JP6118517B2 - Piezoelectric laminate - Google Patents

Description

The present invention relates to a piezoelectric stack using a piezoelectric stack-body uniaxially oriented fill beam.

It is known that a conductive layer is provided on a stretched polylactic acid film to be used as a polymer piezoelectric material (Patent Documents 1 and 2). In addition, such polymer piezoelectric materials are laminated to form a bimorph structure or a multimorph structure, and the piezoelectric characteristics are further enhanced, and vibration bodies such as microphones, pickups, buzzers, speakers, optical switches, fans, and piezoelectric actuators It is known to be used as (Patent Documents 3 to 5)
By the way, in fields unrelated to piezoelectric materials, by providing a polylactic acid film with an acrylic resin layer having heat-sealability, it has excellent environmental friendliness and excellent transparency and high mechanical properties required for packaging materials. It is known that a film having strength and excellent heat sealability can be provided (Patent Document 6). In addition, as a polylactic acid resin laminate sheet with excellent heat resistance, transparency, and impact resistance in fields such as product display packaging, poly (meth) acrylate resin is added to polylactic acid, and impact resistance It is known to contain an improving agent (Patent Document 7).

JP-A-5-152638 JP 2005-213376 A JP 59-115580 A JP 59-2222977 A Japanese Utility Model Publication No. 58-78673 JP 2004-351629 A International Publication No. 2007/063864 Pamphlet JP 2009-155490 A

When a polylactic acid film provided with a conductive layer is thermocompression-bonded to form the above-described bimorph or multimorph piezoelectric laminate, and the number of layers is increased to increase the piezoelectric properties of the piezoelectric laminate, It has been found that there is a drawback that peeling occurs.
It is an object of the present invention, while maintaining the piezoelectric property is to provide a piezoelectric laminate peeling with hard polylactide-fill beam to occur.

  The inventors of the present invention have found that when a polylactic acid film contains an impact resistance improver that is not related to thermocompression bonding, a piezoelectric laminate that has excellent piezoelectric characteristics and is less likely to be peeled off can be obtained. .

Thus, according to the present invention, the following pressure conductive laminate is provided.
(1) A piezoelectric laminate in which (i) uniaxially oriented films and (ii) conductive layers are alternately laminated, wherein the uniaxially oriented film has a poly L-lactic acid or poly D- with an optical purity of 80% or more. It consists lactate, based on the weight of the uniaxially oriented film, containing impact modifier in the range of 0.1 to 10 mass%, the piezoelectric stack.
(2) The piezoelectric laminate as described in 1 above, wherein the impact resistance improver is a multilayer structure polymer composed of a core layer and one or more shell layers covering the core layer.
(3) The piezoelectric laminate according to 1 above, wherein the density of the uniaxially oriented film is 1.22 to 1.27 g / cm ³ .
(4) The piezoelectric laminate as described in 1 above, wherein the thickness of the uniaxially oriented film is 10 μm or less.
(5) The piezoelectric laminate according to 1 above, wherein the total number of layers of the uniaxially oriented film is 2 or more.
(6) The piezoelectric laminate as described in 1 above, wherein uniaxially oriented films made of either poly L-lactic acid or poly D-lactic acid are adjacent to each other via a conductive layer, and the main orientation axes of the adjacent uniaxially oriented films are orthogonal to each other. body.
(7) and the uniaxially oriented film of poly-L- lactic acid, the uniaxially oriented film of poly D- lactic acid, adjoin via the conductive layer, the main orientation axis of the uniaxially oriented film adjacent in the same direction 1 The piezoelectric laminate according to 1.

According to the present invention, a piezoelectric laminate using a uniaxial orientation fill beam of hard polylactide peeling occurs while maintaining the piezoelectric property is provided.

