JPH0851241A - Piezoelectric/electrostrictive film element and its manufacture - Google Patents

Abstract

PURPOSE:To provide a piezoelectric/electrostrictive film element and its advantageous manufacturing method whereby the strain and stress in its piezoelectric/ electrostrictive operation part can be changed efficiently into displacements and the reduction percentages of the displacements in the case of the concurrent operations of a plurality of piezoelectric/electrostrictive operation parts can be made small. CONSTITUTION:A piezoelectric/electrostrictive film element has a ceramic base body 2 wherein a diaphragm part 10 is so provided as to cover a window part 6, and it has a film-like piezoelectric/electrostrictive operation part 18 provided in the diaphragm part 10 which comprises a lower electrode 12, a piezoelectric/ electrostrictive layer 14 and an upper electrode 16. In this piezoelectric/ electrostrictive film element, the shape of the diaphragm part 10 is made protrusive outward. Also, in the case of manufacturing such piezoelectric/ electrostrictive film element, the ceramic base body 2 whose diaphragm part 10 is made protrusive outward is prepared, and its outside surface, at least the lower electrode 12 and the piezoelectric/electrostrictive layer 14 are formed in one body.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a piezoelectric / electrostrictive film type element, and in particular, a filter, a display, a microphone, a sounding body (speaker, etc.), various vibrators and oscillators, and further a unimorph type used for a sensor and the like. The present invention relates to a piezoelectric / electrostrictive film type element of a type that generates a bending displacement or force, or detects a bending displacement or force, and a manufacturing method thereof.
The element called here means not only an element that converts electric energy into mechanical energy, that is, mechanical displacement, stress or vibration, but also an element that performs the opposite conversion.

[0002]

BACKGROUND ART In recent years, in fields such as optics and precision processing,
A displacement element that adjusts the optical path length and position on the order of submicrons and a detection element that detects a minute displacement as an electrical change have been desired, and in response to this, a piezoelectric material such as a ferroelectric substance is used. Development of piezoelectric / electrostrictive elements used for actuators and sensors, which are elements that utilize the phenomenon of displacement due to the inverse piezoelectric effect that occurs when an electric field is applied to a material, or the opposite phenomenon There is. Among them, in a speaker or the like, a conventionally known unimorph type or the like is preferably adopted as such a piezoelectric / electrostrictive element structure.

Therefore, even the applicant of the present application,
As Japanese Patent Laid-Open No. 3-128681 and Japanese Patent Laid-Open No. 5-49270, a piezoelectric / electrostrictive film type element (actuator) made of ceramics, which can be suitably used in various applications, has been proposed. This piezoelectric / electrostrictive film type element has at least one window portion and at least one thin wall portion is formed by integrally providing a thin diaphragm portion so as to cover the window portion. Equipped with a ceramic base,
And on the outer surface of the diaphragm portion of the ceramic substrate,
A piezoelectric / electrostrictive actuating portion including a combination of a lower electrode, a piezoelectric / electrostrictive layer, and an upper electrode has a structure in which the piezoelectric / electrostrictive operating portion is integrally laminated by a film forming method. In addition to being a highly reliable actuator, it has the excellent features that large displacement can be obtained at low drive voltage, and that the response speed is fast and the generated force is large. It is extremely useful as an actuator member.

However, as a result of further study by the present inventors on such a piezoelectric / electrostrictive film type element, such a piezoelectric / electrostrictive film type element was found to have a piezoelectric / electrostrictive film element at a predetermined position of a diaphragm portion of a ceramic substrate. The lower electrode, the piezoelectric / electrostrictive layer, and the upper electrode that form the strain actuating portion are sequentially laminated in layers by a film forming method, and the necessary heat treatment (baking) is performed so that the piezoelectric / electrostrictive actuating portion is formed. Since it is a structure integrally provided on the diaphragm part, the rigidity of the thin diaphragm part is not sufficient and the mechanical strength is low, so the natural frequency is small,
Since the response speed is slow, and in addition, the piezoelectric / electrostrictive actuating portion, specifically, the heat treatment (firing) at the time of forming the piezoelectric / electrostrictive layer has a small operating characteristic of the piezoelectric / electrostrictive film type element. It became clear that they would be affected.

That is, the piezoelectric / electrostrictive layer (piezoelectric / electrostrictive operating portion) is subjected to heat treatment during the formation of the piezoelectric / electrostrictive layer.
Causes stress due to firing shrinkage between it and the diaphragm portion of the ceramic substrate, which prevents sintering of the piezoelectric / electrostrictive layer, making it difficult to perform the sintering sufficiently. It is not possible to obtain sufficient operating characteristics.

Further, in an actuator member or the like of a display, a plurality of windows are provided on a predetermined ceramic substrate in a predetermined arrangement form, and the thin diaphragm portion formed in the windows is provided with the above-mentioned structure. Piezoelectric / electrostrictive operating parts such as those described above are formed. However, due to the firing of the piezoelectric / electrostrictive layer described above, the thin diaphragm portion is bent, and the stress that remains after firing causes the adjacent piezoelectric / electrostrictive layers to move. There is also an inherent problem that the amount of displacement when the electrostrictive actuators are simultaneously driven is significantly lower than that when they are independently driven. When two adjacent piezoelectric / electrostrictive actuating parts are driven simultaneously, the displacements of the diaphragm parts provided with the piezoelectric / electrostrictive actuating parts interfere with each other, which reduces the amount of displacement. is there.

