JP2012056239A - Piezoelectric laminate and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric laminate excellent in adhesiveness with another layer while maintaining high piezoelectricity of polylactic acid resin.SOLUTION: The piezoelectric laminate includes an A layer containing the polylactic acid resin, and a B layer containing an unsaturated carboxylic acid polymer whose one surface is in contact with a surface of the A layer. The ratio of the number of C(=O)-O groups to the number of C(=O)-O-C groups ((the number of C(=O)-O groups)/(the number of C(=O)-O-C groups)) obtained by waveform analysis from a carbon 1s spectrum obtained by measuring a surface of the B layer by an X-ray photoelectron spectroscopy is at least 1.4 to 5.0.

Description

  The present invention relates to a piezoelectric laminate and a method for manufacturing the same.

In recent years, attention has been focused on using optically active polymers (optically active polymers) such as polypeptides and polylactic acids as piezoelectric materials. It is known that an optically active polymer exhibits piezoelectricity only by a mechanical stretching operation.
Among optically active polymers, the piezoelectricity of polymer crystals such as polylactic acid is due to C = O bond permanent dipoles present in the direction of the helical axis. In particular, polylactic acid has a small volume fraction of side chains with respect to the main chain and a large ratio of permanent dipoles per volume, and can be said to be an ideal polymer among the polymers having helical chirality.
It is known that polylactic acid that exhibits piezoelectricity only by stretching treatment does not require poling treatment and the piezoelectricity does not decrease over several years.
As described above, since polylactic acid has various piezoelectric properties, polymer piezoelectric materials using various polylactic acids have been studied.

By the way, polylactic acid pays attention to its biodegradability and the like, and is widely used for various uses such as a decorative sheet, an optical sheet for a display device, and a packaging film, in addition to the piezoelectric material.
Regardless of the application, polylactic acid is generally used in the form of a laminate including a layer containing polylactic acid and another layer. At this time, the adhesion between the polylactic acid-containing layer and other layers may be poor, and various studies have been made to improve the adhesion.

For example, in a laminate of a polylactic acid resin layer / adhesive layer / transparent inorganic thin film layer as a cosmetic sheet, a substrate made of a polylactic acid resin from the viewpoint of improving the adhesion between the polylactic acid resin layer and other layers It is known that the surface of the layer is subjected to surface activation treatment such as corona treatment or ozone treatment (for example, see Patent Document 1).
In addition, in a laminate of a polyester layer / polylactic acid resin layer / polyester layer as a cosmetic sheet, an unsaturated carboxylic acid is graft-polymerized in advance on the polyester layer as a method for obtaining a stable and strong adhesive force over time. A method is known (see, for example, Patent Document 2).
On the other hand, as an optical sheet for plasma display, a laminate composed of a resin composition containing a polylactic acid resin and an acrylic resin / a zinc oxide-based transparent conductive film layer, a polylactic acid resin, and an acrylic resin are included. A laminate of a resin composition layer / hard coat layer / zinc oxide-based transparent conductive film layer is known (see, for example, Patent Documents 3 and 4). In these laminates, the use of a resin composition of a polylactic acid resin and an acrylic resin improves adhesion between the resin composition layer and the zinc oxide-based transparent conductive film layer or hard coat layer. ing.

JP 2009-196288 A JP 2010-52335 A JP 2008-103104 A JP 2008-1003008 A

However, when a laminated body including a layer containing a polylactic acid resin and another layer is used as the piezoelectric material, it may be difficult to achieve both piezoelectricity and adhesiveness.
For example, in a normal surface activation treatment such as corona treatment or ozone treatment, sufficient adhesiveness may not be obtained, and piezoelectricity may decrease due to decomposition of the polylactic acid resin.
Further, in the method of graft polymerization of unsaturated carboxylic acid to polylactic acid resin, the helical structure of the molecular chain of polylactic acid resin is disturbed, and the piezoelectricity may be lowered.
Further, in the method using a resin composition containing a polylactic acid resin and an acrylic resin as described in Patent Documents 3 and 4, an acrylic resin having no helical chirality with respect to a polylactic acid resin having helical chirality is used. By adding a resin, the helical structure of the molecular chain of the polylactic acid resin may be disturbed and the piezoelectricity may be lowered.

This invention is made | formed in view of the above, and makes it a subject to achieve the following objectives.
That is, an object of the present invention is to provide a piezoelectric laminate having excellent adhesion to other layers while maintaining the high piezoelectricity of the polylactic acid resin.
Moreover, the objective of this invention is providing the manufacturing method of the piezoelectric laminated body excellent in adhesiveness with another layer, maintaining the high piezoelectricity of polylactic acid-type resin.

Specific means for solving the above-described problems are as follows.
<1> A layer containing a polylactic acid-based resin, and B layer containing an unsaturated carboxylic acid polymer in contact with the surface of the A layer on one side,
The number of C (= O) -O with respect to the number of C (= O) -O-C groups determined by waveform analysis from the carbon 1s spectrum obtained by measuring the surface of the B layer by X-ray photoelectron spectroscopy. A piezoelectric laminate having a number ratio [(C (= O) -O number) / (C (= O) -O-C group number)] of 1.4 or more and 5.0 or less.

<2> the A layer, the piezoelectric laminate according to <1> piezoelectric constant _{d 14} is 1pC / N~30pC / N at 25 ° C..
<3> The piezoelectric laminate according to <1> or <2>, wherein the film thickness of the B layer is 2 nm or more and 70 nm or less.
<4> The piezoelectric laminate according to any one of <1> to <3>, further including a C layer in contact with the other surface of the B layer.

<5> The piezoelectric laminate according to any one of <1> to <4>, wherein the unsaturated carboxylic acid polymer is an acrylic acid polymer.
<6> The layer B is a layer formed by performing plasma treatment on the surface of the layer A using an inert gas containing an unsaturated carboxylic acid under a pressure near atmospheric pressure < The piezoelectric laminate according to any one of 1> to <5>.

<7> The piezoelectric laminate according to any one of <4> to <6>, wherein the C layer includes a metal oxide compound.
<8> The piezoelectric laminate according to <7>, wherein the metal oxide compound includes at least one selected from the group consisting of zinc oxide (ZnO), indium tin oxide (ITO), and indium zinc oxide (IZO). .

<9> A method for producing the piezoelectric laminate according to any one of <1> to <8>,
Preparing a layer A containing a polylactic acid resin;
A layer B containing an unsaturated carboxylic acid polymer on the surface of the layer A by performing a plasma treatment on the surface of the layer A using an inert gas containing an unsaturated carboxylic acid under a pressure near atmospheric pressure. Forming a step;
Washing the formed B layer with a solvent;
The manufacturing method of the piezoelectric laminated body which has this.
<10> The method for producing a piezoelectric laminate according to <9>, further comprising a step of forming a C layer containing a metal oxide compound by vapor deposition on the surface of the B layer after the step of cleaning the B layer. .

ADVANTAGE OF THE INVENTION According to this invention, the piezoelectric laminated body excellent in adhesiveness with another layer can be provided, maintaining the high piezoelectricity of polylactic acid-type resin.
Moreover, according to this invention, the manufacturing method of the piezoelectric laminated body which is excellent in adhesiveness with another layer can be provided, maintaining the high piezoelectricity of polylactic acid-type resin.

It is a schematic diagram which shows an example of the plasma processing apparatus used in this embodiment.

