JP2019149481A - Piezoelectric substrate, force sensor, and actuator - Google Patents

Abstract

To provide a piezoelectric substrate having excellent piezoelectric sensitivity, and a force sensor and an actuator using the piezoelectric substrate.SOLUTION: A piezoelectric substrate 100 includes a long inner conductor 12A, a piezoelectric body 14A covering the outer peripheral surface of the inner conductor, and an outer conductor 16 disposed on the outer periphery of the piezoelectric body, and includes a functional layer 15 containing a resin having a glass transition point higher than that of the piezoelectric body. Further, the resin includes at least one selected from the group consisting of a cyanoacrylate resin and a polyester resin.SELECTED DRAWING: Figure 1B

Description

  The present invention relates to a piezoelectric substrate, a force sensor, and an actuator.

In recent years, the application of piezoelectric materials containing helical chiral polymers to piezoelectric devices such as sensors and actuators has been studied. In such a piezoelectric device, a film-shaped piezoelectric body is used.
Attention has been focused on the use of polymers having optical activity such as polypeptides and polylactic acid-based polymers as the helical chiral polymer in the piezoelectric body. Among these, it is known that polylactic acid polymers exhibit piezoelectricity only by mechanical stretching operation. It is known that a poling treatment is unnecessary in a piezoelectric body using a polylactic acid polymer and the piezoelectricity does not decrease over several years.
For example, as a piezoelectric body containing a polylactic acid polymer, large piezoelectric constant d ₁₄ is the piezoelectric excellent in transparency has been reported (e.g., see Patent Documents 1 and 2).
Recently, an attempt has been made to use a material having piezoelectricity by covering a conductor.
For example, a piezo cable is known that includes a center conductor, a piezoelectric material layer, an outer conductor, and a jacket that are coaxially arranged in order from the center to the outside (see, for example, Patent Document 3).
Also known is a piezoelectric unit formed by coating a fiber made of a piezoelectric polymer on a conductive fiber (for example, see Patent Document 4).

Japanese Patent No. 4934235 International Publication No. 2010/104196 JP-A-10-132669 International Publication No. 2014/058077

By the way, when a piezoelectric body (for example, the piezoelectric body in Examples of Patent Documents 1 and 2) is used at a temperature higher than the glass transition temperature of a polymer contained in the piezoelectric body, the piezoelectric body extends and breaks into the piezoelectric body due to deformation. When damage such as wrinkles occurs and as a result, piezoelectric sensitivity (for example, sensor sensitivity when a piezoelectric body is used as a sensor and operation sensitivity when a piezoelectric body is used as an actuator; the same applies hereinafter) is reduced. There is.
Further, Patent Document 3 describes a piezo cable composed of a central conductor, a piezoelectric material layer, an outer conductor, and a jacket that are coaxially arranged in order from the center to the outside as described above. Vinylidene chloride (PVDF) is described. However, with PVDF, the piezoelectric constant varies with time, and the piezoelectric constant may decrease with time. PVDF is a ferroelectric material and thus has pyroelectricity. For this reason, the piezoelectric signal output may fluctuate due to ambient temperature changes. Therefore, the piezoelectric cable described in Patent Document 3 may have insufficient piezoelectric sensitivity stability.
In Patent Document 4, a piezoelectric fiber containing polylactic acid (hereinafter referred to as piezoelectric fiber) is coated, and for example, a braided tube or a round braid made of piezoelectric fiber is wound around a conductive fiber. A piezoelectric unit is described. However, when the piezoelectric fiber described in Patent Document 4 is subjected to a high temperature condition, the piezoelectric sensitivity may be insufficient. Therefore, the piezoelectric fiber described in Patent Document 4 may have insufficient piezoelectric sensitivity.

  That is, an object of the present invention is to provide a piezoelectric substrate having excellent piezoelectric sensitivity, and a force sensor and an actuator using the piezoelectric substrate.

Means for solving the above problems include the following aspects.
<1> A long inner conductor, a piezoelectric body covering an outer peripheral surface of the inner conductor, and an outer conductor disposed on the outer periphery of the piezoelectric body, and having a glass transition point higher than that of the piezoelectric body A piezoelectric substrate having a functional layer containing a resin.
<2> The piezoelectric substrate according to <1>, wherein the resin includes at least one selected from the group consisting of a cyanoacrylate resin and a polyester resin.
<3> A long flat plate shape in which the functional layer has a thickness of 0.001 mm to 0.2 mm, a width of 0.1 mm to 30 mm, and a ratio of the width to the thickness of 2 or more. The piezoelectric substrate according to <1> or <2>, which is a layer coated with the film.
<4> The piezoelectric body includes a helical chiral polymer (A) having optical activity, the length direction of the piezoelectric body, and the main orientation direction of the helical chiral polymer (A) included in the piezoelectric body, Are substantially parallel, and the degree of orientation F of the piezoelectric body obtained by the following formula (a) is in the range of 0.5 or more and less than 1.0, and the piezoelectric element according to any one of <1> to <3> Base material.
Degree of orientation F = (180 ° −α) / 180 ° (a)
(In the formula (a), α represents the half width of the peak derived from the orientation measured by X-ray diffraction.)
<5> The piezoelectric body includes a stabilizer (B) 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, and the helical chiral compound. The piezoelectric substrate according to <4>, comprising 0.01 to 10 parts by mass with respect to 100 parts by mass of the polymer (A).
<6> The helical chiral polymer (A) contained in the piezoelectric body is a polylactic acid polymer having a main chain containing a structural unit represented by the following formula (1): <4> or <5> The piezoelectric substrate as described.

<7> The piezoelectric element according to any one of <1> to <6>, wherein the piezoelectric body is elongated and is spirally wound in one direction along an outer peripheral surface of the inner conductor. Base material.
<8> A function that includes a long inner conductor, a piezoelectric body that covers the outer peripheral surface of the inner conductor, and a resin that covers the outer peripheral surface of the inner conductor and has a glass transition point higher than that of the piezoelectric body. A piezoelectric substrate comprising: a functional layer, wherein the functional layer forms at least a part of a braided structure together with the piezoelectric body; and an outer conductor disposed on an outer periphery of the piezoelectric body and the functional layer.
<9> The piezoelectric body according to any one of <1> to <8>, wherein the piezoelectric body is wound while maintaining an angle of 15 ° to 75 ° with respect to an axial direction of the inner conductor. Piezoelectric substrate.
<10> The piezoelectric body has a fiber shape, and an average major axis diameter of a section of the piezoelectric body perpendicular to the major axis direction of the inner conductor is 0.0001 mm to 10 mm. <1> to <9 > The piezoelectric substrate according to any one of the above.
<11> The piezoelectric body has a long flat plate shape, the average thickness of the piezoelectric body is 0.001 mm to 0.2 mm, the width of the piezoelectric body is 0.1 mm to 30 mm, The piezoelectric substrate according to any one of <1> to <10>, wherein the ratio of the width of the piezoelectric body to the average thickness of the piezoelectric body is 2 or more.
<12> The piezoelectric substrate according to any one of <1> to <11>, further comprising at least one selected from the group consisting of an antistatic layer, an antiblock layer, and an electrode layer.
<13> The piezoelectric substrate according to any one of <1> to <12>, wherein the inner conductor is a tinsel wire.
<14> A force sensor comprising the piezoelectric substrate according to any one of <1> to <13>.
<15> An actuator comprising the piezoelectric substrate according to any one of <1> to <13>.

  ADVANTAGE OF THE INVENTION According to this invention, the piezoelectric base material excellent in piezoelectric sensitivity, and the force sensor and actuator using this piezoelectric base material can be provided.

It is a side view of the coaxial line structure which constitutes the piezoelectric substrate concerning a 1st embodiment. It is a side view of the piezoelectric base material concerning a 1st embodiment. It is the X-X 'line sectional view of Drawing 1B. It is a side view of the coaxial line structure which constitutes the piezoelectric substrate concerning a 2nd embodiment. It is a side view of the piezoelectric base material concerning a 2nd embodiment. It is the typical cross-sectional view along the II line which shows the state which has arrange | positioned the outer conductor further to the photograph of the coaxial line structure of Example 1, and the coaxial line structure. It is a perspective view which shows the piezoelectric base material which concerns on 4th Embodiment, and is a figure which shows the polarization direction of PLLA when the torsional force of the arrow X1 direction is applied. It is a perspective view which shows the piezoelectric base material which concerns on 4th Embodiment, and is a figure which shows the polarization direction of PLLA when the twisting force of the arrow X2 direction is applied. It is a perspective view which shows the piezoelectric base material which concerns on 5th Embodiment, and is a figure which shows the polarization direction of PDLA when the twisting force of the arrow X1 direction is applied. It is a perspective view which shows the piezoelectric base material which concerns on 5th Embodiment, and is a figure which shows the polarization direction of PDLA when the twisting force of the arrow X2 direction is applied. It is the schematic which shows the piezoelectric base material which concerns on 1st Embodiment which affixed the flat plate using the adhesive tape. It is the schematic when pressing the piezoelectric base material which concerns on 1st Embodiment which stuck the flat plate using the adhesive tape. It is an example of the piezoelectric substrate which concerns on 1st Embodiment which stuck the flat plate using the adhesive tape. It is an example of the piezoelectric substrate which concerns on 1st Embodiment which stuck the flat plate using the adhesive agent. It is a key map of a force sensor concerning an embodiment of this indication. It is an example of the piezoelectric base material of this indication which coat | covered the piezoelectric material with PET film.

Embodiments that are examples of the present invention will be described below. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.
In this specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the present specification, the long shape means a shape in which the length dimension is sufficiently larger than the width dimension. The length dimension is usually 5 times or more of the width dimension, and preferably 10 times or more.
In this specification, the “main surface” of the long flat plate-like piezoelectric body is a surface orthogonal to the thickness direction of the long flat plate-like piezoelectric body (in other words, a surface including the length direction and the width direction). means.
In this specification, the “surface” of a member means the “main surface” of the member unless otherwise specified.
In this specification, the thickness, width, and length satisfy the relationship of thickness <width <length, as is normally defined.
In this specification, an angle formed by two line segments is expressed in a range of 0 ° to 90 °.
In the present specification, “film” is a concept including not only what is generally called “film” but also what is generally called “sheet”.
In the present specification, the “MD direction” is the direction in which the film flows (machine direction), that is, the stretching direction, and the “TD direction” is a direction orthogonal to the MD direction and parallel to the main surface of the film ( (Transverse Direction).
In this specification, when an embodiment is described with reference to drawings, the composition of the embodiment is not limited to the composition shown in the drawing. Moreover, the magnitude | size of the member in each figure is notional, The relative relationship of the magnitude | size between members is not limited to this.

  Next, the piezoelectric substrate of the present disclosure, and the force sensor and actuator using the piezoelectric substrate will be described in detail.

[Piezoelectric substrate]
The piezoelectric substrate of the present invention includes a long inner conductor, a piezoelectric body covering the outer peripheral surface of the inner conductor, and an outer conductor disposed on the outer periphery of the piezoelectric body, and the outer periphery of the inner conductor. On the side, a functional layer containing a resin having a glass transition point higher than that of the piezoelectric body is provided.

By providing the above configuration, the present invention can provide a piezoelectric substrate excellent in piezoelectric sensitivity, and a force sensor and an actuator using the piezoelectric substrate.
The reason for this effect is presumed as follows.

