JP2014068141A - Piezoelectric loudspeaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric loudspeaker that can output a loud sound by using a piezoelectric laminate made of a polymer and causing a diaphragm to resonate.SOLUTION: There is provided a piezoelectric loudspeaker having a piezoelectric laminate joined to at least one surface of a diaphragm 11, the piezoelectric loudspeaker being characterized in that: (i) the piezoelectric laminate has a conductive layer 2 and an oriented film layer 1 made of polylactic acid laminated alternately and conductive layers adjoining each other with an oriented film layer interposed each have an effective electrode part 6 having one end short-circuited to a negative electrode 10 and the other end short-circuited to a positive electrode 9 and also including a conductive layer between the adjacent oriented film layers and also have immobile parts 7 and 8 where the oriented film layers adjoin each other with no conductive layer interposed; (ii) the piezoelectric laminate and the diaphragm are joined together at both effective electrode part and immobile parts of the piezoelectric laminate; and (iii) oriented film layers sandwiched between respective conductive layers are so laminated as to expand and contract in the same directions when current flows and the diaphragm is caused to resonate through plane-directional expansion and contraction of the piezoelectric laminate.

Description

  The present invention relates to a piezoelectric speaker in which a polymer piezoelectric laminate using an oriented film made of polylactic acid is bonded to a diaphragm.

Patent Document 1 discloses a transparent piezoelectric film speaker that is installed in a curved shape on a display surface of a mobile phone and outputs sound from a wide range to improve listening performance from the speaker. And what is specifically disclosed is that a rectangular PVDF (polyvinylidene fluoride) film is stretched in the opposite direction when electric charge is applied to one surface layer side and the other surface layer side in the thickness direction. A method has been proposed in which a so-called bimorph structure that exhibits behavior is laminated, two short sides thereof are fixed, and a sound is generated by vibration that curves the film.
Further, in Patent Document 2, an effective electrode portion is provided in a direction along a main surface of a polymer piezoelectric sheet, and an electric field vector generated in the thickness direction of the piezoelectric sheet is divided into adjacent effective electrode portions by dividing the effective electrode portion. There has been proposed a piezoelectric speaker that can output a sound by bending the piezoelectric sheet even when the four sides of the rectangular piezoelectric sheet are fixed by applying electric charges so as to be opposite to each other. Further, L-polylactic acid, which is a chiral polymer, has been proposed as a polymer constituting the piezoelectric sheet.

Furthermore, the present inventors have previously proposed in Patent Document 3 and Patent Document 4 that the amount of displacement can be increased by laminating layers made of poly-L-lactic acid or poly-D-lactic acid.
By the way, in order to produce sound by attaching the piezoelectric body to the diaphragm, there is a method in which the diaphragm is warped by expansion and contraction displacement of the piezoelectric body and sound is generated by bending vibration, and the piezoelectric body is expanded and contracted in the plane. There is a method in which in-plane vibration is generated in the bonded diaphragm and a sound is produced by the resonance. Compared with piezoelectric ceramics such as PZT, a piezoelectric body made of a polymer has a low piezoelectric ratio and weak force, so that it is not suitable for resonating a hard diaphragm. As described in Patent Documents 1 and 2 above, A method based on bending vibration of a piezoelectric body has been used.

JP 2003-244792 A International Publication No. 2009/50236 Pamphlet JP 2011-243606 A JP 2011-153023 A

  An object of the present invention is to provide a piezoelectric speaker capable of producing a loud sound by resonating a diaphragm using a piezoelectric laminate made of a polymer.

  As a result of diligent research to solve the above problems, the inventors of the present invention have laminated a plurality of oriented film layers made of polylactic acid, which is a chiral polymer, through a conductive layer as a piezoelectric laminate made of a polymer, Laminate with the conductive layer so that the expansion and contraction of the oriented film layer is in the same direction when hung, and provide the piezoelectric laminate with an effective electrode portion and a non-moving portion, and not only the effective electrode portion but also the non-moving portion. In addition, it has been found that the expansion and contraction of the piezoelectric laminate made of a polymer can be efficiently transmitted to the diaphragm by bonding to the diaphragm, and the present invention has been achieved.

Thus, according to the present invention, the piezoelectric speakers shown in the following (1) and preferred embodiments thereof are also provided as the following (2) to (10) piezoelectric speakers.
(1) A piezoelectric speaker having a piezoelectric laminate bonded to at least one surface of a diaphragm,
(I) In the piezoelectric laminate, conductive layers and oriented film layers made of polylactic acid are alternately laminated, and the adjacent conductive layers via the oriented film layer are short-circuited to the negative electrode and the other to the positive electrode, Having an effective electrode part where a conductive layer exists between adjacent oriented film layers, and a stationary part where an adjacent oriented film layer exists without a conductive layer;
(Ii) The piezoelectric laminate and the diaphragm are bonded to the diaphragm at both the effective electrode portion and the non-moving portion of the piezoelectric laminate, and (iii) the orientation film layer sandwiched between the conductive layers is A piezoelectric speaker that is laminated so that the expansion and contraction directions are the same when an electric current is passed, and resonates the diaphragm by expansion and contraction in the surface direction of the piezoelectric laminate.
(2) The piezoelectric laminate according to the above (1), wherein the piezoelectric laminate has conductive layers on both outermost surfaces.
(3) The piezoelectric speaker according to (1), wherein the piezoelectric laminate is a polygon having two opposite sides, and one of the opposite sides is a negative electrode portion and the other is a positive electrode portion.
(4) The piezoelectric speaker as described in (1) above, wherein a piezoelectric laminate that has the same expansion and contraction direction when an electric current is applied to both surfaces of the diaphragm.
(5) The piezoelectric speaker according to the above (1), wherein the piezoelectric laminated body has an area of the stationary portion of 0.1% or more with respect to the area of the effective electrode portion.
(6) The piezoelectric speaker according to (1), wherein the number of oriented film layers is 3 or more.
(7) The piezoelectric speaker according to (1), wherein one of the adjacent oriented film layers is an oriented film layer L made of poly L-lactic acid and the other is an oriented film layer D made of poly D-lactic acid.
(8) The piezoelectric speaker as described in (1) above, wherein the piezoelectric laminate has a thickness of 3 to 500 μm.
(9) The piezoelectric speaker according to the above (1), wherein the thickness of the oriented film layer is independently 25 μm or less.
(10) The piezoelectric speaker according to (1), wherein the diaphragm is made of a thermoplastic polymer film having a Young's modulus of 3 GPa or more.
(11) The piezoelectric speaker according to (1), wherein the diaphragm is made of a thermoplastic polymer film having a total light transmittance of 85% or more.

  The piezoelectric speaker of the present invention is a piezoelectric laminate in which a plurality of oriented film layers made of polylactic acid are laminated via a conductive layer, and the oriented film layers are stretched in the same direction when charged. And an effective electrode portion and a non-moving portion are provided in the piezoelectric laminate, and not only the effective electrode portion but also the non-moving portion is joined to the diaphragm. As a result, the piezoelectric speaker of the present invention can efficiently transmit the expansion and contraction of the piezoelectric laminate to the diaphragm and can produce a large volume.

It is an example of laminated body A (3) and laminated body B (4) of an oriented film layer (1) and a conductive layer (2). It is an example of lamination | stacking of the oriented film layer (1) and conductive layer (2) which comprise a piezoelectric laminated body, and is the schematic when laminating | stacking the laminated body A (3) and laminated body B (4) of FIG. . 1 is an example of a laminate of an oriented film layer (1) and a conductive layer (2) constituting a piezoelectric laminate, and the piezoelectric laminate when a plurality of laminates A (3) and laminates B (4) in FIG. FIG. It is sectional drawing of a piezoelectric speaker, and is the schematic diagram by which the piezoelectric laminated body was joined with the diaphragm in both the effective electrode part (6) and the non-moving part (7, 8). It is sectional drawing of a piezoelectric speaker, and is a schematic diagram by which the piezoelectric laminated body was joined with the front and back both surfaces of the diaphragm in both the effective electrode part (6) and the non-moving part (7, 8). It is sectional drawing of the piezoelectric speaker which does not show the effect of this invention, and shows the condition where the piezoelectric laminated body shown in FIG. 4 was joined with the diaphragm only in the effective electrode part (6). It is the schematic which shows the example of the other preferable aspect of a piezoelectric laminated body. It is the schematic which shows the example of the other preferable aspect of a piezoelectric laminated body. It is the schematic which shows the example of the other preferable aspect of a piezoelectric laminated body. It is the schematic which shows the example of the other preferable aspect of a piezoelectric laminated body. It is a figure which shows the displacement direction (13) of an effective electrode part (6) when the main orientation axis | shaft (14) of an oriented film layer is parallel to a square side. It is a figure which shows the displacement direction (13) of the effective electrode part (6) when the main orientation axis | shaft (14) of an oriented film layer is an angle of 45 degree | times with respect to the angle | corner which a side of a rectangle makes. It is a schematic diagram which shows a displacement when an electric charge is applied to the piezoelectric speaker of this invention shown in FIG. 4 in the thickness direction. It is a schematic diagram which shows a displacement when an electric charge is applied to the comparative piezoelectric speaker shown in FIG. 6 in the thickness direction. It is the figure which showed the whole piezoelectric speaker in this invention, and is the figure which showed the evaluation method of the characteristic of a piezoelectric speaker in the example which joined the piezoelectric laminated body (5) and the diaphragm (11). It is the schematic which shows the example of the other preferable aspect of the piezoelectric speaker of this invention. It is the schematic which shows sectional drawing of the piezoelectric speaker using PVDF.

