JP2002026409A - Flexible piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both sensitivity and reliability by forming a vapor- deposited electrode, a thermal-sprayed electrode, a metal foil electrode and the like on a flat surface of a composite piezoelectric body sheet. SOLUTION: There are provided a composite piezoelectric body sheet 3 where piezoelectric ceramic powder 2 is entrained in a high polymer parent material 1, and an electrode 4 provided on both surfaces of the sheet 3, with an insert 6 between them. Thus, flexibility is improved, electrostatic capacity is reduced, and sensitivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible piezoelectric element.

[0002]

2. Description of the Related Art Conventionally, as a flexible piezoelectric element, as shown in FIG. 7, a polymer base material 1 and a piezoelectric ceramic powder 2 are mixed and formed into a sheet shape. Is provided. At this time, in general, a metal vapor-deposited electrode of copper, aluminum, gold, or the like, or a metal foil electrode is combined with the adhesive 5 in consideration of the piezoelectric characteristics imparted by the polarization treatment and the heat resistance of the polymer base material 1. The one that is entirely adhered to the surface of the piezoelectric sheet 3 is used.

Further, Japanese Patent Application Laid-Open No. 5-102548 proposes a flexible piezoelectric element using a sprayed electrode obtained by spraying a metal on the composite piezoelectric sheet 3.

[0004]

However, the above-mentioned flexible piezoelectric element has a problem that its reliability is poor or its sensitivity is low. That is, the metal foil electrode is generally made of a metal foil having a thickness of about 6 to 100 μm made of polyester resin, urethane resin, epoxy resin or the like.
It is affixed to the composite piezoelectric sheet via an adhesive of about 40 μm. However, when the metal foil electrodes are provided on both sides of the composite piezoelectric sheet, the sensitivity of the composite piezoelectric body is an important advantage that flexibility is impaired. There was a problem that it was low. In addition, the thickness of the generally provided electrode is 0.02 to 0.1 in the deposition electrode.
When the composite piezoelectric sheet flexes because it is very thin, about μm, cracks occur in the electrodes and the sensitivity decreases, or
There was a problem that no output could be obtained.

[0005] Further, in the case of sprayed electrodes, only the low boiling point metal can be easily spray-formed due to the heat resistance of the composite piezoelectric sheet, and there is a problem that the electrode material used is limited. Since a load such as air pressure is applied to the composite piezoelectric sheet during thermal spraying, there has been a problem in the reliability of the composite piezoelectric sheet.

[0006]

In order to solve the above-mentioned problems, the present invention provides a composite piezoelectric sheet in which a piezoelectric ceramic powder is mixed in a polymer base material, and is disposed on both surfaces of the composite piezoelectric sheet. A flexible piezoelectric element including an electrode and an intervening member between the electrode and the composite piezoelectric sheet.

[0007] According to the invention, by providing an intervening material between the electrode and the composite piezoelectric sheet, an air layer is formed between the electrode and the composite piezoelectric sheet, so that the static electricity of the flexible piezoelectric element is reduced. The capacity is reduced, and as a result, a highly sensitive flexible piezoelectric element can be realized. Further, since it is not necessary to use a thin-film deposited electrode or the like for high sensitivity, it is possible to suppress the occurrence of cracks in the electrode and realize a highly reliable flexible piezoelectric element with a simple configuration.

[0008]

In order to solve the above-mentioned problems, a first aspect of the present invention is a composite piezoelectric sheet in which a piezoelectric ceramic powder is mixed in a polymer matrix, and the composite piezoelectric sheet is disposed on both surfaces of the composite piezoelectric sheet. A flexible piezoelectric element including an electrode and an intervening member between the electrode and the composite piezoelectric sheet.

By providing an intervening material between the electrode and the composite piezoelectric sheet, an air layer is easily formed between the electrode and the composite piezoelectric sheet, thereby realizing a flexible piezoelectric element having high sensitivity and reliability. it can.

According to a second aspect of the present invention, there is provided a flexible piezoelectric element in which an inclusion is formed in a sheet shape with a hole partially formed therein.

[0011] By forming the inclusions into a partially perforated sheet shape, an air layer can be formed in the perforated portion, so that the sensitivity can be improved with a simple configuration.

According to a third aspect of the present invention, there is provided a flexible piezoelectric element in which inclusions are partially provided on the surface of a composite piezoelectric sheet.

