JP2019026691A - High molecule piezoelectric film and manufacturing method therefor, piezoelectric film piece and manufacturing method therefor, laminate and piezoelectric element - Google Patents

Abstract

To provide a high molecule piezoelectric film capable of improving yield when a piezoelectric film piece is collected, and easily manufacturing a piezoelectric element at good efficiency, when the used as a raw fabric for collecting the piezoelectric film piece.SOLUTION: There is provided a high molecule piezoelectric film containing a helical chiral high molecule (A) having weight average molecular weight of 50,000 to 1,000,000 and optical activity, and having crystallinity index obtained by a DSC method of 20% to 80%, a long sized shape, longer direction length of 10 m or more, a plane view angle θ1 between molecule orientation direction La of the helical chiral high molecule (A) at one end part in a width direction and molecule orientation direction Lb of the helical chiral high molecule (A) at another end part of 70° to 110°, a plane view angle θ2 between the longer direction and the molecule orientation direction La of 35° to 55°, and a plane view angle θ3 between the longer direction and the molecule orientation direction Lb of 35° to 55°.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a polymer piezoelectric film and a manufacturing method thereof, a piezoelectric film piece and a manufacturing method thereof, a laminate, and a piezoelectric element.

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

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

In a conventional polymer piezoelectric film such as the polymer piezoelectric material disclosed in Patent Document 1 or Patent Document 2, the molecular orientation direction of polylactic acid and the longitudinal direction of the polymer piezoelectric film are parallel to each other. For this reason, in order to produce a piezoelectric element by using the polymer piezoelectric film as a raw material and collecting a piezoelectric film piece from the raw material, a direction crossing the longitudinal direction of the raw material (for example, in the longitudinal direction of the raw material) On the other hand, it is necessary to collect a piezoelectric film piece having a longitudinal direction of 45 °. Therefore, inevitably, areas that cannot be collected as piezoelectric film pieces (that is, useless areas to be discarded) are generated at both ends in the width direction of the original fabric.
For the above reasons, the conventional polymer piezoelectric film has a problem that the yield is low when the polymer piezoelectric film is used as an original fabric and a piezoelectric film piece is collected from the original fabric.

Conventionally, when a piezoelectric element (actuator, sensor, etc.) using a piezoelectric film piece is manufactured, first, a plurality of piezoelectric film pieces are collected from the piezoelectric film as a raw material, and the plurality of piezoelectric film pieces obtained are collected. A plurality of laminates (piezoelectric film pieces provided with electrode layers on both sides) were manufactured by providing electrode layers on both sides. Next, a piezoelectric film was manufactured by superimposing a plurality of laminated bodies via an adhesive layer (for example, an adhesive layer, a hardened layer, etc.).
However, the above-described conventional method for manufacturing a piezoelectric element is complicated because it requires a large number of parts (that is, laminates) to be manufactured to manufacture the piezoelectric element and a large number of piezoelectric film pieces collected from the original fabric. there were. In addition, the operation of adjusting the angle when stacking a plurality of laminated bodies is complicated.

This indication is made in view of the above, and makes it a subject to achieve the following objects.
That is, an object of the present disclosure is to provide a polymer that can improve the yield when collecting a piezoelectric film piece when used as a raw material for collecting a piezoelectric film piece, and can easily manufacture a piezoelectric element at a high yield. A piezoelectric film and a method for producing a polymer piezoelectric film suitable for producing the polymer piezoelectric film are provided.
Moreover, the objective of this indication is providing the manufacturing method of the piezoelectric film piece suitable for manufacture of the piezoelectric film piece and laminated body which can manufacture a piezoelectric element simply, and the said piezoelectric film piece.
Another object of the present disclosure is to provide a piezoelectric element that can be easily manufactured.

Specific means for solving the above problems include the following modes.
<1> A polymeric piezoelectric film comprising a helical chiral polymer (A) having an optical activity of weight average molecular weight of 50,000 to 1,000,000 and having a crystallinity of 20% to 80% obtained by DSC method. And
Has a long shape,
The longitudinal length is 10 m or more,
The planar view angle θ1 between the molecular orientation direction La of the helical chiral polymer (A) at one end in the width direction and the molecular orientation direction Lb of the helical chiral polymer (A) at the other end in the width direction is 70 °. ~ 110 °,
The planar view angle θ2 between the longitudinal direction and the molecular orientation direction La is 35 ° to 55 °,
A polymer piezoelectric film having a planar view angle θ3 between a longitudinal direction and the molecular orientation direction Lb of 35 ° to 55 °.
<2> The polymer piezoelectric film according to <1>, wherein the internal haze with respect to visible light is 10% or less.
<3> The high molecular weight according to <1> or <2>, wherein the normalized molecular orientation MORc is 3.5 to 15.0 when the reference thickness measured with a microwave transmission type molecular orientation meter is 50 μm. Molecular piezoelectric film.
Polymeric piezoelectric film according to the piezoelectric constant _{d 14} is measured by the displacement method in <4> 25 ° C., one of is 1.0 pm / V or more <1> to <3>.
<5> In any one of <1> to <4>, the helical chiral polymer (A) is a polylactic acid polymer having a main chain including a repeating unit represented by the following formula (1). The polymeric piezoelectric film as described.

<6> The polymeric piezoelectric film according to any one of <1> to <5>, wherein the helical chiral polymer (A) has an optical purity of 95.00% ee or more.
<7> The polymer piezoelectric film according to any one of <1> to <6>, wherein the content of the helical chiral polymer (A) is 80% by mass or more based on the total amount of the polymer piezoelectric film.

<8> A piezoelectric film piece comprising a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000 and having a crystallinity of 20% to 80% obtained by a DSC method. ,
Piezoelectric film in which a planar view angle between the molecular orientation direction of the helical chiral polymer (A) at one end and the molecular orientation direction of the helical chiral polymer (A) at the other end is 70 ° to 110 ° Fragment.

<9> The piezoelectric film piece according to <8>,
An electrode layer disposed on at least one side of the piezoelectric film piece;
A laminate comprising:
<10> Furthermore, the laminated body as described in <9> provided with the contact bonding layer arrange | positioned on the opposite side to the side by which the piezoelectric film piece is arrange | positioned seeing from the said electrode layer.

<11> A piezoelectric element comprising the piezoelectric film piece according to <8> or the laminate according to <9> or <10>.
<12> The laminate according to <10> is provided,
The laminated body is a piezoelectric element in which the adhesive layer is on the inner side and the one end of the piezoelectric film piece and the other end of the piezoelectric film piece are bent and deformed in a direction overlapping in plan view.

<13> preparing a long unstretched film containing a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000;
The difference which subtracted Tc1 which is the temperature of the width direction center part of the film from Te1 which is the temperature of the width direction both ends of the film with respect to the said long unstretched film is 3 to 15 degreeC, and from said Te1 The difference obtained by subtracting Tg which is the glass transition temperature of the helical chiral polymer (A) is 10 ° C to 40 ° C, the longitudinal draw ratio is 2.0 times to 5.0 times, and the transverse draw ratio is 2. A step of obtaining a biaxially stretched film by performing simultaneous biaxial stretching under conditions of 0 times to 5.0 times;
A step of obtaining a polymer piezoelectric film by subjecting the biaxially stretched film to a heat treatment at a temperature of 80 ° C. to 160 ° C .;
A method for producing a polymer piezoelectric film comprising:

<14> a step of preparing the polymer piezoelectric film according to any one of <1> to <7>;
From the polymer piezoelectric film, collecting a piezoelectric film piece including at least a part of the one end in the width direction of the polymer piezoelectric film and at least a part of the other end in the width direction;
The manufacturing method of the piezoelectric film piece containing this.

According to the present disclosure, when used as a raw material for collecting a piezoelectric film piece, the yield at the time of collecting the piezoelectric film piece is improved, and the piezoelectric film can be manufactured easily and at a high yield. And the manufacturing method of the polymeric piezoelectric film suitable for manufacture of the said polymeric piezoelectric film is provided.
Moreover, according to this indication, the manufacturing method of the piezoelectric film piece suitable for manufacture of the piezoelectric film piece and laminated body which can manufacture a piezoelectric element simply, and the said piezoelectric film piece is provided.
Moreover, according to this indication, the piezoelectric element which can be manufactured easily is provided.

1 is a schematic plan view conceptually showing a polymer piezoelectric film according to an embodiment of the present disclosure. It is a schematic perspective view which shows notionally the piezoelectric film piece which concerns on one Embodiment of this indication. It is a schematic perspective view which shows notionally the layered product concerning one embodiment of this indication. It is a schematic perspective view which shows notionally the piezoelectric element (bending actuator) which concerns on one Embodiment of this indication. It is a schematic perspective view which shows only a piezoelectric film piece among the piezoelectric elements (bending actuator) which concern on one Embodiment of this indication. An AC voltage is applied to a piezoelectric element (bending actuator) according to an embodiment of the present disclosure, and a state in which a force in a direction in which one end portion and the other end portion of the piezoelectric film piece are separated from each other is illustrated. It is a schematic sectional drawing. An AC voltage is applied to a piezoelectric element (bending actuator) according to an embodiment of the present disclosure, and shows a state when a force in a direction in which the one end and the other end of the piezoelectric film piece approach each other works. It is a schematic sectional drawing. 1 is a schematic plan view conceptually showing a comparative polymer piezoelectric film.

In this specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
Further, in the present specification, “film” is a concept including not only what is generally called “film” but also what is generally called “sheet”.
Moreover, in this specification, a "main surface" refers to surfaces other than an end surface among all the surfaces of a film, ie, a surface with the largest area. In the following, the term “surface” refers to the main surface.

[Polymer piezoelectric film]
The polymer piezoelectric film of the present disclosure includes a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000, and a crystallinity obtained by a DSC method is 20% to 80%. A polymer piezoelectric film having a long shape, a longitudinal length of 10 m or more, a molecular orientation direction La of the helical chiral polymer (A) at one end in the width direction, and the other end in the width direction The planar viewing angle θ1 of the helical chiral polymer (A) with respect to the molecular orientation direction Lb is from 70 ° to 110 °, and the planar viewing angle θ2 between the longitudinal direction and the molecular orientation direction La is from 35 ° to 55. It is a polymer piezoelectric film in which the planar view angle θ3 between the longitudinal direction and the molecular orientation direction Lb is 35 ° to 55 °.

The molecular orientation directions (that is, the molecular orientation direction La and the molecular orientation direction Lb) in the polymer piezoelectric film of the present disclosure are advanced when the helical chiral polymer (A) is a material having a positive birefringence. It means an axis, and when the helical chiral polymer (A) is a material having a negative birefringence, it means a slow axis.
The molecular orientation direction in the present disclosure can be measured using a “birefringence evaluation system” WPA-100 manufactured by Photonic Lightis Co., Ltd.