It is an explanatory view of the laminate of the invention having a conductive layer on one axis oriented film. The upper side is a laminate A provided with a resin layer and a conductive layer for the right margin, and the lower side is a laminate A provided with a resin layer and a conductive layer for the left margin. 2 is an explanatory diagram of the laminate of the present invention, and the top view of FIG. 2 shows a laminate A provided with a resin layer and a conductive layer for the right margin of FIG. 1, and a resin layer for the left margin of FIG. It is the figure which arranged alternately the laminated body A which provided the conductive layer, the figure of the middle of FIG. 2 is the figure of the laminated body B which laminated | stacked them by crimping | bonding them, and the lowest figure of FIG. FIG. 6 is a diagram in which a conductive paste is provided at both ends of a laminated body B. It is the figure which showed the evaluation method of the adhesiveness of the piezoelectric laminated body of this invention. It is the figure which showed the evaluation method of the piezoelectric characteristic of the piezoelectric laminated body of this invention.

(Polylactic acid)
The polylactic acid in the present invention is poly L-lactic acid (may be abbreviated as PLLA) or poly D-lactic acid (may be abbreviated as PDLA) having an optical purity of 80% or more. If the optical purity is less than the lower limit, the piezoelectric characteristics are low, and the effects of the present invention are hardly exhibited. The optical purity of polylactic acid is preferably 90% or higher, more preferably 95% or higher, and still more preferably 98% or higher. Poly L-lactic acid substantially composed only of L-lactic acid units or poly D-lactic acid composed only of D-lactic acid units is particularly preferred.
Alternatively, a copolymer of PLLA or PDLA and other monomers can also be used. 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%.

Specific examples of the copolymer component are not particularly limited. For example, hydroxycarboxylic acids such as glycolic acid, caprolactone, butyrolactone, propiolactone, ethylene glycol, 1,3-propanediol, 1,2- Propanediol, 1,4-propanediol, 1,5-propanediol, hexanediol, octanediol, decanediol, dodecanediol, aliphatic diols having 2 to 30 carbon atoms, succinic acid, maleic acid, adipic acid, One or more monomers selected from aliphatic dicarboxylic acids having 2 to 30 carbon atoms, terephthalic acid, isophthalic acid, hydroxybenzoic acid, hydroquinone, and other aromatic diols, aromatic dicarboxylic acids and the like can be selected.
The melting point of polylactic acid 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 molecular weight of polylactic acid is a weight average molecular weight (Mw), preferably in the range of 80,000 to 250,000, more preferably in the range of 100,000 to 250,000, particularly in the range of 120,000 to 200,000. It is preferable that it exists in. When the weight average molecular weight Mw is in the above numerical range, the thickness unevenness of the film becomes good, and it is easier to suppress peeling after pressure bonding.

(Uniaxially oriented film)
Polylactic acid film is required to be a uniaxially oriented film. Biaxially oriented films and non-oriented films have low piezoelectric properties and do not sufficiently exhibit the effect of containing an impact resistance improver described below.
The uniaxially oriented film in the present invention refers to the direction of the highest refractive index in the in-plane direction of the film as the main orientation direction, the breaking strength in the main orientation direction is 120 MPa or more, the main orientation direction in the in-plane direction of the film It means a film having a biased orientation such that the breaking strength in the direction perpendicular to is 80 MPa or less. 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. 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.

Further, the breaking strength of the polylactic acid uniaxially oriented film, the direction orthogonal to the main orientation axis direction is preferably less 80 MPa. 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. In the present invention, for convenience of explanation, the film forming direction of the polylactic acid film may be 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. It may be called a horizontal direction and a TD direction.

(Impact resistance improver)
One of the features of the present invention is that the polylactic acid uniaxially oriented film contains an impact resistance improver in the range of 0.1 to 10% by mass based on the mass of the polylactic acid uniaxially oriented film. .
The impact resistance improver used in the present invention is not particularly limited as long as it can be used to improve the impact resistance of polylactic acid, but is a rubber-like substance that exhibits rubber elasticity at room temperature. At least one selected from the following various impact resistance improvers can be used.

