JP2016051890A - Polymer piezoelectric material and method for manufacturing polymer piezoelectric material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer piezoelectric material with high reliability and improved moist heat resistance and heat resistance, and a method for manufacturing the polymer piezoelectric material.SOLUTION: A polymer piezoelectric material includes an optically active polymer having an imide ring structure. A piezoelectric constant dis not less than 0.1pC/N. A method for manufacturing the polymer piezoelectric material includes the steps of: acquiring a film by forming a composition including an optically active polymer having an imide ring structure (filming step); and stretching the film (stretching step).SELECTED DRAWING: None

Description

  The present invention relates to a polymer piezoelectric material and a method for producing the polymer piezoelectric material.

In recent years, attention has been focused on the use of aliphatic polyester having optical activity such as polylactic acid as the polymer piezoelectric material. Optically active polymer piezoelectric materials represented by polylactic acid exhibit piezoelectricity only by mechanical stretching operation, and do not require poling treatment like ferroelectric polymer piezoelectric materials such as polyvinylidene fluoride It has been known.
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.
In addition, it is known that a piezoelectric material formed from polylactic acid does not require a poling process and the piezoelectricity does not decrease over several years.

As described above, since polylactic acid has various piezoelectric characteristics, polymer piezoelectric materials using various polylactic acids have been reported.
For example, a polymer piezoelectric material that exhibits a piezoelectric constant of about 10 pC / N at room temperature by stretching a molded product of polylactic acid has been disclosed (for example, see Patent Document 1).
In addition, in order to make polylactic acid crystals highly oriented, it has also been reported that high piezoelectricity of about 18 pC / N is obtained by a special orientation method called a forging method (see, for example, Patent Document 2).

JP-A-5-152638 JP 2005-213376 A

However, aliphatic polyesters such as polylactic acid used in the piezoelectric materials disclosed in Patent Document 1 and Patent Document 2 may be hydrolyzed in an environment containing moisture. Therefore, when a piezoelectric element is used in an environment where hydrolysis is likely to occur, such as in the atmosphere, there is a problem that the piezoelectric element is likely to deteriorate and reliability is low.
Furthermore, aliphatic polyesters such as polylactic acid have low heat resistance, and there is a problem that use as a piezoelectric element in a high temperature environment is limited.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a polymer piezoelectric material having high reliability and improved wet heat resistance and heat resistance, and a method for producing the polymer piezoelectric material.

Specific means for achieving the above object are as follows, for example.
<1> comprises an optically active polymer having an imide ring structure, is the piezoelectric constant _{d 14} is 0.1pC / N or more, a polymeric piezoelectric material.

<2> The polymeric piezoelectric material according to <1>, wherein the optically active polymer having an imide ring structure is polysuccinimide.

<3> The polymer piezoelectric according to <1> or <2>, wherein the optically active polymer having an imide ring structure has an absolute value of specific rotation at 589 nm of 0.1 deg · cm ² · g ⁻¹ or more. material.

<4> The polymeric piezoelectric material according to any one of <1> to <3>, wherein the optically active polymer having an imide ring structure has a weight average molecular weight of 18,000 or more.

<5> The polymeric piezoelectric material according to any one of <1> to <4>, wherein the content of the optically active polymer having the imide ring structure is 50% by mass or more.

<6> The method for producing a polymeric piezoelectric material according to any one of <1> to <5>, wherein a film is formed by forming a composition containing the optically active polymer having the imide ring structure. A method for producing a polymeric piezoelectric material, comprising: a film forming step to be obtained; and a stretching step for stretching the film.

<7> The composition contains a solvent, and the film forming step includes a step of forming the film by casting the composition to obtain a film, and a step of evaporating and removing the solvent from the film. <6> The method for producing a polymeric piezoelectric material according to <6>.

<8> The method for producing a polymeric piezoelectric material according to <6> or <7>, wherein the stretching step is a step of performing orientation treatment by roll stretching.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a polymeric piezoelectric material with high reliability and improved heat-and-moisture resistance and heat resistance and a polymeric piezoelectric material can be provided.

In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
Further, in the present specification, “film” is a concept including not only what is generally called “film” but also what is generally called “sheet”.

[Polymer piezoelectric material]
Polymeric piezoelectric material according to one embodiment of the present invention includes an optically active polymer having an imide ring structure, is the piezoelectric constant d ₁₄ is 0.1pC / N or more.

Since the piezoelectricity is expressed by stretching a material (for example, a film) containing an optically active polymer having an imide ring structure, the material containing an optically active polymer having an imide ring structure is a polymer piezoelectric material. Can be used.
Furthermore, the optically active polymer having an imide ring structure is less prone to hydrolysis than aliphatic polyesters. Therefore, the polymer piezoelectric material of the present embodiment including an optically active polymer having an imide ring structure contains moisture in the atmosphere as compared with a polymer piezoelectric material including an aliphatic polyester such as polylactic acid. It is difficult to deteriorate in the environment and has high reliability.
That is, the optically active polymer having an imide ring structure is superior in heat resistance and heat and moisture resistance as compared with aliphatic polyester. Therefore, the polymer piezoelectric material of the present embodiment including the optically active polymer having an imide ring structure is suitable for use as a piezoelectric element in a high temperature or high humidity heat environment.

(Optically active polymer with imide ring structure)
The optically active polymer having an imide ring structure is a polymer having an imide ring structure and having optical activity. Here, the polymer having optical activity refers to a polymer having no symmetrical center in the structure. Examples of such a polymer include a polymer having asymmetric carbon, a polymer having axial asymmetry, and a polymer having planar asymmetry. The absence of the center of symmetry in the structure can be confirmed by measuring the optical rotation or specific optical rotation and checking that the absolute value is greater than zero.
An imide ring structure is a cyclic compound having an imide bond in the ring structure. Examples of the imide ring structure include structures shown in the following (I) -1 to (I) -5.

  The optically active polymer having an imide ring structure may have an amide bond, an ester bond, or an ether bond in its skeleton. Such an imide ring structure is a condensed cyclization of one or more compounds selected from amino group and isocyanate group-containing compounds and one or more compounds selected from derivatives such as tetracarboxylic acids, esters thereof and acid anhydrides. It can be formed by reaction. At that time, such compounds may exist almost stoichiometrically, or such reactive groups such as aminodicarboxylic acid may be stoichiometrically coexisted in the molecule to cause a self-condensation cyclization reaction.

