WO2018079739A1 - Structure for use in piezoelectric element, braided piezoelectric element, fabric-like piezoelectric element using braided piezoelectric element, and device using these - Google Patents

Abstract

Provided are: a structure having an oriented piezoelectric polymer arranged into a cylindrical or columnar shape, wherein the oriented angle of the oriented piezoelectric polymer is 0-40° or 50-90° with respect to the center axis direction of the cylindrical or columnar shape in which the oriented piezoelectric polymer is arranged, and the piezoelectric polymer includes, as a main component, a crystal polymer of which the absolute value of piezoelectric constant d14 is 0.1-1000 pC/N when the piezoelectric polymer has three orientation axes; and a braided piezoelectric element and a fabric-like piezoelectric element each using the structure.

Description

Structure used for piezoelectric element, braided piezoelectric element, fabric-like piezoelectric element using braided piezoelectric element, and device using them

The present invention relates to a structure used for a piezoelectric element, a braided piezoelectric element in which a braid using a piezoelectric fiber is covered with a conductive layer, a fabric-like piezoelectric element using the braided piezoelectric element, and a device using them.

Conventionally, many techniques related to elements using piezoelectric materials have been disclosed. For example, Patent Document 1 discloses that an element in which a conductive fiber is coated with a piezoelectric polymer has an excellent electrical response to rubbing. Non-Patent Document 1 discloses an electrical response example of an element in which a piezoelectric polymer is wound in a coil shape, due to expansion and contraction in the axial direction of the coil and torsional deformation around the axis of the coil. Further, Patent Document 2 discloses a fibrous material made of a piezoelectric polymer, and it is described that the piezoelectric material has a large piezoelectric effect when a force (motion) parallel or perpendicular to the fiber axis is applied. ing.
The piezoelectric sheet of Patent Document 3 can output an electrical signal by torsional deformation (stress) with respect to the piezoelectric sheet. However, since it is in the form of a sheet in the first place, it is poor in flexibility, and it cannot be used in a way that it can be freely bent like fibers and cloth.

However, the above-described prior art documents do not disclose a specific configuration that efficiently generates a piezoelectric signal with respect to a torsional motion but does not generate a piezoelectric signal with respect to a motion other than the torsional motion. In addition, there is no disclosure of a specific configuration that generates charges having opposite polarities (that is, charges having opposite signs) between the central axis and the outside of the structure in order to increase the use efficiency of piezoelectric signals. Therefore, the performance as a piezoelectric element that can be used for a sensor or an adsorbent is insufficient.

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 4 discloses a touch panel using 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 also susceptible to material deterioration and damage due to external stress. Further, there is no disclosure about a configuration that allows the piezoelectric element to be easily installed on a substrate such as another fabric, and the piezoelectric element described in Patent Document 1 still has room for improvement for 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 4 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 2014-240842 A JP 2011-253517 A

Japan Journal of Applied Physics, Volume 51, page 09LD16

The present invention has been made in view of the above-mentioned background, and a first object of the present invention is to selectively respond to torsional deformation (stress) and to generate electric polarization that can be used efficiently. It is possible to provide a piezoelectric structure having a cylindrical shape or a cylindrical shape capable of satisfying the requirements.

In addition, the second object of the present invention is to extract a large electric signal even with a stress caused by a relatively small deformation, to suppress a noise signal, and to be less susceptible to external damage. The piezoelectric element is provided.

Furthermore, a third object of the present invention is to use a fibrous piezoelectric element that can extract a large electric signal even by a stress caused by a relatively small deformation, and can suppress a noise signal, and other fabrics, etc. It is providing the cloth-like piezoelectric element which can be easily installed in the base material.

As a result of intensive studies to achieve the first object, the inventors of the present invention have a cylindrical or columnar structure in which piezoelectric polymers having a high piezoelectric constant d14 are aligned in a specific direction. It has been discovered that by forming a body, charges having opposite polarities can be efficiently generated on the central axis side and the outside of the cylindrical or cylindrical shape against torsional deformation, and the present invention has been achieved.

In addition, as a result of intensive studies to achieve the second object, the present inventors have determined that the surface of the conductive fiber serving as the core is a braided piezoelectric fiber as a combination of the conductive fiber and the piezoelectric fiber. It was discovered that a braided piezoelectric element covered with a conductive layer around it could efficiently extract electrical signals and suppress noise signals, and the thickness of the core and piezoelectric fibers. The present invention has been found by making it difficult to receive damage from the outside by making the relationship in a specific range.

Furthermore, as a result of intensive studies to achieve the third object, the present inventors have determined that the surface of the conductive fiber as a core is a braided piezoelectric fiber as a combination of the conductive fiber and the piezoelectric fiber. It is discovered that an electric signal can be efficiently taken out by a braided piezoelectric element that is covered with a conductive layer and is further provided with a conductive layer, and that a noise signal can be further suppressed, and this is fixed to a fabric in a specific shape. Thus, the present inventors have found that it is difficult to be damaged from the outside and can be easily installed on a substrate such as another fabric.

That is, according to the present invention, the following (1) to (12) are provided as means (first invention) for achieving the first object, and means (second) for achieving the second object. The following (13) to (20) are provided as the invention, and the following (21) to (31) are provided as the means for achieving the third object (third invention).
(1) A structure in which oriented piezoelectric polymers are arranged in a cylindrical or cylindrical shape, and the orientation angle of the piezoelectric polymer with respect to the direction of the central axis of the cylindrical or cylindrical shape in which the piezoelectric polymers are arranged is The piezoelectric polymer has an absolute value of the piezoelectric constant d14 of 0.1 pC / N or more and 1000 pC / N or less when the orientation axis is triaxial, from 0 ° to 40 ° or 50 ° to 90 °. A structure containing a crystalline polymer as a main component.
(2) The structure according to (1), wherein the piezoelectric polymer contains poly-L-lactic acid or poly-D-lactic acid as a main component.
(3) When a torsional deformation is applied about the cylindrical or columnar central axis on which the piezoelectric polymer is disposed, charges of opposite polarity are applied to the cylindrical axis or the columnar axis side and the outside. The structure according to (1) or (2), which is generated.
(4) The piezoelectric polymer includes a P body including a crystalline polymer having a positive piezoelectric constant d14 as a main component and an N body including a negative crystalline polymer as a main component, and the structure For the part having a center axis of 1 cm in length, the orientation axis is ZP and the orientation axis is arranged in a spiral direction in the S twist direction. The mass of the P body is SP, the mass of the N body arranged with a spiral in the Z twist direction is ZN, and the mass of the N body is arranged with the orientation axis wound in a spiral in the S twist direction. Any one of (1) to (3), where T is the smaller one of (ZP + SN) and (SP + ZN) and T2 is the larger one, and T1 / T2 is greater than 0.8. The structure according to item.
(5) The piezoelectric polymer is configured in the form of a braid, a twisted string, a covering thread, or an aligned thread in the form of a fiber, filament or tape, (1) to (4) The structure according to any one of claims.
(6) The structure according to any one of (1) to (4), wherein the piezoelectric polymer constitutes only one closed region in a cross section perpendicular to a central axis of a cylindrical shape or a cylindrical shape. .
(7) An element comprising the structure according to any one of (1) to (6) and a conductor disposed adjacent to the structure.
(8) The element according to (7), wherein the piezoelectric polymer is disposed in a cylindrical shape, and the conductor is disposed at a position of a central axis of the cylindrical shape.
(9) The element according to (8), wherein the conductor is made of a conductive fiber, and the piezoelectric polymer is arranged as a piezoelectric fiber in a braid shape around the conductive fiber.
(10) The element according to (7), wherein the conductor is disposed outside a cylindrical or columnar shape in which the piezoelectric polymer is disposed.
(11) The conductor according to (10), wherein the conductor is made of conductive fiber, and the conductive fiber is arranged in a braid shape around a cylindrical shape or a columnar shape in which the piezoelectric polymer is arranged. Elements.
(12) The device according to any one of (7) to (11),
An output terminal that outputs an electrical signal generated in the conductor in response to a charge generated when a torsional deformation is applied in the direction of the central axis of the cylindrical or cylindrical shape in which the piezoelectric polymer is disposed;
An electrical circuit for detecting an electrical signal output through the output terminal;
With a sensor.
(13) The element according to (9), including a core portion formed of the conductive fiber and a sheath portion formed of the braided piezoelectric fiber so as to cover the core portion;
A braided piezoelectric element comprising a conductive layer provided around the sheath portion, wherein a ratio d / Rc of a thickness d of the layer made of piezoelectric fibers to a radius Rc of the core portion is 1.0 or more.
(14) The braided piezoelectric element according to (13), wherein a covering rate of the sheath portion by the conductive layer is 25% or more.
(15) The braided piezoelectric element according to (13) or (14), wherein the conductive layer is formed of fibers.
(16) A fabric-like piezoelectric element comprising the braided piezoelectric element according to any one of (13) to (15).
(17) The cloth-like piezoelectric element according to (16), wherein the cloth further includes a conductive fiber that intersects and contacts at least a part of the braided piezoelectric element.
(18) The cloth-like piezoelectric element according to (17), wherein 30% or more of the fibers forming the cloth and intersecting the braided-piezoelectric element are conductive fibers.
(19) The braided piezoelectric element according to any one of (13) to (15);
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:
(20) The cloth-like piezoelectric element according to (17) or (18),
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:
(21) A cloth-like piezoelectric element in which a braid-like piezoelectric element is fixed to a cloth, wherein the braid-like piezoelectric element is
The element according to (9), comprising: a core portion formed of the conductive fiber; and a sheath portion formed of the braided piezoelectric fiber so as to cover the core portion;
And a conductive layer provided around the sheath portion, wherein the braided piezoelectric element with respect to the fabric has a pull-out strength per 5 cm of 0.1 N or more.
(22) The cloth-like piezoelectric element according to (21), wherein a coverage of the braided piezoelectric element by fibers constituting the cloth exceeds 30% on both sides of the cloth.
(23) The fabric-like piezoelectric element according to (21) or (22), wherein the braid-like piezoelectric element is fixed in a state of being woven or knitted into the fabric.
(24) The fabric-like piezoelectric element according to (21) or (22), wherein the braided piezoelectric element is sandwiched between layers of a double woven fabric or a double knitted fabric.
(25) The braided piezoelectric element is partially exposed from the fabric, and the conductive fiber and / or the conductive layer of the braided piezoelectric element is electrically connected to another member at the exposed portion. The cloth-like piezoelectric element according to any one of (21) to (24).
(26) The cloth-like piezoelectric element according to any one of (21) to (25), wherein a coverage of the sheath portion by the conductive layer is 25% or more.
(27) The cloth-like piezoelectric element according to any one of (21) to (26), wherein the conductive layer is formed of a fiber.
(28) The cloth-like piezoelectric element according to any one of (21) to (27), wherein the total fineness of the piezoelectric fiber is 1 to 20 times the total fineness of the conductive fiber.
(29) The fabric according to any one of (21) to (28), wherein the fineness per one of the piezoelectric fibers is 1/20 or more and 2 or less of the total fineness of the conductive fibers. Piezoelectric element.
(30) The cloth-like piezoelectric element according to any one of (21) to (29), wherein the cloth further includes a conductive fiber that crosses and contacts at least a part of the braided piezoelectric element.
(31) The cloth-like piezoelectric element according to any one of (21) to (30);
An electrical circuit for detecting an electrical signal output from the conductive fiber included in the fabric-like piezoelectric element in accordance with an applied pressure;
A device comprising:

According to the first aspect of the present invention, it is possible to provide a cylindrical or columnar piezoelectric structure that can selectively respond to torsional deformation (stress) and efficiently generate usable electrical polarization.

Further, according to the second invention, it is possible to provide a fibrous piezoelectric element capable of taking out a large electric signal even with a stress caused by a relatively small deformation and further suppressing a noise signal.

Further, according to the third invention, a fiber-like piezoelectric element capable of taking out a large electrical signal and suppressing a noise signal even by a stress caused by a relatively small deformation, and a substrate such as another fabric is used. It is possible to provide a fabric-like piezoelectric element that can be easily installed. Furthermore, according to the third aspect of the invention, by making the coverage of the braided piezoelectric element by the fibers constituting the fabric exceed a predetermined value, for example, 50% on both sides of the fabric, rubbing from outside, heat, It is possible to make it difficult to be damaged by light or the like.

It is a schematic diagram which shows the cylindrical piezoelectric structure which concerns on embodiment of 1st invention. It is a schematic diagram which shows the cylindrical piezoelectric structure which concerns on embodiment of 1st invention. It is a side view showing a cylindrical piezoelectric structure according to an embodiment of the first invention. It is a schematic diagram explaining the calculation method of orientation angle (theta). It is a schematic diagram which shows the structural example of the braided piezoelectric element which concerns on embodiment of 1st invention. It is a schematic diagram which shows the structural example of the fabric-like piezoelectric element which concerns on embodiment of 1st invention. FIG. 4 is a block diagram showing a device including a piezoelectric element according to embodiments of the first invention to the third invention. It is a schematic diagram which shows the structural example of a device provided with the fabric-like piezoelectric element which concerns on embodiment of 1st invention. 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 of 1st invention. It is a microscope picture which shows the cross section of the braided piezoelectric element which concerns on an Example. It is a microscope picture which shows the cross section of the braided piezoelectric element which concerns on an Example. It is a microscope picture which shows the cross section of the braided piezoelectric element which concerns on an Example. It is a schematic diagram which shows the structural example of the braided piezoelectric element which concerns on embodiment of 2nd invention and 3rd invention. It is a microscope picture which shows the cross section of the braided piezoelectric element which concerns on embodiment of 2nd invention. It is a schematic diagram which shows the structural example of the fabric-like piezoelectric element which concerns on embodiment of 2nd invention. It is a schematic diagram which shows the structural example of a device provided with the braided piezoelectric element which concerns on embodiment of 2nd invention. It is a schematic diagram which shows the structural example of the device provided with the fabric-like piezoelectric element which concerns on embodiment of 2nd invention. 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 of 2nd invention. 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 of 2nd invention. It is a schematic diagram which shows the structural example of the fabric-like piezoelectric element which concerns on embodiment of 3rd invention. It is a schematic diagram which shows the other structural example of the fabric-like piezoelectric element which concerns on embodiment of 3rd invention. It is a schematic diagram which shows the other structural example of the fabric-like piezoelectric element which concerns on embodiment of 3rd invention. It is a schematic diagram which shows the structural example of a device provided with the fabric-like piezoelectric element which concerns on embodiment of 3rd invention. 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 of 3rd invention. 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 of 3rd invention.

Hereinafter, the first invention will be described in detail.
(Cylindrical or cylindrical piezoelectric structure)
The structure (piezoelectric structure) of the present invention includes an oriented piezoelectric polymer, and the oriented piezoelectric polymer is arranged in a cylindrical shape or a cylindrical shape. FIG. 1A is a schematic diagram showing a cylindrical piezoelectric structure 1-1 according to the embodiment, and FIG. 1B is a schematic diagram showing a cylindrical piezoelectric structure 1-2 according to the embodiment. The outer and inner edges of the cylindrical or columnar bottom surface on which the piezoelectric polymer is disposed are most preferably perfect circles, but may be elliptical or flat.

(Piezoelectric polymer)
The piezoelectric polymer contained in the piezoelectric structure of the present invention is a molded body of uniaxially oriented polymer, and the absolute value of the piezoelectric constant d14 when the orientation axis is triaxial is 0.1 pC / N or more and 1000 pC. A crystalline polymer having a value of / N or less is included as a main component. In the present invention, “including as a main component” refers to occupying 50% by mass or more of the constituent components. In the present invention, the crystalline polymer is a polymer composed of 1% by mass or more of a crystal part and an amorphous part other than the crystal part, and the mass of the crystalline polymer means the crystal part and the amorphous part. And the total mass.
The absolute value of the piezoelectric constant d14 can be suitably used as a crystalline polymer contained in the piezoelectric polymer of the present embodiment, with three orientation axes, and a value of 0.1 pC / N to 1000 pC / N. Examples of the crystalline polymer having cellulose, collagen, keratin, fibrin, poly-L-, as shown in “Piezoelectricity of biopolymers” (Eiichi Fukada, Biorheology, Vol. 3, No. 6, pp. 593). Examples include alanine, poly-γ-methyl-L-glutamate, poly-γ-benzyl-L-glutamate, and poly-L-lactic acid. In addition, poly-D-alanine, poly-γ-methyl-D-glutamate, poly-γ-benzyl-D-glutamate, and poly-D-lactic acid, which are optical isomers of these polymers, have the sign of d14 reversed. However, it is estimated that the absolute value of d14 takes an equivalent value. The value of d14 varies depending on molding conditions, purity, and measurement atmosphere. To achieve the object of the present invention, the crystallinity and crystal orientation of the crystalline polymer in the piezoelectric polymer actually used are used. The uniaxially stretched film having the same degree of crystallinity and crystal orientation is prepared using the crystalline polymer, and the absolute value of d14 of the film is 0 at the actually used temperature. It is only necessary to show a value of 1 pC / N or more and 1000 pC / N or less, and the crystalline polymer contained in the piezoelectric polymer of the present embodiment is not limited to the specific crystalline polymer listed above. 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.