Hereinafter, the piezoelectric speaker of the present invention will be described.
The piezoelectric speaker of the present invention is a piezoelectric speaker in which a piezoelectric laminate is bonded to at least one surface of a diaphragm, and has the following features (i) to (iii).
(I) In the piezoelectric laminate, the conductive layer (2) and the oriented film layer (1) made of polylactic acid are alternately laminated, and the conductive layer (2) adjacent via the oriented film layer (1) is One is short-circuited to the negative electrode, the other is short-circuited to the positive electrode, and an effective electrode portion (6) in which a conductive layer always exists between adjacent oriented film layers, and a non-moving portion in which adjacent oriented film layers exist without interposing a conductive layer Having (7 or 8),
(Ii) The piezoelectric laminate (5) and the diaphragm (11) are joined to the diaphragm (11) at both the effective electrode portion (6) and the non-moving portions (7 and 8) of the piezoelectric laminate (5). And (iii) the alignment film layer sandwiched between the conductive layers (2) is laminated so that the expansion and contraction directions are the same when an electric current is applied, and the alignment film layer (1) Resonating the diaphragm (11) by expansion and contraction in the film surface direction.

First, the oriented film layer (1) in this invention is demonstrated.
[Oriented film layer (1)]
<Polylactic acid>
As polylactic acid which comprises an oriented film layer, poly L-lactic acid and poly D-lactic acid are mentioned preferably.
The poly L-lactic acid in the present invention is substantially composed of only L-lactic acid units (hereinafter may be abbreviated as PLLA), and the co-polymerization of L-lactic acid and other monomers. It is preferable that it is a coalescence, and in particular, it is preferable that it is poly L-lactic acid substantially composed of only L-lactic acid units. The poly-D-lactic acid in the present invention is composed of poly-D-lactic acid (hereinafter sometimes abbreviated as PDLA) substantially composed only of D-lactic acid units, D-lactic acid and other monomers. A copolymer is preferred, and in particular, poly-D-lactic acid composed substantially only of D-lactic acid units is preferred.
Here, “main” means that 60% by mass or more of polylactic acid (poly L-lactic acid in layer L and poly D-lactic acid in layer D) is 60% by mass or more with respect to the mass of the resin constituting each layer, preferably 75. It indicates that it is at least mass%, more preferably at least 90 mass%, particularly preferably at least 95 mass%. Further, “substantially” indicates that the amount of L- (D-) lactic acid units in poly L- (D-) lactic acid is 90 mol% or more.

The amount of L- (D-) lactic acid units in poly L- (D-) lactic acid is preferably 90 from the viewpoints of crystallinity, enhancing the effect of improving displacement, and film heat resistance. It is -100 mol%, More preferably, it is 95-100 mol%, More preferably, it is 98-100 mol%. That is, the content of units other than L- (D-) lactic acid units is preferably 0 to 10 mol%, more preferably 0 to 5 mol%, and still more preferably 0 to 2 mol%.
Such polylactic acid preferably has crystallinity, and it becomes easy to obtain the above-described orientation / crystal mode, and the effect of improving the displacement can be increased. The melting point is preferably 150 ° C. or higher and 190 ° C. or lower, and more preferably 160 ° C. or higher and 190 ° C. or lower. With such an embodiment, the film has excellent heat resistance.
The polylactic acid in the present invention preferably has a weight average molecular weight (Mw) in the range of 80,000 to 250,000, and more preferably 100,000 to 250,000 or less. Particularly preferred is a range of 120,000 to 200,000. When the weight average molecular weight Mw is in the above numerical range, the rigidity of the film is excellent and the thickness unevenness of the film becomes good.
The poly L-lactic acid and poly D-lactic acid used in the present invention can contain a copolymer component other than L-lactic acid and D-lactic acid, as desired, within a range not impairing the object of the present invention. At this time, it is preferable to contain in the range which does not impair the crystallinity of polylactic acid largely. Such a copolymerization component is not particularly limited.
The method for producing poly L-lactic acid and poly D-lactic acid is not particularly limited, and a conventionally known method can be suitably used. For example, a method of directly dehydrating and condensing L-lactic acid or D-lactic acid, a method of solid-phase polymerizing L- or D-lactic acid oligomers, once dehydrating and cyclizing L- or D-lactic acid into lactide, and then melt-opening The method of superposing | polymerizing is illustrated. Among them, polylactic acid obtained by a direct dehydration condensation method or a melt ring-opening polymerization method of lactides is preferable from the viewpoint of quality and production efficiency, and among them, a melt ring-opening polymerization method of lactides is particularly preferably selected.

  The oriented polylactic acid film constituting the oriented film layer of the present invention is preferably a uniaxially oriented film. Biaxially oriented films and non-oriented films have low piezoelectric properties, and the effect of containing a thermoplastic resin having a glass transition temperature described below of 60 ° C. or lower is not sufficiently exhibited. In addition, the uniaxially oriented film in the present invention refers to the breaking strength in the direction perpendicular to the main orientation direction in the in-plane direction of the film, when the direction with the highest refractive index in the in-plane direction of the film is the main orientation direction. It means a film having a biased orientation such that the difference is 100 MPa or more. In the present invention, for convenience of explanation, the film-forming direction of the oriented polylactic acid film is sometimes referred to as the longitudinal direction and the MD direction, the thickness direction is the Z-direction, and the direction perpendicular to the film-forming direction and the thickness direction is the width direction. , Sometimes referred to as lateral direction and TD direction.

  By the way, it is preferable that the oriented film layer in this invention contains the impact resistance improving agent in the range of 0.1-10 mass% on the basis of the mass of an oriented film layer. The impact resistance improver in the present invention is not particularly limited as long as it can be used to improve the impact resistance of polylactic acid, and is a rubber-like substance that exhibits rubber elasticity at room temperature. Examples include various impact resistance improvers.

  Specific impact resistance improvers include ethylene-propylene copolymers, ethylene-propylene-nonconjugated diene copolymers, ethylene-butene-1 copolymers, various acrylic rubbers, ethylene-acrylic acid copolymers, and Its alkali metal salt (so-called ionomer), ethylene-glycidyl (meth) acrylate copolymer, ethylene- (meth) acrylic acid alkyl ester copolymer (for example, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer) Polymer, ethylene-butyl acrylate copolymer, ethylene-methyl methacrylate copolymer), ethylene-vinyl acetate copolymer, acid-modified ethylene-propylene copolymer, diene rubber (eg, polybutadiene, polyisoprene, polychloroprene) ), Copolymers of diene and vinyl monomers and The hydrogenated product (for example, styrene-butadiene random copolymer, styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene random copolymer, styrene-isoprene block copolymer, styrene) -Isoprene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer, polybutadiene grafted with styrene, butadiene-acrylonitrile copolymer ), Polyisobutylene, copolymers of isobutylene and butadiene or isoprene, natural rubber, thiocol rubber, polysulfide rubber, acrylic rubber, silicone rubber, polyurethane rubber, polyether rubber, epichrome Hydrin may be like that mentioned polyester elastomer or polyamide elastomer. Further, those having various cross-linking degrees, those having various microstructures such as cis structure and trans structure, and multilayer polymers composed of a core layer and one or more shell layers covering it are also used. be able to. In the present invention, as the impact resistance improver, the various (co) polymers mentioned in the above specific examples may be any of random copolymers, block copolymers or graft copolymers. it can. Furthermore, when producing these (co) polymers, it is also possible to copolymerize monomers such as other olefins, dienes, aromatic vinyl compounds, acrylic acid, acrylic ester or methacrylic ester. is there.

Among these impact modifiers, a polymer containing an acrylic unit and a polymer containing a unit having an acid anhydride group and / or a glycidyl group are preferable. Preferable examples of the acrylic unit here include methyl methacrylate unit, methyl acrylate unit, ethyl acrylate unit or butyl acrylate unit, and preferable examples of the unit having an acid anhydride group or glycidyl group. May include maleic anhydride units or glycidyl methacrylate units.
In the present invention, as the impact resistance improver, a multilayer structure polymer composed of a core layer and one or more shell layers covering the core layer is more preferable from the viewpoint of the effect of the present invention. In the present invention, the multilayer structure polymer is composed of a core layer and one or more shell layers covering the core layer, and a so-called core-shell type structure in which adjacent layers are composed of different polymers. It is a polymer having. In addition, the number of layers constituting the multilayer structure polymer is not particularly limited, and may be two or more, and may be three or more or four or more.

  The multilayer structure polymer used in the present invention is preferably a multilayer structure polymer having at least one rubber layer therein. Here, the type of the rubber layer is not particularly limited as long as it is composed of a polymer component having rubber elasticity. For example, the rubber | gum comprised from what polymerized the (meth) acryl component, the silicone component, the styrene component, the nitrile component, the conjugated diene component, the urethane component, or the ethylene propylene component can be mentioned. Preferred rubbers include, for example, (meth) acrylic components such as ethyl (meth) acrylate units, butyl (meth) acrylate units, (meth) acrylic acid-2-ethylhexyl units or benzyl (meth) acrylate units, dimethyl Polymerize silicone components such as siloxane units and phenylmethylsiloxane units, styrene components such as styrene units and α-methylstyrene units, nitrile components such as acrylonitrile units and methacrylonitrile units, or conjugated diene components such as butanediene units and isoprene units. It is a rubber made of In addition to these components, a crosslinked rubber obtained by copolymerizing and crosslinking a crosslinkable component such as a divinylbenzene unit, an (meth) acrylate allyl unit, or a butylene glycol diacrylate unit is also preferable. Among these, from the viewpoint of the effects of the present invention, the rubber layer is preferably a crosslinked rubber, more preferably a crosslinked rubber having a glass transition temperature of 0 ° C. or less. It is more preferable to select an ethyl acid unit, an acrylic acid-2-ethylhexyl unit, a butyl acrylate unit, a benzyl acrylate unit, and an allyl methacrylate unit as appropriate. It is particularly preferable to use in the range of 0.005 to 3% by mass.

