JP2006093424A - Piezoelectric/electrostrictive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric/electrostrictive device which can stably generate a relatively large displacement rapidly at a low driving voltage over a long period of time at least in a two-dimensional space and can sense external stress with high sensitivity at least in a two-dimensional space. <P>SOLUTION: A piezoelectric/electrostrictive unit 5 comprises a ceramic base body 1 having a pair of facing thin boards 12 which are made thin because a through-hole 11 is formed through the base body 1 in a direction perpendicular to the axis direction; and a piezoelectric/electrostrictive element 2 arranged on the outer surface of the thin boards 12 of the ceramic base body 1, with the thin boards 12 of the ceramic base body 1 and the piezoelectric/electrostrictive element 2 working in linkage with each other to serve as a driving portion 3. The piezoelectric/electrostrictive device comprises at least two of such piezoelectric/electrostrictive driving units 5. In the piezoelectric/electrostrictive device, the piezoelectric/electrostrictive units 5 are so integrated together that the through-holes 11 formation directions in the individual ceramic base bodies 1 may cross at right angles or mutually cross each other, and that the ceramic base bodies 1 may be integrated together in series in the axis direction. Between the through-holes 11 of the integrated ceramic base bodies 1, a stress reducing means 4 is formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric / electrostrictive device. More specifically, at least in a two-dimensional space, it can stably generate a large displacement at a high speed with a low driving voltage stably for a long period of time, and at least in a two-dimensional space, it is highly sensitive to external stress. The present invention relates to a piezoelectric / electrostrictive device that can be sensed.

  In recent years, in the fields of optical recording, magnetic recording, precision processing, etc., a displacement element capable of adjusting the optical path length and position on the order of submicron is required. For piezoelectric / electrostrictive materials (for example, ferroelectrics) Development of a displacement element (actuator) using a displacement due to an inverse piezoelectric effect or an electrostrictive effect caused when a voltage is applied is underway.

  For example, an actuator that can utilize displacement in a two-dimensional space is disclosed (see Patent Document 1). However, the actuator disclosed in Patent Document 1 has a structure in which bimorphs are bonded to a fixed member or a relay member, and in addition, the bimorph itself is bonded to two piezoelectrons. Therefore, stress due to heat treatment at the time of bonding and bonding, curing shrinkage of adhesive, etc. is likely to remain, and the internal residual stress hinders the displacement operation, realizing the designed displacement and resonance frequency. It may not be possible. In addition, due to the bonded structure, the rigidity of the joint portion has to be reduced, and twisting is likely to occur during operation, and in addition, there remains a problem in responsiveness.

  Further, by forming through holes perpendicular to each other by cutting or etching in the stainless steel substrate, a structure having two sets of parallel flat plate portions (a thin plate piezoelectric element is provided on the outer surface of the two sets of parallel flat plate portions, and one side parallel plate is provided. A structure is disclosed in which a vibrating gyroscope is used in which the part is used for driving and the remaining one is used for detection (see Patent Document 2). Although the invention disclosed in Patent Document 2 is not an actuator, as a basic structure, the substrate on which the piezoelectric element is formed is an integral body, and at least suppresses problems caused by adhesion of each joint portion as in Patent Document 1. It is thought that.

  Further, the present inventors have disclosed a ceramics integrated piezoelectric / electrostrictive device (see Patent Document 3). In other words, it is an actuator composed of a pair of opposed thin plate portions and a driving portion composed of a piezoelectric / electrostrictive element formed on the thin plate portion, a fixed portion coupled via the driving portion, and a movable portion. An actuator in which holes are formed in the inner walls of the drive unit, the movable unit, and the fixed unit is disclosed. This actuator is characterized by being highly rigid and capable of high-speed operation because there is no boundary between the thin plate portion and the fixed portion, and there is no boundary between the thin plate portion and the drive portion. At the same time, it has a feature that it can operate dominantly in a single axial direction.

Therefore, the present inventors tried to apply the invention disclosed in Patent Document 2 to an actuator capable of displacement to at least a two-dimensional space based on the technique disclosed in Patent Document 3. The prototype actuator uses ceramics mainly composed of zirconia as a base, and forms a precursor of piezoelectric / electrostrictive film type element on the thin plate part which is each parallel plate part. It is an integrated device.
Japanese Unexamined Patent Publication No. 63-64640 JP-A-11-344341 JP 2001-210887 A

  However, when the characteristics of the prototype actuator were evaluated, a predetermined displacement characteristic could not be obtained, and in addition, the capacitance of the piezoelectric element as a capacitor was only small. This is because although the prototype actuator is merely a structure in which two of the actuators disclosed in Patent Document 3 are coupled by shifting by 90 ° from each other, the characteristics of the individual actuators are It shows that it has fallen. Therefore, it has been found that an actuator that operates preferentially in two dimensions cannot be obtained only by using the technique disclosed in Patent Document 3. By the way, it is known that a film type actuator manufactured by firing integration is likely to retain stress during firing, and the residual stress causes deterioration of characteristics. Considering the above results from this point of view, it is considered that the stress is likely to remain in the piezoelectric / electrostrictive film due to the different shapes of the ceramic substrate, that is, the presence of the through holes orthogonal to each other.

  The present invention has been made to solve the above-described problem, and can stably generate a large displacement at a high speed at a low driving voltage stably over a long period of time in at least a two-dimensional space. It is an object of the present invention to provide a piezoelectric / electrostrictive device capable of sensing external stress with high sensitivity in at least a two-dimensional space.