In this embodiment, poly-L-lactic acid and poly-D-lactic acid are particularly preferably used. Poly-L-lactic acid and poly-D-lactic acid, for example, are readily crystallized by uniaxial stretching after melt film formation, and exhibit piezoelectricity exceeding 10 pC / N as the absolute value of d14. On the other hand, a polarization-treated product of a polyvinylidene fluoride molded product, which is a typical piezoelectric polymer, has a high piezoelectric constant of d33, but the absolute value of d14 is very low and is used as the crystalline polymer of the present invention. I can't.

The piezoelectric polymer may be used as an alloy with another polymer that does not exhibit piezoelectricity, but if polylactic acid is used as the main piezoelectric polymer, at least 60% by mass or more based on the total mass of the alloy. And preferably contains polylactic acid, more preferably 70% by mass or more, and most preferably 90% by 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 are not limited thereto.

(Orientation angle of piezoelectric polymer)
In the structure in which the piezoelectric polymer of the present invention is arranged in a cylindrical shape or a cylindrical shape, the direction of the cylindrical or cylindrical central axis (hereinafter simply referred to as “central axis”) in which the piezoelectric polymer is arranged The orientation angle θ of the piezoelectric polymer with respect to is 0 ° to 40 ° or 50 ° to 90 °. When this condition is satisfied, a piezoelectric effect corresponding to the piezoelectric constant d14 of the crystalline polymer included in the piezoelectric polymer is obtained by applying torsional deformation (torsional stress) about the central axis to the piezoelectric structure. It is possible to efficiently use and generate charges of opposite polarity efficiently on the central axis side and the outside of the piezoelectric structure. On the other hand, when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is more than 40 ° and less than 50 °, even if torsional deformation (torsional stress) about the central axis is applied to the piezoelectric structure, Since charges of opposite polarity cannot be efficiently generated on the central axis side and the outside of the piezoelectric structure, the charges cannot be efficiently taken out as a signal or energy. From this viewpoint, the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is preferably 0 ° or more and 35 ° or less, or 55 ° or more and 90 ° or less, and 0 ° or more and 30 ° or less, or 60 ° or more and 90 ° or less. Is more preferably 0 ° or more and 25 ° or less or 65 ° or more and 90 ° or less, and further preferably 0 ° or more and less than 15 ° or more than 75 ° and 90 ° or less. When the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is more than 0 ° and less than 90 °, the orientation direction of the piezoelectric polymer draws a spiral.

In addition, by arranging the piezoelectric polymer in this way, piezoelectric deformation is prevented against shear deformation that rubs the surface of the piezoelectric structure, bending deformation that bends the central axis, and expansion and contraction deformation in the central axis direction. The piezoelectric structure can be configured to prevent a large charge from being generated on the central axis side and the outside of the conductive structure, that is, to generate a large charge selectively with respect to torsion about the central axis.
The orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis refers to the direction of the central axis and the central axis in a parallel projection view of the cylindrical or cylindrical shape in which the piezoelectric polymer is arranged as viewed from the side. The angle formed by the orientation direction of the piezoelectric polymer in the front portion. For example, FIG. 2 is the figure which looked at the cylindrical piezoelectric structure 1 which concerns on embodiment from the side surface. In the example of FIG. 2, the piezoelectric structure is a structure in which a tape of a piezoelectric polymer oriented in the longitudinal direction is spirally wound. The straight line indicating the orientation direction of the tape in front of the central axis CL is OL, and the angle θ formed between CL and OL (0 to 90 degrees) is high in piezoelectricity with respect to the direction of the central axis. This is the orientation angle of the molecule.

In FIG. 2, since a thin piezoelectric polymer such as a tape is used, the orientation direction of the piezoelectric polymer is substantially the same as the orientation direction of the tape surface observed from the side, but the cylinder is formed using a thick piezoelectric polymer. In the case of forming a piezoelectric structure of a cylindrical shape, or in the case of a cylindrical piezoelectric structure, the internal orientation direction is closer to the central axis direction as it is closer to the central axis than the orientation direction of the surface that can be observed from the side. Therefore, a difference occurs between the surface orientation direction and the internal orientation direction. In addition, the orientation direction of the tape surface observed from the side surface may be apparently S-shaped or reverse S-shaped, and high-magnification observation is required for accurate observation.

From this point of view, the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis may be a structure in which fibers, filaments or tape oriented in the longitudinal direction are spirally wound (for example, twisted yarn, covering yarn, braid, etc. ), Measure as much as possible by the following method. A side photograph of the piezoelectric structure is taken and the helical pitch HP of the piezoelectric polymer 2 is measured. As shown in FIG. 3, the helical pitch HP is a linear distance in the central axis direction required for one piezoelectric polymer 2 to travel from the front surface to the back surface again. In addition, after fixing the structure with an adhesive, if necessary, cut out a cross section perpendicular to the central axis of the piezoelectric structure and photograph it to measure the outer radius Ro and the inner radius Ri of the portion occupied by the piezoelectric structure. To do. When the outer edge and inner edge of the cross section are elliptical or flat, the average values of the major axis and the minor axis are Ro and Ri. Ri = 0 when the piezoelectric structure is a cylinder. The orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is calculated from the following formula.
θ = arctan (2πRm / HP) (0 ° ≦ θ ≦ 90 °)
However ^{Rm = 2 (Ro 3 -Ri 3} ) / 3 (Ro 2 -Ri 2), i.e. the radius of the weighted average piezoelectric structure by the cross-sectional area.

When the piezoelectric polymer has a uniform surface in the side view of the piezoelectric structure, or when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is close to 0 °, If the helical pitch cannot be identified, the piezoelectric structure fixed with adhesive or the like is cleaved by a plane passing through the central axis, and X-rays are transmitted in a sufficiently narrow range so that it passes through the central axis in the direction perpendicular to the fractured surface. A wide-angle X-ray diffraction analysis is performed to determine the orientation direction, and the angle with the central axis is taken as θ.

For spirals drawn along the orientation direction of a piezoelectric polymer, such as braids and multiple covering yarns, two or more spirals with different spiral directions (S twist direction or Z twist direction) and spiral pitches exist simultaneously. In the case of a piezoelectric structure, the above measurement is performed for each of the piezoelectric polymers having the respective helical directions and helical pitches, and any one of the piezoelectric polymers having the helical direction and the helical pitch satisfies the above-described conditions. is necessary.

When the orientation direction of the piezoelectric polymer forms a helix, the direction of the helix direction (the S twist direction or the Z twist direction) does not affect the polarity (sign) of the charge generated with respect to torsional deformation. However, when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is 0 ° or more and 40 ° or less and when the orientation angle θ is 50 ° or more and 90 ° or less, the polarity of electric charges generated with respect to torsional deformation is Reverse. In addition, the polarity of electric charges generated with respect to torsional deformation is also reversed in piezoelectric polymers including crystalline polymers having different signs of d14 such as poly-L-lactic acid and poly-D-lactic acid. Therefore, in order to efficiently generate charges having opposite polarities on the central axis side and the outside of the piezoelectric structure against torsional deformation, piezoelectricity containing a crystalline polymer having the same sign of d14 as a main component is used. It is preferable that only the polymer is used, and the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis in the piezoelectric structure is set to only 0 ° to 40 ° or 50 ° to 90 °.

By the way, the polarity (sign) of charges generated on the central axis side and the outside with respect to the expansion and contraction in the central axis direction of the piezoelectric structure is determined by arranging the orientation direction of a certain piezoelectric polymer along the S-twisted helix. When the orientation direction of the same piezoelectric polymer is arranged along the Z-twisted helix, the polarities are opposite to each other. Therefore, the orientation direction of a certain piezoelectric polymer is along the S-twisted helix. When it is placed along the Z-twisted helix at the same time as it is placed (for example, when a braid is formed using both a yarn in the S-twisted direction and a yarn in the Z-twisted direction). Since the generated charges with respect to each other cancel each other in the S twist direction and the Z twist direction, only the charges generated corresponding to the torsional deformation can be detected. Therefore, as an embodiment of the present invention, the piezoelectric polymer includes a P body including a crystalline polymer having a positive piezoelectric constant d14 as a main component, and an N body including a negative crystalline polymer as a main component. In the portion where the central axis of the piezoelectric structure has a length of 1 cm, the orientation axis is ZP and the orientation axis is spiral in the S twist direction. The mass of the P body arranged by winding the SP is SP, the mass of the N body arranged by winding the spiral in the Z twist direction is ZN, and the mass of the N body arranged by winding the spiral in the S twist direction. When the mass of is Z, the smaller one of (ZP + SN) and (SP + ZN) is T1, and the larger is T2, the value of T1 / T2 is preferably more than 0.8, and 0.9 It is preferable that it is super. In particular, the piezoelectric polymer includes a P-form containing poly-D-lactic acid as a main component and an N-form containing poly-L-lactic acid as a main component, and the piezoelectric structure has a long central axis of 1 cm. For the portion having a thickness, the mass of the P body arranged with the spiral in the Z twist direction is ZP, the mass of the P body arranged with the spiral in the S twist direction is SP, the orientation axis Z is the mass of the N body arranged in the Z twist direction and Z is the mass of the N body arranged in the S twist direction and the SN is the mass of the N body arranged in the S twist direction, (ZP + SN) and (SP + ZN) Of these, when T1 is the smaller one and T2 is the larger one, the value of T1 / T2 is more than 0.8, more preferably more than 0.8 and less than 1.0, and more preferably more than 0.9, It is preferably more than 0.9 and 1.0 or less. Here, even when the value of T1 / T2 is not satisfied, when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is 0 ° or more and 10 ° or less, or 80 ° or more and 90 ° or less, it exceeds 10 °. Compared with the case of less than 80 °, the amount of electric charge generated with respect to expansion / contraction deformation is reduced. As a result, an electrical signal can be selectively generated with respect to torsional deformation, which is preferable.
Also, a piezoelectric polymer containing crystalline polymers having different d14 signs, such as poly-L-lactic acid and poly-D-lactic acid, is mixed along one of the S-twisted or Z-twisted helices. Arrangement is preferable because the generated charges for expansion and contraction cancel each other and selectively respond only to torsional deformation.

(Configuration of piezoelectric structure)
As described above, in the piezoelectric structure of the present invention, when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is more than 0 ° and less than 90 °, the orientation direction of the piezoelectric polymer is Draw a helix. As the piezoelectric structure having such an arrangement, for example, a twisted yarn, a covering yarn, a braid using a fiber, a filament or a tape in which a piezoelectric polymer is oriented in the longitudinal direction may be mentioned as a preferable mode. it can. When using a tape, it is possible to use a tape oriented in a direction other than the longitudinal direction of the tape, a spirally wound tape, or a cylinder molded in parallel with the longitudinal direction and the central axis direction. it can. From the standpoint of improving productivity and degree of orientation, fibers, filaments or tapes that are oriented in the longitudinal direction by stretching, twisting yarns, covering yarns, and braids are more preferable. From the viewpoint of structural stability, braids are especially preferable.

When the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is 0 °, the orientation direction of the piezoelectric polymer is parallel to the central axis. Examples of the piezoelectric structure having such an arrangement include, for example, fibers, filaments, or tapes obtained by orienting piezoelectric polymers in the longitudinal direction, those obtained by aligning them, hollow fibers and conjugate yarns, A preferred embodiment is one in which the core yarn is coated with a piezoelectric polymer.
When the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is 90 °, the orientation direction of the piezoelectric polymer forms a circle on a plane perpendicular to the central axis. As the piezoelectric structure having such an arrangement, for example, a piezoelectric polymer tape oriented perpendicularly to the longitudinal direction is preferably used and a cylinder is molded with the longitudinal direction and the central axis direction parallel to each other. It can be mentioned as a mode.

In the piezoelectric structure of the present invention, when torsional deformation is applied in the direction of the central axis, charges having opposite polarities are generated on the central axis side and the outside. The form of use is not particularly limited, and it can be used for operations such as adsorption / desorption of substances, attractive / repulsive force, generation of electromagnetic waves, and electrical stimulation to living bodies. A form in which a conductor is arranged outside and / or is more preferable. In the case where the conductor is disposed outside, it is more preferable that the conductor is disposed so as to cover all the columnar side surface or the cylindrical side surface of the piezoelectric structure from the viewpoint that it can be used as a charge utilization efficiency and a shield. For example, the conductor may be disposed only.
From the viewpoint of productivity, bending durability, and structural stability, a braided piezoelectric structure described below is most preferable.

(Braided piezoelectric element)
FIG. 4 is a schematic diagram illustrating a configuration example of a braided piezoelectric structure (hereinafter referred to as a braided piezoelectric element) according to the embodiment.
The braided piezoelectric element 101 includes a core portion 103 formed of a conductive fiber B, and a sheath portion 102 formed of a braided piezoelectric fiber A so as to cover the core portion 103. The part 102 is a cylindrical piezoelectric structure in the present invention. The piezoelectric fiber A can contain polylactic acid as a main component.

In the braided piezoelectric element 101, a large number of piezoelectric fibers A densely surround the outer peripheral surface of at least one conductive fiber B. When deformation occurs in the braided piezoelectric element 101, stress due to deformation is generated in each of the large number of piezoelectric fibers A, thereby generating an electric field (piezoelectric effect) in each of the large number of piezoelectric fibers A. As a result, the conductive fibers B It is presumed that a voltage change is generated in the conductive fiber B by superimposing the electric fields of a large number of piezoelectric fibers A surrounding the wire. That is, the electrical signal from the conductive fiber B increases as compared with the case where the braided sheath 102 of the piezoelectric fiber A is not used. As a result, the braided piezoelectric element 101 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, it is preferable that the signal intensity detected via the conductive fiber B serving as the core is more strongly constrained as well as the contact state with the piezoelectric fiber A serving as the sheath does not change. For example, it is possible to obtain a braid that is more strongly constrained by increasing the tension when the piezoelectric fibers are braided by a string making machine. On the other hand, polylactic acid (PLA) fibers are weak in strength and high in friction. Therefore, there are cases where the fiber breaks a single yarn on the yarn path of the string making machine and a beautiful braid cannot be obtained. That is, in the string making process, the fiber is assembled while the fibers are stretched and loosened momentarily by the bobbin accumulator along the path on which the carrier holding the bobbin wound with the fibers moves on the board. It is difficult to string with high tension. However, it has been found that such difficulty can be improved by twisting the PLA fiber. Specifically, it is preferable to apply twist processing to the PLA fiber with a twist number of 10 to 5000 T / m. If it is less than 10 T / m, the effect of twisted yarn cannot be obtained, and if it is greater than 5000 T / m, the fibers are likely to be twisted and troubles during processing are likely to occur. In addition, the angle of the PLA in the orientation axis direction with respect to the deformation in the axial direction of the braid when the braid is formed is not appropriate, and the signal strength may be reduced. The number of twists is more preferably 30 T / m or more, and still more preferably 50 T / m or more. Moreover, as an upper limit of the number of twists, 3000 T / m or less is more preferable, More preferably, it is 1500 T / m or less. The twisting method is not particularly limited, and any known twisting method can be applied. Further, the twisted fiber is preferably heat-treated, and the heat-treated fiber fixes the twisted state and facilitates handling of the fiber. The heat treatment method is not particularly limited, and generally, the temperature of Tg to Tm of the target fiber is preferably selected, and the treatment may be performed under humidity.

Here, the piezoelectric fiber A preferably contains polylactic acid as a main component. 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.

In the braided piezoelectric element 101, as long as the object of the present invention is achieved, the sheath portion 102 may be mixed with fibers other than the piezoelectric fiber A, and the core portion 103 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 103 of the conductive fiber B and the sheath portion 102 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 the conductive fiber B is made of an organic fiber coated with a metal having bending resistance, the conductive fiber is hardly broken, and is 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 μm to 50 μm. 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 portion 103 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 103 is the total amount including fibers other than the conductive fibers.

