JP2004140397A - Piezoelectric/electrostrictive film element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a stable piezoelectric/electrostrictive film element in which the displacement, the force, or the like to the direction opposite to a cavity can be stably obtained, and the displacement and an increment in the volume of the cavity generated are almost unchanged even when the formed position of the piezoelectric/electrostrictive operating part is misaligned. <P>SOLUTION: The piezoelectric/electrostrictive film element comprises a lower-electrode-film non-forming region on the outer surface of a thin-walled portion (5a) on the cavity (5b) formed in a ceramic substrate (5), a lower electrode film formed in a specified area that surrounds the lower-electrode-film non-forming region, and a piezoelectric/electrostrictive film and an upper electrode film sequentially stacked on the lower piezoelectric/electrostrictive film, wherein all the circumference of the lower-electrode-film non-forming region is surrounded by the lower electrode film. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to various sensors such as a filter, an acceleration sensor and an impact sensor, a transformer, a microphone, a sounding body (such as a speaker), a vibrator and an oscillator for power and communication, a display and a publication “piezoelectric / electrostrictive”. Electric actuators such as unimorph type actuators that generate bending displacement used in relays and servo displacement elements described in "From Actuator Basics to Applications" (published by Morikita Publishing, Kenji Uchino, edited by Japan Industrial Technology Center) The present invention relates to a piezoelectric / electrostrictive film type element that converts energy, that is, converts mechanical displacement or stress or vibration, and vice versa.

In recent years, in fields such as optics and precision processing, 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. As a matter of course, development of actuators and sensors utilizing displacement caused by an inverse piezoelectric effect or an electrostrictive effect which occurs when an electric field is applied to a piezoelectric / electrostrictive material such as a ferroelectric material or a reverse phenomenon has been advanced.

In such a field, the development of actuators and the like is being promoted so that they can be stably realized at low cost, downsizing, low-voltage operation, and high-speed response.

FIG. 15 shows the piezoelectric / electrostrictive film type element proposed by the present inventor earlier. The element (20) has a lower electrode film (21a), a piezoelectric / electrostrictive film (21b) and an upper electrode film (21c) on a thin portion (5a) of a cavity (5b) formed in a ceramic substrate (5). It comprises a piezoelectric / electrostrictive operating part (21) which is sequentially formed. Here, when a piezoelectric material is used as the material of (21b), a voltage is applied to the upper electrode film (21c) and the lower electrode film (21a) so that the applied voltage at the time of polarization processing of the piezoelectric film is the same as that of the piezoelectric film. When the voltage is applied, (21b) is bent and displaced toward the cavity (5b) due to the transverse effect of the electric field induced strain. Further, when an electrostrictive material is used as the material of (21b), if a voltage is applied to the upper electrode film (21c) and the lower electrode film (21a), (21b) is shown in FIG. As shown in b), it is bent toward the cavity (5b).

By the way, using the element (20) as a relay or the like, the element (20) is displaced in the direction of the contact (22) provided on the upper electrode film (21c), that is, in the direction opposite to the cavity (5b). In this case, if a piezoelectric film is used for (21b), a voltage is applied between the upper electrode film (21c) and the lower electrode film (21a) with a polarity opposite to the polarity of the polarization processing. However, in this case, since the potential is limited to a potential smaller than the coercive electric field at which the polarization inversion occurs, a sufficient displacement cannot be obtained, and the displacement itself is unstable. On the other hand, if an electrostrictive film is used for (21b), the polarization direction cannot be set by performing a polarization process, so that even if the polarity of the applied voltage is changed, the displacement direction is the direction of the cavity (5b), Cannot be displaced in the direction of. That is, in the type using the lateral effect of the electric field induced strain, a large displacement cannot be stably obtained upward.
It is also possible to displace the thin portion displaced toward the cavity in the opposite direction by using the recoil when returning to the original position, but in this case, the displacement amount and displacement speed can be obtained arbitrarily. Is difficult. Further, in the device of FIG. 15, the piezoelectric / electrostrictive operating portion (21) is formed on the outer surface of the thin portion. By forming this on the inner surface of the thin portion, the device can be displaced upward. However, in the case of the cavity structure, it is not easy to form the piezoelectric / electrostrictive operating portion on the inner surface of the thin portion, and there is a problem in manufacturing. Because of the cavity structure as described above, there is a large restriction in raising the displacement direction.

Further, in the element having the conventional structure, the piezoelectric / electrostrictive operating portion (21) may be formed off the center of the thin portion (5a) as shown in FIG. is there. In this case, the displacement amount of the element becomes smaller as the thickness of the ceramic substrate is closer to the thick portion as shown in FIG. Therefore, such an element cannot obtain the original displacement amount even by using the actuation means.

Therefore, an object of the present invention is to realize an element that can stably obtain displacement, force, and the like in a contact direction of a relay, that is, in a direction opposite to a cavity in an actuator used for a relay or the like. Also, even when the formation position of the piezoelectric / electrostrictive operation portion on the thin portion of the ceramic substrate slightly deviates from the center, regardless of the deviation, the generated displacement and the increased volume in the cavity are stable with little change. It is also possible to realize a device that has been implemented.

