and FIG. 26 shows the rotation about the Z axis as the rotation axis. The relationship between the cut angle and the piezoelectric constant in the case of the above is shown. Note that the same applies to the relationship between the cut angle of the substrate made of a PZT piezoelectric single crystal and the piezoelectric constant.

The following Table 2 shows the optimum cut angles of the single-crystal piezoelectric materials having the crystal structure of the group 32 obtained from FIGS. 11 to 13 and the single-crystal piezoelectric materials having the crystal structure of the 3m group described above. A single crystal piezoelectric material having a 4 mm group crystal structure,
This is shown together with the case of a single crystal piezoelectric material having a 6 mm group crystal structure.

[0115]

[Table 2]

In the above (Table 2), the three numbers of the Euler angles described in the column of the optimum cut angle indicate the rotation angles around the X axis, the Y axis, and the Z axis, respectively. The above (Table 2) also shows the maximum piezoelectric constant. As shown in the above (Table 2), when the piezoelectric body having the crystal structure of Group 32 is rotated by 70 ° about the X axis as the rotation axis, the maximum piezoelectric constant is d ₁₃ ′. This means that when the piezoelectric body having the crystal structure of the group 32 is rotated by 70 ° with the X axis as the rotation axis, the piezoelectric substrate is cut out perpendicularly to the rotated X ′ axis (= X axis) direction and Z ′ This indicates that the displacement amount is largest when the longitudinal direction of the piezoelectric substrate is set in the axial direction.

When the Euler angle is (0, 0, 0), the maximum piezoelectric constant is d ₁₂ ′. This means
If the Euler angle is (0,0,0), X 'after rotation
When the piezoelectric substrate is cut out perpendicular to the axis (= X-axis) direction and the longitudinal direction of the piezoelectric substrate is set in the Y′-axis direction, the displacement amount is the largest. When the Euler angle is (0, 0, 90), the maximum piezoelectric constant is d ₂₁ ′.
It is. This means that when the Euler angle is (0, 0, 90), the piezoelectric substrate is cut out perpendicular to the rotated Y′-axis direction, and the longitudinal direction of the piezoelectric substrate is set in the X′-axis direction. This indicates that the displacement amount is the largest.

For example, in the case of a piezoelectric substrate (crystal, langasite type piezoelectric crystal, etc.) having a crystal structure of group 32,
As shown in FIGS. 11 to 13, d ₁₃ ′ is +52.
In the range of ° to + 86 ° (the position of the maximum value is denoted by reference numeral 110 in FIG. 11), ± ₁₂ ° for d ₁₂ ′
(Indicated by reference numeral 120 in FIG. 12)
As for d ₂₁ ′, the piezoelectric constant becomes a value of 90 to 100% based on the maximum value in the range of + 82 ° to + 98 ° (indicated by reference numeral 130 in FIG. 13), which causes a problem due to deterioration of the displacement amount. There is no. Therefore, it is possible to manufacture a precise displacement control actuator having a large displacement amount without finishing the cut angle with high precision, and the processing cost is reduced.

Similarly, in the case of a piezoelectric substrate (such as Li ₂ B ₄ O ₇ ) having a 4 mm group crystal structure, d ₂₃ ′ is +2
In the range of 2 ° to + 41 ° (in FIG.
And d ₃₁ ′ is + 49 ° to + 6 °.
8 ° range (in FIG. 22, reference numeral 220 is attached)
Thus, the piezoelectric constant becomes a value of 90 to 100% of the maximum value, respectively. Further, when the Z axis is rotated, d ₃₁ ′, d ₃₂ ′
Is about 85% of the maximum value, but is constant regardless of the rotation angle. Therefore, it is possible to realize a displacement control actuator having a large displacement without concern for the cut angle (FIG. 2).
3).

In the case of a piezoelectric substrate having a 6 mm group crystal structure (KNbO ₃ , PZT piezoelectric single crystal, etc.),
For d ₂₃ ′, a range of + 23 ° to + 51 ° (FIG. 24)
In FIG. 25, reference numeral 240 is attached, and d ₃₁ ′ is in a range of + 46 ° to + 66 ° (in FIG. 25, attached with reference numeral 250), and the piezoelectric constant is 90 to 10 which is the maximum value.
The value is 0%, and no problem occurs due to the deterioration of the displacement amount.

