JPH10144974A - Piezoelectric actuator and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator that is a face deformation element for obtaining a sufficient generation force or a displacement, while operating at a low voltage and its manufacturing method. SOLUTION: A piezoelectric actuator 1 has an elastic plate 5 that is a thin plate with spring elasticity, a piezoelectric plate 2 that is a thin plate made of a piezoelectric material being jointed onto the surface of the elastic plate 5, and a first electrode 31 and a second electrode 32 that are accommodated in a plurality of grooves 2a formed at the piezoelectric plate 2 with a gap that is equal to or less than the thickness of the piezoelectric plate 2 and are adjacent, while sandwiching a piezoelectric material. The piezoelectric actuator 1 can generate a sufficiently high electric field, even if an applied voltage is small, since the gap between both electrodes 31 and 32 is narrow and can utilize a piezoelectric constant d33 that is approximately two times larger than a piezoelectric constant d33 , so that it can achieve a larger occurrence force and the maximum displacement even at a low voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of a piezoelectric actuator which is a surface deformation element similar to a piezoelectric unimorph or a piezoelectric bimorph.

[0002]

2. Description of the Related Art Piezoelectric unimorphs and piezoelectric bimorphs are known as piezoelectric actuators which are surface deformation elements of the prior art. These are usually formed on or joined to both sides of each piezoelectric plate, and an elastic plate which is a thin plate having spring elasticity, a piezoelectric plate which is a thin plate made of a piezoelectric material joined to at least one surface of the elastic plate. And a pair of electrodes.

When a voltage is applied to the pair of electrodes, an electric field having an electric field strength obtained by dividing the applied voltage by the thickness is generated in the thickness direction of the piezoelectric plate, and is proportional to the product of the electric field strength and the piezoelectric constant d _31. Thus, the piezoelectric plate generates an in-plane displacement (or a pressure that causes an in-plane displacement) perpendicular to the thickness direction. As a result, a surface deformation element such as a unimorph or a bimorph generates a force that warps or warps in one direction.

Taking a piezoelectric unimorph P1 as an example, as shown in FIG. 12, a piezoelectric plate P2 is joined to one side of a metal disc-shaped elastic plate P5, and as shown in FIG. The electrodes P3 are formed on both surfaces of the substrate. When a voltage is applied to both electrodes P3, FIG.
As shown in (b), the piezoelectric plate P2 contracts in an in-plane direction orthogonal to the polarization direction, and the entire unimorph P1 warps and deforms. At this time, the deformation pressure of the piezoelectric plate P2 (the stress at the time of fixing)
It is proportional to the applied voltage to the electric field strength and the piezoelectric constant d ₃₁ divided by the thickness of the piezoelectric plate P2.

[0005]

In the above-described unimorph and bimorph, in order to operate at a low voltage, the thickness of the piezoelectric plate is made thin so that a sufficiently strong electric field strength can be obtained even at a low voltage. There is. However, when the thickness of the piezoelectric plate is reduced, the cross-sectional area in the in-plane direction is reduced, so that the force generated in the in-plane direction is weakened, and a sufficient generated force cannot be obtained. Therefore, according to the above-mentioned prior art, it is not possible to obtain a sufficient generated force and displacement while operating at a low voltage.

Accordingly, the present invention is to provide a piezoelectric actuator which is a surface deformation element capable of obtaining at least one of a sufficient generated force and displacement while operating at a low voltage, and a method of manufacturing the same. And

[0007]

Means for Solving the Problems and Their Functions and Effects In order to solve the above problems, the inventors have invented the following means. [Piezoelectric Actuator] (First Means) A first means of the present invention is the piezoelectric actuator according to claim 1. A high voltage is applied to the piezoelectric plate between the first electrode and the second electrode during the manufacturing process, and the polarization of the piezoelectric material is formed in advance in a direction orthogonal to each electrode surface in the in-plane direction.

Here, the material forming the elastic plate is a conductive material such as a metal such as stainless steel, copper and copper alloy, an insulating material such as synthetic resin and glass, or a silicon or the like. Semiconductor material. Further, the material forming the piezoelectric plate can be appropriately selected from piezoelectric materials that produce a piezoelectric effect or an inverse piezoelectric effect by applying a voltage. For example, PZT of piezoelectric ceramics can be used.
(Lead zirconate titanate) can be employed. On the other hand, the material forming each electrode can be appropriately selected from conductive materials, for example, aluminum, gold,
Metals such as silver, platinum, tungsten, copper and their alloys can be employed.

In this means, a plurality of grooves formed at intervals smaller than the thickness of the piezoelectric plate are filled with a conductive material, and the first electrode and the second electrode are adjacent to each other with the piezoelectric material interposed therebetween. Are formed. Therefore, when the voltage between the both electrodes is applied, an electric field is generated in the in-plane direction, the piezoelectric plate thickness direction and plane direction perpendicular in proportion to the product of the field strength and the piezoelectric constant d ₃₃ An expansion / contraction displacement or an expansion / contraction force occurs in a direction (parallel to the electric field). Here, as the gap between the grooves, that is, the gap between the two electrodes is narrower, a strong electric field is generated even at a low voltage, and the electric field strength is not affected by the thickness of the piezoelectric plate. Can be applied to the piezoelectric plate.

