Conductive fiber and fiber structure comprising the same

Abstract

The object of this invention is to provide conductive fibers that not only have excellent tensile strength, flexural durability, and corrosion resistance, but also do not exhibit magnetization, magnetic field disturbance, heating caused by the magnetic field, or adhesion of iron powder. Furthermore, the object of this invention is to provide a fiber structure containing the conductive fibers of this invention and possessing excellent flexibility. This invention relates to conductive fibers (1) and fiber structures containing the conductive fibers (1), wherein the conductive fibers (1) comprise liquid crystal polyester fibers (10) with a tensile strength of 18 cN / dtex or higher, and a metal foil (20) spirally wound around the liquid crystal polyester fibers (10) and having a relative permeability of less than 3.

Description

[0001] Related applications

[0002] This application claims priority to Japanese Patent Application No. 2023-211647, filed on December 15, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to conductive fibers and fiber structures comprising the conductive fibers. Background Technology

[0004] In recent years, the miniaturization and lightweighting of optoelectronic devices have been continuously developing, leading to increasingly active development of smart textiles and wearable devices that integrate these devices into fabrics. For the conductive fibers used in electrodes, circuits, wires, and electromagnetic shielding of smart textiles, not only conductivity is required, but also durability against bending and tensile strength. Particularly for smart textiles used in electronic devices, medical / care applications, and food, the raw materials must not be magnetized, and must not cause magnetic field disturbances, heat generation due to magnetic fields, or iron powder adhesion. Furthermore, when used as devices that come into direct contact with the skin, such as electrodes for collecting biosignals, they must not easily cause corrosion due to sweat or metal allergies.

[0005] For example, Patent Document 1 (Japanese Patent Application Publication No. 2023-32005) discloses a conductive fiber and a fiber product or electrical / electronic device using the same, which is made into a conductive fiber containing liquid metal and thus possesses both conductivity and flexibility.

[0006] In Patent Document 2 (Japanese Patent Application Publication No. 2018-9259), a sewing thread was proposed as a fiber structure to replace the wires constituting the circuit of a smart textile. This thread is formed by covering a core yarn made by twisting insulated plated wire, enameled wire, natural fiber, and synthetic fiber with a fiber sheath. Patent Document 3 (Japanese Patent Application Publication No. 2016-212960) discloses a conductive wire with a metal plating applied to the surface of a high-strength fiber.

[0007] Patent document 4 (Japanese Patent Application Publication No. 2019-33809) discloses a wearable electrode in which a metal wire and a conductive filament coated with metal and conductive polymer are fixed on a conductor on a fiber structure coated with a conductive polymer.

[0008] Patent document 5 (Japanese Patent Application Publication No. 2006-196232) discloses a strip conductor formed by using a plain weave structure of copper foil wire, which is made by winding copper foil around high-strength fibers, as the bare conductor wire.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2023-32005

[0012] Patent Document 2: Japanese Patent Application Publication No. 2018-9259

[0013] Patent Document 3: Japanese Patent Application Publication No. 2016-212960

[0014] Patent Document 4: Japanese Patent Application Publication No. 2019-33809

[0015] Patent Document 5: Japanese Patent Application Publication No. 2006-196232 Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] Patent document 1 proposes to make conductive fibers containing liquid metal with a melting point below 40°C, which have both conductivity and softness. However, when used as a smart textile, there are potential risks of fiber breakage, leakage of liquid metal from the fibers, and electrical failure.

[0018] Patent document 2 discloses a linear conductive material (conductive fiber) used as the bottom thread of sewing yarn, consisting of plated wire and metal wire with insulation coating. However, when used as sewing yarn, the sheath yarn is covered with non-conductive fibers. Therefore, when used as electrodes or circuits in smart textiles, it not only suffers from insufficient conductivity but also risks breakage due to insufficient tensile strength caused by the use of short fibers in the sheath yarn. Patent document 3 proposes a conductive wire with copper plating on the surface of high-strength fibers to solve the problem of insufficient tensile strength. However, since the copper plating layer is prone to degradation, further bending durability is required.

[0019] Patent document 4 discloses metal wires and conductive wires coated with metal and conductive polymers. However, the bending durability of metal wires is insufficient, and the conductive wires coated with metal and conductive polymers have the problem that the conductive coating may peel off.