  In order to achieve the above object, according to the present invention, the following piezoelectric / electrostrictive device is provided.

[1] A ceramic substrate having a pair of opposed thin plate portions, each of which is thinned by penetrating through a pair of outer surfaces parallel to each other in a direction perpendicular to the axial direction, and the ceramic substrate Piezoelectric / electrostrictive drive having a piezoelectric / electrostrictive element disposed on the outer surface of the thin plate portion and the thin plate portion of the ceramic substrate and the piezoelectric / electrostrictive element functioning as a drive unit in conjunction with each other A piezoelectric / electrostrictive device comprising at least two units, wherein at least two of the piezoelectric / electrostrictive drive units are held in a positional relationship in which the through-directions of the through-holes are orthogonal to or cross each other, and The ceramic substrate is configured in a state of being integrated in series in the axial direction, and stress relaxation means is formed between the through holes of the integrated ceramic substrate. The piezoelectric / electrostrictive device and butterflies.

[2] The piezoelectric / electrostrictive device according to [1], wherein the piezoelectric / electrostrictive element is formed by a film forming method and is integrated with the thin plate portion through heat treatment. .

[3] The [1] or [2], wherein the stress relaxation means is configured by a portion having a gap formed in an axial direction between the through holes of the integrated ceramic base. Piezoelectric / electrostrictive device.

[4] The stress relaxation means includes a portion containing a component of the piezoelectric / electrostrictive material of the piezoelectric / electrostrictive element between the through holes of the integrated ceramic base. The piezoelectric / electrostrictive device according to any one of 1] to [3].

[5] The piezoelectric / electrostrictive device according to any one of [1] to [4], wherein a portion of the integrated ceramic substrate that operates in response to driving of the driving unit functions as a movable unit. .

[6] The piezoelectric / electrostrictive device according to any one of [1] to [5], wherein the through holes of the integrated ceramic substrate function as a fixing portion.

[7] The piezoelectric / electrostrictive device according to any one of [1] to [6], wherein at least one end portion of the two piezoelectric / electrostrictive driving units located at the extreme end functions as a fixed portion. Strain device.

[8] The [1] to [1], wherein the end of the thin plate portion in at least one of the two piezoelectric / electrostrictive drive units located at the extreme end is opened to the outside, and each constitutes a free end. [7] The piezoelectric / electrostrictive device according to any one of [7].

  The “piezoelectric / electrostrictive device” of the present invention means a concept including elements capable of mutually converting electrical energy and mechanical energy by a piezoelectric / electrostrictive material. The “piezoelectric / electrostrictive device” of the present invention is preferably used as an active element such as various actuators and vibrators, particularly as a displacement element utilizing displacement due to the inverse piezoelectric effect or electrostrictive effect. It may be used as a passive element such as a sensor element.

  According to the present invention, it is possible to stably generate a large displacement at a high speed with a low driving voltage stably over a long period of time in at least a two-dimensional space, and to provide high sensitivity to external stress in at least a two-dimensional space. There is provided a piezoelectric / electrostrictive device capable of sensing. More specifically, the stress relaxation means used in the present invention can reduce the firing stress when the piezoelectric / electrostrictive element is integrated with the ceramic substrate by heat treatment. The rigidity of the mutual part can be reduced to a degree of rigidity equivalent to that of the thin plate portion so as not to suppress the sintering of the piezoelectric / electrostrictive material. Due to the reduction of the high-temperature rigidity of this portion, the piezoelectric / electrostrictive material can be sintered uniformly and smoothly, and a piezoelectric / electrostrictive layer without deterioration of material properties can be provided. On the other hand, at room temperature for driving the piezoelectric / electrostrictive device, the portion between the through holes of the ceramic substrate on which the stress relaxation means is formed gives structurally sufficiently high rigidity, so that an electrical signal is sent to the piezoelectric / electrostrictive element. The applied electric field induced strain is efficiently converted into a bending displacement by the thin plate portion. As a result, it can be achieved by simply combining the actuator (piezoelectric / electrostrictive drive unit) disclosed in Patent Document 3 described above. It is possible to realize a piezoelectric / electrostrictive device such as an actuator that can exhibit a large displacement that has not occurred and that operates at high speed, and a sensor that can sense external stress with high sensitivity. Furthermore, since the internal stress remaining in the piezoelectric / electrostrictive element is kept low, it is possible to realize a piezoelectric / electrostrictive device having a feature capable of maintaining stable operation over a long period of time. In the present invention, an action in a two-dimensional space can be obtained by individually operating each piezoelectric / electrostrictive element. In the case of a three-dimensional space, for example, one piezoelectric / electrostrictive drive unit A displacement in the axial direction can be obtained by applying a bias voltage of the same potential to both the piezoelectric / electrostrictive elements (both piezoelectric / electrostrictive elements disposed on the pair of thin plate portions) disposed on the substrate. it can. In other words, by applying a bias voltage, the reference position is changed, and the operation in the three-dimensional space can be obtained by driving the piezoelectric / electrostrictive element similarly to the operation in the two-dimensional space.

  Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.