  Specific examples of impact modifiers include ethylene-propylene copolymers, ethylene-propylene-nonconjugated diene copolymers, ethylene-butene-1 copolymers, various acrylic rubbers, and 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, ethylene-butyl acrylate copolymer, ethylene-methyl methacrylate copolymer), ethylene-vinyl acetate copolymer, acid-modified ethylene-propylene copolymer, diene rubber (for example, polybutadiene, polyisoprene, poly Chloroprene), a copolymer of diene and vinyl monomer And hydrogenated products thereof (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, epic Rohidoringomu can like are 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.

(Multilayer structure polymer)
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 the present invention, the blending amount of the impact resistance improver needs to be in the range of 0.1 to 10% by mass based on the mass of the polylactic acid uniaxially oriented film in view of the effects of the present invention. If it is less than the lower limit, it will be easy to peel off when crimped, or it will be difficult to stabilize the vibration when a voltage is applied. 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, it is possible to suppress peeling after crimping that is not related to impact resistance without deteriorating the piezoelectric properties, and to stabilize vibration when voltage is applied. The reason for this is not clear, but flexibility can be imparted without lowering the orientation of the resulting polylactic acid uniaxially oriented film, resulting in an even transmission of pressure during crimping and local peeling at the interface of the piezoelectric laminate It is presumed that this is because there are no longer any parts that are easily deformed or parts that are locally and strongly crimped.
Hereinafter, a preferred embodiment of the first axis oriented film, will be described.

(density)
Density of polylactic acid uniaxially oriented film is preferably 1.22~1.27g / 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 .

(Thickness)
The thickness of the first shaft oriented film, in view of the tendency to longer exhibited a resonance characteristic too is too thick high rigidity, not particularly limited as long as it is thick enough to achieve the 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 15 μm or less, more preferably 12 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.

(Additives, etc.)
First axis oriented film, without impairing the effect of the present invention may contain a per se known additives and functional agent, for example, hydrolysis inhibitor, a lubricant, an antioxidant, an antistatic agent Colorants, pigments, fluorescent whitening agents, plasticizers, crosslinking agents, ultraviolet absorbers, 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.

Further, first shaft oriented film, for the purpose of improving the winding and traveling properties can contain a lubricant in these film. 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. Further, the lubricant can be blended in the range of 0.01 to 1.0% by mass, more preferably 0.1 to 0.5% by mass with respect to the mass of each layer of the layer L or the layer D.

(Manufacture of polylactic acid)
Next, an axial oriented film, for explaining the method of manufacturing the same. 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, still more preferably 0.5 to 10 equivalents, particularly preferably, per equivalent of metal element of the metal-containing catalyst. 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)
The polylactic acid obtained by the above method is blended with an impact resistance improver, and if desired, the above-mentioned carboxyl group-capping agent, lubricant, other additives, and the like are blended, and poly L-lactic acid (in the case of layer L) In the case of layer D, it is poly D-lactic acid. The same applies hereinafter.) Resin L (when poly L-lactic acid is used. When poly D-lactic acid is used, it is resin D. The same applies hereinafter. .) Is melted in an extruder and extruded from a die onto a cooling drum. In addition, in order to suppress decomposition at the time of melting, the resin supplied to the extruder is preferably subjected to a drying process before being supplied to the extruder so that the water content is about 100 ppm or less.
The resin temperature in the extruder is a temperature at which the resin has sufficient fluidity, that is, when the melting point of the resin L is Tm, it is carried out in the range of (Tm + 20) to (Tm + 50) (° C.), but the resin does not decompose. It is preferable to perform melt extrusion at a temperature, and such a 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.