In the multilayer polymer in the present invention, the type of layer other than the rubber layer is not particularly limited as long as it is composed of a polymer component having thermoplasticity, but transparency, heat resistance and impact resistance are not limited. From the viewpoint of properties, it is preferably a polymer component having a glass transition temperature higher than that of the rubber layer. Polymers having thermoplastic properties include unsaturated carboxylic acid alkyl ester units, glycidyl group-containing vinyl units, unsaturated dicarboxylic anhydride units, aliphatic vinyl units, aromatic vinyl units, and vinyl cyanide units. Examples include polymers containing at least one unit selected from units, maleimide units, unsaturated dicarboxylic acid units and other vinyl units, among others, unsaturated carboxylic acid alkyl ester units, A polymer containing at least one unit selected from an unsaturated glycidyl group-containing unit and an unsaturated dicarboxylic acid anhydride unit is preferred, and further selected from an unsaturated glycidyl group-containing unit or an unsaturated dicarboxylic acid anhydride unit. More preferred is a polymer containing at least one unit.
As the multilayer structure polymer used in the present invention, the type of the shell layer is not particularly limited, and is an unsaturated carboxylic acid alkyl ester unit, a glycidyl group-containing vinyl unit, an aliphatic vinyl unit, an aromatic Examples of the polymer include vinyl units, vinyl cyanide units, maleimide units, unsaturated dicarboxylic acid units, unsaturated dicarboxylic anhydride units, and / or other vinyl units. From the viewpoint of the effect, a multilayer structure polymer composed of a polymer containing methyl methacrylate units and / or methyl acrylate units is preferable.

  As the multilayer structure polymer used in the present invention, a commercially available product may be used as a material satisfying the above-mentioned conditions, and it can also be produced by a known method. “Metablene”, Kaneka “Kane Ace”, Rohm and Haas “Paraloid”, Gantz Kasei “Staffyroid” or Kuraray “Paraface” can be used alone or in combination of two or more. Can do. Moreover, as a well-known method, an emulsion polymerization method is more preferable. As a production method, a desired monomer mixture is first emulsion-polymerized to form core particles, and then another monomer mixture is emulsion-polymerized in the presence of the core particles to form a shell layer around the core particles. Make core-shell particles to form. Further, in the presence of the particles, another monomer mixture is emulsion-polymerized to form core-shell particles that form another shell layer. Such a reaction is repeated to obtain a multilayer polymer composed of a desired core layer and one or more shell layers covering it. The polymerization temperature for forming the (co) polymer of each layer is preferably 0 to 120 ° C, more preferably 5 to 90 ° C for each layer.

The multilayer polymer used in the present invention is more preferably a component having a glass transition temperature of 0 ° C. or lower, and a component having a temperature of −30 ° C. or lower in view of the effects of the present invention. More preferably, it is particularly preferable that it contains a constituent component of −40 ° C. or lower. In the present invention, the glass transition temperature is a value measured using a differential scanning calorimeter at a rate of temperature increase of 20 ° C./min.
In the present invention, the average primary particle diameter of the multilayer structure polymer is not particularly limited, but is preferably 10 to 10,000 nm and more preferably 20 to 1000 nm in terms of the effects of the present invention. More preferably, it is 50-700 nm, and it is most preferable that it is 100-500 nm.

  In this invention, it is preferable that the compounding quantity of an impact resistance improving agent is the range of 0.1-10 mass% on the basis of the mass of an oriented film layer at the point of the effect of this invention. If it is less than the lower limit, the layers may be easily peeled off when a treatment such as a pressure bonding described later is performed. On the other hand, when the upper limit is exceeded, the piezoelectric characteristics deteriorate. From such a viewpoint, the lower limit of the blending amount of the preferred impact modifier is 0.5% by mass and further 1% by mass, and the upper limit is 9% by mass and further 8% by mass. In addition, by blending such an impact resistance improver, peeling after pressure bonding can be suppressed without deteriorating piezoelectric characteristics. The reason is not clear, but flexibility can be imparted without lowering the orientation of the obtained oriented polylactic acid film, resulting in uniform pressure transfer during crimping and easy local separation at the interface of the piezoelectric laminate. It is presumed that this is because there is no longer a part or a part that is locally crimped.

Hereinafter, the preferable aspect of the oriented film layer in this invention is demonstrated.
As for the breaking strength of each oriented film layer in this invention, it is preferable that the main orientation direction is 120 Mpa or more. In addition, the main orientation axis in this invention is a direction with the highest refractive index of the in-plane direction measured using the ellipsometer (model M-220; JASCO). When the breaking strength in the main orientation direction is not less than the above lower limit, the effect of improving the resonance characteristics can be enhanced. When the breaking strength is lower than the above lower limit, the effect of improving the resonance characteristics is lowered. On the other hand, the upper limit of the breaking strength in the main orientation direction is not particularly limited, but is preferably 300 MPa or less from the viewpoint of film forming properties. From such a viewpoint, the lower limit of the breaking strength in the main orientation direction is more preferably 120 MPa or more, further preferably 150 MPa or more, particularly preferably 180 MPa or more, and the upper limit is preferably 300 MPa or less, more preferably 250 MPa or less.

Moreover, it is preferable that the breaking strength of the polylactic acid oriented film in this invention is 80 Mpa or less in the direction orthogonal to the main orientation axis direction. When the breaking strength is less than or equal to the above upper limit, the effect of improving the resonance characteristics can be increased. When the breaking strength in the direction orthogonal to the main alignment axis direction is higher than the above upper limit, the effect of improving the resonance characteristics becomes low. On the other hand, the lower limit of the breaking strength in the direction orthogonal to the main orientation axis direction is not particularly limited, but is preferably 30 MPa or more, and more preferably 50 MPa or more from the viewpoint of handling after film formation.
The density of the oriented film layer in the present invention is preferably 1.22 to 1.27 g / cm ³ . When the density is in the above numerical range, the effect of improving the resonance characteristics can be enhanced. When the density is low, the effect of improving the resonance characteristics tends to be low. On the other hand, when the density is high, the effect of improving the resonance characteristics is high, but the mechanical characteristics of the film tend to be inferior. From such a viewpoint, the density is more preferably 1.225 to 1.26 g / cm ³ , and still more preferably 1.23 to 1.25 g / cm ³ .
The thickness of each layer of the oriented film layer in the present invention is not particularly limited as long as it is thick enough to exhibit resonance characteristics in consideration of the tendency that if it is too thick, the rigidity becomes too high to exhibit resonance characteristics. The thinner one is preferable from the viewpoint of resonance characteristics. In particular, when increasing the number of layers, it is preferable to reduce the thickness of each layer so that the thickness of the entire laminated film does not become too large. From such a viewpoint, the thickness of one layer of the oriented polylactic acid film layer is preferably 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. When the thickness is in the above numerical range, the effect of improving the resonance characteristics can be enhanced. On the other hand, from the viewpoint of handleability and rigidity, a thicker is preferable, for example, 2 μm or more is preferable, and 3 μm or more is more preferable.

By the way, the oriented film layer in the present invention may contain additives and functional agents known per se, as long as the effects of the present invention are not impaired, for example, hydrolysis resistance inhibitors, lubricants, antioxidants. An antistatic agent, a colorant, a pigment, a fluorescent whitening agent, a plasticizer, a crosslinking agent, an ultraviolet absorber, other resins, and the like can be added as necessary.
For example, the polylactic acid used in the present invention preferably has a carboxyl group amount of 10 equivalents / 10 ⁶ g or less from the viewpoint of stability during film casting, suppression of hydrolysis, and suppression of decrease in weight average molecular weight. From such a viewpoint, the amount of carboxyl groups is more preferably 5 equivalents / 10 ⁶ g or less, and particularly preferably 2 equivalents / 10 ⁶ g or less. In order to set it as such an aspect, it is preferable to mix | blend a carboxyl group sealing agent. Carboxyl group sealant seals terminal carboxyl groups of polyesters such as polylactic acid, as well as carboxyl groups generated by decomposition reactions of polyester and various additives, and carboxyl groups of low molecular compounds such as lactic acid and formic acid. The resin can be stabilized, and there is an advantage that the resin temperature at the time of film formation can be raised to a temperature sufficient to suppress flow spots.

As such a carboxyl group-capping agent, it is preferable to use at least one compound selected from a carbodiimide compound, an epoxy compound, an oxazoline compound, an oxazine compound, and an isocyanate compound, and among them, a carbodiimide compound is preferable.
As for the usage-amount of a carboxyl group sealing agent, in resin which comprises each layer, 0.01-10 mass parts is preferable per 100 mass parts of polylactic acid, and 0.03-5 mass parts is further more preferable. In the present invention, a sealing reaction catalyst may be further used.

  Moreover, the oriented film layer in this invention can contain a lubricant in a film for the purpose of improving the winding property in the state of a film, and runnability. Examples of such lubricants include silica produced by a dry method, silica produced by a wet method, zeolite, calcium carbonate, calcium phosphate, kaolin, kaolinite, clay, talc, titanium oxide, alumina, zirconia, aluminum hydroxide, Preferable examples include inorganic particles such as calcium oxide, graphite, carbon black, zinc oxide, silicon carbide, and tin oxide, and organic fine particles such as crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, and crosslinked silicone resin particles. . As the lubricant, fine particles having an average particle diameter of 0.001 to 5.0 μm are preferable, and one kind can be used, or two or more kinds can be used in combination. Moreover, a lubricant can be mix | blended in 0.01-1.0 mass% with respect to the mass of each orientation polylactic acid film, More preferably, it is 0.1-0.5 mass%.

Below, the manufacturing method of the oriented film layer in this invention is demonstrated.
<Method for producing polylactic acid>
The method for producing poly L-lactic acid and poly D-lactic acid in the present invention is not particularly limited, and a conventionally known method can be suitably used. For example, a method of directly dehydrating and condensing L-lactic acid or D-lactic acid, a method of solid-phase polymerizing L- or D-lactic acid oligomers, once dehydrating and cyclizing L- or D-lactic acid into lactide, and then melt-opening The method of superposing | polymerizing etc. is illustrated. Among them, polylactic acid obtained by a direct dehydration condensation method or a melt ring-opening polymerization method of lactides is preferable from the viewpoint of quality and production efficiency, and among them, a melt ring-opening polymerization method of lactides is particularly preferably selected.
The catalyst used in these production methods is not particularly limited as long as polylactic acid can be polymerized so as to have the predetermined characteristics described above, and a known catalyst can be used as appropriate.
The obtained poly L-lactic acid and poly D-lactic acid may be removed by a conventionally known method or the catalytic activity of the polymerization catalyst is deactivated or deactivated using a deactivator. It is preferable for the melt stability and wet heat stability of the film.
When using a deactivator, the amount used is 0.3 to 20 equivalents, more preferably 0.5 to 15 equivalents, and even more preferably 0.5 to 10 equivalents per equivalent of metal element of the specific metal-containing catalyst. Particularly preferably, it may be 0.6 to 7 equivalents. If the amount of the deactivator used is too small, the activity of the catalyst metal cannot be lowered sufficiently, and if used excessively, the deactivator may cause decomposition of the resin, which is not preferable.

