Conductive fibers, and textile products and electrical / electronic devices using the same

Abstract

To provide a fiber having both of conductivity and flexibility, and fiber products and electric and electronic apparatuses including the same.SOLUTION: A conductive fiber has a hollow cross section and contains liquid metal of 40°C or lower.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a conductive fiber that combines conductivity and flexibility, and to a textile product and an electric / electronic device that uses the same. [Background technology]

[0002] In recent years, there has been growing demand for smart textiles, which are knitted or woven textiles that incorporate electronic components such as various devices, sensors, and IC chips. These smart textiles can be designed to suit various purposes, from sports to medical applications, and are therefore expected to be worn in a variety of situations.

[0003] Smart textiles incorporating these electronic components require low-resistance electrical wiring to transmit the electricity that powers the devices and to transmit electrical signals from sensors. While ordinary copper wires are used for this electrical wiring, they are sufficiently conductive for power transmission and signal transmission. However, due to their lack of flexibility, they are unable to adapt to deformations such as bending and stretching of textiles. Therefore, for example, incorporating copper wires into clothing can cause discomfort and hinder human movement, creating a demand for materials that combine conductivity and flexibility.

[0004] Against this background, various technologies have been investigated to impart flexibility and electrical property stability against deformation to conductive fibers. For example, a stretchable core-sheath composite fiber (see Patent Document 1) in which a conductive layer made of copper iodide is formed near the inside of the surface side of a stretchable fiber made using an elastomer, and a technology in which conductive fibers are formed into a spring shape and given high stretchability to produce highly stretchable conductive wiring with excellent durability (see Non-Patent Document 1) have been proposed.

[0005] Furthermore, as a method for imparting electrical conductivity to synthetic fibers having crimps, a composite fiber has been proposed in which a conductive layer containing carbon black and a non-conductive layer having fiber-forming properties form a side-by-side or eccentric core-sheath composite, and the conductive layer forms at least a part of the fiber surface (see Patent Document 2).

[0006] Another technique proposed involves immersing a strand of filaments in a liquid metal bath to coat them. This involves a composite reinforcing insert (see Patent Document 3), which has a metal reinforcing layer covering a strand of filaments made of a metal alloy wound helically around a central fiber. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-209481 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-46785 [Patent Document 3] Special Publication No. 2016-536479 [Non-patent literature]

[0008] [Non-Patent Document 1] [online], February 25, 2015, National Institute of Advanced Industrial Science and Technology, retrieved July 5, 2021, Internet<URL:https: / / www.aist.go.jp / aist_j / press_release / pr2015 / pr20150225 / pr20150225.html> Summary of the Invention [Problem to be solved by the invention]

[0009] The technology of Patent Document 1 is said to produce a sheath-core composite fiber with stretchability and stable electrical properties by imparting conductivity to the sheath of the sheath-core composite fiber using two different types of elastomers. However, with the technology of Patent Document 1, the conductive layer is a thin film relative to the fiber diameter, so the fiber diameter needs to be thicker to achieve sufficient conductivity for power transmission and signal transmission. In addition, the elastic behavior unique to elastomers generates repulsive forces at bent and stretched parts, which causes an uncomfortable feeling when the sheath-core composite fiber is incorporated into clothing.

[0010] The technology in Non-Patent Document 1 claims that conductive fibers with excellent stretchability and durability can be obtained by forming the conductive fibers into a spring shape. However, the outer diameter of the spring-shaped fiber bundle is large, and the elastic behavior of the spring-shaped structure generates a repulsive force at the bent or stretched parts, which creates a problem of discomfort when this conductive fiber is incorporated into clothing.

[0011] The technology of Patent Document 2 claims that a core-sheath type composite fiber with excellent elasticity can be obtained by forming a crimped fiber having a conductive layer containing carbon black. However, the volume resistivity of the obtained fiber is 1×10 -1 The electrical conductivity is high at over Ω·cm, which is insufficient for use in transmitting electricity or transmitting signals from sensors. In addition, the electrical conductivity is due to the dispersibility of the carbon black, which tends to result in large variations in resistance values, making it difficult to ensure sufficient stability of electrical properties.

[0012] The technology in Patent Document 3 is said to produce a composite reinforced fiber by immersing a strand of a core fiber in a liquid metal bath and coating it. However, although sufficient conductivity can be obtained by coating with metal, the material filled in the liquid metal bath contains titanium or aluminum, so the coating layer lacks flexibility and has difficulty following deformations such as bending and stretching of the textile. This creates an uncomfortable feeling when incorporated into clothing and hinders human movement.

[0013] Therefore, an object of the present invention has been made in consideration of the above circumstances, and is to provide a conductive fiber that combines conductivity and flexibility, and a textile product or an electric / electronic device using the same. [Means for solving the problem]

[0014] As a result of further investigations, the inventors have found that for conductive fibers used in smart textiles incorporating electronic components for transmitting electricity and transmitting signals from sensors, it is important that the fibers have high conductivity and stable electrical properties against deformation, as well as excellent flexibility so that they can follow the movement of the textile without causing any discomfort.

