Conductive fiber and fiber structure including conductive fiber

Abstract

An objective of the present invention is to provide a conductive fiber which not only has excellent tensile strength, bending durability and corrosion resistance, but also in which the conductive fiber does not become magnetized and create a magnetic field disturbance, generate heat due to the magnetic field, attract iron powder, and the like. Another objective is to provide a fiber structure that includes the conductive fiber of the present invention and that has excellent flexibility.　The present invention relates to: a conductive fiber (1) including a liquid crystal polyester fiber (10) having a tensile strength of 18 cN / dtex or greater and a metallic foil (20) with a relative permeability of less than 3 spirally wound around the liquid crystal polyester fiber (10); and a fiber structure including the conductive fiber (1).

Description

Conductive fiber and fiber structure containing the conductive fiber Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2023-211647, filed December 15, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a conductive fiber and a textile structure containing the conductive fiber.

[0003] In recent years, advances in the miniaturization and weight reduction of optoelectronic devices have led to active development of smart textiles and wearable devices incorporating optoelectronic devices attached to fabrics. Conductive fibers used in smart textiles for electrodes, circuits, electrical wires, electromagnetic shielding, and other components are required to possess not only electrical conductivity but also durability against bending during use and tensile strength. In particular, smart textiles for electronic devices, medical and nursing care, and food applications require materials that are magnetized and do not cause magnetic field disturbances, magnetic field-induced heat generation, or iron powder adhesion. Furthermore, when used in devices that come into direct contact with the skin, such as electrodes for collecting biosignals, they must also be resistant to sweat corrosion and metal allergies.

[0004] For example, Patent Document 1 (JP 2023-32005 A) proposes a conductive fiber that combines conductivity and flexibility by using a conductive fiber containing liquid metal, and textile products or electrical / electronic devices that use the same.

[0005] Patent Document 2 (JP 2018-9259 A) proposes a sewing thread for machine sewing, which is a fiber structure that can replace the conductors that make up the electrical circuits of smart textiles, and is made by covering a core thread made of insulating coated plated wire or enameled wire with natural or synthetic fibers as a sheath thread and then plating the core thread with fibers as a sheath thread. Patent Document 3 (JP 2016-212960 A) discloses a conductive thread in which the surface of a high-strength fiber is plated with a metal.

[0006] Patent Document 4 (JP 2019-33809 A) proposes a wearable electrode in which a metal wire or a conductive thread coated with a metal or conductive polymer is fixed to a conductor made of a fiber structure coated with a conductive polymer.

[0007] Patent Document 5 (JP 2006-196232 A) discloses a tape-shaped conductor made of a plain weave using copper foil yarn, which is made by wrapping copper foil around high-strength fibers, as conductor wires.

[0008] JP 2023-32005 A JP 2018-9259 A JP 2016-212960 A JP 2019-33809 A JP 2006-196232 A

[0009] Patent Document 1 proposes a conductive fiber that combines conductivity and flexibility by using a conductive fiber containing liquid metal with a melting point of 40°C or less. However, there is a risk that the fiber may break during use as a smart textile, causing the liquid metal in the fiber to leak out and resulting in electrical problems.

[0010] Patent Document 2 discloses an insulating coated plated wire or metal wire as a linear conductor (conductive fiber) for the bobbin thread of a sewing thread, but when used as a sewing thread, the sheath thread is covered with non-conductive fibers, which not only poses the problem of insufficient conductivity when used as an electrode or circuit in a smart textile, but also has the risk of breakage due to insufficient tensile strength because short fibers are used for the sheath thread. Patent Document 3 proposes a conductive thread in which the surface of a high-strength fiber is copper-plated to solve the problem of insufficient tensile strength, but the copper-plated layer is prone to deterioration, so further bending durability is required.

[0011] Patent Document 4 discloses metal wires and conductive threads coated with metal or conductive polymers, but metal wires have insufficient bending durability, and conductive threads coated with metal or conductive polymers have the problem that the coated conductive material tends to peel off or fall off.

[0012] Patent Document 5 discloses a copper foil yarn in which copper foil is wrapped around aramid fiber, but since aramid fiber has hygroscopicity, there are cases in which copper corrodes.

