JP2018182009A - Piezoelectric substrate, force sensor, and actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric base material having excellent piezoelectric sensitivity. SOLUTION: A piezoelectric base material 100 spirals a long inner conductor 12A and an outer peripheral surface of the inner conductor 12A from one end to the other end at a spiral angle β1 in one direction so that the inner conductor 12A cannot be seen. It includes a long first piezoelectric body 14A that is wound and covered without a gap, and an outer conductor 16 arranged on the outer periphery of the first piezoelectric body 14A, and satisfies the following formula (a). Capacitance measured value / theoretical capacitance value ≧ 0.5 ・ ・ (a) [Selection diagram] Fig. 1B

Description

  The present disclosure relates to piezoelectric substrates, force sensors, and actuators.

In recent years, application of a piezoelectric material containing a helical chiral polymer to a piezoelectric device such as a sensor or an actuator has been considered. A film-shaped piezoelectric body is used for such a piezoelectric device.
Attention has been focused on the use of polymers having optical activity such as polypeptides and polylactic acid-based polymers as helical chiral polymers in the piezoelectric body. Among them, polylactic acid-based polymers are known to exhibit piezoelectricity only by mechanical stretching operation. It is known that a piezoelectric material using a polylactic acid-based polymer does not require poling treatment, and that 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).
Also, recently, attempts have been made to use a material having piezoelectricity by coating it on a conductor.
For example, a piezoelectric cable is known which is composed of a center conductor, a piezoelectric material layer, an outer conductor, and an outer jacket coaxially arranged in order from the center to the outer side (see, for example, Patent Document 3).
There is also known a piezoelectric unit obtained by coating a conductive fiber with a fiber made of a piezoelectric polymer (see, for example, Patent Document 4).

Patent No. 4934235 gazette International Publication No. 2010/104196 Japanese Patent Application Laid-Open No. 10-132669 International Publication No. 2014/058077

By the way, when a film-shaped piezoelectric body (for example, the piezoelectric body in the embodiments of Patent Documents 1 and 2) is used in a place having large unevenness or a place having a large amount of deformation (for example, used as a part or all of wearable products In the case where the piezoelectric body is deformed, the piezoelectric body is broken and damages such as wrinkles occur. As a result, the piezoelectric sensitivity (for example, the sensor sensitivity when the piezoelectric body is used as a sensor) and the piezoelectric body when used as an actuator Operating sensitivity, same below.) May decrease.
Further, Patent Document 3 describes a piezoelectric cable composed of a central conductor, a piezoelectric material layer, an outer conductor, and an outer sheath coaxially arranged in order from the center to the outer side as described above, and a polyfluoroelectric material is used as the piezoelectric material. Vinylidene fluoride (PVDF) is described. However, in PVDF, the variation of the piezoelectric constant is observed with time, and the piezoelectric constant may decrease with time. Further, since PVDF is a ferroelectric substance, it has pyroelectric properties, and therefore, the piezoelectric signal output may fluctuate due to a change in temperature around it. Therefore, in the piezoelectric cable described in Patent Document 3, the stability of the piezoelectric sensitivity may be insufficient.
Further, in Patent Document 4, as a piezoelectric unit formed by coating a fiber made of a piezoelectric polymer (hereinafter referred to as a piezoelectric fiber), for example, a braided tube or a braided cord made of a piezoelectric fiber is electrically conductive. Piezoelectric units are described which are wound around fibers. However, in the piezoelectric unit described in Patent Document 4, when the piezoelectric fiber is constituted by a braided tube or a braided cord, a space is easily formed between the inner conductor and the outer conductor, so that the piezoelectric sensitivity may be insufficient. Therefore, in the piezoelectric fiber described in Patent Document 4, the piezoelectric sensitivity may be insufficient.

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

  The specific means for achieving the said subject are as follows.

<1> A long inner conductor, a first piezoelectric body covering an outer peripheral surface of the inner conductor, and an outer conductor disposed on the outer periphery of the first piezoelectric body, the following formula (a A piezoelectric substrate that satisfies
Measured value of capacitance / theoretical value of capacitance ≧ 0.5 · · · (a)
<2> The first piezoelectric body includes a helical chiral polymer (A) having optical activity,
The length direction of the first piezoelectric body and the main alignment direction of the helical chiral polymer (A) contained in the first piezoelectric body are substantially parallel to each other,
The piezoelectric substrate according to <1>, wherein the orientation degree F of the first piezoelectric body determined by the following formula (b) is in the range of 0.5 or more and less than 1.0.
Degree of orientation F = (180 ° -α) / 180 ° ··· (b)
(In formula (b), α represents the half width of the peak derived from the orientation measured by X-ray diffraction.)
<3> The first piezoelectric body is 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 carbodiimide group, epoxy group, and isocyanate group, The piezoelectric base material as described in <2> containing 0.01 mass part-10 mass parts with respect to 100 mass parts of said helical chiral polymer (A).

<4> The helical chiral polymer (A) contained in the first piezoelectric substance is a polylactic acid-based polymer having a main chain containing a structural unit represented by the following formula (1) <2> or The piezoelectric base material as described in 3>.

<5> In any one of <1> to <4>, the first piezoelectric body is elongated and spirally wound in one direction along the outer peripheral surface of the inner conductor. The piezoelectric substrate of description.
<6> A long second piezoelectric member wound in a direction different from the one direction along the outer peripheral surface of the inner conductor, further comprising:
The second piezoelectric body includes a helical chiral polymer (A) having optical activity,
The length direction of the second piezoelectric body and the main alignment direction of the helical chiral polymer (A) contained in the second piezoelectric body are substantially parallel to each other,
The orientation degree F of the second piezoelectric body determined by the equation (b) from X-ray diffraction measurement is in the range of 0.5 to less than 1.0,
The first piezoelectric body and the second piezoelectric body have a braid structure alternately crossed.
The piezoelectric according to <5>, wherein the chirality of the helical chiral polymer (A) contained in the first piezoelectric body and the chirality of the helical chiral polymer (A) contained in the second piezoelectric body are different from each other Base material.
<7> Furthermore, it comprises an insulator wound along the outer peripheral surface of the inner conductor,
The piezoelectric substrate according to <5>, which has a braid structure in which the first piezoelectric body and the insulator are alternately crossed.
<8> Any one of <5> to <7>, wherein the first piezoelectric body is wound while maintaining an angle of 15 ° to 75 ° with respect to the axial direction of the inner conductor The piezoelectric substrate as described in.
<9> The first piezoelectric body has a fiber shape,
The piezoelectric group according to any one of <1> to <8>, wherein an average major axis diameter of a cross section orthogonal to the major axis direction of the internal conductor of the first piezoelectric body is 0.0001 mm to 10 mm. Material.
<10> The first piezoelectric body has a long flat plate shape,
The average thickness of the first piezoelectric body is 0.001 mm to 0.2 mm,
The width of the first piezoelectric body is 0.1 mm to 30 mm,
The piezoelectric substrate according to any one of <1> to <8>, wherein the ratio of the width of the first piezoelectric body to the average thickness of the first piezoelectric body is 2 or more.
The piezoelectric base material as described in any one of <1>-<10> further provided with a <11> functional layer.
<12> The piezoelectric group according to <11>, wherein the functional layer is at least one selected from the group consisting of an adhesive layer, a hard coat layer, an antistatic layer, an antiblock layer, a protective layer, and an electrode layer. Material.
<13> The piezoelectric substrate according to <11> or <12>, wherein the functional layer includes an electrode layer.
<14> The piezoelectric substrate according to <13>, wherein the first piezoelectric body and the functional layer are in a laminate state, and the electrode layer is provided as a surface layer on one surface of the laminate.
<15> The piezoelectric substrate according to any one of <1> to <14>, wherein the internal conductor is a tinsel wire.
The piezoelectric base material as described in any one of <1>-<15> further equipped with an adhesive layer between the <16> above-mentioned internal conductor and the said 1st piezoelectric material.

The force sensor provided with the piezoelectric base material as described in any one of <17> <1>-<16>.

The actuator provided with the piezoelectric base material as described in any one of <18> <1>-<16>.

  According to the present disclosure, a piezoelectric substrate excellent in piezoelectric sensitivity, and a force sensor and an actuator using the piezoelectric substrate are 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 a piezoelectric substrate concerning a 1st embodiment. It is the X-X 'sectional view taken on the line of FIG. 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 substrate concerning a 2nd embodiment. It is a schematic cross section along the I-I line which shows the state which further arrange | positioned the outer conductor to the photograph of the coaxial line structure of Example 1, and a coaxial line structure. It is a schematic cross section along the II-II line which shows the state which has arrange | positioned the outer conductor further to the photograph of the coaxial line structure of the comparative example 1, and a coaxial line structure. It is a schematic cross section along the III-III line which shows the state which has arrange | positioned the outer conductor further to the photograph of the coaxial line structure of the comparative example 2, and a coaxial line structure. In the piezoelectric base material of this indication, it is a schematic diagram of the coaxial line structure for demonstrating the calculation method of electrostatic capacitance theoretical value. 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 arrow X 1 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 arrow X 2 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 arrow X 1 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 arrow X 2 direction is applied. It is the schematic which shows the piezoelectric base material which concerns on 1st Embodiment which stuck the flat plate using the adhesive tape. It is the schematic at the time of 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 base material which concerns on 1st Embodiment which stuck the flat plate using the adhesive tape. It is an example of the piezoelectric base material which concerns on 1st Embodiment which stuck the flat plate using the adhesive agent. 1 is a conceptual view of a force sensor according to an embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described. The present disclosure is not limited to the following embodiments.
In the present specification, a numerical range represented using “to” means a range including numerical values described before and after “to” as the lower limit value and the upper limit value.
In the present specification, the “main surface” of the long flat plate-like piezoelectric material (the first piezoelectric material and the second piezoelectric material) means the plane orthogonal to the thickness direction of the long flat plate-like piezoelectric material For example, it means a plane including the length direction and the width direction.
In the present specification, the "surface" of a member means the "principal surface" of the member unless otherwise specified.
In the present specification, the thickness, width and length satisfy the relationship of thickness <width <length as defined in the ordinary.
In the present specification, an angle formed by two line segments is represented by a range of 0 ° or more and 90 ° or less.
In the present specification, “film” is a concept encompassing not only what is generally called “film” but also what is generally called “sheet”.
In the present specification, the “MD direction” is the machine direction of the film (ie, the stretching direction), and the “TD direction” is orthogonal to the MD direction and parallel to the main surface of the film ( Transverse Direction).
When an embodiment of the present invention is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Further, the sizes of the members in the respective drawings are conceptual, and the relative relationship between the sizes of the members is not limited thereto.

[Piezoelectric substrate]
The piezoelectric substrate of the present disclosure includes an elongated inner conductor, a first piezoelectric body covering an outer peripheral surface of the inner conductor, and an outer conductor disposed on the outer periphery of the first piezoelectric body. , The following formula (a) is satisfied.
Measured value of capacitance / theoretical value of capacitance ≧ 0.5 · · · (a)

Here, “electrostatic capacitance measured value / electrostatic capacitance theoretical value 0.50.5” in the above-mentioned formula (a) indicates that the capacitance measured value of the piezoelectric substrate is larger than that of the conventional one. ing.
In the piezoelectric substrate of the present disclosure, when the tension (which may be a twisting force or the like, and the same applies hereinafter) is applied to the piezoelectric substrate by satisfying the above-mentioned equation (a), the above-mentioned equation (a) is obtained. The amount of generated charge increases compared to a piezoelectric substrate that is not satisfied. As a result, a piezoelectric substrate excellent in piezoelectric sensitivity is realized.
Moreover, since the piezoelectric base material of this indication equips the outer periphery of a 1st piezoelectric material with an outer conductor, it is a structure which can be electrostatically shielded. Thereby, the voltage change of the internal conductor due to the influence of the external static electricity is easily suppressed.
In addition, "the outer periphery" means the outer peripheral part of a 1st piezoelectric material.

First, the method of calculating the “capacitance theoretical value” in the above equation (a) will be described with reference to FIG.
FIG. 6 is a schematic view of a coaxial line structure for explaining a calculation method of theoretical capacitance in the piezoelectric base material of the present disclosure.
The conductor has the function of storing charge. An amount representing how much charge can be stored is referred to as a capacitance, which is defined by the amount of charge stored per unit voltage as in the following formula 1.