[0015] That is, it is achieved by one of the following means: (1) A hollow cross section containing a liquid metal with a melting point of 40°C or less. The liquid metal is gallium alone or a gallium alloy. Conductive fiber. (2) The conductive fiber according to (1) above, characterized in that the area of ​​the hollow portion is 10 to 98% of the cross-sectional area of ​​the fiber. (3) The conductive fiber according to (1) or (2) above, characterized in that the primary yield point elongation is 5 to 300%. (4) The conductive fiber according to any one of (1) to (3) above, characterized in that the fiber diameter is 5 to 5000 μm. (5) Volume resistivity is 1×10 -7 ~1×10 -1 The conductive fiber according to any one of (1) to (4) above, characterized in that the resistivity is Ω·cm. (6) The conductive fiber according to any one of (1) to (5) above, characterized in that at least one of the fiber ends is provided with a liquid sealing portion that suppresses the outflow of liquid metal. (7) The conductive fiber according to any one of (1) to (6) above, characterized in that it is provided with conductive parts at at least two points that come into contact with the liquid metal and conduct electricity. (8) The conductive fiber according to (7) above, characterized in that the liquid sealing portion and the conductive portion are integrated. (9) A textile product at least partly made of the conductive fiber according to any one of (1) to (8) above. (10) An electric or electronic device at least partly made of the conductive fiber according to any one of (1) to (8) above. [Effects of the Invention]

[0016] According to the present invention, it is possible to obtain a conductive fiber having both conductivity and flexibility, and a textile product or an electric / electronic device using the conductive fiber. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is an SEM observation image of a cross section of a conductive fiber of Example 1, which is one embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram of how to determine the primary yield point elongation in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The conductive fiber of the present invention has a hollow cross section and contains a liquid metal with a melting point of 40° C. or less. The components thereof will be described in detail below, but the present invention is not limited to the scope described below as long as it does not deviate from the gist of the invention.

[0019] [Conductive fiber] It is important that the conductive fiber of the present invention has a hollow cross section and contains liquid metal with a melting point of 40°C or lower inside. By continuously filling the interior (i.e., the hollow portion in the hollow cross section) with liquid metal in the fiber axial direction, it is possible to reduce the volume resistivity of the fiber, thereby obtaining a conductive fiber with electrical conductivity. Furthermore, since the liquid metal has a melting point of 40°C or lower, the fiber remains in a liquid metal state and has fluidity at temperatures at least above 40°C. Therefore, the liquid metal can be uniformly present inside, resulting in excellent uniformity of electrical conductivity along the fiber axial direction. Furthermore, even when the fiber is subjected to deformation such as bending or stretching, the liquid metal can be deformed so that it is uniformly present inside in response to the deformation, resulting in excellent uniformity of electrical conductivity along the fiber axial direction even after deformation. In addition, unlike metal materials such as copper, aluminum, and stainless steel that are commonly used in metal wires, the conductive fiber of the present invention is a liquid metal with a melting point of 40°C or lower, and therefore is a flexible fiber that easily follows deformations such as bending and stretching. Therefore, when the conductive fiber of the present invention is incorporated into textile products or electrical / electronic devices, it allows for flexible movement, and in particular, when it is incorporated into textiles such as clothing, it is less likely to cause discomfort and inhibits human movement, making it possible to obtain a conductive fiber that is highly comfortable to wear.

[0020] The liquid metal in the present invention is not particularly limited as long as it has a melting point of 40° C. or less, but is preferably mercury, gallium, cesium, or rubidium, which are metals having a melting point of 40° C. or less. Among these, gallium is preferably used from the viewpoint of safety to the human body, such as toxicity and radioactivity.

[0021] The liquid metal in the present invention may be the above liquid metal alone, or an alloy obtained by mixing the liquid metal with other metals may be used. For example, it is known that an alloy of 68.5% gallium, 21.5% indium, and 10.0% tin can lower the melting point from 29.8°C of gallium alone to -19.0°C. When such a gallium alloy is used in the conductive fiber of the present invention, flexibility can be maintained even at lower temperatures, which is preferable.

[0022] Considering that the conductive fiber of the present invention is used for textile products, particularly clothing, it is more preferable that the melting point of the liquid metal is room temperature (25° C.) or lower.

[0023] The liquid metal in the present invention may be a slurry containing conductive metal particles or non-conductive particles such as ores or resins to control the volume resistivity of the conductive fibers. If these particles have a lower volume resistivity than the liquid metal, the volume resistivity can be lower than when the liquid metal is used alone, thereby reducing power loss during power transmission and signal transmission. Examples of such particle materials include metal particles of gold, silver, copper, aluminum, potassium, magnesium, rhodium, sodium, molybdenum, iridium, tungsten, cobalt, brass, zinc, beryllium, nickel, ruthenium, potassium, cadmium, osmium, indium, lithium, iron, platinum, tin, chromium, and palladium. Furthermore, if the particles have a higher volume resistivity than the liquid metal, the volume resistivity can be higher than when the liquid metal is used alone. Therefore, the conductive fibers can be used, for example, as heaters that utilize the thermal energy generated by passing an electric current through the conductive fibers. Examples of materials that can be used for such particles include inorganic oxides such as titanium oxide, silica, and barium oxide; carbon-based compounds such as carbon black and carbon nanotubes; and conductive polymers such as polyacetylene, polyaniline, polythiophene, and polypyrrole.