In the polymer piezoelectric film of the present disclosure, the “plan view angle” means an angle when viewed from the normal direction of the polymer piezoelectric film.
In the polymer piezoelectric film of the present disclosure, “one end in the width direction” means a region of 25% of the entire width including one end in the width direction of the polymer piezoelectric film.
In the polymer piezoelectric film of the present disclosure, “the other end in the width direction” means a region of 25% of the total width including the other end in the width direction of the polymer piezoelectric film.

In the conventional piezoelectric film, the molecular orientation direction and the longitudinal direction of the piezoelectric film are parallel. For this reason, conventionally, in order to extract a piezoelectric film piece for producing a piezoelectric element from a raw film using a piezoelectric film as a raw fabric, a direction inclined with respect to the longitudinal direction of the original fabric (for example, the longitudinal direction of the original fabric) It was necessary to collect a piezoelectric film piece having a longitudinal direction of 45 ° with respect to the direction. This is because, when a film piece whose longitudinal direction is parallel to the longitudinal direction of the original fabric is collected, the collected film piece does not exhibit piezoelectricity (for example, a piezoelectric constant d ₁₄ described later). Because.
Due to the circumstances described above, when collecting a piezoelectric film piece for producing a piezoelectric element from a conventional piezoelectric film (original fabric), it is inevitably an area that cannot be collected as a piezoelectric film piece at both ends in the width direction of the original fabric. (That is, useless areas to be discarded) have occurred.
For the above reasons, the conventional piezoelectric film has a problem that the yield is low when the piezoelectric film is used as an original fabric and a piezoelectric film piece is collected from the original fabric.

In contrast to the conventional piezoelectric film, in the polymer piezoelectric film of the present disclosure, the molecular orientation direction La and the molecular orientation direction Lb are not parallel to the longitudinal direction of the piezoelectric film, and both are relative to the longitudinal direction of the piezoelectric film. It is inclined at an angle of 35 ° to 55 °.
For this reason, in the polymer piezoelectric film of the present disclosure, when it is used as a raw material for collecting a piezoelectric film piece, it is possible to reduce wasteful areas to be discarded at both ends in the width direction of the raw material.
Therefore, in the polymer piezoelectric film of the present disclosure, the yield when collecting the piezoelectric film pieces (hereinafter also referred to as “material yield”) is improved.

Conventionally, when a piezoelectric element (actuator, sensor, etc.) using a piezoelectric film piece is manufactured, first, a plurality of piezoelectric film pieces are collected from the piezoelectric film as an original fabric, and the plurality of collected piezoelectric films are collected. A plurality of laminates (piezoelectric film pieces provided with electrode layers on both sides) were manufactured by providing electrode layers on both sides of each piece. Next, a piezoelectric film was manufactured by superimposing a plurality of laminated bodies via an adhesive layer (for example, an adhesive layer, a hardened layer, etc.).
However, the above-described conventional method for manufacturing a piezoelectric element is complicated because it requires a large number of parts (that is, laminates) to be manufactured to manufacture the piezoelectric element and a large number of piezoelectric film pieces collected from the original fabric. there were. In addition, the operation of aligning the angles when superimposing a plurality of laminated bodies (specifically, the operation of superposing the plurality of laminated bodies so that the molecular orientation directions are substantially parallel) is also complicated.

When a piezoelectric element is manufactured using the polymer piezoelectric film of the present disclosure, at least a part of one end in the width direction of the polymer piezoelectric film, the width direction of the polymer piezoelectric film, and the like from the polymer piezoelectric film of the present disclosure. Piezoelectric film pieces including at least a part of the end portion are collected, and the collected piezoelectric film pieces are bent and deformed (after an electrode layer and an adhesive layer are formed on the piezoelectric film pieces as necessary) An element can be manufactured. Specifically, in the piezoelectric film piece, the planar view angle between the molecular orientation direction at one end and the molecular orientation direction at the other end is 70 ° to 110 °. This piezoelectric film piece is bent and deformed around the middle point between its one end and the other end, and is superposed so that the molecular orientation direction at one end and the molecular orientation direction at the other end are substantially parallel. A piezoelectric element can be manufactured. Thereby, the number of parts (laminated body and piezoelectric film piece) can be reduced compared with the conventional method of laminating | stacking the several laminated body in which the electrode layer was provided on both surfaces of the piezoelectric film piece.
In addition, when a piezoelectric element is manufactured using the above-described piezoelectric film piece, the piezoelectric film is a raw material as compared with a conventional method in which a plurality of laminated bodies each having electrode layers provided on both sides of the piezoelectric film piece are overlaid. The number of piezoelectric film pieces collected from the film can also be reduced.
Furthermore, when manufacturing a piezoelectric element using the above-mentioned piezoelectric film piece, the piezoelectric film piece is bent and deformed around the middle point between the one end and the other end thereof, so that the molecular orientation direction at one end Angle alignment with the molecular orientation direction of the other end portion (that is, superposition so that the molecular orientation direction of one end portion and the molecular orientation direction of the other end portion are substantially parallel) becomes easy.
For the above reasons, a piezoelectric element can be easily manufactured by using the polymer piezoelectric film of the present disclosure.

In addition, as described above, when the polymer piezoelectric film of the present disclosure is used as a raw material for collecting a piezoelectric film piece, the yield when collecting the piezoelectric film piece is improved.
Therefore, by using the polymer piezoelectric film of the present disclosure, the piezoelectric element can be manufactured with a high yield.

The piezoelectric element using the polymer piezoelectric film of the present disclosure preferably includes a laminated body having a structure in which electrode layers are formed on both surfaces of the piezoelectric film piece, and the laminated body includes one end portion of the piezoelectric film piece and a piezoelectric element. It is a piezoelectric element (hereinafter also referred to as “piezoelectric element A”) having a structure in which the other end of the film piece is bent and deformed in the direction of overlapping in plan view.
The piezoelectric element A is suitable as a bending actuator (for example, the bending actuator 120 shown in FIGS. 4, 6, and 7; details will be described later).

The polymer piezoelectric film of the present disclosure is a long film.
The longitudinal length of the polymer piezoelectric film of the present disclosure is 10 m or more.
When the length in the longitudinal direction is 10 m or more, it is easier to continuously perform the operation of collecting (for example, punching out) the piezoelectric film pieces from the polymer piezoelectric film by the roll-to-roll method.

The longitudinal length of the polymer piezoelectric film of the present disclosure is preferably 15 m or more.
Further, the length in the longitudinal direction of the polymer piezoelectric film of the present disclosure is preferably 3000 m or less, and more preferably 2000 m or less.

  Although there is no restriction | limiting in particular in the width direction length of the polymeric piezoelectric film of this indication, The said width direction length can be 60 mm-2000 mm, for example, 150 mm-1000 mm are preferable, and 200 mm-600 mm are more preferable. .

  Although there is no restriction | limiting in particular in the film thickness of the polymeric piezoelectric film of this indication, 10 micrometers-400 micrometers are preferable, 10 micrometers-200 micrometers are more preferable, 10 micrometers-100 micrometers are still more preferable, 10 micrometers-80 micrometers are especially preferable.

The polymer piezoelectric film of the present disclosure is preferably a biaxially stretched film.
The polymer piezoelectric film of the present disclosure can be manufactured by controlling the extent of the bowing phenomenon during biaxial stretching to an appropriate range.
A preferred method for producing the polymer piezoelectric film of the present disclosure will be described later.

In the polymer piezoelectric film of the present disclosure, the planar view angle (θ1) between the molecular orientation direction La and the molecular orientation direction Lb is 70 ° to 110 ° as described above, preferably 80 ° to 100 °, More preferably, it is 85 ° to 95 °.
In the polymer piezoelectric film of the present disclosure, the planar view angle (θ2) between the longitudinal direction of the polymer piezoelectric film and the molecular orientation direction La is 35 ° to 55 ° as described above, and preferably 40 ° to 50 °. And more preferably 42.5 ° to 47.5 °.
In the polymer piezoelectric film of the present disclosure, the planar view angle (θ3) between the longitudinal direction of the polymer piezoelectric film and the molecular orientation direction Lb is 35 ° to 55 ° as described above, and preferably 40 ° to 50 °. And more preferably 42.5 ° to 47.5 °.
The difference (absolute value) between θ2 and θ3 is preferably 0 ° to 10 °, and more preferably 0 ° to 5 °.

In this specification, the planar view angle θ2 between the longitudinal direction of the polymer piezoelectric film and the molecular orientation direction La is the smaller of the planar view angles between the longitudinal direction of the polymer piezoelectric film and the molecular orientation direction La. Means. For example, when the planar view angles between the longitudinal direction of the polymer piezoelectric film and the molecular orientation direction La are 45 ° and 135 °, θ2 is set to 45 °.
The same applies to the planar viewing angle θ3 between the longitudinal direction of the polymer piezoelectric film and the molecular orientation direction Lb.

<One Embodiment>
Next, an embodiment of the present disclosure will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiment.
Elements common to the drawings may be given the same reference numerals, and redundant description may be omitted.

FIG. 1 is a schematic plan view conceptually showing a polymer piezoelectric film 10 according to an embodiment of the present disclosure.
FIG. 2 is a schematic perspective view conceptually showing the piezoelectric film piece 100 taken from the polymer piezoelectric film 10.
The arrows in FIGS. 1 and 2 indicate the molecular orientation directions of the helical chiral polymer (A) in the polymer piezoelectric film 10 and the piezoelectric film piece 100, respectively.

As shown in FIG. 1, the polymer piezoelectric film 10 is a long film having the MD direction as the longitudinal direction and the TD direction as the width direction.
The longitudinal length of the polymer piezoelectric film 10 (length in the MD direction) is 10 m or more, and the preferred range is as described above.
The preferable range of the width direction length (length in the TD direction) of the polymer piezoelectric film 10 and the preferable range of the thickness of the polymer piezoelectric film 10 are as described above.
The polymer piezoelectric film 10 includes a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000, and a polymer having a crystallinity of 20% to 80% obtained by a DSC method. It is a piezoelectric film.

  Here, “MD direction” refers to the direction in which the film flows (Machine Direction), and “TD direction” refers to the direction (Transverse Direction) that is orthogonal to the MD direction and parallel to the main surface of the film ( The same applies hereinafter).

At one end 12 in the width direction of the polymer piezoelectric film 10, the helical chiral polymer (A) is molecularly oriented in the molecular orientation direction La.
Further, at the other end 14 in the width direction of the polymer piezoelectric film 10, the helical chiral polymer (A) is molecularly oriented in the molecular orientation direction Lb.
In the polymer piezoelectric film 10, the planar view angle θ1 between the molecular orientation direction La and the molecular orientation direction Lb is 90 °. However, θ1 in the polymer piezoelectric film of the present disclosure may be 70 ° to 110 ° as described above.
In the polymer piezoelectric film 10, the planar viewing angle θ2 between the molecular orientation direction La and the longitudinal direction (MD direction) is 45 °. However, θ2 in the polymer piezoelectric film of the present disclosure may be 35 ° to 55 ° as described above.
In the polymer piezoelectric film 10, an angle θ3 formed by the molecular orientation direction Lb and the longitudinal direction (MD direction) is 45 °. However, θ3 in the polymer piezoelectric film of the present disclosure may be 35 ° to 55 ° as described above.