  As shown in FIG. 1, the piezoelectric / electrostrictive device according to the first embodiment of the present invention has a through hole 11 passing through a pair of parallel outer surfaces in a direction perpendicular to the axial direction. The ceramic substrate 1 includes a pair of opposed thin plate portions 12 partially thinned, and the piezoelectric / electrostrictive element 2 disposed on the outer surface of the thin plate portion 12 of the ceramic substrate 1. 1 is a piezoelectric / electrostrictive device 10 having at least two piezoelectric / electrostrictive drive units 5 in which a thin plate portion 12 and a piezoelectric / electrostrictive element 2 function as a drive unit 3 in conjunction with each other (see FIG. The piezoelectric / electrostrictive drive unit 5 is held in a positional relationship in which the penetration directions of the through-holes 11 are orthogonal to or cross each other, and the ceramic substrate 1 Integrated in series in the axial direction In state, it is configured, and, between the through-hole 11 each other integral ceramic substrate 1, wherein the stress relaxing means 4 is formed.

  In the present embodiment, the portion that operates corresponding to the driving of the driving unit 3 of the integrated ceramic base 10 functions as the movable unit 6, and two piezoelectric / electrostrictive driving units located at the extreme ends At least one end portion of 5 functions as the fixing portion 7 (the same applies to the other embodiments). FIG. 1 shows a case where the end portion of the piezoelectric / electrostrictive drive unit 5 located at the lowermost end of FIG. 1 functions as the fixing portion 7. The portion between the through holes 11 of the integrated ceramic base 10 may function as the fixing portion 7. In this case, the lower end functions as the movable portion 6. With this configuration, each unit can be individually operated and moved in different directions. Moreover, in FIG. 1, the code | symbol 8 shows a terminal.

  In the present embodiment, the piezoelectric / electrostrictive element 2 is laminated on the outer surface of the thin plate portion 12 of the ceramic substrate 1 in the order of the first electrode 21, the piezoelectric / electrostrictive film 22, and the second electrode 23. It is arranged in a state. In this case, one end portion of the portion functioning as the driving portion 3 of the piezoelectric / electrostrictive element 2 is disposed between the fixing portion 7 or the through hole 11 and the other end is disposed on the thin plate portion 12. It is preferable that the expansion / contraction displacement based on the electric field induced strain of the piezoelectric / electrostrictive film 22 can be changed to the bending displacement with high efficiency and a large displacement can be obtained.

  Here, the shape of the through-hole 11 is not particularly limited as long as it can form the pair of opposed thin plate portions 12 while reducing the volumes of the drive unit 3, the movable unit 6, and the fixed unit 7. Examples of the cross-sectional shape include a square and a quadrangle. Depending on the use mode and the like, an arbitrary cross-sectional shape may be appropriately selected.

  As shown in FIG. 1, the specific configuration of the stress relaxation means 4 is preferably composed of a portion having a gap 41 formed in the axial direction between the through holes 11 of the integrated ceramic substrate 1. That is, in the present embodiment, an air gap 41 is formed in the axial direction between the through holes 11 of the integrated ceramic base 1 to form a hollow structure between the through holes 11. As in the case of the through hole 11, this hollow structure can be formed by appropriately selecting an axial through hole having a predetermined cross-sectional shape. In this case, the air gap 41 may be formed using a plurality of through holes having a relatively small cross-sectional area. As described above, the stress relaxation means 4 having a hollow structure having the gap 41 between the through holes 11 of the ceramic substrate 1 is structurally flexible in a high temperature environment such as when the piezoelectric / electrostrictive film 22 is fired. Therefore, the piezoelectric / electrostrictive film 22 is hardly inhibited from being sintered. On the other hand, in a low temperature environment of about room temperature when the device is used, a highly rigid structure surrounded by the four surfaces of the ceramic substrate 10. Therefore, responsiveness and handling are not deteriorated. In addition, as thickness in the case where it comprises with one space | gap 41, the same (same size) as a thin plate part-5 times the thin plate part is preferable. With this configuration, the firing stress of the piezoelectric / electrostrictive film 22 can be effectively reduced.

  In the piezoelectric / electrostrictive device 10 of the present embodiment, the piezoelectric / electrostrictive element 2 is formed by a film forming method described later and integrated with the thin plate portion 12 through heat treatment. It is most effective in the case (the same applies to other embodiments). That is, in the piezoelectric / electrostrictive device 10 of the present invention, the ceramic substrate 1 can be maintained in a structurally or compositionally flexible state by the stress relaxation means 4 in a high temperature state where the piezoelectric / electrostrictive film is fired. Therefore, the sintering of the piezoelectric / electrostrictive element 2 (piezoelectric / electrostrictive film 22) is not significantly hindered. That is, it is possible to obtain a dense film necessary for the function expression of the piezoelectric / electrostrictive element 2 and a film having a very low residual internal stress and high piezoelectric characteristics. On the other hand, in a low temperature environment of about room temperature used as a device, since the ceramic substrate 1 has high rigidity, responsiveness and handling properties are not sacrificed.

  As shown in FIG. 2, in the second embodiment of the piezoelectric / electrostrictive device of the present invention, the configuration of the piezoelectric / electrostrictive element 2 is such that the piezoelectric / electrostrictive film 22 has four layers and the first layer is formed between each layer. 1 is the same as that of the first embodiment shown in FIG. 1 except that a so-called multilayer piezoelectric element structure in which the electrode 21 and the second electrode 22 are provided. As described above, the multi-layer piezoelectric element structure has a large driving force and rigidity, and is excellent in high-speed response and large displacement generation capability. In the second embodiment shown in FIG. 2, the first electrode 21 and the second electrode 22 are bundled so as to have the same potential every other layer. As a result, the terminal 8 is connected to each piezoelectric / electrostrictive element. Two elements are formed on each element 2. Note that the first electrode 21 and the second electrode 22 may all be made independent, and may be individually configured so as to have different potentials.