If the fiber diameter is small, the strength decreases and handling becomes difficult, and if the fiber 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 electric output from the piezoelectric polymer, the electric 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 an 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 bending stiffness 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 0.01 × 10 ⁻⁴ N · m ² / m or less.

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.

Piezoelectric fiber A containing polylactic acid as a main component is drawn during 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, the homo PLA crystallinity X _homo (%) and the crystal orientation degree Ao (%) preferably 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 obtained 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 near 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, 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.

Also, the piezoelectric fiber A can be subjected to treatments such as dyeing, twisting, combining, heat treatment, etc., before making the braided one produced 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. 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 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 (6).
Boiling water shrinkage = (L0−L) / L0 × 100 (%) (6)

(Coating)
The surface of the conductive fiber B, that is, the core portion 103 is covered with the piezoelectric fiber A, that is, the braided sheath portion 102. The thickness of the sheath 102 covering the conductive fiber B is preferably 1 μm to 10 mm, more preferably 5 μm to 5 mm, still more preferably 10 μm to 3 mm, and 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 101 may become hard and difficult to deform. Here, the sheath portion 102 refers to a layer adjacent to the core portion 103.

In the braided piezoelectric element 101, the total fineness of the piezoelectric fibers A of the sheath portion 102 is preferably ½ times or more and 20 times or less of the total fineness of the conductive fibers B of the core portion 103, preferably 1 time or more. 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 101 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 101 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 102. For example, in the case of a general 8-strand braid, it is the sum of the finenesses of eight fibers.

In the braided piezoelectric element 101, the fineness per piezoelectric fiber A of the sheath 102 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 101 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 101 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 A or the piezoelectric fiber B, 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.

As the coating method, a method is used in which the conductive fiber B is used as a core thread and the piezoelectric fiber A is wound around the braid in the form of a braid. 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.

Since the braided piezoelectric element 101 of the present invention does not require an electrode to be present on the surface thereof, there is no need to further cover the braided piezoelectric element 101 itself, and there is an advantage that malfunction is unlikely.

(Production method)
The braided piezoelectric element 101 of the present invention covers the surface of at least one conductive fiber B with the braided piezoelectric fiber A. Examples of the manufacturing method thereof 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. Further, the conductive fiber B may be twisted.

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. At this time, it is preferable to use a twisted fiber for the piezoelectric fiber A, but all the piezoelectric fibers may be twisted or a part of them may be twisted. Moreover, the twist direction of the piezoelectric fiber A does not need to be the same direction for all the piezoelectric fibers A to be used. For example, it is possible to use a fiber that rotates in the clockwise direction during stringing, and a fiber that rotates in the counterclockwise direction and a fiber that rotates in the counterclockwise direction. Further, for example, in the case of an 8-strand braid, not all of the 8 need to be piezoelectric fibers, and other fibers can be used as long as the desired signal strength is obtained. Of course, the conductive fibers of the core part and the conductive fibers to be the shield layer may be twisted. 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 braided piezoelectric element 101 in which the surface of the conductive fiber B is covered with the braided piezoelectric fiber A can be obtained by the manufacturing method as described above.

Since the braided piezoelectric element 101 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 101 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 fibers A. However, if the thickness is too thin, problems such as destruction of the protective layer itself are likely to occur. More preferably, it is 50 nm to 50 μm, more preferably 70 nm to 30 μm, and most preferably 100 nm to 10 μm. 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 102, or covering is mentioned.
When conductors are arranged on the central axis side and the outside of the piezoelectric structure as described above, a piezoelectric polymer (dielectric material) is formed using the conductor on the center axis side and the outer conductor as two electrodes. It can be regarded as a sandwiched capacitor-like piezoelectric element. In order to effectively extract an electrical signal induced by polarization generated in the piezoelectric structure due to deformation, the value of the insulation resistance between these electrodes should be 1 MΩ or more when measured at a DC voltage of 3V. Preferably, it is 10 MΩ or more, 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 extract an electrical signal induced in the light and improve 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 an element including a piezoelectric structure and an electrode can operate in a preferable state, an equivalent series resistance value Rs obtained by analyzing a 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 piezoelectric structure. Further, the piezoelectric structure 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 to other electrical stimuli.

(Function)
The braided piezoelectric element 101 of the present invention is particularly large when torsional deformation (stress) about the central axis of the cylindrical piezoelectric structure formed from the sheath portion 102, that is, the conductive fiber B, is used. An electric signal can be output efficiently. On the other hand, no large electrical signal is output for expansion / contraction deformation, bending, or rubbing deformation.

Here, it is preferable that the torsional deformation given to the braided piezoelectric element 101 is given in a range where the fibers in the element do not reach the deformation amount for starting plastic deformation. The amount of deformation depends on the physical properties of the fibers used. However, this does not apply to applications that do not assume repetitive specifications.

(Fabric piezoelectric element)
FIG. 5 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 107 includes a cloth 108 including at least one braided piezoelectric element 101. The fabric 108 is not limited as long as at least one of the fibers (including the braid) constituting the fabric is the braided piezoelectric element 101 and the braided piezoelectric element 101 can 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, it may be woven or knitted in combination with other fibers (including braids). Of course, the braided piezoelectric element 101 may be used as part of a fiber (for example, warp or weft) constituting the fabric, or the braided piezoelectric element 101 may be embroidered or bonded to the fabric. Good. In the example shown in FIG. 5, the cloth-like piezoelectric element 107 has at least one braided piezoelectric element 101 and insulating fibers 109 as warps and alternately has conductive fibers 110 and insulating fibers 109 as wefts. Plain woven fabric. The conductive fiber 110 may be the same type or different type of conductive fiber B, and the insulating fiber 109 will be described later. Note that all or part of the insulating fibers 109 and / or the conductive fibers 110 may be braided.

In this case, when the cloth-like piezoelectric element 107 is deformed by bending or the like, the braided piezoelectric element 101 is also deformed along with the deformation. Therefore, the cloth-like piezoelectric element 107 is generated by an electric signal output from the braided piezoelectric element 101. Can be detected. Since the cloth-like piezoelectric element 107 can be used as a cloth (woven or knitted fabric), it can be applied to, for example, a clothing-shaped wearable sensor.

Further, in the fabric-like piezoelectric element 107 shown in FIG. 5, the conductive fiber 110 intersects and contacts the braided piezoelectric element 101. Therefore, the conductive fiber 110 intersects and covers at least a part of the braided piezoelectric element 101, covers it, and shields at least a part of the electromagnetic wave that goes from the outside toward the braided piezoelectric element 101. Can be seen. Such a conductive fiber 110 has a function of reducing the influence of electromagnetic waves on the braided piezoelectric element 101 by being grounded. That is, the conductive fiber 110 can function as an electromagnetic wave shield for the braided piezoelectric element 101. Thereby, for example, the S / N ratio of the cloth-like piezoelectric element 107 can be remarkably improved without overlapping conductive cloths for electromagnetic wave shielding on and under the cloth-like piezoelectric element 107. In this case, from the viewpoint of electromagnetic shielding, the higher the ratio of the conductive fibers 110 in the wefts (in the case of FIG. 5) intersecting with the braided piezoelectric element 101, the better. Specifically, 30% or more of the fibers forming the fabric 108 and intersecting the braided piezoelectric element 101 are preferably conductive fibers, more preferably 40% or more, and 50% or more. Further preferred. As described above, in the cloth-like piezoelectric element 107, by inserting conductive fibers as at least a part of the fibers constituting the cloth, the cloth-like piezoelectric element 107 with an electromagnetic wave shield can be obtained.

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 107, a plurality of braided piezoelectric elements 101 can be used side by side. For example, the braided piezoelectric elements 101 may be used for all warps or wefts, or the braided piezoelectric elements 101 may be used for several or a part. Alternatively, the braided piezoelectric element 101 may be used as a warp in a certain part, and the braided piezoelectric element 101 may be used as a weft in another part.

Thus, when forming the fabric-like piezoelectric element 107 by arranging a plurality of braided piezoelectric elements 101, the braided piezoelectric element 101 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 101 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 107, an insulating fiber can be used in a portion other than the braided piezoelectric element 101 (and the conductive fiber 110). 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 107.

In this way, by arranging the insulating fiber in addition to the braided piezoelectric element 101 (and the conductive fiber 110), the operability of the cloth-like piezoelectric element 107 (eg, ease of movement as a wearable sensor) is improved. It is possible to make it.

As such an insulating fiber, it can be used if the volume resistivity is 10 ⁶ Ω · cm or more, more preferably 10 ⁸ Ω · cm or more, and further 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 fibers can be used.

(Applied technology for piezoelectric elements)
The piezoelectric element such as the braided piezoelectric element 101 or the cloth-like piezoelectric element 107 of the present invention outputs torsional deformation (stress) about the central axis of the braided piezoelectric element as an electric signal, regardless of the state. Therefore, it can be used as a sensor (device) for detecting the magnitude and / or position of the stress applied to the piezoelectric element. Depending on the arrangement method of the braided piezoelectric element in the cloth-like piezoelectric element, the braided piezoelectric element can be torsionally deformed when subjected to deformation or stress such as bending, stretching, pressing, etc. An electrical signal can also be output by deformation or stress such as bending, expansion / contraction, or pressing of the piezoelectric element. 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. 6 is a block diagram showing a device 111 including the piezoelectric element 112 of the present invention. The device 111 amplifies an electrical signal output from the output terminal of the piezoelectric element 112 in accordance with an applied pressure with the piezoelectric element 112 (example: braided piezoelectric element 101, fabric-like piezoelectric element 107) and, optionally, the pressure. Amplifying means 113; output means 114 for outputting the electric signal amplified by the optional amplifying means 113; and transmitting means 115 for transmitting the electric signal output from the output means 114 to an external device (not shown). An electric circuit is provided. If this device 111 is used, the braided shape applied to the piezoelectric element by arithmetic processing in an external device (not shown) based on the electrical signal output by contact with the surface of the piezoelectric element 112, pressure, and shape change. The magnitude of torsional deformation (stress) about the central axis of the piezoelectric element and / or the applied position can be detected.

Optional amplification means 113, output means 114, and transmission means 115 may be constructed in a software program format, for example, 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 amplification unit 113, output unit 114, and transmission unit 115 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 115 is wireless or wired may be appropriately determined according to the sensor to be configured. Alternatively, calculation means (not shown) for calculating the magnitude and / or position of the stress applied to the piezoelectric element 112 based on the electrical signal output from the output means 114 may be provided in the device 111. Good. In addition to the amplifying means, known signal processing means such as noise removing means and means for processing in combination with other signals may be used in combination. The order of connection of these means can be appropriately changed according to the purpose. Of course, the electrical signal output from the piezoelectric element 112 may be transmitted to an external device as it is, and then signal processing may be performed.

7 and 8 are schematic views showing a configuration example of a device including the braided cloth-like piezoelectric element according to the embodiment. The amplifying unit 113 in FIGS. 7 and 8 corresponds to that described with reference to FIG. 6, but the output unit 114 and the transmitting unit 115 in FIG. 6 are not shown in FIGS. 7 and 8. In the case of configuring a device including the fabric-like piezoelectric element 107, the lead wire from the output terminal of the core portion 103 (formed of the conductive fiber B) of the braided piezoelectric element 101 is connected to the input terminal of the amplifying unit 113, A braided piezoelectric element or conductive fiber 110 different from the braided piezoelectric element 101 connected to the input terminal of the amplifying means 113 is connected to the ground (earth) terminal. For example, as shown in FIG. 7, in the cloth-like piezoelectric element 107, the lead wire from the core portion 103 of the braided piezoelectric element 101 is connected to the input terminal of the amplifying means 113, and crosses the braided piezoelectric element 101 to make contact. The conductive fiber 110 is grounded. Further, for example, as shown in FIG. 8, when a plurality of braided piezoelectric elements 101 are arranged in the cloth-like piezoelectric element 107, the lead wire from the core portion 103 of one braided piezoelectric element 101 is connected to the input terminal of the amplifying unit 113. And the lead wire from the core portion 103 of another braided piezoelectric element 101 aligned with the braided piezoelectric element 101 is grounded (grounded).

When torsional deformation about the central axis of the braided piezoelectric element 101 occurs, the piezoelectric fiber A is deformed to generate polarization. In accordance with 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 output terminal of the conductive fiber B forming the core portion 103 of the braided piezoelectric element 101. The movement of electric charge on the lead line from the conductive fiber B appears as a minute electric signal (that is, current or potential difference). In other words, an electrical signal is output from the output terminal in accordance with the electric charge generated when torsional deformation is applied about the central axis of the braided piezoelectric element 101 (cylindrical central axis on which the piezoelectric polymer is disposed). Is done. The amplifying means 113 and the electric signal are amplified, the output means 114 outputs the electric signal amplified by the amplifying means 113, and the transmitting means 115 outputs the electric signal output from the output means 114 to an external device (not shown). ).

Since the device 111 of the present invention is flexible and can be used in either a string form or a cloth form, a very wide range of uses can be considered. Specific examples of the device 111 of the present invention include a touch panel, a human or animal surface pressure sensor, for example, a glove or a band, in the shape of clothes, supporters, handkerchiefs, etc. including hats, gloves, socks, etc. 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 111 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 pasting or covering all or part of the surface of any structure. Can do.

Furthermore, since the device 111 of the present invention can generate a sufficient electric signal simply by rubbing the surface of the braided piezoelectric element 101, 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 101, it can be used for surface shape measurement and the like.

Hereinafter, the second invention will be described in detail.
(Braided piezoelectric element)
In the braided piezoelectric element according to the second invention, the piezoelectric polymer in the structure according to the first invention is arranged in a cylindrical shape, and an electric conductor made of conductive fibers is arranged at the position of the central axis of the cylindrical shape An element in which a piezoelectric polymer is arranged as a braided cord around a conductive fiber as a piezoelectric fiber can be used. Hereinafter, the braided piezoelectric element according to the second invention will be described in detail.

FIG. 10 is a schematic diagram illustrating a configuration example of a braided piezoelectric element according to the embodiment.
The braided piezoelectric element 201 covers the core portion 203 formed of the conductive fiber B, the sheath portion 202 formed of the braided piezoelectric fiber A so as to cover the core portion 203, and the sheath portion 202. And a conductive layer 204. The conductive layer 204 functions as an electrode serving as a counter electrode of the conductive fiber of the core part 203, and shields the conductive fiber of the core part 203 from external electromagnetic waves, thereby suppressing noise signals generated in the conductive fiber of the core part 203. At the same time, it functions as a shield.

The coverage of the sheath portion 202 by the conductive layer 204 is preferably 25% or more. Here, the coverage is a ratio of the area of the conductive substance 205 contained in the conductive layer 204 to the surface area of the sheath 202 when the conductive layer 204 is projected onto the sheath 202, 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 204 is less than 25%, the noise signal suppression effect may not be sufficiently exhibited. When the conductive material 205 is not exposed to the surface of the conductive layer 204, for example, when the sheath 202 is covered using the fiber containing the conductive material 205 as the conductive layer 204, the sheath of the fiber The ratio of the area when projected onto 202 and the surface area of the sheath portion 202 can be defined as the coverage.
The conductive substance 205 is a conductive substance contained in the conductive layer 204, and any known substance is applicable.

In the braided piezoelectric element 201, a large number of piezoelectric fibers A surround the outer peripheral surface of at least one conductive fiber B densely. When deformation occurs in the braided piezoelectric element 201, stress due to deformation is generated in each of a large number of piezoelectric fibers A, thereby generating an electric field (piezoelectric effect) in each of the large number of piezoelectric fibers A. As a result, the conductive fibers B 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 portion 202 of the piezoelectric fiber A is not used. As a result, the braided piezoelectric element 201 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.