≪Piezoelectric laminate≫
The piezoelectric laminate of the present invention has an A layer containing a polylactic acid-based resin, and a B layer containing an unsaturated carboxylic acid polymer in contact with the surface of the A layer on one side. The ratio of the number of C (= O) -O groups to the number of C (= O) -O-C groups obtained by waveform analysis from the carbon 1s spectrum obtained by measuring the surface by X-ray photoelectron spectroscopy. [(Number of C (= O) -O groups) / (number of C (= O) -O-C groups)] is 1.4 or more and 5.0 or less.
In the present invention, the ratio [(the number of C (═O) —O groups) / (the number of C (═O) —O—C groups)] is expressed as “[C (═O) —O] / [ C (= O) -O-C] ".

According to the piezoelectric laminate of the present invention, a specific B layer containing an unsaturated carboxylic acid polymer is provided as an adhesive layer on an A layer containing a polylactic acid-based resin. Adhesiveness with other layers can be improved.
Further, according to the piezoelectric laminate of the present invention, conventional adhesion improving treatment (for example, surface activation treatment such as corona treatment or ozone treatment, treatment of graft polymerization of unsaturated carboxylic acid to polylactic acid resin, Or, compared with the process of mixing an acrylic resin with a polylactic acid resin, it is possible to suppress a decrease in piezoelectricity of the polylactic acid resin.

The ratio [(C (= O) -O group number) / (C (= O) -O-C group number)] is the surface of the B layer (that is, the side not in contact with the A layer). Surface) is a ratio obtained by waveform analysis from a carbon 1s spectrum obtained by measuring by X-ray photoelectron spectroscopy (XPS (or also called Electron Spectroscopy for Chemical Analysis: ESCA)). .
Here, the number of C (═O) —O groups is within the range measured by the X-ray photoelectron spectroscopy, and ester bonds (C (═O) —O—C bonds) and carboxyl groups (C (= O) -OH groups).
Further, the number of C (═O) —O—C groups is the total number of ester bonds (C (═O) —O—C bonds) within the range measured by the X-ray photoelectron spectroscopy.
Here, the ester bond is mainly contained in the polylactic acid resin in the A layer, and the carboxyl group is mainly contained in the unsaturated carboxylic acid polymer in the B layer.

In the present invention, the ratio [(C (= O) -O group number) / (C (= O) -O-C group number)] is 1.4 or more and 5.0 or less.
The ratio [(the number of C (= O) -O groups) / (the number of C (= O) -O-C groups)] contributes to the adhesion to other layers (for example, a C layer described later). There is a correlation with the amount of the carboxyl group which is a group, and when the ratio is 1.4 or more, the adhesion to other layers becomes good.
When the ratio [(number of C (= O) -O groups) / (number of C (= O) -O-C groups)] is less than 1.4, the amount of carboxyl groups in the B layer is small. Therefore, the adhesiveness with other layers decreases.
On the other hand, when the ratio [(number of C (= O) -O groups) / (number of C (= O) -OC groups)] exceeds 5.0, the weight of unsaturated carboxylic acid in the B layer The cross-linking degree of the coalescence decreases, and the other layer (for example, C layer described later) is easily peeled off in the form that the B layer itself is broken. That is, even when the ratio [(number of C (= O) -O groups) / (number of C (= O) -O-C groups)] exceeds 5.0, adhesion to other layers Decreases.
The ratio [(the number of C (= O) -O groups) / (the number of C (= O) -O-C groups)] is 1.6 or more from the viewpoint of adhesion to other layers. 0 or less is preferable.

In the present invention, the ratio [(the number of C (= O) —O groups) / (the number of C (═O) —O—C groups)] is determined as follows.
First, from the carbon 1s spectrum obtained by measuring the surface of the B layer by X-ray photoelectron spectroscopy, the percentage of the number of C (═O) —O groups with respect to the total number of carbons (%) (%) , “[C (= O) −O] / [C]”).
Next, from the carbon 1s spectrum, the percentage of the number of C (═O) —O—C groups relative to the total number of carbons (%) (hereinafter referred to as “[C (═O) —O—C] / [C] ”).
By dividing (dividing) the “[C (═O) —O] / [C]” by the “[C (═O) —O—C] / [C]”, [C (═O) -O] / [C (= O) -O-C], that is, the ratio [(number of C (= O) -O groups) / (number of C (= O) -O-C groups)]. Ask.

In the present invention, the waveform analysis of the carbon 1s spectrum is performed as follows.
That is, among the plurality of peaks constituting the carbon 1s spectrum, the peak present on the lowest energy side (285.0 eV) is defined as a peak derived from carbon of C—C bond and C—H bond. Furthermore, the peak existing at about 286.5 eV is defined as a peak derived from carbon of C—O bond, and the peak present at about 287.1 eV is peak derived from carbon at the right end of C (═O) —O—C bond. And a peak existing at about 288.0 eV is a peak derived from carbon of C═O bond, and a peak existing at about 289.1 eV is a peak derived from carbon of C (═O) —O bond.

XPS may be measured under normal conditions. For example, X-ray source: monochromatic AlKα, vacuum: 1 × 10 ⁻⁹ mbar, output: 16 mA-10 kV. The waveform analysis may be performed by a normal method. For example, the obtained spectrum may be curve-fitted to separate the peaks with respect to the peak, and obtain the area ratio of the separated peaks.

<A layer containing polylactic acid resin>
The piezoelectric laminate of the present invention has an A layer containing polylactic acid resin as a layer having piezoelectricity.
There is no restriction | limiting in particular in the form of A layer, For example, it can be set as the form of a film, and the form of a board | substrate. The thickness of the A layer is not particularly limited, but is preferably 2 μm or more, for example, from the viewpoint of strength. From the viewpoint of workability, it is preferably 2000 μm or less.
Furthermore, from the viewpoint of piezoelectricity, 10 μm to 500 μm are preferable, and 10 μm to 300 μm are more preferable.

(Piezoelectric constant d ₁₄ )
As the A layer, in view of piezoelectric property such as, preferably a layer piezoelectric constant _{d 14} is 1pC / N~30pC / N at 25 ° C..
When the piezoelectric constant _{d 14} is at 1 pC / N or more, piezoelectricity of A layer is further improved.
When the piezoelectric constant _{d 14} is not more than 30 pC / N, the flexibility of the A layer is further improved.
In the present invention, the “piezoelectric constant d ₁₄ ” is one of the tensors of piezoelectricity, and is applied per unit shear stress when a shear stress is applied in the direction of the stretching axis of the stretched material and polarization occurs in the direction of the shear stress. Represents the generated charge density.
"Piezoelectric constant d _14" in the present invention corresponds to the real part of the complex piezoelectric constant d ₁₄ to be described later.
Numerical piezoelectric constant d ₁₄ indicating that piezoelectricity is higher the larger.
As the piezoelectric constant _{d 14} of the A layer, from the viewpoint of use as a piezoelectric device, more preferably 5pC / N~30pC / N, more preferably 8pC / N~30pC / N. Furthermore, 10 pC / N to 30 pC / N are more preferable, 12 pC / N to 30 pC / N are further preferable, and 15 pC / N to 30 pC / N are particularly preferable.