As described above, according to the present embodiment, the electromechanical transducer 1 is formed by firmly and directly joining the piezoelectric substrates 2a and 2b made of a single crystal piezoelectric material. It is possible to realize a precise displacement control actuator with excellent controllability and excellent linearity of quantity. Without using an adhesive layer such as an adhesive, the piezoelectric substrate 2
Since the electromechanical transducer 1 is formed by firmly joining the a and b to each other, a precision displacement control actuator having a large displacement can be realized without variation in characteristics or loss of strain. Also, the electromechanical transducer 1 can be supported 4a, 4b without using an adhesive.
Since it is configured to directly join the electro-mechanical transducer 1, the positioning of the electromechanical transducer 1 can be performed with high accuracy.

As a result, it is possible to realize a small-sized precision displacement control actuator which has no variation in the length and support state of the cantilever, has high stability, and has extremely small characteristic variations.

In this embodiment, the electrodes 3a,
Although chromium-nickel is used as the material of 3b, the material is not limited to this, and for example, gold, chromium, silver, or an alloy material may be used. <Third Embodiment> FIG. 14 is a sectional view showing a precision displacement control actuator according to a third embodiment of the present invention. As shown in FIG. 14, a rectangular L having a thickness of 50 μm, a width of 1 mm, and a length of 8 mm having two opposing main surfaces is provided.
The main surfaces of the piezoelectric substrates 2a and 2b made of iNbO ₃ are directly bonded to each other, and thus the electromechanical transducer 1 is formed. Here, the piezoelectric substrates 2a and 2b are joined so that the directions of the polarization axes are opposite to each other. One end of the electromechanical transducer 1 is LiNb.
It is fixed while being sandwiched between supports 4a and 4b made of O ₃ . Here, the electromechanical transducer 1 is directly joined to the supports 4a, 4b. The free end of the electromechanical transducer 1 is provided with a reflector 5a for reflecting light, for example, a stainless steel surface plated with gold.

In this case, the electromechanical transducer 1 and the support 4
The bonding with a and 4b may be a direct bonding via a buffer layer made of a silicon oxide thin film or the like. Electrodes 3a and 3b made of chromium-nickel having a thickness of 0.2 μm are formed on two opposing main surfaces of the electromechanical transducer 1, respectively. These electrodes 3a and 3b are provided on supports 4a and 4b. Are also formed continuously. Thus, a precision displacement control actuator 100 for light deflection is configured.

In the precision displacement control actuator 100 shown in FIG. 14, a driving signal is applied in the same direction between the electrodes 3a and 3b of the electromechanical transducer 1 made of LiNbO ₃ or the like, but the piezoelectric substrates 2a and 2b Are bonded in such a manner that the directions of the polarization axes are opposite to each other, so that a strain is generated in the piezoelectric substrate 2a which tends to expand or shrinks, and the piezoelectric substrate 2b is opposite in direction to the piezoelectric substrate 2a. Distortion occurs. Therefore, the electromechanical transducer 1 excites the flexural vibration with reference to the end supported by the supports 4a and 4b, and reflects the incident light (see the arrow) incident from the same direction on the reflector 5a, Light can be deflected at an arbitrary angle by the voltage applied to the element (see FIG. 15).

In this embodiment, LiNb having stable piezoelectric characteristics is used.
Since the piezoelectric substrates 2a and 2b made of O ₃ are used,
The linearity of the displacement with respect to the applied voltage is also excellent. Specifically, it shows linearity up to 85% or more of the breaking limit. As a result, a precise displacement control actuator having high controllability can be realized. In addition, the linearity of a conventional electromechanical transducer using a piezoelectric ceramic substrate is limited to 10% of a breaking limit. Further, the piezoelectric substrates 2a, 2b made of LiNbO ₃ with small material variations
, The variation of the displacement amount of the precision displacement control actuator is small.

On the other hand, in the case of a conventional electromechanical transducer manufactured by bonding a piezoelectric ceramic substrate, since an adhesive softer than the piezoelectric substrate is interposed between the piezoelectric substrates, the electromechanical transducer is not provided with a piezoelectric material. When a drive signal is applied, the strain generated in each piezoelectric substrate is absorbed by the adhesive, and the effective strain effective for bending is reduced. For this reason, the amplitude of the flexural vibration excited by the electromechanical transducer becomes small.