[0020] Patent document 5 discloses copper foil wire made by winding copper foil around aramid fibers, but copper corrosion sometimes occurs because aramid fibers are hygroscopic.

[0021] To address the aforementioned problems, the present invention aims to provide conductive fibers that not only possess excellent tensile strength, flexural durability, and corrosion resistance, but also exhibit non-magnetization, no magnetic field disturbance, no heating caused by magnetic fields, and no adhesion of iron powder. Furthermore, the present invention also aims to provide a fiber structure incorporating the conductive fibers of the present invention and possessing excellent flexibility.

[0022] Problem Solving Methods

[0023] To achieve the above objectives, the inventors of this invention conducted in-depth research and discovered that conductive fibers using liquid crystal polyester fibers with a tensile strength of 18 cN / dtex or higher as the core yarn and spirally winding metal foil with a relative permeability of less than 3 around the core yarn not only have excellent tensile strength, bending durability, and corrosion resistance, but also do not become magnetized, do not experience magnetic field disturbances, heat generation caused by the magnetic field, or iron powder adhesion. Furthermore, it was found that the fiber structure containing the conductive fibers of this invention has excellent flexibility, thus completing this invention.

[0024] That is, the present invention can be constructed in the following ways.

[0025] [Method 1]

[0026] A conductive fiber comprising:

[0027] Liquid crystal polyester fibers with a tensile strength of 18 cN / dtex or more (preferably 20 cN / dtex or more, more preferably 22 cN / dtex or more), and

[0028] A metal foil with a relative permeability of less than 3, which is spirally wound around the liquid crystal polyester fiber.

[0029] [Method 2]

[0030] The conductive fiber according to method 1, wherein...

[0031] The aforementioned metal foil is made of stainless steel.

[0032] [Method 3]

[0033] A fibrous structure comprising the conductive fibers described in method 1 or 2.

[0034] It should be noted that any combination of at least two constituent elements disclosed in the claims and / or description and / or drawings is also included in this invention. In particular, any combination of two or more claims recited in the claims is also included in this invention.

[0035] The effects of the invention

[0036] The conductive fibers of this invention not only exhibit excellent tensile strength, flexural durability, and corrosion resistance, but also remain unmagnetized, preventing magnetic field disturbances, heat generation caused by magnetic fields, and the adhesion of iron powder. Furthermore, the fiber structure incorporating the conductive fibers of this invention possesses excellent flexibility. Attached Figure Description

[0037] Figure 1This is a schematic side view used to illustrate the structure of a conductive fiber according to one embodiment of the present invention.

[0038] Symbol Explanation

[0039] 1. Conductive fiber

[0040] 10-core yarn

[0041] 20 metal foil

[0042] w is the width of the metal foil.

[0043] d Spacing of metal foils

[0044] D. Diameter of the conductive fiber Detailed Implementation

[0045] Figure 1 This is a schematic side view illustrating an example of the structure of the conductive fiber of the present invention, showing the state of the manufacturing process. It should be noted that the scale of the drawing does not reflect all examples.

[0046] The conductive fiber 1 comprises a core yarn (core) 10 and a strip of metal foil 20 wound helically around the core yarn 1. The conductive fiber 10 may substantially consist of the core yarn 10 and the metal foil 20. The core yarn 10 is formed of liquid crystal polyester fiber having a tensile strength of 18 cN / dtex or higher, and the metal foil 20 is a metal foil with a relative permeability of less than 3. In the figure, 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 structure of the conductive fiber 1 will be further explained below.

[0047] [metal foil]

[0048] The metal foil used in the conductive fibers of this invention has a relative permeability of less than 3, preferably less than 1.5, and more preferably less than 1.1. Conductive fibers made using metal foil with a relative permeability of less than 3 will not adhere to permanent magnets such as neodymium magnets. If the relative permeability of the metal foil is 3 or higher, the conductive fibers may become magnetized, resulting in heating due to the magnetic field, adhesion of iron powder, etc., making them particularly unsuitable for use in communication equipment and medical applications. The lower limit of the relative permeability is not particularly limited and can be 1.0. For example, the relative permeability of the metal foil can be 1.0 or higher and less than 3.0, 1.0 or higher and less than 1.5, or 1.0 or higher and less than 1.1.