Piezoelectric constant d ₁₄ in the present invention, the test piece of polymeric piezoelectric material 10 mm × 3 mm square, is a value obtained by measuring using a "Leo b graph Solid S-1 type" of Toyo Seiki Seisakusho Co. . Specifically, at a frequency of 10 Hz, approximately 0.01 N / m ^{2 to} 0.1 N so that the maximum shear strain applied to the test piece at room temperature falls within the range of 0.01% to 0.1%. / M ² shear stress was applied, and the real part of the complex piezoelectric constant d ₁₄ of the test piece was measured.
Here, the complex piezoelectric constant d ₁₄ is calculated as “d ₁₄ = d ₁₄ ′ −id ₁₄ ″”, and “d ₁₄ ′” and “id ₁₄ ″” are “Rheograph Solid” manufactured by Toyo Seiki Seisakusho Co., Ltd. It is obtained from “S-1 type”. “D ₁₄ ′” represents the real part of the complex piezoelectric constant, “id ₁₄ ″” represents the imaginary part of the complex piezoelectric constant, and d ₁₄ ′ (real part of the complex piezoelectric constant) represents the piezoelectric constant in the present invention. corresponding to the d _14.
In addition, it shows that it is excellent in piezoelectricity, so that the real part of complex piezoelectricity is high.

(Crystallinity and orientation)
The layer A preferably has a crystallinity obtained by an X-ray diffraction method of 50% to 80%.
The lower limit of the crystallinity is more preferably 55% from the viewpoint of improving piezoelectricity. On the other hand, the upper limit of the crystallinity is preferably 80% and more preferably 70% from the viewpoint of the flexibility of the film.
Similarly, from the viewpoint of improving piezoelectricity, the orientation degree of the A layer obtained by the X-ray diffraction method is preferably 0.90 or more, and more preferably 0.94 or more.
The crystallinity and orientation degree of the A layer can be confirmed by measuring the A layer with an X-ray diffractometer.
The crystallinity and orientation of the A layer are measured under the following conditions, for example.

~ Crystallinity ~
Using “RINT2500” manufactured by Rigaku Corporation and a crystallinity analysis program manufactured by Rigaku Corporation as the apparatus, the diffraction profile of the sample is peak-separated into a crystal part and an amorphous part, and the crystallinity is calculated from the area ratio. The amorphous halo shape refers to the diffraction profile shape of a sample rapidly cooled from the melt.
The measurement conditions are as follows.
X-ray source: CuKα
Output: 50kV, 300mA
Measurement range: 2θ = 5-35 °
Detector: Scintillation counter

~ Degree of orientation ~
The sample is fixed to the sample holder, and the azimuth distribution intensity of the peak around 2θ = 16 ° is measured.
The apparatus is “RINT 2550” manufactured by Rigaku Corporation, and the measurement conditions are as follows.
X-ray source: CuKα
Output: 40kV, 370mA
Measurement range: β = -100 to 500 °
Detector: The axial orientation degree is calculated from the azimuth distribution curve measured by the scintillation counter according to the following equation.
Axial orientation degree F = (180−α) / 180
[In the above formula, α represents the half width of the orientation-derived peak]

(Haze)
The A layer preferably has a haze of 0.1 to 30 from the viewpoint of transparency required as a piezoelectric laminate. Here, the haze is a value obtained by measuring the A layer having a thickness of 0.05 mm with a haze measuring machine [TC Density Co., Ltd., TC-HIII DPK]. The haze is measured, for example, with respect to a measurement sample (A layer) processed to a width of 3 mm × length of 30 mm and a thickness of 0.05 mm by the method according to JIS-K7105 using the above-described haze measuring machine (25 ° C.). ° C).
The haze of the A layer is more preferably from 0.1 to 10, and particularly preferably from 0.1 to 5.
Further, the lower limit of the haze of the A layer is more preferably 0.5.

(Polylactic acid resin)
The A layer in the present invention contains a polylactic acid resin.
The polylactic acid resin in the present invention refers to “polylactic acid”, “copolymer of L-lactic acid or D-lactic acid and a copolymerizable polyfunctional compound”, or a mixture of both.
The above-mentioned “polylactic acid” is a polymer in which lactic acid is polymerized by ester bonds and is connected for a long time. For example, a lactide method via lactide and direct polymerization in which lactic acid is heated in a solvent under reduced pressure to remove water. It is known that it can be produced by a polymerization method or the like.
Examples of the “polylactic acid” include L-lactic acid homopolymer, D-lactic acid homopolymer, block copolymer including at least one polymer of L-lactic acid and D-lactic acid, and L-lactic acid and D-lactic acid. Examples include graft copolymers containing at least one polymer.

  Examples of the “copolymerizable polyfunctional compound” include glycolic acid, dimethyl glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, 2-hydroxyvaleric acid, 3 -Hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxycaproic acid, 3-hydroxycaproic acid, 4-hydroxycaproic acid, 5-hydroxycaproic acid, 6-hydroxycaproic acid, 6-hydroxy Hydroxycarboxylic acids such as methyl caproic acid and mandelic acid, glycolides, cyclic esters such as β-methyl-δ-valerolactone, γ-valerolactone, and ε-caprolactone, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid , Pimelic acid, azelaic acid, sebacic acid, undecanedioic acid, Polycarboxylic acids such as candioic acid and terephthalic acid, and anhydrides thereof, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1 , 4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, tetra Examples thereof include polyhydric alcohols such as methylene glycol and 1,4-hexanedimethanol, polysaccharides such as cellulose, and aminocarboxylic acids such as α-amino acids.

  Examples of the “copolymer of L-lactic acid or D-lactic acid and a copolymerizable polyfunctional compound” include a block copolymer or a graft copolymer having a polylactic acid sequence capable of forming a helical crystal.

  Examples of the polylactic acid resin include a method obtained by direct dehydration condensation of lactic acid described in JP-A-59-096123 and JP-A-7-033861, or US Pat. Nos. 2,668,182 and 4 , 057,357, etc., can be produced by a ring-opening polymerization method using lactide, which is a cyclic dimer of lactic acid.

-Optical activity-
The polylactic acid resin in the present invention preferably has optical activity from the viewpoint of further improving the piezoelectricity of the A layer.
More preferably, the polylactic acid resin is a helical chiral polymer having optical activity. Here, the helical chiral polymer having optical activity refers to a polymer having molecular optical activity in which the molecular structure is a helical structure.

  From the viewpoint of further improving the piezoelectricity of the A layer, the polylactic acid resin preferably has an optical purity of 99.00% ee or more, more preferably 99.50% ee or more, and 99.99. More preferably, it is% ee or more. Desirably, it is 100.00% ee. By setting the optical purity of the polylactic acid resin in the above range, it is considered that the packing property of the polymer crystal that exhibits piezoelectricity is enhanced, and as a result, the piezoelectricity is enhanced.

  In the present invention, the optical purity of the polylactic acid resin is a value calculated by the following formula.

  Optical purity (% ee) = 100 × | L body weight−D body weight | / (L body weight + D body weight)

That is, “the amount difference (absolute value) between the amount of L-form of polylactic acid resin [mass%] and the amount of D-form of polylactic acid resin [mass%]” (absolute value) ” The value obtained by multiplying (multiplying) the value obtained by dividing (dividing) the amount [mass%] by the total amount of the amount [mass%] and the amount of the D-form of polylactic acid resin [mass%] by (100) And
In addition, the value obtained by the method using a high performance liquid chromatography (HPLC) is used for the quantity [mass%] of the L body of an optically active polymer, and the quantity [mass%] of the optically active polymer D body.