The configuration of the present invention for achieving the above object is to provide a non-piezoelectric / electrostrictive operating portion on the outer surface of a thin portion on a cavity formed in a ceramic substrate, In which a piezoelectric / electrostrictive operating portion is formed in a predetermined range.

Specifically, the non-piezoelectric / electrostrictive operating portion is sandwiched by at least two or more piezoelectric / electrostrictive operating portions.

Also, a configuration may be adopted in which the entire periphery of the non-piezoelectric / electrostrictive operating section is surrounded by a piezoelectric / electrostrictive operating section.

Another aspect of the present invention for achieving the object is that a lower electrode film non-forming portion is provided on a thin portion outer surface on a cavity formed in a ceramic substrate, and the lower electrode film non-forming portion is provided. , A lower electrode film is provided in a predetermined area around the lower electrode film, and a piezoelectric / electrostrictive film and an upper electrode film are sequentially formed on the lower electrode film.

Specifically, the lower electrode film non-forming portion is sandwiched by at least two or more lower electrode films.

Further, a configuration in which the entire periphery of the lower electrode film non-formed portion is surrounded by the lower electrode film may be adopted.

In order to further enhance the effect of the present invention, the end of a portion composed of the lower electrode film, the piezoelectric / electrostrictive film, and the upper electrode film (hereinafter abbreviated as a piezoelectric / electrostrictive operating portion) is formed of ceramic. It is desirable to provide so as to cover the outer surface of the thick part of the substrate.

It is preferable that the ceramic substrate is made of a completely stabilized or partially stabilized material mainly composed of zirconium oxide.

Further, the piezoelectric / electrostrictive film may be made of a material mainly containing a component composed of lead magnesium niobate, lead zirconate, and lead titanate, or a material composed of lead nickel niobate, lead magnesium niobate, lead zirconate, and lead titanate. Or a material mainly composed of lead nickel tantalate and lead magnesium niobate and lead zirconate and lead titanate; or a material mainly composed of lead magnesium tantalate and lead magnesium niobate and zirconate It is desirable to be made of a material mainly containing a component composed of lead and lead titanate.

更 に Further, it is desirable that the thin portion on the cavity has a thickness of 50 μm or less.

[Action]
When a voltage is applied to the upper electrode film and the lower electrode film of the piezoelectric / electrostrictive operating portion provided in a predetermined range around the non-piezoelectric / electrostrictive operating portion, an electric field-induced strain is generated in the piezoelectric / electrostrictive film, and the electric field-induced strain is generated. Due to the effect, the piezoelectric / electrostrictive operating portion is bent downward (toward the cavity).
However, bending ends of the piezoelectric / electrostrictive operating portions near the thick portions on both sides of the thin portion of the ceramic substrate are prevented from bending downward by the thick portions. Therefore, in the piezoelectric / electrostrictive operating portion, the end on the thin portion side is lifted upward (in the direction opposite to the cavity) with the vicinity of the thick portion of the piezoelectric / electrostrictive film as a fulcrum. That is, the element as a whole is displaced upward.

In the configuration in which the non-piezoelectric / electrostrictive operating portion is sandwiched by at least two or more piezoelectric / electrostrictive operating portions, a voltage is applied to the upper electrode film and the lower electrode film of each piezoelectric / electrostrictive operating portion. In each of the piezoelectric / electrostrictive operating portions, the end on the thin portion side is lifted upward (in the direction opposite to the cavity) with the vicinity of the thick portion of the piezoelectric / electrostrictive film as a fulcrum. That is, the element as a whole is displaced upward.

Further, even in a configuration in which the entire periphery of the non-piezoelectric / electrostrictive operating section is surrounded by the piezoelectric / electrostrictive operating section, by applying a voltage to the upper electrode film and the lower electrode film of the piezoelectric / electrostrictive operating section, The / electrostrictive operating portion is lifted upward (in the direction opposite to the cavity) on the thin portion side with the vicinity of the thick portion of the piezoelectric / electrostrictive film as a fulcrum. That is, the element as a whole is displaced upward.

Then, a lower electrode film non-formed portion is provided on the thin portion outer surface on the cavity formed in the ceramic substrate, a lower electrode film is provided in a predetermined range around the lower electrode film non-formed portion, and the lower electrode film is formed on the lower electrode film. In a configuration in which a piezoelectric / electrostrictive film and an upper electrode film are sequentially laminated, a voltage is applied to the upper electrode film and the lower electrode film, so that the piezoelectric / electrostrictive operation on the ceramic substrate provided with the lower electrode film is performed. The portion is lifted upward (in the direction opposite to the cavity) on the thin portion side with the vicinity of the thick portion of the piezoelectric / electrostrictive film as a fulcrum. That is, the element as a whole is displaced upward.