[0049] Relative permeability refers to the ratio of a material's permeability to the permeability of vacuum. Permeability is a coefficient that represents the relationship between magnetic moment and magnetic field strength, and can be calculated mathematically based on values ​​obtained using a magnetic property measurement system using the following formula.

[0050] [Mathematical Expression 1]

[0051]

[0052] In the formula, μ r Where M is the relative permeability, M is the magnetic moment (emu), and V is the volume (cm³). 3 H is the magnetic field (Oe).

[0053] When the width and thickness of the metal foil wound around the core yarn are too small to be measured, the relative permeability of the metal foil before slitting can be used, or, depending on the type of metal, the relative permeability of the metal wire before drawing or rolling can be used. For example, the relative permeability of austenitic stainless steel, which has a relative permeability of less than 3, will not reach 3 or higher due to drawing or rolling; therefore, the relative permeability of the metal wire before it was made into a metal foil can be used.

[0054] Whether conductive fibers are magnetized, whether they generate heat due to a magnetic field, and whether iron powder adheres to them can be easily evaluated by whether they adhere to a permanent magnet such as a neodymium magnet. If conductive fibers adhere to a permanent magnet, they can be considered magnetized.

[0055] The metal foil used in conductive fibers can be manufactured by rolling metal wires. Examples of metals include gold, silver, copper, aluminum, zinc, stainless steel, and titanium.

[0056] Within the scope of not impairing the effects of the present invention, it is permissible to use plated metal foil in the manufacture of the conductive fibers of the present invention. For example, it is desirable to use copper with high conductivity, but if the corrosion resistance of copper is insufficient, a metal foil made by plating copper with nickel, which has a relatively high magnetic permeability, can also be used. If the relative magnetic permeability of the plated metal foil is 3 or higher, heating due to the magnetic field and adhesion of iron powder will occur, which will impair the effects of the present invention, and therefore it cannot be used in the manufacture of the conductive fibers of the present invention.

[0057] From the viewpoints of workability, electrical conductivity, corrosion resistance, and allergy resistance, stainless steel foil is preferred as the metal foil, and more particularly preferred are metal foils made of austenitic stainless steel with low relative magnetic permeability. Among austenitic stainless steels, there are also stainless steels like SUS304 whose relative magnetic permeability increases with cold working; therefore, metal foils made of austenitic stainless steel that have been modified to prevent an increase in relative magnetic permeability due to cold working are particularly preferred. Furthermore, from the viewpoint of allergy resistance, metal foils made of austenitic stainless steels with high corrosion resistance, such as SUS316L and NAS106N, are preferred. Alternatively, titanium foil or aluminum foil can be used instead of stainless steel foil.

[0058] Here, while there are alloys with a relative permeability of less than 3 that can be used as permanent magnets, these alloys possess inherent magnetic force, leading to issues such as magnetic field disturbances and iron powder adhesion. Furthermore, they have very poor machinability, making them difficult to fabricate into metal foil. For example, metal foils made from alloys such as neodymium magnets, ferrite magnets, and aluminum-iron-nickel-cobalt magnets are unsuitable for use as the metal foil with a relative permeability of less than 3 used in this invention, and are also difficult to obtain.

[0059] The thickness of the metal foil used for conductive fibers can be appropriately selected according to the application and specifications. Although it depends on the thickness of the core yarn and the total fineness, it is preferably 0.003~0.05 mm, more preferably 0.004~0.03 mm, and even more preferably 0.005~0.015 mm. The thinner the metal foil, the higher the flexibility of the conductive fibers, which is therefore preferred. However, if the thickness is too small, the conductivity may be insufficient, or the strength may be insufficient depending on the application.

[0060] The width of the metal foil used for conductive fibers ( Figure 1 The width of the metal foil (represented by the symbol w) can be appropriately selected according to the application and specifications. Although it depends on the thickness and total fineness of the core yarn, 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. The smaller the width of the metal foil, the higher the flexibility of the conductive fiber, and therefore it is preferred.

