Magnetic fiber, fiber structure including magnetic fiber, and wristband using fiber structure

Abstract

An objective of the present invention is to provide a magnetic fiber which has excellent strength and flex endurance and which sticks to a magnet. Another objective is to provide a flexible and lightweight fiber structure that includes the magnetic fiber of the present invention, and a wristband for securing a wearable device to the wrist by means of a magnet.　The present invention relates to: a magnetic fiber (1) characterized by including a core thread (10) and a metallic foil (20), the metallic foil (20) having a relative permeability of 3 or more and being spirally wound around the core thread (10); a fiber structure including the magnetic fiber (1); and a wristband including the fiber structure and a magnet.

Description

Magnetic fiber, fiber structure containing the magnetic fiber, and wristband using the fiber structure Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2023-211646, filed December 15, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a magnetic fiber, a fiber structure containing the magnetic fiber, and a wristband using the fiber structure.

[0003] In recent years, the miniaturization and weight reduction of optoelectronic devices has led to active development of wearable devices, such as watch-type optoelectronic devices (smart watches) that can be worn on the wrist. Wristbands, eyeglasses, gloves, innerwear, and other devices have been proposed as means for fastening wearable devices, such as smart watches, to the wrist or other parts of the body. In particular, wristbands used to fasten smart watches to the wrist must be made of materials that not only have tensile strength when putting on and taking off the devices, but also resistance to bending, metal allergies, and corrosion and rust caused by sweat.

[0004] For example, Patent Document 1 (JP 2022-530911 A) proposes a method for fastening a wearable device to the body using a wristband with magnetic coupling. The wristband is a flexible magnet containing a mixture of polymer and ferromagnetic material, and can be easily attached and adjusted for fit.

[0005] Magnetic fibers and fiber structures are considered to be the magnets and magnet-attachable wristband materials required for magnetic coupling. Patent Document 2 (International Publication No. 2014 / 014038) proposes a monofilament in which a magnetic material with a saturation magnetization of 3 emu / g or more is dispersed. If this monofilament breaks and gets mixed into food or medicine, the broken portion of the monofilament can be detected with a metal detector, making it a potential fiber for use in wristbands.

[0006] Patent Document 3 (JP 2015-218378 A) proposes a ferromagnetic metal wire and a magnetic wire mesh product using the same. Even if a portion of the wire mesh breaks and gets mixed into powdered ingredients for food or pharmaceuticals, the broken pieces can be easily detected and removed using a magnetic separator or the like, making it a potential fiber and fiber structure for use in wristbands.

[0007] JP-T-2022-530911 A International Publication No. 2014 / 014038 Japanese Patent Application Laid-Open No. 2015-218378 A

[0008] Patent Document 1 proposes a wristband that can be easily attached and adjusted for fit by using a flexible magnet that contains a mixture of a polymer and a ferromagnetic material. However, because the flexible magnet is a molded polymer, the tensile strength and bending durability of the magnet itself are low, and the magnet must be covered with an adhesive layer or an outer cover, which can make it difficult to achieve lightweight and compact designs.

[0009] Patent Document 2 proposes a monofilament in which a magnetic substance having a saturation magnetization of 3 emu / g or more is dispersed. However, when spinning a polymer in which a magnetic substance is dispersed, it is difficult to obtain a fiber with a small fiber diameter, and the monofilament must have a large single yarn fineness, which poses the problem of making it difficult to obtain a lightweight, thin woven or knitted fabric suitable for a wristband.

[0010] Patent Document 3 proposes a ferromagnetic metal wire and a magnetic wire mesh product using the same, which can also be used for wristbands, but because it is made of metal wire, it does not have sufficient bending durability, and the metal wire may break if it is repeatedly wrapped around the arm as a wristband and then removed.

[0011] The present invention aims to solve the above problems and to provide a magnetic fiber that has excellent strength and flexural durability and is attracted to a magnet. It also aims to provide a fiber structure containing the magnetic fiber of the present invention, which has excellent flexibility and light weight, and a wristband for fixing a wearable device to the wrist with a magnet.