However, the electromechanical transducer 1 of the present embodiment is similar to the second embodiment in that the piezoelectric substrates 2a, 2b
Of the piezoelectric substrates 2a and 2b, there is no adhesive layer such as an adhesive between the piezoelectric substrates 2a and 2b.
That is, when a drive signal is applied to generate strain in the piezoelectric substrates 2a and 2b, there is no one that absorbs the strain, and thus the vibration is converted to flexural vibration without loss. As a result, a precise displacement control actuator having a large displacement can be realized.

Further, as in the second embodiment, since the bonding state of the piezoelectric substrates 2a and 2b becomes uniform, the variation in the resonance frequency and the displacement of the electromechanical transducer 1 becomes extremely small.

Further, since no adhesive layer is interposed between the piezoelectric substrates 2a and 2b, the mechanical-electrical
Does not change the vibration characteristics.

In addition, the relationship between the cut angle and the characteristic variation or displacement is the same as in the second embodiment. <Fourth Embodiment> FIG. 16 is a sectional view showing a precision displacement control actuator according to a fourth embodiment of the present invention. As shown in FIG. 16, a rectangular L having a thickness of 50 μm, a width of 1 mm, and a length of 8 mm having two opposing main surfaces is provided.
a piezoelectric substrate 2a made of iNbO ₃ and having a slightly longer overall length;
The main surfaces of the piezoelectric substrate 2b, which has a slightly shorter overall length, are directly joined to each other, whereby the electromechanical transducer 1 is formed. Here, the piezoelectric substrates 2a and 2b are joined so that the directions of the polarization axes are opposite to each other. Machine - One end of the electrical transducer 1, the support 4a made of LiNbO _3, and is fixed in a state of being sandwiched 4b. Here, the electromechanical transducer 1 includes supporters 4a, 4b
Directly joined to.

In this case, the electromechanical transducer 1 and the support 4
The bonding with a and 4b may be a direct bonding via a buffer layer made of a silicon oxide thin film or the like. On the two opposing main surfaces of the electromechanical transducer 1, in particular, for the piezoelectric substrate 2a, the thickness is 0.2 μm to the same position as the tip of the piezoelectric substrate 2b.
Electrodes 3a and 3b made of chromium-nickel are formed, and these electrodes 3a and 3b are
a, 4b are also formed continuously. The tip of the electrode 3a of the piezoelectric substrate 2a forms an overhang portion, on which a reflective film 5b made of gold having a thickness of 0.1 μm for reflecting light is formed. The precision displacement control actuator 100 is configured.

The precision displacement control actuator 100 shown in FIG. 16 is a mechanical-electrical transducer 1 made of LiNbO ₃ or the like.
A drive signal is applied in the same direction between the electrodes 3a and 3b, but the piezoelectric substrates 2a and 2b are joined so that the directions of the polarization axes are opposite to each other.
A strain to expand or a strain to shrink occurs in a, and a strain opposite to that of the piezoelectric substrate 2a occurs in the piezoelectric substrate 2b. Therefore, the electromechanical transducer 1 excites the flexural vibration with reference to the ends supported by the supports 4a and 4b, and reflects the incident light coming from the same direction into the reflection film 5.
In b, the light can be deflected at an arbitrary angle by the voltage applied to the element.

In this embodiment, LiNb having stable piezoelectric characteristics is used.
Since the piezoelectric substrates 2a and 2b made of O ₃ are used,
The linearity of the displacement with respect to the applied voltage is also excellent. Specifically, it shows linearity up to 85% or more of the breaking limit. As a result, a precise displacement control actuator having high controllability can be realized. In addition, the linearity of a conventional electromechanical transducer using a piezoelectric ceramic substrate is limited to 10% of a breaking limit. Further, the piezoelectric substrates 2a, 2b made of LiNbO ₃ with small material variation
, The variation of the displacement amount of the precision displacement control actuator is small.

On the other hand, in the case of a conventional electromechanical transducer manufactured by bonding a piezoelectric ceramic substrate, since an adhesive softer than the piezoelectric substrate is interposed between the piezoelectric substrates, the electromechanical transducer is not used. When a drive signal is applied, the strain generated in each piezoelectric substrate is absorbed by the adhesive, and the effective strain effective for bending is reduced. For this reason, the amplitude of the flexural vibration excited by the electromechanical transducer becomes small.

