JP5647943B2 - Laminated film - Google Patents

Description

  The present invention relates to a laminated film. More specifically, the present invention relates to a laminated film that exhibits resonance characteristics by applying a voltage.

Conventionally, as the polymeric piezoelectric material, poly (γ-benzyl L-glutamate) type, electret type (polyvinyl chloride), polyvinylidene fluoride, vinylidene fluoride, trifluoride ethylene copolymer, vinylidene There are various types such as a ferroelectric type such as cyanide vinyl acetate copolymer. The most typical one is a ferroelectric type polyvinylidene fluoride film, which is already used for an ultrasonic probe or the like. A stretched product of polylactic acid is also known as a polymer piezoelectric material (Patent Documents 1 and 2).
It is known that such a polymer piezoelectric material is used to form a bimorph structure or a multimorph structure and used as a vibrating body such as a microphone, pickup, buzzer, speaker, optical switch, fan, or piezoelectric actuator ( Patent documents 3 to 5).

However, the invention described in Patent Document 3 joins the polymer piezoelectric film via an adhesive, has a problem that the processing steps such as laminating are complicated, and the productivity is low. Also, with such a joining method, it is difficult to obtain excellent resonance characteristics.
Furthermore, in the inventions described in Patent Documents 4 and 5, it is difficult to obtain excellent resonance characteristics.

JP-A-5-152638 JP 2005-213376 A JP 59-115580 A JP 59-2222977 A Japanese Utility Model Publication No. 58-78673

  Therefore, an object of the present invention is to provide a laminated film that can obtain excellent resonance characteristics when a voltage is applied. Moreover, the objective of this invention is providing the manufacturing method of the laminated | multilayer film which can acquire the outstanding resonance characteristic.

The present invention employs the following configuration in order to solve the above problems.
1. (I) having an oriented film layer L made of a resin L containing poly L-lactic acid as a main component, an oriented film layer D made of a resin D containing poly D-lactic acid as a main component, and a conductive layer M;
(Ii) having a conductive layer M on at least one surface;
(Iii) Layer L and layer D are alternately stacked via conductive layer M, and the total number of layers L and D is 3 or more,
(Iv) There is no adhesive layer exceeding a thickness of 1000 nm between the layer L and the conductive layer M and between the layer D and the conductive layer M.
Laminated film.
2. 2. The laminated film according to 1 above, wherein an angle formed between the main alignment direction of the layer L and the main alignment direction of the layer D is 10 degrees or less.
3. 3. The laminated film according to 1 or 2 above, wherein the refractive indices in the main alignment direction of the layer L and the layer D are each independently 1.45 or more.
4). 4. The laminated film according to any one of 1 to 3 above, wherein the densities of the layer L and the layer D are each independently 1.24 to 1.27 g / cm ³ .

5. The laminated film according to any one of 1 to 4 above, wherein the thicknesses of the layer L and the layer D are each independently 10 μm or less.
6). 6. A piezoelectric structure having the laminated film and the electrode according to any one of 1 to 5 above, wherein the conductive layer M on the surface of the laminated film is the first layer, and the odd-numbered layers are counted sequentially from there. When divided into the conductive layer M and the even-numbered conductive layer M, the odd-numbered conductive layers M are short-circuited by the electrodes and are not short-circuited with the even-numbered conductive layers M. A piezoelectric structure in which the conductive layers M of the eyes are short-circuited by electrodes and are not short-circuited by the odd-numbered conductive layers M.
7). (1) Layer L, layer D, and conductive layer M are stacked, (ii) at least one surface has conductive layer M, and (iii) layer L and layer D alternate via conductive layer M The total number of the layer L and the layer D is 3 or more. (Iv) Adhesion exceeding 1000 nm between the layer L and the conductive layer M and between the layer D and the conductive layer M Prepare a laminate with no agent layer,
(2) The laminate is thermally laminated at a temperature (Tg-5) to (Tsm + 20) ° C., a pressure of 2 to 10 MPa, and a time of 10 to 600 seconds.
(However, Tg is the highest glass transition temperature among the glass transition temperature of the resin L constituting the layer L and the glass transition temperature of the resin L constituting the layer D. The Tsm is the sub-peak temperature of the layer L. And the lowest sub-peak temperature among the sub-peak temperatures of layer D.)
2. The method for producing a laminated film according to 1 above, comprising each step.
8). 8. The manufacturing method according to 7 above, wherein the laminate has an adhesive layer having a thickness of 1000 nm or less between the layer L and the conductive layer M, between the layer D and the conductive layer M, or both.
9. 8. The manufacturing method according to 7 above, wherein the layer L, the layer D, or both of these layers are subjected to corona treatment on at least one side.

  ADVANTAGE OF THE INVENTION According to this invention, the laminated | multilayer film which shows the outstanding resonance characteristic at the time of a voltage application can be provided.

