JP2016172797A - Polymeric piezoelectric material, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymeric piezoelectric material which can be produced while inhibiting the occurrence of isocyanate, and has improved moist heat resistance.SOLUTION: A polymeric piezoelectric material comprises an aliphatic polyester (A), and a stabilizer (B) that is at least one of a specific ketenimine compound and a polymer compound thereof, with a weight average molecular weight of 300-60000, where a content of the stabilizer (B) is 0.01-10 pts.mass relative to 100 pts.mass of the aliphatic polyester (A).SELECTED DRAWING: None

Description

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

Conventionally, PZT (PbZrO ₃ —PbTiO ₃ solid solution), which is a ceramic material, has been used as a piezoelectric material. However, since PZT contains lead, it has a low environmental burden and is highly flexible. Molecular piezoelectric materials are being used.

  Currently known polymeric piezoelectric materials include nylon 11, polyvinyl fluoride, polyvinyl chloride, polyurea, polyvinylidene fluoride (β-type) (PVDF), and vinylidene fluoride-trifluoroethylene copolymer (P ( VDF-TrFE)) (75/25). However, polymeric piezoelectric materials are not as good as PZT in piezoelectricity, and are required to improve piezoelectricity. For this reason, attempts have been made to improve the piezoelectricity of the polymeric piezoelectric material from various viewpoints.

For example, the ferroelectric polymers PVDF and P (VDF-TrFE) have excellent piezoelectricity among the polymers, and the piezoelectric constant d ₃₁ is 20 pC / N or more. The film material formed from PVDF and P (VDF-TrFE), by orienting the polymer chain in the stretching direction by stretching operation, by giving different charges on the front and back of the film by corona discharge, An electric field is generated in the direction perpendicular to the film surface, and permanent dipoles containing fluorine in the side chains of the polymer chain are oriented parallel to the electric field direction to impart piezoelectricity. However, on the polarized film surface, foreign charges such as water and ions in the air tend to adhere in the direction that cancels the orientation, and the orientation of the permanent dipole aligned by the polarization treatment is relaxed, and the piezoelectricity over time. There has been a practical problem such as a noticeable decrease.

  PVDF is the most piezoelectric material among the above polymer piezoelectric materials, but the dielectric constant is relatively high among the polymer piezoelectric materials and is 13. Therefore, the piezoelectric d constant is divided by the dielectric constant. The value of the piezoelectric g constant (open voltage per unit stress) becomes small. Moreover, although PVDF has good conversion efficiency from electricity to sound, improvement in the conversion efficiency from sound to electricity has been expected.

  In recent years, attention has been focused on using aliphatic polyesters having optical activity such as polylactic acid in addition to the above-described polymeric piezoelectric materials. It is known that polylactic acid polymers exhibit piezoelectricity only by mechanical stretching operation.

  Among the polymers having optical activity, the piezoelectricity of a polymer crystal such as polylactic acid is attributed to a C = O bond permanent dipole that exists 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 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 Japanese Patent No. 5259026

However, the piezoelectric materials disclosed in Patent Document 1 and Patent Document 2 are both insufficient in transparency. Furthermore, since aliphatic polyesters such as polylactic acid are hydrolyzable, there is a problem that reliability is low when used as a piezoelectric element in an environment that causes hydrolysis such as moisture in the atmosphere.
On the other hand, a polymer piezoelectric material having improved wet heat resistance by adding a stabilizer such as carbodiimide to an aliphatic polyester has been disclosed (for example, see Patent Document 3). However, since carbodiimide generates isocyanate due to thermal degradation during the production of the piezoelectric polymer material, it is desired to further improve workability. Further, the polymer piezoelectric material disclosed in Patent Document 3 is required to further improve the heat and moisture resistance from the viewpoint of further improving the reliability.
In view of the above circumstances, an object of the present invention is to provide a polymeric piezoelectric material that can be produced in a favorable working environment while suppressing the generation of isocyanate, and has improved wet heat resistance, and a method for producing the same.

Specific means for achieving the above object are as follows.
[1] An aliphatic polyester (A) having a weight average molecular weight of 50,000 to 1,000,000 and having optical activity;
A ketene imine compound represented by the following general formula (B1), a ketene imine compound represented by the following general formula (B2), a ketene imine compound represented by the following general formula (B3), and a structure represented by the following general formula (B4) A stabilizer (B) which is at least one selected from the group consisting of a polymer compound containing a unit and a polymer compound containing a structural unit represented by the following general formula (B5), and having a weight average molecular weight of 300 to 60000 )When,
Including
The crystallinity obtained by DSC method is 20% to 80%,
A polymeric piezoelectric material comprising 0.01 to 10 parts by mass of the stabilizer (B) with respect to 100 parts by mass of the aliphatic polyester (A).

(In General Formula (B1), R ¹ and R ² each independently represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. In general formula (B1), R ³ represents an alkyl group or an aryl group.)

(In the general formula (B2), R ¹ represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. In the general formula (B2), R ² represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group, and R ³ is an alkyl group in the general formula (B2) Or represents an aryl group, n represents an integer of 2 to 4, and L ¹ represents an n-valent linking group.)

(In General Formula (B3), R ¹ represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. General Formula (B3) R ² represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group, and n represents an integer of 2 to 4.)

(In General Formula (B4), R ¹ and R ² each independently represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. In general formula (B4), R ³ represents an alkyl group or an aryl group.)

(In General Formula (B5), R ¹ represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. General Formula (B5) R ² represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group, and R ³ represents an alkylene group in the general formula (B5). Or represents an arylene group.)

[2] The polymeric piezoelectric material according to [1], wherein the stabilizer (B) includes a ketene imine compound in which n is 3 or 4 in the general formula (B2).

[3] The polymeric piezoelectric material according to [1], wherein the stabilizer (B) includes a ketene imine compound represented by the following general formula (B2-1).

(In the general formula (B2-1), R ¹ and R ⁵ each independently represents an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group. In formula (B2-1), R ² and R ⁴ each independently represent an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxy In the general formula (B2-1), R ³ and R ⁶ each independently represents an alkyl group or an aryl group, and in the general formula (B2-1), L ² represents a single bond or two Represents a valent linking group.)

[4] Internal haze to visible light is not less than 50% and piezoelectric constant _{d 14} measured by a displacement method at 25 ° C. is 1 Pm/V least, to any one of [1] to [3] The polymeric piezoelectric material as described.
[5] The polymeric piezoelectric material according to [4], wherein the internal haze is 13% or less.
[6] The product of the normalized molecular orientation MORc and the crystallinity when the reference thickness measured with a microwave transmission type molecular orientation meter is 50 μm is 40 to 700, [1] to [5] The polymeric piezoelectric material according to any one of the above.
[7] Any one of [1] to [6], wherein the aliphatic polyester (A) is a polylactic acid polymer having a main chain containing a repeating unit represented by the following formula (1). The polymeric piezoelectric material described in 1.

[8] The polymeric piezoelectric material according to any one of [1] to [7], wherein the aliphatic polyester (A) has an optical purity of 95.00% ee or more.
[9] The polymeric piezoelectric material according to any one of [1] to [8], wherein the content of the aliphatic polyester (A) is 80% by mass or more.
[10] The polymeric piezoelectric material according to any one of [1] to [9], wherein the area of the main surface is 5 mm ² or more.
[11] A method for producing the polymeric piezoelectric material according to any one of [1] to [10],
A first step of obtaining a pre-crystallized sheet containing the aliphatic polyester (A) and the stabilizer (B);
A second step of stretching the pre-crystallized sheet mainly in a uniaxial direction;
A method for producing a polymeric piezoelectric material, comprising:
[12] The method for producing a polymeric piezoelectric material according to [11], wherein annealing is performed after the second step.
[13] A method for producing the polymeric piezoelectric material according to any one of [1] to [10],
Stretching the sheet containing the aliphatic polyester (A) and the stabilizer (B) mainly in a uniaxial direction;
A method for producing a polymeric piezoelectric material, comprising an annealing process in this order.

  ADVANTAGE OF THE INVENTION According to this invention, the polymeric piezoelectric material which can be manufactured in a favorable working environment, and the heat-and-moisture resistance was improved, suppressing the generation | occurrence | production of isocyanate, and its manufacturing method can be provided.

Hereinafter, embodiments of the present invention will be described.
In this 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.
In this specification, the “main surface” of the polymeric piezoelectric material means a plane orthogonal to the thickness direction of the polymeric piezoelectric material.
In the present specification, the “main surface” may be simply referred to as “surface”.
Further, in the present specification, “film” is a concept including not only what is generally called “film” but also what is generally called “sheet”.

The polymeric piezoelectric material of the present embodiment has an aliphatic polyester (A) having a weight average molecular weight of 50,000 to 1,000,000 and optical activity (hereinafter sometimes simply referred to as “aliphatic polyester (A))”. The ketene imine compound represented by the general formula (B1), the ketene imine compound represented by the general formula (B2), the ketene imine compound represented by the general formula (B3), and the general formula (B4). A stabilizer having at least one selected from the group consisting of a polymer compound containing a structural unit and a polymer compound containing a structural unit represented by the general formula (B5), having a weight average molecular weight of 300 to 60000 ( B) (hereinafter sometimes simply referred to as “stabilizer (B)”), the crystallinity obtained by the DSC method is 20% to 80%, and aliphatic polyester (A) 100 quality Stabilizer (B) is contained 10 parts by 0.01 parts by mass with respect to part.
ADVANTAGE OF THE INVENTION According to this invention, the polymeric piezoelectric material which can be manufactured in a favorable working environment and improved moisture-heat resistance, suppressing generation | occurrence | production of isocyanate is obtained.