At this time, if the distance between the two electrodes adjacent to each other is sufficiently small with respect to the thickness of the piezoelectric plate, a sufficiently high electric field intensity is generated in the in-plane direction even if the applied voltage is low. The piezoelectric actuator of the means generates sufficient bending deformation or bending force. Further, unlike the prior art have utilized piezoelectric constant d _31, elastic deformation or stretching force in the plane direction by the piezoelectric constant d ₃₃ is generated. Here, the piezoelectric constant d
₃₃ is usually about twice as large as the piezoelectric constant d ₃₁ ,
If the electric field strength is the same, the deformation force generated by the piezoelectric actuator of the present means is about twice as large as that of the prior art. This effect is exerted even when the distance between the two electrodes is substantially the same as the thickness of the piezoelectric plate. Even if the electric field intensity is the same, an expansion and contraction force of about twice is obtained.

Since the width of the groove, that is, the width of the two electrodes is usually smaller than the distance between the two electrodes, the magnitude of displacement of the present means is larger than that of the prior art. Moreover, in order to obtain a conventional equivalent displacement piezoelectric actuator of the present means (proportional to the product of the field strength and the piezoelectric constant d _33), the voltage to be applied requires only a person is lower than the prior art of the present means . Therefore, according to this means, it is possible to operate the piezoelectric actuator with an applied voltage much lower than that of the related art, and there is an effect that the deformation force and the amount of deformation are larger than those of the related art.

(Second Means) A second means of the present invention is a piezoelectric actuator according to the second aspect. In this method, since each groove accommodating both electrodes is opened on the surface of the piezoelectric plate, the grooves are precisely formed from the surface of the piezoelectric plate joined to the elastic plate by making full use of fine processing technology. Can be formed. Further, since the grooves are formed by processing from the same surface, precise alignment between the grooves of the first electrode and the grooves of the second electrode can be easily performed, and the processing can be performed while maintaining a precisely constant gap between both grooves. It becomes easier to do. Furthermore, it is possible to form both electrodes at once from one surface of the piezoelectric plate, and the process of forming both electrodes is more complicated than when the grooves of each electrode are opened on both surfaces of the piezoelectric plate. Simplified. in addition,
Since the groove can be formed after the piezoelectric plate is joined to the elastic plate, cracks are less likely to occur in the piezoelectric plate on which the groove is formed, and handling during manufacture becomes easy.

Therefore, according to this means, in addition to the effect of the first means, there is an effect that the manufacture of the piezoelectric actuator of the present invention is facilitated. When the elastic plate is made of a conductive material such as a metal, the depth of the groove is kept within a range where insulation is maintained between both electrodes and the elastic plate, but the elastic plate is made of synthetic resin or glass. In the case where the groove is made of an insulating material such as the above, the groove may penetrate the elastic plate. In the latter case, the grooves are formed after the piezoelectric plate is joined to the elastic plate. However, since the electric field can be applied to the piezoelectric plate wider (deeper) than in the former case, the generated force And the amount of deformation is larger than the former.

(Third Means) A third means of the present invention is a piezoelectric actuator according to the third aspect. In this means, one of the two electrodes is formed in a groove which is open in the joint surface of the piezoelectric plate facing the elastic plate, and the other is open in the surface of the piezoelectric plate facing the elastic plate. Formed in the groove. That is, both electrodes are formed alternately from the front and back of the piezoelectric plate. Therefore, since one surface can be used as a connection surface with one electrode and the other surface can be used as a connection surface with the other electrode, connection between both electrodes and the driving power supply becomes easy, and the same surface is used. There is no risk of short circuit.

Therefore, according to this means, in addition to the effect of the above-mentioned first means, not only the connection between the two electrodes and the drive power supply is facilitated, but also the effect that a short circuit between the two electrodes is prevented. is there. (Fourth Means) A fourth means of the present invention is the piezoelectric actuator according to the fourth aspect.

In this means, the patterns on the piezoelectric plate of both electrodes are formed only in a straight line, and both electrodes can be arranged most densely with respect to the area of the surface of the piezoelectric plate. , A large force can be obtained. Further, the piezoelectric actuator does not warp in a substantially spherical shape as in the related art, but warps in one direction to form a primary curved surface.

Therefore, according to this means, in addition to the effect of the first means, a sufficiently large displacement or generated force can be obtained with a lower applied voltage, and the piezoelectric actuator is deformed into a primary curved surface. . (Fifth Means) A fifth means of the present invention is the piezoelectric actuator according to the fifth aspect.

In this means, since both electrodes are formed on the piezoelectric plate in an arbitrary pattern including a straight line or a curved line, the piezoelectric actuator can be deformed into a primary curved surface or a positive or negative secondary curved surface. Therefore, according to this means, in addition to the effect of the above-described first means, there is an effect that the deformed shape and the direction of the deformation of the piezoelectric actuator can be arbitrarily designed.

(Sixth Means) A sixth means of the present invention is a piezoelectric actuator according to the sixth aspect. In this means, the applied voltage can be controlled independently for each section, so that the direction and amount of deformation can be individually given to each section, and the piezoelectric actuator can be formed into a complicated shape. It can be deformed.

Therefore, according to this means, in addition to the effect of the first means, the deformation can be individually controlled for each section, and the piezoelectric actuator can be deformed into a complicated shape. effective. [Method of Manufacturing Piezoelectric Actuator] (Seventh Means) A seventh means of the present invention is the piezoelectric actuator according to claim 7.