It is a schematic diagram which shows an example of the laminated structure of the laminated | multilayer film of this invention. FIG. 3 is a view showing the arrangement of laminated film conductive layers of Example 1. It is a figure which shows the position of the electrode for evaluating a resonance characteristic.

[Laminated film]
(Laminated structure)
In the laminated film of the present invention, an oriented film layer L made of a resin containing poly-L-lactic acid as a main component and an oriented film layer D made of a resin containing poly-D-lactic acid as a main component are alternately layer L and The total number of layers D is 3 or more, and has a laminated structure having conductive layers M between adjacent layers L and D and at least one surface of the obtained laminated film. 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%.
The laminated structure of the laminated film of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing an example of a laminated structure of the laminated film of the present invention. In FIG. 1, the code | symbol 1 shows the orientation film layer L which consists of resin which has poly L-lactic acid as a main component, and the code | symbol 2 shows the orientation film layer D which consists of resin which has poly D-lactic acid as a main component, respectively. In the laminated film of the present invention, the layer L and the layer D are thus alternately laminated in a total of three or more layers. FIG. 1 shows a case where the total number of layers L and D is seven. Further, as shown in FIG. 1B, the layer L and the layer D may be opposite to those in FIG.

Reference numeral 3 denotes a conductive layer M. In the present invention, the conductive layer M (reference numerals 302 to 307) is provided between the layer L and the layer D. In addition, the conductive film M (reference numeral 301) is provided on at least one surface of the laminated film. Further, as shown in FIG. 1C, a conductive layer M (reference numeral 308) may be provided on the other surface.
The layers L and M, and the layers D and M are 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, it is preferable that the layer L and the layer M, and the layer D and the layer M are fixed without an adhesive layer having a thickness of more than 500 nm, and an adhesive layer having a thickness of more than 200 nm is formed. An embodiment in which they are fixed without being interposed 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.

(Number of layers)
In the laminated film of the present invention, the total number of layers L and D is 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 10 or more, and more preferably 20 or more.
In this way, increasing the total number of layers in the stack tends to increase the momentum obtained by the piezoelectric characteristics, but as the total number of layers increases, the stacked film tends to become stiff, so from a certain point The effect of improving the resonance characteristics may be reduced. From such a viewpoint, the upper limit of the substantial total number is about 10,000, preferably about 1000. 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 and thousands order.

[Characteristics of laminated film]
(Resonance characteristics)
The laminated film of the present invention has a piezoelectric property and vibrates when a voltage having a certain frequency is applied. Particularly, since the piezoelectric property is excellent, a large momentum (force) can be generated at the same time, for example, The actuator can generate a large momentum (force). For this reason, a structure in which the laminated film of the present invention and a plate-like object having a certain natural frequency (for example, an acrylic plate) are bonded together has a voltage of an appropriate frequency in consideration of the natural frequency of the plate-like object. As a result, the phenomenon that the frequency of the laminated film (frequency of applied voltage) and the natural frequency of the plate-like object resonate and the structure moves greatly (resonance characteristics) is observed. Such a phenomenon is a phenomenon that cannot be seen in a conventional polymer film actuator such as PVDF because the momentum (force) that can be generated when a voltage is applied is small.
In the present invention, the fact that the momentum (force) that can be generated is large and the amount of movement of the structure is large is said to be excellent in resonance characteristics.

(Main orientation direction)
In the laminated film of the present invention, the angle formed by the main alignment direction of the layer L and the main alignment direction of the layer D is preferably 10 degrees or less. 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.

(Refractive index)
In the laminated film of the present invention, it is preferable that the refractive indexes in the main alignment direction of the layer L and the layer D are each independently 1.45 or more. When the refractive index is in the above numerical range, the effect of improving the resonance characteristics can be enhanced. When the refractive index is low, the effect of improving the resonance characteristics tends to be low. On the other hand, when the refractive index is high, the effect of improving the resonance characteristics tends to be high, but when too high, the mechanical properties of the film tend to be inferior. It is in. From such a viewpoint, the refractive index in the main alignment direction is more preferably 1.45 to 1.48, and still more preferably 1.45 to 1.47.

(density)
In the laminated film of the present invention, it is preferable that the densities of the layer L and the layer D are each independently 1.24 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 1.24 to 1.26 g / cm ³ , and further preferably 1.245 to 1.255 g / cm ³ .
Hereinafter, each component which comprises the laminated | multilayer film of this invention is demonstrated.

[Oriented film layer L, oriented film layer D]
The oriented film layer L and the oriented film layer D in the present invention are oriented film layers made of a resin having poly L-lactic acid and poly D-lactic acid as main components, respectively.

