JP2018073997A - Braided string piezoelectric element and device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fibrous piezoelectric element capable of extracting a large electric signal even by a stress generated by a relatively small deformation and further suppressing a noise signal.SOLUTION: The braided string piezoelectric element includes: a core portion formed of conductive fibers; a sheath portion formed of a braided string piezoelectric fiber so as to cover the core portion; and a conductive layer provided around the sheath portion. The ratio d/Rc of the thickness d of a layer made of the piezoelectric fiber to the radius Rc of the core portion is 1.0 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fabric-like piezoelectric element using a braided piezoelectric element in which a braid using a piezoelectric fiber is covered with a conductive layer, 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. Further, the piezoelectric element described in Patent Document 1 is easily affected by noise because the conductive fibers serving as signal lines are exposed, and is easily damaged by external stress. The piezoelectric element described in Patent Document 1 still has room for improvement with respect to practical use.

  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 JP 2000-144545 A JP 2011-253517 A

  An object of the present invention is to provide a fibrous piezoelectric element that can extract a large electrical signal even with a stress caused by a relatively small deformation, can suppress a noise signal, and is less susceptible to external damage. It is to be.

  As a combination of a conductive fiber and a piezoelectric fiber, the present inventors have coated a braided piezoelectric element in which the surface of the conductive fiber as a core is covered with a braided piezoelectric fiber and a conductive layer is further provided around the surface. It has been found that the electrical signal can be extracted more efficiently and the noise signal can be suppressed, and the relationship between the thickness of the core and the piezoelectric fiber is made within a specific range so that it is less susceptible to external damage. And the present invention has been reached.

That is, the present invention includes the following inventions.
(1) A core part formed of conductive fibers, a sheath part formed of braided piezoelectric fibers so as to cover the core part, and a conductive layer provided around the sheath part A braided piezoelectric element having a ratio d / Rc of a thickness d of a layer made of piezoelectric fibers to a radius Rc of the core part of 1.0 or more.
(2) The braided piezoelectric element according to (1), wherein a covering rate of the sheath portion by the conductive layer is 25% or more.
(3) The braided piezoelectric element according to (1) or (2), wherein the conductive layer is formed of fibers.
(4) A fabric-like piezoelectric element including the braided piezoelectric element according to any one of (1) to (3).
(5) The cloth-like piezoelectric element according to (4), wherein the cloth further includes a conductive fiber that intersects and contacts at least a part of the braid-like piezoelectric element.
(6) The fabric-like piezoelectric element according to (5), wherein 30% or more of the fibers that form the fabric and intersect with the braided piezoelectric element are conductive fibers.
(7) The braided piezoelectric element according to any one of (1) to (3);
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:
(8) The cloth-like piezoelectric element according to (5) or (6),
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:

  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 can further suppress a noise signal.

It is a schematic diagram which shows the structural example of the braided piezoelectric element which concerns on embodiment. It is a microscope picture which shows the cross section of the braided piezoelectric element 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 braided 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. 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 covers the core 3 formed of the conductive fiber B, the sheath 2 formed of the braided piezoelectric fiber A so as to cover the core 3, and the sheath 2. And a conductive layer 4. The conductive layer 4 functions as an electrode serving as a counter electrode of the conductive fiber of the core part 3 and as a shield that shields the conductive fiber of the core part 3 from external electromagnetic waves and suppresses a noise signal generated in the conductive fiber of the core part 3. It has the function of.

The coverage of the sheath 2 by the conductive layer 4 is preferably 25% or more. Here, the coverage is the ratio of the area of the conductive material 5 contained in the conductive layer 4 to the surface area of the sheath 2 when the conductive layer 4 is projected onto the sheath 2, and the value is preferably 25% or more. 50% or more is more preferable, and 75% or more is more preferable. If the coverage of the conductive layer 4 is less than 25%, the noise signal suppressing effect may not be sufficiently exhibited. When the conductive material 5 is not exposed to the surface of the conductive layer 4, for example, when the sheath 2 is covered using the fiber containing the conductive material 5 as the conductive layer 4, the sheath of the fiber The ratio of the area when projected onto 2 and the surface area of the sheath 2 can be defined as the coverage.
The conductive substance 5 is a conductive substance contained in the conductive layer 4, and any known substance is applicable.