In this means, at least a groove forming step of forming a plurality of grooves in the piezoelectric plate from the surface of the piezoelectric plate, which is a thin plate made of a piezoelectric material, at intervals shorter than the thickness of the piezoelectric plate; The piezoelectric actuator of the first means is manufactured by an electrode forming step of filling the conductive material to form the first electrode and the second electrode, and a polarizing step of applying a high voltage between the two electrodes to polarize the piezoelectric material. Is done. In the groove forming step, the microfabrication technology of the semiconductor can be diverted, and the groove can be easily formed. In addition, the processing technology matured in each engineering field can be diverted to the electrode forming step. Also, the polarization step is basically the same as the step performed by a normal piezoelectric element, and there is no technical difficulty in the manufacturing method of the present means.

Therefore, according to this means, there is an effect that the above-mentioned piezoelectric actuator of the first means can be easily manufactured by diverting an already matured processing technique. (Eighth Means) An eighth means of the present invention is a method of manufacturing a piezoelectric actuator according to claim 8. In this means, any one of dicing, laser processing, and reactive ion etching is used in the groove forming step. The dicing process has an advantage that processing can be performed promptly by using inexpensive and simple processing equipment. on the other hand,
The laser processing and the reactive ion etching processing have an advantage that a groove pattern on the surface of the piezoelectric plate can be arbitrarily designed including a curve.

(Ninth Means) A ninth means of the present invention is a method for manufacturing a piezoelectric actuator according to the ninth aspect. In this means, the electrode forming step includes CVD (Chemical Vapor Deposition),
One of the processing techniques of sputtering, printing of a conductive paste, electroless plating, and vapor deposition is used. CVD, vapor deposition and sputtering have the advantage that both electrodes can be formed relatively densely and that a plurality of electrodes can be formed at once. On the other hand, the imprinting of the conductive paste and the electroless plating have the advantage that the processing equipment can be inexpensive and simple and the processing time can be relatively short.

If a mask material is bonded to the surface of the piezoelectric plate in the groove forming step, the mask material is used in the electrode forming step and is removed after the electrode forming step. At the same time, excess conductive material is removed, which is reasonable. Conversely, if the mask material is not bonded to the surface of the piezoelectric plate in the groove forming step, excess conductive material deposited on the surface of the piezoelectric plate may be removed by machining such as grinding.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the piezoelectric actuator and the method of manufacturing the same according to the present invention will be clearly and fully described in the following examples so that those skilled in the art can understand the present invention. [First Embodiment] (Configuration of First Embodiment) Piezoelectric actuator 1 of the present embodiment
Has a rectangular planar shape as shown in FIG. That is, the piezoelectric actuator 1 has a rectangular elastic plate 5.
A rectangular piezoelectric plate 2 joined to one surface thereof with an epoxy adhesive, and a groove 2 a formed in the piezoelectric plate 2.
And the electrodes 31, 32, 41, and 42 housed therein.

The elastic plate 5 is a thin plate having spring elasticity.
It is a stainless steel flat plate having a width of 10 mm, a depth of 15 mm, and a thickness of 0.05 mm. The piezoelectric plate 2 is a thin plate made of a PZT piezoelectric material, and is a flat plate having a width of 8 mm, a depth of 12 mm, and a thickness of 0.05 mm. A groove 2a is formed in the piezoelectric plate 2.
It is formed alternately in a plane parallel to the surface in a tooth shape of two opposing combs. The first electrode 31 is formed by filling a conductive material into one of the comb-shaped grooves 2a, and the same conductive material is filled into the other comb-shaped groove 2a. Two electrodes 32 are formed. First electrode 31 and second electrode 3
2 are insulated from each other with the piezoelectric material of the piezoelectric plate 2 interposed therebetween. All the first electrodes 31 are connected at one end thereof to the first common electrode 41 formed of the same conductive material in the groove 2a, and similarly, all the second electrodes 32 are connected to the same conductive material at one end thereof. The second common electrode 42 formed in the groove 2a
Is connected to The conductive material is aluminum,
It is also possible to appropriately change to gold, tungsten, or the like.

As shown in FIG. 2, all the grooves 2a are open on the surface of the piezoelectric plate 2 facing the elastic plate 5, and a conductive material is introduced into the grooves 2a from these openings to make each of the grooves 2a. Electrodes 31,
32, 41, and 42 are formed. The first common electrode 41 and the second common electrode 42 are connected to bonding wires or lead wires, respectively, so as to receive an applied voltage from a driving power supply (not shown).

Each of the electrodes 31, 32, 41, 42 has a depth of 0.045 mm (90% of the thickness of the piezoelectric plate 2) and a width of 0.045 mm.
The distance between the first electrode 31 and the second electrode 32 is constant and is 0.03 mm (厚 of the thickness of the piezoelectric plate 2). That is, as shown in FIG. 3, the first electrode 31 and the second electrode 3 have a thickness corresponding to the distance between the electrodes.
2, a piezoelectric material polarized in a direction perpendicular to the surfaces of both electrodes is sandwiched.