(Polylactic acid)
The poly L-lactic acid, which is a main component in the resin constituting the oriented film layer L in the present invention, is substantially composed of only L-lactic acid units (hereinafter sometimes abbreviated as PLLA). Or a copolymer of L-lactic acid and other monomers, and is particularly preferably poly-L-lactic acid substantially composed of only L-lactic acid units.
In addition, poly D-lactic acid, which is a main component in the resin constituting the oriented film layer D in the present invention, may be abbreviated as poly D-lactic acid (hereinafter referred to as PDLA) substantially composed of only D-lactic acid units. ), And a copolymer of D-lactic acid and other monomers, etc., particularly poly-D-lactic acid which is substantially composed only of D-lactic acid units.
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.

(Copolymerization component)
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 copolymerization component is 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, 2 carbon atoms To 30 or more monomers selected from aromatic diols such as aliphatic dicarboxylic acid, terephthalic acid, isophthalic acid, hydroxybenzoic acid, hydroquinone, and aromatic dicarboxylic acid.

(Polylactic acid production method)
The method for producing poly L-lactic acid and poly D-lactic acid is not particularly limited, and conventionally known methods 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 above-mentioned predetermined characteristics. For example, lactide melt-opening polymerization catalysts include alkali metals, alkaline earth metals, rare earths, transition metals, fatty acid salts such as aluminum, germanium, tin, antimony, carbonates, sulfates, phosphates, oxides, Examples include hydroxides, halides, alcoholates and the like. Among these, a catalyst containing at least one selected from the group consisting of tin, aluminum, zinc, calcium, titanium, germanium, manganese, magnesium and rare earth elements is preferable (hereinafter, such a catalyst is referred to as a specific metal-containing catalyst). May be.)

Such specific metal-containing catalysts are conventionally known and exemplified as follows. Stannous chloride, stannous bromide, stannous iodide, stannous sulfate, stannic oxide, tin myristate, tin octylate, tin stearate, tetraphenyltin, tin methoxide, tin ethoxide, tin Butoxide, aluminum oxide, aluminum acetylacetonate, aluminum isopropoxide, aluminum-imine complex titanium tetrachloride, ethyl titanate, butyl titanate, glycol titanate, titanium tetrabutoxide, zinc chloride, zinc oxide, diethyl zinc, trioxide Examples include antimony, antimony tribromide, antimony acetate, calcium oxide, germanium oxide, manganese oxide, manganese carbonate, manganese acetate, magnesium oxide, and yttrium alkoxide.
Of these, stannous chloride, stannous bromide, stannous iodide, stannous sulfate, stannic oxide, tin myristate from the viewpoint of good catalytic activity and few side reactions. , Tin-containing compounds such as tin octylate, tin stearate, and tetraphenyltin, and aluminum-containing compounds such as aluminum acetylacetonate, aluminum butoxide, and aluminum-imine complexes are preferred. More preferred are diethoxytin, dinonyloxytin, tin myristate, tin octylate, tin stearate, tin chloride, aluminum acetylacetonate, aluminum isopropoxide and the like.

The amount of the catalyst used is 0.42 × 10 ⁻⁴ to 100 × 10 ⁻⁴ mol per kg of lactide, and is preferably 1.68 × from the viewpoint of reactivity, color tone of the resulting polylactide, and stability. 10 ⁻⁴ to 42.1 × 10 ⁻⁴ mol, particularly preferably 2.53 × 10 ⁻⁴ to 16.8 × 10 ⁻⁴ mol.
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.

(Thickness of layer L and layer D)
In the laminated film of the present invention, the thicknesses of the layer L and the layer D should be thick enough to exhibit resonance characteristics in consideration of the tendency that the rigidity becomes too high and the resonance characteristics are not achieved. If it does not specifically limit. 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 of the layers L and D is preferably 10 μm or less, more preferably 8 μm or less, and particularly preferably 7 or less μm. 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.

[Conductive layer M]
The type of the conductive layer M in the present invention is not particularly limited as long as the laminated film of the present invention has conductivity sufficient to exhibit piezoelectric characteristics when a voltage is applied, but the type of the conductive layer M is more preferably piezoelectric. From the viewpoint of exhibiting characteristics and resonance characteristics, a layer made of a metal or metal oxide is preferable.
The 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 1 × 10 ⁴ Ω / □ or less, preferably 5 × 10 ³ Ω / □ or less, more preferably 1 × 10 ³ Ω / □ or less. Such a thickness may be selected. For example, the thickness is preferably 10 nm 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, and it is difficult to form a laminated film, or the strength between layers of the laminated film tends to be weak.
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. In addition, an appropriate method can be adopted depending on the required film thickness. 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.

