JPS6165488A - Flexible piezoelectric element - Google Patents

Abstract

PURPOSE:To enable voltage impressing at another part even when part of the fine width electrodes is cut, by a method wherein streaks of fine width electrode are formed by providing streaks of cutout on the side of flexible leads. CONSTITUTION:A thin film electrode 11a is formed on one surface of a polymer piezoelectric substance 1. A flexible electrode sheet 9 consists of a polymer film 14 and a thin film electrode 11 which has a thin film lead part 13a and a lead part 13b. The lead part 13a is connected to the thin film electrode 11a. Both the lead parts 13a and 13b are arranged side by side in adjacency in the width direction at one end. Streaks of cutout 113 are provided on the lead part 13b side in the width direction.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a piezoelectric element with excellent flexibility that can be used as a displacement generating element, a pyroelectric element, or a vibrator, and particularly relates to a piezoelectric element with excellent flexibility that can be used as a displacement generating element, a pyroelectric element, or a vibrator. The present invention relates to a flexible piezoelectric element that is composed of an electrode sheet and a protective film, and to which lead wires for signal extraction and voltage application can be directly soldered.

[Conventional technology]

Polymer piezoelectric materials are easy to form into thin films and are flexible, so they can be installed in a small space, and they have excellent properties such as being especially easy to install on bends and being able to give large deformations. have.

In order to extract electrical signals from the surface of the polymer piezoelectric material through the electrodes, or to apply voltage to the electrodes to cause displacement, lead wires for signal extraction and voltage application may be connected to both electrodes.

However, since polymer piezoelectric materials have a low softening temperature,
Unlike inorganic piezoelectric materials that can withstand high temperatures, lead wires cannot be directly soldered to both electrodes. Also, if you insert a polymer piezoelectric material directly into the socket and try to extract the signal from the electrode through the socket, depending on the type of polymer piezoelectric material, it may be too soft to insert, or it may be too hard to insert. It has drawbacks such as being brittle and unable to withstand repeated insertion and removal.

Conventionally, means as shown in FIGS. 4A to 4C have been used to connect lead wires to both electrodes of a polymer piezoelectric material.

[Problem that the invention seeks to solve]

The example in FIG. 4(A) shows both electrodes 2a of the polymer piezoelectric material 1.

This is a case where lead wires 3a and 3b are bonded to 2b using a conductive adhesive 4. The conductive adhesive 4 is the polymer piezoelectric material 1
Since it is applied only to a portion of the lead wires 3a, 3b and the electrodes 2a, 2b so as not to impair their flexibility, the adhesive strength between the lead wires 3a, 3b and the electrodes 2a, 2b is weak, and the adhesive strength is insufficient especially for use as a vibrator, resulting in poor durability. It has a flaw in its lack of sex.

Furthermore, since the amount of charge generated on both sides of the piezoelectric body 1 during bending deformation is approximately equal, there is a fatal drawback in that only a small output signal can be obtained.

In the example shown in FIG. 4(B), conductive rubber sheets 5a and 5b, which also serve as electrodes, are crimped onto both sides of the polymer piezoelectric material 1, and between the conductive rubber sheets 5a and 5b and the polymer piezoelectric material 1. This is a case where metal pieces 6a, 6b are partially inserted into each metal piece, and lead wires 3a, 3b are soldered to each metal piece 6a, 6b. In order to achieve low conductor resistance, the conductive rubber sheets 5a and 5b have a thickness of, for example, 11 or more on both sides, making it difficult to cause large displacements and making it impossible to install them in a space-saving manner. There is. Furthermore, there are structural drawbacks such as the need to provide a large difference in the thickness of the conductive rubber sheets 5a and 5b in order to increase the signal during bending deformation.

In the example shown in FIG. 4(C), thin electrodes 8a and 8b made of metal foil having IJ + lead wire connection portions 7a and 7b are attached to both sides of the polymer piezoelectric material l, and each of the lead wire connection portions 7a
, 7b are soldered to the lead wires 3a, 3b.