[0024] The conductive fiber of the present invention contains a liquid metal in the hollow of the hollow fiber, and the hollow fiber is preferably made of a thermoplastic polymer. By using a thermoplastic polymer for the hollow fiber, the melt spinning method can be used for production, which makes it easy to form the fiber into a fiber shape, and it is possible to obtain a conductive fiber that contains a liquid metal inside and has a uniform shape in the fiber axis direction.

[0025] Examples of thermoplastic polymers that can be used in the conductive fiber of the present invention include polyester polymers and copolymers thereof, such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyhexamethylene terephthalate; aliphatic polyester polymers and copolymers thereof, such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutyrate-polyhydroxyvalerate copolymer, and polycaprolactone; aliphatic polyamide polymers and copolymers thereof, such as polyamide 6, polyamide 66, polyamide 610, polyamide 10, polyamide 12, and polyamide 6-12; polyolefin polymers and copolymers thereof, such as polyethylene, polypropylene, polybutene, and polymethylpentene; and elastomer polymers, such as water-insoluble ethylene-vinyl alcohol copolymer polymers containing 25 mol% to 70 mol% of ethylene units, polystyrene-based, polydiene-based, chlorine-based, polyolefin-based, polyester-based, polyurethane-based, polyamide-based, and fluorine-based, among others, from which the polymer can be selected and used. Among these, polyester polymers and copolymers thereof, aliphatic polyamide polymers and copolymers thereof, and polyolefin polymers and copolymers thereof are preferably used because of their excellent mechanical properties and durability, with polyethylene terephthalate, polyamide 6, polyamide 66, and polypropylene being particularly preferred. Furthermore, elastomeric polymers are preferably used because of their excellent stretch recovery, with polyurethane elastomers being particularly preferred. These thermoplastic polymers may be used alone or in combination of two or more.

[0026] The conductive fiber of the present invention may contain various additives in the thermoplastic polymer, such as inorganic oxides such as titanium oxide, silica, and barium oxide, carbon-based compounds such as carbon black and carbon nanotubes, metal particles such as gold, silver, and copper, colorants such as dyes and pigments, flame retardants, fluorescent brighteners, antioxidants, and ultraviolet absorbers, as long as the effects of the present invention are not impaired.

[0027] The hollow cross-section fiber of the present invention is not particularly limited in terms of the cross-sectional shape of the fiber as long as it has a hollow portion, and can be appropriately selected depending on the application and required properties. It may have a circular cross-section or a non-circular cross-section. Specific examples of non-circular cross-sections include, but are not limited to, multi-lobal, polygonal, flat, and elliptical. Furthermore, the circular cross-section may be a concentric hollow type in which the hollow portions are arranged concentrically, or an eccentric hollow type in which the hollow portions are arranged eccentrically. Furthermore, the cross-section may be a multi-hollow type having multiple hollow portions. Whether there is one hollow portion or multiple hollow portions, the shape of the hollow portion in the fiber cross-section is not particularly limited, and it may have a circular cross-section or a non-circular cross-section. Specific examples of non-circular cross-sections include, but are not limited to, multi-lobal, polygonal, flat, and elliptical.

[0028] In the conductive fiber of the present invention, the area of ​​the hollow portion is preferably 10 to 98% of the cross-sectional area of ​​the fiber. By making the area of ​​the hollow portion preferably 10% or more of the cross-sectional area of ​​the fiber, more preferably 20% or more of the cross-sectional area of ​​the fiber, and even more preferably 30% or more of the cross-sectional area of ​​the fiber, a certain amount or more of liquid metal can be contained, and the fiber can be made conductive. Furthermore, by making the area of ​​the hollow portion preferably 98% or less of the cross-sectional area of ​​the fiber, more preferably 90% or less of the cross-sectional area of ​​the fiber, and even more preferably 80% or less of the cross-sectional area of ​​the fiber, the proportion of the hollow portion containing the liquid metal in the cross section is reduced, and mechanical properties such as strength are improved.

[0029] The conductive fiber of the present invention preferably has a primary yield elongation of 5 to 300%. By setting the primary yield elongation to preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more, the fiber becomes flexible and easily adapts to deformations such as bending and stretching, allowing for flexible movement when incorporated into textile products or electrical and electronic devices. In particular, when incorporated into textiles such as clothing, the conductive fiber does not cause discomfort and does not hinder human movement, resulting in a conductive fiber with excellent wearing comfort. Furthermore, by setting the primary yield elongation to preferably 300% or less, more preferably 250% or less, and even more preferably 200% or less, it is possible to suppress changes in resistance during stretching.

[0030] The primary yield point elongation in the present invention is calculated as the elongation at the primary yield point, which is obtained by setting a conductive fiber, which has been sealed with an adhesive so as to cover both openings at the fiber end (described later), without applying tension, using a Tensilon tensile tester, and measuring the stress-strain curve under conditions of a sample length of 200 mm and a tensile speed of 200 mm / min (see Figure 2), with five measurements per level being made and the arithmetic average value being determined.

