JPH03128681A - Piezoelectric/electrostrictive film type actuator - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric/electrostrictive film type actuator having the high speed of response and large generating force by laminating a first electrode film, a piezoelectric/electrostrictive film and a second electrode film onto a ceramic substrate. CONSTITUTION:A lower electrode film 4, a piezoelectric/electrostrictive film 6 and an upper electrode film 8 are laminated successively onto one surface of a ceramic substrate 2. The lower and upper electrode films 4, 8 are extended from the end section of the piezoelectric/electrostrictive film 6 respectively, lead sections 4a, 8a are shaped, and electricity is conducted through each electrode film 4, 8 through these lead sections 4a, 8a. The electric-field induced strain of the piezoelectric/electrostrictive film 6 is induced by conduction, and flexing displacement in the direction vertical to the board surface of the ceramic substrate 2 or generating force is developed by the transversal effect of the strain. Accordingly, large displacement is acquired at low driving voltage, and a piezoelectric/electrostrictive film type actuator, the speed of response of which is increased and the degree of integration of which can be improved, is obtained.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a piezoelectric/electrostrictive film actuator used in displacement control elements, solid element motors, inkjet heads, relays, switches, shutters, print heads, pumps, fans, etc. It is something. Note that the actuator described here means an element that converts electrical energy into mechanical energy, that is, into mechanical displacement or stress.

(Background Art) In recent years, in fields such as optics and precision processing, there has been a demand for displacement elements that adjust optical path length and position on the order of submicrons.
The development of piezoelectric/electrostrictive actuators, which are elements that utilize displacement based on the inverse piezoelectric effect and electrostrictive effect induced when an electric field is applied to piezoelectric/electrostrictive materials such as ferroelectrics, is underway. .

By the way, as the structure of this piezoelectric/electrostrictive actuator, monomorph type, unimorph type, bimorph type, laminated type, etc. are known, but among these, the monomorph type, unimorph type, and bimorph type are Although a relatively large displacement can be obtained by using the transverse effect of induced strain, it has the inherent problems of a small generated force, slow response speed, and poor electromechanical conversion efficiency. Ta. On the other hand, the laminated type utilizes the longitudinal effect of electric field-induced strain, so it is superior in terms of generated force and response speed, and also has high electromechanical conversion efficiency, but it has the inherent problem of small generated displacement. ing.

Moreover, these conventional unimorph and bimorph actuators each employ a structure in which plate-shaped components such as piezoelectric/electrostrictive plates are attached using adhesive. There were also problems with the reliability of its operation.

As described above, conventional piezoelectric/electrostrictive actuators each have their own advantages and disadvantages, and also have several inherent problems that need to be solved.

(Solution Division B) The present invention was made against this background, and its problem is not a structure stuck with an adhesive or the like, but a relatively low driving voltage. The present invention aims to provide a piezoelectric/electrostrictive film type actuator that has a structure that allows large displacement, fast response speed, and large generated force, and allows for high integration.

(Solution Means) In order to solve such problems, the present invention includes a first electrode film, a piezoelectric/electrostrictive film, and a second electrode film on at least one surface of a ceramic substrate. At least one of the piezoelectric/electrostrictive actuators consisting of a combination of the following is characterized by a piezoelectric/electrostrictive film type actuator having a structure in which these films are sequentially laminated in a layered manner.

(Operation/Effect) According to the piezoelectric/electrostrictive film type actuator structure according to the present invention, since it is a film-like piezoelectric/electrostrictive body, large displacement can be achieved at a relatively low driving voltage. Furthermore, it exhibits characteristics such as fast response speed, large generated force, and furthermore, enables high integration. In other words, by stacking the films in layers on a substrate to create an integrated laminated structure, large bending displacements due to the lateral effect of electric field-induced strain can be avoided, despite the structure being somewhat similar to the conventional bulk laminated type. This results in a piezoelectric/electrostrictive film actuator that has the characteristics of high response speed and large generated force.

Further, the present invention provides a substrate and an electrode film, or a piezoelectric/electrode film and a piezoelectric/electrode film.
Since the electrostrictive film is a constituent element, it can be used to
Because the piezoelectric/electrostrictive film actuator is integrated without the use of so-called adhesives, as is used in conventional unimorph and bimorph actuators, it is highly reliable for long-term use, and has low displacement. It also exhibits the characteristic of small quantity drift.