(Effects of Embodiment 1) The piezoelectric actuator 1 of the present embodiment operates in a state where no voltage is applied.
As shown in FIG. 4 (a), it has a flat plate shape as a whole. On the other hand, as shown in FIG. 4B, in a state where the switch 6 is closed and a voltage is applied from the battery 7 as a driving power source, the electrodes 31 and 32 are alternately stacked (in a direction parallel to the electric field). The piezoelectric material expands in a certain direction. On this occasion,
The expansion rate is proportional to the product of the piezoelectric constant d ₃₃ (constant) of the piezoelectric plate 2 and the electric field strength due to the applied voltage of the battery 7 (when the applied voltage is within a predetermined range). This electric field strength is determined by applying an applied voltage to each electrode 3.
Since the value is divided by the interval of 1, 32, as described above, the piezoelectric actuator 1 of the present embodiment, in which the interval is much smaller than the thickness of the piezoelectric plate 2, has a sufficiently large electric field intensity even at a low applied voltage. Occurs. Also, the thickness of the piezoelectric plate 2 is
The thickness is sufficient to generate a bending moment sufficient to bend the elastic plate 5.

As a result, the piezoelectric plate 2 generates a sufficiently large elongating force, and is extended by a predetermined amount in the laminating direction of the electrodes 31 and 32 to bend the elastic plate 5 at a predetermined curvature (the piezoelectric plate 2 is also elastic plate). 5). Due to this bending deformation, the piezoelectric actuator 1 of the present embodiment forms a primary curved surface as a whole. As described in detail above, according to the piezoelectric actuator 1 of the present embodiment, even if the applied voltage is relatively low, a sufficient bending deformation force is generated, and as a result, a sufficiently large bending deformation amount can be generated. effective.

(Application of Embodiment 1) When the piezoelectric actuator 1 of this embodiment is employed in a micromachine, since the applied voltage required for driving is relatively low, the micromachine does not require a high voltage generator. The piezoelectric actuator 1 can be driven by a battery mounted on the piezoelectric actuator 1. Therefore, there is an effect that it is easy to configure the micromachine as a single unit without a power supply cable. In addition, since a high voltage is not required, short circuit can be easily prevented, and accordingly, there is an effect that the micromachine can be reduced in size and weight.

(Modification of Embodiment 1) In the piezoelectric actuator 1 of Embodiment 1 described above, the elastic plate 5 is formed of insulating glass or synthetic resin, and extends through the piezoelectric plate 2 to form the groove 2.
A modification in which a is formed to form both electrodes 31 and 32 over the entire thickness of the piezoelectric plate 2 is also possible. According to this modification, there is an effect that a larger generated force and a larger amount of deformation can be obtained.

Since the common electrodes 41 and 42 only function as conductive paths, they do not need to be formed over the entire thickness of the piezoelectric plate 2. Further, as in the first embodiment, it is desirable that the common electrodes 41 and 42 be formed to have a wider width than the electrodes 31 and 32 in order to secure conduction between the electrodes 31 and 32 and the electrode pad P. .

Further, with a configuration similar to that of the first embodiment or its modified embodiment, a modified embodiment such as a bimorph in which the piezoelectric plates 2 are bonded to both the front and back surfaces of the elastic plate 5 is also possible. (Manufacturing Method of First Embodiment) The manufacturing method of the piezoelectric actuator 1 of the present embodiment includes a joining step, a groove forming step, an electrode forming step, and a polarization step in this order.

In the joining step, an elastic plate 5 and a piezoelectric plate 2 which are formed into a thin plate having a predetermined size are prepared, and the piezoelectric plate 2 is joined to one surface of the elastic plate 5 with an adhesive by aligning the orientation of each other. This is the step of fixing. In this step, the adhesive is sufficiently cured to completely join the piezoelectric plate 2 and the elastic plate 5 before moving to the next groove forming step. Here, the elastic plate 5 and the piezoelectric plate 2 have a predetermined size to constitute the piezoelectric actuator 1.
Before the is cut, the two 5 and 2 are joined together,
After all the steps are completed, a manufacturing method of cutting into the above-mentioned predetermined dimensions can be adopted. According to this method, it is possible to manufacture a large number of piezoelectric actuators 1 at a time, like many semiconductor chips.

In the groove forming step, a plurality of grooves 2a are formed from the surface of the piezoelectric plate 2 joined to the surface of the elastic plate 5 at intervals shorter than the thickness of the piezoelectric plate 2 in the above-described pattern (see FIG. 1). This is a step of forming the plate 2. In the present embodiment, since all the patterns of the grooves 2a are composed of straight line segments, dicing is used in the groove forming step, and the grooves 2a having a predetermined depth are formed by mechanical cutting.

The electrode forming step is a step of filling the groove 2a with a conductive material to form the first electrode 31 and the second electrode 32 adjacent to each other with the piezoelectric material of the piezoelectric plate 2 interposed therebetween. In this embodiment, a processing method is employed in which a conductive paste containing a large amount of fine silver powder in a small amount of solvent is printed in all the grooves 2a with a roller. At the time of printing, the roller reciprocates in an oblique direction with respect to the grooves 2a and completely fills all the grooves 2a with the paste. Here, it is more preferable to perform the above-described printing in a reduced-pressure atmosphere because bubbles (voids) hardly remain in the depth of the groove 2a. The excess conductive paste adhering to the surface of the piezoelectric plate 2 is wiped off with a solvent after printing with a roller, and is removed cleanly.