  Examples of the compound capable of self-condensation cyclization include a reaction product of maleic acid and ammonia, maleamic acid, aspartic acid, and the like. In addition, maleic acid and ammonia may be used in combination. Maleic acid includes its anhydrides, partials and derivatives such as complete esters, and ammonia can be either a gas or a solution. In the case where ammonia is a solution, examples include an aqueous solution of ammonium hydroxide dissolved in water, an alcohol such as methanol and ethanol, and another organic solvent. Aspartic acid includes D-form, L-form, or a mixture thereof.

  As a raw material for the optically active polymer having an imide ring structure, other monomers that can be copolymerized within a range not impairing the effects of the present invention can be used in combination. Specific examples of other copolymerizable monomers include aspartate, glutamic acid and salts thereof; amino acids such as alanine, leucine and lysine; hydroxycarboxylic acids such as glycolic acid, lactic acid and 3-hydroxybutyric acid; 2-hydroxyethanol , A compound having two or more functional groups that react with at least one of an amino group and a carboxylic acid group such as maleic acid and 6-aminocaproic acid. The amount of other copolymerizable monomers used is preferably not more than 50 mol% of the total monomers.

  In order to obtain a polymer having no symmetry center, all or part of the aminodicarboxylic acid capable of self-condensation cyclization and other monomers capable of copolymerization, or the polymer after polymerization may be asymmetric carbon. Any of axial asymmetry or planar asymmetry may be present.

  A solvent may be used for the production of the optically active polymer having such an imide ring structure. When a solvent is used, o-xylene, m-xylene, p-xylene, o-cresol, m-cresol, p-cresol, o-diethylbenzene, m-diethylbenzene, p-diethylbenzene, toluene, amylbenzene, cumene , Aromatic hydrocarbon solvents such as mesitylene and tetralin; chlorobenzene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, 1,4-dichloro Halogenated hydrocarbon solvents such as butane; ether solvents such as dichloroethyl ether, butyl ether, diisoamyl ether, and anisole; acetic acid-n-amyl, isoamyl acetate, methyl isoamyl acetate, cyclohexyl acetate, benzyl acetate, propionic acid-n -Butyl, Propionate, isoamyl butyrate, isoamyl, include ester solvents such as butyric -n- butyl. In addition, an aprotic polar solvent may be used as the solvent, for example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolide. Amide solvents such as non- and tetramethylurea; and sulfur-based solvents such as dimethyl sulfoxide, sulfolane and hexamethylphosphoramide. These solvents may be used alone or in combination.

  The production of the optically active polymer having such an imide ring structure does not require the use of a solvent. When no solvent is used, an optically active polymer having an imide ring structure can be produced by a melt polymerization method, a solid phase polymerization method or the like.

  Examples of the optically active polymer having an imide ring structure include a polymer having a succinimide skeleton represented by the following general formula (II).

In general formula (II), R ₁ , R ₂ and R ₃ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, Alternatively, it represents an aromatic hydrocarbon group having 6 to 20 carbon atoms. The alkyl group, alkoxy group and alkylthio group may be substituted, may be linear or branched, and may be cyclic. R ₁ , R ₂ and R ₃ may each independently be saturated or unsaturated.
In general formula (II), n represents 0 to 10 and * represents an asymmetric carbon (the same applies to the following reaction formula (III) and general formulas (IV) to (VI)).

Among them, in general formula (II), R _{1 to} R ₃ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylthio group having 1 to 6 carbon atoms, or It is preferably an aromatic hydrocarbon group having 6 to 10 carbon atoms, more preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a methylthio group, an ethylthio group or a phenyl group, and a hydrogen atom or It is more preferably a methyl group, and most preferably a hydrogen atom.
In general formula (II), n is preferably 0 to 6, more preferably 0 to 4, still more preferably 0 to 2, particularly preferably 0 or 1. Most preferably it is zero.

In general formula (II), polysuccinimide in which R ₁ , R ₂ , and R ₃ are hydrogen atoms and n = 0 is preferable. Poliscinimide is an aspartic acid polymer and is synthesized, for example, by dehydration condensation of L-aspartic acid or D-aspartic acid as shown in the following reaction formula (III).

  For such dehydration condensation reaction, a commonly used dehydration condensation catalyst may be used. Examples of the dehydration condensation catalyst include inorganic acid catalysts such as sulfuric acid, sulfuric anhydride, phosphoric acid, polyphosphoric acid, metaphosphoric acid, and condensed phosphoric acid; p-toluenesulfonic acid, trichloroacetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, 3 Organic acid catalysts such as 1,4,5-trifluorophenylboronic acid; organic bases such as creatinine and 1,5,7-triazabicyclo [4.4.0] dec-5-ene; tin (II) chloride; And metal catalysts (may be hydrates) such as tin (IV) chloride, tin (II) oxide, and zinc (II) chloride.

  As a method for synthesizing polysuccinimide, ring-opening polymerization using aspartic acid-N-carboxy anhydride (NCA) as a monomer and ring-closing reaction to a succinimide ring may be combined.

  In addition, examples of the optically active polymer having an imide ring structure include compounds represented by the following general formulas (IV), (V), and (VI).

In general formulas (IV), (V), (VI), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are each independently a hydrogen atom, A 20-alkyl group, a C1-C20 alkoxy group, a C1-C20 alkylthio group, or a C6-C20 aromatic hydrocarbon group is represented. The alkyl group, alkoxy group and alkylthio group may be substituted, may be linear or branched, and may be cyclic. R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ may each independently be saturated or unsaturated.

The preferable range of R _{1 to} R ₈ in the general formulas (IV) to (VI) is the same as the preferable range of R _{1 to} R ₃ in the general formula (II).

The polymeric piezoelectric material of this embodiment may contain only one type of optically active polymer having an imide ring structure, or may contain two or more types.
In addition, the content of the optically active polymer having an imide ring structure in the polymer piezoelectric material (the total content when there are two or more types) is 50% by mass or more based on the total amount of the polymer piezoelectric material. It is preferably 60% by mass or more, and more preferably 80% by mass or more.