[0031] The conductive fiber of the present invention has a volume resistivity of 1×10 -7 ~1×10 -1 The volume resistivity is preferably 1×10 -7 Ω·cm or more, preferably 1×10 -6 By making the volume resistivity at least Ω·cm, the proportion of the core component containing the liquid metal in the cross section of the conductive fiber is substantially reduced, and mechanical properties such as strength are improved. -1 Ω·cm or less, preferably 1×10 -2 Ω·cm or less, more preferably 1×10 -3 Higher conductivity can be achieved by keeping the electrical resistance at Ω·cm or less.

[0032] The conductive fiber of the present invention preferably has a liquid sealing portion at at least one of the fiber ends to prevent the liquid metal inside from leaking out of the fiber ends. The liquid sealing portion may be in any form as long as it can close the opening (hollow portion) at the fiber end of the conductive fiber by injecting a fluid resin or adhesive into the opening at the fiber end of the conductive fiber and then solidifying it, applying a resin or adhesive to cover the opening at the fiber end, inserting a solid material such as a metal, resin, or mineral into the opening at the fiber end, or twisting, tying, or crushing the conductive fiber itself. In this way, the liquid metal can be prevented from leaking out of the fiber end of the conductive fiber.

[0033] Examples of resins used for the liquid sealing portion include, but are not limited to, epoxy resin, urethane resin, modified silicone, polyester resin, nylon resin, polypropylene resin, polystyrene resin, and polylactic acid.

[0034] The adhesive used for the liquid sealing portion may be inorganic, organic, natural, or synthetic, but is not limited to these.

[0035] Examples of metals used for the liquid sealing portion include gold, silver, copper, aluminum, potassium, magnesium, rhodium, sodium, molybdenum, iridium, tungsten, cobalt, brass, zinc, beryllium, nickel, ruthenium, potassium, cadmium, osmium, indium, lithium, iron, platinum, tin, chromium, and palladium. From the viewpoint of corrosion resistance, however, gold or silver alone, or the above metals plated with gold or silver, are preferred.

[0036] The conductive fiber of the present invention preferably has at least two conductive parts that contact the liquid metal inside the conductive fiber from the outside to pass electricity. The conductive parts may be in any form that allows electricity to pass from the outside to the liquid metal inside the conductive fiber, such as penetrating the surface layer of the conductive fiber to pass electricity to the liquid metal inside, or in any form that allows electricity to pass electricity to the liquid metal inside the conductive fiber from the outside, such as passing electricity through an opening at the fiber end of the conductive fiber to pass electricity to the liquid metal inside.

[0037] The conductive portion may be made of any conductive material, such as gold, silver, copper, aluminum, potassium, magnesium, rhodium, sodium, molybdenum, iridium, tungsten, cobalt, brass, zinc, beryllium, nickel, ruthenium, potassium, cadmium, osmium, indium, lithium, iron, platinum, tin, chromium, or palladium, or a carbon-based material such as carbon, graphene, fullerene, or carbon nanotubes. Resins containing these metals or carbon-based particles may also be used to achieve conductivity. When using these metals, it is preferable to use gold or silver alone, or to plate the metals with gold or silver, in terms of corrosion resistance.

[0038] In the present invention, the liquid sealing portion and the current-carrying portion may be integrated. For example, two cylindrical metal pieces having a diameter approximately equal to the diameter of the hollow portion of the conductive fiber are prepared, and are inserted into the openings at both ends of the fiber end of the conductive fiber until they come into contact with the liquid metal. This allows current to flow while preventing the internal liquid metal from leaking out of the fiber end, and as a result, current can be passed between the cylindrical metal pieces at both ends through the liquid metal. As the cylindrical metal pieces, the materials described above as the materials for the current-carrying portion can preferably be used.

[0039] In the present invention, the resistance value, resistivity, and volume resistivity are determined as follows. (1) Fix the conductive fiber in a state where it is stretched without tension or at an arbitrary elongation rate, and set the probe of a resistance meter set to the resistance measurement range so that it comes into contact with the liquid metal inside the conductive fiber, and measure the resistance value (Ω). (2) Divide the resistance value (Ω) obtained in (1) above by the fiber length (cm) to determine the resistivity (Ω / cm). (3) The resistivity (Ω / cm) obtained in (2) above is multiplied by the cross-sectional area (cm) of the conductive fiber measured by the method described below. 2 ) to find the value. (4) The above measurement is carried out five times for each level, changing the measurement location, and the arithmetic mean value is the volume resistivity (Ω·cm).

[0040] In the conductive fiber of the present invention, if the volume resistivity of the liquid metal is known, the resistance value of the conductive fiber can be calculated mathematically.

[0041] The volume resistivity of the liquid metal is ρ [Ω cm], the length is L [cm], and the cross-sectional area of ​​the enclosed liquid metal is S [cm 2 ], the resistance value R [Ω] of the conductive fiber can be calculated using equation (1). R=ρ×L / S (1)

[0042] The resistance value of the conductive fiber of the present invention changes as the conductive fiber is stretched. This can be explained using the above formula (1). When the fiber length is stretched twice, L [cm] doubles, and S [cm 2 ] becomes 1 / 2, so the resistance value R [Ω] becomes four times that before stretching. Therefore, it can be used as a sensor for stretching rate, taking advantage of the fact that the resistance value can be converted into the stretching rate simply by measuring the resistance value. On the other hand, since the resistance value changes depending on the stretching rate of the conductive fiber, when using conductive fiber for power transmission or signal transmission, it is necessary to ensure that the cross-sectional area of ​​the liquid metal is sufficient to maintain a sufficient resistance value even when stretched.