[0007]

The present invention has been made in view of such circumstances, and a problem to be solved by the present invention is to provide a piezoelectric element on an outer surface of a diaphragm portion forming a thin wall portion of a ceramic substrate. In a piezoelectric / electrostrictive film type element in which an electrostrictive actuating portion is formed by a film forming method, strain or stress generated in the piezoelectric / electrostrictive actuating portion can be efficiently converted into displacement, and a plurality of piezoelectric / electrostrictive Even in the case where the actuating portion is provided, it is to make it possible to reduce the displacement reduction rate when they are simultaneously driven.

Another object of the present invention is to provide a method capable of advantageously manufacturing a piezoelectric / electrostrictive film type element having such excellent characteristics.

[0009]

In order to solve the above problems, the present invention has at least one window part, and
A ceramic substrate integrally provided with a thin diaphragm portion so as to cover the window portion, a lower electrode, a piezoelectric / electrostrictive layer and an upper portion which are sequentially provided in layers on the outer surface of the diaphragm portion by a film forming method. A piezoelectric / electrostrictive film type element including a film-shaped piezoelectric / electrostrictive actuating portion composed of electrodes,
The diaphragm portion of the ceramic substrate has a shape that is convex outward, and the film-shaped piezoelectric / piezoelectric element is formed on the convex outer surface.
A piezoelectric / electrostrictive film type element characterized in that an electrostrictive actuating portion is formed is its gist.

According to the preferred embodiment of the piezoelectric / electrostrictive film type element according to the present invention, the protrusion amount of the diaphragm portion of the ceramic substrate protruding outward passes through the center of the window portion. It will be 5% or less of the shortest dimension.

According to another preferred embodiment of the present invention, the average crystal grain diameter of the diaphragm portion of the piezoelectric / electrostrictive film type element is 5 μm or less, and the thickness of the diaphragm portion is 50 μm or less. Piezo /
The thickness of the electrostrictive operating portion will be 100 μm or less.

Further, according to one of the preferred embodiments of the piezoelectric / electrostrictive film type element according to the present invention, the ceramic substrate has a plurality of windows, and the diaphragms project outward in the windows. A structure in which the piezoelectric / electrostrictive operating portion is formed on the outer surface of each of the diaphragm portions is adopted.

In order to advantageously obtain such a piezoelectric / electrostrictive film type element, the present invention has at least one window portion, and a thin diaphragm portion is integrally formed so as to cover the window portion. A ceramic substrate provided, and a film-shaped piezoelectric / electrostrictive actuating portion composed of a lower electrode, a piezoelectric / electrostrictive layer, and an upper electrode, which are sequentially formed in layers on the outer surface of the diaphragm by a film forming method. A method of manufacturing a piezoelectric / electrostrictive film type element having the above-mentioned method, in which a diaphragm portion of the ceramic substrate has an outwardly convex shape, and then on the outer surface of the outwardly convex diaphragm portion Then, the lower electrode and the piezoelectric / electrostrictive layer are sequentially formed into a layer by a film forming method, and the upper electrode is further provided if necessary, and then the piezoelectric / electrostrictive layer is fired to form the diaphragm portion. Convex Also a method for manufacturing a piezoelectric / electrostrictive film type element characterized in that integrally formed at least said lower electrode and the piezoelectric / electrostrictive layer on the outer surface, is to its gist.

[0014]

As described above, according to the present invention, the film-like film formed by the film-forming method is formed on the outer surface of the diaphragm portion integrally formed so as to cover the window provided on the ceramic substrate. In the piezoelectric / electrostrictive film type element having the piezoelectric / electrostrictive operation part, the diaphragm portion is formed in a convex shape outward, and a film-shaped piezoelectric / electrostrictive operation part is formed on the outer surface thereof. However, an example of such a piezoelectric / electrostrictive film type element to which the present invention is applied is shown in FIGS. 1 and 2. In the specific example illustrated here, the number of windows is one.

That is, in these figures, the ceramic substrate 2 is superposed on one surface of a base plate 4 having a predetermined thickness as a support having a rectangular window 6 of a predetermined size, and the window 6 is formed. The thin diaphragm plate 8 that covers the base plate 4 is integrally formed, and the portion of the diaphragm plate 8 located in the window portion 6 of the base plate 4 serves as the diaphragm portion 10. Then, on the outer surface of the diaphragm portion 10 of the plate-shaped ceramic substrate 2, the thin film-shaped lower electrode 1 is formed.
2. The piezoelectric / electrostrictive layer 14 and the upper electrode 16 are sequentially laminated and formed by a normal film forming method, and are integrally formed as a film-shaped piezoelectric / electrostrictive operating portion 18. It is to be noted that, as is well known, a predetermined voltage is applied to the lower electrode 12 and the upper electrode 16 through respective lead portions (not shown).

Therefore, in the piezoelectric / electrostrictive film type element having such a structure, when it is to function as an actuator, it is provided between the two electrodes 12 and 16 constituting the piezoelectric / electrostrictive actuating portion 18. When electricity is applied in the same manner as in the conventional case and an electric field is caused to act on the piezoelectric / electrostrictive layer 14 by this, an electric field induced strain caused by such an electric field is induced, and a lateral effect of this electric field induced strain is caused. The bending displacement or force in the direction perpendicular to the plate surface of the ceramic base 2 (diaphragm portion 10) is exhibited.

In the piezoelectric / electrostrictive film type element according to the present invention, the diaphragm portion 10 of the ceramic substrate 2 is provided.
As shown in FIG. 3, a convex shape outward, in other words, a curved shape protruding to the side opposite to the window 6 is formed, and the piezoelectric / electrostrictive actuating portion is attached to the curved outer surface. 18 is formed so that the piezoelectric /
The strain and stress generated in the electrostrictive actuating portion 18 can be efficiently converted into the displacement, and the displacement reduction rate when the adjacent piezoelectric / electrostrictive operating portions 18 are simultaneously driven can be effectively reduced.