[0013] The present invention solves the above problems and aims to provide a conductive fiber that not only has excellent tensile strength, flexural durability, and corrosion resistance, but also does not become magnetized, causing magnetic field disturbance, heat generation due to the magnetic field, adhesion of iron powder, etc. Another aim is to provide a fiber structure that contains the conductive fiber of the present invention and has excellent flexibility.

[0014] As a result of intensive research to achieve the above-mentioned object, the inventors of the present invention have found that a conductive fiber having a core yarn made of a liquid crystal polyester fiber with a tensile strength of 18 cN / dtex or more and a metal foil with a relative magnetic permeability of less than 3 spirally wound around this core yarn not only has excellent tensile strength, bending durability, and corrosion resistance, but also that the conductive fiber is not magnetized, and does not cause magnetic field disturbance, heat generation due to the magnetic field, or adhesion of iron powder, and further found that a fiber structure containing the conductive fiber of the present invention has excellent flexibility, which led to the completion of the present invention.

[0015] That is, the present invention can be configured in the following aspects. [Aspect 1] A conductive fiber comprising a liquid crystal polyester fiber having a tensile strength of 18 cN / dtex or more (preferably 20 cN / dtex or more, more preferably 22 cN / dtex or more), and a metal foil spirally wound around the liquid crystal polyester fiber and having a relative magnetic permeability of less than 3. [Aspect 2] The conductive fiber according to Aspect 1, wherein the metal foil is stainless steel. [Aspect 3] A fiber structure comprising the conductive fiber according to Aspect 1 or 2.

[0016] It should be noted that any combination of at least two elements disclosed in the claims and / or the specification and / or the drawings is included in the present invention, and in particular any combination of two or more of the claims set forth in the claims is included in the present invention.

[0017] The conductive fiber of the present invention not only has excellent tensile strength, bending durability, and corrosion resistance, but also is not magnetized, and does not cause magnetic field disturbance, heat generation due to magnetic field, adhesion of iron powder, etc. Furthermore, a fiber structure containing the conductive fiber of the present invention has excellent flexibility.

[0018] FIG. 2 is a schematic side view illustrating the configuration of a conductive fiber according to one embodiment of the present invention.

[0019] FIG. 1 is a schematic side view showing an example of the configuration of the conductive fiber of the present invention, illustrating the manufacturing process. Note that the dimensional ratios in the drawing do not reflect individual examples. The conductive fiber 1 includes a core 10 and a tape-shaped metal foil 20 spirally wound around the core 1. The conductive fiber 10 may essentially consist of the core 10 and the metal foil 20. The core 10 is made of a liquid crystal polyester fiber having a tensile strength of 18 cN / dtex or more, and the metal foil 20 is a metal foil with a relative magnetic permeability of less than 3. In the drawing, w represents the width of the metal foil, d represents the spacing between the metal foils, and D represents the diameter of the conductive fiber 1. The configuration of the conductive fiber 1 will be further described below.

[0020] [Metal Foil] The metal foil used in the conductive fiber of the present invention has a relative magnetic permeability of less than 3. Preferably, it is less than 1.5, more preferably less than 1.1. Conductive fibers produced using metal foil with a relative magnetic permeability of less than 3 do not adhere to permanent magnets such as neodymium magnets. If the relative magnetic permeability of the metal foil is 3 or more, the conductive fiber may be magnetized, causing heat generation due to a magnetic field or adhesion of iron powder, making it unsuitable for communication equipment and medical applications in particular. The lower limit of the relative magnetic permeability is not particularly limited, but may be 1.0. For example, the relative magnetic permeability of the metal foil may be 1.0 or more but less than 3.0, 1.0 or more but less than 1.5, or 1.0 or more but less than 1.1.

[0021] Relative permeability is the ratio of the magnetic permeability of a material to the magnetic permeability of a vacuum. The magnetic permeability is a coefficient that represents the relationship between the magnetic moment and the strength of the magnetic field, and can be calculated using the following formula based on values ​​measured using a magnetic property measurement system. In the formula, μ ｒ is the relative permeability, M is the magnetic moment (emu), and V is the volume (cm ３ ), H is the magnetic field (Oe).

