JP2019019277A - Polymeric piezoelectric material and production method thereof - Google Patents

Abstract

To provide a polymeric piezoelectric material which has improved moist-heat resistance, can be produced in a good working environment, and can inhibit discoloration.SOLUTION: A polymeric piezoelectric material comprises: an aliphatic polyester (A) having a weight-average molecular weight of 50 thousand to 1 million and optical activity; and a stabilizer (B) being an imino ether compound represented by general formula (B1) having a weight-average molecular weight from 300 to 60000. The crystallinity measured by the differential scanning calorimetry is 20%-80%. The content of the stabilizer (B) is 0.01 to 10 pts.mass relative to 100 pts.mass of the aliphatic polyester (A).SELECTED DRAWING: None

Description

  The present disclosure relates to a polymeric piezoelectric material and a method for manufacturing the same.

Conventionally, PZT (PbZrO ₃ —PbTiO ₃ -based solid solution), which is a ceramic material, has been frequently used as a piezoelectric material. However, since PZT contains lead, the environmental load is high. From the viewpoint of flexibility, polymer piezoelectric materials have been used.

  Currently known polymer piezoelectric materials include nylon 11, polyvinyl fluoride, polyvinyl chloride, polyurea, polyvinylidene fluoride (β-type) (PVDF), 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.

Ferroelectric polymers such as 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) is formed as follows. First, the polymer chain is oriented in the stretching direction by a stretching operation. Then, by applying different charges to the front and back of the film by corona discharge etc., an electric field is generated in the direction perpendicular to the film surface, and the permanent dipole containing fluorine in the side chain of the polymer chain is made parallel to the electric field direction. Orient and 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 has a dielectric constant of 13 and is relatively high among polymer piezoelectric materials, and is a value obtained by dividing the piezoelectric d constant by the dielectric constant. 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).

  Moreover, in order to make polylactic acid crystal highly oriented, it has been reported that high piezoelectricity of about 18 pC / N is exhibited by a special orientation method called a forging method (see, for example, Patent Document 2).

  Furthermore, from the viewpoint of improving heat and humidity resistance, a method of adding a stabilizer such as carbodiimide to an aliphatic polyester (for example, see Patent Document 3), a method of adding a stabilizer such as ketene imine (for example, Patent Document 4). Reference) etc. have been reported.

JP-A-5-152638 JP 2005-213376 A Japanese Patent No. 5259026 JP 2016-172797 A

However, since aliphatic polyesters such as polylactic acid are hydrolyzable, improvement in reliability has been an issue when used as a piezoelectric element in an environment that causes hydrolysis such as the presence of moisture in the atmosphere.
Further, in the polymer piezoelectric material disclosed in Patent Document 3, since isocyanate is generated due to thermal degradation of carbodiimide during the production of the polymer piezoelectric material, it is desired to further improve workability. Further, in the polymer piezoelectric material disclosed in Patent Document 4, ketene imine is likely to turn yellow due to thermal deterioration during the production of the polymer piezoelectric material, and improvement in reliability is expected when the polymer piezoelectric material is used as a touch panel or the like. It was rare.
In view of the above circumstances, an object of the present disclosure is to provide a polymeric piezoelectric material that has improved heat and heat resistance, can be manufactured in a good working environment, and can suppress discoloration, and a method for manufacturing 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, and an imino ether compound represented by the following general formula (B1), having a weight average molecular weight of 300 to 60000 A stabilizer (B), having a crystallinity of 20% to 80% obtained by differential scanning calorimetry, and the stabilizer based on 100 parts by mass of the aliphatic polyester (A) A polymeric piezoelectric material containing 0.01 to 10 parts by mass of (B).

(In General Formula (B1), R ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. R ³ represents an alkyl group represented by the following general formula (2) or an aryl group represented by the following general formula (3), and R ¹¹ , R ¹² and R ¹³ are Each independently represents a hydrogen atom, an optionally substituted alkyl group or an optionally substituted aryl group, and R ² , R ³ , R ¹¹ , R ¹² and R ¹³ are bonded to each other; To form a ring.)

(In the general formula (2), R ³¹ , R ³² and R ³³ each independently represents a hydrogen atom or a substituent. R ³¹ , R ³² and R ³³ may be linked to each other to form a ring. In formula (3), R ⁴¹ represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different, and n represents an integer of 0 to 5. (In (2) and (3), * represents the position bonded to the nitrogen atom.)
[2] The polymeric piezoelectric material according to [1], wherein the imino ether compound represented by the general formula (B1) includes an imino ether compound represented by the following general formula (B2).

(In General Formula (B2), R ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. represents an alkoxy group, .R ⁴¹ representing a R ^11, R ¹² and R ¹³ are each independently a hydrogen atom, which may have a an optionally substituted alkyl group or an optionally substituted aryl group Represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different, and n represents an integer of 0 to 5.)
[3] The polymeric piezoelectric material according to [1], wherein the imino ether compound represented by the general formula (B1) includes an imino ether compound represented by the following general formula (B3).

(In the general formula (B3), R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. R ²¹ and R ⁴¹ each independently represents a substituent, and when there are a plurality of R ²¹ and R ⁴¹ , they may be the same or different, n represents an integer of 0 to 5, and m represents 0 to 5 Represents an integer.)
[4] The polymer piezoelectric material according to [1], wherein the imino ether compound represented by the general formula (B1) includes a polymer compound including a structural unit represented by the following general formula (B4).

(In the general formula ^{(B4), .R 41} representing a R ^{11, R 12} and ^{R 13} are each independently a hydrogen atom, which may have a an optionally substituted alkyl group or an optionally substituted aryl group When a plurality of R ⁴¹ are present, they may be the same or different, n represents an integer of 0 to 5, p represents an integer of 2 to 4, and L ¹ represents And the bond terminal to the carbon atom has an alkylene part which may have a substituent, a cycloalkylene part which may have a substituent, an arylene part which may have a substituent, or a substituent. Represents a p-valent group which may be an alkoxylene moiety.)
[5] The polymer piezoelectric material according to [1], wherein the imino ether compound represented by the general formula (B1) includes a polymer compound including a structural unit represented by the following general formula (B5).

(In General Formula (B5), R ² has an alkyl group that may have a substituent, a cycloalkyl group that may have a substituent, an aryl group that may have a substituent, or a substituent. R ¹¹ , R ¹² and R ¹³ each independently represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. Represents an integer of 2 to 4, and L ² is a p-valent which is an arylene part that may have a substituent, or a cycloalkylene part that may have a substituent, at the bond terminal to the nitrogen atom. Represents a group.)
[6] The polymer piezoelectric material according to [1], wherein the imino ether compound represented by the general formula (B1) includes a polymer compound including a structural unit represented by the following general formula (B6).