The operation of the present invention is not clear, but is considered as follows.
Hydrolysis of the aliphatic polyester (A) is presumed to proceed according to the following scheme. Therefore, in order to suppress hydrolysis, a method of suppressing contact with moisture by a laminate or the like, or forming a crosslinked structure in a hydrolyzed part in the system, or blocking a free carboxy group is considered. It is done. In the present invention, a stabilizer having a functional group that easily forms an interaction with both functional groups of a hydroxyl group and a carboxy group, more preferably a functional group that easily forms an interaction with a plurality of hydroxyl groups or carboxy groups. It is thought that the hydrolysis can be suppressed by using a stabilizer.
This is a stabilizer having a functional group that interacts with both a hydroxyl group and a carboxy group. When a compound having a molecular weight within a specific range is used, the aliphatic polyester (A) is crystallized. In addition, it tends to move from a portion that tends to become a crystal (specifically, a region where the molecular chain is not broken) to a portion that is difficult to become a crystal (a region where a part of the molecular chain is broken and a hydroxyl group or a carboxy group is generated). For this reason, the stabilizer is present in a portion having a low crystallinity, which is less heat and heat resistant than a portion having a high crystallinity, and is present uniformly without inhibiting the crystallization of the portion that tends to be crystallized. It is considered that the moisture and heat resistance can be improved efficiently. In the present invention, the stabilizer (B) is used as this stabilizer.
On the other hand, when a compound having an oxazoline group known as a stabilizer for the aliphatic polyester (A) is used, the oxazoline group reacts with a carboxy group, but hardly reacts with a hydroxyl group. For this reason, when the aliphatic polyester (A) is crystallized, oxazoline is also present in a portion that is likely to be crystallized, which makes it difficult to crystallize. Large crystals may be formed. Therefore, there is a concern that the transparency of the polymeric piezoelectric material is lowered. In addition, since oxazoline is difficult to move to a portion having lower crystallinity, it is considered that it is difficult to sufficiently obtain a moist heat resistance improving effect.

  Hereinafter, preferred modes of the polymeric piezoelectric material of the present embodiment will be described.

<Aliphatic polyester (A)>
The polymeric piezoelectric material of this embodiment contains an aliphatic polyester (A).
The aliphatic polyester (A) in this embodiment is an aliphatic polyester having a weight average molecular weight of 50,000 to 1,000,000 and optical activity.
Here, the “aliphatic polyester having optical activity” refers to a polymer having a helical structure and a molecular optical activity.
The aliphatic polyester (A) in the present embodiment is a polymer having a weight average molecular weight of 50,000 to 1,000,000 among the above-mentioned “aliphatic polyester having optical activity”.
Examples of the aliphatic polyester (A) include polylactic acid polymers and poly (β-hydroxybutyric acid). The aliphatic polyester (A) is preferably a helical chiral polymer that easily increases piezoelectricity.

  From the viewpoint of improving the piezoelectricity of the polymeric piezoelectric material, the aliphatic polyester (A) preferably has an optical purity of 95.00% ee or more, more preferably 96.00% ee or more, More preferably, it is 99.00% ee or more, and even more preferably 99.99% ee or more. Desirably, it is 100.00% ee. By setting the optical purity of the aliphatic polyester (A) within 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.

Here, the optical purity of the aliphatic polyester (A) 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 optical purity of the aliphatic polyester (A) is
“The amount difference (absolute value) between the amount of L-form [mass%] of aliphatic polyester (A) and the amount of D-form [mass%] of aliphatic polyester (A)” is expressed as “aliphatic polyester Multiply by (100) the number divided by (total amount of (A) L-form [mass%] and aliphatic polyester (A) D-form [mass%]]. (Multiplied).

The amount of L-form [mass%] of the aliphatic polyester (A) and the amount of D-form [mass%] of the aliphatic polyester (A) are obtained by a method using high performance liquid chromatography (HPLC). Use the value obtained. The measurement method is as follows.
A sample (polymer piezoelectric material) of 1.0 g is weighed into a 50 mL Erlenmeyer flask, and 2.5 mL of IPA (isopropyl alcohol) and 5 mL of 5.0 mol / L sodium hydroxide solution are added. Next, the Erlenmeyer flask containing the sample solution is placed in a water bath at a temperature of 40 ° C. and stirred for about 5 hours until the aliphatic polyester (A) is completely hydrolyzed.

The sample solution is cooled to room temperature, neutralized by adding 20 mL of a 1.0 mol / L hydrochloric acid solution, and the Erlenmeyer flask is sealed and mixed well. Dispense 1.0 mL of the sample solution into a 25 mL volumetric flask and prepare HPLC sample solution 1 with 25 mL of mobile phase. 5 μL of the HPLC sample solution 1 is injected into the HPLC apparatus, the D / L body peak area of the aliphatic polyester (A) is determined under the following HPLC conditions, and the amounts of L body and D body are calculated.
-HPLC measurement conditions-
・ Column Optical resolution column, SUMICHIRAL OA5000, manufactured by Sumika Chemical Analysis Co., Ltd. ・ Measurement device, liquid chromatography manufactured by JASCO Corporation, column temperature: 25 ° C.
Mobile phase 1.0 mM-copper (II) sulfate buffer / IPA = 98/2 (V / V)
Copper (II) sulfate / IPA / water = 156.4 mg / 20 mL / 980 mL
・ Mobile phase flow rate 1.0ml / min ・ Detector UV detector (UV254nm)

  As said aliphatic polyester (A), the compound which has a principal chain containing the repeating unit represented by following formula (1) from a viewpoint of raising optical purity and improving piezoelectricity is preferable.

Among the compounds having the repeating unit represented by the formula (1) as a main chain, a polylactic acid polymer is preferable.
Here, the polylactic acid polymer is “polylactic acid (polymer consisting only of repeating units derived from a monomer selected from L-lactic acid and D-lactic acid)”, “L-lactic acid or D-lactic acid, and L -Copolymer of lactic acid or a compound copolymerizable with D-lactic acid "or a mixture of both.
Among the polylactic acid polymers, polylactic acid is preferable, and L-lactic acid homopolymer (PLLA) or D-lactic acid homopolymer (PDLA) is most preferable.

Polylactic acid is a polymer in which lactic acid is polymerized by an ester bond and connected for a long time.
It is known that polylactic acid can be produced by a lactide method via lactide; a direct polymerization method in which lactic acid is heated in a solvent under reduced pressure and polymerized while removing water.
As polylactic acid, homopolymer of L-lactic acid, homopolymer of D-lactic acid, block copolymer containing at least one polymer of L-lactic acid and D-lactic acid, and at least one of L-lactic acid and D-lactic acid A graft copolymer containing a polymer may be mentioned.

  Examples of the “compound copolymerizable with L-lactic acid or D-lactic acid” 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-hydroxycaprone Acids, hydroxycarboxylic acids such as 6-hydroxymethylcaproic acid, mandelic acid; cyclic esters such as glycolide, β-methyl-δ-valerolactone, γ-valerolactone, ε-caprolactone; oxalic acid, malonic acid, succinic acid, Glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, urine Polycarboxylic acids such as decanedioic acid, dodecanedioic acid, terephthalic acid and their anhydrides; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butane Diol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, neopentyl Polyhydric alcohols such as glycol, tetramethylene glycol and 1,4-hexanedimethanol; polysaccharides such as cellulose; aminocarboxylic acids such as α-amino acids;

  The “copolymer of L-lactic acid or D-lactic acid and a compound copolymerizable with the L-lactic acid or D-lactic acid” includes a block copolymer or graft copolymer having a polylactic acid sequence capable of forming a helical crystal. Can be mentioned.

The concentration of the structure derived from the copolymer component in the aliphatic polyester (A) is preferably 20 mol% or less.
For example, when the aliphatic polyester (A) is a polylactic acid polymer, the structure derived from lactic acid and the structure derived from a compound copolymerizable with lactic acid (copolymer component) in the polylactic acid polymer It is preferable that the concentration of the structure derived from the copolymer component is 20 mol% or less with respect to the total number of moles.

  Polylactic acid polymers are obtained by, for example, direct dehydration condensation of lactic acid described in JP-A-59-096123 and JP-A-7-033861; US Pat. No. 2,668,182 and A method of ring-opening polymerization using lactide, which is a cyclic dimer of lactic acid, as described in US Pat. No. 4,057,357.

  Furthermore, the polylactic acid polymer obtained by the above production methods has an optical purity of 95.00% ee or higher. For example, when polylactic acid is produced by the lactide method, the optical purity is improved by crystallization operation. It is preferable to polymerize lactide having an optical purity of 95.00% ee or higher.

-Weight average molecular weight-
The weight average molecular weight (Mw) of the aliphatic polyester (A) is 50,000 to 1,000,000 as described above.
When the Mw of the aliphatic polyester (A) is 50,000 or more, the mechanical strength of the polymeric piezoelectric material is improved. The Mw is preferably 100,000 or more, and more preferably 200,000 or more.
On the other hand, when the Mw of the aliphatic polyester (A) is 1,000,000 or less, the moldability when obtaining a polymeric piezoelectric material by molding (for example, extrusion molding) is improved. The Mw is preferably 800,000 or less, and more preferably 300,000 or less.