This makes the entire element hard, making it unsuitable for elements that require large bending displacements. If the electrodes 8a and 8b are made too thin in order to provide flexibility to the device, the strength of the lead wire connection portions 7a and 7b will be reduced, resulting in the disadvantage that they are unusable.

In order to improve the drawbacks of the conventional examples, the present inventor has proposed a piezoelectric element that is thin, has excellent flexibility and mechanical strength, and has a suitable degree of rigidity, and has already filed an application.

This flexible piezoelectric element will be explained with reference to FIGS. 1 and 2. It consists of a polymer piezoelectric material 1 having a thin film electrode 11a on one surface, and a A flexible electrode sheet 9 comprising a thin film lead portion 13a connected to the thin film electrode 11a and a thin film electrode 11 having a lead portion 13b bonded to the other surface of the polymer piezoelectric material 1; Thin film electrode 11a and thin film lead portion 13 on one side of
It consists of a connecting conductor 12 joined across a, and a protective film 10 joined to the surface of this connecting conductor 12 and the exposed surface of the thin film electrode 11a on one side of the polymer piezoelectric body 1. ,
As shown in the third figure, a narrow electrode part 113 is provided at least on the thin film lead part 13b side of the thin film electrode 11 of the flexible electrode sort 9.
11□, and the lead portions 13a, 13
The IJ-wire can be attached to b with sufficient strength by soldering, etc., and the lead parts 13a and 13b can be attached with sufficient strength.
The thin film electrode 11 is large enough to cover the entire surface of the polymer piezoelectric material 1, and can be easily inserted into and extracted from the socket.
Since it is possible to provide more flexibility than when using the narrow electrode part 111, the sensitivity of the element can be increased, and the sensitivity in the low frequency range can be particularly improved. There was a problem that it was easy to break and could not withstand long-term use.

The present invention improves the drawbacks of the above conventional example, and provides a prior application flexible piezoelectric element (hereinafter referred to as "prior application element") proposed by the present inventor.
The purpose is to provide a flexible piezoelectric element that can withstand long-term use and whose resonant frequency can be easily adjusted. .

[Means for solving problems]

In order to solve the above-mentioned problems and achieve the above-mentioned objects, the device of the present invention includes a polymer piezoelectric material 1 having a thin film electrode 11a on one surface as shown in FIGS. 1, and a thin film electrode 11 having a lead portion 13b connected to the other surface of the piezoelectric polymer. , a thin film electrode 11 on one side of the polymer piezoelectric material 1
A connection conductor 12 is bonded across the thin film lead portion 13a, and a protection bonded to the surface of the connection conductor 12 and the exposed surface of the thin film electrode 11a on one side of the polymer piezoelectric body 1. In a flexible piezoelectric element consisting of a membrane 10, at least the thin film lead portion 1 of the thin film electrode 11 of the flexible electrode sheet 9
By providing a plurality of notches 113 on the 3b side and forming a plurality of narrow electrode parts 113, a plurality of narrow electrode parts 1 are formed.
Even if a part of 14 is cut off, signal extraction and voltage application are ensured in other parts, so that it can withstand long-term use.

The polymeric piezoelectric body 1 is made by dispersing fine powder of ferroelectric ceramic such as lead titanate/lead zirconate, lead titanate, or barium titanate in a plastic such as a mixture of polyacetal resin and acrylonitrile/butadiene rubber. A piezoelectric material obtained by polarizing this material under high voltage, or an oriented film made by stretching a cast film or thermoformed film of polyvinylidene fluoride resin or poly(vinylidene cyanide/vinyl acetate) copolymer resin, etc. A piezoelectric material obtained by polarization treatment under high voltage can be used, but when using a piezoelectric material with orientation obtained through a stretching process as a unimorph type element, it is necessary to Since only a small piezoelectric property can be obtained, it is necessary to construct the element so that its stretching direction is the same as the bending direction of the element. Further, it goes without saying that when the element according to the present invention is used as a flexible pyroelectric element by being attached to a bent part, there is no need to pay attention to the direction.

The thin film electrode 11a is provided on the surface of the polymer piezoelectric material 1 by a known method such as vapor deposition or sputtering.

