JP6082511B2 - Laminated film - Google Patents

Description

  The present invention relates to a laminated film. More specifically, the present invention relates to a laminated film that generates displacement by applying a voltage.

Conventional polymer piezoelectric materials include poly-γ benzyl L-glutamate and the like, electret type such as polyvinyl chloride, polyvinylidene fluoride, vinylidene fluoride trifluoride ethylene copolymer, vinylidene cyana There are various types such as ferroelectric type ones such as id 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 and used as a vibrating body such as a microphone, pickup, buzzer, speaker, optical switch, and fan (Patent Document 3).
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. In addition, in such a joining method, it is difficult to make the polarization directions of the polymer piezoelectric films the same, and there is a problem that the amount of displacement when a voltage is applied is insufficient.

JP-A-5-152638 JP 2005-213376 A JP 59-115580 A

  Accordingly, an object of the present invention is to provide a laminated film that causes a large displacement when a voltage is applied. Moreover, the objective of this invention is providing the method of manufacturing this laminated | multilayer film, without requiring complicated processes, such as a lamination process.

The present invention adopts the following configuration in order to solve the above problems.
(1) The main component is layer A containing poly (L-lactic acid) containing 90 to 100 mol% of L-lactic acid units, and poly (D-lactic acid) containing 90 to 100 mol% of D-lactic acid units. Having layer B as a component;
(I) the main alignment direction of layer A and the main alignment direction of layer B are substantially the same;
(Ii) Layer A and Layer B are joined without an adhesive.
Laminated film for piezoelectric materials.
(2) The laminated film for piezoelectric materials according to (1), wherein the refractive index in the main orientation direction is 1.45 or more.
(3) density of 1.24~1.27g / cm ³ above (1) or laminate fill beam piezoelectric material according to (2).

Moreover, this invention includes the following manufacturing methods.
(4) Resin composition A mainly composed of poly-L-lactic acid having a content of L-lactic acid units for forming layer A of 90 to 100 mol%, and D-lactic acid units for forming layer B The resin composition B mainly containing poly D-lactic acid having a content of 90 to 100 mol% is melted in separate extruders, and then the resin composition A and the resin composition B are melted. A method for producing a laminated film for a piezoelectric material that is laminated with a die and extruded from a die.
(5) The production method according to (4) , wherein the resin composition A and the resin composition B are in contact with each other when laminated in a molten state.
(6) Described in (4) or (5) above, after being extruded from a die, stretched at least 1.1 to 10 times in a uniaxial direction, and heat-treated at a temperature lower than the melting point of poly L-lactic acid and poly D-lactic acid. Manufacturing method.

  The laminated film of the present invention produces a large displacement when a voltage is applied. According to the production method of the present invention, it is possible to provide a laminated film that generates a displacement having a sufficient size when a voltage is applied without going through a complicated process such as a laminating process.

[Laminated film]
The laminated film of the present invention comprises a layer A mainly composed of poly-L-lactic acid having an L-lactic acid unit content of 90 to 100 mol%, and a poly-D having a D-lactic acid unit content of 90 to 100 mol%. -It has the layer B which has lactic acid as a main component. Hereinafter, poly L-lactic acid and poly D-lactic acid may be collectively referred to as polylactic acid. Here, “main” means that the polylactic acid contained in each layer is 60% by mass or more, preferably 75% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass with respect to the mass of each layer. % Or more.
In the present invention, as long as it has at least one layer A and one layer B in the laminated film, it may have other layers as long as the object of the present invention is not impaired. You may have between B and you may have on the outer layer side of the layer A or the layer B. In the present invention, an aspect in which the layer A and the layer B are in contact with each other is preferable, and by adopting such an aspect, the effect of improving the amount of displacement can be further increased.

[Characteristics of laminated film]
(Displacement)
The laminated film of the present invention is bent by applying a voltage, so that when one end is fixed, the other end on the opposite side is displaced. In this invention, it is preferable that the displacement amount calculated | required by the measuring method mentioned later is 1 mm or more. When the amount of displacement is large, a vibrating body with better performance can be obtained when used as a vibrating body in the above-described applications. From such a viewpoint, the amount of displacement is more preferably 1.3 mm or more, further preferably 1.5 mm or more, and particularly preferably 3 mm or more.
In order to achieve such a displacement, the layers A and B in the present invention may be laminated by a coextrusion method. By laminating by the coextrusion method, it is possible to increase the identity of the main alignment directions of the layer A and the layer B, thereby increasing the amount of displacement. In order to further increase the amount of displacement, the thickness, orientation mode, crystallinity, density, and the like of each layer may be adjusted as appropriate. For example, the amount of displacement tends to increase by increasing the orientation, crystallinity, and density.