In a configuration in which the lower electrode film non-formed portion is sandwiched by at least two or more lower electrode films, a voltage is applied to the upper electrode film and the lower electrode film to form the lower electrode film on the ceramic substrate provided with each lower electrode film. The piezoelectric / electrostrictive operating portion is lifted upward (in the direction opposite to the cavity) on the thin portion side with the vicinity of the thick portion of the piezoelectric / electrostrictive film as a fulcrum. That is, the element as a whole is displaced upward.

Further, even in a configuration in which the entire periphery of the lower electrode film non-formed portion is surrounded by a lower electrode film, a voltage is applied to the upper electrode film and the lower electrode film to form a piezoelectric / electrode on the ceramic substrate provided with the lower electrode film. The electrostriction actuating portion is lifted upward (in the direction opposite to the cavity) at the thin portion side end with the vicinity of the thick portion of the piezoelectric / electrostrictive film as a fulcrum. That is, the element as a whole is displaced upward.

Incidentally, the term “piezoelectric / electrostrictive” means that either piezoelectric or electrostrictive can be selected. When called “piezoelectric / electrostrictive film”, the piezoelectric film or the electrostrictive film is used as a piezoelectric / electrostrictive operating section. When it is referred to, it means a piezoelectric actuator or an electrostrictive actuator.

According to the present invention, when a voltage is applied between the upper and lower electrode films so that the applied voltage is the same as the applied voltage during the polarization processing of the piezoelectric film layer, the thin portion on the cavity formed on the ceramic substrate when the voltage is applied is changed to the opening of the cavity. In the opposite direction to increase the volume in the cavity (a negative pressure can be generated in the cavity). In addition, since the polarization characteristics of the piezoelectric film are not impaired, the characteristics inherent to the element are not reduced. When an electrostrictive film is used, the thin portion can be curved in a direction opposite to the opening of the cavity regardless of the polarity of the applied voltage. Furthermore, even if the formation position of the piezoelectric / electrostrictive operation portion is shifted, a displacement amount substantially equal to that when there is no shift can be obtained, so that the yield in element manufacturing can be improved.

Hereinafter, the device of the present invention will be described in detail with reference to the drawings. To facilitate understanding, the same reference numerals are given to components having the same structure and function throughout the drawings.

FIG. 1 is an explanatory cross-sectional view showing one embodiment of the device of the present invention. FIG. 2 (a) is an external perspective view of a device in which a piezoelectric / electrostrictive operating portion is formed in each cavity on a ceramic substrate having a plurality of cavities. FIG. 3B is a sectional view taken along the line AA. (1) shows an element, and (2) and (3) show piezoelectric / electrostrictive operation parts, respectively. The piezoelectric / electrostrictive operating part (2) is composed of a piezoelectric / electrostrictive film (2b) and a lower electrode film (2a) formed on a thin portion (5a) of a ceramic substrate (5) having a cavity (5b). The upper electrode film (2c) is integrally formed by sequentially laminating the upper electrode film (2c), and the piezoelectric / electrostrictive operating section (3) also has a piezoelectric / electrostrictive film (3b) and an upper electrode film (3b) on the lower electrode film (3a). 3c) is integrally formed by sequentially laminating. Each piezoelectric / electrostrictive operating portion is provided on a thin portion (5a) such that one end of the piezoelectric / electrostrictive operating portion extends on an outer surface of a thick portion (5c) of a ceramic substrate (5), and each lower electrode film (2a), (3a) is provided at appropriate intervals between them. (4) is a resin layer formed between the piezoelectric / electrostrictive actuators (2) and (3) and the upper electrode films (2c) and (3c) for the purpose of improving insulation and reliability. The portion (8) sandwiched between the / electrostrictive operating portions (2) and (3) is the non-piezoelectric / electrostrictive operating portion.

FIG. 3 is an explanatory sectional view showing the operation of the device of the present invention. Here, a piezoelectric film is used for (2b) and (3b), and (2) and (3) are piezoelectric actuators, respectively. In the same figure (a), the upper and lower electrode films (2c) and (3c) and the lower electrode films (2a) and (3a) have the same polarity as the applied voltage during the polarization processing of the piezoelectric films (2b) and (3b). When a voltage is applied so as to generate electric field, an electric field-induced strain is generated, and the transverse effect causes the piezoelectric film (2b) to bend toward the cavity (5b). However, one end of the piezoelectric actuating portion (2) is formed on the outer surface of the thick rigid portion (5c) on both sides of the thin portion (5a), and the other end is formed on the thin rigid portion (5a). Therefore, the portion near the thick portion (5c) of the piezoelectric film (2b) is hardly bent and displaced, and the portion on the thin portion (5a) side is easily bent and displaced. That is, the piezoelectric film (2b) tends to lift upward on the thin portion (5a) side (the opposite side to the cavity (5b)) with a large displacement with the thick portion (5c) side as a fulcrum. The portion (5a) curves upwardly convex as shown in FIG. 3 (b). At this time, the other piezoelectric actuator (3) also bends in the same manner, so that the entire thin portion (5a) of the ceramic substrate (5) has a shape curved upwardly convex. Also, a displacement equivalent to that of the conventional element shown in FIG. 15 can be obtained upward by the synergistic effect of the displacement of the two piezoelectric actuators (2) and (3). In the case where the electrostrictive film is used in (2b) and (3b), the displacement of the element can be obtained according to the same principle as the case where the piezoelectric film is used regardless of the polarity of the applied voltage. Further, according to the element of the present invention, the volume of the cavity is increased as a result of the element being displaced upward, so that, for example, a hole (7) is formed through the bottom of the cavity as shown in FIG. In this way, the thick portion (5c) is formed so as to communicate between the adjacent cavities (5b), and can be used as a pump for sucking a fluid.

