KR101442632B1 - piezoelectric composite film and piezoelectric apparatus using the same - Google Patents

Abstract

According to the piezoelectric composite film of the present invention, the electric flow can be improved in the matrix by dispersing the piezoelectric filler and the conductive filler together in the matrix, or by forming a conductive coating film on the surface of the piezoelectric filler and dispersing the matrix in the matrix have. That is, the electric signals can be easily transmitted to the plurality of piezoelectric pillars dispersed in the matrix, irrespective of the region adjacent to the electrode and the region not adjacent to the electrode in the matrix. Thus, it is possible to minimize other problems such as the degree of displacement or the magnitude of the mechanical vibration in each region of the piezoelectric layer.

Description

TECHNICAL FIELD The present invention relates to a piezoelectric composite film and a piezoelectric device including the piezoelectric composite film.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric composite film and a piezoelectric device including the piezoelectric composite film, and more particularly, to a piezoelectric composite film having improved electrical current flow and a piezoelectric device including the same.

Generally, a piezoelectric element is a device having a characteristic capable of changing electric energy and mechanical energy with each other. Such a piezoelectric element includes an O-3 type piezoelectric composite, that is, an O-3 type piezoelectric layer and electrodes formed on the upper and lower portions of the piezoelectric layer, as disclosed in Korean Patent No. 10-0707949. Here, the O-3 type piezoelectric layer is a structure in which a piezoelectric powder such as PZT is dispersed in a matrix made of a polymer. When an electric signal is applied from the upper and lower electrodes, the electric signal is transferred to the piezoelectric powder, which causes displacement of the piezoelectric layer, thereby generating mechanical vibration.

However, among the piezoelectric powders dispersed in the matrix, the piezoelectric powder located in the upper or lower region of the matrix and located adjacent to the upper and lower electrodes relatively facilitates the transmission of electrical signals, but is located in the central region of the matrix, It is difficult to transfer electrical signals to piezoelectric powder, which is relatively far away from the electrodes. That is, it is difficult to transmit electric signals to the piezoelectric powder dispersed in the central region of the matrix, or electric current is small, as compared with the piezoelectric powder dispersed in the upper region or the lower region of the matrix. Therefore, the piezoelectric characteristics or the magnitude of the vibration of the central region of the piezoelectric layer may be smaller than those of the upper and lower regions, which may deteriorate the characteristics of various devices using the O-3 piezoelectric layer.

Korean Patent No. 10-0707949

The present invention provides a piezoelectric composite film with improved electrical current flow and a piezoelectric device including the piezoelectric composite film.

In addition, the present invention provides a piezoelectric composite film in which an electrical signal can be easily transferred into a piezoelectric layer regardless of the position of an electrode, and a piezoelectric device including the piezoelectric composite film.

A piezoelectric composite film according to the present invention includes: a piezoelectric layer in which a plurality of fillers are dispersed in a matrix; And electrodes formed on both surfaces of the piezoelectric layer. The plurality of fillers dispersed in the matrix include a plurality of first fillers made of a piezoelectric material and a plurality of second fillers made of a conductive material.

A piezoelectric composite film according to the present invention includes: a piezoelectric layer in which a plurality of fillers are dispersed in a matrix; And electrodes formed on both surfaces of the piezoelectric layer. The plurality of pillars dispersed in the matrix are made of a piezoelectric material, and a coating film made of a conductive material is formed on the surface of the filler.

The matrix is a polymer.

The matrix may be selected from the group consisting of polydimethyl siloxane (PDMS), polyvinylidene fluoride (PVDF), epoxy, silicone rubber, polyurethane (PU), polymethylmethacrylate or polymethylmethacrylate (PMMA) is preferably used.

It is preferable that any one of PZT, PMN-PT, PZN-PT, PIN-PT, PYN-PT, VDF, PVDF-TrFE, BNT (BaNiTiO3) and BZT-BCT is used as the piezoelectric material.

The conductive material is any one of a carbon nanotube (CNT) and a metal material.

The present invention provides a piezoelectric device comprising a piezoelectric composite film in one of a piezoelectric speaker, a piezoelectric actuator, and piezoelectric energy harvesting, wherein the piezoelectric composite film comprises: a piezoelectric layer in which a plurality of fillers are dispersed in a matrix; And electrodes formed on both surfaces of the piezoelectric layer. The plurality of fillers dispersed in the matrix include a plurality of first fillers made of a piezoelectric material and a plurality of second fillers made of a conductive material.