(Thickness of each layer)
In the laminated film of the present invention, the thickness (T (A)) of the layer A is preferably 1 to 200 μm, more preferably 2 to 150 μm, and particularly preferably 5 to 60 μm. The thickness (T (B)) of the layer B is preferably 1 to 200 μm, more preferably 2 to 150 μm, and particularly preferably 5 to 60 μm. When the thicknesses of the layer A and the layer B are in the above numerical range, the effect of improving the amount of displacement can be increased.
Moreover, it is preferable that the ratio (T (A) / T (B)) of the thickness of the layer A and the thickness of the layer B is 0.05-19. When the thickness ratio is in the above numerical range, the effect of improving the displacement can be increased. From such a viewpoint, the thickness ratio is more preferably 0.2 to 5, and particularly preferably 0.5 to 2.

(Main orientation direction)
In the laminated film of the present invention, the main alignment direction of layer A and the main alignment direction of layer B are substantially the same. Here, the “main alignment direction” indicates the maximum alignment direction in the in-plane direction of the layer A or the layer B. Further, “substantially the same” means that the angle formed between the main alignment direction of the layer A and the main alignment direction of the layer B is 10 degrees or less, preferably 5 degrees or less, more preferably 3 degrees or less, and particularly preferably 1 It is less than or equal to degrees, and ideally it is 0 degrees. When the main orientation directions of the layer A and the layer B are substantially the same, the amount of displacement can be increased. In the present invention, by obtaining a laminated film by a co-extrusion method, it is possible to easily achieve the above-described aspect of the main orientation direction and obtain a laminated film having a large displacement.

(Refractive index)
The laminated film of the present invention preferably has a refractive index in the main alignment direction of 1.45 or more. When the refractive index is in the above numerical range, the effect of improving the displacement can be increased. When the refractive index is low, the displacement improvement effect tends to be low. On the other hand, when the refractive index is high, the displacement improvement effect tends to be high, but when it is 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)
The laminated film of the present invention preferably has a density of 1.24 to 1.27 g / cm ³ . When the density is in the above numerical range, the effect of improving the displacement can be increased. When the density is low, the effect of improving the amount of displacement tends to be low. On the other hand, when the density is high, the effect of improving the amount of displacement is high, but the mechanical properties 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.

[Polylactic acid]
(Poly L-lactic acid)
The content of the L- lactic acid unit in Lupo Li L- lactic acid make up the layer A in the present invention, crystalline aspect, also the viewpoint of high effect of improving the displacement amount, and Ri by the viewpoint of the film heat resistance 90 100 mol%, favorable Mashiku 95 to 100 mol%, more preferably from 98 to 100 mol%. That is, the content of units other than L- lactic acid units, 0 - 10 mol%, favorable Mashiku 0-5 mol%, more preferably from 0 to 2 mol%.

Such poly-L-lactic acid preferably has crystallinity, and it becomes easy to obtain the above-described orientation / crystal mode, and the effect of improving the amount of displacement can be enhanced. 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 poly L-lactic 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.

(Poly D-lactic acid)
The content of D- lactic acid unit in Lupo Li D- lactic acid make up the layer B in the present invention, crystalline aspect, also the viewpoint of high effect of improving the displacement amount, and Ri by the viewpoint of the film heat resistance 90 100 mol%, favorable Mashiku 95 to 100 mol%, more preferably from 98 to 100 mol%. That is, the content of units other than D- lactic acid unit is 0 - 10 mol%, favorable Mashiku 0-5 mol%, more preferably from 0 to 2 mol%.

Such poly-D-lactic 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 enhanced. 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 poly D-lactic 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. 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.
In the present invention, the poly L-lactic acid having the above preferred embodiment and the poly D-lactic acid having the above preferred embodiment are preferably used at the same time because the effect of improving the displacement can be further enhanced.

(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.

[Production method of polylactic acid]
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.