[0022] If the width or thickness of the metal foil wrapped around the core yarn is too small to measure, the relative permeability of the metal foil before slitting or, depending on the type of metal, the relative permeability of the metal wire before wire drawing or rolling may be used. For example, the relative permeability of austenitic stainless steel, etc., which has a relative permeability of less than 3, will not become 3 or more after wire drawing or rolling, so the relative permeability of the metal wire before being made into metal foil can be used.

[0023] Whether conductive fibers are magnetized and generate heat due to the magnetic field or attract iron powder can be evaluated simply by checking whether they stick to a permanent magnet such as a neodymium magnet. If the conductive fibers stick to a permanent magnet, they are considered to be magnetized.

[0024] The metal foil used for the conductive fiber can be produced, for example, by rolling a metal wire. Examples of metals include gold, silver, copper, aluminum, zinc, stainless steel, and titanium.

[0025] As long as the effects of the present invention are not impaired, plated metal foil may be used to produce the conductive fiber of the present invention. For example, if copper, which has high conductivity, is desired but copper lacks corrosion resistance, metal foil made by plating copper with nickel, which has a high relative permeability, may be used. If the relative permeability of the plated metal foil is 3 or higher, heat generation due to a magnetic field and adhesion of iron powder will occur, impairing the effects of the present invention, and therefore it cannot be used to produce the conductive fiber of the present invention.

[0026] From the viewpoints of rolling workability, electrical conductivity, corrosion resistance, and allergy resistance, stainless steel foil is preferred as the metal foil, and metal foil made of austenitic stainless steel, which has a low relative magnetic permeability, is particularly preferred. However, since some austenitic stainless steels, such as SUS304, have a high relative magnetic permeability due to cold working, it is particularly preferred to use metal foil made of austenitic stainless steel that has been improved so that the relative magnetic permeability does not increase due to cold working. Furthermore, from the viewpoint of allergy resistance, it is preferred to use metal foil made of austenitic stainless steel with high corrosion resistance, such as SUS316L or NAS106N. Titanium foil or aluminum foil may also be used instead of stainless steel foil.

[0027] Some alloys that can be used as permanent magnets have a relative magnetic permeability of less than 3, but these alloys themselves are magnetic, which not only causes magnetic field disturbances and iron powder adhesion, but also makes them very difficult to process and difficult to form into metal foil. For example, metal foils of alloys such as neodymium magnets, ferrite magnets, and alnico magnets, which have a relative magnetic permeability of less than 3, are not suitable for use in the present invention, and are difficult to obtain.

[0028] The thickness of the metal foil used in the conductive fiber can be selected appropriately depending on the application and specifications. Depending on the thickness of the core yarn and the total fineness, it is preferably 0.003 to 0.05 mm, more preferably 0.004 to 0.03 mm, and even more preferably 0.005 to 0.015 mm. A smaller thickness of the metal foil is preferable because it increases the flexibility of the conductive fiber, but if the thickness is too small, the conductivity may be insufficient or the strength may be insufficient depending on the application.

[0029] The width of the metal foil used in the conductive fiber (indicated by the symbol w in FIG. 1) can be selected appropriately depending on the application and specifications. Although it depends on the thickness of the core yarn and the total fineness, it is preferably 0.1 to 0.5 mm, more preferably 0.13 to 0.4 mm, and even more preferably 0.15 to 0.3 mm. A narrow metal foil width is preferable because it increases the flexibility of the conductive fiber.

[0030] [Core Yarn] The core yarn used in the conductive fiber of the present invention is a liquid crystal polyester fiber having a tensile strength of 18 cN / dtex or more from the viewpoints of excellent creep properties, excellent flexural durability, etc. Examples of liquid crystal polyester fibers that can be used include products known under trade names such as "Vectran (registered trademark)," "Scivelas (registered trademark)," and "Zexion (registered trademark)." A more preferred tensile strength is 20 cN / dtex or more, and an even more preferred tensile strength is 22 cN / dtex or more. If the tensile strength is lower than 18 cN / dtex, the conductive fibers constituting the fiber structure may be broken by tension or may be broken due to insufficient flexural durability during use as a fiber structure containing conductive fibers. The upper limit of the tensile strength is not particularly limited, but may be, for example, about 40 cN / dtex. The tensile strength of high-strength fibers is a value measured by the method described in the Examples below. The tensile strength of the core yarn may be 18 to 40 cN / dtex, 20 to 38 cN / dtex, or 22 to 35 cN / dtex.