The present invention provides a piezoelectric device comprising a piezoelectric composite film in one of a piezoelectric speaker, a piezoelectric actuator, and piezoelectric energy harvesting, wherein the piezoelectric composite film comprises: a piezoelectric layer in which a plurality of fillers are dispersed in a matrix; And electrodes formed on both surfaces of the piezoelectric layer. The plurality of pillars dispersed in the matrix are made of a piezoelectric material, and a coating film made of a conductive material is formed on the surface of the filler.

The piezoelectric material is preferably any one of PZT, PMN-PT, PZN-PT, PIN-PT, PYN-PT, VDF, PVDF-TrFE, BNT (BaNiTiO3) and BZT-BCT.

The conductive material is preferably any one of carbon nanotubes (CNTs) and metal materials.

According to the piezoelectric composite film according to the embodiments of the present invention, the piezoelectric filler and the conductive filler are dispersed together in the matrix, or a conductive coating film is formed on the surface of the piezoelectric filler and dispersed in the matrix, Can be improved. That is, the electric signals can be easily transmitted to the plurality of piezoelectric pillars dispersed in the matrix, irrespective of the region adjacent to the electrode and the region not adjacent to the electrode in the matrix. In other words, it is possible to prevent the problem of a weak electrical signal or flow as it is farther away from the electrode as in the conventional art, so that the problem of the degree of displacement or the magnitude of the mechanical vibration can be minimized in each region of the piezoelectric layer. Therefore, the piezoelectric characteristics and the mechanical vibration effect of the piezoelectric composite film are improved, and the characteristics of the piezoelectric devices such as the piezoelectric speaker, the piezoelectric actuator, and the piezoelectric energy harvester to which the piezoelectric composite film is applied are also improved.

1 is a cross-sectional view of a piezoelectric composite film according to a first embodiment of the present invention
2 is a cross-sectional view showing a piezoelectric composite film according to a second embodiment of the present invention
3 is a cross-sectional view of a piezoelectric speaker to which a piezoelectric composite film according to embodiments of the present invention is applied

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Wherein like reference numerals refer to like elements throughout.

1 is a cross-sectional view illustrating a piezoelectric composite film according to a first embodiment of the present invention. 2 is a cross-sectional view illustrating a piezoelectric composite film according to a second embodiment of the present invention.

1, a piezoelectric composite film 100 according to a first embodiment of the present invention includes a piezoelectric layer 110 in which a plurality of pillars 112a and 112b are dispersed in a matrix 111, For example, a first electrode 120a formed on the upper surface, and a second electrode 120b formed on the other surface, for example, the lower surface of the piezoelectric layer 110. [

The piezoelectric layer 110 is a means having a piezoelectric property by poling in a thickness direction, and is formed in the form of a film having a substantially rectangular shape in the present embodiment. The shape of the piezoelectric layer 110 is not limited to the rectangle described above, and may be changed into various shapes depending on the structure of the pad and the purpose of use.

The piezoelectric layer 110 is a composite of a 0-3 structure in which a plurality of pillars 112a and 112b are dispersed in a matrix 111 as described above and the matrix 111 is a polydimethyl siloxane polymer material. PDMS). ≪ / RTI > (PVDF), epoxy, silicone rubber, polyurethane (PU), polymethylmethacrylate (PVDF), and the like, as well as polydimethylsiloxane (PDMS) Various polymer materials such as polymethylmethacrylate (PMMA) can be used.

The plurality of pillars 112a and 112b are for imparting piezoelectric characteristics to the piezoelectric composite film 100 and include a plurality of first pillars 112a made of a piezoelectric material and a plurality of second pillars 112b made of a conductive material The plurality of first pillar 112a and the plurality of second pillar 112b are dispersed to be spaced apart from each other. The plurality of first pillars 112a have a piezoelectric characteristic and are in the form of a powder composed of a plurality of particles. The first pillar 112a may be formed of PMN-PT, PZN-PT, PIN-PT, PYN-PT , Piezoelectric polymer materials such as PVDF and PVDF-TrFE, BNT (BaNiTiO ₃ ), and BZT-BCT.

