INFRARED SHIELDING FIBER STRUCTURE AND CLOTHING EMPLOYING SAME

Abstract

An object to be achieved by the invention is to provide an infrared-shielding fiber structure that does not deteriorate over time in its ability to prevent voyeuristic photography using infrared rays and that can also prevent discoloration of the knitted fabric over time, and clothing using the same.

The infrared-shielding fiber structure of the present invention is an infrared-shielding fiber structure obtained by processing infrared-shielding fibers containing, on a surface and/or inside thereof, infrared-shielding fine particles selected from tungsten oxide fine particles represented by the general formula WO.sub.X (where W is tungsten, O is oxygen, and 2.45X2.999) or composite tungsten oxide fine particles represented by the general formula M.sub.YWO.sub.Z (where element M is an element selected from Cs, Rb, K, Tl, In, etc.; 0.001Y1.0; and 2.2z3.0), wherein the particle size of the fine particles is 1 nm or more and 800 nm or less, and the content of the fine particles per unit area of the structure is 0.10 g/m.sup.2 or more and 4.5 g/m.sup.2 or less; because the average reflectance of the structure at wavelengths of 800 nm to 1300 nm is 65% or less, the function of preventing voyeuristic photography using infrared rays can be maintained for a long period of time.

Claims

1. An infrared-shielding fiber structure obtained by processing infrared-shielding fibers containing, on a surface and/or inside thereof, one or more infrared-shielding fine particles selected from tungsten oxide fine particles or composite tungsten oxide fine particles, wherein a particle size of the infrared-shielding fine particles is 1 nm or more and 800 nm or less, and a content of the infrared-shielding fine particles per unit area of the infrared-shielding fiber structure is 0.10 g/m.sup.2 or more and 4.5 g/m.sup.2 or less.

2. The infrared-shielding fiber structure according to claim 1, wherein an average reflectance at a wavelength of 800 nm to 1300 nm is 65% or less.

3. The infrared-shielding fiber structure according to claim 1, wherein the tungsten oxide fine particles are tungsten oxide fine particles represented by the general formula WO.sub.X (where W is tungsten, O is oxygen, and 2.45X2.999), and the composite tungsten oxide fine particles are represented by the general formula M.sub.YWO.sub.Z (where element M is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; O is oxygen; 0.001Y1.0; and 2.2Z3.0), and are composite tungsten oxide fine particles having a hexagonal crystal structure.

4. The infrared-shielding fiber structure according to claim 3, wherein the element M of the composite tungsten oxide fine particles is one or more elements selected from Cs, Rb, K, Tl, In, Ba, Li, Ca, Sr, Fe, and Sn.

5. The infrared-shielding fiber structure according to claim 1, wherein the infrared-shielding fibers are fibers selected from synthetic fibers, semi-synthetic fibers, natural fibers, regenerated fibers, inorganic fibers, or mixed yarns obtained by blending, combining, or mixing any of these fibers.

6. The infrared-shielding fiber structure according to claim 5, wherein the synthetic fibers are synthetic fibers selected from polyurethane fibers, polyamide-based fibers, acrylic fibers, polyester-based fibers, polyolefin-based fibers, polyvinyl alcohol-based fibers, polyvinylidene chloride-based fibers, polyvinyl chloride-based fibers, and polyether ester-based fibers.

7. The infrared-shielding fiber structure according to claim 5, wherein the semi-synthetic fibers are semi-synthetic fibers selected from cellulose-based fibers, protein-based fibers, chlorinated rubber, and hydrochlorinated rubber.

8. The infrared-shielding fiber structure according to claim 5, wherein the natural fibers are natural fibers selected from vegetable fibers, animal fibers, and mineral fibers.

9. The infrared-shielding fiber structure according to claim 5, wherein the regenerated fibers are regenerated fibers selected from cellulose-based fibers, protein-based fibers, algin fibers, rubber fibers, chitin fibers, and mannan fibers.

10. Clothing using the infrared-shielding fiber structure according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a graph showing the relationship between wavelength (nm) and reflectance (%) of the knitted products (fiber structure) according to Examples 1 to 7 and Comparative Examples 1 and 2.

BEST MODES FOR PRACTICING THE INVENTION

[0030] Embodiments of the present invention will be described in detail below.

[0031] First, the infrared-shielding fiber structure according to the present invention is configured by processing infrared-shielding fibers containing inorganic infrared-shielding fine particles (tungsten oxide fine particles or composite tungsten oxide fine particles) on the surface and/or inside thereof, and examples of the infrared-shielding fiber structure include woven fabrics, knitted fabrics, and non-woven fabrics.