  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. When the braided piezoelectric element 1 is deformed, a stress due to the deformation is generated in each of the large number of piezoelectric fibers A, thereby generating an electric field in each of the large number of piezoelectric fibers A (piezoelectric effect). A voltage change is generated in the conductive fiber B by superimposing the electric fields of many piezoelectric fibers A surrounding the. 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.

The braided piezoelectric element 1 selectively outputs a large electric signal with respect to expansion / contraction deformation in the central axis direction or selectively outputs a large electric signal with respect to torsional deformation about the central axis. What outputs is preferable, and what outputs a big electric signal selectively with respect to the expansion-contraction deformation to the central-axis direction is more preferable.
As the braided piezoelectric element 1 that selectively outputs a large electric signal with respect to expansion and contraction in the central axis direction, for example, an oriented piezoelectric polymer is arranged in a cylindrical shape or a cylindrical shape as the piezoelectric fiber A. The orientation angle of the piezoelectric polymer with respect to the direction of the central axis of the cylindrical or columnar shape in which the piezoelectric polymer is arranged is 15 ° or more and 75 ° or less, and the piezoelectric polymer has an orientation axis of 3 The structure preferably includes a crystalline polymer having an absolute value of the piezoelectric constant d14 of 0.1 pC / N or more and 1000 pC / N or less as a main component as the axis. Further, the piezoelectric polymer includes a P body containing a crystalline polymer having a positive value of the piezoelectric constant d14 as a main component and an N body containing a negative crystalline polymer as a main component. For a portion having a center axis of 1 cm in length, the orientation axis is ZP, and the orientation axis is arranged in a S-twist direction. SP is the mass of the body, ZN is the mass of the N body arranged with a spiral in the Z twist direction, and SN is the mass of the N body arranged with a spiral in the S twist direction. And when the smaller one of (ZP + SN) and (SP + ZN) is T1, and the larger one is T2, the T1 / T2 value is 0 or more and 0.8 or less. preferable.

  On the other hand, as the braided piezoelectric element 1 that outputs a large electrical signal selectively with respect to torsional deformation about the central axis, for example, as a piezoelectric fiber A, an oriented piezoelectric polymer is cylindrical or cylindrical. The orientation angle of the piezoelectric polymer with respect to the direction of the central axis of the cylindrical or columnar shape in which the piezoelectric polymer is arranged is 0 ° or more and 40 ° or less, or 50 ° or more and 90 ° or less. The piezoelectric polymer is a structure containing, as a main component, a crystalline polymer having an absolute value of the piezoelectric constant d14 of 0.1 pC / N or more and 1000 pC / N or less when the orientation axes are three axes. It is preferable. Further, the piezoelectric polymer includes a P body containing a crystalline polymer having a positive value of the piezoelectric constant d14 as a main component and an N body containing a negative crystalline polymer as a main component. For a portion having a center axis of 1 cm in length, the orientation axis is ZP, and the orientation axis is arranged in a S-twist direction. SP is the mass of the body, ZN is the mass of the N body arranged with a spiral in the Z twist direction, and SN is the mass of the N body arranged with a spiral in the S twist direction. The structure is such that the value of T1 / T2 is more than 0.8 and 1.0 or less, where T1 is the smaller one of (ZP + SN) and (SP + ZN) and T2 is the larger one. Is more preferable.

