JP2017120859A - Braid-like piezoelectric element, cloth-like piezoelectric element using braid-like piezoelectric element, and device using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fibrous piezoelectric element enabling extraction of a large electric signal even by stress generated by comparative small deformation and having an excellent repeated reproducibility of the electric signal.SOLUTION: A braid-like piezoelectric element 1 includes a core part 3 formed with a conductive fiber B and a sheath part 2 formed with a braid-like piezoelectric fiber A so as to cover the core part 3 and its bending recovery is 70 or more. In the core part 3 and/or the sheath part 2, a filament for bending recovery adjustment is included, whose cross-sectional area is 0.001 to 1.0 square millimeters.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a braided piezoelectric element using piezoelectric fibers, a fabric-like piezoelectric element using a braided piezoelectric element, and a device using the same.

  In recent years, so-called wearable sensors have attracted attention, and products such as glasses and watches have begun to appear in the world. However, these devices have a feeling that they are worn, and a cloth-like shape, that is, a clothing-like shape that is the ultimate wearable is desired. As such a sensor, a piezoelectric element using a piezoelectric effect of a piezoelectric fiber is known. For example, Patent Document 1 discloses a piezoelectric element that includes two conductive fibers and one piezoelectric fiber, and these include piezoelectric units that are disposed on substantially the same plane while having contact with each other. Has been. Patent Document 2 discloses a fibrous or molded product made of a piezoelectric polymer, and in order to generate piezoelectricity by the tension applied in the axial direction thereof, the direction in which the tension is applied is different. A piezoelectric material characterized by being twisted is disclosed.

  On the other hand, in recent years, the number of input devices adopting a so-called touch panel method, that is, touch-type input devices has increased significantly. In addition to bank ATMs and station ticket vending machines, smartphones, mobile phones, portable game consoles, portable music players, etc., coupled with the development of thin display technology, the number of devices that use the touch panel method as an input interface has increased significantly. . As means for realizing such a touch panel system, a system using a piezoelectric sheet or piezoelectric fiber is known. For example, Patent Document 3 discloses a touch panel that uses a piezoelectric sheet made of L-type polylactic acid having an extending axis facing a predetermined direction.

  In these wearable sensors and touch panel type sensors, it is desired to extract a large electric signal even with a small stress generated in the piezoelectric material due to a small deformation applied to the piezoelectric material. For example, it is desired to stably extract a large electric signal even by a relatively small stress generated in a piezoelectric material due to a bending and stretching operation of a finger or an action of rubbing the surface with a finger or the like.

  The piezoelectric fiber of Patent Document 1 is an excellent material applicable to various uses, but it cannot necessarily output a large electric signal with respect to stress generated by a relatively small deformation, and obtains a large electric signal. The technology is not specified. In many cases, the piezoelectric fiber does not return to its original state after being deformed once, and in Patent Document 1, sufficient examination has not been made from the viewpoint of improving the repeatability of electric signals.

  The piezoelectric fiber of Patent Document 2 can output an electrical signal in response to tension or compression on the piezoelectric fiber by previously twisting the piezoelectric fiber by a special manufacturing method. However, Patent Document 2 does not disclose a technique for generating a sufficient electric signal with respect to a bending stress caused by bending or stretching a piezoelectric fiber or a shearing stress caused by rubbing the surface of the piezoelectric fiber. Therefore, when such a piezoelectric fiber is used, it is difficult to extract a sufficient electric signal only with a stress generated by a relatively small deformation that rubs the surface.

  The piezoelectric sheet of Patent Document 3 can output an electric signal by deformation (stress) with respect to the piezoelectric sheet. However, since it is in the form of a sheet in the first place, it is not flexible and cannot be used such that it can be bent freely like a cloth.

International Publication No. 2014/058077 Japanese Patent No. 3540208 JP 2011-253517 A

  An object of the present invention is to provide a fibrous piezoelectric element that can extract a large electric signal even with a stress caused by a relatively small deformation and has a good repeatability of the electric signal.

  As a combination of conductive fibers and piezoelectric fibers, the inventors of the present invention provide a braided piezoelectric element in which the surface of the conductive fiber serving as a core is covered with a braided piezoelectric fiber and the bending recovery rate is 70 or more. The present inventors have found that it is possible to efficiently extract an electric signal and that the repeatability of the electric signal is good, and the present invention has been achieved.

That is, the present invention includes the following inventions.
1. A braided piezoelectric element comprising a core formed of conductive fibers and a sheath formed of braided piezoelectric fibers so as to cover the core, and having a bending recovery rate of 70 or more.
2. The braided piezoelectric element according to 1 above, wherein the core and / or the sheath includes a bending recovery rate adjusting filament having a cross-sectional area of 0.001 to 1.0 square millimeter.
3. The braided piezoelectric element according to 1 or 2 above, further comprising a coating layer having a thickness of 0.05 to 2.0 mm on the outer side of the sheath portion.
4). The braided piezoelectric element according to 1 above, wherein the core part and / or the sheath part includes a high elastic fiber having an elastic modulus of 15.0 GPa or more.
5. The braid according to any one of 1 to 4, wherein the piezoelectric fiber includes polylactic acid as a main component, and a winding angle of the piezoelectric fiber with respect to the conductive fiber is 15 ° or more and 75 ° or less. Piezoelectric element.
6). The braided piezoelectric element according to any one of the above 1 to 5, wherein the total fineness of the piezoelectric fibers is 1 to 20 times the total fineness of the conductive fibers.
7). The braided piezoelectric element according to any one of 1 to 6, wherein a fineness per one of the piezoelectric fibers is 1/20 or more and 2 or less of a total fineness of the conductive fibers.
8). A fabric-like piezoelectric element comprising a fabric including the braided piezoelectric element according to any one of 1 to 7 above.
9. 9. The cloth-like piezoelectric element according to 8, wherein the cloth further includes a conductive fiber that intersects and contacts at least a part of the braided piezoelectric element.
10. 10. The cloth-like piezoelectric element according to 9 above, wherein 30% or more of the fibers forming the cloth and intersecting the braided-piezoelectric element are conductive fibers.
11. The braided piezoelectric element according to any one of 1 to 7 above, an amplification unit that amplifies an electrical signal output from the braided piezoelectric element in accordance with an applied pressure, and the amplification unit An output means for outputting an electrical signal.
12 The cloth-like piezoelectric element according to any one of 8 to 10 above, an amplification means for amplifying an electric signal output from the cloth-like piezoelectric element in accordance with an applied pressure, and amplified by the amplification means An output means for outputting an electrical signal.

  According to the present invention, it is possible to provide a fibrous piezoelectric element that can extract a large electric signal even with a stress caused by a relatively small deformation and has good reproducibility of the electric signal.

It is a schematic diagram which shows the structural example of the braided piezoelectric element which concerns on embodiment. It is a figure which shows the apparatus which measures the bending recovery rate which concerns on embodiment. It is a schematic diagram which shows the structural example of the fabric-like piezoelectric element which concerns on embodiment. It is a block diagram which shows a device provided with the piezoelectric element which concerns on embodiment. It is a schematic diagram which shows the structural example of a device provided with the fabric-like piezoelectric element which concerns on embodiment. It is a schematic diagram which shows the other structural example of a device provided with the fabric-like piezoelectric element which concerns on embodiment.

(Braided piezoelectric element)
FIG. 1 is a schematic diagram illustrating a configuration example of a braided piezoelectric element according to the embodiment.
The braided piezoelectric element 1 includes a core portion 3 formed of a conductive fiber B and a sheath portion 2 formed of a braided piezoelectric fiber A so as to cover the core portion 3.
The braided piezoelectric element 1 has a bending recovery rate of 70 or more, preferably 80 or more, more preferably 90 or more, and still more preferably 95 or more.
Here, the bending recovery rate is a value defined by Equation 1 below.
X = L / 3 × 100 (Formula 1)
X: Bending restoration rate L: Braid protruding distance after bending restoring rate measurement test The braiding protruding distance L after the test is measured by the following method. That is, first, in the apparatus as shown in FIG. 2, the braided piezoelectric element 1 is fixed so as to protrude 3 cm from a pedestal having a corner with a radius of curvature of 1 cm, and then the braided piezoelectric element 1 is braided along the pedestal. Bend so that the surface facing the base is fully in contact with the base. Thereafter, the external force applied to the braided piezoelectric element 1 is immediately removed. After the bent braided piezoelectric element 1 is restored by stress, the distance protruding from the pedestal is measured, and this value is taken as L. At this time, the unit of L is cm. When the braid is short and it is difficult to protrude 3 cm, the length of the protruding portion can be set to L0 and can be substituted by the following formula (2).
X = L / L0 × 100 (Formula 2)

  In the braided piezoelectric element 1, a large number of piezoelectric fibers A densely surround the outer peripheral surface of at least one conductive fiber B. Although not bound by a specific theory, when the braided piezoelectric element 1 is deformed, a stress due to the deformation is generated in each of the many piezoelectric fibers A, thereby generating an electric field in each of the many piezoelectric fibers A. (Piezoelectric effect) As a result, it is presumed that a voltage change in which electric fields of a large number of piezoelectric fibers A surrounding the conductive fiber B are superimposed is generated in the conductive fiber B. That is, the electrical signal from the conductive fiber B increases as compared with the case where the braided sheath 2 of the piezoelectric fiber A is not used. As a result, the braided piezoelectric element 1 can extract a large electric signal even by a stress generated by a relatively small deformation. A plurality of conductive fibers B may be used.