  As shown in FIG. 3, in the third embodiment of the piezoelectric / electrostrictive device of the present invention, as the stress relaxation means 4, the through-holes 11 of the integrated ceramic substrate 1 are simply made hollow. In addition, the movable portion 6 and the fixed portion 7 are the same as those of the first embodiment shown in FIG. 1 except that the movable portion 6 and the fixed portion 7 have a hollow structure (the entire ceramic substrate 10 has a hollow structure). In FIG. 3, the hollow structure is denoted by reference numeral 14. Thus, the rigidity of the ceramic substrate 10 at a high temperature can be further reduced by making the entire ceramic substrate 10 have a hollow structure. In addition, since the entire mass of the piezoelectric / electrostrictive device is reduced, the high-speed response can be further improved.

  As shown in FIG. 4, in the fourth embodiment of the piezoelectric / electrostrictive device of the present invention, the piezoelectric / electrostrictive element is provided between the through holes 11 of the ceramic substrate 1 in which the stress relaxation means 4 is integrated. The second embodiment is the same as the first embodiment shown in FIG. 1 except that the second piezoelectric / electrostrictive material component is included. Note that the stress relaxation means 4 in the present embodiment does not require the function of the structure of the ceramic base 1 but requires the function of the material composition of the ceramic base 1. Therefore, the structure of the piezoelectric / electrostrictive device has the original material characteristics of the piezoelectric / electrostrictive material that is the driving source while adopting a design that can maximize the function as a displacement device or sensor device. It is characterized in that it can be pulled out and used. By comprising in this way, the material between the through-holes 11 of the integrated ceramic base | substrate 1 can be made flexible at high temperature. In the present embodiment, the piezoelectric / electrostrictive film 22 is arranged on the four surfaces between the through holes 11 of the integrated ceramic substrate 1 so as to be piezoelectric when the piezoelectric / electrostrictive film 22 is fired. The stress relaxation means 4 can be effectively formed by diffusing the piezoelectric / electrostrictive material between the electrostrictive film 22 and the through holes 11 of the ceramic substrate 1. Thus, the present embodiment has an advantage that the stress relaxation means 4 can be formed simultaneously with the firing of the piezoelectric / electrostrictive film 22. Further, since the terminals 8 can be concentrated in the central portion of the piezoelectric / electrostrictive device (between the through holes 11 of the ceramic substrate 1), the movable portion 3 and the fixed portion 7 can exert their functions to the maximum. Can do. Apart from the firing of the piezoelectric / electrostrictive film 22, at least the material composition of this part may be set to a desired composition in advance, or a gap may be provided.

  As shown in FIG. 5, in the fifth embodiment of the piezoelectric / electrostrictive device of the present invention, the first electrode 21 and the piezoelectric / electrostrictive film 22 are connected from the fixing portion 7 to the stress relaxation means 4 (ceramic substrate 1). 4) and the movable portion 6 from there. The fourth embodiment is the same as the fourth embodiment shown in FIG. With this configuration, the same effect as that of the fourth embodiment shown in FIG. 4 can be obtained. However, the thin plate portion 12 is entirely covered with the first electrode 21 and the piezoelectric / electrostrictive film 22. Therefore, the generated displacement is slightly inferior. The drive unit 3 is arranged so that one end is on the fixing unit 7 or the stress relaxation means 4 (between the through holes 11 of the ceramic substrate 1) and the other end is on the thin plate 12. Yes.

  As shown in FIG. 6, the sixth embodiment of the piezoelectric / electrostrictive device of the present invention is the same as that shown in FIG. 4 except that two piezoelectric / electrostrictive elements 2 are provided for each thin plate portion 12. This is similar to the fourth embodiment shown. As for the part which functions as the drive part 3 of each piezoelectric / electrostrictive element 2, the end part on one side is on the movable part 6, the stress relaxation means 4 (between the through holes 11 of the ceramic substrate 1), or the fixed part 7. One end portion is disposed on the thin plate portion 12. With this configuration, it is possible to cause more complicated displacements by sending different commands, for example, electric signals, to the piezoelectric / electrostrictive elements 2. In addition, since there are four fulcrum points of displacement, the driving force can be doubled by driving the piezoelectric / electrostrictive element 2 at the same time. It is possible to convert efficiently. In this case, the piezoelectric / electrostrictive elements 2 having different strain directions (stretching and contracting) are formed on the same driving unit 3 (thin plate portion 12), or the piezoelectric / electrostrictive elements formed on the same driving unit 3 are strained. Are driven differently from each other. Further, by adopting such an element arrangement or driving method, for example, in the upper driving unit, the movable portion 6 can be operated (operated) predominantly in the lateral direction, that is, in the X direction. Note that the dominant operation can be realized by driving at least diagonal elements in pairs, without simultaneously operating the four elements. In addition, in this aspect, since the piezoelectric / electrostrictive element 2 is formed on a portion where the fixed portion 7 and the movable portion 6 and the thin plate portion 12 are continuous, the strength at that portion is ensured. There are advantages.