  The value of d14 varies depending on the molding conditions, purity, and measurement atmosphere. In the present invention, the crystallinity and crystal orientation of the crystalline polymer in the actually used piezoelectric polymer are measured. Then, a uniaxially stretched film having the same crystallinity and crystal orientation is prepared using the crystalline polymer, and the absolute value of d14 of the film is 0.1 pC / A value of N or more and 1000 pC / N or less may be shown, and the crystalline polymer contained in the piezoelectric polymer of the present embodiment is not limited to a specific crystalline polymer as described later. Various known methods can be used to measure d14 of a film sample. For example, a sample having electrodes formed by vapor-depositing metal on both sides of a film sample is a rectangle having four sides in a direction inclined 45 degrees from the stretching direction. The value of d14 can be measured by measuring the charge generated in the electrodes on both sides when a tensile load is applied in the longitudinal direction.

  When a fiber containing polylactic acid as a main component is used as the piezoelectric fiber of the present invention, the lactic acid unit in the polylactic acid is preferably 90 mol% or more, more preferably 95 mol% or more, and 98 mol % Or more is more preferable.

  In the braided piezoelectric element 1, as long as the object of the present invention is achieved, the sheath 2 may be mixed with fibers other than the piezoelectric fiber A, and the core 3 may be conductive. Mixing or the like may be performed in combination with fibers other than the fiber B.

The length of the braided piezoelectric element constituted by the core portion 3 of the conductive fiber B, the sheath portion 2 of the braided piezoelectric fiber A, and the conductive layer 4 covering the sheath portion 2 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 preferable to include a crystalline polymer having a high absolute value of the piezoelectric constant d14 when the orientation axes are three axes, particularly 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, and the absolute value of d14 is increased.

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 (1).
X _homo × Ao × Ao ÷ 10 ⁶ ≧ 0.26 (1)
If the above formula (1) is not satisfied, the crystallinity and / or uniaxial orientation is not sufficient, and the output value of the electric signal with respect to the operation may decrease, or the sensitivity of the signal with respect to the operation in a specific direction may decrease. is there. The value on the left side of the formula (1) 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 (2).
Homopolylactic acid crystallinity X _homo (%) = ΣI _HMi / I _total × 100 (2)
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 (3).
Crystal orientation degree Ao (%) = (360−ΣW _i ) ÷ 360 × 100 (3)

  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.

  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 (4). .
| S (p) −S (c) | ≦ 10 (4)
The left side of the above formula (4) 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 (5).
| S (p) −S (i) | ≦ 10 (5)
The left side of the above formula (5) 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, suspended on a scale plate, and the shrinkage casket length L was measured. Using the measured L0 and L, the boiling water shrinkage is calculated by the following equation (6).
Boiling water shrinkage = (L0−L) / L0 × 100 (%) (6)

(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.

(Conductive layer)
The conductive layer 4 functions as an electrode serving as a counter electrode of the conductive fiber of the core part 3 and as a shield that shields the conductive fiber of the core part 3 from external electromagnetic waves and suppresses a noise signal generated in the conductive fiber of the core part 3. It is possible to have these functions simultaneously. Since the conductive layer 4 functions as a shield, it is preferably grounded (connected to the earth or the ground of the electronic circuit). Accordingly, for example, the S / N ratio (signal-to-noise ratio) of the braided 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. As an aspect of the conductive layer 4, in addition to coating, a film, a fabric, and a fiber may be wound, or they may be combined.

  The coating for forming the conductive layer 4 may be any coating containing a substance exhibiting conductivity, and any known one may be used. For example, a metal, a conductive polymer, and a polymer in which a conductive filler is dispersed can be given.

  When the conductive layer 4 is formed by winding a film, a film obtained by forming a conductive polymer and a polymer dispersed with a conductive filler is used, and a conductive layer is provided on the surface. A film may be used.

  In the case where the conductive layer 4 is formed by winding a fabric, a fabric having a conductive fiber 6 described later as a constituent component is used.