  Further, the molecular weight distribution (Mw / Mn) of the aliphatic polyester (A) is preferably 1.1 to 5 and more preferably 1.2 to 4 from the viewpoint of the strength of the polymeric piezoelectric material. preferable. Furthermore, it is preferable that it is 1.4-3.

In addition, the weight average molecular weight Mw and molecular weight distribution (Mw / Mn) of aliphatic polyester (A) point out the value measured using the gel permeation chromatograph (GPC). Here, Mn is the number average molecular weight of the aliphatic polyester (A).
Hereinafter, an example of a method for measuring Mw and Mw / Mn of the aliphatic polyester (A) by GPC is shown.
-GPC measuring device-
Waters GPC-100
-Column-
Made by Showa Denko KK, Shodex LF-804
-Sample preparation-
A polymeric piezoelectric material is dissolved in a solvent (for example, 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 is introduced into the column at a solvent [chloroform], a temperature of 40 ° C., and a flow rate of 1 ml / min.

The sample concentration in the sample solution separated by the column is measured with a differential refractometer.
A universal calibration curve is prepared using a polystyrene standard sample, and the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the aliphatic polyester (A) are calculated.

Commercially available polylactic acid can be used as the polylactic acid polymer that is an example of the aliphatic polyester (A).
Examples of commercially available products, PURAC Co. PURASORB (PD, PL), manufactured by Mitsui Chemicals, Inc. of LACEA (H-100, H- 400), NatureWorks LLC Corp. ^Ingeo TM Biopolymer, and the like.
When a polylactic acid polymer is used as the aliphatic polyester (A), in order to make the polylactic acid polymer have a weight average molecular weight (Mw) of 50,000 or more, polylactic acid is obtained by a lactide method or a direct polymerization method. It is preferable to produce a polymer.

The polymeric piezoelectric material of the present embodiment may contain only one kind of the above-described aliphatic polyester (A), or may contain two or more kinds.
The content of the aliphatic polyester (A) in the polymeric piezoelectric material of the present embodiment (the total content in the case of two or more types) is preferably 80% by mass or more with respect to the total amount of the polymeric piezoelectric material. .

<Stabilizer (B)>
The polymeric piezoelectric material of this embodiment contains a stabilizer (B).
The stabilizer (B) is a ketene imine compound represented by the following general formula (B1), a ketene imine compound represented by the following general formula (B2), a ketene imine compound represented by the following general formula (B3), and the following general formula It is at least one selected from the group consisting of a polymer compound containing a structural unit represented by (B4) and a polymer compound containing a structural unit represented by the following general formula (B5).

(Keteneimine compound represented by formula (B1))
The ketene imine compound used as the stabilizer (B) is represented by the following general formula (B1).

Here, in general formula (B1), R ¹ and R ² each independently represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. Represent. In General Formula (B1), R ³ represents an alkyl group or an aryl group.

In general formula (B1), the alkyl group represented by R ¹ and R ² is preferably an alkyl group having 1 to 20 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. The alkyl group represented by R ¹ and R ² may be linear, branched or cyclic. In general formula (B1), examples of the alkyl group represented by R ¹ and R ² include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a tert-butyl group, a sec-butyl group, Examples include iso-butyl group, n-pentyl group, sec-pentyl group, iso-pentyl group, n-hexyl group, sec-hexyl group, iso-hexyl group, cyclohexyl group, and the like. Of these, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an iso-butyl group, and a cyclohexyl group are more preferable.
In general formula (B1), the alkyl group represented by R ¹ and R ² may further have a substituent. Unless the reactivity of a ketene imine group and a carboxyl group is lowered, the substituent is not particularly limited, and the above substituents can be exemplified similarly. The number of carbon atoms of the alkyl group represented by R ¹ and R ² indicate the number of carbon that does not contain a substituent group.

In general formula (B1), the aryl group represented by R ¹ and R ² is preferably an aryl group having 6 to 20 carbon atoms, and more preferably an aryl group having 6 to 12 carbon atoms. In general formula (B1), examples of the aryl group represented by R ¹ and R ² include a phenyl group and a naphthyl group, and among them, a phenyl group is particularly preferable.
In the general formula (B1), the aryl group represented by R ¹ and R ² includes a heteroaryl group. A heteroaryl group refers to a 5-membered, 6-membered or 7-membered ring showing aromaticity, or at least one of the ring atoms of the condensed ring substituted with a heteroatom. Examples of heteroaryl groups include imidazolyl, pyridyl, quinolyl, furyl, thienyl, benzoxazolyl, indolyl, benzimidazolyl, benzthiazolyl, carbazolyl, and azepinyl groups. . The hetero atom contained in the heteroaryl group is preferably an oxygen atom, a sulfur atom, or a nitrogen atom, and particularly preferably an oxygen atom or a nitrogen atom.
In general formula (B1), the aryl group or heteroaryl group represented by R ¹ and R ² may further have a substituent, and unless the reactivity between the ketene imine group and the carboxyl group is lowered, the substituent is There is no particular limitation. Incidentally, the number of carbon atoms of the aryl or heteroaryl group represented by R ¹ and R ² indicate the number of carbon that does not contain a substituent group.

In general formula (B1), the alkoxy group represented by R ¹ and R ² is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, It is especially preferable that it is a C2-C6 alkoxy group. The alkoxy group represented by R ¹ and R ² may be linear, branched or cyclic. In the general formula (B1), preferred examples of the alkoxy group represented by R ¹ and R ² include a group in which —O— is linked to the terminal of the alkyl group represented by R ¹ and R ² . The alkoxy group represented by R ¹ and R ² may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered. The number of carbon atoms of the alkoxy group represented by R ¹ and R ² may indicate the number of carbon that does not contain a substituent group.

In general formula (B1), the alkoxycarbonyl group represented by R ¹ and R ² is preferably an alkoxycarbonyl group having 2 to 20 carbon atoms, and more preferably an alkoxycarbonyl group having 2 to 12 carbon atoms. An alkoxycarbonyl group having 2 to 6 carbon atoms is particularly preferable. In the general formula (B1), examples of the alkoxy group of the alkoxycarbonyl group represented by R ¹ and R ² include the examples of the alkoxy group described above.

In general formula (B1), the aminocarbonyl group represented by R ¹ and R ² is preferably an alkylaminocarbonyl group having 1 to 20 carbon atoms or an arylaminocarbonyl group having 6 to 20 carbon atoms. Preferable examples of the alkylamino part of the alkylaminocarbonyl group include a group in which —NH— is linked to the terminal of the alkyl group represented by R ¹ and R ^{2 in} formula (B1). The alkylaminocarbonyl group represented by R ¹ and R ² may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered. The number of carbon atoms in the alkyl amino group represented by R ¹ and R ² indicate the number of carbon that does not contain a substituent group.
Preferable examples of the arylamino moiety of the arylaminocarbonyl group having 6 to 20 carbon atoms include a group in which —NH— is linked to the terminal of the aryl group represented by R ¹ and R ^{2 in} the general formula (B1). it can. The arylaminocarbonyl group represented by R ¹ and R ² may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered. In addition, carbon number of the arylaminocarbonyl group which R < ¹ > and R < ² > represent shows carbon number which does not contain a substituent.

In general formula (B1), the aryloxy group represented by R ¹ and R ² is preferably an aryloxy group having 6 to 20 carbon atoms, and more preferably an aryloxy group having 6 to 12 carbon atoms. preferable. In the general formula (B1), examples of the aryl group of the aryloxy group represented by R ¹ and R ² include the examples of the aryl group described above.

In general formula (B1), the acyl group represented by R ¹ and R ² is preferably an acyl group having 2 to 20 carbon atoms, more preferably an acyl group having 2 to 12 carbon atoms, Particularly preferred is an acyl group of 2-6. The acyl group represented by R ¹ and R ² may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered. The number of carbon atoms in the acyl group represented by R ¹ and R ² may indicate the number of carbon that does not contain a substituent group.

In general formula (B1), the aryloxycarbonyl group represented by R ¹ and R ² is preferably an aryloxycarbonyl group having 7 to 20 carbon atoms, and is an aryloxycarbonyl group having 7 to 12 carbon atoms. It is more preferable. In the general formula (B1), examples of the aryl group of the aryloxycarbonyl group represented by R ¹ and R ² include the above-described aryl groups.

In General Formula (B1), each R ³ independently represents an alkyl group or an aryl group. In general formula (B1), the alkyl group represented by R ³ is preferably an alkyl group having 1 to 20 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. The alkyl group represented by R ³ may be linear, branched or cyclic. In general formula (B1), examples of the alkyl group represented by R ³ include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, tert-butyl group, sec-butyl group, and iso-butyl. Group, n-pentyl group, sec-pentyl group, iso-pentyl group, n-hexyl group, sec-hexyl group, iso-hexyl group, cyclohexyl group, and the like. Of these, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, and a cyclohexyl group are more preferable.
In general formula (B1), the alkyl group represented by R ³ may further have a substituent. Unless the reactivity of a ketene imine group and a carboxyl group is lowered, the substituent is not particularly limited, and the above substituents can be exemplified similarly.
In general formula (B1), the aryl group represented by R ³ is preferably an aryl group having 6 to 20 carbon atoms, and more preferably an aryl group having 6 to 12 carbon atoms. In general formula (B1), examples of the aryl group represented by R ³ include a phenyl group and a naphthyl group, and among them, a phenyl group is particularly preferable.