<Extrusion process>
If desired, the polylactic acid obtained by the above method is blended with the above-mentioned impact resistance improver, carboxyl group-capping agent, lubricant, other additives, etc., and the polylactic acid is melted in an extruder, Extrude onto cooling drum. In addition, in order to suppress the decomposition | disassembly at the time of a fusion | melting, the polylactic acid supplied to an extruder is preferable to perform a drying process before an extruder supply, and to make a water content into about 100 ppm or less.
The resin temperature in the extruder is a temperature at which polylactic acid is sufficiently fluid, that is, when the melting point of polylactic acid is Tm, it is carried out in the range of (Tm + 20) to (Tm + 50) (° C.). It is preferable to melt and extrude at a temperature that does not decompose, and the temperature is preferably 200 to 260 ° C, more preferably 205 to 240 ° C, and particularly preferably 210 to 235 ° C. Within the above temperature range, flow spots are unlikely to occur.

<Casting process>
After extruding from the die, the film is cast on a cooling drum to obtain an unstretched film. At that time, it is preferable that the electrostatic charge is applied from the electrode by an electrostatic contact method so that it is sufficiently brought into close contact with the cooling drum and cooled and solidified. At this time, the electrode to which an electrostatic charge is applied preferably has a wire shape or a knife shape. The surface material of the electrode is preferably platinum, and can prevent impurities sublimated from the film from adhering to the electrode surface. Further, it is possible to prevent adhesion of impurities by blowing a high-temperature air flow on or near the electrode, keeping the temperature of the electrode at 170 to 350 ° C., and installing an exhaust nozzle above the electrode.

<Extension process>
The unstretched film obtained above is stretched in a uniaxial direction. The stretching direction is not particularly limited, but it is preferable to stretch in a film forming direction, a width direction, or an oblique direction that is 45 degrees with respect to the film forming direction and the width direction. In order to perform such stretching, the unstretched film is stretched by heating to a temperature at which it can be stretched, for example, a glass transition temperature (Tg) or higher (Tg + 80) ° C. of polylactic acid.
The draw ratio in the main orientation direction is preferably 3 times or more, more preferably 3.5 times or more, still more preferably 4.0 times or more, and particularly preferably 4.5 times or more. The effect of improving the amount of displacement can be increased by setting the draw ratio to the above upper limit or more. On the other hand, the upper limit of the draw ratio is not particularly limited, but is preferably 10 times or less from the viewpoint of film forming property, and further preferably 8 times or less, particularly preferably 7 times or less. On the other hand, the direction orthogonal to the main orientation direction does not need to be stretched, but may be stretched within a range satisfying the above-described relationship of breaking strength. In that case, the draw ratio is preferably 1.5 times or less, more preferably 1.3 times or less.

<Heat treatment process>
The stretched film obtained above is preferably heat treated. The heat treatment temperature may be higher than the above-described stretching temperature and lower than the melting point (Tm) of the resin, and preferably has a glass transition temperature (Tg + 15) ° C. or higher and (Tm−10) ° C. or lower, resulting in more piezoelectric characteristics. Can be high. When the heat treatment temperature is low, the displacement improvement effect tends to be low. On the other hand, when the heat treatment temperature is high, the flatness and mechanical properties of the film tend to be inferior, and the displacement improvement effect tends to be low. . From such a viewpoint, the heat treatment temperature is more preferably (Tg + 20) ° C. or higher (Tm−20) ° C., and particularly preferably (Tg + 30) ° C. or higher (Tm−35) ° C. The heat treatment time is preferably 1 to 120 seconds, more preferably 2 to 60 seconds, and the effect of improving the displacement can be increased.
Furthermore, in the present invention, it is possible to adjust the thermal dimensional stability by performing a relaxation treatment in the heat treatment step.

<Easy adhesion treatment>
The oriented polylactic acid film layer thus obtained can be subjected to surface activation treatment such as plasma treatment, amine treatment or corona treatment by a conventionally known method if desired.
Among these, from the viewpoint of improving the adhesion with the conductive layer described later and enhancing the durability of the piezoelectric laminate, it is also preferable to perform corona treatment on at least one side, preferably both sides, of the oriented film layer. As conditions for such corona treatment, for example, when the electrode distance is 5 mm, the voltage is preferably 1 to 20 kV, more preferably 5 to 15 kV, preferably 1 to 60 seconds, more preferably 5 to 30 seconds, particularly Preferably it is 10 to 25 seconds. Further, such treatment can be performed in the atmosphere.

[Conductive layer]
The type of the conductive layer in the present invention is not particularly limited as long as it has a degree of conductivity that can exhibit piezoelectric characteristics when a voltage is applied, but it can more suitably exhibit piezoelectric characteristics and resonance characteristics. From the viewpoint of being capable of being formed, a layer made of a metal or a metal oxide and a layer made of a conductive polymer are preferable.
Such metal or metal oxide is not particularly limited, but is selected from the group consisting of indium, tin, zinc, gallium, antimony, titanium, silicon, zirconium, magnesium, aluminum, gold, silver, copper, palladium, tungsten. Preferably, at least one metal selected from the group described above or an oxide of at least one metal selected from the above group is preferably used. Further, the metal oxide may further contain an oxide of a metal shown in the above group or another metal shown in the above group, if necessary. For example, aluminum, gold, indium oxide containing tin oxide, tin oxide containing antimony, or the like is preferably used. Examples of the conductive polymer include polythiophene-based, polyaniline-based, and polypyrrole-based polymers, and selection may be made in consideration of conductivity and transparency as necessary. For example, when used for a display panel or the like, a polythiophene-based or polyaniline-based polymer excellent in transparency is preferably used.
The thickness of each layer of the conductive layer is not particularly limited, but the surface resistance value is 1 × 10 ⁴ Ω / □ or less, preferably 5 × 10 ³ Ω / □ or less, more preferably 1 × 10 ³ Ω / □ or less. For example, a thickness of 10 nm or more is preferable. Furthermore, it is preferable that it is 15-35 nm from a viewpoint of electroconductivity and the ease of layer formation, More preferably, it is 20-30 nm. If the thickness is too thin, the surface resistance value tends to be high, and it becomes difficult to form a continuous film. On the other hand, if it is too thick, the quality is excessive, and it is difficult to form a laminated film, or the strength between layers of the laminated film tends to be weak.
By the way, as shown in FIG. 1, the conductive layer is not formed on the entire surface of the oriented film layer, but a margin is provided. It is preferable to provide this margin at a portion close to the end face from the viewpoint of causing the diaphragm to resonate more efficiently. It is preferable that the electrode and the conductive layer are not short-circuited on the side having a margin, and the electrode and the conductive layer are short-circuited on the side having no margin. By adopting such a configuration, each conductive layer sandwiching the orientation film layer can be short-circuited with the electrode so that the sign is easily different from each other, and the margin portion becomes a non-moving portion as described later. The diaphragm can be resonated more efficiently by joining the stationary part to the diaphragm.

[Piezoelectric laminate]
An example of the piezoelectric laminate in the present invention will be described with reference to FIGS. FIG. 1 is an example of a laminate A (3) and a laminate B (4) of an oriented film layer (1) and a conductive layer (2) in the present invention.
FIG. 2 is an example of the lamination of the oriented film layer (1) and the conductive layer (2) constituting the piezoelectric laminate in the present invention. A plurality of laminates A (3) and laminates B (4) in FIG. 1 are laminated. FIG.
FIG. 3 is an example of the lamination of the oriented film layer (1) and the conductive layer (2) constituting the piezoelectric laminate in the present invention. A plurality of laminates A (3) and laminates B (4) in FIG. 1 are laminated. It is the schematic of the piezoelectric laminated body at the time.
4 and 5 are cross-sectional views of the piezoelectric speaker of the present invention, and are schematic views in which the piezoelectric laminate is joined to the diaphragm at both the effective electrode portion (6) and the non-moving portion (7, 8). 4 is a diagram in which the piezoelectric laminate is bonded to one side of the diaphragm, and FIG. 5 is a diagram in which the piezoelectric laminate is bonded to both the front and back surfaces of the diaphragm (11). 4 and 5, the thickness of each element constituting the piezoelectric speaker is exaggerated.
In these drawings, reference numeral 1 denotes an oriented film layer, reference numeral 2 denotes a conductive layer, reference numeral 3 denotes a laminate A having a left margin, reference numeral 4 denotes a laminate B having a right margin, and reference numeral 5 denotes a piezoelectric laminate. Body, reference numeral 6 is an effective electrode part, reference numerals 7 and 8 are immobile parts, reference numeral 9 is an electrode short-circuited to the positive electrode, reference numeral 10 is an electrode short-circuited to the negative electrode, reference numeral 11 is a diaphragm, reference numeral 12 is an adhesive layer, etc. The junction part of a piezoelectric laminated body and a diaphragm is shown.