(1) Infrared-Shielding Fine Particles

[0032] The infrared-shielding fibers (near-infrared shielding fibers) according to the present invention can be obtained by containing infrared-shielding fine particles (fine particles having an infrared-shielding function) on and/or inside the fiber surface.

[0033] The tungsten oxide fine particles and composite tungsten oxide fine particles having an infrared-shielding function will be described below.

[0034] The tungsten oxide fine particles having an infrared-shielding function are fine particles represented by the general formula WO.sub.X (where W is tungsten, O is oxygen, and 2.45X2.999); the composite tungsten oxide fine particles having an infrared-shielding function are represented by the general formula M.sub.YWO.sub.Z (where the element M is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; O is oxygen; 0.001Y1.0; and 2.2z3.0), and are fine particles having a hexagonal crystal structure.

[0035] When tungsten oxide fine particles or composite tungsten oxide fine particles are applied to various fibers, they function as infrared-shielding components.

[0036] Examples of the tungsten oxide fine particles represented by the general formula WO.sub.X (2.45X2.999) include W.sub.18O.sub.49, W.sub.20O.sub.58, and W.sub.4O.sub.11. If the value of X is 2.45 or more, the appearance of the unintended WO.sub.2 crystal phase in the infrared-shielding fine particles can be completely avoided, and chemical stability of the material can be obtained. Further, if the value of X is 2.999 or less, a sufficient amount of free electrons are generated, so that the fine particles become efficient infrared-shielding fine particles.

[0037] WO.sub.X compounds in which the range of X is 2.45X2.95 are included in compounds called Magnli phases.

[0038] Examples of the composite tungsten oxide fine particles represented by the general formula M.sub.YWO.sub.Z and having a hexagonal crystal structure include composite tungsten oxide fine particles containing, as a preferable element M, one or more elements selected from Cs, Rb, K, Tl, In, Ba, Li, Ca, Sr, Fe, and Sn.

[0039] The added amount Y of the added element M needs to be 0.001 or more and 1.0 or less, and is preferably around 0.33. This is because the theoretically calculated value of Y from the hexagonal crystal structure is 0.33, and preferable optical properties are obtained with the added amount around this value. Typical examples include Cs.sub.0.33WO.sub.3, Rb.sub.0.33WO.sub.3, K.sub.0.33WO.sub.3, and Ba.sub.0.33WO.sub.3, but useful infrared-shielding properties can be obtained as long as Y and Z are within the above ranges.

(2) Particle Size of Infrared-Shielding Fine Particles

[0040] Regarding the particle size of the infrared-shielding fine particles, it is important that no problems occur during fiber forming processes such as spinning and drawing, and it is preferable that the average particle size of the infrared-shielding fine particles is 800 nm or less. If the average particle size of the fine particles is 800 nm or less, it is possible to avoid a decrease in spinnability, such as clogging of the spinneret (nozzle) and yarn breakage, in the spinning process. Moreover, even if spinning can be performed, problems such as yarn breakage may occur in the drawing process, and it may be difficult to uniformly mix and disperse the particles in the spinning raw material; therefore, from this viewpoint as well, it is preferable that the average particle size is 800 nm or less.

[0041] On the other hand, considering the designability, such as dyeability, of the infrared-shielding fiber structure containing infrared-shielding fine particles on and/or inside the fiber surface, it is necessary for the infrared-shielding fine particles to efficiently absorb near-infrared rays while maintaining transparency and perform infrared shielding. Infrared-shielding fine particles selected from tungsten oxide fine particles or composite tungsten oxide fine particles transmit visible light (wavelength 380 nm to 780 nm) and largely absorb near-infrared light, particularly light near a wavelength of 780 to 2200 nm; therefore, the transmission color tone is often blue to green. For this reason, transparency can be ensured if the particle size (particle diameter) of the infrared-shielding fine particles is smaller than 800 nm, but when transparency is emphasized, the particle diameter is preferably 200 nm or less, and more preferably 100 nm or less. On the other hand, if the particle diameter is 1 nm or more, industrial production is easy; therefore, the particle size (particle diameter) of the infrared-shielding fine particles needs to be 1 nm or more and 800 nm or less.