[0061] [Core Yarn]

[0062] From the viewpoint of excellent creep characteristics and excellent bending durability, the core yarn used in the conductive fiber of the present invention is a liquid crystal polyester fiber with a tensile strength of 18 cN / dtex or higher. As the liquid crystal polyester fiber, products known by trade names such as "Vectran (registered trademark)", "Siveras (registered trademark)", and "Zxion (registered trademark)" can be used. A more preferred tensile strength is 20 cN / dtex or higher, and a further preferred tensile strength is 22 cN / dtex or higher. When the tensile strength is lower than 18 cN / dtex, in use as a fiber structure containing conductive fibers, the conductive fibers constituting the fiber structure may sometimes break due to stretching or insufficient bending durability. The upper limit of the tensile strength is not particularly limited; for example, it can be around 40 cN / dtex. The tensile strength of the high-strength fiber is a value measured by the method described in the examples described later. The tensile strength of the core yarn can be 18 to 40 cN / dtex, 20 to 38 cN / dtex, or 22 to 35 cN / dtex.

[0063] Liquid crystal polyester fiber is a fiber containing liquid crystal polyester. As a liquid crystal polyester, it can be formed from structural units derived from aromatic diols, aromatic dicarboxylic acids, aromatic hydroxycarboxylic acids, etc. The chemical composition of these structural units is not particularly limited, provided it does not impair the effects of the present invention. Furthermore, within the scope of not impairing the effects of the present invention, the liquid crystal polyester may contain structural units derived from aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids. For example, the examples shown in Table 1 can be cited as preferred structural units.

[0064] [Table 1]

[0065]

[0066] (Where, X in the formula is selected from the following structure)

[0067]

[0068] (Where, m = 0~2, Y = substituents selected from hydrogen, halogen atom, alkyl, aryl, aralkyl, alkoxy, aryloxy, and arylalkoxy)

[0069] In the structural units in Table 1, m is an integer from 0 to 2, and Y in the formula can be any independent hydrogen atom, halogen atom (e.g., fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl (e.g., methyl, ethyl, isopropyl, tert-butyl, etc., with 1 to 4 carbon atoms), alkoxy (e.g., methoxy, ethoxy, isopropoxy, n-butoxy, etc.), aryl (e.g., phenyl, naphthyl, etc.), aralkyl (e.g., benzyl (benzyl), phenethyl (phenylethyl) etc.), aryloxy (e.g., phenoxy, etc.), arylalkoxy (e.g., benzyloxy, etc.), etc., within the range of 1 to the maximum number of substitutable atoms.

[0070] As a more preferred structural unit, examples (1) to (20) shown in Tables 2, 3 and 4 below can be cited. It should be noted that when the structural unit in the formula is a structural unit that can represent multiple structures, two or more such structural units can be combined as structural units constituting the polymer.

[0071] [Table 2]

[0072]

[0073] [Table 3]

[0074]

[0075] [Table 4]

[0076]

[0077] In the structural units of Tables 2, 3, and 4, n is an integer of 1 or 2. Each structural unit n=1 and n=2 can exist alone or in combination. Y1 and Y2 can be independently hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.), alkyl (e.g., methyl, ethyl, isopropyl, tert-butyl, etc., alkyl with 1 to 4 carbon atoms), alkoxy (e.g., methoxy, ethoxy, isopropoxy, n-butoxy, etc.), aryl (e.g., phenyl, naphthyl, etc.), alkoxy (e.g., benzyl (benzyl), phenethyl (phenylethyl), etc.), aryloxy (e.g., phenoxy), arylalkoxy (e.g., benzyloxy, etc.). Among them, hydrogen atoms, chlorine atoms, bromine atoms, or methyl atoms are preferred.

[0078] In addition, as Z, substituents represented by the following formula can be cited.

[0079] [Chemical Formula 1]

[0080]

[0081] In one embodiment, the liquid crystal polyester may contain structural units derived from hydroxycarboxylic acids as a main component. The liquid crystal polyester may preferably contain structural units (A) derived from hydroxybenzoic acid and structural units (B) derived from hydroxynaphthoic acid. For example, structural units (A) derived from 4-hydroxybenzoic acid (hereinafter formula (A)) may be used as structural unit (B), and structural units (B) derived from 6-hydroxy-2-naphthoic acid (hereinafter formula (B)) may be used as structural unit (B). From the viewpoint of improving melt-forming properties, the ratio of structural unit (A) to structural unit (B) is preferably in the range of 9 / 1 to 1 / 1, more preferably 7 / 1 to 1 / 1, and even more preferably in the range of 5 / 1 to 1 / 1.

