JPS59115580A - Bimorph supporting structure - Google Patents

Abstract

PURPOSE:To suppress the vibration, to prevent lead wirings from being removed and to improve the durability of a bimorph supporting structure by securing the terminal of lead wirings at the position except the vicinity of a stationary unit of a bimorph through a conductive elastic material to a support. CONSTITUTION:A bimorph 1 is interposed at a support 6 between a stationary unit A and a connector B. Lead wirings 10 and part of the support 6 are not inserted into an adhesive layer 3a which forms the bimorph at the stationary unit position A and a main movable unit position, but are inserted at the connector B. When internal electrodes 5a, 5b are provided, an air gap 9 is formed and spaced between the unit A position and the connector B. Thus, irregular stress applied to the bimorph 1 at the connector B does not affect directly the unit A, thereby preventing the exfoliation of the adhesive layer 3a at the unit A. A lead terminal 8 is conducted with electrodes 4a, 4b, 5a, 5b of the bimorph 1 through a thin conductive rubber film 11. Even if the bimorph is vibrated at the unit A as a fulcrum, the connector B is held at the support 6 through the conductive rubber, and the vibration is less. Further, the damage of the electrodes 4, 5 due to the vibration of the lead terminal does not occur, and a durable bimorph can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bimorph support structure comprising a piezoelectric polymer film.

BACKGROUND ART In recent years, Nonoimorph has been attracting attention as a mechanoelectric transducer made of a piezoelectric polymer film and used as a vibrating body for microphones, pickups, buzzers, speakers, optical switches, fans, and the like. In its broadest sense, the ζimolar made of such a polymeric piezoelectric film is shown in Figures 1(a) to 1(a).
It includes a series of laminated structures as shown in (i). In these drawings, the same or similar symbols are used for similar parts, and 1 is / imorua: 2.2 ”
% 2b, 2c.

2d is a polymer piezoelectric film; addition is a thin film body; 3.3a, 3b.

3c is adhesive layer; 4.4a, 4b are surface electrodes (film): 5
．． 5a) 5bs 5 (4%) 5d, 5e, and 5f represent intermediate or inner electrodes (membranes) (electrodes that serve as internal layers of the immorph laminated structure), respectively. In any morph, when the electrodes 4a, 4b, 15'a, s5b, etc. are energized and voltage is applied to the piezoelectric films 2a, 2b, etc.,
The piezoelectric films 2a, 2b, etc. expand or contract depending on whether the direction and the direction of polarization that causes the piezoelectric material to develop (hereinafter simply referred to as the "polarization direction") are the same or different directions, and the resultant force is As a result, bimorph 1 bends upward or downward. Also, if you bend Nonoimorph 1 upward or downward,
A constant voltage is generated across the electrodes 4a, 4b, etc.

Figures 1(,) to (C) each show the most typical Nonoimorph stacked structure. The adhesive layer 3 is bonded to the adhesive layer 3, and the electrode films 4a are formed on both sides of the adhesive layer 3.

4b is arranged. During manufacturing, the surface electrode film 4a,
A pair of piezoelectric films 2a each provided with 4b.

2b may be bonded with adhesive 3. The zeta morph shown in FIG. 1(b) has electrode films 4a and 5a on both sides, respectively.
Alternatively, it has a structure in which the electrode films 4b and 5b are bonded with a non-conductive adhesive 3. Figure 1(c) is
), a low melting point metal is used instead of the non-conductive adhesive 3, and the pair of piezoelectric films 2a, 2b are
It shows a Nonoimorph that has been joined with. In the structure shown in FIG. 1(a), when a single voltage is applied to the piezoelectric films 2a and 2b in a certain direction from the electrode films 4a and 4b, the piezoelectric films expand or contract (i.e., in the polarization direction). are opposite to each other, and in the structure of FIG. 1(C), the piezoelectric films 2a and 2
The polarization characteristics of b are the same. On the other hand, Fig. 1(b)
In this structure, the polarization directions of the piezoelectric films 2& and 2b are usually different directions, but by providing a non-conductive adhesive layer 3, the polarization directions can be made the same. Note that when a low melting point metal is used as the adhesive 3 in the structure of FIG. 1(b), the structure is substantially the same as that of FIG. 1(c).