[Production method of laminated film]
In the laminated film of the present invention, the layer L may be referred to as a resin for forming the layer D (hereinafter referred to as the resin D) from the resin for forming the layer L (hereinafter sometimes referred to as the resin L). ) To D are separately formed, the conductive layer M is provided on the surface of each obtained layer, the layer L and the layer D alternate, and between the layer L and the layer D, and the resulting laminated film It can obtain by laminating | stacking and adhering so that it may become the structure which has the conductive layer M on the at least one surface.
Hereinafter, an example of a preferable method for producing the laminated film of the present invention will be described. Moreover, about manufacture of an oriented film layer, although the method to manufacture the oriented film layer L is demonstrated, the raw material to be used is similarly manufactured also about the oriented film layer D as resin D which uses poly D-lactic acid as a main component. be able to.

(Extrusion process)
First, poly L-lactic acid (in the case of layer L. In the case of layer D, it is referred to as poly D-lactic acid) containing a carboxyl group-capping agent, a lubricant, and other additives, which will be described later, if desired. Resin L (when poly L-lactic acid is used. When poly D-lactic acid is used, 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 240 to 300 ° C, more preferably 245 to 280 ° C, and particularly preferably 250 to 275 ° 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 or a biaxial direction to obtain a uniaxially stretched film or a biaxially stretched film. In order to obtain such a uniaxially stretched film or a biaxially stretched film, the unstretched film is stretched by heating to a temperature at which the unstretched film can be stretched, for example, a glass transition temperature (Tg) to (Tg + 80) ° C. of the resin L.
In the case of a uniaxially stretched film, the film may be uniaxially stretched in the machine axis direction (hereinafter sometimes referred to as the longitudinal direction or the longitudinal direction or MD), or in a direction perpendicular to the machine axis direction (hereinafter referred to as the transverse direction or It may be uniaxially stretched in the width direction or TD). The draw ratio is preferably 1.1 to 10 times, more preferably 1.1 to 7 times. The effect of improving the amount of displacement can be increased by setting the draw ratio within the above numerical range. When the draw ratio is high, the mechanical properties of the film tend to be inferior. On the other hand, when the draw ratio is low, the effect of improving the displacement tends to be low. From such a viewpoint, the draw ratio is more preferably 1.2 to 6, particularly preferably 2 to 5.

In the case of a biaxially stretched film, the stretching ratio in the longitudinal direction (hereinafter sometimes referred to as the longitudinal stretching ratio) is preferably 1.1 to 10 times, more preferably 1.1 to 7 times. is there. The stretching ratio in the transverse direction (hereinafter sometimes referred to as the transverse stretching ratio) is 1.1 to 10 times, preferably 1.1 to 7 times. By setting the draw ratio within the above numerical range, a preferred orientation mode in the present invention can be obtained, and the effect of improving the displacement can be increased. When the draw ratio in the longitudinal and / or transverse direction is high, the film tends to break and the productivity may be inferior. On the other hand, when it is low, it tends to be difficult to obtain a preferred orientation mode. Therefore, the effect of improving the displacement amount tends to be low. From such a viewpoint, the longitudinal draw ratio is more preferably 1.1 to 6 times, and particularly preferably 1.1 to 4.5 times. Further, the transverse draw ratio is more preferably 1.1 to 5.5 times, particularly preferably 1.1 to 4.5 times. Furthermore, when the difference between the longitudinal draw ratio and the transverse draw ratio is preferably 1 or more, more preferably 2 or more, and particularly preferably 2.5 or more, it is easy to obtain a preferred orientation mode in the present invention. Thus, the effect of improving the amount of displacement can be increased.
The biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching. Further, after biaxial stretching, it can be re-stretched in the longitudinal direction or the uniaxial direction of the lateral direction, or in the biaxial direction of the longitudinal direction and the lateral direction.

(Heat treatment process)
The unstretched film, uniaxially stretched film, and biaxially stretched film obtained above are preferably heat-treated. The heat treatment temperature is a temperature lower than the melting point of the resin L, and preferably 50 to 160 ° C., and the effect of improving the displacement can be increased. 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 60 to 150 ° C, and particularly preferably 80 to 130 ° 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.
As for the film forming conditions described above, it is preferable from the viewpoint of resonance characteristics that the layer forming conditions for the layer L and the layer D constituting the laminate are as close as possible to the physical properties.

(Corona treatment, primer treatment)
The oriented film layer thus obtained can be subjected to surface activation treatment, for example, plasma treatment, amine treatment, and corona treatment by a conventionally known method if desired.
Among these, from the viewpoint of improving the adhesion with the conductive layer M and enhancing the durability of the laminated film, it is 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.

Similarly, from the viewpoint of improving the adhesion with the conductive layer M, at least one surface, preferably both surfaces, of the oriented film layer can be subjected to primer treatment to form an adhesive layer. In this case, the thickness of the adhesive layer needs to be 1000 nm or less. When the thickness of the adhesive layer is too thick, the resonance characteristics are inferior. As described above, from the viewpoint of adhesiveness, the thickness of the adhesive layer may be appropriately selected so that appropriate adhesiveness can be imparted. However, from the viewpoint of resonance characteristics, the thinner one is preferable, preferably Is 500 nm or less, more preferably 200 nm or less. In the present invention, from the viewpoint of resonance characteristics, a particularly preferred embodiment is an embodiment that does not have an adhesive layer.
Such primer treatment can be performed by a so-called in-line coating method in the process of producing a film, or by a so-called offline coating method after producing the film.