  Here, the piezoelectric fiber A preferably contains polylactic acid as a main component. “As a main component” means that the most component of the components of the piezoelectric fiber A is polylactic acid. The lactic acid unit in the polylactic acid is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 98 mol% or more.

The winding angle α of the piezoelectric fiber A with respect to the conductive fiber B is preferably 15 ° or more and 75 ° or less. That is, the winding angle α of the piezoelectric fiber A is 15 ° or more and 75 ° or less with respect to the direction of the central axis CL of the conductive fiber B (core portion 3). However, in the present embodiment, the central axis CL of the conductive fiber B overlaps with the central axis (hereinafter, also referred to as “braid axis”) of the braided cord (sheath portion 2) of the piezoelectric fiber A. It can also be said that the winding angle α of the piezoelectric fiber A is 15 ° or more and 75 ° or less with respect to the direction of the braid axis of A. From the viewpoint of extracting a larger electric signal, the angle α is preferably 25 ° or more and 65 ° or less, more preferably 35 ° or more and 55 ° or less, and 40 ° or more and 50 ° or less. Is more preferable. This is because when the angle α is out of this angle range, the electric field generated in the piezoelectric fiber A is remarkably lowered, and the electrical signal obtained from the conductive fiber B is thereby remarkably lowered.
The angle α can also be referred to as an angle formed by the main direction of the piezoelectric fiber A forming the sheath portion 2 and the central axis CL of the conductive fiber B, and a part of the piezoelectric fiber A is slackened. Or may be fuzzy.

  Here, the reason why the electric field generated in the piezoelectric fiber A is remarkably lowered is as follows. The piezoelectric fiber A has polylactic acid as a main component and is uniaxially oriented in the fiber axis direction of the piezoelectric fiber A. Here, polylactic acid generates an electric field when shear stress is generated in the orientation direction (in this case, the direction of the fiber axis of the piezoelectric fiber A), but tensile stress or compression is applied in the orientation direction. Less electric field is generated when stress occurs. Therefore, in order to generate shear stress in the piezoelectric fiber A when deformed parallel to the direction of the braid axis, the orientation direction of the piezoelectric fiber A (polylactic acid) is within a predetermined angular range with respect to the braid axis. It is speculated that it is good to be.

  The core portion 3 and / or the sheath portion 2 is a filament (hereinafter referred to as “bending”) for adjusting the bending recovery rate so that the bending recovery rate becomes 70 or more in a range where the braided piezoelectric element 1 functions sufficiently as a sensor. A restoration rate adjusting filament ”). The cross-sectional area of the bending recovery rate adjusting filament is 0.001 to 1.0 square millimeter, preferably 0.005 to 0.5 square millimeter, more preferably 0.01 to 0.3 square millimeter. If the bending recovery rate adjusting filament is too thin, the bending recovery rate is not 70 or more, and if the bending recovery rate adjusting filament is too thick, the flexibility of the braided piezoelectric element 1 is lost. The ratio of the bending recovery rate adjusting filament to the core 3 and / or the sheath 2 is preferably 50% or less, more preferably 30% or less, and still more preferably 10% or less. If the ratio of the bending recovery rate adjusting filament to the core portion 3 and / or the sheath portion 2 is too small, the bending recovery rate does not become 70 or more, and if the ratio of the bending recovery rate adjusting filament is too large, the braided piezoelectric element 1 In some cases, the electrical signal obtained from the braided piezoelectric element may be reduced. The bending recovery rate adjusting filament may be used alone as a single fiber for producing a braid structure, or may be mixed with the fibers of the core 3 and / or the sheath 2. By including the bending recovery rate adjusting filament in the core part 3 and / or the sheath part 2, the braided piezoelectric element 1 is likely to return to its original state after being deformed once, so that the repeatability of electric signals is improved. .

  The braided piezoelectric element 1 can include a coating layer on the outside of the sheath portion 2 so that the bending recovery rate is 70 or more in a range where the braided piezoelectric element 1 functions sufficiently as a sensor. The thickness of the coating layer is 0.05 to 2.0 mm, preferably 0.04 mm to 1.0 mm, and more preferably 0.03 to 0.5 mm. If the coating layer is too thin, the bending recovery rate does not exceed 70, and if the coating layer is too thick, the flexibility of the braided piezoelectric element 1 is lost or the electrical signal obtained from the braided piezoelectric element becomes small. Sometimes By including the coating layer on the outside of the sheath portion 2, the braided piezoelectric element 1 is likely to return to its original state after being deformed once, so that the repeatability of electric signals is improved. Moreover, by including a coating layer, the restraint force of the sheath part 2 becomes large, so that stress is efficiently applied to the piezoelectric fiber A and the signal strength may be increased.

  The core part 3 and / or the sheath part 2 can contain highly elastic fibers so that the bending recovery rate is 70 or more in a range where the braided piezoelectric element 1 functions sufficiently as a sensor. The elastic modulus of the highly elastic fiber is 15.0 GPa, preferably 30.0 GPa or more, more preferably 0.0 GPa or more, and still more preferably 100.0 GPa or more. If the elastic modulus of the high elastic fiber is low, the bending recovery rate is not 70 or more, and if the elastic modulus of the high elastic fiber is too high, the flexibility of the braided piezoelectric element 1 is lost. The ratio of the highly elastic fiber to the core part 3 and / or the sheath part 2 is preferably 50% or less, more preferably 30% or less, still more preferably 10% or less. If the ratio of the high elastic fiber to the core part 3 and / or the sheath part 2 is too small, the bending recovery rate does not become 70 or more, and if the ratio of the bending recovery rate adjusting filament is too high, the flexibility of the braided piezoelectric element 1 May be lost, or the electrical signal obtained from the braided piezoelectric element may be small. The high-elasticity fiber may be used alone as one fiber for producing a braided structure, or may be mixed with the fibers of the core 3 and / or the sheath 2. By including the highly elastic fiber in the core part 3 and / or the sheath part 2, the braided piezoelectric element 1 is likely to return to its original state after being deformed once, so that the repeatability of electric signals is improved.

  The length of the braided piezoelectric element composed of the core portion 3 of the conductive fiber B and the sheath portion 2 of the braided piezoelectric fiber A is not particularly limited. For example, the braided piezoelectric element may be manufactured continuously in manufacturing, and then cut to a required length for use. The length of the braided piezoelectric element is 1 mm to 10 m, preferably 5 mm to 2 m, more preferably 1 cm to 1 m. If the length is too short, the convenience of the fiber shape will be lost, and if the length is too long, it will be necessary to consider the resistance value of the conductive fiber B.

  Hereinafter, each configuration will be described in detail.

(Conductive fiber)
As the conductive fiber B, any known fiber may be used as long as it exhibits conductivity. As the conductive fiber B, for example, metal fiber, fiber made of a conductive polymer, carbon fiber, fiber made of a polymer in which a fibrous or granular conductive filler is dispersed, or conductive on the surface of a fibrous material. The fiber which provided the layer which has is mentioned. Examples of the method for providing a conductive layer on the surface of the fibrous material include a metal coat, a conductive polymer coat, and winding of conductive fibers. Among these, a metal coat is preferable from the viewpoint of conductivity, durability, flexibility and the like. Specific methods for coating the metal include vapor deposition, sputtering, electrolytic plating, and electroless plating, but plating is preferable from the viewpoint of productivity. Such a metal-plated fiber can be referred to as a metal-plated fiber.

  As a base fiber coated with a metal, a known fiber can be used regardless of conductivity, for example, polyester fiber, nylon fiber, acrylic fiber, polyethylene fiber, polypropylene fiber, vinyl chloride fiber, aramid fiber, In addition to synthetic fibers such as polysulfone fibers, polyether fibers and polyurethane fibers, natural fibers such as cotton, hemp and silk, semi-synthetic fibers such as acetate, and regenerated fibers such as rayon and cupra can be used. The base fibers are not limited to these, and known fibers can be arbitrarily used, and these fibers may be used in combination.