  As shown in FIG. 7, in the seventh embodiment of the piezoelectric / electrostrictive device of the present invention, the end of the thin plate portion 12 in at least one of the two piezoelectric / electrostrictive drive units 5 located at the extreme end. 4 is the same as that of the fourth embodiment shown in FIG. 4 except that the portions are opened to the outside to form the free ends 13 respectively. With this configuration, the firing residual stress remaining in the piezoelectric / electrostrictive film 22 can be greatly reduced. In addition, since the movable part 6 and the fixed part 7 can be reduced in weight by selecting a material having a lower specific gravity than the ceramic base and inserting it into the gap, the resonance frequency can be reduced without reducing the amount of displacement. Can be increased. Furthermore, as will be described later, any target member is attached to the movable part or the fixed part, or is attached to any target member. At this time, these target members themselves are attached to the inside of the piezoelectric / electrostrictive device. Since it can be accommodated in (and does not protrude), it is possible to further reduce the size.

  Hereinafter, each component used for the piezoelectric / electrostrictive device of the present invention and a method for manufacturing the piezoelectric / electrostrictive device of the present invention will be specifically described.

  As described above, the ceramic substrate used in the present invention is configured to be integrated in series in the axial direction, and specific materials include fully stabilized zirconia, partially stabilized zirconia, Examples of the material include silicon nitride, aluminum nitride, alumina, magnesia, and titanium oxide. Among these, a material mainly composed of fully stabilized or partially stabilized zirconia is preferable. A material mainly composed of fully stabilized or partially stabilized zirconia is preferable because it has high mechanical strength, high toughness, and low reactivity with piezoelectric / electrostrictive films and electrode materials even if it is thin. Compounds that stabilize zirconia include yttrium oxide, ytterbium oxide, cerium oxide, calcium oxide, and magnesium oxide. By adding and including at least one of these compounds, zirconia is partially or completely stable. Will be converted. The stabilization may be performed not only by adding one kind of compound but also by combining these compounds. Further, at least the thin plate portion, the movable portion, and the fixed portion are preferably those obtained by firing a ceramic green laminate. With such a configuration, it is possible to obtain a structure without a boundary due to integrated firing, and it is possible to improve the long-term reliability over time, and also to extremely reduce phenomena such as drift as changes in displacement over time. It is possible to suppress and express high displacement with good reproducibility.

  The ceramic substrate is distinguished from the shape surface, in particular, as a drive portion, a thin portion for driving in conjunction with the piezoelectric / electrostrictive element as a thin plate portion, and from the functional surface, the drive portion and the movable portion. And it is divided roughly into fixed parts.

  The thin plate part is flexible because it is thin, and configures the drive unit in conjunction with the piezoelectric / electrostrictive element disposed on the surface. As the drive unit, the expansion / contraction displacement of the piezoelectric / electrostrictive element is flexed and displaced. And has a function of transmitting to the movable part. In general, the thickness of the thin plate portion is preferably about 2 μm to 100 μm, and the combined thickness of the thin plate portion and the piezoelectric / electrostrictive element is preferably 7 μm to 500 μm. Moreover, as a width | variety of a thin-plate part, 50 micrometers-2000 micrometers are preferable.

  A movable part is a part which respond | corresponds to the drive of a drive part, and various members are attached to a movable part according to the intended purpose of a piezoelectric / electrostrictive device. For example, if a piezoelectric / electrostrictive device is used as a displacement element, a shielded plate of an optical shutter, a magnetic head, a slider equipped with a magnetic head, if used as a positioning or ringing suppression mechanism for a hard disk, A member that requires positioning such as a suspension on which a slider is mounted, an optical pickup having an autofocus function, a stylus for an electron microscope, and the like are attached.

  The fixed part is a part that supports the drive part and the movable part. When the fixed part is used for positioning a certain substrate, for example, a hard disk, it is attached to a carriage arm attached to a VCM (voice coil motor) or a carriage arm. The entire piezoelectric / electrostrictive device is fixed by being fixed to a fixed plate or the like. In some cases, electrode leads and other members for controlling the piezoelectric / electrostrictive element are arranged.

  The piezoelectric / electrostrictive element is composed of at least a piezoelectric / electrostrictive film and a pair of electrodes for applying a voltage to the piezoelectric / electrostrictive film, and is a conventionally known piezoelectric / electrostrictive such as a unimorph type or a bimorph type. Although a strain element can be used, the unimorph type is preferable because it is excellent in stability of the amount of displacement generated and is advantageous for weight reduction. For example, a laminated piezoelectric element in which a first electrode (lower electrode), a piezoelectric / electrostrictive film, and a second electrode (upper electrode) are laminated in layers can be suitably used. In addition to a structure in which a piezoelectric / electrostrictive film is sandwiched between a pair of upper and lower electrodes, a piezoelectric / electrostrictive film is further formed on the upper electrode, and an electrode is further formed on the piezoelectric / electrostrictive film. / It may be an electrostrictive element. The first electrode and the second electrode have a comb-shaped structure, and the first electrode and the second electrode are opposed to each other with a constant gap between the comb teeth. You may have. Note that the piezoelectric / electrostrictive element is preferably formed on the outer surface side like the piezoelectric / electrostrictive device shown in FIG. 1 in that the drive unit can be driven more greatly. It may be formed on the inner surface side (in the through hole) or on both the inner surface side and the outer surface side.

  The material of the piezoelectric / electrostrictive film is preferably a material having a high piezoelectric constant and a high electromechanical coupling coefficient. Specifically, lead zirconate, lead manganese tungstate, sodium bismuth titanate, bismuth ferrate, niobic acid Sodium potassium, strontium bismuth tantalate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony stannate, lead titanate, barium titanate , Copper barium tungstate, lead magnesium tungstate, lead cobalt niobate, or a composite oxide composed of two or more of these. These piezoelectric materials include lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium, tantalum, lithium, bismuth, tin An oxide such as copper may be dissolved. In addition, a material obtained by adding lithium bismutate, lead germanate, or the like to the above materials, for example, a composite oxide of lead zirconate, lead titanate and lead magnesium niobate, lithium bismutate and / or lead germanate A material to which is added is preferable because it can exhibit high material properties while realizing low-temperature firing of the piezoelectric layer.