-Weight average molecular weight-
The weight average molecular weight (Mw) of the optically active polymer having an imide ring structure is preferably 18,000 or more. As a result, the mechanical strength of the polymeric piezoelectric material is improved, and the polymer chain is oriented by the stretching operation to exhibit piezoelectricity. The Mw is preferably 20,000 or more, more preferably 30,000 or more, and further preferably 50,000 or more.
The Mw of the optically active polymer having an imide ring structure is preferably 1,000,000 or less. Thereby, the moldability at the time of obtaining a polymeric piezoelectric material by shaping | molding (for example, extrusion molding) improves. The Mw is preferably 800,000 or less, and more preferably 300,000 or less.

  The molecular weight distribution (Mw / Mn) of the optically active polymer having an imide ring structure is preferably 1.1 to 20, and preferably 1.5 to 15 from the viewpoint of the strength of the polymer piezoelectric material. Is more preferable, it is more preferable that it is 2-15, and it is especially preferable that it is 3-15. The upper limit of Mw / Mn may be 10 or 7.

  In addition, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the optically active polymer having an imide ring structure indicate values measured by the following GPC measurement method using gel permeation chromatograph (GPC). . Here, Mn is the number average molecular weight of the optically active polymer having an imide ring structure.

-GPC measuring device-
Showex DPC, Shodex GPC-101
-Column-
Showex Denko, Shodex OHpak SB-804 HQ
-Sample preparation-
An optically active polymer having an imide ring structure (for example, polysuccinimide) is dissolved in dimethylformamide as a solvent at 40 ° C. to prepare a sample solution having a concentration of 1 mg / mL.
-Measurement conditions-
0.1 mL of the sample solution was introduced into the column with a solvent (dimethylformamide (containing 0.1% by mass of LiBr)) at a temperature of 40 ° C. and a flow rate of 0.7 mL / min, and the sample concentration in the sample solution separated by the column was determined. Measure with a differential refractometer. The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the optically active polymer having an imide ring structure are calculated based on a calibration curve created using Standard Shodex SM-105 manufactured by Showa Denko KK.

-Absolute value of specific rotation-
The absolute value of the specific rotation at 589 nm of the optically active polymer having an imide ring structure is preferably 0.1 deg · cm ² · g ⁻¹ or more. This shows that the polymer having an imide ring structure has optical activity.

-Measurement conditions-
An optically active polymer having an imide ring structure (for example, polysuccinimide) is dissolved in dimethylformamide so as to be 1.5% by mass, and a measurement wavelength is measured using a fully automatic polarimeter AUTOPOL V (manufactured by Rudolph Research Analytical). The optical rotation α at 589 nm and 20 ° C. is measured. The specific rotation [α] is calculated from the optical rotation α using the following formula.
[Formula 1]
[α] = α / (c × l)
c: Measurement sample concentration (g / dL)
l: Cell length (100 mm)

<Other optically active polymers>
The polymeric piezoelectric material of the present embodiment includes an optically active polymer other than the optically active polymer having an imide ring structure (hereinafter referred to as “other optically active polymer”) as long as the effects of the present invention are not impaired. You may go out.
Examples of other optically active polymers include polypeptides, cellulose derivatives, polylactic acid resins, polypropylene oxide, poly (β-hydroxybutyric acid), and the like.
Examples of the polypeptide include poly (glutaric acid γ-benzyl), poly (glutaric acid γ-methyl), and the like.
Examples of the cellulose derivative include cellulose acetate and cyanoethyl cellulose.
Examples of the polylactic acid-based resin include polylactic acid. Among them, L-lactic acid homopolymer (PLLA) or D-lactic acid homopolymer (PDLA) is preferable.

<Stabilizer>
The polymeric piezoelectric material of the present embodiment includes a compound having a weight average molecular weight of 200 to 60000 having at least one functional group selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group as a stabilizer. Is preferred.
Thereby, the hydrolysis reaction of the optically active polymer having an imide ring structure can be suppressed, and the moisture and heat resistance of the resulting film can be further improved.
As for the stabilizer, paragraph 003 of International Publication No. 2013/054918 pamphlet.
The description of 9 to 0055 can be referred to as appropriate.

<Antioxidant>
Moreover, the polymeric piezoelectric material of this embodiment may contain an antioxidant. The antioxidant is at least one compound selected from a hindered phenol compound, a hindered amine compound, a phosphite compound, and a thioether compound.
Moreover, it is preferable to use a hindered phenol compound or a hindered amine compound as the antioxidant. Thereby, the polymeric piezoelectric material which is excellent also in heat-and-moisture resistance and transparency can be provided.

<Other ingredients>
The polymer piezoelectric member of the present embodiment is a known resin represented by polyvinylidene fluoride, polyethylene resin or polystyrene resin, inorganic fillers such as silica, hydroxyapatite, montmorillonite, phthalocyanine, as long as the effects of the present invention are not impaired. It may contain other components such as known crystal nucleating agents.
As for other components such as an inorganic filler and a crystal nucleating agent, the description in paragraphs 0057 to 0060 of International Publication No. 2013/054918 can be referred to as appropriate.

  When the polymer piezoelectric member contains a component other than the optically active polymer having an imide ring structure, the content of the component other than the optically active polymer having an imide ring structure is 20 with respect to the total mass of the polymer piezoelectric member. The content is preferably at most 10 mass%, more preferably at most 10 mass%.

  In addition, it is preferable that a polymeric piezoelectric material does not contain components other than the optically active polymer which has an imide ring structure from a transparency viewpoint.

[Method for producing polymeric piezoelectric material]
Hereinafter, a method for producing a polymeric piezoelectric material according to an embodiment of the present invention will be described. The method for producing a polymeric piezoelectric material according to the present embodiment includes a film-forming process for forming a film by forming a composition containing the optically active polymer having the imide ring structure, and a stretching process for stretching the film. Have.

(Film forming process)
The method for producing a polymeric piezoelectric material according to the present embodiment includes a film forming step of forming a film by forming a composition containing an optically active polymer having an imide ring structure. In the film forming step, various film forming methods such as a melt film forming method and a solution casting method can be used.