(In General Formula (B6), R ² has an alkyl group that may have a substituent, a cycloalkyl group that may have a substituent, an aryl group that may have a substituent, or a substituent. R ⁴¹ represents a substituent and may be the same or different when a plurality of R ⁴¹ are present, n represents an integer of 0 to 5, and p represents L represents an integer of 2 to 4, and L ³ represents a p-valent group in which the bond terminal with an oxygen atom is an alkylene part, provided that a part or all of the hydrogen atoms are substituted in the alkylene part of L ³ (It may be substituted with an alkyl group which may have a group or an aryl group which may have a substituent.)
[7] is 50% or less internal haze to visible light, and the piezoelectric constant _{d 14} measured by a displacement method at 25 ° C. is 1.0 pm / V or more, one of [1] to [6] 1 The polymeric piezoelectric material according to Item.
[8] The polymeric piezoelectric material according to [7], wherein the internal haze is 13% or less.
[9] 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 [8] The polymeric piezoelectric material according to any one of the above.
[10] The high according to any one of [1] to [9], wherein the aliphatic polyester (A) includes a compound having a main chain containing a repeating unit represented by the following formula (1). Molecular piezoelectric material.

[11] The polymeric piezoelectric material according to any one of [1] to [10], wherein the aliphatic polyester (A) has an optical purity of 95.00% ee or more.
[12] The polymeric piezoelectric material according to any one of [1] to [11], wherein the content of the aliphatic polyester (A) is 80% by mass or more.
[13] The polymeric piezoelectric material according to any one of [1] to [12], wherein the area of the main surface is 5 mm ² or more.
[14] The method for producing a polymeric piezoelectric material according to any one of [1] to [13], wherein the amorphous state includes the aliphatic polyester (A) and the stabilizer (B). A method for producing a piezoelectric polymer material, comprising: a first step of crystallizing the sheet to obtain a pre-crystallized sheet; and a second step of stretching the pre-crystallized sheet.
[15] The method for producing a polymeric piezoelectric material according to [14], wherein annealing is performed after the second step.
[16] A step of stretching an amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B) and a step of annealing treatment are included in this order. [13] The method for producing a polymeric piezoelectric material according to any one of [13].

  According to the present disclosure, there is provided a polymeric piezoelectric material that has improved heat and moisture resistance, can be manufactured in a good working environment, and can suppress discoloration, and a method for manufacturing the same.

Hereinafter, embodiments of the present invention will be described.
In the present disclosure, 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 the present disclosure, the “main surface” of the polymeric piezoelectric material means a surface having the largest area among the surfaces of the polymeric piezoelectric material.
In the present disclosure, the “main surface” may be simply referred to as “surface”.
Further, in the present disclosure, the “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 disclosure is an aliphatic polyester (A) having a weight average molecular weight of 50,000 to 1,000,000 and optical activity, and an imino ether compound represented by the following general formula (B1). A stabilizer (B) having a molecular weight of 300 to 60000, a crystallinity of 20% to 80% obtained by a differential scanning calorimetry (DSC) method, and the aliphatic polyester (A) 100 The polymeric piezoelectric material contains 0.01 to 10 parts by mass of the stabilizer (B) with respect to parts by mass.
According to the polymer piezoelectric material of the present disclosure, it is possible to obtain a polymer piezoelectric material that has improved heat and moisture resistance, can be manufactured in a favorable working environment, and can suppress discoloration.

In General Formula (B1), R ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. R ³ represents an alkyl group represented by the following general formula (2) or an aryl group represented by the following general formula (3), and R ¹¹ , R ¹² and R ¹³ are each represented by Independently, it represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. R ² , R ³ , R ¹¹ , R ¹² and R ¹³ may be bonded to each other to form a ring.

In the general formula (2), R ³¹ , R ³² and R ³³ each independently represent a hydrogen atom or a substituent. R ³¹ , R ³² and R ³³ may be connected to each other to form a ring. In General Formula (3), R ⁴¹ represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different. N represents an integer of 0 to 5. In general formulas (2) and (3), * represents a position bonded to a nitrogen atom.

The reason why the above-described effect can be obtained by the polymer piezoelectric material of the present disclosure is not clear, but is considered as follows.
Hydrolysis of the aliphatic polyester is presumed to proceed, for example, according to the following scheme.

In order to suppress this hydrolysis, a method of suppressing contact with moisture by lamination with a gas barrier film or the like, or a method of forming a crosslinked structure in a hydrolyzed portion in the system, a cap on a free carboxyl group The method of doing etc. can be considered.
Among these, in the polymeric piezoelectric material of the present disclosure, the free carboxyl group is capped by the reaction of the imino ether group of the stabilizer (B) with the carboxyl group of the aliphatic polyester (A), thereby preventing hydrolysis. It is thought that sex is obtained. The presumed mechanism is shown below.

  Chemical modification of the terminal carboxyl group of the polyester can be performed by reacting an imino ether compound with a compound having a carboxylic acid group such as an aliphatic polyester in a temperature range of 100 ° C to 350 ° C. The reaction temperature can be selected depending on the melting point (Tm) of the polyester used.

  Further, the reaction between the stabilizer (B) and the aliphatic polyester (A) is excellent in workability as compared with the case where carbodiimide is used as the stabilizer. Furthermore, compared to the case where ketene imine is used as a stabilizer, since the stabilizer (B), the free substance produced by the reaction of the stabilizer (B) and the carboxyl group, and the coloration of those deteriorated products are less, It is considered that discoloration of the piezoelectric polymer material due to thermal degradation is suppressed.

  Hereinafter, preferred embodiments of the polymeric piezoelectric material of the present disclosure will be described.

<Aliphatic polyester (A)>
The polymeric piezoelectric material of the present disclosure contains an aliphatic polyester (A) having a weight average molecular weight of 50,000 to 1,000,000 and having optical activity (hereinafter also simply referred to as “aliphatic polyester (A)”).
Here, the “aliphatic polyester having optical activity” refers to a polymer having a helical structure and a molecular optical activity.
Examples of the aliphatic polyester (A) include polylactic acid polymers and poly (β-hydroxybutyric acid). In addition, the aliphatic polyester (A) is preferably a helical chiral polymer from the viewpoint of easily increasing 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.
・ Measuring device: JASCO Corporation liquid chromatography column temperature: 25 ℃
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)

  The aliphatic polyester (A) preferably contains a compound having a main chain containing a repeating unit represented by the following formula (1) from the viewpoint of increasing optical purity and improving piezoelectricity.

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 -A copolymer of a compound copolymerizable with lactic acid or D-lactic acid ", or a mixture of both.
Among them, as the polylactic acid polymer, “L-lactic acid homopolymer (PLLA)”, “copolymer of L-lactic acid and a compound copolymerizable with L-lactic acid”, a mixture of both, and “ "Homopolymer of D-lactic acid" (PDLA), "copolymer of D-lactic acid and a compound copolymerizable with D-lactic acid" and a mixture thereof are preferable, and "homopolymer of L-lactic acid" and "D-lactic acid" Are more preferred.

