JPH10190086A - Piezo-electric/electrostrictive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To greatly expand the amount of relative displacement in a voltage non-load state and a voltage application state or the amount of relative displacement in a field applied state in the reverse direction mutually and contrive to enhance the easiness of control when it is used as an actuator or improve the sensibility in the case when it is used as a sensor. SOLUTION: A piezo-electric/electric-strain device is provided with a piezo- electric/electrostrictive layer 20, an actuator main body 24 having a pair of electrodes 22a and 22b formed on one main surface of the piezo-electric/ electrostrictive layer 20a, a vibrating part 16 which is faced with the other main surface of the piezo-electric/electrostrictive layer 20 and supports the actuator body 24 and a unimorph type actuator 12 having a fixing part 18 which supports the vibrating part 16 so that it may vibrate. In this case, there are established the following relationship that y=ax while the following relation that 1/10<=a<=100, assuming that the distance between the paired electrodes 22a and 22b is X where (1μm<=x<=200μm and the thickness of the piezo-electric/ electrostrictive layer 20 is y where 1μm<=y<=100μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a piezoelectric / electrostrictive element,
Actuators, filters, displays, transformers,
The present invention relates to a microphone, a sounding body (such as a speaker), various vibrators, a resonator, an oscillator, a discriminator, and a unimorph type piezoelectric / electrostrictive element used for a gyro, a sensor, and the like. The element referred to here is:
It includes an element that converts electrical energy into mechanical energy, that is, an element that converts mechanical energy into mechanical displacement, force, or vibration, as well as an element that performs the reverse conversion.

[0002]

2. Description of the Related Art In recent years, in the fields of optics and precision machining, a displacement element for adjusting an optical path length and a position on the order of submicrons and a detection element for detecting a minute displacement as an electrical change have been desired. Is coming.

[0003] In response to this, an actuator utilizing the development of displacement based on the inverse piezoelectric effect which occurs when an electric field is applied to a piezoelectric material such as a ferroelectric substance, and a sensor utilizing the opposite phenomenon (piezoelectric effect). The development of a piezoelectric / electrostrictive element used for such purposes is underway.

[0004] Among them, in a speaker or the like, a conventionally known unimorph type is suitably adopted as such a piezoelectric / electrostrictive element structure.

[0005] For this reason, even the applicant of the present invention has previously disclosed in Japanese Patent Application Laid-Open Nos. 3-128681 and 5-49270 a ceramic piezoelectric / electrode which can be suitably used for various applications. A strain film type device was proposed.

The piezoelectric / electrostrictive film type element according to this proposal example is
As shown in FIG. 30, at least one window (vacant space) 1
By providing the thin vibrating part 102 integrally so as to cover the at least one thin wall, at least one thin wall part (ie,
A vibrating part 102) is formed on the ceramic base 104, and a piezoelectric / electrode comprising a combination of a lower electrode 106, a piezoelectric / electrostrictive layer 108, and an upper electrode 110 is formed on the outer surface of the vibrating part 102 of the ceramic base 104. Strain operating unit 1
12 are integrally laminated by a film forming method. In the ceramic substrate 104, the space 10
Portions other than 0 function as fixed portions 114 that support the vibrating portion 102.

The piezoelectric / electrostrictive element according to the above proposed example is a small, inexpensive, highly reliable electromechanical transducer,
It has excellent features that a large displacement can be obtained with a low driving voltage, a high response speed, and a large generating force, and is useful as a constituent member of an actuator, a filter, a display, a sensor, and the like.

[0008]

By the way, the piezoelectric /
In the electrostrictive element, the configuration of the piezoelectric / electrostrictive operating section 112 is such that the upper electrode 110 and the lower electrode 106
Is formed in a so-called sandwich structure. The piezoelectric / electrostrictive operating section 112 and the vibrating section 1 having this sandwich structure
When the bending displacement characteristics of the piezoelectric / electrostrictive element main body composed of the piezoelectric element 02 and the fixed portion 114 are viewed, as shown in FIG. 31B, the positive and negative directions of the electric field center around the reference electric field point (point of electric field E = 0). Is symmetrical.

Here, the bending displacement is when the piezoelectric / electrostrictive element body is displaced in a convex shape in one direction (the direction in which the upper electrode 110 formed on the piezoelectric / electrostrictive layer 108 faces free space). Is defined as the positive direction, and the case where it is displaced concavely is defined as the negative direction.

The displacement characteristic is obtained by applying a predetermined voltage between the upper electrode 110 and the lower electrode 106 and applying a voltage to the piezoelectric / electrostrictive layer 108.
After the polarization process, the voltage applied between the upper electrode 110 and the lower electrode 106 was continuously changed so that the electric field applied to the piezoelectric / electrostrictive element became, for example, an electric field of + 3E → −3E → + 3E. In this case, the displacement of the piezoelectric / electrostrictive element main body is observed.

That is, first, a polarization electric field (for example, + 5E) is applied to the piezoelectric / electrostrictive element in the positive direction to polarize the piezoelectric / electrostrictive layer 108, and then, between the upper electrode 110 and the lower electrode 106. Is stopped and the voltage is not loaded. Simultaneously with the start of the measurement, a sine wave having a frequency of 1 Hz and a peak value of ± 3E (see FIG. 31A) is applied to the piezoelectric / electrostrictive element, and the displacement amount at each point (points A to D) at that time is determined by laser displacement. Measure continuously using a meter. FIG. 31B is a characteristic diagram in which the measurement result at that time is plotted on an electric field-bending displacement graph. As indicated by the arrow in FIG. 31B, the displacement amount of the bending displacement changes continuously due to the continuous increase and decrease of the electric field.

More specifically, assuming that the measurement is started from the electric field + 3E, first, as shown in FIG. 32A, an electric field is applied to the piezoelectric / electrostrictive element in the same direction as the polarization direction. The / electrostrictive layer 108 extends in the direction between the upper electrode 110 and the lower electrode 106, and the upper electrode 110 and the lower electrode 1
Shrinkage occurs in a direction parallel to 06. As a result, the entire piezoelectric / electrostrictive element is displaced in the negative direction by about 0.9Δy.

Thereafter, when the electric field is changed from + 3E to -0.5E, the displacement gradually decreases. When the electric field is in the negative direction, as shown in FIG. 32B, an electric field is applied in a direction opposite to the direction of polarization.
Elongation occurs in a direction parallel to the upper electrode 110 and the lower electrode 106, and the displacement changes in the positive direction.

Next, when the electric field is changed from -0.5E to -3E, the direction of polarization gradually starts to be inverted. That is, the direction of the electric field and the direction of the polarization start to be aligned. FIG.
It is considered that the polarization is almost completely reversed at point c among points B → point c → point C of B. The reason is that no hysteresis is observed between point c and point C.

Then, as shown in FIG. 33A, when the direction of the electric field and the direction of the polarization are aligned, the piezoelectric / electrostrictive layer 1 is formed.
08 changes from a state of extending in the horizontal direction to a state of contracting. At the stage when the electric field becomes -3E, the amount of displacement is almost the same as the amount of displacement (0.9Δy) at the start of measurement.

That is, when the polarization direction and the electric field direction match, the piezoelectric / electrostrictive layer 108 contracts in the direction parallel to the electrodes 110 and 106 (extends in the direction between the electrodes 110 and 106).
That is, the states of the points A and C correspond to each other. When the polarization direction and the electric field direction are opposite to each other, the piezoelectric / electrostrictive layer 108 extends in the direction parallel to the electrodes 110 and 106 (shrinks in the direction between the electrodes 110 and 106). The state of D corresponds. Note that 1E = about 1.7 kV / mm and 1Δy = about 1.6 μm.

Thereafter, when the electric field is changed from -3E to + 0.5E, the amount of displacement gradually decreases, and when the electric field becomes positive, as shown in FIG. 33B, the electric field is changed in the direction opposite to the polarization direction. Therefore, the piezoelectric / electrostrictive layer 108 expands in a direction parallel to the upper electrode 110 and the lower electrode 106, and the displacement changes in the positive direction.

When the electric field is changed from + 0.5E to + 3E, the direction of polarization gradually starts to be reversed, and the direction of the electric field and the direction of polarization are aligned. It changes from a state of extending horizontally to a state of contracting.

As described above, in the conventional piezoelectric / electrostrictive element, the bending displacement characteristic is symmetrical with respect to the reference electric field point (electric field E = 0) in the positive and negative directions of the electric field. , The relative displacement between the no-load state and the applied voltage state,
The relative amount of displacement when electric fields in opposite directions are applied to each other is small, for example, the amount of displacement when used as an actuator by the inverse piezoelectric effect may be small, and the sensitivity when used as a sensor by the piezoelectric effect may be low. is there.

Therefore, when the piezoelectric / electrostrictive element is used as an actuator, it may be difficult to control the actuator. When the piezoelectric / electrostrictive element is used as a sensor,
After that, it is necessary to connect a high-priced amplifier having a large amplification factor and taking noise suppression into consideration.

This problem is particularly caused by the use of a large number of piezoelectric / electrostrictive element bodies and the need to keep the quality of each piezoelectric / electrostrictive element body constant, for example, a large number of piezoelectric / electrostrictive elements corresponding to pixels. When a display device configured by arranging the electrostrictive element bodies is manufactured, there is a possibility that it becomes very disadvantageous.

The present invention has been made in consideration of such problems, and has been made to reduce the relative displacement between a state where no voltage is applied and a state where a voltage is applied, and the amount of relative displacement when applying electric fields in opposite directions. It is an object of the present invention to provide a piezoelectric / electrostrictive element which can be greatly expanded, and which can realize easy control when used as an actuator and improved sensitivity when used as a sensor.

[0023]

According to a first aspect of the present invention, there is provided a piezoelectric / electrostrictive element comprising a piezoelectric / electrostrictive layer and a pair of electrodes formed on one main surface of the piezoelectric / electrostrictive layer. A piezoelectric / electrostrictive operating section, a vibrating section that is in contact with the other main surface of the piezoelectric / electrostrictive layer and supports the piezoelectric / electrostrictive operating section, and a fixing section that supports the vibrating section so that it can vibrate. In a piezoelectric / electrostrictive element provided with a unimorph type piezoelectric / electrostrictive element main body, the bending displacement characteristic of the piezoelectric / electrostrictive element main body due to an applied electric field of four times or more of a predetermined electric field between the pair of electrodes is changed to a reference electric field. It is configured to be asymmetric about the point.

The bending displacement characteristic is obtained by applying a voltage for polarization between a pair of electrodes in the piezoelectric / electrostrictive operating section to polarize the piezoelectric / electrostrictive layer, and then applying an electric field applied to the piezoelectric / electrostrictive element. The bending displacement of the piezoelectric / electrostrictive element body when the voltage applied between the pair of electrodes is continuously changed so as to change alternately is obtained. / Positive direction when the electrostrictive element body is displaced convexly in one direction (direction in which a pair of electrodes formed on the piezoelectric / electrostrictive layer faces free space), and negative direction when displaced concavely. And Here, the predetermined electric field refers to an electric field in which the direction of polarization of a portion near one main surface (surface) of the piezoelectric / electrostrictive layer is reversed by application of a reverse electric field.

Specifically, for example, when a predetermined voltage is applied between a pair of electrodes in a positive direction, for example, in order to polarize the piezoelectric / electrostrictive layer, a positive direction in a plane direction is applied to one main surface of the piezoelectric / electrostrictive layer. Electric field is generated. The strength of the electric field generated in the piezoelectric / electrostrictive layer is greatest on the one main surface and gradually decreases in the depth direction. The generation of the electric field in the positive direction causes the piezoelectric / electrostrictive layer to be polarized in the same direction as the electric field. Thereafter, for example, the application of the voltage between the pair of electrodes is stopped, and the state is set to the no-load state.

Then, the voltage applied between the pair of electrodes is continuously changed so that the electric field applied to the piezoelectric / electrostrictive element changes alternately. At this time, for example, at a stage where the electric field is generated in the same direction as the direction of the electric field generated during the polarization process (for example, the positive direction), the polarization direction in the piezoelectric / electrostrictive layer matches the direction of the electric field, and Since a strong electric field is applied near the surface of the electrostrictive layer, the piezoelectric / electrostrictive layer extends in the horizontal direction. This allows the piezoelectric /
It is considered that the electrostrictive element body is displaced in one of the one direction and the other direction.