However, the electromechanical transducer 1 of the present embodiment is similar to the second embodiment in that the piezoelectric substrates 2a, 2b
Of the piezoelectric substrates 2a and 2b, there is no adhesive layer such as an adhesive between the piezoelectric substrates 2a and 2b.
That is, when a drive signal is applied to generate strain in the piezoelectric substrates 2a and 2b, there is no one that absorbs the strain, and thus the vibration is converted to flexural vibration without loss. As a result, a precise displacement control actuator having a large displacement can be realized.

Further, as in the second embodiment, since the bonding state of the piezoelectric substrates 2a and 2b becomes uniform, the variation in the resonance frequency and the displacement of the electromechanical transducer 1 becomes extremely small.

Further, since no adhesive layer is interposed between the piezoelectric substrates 2a and 2b, the mechanical-electrical
Does not change the vibration characteristics.

In addition, the relationship between the cut angle and the characteristic variation and displacement is the same as in the second embodiment. <Fifth Embodiment> FIG. 17 is a sectional view showing a precision displacement control actuator according to a fifth embodiment of the present invention. As shown in FIG. 17, a rectangular L having a thickness of 50 μm, a width of 1 mm, and a length of 8 mm having two opposing main surfaces is provided.
consists LiNbO _3, the piezoelectric substrate 2a and 2b, the main surfaces is bonded directly, thereby mechanical - electrical transducer 1 is constituted. Here, the piezoelectric substrates 2a and 2b are joined so that the directions of the polarization axes are opposite to each other. One end of the electromechanical transducer 1 is LiNb.
It is fixed while being sandwiched between supports 4a and 4b made of O ₃ . Here, the electromechanical transducer 1 is directly joined to the supports 4a, 4b.

In this case, the electromechanical transducer 1 and the support 4
The bonding with a and 4b may be a direct bonding via a buffer layer made of a silicon oxide thin film or the like. Electrodes 3a, 3 having a role of a reflection film 5b made of chrome-gold having a thickness of 0.2 μm are provided on two opposing main surfaces of the electromechanical transducer 1.
b are formed respectively, and these electrodes 3a, 3b
Are also formed continuously on the supports 4a and 4b. Thereby, the precision displacement control actuator 100 for light deflection
Is configured.

A precision displacement control actuator 100 shown in FIG. 17 is a mechanical-electrical transducer 1 made of LiNbO ₃ or the like.
A drive signal is applied in the same direction between the electrodes 3a and 3b, but the piezoelectric substrates 2a and 2b are joined so that the directions of the polarization axes are opposite to each other.
A strain to expand or a strain to shrink occurs in a, and a strain opposite to that of the piezoelectric substrate 2a occurs in the piezoelectric substrate 2b. Therefore, the electromechanical transducer 1 excites the flexural vibration with reference to the ends supported by the supports 4a and 4b, and reflects the incident light coming from the same direction into the reflection film 5.
b (electrode 3b) can be deflected at an arbitrary angle by the voltage applied to the element.

In this embodiment, LiNb having stable piezoelectric characteristics is used.
Since the piezoelectric substrates 2a and 2b made of O ₃ are used,
The linearity of the displacement with respect to the applied voltage is also excellent. Specifically, it shows linearity up to 85% or more of the breaking limit. As a result, a precise displacement control actuator having high controllability can be realized. In addition, the linearity of a conventional electromechanical transducer using a piezoelectric ceramic substrate is limited to 10% of a breaking limit. Further, the piezoelectric substrates 2a, 2b made of LiNbO ₃ with small material variation
, The variation of the displacement amount of the precision displacement control actuator is small.

On the other hand, in the case of a conventional electromechanical transducer manufactured by bonding a piezoelectric ceramic substrate, an adhesive softer than the piezoelectric substrate is interposed between the piezoelectric substrates. When a drive signal is applied, the strain generated in each piezoelectric substrate is absorbed by the adhesive, and the effective strain effective for bending is reduced. For this reason, the amplitude of the flexural vibration excited by the electromechanical transducer becomes small.