Conventionally, a coaxial line structure piezoelectric sensor, for example, a resin such as PLA has been used as a piezoelectric member. When the piezoelectric sensor is used in a high temperature environment exceeding the glass transition point of the resin contained in the piezoelectric member, Sensitivity will decrease.
As a cause of this, when tension is applied to the coaxial line structure piezoelectric sensor, a force is applied in the direction of 45 ° with respect to the orientation direction of the PLA, but when used in the above high temperature environment, the temperature of the PLA is higher than the glass transition point. In this case, it is considered that the PLA orientation is broken due to the influence of the tension. When this coaxial line structure piezoelectric sensor was returned to room temperature and used again, the piezoelectricity was deteriorated.
On the other hand, a piezoelectric substrate (for example, a coaxial line structure piezoelectric sensor or the like) of the present disclosure is made of a resin having a glass transition point higher than that of a piezoelectric body (for example, a material having a glass transition point higher than that of PLA). A layer to be contained (hereinafter also referred to as “functional layer”) is provided. Therefore, it is considered that even in the high temperature environment described above, the functional layer exhibits a high elastic force, relieves stress on the PLA due to the tension, and prevents the orientation direction of the PLA from collapsing.
Therefore, the piezoelectric substrate of the present disclosure, and the force sensor and actuator using the piezoelectric substrate are excellent in piezoelectric sensitivity.

<Inner conductor>
The inner conductor in the piezoelectric substrate is preferably a signal line conductor. The signal line conductor means a conductor for efficiently detecting an electrical signal from the piezoelectric body. More specifically, it is a conductor for detecting a voltage signal (charge signal) corresponding to the applied tension when a tension is applied to the piezoelectric substrate.

As the internal conductor, a cord-like object including a core material and a conductor A covering the periphery of the core material can be used. The internal conductor having such a configuration is also referred to as a tinsel wire.
Moreover, a conductive fiber can also be used as an internal conductor. Any known conductive fibers may be used as long as they exhibit conductivity. For example, metal fibers, fibers made of a conductive polymer, carbon fibers, fibrous or granular conductive fillers are dispersed. Examples thereof include fibers made of a polymer, or fibers having a conductive layer on the surface of a fibrous material. Examples of the method for providing a conductive layer on the surface of the fibrous material include a metal coat, a conductive polymer coat, and winding of conductive fibers. Among these, a metal coat is preferable from the viewpoint of conductivity, durability, flexibility and the like. Specific methods for coating the metal include vapor deposition, sputtering, electrolytic plating, and electroless plating. From the viewpoint of productivity, electrolytic plating or electroless plating is preferable. Such a metal-plated fiber can be referred to as a metal-plated fiber.

  By appropriately selecting the types of the core material and the conductor A, it is possible to obtain a piezoelectric substrate suitable for high flexibility and flexibility (for example, a wearable sensor used in clothes).

  Specifically, for example, the inner conductor has a structure in which a metal foil is spirally wound around a core made of a fiber obtained by twisting a short fiber such as cotton yarn, a long fiber such as a polyester yarn or a nylon yarn. The thing which has.

  When a metal foil is wound around the core material to produce an internal conductor, the metal foil is preferably a flat wire. A rectangular metal foil can be produced by rolling a metal wire or slitting the metal foil into a narrow width. By making the metal foil into a rectangular wire shape, it is possible to reduce the gap between the inner periphery of the inner conductor and the piezoelectric body and to improve the adhesion to the piezoelectric body. As a result, charge fluctuations generated from the piezoelectric body can be easily detected, and the sensitivity to tension is further improved.

  When the metal foil has a rectangular wire shape, the width to thickness ratio is preferably 2 or more in its cross section (preferably a rectangular cross section).

  The material of the metal foil is not particularly limited, but copper foil is preferable. By using copper having high electrical conductivity, it is possible to reduce the output impedance. Therefore, when a tension is applied to the piezoelectric substrate, a voltage signal corresponding to the tension is more easily detected. As a result, the piezoelectric sensitivity tends to be further improved. Further, since the copper foil fits into the deformation of the elastic deformation region at the time of bending deformation and becomes difficult to be plastically deformed, metal fatigue failure hardly occurs, and repeated bending resistance can be remarkably improved.

  The core material in the inner conductor is located at the center of the inner conductor and has a function as a structural material that supports tension. By appropriately selecting the material, cross-sectional area, etc. of the core material, it is possible to design in accordance with the values such as the tension and strain applied to the internal conductor.

  The material of the core material is not particularly limited, and can be selected according to desired characteristics of the piezoelectric substrate. From the viewpoint of achieving both flexibility and strength at a high level, fibers (filaments) such as natural fibers and synthetic fibers can be mentioned.

  The thickness of the core material is not particularly limited and can be selected according to desired characteristics of the piezoelectric substrate. For example, the wire outer diameter is preferably within a range of 0.1 mm to 10 mm.

<Piezoelectric body>
The piezoelectric substrate of the present disclosure includes a piezoelectric body.
The piezoelectric body preferably has a long flat plate shape or a fiber shape from the viewpoint of improving the piezoelectric sensitivity.
Hereinafter, a piezoelectric body having a long flat plate shape (hereinafter also referred to as a long flat plate piezoelectric body) and a piezoelectric body having a fiber shape (hereinafter also referred to as a fibrous piezoelectric body) will be described in order.

-Long plate piezoelectric material-
By using a long plate-like piezoelectric body as the piezoelectric body, it is possible to increase the adhesion surface with respect to the inner conductor, and to efficiently detect the charge generated by the piezoelectric effect as a voltage signal.
Hereinafter, the dimensions of the long plate-like piezoelectric body will be described in more detail.

  The average thickness (hereinafter also simply referred to as “thickness”) of the long plate-like piezoelectric body is preferably 0.001 mm to 0.2 mm. When the thickness of the long plate-like piezoelectric body is 0.001 mm or more, sufficient strength tends to be secured. Furthermore, the manufacturing suitability tends to be excellent. On the other hand, when the thickness of the long plate-like piezoelectric body is 0.2 mm or less, the degree of freedom of deformation (flexibility) in the thickness direction tends to be improved.

  The width of the long plate-like piezoelectric body is preferably 0.1 mm to 30 mm, and more preferably 0.5 mm to 15 mm. When the width of the long plate-like piezoelectric body is 0.1 mm or more, sufficient strength tends to be secured. Furthermore, it exists in the tendency which is excellent also in manufacturing aptitude (for example, manufacturing aptitude in the slit process mentioned later). On the other hand, when the width of the long flat piezoelectric member is 30 mm or less, the degree of freedom of deformation (flexibility) tends to be improved.

  The ratio of the width to the thickness of the long plate-like piezoelectric body (hereinafter also referred to as “ratio [width / thickness]”) is preferably 2 or more. If the ratio (width / thickness) of the long plate-like piezoelectric material is 2 or more, the main surface becomes clear, so the outer conductor is formed by aligning the direction of the long plate-like piezoelectric material in the length direction. Easy to do.

  The width of the long plate-like piezoelectric body is more preferably 0.5 mm to 15 mm. When the width of the long plate-like piezoelectric body is 0.5 mm or more, the strength tends to be further improved. Furthermore, since the twist of the long plate-like piezoelectric body can be further suppressed, the piezoelectric sensitivity and its stability tend to be further improved. On the other hand, when the width of the long plate-like piezoelectric material is 15 mm or less, the degree of freedom (flexibility) of deformation of the long plate-like piezoelectric material tends to be further improved.

  The long plate-like piezoelectric body preferably has a ratio of length to width (hereinafter also referred to as ratio [length / width]) of 10 or more. When the ratio [length / width] of the long plate-like piezoelectric body is 10 or more, the degree of freedom of deformation (flexibility) is further improved.

There is no limitation in the manufacturing method of a long flat piezoelectric material, It can manufacture by a well-known method.
For example, as a method for producing a long plate-like piezoelectric body from a piezoelectric film, a raw material is formed into a film to obtain an unstretched film, and the obtained unstretched film is stretched and crystallized. The piezoelectric film can be obtained by slitting (cutting the piezoelectric film into a long shape).
Moreover, you may manufacture a elongate flat piezoelectric material using a well-known flat yarn manufacturing method. For example, after slitting a wide film obtained by inflation molding into a narrow film, stretching by hot plate stretching, roll stretching, etc., and crystallization, a long plate-like piezoelectric body is obtained. Also good.
Any one of the stretching and crystallization may be performed first. Moreover, the method of performing preliminary crystallization, extending | stretching, and crystallization (annealing) sequentially with respect to an unstretched film may be sufficient. The stretching may be uniaxial stretching or biaxial stretching. In the case of biaxial stretching, the stretching ratio of one (main stretching direction) is preferably increased.
Regarding the method for producing the piezoelectric film, known documents such as Japanese Patent No. 4934235, International Publication No. 2010/104196, International Publication No. 2013/054918, International Publication No. 2013/088948 can be referred to as appropriate.

-Fibrous piezoelectric material-
By using a fibrous piezoelectric body as a piezoelectric body, it can be used as a form with more flexibility and flexibility, and it is possible to efficiently detect a charge generated by the piezoelectric effect as a voltage signal. Become.
Although there is no restriction | limiting in particular as a fiber shape, For example, the shape of a single fiber and the shape of a fiber bundle (bundle which consists of a some fiber) are mentioned.
Hereinafter, the dimensions of the fibrous piezoelectric body will be described in more detail.
The average major axis diameter (hereinafter, also simply referred to as “major axis diameter”) of the cross section perpendicular to the major axis direction of the inner conductor of the fibrous piezoelectric body is 0.0001 mm to 10 mm from the viewpoint of improving the piezoelectric sensitivity. It is preferable that it is 0.001 mm-5 mm, and it is still more preferable that it is 0.002 mm-1 mm.
When the major axis diameter of the fibrous piezoelectric body is 0.0001 mm or more, the strength tends to be further improved. On the other hand, when the major axis diameter of the fibrous piezoelectric body is 10 mm or less, the degree of freedom (flexibility) of deformation of the fibrous piezoelectric body tends to be further improved.
Here, the “long axis diameter of the cross section” corresponds to the “diameter” when the cross section of the fibrous piezoelectric body is circular.
When the cross section of the fibrous piezoelectric body has a shape different from a circular shape, the “major axis diameter of the cross section” is the longest distance in the cross section.
When the fibrous piezoelectric body is a piezoelectric body made of a fiber bundle, the “long-axis diameter of the cross section” is the long-axis diameter of the cross section of the piezoelectric body made of the fiber bundle.
Specifically, examples of the fibrous piezoelectric material include monofilament yarn and multifilament yarn.

-Monofilament yarn The monofilament yarn has a single yarn fineness of preferably 3 dtex to 30 dtex, more preferably 5 dtex to 20 dtex.
When the single yarn fineness is less than 3 dtex, it becomes difficult to handle the yarn in the fabric preparation process and the weaving process. On the other hand, if the single yarn fineness exceeds 30 dtex, fusion between yarns is likely to occur.
The monofilament yarn is preferably obtained by directly spinning and drawing in consideration of cost. The monofilament yarn may be obtained.

-Multifilament yarn The total fineness of the multifilament yarn is preferably 30 dtex to 600 dtex, more preferably 100 dtex to 400 dtex.
As the multifilament yarn, for example, any one-step yarn such as a spin draw yarn or two-step yarn obtained by drawing UDY (undrawn yarn), POY (highly oriented undrawn yarn) or the like can be used. . Multifilament yarns may be obtained.
Polylactic acid monofilament yarns, as the polylactic acid multifilament yarns commercially available, manufactured by Toray Industries of Ekodia _{(R) PLA,} Unitika of Terramac _(R), manufactured by Kuraray Co. Purasutachi _(R) can be used.