Formula 1: C = Q / V
In Formula 1, C represents capacitance [F], Q represents charge amount [C], and V represents voltage [V].

Assuming that the coaxial line structure 30 shown in FIG. 6 is a coaxial line structure consisting of the inner conductor 32 and the first piezoelectric body 34 in the present disclosure, the electrostatic capacity per unit length of the coaxial line structure 30 is taken. The theoretical capacity value [F / m] is expressed by the following equation 2. The lengths of the internal conductor 32 and the first piezoelectric member 34 are both L [m].
In the piezoelectric base material of the present disclosure, the value calculated by the following formula 2 is used as the “capacitance theoretical value” of the piezoelectric base material in the above formula (a).

Equation _{2: C = 2πε 0 ε S} / ln (b / a)
C: Capacitance per unit length [F / m]
a: Average radius of the inner conductor 32 [m]
b: total length of the average radius [m] of the inner conductor 32 and the average thickness T [m] of the first piezoelectric body 34 ε ₀ : dielectric constant of vacuum (8.85 × 10 ⁻¹² ) [F / M]
ε _S : relative dielectric constant of first piezoelectric body 34 [-]

The measuring method of the "capacitance measurement value" in the said Formula (a) is demonstrated.
The “capacitance measurement value” in the above formula (a) is a value measured using a Yokogawa Hewlett Packard precision LCR meter HP 4284A.
The measurement conditions will be described in the section of Examples.

A method of measuring the “average thickness T of the first piezoelectric body 34” in the above-described equation 2 will be described.
The average thickness T of the first piezoelectric body 34 is a value measured by the following method using the piezoelectric substrate of the present disclosure.
An arbitrary cross section orthogonal to the long axis direction of the piezoelectric substrate is observed by SEM (scanning electron microscope), the thickness of the first piezoelectric body is measured at any six places in the above cross section, and the average value is measured The average thickness T of the piezoelectric body of 1 is taken.
That is, the average thickness T of the first piezoelectric member means the gap between the inner conductor and the first piezoelectric member, and the gap between the first piezoelectric member and the outer conductor (that is, the gap between the inner conductor and the outer conductor) It means the value calculated without considering).
Further, when the first piezoelectric body has a braided structure with another member (for example, the second piezoelectric body, an insulator, etc.), the surface of the braided structure has a bulged portion (convex portion) and a dented portion (convexity) There is a recess). In such a case, when observing an arbitrary cross section orthogonal to the long axis direction of the piezoelectric substrate, the thickness of any three places corresponding to the convex part of the braid structure and the optional three places corresponding to the concave part ( That is, the thickness (thickness) of the braided structure is measured, and the average value thereof is taken as the average thickness T of the first piezoelectric body.

A method of measuring the “average radius a of the inner conductor 32” in the above-described equation 2 will be described.
The average radius a of the inner conductor 32 is a value measured by the following method using the piezoelectric substrate of the present disclosure.
First, measure the average diameter of the inner conductor. Specifically, any cross section orthogonal to the long axis direction of the piezoelectric substrate is observed by SEM (scanning electron microscope), and the sum of the maximum diameter and the minimum diameter of the inner conductor in the above cross section is divided by 2 Value is defined as "average diameter of inner conductor". The average radius a of the inner conductor 32 is a value obtained by dividing the above “average diameter of the inner conductor” by two.

  In the piezoelectric substrate of the present disclosure, assuming that the average radius of the inner conductor calculated as described above is “a” in the equation 2, the sum of the average radius of the inner conductor and the average thickness T of the first piezoelectric body Let "b" in said Formula 2 be the length of.

Here, although the “electrostatic capacitance measured value / electrostatic capacitance theoretical value” is 0.5 or more, the piezoelectric substrate of the present disclosure “electrostatic capacitance measured value / static capacitance” from the viewpoint of further improving the piezoelectric sensitivity. The theoretical capacitance value is preferably 0.6 or more, and more preferably 0.7 or more.
The upper limit of “capacitance measurement value / capacitance theoretical value” is preferably 1, but it is preferably 0.95 or less from the viewpoint of manufacturing suitability of the piezoelectric substrate, and 0.9 It is more preferable that it is the following, and it is more preferable that it is 0.8 or less.

In the present disclosure, a piezoelectric substrate satisfying the capacitance measurement value / the capacitance theoretical value ≧ 0.5 can be easily obtained by adjusting the method of coating the first piezoelectric body on the outer peripheral surface of the inner conductor.
As a method of covering the first piezoelectric body, the first piezoelectric body is covered so that the inner conductor can not be seen on the outer peripheral surface of the inner conductor and the adjacent first piezoelectric bodies do not overlap with each other (preferably Is preferably spirally wound in one direction.
As a result, an air layer (gap) having a relative dielectric constant lower than that of the first piezoelectric member is less likely to be formed between the inner conductor and the outer conductor, and the electrostatic capacitance is likely to be larger (see Equation 2).
More specifically, the inner conductor and the outer peripheral surface of the inner conductor are covered by covering the first piezoelectric body so that the inner conductor can not be seen and the adjacent first piezoelectric bodies do not overlap with each other. Since the gap between the outer conductors is adjusted to be small, the capacitance measurement value can more easily approach the theoretical capacitance value. As a result, the capacitance is increased and the piezoelectric sensitivity is improved.
Further, in the above-described covering method, when the first piezoelectric body is spirally wound in one direction around the outer peripheral surface of the inner conductor, it is preferable to adjust the number of turns of the first piezoelectric body. As a result, the exposure of the inner conductor can be easily suppressed, and hence the capacitance can be further increased.
The number of turns of the first piezoelectric body may be appropriately selected according to the diameter of the internal conductor, the thickness and the width of the first piezoelectric body, and the like.

  Next, preferred embodiments of the piezoelectric substrate of the present disclosure will be described.

In the piezoelectric substrate of the present disclosure,
The first piezoelectric body includes a helical chiral polymer (A) having optical activity,
The length direction of the first piezoelectric body and the main alignment direction of the helical chiral polymer (A) contained in the first piezoelectric body are substantially parallel to each other,
It is preferable that the orientation degree F of the first piezoelectric body determined by the following formula (b) be in the range of 0.5 or more and less than 1.0.
Degree of orientation F = (180 ° -α) / 180 ° ··· (b)
(In formula (b), 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 first piezoelectric body is an index indicating the degree of orientation of the helical chiral polymer (A) contained in the first piezoelectric body, and, for example, a wide-angle X-ray diffractometer (manufactured by RIGAKU Co., Ltd.) RINT 2550, attached device: rotating sample stage, X-ray source: CuKα, output: 40 kV, 370 mA, detector: scintillation counter)
In addition, an example of a method of measuring the degree of orientation F of the first piezoelectric body is as shown in Examples described later.

More specifically, in the piezoelectric substrate of the above aspect, the first piezoelectric body includes the helical chiral polymer (A), and the length direction of the first piezoelectric body and the main orientation of the helical chiral polymer (A) Piezoelectricity is expressed by the fact that the direction is substantially parallel and the orientation degree F of the first piezoelectric member is 0.5 or more and less than 1.0.
As a result, when, for example, tension is applied to the piezoelectric substrate, the generated charge amount is further increased.

Further, in the piezoelectric base material of the present disclosure, it is preferable that the first piezoelectric body is elongated, and spirally wound in one direction along the outer peripheral surface of the inner 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 inner conductor, the first piezoelectric body is wound from the front side to the back side of the inner conductor. Say the direction in which you are Specifically, it means rightward (right-handed or clockwise) or left-handed (left-handed or counterclockwise).

In addition, since the first piezoelectric body is elongated, the first piezoelectric body can be easily disposed in a spiral shape in one direction while maintaining the helical angle β with respect to the axial direction of the internal conductor.
Here, “helical angle β” refers to the axial direction of the inner conductor and the direction in which the first piezoelectric body is disposed with respect to the axial direction of the inner conductor (the length direction of the first piezoelectric body). Means an angle.
Thereby, for example, when tension is applied in the longitudinal direction of the piezoelectric substrate, polarization of the helical chiral polymer (A) is easily generated in the radial direction of the piezoelectric substrate. As a result, a voltage signal (charge signal) proportional to tension is effectively detected, and the piezoelectric sensitivity is likely to be improved.
Furthermore, since the piezoelectric substrate of the present disclosure comprises the same coaxial line structure (inner conductor and dielectric) as the internal structure provided in the coaxial cable, for example, when the above-mentioned piezoelectric substrate is applied to a coaxial cable, electromagnetic It can be a structure that is highly shielding and resistant to noise.

In the piezoelectric substrate of the present disclosure, from the viewpoint of improving the piezoelectric sensitivity, the first piezoelectric member has an angle (that is, a helical angle) of 15 ° to 75 ° (45 ° ± 30 °) with respect to the axial direction of the inner conductor. It is preferable to hold | maintain winding (beta), and it is more preferable to hold | maintain holding the angle of 35 degrees-55 degrees (45 degrees +/- 10 degrees).
By this, when tension (stress) is applied in the longitudinal direction of the piezoelectric substrate, a shear force is easily applied to the helical chiral polymer (A), and the helical chiral polymer (A) in the radial direction of the piezoelectric substrate Polarization is likely to occur.
Further, in the piezoelectric substrate of the present disclosure, when a tension (stress) is applied in the longitudinal direction of the piezoelectric substrate by arranging the first piezoelectric body in a spiral in one direction, the helical chiral polymer A shearing force is applied to (A), and polarization of the helical chiral polymer (A) occurs in the radial direction of the piezoelectric substrate. When the first piezoelectric body spirally wound is regarded as an aggregate of minute regions that can be regarded as a plane in the longitudinal direction, the polarization direction is the plane of the minute regions constituting the first piezoelectric body. When a shear force caused by tension (stress) is applied to the helical chiral polymer, the direction of the electric field generated due to the piezoelectric constant d ₁₄ substantially matches.
Specifically, for example, in polylactic acid, in the case of L-lactic acid homopolymer (PLLA) whose molecular structure is a left-handed helical structure, the first piezoelectric body in which the main orientation direction of PLLA and the length direction are approximately parallel is used. When tension (stress) is applied to the left-handed helically wound structure with respect to the inner conductor, the radial direction is parallel to the outside from the center of the circle of the circular cross section perpendicular to the tension. An electric field (polarization) is generated. Also, contrary to this, in the structure in which the first piezoelectric body whose length direction is substantially parallel to the main orientation direction of PLLA is spirally wound on the inner conductor in a right-handed manner, tension (stress) When is applied, an electric field (polarization) is generated parallel to the radial direction from the outside to the center of the circle of the circular cross section perpendicular to the tension.

Also, for example, in the case of a homopolymer of D-lactic acid (PDLA) whose molecular structure is a right-handed helical structure, the first piezoelectric body whose length direction is substantially parallel to the main orientation direction of PDLA is compared to the internal conductor, When tension (stress) is applied to the structure wound spirally in the left-handed direction, the electric field (polarization) from the outside to the center of the circle of the circular cross section perpendicular to the tension is approximately parallel to the radial direction. Occur. Also, contrary to this, tension (stress) in a structure in which the first piezoelectric body whose length direction is substantially parallel to the main orientation direction of PDLA is spirally wound on the inner conductor in a right-handed manner. When is applied, an electric field (polarization) is generated parallel to the radial direction from the center of the circle of the circular cross section perpendicular to the tension.
As a result, when tension is applied in the longitudinal direction of the piezoelectric substrate, potential differences proportional to the tension occur at the same phase at each portion of the first piezoelectric body disposed in a spiral, It is believed that a voltage signal proportional to tension is effectively detected.
As a result, it is easy to obtain a piezoelectric substrate that is more excellent in piezoelectric sensitivity.
In addition, the piezoelectric base material of the present disclosure includes a structure in which a piezoelectric body is spirally wound around the inner conductor in a right-handed manner and a part of the piezoelectric body is spirally wound around a left-handed body. May be In the case of spirally winding a part of the piezoelectric body in the left-handed direction, it is preferable that the left-handed ratio is less than 50% with respect to the whole (total of right-handed and left-handed) from the viewpoint of suppressing decrease in piezoelectric sensitivity. .
In addition, the piezoelectric base material of the present disclosure includes a structure in which a piezoelectric body is spirally wound to the left and a part of the piezoelectric body is spirally wound to the right. May be In the case of spirally winding a part of the piezoelectric body in the right-handed direction, the proportion of the right-handed region is less than 50% with respect to the entire (total of right-handed and left-handed) from the viewpoint of suppressing the decrease in piezoelectric sensitivity. Is preferred.