From the viewpoint of achieving the object of the second invention, the braided piezoelectric element 201 has features other than the characteristic of the ratio d / Rc of the thickness d of the layer made of piezoelectric fibers to the radius Rc of the core 203 described later. 10 is not particularly limited as long as it has the configuration shown in FIG. 10. From the viewpoint of selectively outputting a large electrical signal with respect to torsional deformation about the central axis, the following configuration is provided. Those are preferred.
The braided piezoelectric element 201 that selectively outputs a large electrical signal with respect to torsional deformation about the central axis is a structure in which oriented piezoelectric polymers are arranged in 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 shape in which the piezoelectric polymer is disposed is 0 ° to 40 °, or 50 ° to 90 °, preferably 0 ° to 35 ° or 55 °. 90 ° or less, more preferably 0 ° or more and 30 ° or less, or 60 ° or more and 90 ° or less, more preferably 0 ° or more and 25 ° or less, or 65 ° or more and 90 ° or less, and even more preferably 0 ° or more and less than 15 ° or More than 75 ° and not more than 90 °, most preferably not less than 0 ° and not more than 10 °, or not less than 80 ° and not more than 90 °, and the piezoelectric polymer has an absolute value of piezoelectric constant d14 of 0.1 pC when the orientation axes are three axes. / N or more 100 Comprising a crystalline polymer having the following values pC / N as main components, structures are used. 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. When the smaller one of (ZP + SN) and (SP + ZN) is T1, and the larger one is T2, the value of T1 / T2 is more than 0.8, particularly more than 0.8 and less than 1.0 or 0.9 It is more preferable that such a structure is more than 0.9, particularly more than 0.9 and not more than 1.0.

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 201, as long as the object of the present invention is achieved, the sheath 202 may be mixed with fibers other than the piezoelectric fiber A, and the core 203 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 203 of the conductive fiber B, the sheath portion 202 of the braided piezoelectric fiber A, and the conductive layer 204 covering the sheath portion 202 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 the conductive fiber B is made of an organic fiber coated with a metal having bending resistance, the conductive fiber is hardly broken, and is 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 μm to 50 μm. 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 portions 203 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 203 is the total amount including fibers other than conductive fibers.

If the fiber diameter is small, the strength decreases and handling becomes difficult, and if the fiber 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 an 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.

Piezoelectric fiber A containing polylactic acid as a main component is drawn during 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 near 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, 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.

Also, the piezoelectric fiber A can be subjected to treatments such as dyeing, twisting, combining, heat treatment, etc., before making the braided one produced 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. 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 203 is covered with the piezoelectric fiber A, that is, the braided sheath portion 202. The thickness of the sheath portion 202 covering the conductive fiber B is preferably 1 μm to 10 mm, more preferably 5 μm to 5 mm, still more preferably 10 μm to 3 mm, and 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 201 may become hard and difficult to deform. In addition, the sheath part 202 said here refers to the layer adjacent to the core part 203. FIG.

In the braided piezoelectric element 201, the total fineness of the piezoelectric fibers A of the sheath portion 202 is preferably ½ or more and 20 times or less of the total fineness of the conductive fibers B of the core portion 203, preferably 1 or more times. 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 201 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 201 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 202. For example, in the case of a general 8-strand braid, it is the sum of the finenesses of eight fibers.

In the braided piezoelectric element 201, the fineness per piezoelectric fiber A of the sheath portion 202 is preferably 1/20 times or more and 2 times or less the total fineness of the conductive fibers 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 201 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 201 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.

As the coating method, a method is used in which the conductive fiber B is used as a core thread and the piezoelectric fiber A is wound around the braid in the form of a braid. 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 204 functions as an electrode serving as a counter electrode of the conductive fiber of the core part 203, and shields the conductive fiber of the core part 203 from external electromagnetic waves, thereby suppressing noise signals generated in the conductive fiber of the core part 203. And a function as a shield. Since the conductive layer 204 functions as a shield, it is preferably grounded (connected to the earth or the ground of an electronic circuit). Accordingly, for example, the S / N ratio (signal-to-noise ratio) of the cloth-like piezoelectric element 207 can be remarkably improved without overlapping conductive cloths for electromagnetic wave shielding on and under the cloth-like piezoelectric element 207. As a mode of the conductive layer 204, in addition to coating, a film, a fabric, or a fiber can be wound, or a combination thereof may be used.

As the coating for forming the conductive layer 204, any coating containing a substance exhibiting conductivity may be used, 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 204 is formed by winding a film, a film obtained by forming a conductive polymer and a polymer in which a conductive filler is dispersed is used, and a conductive layer is provided on the surface. A film may be used.

When the conductive layer 204 is formed by winding a fabric, a fabric including a conductive fiber 206 described later as a constituent component is used.

When the conductive layer 204 is formed by winding a fiber, a covering, a knitted fabric, or a braid can be considered as the technique. Moreover, the fiber used is the conductive fiber 206, and the conductive fiber 206 may be the same type as the conductive fiber B or a different type of conductive fiber. Examples of the conductive fiber 206 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 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.

If the conductive fiber 206 is made of an organic fiber coated with metal having bending resistance, the conductive fiber is hardly broken, and is excellent in durability and safety as a sensor using a piezoelectric element.

The conductive fiber 206 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 μm to 50 μm. 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 fiber diameter is small, the strength decreases and handling becomes difficult, and if the fiber diameter is large, flexibility is sacrificed. The cross-sectional shape of the conductive fiber 206 is preferably a circle or an ellipse from the viewpoint of the 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 206 must be resistant to movement such as repeated bending and twisting for the purposes 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.

Also, it can be regarded as a capacitor-like piezoelectric element having a piezoelectric polymer (dielectric) sandwiched between a core conductor and an electromagnetic shield layer conductor as bipolar electrodes. 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 201 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 fibers A. However, if the thickness is too thin, problems such as destruction of the protective layer itself are likely to occur. More preferably, it is 50 nm to 50 μm, more preferably 70 nm to 30 μm, and most preferably 100 nm to 10 μm. The shape of the piezoelectric element can also be formed by this protective layer.

Further, a plurality of layers made of piezoelectric fibers can be provided, or a plurality of layers made of conductive fibers for taking out 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 202 further, or covering is mentioned.

The braided piezoelectric element 201 of the present invention can detect deformation and stress using the electrical signal output due to the piezoelectric effect described above, and the conductive fibers B and the conductive layer at the core of the braided piezoelectric element 201. It is also possible to detect deformation due to the pressure applied to the braided piezoelectric element 201 by measuring the change in capacitance between 204. Further, when a plurality of braided piezoelectric elements 201 are used in combination, the pressure applied to the braided piezoelectric element 201 is measured by measuring the capacitance change between the conductive layers 204 of each braided piezoelectric element 201. It is also possible to detect deformation due to.

(Insulating fiber)
In the cloth-like piezoelectric element 207, an insulating fiber can be used in a portion other than the braided piezoelectric element 201 (and the conductive fiber 210). In this case, 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 207.

In this way, by arranging the insulating fiber in addition to the braided piezoelectric element 201 (and the conductive fiber 210), the operability of the cloth-like piezoelectric element 207 (eg, 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 201 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 204 is manufactured by coating or winding of fibers, but from the viewpoint of ease of manufacturing, winding of fibers is preferable. 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 201 in which the surface of the conductive fiber B is covered with the braided piezoelectric fiber A and the conductive layer 204 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 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 deformation of the practical 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 as follows from the microscopic image of the cross section shown in FIG. 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. 11A, the radius Rc of the core portion is an average value of the radius of the largest circle X consisting only of the fiber bundle of the core portion and the radius of the smallest circle Y that completely includes the fiber bundle. And As shown in FIG. 11-2, 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. 12 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 207 includes a cloth 208 including at least one braided piezoelectric element 201. The fabric 208 is not limited as long as at least one of the fibers (including braids) constituting the fabric is a braided piezoelectric element 201 and the braided piezoelectric element 201 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, it may be woven or knitted in combination with other fibers (including braids). Of course, the braided piezoelectric element 201 may be used as a part of a fiber (for example, warp or weft) constituting the fabric, or the braided piezoelectric element 201 may be embroidered or bonded to the fabric. Good. In the example shown in FIG. 12, the fabric-like piezoelectric element 207 includes at least one braided piezoelectric element 201 and insulating fibers 209 as warps, and alternately includes conductive fibers 210 and insulating fibers 209 as wefts. Plain woven fabric. The conductive fiber 210 may be the same type or different type of conductive fiber B, and the insulating fiber 209 will be described later. Note that all or part of the insulating fibers 209 and / or the conductive fibers 210 may be braided.

In this case, when the cloth-like piezoelectric element 207 is deformed by bending or the like, the braided piezoelectric element 201 is also deformed along with the deformation, so that the cloth-like piezoelectric element 207 is generated by an electric signal output from the braided piezoelectric element 201. Can be detected. Since the cloth-like piezoelectric element 207 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 207 shown in FIG. 12, the conductive fibers 210 are in contact with the braided piezoelectric element 201 so as to intersect with each other. Accordingly, the conductive fiber 210 intersects with and covers at least a part of the braided piezoelectric element 201 and covers at least a part of the electromagnetic wave that is directed to the braided piezoelectric element 201 from the outside. Can be seen. Such a conductive fiber 210 has a function of reducing the influence of electromagnetic waves on the braided piezoelectric element 201 by being grounded. That is, the conductive fiber 210 can function as an electromagnetic wave shield for the braided piezoelectric element 201. Thereby, for example, the S / N ratio of the cloth-like piezoelectric element 207 can be remarkably improved without overlapping conductive cloths for electromagnetic wave shielding on and under the cloth-like piezoelectric element 207. In this case, from the viewpoint of electromagnetic shielding, the higher the proportion of the conductive fibers 210 in the wefts (in the case of FIG. 12) intersecting the braided piezoelectric element 201, the better. Specifically, 30% or more of the fibers forming the fabric 208 and intersecting the braided piezoelectric element 201 are preferably conductive fibers, more preferably 40% or more, and 50% or more. Further preferred. As described above, in the cloth-like piezoelectric element 207, by inserting conductive fibers as at least part of the fibers constituting the cloth, the cloth-like piezoelectric element 207 with an electromagnetic wave shield can be obtained.

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 207, a plurality of braided piezoelectric elements 201 can be used side by side. For example, the braided piezoelectric elements 201 may be used for all warps or wefts, or the braided piezoelectric elements 201 may be used for several or a part of them. Alternatively, the braided piezoelectric element 201 may be used as a warp in a certain part, and the braided piezoelectric element 201 may be used as a weft in another part.

In this way, when forming the fabric-like piezoelectric element 207 by arranging a plurality of braided piezoelectric elements 201, the braided piezoelectric element 201 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 201 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 201 and the cloth-like piezoelectric element 207 of the present invention can output contact, pressure, and shape change to the surface as an electric signal in any form, so that the piezoelectric element 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. 6 is a block diagram showing a device 111 including the piezoelectric element 112 of the present invention. The device 111 includes a piezoelectric element 112 (e.g., braided piezoelectric element 201, cloth-shaped piezoelectric element 207) and, optionally, amplification means 113 that amplifies an electric signal output from the piezoelectric element 112 in accordance with an applied pressure. And an output circuit 114 for outputting the electric signal amplified by the optional amplification means 113, and a transmission means 115 for transmitting the electric signal output from the output means 114 to an external device (not shown). With. If this device 111 is used, the stress applied to the piezoelectric element can be 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 112, pressure, or shape change. The magnitude and / or applied position can be detected.

Optional amplification means 113, output means 114, and transmission means 115 may be constructed in a software program format, for example, 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 amplification unit 113, output unit 114, and transmission unit 115 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 115 is wireless or wired may be appropriately determined according to the sensor to be configured. Alternatively, calculation means (not shown) for calculating the magnitude and / or position of the stress applied to the piezoelectric element 112 based on the electrical signal output from the output means 114 may be provided in the device 111. 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 electrical signal output from the piezoelectric element 112 may be transmitted to an external device as it is, and then signal processing may be performed.

FIG. 13 is a schematic diagram illustrating a configuration example of a device including the braided piezoelectric element according to the embodiment. The amplification unit 113 in FIG. 13 corresponds to that described with reference to FIG. 6, but the output unit 114 and the transmission unit 115 in FIG. 6 are not shown in FIG. 13. When a device including the braided piezoelectric element 201 is configured, a lead wire from the core 203 of the braided piezoelectric element 201 is connected to the input terminal of the amplifying unit 113, and the braided piezoelectric element 201 is connected to the ground (earth) terminal. The conductive layer 204 is connected. For example, as shown in FIG. 13, in the braided piezoelectric element 201, the lead wire from the core part 203 of the braided piezoelectric element 201 is connected to the input terminal of the amplifying means 113, and the conductive layer 204 of the braided piezoelectric element 201 is connected. Ground (earth).

FIGS. 14 to 16 are schematic diagrams showing a configuration example of a device including a braided cloth-like piezoelectric element according to the embodiment. The amplification means 113 in FIGS. 14 to 16 corresponds to that described with reference to FIG. 6, but the output means 114 and the transmission means 115 in FIG. 6 are not shown in FIGS. In the case of configuring a device including the fabric-like piezoelectric element 207, the lead wire from the core portion 203 (formed of the conductive fiber B) of the braided piezoelectric element 201 is connected to the input terminal of the amplifying means 113 and grounded (grounded) ) A braided piezoelectric element different from the braided piezoelectric element 201 connected to the conductive layer 204 of the braided piezoelectric element 201, the conductive fiber 210 of the fabric-like piezoelectric element 207, or the input terminal of the amplifying means 113 is connected to the terminal. To do. For example, as shown in FIG. 14, in the cloth-like piezoelectric element 207, the lead wire from the core portion 203 of the braided piezoelectric element 201 is connected to the input terminal of the amplifying means 113, and the conductive layer 204 of the braided piezoelectric element 201 is connected. Ground (earth). Further, for example, as shown in FIG. 15, in the cloth-like piezoelectric element 207, the lead wire from the core portion 203 of the braided piezoelectric element 201 is connected to the input terminal of the amplifying means 113 and intersects the braided piezoelectric element 201. The contacted conductive fiber 210 is grounded. Further, for example, as shown in FIG. 16, when a plurality of braided piezoelectric elements 201 are arranged in the cloth-like piezoelectric element 207, the lead wire from the core portion 203 of one braided piezoelectric element 201 is connected to the input terminal of the amplifying unit 113. The lead wire from the core part 203 of another braided piezoelectric element 201 arranged in the braided piezoelectric element 201 is grounded (grounded).

When the braided piezoelectric element 201 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 forming the core portion 203 of the braided piezoelectric element 201. 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 unit 113 amplifies the electric signal, the output unit 114 outputs the electric signal amplified by the amplifying unit 113, and the transmitting unit 115 outputs the electric signal output from the output unit 114 to an external device (not shown). Send to

Since the device 111 of the present invention is flexible and can be used in either a string form or a cloth form, a very wide range of uses can be considered. Specific examples of the device 111 of the present invention include a touch panel, a human or animal surface pressure sensor, for example, a glove or a band, in the shape of clothes, supporters, handkerchiefs, etc. including hats, gloves, socks, etc. 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 111 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 pasting or covering all or part of the surface of any structure. Can do.

Furthermore, since the device 111 of the present invention can generate a sufficient electric signal simply by rubbing the surface of the braided piezoelectric element 201, 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 201, it can be used for surface shape measurement and the like.

Hereinafter, the third invention will be described in detail.
(Braided piezoelectric element)
In the braided piezoelectric element according to the third invention, the piezoelectric polymer in the structure according to the first invention is arranged in a cylindrical shape, and a conductor made of conductive fibers is arranged at the position of the central axis of the cylindrical shape. An element in which a piezoelectric polymer is arranged as a braided cord around a conductive fiber as a piezoelectric fiber can be used. The braided piezoelectric element according to the third invention will be described in detail below.

FIG. 10 is a schematic diagram illustrating a configuration example of a braided piezoelectric element according to the embodiment.
The braided piezoelectric element 201 covers the core portion 203 formed of the conductive fiber B, the sheath portion 202 formed of the braided piezoelectric fiber A so as to cover the core portion 203, and the sheath portion 202. And a conductive layer 204. The conductive layer 204 functions as an electrode serving as a counter electrode of the conductive fiber of the core part 203, and shields the conductive fiber of the core part 203 from external electromagnetic waves, thereby suppressing noise signals generated in the conductive fiber of the core part 203. At the same time as a shield.

The covering rate of the sheath portion 202 by the conductive layer 204 is preferably 25% or more. Here, the coverage is a ratio of the area of the conductive substance 205 contained in the conductive layer 204 to the surface area of the sheath 202 when the conductive layer 204 is projected onto the sheath 202, 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 204 is less than 25%, the noise signal suppression effect may not be sufficiently exhibited. When the conductive material 205 is not exposed to the surface of the conductive layer 204, for example, when the sheath 202 is covered using the fiber containing the conductive material 205 as the conductive layer 204, the sheath of the fiber The ratio of the area when projected onto 202 and the surface area of the sheath portion 202 can be defined as the coverage.

The conductive substance 205 is a conductive substance contained in the conductive layer 204, and any known substance is applicable.