  First, when manufacturing the polymeric piezoelectric material of this embodiment, it is preferable to collect a predetermined amount of an optically active polymer having an imide ring structure and dissolve it in a solvent. The solvent is not particularly limited as long as it can dissolve an optically active polymer having an imide ring structure and can form a film. Preferably, N, N-dimethylformamide, N-methylformamide, N, N -Diethylformamide, dimethyl sulfoxide, N, N-dimethylacetamide, methanol, ethanol, propanol, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, tetrahydrofuran, chloroform, methylene chloride, ether, benzene, toluene, xylene, acetonitrile or mixtures thereof Liquid and the like.

The concentration of the solution is not particularly limited as long as film formation is possible, but it is preferably 0.1% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.
When the content is 0.1% by mass or more, damage to the film can be suppressed, and film formation is easy without repeated film formation such as lamination.
Moreover, the viscosity of a solution does not become too high because it is 30 mass% or less, and uniform film formation by a casting method is easy.
Here, the solution is preferably a solution in which part or all of the optically active polymer is dissolved in a solvent, and more preferably a solution in which substantially all of the optically active polymer is dissolved.

  The method for forming a film by casting a solution is not particularly limited, but includes roller coating, dip coating, spray coating, spinner coating, curtain coating, slot coating, screen printing, casting, and the like. In particular, a casting method capable of casting and forming a film-forming surface flat and uniformly is preferable.

In the casting method, it is desirable to pour the above-mentioned solution onto the substrate and evaporate the solvent. Although it does not specifically limit as a board | substrate, Teflon (trademark) with which peeling of a film is easy is preferable.
Examples of the method for removing the solvent include methods such as heating, decompression, and ventilation. Of these, it is preferable to evaporate the solvent by heating from the viewpoint of production efficiency and handling. Moreover, the temperature at the time of solvent evaporation is although it does not specifically limit, It is preferable that it is 0 to 200 degreeC, and it is more preferable that it is 10 to 150 degreeC.
After the solvent evaporates, a treatment such as vacuum drying may be further performed as necessary. Although the temperature at the time of vacuum drying is not specifically limited, It is preferable that it is 0 degreeC-200 degreeC. In addition, it can suppress that optically active polymer raise | generates modification | denaturation, such as oxidation, by setting it as 300 degrees C or less.

(Stretching process)
The method for producing the polymeric piezoelectric material of the present embodiment includes a stretching step of stretching the film obtained by the film forming step. The stretching method is not particularly limited, and various stretching methods such as uniaxial stretching, biaxial stretching, solid phase stretching described below, and roll stretching can be used.
By stretching an optically active polymer having an imide ring structure, a piezoelectric polymer can be obtained that exhibits piezoelectricity and has a large principal surface area.

  Furthermore, as a result of intensive studies, the present inventors have produced a polymer piezoelectric material having higher piezoelectricity by orienting molecular chains of an optically active polymer having an imide ring structure at high density in one direction. I found it possible. Therefore, it is preferable to orient the molecular chains of the optically active polymer having an imide ring structure in one direction at a high density by performing the above-described stretching treatment.

  The stretching ratio in the stretching step is optimized to a ratio that exhibits high piezoelectricity. The draw ratio varies depending on the polymer piezoelectric material, the drawing method, etc., but in the case of producing a polymer piezoelectric material using an optically active polymer having an imide ring structure, it is generally in the range of 1.5 to 30 times. It is preferable to stretch at a ratio of 1.8 times to 15 times.

  In the stretching step, the orientation treatment is preferably performed by solid phase stretching or roll stretching. According to these methods, mass production of the film is easy.

In solid-phase stretching, it is preferable to stretch and align in at least one direction parallel to the principal surface while applying a compressive stress to the principal surface of the formed film. In solid phase stretching, it is preferable to perform stretching under a compressive stress of 5 MPa to 10,000 MPa at a temperature higher than the glass transition temperature Tg of the polymer piezoelectric material and lower than the melting point Tm of the polymer piezoelectric material. Thereby, the piezoelectricity of the polymer piezoelectric material can be further improved, and the transparency and elasticity can be improved.
Here, the glass transition temperature Tg [° C.] of the polymer piezoelectric material and the melting point Tm [° C.] of the polymer piezoelectric material are raised with respect to the polymer piezoelectric material using the differential scanning calorimeter (DSC). From the melting endothermic curve when the temperature is increased at a rate of 10 ° C./min, the glass transition temperature (Tg) obtained as the inflection point of the curve and the temperature (Tm) confirmed as the peak value of the endothermic reaction It is.
The compressive stress is preferably 50 MPa to 5000 MPa, more preferably 100 MPa to 3000 MPa.

  In roll stretching, it is preferable to stretch and align in at least one direction parallel to the principal surface while applying compressive stress to the two principal surfaces of the film formed by two rolls. Roll stretching methods include inter-roll stretching in which stretching is performed with a peripheral speed difference between two rolls, roll rolling described below, and the like.

Roll rolling is preferable because not only non-crystalline resin but also crystalline resin can be easily stretched. In general, when a crystalline resin is uniaxially stretched, necking in which the thickness and width of the film (film) is locally reduced tends to occur, whereas roll rolling prevents necking in even when crystalline resin is used. And the film stretching process can be stabilized.
In roll rolling, there is little decrease in the film width before and after stretching, and the thickness in the width direction can be made uniform. Therefore, the light scattering characteristics can be made uniform in the width direction of the film, the product quality can be easily maintained, and the usage rate (yield) of the film can be improved. Furthermore, a wide stretch ratio can be set.

  The draw ratio of roll rolling can be selected from a wide range. For example, the draw ratio is preferably in the range of about 1.1 to 10 times, more preferably in the range of about 1.3 to 5 times. More preferably, the range is about 1.5 to 3 times.

The heating temperature of roll rolling is not particularly limited as long as it is lower than the melting point of the polymeric piezoelectric material and can be molded, and may be a temperature equal to or higher than the glass transition temperature. In addition, when the continuous phase resin is a crystalline resin, the heating temperature of the roll rolling may be a temperature near the melting point below the melting point, and when the continuous phase resin is an amorphous resin, the glass transition temperature below the glass transition temperature. The temperature may be near the temperature.
The heating temperature (stretching temperature) of roll rolling is preferably, for example, about 20 ° C to 200 ° C, more preferably about 40 ° C to 150 ° C, and further preferably about 60 ° C to 120 ° C. It is particularly preferable that the temperature is about 80 ° C to 120 ° C.