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 under reduced pressure in a solvent and polymerized while removing water;

  Examples of the “compound copolymerizable with L-lactic acid or D-lactic acid” (hereinafter also referred to as a copolymer component) 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- Hydroxycarboxylic acids such as hydroxycaproic acid, 6-hydroxycaproic acid, 6-hydroxymethylcaproic acid and mandelic acid; cyclic esters such as glycolide, β-methyl-δ-valerolactone, γ-valerolactone and ε-caprolactone; Acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid Polycarboxylic acids such as azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, terephthalic acid and their anhydrides; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 3-methyl-1,5 -Polyhydric alcohols such as pentanediol, neopentyl glycol, tetramethylene glycol and 1,4-hexanedimethanol; polysaccharides such as cellulose; aminocarboxylic acids such as α-amino acids;

  Examples of the copolymer include a block copolymer and a graft copolymer. For example, a block copolymer or a graft copolymer having a polylactic acid sequence capable of forming a helical crystal can be mentioned.

  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 The concentration of the structure derived from the copolymer component is preferably 20 mol% or less with respect to the total number of moles.

  A polylactic acid polymer is obtained, for example, by direct dehydration condensation of lactic acid described in JP-A-59-096123 and JP-A-7-033861; US Pat. No. 2,668,182 And ring-opening polymerization using lactide which is a cyclic dimer of lactic acid described in the specification and US Pat. No. 4,057,357, etc.

  Furthermore, when manufacturing a polylactic acid-type polymer by each said manufacturing method, it is preferable to manufacture so that optical purity may become 95.00% ee or more. For example, when polylactic acid is produced by the lactide method, it is preferable to polymerize lactide whose optical purity is improved to 95.00% ee or higher by crystallization operation.

-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 Mw of the aliphatic polyester (A) is 50,000 or more, the mechanical strength of the polymer piezoelectric material tends to be 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) tends to be 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 5.0, and preferably 1.2 to 4.0 from the viewpoint of the strength of the polymeric piezoelectric material. More preferably. Furthermore, it is preferable that it is 1.4-3.0.

  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-
The polymer 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 created with 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.
From the viewpoint of setting the weight average molecular weight (Mw) of the polylactic acid polymer to 50,000 or more when the polylactic acid polymer is used as the aliphatic polyester (A), the polylactic acid polymer is obtained by the lactide method or the direct polymerization method. It is preferable to produce a polymer.

The polymeric piezoelectric material of the present disclosure 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 polymer piezoelectric material of the present disclosure (the total content when there are two or more) is 80% by mass or more with respect to the total amount of the polymer piezoelectric material. Is preferred.

<Stabilizer (B)>
(Imino ether compound represented by formula (B1))
The polymeric piezoelectric material of the present disclosure is an imino ether compound represented by the following general formula (B1), and contains a stabilizer (B) having a weight average molecular weight of 300 to 60000.

In General Formula (B1), R ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. R ³ represents an alkyl group represented by the following general formula (2) or an aryl group represented by the following general formula (3), and R ¹¹ , R ¹² and R ¹³ are each represented by Independently, it represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. R ² , R ³ , R ¹¹ , R ¹² and R ¹³ may be bonded to each other to form a ring.

In the general formula (2), R ³¹ , R ³² and R ³³ each independently represent a hydrogen atom or a substituent. R ³¹ , R ³² and R ³³ may be connected to each other to form a ring. In General Formula (3), R ⁴¹ represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different. N represents an integer of 0 to 5. In general formulas (2) and (3), * represents a position bonded to a nitrogen atom.

In General Formula (B1), the alkyl group represented by 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 ² may be linear or branched. Further, the alkyl group represented by R ² may be a cycloalkyl group. Examples of the alkyl group represented by R ² include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, s-butyl group, isobutyl group, n-pentyl group, s- Examples include pentyl group, isopentyl group, n-hexyl group, s-hexyl group, isohexyl group, cyclohexyl group and the like. Of these, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an isobutyl group, and a cyclohexyl group are more preferable.
The alkyl group represented by R ² may further have a substituent. Examples of the substituent include an alkyl group, an aryl group, an alkoxy group, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group. In addition, the carbon number of the alkyl group represented by R ² does not include the carbon number of the substituent.

The aryl group represented by 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. Examples of the aryl group represented by R ² include a phenyl group and a naphthyl group, and a phenyl group is preferable. The aryl group represented by R ² may further have a substituent. As the substituent, can be R ² is exemplified similarly substituents when representing a alkyl group, as long as it can cause the reaction to proceed with the imino ether group and a carboxyl group, a substituted group is not particularly limited. In addition, the carbon number of the aryl group represented by R ² does not include the carbon number of the substituent.

The alkoxy group represented by R ² is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, and an alkoxy group having 2 to 6 carbon atoms. Is particularly preferred. The alkoxy group represented by R ² may be linear, branched or cyclic. Preferable examples of the alkoxy group represented by R ² include a group in which —O— is linked to the terminal of the alkyl group represented by R ² described above. The alkoxy group represented by R ² may further have a substituent. As the substituent, can be R ² is exemplified similarly substituents when representing a alkyl group, as long as it can cause the reaction to proceed with the imino ether group and a carboxyl group, a substituted group is not particularly limited. In addition, the carbon number of the alkoxy group represented by R ² does not include the carbon number of the substituent.

R ³ represents an alkyl group represented by the general formula (2) or an aryl group represented by the general formula (3). In the general formula (2), R ³¹ , R ³² and R ³³ each independently represent a hydrogen atom or a substituent. When R ³¹ , R ³² and R ³³ are substituents, they may be linked to each other to form a ring. Examples of the substituent include an alkyl group, an aryl group, an alkoxy group, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group. R ³¹ , R ³² and R ³³ may be all hydrogen atoms or the same substituent or different substituents. Further, the alkyl group represented by the general formula (2) may be linear or branched. Further, the alkyl group represented by the general formula (2) may be a cycloalkyl group.
In General Formula (3), R ⁴¹ represents a substituent, and n represents an integer of 0 to 5. When n is 2 or more, R ⁴¹ may be the same or different. As the substituent, can be R ² is exemplified similarly substituents when representing an alkyl group. In addition, it is more preferable that n is 0-3, and it is further more preferable that it is 0-2.

R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. The alkyl group and aryl group can be exemplified similarly an alkyl group and aryl group R ² can be taken.