First, two types of piezoelectric laminates according to the present invention are produced, for example, a laminate A (3) having a margin on the left side and a laminate B (4) having a margin on the right side as shown in FIG. As shown in FIG. 2, it can manufacture by laminating | stacking so that the above-mentioned conductive layer and orientation film layer may alternately exist, and a conductive layer may alternately exist in one end, but does not exist in the other end.
The conductive layers and the oriented film layers are alternately laminated so that one can be short-circuited with the negative electrode and the other with the positive electrode. By setting it as such lamination | stacking, the reverse electric charge can be added to the thickness direction of an adjacent orientation film layer.
4 and 5, the effective electrode portion 6 in which both the conductive layer short-circuited to the positive electrode and the conductive layer short-circuited to the negative electrode are present, and the stationary portion 7 having no at least one conductive layer or 8. At this time, the negative electrode conductive layer is present at the end of the piezoelectric laminate, the non-moving portion 7 where the positive electrode conductive layer is not present, and the non-moving portion 8 where the positive electrode conductive layer is present and the negative electrode conductive layer is not present. 4 and 5, an electrode 9 that is short-circuited to the negative electrode is provided at the end where the stationary part is present, and an electrode 10 that is short-circuited to the positive electrode is provided at the end where the stationary part is present. Thus, each conductive layer can be easily short-circuited to the positive electrode and the negative electrode.

By the way, the oriented film layers sandwiched between the conductive layers need to be laminated so that the expansion and contraction directions are the same when an electric current is passed. If an oriented film layer with a different expansion / contraction direction exists in a part of the piezoelectric laminate, the piezoelectric characteristics cancel each other, and the effect of resonating the diaphragm is impaired. The method for aligning the stretching direction of the oriented film layer in the piezoelectric laminate is not particularly limited, but the oriented film layer L made of L-polylactic acid and the oriented film layer D made of D-polylactic acid are alternately laminated. It is preferable that the configuration is the same because it is only necessary to alternately laminate the oriented polylactic acid films formed and stretched in the same manner. This is because when the film layer L and the film layer D add opposite charges in the thickness direction, they exhibit stretch characteristics in the same direction. On the other hand, when the adjacent oriented film layers are both the oriented film layer L or the oriented film layer D, one film layer is fixed, and the other film layer is turned over or in the plane direction of the film before being overlapped. It is necessary to perform operations such as rotating so that the directions of expansion and contraction are aligned when reverse charges are applied. In addition, when polylactic acid is formed into a film and it is going to laminate | stack with the roll to roll excellent in productivity, it understands that the former structure which laminated | stacked the orientation film layer L and the orientation film layer D alternately is preferable. Let's go.
And when using the oriented film layer L and the oriented film layer D, the oriented film layer which comprises the laminated body A shown by the code | symbol 3 of FIG. What is necessary is just to laminate | stack a film layer so that it may become the oriented film layer D.

By the way, as shown in FIGS. 3 and 4, there is a conductive layer on at least one surface of the piezoelectric laminate, and from the point of the effect of the present invention, that is, from the point of making the diaphragm more efficiently resonate, It is preferable that the oriented polylactic acid film layer similarly exhibits the piezoelectric characteristics, and it is preferable that the conductive layers are disposed on both surfaces of the piezoelectric laminate. When one or both surfaces are oriented polylactic acid film layers, the oriented polylactic acid film layer on the surface has a conductive layer only on one side, so there is no charge in the thickness direction, so piezoelectric properties are not manifested and charges are applied. The deformation of the piezoelectric laminate at that time becomes a curved deformation like a bimorph, and vibrations cannot be efficiently propagated to the diaphragm.
Moreover, it is preferable that the oriented film layer and the conductive layer are fixed without an adhesive layer having a thickness exceeding 1000 nm because excellent resonance characteristics are easily exhibited. From such a viewpoint, in the present invention, it is preferable that the oriented film layer and the conductive layer are fixed without using an adhesive layer having a thickness of more than 500 nm, and are fixed without using an adhesive layer having a thickness of more than 200 nm. The embodiment is more preferable. From the viewpoint of resonance characteristics, the most preferable embodiment is an embodiment in which the oriented film layer and the conductive layer are fixed without using an adhesive layer.
In the present invention, as long as it has the laminated structure as described above, it may further have other layers within a range not impairing the object of the present invention. For example, an aromatic polyester layer such as polyethylene terephthalate or polyethylene naphthalate for increasing the rigidity of the laminate can be provided on the surface of the piezoelectric laminate. On the other hand, from the viewpoint of resonance characteristics, such a layer is preferably thin and particularly preferably not.

<Number of layers>
In the piezoelectric laminate of the present invention, the total number of oriented film layers is preferably 3 or more. By adopting such an aspect, excellent resonance characteristics can be obtained. From the viewpoint of resonance characteristics, the total number of layers is preferably as large as possible, preferably 5 or more, and more preferably 6 or more.
On the other hand, the upper limit is not particularly limited. In addition, what is necessary is just to manufacture like a winding capacitor | condenser, for example in order to set it as the total total of such tens of thousands order.

<Resonance characteristics>
The piezoelectric laminate in the present invention has a piezoelectric characteristic and vibrates when a voltage of a certain frequency is applied, but in particular, an oriented polylactic acid film having a piezoelectric characteristic aligned in one direction as compared with PVDF is selected. And by laminating them, the piezoelectric characteristics are extremely excellent, and a large momentum (force) can be generated. Therefore, such a phenomenon is small in the momentum (force) that can be generated when a voltage is applied in a conventional polymer film such as PVDF or a laminated film such as a single layer or two layers of an alignment film made of polylactic acid. Therefore, this phenomenon is not seen.

<Main orientation direction>
In the present invention, it is preferable that the piezoelectric laminate is aligned in the range of 10 degrees or less when viewed from the thickness direction of the piezoelectric laminate when the direction of expansion and contraction when the charge of each oriented film layer is added. By setting it as such an aspect, the improvement effect of a resonance characteristic can be made high. From such a viewpoint, the angle formed is more preferably 5 degrees or less, further preferably 3 degrees or less, particularly preferably 1 degree or less, and ideally 0 degrees. In order to obtain the main orientation direction as described above, sampling may be performed in the same direction during sampling, or stacked so as to be in the same direction during stacking.

<Method for producing piezoelectric laminate>
The piezoelectric laminate according to the present invention, for example, when the oriented film alternately laminates the oriented film layer L and the oriented film layer D, is formed separately, and a conductive layer is provided on the surface of each obtained layer. And layers D are alternately laminated, and are laminated so as to have a conductive layer between layers L and D and at least one surface of the obtained piezoelectric laminate, preferably both surfaces of the piezoelectric laminate. It can be obtained by fixing.
Moreover, when the piezoelectric laminated body in this invention is only the oriented film layer L or the oriented film layer D, for example, two oriented film layers L (D) are prepared, and one side has a conductive layer on the surface side. Provided, and the other is provided with a conductive layer by changing the back side and the direction, formed separately, and the layers L and D are alternately arranged, between the layers L and D, and at least one of the obtained piezoelectric laminates It can obtain by laminating | stacking and adhering so that it may become the structure which has a conductive layer on the surface of this, Preferably both surfaces of a piezoelectric laminated body.
The method for forming the conductive layer on the surfaces of the oriented film L and the oriented film D obtained as described above is not particularly limited as long as it is a conventionally known method for forming a conductive layer, but the conductive layer having excellent conductivity is uniformly formed. In addition, it is preferable to employ a vapor deposition method or a sputtering method from the viewpoint that it can be easily obtained.
Moreover, although you may form on both surfaces of a conductive layer and an oriented film, it is preferable from a viewpoint of adhesiveness to form a conductive layer only on one side and to crimp them.

<Thermal lamination process>
The oriented film having the conductive layer obtained as described above is laminated so as to have a laminated structure defined by the present invention to prepare a laminated body, and is fixed by thermal lamination. Here, the heat lamination is preferably performed without using an adhesive layer. Further, the pressure-bonding property can be further improved by including the above-described impact resistance improver.
The temperature condition in such a heat laminate is preferably (Tg-5) to (Tsm + 20) ° C. Here, Tg indicates the highest glass transition temperature among the glass transition temperature of the resin L constituting the oriented film layer L used for forming the laminate and the glass transition temperature of the resin D constituting the oriented film layer D. Tsm indicates the lowest sub-peak temperature among the sub-peak temperature of the oriented film L and the sub-peak temperature of the oriented film layer D used for forming the laminate. In addition, subpeak temperature is temperature resulting from the heat setting temperature in a film manufacturing process. By adopting the above temperature condition, a piezoelectric laminate having excellent resonance characteristics can be obtained. At the same time, the adhesion of each layer of the laminate is excellent. If the temperature is too low, the adhesion tends to be inferior. On the other hand, if the temperature is too high, the orientation is lost and the resonance characteristics tend to be inferior. From such a viewpoint, more preferable temperature conditions are Tg to Tsm + 15, and particularly preferably Tg + 10 to Tsm + 10.
Further, the pressure condition is not particularly limited as long as it can be sufficiently pressure-bonded and the orientation of the oriented polylactic acid film does not collapse. For example, it is preferably 1 to 100 MPa. As a result, it is possible to obtain a laminate having excellent adhesion while having excellent resonance characteristics. If the pressure is too low, the adhesion tends to be inferior, whereas if the pressure is too high, the resonance characteristics tend to be inferior. From such a viewpoint, the more preferable pressure condition is 2 to 80 MPa, and particularly preferably 2 to 50 MPa.
It is preferable to perform thermal lamination for 10 to 600 seconds under the above temperature and pressure conditions. As a result, it is possible to obtain a laminate having excellent adhesion while having excellent resonance characteristics. If the time is too short, the adhesion tends to be inferior, while if too long, the resonance characteristics tend to be inferior. From such a viewpoint, a more preferable time condition is 30 to 300 seconds, and particularly preferably 60 to 180 seconds.