- The number of piezoelectric films constituting the immorph may be two or more. However, in order to obtain good conversion efficiency, usually n
An even number of piezoelectric films of 4 or more is used (FIGS. 1(d) and (e)). Furthermore, one of the pair of piezoelectric films may not be a polymer piezoelectric film, but may be a thin film cylinder such as cloth, paper, or a polymer thin film that does not have piezoelectricity (FIG. 1(f)). In this case as well, since the thin film cylinder suppresses the expansion or contraction of the piezoelectric film 2a on one side, the application of voltage causes bending deformation of the Nonoimorph. In this case, since it is not necessary to apply a voltage to the non-piezoelectric thin film cylinder, the thin film (a) can also be attached outside the electrode 5 (FIG. 1(g)).

Furthermore, as shown in FIGS. 1(h) and (i), the thin film body 20 (
It is sufficient that the polymer piezoelectric film (which may be a polymer piezoelectric film) is provided on most of the polymer piezoelectric film. For example, in the case of FIG. 1(i), the exposed portion of the internal electrode 5 is used as an electrode terminal. (See Japanese Patent Laid-Open No. 125687/1987).

Including those with the above-mentioned structure, the nomaimorph referred to in this specification has at least two thin film layers, at least one of which is a polymeric piezoelectric film, bonded together with an adhesive, and at least one of the at least one layer is a piezoelectric polymer film. It can be said to be a flexible laminated structure in which electrode films are arranged in such a manner that a polymer piezoelectric film is sandwiched and a voltage is applied thereto.

When such a Nonoimorph is used as a vibrating body for a microphone or the like, the supporting structure is, for example, the bimorph shown in FIG. 1(b).
A structure as shown in FIG. 2, which is an enlarged perspective view of a partially cutaway part near the bimorph support part, and FIG. 3, which is a sectional view taken along the line ■-■ in FIG. 2, has been conventionally adopted. ing. That is, Nonoimorph 1 has its supporting and fixing part A.
At this time, the support body 6 is adhesively fixed via the conductive adhesives 7m and 7b and the lead terminals 8a and 8b.

Further, a lead wire terminal 8c is connected to the inner surface electrodes 5a and 5b of the bimorph. In this way, the support 6 or the support 6 and the adhesives 3a, 3b.

The reason why the lead wire terminals 88 to 8C are provided at the part A that is supported and fixed by the parts 7a and 7b is because the part A is a fixed part against the vibrations of the nonimorph 1. This is because it was thought that the immorph's vibrations would prevent it from separating easily.

However, according to the research conducted by the present inventors, it was found that due to the existence of the support 6 and the region A beam-r wire terminal 8c in the vicinity thereof, the structure of Nonoimorph 1 is subjected to significantly non-uniform stress. . The lead wire terminals 8a and 8b that hold the Nonoimorph from the outside are shaped like flat plates, and if they have the same shape and size as the parts of the supports 6a and 6b that hold the Nonoimorph 1, uneven stress can be avoided. Although it does not receive, the inner surface electrode 5a.

The lead wire terminal 8C held between the terminals 5b may be wire-like as shown in FIG. 2 or film-like (not shown) as long as it is thicker than the adhesive 3a of the bimorph 1. The immorph 1 has to be thick at the portion where the lead wire terminal 8C is provided. Therefore, the polymer piezoelectric film 2a and the thin film body 2b that constitute the nanoimolar 1 are subjected to non-uniform stress at this location. In order to provide the lead wire terminal 8c with a thickness comparable to the thickness of the adhesive 3a of the immorph 1 so as not to receive uneven stress, the thickness of the adhesive 3a must be increased to a certain extent. The imamorph 1 having such a thickness increases its overall rigidity and deforms less with respect to a constant electrical input, making it impractical. Therefore, such non-uniform stress is unavoidable as long as such a structure is adopted, but if such non-uniform stress exists, the adhesive 3a, 3 that bonds one inner surface electrode 5a and the other inner surface electrode 5b
The adhesive portion near the lead fpJBc caused by b is likely to peel off. Moreover, as can be seen from FIG. 4, which is an enlarged view of the lead 798c arrangement part in FIG. 3, although there should be adhesives 3a and 3b near the support, During the process of use, voids 9 are likely to be created where no adhesive is present, making it even more likely that the adhesive will peel off. Such peeling of the adhesive part does not simply result in the Immorph 1 becoming unable to hold it, but in the process it also causes poor imaging and non-uniform vibration, causing the electrode to break and the lead wire to come off. It also leads to separation.