(Deposition process, sputtering process)
The conductive layer M is formed on the surfaces of the oriented film layer L and the layer D obtained as described above. The formation of the conductive layer M is not particularly limited as long as it is a conventionally known method for forming a conductive layer, but from the viewpoint that a conductive layer having excellent conductivity can be obtained uniformly and easily, vapor deposition or sputtering. It is preferable to adopt the method.
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.

(Thermal lamination process)
The oriented 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.
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.

The pressure condition is preferably 2 to 10 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. From such a viewpoint, the more preferable pressure condition is 2 to 8 MPa, and particularly preferably 2 to 5 MPa.
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.

As described above, the laminated film of the present invention comprises (i) the layer L, the layer D, and the conductive layer M, (ii) the conductive layer M on at least one surface, and (iii) the layer L The layers D are alternately stacked via the conductive layer M, and the total number of the layers L and D is 3 or more. (Iv) Between the layer L and the conductive layer M, and between the layer D and the conductive layer Prepare a laminate with no adhesive layer exceeding 1000 nm in thickness between M and
(2) The laminate is thermally laminated at a temperature (Tg-5) to (Tsm + 20) ° C., a pressure of 2 to 10 MPa, and a time of 10 to 600 seconds.
(However, Tg is the highest glass transition temperature among the glass transition temperature of the resin L constituting the layer L and the glass transition temperature of the resin L constituting the layer D. The Tsm is the sub-peak temperature of the layer L. And the lowest sub-peak temperature among the sub-peak temperatures of layer D.)
It can be manufactured by each process.

[Components that may be added to Layer L and / or Layer D]
(Carboxyl group blocking agent)
The layer L and the layer D that constitute the laminated film of the present invention, that is, the resin L that constitutes the layer L and the resin D that constitutes the layer D each independently have a carboxyl group amount of 10 equivalents / 10 ^6. g or less is preferable from the viewpoints of stability during film casting, hydrolysis inhibition, and weight average molecular weight reduction suppression, and from this viewpoint, the carboxyl group amount is further 5 equivalents / 10 ⁶ g or less. It is preferably 2 equivalents / 10 ⁶ g or less. In order to set it as such an aspect, in this invention, it is preferable to mix | blend a carboxyl group sealing agent with the layer L and / or the layer D according to a use. 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.
The amount of the carboxyl group sealing agent used is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass per 100 parts by mass of polylactic acid in the resin constituting each layer of layer L or layer D. . In the present invention, a sealing reaction catalyst may be further used.

(Lubricant)
In the present invention, a lubricant may be contained in these films for the purpose of improving the winding and running properties of each oriented film layer and laminated 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. Moreover, a lubricant can be mix | blended in 0.01-0.5 mass% with respect to the mass of each layer of the layer L or the layer D. FIG.

(Resin component)
The layer L and / or the layer D in the present invention can each independently contain a resin component having a melting point higher than that of polylactic acid for the purpose of imparting heat resistance.
Such a resin component preferably has a melting point equal to or higher by 3 ° C. or more than polylactic acid, and can improve the heat resistance improvement effect. From such a viewpoint, the melting point of the resin component is more preferably 5 ° C. or more higher than that of polylactic acid, and particularly preferably 10 ° C. or more.
Preferred examples of the resin component include polyethylene naphthalate, polyethylene terephthalate, stereocomplex phase polylactic acid, polyetherimide, polyphenylene ether, poly (meth) acrylamide, and polystyrene.

The content of the resin component is preferably 10 to 50% by mass based on the mass of each layer. When the content is in the above numerical range, excellent heat resistance can be imparted while maintaining excellent resonance characteristics. When the content is too small, the effect of improving heat resistance tends to be low. From such a viewpoint, the content of the resin component is more preferably 20% by mass or more, and particularly preferably 30% by mass or more. On the other hand, when the content is too large, the piezoelectricity of each layer tends to be low, and the effect of improving the resonance characteristics tends to be low. From such a viewpoint, the content of the resin component is more preferably 45% by mass or less, and particularly preferably 40% by mass or less.
The method of containing the resin component is not particularly limited. For example, a mixture of pellets of polylactic acid constituting the oriented film layer and pellets of the resin component are obtained in advance, and the mixture is put into an extruder. Thus, the polylactic acid and the resin component can be melt-kneaded in the extruder.