Here, the fact that the length direction of the first piezoelectric body and the main orientation direction of the helical chiral polymer (A) are substantially parallel means that the first piezoelectric body is resistant to tension in the length direction ((1) That is, it has the advantage of being excellent in the tensile strength in the longitudinal direction. Therefore, even if the first piezoelectric body is spirally wound in one direction with respect to the inner conductor, it is difficult to break it.
Furthermore, the fact that the longitudinal direction of the first piezoelectric body and the main orientation direction of the helical chiral polymer (A) are substantially parallel means that, for example, the stretched piezoelectric film is slit to form the first piezoelectric body. It is also advantageous in terms of productivity in obtaining (for example, a slit ribbon).
In the present specification, “substantially parallel” means that an 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).
Further, 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 first piezoelectric body.
When the raw material is melt-spun and drawn to produce the first piezoelectric body, the main orientation direction of the helical chiral polymer (A) in the manufactured first piezoelectric body is the main drawing direction. means. The main stretching direction refers to the stretching direction.
Similarly, in the case of producing a first piezoelectric body by forming a drawn film and a slit of the drawn film, the main orientation direction of the helical chiral polymer (A) in the manufactured first piezoelectric body is mainly It means the stretching 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.

In addition, the piezoelectric base material of the present disclosure further includes an elongated second piezoelectric body spirally wound in a direction different from the one direction along the outer peripheral surface of the inner conductor,
The second piezoelectric body includes a helical chiral polymer (A) having optical activity,
The length direction of the second piezoelectric body and the main orientation direction of the helical chiral polymer (A) contained in the second piezoelectric body are substantially parallel;
The orientation degree F of the second piezoelectric body determined by the above equation (b) from X-ray diffraction measurement is in the range of 0.5 or more and less than 1.0,
The first piezoelectric body and the second piezoelectric body have a braid structure alternately crossed,
It is also preferable that the chirality of the helical chiral polymer (A) contained in the first piezoelectric body and the chirality of the helical chiral polymer (A) contained in the second piezoelectric body are different from each other.
Thus, for example, when tension is applied in the longitudinal direction of the piezoelectric substrate, the helical chiral polymer (A) contained in the first piezoelectric body and the helical chiral polymer contained in the second piezoelectric body Polarization occurs in both (A). The polarization directions are all in the radial direction of the piezoelectric substrate.
Thereby, a voltage signal proportional to tension can be detected more effectively. As a result, the piezoelectric sensitivity can be more easily improved.
Further, by forming the braided structure with the first piezoelectric body and the second piezoelectric body, the flexible substrate is flexible even when a force is applied that causes the piezoelectric substrate to be flexible, as compared with the case where the braided structure is not formed. It becomes easy to bend and deform. Therefore, the piezoelectric substrate having the braid structure is suitable as one component of, for example, a wearable product (for example, a piezoelectric fabric, a piezoelectric fabric, a piezoelectric device, a force sensor, a biological information acquisition device, etc.) along a three-dimensional plane. It can be used for
However, from the viewpoint of satisfying the capacitance measurement value / the capacitance theoretical value 圧 電 0.5, it is preferable that the gap between the first piezoelectric body and the second piezoelectric body be smaller.

In addition, the piezoelectric substrate of the present disclosure further includes an insulator wound along the outer circumferential surface of the inner conductor,
It is also preferable that the first piezoelectric body and the insulator form a braid structure alternately crossed.
As a result, when the piezoelectric base material is bent and deformed, the first piezoelectric body can be easily held in one direction with respect to the inner conductor.
However, from the viewpoint that tension is easily applied to the first piezoelectric body, it is preferable that the gap between the first piezoelectric body and the insulator be smaller.

  Next, the inner conductor, the first piezoelectric body, the outer conductor, and the like included in the piezoelectric substrate of the present disclosure will be described.

<Internal 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 first piezoelectric body. More specifically, it is a conductor for detecting a voltage signal (charge signal) corresponding to the applied tension when tension is applied to the piezoelectric substrate.

The inner conductor can be a cord-like object provided with a core and a conductor A covering the periphery of the core. The inner conductor of such a configuration is also referred to as a tinsel wire.
Moreover, a conductive fiber can also be used as an internal conductor. Any conductive fiber may be used as the conductive fiber, and any known fiber may be used. For example, metal fibers, fibers made of a conductive polymer, carbon fibers, fibrous or particulate conductive fillers are dispersed. And fibers obtained by providing a layer having conductivity on the surface of a fibrous material. As a method of providing the layer which has electroconductivity on the surface of a fibrous material, a metal coat, a conductive polymer coat, winding of a conductive fiber etc. are mentioned. Among them, metal coatings are preferred from the viewpoints of conductivity, durability, flexibility and the like. Specific methods for coating a metal include vapor deposition, sputtering, electrolytic plating, electroless plating and the like, but electrolytic plating or electroless plating is preferable from the viewpoint of productivity and the like. Such metal-plated fibers can be referred to as metal-plated fibers.

  By appropriately selecting the types of core material and conductor A, a piezoelectric substrate suitable for high flexibility and flexibility (for example, applications such as wearable sensors installed in clothes) can be obtained.

  Specifically, for example, a structure in which a metal foil is spirally wound around a core material such as a fiber obtained by twisting a short fiber such as cotton yarn, a polyester fiber, a nylon fiber such as nylon yarn, etc. What has is mentioned.

  When metal foil is wound around a core material and an internal conductor is produced, it is preferable that metal foil is flat wire shape. A flat rectangular wire metal foil can be produced by rolling a metal wire or slitting the metal foil into a narrow width. By forming the metal foil into a rectangular wire shape, it is possible to reduce the gap with the first piezoelectric body wound around the inner conductor and to improve the adhesion to the first piezoelectric body. As a result, it becomes easy to detect the charge variation generated from the first piezoelectric body, and the sensitivity to tension is further improved.

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

  Although the material in particular of metal foil is not restrict | limited, Copper foil is preferable. By using copper with high electrical conductivity, it is possible to reduce the output impedance. Therefore, when 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. In addition, since the copper foil fits into the deformation of the elastic deformation region at the time of bending deformation and becomes less likely to be plastically deformed, metal fatigue failure hardly occurs and it becomes possible to remarkably improve the repeated bending resistance.

  The core material in the inner conductor is located at the center of the inner conductor and has a function as a structural material to support tension. By appropriately selecting the material, the cross-sectional area, and the like of the core material, it is possible to design according to the values of the tension, the amount of strain, and the like applied to the internal conductor.

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

<First piezoelectric body>
The piezoelectric substrate of the present disclosure comprises a first piezoelectric body.
The first 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-like 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 flat plate-like piezoelectric body-
By using a long flat plate-like piezoelectric member as the first piezoelectric member, the contact surface to the internal conductor can be enlarged, and the charge generated by the piezoelectric effect can be efficiently detected as a voltage signal.
Hereinafter, the dimensions of the long flat piezoelectric material will be described in more detail.

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

  The width of the long flat 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 flat piezoelectric material is 0.1 mm or more, sufficient strength tends to be secured. Furthermore, it tends to be excellent also in manufacturing aptitude (for example, the manufacturing aptitude in the slit process mentioned later). On the other hand, when the width of the long flat piezoelectric material is 30 mm or less, the degree of freedom (flexibility) of deformation tends to be improved.

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

  It is more preferable that the width of the long flat piezoelectric body is 0.5 mm to 15 mm. When the width of the long flat piezoelectric material is 0.5 mm or more, the strength tends to be further improved. Furthermore, since the twist of the long flat plate-like piezoelectric material 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 flat piezoelectric material is 15 mm or less, the degree of freedom (flexibility) of deformation of the long flat piezoelectric material tends to be further improved.

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

There is no limitation in particular in the manufacturing method of a long flat plate-like piezoelectric material, It can manufacture by a well-known method.
For example, as a method for producing a long flat plate-like piezoelectric material from a piezoelectric film, a raw material is formed into a film to obtain an unstretched film, and the obtained unstretched film is subjected to stretching and crystallization. The piezoelectric film can be obtained by slitting (cutting the piezoelectric film into a long shape).
Alternatively, the long flat piezoelectric body may be manufactured using a known flat yarn manufacturing method. For example, after a wide film obtained by inflation molding is slit into a narrow film, stretching by heat plate stretching, stretching by roll stretching, and crystallization are performed to obtain a long flat plate-like piezoelectric body. It is also good.
In addition, as for the said extending | stretching and crystallization, any may be first. Alternatively, the unstretched film may be sequentially subjected to preliminary crystallization, stretching, and crystallization (annealing). Stretching may be uniaxial stretching or biaxial stretching. In the case of biaxial stretching, preferably the stretching ratio of one (main stretching direction) is increased.
With respect to a method of producing a piezoelectric film, publicly known documents such as Japanese Patent No. 4934235, International Publication No. 2010/104196, International Publication No. 2013/054918, International Publication No. 2013/089148, etc. can be referred to as appropriate.

-Fibrous piezoelectric material-
By using a fibrous piezoelectric material as the first piezoelectric material, it can be used as a form excellent in flexibility and flexibility, and efficiently detecting the charge generated by the piezoelectric effect as a voltage signal Is possible.
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 several fibers) are mentioned.
Hereinafter, the dimensions of the fibrous piezoelectric material will be described in more detail.
The average major axis diameter (hereinafter, also simply referred to as “major axis diameter”) of the cross section of the fibrous piezoelectric body orthogonal to the major axis direction of the internal conductor is 0.0001 mm to 10 mm from the viewpoint of improving the piezoelectric sensitivity Is preferable, 0.001 mm to 5 mm is more preferable, and 0.002 mm to 1 mm is further preferable.
If the major axis diameter of the fibrous piezoelectric material 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 material is 10 mm or less, the degree of freedom (flexibility) of deformation of the fibrous piezoelectric material tends to be further improved.
Here, "the major axis diameter of the cross section" corresponds to the "diameter" when the cross section of the fibrous piezoelectric body is circular.
In the case where the cross section of the fibrous piezoelectric material 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 material is a piezoelectric material composed of fiber bundles, "the major axis diameter of the cross section" is the major diameter of the cross section of the piezoelectric material composed of the fiber bundles.
Specifically, examples of fibrous piezoelectric materials include monofilament yarns and multifilament yarns.

Monofilament Yarn The single yarn fineness of the monofilament yarn is preferably 3 dtex to 30 dtex, and 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 tends to occur between the yarns.
The monofilament yarn is preferably obtained by direct spinning and drawing in consideration of cost. The monofilament yarn may be one obtained.

Multifilament Yarn The total fineness of the multifilament yarn is preferably 30 dtex to 600 dtex, and more preferably 100 dtex to 400 dtex.
As the multifilament yarn, for example, in addition to one-step yarn such as spin-draw yarn, any two-step yarn obtained by drawing UDY (undrawn yarn) or POY (highly oriented undrawn yarn) can be adopted. . The multifilament yarn 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 is no limitation in particular in the manufacturing method of a fibrous piezoelectric material, It can manufacture by a well-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 ambient temperature in the vicinity of the yarn until cooling and solidification in a constant temperature range.
Also, the filament yarn may be obtained, for example, by further separating the filament yarn obtained by the above-mentioned melt spinning drawing method.

(Helical chiral polymer (A))
The first 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 molecular structure and molecular optical activity.

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

  The helical chiral polymer (A) preferably has an optical purity of 95.00% ee or more, and more preferably 96.00% ee or more, from the viewpoint of improving the piezoelectricity of the first piezoelectric body. And 99.00% ee or more is more preferable, and 99.99% ee or more is even more preferable. Desirably, it is 100.00% ee. By setting the optical purity of the helical chiral polymer (A) in the above range, it is considered that the packing property of the polymer crystal expressing piezoelectricity is enhanced, and as a result, the piezoelectricity is enhanced.

Here, the optical purity of the helical chiral polymer (A) is a value calculated by the following equation.
Optical purity (% ee) = 100 × | L volume-D volume | / (L volume + D volume)
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 [mass%] of D form of helical chiral polymer (A)” to “helical chiral polymer "(N) divided by the total amount of the amount of L-form (mass%) of (A) [mass%] and the amount of the D-form of helical chiral polymer (A) (mass%)" (Multiplied) value.