The object of the present invention is to improve the durability of the conventional Nonoimorph support structure made of a piezoelectric polymer.

As a result of further research based on the above-mentioned consideration of the prior art, the present inventors found! J-)' It has been found that contrary to the conventional common sense that the wire terminal should be placed near the fixed part of the bimorph, it is effective to place it at a different position in order to achieve the above-mentioned object. However, if the lead wire terminal is placed in a different position from the fixing part, another problem will occur in that the lead wire terminal will easily come off from the electrode due to the vibration of Nonoimorph. It has also been found that the problem can be solved by suppressing vibration by supporting and fixing the wire terminal with a support via a conductive elastic body.

The Nonoimorph support structure of the present invention is based on the above-mentioned findings, and more specifically, the following components (,) to
(c).

(a) At least two thin film layers, at least one of which is a polymeric piezoelectric film, are joined together with an adhesive, and an electrode film is formed by sandwiching the at least one layer of the polymeric piezoelectric film and applying a voltage thereto. (b) a support that clamps the Nonoimorph at a part adjacent to its main movable part, and (c) a part different from the part adjacent to the main movable part of the bimorph, A lead wire terminal that is electrically connected to a bimorph electrode via a conductive body and held by a support together with the bimorph and the conductive body.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The bimorph targeted by the present invention has the broadest meaning including those shown in FIGS. 1(a) to (i) as defined above, but here, the bimorph as shown in FIG. 1(b) 5 and 6, and FIGS. 7 and 8 show examples including the immorphs of FIG. 1 (,).

In either of these two embodiments, the Nonoimorph 1 is supported and fixed by being held between the supports 6 at the fixing site A, similar to the conventional example shown in FIG. The point where the support structure of the present invention is different from that of the conventional one is that the support structure of the present invention has a connection part B, which is a part different from the fixation part A of the bimorph 1.
Terminals 8a and 8b of the lead wire 10 that conducts between the electrodes 4a and 4b of the bimorph 1 and a power source (not shown), and terminal 8c (the first 5 and 6. In this case, the lead wire terminals 8a and 8b do not come into direct contact with the electrodes 4& and 4b, respectively, but are connected to the conductive elastic bodies Lla and llb, respectively. through electrode 4
Conducts with a and 4b. Moreover, the terminal 8c is a conductive elastic body li
It is electrically connected to the inner surface electrodes 5a and 5b via e. Also, these conductive elastic bodies 11a, llb (lie) and lead wire terminals 13a, 8b.

8C is held by support body 6.

To briefly touch on the structure of the bimorph 1, the polymer piezoelectric films 2a and 2b are polymer films that have piezoelectricity with or without polarization, and are polymer films that do not themselves have piezoelectricity. Any piezoelectric material such as a piezoelectric material formed by dispersing a ceramic ferroelectric material into a film can be used. The thickness of the polymeric piezoelectric films 2a, 2b is not particularly limited, but a thickness in the range of 2 to 500 μm is usually used. The thicknesses of the piezoelectric films 2a and 2b do not need to be the same. Further, when a non-piezoelectric thin film body is used in place of one of the piezoelectric films 2a and 2b, the thickness of the thin film body is preferably in the range of 2 to 500 μm as described above.

As the adhesive 3a for bonding the piezoelectric films 2a and 2b, any adhesive can be used as long as it has the ability to bond or bond them together. Specifically, for example, a thermoplastic resin adhesive, a thermosetting resin adhesive, a natural polymer adhesive, a low melting point alloy, etc. are used.

As the support 6, any support can be used as long as it can hold at least one part of the Nonoimorph and support the conductive elastic bodies 11a and Llb via the lead wire terminals 8a and 8b. In addition, in FIGS. 5 to 8, the support body that holds the Nonoimorph 1 at the fixed part A and the support body that supports the conductive elastic bodies 11a, llb, etc. at the connection part B are integrated. Although the case where they are shown is shown, these may be separate bodies.