[0031] Liquid crystal polyester fibers are fibers containing liquid crystal polyesters, and the liquid crystal polyesters are composed of structural units derived from, for example, aromatic diols, aromatic dicarboxylic acids, aromatic hydroxycarboxylic acids, etc., and the structural units derived from aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids are not particularly limited in terms of their chemical structure, as long as the effects of the present invention are not impaired. Furthermore, the liquid crystal polyesters may also contain structural units derived from aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids, provided that the effects of the present invention are not impaired. For example, preferred structural units include those shown in Table 1.

[0032]

[0033] In the structural units in Table 1, m is an integer of 0 to 2, and Y in the formula, in the range of 1 to the maximum number of possible substitutions, each independently represents a hydrogen atom, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, etc.), an alkoxy group (for example, a methoxy group, an ethoxy group, an isopropoxy group, a n-butoxy group, etc.), an aryl group (for example, a phenyl group, a naphthyl group, etc.), an aralkyl group (for example, a benzyl group (phenylmethyl group), a phenethyl group (phenylethyl group), etc.), an aryloxy group (for example, a phenoxy group), an aralkyloxy group (for example, a benzyloxy group), etc.

[0034] More preferred structural units include the structural units described in Examples (1) to (20) shown in the following Tables 2, 3, and 4. When the structural unit in the formula is a structural unit that can exhibit multiple structures, two or more of such structural units may be combined and used as structural units that constitute the polymer.

[0035]

[0036]

[0037]

[0038] In the structural units of Tables 2, 3, and 4, n is an integer of 1 or 2, and each of the structural units n=1 and n=2 may exist alone or in combination. Y1 and Y2 may each independently be a hydrogen atom, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (e.g., an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, etc.), an alkoxy group (e.g., a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, etc.), an aryl group (e.g., a phenyl group, a naphthyl group, etc.), an aralkyl group (e.g., a benzyl group (phenylmethyl group), a phenethyl group (phenylethyl group), etc.), an aryloxy group (e.g., a phenoxy group), an aralkyloxy group (e.g., a benzyloxy group), etc. Of these, a hydrogen atom, a chlorine atom, a bromine atom, or a methyl group is preferred.

[0039] Examples of Z include substituents represented by the following formulas.

[0040]

[0041] In one embodiment, the liquid crystal polyester may contain a structural unit derived from a hydroxycarboxylic acid as a main component. The liquid crystal polyester may preferably contain a structural unit (A) derived from hydroxybenzoic acid and a structural unit (B) derived from hydroxynaphthoic acid. For example, the structural unit (A) may be a structural unit derived from 4-hydroxybenzoic acid (formula (A) below), and the structural unit (B) may be a structural unit derived from 6-hydroxy-2-naphthoic acid (formula (B) below). From the viewpoint of improving melt moldability, the ratio of the structural unit (A) to the structural unit (B) may preferably be in the range of 9 / 1 to 1 / 1, more preferably 7 / 1 to 1 / 1, and even more preferably 5 / 1 to 1 / 1.

[0042]

[0043]

[0044] The liquid crystal polyester fiber may contain thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyether ether ketone, fluororesin, etc., within the range that does not impair the effects of the present invention. Furthermore, the liquid crystal polyester fiber may contain various additives such as inorganic substances such as titanium oxide, kaolin, silica, barium oxide, etc., colorants such as carbon black, dyes, and pigments, antioxidants, ultraviolet absorbers, and light stabilizers.

[0045] The liquid crystal polyester fiber may be a mixed spun fiber obtained by mixing and spinning a liquid crystal polyester with the above-mentioned thermoplastic polymer and various additives, or a conjugated spun fiber obtained by simultaneously spinning different components of the liquid crystal polyester and the above-mentioned thermoplastic polymer from separate spinnerets, as long as the effects of the present invention are not impaired. The liquid crystal polyester fiber may be a non-conjugated spun fiber or a conjugated spun fiber.

[0046] The single filament fineness of the liquid crystal polyester fiber used for the conductive fiber can be appropriately selected depending on the application, etc. For example, the single filament fineness may be 50 dtex or less, preferably 15 dtex or less, and more preferably 10 dtex or less. However, in order to obtain the flexibility required for smart textiles, a finer fineness is preferred, for example, 7 dtex or less. Furthermore, the lower limit of the single filament fineness is not particularly limited, but may be, for example, about 0.01 dtex. The single filament fineness is a value measured by the method described in the Examples below.