Thereafter, at the stage where the voltage applied between the pair of electrodes changes and an electric field is generated in the piezoelectric / electrostrictive element in a direction opposite to the direction of the electric field during the polarization process, the following is performed. Function.

First, when the electric field is weak, the direction of polarization of the piezoelectric / electrostrictive layer and the direction of the electric field are opposite to each other, and the piezoelectric / electrostrictive layer contracts in the horizontal direction. As a result, the piezoelectric / electrostrictive element body is bent and displaced in the other direction. Thereafter, when the electric field becomes stronger, the polarization of the surface portion of the piezoelectric / electrostrictive layer starts to be inverted, and near the surface of the piezoelectric / electrostrictive layer, the direction of the polarization matches the direction of the electric field. In a deep part, a phenomenon occurs that the direction of polarization and the direction of electric field are reversed. That is, in the piezoelectric / electrostrictive layer, two types of polarization exist, and a pseudo bimorph type piezoelectric /
It will function as an electrostrictive element.

As a result, the directions of distortion in the portion near one main surface of the piezoelectric / electrostrictive layer and the portion near the vibrating portion are opposite to each other, and as a whole, one direction (formed on the piezoelectric / electrostrictive layer) The pair of electrodes is displaced in a convex shape in the direction facing the free space), and the amount of displacement is extremely large due to the pseudo bimorph-like action.

In particular, according to the present invention, since the displacement characteristics are asymmetrical in the positive and negative directions of the electric field with respect to the reference electric field point, for example, two peak values of the periodically changing electric field are obtained. A difference occurs in each bending displacement amount. As a result, the relative displacement between the voltage-unloaded state and the voltage-applied state and the relative displacement when the electric field in the opposite direction is applied are increased, and the control when the piezoelectric / electrostrictive element is used as an actuator is increased. It is possible to realize easiness and improvement in sensitivity when used as a sensor.

When the piezoelectric / electrostrictive element is used for an actuator, a sensor, or the like, when an electric field of four times or more of two predetermined electric fields having the same absolute value and different directions is applied with respect to the reference electric field point. When the bending displacement amounts are A and B, it is preferable to have a relationship of A ≧ 1.5B (the invention according to claim 2). According to this relationship, it is possible to obtain a characteristic that is asymmetrical about the reference electric field point as the bending displacement characteristic, and it is easy to control when the piezoelectric / electrostrictive element is used as an actuator, and the sensitivity when the sensor is used as a sensor. The improvement can be reliably realized.

Next, according to the third aspect of the present invention,
An electrostriction element having a piezoelectric / electrostrictive layer having a piezoelectric / electrostrictive layer and a pair of electrodes formed on one main surface of the piezoelectric / electrostrictive layer;
A unimorph type piezoelectric / electrostrictive element main body including a vibrating portion that contacts the other main surface of the piezoelectric / electrostrictive layer and supports the piezoelectric / electrostrictive operating portion, and a fixed portion that supports the vibrating portion so as to vibrate. And the distance between the pair of electrodes is x (1 μm ≦ x ≦
200 μm), and the thickness of the piezoelectric / electrostrictive layer is set to y (1 μm ≦
y ≦ 100 μm), there is a relation of y = ax,
In addition, it is configured such that 1/10 ≦ a ≦ 100.

In this case, the displacement characteristic of the piezoelectric / electrostrictive element body due to the applied electric field between the pair of electrodes is such that the displacement characteristic is as shown in the first aspect of the present invention, that is, the displacement characteristic is asymmetric about the reference electric field point. Characteristics can be obtained. for that reason,
In the piezoelectric / electrostrictive element according to the third aspect of the present invention, as in the case of the piezoelectric / electrostrictive element according to the first aspect, ease of control when the piezoelectric / electrostrictive element is used as an actuator, An improvement in sensitivity when used as a sensor can be realized.

In the invention according to any one of claims 1 to 3, the vibrating portion and the fixed portion are integrally formed of ceramics, and a void is formed at a position corresponding to the vibrating portion. If the vibrating portion is made thin (the invention according to claim 4), the fixed portion and the vibrating portion can be easily manufactured, and the manufacturing cost of the piezoelectric / electrostrictive element can be reduced. The above is advantageous.

Further, since a thick fixed portion and a thin vibrating portion are formed by providing a space in the ceramic base, the vibrating portion is sensitive to the displacement of the piezoelectric / electrostrictive layer. In response to the change of the voltage signal, it is possible to form a vibrating portion having a high followability to a change in the voltage signal. In addition, since the rigidity of the boundary between the vibrating part and the fixed part is sufficiently ensured, the boundary part due to the vibration of the vibrating part hardly breaks due to fatigue.

In the above construction, it is preferable that 1 / 5≤a≤10 (the invention according to claim 5), and 1 / 2≤a
≦ 5 and 1 μm ≦ x ≦ 60 μm, 1 μm ≦ y
It is more preferred that ≦ 40 μm (the invention according to claim 6).

Further, in the above structure, when the thickness of the vibrating portion is z (1 μm ≦ z ≦ 50 μm), the relationship y = bz is satisfied, and 1/5 ≦ b ≦ 10. 7
Described invention), it is possible to increase the amount of bending displacement.

In the above structure, it is preferable that 1 / 3≤b≤5 (the invention of claim 8), and 1 / 3≤b≤
5 and 1 μm ≦ y ≦ 40 μm, 1 μm ≦ z ≦
It is more preferable that the thickness be 20 μm (the invention according to claim 9).

Further, in the above-mentioned structure, if the cross-sectional shape in the shortest dimension passing through the center of the vibrating part satisfies the following condition in the state of no voltage load (claim 10).
The displacement characteristics of the piezoelectric / electrostrictive element main body due to an applied electric field between the pair of electrodes are asymmetrical about a reference electric field point, similar to the piezoelectric / electrostrictive element according to claim 1, It is possible to realize easiness of control when the piezoelectric / electrostrictive element is used as an actuator, and improvement in sensitivity when used as a sensor.

In addition, the produced piezoelectric / electrostrictive main body can be always subjected to a large bending displacement in one direction, and an improvement in the yield when used in various electronic devices and the like can be achieved.

(1) An upper surface near the center of the piezoelectric / electrostrictive layer is defined by a reference line formed by connecting one outermost minimum point and the other outermost minimum point close to the fixed portion. At least a part thereof projects in a direction opposite to the vibrating section.

(2) When the outermost minimum point does not exist,
A point corresponding to a boundary point with the fixed portion on the upper surface of the vibrating portion along the shortest dimension is defined as an outermost minimum point.

(3) Assuming that the boundary between the vibrating portion and the fixed portion is point 0, and the shortest dimension length of the vibrating portion is 100, the outermost minimum point is the shortest point in the vibrating portion from the point 0. When the length is not within the range of 40% of the dimension length, a point corresponding to a boundary point with the fixed portion on the upper surface of the vibrating portion along the shortest dimension is set as an outermost minimum point.

In particular, in the invention according to the tenth aspect, it is more preferable that the protrusion amount t satisfies m / 1000 ≦ t ≦ m / 10 (the invention according to the eleventh aspect).

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a piezoelectric / electrostrictive element according to the present invention (hereinafter simply referred to as a piezoelectric / electrostrictive
An electrostrictive element will be described with reference to FIGS. 1 to 19, and an example in which the piezoelectric / electrostrictive element according to the present embodiment is applied to a display device (hereinafter, a display device according to an example and Will be described with reference to FIGS.

First, as shown in FIG. 1, the piezoelectric / electrostrictive element according to the present embodiment has a base 10 made of ceramics, for example, and an actuator section 12 is arranged at a predetermined position on the base 10. Has been established. The base 10 has one main surface as a continuous surface (the same surface), and the other main surface has a concave portion 14 at a position corresponding to the actuator section 12.

That is, the portion of the substrate 10 where the concave portion 14 is formed is made thin, and the other portions are made thick. The thin portion has a structure that is susceptible to vibration against external stress and functions as the vibrating portion 16, and the portion other than the concave portion 14 is thick and functions as the fixing portion 18 that supports the vibrating portion 16. It has become. Although not shown, a wiring substrate is bonded to the other main surface of the base 10. Further, the base 10 may be integrally fired or may be retrofitted.

As shown in FIG. 1, the actuator section 12 includes a piezoelectric / electrostrictive layer 20 formed directly on the vibrating section 16 in addition to the vibrating section 16 and the fixed section 18.
It has an actuator section main body 24 having a pair of electrodes (one electrode 22 a and the other electrode 22 b) formed on the upper surface of the electrostrictive layer 20.

Here, the shape of each member will be described with reference to FIGS. First, as shown in FIG. 3, the peripheral surface shape of the concave portion 14 formed on the other main surface of the base 10, that is, the planar shape of the vibrating portion 16 is, for example, circular (see the broken line). The planar shape (dotted line) and the outer peripheral shape (see the solid line) formed by the pair of electrodes 22a and 22b are also circular. In this case, the size of the vibrating part 16 is the largest, and then the pair of electrodes 22
a and 22b, and the planar shape of the piezoelectric / electrostrictive layer 20 is set to be the smallest. Note that the pair of electrodes 22a and 22b may be set so that the outer peripheral shape is maximized.

The planar shape of the pair of electrodes 22a and 22b formed on the piezoelectric / electrostrictive layer 20 is such that the pair of electrodes 22a and 22b are parallel to each other and separated from each other, as shown in FIG. It is a spiral of several turns. The number of turns of the spiral is actually five or more, but in the example of FIG. 4, it is described as three turns in order to avoid complication of the drawing.

The planar shape of the pair of electrodes 22a and 22b may be a shape shown in FIG. 5 in addition to the spiral shape shown in FIG. Specifically, a pair of electrodes 2
2a and 22b are both stems 26 and 28 extending toward the center on the piezoelectric / electrostrictive layer 20;
8, and a shape in which a pair of electrodes 22a and 22b are spaced apart from each other and arranged in a complementary manner (hereinafter referred to as a multi-branched shape for convenience). It may be.

In the above example, the planar shape of the vibrating section 16, the planar shape of the piezoelectric / electrostrictive layer 20, and the pair of electrodes 22a and 22a
Although the case where the outer peripheral shape formed by 2b is a circular shape is shown, an elliptical shape (see FIGS. 22 and 23) or an elliptical shape (see FIG. 24) may be used. Also, the vibrating section 1
6 and the piezoelectric / electrostrictive layer 20 may both have a rectangular shape, with corners having rounded corners (see FIG. 25), or the planar shape and the piezoelectric / electrostrictive The plane shape of the layer 20 may be both polygonal (octagonal in the example of FIG. 26), and each vertex may be rounded.

The shape of the vibrating part 16 and the piezoelectric / electrostrictive layer 2
0, the outer peripheral shape formed by the pair of electrodes 22a and 22b may be a combination of a circle and an ellipse,
A combination of a rectangle and an ellipse may be used, and there is no particular limitation.

As shown in FIGS. 6 and 7, the planar shape of the piezoelectric / electrostrictive layer 20 is preferably ring-shaped (hollow). Also in this case, FIGS.
As shown in FIG. 7, various shapes such as a circle, an ellipse, and a rectangle can be given as the outer peripheral shape. FIG. 8 shows an example in which the planar shape of the piezoelectric / electrostrictive layer 20 is annular, and the pair of electrodes 22a and 22b is multi-branched.

By making the planar shape of the piezoelectric / electrostrictive layer 20 into a ring shape, it is not necessary to form an electrode in a hollow portion, so that the capacitance can be reduced without reducing the amount of displacement.

Next, the operating principle of the piezoelectric / electrostrictive element according to the present embodiment will be described with reference to FIGS.

First, in the piezoelectric / electrostrictive element according to the present embodiment, as shown in FIG. 10B, the bending displacement characteristic of the actuator section 12 due to the electric field applied between the pair of electrodes 22a and 22b is changed to a reference electric field point ( (The point of the electric field E = 0).

This bending displacement characteristic is obtained by applying a predetermined voltage between the pair of electrodes 22a and 22b of the actuator section main body 24 to polarize the piezoelectric / electrostrictive layer 20, and then continuously applying the voltage applied to the actuator section 12 to the piezoelectric / electrostrictive layer 20. FIG. 9 shows the bending displacement of the actuator section 12 when changing to. As shown in FIG. 2, the bending displacement in this case means that the actuator portion 12 is convex in one direction (a direction in which the pair of electrodes 22a and 22b formed on the piezoelectric / electrostrictive layer 20 faces free space). The case of bending and displacing in a concave shape is defined as a positive direction, and the case of bending and displacing in a concave shape is defined as a negative direction.