In general formula (B1), the aryl group represented by R ³ includes a heteroaryl group. A heteroaryl group refers to a 5-membered, 6-membered or 7-membered ring showing aromaticity, or at least one of the ring atoms of the condensed ring substituted with a heteroatom. Examples of heteroaryl groups include imidazolyl, pyridyl, quinolyl, furyl, thienyl, benzoxazolyl, indolyl, benzimidazolyl, benzthiazolyl, carbazolyl, and azepinyl groups. . The hetero atom contained in the heteroaryl group is preferably an oxygen atom, a sulfur atom, or a nitrogen atom, and particularly preferably an oxygen atom or a nitrogen atom.
In general formula (B1), the aryl group or heteroaryl group represented by R ³ may further have a substituent, and the substituent is not particularly limited unless the reactivity between the ketene imine group and the carboxyl group is reduced. The above substituents can be exemplified similarly.

Note that the general formula (B1) may include a repeating unit. In this case, at least one of R ¹ or R ² is a repeating unit, and this repeating unit preferably includes a ketene imine moiety.

  The ketene imine compound represented by the general formula (B1) may be used alone or in combination of two or more.

(Keteneimine compound represented by formula (B2))
The ketene imine compound used as the stabilizer (B) is represented by the following general formula (B2).

Here, in General Formula (B2), R ¹ represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. In General Formula (B2), R ² represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. In General Formula (B2), R ³ represents an alkyl group or an aryl group. n represents an integer of 2 to 4, and L ¹ represents an n-valent linking group.

In the general formula (B2), ^{R 1} has the same meaning as ^{R 1} in the general formula (B1), and preferred ranges are also the same.

In the general formula (B2), preferred examples of R ² include removing one residue a hydrogen atom from each of the preferred embodiment R ² are mentioned in the general formula (B1).

In the general formula (B2), ^{R 3} has the same meaning as ^{R 3} in the general formula (B1), and preferred ranges are also the same.

In General Formula (B2), L ¹ represents an n-valent linking group. In general formula (B2), n represents the integer of 2-4. Especially, it is preferable that n is 3-4. In addition, as a ketene imine compound whose n is 2, the ketene imine compound represented by the following general formula (B2-1) mentioned later is mentioned.
Specific examples of the divalent linking group include, for example, —NR ⁸ — (R ⁸ represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. A hydrogen atom is preferred), —SO ₂ —, —CO—, a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, an alkynylene group, a substituted or unsubstituted phenylene group, substituted or Examples thereof include an unsubstituted biphenylene group, a substituted or unsubstituted naphthylene group, —O—, —S— and —SO—, and a group obtained by combining two or more thereof.
Moreover, as a specific example of a bivalent coupling group, the following structural formula is also mentioned, for example. * In the structural formula represents a bonding position.

Specific examples of the trivalent linking group include a group obtained by removing one hydrogen atom from those having a substituent among the linking groups mentioned as examples of the divalent linking group.
Specific examples of the tetravalent linking group include a group in which two hydrogen atoms are removed from those having a substituent among the linking groups mentioned as examples of the divalent linking group.

  In the present invention, from the viewpoint of exhibiting a moist heat resistance improving effect, n is 2 to 4, preferably 3 to 4, in the general formula (B2). By setting n to 2 to 4, the ketene imine compound becomes a compound having two or more ketene imine groups in one molecule. Thereby, reaction with a ketene imine group and aliphatic polyester (A) advances efficiently. Moreover, volatilization of the ketene imine compound is also suppressed. For these reasons, the effect of improving the heat and moisture resistance is effectively exhibited.

  The ketene imine compound represented by formula (B2) may be used alone or in combination of two or more.

(Keteneimine compound represented by formula (B3))
The ketene imine compound used as the stabilizer (B) is represented by the following general formula (B3).

Here, in General Formula (B3), R ¹ represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. In General Formula (B3), R ² represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. n represents an integer of 2 to 4.

In the general formula (B3), preferred examples of R ¹ include removing one residue a hydrogen atom from each of the preferred embodiment R ¹ can be mentioned in the general formula (B1).

In the general formula (B3), ^{R 2} has the same meaning as ^{R 2} in the general formula (B1), and preferred ranges are also the same.

  In general formula (B3), n represents the integer of 2-4. Especially, it is preferable that n is 3-4. By setting n to 2 to 4, the ketene imine compound becomes a compound having two or more ketene imine groups in one molecule, and therefore, the moist heat resistance improving effect is effectively exhibited for the same reason as described above.

  The ketene imine compound represented by formula (B3) may be used alone or in combination of two or more.

(High molecular compound containing the structural unit represented by formula (B4))
The polymer compound used as the stabilizer (B) includes a structural unit represented by the following general formula (B4).

Here, in general formula (B4), R ¹ and R ² are each independently an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl. Represents a group. In General Formula (B4), R ³ represents an alkyl group or an aryl group.

In the general formula (B4), preferred examples of R ¹ include removing one residue a hydrogen atom from each of the preferred embodiment R ¹ can be mentioned in the general formula (B1).
In the general formula (B4), preferred examples of R ² include removing one residue a hydrogen atom from each of the preferred embodiment R ² are mentioned in the general formula (B1).

In General Formula (B4), R ³ has the same meaning as R ³ in General Formula (B1), and the preferred range is also the same.

  The polymer compound containing the structural unit represented by the general formula (B4) may be used alone or in combination of two or more.

(High molecular compound containing the structural unit represented by the general formula (B5))
The polymer compound used as the stabilizer (B) includes a structural unit represented by the following general formula (B5).

Here, in General Formula (B5), R ¹ represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. In General Formula (B5), R ² represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. In General Formula (B5), R ³ represents an alkylene group or an arylene group.

In the general formula (B5), preferred examples of R ¹ include removing one residue a hydrogen atom from each of the preferred embodiment R ¹ can be mentioned in the general formula (B1).
In the general formula (B5), as preferable examples of ^{R 2} has the same meaning as ^{R 2} in the general formula (B1), and preferred ranges are also the same.

In General Formula (B5), R ³ is a residue obtained by removing one hydrogen atom from each of the preferred examples of R ³ in General Formula (B1).

  The polymer compound containing the structural unit represented by the general formula (B5) may be used alone or in combination of two or more.

  Weight average molecular weight (Mw) of stabilizer (B), that is, ketene imine compound represented by general formula (B1), ketene imine compound represented by general formula (B2), ketene imine represented by general formula (B3) The weight average molecular weight selected from the group consisting of a compound, a polymer compound containing a structural unit represented by general formula (B4), and a polymer compound containing a structural unit represented by general formula (B5) is: 300 to 60000, preferably 300 to 40000, more preferably 300 to 20000, and still more preferably 300 to 10000. By making the weight average molecular weight of the stabilizer (B) within the above range, the volatilization of the stabilizer (B) is suppressed, and the hydrolysis of the aliphatic polyester (A) is suppressed with a low addition amount. It can carry out with an agent (B).

The weight average molecular weight of the ketene imine compound represented by the general formula (B1), the weight average molecular weight of the ketene imine compound represented by the general formula (B2), and the weight average molecular weight of the ketene imine compound represented by the general formula (B3) are: Independently, it is preferably 300 to 1500, more preferably 400 to 1500, and still more preferably 500 to 1000.
The weight average molecular weight of the polymer compound containing the structural unit represented by the general formula (B4) and the weight average molecular weight of the polymer compound containing the structural unit represented by the general formula (B5) are each independently It is preferably 600 to 60000, more preferably 1000 to 20000, and still more preferably 2000 to 10000.

  The weight average molecular weight (Mw) of the stabilizer (B) is any of the measuring method using the gel permeation chromatograph (GPC) described in the paragraph of the aliphatic polyester (A), and GC-MS. , FAB-MS, ESI-MS, TOF-MS, etc.

(Keteneimine compound represented by formula (B2-1))
It is preferable that a stabilizer (B) contains the ketene imine compound represented by the following general formula (B2-1). The ketene imine compound represented by the following general formula (B2-1) corresponds to the ketene imine compound in which n is 2 in the general formula (B2).

In General Formula (B2-1), R ¹ and R ⁵ each independently represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. . In general formula (B2-1), R ² and R ⁴ are each independently an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. Represents. In General Formula (B2-1), R ³ and R ⁶ each independently represents an alkyl group or an aryl group. In General Formula (B2-1), L ² represents a single bond or a divalent linking group.

In General Formula (B2-1), R ¹ has the same meaning as R ¹ in General Formula (B1), and the preferred range is also the same.
In the general formula (B2-1), ^{R 5} has the same meaning as ^{R 1} in the general formula (B1), and preferred ranges are also the same.

In General Formula (B2-1), R ² is a residue obtained by removing one hydrogen atom from each of the preferred examples of R ¹ in General Formula (B1).
In General Formula (B2-1), R ⁴ is a residue obtained by removing one hydrogen atom from each of the preferred examples of R ¹ in General Formula (B1).

In the general formula (B 2 - 1), ^{R 3} has the same meaning as ^{R 3} in the general formula (B1), and preferred ranges are also the same. Further, in the general formula (B2-1), ^{R 6} has the same meaning as ^{R 3} in the general formula (B1), and preferred ranges are also the same.