By the way, in order to efficiently manufacture the piezoelectric laminate by roll-to-roll, each of the oriented polylactic acid film L and the oriented polylactic acid film D is formed and wound up, and one width direction of each oriented polylactic acid film is obtained. The conductive layer is formed on the part along the film forming direction. And the oriented film layer L which has a conductive layer, and the oriented film layer D which has a conductive layer are overlapped along the film forming direction. At this time, when viewed in the width direction of the oriented film layer, the conductive layer existing in the thickness direction is both the conductive layer provided in the oriented film layer L and the conductive layer provided in the oriented film layer D, as described above. An effective electrode part, a stationary part 7 having only a conductive layer provided with an oriented film layer L in the thickness direction, and a stationary part 8 having only a conductive layer provided with a conductive layer provided in the oriented film layer D in the thickness direction; And stacking with slits so that one end in the width direction of the piezoelectric laminate is a fixed portion 7 and the other end is a fixed portion 8 and cut to a desired size. preferable.
From such a viewpoint, the piezoelectric laminate is a polygon having two opposite sides, and one of the opposite sides is a stationary part 7 and the other is a stationary part 8, and each is short-circuited to the positive electrode and the negative electrode. preferable.
Also, since the piezoelectric laminate displacement of the piezoelectric laminate is 0.1%, in the piezoelectric laminate in the present invention, the area of the non-moving portion is 0.1% or more, more preferably 0.5% or more of the area of the effective electrode portion. It is preferable that it is 1% or more. If the stationary part is too narrow, the positive electrode and the negative electrode are easily short-circuited. On the other hand, the upper limit is not particularly limited, but is preferably 70% or less from the viewpoint of handling.
Further, as described above, the shape of the piezoelectric laminated body in the present invention is not particularly limited by a polygon, but when manufactured by the roll-to-roll method as described above, a portion that does not become a product can be reduced as much as possible so that it is a parallel square. It is preferable that there is a rectangle or square. Further, when the piezoelectric laminate is a parallelogram, it is preferable that one side of the pair of sides facing each other is the stationary part 7 and the other side is the stationary part 8 as described above.
From such a viewpoint, a part of a preferable shape of the piezoelectric laminate of the present invention is illustrated in FIGS. 7-10.

  By the way, when the effective electrode of the piezoelectric laminate is a quadrangle such as a rectangle or a square, and the main alignment axis of the oriented film layer is parallel to the side of the quadrangle, the shape of the effective electrode part is as shown in FIG. A shape close to a square is preferable because it is easier to resonate the diaphragm. From such a viewpoint, the ratio of long side to short side (long side / short side) in the quadrangle is preferably less than 1.3, more preferably less than 1.2, and particularly preferably less than 1.1. The reason for this is that when an electric charge is applied in the thickness direction of the piezoelectric laminate, the effective electrode portion expands and contracts at an angle of 45 degrees with respect to the main alignment axis, so the square is shaped like a rhombus. It is thought that it is deformed and resonance can be transmitted more evenly than the rectangle.

  On the other hand, when the effective electrode of the piezoelectric laminate is a quadrangle such as a rectangle or a square, and the main orientation axis of the oriented film layer is an angle of 45 degrees with respect to the angle formed by the sides of the quadrangle, As shown in FIG. 12, it is preferable that the shape of the effective electrode portion is a rectangle whose long side is very long compared to the short side because the diaphragm is more easily resonated. From such a viewpoint, the ratio of the long side to the short side (long side / short side) in the quadrangle is preferably 1.3 or more, more preferably 1.5 or more, and particularly preferably 1.7 or more. The reason for this is that when an electric charge is applied in the thickness direction of the piezoelectric laminate, the effective electrode portion develops expansion and contraction at an angle of 45 degrees with respect to the main alignment axis, so the direction along the long side of the rectangle This is considered to be because it is easy to convey vibrations due to the larger expansion and contraction to the diaphragm than the square. On the other hand, since the expansion / contraction displacement tends to increase as the ratio of the long side to the short side increases, the upper limit is not particularly limited, but if the long side is too long compared to the short side, handling such as assembly is difficult. become. From such a viewpoint, the upper limit of the ratio of the substantial long side to the short side is about 100,000.

[Diaphragm]
The diaphragm (11) in the present invention has a Young's modulus that is slightly larger than that of the piezoelectric laminate, which makes it easier to resonate the diaphragm. From such a point of view, the Young's modulus of the diaphragm is preferably 3 GPa or more, and those having good adhesiveness are preferable from the viewpoint of joining the piezoelectric laminate. Moreover, since it can arrange | position on displays, such as a touch panel and a mobile telephone, by having transparency, a total light transmittance is preferable to be 85% or more. From the above viewpoint, the material of the diaphragm is not particularly limited as long as the material has the above characteristics, and may be either an organic material or an inorganic material, or a combination thereof. Among them, an organic polymer material is preferable because of ease of handling as a diaphragm, PLA (polylactic acid), PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PS (polystyrene), PC (polycarbonate), COC (cycloolefin copolymer) and PMMA (polymethacrylic acid) are preferable, and PLA, PET, and PEN are more preferable.
Further, the shape of the diaphragm may be appropriately selected depending on the frequency to be resonated. For example, if there is only one wavelength to be resonated, it may be circular, and if it is desired to resonate in a plurality of frequency ranges, it may be a polygon corresponding to it.
The thickness is preferably about the same as that of the piezoelectric laminate. Depending on the material used, in the case of a plastic film such as polyester, the range of 3 to 500 μm is preferable, and the range of 25 to 300 μm is more preferable.

[Joint part]
The joint in the present invention is not particularly limited, and is not particularly limited as long as both can be fixed so that the vibration of the piezoelectric laminate (5) can be transmitted to the diaphragm (12). For example, an adhesive is used. Alternatively, the piezoelectric laminate and the diaphragm may be pressure bonded.
When using an adhesive, it is not particularly limited as long as it is an adhesive that does not peel in the environment in which it is used, and can efficiently transmit the vibration of the piezoelectric laminate to the diaphragm and does not impair this purpose. From the viewpoint of versatility and ease of handling, an epoxy resin adhesive and a vinyl acetate resin adhesive are preferable. In particular, a vinyl acetate resin adhesive has removability and is preferable in terms of ease of work.

[electrode]
As described above, the piezoelectric laminate in the present invention is short-circuited to the electrode so that an electric field in the opposite direction is applied to the adjacent resin layer via each conductive layer. There are no particular restrictions on the electrodes, and those known per se can be employed. For example, aluminum, gold, silver, and copper can be exemplified, and among these, silver paste is preferred because of its price and ease of handling. Further, a commonly used metallicon may be used, and further, a means for causing each laminate to be short-circuited with a metal may be used more simply.

[Piezoelectric speaker]
The piezoelectric speaker of the present invention is a piezoelectric speaker in which the above-described piezoelectric laminate (5) is bonded to at least one surface of the diaphragm (11).
At this time, the piezoelectric laminate (5) and the diaphragm (11) are joined to the diaphragm (11) at both the effective electrode portion (6) and the non-moving portion (7 and 8) of the piezoelectric laminate (5). It is necessary to be. This is because, when viewed in the thickness direction of the piezoelectric laminate, since it is bonded to the diaphragm, expansion and contraction of the oriented film layer 1 on the side close to the diaphragm is limited, and the oriented film on the side far from the diaphragm The stretch of the layer remains relatively unconstrained. As a result, the expansion and contraction of the piezoelectric laminate is deformed in a direction in which the expansion and contraction of the oriented film layer closer to the vibration plate is closer to the vibration plate than the direction along the film surface direction of the film layer. As a result, the expansion / contraction direction varies in the thickness direction of the piezoelectric laminate, and as a result, the vibration transmitted to the diaphragm is weakened. The feature of the present invention is to suppress the variation in the direction of expansion and contraction in the thickness direction of such a piezoelectric laminate as shown in FIG. 13 by joining the above-mentioned stationary parts 7 and 8 to the diaphragm. They found that the expansion and contraction of each oriented film layer can be efficiently propagated to the diaphragm.
FIG. 14 is a schematic view when the immovable portions 7 and 8 are not joined, but it is not possible to prevent the direction of expansion and contraction in the thickness direction of the piezoelectric laminate from being suppressed. It cannot propagate efficiently to the diaphragm.

Moreover, in order to make it easier to convey the expansion and contraction of the alignment film layer in the effective electrode portion to the diaphragm by joining the non-moving portions 7 and 8, the non-moving portions 7 and 8 sandwich the effective electrode portion. It is preferable. From such a viewpoint, as described above, when the piezoelectric laminated body is polygonal, as described above, it is preferable that one side is the stationary part 7 and the other side is the stationary part 8 in the pair of opposing sides. Similarly, in the case of a quadrangle such as a square or a rectangle, it is preferable that one side of the pair of sides facing each other is the stationary part 7 and the other side is the stationary part 8.
Further, when the main alignment axis of the oriented film layer is parallel to the quadrangular sides, it is preferable that all of the two opposing sides are immobile portions as the effective electrode portion is closer to a square.
FIG. 15 shows an example of a piezoelectric speaker in which the piezoelectric laminate (5) and the diaphragm (11) according to the present invention are joined.
Moreover, there is no restriction | limiting in the position of the piezoelectric laminated body to join, What is necessary is just to select suitably according to the frequency to make it resonate. On the other hand, it is effective for use in a display speaker or the like by not bonding the piezoelectric laminate to the center of the diaphragm. From such a viewpoint, a part of another preferred embodiment of the piezoelectric speaker of the present invention is illustrated in FIG.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention does not receive limitation at all by this. The physical properties of each layer and the evaluation of the piezoelectric speaker were performed by the following methods.
(1) Physical properties of each layer Notches were formed by squeezing the end of the laminate, and each layer was peeled off to evaluate the physical properties of each layer.
(1-1) Main orientation direction Using an ellipsometer (model M-220; JASCO), the obtained film was subjected to transmitted light measurement in which the incident angle of 550 nm monochromatic light was changed, and a sample stage on which the film was fixed was used. Rotating in the plane perpendicular to the optical axis around the optical axis, the direction with the highest refractive index in the in-plane direction was determined, and that direction was defined as the main alignment axis.
(1-2) Young's modulus Young's modulus was calculated | required using the Tensilon UCT-100 type | mold made from Orientec Co., Ltd. using the test piece which cut out the film into 150 mm length x 10 mm width. The measurement was performed in a room adjusted to a temperature of 23 ° C. and a humidity of 65% RH, with a sample mounted at a distance of 100 mm between chucks, and at a tensile speed of 10 mm / min according to JIS-C2151. The Young's modulus was calculated from the slope of the rising portion tangent of the obtained load-elongation curve.
(1-3) Total light transmittance The total light transmittance (unit:%) of the film was measured using the haze measuring device (NDH-2000) by Nippon Denshoku Industries Co., Ltd. according to JISK7361.
(1-4) Surface resistivity It measured based on JISK7194 using Mitsubishi Chemical Corporation make and brand name: Lorester MCP-T600. The measurement was performed by taking three measurement sample pieces from one film and carrying out the measurement at five arbitrary locations, and taking the average value as the surface resistivity (unit: Ω / □).
(1-5) Breaking strength The breaking strength was calculated | required using the tensilon UCT-100 type | mold by Orientec Co., Ltd. using the test piece which cut out the film to 150 mm length x 10 mm width. The measurement was performed in a room adjusted to a temperature of 23 ° C. and a humidity of 65% RH at a distance between chucks of 100 mm and a speed between chucks of 100 mm / min. The term “breaking strength” as used herein means the value of stress per unit area obtained by dividing the value of the load at the time of breaking the sample when the tensile test is performed by the cross-sectional area of the sample before the test.