[Production method of laminated film]
In the laminated film of the present invention, the resin composition A for forming the layer A and the resin composition B for forming the layer B are melted in separate extruders, and the respective molten resins are extruded. It is manufactured by a so-called co-extrusion method in which it is laminated and extruded in a machine or a die. By adopting such a manufacturing method, the angle formed by the main orientation directions of the layer A and the layer B can be reduced, whereby the amount of displacement can be increased, and the productivity is excellent.
Hereinafter, a preferred method for producing the laminated film of the present invention by a coextrusion method will be described.

(Extrusion process)
First, a resin composition A containing poly L-lactic acid as a main component and a resin composition B containing poly D-lactic acid as a main component, which contains a carboxyl group-blocking agent, a lubricant, and other additives as described later if desired. Are melted in separate extruders, laminated in a molten state, and extruded from a die onto a cooling drum. In addition, in order to suppress decomposition | disassembly at the time of a fusion | melting, the resin composition supplied to an extruder is preferable to perform a drying process before an extruder supply, and to make a water content into about 100 ppm or less.
The resin temperature in the extruder is a temperature at which the resin has sufficient fluidity, that is, a range of (melting point (Tm) +20 of polylactic acid) to (Tm + 50) (° C.), but melting at a temperature at which the resin does not decompose. It is preferable to extrude, 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.

  The molten resin is laminated by a conventionally known method such as a method using a feed block or a method using a multi-manifold die. In such lamination, the layer A and the layer B are not necessarily limited to the mode in which they are in contact with each other. For example, other layers may be provided between the layer A and the layer B. In the present invention, the resin composition A for forming the layer A and the resin composition for forming the layer B are used. A mode in which the product B is in contact with the product B in a molten state can be given as a preferable mode. With such an embodiment, the adhesion between the layer A and the layer B is improved, and thereby the effect of improving the displacement can be increased.

(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 as necessary 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, that is, a glass transition temperature (Tg) to (Tg + 80) ° C. of polylactic acid.
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 polylactic acid component, 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.
The laminated film of the present invention thus obtained can be subjected to surface activation treatment such as plasma treatment, amine treatment and corona treatment by a conventionally known method if desired. Moreover, you may provide coating layers, such as a slippery layer, an easily bonding layer, a mold release layer, by what is called an in-line coating method in the process of manufacturing a film, or what is called an offline coating method after manufacturing a film.

[Ingredients that may be added to Layer A and / or Layer B]
(Carboxyl group blocking agent)
In the laminated film of the present invention, the amount of carboxyl groups is preferably 10 equivalents / 10 ⁶ g or less from the viewpoint of stability during film casting, hydrolysis inhibition, and weight average molecular weight reduction inhibition. 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 obtain such an embodiment, in the present invention, it is preferable to add a carboxyl group sealing agent to the layer A and / or the layer B depending on the application. In addition to sealing the terminal carboxyl group of polylactic acid, the carboxyl group sealing agent seals the carboxyl group of low molecular weight compounds such as carboxyl group, lactic acid, and formic acid generated by the decomposition reaction of polylactic acid and various additives. The resin temperature at the time of film formation can be increased 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 constituting each layer of layer A or layer B. In the present invention, a sealing reaction catalyst may be further used.

(Lubricant)
In the laminated film of the present invention, a lubricant can be contained in the laminated film for the purpose of improving film winding and running properties.
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 polylactic acid which comprises each layer of the layer A or the layer B.

(Other additives)
In addition, the layer A and / or the layer B 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 the gist of the present invention is not exceeded. These resins can be added as necessary.

  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) Displacement Electrode is deposited on both sides of the sample with a thickness such that the surface resistance value is about 100Ω / □ to form an electrode, and 10 mm (perpendicular to the main alignment direction) × 40 mm (main alignment direction) Cut out. Next, the cut sample was horizontally fixed so that the A layer was on the upper side, and electrodes were connected to the A layer side and the B layer side, respectively, and 25 V (Vpp) from both sides of the film. A voltage was applied at a frequency of 15 Hz, and the amount of displacement on the other short side was measured using a scale.
(2) Refractive index It measured with the prism coupler (633 nm) wavelength using the laser refractive index measuring apparatus made from 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.
(3) Density Measured according to JIS standard C2151.
(4) Glass transition temperature (Tg), melting point (Tm)
About 10 mg of sample was sealed in an aluminum pan for measurement and attached to a differential calorimeter (trade name “DSC2920” manufactured by TA instruments), heated from 25 ° C. to 250 ° C. at a rate of 20 ° C./min, 250 ° C. Hold for 5 minutes, then remove, immediately transfer to ice and quench. The pan was again attached to the differential calorimeter, and the glass transition temperature (Tg: ° C.) and melting point (Tm: ° C.) were measured by raising the temperature from 25 ° C. at a rate of 10 ° C./min.
(5) Main orientation direction In the plane of the film, the in-plane refractive index is measured by the method described in (2) at a pitch of 5 ° as 0 ° (MD) to 90 ° (TD) to 180 °. The direction with the highest refractive index was defined as the main orientation direction. This was measured on both surfaces, and the angle difference between the main orientation directions on each surface was defined as “angle formed”.