That is, as shown in FIG. 3, by driving the piezoelectric / electrostrictive actuating portion 18 formed on the outer surface of the diaphragm portion 10 having a convex shape, the element displacement direction is
The direction of the stress generated in the piezoelectric / electrostrictive actuating portion 18 during driving (arrow in the figure:
According to the (B direction), a force in the arrow direction: A acts on the diaphragm portion 10 at its base portion, and a force acts in a direction to push the main body portion (base plate 4 portion) of the ceramic base 2. . Therefore, even if the adjacent piezoelectric / electrostrictive actuating portions 18 are simultaneously driven, the decrease in the displacement amount is small, and the change in the displacement amount can be reduced as compared with the case where they are independently driven. Moreover, the diaphragm portion 10
Of the piezoelectric / electrostrictive operating portion 18 (specifically, at least the lower electrode 12 and
By forming the electrostrictive layer 14), the rigidity of the site can be advantageously increased. Further, due to the convex shape of the diaphragm portion 10, the load due to the pressing force in the direction of entering the window portion 6 from the outside of the diaphragm portion 10 mainly enters the diaphragm portion 10 as a compressive stress. In addition, the mechanical strength against pressing force from such a direction is also excellent, and further, the natural frequency of the diaphragm portion 10 including the piezoelectric / electrostrictive operating portion 18 is increased, and the response speed is increased. It also demonstrates.

In this piezoelectric / electrostrictive film type element,
The amount of protrusion of the ceramic substrate 2 in a shape that is convex outward of the diaphragm portion 10 will be appropriately determined so that the object of the present invention can be achieved, but generally in order to secure an effective displacement amount. , The amount of protrusion is
The protrusion rate (h) in the vicinity of the central portion of the diaphragm portion 10 with respect to the shortest dimension (m) passing through the center of the window 6 in the ceramic base 2, in other words, the maximum protrusion amount (h) in percentage, the protrusion rate [y. = (H / m) × 100] is 50
% Or less, and in order to obtain a particularly large amount of displacement, the amount of protrusion is preferably 5 which is the shortest dimension passing through the center of the window portion 6.
% Or less [(h / m) × 100 ≦ 5].

In the piezoelectric / electrostrictive film type element according to the present invention as described above, various known materials are appropriately selected as a material for providing the ceramic substrate 2 on which the piezoelectric / electrostrictive operating portion 18 is formed. In general, stabilized zirconia materials, partially stabilized zirconia materials, alumina materials, and mixed materials thereof are preferably used. Among them, in particular, the inventors of the present invention described in JP-A-5-270912. As has been clarified, by adding a compound such as yttrium oxide, the crystal phase is mainly tetragonal, or a mixed crystal mainly composed of at least two crystal phases of cubic, tetragonal and monoclinic. A partially stabilized zirconia-based material is preferably used. Ceramic substrate 2 formed from such a material
The reason is that, even when the plate thickness is thin, it exhibits great mechanical strength and high toughness, and has a small chemical reaction with the piezoelectric / electrostrictive material. The ceramic base 2
Using a machining method such as a die or ultrasonic machining,
The diaphragm plate 8 (diaphragm portion 1
It is preferable from the viewpoint of high reliability that thin green sheets giving 0) are laminated, thermocompression-bonded, and then fired and integrated. The ceramic constituting the diaphragm portion 10 in which the piezoelectric / electrostrictive operating portion 18 of the ceramic base 2 is formed generally has a crystal grain diameter of 5 μm or less, preferably 2 μm or less, from the viewpoint of mechanical strength. Further, the thickness of the diaphragm portion 10 is generally 50 μm or less, preferably 30 μm or less, and more preferably 15 μm in order to obtain high-speed response and large displacement of the element.
The following is desirable.

Further, each green sheet for providing the base plate 4 and the diaphragm plate 8 can be formed by superposing a plurality of sheet components. Further, here, the shape of the window portion 6 of the ceramic base 2, that is, the shape of the diaphragm portion 10 is
Although the shape is a rectangle (quadrangle), the shape is not limited to this, and may be, for example, a circle, a polygon, an ellipse, or a combination thereof depending on the application of the piezoelectric / electrostrictive film type element. An arbitrary shape such as the above will be appropriately selected. In the shape of the window portions 6, the shortest dimension (m) passing through the center thereof is, for example, in the case of a circle, its diameter,
In the illustrated rectangle, it corresponds to the length of its short side, and in the case of an ellipse, it corresponds to the length of its short axis.

Then, on the diaphragm portion 10 of the ceramic substrate 2 thus obtained, predetermined electrodes 12, 16 are provided.
The piezoelectric / electrostrictive layer 14 is provided, and the piezoelectric / electrostrictive operating portion 18 is provided.
Various known film forming methods are appropriately adopted to form the piezoelectric film. However, when forming the piezoelectric / electrostrictive layer 14, a thick film forming process such as screen printing, spraying, coating, dipping, or coating is performed. The method is preferably adopted. If this thick film forming method is used, the average particle diameter is 0.0
About 1 μm to 7 μm, preferably 0.05 μm to 5 μm
This is because a film can be formed on the outer surface of the diaphragm portion 10 of the ceramic base 2 by using a paste or slurry containing piezoelectric / electrostrictive ceramic particles of about m as the main component, and good element characteristics can be obtained. . Among the thick film forming methods, the screen printing method is particularly preferably used because fine patterning can be formed at low cost. The thickness of the piezoelectric / electrostrictive layer 14 is preferably 50 μm in order to obtain a large displacement at a low operating voltage.
It is desirable that the thickness is more preferably 3 μm or more and 40 μm or less.