[0043] When the conductive fiber of the present invention is made into a multifilament, the total fineness is preferably 10 to 300,000 dtex. By making the total fineness preferably 10 dtex or more, more preferably 20 dtex or more, and even more preferably 30 dtex or more, the breaking strength of the fiber is high, resulting in a conductive fiber that is easy to process and has excellent durability during use. Furthermore, by making the total fineness preferably 300,000 dtex or less, more preferably 100,000 dtex or less, and even more preferably 10,000 dtex or less, the conductive fiber is flexible and easily follows deformations such as bending, allowing for flexible movement when incorporated into textile products or electrical and electronic devices. In particular, the conductive fiber is comfortable to wear even when incorporated into textiles such as clothing.

[0044] The total fineness in the present invention is determined by reeling in 100 m of conductive fiber, multiplying the mass of the skein by 100 to calculate the total fineness (dtex), measuring five times per level, and calculating the arithmetic average value. If the conductive fiber is shorter than 100 m or cannot be reeled in, the length (m) and mass (g) of the conductive fiber may be measured, and the total fineness (dtex) may be calculated by mass (g) ÷ length (m) × 10,000.

[0045] The conductive fiber of the present invention preferably has a fiber diameter of 5 to 5,000 μm. By setting the fiber diameter to preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, the strength of the fiber is increased, reducing thread breakage due to abrasion such as friction, resulting in a conductive fiber with good processability and excellent durability during use. Furthermore, by setting the fiber diameter to preferably 5,000 μm or less, more preferably 3,000 μm or less, and even more preferably 1,000 μm or less, the fiber becomes flexible and easily conforms to deformations such as bending, allowing for flexible movement when incorporated into textile products or electrical and electronic devices. In particular, when incorporated into textiles such as clothing, the conductive fiber provides a natural feeling of discomfort and excellent wearing comfort.

[0046] In the present invention, the cross-sectional area, fiber diameter, and hollow area are determined as follows. (1) A single fiber is cut perpendicular to the fiber axis, and an image is taken using a scanning electron microscope at a magnification that allows the entire cross section of the single fiber to be observed. (2) Using image analysis software, the cross-sectional area (cm) formed by the cross-sectional contour of the single fiber was calculated for the captured image. 2 ) and measure this cross-sectional area (cm 2 ) and calculate the diameter (μm) of a perfect circle that has the same area as the (3) The measurement is carried out at 20 randomly selected locations, and the arithmetic mean value is taken as the fiber diameter (μm). (4) Using image analysis software, the area of ​​the hollow space (cm) formed by the interface between the inner wall of the hollow space of the single fiber and the liquid metal was calculated for the above-mentioned photographed image. 2 ) is measured.

[0047] The conductive fiber of the present invention preferably has a breaking strength of 1.0 cN / dtex or more. By making the breaking strength preferably 1.0 cN / dtex or more, more preferably 1.5 cN / dtex or more, and even more preferably 2.0 cN / dtex or more, yarn breakage during post-processing steps such as weaving and knitting, and when incorporated into electrical and electronic devices is reduced, and yarn breakage during use of the textile products and electrical and electronic devices is also reduced, resulting in a conductive fiber with good processability and excellent durability during use. On the other hand, there is no particular upper limit to the breaking strength in the present invention, but a practical upper limit is about 10.0 cN / dtex.

[0048] The breaking strength in the present invention is determined based on the tensile strength and elongation percentage specified in JIS L 1013:2010 8.5, in which a conductive fiber is set without tension, with an adhesive applied to cover and seal both openings at the fiber end as described above, and the strength (cN) at break is measured under conditions of a sample length of 200 mm and a pulling speed of 200 mm / min, and the strength (cN / dtex) is calculated by dividing by the total fineness (dtex), and the measurement is carried out five times per level, and the arithmetic average value is calculated.

[0049] The conductive fiber of the present invention preferably has a breaking elongation of 15 to 500%. By setting the breaking elongation to preferably 15% or more, more preferably 20% or more, and even more preferably 30% or more, yarn breakage during post-processing steps such as weaving and knitting, and when incorporated into electrical and electronic devices is reduced, and yarn breakage during use of textile products and electrical and electronic devices is also reduced, resulting in a conductive fiber with good processability and excellent durability during use. Furthermore, by setting the breaking elongation to preferably 500% or less, more preferably 450% or less, and even more preferably 400% or less, the fiber is less likely to undergo plastic deformation when stretched, resulting in a conductive fiber with excellent durability during use.

[0050] The breaking elongation in the present invention is determined by measuring the elongation (%) at break of a conductive fiber that has been sealed with an adhesive so as to cover both openings at the fiber end as described above, in accordance with the tensile strength and elongation percentage specified in JIS L 1013:2010 8.5, without applying tension, under conditions of a sample length of 200 mm and a pulling speed of 200 mm / min, with five measurements per level, and calculating the arithmetic average value.