The roll rolling pressure is preferably, for example, about 9.8 × 10 ³ N / m to 9.8 × 10 ⁶ N / m, and 9.8 × 10 ⁴ N / m to 9.8 × 10 ^6. More preferably, it is about N / m.

The film is stretched by applying a pressure with the film sandwiched between rolls or burettes. When the film is stretched using a burette, the film is preliminarily heated at 60 to 170 ° C. for 1 to 60 minutes before applying pressure to the film sandwiched between the burettes, that is, before stretching. It is preferable to perform pre-preheating.
The pre-stretching preheat treatment temperature is preferably 100 ° C. to 160 ° C., and the preheating time is preferably 5 minutes to 30 minutes.

From the viewpoint of improving the piezoelectric constant, it is preferable that the polymer piezoelectric material after the stretching treatment is subjected to a certain heat treatment (hereinafter also referred to as “annealing treatment”).
The temperature of the annealing treatment is preferably about 80 ° C to 160 ° C, and more preferably 100 ° C to 155 ° C.

The temperature application method for the annealing treatment is not particularly limited, and examples thereof include direct heating using a hot air heater or infrared heater, or immersing a polymer piezoelectric material in a heated liquid such as heated silicon oil. .
At this time, if the polymer piezoelectric material is deformed due to linear expansion or dimensional change, it becomes difficult to obtain a practically flat film. Therefore, a certain tensile stress (for example, 0.01 MPa to 100 MPa) is applied to the polymer piezoelectric material. It is preferable to apply the temperature while preventing the polymer piezoelectric material from sagging.

  The temperature application time for the annealing treatment is preferably from 1 second to 300 seconds, and more preferably from 1 second to 60 seconds. When annealing is performed for more than 300 seconds, the degree of orientation may decrease due to the growth of spherulites from the molecular chains of the amorphous portion at a temperature higher than the glass transition temperature of the polymeric piezoelectric material. May decrease.

The polymeric piezoelectric material annealed as described above is preferably cooled rapidly after the annealing treatment. In the annealing process, “rapidly cool” means that the annealed polymer piezoelectric material is immersed in, for example, ice water immediately after the annealing process and cooled to at least the glass transition temperature Tg or less. It means that no other treatment is included in the dipping time.
The rapid cooling method includes a method of immersing the annealed polymer piezoelectric material in a coolant such as ethanol, methanol, or liquid nitrogen containing water, ice water, ethanol, or dry ice, or by spraying a liquid spray with a low vapor pressure to evaporate. The method of cooling by latent heat is mentioned. To continuously cool the polymer piezoelectric material, it is possible to rapidly cool the polymer piezoelectric material by bringing it into contact with a metal roll controlled to a temperature not higher than the glass transition temperature Tg of the polymer piezoelectric material. It is.

  Further, the number of times of cooling may be only once, or may be two or more. Furthermore, annealing and cooling can be alternately repeated.

<Physical properties of polymer piezoelectric material>
Hereinafter, the physical properties of the polymeric piezoelectric material of the present embodiment will be described.

- piezoelectric constant _{d 14} -
Piezoelectricity of polymeric piezoelectric material, for example, can be evaluated by measuring the piezoelectric constant d ₁₄ of the piezoelectric polymer.
Polymeric piezoelectric material of the present embodiment is the piezoelectric constant _{d 14} is 0.1pC / N or more. Incidentally, as the piezoelectric constant d ₁₄ is large, indicating that high piezoelectricity.

Piezoelectric constant d ₁₄ in the present invention, the test piece of piezoelectric polymer length 10 mm × width 3 mm, is a value calculated from the amount of charge generated and stresses gained by using a dynamic viscoelasticity measuring apparatus.
Specifically, using a dynamic viscoelasticity measuring device, 0.01 N so that the maximum shear strain applied to the test piece at a frequency of 10 Hz at room temperature falls within a range of 0.01% to 0.1%. When the shear stress of / m ^{2 to} 0.1 N / m ² is applied, the real part of the complex piezoelectric constant d ₁₄ of the test piece is measured, and the real part is defined as the piezoelectric constant d ₁₄ .
As the dynamic viscoelasticity measuring device, for example, “Rheograph Solid S-1” manufactured by Toyo Seiki Seisakusho may be used.

The higher the piezoelectric constant d ₁₄ is, the larger the displacement of the polymer piezoelectric member with respect to the voltage applied to the polymer piezoelectric member, and conversely, the voltage generated with respect to the force applied to the polymer piezoelectric member increases. It is useful as a member.
Specifically, in a polymeric piezoelectric member in the present embodiment, the piezoelectric constant _{d 14} is at 0.1pC / N or more, preferably at least 0.3pC / N, more preferably at least 0.5 pC / N. The upper limit of the piezoelectric constant _{d 14} is not particularly limited, from the viewpoint of the balance, such as transparency, which will be described later, is preferably from 50pc / N, more preferably not more than 20 pC / N or less, and more preferably 10pC / N.

  Other piezoelectric constants d14 include those measured by the displacement method (unit: pm / V) and those measured by the stress-charge method (unit: pC / N). In one aspect of this embodiment, the piezoelectric constant d14 by the stress-charge method may be 0.1 pC / N or more, and the piezoelectric constant d14 by the displacement method may be 0.1 pm / V or more.

  In the present specification, the “MD direction” is a direction in which the film flows (Machine Direction), and the “TD direction” is a direction perpendicular to the MD direction and parallel to the main surface of the film (Transverse Direction). ).

-Elastic modulus-
Modulus in the present invention, when the piezoelectric constant d ₁₄ measured with a dynamic viscoelasticity measuring apparatus described above, a value obtained from the shear strain and stress.
Specifically, using a dynamic viscoelasticity measuring device, 0.01 N so that the maximum shear strain applied to the test piece at a frequency of 10 Hz at room temperature falls within a range of 0.01% to 0.1%. It is an elastic modulus of the test piece when a shear stress of / m ^{2 to} 0.1 N / m ² is applied.
The elastic modulus of the polymeric piezoelectric material of the present embodiment is preferably 0.1 GPa to 100 GPa, more preferably 0.2 GPa to 50 GPa, still more preferably 0.3 GPa to 30 GPa, and particularly preferably 0.8. 5 GPa to 10 GPa.
When the elastic modulus of the polymeric piezoelectric material is 0.1 GPa or more, sufficient shape retention can be secured, and when the elastic modulus is 100 GPa or less, the film can be prevented from becoming brittle.
The elastic modulus of the polymeric piezoelectric material can be adjusted by the film composition, stretching ratio, heating conditions, and the like. For example, if the draw ratio is increased, the elastic modulus of the polymeric piezoelectric material can be increased.