(3) Content of Infrared-Shielding Fine Particles Contained on and/or Inside Fiber Surface

[0042] Because the infrared absorption capacity per unit weight of the tungsten oxide fine particles and composite tungsten oxide fine particles is very high, compared to ITO and ATO, they exhibit their effect with about to 1/10 the amount used. In the case of composite tungsten oxide fine particles having a hexagonal crystal structure and using K, Rb, or Cs for the element M, the infrared absorption capacity at a wavelength of 780 nm or more is particularly excellent; therefore, they are suitable for preventing voyeuristic photography using infrared rays (preventing penetration imaging with a CCD camera). On the other hand, in the above-mentioned ITO and ATO, absorption of infrared rays in the wavelength range of 780 nm to 900 nm cannot be expected. Therefore, the effect of preventing voyeuristic photography using infrared rays (preventing penetration imaging with a CCD camera) cannot be expected with an infrared-shielding fiber structure using ITO or ATO.

[0043] The content of the infrared-shielding fine particles (tungsten oxide fine particles or composite tungsten oxide fine particles) contained on and/or inside the fiber surface is preferably set between 0.001 wt % and 80 wt %, and when the weight of the fibers after the addition of the infrared-shielding fine particles and the raw material cost are taken into consideration, the content is more preferably set between 0.005 wt % and 50 wt %. If the content of the infrared-shielding fine particles is 0.001 wt % or more, a sufficient infrared absorption effect can be obtained even if the fabric (infrared-shielding fiber structure) is thin, and if it is 80 wt % or less, a decrease in spinnability due to clogging of the spinneret (nozzle) and yarn breakage, etc., in the spinning process can be avoided, and if it is 50 wt % or less, the amount of infrared-shielding fine particles added can be reduced, so that the physical properties of the fibers are not impaired.

(4) Content of Infrared-Shielding Fine Particles Per Unit Area of Infrared-Shielding Fiber Structure

[0044] As described above, the content of the infrared-shielding fine particles per unit area of the infrared-shielding fiber structure is 0.10 g/m.sup.2 or more and 4.5 g/m.sup.2 or less, preferably 0.15 g/m.sup.2 or more, and more preferably 0.20 g/m.sup.2 or more. If the content of the infrared-shielding fine particles per unit area of the infrared-shielding fiber structure is 0.10 g/m.sup.2 or more, the average reflectance of the infrared-shielding fiber structure in the infrared region (wavelength 800 nm to 1300 nm) can be made 65% or less. If the average reflectance of the infrared-shielding fiber structure is 65% or less, voyeuristic photography using infrared rays (penetration imaging with a CCD camera) can be prevented in clothing using the infrared-shielding fiber structure as a woven or knitted fabric, and it is more preferable if the average reflectance of the infrared-shielding fiber structure is 60% or less, and further preferable if it is 55% or less. In order to make the average reflectance of the infrared-shielding fiber structure 60% or less, it is necessary to make the above-mentioned content of infrared-shielding fine particles per unit area of the infrared-shielding fiber structure 0.15 g/m.sup.2 or more, and in order to make the average reflectance 55% or less, it is necessary to make the above-mentioned content of infrared-shielding fine particles 0.20 g/m.sup.2 or more.

[0045] On the other hand, if the content of the infrared-shielding fine particles per unit area of the infrared-shielding fiber structure exceeds 4.5 g/m.sup.2, the average reflectance becomes lower than 0.07%, but even if the average reflectance is adjusted to a lower value, the effect of preventing voyeuristic photography using infrared rays does not improve any further. Therefore, the upper limit of the content of the infrared-shielding fine particles per unit area of the infrared-shielding fiber structure is desirably 3.5 g/m.sup.2. If the content of the infrared-shielding fine particles per unit area is 3.5 g/m.sup.2, the average reflectance is 0.2% or less, and the effect of preventing voyeuristic photography using infrared rays is sufficiently exhibited. However, if the infrared-shielding fiber structure contains an excessive amount of infrared-shielding fine particles per unit area, it may be difficult to develop the color depending on the color used to dye the infrared-shielding fiber structure.

[0046] The average reflectance in the infrared region (wavelength 800 nm to 1300 nm) of a fiber structure containing no infrared-shielding fine particles is 77%, as confirmed in Comparative Example 1 below, and at this reflectance, voyeuristic photography using infrared rays (penetration imaging with a CCD camera) becomes possible.

[0047] The average reflectance is the average value of the reflectance of the infrared-shielding fiber structure measured by a spectrophotometer when the wavelength is increased at 5 nm intervals in the wavelength range of 800 nm to 1300 nm.