  In order to increase the optical purity of the polylactic acid resin to 99.00% ee or more, for example, when polylactic acid is produced by the lactide method, the optical purity is increased to 99.00% ee or more by crystallization operation. It is preferred to polymerize the improved lactide.

-Weight average molecular weight-
The polylactic acid resin in the present invention preferably has a weight average molecular weight (Mw) of 50,000 to 1,000,000.
When the weight average molecular weight of the polylactic acid-based resin is less than 50,000, the mechanical strength when the optically active polymer is molded may be insufficient. The lower limit of the weight average molecular weight of the polylactic acid-based resin is preferably 100,000, and more preferably 200,000. On the other hand, when the weight average molecular weight of the polylactic acid-based resin exceeds 1,000,000, it may be impossible to perform molding such as extrusion molding of a film using an optically active polymer as a molded body. The upper limit of the weight average molecular weight is preferably 800,000, and more preferably 300,000.

  In addition, the molecular weight distribution (Mw / Mn) of the polylactic acid-based resin is preferably 1.1 to 5 and more preferably 1.2 to 4 from the viewpoint of the strength and orientation degree of the stretched film. . Furthermore, it is preferable that it is 1.4-3.

  In order to make the polylactic acid resin have a weight average molecular weight (Mw) of 50,000 or more, it is preferable to produce an optically active polymer by a lactide method or a direct polymerization method.

  In the A layer in the present invention, the polylactic acid-based resin may be used alone or in combination of two or more.

(Other ingredients)
The layer A in the present invention may contain other components other than the polylactic acid resin as long as the effects of the present invention are not impaired.
Examples of other components include known resins typified by polyethylene resins and polystyrene resins, inorganic compounds such as silica, hydroxyapatite, and montmorillonite, and known crystal nucleating agents such as phthalocyanine.
For example, an inorganic filler such as hydroxyapatite may be nano-dispersed in the A layer in order to make the A layer a transparent film in which voids such as bubbles are suppressed, but the inorganic filler is nano-dispersed. For this purpose, large energy is required for crushing the agglomerates, and when the filler is not nano-dispersed, the transparency of the film may be lowered. When the A layer contains an inorganic filler, the content of the inorganic filler with respect to the total mass of the A layer is preferably less than 1% by mass.
When the layer A in the present invention contains a high-purity polylactic acid resin having an optical purity of 99.00% ee or more, a transparent film can be obtained without nano-dispersing an inorganic filler such as hydroxyapatite. Also, from the viewpoint of improving the optical purity and piezoelectric constant of the optically active polymer, the A layer in the present invention is preferably composed only of the polylactic acid resin.

  When A layer in this invention contains other components other than the said polylactic acid-type resin, it is preferable that content of the said other component is 20 mass% or less with respect to A layer total mass, and is 10 mass. % Or less is more preferable.

(Method for forming layer A)
The method for forming the A layer in the present invention is not particularly limited, and a known method for forming a raw material containing the polylactic acid resin into a film-like molded body (A layer) by extrusion molding can be used.
From the viewpoint of more effectively expressing the piezoelectricity, it is preferable to further perform a stretching treatment on the film-like molded body obtained by extrusion molding.

The stretching method is not particularly limited, and various stretching methods such as uniaxial stretching, biaxial stretching, and solid phase stretching can be used.
The stretching ratio in the stretching treatment is preferably 2 to 10 times, more preferably 3 to 9 times.
The temperature in the stretching process is preferably 40 ° C to 100 ° C, more preferably 50 ° C to 90 ° C.
Moreover, it is preferable to heat-process after the said extending | stretching process. The temperature of the heat treatment is preferably 70 ° C to 150 ° C, more preferably 90 ° C to 130 ° C. The heat treatment time is preferably 0.1 to 3 hours, more preferably 0.1 to 2 hours.

<B layer containing unsaturated carboxylic acid polymer>
The B layer in the present invention is a layer in contact with the surface of the A layer on one surface, and is a layer containing an unsaturated carboxylic acid polymer.
The B layer is a layer that functions as an adhesive layer with other layers (for example, a C layer described later).

  The B layer may cover the entire one surface of the A layer, or may cover a part of the region. From the viewpoint of further improving the adhesiveness, it is preferable that the B layer is provided on the entire one surface of the A layer. Further, the B layer may be formed, for example, in the form of a film on the surface of the A layer.

The film thickness of the B layer is preferably 70 nm or less, and more preferably 60 nm or less.
By setting the film thickness of the B layer to 70 nm or less, peeling due to the destruction of the B layer itself can be more effectively suppressed, and adhesion with other layers can be further improved. Moreover, the fall of the piezoelectricity by having provided the B layer can be suppressed more by making the film thickness of the said B layer into 70 nm or less.
Although there is no limitation in particular in the minimum of the film thickness of the said B layer, 2 nm is preferable from an adhesive viewpoint.

(Unsaturated carboxylic acid polymer)
The B layer contains at least one unsaturated carboxylic acid polymer.
Examples of the unsaturated carboxylic acid that is a raw material monomer of the unsaturated carboxylic acid polymer include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and the like.
Among these, acrylic acid or methacrylic acid is preferable, and acrylic acid is particularly preferable.

The presence of the unsaturated carboxylic acid polymer in the B layer confirms that at least a part of the B layer remains on the A layer even after a later-described cleaning step (step of cleaning the B layer using a solvent). Can be done. That is, when at least a part of the B layer remains on the A layer even after the cleaning step described later, it indicates that the unsaturated carboxylic acid polymer is contained in the B layer.
On the other hand, when an unsaturated carboxylic acid polymer is not contained in the B layer, as in the case where a layer composed of an unsaturated carboxylic acid monomer is formed by applying an unsaturated carboxylic acid on the A layer, The B layer is completely dissolved by the cleaning process described later, and the B layer does not remain after the cleaning process.

  The number average molecular weight of the unsaturated carboxylic acid polymer is not particularly limited, but is preferably 120 or more and more preferably 200 or more from the viewpoint of further improving the adhesiveness.

  The layer B may contain other components other than the unsaturated carboxylic acid polymer, but from the viewpoint of obtaining adhesiveness, the content of the unsaturated carboxylic acid polymer in the total amount of the layer B is 80 The content is preferably at least mass%, more preferably at least 90 mass%.

(Method for forming layer B)
Examples of the method of forming the B layer in the present invention include a method of forming by a known film forming method such as vapor deposition, coating, and plasma treatment. Among these, plasma treatment is preferable.
As a preferable form of forming the B layer by plasma treatment, a mixed gas in which an unsaturated carboxylic acid is mixed in an inert gas (main gas) is used as a discharge gas, and the surface of the A layer is plasma at a pressure near atmospheric pressure. The form which forms B layer on A layer by processing is mentioned.
That is, the B layer is a layer formed by performing plasma treatment on the surface of the A layer using an inert gas containing an unsaturated carboxylic acid under a pressure near atmospheric pressure. preferable.
Here, a preferable embodiment in the case where the plasma treatment is performed under a pressure near atmospheric pressure will be described in detail in the section <Plasma treatment step> in <Method for producing piezoelectric laminate> described later.

<C layer>
The piezoelectric laminate of the present invention has a C layer in contact with the other surface (the surface not in contact with the A layer) of the B layer as another layer different from both the A layer and the B layer. It may be.
That is, the piezoelectric laminate of the present invention is configured as a laminate having a laminate structure of C layer / B layer / A layer in which the A layer and the C layer are bonded via the B layer which is an adhesive layer. May be.