In General Formula (B2-1), L ² represents a single bond or a divalent linking group. Specific examples of the divalent linking group include the linking groups exemplified for L ¹ in formula (B2).

  The ketene imine compound represented by formula (B2-1) may be used alone or in combination of two or more.

  The ketene imine compound represented by the general formulas (B1) to (B3) used as the stabilizer (B) and the polymer compound containing the structural units represented by the general formulas (B4) and (B5) are ketene imine groups. A compound having at least one of Am. Chem. Soc. , 1953, 75 (3), pp 657-660 and the like.

  Although the preferable specific example of the high molecular compound containing the structural unit represented by the ketene imine compound represented by the general formula (B1)-(B3) below or general formula (B4), (B5) below is shown, it is limited to this. Not.

  The exemplified compound (10) is a specific example of a polymer compound containing a structural unit represented by the general formula (B5). Moreover, exemplary compound (32) is a specific example of the high molecular compound containing the structural unit represented by general formula (B4). In addition, both ends of the polymer compound represented by the exemplary compounds (10) and (32) are not particularly limited, but the left terminal of the polymer compound represented by the exemplary compound (10) is preferably a hydrogen atom, and the right terminal is A phenyl group is preferred. Moreover, the left end of the polymer compound represented by the exemplified compound (32) is preferably a hydrogen atom, and the right end is preferably a phenyl group or a benzyl group.

Content of a stabilizer (B) is 0.01 mass part-10 mass parts with respect to 100 mass parts of aliphatic polyester (A) from a viewpoint of exhibiting the heat-and-moisture resistance improvement effect, 0.1 mass Part to 5 parts by weight, preferably 0.5 part to 2.8 parts by weight.
In addition, the said content shows those total amounts, when using 2 or more types of stabilizers (B) together.

<Stabilizer (C)>
The polymeric piezoelectric material of the present embodiment may further have a stabilizer (C) as a stabilizer other than the stabilizer (B) as long as the effects of the present invention are not impaired.
The stabilizer (C) in the present embodiment preferably contains at least one selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group in one molecule, and has a weight average molecular weight of 200 to 60,000. .

  As the stabilizer (C) in the present embodiment, “stabilizer (B)” described in paragraphs 0039 to 0055 of WO 2013/054918 pamphlet can be used.

(Carbodiimide compound)
Examples of the compound containing a carbodiimide group (carbodiimide compound) that can be used as the stabilizer (C) include a monocarbodiimide compound, a polycarbodiimide compound, and a cyclic carbodiimide compound.
As the monocarbodiimide compound, dicyclohexylcarbodiimide, bis-2,6-diisopropylphenylcarbodiimide, and the like are preferable.
Moreover, as a polycarbodiimide compound, what was manufactured by the various method can be used. Conventional methods for producing polycarbodiimides (for example, U.S. Pat. No. 2,941,956, JP-B-47-33279, J.0rg.Chem.28, 2069-2075 (1963), Chemical Review 1981, Vol. 81 No. 1). 4, p619-621) can be used. Specifically, a carbodiimide compound described in Japanese Patent No. 4084953 can also be used.
Examples of the polycarbodiimide compound include poly (4,4′-dicyclohexylmethanecarbodiimide), poly (N, N′-di-2,6-diisopropylphenylcarbodiimide), poly (1,3,5-triisopropylphenylene-2, 4-carbodiimide and the like.
The cyclic carbodiimide compound can be synthesized based on the method described in JP2011-256337A.
Commercially available products may be used as the carbodiimide compound, for example, manufactured by Tokyo Chemical Industry, B2756 (trade name), manufactured by Nisshinbo Chemical Co., Ltd., Carbodilite LA-1, manufactured by Rhein Chemie, Stabaxol P, Stabaxol P400, Stabaxol I (all Product name).

(Isocyanate compound)
Examples of the compound (isocyanate compound) containing an isocyanate group in one molecule that can be used as the stabilizer (C) include 3- (triethoxysilyl) propyl isocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate. Diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, Etc.

(Epoxy compound)
The compound (epoxy compound) containing an epoxy group in one molecule that can be used as the stabilizer (C) includes phenyl glycidyl ether, diethylene glycol diglycidyl ether, bisphenol A-diglycidyl ether, hydrogenated bisphenol A-diglycidyl ether. Phenol novolac type epoxy resin, cresol novolac type epoxy resin, epoxidized polybutadiene and the like.

As described above, the weight average molecular weight of the stabilizer (C) is preferably 200 to 60000, more preferably 200 to 30000, and further preferably 300 to 18000.
In addition, the weight average molecular weight of a stabilizer (C) can be measured with the measuring method similar to the weight average molecular weight of the stabilizer (B) mentioned above.

When the polymeric piezoelectric material of this embodiment contains a stabilizer (C), the polymeric piezoelectric material may contain only one type of stabilizer (C), or two or more types. Also good.
When the polymeric piezoelectric material of this embodiment contains a stabilizer (C), the content of the stabilizer (C) is 0.01 parts by mass to 10 parts by mass with respect to 100 parts by mass of the aliphatic polyester (A). It is preferably mass parts, preferably 0.01 parts by mass to 5 parts by mass, more preferably 0.1 parts by mass to 3 parts by mass, and 0.5 parts by mass to 2 parts by mass. It is particularly preferred.

A preferred embodiment of the stabilizer (C) is a stabilizer having at least one functional group selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group, and having a weight average molecular weight of 200 to 900. A stabilizer having (C-1) and one or more functional groups selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group in one molecule, and having a weight average molecular weight of 1000 to 60000 The aspect of using together (C-2) is mentioned.
When the stabilizer (C-1) and the stabilizer (C-2) are used in combination as the stabilizer, it is preferable that a large amount of the stabilizer (C-1) is contained from the viewpoint of improving the transparency.
Specifically, the stabilizer (C-2) is in the range of 10 parts by mass to 150 parts by mass with respect to 100 parts by mass of the stabilizer (C-1). It is preferable from a viewpoint, and it is more preferable that it is the range of 50-100 mass parts.

  Hereinafter, specific examples (stabilizers C-1 to C-3) of the stabilizer (C) are shown.

Hereinafter, with respect to the stabilizers C-1 to C-3, compound names, commercial products, and the like are shown.
Stabilizer C-1 The compound name is bis-2,6-diisopropylphenylcarbodiimide. The weight average molecular weight is 363. Commercially available products include “Stabaxol I” manufactured by Rhein Chemie and “B2756” manufactured by Tokyo Chemical Industry.
Stabilizer C-2 The compound name is poly (4,4′-dicyclohexylmethanecarbodiimide). As a commercially available product, “Carbodilite LA-1” manufactured by Nisshinbo Chemical Co., Ltd. may be mentioned as having a weight average molecular weight of about 2000.
Stabilizer C-3 The compound name is poly (1,3,5-triisopropylphenylene-2,4-carbodiimide). As a commercially available product, “Stabaxol P” manufactured by Rhein Chemie Co., Ltd. can be mentioned as having a weight average molecular weight of about 3000. Further, “Stabaxol P400” manufactured by Rhein Chemie is listed as having a weight average molecular weight of 20,000.

<Other ingredients>
The polymeric piezoelectric material of this embodiment may contain other components as necessary.
Other components include antioxidants such as hindered phenol compounds, hindered amine compounds, phosphite compounds, thioether compounds; known resins such as polyvinylidene fluoride, polyethylene resins, polystyrene resins; silica, hydroxyapatite, And a known inorganic filler such as montmorillonite; a known crystal nucleating agent such as phthalocyanine; and the like.
Examples of the inorganic filler and the crystal nucleating agent include components described in paragraphs 0057 to 0058 of International Publication No. 2013/054918.

  Further, as described above, from the viewpoint of more effectively exerting the effects of the present invention, the content of the aliphatic polyester (A) in the polymer piezoelectric material of the present embodiment is the total amount of the polymer piezoelectric material. On the other hand, it is preferable that it is 80 mass% or more.

<Physical properties of polymer piezoelectric material>
(Transparency (internal haze))
In the polymer piezoelectric material of the present embodiment, the internal haze with respect to visible light (hereinafter also simply referred to as “internal haze”) is preferably 50% or less, more preferably 20% or less, and 15% or less. It is more preferable that it is 13% or less. The internal haze of the polymer piezoelectric material is preferably as low as possible, but is preferably 0.01% to 13%, more preferably 0.01% to 5% from the viewpoint of balance with the piezoelectric constant and the like. More preferably. 0.01% to 3%, 0.01% to 2%, 0.01% to 1%
In the present embodiment, “internal haze” refers to haze excluding haze due to the shape of the outer surface of the polymeric piezoelectric material.
Further, the “internal haze” herein is a value when measured at 25 ° C. in accordance with JIS-K7105 for a polymer piezoelectric material.