[0012] As a result of intensive research into achieving the above-mentioned object, the inventors of the present invention discovered that magnetic fibers in which metal foil having a relative magnetic permeability of 3 or more is spirally wound around a core thread adhere to a magnet and have excellent strength and bending durability, and that when a wristband that is fixed with a magnet for fixing an electronic device to the body is manufactured using a fiber structure containing the magnetic fibers of the present invention, the wristband not only has sufficient fixing strength, but also has excellent flexibility and light weight, resulting in a small and thin wristband, which led to the completion of the present invention.

[0013] The present invention can be configured in the following aspects. [Aspect 1] A magnetic fiber comprising a core yarn and a metal foil, wherein the metal foil has a relative magnetic permeability of 3 or more (preferably 6 or more, more preferably 10 or more, and even more preferably 20 or more), and the metal foil is spirally wound around the core yarn. [Aspect 2] The magnetic fiber according to Aspect 1, wherein the metal foil is made of stainless steel. [Aspect 3] The magnetic fiber according to Aspect 1 or 2, wherein the core yarn is an organic fiber having a tensile strength of 18 cN / dtex or more. [Aspect 4] A fiber structure comprising the magnetic fiber according to any one of Aspects 1 to 3. [Aspect 5] A wristband comprising the fiber structure according to Aspect 4 and a magnet.

[0014] 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.

[0015] The magnetic fiber of the present invention has excellent strength and flexural durability, and is easily attached to a magnet and easily processed, so that the magnetic fiber can be used to provide a fiber structure having excellent flexibility and light weight. Furthermore, when the fiber structure is used to make a wristband for fastening a wearable device to the body, a lightweight, small, and thin wristband can be provided.

[0016] 1 is a schematic diagram showing the configuration of a magnetic fiber according to an embodiment of the present invention; 2 is a schematic perspective view showing an example of a wristband according to an embodiment of the present invention;

[0017] FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic fiber of the present invention, illustrating the state of the manufacturing process. Note that the dimensional ratios in the diagram do not reflect individual examples. The magnetic fiber 1 includes a core 10 and a tape-like metal foil 20 spirally wound around the core 10. The magnetic fiber 1 may essentially consist of the core 10 and the metal foil 20. The metal foil 20 is a metal foil with a relative magnetic permeability of 3 or more. In the diagram, w represents the width of the metal foil, d represents the spacing between the metal foils, and D represents the diameter of the magnetic fiber 1. The configuration of the magnetic fiber 1 will be further explained below.

[0018] [Metal Foil] The metal foil used in the magnetic fiber of the present invention has a relative magnetic permeability of 3 or more. The relative magnetic permeability of the metal foil is preferably 6 or more, more preferably 10 or more, and even more preferably 20 or more. If the relative magnetic permeability is less than 3, the magnetic fiber of the present invention may not be sufficiently strongly attracted to a magnet. For example, when a wristband including a magnet and a fiber structure containing the magnetic fiber of the present invention is wrapped around the wrist and an electronic device is secured to the wrist by the force of the magnet, the securing may not be strong enough, causing the electronic device to shift position or the electronic device to fall off the wrist along with the wristband. If the metal foil used in the magnetic fiber has a relative magnetic permeability of 20 or more, the fiber structure containing the magnetic fiber and the magnet will adhere strongly, making it easy to adjust the tightness of the wristband when wrapped around the wrist. Furthermore, the metal foil used in the magnetic fiber may preferably have a relative magnetic permeability of 2000 or less, more preferably 1000 or less. If the relative magnetic permeability of the metal foil used in the magnetic fiber exceeds 2000, a wristband equipped with a fiber structure containing magnetic fiber and a magnet may have the fiber structure containing magnetic fiber fixed to the magnet more firmly than necessary, making it difficult to remove the wristband.

[0019] For example, the relative magnetic permeability of the metal foil may be 3 to 2,000, 6 to 2,000, 10 to 1,000, or 20 to 1,000.

[0020] 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).

[0021] 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 / ferritic stainless steel, which has a relative permeability of 3 or more, will not become less than 3 after wire drawing or rolling, so the relative permeability of the metal wire before being made into metal foil can be used.