  In addition, examples of the elastic modulus of the polymer piezoelectric material of the present embodiment include a tensile elastic modulus measured by a method based on JIS K7161. Specifically, the film is cut to prepare a strip-shaped test piece having a width (direction orthogonal to the stretching direction of the polymer piezoelectric material) of 10 mm and a length (stretching direction of the polymer piezoelectric material) of 120 mm; What is necessary is just to measure the tensile elasticity modulus of a test piece on the conditions of the distance between chuck | zippers of 100 mm, and the tensile speed of 100 mm / min using a test machine at the temperature of 23 degreeC. The tensile modulus of the test piece is preferably 0.1 GPa to 100 GPa, more preferably 0.1 GPa to 50 GPa.

  In the present embodiment, the “stretching direction” is the direction in which the molecular chain of the polymeric piezoelectric material extends; or the direction in which the tensile modulus is 0.1 GPa to 100 GPa. The “direction orthogonal to the stretching direction” is a direction orthogonal to the direction in which the molecular chain of the polymeric piezoelectric material extends.

Although there is no restriction | limiting in particular in the shape of the polymeric piezoelectric material of this embodiment, A film shape is preferable.
The thickness of the polymeric piezoelectric material (for example, the thickness of the polymeric piezoelectric material in the case of a film shape) is not particularly limited, but is preferably 10 μm to 400 μm, more preferably 20 μm to 300 μm, and more preferably 20 μm to 250 μm. Is more preferable, and 20 μm to 200 μm is particularly preferable.

[Laminate]
You may form a laminated body using the polymeric piezoelectric material of this embodiment. The laminate is, for example, a polymer piezoelectric layer containing a polymer piezoelectric material, and a surface made of a thermoplastic resin other than an optically active polymer having an imide ring structure and disposed on at least one main surface of the polymer piezoelectric layer. And a layer.

The aforementioned laminate includes a surface layer made of a thermoplastic resin. The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resins such as polyethylene resins and polypropylene resins, polyvinyl chloride resins, polystyrene resins, polyester resins, polycarbonate resins, polyurethane resins, and acrylic resins. preferable.
As the polyester resin, polyethylene terephthalate (PET) resin is preferable.

  The laminate preferably has an adhesive layer between the polymer piezoelectric layer and the surface layer. As the adhesive layer, for example, an OCA (Optical Clear Adhesive) tape can be employed.

[Applications of polymer piezoelectric materials and laminates]
Polymer piezoelectric materials and laminates are speakers, headphones, touch panels, remote controllers, microphones, underwater microphones, ultrasonic transducers, ultrasonic applied measuring instruments, piezoelectric vibrators, mechanical filters, piezoelectric transformers, delay devices, sensors, accelerations Sensor, Shock sensor, Vibration sensor, Pressure sensor, Tactile sensor, Electric field sensor, Sound pressure sensor, Display, Fan, Pump, Variable focus mirror, Sound insulation material, Sound insulation material, Keyboard, Sound device, Information processing machine, Measurement device, It can be used in various fields such as medical equipment.

  At this time, the polymer piezoelectric material preferably has at least two surfaces and is used as a piezoelectric element having electrodes on the surfaces. The electrodes only need to be provided on at least two surfaces of the polymeric piezoelectric material. Further, an adhesive layer or a base material layer may be provided between the electrode and the polymer piezoelectric material. The electrode is not particularly limited. For example, opaque materials such as Al, Cu, Ag, Ag paste, carbon black, ITO (crystallized ITO and amorphous ITO), ZnO, IGZO, IZO, conductive polymer ( Transparent materials such as polythiophene, PEDOT), Ag nanowires, carbon nanotubes, and graphene are used.

  In addition, a polymer piezoelectric material and electrodes can be repeatedly stacked to be used as a laminated piezoelectric element. As an example, a unit in which an electrode and a polymer piezoelectric material unit are repeatedly stacked, and the main surface of the polymer piezoelectric material that is not covered with an electrode is covered with an electrode. Specifically, the unit having two repetitions is a laminated piezoelectric element in which electrodes, polymer piezoelectric material, electrodes, polymer piezoelectric material, and electrodes are stacked in this order. The polymer piezoelectric material used for the laminated piezoelectric element may be one of the piezoelectric polymer materials according to the present embodiment, and the other layers may not be the polymer piezoelectric material according to the present embodiment. Also good.

  The piezoelectric element using the polymeric piezoelectric material of the present embodiment can be applied to the above-described 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.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof.

[Production Example 1]
<Production of piezoelectric material>
A round bottom flask equipped with a Dean-Stark trap was charged with 150 g of L-aspartic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 340 mL of mesitylene, 140 mL of sulfolane, 200 mL of distilled water, and 13 g of 85% phosphoric acid aqueous solution (catalyst). The Dean Stark trap was previously filled with a mixed solvent of mesitylene and sulfolane. After the inside of the round bottom flask was purged with nitrogen, it was stirred with a mechanical stirrer and subjected to dehydration condensation at 180 ° C. for 36 hours under normal pressure and nitrogen atmosphere. Further, this reaction residue was put in a heat-resistant vat and heated in an oven set at 200 ° C. under a nitrogen stream to volatilize the residual solvent, and then solid phase polymerization was performed for 48 hours.
The obtained residue was dissolved in 1200 mL of dimethylformamide, and insoluble matters were removed by filtration. The resulting filtrate was added with 1200 mL of acetone to filter off the slightly yellow solid produced, washed with distilled water until the filtrate became neutral, further washed with methanol, dried, and dried to obtain polysuccinimide (optically active polymer). A) was obtained.