(Other additives)
In addition, the layer L and / or the layer D are provided with an antioxidant, an antistatic agent, a colorant, a pigment, a fluorescent whitening agent, a plasticizer, a cross-linking agent, an ultraviolet absorber, and the like, as long as they do not contradict the spirit of the present invention. These resins can be added as necessary.

[Piezoelectric structure]
According to this invention, the piezoelectric structure which has the laminated | multilayer film and electrode of this invention is provided. When the piezoelectric structure is divided into an odd-numbered conductive layer M and an even-numbered conductive layer M, counting from the conductive layer M on the surface of the laminated film of the present invention as the first layer. The odd-numbered conductive layers M are short-circuited by the electrodes and are not short-circuited by the even-numbered conductive layers M, and the even-numbered conductive layers M are short-circuited by the electrodes. The conductive layer M has a structure that is not short-circuited.

  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) Resonance characteristics As shown in FIG. 3, a conductive adhesive (made by Fujikura Kasei, Dotite D550) is applied to both short sides of the obtained laminated film to form an electrode (symbol 6), and piezoelectricity 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.
Next, an acrylic plate (10 cm x 5 cm, thickness 5 mm) is bonded to one surface of this laminate with grease so that the long side of the laminated film and the long side of the acrylic plate are in the same direction. It was.
The acrylic plate was placed on the lower surface, and the plate was placed on a horizontal desk. A voltage was applied to the electrode formed as described above at a voltage of 600 Vpp and a frequency of 5.0 kHz, and the movement of the sample was observed.
A: Vibrates very vigorously and moves 5 cm or more.
○: Vibrates vigorously and moves from 1 cm to less than 5 cm.
Δ: Vibrates and moves less than 1 cm.
X: It does not vibrate and does not move.

(2) Peeling of laminated film The end of the laminated film was squeezed to make a notch, each layer was peeled off, the oriented film layer L and layer D were peeled off, and used for evaluating physical properties of each layer.
(3) Refractive index The film sample peeled from the laminated film was measured at a prism coupler (633 nm) wavelength using a laser refractive index measuring device manufactured by Metricon. Laser light is incident on the sample in close contact with the prism through the prism, and the prism is rotated to change the incident angle on the sample. The light reflected from the sample surface was measured, and the dependence of the amount of light on the incident angle was monitored to determine the refractive index corresponding to the critical angle.
(4) Density The film sample peeled from the laminated film was measured according to JIS standard C2151.
(5) Main orientation direction About the film sample which peeled from the laminated | multilayer film, in the plane of a film, it is 0 degrees (MD)-90 degrees (TD)-180 degrees, and the method as described in said (2) by 5 degree pitch The in-plane refractive index was measured, and the direction with the highest refractive index was defined as the main orientation direction. This was measured for all the oriented film layers, and the difference between the maximum angle and the minimum angle in the main alignment direction was defined as an “angle”.

(6) 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 250 ° C. to 250 ° C. at a rate of 20 ° C./min, and the sub-peak temperature (Tsm: ° C.) and melting point (Tm: ° C.) of the film were measured. Subsequently, after continuously holding at 250 ° C. for 5 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.
(7) 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 / □).

[Reference Example 1] Synthesis of poly L-lactic acid (PLLA) by melt ring-opening polymerization of lactide Vertical type equipped with full zone blades equipped with vacuum piping and nitrogen gas piping, catalyst, L-lactide solution addition piping, and alcohol initiator addition piping The stirring tank (40 L) was purged 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) by melt ring-opening polymerization of lactide Glass transition temperature (Tg) in the same manner as above except that D-lactide was used instead of L-lactide. Poly-D-lactic acid (PDLA) having a temperature 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 was obtained.

[Example 1]
(Manufacture of oriented film layer L)
The PLLA obtained in Reference Example 1 was sufficiently dried using a dryer, then charged into an extruder, melted at 210 ° C., and the molten resin was extruded from a die and formed into a single-layer sheet, 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, the both ends of the longitudinally stretched film were guided to a tenter while being held by clips, and stretched 4.0 times in the transverse direction in an atmosphere heated to 80 ° C. Thereafter, a heat treatment is performed in a tenter at a temperature of 110 ° C. for 30 seconds, followed by heat relaxation at 100 ° C. in the 1% width direction, and then uniformly cooled and cooled to room temperature, and 5 μm thick biaxially oriented poly L- A lactic acid monolayer film was obtained.

(Manufacture of oriented film layer D)
Using the PDLA obtained in Reference Example 2, a biaxially oriented poly-D-lactic acid monolayer film having a thickness of 5 μm was obtained in the same manner as the oriented film layer L.

(Corona treatment)
The surface of each oriented film layer obtained above on the side where the conductive layer M is to be 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. .