The C layer is not particularly limited as long as it is another layer different from both the A layer and the B layer, but the C layer is a layer having poor adhesion to the A layer (in other words, with the A layer. In the case where the layer is required to improve adhesiveness, the effect of improving adhesiveness by the B layer is more effectively exhibited.
An example of such a C layer is a C layer containing a metal oxide compound.
In the C layer containing the metal oxide compound, the content of the metal oxide compound in the total amount of the C layer is preferably 80% by mass or more, and more preferably 90% by mass or more.

The metal oxide compound is preferably a metal oxide compound containing at least one selected from the group consisting of zinc oxide (ZnO), indium tin oxide (ITO), and indium zinc oxide (IZO).
Examples of the metal oxide compound containing zinc oxide (ZnO) include zinc oxide (ZnO) doped with gallium oxide (Ga ₂ O ₃ ) and non-doped zinc oxide (ZnO).

The C layer containing the metal oxide compound is formed by, for example, vapor deposition, coating, or the like.
Examples of the vapor deposition include physical vapor deposition (PVD: Physical Vapor Deposition, also called “sputter”), chemical vapor deposition (CVD: Chemical Vapor Deposition), and the like.
The sputtering may be DC magnetron sputtering using a DC power source or RF magnetron sputtering using an RF power source.
The sputtering is performed using a metal oxide compound target (for example, a ZnO target, a ZnO target doped with gallium oxide (Ga ₂ O ₃ ), or the like) in an inert gas (argon or the like) atmosphere. Even sputtering may be reactive sputtering performed using a metal target (for example, a Zn target) or a metal compound target in a mixed gas atmosphere in which an oxygen gas is mixed in an inert gas such as argon.
Further, the sputtering may be heating sputtering performed by positively heating the layered structure having the B layer / A layer structure, or room temperature sputtering (non-heated sputtering) performed without heating the layered body. There may be.

Among the sputters, when the C layer is formed by sputtering under conditions where film peeling from the base film is likely to occur, the effect of improving the adhesiveness according to the present invention is more effectively exhibited.
As a condition where film peeling is likely to occur, for example, a Ga ₂ O ₃ film is formed as a C layer on the B layer of a B layer / A layer laminate at 50 ° C. or lower by a magnetron sputtering apparatus using a DC pulse power source. The conditions etc. which sputter | sputter the ZnO film | membrane doped with are mentioned.

  Since the piezoelectric laminate of the present invention is a piezoelectric laminate having excellent adhesion to other layers while maintaining the high piezoelectricity of the polylactic acid resin, for example, a speaker, a headphone, a microphone, an underwater microphone, Ultrasonic transducer, ultrasonic applied measuring instrument, piezoelectric vibrator, mechanical filter, piezoelectric transformer, delay device, sensor, acceleration sensor, impact sensor, vibration sensor, pressure sensor, tactile sensor, electric field sensor, sound pressure sensor, display It can be used in various fields such as fans, pumps, variable focus mirrors, sound insulation materials, sound insulation materials, keyboards, acoustic equipment, information processing equipment, measurement equipment, medical equipment, and the like.

A piezoelectric element including the piezoelectric laminate of the present invention can be configured. Specifically, the piezoelectric layer can be formed by providing the C layer as an electrode layer on the B layer of the piezoelectric laminate of the present invention.
In addition, a piezoelectric device including this piezoelectric element can be configured.
The C layer as the electrode layer in the piezoelectric element or piezoelectric device is preferably a transparent layer.
Specifically, the C layer including the above-described metal oxide compound (for example, ZnO, ZnO doped with gallium oxide (Ga ₂ O ₃ ), ITO, IZO) is preferable.
Here, the transparent C layer is preferably a layer having a haze of 20 or less (total light transmittance of 80% or more).

  The piezoelectric element using the piezoelectric laminate of the present invention can be applied to various piezoelectric devices such as speakers and touch panels. In particular, a piezoelectric element provided with a transparent electrode is suitable for application to a speaker, a touch panel, an actuator, and the like.

The method for producing the piezoelectric laminate of the present invention described above is not particularly limited. For example, the B layer is formed on the A layer by a known film forming method such as vapor deposition, coating, or plasma treatment. A method is mentioned.
Among these methods, the method for producing a piezoelectric laminate of the present invention described below is preferable.

<< Method for manufacturing piezoelectric laminate >>
The method for producing a piezoelectric laminate of the present invention includes a step of preparing an A layer containing a polylactic acid resin (hereinafter also referred to as “A layer preparation step”), and an unsaturated carboxylic acid with respect to the surface of the A layer. A step of forming a B layer containing an unsaturated carboxylic acid polymer on the surface of the A layer by performing a plasma treatment under a pressure in the vicinity of the atmospheric pressure using an inert gas containing oxygen (hereinafter referred to as a “plasma treatment step”). And a step of cleaning the formed B layer with a solvent (hereinafter also referred to as “cleaning step”).
According to this manufacturing method, the above-described piezoelectric laminate of the present invention can be preferably manufactured.

<A layer preparation process>
The A layer preparation step is a step for convenience, and may be a step of preparing a previously prepared A layer containing a polylactic acid-based resin, or an A layer containing a polylactic acid-based resin by the method described above. It may be a manufacturing step.
The details of the A layer are as described in the above-mentioned “piezoelectric laminate”, and the preferred range is also the same.

<Plasma treatment process>
In the plasma treatment step, the surface of the A layer is subjected to a plasma treatment under an atmospheric pressure using an inert gas containing an unsaturated carboxylic acid, whereby the surface of the A layer is unsaturated carboxylic acid. This is a step of forming a B layer containing a polymer.
The details of the unsaturated carboxylic acid and the B layer are as described in the above-mentioned “piezoelectric laminate”, and the preferred ranges are also the same.

Here, “plasma treatment is performed under a pressure close to atmospheric pressure” means that the plasma treatment is performed in an atmospheric pressure atmosphere that is open to the atmosphere, and that the atmosphere is slightly reduced compared to atmospheric pressure in a sealed container. It means that the plasma treatment is performed under the pressure, and the plasma treatment is performed in an airtight container in an atmosphere slightly pressurized compared to the atmospheric pressure.
The pressure in the vicinity of the atmospheric pressure refers to a pressure of 100 to 800 Torr (0.013 to 0.105 MPa). A range of 700 to 780 Torr (0.092 to 0.103 MPa) is preferable because the apparatus is simple.

In the plasma treatment step, an inert gas containing 0.1% by volume or more of an unsaturated carboxylic acid is preferably used as the inert gas containing an unsaturated carboxylic acid.
Here, the “inert gas containing an unsaturated carboxylic acid” specifically means an inert gas as a main gas (carrier gas) and an unsaturated carboxylic acid gas obtained by vaporizing the unsaturated carboxylic acid (treatment agent). (Processing gas).
The “inert gas containing 0.1% by volume or more of unsaturated carboxylic acid” is the mixed gas, wherein the volume of the unsaturated carboxylic acid gas with respect to the volume of the main gas is 0.1% by volume or more. It refers to a certain mixed gas.

  In the plasma processing method, activated species are generated by exciting the inert gas containing the unsaturated carboxylic acid into a plasma under a pressure near atmospheric pressure.