[0048] Here, regarding the solution to prevent voyeuristic photography using infrared rays (penetration imaging with a CCD camera), it will be explained that the present invention focuses on the reflectance of the infrared-shielding fiber structure.

[0049] When an object is viewed with the eye, it can be recognized because the light directed onto the object is reflected and an image of the object can be formed by the eye, and the same applies to images captured by a camera.

[0050] In the infrared-shielding fiber structure according to the present invention, infrared-absorbing infrared-shielding fine particles are contained on and/or inside the fiber surface, and when light is directed onto the infrared-shielding fiber structure, the infrared-shielding fine particles absorb infrared rays; therefore, the reflectance in the infrared region (wavelength 800 nm to 1300 nm) decreases. That is, among the light components directed onto the infrared-shielding fiber structure according to the present invention, the reflectance of infrared rays is reduced. As a result, even if an attempt is made to photograph the infrared-shielding fiber structure according to the present invention with a CCD camera, the image becomes unclear because the reflectance at wavelengths of 800 nm to 1300 nm is reduced.

[0051] It is known that the wavelength range of widely used CCD sensors is 400 nm to 1200 nm. In the infrared-shielding fiber structure according to the present invention, among the incident light components, the reflectance in the infrared region (wavelength 800 nm to 1300 nm) is reduced, so it is possible to prevent voyeuristic photography using infrared rays (penetration imaging with a CCD camera).

[0052] On the other hand, the absorption of light in the visible light region by the infrared-shielding fine particles (tungsten oxide fine particles or composite tungsten oxide fine particles) applied in the present invention is slight compared to the absorption of light in the infrared region (wavelength 800 nm to 1300 nm). That is, because the absorption of light in the visible light region by the infrared-shielding fine particles according to the present invention is small, colors can be freely imparted to the infrared-shielding fiber structure by dyeing or the like. Furthermore, when the infrared-shielding fiber structure according to the present invention is used for clothing, the amount of infrared rays contained in natural light that reach the skin of the human body can be reduced; therefore, damage to the skin can be reduced.

(5) Infrared-Shielding Fibers

[0053] The fibers used in the infrared-shielding fibers according to the present invention can be variously selected depending on the application, and any of synthetic fibers, semi-synthetic fibers, natural fibers, regenerated fibers, inorganic fibers, and mixed yarns obtained by e.g. blending, combining, or mixing any of these fibers may be used. Further, synthetic fibers are preferable in view of containing inorganic fine particles in the fibers by a simple method and maintaining heat retention.

(5-1) Synthetic Fibers

[0054] The synthetic fibers used for the infrared-shielding fibers according to the present invention are not particularly limited, and examples thereof include polyurethane fibers, polyamide-based fibers, acrylic fibers, polyester-based fibers, polyolefin-based fibers, polyvinyl alcohol-based fibers, polyvinylidene chloride-based fibers, polyvinyl chloride-based fibers, and polyether ester-based fibers.

[0055] For example, examples of the polyamide-based fibers include nylon, nylon 6, nylon 66, nylon 11, nylon 610, nylon 612, aromatic nylon, and aramid.

[0056] Examples of the acrylic fibers include polyacrylonitrile, acrylonitrile-vinyl chloride copolymer, and modacrylic.

[0057] Examples of the polyester-based fibers include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate.

[0058] Examples of the polyolefin-based fibers include polyethylene, polypropylene, and polystyrene.

[0059] Examples of the polyvinyl alcohol-based fibers include vinylon.

[0060] Examples of the polyvinylidene chloride-based fibers include vinylidene.

[0061] Examples of the polyvinyl chloride-based fibers include polyvinyl chloride.

[0062] Examples of the polyether ester-based fibers include Rexe and Success.

(5-2) Semi-Synthetic Fibers

[0063] When the fibers used in the infrared-shielding fibers according to the present invention are semi-synthetic fibers, examples thereof include cellulose-based fibers, protein-based fibers, chlorinated rubber, and hydrochlorinated rubber.

[0064] Examples of the cellulose-based fibers include acetate, triacetate, and oxidized acetate.

[0065] Examples of the protein fibers include Promix.

(5-3) Natural Fibers

[0066] When the fibers used in the infrared-shielding fibers according to the present invention are natural fibers, examples thereof include vegetable fibers, animal fibers, and mineral fibers.