R ² , R ³ , R ¹¹ , R ¹² and R ¹³ are preferably not bonded to form a ring, but R ² , R ³ , R ¹¹ , R ¹² and R ¹³ are bonded to each other to form a ring. May be. For example, when R ³ is represented by the general formula (3), R ⁴¹ and at least one of R ^{11 to} R ¹³ may be bonded to form a ring, and a benzene ring and R ^{11 to} R ¹³ A ring containing any of the above may form a condensed ring. When R ³ is represented by the general formula (3), it is preferable that R ⁴¹ and at least one of R ^{11 to} R ¹³ are not bonded to form a ring.
When R ³ is represented by the general formula (2), the bond formed by at least one of R ^{11 to} R ¹³ and at least one of R ^{31 to} R ³³ is preferably a bond having two or more linking atoms. . When R ³ is represented by the general formula (2), a bond formed by one of R ^{11 to} R ¹³ and one of R ^{31 to} R ³³ is a bond having two or more linking atoms, and a double bond More preferably, it is a bond. When R ³ is represented by the general formula (2), it is preferable that at least one of R ^{11 to} R ¹³ and at least one of R ^{31 to} R ³³ are not bonded to form a ring.

General formula (B1) may contain a repeating unit. In this case, at least one of R ² , R ³ or R ^{11 to} R ¹³ represents a structure containing a repeating unit. When the general formula (B1) includes a repeating unit, the repeating unit preferably includes an imino ether portion.

(Imino ether compound represented by formula (B2))
A preferred embodiment of the imino ether compound represented by the general formula (B1) includes an imino ether compound represented by the following general formula (B2).

In General Formula (B2), R ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. R ¹¹ , R ¹² and R ¹³ each independently represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. R ⁴¹ represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different. n represents an integer of 0 to 5.

In the general formula (B2), R ² , R ¹¹ , R ¹² and R ¹³ are the same as those in the general formula (B1), and preferred ranges are also the same. Further, in the general formula ^{(B2), R 41} is synonymous with ^{R 41} in the general formula (3), and preferred ranges are also the same. In addition, n is preferably 0 to 3, and more preferably 0 to 2.

(Imino ether compound represented by formula (B3))
A preferred embodiment of the imino ether compound represented by the general formula (B1) includes an imino ether compound represented by the following general formula (B3).

In General Formula (B3), R ¹¹ , R ^12, and R ¹³ each independently represent a hydrogen atom, an alkyl group that may have a substituent, or an aryl group that may have a substituent. R ²¹ and R ⁴¹ each independently represent a substituent. When a plurality of R ²¹ and R ⁴¹ are present, they may be the same or different. n represents an integer of 0 to 5, and m represents an integer of 0 to 5.

In General Formula (B3), R ¹¹ , R ¹² and R ¹³ are the same as those in General Formula (B1), and the preferred ranges are also the same. In the general formula ^{(B3), R 41} is synonymous with ^{R 41} in the general formula (3), and preferred ranges are also the same. ^{Incidentally,} it is possible to illustrate the same substituents as ^{R 41} in the ^{R 21} also, the general formula (3).

  Moreover, in general formula (B3), it is preferable that n is 0-3, and it is more preferable that it is 0-2. Moreover, m is preferably 0 to 3, and more preferably 0 to 2.

(High molecular compound containing the structural unit represented by formula (B4))
As a preferable embodiment of the imino ether compound represented by the general formula (B1), a polymer compound containing a structural unit represented by the following general formula (B4) can be given.

In General Formula (B4), R ¹¹ , R ^12, and R ¹³ each independently represent a hydrogen atom, an alkyl group that may have a substituent, or an aryl group that may have a substituent. R ⁴¹ represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different. n represents an integer of 0 to 5. P represents an integer of 2 to 4, and L ¹ represents an alkylene part that may have a substituent, a cycloalkylene part that may have a substituent, or a substituent at the bond end to the carbon atom. The p-valent group which is the arylene part which may have or the alkoxylene part which may have a substituent is represented.

In the general formula (B4), R ¹¹ , R ¹² and R ¹³ are the same as those in the general formula (B1), and preferred ranges thereof are also the same. Further, in the general formula ^{(B4), R 41} is synonymous with ^{R 41} in the general formula (3), and preferred ranges are also the same. In addition, n is preferably 0 to 3, and more preferably 0 to 2.

In General Formula (B4), L ¹ may have an alkylene part that may have a substituent, a cycloalkylene part that may have a substituent, or a substituent, at the bond end to the carbon atom. A p-valent group which is an arylene part or an alkoxylene part which may have a substituent is represented. p represents an integer of 2 to 4, and p is preferably 2 or 3.
Specific examples of the divalent group include an alkylene group that may have a substituent, a cycloalkylene group that may have a substituent, an arylene group that may have a substituent, and a substituent. And an alkoxylene group which may be used. In addition, the bond terminal to the carbon atom has an alkylene part which may have a substituent, a cycloalkylene part which may have a substituent, an arylene part which may have a substituent, or a substituent. a good alkoxylene unit also, as a partial structure, -SO 2 _-, - CO-, an alkylene unit substituted or unsubstituted alkenylene of substituted or unsubstituted, alkynylene portion, a substituted or unsubstituted phenylene unit, And a group containing at least one selected from a substituted or unsubstituted biphenylene moiety, a substituted or unsubstituted naphthylene moiety, -O-, -S- and -SO-.
Preferably, for example, substituted or unsubstituted phenylene, substituted or unsubstituted biphenylene, substituted or unsubstituted naphthylene, ethylene, n-butylene, substituted or unsubstituted cyclohexylene, substituted or unsubstituted —C ₆ H _{10 -C 6} H ₁₀ -, -C substituted or unsubstituted _{6 H 10 -CH 2 -C 6 H} 10 -, substituted or unsubstituted _{-C 6 H 4 -C (CH 3} ) 2 -C 6 H 4 - , Substituted or unsubstituted —C ₆ H ₄ —CH ₂ —C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —C (O) —C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —S—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —SO ₂ —C ₆ H ₄ — , substituted or unsubstituted _{-C 6 H 4 -C (CF 3} ) 2 -C 6 H 4 -, location Or unsubstituted _{-C 6 H 4 -NHC (O)} -C 6 H 4 -, substituted or unsubstituted _{-C 6 H 4 -O-C 6} H 4 -C (CH 3) 2 -C 6 H 4 —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —O—C ₆ H ₄ —C (O) —C ₆ H ₄ —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —O—C ₆ H ₄ —SO ₂ —C ₆ H ₄ —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —O—C ₆ H ₄ —S—C ₆ H ₄ —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —O— (C ₆ H ₄ ) ₂ —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H _{4 -O-C 6 H 4 -C} (CF 3) 2 -C 6 H 4 -O-C 6 H 4 -, and the like.
Specific examples of the trivalent group include, for example, a group obtained by removing one hydrogen atom from those having a substituent among the groups listed as examples of the divalent group.
Specific examples of the tetravalent group include, for example, a group obtained by removing two hydrogen atoms from those having a substituent among the groups listed as examples of the divalent group.