The internal haze (hereinafter also referred to as internal haze (H1)) of the polymeric piezoelectric material of the present embodiment is measured by the following method.
First, the haze (H2) (%) is measured by sandwiching only silicone oil (Shin-Etsu Chemical Co., Ltd., Shin-Etsu Silicone (trademark), model number: KF96-100CS) between two glass plates in advance. A polymer piezoelectric material (piezoelectric film) whose surface is uniformly coated with oil is sandwiched between two glass plates, and haze (H3) (%) is measured.
Next, the internal haze (H1) (%) of the polymeric piezoelectric material is obtained by taking these differences as in the following formula.
Internal haze (H1) = Haze (H3) -Haze (H2)

Haze (H2) and haze (H3) (both units are%) are each measured using the following apparatus under the following measurement conditions.
Measuring device: manufactured by Tokyo Denshoku Co., Ltd., HAZE METER TC-HIIIDPK
Sample size: width 30 mm x length 30 mm, thickness 0.05 mm
Measurement conditions: Conforms to JIS-K7136 (2000) Measurement temperature: Room temperature (25 ° C.)

(Piezoelectric constant d ₁₄ (displacement method))
Piezoelectricity of polymeric piezoelectric material, for example, can be assessed by measuring the piezoelectric constant d ₁₄ of the piezoelectric polymer.
In the present embodiment, “piezoelectric constant d ₁₄ ” refers to the piezoelectric constant d ₁₄ measured by the displacement method at 25 ° C.
Here, the “piezoelectric constant d ₁₄ measured by the displacement method” is 10 Hz between a pair of conductive layers of a piezoelectric constant measurement sample (film) in which a conductive layer is formed on both surfaces of a 32 mm × 5 mm polymer piezoelectric material. A 300 Vpp sine wave AC voltage is applied, and the difference distance between the maximum and minimum displacements at this time is measured as a displacement (mp-p), and the measured displacement (mp-p) is used as a reference. A value obtained by dividing the length by 30 mm is taken as a strain amount, and a value obtained by dividing the strain amount by the electric field strength ((applied voltage (V)) / (film thickness)) applied to the film is multiplied by 2.
This “piezoelectric constant d ₁₄ measured by the displacement method” can be measured, for example, by the method described in paragraphs 0058 to 0059 of Japanese Patent No. 4934235.

Hereinafter, an example of a method for measuring the piezoelectric constant d ₁₄ (displacement method) will be described.
First, an aluminum conductive layer is deposited on both sides of a polymeric piezoelectric material cut into a square shape of 40 mm × 40 mm by vapor-depositing aluminum (Al) using a vapor deposition apparatus (for example, Showa Vacuum SIP-600 Co., Ltd.). Form.
Next, a 40 mm × 40 mm test piece (polymer piezoelectric material) having a conductive layer of Al formed on both sides is 32 mm, 45 ° in a direction that makes 45 ° with respect to the stretching direction (MD direction) of the polymer piezoelectric material. Cut to 5 mm in a direction perpendicular to the direction to be made, and cut out a rectangular film of 32 mm × 5 mm. This is a piezoelectric constant measurement sample. The difference distance between the maximum value and the minimum value of the displacement of the film when a sine wave AC voltage of 10 Hz, 300 Vpp was applied to the obtained piezoelectric constant measurement sample was measured using the Keyence Corporation Laser Spectral Interference Displacement Meter SI- Measured by 1000. The value obtained by dividing the measured displacement (mp-p) by the reference length of the film 30 mm is used as the amount of strain, and the amount of strain is expressed by the electric field intensity ((applied voltage (V)) / (film thickness)) applied to the film. A value obtained by multiplying the divided value by 2 is defined as a piezoelectric constant d ₁₄ (pm / V). In addition, this measurement is performed on 25 degreeC conditions.

The higher piezoelectric constant d _14, the displacement of the piezoelectric polymer is increased with respect to the voltage applied to the piezoelectric polymer, also increases the voltage generated against the force applied to the piezoelectric polymer It is useful as a polymer piezoelectric material.
Specifically, the piezoelectric constant d ₁₄ (that is, the piezoelectric constant d ₁₄ measured by the displacement method at 25 ° C.) of the polymeric piezoelectric material of the present embodiment is preferably 1.0 pm / V or more. More preferably, it is 0 pm / V or more, further preferably 4.0 pm / V or more, further preferably 6.0 pm / V or more, and further preferably 8.0 pm / V or more.
The upper limit of the piezoelectric constant d ₁₄ is not particularly limited, from the viewpoint of the balance, such as transparency, preferably 50 Pm/V less in polymeric piezoelectric material using the aliphatic polyester (A), 30pm / V or less Is more preferable.

  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). ).

Here, a polymeric piezoelectric material of the present embodiment is 50% or less internal haze to visible light, and is preferably a piezoelectric constant d ₁₄ is 1 Pm/V or more as measured by a displacement method at 25 ° C.. Incidentally, each of the preferred range of the piezoelectric constant d ₁₄ measured by the displacement method in the internal haze, and 25 ° C. to visible light is as previously described.

(Standardized molecular orientation MORc)
The polymer piezoelectric material of this embodiment preferably has a normalized molecular orientation MORc of 2.0 to 15.0, preferably 3.0 to 10.0, and 4.0 to 8.0. More preferably.
The normalized molecular orientation MORc is a value determined based on “molecular orientation degree MOR” which is an index indicating the degree of orientation of the aliphatic polyester (A).
If the normalized molecular orientation MORc is in the range of 2.0 to 15.0, there are many molecular chains of the aliphatic polyester (A) arranged in the stretching direction, and as a result, the rate of formation of oriented crystals increases. High piezoelectricity can be expressed.

  Here, the molecular orientation degree MOR (Molecular Orientation Ratio) is measured by the following microwave measurement method. That is, a polymer piezoelectric material is placed in a microwave resonant waveguide of a well-known microwave transmission type molecular orientation meter (also referred to as a microwave molecular orientation degree measuring device), and the surface of the polymer piezoelectric material in the microwave traveling direction. Arrange so that (film surface) is vertical. Then, in a state where the sample is continuously irradiated with the microwave whose vibration direction is biased in one direction, the polymer piezoelectric material is rotated by 0 to 360 ° in a plane perpendicular to the traveling direction of the microwave, and the sample is transmitted. The degree of molecular orientation MOR is obtained by measuring the measured microwave intensity.

The normalized molecular orientation MORc is a molecular orientation degree MOR when the reference thickness tc is 50 μm, and can be obtained by the following formula.
MORc = (tc / t) × (MOR-1) +1
(Tc: reference thickness to be corrected, t: thickness of the piezoelectric polymer material)
The normalized molecular orientation MORc can be measured with a known molecular orientation meter such as a microwave molecular orientation meter MOA-2012A or MOA-6000 manufactured by Oji Scientific Instruments Co., Ltd., at a resonance frequency in the vicinity of 4 GHz or 12 GHz.

  For example, when the polymer piezoelectric material is a stretched film, the normalized molecular orientation MORc can be controlled by heat treatment conditions (heating temperature and heating time) before stretching, stretching conditions (stretching temperature and stretching speed), and the like. .

The normalized molecular orientation MORc can be converted into a birefringence Δn obtained by dividing the retardation amount (retardation) by the thickness of the film. Specifically, retardation can be measured using RETS100 manufactured by Otsuka Electronics Co., Ltd. MORc and Δn are approximately in a linear proportional relationship, and when Δn is 0, MORc is 1.
For example, when the aliphatic polyester (A) is a polylactic acid polymer and the birefringence Δn of the polymer piezoelectric material is measured at a measurement wavelength of 550 nm, the normalized molecular orientation MORc is 2.0. The birefringence Δn 0.005 can be converted, and if the normalized molecular orientation MORc is 4.0, the birefringence Δn 0.01 can be converted.

(Crystallinity)
The crystallinity of the polymer piezoelectric material of the present embodiment is determined by the DSC method, and the crystallinity of the polymer piezoelectric material is 20% to 80%, preferably 25% to 70%, more preferably Is preferably 30% to 50%. If the crystallinity is in the above range, the piezoelectricity and transparency of the polymeric piezoelectric material are well balanced, and when the polymeric piezoelectric material is stretched, whitening and breakage are unlikely to occur and it is easy to manufacture.

(Product of normalized molecular orientation MORc and crystallinity)
The polymer piezoelectric material of this embodiment preferably has a product of the normalized molecular orientation MORc and the crystallinity obtained by the DSC method when the reference thickness measured with a microwave transmission type molecular orientation meter is 50 μm. It is 40-700, More preferably, it is 75-680, More preferably, it is 90-660, More preferably, it is 125-650, More preferably, it is 180-350. If the product of the normalized molecular orientation MORc and the crystallinity obtained by the DSC method is in the range of 40 to 700, the balance between piezoelectricity and transparency of the polymeric piezoelectric material is good, and dimensional stability Therefore, it can be suitably used as a piezoelectric element described later.

<Applications of polymer piezoelectric materials>
Polymeric piezoelectric material of the present embodiment, explained above large piezoelectric constant d ₁₄ is as transparency, resistance to moist heat, since it is excellent piezoelectric material dimensional stability, speakers, headphones, a touch panel, remote controller, a microphone , 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 It can be used in various fields such as a pressure sensor, a display, a fan, a pump, a variable focus mirror, a sound insulation material, a sound insulation material, a keyboard, an acoustic device, an information processing device, a measurement device, and a medical device.

  At this time, the polymeric piezoelectric material of the present embodiment 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. Although it does not restrict | limit especially as said electrode, For example, ITO, ZnO, IZO (trademark), a conductive polymer, etc. are used.