FIG. 4 is a cross-sectional explanatory view showing the operation when the formation position of the piezoelectric / electrostrictive operating portion forming the element of the present invention is shifted. As shown in FIG. 7A, both piezoelectric / electrostrictive actuating parts (2) and (3) are formed so as to be shifted toward the right thick part (5c) of the ceramic substrate (5). Similarly, when a predetermined voltage is applied to each of the upper electrode films (2c) and (3c) and each of the lower electrode films (2a) and (3a), the thin portion (5a) is moved upward as shown in FIG. It can be curved in a convex shape. In this case, the displacement of the piezoelectric / electrostrictive operating part (3) shifted to the thick part (5c) on the right side is reduced by the amount shifted to the thick part (5c), but to the thin part (5a) side. Since the displacement of the displaced piezoelectric / electrostrictive operating section (2) increases by the amount of the displacement, as a result, the increased displacement of the piezoelectric / electrostrictive operating section (2) increases. ) Compensates for the insufficient displacement amount, and a displacement amount substantially equal to that when formed without displacement can be obtained. As described above, even if the film formation position is allowed to some extent as a secondary effect of the configuration of the present invention, the characteristics of the element are not affected, and thus there is an advantage that the yield in element manufacturing can be improved.

FIG. 5 is an explanatory sectional view showing another configuration of the element of the present invention. The feature of this element (14) is that, unlike the element of the above embodiment, the lower electrode film non-formed portion (9) provided on the thin portion (5a) is sandwiched between the lower electrode films (15a) and (16a). The piezoelectric / electrostrictive film (17) covering the lower electrode films (15a) and (16a) and the upper electrode film (18) are formed in common. In this way, by using only one piezoelectric / electrostrictive film, the manufacture of the element becomes easier and the cost can be reduced as compared with the case where the piezoelectric / electrostrictive films are individually formed as in the above embodiment. However, since the piezoelectric / electrostrictive film (17) is also provided in the central portion of the device, the rigidity of the device is increased as compared with the device having the resin layer in the central portion. Is smaller than the displacement of the separated element.

FIG. 6 shows another embodiment of the element of the present invention in which one end of each of the piezoelectric / electrostrictive actuating parts (15) and (16) on the thick part (5c) side does not cover the outer surface of the thick part (5c). It is sectional explanatory drawing which shows an example. Even in such a structure, the piezoelectric / electrostrictive operating portions (15) and (16) can be displaced upward (in the direction opposite to the cavity (5b)) as a whole by the same principle as described above. However, since the fulcrum of each piezoelectric / electrostrictive operating part (15), (16) at the time of displacement is on the thin part (5a) having low rigidity, the thick part ( The element is smaller than the element having a structure in which one end on the 5c) side is on the outer surface of the thick portion (5c).

FIG. 7 is a sectional explanatory view of an example in which a plurality of elements (1),... (1) are formed on a ceramic substrate. As shown in the figure, only necessary elements among a plurality of elements can be operated and used for switching.

Also, as in the element (19) in FIG. 8, the piezoelectric / electrostrictive operating portion and the thin portion are curved in a convex shape in advance so that the thin portion (5a) can be easily moved upward even with a low stress. It can also be curved.

FIG. 9 is an explanatory cross-sectional view of a device in which a groove (6) deeper than the thin portion (5a) is formed in the thick portion (5c) of the ceramic substrate. With this configuration, the rigidity of the substrate around the piezoelectric / electrostrictive operating portion is reduced, and the thin portion (5a) is easily displaced. Therefore, since the substrate easily follows the behavior of the thermal contraction of the piezoelectric / electrostrictive operating portion, the substrate material and the piezoelectric / electrostrictive generated in the heat treatment process for integrating the piezoelectric / electrostrictive operating portion with the ceramic substrate are facilitated. It is possible to suppress the residual stress due to the difference in thermal expansion coefficient from the film material and the force that hinders the firing / shrinkage of the piezoelectric / electrostrictive film to a low level, so that the material characteristics inherent to the piezoelectric / electrostrictive film material can be sufficiently obtained. . In addition, since grooves are formed between adjacent elements, it is possible to buffer the force of the thin portions of adjacent cavities pulling each other, and to reduce interference due to displacement of other elements. Therefore, it is possible to draw out the original displacement of the element. The shape of the groove is not limited to the V-shaped shape as in the present embodiment, but may be a shape formed in a direction perpendicular to the substrate surface or a trapezoidal shape, and the number of grooves may be appropriately changed. .