  In general formula (B4), by setting p to 2 to 4, a compound having two or more imino ether moieties in one molecule can be obtained, and a more excellent end-capping effect can be exhibited. is there. Furthermore, by using a compound having two or more imino ether moieties in one molecule, the imino ether value (total molecular weight / number of functional groups of imino ether) can be lowered, and the imino ether compound and the terminal carboxyl group of the polyester can be efficiently produced. Can be reacted. The same applies to general formulas (B5) and (B6) described later.

  As a preferable embodiment of the imino ether compound represented by the general formula (B1), a polymer compound containing a structural unit represented by the following general formula (B5) can be given.

In general formula (B5), R ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. R ¹¹ , R ¹² and R ¹³ each independently represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. P represents an integer of 2 to 4, and L ² is an arylene moiety that may have a substituent, or a cycloalkylene moiety that may have a substituent, at the terminal end of the bond with the nitrogen atom. Represents a p-valent group.

In General Formula (B5), R ² , R ¹¹ , R ¹² and R ¹³ are the same as in General Formula (B1), and the preferred ranges are also the same.

In General Formula (B5), L ² represents a p-valent group in which the bond terminal to the nitrogen atom is an arylene part that may have a substituent or a cycloalkylene part that may have a substituent. Represent. L ² is preferably a p-valent group whose bond terminal to the nitrogen atom is an arylene moiety that may have a substituent. p represents an integer of 2 to 4, and p is preferably 2 or 3.
Specific examples of L ² include an arylene group which may have a substituent and a cycloalkylene group which may have a substituent. Moreover, the bond terminal with a nitrogen atom is an arylene part which may have a substituent or a cycloalkylene part which may have a substituent, and —SO ₂ —, —CO—, Substituted or unsubstituted alkylene part, substituted or unsubstituted alkenylene part, alkynylene part, substituted or unsubstituted phenylene part, substituted or unsubstituted biphenylene part, substituted or unsubstituted naphthylene part, -O-, -S- And a group containing at least one selected from -SO-.
Preferably, for example, substituted or unsubstituted phenylene, substituted or unsubstituted biphenylene, substituted or unsubstituted naphthylene, substituted or unsubstituted cyclohexylene, substituted or unsubstituted —C ₆ H ₁₀ —C ₆ H ₁₀ — Substituted or unsubstituted —C ₆ H ₁₀ —CH ₂ —C ₆ H ₁₀ —, substituted or unsubstituted —C ₆ H ₄ —C (CH ₃ ) ₂ —C ₆ H ₄ —, substituted or unsubstituted _{-C 6 H 4 -CH 2 -C 6} H 4 -, substituted or unsubstituted _{-C 6 H 4 -C (O)} -C 6 H 4 -, -C 6 substituted or unsubstituted _H 4 -O- _{C 6 H 4 -, -C 6} H 4 substituted or unsubstituted _-S-C 6 _{H 4} -, substituted or unsubstituted _{-C 6 H 4 -SO 2 -C 6} H 4 -, substituted or unsubstituted _{-C 6 H 4 -C (CF 3} ) 2 -C 6 H 4 -, substituted or unsubstituted _-C 6 H _{-NHC (O) -C 6 H 4} -, substituted or unsubstituted _{-C 6 H 4 -O-C 6} H 4 -C (CH 3) 2 -C 6 H 4 -O-C 6 H 4 -, Substituted or unsubstituted —C ₆ H ₄ —O—C ₆ H ₄ —C (O) —C ₆ H ₄ —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —O—C ₆ H ₄ —SO ₂ —C ₆ H ₄ —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —O—C ₆ H ₄ —S—C ₆ H ₄ —O—C ₆ H _4- , substituted or unsubstituted —C ₆ H ₄ —O— (C ₆ H ₄ ) ₂ —O—C ₆ H ₄ —, substituted or unsubstituted —C ₆ H ₄ —O—C ₆ H ₄ — _{C (CF 3) 2 -C 6} H 4 -O-C 6 H 4 -, and the like.

(High molecular compound containing the structural unit represented by the general formula (B6))
As a preferable embodiment of the imino ether compound represented by the general formula (B1), a polymer compound containing a structural unit represented by the following general formula (B6) can be given.

In General Formula (B6), R ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. R ⁴¹ represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different. n represents an integer of 0 to 5. P represents an integer of 2 to 4, and L ³ represents a p-valent group in which the bond terminal to the oxygen atom is an alkylene part. However, in the alkylene part of L ³ , part or all of the hydrogen atoms may be substituted with an alkyl group which may have a substituent or an aryl group which may have a substituent.

In the general formula (B6), ^{R 2} are each as agreed in the general formula (B1), and preferred ranges are also the same. Further, in the general formula ^{(B6), R 41} is synonymous with ^{R 41} in the general formula (3), and preferred ranges are also the same. In addition, n is preferably 0 to 3, and more preferably 0 to 2.

In General Formula (B6), L ³ represents a p-valent group in which a bond terminal with an oxygen atom is an alkylene part. In the alkylene part of L ³ , part or all of the hydrogen atoms may be substituted with an alkyl group which may have a substituent or an aryl group which may have a substituent. p represents an integer of 2 to 4, and p is preferably 2 or 3.
Specific examples of L ³ include an alkylene group. In addition, the bond terminal to the oxygen atom is an alkylene moiety, and as a partial structure, —SO ₂ —, —CO—, a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, an alkynylene group, substituted or unsubstituted And a group containing at least one selected from a substituted phenylene group, a substituted or unsubstituted biphenylene group, a substituted or unsubstituted naphthylene group, —O—, —S—, and —SO—.
Preferably, for example, ethylene, n-butylene, substituted or unsubstituted —CH ₂ —C (CH ₃ ) ₂ —CH ₂ —, substituted or unsubstituted —CH ₂ —C ₆ H ₄ —CH ₂ —, etc. Can be mentioned.

The weight average molecular weight of the stabilizer (B) is 300 to 60000. The weight average molecular weight of the stabilizer (B) is preferably 300 to 10,000, and more preferably 300 to 1,000. In addition, the weight average molecular weight of a stabilizer (B) can be measured with the measuring method and mass spectrum similar to the weight average molecular weight of the aliphatic polyester (A) mentioned above. When the stabilizer (B) is a single component having no molecular weight distribution, the weight average molecular weight and the number average molecular weight are the same.
When the weight average molecular weight of the stabilizer (B) is 300 or more, volatilization can be effectively suppressed. Further, when the weight average molecular weight of the stabilizer is 60000 or less, the stabilizer (B) is likely to be present in the part of the aliphatic polyester (A) where a part of the molecular chain is broken, and the aliphatic polyester (A). It is considered that the carboxyl group of can be efficiently protected.