[0022] The metal foil used in the magnetic fibers can be produced, for example, by rolling a metal wire. Examples of metals include iron, cobalt, nickel, iron-chromium, iron-cobalt-vanadium, iron-nickel, iron-silicon, iron-aluminum-silicon, stainless steel, iron-silicon-boron amorphous alloys, and nanocrystalline alloys such as iron-copper-niobium-silicon-boron alloys. Among these, stainless steel is preferred from the viewpoints of rolling workability, corrosion resistance, and allergy resistance. Furthermore, martensitic stainless steel, ferritic stainless steel, and austenitic-ferritic stainless steel, which have high relative magnetic permeability, are more preferred. Among these stainless steels, it is preferable to select one with high corrosion resistance, and austenitic-ferritic stainless steel such as SUS329J4L is particularly preferred.

[0023] The metal foil used for the magnetic fibers may be made of the above metal alone, or may be a multi-layered metal foil made by plating, etc. For example, depending on the application, a metal foil made of iron plated with chromium or nickel to prevent rust can be used.

[0024] The thickness of the metal foil used in the magnetic 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 magnetic fiber, but if the thickness is too small, the strength may be insufficient depending on the application.

[0025] The width of the metal foil used in the magnetic fiber 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 magnetic fiber.

[0026] [Core Yarn] The core yarn used in the magnetic fiber of the present invention is preferably an organic fiber. The organic fiber may be a synthetic fiber such as polyester fiber, polyamide fiber, semi-aromatic polyamide fiber, polyethylene fiber, polypropylene fiber, polyvinyl alcohol fiber, aramid fiber, liquid crystal polyester fiber, PBO fiber (polyparaphenylene benzobisoxazole fiber), or polyurethane fiber, or may be a regenerated fiber, semi-regenerated fiber, or natural fiber, and can be selected according to the application. If necessary, two types of fiber may be used in combination.

[0027] The core yarn used in the present invention is preferably a high-strength organic fiber having a tensile strength of 18 cN / dtex or more. Examples of such fibers include aramid fibers known under the trade names "Kevlar (registered trademark)," "Twaron (registered trademark)," and "Technora (registered trademark)," ultra-high molecular weight polyethylene fibers known under the trade names "Dyneema (registered trademark)," "Izanas (registered trademark)," and "Spectra (registered trademark)," liquid crystal polyester fibers known under the trade names "Vectran (registered trademark)," "Scivelas (registered trademark)," and "Zexion (registered trademark)," and PBO fibers known under the trade name "Zylon (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 magnetic fibers constituting the fiber structure may be broken by pulling or may be broken due to insufficient bending durability during use as a fiber structure containing magnetic fibers. The upper limit of the tensile strength is not particularly limited, but may be, for example, about 40 cN / dtex. For example, the tensile strength may be 18 to 40 cN / dtex, 20 to 38 cN / dtex, or preferably 22 to 35 cN / dtex. The tensile strength of the core yarn is a value measured by the method described in the examples below.

[0028] When the core yarn used in the present invention is a high-strength fiber having a tensile strength of 18 cN / dtex or more, the tensile modulus is also high and the stretchability is small, and when used in a wristband or the like, the dimensional stability is excellent and the fit is excellent.

[0029] The core yarn used in the present invention is particularly preferably a liquid crystal polyester fiber from the viewpoints of excellent creep characteristics, excellent flexural durability, and the like.

[0030] 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.

[0031]

[0032] 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.

[0033] 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.

[0034]

[0035]

[0036]

[0037] In the structural units of Tables 2, 3 and 4, n is an integer of 1 or 2, and each structural unit n=1 and n=2 may exist alone or in combination; Y １ and Y ２ 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.

[0038] Examples of Z include substituents represented by the following formulas.

[0039]

[0040] 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.

[0041]

[0042]

[0043] 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.

[0044] As long as the effects of the present invention are not impaired, 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. The liquid crystal polyester fiber may be a non-conjugated spun fiber or a conjugated spun fiber. In particular, it is preferable that the liquid crystal polyester is present on the fiber surface.