  In the case where the conductive layer 4 is formed by winding a fiber, a cover ring, a knitted fabric, or a braid can be considered as the technique. Moreover, the fiber used is the conductive fiber 6, and the conductive fiber 6 may be the same type as the conductive fiber B or a different type of conductive fiber. Examples of the conductive fiber 6 include metal fibers, fibers made of a conductive polymer, carbon fibers, fibers made of a polymer in which a fibrous or granular conductive filler is dispersed, or conductive on the surface of the 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 the metal fiber-coated organic fiber having bending resistance is used for the conductive fiber 6, the conductive fiber is hardly broken and excellent in durability and safety as a sensor using a piezoelectric element.

  The conductive fiber 6 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.

  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 6 is preferably a circle or an ellipse from the viewpoint of design and manufacture of the piezoelectric element, but is not limited thereto.

In order to enhance the noise signal suppression effect, the electrical resistance is preferably low, and the volume resistivity is preferably 10 ⁻¹ Ω · cm or less, more preferably 10 ⁻² Ω · cm or less, and still more preferably. Is 10 ⁻³ Ω · cm or less. However, the resistivity is not limited as long as a noise signal suppressing effect can be obtained.

The conductive fiber 6 must be resistant to movement such as repeated bending and twisting from the application 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.

  Further, it can be regarded as a capacitor-like piezoelectric element having a piezoelectric polymer (dielectric) sandwiched between a conductor in the core portion and a conductor in the electromagnetic wave shield layer as a bipolar electrode. In order to effectively take out the polarization generated in the piezoelectric structure due to deformation, the value of the insulation resistance between these electrodes is preferably 1 MΩ or more, preferably 10 MΩ or more when measured at a DC voltage of 3 V. More preferably, it is more preferably 100 MΩ or more. In addition, the equivalent series resistance value Rs and equivalent series capacitance Cs obtained by analyzing the response when an AC voltage of 1 MHz is applied between these electrodes are also polarized in the piezoelectric structure due to deformation. In order to effectively take out and improve the responsiveness, it is preferably within a specific value range. That is, the value of Rs is preferably 1 μΩ or more and 100 kΩ or less, more preferably 1 mΩ or more and 10 kΩ or less, further preferably 1 mΩ or more and 1 kΩ or less, and the value of Cs is the length (cm) in the central axis direction of the piezoelectric structure. The value divided by is preferably from 0.1 pF to 1000 pF, more preferably from 0.2 pF to 100 pF, and even more preferably from 0.4 pF to 10 pF.

  As described above, when the element including the piezoelectric fiber A and the electrode is operable in a preferable state, the value Rs of the equivalent series resistance obtained by analyzing the response when an AC voltage of 1 MHz is applied between these electrodes. Since the value of the equivalent series capacitance Cs takes a value within a specific range, it is also preferable to use these values for the inspection of the braided piezoelectric element. Further, the braided piezoelectric element can be inspected by analyzing not only the values of Rs and Cs obtained by the analysis using the AC voltage but also the transient response of other voltages.

(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.

  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, 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.

  The braided piezoelectric element 1 of the present invention can detect deformation and stress using the electrical signal output due to the piezoelectric effect described above, as well as the conductive fiber B and the conductive layer at the core of the braided piezoelectric element 1. It is also possible to detect deformation due to the pressure applied to the braided piezoelectric element 1 by measuring the capacitance change between 4. Further, when a plurality of braided piezoelectric elements 1 are used in combination, the pressure applied to the braided piezoelectric element 1 is measured by measuring the capacitance change between the conductive layers 4 of each braided piezoelectric element 1. It is also possible to detect deformation due to.

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

  In this way, by arranging the insulating fiber in addition to the braided piezoelectric element 1 (and the conductive fiber 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 make it.

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.

Insulating fibers such as polyester fibers, nylon fibers, acrylic fibers, polyethylene fibers, polypropylene fibers, vinyl chloride fibers, aramid fibers, polysulfone fibers, polyether fibers, polyurethane fibers, etc., 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 may be used in combination, or may be combined with a fiber having no insulating property to form a fiber having insulating properties as a whole.
Also, any known cross-sectional shape fiber can be used.

(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.

  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.