The measurement of the bending displacement characteristic will be specifically described with reference to an example. First, as shown in FIG. 11A,
For example, when a predetermined voltage is applied, for example, in the positive direction between the pair of electrodes 22a and 22b in order to polarize the piezoelectric / electrostrictive layer 20, an electric field in a positive direction in the plane direction on one main surface of the piezoelectric / electrostrictive layer 20 ( For example, the electric field indicated by + 5E in FIG. 10B)
Occurs. Here, 1E = about 2.5 kV / mm.

The intensity of the electric field generated in the piezoelectric / electrostrictive layer 20 is greatest on the one main surface and gradually decreases in the depth direction. Therefore, although the polarization of the deep portion hardly progresses, the polarization can be advanced to the depth direction by applying a sufficient electric field, a sufficient time, and appropriate heat.

Use range of the electric field used as the actuator (for example, the range of + 3E to -3E in FIG. 10B)
For example, by applying an electric field (+ 5E) exceeding the above-mentioned value at an appropriate temperature for 7 hours, polarization processing is performed in the same direction as the applied electric field.

Thereafter, as shown in FIG. 11B, the application of the voltage between the pair of electrodes is stopped to bring the voltage into a no-load state. When the measurement is started, the frequency of 1H is applied to the piezoelectric / electrostrictive element.
A sine wave (see FIG. 10A) with z and a peak value of ± 3E is applied, and the displacement at each point (points A to D) at that time is continuously measured by a laser displacement meter. FIG. 10B is a plot of the measurement results at that time in an electric field-bending displacement graph.
FIG. As shown by the arrow in FIG. 10B, the displacement amount of the bending displacement continuously changes with a certain degree of hysteresis due to the continuous increase and decrease of the electric field.

Specifically, assuming that the measurement is started at the time of the electric field + 3E indicated by the point A, first, at the point A, as shown in FIG. 12A, the polarization direction of the piezoelectric / electrostrictive layer 20 and the direction of the electric field. And the electric field is strongly applied near the surface of the piezoelectric / electrostrictive layer 20, so that the piezoelectric / electrostrictive layer 20 extends in the horizontal direction,
Is about 0.8 in one direction (the direction in which the pair of electrodes 22a and 22b formed on the piezoelectric / electrostrictive layer 20 faces free space).
The bending displacement is as much as Δy (see FIG. 10B). Note that 1Δy
= About 1.6 μm.

Thereafter, when the voltage applied between the pair of electrodes 22a and 22b is changed and an electric field in the direction opposite to the direction of the electric field during the polarization process is generated in the piezoelectric / electrostrictive element, the following steps are taken. The following operation is performed.

First, for example, at a point B (-0.6
At the stage E), as shown in FIG. 12B, the direction of polarization of the piezoelectric / electrostrictive layer 20 and the direction of the electric field are opposite to each other, and the piezoelectric / electrostrictive layer 20 contracts in the horizontal direction. .
As a result, the actuator section 12 moves about −0.0 in the other direction (the direction from the piezoelectric / electrostrictive layer 20 toward the vibrating section 16).
The bending displacement is about 3Δy. In addition, this stage is a stage where the polarization at the surface portion of the piezoelectric / electrostrictive layer 20 starts to be inverted. Therefore, the electric field (−0.6E) at this point B can be defined as a predetermined electric field.

Thereafter, when the electric field in the negative direction becomes stronger, as shown in FIG. 13A, the polarization inversion proceeds on the surface of the piezoelectric / electrostrictive layer 20, and the polarization near the surface of the piezoelectric / electrostrictive layer 20 is increased. And the direction of the electric field coincide with each other, and in a deep portion of the piezoelectric / electrostrictive layer 20, a phenomenon occurs in which the direction of the polarization is opposite to the direction of the electric field. That is, the piezoelectric / electrostrictive layer 20 has two types of polarization, and functions as a pseudo bimorph type piezoelectric / electrostrictive element.
In particular, at the stage when the electric field becomes -3E, the displacement amount of the actuator section 12 becomes very large due to the pseudo bimorph-like action, and in the example of FIG. 10B, the displacement becomes about 2.6Δy. ing.

Next, at the stage where the electric field shifts from the negative direction to the positive direction and the electric field is weak, for example, at point D (+ 0.6E), FIG.
As shown in B, the direction of the polarization and the direction of the electric field are opposite in the vicinity of the surface of the piezoelectric / electrostrictive layer 20, and the direction of the polarization and the direction of the electric field coincide in the deep part of the piezoelectric / electrostrictive layer 20. The piezoelectric / electrostrictive layer 20 shrinks in the horizontal direction near its surface and extends in the horizontal direction at a deep portion.

As a result, the actuator section 12
In the other direction (the direction from the piezoelectric / electrostrictive layer 20 toward the vibrating section 16), the bending displacement is about -1.0Δy. In addition, this stage is a stage in which the polarization at the surface portion of the piezoelectric / electrostrictive layer 20 starts to be inverted. Therefore, the electric field (+
0.6E) can be defined as a predetermined electric field similarly to the point B.

As the electric field in the positive direction gradually increases, the polarization inversion near the surface of the piezoelectric / electrostrictive layer 20 progresses, and the direction of polarization of the piezoelectric / electrostrictive layer 20 matches the direction of the electric field. It will be. Therefore, the stage from point D to point A can also be called a repolarization stage.

As described above, in order to evaluate whether the bending displacement characteristic has symmetry or asymmetry, it is necessary to measure an electric field sufficiently larger than a predetermined electric field (± 0.6E). However, when the measurement is performed with an electric field slightly larger than the predetermined electric field, a case may occur in which the asymmetry, which is a characteristic characteristic of the piezoelectric / electrostrictive element according to the present embodiment, cannot be determined.

Therefore, in order to determine the asymmetry of the bending displacement characteristic, an electric field four times or more the electric field (defined as a predetermined electric field) where the direction of polarization starts to be partially reversed is alternately applied. It is desirable to evaluate the displacement characteristics.
That is, if the measurement is performed with the absolute displacement amount increased, the asymmetry of the bending displacement characteristic can be easily evaluated.

For example, in the piezoelectric / electrostrictive element according to the conventional example, since the coercive electric field is ± 0.5E, the electric field in the positive direction is set to + 2.0E or more and the electric field in the negative direction is set to -2.0E or less. Measurement. Further, in the piezoelectric / electrostrictive element according to the present embodiment, since the coercive electric field is ± 0.6E, the electric field in the positive direction is set to + 2.4E or more and the electric field in the negative direction is set to -2.4E or less. What is necessary is just to measure.

In FIG. 10B, the bending displacement characteristic is measured by alternately applying an electric field (± 3E) sufficiently larger than the predetermined electric field (± 0.6E). In this case, the peak value of the electric field in the positive direction (point The displacement ya in the case A) is 0.8Δy, and the displacement yc at the peak value of the electric field in the negative direction (point C) is 2.
6Δy, and has a relationship of yc = 3.25ya.

Next, the dimensional relationship for providing the bending displacement characteristic with asymmetry will be described. First, the distance x between the pair of electrodes 22a and 22b and the piezoelectric / electrostrictive layer 20
As shown in FIG. 14, when the thickness y of 1 ≦ x ≦ 2
00 μm, 1 ≦ y ≦ 100 μm, and the relation of y = ax is satisfied so that the range of 1/10 ≦ a ≦ 100 is satisfied.

In particular, the proportionality constant a is preferably 1
/ 5 ≦ a ≦ 10, more preferably 1/2 ≦ a ≦
5 In this case, 1 ≦ x ≦ 60 μm, 1 ≦ y ≦ 40
If μm is satisfied, when applying an electric field in the direction opposite to the polarization direction,
The polarization direction of the piezoelectric / electrostrictive layer 20 is easily inverted to an appropriate depth, and the displacement can be effectively increased.

Here, when the planar shape of the pair of electrodes 22a and 22b is spiral, the distance x between the pair of electrodes 22a and 22b is, for example, as shown in FIG. One normal R from the side edge
When 1 is subtracted, it indicates the distance between the starting point Q1 of the normal R1 and the intersection Q2 between the normal R1 and the inner peripheral edge of the other electrode 22b.

When the planar shape of the pair of electrodes 22a and 22b is a multi-branched shape, as shown in FIG.
For example, when one normal R2 is drawn from the outer peripheral edge of the branch 30 of one electrode 22a, the starting point Q of the normal R2
3 and the distance between the normal line R2 and the intersection Q4 between the branch 32 of the other electrode 22b and the inner peripheral edge.

Next, when the thickness y of the piezoelectric / electrostrictive layer 20 and the thickness z of the vibrating portion 16 are viewed, as shown in FIG.
y ≦ 100 μm, 1 ≦ z ≦ 50 μm, and y = b
z so as to satisfy the range of 1/5 ≦ b ≦ 10. Particularly, the proportionality constant b is preferably 1/3 ≦ b ≦ 5. In this case, 1 ≦ y ≦ 40
If μm and 1 ≦ z ≦ 20 μm are satisfied, the polarization direction of the piezoelectric / electrostrictive layer 20 is easily inverted to an appropriate depth when an electric field is applied in the direction opposite to the polarization direction, and the displacement is effectively increased. Therefore, the actuator section 12 is optimal.

Further, in the piezoelectric / electrostrictive element according to the present embodiment, as shown in FIGS. 17 and 18, the sectional shape at the shortest dimension m passing through the center of the vibrating portion 16 satisfies the following conditions. Is preferred. 17 and 18, illustration of the pair of electrodes 22a and 22b is omitted to avoid complicating the drawings.

That is, as shown in FIG. 17B, a reference line L formed by connecting one outermost minimum point P1 close to the fixing portion 18 and the other outermost minimum point P2 is
At least a portion of the upper surface near the center of the piezoelectric / electrostrictive layer 20 is in a no-load state (state of electric field E = 0).
And protrudes in the opposite direction to the vibrating portion 16.

Here, the vicinity of the center of the piezoelectric / electrostrictive layer 20 means, as shown in FIG.
The boundary between the upper surface of the fixed part 18 and the upper surface of the vibrating part 16 is defined as one boundary point K1 and the other boundary point K2, respectively, and when the shortest dimension is 100, the shortest dimension from the one boundary point K1 is defined. 30% range a toward the center of m
1 and a range 40% at the center excluding a range a2 of 30% from the other boundary point K2 toward the center of the shortest dimension m.
Point to 3.

As shown in FIG. 17B, the one outermost minimum point P1 is defined as the shortest dimension of the main surface of the piezoelectric / electrostrictive layer 20 and the upper surface of the vibrating portion 16 in the shortest dimension m. Among the plurality of minimum points formed on the projection line with respect to the plane, the minimum point closest to the one boundary point K1 is referred to, and the other outermost minimum point P2 is the other of the plurality of minimum points. The minimum point closest to the boundary point K2.

In this case, assuming that the shortest dimension is 100, the shortest dimension exists within a range of 40% from the one boundary point K1 toward the center of the shortest dimension m (one minimum point existence area b1). The minimum point closest to one boundary point K1 is recognized as one outermost minimum point P1, and a range of 40% from the other boundary point K2 toward the center of the shortest dimension m (the other minimum point existing area) The minimum point existing in b2) and closest to the other boundary point K2 is recognized as the other outermost minimum point P2.

The outermost minimum points P1 and P2 are shown in FIG.
As shown in FIG. 17A, there may be a case where it exists below the upper surface of the fixing unit 18, and as shown in FIG.

As shown in FIG. 18A, for example, when the other outermost minimum point P2 does not exist in the other minimum point existing area b2, the other boundary point K2 is set as the other outermost minimum point P2. Be certified. This is one of the outermost minimum points P
The same applies to 1. Also, as shown in FIG. 18B, when the outermost minimum points P1 and P2 do not exist in both the minimum point existence regions b1 and b2, respectively, one boundary point K1 and the other boundary point K2 are each one of the minimum points. It is recognized as the outer minimum point P1 and the other outermost minimum point P2.