[0051] The conductive fiber of the present invention preferably has a 10% modulus of 1.50 cN / dtex or less. By setting the 10% modulus to preferably 1.50 cN / dtex or less, more preferably 1.00 cN / dtex or less, and even more preferably 0.50 cN / dtex or less, the stress generated by deformation is reduced, resulting in a conductive fiber with excellent flexibility. On the other hand, there is no particular lower limit for the 10% modulus in the present invention, but 0.00 cN / dtex is a substantial lower limit.

[0052] The 10% modulus in the present invention is determined by measuring the stress (cN / dtex) when a conductive fiber, which has been sealed with an adhesive so as to cover both openings at the fiber end as described above, is set without applying tension and stretched by 10% under conditions of a sample length of 200 mm and a pulling speed of 200 mm / min, based on the tensile strength and elongation percentage specified in JIS L 1013:2010 8.5, with the stress measured five times per level, and then calculating the arithmetic average value.

[0053] The conductive fiber of the present invention has excellent flexibility in addition to high conductivity and stability of electrical properties against deformation, and these characteristics can be utilized to find a variety of applications, such as antistatic materials for clothing such as stockings, tights, and dustproof clothing, textiles such as curtains, or carpets and mats for indoor and outdoor use, as well as in vehicles, and flooring materials. The conductive fiber is particularly suitable for smart textiles, such as those for transmitting electricity as a driving source for devices incorporated into the fabric and transmitting electrical signals from sensors. Furthermore, by incorporating the conductive fiber of the present invention into parts of electrical and electronic devices that require movements such as expansion and contraction, the fiber can be used favorably for transmitting electricity and transmitting electrical signals from sensors, and the conductive fiber itself can be used as a sensor, heater, etc.

[0054] The conductive fiber of the present invention uses a liquid metal with a melting point higher than the ambient temperature, allowing it to be made into a textile that can be freely reshaped using a heat source such as body heat or a hair dryer, and then maintains its shape by lowering the ambient temperature below the melting point of the liquid metal. This property can be used to create objects whose shapes can be freely changed, or screens that can be spread out into a flat surface when needed.

[0055] [Textile products] The textile product of the present invention is at least partially composed of the conductive fiber of the present invention. Examples of textile products include textiles such as woven fabrics and knitted fabrics, as well as clothing sewn from such textiles. By including the conductive fiber of the present invention at least in part, the textile or clothing can be made to have excellent wearing comfort, with no or little discomfort when worn.

[0056] The clothing of the present invention refers to an article worn to cover the body partially or entirely, and includes not only tops and bottoms, or clothing such as kimonos and coveralls, but also hats, gloves, socks, etc. Among these, application to smart textiles, which are clothing incorporating electronic components such as various devices, sensors, and IC chips, is more preferable, since it makes it possible to fully utilize the characteristics of the conductive fiber of the present invention, such as high conductivity, stable electrical properties against deformation, and flexibility.

[0057] For example, when the conductive fiber of the present invention is applied to smart textiles, unlike ordinary metal wires such as copper, aluminum, and stainless steel, the high flexibility resulting from the fiber material and the liquid metal interior allows it to easily follow deformations such as bending and stretching, causing no or little discomfort when worn, and inhibiting human movement, resulting in smart textiles with excellent wearing comfort. Furthermore, the conductive fiber of the present invention has a lower volume resistivity than fibers containing carbon black, making it possible to transmit electricity that powers devices and transmit electrical signals from sensors, as well as having excellent electrical property stability against deformation. Therefore, the conductive fiber of the present invention can be applied to smart textiles for a variety of applications.

[0058] The clothing of the present invention is suitable when the conductive fiber is used for transmitting electricity, because the surface component material is non-conductive, which can prevent electric shock and leakage when worn.

[0059] [Electrical and electronic equipment] The electrical and electronic devices of the present invention are at least partially composed of the conductive fiber of the present invention. By including the conductive fiber of the present invention at least in part, the electrical and electronic devices can smoothly perform operations such as bending and stretching, and have excellent stability of electrical properties against deformation.

[0060] The conductive fiber of the present invention is capable of transmitting electricity and transmitting electrical signals from sensors, and also has excellent stability of electrical properties against deformation, making it applicable to a variety of electrical and electronic devices that require movements such as bending and stretching.

[0061] When the conductive fiber is used for transmitting electricity, the electrical and electronic devices of the present invention are suitable because the surface component material is non-conductive, which can prevent leakage of electricity.

[0062] The conductive fiber of the present invention can be bundled and used. The fibers can be bundled into a compact form using a doubled / twisted yarn, a covered yarn, a braided cord, or the like, which is preferable because it improves handling and makes the fibers easier to handle. Furthermore, by using the conductive fiber as the warp and / or weft of a woven fabric, the fabric can be used as a flat cable, and by using conductive fiber for both the warp and weft, a matrix-shaped flat cable can be produced.

[0063] [Conductive fibers, and methods for manufacturing textile products and electrical and electronic devices] Next, a preferred embodiment for producing the conductive fiber of the present invention will be specifically described.

[0064] The method for producing the fiber of the present invention can be selected from melt spinning, solution spinning, etc., but it is preferable to apply melt spinning because it has a small environmental impact and is easy to produce.