[0047] The liquid crystal polyester fiber used for the conductive fiber may be a monofilament or a multifilament. In the case of a multifilament, the number of filaments can be appropriately selected depending on the application, etc. For example, the number of filaments may be 2 to 100, preferably 3 to 50, and more preferably 5 to 20.

[0048] The total fineness of the liquid crystal polyester fiber used for the conductive fiber can be appropriately selected depending on the application, etc. For example, the total fineness may be 440 dtex or less, preferably 220 dtex or less, and more preferably 110 dtex or less. To obtain flexibility in the smart textile, it is preferable to make the fiber diameter of the conductive yarn small, and a fine fineness is preferable. Furthermore, the lower limit of the total fineness is not particularly limited, but it may be, for example, about 1 dtex.

[0049] The liquid crystal polyester fiber used as the conductive fiber may be in the form of an untwisted monofilament or multifilament as it is wound from a bobbin or the like, or may be a fiber processed into a twisted yarn, a doubled twisted yarn, a braided cord, or the like.

[0050] [Diameter of Conductive Fiber] The diameter (D) of the conductive fiber of the present invention may be 0.3 mm or less. Preferably, it is 0.25 mm or less, more preferably 0.20 mm or less. If the diameter of the conductive fiber exceeds 0.3 mm, it becomes more difficult to obtain sufficient flexibility when the fiber is made into a fiber structure. There is no particular restriction on the lower limit of the diameter of the conductive fiber, but it may be, for example, about 0.05 mm. The diameter of the conductive fiber may be 0.05 to 0.30 mm, 0.07 to 0.25 mm, or 0.10 to 0.20 mm.

[0051] [Method for Manufacturing Conductive Fiber] The conductive fiber of the present invention is a metal foil yarn formed by wrapping a metal foil around a liquid crystal polyester fiber core yarn, and can be manufactured by a method similar to the known copper foil yarn manufacturing method. There are no particular limitations. For example, a metal foil can be manufactured by first drawing a metal wire with a diameter of 0.2 to 0.3 mm to 0.025 to 0.18 mm and then rolling the material. Next, the foil can be spirally wrapped around the liquid crystal polyester fiber core yarn to manufacture a conductive fiber with flexibility and pliability. The conductive fiber of the present invention has excellent bending durability because the deformation (strain) of the metal portion when bent is smaller than that of a metal wire of the same diameter. In particular, when the metal foil is stainless steel foil, it has better bending durability than when copper foil is used.

[0052] The spacing (d) of the metal foil wrapped around the liquid crystal polyester fiber can be appropriately set depending on the application and specifications. Depending on the thickness and width of the metal foil and the total fineness of the liquid crystal polyester fiber, the spacing is preferably 0.3 mm or less, more preferably 0.25 mm or less, and even more preferably 0.2 mm or less. A smaller spacing is preferable because it increases conductivity. The lower limit of the spacing is not particularly limited, and the metal foil can be wrapped in layers, but this may be undesirable depending on the application due to reduced flexural durability. From the perspective of flexural durability, the spacing between the metal foils is preferably 0.001 mm or more, more preferably 0.005 mm or more, and even more preferably 0.01 mm or more. If the spacing is too narrow, snare may occur in the conductive fiber or the flexibility of the conductive fiber may decrease. By leaving small gaps between the metal foils of the conductive fiber, the inner gap becomes smaller and the outer gap becomes larger when bending, minimizing the deformation (strain) of the metal foil. This improves flexural durability, which is a problem when using metal foil alone. The spacing between the metal foils may be 0.001 to 0.3 mm, 0.005 to 0.25 mm, or 0.01 to 0.3 mm. Here, the spacing between the metal foils refers to the spacing between adjacent edges of the tape-shaped metal foil as shown by the symbol d in Fig. 1, and may be measured from an enlarged image such as a scanning electron microscope (SEM) image.