There are no particular limitations on the method of manufacturing the fibrous piezoelectric body, and it can be manufactured by a known method.
For example, a filament yarn (monofilament yarn, multifilament yarn) as a fibrous piezoelectric material can be obtained by melt spinning a raw material (for example, polylactic acid) and then stretching it (melt spinning stretching method). In addition, after spinning, it is preferable to maintain the atmospheric temperature in the vicinity of the yarn until cooling and solidification within a certain temperature range.
The filament yarn may be obtained, for example, by further dividing the filament yarn obtained by the melt spinning drawing method.

(Helical chiral polymer (A))
The piezoelectric body in the present disclosure preferably includes a helical chiral polymer (A) having optical activity.
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 (glutaric acid γ-benzyl), poly (glutaric acid γ-methyl), and the like.
Examples of the cellulose derivative include cellulose acetate and cyanoethyl cellulose.

  From the viewpoint of improving the piezoelectricity of the piezoelectric body, the helical chiral polymer (A) preferably has an optical purity of 95.00% ee or more, more preferably 96.00% ee or more, and 99.99. More preferably, it is 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 structural unit represented by the following formula (1) from the viewpoint of increasing optical purity and improving piezoelectricity.

Examples of the polymer having the structural 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 a structural unit 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-based polymers, polylactic acid is preferable, and L-lactic acid homopolymer (PLLA, also simply referred to as “L-form”) or D-lactic acid homopolymer (PDLA, also simply referred to as “D-form”) is the most. preferable.

Polylactic acid is a polymer in which lactic acid is polymerized by an ester bond and connected for a long time.
It is known that polylactic acid can be produced by a lactide method via lactide; a direct polymerization method in which lactic acid is heated in a solvent under reduced pressure and polymerized while removing water.
As polylactic acid, homopolymer of L-lactic acid, homopolymer of D-lactic acid, block copolymer containing at least one polymer of L-lactic acid and D-lactic acid, and at least one of L-lactic acid and D-lactic acid A graft copolymer containing a polymer may be mentioned.
The glass transition point of polylactic acid is about 50 ° C. to 70 ° C., although it varies depending on the molecular weight and the degree of crystallinity due to stretching.

  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 and mandelic acid; cyclic esters such as glycolide, β-methyl-δ-valerolactone, γ-valerolactone and ε-caprolactone; oxalic acid, malonic acid, succinic acid, Glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 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 preferably 50,000 to 1,000,000.
When Mw of the helical chiral polymer (A) is 50,000 or more, the mechanical strength of the piezoelectric body 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 million or less, the moldability when obtaining a piezoelectric body by molding (for example, extrusion molding, melt spinning) 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 piezoelectric body. 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 using the gel permeation chromatograph (GPC). Here, Mn is the number average molecular weight of the helical chiral polymer (A).
Hereinafter, an example of a method for measuring Mw and Mw / Mn of the helical chiral polymer (A) by GPC will be described.

-GPC measuring device-
Waters GPC-100
-Column-
Made by Showa Denko KK, Shodex LF-804
-Sample preparation-
The piezoelectric body 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 as 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, the polylactic acid is obtained by the lactide method or the direct polymerization method. It is preferable to produce a polymer.

The piezoelectric body in the present disclosure may contain only one kind of the above-described helical chiral polymer (A), or may contain two or more kinds.
In the present disclosure, the content of the helical chiral polymer (A) in the piezoelectric body (the total content in the case of two or more) is preferably 80% by mass or more with respect to the total amount of the piezoelectric body.

(Stabilizer)
The piezoelectric body further contains a stabilizer (B) having a weight average molecular weight of 200 to 60000 having at least one functional group selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group in one molecule. It is preferable to do. 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 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. 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.
As the carbodiimide compound, a commercially available product may be used. For example, B2756 (trade name) manufactured by Tokyo Chemical Industry Co., Ltd., Carbodilite LA-1 (trade name) manufactured by Nisshinbo Chemical Co., Ltd. Stabaxol I (all are trade names) and the like.

  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 above-mentioned, 200-60000 are preferable, as for the weight average molecular weight of a stabilizer (B), 200-30000 is more preferable, and 300-18000 is more preferable.
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”. .

  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.

When the piezoelectric body contains the stabilizer (B), the piezoelectric body may contain only one kind of stabilizer or two or more kinds.
When the piezoelectric body 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). Preferably, it is 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, and particularly preferably 0.5 to 2 parts by mass.
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.

<Other ingredients>
The piezoelectric body 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.

The piezoelectric body of the present disclosure is a piezoelectric substrate, wherein the piezoelectric body includes a helical chiral polymer (A) having optical activity, the length direction of the first piezoelectric body, and the helical chiral polymer included in the piezoelectric body. It is preferable that the main orientation direction of (A) is substantially parallel and the degree of orientation F of the piezoelectric body obtained by the following formula (a) is in the range of 0.5 or more and less than 1.0.
Degree of orientation F = (180 ° −α) / 180 ° (a)
(In the formula (a), α represents the half width of the peak derived from the orientation measured by X-ray diffraction.)

Here, the degree of orientation F of the piezoelectric body is an index indicating the degree of orientation of the helical chiral polymer (A) contained in the piezoelectric body. For example, a wide-angle X-ray diffractometer (RINT 2550 manufactured by Rigaku Corporation, accessory: rotation) C-axis orientation measured by a sample stage, X-ray source: CuKα, output: 40 kV, 370 mA, detector: scintillation counter).
An example of a method for measuring the orientation degree F of the piezoelectric body is as shown in Examples described later.

More specifically, in the piezoelectric substrate of the above aspect, the piezoelectric body includes the helical chiral polymer (A), and the length direction of the piezoelectric body and the main orientation direction of the helical chiral polymer (A) are substantially parallel. The piezoelectricity is manifested by the presence of the piezoelectric body and the degree of orientation F of the piezoelectric body being 0.5 or more and less than 1.0.
Thereby, for example, when a tension is applied to the piezoelectric substrate, the amount of generated charges is further increased.

Moreover, in the piezoelectric base material of the present disclosure, the piezoelectric body is preferably long and is wound spirally in one direction along the outer peripheral surface of the internal conductor.
Here, “one direction” means that when the piezoelectric substrate of the present disclosure is viewed from one end side in the axial direction of the internal conductor, the piezoelectric body is wound from the near side to the far side of the internal conductor. The direction. Specifically, it means the right direction (right-handed, that is, clockwise) or the left direction (left-handed, that is, counterclockwise).

Further, since the piezoelectric body is long, the piezoelectric body is easily arranged in a spiral shape in one direction while maintaining the spiral angle β with respect to the axial direction of the internal conductor.
Here, the “spiral angle β” means an angle formed by the axial direction of the internal conductor and the direction in which the piezoelectric body is disposed (the length direction of the piezoelectric body) with respect to the axial direction of the internal conductor.
Thereby, for example, when tension is applied in the length direction of the piezoelectric substrate, the polarization of the helical chiral polymer (A) is likely to occur in the radial direction of the piezoelectric substrate. As a result, a voltage signal (charge signal) that is effectively proportional to the tension is detected, and the piezoelectric sensitivity is easily improved.
Furthermore, since the piezoelectric substrate of the present disclosure includes the same coaxial line structure (internal conductor and dielectric) as the internal structure provided in the coaxial cable, for example, when the piezoelectric substrate is applied to a coaxial cable, It can be a structure with high shielding properties and noise resistance.

In the piezoelectric substrate of the present disclosure, from the viewpoint of improving the piezoelectric sensitivity, the piezoelectric body has an angle of 15 ° to 75 ° (45 ° ± 30 °) with respect to the axial direction of the inner conductor (that is, the spiral angle β). It is preferably wound while being held, and is more preferably wound while being held at an angle of 35 ° to 55 ° (45 ° ± 10 °).
As a result, when a tension (stress) is applied in the length direction of the piezoelectric substrate, a shearing force is easily applied to the helical chiral polymer (A), and the helical chiral polymer (A) extends in the radial direction of the piezoelectric substrate. The polarization is likely to occur.
Moreover, in the piezoelectric substrate of the present disclosure, the helical chiral polymer (A) is arranged when tension is applied in the length direction of the piezoelectric substrate by arranging the piezoelectric body in a spiral shape in one direction. A shear force is applied, and polarization of the helical chiral polymer (A) occurs in the radial direction of the piezoelectric substrate. When the first piezoelectric body wound spirally is regarded as an aggregate of minute regions that can be considered as a plane with respect to the length direction, the polarization direction is the plane of the minute region that constitutes the first piezoelectric member. , the shear force caused by the tension (stress) when it is applied to the helical chiral polymer, substantially coincides with the direction of the electric field generated due to the piezoelectric constant d _14.
Specifically, for example, in the case of polylactic acid, in the case of an L-lactic acid homopolymer (PLLA) having a left-handed spiral molecular structure, a piezoelectric body whose length direction is substantially parallel to the main orientation direction of PLLA is used as an internal conductor. On the other hand, when tension (stress) is applied to the structure wound spirally in a left-handed manner, the electric field (from the center of the circular cross section perpendicular to the tension to the outer side in the radial direction) Polarization) occurs. On the other hand, tension (stress) is applied to a structure in which a piezoelectric body whose length direction is substantially parallel to the main orientation direction of PLLA is spirally wound around the inner conductor in a right-handed manner. In this case, an electric field (polarization) from the outside of the circle having a circular cross section perpendicular to the tension to the center direction is generated parallel to the radial direction.

For example, in the case of a D-lactic acid homopolymer (PDLA) having a right-handed spiral molecular structure, a piezoelectric body whose length direction is substantially parallel to the main orientation direction of PDLA is spirally wound left-handed with respect to the internal conductor. When a tension (stress) is applied to the structure wound in a shape, an electric field (polarization) from the outside of a circle having a circular cross section perpendicular to the tension to the center direction is generated substantially parallel to the radial direction. On the contrary, tension (stress) is applied to a structure in which a piezoelectric body whose length direction is substantially parallel to the main orientation direction of PDLA is spirally wound around the inner conductor in a right-handed manner. Then, an electric field (polarization) is generated parallel to the radial direction from the center of the circular cross section perpendicular to the tension to the outer side.
As a result, when tension is applied in the length direction of the piezoelectric base material, potential differences proportional to the tension are generated in a phase-matched state at each part of the piezoelectric body arranged in a spiral shape, so that it is effective. It is considered that a voltage signal proportional to the tension is detected.
Thereby, it is easy to obtain a piezoelectric substrate superior in piezoelectric sensitivity.
In addition, the piezoelectric substrate of the present disclosure includes a structure in which a piezoelectric body is wound in a right-handed spiral with respect to an inner conductor, and a part of the piezoelectric body is wound in a left-handed spiral. May be. When a part of the piezoelectric body is spirally wound in a left-handed manner, it is preferable that the ratio of the left-handed winding is less than 50% with respect to the whole (the total of the right-handed winding and the left-handed winding) from the viewpoint of suppressing a decrease in piezoelectric sensitivity. .
In addition, the piezoelectric substrate of the present disclosure includes a structure in which a piezoelectric body is wound in a left-handed spiral with respect to an inner conductor, and a part of the piezoelectric body is wound in a right-handed spiral. May be. When part of the piezoelectric body is wound in a right-handed spiral, the ratio of right-handed winding is less than 50% with respect to the whole (total of right-handed and left-handed winding) from the viewpoint of suppressing a decrease in piezoelectric sensitivity. Is preferred.