  The stabilizer (B) in the polymeric piezoelectric material is preferably a bifunctional or higher functional compound, more preferably a bifunctional, trifunctional or tetrafunctional compound from the viewpoint of ease of synthesis. More preferably, it is a functional or trifunctional compound. Here, the functional number represents the number of imino ether parts contained in the compound, and the bifunctional imino ether compound means a compound containing two imino ether parts. When the imino ether compound is a bifunctional or higher compound, the end-capping effect tends to be further enhanced.

Content of a stabilizer (B) is 0.01 mass part-10 mass parts with respect to 100 mass parts of aliphatic polyester (A). The amount is preferably 0.1 parts by mass to 5 parts by mass and more preferably 0.5 parts by mass to 2.8 parts by mass with respect to 100 parts by mass of the aliphatic polyester (A). When the content of the stabilizer (B) is in the above range, an excellent effect of improving heat and moisture resistance tends to be obtained.
In addition, the said content shows those total amounts, when using 2 or more types of stabilizers (B) together.

  The preferable specific example of general formula (B1) is shown below.

<Stabilizer (C)>
The polymeric piezoelectric material of the present disclosure may further include a stabilizer (C) as a stabilizer other than the stabilizer (B) as long as the effects of the present invention are not impaired.
It is preferable that a stabilizer (C) contains at least 1 sort (s) chosen from the group which consists of a carbodiimide group, an epoxy group, and an isocyanate group in 1 molecule, and is a weight average molecular weights 200-60000.

  As the stabilizer (C) in the present disclosure, “stabilizer (B)” described in paragraphs 0039 to 0055 of International Publication No. 2013/054918 may 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, US Pat. No. 2,941,956, Japanese Patent Publication No. 47-33279, J. Org. Chem. 28, 2069-2075 (1963), Chemical Review 1981, Vol. 81 No. 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 the present disclosure contains a stabilizer (C), the polymeric piezoelectric material may contain only one kind of stabilizer (C), or may contain two or more kinds. Good.
When the polymeric piezoelectric material of the present disclosure includes 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). Parts, preferably 0.01 parts by weight to 5 parts by weight, more preferably 0.1 parts by weight to 3 parts by weight, and 0.5 parts by weight to 2 parts by weight. Is more preferable.

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. (C1) and a stabilizer (c2) having two 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 ) In combination.
When the stabilizer (c1) and the stabilizer (c2) are used in combination as the stabilizer, it is preferable that a large amount of the stabilizer (c1) is contained from the viewpoint of improving transparency.
Specifically, the stabilizer (c2) is preferably in the range of 10 parts by mass to 150 parts by mass with respect to 100 parts by mass of the stabilizer (c1), from the viewpoint of achieving both transparency and wet heat resistance. More preferably, it is in the range of 50 to 100 parts by mass.

  Hereinafter, specific examples (stabilizers C-1 to C-3) of the stabilizer (C) are shown. In the following chemical formula, a part surrounded by [] represents a structural unit, and i-Pr represents isopropyl.

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 the present disclosure 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 disclosure is based on the total amount of the polymer piezoelectric material. 80% by mass or more is preferable.

<Physical properties of polymer piezoelectric material>
(Transparency (internal haze))
The polymeric piezoelectric material of the present disclosure has an internal haze with respect to visible light (hereinafter also simply referred to as “internal haze”) of preferably 50% or less, more preferably 20% or less, and 15% or less. More preferably, it is more preferably 13% or less. The internal haze of the polymeric 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 disclosure, “internal haze” refers to haze excluding haze due to the shape of the outer surface of the polymeric piezoelectric material.
Further, the “internal haze” here is a value when measured at 25 ° C. in accordance with JIS-K7136 (2000) with respect to the polymer piezoelectric material.

The internal haze (hereinafter also referred to as internal haze (H1)) of the polymeric piezoelectric material of the present disclosure is measured by the following method.
First, the haze (H2) (%) is measured by sandwiching only silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., model number: KF96-100CS) between two glass plates in advance, and then the surface is made uniform with silicone oil. The polymer piezoelectric material (piezoelectric film) coated on the substrate is sandwiched between two glass plates, and the 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 disclosure, the “piezoelectric constant d ₁₄ ” refers to the piezoelectric constant d ₁₄ measured by a 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 by the method described in paragraphs 0058 to 0059 of Japanese Patent No. 4934235, for example.

Hereinafter, an example of a method for measuring the piezoelectric constant d ₁₄ (displacement method) will be described.
First, by depositing aluminum (Al) on both surfaces of a polymeric piezoelectric material cut into a square shape of 40 mm × 40 mm by using a vapor deposition apparatus (for example, Showa Vacuum Corp. SIP-600), an Al conductive layer is formed. Form.
Next, a 40 mm × 40 mm test piece (polymer piezoelectric material) having a conductive layer of Al formed on both sides thereof is 32 mm in a direction that forms 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 forming 0 °, 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)) 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 polymer piezoelectric material of the present disclosure is preferably 1.0 pm / V or more, and 3.0 pm. / V or more is more preferable, 4.0 pm / V or more is further preferable, 6.0 pm / V or more is further preferable, and 8.0 pm / V or more is more preferable.
The upper limit of the piezoelectric constant d ₁₄ is not particularly limited, from the viewpoint of the balance between transparency and the like, preferably 50 Pm/V less in polymeric piezoelectric material using the aliphatic polyester (A), 30pm / V or less Is more preferable.

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

Here, a polymeric piezoelectric material of the present disclosure, 50% or less internal haze to visible light, and is preferably a piezoelectric constant d ₁₄ is 1.0 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 the present disclosure 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. It is more preferable.
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. It tends to be possible to express high piezoelectricity.

  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 at a resonance frequency in the vicinity of 4 GHz or 12 GHz with a known molecular orientation meter such as a microwave molecular orientation meter MOA-2012A or MOA-6000 manufactured by Oji Scientific Instruments.

  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 linearly correlated, 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. , Birefringence Δn 0.005, and can be converted to birefringence Δn 0.01 if the normalized molecular orientation MORc is 4.0.

(Crystallinity)
The crystallinity of the polymer piezoelectric material of the present disclosure is determined by the DSC method, and the crystallinity of the polymer piezoelectric material is 20% to 80%, preferably 25% to 70%, more preferably 30% to 50% is preferable. 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, it tends to be easy to manufacture without being whitened or broken.

(Product of normalized molecular orientation MORc and crystallinity)
The polymer piezoelectric material of the present disclosure preferably has a product of the normalized molecular orientation MORc and the crystallinity obtained by the DSC method when the reference thickness measured by a microwave transmission type molecular orientation meter is 50 μm. -700, more preferably 75-680, still more preferably 90-660, still more preferably 125-650, and still more preferably 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 It has a high property and tends to be suitably used as a piezoelectric element described later.