(Formation of conductive layer M)
A sample was cut into a rectangle with a long side of 6 cm and a short side of 3 cm so that the long side was 45 ° with respect to the main alignment axis direction of each oriented film layer obtained above. Then, in such a sample, as shown in FIG. 2, a 1 cm region (3 cm × 1 cm region) from one short side is masked as a margin to leave as a non-deposited portion (reference numeral 5), and the remaining region (3 cm In a region of × 5 cm, aluminum was deposited with a thickness such that the surface resistance value was 50Ω / □ (reference numeral 4). A total of 20 such samples were prepared for the oriented film layer L and 10 for the layer D. In addition, as shown in FIG. 2, margins were created on the short sides on the opposite sides of layer L and layer D, respectively.

(Create laminate)
As shown in FIG. 2, the obtained oriented film layer L and layer D having the conductive layer M are arranged so that the surfaces having the conductive layer M face up and the long sides and the short sides are combined, and the layers L and D And the margins of the conductive layer M on the layer L are aligned with one short side, and the margin of the conductive layer M on the layer D is aligned with the other short side. And a total of 20 sheets were laminated to make a laminate.

(Thermal lamination)
The obtained laminate was subjected to a heat press treatment for 3 minutes under conditions of a temperature of 110 ° C. and a pressure of 2 MPa to give a heat laminate, thereby obtaining a laminated film.
Table 1 shows the results of each evaluation performed on the obtained laminated film.

[Examples 2 to 13]
A laminated film was obtained in the same manner as in Example 1 except that the production conditions, configuration and lamination conditions of each layer were as shown in Table 1, and each evaluation was performed. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, when creating a laminate, an epoxy adhesive was applied to the surface of the oriented film layer L and the layer D on the side not having the conductive layer M to form an adhesive layer having a thickness of 2 μm. A laminated film was obtained in the same manner as in Example 1 except that thermal lamination was performed, and each evaluation was performed. The results are shown in Table 1.

[Example 14]
(Production of oriented film layer L having an adhesive layer)
The PLLA obtained in Reference Example 1 was sufficiently dried using a dryer, then charged into an extruder, melted at 210 ° C., and the molten resin was extruded from a die and formed into a single-layer sheet, 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. Next, an aqueous coating solution having a solid content concentration of 3% composed of the following coating layer composition was uniformly coated on one side of the longitudinally stretched film with a roll coater. Subsequently, both ends of the film were guided to a tenter while being held by clips, and stretched 4.0 times in the transverse direction in an atmosphere heated to 85 ° C. After that, heat treatment is performed in a tenter at a temperature of 110 ° C. for 30 seconds, then heat relaxed at 100 ° C. in the 1% width direction, and then uniformly cooled and cooled to room temperature to have a 5 μm thickness having an adhesive layer A biaxially oriented poly L-lactic acid monolayer film was obtained. In addition, it apply | coated so that the thickness of the adhesive bond layer after drying might be set to 200 nm.

Composition for coating layer:
The composition for coating layer is composed of the following acrylic, polyester, particles, wetting agent, and additive, and the solid content ratio of each component in the resulting adhesive layer is 25% by mass of acrylic, 62% by mass of polyester, and 3% by mass of particles. Each component was mixed and diluted with ion-exchanged water so that the wetting agent was 5% by mass and the additive was 5% by mass.
Acrylic: acrylic resin (Tg = 50 ° C.) composed of 30% by mole of methyl methacrylate / 2% by mole of 2-isopropenyl-2-oxazoline / 10% by mole of polyethylene oxide (n = 10) methacrylate / 30% by mole of acrylamide Using. The acrylic resin was produced by the following method, and conformed to the method described in Production Examples 1 to 3 of JP-A No. 63-37167. That is, 302 parts of ion-exchanged water was charged into a four-necked flask and heated to 60 ° C. in a nitrogen stream, and then 0.5 parts of ammonium persulfate and 0.2 part of sodium hydrogen nitrite were added as a polymerization initiator. Furthermore, a mixture of monomers, 23.3 parts of methyl methacrylate, 22.6 parts of 2-isopropenyl-2-oxazoline, 40.7 parts of polyethylene oxide (n = 10) methacrylic acid, and 13.3 parts of acrylamide. The solution was added dropwise over 3 hours while adjusting the liquid temperature to 60 to 70 ° C. After completion of dropping, the reaction was continued with stirring while maintaining the same temperature range for 2 hours, and then cooled to obtain an acrylic aqueous dispersion having a solid content of 25%.