  Any metal may be used as long as the metal coated on the base fiber exhibits conductivity and exhibits the effects of the present invention. For example, gold, silver, platinum, copper, nickel, tin, zinc, palladium, indium tin oxide, copper sulfide, and a mixture or alloy thereof can be used.

  When an organic fiber coated with metal having bending resistance is used for the conductive fiber B, the conductive fiber is hardly broken and excellent in durability and safety as a sensor using a piezoelectric element.

  The conductive fiber B may be a multifilament in which a plurality of filaments are bundled, or may be a monofilament composed of a single filament. A multifilament is preferred from the viewpoint of long stability of electrical characteristics. In the case of monofilament (including spun yarn), the single yarn diameter is 1 μm to 5000 μm, preferably 2 μm to 100 μm. More preferably, it is 3 micrometers-50 micrometers. In the case of a multifilament, the number of filaments is preferably 1 to 100,000, more preferably 5 to 500, and still more preferably 10 to 100. However, the fineness and the number of the conductive fibers B are the fineness and the number of the core part 3 used when producing the braid, and the multifilament formed of a plurality of single yarns (monofilaments) is also one conductive. It shall be counted as fiber B. Here, the core portion 3 is the total amount including the fibers other than the conductive fibers.

  If the diameter of the fiber is small, the strength is reduced and handling becomes difficult, and if the diameter is large, flexibility is sacrificed. The cross-sectional shape of the conductive fiber B is preferably a circle or an ellipse from the viewpoint of the design and manufacture of the piezoelectric element, but is not limited thereto.

Further, in order to efficiently extract the electrical output from the piezoelectric polymer, the electrical resistance is preferably low, and the volume resistivity is preferably 10 ⁻¹ Ω · cm or less, more preferably 10 ⁻² Ω · cm. cm or less, more preferably 10 ⁻³ Ω · cm or less. However, the resistivity of the conductive fiber B is not limited to this as long as sufficient strength can be obtained by detection of the electric signal.

The conductive fiber B must be resistant to movement such as repeated bending and twisting from the use of the present invention. As the index, one having a greater nodule strength is preferred. The nodule strength can be measured by the method of JIS L1013 8.6. The degree of knot strength suitable for the present invention is preferably 0.5 cN / dtex or more, more preferably 1.0 cN / dtex or more, and further preferably 1.5 cN / dtex or more. 2.0 cN / dtex or more is most preferable. As another index, one having a smaller bending rigidity is preferred. The bending rigidity is generally measured by a measuring device such as KES-FB2 pure bending tester manufactured by Kato Tech Co., Ltd. The degree of bending rigidity suitable for the present invention is preferably smaller than the carbon fiber “Tenax” (registered trademark) HTS40-3K manufactured by Toho Tenax Co., Ltd. Specifically, the flexural rigidity of the conductive fiber is preferably 0.05 × 10 ⁻⁴ N · m ² / m or less, and preferably 0.02 × 10 ⁻⁴ N · m ² / m or less. More preferably, it is more preferably 0.01 × 10 ⁻⁴ N · m ² / m or less.

(Piezoelectric fiber)
As the piezoelectric polymer that is the material of the piezoelectric fiber A, a polymer exhibiting piezoelectricity such as polyvinylidene fluoride or polylactic acid can be used. However, in the present embodiment, the piezoelectric fiber A is used as a main component as described above. It is preferred to include polylactic acid. Polylactic acid, for example, is easily oriented by drawing after melt spinning and exhibits piezoelectricity, and is excellent in productivity in that it does not require an electric field alignment treatment required for polyvinylidene fluoride and the like. However, this is not intended to exclude the use of polyvinylidene fluoride or other piezoelectric materials in the practice of the present invention.

  As polylactic acid, depending on its crystal structure, poly-L-lactic acid obtained by polymerizing L-lactic acid and L-lactide, D-lactic acid, poly-D-lactic acid obtained by polymerizing D-lactide, and those There are stereocomplex polylactic acid having a hybrid structure, and any of them can be used as long as it exhibits piezoelectricity. From the viewpoint of high piezoelectricity, poly-L-lactic acid and poly-D-lactic acid are preferable. Since poly-L-lactic acid and poly-D-lactic acid are reversed in polarization with respect to the same stress, they can be used in combination according to the purpose.

  The optical purity of polylactic acid is preferably 99% or more, more preferably 99.3% or more, and further preferably 99.5% or more. If the optical purity is less than 99%, the piezoelectricity may be remarkably lowered, and it may be difficult to obtain a sufficient electrical signal due to the shape change of the piezoelectric fiber A. In particular, the piezoelectric fiber A preferably contains poly-L-lactic acid or poly-D-lactic acid as a main component, and the optical purity thereof is preferably 99% or more.

  The piezoelectric fiber A containing polylactic acid as a main component is drawn at the time of production and is uniaxially oriented in the fiber axis direction. Furthermore, the piezoelectric fiber A is not only uniaxially oriented in the fiber axis direction but also preferably contains polylactic acid crystals, and more preferably contains uniaxially oriented polylactic acid crystals. This is because polylactic acid exhibits higher piezoelectricity due to its high crystallinity and uniaxial orientation.

Crystallinity and uniaxial orientation are determined by homo PLA crystallinity X _homo (%) and crystal orientation Ao (%). As the piezoelectric fiber A of the present invention, it is preferable that the _homo PLA crystallinity X _homo (%) and the crystal orientation Ao (%) satisfy the following formula (3).
X _homo × Ao × Ao ÷ 10 ⁶ ≧ 0.26 (3)
If the above formula (3) is not satisfied, the crystallinity and / or uniaxial orientation may not be sufficient, and the output value of the electric signal for the operation may decrease, or the sensitivity of the signal for the operation in a specific direction may decrease. is there. The value on the left side of the formula (3) is more preferably 0.28 or more, and further preferably 0.3 or more. Here, each value is obtained according to the following.

Homopolylactic acid crystallinity X _homo :
The homopolylactic acid crystallinity X _homo is determined from crystal structure analysis by wide angle X-ray diffraction analysis (WAXD). In wide-angle X-ray diffraction analysis (WAXD), an X-ray diffraction pattern of a sample is recorded on an imaging plate under the following conditions by a transmission method using an Ultrax 18 type X-ray diffractometer manufactured by Rigaku.
X-ray source: Cu-Kα ray (confocal mirror)
Output: 45kV x 60mA
Slit: 1st: 1mmΦ, 2nd: 0.8mmΦ
Camera length: 120mm
Accumulation time: 10 minutes Sample: 35 mg of polylactic acid fibers are aligned to form a 3 cm fiber bundle.
In the obtained X-ray diffraction pattern, the total scattering intensity Itotal is obtained over the azimuth angle, and here, the integrated intensity of each diffraction peak derived from the homopolylactic acid crystal appearing in the vicinity of 2θ = 16.5 °, 18.5 °, 24.3 °. Is obtained as a sum ΣIHMi. From these values, the homopolylactic acid crystallinity X _homo is determined according to the following formula (4).
Homopolylactic acid crystallinity X _homo (%) = ΣI _HMi / I _total × 100 (4)
Note that ΣI _HMi is calculated by subtracting diffuse scattering due to background and amorphous in the total scattering intensity.

(2) Crystal orientation degree Ao:
Regarding the crystal orientation degree Ao, in the X-ray diffraction pattern obtained by the above wide-angle X-ray diffraction analysis (WAXD), the diffraction peak derived from the homopolylactic acid crystal appearing in the vicinity of 2θ = 16.5 ° in the radial direction is oriented. The intensity distribution with respect to the angle (°) is taken, and the total half-value width Σ _Wi (°) of the obtained distribution profile is calculated from the following equation (5).
Crystal orientation degree Ao (%) = (360−ΣW _i ) ÷ 360 × 100 (5)

  In addition, since polylactic acid is a polyester that is hydrolyzed relatively quickly, in the case where heat and humidity resistance is a problem, a known hydrolysis inhibitor such as an isocyanate compound, an oxazoline compound, an epoxy compound, or a carbodiimide compound is added. Also good. Further, if necessary, the physical properties may be improved by adding an antioxidant such as a phosphoric acid compound, a plasticizer, a photodegradation inhibitor, and the like.

  Polylactic acid may be used as an alloy with other polymers. However, if polylactic acid is used as the main piezoelectric polymer, it contains at least 50% by mass or more based on the total mass of the alloy. Preferably, it is 70 mass% or more, Most preferably, it is 90 mass% or more.

  Examples of the polymer other than polylactic acid in the case of alloy include polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate copolymer, polymethacrylate, and the like, but the invention is not limited thereto. Any polymer may be used as long as the desired piezoelectricity is exhibited.