[0045] The single yarn fineness of the core yarn used in the magnetic fiber can be selected appropriately depending on the application, etc. For example, the single yarn fineness may be 50 dtex or less, preferably 15 dtex or less, and more preferably 10 dtex or less, but in order to obtain the flexibility required for a wristband, a finer fineness is preferable, and may be, for example, 7 dtex or less. Furthermore, there is no particular restriction on the lower limit of the single yarn fineness, but it may be, for example, about 0.01 dtex. The single yarn fineness is a value measured by the method described in the Examples below.

[0046] The core yarn used in the magnetic 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.

[0047] The total fineness of the core yarn used in the magnetic fiber can be selected appropriately 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 wristband, it is preferable to make the fiber diameter of the magnetic fiber small, and a fine fineness is preferable. Furthermore, there is no particular lower limit on the total fineness, but it may be, for example, about 1 dtex.

[0048] The form of the core yarn used for the magnetic fiber may be an untwisted monofilament or multifilament as it is wound from a bobbin, or may be a fiber that has been processed into a twisted yarn, a doubled-twisted yarn, a braided cord, or the like.

[0049] [Magnetic Fiber Diameter] The diameter (D) of the magnetic fiber of the present invention may be 0.3 mm or less, preferably 0.25 mm or less, and more preferably 0.20 mm or less. If the magnetic fiber diameter exceeds 0.3 mm, sufficient flexibility may not be obtained when the magnetic fiber is formed into a fiber structure. The lower limit of the magnetic fiber diameter is not particularly limited, but may be, for example, about 0.05 mm. For example, the magnetic fiber diameter may be 0.05 to 0.3 mm, 0.07 to 0.25 mm, or 0.10 to 0.20 mm.

[0050] [Method for manufacturing magnetic fibers] The magnetic fiber of the present invention is a metal foil yarn formed by wrapping a metal foil around a core yarn, and can be manufactured by a method similar to a known copper foil yarn manufacturing method. The manufacturing method for the magnetic fiber is not particularly limited. For example, a metal wire having a diameter of 0.2 to 0.3 mm is first drawn to a diameter of 0.025 to 0.18 mm, and the material is then rolled to produce a metal foil. Next, the metal foil is spirally wrapped around the core yarn to produce a magnetic fiber that is a metal foil yarn with flexibility and pliability. The magnetic fiber of the present invention has excellent bending durability because the deformation (strain) of the metal portion is smaller when bent than a metal wire of the same diameter.

[0051] The spacing (d) of the metal foil wrapped around the core yarn can be set appropriately depending on the application and specifications. Depending on the thickness and width of the metal foil and the total fineness of the core yarn, 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 easier it is to attach to a magnet, which is preferable because it allows for stronger fixation when used in, for example, a wristband. The lower limit of the spacing is not particularly limited, and the metal foil can be wrapped so that it overlaps, but this may not be preferable 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 magnetic fiber or the flexibility of the magnetic fiber may decrease. By leaving small gaps between the metal foils of the magnetic fiber, the inner gap becomes smaller when bent, and the outer gap becomes larger, minimizing the deformation (strain) of the metal foil. This improves flexural durability, which is a problem when using metal foil alone. For example, the distance between the metal foils may be 0.001 to 0.3 mm, 0.005 to 0.25 mm, or 0.01 to 0.2 mm. Here, the distance between the metal foils refers to the distance 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.

[0052] The magnetic fiber of the present invention may be manufactured by wrapping a single metal foil around a core thread, or may be manufactured by wrapping multiple metal foils in multiple layers depending on the desired magnetic property. Magnetic fibers can be effectively manufactured by wrapping up to four metal foils around a core thread 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 magnetic fiber already wrapped in metal foil, selecting the winding direction of the next metal foil in the Z-winding direction if the winding direction of the previously wrapped metal foil is the S-winding direction, or the S-winding direction if the winding direction of the previously wrapped metal foil is the Z-winding direction, suppresses twisting of the magnetic fiber and improves processability when manufacturing a fiber structure containing the magnetic fiber wrapped in multiple layers of metal foil.