Furthermore, in the piezoelectric/electrostrictive film actuator according to the present invention, since the piezoelectric/electrostrictive driving section is formed in a film shape, it is possible to easily form a large number of elements on the same substrate surface. It also has the feature of allowing high integration of the strain drive section.

In addition, in the piezoelectric/electrostrictive film type actuator according to the present invention, in order to be able to drive at low voltage and obtain large bending displacement and generated force, it is advantageous that the thickness is 300 μm or less,
It is preferably 150 μm or less, and the bending strength of the ceramic substrate used at that time is generally 1200 μm or less.
kgf/c angle 2 or more, preferably 1500 kgf
It will be adjusted to a value of /cm2 or more.

(Specific Structure/Examples) The present invention will be explained in more detail below with reference to drawings showing a specific structure of a piezoelectric/electrostrictive film type actuator according to the present invention.

First, FIG. 1 shows an example of a piezoelectric/electrostrictive film type actuator according to the present invention in which a piezoelectric/electrostrictive driving section is provided on one side of a ceramic substrate 2. On top, a lower electrode film 4, a piezoelectric/electrostrictive film 6, and an upper electrode film 8 are sequentially laminated to form a multilayer integrated structure. Note that the lower and upper electrode films 4 and 8
are extended from the ends of the piezoelectric/electrostrictive film 6 to form lead portions 4a, 8a, and current is applied to the respective electrode films 4.8 through these lead portions 4a, 8a. It looks like this.

Further, FIG. 2 shows an example of a piezoelectric/electrostrictive film type actuator according to the present invention, in which piezoelectric/electrostrictive driving parts are provided on both sides of a ceramic substrate.
The lower electrode film 4, the piezoelectric/electrostrictive film 6, and the upper electrode film 8 are sequentially laminated on each surface of the substrate 2 and the piezoelectric/electrostrictive drive unit (4, 6, 8) by heat treatment. are formed as an integrated structure.

Further, FIGS. 3 to 7 respectively show different examples of the actuator according to the present invention in which a plurality of piezoelectric/electrostrictive driving sections are provided on a ceramic substrate, and each of the plurality of piezoelectric/electrostrictive actuators is provided on a ceramic substrate. The electrostrictive drive unit is provided on the ceramic substrate in a stacked or side-by-side configuration.

For example, in the examples shown in FIGS. 3 to 5, a plurality of piezoelectric/electrostrictive drive units (4, 6, 8)
provided in side-by-side form on tfi2, in particular:
In the actuator shown in FIGS. 3 and 4, a ceramic substrate 2 (surin) 10 is placed between the plurality of piezoelectric/electrostrictive actuators (4, 6, 8), and each piezoelectric /The electrostrictive drive sections are independent from each other. Further, in the actuator shown in FIG. 5, long rectangular holes 12 are provided in the ceramic substrate 2 at a predetermined pitch to form a ladder-shaped ceramic substrate 2, and the rectangular holes 12 of the ladder-shaped ceramic substrate 2. 12
A piezoelectric/electrostrictive driving section consisting of a lower electrode film 4, a piezoelectric/electrostrictive film 6, and an upper electrode film 8 is formed on the connecting portion 2a sandwiched between the two. In addition, in FIG. 3, 14 is
This is an insulating film that electrically insulates the lower electrode 11g4 and the upper electrode film 8 at the back of the piezoelectric/electrostrictive film 6.

Further, the actuator according to the present invention shown in FIG. 6 is an example of a structure in which a plurality of piezoelectric/electrostrictive driving parts are provided in a stacked form on a ceramic substrate 2, and the actuator shown in FIG. Two piezoelectric/electrostrictive drive parts each consisting of a side electrode film 4, a piezoelectric/electrostrictive film 6, and an upper electrode film 8 are integrally formed in two stacked layers on a ceramic substrate 2. ing. Note that here, the upper electrode film 8
is used as a common electrode film for the two piezoelectric/electrostrictive drive units.