FIG. 10 is an explanatory view showing another configuration of the element of the present invention. FIG. 2A is a plan view of the element 23 viewed from above, and FIG. 2B is a cross-sectional view taken along line BB of FIG. The feature of this element (23) is that, unlike the element of each of the above embodiments, four piezoelectric / electrostrictive operating parts (24) opposed to each other on a thin part (5a) of one cavity (5b),. (24) is formed, and the non-piezoelectric / electrostrictive operating portion (11) is formed on the thin portion (5a) where the piezoelectric / electrostrictive operating portion (24) is not formed. When a voltage is applied to each of the upper electrode film (24c) and the lower electrode film (24a) of each piezoelectric / electrostrictive operating portion (24), each piezoelectric / electrostrictive operating portion (24) With the vicinity of the substrate thick part (5c) of (24b) as a fulcrum, the end on the thin part (5a) side is lifted in the direction of the contact (22) (the direction opposite to the cavity (5b)). That is, the element (23) is displaced so that the contact (22) is a vertex and the whole is raised. Even if the shape of the cavity (5b) is a columnar shape, a columnar shape having an oblong cross section, or the like, a non-piezoelectric / electrostrictive operating portion is provided in at least two or more places of the cavity thin portion as in the case of the quadrangular prism shape. By disposing the piezoelectric / electrostrictive operating portion so as to sandwich or surround it, the entire element can be displaced so as to rise.

FIG. 11 is an explanatory view showing another embodiment of the device of the present invention. FIG. 11A is a plan view of the element 25 as viewed from above, and FIG. 10B is a cross-sectional view taken along the line CC of FIG. The feature of this element (25) is that it has a configuration in which one piezoelectric / electrostrictive operating portion is provided for one cavity thin portion, but along the upper peripheral edge of the thin portion (5a) of the cylindrical cavity (5b). Thus, a piezoelectric / electrostrictive operating section (26) is formed, and the inside surrounded by the piezoelectric / electrostrictive operating section (26) is used as a non-piezoelectric / electrostrictive operating section (11). Then, when a voltage is applied to the upper electrode film (26c) and the lower electrode film (26a), the element (25) is displaced so as to swell with the contact (22) as a vertex. Even when the shape of the cavity is a quadrangular prism, a column having an oblong cross section, or the like, the piezoelectric / electrostrictive operating portion is arranged along the upper peripheral edge of the cavity as in the case of the cylindrical shape. It can be displaced so that the whole swells. When a piezoelectric film is used for (24b) of the element (23) shown in FIG. 10 and (26b) of the element (25) shown in FIG. 11, a voltage having the same polarity as the applied voltage at the time of polarization processing of the piezoelectric film is used. Is applied, the displacement of the element can be obtained when the electrostrictive film is used, and the displacement of the element can be obtained according to the same principle as when the piezoelectric film is used regardless of the polarity of the applied voltage.

In the above embodiments, the case where the contact (22) is formed on the upper electrode film has been described. However, as shown in FIG. 12, the contact may not be formed and the upper electrode film may be used instead of the contact. In the case of this element, the principle and method of displacement are the same as those of the above embodiments.

Also, as shown in FIG. 13, the piezoelectric / electrostrictive operating portions (28), (28) in which the upper electrode film is divided are formed, and an element structure in which no resin is formed between the piezoelectric / electrostrictive operating portions, The element can be displaced upward by the same principle and method as the element of each of the above embodiments.

Further, as shown in FIG. 14, the element structure in which the upper electrode film is divided and the piezoelectric / electrostrictive operating portions (29), (29) sharing the piezoelectric / electrostrictive film are formed may be used. The element can be displaced upward by the same principle and method.
The elements shown in FIGS. 12 to 14 may have the element structure shown in FIG. 10 or FIG. 11, and the shape of the cavity may be a quadrangular prism, a cylinder, a column having an oblong cross section, or the like.

By the way, the dimensions and the material composition of the piezoelectric / electrostrictive operating portions described above may be the same between the paired piezoelectric / electrostrictive operating portions, but different dimensions, configurations and materials within the range described in the present application. A filter, a transformer, and the like can also be formed using the piezoelectric / electrostrictive operation section pair having the configuration.

The thickness of the thin portion (5a) of the cavity serving as the diaphragm is generally 50 μm or less, preferably 30 μm or less, and more preferably 10 μm or less, in order to obtain high-speed response and large displacement of the piezoelectric / electrostrictive operating portion. Formed.