  The piezoelectric fiber A may be a multifilament in which a plurality of filaments are bundled, or may be a monofilament composed of a single filament. In the case of monofilament (including spun yarn), the single yarn diameter is 1 μm to 5 mm, preferably 5 μm to 2 mm, and more preferably 10 μm to 1 mm. In the case of a multifilament, the single yarn diameter is 0.1 μm to 5 mm, preferably 2 μm to 100 μm, and more preferably 3 μm to 50 μm. The number of filaments of the multifilament is preferably 1 to 100,000, more preferably 50 to 50,000, and still more preferably 100 to 20,000. However, the fineness and the number of the piezoelectric fibers A are the fineness and the number per carrier when producing the braid, and the multifilament formed by a plurality of single yarns (monofilaments) is also one piezoelectric. It shall be counted as fiber A. Here, even if a fiber other than the piezoelectric fiber is used in one carrier, the total amount including that is used.

  In order to use such a piezoelectric polymer as the piezoelectric fiber A, any known technique for forming a fiber from the polymer can be employed as long as the effects of the present invention are exhibited. For example, a method of extruding a piezoelectric polymer to form a fiber, a method of melt-spinning a piezoelectric polymer to make a fiber, a method of making a piezoelectric polymer fiber by dry or wet spinning, a method of making a piezoelectric polymer A technique of forming fibers by electrostatic spinning, a technique of cutting thinly after forming a film, and the like can be employed. As these spinning conditions, a known method may be applied according to the piezoelectric polymer to be employed, and a melt spinning method that is industrially easy to produce is usually employed. Furthermore, after forming the fiber, the formed fiber is stretched. As a result, a piezoelectric fiber A that is uniaxially oriented and exhibits large piezoelectricity including crystals is formed.

  In addition, the piezoelectric fiber A can be subjected to treatments such as dyeing, twisting, blending, and heat treatment before making the braided braid as described above.

  Furthermore, since the piezoelectric fiber A may be broken when the braid is formed, the piezoelectric fiber A may be cut off or fluff may come out, so that the strength and wear resistance are preferably high. It is preferably 5 cN / dtex or more, more preferably 2.0 cN / dtex or more, further preferably 2.5 cN / dtex or more, and most preferably 3.0 cN / dtex or more. The abrasion resistance can be evaluated by JIS L1095 9.10.2 B method, etc., and the number of friction is preferably 100 times or more, more preferably 1000 times or more, and further preferably 5000 times or more. Most preferably, it is 10,000 times or more. The method for improving the wear resistance is not particularly limited, and any known method can be used. For example, the crystallinity is improved, fine particles are added, or the surface is processed. Can do. In addition, when processing into braids, a lubricant can be applied to the fibers to reduce friction.

Moreover, it is preferable that the shrinkage rate of the piezoelectric fiber is small from the shrinkage rate of the conductive fiber described above. If the difference in shrinkage rate is large, the braid may bend due to heat treatment during post-fabrication after fabric production or after fabric production or during actual use, or due to changes over time, the flatness of the fabric may deteriorate, or the piezoelectric signal will become weak. May end up. When the shrinkage rate is quantified by the boiling water shrinkage rate described later, it is preferable that the boiling water shrinkage rate S (p) of the piezoelectric fiber and the boiling water shrinkage rate S (c) of the conductive fiber satisfy the following formula (6). .
| S (p) −S (c) | ≦ 10 (6)
The left side of the above formula (6) is more preferably 5 or less, and even more preferably 3 or less.

Further, it is preferable that the contraction rate of the piezoelectric fiber is small in difference from the contraction rate of fibers other than the conductive fibers, for example, insulating fibers. If the difference in shrinkage rate is large, the braid may bend due to heat treatment during post-fabrication after fabric production or after fabric production or during actual use, or due to changes over time, the flatness of the fabric may deteriorate, or the piezoelectric signal will become weak. May end up. When the shrinkage rate is quantified by the boiling water shrinkage rate, it is preferable that the boiling water shrinkage rate S (p) of the piezoelectric fiber and the boiling water shrinkage rate S (i) of the insulating fiber satisfy the following formula (7).
| S (p) −S (i) | ≦ 10 (7)
The left side of the formula (7) is more preferably 5 or less, and even more preferably 3 or less.

Further, it is preferable that the shrinkage rate of the piezoelectric fiber is small. For example, when the shrinkage rate is quantified by boiling water shrinkage rate, the shrinkage rate of the piezoelectric fiber is preferably 15% or less, more preferably 10% or less, further preferably 5% or less, and most preferably 3% or less. is there. As a means for lowering the shrinkage rate, any known method can be applied. For example, the shrinkage rate can be reduced by relaxing the orientation of the amorphous part or increasing the crystallinity by heat treatment, and the heat treatment is performed. The timing is not particularly limited, and examples thereof include after stretching, after twisting, after braiding, and after forming into a fabric. In addition, the above-mentioned boiling water shrinkage shall be measured with the following method. A casserole of 20 times was made with a measuring machine having a frame circumference of 1.125 m, a load of 0.022 cN / dtex was applied, it was hung on a scale plate, and the initial casket length L0 was measured. After that, this casserole was treated in a boiling water bath at 100 ° C. for 30 minutes, allowed to cool, and again subjected to the above load and hung on the scale plate to measure the length L after shrinkage. Using the measured L0 and L, the boiling water shrinkage is calculated by the following equation (8).
Boiling water shrinkage = (L0−L) / L0 × 100 (%) (8)

(Filament for adjusting bending recovery rate)
The bending recovery rate adjusting filament may be included in the core portion 3 and / or the sheath portion 2. The cross-sectional area of the bending recovery rate adjusting filament is 0.001 to 1.0 square millimeter, preferably 0.005 to 0.5 square millimeter, more preferably 0.01 to 0.3 square millimeter. If the bending recovery rate adjusting filament is too thin, the bending recovery rate is not 70 or more, and if the bending recovery rate adjusting filament is too thick, the flexibility of the braided piezoelectric element 1 is lost.

  Any known filament can be used as the bending recovery rate adjusting filament. For example, synthetic polymer filaments such as polyester filament, nylon filament, acrylic filament, polyethylene filament, polypropylene filament, vinyl chloride filament, aramid filament, polysulfone filament, polyether filament, polyurethane filament can be used. The bending recovery rate adjusting filament is not limited to these, and any known filament can be used arbitrarily. Further, these filaments may be used in combination. In addition, as the bending recovery rate adjusting filament, any known cross-sectional fiber can be used. Further, the filament for adjusting the bending recovery rate may be a monofilament or a multifilament. When the bending recovery rate adjusting filament is a multifilament, the total cross-sectional area of the single yarn is considered as the cross-sectional area.

(Coating layer)
The covering layer may be formed outside the sheath portion 2 of the braided piezoelectric element 1. The thickness of the coating layer is 0.05 to 2.0 mm, preferably 0.04 mm to 1.0 mm, and more preferably 0.03 to 0.5 mm. If the coating layer is too thin, the bending recovery rate is not 70 or more, and if the coating layer is too thick, the flexibility of the braided piezoelectric element 1 is lost. In addition, when the braided piezoelectric element 1 is strongly restrained by the covering layer, an electric signal generated by the braided piezoelectric element 1 may increase.

  As a mode of the coating layer, in addition to coating, a film, a fabric, a fiber, or the like may be wound, a mode of being inserted into a tube, or a combination thereof. Any known polymer is used for the coating layer regardless of its form. For example, polyester, nylon, acrylic, polyethylene, polypropylene, vinyl chloride, aramid, polysulfone, polyether, polyurethane, rubber and the like can be used. Further, these polymers may be used in combination.

(High elastic fiber)
The highly elastic fiber may be included in the core portion 3 and / or the sheath portion 2. The elastic modulus of the highly elastic fiber is 15.0 GPa, preferably 20.0 GPa or more, more preferably 30.0 GPa or more, and further preferably 50.0 GPa or more. If the elastic modulus of the high elastic fiber is low, the bending recovery rate is not 70 or more, and if the elastic modulus of the high elastic fiber is too high, the flexibility of the braided piezoelectric element 1 is lost. The ratio of the highly elastic fiber to the core part 3 and / or the sheath part 2 is preferably 50% or less, more preferably 30% or less, still more preferably 10% or less. If the ratio of the high elastic fiber to the core part 3 and / or the sheath part 2 is too small, the bending recovery rate does not become 70 or more, and if the ratio of the bending recovery rate adjusting filament is too high, the flexibility of the braided piezoelectric element 1 Will be lost. By including the highly elastic fiber in the core part 3 and / or the sheath part 2, the braided piezoelectric element 1 is likely to return to its original state after being deformed once, so that the repeatability of electric signals is improved.