  Among these piezoelectric / electrostrictive materials, materials composed mainly of components composed of lead magnesium niobate, lead zirconate and lead titanate, and components composed of lead nickel niobate, lead zirconate and lead titanate. Preferred is a material containing as a main component, or a material containing as a main component a component composed of lead nickel niobate, lead magnesium niobate, lead zirconate and lead titanate, and more particularly, lead magnesium niobate and lead zirconate. Since the material mainly composed of the component consisting of lead titanate has little reaction with the ceramic substrate material during the heat treatment, the introduction of the piezoelectric / electrostrictive material component into the ceramic substrate during the heat treatment is not excessive. Since it is controllable, the stress relaxation means can be preferably formed simultaneously with the heat treatment, and because of this low reactivity, It is advantageously used in conjunction with having a high piezoelectric constant and electromechanical coupling coefficient, such as the intended composition and crystal structure of the piezoelectric / electrostrictive material being easily obtained, such as screen printing, spraying, dipping, coating, etc. described later. It is preferable as a material for forming a piezoelectric / electrostrictive film by a thick film forming method.

  The electrode is preferably made of a metal that is solid at room temperature and has excellent conductivity, such as aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium, palladium, Examples thereof include simple metals such as rhodium, silver, tin, tantalum, tungsten, iridium, platinum, gold, lead, and alloys thereof. A cermet material in which the same material as the piezoelectric / electrostrictive film or the thin plate portion is dispersed may be used. The material selection of the electrode in the piezoelectric / electrostrictive element is determined depending on the method of forming the piezoelectric / electrostrictive film. For example, when the piezoelectric / electrostrictive film is formed on the first electrode by firing after the first electrode is formed on the thin plate portion, the first electrode is applied at the firing temperature of the piezoelectric / electrostrictive film. It is preferable to use a refractory metal such as platinum that does not change, but the second electrode formed on the piezoelectric / electrostrictive film after forming the piezoelectric / electrostrictive film may be formed at a low temperature. Therefore, low melting point metals such as aluminum, gold, and silver can be used. In addition, since the thickness of the electrode is a factor that lowers the displacement of the piezoelectric / electrostrictive element, the upper electrode and the comb-shaped electrode formed after firing the piezoelectric / electrostrictive film are dense after firing. It is preferable to use a material such as a metal resin paste, a gold resinate paste, a platinum resinate paste, or a silver resinate paste that can provide a thinner film.

  The terminal 8 is used for application of a drive signal, detection of generated charges, and the like. As such a terminal 8, what consists of a material equivalent to the above-mentioned electrode material can be mentioned. The terminal 8 can be disposed on the same surface as the surface on which the piezoelectric / electrostrictive element 2 is formed. With this configuration, the piezoelectric / electrostrictive device can be fixed independently of the surface on which the terminal is arranged. As a result, the piezoelectric / electrostrictive device is fixed and the circuit and the terminal are joined to each other. High reliability can be obtained. In this embodiment, the terminal and the circuit are joined by a flexible printed circuit (FPC), a flexible flat cable (FFC), wire bonding, or the like. Alternatively, the piezoelectric / electrostrictive element 2 may be disposed on a surface orthogonal to the formation surface.

  Hereinafter, the manufacturing method of the piezoelectric / electrostrictive device of the present invention will be described. In the production of the piezoelectric / electrostrictive device of the present invention, it is preferable that all are fired and integrated. Since there is no discontinuous joint as a structure, even if stress is applied to the piezoelectric / electrostrictive device by the operation of the drive unit, it will be excellent in terms of stability and reliability. Are preferably formed by firing and integration (without using an adhesive or the like).

  In the method for manufacturing a piezoelectric / electrostrictive device of the present invention, it is preferable to manufacture a ceramic substrate excluding a piezoelectric / electrostrictive element, that is, a thin plate portion, a fixed portion, and a movable portion using a ceramic green sheet lamination method, On the other hand, the piezoelectric / electrostrictive element, the electrode, and the terminal are preferably manufactured using a film forming method such as a thin film or a thick film. According to the ceramic green sheet laminating method capable of integrally forming the ceramic substrate of the piezoelectric / electrostrictive device, there is no joint and its state change with time does not occur, so it is highly reliable and rigid. Can be easily secured. Since the ceramic green sheet lamination method is excellent in productivity and formability, a piezoelectric / electrostrictive device having a predetermined shape can be obtained in a short time with good reproducibility.

  The manufacturing method of the piezoelectric / electrostrictive device of the present invention using the ceramic green sheet lamination method will be specifically described with reference to FIG.

  As shown in FIG. 8 (a), first, a binder, a solvent, a dispersant, a plasticizer, and the like are added to and mixed with ceramic powder such as zirconia to prepare a slurry, and after defoaming treatment, a reverse roll coater method, A ceramic green sheet having a predetermined thickness (before punching) (not shown) is prepared by a doctor blade method or the like, and then a through hole is formed by a method such as punching using a mold or laser processing. The formed ceramic green sheet 9 (the ceramic green sheet 91 in which the through hole 11a is formed and the ceramic green sheet 92 in which the through hole 11b is formed in addition to the through hole 11a) is obtained. The through-holes 11a and 11b are for forming the through-holes 11 that are held in a positional relationship in which the through directions are orthogonal to or cross each other in the piezoelectric / electrostrictive device of the present invention. The ceramic green sheet 91 is a member that mainly becomes a thin plate portion (driving portion) after firing, and closes the through hole 11b. The ceramic green sheet 92 is a member that mainly becomes the movable portion 6 and the fixed portion 7 after firing.