Here, the fact that the length direction of the piezoelectric body and the main orientation direction of the helical chiral polymer (A) are substantially parallel means that the piezoelectric body is resistant to tension in the length direction (that is, in the length direction). (Excellent tensile strength). Therefore, even if the piezoelectric body is spirally wound in one direction around the internal conductor, it is difficult to break.
Furthermore, the length direction of the piezoelectric body and the main orientation direction of the helical chiral polymer (A) are substantially parallel. For example, a stretched piezoelectric film is slit to form a piezoelectric body (for example, a slit ribbon). It is also advantageous in terms of productivity when obtaining.
In this specification, “substantially parallel” means that the angle formed by two line segments is 0 ° or more and less than 30 ° (preferably 0 ° or more and 22.5 ° or less, more preferably 0 ° or more and 10 ° or less, More preferably, it is 0 ° or more and 5 ° or less, and particularly preferably 0 ° or more and 3 ° or less.
In the present specification, the main orientation direction of the helical chiral polymer (A) means the main orientation direction of the helical chiral polymer (A). The main orientation direction of the helical chiral polymer (A) can be confirmed by measuring the orientation degree F of the piezoelectric body.
In addition, when a piezoelectric material is manufactured by melt spinning the raw material, the main orientation direction of the helical chiral polymer (A) in the manufactured piezoelectric material means the main stretching direction. The main stretching direction refers to the stretching direction.
Similarly, when a piezoelectric body is manufactured by forming a film stretch and slits of the stretched film, the main orientation direction of the helical chiral polymer (A) in the manufactured piezoelectric body means the main stretch direction. Here, the main stretching direction refers to the stretching direction in the case of uniaxial stretching, and refers to the stretching direction in which the stretching ratio is higher in the case of biaxial stretching.

The piezoelectric body of the present disclosure is elongated, and includes a “first piezoelectric body” spirally wound in one direction along the outer peripheral surface of the inner conductor, and further on the outer peripheral surface of the inner conductor. A mode in which a long “second piezoelectric body” wound in a direction different from the one direction is provided.
The second piezoelectric body preferably has the same characteristics as the first piezoelectric body.
However, the winding direction of the first piezoelectric body and the second piezoelectric body, and the chirality of the helical chiral polymer (A) contained in the first piezoelectric body and the second piezoelectric body are the effects of the present disclosure. From the viewpoint of achieving the above, it may be appropriately selected according to the mode of the piezoelectric substrate.
Further, the second piezoelectric body may have different characteristics from the first piezoelectric body.

(Orientation degree F)
As described above, the orientation degree F of the piezoelectric body in the present disclosure is preferably 0.5 or more and less than 1.0, more preferably 0.7 or more and less than 1.0, and 0.8 or more and 1. More preferably, it is less than 0.
If the orientation degree F of the piezoelectric body is 0.5 or more, there are many molecular chains (for example, polylactic acid molecular chains) of the helical chiral polymer (A) arranged in the stretching direction, and as a result, the rate of formation of oriented crystals is high. It becomes high and it becomes possible to express higher piezoelectricity.
If the degree of orientation F of the piezoelectric body is less than 1.0, the longitudinal crack strength is further improved.

(Crystallinity)
The crystallinity of the piezoelectric body in the present disclosure is a value measured by the above-described X-ray diffraction measurement (wide-angle X-ray diffraction measurement).
The crystallinity of the piezoelectric body in the present disclosure is preferably 20% to 80%, more preferably 25% to 70%, and still more preferably 30% to 60%.
When the crystallinity is 20% or more, high piezoelectricity is maintained. When the degree of crystallinity is 80% or less, the transparency of the piezoelectric body is maintained high.
When the degree of crystallinity is 80% or less, for example, when a piezoelectric film that is a raw material of a piezoelectric body is manufactured by stretching, whitening and breakage are unlikely to occur, so that the piezoelectric body is easy to manufacture. Further, when the degree of crystallinity is 80% or less, for example, when a piezoelectric material (for example, polylactic acid) is manufactured by drawing after melt spinning, it becomes a fiber having high flexibility and flexible properties. Easy to manufacture.

(Transparency (internal haze))
In the piezoelectric body according to the present disclosure, transparency is not particularly required, but it may of course have transparency.
The transparency of the piezoelectric body can be evaluated by measuring internal haze. Here, the internal haze of the piezoelectric body refers to the haze excluding the haze due to the shape of the outer surface of the piezoelectric body.
When transparency is required, the piezoelectric body preferably has an internal haze of 5% or less for visible light. From the viewpoint of further improving the transparency and longitudinal crack strength, 2.0% or less is more preferable. Preferably, it is 1.0% or less. The lower limit value of the internal haze of the piezoelectric body is not particularly limited, but examples of the lower limit value include 0.01%.
The internal haze of the piezoelectric body is measured according to JIS-K7105 with respect to a piezoelectric body having a thickness of 0.03 mm to 0.05 mm. It is a value when used and measured at 25 ° C.
Hereinafter, an example of a method for measuring the internal haze of the piezoelectric body will be described.
First, sample 1 in which only silicone 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 haze in the thickness direction of sample 1 is prepared. (Hereinafter referred to as haze (H2)) is measured.
Next, a sample 2 is prepared in which a plurality of piezoelectric bodies whose surfaces are uniformly coated with silicone oil are arranged without gaps between the two glass plates described above. Measure haze (referred to as H3).
Next, the internal haze (H1) of the piezoelectric body is obtained by taking these differences as in the following formula.
Internal haze (H1) = Haze (H3) -Haze (H2)
Here, haze (H2) and haze (H3) are measured 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.)

<Insulator>
The piezoelectric substrate of the present disclosure may include an insulator. For example, the piezoelectric substrate of the second embodiment described later may further include an insulator.
The insulator is preferably wound spirally along the outer peripheral surface of the inner conductor. In this case, it is preferable that the piezoelectric body and the insulator have a braided structure in which they are alternately crossed.
In addition, the winding direction of the insulator may be the same direction as the winding direction of the piezoelectric body, or may be a different direction.
Although details will be described later, in the piezoelectric base material according to the second embodiment, when the piezoelectric base material is bent and deformed by the piezoelectric body forming a braid structure, an electrical short circuit between the internal conductor and the external conductor is generated. There is an advantage that it becomes easy to suppress.

The insulator is not particularly limited. For example, vinyl chloride resin, polyethylene resin, polypropylene resin, ethylene / tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP) ), Tetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoropropyl vinyl ether copolymer (PFA), fluoro rubber, polyester resin, polyimide resin, polyamide resin, polyethylene terephthalate resin (PET), rubber (elastomer Included).
The shape of the insulator is preferably a long shape from the viewpoint of winding around the inner conductor.

<External conductor>
The piezoelectric base material of the present disclosure includes an outer conductor disposed on the outer periphery of the piezoelectric body.
The outer conductor in the present disclosure is preferably a ground conductor.
The ground conductor refers to, for example, a conductor that forms a pair of internal conductors (preferably signal line conductors) when detecting a signal.

Although there is no limitation in particular in a ground conductor, the following are mainly mentioned by a cross-sectional shape.
For example, as the ground conductor having a rectangular cross section, it is possible to use a copper foil ribbon obtained by rolling a copper wire having a circular cross section into a flat plate, an aluminum foil ribbon, or the like.
For example, as a ground conductor having a circular cross section, copper wire, aluminum wire, SUS wire, metal wire covered with an insulating film, carbon fiber, resin fiber integrated with carbon fiber, copper foil is wound around the fiber in a spiral It is possible to use a tinted wire.
Further, as the ground conductor, an organic conductive material coated with an insulating material may be used.
Moreover, a conductive fiber can also be used as the ground conductor. A conductive fiber is synonymous with the conductive fiber which can be applied as an internal conductor as stated above, The preferable range is also the same.

The ground conductor is preferably arranged so as to enclose the inner conductor and the piezoelectric body so as not to be short-circuited with the inner conductor (preferably the signal line conductor).
As a method of wrapping such an internal conductor, it is possible to select a method of wrapping a copper foil or the like in a spiral shape, a method of wrapping a copper wire or the like in a tubular braid, and the like. is there.
Note that the method of wrapping the inner conductor is not limited to these methods. By wrapping the inner conductor, electrostatic shielding can be performed, and voltage change of the inner conductor due to the influence of external static electricity can be prevented.
In addition, the arrangement of the ground conductor is also one of preferable modes in which the inner conductor and the piezoelectric body in the present disclosure are arranged so as to be enclosed in a cylindrical shape.
As the cross-sectional shape of the ground conductor, various cross-sectional shapes such as a circular shape, an elliptical shape, a rectangular shape, and an irregular shape can be applied. In particular, the rectangular cross section can be brought into close contact with an inner conductor (preferably a signal line conductor), a piezoelectric body, and an insulator as needed, so that charges generated by the piezoelectric effect can be efficiently obtained. Can be detected as a voltage signal.

<Functional layer>
The piezoelectric substrate of the present disclosure includes a functional layer containing a resin having a glass transition point higher than that of the piezoelectric body.
The glass transition point of the resin contained in the functional layer only needs to be higher than that of the piezoelectric body, and the piezoelectric base material includes the functional layer, so that a decrease in piezoelectric sensitivity can be suppressed even when used in a high temperature environment. Further, from the viewpoint that the higher the glass transition point of the resin contained in the functional layer, the higher the heat resistance, a temperature higher by 3 ° C. to 90 ° C. than the piezoelectric body is preferable, and a temperature higher by 5 ° C. to 80 ° C. than the piezoelectric body. More preferably, a temperature higher by 10 ° C. to 70 ° C. than the piezoelectric body is more preferable.
The glass transition point of the resin used for the functional layer is preferably 65 ° C. or higher and lower than 140 ° C., more preferably 80 ° C. or higher and lower than 135 ° C., and further preferably 100 ° C. or higher and lower than 130 ° C.

The resin used as the functional layer is not particularly limited, but acrylic resin, methacrylic resin, urethane resin, cellulose resin, vinyl acetate resin, ethylene-vinyl acetate resin, epoxy resin, nylon-epoxy resin, vinyl chloride resin , Chloroprene rubber resin, cyanoacrylate resin, silicone resin, modified silicone resin, aqueous polymer-isocyanate resin, styrene-butadiene rubber resin, nitrile rubber resin, acetal resin, phenol resin, polyamide resin, polyimide Resins, melamine resins, urea resins, bromine resins, starch resins, polyester resins, polyolefin resins and the like can be mentioned.
Among these, from the viewpoint of obtaining a piezoelectric substrate excellent in piezoelectric sensitivity, it is preferable to include at least one selected from the group consisting of a cyanoacrylate resin and a polyester resin, and more preferable to include a cyanoacrylate resin. .

(Measurement of glass transition point)
In addition, the glass transition point of resin contained in a piezoelectric material and a functional layer was measured by the following method.
Using a dynamic viscoelastic device RSA-III manufactured by TA Instruments Inc., the temperature of the sample was raised in a nitrogen atmosphere from 0 to 150 ° C. at 3 ° C./min. The strain applied to the sample was 0.1%, and the frequency was 1 Hz. The temperature at which the loss elastic modulus (E ″) reached the maximum value was defined as the glass transition point (Tg).