  Here, the main gas specifically refers to one or more kinds of single or mixed gases selected from rare gases such as helium, neon, argon, and xenon. It is desirable that helium and / or argon be the main gas as the main gas in order to facilitate the formation of discharge.

  The addition amount of the unsaturated carboxylic acid gas is preferably 0.1% by volume or more with respect to the main gas. Moreover, it is more preferable to set it as 0.2 volume% or more from a viewpoint of improving the joining strength of a laminated body reliably. Moreover, although there is no restriction | limiting in particular in the upper limit of the addition amount of unsaturated carboxylic acid gas, From a viewpoint of improving safety | security further, it is set as less than 2.9 volume% of explosion limits, for example.

  As a means for adding the processing gas (unsaturated carboxylic acid gas) to the main gas, for example, a part of the main gas is injected into the liquid containing the processing agent (unsaturated carboxylic acid), and the temperature of the liquid raw material and the main gas are injected. There is a so-called bubbling method in which the amount of the processing agent added to the main gas as the processing gas is controlled depending on the amount, but is not limited thereto.

  Moreover, as a method of the plasma treatment, a so-called direct method in which a substrate to be treated (A layer in the present invention) is disposed in a discharge plasma space to perform surface treatment may be used, or a substrate to be treated (in the present invention, A so-called remote method may be employed in which the layer A) is disposed outside the discharge plasma space, and the active species generated in the plasma space are sprayed onto the surface of the substrate to be processed.

Moreover, the said plasma processing can be suitably performed with an atmospheric pressure plasma apparatus.
FIG. 1 is a schematic view showing an example of a plasma processing apparatus used in the present embodiment.

  The plasma processing apparatus of FIG. 1 is a so-called direct type apparatus, in which a voltage application electrode 50 and a ground electrode 55 are arranged to face each other. A dielectric 70 and a dielectric 75 are disposed on the electrode facing surfaces of the voltage application electrode 50 and the ground electrode 55, respectively. In the present embodiment, for example, aluminum oxide is used as the dielectrics 70 and 75. The dielectric 70 and the dielectric 75 are arranged with a specific distance (gap) therebetween, and this space becomes a plasma space 80.

  A pulse power supply 60 is connected to the voltage application electrode 50, and the ground electrode 55 is grounded. Since the voltage application electrode 50 is connected to the gas supply unit 40 and the gas exhaust unit 45 and integrally moves, it is possible to process a wide range of the substrate 90 to be processed disposed on the ground electrode 55. In addition, it is possible to process a narrow range for a long time.

  Main gas is injected from the bubbling main gas supply line 11 into the liquid raw material of the processing agent 20 that has entered the bubbling device 30. The processing agent vaporized inside the bubbling apparatus 30 by the vapor pressure is accompanied by the bubbling main gas, passes through the processing gas addition line 12 as a processing gas, and is mixed with the main gas from the main gas supply line 10. Further, the gas is supplied to the plasma space 80 through the gas supply line 13 and the gas supply unit 40. The gas that has passed through the plasma space 80 is exhausted through the gas exhaust part 45 and the gas exhaust line 14. In addition, the supply amount of the main gas and the processing agent can be controlled by installing a flow meter in the line and installing a ribbon heater in the line and the bubbling device to control the temperature.

  The plasma apparatus used in the present invention preferably includes temperature control means for adjusting the temperature of the gas line, the plasma processing space, and the surface of the workpiece from room temperature to about 100 ° C. Thereby, the processing agent can be introduced into the plasma processing space without causing condensation.

  Examples of the means for introducing the processing gas and / or the main gas into the discharge plasma space include a pipe, a pipe, a joint such as a joint, a mass flow controller, and the like. The flow rate of the gas to be introduced is not particularly limited and can be appropriately set, but is usually preferably 1 L / min to 100 L / min.

  Various types of voltage application means can be used as the voltage application means in the plasma treatment, and the voltage application means is not limited to these types. Preferably, the voltage applying means includes at least a means for applying a pulse-modulated high-frequency voltage or a means for applying a periodic pulse voltage.

  The gas introduced into the plasma space is turned into plasma by application of a voltage to form radicals and become active species.

  As a method for transporting the active species to the surface of the substrate to be treated, specifically, after generating the active species, a method of moving the active species with the main gas, or a method of moving by diffusion of the active species However, it is not particularly limited.

  The atmosphere in the plasma space preferably does not contain a large amount of oxygen. This is because oxygen generates active species having strong oxidizing power, and the desired functional group may not be maintained by reaction with the treatment agent, and the surface of the polylactic acid resin constituting the A layer may be eroded. Because of that. From such a viewpoint, the oxygen concentration in the atmosphere is preferably 10,000 ppm or less.

<Washing process>
The cleaning step in the present invention is a step of cleaning the B layer formed by the plasma treatment using a solvent.
Specifically, the laminate obtained by performing the plasma treatment is a polymer film. In order to remove the low molecular weight component generated on the film surface, the surface to be treated (surface treated with plasma) is washed with a solvent. By washing, even when a low molecular weight component remains, adverse effects on adhesion can be suppressed. Moreover, a low molecular weight component can be easily removed by using a solvent at the time of washing.

The cleaning solvent can be selected from those that do not attack the polymer film. Specific examples of the solvent include water, methanol, and ethanol.
Further, the cleaning method is not particularly limited, and examples thereof include ultrasonic cleaning.

<Step of forming C layer>
The manufacturing method of the piezoelectric laminated body of this invention has the process of forming the C layer containing a metal oxide compound by vapor deposition on the surface of the said B layer after the process of wash | cleaning the said B layer as needed. May be. The preferred form and formation method of the C layer are as described in the above-mentioned “piezoelectric laminate”, and the preferred range is also the same.

  The embodiments of the piezoelectric laminate and the manufacturing method thereof according to the present invention have been described above. However, these are merely examples, and various modifications are possible, and such modifications are also within the scope of the present invention. It will be understood by those skilled in the art.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following, “room temperature” refers to 25 ° C.

[Example 1]
<Preparation of Evaluation Film (Layer A)>
A polylactic acid resin (registered trademark LACEEA, H-100 (weight average molecular weight Mw: 150,000)) manufactured by Mitsui Chemicals Co., Ltd. was melt-kneaded at 230 ° C. with an extruder, and then discharged from a T-die to obtain a thickness. A film having a thickness of 300 μm was formed, and this film was uniaxially stretched at a draw ratio of 5 while being heated to 70 ° C. with a heating roll to obtain a uniaxially stretched film having a thickness of 60 μm. After the uniaxially stretched film was cut into A4 size, after fixing the four sides, it was heat-treated in an oven at 110 ° C. for 30 minutes to obtain an evaluation film (A layer).