The above condition, that is, “at least a part of the upper surface near the center of the piezoelectric / electrostrictive layer 20 protrudes from the reference line L in the direction opposite to the vibrating portion 16 in the no-load state”. In the condition, when the shortest dimension length is m, the protrusion amount t is m / 1000 ≦ t ≦
It is more preferable to satisfy m / 10.

By satisfying the above conditions, the produced actuator section 12 can be made to undergo a large displacement in one direction without fail, and an improvement in the yield when used in various electronic devices and the like can be achieved. .

As described above, in the piezoelectric / electrostrictive element according to the present embodiment, the actuator section main body 24 is
The electrostrictive layer 20 includes a pair of electrodes 22a and 22b formed on one main surface of the piezoelectric / electrostrictive layer 20, and an applied electric field that is at least four times a predetermined electric field between the pair of electrodes 22a and 22b. Is made asymmetric about the reference electric field point, so that when an electric field is applied in the opposite direction after the polarization processing on the piezoelectric / electrostrictive layer 20, In the vicinity of the surface, the electric field intensity is large, and the polarization direction is reversed to be the same as the direction of the electric field. However, the deep portion of the piezoelectric / electrostrictive layer 20 has a small electric field intensity. The polarization direction will not be reversed. That is, the piezoelectric / electrostrictive layer 20 has two types of polarization, and functions as a pseudo bimorph type piezoelectric / electrostrictive element.

As a result, the strain directions in the vicinity of the surface of the piezoelectric / electrostrictive layer 20 and in the deep portion are opposite to each other, so that the whole is displaced convexly in one direction, and the amount of the displacement is similar to the pseudo bimorph-like shape. It becomes very large due to the action.

In particular, in the piezoelectric / electrostrictive element according to the present embodiment, the displacement characteristics are asymmetrical in the positive and negative directions of the electric field with respect to the reference electric field point (point of electric field E = 0). Therefore, for example, there is a difference in the amount of bending displacement between two peak values of the periodically changing electric field.
As a result, the relative displacement between the voltage-unloaded state and the voltage-applied state and the relative displacement when the electric field in the opposite direction is applied are increased, and the control when the piezoelectric / electrostrictive element is used as an actuator is increased. It is possible to realize easiness and improvement in sensitivity when used as a sensor.

In the piezoelectric / electrostrictive element according to the present embodiment, the distance between the pair of electrodes 22a and 22b is x
(1 μm ≦ x ≦ 200 μm), and when the thickness of the piezoelectric / electrostrictive layer 20 is y (1 μm ≦ y ≦ 100 μm), y =
ax, and 1/10 ≦ a ≦ 100.

In this case, the pair of electrodes 22a and 22
As shown in FIG. 10B, the displacement characteristics of the actuator section 12 due to the applied electric field between the reference electric field point (the electric field E =
A characteristic that is asymmetric about the point (point 0) can be obtained.

In the piezoelectric / electrostrictive element according to the present embodiment, the vibrating portion 16 and the fixed portion 18 are integrally formed of ceramics, and the concave portion 14 is formed at a position corresponding to the vibrating portion 16. Since the vibrating portion 16 is made thin, the fixing portion 18 and the vibrating portion 16 can be easily manufactured, which is advantageous in reducing the manufacturing cost of the piezoelectric / electrostrictive element.

The base 10 made of ceramic is
By providing the concave portion 14 in the shape, a thick fixed portion 18 and a thin vibrating portion 16 are formed, so that the vibrating portion 16 is sensitive to the displacement of the piezoelectric / electrostrictive layer 20 and changes in the voltage signal. The vibrating section 16 can be highly compliant with the vibration section 16. In addition, since the rigidity of the boundary between the vibrating part 16 and the fixed part 18 is sufficiently ensured, the boundary part due to the vibration of the vibrating part 16 is less likely to be broken due to fatigue.

In the piezoelectric / electrostrictive element according to the present embodiment, the thickness of piezoelectric / electrostrictive layer 20 is set to y (1 μm ≦ y
≦ 100 μm) and the thickness of the vibrating part 16 is z (1 μm ≦ z ≦
50 μm), the relation y = bz is satisfied, and
Since 1/5 ≦ b ≦ 10, the pair of electrodes 22a and 22
As shown in FIG. 10B, the bending displacement characteristic of the actuator section 12 due to the applied electric field between 2b can be made asymmetric about the reference electric field point.

Although the planar shape of the piezoelectric / electrostrictive element according to the above-described embodiment, in particular, the pair of electrodes 22a and 22b has a spiral shape or a multi-branched shape, as shown in FIG. I don't care. In this case, the shape of the vibrating portion 16 is set to an aspect ratio (aspect ratio) of 0.25 or less or 4.0 or more, and a pair of comb-shaped electrodes is arranged so that the arrangement direction of a large number of comb teeth portions is along the longitudinal direction of the vibrating portion. Is preferably formed. If this condition is satisfied, a pair of electrodes 22a and 22a
Even if b has a comb shape, the same effect as that of the spiral shape or the multi-branched shape can be obtained.

However, the shape of the vibrating portion 16 is 0.25 to 4.0, preferably 0.5 to 2.0 in aspect ratio, and the planar shape of the pair of electrodes 22a and 22b is a spiral shape or a multi-branched shape. The shape is most preferable for increasing the relative displacement.

Next, the selection of each component of the actuator section 12, particularly the material and the like of each component will be described.

First, the vibrating section 16 is preferably made of a material having high heat resistance. The reason is that the actuator section 12 does not use a material having poor heat resistance such as an organic adhesive,
In the case where the vibrating part 16 is directly supported by the vibrating part 8, at least when the piezoelectric / electrostrictive layer 20 is formed,
The vibrating part 16 is preferably made of a highly heat-resistant material so that the material 6 does not deteriorate.

Further, the vibrating section 16 is provided on one of the electrodes 22a and 22b formed on the base body 10.
In order to electrically separate a wiring (vertical selection line 48: see FIG. 21) leading to 2a and a wiring (signal line 50: see FIG. 21) leading to the other electrode 22b, it is preferable to use an electrically insulating material. .

Therefore, the vibrating section 16 may be made of a metal having high heat resistance or a material such as an enamel whose metal surface is coated with a ceramic material such as glass, but ceramics is most suitable.

As the ceramics constituting the vibrating portion 16, for example, stabilized zirconium oxide, aluminum oxide, magnesium oxide, titanium oxide, spinel, mullite, aluminum nitride, silicon nitride, glass, a mixture thereof, or the like can be used. it can. The stabilized zirconium oxide has high mechanical strength even when the thickness of the vibrating portion 16 is small, high toughness, and low chemical reactivity between the piezoelectric / electrostrictive layer 20 and the pair of electrodes 22a and 22b. For example, it is particularly preferable. The stabilized zirconium oxide includes stabilized zirconium oxide and partially stabilized zirconium oxide. The stabilized zirconium oxide has a crystal structure such as a cubic system, so that no phase transition occurs.

On the other hand, zirconium oxide undergoes a phase transition between a monoclinic system and a tetragonal system at around 1000 ° C., and cracks may occur during this phase transition. The stabilized zirconium oxide contains 1 to 30 mol% of a stabilizer such as calcium oxide, magnesium oxide, yttrium oxide, scandium oxide, ytterbium oxide, cerium oxide or a rare earth metal oxide. In order to increase the mechanical strength of the vibrating section 16, the stabilizer preferably contains yttrium oxide. At this time, the content of yttrium oxide is preferably 1.5 to 6 mol%, more preferably 2 to 6 mol%.
4 mol%, and preferably 0.1 to 5 mol% aluminum oxide. Furthermore, 0.1 to 10 mol% of titanium oxide or 0.1 to 10 mol%
It is also preferable to contain 10 mol% of aluminum oxide + titanium oxide in view of increasing the relative displacement and ensuring close contact with the piezoelectric / electrostrictive material.

The crystal phase may be a mixed phase of cubic + monoclinic, a mixed phase of tetragonal + monoclinic, a mixed phase of cubic + tetragonal + monoclinic, etc. Those in which the main crystal phase is a tetragonal or a mixed phase of tetragonal and cubic are most preferable from the viewpoints of strength, toughness and durability.

When the vibrating part 16 is made of ceramics,
Although a large number of crystal grains constitute the vibrating section 16, the average grain size of the crystal grains is 0.0
It is preferably from 5 to 2 μm, more preferably from 0.1 to 1 μm.

The fixing portion 18 is preferably made of ceramics, but may be made of the same ceramics as the material of the vibrating portion 16 or may be different. As the ceramics constituting the fixed portion 18, similarly to the material of the vibrating portion 16,
For example, stabilized zirconium oxide, aluminum oxide, magnesium oxide, titanium oxide, spinel, mullite, aluminum nitride, silicon nitride, glass, a mixture thereof, or the like can be used.

In particular, the base 10 used in the piezoelectric / electrostrictive element according to the present embodiment is mainly made of a material mainly composed of zirconium oxide, a material mainly composed of aluminum oxide, or a mixture thereof. Materials and the like are suitably adopted. Among them, those containing zirconium oxide as a main component are more preferable. Clay or the like may be added as a sintering aid, but it is necessary to adjust the auxiliary component so as not to include excessively vitrified substances such as silicon oxide and boron oxide. This is because these materials that are easily vitrified are advantageous in joining the base 10 and the piezoelectric / electrostrictive layer 20, but promote the reaction between the base 10 and the piezoelectric / electrostrictive layer 20 and have a predetermined piezoelectric / electrostrictive layer. This is because it becomes difficult to maintain the composition of the strained layer 20, and as a result, the element characteristics are degraded.

That is, it is preferable that the weight ratio of silicon oxide and the like in the base 10 be 3% or less, more preferably 1% or less. Here, the main component is 50% by weight.
% Or more.

As the constituent material of the piezoelectric / electrostrictive layer 20, piezoelectric ceramics can be preferably used, but electrostrictive ceramics or ferroelectric ceramics may be used. Furthermore, not limited to ceramics, PVDF
A piezoelectric body composed of a polymer represented by (polyvinylidene fluoride) or a composite of these polymers and ceramics may be used.

As the piezoelectric / electrostrictive material for providing the film-shaped piezoelectric / electrostrictive layer 20 in the actuator section main body 24, preferably, a material mainly composed of lead zirconate titanate (PZT), lead magnesium niobate (PMN-based) material, lead nickel niobate (PNN-based) material, lead manganese niobate-based material, lead antimony stannate-based material, zinc niobium Lead acid-based material, Lead titanate-based material, Magnesium lead tantalate-based material,
A material containing lead nickel tantalate as a main component, and a composite material thereof are used.

Further, lanthanum, barium, niobium, zinc, cerium, cadmium,
Materials containing oxides such as chromium, cobalt, antimony, iron, yttrium, tantalum, tungsten, nickel, manganese, lithium, strontium, bismuth, and other compounds as additives, such as P
A material obtained by appropriately adding a predetermined additive to the above material so as to be an LZT-based material is also suitably used.

Among these piezoelectric / electrostrictive materials, a material mainly composed of a component consisting of lead magnesium niobate, lead zirconate and lead titanate, lead nickel niobate, lead magnesium niobate and zirconate Material mainly composed of lead and lead titanate, material mainly composed of lead magnesium niobate, lead nickel tantalate, lead zirconate and lead titanate, or lead magnesium tantalate and magnesium A material mainly composed of components of lead niobate, lead zirconate and lead titanate is advantageously used, and is recommended as a material for forming the piezoelectric / electrostrictive layer 20 by a thick film forming method such as screen printing. Is done.

In the case of a multi-component piezoelectric / electrostrictive material, although the piezoelectric / electrostrictive characteristics change depending on the composition of the components, magnesium niobate which is suitably employed in the piezoelectric / electrostrictive element according to the present embodiment is preferred. Three component materials of lead-lead zirconate-lead titanate, lead magnesium niobate-lead nickel tantalate-lead zirconate-lead titanate, and lead magnesium tantalate-lead magnesium niobate-lead zirconate-titanium In the quaternary material of lead acid, pseudo-cubic-tetragonal-
A composition near a rhombohedral phase boundary is preferable, and in particular, lead magnesium niobate: 15 to 50 mol%, lead zirconate: 1
0 to 45 mol%, lead titanate: 30 to 45 mol%, lead magnesium niobate: 15 to 50 mol%, lead nickel tantalate: 10 to 40%, lead zirconate: 10
~ 45 mol%, lead titanate: composition of 30 ~ 45 mol%,
Further, the composition of lead magnesium niobate: 15 to 50 mol%, lead magnesium tantalate: 10 to 40 mol%, lead zirconate: 10 to 45 mol%, and lead titanate: 30 to 45 mol% has a high piezoelectric constant. Is advantageously employed because it has an electromechanical coupling coefficient.