[0067] Examples of the vegetable fibers include cotton, kapok, flax, hemp, jute, manila hemp, sisal hemp, New Zealand hemp, sword-leaf dogbane, coconut palm, rush, and straw.

[0068] Examples of the animal fibers include wool such as sheep wool, goat hair, mohair, cashmere, alpaca, angora, camel, and vicua, as well as silk, down, and feather.

[0069] Examples of the mineral fibers include asbestos.

(5-4) Regenerated Fibers

[0070] When the fibers used in the infrared-shielding fibers according to the present invention are regenerated fibers, examples thereof include cellulose-based fibers, protein-based fibers, algin fibers, rubber fibers, chitin fibers, and mannan fibers.

[0071] Examples of the cellulose-based fibers include rayon, viscose rayon, cupra, polynosic, and cuprammonium rayon.

[0072] Examples of the protein-based fibers include casein fiber, peanut protein fiber, corn protein fiber, soybean protein fiber, and regenerated silk yarn.

(5-5) Inorganic Fibers

[0073] When the fibers used in the infrared-shielding fibers according to the present invention are inorganic fibers, examples thereof include metal fibers, carbon fibers, and silicate fibers.

[0074] Examples of the metal fibers include metal fibers, gold thread, silver thread, and heat-resistant alloy fibers.

[0075] Examples of the silicate fibers include glass fibers, mineral slag fibers, and rock fibers.

(6) Cross-Sectional Shape, Etc., of Infrared-Shielding Fibers

[0076] The cross-sectional shape of the infrared-shielding fibers according to the present invention is not particularly limited, and examples thereof include circular, triangular, hollow, flat, Y-shaped, star-shaped, and core-sheath shapes. The fine particles can be contained on and/or inside the surface of the fibers in various shapes; for example, in the case of a core-sheath type, the fine particles may be contained in the core portion or the sheath portion of the fibers. Further, the shape of the infrared-shielding fibers may be filament (long fiber) or staple (short fiber).

[0077] The infrared-shielding fibers according to the present invention can contain antioxidants, flame retardants, deodorants, insect repellents, antibacterial agents, ultraviolet absorbers, etc., as needed within a range that does not impair the performance of the fibers.

(7) Method of Containing Infrared-Shielding Fine Particles on and/or Inside Fiber Surface

[0078] The method of containing infrared-shielding fine particles on and/or inside the fiber surface according to the present invention is not particularly limited. Examples thereof include (A) a method of directly mixing the infrared-shielding fine particles into a raw material polymer for synthetic fibers and spinning the mixture, (B) a method of producing a masterbatch containing a high concentration of the infrared-shielding fine particles in a part of the raw material polymer in advance, diluting and adjusting this to a predetermined concentration at the time of spinning, and then spinning, (C) a method of uniformly dispersing the infrared-shielding fine particles in a raw material monomer or oligomer solution in advance, synthesizing a target raw material polymer using this dispersion solution, and at the same time, uniformly dispersing the infrared-shielding fine particles in the raw material polymer, and then spinning, and (D) a method of attaching the infrared-shielding fine particles to the surface of fibers obtained by spinning in advance using a binder or the like.

[0079] Here, a preferred example of the method described in (B) above, in which a masterbatch is produced, diluted and adjusted at the time of spinning, and then spun, will be described in detail below.

[0080] The method for producing the masterbatch is not particularly limited; for example, a tungsten oxide fine particle and/or composite tungsten oxide fine particle dispersion liquid, a thermoplastic resin powder or pellet, and other additives as necessary are mixed in a mixer such as a ribbon blender, tumbler, Nauta mixer, Henschel mixer, super mixer, or planetary mixer, and a kneader such as a Banbury mixer, kneader, roll, kneader-ruder, single-screw extruder, or twin-screw extruder, and are uniformly melt-mixed while removing the solvent, whereby a masterbatch can be prepared as a mixture in which the fine particles are uniformly dispersed in the thermoplastic resin.

[0081] Further, after preparing a tungsten oxide fine particle and/or composite tungsten oxide fine particle dispersion liquid, the solvent in the dispersion liquid may be removed by a known method, and the obtained powder, a thermoplastic resin powder or pellet, and other additives as necessary may be uniformly melt-mixed to produce a mixture in which the fine particles are uniformly dispersed in the thermoplastic resin. In addition, a method of directly adding a powder of tungsten oxide fine particles and/or composite tungsten oxide fine particles to a thermoplastic resin and uniformly melt-mixing them can also be used.