However, the electromechanical transducer 1 of the present embodiment is similar to the second embodiment in that the piezoelectric substrates 2a, 2b
Of the piezoelectric substrates 2a and 2b, there is no adhesive layer such as an adhesive between the piezoelectric substrates 2a and 2b.
That is, when a drive signal is applied to generate strain in the piezoelectric substrates 2a and 2b, there is no one that absorbs the strain, and thus the vibration is converted to flexural vibration without loss. As a result, a precise displacement control actuator having a large displacement can be realized.

Further, as in the second embodiment, since the bonding state of the piezoelectric substrates 2a and 2b becomes uniform, the variation in the resonance frequency and the displacement of the electromechanical transducer 1 becomes extremely small.

Furthermore, since no adhesive layer is interposed between the piezoelectric substrates 2a and 2b, the mechanical-electrical
Does not change the vibration characteristics.

In addition, the relationship between the cut angle and the characteristic variation or displacement is the same as in the second embodiment.

In the present embodiment, as shown in FIG. 18, a drive signal is applied between the electrodes 3a and 3b of the electromechanical transducer 1 to excite the flexural vibration of the electromechanical transducer 1. I do. Due to this deflection, a pseudo concave mirror can be produced by using a highly efficient reflector such as chrome-gold for the electrodes 3a and 3b. Thereby, it can be used as a light collecting device.

It should be noted that the mechanical-electrical converter of the actuator according to the first to fifth embodiments can cause flexural vibration and can maintain a constant deformed state.

[0150]

As apparent from the above description, the present invention has an advantage that a larger displacement can be secured with a simple structure.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a mechanical-electrical converter used for a precision displacement control actuator according to a first embodiment of the present invention.

FIGS. 2 (a) to 2 (c): Interface states of a piezoelectric substrate at respective stages of direct bonding in a method for manufacturing a mechanical-electrical transducer used for a precision displacement control actuator according to a first embodiment of the present invention. Illustration

FIG. 3 is a perspective view showing another example of the electromechanical transducer used in the precision displacement control actuator according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing a precision displacement control actuator according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing a precision displacement control actuator according to the first embodiment of the present invention.

FIG. 6 is an explanatory view showing a state of bending vibration excitation of a bimorph type mechanical-electrical transducer having a cantilever structure according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a crystal axis of a piezoelectric substrate and a cut angle.

FIG. 8 is a diagram showing a relationship between a cut angle of a LiNbO ₃ substrate and a piezoelectric constant.

FIG. 9 is a frequency characteristic diagram of the precision displacement control actuator according to the first embodiment of the present invention.

FIG. 10 is a diagram showing a cut angle of the precision displacement control actuator according to the first embodiment of the present invention.

FIG. 11 is a diagram showing a relationship between a cut angle of a quartz substrate and a piezoelectric constant.

FIG. 12 is a diagram showing a relationship between a cut angle of a quartz substrate and a piezoelectric constant.

FIG. 13 is a diagram showing a relationship between a cut angle of a quartz substrate and a piezoelectric constant.

FIG. 14 is a sectional view showing a precision displacement control actuator according to a third embodiment of the present invention.

FIG. 15 is an explanatory diagram showing a state in which bending vibration is excited and deflected in the precision displacement control actuator according to the third embodiment of the present invention.

FIG. 16 is a sectional view showing a precision displacement control actuator according to a fourth embodiment of the present invention.

FIG. 17 is a sectional view showing a precision displacement control actuator according to a fifth embodiment of the present invention.

FIG. 18 is an explanatory view showing how light is condensed when the precision displacement control actuator according to the fifth embodiment of the present invention is used in a light condensing device.

FIG. 19 is an actuator characteristic diagram of a precision displacement control actuator according to the second embodiment of the present invention.

FIG. 20 is an actuator characteristic diagram of a bimorph-type actuator having a cantilever structure according to the related art.

FIG. 21 shows Li ₂ B _{4 according to} the second embodiment of the present invention.
Diagram showing the relationship between the cut angle of O ₇ and the piezoelectric constant

FIG. 22 is a view showing a relationship between a cut angle of Li ₂ B ₄ O ₇ and a piezoelectric constant in the embodiment.

FIG. 23 is a view showing a relationship between a cut angle of Li ₂ B ₄ O ₇ and a piezoelectric constant in the embodiment.

FIG. 24 is a view showing a relationship between a cut angle of KNbO ₃ and a piezoelectric constant in the embodiment.

FIG. 25 is a diagram showing a relationship between a cut angle of KNbO ₃ and a piezoelectric constant in the embodiment.