[0013] By providing the inclusion partially on the surface of the composite piezoelectric sheet, an air layer can be easily formed between the electrode and the composite piezoelectric sheet. A sensitive flexible piezoelectric element can be realized. Further, by adjusting the number of inclusions provided on the surface of the composite piezoelectric sheet, it is possible to easily control the ratio of the air layer.

According to a fourth aspect of the present invention, there is provided a flexible piezoelectric element in which the inclusions are spherical and are partially provided on the composite piezoelectric sheet.

By providing the inclusions in a spherical shape and partially providing them on the composite piezoelectric sheet, an air layer can be easily formed between the electrodes and the composite piezoelectric sheet. Therefore, a highly sensitive flexible piezoelectric element can be realized. Further, the thickness of the air layer can be controlled with high precision by the diameter of the sphere, and the point of contact between the composite piezoelectric sheet and the electrode is a point, so that the flexibility of the electrode is improved and the sensitivity can be increased.

According to a fifth aspect of the present invention, there is provided a flexible piezoelectric element in which inclusions are melted by heat to bond an electrode and a composite piezoelectric sheet.

By applying heat to the inclusions and thermally welding or thermocompressing the composite piezoelectric sheet and the electrodes, it is not necessary to newly provide an adhesive, thereby improving productivity and enabling a thin structure. Flexibility is improved.

The invention according to claim 6 is a flexible piezoelectric element in which the inclusions are made of chlorinated polyethylene.

Since chlorinated polyethylene has excellent heat resistance and excellent flexibility, a flexible piezoelectric element having these characteristics can be constructed.

[0020] The invention according to claim 7 is a flexible piezoelectric element in which the polymer base material is made of chlorinated polyethylene.

Since chlorinated polyethylene has excellent heat resistance and excellent flexibility, a composite piezoelectric sheet having these characteristics can be obtained.

According to an eighth aspect of the present invention, there is provided a flexible piezoelectric element comprising piezoelectric ceramic powder formed of a solid solution of lead titanate and lead zirconate.

Since the piezoelectric ceramic powder, which is a solid solution of lead titanate and lead zirconate, is used in large quantities in industry, it is inexpensive and easily available, so it is highly sensitive and inexpensive. A piezoelectric element can be provided.

According to a ninth aspect of the present invention, there is provided a flexible piezoelectric element comprising piezoelectric ceramic powder made of lead titanate.

Since the dielectric constant of lead titanate is smaller than the dielectric constant of a solid solution of lead titanate and lead zirconate,
Since the dielectric constant of the piezoelectric ceramic powder can be reduced, the polarization process is facilitated, and a highly sensitive flexible piezoelectric element can be easily provided.

According to a tenth aspect of the present invention, there is provided a flexible piezoelectric element having an electrode formed of a metal foil electrode.

By forming the electrodes with metal foil electrodes, a highly reliable flexible piezoelectric element can be realized while maintaining flexibility.

An eleventh aspect of the present invention is a flexible piezoelectric element in which an electrode is composed of a composite conductor comprising a polymer for an electrode and conductive particles.

Then, the conductivity of the composite conductor is ensured through the contact of the conductive particles, and the flexibility of the composite conductor is also secured through the flexibility of the polymer for electrode itself. High sensitivity can be achieved.

The twelfth aspect of the present invention is a flexible piezoelectric element in which conductive particles are made of carbon.

Since carbon particles are industrially used in large quantities, they are inexpensive and easily available.

According to a thirteenth aspect of the present invention, there is provided a flexible piezoelectric element in which a polymer for an electrode is made of chlorinated polyethylene.

Since chlorinated polyethylene has excellent heat resistance and excellent flexibility, a composite conductor having these characteristics can be realized.

According to a fourteenth aspect of the present invention, there is provided a flexible piezoelectric element in which a polymer for an electrode, a polymer base material and inclusions are made of the same material.

[0035] When the electrode polymer, the polymer base material and the inclusions are made of the same material, they can be easily bonded by thermocompression bonding or the like, and the reliability is improved because of the same material.

[0036]

FIG. 1 to FIG. 6 show an embodiment of the present invention.
This will be described with reference to FIG.

(Embodiment 1) The invention of Embodiment 1 will be described with reference to FIGS.