  Any known fiber having an elastic modulus of 15.0 GPa or more can be used as the highly elastic fiber. For example, aramid fiber, PBO fiber, LCP fiber, ultra high molecular weight polyethylene fiber, carbon fiber, metal fiber, glass fiber, ceramic fiber and the like can be mentioned. These may be used in combination. The high-strength fiber not only has high elasticity but also preferably has an elongation of 1% or more, more preferably 3% or more, and further preferably 5% or more. If the elongation is low, when the braid is deformed, the fiber breaks, the quality is deteriorated, and the repeatability of the electrical signal may not be improved.

(Coating)
The surface of the conductive fiber B, that is, the core portion 3 is covered with the piezoelectric fiber A, that is, the braided sheath portion 2. The thickness of the sheath part 2 covering the conductive fiber B is preferably 1 μm to 10 mm, more preferably 5 μm to 5 mm, further preferably 10 μm to 3 mm, most preferably 20 μm to 1 mm. preferable. If it is too thin, there may be a problem in terms of strength. If it is too thick, the braided piezoelectric element 1 may become hard and difficult to deform. In addition, the sheath part 2 said here refers to the layer adjacent to the core part 3. FIG.

In the braided piezoelectric element 1, the total fineness of the piezoelectric fibers A in the sheath 2 is preferably not less than 1/2 times and not more than 20 times the total fineness of the conductive fibers B in the core 3. 15 times or less, more preferably 2 times or more and 10 times or less. If the total fineness of the piezoelectric fiber A is too small relative to the total fineness of the conductive fiber B, the piezoelectric fiber A surrounding the conductive fiber B is too small and the conductive fiber B cannot output a sufficient electrical signal, Furthermore, there exists a possibility that the conductive fiber B may contact the other conductive fiber which adjoins. If the total fineness of the piezoelectric fiber A is too large relative to the total fineness of the conductive fiber B, there are too many piezoelectric fibers A surrounding the conductive fiber B, and the braided piezoelectric element 1 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 1 does not sufficiently function as a sensor.
The total fineness referred to here is the sum of the finenesses of all the piezoelectric fibers A constituting the sheath portion 2. For example, in the case of a general 8-strand braid, it is the sum of the finenesses of 8 fibers.

  In the braided piezoelectric element 1, the fineness per piezoelectric fiber A of the sheath 2 is preferably 1/20 or more and 2 or less the total fineness of the conductive fiber B. It is more preferably 15 times or more and 1.5 times or less, and further preferably 1/10 time or more and 1 time or less. If the fineness per piezoelectric fiber A is too small with respect to the total fineness of the conductive fiber B, the piezoelectric fiber A is too small and the conductive fiber B cannot output a sufficient electric signal. A may be cut off. If the fineness per piezoelectric fiber A is too large relative to the total fineness of the conductive fiber B, the piezoelectric fiber A is too thick and the braided piezoelectric element 1 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 1 does not sufficiently function as a sensor.

  In addition, when a metal fiber is used for the conductive fiber B, or when the metal fiber is mixed with the conductive fiber B or the piezoelectric fiber A, the fineness ratio is not limited to the above. This is because, in the present invention, the ratio is important in terms of contact area and coverage, that is, area and volume. For example, when the specific gravity of each fiber exceeds 2, it is preferable that the ratio of the average cross-sectional area of the fiber is the ratio of the fineness.

  Although it is preferable that the piezoelectric fiber A and the conductive fiber B are as close as possible, an anchor layer or an adhesive layer is provided between the conductive fiber B and the piezoelectric fiber A in order to improve the adhesiveness. May be.

  The covering method is a method in which the conductive fiber B is used as a core yarn, and the piezoelectric fiber A is wound around in a braid shape around the conductive fiber B. On the other hand, the shape of the braid of the piezoelectric fiber A is not particularly limited as long as an electric signal can be output with respect to the stress generated by the applied load. A braided string is preferred.

  The shape of the conductive fiber B and the piezoelectric fiber A is not particularly limited, but is preferably as close to a concentric circle as possible. When a multifilament is used as the conductive fiber B, the piezoelectric fiber A only needs to be covered so that at least a part of the surface (fiber peripheral surface) of the multifilament of the conductive fiber B is in contact. The piezoelectric fibers A may or may not be coated on all filament surfaces (fiber peripheral surfaces) constituting the multifilament. What is necessary is just to set suitably the covering state of the piezoelectric fiber A to each internal filament which comprises the multifilament of the conductive fiber B, considering the performance as a piezoelectric element, the handleability, etc.

  The braided piezoelectric element 1 of the present invention does not need to have an electrode on the surface thereof, so that there is no need to further cover the braided piezoelectric element 1 itself, and there is an advantage that malfunction is unlikely.

(Production method)
In the braided piezoelectric element 1 of the present invention, the surface of at least one conductive fiber B is covered with the braided piezoelectric fiber A. Examples of the manufacturing method include the following methods. In other words, the conductive fiber B and the piezoelectric fiber A are produced in separate steps, and the conductive fiber B is wrapped around the conductive fiber B in a braid shape and covered. In this case, it is preferable to coat so as to be as concentric as possible.

  When producing the conductive fiber B and the piezoelectric fiber A, the conductive fiber B may be mixed with a bending recovery rate adjusting filament and / or a highly elastic fiber, and the piezoelectric fiber A may be adjusted with a bending recovery rate. Filaments and / or highly elastic fibers may be mixed. Further, the fiber covering the conductive fiber B may be a combination of the piezoelectric fiber A, a bending recovery rate adjusting filament, and / or a highly elastic fiber. Furthermore, these manufacturing methods can also be combined.

  In this case, as preferred spinning and stretching conditions when polylactic acid is used as the piezoelectric polymer for forming the piezoelectric fiber A, the melt spinning temperature is preferably 150 ° C. to 250 ° C., and the stretching temperature is preferably 40 ° C. to 150 ° C. The draw ratio is preferably 1.1 to 5.0 times, and the crystallization temperature is preferably 80 ° C to 170 ° C.

  As the piezoelectric fiber A wound around the conductive fiber B, a multifilament in which a plurality of filaments are bundled may be used, or a monofilament (including spun yarn) may be used. In addition, as the conductive fiber B around which the piezoelectric fiber A is wound, a multifilament in which a plurality of filaments are bundled may be used, or a monofilament (including spun yarn) may be used.

  As a preferable form of the coating, the conductive fiber B can be used as a core yarn, and the piezoelectric fiber A can be formed in a braid shape around the conductive fiber B to form a round braid. . More specifically, an 8-strand braid having 16 cores and a 16-strand braid are included. However, for example, the piezoelectric fiber A may be shaped like a braided tube, and the conductive fiber B may be used as a core and inserted into the braided tube.

  A coating layer can also be formed on the outside of the sheath portion 2 including the piezoelectric fiber A. The coating layer is manufactured by winding a coating, a film, a fabric, a fiber or the like.

  By the manufacturing method as described above, the braided piezoelectric element 1 in which the surface of the conductive fiber B is covered with the braided piezoelectric fiber A can be obtained.

  Since the braided piezoelectric element 1 of the present invention does not require the formation of an electrode for detecting an electric signal on the surface, it can be manufactured relatively easily.

(Protective layer)
A protective layer may be provided on the outermost surface of the braided piezoelectric element 1 of the present invention. This protective layer is preferably insulative, and more preferably made of a polymer from the viewpoint of flexibility. In the case of providing the protective layer with insulation, of course, in this case, the entire protective layer is deformed or rubbed on the protective layer, but these external forces reach the piezoelectric fiber A, There is no particular limitation as long as it can induce polarization. The protective layer is not limited to those formed by coating with a polymer or the like, and may be a film, fabric, fiber or the like, or a combination thereof.

  The thinner the protective layer is, the easier it is to transmit shear stress to the piezoelectric fiber A. However, if it is too thin, problems such as destruction of the protective layer itself are likely to occur, and preferably 10 nm to 200 μm. More preferably, they are 50 nm-50 micrometers, More preferably, they are 70 nm-30 micrometers, Most preferably, they are 100 nm-10 micrometers. The shape of the piezoelectric element can also be formed by this protective layer.

It is also possible to incorporate an electromagnetic shielding layer into the braid structure for the purpose of noise reduction. The electromagnetic wave shielding layer is not particularly limited, but may be coated with a conductive substance, or may be wound with a conductive film, fabric, fiber, or the like. The volume resistivity of the electromagnetic wave shielding layer is preferably 10 ⁻¹ Ω · cm or less, more preferably 10 ⁻² Ω · cm or less, still more preferably 10 ⁻³ Ω · cm or less. However, the resistivity is not limited as long as the effect of the electromagnetic wave shielding layer can be obtained. This electromagnetic wave shielding layer may be provided on the surface of the piezoelectric fiber A of the sheath, or may be provided outside the protective layer described above. Of course, a plurality of layers of electromagnetic shielding layers and protective layers may be laminated, and the order thereof is appropriately determined according to the purpose.