[0114] The piezoelectric / electrostrictive layer 20 may be dense or porous.
% Is preferable.

The vibrating section 16 of the base 10
Thickness of the piezoelectric / electrostrictive layer 20 formed on the vibrating part 16
Is preferably the same thickness. This is because if the thickness of the vibrating portion 16 is extremely large (if it differs by one digit or more) and becomes larger than the thickness of the piezoelectric / electrostrictive layer 20, the
Since the vibrating portion 16 acts to prevent shrinkage of the electrostrictive layer 20 during firing, the piezoelectric / electrostrictive layer 20 and the base 10
The stress at the interface with the substrate increases, making it easier to peel off. Conversely, if the thickness dimension is substantially the same, the base 10 (vibrating portion 16) can easily follow the firing shrinkage of the piezoelectric / electrostrictive layer 20, which is suitable for integration. Specifically, the thickness of the vibrating section 16 is preferably 1 to 50 μm, and 3 to 50 μm.
μm is more preferred, and 3-20 μm is even more preferred. On the other hand, the piezoelectric / electrostrictive layer 20 has a thickness of 1 to 1
00 μm is preferable, and 3 to 50 μm is more preferable.
Even more preferred is ４０40 μm.

The pair of electrodes 22a and 22b formed on the piezoelectric / electrostrictive layer 20 has an appropriate thickness depending on the application, but preferably has a thickness of 0.01 to 50 μm. 1-5 μm is more preferred. Preferably, the pair of electrodes 22a and 22b are solid at room temperature and made of a conductive metal. For example, aluminum, titanium, chromium, iron, cobalt, nickel,
Copper, zinc, niobium, molybdenum, ruthenium, rhodium, silver, tin, tantalum, tungsten, iridium,
A metal simple substance or alloy containing platinum, gold, lead and the like can be mentioned. Needless to say, these elements may be contained in any combination.

Next, a method for manufacturing the piezoelectric / electrostrictive element according to the present embodiment will be described. The base body 10 including the vibrating part 16 and the fixing part 18 can be integrated by laminating formed layers, which are green sheets or green tapes, by thermocompression bonding or the like, and then firing. For example, in the base 10 of FIG.
Two layers of green sheets or green tapes are laminated, and a through hole of a predetermined shape serving as the concave portion 14 may be provided in the second layer before lamination.

Further, a molded layer is formed by pressure molding using a molding die, casting molding, injection molding or the like, and the concave portion 14 or the like is provided by machining such as cutting, grinding, laser processing, or punching by press working. You may. In FIG. 1, 2
Although it has a layer structure, the base 1
It may be formed by simultaneously increasing the rigidity of 0 or by simultaneously laminating layers used as a back wiring board.

Next, the actuator section main body 24 is formed on the vibrating section 16 of the base 10. In this case, the piezoelectric / electrostrictive layer 20 is formed by a press forming method using a mold or a tape forming method using a slurry raw material, and the piezoelectric / electrostrictive layer 20 before firing is vibrated in the base 10 before firing. Part 1
The piezoelectric / electrostrictive layer 20 is formed on the vibrating portion 16 of the substrate 10 by laminating the piezoelectric / electrostrictive layer on the vibrating part 16 of the base 10 by thermocompression bonding, and the following film forming method.

The film forming method is a method of laminating the piezoelectric / electrostrictive layer 20 and the pair of electrodes 22a and 22b on the vibrating portion 16 in this order. For example, a thick film method such as screen printing, dipping, etc. Coating method, ion beam, sputtering, vacuum evaporation, ion plating, chemical vapor deposition (CVD), thin film method such as plating and the like are appropriately used. The wiring (the vertical selection line 48 and the signal line 50: see FIG. 21) connected to the pair of electrodes 22a and 22b and the terminal pads are also formed by the thick film method or the thin film method.

As an example of the piezoelectric / electrostrictive element according to the present embodiment, for example, the following manufacturing method is adopted.
First, the piezoelectric / electrostrictive layer 20 is formed on the vibrating part 16 of the base 10 by a screen printing method. Thereafter, firing is performed to join the piezoelectric / electrostrictive layer 20 on the vibrating portion 16 of the base 10. In this case, in order to improve the bondability between the base 10 and the piezoelectric / electrostrictive layer 20 and to advantageously integrate the base 10 and the piezoelectric / electrostrictive layer 20, it is necessary to fire the piezoelectric / electrostrictive layer 20. Is preferably performed in a closed container under an atmosphere of a piezoelectric / electrostrictive material. More preferably, it is desirable to increase the atmospheric concentration.

The firing in the atmosphere is performed by the following method or the like. (1) A powder having the same composition as the piezoelectric / electrostrictive material is placed together in an airtight container as an evaporation source. (2) A lead component is excessively added in advance as a composition of the piezoelectric / electrostrictive material. (3) A piezoelectric / electrostrictive material plate is used as a setter.

The firing temperature is preferably from 900 to 1400 ° C., more preferably from 1100 to 1400 ° C.

After the joining of the base 10 and the piezoelectric / electrostrictive layer 20 is completed, a wiring layer including a pair of electrodes 22a and 22b is laminated by screen printing. The pattern of the wiring layer is, for example, as shown in FIG. 21, the pattern of the vertical selection line 48, the pattern of the signal line 50, and the electrode pattern.
In this case, the shape is not a spiral shape as shown in FIG. 4 or a multi-branched shape as shown in FIG. 5, but is simply a circular shape.

Thereafter, a desired portion of the circular electrode pattern is evaporated by, for example, an excimer laser, so as to be patterned into a spiral shape as shown in FIG. 4 or a multi-branched shape as shown in FIG. 22b
And

After the patterning by the excimer laser is completed, a heat treatment is performed to complete the formation of the actuator section main body 24 on the base 10. In the case where the pair of electrodes 22a and 22b are formed by a thin film method, the heat treatment is not necessarily required.

[0127]

Next, a display device according to an example in which the piezoelectric / electrostrictive element according to the present embodiment is applied to a display device will be described. Components corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

As shown in FIG. 20, the display device according to this embodiment is provided with an optical waveguide plate 42 into which light 40 is introduced, and a plurality of actuator units provided opposite to the rear surface of the optical waveguide plate 42. 12 is a drive unit 44 arranged corresponding to pixels
Is configured.

The optical waveguide plate 42 has a flat and smooth front and rear surface, and is such that light introduced therein is totally reflected at the front and rear surfaces without transmitting to the outside of the optical waveguide plate 42. It is necessary to have a light refractive index and a uniform and high transmittance in a visible light wavelength region. The material is not particularly limited as long as it has such characteristics. Specifically, for example, glass, quartz, a light-transmitting plastic such as acrylic, a light-transmitting ceramic, or a material having a different refractive index. A general structure includes a multi-layered structure of a material having the same or a structure provided with a coating layer on the surface.

The drive section 44 has a base 10 made of, for example, ceramics, and the actuator section 12 is disposed at a position corresponding to each pixel of the base 10. The base 10 is disposed such that one main surface is opposed to the back surface of the optical waveguide plate 42, the one main surface is a continuous surface (one surface), and the other main surface corresponds to each pixel. Each position has a recess 14.

A displacement transmitting section 46 is connected on each actuator section 12 to increase the area of contact with the optical waveguide plate 42 so as to have an area corresponding to the pixel. This displacement transmitting section 46
Has a plate member 46a for defining a substantial light emitting area and a displacement transmitting member 46b for transmitting the displacement of the actuator section 12 to the plate member 46a.

The displacement transmitting member 46b preferably has such a hardness that the displacement of the actuator section 12 can be transmitted directly to the optical waveguide plate 42. Accordingly, as a material of the displacement transmitting member 46b, rubber, an organic resin, an organic resin film, an organic adhesive film, glass or the like is preferable. However, the material such as the electrode layer itself or a piezoelectric material or the above-mentioned ceramics is preferable. It doesn't matter. Most preferably, an organic resin or an organic adhesive film such as an epoxy-based, polyphenylene sulfide-based, polyester-based, polyimide-based, acrylic-based, silicone-based, or polyolefin-based resin is used. It is also effective to mix fillers with these materials to suppress curing shrinkage and expansion.

As the material of the plate member 46a, in addition to the material of the displacement transmitting member 46b, epoxy-based, acrylic-based,
A material obtained by highly dispersing a ceramic powder having a high refractive index in an organic resin such as a silicone resin, for example, a zirconia powder, a titania powder, a lead oxide powder, a mixed powder thereof, or the like is desirable from the viewpoint of maintaining luminous efficiency and flatness. At this time, the average particle diameter of the ceramic powder is desirably 1 μm or less.
5 μm or less is more desirable. In this case, the weight of the resin: the weight of the ceramic powder = 1: (0.1 to 10) is preferable. Furthermore,
In the above composition, glass powder having an average particle size of 0.5 to 10 μm was added to the ceramic powder in a volume ratio of 1: (0.1 to 1.
0) It is preferable to add ｛= ceramic powder: glass powder｝ because the contact property with the surface of the optical waveguide plate 42 and the releasability are improved.

The plate member 46a of the displacement transmitting section 46 has a flatness and a smoothness (Ra) of a portion (surface) in contact with the optical waveguide plate 42.
However, it is preferable to make the displacement amount sufficiently smaller than the displacement amount of the actuator section 12, specifically, 1 μm or less, more preferably 0.5 μm, and particularly preferably 0.1 μm or less. However, the flatness of the portion (surface) of the displacement transmitting section 46 that comes into contact with the optical waveguide plate 42 depends on whether the displacement transmitting section 46
It is important to reduce the gap in the state of contact with No. 2, and the flatness is not necessarily limited as long as the contact portion deforms in the state of contact.

When the above-described material is used for the displacement transmitting section 46, the displacement transmitting section 46 is connected to the actuator section main body 24 by laminating the displacement transmitting section 46 using an adhesive. It may be performed by forming the above-mentioned solution, paste or slurry on the upper part of the actuator unit main body 24 by a method such as coating. The displacement transmitting member 46b and the plate member 46a may be made of the same material and integrally formed. That is, the displacement transmitting section 46 may have both functions of the displacement transmitting member 46b and the plate member 46a.

As shown in FIG. 21, the wiring leading to each of the electrodes 22a and 22b has a number of vertical selection lines 48 corresponding to the number of rows of many pixels and a number of lines corresponding to the number of columns of many pixels. And a signal line 50.

Each vertical selection line 48 is electrically connected to one electrode 22a of each pixel (actuator section) 12, and each signal line 50 is connected to the other electrode 22b of each pixel 12.
Is electrically connected to

Each of the vertical selection lines 48 is derived from one electrode 22a for the pixel 12 in the preceding column, connected to one electrode 22a for the pixel 12, and wired in series for one row. It has become.

The signal line 50 has a main line 50a extending in the column direction.
And the other electrode 2 of each pixel 12 branched from the main line 50a.
It consists of a branch line 50b connected to 2b. Each vertical selection line 4
8 is supplied to a wiring board (not shown)
0 is attached to the other main surface) to through-hole 5
2, and the supply of the voltage signal to each signal line 50 is also performed through the through hole 54 from the wiring board (not shown).

Although various arrangement patterns of the through holes 52 and 54 are conceivable, in the example of FIG.
When the number of rows is M and the number of columns is N, the through-hole 52 of the vertical selection line 48 has N = M or N> M.
are formed in the vicinity of pixels of n rows and n columns (n = 1, 2,...) and near signal lines (main lines) of (n−1) columns;
In the case of N <M, (αN + n) rows and n columns (α =
0, 1... (Quotient of M / N-1)) and near the signal line (main line) in the (n-1) th column.

On the other hand, the through hole 54 of the signal line 50 is
In the case of N = M or N <M, it is on the main line 50a of each signal line 50 and n rows and n columns (n = 1, 2,...)
) Is formed at a position close to the pixel 12, and when N> M, on the main line 50 a of each signal line 50,
In addition, it is formed at a position close to the pixel 12 of n rows (βM + n) columns (β = 0, 1... (N / M quotient−1)). The through hole 52 of the vertical selection line 48 is connected to the signal line 50.
Unlike in the case of (1), since it is not formed on the vertical selection line 48, a relay conductor 56 is formed between the through-hole 52 and one of the electrodes 22a for electrical conduction therebetween.