<Applications of polymer piezoelectric materials>
The polymer piezoelectric material of the present disclosure includes a speaker, a headphone, a touch panel, a remote controller, a microphone, an underwater microphone, an ultrasonic transducer, an ultrasonic applied measuring instrument, a piezoelectric vibrator, a mechanical filter, a piezoelectric transformer, a delay device, a sensor, and an acceleration. Sensor, Shock sensor, Vibration sensor, Pressure sensor, Tactile sensor, Electric field sensor, Sound pressure sensor, Display, Fan, Pump, Variable focus mirror, Sound insulation material, Sound insulation material, Keyboard, Sound device, Information processing machine, Measurement device, It can be used in various fields such as medical equipment.

  At this time, the polymeric piezoelectric material of the present disclosure is preferably used as a piezoelectric element having at least two surfaces, of which electrodes are provided on at least two surfaces. At this time, the electrodes need only 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.

The polymer piezoelectric material of the present disclosure can also be used as a laminated piezoelectric element in which a polymer piezoelectric material and an electrode are repeatedly stacked. As an example, an electrode and a unit of a polymer piezoelectric material are repeatedly stacked, and finally, a main surface of the polymer piezoelectric material that is not covered with the electrode is covered with an electrode. For example, a laminated piezoelectric element in which an electrode, a polymer piezoelectric material, an electrode, a polymer piezoelectric material, and an electrode are stacked in this order and the unit is repeated twice is mentioned. When the polymer piezoelectric material of the present disclosure is used as a laminated piezoelectric element, one of the plurality of layers may be the polymer piezoelectric material of the present disclosure, and the other layers may be the polymer of the present disclosure. It does not have to be a piezoelectric material.
In addition, when the polymer piezoelectric material of the present disclosure is included in a plurality of layers of the laminated piezoelectric element, the optical activity of the aliphatic polyester (A) included in the polymer piezoelectric material of a certain layer is L, The aliphatic polyester (A) contained in the polymer piezoelectric material of this layer 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 L-type aliphatic polyester (A) as the main component via the electrode. When laminated with the polymeric 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 It is preferable to make them orthogonal to each other because the directions 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 D-type aliphatic polyester (A) as the main component via the electrode. When laminated with the polymeric 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. Such a disposition is preferable because the directions 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.

  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 polymer piezoelectric material of the present disclosure can be applied to the above-described various piezoelectric devices such as a speaker and a touch panel. 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, a preferable aspect of the method for producing the polymeric piezoelectric material of the present disclosure will be described.

<Method for producing polymer piezoelectric material>
As a preferred embodiment of the method for producing a polymeric piezoelectric material of the present disclosure, a non-crystalline sheet containing an aliphatic polyester (A) and a stabilizer (B) is crystallized to obtain a pre-crystallized sheet (crystallization raw material). And a second step of stretching the preliminary crystallization sheet.

  In general, increasing the force applied to the film during stretching promotes the orientation of the aliphatic polyester (A) and increases the piezoelectric constant, but the crystallization proceeds, the crystal size increases, and microcracks are generated. The haze tends to increase. Also, the dimensional deformation rate tends to increase due to an increase in internal stress. In addition, when the film is simply heated regardless of stretching, crystals that are not oriented, such as spherulites, are formed. A coarse crystal having a low orientation such as a spherulite increases the haze but hardly contributes to an increase in the piezoelectric constant. Therefore, in order to form a film having a high piezoelectric constant and a low haze and dimensional deformation rate, it is preferable to efficiently form an oriented crystal that contributes to the piezoelectric constant with a minute size that does not increase haze.

  In the method for producing a polymeric piezoelectric material including the first step and the second step described above, the inside of the sheet is pre-crystallized before stretching to obtain a pre-crystallized sheet, and then stretched. When the preliminary crystallization is performed, fine crystals are formed. As a result, when a force is applied to the film by stretching, the force is 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, it exists in the tendency which can obtain a sheet | seat with a low value of a haze and a dimensional deformation rate, without significantly reducing a piezoelectric constant.

(First step (pre-crystallization step))
In the first step, an amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B) is crystallized to obtain a pre-crystallized sheet.

  The raw material for the piezoelectric polymer material is the aliphatic polyester (A) such as the polylactic acid polymer described above, the stabilizer (B), and other components (stabilizer (C), etc., if necessary) ) 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. Even if a blend of the aliphatic polyester (A) and the stabilizer (B) or a blend of the aliphatic polyester (A), the stabilizer (B) and other components such as an inorganic filler is obtained. Good.

  The amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B) may be produced by a known film forming means such as extrusion. Alternatively, the amorphous sheet may be available from the market. The amorphous sheet may be a single layer or a multilayer.

  The pre-crystallized sheet can be obtained by heat-treating an amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B) for crystallization. In addition, 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 extrusion molding or the like, and is extruded into a sheet shape. After that, the pre-crystallized sheet having a desired 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 amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B) is not particularly limited, but the piezoelectricity and transparency of the polymeric piezoelectric material are not limited. From the viewpoint of increasing, 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 preferably set to 3% to 70%.
Tg−40 ° C. ≦ T ≦ Tg + 40 ° C.
(Tg represents the glass transition temperature (° C.) 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 same as that of the polymer piezoelectric material after stretching (after the second step). The product of the normalized molecular orientation MORc and the crystallinity obtained by the DSC method of the polymer piezoelectric material after stretching is preferably 40 to 700, more preferably 75 to 680, still more preferably 90 to 660, still more preferably 125 to It is preferably adjusted to 650, more preferably 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 additives, and the like. In the preheating that may be performed before the stretching step (second step) described below, the substantial heating time for crystallizing the sheet is preheated at a temperature at which the amorphous sheet crystallizes. This corresponds to the sum of the preheating 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 preferable 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%, more preferably 15% to 50%.

  What is necessary is just to perform the crystallinity degree of a pre-crystallization sheet | seat similarly to the measurement of the crystallinity degree of the polymeric piezoelectric material of this indication after extending | 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))
In the second step, the pre-crystallized sheet is stretched. The stretching method 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 the present disclosure 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 the present disclosure, 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. The area of the main surface 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”. Say. Solid-phase stretching tends to improve the piezoelectricity of the polymeric piezoelectric material and improve the transparency and elasticity.

  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 by using a differential scanning calorimeter. These are 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 from the melting endothermic curve when the temperature is raised under the condition of minutes.

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

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

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

  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.

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

  When the pre-crystallized sheet is stretched, preheating may be performed to facilitate stretching of the sheet immediately before stretching. 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 disclosure, since pre-crystallization may be performed before stretching, the pre-heating may be performed in combination with pre-crystallization. Specifically, preheating is performed at a temperature higher or higher than the normal temperature in accordance with the heating temperature and heat treatment time in the above-described precrystallization step, so that both preheating and precrystallization are performed. Can do.

(Annealing process)
From the viewpoint of improving the piezoelectric constant, it is preferable to heat-treat (hereinafter also referred to as “annealing process”) the polymer piezoelectric material after the stretching process (after the second step). 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.