[0053] The conductive fiber of the present invention may be manufactured by wrapping a single metal foil around a core yarn, or may be manufactured by wrapping multiple metal foils in multiple layers depending on the desired conductivity. A conductive fiber can be effectively manufactured by wrapping up to four metal foils around a core yarn in four layers. Wrapping more than four metal foils is undesirable because it increases the weight and reduces flexural durability. When multiple metal foils are wrapped in multiple layers, the metal foils may be of different types. When wrapping additional metal foil around a conductive fiber already wrapped in metal foil, selecting the wrapping direction of the next metal foil in the Z-winding direction if the previously wrapped metal foil is wrapped in the S-winding direction, or in the S-winding direction if the previously wrapped metal foil is wrapped in the Z-winding direction, suppresses twisting of the conductive fiber and improves processability when manufacturing a fiber structure containing the conductive fiber wrapped in multiple layers of metal foil.

[0054] [Textile structure containing conductive fiber] The textile structure containing the conductive fiber of the present invention can be produced by processing the conductive fiber of the present invention and can be used in any fiber form, such as staple fiber, short-cut fiber, filament yarn, spun yarn, string-like material, twisted material, rope, etc. The conductive fiber of the present invention can also be used to produce various fabrics and sheet-like materials, such as nonwoven fabrics, woven fabrics, and knitted fabrics. Such textile structures containing conductive fibers can be produced by using the conductive fiber of the present invention by known methods.

[0055] The fiber structure containing the conductive fiber of the present invention may be resin-treated. For example, after producing a plain weave fabric from the conductive fiber of the present invention, the fabric may be coated with a urethane resin to impart shape stability and stain resistance.

[0056] The textile structure containing the conductive fiber of the present invention may be a combination of the conductive fiber of the present invention with other fibers, as long as the effects of the present invention are not impaired. For example, composite fibers using the conductive fiber and other fibers (e.g., blended yarns in which the conductive fiber is blended with other fibers) can be used. Also, composite fabrics using the conductive fiber and other fibers (e.g., blended fabrics in which the conductive fiber is blended with other fibers, and laminates of fabrics made of conductive fibers and fabrics made of other fibers) can be used. When the textile structure is used to manufacture a composite material, the textile structure may be a composite fiber or composite fabric containing fusion fibers that form the matrix of the composite material as the other fibers.

[0057] The fiber structure containing the conductive fiber of the present invention can be used for various purposes such as smart textiles, electrical and electronic component materials, electromagnetic wave shielding, general industrial materials, various reinforcing materials, and protective clothing.

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, various physical properties were measured by the following methods.

[0059] (Relative Permeability of Metal Foil) The relative permeability was measured by measuring the magnetic moment at 20° C. in VSM mode using a magnetic property measurement system (MPMS3, manufactured by Quantum Design), and calculating the relative permeability at 1000 Oe using the following formula. In the formula, μ ｒ is the relative permeability, M is the magnetic moment (emu), and V is the volume (cm ３ ), H is the magnetic field (Oe).

[0060] (Thickness and width of metal foil) Using a tabletop scanning electron microscope (JCM-6000PLUS, manufactured by JEOL Ltd.), the thickness (mm) and width (mm) of a 3 mm long metal foil were measured at three locations, and the average values ​​were used as the thickness (mm) and width (mm) of the metal foil.

[0061] (Total fineness of core yarn, single yarn fineness) Based on JIS L 1013:2010 8.3.1 A method, the core yarn was wound into a skein of 1 m per skein x 100 skeins (total 100 m) using a measuring instrument "Wrap Reel by Motor Driven" manufactured by Daiei Scientific Instruments Manufacturing Co., Ltd., and the weight (g) was multiplied by 100 and measured twice per level, and the average value was taken as the total fineness (dtex) of the obtained core yarn. In addition, the quotient obtained by dividing the total fineness by the number of filaments was taken as the single yarn fineness (dtex).

[0062] (Tensile strength of core yarn) With reference to JIS L 1013:2010 8.5.1, a precision universal testing machine "AGS-100B" manufactured by Shimadzu Corporation was used to perform 10 tensile tests for one core yarn sample under conditions of a test length of 20 cm and a tensile speed of 10 cm / min. The tensile strength of the core yarn (cN / dtex) was calculated by dividing the average value of the breaking load (cN) by the fineness (dtex) of the core yarn.