(Stretching 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 of 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 being heated to a temperature at which the unstretched film can be stretched, for example, a glass transition temperature (Tg) or higher (Tg + 80) ° C. of the resin L.
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, more preferably 8 times or less, and particularly preferably 7 times or less from the viewpoint of film forming property. 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 oriented polylactic acid film obtained above is preferably heat-treated. The heat treatment temperature may be higher than the above-mentioned stretching temperature and lower than the melting point (Tm) of the resin, preferably the glass transition temperature (Tg + 15) ° C. or more and (Tm−10) ° C. or less, more preferably (Tg + 20). ) ° C. or higher (Tm−20) ° C., particularly preferably (Tg + 30) ° C. or higher (Tm−35) ° C. When the heat treatment temperature is in the above range, the main alignment axis can be easily aligned and the mechanical properties can be excellent while improving the thickness unevenness and surface flatness. The heat treatment time is preferably 1 to 120 seconds, more preferably 2 to 60 seconds.
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.
Especially, it is preferable to perform a corona treatment on at least one side, preferably both sides of the oriented film layer, from the viewpoint of improving the adhesion with the conductive layer M described later and enhancing the durability of the piezoelectric laminate. 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.

[Piezoelectric laminate]
Next , the piezoelectric laminate of the present invention will be described below.
Piezoelectric laminate of the present invention is obtained by laminating an upper Kipo polylactic acid uniaxially oriented film and a conductive layer alternately. At this time, the adjacent conductive layer is allowed to be charged with the opposite charge, while the adjacent polylactic acid uniaxially oriented film has the main alignment axis so that the piezoelectric characteristics are enhanced in the state where the opposite charge is applied. Arrange the orientation.
For example, uniaxially oriented films made of either one of poly L-lactic acid or poly D-lactic acid are laminated so as to be adjacent to each other via a conductive layer, and the main orientation axes of adjacent uniaxially oriented films are orthogonal to each other.
Further, the uniaxially oriented film made of poly L-lactic acid and the uniaxially oriented film made of poly D-lactic acid are adjacent to each other through the conductive layer, and the main orientation axes of the adjacent uniaxially oriented films are in the same direction. Laminate.

In the piezoelectric laminate of the present invention, the adjacent polylactic acid uniaxially oriented films only need to satisfy the above relationship, and all the polylactic acid uniaxially oriented films are either L-form or D-form. The polylactic acid uniaxially oriented film may be in an L-form and a D-form, in which they are alternately laminated, or in an aspect in which they are partially combined.
In addition, the fact that the main orientation axes of adjacent oriented polylactic acid films in the present invention are orthogonal means an angle of approximately 90 degrees, and the closer to 90 degrees, the more effectively the piezoelectric characteristics are expressed. From such a viewpoint, the acute angle formed by the main orientation axes of the adjacent oriented polylactic acid films is preferably 80 degrees or more, more preferably 85 degrees or more, and particularly 88 degrees or more. Is preferred. In addition, the main orientation axis of adjacent oriented polylactic acid films in the present invention being in the same direction means an angle of almost 0 degrees, and the closer to 0 degrees, the more effectively the piezoelectric characteristics are expressed. From such a viewpoint, the acute angle formed by the main orientation axes of the adjacent oriented polylactic acid films is preferably 10 degrees or less, more preferably 5 degrees or less, particularly 2 degrees or less. Is preferred.

  In the piezoelectric laminate of the present invention, the total number of polylactic acid uniaxially oriented films is preferably 4 or more, more preferably 8 or more, and particularly preferably 10 or more, from the viewpoint of enhancing the piezoelectric characteristics. . On the other hand, the upper limit of the total number is 300 or less, from the viewpoint of preventing the thickness of the entire piezoelectric laminate from becoming excessively strong while giving the polylactic acid uniaxially oriented film a thickness that provides a certain degree of handleability. It is preferable that it is 200 or less.