At the intersection of each vertical select line 48 and each signal line 50, an insulating film made of a silicon oxide film, a glass film, a resin film or the like is used to insulate the wirings 48 and 50 from each other. 58 (indicated by a two-dot chain line).

The planar shape of the pair of electrodes 22a and 22b includes a spiral shape (see FIG. 4) and a multi-branched shape (see FIG. 5). The planar shape of the vibrating portion 16 and the piezoelectric / electrostrictive layer 20 As the planar shape and the outer peripheral shape formed by the pair of electrodes 22a and 22b, in addition to the circular shape shown in FIG. 21, there are an oval shape shown in FIGS. 22 and 23 and an elliptical shape shown in FIG.

Further, as shown in FIG. 25, the planar shape of the vibrating portion 16 and the planar shape of the piezoelectric / electrostrictive layer 20 are both rectangular, and the corners are rounded, as shown in FIG. Preferably, both the planar shape of the vibrating section 16 and the planar shape of the piezoelectric / electrostrictive layer 20 are polygonal (for example, octagonal), and each vertex is preferably rounded.

The shape of the vibrating portion 16 and the piezoelectric / electrostrictive layer 2
0, the outer peripheral shape formed by the pair of electrodes 22a and 22b may be a combination of a circle and an ellipse,
A combination of a rectangle and an ellipse may be used, and there is no particular limitation.

In the example of FIG. 21, the arrangement of the actuator units (pixels) 12 on the base 10 is shown as a matrix, but in addition, as shown in FIG. The parts 12 may be arranged in a staggered manner.

In the case of the arrangement pattern shown in FIG. 24, since the arrangement of the actuator units (pixels) 12 in each row is staggered, the vertical selection lines 48 are provided in each row.
(Indicated by a dashed line a) are zigzag. As shown by a broken line b, two signal lines 50 are provided at positions corresponding to, for example, pixels (actuator portions) 12 located vertically above the pixels 12 arranged in a zigzag pattern on a wiring board (not shown). Are arranged close to each other.

In FIG. 24, among the pixels arranged in a zigzag pattern, for example, the other electrode 22b of the pixel (actuator section) 12 located on the upper side in the vertical direction is connected to the two signal lines 50 and 50, the right signal line 5
0 through the relay conductor 60 and the through hole 62, and the other electrode 22b of the pixel (actuator section) 12 located on the lower side in the vertical direction is connected to the two signal lines 50 and 50 close to each other. , Left signal line 50
Is electrically connected to the relay conductor 64 and the through hole 66.

Next, the operation of the display device according to the above embodiment will be described. First, the operation of each actuator section 12 will be described, and then the operation of the display device itself will be described.

First, in the display device according to the present embodiment shown in FIG. 20, a polarization process (initial polarization process) is performed on each pixel (actuator section) 12 separately from its driving. This initial polarization process is performed by applying an electric field (+ 5E) exceeding the range of use of the electric field used as the actuator (for example, the range of + 3E to −3E in FIG. 10) for, for example, 7 hours at an appropriate temperature. Thereby, the piezoelectric / electrostrictive layer 20 in each pixel is polarized in the same direction as the applied electric field.

At the stage where the initial polarization process is completed for all the pixels, the application of the voltage between the pair of electrodes 22a and 22b is stopped to bring the voltage into a no-load state.

In driving the display device, there are basically three operations (ON selection,
(OFF selection, non-selection) to display an image.

In the ON selection, as shown in FIG. 27A, during a predetermined selection period Ts, a pair of electrodes 22a of the pixel 12
And 22b by applying a voltage Va to generate a negative electric field Ea (see FIG. 10B) between the pair of electrodes 22a and 22b. In the OFF selection, as shown in FIG. 27B, during a predetermined selection period Ts, a voltage Vd is applied to the pair of electrodes 22a and 22b of the pixel 12, and a negative or positive electric field is applied between the pair of electrodes 22a and 22b. This is done by generating Ed (see FIG. 10B).

In the non-selection, as shown in FIG. 27A or FIG. 27B, in a period other than the selection period Ts (non-selection period Ta), the voltage Vf or Vg is applied to the pair of electrodes 22a and 22b of the pixel, and By generating a positive electric field Ef or Eg (see FIG. 10B) between the electrodes 22a and 22b. In this non-selection period Ta,
Since an electric field in the positive direction is generated similarly to the initial polarization processing, the piezoelectric / electrostrictive layer 20 of the pixel in the non-selected state is subjected to the processing according to the polarization processing (referred to as repolarization processing for convenience). .

The driving operation of the display device according to the present embodiment will be specifically described. Based on the input of an image signal to the display device, for example, a vertical shift circuit constituted by a shift register is applied to a vertical selection line 48. According to the potential supply,
For each horizontal scanning period, for example, the first row, the second row,.
Pixel groups are selected line by line as in the row.
In the selected row, a potential is supplied to the signal line 50 related to the pixel 12 to be turned on from a horizontal shift circuit formed of, for example, a shift register for a predetermined selection period Ts.

As a result, in the pixel 12 selected ON by the vertical shift circuit and the horizontal shift circuit, a predetermined negative potential is applied to one electrode 22a, and a positive potential is applied to the other electrode 22b. The voltage between the electrodes 22a and 22b is a predetermined negative voltage Va (see FIG. 27A).

At this time, as shown in FIGS. 10B and 13A, for example, a negative direction electric field Ea (eg, −3E: the electric field in the opposite direction to the electric field at the time of initial polarization processing or non-selection) is present between the pair of electrodes 22a and 22b. An electric field is generated, and the actuator section 12 in the pixel is displaced in one direction by about 2.6 Δy.

This state shows the ON selection state when viewed from the display device. In this ON selection state, the displacement transmitting section 46 is moved by the optical waveguide plate 42 due to the convex deformation of the actuator section 12.
And the displacement transmitting portion 46 comes into contact with the optical waveguide plate 42.

The displacement transmitting section 46 comes into contact with the back surface of the optical waveguide plate 42 in accordance with the displacement of the actuator section 12. The light 40 totally reflected in the corrugated plate 42 is transmitted through the rear surface of the optical waveguide plate 42 and
, And is scattered and reflected on the surface of the displacement transmitting section 46.

The displacement transmitting section 46 scatters and reflects the light transmitted through the rear surface of the optical waveguide plate 42.
It is provided in order to increase the contact area with 2 above a predetermined value. That is, the light emitting area is defined by the contact area between the displacement transmitting section 46 and the optical waveguide plate 42.

The contact between the displacement transmitting portion 46 and the optical waveguide plate 42 means that the distance between the displacement transmitting portion 46 and the optical waveguide plate 42 is equal to or less than the wavelength of the light (light introduced into the optical waveguide plate) 40. Means to be located.

On the other hand, among the pixels related to the row selected by the vertical shift circuit, for the pixels 12 not selected for ON or the pixels 12 selected for OFF, the potential of the signal line 50 related to the pixel 12 is kept ON for a predetermined selection period Ts. The potential is different from the potential at the time of selection, a predetermined negative potential is applied to one electrode 22 a of the pixel 12, and the other electrode 22
b, a negative or positive potential is applied, and the voltage between the pair of electrodes 22a and 22b becomes a predetermined voltage Vd in the negative or positive direction.
(See FIG. 27B).

At this time, as shown in FIG. 10B, a negative or positive electric field Ed (for example, −0.6E to + 0.6E) is generated between the pair of electrodes 22a and 22b.
The actuator section 12 in the pixel is about -0.5
It is displaced in one direction by Δy to 1Δy.

This state is OFF when viewed from the display device.
Indicates the selected state. In the OFF selection state, the displacement transmitting section 46 is separated from the optical waveguide plate 42 by the displacement operation of the actuator section 12.

The actuator section 12 relating to the pixel selected ON or OFF is subjected to repolarization processing in the non-selected state thereafter, so that the pair of electrodes 22a and 22b formed on the piezoelectric / electrostrictive layer 20 are (In a direction facing free space) by about 1Δy. In this non-selected state, voltage levels Vg and Vf on which voltage changes based on ON selection and OFF selection in other rows are superimposed.
(See FIG. 27A and FIG. 27B.) The presence of this superimposed component (crosstalk component) causes the actuator unit 12 in a non-selected state to perform a certain amount of repolarization processing. This will help to recover responsiveness. That is, the crosstalk component also serves to recover responsiveness.

The voltage level for performing the ON selection is the voltage level Vb (the electric field Eb in FIG. 10B).
A voltage level in the negative direction than the voltage level (for example, a voltage level corresponding to -2E) may be used, and the voltage level for performing the OFF selection is in the range of the voltage levels Vc to Ve (FIG. 1).
At 0B, the electric field Ec (for example, -0.6E) to Ee (+
The voltage level may be any voltage level within a voltage level corresponding to the range of 0.6E). Further, the voltage level for performing the repolarization process may be any voltage level that is more positive than the voltage level Ve (the voltage level corresponding to the electric field Ee (for example, + 0.6E) in FIG. 10B).

Next, the operation of the display device according to the present embodiment will be described. First, for example, the light 4
0 is introduced. In this case, by adjusting the size of the refractive index of the optical waveguide plate 42, all the light 40 can be transmitted to the optical waveguide plate 4.
The light is totally internally reflected without being transmitted on the front and rear surfaces of the light emitting element 2.

In this state, when a certain actuator section 12 is set in an excited state, and the displacement transmission section 46 corresponding to the actuator section 12 comes into contact with the rear surface of the optical waveguide plate 42 at a distance shorter than the wavelength of light, the entire actuator section 12 has been activated. The reflected light 40 is transmitted to the surface of the displacement transmitting section 46 which is in contact with the back surface of the optical waveguide plate 42. The light 40 that has once reached the surface of the displacement transmitting unit 46 is reflected on the surface of the displacement transmitting unit 46 to be scattered light 70 (see FIG. 20), and a part of the light 40 is again reflected in the optical waveguide plate 42. Most of the scattered light 70 passes through the front surface of the optical waveguide plate 42 without being reflected by the optical waveguide plate 42.

That is, the presence or absence of light emission (leakage light) on the front surface of the optical waveguide plate 42 can be controlled by the presence or absence of the contact of the displacement transmitting portion 46 on the rear surface of the optical waveguide plate 42. In particular, in the display device according to the present embodiment, the optical waveguide plate 42
One unit for displacing the displacement transmitting unit 46 in the contact / separation direction is one pixel, and a large number of pixels are arranged in a matrix or in a staggered manner for each row. By controlling the displacement operation in each pixel according to the attribute of the signal, it is possible to display an image (characters, figures, etc.) corresponding to an image signal on the front surface of the optical waveguide plate, similarly to a cathode ray tube or a liquid crystal display device. Can be.

Next, a case where the display device according to this embodiment is applied to a color display system will be described. First, the principle of color development of the display device according to the present embodiment is the same as the current color display system, ie, the three primary colors R (red), G (green), and B.
(Blue). Here, in a case where the maximum light emission time of RGB is divided into three with the cycle of color development as T, as shown in FIG. 28A, if the ratio of the light emission time of RGB is 1: 1: 1, white light is emitted. And FIG. 28
As shown in B, the ratio of the RGB light emission time is 4: 1: 5.
If so, an intermediate color according to the ratio is obtained.

Accordingly, the control of the color development time may be performed by synchronizing the contact time between the optical waveguide plate 42 and the displacement transmitting section 46 with the color development cycle T to control the light emission time of the three primary colors, or by controlling the light emission of the three primary colors. The contact time between the optical waveguide plate 42 and the displacement transmitting section 46 can be controlled in synchronization with the time period T at which the color is developed.

As described above, the display device according to the present embodiment has an advantage that the number of pixels does not need to be increased as compared with the case of a monochrome screen even when applied to the color display system. is there.

In the above embodiment, the repolarization process for each pixel 12 is performed during the non-selection period.
In addition, a period from the end of emission of R to the start of emission of the next G, a period from the end of emission of G to the start of emission of the next B, and the end of emission of B to the start of emission of the next R. During the three periods, the same electric field as in the initial polarization processing may be applied to perform the repolarization processing. In this case, it may be combined with the repolarization process in the non-selection period.