  The amount of L form [mass%] of the helical chiral polymer (A) and the amount [mass%] of the D form of the helical chiral polymer (A) are obtained by a method using high performance liquid chromatography (HPLC). Use the value 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 enhancing the optical purity and improving the piezoelectricity.

As a polymer which has a structural unit represented by the said Formula (1) as a principal chain, polylactic acid type polymer is mentioned.
Here, the polylactic acid-based polymer refers to “polylactic acid (polymer having only a structural unit derived from a monomer selected from L-lactic acid and D-lactic acid)”, “L-lactic acid or D-lactic acid, -A copolymer of lactic acid or a compound copolymerizable with D-lactic acid "or a mixture of both.
Among polylactic acid-based polymers, polylactic acid is preferred, and homopolymers of L-lactic acid (PLLA, also simply referred to as "L-form") or homopolymers of D-lactic acid (PDLA, also simply referred to as "D-form") are most preferred. preferable.

Polylactic acid is a polymer in which lactic acid is polymerized by ester bonds and is long connected.
It is known that polylactic acid can be produced by a lactide method via lactide; a direct polymerization method in which lactic acid is heated under reduced pressure in a solvent and polymerized while removing water;
As polylactic acid, homopolymers of L-lactic acid, homopolymers of D-lactic acid, block copolymers containing polymers of at least one of L-lactic acid and D-lactic acid, and at least one of L-lactic acid and D-lactic acid Included are graft copolymers comprising a polymer.

  Examples of the above-mentioned "compounds 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-hydroxybutanoic acid Hydroxy valeric acid, 3-hydroxy valeric acid, 4-hydroxy valeric acid, 5-hydroxy valeric acid, 2-hydroxy caproic acid, 3-hydroxy caproic acid, 4-hydroxy caproic acid, 5-hydroxy caproic acid, 6-hydroxy caprone Acid, 6-hydroxymethyl caproic acid, hydroxycarboxylic acid such as mandelic acid; glycolide, β-methyl-δ-valerolactone, γ-valerolactone, cyclic ester such as ε-caprolactone; oxalic acid, malonic acid, succinic acid, Glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, ung Polyvalent carboxylic acids such as cannic acid, dodecanedioic acid and terephthalic acid and anhydrides thereof; 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 acid; and the like.

  As the above-mentioned “copolymer of L-lactic acid or D-lactic acid and a compound copolymerizable with the L-lactic acid or D-lactic acid”, a block copolymer or graft copolymer having a polylactic acid sequence capable of forming helical crystals is used. It 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-based polymer, a structure derived from lactic acid and a structure derived from a compound copolymerizable with lactic acid (copolymer component) in the polylactic acid-based polymer The concentration of the structure derived from the copolymer component is preferably 20 mol% or less based on the sum of the number of moles of and.

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

  Furthermore, in order to make the optical purity 95.00% ee or more, for example, when polylactic acid is produced by the lactide method, the polylactic acid-based polymer obtained by each of the above-mentioned production methods is subjected to the optical purity by crystallization operation. It is preferable to polymerize lactide which has been improved to an optical purity of 95.00% ee or more.

-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 the Mw of the helical chiral polymer (A) is 50,000 or more, the mechanical strength of the first 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 1,000,000 or less, the formability at the time of obtaining the first piezoelectric body by forming (for example, extrusion forming, 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 1.2 to 4 from the viewpoint of the strength of the first piezoelectric body. More preferable. Furthermore, it is preferable that it is 1.4-3.

The weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) of the helical chiral polymer (A) refer to values measured using gel permeation chromatography (GPC). Here, Mn is the number average molecular weight of the helical chiral polymer (A).
Hereafter, an example of the measuring method of Mw and Mw / Mn of helical chiral polymer (A) by GPC is shown.

-GPC measuring device-
GPC-100 manufactured by Waters
-Column-
Showa Denko KK Shodex LF-804
-Preparation of sample-
The first piezoelectric body is dissolved in a solvent (eg, 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 flow rate of 1 ml / min with a solvent [chloroform] at a temperature of 40 ° C.

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

A commercially available polylactic acid can be used as a polylactic acid-type polymer which is an example of a 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 a polylactic acid-based polymer is used as the helical chiral polymer (A), the polylactic acid polymer can have a weight-average molecular weight (Mw) of 50,000 or more by the lactide method or direct polymerization method. It is preferable to produce a system polymer.

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

(Stabilizer)
The first piezoelectric body may further contain a stabilizer having a weight average molecular weight of 200 to 60,000 having one or more functional groups selected from the group consisting of carbodiimide group, epoxy group, and isocyanate group in one molecule. Is preferred. Thereby, the heat and humidity resistance can be further improved.

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

As a compound (carbodiimide compound) which contains a carbodiimide group in one molecule which can be used as a stabilizer (B), a monocarbodiimide compound, a polycarbodiimide compound, and a cyclic carbodiimide compound are mentioned.
As the monocarbodiimide compound, dicyclohexyl carbodiimide, bis-2,6-diisopropylphenyl carbodiimide and the like are preferable.
Moreover, as a polycarbodiimide compound, what was manufactured by various methods can be used. Conventional methods for producing polycarbodiimides (for example, U.S. Pat. No. 2,941,956, JP-B-47-33279, J. 0 rg. Chem. 28, 2069-2075 (1963), Chemical Review 1981, Vol. 4, p 619-621) can be used. Specifically, the carbodiimide compound described in Japanese Patent No. 4084953 can also be used.
As polycarbodiimide compounds, poly (4,4'-dicyclohexylmethanecarbodiimide), poly (N, N'-di-2,6-diisopropylphenylcarbodiimide), poly (1,3,5-triisopropylphenylene-2, 4-carbodiimide, etc. are mentioned.
The cyclic carbodiimide compound can be synthesized based on the method described in JP-A-2011-256337 or the like.
As the carbodiimide compound, a commercially available product may be used. For example, B2756 (trade name) manufactured by Tokyo Kasei Kogyo Co., Ltd., Carbodilite LA-1 (trade name) manufactured by Nisshinbo Chemical Co., Ltd., Stabaxol P, Stabaxol P400 manufactured by Line Chemie Stabaxol I (all trade names) and the like.

  As a compound (isocyanate compound) containing an isocyanate group in one molecule, which can be used as the stabilizer (B), 3- (triethoxysilyl) propyl isocyanate, 2,4-tolylene diisocyanate, 2,6-tridiisocyanate Di-isocyanate, 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.

  As a compound (epoxy compound) containing an epoxy group in one molecule which can be used as a stabilizer (B), phenyl glycidyl ether, diethylene glycol diglycidyl ether, bisphenol A-diglycidyl ether, hydrogenated bisphenol A-diglycidyl ether And phenol novolac epoxy resins, cresol novolac epoxy resins, epoxidized polybutadiene and the like.

As described above, the weight average molecular weight of the stabilizer (B) is preferably 200 to 60,000, more preferably 200 to 30,000, and still more preferably 300 to 18,000.
When the molecular weight is within the above range, the stabilizer (B) is more easily moved, and the moist heat resistance improving effect is more effectively exerted.
The weight average molecular weight of the stabilizer (B) is particularly preferably 200 to 900. In addition, the weight average molecular weights 200-900 substantially correspond to the number average molecular weights 200-900. Moreover, in the case of weight average molecular weight 200-900, molecular weight distribution may be 1.0, and in this case, "weight average molecular weight 200-900" can also be rephrased simply as "molecular weight 200-900". .

  Hereinafter, specific examples (stabilizers B-1 to B-3) of the stabilizer (B) will be shown.

Hereinafter, the compound name, commercial item etc. are shown about said stabilizer B-1 to B-3.
-Stabilizer B-1 ... The compound name is bis-2, 6-diisopropylphenyl carbodiimide. The weight average molecular weight (in this example, equal to just "molecular weight") is 363. Examples of commercially available products include "Stabaxol I" manufactured by Rhine Chemie, and "B2756" manufactured by Tokyo Kasei.
-Stabilizer B-2 ... The compound name is poly (4,4'-dicyclohexylmethane carbodiimide). As a commercial item, "Nisshinbo Chemical Co., Ltd." carbodiimide light LA-1 "is mentioned as a thing of weight average molecular weight about 2000.
Stabilizer B-3 The compound name is poly (1,3,5-triisopropylphenylene-2,4-carbodiimide). As a commercial item, "Stabaxol P" manufactured by Line Chemie Co., Ltd. is mentioned as one having a weight average molecular weight of about 3,000. Moreover, "Stabaxol P400" by a line chemistry company is mentioned as a thing of the weight average molecular weight 20000.

When the first piezoelectric body contains a stabilizer (B), the first piezoelectric body may contain only one type of stabilizer, or may contain two or more types.
When the first piezoelectric body contains a 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). Is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, and still more preferably 0.5 to 2 parts by mass Particularly preferred.
When the content is 0.01 parts by mass or more, heat and humidity resistance is further improved.
Moreover, the fall of transparency is suppressed more as the said content is 10 mass parts or less.

As a preferable aspect of a stabilizer (B), it has one or more types of functional groups chosen from the group which consists of a carbodiimide group, an epoxy group, and an isocyanate group, and a number average molecular weight is a stabilizer of 200-900. (B1) 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 a weight average molecular weight of 1,000 to 60,000 (B1) The aspect of using B2) together is mentioned. The weight average molecular weight of the stabilizer (B1) having a number average molecular weight of 200 to 900 is approximately 200 to 900, and the number average molecular weight and the weight average molecular weight of the stabilizer (B1) have substantially the same value. .
When using a stabilizer (B1) and a stabilizer (B2) together as a stabilizer, it is preferable from a viewpoint of transparency improvement to contain many stabilizers (B1).
Specifically, the amount of the stabilizer (B2) is preferably in the range of 10 parts by mass to 150 parts by mass with respect to 100 parts by mass of the stabilizer (B1) from the viewpoint of achieving both transparency and moist heat resistance The range of 50 parts by mass to 100 parts by mass is more preferable.

<Other ingredients>
The first piezoelectric body may contain other components as needed.
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.
As the inorganic filler and the crystal nucleating agent, the components described in paragraphs 0057 to 0058 of WO 2013/054918 can also be mentioned.

(Degree of orientation F)
As described above, the orientation degree F of the first 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 More preferably, it is at least 1.0.
If the orientation degree F of the first piezoelectric body is 0.5 or more, the molecular chains (for example, polylactic acid molecular chains) of the helical chiral polymer (A) arranged in the stretching direction are large, and as a result, formation of oriented crystals Rate is high, and higher piezoelectricity can be expressed.
If the orientation degree F of the first piezoelectric body is less than 1.0, the longitudinal tear strength is further improved.

(Degree of crystallinity)
The crystallinity of the first piezoelectric body in the present disclosure is a value measured by the above-mentioned X-ray diffraction measurement (wide-angle X-ray diffraction measurement).
The crystallinity of the first 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 degree of crystallinity is 20% or more, high piezoelectricity is maintained. When the crystallinity degree is 80% or less, the transparency of the first piezoelectric body is maintained high.
When the crystallization degree is 80% or less, for example, when producing a piezoelectric film to be a raw material of the first piezoelectric body by stretching, whitening and breakage do not easily occur, and thus the first piezoelectric body can be easily manufactured. In addition, when the degree of crystallinity is 80% or less, for example, when manufacturing the raw material of the first piezoelectric body (for example, polylactic acid) by melt spinning and drawing by stretching, it becomes a fiber having high flexibility and flexible properties. , And easy to manufacture the first piezoelectric body.