FIG. 1 is a perspective view of the flexible piezoelectric element of the present invention, FIG. 2A is a sectional view of the flexible piezoelectric element before an external force is applied, and FIG. It is sectional drawing of the flexible piezoelectric element of. In FIG. 2, a flexible piezoelectric element is obtained by dispersing and mixing a piezoelectric ceramic powder 2 into a polymer base material 1 and then forming a sheet having a thickness of 0.5 mm. 0.3 mm. The inclusions 6 were placed on both surfaces of the composite piezoelectric sheet 3, and the electrodes 4 were placed on the surface of the inclusions 6. Composite piezoelectric sheet 3 and electrode 4
Was bonded by the adhesive 5 applied to the surface of the inclusion 6.

In this embodiment, the electrode 4 is made of aluminum 1
A 5 μm metal foil electrode and a conductive sheet having excellent flexibility were used as the inclusions 6. The conductive sheet was formed into a mesh shape having holes at certain intervals, and the ratio of the holes in the conductive sheet was about 50% by volume. By providing the inclusion 6, an air layer 7 is formed between both the composite piezoelectric sheet 3 and the electrode 4, so that the capacitance of the flexible piezoelectric element decreases and the electrode 4 , The tensile force of the electrode 4 was reduced, and the flexibility was improved. In particular, by controlling the thickness of the inclusion 6, the volume of the air layer 7 formed between the composite piezoelectric sheet 3 and the electrode 4 can be controlled. Further, the size of the hole provided in the inclusion 6 and the proportion of the hole,
The flexibility of the electrode 4 can be controlled by controlling its own thickness and material.

Next, in order to impart piezoelectric characteristics, a DC high voltage was applied between the electrodes 4 to polarize the piezoelectric ceramic powder 2 to form a flexible piezoelectric element. Piezoelectric ceramic powder 2
The polarization was performed after the electrode 4 was placed. However, after polarization was performed using an electrode that was entirely adhered to the composite piezoelectric sheet 3 by hot pressing, the electrode was peeled off and the electrode 4 was removed.
May be adhered. By performing this polarization process,
The flexible piezoelectric element generates an electric charge when an external force is applied.
The charge generation amount Q is determined by the amount of external force, and the output voltage V is given by:
The output voltage V is determined by the relational expression of Q / c, and depends on the capacitance c. For this reason, the output voltage V increases as the capacitance c decreases, and the apparent sensitivity improves.

The capacitance c depends on the electrode 4 and the air layer 7 formed on the composite piezoelectric sheet 3. As the proportion of the air layer 7 increases, the capacitance of the flexible piezoelectric element decreases. , And the sensitivity is improved. In the flexible piezoelectric element of the present invention, when no external force is applied, the contact area between the composite piezoelectric sheet 3 and the electrode 4 is small as shown in FIG.
When an external force is applied, the air layer 7 is removed as shown in FIG. 2B, and the electrode 4 corresponding to the external force application area comes into contact with the composite piezoelectric sheet 3 to obtain an output voltage. That is, even if the electrode 4 and the composite piezoelectric sheet 3 are not completely adhered to the entire surface by the adhesive 5, if an external force is applied, the electrode 4 adheres to the composite piezoelectric sheet 3 and an output voltage is obtained. In particular, when the electrode 4 and the composite piezoelectric sheet 3 are completely adhered by the adhesive 5, the electrode 4 and the composite piezoelectric sheet 3 are adhered to portions other than the external force application section, and thus the static resistance of the flexible piezoelectric element itself is reduced. Electric capacity is large.

However, in the case of the flexible piezoelectric element of the present invention, since the inclusion 6 is provided between the electrode 4 and the composite piezoelectric sheet 3, the capacity can be suppressed to the minimum. The output voltage can be increased. Further, since the electrode 4 is partially adhered, the flexibility of the electrode 4 itself is improved and the sensitivity is improved.

In this embodiment, the ratio of the air layer 7 existing between the electrode 4 and the composite piezoelectric sheet 3 and the output voltage of the flexible piezoelectric element are changed by changing the ratio of the holes occupied by the inclusions 6. It was measured. The result is shown in FIG. At this time, a pressure for distorting the flexible piezoelectric element by 1 mm was applied as an external force, and the applied area was kept constant. From this result, it was found that the sensitivity was improved by providing the inclusions 6 and forming the air layer 7, and it was found that this tendency was higher as the proportion occupied by the air layer 7 was larger. Therefore, the flexible piezoelectric element of the present invention has high sensitivity without using a vapor deposition electrode as the electrode 4 and has high reliability since there is no fear of cracking in the electrode which is a problem peculiar to the vapor deposition electrode. A piezoelectric element was realized.