  Next, the ceramic green sheets 91 and 92 are laminated and pressure-bonded in the order shown in FIG. 8A to obtain a ceramic green laminated body (not shown), and the ceramic green laminated body is fired to obtain FIG. 8B. The ceramic fired body 93 shown is obtained.

  Next, as shown in FIG. 8 (c), the first piezoelectric / electrostrictive element 2a is formed on both surfaces of the ceramic fired body 93 in the portion to be a thin plate portion of the ceramic fired body 93 to form the piezoelectric / electrostrictive element. A ceramic fired body 94 is obtained. The piezoelectric / electrostrictive element 2a is formed by a thick film forming method such as a screen printing method, a dipping method, a coating method, a powder spraying method, an electrophoresis method or the like on the surface of a portion to be a thin plate portion of the ceramic fired body 93 or an ion beam method. , Sputtering, vacuum deposition, ion plating, chemical vapor deposition (CVD), and thin film formation methods such as plating. Of these, the thick film forming method is preferable. According to the thick film forming method, paste or slurry, or suspension, emulsion, sol, aerosol, or the like mainly composed of piezoelectric ceramic particles having an average particle diameter of 0.01 to 5 μm, preferably 0.05 to 3 μm is used. The piezoelectric / electrostrictive film 2a can be formed, and good piezoelectric operating characteristics can be obtained. In particular, the electrophoresis method can form a piezoelectric / electrostrictive film with high density and high shape accuracy. The screen printing method is preferable because the piezoelectric / electrostrictive element 2a and the pattern can be formed simultaneously. The piezoelectric / electrostrictive element 2a is preferably formed so that at least one end portion of the piezoelectric operation site (strain generating portion) is present on the fixed portion and / or the movable portion.

  The firing temperature of the piezoelectric / electrostrictive film 2a is appropriately determined depending on the material constituting the piezoelectric / electrostrictive film 2a, but is generally 800 ° C to 1400 ° C, preferably 1000 ° C to 1400 ° C. In this case, in order to control the composition of the piezoelectric / electrostrictive film 2a, the sintering is preferably performed in the presence of an evaporation source of the material of the piezoelectric / electrostrictive film 2a. When the piezoelectric / electrostrictive film 2a and the ceramic fired body 93 are fired simultaneously, it is necessary to unify the firing conditions of both.

  Next, as shown in FIG. 8 (d), in FIG. 8 (c), the portion indicated by the broken line of the piezoelectric / electrostrictive element-formed ceramic fired body 94 is cut in the stacking direction, and the first piezoelectric / electrostrictive is obtained. A piezoelectric / electrostrictive structure 95 in which the element 2a is formed is obtained. Preferred examples of cutting methods include dicing with a dicer, slicing with a slicer, wire saw with a wire saw (machine processing), laser processing with a YAG laser, excimer laser, etc., electron beam processing, etc. Can do.

  The piezoelectric / electrostrictive structure 95 obtained by cutting is preferably heat-treated at 300 to 800 ° C. Although defects such as microcracks tend to occur inside the fired body due to the processing, the defects can be removed by heat treatment, and the reliability is improved. Further, after the heat treatment, it is also preferable to perform an aging treatment by leaving it at a temperature of about 80 ° C. for at least about 10 hours. This treatment alleviates various stresses and the like received during the manufacturing process, and contributes to improvement of characteristics.

  Next, as shown in FIG. 8E, the second piezoelectric / electrostrictive element 2b is similarly applied to the thin plate portion 12v perpendicular to the surface of the piezoelectric / electrostrictive structure 95 on which the first piezoelectric / electrostrictive element 2a is formed. The piezoelectric / electrostrictive element device 10 is obtained. FIG. 8E shows a case where the thicknesses of the first piezoelectric / electrostrictive element 2a and the second piezoelectric / electrostrictive element 2b of the obtained piezoelectric / electrostrictive element device 10 are different. However, the same thickness may be used. In addition, although both the first piezoelectric / electrostrictive element 2a and the second piezoelectric / electrostrictive element 2b have the same end face as the ceramic substrate 1 (thin plate portion 12), the end faces are different. You may do it. Further, if necessary, terminals are appropriately formed according to a conventional method.

  In the case of an embodiment in which at least one of the two piezoelectric / electrostrictive drive units located at the extreme end as shown in FIG. 7 is open to the outside, and each of which forms a free end. Can be manufactured by further appropriately cutting the piezoelectric / electrostrictive element device 10 shown in FIG.

  Moreover, as shown in FIG. 9, as a structure of the stress relaxation means as shown in FIGS. 1-3, the 1st-3rd implementation which formed the space | gap in the axial direction (it was made into the hollow structure between through-holes). In the case of the embodiment, as the ceramic green sheet 92a having the through hole 11c having a shape in which the through hole 11a and the through hole 11b in the ceramic green sheet 92 shown in FIG. And the ceramic green sheet 92a are laminated and fired to obtain a ceramic fired body 93, and finally, the piezoelectric / electrostrictive element device 10 having the voids 41 as stress relaxation means can be obtained. In this case, formation and cutting of the piezoelectric / electrostrictive element can be performed in the same manner as shown in FIG.