The thickness of the functional layer is preferably 0.001 mm to 0.2 mm from the viewpoint of obtaining a piezoelectric substrate having excellent piezoelectric sensitivity. If the thickness is 0.001 mm or more, it is advantageous in that the functional layer maintains a high elastic modulus even in a high temperature environment, and that the thickness is 0.2 mm or less has excellent piezoelectric sensitivity. From the viewpoint of obtaining a piezoelectric substrate, it is preferably 0.1 mm or less, and more preferably 0.05 mm or less.
The width of the functional layer is preferably 0.1 mm or more, more preferably 0.2 mm or more from the viewpoint of maintaining durability, preventing breakage in covering processing when manufacturing a piezoelectric substrate, and improving yield. 0.3 mm or more is more preferable.
Further, from the viewpoint that flexibility is improved when the number of windings per unit length of the piezoelectric base material is large, the width of the functional layer is preferably 30 mm or less, more preferably 20 mm or less, and even more preferably 10 mm or less. .
The functional layer is preferably a layer coated with a long flat film having a width ratio with respect to the thickness of the functional layer of 2 or more.

The mode in which the functional layer is provided is not particularly limited.
The functional layer can be provided at any location. The outer peripheral side means the radially outer side of the inner conductor.
The functional layer may be provided, for example, between the inner conductor and the piezoelectric body, may be provided between the piezoelectric body and the outer conductor, or may be provided on the outermost layer of the piezoelectric substrate. May be.
The aspect in which the functional layer is provided between the internal conductor and the piezoelectric body includes an aspect in which the functional layer is provided directly on the outer peripheral surface of the internal conductor and an aspect in which the functional layer is provided through another layer. Moreover, the aspect provided in the outer peripheral surface of an internal conductor may be the aspect provided in the whole outer peripheral surface of an internal conductor, and the aspect provided in the surface except a part of outer peripheral surface.
Moreover, when using a tinsel wire for an internal conductor, the aspect which provides a functional layer between a center yarn and the conductor which coat | covers it may be sufficient.
In the piezoelectric substrate, the functional layer of the present disclosure may be provided with only one layer, or may be provided with two or more layers. When two or more functional layers are provided, the properties of each functional layer may be the same or different.

The method for forming the functional layer of the present disclosure is not particularly limited.
The functional layer is provided by, for example, applying or impregnating a resin dispersion, providing a long slit by spirally winding it in one direction, or forming a film-shaped one around the inner conductor. It can be provided by wrapping around in the direction, or can be formed by a conventionally known coating method.
The functional layer is preferably wound spirally along the outer peripheral surface of the inner conductor. In this case, it is preferable that the functional layer forms at least a part of the braid structure together with the piezoelectric body.

(Other layers)
The piezoelectric base material may be provided with other layers as required. The type of other layers is not particularly limited and can be selected according to the application. For example, it is preferably at least one selected from the group consisting of an antistatic layer, an antiblock layer, and an electrode layer. By providing the piezoelectric substrate with other layers, for example, application to piezoelectric devices, force sensors, actuators, and biological information acquisition devices becomes easier. Other layers may include only one layer or two or more layers, and may include different types of layers when two or more other layers are provided.

  When the piezoelectric substrate includes other layers, the piezoelectric substrate may be in a state where other layers are provided on at least one main surface side of the piezoelectric body. When other layers are provided on both main surfaces of the piezoelectric body, the other layers disposed on the front surface side and the other layers disposed on the back surface side are different even if they are the same layer. It may be a layer.

  The film thickness of the other layers is not particularly limited, but is preferably in the range of 0.01 μm to 10 μm. The upper limit value of the thickness is more preferably 6 μm or less, and further preferably 3 μm or less. Further, the lower limit is more preferably 0.01 μm or more, and further preferably 0.02 μm or more. When the other layer is composed of a plurality of layers, the thickness represents the total thickness of the plurality of other layers.

  In the piezoelectric substrate of the present disclosure, the other layer preferably includes an electrode layer. When the piezoelectric substrate includes an electrode layer, the piezoelectric substrate is used as one of the components of a piezoelectric device (piezoelectric fabric, piezoelectric knitted fabric, etc.), force sensor, actuator, biological information acquisition device, for example. Connection between the inner conductor and the outer conductor can be performed more easily. For this reason, when a tension is applied to the piezoelectric substrate, a voltage signal corresponding to the tension is easily detected.

  As an aspect in the case where the piezoelectric substrate includes other layers, there is a state of a laminate in which the other layers are arranged on at least one surface of the first piezoelectric body. In this case, the first other layer and the functional layer are in the state of a laminate, and it is preferable to have an electrode layer as a surface layer on one surface of the laminate.

  Hereinafter, the first to fifth embodiments of the piezoelectric substrate of the present disclosure will be described in order.

[First Embodiment]
FIG. 1A shows a side view of the coaxial line structure constituting the piezoelectric substrate according to the first embodiment, FIG. 1B shows a side view of the piezoelectric substrate according to the first embodiment, and FIG. FIG. 1B is a cross-sectional view taken along line XX ′ of 1B.
As shown in FIG. 1A, the coaxial line structure 10 constituting the piezoelectric substrate 100 (see FIG. 1B) includes a long internal conductor 12 </ b> A, a long piezoelectric body 14 </ b> A, and a functional layer 15. ing.
As shown in FIG. 1A, the piezoelectric body 14A is spirally wound in one direction along the outer circumferential surface of the inner conductor 12A from one end to the other end at a spiral angle β1 in a spiral shape without gaps so that the inner conductor 12A cannot be seen. Has been.
“Helix angle β1” means an angle formed by the axial direction G1 of the inner conductor 12A and the arrangement direction of the piezoelectric body 14A with respect to the axial direction of the inner conductor 12A.
In the coaxial line structure 10, the piezoelectric body 14 </ b> A is wound left-handed around the inner conductor 12 </ b> A. Specifically, when the coaxial line structure 10 is viewed from one end side in the axial direction of the internal conductor 12A (the right end side in the case of FIG. 1A), the piezoelectric body 14A extends from the near side to the far side of the internal conductor 12A. It is wound in a left-handed direction.
In FIG. 1A, the main orientation direction of the helical chiral polymer (A) contained in the piezoelectric body 14A is indicated by a double-pointed arrow E1. That is, the main orientation direction of the helical chiral polymer (A) and the arrangement direction of the piezoelectric body 14A (the length direction of the piezoelectric body 14A) are substantially parallel.
The functional layer 15 is provided on the outer peripheral surface of the inner conductor 12A and is located between the inner conductor 12A and the piezoelectric body 14A.
As shown in FIG. 1B, the piezoelectric substrate 100 according to the first embodiment is arranged with the outer conductor 16 wound in a spiral in one direction on the outer periphery of the coaxial line structure 10 shown in FIG. 1A. . That is, the piezoelectric substrate 100 includes a long internal conductor 12A, a functional layer 15, a long piezoelectric body 14A, and an external conductor 16 in order from the inside.

Hereinafter, the operation of the piezoelectric substrate 100 according to the first embodiment will be described.
For example, when a tension is applied in the length direction of the piezoelectric substrate 100, a shearing force is applied to the helical chiral polymer (A) included in the piezoelectric body 14A, and the helical chiral polymer (A) is polarized. The polarization of this helical chiral polymer (A) occurs in the radial direction of the piezoelectric substrate 100 (the radial direction of the coaxial line structure 10) as shown by the arrow in FIG. 1C, and the polarization direction is aligned in phase. It is thought that it occurs. This effectively detects a voltage signal proportional to the tension.
In particular, in the piezoelectric substrate 100 according to the first embodiment, the piezoelectric body 14A is spirally wound in one direction without gaps so that the inner conductor 12A is not visible along the outer peripheral surface of the inner conductor 12A. Adhesion between the inner conductor 12A and the piezoelectric body 14A is enhanced, and a gap is hardly formed between the inner conductor 12A and the outer conductor 16.
In particular, in the piezoelectric substrate 100 according to the first embodiment, the functional layer 15 is provided on the outer peripheral surface of the internal conductor 12A. Even when the piezoelectric substrate 100 is used in a high temperature environment, the piezoelectric substrate 100A is more than the piezoelectric body 14A. Since the influence of the tension applied to the piezoelectric body 14A is mitigated by the elastic force of the functional layer 15 including a resin having a high glass transition point, the orientation of the resin included in the piezoelectric body 14A is prevented from being lost. As a result, when tension is applied to the piezoelectric substrate 100, the piezoelectric substrate 100A is piezoelectric even when used in a higher temperature environment than a piezoelectric substrate that does not have a functional layer containing a resin having a glass transition point higher than that of the piezoelectric body 14A. Excellent sensitivity.
Therefore, according to the piezoelectric substrate 100, the piezoelectric sensitivity is excellent.

The piezoelectric substrate 100 according to the first embodiment is not limited to the above form. For example, in the piezoelectric substrate 100, an adhesive layer may be disposed between the inner conductor 12A and the piezoelectric body 14A. Thereby, even if tension is applied in the length direction of the piezoelectric substrate 100, the relative position between the piezoelectric body 14A and the inner conductor 12A is not easily displaced, and therefore tension is more easily applied to the piezoelectric body 14A.
In the piezoelectric substrate 100 according to the first embodiment, as described above, the functional layer 15 is provided between the inner conductor 12A and the piezoelectric body 14A. However, the functional layer may be appropriately provided in addition to this.
Further, in the piezoelectric substrate 100, the outer conductor 16 is spirally wound in one direction on the outer peripheral surface of the coaxial line structure 10, but the arrangement method of the outer conductor 16 is not limited thereto. That is, the outer conductor 16 only needs to be disposed on at least a part of the outer periphery of the piezoelectric body 14A. Further, the winding direction of the outer conductor 16 is not particularly limited.

  Next, the piezoelectric substrate according to the second embodiment will be described. In the following description, the same components as those of the piezoelectric substrate according to the first embodiment are denoted by the same reference numerals, and redundant descriptions are omitted.

[Second Embodiment]
FIG. 2A shows a side view of the coaxial line structure constituting the piezoelectric substrate according to the second embodiment, and FIG. 2B shows a side view of the piezoelectric substrate according to the second embodiment.
As shown in FIG. 2A, the coaxial line structure 10A constituting the piezoelectric substrate 100A (see FIG. 2B) has a long shape in addition to the piezoelectric body 14A (hereinafter referred to as “first piezoelectric body”). The piezoelectric substrate 100 according to the first embodiment is different from the piezoelectric substrate 100 according to the first embodiment in that the second piezoelectric body 14B is provided, and that the first piezoelectric body 14A and the second piezoelectric body 14B have a braided structure. Here, the chirality of the helical chiral polymer (A) contained in the first piezoelectric body 14A and the chirality of the helical chiral polymer (A) contained in the second piezoelectric body 14B are different from each other. In addition, the functional layer is provided in the second embodiment as in the first embodiment, but the illustration is omitted.
Specifically, as shown in FIG. 2A, the coaxial line structure 10A includes a first piezoelectric body 14A that is spirally wound left-handed from one end to the other end at a spiral angle β1 with respect to the axial direction G2 of the internal conductor 12A. The second piezoelectric body 14B is spirally wound in a spiral manner from one end to the other end at a spiral angle β2, and the first piezoelectric body 14A and the second piezoelectric body 14B are alternately crossed. And has a braid structure. That is, the first piezoelectric body 14A and the second piezoelectric body 14B form a braid structure on the outer peripheral surface of the internal conductor 12A so that the internal conductor 12A cannot be seen.
“Right-handed and spirally wound” means that when the coaxial line structure 10A is viewed from one end side in the axial direction of the internal conductor 12A (the right end side in the case of FIG. 2A), the second piezoelectric body 14B This means that the inner conductor 12A is wound clockwise from the near side toward the far side.
The “helical angle β2” is synonymous with the aforementioned helical angle β1.
In the braided structure of the coaxial line structure 10A, the main orientation direction (double arrow E1) of the helical chiral polymer (A) included in the first piezoelectric body 14A and the arrangement direction of the first piezoelectric body 14A are , Almost parallel. Similarly, the main orientation direction (double arrow E2) of the helical chiral polymer (A) included in the second piezoelectric body 14B and the arrangement direction of the second piezoelectric body 14B are substantially parallel.