[0053] [Fiber structure containing magnetic fiber] The fiber structure containing the magnetic fiber of the present invention can be produced by processing the magnetic 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 magnetic fiber of the present invention can also be used to produce and use various fabrics and sheet-like materials, such as nonwoven fabrics, woven fabrics, and knitted fabrics. Such fiber structures containing magnetic fiber can be produced using the magnetic fiber of the present invention by known methods.

[0054] The fiber structure containing the magnetic fiber of the present invention may be resin-treated. For example, after producing a plain weave fabric from the magnetic fiber of the present invention, the fabric may be coated with a urethane resin to impart shape stability and stain resistance.

[0055] A fiber structure containing the magnetic fiber of the present invention may combine the magnetic fiber of the present invention with other fibers, as long as the effects of the present invention are not impaired. For example, a mixed yarn in which the magnetic fiber is mixed with other fibers can be used. Also, composite fabrics using the magnetic fiber of the present invention and other fibers (for example, mixed fabrics in which the magnetic fiber of the present invention is mixed with other fibers, or laminates of fabrics made of the magnetic fiber of the present invention and fabrics made of other fibers) can be used. When the fiber structure is used to produce a composite material, the fiber structure may be a composite fiber or composite fabric containing fusion fibers that form the matrix of the composite material as the other fibers.

[0056] [Wristband] The wristband of the present invention comprises a fiber structure containing the magnetic fiber of the present invention and a magnet. The magnetic fiber-containing fiber structure and the magnet are attached to each other by magnetic force, allowing an electronic device or the like to be fixed to the wrist. For example, a fiber structure containing magnetic fiber is joined to an electronic device, a magnet is attached to one free end of the fiber structure, and the free end with the magnet is overlapped and fixed to the other free end. By adjusting the position of the free end with the magnet, the tightness when wrapped around the wrist can be adjusted. Methods for attaching the magnet to a fiber structure containing magnetic fiber include fixing the magnet to the fiber structure with an adhesive, coating the magnet together with the fiber structure with resin and embedding it in resin, folding the fiber structure and sandwiching the magnet, and sewing the magnet like a button. Coating the magnet together with the fiber structure with resin and embedding it in resin is preferred because it stabilizes the shape of the wristband. When coating the magnet together with the fiber structure with resin and embedding it in resin, the entire fiber structure may be resin-coated, or only the portion where the magnet will be embedded may be resin-coated. The magnet may be located at one free end of the wristband, at both free ends, or at multiple portions of the wristband.

[0057] The magnetic fiber-containing fiber structure used in the wristband of the present invention is preferably a woven fabric, as it has little stretch. When a woven fabric is used, for example, a plain weave fabric with selvedge, using magnetic fibers with a diameter of 0.03 to 0.3 mm (e.g., 0.15 mm), and a weave density of approximately 40 to 120 warp threads per inch (e.g., 80 threads per inch) and approximately 25 to 80 weft threads per inch (e.g., 50 threads per inch), is preferred. The thickness of the wristband is preferably in the range of 0.5 to 5.0 mm, from the viewpoints of flexibility, lightness, and shape retention of the wristband.

[0058] The magnet used in the wristband of the present invention may be attached to a wristband member including a fiber structure containing the magnetic fiber of the present invention. For example, permanent magnets such as neodymium (neodymium-iron-boron), samarium-cobalt (samarium-cobalt), alnico (aluminum-nickel-cobalt), ferrite, etc. may be used.

[0059] 2 is a schematic perspective view showing an example of a wristband of the present invention. In this example, the wristband 2 comprises a band-shaped fiber structure 30 made of a woven magnetic fiber fabric and a magnet 40 attached to one end of the fiber structure 30. When worn, the other end of the fiber structure 30 is placed inside and overlapped with the end to which the magnet 40 is attached. The magnet 40 may be disposed on the outside of the band-shaped fiber structure 30 or may be embedded within the fiber structure 30. An electronic device 50 can be detachably attached to the fiber structure 30 by utilizing its magnetism.

[0060] 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.

[0061] (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).