(2) Evaluation of Piezoelectric Speaker As shown in FIG. 15, the positive and negative electrodes of the piezoelectric speaker are connected to an AC / DC high-voltage amplifier (trade name: power supply PZP350, manufactured by TREK Inc.), and a voltage of 200V An alternating current with a current of 200 mA was passed, and the maximum volume in a frequency range of 30 Hz to 20 kHz was measured. In addition, the measurement was performed in a place 30 cm away from the piezoelectric speaker using a sound level meter (manufactured by Ono Sokki Co., Ltd., trade name: high-performance type sound level meter LA-2560). The higher the volume, the more efficient the piezoelectric speaker.

[Reference Example 1] Synthesis of poly-L-lactic acid (PLLA) Vertical stirring tank (40L) equipped with full zone blades equipped with vacuum piping, nitrogen gas piping, catalyst addition piping, L-lactide solution addition piping, alcohol initiator addition piping Was replaced with nitrogen. Thereafter, 30 kg of L-lactide, 0.90 kg of stearyl alcohol (0.030 mol / kg), and 6.14 g of tin octylate (5.05 × 10 ⁻⁴ mol / 1 kg) were charged in an atmosphere with a nitrogen pressure of 106.4 kPa. The temperature was raised to 150 ° C. When the contents were dissolved, stirring was started and the internal temperature was further raised to 190 ° C. Since the reaction started when the internal temperature exceeded 180 ° C., the internal temperature was maintained from 185 ° C. to 190 ° C. while cooling and the reaction was continued for 1 hour. The reaction was further carried out at a nitrogen pressure of 106.4 kPa and an internal temperature of 200 ° C. to 210 ° C. for 1 hour while stirring, and then stirring was stopped and a phosphorus-based catalyst deactivator was added.
After removing the bubbles by standing still for 20 minutes, the internal pressure was increased from 2 to 3 atm with nitrogen pressure, the prepolymer was pushed out to a chip cutter, and a prepolymer having a weight average molecular weight of 130,000 and a molecular weight dispersion of 1.8 was obtained. Pelletized.
Further, the pellets were dissolved by an extruder, charged into a non-axial vertical reactor at 15 kg / hr, reduced in pressure to 10.13 kPa to reduce the remaining lactide, and chipped again. The obtained poly L-lactic acid (PLLA) has a glass transition temperature (Tg) of 55 ° C., a melting point (Tm) of 175 ° C., a weight average molecular weight of 120,000, a molecular weight dispersion of 1.8, and a lactide content of 0.005% by mass. there were.

[Reference Example 2] Synthesis of poly-D-lactic acid (PDLA) In the same manner as Reference Example 1 except that D-lactide was used instead of L-lactide, the glass transition temperature (Tg) was 55 ° C, the melting point ( Tm) Poly D-lactic acid (PDLA) having a weight average molecular weight of 120,000, a molecular weight dispersion of 1.8, and a lactide content of 0.005% by mass was obtained.

[Reference Example 3] (Production of oriented film L1)
After sufficiently drying the PLLA obtained in Reference Example 1 using a dryer, 5% by mass of a core shell structure (Paraloid ^TM BPM-500) manufactured by Rohm and Haas Japan Co., Ltd. is added. The molten resin was poured into an extruder, melted at 220 ° C., the molten resin was extruded from a die and formed into a single-layer sheet, and the sheet was cooled and solidified with a cooling drum having a surface temperature of 20 ° C. to obtain an unstretched film. . The obtained unstretched film was led to a roll group heated to 75 ° C., stretched 1.1 times in the longitudinal direction, and cooled by a roll group at 25 ° C. Subsequently, both ends of the longitudinally stretched film were guided to a tenter while being held with clips, and stretched 4.0 times in the transverse direction in an atmosphere heated to 75 ° C. Thereafter, heat treatment was performed in a tenter at a temperature of 110 ° C. for 30 seconds, and the mixture was gradually and gradually cooled to room temperature to obtain a 7 μm-thick biaxially oriented poly L-lactic acid monolayer film (aligned film L1). The surface on the side where a conductive layer described later is formed was subjected to corona treatment under the conditions of a voltage of 10 kV and a treatment time of 20 seconds using a high-frequency power source CG-102 manufactured by Kasuga.

[Reference Example 4] (Production of oriented film D1)
Using PDLA obtained in Reference Example 2, a biaxially oriented poly D-lactic acid monolayer film (aligned film D1) having a thickness of 7 μm was obtained in the same manner as Reference Example 3. The surface on the side where a conductive layer described later is formed was subjected to corona treatment under the conditions of a voltage of 10 kV and a treatment time of 20 seconds using a high-frequency power source CG-102 manufactured by Kasuga.

[Reference Example 5] (Production of oriented film L2)
7 μm in the same manner as in Reference Example 3 except that the PLLA obtained in Reference Example 1 was used and the core shell structure (Paraloid ^TM BPM-500) manufactured by Rohm and Haas Japan Co., Ltd. was not added. A biaxially oriented poly-D-lactic acid monolayer film (aligned film L2) having a thickness was obtained. The surface on the side where a conductive layer described later is formed was subjected to corona treatment under the conditions of a voltage of 10 kV and a treatment time of 20 seconds using a high-frequency power source CG-102 manufactured by Kasuga.
[Reference Example 6] (Production of oriented film D2)
7 μm in the same manner as in Reference Example 3 except that PDLA obtained in Reference Example 2 was used and the core shell structure (Paraloid ^TM BPM-500) manufactured by Rohm and Haas Japan Co., Ltd. was not added. A biaxially oriented poly-D-lactic acid monolayer film (alignment film D2) having a thickness was obtained. The surface on the side where a conductive layer described later is formed was subjected to corona treatment under the conditions of a voltage of 10 kV and a treatment time of 20 seconds using a high-frequency power source CG-102 manufactured by Kasuga.

[Example 1]
(Cut out)
The oriented film L1 obtained in Reference Example 3 and the oriented film D1 obtained in Reference Example 4 were cut out at 3 cm × 7 cm so that the transverse direction of the stretching was an angle of 45 degrees with respect to the long side.
(Formation of conductive layer)
Next, as shown in FIG. 1, a 1 cm region (3 cm × 1 cm region) from one short side is masked as a margin to leave a portion not to be deposited, and the remaining region (3 cm × 6 cm region) is surfaced. Aluminum deposition was performed with a thickness such that the resistance value was 10Ω / □. In addition, the positions of the margins were the alignment film L1 and the alignment film D1, and the margins were created on the opposite short sides.
(Laminated)
The obtained oriented film L1 and oriented film D1 thus deposited were alternately laminated in a total of 6 sheets. And thermocompression bonding was performed for 3 minutes under the pressure of 110 degreeC20MPa, and it was set as the piezoelectric laminated body.
(electrode)
A conductive adhesive (Dotite D550, manufactured by Fujikura Kasei Co., Ltd.) was applied to both short sides of the obtained laminate to form an electrode (6), thereby producing a piezoelectric structure. Thus, in each aluminum vapor deposition layer, the conductive adhesive and the aluminum vapor deposition layer are not short-circuited on the side having a margin, and the conductive adhesive and the aluminum vapor deposition layer are short-circuited on the side having no margin. It becomes composition.
(assembly)
On the front and back surfaces of a polystyrene film (thickness: 200 μm) having a length of 25.7 cm and a width of 36.4 cm, the surface of the piezoelectric laminate on which the electrode is formed without the conductive layer is used as a vibration plate, and an epoxy resin adhesive (Huntsman Using an Advanced Materials, product name: Araldite Standard), both the effective electrode portion and the immobile portion were bonded together as shown in FIG. At this time, the average thickness of the adhesive layer was 10 μm. Thereafter, the adhesive was dried. The obtained piezoelectric speaker was used for the evaluation method (2) described above, and the characteristics as a speaker were evaluated. The results are shown in Table 1.

[Example 2]
Of the six oriented films to be laminated, the same operation as in Example 1 was performed, except that double-sided vapor deposition was performed on one of the outermost surfaces and the piezoelectric laminate was laminated so that both sides of the piezoelectric laminate became conductive layers. At this time, aluminum vapor deposition was performed so that the film which carries out double-sided vapor deposition had a margin on the opposite short side, respectively.

[Example 3]
The oriented film L1 and the oriented film D1 were cut out at 4 cm × 6 cm so that the transverse direction of the stretching was an angle of 45 degrees with respect to the long side. Next, a 1 cm region (4 cm × 1 cm region) from the short side is masked as a margin, leaving a portion not to be deposited, and a surface resistance value of 10 Ω / □ in the remaining region (4 cm × 5 cm region). Aluminum deposition was performed with a sufficient thickness, and the same operation as in Example 1 was performed.

[Example 4]
The oriented film L1 and the oriented film D1 were cut out at 3 cm × 14 cm so that the transverse direction of the stretching was an angle of 45 degrees with respect to the long side. Next, a 1 cm region (3 cm × 1 cm region) from the short side is masked as a margin, leaving a portion not to be deposited, and a surface resistance value of 10 Ω / □ in the remaining region (3 cm × 13 cm region). Aluminum deposition was performed with a sufficient thickness, and the same operation as in Example 1 was performed.