  As shown in FIG. 2B, the piezoelectric substrate 100A according to the second embodiment is arranged such that the outer conductor 16 is spirally wound in one direction on the outer peripheral surface of the coaxial line structure 10A shown in FIG. 2A. Yes. That is, the piezoelectric substrate 100A includes a long inner conductor 12A, a first piezoelectric body 14A and a second piezoelectric body 14B having a braid structure, and an outer conductor 16 in order from the inside.

Hereinafter, the operation of the piezoelectric substrate 100A according to the second embodiment will be described.
For example, when a tension is applied in the longitudinal direction of the piezoelectric substrate 100A, the helical chiral polymer (A) included in the first piezoelectric body 14A and the helical chiral polymer (A) included in the second piezoelectric body 14B. ) A shear stress is applied to both, causing polarization. It is considered that the polarization directions are all generated in the radial direction of the piezoelectric substrate 100A (the radial direction of the coaxial line structure 10A) and the phases are aligned. This effectively detects a voltage signal proportional to the tension.
In particular, in the piezoelectric substrate 100A according to the second embodiment, the braid structure is formed by forming the braid structure with the first piezoelectric body 14A and the second piezoelectric body 14B along the outer peripheral surface of the internal conductor 12A. Compared with the case where the piezoelectric base material is not formed, the piezoelectric base material is flexibly deformed easily even when a force that causes the piezoelectric base material to bend and deform is applied. Thereby, for example, the amount of generated charges when a tensile force is applied to the piezoelectric substrate is likely to increase.
Therefore, according to the piezoelectric substrate 100A, the piezoelectric sensitivity is excellent.

  Next, a piezoelectric substrate according to the third embodiment will be described. In the following description, the same components as those of the piezoelectric base materials according to the first and second embodiments are denoted by the same reference numerals, and redundant description is omitted.

[Third Embodiment]
A piezoelectric substrate (not shown) according to the third embodiment is a piezoelectric substrate in which the second piezoelectric body 14B of the piezoelectric substrate 100A according to the second embodiment is replaced with a functional layer.
That is, in the piezoelectric substrate according to the third embodiment, the piezoelectric body 14A is spirally wound in a left-handed spiral from one end to the other end at a spiral angle β1 with respect to the axial direction G2 of the internal conductor 12A, and the functional layer spirals. A right-handed spiral is wound from one end to the other at an angle β2, and the piezoelectric body 14A and the functional layer are alternately crossed to form a braid structure.

In the piezoelectric substrate according to the third embodiment, when a functional layer having a flexibility equal to or greater than that of the piezoelectric body 14A is used as the functional layer, for example, when tension is applied in the length direction of the piezoelectric substrate, Shear stress is easily applied to the helical chiral polymer (A) contained in the piezoelectric body 14A. That is, polarization is likely to occur. This effectively detects a voltage signal proportional to the tension.
Also, in the piezoelectric base material according to the third embodiment, similarly to the piezoelectric base material according to the second embodiment, the braid structure is formed by the piezoelectric body and the functional layer, compared with the case where the braid structure is not formed. Even when a force that causes the piezoelectric base material to bend and deform works, it becomes flexible and easily deformed. Thereby, for example, the amount of generated charges when a tensile force is applied to the piezoelectric substrate is likely to increase.
Therefore, the piezoelectric substrate according to the third embodiment also has excellent piezoelectric sensitivity.

By forming a braid structure between the piezoelectric body and the functional layer, the thickness of the entire piezoelectric base material can be reduced, and at the same time, the initial sensitivity of the piezoelectric base material can be improved. Furthermore, the presence of a resin having a high glass transition point can suppress a decrease in sensitivity due to thermal history.
In addition, the piezoelectric base material which concerns on 3rd Embodiment is not limited to the said form. For example, the winding direction of the functional layer is not limited to the above form. Further, for example, a melt-spun PLA may be used for the piezoelectric body 14A, or a PET film may be used for the functional layer. At this time, the melt-spun PLA and PET film form a braided structure.

[Piezoelectric Substrates of Fourth and Fifth Embodiments]
Hereinafter, the piezoelectric substrate according to the fourth embodiment and the fifth embodiment will be described. Although the method for providing the functional layer in the fourth embodiment and the fifth embodiment is omitted, the functional layer may be provided in the same manner as in the first embodiment or in other modes. The aspect of the functional layer and how to provide it are as described above.
The piezoelectric substrate of the present disclosure is not limited to a configuration in which electric charge (electric field) generated when a tension is applied is taken out as a voltage signal. It may be configured to take out as

  The piezoelectric substrate 100B of the fourth embodiment and the piezoelectric substrate 100C of the fifth embodiment include a long internal conductor 12A as an internal conductor and a long piezoelectric body, as shown in FIGS. 14A, an adhesive layer (not shown) disposed between the inner conductor 12A and the piezoelectric body 14A, and an outer conductor 13 disposed on the outer surface of the piezoelectric body 14A. Moreover, in the piezoelectric base materials 100B and 100C, the piezoelectric body 14A is spirally wound around the inner conductor 12A in the main orientation direction (double arrow E1), and the helical chiral polymer contained in the piezoelectric body 14A. The main orientation direction (double arrow E1) of (A) and the arrangement direction of the piezoelectric body 14A are substantially parallel.

  The piezoelectric substrate 100B of the fourth embodiment is a homopolymer (PLLA) in which the helical chiral polymer (A) contained in the piezoelectric body 14A is L-lactic acid, while the piezoelectric substrate 100C of the fifth embodiment is The helical chiral polymer (A) contained in the piezoelectric body 14A is a D-lactic acid homopolymer (PDLA). 4 and 5 show the relationship between the twist direction and the generated polarization direction in the piezoelectric substrate 100B of the fourth embodiment, and FIG. 6 shows the relationship between the twist direction and the generated polarization direction in the piezoelectric substrate 100C of the fifth embodiment. As shown in FIG.

  In FIG. 4, when a torsional force in the direction of the arrow X1 is applied to the piezoelectric substrate 100B with the helical axis as a central axis, a shearing stress is applied to the piezoelectric body 14A wound in a spiral shape, and from the central direction of the circular cross section. PLLA polarization occurs in the outward direction. On the other hand, in FIG. 5, when a torsional force in the direction of the arrow X2 opposite to the arrow X1 direction is applied to the piezoelectric substrate 100B with the helical axis as the central axis, a shear stress is applied to the spirally wound piezoelectric body 14A. Thus, the polarization of PLLA occurs from the outer side of the circular cross section toward the center. Therefore, in the piezoelectric substrate 100B, a charge (electric field) proportional to the torsional force is generated, and the generated charge is detected as a voltage signal (charge signal).

  In FIG. 6, when a torsional force in the direction of arrow X1 is applied to the piezoelectric substrate 100C with the helical axis as the central axis, a shearing stress is applied to the spirally wound piezoelectric body 14A, and the outer side of the circular cross section. PDLA polarization occurs from the direction toward the center. On the other hand, in FIG. 7, when a torsional force in the direction of the arrow X2 opposite to the direction of the arrow X1 is applied to the piezoelectric substrate 100C with the helical axis as the central axis, a shearing stress is applied to the piezoelectric body 14A wound spirally. Thus, the polarization of PDLA occurs from the center direction of the circular cross section toward the outer side. Accordingly, a charge (electric field) proportional to the torsional force is generated in the piezoelectric substrate 100C, and the generated charge is detected as a voltage signal (charge signal).

<Method for manufacturing piezoelectric substrate>
Although there is no particular limitation on the method for manufacturing a piezoelectric substrate of the present disclosure, for example, a piezoelectric body is prepared, and a separately prepared internal conductor (preferably a signal line conductor) is covered with the piezoelectric body (preferably And can be manufactured by arranging an outer conductor (preferably a ground conductor) on the outer periphery of the piezoelectric body.
The piezoelectric body may be manufactured by a known method or may be obtained.
Moreover, the piezoelectric base material of this indication may be equipped with the 1st piezoelectric material and the 2nd piezoelectric material, and also the insulator as a piezoelectric material. Such a piezoelectric substrate can be manufactured according to a method of winding the first piezoelectric body in a spiral shape.
However, the winding directions of the first piezoelectric body and the second piezoelectric body, and the chirality of the helical chiral polymer (A) contained in the first piezoelectric body and the second piezoelectric body are as follows. It is preferable to select appropriately according to the embodiment.
In addition, you may stick together between each member with which the piezoelectric base material of this indication is provided between at least one of an internal conductor and an external conductor, and a piezoelectric material as needed.

<Usage of piezoelectric substrate>
In the piezoelectric substrate of the present disclosure (for example, the piezoelectric substrate according to the first embodiment), for example, by applying a tensile force, a shear strain proportional to the tensile force is applied to the helical chiral (A), and a voltage signal ( The charge signal is detected from at least one of the inner conductor and the outer conductor. There are various methods for applying a tensile force to the piezoelectric substrate, such as a method of directly applying a tension to the piezoelectric substrate, or using an adhesive tape 51 on the flat plate 52 as shown in FIGS. 8A and 8B. A piezoelectric substrate 100 (a piezoelectric substrate according to the first embodiment, hereinafter the same) is attached to form a piezoelectric substrate 50 with a flat plate, a pressing force is applied to the flat plate 52, and the piezoelectric substrate is subjected to bending deformation that occurs on the flat plate 52. A voltage signal may be detected by applying tension to the material 100. 8A is a schematic view showing the piezoelectric substrate 100 (the piezoelectric substrate 50 with a flat plate) on which the flat plate 52 is attached using the adhesive tape 51, and FIG. It is the schematic when pressing the attached piezoelectric substrate 100 (piezoelectric substrate with a flat plate 50).

  Various methods may be used as a method for attaching the piezoelectric substrate 100 to the flat plate 52 and mechanically integrating them. For example, as shown in FIG. 9, a method of attaching a part of the piezoelectric substrate 100 to the flat plate 52 using an adhesive tape 51 such as a cellophane tape or a gummed tape, and a thermosetting property such as an epoxy resin as shown in FIG. Examples thereof include a method of attaching a part of the piezoelectric substrate 100 to the flat plate 52 using an adhesive 61 such as an adhesive or a thermoplastic adhesive such as a hot melt adhesive.

  In the piezoelectric substrate 60 with a flat plate in FIG. 9, a part of the piezoelectric substrate 100 is attached to the flat plate 52 using the adhesive tape 51, and an FPC (flexible printed circuit board) 54 is disposed on the flat plate 52. A copper foil 53 that is electrically connected to the piezoelectric substrate 100 is disposed on the FPC 54. Further, the piezoelectric substrate 60 with a flat plate includes a signal processing circuit unit 55 that detects and processes a piezoelectric signal detected by applying a tensile force to the piezoelectric substrate 100. Further, in the piezoelectric substrate 70 with a flat plate in FIG. 10, the above-mentioned piezoelectric substrate with a flat plate is the same as that described above except that a part of the piezoelectric substrate 100 is attached to the flat plate 52 using an adhesive 61 instead of the adhesive tape 51. The same as the substrate 60.