[0062] (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.

[0063] (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 Drive" manufactured by Daiei Scientific Instruments Manufacturing Co., Ltd., and the weight (g) was multiplied by 100 to perform measurements twice per level, and the average value was taken as the total fineness (dtex) of the obtained liquid crystal polyester fiber. In addition, the quotient obtained by dividing the total fineness by the number of filaments was taken as the single yarn fineness (dtex).

[0064] (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.

[0065] (Diameter of metal foil thread) Using a digital caliper (measurement range 0 to 150 mm, minimum reading value 0.01 mm, manufactured by AS ONE Corporation), the diameter (mm) of the metal foil thread obtained in the examples and comparative examples was measured at five locations, and the average value was taken as the diameter (mm) of the metal foil thread.

[0066] (Spacing of metal foils in metal foil yarn) Using a tabletop scanning electron microscope (JCM-6000PLUS, manufactured by JEOL Ltd.), the parallel line spacing between the metal foils of the metal foil yarns 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.

[0067] (Breaking Load of Metal Foil 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 conduct 10 tensile tests for one sample of metal foil yarn 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 (N) of the metal foil yarn.

[0068] (Magnetic adhesion of metal foil thread) Three metal foil threads cut to a length of 3 cm were prepared and placed upside down on a permanent magnet (neodymium magnet, diameter: 16 mm, thickness: 2.5 mm, magnetic flux density: 170 mT). If none of the three metal foil threads fell off, the magnetic adhesion was evaluated as sufficient and rated A. If even one metal foil thread fell off, the magnetic adhesion was evaluated as insufficient and rated B.

[0069] Example 1 The metal foil was a stainless steel foil (relative permeability: 11, thickness: 0.008 mm, width: 0.150 mm) obtained by rolling an austenitic-ferritic stainless steel wire (SUS329J4L, relative permeability: 40, diameter: 0.25 mm, manufactured by Nippon Seisen Co., Ltd.). The core yarn was a liquid crystal polyester (LCP) fiber "Vectran HT" (total fineness: 56 dtex, number of filaments: 10, manufactured by Kuraray Co., Ltd.) 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 core yarn in the S direction with a spacing of 0.02 mm between the stainless steel foil strands to obtain a metal foil yarn. The diameter (mm), breaking load (N), and magnetic adhesion of the obtained metal foil yarn are shown in Table 5.

[0070] [Example 2] A metal foil yarn 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 stainless steel foils was 0.03 mm. The diameter (mm), breaking load (N), and magnetic adhesion of the obtained metal foil yarn are shown in Table 5.

[0071] [Example 3] The metal foil used was a stainless steel foil (relative permeability: 7, thickness: 0.018 mm, width: 0.220 mm) obtained by rolling an austenitic-ferritic stainless steel wire. The core yarn used was a liquid crystal polyester fiber with a total fineness of 280 dtex and 50 filaments. The rest of the procedure was the same as in Example 1, and a metal foil yarn was obtained. The diameter (mm), breaking load (N), and magnetic adhesion of the obtained metal foil yarn are shown in Table 5.

[0072] [Example 4] The metal foil used was a stainless steel foil (relative permeability: 9, thickness: 0.010 mm, width: 0.142 mm) obtained by rolling an austenitic-ferritic stainless steel wire. The core yarn used was a liquid crystal polyester fiber with a total fineness of 56 dtex and 10 filaments. The rest of the procedure was the same as in Example 1, and a metal foil yarn was obtained. The diameter (mm), breaking load (N), and magnetic adhesion of the obtained metal foil yarn are shown in Table 5.

[0073] [Example 5] The metal foil used was a stainless steel foil (relative permeability: 21, thickness: 0.005 mm, width: 0.120 mm) obtained by rolling an austenitic-ferritic stainless steel wire. The core yarn was a liquid crystal polyester fiber with a total fineness of 56 dtex and 10 filaments. The rest of the procedure was the same as in Example 1 to obtain a metal foil yarn. The diameter (mm), breaking load (N), and magnetic adhesion of the obtained metal foil yarn are shown in Table 5.