  Furthermore, a plurality of layers made of piezoelectric fibers can be provided, or a plurality of layers made of conductive fibers for extracting signals can be provided. Of course, the order and the number of layers of these protective layers, electromagnetic wave shielding layers, layers made of piezoelectric fibers, and layers made of conductive fibers are appropriately determined according to the purpose. In addition, as a method of winding, the method of forming a braid structure in the outer layer of the sheath part 2, or covering it is mentioned.

(Function)
The braided piezoelectric element 1 of the present invention is, for example, a stress generated when a load is applied to the braided piezoelectric element 1 by rubbing the surface of the braided piezoelectric element 1, that is, a stress applied to the braided piezoelectric element 1. It can be used as a sensor for detecting the size and / or application position. In addition, the braided piezoelectric element 1 of the present invention can take out an electrical signal as long as shear stress is applied to the piezoelectric fiber A by pressing force other than rubbing or bending deformation. For example, the “applied stress” to the braided piezoelectric element 1 includes the frictional force between the surface of the piezoelectric element, that is, the surface of the piezoelectric fiber A and the surface of the contacted object such as a finger, or the piezoelectric fiber. Examples thereof include a resistance force in the vertical direction with respect to the surface or tip of A and a resistance force against bending deformation of the piezoelectric fiber A. In particular, the braided piezoelectric element 1 of the present invention can efficiently output a large electric signal when bent or rubbed in a parallel direction with respect to the conductive fiber B.

  Here, the “applied stress” applied to the braided piezoelectric element 1 is, for example, approximately 1-1000 Pa as a guide when the stress is of a magnitude that rubs the surface with a finger. Of course, it goes without saying that the magnitude of the applied stress and the position of the applied stress can be detected even if it is more than this. When inputting with a finger or the like, it is preferable to operate even with a load of 1 Pa to 500 Pa, and more preferable to operate with a load of 1 Pa to 100 Pa. Of course, as described above, it operates even with a load exceeding 500 Pa.

(Fabric piezoelectric element)
FIG. 3 is a schematic diagram illustrating a configuration example of a fabric-like piezoelectric element using the braided piezoelectric element according to the embodiment.
The cloth-like piezoelectric element 7 includes a cloth 8 including at least one braided piezoelectric element 1. The fabric 8 is not limited as long as at least one of the fibers (including the braid) constituting the fabric is the braided piezoelectric element 1 and the braided piezoelectric element 1 can exhibit the function as a piezoelectric element. Any woven or knitted fabric may be used. In forming the cloth, as long as the object of the present invention is achieved, weaving, knitting and the like may be performed in combination with other fibers (including braids). Of course, the braided piezoelectric element 1 may be used as a part of a fiber (for example, warp or weft) constituting the fabric, or the braided piezoelectric element 1 may be embroidered or bonded to the fabric. Good. In the example shown in FIG. 3, the fabric-like piezoelectric element 7 has at least one braid-like piezoelectric element 1 and insulating fibers 9 as warps and alternately has conductive fibers 10 and insulating fibers 9 as wefts. Plain woven fabric. The conductive fiber 10 may be the same type or different type of conductive fiber B, and the insulating fiber 9 will be described later. Note that all or part of the insulating fibers 9 and / or the conductive fibers 10 may be braided.

  In this case, when the cloth-like piezoelectric element 7 is deformed by bending or the like, the braided piezoelectric element 1 is also deformed along with the deformation, so that the cloth-like piezoelectric element 7 is generated by an electric signal output from the braided piezoelectric element 1. Can be detected. Since the cloth-like piezoelectric element 7 can be used as a cloth (woven or knitted fabric), it can be applied to, for example, a garment-shaped wearable sensor.

  Further, in the fabric-like piezoelectric element 7 shown in FIG. 3, the conductive fiber 10 intersects and contacts the braided piezoelectric element 1. Therefore, the conductive fiber 10 intersects and covers at least a part of the braided piezoelectric element 1, covers it, and shields at least a part of the electromagnetic wave going to the braided piezoelectric element 1 from the outside. Can be seen. Such a conductive fiber 10 has a function of reducing the influence of electromagnetic waves on the braided piezoelectric element 1 by being grounded. That is, the conductive fiber 10 can function as an electromagnetic wave shield for the braided piezoelectric element 1. Thereby, for example, the S / N ratio of the cloth-like piezoelectric element 7 can be remarkably improved without overlapping the conductive cloth for electromagnetic wave shielding above and below the cloth-like piezoelectric element 7. In this case, it is preferable that the ratio of the conductive fibers 10 in the wefts (in the case of FIG. 3) intersecting with the braided piezoelectric element 1 is higher from the viewpoint of electromagnetic shielding. Specifically, 30% or more of the fibers forming the fabric 8 and intersecting the braided piezoelectric element 1 are preferably conductive fibers 10, more preferably 40% or more, and 50% or more. Is more preferable. Thus, in the cloth-like piezoelectric element 7, the cloth-like piezoelectric element 7 with an electromagnetic wave shield can be obtained by inserting the conductive fiber 10 as at least a part of the fibers constituting the cloth.

  Examples of the woven structure of the woven fabric include a three-layer structure such as plain weave, twill weave, and satin weave, a change structure, a single double structure such as a vertical double weave and a horizontal double weave, and a vertical velvet. The type of knitted fabric may be a circular knitted fabric (weft knitted fabric) or a warp knitted fabric. Preferable examples of the structure of the circular knitted fabric (weft knitted fabric) include flat knitting, rubber knitting, double-sided knitting, pearl knitting, tuck knitting, floating knitting, one-side knitting, lace knitting, and bristle knitting. Examples of the warp knitting structure include single denby knitting, single atlas knitting, double cord knitting, half tricot knitting, back hair knitting, jacquard knitting, and the like. The number of layers may be a single layer or a multilayer of two or more layers. Further, it may be a napped woven fabric or a napped knitted fabric composed of a napped portion made of a cut pile and / or a loop pile and a ground tissue portion.

(Multiple piezoelectric elements)
In the cloth-like piezoelectric element 7, a plurality of braided piezoelectric elements 1 can be used side by side. For example, the braided piezoelectric elements 1 may be used for all warps or wefts, or the braided piezoelectric elements 1 may be used for several or a part of them. Alternatively, the braided piezoelectric element 1 may be used as a warp in a certain part, and the braided piezoelectric element 1 may be used as a weft in another part.

  Thus, when forming the fabric-like piezoelectric element 7 by arranging a plurality of braided piezoelectric elements 1, the braided piezoelectric element 1 does not have an electrode on the surface, so that the arrangement and knitting methods can be selected widely. There is an advantage.

  Further, when a plurality of braided piezoelectric elements 1 are used side by side, since the distance between the conductive fibers B is short, it is efficient in taking out an electric signal.

(Insulating fiber)
In the cloth-like piezoelectric element 7, the insulating fiber 9 can be used in portions other than the braided piezoelectric element 1 (and the conductive fiber 10). At this time, the insulating fiber 9 can be a stretchable material or a fiber having a shape for the purpose of improving the flexibility of the cloth-like piezoelectric element 7.

  Thus, by arranging the insulating fibers 9 in this manner in addition to the braided piezoelectric element 1 (and the conductive fibers 10), the operability of the cloth-like piezoelectric element 7 (e.g., ease of movement as a wearable sensor) is improved. It is possible to improve.

Such an insulating fiber can be used if the volume resistivity is 10 ⁶ Ω · cm or more, more preferably 10 ⁸ Ω · cm or more, and still more preferably 10 ¹⁰ Ω · cm or more.

  Examples of the insulating fiber 9 include polyester fiber, nylon fiber, acrylic fiber, polyethylene fiber, polypropylene fiber, vinyl chloride fiber, aramid fiber, polysulfone fiber, polyether fiber, polyurethane fiber and the like, cotton, hemp, silk, etc. Natural fibers, semi-synthetic fibers such as acetate, and regenerated fibers such as rayon and cupra can be used. It is not limited to these, A well-known insulating fiber can be used arbitrarily. Furthermore, these insulating fibers 9 may be used in combination, or may be combined with fibers that do not have insulating properties to form fibers having insulating properties as a whole.

  Also, any known cross-sectional shape fiber can be used.