<Plasma treatment of evaluation film>
The film for evaluation obtained above was subjected to plasma treatment under the conditions shown in Table 1 below using an atmospheric pressure plasma surface treatment apparatus (AP-T02-L) manufactured by Sekisui Chemical Co., Ltd.
Here, the plasma treatment was performed under atmospheric pressure (760 Torr).
At this time, as the discharge gas, a mixed gas obtained by adding an additive gas obtained by vaporizing acrylic acid (treatment agent) to an argon gas as a main gas (carrier gas) was used.
The flow rate of argon gas was 20 L / min.
The mixing ratio of the processing gas vaporized from acrylic acid to the argon gas at 23 ° C. and a pressure of 760 Torr was set to 0.2% by volume. This mixing ratio was adjusted by controlling the flow rate of argon gas introduced into the bubbling device and the temperature of the bubbling device, thereby controlling the amount of acrylic acid vaporized by the bubbling device and supplied to the electrodes accompanying the argon.
The conveyance speed of the film for evaluation during plasma treatment was 0.2 m / min.
In addition, by adjusting the conveyance speed, the film thickness of the plasma treatment layer formed by the plasma treatment or the ratio [(C (= O) -O number) / (C (= O) -O-C] described later. The number of groups)] can be adjusted. For example, the film thickness of the plasma treatment layer can be increased by reducing the transport speed, and the ratio [(number of (C (= O) -O) / (C (= O) -O-C group)] )]) Can be increased. On the other hand, by increasing the conveyance speed, the thickness of the plasma treatment layer can be reduced, and the ratio [(number of (C (= O) -O)) / (C (= O) -O-C group )] Can be lowered.

<Ultrasonic cleaning>
The film for evaluation after the plasma treatment was subjected to ultrasonic cleaning in pure water for 1 minute under conditions of a high frequency output of 70 W and 35 kHz, thereby removing water-soluble low molecular weight components generated on the plasma treatment surface by the plasma treatment. .

<Measurement of film thickness change>
About the said evaluation film, the film thickness change before the said ultrasonic treatment before the said ultrasonic cleaning (after the said plasma processing) (unit nm; hereafter, this film thickness change is also called "film thickness change (nm) unwashed") Was measured.
Hereinafter, a measuring method of this “film thickness change (nm) unwashed” will be described.
First, the difference (b−a) between the mass (a) of the evaluation film before the plasma treatment and the mass (b) of the evaluation film before the ultrasonic cleaning (after the plasma treatment) was measured. Here, each mass was measured using an electronic balance.
Next, “film thickness change (nm) unwashed” was determined from the obtained difference (b−a), the density of the plasma treatment layer, the density of the evaluation film, and the area of the evaluation film (plasma treatment layer). . Here, the density of the plasma treatment layer and the density of the evaluation film were assumed to be equal.
The measurement results of “film thickness change (nm) unwashed” are shown in Table 1 below.

Similarly to the measurement of “film thickness change (nm) unwashed”, the film thickness change (unit: nm; hereinafter referred to as “film thickness change”) from before the plasma treatment to after the ultrasonic cleaning was performed on the evaluation film. Change (nm) after washing with water) was measured.
Hereinafter, the measurement method after the film thickness change (nm) washing with water will be described.
First, the difference (c−a) between the mass (a) of the evaluation film before the plasma treatment and the mass (c) of the evaluation film after the ultrasonic cleaning was measured.
Next, from the obtained difference (c−a), the density of the plasma treatment layer, the density of the evaluation film, and the area of the evaluation film (plasma treatment layer), “after film thickness change (nm) after washing with water” is obtained. It was.
The measurement results of “After film thickness change (nm) after washing with water” are shown in Table 1 below.

Here, “after film thickness change (nm) after water washing” is a positive value (for example, Examples 1 and 2 in Table 1) that the plasma treatment layer remains even after ultrasonic cleaning. Show. That is, “after film thickness change (nm) after washing with water” is a positive value that the plasma treatment layer (B layer) containing an acrylic acid polymer was formed on the A layer by the plasma treatment. Show.
In addition, when acrylic acid is applied on the A layer (that is, when an acrylic acid layer made of an acrylic acid monomer is formed on the A layer), the acrylic acid layer is dissolved by ultrasonic cleaning, An acrylic acid layer does not remain after ultrasonic cleaning.
Further, “film thickness change (nm) unwashed” is a negative value (for example, Comparative Example 1 in Table 1) that the A layer has been reduced by the plasma treatment (the B layer is formed). Not).

<Measurement of surface functional groups>
After the ultrasonic cleaning, the surface of the evaluation film on the plasma-treated side (B layer surface in Example 1) was measured by X-ray photoelectron spectroscopy (XPS) to obtain a carbon 1s spectrum.
From the obtained carbon 1s spectrum, by waveform analysis, the percentage (%) of the number of C (═O) —O—C groups with respect to the total number of carbons ([C (═O) —O—C] / [C]) The percentage (%) of the number of C (═O) —O groups relative to the total number of carbon atoms ([C (═O) —O] / [C]) was determined.
Further, from the ratio of [C (= O) -O] / [C] and [C (= O) -O-C] / [C], [C (= O) -O] / [C (= O) —O—C], ie the ratio of the number of C (═O) —O to the number of C (═O) —O—C groups [(number of C (═O) —O) / (C ( = O) -O-C group number)].

Next, details of the waveform analysis will be described.
First, the peak which exists in the lowest energy side (285.0 eV) among several peaks which comprise a carbon 1s spectrum was made into the peak originating in carbon of a C-C bond and a C-H bond. Furthermore, the peak existing at about 286.5 eV is defined as a peak derived from carbon of C—O bond, and the peak present at about 287.1 eV is peak derived from carbon at the right end of C (═O) —O—C bond. And a peak present at about 288.0 eV was defined as a peak derived from carbon having a C═O bond, and a peak present at about 289.1 eV was defined as a peak derived from carbon having a C (═O) —O bond.
From the area ratio of these peaks, [C (═O) —O—C] / [C] and [C (═O) —O] / [C] were determined. Further, by dividing (dividing) [C (= O) -O] / [C] by [C (= O) -O-C] / [C], "[C (= O) -O]" is obtained. / [C (= O) -O-C] ".
Here, XPS was measured under the conditions of X-ray source: monochromatic AlKα, degree of vacuum: 1 × 10 ⁻⁹ mbar, output: 16 mA-10 kV. The waveform analysis was performed by curve fitting the obtained spectrum to separate the peaks with respect to the peak, and measuring the area ratio of each peak.
The above results are shown in Table 1 below.

<Measurement of the piezoelectric constant _{d 14>}
The test film was prepared by cutting the film for evaluation after ultrasonic cleaning (a laminate having a structure of B layer / A layer in Example 1) into a length of 10 mm and a width of 3 mm.
On both surfaces of the test piece (A layer side and the B layer side), as an electrode for measuring the piezoelectric constant d _14, it was formed by sputtering an Ag thin film.
For specimens Ag thin film is formed on both sides, with "Leo b graph Solid S-1 type" of Toyo Seiki Seisakusho Co., frequency 10 Hz, the complex piezoelectric constant d ₁₄ of each specimen was measured at room temperature . The complex piezoelectric constant d ₁₄ was calculated as “d ₁₄ = d ₁₄ ′ −id ₁₄ ″”. The piezoelectric constant was measured five times, and the average value of d ₁₄ ′ is shown in Table 1 as the piezoelectric constant.
The shear strain when measuring the piezoelectric constant was measured at 0.05%.
In the above measurement, but apparently measures the piezoelectric constant d ₁₄ of the laminate structure of the B layer / A layer, substantially measures the piezoelectric constant d ₁₄ of the A layer. The reason is that the B layer is sufficiently thinner than the A layer, and the B layer does not have piezoelectricity.

<Formation of C layer>
A ZnO film having a film thickness of 100 nm and doped with Ga ₂ O _{3 on} the plasma-treated surface (B layer surface in Example 1) of the evaluation film after the above-described plasma treatment and ultrasonic cleaning by magnetron sputtering under the following conditions: (C layer) was formed.
As described above, in Example 1, a laminate having a configuration of ZnO film (C layer) / plasma treatment layer (B layer) / evaluation film (A layer) doped with Ga ₂ O ₃ was obtained.