  The conductive layer 4 is manufactured by coating or fiber winding, but fiber winding is preferable from the viewpoint of ease of manufacturing. As a method for winding the fiber, a cover ring, a knitted fabric, and a braid are conceivable, and any method may be used.

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 and the conductive layer 4 is provided around the surface can be obtained.
Here, in the braided piezoelectric element of the present invention, the relationship between the diameter of the core part and the thickness of the layer (sheath part) made of piezoelectric fibers is very important. The piezoelectric element of the present invention is used as it is in the form of a fiber, or is woven or knitted into a fabric, but the core signal line and the shield layer (conductive layer) are used during use and during processing. There may be a short circuit. As a result of intensive studies, the present inventor needs to have a relationship in which the radius Rc of the core portion and the thickness d of the layer made of piezoelectric fibers are d / Rc ≧ 1.0.

Assuming that when the braided piezoelectric element is bent at a curvature R, the center of the element is bent as a reference line, the deformation rate of the core surface is:
(R + Rc) / R
It becomes. For example, when the radius of curvature R = 2 mm, the deformation rate is 1.1 when Rc = 0.2 mm, and the deformation is 1.1% on the outside of the bend, and 10% on the inside of the bend. At this time, there is a case where the layer of the layers made of the assembled piezoelectric fibers is disturbed and the layer forming the shield layer and the signal line of the core portion are short-circuited. Here, even if the layer made of the piezoelectric fiber is disturbed by deformation, the thickness of the layer made of the piezoelectric fiber has the following conditions in relation to the core part so that the shield layer does not short-circuit with the signal line of the core part. It is necessary to satisfy.

  The practical deformation of the core surface of the braided piezoelectric element is preferably suppressed to about 20%. Therefore, the practical radius of curvature is almost uniquely determined by the thickness of the core. Furthermore, in that case, the thickness of the layer made of piezoelectric fibers for preventing short-circuiting is almost uniquely determined. That is, Rc> R / 10 is preferable, and Rc> R / 10 is more preferable. Furthermore, d / Rc is preferably 1.0 or more, more preferably 1.2 or more, and further preferably 1.5 or more.

The layer made of piezoelectric fibers may be formed by laminating piezoelectric fibers a plurality of times. Even if the number of times of lamination is the same, it tends to be difficult to short-circuit, and when the number of laminations is n, d / Rc × n is preferably 0.8 or more, more preferably 1. 0 or more, more preferably 1.2 or more.
In terms of short-circuiting, the thickness of the layer made of piezoelectric fibers is better, but from the viewpoint of the braided piezoelectric element, the thinner one has better handling properties, so the shield layer is preferably thin.

  Here, the radius Rc of the core portion of the braided piezoelectric element and the thickness d of the layer made of the piezoelectric fiber are calculated from the microscopic image of the cross section shown in FIG. 2 as follows. Regarding the observation of the cross section, the braided piezoelectric element was soaked with a low-viscosity instant adhesive “Aron Alpha EXTRA2000” (Toagosei) and solidified, then a cross section perpendicular to the long axis of the braid was cut out and a cross-sectional photograph taken. You may shoot. As shown in FIG. 2-1, the radius Rc of the core part is an average value of the radius of the maximum circle X consisting only of the fiber bundle of the core part and the radius of the minimum circle Y completely including the fiber bundle. And As shown in FIG. 2B, the thickness d of the layer made of the piezoelectric fiber is such that the radius of the maximum circle X ′ consisting only of the fiber bundle of the piezoelectric fiber including the core portion and the fiber bundle completely A value obtained by subtracting the radius Rc of the core portion from the average value with the radius of the smallest circle Y ′ to be included.

(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 5 includes a cloth 6 including at least one braided piezoelectric element 1. The fabric 6 is not limited in any way 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 a 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 cloth-like piezoelectric element 5 has at least one braided piezoelectric element 1 and insulating fibers 9 as warps and alternately has conductive fibers 8 and insulating fibers 9 as wefts. Plain woven fabric. The conductive fiber 8 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 8 may be braided.