FIG. 26 is a diagram showing a relationship between a cut angle of KNbO ₃ and a piezoelectric constant in the embodiment.

FIG. 27 is a sectional view showing a precision displacement control actuator according to a second embodiment of the present invention.

FIG. 28 is a perspective view showing a bimorph-type electromechanical transducer according to the related art.

FIG. 29 is a cross-sectional view showing a bimorph actuator having a cantilever structure according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mechano-electric converter 2a, 2b Piezoelectric substrate 3a, 3b Electrode 4a, 4b Support 5a Reflector 5b Reflective film 46 Buffer layer 100 Precision displacement control actuator

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshihiro Tomita 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In company

Claims (25)

[Claims] 1. A piezoelectric element in which said first main surfaces of at least two piezoelectric substrates having opposing first and second main surfaces are bonded to each other using direct bonding, A displacement control actuator, comprising: a electromechanical transducer having an electrode formed on the second main surface; and a support for supporting the electromechanical transducer. 2. The first main surfaces of the two piezoelectric substrates, wherein constituent atoms of the two piezoelectric substrates are mutually bonded via at least one selected from the group consisting of oxygen and a hydroxyl group. The displacement control actuator according to claim 1, wherein the displacement control actuator is directly joined by: 3. The displacement control actuator according to claim 1, wherein the two piezoelectric substrates are joined so that directions of polarization axes thereof are opposite to each other. 4. The method according to claim 1, wherein a buffer layer formed on one of the two piezoelectric substrates is directly bonded to the other of the two piezoelectric substrates. Item 3. The displacement control actuator according to Item 1. 5. The displacement control actuator according to claim 1, wherein one end of the electromechanical transducer is supported by a support. 6. The main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of 3m group, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes. However, the angle formed with the Y axis is +
The line perpendicular to the axis of 129 ° to + 152 ° and including the X-axis, and connecting the center of gravity of the piezoelectric substrate and the center of the supporting portion is the X-axis.
The displacement control actuator according to claim 1, wherein the displacement control actuator is perpendicular to the axis. 7. The main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of 3m group, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes. Has an angle of-
A line perpendicular to the axis of 26 ° to + 26 °, including the X axis, and connecting the center of gravity of the piezoelectric substrate to the center of the support portion is the X axis.
The displacement control actuator according to claim 1, wherein the displacement control actuator is parallel to the axis. 8. The main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of Group 32, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes. Is perpendicular to the X-axis, and the line connecting the center of gravity of the piezoelectric substrate and the center of the support is
The displacement control actuator according to claim 1, wherein the axis forms an angle of + 52 ° to + 86 ° with the axis. 9. The piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of Group 32, and the crystal axis of the single-crystal piezoelectric material is set to X.
Axis, Y axis, and Z axis, the main surface of the piezoelectric substrate is
An angle between the X axis and the axis of −26 ° to + 26 ° is perpendicular to the axis and includes the Y axis. A line connecting the center of gravity of the piezoelectric substrate and the center of the supporting portion is the Y axis.
The displacement control actuator according to claim 1, wherein the displacement control actuator is parallel to the axis. 10. A main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of Group 32, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes. Is perpendicular to an axis having an angle of + 82 ° to + 98 ° with respect to the X axis, and includes the Z axis, and a line connecting the center of gravity of the piezoelectric substrate and the center of the support portion is the Z line.
The displacement control actuator according to claim 1, wherein the displacement control actuator is perpendicular to the axis. 11. The main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single crystal piezoelectric material having a crystal structure of 4 mm group, and the crystal axes of the single crystal piezoelectric material are X, Y, and Z axes. Is perpendicular to an axis having an angle of + 22 ° to + 41 ° with respect to the Y axis, includes the X axis, and a line connecting the center of gravity of the piezoelectric substrate and the center of the supporting portion is the X axis.
The displacement control actuator according to claim 1, wherein the displacement control actuator is perpendicular to the axis. 12. The main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of 4 mm group, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes. Is perpendicular to an axis having an angle of + 49 ° to + 68 ° with respect to the Z axis and includes the Y axis, and a line connecting the center of gravity of the piezoelectric substrate and the center of the supporting portion is the Y axis.