The second pillar 112b allows an electric signal, that is, a voltage applied from the first and second electrodes 120a and 120b, to be easily transmitted to the entire piezoelectric layer 110, CNT) and metal, and is in the form of a powder composed of a plurality of particles. As the metal, various materials having electrical conductivity such as carbon (C), Ag, Cu, Al, Ni, and Fe may be used.

The first and second electrodes 120a and 120b are formed on the top and bottom surfaces of the piezoelectric layer 110 to apply an electric signal or voltage to the piezoelectric layer 110, respectively. The first and second electrodes 120a and 120b are formed of a conductive material and may be formed using a metal paste such as carbon nanotube (CNT), Ag, carbon (C) powder or Al, polyaniline, polythiophene , PEDOT (poly (3,4-ethylene-dioxythiophene)), polypyrrole, PPV (polyphenylenevinylene), derivatives thereof and organic conductors. The first and second electrodes 120a and 120b may be formed in various polygonal shapes such as a square, a sector, and the like.

When an electric signal, that is, a voltage is applied to the first and second electrodes 120a and 120b for the operation of the piezoelectric composite film 100 according to the first embodiment, the applied electric signal is applied to the piezoelectric layer 110 . As described above, the piezoelectric layer 110 is composed of a composite of 0-3 structures, in which a plurality of first fillers 112a that are piezoelectric and a plurality of second fillers 112b that are electrically conductive are mixed and dispersed in the matrix 111 . The electric signals applied from the first and second electrodes 120a and 120b are transmitted to the plurality of first pillars 112a and the plurality of second pillars 112b through the matrix 111, Displacement of the piezoelectric layer 110 is caused by the vibration of the piezoelectric layer 110 and mechanical vibration is generated.

On the other hand, since the electrodes 120a and 120b are formed on the top and bottom surfaces of the piezoelectric layer 110, the first and second electrodes 120a and 120b are relatively adjacent to the first and second pillars 112a and 120b, It is difficult for the electric signals to be transmitted to the first pillars 112a which are relatively far from the first and second electrodes 120a and 120b. In other words, it is difficult to transmit an electric signal to the first filler 112a dispersed in the central region of the matrix 111, compared to the first filler 112a dispersed in the upper region or the lower region of the matrix 111 .

However, in this embodiment, a plurality of electrically conductive second pillars 112b are dispersed in the matrix 111 in addition to the piezoelectric first pillar 112a. The second pillars 112b are distributed over the entire region of the matrix 111 and serve as a kind of electrical network or medium that facilitates the flow of electrical signals in the matrix 111. [ Accordingly, at least a part of the electrical signals applied from the first and second electrodes 120a and 120b are transmitted to the first pillar 112a adjacent to the second pillar 112b or transmitted to the second pillar 112b, The electric signal is transmitted to the adjacent first pillar 112a through the second pillar 112b and can be uniformly transmitted to the entirety of the matrix 111 or the piezoelectric layer 110. [ Accordingly, electric signals are also easily transmitted to the first filler 112a dispersed in the central region of the matrix 111, which is relatively distant from the first and second electrodes 120a and 120b. As a result, the flow of electric current into the matrix 111 is improved irrespective of the region adjacent to the first electrode 120a and the region adjacent to the second electrode 120b, and an electric signal of a uniform size can be transmitted, The characteristics of the piezoelectric composite film 100 can be improved.

Hereinafter, a piezoelectric composite film according to a second embodiment of the present invention will be described with reference to FIG. At this time, the description overlapping with the first embodiment will be omitted or briefly explained.

The piezoelectric composite film 100 according to the second embodiment includes a piezoelectric layer 110 in which a plurality of pillars 112a are dispersed in a matrix 111, a first electrode 120a formed on one surface of the piezoelectric layer 110, And a second electrode 120b formed on the other surface of the piezoelectric layer 110, for example, on the lower surface. In the piezoelectric layer 110 according to the present embodiment, the plurality of pillars 112a dispersed in the matrix 111 are made of a piezoelectric material, and a coating film 112c made of a conductive material is formed on the surface of the filler 112a. .

The plurality of pillars 112a having piezoelectricity can be made of a single crystal piezoelectric material such as PMN-PT, PZN-PT, PIN-PT or PYN-PT as well as polycrystalline ceramics such as PZT Material, a piezoelectric polymer material such as PVDF or PVDF-TrFE, BNT (BaNiTiO3), or BZT-BCT.