-Sputtering condition of ZnO film (C layer) doped with Ga ₂ O _3-
Apparatus: magnetron sputtering system Target: _Ga 2 _{O 3} is 10 wt% doped ZnO target Ultimate ^{vacuum: 6 × 10 -5 Pa~7 × 10} -5 Pa
・ Power supply: DC pulse power supply ・ Power: 0.67 W / cm ²
・ Temperature of substrate (layer of B layer / A layer): room temperature

<Adhesion evaluation (tape peeling test)>
About the laminated body in which the C layer is formed (the laminated body having a structure of C layer / B layer / A layer in Example 1), by a tape peeling test according to a method according to JIS H8504 (plating adhesion test method), The adhesiveness of the C layer was evaluated.
Cell tape (registered trademark) CT405AP-18 manufactured by Nichiban Co., Ltd. was used as a test tape used in the tape peeling test.
In the tape peeling test, first, the test tape was attached to the surface of the C layer, leaving 30 mm of a portion to be not attached. Next, the portion of the test tape that was attached to the surface of the C layer was kept pressed for about 10 seconds with a finger in a direction perpendicular to the surface of the C layer. Next, the test tape was held on the part not to be attached and pulled strongly in a direction perpendicular to the surface of the C layer, and the test tape was instantaneously peeled off from the surface of the C layer.
The test part (the part where it was peeled off) was observed visually and with an optical microscope, and when no peeling of the C layer was observed, the adhesion was considered good.
This test was performed three times per treatment condition.
The results of the above tape peel test are shown in the following Table 1 ("Peel test" column).
In Table 1, the results of the tape peel test were classified as follows.
-Classification of tape peel test results-
“0/3”: C layer peeling was not observed in all three of the tests.
“1/3”: C layer peeling was observed only once in 3 tests.
“2/3”: Peeling of the C layer was observed only twice in three tests.
“3/3”: Peeling of the C layer was observed in all three of the tests.
The tape peel test result of “0/3” indicates that the adhesion of the C layer is the best.

[Example 2]
In Example 1, except that the plasma treatment conditions were changed as shown in Table 1 below, the same operation as in Example 1 was performed to obtain a ZnO film (C layer) / plasma treatment layer (B layer) / evaluation film. A laminate having the configuration of (A layer) was formed and evaluated in the same manner as in Example 1.
The evaluation results are shown in Table 1 below.

[Comparative Example 1]
In Example 2, except that acrylic acid was not mixed in the plasma treatment discharge gas (that is, plasma treatment was performed only with argon gas) and ultrasonic cleaning after the plasma treatment was not performed. The same operation as in Example 2 was performed to form a laminate having the structure of ZnO film (C layer) / evaluation film (A layer), and the same evaluation as in Example 1 was performed.
In Comparative Example 1, measurement of film thickness change and measurement of surface functional groups were performed without performing ultrasonic cleaning after plasma treatment.
The evaluation results are shown in Table 1 below.
In Comparative Example 1, since the discharge gas does not contain acrylic acid, the B layer was not formed even by the plasma treatment, but rather, the A layer was reduced by 22 nm by the plasma treatment. Thickness change (nm) unwashed ").

[Comparative Example 2]
In Example 1, a laminate having the structure of ZnO film (C layer) / evaluation film (A layer) was formed in the same manner as in Example 1 except that plasma treatment and subsequent ultrasonic cleaning were not performed. Evaluation similar to Example 1 was performed.
In Comparative Example 2, after the production of the film for evaluation (A layer), without performing the plasma treatment and subsequent ultrasonic cleaning, measurement of the film thickness changes, the measurement of surface functional groups, measurement of the piezoelectric constant d _14, C Layer formation and adhesion evaluation were performed.
The evaluation results are shown in Table 1 below.

As shown in Table 1, it has a laminated structure of A layer containing polylactic acid resin / B layer containing unsaturated carboxylic acid polymer, and [C (= O) -O] / [C (= O)- Example 1 wherein the ratio [(C (= O) -O) / (C (= O) -O-C group)]] is 1.4 or more and 5.0 or less. 2 and 2 were excellent in adhesiveness to the C layer, and the high piezoelectric constant d ₁₄ (that is, high piezoelectricity) of the A layer containing the polylactic acid resin was sufficiently maintained.
On the other hand, in Comparative Example 1, the plasma treatment layer (B layer) was not formed even by the plasma treatment, but rather the A layer was reduced.
Moreover, in the comparative example 2 which does not have a plasma processing layer (B layer), adhesiveness with C layer was bad.

DESCRIPTION OF SYMBOLS 10 Main gas supply line 11 Main gas supply line 12 for bubbling Process gas addition line 13 Gas supply line 14 Gas exhaust line 20 Processing agent 30 Bubbling apparatus 40 Gas supply part 45 Gas exhaust part 50 Voltage application electrode 55 Ground electrode 60 Pulse power supply 70 Dielectric 75 Dielectric 80 Plasma space 90 Substrate to be processed

Claims (10)

A layer containing a polylactic acid-based resin, and B layer containing an unsaturated carboxylic acid polymer in contact with the surface of the A layer on one side,
The number of C (= O) -O with respect to the number of C (= O) -O-C groups determined by waveform analysis from the carbon 1s spectrum obtained by measuring the surface of the B layer by X-ray photoelectron spectroscopy. A piezoelectric laminate in which the ratio of numbers [(number of C (= O) -O) / (number of C (= O) -O-C groups)] is 1.4 or more and 5.0 or less. 2. The piezoelectric laminate according to claim 1, wherein the A layer has a piezoelectric constant d _{14 at} 25 ° C. of 1 pC / N to 30 pC / N.   The piezoelectric laminate according to claim 1 or 2, wherein the thickness of the B layer is 2 nm or more and 70 nm or less.   The piezoelectric laminate according to any one of claims 1 to 3, further comprising a C layer in contact with the other surface of the B layer.   The piezoelectric laminate according to any one of claims 1 to 4, wherein the unsaturated carboxylic acid polymer is an acrylic acid polymer.   The B layer is a layer formed by performing a plasma treatment on the surface of the A layer using an inert gas containing an unsaturated carboxylic acid under a pressure near atmospheric pressure. The piezoelectric laminated body of any one of Claim 5.   The piezoelectric laminate according to claim 4, wherein the C layer contains a metal oxide compound.   The piezoelectric laminate according to claim 7, wherein the metal oxide compound includes at least one selected from the group consisting of zinc oxide (ZnO), indium tin oxide (ITO), and indium zinc oxide (IZO). A method for producing a piezoelectric laminate according to any one of claims 1 to 8,
Preparing a layer A containing a polylactic acid resin;
A layer B containing an unsaturated carboxylic acid polymer on the surface of the layer A by performing a plasma treatment on the surface of the layer A using an inert gas containing an unsaturated carboxylic acid under a pressure near atmospheric pressure. Forming a step;
Washing the formed B layer with a solvent;
The manufacturing method of the piezoelectric laminated body which has this.   Furthermore, the manufacturing method of the piezoelectric laminated body of Claim 9 which has the process of forming C layer containing a metal oxide compound by vapor deposition on B layer after this washing | cleaning B layer.