[0082] [Chemical Formula 2]

[0083]

[0084] [Chemical Formula 3]

[0085]

[0086] It should be noted that, without impairing the effects of the present invention, the liquid crystal polyester fiber may contain thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefins, polycarbonate, polyamide, polyphenylene sulfide, polyetheretherketone, and fluororesins. Additionally, it may contain inorganic substances such as titanium dioxide, kaolin, silicon dioxide, and barium oxide, as well as colorants such as carbon black, dyes, and pigments, antioxidants, ultraviolet absorbers, and light stabilizers, and various other additives.

[0087] Provided that the effects of the present invention are not compromised, the liquid crystal polyester fiber can be a mixed spun fiber formed by mixing and spinning liquid crystal polyester with the aforementioned thermoplastic polymer and various additives, or it can be a composite spun fiber formed by simultaneously spinning from a spinning spinneret that separates different components of liquid crystal polyester and the aforementioned thermoplastic polymer. The liquid crystal polyester fiber can be a non-composite spun fiber or a composite spun fiber.

[0088] The fineness of the liquid crystal polyester fibers used in conductive fibers can be appropriately selected according to the application, etc. For example, the fineness can be 50 dtex or less, preferably 15 dtex or less, and more preferably 10 dtex or less. To obtain the softness required for smart textiles, a fineness of, for example, 7 dtex or less is preferred. Furthermore, there is no particular limitation on the lower limit of the fineness of the filaments; for example, it can be around 0.01 dtex. The fineness of the filaments is a value measured by the method described in the examples described later.

[0089] The liquid crystal polyester fiber used in the conductive fiber can be a monofilament or a multifilament. In the case of a multifilament, the number of filaments can be appropriately selected according to the application, etc. For example, the number of filaments can be 2 to 100, preferably 3 to 50, and more preferably 5 to 20.

[0090] The total fineness of the liquid crystal polyester used in the conductive fibers can be appropriately selected depending on the application and other factors. For example, the total fineness can be 440 dtex or less, preferably 220 dtex or less, and more preferably 110 dtex or less. To obtain the softness of the smart textile, it is preferable to make the fiber diameter of the conductive filaments thinner, preferably finer. In addition, there is no particular limitation on the lower limit of the total fineness, for example, it can be around 1 dtex.

[0091] Liquid crystal polyester fibers used as conductive fibers can be in the form of untwisted fibers, where monofilaments or multifilaments are directly wound from bobbins, or they can be processed into twisted yarns, combined twisted yarns, braided ropes, etc.

[0092] [Diameter of conductive fiber]

[0093] The diameter (D) of the conductive fiber of the present invention can be 0.3 mm or less, preferably 0.25 mm or less, and more preferably 0.20 mm or less. If the diameter of the conductive fiber is greater than 0.3 mm, it is more difficult to obtain sufficient flexibility when forming a fiber structure. The lower limit of the diameter of the conductive fiber is not particularly limited, for example, it can be about 0.05 mm. The diameter of the conductive fiber can be 0.05 to 0.30 mm, 0.07 to 0.25 mm, or 0.10 to 0.20 mm.

[0094] [Manufacturing method of conductive fibers]

[0095] The conductive fiber of the present invention is a metal foil filament formed by winding a metal foil around a liquid crystal polyester fiber as a core yarn, and can be manufactured using the same method as known copper foil wire manufacturing methods. There are no particular limitations. For example, firstly, a metal wire with a diameter of 0.2 to 0.3 mm is drawn until its diameter is 0.025 to 0.18 mm, and then the material is rolled to manufacture a metal foil. Next, by spirally winding the foil around a liquid crystal polyester fiber as a core yarn, a conductive fiber with flexibility and suppleness can be manufactured. Compared to a metal wire of the same diameter, the conductive fiber of the present invention exhibits less deformation (strain) in the metal portion when bent, thus providing excellent bending durability. Particularly when the metal foil is stainless steel, the bending durability is even better than when copper foil is used.