  In this case, when the cloth-like piezoelectric element 5 is deformed by bending or the like, the braided piezoelectric element 1 is also deformed along with the deformation. Therefore, the cloth-like piezoelectric element 5 is generated by an electric signal output from the braided piezoelectric element 1. Can be detected. Since the cloth-like piezoelectric element 5 can be used as a cloth (woven or knitted fabric), the cloth-like piezoelectric element 5 can be applied to, for example, a garment-shaped wearable sensor.

  Further, in the fabric-like piezoelectric element 5 shown in FIG. 3, the conductive fibers 8 intersect and contact the braided piezoelectric element 1. Therefore, the conductive fiber 8 intersects and covers at least a part of the braided piezoelectric element 1 and 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 8 has a function of reducing the influence of electromagnetic waves on the braided piezoelectric element 1 by being grounded. That is, the conductive fiber 8 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 5 can be remarkably improved without overlapping conductive cloths for electromagnetic wave shielding on and under the cloth-like piezoelectric element 5. In this case, from the viewpoint of electromagnetic shielding, the higher the proportion of the conductive fibers 8 in the wefts (in the case of FIG. 3) intersecting with the braided piezoelectric element 1, the better. Specifically, 30% or more of the fibers forming the fabric 6 and intersecting the braided piezoelectric element 1 are preferably conductive fibers, more preferably 40% or more, and 50% or more. Further preferred. Thus, in the cloth-like piezoelectric element 5, the cloth-like piezoelectric element 5 with an electromagnetic wave shield can be obtained by inserting conductive fibers 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, single-sided 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 fabric-like piezoelectric element 5, 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.

  When the fabric-like piezoelectric element 5 is formed by arranging a plurality of braided piezoelectric elements 1 in this way, the braided piezoelectric element 1 does not have electrodes 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.

(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 (e.g., braided piezoelectric element 1, fabric-like piezoelectric element 7) and, optionally, amplification means 13 that amplifies an electrical signal output from the piezoelectric element 12 in accordance with an applied pressure. And an output circuit 14 for outputting the electrical signal amplified by the optional amplifying means 13, and a transmission means 15 for transmitting the electrical signal output from the output means 14 to an external device (not shown). With. 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.

  The optional amplification means 13, output means 14, and transmission means 15 may be constructed, for example, in a software program format, or may be constructed by a combination of various electronic circuits and software programs. For example, the software program is installed in an arithmetic processing device (not shown), and the arithmetic processing device operates according to the software program, thereby realizing the functions of each unit. Alternatively, the optional amplifying means 13, the output means 14, and the transmitting means 15 may be realized as a semiconductor integrated circuit in which a software program for realizing the functions of these units is written. Whether the transmission method by the transmission means 15 is wireless or wired may be appropriately determined according to the sensor to be configured. 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.

  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.

  FIG. 5 is a schematic diagram illustrating a configuration example of a device including the braided piezoelectric element according to the embodiment. The amplifying unit 13 in FIG. 5 corresponds to that described with reference to FIG. 4, but the output unit 14 and the transmitting unit 15 in FIG. 4 are not shown in FIG. When a device including the braided piezoelectric element 1 is configured, a lead wire from the core portion 3 of the braided piezoelectric element 1 is connected to the input terminal of the amplifying unit 13, and the braided piezoelectric element 1 is connected to the ground (earth) terminal. The conductive layer 4 is connected. For example, as shown in FIG. 5, in the braided piezoelectric element 1, the lead wire from the core 3 of the braided piezoelectric element 1 is connected to the input terminal of the amplifying means 13, and the conductive layer 4 of the braided piezoelectric element 1 is connected. Ground (earth).