The displacement control actuator according to claim 1, wherein the displacement control actuator is perpendicular to the axis. 13. The main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single crystal piezoelectric material having a crystal structure of 4 mm group, and the crystal axes of the single crystal piezoelectric material are X, Y, and Z axes. The displacement control actuator according to claim 1, wherein is perpendicular to the Z axis. 14. The main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of 6 mm group, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes. Is perpendicular to an axis having an angle of + 23 ° to + 51 ° with respect to the Y axis, and includes the X axis, and a line connecting the center of gravity of the piezoelectric substrate and the center of the supporting portion is the X axis.
The displacement control actuator according to claim 1, wherein the displacement control actuator is perpendicular to the axis. 15. The main surface of the piezoelectric substrate, wherein the piezoelectric substrate is made of a single-crystal piezoelectric material having a crystal structure of 6 mm group, and the crystal axes of the single-crystal piezoelectric material are X, Y, and Z axes. Is perpendicular to an axis having an angle of + 46 ° to + 66 ° with respect to the Z axis and includes the Y axis, and a line connecting the center of gravity of the piezoelectric substrate and the center of the support portion is the Y line.
The displacement control actuator according to claim 1, wherein the displacement control actuator is perpendicular to the axis. 16. A piezoelectric element in which the first main surfaces of at least two piezoelectric substrates having opposing first and second main surfaces are joined by direct joining, and a piezoelectric element of each of the piezoelectric elements is provided. A mechanical-electrical converter having an electrode formed on the second main surface; and a support for supporting the mechanical-electrical converter, wherein the mechanical-electrical converter and the support are directly joined. A displacement control actuator, wherein the displacement control actuator is joined by using a liquid crystal. 17. The piezoelectric substrate and the support constituting the electromechanical transducer, wherein the constituent atoms of the piezoelectric substrate and the constituent atoms of the support are at least one selected from the group consisting of oxygen and hydroxyl groups. 17. Directly joined by coupling with each other via a wire.
3. The displacement control actuator according to item 1. 18. The apparatus according to claim 16, wherein the piezoelectric substrate and the support are made of the same material.
3. The displacement control actuator according to item 1. 19. A piezoelectric element in which the first main surfaces of at least two piezoelectric substrates having opposing first and second main surfaces are joined using direct joining, and a piezoelectric element of each of the piezoelectric elements is provided. A mechanical-electrical converter having an electrode formed on the second main surface; and a support for supporting the mechanical-electrical converter, wherein the mechanical-electrical converter and the support are directly joined. A displacement control actuator, wherein a reflection plate is attached to a free end of the electromechanical transducer. 20. A piezoelectric element in which the first main surfaces of at least two piezoelectric substrates having opposing first and second main surfaces are joined using direct joining, and a piezoelectric element of each of the piezoelectric elements. A mechanical-electrical converter having an electrode formed on the second main surface; and a support for supporting the mechanical-electrical converter, wherein the mechanical-electrical converter and the support are directly joined. The length of one piezoelectric substrate constituting the piezoelectric element is longer than the other, and the surface of a portion of the longer piezoelectric substrate protruding from the tip of the other piezoelectric substrate. A displacement control actuator, further comprising a reflection film. 21. A piezoelectric element in which the first main surfaces of at least two piezoelectric substrates having opposing first and second main surfaces are bonded to each other using direct bonding, A mechanical-electrical converter having an electrode formed on the second main surface; and a support for supporting the mechanical-electrical converter, wherein the mechanical-electrical converter and the support are directly joined. A displacement control actuator, wherein a reflection film is formed on a surface of the piezoelectric substrate. 22. The piezoelectric substrate and the support constituting the electromechanical transducer, wherein the constituent atoms of the piezoelectric substrate and the constituent atoms of the support are at least one selected from the group consisting of oxygen and hydroxyl groups. 2. Directly joined by coupling with each other through a
22. The displacement control actuator according to 9, 20, or 21. 23. A buffer layer formed on the piezoelectric substrate and the support are directly bonded, or a buffer layer formed on the support and the piezoelectric substrate are directly bonded. Claims 16, 19, and 2 characterized in that:
22. The displacement control actuator according to 0 or 21. 24. The apparatus according to claim 1, wherein the piezoelectric substrate and the support are made of the same material.
22. The displacement control actuator according to 9, 20, or 21. 25. The displacement control actuator according to claim 21, wherein all or a part of the electrode also serves as a reflection film.