[0096] The spacing (d) of the metal foil wound around the liquid crystal polyester fibers can be appropriately set according to the application and specifications. Although it also depends on the thickness and width of the metal foil and the total fineness of the liquid crystal polyester fibers, 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. The smaller the spacing, the higher the conductivity, and therefore it is preferred. There is no particular limitation on the lower limit of the spacing, and the metal foil can also be wound in an overlapping manner, but this is sometimes not preferred depending on the application due to the decrease in bending durability. From the viewpoint of bending durability, the spacing of the metal foil 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, entanglement will occur in the conductive fibers, or the flexibility of the conductive fibers will decrease. By making a slight gap between the metal foils of the conductive fibers, when bending, the gap on the inside becomes smaller and the gap on the outside becomes larger, thereby limiting the deformation (strain) of the metal foil to a minimum, thus improving the bending durability that is a problem in the case of a single metal foil. The spacing of the metal foil can be 0.001~0.3mm, 0.005~0.25mm, or 0.01~0.3mm. Here, for example... Figure 1 As indicated by the symbol d, the spacing of a metal foil refers to the distance between adjacent edges of a strip of metal foil, which can be measured, for example, by magnified images such as scanning electron microscope (SEM) images.

[0097] The conductive fiber of the present invention can be manufactured by winding a single metal foil around a core yarn, or by winding multiple metal foils together according to the required conductivity. As a conductive fiber, a maximum of four metal foils wound four times around the core yarn can be effectively utilized. If more than four metal foils are wound, the weight increases and the bending durability decreases, which is undesirable. When multiple metal foils are wound together, the types of metal foils can be different. When further winding metal foils onto a conductive fiber already wrapped with metal foils, if the winding direction of the already wound metal foils is the S-winding direction, the winding direction of the next wound metal foil can be selected as the Z-winding direction; if the Z-winding direction is used, the winding direction of the next wound metal foil can be selected as the S-winding direction. This suppresses twisting within the conductive fiber and improves the process throughput when manufacturing a fiber structure comprising the conductive fiber formed by multiple windings of multiple metal foils.

[0098] [Fiber structure containing conductive fibers]

[0099] The fiber structure incorporating the conductive fibers of the present invention can be processed to be used in all fiber forms, such as short fibers, chopped fibers, filament yarns, textile yarns, ropes, twisted yarns, and cords. Furthermore, the conductive fibers of the present invention can be used to manufacture various fabrics and sheets, such as nonwoven fabrics, textiles, and woven fabrics. Such a fiber structure incorporating conductive fibers can be manufactured using known methods employing the conductive fibers of the present invention.

[0100] The fiber structure containing the conductive fibers of the present invention can be resin-processed. For example, after a plain-weave textile is manufactured using the conductive fibers of the present invention, a urethane resin coating can be applied to impart morphological stability and stain resistance.

[0101] For fiber structures incorporating the conductive fibers of the present invention, the conductive fibers of the present invention can be combined with other fibers as long as the effects of the present invention are not impaired. For example, composite fibers using conductive fibers and other fibers can be used (e.g., blended filaments formed by mixing conductive fibers with other fibers). Additionally, composite fabrics using conductive fibers and other fibers can be used (e.g., blended fabrics formed by mixing conductive fibers with other fibers, laminates of fabrics formed from conductive fibers and fabrics formed from other fibers, etc.). When the fiber structure is used in the manufacture of composite materials, the fiber structure can be a composite fiber or a composite fabric containing melt-bonded fibers as the matrix forming the composite material and other fibers.

[0102] The fiber structure containing the conductive fibers of the present invention can be used in a variety of applications such as smart textiles, electrical / electronic component materials, electromagnetic wave shielding, general industrial materials, various reinforcing materials, and protective clothing.

[0103] Example

[0104] The present invention will now be described in further detail based on embodiments, but the present invention is not limited to these embodiments in any way. It should be noted that in the following embodiments and comparative examples, various physical properties were measured using the methods described below.

[0105] (Relative permeability of the metal foil)

[0106] For relative permeability, the magnetic moment at 20°C was measured using a magnetic property measurement system (MPMS3, manufactured by QUANTUM DESING) in VSM mode, and the relative permeability at 1000 Oe was calculated using the following formula.

[0107] [Mathematical Expression 2]

[0108]

[0109] In the formula, μ r Where M is the relative permeability, M is the magnetic moment (emu), and V is the volume (cm³). 3 H is the magnetic field (Oe).

[0110] (Thickness and width of the metal foil)

[0111] For a 3mm long metal foil, the thickness (mm) and width (mm) of the metal foil were measured at three locations using a desktop scanning electron microscope (JCM-6000PLUS, manufactured by Nippon Electron Ltd.), and the average value was taken as the thickness (mm) and width (mm) of the metal foil.