The display device according to the present embodiment can be used alone, or the display device according to the present embodiment can be used as one display element 74 of the large screen display device 72 as shown in FIG. It is. The example of FIG. 29 shows an example in which seven display elements 74 are arranged in the vertical direction and eighteen in the horizontal direction on the back surface of the light guide plate 76 having a large display area. In this case, the light guide plate 76 has a large light transmittance in the visible light region and is uniform such as a glass plate or an acrylic plate, and wire bonding, soldering, and end face connectors are used between the display elements 74. The signals can be supplied to each other by connecting with a backside connector or the like.

In the large screen display device 72 shown in FIG. 29, for example, the display device shown in FIG. 24 is used as a display device applied to each display element 74, and the arrangement of the pixels 12 is 32 pixels in the horizontal direction. , 32 in the vertical direction. In the display device illustrated in FIG. 24, the arrangement of the pixels 12 in each row is staggered, so that the horizontal arrangement pitch of the pixels 12 can be extremely small, and the number of pixels arranged in the horizontal direction and the vertical direction is the same. If you do
The overall planar shape is a vertically long shape.

In the large screen display device 72 shown in FIG. 29, an example is shown in which display elements 74 including the optical waveguide plate 42 are arranged in a matrix on the surface of a large light guide plate 76. The light guide plate 76 may be omitted, and the large-screen display device 72 may be configured by arranging the display elements 74 including the optical waveguide plate 42 in a matrix. in this case,
A large number of light guide plates 42 arranged in a matrix form also serve as the large light guide plate 76. In addition to the above configuration,
The large screen display device 72 may be configured by arranging display elements 74 that do not include the optical waveguide plate 42 in a matrix on the plate surface of the large light guide plate 76.

The light guide plate 76 and the optical waveguide plate 42 preferably have similar refractive indices.
In the case of bonding together, a transparent adhesive may be used. This adhesive is preferably uniform and has a high transmittance in the visible light region, similarly to the light guide plate 42 and the light guide plate 76, and has a refractive index close to that of the light guide plate 76 and the light guide plate 42. It is desirable to set the screen brightness to secure the brightness of the screen.

In the display device according to the above-described embodiment, the main surface of the piezoelectric / electrostrictive layer 20 formed on the vibrating portion 16 is formed as the structure of the actuator portion main body 24 for selectively displacing the displacement transmitting portion 46. Since the pair of electrodes 22a and 22b are formed on the side, the pair of electrodes 22a and 22b
Air or a constituent material of the displacement transmitting portion 46 (which has a very small dielectric constant as compared with the piezoelectric / electrostrictive layer 20) is interposed between the b. Therefore, the capacitance of the actuator section main body 24 is smaller than that obtained by forming electrodes on the upper and lower sides of the piezoelectric / electrostrictive layer 20, and accordingly, the CR time constant for signal transmission is also reduced. That is, the signal waveform of the voltage signal according to the attribute of the image signal is less likely to be rounded.

As a result, it is possible to selectively apply a specified voltage to the pair of electrodes 22a and 22b in each pixel 12, and to give each piezoelectric / electrostrictive layer 20 the necessary elongation. In addition, it is also possible to suppress a decrease in display luminance at a portion (for example, a peripheral portion or a central portion, etc., of the screen) corresponding to the actuator portion 12 disposed at a position far from the portion to which the voltage signal is supplied.

That is, the display device according to the present embodiment has the advantage that the number of pixels does not need to be increased as compared with the case of a black-and-white screen even when applied to the color display system. This has the advantage that the capacitance in the unit 12 can be reduced, and when white is displayed on the entire display screen, uniform display luminance can be obtained and image quality can be improved. .

In particular, in the display device according to the present embodiment, as shown in FIGS. 4 and 5, one of the pair of electrodes 22a and 22b has one electrode 2 connected to the vertical selection line 48.
Since 2a is a pattern connected in series with respect to one row, it is easy to increase the width of the outer peripheral portion of the one electrode 22a (shown by a broken line). In this case, the wiring resistance of the vertical selection line 48 is reduced. Therefore, the CR time constant in signal transmission can be further reduced.

Then, in the display device according to the present embodiment, as shown in FIGS.
2 is upward in the drawing (direction on the side of the optical waveguide plate 42), the displacement transmitting portion 46 can be pressed against the optical waveguide plate 42 with the displacement force of the actuator portion 12, and furthermore, the optical waveguide Since the gap between the plate 42 and the actuator unit 12 is easily adjusted, it is advantageous for ensuring that the displacement transmitting unit 46 and the optical waveguide plate 42 are in contact with each other.

In the display device according to this embodiment, for example, during the manufacturing process, a part of the piezoelectric / electrostrictive layer 20 is partially broken due to dielectric breakdown or the like.
When the electrode 22a disappears together with a part of the electrode b, the electrode 22a and 22b which have disappeared without repairing the piezoelectric / electrostrictive layer 20 can be sufficiently functioned as the actuator portion 12 only by repairing the electrode 22a and 22b. Can be eliminated, and the yield of the display device can be improved.

In the display device according to this embodiment, the vibrating portion 16 and the fixed portion 18 are formed integrally with the base 10 (ceramic), and the concave portion 14 is formed at a position corresponding to the vibrating portion 16. Since the vibrating part 16 is made thin, the fixing part 18 and the vibrating part 16 can be easily formed on the base 10, which is advantageous in reducing the manufacturing cost of the display device.

Also, the base 10 made of ceramics
By providing the concave portion 14 in the shape, the thick fixed portion 18 and the thin vibrating portion 16 are formed, and the vibrating portion 16 is sensitive to the elongation of the piezoelectric / electrostrictive layer 20 and changes in the voltage signal. The vibrating section 16 can be highly compliant with the vibration section 16. In addition, compared to an actuator having a double-supported structure or a cantilevered structure, the rigidity at the boundary between the vibrating portion 16 and the fixed portion 18 is sufficiently ensured. Destruction is less likely to occur.
Further, since the rigidity of the base 10 and the vibrating section 16 is high, the bonding of the optical waveguide plate 42 and the driving section 44 becomes easy.

Further, in the display device according to the present embodiment, each of the concave portions 14 and the piezoelectric / electrostrictive layer 20 has a planar shape with an angle, and the planar shape of the concave portions 14 is Since it is larger than that of the electrostrictive layer 20, the boundary between the vibrating portion 16 and the fixed portion 18 has an angled shape like the planar shape of the concave portion 14, and the stress generated by the vibration of the vibrating portion 16 is reduced. There is no need to concentrate locally. In addition, the entire periphery of the vibrating part 16 is supported by the fixed part 18, so that the rigidity at the peripheral part of the vibrating part 16 can be increased. As a result, the fatigue limit at the boundary can be greatly improved, and the life of the actuator section 12 and the display device can be extended.

In the display device according to this embodiment, the planar shape of the pair of electrodes 22a and 22b on the piezoelectric / electrostrictive layer 20 is set such that the pair of electrodes 22a and 22b are parallel to each other and separated from each other. And a pair of electrodes 22a and 22b.
When a predetermined voltage is applied to the piezoelectric / electrostrictive layer 20, a radial (isotropic) electric field is generated on one main surface of the piezoelectric / electrostrictive layer 20. Radial (isotropic) elongation occurs, and radial (isotropic) shrinkage occurs at a deep portion, whereby the piezoelectric / electrostrictive layer 20 is efficiently displaced so that its central portion is convex. In addition, variations in displacement between the pixels 12 are reduced.

When the planar shape of the pair of electrodes 22a and 22b on the piezoelectric / electrostrictive layer 20 is a multi-branched shape, when a predetermined voltage is applied to the pair of electrodes 22a and 22b, The electrostrictive layer 20 has one principal surface (front surface)
In this case, radial (isotropic) elongation occurs, and radial (isotropic) shrinkage occurs in a deep portion. Therefore, the center is efficiently displaced so as to be convex, and the displacement between the pixels 12 is increased. Is also reduced.

In particular, the display device shown in FIGS.
Since the trunks 26 and 28 and the branches 30 and 32 are separated, a part of the piezoelectric / electrostrictive layer 20, for example, the branches 30 or 3
Even if the portion corresponding to 2 disappears together with the branch portion 30 or 32 due to dielectric breakdown or the like, the influence on other portions is very small, and as long as the trunk portions 26 and 28 remain, the actuator portion 12 functions sufficiently. Becomes Of course, by simply repairing the lost electrode branch 26 or 28, the function before the disappearance can be restored, and maintenance of the display device can be simplified.

In the display device according to the above-described embodiment, the optical waveguide plate 42 has a high flatness and a high smoothness on both sides, but a so-called ground glass having a roughened rear surface may be used. Is also possible. In this case, one main surface of the displacement transmitting unit 46 (the surface facing the rear surface of the ground glass) is subjected to a roughening process along the rough surface shape of the rear surface of the ground glass, or the one main surface portion of the displacement transmitting unit 46 is subjected to roughening. It is preferable to use an elastomer having a relatively low viscosity.

As a result, first, light incident from the front is reflected by the rough surface of the ground glass and transmitted as scattered light toward the front surface of the ground glass. In this state, when a certain actuator unit 12 is set in an excited state and the displacement transmitting unit 46 corresponding to the actuator unit 12 comes into contact with the back surface of the ground glass, the rough surface of the contact portion becomes the rough surface or the elasticity of the displacement transmitting unit 46. Since the shape is canceled by the deformation, the light that has been reflected on the rough surface portion of the ground glass is transmitted through the displacement transmitting portion 46 that is in contact with the back surface of the ground glass.

That is, even when the ground glass is used as the optical waveguide plate 42, the displacement transmitting portion 46 on the back of the ground glass is also used.
Depending on the presence or absence of the contact, the presence or absence of light emission on the front surface of the ground glass can be controlled, and the same effect as the display device according to the above-described embodiment can be obtained. In particular, in the case where the ground glass is used, an illuminating means for positively introducing light into the ground glass becomes unnecessary, so that the configuration is simplified.

In this embodiment, an example is shown in which the piezoelectric / electrostrictive element according to the present invention is applied to a display device. In addition, filters, various sensors such as an ultrasonic sensor, an angular velocity sensor, an acceleration sensor, an impact sensor, and the like, It can be applied to microphones, sound generators (speakers, etc.), discriminators, oscillators for power or communication, oscillators and resonators, servo displacement elements, pulse drive motors, ultrasonic motors, piezoelectric fans, etc. The present invention can also be applied to actuators and the like that are used for

Although the embodiments of the piezoelectric / electrostrictive element according to the present invention and the examples in which the piezoelectric / electrostrictive element is applied to a display device have been described in detail, the present invention The present invention is not construed as being limited to the display devices according to the embodiments and the examples, and various changes, modifications, improvements, and the like can be made without departing from the scope of the present invention.

[0195]

As described above, the piezoelectric / electrostrictive element according to the present invention has a piezoelectric / electrostrictive layer and a pair of electrodes formed on one main surface of the piezoelectric / electrostrictive layer. A piezoelectric / electrostrictive operating portion, which is in contact with the other main surface of the piezoelectric / electrostrictive layer, and
In a piezoelectric / electrostrictive element including a unimorph type piezoelectric / electrostrictive element main body having a vibrating section supporting an electrostrictive operation section and a fixed section supporting the vibrating section so as to be capable of vibrating, a portion between the pair of electrodes The displacement characteristic of the piezoelectric / electrostrictive element body due to an applied electric field that is four times or more the predetermined electric field is made asymmetric about the reference electric field point.

As a result, the relative displacement between the no-load state and the voltage-applied state and the relative displacement when the electric field in the opposite direction is applied can be greatly expanded, and the control when the actuator is used can be easily controlled. And an improvement in sensitivity when used as a sensor.

Further, according to the piezoelectric / electrostrictive element of the present invention, the piezoelectric / electrostrictive operating section having the piezoelectric / electrostrictive layer and the pair of electrodes formed on one main surface of the piezoelectric / electrostrictive layer. A unimorph type piezoelectric / electrostrictive comprising: a vibrating portion that contacts the other main surface of the piezoelectric / electrostrictive layer to support the piezoelectric / electrostrictive operating portion; and a fixed portion that supports the vibrating portion to be able to vibrate. In a piezoelectric / electrostrictive element including an element body, when the distance between the pair of electrodes is x (1 μm ≦ x ≦ 200 μm) and the thickness of the piezoelectric / electrostrictive layer is y (1 μm ≦ y ≦ 100 μm), y = a
x, and 1/10 ≦ a ≦ 100.