Although a conductive sheet is used as the inclusion 6 in this embodiment, the inclusion 6 may be an insulating material. In particular, chlorinated polyethylene as the inclusion 6 is excellent in heat resistance and flexibility, so that a flexible piezoelectric element having both of these features can be realized.

Further, in the present embodiment, the composite piezoelectric sheet 3, the inclusions 6, and the electrodes 4 are bonded by the adhesive 5, but the same effect can be obtained by bonding by thermocompression bonding.
In particular, when the inclusions 6 are melted by heat and exhibit an adhesive property, the composite piezoelectric sheet 3 and the electrodes 4 can be easily bonded without using the adhesive 5, so that productivity is reduced. In addition, since the adhesive 5 is removed, the thickness of the flexible piezoelectric element can be reduced, and the flexibility can be improved, so that high sensitivity can be achieved.

In this embodiment, the inclusions 6 are provided on both surfaces of the composite piezoelectric sheet 3. However, similar effects can be obtained by providing the inclusions on only one surface.

The material of the piezoelectric ceramic powder 2 is preferably a solid solution of lead titanate and lead zirconate. Piezoelectric ceramics of this composition are industrially used in large quantities as ceramics for electronic components, and are inexpensive and easily available.

In addition to the solid solution of lead titanate and lead zirconate, lead titanate is also preferable as the material of the piezoelectric ceramic powder 2. The relative permittivity of the solid solution of lead titanate and lead zirconate is a large value of about (800 to 3000), but the relative permittivity of lead titanate is a small value of about (200 to 300). Generally, when polarizing the composite piezoelectric sheet 3, the polarization voltage applied to the composite piezoelectric sheet 3 is applied to both the piezoelectric ceramic powder 2 and the polymer base material 1.
At this time, the voltage applied to the piezoelectric ceramic powder 2 depends on the relative permittivity of the polymer base material 1 and the piezoelectric ceramic powder 2.

That is, since the applied voltage is proportional to the reciprocal of the relative permittivity, it is desirable to lower the relative permittivity of the piezoelectric ceramic powder 2 in order to apply a large voltage to the piezoelectric ceramic powder 2. Therefore, by using a piezoelectric ceramic powder having a low relative dielectric constant such as lead titanate,
The piezoelectric ceramic powder 2 can be easily polarized.

An epoxy resin as the polymer base material 1
Urethane resin, chloroprene resin, chlorinated polyethylene resin, etc. are used. Epoxy resin and urethane resin have heat resistance of about (60 to 80 ° C), while chlorinated polyethylene has high heat resistance of 120 ° C. Excellent in point. Chlorinated polyethylene is also preferable in that the above high heat resistance can be realized without vulcanization by appropriately selecting the molecular weight, the crystallinity, and the like.

Further, since chlorinated polyethylene is excellent in flexibility, electrode peeling or the like due to external force is suppressed, and the reliability and sensitivity are high.

(Embodiment 2) FIG. 4 is a perspective view of this embodiment. The difference from the first embodiment is that a plurality of the inclusions 6 are provided on the surface of the composite piezoelectric sheet 3 instead of a single sheet. Also in this configuration, since the air layer 7 can be formed between the composite piezoelectric sheet 3 and the electrode 4, the same result as in Example 1 was obtained. Particularly, in the present configuration, the ratio of the air layer 7 can be adjusted only by changing the number of the inclusions 6 provided on the surface of the composite piezoelectric sheet 3, so that the holes as in the case of the sheet shape are formed. It is not necessary to use a punching process or a mold for the process. Therefore, the air layer 7 can be formed easily and inexpensively, and a highly sensitive flexible piezoelectric element can be easily provided.

(Embodiment 3) A perspective view of this embodiment is shown in FIG.
FIG. 5A shows a cross-sectional view of FIG. The difference from the first and second embodiments is that the inclusion 6 has a spherical shape. Also in this configuration, since the air layer 7 can be formed between the composite piezoelectric sheet 3 and the electrode 4 by providing the inclusion 6,
The same results as in Example 1 were obtained. In particular, in this configuration, since the inclusions 6 are spherical, the air space 7
Thickness can be controlled with high accuracy. The electrode 4 and the inclusion 6
Also, since the bonding of the composite piezoelectric sheet 3 is a point, the flexibility of the electrode 4 under a constant external force is improved, and high sensitivity can be achieved.

(Embodiment 4) FIG. 6 is a sectional view of this embodiment. The difference from Examples 1 to 3 is that a composite conductor 8 was used as the electrode 4 instead of a metal foil electrode. The composite conductor 8 is composed of an electrode polymer 8a and conductive particles 8b. At this time, the conductive particles 8b are
a, the electrical conductivity of the composite conductor 8 is secured through these contacts, and the flexibility of the composite conductor 8 is maintained through the flexibility of the polymer 8b for the electrode itself. Is secured. For this reason, more flexibility than when the metal foil electrode 4 is used is obtained.

As the polymer 8a for the electrode, an epoxy resin, a urethane resin, a chloroprene resin, a chlorinated polyethylene resin, or the like is used as in the case of the polymer base material 1. Further, carbon particles or silver particles are used as the conductive particles 8b. When silver particles are used, the specific resistance of the composite conductor 8 shows a small value of about 5 × 10 ⁻³ Ω · cm. However, when carbon particles are used, the specific resistance becomes about one digit or more. Show. Since the frequency range when this piezoelectric element is used for human body detection is about 5 Hz, the impedance of the composite piezoelectric sheet 3 at this time is about 100 kΩ or more, and the specific resistance value of the electrode 4 is about 1 kΩ or less. Therefore, it is desirable to use inexpensive carbon particles as the conductive particles 8b.

It is desirable to use chlorinated polyethylene for the electrode polymer 8a. This is because, as described in the description of the polymer base material 1 of the composite piezoelectric sheet 3 in Example 1, the chlorinated polyethylene has high sensitivity due to its excellent flexibility and also has excellent heat resistance so that it is reliable. The nature is also high.

By forming the electrode polymer 8a, the polymer matrix 1, and the inclusions 6 from the same material, the reliability of the flexible piezoelectric element itself is improved, and the adhesive 5 is not used. By selecting an appropriate temperature, bonding can be performed by thermocompression bonding or the like. In particular, as mentioned earlier,
By constituting the electrode polymer 8a, the polymer matrix 1, and the inclusions 6 with chlorinated polyethylene, a flexible piezoelectric element having excellent flexibility and heat resistance can be provided.

[0058]

As is apparent from the above description, according to the first aspect of the present invention, by providing an intervening material between the electrode and the composite piezoelectric sheet, the interposition between the electrode and the composite piezoelectric sheet is facilitated. An air layer is formed, and a flexible piezoelectric element having high sensitivity and high reliability can be realized with a simple configuration.

According to the second aspect of the present invention, since the inclusions are formed into a partially perforated sheet shape, air can be formed in the perforated portions. Can be formed, and sensitivity can be improved.

According to the third aspect of the present invention, the inclusion is partially provided on the surface of the composite piezoelectric sheet,
Since an air layer can be easily formed between the electrode and the composite piezoelectric sheet, the capacitance is reduced, and a highly sensitive flexible piezoelectric element can be realized.

According to the fourth aspect of the present invention, by forming the inclusions in a spherical shape and partially providing them on the composite piezoelectric sheet, an air layer can be easily formed between the electrodes and the composite piezoelectric sheet. it can. Therefore, a highly sensitive flexible piezoelectric element can be realized. Further, the thickness of the air layer can be controlled with high accuracy by the diameter of the sphere, and the point of contact between the composite piezoelectric sheet and the electrode is a point, so that the flexibility of the electrode is improved and the sensitivity can be increased.

According to the fifth aspect of the present invention, by performing heat welding with inclusions, it is not necessary to newly provide an adhesive, and an air layer can be formed with a simple structure. Therefore, a highly sensitive flexible piezoelectric element can be easily realized.

According to the invention of claim 6, since the inclusions are made of chlorinated polyethylene, they have heat resistance and excellent flexibility, so that a flexible piezoelectric element having these characteristics can be constructed. .

According to the seventh aspect of the present invention, since the polymer base material is made of chlorinated polyethylene, it has excellent heat resistance and excellent flexibility, so that it has a combination of these characteristics. Is obtained.

According to the invention of claim 8, since a solid solution of lead titanate and lead zirconate is used as the piezoelectric ceramic powder, it is inexpensive and easily available.