The laminated structure of the piezoelectric body of the present invention will be described with reference to FIGS. 1 and 2 are schematic views showing an example of the laminated structure of the piezoelectric body of the present invention. In FIG. 1, reference numeral 1 denotes a resin layer for the right margin, which is an oriented polylactic acid film layer (1), and reference numeral 2 denotes a resin layer for the left margin, which is adjacent to the oriented polylactic acid film layer (1). Each layer (2) is shown. In the piezoelectric body of the present invention, a plurality of oriented polylactic acid film layers (1) and (2) are alternately laminated as described above. FIG. 2 shows a case where the number of oriented polylactic acid film layers (1) is three and the number of oriented polylactic acid film layers (2) is six, for a total of six.
Reference numeral 3 denotes a conductive layer M. In the present invention, a conductive layer M (3) is provided between the oriented polylactic acid film layers (1) and (2). In addition, the conductive layer M (3) is preferably provided on at least one surface of the piezoelectric body, and the conductive layer M (3) may be provided on the other surface.

The oriented polylactic acid film layer (1) and the conductive layer M, and the oriented polylactic acid film layer (2) and the conductive layer M are preferably fixed without an adhesive layer having a thickness exceeding 1000 nm. In the present invention, excellent resonance characteristics can be achieved by adopting such an embodiment. From such a viewpoint, in the present invention, an embodiment in which the adhesive layer is fixed without using an adhesive layer having a thickness exceeding 500 nm is preferable, and an embodiment in which the adhesive layer is fixed without using an adhesive layer having a thickness exceeding 200 nm is more preferable. From the viewpoint of resonance characteristics, it is most preferable to fix the adhesive layer 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 laminated film can be provided on the surface of the laminated film. On the other hand, from the viewpoint of resonance characteristics, such a layer is preferably thin and particularly preferably not.

(Conductive layer M)
The type of the conductive layer M in the present invention is not particularly limited as long as the piezoelectric laminate of the present invention has a conductivity sufficient to exhibit piezoelectric characteristics when a voltage is applied. From the viewpoint that piezoelectric characteristics and resonance characteristics can be exhibited, a layer made of metal or metal oxide is 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, indium oxide containing tin oxide and tin oxide containing antimony are preferably used.

The thickness of the conductive layer M is not particularly limited, but the surface resistance value is preferably 1 × 10 ⁴ Ω / □ or less, more preferably 5 × 10 ³ Ω / □ or less, and further preferably 1 × 10 ³ Ω / □. What is necessary is just to select the thickness which becomes the following, for example, it is preferable to set it as thickness 10nm or more. 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, the formation of the piezoelectric laminate is difficult, and the strength between the layers of the piezoelectric laminate tends to be weak.

(Manufacture of piezoelectric laminate)
The piezoelectric laminate manufacturing method of the present invention is prepared by preparing a laminate in which a conductive layer is formed on one surface of a uniaxially oriented film obtained by the above-described manufacturing method, and uniaxially oriented so as to have the above-described main orientation direction relationship. Lamination is performed so that the film and the conductive layer alternate.
It does not specifically limit as a formation method of the conductive layer M, A conventionally well-known method is employable. Specifically, for example, a vacuum deposition method, a sputtering method, and an ion plating method can be exemplified, and a vapor deposition method or a sputtering method is adopted from the viewpoint that a conductive layer having excellent conductivity can be obtained uniformly and easily. It is preferable to do. In addition, after forming a metal layer, it can crystallize by giving an annealing process within the range of 100-150 degreeC as needed. For this reason, it is preferable that the layer L and the layer D have heat resistance of 100 ° C. or higher, more preferably 110 ° C. or higher. Moreover, although the conductive layer M may be formed on both surfaces of the oriented film layer, it is preferable to form the conductive layer M only on one surface from the viewpoint of adhesion. In that case, since the adjacent oriented polylactic acid film layer is turned upside down, the conductive layer is formed on one surface of the oriented polylactic acid film layer and the conductive layer is formed on the other surface of the oriented polylactic acid film layer. It is preferable to prepare the product.
The oriented polylactic acid film layer having the conductive layer M obtained as described above is laminated so as to have a laminated structure defined by the present invention to prepare a laminate, and is fixed by thermal lamination. Here, the thermal lamination is performed without using an adhesive layer.