For this reason, the displacement characteristic of the piezoelectric / electrostrictive element main body due to an applied electric field that is four times or more the predetermined electric field between the pair of electrodes can be made asymmetrical about the reference electric field point.
This achieves an effect that controllability when used as an actuator and sensitivity improvement when used as a sensor can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a piezoelectric / electrostrictive element according to the present embodiment.

FIG. 2 is a cross-sectional view showing a state where an actuator section of the piezoelectric / electrostrictive element according to the present embodiment is displaced in one direction.

FIG. 3 is a plan view showing a planar shape of a vibrating portion, a planar shape of a piezoelectric / electrostrictive layer, and an outer peripheral shape formed by a pair of electrodes, which constitute an actuator body of the piezoelectric / electrostrictive element according to the present embodiment. It is.

FIG. 4 is a plan view (spiral shape) of a pair of electrodes formed on a piezoelectric / electrostrictive layer of the piezoelectric / electrostrictive element according to the present embodiment.
FIG.

FIG. 5 is a plan view (a multi-branched shape) of a pair of electrodes formed on a piezoelectric / electrostrictive layer of the piezoelectric / electrostrictive element according to the present embodiment.
FIG.

FIG. 6 is a plan view schematically showing a case where the piezoelectric / electrostrictive layer of the actuator section in the display device according to the present embodiment has a ring shape.

FIG. 7 is a sectional view taken along line AA in FIG.

FIG. 8 is a plan view showing an example in which the planar shape of the piezoelectric / electrostrictive layer is annular and the pair of electrodes is multi-branched in the actuator section of the display device according to the present embodiment.

9A is a plan view showing a case where the outer peripheral shape of the ring-shaped piezoelectric / electrostrictive layer is circular, and FIG. 9B is a plan view showing a case where the outer peripheral shape of the ring-shaped piezoelectric / electrostrictive layer is elliptical. FIG. 9C is a plan view showing a case where the outer peripheral shape of the ring-shaped piezoelectric / electrostrictive layer is rectangular.

FIG. 10A is a timing chart showing a potential waveform to be applied to a pair of electrodes in order to measure a bending displacement characteristic of the piezoelectric / electrostrictive element according to the present embodiment.
FIG. 0B is a characteristic diagram showing a bending displacement characteristic of the piezoelectric / electrostrictive element according to the present embodiment.

11A is an explanatory diagram showing a polarization direction and an electric field direction when an initial polarization process is performed on a piezoelectric / electrostrictive layer, and FIG. 11B is a state in which voltage application to a pair of electrodes is stopped (voltage application). It is explanatory drawing which shows the polarization direction in a (no-load state).

FIG. 12A is an explanatory diagram showing a polarization direction and an electric field direction when an electric field (+ 3E) is applied to the piezoelectric / electrostrictive element according to the present embodiment in a positive direction, and FIG.
FIG. 4 is an explanatory diagram showing a polarization direction and an electric field direction when a predetermined negative electric field (−0.6E) is applied to an electrostrictive element.

FIG. 13A is an explanatory diagram showing a polarization direction and an electric field direction when an electric field (−3E) is applied to the piezoelectric / electrostrictive element according to the present embodiment in a negative direction, and FIG. /
FIG. 4 is an explanatory diagram showing a polarization direction and an electric field direction when a predetermined positive electric field (+ 0.6E) is applied to an electrostrictive element.

FIG. 14 is a characteristic diagram showing a dimensional relationship between a distance between a pair of electrodes and a thickness of a piezoelectric / electrostrictive layer in the piezoelectric / electrostrictive element according to the present embodiment.

FIG. 15A is an explanatory diagram showing a distance between electrodes when the planar shape of a pair of electrodes is a spiral shape, and FIG. 15B.
FIG. 4 is an explanatory diagram showing a distance between electrodes when the planar shape of a pair of electrodes is a multi-branched shape.

FIG. 16 is a characteristic diagram showing a dimensional relationship between the thickness of the vibrating portion and the thickness of the piezoelectric / electrostrictive layer in the piezoelectric / electrostrictive element according to the present embodiment.

FIG. 17A is a cross-sectional view showing a part of the cross-sectional shape of the actuator portion in the shortest dimension, which is partially omitted. FIG. 17B is a diagram in which one outermost minimum point and the other outermost minimum point are located on the upper surface of the fixed portion. FIG. 17C is a cross-sectional view showing a case where one of the outermost minimum points and the other outermost minimum point are present above the upper surface of the fixed part. FIG.

FIG. 18A omits a part of an example in which the other outermost minimum point does not exist in the other minimum point existing area and the other boundary point is recognized as the other outermost minimum point. FIG. 18B is a cross-sectional view of FIG. 18B. In FIG. 18B, the outermost minimum points do not exist in both the minimum point existing regions, and one boundary point and the other boundary point are one outermost minimum point and the other outermost minimum point, respectively. It is sectional drawing which shows the example in the case of being recognized as a point partially omitted.

FIG. 19 is a plan view showing a preferred example in a case where the planar shape of a pair of electrodes is a comb shape.

FIG. 20 is a configuration diagram showing an example (hereinafter, simply referred to as a display device according to an example) in which the piezoelectric / electrostrictive element according to the present embodiment is applied to a display device.

FIG. 21 is an enlarged plan view showing an arrangement of actuator units (pixels) in the display device according to the present example.

FIG. 22 is a plan view showing a planar shape (an oval shape or a spiral shape) of a display device according to the present example, particularly, a vibrating portion, a piezoelectric / electrostrictive layer, and a pair of electrodes.

FIG. 23 is a plan view showing a planar shape (an oval shape, a multi-branched shape) of a display device according to the present example, particularly, a vibrating portion, a piezoelectric / electrostrictive layer, and a pair of electrodes.

FIG. 24 is an enlarged plan view showing another example of the arrangement of the actuator units (pixels) in the display device according to the embodiment.

FIG. 25 is a plan view showing a display device according to the present example, in particular, a vibrating portion and a piezoelectric / electrostrictive layer (rectangular shape).

FIG. 26 is a plan view showing a display device according to this example, particularly a vibrating portion and a piezoelectric / electrostrictive layer (octagonal shape).

FIG. 27A is a timing chart showing a voltage level change in a non-selection state and an ON selection state in an actuator unit, and FIG. 27B is a timing chart showing a voltage level change in a non-selection state and an OFF selection state in the actuator unit. It is a timing chart shown.

FIG. 28A is a timing chart when the ratio of the RGB light emission time is set to 1: 1: 1 when the display device according to the present embodiment is applied to the color display method, and FIG. 28B is the timing chart of the RGB. It is a timing chart when the ratio of light emission time is set to 4: 1: 5.

FIG. 29 is a perspective view showing a large-screen display device using the display device according to the present embodiment as viewed from the rear side.

FIG. 30 is a sectional view showing a piezoelectric / electrostrictive element according to a conventional example.

FIG. 31A is a timing chart showing potential waveforms to be applied to an upper electrode and a lower electrode in order to measure a bending displacement characteristic of a piezoelectric / electrostrictive element according to a conventional example;
FIG. 31B is a characteristic diagram showing a bending displacement characteristic of the piezoelectric / electrostrictive element according to the conventional example.

FIG. 32A is an explanatory diagram showing a polarization direction and an electric field direction in a state where an electric field (+ 3E) is applied in a positive direction to a piezoelectric / electrostrictive element according to a conventional example, and FIG. It is explanatory drawing which shows the polarization direction and electric field direction in the state which applied the predetermined negative electric field (-0.5E) to the element.

FIG. 33A is an explanatory view showing a polarization direction and an electric field direction in a state where an electric field (−3E) is applied to a piezoelectric / electrostrictive element according to a conventional example in a negative direction, and FIG. FIG. 4 is an explanatory diagram showing a polarization direction and an electric field direction when a predetermined positive electric field (+ 0.5E) is applied to a strain element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Base 12 ... Actuator part 14 ... Depressed part 16 ... Vibration part 18 ... Fixed part 20 ... Piezoelectric / electrostrictive layer 22a, 22b ... A pair of electrodes 24 ... Actuator part main body

Claims (11)

[Claims] A piezoelectric / electrostrictive section having a piezoelectric / electrostrictive layer and a pair of electrodes formed on one main surface of the piezoelectric / electrostrictive layer; and another main surface of the piezoelectric / electrostrictive layer. A piezoelectric / electrostrictive element including a unimorph type piezoelectric / electrostrictive element main body having a vibrating section that supports the piezoelectric / electrostrictive operating section in contact with the main body, and a fixed section that supports the vibrating section so as to vibrate; A piezoelectric / electrostrictive element, wherein a bending displacement characteristic of the piezoelectric / electrostrictive element body due to an applied electric field which is four times or more a predetermined electric field between the pair of electrodes is asymmetric about a reference electric field point. 2. The piezoelectric / electrostrictive element according to claim 1, wherein an electric field is applied to the reference electric field point when the electric field is at least four times as large as two predetermined electric fields having the same absolute value and different directions. A piezoelectric / electrostrictive element having a relationship of A ≧ 1.5B, where the amounts are A and B. 3. A piezoelectric / electrostrictive operating portion having a piezoelectric / electrostrictive layer, and a pair of electrodes formed on one main surface of the piezoelectric / electrostrictive layer, and another main surface of the piezoelectric / electrostrictive layer. A unimorph-type piezoelectric / electrostrictive element main body having a vibrating portion that contacts the piezoelectric / electrostrictive operating portion and supports the vibrating portion so that it can vibrate; Let the distance be x (1 μm ≦ x ≦ 200 μ
m), and the thickness of the piezoelectric / electrostrictive layer is set to y (1 μm ≦ y ≦ 10
0 μm), wherein y = ax, and 1/10 ≦ a ≦ 100. 4. The piezoelectric / electrostrictive element according to claim 1, wherein the vibrating portion and the fixed portion are integrally formed of ceramics, and a space corresponding to the vibrating portion is vacant. A piezoelectric / electrostrictive element, wherein the vibrating portion is formed to be thin. 5. The piezoelectric / electrostrictive element according to claim 3, wherein 1/5 ≦ a ≦ 10. 6. The piezoelectric / electrostrictive element according to claim 5, wherein 1/2 ≦ a ≦ 5 and 1 μm ≦ x ≦ 60 μm,
A piezoelectric / electrostrictive element, wherein 1 μm ≦ y ≦ 40 μm. 7. The piezoelectric / electrostrictive element according to claim 3, wherein when the thickness of the vibrating portion is z (1 μm ≦ z ≦ 50 μm), the relationship y = bz is satisfied. And 1/5 ≦ b ≦ 10.
Electrostrictive element. 8. The piezoelectric / electrostrictive element according to claim 7, wherein 1/3 ≦ b ≦ 5. 9. The piezoelectric / electrostrictive element according to claim 8, wherein 1/3 ≦ b ≦ 5 and 1 μm ≦ y ≦ 40 μm,
A piezoelectric / electrostrictive element, wherein 1 μm ≦ z ≦ 20 μm. 10. The piezoelectric / electrostrictive element according to claim 4, wherein a cross-sectional shape in a shortest dimension passing through the center of the vibrating portion is:
A piezoelectric / electrostrictive element which satisfies the following conditions in a no-load state. (1) At least a part of the upper surface near the center of the piezoelectric / electrostrictive layer is formed from a reference line formed by connecting one outermost minimum point and the other outermost minimum point close to the fixed portion. , Projecting in a direction opposite to the vibrating portion. (2) When the outermost minimum point does not exist, a point corresponding to a boundary point with the fixed portion on the upper surface of the vibrating portion along the shortest dimension is set as the outermost minimum point. (3) When the boundary between the vibrating portion and the fixed portion is point 0, and the shortest dimension length of the vibrating portion is 100, the outermost minimum point is the shortest dimension length of the vibrating portion from the point 0. If it is not within the range of 40%, a point corresponding to a boundary point with the fixed portion on the upper surface of the vibrating portion along the shortest dimension is set as the outermost minimum point. 11. The piezoelectric / electrostrictive element according to claim 10, wherein the protrusion amount t satisfies m / 1000 ≦ t ≦ m / 10.