In the braided piezoelectric element 201, a large number of piezoelectric fibers A surround the outer peripheral surface of at least one conductive fiber B densely. When deformation occurs in the braided piezoelectric element 201, stress due to deformation is generated in each of a large number of piezoelectric fibers A, thereby generating an electric field (piezoelectric effect) in each of the large number of piezoelectric fibers A. As a result, the conductive fibers B 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 portion 202 of the piezoelectric fiber A is not used. As a result, the braided piezoelectric element 201 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 201 is not particularly limited as long as the braided piezoelectric element 201 has the configuration shown in FIG. 10 from the viewpoint of achieving the object of the third invention. However, the braided piezoelectric element 201 is selected for torsional deformation about the central axis. From the viewpoint of outputting a large electrical signal, it is preferable to have the following configuration.

(A braided piezoelectric element that selectively outputs a large electric signal against torsional deformation)
The braided piezoelectric element 201 that selectively outputs a large electric signal with respect to torsional deformation about the central axis is a uniaxially oriented polymer molded body as the piezoelectric fiber A, and the orientation axis is three axes. In this case, a piezoelectric polymer 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 can be used. In the present invention, “including as a main component” means occupying 50% by mass or more of the constituent components. In the present invention, the crystalline polymer is a polymer composed of 1% by mass or more of a crystal part and an amorphous part other than the crystal part, and the mass of the crystalline polymer means the crystal part and the amorphous part. And the total mass. 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.

Further, in the braided piezoelectric element 201 that outputs a large electrical signal selectively with respect to torsional deformation about the central axis, an angle formed by the direction of the central axis and the orientation direction of the piezoelectric polymer (orientation angle θ ) Is from 0 ° to 40 ° or from 50 ° to 90 °. When this condition is satisfied, the piezoelectric effect corresponding to the piezoelectric constant d14 of the crystalline polymer included in the piezoelectric polymer is obtained by applying torsional deformation (torsional stress) about the central axis to the braided piezoelectric element 201. Can be efficiently used, and charges of opposite polarity can be efficiently generated on the central axis side and the outer side of the braided piezoelectric element 201. From this viewpoint, the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is preferably 0 ° or more and 35 ° or less, or 55 ° or more and 90 ° or less, and 0 ° or more and 30 ° or less, or 60 ° or more and 90 ° or less. Is more preferably 0 ° or more and 25 ° or less or 65 ° or more and 90 ° or less, and further preferably 0 ° or more and less than 15 ° or more than 75 ° and 90 ° or less. When the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is more than 0 ° and less than 90 °, the orientation direction of the piezoelectric polymer draws a spiral.

In addition, by arranging the piezoelectric polymer in this way, for shear deformation that rubs the surface of the braided piezoelectric element 201, bending deformation that bends the central axis, and expansion and contraction deformation in the central axis direction, The braided piezoelectric element 201 is configured not to generate a large charge on the central axis side and the outside of the braided piezoelectric element 201, that is, to generate a large charge selectively with respect to torsion about the central axis. Can do.

When the orientation direction of the piezoelectric polymer forms a helix, the direction of the helix direction (the S twist direction or the Z twist direction) does not affect the polarity of the charge generated with respect to the torsional deformation. However, when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is 0 ° or more and 40 ° or less and when the orientation angle θ is 50 ° or more and 90 ° or less, the polarity of electric charges generated with respect to torsional deformation is Reverse. In addition, the polarity of electric charges generated with respect to torsional deformation is also reversed in piezoelectric polymers including crystalline polymers having different signs of d14 such as poly-L-lactic acid and poly-D-lactic acid. Therefore, in order to efficiently generate charges having opposite polarities on the central axis side and the outer side of the braided piezoelectric element 201 against torsional deformation, a piezoelectric element containing a crystalline polymer having the same sign of d14 as a main component. The orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis of the braided piezoelectric element 201 is preferably set to only 0 ° to 40 ° or 50 ° to 90 °.

The orientation angle θ is measured by the following method as much as possible. A side photograph of the braided piezoelectric element 201 (corresponding to the piezoelectric structure 1 in FIG. 3) is taken, and the helical pitch HP of the piezoelectric polymer 2 is measured. As shown in FIG. 3, the helical pitch HP is a linear distance in the central axis direction required for one piezoelectric polymer 2 to travel from the front surface to the back surface again. Further, after fixing the structure with an adhesive as necessary, a cross section perpendicular to the central axis of the braided piezoelectric element 201 is cut out and a photograph is taken to measure the outer radius Ro and the inner radius Ri of the portion occupied by the sheath portion 202 To do. When the outer edge and inner edge of the cross section are elliptical or flat, the average values of the major axis and the minor axis are Ro and Ri. The orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is calculated from the following formula.
θ = arctan (2πRm / HP) (0 ° ≦ θ ≦ 90 °)
However, Rm = 2 (Ro ³ −Ri ³ ) / 3 (Ro ² −Ri ² ), that is, the radius of the braided piezoelectric element 201 obtained by weighted averaging with the cross-sectional area.

When the piezoelectric polymer has a uniform surface in the side view photograph of the braided piezoelectric element 201 and the helical pitch of the piezoelectric polymer cannot be discriminated, the braided piezoelectric element 201 fixed with an adhesive or the like is the central axis. A wide-angle X-ray diffraction analysis is performed so that X-rays are transmitted in a sufficiently narrow range so as to pass through the central axis in a direction perpendicular to the fracture plane, and the orientation direction is determined to determine the angle with respect to the central axis. Is taken as θ.

In the braided piezoelectric element 201 according to the present invention, the spiral drawn along the orientation direction of the piezoelectric polymer has two or more spirals having different spiral directions (S twist direction or Z twist direction) and spiral pitches. It may exist at the same time, but the above measurement is performed for each of the piezoelectric polymers of each helical direction and helical pitch, and any one of the piezoelectric polymers of helical direction and helical pitch must satisfy the above-mentioned conditions. It is.

From the viewpoint of preventing large charges from being generated on the central axis side and the outside of the braided piezoelectric element 201 with respect to expansion and contraction, the above-described piezoelectric polymer is a crystalline polymer having a positive value of the piezoelectric constant d14. In the portion where the central axis of the braided piezoelectric element 201 has a length of 1 cm, the orientation axis is the Z twist direction. The mass of P body arranged by winding a helix is ZP, the orientation axis is SP and the mass of P body arranged by winding a helix in the S twist direction is SP, and the orientation axis is arranged by winding a helix in the Z twist direction. The mass of the N body is ZN, the mass of the N body arranged with its orientation axis wound in the S-twist direction is SN, the smaller of (ZP + SN) and (SP + ZN) is T1, and the larger is T2. When the value of T1 / T2 is greater than 0.8, especially 0. More preferably ultra 1.0 or less, more 0.9 than, and particularly preferably 0.9 Ultra 1.0. Here, even when the value of T1 / T2 is not satisfied, when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is 0 ° or more and 10 ° or less, or 80 ° or more and 90 ° or less, it exceeds 10 °. Compared with the case of less than 80 °, the amount of electric charge generated with respect to expansion / contraction deformation is reduced. As a result, an electrical signal can be selectively generated with respect to torsional deformation, which is preferable.

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 201, as long as the object of the present invention is achieved, the sheath 202 may be mixed with fibers other than the piezoelectric fiber A, and the core 203 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 203 of the conductive fiber B, the sheath portion 202 of the braided piezoelectric fiber A, and the conductive layer 204 covering the sheath portion 202 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 the conductive fiber B is made of an organic fiber coated with a metal having bending resistance, the conductive fiber is hardly broken, and is 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 μm to 50 μm. 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 portions 203 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 203 is the total amount including fibers other than conductive fibers.

If the fiber diameter is small, the strength decreases and handling becomes difficult, and if the fiber 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 an 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.

Piezoelectric fiber A containing polylactic acid as a main component is drawn during 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 near 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, 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.

Also, the piezoelectric fiber A can be subjected to treatments such as dyeing, twisting, combining, heat treatment, etc., before making the braided one produced 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. 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 203 is covered with the piezoelectric fiber A, that is, the braided sheath portion 202. The thickness of the sheath portion 202 covering the conductive fiber B is preferably 1 μm to 10 mm, more preferably 5 μm to 5 mm, still more preferably 10 μm to 3 mm, and 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 201 may become hard and difficult to deform. In addition, the sheath part 202 said here refers to the layer adjacent to the core part 203. FIG.

In the braided piezoelectric element 201, the total fineness of the piezoelectric fibers A of the sheath portion 202 is preferably ½ or more and 20 times or less of the total fineness of the conductive fibers B of the core portion 203, preferably 1 or more times. 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 201 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 201 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 202. For example, in the case of a general 8-strand braid, it is the sum of the finenesses of eight fibers.

In the braided piezoelectric element 201, the fineness per piezoelectric fiber A of the sheath portion 202 is preferably 1/20 times or more and 2 times or less the total fineness of the conductive fibers 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 201 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 201 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.

As the coating method, a method is used in which the conductive fiber B is used as a core thread and the piezoelectric fiber A is wound around the braid in the form of a braid. 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 204 functions as an electrode serving as a counter electrode of the conductive fiber of the core part 203, and shields the conductive fiber of the core part 203 from external electromagnetic waves, thereby suppressing noise signals generated in the conductive fiber of the core part 203. And a function as a shield. Since the conductive layer 204 functions as a shield, it is preferably grounded (connected to the earth or the ground of an electronic circuit). Accordingly, for example, the S / N ratio (signal-to-noise ratio) of the cloth-like piezoelectric element 207 can be remarkably improved without overlapping conductive cloths for electromagnetic wave shielding on and under the cloth-like piezoelectric element 207. As a mode of the conductive layer 204, in addition to coating, a film, a fabric, or a fiber can be wound, or a combination thereof may be used.

As the coating for forming the conductive layer 204, any coating containing a substance exhibiting conductivity may be used, 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 204 is formed by winding a film, a film obtained by forming a conductive polymer and a polymer in which a conductive filler is dispersed is used, and a conductive layer is provided on the surface. A film may be used.

When the conductive layer 204 is formed by winding a fabric, a fabric including a conductive fiber 206 described later as a constituent component is used.

When the conductive layer 204 is formed by winding a fiber, a covering, a knitted fabric, or a braid can be considered as the technique. Moreover, the fiber used is the conductive fiber 206, and the conductive fiber 206 may be the same type as the conductive fiber B or a different type of conductive fiber. Examples of the conductive fiber 206 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 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.

If the conductive fiber 206 is made of an organic fiber coated with metal having bending resistance, the conductive fiber is hardly broken, and is excellent in durability and safety as a sensor using a piezoelectric element.

The conductive fiber 206 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 μm to 50 μm. 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 fiber diameter is small, the strength decreases and handling becomes difficult, and if the fiber diameter is large, flexibility is sacrificed. The cross-sectional shape of the conductive fiber 206 is preferably a circle or an ellipse from the viewpoint of the 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 206 must be resistant to movement such as repeated bending and twisting for the purposes 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.

(Protective layer)
A protective layer may be provided on the outermost surface of the braided piezoelectric element 201 according to 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. Further, the fabric according to the present invention described later can be used as a protective layer, which is preferable from the viewpoint of simplification of the configuration.

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

Further, a plurality of layers made of piezoelectric fibers can be provided, or a plurality of layers made of conductive fibers for taking out 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 202 further, or covering is mentioned.

The braided piezoelectric element 201 according to the present invention can detect deformation and stress using the electrical signal output due to the piezoelectric effect described above, and can also conduct electricity with the conductive fibers B at the core of the braided piezoelectric element 201. By measuring the capacitance change between the layers 204, it is also possible to detect deformation due to pressure applied to the braided piezoelectric element 201. Further, when a plurality of braided piezoelectric elements 201 are used in combination, the pressure applied to the braided piezoelectric element 201 is measured by measuring the capacitance change between the conductive layers 204 of each braided piezoelectric element 201. It is also possible to detect deformation due to.

(Fabric piezoelectric element)
In the cloth-like piezoelectric element of the present invention, at least one braided piezoelectric element is fixed to the cloth. In this way, the fabric itself can be processed into a desired shape such as clothes to make a device, and can be installed on a base material that does not have a sensor function such as existing clothes and structures by various methods such as sewing and bonding. In addition, the sensor function can be easily provided. FIG. 17 is a schematic diagram illustrating a configuration example of a fabric-like piezoelectric element using the braided piezoelectric element according to the embodiment.

In the example of FIG. 17, at least one braided piezoelectric element 201 is fixed to the cloth 208 in the cloth-like piezoelectric element 207. The fabric 208 is not limited as long as at least one of the fibers (including braids) constituting the fabric is a braided piezoelectric element 201 and the braided piezoelectric element 201 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 201 may be used as a part of a fiber (for example, warp or weft) constituting the fabric, or the braided piezoelectric element 201 may be embroidered or bonded to the fabric. Good. In the example shown in FIG. 17, the fabric-like piezoelectric element 207 is a plain woven fabric in which at least one braided piezoelectric element 201 and insulating fibers 209 are arranged as warps, and insulating fibers 209 are arranged as wefts. The insulating fiber 209 will be described later. Note that all or part of the insulating fiber 209 may be in a braid form.

In this case, when the cloth-like piezoelectric element 207 is deformed by bending or the like, the braided piezoelectric element 201 is also deformed along with the deformation, so that the cloth-like piezoelectric element 207 is generated by an electric signal output from the braided piezoelectric element 201. Can be detected. Since the cloth-like piezoelectric element 207 can be used as a cloth (woven or knitted fabric), it can be applied to, for example, a garment-shaped wearable sensor.

In the configuration in which the weft insulating fibers of the fabric-like piezoelectric element 207 shown in FIG. 17 are partially replaced with the conductive fibers 210 (FIG. 18), the conductive fibers 210 intersect the braided piezoelectric element 201. In contact. Therefore, the conductive fiber 210 is in contact with at least a part of the conductive layer 204 of the braided piezoelectric element 201, and the conductive fiber 210 is connected to an electronic circuit instead of the conductive layer 204. Can do. The conductive fiber 210 may be the same type as the conductive fiber B or a different type of conductive fiber, and all or a part thereof may be in the form of a braid.

In the cloth-like piezoelectric element of the present invention, the pull-out strength per 5 cm of the braid-like piezoelectric element with respect to the cloth is 0.1 N or more. By doing this, the difference between the deformation of the fabric and the deformation of the braided piezoelectric element is minimized, so that the deformation of the fabric is determined using the deformation amount of the braided piezoelectric element detected by the electrical signal of the braided piezoelectric element. Can be minimized, and reproducibility can be improved. When the pull-out strength per 5 cm of the braided piezoelectric element with respect to the fabric is less than 0.1 N, for example, even if the fabric is stretched or deformed, slippage occurs between the braided piezoelectric element and the fabric, and the braided piezoelectric element is sufficiently Without expansion / contraction deformation, the expansion / contraction amount detected by the electrical signal of the braided piezoelectric element is significantly smaller than the expansion / contraction amount of the fabric, and the reproducibility is low. From this viewpoint, the pulling strength per 5 cm of the braided piezoelectric element with respect to the fabric is preferably 0.2 N or more, more preferably 0.3 N or more, and particularly preferably 0.4 N or more. The pull-out strength is most preferably greater than the strength of the braided piezoelectric element.

In the present invention, the “pullout strength per 5 cm of the braided piezoelectric element with respect to the fabric” is determined as follows. First, if there is a place where the braided piezoelectric element is exposed from the cloth-like piezoelectric element, the exposed braided piezoelectric element is held by one of the gripping jigs of the tensile tester, and the braided form on the gripped side The braided piezoelectric element and the cloth-like piezoelectric element are cut at a portion 5 cm from the end to which the piezoelectric element is fixed. A U-shaped gripping treatment for 5 cm in the length direction of the braided piezoelectric element on both sides of the 5 cm part where the braided piezoelectric element is fixed to the fabric, excluding the area within 1 mm from the braided piezoelectric element. Hold it with a tool and connect it to the other side of the holding jig of the tensile tester. Further, in this state, a tensile test is performed at a speed of 10 mm / min, the maximum strength is measured, and the pulling strength is obtained. In addition, when there is not enough place where the braided piezoelectric element is exposed from the cloth-like piezoelectric element, a part of the fabric (part other than the braided piezoelectric element) is cut to expose the braided braided piezoelectric element, What is necessary is just to perform said measurement. In addition, when it is difficult to secure the length of the portion where the braided piezoelectric element is fixed to the cloth, the pulling strength is measured at a fixed portion of an arbitrary length, and converted to the strength per 5 cm. Also good.