As shown in FIG. 1 and FIG. 2, a piezoelectric film piece 100 that includes a polymer piezoelectric film 10 as a raw material and includes a part of one end 12 in the width direction and a part of the other end 14 of the polymer piezoelectric film 10. Can be collected.
The piezoelectric film piece 100 is a rectangular (strip-shaped) film piece.
In the piezoelectric film piece 100, the longitudinal direction one end portion 12 </ b> A of the piezoelectric film piece 100 is a part of the width direction one end portion 12 of the polymer piezoelectric film 10.
In the piezoelectric film piece 100, the other end portion 14 </ b> A in the longitudinal direction of the piezoelectric film piece 100 is a part of the other end portion 14 in the width direction of the polymer piezoelectric film 10.
In other words, the longitudinal direction of the polymer piezoelectric film 10 coincides with the width direction of the piezoelectric film piece 100.
Therefore, a large number of rectangular (strip-shaped) piezoelectric film pieces 100 can be collected from the polymer piezoelectric film 10 without waste (that is, at a high yield). That is, when collecting a large number of piezoelectric film pieces 100 from the polymer piezoelectric film 10, it is possible to reduce wasteful areas to be discarded, particularly at both ends in the width direction of the polymer piezoelectric film 10.

Next, the bending actuator 120 using the piezoelectric film piece 100 will be described with reference to FIGS. The bending actuator 120 is an example of the piezoelectric element A described above.
FIG. 3 is a schematic perspective view conceptually showing a stacked body 110 (a stacked body before bending deformation) used for manufacturing the bending actuator 120 according to an embodiment of the present disclosure.
FIG. 4 is a schematic perspective view conceptually showing a bending actuator 120 according to an embodiment of the present disclosure.
FIG. 5 is a schematic perspective view showing only the piezoelectric film piece 100 in the bending actuator 120 according to the embodiment of the present disclosure.

In order to manufacture the bending actuator 120, first, as shown in FIG. 3, the piezoelectric film piece 100, the entire surface electrode layer 102 formed on the entire surface of one surface of the piezoelectric film piece 100, and the piezoelectric film piece 100 The entire surface electrode layer 104 formed on the entire other surface of the electrode and the side opposite to the side where the piezoelectric film piece 100 is disposed when viewed from the entire surface electrode layer 102 (that is, the entire surface electrode when viewed from the piezoelectric film piece 100) A laminate 110 is provided comprising an adhesive layer 106 disposed on the outside of the layer 102.
Other layers (not shown) such as an anchor coating layer may be interposed between the entire surface electrode layer 102 and the adhesive layer 106. As the adhesive layer 106, an adhesive layer or a cured layer can be used.

Next, the laminate 110 shown in FIG. 3 is bent in a direction in which the adhesive layer 106 is inside and the one end 12A of the piezoelectric film piece 100 and the other end 14A of the piezoelectric film piece 100 overlap in plan view. By deforming, the bending actuator 120 shown in FIG. 4 is manufactured.
As shown in FIG. 5, the piezoelectric film piece 100 in the bending actuator 120 is bent at the center line in the longitudinal direction of the piezoelectric film piece 100, and the longitudinal direction one end portion 12 </ b> A and the other end portion 14 </ b> A of the piezoelectric film piece 100 are formed. Opposite. As a result, the molecular orientation direction La of the one end portion 12 and the molecular orientation direction Lb of the other end portion 14 are substantially parallel.
As shown in FIG. 2, in the piezoelectric film piece 100 before bending deformation, the molecular orientation direction La and the molecular orientation direction Lb are axisymmetric with respect to the center line in the longitudinal direction. For this reason, it is easy to make the molecular orientation direction La and the molecular orientation direction Lb substantially parallel by bending and deforming the piezoelectric film piece 100 along the center line in the longitudinal direction (see FIG. 5). That is, by manufacturing the bending actuator 120 by the above-described method in which the piezoelectric film piece 100 is bent and deformed, the angle alignment in the molecular orientation direction in the upper layer (the other end portion 14A) and the lower layer (the one end portion 12A) becomes easy.

Next, the operation of the bending actuator 120 will be described with reference to FIGS.
6 and 7 are schematic cross-sectional views showing a state in which an AC voltage is applied to the bending actuator 120. FIG.
FIG. 6 shows a state in which a force F1 in a direction in which the one end portion 12A and the other end portion 14A of the piezoelectric film piece 100 are separated acts in the bending actuator 120. FIG. The state when the force F2 in the direction in which the one end portion 12A and the other end portion 14A of the piece 100 approach is shown.

As shown in FIGS. 6 and 7, an alternating voltage is applied to the bending actuator 120 between the entire surface electrode layer 104 positioned on the outer side and the entire surface electrode layer 102 positioned on the inner side. The application of the AC voltage generates an electric field in the thickness direction of the piezoelectric film piece 100. At this time, an electric field in the opposite direction (in other words, in reverse phase) is generated in the one end portion 12A and the other end portion 14A of the piezoelectric film piece 100. On the other hand, in the bending actuator 120, the molecular orientation directions (the molecular orientation direction La and the molecular orientation direction Lb) of the one end portion 12A and the other end portion 14A of the piezoelectric film piece 100 are substantially parallel.
Therefore, in the bending actuator 120, an alternating voltage is applied between the one end portion 12A and the other end portion 14A of the piezoelectric film piece 100 (force F1 in FIG. 6 and FIG. 7). Force F2) is generated alternately.
As a result, in the bending actuator 120, the alternating voltage is applied, whereby the one end portion 12 and the other end portion 14 of the piezoelectric film piece 100 bend and vibrate (that is, the bending actuator 120 operates).

Next, for comparison with the polymer piezoelectric film 10 according to the above-described embodiment, a comparative polymer piezoelectric film 210 as an example of a conventional polymer piezoelectric film will be described with reference to FIG.
FIG. 8 is a schematic plan view conceptually showing the comparative polymer piezoelectric film 210.
As shown in FIG. 8, in the comparative polymer piezoelectric film 210, the molecular orientation directions of the helical chiral polymer (A) are all the same in the plane (longitudinal direction, that is, MD direction). That is, in the comparative polymer piezoelectric film 210, the molecular orientation direction R1 of the helical chiral polymer (A) at one end portion 212 in the width direction and the molecular orientation direction R2 of the helical chiral polymer (A) at the other end portion 214 in the width direction. And are parallel.
When collecting a piezoelectric film piece from the comparative polymer piezoelectric film 210, for example, a direction intersecting the longitudinal direction of the comparative polymer piezoelectric film 210 (for example, the comparative piezoelectric film pieces 300A and 300B) (for example, It is necessary to collect a piezoelectric film piece having a longitudinal direction of 45 ° with respect to the longitudinal direction of the comparative polymer piezoelectric film 210. This is because sufficient piezoelectricity (for example, the piezoelectric constant d ₁₄ ) cannot be obtained unless it is collected in this way. For this reason, when the piezoelectric film piece is collected from the comparative polymer piezoelectric film 210, there are portions to be discarded such as the discarding portions 220A and 220B.
Therefore, the yield when collecting the piezoelectric film piece from the comparative polymer piezoelectric film 210 is lower than the yield when collecting the piezoelectric film piece 100 from the polymer piezoelectric film 10.

In the case of manufacturing a bending actuator having the same function as that of the above-described bending actuator 120 using the comparative polymer piezoelectric film 210 as a material, two piezoelectric films are used like the comparative piezoelectric film pieces 300A and 300B. It is necessary to collect a piece. Then, it is necessary to form full-surface electrode layers on both surfaces of each of the comparative piezoelectric film pieces 300A and 300B, and to superimpose them so that their molecular orientation directions are substantially parallel to each other. That is, in this case, in order to manufacture a bending actuator, it is necessary to prepare two laminates having a structure in which electrode layers are formed on both sides of a piezoelectric film piece, and to bond the two laminates through an adhesive layer. There is. The reason for this is that a single piezoelectric film piece is taken from the comparative polymer piezoelectric film 210 and a bending actuator is manufactured by the same method as in the embodiment of the present disclosure, that is, by bending the piezoelectric film piece. This is because it is difficult to make the molecular orientation directions of the one end and the other end of the piezoelectric film piece substantially parallel.
On the other hand, as described above, in the embodiment of the present disclosure, only one piezoelectric film piece is collected from the polymer piezoelectric film 10.
As described above, when manufacturing a bending actuator having the same function as that of the bending actuator 120 using the comparative polymer piezoelectric film 210 as a material, the number of components is doubled as compared with the embodiment of the present disclosure. Therefore, the manufacturing process becomes complicated.
Furthermore, the operation of adjusting the angle of the two stacked bodies is also complicated as compared with the embodiment of the present disclosure.

Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the one embodiment.
More specifically, the piezoelectric film piece collected from the polymer piezoelectric film 10 is not limited to the piezoelectric film piece 100.
For example, from the polymer piezoelectric film 10, one end in the width direction corresponds to a part of one end in the width direction of the polymer piezoelectric film 10, and the other end in the width direction corresponds to the other end in the width direction of the polymer piezoelectric film 10. A rectangular piezoelectric film piece may be collected.
Moreover, you may extract | collect the rectangular-shaped film piece containing either one of the width direction one end part and the other end part of the polymer piezoelectric film 10 from the polymer piezoelectric film 10. FIG.
Furthermore, the shape of the piezoelectric film to be collected is not limited to a rectangular shape, and may be a polygonal shape other than a rectangular shape, an elliptical shape (including a circular shape), or an indefinite shape.

  The polymer piezoelectric film of the present disclosure can be used not only as a material for a bending actuator but also as a material for other piezoelectric elements such as a sensor.

  Next, the polymer piezoelectric film of the present disclosure (for example, the polymer piezoelectric film 10 described above) will be described in more detail.

<Helical chiral polymer (A)>
The polymer piezoelectric film of the present disclosure includes a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000.
Here, the “helical chiral polymer having optical activity” refers to a polymer having a helical structure and a molecular optical activity.

Examples of the helical chiral polymer (A) include polypeptides, cellulose derivatives, polylactic acid polymers, polypropylene oxide, poly (β-hydroxybutyric acid), and the like.
Examples of the polypeptide include poly (glutarate γ-benzyl), poly (glutarate γ-methyl), and the like.
Examples of the cellulose derivative include cellulose acetate and cyanoethyl cellulose.