The electrode material for the lower electrode 12 and the upper electrode 16 constituting the piezoelectric / electrostrictive operating portion 18 is not particularly limited as long as it is a conductor that can withstand a high temperature oxidizing atmosphere. For example, it may be a simple metal or an alloy, a mixture of an insulating ceramic and a simple metal, or a mixture thereof, or a conductive ceramic.
However, more preferably, high melting point noble metals such as platinum, palladium and rhodium, or silver-palladium, silver-platinum,
An electrode material containing an alloy such as platinum-palladium as a main component, or a cermet material of platinum and a ceramic substrate material or a piezoelectric material is preferably used. Among these, it is more preferable to use only platinum or a material containing a platinum-based alloy as a main component. The ratio of the ceramic base material added to the electrode material is preferably about 5 to 30% by volume, and the ratio of the piezoelectric / electrostrictive material is preferably about 5 to 20% by volume.

The electrodes 12 and 16 are respectively
By using such a conductor material, the thick film forming method described above or a normal film forming method by a thin film forming method such as sputtering, ion beam, vacuum deposition, ion plating, CVD, or plating will be formed.
Among them, for forming the lower electrode 12, a thick film forming method such as screen printing, spraying, dipping or coating is preferably adopted, and for the upper electrode 16, a similar thick film forming method or the above-mentioned thin film is used. A forming method is also suitably adopted, and the electrodes 12 and 16 are both formed to have a thickness of generally 20 μm or less, preferably 5 μm or less. The total thickness of the piezoelectric / electrostrictive operating portion 18, which is obtained by adding the thickness of the piezoelectric / electrostrictive layer 14 to the thickness of these electrodes 12 and 16, is generally 100 μm or less, preferably 50 μm or less. It

Further, as the piezoelectric / electrostrictive material for providing the film-shaped piezoelectric / electrostrictive layer 14 in the piezoelectric / electrostrictive operating portion 18,
Preferably, a material containing lead zirconate titanate (PZT system) as a main component, a material containing lead magnesium niobate (PMN system) as a main component, a material containing lead nickel niobate (PNN system) as a main component, and manganese. Lead niobate-based material, lead antimony stannate-based material, lead zinc niobate-based material, lead titanate-based material, lead magnesium tantalate-based material A material, a material containing lead nickel tantalate as a main component, a composite material thereof, or the like is used. Furthermore, lanthanum, barium, niobium, zinc, cerium,
Materials containing oxides such as cadmium, chromium, cobalt, antimony, iron, yttrium, tantalum, tungsten, nickel, manganese, lithium, strontium, and bismuth, and other compounds as additives, such as PLZT-based materials As described above, a material obtained by appropriately adding a predetermined additive to the above material is also suitably used.

Among these piezoelectric / electrostrictive materials, materials containing lead magnesium niobate, lead zirconate, and lead titanate as main components, lead nickel niobate, lead magnesium niobate, and zirconate. A material containing a component consisting of lead and lead titanate as a main component, a material containing a component consisting of lead magnesium niobate, lead nickel tantalate, lead zirconate and lead titanate, or lead magnesium tantalate. Materials containing a main component of lead magnesium niobate, lead zirconate, and lead titanate as the main components, and those obtained by substituting a part of lead with strontium and / or lanthanum, etc. are advantageously used. It is recommended as a material for forming the piezoelectric / electrostrictive layer 14 by a thick film forming method such as the screen printing described above. In the case of a multi-component piezoelectric / electrostrictive material, the piezoelectric / electrostrictive characteristics change depending on the composition of the components. However, lead magnesium niobate-lead zirconate-which is preferably used in the present invention
Three component materials of lead titanate, lead magnesium niobate-lead nickel tantalate-lead zirconate-lead titanate,
In addition, in the four-component material of lead magnesium tantalate-lead magnesium niobate-lead zirconate-lead titanate,
A composition in the vicinity of the phase boundary of pseudo-cubic crystal-tetragonal crystal-rhombohedral crystal is preferable, and particularly, lead magnesium niobate: 15 to 50 mol%, lead zirconate: 10 to 45 mol%, lead titanate: 3
0-45 mol% composition and lead magnesium niobate: 1
5 to 50 mol%, lead nickel tantalate: 10 to 40 mol%, lead zirconate: 10 to 45 mol%, lead titanate:
30-45 mol% composition, further lead magnesium niobate: 15-50 mol%, lead magnesium tantalate: 1
A composition of 0 to 40 mol%, lead zirconate: 10 to 45 mol%, and lead titanate: 30 to 45 mol% is advantageously adopted because it has a high piezoelectric constant and an electromechanical coupling coefficient.

The respective films (12, 14, 16) formed on the outer surface of the diaphragm portion 10 of the ceramic substrate 2 as described above are heat-treated (baked) each time the respective films are formed. Then, the ceramic substrate 2, specifically, the diaphragm portion 10 may be formed into an integral structure. Further, after all the films are formed, they are heat treated (baked) at the same time so that the respective films are simultaneously formed. It may be configured to be integrally connected to. Depending on the method of forming the electrode films (12, 16), heat treatment (baking) of the electrode films for such integration may not be necessary. Further, as the heat treatment (baking) temperature for integrating the film thus formed and the diaphragm portion, a temperature of about 500 ° C to 1400 ° C is generally adopted, and particularly preferably 1000 ° C to 140 ° C.
Temperatures in the range of 0 ° C. are advantageously chosen. Further, when the film-shaped piezoelectric / electrostrictive layer 14 is heat-treated (baked), the composition of the piezoelectric / electrostrictive layer is prevented from becoming unstable at a high temperature together with an evaporation source of such piezoelectric / electrostrictive material. It is preferable to perform heat treatment (baking) while controlling the atmosphere, and also to mount the appropriate cover member on the piezoelectric / electrostrictive layer 14 so that the surface of the piezoelectric / electrostrictive layer 14 is directly exposed to the baking atmosphere. It is also recommended to use a method of baking so as not to expose it.
In that case, a material similar to that of the substrate is used as the cover member.