Further, the piezoelectric / electrostrictive film forming the element of the present invention covers the lower electrode film as shown in FIG. 1 and the like, and is formed in such a size that an end protrudes above the ceramic substrate. Precise positioning of aligning the end of the piezoelectric / electrostrictive film with the end of the lower electrode film becomes unnecessary, and short circuit can be easily prevented.

Further, in order to sufficiently exhibit the material characteristics of the piezoelectric / electrostrictive film of the element of the present invention, the ceramic substrate is made of a completely stabilized or partially stabilized material mainly composed of zirconium oxide. It is desirable.

In order to completely or partially stabilize zirconium oxide, as is generally known, an alkaline earth or rare earth oxide can be used. Preferably, yttrium oxide, cerium oxide, At least one of magnesium and calcium oxide is used. The content of yttrium oxide is preferably 1 mol% to 30 mol%, that of cerium oxide is 6 mol% to 50 mol%, and that of magnesium oxide and calcium oxide is 5 mol% to 40 mol%. In particular, yttrium oxide is desirably 2 mol% to 4 mol%. This is because zirconium oxide to which yttrium oxide is added in such a range has its crystal layer partially stabilized, and exhibits excellent substrate characteristics particularly in strength, toughness, and reliability.

Also, a sintering aid such as clay may be added to the substrate material, but at least in the ceramic substrate constituting the thin portion, silicon oxide, boron oxide, phosphorus oxide, germanium oxide, etc. are easily vitrified. It is desirable to adjust the composition and amount of the auxiliary agent so that the material is not contained in an amount of 1% by weight or more. This is because if the substrate contains the material that is easily vitrified, a reaction is likely to occur during heat treatment with the piezoelectric / electrostrictive film, and it is difficult to control the composition of the piezoelectric / electrostrictive film.

By the way, such a ceramic substrate effectively receives the operating characteristics of the piezoelectric / electrostrictive operating portion formed thereon, in other words, the strain and force generated therein, and effectively performs the opposite operation. Therefore, the surface roughness represented by Ra is adjusted to be in the range of 0.03 to 0.9 μm. Such adjustment of the surface roughness Ra is also effective in securing the strength of a thin substrate.

In order to form a piezoelectric / electrostrictive operating portion by providing a predetermined lower electrode film, an upper electrode film, and a piezoelectric / electrostrictive film on such a ceramic substrate, various known film forming techniques are appropriately used. For example, a method of forming a thick film such as screen printing, spraying, dipping, or coating, and a method of forming a thin film such as ion beam, sputtering, vacuum deposition, ion plating, CVD, or plating are appropriately selected. In particular, in order to form a piezoelectric / electrostrictive film, a thick film forming method by screen printing, spraying, dipping, coating, or the like is suitably adopted. This is because, according to those thick film forming techniques, a paste or slurry containing, as a main component, a ceramic particle of a piezoelectric / electrostrictive material having an average particle diameter of 0.01 μm or more and 5 μm or less, preferably 0.05 μm or more and 3 μm or less is used. This is because a film can be formed on the ceramic substrate, and good device characteristics can be obtained. In addition, as for the shape of such a film, in addition to pattern formation using a screen printing method, a photolithography method, or the like, a laser processing method, a slicing, a mechanical processing method such as an ultrasonic processing is used, and unnecessary portions are formed. It may be removed and a pattern may be formed.

The structure of the element manufactured here and the shape of the film-shaped piezoelectric / electrostrictive operating portion are not limited at all, and any shape can be adopted according to the application, for example, a triangle, a square, etc. , A circular shape such as a circle, an ellipse, a ring, a comb shape, a lattice shape, or a special shape obtained by combining these shapes.

In addition, each film thus formed on the ceramic substrate by the above method may be heat-treated each time the film is formed, so that the film becomes an integral structure with the substrate. May be formed and then heat-treated at the same time so that each film is simultaneously integrally bonded to the substrate. When an electrode film is formed by such a film forming technique, heat treatment may not always be required for integration. For example, before forming the upper electrode film, in order to ensure insulation with the lower electrode film, there may be a case where an insulating coat is applied around the element with an insulating resin or the like. For such a method, a method such as vapor deposition, sputtering, or plating that does not require heat treatment is employed.

Further, as a heat treatment temperature for integrating the thus formed film and the substrate, a temperature of about 900 ° C. to 1400 ° C. is generally adopted, and preferably in a range of 1000 ° C. to 1400 ° C. The temperature is advantageously chosen. When the piezoelectric / electrostrictive film is subjected to heat treatment, the heat treatment is performed while controlling the atmosphere together with the evaporation source of the piezoelectric / electrostrictive material so that the composition of the piezoelectric / electrostrictive layer becomes unstable at a high temperature. Is preferred. It is also recommended to employ a baking method in which an appropriate cover member is placed on the piezoelectric / electrostrictive film so that its surface is not directly exposed to the baking atmosphere. In this case, a material similar to the substrate is used as the cover member.