[0065] The thermoplastic polymer used in the present invention is preferably dried before spinning to prevent water contamination and remove oligomers, in order to improve spinnability. Drying conditions usually include vacuum drying at 80 to 200°C for 1 to 24 hours.

[0066] In melt spinning, a melt spinning method using an extruder such as a pressure melter type, single-screw extruder, or twin-screw extruder type can be applied. The extruded thermoplastic polymer passes through a pipe, is metered by a metering device such as a gear pump, passes through a filter to remove foreign matter, and is then guided to a spinneret and discharged with a hollow cross section.

[0067] When polyester or polyamide is used as the thermoplastic polymer, the temperature from the polymer pipe to the spinneret (spinning temperature) is preferably the melting point of the thermoplastic polymer + 20°C or higher to increase fluidity, and is preferably 320°C or lower to suppress thermal decomposition of the thermoplastic polymer.

[0068] The liquid metal used in the present invention can be melted by heating a container of solidified liquid metal using a band heater, a hot water bath, etc. After melting, it can be metered using a positive displacement pump such as a gear pump or a tube pump, or a syringe pump, and is guided through piping to a spinneret, where it is discharged while filling the interior of the thermoplastic polymer with the hollow cross section.

[0069] The melting temperature of the liquid metal is preferably the melting point of the liquid metal +20° C. or higher in order to increase fluidity.

[0070] The undrawn fibers discharged from the spinneret are preferably cooled and solidified by blowing cooling air (air). The temperature of the cooling air can be determined in consideration of the cooling efficiency and the balance with the cooling air speed, but a preferred embodiment is 30°C or less. By setting the temperature of the cooling air to 30°C or less, the solidification behavior due to cooling is stabilized, resulting in conductive fibers with highly uniform fiber diameters.

[0071] The undrawn fibers discharged from the spinneret may be introduced into a cooling bath and rapidly cooled. The temperature of the cooling bath is preferably 10 to 90°C. A cooling bath temperature of 10°C or higher is preferable because the fibers do not meander in the cooling bath and conductive fibers with a highly uniform fiber diameter can be obtained. On the other hand, a cooling bath temperature of 90°C or lower is preferable because the solidification behavior due to cooling is stable and conductive fibers with a highly uniform fiber diameter can be obtained. The cooling time can be adjusted appropriately depending on the discharge rate, take-up speed, etc.

[0072] The cooling bath coolant is a substance that can be easily removed from the fiber surface, does not cause physical or chemical changes to the fiber, and is liquid within the above-mentioned temperature range of the cooling bath, and can be used without any particular limitation. Specific examples of the cooling bath coolant include, but are not limited to, water, paraffin, ethylene glycol, glycerin, amyl alcohol, xylene, etc.

[0073] The cooling air is preferably blown in a direction substantially perpendicular to the undrawn fibers discharged from the spinneret. In this case, the speed of the cooling air is preferably 10 m / min or more from the viewpoints of cooling efficiency and fiber diameter uniformity, and is preferably 100 m / min or less from the viewpoint of spinning stability.

[0074] The cooled and solidified undrawn fibers may be directly wound up by a winder, or may be taken up by a roller (godet roller) rotating at a constant speed and then wound up by a winder.

[0075] The undrawn fiber thus obtained may be subjected to a drawing step after being taken up or taken up. Drawing is performed by running the fiber over a heated first roller or a heating device provided between the first and second rollers, such as a heating bath or a hot plate. Drawing conditions are determined by the mechanical properties of the undrawn fiber obtained, but the drawing temperature is determined by the temperature of the heated first roller or the heating device provided between the first and second rollers, and the draw ratio is determined by the ratio of the peripheral speeds of the first roller and the second roller.

[0076] Furthermore, after passing through the second roller, the drawn fiber can be heat-set by heating it with a heated third roller or a heating device installed between the second and third rollers. Heat-setting promotes crystallization, resulting in a conductive fiber with excellent shape stability.

[0077] The conductive fiber obtained by the above manufacturing method is incorporated into textiles such as woven fabrics and knitted fabrics. When incorporated into woven or knitted fabrics, the conductive fiber of the present invention may be used for some or all of the fibers used in the manufacturing process, or the conductive fiber of the present invention may be sewn into a greige or knitted fabric made of other fibers. The textile (woven or knitted fabric) obtained in this manner is used to sew the garment of the present invention. Another method is to directly sew the conductive fiber of the present invention into the garment. Furthermore, when the conductive fiber of the present invention is incorporated into electrical or electronic devices, methods similar to those used for ordinary electrical wiring such as copper wire can be used. [Example]

[0078] Next, the present invention will be described in detail based on examples. However, the present invention is not limited to these examples. In addition, in measuring each physical property, unless otherwise specified, the measurement was performed according to the above-mentioned method.

[0079] (1) Fiber diameter, cross-sectional area, hollow area Images of single fibers were taken using a scanning electron microscope "S-5500" manufactured by Hitachi High-Technologies Corporation at a magnification that allowed the entire cross section of the single fiber to be observed. Then, measurements were carried out as described above using image analysis software "WinROOF2015" manufactured by Mitani Shoji Co., Ltd.

[0080] (2) Elongation rate The elongation rate was calculated by measuring the length of the conductive fiber when no tension was applied and when it was stretched to an arbitrary elongation rate using an ABS Digimatic Caliper "CD-20-AX" manufactured by Mitutoyo Corporation.