Moreover, the polymeric piezoelectric material of this embodiment and an electrode can be repeatedly stacked and 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 in the laminated piezoelectric element may be any one of the polymer piezoelectric materials as long as the polymer piezoelectric material according to the present embodiment is used, and the other layers may not be the polymer piezoelectric material according to the present embodiment. .
In addition, when the laminated piezoelectric element includes a plurality of the piezoelectric polymer materials of the present embodiment, if the aliphatic polyester (A) contained in a certain layer of the piezoelectric polymer material has an L-form optical activity, the other layers The aliphatic polyester (A) contained in the polymeric piezoelectric material may be L-form or D-form. The arrangement of the polymeric piezoelectric material can be appropriately adjusted according to the use of the piezoelectric element.

  For example, the first layer of the piezoelectric polymer material containing the L-type aliphatic polyester (A) as the main component contains the second high-density polyester containing the L-type aliphatic polyester (A) as the main component via the electrode. When laminated with a molecular piezoelectric material, the uniaxial stretching direction (main stretching direction) of the first polymeric piezoelectric material intersects the uniaxial stretching direction (main stretching direction) of the second polymeric piezoelectric material, preferably orthogonal This is preferable because the direction of displacement of the first polymer piezoelectric material and the second polymer piezoelectric material can be made uniform, and the piezoelectricity of the entire laminated piezoelectric element is enhanced.

  On the other hand, the first layer of the piezoelectric polymer material containing the L-type aliphatic polyester (A) as the main component contains the second high-density polyester containing the D-type aliphatic polyester (A) as the main component via the electrode. When laminated with a molecular piezoelectric material, the uniaxial stretching direction (main stretching direction) of the first polymeric piezoelectric material is substantially parallel to the uniaxial stretching direction (main stretching direction) of the second polymeric piezoelectric material. It is preferable that the first and second polymer piezoelectric materials can be arranged in the same direction, and the piezoelectricity of the entire laminated piezoelectric element is enhanced.

  In particular, when an electrode is provided on the main surface of the polymeric piezoelectric material, it is preferable to provide a transparent electrode. Here, the transparency of the electrode specifically means that the internal haze is 20% or less (total light transmittance is 80% or more).

  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.

  Next, the preferable aspect of the manufacturing method of the polymeric piezoelectric material of this embodiment is demonstrated.

<Method for producing polymer piezoelectric material>
The raw material of the polymeric piezoelectric material of the present embodiment includes the aliphatic polyester (A) such as the polylactic acid-based polymer described above, a stabilizer (B), and other components (stabilizer) as necessary. (C) etc.) are mixed to obtain a mixture. The mixture may be melt kneaded. Specifically, the aliphatic polyester to be mixed (A) and the stabilizer (B) and other components used as necessary, using a melt-kneader (Toyo Seiki Co., Ltd., Labo Plast Mill), Blending of aliphatic polyester (A) and stabilizer (B), multiple kinds of fats by melt-kneading for 5 to 20 minutes under conditions of mixer rotation speed 30 rpm to 70 rpm and 180 ° C. to 250 ° C. To obtain a blend of an aliphatic polyester (A) and a stabilizer (B), or a blend of an aliphatic polyester (A), a stabilizer (B) and other components such as an inorganic filler. it can.

  The polymeric piezoelectric material of the present embodiment is a pre-crystallized sheet (also referred to as a crystallization raw material) obtained by crystallizing an amorphous sheet containing, for example, an aliphatic polyester (A) and a stabilizer (B). And a second step of stretching the pre-crystallized sheet mainly in the uniaxial direction.

  In general, by increasing the force applied to the film during stretching, the orientation of the aliphatic polyester (A) is promoted and the piezoelectric constant is increased, crystallization proceeds, and the crystal size increases and the haze tends to increase. is there. Also, the dimensional deformation rate tends to increase due to an increase in internal stress. If force is simply applied to the film, crystals that are not oriented like spherulites are formed. Crystals with low orientation, such as spherulites, increase haze, but do not easily contribute to an increase in piezoelectric constant. Therefore, in order to form a film having a high piezoelectric constant and a low haze and dimensional deformation rate, it is necessary to efficiently form an oriented crystal that contributes to the piezoelectric constant with a small size that does not increase haze.

  In the method for producing the piezoelectric polymer material of the present embodiment, for example, the inside of the sheet is pre-crystallized to form fine crystals before stretching, and then stretched. As a result, the force applied to the film during stretching can be efficiently applied to the polymer part having low crystallinity between the microcrystals, and the aliphatic polyester (A) is efficiently used in the main stretching direction. It can be well oriented. Specifically, finely oriented crystals are formed in the polymer portion where the crystallinity between the microcrystals is low, and at the same time, the spherulites generated by the precrystallization are broken down to form spherulites. The desired lamellar crystals are oriented in the stretching direction in a daisy chain connected to tie molecular chains, whereby a desired value of MORc can be obtained. For this reason, a sheet having a low haze and dimensional deformation rate can be obtained without greatly reducing the piezoelectric constant.

  In order to control the normalized molecular orientation MORc, the crystallinity of the crystallization raw material is adjusted by the heat treatment time and the heat treatment temperature in the first step, and the stretching speed and the stretching temperature in the second step. is important. As described above, the aliphatic polyester (A) is a polymer having molecular optical activity. The amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B) may be commercially available, or may be produced by a known film forming means such as extrusion. The amorphous sheet may be a single layer or a multilayer.

(First step (pre-crystallization step))
The pre-crystallized sheet can be obtained by heat-treating an amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B) for crystallization. Also, the raw material containing the aliphatic polyester (A) and the stabilizer (B) is heated to a temperature higher than the glass transition temperature of the aliphatic polyester (A) by an extrusion molding method or the like, and extruded into a sheet form. After that, the pre-crystallized sheet having a predetermined crystallinity can be obtained by rapidly cooling the sheet extruded by a caster.

  Also, 1) a pre-crystallized pre-crystallized sheet may be sent to a stretching step (second step) described later and set in a stretching apparatus to be stretched (off-line heat treatment), or 2) by heat treatment A non-crystallized amorphous sheet is set in a stretching apparatus, heated in a stretching apparatus to be pre-crystallized, and then continuously sent to a stretching process (second process) for stretching. Good (heat treatment by in-line).

The heating temperature T for pre-crystallization of the sheet containing the aliphatic polyester (A) in the amorphous state is not particularly limited, but the piezoelectricity and transparency of the polymer piezoelectric material produced by this production method are enhanced. Thus, it is preferable that the glass transition temperature Tg of the aliphatic polyester (A) satisfies the relationship of the following formula, and the crystallinity obtained by the DSC method is set to 3% to 70%.
Tg−40 ° C. ≦ T ≦ Tg + 40 ° C.
(Tg represents the glass transition temperature of the aliphatic polyester (A))

  The heating time for pre-crystallization or the heating time for crystallization when extruding into a sheet form satisfies the desired degree of crystallinity and is the standard for the polymeric piezoelectric material after stretching (after the second step) The product of the crystallinity obtained by the DSC method of the polymerized molecular orientation MORc and the stretched polymer piezoelectric material is preferably 40 to 700, more preferably 75 to 680, still more preferably 90 to 660, and still more preferably 125 to 650. More preferably, it may be adjusted to 180 to 350. As the heating time becomes longer, the degree of crystallinity after stretching increases, and the normalized molecular orientation MORc after stretching also increases. When the heating time is shortened, the crystallinity after stretching also decreases, and the normalized molecular orientation MORc after stretching tends to decrease.

  When the degree of crystallization of the pre-crystallized sheet before stretching increases, the sheet becomes harder and a greater stretching stress is applied to the sheet, so that the portion with relatively low crystallinity in the sheet also becomes more oriented, and after stretching The normalized molecular orientation MORc is also increased. On the contrary, when the crystallinity of the pre-crystallized sheet before stretching becomes low, the sheet becomes soft and the stretching stress becomes more difficult to be applied to the sheet, so that the portion with relatively low crystallinity in the sheet becomes weakly oriented. The normalized molecular orientation MORc after stretching is also considered to be low.

  The heating time varies depending on the heating temperature, the thickness of the sheet, the molecular weight of the resin constituting the sheet, the type or amount of the additive. Further, the substantial heating time for crystallizing the sheet is the preheating when preheating at a temperature at which the amorphous sheet crystallizes in preheating that may be performed before the stretching step (second step) described later. This corresponds to the sum of the time and the heating time in the precrystallization step before preheating.

  The heating time of the amorphous sheet or the heating time in the case of crystallization when extruding into a sheet is usually 5 seconds to 60 minutes, and 1 minute to 30 minutes from the viewpoint of stabilizing the manufacturing conditions. But you can. For example, when pre-crystallizing an amorphous sheet containing a polylactic acid polymer as the aliphatic polyester (A), it is preferably heated at 20 ° C. to 170 ° C. for 5 seconds to 60 minutes. It may be up to 30 minutes.

In order to efficiently impart piezoelectricity, transparency, and high dimensional stability to the stretched sheet, it is important to adjust the crystallinity of the pre-crystallized sheet before stretching. That is, the reason why the piezoelectricity and dimensional stability are improved by stretching is that the stress due to stretching is concentrated in a portion where the crystallinity in the pre-crystallized sheet presumed to be in a spherulitic state is relatively high. While the piezoelectric d ₁₄ is improved by being oriented while being broken, it is considered that the stretching stress is applied to a portion having a relatively low crystallinity through the spherulite to promote the orientation and improve the piezoelectric d _14. Because.