Examples of the helical chiral polymer (A) include polypeptides, cellulose derivatives, polylactic acid polymers, polypropylene oxide, poly (β-hydroxybutyric acid), and the like.
Examples of the polypeptide include poly (glutarate γ-benzyl), poly (glutarate γ-methyl), and the like.
Examples of the cellulose derivative include cellulose acetate and cyanoethyl cellulose.

  The helical chiral polymer (A) preferably has an optical purity of 95.00% ee or more, more preferably 96.00% ee or more, from the viewpoint of improving the piezoelectricity of the polymer piezoelectric film. 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 helical chiral polymer (A) within the above range, the packing property of the polymer crystal that exhibits piezoelectricity is enhanced, and as a result, the piezoelectricity is considered to be enhanced.

Here, the optical purity of the helical chiral polymer (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 helical chiral polymer (A) is
“The amount difference (absolute value) between the amount of L-form (mass%) of helical chiral polymer (A) and the amount of D-form (mass%) of helical chiral polymer (A)” (absolute value) ” Multiply by (100) the value divided by (the total amount of (A) L-form [mass%] and helical chiral polymer (A) D-form [mass%]] ". (Multiplied).

  The amount of L-form [mass%] of the helical chiral polymer (A) and the amount of D-form [mass%] of the helical chiral polymer (A) are obtained by a method using high performance liquid chromatography (HPLC). Use the value obtained. Details of the specific measurement will be described later.

  The helical chiral polymer (A) is preferably a polymer having a main chain containing a repeating unit represented by the following formula (1) from the viewpoint of increasing optical purity and improving piezoelectricity.

Examples of the polymer having the repeating unit represented by the formula (1) as a main chain include polylactic acid-based polymers.
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 the polylactic acid polymers, polylactic acid is preferable, and L-lactic acid homopolymer (PLLA) or D-lactic acid homopolymer (PDLA) is most preferable.

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

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

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

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

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

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

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

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

  In addition, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of helical chiral polymer (A) point out the value measured by the following GPC measuring method using gel permeation chromatograph (GPC). Here, Mn is the number average molecular weight of the helical chiral polymer (A).

-GPC measuring device-
Waters GPC-100
-Column-
Made by Showa Denko KK, Shodex LF-804
-Sample preparation-
The helical chiral polymer (A) 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 helical chiral polymer (A) are calculated.

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

The polymer piezoelectric film of the present disclosure may contain only one type of the helical chiral polymer (A) described above, or may contain two or more types.
The content of the helical chiral polymer (A) in the polymer piezoelectric film (the total content when there are two or more) is from the viewpoint of more effectively achieving the effects of the present disclosure. 80 mass% or more is preferable with respect to the whole quantity.

<Stabilizer>
The polymer piezoelectric film of the present disclosure further includes a stabilizer having a weight average molecular weight of 200 to 60000 having one or more functional groups selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group in one molecule. It is preferable to contain (B). Thereby, heat-and-moisture resistance can be improved more.

  As the stabilizer (B), “stabilizer (B)” described in paragraphs 0039 to 0055 of International Publication No. 2013/054918 pamphlet can be used.

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

  Examples of the compound (isocyanate compound) containing an isocyanate group in one molecule that can be used as the stabilizer (B) 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.

  Examples of the compound (epoxy compound) containing an epoxy group in one molecule that can be used as the stabilizer (B) include 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 (B) is 200 to 60000, more preferably 200 to 30000, and still more preferably 300 to 18000.
When the molecular weight is within the above range, the stabilizer (B) is more easily moved, and the effect of improving heat and moisture resistance is more effectively exhibited.
The weight average molecular weight of the stabilizer (B) is particularly preferably 200 to 900. In addition, the weight average molecular weight 200-900 substantially corresponds with the number average molecular weight 200-900. Further, when the weight average molecular weight is 200 to 900, the molecular weight distribution may be 1.0. In this case, “weight average molecular weight 200 to 900” can be simply referred to as “molecular weight 200 to 900”. .

When the polymer piezoelectric film contains the stabilizer (B), the polymer piezoelectric film may contain only one kind of stabilizer or two or more kinds.
When the polymeric piezoelectric film contains the stabilizer (B), the content of the stabilizer (B) is 0.01 parts by mass to 10 parts by mass with respect to 100 parts by mass of the helical chiral polymer (A). It is preferably 0.01 parts by mass to 5 parts by mass, more preferably 0.1 parts by mass to 3 parts by mass, and particularly preferably 0.5 parts by mass to 2 parts by mass. preferable.
When the content is 0.01 parts by mass or more, the heat and humidity resistance is further improved.
Moreover, the transparency fall is suppressed more as the said content is 10 mass parts or less.

A preferred embodiment of the stabilizer (B) is a stabilizer having one or more functional groups selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group, and having a number average molecular weight of 200 to 900. (B1) and a stabilizer 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 ( A mode in which B2) is used in combination is exemplified. The weight average molecular weight of the stabilizer (B1) having a number average molecular weight of 200 to 900 is about 200 to 900, and the number average molecular weight and the weight average molecular weight of the stabilizer (B1) are almost the same value. .
When the stabilizer (B1) and the stabilizer (B2) are used in combination as the stabilizer, it is preferable that a large amount of the stabilizer (B1) is contained from the viewpoint of improving the transparency.
Specifically, it is preferable that the stabilizer (B2) is in the range of 10 parts by mass to 150 parts by mass with respect to 100 parts by mass of the stabilizer (B1) 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 B-1 to B-3) of the stabilizer (B) are shown.

Hereinafter, with respect to the stabilizers B-1 to B-3, compound names, commercial products, and the like are shown.
Stabilizer B-1 The compound name is bis-2,6-diisopropylphenylcarbodiimide. The weight average molecular weight (in this example, simply equal to “molecular weight”) is 363. Commercially available products include “Stabaxol I” manufactured by Rhein Chemie and “B2756” manufactured by Tokyo Chemical Industry.
Stabilizer B-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 B-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 polymer piezoelectric film of the present disclosure may contain other components as necessary.
Other components include known resins such as polyvinylidene fluoride, polyethylene resin and polystyrene resin; known inorganic fillers such as silica, hydroxyapatite and montmorillonite; known crystal nucleating agents such as phthalocyanine; other than stabilizer (B) 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.

<Piezoelectric constant d ₁₄ (displacement method)>
Polymeric piezoelectric film of the present disclosure, it piezoelectric constant is large (preferably, it is the piezoelectric constant d ₁₄ measured by a displacement method at 25 ° C. is 1.0 pm / V or more) is preferable.
Here, the “piezoelectric constant d ₁₄ measured by the displacement method” is 10 Hz, 300 Vpp between a pair of conductive layers of a piezoelectric constant measurement sample in which a conductive layer is formed on both sides of a 32 mm × 5 mm polymer piezoelectric film. A sine wave AC voltage is applied, and the difference distance between the maximum value and the minimum value of the displacement at this time is measured as a displacement amount (mp-p), and the measured displacement amount (mp-p) is measured at a reference length of 30 mm. A value obtained by dividing the value obtained by dividing the value obtained by dividing the value by the electric field strength ((applied voltage (V)) / (film thickness)) applied to the film by 2 is indicated.
This “piezoelectric constant d ₁₄ measured by the displacement method” can be measured, for example, by the method described in paragraphs 0058 to 0059 of Japanese Patent No. 4934235.

Hereinafter, an example of a method for measuring the piezoelectric constant d ₁₄ (displacement method) will be described.
First, aluminum (Al) is vapor-deposited on both surfaces of a 40 mm × 40 mm square test piece collected from a polymer piezoelectric film using a vapor deposition apparatus (for example, Showa Vacuum SIP-600 Co., Ltd.). The conductive layer is formed.
Next, a 40 mm × 40 mm test piece with an Al conductive layer formed on both sides is 32 mm in the direction of 45 ° with respect to the stretching direction (MD direction) of the polymer piezoelectric film, and the direction perpendicular to the direction of 45 °. Cut to 5 mm and collect 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 film to the voltage applied to the piezoelectric polymer film is increased, also increases the voltage generated with respect to force applied to the piezoelectric polymer film It is useful as a polymer piezoelectric film.
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 film of the present disclosure is preferably 1.0 pm / V or more, and 2.0 pm. / V or higher is more preferable, 2.5 pm / V or higher is further preferable, and 3.0 pm / V or higher is further preferable.
The upper limit of the piezoelectric constant d ₁₄ is not particularly limited, from the viewpoint of balance between and transparency, it is preferably not more than 15 pm / V.

<Transparency (internal haze)>
The polymer piezoelectric film of the present disclosure preferably has an internal haze with respect to visible light (hereinafter also simply referred to as “internal haze”) of 10% or less.
Here, the internal haze with respect to visible light is an index relating to the transparency of the polymer piezoelectric film.
The internal haze of the polymer piezoelectric film is preferably 5.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less from the viewpoint of further improving transparency and longitudinal crack strength. The lower limit value of the internal haze of the polymer piezoelectric film is not particularly limited, and examples of the lower limit value include 0.01%.
Here, the internal haze of the polymer piezoelectric film refers to the haze excluding the haze due to the shape of the outer surface of the polymer piezoelectric film.
The internal haze of the polymer piezoelectric film was measured according to JIS-K7105 with respect to the polymer piezoelectric film having a thickness of 0.03 mm to 0.05 mm [TC Density Co., Ltd., TC- HIII DPK] is a value measured at 25 ° C., and details of the measuring method will be described in detail in Examples.

<Normalized molecular orientation MORc>
The polymer piezoelectric film of the present disclosure preferably has a normalized molecular orientation MORc of 3.5 to 15.0.
Here, 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 helical chiral polymer (A).
The molecular orientation degree MOR (Molecular Orientation Ratio) is measured by the following microwave measurement method.
That is, a polymer piezoelectric film (for example, a film-like polymer piezoelectric film) is placed in a microwave resonant waveguide of a well-known microwave molecular orientation measuring device (also referred to as a microwave transmission type molecular orientation meter). It arrange | positions so that the surface (film surface) of a polymeric piezoelectric film may become perpendicular | vertical to the advancing direction of a wave. Then, in a state where the sample is continuously irradiated with the microwave whose vibration direction is biased in one direction, the polymer piezoelectric film is rotated 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 polymer piezoelectric film)
The normalized molecular orientation MORc can be measured with a known molecular orientation meter such as a microwave molecular orientation meter MOA-2012A or MOA-6000 manufactured by Oji Scientific Instruments Co., Ltd., at a resonance frequency in the vicinity of 4 GHz or 12 GHz.