(Transparency (internal haze))
In the first piezoelectric body in the present disclosure, although transparency is not particularly required, it may be of course possible to have transparency.
The transparency of the first piezoelectric body can be evaluated by measuring the internal haze. Here, the internal haze of the first piezoelectric body refers to the haze excluding the haze due to the shape of the outer surface of the first piezoelectric body.
When transparency is required for the first piezoelectric body, the internal haze to visible light is preferably 5% or less, and from the viewpoint of further improving the transparency and longitudinal tear strength, 2.0% The following are more preferable, and 1.0% or less is still more preferable. The lower limit value of the internal haze of the first piezoelectric body is not particularly limited, and the lower limit value is, for example, 0.01%.
The internal haze of the first piezoelectric body is a haze measuring machine [manufactured by Tokyo Densaku Co., Ltd., based on JIS-K7105, with respect to the first piezoelectric body having a thickness of 0.03 mm to 0.05 mm. It is a value when it measures at 25 degreeC using TC-HIII DPK].
Hereinafter, an example of a method of measuring the internal haze of the first piezoelectric body will be shown.
First, prepare a sample 1 in which only silicone oil (Shin-Etsu Chemical Co., Ltd. Shin-Etsu Silicone (trade name), model number: KF 96-100 CS) is sandwiched between two glass plates, and the haze in the thickness direction of this sample 1 is prepared. (Hereinafter, the haze (H2)) is measured.
Next, a sample 2 is prepared in which a plurality of first piezoelectrics whose surfaces are uniformly coated with silicone oil are evenly arranged between two glass plates described above without any gaps. (Hereafter, the haze (H3)) is measured.
Next, the internal haze (H1) of the first piezoelectric body is obtained by taking these differences as in the following formula.
Internal haze (H1) = haze (H3)-haze (H2)
Here, the measurement of the haze (H2) and the haze (H3) is performed using the following apparatus under the following measurement conditions, respectively.
Measuring device: HAZE METER TC-HIIIDPK manufactured by Tokyo Denshoku Co., Ltd.
Sample size: Width 30 mm × length 30 mm
Measurement conditions: conform to JIS-K7105 Measurement temperature: room temperature (25 ° C)

(Functional layer)
If necessary, the piezoelectric substrate may be provided with a functional layer. The type of functional layer 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 adhesive layer, a hard coat layer, an antistatic layer, an antiblock layer, a protective layer, and an electrode layer. The piezoelectric substrate having the functional layer makes it easier to apply to, for example, a piezoelectric device, a force sensor, an actuator, and a biological information acquisition device. The functional layer may be a single layer or two or more layers, and in the case of including two or more functional layers, the functional layers may be provided with different types of functional layers.

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

  Although the film thickness of a functional layer is not specifically limited, The range of 0.01 micrometer-10 micrometers is preferable. The upper limit value of the thickness is more preferably 6 μm or less, still more preferably 3 μm or less. The lower limit value is more preferably 0.01 μm or more, and still more preferably 0.02 μm or more. When the functional layer comprises a plurality of functional layers, the thickness represents the total thickness of the plurality of functional layers.

  In the piezoelectric substrate of the present disclosure, the functional layer preferably includes an electrode layer. When the piezoelectric substrate is provided with the electrode layer, the piezoelectric substrate is used as one of components of, for example, a piezoelectric device (piezoelectric fabric, piezoelectric knit, etc.), a force sensor, an actuator, or a biological information acquisition device. The connection between the inner conductor and the outer conductor can be made more easily. Therefore, when tension is applied to the piezoelectric substrate, a voltage signal corresponding to the tension is easily detected.

  As a mode in case a piezoelectric base material is equipped with a functional layer, the state of the layered product by which a functional layer is arranged at least one side of the 1st piezoelectric material is mentioned. In this case, it is preferable that the first piezoelectric body and the functional layer be in a state of a laminate, and an electrode layer be provided as a surface layer on one surface of the laminate.

(Adhesive layer)
The piezoelectric substrate preferably comprises an adhesive layer between the inner conductor and the first piezoelectric body. When the first piezoelectric body includes the adhesive layer, the relative position between the internal conductor and the first piezoelectric body is unlikely to be shifted. Therefore, tension is easily applied to the first piezoelectric body, and shear stress is easily applied to the helical chiral polymer contained in the first piezoelectric body. Therefore, it is possible to detect a voltage output that is effectively proportional to tension from the inner conductor (preferably the signal line conductor). In addition, the provision of the adhesive layer tends to further increase the absolute value of the generated charge amount per unit tensile force.
In the present specification, “adhesion” is a concept including “adhesion”. Also, "adhesive layer" is a concept including "adhesive layer".

  The material of the adhesive forming the adhesive layer is not particularly limited. For example, epoxy adhesives, urethane adhesives, vinyl acetate resin emulsion adhesives, (EVA) emulsion adhesives, acrylic resin emulsion adhesives, styrene-butadiene rubber latex adhesives, silicone resins Adhesive, α-olefin (isobutene-maleic anhydride resin) adhesive, vinyl chloride resin solvent type adhesive, rubber adhesive, elastic adhesive, chloroprene rubber solvent type adhesive, nitrile rubber solvent type An adhesive or the like, or a cyanoacrylate adhesive or the like can be used.

  The adhesive layer preferably has a modulus of elasticity equal to or greater than that of the first piezoelectric body. In this case, strain (piezoelectric strain) due to tension applied to the piezoelectric substrate is less likely to be relaxed in the adhesive layer, and the strain transmission efficiency to the first piezoelectric body is likely to be maintained. Therefore, when the piezoelectric substrate is applied to, for example, a sensor (preferably a force sensor), the sensitivity of the sensor is well maintained.

  The thickness of the adhesive layer is preferably as thin as possible, as long as no gap is formed between the piezoelectric substrate and the first piezoelectric member and the bonding strength is not reduced. By reducing the thickness of the bonding portion, strain due to tension applied to the piezoelectric substrate is less likely to be relaxed in the adhesive portion, and the strain transmission efficiency to the first piezoelectric body is likely to be maintained. Therefore, when the piezoelectric substrate is applied to, for example, a sensor (preferably a force sensor), the sensitivity of the sensor is well maintained.

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

The ground conductor is not particularly limited, but mainly includes the following depending on the cross-sectional shape.
For example, as a ground conductor having a rectangular cross section, it is possible to use a copper foil ribbon obtained by rolling a copper wire of a circular cross section into a flat plate shape, an aluminum foil ribbon, or the like.
For example, as a ground conductor having a circular cross section, a copper wire is spirally wound around a copper wire, an aluminum wire, a SUS wire, a metal wire coated with an insulation film, a carbon fiber, a resin fiber integrated with the carbon fiber, and a fiber It is possible to use a cocoon thread.
Further, as the ground conductor, one obtained by coating an organic conductive material with an insulating material may be used.
Moreover, a conductive fiber can also be used as a ground conductor. A conductive fiber is synonymous with the conductive fiber applicable as an above-mentioned internal conductor, The preferable range is also the same.

The ground conductor is preferably disposed to wrap the inner conductor and the first piezoelectric member so as not to short circuit the inner conductor (preferably, the signal line conductor).
As a method of wrapping such an inner conductor, it is possible to select a method of winding by wrapping a copper foil etc. in a spiral and wrapping, or a method of wrapping a copper wire etc. in a tubular braid and wrapping in it. is there.
In addition, how to wrap the inner conductor is not limited to these methods. By enclosing the internal conductor, it becomes possible to perform electrostatic shielding, and it is possible to prevent the voltage change of the internal conductor due to the influence of external static electricity.
In addition, the arrangement of the ground conductor is one of the preferable modes in which the inner conductor and the first piezoelectric body in the present disclosure are cylindrically enclosed.

  As a 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, since the rectangular cross section can be in close contact with the inner conductor (preferably the signal line conductor), the first piezoelectric body, the insulator if necessary, the second piezoelectric body, etc. It becomes possible to efficiently detect the charge generated by the piezoelectric effect as a voltage signal.

<Second piezoelectric>
The piezoelectric substrate of the present disclosure may include an elongated second piezoelectric body.
The second piezoelectric body preferably has the same characteristics as the first piezoelectric body.
That is, the second piezoelectric body includes a helical chiral polymer (A) having optical activity,
The length direction of the second piezoelectric body and the main orientation direction of the helical chiral polymer (A) contained in the second piezoelectric body are substantially parallel;
It is preferable that the orientation degree F of the second piezoelectric body determined by the above equation (a) from X-ray diffraction measurement is in the range of 0.5 or more and less than 1.0.
The second piezoelectric body preferably has the same characteristics as the first piezoelectric body also in the characteristics other than the above.
However, with regard to 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, the effects of the present disclosure can be obtained. From the viewpoint of achieving the above, it may be appropriately selected according to the aspect of the piezoelectric substrate.
In addition, about the winding direction of a 1st piezoelectric material and a 2nd piezoelectric material, and an example of the preferable combination of the chirality of the helical chiral polymer (A) contained in a 1st piezoelectric material and a 2nd piezoelectric material, As described in the second embodiment described above.
In addition, the second piezoelectric body may have characteristics different from those of the first piezoelectric body.

<Insulator>
The piezoelectric substrate of the present disclosure may comprise an insulator. For example, the piezoelectric substrate of the second embodiment may include an insulator.
The insulator is preferably spirally wound along the outer circumferential surface of the inner conductor. In this case, it is preferable that the first piezoelectric body and the insulator have a braid structure alternately crossed.
The winding direction of the insulator may be the same as or different from the winding direction of the first piezoelectric body.
In the piezoelectric substrate according to the second embodiment, by forming the braid structure with the first piezoelectric body and the insulator, when the piezoelectric substrate is bent and deformed, generation of an electrical short circuit between the inner conductor and the outer conductor is caused. There is an advantage that it becomes easy to control.

The insulator is not particularly limited, and examples thereof include vinyl chloride resin, polyethylene resin, polypropylene resin, ethylene / tetrafluoroethylene copolymer (ETFE), and tetrafluoroethylene / hexafluoropropylene copolymer (FEP). ), Tetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoropropylvinylether copolymer (PFA), fluororubber, polyester resin, polyimide resin, polyamide resin, polyethylene terephthalate resin (PET), rubber (elastomer And the like.
The shape of the insulator is preferably an elongated shape in view of the winding on the inner conductor.

  Hereinafter, 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 base according to the first embodiment, FIG. 1B shows a side view of the piezoelectric base according to the first embodiment, and FIG. The XX 'line sectional view of 1B is shown.
As shown in FIG. 1A, the coaxial line structure 10 constituting the piezoelectric base 100 (see FIG. 1B) includes the elongated internal conductor 12A and the elongated first piezoelectric body 14A. .
As shown in FIG. 1A, the first piezoelectric member 14A has a spiral gap in one direction so that the internal conductor 12A can not be seen from one end to the other at a helical angle β1 along the outer peripheral surface of the internal conductor 12A. It is wound without.
The “helical angle β1” means an angle formed by the axial direction G1 of the inner conductor 12A and the arrangement direction of the first piezoelectric body 14A with respect to the axial direction of the inner conductor 12A.
Further, in the coaxial wire structure 10, the first piezoelectric body 14A is wound around the internal conductor 12A in a left-handed manner. Specifically, when the coaxial line structure 10 is viewed from one end side (right end side in the case of FIG. 1A) of the inner conductor 12A in the axial direction, the first piezoelectric body 14A is from the front side of the inner conductor 12A. It is wound by left winding toward the back side.
Further, in FIG. 1A, the main alignment direction of the helical chiral polymer (A) contained in the first piezoelectric body 14A is indicated by a double arrow E1. That is, the main alignment direction of the helical chiral polymer (A) and the arrangement direction of the first piezoelectric body 14A (the longitudinal direction of the first piezoelectric body 14A) are substantially parallel.
As shown in FIG. 1B, in the piezoelectric base 100 according to the first embodiment, the outer conductor 16 is spirally wound in one direction in the outer periphery of the coaxial line structure 10 shown in FIG. 1A. . That is, the piezoelectric base 100 includes the elongated internal conductor 12A, the elongated first piezoelectric body 14A, and the outer conductor 16 in this order from the inside.

Hereinafter, the operation of the piezoelectric base 100 according to the first embodiment will be described.
For example, when tension is applied in the longitudinal direction of the piezoelectric substrate 100, a shear force is applied to the helical chiral polymer (A) contained in the first piezoelectric body 14A, and the helical chiral polymer (A) is polarized. . The polarization of the 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 arrows in FIG. 1C, and the polarization directions are the same in phase. It is thought that it will occur. This effectively detects a voltage signal proportional to the tension.
In particular, in the piezoelectric base 100 according to the first embodiment, the first piezoelectric body 14A is spirally wound in one direction without a gap so that the inner conductor 12A can not be seen along the outer peripheral surface of the inner conductor 12A. As a result, the adhesion between the inner conductor 12A and the first piezoelectric body 14A is enhanced, and a gap is less likely to be formed between the inner conductor 12A and the outer conductor 16. As a result, the piezoelectric substrate 100 satisfying the capacitance measurement value / the capacitance theoretical value ≧ 0.5 (formula (a)) is obtained. As a result, when tension is applied to the piezoelectric substrate 100, The amount of generated charges increases as compared with a piezoelectric substrate not satisfying the formula (a).
Therefore, according to the piezoelectric substrate 100, the piezoelectric sensitivity is excellent.