[0063] (Diameter of conductive fiber) Using a digital caliper (measurement range 0 to 150 mm, minimum reading value 0.01 mm, manufactured by AS ONE Corporation), the diameter of the fibers obtained in the examples and comparative examples was measured at five locations, and the average value was taken as the diameter (mm) of the conductive fiber.

[0064] (Spacing of metal foils of conductive fibers) Using a tabletop scanning electron microscope (JCM-6000PLUS, manufactured by JEOL Ltd.), the parallel line spacing between the metal foils of the conductive fibers obtained in the examples and comparative examples was measured at three random locations, and the average value was taken as the spacing (mm) of the metal foils.

[0065] (Breaking Load of Conductive Fiber) With reference to JIS L 1013:2010 8.5.1, a precision universal testing machine "AGS-100B" manufactured by Shimadzu Corporation was used to conduct 10 tensile tests for one sample of conductive fiber thread under conditions of a test length of 20 cm and a tensile speed of 10 cm / min, and the average value of the breaking loads (N) was taken as the breaking load of the conductive fiber.

[0066] (Magnetization Evaluation) Three conductive fibers cut to a length of 3 cm were placed on a permanent magnet (neodymium magnet, diameter 16 mm, thickness 2.5 mm, magnetic flux density 170 mT) and inverted. If none of the three conductive fibers fell off, the conductive fibers were evaluated as being magnetized and rated B. If even one conductive fiber fell off, the conductive fiber was evaluated as not being magnetized and rated A.

[0067] (Electrical Resistance Value) The electrical resistance values ​​of the conductive fibers obtained in the examples and comparative examples were measured using a resistance value measuring device (manufactured by Texio Technology Co., Ltd.) The distance between the terminals sandwiching the conductive fiber was 10 cm, and the electrical resistance values ​​(Ω / m) were measured at five locations, and the average value was taken as the electrical resistance value (Ω / m).

[0068] Example 1 The metal foil was a stainless steel foil (relative permeability: 1.0, thickness: 0.01 mm, width: 0.2 mm) made by rolling a 0.27 mm diameter austenitic stainless steel wire (NAS106N, manufactured by Nippon Seisen Co., Ltd.). The core yarn was a liquid crystal polyester fiber "Vectran HT" (total fineness: 56 dtex, number of filaments: 10, manufactured by Kuraray Co., Ltd., designated LCP1 in Table 5), which is composed of structural units derived from 4-hydroxybenzoic acid and structural units derived from 6-hydroxy-2-naphthoic acid. The stainless steel foil was spirally wound around the liquid crystal polyester fiber in an S-winding direction with a spacing of 0.02 mm between the metal foils to obtain a conductive fiber. The diameter (mm), breaking load (N), magnetization evaluation, and electrical resistance (Ω / m) of the obtained conductive fiber are shown in Table 5.

[0069] [Example 2] A conductive fiber was obtained in the same manner as in Example 1, except that the total fineness of the liquid crystal polyester fiber was 110 dtex, the number of filaments was 20, and the interval between the metal foils was 0.03 mm. The diameter (mm), breaking load (N), magnetization evaluation, and electrical resistance value (Ω / m) of the obtained conductive fiber are shown in Table 5.

[0070] [Example 3] Conductive fibers were obtained in the same manner as in Example 1, except that copper foil (pure copper, relative magnetic permeability: 1.0, thickness: 0.01 mm, width: 0.2 mm, manufactured by Meisei Sangyo Co., Ltd.) was used as the metal foil. The diameter (mm), breaking load (N), magnetization evaluation, and electrical resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0071] [Example 4] A conductive fiber was obtained in the same manner as in Example 3, except that the total fineness of the liquid crystal polyester fiber was 110 dtex, the number of filaments was 20, and the interval between the metal foils was 0.03 mm. The diameter (mm), breaking load (N), magnetization evaluation, and electrical resistance value (Ω / m) of the obtained conductive fiber are shown in Table 5.