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

The normalized molecular orientation MORc can be converted into a birefringence Δn obtained by dividing the retardation amount (retardation) by the thickness of the film. Specifically, retardation can be measured using RETS100 manufactured by Otsuka Electronics Co., Ltd. MORc and Δn are approximately in a linear proportional relationship, and when Δn is 0, MORc is 1.
For example, when the helical chiral polymer (A) is a polylactic acid polymer and the birefringence Δn of the polymer piezoelectric film is measured at a measurement wavelength of 550 nm, it is the lower limit of the preferred range of the normalized molecular orientation MORc. 2.0 can be converted to birefringence Δn 0.005. Further, 40, which is the lower limit of the preferred range of the product of the normalized molecular orientation MORc and crystallinity of the polymer piezoelectric film, described later, is the product of the birefringence Δn and crystallinity of the polymer piezoelectric film of 0.1. Can be converted to

<Crystallinity>
The crystallinity of the polymer piezoelectric film of the present disclosure is 20% to 80% as described above.
Here, the degree of crystallinity of the polymer piezoelectric film is determined by the DSC method.
When the degree of crystallinity is 20% or more, the piezoelectricity of the polymer piezoelectric film is maintained high. When the degree of crystallinity is 80% or less, the transparency of the polymer piezoelectric film is maintained high, and when the degree of crystallinity is 80% or less, whitening and breakage hardly occur during stretching. Easy to manufacture piezoelectric film.
Therefore, the crystallinity of the polymer piezoelectric film is 20% to 80%, but the crystallinity is preferably 25% to 70%, more preferably 30% to 50%.

<Product of normalized molecular orientation MORc and crystallinity>
In the polymer piezoelectric film of the present disclosure, the product of the normalized molecular orientation MORc and the crystallinity is preferably 40 to 700, more preferably 75 to 680, still more preferably 90 to 660, still more preferably 125 to 650, Especially preferably, it is 150-350.
When the above product is in the range of 40 to 700, the polymer piezoelectric film has a good balance between piezoelectricity and transparency and has high dimensional stability, and can be suitably used as a piezoelectric element.
In the polymer piezoelectric film of the present disclosure, for example, the product can be adjusted to the above range by adjusting the crystallization and stretching conditions when the polymer piezoelectric film is manufactured.

As described above, the polymer piezoelectric film of the present disclosure described above is preferably used as an original fabric (material) for collecting a piezoelectric film piece.
The cut-out piezoelectric film piece is preferably used in the state of a laminate in which an electrode layer is disposed on at least one surface side and the electrode layer and the piezoelectric film piece are provided.
The piezoelectric film piece and the laminate are preferably used as components of a piezoelectric element.

  There is no restriction | limiting in particular about a piezoelectric film piece, a laminated body, and a piezoelectric element, For example, the description of international publication 2013/054918 can be referred suitably.

<Preferred production method of polymer piezoelectric film>
Next, production method A, which is a preferred method for producing the polymer piezoelectric film of the present disclosure, will be described.
Process A is
A step of preparing an elongated unstretched film containing the helical chiral polymer (A) (hereinafter also referred to as “preparation step”);
The difference obtained by subtracting Tc1 which is the temperature of the central part in the width direction of the film from Te1 which is the temperature at both ends in the width direction of the long-shaped unstretched film is 3 ° C to 15 ° C. The difference obtained by subtracting Tg which is the glass transition temperature of the chiral polymer (A) is 10 ° C to 40 ° C, the longitudinal draw ratio is 2.0 times to 5.0 times, and the transverse draw ratio is 2.0 times. A step of obtaining a biaxially stretched film by performing simultaneous biaxial stretching under a condition of ˜5.0 times (hereinafter also referred to as “stretching step”);
A step of obtaining the polymer piezoelectric film by subjecting the biaxially stretched film to a heat treatment at a temperature of 80 ° C. to 160 ° C. (hereinafter, also referred to as “heat treatment step”);
including.
The manufacturing method A may include other steps as necessary.

  In production method A, the degree of the bowing phenomenon (that is, the amount of bowing) can be controlled within an appropriate range by simultaneous biaxial stretching that satisfies the above conditions. By controlling the bowing amount to an appropriate range, the polymer piezoelectric film of the present disclosure in which θ1 is 70 ° to 110 °, θ2 is 35 ° to 55 °, and θ3 is 35 ° to 55 °. Can be manufactured.

(Preparation process)
The manufacturing method A includes a preparation step of preparing an elongated unstretched film containing the helical chiral polymer (A).

The unstretched film may be an amorphous film or a pre-crystallized film (hereinafter also referred to as “pre-crystallized film”).
Here, the amorphous film refers to a film having a crystallinity of less than 3%.
The pre-crystallized film refers to a film having a crystallinity of 3% or more (preferably 3% to 70%).
The crystallinity indicates a value measured by the same method as the crystallinity of the polymer piezoelectric film of the present disclosure described above.

The thickness of the unstretched film is mainly determined by the thickness of the polymer piezoelectric film finally obtained and the stretch ratio, but is preferably 50 μm to 1000 μm, more preferably about 200 μm to 800 μm.
The preparation step may be a step of simply preparing an unstretched film manufactured in advance, or a step of manufacturing an unstretched film.

The production of the unstretched film is performed, for example, by heating the helical chiral polymer (A) alone or a composition containing the helical chiral polymer (A) to a temperature equal to or higher than the melting point Tm (° C.) of the helical chiral polymer (A). Then, it can carry out by shape | molding in a film shape.
Molding can be performed by a known method such as extrusion molding.
As a method for producing an unstretched film, for example, a method for producing a pre-crystallized film described in paragraphs 0065 to 0080 of International Publication No. 2013/054918 may be referred to.

A pre-crystallized film as an unstretched film can be obtained by holding an amorphous film immediately after extrusion at a temperature T in the following range.
The holding time at the temperature T is preferably 5 seconds to 60 minutes, and more preferably 10 seconds to 30 minutes.
Tg−40 ° C. ≦ T ≦ Tg + 40 ° C.
(Tg represents the glass transition temperature of the helical chiral polymer (A))

(Stretching process)
In the production method A, for a long unstretched film, a difference obtained by subtracting Tc1 which is the temperature at the center in the width direction of the film from Te1 which is the temperature at both ends in the width direction of the film (hereinafter referred to as “difference [Te1-Tc1 ] ”Is 3 ° C. to 15 ° C., and a difference obtained by subtracting Tg which is the glass transition temperature of the helical chiral polymer (A) from Te1 (hereinafter also referred to as“ difference [Te1-Tg] ”) is 10 By performing simultaneous biaxial stretching that satisfies the conditions of -40 ° C to 40 ° C, a longitudinal draw ratio of 2.0 times to 5.0 times, and a transverse draw ratio of 2.0 times to 5.0 times And a stretching step for obtaining a biaxially stretched film.

In simultaneous biaxial stretching, the difference [Te1-Tc1] is 3 ° C to 15 ° C.
When the difference [Te1−Tc1] is 3 ° C. or more, the amount of stretching deformation at both ends in the width direction becomes larger than the amount of stretching deformation at the center portion in the width direction, and as a result, an appropriate amount of bowing is easily obtained. For this reason, when the difference [Te1-Tc1] is 3 ° C. or more, it is easy to produce the polymer piezoelectric film of the present disclosure in which θ2 is 35 ° to 55 ° and θ3 is 35 ° to 55 °. From the viewpoint of obtaining the above effect more effectively, the difference [Te1-Tc1] is preferably 5 ° C. or more.
When the difference [Te1-Tc1] is 15 ° C. or less, it is possible to suppress an excessive amount of stretching deformation at both ends in the width direction, and as a result, it is possible to suppress an excessive amount of bowing in the entire film. For this reason, it can suppress that each of (theta) 2 and (theta) 3 will be less than 35 degrees that difference [Te1-Tc1] is 15 degrees C or less. From the viewpoint of obtaining the above effect more effectively, the difference [Te1-Tc1] is preferably 10 ° C. or less.

In simultaneous biaxial stretching, the difference [Te1-Tg] is a condition of 10 ° C to 40 ° C.
When the difference [Te1−Tg] is 10 ° C. or more, the amount of stretching deformation at both ends in the width direction can be increased to some extent, so that an appropriate amount of bowing is easily obtained. For this reason, when the difference [Te1-Tg] is 10 ° C. or more, it is easy to produce the polymer piezoelectric film of the present disclosure in which θ2 is 35 ° to 55 ° and θ3 is 35 ° to 55 °.
When the difference [Te1−Tg] is 40 ° C. or less, it is possible to suppress the amount of stretching deformation at both ends in the width direction from being excessive, and thus it is possible to suppress each of θ2 and θ3 from being less than 35 °. From the viewpoint of obtaining the above effect more effectively, the difference [Te1-Tg] is preferably 35 ° C. or less, and more preferably 30 ° C. or less.

  Moreover, as Te1, 60 to 100 degreeC is also preferable, 70 to 95 degreeC is also preferable, and 75 to 90 degreeC is also preferable.

  In addition, in simultaneous biaxial stretching, a difference obtained by subtracting Tg, which is the glass transition temperature of the helical chiral polymer (A), from Tc1, which is the temperature in the center in the width direction of the film (hereinafter referred to as “difference [Tc1-Tg]”). The difference [Tc1-Tg] is preferably 5 ° C to 35 ° C, more preferably 10 ° C to 30 ° C.

Te1 (temperature at both ends in the width direction of the film) is a width direction length including the width direction end of the film (hereinafter referred to as "region A") including the width direction end of the film and the width direction length of the film. It means an average value of 10 temperatures in a 50 mm region (hereinafter referred to as “region B”).
Tc1 (temperature in the center in the width direction of the film) means an average value of 10 temperatures in the region excluding the region A and the region B.
The temperature of the film can be measured using a non-contact infrared thermometer (for example, a non-contact infrared thermometer manufactured by Keyence Corporation).

In simultaneous biaxial stretching, the longitudinal stretching ratio is 2.0 to 5.0 times. In this range, the bowing amount can be adjusted to an appropriate range. The longitudinal draw ratio is preferably 2.5 times to 4.5 times, more preferably 3.0 times to 4.0 times.
Here, the longitudinal stretch ratio means the stretch ratio in the longitudinal direction of the film (that is, the stretch ratio in the MD direction).

In the simultaneous biaxial stretching, the transverse stretching ratio is 2.0 times to 5.0 times. In this range, the bowing amount can be adjusted to an appropriate range.
The transverse stretch ratio is preferably 2.5 times to 4.5 times, more preferably 3.0 times to 4.0 times.
Here, the transverse stretch ratio means the stretch ratio in the width direction of the film (that is, the stretch ratio in the TD direction).

(Heat treatment process)
Manufacturing method A includes a heat treatment step of obtaining a polymer piezoelectric film of the present disclosure by performing a heat treatment at a temperature of 80 ° C. to 160 ° C. on the biaxially stretched film.
By the heat treatment, crystallization of the biaxially stretched film can be advanced. Thereby, the polymer piezoelectric film of the present disclosure having a crystallinity of 20% to 80% is obtained.
The temperature of the heat treatment is preferably 100 ° C to 155 ° C.