After the solvent evaporates from the paste filled in the groove 2a, the piezoelectric plate 2 and the elastic plate 5 are placed in a heat treatment furnace, and the temperature is raised to an appropriate temperature to dissolve the fine silver powder to form a silver powder. The electrodes 31, 32, 41, 42 are fired. That is, after cooling after the heat treatment, silver is continuously solidified in the groove 2a, and the electrodes 31, 32, 41, and 42 are formed. After the electrodes 31, 32, 41, and 42 are formed in the electrode forming step, one of the first electrode 31 and the first common electrode 41 and one of the second electrode 32 and the second common electrode 42 are formed. One other lead wire is joined to the crab. In the case of the present embodiment, as shown in FIG. 5, a conductive paste containing silver as a main component is provided at the end of the first electrode 31 and the end of the second electrode 32 which are closest to the periphery of the piezoelectric plate 2. Are printed and fired to form respective electrode pads P. A lead wire L is connected to each electrode pad P by soldering (adhesion with a conductive adhesive may be used).

Finally, in the polarization step, a high voltage is applied between the first electrode 31 and the second electrode 32 via each lead wire L, and the piezoelectric plate 2 sandwiched between the two electrodes 31, 32 is applied. Polarize the piezoelectric material. According to the manufacturing method of the present embodiment described above,
The piezoelectric actuator of this embodiment is manufactured. According to the manufacturing method of this embodiment, there is an effect that the equipment required for manufacturing is inexpensive and simple, and the above-described piezoelectric actuator can be manufactured particularly quickly and inexpensively in small-quantity production of prototypes and the like.

(Modification 1 of Manufacturing Method of Example 1) As a modification of the manufacturing method of this example, after the same bonding step as in Example 1, a laser processing method is used in a groove forming step, and an electrode is formed. A manufacturing method using CVD in the process is possible. In the groove forming step by the laser processing method, as shown in FIG.
Focusing lens 1 for infrared laser light 10 having a wavelength of about 1 μm
The light is condensed at 1 and irradiates a portion of the piezoelectric plate 2 immersed in pure water 9 where the groove 2a is to be formed. Then, due to the local temperature rise due to the concentrated irradiation of the infrared laser beam, the PZT forming the piezoelectric plate 2 chemically reacts with the pure water 9 at the irradiated portion to be eroded, and the groove 2a is gradually formed. . Groove 2 on piezoelectric plate 2
By scanning the laser beam 10 along the pattern in which a is to be formed, all the grooves 2a in which the electrodes 31, 32, 41, and 42 are to be accommodated are formed.

In the electrode forming step by CVD, a mask is formed with a resist on the surface of the piezoelectric plate 2 other than the groove 2a, and patterning is performed so that a conductive material (in this embodiment, silver) adheres in the groove 2a. Keep it. As a result, the electrodes 31, 32, 41, and 42 are formed in the groove 2a, and the other surfaces of the piezoelectric plate 2 are kept clean. Note that the conductive material deposited on the surface of the piezoelectric plate 2 may be removed by machining such as cutting or polishing or chemical treatment without patterning by the mask material.

The electrode pad P to which a bonding wire instead of the lead wire L is to be connected is formed by the groove 2a in the above-described electrode forming step.
Formed at the same time. The advantages of the manufacturing method of this modification are as follows.
Since the grooves 2a are formed by laser processing instead of mechanical processing,
Since the grooves 2a having a smaller width can be formed at smaller intervals, there is an effect that the operation can be performed at a lower voltage. Incidentally, the minimum width of the groove 2a is about 5 μm for the infrared laser and about 2 μm for the ultraviolet laser, and the minimum interval between the grooves 2a is about 30 μm for the infrared laser and about 10 μm for the ultraviolet laser.

(Modification 2 of the manufacturing method of the first embodiment) As a modification of the manufacturing method of the first embodiment, reactive ion etching is used in the groove forming step after the joining step similar to that of the first embodiment. A manufacturing method using sputtering in the forming step is possible. In the groove forming step by reactive ion etching, as shown in FIG. 7, a piezoelectric plate 2 whose surface is patterned with a resist mask material is put into a processing vacuum chamber 13 of a reactive ion etching apparatus and processed. . In this device, a plasma 17 of a reactive gas is generated in an AC magnetic field generated by a magnetic field coil 14 driven by a high-frequency AC power supply 15, and erosion due to a chemical reaction occurs in a portion of the piezoelectric plate 2 where a groove 2a is to be formed. . At this time, CF ₄ , Cl ₂ or the like can be used as the reactive gas. On the other hand, a plurality of piezoelectric plates 2 joined to the elastic plate 5 are arranged on the electrode substrate 12, and a high voltage is applied from the high-frequency AC power supply 15 via the electrode substrate 12. The vacuum chamber for processing is maintained at an appropriate vacuum level by the vacuum exhaust system 16.

In the electrode forming step by sputtering,
The mask used in the above-described groove forming step is left on the surface of the piezoelectric plate 2 other than the grooves 2a, and a conductive substance is attached to the inside of the grooves 2a by sputtering. As a result, the electrodes 31, 32, 41, and 42 are formed in the groove 2a, and the other piezoelectric plates 2 are formed.
The surface is kept clean when the mask is removed. The electrode pad P to which a bonding wire instead of the lead wire L is to be connected is formed simultaneously with the groove 2a in the above-described electrode forming step.