[0112] (Total fineness of core yarn, fineness of single filament)

[0113] Based on JIS L 1013:2010 8.3.1 A method, the core yarn was wound into a 1m × 100 turns (total 100m) skein using a measuring instrument "Wrap Reel by Motor Driven" manufactured by Daiei Scientific Precision Manufacturing Co., Ltd. Its weight (g) was multiplied by 100, and measurements were taken twice at each level. The average value was taken as the total fineness (dtex) of the obtained core yarn. Furthermore, the quotient obtained by dividing the total fineness by the number of filaments was taken as the single filament fineness (dtex).

[0114] (Tensile strength of the core yarn)

[0115] Referring 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 on each sample of the core yarn under the 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 breaking load (cN) at this time by the fineness (dtex) of the core yarn.

[0116] (Diameter of the conductive fiber)

[0117] Using a digital vernier caliper (measuring range 0~150mm, minimum reading 0.01mm, manufactured by AS ONE Co., Ltd.), the diameter of the fibers obtained in the examples and comparative examples was measured at 5 locations, and the average value was taken as the diameter (mm) of the conductive fiber.

[0118] (The spacing between the metal foils of the conductive fiber)

[0119] The parallel line spacing of the metal foils of conductive fibers obtained in the examples and comparative examples was randomly measured at three points using a desktop scanning electron microscope (JCM-6000PLUS, manufactured by Nippon Electron Ltd.), and the average value was taken as the spacing (mm) of the metal foils.

[0120] (Break load of conductive fiber)

[0121] Referring 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 on each sample of conductive fiber filaments under the conditions of a test length of 20 cm and a tensile speed of 10 cm / min. The average value of the breaking load (N) was taken as the breaking load of the conductive fiber.

[0122] (Magneticization Evaluation)

[0123] Three conductive fibers, each 3 cm long, were placed on a permanent magnet (neodymium magnet, 16 mm in diameter, 2.5 mm thick, magnetic flux density 170 mT) and then inverted. If none of the three conductive fibers fell off, the fiber was considered magnetized and denoted as B. If even one conductive fiber fell off, the fiber was considered unmagnetized and denoted as A.

[0124] (Resistance value)

[0125] The resistance values ​​of the conductive fibers obtained in the examples and comparative examples were measured using a resistance meter (manufactured by Texio Technology). The spacing between the terminals holding the conductive fibers was set to 10 cm, and the resistance values ​​(Ω / m) were measured at 5 locations. The average value was taken as the resistance value (Ω / m).

[0126] [Example 1]

[0127] The metal foil used was stainless steel foil obtained by rolling austenitic stainless steel wire (NAS106N, manufactured by Nippon Seiki Co., Ltd.) with a diameter of 0.27 mm (relative magnetic permeability: 1.0, thickness: 0.01 mm, width: 0.2 mm). The core yarn used was liquid crystal polyester fiber "Vectran HT" (total fineness 56 dtex, number of filaments 10, manufactured by Kuraray Co., Ltd., listed as LCP1 in Table 5) formed from structural units from 4-hydroxybenzoic acid and structural units from 6-hydroxy-2-naphthoic acid. The stainless steel foil was spirally wound around the liquid crystal polyester fiber in the S direction with a metal foil spacing of 0.02 mm to obtain conductive fibers. The diameter (mm), breaking load (N), magnetization evaluation, and resistivity (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0128] [Example 2]

[0129] The total fineness of the liquid crystal polyester fiber was set to 110 dtex, the number of filaments was set to 20, and the spacing of the metal foil was set to 0.03 mm. Otherwise, conductive fibers were obtained in the same manner as in Example 1. The diameter (mm), breaking load (N), magnetization evaluation, and resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0130] [Example 3]

[0131] The metal foil used was copper foil (pure copper, relative permeability: 1.0, thickness: 0.01 mm, width: 0.2 mm, manufactured by Meisei Sangyo Co., Ltd.). Otherwise, conductive fibers were obtained in the same manner as in Example 1. The diameter (mm), breaking load (N), magnetization evaluation, and resistance (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0132] [Example 4]

[0133] The total fineness of the liquid crystal polyester fiber was set to 110 dtex, the number of filaments was set to 20, and the spacing of the metal foil was set to 0.03 mm. Otherwise, conductive fibers were obtained in the same manner as in Example 3. The diameter (mm), breaking load (N), magnetization evaluation, and resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0134] [Example 5]