[0074] [Example 6] The metal foil used was a stainless steel foil (relative permeability: 7, thickness: 0.018 mm, width: 0.220 mm) obtained by rolling an austenitic-ferritic stainless steel wire. The core yarn used was a polyethylene terephthalate (PET) fiber "Tetron" (total fineness: 280 dtex, number of filaments: 48, manufactured by Toray Industries, Inc.). The rest of the procedure was the same as in Example 1, and a metal foil yarn was obtained. The diameter (mm), breaking load (N), and magnetic adhesion of the obtained metal foil yarn are shown in Table 5.

[0075] [Comparative Example 1] A metal foil thread was obtained in the same manner as in Example 1, except that a copper foil (pure copper, relative magnetic permeability: 1.0, thickness: 0.012 mm, width: 0.170 mm, manufactured by Meisei Sangyo Co., Ltd.) was used as the metal foil. The diameter (mm), breaking load (N) and magnetic adhesion of the obtained metal foil thread are shown in Table 5.

[0076] [Comparative Example 2] A metal foil thread was obtained in the same manner as in Example 1, except that a stainless steel foil (relative magnetic permeability: 1.0, thickness: 0.010 mm, width: 0.200 mm) obtained by rolling an austenitic stainless steel wire (NAS106N, manufactured by Nippon Seisen Co., Ltd.) with a diameter of 0.27 mm was used as the metal foil. The diameter (mm), breaking load (N) and magnetic adhesion of the obtained metal foil thread are shown in Table 5.

[0077] [Comparative Example 3] The metal foil used was a stainless steel foil (relative permeability: 2.4, thickness: 0.027 mm, width: 0.320 mm) obtained by rolling an austenitic-ferritic stainless steel wire. A metal foil yarn was obtained in the same manner as in Example 1, except that the core yarn contained liquid crystal polyester fibers with a total fineness of 280 dtex and 50 filaments. The diameter (mm), breaking load (N), and magnetic adhesion of the obtained metal foil yarn are shown in Table 5.

[0078]

[0079] As shown in Table 5, the metal foil yarns wrapped with stainless steel foil in Examples 1 to 6 were magnetic fibers with sufficient magnetic force because they had a relative permeability of 3 or more. In particular, the metal foil in Example 5 had a high relative permeability, so it was a magnetic fiber with strong magnetic force. The metal foil yarn in Example 6 had a polyethylene terephthalate core fiber, so it was a magnetic fiber with low tensile strength but flexibility.

[0080] On the other hand, the metal foil yarn wrapped with copper foil in Comparative Example 1 and the metal foil yarn wrapped with stainless steel foil in Comparative Examples 2 and 3 exhibited high breaking loads but did not exhibit magnetic adhesion and could not be used as magnetic fibers.

[0081] The magnetic fiber of the present invention can be used in the form of various fiber structures containing the magnetic fiber, such as wristbands for smart watches worn around the wrist, as well as for various applications including smart textiles, electrical and electronic component materials, electromagnetic wave shielding, general industrial materials, various reinforcing materials, and protective clothing. For example, it 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 magnetic fiber, the magnetic fiber 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 the information and recording fields, it can be used for magnetic displays, electromagnetic response devices, unauthorized removal control labels, identification markers, and the like, and can also be applied to fields such as sporting goods and composite materials.

[0082] As described above, the preferred embodiment of the present invention has 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.

[0083] REFERENCE SIGNS LIST 1 magnetic fiber 2 wristband 10 core thread 20 metal foil 30 fiber structure 40 magnet 50 electronic device w width of metal foil d spacing of metal foil D diameter of conductive fiber

Claims

1. A magnetic fiber comprising a core yarn and a metal foil, the metal foil having a relative magnetic permeability of 3 or more, and the metal foil being spirally wound around the core yarn.

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

3. The magnetic fiber according to claim 1, wherein the core yarn is an organic fiber having a tensile strength of 18 cN / dtex or more.

4. A fiber structure comprising the magnetic fiber according to any one of claims 1 to 3.

5. A wristband comprising the fiber structure according to claim 4 and a magnet.

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