In addition, the piezoelectric base material 100 which concerns on 1st Embodiment is not limited to the said form. For example, in the piezoelectric substrate 100, an adhesive layer may be disposed between the internal conductor 12A and the first piezoelectric body 14A. As a result, even if tension is applied in the longitudinal direction of the piezoelectric base 100, the relative position between the first piezoelectric body 14A and the internal conductor 12A does not easily shift, so more tension is applied to the first piezoelectric body 14A. It becomes easy to be done.
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 method of arranging the outer conductor 16 is not limited to this. That is, the outer conductor 16 may be disposed on at least a part of the outer periphery of the first piezoelectric body 14A. Also, the winding direction of the outer conductor 16 is not particularly limited.

  Next, a piezoelectric substrate according to a 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 the redundant description will be omitted.

Second Embodiment
FIG. 2A shows a side view of the coaxial line structure constituting the piezoelectric base according to the second embodiment, and FIG. 2B shows a side view of the piezoelectric base according to the second embodiment.
As shown in FIG. 2A, the coaxial line structure 10A constituting the piezoelectric base 100A (see FIG. 2B) includes a long second piezoelectric body 14B, and a first piezoelectric body 14A. The second piezoelectric body 14B differs from the piezoelectric base 100 according to the first embodiment in that the second piezoelectric body 14B has a braided structure.
Specifically, as shown in FIG. 2A, in the coaxial cable structure 10A, the first piezoelectric body 14A is helically wound in a left-handed direction from one end to the other at a helical angle β1 with respect to the axial direction G2 of the internal conductor 12A. , And the second piezoelectric body 14B is spirally wound in a right-handed manner from one end to the other at a helical angle β2, and the first piezoelectric body 14A and the second piezoelectric body 14B are alternately intersected. It has a braided structure. That is, the first piezoelectric body 14A and the second piezoelectric body 14B form a braid structure so that the inner conductor 12A can not be seen on the outer peripheral surface of the inner conductor 12A.
The “right-handed and spirally wound” means that the second piezoelectric body 14B is the coaxial wire structure 10A viewed from one end side (right end side in the case of FIG. 2A) of the inner conductor 12A in the axial direction This means that the right-handed winding is performed from the front side to the back side of the inner conductor 12A.
The “helical angle β2” is synonymous with the aforementioned helical angle β1.
In the braid structure of the coaxial line structure 10A, the main orientation direction (double arrow E1) of the helical chiral polymer (A) contained in the first piezoelectric body 14A and the arrangement direction of the first piezoelectric body 14A It is almost parallel. Similarly, the main alignment direction (double arrow E2) of the helical chiral polymer (A) contained in the second piezoelectric body 14B and the arrangement direction of the second piezoelectric body 14B are substantially parallel.

  As shown in FIG. 2B, in the piezoelectric base 100A according to the second embodiment, the outer conductor 16 is spirally wound in one direction and disposed on the outer peripheral surface of the coaxial line structure 10A shown in FIG. 2A. There is. That is, the piezoelectric base 100A includes, in order from the inside, the elongated inner conductor 12A, the first piezoelectric body 14A and the second piezoelectric body 14B having a braided structure, and the outer conductor 16.

Hereinafter, the operation of the piezoelectric base 100A according to the second embodiment will be described.
For example, when tension is applied in the longitudinal direction of the piezoelectric substrate 100A, the helical chiral polymer (A) contained in the first piezoelectric body 14A and the helical chiral polymer (A) contained in the second piezoelectric body 14B. The shear stress is applied to both, and polarization occurs. It is considered that the polarization directions are all generated in the radial direction of the piezoelectric base 100A (the radial direction of the coaxial line structure 10A), and are generated with the phases aligned. This effectively detects a voltage signal proportional to the tension.
In particular, in the piezoelectric base 100A according to the second embodiment, the braid structure is formed by forming a braid structure by the first piezoelectric body 14A and the second piezoelectric body 14B along the outer peripheral surface of the internal conductor 12A. Even when a force that causes the piezoelectric substrate to be bent and deformed acts more flexibly than when not formed, the piezoelectric substrate is more easily bent and deformed. As a result, for example, the amount of charge generated when a tensile force is applied to the piezoelectric substrate is likely to increase.
Therefore, according to the piezoelectric base 100A, the piezoelectric sensitivity is excellent.
However, from the viewpoint of satisfying the capacitance measurement value / the capacitance theoretical value ≧ 0.5, the braid structure is formed such that the gap between the first piezoelectric body and the second piezoelectric body is adjusted to be small. Is preferred.

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

Third Embodiment
The 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 an insulator.
That is, in the piezoelectric substrate according to the third embodiment, the first piezoelectric body 14A is spirally wound in a left-handed manner from one end to the other at a helical angle β1 with respect to the axial direction G2 of the internal conductor 12A, The body is spirally wound in a right-handed manner from one end to the other at a helical angle β2 and the first piezoelectric body 14A and the insulator are alternately crossed to form a braid structure.

In the piezoelectric substrate according to the third embodiment, tension is applied, for example, in the longitudinal direction of the piezoelectric substrate by using, as the insulator, an insulator having flexibility equal to or higher than that of the first piezoelectric body 14A. Sometimes, shear stress is likely to be applied to the helical chiral polymer (A) contained in the first piezoelectric body 14A. That is, polarization is likely to occur. This effectively detects a voltage signal proportional to the tension.
Further, in the piezoelectric base according to the third embodiment, as in the piezoelectric base according to the second embodiment, the braid structure is not formed by forming the braid structure with the first piezoelectric body and the insulator. As compared with the case, even when a force that causes the piezoelectric substrate to be bent and deformed is applied, the piezoelectric substrate is easily bent and deformed easily. As a result, for example, the amount of charge generated when a tensile force is applied to the piezoelectric substrate is likely to increase.
Therefore, the piezoelectric substrate according to the third embodiment is also excellent in piezoelectric sensitivity.
However, from the viewpoint of satisfying the measured capacitance value / the calculated theoretical capacitance value ≧ 0.5, it is preferable to form the braid structure so that the gap between the first piezoelectric member and the insulator is adjusted to be small.

  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 insulator is not limited to the above embodiment.

Piezoelectric Substrates of Fourth and Fifth Embodiments
The piezoelectric substrate of the present disclosure is not limited to the configuration in which the electric charge (electric field) generated when tension is applied is extracted as a voltage signal, and for example, the electric charge (electric field) generated when torsional force is applied The configuration may be taken out as

  The piezoelectric base 100B of the fourth embodiment and the piezoelectric base 100C of the fifth embodiment are, as shown in FIGS. 7 to 10, a long inner conductor 12A as an inner conductor and a long first inner conductor 12A. A piezoelectric layer 14A, an adhesive layer (not shown) disposed between the inner conductor 12A and the first piezoelectric member 14A, and an outer conductor 13 disposed on the outer surface of the first piezoelectric member 14A; Have. Further, in the piezoelectric base members 100B and 100C, the first piezoelectric body 14A is spirally wound on the internal conductor 12A in the main alignment direction (double arrow E1), and the first piezoelectric body 14A is wound on the first piezoelectric body 14A. The main orientation direction (double arrow E1) of the contained helical chiral polymer (A) and the arrangement direction of the first piezoelectric body 14A are substantially parallel.

  In the piezoelectric substrate 100B of the fourth embodiment, the helical chiral polymer (A) contained in the first piezoelectric body 14A is a homopolymer (PLLA) of L-lactic acid, while the piezoelectric substrate of the fifth embodiment In 100C, the helical chiral polymer (A) contained in the first piezoelectric body 14A is a homopolymer (PDLA) of D-lactic acid. The relationship between the twisting direction and the generated polarization direction in the piezoelectric substrate 100B of the fourth embodiment is shown in FIGS. 7 and 8, and the relationship between the twisting direction and the generated polarization direction in the piezoelectric substrate 100C of the fifth embodiment is shown in FIG. , Shown in FIG.

  In FIG. 7, when a twisting force in the direction of arrow X1 is applied to the piezoelectric base 100B with the helical axis as the central axis, a shear stress is applied to the first piezoelectric body 14A wound helically, and a circular cross section is obtained. Polarization of PLLA occurs from the central direction to the outer direction. On the other hand, in FIG. 8, when a twisting force in the direction of arrow X2 opposite to the direction of arrow X1 is applied to the piezoelectric base 100B with the helical axis as the central axis, the first piezoelectric body 14A wound in a spiral is sheared. Stress is applied to cause polarization of PLLA from the outside direction to the center direction of the circular cross section. Therefore, a charge (electric field) proportional to the twisting force is generated in the piezoelectric substrate 100B, and the generated charge is detected as a voltage signal (charge signal).

  Further, in FIG. 9, when a twisting force in the direction of arrow X1 is applied to the piezoelectric base 100C with the helical axis as the central axis, a shear stress is applied to the first piezoelectric body 14A wound helically, and a circle is formed. Polarization of PDLA occurs from the outer direction to the center direction of the cross section. On the other hand, in FIG. 10, when a twisting force in the direction of arrow X2 opposite to the direction of arrow X1 is applied to piezoelectric substrate 100C with the helical axis as the central axis, the first piezoelectric body 14A spirally wound is sheared. Stress is applied to cause polarization of PDLA from the center direction of the circular cross section to the outer direction. Therefore, in the piezoelectric base 100C, a charge (electric field) proportional to a twisting force is generated, and the generated charge is detected as a voltage signal (charge signal).

<Method of manufacturing piezoelectric substrate>
There is no particular limitation on the method of manufacturing the piezoelectric base material of the present disclosure, but for example, the first piezoelectric body is prepared, and the first piezoelectric body is preferably prepared for the separately prepared internal conductor (preferably signal line conductor). (Preferably spirally wound in one direction), and can be manufactured by disposing an outer conductor (preferably a ground conductor) on the outer periphery of the first piezoelectric body.
The first piezoelectric body may be manufactured by a known method or may be obtained.
In addition, when the piezoelectric base material of the present disclosure includes the second piezoelectric body and the insulator as needed, the piezoelectric base body is manufactured according to the method of spirally winding the first piezoelectric body. can do.
However, as described above, 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, It is preferable to select suitably according to the aspect of a piezoelectric base material.
In addition, between at least one of the inner conductor and the outer conductor and the first piezoelectric body, if necessary, between the members provided in the piezoelectric substrate of the present disclosure is adhered, for example, by the above-mentioned method via an adhesive. You may combine.

<Use mode 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, and a method of applying a tension directly to the piezoelectric substrate or using an adhesive tape 51 for the flat plate 52 as shown in FIGS. 11A and 11B. A piezoelectric substrate 100 (the piezoelectric substrate according to the first embodiment, and the same applies hereinafter) is adhered to form a flat plate-attached piezoelectric substrate 50, and a pressing force is applied to the flat plate 52 to generate piezoelectric substrate Tension may be applied to the material 100 to detect a voltage signal. 11A is a schematic view showing the piezoelectric substrate 100 (piezoelectric substrate 50 with a flat plate) to which the flat plate 52 is attached using the adhesive tape 51, and FIG. 11B is a schematic view showing the flat plate 52 attached using the adhesive tape 51. It is the schematic at the time of pressing the attached piezoelectric base material 100 (piezoelectric base material 50 with a flat plate).

  Various methods may be mentioned as methods for attaching the piezoelectric substrate 100 to the flat plate 52 and mechanically integrating them. For example, as shown in FIG. 12, a method of bonding a part of the piezoelectric substrate 100 to the flat plate 52 using an adhesive tape 51 such as cellophane tape, gum tape or the like, as shown in FIG. An example is 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. 12, a part of the piezoelectric substrate 100 is attached to the flat plate 52 using an adhesive tape 51, and an FPC (flexible printed circuit board) 54 is disposed on the flat plate 52. The copper foil 53 electrically connected to the piezoelectric substrate 100 is disposed on the FPC 54. Further, the flat-plate-attached piezoelectric base 60 includes a signal processing circuit unit 55 that detects and processes a piezoelectric signal detected by applying a tensile force to the piezoelectric base 100. Further, in the flat-plate-attached piezoelectric base 70 in FIG. 13, the above-described flat-plate-attached piezoelectric except that a part of the piezoelectric base 100 is attached to the flat 52 using the adhesive 61 instead of the adhesive tape 51. The same as the base material 60.