In the cloth-like piezoelectric element of the present invention, it is preferable that the coverage of the braid-like piezoelectric element by the fibers constituting the cloth exceeds 30% on both sides of the cloth. This increases the pull-out strength of the braided piezoelectric element to the fabric and minimizes the difference between the deformation of the fabric and the deformation of the braided piezoelectric element, as well as damage from external rubbing, heat, light, etc. It can be made difficult to receive. From this point of view, the coverage of the braided piezoelectric element by the fibers constituting the fabric is more preferably more than 50%, more preferably more than 70%, and most preferably 100% on both sides of the fabric.

The coverage of the braided piezoelectric element by the fibers constituting the fabric is determined by the fibers constituting the fabric with respect to the projected area of the braided piezoelectric element in the image observed perpendicularly from one surface of the fabric piezoelectric element. The area ratio of the portion where the piezoelectric element is hidden is calculated. The observation image from the other side is also evaluated in the same manner, and the coverage is calculated on each side of the fabric. When calculated in this way, it is difficult for a fabric with a normal woven structure (plain weave, twill, satin, etc.) to have a coverage of more than 50% on both sides, but when weaving with a plain weave or twill weave, spun yarn More than 50% on both sides of the fabric by using a multifilament yarn, increasing the density of the yarn orthogonal to the braided piezoelectric element, or relatively lowering the density of the yarn parallel to the braided piezoelectric element Rate. However, if the tension of the thread orthogonal to the braided piezoelectric element is excessively lowered to increase the density of the thread orthogonal to the braided piezoelectric element, the force that restrains the braided piezoelectric element is weakened, resulting in the desired pullout strength. Can not be achieved, which is not preferable. In addition, by manufacturing the fabric so that the braided piezoelectric element is sandwiched between the layers of the double woven fabric or the double knitted fabric, the coverage on both sides of the fabric is greatly improved, and may be close to 100% or 100%. it can. On the other hand, when the coverage is 30% or less, there are many portions where the braided piezoelectric elements are exposed between the fibers of the fabric, and the protection is not sufficient. Even if the fiber constituting the fabric is transparent, it is considered to be coated. When the braided piezoelectric element includes a protective layer on the outer layer of the conductive layer 204, the braided piezoelectric element including the protective layer is considered.

(Multiple piezoelectric elements)
In the fabric-like piezoelectric element 207, a plurality of braided piezoelectric elements 201 can be used side by side. For example, the braided piezoelectric elements 201 may be used for all warps or wefts, or the braided piezoelectric elements 201 may be used for several or a part of them. Alternatively, the braided piezoelectric element 201 may be used as a warp in a certain part, and the braided piezoelectric element 201 may be used as a weft in another part.

FIG. 19 is a schematic diagram showing another configuration example of a cloth-like piezoelectric element using the braided piezoelectric element according to the embodiment. The cloth-like piezoelectric element 207 includes a cloth 208 including at least two braid-like piezoelectric elements 201, and these braid-like piezoelectric elements 201 are arranged substantially in parallel. The fabric 208 has at least two fibers (including braids) constituting the fabric are braided piezoelectric elements 201, and there is no limitation as long as the braided piezoelectric element 201 can exhibit a function as a piezoelectric element. Any woven or knitted fabric may be used. In the example shown in FIG. 19, the cloth-like piezoelectric element 207 is a plain fabric in which at least two braided piezoelectric elements 201 and insulating fibers 209 are arranged as warps, and insulating fibers 209 are arranged as wefts. The insulating fiber 209 will be described later. Note that all or part of the insulating fiber 209 may be in a braid form. Similarly to the case of FIG. 18, the weft insulating fibers of the fabric-like piezoelectric element 207 shown in FIG. 19 may be partially replaced with conductive fibers.

The braided piezoelectric element 201 emits a piezoelectric signal when it is deformed, and the size and shape of this signal change according to the state of deformation. In the case of the cloth-like piezoelectric element 207 shown in FIG. 19, when the cloth-like piezoelectric element 207 is bent and deformed with a line perpendicular to the two braid-like piezoelectric elements 201 as a bent portion, the two braid-like piezoelectric elements 201 are identical. Deform. Therefore, the same signal is detected from the two braided piezoelectric elements 201. On the other hand, when complicated deformation such as torsion is given, separate deformation is induced in the two braided piezoelectric elements 201, and the signals generated by the respective braided piezoelectric elements 201 are different. . Based on this principle, it is possible to analyze a complicated deformation of the braided piezoelectric element 201 by combining a plurality of braided piezoelectric elements 201 and comparing and calculating signals generated by the braided piezoelectric elements 201. For example, complex deformation such as torsion can be detected based on the result obtained by comparing the polarity, amplitude, phase, etc. of the signal generated in each braided piezoelectric element 201.

In the above embodiment, the two braided piezoelectric elements 201 are arranged at intervals from each other from the viewpoint of causing the two braided piezoelectric elements 201 to undergo different deformations with respect to the bending of the fabric. The distance between the piezoelectric fibers closest to each other is preferably 0.05 mm or more and 500 mm or less, more preferably 0.1 mm or more and 200 mm or less, and 0.5 mm or more and 100 mm or less. Is more preferable. When the braided piezoelectric element that is not used for signal detection is included in the fabric, the distance between the braided piezoelectric element and the other braided piezoelectric element may be less than 0.05 mm.

As described above, by combining a plurality of braided piezoelectric elements 201 and comparing and calculating signals generated by the braided piezoelectric elements 201, it becomes possible to analyze complicated deformations such as bending and twisting. It can be applied to a wearable sensor of shape. In this case, when the cloth-like piezoelectric element 207 is deformed by being bent or the like, the braided piezoelectric element 201 is also deformed along with the deformation, so that the cloth-like piezoelectric element 201 is based on the electric signal output from the braided piezoelectric element 201. The deformation of the element 207 can be detected. Since the cloth-like piezoelectric element 207 can be used as a cloth (woven or knitted fabric), it can be applied to, for example, a garment-shaped wearable sensor.

(Insulating fiber)
In the cloth-like piezoelectric element 207, an insulating fiber can be used in a portion other than the braided piezoelectric element 201 (and the conductive fiber 210). In this case, 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 207.

In this way, by arranging the insulating fiber in addition to the braided piezoelectric element 201 (and the conductive fiber 210), the operability of the cloth-like piezoelectric element 207 (eg, 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 fibers can be used.

(Production method)
The braided piezoelectric element 201 according to the present invention covers the surface of at least one conductive fiber B 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 204 is manufactured by coating or winding of fibers, but from the viewpoint of ease of manufacturing, winding of fibers is preferable. 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 201 in which the surface of the conductive fiber B is covered with the braided piezoelectric fiber A and the conductive layer 204 is further provided around the surface can be obtained.

The fabric-like piezoelectric element 207 of the present invention is manufactured by weaving or knitting. As long as the object of the present invention is achieved, combination with other fibers (including braids) may be performed, such as union, union, union, and the like. Of course, the braided piezoelectric element 201 may be used as a part of a fiber (for example, warp or weft) constituting the fabric, or the braided piezoelectric element 201 may be embroidered or bonded to the fabric. Well, you may combine those methods. In addition, a tape-shaped cloth-shaped piezoelectric element in which a cloth exists only in the vicinity of the braided-shaped piezoelectric element 201 is preferable because it can be easily installed on other cloth by sewing or sticking. At this time, the distance between the end of the tape and the braided piezoelectric element (distance in the width direction of the tape) is preferably 1 mm or more and 100 mm or less, more preferably 3 mm or more and 50 mm or less, and further preferably 5 mm or more and 20 mm or less. When a tape-shaped cloth-like piezoelectric element is used, it may be manufactured by cutting a wide-width cloth-like piezoelectric element in parallel with the braid-like piezoelectric element 201. However, when weaving or knitting the cloth tape, It is preferable from the viewpoint of simplification of the manufacturing process to perform crossing and the like, and to embroider and bond the braided piezoelectric element 201 to the cloth tape.

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.

From the viewpoint of simplification of the manufacturing process and improvement of pulling strength and coverage, it is more preferable that the braided piezoelectric element is fixed in a state of being woven or knitted into the fabric, and the layers of the multi-woven fabric or the multi-knitted fabric are More preferably, the braided piezoelectric element is sandwiched between the two. Multiple refers to more than double.

(Applied technology for piezoelectric elements)
The piezoelectric element such as the braided piezoelectric element 201 and the cloth-like piezoelectric element 207 of the present invention can output contact, pressure, and shape change to the surface as an electric signal in any form, so that the piezoelectric element 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. 6 is a block diagram showing a device 111 including the piezoelectric element 112 of the present invention. The device 111 includes a piezoelectric element 112 (cloth-like piezoelectric element 207), and optionally, an amplifying means 113 for amplifying an electric signal output from the output terminal of the piezoelectric element 112 in accordance with an applied pressure, the optional element And an output circuit 114 for outputting the electric signal amplified by the amplification means 113 and an electric circuit having a transmission means 115 for transmitting the electric signal output from the output means 114 to an external device (not shown). If this device 111 is used, the stress applied to the piezoelectric element can be 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 112, pressure, or shape change. The magnitude and / or applied position can be detected.

Optional amplification means 113, output means 114, and transmission means 115 may be constructed in a software program format, for example, 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 amplification unit 113, output unit 114, and transmission unit 115 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 115 is wireless or wired may be appropriately determined according to the sensor to be configured. Alternatively, calculation means (not shown) for calculating the magnitude and / or position of the stress applied to the piezoelectric element 112 based on the electrical signal output from the output means 114 may be provided in the device 111. 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 electrical signal output from the piezoelectric element 112 may be transmitted to an external device as it is, and then signal processing may be performed.

20 to 22 are schematic views showing configuration examples of a device including a braided cloth-like piezoelectric element according to the embodiment. 20 to 22 correspond to those described with reference to FIG. 6, but the output means 114 and the transmission means 115 of FIG. 6 are not shown in FIGS. When configuring a device including the cloth-like piezoelectric element 207, the lead wire from the output terminal of the core portion 203 (formed of the conductive fiber B) of the braided piezoelectric element 201 is connected to the input terminal of the amplifying means 113, The grounding (ground) terminal has a braided piezoelectric element different from the braided piezoelectric element 201 connected to the conductive layer 204 of the braided piezoelectric element 201, the conductive fiber 210 of the cloth-like piezoelectric element 207, or the input terminal of the amplifying means 113. Connect the elements. For example, as shown in FIG. 20, in the cloth-like piezoelectric element 207, the lead wire from the output terminal of the core portion 203 of the braided piezoelectric element 201 is connected to the input terminal of the amplifying means 113, Layer 204 is grounded. For example, as shown in FIG. 21, in the cloth-like piezoelectric element 207, the lead wire from the core portion 203 of the braided piezoelectric element 201 is connected to the input terminal of the amplifying means 113 and intersects the braided piezoelectric element 201. The contacted conductive fiber 210 is grounded. Further, for example, as shown in FIG. 22, when a plurality of braided piezoelectric elements 201 are arranged in the cloth-like piezoelectric element 207, the lead wire from the output terminal of the core portion 203 of one braided piezoelectric element 201 is amplified by the amplifying means 113. The lead wire from the core part 203 of another braided piezoelectric element 201 aligned with the braided piezoelectric element 201 is grounded (grounded).

When the braided piezoelectric element 201 is deformed, the piezoelectric fiber A is deformed to generate polarization. In accordance with the arrangement of the positive and negative charges generated by the polarization of the piezoelectric fiber A, movement of charges occurs on the lead line from the output terminal of the conductive fiber B forming the core portion 203 of the braided piezoelectric element 201. The movement of electric charge on the lead line from the conductive fiber B appears as a minute electric signal (that is, current or potential difference). That is, the amplifying means 113 that outputs an electric signal from the output terminal amplifies the electric signal according to the electric charge generated when the braided piezoelectric element 201 is deformed, and the output means 114 is the amplifying means 113. Output the amplified electrical signal. Since the polarity, amplitude, phase, etc. of the electrical signal output from the output means 114 differ depending on the type of deformation of the braided piezoelectric element 201, the polarity, amplitude, phase, etc. of the electrical signal output from the output means 114 are compared. Based on the obtained result, a complicated deformation mode such as torsion is determined.

In order to electrically connect the braided piezoelectric element and other members (connectors, conductors, etc.) in order to connect the braided piezoelectric element and the electronic circuit such as the amplifying means 113 in FIGS. It is difficult to connect the elements while the elements are still covered with the fabric. For this reason, the braided piezoelectric element is partially exposed from the fabric, and the conductive fiber and / or conductive layer of the braided piezoelectric element and other members are electrically connected to the exposed portion. preferable. The exposed portion is preferably 2 mm or greater and 100 mm or less, more preferably 5 mm or greater and 50 mm or less, and even more preferably 10 mm or greater and 30 mm or less from the balance between simplicity of connection work and performance.

It is not preferable to apply the exposed portion to the cloth-like piezoelectric element later because it requires post-processing such as partial cutting of the cloth and may damage the physical properties of the cloth. It is preferable that weaving or knitting is performed in advance as a structure in which the braided piezoelectric element is exposed at a connection point with another member at the time of manufacture.

Since the device 111 of the present invention is in the form of a fabric and has flexibility, it can be used in a wide variety of applications. Specific examples of the device 111 of the present invention include a touch panel, a human or animal surface pressure sensor, for example, a glove or a band, in the shape of clothes, supporters, handkerchiefs, etc. including hats, gloves, socks, etc. 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 111 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 pasting or covering all or part of the surface of any structure. Can do.

Furthermore, since the device 111 of the present invention can generate a sufficient electric signal simply by rubbing the surface of the braided piezoelectric element 201, 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 201, 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.

Each characteristic of the piezoelectric fiber (piezoelectric structure), braided piezoelectric element, and cloth-like piezoelectric element shown in this example was determined by the following method.

[Piezoelectric fiber]
(1) Poly-L-lactic acid crystallinity X _homo :
The poly-L-lactic acid crystallinity X _homo was obtained 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 was recorded on an imaging plate under the following conditions by a transmission method using a Rigaku ultra 18 type X-ray diffractometer.
X-ray source: Cu-Kα ray (confocal mirror)
Output: 45kV x 60mA
Slit: 1st: 1mmΦ, 2nd: 0.8mmΦ
Camera length: 120mm
Integration time: 10 minutes Sample: 35 mg of polylactic acid fibers are aligned to form a 3 cm fiber bundle The total scattering intensity I _total is obtained over the azimuth angle in the obtained X-ray diffraction pattern, where 2θ = 16.5 °, 18 The sum ΣI _HMi of the integrated intensities of the diffraction peaks derived from the poly-L-lactic acid crystals appearing around .5 ° and 24.3 ° was obtained. From these values, poly-L-lactic acid crystallinity X _homo was determined according to the following formula (3).
[Equation 3]
Poly-L-lactic acid crystallinity X _homo (%) = ΣI _HMi / I _total × 100 (3)
Note that ΣI _HMi was calculated by subtracting diffuse scattering due to background and amorphous in the total scattering intensity.