An advantage of the manufacturing method of this modification is that the grooves 2a and the electrodes 31, 32, 41, 42 are formed by using reactive ion etching and sputtering, so that a large number of piezoelectric plates 2 can be formed at one time. It can be processed and mass production is facilitated. (Formation of Electrode Pad of Example 1) The electrode pad P
D, it can be formed by film formation of aluminum, silver, gold, nickel or the like by sputtering, vapor deposition or electroless plating. Therefore, as described above, the electrodes 31, 32,
When forming 41 and 42 by these processing methods, it is reasonable to form them simultaneously. The electrode pad P for film formation can be connected to a voltage source by wire bonding.

(Modification of Embodiment 1) In the piezoelectric actuator 1 of Embodiment 1 described above, the piezoelectric plate 2 was bonded to only one surface of the elastic plate 5 as in the unimorph, but the elastic plate was bonded in the same manner as in the bimorph. A modification in which the piezoelectric plates 2 are respectively bonded to both surfaces of the plate 5 is also possible. According to the piezoelectric actuator of this modification, there is an effect that the generated force can be doubled as compared with the piezoelectric actuator 1 described above.

Embodiment 2 (Structure of Embodiment 2) As shown in FIGS. 8 and 9, a piezoelectric actuator 1 'as Embodiment 2 of the present invention is a single disk-shaped stainless steel thin plate. And two piezoelectric plates 2 'bonded to the front and back surfaces of the elastic plate 5 with a conductive adhesive, respectively. The piezoelectric plate 2 is a thin plate made of PZT similarly to the first embodiment, and has a disk shape having a diameter slightly smaller than that of the elastic plate 5.

The two piezoelectric plates 2 'are divided into two sections as shown in FIG. 8, and these two sections correspond to the front and back sides of the two piezoelectric plates 2'. Piezoelectric plate 2 '
Is a plurality of first electrodes 3 forming a pair for each section.
1 ′ and a second electrode 32 ′. Further, each piezoelectric plate 2 has a first common electrode 41 ′ connecting each first electrode 31 ′ in each section, and a second common electrode 42 connecting each second electrode 32 ′ in each section. .

Each of the plurality of first electrodes 31 ′ is formed by drawing a substantially semicircular pattern on the surface of the piezoelectric plate 2 ′, and two first common electrodes 41 ′ are also formed on the surface of the piezoelectric plate 2 ′. It is formed by drawing a pattern in a straight line. On the other hand, the plurality of second electrodes 32 'are also formed by drawing substantially semicircular arc-shaped patterns on the back surface of the piezoelectric plate 2' (the surface joined to the elastic plate 5 '), and the two second common electrodes 42' are formed. Also, a pattern is drawn linearly on the back surface of the piezoelectric plate 2 '.

That is, as shown in FIG. 9, the first electrode 31 ′ and the second electrode 32 ′ are alternately formed in two comb-tooth-like shapes facing each other in the thickness direction of each piezoelectric plate 2 ′. It is arranged in. The first electrode 31 'and the first common electrode 41' are connected to lead wires by electrode pads (not shown) formed for each section. On the other hand, the second
The electrode 32 'and the second common electrode 42 are connected to the elastic plate 5 via a conductive adhesive, and further connected to another lead wire (not shown) via the elastic plate 5. Therefore, there is no need for the second common electrode 42 ', and the second common electrode 42' can be omitted.

The piezoelectric material sandwiched between the first electrode 31 'and the second electrode 32' is the second piezoelectric material on the upper piezoelectric plate 2 'in FIG.
It is polarized in the in-plane direction of the piezoelectric plate 2 'from the electrode 32' to the first electrode 31 '. On the other hand, the piezoelectric material forming the lower piezoelectric plate 2 'in FIG.
Polarized in the direction of the electrode 32 '. (Effects of Embodiment 2) The piezoelectric actuator 1 'of this embodiment has two electrodes 3 formed in two piezoelectric plates 2'.
Since 1 'and 32' are divided into two sections on the left and right as shown in FIG. 10A, each section can be controlled separately. At this time, the piezoelectric plate 2 ′, the second electrode 32 ′, and the second common electrode 42 ′ are grounded via the ground wire 8. On the other hand, the piezoelectric plates 2 ′ on the front and back of the section on the right half surface in FIG.
The first electrode 31 ′ is connected to the circuit 4 ′, and can be connected to the positive drive power supply 7 via the switch 6. On the other hand, the first electrodes 31 'of the piezoelectric plates 2' on the front and back sides of the left half section in the figure are connected to another circuit 4 ', and are further connected to a negative drive power supply 7' via a switch 6 '. Can.

That is, as shown in FIG. 10B, when the switch 6 is closed and a positive voltage is applied only to the circuit 4 'in the right section in the figure, only the right half surface of the piezoelectric actuator 1' is raised. It bends convexly and deforms. Further, FIG.
When the switch 6 'is closed and a negative voltage is applied only to the circuit 4' in the left section in the figure, the left half surface of the piezoelectric actuator 1 'is bent downward and deformed.

As described above in detail, in the piezoelectric actuator 1 'of the present embodiment, the paired electrodes 31' and 32 'are divided into two sections, so that the two sections can be controlled separately. This has the effect. Further, since the piezoelectric plates 2 'are bonded to both surfaces of the elastic plate 5', the piezoelectric actuator 1 having a configuration in which the piezoelectric plate 2 is provided only on one side of the elastic plate 5 as in the first embodiment is similar to the bimorph for the unimorph. In comparison, there is also an effect that the generation force can be doubled.