By the way, the piezoelectric / electrostrictive film type element having such a structure is manufactured by various methods based on the knowledge of those skilled in the art. For example, the coefficient of thermal expansion of the ceramic substrate 2 portion and the piezoelectric / electrostrictive actuating portion. A method of controlling the coefficient of thermal expansion of the 18th portion to simultaneously fire the piezoelectric / electrostrictive layer 14 of the piezoelectric / electrostrictive operating portion 18 and to make the diaphragm portion 10 of the ceramic substrate 2 have a convex shape; Piezoelectric / electrostrictive layer 1 of portion 18
When firing No. 4, a method of exerting a pressing force on the diaphragm portion 10 to form an outwardly convex shape; taking into consideration the firing shrinkage rate of the piezoelectric / electrostrictive layer 14 of the piezoelectric / electrostrictive operating portion 18. At the same time as the formation of the piezoelectric / electrostrictive actuating portion 18 (specifically, at least the lower electrode 12 and the piezoelectric / electrostrictive layer 14), the method of controlling the two coefficients of thermal expansion is applied to the outside of the diaphragm portion 10. Although it is possible to adopt a method of forming the convex shape of the ceramic base 2, it is advantageous to prepare the ceramic base 2 in which the diaphragm portion 10 is projected outward as shown in FIG. The method of forming the predetermined piezoelectric / electrostrictive operating portion 18 on the outer surface of the portion 10 protruding outward is preferably adopted from the viewpoint of industrial productivity.

That is, in such an advantageous method, as shown in FIG. 4 (a), first, the diaphragm portion 10 of the ceramic base 2 has a shape protruding outward, in other words, opposite to the window portion 6. Shape protruding to the side (projection amount: H)
Then, as shown in (b), the lower electrode 12 and the piezoelectric / electrostrictive layer 14 are sequentially layered on the outer surface of the outwardly convex diaphragm portion 10 by a film forming method. And then, if necessary, the upper electrode 16 is formed, the piezoelectric / electrostrictive layer 14 is fired to obtain the desired piezoelectric / electrostrictive film type element as shown in (c). It is designed to be manufactured. The firing shrinkage caused by the firing of the piezoelectric / electrostrictive layer 14 is absorbed by the large convex shape (projection amount: H) of the diaphragm portion 10, whereby the protrusion amount: h of the diaphragm portion 10 after firing is Therefore, the stress generated when the piezoelectric / electrostrictive layer 14 is contracted by firing is effectively reduced, and the piezoelectric / electrostrictive layer 14 is reduced in size (h <H).
The sintering of the electrostrictive layer 14 can be effectively advanced, and the compactness thereof can be advantageously improved.

The ceramic substrate 2 used in such a method, in which the diaphragm portion 10 has an outwardly convex shape, has a sintering rate of the base plate 4 and the diaphragm plate 8 (see FIGS. 1 and 2) constituting the ceramic substrate 2. It can be easily obtained by a method of controlling the shrinkage rate, controlling the shape of the diaphragm plate 8 before firing, or a method of making the diaphragm plate 8 project by utilizing the difference in thermal expansion between them. More specifically, the sintering of the green sheet that provides the diaphragm plate 8 proceeds first, the sintering of the green sheet that provides the base plate 4 is delayed, or the contraction rate of the green sheet for the diaphragm plate 8 due to the sintering does not exceed the base plate. Four
The firing shrinkage of the green sheet for use is increased, and the difference in sintering shrinkage is used to cause the diaphragm portion 10 to project outward.

Further, the protrusion amount H of the diaphragm portion 10 of the ceramic substrate 2 before the piezoelectric / electrostrictive operating portion 18 is formed is defined as the firing shrinkage ratio of the piezoelectric / electrostrictive layer 14 and the final diaphragm portion. The amount of protrusion of 10: will be appropriately determined depending on the degree of h, etc., but in general, it is 1 to 55 of the shortest dimension (m) passing through the center of the window portion 6.
%, Preferably 2-10% will be advantageously employed. This is because if the protrusion amount: H is too small, the diaphragm portion 10 will be recessed inward by firing the piezoelectric / electrostrictive layer 14, and if it is too large, This is because it becomes difficult to generate an effective displacement by driving the piezoelectric / electrostrictive operating unit 18.

Further, in this method, the lower electrode 12, the piezoelectric / electrostrictive layer 14, and the upper electrode 16 formed on a predetermined portion of the outer surface of the diaphragm portion 10 of the ceramic substrate 2 are all formed by the above-mentioned film forming method. And the piezoelectric / electrostrictive operating portion 18 is integrally formed on the diaphragm portion 10 by being formed into a layer having a desired thickness as described above. It is formed as a result. The firing of the piezoelectric / electrostrictive layer 14 is preferably performed at the stage where it is formed on the lower electrode 12 (therefore, the upper electrode 16 is not formed), but the upper electrode 16 is further formed thereon. Piezoelectric / electrostrictive layer 14
There is no problem even if firing is performed.

The piezoelectric / electrostrictive film type element according to the present invention thus obtained has a high rigidity at the diaphragm portion, and has a high rigidity at the diaphragm portion, and the outside of the diaphragm portion. It has excellent mechanical strength against pressing force from, and has a characteristic that the natural frequency is large and the response speed is fast, and the displacement amount when adjacent piezoelectric / electrostrictive actuating parts are driven simultaneously is
It exhibits a special feature that it is almost the same as the displacement amount in the case of each individual drive, and it can be advantageously used for various applications such as sensors and actuators. Of.