The material of the lower electrode film constituting the piezoelectric / strain operating portion manufactured by the above method is not particularly limited as long as it is a conductor that can withstand a high temperature oxidizing atmosphere at about the heat treatment temperature and the firing temperature. For example, a simple metal or an alloy may be used, and a mixture of an insulating ceramic and a metal or an alloy, or a conductive ceramic may be used. More preferably, platinum, palladium, an electrode material mainly containing an alloy such as silver-palladium, silver-platinum, platinum-palladium or the like, or a platinum and ceramic substrate material. Cermet material, platinum and a piezoelectric / electrostrictive material, and platinum, a substrate material and a piezoelectric / electrostrictive cermet material are preferably used. Among them, a material containing platinum as a main component is more preferable. Is desirable. Further, as a material to be added to the electrode, glass such as silicon oxide easily reacts during heat treatment with the piezoelectric / electrostrictive film and tends to cause a decrease in actuator characteristics. Therefore, it is desirable to avoid using glass. Preferably, the substrate material added to the electrode is about 5 to 30% by volume, and the piezoelectric / electrostrictive material is about 5 to 20% by volume. On the other hand, the material of the upper electrode film is not particularly limited, and may be a sputtered film of gold, chromium, copper, or the like, or a resinate printed film of gold or silver.

In general, the electrode film formed using such a conductive material is formed so that the lower electrode film has a thickness of 20 μm or less, preferably 5 μm or less, and the upper electrode film has a thickness of 1 μm or less, preferably 0.5 μm or less. It becomes.

Further, as the piezoelectric / electrostrictive material constituting the piezoelectric / electrostrictive operating portion, any material can be adopted as long as it shows an electric field induced strain such as a piezoelectric effect or an electrostrictive effect. It may be a crystalline material, an amorphous material, a semiconductor material, a dielectric ceramic material or a ferroelectric ceramic material. May be a material that requires a polarization treatment or a material that does not require a polarization treatment.

The piezoelectric / electrostrictive material used in the present invention is preferably a material mainly composed of lead zirconate titanate (PZT), a material mainly composed of lead titanate, or lead zirconate. Material as a component, furthermore, a material mainly containing lead magnesium niobate (PMN-based), a material mainly containing lead nickel niobate (PNN-based), a material mainly containing lead magnesium tungstate, manganese niobium Lead acid-based material, Lead antimony stannate-based material, Lead zinc niobate-based material, Lead magnesium tantalate-based material, Nickel lead tantalate-based Materials, and further, a composite material of these materials and the like are used. In addition, oxides such as lanthanum, barium, niobium, zinc, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium, tantalum, tungsten, nickel, manganese, lithium, strontium, magnesium, calcium, bismuth, etc. Alternatively, lanthanum may be added to a material containing such other compounds as an additive, for example, a material mainly containing PZT, and the above-mentioned additive may be appropriately added to the material so that the material becomes PLZT. No problem. Note that the addition of a glass material such as silicon oxide should be avoided. This is because a lead-based piezoelectric / electrostrictive material such as PZT easily reacts with glass, making it difficult to control the composition of a desired piezoelectric / electrostrictive film, causing variations and deterioration in actuator characteristics. .

Among these piezoelectric / electrostrictive materials, a material mainly containing a component composed of lead magnesium niobate, lead zirconate and lead titanate, or lead nickel niobate, lead magnesium niobate, lead zirconate and lead titanate Or a material mainly composed of a component consisting of lead nickel tantalate and lead magnesium niobate and lead zirconate and lead titanate, or a material mainly composed of lead magnesium tantalate and lead magnesium niobate and A material mainly composed of components composed of lead zirconate and lead titanate is preferable, and among them, a material mainly composed of components composed of lead magnesium niobate and lead zirconate and lead titanate is particularly preferable during the heat treatment. Since the reaction with the substrate material is particularly small, for example, the tension of the piezoelectric / electrostrictive film In addition to keeping the bonding state between the metal part and the ceramic substrate low enough not to affect the required performance of the piezoelectric / electrostrictive operating part, the segregation of components is unlikely to occur, and the process for maintaining the composition is difficult. It is advantageously used in combination with having a high piezoelectric constant, such as being able to be suitably carried out and easily obtaining a target composition and a crystal structure, and is used in a thick film forming technique such as screen printing, spraying, dipping, coating or the like. It is recommended as a material for forming an electrostrictive film.
In the case of a multi-component piezoelectric / electrostrictive material, although the piezoelectric / electrostrictive characteristics change depending on the composition of the components, three components of lead magnesium niobate-lead zirconate-lead titanate which are preferably employed in the present invention. In the system material, the composition near the phase boundary of pseudo-cubic-tetragonal-rhombohedral is preferable. In particular, lead magnesium niobate: 15 mol% to 50 mol%, lead zirconate: 10 mol% to 45 mol%, titanium Lead acid: A composition of 30 mol% to 45 mol% is advantageously employed because of its high piezoelectric constant and electromechanical coupling coefficient.