[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]
A poly L-lactic acid (PLLA) having a weight average molecular weight Mw of 120,000 obtained in Reference Example 1 and a poly D-lactic acid (PDLA) having a weight average molecular weight Mw of 120,000 obtained in Reference Example 2, respectively. After sufficiently drying using a dryer, each is put into separate extruders, melted at 210 ° C., the molten resins are merged inside the die, laminated, and extruded from the die to form a two-layer sheet. The sheet was molded and 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 by clips, and stretched 4 times in the transverse direction in an atmosphere heated to 80 ° C. After that, heat treatment is performed in a tenter for 30 seconds at a temperature of 110 ° C., followed by heat relaxation at 100 ° C. in the 1% width direction, and then uniformly cooled and cooled to room temperature, and a biaxially oriented two-layer laminate having a thickness of 80 μm A film was obtained. Table 1 shows the characteristics of the obtained laminated film.

[Examples 2 to 6]
A laminated film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 1. Table 1 shows the characteristics of the obtained laminated film.

[Comparative Example 1]
Poly L-lactic acid (PLLA) having a weight average molecular weight Mw of 120,000 obtained in Reference Example 1 is sufficiently dried using a dryer, and then charged into an extruder, melted at 210 ° C., and melted 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 by clips, and stretched 4 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 to obtain a 40 μm thick biaxially oriented poly L- A lactic acid monolayer film was obtained.

Next, using the poly D-lactic acid (PDLA) having a weight average molecular weight Mw of 120,000 obtained in Reference Example 2, a biaxially oriented poly D-lactic acid single layer film having a thickness of 40 μm was obtained in the same manner as described above.
Using these obtained films, an epoxy-based pressure-sensitive adhesive was applied in a thickness of 20 μm and bonded together by a laminating process at a temperature of 120 ° C. and a pressure of 2 atm for 1 minute to obtain a laminated film. At this time, the angle formed by the main orientation direction of each film was set to 15 degrees. Table 1 shows the characteristics of the obtained laminated film.

According to the present invention, it is possible to easily obtain a laminated film that is bent by voltage application and exhibits displacement. Further, since such a laminated film has a large displacement, when it is used as a vibrating body such as a microphone, a pickup, a buzzer, a speaker, an optical switch, or a fan, it can have a more excellent performance.

Claims (6)

Layer A containing poly-L-lactic acid as a main component having a content of L-lactic acid units of 90 to 100 mol% and poly-D-lactic acid having a content of 90 to 100 mol% as a main component Having layer B;
(I) the main alignment direction of layer A and the main alignment direction of layer B are substantially the same;
(Ii) Layer A and Layer B are joined without an adhesive.
Laminated film for piezoelectric materials. The laminated film for piezoelectric materials according to claim 1, wherein the refractive index in the main orientation direction is 1.45 or more. ^{3. The} laminated film for piezoelectric material according to claim 1, wherein the density is 1.24 to 1.27 g / cm ³ . Content of L-lactic acid unit for forming layer A having a main component of poly L-lactic acid having a content of 90 to 100 mol% and content of D-lactic acid unit for forming layer B Is melted in a separate extruder, and then the resin composition A and the resin composition B are laminated in a molten state. And a method for producing a laminated film for piezoelectric material extruded from a die. The manufacturing method according to claim 4 , wherein the resin composition A and the resin composition B are in contact with each other when laminated in a molten state. The method according to claim 4 or 5 , wherein after being extruded from the die, the film is stretched 1.1 to 10 times in at least a uniaxial direction and heat-treated at a temperature lower than the melting point of poly L-lactic acid and poly D-lactic acid.