  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 laminated film 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 layer L and the sub-peak temperature of the oriented film layer D used for forming the laminated film. In addition, subpeak temperature is temperature resulting from the heat setting temperature in a film manufacturing process. By adopting the above temperature condition, a laminated film having excellent resonance characteristics can be obtained. At the same time, the adhesion of each layer of the laminated film 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.

Moreover, it is preferable that pressure conditions shall be 1-30 MPa, 2-28 MPa, and 5-25 MPa. Thereby, it is possible to obtain a laminated film excellent in 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.
It is preferable to perform thermal lamination for 10 to 600 seconds under the above temperature and pressure conditions. Thereby, it is possible to obtain a laminated film excellent in 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.
And according to this invention, even if it thermocompression-bonds on the conditions which do not impair such a piezoelectric characteristic, there is no problem of peeling etc. and a piezoelectric characteristic can be expressed highly.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention does not receive limitation at all by this. In addition, each value in an Example was calculated | required according to the following method.

(1) Peeling of laminated film The ends of the laminated film were squeezed to make notches, each layer was peeled off, the oriented film layer L and the layer D were peeled off, and used for evaluating physical properties of each layer.

(2) Density The film sample peeled from the laminated film was measured according to JIS standard C2151.

(3) 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. By rotating in a plane perpendicular to the optical axis about the axis, the direction with the highest refractive index in the in-plane direction was determined, and that direction was defined as the main orientation direction. The angle in the main orientation direction was calculated with the width direction being 0 ° and the film forming direction being 90 °.

(4) Glass transition temperature (Tg), sub-peak temperature (Tsm), melting point (Tm)
About the oriented film layer obtained as a laminated film before forming a laminated film, about 10 mg of a sample is enclosed in an aluminum pan for measurement and attached to a differential calorimeter (trade name “DSC2920” manufactured by TA instruments), 25 The film was heated from 210 ° C. to 210 ° C. at a rate of 10 ° C./min, and the sub-peak temperature (Tsm: ° C.) and melting point (Tm: ° C.) of the film were measured. Next, after continuously holding at 210 ° C. for 3 minutes, it is taken out, immediately transferred onto ice and rapidly cooled, this pan is again attached to the differential calorimeter, and the temperature is raised from 25 ° C. at a rate of 10 ° C./min. The glass transition temperature (Tg: ° C.) and melting point (Tm: ° C.) of the resin constituting the film were measured.

(5) Conductivity (surface resistance value)
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 resistance value (unit: Ω / □).

(6) Peeling test The piezoelectric laminate having a length of 7 cm and a width of 3 cm prepared in each example is used as a test piece, the short side A side of the test piece is fixed, and the opposite short side B is set to the A side as shown in FIG. Observe the state change.
○: No peeling even when the short side A and the short side B are overlapped. Δ: The peeling is observed when the short side A and the short side B are overlapped. ×: The peeling is seen before the short side A and the short side B are overlapped.

(7) Piezoelectric characteristics As shown in FIG. 2, a conductive adhesive (manufactured by Fujikura Kasei, Dotite D550) is applied to both short sides of the obtained piezoelectric laminate to form an electrode (6). Created a 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.
An aluminum foil is attached to each electrode of this piezoelectric laminate, and as shown in FIG. 4, it is attached to a piezoelectric characteristic measuring device (12) (manufactured by Agilent Technologies, trade name: Precision Impedance Analyzer 4294A), and admittance by a two-terminal method. The resonance measurement was performed. At this time, the piezoelectric laminate was placed on the column (11) as shown in FIG. 4 so as not to affect the resonance, and was installed so that the contact area with the desk surface was reduced. The admittance resonance was measured by a method of measuring a piezoelectric resonance waveform with the equivalent circuit pattern E, and the piezoelectric ratio (unit: pC / N) was calculated from the various parameters obtained. Higher piezoelectricity means better piezoelectric performance.

(8) Breaking strength Tensilon manufactured by Toyo Baldwin Co. was used and measured under conditions of 23 ° C. and 65% RH. The term “breaking strength” as used herein means a value of stress per unit cross-sectional area obtained by dividing the value of the load at the time of the sample breaking when the tensile test is performed by the cross-sectional area of the sample before the test. The sample width was 10 mm, the distance between chucks was 100 mm, and the speed between chucks was 100 mm / min.