  Moreover, as a target to which the piezoelectric base material is to be attached, it may be attached to the inside or outside or the like of the case of the electronic circuit configured by a curved surface or the like other than the flat plate described above.

<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, bats, etc.) Acceleration sensors and impact sensors when hitting sports equipment, touch and impact sensors for stuffed animals such as stuffed animals, security sensors for beds and windows, security sensors for glass and window frames, etc., actuators (sheet transport devices, etc.), energy harvesting applications (Power generation wear, power generation shoes, etc.), health care related applications (T-shirts, sports wear, spats, socks, various 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 can be used in various types of clothing (shirts, suits, blazers, blouses, coats, jackets, jackets, jackets, jumpers, vests, dresses, pants, pants, underwear (slip, petticoat, camisole, bra), socks, gloves, Japanese clothes, belts, gold bands, cool clothes, neckties, handkerchiefs, scarves, scarves, stalls, eye masks, supporters (neck support, shoulder support, chest support, belly support, waist support, arm support, Foot supporters, elbow supporters, knee supporters, wrist supporters, ankle supporters, footwear (sneakers, boots, sandals, pumps, mules, slippers, ballet shoes, kung fu shoes), insoles, towels, rucksacks, hats (Hat, cap, Casquette, hunting cap, ten gallon hat, tulip hat, sun visor, beret), hat chin strap, helmet, helmet chin strap, headrest, belt, seat cover, sheet, cushion, cushion, duvet cover, blanket, pillow, Pillowcase, sofa, chair, desk, table, seat, seat, toilet seat, massage chair, bed, bed pad, carpet, basket, mask, bandage, rope, stuffed toy, various nets, bathtub, wall material, floor material, window material , Window frame, door, door knob, personal computer, mouse, keyboard, printer, housing, robot, musical instrument, artificial hand, artificial leg, bicycle, skateboard, roller skate, rubber ball, shuttlecock, handle, pedal, fishing rod, fishing float Fishing reel, fishing rod holder, luer, 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 placed on articles and used for sensors, actuators, energy harvesting applications.
Examples of the disposition method include various methods such as sewing a piezoelectric substrate into an object, sandwiching the object with an object, and fixing the object to an object with a tacky adhesive.
For example, piezoelectric fabrics, piezoelectric knits, and piezoelectric devices can be applied to these applications.
Among the above applications, the piezoelectric substrate of the present disclosure is preferably used as a sensor application or an actuator application.
Specifically, the piezoelectric substrate of the present disclosure is preferably mounted on a force sensor or used mounted on an actuator.
In addition, the aforementioned piezoelectric substrate, piezoelectric fabric, piezoelectric knitted fabric, and piezoelectric device 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 an ON-OFF switch.
The piezoelectric substrate of the present disclosure can also be used in other applications besides the applications described above.
Other applications include bedding for turning over, carpets for movement detection, insoles for movement detection, chest bands for respiration detection, masks for respiration detection, arm bands for detection of bruises, There are foot bands for detecting a reed, seating sheets for detecting a seating, and a stuffed toy and a stuffed toy-type social robot capable of determining a contact state. With a stuffed toy, a stuffed toy type social robot or the like that can determine the contact state, for example, a pressure sensor is detected by a contact sensor locally disposed on the stuffed toy or the like, and the person "struck" the stuffed toy etc. It is possible to determine each operation, such as whether it's "held" or not.
In addition, the piezoelectric substrate of the present disclosure is used, for example, in-vehicle applications; vehicle handle grip detection applications using vibration and acoustic sensing, in-vehicle device operation system applications using resonance spectrum using vibration and acoustic sensing, and touch sensor applications of in-vehicle displays It is particularly suitable for vibration body applications, automobile door and window pinch detection sensor applications, car body vibration sensor applications and the like.

  A well-known extraction electrode can be bonded to the piezoelectric substrate of the present disclosure. As a lead-out electrode, electrode parts, such as a connector, a crimp terminal, etc. are mentioned. The electrode component can be joined 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 comprises the piezoelectric substrate described above.
Since the force sensor according to the present disclosure includes the piezoelectric substrate excellent in piezoelectric sensitivity, improvement in sensor sensitivity is expected.
Hereinafter, specific aspects of a force sensor according to an embodiment of the present disclosure will be described with reference to the drawings.
FIG. 14 is a conceptual view of a force sensor according to the present disclosure.
The force sensor 40 according to the present disclosure includes a piezoelectric base 100D, a cylindrical rubber-based heat-shrinkable tube (hereinafter, also simply referred to as a “shrinkable tube”) 44 disposed on the outer periphery of the piezoelectric base 100D, and a shrinkable tube 44. And a pair of crimp terminals (extraction electrodes) 46 disposed at both ends of the The pair of crimp terminals 46 includes a main body portion 46a and a crimp portion 46b, and has a through hole 46c at a central portion. The piezoelectric base 100D includes an internal conductor 12C, a first piezoelectric member 14D spirally wound in one direction around the internal conductor 12C, and a peripheral surface of the first piezoelectric member 14D. And an outer conductor 42 (ground conductor) wound around.
In the piezoelectric base 100D, one end (right end in FIG. 14) of the inner conductor 12C extends to the outside of the contraction tube 44, and is crimped by the crimping portion 46b and 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. 14) of the inner conductor 12C. The stress relieving portion 42 a is formed in the contraction tube 44.
After passing through the stress relieving portion 42a, the outer conductor 42 extends further outside the contraction tube 44 (left end in FIG. 14) and is crimped by the crimping portion 46b and electrically connected to the crimp terminal 46. .
The stress relieving portion 42a is formed of a slack outer conductor 42 as shown in FIG. In the stress relieving portion 42a, when tension (stress) is applied to the force sensor 40, the slack portion is extended, thereby suppressing the application of an excessive force to the first piezoelectric body 14D.
The first piezoelectric body 14D is formed of a long flat plate-like piezoelectric body, and an aluminum vapor deposition film (not shown) is vapor deposited as a functional layer on both sides. The pair of crimp terminals 46 are connected to an external circuit or the like (not shown) that processes the output signal of the force sensor 40.
In the embodiment illustrated in FIG. 14, the slack outer conductor 42 is disposed as the stress relieving portion 42 a, but the embodiment of the present disclosure is not limited thereto, and at least one of the piezoelectric substrates 100 D is not limited thereto. The force sensor 40 may be provided with a function of relieving stress by disposing a linear stress relieving portion at the end or both ends so as to transmit tension by a method such as bonding or thread knotting.
At this time, although the function of electrical connection does not exist in the linear stress relieving part, the electrical connecting function is coaxial cable of the inner conductor and the outer conductor from the end of the piezoelectric substrate independently of the stress relieving part. By connecting to etc., it becomes possible to detect a voltage signal of stress or strain.
At this time, the material and the form of the stress relieving portion are not particularly limited. For example, a yarn, a cord, a tube, etc. made of an elastic elastic material such as natural rubber, silicon rubber, urethane rubber etc .; And the like. By arranging the stress relieving portion and the electrical connection portion independently in different portions, the limitation of the strain amount of the stress relieving portion due to the maximum elongation amount of the electrical connection portion is eliminated, and the maximum strain as a tension sensor It is possible to increase the quantity.

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 first piezoelectric body 14D of the piezoelectric substrate 100D. The shear force causes polarization of the helical chiral polymer (A) in the radial direction of the piezoelectric substrate 100D. The polarization direction is the radial direction of the piezoelectric substrate 100D. As a result, 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 (not shown) connected to the crimp terminal 46.
In particular, in the force sensor 40, the first piezoelectric body 14D is spirally wound in one direction around the inner conductor 12C so that the inner conductor 12C is not visible and does not overlap. A gap is unlikely to be formed between 12C and the first piezoelectric body 14D (that is, between the inner conductor 12C and the outer conductor 42). As a result, the force sensor 40 including the piezoelectric base 100D satisfying the capacitance measurement value / the capacitance theoretical value 値 0.5 (formula (a)) is obtained. As a result, the tension is applied to the force sensor 40. Sometimes, more charge is generated compared to a force sensor with a piezoelectric substrate that does not satisfy equation (a) above.
Therefore, the force sensor 40 has excellent sensitivity.
In addition, since the force sensor 40 of the present disclosure includes the same coaxial line structure (the inner conductor 12C and the first piezoelectric body 14D) as the internal structure provided in the coaxial cable, the structure has high electromagnetic shielding properties and is resistant to noise. It can be In addition, because of its simple structure, it can be used by being attached to a part of the body, for example, as a wearable sensor.

  The force sensor of the present disclosure is not limited to a configuration in which a charge (electric field) generated when a tension is applied to the piezoelectric substrate is extracted as a voltage signal, for example, generated when a twisting force is applied to the piezoelectric substrate The charge (electric field) may be extracted as a voltage signal.

[Actuator]
An actuator according to the present disclosure comprises the above-described piezoelectric substrate.
The actuator according to the present disclosure is expected to have improved sensitivity because it includes a piezoelectric substrate excellent in piezoelectric sensitivity.

  Hereinafter, the present invention will be more specifically described by way of examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

<Preparation of First Piezoelectric Body (Slit Ribbon)>
Helical chiral polymer (A) as NatureWorks LLC Corp. polylactic acid (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, weight average molecular weight 20000), a mixture of Stabaxol I (70 parts by weight, weight average molecular weight 363) manufactured by Line Chemie, and carbodilite LA-1 (20 parts by weight, weight average molecular weight 2000) manufactured by Nisshinbo Chemical Co., Ltd.] 1.0 parts by weight It dry-blended and produced the raw material.
The prepared raw material was put into an extruder hopper, extruded from a T die while heating to 210 ° C., and brought into contact with a 50 ° C. cast roll for 0.3 minutes to form a 150 μm thick pre-crystallized sheet ( Pre-crystallization step). It was 6% when the crystallinity degree of the said precrystallization sheet was measured.
The obtained pre-crystallized sheet was heated at 70 ° C. while starting stretching at a stretching speed of 10 m / min by roll-to-roll, and uniaxially stretched in the MD direction to 3.5 times (stretching step).
Thereafter, the uniaxially stretched film was subjected to annealing treatment by contact with a roll heated to 145 ° C. for 15 seconds by roll-to-roll, and then quenching was performed to prepare a piezoelectric film (annealing step).
Next, using a slit processing machine, the piezoelectric film was slit so that the direction in which the piezoelectric film was slitted and the stretching direction of the piezoelectric film were substantially parallel. Thereby, as the first piezoelectric body (hereinafter, also simply referred to as “piezoelectric body”), the width is 0.6 mm, the average thickness is 50 μm, and the ratio of the width to the average thickness (width / average thickness) is 12 An elongated flat slit ribbon was obtained. The cross-sectional shape of the obtained slit ribbon was rectangular.
The average thickness of the slit ribbon was determined by the following method.
An arbitrary cross section orthogonal to the long axis direction of the slit ribbon is observed by SEM (scanning electron microscope), the thickness of the slit ribbon is measured at any six places in the above cross section, and the average value is the average thickness of the slit ribbon It was

<Measurement of physical properties of piezoelectric>
The following physical property measurements were performed on the obtained piezoelectric body. The results are shown in Table 1.

<Degree of orientation F of piezoelectric body>
For measurement, use a wide-angle X-ray diffractometer (RINT2550 manufactured by RIGAKU Co., Ltd .; attached device: rotating sample stand, X-ray source: CuKα, output: 40 kV 370 mA, detector: scintillation counter) The measurement was carried out by fixing and measuring the azimuth angle distribution intensity of the crystal plane peak [(110) plane / (200) plane].
In the obtained azimuth angle distribution curve (X-ray interference diagram), the crystallinity and the half width (α) of the peak were determined, and the orientation F (C-axis orientation) of the piezoelectric body was calculated from the following equation.
Degree of orientation (F) = (180 °-α) / 180 °
(Α is the half width of the orientation-derived peak)

<Dielectric Permittivity of Piezoelectric>
The measurement was performed according to JIS C2151 (2006) using a dielectric constant measuring apparatus (precision LCR meter HP4284A manufactured by Agilent Technologies) at a measurement frequency of 1 kHz and a test environment of 22 ° C. and 60% RH. As a result, the relative dielectric constant ε _S of the piezoelectric body (slit ribbon) was 2.75.