Furthermore, the thickness of the piezoelectric / electrostrictive operating portion composed of the electrode film and the piezoelectric / electrostrictive film formed as described above is generally 100 μm or less, and the thickness of the piezoelectric / electrostrictive film is In order to obtain a large displacement or the like at a low operating voltage, the thickness is preferably 50 μm or less, more preferably 3 μm or more and 40 μm or less.

From the experimental results shown in Table 1, according to the element of the present invention, the element can be displaced upward by the same amount of displacement when the element of the conventional structure shown in FIG. 15 is displaced downward. It can be seen that the displacement is stable. The element structure of the present invention used in this experiment was the same as that shown in FIG. 3, and the thickness of the thin portion of the ceramic substrate was 10 μm, the thickness of the lower electrode film was 5 μm, and the thickness of the piezoelectric / electrostrictive film was 30 μm. is there. These films were patterned by screen printing, integrated with the substrate by firing, and the upper electrode film was formed by sputtering Au. The displacement was measured with an applied voltage of 30 V using a laser displacement meter.

In the above embodiment, the present invention is mainly described as a case where the present invention is used as a relay. However, the present invention can be used for other applications without departing from the scope of the present invention, and can be changed, modified, and improved. .

FIG. 3 is an explanatory cross-sectional view of the device of the present invention. 2A is an explanatory diagram of a ceramic substrate on which a plurality of elements of the present invention are formed, and FIG. 2B is an explanatory diagram of an AA cross section of FIG. FIG. 3 is an explanatory diagram showing the operation of the device of the present invention. FIG. 4 is an explanatory diagram when a formation position of a piezoelectric operating portion is shifted. FIG. 3 is an explanatory view showing an element of the present invention in which a pair of lower electrode films are covered with one piezoelectric film. It is explanatory drawing which shows the element of this invention in which one end of each piezoelectric operation part does not hang on the outer surface of a thick part. It is explanatory drawing which shows the case where an arbitrary element is operated in the ceramic substrate in which the element of this invention formed two or more. It is explanatory drawing which shows the element of this invention which formed the piezoelectric operation part and the thin-walled part in the upward convex shape beforehand. It is explanatory drawing which shows the element of this invention which formed the groove | channel in the thick part. It is explanatory drawing which shows the element of this invention which formed the piezoelectric operation part in four places of the thin part. It is explanatory drawing which shows the element of this invention which formed the piezoelectric operation part in the periphery of the thin part upper part. It is explanatory drawing which shows the element which does not form a contact. FIG. 3 is an explanatory diagram showing an element in which an upper electrode film is divided. FIG. 4 is an explanatory diagram showing an element in which an upper electrode film is divided and shares a piezoelectric / electrostrictive film. FIG. 4 is an explanatory view showing the operation of an element having a conventional structure. It is explanatory drawing which shows the operation | movement of the element of the conventional structure in which the formation position of the piezoelectric operation part shifted.

Explanation of reference numerals

1,14,19,20,23,25... Element, 2,3,15,16,21,24,26,28,29..piezoelectric / electrostrictive operating section, 2a, 3a, 15a, 16a, 21a , 24a, 26a ··· lower electrode film, 2b, 3b, 17, 21b, 24b, 26b ··· piezoelectric / electrostrictive film, 2c, 3c, 18, 21c, 24c, 26c · · · upper electrode film, 4 · · · resin Layer, 5 ceramic substrate, 5a thin section, 5b cavity, 5c thick section, 6 groove, 7 hole, 8, 11 non-piezoelectric / electrostrictive operating section, 9 ..The lower electrode film non-formed portion, 22.

Claims (4)

A lower electrode film non-formed portion is provided on the thin portion outer surface on the cavity formed in the ceramic substrate, a lower electrode film is provided in a predetermined range around the lower electrode film non-formed portion, and the lower electrode film is provided on the lower electrode film. A piezoelectric / electrostrictive film type device comprising a piezoelectric / electrostrictive film and an upper electrode film sequentially laminated, and wherein the entire periphery of the lower electrode film-free portion is surrounded by a lower electrode film. 2. The piezoelectric / electrostrictive film element according to claim 1, wherein the ceramic substrate is made of a completely stabilized or partially stabilized material containing zirconium oxide as a main component. A material in which the piezoelectric / electrostrictive film is mainly composed of a component composed of lead magnesium niobate, lead zirconate and lead titanate, or a component composed of lead nickel niobate, lead magnesium niobate, lead zirconate and lead titanate Or a material mainly containing a component consisting of lead nickel tantalate and lead magnesium niobate and lead zirconate and lead titanate, or lead magnesium tantalate and lead magnesium niobate and lead zirconate and 3. The piezoelectric / electrostrictive film element according to claim 1, wherein the piezoelectric / electrostrictive film element is made of a material mainly containing a component composed of lead titanate. 4. The piezoelectric / electrostrictive film type device according to claim 1, wherein the thickness of the thin portion on the cavity is 50 μm or less.

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