[ Synthesis Example 1] Synthesis of poly L-lactic acid (PLLA) Full-zone blade equipped vertical stirring tank (40L) 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.

[ Synthesis Example 2] Synthesis of poly-D-lactic acid (PDLA) Further, except that D-lactide was used instead of L-lactide, the same procedure as in Synthesis Example 1 was followed, except that 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 1]
After sufficiently drying the PLLA obtained in Synthesis Example 1 using a dryer, 5% by mass of Rohm & Haas Japan Co., Ltd. core shell structure (Paraloid ^TM BPM-500) 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 for 30 seconds under a temperature condition of 110 ° C., and the mixture was uniformly cooled and cooled to room temperature to obtain a uniaxially oriented poly L-lactic acid monolayer film (PLLA oriented film) having a thickness of 7 μm.

[ Reference Example 2]
The same operation as in Reference Example 1 was repeated except that PDLA obtained in Synthesis Example 2 was used.

[ Reference Examples 3 to 6]
The same operation as in Reference Example 1 was repeated except that the type and amount of the impact resistance improver contained were changed as shown in Table 1.

[ Reference Examples 7 to 10]
The same operation as in Reference Example 2 was repeated except that the type and amount of the impact resistance improver contained were changed as shown in Table 1.

[ Reference Example 11]
The same operation as in Reference Example 1 was repeated except that 0.5 mass% of crosslinked polymethyl methacrylate particles having an average particle diameter of 2 μm was contained as a filler with respect to the mass of the film.

[ Reference Example 12]
The same operation as in Reference Example 2 was repeated except that 0.5 mass% of crosslinked polymethyl methacrylate particles having an average particle diameter of 2 μm was contained as a filler with respect to the mass of the film.

[ Reference Comparative Example 1]
The same operation as in Reference Example 1 was repeated except that no impact modifier was added.

[ Reference Comparative Example 2]
The same operation as in Reference Example 2 was repeated except that no impact modifier was added.

[ Reference Comparative Example 3]
The same operation as in Reference Example 1 was repeated except that the addition amount of the impact modifier was changed to 15% by mass.

[ Reference Comparative Example 4]
The same operation as in Reference Example 2 was repeated except that the addition amount of the impact modifier was changed to 15% by mass.

In Table 1, A is a Rohm and Haas Japan Co., Ltd. core shell structure (Paraloid ^TM BPM-500), B is a Kuraray Co., Ltd. thermoplastic elastomer (Clarity LA2250), and C is a Rohm and Haas. It means a core shell structure (Paraloid ^TM BPM-515) manufactured by Hearth Japan.

[Example 13]
The PLLA film of Reference Example 1 and the PDLA film of Reference Example 2 were cut into a strip shape (width is 3 cm) having a length of 7 cm along the main alignment axis.
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 was vapor-deposited on the surface that had a resistance value of 10Ω / □ and was not in contact with the cooling drum at the time of film formation. The conductive layer had a thickness of 50 nm. Moreover, the margin position was created on the short side on the opposite side between the PLLA oriented film and the PDLA oriented film.

(Laminated)
Furthermore, the vapor deposited PLLA oriented film and the PDLA oriented film were alternately laminated as shown in FIG. The laminate was bonded by thermal lamination at 110 ° C. and a pressure of 20 MPa over 3 minutes.

(electrode)
As shown in FIG. 2, a conductive adhesive (manufactured by Fujikura Kasei, Dotite D550) was applied to both short sides of the obtained piezoelectric 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. Table 2 shows the piezoelectric properties and adhesion of the obtained piezoelectric laminate.