[Example 5]
The oriented film L1 and the oriented film D1 were cut out at 3 cm × 14 cm so that the transverse direction of the stretching was an angle of 45 degrees with respect to the long side. Next, a 0.5 cm region (3 cm × 0.5 cm region) from the short side is masked as a margin to leave a portion that is not evaporated, and the surface resistance value is in the remaining region (3 cm × 13.5 cm region). Aluminum deposition was performed with a thickness of 10Ω / □, and the same operation as in Example 1 was performed.

[Example 6]
The same operation as in Example 1 was performed except that the thickness of the oriented film L1 obtained in Reference Example 3 and the oriented film D1 obtained in Reference Example 4 were each 20 μm.

[Example 7]
The same operation as in Example 1 was performed except that the thickness of the oriented film L1 obtained in Reference Example 3 and the oriented film D1 obtained in Reference Example 4 were each 5 μm.

[Example 8]
The same operation as in Example 1 was performed except that 20 oriented film layers were used so that the oriented film L1 and the oriented film D1 were alternated.

[Example 9]
The same operation as in Example 1 was performed except that the number of the oriented film layers was changed to 3 so that the oriented film L1 and the oriented film D1 were alternated.

[Example 10]
As shown in FIG. 4, the same operation as in Example 1 was performed except that the piezoelectric laminate was bonded to only one surface of the diaphragm.

[Example 11]
The same operation as in Example 1 was performed except that a 200 μm thick polyethylene-2,6-naphthalate film (manufactured by Teijin DuPont Films Ltd., registered trademark: Teonex product name: Q65) was used as the diaphragm.

[Example 12]
The oriented film L1 and the oriented film D1 were cut out at 3 cm × 7 cm so that the transverse direction of the stretching was an angle of 45 degrees with respect to the long side. Next, a 1 cm region (3 cm × 1 cm region) from the short side is masked as a margin, leaving a portion that is not applied, and a surface resistance value of 500 Ω / □ in the remaining region (3 cm × 6 cm region). Poly (3,4-ethylenedioxythiophene) was applied in a thickness of sufficient thickness and dried at 80 ° C. for 5 minutes to form a conductive layer. Thereafter, the same operation as in Example 1 was performed.

[Example 13]
The same operation as in Example 1 was performed except that the oriented film L2 obtained in Reference Example 5 and the oriented film D2 obtained in Reference Example 6 were used. However, in the case of no addition of Paraloid ^TM BPM-500, the adhesiveness was lower than in the case of addition, and therefore, the pressure bonding conditions were 110 ° C. and a pressure of 40 MPa for 3 minutes.

[Example 14]
One obtained by subjecting one surface of the oriented film L1 obtained in Reference Example 3 to corona treatment was designated as an oriented film L1-A, and one obtained by subjecting the other surface to corona treatment was designated as an oriented film L1-D. The obtained oriented film L1-A and oriented film L1-D were cut out at 3 cm × 7 cm so that the transverse direction of stretching was an angle of 45 degrees with respect to the long side. Next, the corona-treated surface is masked with a 1 cm region (3 cm × 1 cm region) from the short side as a margin, leaving a portion not to be deposited, and then the remaining region (3 cm × 6 cm region). Aluminum vapor deposition was performed at a thickness such that the surface resistance value was 10Ω / □, and the same operation as in Example 1 was performed.

[Example 15]
The oriented film L1 obtained in Reference Example 3 and the oriented film D1 obtained in Reference Example 4 were cut out at 3 cm × 7 cm so that the direction parallel to the transverse direction of the stretching was the long side. Otherwise, the same operation as in Example 1 was performed.

[Example 16]
Of the six oriented films to be laminated, the same operation as in Example 15 was performed, except that double-sided vapor deposition was performed on one of the outermost surfaces and the both sides of the piezoelectric laminate were laminated to be conductive layers. At this time, aluminum vapor deposition was performed so that the film which carries out double-sided vapor deposition had a margin on the opposite short side, respectively.

[Example 17]
The oriented film L1 and the oriented film D1 were cut out at 4 cm × 6 cm so that the direction parallel to the transverse direction of the stretching was the long side. Next, a 1 cm region (4 cm × 1 cm region) from the short side is masked as a margin, leaving a portion not to be deposited, and a surface resistance value of 10 Ω / □ in the remaining region (4 cm × 5 cm region). Aluminum deposition was performed with a sufficient thickness, and the same operation as in Example 1 was performed.

[Example 18]
The oriented film L1 and the oriented film D1 were cut out at 5 cm × 5 cm so as to be parallel to the transverse direction of stretching. Next, as shown in FIG. 9, an L-shaped region having a width of 0.5 cm from the end is masked as a margin, a portion not deposited is left, and a surface resistance value is applied to the remaining region (4.5 cm × 4.5 cm region). The aluminum was vapor-deposited at a thickness such that becomes 10Ω / □. In addition, the margin was created so that the positions of the margins would be diagonal between the oriented film L1 and the oriented film D1. Otherwise, the same operation as in Example 1 was performed.

[Example 19]
As shown in FIG. 4, the same operation as in Example 15 was performed except that the piezoelectric laminate was bonded to only one surface of the diaphragm.

[Example 20]
The same operation as in Example 15 was performed, except that a polyethylene-2,6-naphthalate film (registered trademark: Teonex product name: Q65, manufactured by Teijin DuPont Films Ltd.) having a thickness of 200 μm was used as the diaphragm.

[Example 21]
The same operation as in Example 1 was performed except that a 200 μm-thick stereocomplex polylactic acid film (registered trademark: Biofront, manufactured by Teijin Ltd.) was used as the diaphragm.

[Example 22]
The same operation as in Example 1 was performed except that a 200 μm thick polyethylene-terephthalate film (registered trademark: Tetron, trade name: HS, manufactured by Teijin DuPont Films Ltd.) was used as the diaphragm.

[Example 23]
Example 1 except that the piezoelectric laminate was joined to the diaphragm using a vinyl acetate resin adhesive (manufactured by Shionogi Pharmaceutical Co., Ltd., trade name: for cushion collect plastic) instead of the epoxy resin adhesive. The operation was repeated. At this time, the thickness of the adhesive layer was 5 μm.

[Comparative Example 1]
As shown in FIG. 6, the same operation as in Example 1 was performed except that the piezoelectric laminate was bonded to only one side of the diaphragm only at the effective electrode portion.

[Comparative Example 2]
As shown in FIG. 6, the same operation as in Example 15 was performed, except that the piezoelectric laminate was bonded to only one side of the diaphragm only at the effective electrode portion.

[Comparative Example 3]
As shown in FIG. 17, samples shown in Table 1 were prepared using a polyvinylidene fluoride film having a thickness of 80 μm (KF Piezo Film manufactured by Kureha Extec Co., Ltd.), and electrodes shown in Table 1 were formed on both sides. The piezoelectric speaker was evaluated by performing the same operation as in Example 1 except that only the effective electrode was bonded to only one surface of the diaphragm.
The results of Examples and Comparative Examples are shown in Table 1.

1 Oriented Film Layer 2 Conductive Layer 3 Laminate A
4 Laminate B
DESCRIPTION OF SYMBOLS 5 Piezoelectric laminated body 6 Effective electrode part 7 Immobility part 8 Immobility part 9 Positive electrode 10 Negative electrode 11 Diaphragm 12 Adhesive layer 13 Displacement direction 14 Main orientation axial direction 15 Amplifier 16 Sound source 17 Conductor 18 Clip 19 Aluminum foil 20 PVDF film

Claims (11)

A piezoelectric speaker having a piezoelectric laminate bonded to at least one surface of a diaphragm,
(I) In the piezoelectric laminate, conductive layers and oriented film layers made of polylactic acid are alternately laminated, and the adjacent conductive layers via the oriented film layer are short-circuited to the negative electrode and the other to the positive electrode, Having an effective electrode part where a conductive layer exists between adjacent oriented film layers, and a stationary part where an adjacent oriented film layer exists without a conductive layer;
(Ii) The piezoelectric laminate and the diaphragm are bonded to the diaphragm at both the effective electrode portion and the non-moving portion of the piezoelectric laminate, and (iii) the orientation film layer sandwiched between the conductive layers is A piezoelectric speaker that is laminated so that the expansion and contraction directions are the same when an electric current is passed, and resonates the diaphragm by expansion and contraction in the surface direction of the piezoelectric laminate.   The piezoelectric speaker according to claim 1, wherein the piezoelectric laminate has conductive layers on both outermost surfaces.   The piezoelectric speaker according to claim 1, wherein the piezoelectric laminate is a polygon having two opposite sides, and one of the opposite sides is a negative electrode portion and the other is a positive electrode portion.   The piezoelectric speaker according to claim 1, wherein a piezoelectric laminated body whose expansion and contraction directions are the same when an electric current is passed is bonded to both surfaces of the diaphragm.   2. The piezoelectric speaker according to claim 1, wherein the piezoelectric laminated body has an area of a stationary portion of 0.1% or more with respect to an area of an effective electrode portion.   The piezoelectric speaker according to claim 1, wherein the piezoelectric laminate has three or more oriented film layers.   2. The piezoelectric speaker according to claim 1, wherein one of the adjacent oriented film layers is an oriented film layer L made of poly L-lactic acid and the other is an oriented film layer D made of poly D-lactic acid.   The piezoelectric speaker according to claim 1, wherein the piezoelectric laminate has a thickness of 3 to 500 μm.   2. The piezoelectric speaker according to claim 1, wherein the orientation film layers each independently have a thickness of 25 μm or less.   The piezoelectric speaker according to claim 1, wherein the diaphragm is made of a thermoplastic polymer film having a Young's modulus of 3 GPa or more.   The piezoelectric speaker according to claim 1, wherein the diaphragm is made of a thermoplastic polymer film having a total light transmittance of 85% or more.

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