[Production Example 2]
A round bottom flask equipped with a Dean-Stark trap was charged with 50 g of L-aspartic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 100 mL of distilled water, and 21.7 g of 85% phosphoric acid aqueous solution (catalyst). After replacing the inside of the round bottom flask with nitrogen, the mixture was stirred with a mechanical stirrer, and water in the flask was distilled off with an oil bath heated to 120 ° C. under normal pressure and nitrogen atmosphere. The temperature in the flask was raised to 180 ° C. and the reaction was carried out for 2.5 hours. Further, the pressure in the flask was reduced to 70 mmHg, and the reaction was continued for 1 hour.
The obtained residue was dissolved in 400 mL of dimethylformamide, and insoluble matters were removed by filtration. To the obtained filtrate, 800 mL of acetone was added to filter out the slightly yellow solid produced, and the filtrate was washed with distilled water until the filtrate became neutral, further washed with methanol, and dried to obtain polysuccinimide (optically active polymer). B) was obtained.

[Production Example 3]
A round bottom flask equipped with a Dean-Stark trap was charged with 50 g of L-aspartic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 112 mL of mesitylene, 50 mL of sulfolane, 100 mL of distilled water and 4.4 g of 85% aqueous phosphoric acid solution (catalyst). The Dean Stark trap was previously filled with a mixed solvent of mesitylene and sulfolane. The inside of the round bottom flask was purged with nitrogen, stirred with a mechanical stirrer, and dehydrated and condensed at 180 ° C. for 4.5 hours under normal pressure and nitrogen atmosphere.
The residue obtained by removing the solvent was dissolved in 400 mL of dimethylformamide, and the insoluble material was removed by filtration. To the obtained filtrate, 600 mL of acetone was added to filter out the slightly yellow solid formed. The filtrate was washed with distilled water until the filtrate became neutral, further washed with methanol, and dried to obtain polysuccinimide (optically active polymer). C) was obtained.

[Production Example 4]
A polysuccinimide (optically active polymer D) was obtained in the same manner as in Production Example 3 except that 4.4 g of the 85% phosphoric acid aqueous solution was changed to 8.6 g of tin (II) chloride dihydrate.

[Production Example 5]
The catalyst was changed from 4.4 g of 85% phosphoric acid aqueous solution to 8.6 g of tin (II) chloride dihydrate, and for dehydration condensation, “dehydration condensation at 180 ° C. for 4.5 hours under atmospheric pressure and nitrogen atmosphere” The operation was performed after “dehydration condensation was performed at 180 ° C. for 4 hours under normal pressure and nitrogen atmosphere, and then 8.8 g of 85% phosphoric acid aqueous solution was added, and dehydration condensation was performed for 4 hours at 180 ° C. under normal pressure and nitrogen atmosphere. A polysuccinimide (optically active polymer E) was obtained in the same manner as in Production Example 3 except that the operation was changed to “Performed”.

  By the method shown below, the weight average molecular weight and specific rotation of the polysuccinimide (optically active polymers A to E) synthesized by the above-described method were measured. The measurement results are as shown in Table 1 below.

(Measurement of number average molecular weight and weight average molecular weight)
The number average molecular weight (Mn) and weight average molecular weight (Mw) of polysuccinimide indicate values measured by gel permeation chromatograph (GPC) by the following GPC measurement method.
-GPC measuring device-
Showex DPC, Shodex GPC-101
-Column-
Showex Denko, Shodex OHpak SB-804 HQ
-Sample preparation-
Poliscinimide was dissolved in dimethylformamide as a solvent at 40 ° C. to prepare a sample solution having a concentration of 1 mg / mL.
-Measurement conditions-
0.1 mL of the sample solution was introduced into the column with a solvent (dimethylformamide (containing 0.1% by mass of LiBr)) at a temperature of 40 ° C. and a flow rate of 0.7 mL / min, and the sample concentration in the sample solution separated by the column was determined. Measured with a differential refractometer. The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polysuccinimide were calculated based on a calibration curve prepared using Standard Shodex SM-105 manufactured by Showa Denko K.K.

(Measurement of specific rotation)
The specific rotation at 589 nm of poriscinimide was measured by the following method.
-Measurement conditions-
Poliscinimide was dissolved in dimethylformamide so as to be 1.5% by mass, and the optical rotation α at a measurement wavelength of 589 nm and 20 ° C. was measured using a fully automatic polarimeter AUTOPOL V (manufactured by Rudolph Research Analytical). The specific rotation [α] was calculated from the optical rotation α using the following formula.
[Formula 1]
[α] = α / (c × l)
c: Measurement sample concentration (g / dL)
l: Cell length (100 mm)

  The measurement results of the weight average molecular weight and specific rotation of polysuccinimide (optically active polymers A to E) are as shown in Table 1 below.

[Example 1]
1 g of polysuccinimide (optically active polymer A) obtained in Production Example 1 is dissolved in 10 mL of dimethylformamide, cast into a Teflon (registered trademark) petri dish, and allowed to stand at room temperature for 24 hours in a nitrogen stream. Obtained. The obtained cast film was roll-rolled at a draw ratio of 2 using a heat-stretching roller (manufactured by Imoto Seisakusho) set to 100 ° C., and subjected to orientation treatment. Thereby, a polymer piezoelectric material was produced.
The thickness of the obtained polymer piezoelectric material was 46 μm.

[Comparative Example 1]
A polymeric piezoelectric material was produced in the same manner as in Example 1 except that the set temperature of the heat-stretching roller (manufactured by Imoto Seisakusho) was changed from 100 ° C to 120 ° C.

[Example 2]
Except that 1 g of polysuccinimide (optically active polymer A) obtained in Production Example 1 was changed to 1 g of polysuccinimide (optically active polymer B) obtained in Production Example 2, the same procedure as in Example 1 was carried out. A molecular piezoelectric material was prepared.

Example 3
1 g of the polysuccinimide (optically active polymer A) obtained in Production Example 1 was changed to 1 g of the polysuccinimide (optically active polymer C) obtained in Production Example 3, and the heat stretching roller (manufactured by Imoto Seisakusho) A polymeric piezoelectric material was produced in the same manner as in Example 1 except that the set temperature was changed from 100 ° C. to 80 ° C.

Example 4
Except that 1 g of polysuccinimide (optically active polymer A) obtained in Production Example 1 was changed to 1 g of polysuccinimide (optically active polymer C) obtained in Production Example 3, the same procedure as in Example 1 was carried out. A molecular piezoelectric material was prepared.