Furthermore, in the example of the piezoelectric/electrostrictive film type actuator according to the present invention shown in FIG. A plurality of piezoelectric/electrostrictive driving parts each consisting of a membrane 8 are provided in a structure in which they are integrally arranged in parallel at a predetermined pitch.

In the piezoelectric/electrostrictive film type actuator having the structure according to the present invention as described above, current is applied between the lower electrode film 4 and the upper electrode film 8 in the same manner as in the conventional method, thereby causing piezoelectric/electrostrictive When an electric field is applied to the strained film 6,
Electric field-induced strain in the piezoelectric/electrostrictive film 6 based on such an electric field is induced, and due to its lateral effect, bending displacement or generated force in the direction perpendicular to the plate surface of the ceramic substrate 2 is expressed. They are forced to do so.

By the way, in the piezoelectric/electrostrictive release actuator according to the present invention, as described above, each film is formed of an electrode material, a piezoelectric or electrostrictive material, and an electrode material on a ceramic substrate 2 that serves as an actuating plate such as a diaphragm. 4.6.8 has a multilayer structure, and the substrate 2 is heated by heat treatment.
and piezoelectric/electrostrictive drive unit (lower electrode film 4 + piezoelectric/electrostrictive film 6 +
The piezoelectric/electrostrictive release actuator is characterized in that it forms an integral structure with the upper electrode film 8) and does not use any adhesive, and can be manufactured as follows. becomes.

That is, first, in order to form the films 4, 6.8 made of each material on the ceramic substrate 2, various known film forming methods are appropriately used, such as thick film methods such as screen printing, dipping, etc. When forming the piezoelectric/electrostrictive film 6, thin film methods such as sputtering, vacuum evaporation, plating, etc. are used, and there are no particular limitations, but when forming the piezoelectric/electrostrictive film 6, methods such as screen printing, dipping, coating, etc. are used. is preferably adopted. This is because a film can be formed on a substrate using a paste or slurry containing piezoelectric/electrostrictive ceramic particles as a main component, and good actuator characteristics can be obtained. In addition, the shape of such a film can be obtained by using screen printing methods, photolithography methods, etc.
In addition to forming a pattern, unnecessary parts may be removed using a machining method such as laser processing or slicing. It is preferable to process them simultaneously to improve the degree of integration of the piezoelectric/electrostrictive drive section.

In addition, the structure of the actuator and the shape of the membrane to be manufactured are
It is not particularly stipulated, and may have any shape or structure depending on the purpose, such as polygons such as triangles and quadrilaterals, circles such as circles, ellipses, and rings, comb shapes, lattice shapes, and the like. Even if it is a special shape that combines the following, there is no problem. However, in order to take advantage of the features of the present invention, it is necessary to
A configuration in which two or more piezoelectric/electrostrictive drive sections are stacked on the same ceramic substrate as shown in the figure is advantageously adopted. In particular, an element having a comb-shaped actuator structure as shown in FIGS. 3 to 4 and 5 is preferable because the piezoelectric/electrostrictive drive unit has good integration, displacement, and vibration characteristics. This is desirable.

In addition, in the actuator according to the present invention in which a large number of piezoelectric/electrostrictive actuators are integrated on the same ceramic substrate, the piezoelectric/electrostrictive actuators are provided at a pitch narrower than at least 3000 μm, resulting in a high degree of integration. It is preferable to provide an actuator with a high degree of integration, in which the piezoelectric/electrostrictive actuator is preferably provided with a pitch narrower than 1000 μm, more preferably narrower than 500 μm.

Further, each M4.6.8 formed by the above method on the ceramic substrate 2 may be heat-treated each time the film is formed to have an integral structure with the substrate, or all layers may be formed. The layers may then be heat treated simultaneously so that each layer is integrally bonded to the substrate at the same time. In addition,
The heat treatment temperature for integrating the formed film with the substrate is generally about 800'C to 1400'C, preferably 1100'C to 140'C.
Temperatures in the range of 0° C. are used advantageously. In addition, piezoelectric/
When heat-treating an electrostrictive film, it is necessary to perform the heat treatment while controlling the atmosphere together with an evaporation source for the piezoelectric/electrostrictive material so that the composition of the piezoelectric/electrostrictive film does not become unstable at high temperatures. preferable. Furthermore, although the lower electrode film is generally provided directly on the ceramic substrate, an intermediate layer may be provided between the substrate and the electrode film for the purpose of improving bonding properties with such a substrate. In some cases, it is preferable.