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

  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 of the annealing treatment is not particularly limited, but a method of heating directly using a hot air heater or an infrared heater, a method of heating a polymer piezoelectric material by contacting with a heated roll, heating silicon oil, etc. For example, a method of immersing the polymer piezoelectric material in the liquid and heating it.

  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 even more preferably 1 second to 60 seconds. When the temperature application time of annealing treatment is within 60 minutes, it tends to be able to suppress the spherulite from growing from the molecular chain of the amorphous part and lowering the degree of orientation at a temperature higher than the glass transition temperature of the polymeric piezoelectric material. As a result, there is a tendency that a decrease in piezoelectricity and transparency can be suppressed.

  The polymeric piezoelectric material annealed as described above is preferably cooled rapidly after the annealing treatment. In the annealing process, “rapidly cool” means that the annealed polymer piezoelectric material is immersed in, for example, ice water immediately after the annealing process and cooled to a glass transition temperature Tg or lower. This means that no other treatment is included in the dipping process.

  The rapid cooling method can be achieved by 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. In order to continuously cool the polymer piezoelectric material, the polymer piezoelectric material may be rapidly cooled by bringing the polymer roll into contact with a metal roll controlled to a temperature equal to or lower than the glass transition temperature Tg of the polymer piezoelectric material. . 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.

Claims (16)

An aliphatic polyester (A) having a weight average molecular weight of 50,000 to 1,000,000 and optical activity;
A stabilizer (B) which is an imino ether compound represented by the following general formula (B1) and has a weight average molecular weight of 300 to 60000,
Containing
The crystallinity obtained by differential scanning calorimetry 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 ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. R ³ represents an alkyl group represented by the following general formula (2) or an aryl group represented by the following general formula (3), and R ¹¹ , R ¹² and R ¹³ are Each independently represents a hydrogen atom, an optionally substituted alkyl group or an optionally substituted aryl group, and R ² , R ³ , R ¹¹ , R ¹² and R ¹³ are bonded to each other; To form a ring.)

(In the general formula (2), R ³¹ , R ³² and R ³³ each independently represents a hydrogen atom or a substituent. R ³¹ , R ³² and R ³³ may be linked to each other to form a ring. In formula (3), R ⁴¹ represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different, and n represents an integer of 0 to 5. (In (2) and (3), * represents the position bonded to the nitrogen atom.) The polymeric piezoelectric material according to claim 1, wherein the imino ether compound represented by the general formula (B1) includes an imino ether compound represented by the following general formula (B2).

(In General Formula (B2), R ² has an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. represents an alkoxy group, .R ⁴¹ representing a R ^11, R ¹² and R ¹³ are each independently a hydrogen atom, which may have a an optionally substituted alkyl group or an optionally substituted aryl group Represents a substituent, and when a plurality of R ⁴¹ are present, they may be the same or different, and n represents an integer of 0 to 5.) The polymeric piezoelectric material according to claim 1, wherein the imino ether compound represented by the general formula (B1) includes an imino ether compound represented by the following general formula (B3).

(In the general formula (B3), R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. R ²¹ and R ⁴¹ each independently represents a substituent, and when there are a plurality of R ²¹ and R ⁴¹ , they may be the same or different, n represents an integer of 0 to 5, and m represents 0 to 5 Represents an integer.) The polymeric piezoelectric material according to claim 1, wherein the imino ether compound represented by the general formula (B1) includes a polymeric compound including a structural unit represented by the following general formula (B4).

(In the general formula ^{(B4), .R 41} representing a R ^{11, R 12} and ^{R 13} are each independently a hydrogen atom, which may have a an optionally substituted alkyl group or an optionally substituted aryl group When a plurality of R ⁴¹ are present, they may be the same or different, n represents an integer of 0 to 5, p represents an integer of 2 to 4, and L ¹ represents And the bond terminal to the carbon atom has an alkylene part which may have a substituent, a cycloalkylene part which may have a substituent, an arylene part which may have a substituent, or a substituent. Represents a p-valent group which may be an alkoxylene moiety.) The polymer piezoelectric material according to claim 1, wherein the imino ether compound represented by the general formula (B1) includes a polymer compound including a structural unit represented by the following general formula (B5).

(In General Formula (B5), R ² has an alkyl group that may have a substituent, a cycloalkyl group that may have a substituent, an aryl group that may have a substituent, or a substituent. R ¹¹ , R ¹² and R ¹³ each independently represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. Represents an integer of 2 to 4, and L ² is a p-valent which is an arylene part that may have a substituent, or a cycloalkylene part that may have a substituent, at the bond terminal to the nitrogen atom. Represents a group.) The polymer piezoelectric material according to claim 1, wherein the imino ether compound represented by the general formula (B1) includes a polymer compound including a structural unit represented by the following general formula (B6).

(In General Formula (B6), R ² has an alkyl group that may have a substituent, a cycloalkyl group that may have a substituent, an aryl group that may have a substituent, or a substituent. R ⁴¹ represents a substituent and may be the same or different when a plurality of R ⁴¹ are present, n represents an integer of 0 to 5, and p represents L represents an integer of 2 to 4, and L ³ represents a p-valent group in which the bond terminal with an oxygen atom is an alkylene part, provided that a part or all of the hydrogen atoms are substituted in the alkylene part of L ³ (It may be substituted with an alkyl group which may have a group or an aryl group which may have a substituent.) 7. The internal haze with respect to visible light is 50% or less, and the piezoelectric constant d ₁₄ measured by a displacement method at 25 ° C. is 1.0 pm / V or more. High molecular piezoelectric material.   The polymeric piezoelectric material according to claim 7, wherein the internal haze is 13% or less.   9. The product of any one of claims 1 to 8, wherein a 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. 2. The polymeric piezoelectric material according to item 1. The polymeric piezoelectric material according to any one of claims 1 to 9, wherein the aliphatic polyester (A) includes a compound having a main chain containing a repeating unit represented by the following formula (1). .
  11. The polymeric piezoelectric material according to claim 1, wherein the aliphatic polyester (A) has an optical purity of 95.00% ee or more.   The polymeric piezoelectric material according to any one of claims 1 to 11, wherein a content of the aliphatic polyester (A) is 80% by mass or more. The polymeric piezoelectric material according to any one of claims 1 to 12, wherein an area of the main surface is 5 mm ² or more. A method for producing a polymeric piezoelectric material according to any one of claims 1 to 13,
A first step of crystallizing an amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B) to obtain a pre-crystallized sheet;
A second step of stretching the pre-crystallized sheet;
A method for producing a polymeric piezoelectric material, comprising:   The method for producing a polymeric piezoelectric material according to claim 14, wherein an annealing treatment is performed after the second step. Stretching an amorphous sheet containing the aliphatic polyester (A) and the stabilizer (B);
An annealing process;
The manufacturing method of the polymeric piezoelectric material of any one of Claims 1-13 containing these in this order.