[0081] (3) Resistance, resistivity, volume resistivity The resistance value was measured as described above using a resistance meter "RM3544" manufactured by Hioki E.E. Corp. The resistivity and volume resistivity were calculated as described above.

[0082] (4) Primary yield point elongation The primary yield elongation was measured as described above using a Tensilon tensile tester for conductive fibers in which an adhesive was applied so as to cover and seal the openings at both ends of the fiber.

[0083] [Example 1] A spinneret with a cylindrical structure (so-called core-sheath structure) was designed and fabricated. The thermoplastic polymer for the hollow cross-section conductive fiber was "Lycra" T-127 polyurethane manufactured by Toray Opelontex Co., Ltd., and the liquid metal was gallium melted in a 50°C water bath for 1 hour. Melt spinning was performed at a spinning temperature of 220°C. During melt spinning, polyurethane was metered using a gear metering method, and gallium was metered using a syringe pump and introduced to the spinneret. The spinneret nozzle then discharged polyurethane and gallium at a single fiber output volume of 1.6 mL / min and 1.6 mL / min, respectively. The fiber was wound on a winder at 20 m / min to obtain conductive fiber. Figure 1 shows an SEM image of the cross section of the resulting conductive fiber. The evaluation results are shown in Table 1.

[0084] [Example 2] Conductive fibers were obtained in the same manner as in Example 1, except that the single-hole discharge rates in the spinning step were set to 1.6 mL / min of polyurethane and 14.4 mL / min of gallium. The evaluation results of the obtained conductive fibers are shown in Table 1.

[0085] [Comparative Example 1] We designed and fabricated a core-sheath spinneret capable of discharging a cylindrical liquid metal and a polymer into the interior. Gallium, melted by standing in a water bath at 50°C for 1 hour, was used as the liquid metal for the conductive fibers. The thermoplastic polymer was a polyurethane called "Lycra" T-127 manufactured by Toray Opelontex Co., Ltd., and melt-spun at a spinning temperature of 220°C. During melt spinning, the gallium was metered using a syringe pump, and the polyurethane was metered using a gear-based metering method and introduced into the spinneret. The spinneret then discharged 1.6 mL / min of gallium and 1.6 mL / min of polyurethane into a single fiber. The fiber was then wound on a winder at 20 m / min to obtain conductive fibers. However, because the liquid metal was exposed on the surface of the conductive fibers, the fibers stuck together immediately after winding onto the bobbin, making unwinding from the bobbin difficult. Furthermore, the liquid metal adhered to the hands during the unwinding operation, causing the liquid metal to peel off from the fibers and break, making it impossible to evaluate.

[0086] [Table 1]

[0087] Table 1 shows the evaluation results for Examples 1 and 2. The conductive fibers obtained in Examples 1 and 2 were cut to 10 cm lengths in an unstretched state, and the measured resistance values ​​were 0.769 Ω and 0.085 Ω, respectively. The volume resistivity calculated from the fiber length and cross-sectional area of ​​the conductive fibers was 2.7 × 10 -5 Ω cm, 1.5 × 10 -5 The resistance and volume resistivity were sufficiently low for use in power transmission applications such as electrical wiring.

[0088] Furthermore, the resistance values ​​of the conductive fibers obtained in Examples 1 and 2, measured after stretching them 100% to a length of 20 cm, were 3.078 Ω and 0.342 Ω, respectively, and even when stretched 100%, the conductive fibers had a resistance value low enough for use in power transmission, such as electrical wiring. By stretching the conductive fibers 100% (doubling the length), the resistance value in both Examples 1 and 2 increased fourfold compared to the unstretched state. In other words, since the resistance value changes depending on the stretch rate, it is possible to convert the resistance value into the stretch rate simply by measuring the resistance value, and it was confirmed that the fibers can be used as a stretch rate sensor.

Claims

1. A conductive fiber having a hollow cross section and containing therein a liquid metal having a melting point of 40°C or less, the liquid metal being gallium alone or a gallium alloy.

2. 2. The conductive fiber according to claim 1, wherein the area of ​​the hollow portion is 10 to 98% of the cross-sectional area of ​​the fiber.

3. 3. The conductive fiber according to claim 1, wherein the primary yield point elongation is 5 to 300%.

4. The conductive fiber according to any one of claims 1 to 3, characterized in that the fiber diameter is 5 to 5000 µm.

5. Volume resistivity is 1 x 10 －７ ~1 x 10 －１ The conductive fiber according to any one of claims 1 to 4, characterized in that it has a resistivity of Ω·cm.

6. 6. The conductive fiber according to claim 1, wherein at least one of the fiber ends is provided with a liquid sealing portion that suppresses the outflow of liquid metal.

7. 7. The conductive fiber according to claim 1, characterized in that it is provided with conductive parts at at least two points that come into contact with the liquid metal and conduct electricity.

8. 8. The conductive fiber according to claim 7, wherein the liquid sealing portion and the conductive portion are integral with each other.

9. A textile product, at least a part of which is made of the conductive fiber according to any one of claims 1 to 8.

10. An electric or electronic device at least partly made of the conductive fiber according to any one of claims 1 to 8.

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