  The heat treatment time is preferably 1 second to 5 minutes, more preferably 5 seconds to 3 minutes, and further preferably 10 seconds to 2 minutes. When the heat treatment time is 5 minutes or less, the productivity is excellent. On the other hand, when the heat treatment time is 1 second or longer, the crystallinity of the film can be further improved.

For the heat treatment, for the biaxially stretched film obtained by simultaneous biaxial stretching, at least one of the longitudinal stretching ratio and the lateral stretching ratio at the time of simultaneous biaxial stretching is, for example, 5% to 30% (preferably 5% to 20%). It is preferable to carry out in a reduced state.
Generally, in heat treatment, the crystallization of a biaxially stretched film causes a change in volume of the biaxially stretched film, and as a result, the molecular orientation direction La and the molecular orientation direction Lb change.
Therefore, the biaxially stretched film obtained by simultaneous biaxial stretching is reduced by 5% to 30% (preferably 5% to 20%) at least one of the longitudinal stretching ratio and the lateral stretching ratio during simultaneous biaxial stretching. By performing the heat treatment in the above state, each of θ1, θ2, and θ3 can be easily adjusted within the above-described range.

The simultaneous biaxial stretching step and the heat treatment step are preferably performed using a simultaneous biaxial stretching tenter.
As the structure of the simultaneous biaxial stretching tenter,
A structure in which the temperature in each of the plurality of regions in the simultaneous biaxial stretching tenter can be adjusted independently,
A structure in which the simultaneous biaxial stretching tenter is divided into a plurality of areas, and the temperature of each area can be adjusted independently,
Etc.

There is no particular limitation on the specific method for satisfying that the difference [Te1-Tc1] is 3 ° C. to 15 ° C.,
A method in which both ends of the film are heated using a roll or drum heated only in portions corresponding to both ends of the film, and the center of the film is heated with a heater;
A method of heating both ends of the film using a heater having a structure fitted to both ends of the film, and heating the center of the film with a heater;
Etc.

Examples of the driving method of the clip in the simultaneous biaxial stretching tenter include a pantograph driving method, a screw driving method, a linear motor driving method, and the like.
In particular, the simultaneous biaxial stretching tenter in which the clip driving method is a linear motor driving method is extremely effective in carrying out the manufacturing method A because of high productivity and high flexibility in stretching conditions.

[Piezoelectric film piece]
The piezoelectric film piece of the present disclosure includes a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000, and a crystallinity obtained by DSC method is 20% to 80%. It is a film piece, Comprising: The planar view angle of the molecular orientation direction of the helical chiral polymer (A) in one end part and the molecular orientation direction of the helical chiral polymer (A) in the other end part is 70 ° to 110 °. It is.

An example of the piezoelectric film piece of the present disclosure includes the piezoelectric film piece 100 described above.
The material and physical properties (such as crystallinity) of the piezoelectric film piece of the present disclosure are the same as those of the polymer piezoelectric film of the present disclosure, and the preferred range is also the same.

The shape of the piezoelectric film piece of the present disclosure in plan view is preferably a rectangular shape, more preferably a rectangular shape, from the viewpoint of yield (ie, material yield) when collected from the polymer piezoelectric film of the present disclosure.
The piezoelectric film piece of the present disclosure includes a molecular orientation direction of the helical chiral polymer (A) at one longitudinal end portion of the piezoelectric film piece and a molecular orientation of the helical chiral polymer (A) at the other longitudinal end portion of the piezoelectric film piece. It is preferable that the planar view angle with respect to the direction is 70 ° to 110 °.

<Preferable manufacturing method of piezoelectric film piece>
Next, production method X, which is a preferred method for producing the piezoelectric film piece of the present disclosure, will be described.
Process X is
Preparing a polymer piezoelectric film of the present disclosure;
A step of collecting a piezoelectric film piece including at least a part of one end in the width direction of the polymer piezoelectric film and at least a part of the other end in the width direction from the polymer piezoelectric film;
including.

The step of preparing the polymer piezoelectric film of the present disclosure may be a step of merely preparing a polymer piezoelectric film prepared in advance, or a step of manufacturing a polymer piezoelectric film.
As a process for producing a polymer piezoelectric film, a process for producing a polymer piezoelectric film by the above-mentioned production method A (a preferred method for producing a polymer piezoelectric film of the present disclosure) is preferable.

The collected piezoelectric film piece is preferably a rectangular piezoelectric film piece.
In this case, one end in the longitudinal direction of the collected rectangular piezoelectric film piece corresponds to at least a part of one end in the width direction of the polymer piezoelectric film, and the longitudinal direction of the collected rectangular piezoelectric film piece It is preferable to collect a rectangular piezoelectric film piece with the other end portion corresponding to at least a part of the other end portion in the width direction of the polymer piezoelectric film.

  Collection of the piezoelectric film piece from the polymer piezoelectric film can be performed by a known method such as punching or cutting.

[Laminate]
The laminate of the present disclosure includes the above-described piezoelectric film piece of the present disclosure and an electrode layer disposed on at least one (preferably both) surfaces of the piezoelectric film piece.
The laminated body of this indication may be provided with other members as needed.
The laminate of the present disclosure can function as a piezoelectric element.
As an example of the laminated body of the present disclosure, the above-described laminated body 110 can be cited (FIG. 3).

<Electrode layer>
The laminated body of this indication may be provided with the electrode layer only in the side of one surface, and may be provided with the electrode layer in the side of both surfaces.
Moreover, the laminated body of this indication may be provided with two or more electrode layers per one surface side.

Moreover, the electrode layer may be provided in contact with the piezoelectric film piece, or may be provided via another layer such as a known anchor coating layer between the piezoelectric film piece.
Further, when the electrode layer is provided in contact with the piezoelectric film piece, the contact surface with the electrode layer of the piezoelectric film piece may be subjected to surface activation treatment such as corona discharge treatment, flame treatment, ozone treatment, etc. Good.

The electrode layer is preferably a full surface electrode layer formed on the entire surface of the piezoelectric film piece (that is, the entire surface). Furthermore, the entire surface electrode layer is preferably formed on both surfaces of the piezoelectric film piece.
That is, a preferable aspect of the laminate of the present disclosure includes the above-described piezoelectric film piece according to the first aspect or the second aspect, and a pair of full-surface electrode layers respectively formed on both surfaces of the piezoelectric film piece. It is an aspect.
More preferably, the laminate according to the preferred aspect further includes an adhesive layer disposed outside at least one of the pair of full-surface electrode layers as viewed from the piezoelectric film piece.
As a laminated body of an aspect provided with an adhesive layer, the above-described laminated body 110 (FIG. 3) is exemplified.

The material of the electrode layer (for example, the entire surface electrode layer; the same shall apply hereinafter) is not particularly limited. For example, Al, Ag, Au, Cu, Ag—Pd alloy, ITO, ZnO, IZO (registered trademark), conductive Include a functional polymer.
The electrode layer may contain only one type of the above material or two or more types.
The electrode layer may contain a component having no conductivity (such as a binder component) in addition to the above materials as long as the conductivity of the electrode layer can be maintained.

The electrode layer preferably has transparency.
Specifically, the electrode layer preferably has an internal haze with respect to visible light of 50% or less, more preferably 40% or less, further preferably 30% or less, and 20% or less. It is particularly preferred.
From the viewpoint of transparency, the material of the electrode layer is preferably ITO, ZnO, IZO (registered trademark), conductive polymer, or the like.

Although there is no restriction | limiting in particular in the thickness of an electrode layer, 10 nm-1000 nm are preferable, 30 nm-600 nm are more preferable, 50 nm-300 nm are especially preferable.
When the thickness is 10 nm or more, the conductivity can be further increased.
Further, when the thickness is 1000 nm or less, the piezoelectricity of the entire laminate is maintained higher.

  The electrode layer can be formed by a known method such as vapor deposition, sputtering, coating formation (including further drying and baking as necessary).

<Adhesive layer>
It is preferable that the laminated body of this indication is equipped with the contact bonding layer arrange | positioned on the opposite side to the side by which the piezoelectric film piece is arrange | positioned seeing from an electrode layer.
In the laminated body of the present disclosure, when the electrode layers are disposed on both sides of the piezoelectric film piece, the adhesive layer may be provided on at least one of the electrode layers.
The adhesive layer may be provided in contact with the electrode layer, or may be provided between the electrode layer via another layer such as a known anchor coating layer.
In the case where the adhesive layer is provided in contact with the electrode layer, a surface activation treatment such as corona discharge treatment, flame treatment, or ozone treatment may be performed on the contact surface of the electrode layer with the adhesive layer.

In the adhesive layer, “adhesion” means adhesion in a broad sense, and the concept of “adhesion” includes tackiness.
Examples of the adhesive layer include an adhesive layer and a cured layer.

  Although the film thickness of an adhesion layer is not specifically limited, The said film thickness can be 0.01 micrometer-10 micrometers, for example.

(Adhesive layer)
As the adhesive layer, for example, an adhesive layer of a double-sided tape (OCA; Optical Clear Adhesive) in which both surfaces are laminated with a separator can be used.
The pressure-sensitive adhesive layer can also be formed using a solvent-based, solvent-free, water-based or other pressure-sensitive adhesive coating solution, UV curable OCR (Optical Clear Resin), hot melt adhesive, or the like.

  As OCA, optical transparent adhesive sheet LUCIACS series (manufactured by Nitto Denko Corporation), highly transparent double-sided tape 5400A series (manufactured by Sekisui Chemical Co., Ltd.), optical adhesive sheet Optia series (manufactured by Lintec Corporation), high transparency adhesive Agent transfer tape series (manufactured by Sumitomo 3M Co., Ltd.), SANCUARY series (manufactured by Sanei Kaken Co., Ltd.), etc.

  Adhesive coating liquids include SK Dyne Series (manufactured by Soken Chemical Co., Ltd.), Fine Tack Series (manufactured by DIC Corporation), Bon Coat Series, LKG Series (manufactured by Fujikura Kasei Co., Ltd.), Coponille Series (Nippon Gosei Chemical Co., Ltd.) Company-made).

  As the adhesive layer, from the viewpoint of preventing the heating of the polymer piezoelectric film, an OCA adhesive layer, an adhesive layer formed using OCR, an adhesive layer formed by applying an adhesive coating solution to a member other than the polymer piezoelectric film An adhesive layer formed using a hot melt adhesive on a member other than the polymer piezoelectric film is preferred.