[0072] [Example 5] Liquid crystal polyester chips (granular molded bodies) composed of 6-hydroxy-2-naphthoic acid-derived structural units, 2,6-naphthalenedicarboxylic acid-derived structural units, hydroquinone-derived structural units, and 4,4'-dihydroxybiphenyl-derived structural units in a 60 / 20 / 15 / 5 (mol%) ratio were melt-kneaded in a twin-screw extruder, extruded from a nozzle at a spinning head temperature of 330°C, and wound around a bobbin at a take-up speed of 1000 m / min to obtain a liquid crystal polyester fiber spinning yarn. Next, 500 m of the resulting spinning yarn was rewound around an aluminum bobbin and heat-treated in a closed oven at 300°C for 16 hours under a nitrogen atmosphere to obtain a liquid crystal polyester filament having a total fineness of 280 dtex, 50 filaments, and a tensile strength of 31.0 cN / dtex (referred to as LCP2 in Table 5). Using the obtained liquid crystal polyester fiber, conductive fibers were obtained in the same manner as in Example 1, except that the interval between the metal foils was 0.05 mm. The diameter (mm), breaking load (N), magnetization evaluation, and electrical resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0073] [Example 6] Conductive fibers were obtained in the same manner as in Example 1, except that aluminum foil (pure aluminum, relative magnetic permeability: 1.0, thickness: 0.01 mm, width: 0.2 mm, manufactured by Meisei Sangyo Co., Ltd.) was used as the metal foil. The diameter (mm), breaking load (N), magnetization evaluation, and electrical resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0074] Comparative Example 1 Conductive fibers were obtained in the same manner as in Example 1, except that a stainless steel foil (relative permeability: 11, thickness: 0.01 mm, width: 0.2 mm) obtained by rolling an austenitic-ferritic stainless steel wire (SUS329J4L, relative permeability: 40, diameter: 0.25 mm, manufactured by Nippon Seisen Co., Ltd.) was used as the metal foil. The diameter (mm), breaking load (N), magnetization evaluation, and electrical resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0075] [Comparative Example 2] A conductive fiber was obtained in the same manner as in Comparative Example 1, except that the total fineness of the liquid crystal polyester fiber was 110 dtex, the number of filaments was 20, and the interval between the metal foils was 0.03 mm. The diameter (mm), breaking load (N), magnetization evaluation, and electrical resistance value (Ω / m) of the obtained conductive fiber are shown in Table 5.

[0076]

[0077] As shown in Table 5, the conductive fibers of Examples 1 to 6 have sufficient breaking load, are not magnetized, and have low electrical resistance, and therefore have sufficient conductivity.

[0078] On the other hand, the conductive fibers of Comparative Examples 1 and 2 had sufficient breaking load and low electrical resistance, and therefore were conductive, but they were magnetized, which could cause heat generation due to magnetic fields and adhesion of iron powder.

[0079] From the viewpoint of bending durability, the conductive fibers of Examples 1 to 6 are all constructed by wrapping a thin tape-shaped metal foil around a core thread made of liquid crystal polyester, and therefore can be expected to have better durability than when metal fibers are used.

[0080] The conductive fibers of the present invention can be used in the form of various fiber structures for various applications such as smart textiles, electrical and electronic component materials, electromagnetic wave shielding, general industrial materials, various reinforcing materials, and protective clothing. For example, they can be used for circuits, electrodes, electric wires, communication lines, heater wires, and the like that constitute smart textiles. In particular, when used as fiber structures such as sewing threads and woven and knitted fabrics containing the conductive fibers, conductive fibers having a small diameter can be used for smart textile applications (displays, keyboards, circuit boards, clothing, hats, goggles, eyeglasses, masks, gloves, socks, and the like) that are flexible and have excellent drapeability. In addition, they can also be used favorably in the medical and food fields because they are resistant to iron powder adhesion.

[0081] As described above, the preferred embodiments of the present invention have been described, but various additions, modifications, or deletions can be made without departing from the spirit of the present invention, and such additions, modifications, or deletions are also included within the scope of the present invention.

[0082] 1 Conductive fiber 10 Core thread 20 Metal foil w Width of metal foil d Distance between metal foils D Diameter of conductive fiber

Claims

1. A conductive fiber comprising: a liquid crystal polyester fiber having a tensile strength of 18 cN / dtex or more; and a metal foil having a relative magnetic permeability of less than 3 wound in a spiral shape around the liquid crystal polyester fiber.

2. The conductive fiber according to claim 1, wherein said metal foil is stainless steel.

3. A fiber structure comprising the conductive fiber according to claim 1 or 2.

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