(Manufacturing Method of Embodiment 2) The piezoelectric actuator 1 'of this embodiment is obtained by applying the manufacturing method of Modification 1 or Modification 2 of the manufacturing method of Embodiment 1 to the front and back of the piezoelectric plate 2'. By carrying out, it can be manufactured. Differences in the features and advantages of each manufacturing method are also the same as those in each variation of the first embodiment.

The electrodes 31 'on the front and back of the piezoelectric plate 2',
The alignment of 32 'can be easily and precisely performed by applying a microfabrication technique of an integrated circuit such as an LSI. (Modification 1 of Example 2) A conductive paste is printed on each surface of each piezoelectric plate 2 ′ for each section and baked to form a conductive metal (for example, silver) film, thereby forming each section. It is possible to replace the electrode pad of the second embodiment entirely. That is, in the present modification, the elastic plate 5 'and the conductive film in each section can be used as the common electrode.

Therefore, in this modification, the first common electrode 4
The 1 ′ and second common electrodes 42 ′ are not required, and the groove forming process can be simplified. Therefore, according to this modification, the conductive film in each section also acts as a common electrode, and in addition to the effect of the first embodiment, the possibility of poor conduction of the first electrode 31 'is reduced, and the reliability is improved. There is an effect of doing.

(Modification 2 of Embodiment 2) In Embodiment 2,
The piezoelectric plate 2 'is divided into two sections and both electrodes 31', 3
Although 2 'has been arranged, a modified mode in which it is divided into three or more sections is also possible, and the way of dividing the sections may be concentric. For example, when the outer peripheral portion of the elastic plate 5 'is rigidly fixed, the disk-shaped piezoelectric plate 2' is concentrically partitioned into two portions, an inner peripheral portion and an outer peripheral portion, and one of the two partitions is provided. A modification in which an applied voltage is applied to the other side is also possible. In this modification, since the inner and outer peripheral portions have opposite curvatures, there is an effect that both the generated force and the maximum displacement of the piezoelectric actuator are increased.

Embodiment 3 (Manufacturing Method of Embodiment 3) As shown in FIG. 11, a piezoelectric actuator 1 ″ according to Embodiment 3 of the present invention is joined to one side (or both sides) of an elastic plate 5 ″. Piezoelectric plate 2 "
Then, a double spiral pattern is drawn on the surface to form the first electrode 31 ″.
And the second electrode 32 ". The elastic plate 5"
Is a disk-shaped thin plate made of an insulating material such as glass, and a groove for accommodating the electrodes 31 "and 32" is formed over almost the entire thickness of the elastic plate 5 ". The first electrode 31 ″ and the second electrode 32 ″ are formed adjacent to each other at a very narrow predetermined interval, and
One end of each of 1 "and 32" is exposed with a predetermined area on the outer peripheral surface of the disk-shaped piezoelectric plate 2 ".

On the surface of the elastic plate 5 "adjacent to the exposed portion, electrode pads P" having a predetermined area are formed by vapor deposition or sputtering. The exposed portions of the electrodes 31 "and 32" on the outer peripheral surface of the piezoelectric plate 2 "and the electrode pads P"
Are electrically conductive with each other by a conductive resin (or a conductive paste or a conductive adhesive). The electrode pad P "
A bonding wire or lead wire (not shown) is connected.

The direction of polarization of the piezoelectric material of the piezoelectric plate 2 ″ is the same as in the above-described first and second embodiments. (Operation and effect of the third embodiment) According to this embodiment, the piezoelectric plate 3 '
Since the whole acts in piezoelectric constant d ₃₃ of the piezoelectric material, that while it can be driven at a low voltage, generated force compared to the unimorph or bimorph prior art has doubled, also improved several percent maximum displacement effective.

(Manufacturing Method of Third Embodiment) The piezoelectric actuator 1 ″ of the present embodiment is obtained by implementing the manufacturing method of the first or second modification of the manufacturing method of the first embodiment.
Can be manufactured. Differences in the features and advantages of the respective manufacturing methods are the same as those of the respective modifications of the manufacturing method of the first embodiment. (Modification of Embodiment 3) In this embodiment, similarly to Embodiment 2, the elastic plate 5 "is formed of a conductive spring elastic material such as stainless steel, and each of the electrodes 31" and 32 "is made of the piezoelectric plate 2". A modification is possible in which both sides are alternately formed in a comb tooth shape. In this modification, the back surface of the piezoelectric plate 2 "is joined to the conductive elastic plate 5" with a conductive adhesive, and a conductive film is formed on the entire surface of the piezoelectric plate 2 ". The elastic plate 5 "and the conductive film are provided on the respective electrodes 31", 32 ".
Respectively, and a lead wire or a bonding wire is connected to each of the elastic plate 5 ″ and the conductive film. Therefore, the electrode pad P ″ is not necessary for this modification. Here, the conductive film can be formed by a method such as printing and baking of a conductive paste, vapor deposition, CVD, and sputtering.

According to this modification, the elastic plate 5 "and the conductive film act as common electrodes which are electrically connected to the whole of the electrodes 31" and 32 ", respectively. In addition, it is difficult to cause a conduction failure between the driving power supply circuit and the electrodes 31 "and 32", and there is no problem even if the electrodes 31 "and 32" are disconnected in the middle, so that the reliability is improved as compared with the third embodiment. effective.