Of course, the piezoelectric / electrostrictive film type element according to the present invention can be effectively displaced by the operation of the piezoelectric / electrostrictive operating portion provided on the outer surface side of the diaphragm portion. Various piezoelectric /
It can be advantageously used as an electrostrictive film type element. That is, in addition to filters, various sensors such as acceleration sensors and shock sensors, transformers, microphones, sounding bodies (speakers, etc.), power and communication oscillators and oscillators, displays and Kenji Uchino (ed. ) "Piezoelectric /
Electrostrictive Actuator From Basic to Applied "(Morikita Publishing)
As a piezoelectric / electrostrictive film type actuator of a type that causes a bending displacement, such as a unimorph type used in a servo displacement element, a pulse drive motor, an ultrasonic motor, etc.
It can be used particularly advantageously.

Incidentally, FIG. 5 schematically shows an example of the piezoelectric / electrostrictive film type element according to the present invention, and FIG. 6 shows an exploded perspective view thereof. The piezoelectric / electrostrictive film type device 20 shown in the figure is the ceramic base 2
2 and the piezoelectric / electrostrictive actuating portion 24 arranged on the outer surface of the diaphragm portion (26) projecting outward, and the piezoelectric / electrostrictive actuating portion 24 is integrated.
However, the thin diaphragm portion (26) of the ceramic base 22 is bent and deformed according to the applied voltage.

More specifically, in the ceramic base 22, the closing plate (diaphragm plate) 26 and the connecting plate (base plate) 28, which are each made of a zirconia material and have a thin flat plate shape, are spacer plates (base plates) that are also made of a zirconia material. It is integrally formed with a structure in which 30 is sandwiched in between. A plurality of communication opening portions 32 (here, three) are formed on the connection plate 28 at predetermined intervals, and are configured to serve as communication portions with the outside. The number, shape, size, position, etc. of the communication openings 32 are appropriately selected depending on the application of the piezoelectric / electrostrictive film type element 20. In addition, the spacer plate 30 includes
A plurality of (here, three) square windows 36 are formed. Then, the spacer plate 30 is formed so that each one communication opening 32 provided in the connection plate 28 is opened in each of the windows 36.
Are superposed on the connection plate 28. Furthermore, a closing plate 26 is placed on the surface of the spacer plate 30 opposite to the side on which the connection plate 28 is placed, and the opening of the window portion 36 is covered by the closing plate 26. There is. As a result, a pressure chamber 38 that communicates with the outside through the communication opening 32 is formed inside the ceramic substrate 22. It should be noted that such a ceramic substrate 22 is formed as an integrally fired product by using a predetermined ceramic material, here, a zirconia material, as described above. In addition, here, the three-layer structure product including the closing plate (diaphragm plate), the spacer plate (base plate), and the connection plate (base plate) is illustrated, but a four-layer structure product or that as shown in FIG. 7 is used. It is also possible to use the above multi-layer structure product. In FIG. 7, reference numerals 46 and 48 respectively denote an intermediate chamber and a communication hole.

In addition, in the ceramic base 22, the film-shaped piezoelectric / electrostrictive actuating portion 2 is provided on the outer surface of the closing plate 26 at a portion corresponding to each pressurizing chamber 38.
4 are provided. The piezoelectric / electrostrictive actuating portion 24 has a lower electrode 40, a piezoelectric / electrostrictive layer 42, and an upper electrode 44 formed on the outer surface of the closing plate 26 located at the window portion 36 of the ceramic base 22, that is, the diaphragm portion. It is configured by sequentially forming by a forming method.

Therefore, in the piezoelectric / electrostrictive film type element 20 in which the piezoelectric / electrostrictive operating portion 24 is integrally provided on the diaphragm portion (26) of the ceramic substrate 22 as described above, Based on the operation of the electrostrictive operating unit 24, the inside of the pressurizing chamber 38 is pressurized, and thus the discharge of the fluid in the pressurizing chamber 38 can be effectively realized. Further, the piezoelectric / electrostrictive film type element of this structure can be used not only as an actuator but also as a sensor by taking out the bending displacement of the diaphragm portion as a voltage signal.

As described above, the piezoelectric / electrostrictive film type element according to the present invention is used as an actuator or a sensor, and is preferably a display, a speaker, a servo displacement element, a pulse drive motor, an ultrasonic motor, an acceleration sensor, or an impact sensor. It is needless to say that it can be used as a member, but of course, it can be advantageously used for various other known uses.

[0040]

Hereinafter, typical examples of the present invention will be described to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. It goes without saying that it is not what you receive.
Further, in addition to the specific description above, in addition to the following examples, the present invention, various modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention,
It should be understood that modifications, improvements, etc. can be made.

Example 1 0.5 mm in the longitudinal direction of a rectangular ceramic substrate with an arrangement similar to that shown in FIG. 6 at intervals of 0.2 mm.
Four rectangular windows having a size of 0.7 mm are arranged along the extending direction of the sides having a length of 0.5 mm of the rectangular windows, and the windows have a size of 10 μm. A ceramic base body having an integral structure in which a diaphragm portion having a thickness is covered is prepared. This ceramic substrate is formed by a conventional method using a green sheet formed by using a powder of a zirconia material partially stabilized with yttria and having an average particle diameter of 0.4 μm for both the substrate body and the diaphragm. The substrate body was molded and fired according to the procedure described above, and the thickness of the base body was 200 μm after firing.