[Examples 14-17, Comparative Examples 5 and 6]
Instead of the films of Reference Examples 1 and 2, as shown in Table 2, the same operations as in Example 13 were repeated except that the films of Reference Examples 3 to 10 or Reference Comparative Examples 1 to 4 were used. Table 2 shows the piezoelectric properties and adhesion of the obtained piezoelectric laminate.

[Example 18]
Instead of the film of Reference Example 2, the film of Reference Example 1 was used and cut into a strip shape (width: 3 cm) having a length of 7 cm along the direction orthogonal to the main orientation axis. Furthermore, the same operation as in Example 13 was repeated except that the film of Reference Example 1 used instead of Reference Example 2 was subjected to aluminum vapor deposition on the surface that was in contact with the cooling drum during film formation. Table 2 shows the piezoelectric properties and adhesion of the obtained piezoelectric laminate.

[Examples 19 and 20]
The same operation as in Example 13 was repeated except that the number of layers was changed as shown in Table 2. Table 2 shows the piezoelectric properties and adhesion of the obtained piezoelectric laminate.

[Examples 21 to 23 ]
The same operation as in Example 13 was repeated except that the crimping conditions were changed as shown in Table 2. Table 2 shows the piezoelectric properties and adhesion of the obtained piezoelectric laminate.

[Comparative Examples 7 and 8]
The same operation as in Comparative Example 5 was repeated except that the crimping conditions were changed as shown in Table 2. Table 2 shows the piezoelectric properties and adhesion of the obtained piezoelectric laminate.

[Comparative Example 9]
In Comparative Example 5, after vapor deposition, a Huntsman Advanced Materials epoxy adhesive (Araldite Standard) was applied as an adhesive layer between each layer and adhered using a hand-held steel roller. Comparative Example The same operation as 5 was repeated. The thickness of the adhesive layer was 5 μm. Table 2 shows the piezoelectric properties and adhesion of the obtained piezoelectric laminate.

[Comparative Example 10]
In Comparative Example 5, the surface on the side not in contact with the cooling drum during film formation 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. After the vapor deposition step, a piezoelectric laminate was produced in the same manner as in Comparative Example 5 .

  According to the present invention, it is possible to provide a piezoelectric laminate that has excellent piezoelectric characteristics and is prevented from being peeled off, and can be used as a vibrating body such as a microphone, a pickup, a buzzer, a speaker, an optical switch, a fan, or a piezoelectric actuator.

1 Resin layer for right margin 2 Resin layer for left margin 3 Conductive layer 4 Laminate A
5 Laminate B
6 Silver paste electrode 7 Grip 8 Conductor 9 Clip 10 Aluminum foil 11 Cylinder 12 Piezoelectric characteristic measuring device

Claims (7)

(I) a piezoelectric laminate of alternately laminated uniaxially oriented film and (ii) a conductive layer, the uniaxially oriented film is made optical purity of 80% or more, poly L- lactic acid or poly D- lactic acid A piezoelectric laminate comprising an impact resistance improver in the range of 0.1 to 10% by mass based on the mass of the uniaxially oriented film . The piezoelectric laminate according to claim 1, wherein the impact resistance improver is a multilayer structure polymer composed of a core layer and one or more shell layers covering the core layer. 2. The piezoelectric laminate according to claim 1, wherein the uniaxially oriented film has a density of 1.22 to 1.27 g / cm ³ . The piezoelectric laminate according to claim 1, wherein the uniaxially oriented film has a thickness of 10 μm or less. The piezoelectric laminate according to claim 1 , wherein the total number of layers of the uniaxially oriented film is 2 or more. 2. The piezoelectric laminate according to claim 1 , wherein the uniaxially oriented films made of either one of poly L-lactic acid or poly D-lactic acid are adjacent to each other through the conductive layer, and the main orientation axes of the adjacent uniaxially oriented films are orthogonal to each other. A uniaxially oriented film of poly-L- lactic acid, the uniaxially oriented film of poly D- lactic acid, adjoin via the conductive layer, according to claim 1 main orientation axis of the uniaxially oriented film adjacent in the same direction Piezoelectric laminate.

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