The coating film 112c is coated to cover the surface of each of the plurality of fillers 112a and may be formed of any one of carbon nanotubes (CNTs) and metal materials. Examples of the metal material include carbon (C), Ag, Cu, Al , Ni, Fe, and the like can be used. The method of forming the coating film 112c on the surface of the filler 112a can be formed by various surface coating methods by electroless plating electroplating or sol-gel reaction.

The coating layer 112c serves as a kind of electrical network or medium so that electric signals applied from the first and second electrodes 120a and 120b can be easily transmitted to the entire piezoelectric layer 110. [ In other words, the electric signals applied from the first electrode 120a and the second electrode 120b are transmitted to the piezoelectric filler 112a through the conductive coating film 112c which is the outermost layer. At this time, electric signals are also easily transmitted to the filler 112a, which is dispersed in the central region of the matrix 111, which is relatively far from the first and second electrodes 120a and 120b. This is because the filler 112a, Since the conductive coating film 112c is formed on the surface of the matrix 111 and the electric conduction flow in the matrix 111 is improved by the coating film 112c. As described above, the filler 112a having the conductive coating film 112c formed on each surface forms a domain in the matrix 111, and each domain becomes a generator. This makes it possible to apply a uniform electrical signal to the entire matrix 111 irrespective of the region adjacent to the first electrode 120a and the region adjacent to the second electrode 120b, The characteristics can be improved.

3 is a cross-sectional view of a piezoelectric speaker to which a piezoelectric composite film according to an embodiment of the present invention is applied.

Hereinafter, a piezoelectric speaker to which the piezoelectric composite film 100 of the present invention is applied will be described with reference to FIG. At this time, the contents overlapping with the piezoelectric composite film described above will be omitted or briefly explained.

3, a piezoelectric speaker according to an embodiment of the present invention includes a piezoelectric composite film 100, a frame 400 for supporting the piezoelectric composite film 100, A cap 600 covering the piezoelectric composite film 100 and an adhesive layer 500 bonding the piezoelectric composite film 100 and the frame 400. Further, although not shown, a vibration member may be attached to the lower portion of the piezoelectric composite film 100, and the vibration member may be in the form of a film made of metal, natural pulp or polymer resin.

The piezoelectric composite film 100 includes a piezoelectric layer 110 and electrodes 120a and 120b formed on the upper and lower surfaces of the piezoelectric layer 110. The piezoelectric layer 110 includes a plurality Of the O-3 complex structure. The piezoelectric layer 110 may have a structure in which a piezoelectric first filler 112a and a conductive second filler 112b are dispersed in the matrix 111 as in the first embodiment shown in FIG. 1, The conductive coating film 112c is coated on the surface of the piezoelectric filler 112a as in the second embodiment shown in FIG.

The adhesive layer 500 is applied between the piezoelectric composite film 100 and the frame 400 to bond the frame 400 to the lower portion of the piezoelectric composite film 100. The adhesive layer 500 is effective to use a material having a high modulus of elasticity. In the present embodiment, at least one of an epoxy silicone resin and an acryl oligomer is used.

The frame 400 is attached by the adhesive layer 500 at least in the form of surrounding the lower portion of the piezoelectric composite film 100 to support the piezoelectric composite film 100. Such a frame 400 may be formed of a plastic material such as polybutylene terephthalate (PBT), polyacetal (POM), and polycarbonate (PC) or the like in order to minimize the half vibration when the piezoelectric composite film 100 is vibrated Aluminum, or the like. In the case of the frame 400 according to the embodiment, the area corresponding to the lower side of the piezoelectric composite film 100, that is, the lower part of the frame 400 may be closed, but not limited thereto, .

The cap 600 covers the piezoelectric composite film 100 and is connected to the frame 400 at the upper side of the piezoelectric composite film 100 to protect the piezoelectric speaker and includes a plurality of acoustic holes 610, . The shape of the acoustic hole 610 can be variously changed into a circular shape, an elliptic shape, and the like.