  In addition to the above-described flat plate, the piezoelectric substrate may be attached to the inside or the outside of a casing of an electronic circuit composed of a curved surface or the like.

<Application of piezoelectric substrate>
The piezoelectric substrate of the present disclosure is used for various ball games such as sensor applications (force sensors such as seating sensors, pressure sensors, displacement sensors, deformation sensors, vibration sensors, ultrasonic sensors, biological sensors, rackets, golf clubs, and bats). Accelerometers and impact sensors for hitting sports equipment, plush touch / impact sensors, bed guard sensors, security sensors such as glass and window frames), actuator applications (sheet transport devices, etc.), energy harvesting applications (Power generation wear, power generation shoes, etc.), Health care related applications (T-shirts, sportswear, spats, socks and other clothing, supporters, casts, diapers, baby wheelbarrow seats, wheelchair seats, medical incubators This sensor is installed on mats, shoes, insoles, watches, etc. , It can be used as such as a wearable sensor or the like).
In addition, the piezoelectric substrate of the present disclosure includes various clothing (shirts, suits, blazers, blouses, coats, jackets, blousons, jumpers, vests, dresses, trousers, pants, underwear (slip, petticoats, camisole, bras), socks, gloves, Japanese clothes, obi, gold candy, cool clothing, tie, handkerchief, scarf, scarf, stall, eye mask), supporters (neck supporter, shoulder supporter, chest supporter, abdominal supporter, waist supporter, arm supporter, Foot supporter, elbow supporter, knee supporter, wrist supporter, ankle supporter), footwear (sneakers, boots, sandals, pumps, mules, slippers, ballet shoes, kungfu shoes), insole, towel, rucksack, hat (Hat, cap, Jacket, hunting cap, ten gallon hat, tulip hat, sun visor, beret), hat chin strap, helmet, helmet chin strap, hood, belt, seat cover, sheets, cushion, cushion, duvet, duvet cover, blanket, pillow, Pillowcase, sofa, chair, desk, table, seat, seat, toilet seat, massage chair, bed, bed pad, carpet, basket, mask, bandage, rope, plush, various nets, bathtub, wall material, flooring, window material , Window frame, door, door knob, PC, mouse, keyboard, printer, housing, robot, musical instrument, prosthetic hand, artificial leg, bicycle, skateboard, roller skates, rubber ball, shuttlecock, handle, pedal, fishing rod, fishing float , Fishing reel, fishing rod receiver, lure, switch, safe, fence, ATM Handles, dials, bridges, buildings, structures, tunnels, chemical reaction vessels and their piping, pneumatic equipment and piping, hydraulic equipment and piping, steam pressure equipment and piping, motors, electromagnetic solenoids, gasoline engines, etc. It is arranged in articles and used for sensors, actuators, and energy harvesting applications.
Examples of the arrangement method include various methods such as sewing a piezoelectric substrate into an object, sandwiching the piezoelectric substrate with the object, and fixing the object to the object with an adhesive.
For example, piezoelectric fabrics, piezoelectric knitted fabrics, and piezoelectric devices can be applied to these applications.
Among the applications described above, the piezoelectric substrate of the present disclosure is preferably used as a sensor application or an actuator application.
Specifically, the piezoelectric base material of the present disclosure is preferably used by being mounted on a force sensor or by being mounted on an actuator.
In addition, the piezoelectric substrate, piezoelectric fabric, piezoelectric knitted fabric, and piezoelectric device described above can switch FETs by applying a voltage generated by stress between the gate and source of a field effect transistor (FET). It can also be used as a switch that can be turned on and off.
The piezoelectric substrate of the present disclosure can also be used for other uses other than those described above.
Other uses include bedding for rollback detection, carpet for movement detection, insole for movement detection, chest band for respiratory detection, mask for respiratory detection, arm band for detection of creaking, Examples include a leg band for detecting slipping, a seat for detecting sitting, a stuffed toy, and a stuffed toy social robot that can determine a contact state. In a stuffed toy, stuffed toy social robot, etc. that can determine the contact state, for example, a pressure sensor is detected by a contact sensor locally disposed on the stuffed toy, etc., so that a person `` strokes '' the stuffed toy etc. It is possible to discriminate each operation such as whether it is “pulled” or not.
In addition, the piezoelectric substrate of the present disclosure can be used, for example, in an in-vehicle application; an automotive handle grip detection application using vibration / acoustic sensing; an in-vehicle device operation system application using a resonance spectrum using vibration / acoustic sensing; It is particularly suitable for vibration body applications, automobile door and automobile window pinching detection sensor applications, vehicle body vibration sensor applications, and the like.

  A known extraction electrode can be bonded to the piezoelectric substrate of the present disclosure. Examples of the extraction electrode include electrode parts such as connectors and crimp terminals. The electrode component can be bonded to the piezoelectric substrate by brazing such as soldering, a conductive bonding agent, or the like.

[Force sensor]
A force sensor according to the present disclosure includes the piezoelectric substrate described above.
Since the force sensor according to the present disclosure includes a piezoelectric substrate having excellent piezoelectric sensitivity, improvement in sensor sensitivity is expected.
Hereinafter, specific modes of the force sensor according to the embodiment of the present disclosure will be described with reference to the drawings.
FIG. 11 is a conceptual diagram of a force sensor according to the present disclosure.
The force sensor 40 according to the present disclosure includes a piezoelectric substrate 100D, a cylindrical rubber-based heat-shrinkable tube (hereinafter also simply referred to as “shrinkable tube”) 44 disposed on the outer periphery of the piezoelectric substrate 100D, and a shrinkable tube 44. And a pair of crimping terminals (extraction electrodes) 46 disposed at both ends. The pair of crimp terminals 46 includes a main body portion 46a and a crimp portion 46b, and has a through hole 46c at the center. The piezoelectric substrate 100D includes an inner conductor 12C, a piezoelectric body 14D spirally wound around the inner conductor 12C in one direction, and an outer periphery spirally wound around the outer periphery of the piezoelectric body 14D. A conductor 42 (ground conductor).
In the piezoelectric substrate 100 </ b> D, one end (the right end in FIG. 11) of the inner conductor 12 </ b> C extends to the outside of the contraction tube 44, is crimped by the crimping portion 46 b, and is electrically connected to the crimping terminal 46. On the other hand, the outer conductor 42 is wound from one end side to the other end side of the inner conductor 12C and then extends beyond the other end (left end in FIG. 11) of the inner conductor 12C. A stress relaxation portion 42 a is formed in the contraction tube 44.
After passing through the stress relaxation part 42a, the outer conductor 42 extends further to the outer side of the contraction tube 44 (the left end in FIG. 11), is crimped by the crimping part 46b, and is electrically connected to the crimping terminal 46. .
As shown in FIG. 11, the stress relaxation portion 42 a includes a slack outer conductor 42. In the stress relaxation part 42a, when a tension (stress) is applied to the force sensor 40, an excessive force is suppressed from being applied to the piezoelectric body 14D by extending a slack portion.
The piezoelectric body 14D is made of a long plate-shaped piezoelectric body, and an aluminum vapor deposition film (not shown) is vapor-deposited as a functional layer on both surfaces. The pair of crimp terminals 46 are connected to an external circuit (not shown) that processes the output signal of the force sensor 40.
In the embodiment shown in FIG. 11, the loose outer conductor 42 is disposed as the stress relaxation portion 42a. However, the embodiment of the present disclosure is not limited to this, and at least one of the piezoelectric base materials 100D is not limited thereto. A function to relieve stress may be imparted to the force sensor 40 by disposing a linear stress relieving portion at the end portion or both end portions so that tension is transmitted by a method such as adhesion or yarn knot.
At this time, the linear stress relaxation part does not have an electrical connection function. However, the electrical connection function is independent of the stress relaxation part, and connects the inner conductor and the outer conductor from the end of the piezoelectric base material to the coaxial cable. For example, stress or strain voltage signals can be detected.
At this time, the material and form of the stress relieving part are not particularly limited. For example, a thread, string, tube, etc. made of elastic elastic material such as natural rubber, silicon rubber, urethane rubber, etc .; metal material such as phosphor bronze, wire And a spring made of a polymer or the like. By placing the stress relaxation part and the electrical connection part independently at different sites, there is no restriction on the amount of strain of the stress relaxation part due to the maximum extension of the electrical connection part, and the maximum strain as a tension sensor. The amount can be increased.

Hereinafter, the operation of the force sensor 40 of the present disclosure will be described.
When tension (stress) is applied to the force sensor 40, tension is applied to the piezoelectric substrate 100D, and shear force is applied to the helical chiral polymer (A) contained in the piezoelectric body 14D of the piezoelectric substrate 100D. Due to the force, the helical chiral polymer (A) is polarized in the radial direction of the piezoelectric substrate 100D. The polarization direction is the radial direction of the piezoelectric substrate 100D. Thereby, a charge (electric field) proportional to the tension is generated, and the generated charge is detected as a voltage signal (charge signal). The voltage signal is detected by an external circuit or the like (not shown) connected to the crimp terminal 46.
Therefore, the force sensor 40 has excellent sensitivity.
Moreover, since the force sensor 40 of the present disclosure includes the same coaxial line structure (internal conductor 12C and piezoelectric body 14D) as the internal structure provided in the coaxial cable, it can have a high electromagnetic shielding property and a structure resistant to noise. In addition, since the structure is simple, the wearable sensor can be used by being worn on a part of the body, for example.

  The force sensor of the present disclosure is not limited to a configuration in which an electric charge (electric field) generated when a tension is applied to the piezoelectric substrate is taken out as a voltage signal. For example, the force sensor is generated when a torsional force is applied to the piezoelectric substrate. The structure which takes out an electric charge (electric field) as a voltage signal may be sufficient.

[Actuator]
An actuator according to the present disclosure includes the piezoelectric substrate described above.
Since the actuator according to the present disclosure includes a piezoelectric substrate having excellent piezoelectric sensitivity, an improvement in sensitivity is expected.

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

<Production of piezoelectric body>
NatureWorks LLC Inc. polylactic acid as a helical chiral polymer (product ^name: Ingeo TM Biopolymer, brand: 4032D) with respect to 100 parts by weight of stabilizer [manufactured by Rhein Chemie Corporation Stabaxol P400 (10 parts by weight), manufactured by Rhein Chemie Corporation Stabaxol I (70 parts by mass) and Nisshinbo Chemical Carbodilite LA-1 (20 parts by mass)] 1.0 part by mass was added and dry blended to prepare a raw material.
The prepared raw material was put into an extrusion molding machine hopper, extruded from a T-die while being heated to 210 ° C., and contacted with a cast roll at 50 ° C. for 0.3 minutes to form a pre-crystallization sheet having a thickness of 150 μm ( Pre-crystallization step). The crystallinity of the pre-crystallized sheet was measured and found to be 6%.
The obtained pre-crystallized sheet was stretched at a stretching speed of 10 m / min by roll-to-roll while heating to 70 ° C., and uniaxially stretched in the MD direction up to 3.5 times (stretching step). The thickness of the obtained film was 49.2 μm.
Thereafter, the uniaxially stretched film was roll-rolled and contacted on a roll heated to 145 ° C. for 15 seconds for annealing treatment, and then rapidly cooled to produce a piezoelectric film (annealing step).
Next, the piezoelectric film was slit using a slitting machine so that the slitting direction and the extending direction of the piezoelectric film were substantially parallel. As a result, a ribbon-like piezoelectric body (slit ribbon) having a width of 0.39 mm and a thickness of 50 μm was obtained. The obtained piezoelectric body had a rectangular cross-sectional shape.
Further, the glass transition point of the obtained piezoelectric body was 68.8 ° C.