The flexible electrode sheet 9 is called a flexible printed circuit (FPC), and the polymer piezoelectric material 1
A thin film lead portion 13 is formed on the polymer film 14, and serves for signal extraction and voltage application.
a and a thin film electrode 11 having a lead portion 13b, and a plurality of notches 11° are provided at least on the thin film lead portion 13b side of the thin film electrode 11 to form a plurality of narrow electrode portions 1.
14.

The thin film lead portion 13a and the thin film electrode 11 can be formed into a desired pattern by adhering a metal foil to the polymer film 14 and etching this metal foil.

Polymer films such as polyimide with a thickness of 25 to 50 μm, polyester or nylon with a thickness of 50 to 250 μm have excellent chemical resistance and heat resistance, and are also highly rigid (plastic films with high mechanical strength are used). As the metal foil, a copper foil or the like having a thickness of about 35 μm is used.

The lead parts 13a and 13b are arranged side by side at the end of the film 14, but they can also be arranged side by side on the same surface as shown in the first figure, or one lead part 13b can be formed by using a known technique such as a through hole. may be arranged in parallel and facing each other on the surface opposite to the other lead portion 13a side.

Copper foil or the like is used as the connection conductor 12, and the protective film 1
0 is a material that protects the inside together with the flexible electrode sheet 9, and is preferably flexible and has a lower elastic modulus than the polymer piezoelectric material 1 because it does not impair the characteristics of the piezoelectric element.
A material similar to the polymer film 14 described above, a flexible rubber sheet such as silicone rubber, or various coating agents can be used.

Polymer piezoelectric material 1. The mutually conductive parts of the flexible electrode sheet 9 and the connecting conductor 12 are bonded using various known conductive adhesives or adhesives that have flexibility and do not deteriorate piezoelectric properties. The surface charge generated on the sheet 9 is effectively collected on the lead parts 13a, 13b on the sheet 9, and the lead part 1 on the sheet 9 is collected through the lead wire or socket.
In order to effectively apply the electrical signals supplied to 3a and 13b to the polymeric piezoelectric material 1, it is preferable that the adhesive or adhesive be thin enough to transmit the electrical signals. It is also possible to use an insulating adhesive or an adhesive, but in this case, it goes without saying that it should be partially adhered to ensure conduction so that signals can be taken out and voltage can be applied.

When a metal foil is used as the connection conductor 12, it is preferable to use a conductive adhesive or one with an adhesive because the metal foil is reinforced and workability is increased. When the lead portions 13a, 13b are electrically connected by adhesion of metal foil, an insulating paint 15 may be applied to the corresponding portion of the lead portion 13b as shown in the first figure.

When a sheet is used as the protective film 10, various known pressure-sensitive adhesives and adhesives can be used for adhesion, and instead of the sheet, an insulating paint may be applied to the entire element except for the ends of the lead parts 13a and 13b. In this way, it is also possible to form a retainer III.

When connecting lead wires for taking out signals or applying voltage, connect the lead wires to the lead parts L3a and 13b by soldering, and when using a socket, just insert the lead parts 13a and 13b into the socket. . In this case, the element has flexibility and appropriate rigidity, so
The lead portions 13a, 13b can be easily inserted into and removed from the socket.

In the flexible piezoelectric element constructed according to the present invention, a plurality of notches 113 are provided in at least a portion of the thin film electrode 11 of the flexible electrode sheet 9 to form a plurality of narrow electrode portions 114. It is possible to provide more flexibility than when using a thin film electrode 11 having a size that covers the entire surface of the polymer piezoelectric material 1.

Therefore, the sensitivity of the element can be increased, particularly in the low frequency range.

In addition, the width of the plurality of notches 11+ or the narrow electrode portion 11,
By changing the width, the area occupied by the electrode 11 in the width direction changes, so the resonant frequency of the reed sensor can be easily changed.

〔Example〕

FIG. 1 is a partially exploded perspective view showing an embodiment of the device of the present invention;
FIG. 2 is a sectional view thereof.

1st. In FIG. 2, 1 is a polymer piezoelectric material, and lla is a thin film electrode formed on one surface thereof. A flexible electrode sheet 9 is bonded to one surface of the polymer film 14, a thin film lead portion 13a connected to one thin film electrode 11a, and the other surface of the polymer piezoelectric material 1. The thin film electrode 11 having a lead part '13b is connected to both lead parts 13a and 13b.
A plurality of notches 113 are provided in the width direction at least on the side of the thin film lead portion 13b in the plane of the thin film electrode 11 to form a plurality of narrow width electrodes. A portion 114 is formed.

12 is a copper foil with a conductive adhesive, and 10 is a protective sheet made of a polymer film.

Then, the other surface of the polymer piezoelectric material 1 is adhered to the thin film electrode 11 of the flexible electrode sheet 9 with an adhesive, and a conductive adhesive is applied across the one thin film electrode 11a and the thin film lead portion 13a. The protective film 10 is bonded to the surface of the copper foil 12 and the exposed surface of one of the thin film electrodes 11a using an adhesive. 15 is 8M
It's paint.

The device of the present invention having the above structure can also be connected to an external electric circuit by connecting lead wires to the lead portions 13a and 13b or by inserting the lead portions 13a and 13b into sockets for signal extraction and voltage application.

〔Effect of the invention〕

As described above, according to the device of the present invention, a thin Ill is formed on one surface.
A polymer piezoelectric material 1 having an electrode 11a, a thin film lead portion 13a connected to the thin film electrode 11a on one surface of the polymer piezoelectric material 1, and a lead portion 13b bonded to the other surface of the polymer piezoelectric material 1. a thin film electrode 1 on one side of the polymer piezoelectric material 1;
A connecting conductor 12 is bonded across the thin film lead portion 1a and the thin film lead portion 13a. In the flexible piezoelectric element comprising the protective film 10, a plurality of notches 113 are provided at least on the thin film lead portion 13b side of the thin film electrode 11 of the flexible electrode sheet 9 to form a plurality of narrow electrode portions 114. Therefore, even if a part of the plurality of narrow electrode parts 114 is cut off, signal extraction and voltage application can be ensured in other parts, which not only makes it possible to withstand long-term use. Since the area occupied by the electrode 11 in the width direction changes by changing the width of the notch 113 or the width of the narrow electrode section 114, the resonant frequency of the REIT sensor can be easily changed.

[Brief explanation of drawings]

FIG. 1 is a partially exploded perspective view showing an embodiment of the device of the present invention;
Fig. 2 is a cross-sectional view thereof, Fig. 3 is a plan view showing the flexible electrode sheet of the prior application proposed by the present inventor, and Figs. 4 (A) to (C).
1 is a perspective view showing each side of a conventional device; FIG. DESCRIPTION OF SYMBOLS 1... Polymer piezoelectric material, 9... Flexible electrode sheet, 10... Protective film, lla, 11...
... Thin film electrode, 12 ... Connection conductor, 1
3a... Thin film lead part, 13b...
Lead part, 113... Notch, 114...
...Narrow electrode part. Jun 1 calculation 2Ω

Claims (1)

[Claims] A polymer piezoelectric material 1 having a thin film electrode 11a on one surface, a thin film lead portion 13a connected to the thin film electrode 11a on one surface of the polymer piezoelectric material 1, and a thin film lead portion 13a connected to the thin film electrode 11a on one surface of the polymer piezoelectric material 1; A flexible electrode sheet 9 equipped with a thin film electrode 11 having a lead portion 13b to be joined, and a connecting sheet straddling the thin film electrode 11a on one side of the polymer piezoelectric material 1 and the thin film lead portion 13a. Conductor 12 and this connecting conductor 12
In a flexible piezoelectric element comprising a protective film 10 attached to the exposed surface of the thin film electrode 11a on one side of the polymer piezoelectric material 1, at least the thin film lead of the thin film electrode 11 of the flexible electrode sheet 9 A flexible piezoelectric element characterized in that a plurality of notches 11_3 are provided on the portion 13b side to form a plurality of narrow electrode portions 11_4.