  FIGS. 6-8 is a schematic diagram which shows the structural example of a device provided with the braided cloth-like piezoelectric element which concerns on embodiment. The amplifying unit 13 in FIGS. 6 to 8 corresponds to that described with reference to FIG. 4, but the output unit 14 and the transmitting unit 15 in FIG. 4 are not shown in FIGS. When a device including the fabric-like piezoelectric element 7 is configured, a lead wire from the core portion 3 (formed of the conductive fiber B) of the braided piezoelectric element 1 is connected to the input terminal of the amplifying means 13 and grounded (grounded) ) A braided piezoelectric element different from the braided piezoelectric element 1 connected to the conductive layer 4 of the braided piezoelectric element 1 or the conductive fiber 10 of the fabric-like piezoelectric element 7 or the input terminal of the amplifying means 13 is connected to the terminal. To do. For example, as shown in FIG. 6, 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 the conductive layer 4 of the braided piezoelectric element 1 is connected. Ground (earth). Further, for example, as shown in FIG. 7, 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 the braided piezoelectric element 1. The contacted conductive fiber 10 is grounded. Further, for example, as shown in FIG. 8, 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).

  When the braided piezoelectric element 1 is deformed, the piezoelectric fiber A is deformed to generate polarization. Due to the arrangement of positive and negative charges generated by the polarization of the piezoelectric fiber A, movement of charges occurs on the lead line from the conductive fiber B that forms the core portion 3 of the braided piezoelectric element 1. The movement of electric charge on the lead line from the conductive fiber B appears as a flow of a minute electric signal (that is, current). The amplifying means 13 amplifies the electric signal, the output means 14 outputs the electric signal amplified by the amplifying means 13, and the transmitting means 15 outputs the electric signal output from the output means 14 to an external device (not shown). Send to

  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 22 g / min and taken up at 1300 m / min. This unstretched multifilament yarn was stretched 2.0 times at 80 ° C. and heat-set at 150 ° C. to obtain a piezoelectric fiber A1 having 84 dTex / 24 filaments.
Further, PLLA1 melted at 240 ° C. was discharged from a 12-hole cap at 8 g / min and taken up at 1300 m / min. This unstretched multifilament yarn was stretched 2.0 times at 80 ° C. and heat-set at 150 ° C. to obtain a piezoelectric fiber A2 having 33 dTex / 12 filaments.

(Conductive fiber)
Silver plated nylon manufactured by Mitsufuji Corporation, product names “AGposs” 100d34f and 30d10f were used as conductive fiber B, conductive fiber 6 and conductive fiber 10. The volume resistivity of this fiber was 1.1 × 10 ⁻³ Ω · cm.

(Braided piezoelectric element)
As a sample of Example 1, the above-mentioned conductive fiber “AGposs” 100d34f is used as a core yarn, and the above-mentioned piezoelectric fiber A1 is wound around the eight core yarns in a braid form to form an eight-ply braid. The fiber “AGposs” 30d10f was wrapped in a braid shape around the piezoelectric fiber A1 of the sheath portion to form a shield layer, and the braided piezoelectric element 1A was formed. Here, the winding angle α of the piezoelectric fiber A1 with respect to the fiber axis CL of the conductive fiber B was set to 30 °. The d / Rc of the braided piezoelectric element 1A was 1.76.

  As a sample of Example 2, the conductive fiber “AGposs” 100d34f is used as a core yarn, and the piezoelectric fiber A2 is wound around the eight core yarns in a braid shape to form an eight-strand braid. Further, eight piezoelectric fibers 2 were wound in a braid shape. Further, the conductive fiber “AGposs” 30d10f was wound around the piezoelectric fiber A2 in a braid shape to form a shield layer, and the braided piezoelectric element 1B 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 set to 30 °. The d / Rc of the braided piezoelectric element 1B was 1.52.

  As a sample of Comparative Example 1, a braided piezoelectric element 1C was formed in the same manner as in Example 1 except that the piezoelectric fiber A2 was used instead of the piezoelectric fiber A1 of Example 1. The d / Rc of the braided piezoelectric element 1C was 0.84.

(Manufacturing)
Circular braided knits 1 to 3 were produced using the braided piezoelectric elements 1 to 3, respectively.