According to the ninth aspect of the present invention, since lead titanate is used as the piezoelectric ceramic powder,
Since the dielectric constant of the piezoelectric ceramic powder can be reduced, the polarization process is facilitated.

According to the tenth aspect of the present invention, since the electrodes are formed of metal foil electrodes, a flexible piezoelectric element which maintains flexibility and has high reliability can be realized.

According to the eleventh aspect of the present invention, since the electrode is composed of the composite conductor composed of the polymer for the electrode and the conductive particles, the composite conductor can be formed through the flexibility of the polymer for the electrode itself. Flexibility is ensured and bonding can be easily performed by heat welding such as hot pressing.

According to the twelfth aspect of the present invention, since the conductive particles are made of carbon, they are inexpensive and easily available.

According to the thirteenth aspect of the present invention, a flexible piezoelectric element having excellent flexibility and heat resistance can be realized by forming the polymer for an electrode from chlorinated polyethylene.

According to the fourteenth aspect of the present invention, since the electrode polymer, the polymer base material, and the inclusion are made of the same material, they can be easily bonded by thermocompression bonding or the like. The performance is also improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a flexible pressure element according to a first embodiment of the present invention.

2A is a cross-sectional view of the flexible piezoelectric element before an external force is applied. FIG. 2B is a cross-sectional view of the flexible piezoelectric element when an external force is applied.

FIG. 3 is a characteristic diagram showing a relationship between an air layer ratio and an output voltage of the flexible piezoelectric element.

FIG. 4 is an exploded perspective view of a flexible piezoelectric element according to a second embodiment of the present invention.

5A is an exploded perspective view of a flexible piezoelectric element according to a third embodiment of the present invention. FIG. 5B is a cross-sectional view of the flexible piezoelectric element.

FIG. 6 is a sectional view of a flexible piezoelectric element according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a conventional flexible piezoelectric element.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 polymer base material 2 piezoelectric ceramic powder 3 composite piezoelectric sheet 4 electrode 5 adhesive 6 inclusion 7 air layer 8 composite conductor 8a polymer for electrode 8b conductive particles

Continued on the front page (72) Inventor Naruhisa Kanazawa 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Naoji Nakatani 1006 Kadoma, Kazuma, Kazuma, Osaka Pref., Matsushita Electric Industrial Co., Ltd. (72) Inventor Hiroyuki Ogino 1006 Kadoma, Kazuma, Kadoma, Osaka Pref. 1006 Kadoma Matsushita Electric Industrial Co., Ltd. (72) Koji Yoshino 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (14)

[Claims] 1. A composite piezoelectric sheet in which a piezoelectric ceramic powder is mixed into a polymer matrix, electrodes disposed on both sides of the composite piezoelectric sheet, and an intervening member between the electrode and the composite piezoelectric sheet The flexible piezoelectric element provided with. 2. The flexible piezoelectric element according to claim 1, wherein the inclusion has a partially perforated sheet shape. 3. The flexible piezoelectric element according to claim 1, wherein the inclusion is partially provided on the surface of the composite piezoelectric sheet. 4. The flexible piezoelectric element according to claim 1, wherein the inclusion is spherical. 5. The flexible piezoelectric element according to claim 1, wherein the inclusions are melted by heat and bond the electrode and the composite piezoelectric sheet. 6. The flexible piezoelectric element according to claim 1, wherein the inclusion is chlorinated polyethylene. 7. The flexible piezoelectric element according to claim 1, wherein the polymer base material is chlorinated polyethylene. 8. The flexible piezoelectric element according to claim 1, wherein the piezoelectric ceramic powder is a solid solution of lead titanate and lead zirconate. 9. The flexible piezoelectric element according to claim 1, wherein the piezoelectric ceramic powder is lead titanate. 10. The electrode according to claim 1, wherein the electrode is a metal foil electrode.
The flexible piezoelectric element according to any one of the above items. 11. The flexible piezoelectric element according to claim 1, wherein the electrode is a composite conductor comprising a polymer for an electrode and conductive particles. 12. The method according to claim 1, wherein the conductive particles are carbon.
2. The flexible piezoelectric element according to 1. 13. The flexible piezoelectric element according to claim 11, wherein the polymer for an electrode is made of chlorinated polyethylene. 14. The flexible piezoelectric element according to claim 1, wherein the polymer for an electrode, the polymer base material, and the inclusion are made of the same material.