Polyester: The acid component is composed of 63 mol% of 2,6-naphthalenedicarboxylic acid / 32 mol% of isophthalic acid / 5 mol% of 5-sodium sulfoisophthalic acid, and the glycol component is composed of 90 mol% of ethylene glycol / 10 mol% of diethylene glycol. Polyester (Tg = 76 ° C., average molecular weight 12000) was used. Polyester was produced by the following method and conformed to the method described in Example 1 of JP-A No. 06-116487. That is, 42 parts of dimethyl 2,6-naphthalenedicarboxylate, 17 parts of dimethyl isophthalate, 4 parts of dimethyl 5-sodium sulfoisophthalate, 33 parts of ethylene glycol and 2 parts of diethylene glycol were charged into a reactor. 05 parts were added, the temperature was controlled at 230 ° C. in a nitrogen atmosphere, and the resulting methanol was distilled off to conduct a transesterification reaction. Subsequently, the temperature of the reaction system was gradually raised to 255 ° C., and the pressure inside the system was reduced to 1 mmHg to carry out a polycondensation reaction to obtain a polyester.

Particles: Silica inorganic particles (average particle size: 100 nm) were used.

Wetting agent: Polyoxyethylene (n = 7) lauryl ether (manufactured by Sanyo Chemical Co., Ltd., trade name “Naroacty N-70”) was used.

Additive: Carnauba wax (manufactured by Chukyo Yushi Co., Ltd., trade name “Cerosol 524”) was used.

(Production of oriented film layer D having an adhesive layer)
Using the PDLA obtained in Reference Example 2, a biaxially oriented poly D-lactic acid monolayer film having a thickness of 5 μm having an adhesive layer was obtained in the same manner as the oriented film layer L having the adhesive layer. .
Using each of the oriented film layers obtained above, no corona treatment was performed, and a laminated film was obtained in the same manner as in Example 1 except that the conductive layer M was formed on the adhesive layer of each oriented film. It was. Table 1 shows the results of each evaluation performed on the obtained laminated film.

  According to the present invention, it is possible to easily obtain a laminated film that exhibits resonance characteristics by voltage application. Therefore, the laminated film of the present invention can be used as a vibrating body such as a microphone, a pickup, a buzzer, a speaker, an optical switch, or a fan.

1 Oriented film layer L
2 Oriented film layer D
3 Conductive layer M
4 Locations where vapor deposition 5 Locations where vapor deposition is not performed 6 Electrode

Claims (9)

(I) having an oriented film layer L made of a resin L containing poly L-lactic acid as a main component, an oriented film layer D made of a resin D containing poly D-lactic acid as a main component, and a conductive layer M;
(Ii) having a conductive layer M on at least one surface;
(Iii) Layer L and layer D are alternately stacked via conductive layer M, and the total number of layers L and D is 3 or more,
(Iv) There is no adhesive layer exceeding a thickness of 1000 nm between the layer L and the conductive layer M and between the layer D and the conductive layer M.
Laminated film. The laminated film according to claim 1, wherein an angle formed by the main alignment direction of the layer L and the main alignment direction of the layer D is 10 degrees or less. The laminated film according to claim 1 or 2, wherein the refractive indices in the main alignment direction of the layer L and the layer D are each independently 1.45 or more. The laminated film according to any one of claims 1 to ³ , wherein the densities of the layer L and the layer D are each independently from 1.24 to 1.27 g / cm ³ . The thickness of the layer L and the layer D is 10 micrometers or less each independently, The laminated | multilayer film of any one of Claims 1-4. It is a piezoelectric structure which has a laminated | multilayer film and an electrode of any one of Claims 1-5, Comprising: The conductive layer M of the surface of this laminated film is made into the 1st layer, and it counts from there in order, and is an odd-numbered layer. When the conductive layer M is divided into the even-numbered conductive layer M, the odd-numbered conductive layers M are short-circuited by the electrodes and are not short-circuited with the even-numbered conductive layers M. A piezoelectric structure in which the conductive layers M are short-circuited by electrodes and are not short-circuited by the odd-numbered conductive layers M. (1) Layer L, layer D, and conductive layer M are stacked, (ii) at least one surface has conductive layer M, and (iii) layer L and layer D alternate via conductive layer M The total number of the layer L and the layer D is 3 or more. (Iv) Adhesion exceeding 1000 nm between the layer L and the conductive layer M and between the layer D and the conductive layer M Prepare a laminate with no agent layer,
(2) The laminate is thermally laminated at a temperature (Tg-5) to (Tsm + 20) ° C., a pressure of 2 to 10 MPa, and a time of 10 to 600 seconds.
(However, Tg is the highest glass transition temperature among the glass transition temperature of the resin L constituting the layer L and the glass transition temperature of the resin L constituting the layer D. The Tsm is the sub-peak temperature of the layer L. And the lowest sub-peak temperature among the sub-peak temperatures of layer D.)
The manufacturing method of the laminated | multilayer film of Claim 1 containing each process. The manufacturing method according to claim 7, wherein the laminate includes an adhesive layer having a thickness of 1000 nm or less between the layer L and the conductive layer M, between the layer D and the conductive layer M, or both. 8. The manufacturing method according to claim 7, wherein the layer L, the layer D, or both of these layers are subjected to corona treatment on at least one side.