Example 1
<Fabrication of piezoelectric substrate>
A tin wire with a radius of 0.135 mm and a length of 100 mm was prepared as an internal conductor. A slit ribbon (piezoelectric body) having a width of 0.6 mm and an average thickness of 50 μm obtained as described above is left-handed on the tinsel wire at an angle (helical angle) of 45 ° to the long axis direction of the tinsel wire. The spirally wound was wound without clutter so that the tinsel wire was not visible (not exposed), and the tinsel wire was included. Thereby, the coaxial wire structure which consists of a tinsel wire and a slit ribbon was obtained. The number of turns of the slit ribbon around the tinsel wire at this time is 17 times / cm.
“Left-handed” means that the slit ribbon is left-handed from the front side to the back side of the tinsel wire when viewed from one end (right end side in the case of FIG. 1A) of the inner conductor (the tinsel wire). It says that it is winding.
Next, a copper foil ribbon slit-cut to a width of 0.6 mm and a thickness of 100 mm was prepared as an outer conductor. This copper foil ribbon was wound and wound around the slit ribbon of the coaxial line structure without gaps so that the slit ribbon could not be seen, in the same manner as the slit ribbon.
As described above, a piezoelectric substrate of Example 1 was obtained.
When the average radius a of the tinsel wire and the average thickness T of the slit ribbon were measured by the method described above using a piezoelectric substrate, the average radius a was 0.000135 m, and the average thickness T was 0. 0. It was 00005 m.

  FIG. 3 shows a photograph of the coaxial line structure obtained in Example 1 and a schematic cross-sectional view along the line I-I showing a state in which the outer conductor is further disposed on the coaxial line structure. The piezoelectric base material 101 of Example 1 includes a coaxial wire structure (the tinsel wire 22 and the slit ribbon 24) and the copper foil ribbon 26 on the outer peripheral surface thereof. In the piezoelectric substrate 101 of Example 1, the slit ribbon 24 is wound around the tinsel wire 22 without gaps so that the tinsel wire 22 can not be seen. Therefore, as shown in FIG. 3, between the tinsel wire 22 and the copper foil ribbon 26. The gap is considered to be a structure adjusted to be small.

Comparative Example 1
A piezoelectric substrate was obtained in the same manner as in Example 1 except that the slit ribbon was wound on the winding ribbon in a spiral manner while leaving a gap so that the winding filament could be seen. The number of turns of the slit ribbon around the tinsel wire at this time is 9 times / cm.

  FIG. 4 shows a photograph of the coaxial line structure obtained in Comparative Example 1 and a schematic cross-sectional view along the line II-II showing a state in which the outer conductor is further disposed on the coaxial line structure. The piezoelectric base material 102 of Comparative Example 1 includes a coaxial wire structure (the tinsel wire 22 and the slit ribbon 24A) and the copper foil ribbon 26A on the outer peripheral surface thereof. In the piezoelectric substrate 102 of Comparative Example 1, since the slit ribbon 24A is wound around the tinsel wire 22 so that the tinsel wire 22 can be seen, the distance from the tinsel wire 22 to the copper foil ribbon 26A is the same as that in FIG. It is considered that the gap S is formed between the wire 22 and the copper foil ribbon 26A.

Comparative Example 2
A piezoelectric substrate was obtained in the same manner as in Example 1, except that the slit ribbon was spirally wound on the tinsel wire so that adjacent slit ribbons overlap each other by 0.1 mm. The number of turns of the slit ribbon around the tinsel wire at this time is 20 times / cm.

  FIG. 5 shows a photograph of the coaxial line structure obtained in Comparative Example 2 and a schematic cross-sectional view along the line III-III showing a state in which the outer conductor is further disposed on the coaxial line structure. The piezoelectric base material 103 of Comparative Example 2 includes a coaxial wire structure (the tinsel wire 22 and the slit ribbon 24B) and a copper foil ribbon 26B on the outer peripheral surface thereof. Since the piezoelectric ribbon 103 of Comparative Example 2 is wound by overlapping the slit ribbons 24B by 0.1 mm each, the distance from the tinsel wire 22 to the copper foil ribbon 26B becomes longer than that in FIG. It is considered that this is a structure in which the gap S is formed between the copper foil ribbons 26B.

<Evaluation>
(Amount of generated charge per unit tensile force (sensitivity))
Using the piezoelectric substrates of Example 1 and Comparative Examples 1 and 2, the amount of charge generated when the tensile force is applied to the piezoelectric substrate (the amount of generated charge) is measured by the following method, and the amount of generated charge is unit tension The amount of generated charge per force was calculated. The results are shown in Table 2.
Specifically, the piezoelectric substrates of Example 1 and Comparative Examples 1 and 2 were used as samples, and chucked by a tensile tester (Tensilon RTG 1250 manufactured by A & D Co., Ltd.) with a distance between chucks of 50 mm.
In a tensile tester, the sample is repeatedly and periodically applied in a triangular wave shape at 0.5 Hz in a stress range of 1.0 N to 2.0 N, and the amount of charge generated on the front and back of the sample at that time is an electrometer (Keithley It measured by company made 617).
From the slope of the correlation line of the scatter diagram when the measured generated charge amount Q [C] is taken as the Y axis and the tensile force F [N] of the sample is taken as the X axis, the sensitivity per unit tensile force is taken as the sensitivity of the piezoelectric substrate. The amount of charge generated was calculated.

(Theoretical capacitance value)
Since the average radius a of tinsel wire is 0.000335 m (0.00027 / 2), the average thickness T of the slit ribbon is 0.00005 m, and the relative dielectric constant ε _S of the slit ribbon is 2.75, In the equation 2 already described, a = 0.001 35 m, b = 0.000185 m (average radius a of tinsel wire + total length of average thickness T of slit ribbons), ε _s = 2.75, and static The theoretical capacity was calculated.
As a result, the theoretical capacitance value was calculated to be 4.9 × 10 ⁻¹⁰ F / m, that is, 0.49 pF / mm.

(Capacitance measurement value)
Using the piezoelectric substrate of each example as a sample, the capacitance was measured using a Yokogawa Hewlett Packard precision LCR meter HP 4284A, and the obtained value was used as a capacitance measurement value. The measurement conditions are as follows. The results are shown in Table 2.
-Measurement conditions-
Frequency: 1 kHz
Temperature: 25 ° C

  From the capacitance measurement value, the ratio (relative ratio) of the capacitance of each example to the theoretical capacitance value “0.49 pF / mm” was determined by the following equation 3. The results are shown in Table 2.

Equation 3: Relative ratio of electrostatic capacitance = (capacitance measurement value per 1 mm of sample in each example [pF / mm] / electrostatic capacitance theoretical value per 1 mm of sample [pF / mm])

As shown in Table 2, in the piezoelectric substrate of Example 1 in which the relative ratio of capacitance (measured capacitance / theoretical capacitance) is 0.5 or more, the relative ratio is less than 0.5. As compared with the piezoelectric substrates of Comparative Examples 1 and 2 of the above, the generated charge amount per unit tensile force was increased. That is, the piezoelectric substrate of Example 1 was excellent in piezoelectric sensitivity.
This is because the gap between the inner conductor and the outer conductor is adjusted to be small by winding the slit ribbon (piezoelectric body) with no gaps so that the tinsel wire can not be seen with respect to the tinsel wire (inner conductor). It is considered to be a thing.

10, 10A, 30 coaxial wire structure, 12A, 12C, 32 inner conductor, 14A, 14D, 34 first piezoelectric body 13, 16, 42 outer conductor, 14B second piezoelectric body, 22 tinsel wire, 24 slits Ribbon, 26 copper foil ribbon, 40 force sensor, 42a stress relaxation portion, 44 contraction tube, 46 crimp terminal, 46a main body portion, 46b crimp portion, 46c through hole, 50, 60, 70 piezoelectric substrate with flat plate, 51 adhesive tape , 52 flat plate, 53 copper foil, 55 signal processing circuit unit, 61 adhesive, 100, 100 A, 100 B, 100 C, 100 D, 101 piezoelectric substrate

Claims (18)

A long inner conductor, a first piezoelectric body covering the outer peripheral surface of the inner conductor, and an outer conductor disposed on the outer periphery of the first piezoelectric body, and satisfying the following formula (a) Piezoelectric substrate.
Measured value of capacitance / theoretical value of capacitance ≧ 0.5 · · · (a) The first piezoelectric body includes a helical chiral polymer (A) having optical activity,
The length direction of the first piezoelectric body and the main alignment direction of the helical chiral polymer (A) contained in the first piezoelectric body are substantially parallel to each other,
The piezoelectric substrate according to claim 1, wherein the orientation degree F of the first piezoelectric body determined by the following formula (b) is in the range of 0.5 or more and less than 1.0.
Degree of orientation F = (180 ° -α) / 180 ° ··· (b)
(In formula (b), α represents the half width of the peak derived from the orientation measured by X-ray diffraction.)   The first piezoelectric body comprises 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 carbodiimide group, epoxy group, and isocyanate group; The piezoelectric substrate according to claim 2, comprising 0.01 part by mass to 10 parts by mass with respect to 100 parts by mass of the polymer (A). The helical chiral polymer (A) contained in the first piezoelectric body is a polylactic acid-based polymer having a main chain containing a structural unit represented by the following formula (1). The piezoelectric substrate of description.
  The piezoelectric according to any one of claims 1 to 4, wherein the first piezoelectric body is elongated and spirally wound in one direction along the outer peripheral surface of the inner conductor. Base material. And a second elongated piezoelectric member wound in a direction different from the one direction along the outer peripheral surface of the inner conductor.
The second piezoelectric body includes a helical chiral polymer (A) having optical activity,
The length direction of the second piezoelectric body and the main alignment direction of the helical chiral polymer (A) contained in the second piezoelectric body are substantially parallel to each other,
The orientation degree F of the second piezoelectric body determined by the equation (b) from X-ray diffraction measurement is in the range of 0.5 to less than 1.0,
The first piezoelectric body and the second piezoelectric body have a braid structure alternately crossed.
The piezoelectric according to claim 5, wherein the chirality of the helical chiral polymer (A) contained in the first piezoelectric body and the chirality of the helical chiral polymer (A) contained in the second piezoelectric body are different from each other. Base material. And an insulator wound along an outer circumferential surface of the inner conductor,
The piezoelectric substrate according to claim 5, wherein the first piezoelectric body and the insulator form a braid structure alternately crossed.   The first piezoelectric body according to any one of claims 5 to 7, wherein the first piezoelectric body is wound at an angle of 15 ° to 75 ° with respect to the axial direction of the inner conductor. Piezoelectric substrate. The first piezoelectric body has a fiber shape,
The piezoelectric substrate according to any one of claims 1 to 8, wherein an average major axis diameter of a cross section orthogonal to the major axis direction of the internal conductor of the first piezoelectric body is 0.0001 mm to 10 mm. Material. The first piezoelectric body has a long flat plate shape,
The average thickness of the first piezoelectric body is 0.001 mm to 0.2 mm,
The width of the first piezoelectric body is 0.1 mm to 30 mm,
The piezoelectric substrate according to any one of claims 1 to 8, wherein a ratio of a width of the first piezoelectric body to an average thickness of the first piezoelectric body is 2 or more.   The piezoelectric substrate according to any one of claims 1 to 10, further comprising a functional layer.   The piezoelectric substrate according to claim 11, wherein the functional layer is at least one selected from the group consisting of an adhesive layer, a hard coat layer, an antistatic layer, an antiblock layer, a protective layer, and an electrode layer.   The piezoelectric substrate according to claim 11, wherein the functional layer comprises an electrode layer.   The piezoelectric substrate according to claim 13, wherein the first piezoelectric body and the functional layer are in a laminate state, and the electrode layer is provided as a surface layer on one surface of the laminate.   The piezoelectric substrate according to any one of claims 1 to 14, wherein the internal conductor is a tinsel wire.   The piezoelectric substrate according to any one of claims 1 to 15, further comprising an adhesive layer between the internal conductor and the first piezoelectric body.   A force sensor comprising the piezoelectric substrate according to any one of claims 1 to 16.   An actuator comprising the piezoelectric substrate according to any one of claims 1 to 16.