  The piezoelectric / electrostrictive device manufacturing method of the present invention is not limited to the case where the above-described ceramic green sheet is used, but a pressure molding method using a mold, a casting method, an injection molding method, photolithography, etc. You may manufacture using. Furthermore, in the above example, the piezoelectric / electrostrictive element is disposed on both of the opposing thick plate portions. However, the piezoelectric / electrostrictive element may be disposed only on one thick plate portion. Good.

  The piezoelectric / electrostrictive device of the present invention is effectively used as a displacement element (actuator), a vibrator, a filter, a sensor, etc. in various fields such as optical recording, magnetic recording, precision processing, and surface analysis.

1 is a perspective view schematically showing a first embodiment of a piezoelectric / electrostrictive device of the present invention. It is a perspective view which shows typically 2nd Embodiment of the piezoelectric / electrostrictive device of this invention. It is a perspective view which shows typically 3rd Embodiment of the piezoelectric / electrostrictive device of this invention. It is a perspective view which shows typically 4th Embodiment of the piezoelectric / electrostrictive device of this invention. It is a perspective view which shows typically 5th Embodiment of the piezoelectric / electrostrictive device of this invention. It is a perspective view which shows typically 6th Embodiment of the piezoelectric / electrostrictive device of this invention. It is a perspective view which shows typically 7th Embodiment of the piezoelectric / electrostrictive device of this invention. FIG. 8 is a perspective view schematically showing one manufacturing method of the piezoelectric / electrostrictive device of the present invention. FIG. 8 (a) is a state of lamination of ceramic green sheets, and FIG. 8 (b) is an obtained ceramic. FIG. 8 (c) shows the obtained piezoelectric / electrostrictive element-formed ceramic fired body, FIG. 8 (d) shows the obtained piezoelectric / electrostrictive structure, and FIG. 8 (e) shows the obtained piezoelectric / electrostrictive structure. Each strain device is shown. FIG. 9 is a perspective view schematically showing another method for manufacturing the piezoelectric / electrostrictive device of the present invention. FIG. 9 (a) is a state of lamination of ceramic green sheets, and FIG. 9 (b) is an obtained ceramic. FIG. 9C shows the obtained piezoelectric / electrostrictive element-formed ceramic fired body, FIG. 9D shows the obtained piezoelectric / electrostrictive structure, and FIG. 9E shows the obtained piezoelectric / electrostrictive structure. Each strain device is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ceramic base | substrate, 2 (2a, 2b) ... Piezoelectric / electrostrictive element, 3 ... Drive part, 4 ... Stress relaxation means, 5 ... Piezoelectric / electrostrictive drive unit, 6 ... Movable part, 7 ... Fixed part, 8 ... Terminal, 9 ... Ceramic green sheet, 10 ... Piezoelectric / electrostrictive device, 11 (11a, 11b, 11c) ... Through hole, 12 (12v) ... Thin plate part, 13 ... Free end, 14 ... Hollow structure, 21 ... First 22 ... Piezoelectric / electrostrictive film, 23 ... Second electrode, 41 ... Gap, 91, 92, 92 (a) ... Ceramic green sheet, 93 ... Ceramic fired body, 94 ... Piezoelectric / electrostrictive element forming ceramic Fired body, 95... Piezoelectric / electrostrictive structure.

Claims (8)

A ceramic substrate having a pair of opposed thin plate portions, each of which is thinned by passing through holes in a direction perpendicular to the axial direction between a pair of outer surfaces parallel to each other, and the thin plate portion of the ceramic substrate At least a piezoelectric / electrostrictive drive unit that functions as a drive unit in conjunction with the thin plate portion of the ceramic substrate and the piezoelectric / electrostrictive element. Two piezoelectric / electrostrictive devices comprising:
In a state where at least two of the piezoelectric / electrostrictive drive units are held in a positional relationship in which the through-directions of the through-holes are orthogonal or cross each other, and the ceramic base is integrated in series in the axial direction, Composed of, and
A piezoelectric / electrostrictive device, wherein stress relaxation means is formed between the through holes of the integrated ceramic substrate.   2. The piezoelectric / electrostrictive device according to claim 1, wherein the piezoelectric / electrostrictive element is formed by a film forming method and is integrated with the thin plate portion through heat treatment.   3. The piezoelectric / electrostrictive device according to claim 1, wherein the stress relaxation means is configured by a portion having a gap formed in an axial direction between the through holes of the integrated ceramic base.   The said stress relaxation means is comprised from the part in which the component of the piezoelectric / electrostrictive material of the said piezoelectric / electrostrictive element contained between the said through-holes of the integrated said ceramic base | substrate. The piezoelectric / electrostrictive device according to any one of the above.   5. The piezoelectric / electrostrictive device according to claim 1, wherein a portion of the integrated ceramic base that operates in response to driving of the driving unit functions as a movable unit.   The piezoelectric / electrostrictive device according to any one of claims 1 to 5, wherein a space between the through holes of the integrated ceramic base functions as a fixing portion.   The piezoelectric / electrostrictive device according to any one of claims 1 to 6, wherein at least one of the two piezoelectric / electrostrictive drive units located at the extreme end functions as a fixed portion.   The end of the thin plate portion in at least one of the two piezoelectric / electrostrictive drive units located at the outermost ends is opened to the outside, and each of them forms a free end. The piezoelectric / electrostrictive device according to 1.

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