  In the case where the crystallization degree of the sheet after stretching or the annealing treatment described later is performed, the crystallization degree after the annealing treatment is set to 20% to 80%, preferably 40% to 70%. Therefore, the degree of crystallinity of the pre-crystallized sheet immediately before stretching is set to 3% to 70%, preferably 10% to 60%, and more preferably 15% to 50%.

  The crystallinity of the pre-crystallized sheet may be the same as the measurement of the crystallinity of the polymer piezoelectric material of the present embodiment after stretching.

  The thickness of the pre-crystallized sheet is mainly determined by the thickness of the polymeric piezoelectric material to be obtained by stretching in the second step and the stretching ratio, but is preferably 50 μm to 1000 μm, more preferably about 200 μm to 800 μm. It is.

(Second step (stretching step))
The stretching method in the stretching step, which is the second step, is not particularly limited, and various stretching methods such as uniaxial stretching, biaxial stretching, and solid phase stretching described later can be used. By stretching the polymer piezoelectric material, a polymer piezoelectric material having a large principal surface area can be obtained.

  Here, the “main surface” refers to the surface having the largest area among the surfaces of the polymeric piezoelectric material. The polymeric piezoelectric material of this embodiment may have two or more main surfaces. For example, when the polymer piezoelectric material is a plate-like body having two surfaces A each having a surface A of 10 mm × 0.3 mm square, a surface B having 3 mm × 0.3 mm square, and a surface C having 10 mm × 3 mm square. The main surface of the polymeric piezoelectric material is a surface C, which has two main surfaces.

In this embodiment, that the area of the main surface is large means that the area of the main surface of the polymeric piezoelectric material is 5 mm ² or more. Area of the main surface also is preferably 5 mm ² or more, and more preferably 10 mm ² or more.

  “Solid phase stretching” means “stretching at a temperature higher than the glass transition temperature Tg of the polymeric piezoelectric material and lower than the melting point Tm of the polymeric piezoelectric material and under a compressive stress of 5 MPa to 10,000 MPa”. In other words, the piezoelectricity of the polymer piezoelectric material can be further improved, and the transparency and elasticity can be improved.

  By stretching the piezoelectric polymer material in a solid phase or mainly in one direction, the molecular chains of the aliphatic polyester (A) contained in the piezoelectric polymer material are aligned in one direction and aligned at high density. It is estimated that higher piezoelectricity can be obtained.

  Here, the glass transition temperature Tg [° C.] of the polymer piezoelectric material and the melting point Tm [° C.] of the polymer piezoelectric material are measured with respect to the polymer piezoelectric material using a differential scanning calorimeter (DSC). From the melting endothermic curve when the temperature is raised at 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.

  The stretching temperature of the polymeric piezoelectric material is 10 ° C. to 20 ° C. from the glass transition temperature of the polymeric piezoelectric material when the polymeric piezoelectric material is stretched only by a tensile force, such as a uniaxial stretching method or a biaxial stretching method. It is preferable that the temperature range be as high as about ° C.

  In the case of the solid phase stretching method, the compression stress is preferably 50 MPa to 5000 MPa, and more preferably 100 MPa to 3000 MPa.

  The stretching ratio in the stretching treatment is preferably 3 to 30 times, and more preferably 4 to 15 times.

  Solid phase stretching of the pre-crystallized sheet is performed by applying pressure by sandwiching a polymer piezoelectric material between, for example, a roll or a burette.

  When the pre-crystallized sheet is stretched, preheating may be performed immediately before stretching in order to facilitate stretching of the sheet. This preheating is generally performed in order to soften the sheet before stretching and facilitate stretching, so that the sheet before stretching is crystallized and does not harden the sheet. It is normal. However, as described above, in the present embodiment, since pre-crystallization may be performed before stretching, the pre-heating may be performed together with pre-crystallization. Specifically, preheating and precrystallization can be performed by performing preheating at a temperature higher or longer than the normal temperature in accordance with the heating temperature and heat treatment time in the precrystallization step described above.

(Annealing process)
From the viewpoint of improving the piezoelectric constant, it is preferable that the polymer piezoelectric material after the stretching treatment (after the second step) is subjected to a certain heat treatment (hereinafter also referred to as “annealing treatment”). Note that in the case where crystallization is mainly performed by the annealing treatment, the preliminary crystallization performed in the above-described preliminary crystallization step may be omitted.

  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 include a method of directly heating using a hot air heater or an infrared heater, a method of immersing a polymer piezoelectric material in a heated liquid, such as heated silicone oil, and the like. It is done.

  At this time, if the polymer piezoelectric material is deformed by linear expansion, it is 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 temperature while preventing the piezoelectric polymer material from sagging.

  The temperature application time for the annealing treatment is preferably 1 second to 60 minutes, more preferably 1 second to 300 seconds, and further preferably heating in the range of 1 second to 60 seconds. When annealing is performed for more than 60 minutes, 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. And transparency may be reduced.

  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 ice water or the like immediately after the annealing process and cooled to at least the glass transition point 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.

  The method for producing a polymeric piezoelectric material of the present embodiment includes a step of stretching a sheet containing the aliphatic polyester (A) and the stabilizer (B) mainly in a uniaxial direction and a step of annealing. It may be included in this order. The stretching process and the annealing process can be the same processes as described above. Moreover, in this manufacturing method, it is not necessary to implement the above-mentioned preliminary crystallization process.

Claims (13)

An aliphatic polyester (A) having a weight average molecular weight of 50,000 to 1,000,000 and optical activity;
A ketene imine compound represented by the following general formula (B1), a ketene imine compound represented by the following general formula (B2), a ketene imine compound represented by the following general formula (B3), and a structure represented by the following general formula (B4) A stabilizer (B) which is at least one selected from the group consisting of a polymer compound containing a unit and a polymer compound containing a structural unit represented by the following general formula (B5), and having a weight average molecular weight of 300 to 60000 )When,
Including
The crystallinity obtained by DSC method is 20% to 80%,
A polymeric piezoelectric material comprising 0.01 to 10 parts by mass of the stabilizer (B) with respect to 100 parts by mass of the aliphatic polyester (A).

(In General Formula (B1), R ¹ and R ² each independently represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. In general formula (B1), R ³ represents an alkyl group or an aryl group.)

(In the general formula (B2), R ¹ represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. In the general formula (B2), R ² represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group, and R ³ is an alkyl group in the general formula (B2) Or represents an aryl group, n represents an integer of 2 to 4, and L ¹ represents an n-valent linking group.)

(In General Formula (B3), R ¹ represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. General Formula (B3) R ² represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group or an aryloxycarbonyl group, and n represents an integer of 2 to 4.)

(In General Formula (B4), R ¹ and R ² each independently represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. In general formula (B4), R ³ represents an alkyl group or an aryl group.)

(In General Formula (B5), R ¹ represents an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxycarbonyl group. General Formula (B5) R ² represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group, and R ³ represents an alkylene group in the general formula (B5). Or represents an arylene group.)   The polymeric piezoelectric material according to claim 1, wherein the stabilizer (B) includes a ketene imine compound in which n is 3 or 4 in the general formula (B2). The polymeric piezoelectric material according to claim 1, wherein the stabilizer (B) contains a ketene imine compound represented by the following general formula (B2-1).


(In the general formula (B2-1), R ¹ and R ⁵ each independently represents an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group. In formula (B2-1), R ² and R ⁴ each independently represent an alkylene group, an arylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an amide group, an aryleneoxy group, an alkylenecarbonyl group, or an aryleneoxy In the general formula (B2-1), R ³ and R ⁶ each independently represents an alkyl group or an aryl group, and in the general formula (B2-1), L ² represents a single bond or two Represents a valent linking group.) 50% or less internal haze to visible light, and 25 piezoelectric constant d ₁₄ is 1 Pm/V or more as measured by a displacement method at ° C., high according to any one of claims 1 to 3 Molecular piezoelectric material.   The polymeric piezoelectric material according to claim 4, wherein the internal haze is 13% or less.   The product of the normalized molecular orientation MORc and the crystallinity when the reference thickness measured by a microwave transmission type molecular orientation meter is 50 μm is 40 to 700. 6. 2. The polymeric piezoelectric material according to item 1. The aliphatic polyester (A) is a polylactic acid polymer having a main chain containing a repeating unit represented by the following formula (1), according to any one of claims 1 to 6. Polymer piezoelectric material.
  The polymeric piezoelectric material according to any one of claims 1 to 7, wherein the aliphatic polyester (A) has an optical purity of 95.00% ee or higher.   The polymeric piezoelectric material according to any one of claims 1 to 8, wherein the content of the aliphatic polyester (A) is 80% by mass or more. The polymeric piezoelectric material according to any one of claims 1 to 9, wherein an area of the main surface is 5 mm ² or more. A method for producing the polymeric piezoelectric material according to any one of claims 1 to 10,
A first step of obtaining a pre-crystallized sheet containing the aliphatic polyester (A) and the stabilizer (B);
A second step of stretching the pre-crystallized sheet mainly in a uniaxial direction;
A method for producing a polymeric piezoelectric material, comprising:   The method for producing a polymeric piezoelectric material according to claim 11, wherein an annealing treatment is performed after the second step. A method for producing the polymeric piezoelectric material according to any one of claims 1 to 10,
Stretching the sheet containing the aliphatic polyester (A) and the stabilizer (B) mainly in a uniaxial direction;
A method for producing a polymeric piezoelectric material, comprising an annealing process in this order.