The piezoelectric actuator 1 "of this modified embodiment can be manufactured by the same manufacturing method as that of the embodiment 2. Further, the electrodes 31", 31 ",
The alignment of 32 "can be easily and precisely performed by applying a microfabrication technique of an integrated circuit such as an LSI.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a shape of a piezoelectric actuator according to a first embodiment.

FIG. 2 is a cross-sectional view illustrating a configuration of a piezoelectric actuator according to the first embodiment.

FIG. 3 is a sectional view showing the polarization direction and both electrodes of the piezoelectric plate according to the first embodiment.

FIG. 4 is a set diagram showing the operation of the piezoelectric actuator according to the first embodiment; (a) a sectional view showing a shape without applied voltage; and (b) a sectional view showing a shape with applied voltage.

FIG. 5 is a perspective view showing connection of a lead wire to the piezoelectric actuator according to the first embodiment.

FIG. 6 is a schematic view showing a groove forming step by laser processing.

FIG. 7 is a schematic view showing a groove forming step by reactive ion etching.

FIG. 8 is a perspective view showing the shape of a piezoelectric actuator according to a second embodiment.

FIG. 9 is a cross-sectional view illustrating a configuration of a piezoelectric actuator according to a second embodiment.

FIG. 10 is a set diagram showing the operation of the piezoelectric actuator according to the second embodiment. (A) A cross-sectional view showing a shape without an applied voltage. (B) A cross-sectional view showing a shape with a partially applied voltage. (C) A cross-sectional view showing a shape in a state where an applied voltage is present over the entire surface.

FIG. 11 is a perspective view showing the shape of a piezoelectric actuator according to a third embodiment.

FIG. 12 is a perspective view showing the shape of a conventional piezoelectric unimorph.

FIG. 13 is a set diagram showing the operation of a piezoelectric unimorph as a conventional technique. (A) Cross-sectional view showing a shape without applied voltage. (B) Cross-sectional view showing a shape with applied voltage.

[Explanation of symbols]

1, 1 ', 1 ": piezoelectric actuator 2, 2', 2": piezoelectric plate 2a, 2a ': groove 31, 31', 31 ": first electrode 32, 32 ', 3
2 ″: second electrode 41, 41 ′: first common electrode 42, 42 ′: second common electrode 5, 5 ′, 5 ″: elastic plate 6, 6 ′: switch 7, 7 ′: drive power source (relatively low voltage) 8: grounding wire 9: pure water 10: infrared laser 11: laser beam focusing optics 12: electrode substrate 13: a vacuum chamber 14: the field coil 15: high-frequency power source 16: vacuum evacuation system 17: plasma d _31, d ₃₃ : piezoelectric constant L: lead wire P, P ':
Electrode pad P1: piezoelectric unimorph (prior art) P2: piezoelectric plate P3: electrode P5: disc-shaped elastic plate P6: switch P7: drive power supply (relatively high voltage)

Claims (9)

[Claims] 1. An elastic plate which is a thin plate having spring elasticity, a piezoelectric plate which is a thin plate made of a piezoelectric material joined to at least one surface of the elastic plate, and is spaced apart by a thickness equal to or less than the thickness of the piezoelectric plate. A plurality of grooves formed in the piezoelectric plate are filled with a conductive material, and a first electrode and a second electrode formed of the conductive material adjacent to each other across the piezoelectric material, A piezoelectric actuator, comprising: 2. The piezoelectric actuator according to claim 1, wherein said groove accommodating said first electrode and said second electrode is opened on a surface of said piezoelectric plate facing away from said elastic plate. 3. The piezoelectric element according to claim 1, wherein the first electrode and the second electrode are alternately arranged in a comb-like shape in a face of the piezoelectric plate in a thickness direction of two opposing combs. Piezo actuator. 4. The piezoelectric device according to claim 1, wherein the first electrode and the second electrode are alternately arranged in a plane parallel to the surface of the piezoelectric plate in a tooth shape of two opposing combs. Piezo actuator. 5. The first electrode and the second electrode are formed in a plane parallel to the surface of the piezoelectric plate, such as a straight line, a bent straight line, an arc shape, and a curved shape including a double helix. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator is disposed in any one of composite shapes. 6. The piezoelectric plate is divided into a plurality of sections, and each of the plurality of the first plates forms a pair with each section.
The piezoelectric actuator according to claim 1, comprising an electrode and the second electrode. 7. A thin plate made of a piezoelectric material joined to or joined to a surface of an elastic plate which is a thin plate having spring elasticity. A groove forming step of forming a groove in the piezoelectric plate; an electrode forming step of filling a conductive material in the groove and forming a first electrode and a second electrode adjacent to each other with the piezoelectric material interposed therebetween; Applying a high voltage between the first electrode and the second electrode to polarize the piezoelectric material sandwiched between the two electrodes. Actuator manufacturing method. 8. The method according to claim 7, wherein said groove forming step is a step of forming said groove by any one of dicing, laser processing and reactive ion etching. 9. The electrode forming step is a step of forming the first electrode and the second electrode by any one of CVD, sputtering, printing of a conductive paste, electroless plating, and vapor deposition. Item 8. The method for manufacturing a piezoelectric actuator according to Item 7.