-Measurement of physical properties of piezoelectric material-
The following physical property measurements were performed on the ribbon-like piezoelectric body obtained as described above. The results are shown in Table 1.
The measurement is performed using a wide-angle X-ray diffractometer (RINT2550, manufactured by Rigaku Corporation, attached device: rotating sample stage, X-ray source: CuKα, output: 40 kV 370 mA, detector: scintillation counter), and a sample (piezoelectric body) in the holder. The measurement was performed by fixing and measuring the azimuth distribution intensity of the crystal plane peak [(110) plane / (200) plane].
In the obtained azimuth distribution curve (X-ray interference diagram), the degree of orientation F (C-axis orientation) of polylactic acid was calculated and evaluated from the following formula from the crystallinity and the half-value width (α) of the peak. . As a result, the degree of crystallinity was 45% and the degree of orientation F was 0.97.
Degree of orientation (F) = (180 ° −α) / 180 °
(Α is the half width of the peak derived from orientation)

<Relative permittivity of piezoelectric material>
The measurement was performed in accordance with JIS C2151 (2006) using a dielectric constant measuring device (Precision LCR meter HP4284A manufactured by Agilent Technologies) at a measurement frequency of 1 kHz, a test environment of 22 ° C., and 60% RH. As a result, the dielectric constant ε _S of the piezoelectric body (slit ribbon) was 2.75.

[Example 1]
<Production of piezoelectric substrate>
A piezoelectric substrate provided with a copper foil ribbon as an outer conductor (ground conductor) on a piezoelectric substrate having the same configuration as that of the piezoelectric substrate 10 shown in FIG. 1A was produced by the following method.
First, as an internal conductor (signal line conductor), Meishin Sangyo Kinshi Line U24-01-00 (wire outer diameter: 0.3 mm, length: 250 mm) was prepared. In addition, the used tinsel wire uses a meta-aramid fiber (twisted 40 counts) for the center line, and uses two rolled copper foils (width 0.3 mm × thickness 0.02 mm), and the center line is exposed. In order to avoid this, 22 times per 10 mm, a left-handed spiral was wound twice in a spiral manner and included. Crimp terminals were crimped and provided at both ends of the tinsel wire as electrical connection portions and mechanical connection portions.
Next, the ribbon-shaped piezoelectric body (slit ribbon) having a width of 0.6 mm and a thickness of 49.2 μm obtained as described above is wound around the tinsel wire in a left-handed manner and is 45 ° with respect to the major axis direction of the tinsel wire. It was wound in a spiral shape without gaps so that the tinsel line was exposed and could not be seen so as to face the direction (spiral angle 45 °), and the tinsel line was wrapped around. Note that “left-handed” means a ribbon-like piezoelectric element from the front side to the back side of the signal line conductor when viewed from one axial end (in the case of FIG. 1A, the right end side) of the signal line conductor. It means that the body is wound left-handed.
Next, in order to mechanically integrate the tinsel wire and the ribbon-shaped piezoelectric body, Aron Alpha (cyanoacrylate adhesive) 911P2 manufactured by Toagosei Co., Ltd. is used as an adhesive on the portion where the ribbon-shaped piezoelectric body is wound. A functional layer was prepared by dripping and impregnation.
Next, a copper foil ribbon with an adhesive slit to a width of 0.6 mm was prepared. The copper foil ribbon was wrapped and wrapped around the ribbon-shaped piezoelectric body without gap so as not to expose the ribbon-shaped piezoelectric body by the same method as the ribbon-shaped piezoelectric body.
As described above, the piezoelectric substrate of Example 1 was obtained.
The tinsel wire corresponds to the inner conductor 12A in FIG. 1A. The ribbon-like piezoelectric body corresponds to the piezoelectric body 14A in FIG. 1A. Although not shown in FIG. 1A, the adhesive is disposed between the inner conductor 12A and the piezoelectric body 14A. The ground conductor is also not shown in FIG. 1A.

<Evaluation>
Those shown in Table 2 below were applied to the surface (outermost layer) of the piezoelectric line, and temperature-sensitivity characteristics were measured.
Further, using the obtained piezoelectric substrate of Example 1, the amount of charge generated when a tensile force was applied to the piezoelectric substrate (generated charge amount) was measured, and the generated charge per unit tensile force was determined from the generated charge amount. The amount was calculated. Further, for Example 1, the amount of generated charge due to temperature change was also evaluated, and the rate of change with respect to the initial value was obtained. The results are shown in Table 3.

Detailed information on the products shown in Table 2 is shown below.
・ "Almatex L1043 (trade name)" ... Acrylic resin, manufactured by Mitsui Chemicals, Ltd. ・ "Aron Alpha # 911P2 (trade name)" ... Cyanoacrylate adhesive, manufactured by Toagosei Co., Ltd. "" Aron Alpha # 901H2 (product) Name) ”… cyanoacrylate adhesive, manufactured by Toagosei Co., Ltd.“ Aron Alpha # 901H3 (trade name) ”... cyanoacrylate adhesive, manufactured by Toagosei Co., Ltd.,“ Aron Alpha # 201 ”... cyanoacrylate Adhesive, manufactured by Toagosei Co., Ltd.

As shown in Table 3, in Examples 1 to 5, the rate of change with respect to the initial value is smaller than the piezoelectric substrate of Comparative Example 1 in that the amount of generated charge per unit tensile force with respect to temperature change is small. The piezoelectric substrate was excellent in piezoelectric sensitivity.
This is because the slit ribbon (piezoelectric body) is provided with a functional layer higher than the glass transition point of the piezoelectric body, so that the functional layer of a material (material having a Tg higher than PLA) that can maintain a high elastic modulus even in a high temperature environment. It is considered that the stress on the slit ribbon (piezoelectric body) was relaxed by preventing the collapse of the orientation direction of the slit ribbon (piezoelectric body).

<Production of piezoelectric substrate>
Next, as shown in FIG. 12, a piezoelectric substrate 101 was produced by interposing a PET film as the functional layer 15 between the piezoelectric body 14 </ b> A and the external conductor 16.
Specifically, the tinsel wire used in Example 1 as the internal conductor 12A and the ribbon-shaped piezoelectric material used in Example 1 as the piezoelectric body 14A are integrated without using an adhesive, and the PET film is formed on the ribbon-shaped piezoelectric body. (Tg of about 100 ° C.) was covered (the winding accuracy was not particularly limited), and a piezoelectric substrate provided with the copper foil ribbon used in Example 1 as an outer conductor (ground conductor) was produced. The temperature-sensitivity characteristics of the obtained piezoelectric substrate were measured. The results are shown in Table 4.

  As shown in Table 4, the piezoelectric substrates of Examples 6 and 7 are piezoelectric in that the sensitivity does not decrease from the initial value (that is, the rate of change is not negative) compared to the piezoelectric substrate of Comparative Example 3. It can be said that there was an effect of preventing body orientation deterioration. The sensitivity is higher than the initial value because the piezoelectric base materials of Examples 6 and 7 do not use an adhesive, and therefore each layer wound when a tensile force is applied to the piezoelectric base material. This is considered to be due to the tightness of the winding and the decrease in the gaps between the layers.

10, 10A coaxial line structure, 12A, 12C inner conductor, 14A, 14D piezoelectric body (first piezoelectric body), 13, 16, 42 outer conductor, 14B second piezoelectric body, 15 functional layer, 22 tinsel wire, 24 Slit Ribbon, 26 Copper Foil Ribbon, 40 Force Sensor, 42a Stress Relaxation Part, 44 Shrinkable Tube, 46 Crimp Terminal, 46a Main Body Part, 46b Crimp Part, 46c Through Hole, 50, 60, 70 Piezoelectric Base with Flat Plate, 51 Adhesive tape, 52 flat plate, 53 copper foil, 55 signal processing circuit unit, 61 adhesive, 100, 100A, 100B, 100C, 100D, 101 piezoelectric substrate

Claims (15)

A long inner conductor;
A piezoelectric body covering the outer peripheral surface of the inner conductor;
An outer conductor disposed on the outer periphery of the piezoelectric body,
Having a functional layer containing a resin having a glass transition point higher than that of the piezoelectric body;
Piezoelectric substrate.   The piezoelectric substrate according to claim 1, wherein the resin includes at least one selected from the group consisting of a cyanoacrylate resin and a polyester resin.   A long plate-shaped film in which the functional layer has a thickness of 0.001 mm to 0.2 mm, a width of 0.1 mm to 30 mm, and a ratio of the width to the thickness of 2 or more. The piezoelectric substrate according to claim 1 or 2, wherein the piezoelectric substrate is a coated layer. The piezoelectric body includes a helical chiral polymer (A) having optical activity,
The length direction of the piezoelectric body and the main orientation direction of the helical chiral polymer (A) included in the piezoelectric body are substantially parallel,
The piezoelectric substrate according to any one of claims 1 to 3, wherein an orientation degree F of the piezoelectric body obtained by the following formula (a) is in a range of 0.5 or more and less than 1.0.
Degree of orientation F = (180 ° −α) / 180 ° (a)
(In the formula (a), α represents the half width of the peak derived from the orientation measured by X-ray diffraction.)   The piezoelectric body includes a stabilizer (B) 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 weight average molecular weight of 200 to 60,000, and the helical chiral polymer ( A) The piezoelectric substrate according to claim 4, comprising 0.01 to 10 parts by mass with respect to 100 parts by mass. The piezoelectric according to claim 4 or 5, wherein the helical chiral polymer (A) contained in the piezoelectric material is a polylactic acid polymer having a main chain containing a structural unit represented by the following formula (1). Base material.
  The piezoelectric substrate according to any one of claims 1 to 6, wherein the piezoelectric body has a long shape and is spirally wound in one direction along the outer peripheral surface of the internal conductor. A long inner conductor;
A piezoelectric body covering the outer peripheral surface of the inner conductor;
A functional layer covering a peripheral surface of the inner conductor and containing a resin having a glass transition point higher than that of the piezoelectric body, wherein the functional layer forms at least a part of a braided structure together with the piezoelectric body When,
An outer conductor disposed on the outer periphery of the piezoelectric body and the functional layer;
A piezoelectric substrate comprising:   The piezoelectric substrate according to any one of claims 1 to 8, wherein the piezoelectric body is wound while maintaining an angle of 15 ° to 75 ° with respect to an axial direction of the inner conductor. . The piezoelectric body has a fiber shape;
The piezoelectric base material according to any one of claims 1 to 9, wherein an average major axis diameter of a section of the piezoelectric body perpendicular to the major axis direction of the inner conductor is 0.0001 mm or more and 10 mm or less. The piezoelectric body has a long flat plate shape,
The average thickness of the piezoelectric body is 0.001 mm or more and 0.2 mm or less,
The width of the piezoelectric body is 0.1 mm or more and 30 mm or less,
11. The piezoelectric substrate according to claim 1, wherein a ratio of a width of the piezoelectric body to an average thickness of the piezoelectric body is 2 or more.   The piezoelectric substrate according to any one of claims 1 to 11, further comprising at least one selected from the group consisting of an antistatic layer, an antiblock layer, and an electrode layer.   The piezoelectric substrate according to claim 1, wherein the inner conductor is a tinsel wire.   A force sensor comprising the piezoelectric substrate according to any one of claims 1 to 13.   An actuator provided with the piezoelectric base material of any one of Claims 1-13.