(Applied technology for piezoelectric elements)
The piezoelectric element such as the braided piezoelectric element 1 or the cloth-like piezoelectric element 7 of the present invention can output the contact, pressure, and shape change to the surface as an electric signal in any form. It can be used as a sensor (device) for detecting the magnitude of stress applied to the element and / or the applied position. Further, this electric signal can be used as a power generation element such as a power source for moving other devices or storing electricity. Specifically, power generation by using it as a moving part of a human, animal, robot, machine, etc. that moves spontaneously, power generation on the surface of a shoe sole, rug, or structure that receives pressure from the outside, shape change in fluid Power generation, etc. In addition, in order to generate an electrical signal due to a shape change in the fluid, it is possible to adsorb a chargeable substance in the fluid or suppress adhesion.

  FIG. 4 is a block diagram showing a device 11 including the piezoelectric element 12 of the present invention. The device 11 includes a piezoelectric element 12 (example: braided piezoelectric element 1, fabric-like piezoelectric element 7), an amplifying means 13 for amplifying an electrical signal output from the piezoelectric element 12 in accordance with an applied pressure, and an amplifying means. 13 is provided with output means 14 for outputting the electric signal amplified at 13, and transmission means 15 for transmitting the electric signal output from the output means 14 to an external device (not shown). If this device 11 is used, the stress applied to the piezoelectric element is calculated by an arithmetic process in an external device (not shown) based on an electrical signal output by contact with the surface of the piezoelectric element 12, pressure, or shape change. The magnitude and / or applied position can be detected. Alternatively, calculation means (not shown) for calculating the magnitude of the stress applied to the piezoelectric element 12 and / or the applied position based on the electrical signal output from the output means 14 may be provided in the device 11. Good. Whether the transmission method by the transmission means 15 is wireless or wired may be appropriately determined according to the sensor to be configured.

  Further, not only the amplification means but also known signal processing means such as noise removing means and means for processing in combination with other signals can be used in combination. The order of connection of these means can be appropriately changed according to the purpose. Of course, the electric signal output from the piezoelectric element 12 may be processed as it is after being transmitted to the external device as it is.

  5 and 6 are schematic views showing a configuration example of a device including the braided cloth-like piezoelectric element according to the embodiment. 5 and 6 corresponds to that described with reference to FIG. 4, but the output unit 14 and the transmission unit 15 of FIG. 4 are not shown in FIGS. In the case of configuring a device including the fabric-like piezoelectric element 7, a lead wire from the core portion 3 of the braided piezoelectric element 1 is connected to the input terminal of the amplifying means 13, and the input of the amplifying means 13 is connected to the ground (earth) terminal. A braided piezoelectric element or conductive fiber 10 different from the braided piezoelectric element 1 connected to the terminal is connected. For example, as shown in FIG. 5, in the cloth-like piezoelectric element 7, the lead wire from the core portion 3 of the braided piezoelectric element 1 is connected to the input terminal of the amplifying means 13, and intersects and contacts the braided piezoelectric element 1. The conductive fiber 10 is grounded. Further, for example, as shown in FIG. 6, when a plurality of braided piezoelectric elements 1 are arranged in the cloth-like piezoelectric element 7, the lead wire from the core portion 3 of one braided piezoelectric element 1 is used as the input terminal of the amplifying means 13. The lead wire from the core part 3 of another braided piezoelectric element 1 aligned with the braided piezoelectric element 1 is grounded (grounded).

  Since the device 11 of the present invention is flexible and can be used in either a string form or a cloth form, a very wide range of applications can be considered. Specific examples of the device 11 of the present invention include a touch panel, a human or animal surface pressure sensor, for example, a glove or a band, which has a shape such as a hat, gloves, clothes including a sock, a supporter, or a handkerchief. Sensors that detect bending, twisting, and expansion / contraction of joints shaped like supporters. For example, when used for humans, it can be used as an interface for detecting contact and movement, collecting information on movement of joints and the like for medical purposes, amusement purposes, and moving lost tissues and robots. In addition, it can be used as a stuffed animal that imitates animals and humanoids, a surface pressure sensor of a robot, a sensor that detects bending, twisting, and expansion / contraction of a joint. In addition, it can be used as a surface pressure sensor or shape change sensor for bedding such as sheets and pillows, shoe soles, gloves, chairs, rugs, bags, and flags.

  Furthermore, since the device 11 of the present invention is braided or cloth-like and flexible, it can be used as a surface pressure sensor or a shape change sensor by sticking or covering the whole or part of the surface of any structure. Can do.

  Furthermore, since the device 11 of the present invention can generate a sufficient electric signal simply by rubbing the surface of the braided piezoelectric element 1, it can be used for a touch input device such as a touch sensor, a pointing device, or the like. . Further, since the position information and shape information in the height direction of the measurement object can be obtained by rubbing the surface of the measurement object with the braided piezoelectric element 1, it can be used for surface shape measurement and the like.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples.

The fabric for piezoelectric elements was manufactured by the following method.
(Manufacture of polylactic acid)
The polylactic acid used in the examples was produced by the following method.
To 100 parts by mass of L-lactide (manufactured by Musashino Chemical Laboratory, Inc., optical purity 100%), 0.005 part by mass of tin octylate was added, and 180 ° C. in a reactor equipped with a stirring blade in a nitrogen atmosphere. Then, 1.2 times equivalent of phosphoric acid was added to tin octylate, and then the remaining lactide was removed under reduced pressure at 13.3 Pa to obtain chips to obtain poly-L-lactic acid (PLLA1). . The obtained PLLA1 had a mass average molecular weight of 152,000, a glass transition point (Tg) of 55 ° C., and a melting point of 175 ° C.

(Piezoelectric fiber)
PLLA1 melted at 240 ° C. was discharged from a 24-hole cap at 20 g / min and taken up at 887 m / min. This unstretched multifilament yarn was stretched 2.3 times at 80 ° C. and heat-set at 100 ° C. to obtain a multifilament uniaxially stretched yarn of 84 dTex / 24 filament.

(Conductive fiber)
Silver-plated nylon manufactured by Mitsufuji Corporation, product name “AGposs” 100d34f was used as the conductive fiber B. The volume resistivity of this fiber was 1.1 × 10 ⁻³ Ω · cm.

(Insulating fiber)
Polyethylene terephthalate melted at 280 ° C. was discharged from a 24-hole cap at 45 g / min and taken up at 800 m / min. The undrawn yarn was drawn at 80 ° C. and 2.5 times, and heat-fixed at 180 ° C. to obtain a multifilament drawn yarn of 84 dTex / 24 filament.

(filament)
Polyethylene terephthalate melted at 280 ° C. was discharged from a 1-hole cap at 104 g / min and taken up at 800 m / min. The undrawn yarn was drawn at 80 ° C. and 2.5 times and heat-fixed at 180 ° C. to obtain a monofilament having a cross-sectional area of 0.04 square millimeters. did.

(Coating layer)
A heat-shrinkable tube manufactured by Esco Co., Ltd., product name “1.5 mm × 10 m heat-shrinkable tube (black)” was used as the coating layer.

(High elastic fiber)
“Technora” (registered trademark) manufactured by Teijin Ltd. was used as a highly elastic fiber. The elastic modulus of this highly elastic fiber was 72.3 GPa.

(Braided piezoelectric element)
As a sample of Example 1, as shown in FIG. 1, the conductive fiber B is a core yarn, the four piezoelectric fibers A are wound clockwise, and the four bending recovery rate adjusting filaments are wound counterclockwise. A braided piezoelectric element 1 was formed by wrapping around the core yarn in a braid shape to form an eight-strand braid. The braided piezoelectric element 1 had a bending recovery rate of 83. Here, the winding angle α of the piezoelectric fiber A and the bending recovery rate adjusting filament with respect to the fiber axis CL of the conductive fiber B was set to 45 °.

  As a sample of Example 2, as shown in FIG. 1, one conductive fiber B and a bending recovery rate adjusting filament are combined to form a core yarn, and the above eight piezoelectric fibers A are arranged around the core yarn. The braided piezoelectric element 1 was formed by winding it into a braid to form an eight-strand braid. The braided piezoelectric element 1 had a bending recovery rate of 78. Here, the winding angle α of the piezoelectric fiber A with respect to the fiber axis CL of the conductive fiber B was 45 °.

  As a sample of Example 3, as shown in FIG. 1, the conductive fiber B was used as a core yarn, and the eight piezoelectric fibers A were wound around the core yarn in a braid shape to form an eight-punch braid. The eight-strand braid was inserted into the coating layer, heated to 90 ° C. with an iron, and the eight-strand braid was covered with the coating layer to form the braided piezoelectric element 1. The bending recovery rate of the braided piezoelectric element 1 was 75. Here, the winding angle α of the piezoelectric fiber A with respect to the fiber axis CL of the conductive fiber B was 45 °. Moreover, the thickness of the coating layer after heat shrinkage was 0.2 mm.