(2) Poly-L-lactic acid crystal orientation degree A:
Regarding the poly-L-lactic acid crystal orientation degree A, in the X-ray diffraction pattern obtained by the above wide-angle X-ray diffraction analysis (WAXD), poly-L-lactic acid appears in the vicinity of 2θ = 16.5 ° in the radial direction. for diffraction peaks derived from crystals, taking the intensity distribution for azimuthal (°), it was calculated from the following equation (4) from the half width of the sum of the resulting distribution profile .SIGMA.W i _(°).
[Equation 4]
Poly-L-lactic acid crystal orientation degree A (%) = (360−ΣW _i ) ÷ 360 × 100 (4)

(3) Optical purity of polylactic acid:
Collect 0.1 g of polylactic acid fiber (one bundle in the case of multifilament) constituting the fabric, add 1.0 mL of 5 mol / L sodium hydroxide aqueous solution and 1.0 mL of methanol, and heat to 65 ° C. Set in a set water bath shaker, hydrolyze for about 30 minutes until the polylactic acid becomes a homogeneous solution, and further neutralize to pH 7 by adding 0.25 mol / liter of sulfuric acid to the hydrolyzed solution. Then, 0.1 mL of the decomposition solution was collected, diluted with 3 mL of high-performance liquid chromatography (HPLC) mobile phase solution, and filtered through a membrane filter (0.45 μm). This adjustment solution was subjected to HPLC measurement to determine the ratio of L-lactic acid monomer to D-lactic acid monomer. When the amount of one polylactic acid fiber is less than 0.1 g, the amount of other solution used is adjusted according to the amount that can be collected, and the concentration of polylactic acid in the sample solution used for HPLC measurement is 100 minutes from the above. It was made to be in the range of 1.
<HPLC measurement conditions>
Column: “Sumichiral (registered trademark)” OA-5000 (4.6 mmφ × 150 mm) manufactured by Sumika Chemical Analysis Co., Ltd.
Mobile phase: 1.0 mmol / liter copper sulfate aqueous solution Mobile phase flow rate: 1.0 ml / min Detector: UV detector (wavelength 254 nm)
Injection amount: 100 microliters When the peak area derived from L-lactic acid monomer is S _LLA and the peak area derived from D-lactic acid monomer is S _DLA , S _LLA and S _DLA are the molar concentrations of L-lactic acid monomer M _LLA and Since it was proportional to the molar concentration M _DLA of the D-lactic acid monomer, the larger value of S _LLA and S _DLA was taken as S _MLA , and the optical purity was calculated by the following formula (5).
[Equation 5]
Optical purity (%) = S _MLA ÷ (S _LLA + S _DLA ) × 100 (5)

[Fabric piezoelectric element]
(4) Pull-out strength When there is a place where the braided piezoelectric element is exposed from the cloth-like piezoelectric element, the exposed braided piezoelectric element is removed from the tensile testing machine (universal testing machine “Tensilon RTC- 1225A ") was held by one of the holding jigs, and the braided piezoelectric element and the cloth-like piezoelectric element were cut at a portion 5 cm from the end to which the braided piezoelectric element on the gripping side was fixed. A U-shaped gripping treatment for 5 cm in the length direction of the braided piezoelectric element on both sides of the 5 cm part where the braided piezoelectric element is fixed to the fabric, excluding the area within 1 mm from the braided piezoelectric element. It was gripped with a tool and connected to the other gripping jig of the tensile tester. In this state, a tensile test was performed at a speed of 10 mm / min, the maximum strength was measured, and the pullout strength was obtained. In addition, when there is not enough place where the braided piezoelectric element is exposed from the cloth-like piezoelectric element, a part of the fabric (part other than the braided piezoelectric element) is cut to expose the braided braided piezoelectric element, The above measurements were made. In addition, when it was difficult to secure 5 cm of the length of the portion where the braided piezoelectric element was fixed to the fabric, the pullout strength was measured at a fixed portion of an arbitrary length, and converted into strength per 5 cm.

(5) Coverage 10 times or more of the width of the braided piezoelectric element for each of the six photographs taken from both the front and back sides with a microscope at any three points of the braided piezoelectric element in the fabric-like piezoelectric element The ratio of the area where the braid surface appears to be exposed to the area calculated from the product of the width of the braid and the length of the observed part in the part spanning the length, and the ratio is reduced from 100% Was the coverage, the average value of the three front photos was the coverage (table), and the average of the three back photos was the coverage (back).

(6) Electrical signal measurement With the electrometer (Keysight B2987A) connected to the conductor of the piezoelectric element via a coaxial cable (core: Hi pole, shield: Lo pole), the following bending operation is performed on the piezoelectric element. The current value was measured at intervals of 50 msec.

(6-1) Bending test Two chucks, upper and lower, are provided, the lower chuck is fixed on a rail that moves only in the vertical direction, and a load of 0.5 N is always applied downward. The chuck is located 72 mm above the lower chuck, and the upper chuck moves on a virtual circumference whose diameter is a line segment connecting the two chucks, and is 16 mm to the left and right from the center of the virtual circle. Two cylinders (a plain woven fabric made of 50th cotton yarn is affixed to the side surface) having a cross-section of a circle with a diameter of 15 mm centered on the fabric is fixed, and the cloth passes between the two cylinders. Using a test device in which the piezoelectric element is fixed and bending deformation is applied using the two cylinders as fulcrums, the fabric piezoelectric element is held by the upper and lower chucks so that the braided piezoelectric element is held by the upper and lower chucks. And fix the When the upper chuck is set to the 12 o'clock position and the lower chuck is set to the 6 o'clock position on the virtual circumference, the upper chuck is moved from the 12 o'clock position to 1 o'clock and 2 o'clock on the virtual circumference. After moving through the position to the 3 o'clock position for 0.9 seconds at a constant speed, it was moved through the 12 o'clock position to the 9 o'clock position over 1.8 seconds and again 0.9. The reciprocating bending operation to return to the 12 o'clock position over 10 seconds is repeated 10 times, the current value during that time is measured, and the peak value of the current value during the movement from the 12 o'clock position to the 3 o'clock position is calculated 10 times. The average value was taken as the signal value.

(7) Appearance of braided piezoelectric element After the bending test of (6-1) was repeated 1000 times, the braided piezoelectric element in the cloth-like piezoelectric element was pulled out, and the peeling of the silver plating on the surface of the outer conductive layer was observed with a microscope. Observed at. The case where no peeling was observed was judged as an excellent pass, the case where slight peeling was seen was accepted, and the case where peeling was observed frequently was rejected.

[Braided piezoelectric element]
(8) Orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis
The orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis was calculated from the following formula.
θ = arctan (2πRm / HP) (0 ° ≦ θ ≦ 90 °)
However, Rm = 2 (Ro ³ −Ri ³ ) / 3 (Ro ² −Ri ² ), that is, the radius of the braided piezoelectric element (or other structure) weighted average by the cross-sectional area. The outer radius Ro and the inner radius Ri of the portion occupied by the helical pitch HP, the braided piezoelectric element (or other structure) were measured as follows.
(8-1) In the case of a braided piezoelectric element (if the braided piezoelectric element is coated with something other than a piezoelectric polymer, the piezoelectric polymer can be observed from the side surface by removing the coating if necessary. Side view photographs were taken (from the state), and the helical pitch HP (μm) of the piezoelectric polymer was measured at any five locations as shown in FIG. In addition, 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 was taken. As described later, the outer radius Ro (μm) and the inner radius Ri (μm) of the portion occupied by the braided piezoelectric element are measured as described later, and the same measurement is performed at another arbitrary five cross-sections, and an average value is obtained. It was. When the piezoelectric polymer and the insulating polymer are assembled at the same time, for example, when a combination of piezoelectric fiber and insulating fiber is used, or when four fibers of 8-strand braid are high in piezoelectricity When the remaining four fibers are insulating polymers, when the cross section is taken at various locations, the region where the piezoelectric polymer is present and the region where the insulating polymer is present are interchanged. Therefore, the region where the piezoelectric polymer is present and the region where the insulating polymer is present are regarded as a portion occupied by the braided piezoelectric element. However, a portion where the insulating polymer is not assembled at the same time as the piezoelectric polymer is not regarded as a part of the braided piezoelectric element.
The outer radius Ro and the inner radius Ri were measured as follows. As shown in the cross-sectional photograph of FIG. 9A, a region (hereinafter referred to as PSA) occupied by the piezoelectric structure (sheath portion 2 formed of piezoelectric fiber A) and a region in the center of PSA that is not PSA (hereinafter CA). Defined). The average value of the diameter of the smallest perfect circle that is outside the PSA and does not overlap the PSA and the diameter of the largest perfect circle that does not pass outside the PSA (CA may pass) is defined as Ro (FIG. 9B). . Further, Ri is the average value of the diameter of the smallest perfect circle that is outside the CA and does not overlap the CA, and the diameter of the largest perfect circle that does not pass outside the CA (FIG. 9C).
(8-2) In the case of a covering thread-like piezoelectric element, when the winding speed when covering the piezoelectric polymer is T turns / m (the number of rotations of the piezoelectric polymer per covering thread length), the helical pitch HP (μm) = 1000000 / T. In addition, a low-viscosity instantaneous adhesive “Aron Alpha EXTRA2000” (Toagosei) was infiltrated into the covering yarn-shaped piezoelectric element and solidified, and then a cross-section perpendicular to the long axis of the braid was cut out and a cross-sectional photograph was taken. As with the braided piezoelectric element, the outer radius Ro (μm) and the inner radius Ri (μm) of the portion occupied by the covering thread-shaped piezoelectric element are measured in the same manner as in the case of the braided piezoelectric element. And averaged. When the piezoelectric polymer and the insulating polymer are covered at the same time, for example, when the piezoelectric fiber and the insulating fiber are covered, or the piezoelectric fiber and the insulating fiber do not overlap. If the cross section is taken at various locations, the region where the piezoelectric polymer is present and the region where the insulating polymer is present are interchanged with each other, so that the piezoelectric polymer exists. The region and the region where the insulating polymer exists are combined and regarded as the portion occupied by the covering thread-like piezoelectric element. However, the insulating polymer is not covered simultaneously with the piezoelectric polymer, that is, the portion where the insulating polymer is always inside or outside the piezoelectric polymer regardless of the cross section, Not considered part of it.

(9) Electrical signal measurement An electrometer (Keysight B2987A) is connected to the piezoelectric element conductor via a coaxial cable (core: Hi pole, shield: Lo pole). The current value was measured at intervals of 50 milliseconds while performing the operation test of any one of .about.5.
(9-1) Tensile test Using a universal testing machine “Tensilon RTC-1225A” manufactured by Orientec Co., Ltd., holding the piezoelectric element with a chuck at a distance of 12 cm in the longitudinal direction of the piezoelectric element, 0.0N, the displacement is 0mm in the state pulled to 0.5N tension, pulling to 1.2mm at 100mm / min operating speed, then returning to 0mm at the operating speed of -100mm / min 10 times Repeated.
(9-2) Torsion test Of the two chucks that grip the piezoelectric element, one of the chucks is placed on a rail that moves freely in the major axis direction of the piezoelectric element without performing a twisting operation. .5N tension is always applied, and the other chuck uses a torsion test device designed to perform a torsional movement without moving in the longitudinal direction of the piezoelectric element, and is spaced 72 mm in the longitudinal direction of the piezoelectric element. The piezoelectric element is gripped by these chucks, rotated from 0 ° to 45 ° at a speed of 100 ° / s so that the chuck is viewed from the center of the element and twisted clockwise, and then 45 ° at a speed of −100 / s. The reciprocating torsional motion rotating from 0 to 0 ° was repeated 10 times.
(9-3) Bending test Two chucks, upper and lower, are provided, the lower chuck is fixed, the upper chuck is positioned 72 mm above the lower chuck, and the line segment connecting the two chucks is the diameter. Using a test device in which the upper chuck moves on a virtual circumference, the piezoelectric element is held and fixed on the chuck, and the upper chuck is positioned at 12 o'clock and the lower chuck at 6 o'clock on the circumference. When the position is set, the piezoelectric element is slightly bent convexly in the 9 o'clock direction, and then the upper chuck is moved from the 12 o'clock position through the 1 o'clock and 2 o'clock positions on the circumference. The reciprocating bending operation of moving to the hour position at a constant speed over 0.9 seconds and then moving to the 12 o'clock position over 0.9 seconds was repeated 10 times.
(9-4) Shear test The 64 mm central part of the piezoelectric element is sandwiched horizontally from above and below by two rigid metal plates with a plain woven fabric woven with 50th cotton yarn on the surface. (The lower metal plate is fixed to the base.) A vertical load of 3.2 N is applied from the top, and the upper metal plate remains in a state where it does not slip between the cotton cloth on the surface of the metal plate and the piezoelectric element. Was pulled in the longitudinal direction of the piezoelectric element over 1 second from 0N to 1N load, and then the shearing operation for returning the tensile load to 0N over 1 second was repeated 10 times.
(9-5) Pressing test Using a universal testing machine “Tensilon RTC-1225A” manufactured by Orientec Co., Ltd. The piezoelectric element is sandwiched horizontally by a rigid metal plate installed on the crosshead, and the upper crosshead is lowered over 0.6 seconds until the reaction force from the piezoelectric element to the upper metal plate becomes 0.01N to 20N. Then, the operation of depressurizing over 0.6 seconds until the reaction force became 0.01 N was repeated 10 times.

The fabric for the piezoelectric element 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 the mixture was stirred at 180 ° C. in a reactor equipped with a stirring blade in a nitrogen atmosphere. For 2 hours, 1.2 times equivalent of phosphoric acid to tin octylate was added, 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 PF1 of 84 dTex / 24 filament. Further, PLLA1 melted at 240 ° C. was discharged from a 12-hole cap at 8 g / min and taken up at 1050 m / min. This unstretched multifilament yarn was stretched 2.3 times at 80 ° C. and heat-set at 150 ° C. to obtain a multifilament uniaxially stretched yarn PF2 of 33 dtex / 12 filament. These piezoelectric fibers PF1 and PF2 were used as piezoelectric polymers. The poly-L-lactic acid crystallinity, poly-L-lactic acid crystal orientation, and optical purity of PF1 and PF2 were measured by the above-described methods and were as shown in Table 1.

(Conductive fiber)
Silver-plated nylon manufactured by Mitsufuji Corporation, product name “AGposs” 100d34f (CF1) was used as the conductive fiber B. The resistivity of CF1 was 250Ω / m.
Further, silver-plated nylon manufactured by Mitsufuji Corporation, product name “AGposs” 30d10f (CF2) was used as the conductive fiber B and the conductive fiber 206. The conductivity of CF2 was 950 Ω / m.

(Insulating fiber)
The 84dTex / 24 filament drawn yarn IF1 and 33dTex / 12 filament drawn yarn IF2 manufactured by drawing polyethylene terephthalate after melt spinning were used as insulating fibers.

Example 1
In this example, the effects of the orientation angle θ and T1 / T2 of the piezoelectric polymer on the electrical signal with respect to torsional deformation were examined with respect to the piezoelectric elements used in the first to third inventions.

(Example AA)
As a sample of Example 1, as shown in FIG. 10, the conductive fiber CF1 is used as the core yarn, and among the eight carriers of the 8-punch round braid stringing machine, four carriers assembled in the Z twist direction and S A braid in which the piezoelectric fiber PF1 is spirally wound in both the Z twist direction and the S twist direction around the core yarn by setting and assembling the piezoelectric fiber PF1 on all four carriers assembled in the twist direction. A piezoelectric element 1-AA was produced.

(Example AB)
The braided piezoelectric element 1-AA is used as a core thread, and among the eight carriers of the string making machine, all four carriers assembled in the Z twist direction and all four carriers assembled in the S twist direction have the above conductivity. By setting and assembling the fiber CF2, a braided piezoelectric element 1-AA covered with a conductive fiber was produced to obtain a braided piezoelectric element 1-AB.

(Example AC)
A braided piezoelectric element is produced in the same manner as the braided piezoelectric element 1-AA, except that PF2 is used instead of PF1 and the winding speed is adjusted. A braided piezoelectric element 1-AC was prepared by covering a conductive fiber in the same manner as the piezoelectric element 1-AB.

(Example AD)
A braided piezoelectric element is produced in the same manner as the braided piezoelectric element 1-AA except that CF2 is used instead of CF1 and the winding speed is adjusted. The braided piezoelectric element 1-AA is used as a core yarn, A braided piezoelectric element 1-AD was prepared by covering with a conductive fiber in the same manner as the piezoelectric element 1-AB.

(Example AE)
Using the conductive fiber CF1 as a core yarn, among the 16 carriers of the 16 punched round braid making machine, all of the 8 carriers assembled in the Z twist direction and the 8 carriers assembled in the S twist direction are applied to the above-mentioned piezoelectric element. By setting and assembling the conductive fiber PF1, a braided piezoelectric element in which the piezoelectric fiber PF1 is spirally wound around the core yarn in both the Z twist direction and the S twist direction is created. A thread was formed by covering with a conductive fiber in the same manner as the braided piezoelectric element 1-AB, and a braided piezoelectric element 1-AE was produced.

(Example AF)
CF1 is used as a core yarn, PF1 is wound around the core yarn in the S twist direction at a covering number of 3000 times / m, and further PF1 is wound around the outer side at a covering number of 3000 times / m in the Z twist direction. Further, CF2 is wound around the outer side at a covering number of 3000 times / m in the S twist direction, and further CF2 is wound around the outer side at a covering number of 3000 times / m in the Z twist direction. A covering thread-like piezoelectric element 1-AF in which the piezoelectric fiber PF1 was spirally wound in the S twist direction and the outer side was covered with the conductive fiber was produced.