(Performance evaluation and evaluation results)
The evaluation results of the braided piezoelectric elements 1 to 3 and the circular knitting knits 1 to 3 are as follows.

(Example 1)
The conductive fiber B in the braided piezoelectric element 1A is connected as a signal line to an oscilloscope (a digital oscilloscope DL6000 series product name “DL6000” manufactured by Yokogawa Electric Corporation) via a 100 × amplification circuit via a wiring, The conductive layer 4 of the braided piezoelectric element 1A was grounded. Torsional deformation was applied to the braided piezoelectric element 1A.
As a result, a potential difference of about 10 mV was detected by an oscilloscope as an output from the braided piezoelectric element 1A, and it was confirmed that a sufficiently large electric signal could be detected by deformation of the braided piezoelectric element 1A.
Moreover, also about the circular knitted knit 1, the core part and the shield wire were not short-circuited, and a signal corresponding to the deformation could be detected.

(Example 2)
The conductive fiber B in the braided piezoelectric element 1B is connected as a signal line to an oscilloscope (a digital oscilloscope DL6000 series product name “DL6000” manufactured by Yokogawa Electric Corporation) via a wiring through a 100-times amplification circuit. The conductive layer 4 of the braided piezoelectric element 1B was grounded. Torsional deformation was applied to the braided piezoelectric element 1B.
As a result, a potential difference of about 10 mV was detected by an oscilloscope as an output from the braided piezoelectric element 1B, and it was confirmed that a sufficiently large electric signal could be detected by deformation of the braided piezoelectric element 1B.
Further, in the circular knitted knit 2, the core portion and the shield wire were not short-circuited, and a signal corresponding to the deformation could be detected.

(Comparative Example 1)
The conductive fiber B in the braided piezoelectric element 1C is connected as a signal line to an oscilloscope (a digital oscilloscope DL6000 series product name “DL6000” manufactured by Yokogawa Electric Corporation) via a 100 × amplification circuit via a wiring, The conductive layer 4 of the braided piezoelectric element 1C was grounded. Torsional deformation was applied to the braided piezoelectric element 1C.
As a result, a potential difference of about 10 mV was detected by an oscilloscope as an output from the braided piezoelectric element 1C, and it was confirmed that a sufficiently large electric signal could be detected by deformation of the braided piezoelectric element 1C.
However, for the circular knitted knit 3, the core portion and the shield wire were short-circuited, and a signal corresponding to the deformation could not be detected.

DESCRIPTION OF SYMBOLS A Piezoelectric fiber B Conductive fiber 1 Braided piezoelectric element 2 Sheath part 3 Core part 4 Conductive layer 5 Conductive substance 6 Conductive fiber 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 axis α Wrapping angle X Maximum circle consisting only of the core fiber bundle Y Minimum circle Y completely including the core fiber bundle
X ′ The largest circle consisting only of fiber bundles of piezoelectric fibers including the core portion Y ′ The smallest circle completely including fiber bundles of piezoelectric fibers

Claims (8)

  A core portion formed of conductive fibers; a sheath portion formed of braided piezoelectric fibers so as to cover the core portion; and a conductive layer provided around the sheath portion; A braided piezoelectric element having a ratio d / Rc of a thickness d of a layer made of piezoelectric fibers to a radius Rc of the portion is 1.0 or more.   The braided piezoelectric element according to claim 1, wherein a coverage of the sheath portion by the conductive layer is 25% or more.   The braided piezoelectric element according to claim 1 or 2, wherein the conductive layer is formed of fibers.   A fabric-like piezoelectric element comprising the braided piezoelectric element according to any one of claims 1 to 3.   The cloth-like piezoelectric element according to claim 4, 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 5, wherein 30% or more of the fibers forming the cloth and intersecting the braided piezoelectric element are conductive fibers. The braided piezoelectric element according to any one of claims 1 to 3,
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 claim 5 or 6,
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: