Sensing fiber member and sensing fabric

Abstract

To provide a sensing fiber member capable of processing in long lengths, excellent in mass productivity, and inexpensive as compared with a conventional contact sensing fiber member made of piezoelectric material (piezoelectric yarn), and cloth made of the sensing fiber member.SOLUTION: A composite yarn strip composed of at least two sheath yarns with sheath yarns is provided around a core yarn, which is a linear conductor, in close proximity to each other via the sheath yarns. A coating resin, which is a pressure sensitive material, is placed on periphery of the composite yarn strips. A sensing fiber member is fixed with the coating resin in a state where the coating resin is in contact with the composite yarn. The sensing fiber member is capable of sensing an applied stress on the sensing fiber member through a change in the electrical characteristics between the linear conductors. A fabric is obtained using the sensing fiber member.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sensing fiber, and more specifically to a sensing fabric capable of detecting contact or the application of a load, which comprises at least two core-sheath structure yarns, each having a core yarn that is a linear conductor and a sheath yarn disposed around the core yarn, and a pressure-sensitive coating resin disposed around the outer periphery of the composite yarn, which is adjacent to each other via the sheath yarn, and a sensing fabric having the sensing fiber disposed thereon. [Background technology]

[0002] Smart textile technology has been proposed in the past, in which electrical functional elements are mounted on flexible and stretchable textile substrates. These involve mounting various functional elements such as sensors, batteries, heaters, and Peltier elements on a flexible textile substrate, and because they enable the creation of products that are extremely flexible and suitable for mounting on the human body or curved surfaces, they are extremely important in the future super-smart society known as Society 5.0, which highly integrates cyberspace and physical space.

[0003] As one of the above sensors, piezoelectric textured yarn (hereinafter also referred to as piezoelectric yarn) and piezoelectric sensors, as shown in FIG. 1, have been proposed as fiber components with touch-sensing capabilities. As described in the following Patent Documents 1 to 5, piezoelectric textured yarn (also referred to as piezoelectric yarn or piezoelectric fiber) generally has a structure in which conductive fibers (1) are coated with a piezoelectric material (2) such as polylactic acid or polyvinylidene fluoride, and this is further coated with a conductor (3) such as metal plating. Polylactic acid is a crystalline helical chiral polymer, and its uniaxially stretched film exhibits piezoelectricity. Piezoelectricity is the property in which surface charge is generated when stress is applied, resulting in polarization. This generates charge between the inner layer conductive fiber (1) and the outer conductor (3), as shown in FIG. 1, for example. The reverse can also occur. In this case, the piezoelectric material needs to be oriented, which poses a problem of difficulty in increasing productivity in the plating process, making textured yarn currently very expensive, costing approximately 1,000 to 10,000 yen per meter. Furthermore, with the structure shown in Figure 1, it is currently difficult to produce long processed yarns of more than 10,000 m, making it extremely difficult to use piezoelectric yarns as warp yarns for woven fabrics or warp knitting.

[0004] Furthermore, as described in Patent Documents 6 and 7 below, a contact-sensing fiber member is known that senses contact or load by detecting a change in capacitance between two adjacent electrodes when contact or a load is applied. Other known technologies include detecting a change in capacitance when a conductor (such as a human body) approaches a single electrode. However, conventional technologies primarily use insulators such as urethane or silicone between the two electrodes, making it difficult to significantly change the distance between the electrodes, resulting in high costs and numerous design constraints. Furthermore, as described in Patent Document 8, when using a single electrode, the change in capacitance is extremely small, requiring the use of an advanced signal processing circuit to detect this small signal. However, current technologies only offer low contact sensitivity and low sensitivity as a proximity sensor.

[0005] On the other hand, as described in Patent Documents 9 and 10 below, technologies relating to sheath-core yarns with excellent bulkiness and highly productive and high-quality sheath-core yarns are known, but there is no description or suggestion of using these technologies relating to sheath-core yarns as sensing fiber components. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6025854 [Patent Document 2] Patent No. 6689943 [Patent Document 3] Japanese Patent Application Publication No. 2020-090768 [Patent Document 4] Japanese Patent Publication No. 2020-036027 [Patent Document 5] Patent No. 6107069 [Patent Document 6] Patent No. 5754946 [Patent Document 7] Japanese Patent Application Laid-Open No. 2006-234716 [Patent Document 8] Japanese Patent Application Laid-Open No. 2016-173685 [Patent Document 9] Japanese Patent Application Publication No. 10-25635 [Patent Document 10] Japanese Patent Application Laid-Open No. 2013-231246 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above-mentioned state of the art, the problem that the present invention aims to solve is to provide a sensing fiber member, and a sensing fabric in which the sensing fiber member is arranged, which can be processed in long lengths, is easy to mass-produce, can be used as a woven yarn for textiles or a knitted yarn for knitting, and is significantly less expensive than conventional contact sensing fiber members (piezoelectric yarns) that use piezoelectric materials for contact. [Means for solving the problem]

[0008] In order to solve the above problems, the present inventors have conducted extensive research and experiments, and as a result have unexpectedly found that the above problems can be solved by using the following structure, which has led to the completion of the present invention.

[0009] That is, the present invention is as follows. [1] A sensing fiber member in which at least two core-sheath structure yarns, each having a core yarn that is a linear conductor and a sheath yarn disposed around it, are arranged around the outer periphery of a composite yarn that is close to each other via the sheath yarn, and a coating resin that is a pressure-sensitive material is arranged around the outer periphery of the composite yarn, and the coating resin is fixed in contact with the composite yarn, and the sensing fiber member can sense the application of stress to the sensing fiber member by changes in the electrical properties between the linear conductors. [2] The sensing fiber member described in [1], wherein the sensing fiber member detects contact of an object with the sensing fiber member, or expansion / contraction or bending deformation of the sensing fiber member. [3] A sensing fiber element according to [1] or [2], wherein the sheath yarn is an insulator or a piezoelectric material. [4] The following formula of the core-sheath structure yarn: Twist factor K=(SS+SC) 1 / 2 ×R The sensing fiber member according to any one of [1] to [3] above, wherein the twist coefficient K, represented by the formula {where SS is the fineness (dtex) of the linear conductor as the core yarn, SC is the total fineness (dtex) of the sheath yarn as the sheath yarn, and R is the number of turns (twists) of the sheath yarn (turns / m)}, is 7,000 or more and 30,000 or less. [5] A sensing fiber member described in any of [1] to [4], wherein the core-sheath structure yarn is a double core-sheath structure yarn in which two sheath yarns are wrapped around a linear conductor serving as a core yarn, and the winding directions of the two sheath yarns are the same. [6] The sensing fiber according to any one of [1] to [5], wherein the linear conductor serving as the core thread is a multifilament conductive fiber. [7] A sensing fiber member described in any of [1] to [6] above, wherein the two sheath-core structure yarns arranged close to each other have the same winding direction of the sheath yarns, and the two sheath-core structure yarns are twisted in the opposite direction to the winding direction of the sheath yarns, and the twisted yarns are fixed by a coating resin. [8] The sensing fiber according to any one of [1] to [7], wherein the sheath yarn is made of spun yarn. [9] A sensing fabric in the form of a woven fabric, knitted fabric or braided cord, in which the sensing fiber member according to any one of [1] to [8] is arranged.

[10] A sensing fabric in which at least one core-sheath structure yarn, in which a sheath yarn is provided around a core yarn that is a linear conductor, is arranged in each warp and weft directions of the fabric, and a coating resin that is a pressure-sensitive material is arranged at the intersection of the core-sheath structure yarns arranged in the warp and weft directions, and the coating resin is fixed in a state in which it is in contact with the intersection.

[11] A sensing fiber component in which at least two coated-sheath-core structure yarns are arranged, in which a sheath yarn is arranged around a core yarn that is a linear conductor, and a coating resin that is a pressure-sensitive material is arranged around the outer periphery of the core-sheath structure yarn, and the coating resins are fixed in a state where they are in contact with each other when stress is applied. [Effects of the Invention]

[0010] The contact sensing fiber according to the present invention can be processed in long lengths, is highly mass-producible, and can be used as a woven yarn or a knitted yarn. It is significantly less expensive than conventional contact sensing fiber materials (piezoelectric yarns) that use piezoelectric materials. Specifically, the sensing fiber according to the present invention comprises at least two core-sheath structured yarns, each of which has a core yarn that is a linear conductor and a sheath yarn made of an insulator such as a common polyester, nylon, cotton, or cellulose-based fiber, or a piezoelectric (piezoelectric material) such as polylactic acid, around the core yarn. The composite yarns are then secured to each other via the sheath yarns, and a coating resin, which is a pressure-sensitive material such as a piezoelectric (piezoelectric material) or a material whose electrical resistance changes in response to pressure (piezo-resistive material), is applied to the outer periphery of the composite yarns. This allows for the realization of contact sensing fibers at very low cost. Furthermore, because the sensing fiber uses covering and spinning techniques, which are well-established fiber processing techniques, the sensing fiber can be processed in long lengths and is highly mass-producible, making it easy to process into fiber components such as woven fabrics and knitted fabrics. Therefore, the contact sensing fiber member of the present invention and sensing fabrics using the same can be widely used in a variety of applications, such as smart textile applications in which electrical functional elements are provided on a flexible and stretchable fiber substrate, such as rugs that can detect when stepped on, security mats for detecting people entering and exiting, mats for counting people, sensors for biological signals such as pulse and heart rate, contact sensing woven and knitted fabrics, such as monitoring sensors in nursing and care settings, contact sensors in production sites such as factories, and components for embedding sensors in vehicle seat belts, etc., such as embedding contact sensors in vehicle seat belts, steering wheels, dashboards, etc. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a conventional piezoelectric textured yarn (piezoelectric yarn). [Figure 2] FIG. 2 is a schematic diagram of a sensing fiber according to the present embodiment. [Figure 3] 1 shows the appearance of the sensing fiber member of this embodiment before being impregnated and coated with a coating resin, and an enlarged photograph. [Figure 4]1 is an enlarged photograph of the appearance of the sensing fiber member of this embodiment after being coated with resin. [Figure 5] FIG. 1 is a schematic diagram of a manufacturing device for a core-sheath structure yarn. [Figure 6] 6 is a schematic diagram of a sheath-core structure yarn obtained by the above-mentioned manufacturing apparatus in part B of FIG. 5. FIG. [Figure 7] 1 is a graph showing the change in current value when a load is applied to the plied yarn fixed with the coating resin (piezoelectric body) obtained in Example 1. [Figure 8] 10 is a graph showing the change in current value when a load is applied to the plied yarn fixed with the coating resin (piezoelectric body) obtained in Example 2. [Figure 9] 10 is a graph showing the change in current value when a load is applied to the ply-twisted yarn fixed with the coating resin (piezoelectric body) obtained in Example 3. [Figure 10] 10 is a graph showing the change in current value when a load is applied to the ply-twisted yarn fixed with the coating resin (piezoelectric body) obtained in Example 4. [Figure 11] 10 is a graph showing the change in current value when a load is applied to the plied yarn fixed with the coating resin (piezoelectric body) obtained in Example 5. [Figure 12] 10 is a graph showing the change in current value when a load is applied to a plied yarn fixed with a coating resin (piezoelectric body) obtained in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail. The first embodiment of the present invention is a sensing fiber member in which at least two core-sheath structure yarns, each having a core yarn that is a linear conductor and a sheath yarn disposed around it, are adjacent to each other via the sheath yarn, and a coating resin that is a pressure-sensitive material is arranged on the outer periphery of the composite yarn, and the coating resin is fixed in contact with the composite yarn, and the sensing fiber member is capable of detecting the application of stress to the sensing fiber member by changes in the electrical properties between the linear conductors. The sensing fiber of this embodiment is preferably a sensing fiber that can sense contact of an object with the sensing fiber, or the expansion, contraction, or bending deformation of the sensing fiber. The sheath yarn is preferably an insulator or a piezoelectric material.

[0013] The linear conductor used as the core thread is not particularly limited as long as it is conductive. It may be a conductive fiber, such as a carbon fiber or a metal fiber, which is a linear conductor made of a conductive material itself, or a non-conductive fiber that has been given conductivity. As the former, one or more metal wires made of various metals can be used. When using multiple metal wires (multifilaments), it is preferable to use wires with a large number of filaments and a relatively small diameter, as this can improve flexibility and texture. For example, using a metal multifilament with a diameter of approximately 1 μm to 1 mm and a number of filaments of approximately 10 to 200 can easily achieve both strength and texture. Among these, stainless steel multifilaments are preferred because they are highly durable, corrosion-resistant, and relatively inexpensive. As the latter, it is preferable to use nylon or other fibers plated with a metal such as silver or copper to improve texture and flexibility. In this case, it is preferable for the conductive fiber to be made of multifilaments, as this can improve conductivity and strength. Instead of metal plating, fibers may be wrapped with metal foil such as copper foil, or sprayed with a conductive material such as metal. Furthermore, using polyarylate or the like instead of nylon can further increase tensile strength. Alternatively, a linear conductor may be used in which conductivity is imparted to an elastic body such as urethane or silicone by applying a stretchable metal ink. In this case, a stretchable fiber member can be obtained. Furthermore, a linear conductor made of a mixture of a conductive material and an insulating material may be used. For example, a linear conductor made of a material obtained by processing a material made by mixing a carbon-based conductive material or metal with a resin such as nylon or polyester into a linear shape can be used to obtain a linear conductor with poor conductivity but a good texture.

[0014] The fineness of the linear conductor, for example, the conductive fiber, is preferably 10 dtex to 15,000 dtex, more preferably 20 dtex to 5,000 dtex, from the viewpoint of easily obtaining a good texture and easily obtaining high conductivity. Furthermore, in the case of a multifilament, the single yarn fineness is preferably 1 dtex to 30 dtex, more preferably 2 dtex to 10 dtex, from the viewpoint of easily obtaining a good texture and easily obtaining high conductivity. The number of filaments is more preferably 10 to 200. Having 10 or more filaments is preferable because it is easy to obtain a good texture and to ensure good conductivity. However, if the number of filaments is too high, costs will increase and rigidity will also increase, which may conversely result in a deterioration in texture. Taking all of these factors into consideration, it is preferable to keep the number of filaments within the above range.

[0015] The conductive material forming the linear conductor may be the same for at least two core-sheath structure yarns constituting the composite yarn, or different materials may be used, and any combination of materials may be used. However, using the same conductive material is preferred in terms of efficient production. Any combination of different materials may be used, for example, iron and copper, iron and silver, aluminum and copper, silver and copper, etc.

[0016] In this specification, the term "sheath yarn" is not particularly limited as long as it can electrically insulate two of the linear conductors serving as core yarns in the composite yarn, and includes common fibers such as polyester and nylon (polyamide), as well as piezoelectric materials such as polylactic acid (PLA), and ferroelectric materials such as polyvinylidene fluoride (PVDF). However, in order to prevent electrical shorts from occurring between the linear conductors serving as core yarns in an unloaded state, during the production of the sheath-core yarn, or during fixation with a coating resin (described below), the sheath yarn is preferably either a multifilament synthetic continuous fiber or a spun yarn that can achieve a uniform coating thickness without unevenness, from the viewpoints of coating properties and sensing performance. The sheath yarn material is not particularly limited as long as it can maintain insulation when there is no sensing action, such as when the sensor is idle. However, from the standpoints of cost and availability, synthetic fibers such as polyester (PET, PBT, etc.), nylon (Ny, polyamide), epoxy, and acrylic are preferred. Natural fibers such as cellulose fibers, semi-synthetic fibers, and regenerated fibers are also acceptable. Furthermore, piezoelectric materials such as polylactic acid (PLA) and polyvinylidene fluoride (PVDF), ferroelectric materials, and biodegradable resins can be used for the sheath yarn. Piezoelectric materials can maintain insulation when the sensor is idle, and when stress is applied, an output signal corresponding to their piezoelectric properties can also be obtained, resulting in high sensor sensitivity. However, from the standpoints of cost and the texture of the woven or knitted fabric, it is preferable to use fibers used for clothing, such as polyester, nylon, and acrylic, as the sheath yarn.

[0017] The sheath yarn has a fineness of preferably 15 dtex to 25,000 dtex, more preferably 30 dtex to 8,000 dtex, from the viewpoint of easily ensuring insulation under no load. In addition, in the case of a multifilament, the single yarn fineness is preferably 1 dtex to 10 dtex, more preferably 2 dtex to 8 dtex, from the viewpoint of more easily obtaining a good texture.

[0018] There are no particular limitations on the method for producing the core-sheath structure yarn, and an example thereof is the following method described in Patent Document 9. In this specification, the term "core-sheath structure yarn" means a yarn in which the sheath yarn is formed around the linear conductor. Figure 5 is a schematic diagram of a covering device in which a bobbin (11) wound with a sheath yarn (14) is set and operated on a covering device equipped with a two-legged flyer (12). Figure 6 shows an enlarged view of part B in Figure 5. The core yarn 9 passes through the hollow portion of the hollow spindle 10, passes through an upper snail guide (not shown), and is taken up by a take-up roll (not shown). The sheath yarn 14 is passed through one of the leg guides 15 and 16 of the two-legged flyer 12, and is unwound from the bobbin by the rotation of the hollow spindle (synchronization of the bobbin). The sheath yarn 14 passes through the snail guide while being wound around the core yarn 9, and is taken up. The flyer 12 has two legs in order to balance the flyer 12 when it rotates. The above-mentioned covering devices may be arranged in two vertical rows, and two types of cover yarns (which may be the same or different) may be sequentially covered from two bobbins, thereby performing so-called double covering. In this case, if each cover yarn is covered in the same direction (both types of cover yarns are S-twisted or Z-twisted), the thickness can be made uniform, and gaps between the insulating fibers can be reliably filled, improving sensing performance, which is particularly preferable. The cover yarn may be a false twisted yarn (woolly yarn) from the viewpoint of easily improving the texture and covering property.

[0019] Figures 2, 3, and 4 show an example of a sensing fiber member of this embodiment in which two sheath-core yarns (7) are twisted together. In this case, it is preferable that the sheath yarns (6) arranged around the linear conductors (5) serving as core yarns in the two sheath-core yarns (7) arranged close to each other are wound in the same direction, and that the two sheath-core yarns are plied together in the opposite direction to the winding direction of the sheath yarns (8). Plying (twisting in the opposite direction to the winding direction of the covering) reduces the torque of the resulting yarn (sheath-core yarn), making it easier to handle during the manufacturing process. Furthermore, with a plied yarn, the two sheath-core yarns are naturally arranged close to each other, and the two sheath-core yarns have points of contact where they intersect.

[0020] The sheath-core yarn has the following formula: Twist factor K=(SS+SC) 1 / 2 ×R The twist factor K, expressed by the formula {where SS is the fineness (dtex) of the linear conductor serving as the core material, SC is the total fineness (dtex) of the covering material, and R is the number of turns (twists) of the covering material (turns / m)}, is preferably 7,000 or more and 30,000 or less. If the twist factor K is 7,000 or more, electrical short-circuiting between two linear conductors is less likely to occur, while if it is 30,000 or less, it becomes easier to obtain a large sensor output. In the case of double covering, the twist factors for the first and second covering layers are calculated and the average value is used. The twist factor K is more preferably 10,000 or more and 20,000 or less.

[0021] In the sensing fiber of this embodiment, the two sheath-core yarns thus obtained are placed close to each other via the sheath yarn, impregnated with a coating resin that is a pressure-sensitive material, and fixed in place by the coating resin while in contact with the linear conductors, so that the application of a load to the sensing fiber can be detected by a change in the electrical properties between the linear conductors.

[0022] The coating resin, which is the pressure-sensitive material, is impregnated into the gap between the sheath yarns, and at least a portion of the space between the two linear conductors (the sensing point of application) is made up of only the pressure-sensitive material. Here, the pressure-sensitive material can be fixed by using a continuously formed coating resin to completely fix the two linear conductors at the sensing point of application, or by using at least two core-sheath yarns impregnated with the pressure-sensitive material and bringing them into close contact with each other. In terms of increasing the sensor output, the former method of completely fixing the two linear conductors and producing the coating resin as a continuous medium is more preferable. As described above, during impregnation with a coating resin, the gaps between the contacting sheath yarns are filled with the coating resin, while the sheath-core yarn is coated with the coating resin, and the shape of the sheath-core yarn is fixed as the coating resin hardens. When two sheath-core yarns are ply-twisted to bring them closer together, the shapes of the two sheath-core yarns are fixed as the coating resin hardens. Furthermore, if the sheath yarn is an insulator, the two sheath-core yarns are fixed by the coating resin while in contact with a linear conductor. This makes it possible to electrically sense, via the linear conductor, changes in polarization and electrical resistance generated from the coating resin (piezoelectric or pressure-sensitive material) when a load is applied. Furthermore, if the sheath yarn is a piezoelectric material, the voltage generated not only from the coating resin but also from the sheath yarn when a load is applied can be electrically sensed via the linear conductor.

[0023] The coating resin is a pressure-sensitive material. In this embodiment, the pressure-sensitive material used for the coating resin refers to a material that can electrically detect the application of stress, and includes a piezoelectric material or a material whose electrical properties change when pressure is applied (pressure-sensitive material in the narrow sense). Examples of piezoelectric materials include a copolymer of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) (hereinafter, P(VDF / TrFE)) polymer or polylactic acid. Examples of materials whose electrical properties change when pressure is applied include elastic materials such as silicone and urethane, or materials in which conductive particles made of metal or the like are dispersed in rubber. In this case, when pressure is applied, the dispersed particles become closer to each other or come into electrical contact with each other, reducing the electrical resistance, thereby enabling the application of pressure to be detected.

[0024] An example of a method for impregnating the coating resin will be described below. For example, a sensing fiber can be fabricated by impregnating a ply-twisted yarn in a P(VDF / TrFE) polymer solution and drying it to fix it with a coating resin. For example, if a P(VDF / TrFE) material with a VDF:TrFE ratio of 75:25 mol% is used, this is dissolved in diethyl carbonate to prepare solutions with concentrations of 6.9 wt% and 10.1 wt%. The solution concentration should be sufficient to fill the gaps between the two core-sheath yarns. The solution is heated and stirred overnight while maintaining a temperature between 88°C and 94°C. The solution is then returned to room temperature, and the ply-twisted yarn is immersed in the solution, removed, and vacuum-dried at 80°C for 10 hours at 10 hPa, resulting in a ply-twisted yarn in which the sheath yarn is coated and fixed with the piezoelectric resin while the piezoelectric resin is impregnated between the sheath yarns. In this embodiment, the materials, solvents, and manufacturing methods are not limited to those described above. When using the method of impregnating a piezoelectric material with a solution, any solvent can be used as long as it dissolves the piezoelectric material uniformly. A printing paste in which a P(VDF / TrFE) polymer is dispersed can also be used.

[0025] Another embodiment of the present invention is a sensing fabric in the form of a woven, knitted or braided cord having the sensing fabric described above disposed thereon. The sensing fabric is a woven, knitted, or braided fabric that incorporates the sensing fiber. The sensing fabric exhibits sensing performance within a certain range. The sensing fabric of this embodiment can be woven in the form of a woven fabric in which the above-described sensing fiber member is continuously present in at least one direction of the fabric. The sensing fiber member may be woven as a warp thread in the center of the width direction of the fabric, or the sensing fiber member may be used as either the warp thread or the weft thread, or both. Any number of sensing fiber members may be arranged depending on the number of locations to be sensed. For example, five warp threads may be arranged parallel to each other, and weft threads may be woven to the left and right. From the perspective of continuous production, it is preferable to arrange the sensing fiber member as part of the warp or weft thread. This allows the sensing fabric to detect contact of an object with the portion woven with the sensing fiber member, as well as the expansion, contraction, and bending of the portion. When the sensing fiber member is woven into a portion of a narrow-width fabric, the fiber member takes on a tape-like shape, which has the advantage of being easier to attach to textile products such as clothing and bags compared to a case in which only the sensing fiber member is used. For narrow-width fabrics, the width is preferably 1 to 200 mm, more preferably 5 to 30 mm. There are no particular restrictions on the use of yarns other than the sensing fiber member, and there are no particular restrictions on the weave.

[0026] For example, a sensing fabric can be constructed by weaving the above-mentioned sensing fiber members into a fabric approximately 150 cm to 200 cm wide and 50 m long at a 5-10 cm pitch in both the warp and weft. Using a sensing fabric woven with multiple sensing fiber members allows simultaneous measurement of contact at the position of each sensing fiber member, enabling mapping and measurement of the position of a given contact. Such sensing fabrics can be used in, for example, bed pads, sheets, pillowcases, and the like, to measure the presence and movement of a human body, as well as biological signals such as pulse and heart rate. The sensing fabric may also be in the form of a braid or knitted fabric incorporating the above-mentioned sensing yarn.

[0027] A second embodiment of the present invention in the form of a fabric is a sensing fabric in which at least one core-sheath structure yarn, in which a sheath yarn is provided around a core yarn that is a linear conductor, is arranged in each warp and weft directions of a woven fabric, knitted fabric, or braid, and a coating resin, which is a pressure-sensitive material, is arranged at the intersection of the core-sheath structure yarns arranged in the warp and weft directions, and the coating resin is fixed in a state in which it is in contact with the intersection. In the case of a woven fabric, at least one sheath-core yarn as described above can be arranged in each of the warp and weft yarns, and the above-described coating resin can be arranged around the outer periphery of the composite yarn at the intersection of the warp and weft yarns, thereby creating a woven sensing fabric having a sensing fiber member structure within the woven fabric. In this case, the two sheath-core yarns are arranged closely at the intersection of the warp and weft yarns, so that the sensing function described above is realized in this area, making it applicable as a sensing fiber member. Any shape of such a woven fabric can be used. This includes one aspect of the sensing fabric, which is another embodiment of the present invention, namely, a sensing fabric in which at least one sheath-core yarn, in which a sheath yarn is arranged around a core yarn that is a linear conductor, is arranged in each of the warp and weft yarns of the woven fabric, and a coating resin that is a pressure-sensitive material is arranged at the intersection of the sheath-core yarns arranged in the warp and weft yarns, and the coating resin is fixed in contact with the intersection. Similarly, in knitted fabrics and braided cords, at least one sheath-core yarn can be arranged in each of the warp and weft directions, and they can be used as sensing fabrics in the same way as woven fabrics. Specifically, in the case of warp knitted fabrics, there is a structure in which sheath-core yarns are arranged in each of multiple reeds and partially crossed, or there is a structure in which sheath-core yarns are arranged in both the warp and insertion yarns and crossed, in the case of weft knitted fabrics, there is a structure in which sheath-core yarns arranged at intervals are partially in contact with each other and crossed, and in the case of braided cords, there is a structure in which sheath-core yarns are arranged at intervals and braided to partially cross each other.

[0028] A third embodiment of the present invention is a sensing fiber member in which at least two coated-sheath-core structure yarns are arranged, in which a coating resin, which is a pressure-sensitive material, is disposed on the outer periphery of a core-sheath structure yarn, in which a sheath yarn is disposed around a core yarn, which is a linear conductor, and the coating resins are fixed in place in a state where they are in contact with each other when stress is applied. In the first or second embodiment of the present invention, at least two sheath-core yarns are arranged in proximity to each other via the sheath yarn, with a coating resin, which is a pressure-sensitive material, disposed around the outer periphery of the composite yarn, thereby securing the composite yarns to each other. In contrast, in the third embodiment of the present invention, at least two coated sheath-core yarns, each coated with a pressure-sensitive material, are arranged around a single sheath-core yarn. This includes a configuration in which the composite yarns themselves are not secured together when no stress is applied, but when stress is applied, the coating resins come into contact with each other and are secured together by the stress, thereby achieving sensing performance. That is, in the third embodiment, pressure is applied to the overlapping portion of the two sheath-core fibers during sensing, creating a state equivalent to when the sheath-core fibers are secured together in advance, thereby enabling performance similar to that of the first or second embodiment to be achieved. The arrangement of the at least two core-sheath structure yarns in this embodiment is not particularly limited as long as they satisfy the condition that they come into contact and are fixed when stress is applied. For example, as in the second embodiment, each covered sheath-core structure yarn can be arranged in the warp and weft directions of the fabric so that they partially intersect, or they can be arranged on a sheet or resin other than fabric, or they can be in a switch-like shape that comes into contact only when stress is applied.

[0029] The electrical properties between the two linear conductors of a pair of core-sheath yarns can be measured using an appropriate measurement system depending on the pressure-sensitive material used. When the pressure-sensitive material contained in the sheath yarn is a piezoelectric material, any measurement system capable of detecting the charge generated in response to the application of stress can be used. For example, a method can be used in which the current value between the two linear conductors is constantly monitored using a source meter or the like, and the current generated by the charge generated by the application of stress is detected. When using another example of a pressure-sensitive material, such as a material whose resistance value changes with pressure, a measurement system capable of reading the change in resistance between the two linear conductors can be used. [Example]

[0030] The following examples and comparative examples will be used to describe the present invention, but the present invention is not limited to these examples. As examples, examples relating to the sensing of contact with the sensing fiber will be presented as examples of the sensing fiber of this embodiment. The methods for measuring the respective property values ​​used in the following Examples and Comparative Examples are as follows.

[0031] <Measurement of contact sensing characteristics> The contact sensing characteristics were evaluated as follows. Two adjacent linear conductors were electrically disconnected at one end of the core-sheath yarn, and a constant voltage was applied to the other end, at which point the output current was monitored. The voltage application and current measurement were performed using a source meter (SMU: Source Measure Unit, Keithley 2614B), and the output current was constantly monitored using a homemade program. For the ply-twisted yarn, a sample was prepared in which the length of the paired linear conductors (the length at which sensing is effective) was 10 cm, and the sensing characteristics were measured.

[0032] <Applying pressure> The sensing fiber member was placed on a flat stage, and a load of 5 N was applied from above using a force gauge (manufactured by IMADA, full-range 20 N). The indenter used was a circular one with an insulating surface and a diameter of 12.5 mm.

[0033] <Evaluation criteria for contact sensing characteristics> The current value when a voltage of 3 V is applied between two linear conductors when there is no contact or load applied is defined as I0, and the difference between the current value when a load of 5 N is applied to the sensing fiber member using the above method and I0 is defined as ΔI.The absolute value of the change in current value |ΔI / I0| was evaluated using the following criteria. (Evaluation criteria) ◎: |ΔI / I0| is 30 or more. Good: |ΔI / I0| is 10 or more and less than 30. ×: |ΔI / I0| is less than 10.

[0034] [Example 1: Sheath yarn PLA + coating resin P (VDF / TrFE)] The linear conductor used was a conductive multifilament made of silver-plated nylon 66. The nylon fiber had a fineness of 220 dtex, and after silver plating, the fineness was 300 dtex, with 68 filaments. A double core-sheath structure yarn was produced using the above linear conductor as the core yarn and a fiber made of polylactic acid as the sheath yarn. The covering conditions were as follows: 280 dtex / 48 f multifilament polylactic acid fiber manufactured by NatureWorks was used as the sheath yarn, and two bobbins were used, each Z-twisted to a twist of 732 T / m. The two obtained double core-sheath structure yarns were further S-twisted together to produce a ply yarn with a twist of 170 T / m. The fineness of this insulating fiber was 2000 dtex. The twist factor K of this ply yarn was = (300 + 252 × 2) 1 / 2 ×732=20756. The above plied yarn was impregnated in a vinylidene fluoride (VDF) / trifluoroethylene (TrFE) copolymer (P(VDF / TrFE)) polymer solution and dried to prepare a sensing fiber fixed with a coating resin. Kureha KF-2 Polymer W2200P(VDF / TrFE) = 75 / 25 was used for the P(VDF / TrFE), which was dissolved in diethyl carbonate to prepare solutions with concentrations of 6.9 wt% and 10.1 wt%. The solution concentration was sufficient to fill the gaps between the two core-sheath yarns. The solution was heated and stirred overnight at a temperature between 88°C and 94°C. The solution was then returned to room temperature, and the above plied yarn was immersed in the solution, removed, and dried in a vacuum at 80°C for 10 hours at 10 hPa. This produced a plied yarn in which the sheath yarn was coated and fixed with the piezoelectric resin, with the piezoelectric resin impregnated between the sheath yarns. Figure 7 shows the change in current value when a load is applied to the ply-twisted yarn fixed with the piezoelectric resin obtained in this way.

[0035] [Example 2: PLA sheath yarn + PLA coating resin] Ply-twisted yarns were produced in the same manner as in Example 1, except that the coating resin was changed from P(VDF / TrFE) to PLA. Polylactic acid pellets manufactured by NatureWorks Inc. were dissolved in anhydrous tetrahydrofuran to prepare a solution with a concentration of 0.05 wt%, which was then heated to 65°C for approximately 4 hours to dissolve the solution, producing a polylactic acid solution. This solution was returned to room temperature, and the PLA-covered ply-twisted yarns described in Example 1 were immersed in the solution, removed, and air-dried to produce ply-twisted yarns coated with PLA resin. The change in current value when a load was applied to the ply-twisted yarns thus obtained, fixed with piezoelectric resin, is shown in Figure 8.

[0036] [Example 3: Sheath Polyester + Coating Resin P(VDF / TrFE)] Except for using a woolly yarn of polyethylene terephthalate (PET) 252 dtex / 108 filaments as the sheath yarn, a ply yarn coated with P(VDF / TrFE) was produced in the same manner as in Example 1. Figure 9 shows the change in current value when a load was applied to the ply yarn thus obtained and fixed with a piezoelectric resin.

[0037] [Example 4: Sheath Yarn Polyester + Coating Resin PLA] Except for using a woolly yarn of polyethylene terephthalate (PET) 252 dtex / 108 filaments as the sheath yarn, a ply-twisted yarn fixed with polylactic acid as the piezoelectric resin was produced in the same manner as in Example 2. Fig. 10 shows the change in current value when a load was applied to the ply-twisted yarn thus obtained fixed with the piezoelectric resin.

[0038] [Example 5: Sheath nylon thread + PLA coating resin] Except for using a multifilament made of 276 dtex / 96 f nylon as the sheath yarn, a ply yarn was produced in the same manner as in Example 2. Fig. 11 shows the change in current value when a load was applied to the ply yarn thus obtained and fixed with a piezoelectric resin.

[0039] [Comparative example: Polyester sheath yarn + olefin resin coating resin] A plied yarn was produced in which the gaps in the polyester sheath yarn used in Example 3 were fixed with ZEOCOAT (registered trademark) ES2110-10 (manufactured by Zeon Corporation), an olefin-based resin that does not exhibit piezoelectric properties. Fig. 12 shows the change in current value when a load was applied to the plied yarn thus obtained that was fixed with the resin.

[0040] The configurations and piezoelectric sensing characteristics of the sensing fiber members produced in Examples 1 to 5 and the Comparative Example are shown in Table 1 below. [Table 1]

[0041] Example 6: Sensing Fabric A plain-woven sensing fabric was obtained using the sensing fiber members obtained in Example 3 as part of the warp threads, with the remaining threads being made of 84 dtex, 36-filament polyester fiber in both the warp and weft directions, using a conventional weaving method. The fabric was 150 cm wide, with 30 sensing fiber members spaced 5 cm apart and 2.5 cm apart on both ends in the width direction. A 1-m-long section containing the fiber sensing members was cut from this fabric, and the sensing characteristics of all 30 sensing fiber members were measured at three random locations. The results confirmed that all of the piezoelectric sensing characteristics were rated as excellent.

[0042] Example 7: Sensing fiber member The linear conductor used was a conductive multifilament made of silver-plated nylon 66. The nylon fiber had a fineness of 220 dtex, and after silver plating, the fineness was 300 dtex, with 68 filaments. A double-core / sheath yarn was fabricated using the above linear conductor as the core yarn and a polylactic acid fiber as the sheath yarn. The covering conditions were two bobbins of NatureWorks polylactic acid fiber 280 dtex / 48 f multifilament as the sheath yarn, one of which was S-twisted and the other Z-twisted, with a twist of 732 T / m. Two sheath-core yarns with a resin coating were produced by impregnating each of the sheath-core yarns with a P(VDF / TrFE) resin under the same conditions as in Example 1 without plying them individually. These yarns were then crossed, and the two sheath-core yarns with resin coatings were arranged in close contact with each other at the crossing point. Sensing characteristics were measured at the crossing point, and it was confirmed that all of the piezoelectric sensing characteristics were rated as excellent.

[0043] Example 8: Sensing Fabric The linear conductor was made of nylon fiber with a fineness of 220 dtex, which after silver plating was 300 dtex, and 68 filaments. The sheath yarn was made of polyethylene terephthalate (PET) woolly yarn with 252 dtex / 108 filaments. The covering conditions were two bobbins, one of which was S-twisted and the other Z-twisted, with a twist of S and Z of 732 T / m. The resulting sheath-core yarns were used in some of the warp and weft yarns, while the remaining weft and warp yarns were made of 78 dtex, 34-filament nylon fibers. A plain-woven sensing fabric was obtained using a conventional weaving method. The fabric was 150 cm wide and featured six sensing fiber elements, three on each side of the warp and weft yarns spaced 5 cm apart. A 1-m-long section containing the fiber sensing elements was cut from the fabric. Nine intersections between the sheath-core yarns were impregnated with P(VDF / TrFE) resin, and the two linear conductors at the intersections were fixed with P(VDF / TrFE) resin. As described in Example 1, a 6.9 wt% P(VDF / TrFE) solution of Kureha KF-2 Polymer W2200P(VDF / TrFE) = 75 / 25 dissolved in diethyl carbonate was used to impregnate the intersections between the sheath-core yarns using a dip coater. A sensing fabric was produced by drying this under the same drying conditions as described in Example 1. The sensing characteristics were measured at all nine intersections, and it was confirmed that the piezoelectric sensing characteristics were all rated as excellent. [Industrial Applicability]

[0044] The contact-sensing fiber according to the present invention can be processed in long lengths, is highly mass-producible, and can be used as warp yarns for woven fabrics or warp knitting, and is significantly less expensive than conventional contact-sensing fiber components (piezoelectric yarns) that sense contact using piezoelectric materials. Specifically, the contact-sensing fiber according to the present invention does not require the special arrangement of piezoelectric materials required for conventional piezoelectric yarns (see FIG. 1 ). Load sensing is possible simply by using a sheath yarn made of a common fiber material, such as polyester or nylon, and securing it with a coating resin that is a piezoelectric or pressure-sensitive material. This allows for the production of a contact-sensing fiber at very low cost. Furthermore, the use of a core-sheath composite yarn manufacturing technique, such as covering technology, which is a fiber processing technique with established know-how, allows for long lengths to be processed, is highly mass-producible, and can produce textured yarns with a much better feel than piezoelectric yarns, facilitating processing into fiber components such as woven fabrics and knitted fabrics. The contact sensing fiber according to the present invention changes not only the capacitance but also the resistance, and therefore can detect the state in which a load is being continuously applied. Therefore, the contact sensing fiber member and sensing fabric of the present invention can be widely used in a variety of applications, including smart textile applications in which electrical functional elements are provided on a flexible and stretchable fiber substrate, such as rugs that can detect when stepped on, security mats that detect people entering and exiting, mats for counting people, sensors for biological signals such as pulse and heart rate, contact sensing woven and knitted fabrics, such as monitoring sensors in nursing and care settings, sensors that digitize and transmit tactile sensations in production sites such as factories, components for embedding sensors in vehicle seat belts, etc., such as embedding contact sensors (biological sensors) in vehicle seat belts, steering wheels, dashboards, etc., sensors for detecting human movement, and monitoring sensors. [Explanation of symbols]

[0045] 1. Conductive fiber 2. Piezoelectric materials 3 Conductors 4. Conventional piezoelectric yarn 5. Linear conductor as core thread 6. Sheath thread (piezoelectric or insulating material) 6' Pressure-sensitive coating resin 7. Core-sheath structure yarn 8 Ply-twisted yarn made by plying core-sheath yarn 9 Core yarn 10 spindles 11 Bobbin 12 Flyer 13 Flyer Cap 14 Sheath thread 15 Flyer Foot Guide 16 Flyer Foot Guide 17 Flyer Foot Guide 18 Flyer Foot Guide

Claims

1. A sensing fiber member in which at least two core-sheath structure yarns, each having a core yarn that is a linear conductor and a sheath yarn disposed around it, are arranged around the outer periphery of a composite yarn that is close to each other via the sheath yarn, and a coating resin that is a pressure-sensitive material is arranged around the outer periphery of the composite yarn, and the coating resin is fixed in contact with the composite yarn, and the sensing fiber member can sense the application of stress to the sensing fiber member by changes in the electrical properties between the linear conductors.

2. The sensing fiber according to claim 1 , wherein the sensing fiber detects contact of an object with the sensing fiber, or deformation of the sensing fiber by expansion, contraction, or bending.

3. The sensing fiber element according to claim 1 or 2, wherein the sheath yarn is an insulator or a piezoelectric material.

4. The sheath-core yarn has the following formula: Twist factor K = (SS + SC) 1 / 2 ×R 4. The sensing fiber element according to claim 1, wherein the twist coefficient K, expressed by the formula {where SS is the fineness (dtex) of the linear conductor as the core yarn, SC is the total fineness (dtex) of the sheath yarn as the sheath yarn, and R is the number of turns (twists) of the sheath yarn (turns / m)}, is 7,000 or more and 30,000 or less.

5. A sensing fiber member described in any one of claims 1 to 4, wherein the core-sheath structure yarn is a double core-sheath structure yarn in which two sheath yarns are wrapped around a linear conductor serving as a core yarn, and the winding directions of the two sheath yarns are the same.

6. A sensing fiber element according to any one of claims 1 to 5, wherein the linear conductor serving as the core thread is a multifilament conductive fiber.

7. A sensing fiber member as described in any one of claims 1 to 6, wherein the two core-sheath structure yarns arranged close to each other have the same winding direction of the sheath yarn, and the two core-sheath structure yarns are twisted in the opposite direction to the winding direction of the sheath yarn, and the twisted yarns are fixed by a coating resin.

8. The sensing fiber element according to any one of claims 1 to 7, wherein the sheath yarn is made of spun yarn.

9. A sensing fabric in the form of a woven fabric, knitted fabric or braided cord, on which the sensing fiber member according to any one of claims 1 to 8 is arranged.

10. A sensing fabric in which at least one core-sheath structure yarn, in which a sheath yarn is provided around a core yarn that is a linear conductor, is arranged in each warp and weft directions of the fabric, and a coating resin that is a pressure-sensitive material is arranged at the intersection of the core-sheath structure yarns arranged in the warp and weft directions, and the coating resin is fixed in a state in which it is in contact with the intersection.

11. A sensing fiber member in which at least two coated sheath-core structure yarns are arranged, in which a coating resin, which is a pressure-sensitive material, is arranged on the outer periphery of a core-sheath structure yarn in which a sheath yarn is arranged around a core yarn, which is a linear conductor, and the coating resins are fixed in a state where they are in contact with each other when stress is applied.

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