Note that the term "bondability" as used herein refers to consistency between adhesiveness and coefficient of thermal expansion.

Regarding the ceramic substrate 2 used in manufacturing the actuator according to the present invention, as long as the substrate material is an insulator or dielectric material that has high mechanical strength and can be subjected to the above heat treatment, even if it is an oxide-based material, a non-oxide material can be used. Among them, a substrate formed using a material containing at least one of aluminum oxide, magnesium oxide, zirconium oxide, aluminum nitride, and silicon nitride as a main component is preferable, and particularly aluminum oxide or silicon nitride is preferable. A substrate containing zirconium oxide as a main component is advantageously used because excellent substrate characteristics can be obtained even if the plate thickness is thin. Note that silicon oxide (Si◯) contained in such a ceramic substrate material.

The amount of 5iOz) is preferably 10% by weight or less, especially 3iOz).
It is desirable that the amount is less than % by weight. Such regulation of the silicon oxide content is important in order to avoid the aforementioned reaction with the piezoelectric/electrostrictive material during heat treatment and to obtain good actuator characteristics.

Furthermore, in order to obtain high-speed response and large bending displacement in the piezoelectric/electrostrictive film actuator according to the present invention,
The thickness of such ceramic substrate 2 is generally 100 μm.
Below, preferably 50μm or less, more preferably 30μm
m or less, and its Young's modulus is 1
．． 5 x 106 kg/cm" or more, 4.5 x 106k
g/cm2 or less, especially 2. OX 106kg/cm2
Above, 4. It is preferable that OX is 106 kg/cm2 or less. Furthermore, its bending strength is 1200
kgf 7cm2 or more is preferable, especially 1500k
It is desirable that gf is 7 cm2 or more.

Note that as the ceramic substrate 2, a pre-sintered substrate may be used, or a green sheet of the substrate material may be used and sintered after the above-mentioned film formation. A pre-sintered substrate is advantageously used because it can reduce the warpage of the device and provide pattern dimensional accuracy.

Further, the shape of the ceramic substrate 2 is not particularly specified, and any shape can be adopted depending on the purpose. For example, polygons such as triangles and quadrangles, circles, ellipses, rings, etc. A special shape such as a circle, a comb shape, a lattice shape, or a combination of these may be used.

Next, the material of the electrode films 4 and 8 in the piezoelectric/electrostrictive film actuator according to the present invention is not particularly limited as long as it is a conductor that can withstand a high-temperature oxidizing atmosphere similar to the heat treatment temperature, such as metal. It may be a single substance, an alloy, a mixture of a metal or an alloy with an additive such as an insulating ceramic, and an insulating ceramic, or even a conductive ceramic. Of course, among these, electrode materials whose main components are high-melting point noble metals such as platinum, palladium, and rhodium, and alloys such as silver-palladium, platinum-platinum, and platinum-palladium are preferably used.

In addition, in the above mixture, the ceramic added to the metal or alloy is preferably the same material as the substrate material or the piezoelectric/electrostrictive material described later, and the amount added is 5 to 30 vol. %degree,
In piezoelectric/electrostrictive materials, the content is preferably about 5 to 20% by volume. In particular, a mixture in which the substrate material and the piezoelectric/electrostrictive material are mixed together with the above metal or alloy is advantageously used for forming the intended electrode film. This is those 2
This is because by blending the seed additive, the same effect as the above-mentioned intermediate layer film can be obtained.

The lower electrode film 4 and upper electrode film 8 formed using such electrode film materials will have an appropriate thickness depending on the application, but −C is preferably 15 μm or less, and preferably 15 μm or less. will be formed to a thickness of 5 μm or less.

Furthermore, in the piezoelectric/electrostrictive film actuator according to the present invention, the piezoelectric/electrostrictive film 6 constituting the piezoelectric/electrostrictive drive section may be made of any material that exhibits electric field induced distortion such as piezoelectric or electrostrictive effects. It can also be formed using the following materials.

Further, such piezoelectric/electrostrictive film materials may be crystalline materials or amorphous materials, and may be semiconductors, dielectric ceramics, or ferroelectric ceramics. Furthermore, it may be a material that requires polarization treatment or a material that does not require polarization treatment.

Of course, the piezoelectric/electrostrictive film materials used in the present invention include:
Preferably, a material whose main component is lead zirconate titanate (PZT series), a material whose main component is lead magnesium triobate (PMN series), a material whose main component is lead nickel niobate (PNN series), Materials whose main ingredient is lead manganese niobate, materials whose main ingredient is lead antimony stannate, materials whose main ingredient is lead titanate, materials whose main ingredient is barium titanate, and even composite materials of these. In addition, materials containing oxides such as lanthanum, barium, niobium, zinc, nickel, manganese, and other compounds thereof as additives to materials whose main component is PZT, such as PZT-based materials, are used.
There is no problem in adding a predetermined additive to the material as appropriate so that the material becomes LZT-based.

In the actuator having the structure according to the present invention, from the viewpoint of actuator characteristics, the piezoelectric constant is la3+1
is 50 x 10-” (C/N) or more, especially 10
0 x 10-” (C/N) or more is piezoelectric/
Therefore, it can be advantageously used as the electrostrictive film 6.

Further, the thickness of such a piezoelectric/electrostrictive film 6 is 100 μm or less, preferably 50 μm or less so that it can be driven at a low voltage.
The thickness is selected to be .mu.m or less, more preferably 30 .mu.m or less.

The piezoelectric/electrostrictive release actuator according to the present invention has been described above in detail based on the specific examples shown in the drawings, but the present invention is not limited in any way by such specific examples. It goes without saying.

In addition to the above-mentioned specific description, it is understood that various changes, modifications, improvements, etc. can be made to the present invention based on the knowledge of those skilled in the art, without departing from the spirit of the present invention. should be understood.

[Brief explanation of the drawing]

1 to 7 are perspective partial explanatory views showing different examples of piezoelectric/electrostrictive release actuators according to the present invention, respectively. 2: Ceramic substrate 42 Lower electrode film 6: Piezoelectric/electrostrictive film 8: Upper electrode film 10 Nislit
12: Rectangular hole: Insulating film

Claims (1)

[Scope of Claims] (1) On at least one surface of the ceramic substrate, at least one of the piezoelectric/electrostrictive drive parts consisting of a combination of a first electrode film, a piezoelectric/electrostrictive film, and a second electrode film is disposed on at least one surface of the ceramic substrate. A piezoelectric/electrostrictive film actuator has a structure in which these films are sequentially laminated in a layered manner. (2) The ceramic substrate weighs 1.5 x 10^6 kg/
The piezoelectric/electrostrictive film actuator according to claim 1, which has a Young's modulus of not less than cm^2 and not more than 4.5 x 10^6 kg/cm^2. (3) The thickness of the actuator is 300 μm or less, and the bending strength of the ceramic substrate is 1200 kg.
The piezoelectric/electrostrictive film actuator according to claim 1, wherein the piezoelectric/electrostrictive film actuator has a f/cm^2 or more. (4) The piezoelectric/electroelectric material according to claim (1), wherein the ceramic substrate is made of a material containing at least one of aluminum oxide, magnesium oxide, zirconium oxide, aluminum nitride, and silicon nitride. Strain film actuator. (5) The piezoelectric/electrostrictive film actuator according to claim 1 or 4, wherein a ceramic plate having a silicon oxide content of 10% by weight or less is used as the ceramic substrate. (6) The piezoelectric/electrostrictive film type actuator according to claim 1, wherein two or more piezoelectric/electrostrictive actuators are provided on the surface of the ceramic substrate in a stacked form or in a juxtaposed form. (7) The piezoelectric/electrostrictive film actuator according to claim (1) or (3), wherein the ceramic substrate has a thickness of 100 μm or less. (8) The piezoelectric/electrostrictive film actuator according to claim 1 or (7), wherein the piezoelectric/electrostrictive film has a thickness of 100 μm or less.