Example 5
1 g of the polysuccinimide (optically active polymer A) obtained in Production Example 1 was changed to 1 g of the polysuccinimide (optically active polymer C) obtained in Production Example 3, and the heat stretching roller (manufactured by Imoto Seisakusho) A polymeric piezoelectric material was produced in the same manner as in Example 1 except that the set temperature was changed from 100 ° C. to 120 ° C.

Example 6
Except that 1 g of polysuccinimide (optically active polymer A) obtained in Production Example 1 was changed to 1 g of polysuccinimide (optically active polymer D) obtained in Production Example 4, the same procedure as in Example 1 was carried out. A molecular piezoelectric material was prepared.

Example 7
Except that 1 g of polysuccinimide (optically active polymer A) obtained in Production Example 1 was changed to 1 g of polysuccinimide (optically active polymer E) obtained in Production Example 5, the same procedure as in Example 1 was carried out. A molecular piezoelectric material was prepared.

(Measurement of piezoelectric constant _{d 14)}
According measuring method of the piezoelectric constant d ₁₄ as described above, it was measured piezoelectric constant d ₁₄ of the piezoelectric polymer of Example 7 and Comparative Example 1. As a dynamic viscoelasticity measuring apparatus, “Rheograph Solid S-1” manufactured by Toyo Seiki Seisakusho Co., Ltd. was used.
The measurement results of the piezoelectric constant d ₁₄ in Table 2 below.

(Measurement of elastic modulus)
According to the elastic modulus measurement method described above, the elastic modulus of the polymeric piezoelectric materials of Examples 1 to 7 and Comparative Example 1 was measured. As a dynamic viscoelasticity measuring apparatus, “Rheograph Solid S-1” manufactured by Toyo Seiki Seisakusho Co., Ltd. was used.
The measurement results of the elastic modulus are shown in Table 2 below.

As shown in Table 2, even in the case of using the polysuccinimide as an optically active polymer A-E, the piezoelectric constant d ₁₄ is a polymeric piezoelectric material is obtained at 0.1pC / N or more.

[Reference Example 1]
NatureWorks LLC manufactured by polylactic acid (PLA) (product ^name: Ingeo TM ^biopolymer, brand: 4032D, weight average molecular weight Mw: 20 50,000) press set at 20 ° C. after the heat pressing for one minute at 205 ° C. pellets To obtain a quenched film. Two opposite sides of the quenched film were fixed with a clip, and stretched up to 4 times while heating at 70 ° C. in a direction perpendicular to the two fixed sides to obtain a stretched film. The obtained film was annealed at 130 ° C. for 600 seconds and then rapidly cooled to obtain the polymeric piezoelectric material of Reference Example 1. Further, Mw of polylactic acid was measured by the following GPC measurement method.
-GPC measurement method-
・ Measurement device Waters GPC-100
・ Column Showa Denko KK, Shodex LF-804
Sample Preparation The polymer piezoelectric material of Reference Example 1 was dissolved in a solvent (chloroform) at 40 ° C. to prepare a sample solution having a concentration of 1 mg / mL.
Measurement conditions 0.1 mL of the sample solution was introduced into the column at a solvent (chloroform), a temperature of 40 ° C. and a flow rate of 1 mL / min, and the sample concentration in the sample solution separated by the column was measured with a differential refractometer. For the molecular weight of polylactic acid, a universal calibration curve was prepared using a polystyrene standard sample, and the weight average molecular weight (Mw) of polylactic acid was calculated.

<Heat and heat resistance>
The weight average molecular weight of the polymeric piezoelectric material (Example 1, Reference Example 1) immediately after production (within 24 hours from production) was measured (initial Mw). Next, from a laminate immediately after production (within 24 hours from production), a rectangular test piece of 50 mm in the longitudinal direction and 50 mm in the width direction was prepared, and the test piece was kept in a constant temperature and humidity chamber maintained at 85 ° C. and 85% RH. And held for a predetermined time (24 hours or 192 hours). With respect to this test piece, the weight average molecular weight of the polymeric piezoelectric material was measured (Mw after the wet heat resistance test), and the Mw maintenance rate represented by the following formula was evaluated according to the following criteria. The results are shown in Table 3.
Formula: Mw retention rate = Mw after wet heat resistance test / initial Mw
〔Evaluation criteria〕
A: Mw maintenance rate ≧ 0.8
B: 0.8> Mw maintenance rate ≧ 0.5
C: Mw maintenance rate <0.5

As shown in Table 3, the polymeric piezoelectric material obtained in Example 1 has a high Mw retention rate even after 192 hours under the condition of 85 ° C. and 85% RH, and is excellent in heat and moisture resistance. I understand that
On the other hand, it can be seen that the polymer piezoelectric material obtained in Reference Example 1 has a low Mw retention rate after 24 hours under the condition of 85 ° C. and 85% RH, and has insufficient moisture and heat resistance.

Claims (8)

Comprises an optically active polymer having an imide ring structure, is the piezoelectric constant _{d 14} is 0.1pC / N or more, a polymeric piezoelectric material.   The polymeric piezoelectric material according to claim 1, wherein the optically active polymer having an imide ring structure is polysuccinimide. The polymeric piezoelectric material according to claim 1 or 2, wherein the optically active polymer having an imide ring structure has an absolute value of specific rotation at 589 nm of 0.1 deg · cm ² · g ^-1 or more.   The polymeric piezoelectric material according to any one of claims 1 to 3, wherein the optically active polymer having the imide ring structure has a weight average molecular weight of 18,000 or more.   5. The polymeric piezoelectric material according to claim 1, wherein the content of the optically active polymer having an imide ring structure is 50% by mass or more. It is a manufacturing method of the polymeric piezoelectric material of any one of Claims 1-5,
A film forming step of obtaining a film by forming a composition containing the optically active polymer having the imide ring structure; and
A stretching step of stretching the film;
A method for producing a polymeric piezoelectric material, comprising: The composition comprises a solvent;
The method for producing a piezoelectric polymer material according to claim 6, wherein the film forming step includes a step of forming a film by forming the composition by a casting method and a step of evaporating and removing the solvent from the film. Method.   The method for producing a polymeric piezoelectric material according to claim 6 or 7, wherein the stretching step is a step of performing orientation treatment by roll stretching.