[0135] A granular form of liquid crystal polyester, composed of structural units from 6-hydroxy-2-naphthoic acid, 2,6-naphthoic acid, hydroquinone, and 4,4'-dihydroxybiphenyl in a 60 / 20 / 15 / 5 (mol%) configuration, was melt-blended using a twin-screw extruder. The granules were then extruded from a nozzle at a spinneret temperature of 330°C and wound onto a bobbin at a take-up speed of 1000 m / min to obtain a liquid crystal polyester fiber precursor. Next, 500 m of the precursor was wound back into an aluminum bobbin and heat-treated in a sealed oven at 300°C for 16 hours under a nitrogen atmosphere to obtain a long liquid crystal polyester fiber (LCP2, listed in Table 5) with a total fineness of 280 dtex, 50 filaments, and a tensile strength of 31.0 cN / dtex. Using the obtained liquid crystal polyester fiber and maintaining a metal foil spacing of 0.05 mm, conductive fibers were obtained in the same manner as in Example 1. The diameter (mm), breaking load (N), magnetization evaluation, and resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0136] [Example 6]

[0137] The metal foil used was aluminum foil (pure aluminum, relative permeability: 1.0, thickness: 0.01 mm, width: 0.2 mm, manufactured by Meisei Sangyo Co., Ltd.). Otherwise, conductive fibers were obtained in the same manner as in Example 1. The diameter (mm), breaking load (N), magnetization evaluation, and resistance (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0138] [Comparative Example 1]

[0139] As the metal foil, stainless steel foil (relative permeability: 11, thickness: 0.01 mm, width: 0.2 mm) obtained by rolling austenitic / ferritic stainless steel wire (SUS329J4L, relative permeability: 40, diameter: 0.25 mm, manufactured by Nippon Seiki Co., Ltd.) was used. In addition, conductive fibers were obtained in the same manner as in Example 1. The diameter (mm), breaking load (N), magnetization evaluation, and resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0140] [Comparative Example 2]

[0141] The total fineness of the liquid crystal polyester fiber was set to 110 dtex, the number of filaments was set to 20, and the spacing of the metal foil was set to 0.03 mm. Otherwise, conductive fibers were obtained in the same manner as in Comparative Example 1. The diameter (mm), breaking load (N), magnetization evaluation, and resistance value (Ω / m) of the obtained conductive fibers are shown in Table 5.

[0142]

[0143] As shown in Table 5, the conductive fibers of Examples 1 to 6 have sufficient breaking load, do not become magnetized, and have low resistance, thus exhibiting sufficient conductivity.

[0144] On the other hand, although the conductive fibers of Comparative Examples 1 and 2 have sufficient breaking load and low resistance, thus possessing conductivity, they are conductive fibers that are susceptible to problems such as heating caused by magnetic fields and iron powder adhesion due to magnetization.

[0145] From the viewpoint of bending durability, the conductive fibers of Examples 1 to 6 are all conductive fibers made by winding a thin strip of metal foil around a core yarn made of liquid crystal polyester. Therefore, compared with the case of using metal fibers, durability can be expected.

[0146] Industrial applicability

[0147] The conductive fibers of this invention can be used in various fiber structures for a wide range of applications, including smart textiles, electrical / electronic component materials, electromagnetic wave shielding, general industrial materials, various reinforcing materials, and protective clothing. For example, they can be used to construct circuits, electrodes, wires, communication lines, heating wires, etc., in smart textiles. In particular, when fine-diameter conductive fibers are used to form fiber structures such as sewing threads and braids containing these fibers, they can be used in smart textile applications (displays, keyboards, circuit boards, clothing, hats, goggles, glasses, masks, gloves, socks, etc.) where they offer excellent softness and drape. Furthermore, they are suitable for use in the medical and food industries because iron powder is difficult to adhere to.

[0148] As described above, preferred embodiments of the present invention have been explained, but various additions, modifications or deletions can be made without departing from the spirit of the present invention, and such modifications are also included within the scope of the present invention.

Claims

1. A conductive fiber comprising: Liquid crystal polyester fibers with a tensile strength of 18 cN / dtex or higher, and A metal foil with a relative permeability of less than 3, spirally wound around the liquid crystal polyester fiber.

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

3. A fiber structure comprising the conductive fiber as described in claim 1 or 2.

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