The material of the support 6 may be, for example, metal, hard plastic, glass, or a composite material mainly made of these materials. In order to prevent this from occurring, it is preferable that at least the contact portion with the ζimorph is made of a rubber elastic body. In addition, in order to hold the immorph 1 at the fixed part A and the conductive elastic bodies 11a, llb, etc. at the connection part B by the support body 6, it is necessary to A method is preferably adopted in which the bimorph 1, etc. is sandwiched between the two halves obtained by dividing the body (they do not necessarily have to be completely symmetrical), and then the two halves are supported and fixed to each other. This divided structure of the support body 60 is similar to the divided structure of an electrical plug. In order to support and fix the two halves of the support body to each other, known fixing means such as adhesives, screws, compression with springs, etc. are used. Regardless of the fixation method used, bimorph 1 at fixation site A
and the support body 6, between the Imorph 1 and the conductive elastic bodies 11a111b and 'lie at the connection site B, and between these conductive elastic bodies and the support body 6, as necessary. Adhesive can be applied to strengthen the support and fixation, but the main movable region of bimorph 1 (i.e. the left extension in FIGS. 5 to 8) and the fixed region adjacent to this main movable region It is better not to apply adhesive near the boundary with A (within about 2 mm from the boundary).

This is because it is difficult to apply the adhesive to a uniform thickness and to make the boundary line between the applied area and the non-applied area a straight line, but if these application conditions are not met, the Nonoimorph This is because vibrations of 1 may be in the same phase, resulting in non-uniform vibrations, resulting in a decrease in electromechanical conversion efficiency.

The lead wire terminals 8a, 8b are not limited to thin film conductors as shown in FIGS. 5 to 8, but may also include the conductive adhesive layers 7a, 7b shown in FIG. 2 or the lead wires shown in FIG. It may be the shaped terminal 8c itself, and generally refers to a conductor near the end of the lead wire that is electrically connected to the terminal of the lead wire, and the shape is not limited to a film shape or a wire shape. The number of lead wire terminals increases as the number of electrodes of the bimorph 1 increases, and all lead wire terminals are provided at the connection site B of the bimorph 1. Site B may be adjacent to site A as long as it is a separate site in the immorph, but is preferably configured as a separate site.

In the support structure of the present invention, the support body 6 has two parts, a fixed part A and a connecting part B, for holding the immorph 1. Of these, in the fixed part A and the main movable part, the structure of the bimorph, for example, the IJ-), 4-wire terminal, support part, etc., are not inserted into the adhesive layer 3a. However, in the adhesive layer 3a of the connection part B, a part 60 of the support body or the like may be inserted, for example, as shown in FIGS. 7 and 8. In the case of such an insertion structure, and in the case of having inner surface electrodes 5a and 5b as shown in FIGS. 5 and 6, a gap 9 is formed between the fixed part A and the connecting part B, and both The parts inevitably separate. However, if there is no inner surface electrode and if part of the support is not inserted into the Nonoimorph at the connection part B, the gap 9 will not be formed and the fixed part A and the connection part will be adjacent to each other. It can also be provided. However, if these parts are spaced apart, the uneven stress that may be applied to the bimorph 1 at the connection part B will not be directly applied to the fixed part A, and there is a risk of peeling of the adhesive layer 3a, etc. at the part A. This is preferable because it can further reduce υ.

The lead wire terminals 8a, 8b, 8c are in direct contact with the electrodes 4a, 4b, 5a, 5b of the bimorph 1, and are electrically connected to these electrodes via the conductive elastic bodies 11a, Llb%11c. Conductive elastic bodies 11a, 11
b, 11c are electrodes 4a, 4b, 5a, 5
b, respectively, but when contacting with lead wire terminals 8a, 8b, and 8c, as shown in FIGS. 7 and 8, contact is made with a surface different from the contact surface with the electrode. Alternatively, as shown in FIGS. 5 and 6, the lead wire terminals 8a, etc. can be inserted or embedded in the conductive elastic bodies 11a, etc., so that the contact between the two can be achieved.

As a conductive elastic body, the Young's modulus is smaller than that of the polymer piezoelectric films 2a and 2b, and the volume resistivity is 1o-1 to to5.
Any material can be used as long as it is -5 Ωcm or less, satisfies the relationship with the lead wire terminal described above, can be provided on the electrode, and can be held by the support 6. Preferably used examples include copper, silver, aluminum, iron,
Examples include so-called conductive rubber in which conductive fine powder of tin, carbon, etc. is dispersed in rubber.

The thickness of each of the conductive elastic bodies 11a, 11b and S11c is usually 0.05 to 3 mm, but the thinner the better since the support structure can be made smaller.