Then, a platinum paste was used at a predetermined position on the outer surface of the diaphragm portion of the ceramic substrate by screen printing so as to have a thickness of 5 μm after firing, and dried at 120 ° C. for 10 minutes. After 1350
A lower electrode is formed by firing at 2 ° C. for 2 hours, and a material made of lead magnesium niobate, lead zirconate, and lead titanate is used as a piezoelectric / electrostrictive material on the lower electrode, and after firing, To be 30 μm in thickness by screen printing, drying at 120 ° C. for 20 minutes, and then firing the piezoelectric / electrostrictive layer at 1300 ° C.,
A piezoelectric / electrostrictive layer was formed. Further, by using the ceramic substrate having the lower electrode and the piezoelectric / electrostrictive layer formed on the diaphragm portion in this way, the alumina ceramic pins having a convex shape are fitted into the respective window portions, and the respective diaphragm portions are placed inside. By pressing from the side (where the lower electrode and the piezoelectric / electrostrictive layer are not formed) and re-baking at a temperature of 1300 ° C., each diaphragm part is projected outward at a rate of 20 μm (h). A shaped ceramic substrate was obtained.

Thereafter, on the lower electrode and the piezoelectric / electrostrictive layer provided on the diaphragm portion of the ceramic substrate thus obtained, which is convex outward, Cr thin film and Cu thin film are further used as upper electrodes. A piezoelectric / electrostrictive film type element (element of the present invention) which is formed by a sputtering method and is thus intended
I got The total thickness of the upper electrode is 0.3 μm.
m. In addition, a voltage of 100 V was applied between the upper electrode and the lower electrode of each piezoelectric / electrostrictive actuating portion in the obtained piezoelectric / electrostrictive film type element to perform polarization treatment.

On the other hand, as a conventional element, the ceramic substrate prepared as described above was used, and a plate of a piezoelectric / electrostrictive material having a thickness of 30 μm was pasted on the diaphragm portion using a conductive adhesive. A piezoelectric / electrostrictive element similar to the above was produced.

With respect to the two elements thus obtained, the ratio of the displacement amount at the time of full drive / the displacement amount at the time of single drive when the voltage is applied to each piezoelectric / electrostrictive operating portion to drive it is obtained, and The natural frequency and the breaking load of the diaphragm portion of the device were determined, and the results are shown in Table 1 below.

In the operation evaluation of the piezoelectric / electrostrictive actuating portion in each element, a voltage of 30 is applied in the same direction as the polarization process.
V is applied between the upper electrode and the lower electrode of each piezoelectric / electrostrictive operating portion of each element, and the displacement amount (single displacement amount) of each piezoelectric / electrostrictive operating portion is measured by a laser Doppler device. , Its natural frequency was measured. In addition, a voltage of 30 V is applied to all four piezoelectric / electrostrictive operating parts of each element, the displacement amount of each piezoelectric / electrostrictive operating part is measured, and the average value thereof is taken as the displacement amount at the time of full driving. did. Then, from these obtained values, (total driving displacement / single displacement) × 100
The ratio (%) of the total drive amount / single drive displacement amount was calculated in (%). Further, the breaking load is obtained by pressing the vicinity of the center of each diaphragm part of each element from the outside (the side on which the lower electrode and the piezoelectric / electrostrictive layer are formed) with an indenter having a diameter of 0.2 mm. It was

[0047]

As is clear from the results shown in Table 1, there is an element in which the diaphragm portion of the ceramic substrate is convex outward and the piezoelectric / electrostrictive operating portion is formed on the convex outer surface according to the present invention. It is recognized that the amount of displacement of the piezoelectric / electrostrictive actuating portion at the time of full driving is substantially equal to the amount of displacement at the time of single driving, which is significantly improved compared to 50% of the conventional element. Further, also in the natural frequency and the breaking load, in the element according to the present invention, compared with the conventional element,
A remarkable improvement effect is recognized.

Example 2 A ceramic mixed powder consisting of 3 mol% yttria partially stabilized zirconia powder: 80% by weight and alumina powder: 20% by weight and having an average particle size of 0.4 μm was used, and a binder and a plastic were prepared in accordance with a conventional method. A slurry was prepared by mixing the agent and the organic solvent, and a green sheet for a base plate was formed from the slurry by a doctor blade method so that the thickness after firing was 200 μm.

On the other hand, a 3 mol% yttria partially stabilized zirconia powder having an average particle diameter of 0.3 μm was mixed with a binder, a plasticizer and an organic solvent according to a conventional method to prepare a slurry, which was then placed in a reverse roll coater apparatus. A green sheet for a diaphragm plate was formed so that the thickness after firing was 10 μm.

Then, the green sheet for base plate obtained as described above is punched out with a predetermined die (formation of a window portion), and the green sheet for diaphragm plate produced above is superposed on it. , 100 kg
Thermocompression bonding was performed under the condition of 80 ° C. × 1 minute under a pressure of / cm ² . Then, the obtained monolithic laminate was fired at a temperature of 1500 ° C. for 2 hours to obtain a ceramic substrate in which the diaphragm portion was projected outward (protrusion amount: H = 30 μm).

Next, using the obtained ceramic substrate, on the outer surface of the diaphragm portion protruding outward,
When the lower electrode and the piezoelectric / electrostrictive layer were formed and fired in the same manner as in Example 1, the protrusion amount of the diaphragm portion was about 20 μm (=
h). Then, an upper electrode was formed on the fired piezoelectric / electrostrictive layer in the same manner as in Example 1 to obtain a piezoelectric / electrostrictive film type element according to the present invention.

With respect to the piezoelectric / electrostrictive film type element thus obtained, the total drive / single drive displacement amount, natural frequency and breaking load were measured in the same manner as in Example 1, and the element in Example 1 was obtained. Similar excellent results were obtained.