(Cured layer)
The material of the hardened layer is not particularly limited. For example, acrylic compound, methacrylic compound, vinyl compound, allyl compound, urethane compound, epoxy compound, epoxide compound, glycidyl compound, oxetane Compound, melamine compound, cellulose compound, ester compound, silane compound, silicone compound, siloxane compound, silica-acryl hybrid compound, and at least one material selected from the group consisting of silica-epoxy hybrid compounds (Curable resin) is preferably included.
Among these, acrylic compounds, epoxy compounds, and silane compounds are more preferable.

As the material contained in the cured layer, among the curable resins, active energy ray curable resins cured by irradiation with active energy rays (ultraviolet rays, electron beams, radiations, etc.) are preferable.
In addition, various organic substances such as a refractive index adjusting agent, an ultraviolet absorber, a leveling agent, an antistatic agent, and an antiblocking agent, and inorganic substances can be added to the cured layer depending on the purpose.

As a method for forming the cured layer, known methods that have been conventionally used can be used as appropriate, and examples thereof include a wet coating method. For example, the hardened layer is formed by applying a coating liquid in which a material for forming the hardened layer (curable resin, additive, etc.) is dispersed or dissolved.
Further, if necessary, the curable resin is cured by applying heat or active energy rays (ultraviolet rays, electron beams, radiation, etc.) to the material (curable resin or the like) applied as described above.

  In addition, as a material contained in a hardened layer, the active energy ray curable resin hardened | cured by irradiation of active energy rays (an ultraviolet ray, an electron beam, radiation, etc.) among the said curable resin is preferable. By including the active energy ray-curable resin, the production efficiency is improved, and the performance degradation of the polymer piezoelectric film caused by the formation of the cured resin layer can be further suppressed.

Moreover, it is preferable that the said curable resin layer contains the three-dimensional crosslinked resin which has a three-dimensional crosslinked structure from a viewpoint of raising a crosslinking density.
As a means for producing a cured product having a three-dimensional crosslinked structure, a method using a monomer having three or more polymerizable functional groups (a monomer having three or more functional groups) as a curable resin, or a crosslinking having three or more polymerizable functional groups. Examples include a method using a crosslinking agent (a trifunctional or higher functional crosslinking agent), and a method using a crosslinking agent such as an organic peroxide as a crosslinking agent. A plurality of these means may be used in combination.

  Examples of the tri- or higher functional monomer include (meth) acrylic compounds having three or more (meth) acrylic groups in one molecule, and epoxy compounds having three or more epoxy groups in one molecule. .

In the present specification, “(meth) acrylic group” represents at least one of an acrylic group and a methacrylic group.
Further, “having three or more (meth) acrylic groups in one molecule” means having at least one of an acrylic group and a methacrylic group in one molecule, and an acrylic group and a methacrylic group in one molecule. The total number is 3 or more.

Here, as a method for confirming whether or not the material contained in the cured layer is a cured product having a three-dimensional cross-linked structure, a method of measuring the gel fraction can be mentioned.
Specifically, the gel fraction can be derived from the insoluble matter after the cured layer is immersed in a solvent for 24 hours. In particular, it can be presumed that a solvent having a gel fraction of a certain level or more has a three-dimensional crosslinked structure, whether the solvent is a hydrophilic solvent such as water or a new oily solvent such as toluene.

〔Piezoelectric element〕
The piezoelectric element of the present disclosure includes the above-described piezoelectric film piece of the present disclosure or the above-described laminated body.
A particularly preferable aspect of the piezoelectric element of the present disclosure includes the above-described laminated body of the present disclosure that includes an adhesive layer, and the laminated body includes the adhesive layer on the inner side and the piezoelectric film piece. The one end of the piezoelectric film and the other end of the piezoelectric film piece are bent and deformed so as to overlap in a plan view.
An example of such a preferred embodiment is the bending actuator 120 described above.
Details (modifications, variations, etc.) of the piezoelectric element of the present disclosure are as described in the section “Polymer Piezoelectric Film”.

  Hereinafter, the present disclosure will be described in more detail with reference to examples. However, the present disclosure is not limited to the following examples unless the gist of the present disclosure is exceeded.

[Example 1]
<Production of polymer piezoelectric film>
As the raw material, which is an example of a helical chiral polymer (A), NatureWorks LLC Corp. polylactic acid (product ^name: Ingeo TM Biopolymer, brand: 4032D, weight average molecular weight Mw: 20 million in the melting point (Tm): 166 ° C., a glass A transition temperature (Tg): 57 ° C. to 60 ° C. was prepared.
The prepared raw material is put into an extrusion molding machine hopper, extruded from a T-die while being heated to 220 ° C. to 230 ° C., and brought into contact with a cast roll at 55 ° C. for 0.5 minutes. A pre-crystallized film having a thickness of 150 μm was formed. The crystallinity of the pre-crystallized film was measured and found to be 5.63%.

  The preliminary crystallized film was subjected to simultaneous biaxial stretching and heat treatment using a linear motor driven simultaneous biaxial stretching tenter. Details will be described below.

The simultaneous biaxial stretching tenter of the present embodiment includes two rows of guide rails parallel to the MD direction, and includes two rows of clip groups provided along these two rows of guide rails. The two groups of clips hold both ends of the film in the width direction.
Each clip in the two rows of clip groups can move along the guide rail by a linear motor drive. Thereby, the clip interval in the MD direction can be changed (that is, enlarged or reduced) by driving the linear motor.
On the other hand, the interval between the two guide rails can also be changed by driving the linear motor. The clip interval in the TD direction can be changed by changing the interval between the two guide rails by driving the linear motor.
Moreover, the simultaneous biaxial stretching tenter of the present embodiment includes a stretching zone for performing simultaneous biaxial stretching and a heat treatment zone for performing heat treatment in order from the upstream side in the MD direction.
In the stretching zone, independent heating and temperature adjustment can be performed on both ends in the width direction of the film and the central portion in the width direction of the film. In the stretching zone, simultaneous biaxial stretching can be performed at a desired longitudinal stretching ratio and lateral stretching ratio by increasing the clip interval in the MD direction and the clip interval in the TD direction.
In the heat treatment zone, heating and temperature adjustment can be performed independently of the stretching zone. In the heat treatment zone, by reducing the clip interval in the MD direction and the clip interval in the TD direction, each of the longitudinal draw ratio and the transverse draw ratio during simultaneous biaxial stretching can be reduced.

The pre-crystallized film was supplied to the simultaneous biaxial stretching tenter, and both end portions in the width direction of the pre-crystallized film were held by two rows of clip groups.
Next, with respect to the pre-crystallized film, Te1 which is the temperature at both ends in the width direction of the film is 85 ° C., Tc1 which is the temperature at the center portion in the width direction of the film is 80 ° C., and the longitudinal direction (MD direction) The film was subjected to simultaneous biaxial stretching under the conditions that the stretching ratio (that is, the longitudinal stretching ratio) was 3.5 times and the shrinkage rate (that is, the transverse stretching ratio) in the width direction (TD direction) was 3.5 times. . Simultaneous biaxial stretching of the longitudinal stretching ratio and the lateral stretching ratio was performed by enlarging the clip interval in the MD direction and the clip interval in the TD direction.
Next, the biaxially stretched film after the simultaneous biaxial stretching is subjected to heat treatment under conditions of 110 ° C. for 5 seconds with the longitudinal stretching ratio reduced by 10% and the transverse stretching ratio reduced by 15%. By applying, an elongated polymer piezoelectric film having a thickness of 16 μm, a length in the longitudinal direction of 50 m, and a total width (length in the width direction) of 200 mm was obtained. The reduction in the longitudinal draw ratio and the transverse draw ratio was performed by reducing the clip interval in the MD direction and the clip interval in the TD direction.

<Measurement and evaluation>
The polymer piezoelectric film obtained above was subjected to the following measurements and evaluations.

(Weight average molecular weight and molecular weight distribution of helical chiral polymer (A))
Using gel permeation chromatograph (GPC), the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of helical chiral polymer (A) (polylactic acid) contained in the polymer piezoelectric film by the following GPC measurement method Was measured.
The results are shown in Table 1.

-GPC measurement method-
・ Measurement device Waters GPC-100
・ Column Showa Denko KK, Shodex LF-804
-Preparation of sample solution The sample which extract | collected the said polymeric piezoelectric film was dissolved in the solvent [chloroform], and the sample solution with a density | concentration of 1 mg / mL was prepared.
Measurement conditions 0.1 mL of the sample solution was introduced into the column at a solvent (chloroform), a temperature of 40 ° C. and a flow rate of 1 mL / min, and the sample concentration in the sample solution separated by the column was measured with a differential refractometer. The weight average molecular weight (Mw) of polylactic acid was calculated based on a universal calibration curve created based on a polystyrene standard sample.

(Optical purity of helical chiral polymer (A))
The optical purity of the helical chiral polymer (A) (polylactic acid) contained in the polymer piezoelectric film was measured as follows.

First, in a 50 mL Erlenmeyer flask, 1.0 g of a sample collected from the above polymer piezoelectric film is put, and 2.5 mL of IPA (isopropyl alcohol) and 5 mL of a 5.0 mol / L sodium hydroxide solution are added to the sample. It was set as the solution.
Next, the Erlenmeyer flask containing the sample solution was placed in a water bath at a temperature of 40 ° C. and stirred for about 5 hours until the polylactic acid was completely hydrolyzed.
The sample solution after stirring for about 5 hours was cooled to room temperature, neutralized by adding 20 mL of 1.0 mol / L hydrochloric acid solution, and the Erlenmeyer flask was sealed and mixed well.
Next, 1.0 mL of the sample solution stirred above was placed in a 25 mL volumetric flask, and a mobile phase having the following composition was added thereto to obtain 25 mL of HPLC sample solution 1.
5 μL of the obtained HPLC sample solution 1 was injected into the HPLC apparatus, and HPLC measurement was performed under the following HPLC measurement conditions. From the obtained measurement results, the area of the peak derived from the D-form of polylactic acid and the area of the peak derived from the L-form of polylactic acid were determined, and the amount of L-form and the amount of D-form were calculated.
Based on the obtained results, the optical purity (% ee) was determined.
The results are shown in Table 1.

-HPLC measurement conditions-
・ Column Optical resolution column, SUMICHIRAL OA5000 manufactured by Sumika Chemical Analysis Co., Ltd.
・ HPLC equipment: JASCO Corporation liquid chromatography column temperature: 25 ℃
-Composition of mobile phase 1.0 mM-copper (II) sulfate buffer / IPA = 98/2 (V / V)
(In this mobile phase, the ratio of copper (II) sulfate, IPA, and water is copper (II) sulfate / IPA / water = 156.4 mg / 20 mL / 980 mL).
・ Mobile phase flow rate 1.0mL / min ・ Detector UV detector (UV254nm)

(Crystallinity)
A sample of 10 mg was collected from the polymer piezoelectric film, and the collected sample was measured using a differential scanning calorimeter (DSC-1 manufactured by Perkin Elmer Co., Ltd.) at a temperature rising rate of 10 ° C./min. A melting endotherm curve was obtained. The crystallinity of the polymer piezoelectric film was determined from the obtained melting endotherm curve.
The results are shown in Table 1.