(Example AG)
CF1 is a core yarn, PF1 is wound around the core yarn in the S twist direction at a covering number of 6000 times / m, and PF1 is further wound around the outer side at a covering number of 6000 times / m in the Z twist direction. Further, CF2 is wound around the outer side at a covering number of 3000 times / m in the S twist direction, and further CF2 is wound around the outer side at a covering number of 3000 times / m in the Z twist direction. A covering yarn-like piezoelectric element 1-AG in which the piezoelectric fiber PF1 was spirally wound in the S twist direction and the outer side was covered with the conductive fiber was produced.

(Example AH)
A braided piezoelectric element is produced in the same manner as the braided piezoelectric element 1-AA, except that IF1 is used instead of PF1, and this braided element is used as a core thread, and the same as the braided piezoelectric element 1-AB. What was covered with the fiber was produced, and it was set as braided element 1-AH.

(Example AI)
A covering thread-like element was produced in the same manner as the covering thread-like piezoelectric element 1-AF except that IF1 was used instead of PF1, and was designated as covering thread-like element 1-AI.

(Example AJ, AK)
Two braided piezoelectric elements were created in the same manner as braided piezoelectric elements 1-AB and 1-AC except that the winding speed of PF1 or PF2 was changed, and braided piezoelectric elements 1-AJ and 1-AK were created. It was.

(Example AL)
A braided piezoelectric element 1-AL was produced in the same manner as the braided piezoelectric element 1-AB except that IF1 was used instead of PF1 wound in the S twist direction.

(Example AM)
A braided piezoelectric element 1-AM was produced in the same manner as the braided piezoelectric element 1-AC except that IF2 was used instead of PF2 wound in the Z twist direction.

(Example AN)
A covering thread-like piezoelectric element 1-AN was prepared in the same manner as the covering thread-like piezoelectric element 1-AF except that IF1 was used instead of PF1 wound in the Z twist direction.

Measured Ri, Ro, and HP of each piezoelectric element, and Table 2 shows the calculated value of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the value of T1 / T2. For braided piezoelectric elements, Ri and Ro were measured as the area occupied by the piezoelectric elements by combining the areas where the piezoelectric fibers and insulating fibers exist in the cross section. For the covering yarn-like piezoelectric element, Ri and Ro were measured as the area occupied by the piezoelectric element in the cross section. Further, each piezoelectric element is cut to a length of 15 cm, the core conductive fiber is set as the Hi pole, and the surrounding wire mesh or sheath conductive fiber is connected as the Lo pole to the electrometer (Keysight B2987A). The current value was monitored. Table 2 shows current values in the tensile test, torsion test, bending test, shear test, and pressing test. Since Examples AH and AI do not contain a piezoelectric polymer, the values of θ and T1 / T2 cannot be measured.

From the results of Table 2, when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is more than 40 ° and less than 50 °, a large signal is not generated for torsional operation (torsional deformation). When the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is 0 ° or more and 40 ° or less or 50 ° or more and 90 ° or less, it can be seen that a large signal is generated for torsional operation (torsional deformation). . Further, when the value of T1 / T2 exceeds 0.8 and is 1.0 or less as in Examples AA to AG, a large signal is generated with respect to torsional operation (torsional deformation), and is large for operations other than torsion. It can be seen that the element does not generate a signal and selectively responds to a torsional motion. In addition, when Examples AA to AE, AL, and AM are compared with Examples AF, AG, and AN, θ is 0 ° or more and 40 ° or less, and θ is 50 ° or more and 90 ° or less. It can be seen that the polarity of the signal is reversed, and θ corresponds to the polarity of the signal in the torsion test.

Furthermore, although not shown in the table, when the elements of Examples AA to AG and AL to AN are twisted in the S twist direction and the signals when twist is applied in the Z twist direction, Since the signals having opposite polarities and substantially the same absolute value are generated, it can be seen that these elements are suitable for quantification of torsional load and displacement. On the other hand, the elements of Example AJ and Example AK are the same when the signal when twisted in the S twist direction and the signal when twisted in the Z twist direction are opposite in polarity. In some cases, it can be seen that these elements are not suitable for quantification of torsional load and displacement. Although not shown in the table, the noise level in the torsion test in Example AB is lower than the noise level in the torsion test in Example AA, and the conductive fiber is formed outside the braided piezoelectric element (piezoelectric structure). It can be seen that noise can be reduced in an element having a conductive layer disposed as a shield.

(Example 2)
The fabric for a piezoelectric element according to the second invention 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 the mixture was stirred at 180 ° C. in a reactor equipped with a stirring blade in a nitrogen atmosphere. For 2 hours, 1.2 times equivalent of phosphoric acid to tin octylate was added, 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 2-1, the conductive fiber “AGposs” 100d34f is used as a core yarn, and the piezoelectric fiber A1 is wound around the eight core yarns in a braid shape to form an eight-punch braid. Conductive fiber “AGposs” 30d10f was wrapped in a braid shape around the piezoelectric fiber A1 of the sheath portion to form a shield layer, thereby forming a braided piezoelectric element 1A. 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 2-2, 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-punch braid. On the braid, eight more 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.

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 in Example 2-1 as a sample of Comparative Example 2-1. The d / Rc of the braided piezoelectric element 1C was 0.84.

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

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

Example 2-1
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 204 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 2-2)
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 204 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 2-1)
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 204 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.

(Example 3)
The fabric-like piezoelectric element according to the third invention was manufactured by the following method.
(Braided piezoelectric element)
As shown in FIG. 10, the conductive fiber CF1 is used as a core yarn, and the piezoelectric fiber PF1 is set on four carriers assembled in the Z-twist direction among the eight carriers of the 8-punch round braid stringing machine. Then, the braided piezoelectric element in which the piezoelectric fiber PF1 is spirally wound around the core yarn in the Z twist direction by setting the insulating fiber IF1 on the four carriers assembled in the S twist direction. A device was created. Next, the braided piezoelectric element is used as a core thread, and among the eight carriers of the string making machine, all four carriers assembled in the Z twist direction and all four carriers assembled in the S twist direction are electrically conductive. By setting and assembling the fiber CF2, a braided piezoelectric element 201 was manufactured by covering the braided piezoelectric element with a conductive layer made of conductive fibers.

(Weaving)
Example 3-1
Five cylindrical portions were formed in parallel between the warp yarns between layers of double woven tape (16 mm wide, 0.3 mm thick) with polyester spun yarn, and braided piezoelectric elements 201 were woven into each cylinder. A cloth-like piezoelectric element was prepared. The cylindrical portion was composed of 16 84dTex warps in two layers, and the portion other than the cylindrical portion was composed of 167dTex warp. As the weft, 84 dTex was used. Two 167 dTex warps (one for each layer) were put between five braided piezoelectric elements. With respect to the braided piezoelectric element 201 at the center of the cloth-like piezoelectric element, the pullout strength and the coverage were measured, and the signal strength of the bending test and the outer conductive layer appearance of the braided piezoelectric element after the bending test were confirmed. The results are shown in Table 3.

(Example 3-2)
A fabric-like piezoelectric element woven using a braided piezoelectric element 201 on a part of a warp of a plain woven fabric using polyester yarn (330 dTex / 72 filament) as warp and weft was prepared. This plain woven fabric had a warp density higher than the weft density, and there was almost no gap between the warps. With respect to the braided piezoelectric element 201 in the fabric-like piezoelectric element, the drawing strength and the coverage were measured, and the signal strength of the bending test and the outer conductive layer appearance of the braided piezoelectric element after the bending test were confirmed. The results are shown in Table 3.

(Example 3-3)
In the same manner as in Example 3-2, a cloth-like piezoelectric element woven using a braided piezoelectric element 201 on a part of a weft of a plain woven cloth woven using polyester spun yarn as warp and weft was prepared. With respect to the braided piezoelectric element 201 in the fabric-like piezoelectric element, the drawing strength and the coverage were measured, and the signal strength of the bending test and the outer conductive layer appearance of the braided piezoelectric element after the bending test were confirmed. The results are shown in Table 3.

(Example 3-4)
The braided piezoelectric element 201 is placed on the plain woven fabric woven in Example 3-2, and zigzag sewing (width 2 mm, pitch 1 mm) with a 60th polyester spun sewing thread is performed across the braided piezoelectric element 201. A braided piezoelectric element was prepared by fixing the braided piezoelectric element to a plain woven fabric. With respect to the braided piezoelectric element 201 in the fabric-like piezoelectric element, the drawing strength and the coverage were measured, and the signal strength of the bending test and the outer conductive layer appearance of the braided piezoelectric element after the bending test were confirmed. The results are shown in Table 3.

(Comparative Example 3-1)
A cloth-like piezoelectric element was prepared in the same manner as in Example 3-4 except that the width of zigzag stitching with a polyester spun sewing thread was changed to 4 mm and the pitch was changed to 2 mm. With respect to the braided piezoelectric element 201 in the fabric-like piezoelectric element, the drawing strength and the coverage were measured, and the signal strength of the bending test and the outer conductive layer appearance of the braided piezoelectric element after the bending test were confirmed. The results are shown in Table 3.

From the results shown in Table 3, in Examples 3-1 to 3-4 where the pullout strength per 5 cm is 0.1 N or more, a strong signal is observed in the bending test, whereas the comparison is less than 0.1 N In Example 3-1, only a weak signal was observed in the bending test, and it can be seen that the fabric-like piezoelectric elements of Examples 3-1 to 3-4 are excellent in sensor performance. Further, in Examples 3-1 to 3-4 in which the coverage ratio exceeds 30% on both the front surface and the back surface, deterioration of the conductive layer of the braided piezoelectric element after the bending test is suppressed as compared with Comparative Example 3-1. It can be seen that the fabric-like sensor is excellent in durability.

1 Piezoelectric Structure 1-1 Cylindrical Piezoelectric Structure 1-2 Cylindrical Piezoelectric Structure 2 Piezoelectric Polymer OL Orientation Direction HP Spiral Pitch A Piezoelectric Fiber B Conductive Fiber 101, 201 Braided Piezoelectric Element 102, 202 Sheath part 103, 203 Core part 107, 207 Fabric-like piezoelectric element 108, 208 Fabric 109, 209 Insulating fiber 110, 210 Conductive fiber 111 Device 112 Piezoelectric element 113 Amplifying means 114 Output means 115 Transmitting means 204 Conductive Layer 205 Conductive material 206 Conductive fiber X The largest circle consisting of only the core fiber bundle Y The smallest circle Y completely including the core fiber bundle
X ′ Maximum circle consisting only of fiber bundles of piezoelectric fibers including the core Y ′ Minimum circle completely including fiber bundles of piezoelectric fibers CL Central axis or fiber axis α Winding angle

Claims (31)

A structure in which oriented piezoelectric polymers are arranged in a cylindrical or cylindrical shape, and the orientation angle of the piezoelectric polymer with respect to the direction of the central axis of the cylindrical or cylindrical shape in which the piezoelectric polymers are arranged is 0 ° or more. Crystallinity of 40 ° or less or 50 ° or more and 90 ° or less, and the piezoelectric polymer has a piezoelectric constant d14 having an absolute value of 0.1 pC / N or more and 1000 pC / N or less with three orientation axes. A structure containing a polymer as a main component. The structure according to claim 1, wherein the piezoelectric polymer contains poly-L-lactic acid or poly-D-lactic acid as a main component. When a torsional deformation is given about the cylindrical or columnar central axis on which the piezoelectric polymer is disposed, charges having opposite polarities are generated on the cylindrical axis or the columnar axis side and the outside. The structure according to claim 1 or 2. The piezoelectric polymer includes a P body including a crystalline polymer having a positive piezoelectric constant d14 as a main component and an N body including a negative crystalline polymer as a main component, and the center of the structure. For a portion having an axis of 1 cm in length, the orientation axis is ZP, and the orientation body is arranged with a spiral in the S twist direction. SP, the mass of the N body arranged with a spiral in the Z twist direction is ZN, and the mass of the N body arranged with a spiral in the S twist direction is SN, The structure according to any one of claims 1 to 3, wherein a value of T1 / T2 is greater than 0.8, where T1 is the smaller of (ZP + SN) and (SP + ZN), and T2 is the larger. body. 5. The piezoelectric polymer according to claim 1, wherein the piezoelectric polymer is in the form of a braid, a filament, a tape, a braid, a twisted string, a covering thread, or an aligned thread. The structure described. The structure according to any one of claims 1 to 4, wherein the piezoelectric polymer constitutes only one closed region in a cross section perpendicular to a central axis of a cylindrical shape or a cylindrical shape. An element comprising the structure according to any one of claims 1 to 6 and a conductor disposed adjacent to the structure. The element according to claim 7, wherein the piezoelectric polymer is arranged in a cylindrical shape, and the conductor is arranged at a position of a central axis of the cylindrical shape. The element according to claim 8, wherein the conductor is made of a conductive fiber, and the piezoelectric polymer is arranged as a piezoelectric fiber in a braid shape around the conductive fiber. The element according to claim 7, wherein the conductor is disposed outside a cylindrical shape or a columnar shape where the piezoelectric polymer is disposed. The element according to claim 10, wherein the conductor is made of a conductive fiber, and the conductive fiber is arranged in a braid shape around a cylindrical shape or a columnar shape in which the piezoelectric polymer is arranged. An element according to any one of claims 7 to 11,
An output terminal that outputs an electrical signal generated in the conductor in response to a charge generated when a torsional deformation is applied in the direction of the central axis of the cylindrical or cylindrical shape in which the piezoelectric polymer is disposed;
An electrical circuit for detecting an electrical signal output through the output terminal;
With a sensor. The element according to claim 9, comprising: a core portion formed of the conductive fiber; and a sheath portion formed of the piezoelectric fiber in a braid shape so as to cover the core portion;
A braided piezoelectric element comprising a conductive layer provided around the sheath portion, wherein a ratio d / Rc of a thickness d of the layer made of piezoelectric fibers to a radius Rc of the core portion is 1.0 or more. The braided piezoelectric element according to claim 13, wherein a covering ratio of the sheath portion by the conductive layer is 25% or more. The braided piezoelectric element according to claim 13 or 14, wherein the conductive layer is formed of a fiber. A fabric-like piezoelectric element comprising the braided piezoelectric element according to any one of claims 13 to 15. The cloth-like piezoelectric element according to claim 16, wherein the cloth further includes a conductive fiber that intersects and contacts at least a part of the braid-like piezoelectric element. The cloth-like piezoelectric element according to claim 17, wherein 30% or more of the fibers that form the cloth and intersect the braided piezoelectric element are conductive fibers. A braided piezoelectric element according to any one of claims 13 to 15,
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 fabric-like piezoelectric element according to claim 17 or 18,
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: A braided piezoelectric element having a braided piezoelectric element fixed to a fabric, wherein the braided piezoelectric element is
The element according to claim 9, comprising: a core portion formed of the conductive fiber; and a sheath portion formed of the piezoelectric fiber in a braid shape so as to cover the core portion;
And a conductive layer provided around the sheath portion, wherein the braided piezoelectric element with respect to the fabric has a pull-out strength per 5 cm of 0.1 N or more. The cloth-like piezoelectric element according to claim 21, wherein a coverage of the braided piezoelectric element by fibers constituting the cloth exceeds 30% on both surfaces of the cloth. The fabric-like piezoelectric element according to claim 21 or 22, wherein the braid-like piezoelectric element is fixed to the fabric in a woven or knitted state. The fabric-like piezoelectric element according to claim 21 or 22, wherein the braided piezoelectric element is sandwiched between layers of a double woven fabric or a double knitted fabric. The braided piezoelectric element is partially exposed from the fabric, and the conductive fiber and / or the conductive layer of the braided piezoelectric element and another member are electrically connected to the exposed portion. The fabric-like piezoelectric element according to any one of claims 21 to 24. The cloth-like piezoelectric element according to any one of claims 21 to 25, wherein a covering ratio of the sheath portion by the conductive layer is 25% or more. The cloth-like piezoelectric element according to any one of claims 21 to 26, wherein the conductive layer is formed of a fiber. The cloth-like piezoelectric element according to any one of claims 21 to 27, wherein a total fineness of the piezoelectric fibers is 1 to 20 times the total fineness of the conductive fibers. The fabric-like piezoelectric element according to any one of claims 21 to 28, wherein the fineness per one of the piezoelectric fibers is not less than 1/20 times and not more than 2 times the total fineness of the conductive fibers. The cloth-like piezoelectric element according to any one of claims 21 to 29, wherein the cloth further includes a conductive fiber that intersects and contacts at least a part of the braided piezoelectric element. The cloth-like piezoelectric element according to any one of claims 21 to 30,
An electrical circuit for detecting an electrical signal output from the conductive fiber included in the fabric-like piezoelectric element in accordance with an applied pressure;
A device comprising:

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