Example 3 A piezoelectric / electrostrictive film type according to the present invention was carried out in the same manner as in Example 1 except that the convex shape (amount of protrusion) of the alumina ceramic pin that pressed the diaphragm portion of the ceramic substrate during re-baking was changed. A device was produced. By changing the alumina ceramic pins, the element obtained in this example has a diaphragm portion with a height of 40 μm (= h).
The shape became convex outward.

With respect to the piezoelectric / electrostrictive film type element thus obtained, the total drive / single drive displacement amount, natural frequency and breaking load were measured in the same manner as in Example 1, and the results are shown in Table 2 below. Indicated. Table 2 also shows the evaluation results for the element of the present invention obtained in Example 1. As is clear from the comparison of the evaluation results, the convexity of the diaphragm portion of the ceramic substrate is shown. 8%, it is recognized that the natural frequency and the breaking load are excellent. On the other hand, in the single drive displacement amount, a convexity of 4% makes it possible to obtain a large displacement. is there.

[0056] Convex rate: (h / m) x 100 (%)

[0057]

As is apparent from the above description, according to the present invention, the rigidity of the diaphragm portion of the ceramic substrate where the piezoelectric / electrostrictive operating portion is provided can be effectively enhanced, and the outside of the diaphragm portion can be effectively improved. The mechanical strength and natural frequency against the pressure from can be effectively increased, the response speed can be advantageously increased, and the strain and stress generated in the piezoelectric / electrostrictive operating part can be efficiently displaced. A piezoelectric / electrostrictive film type element having excellent characteristics such as changeability can be effectively realized.

Further, in the piezoelectric / electrostrictive film type element according to the present invention, even when the plurality of piezoelectric / electrostrictive actuating portions are simultaneously driven, the respective displacement amounts are the same. Compared to the case where the parts are driven independently, it does not decrease so much, and in the drive form of these piezoelectric / electrostrictive actuating parts, there is no problem that the amount of displacement changes, etc. Therefore, it becomes an element of uniform quality.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an example of a basic structure of a piezoelectric / electrostrictive film type element according to the present invention.

2 is a cross-sectional explanatory view of the piezoelectric / electrostrictive film type device shown in FIG.

3 is an enlarged explanatory view of a cross section in the direction of the shortest dimension (the short side direction of the window portion 6) passing through the center of the window portion in the piezoelectric / electrostrictive film type element shown in FIG.

FIG. 4 is an enlarged partial cross-sectional explanatory view showing steps of an example of a method for manufacturing a piezoelectric / electrostrictive film type element according to the present invention.

FIG. 5 is a cross-sectional view showing an example of a piezoelectric / electrostrictive film type element according to the present invention.

FIG. 6 is an exploded perspective view of the piezoelectric / electrostrictive film type element shown in FIG.

FIG. 7 is a cross-sectional view showing another example of the piezoelectric / electrostrictive film type element according to the present invention.

[Explanation of symbols]

 2 Ceramic Base 4 Base Plate 6 Window 8 Diaphragm Plate 10 Diaphragm Part 12 Lower Electrode 14 Piezoelectric / Electrostrictive Layer 16 Upper Electrode 18 Piezoelectric / Electrostrictive Actuator

Claims (7)

[Claims] 1. Having at least one window,
A ceramic substrate integrally provided with a thin diaphragm part so as to cover the window part, a lower electrode, a piezoelectric / electrostrictive layer and an upper part which are sequentially provided in layers on the outer surface of the diaphragm part by a film forming method. A piezoelectric / electrostrictive film type element comprising a film-shaped piezoelectric / electrostrictive operating portion composed of electrodes, wherein a diaphragm portion of the ceramic substrate has a shape protruding outward, and an outer surface of the protruding shape The film-shaped piezoelectric /
A piezoelectric / electrostrictive film type element, wherein an electrostrictive actuating portion is formed. 2. The piezoelectric / electrostrictive element according to claim 1, wherein the protrusion amount of the shape protruding outward of the diaphragm portion of the ceramic substrate is 5% or less of the shortest dimension passing through the center of the window portion. Membrane type device. 3. The piezoelectric / electrostrictive film type element according to claim 1, wherein the average crystal grain size of the diaphragm portion is 5 μm or less. 4. The thickness of the diaphragm portion is 50 μm
The piezoelectric / electrostrictive film type element according to any one of claims 1 to 3, which is as follows. 5. The piezoelectric / electrostrictive operating portion has a thickness of 100.
The piezoelectric / electrostrictive film type element according to any one of claims 1 to 4, which has a thickness of not more than μm. 6. The ceramic substrate has a plurality of windows, and the diaphragms are integrally formed in the windows so as to project outward, and the diaphragms are formed on the outer surfaces of the respective diaphragms. The piezoelectric / electrostrictive film type element according to any one of claims 1 to 5, wherein the piezoelectric / electrostrictive operating portion is formed. 7. Having at least one window,
A ceramic substrate integrally provided with a thin diaphragm part so as to cover the window part, a lower electrode, a piezoelectric / electrostrictive layer and an upper part which are sequentially provided in layers on the outer surface of the diaphragm part by a film forming method. A method for manufacturing a piezoelectric / electrostrictive film type element having a film-like piezoelectric / electrostrictive actuating portion composed of electrodes, in which a diaphragm portion of the ceramic substrate has an outwardly convex shape is prepared. Then, the lower electrode and the piezoelectric / electrostrictive layer are sequentially formed in layers on the outer surface of the outwardly convex diaphragm portion by a film forming method, and after the upper electrode is further provided as necessary. A piezoelectric / electrostrictive film type element, characterized in that the piezoelectric / electrostrictive layer is fired to integrally form at least the lower electrode and the piezoelectric / electrostrictive layer on the convex outer surface of the diaphragm portion. Manufacturing method.