Since the supporting structure of the telemorph 1 in the present invention is as shown above, the fixed part A, which is the part where the bimorph 1 is held and is adjacent to the part where the bimorph 1 can independently move, has the structure shown above. There is no uneven stress, and peeling is less likely to occur on the adhesive surface 3a. Also bimorph 1
Since the connection part B vibrates with the fixed part A as a fulcrum, the connection part B originally vibrates, but since it is held by the support body 6 via the conductive elastic body, the vibration is slight. In addition, the -R line terminal and the bimorph electrode do not come into direct contact with each other, but through a conductive elastic body. Therefore, the S wire terminal is caused by the vibration of Bimorph 1! Even if stress is applied to the ll electrode, it is indirect, does not damage the electrode, and the electrical connection is maintained over a long period of time, making it useful.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(i) are cross-sectional views in the thickness direction showing examples of bimorph laminated structures that can be used in the structure of the present invention, respectively. 2 to 4 show an example of a conventional bimorph support structure. FIG. 3 is a cross-sectional view taken along line NI in FIG. 2, and FIG. 4 is an enlarged view of the joint and fixing portion in FIG. 3. The set of FIGS. 5 and 6 and the set of FIGS. 7 and 8 each show an example of the Nonoimorph support structure of the present invention. The partially cutaway enlarged perspective view of the vicinity of the support portion, FIGS. 6 and 8 are sectional views taken along the -X line in FIG. 5 and the -X line in FIG. 7, respectively. 1. Sumo imora, 2.2a to 2C... Polymer piezoelectric film, additive... Thin film body, 3.3a to 3c... Adhesive layer,
4.4 a, 4 b... surface electrode, 5.5a to 5C
...Inner surface electrode, 6...Support, 7a, 7b...Conductive adhesive, 8a-8C...IJ-F%S wire terminal 1
0...Lead wire, Lla-1ie...Electroconductive elastic body, A...Fixing site of Reiseimor 7, B.../Connecting site of Imorph. Applicant's agent Kiyoshi Inomata Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure J' ■ Figure 6 ln Figure 7

Claims (1)

[Scope of Claims] 1. (a) At least two thin film layers, at least one of which is a polymeric piezoelectric film, are bonded together with an adhesive, and the at least one layer of the polymeric piezoelectric film is sandwiched and a voltage is applied thereto. (b) a support that holds the bimorph at a portion adjacent to its main movable region; and (c) a main movable region of the bimorph. iE of the immorph via a conductive elastic body at a site different from the site adjacent to the
A Nonoimorph support structure comprising a lead wire terminal electrically connected to Nonoimorph 6'A and held by a support together with Nonoimorph and a conductive elastic body. 2. The structure according to claim 1, wherein at least two thin film layers constituting the bimorph are sandwiched between a pair of electrode films provided on the outside thereof. 3. If the at least two thin film layers are both made of polymer piezoelectric films, and the two adjacent layers of polymer piezoelectric films have the same properties of expanding or contracting when a voltage is applied in a certain direction, A patent claim that uses a bimorph in which two layers are joined via an intermediate electrode film, and if the opposite is true for two adjacent polymer piezoelectric films, the two intermediate layers are joined without an intermediate electrode film. Structure of the second term of the range. 4. Regarding two adjacent polymer piezoelectric films in which Nonoimorph is composed of two or four or more even-numbered polymer piezoelectric films, and the direction in which the piezoelectric film expands or contracts when a voltage is applied in a certain direction is arbitrary. 5. A structure according to claim 4, all of which are opposites of each other. 5. The bimorph consists of two or more pairs of polymer piezoelectric films whose properties of expanding or contracting are opposite to each other when a voltage is applied, and a pair of unit polymer piezoelectric films inside two adjacent polymer piezoelectric film pairs. 4. The structure according to claim 3, which has the same characteristic of expanding or contracting when a voltage is applied in a certain direction, and is therefore joined through an intermediate electrode film. 6. The structure according to any one of claims 1 to 5, wherein the front packing support is composed of two divided half-holes, and the pi-morph is held between the divided half-holes. 7. Claim 6, wherein the two divided halves are fixed to each other by an adhesive applied to a non-contact area between the main movable part of the Nonoimorph and the vicinity of the boundary between the main movable part and the adjacent part. structure.