(Internal haze)
The internal haze (H1) of the polymer piezoelectric film was measured by the following method.
The results are shown in Table 1.
First, a laminate 1 in which only silicon oil (Shin-Etsu Silicone (trademark) manufactured by Shin-Etsu Chemical Co., Ltd., model number: KF96-100CS) is sandwiched between two glass plates is prepared, and the thickness direction of the laminate 1 is prepared. The haze (hereinafter referred to as haze (H2)) was measured.
Next, the surface of the sample collected from the polymer piezoelectric film is uniformly wetted with silicon oil, and then the sample is sandwiched between the two glass plates to prepare the laminate 2. The haze in the thickness direction (hereinafter referred to as haze (H3)) was measured.
Next, the internal haze (H1) of the polymer piezoelectric film was obtained by taking these differences as in the following formula.
Internal haze (H1) = Haze (H3) -Haze (H2)

Here, the measurement of haze (H2) and haze (H3) was respectively performed using the following apparatus under the following measurement conditions.
Measuring device: manufactured by Tokyo Denshoku Co., Ltd., HAZE METER TC-HIIIDPK
Sample size: 30mm width x 30mm length
Measurement conditions: Conforms to JIS-K7105 Measurement temperature: Room temperature (25 ° C.)

(Standardized molecular orientation MORc)
The polymer piezoelectric film has a size of 50 mm (longitudinal direction of the polymer piezoelectric film) × 30 mm (width direction of the polymer piezoelectric film) from one end in the width direction (region having a width direction length of 50 mm including one end in the width direction). Samples were collected, and with respect to the collected samples, normalized molecular orientation MORc was measured using a microwave molecular orientation meter MOA6000 manufactured by Oji Scientific Instruments. The reference thickness tc was set to 50 μm.
The results are shown in Table 1.

(Product of MORc and crystallinity)
The product of the normalized molecular orientation MORc and the crystallinity in the polymer piezoelectric film was calculated.
The results are shown in Table 1.

(Piezoelectric constant d ₁₄ )
A sample having a size of 40 mm × 40 mm is collected from one end in the width direction of the polymer piezoelectric film (a region having a width direction length of 50 mm including one end in the width direction, the same applies hereinafter), and the displacement method described above is performed using the collected sample. The piezoelectric constant d ₁₄ was measured according to an example of a method for measuring the piezoelectric constant d ₁₄ at (25 ° C.).
The results are shown in Table 1.

(Planar angle θ2 between the molecular orientation direction La and the longitudinal direction of the polymer piezoelectric film)
Using a “birefringence evaluation system” WPA-100 manufactured by Photonic Lightis Co., Ltd., progress in one end of the polymer piezoelectric film in the width direction (specifically, a region having a width direction length of 50 mm including one end in the width direction) The phase axis direction is displayed as a vector, and this direction is defined as a molecular orientation direction La. Based on this result, the planar viewing angle θ2 between the molecular orientation direction La and the longitudinal direction of the polymer piezoelectric film was determined.
The results are shown in Table 1.

(Planar angle θ3 between the molecular orientation direction Lb and the longitudinal direction of the polymer piezoelectric film)
Using the “birefringence evaluation system” WPA-100 manufactured by Photonic Lightis Co., Ltd., the other end in the width direction of the polymer piezoelectric film (specifically, a region having a length in the width direction of 50 mm including the other end in the width direction) The fast axis direction in is represented by a vector, and this direction was defined as the molecular orientation direction Lb. Based on this result, the planar viewing angle θ3 between the molecular orientation direction Lb and the longitudinal direction of the polymer piezoelectric film was determined.
The results are shown in Table 1.

(Plane viewing angle θ1 between molecular orientation direction La and molecular orientation direction Lb)
Based on the molecular orientation direction La and the molecular orientation direction Lb obtained by the above methods, the planar viewing angle θ1 between the molecular orientation direction La and the molecular orientation direction Lb was obtained.
The results are shown in Table 1.

[Example 2]
In Example 1, the same operation as in Example 1 was performed except that the conditions for simultaneous biaxial stretching and heat treatment were changed as follows.
The results are shown in Table 1.

-Conditions for simultaneous biaxial stretching in Example 2 (Differences from Example 1)-
The longitudinal draw ratio was changed to 3.7 times, Tc1 was changed to 85 °, and Te1 was changed to 90 °.
-Conditions for heat treatment of Example 2 (Differences from Example 1)-
The biaxially stretched film after simultaneous biaxial stretching was subjected to a heat treatment without reducing the longitudinal stretching ratio and the lateral stretching ratio.

As shown in Table 1, Examples 1 and 2 include a helical chiral polymer (A) having an optical activity with a weight average molecular weight of 50,000 to 1,000,000, and a crystallinity of 20% to 80%. , Θ1 is 70 ° to 110 °, θ2 is 35 ° to 55 °, and θ3 is 35 ° to 55 °.
Therefore, from the polymer piezoelectric films of Examples 1 and 2, a rectangular piezoelectric film piece whose longitudinal direction is the width direction (TD direction) of the polymer piezoelectric film (for example, the piezoelectric film piece 100 shown in FIGS. 1 and 2). Can be collected without waste (ie, with high yield). Specifically, when a large number of the piezoelectric film pieces are collected from the polymer piezoelectric film, it is possible to reduce wasteful areas to be discarded, particularly at both ends in the width direction of the polymer piezoelectric film.
For example, in the case where 5% margin is provided for each side of one piezoelectric film piece, it is theoretically possible to collect the piezoelectric film piece from a polymer piezoelectric film with a material yield of 81%.
Formula:
Material yield = (1-0.05 × 2) × (1-0.05 × 2) × 100 = 81 (%)

DESCRIPTION OF SYMBOLS 10 Polymer piezoelectric film 12 The width direction one end part 12A of a polymer piezoelectric film The longitudinal direction one end part 12A of a piezoelectric film piece The longitudinal direction one end part 14 The width direction other end part 14A of a polymer piezoelectric film The longitudinal direction other end part 100 Piezoelectric film pieces 102, 104 Whole surface electrode layer 106 Adhesive layer 110 Laminate 120 Actuator 120 Bending actuator 210 Comparative polymer piezoelectric film 212 Width direction one end 214 Width direction other end 220A, 220B Discarded portion 300A, 300B Comparative piezoelectric Film piece La Molecular orientation direction L of the helical chiral polymer (A) at one end in the width direction of the polymer piezoelectric film Lb Molecular orientation direction θ1 of the helical chiral polymer (A) at the other end in the width direction of the polymer piezoelectric film Molecular orientation Plane of direction La and molecular orientation direction Lb Viewing angle θ2 Planar viewing angle θ3 between the longitudinal direction of the polymer piezoelectric film and the molecular orientation direction La3 Planar viewing angle between the longitudinal direction of the polymer piezoelectric film and the molecular orientation direction Lb

Claims (14)

A polymer piezoelectric film comprising a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000 and having a crystallinity of 20% to 80% obtained by a DSC method,
Has a long shape,
The longitudinal length is 10 m or more,
The planar view angle θ1 between the molecular orientation direction La of the helical chiral polymer (A) at one end in the width direction and the molecular orientation direction Lb of the helical chiral polymer (A) at the other end in the width direction is 70 °. ~ 110 °,
The planar view angle θ2 between the longitudinal direction and the molecular orientation direction La is 35 ° to 55 °,
A polymer piezoelectric film having a planar view angle θ3 between a longitudinal direction and the molecular orientation direction Lb of 35 ° to 55 °.   The polymer piezoelectric film according to claim 1, wherein an internal haze with respect to visible light is 10% or less.   The polymer piezoelectric film according to claim 1 or 2, wherein the normalized molecular orientation MORc is 3.5 to 15.0 when the reference thickness measured by a microwave transmission type molecular orientation meter is 50 µm. . Piezoelectric constant _{d 14} measured by the displacement method at 25 ° C. is polymeric piezoelectric film according to any one of claims 1 to 3 is 1.0 pm / V or more. The high helical polymer according to any one of claims 1 to 4, wherein the helical chiral polymer (A) is a polylactic acid polymer having a main chain containing a repeating unit represented by the following formula (1). Molecular piezoelectric film.
  The polymeric piezoelectric film according to any one of claims 1 to 5, wherein the helical chiral polymer (A) has an optical purity of 95.00% ee or higher.   The polymer piezoelectric film according to any one of claims 1 to 6, wherein the content of the helical chiral polymer (A) is 80% by mass or more based on the total amount of the polymer piezoelectric film. A piezoelectric film piece comprising a helical chiral polymer (A) having an optical activity of a weight average molecular weight of 50,000 to 1,000,000 and having a crystallinity of 20% to 80% obtained by a DSC method,
Piezoelectric film in which a planar view angle between the molecular orientation direction of the helical chiral polymer (A) at one end and the molecular orientation direction of the helical chiral polymer (A) at the other end is 70 ° to 110 ° Fragment. A piezoelectric film piece according to claim 8,
An electrode layer disposed on at least one side of the piezoelectric film piece;
A laminate comprising:   Furthermore, the laminated body of Claim 9 provided with the contact bonding layer arrange | positioned on the opposite side to the side by which the piezoelectric film piece is arrange | positioned seeing from the said electrode layer.   A piezoelectric element provided with the piezoelectric film piece of Claim 8, or the laminated body of Claim 9 or Claim 10. A laminate according to claim 10 is provided,
The laminated body is a piezoelectric element that is bent and deformed so that the adhesive layer is inside, and the one end portion of the piezoelectric film piece and the other end portion of the piezoelectric film piece overlap in a plan view. Preparing an elongated unstretched film containing a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000,
The difference which subtracted Tc1 which is the temperature of the width direction center part of the film from Te1 which is the temperature of the width direction both ends of the film with respect to the said long unstretched film is 3 to 15 degreeC, and from said Te1 The difference obtained by subtracting Tg which is the glass transition temperature of the helical chiral polymer (A) is 10 ° C to 40 ° C, the longitudinal draw ratio is 2.0 times to 5.0 times, and the transverse draw ratio is 2. A step of obtaining a biaxially stretched film by performing simultaneous biaxial stretching under conditions of 0 times to 5.0 times;
A step of obtaining a polymer piezoelectric film by subjecting the biaxially stretched film to a heat treatment at a temperature of 80 ° C. to 160 ° C .;
A method for producing a polymer piezoelectric film comprising: Preparing a polymer piezoelectric film according to any one of claims 1 to 7,
From the polymer piezoelectric film, collecting a piezoelectric film piece including at least a part of the one end in the width direction of the polymer piezoelectric film and at least a part of the other end in the width direction;
The manufacturing method of the piezoelectric film piece containing this.