  As a sample of Example 4, as shown in FIG. 1, the conductive fiber B is a core yarn, the four piezoelectric fibers A are clockwise, and the four high-elastic fibers are left-handed. The braided piezoelectric element 1 was formed by winding it around in a braid shape to form an eight-strand braid. The braided piezoelectric element 1 had a bending recovery rate of 78. Here, the winding angle α of the piezoelectric fiber A and the bending recovery rate adjusting filament with respect to the fiber axis CL of the conductive fiber B was set to 45 °.

(Weaving)
As a sample of Example 5, as shown in FIG. 3, the insulating fiber 9 and one braided piezoelectric element 1 (same as the sample of Example 1) are arranged on the warp, and the insulating fiber 9 and the conductive material are arranged on the weft. A plain woven fabric was prepared by alternately arranging the fibers 10, and the fabric-like piezoelectric element 7 was obtained.
As a sample of Comparative Example 1, as shown in FIG. 1, the conductive fiber B is used as a core yarn, and the eight piezoelectric fibers A are wound around the core yarn in a braid shape to form an eight-ply braid. A piezoelectric element 1 was formed. Here, the winding angle α of the piezoelectric fiber A with respect to the fiber axis CL of the conductive fiber B was 45 °.

(Performance evaluation and evaluation results)
Performance evaluation and evaluation results of the braided piezoelectric element 1 and the cloth-like piezoelectric element 7 are as follows.

Example 1
The conductive fiber B in the braided piezoelectric element 1 was connected as a signal line to an oscilloscope (digital oscilloscope DL6000 series trade name “DL6000” manufactured by Yokogawa Electric Corporation) via a 1000 × amplification circuit via wiring. The braided piezoelectric element 1 was bent 90 degrees in an electromagnetic wave shield box protected by a grounded metal mesh.
As a result, a potential difference of about 120 mV was detected by an oscilloscope as an output from the braided piezoelectric element 1, and it was confirmed that a sufficiently large electric signal could be detected by deformation of the braided piezoelectric element 1. Moreover, the electric signal after repeating 90 degree | times bending 50 times was 115 mV, and it was confirmed that repeatability is favorable.

(Example 2)
The conductive fiber B in the braided piezoelectric element 1 was connected as a signal line to an oscilloscope (digital oscilloscope DL6000 series trade name “DL6000” manufactured by Yokogawa Electric Corporation) via a 1000 × amplification circuit via wiring. The braided piezoelectric element 1 was bent 90 degrees in an electromagnetic wave shield box protected by a grounded metal mesh.
As a result, a potential difference of about 125 mV was detected by an oscilloscope as an output from the braided piezoelectric element 1, and it was confirmed that a sufficiently large electric signal could be detected by deformation of the braided piezoelectric element 1. Moreover, the electric signal after repeating 90 degree | times bending 50 times was 120 mV, and it was confirmed that repetition reproducibility is favorable.

(Example 3)
The conductive fiber B in the braided piezoelectric element 1 was connected as a signal line to an oscilloscope (digital oscilloscope DL6000 series trade name “DL6000” manufactured by Yokogawa Electric Corporation) via a 1000 × amplification circuit via wiring. The braided piezoelectric element 1 was bent 90 degrees in an electromagnetic wave shield box protected by a grounded metal mesh.
As a result, a potential difference of about 125 mV was detected by an oscilloscope as an output from the braided piezoelectric element 1, and it was confirmed that a sufficiently large electric signal could be detected by deformation of the braided piezoelectric element 1. Moreover, the electric signal after repeating 90 degree | times bending 50 times was 120 mV, and it was confirmed that repetition reproducibility is favorable.

Example 4
The conductive fiber B in the braided piezoelectric element 1 was connected as a signal line to an oscilloscope (digital oscilloscope DL6000 series trade name “DL6000” manufactured by Yokogawa Electric Corporation) via a 1000 × amplification circuit via wiring. The braided piezoelectric element 1 was bent 90 degrees in an electromagnetic wave shield box protected by a grounded metal mesh.
As a result, a potential difference of about 110 mV was detected as an output from the braided piezoelectric element 1 by an oscilloscope, and it was confirmed that a sufficiently large electric signal could be detected by deformation of the braided piezoelectric element 1. Moreover, the electrical signal after repeating 90 degree | times bending 50 times was 105 mV, and it was confirmed that repeatability is favorable.

(Example 5)
A 1000-times amplification circuit is connected to the oscilloscope (digital oscilloscope DL6000 series product name “DL6000” manufactured by Yokogawa Electric Corporation) via the wiring using the conductive fiber 3 in the braided piezoelectric element 1 of the fabric-like piezoelectric element 7 as a signal line. Connected via. Further, the conductive fibers 10 of the wefts of the cloth-like piezoelectric element 7 were grounded as grounding (earth) wires. In this state, the cloth-like piezoelectric element 7 was bent 90 degrees in a direction perpendicular to the braided piezoelectric element 1.
As a result, an electrical signal with almost no noise was obtained by an oscilloscope as an output from the braided piezoelectric element 1 of the fabric-like piezoelectric element 7, and a potential difference of about 100 mV was detected. Moreover, the electrical signal after repeating 90 degree | times bending 50 times was 95 mV, and it was confirmed that repeatability is favorable. From the above results, it was confirmed that a sufficiently large electric signal can be detected with low noise by deformation of the cloth-like piezoelectric element 7.

(Comparative Example 1)
The conductive fiber B in the braided piezoelectric element 1 was connected as a signal line to an oscilloscope (digital oscilloscope DL6000 series trade name “DL6000” manufactured by Yokogawa Electric Corporation) via a 1000 × amplification circuit via wiring. The braided piezoelectric element 1 was bent 90 degrees in an electromagnetic wave shield box protected by a grounded metal mesh.
As a result, a potential difference of about 100 mV was detected by an oscilloscope as an output from the braided piezoelectric element 1. Moreover, the electric signal after repeating 90 degree | times bending 50 times was 55 mV.

DESCRIPTION OF SYMBOLS A Piezoelectric fiber B Conductive fiber 1 Braided piezoelectric element 2 Sheath part 3 Core part 7 Fabric-like piezoelectric element 8 Fabric 9 Insulating fiber 10 Conductive fiber 11 Device 12 Piezoelectric element 13 Amplifying means 14 Output means 15 Transmitting means CL fiber Shaft α Wound angle L Braid protrusion distance after bending recovery rate measurement test

Claims (12)

  A braided piezoelectric element comprising a core formed of conductive fibers and a sheath formed of braided piezoelectric fibers so as to cover the core, and having a bending recovery rate of 70 or more.   The braided piezoelectric element according to claim 1, wherein the core and / or the sheath includes a bending recovery rate adjusting filament having a cross-sectional area of 0.001 to 1.0 square millimeters.   The braided piezoelectric element according to claim 1 or 2, further comprising a coating layer having a thickness of 0.05 to 2.0 mm on an outer side of the sheath portion.   The braided piezoelectric element according to claim 1, wherein the core part and / or the sheath part includes a highly elastic fiber having an elastic modulus of 15.0 GPa or more.   The said piezoelectric fiber contains polylactic acid as a main component, The winding angle of the said piezoelectric fiber with respect to the said conductive fiber is 15 degrees or more and 75 degrees or less, It is any one of Claims 1-4. Braided piezoelectric element.   The braided piezoelectric element according to any one of claims 1 to 5, wherein the total fineness of the piezoelectric fibers is 1 to 20 times the total fineness of the conductive fibers.   The braided piezoelectric element according to any one of claims 1 to 6, wherein a fineness per one of the piezoelectric fibers is 1/20 or more and 2 or less of a total fineness of the conductive fibers.   A fabric-like piezoelectric element comprising a fabric including the braided piezoelectric element according to any one of claims 1 to 7.   The cloth-like piezoelectric element according to claim 8, wherein the cloth further includes conductive fibers that intersect and come into contact with at least a part of the braid-like piezoelectric element.   The cloth-like piezoelectric element according to claim 9, wherein 30% or more of the fibers forming the cloth and intersecting the braided piezoelectric element are conductive fibers. Braided piezoelectric element according to any one of claims 1 to 7,
Amplifying means for amplifying an electrical signal output from the braided piezoelectric element in accordance with the applied pressure;
Output means for outputting the electrical signal amplified by the amplification means;
A device comprising: The cloth-like piezoelectric element according to any one of claims 8 to 10,
Amplifying means for amplifying an electrical signal output from the cloth-like piezoelectric element in accordance with an applied pressure;
Output means for outputting the electrical signal amplified by the amplification means;
A device comprising:

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