In order to operate the above-described piezoelectric speaker, an electric signal, that is, a voltage is applied through the first and second electrodes 120a and 120b. An electric signal applied through the first and second electrodes 120a and 120b is transmitted into the matrix 111 of the piezoelectric layer 100. According to the piezoelectric composite film 100 according to the first embodiment ), A part of which is directly transmitted to a plurality of piezoelectric first pillar 112a, and at least part of which can be transmitted to the first pillar 112a through a plurality of conductive second pillar 112b. Particularly, electric signals are directly transmitted to the first pillars 112a dispersed in the upper or lower region of the matrix 111 so as to be adjacent to the first and second electrodes 120a and 120b, The first filler 112a dispersed in the central region can be transmitted through the conductive second filler 112b. Therefore, electric signals can be easily transmitted over the entirety of the matrix 111 or the piezoelectric layer 110 irrespective of the region adjacent to the first electrode 120a and the second electrode 120b, The problem that the degree of displacement or the magnitude of the mechanical vibration differs depending on the area of the piezoelectric speaker 110 can be minimized, thereby improving the characteristics of the piezoelectric speaker.

2), the electric signal applied from the first electrode 120a and the second electrode 120b is an outermost layer of a conductive coating film 112c. In this case, To the piezoelectric filler 112a. At this time, electrical signals can be easily transmitted to the filler 112a, which is dispersed in the center region of the matrix 111, that is, far away from the first and second electrodes 120a and 120b by the conductive coating film 112c . A filler 112a having a conductive coating film 112c on each surface forms a domain in the matrix 111, and each domain becomes a generator. Therefore, electric signals can be easily transmitted to the entire matrix 111 or the piezoelectric layer 110 irrespective of the region adjacent to the first electrode 120a and the region adjacent to the second electrode 120b. Thus, the phenomenon that the degree of displacement or the magnitude of the mechanical vibration varies depending on the region of the piezoelectric layer 110 can be minimized, thereby improving the characteristics of the piezoelectric speaker.

In the above description, a piezoelectric speaker to which a piezoelectric composite film according to an embodiment of the present invention is applied has been described as an example. However, it can be applied to various piezoelectric devices, for example, a piezoelectric actuator for generating mechanical displacement or motion, or a piezoelectric energy harvesting for receiving a displacement to convert it into electric energy.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the appended claims. You will understand.

100: Piezoelectric composite film 110: Piezoelectric layer
111: Matrix 112a: First filler,
112b: second filler 112c: coating film
120a, 120b: electrode 400: frame
500: adhesive layer 600: cap

Claims (10)

delete A plurality of fillers in a matrix of any one of polydimethyl siloxane (PDMS), epoxy, silicone rubber, polyurethane (PU), and polymethylmethacrylate (PMMA) A dispersed piezoelectric layer; And
An electrode formed on either side of the piezoelectric layer and formed of any one of carbon nanotube (CNT), Ag, carbon (C), and Al;
/ RTI >
The plurality of pillars dispersed in the matrix are made of a piezoelectric material,
A coating film formed of a conductive material selected from the group consisting of carbon nanotubes (CNT), Ag, carbon (C), and aluminum (Al) on the surface of the filler and having an electrical network in the matrix, Formed piezoelectric composite film. delete delete The method of claim 2,
Wherein the piezoelectric material is any one of PZT, PMN-PT, PZN-PT, PIN-PT, PYN-PT, VDF, PVDF-TrFE, BNT (BaNiTiO ₃ ) and BZT-BCT. delete delete A piezoelectric device in which a piezoelectric composite film is provided in any one of a piezoelectric speaker, a piezoelectric actuator and a piezoelectric energy harvesting,
In the piezoelectric composite film,
A plurality of fillers in a matrix of any one of polydimethyl siloxane (PDMS), epoxy, silicone rubber, polyurethane (PU), and polymethylmethacrylate (PMMA) A dispersed piezoelectric layer; And
An electrode formed on either side of the piezoelectric layer and formed of any one of carbon nanotube (CNT), Ag, carbon (C), and Al;
/ RTI >
The plurality of pillars dispersed in the matrix are made of a piezoelectric material,
A coating film formed of a conductive material selected from the group consisting of carbon nanotubes (CNT), Ag, carbon (C), and aluminum (Al) on the surface of the filler and having an electrical network in the matrix, Lt; / RTI > The method of claim 8,
Wherein the piezoelectric material is any one of PZT, PMN-PT, PZN-PT, PIN-PT, PYN-PT, VDF, PVDF-TrFE, BNT (BaNiTiO ₃ ) and BZT-BCT. delete

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