[0082] An infrared-shielding fine particle-containing masterbatch can be obtained by kneading the mixture of tungsten oxide fine particles and/or composite tungsten oxide fine particles and the thermoplastic resin obtained by the methods described above with a vent-type single-screw or twin-screw extruder and processing it into pellets.

[0083] Here, the methods (A) to (D) described above will be specifically described below.

[0084] Method (A): For example, when polyester fibers are used as the fibers, a tungsten oxide fine particle and/or composite tungsten oxide fine particle dispersion liquid is added to polyethylene terephthalate resin pellets, which are a thermoplastic resin, and the mixture is uniformly mixed with a blender, and then the solvent is removed. The mixture from which the solvent has been removed is melt-kneaded with a twin-screw extruder to obtain a tungsten oxide fine particle and/or composite tungsten oxide fine particle-containing masterbatch. The obtained tungsten oxide fine particle and/or composite tungsten oxide fine particle-containing masterbatch is melt-mixed near the melting temperature of the resin and spun according to a conventional method.

[0085] Method (B): In the same manner as in (A), except that a tungsten oxide fine particle and/or composite tungsten oxide fine particle-containing masterbatch prepared in advance is used, a target amount of the tungsten oxide fine particle and/or composite tungsten oxide fine particle-containing masterbatch and a fine particle-free polyethylene terephthalate masterbatch are melt-mixed near the melting temperature of the resin and spun according to a conventional method.

[0086] Method (C): For example, when urethane fibers are used as the fibers, a polymer diol containing tungsten oxide fine particles and/or composite tungsten oxide fine particles and an organic diisocyanate are reacted in a twin-screw extruder to synthesize an isocyanate group-terminated prepolymer, and then a chain extender is reacted therewith to produce a polyurethane solution (raw material polymer). The polyurethane solution is spun according to a conventional method.

[0087] Method (D): For example, in order to attach infrared-shielding fine particles to the surface of natural fibers, first, a treatment liquid is prepared by mixing tungsten oxide fine particles and/or composite tungsten oxide fine particles, at least one binder resin selected from acrylic, epoxy, urethane, and polyester resins, and a solvent such as water. Next, the natural fibers are immersed in the prepared treatment liquid, or the prepared treatment liquid is impregnated into the natural fibers by padding, printing, spraying, or the like, and dried, whereby the tungsten oxide fine particles and/or composite tungsten oxide fine particles can be attached to the natural fibers. The method (D) can be applied to semi-synthetic fibers, regenerated fibers, inorganic fibers, or any blends, combined yarns, mixed fibers, etc. thereof, in addition to the natural fibers described above.

[0088] When carrying out the methods according to (A) to (D) above, the method of dispersing the tungsten oxide fine particles and/or composite tungsten oxide fine particles may be any method as long as it can uniformly disperse the fine particles in a liquid; for example, methods such as media stirring mill, ball mill, sand mill, and ultrasonic dispersion can be suitably applied.

[0089] The dispersion medium for the infrared-shielding fine particles is not particularly limited and can be selected according to the fibers to be mixed; for example, various general organic solvents such as alcohols, ethers, esters, ketones, and aromatic compounds, and water can be used.

[0090] Further, when attaching and mixing the infrared-shielding fine particles to the fibers or the polymer serving as a raw material therefor, the dispersion liquid of the infrared-shielding fine particles may be directly mixed with the fibers or the polymer serving as a raw material therefor. Additionally, if necessary, an acid or alkali may be added to the dispersion liquid of the infrared-shielding fine particles to adjust the pH, and it is also preferable to add various surfactants, coupling agents, etc., to further improve the dispersion stability of the fine particles.

[0091] In order to improve the weather resistance of the infrared-shielding fine particles, it is also preferable to coat the surface of the tungsten oxide fine particles and/or composite tungsten oxide fine particles with a compound containing one or more elements selected from silicon, zirconium, titanium, and aluminum. These compounds are basically transparent and do not reduce the visible light transmittance of the infrared-shielding fine particles by adding them; therefore, the designability of the fibers is not impaired.

[0092] Furthermore, in order to improve the chemical resistance of the infrared-shielding fine particles, the surface of the tungsten oxide fine particles and/or composite tungsten oxide fine particles may be coated with a thermoplastic resin such as polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, polyamide resin, vinyl chloride resin, olefin resin, fluororesin, polyvinyl acetate resin, thermoplastic polyurethane resin, acrylonitrile butadiene styrene resin, polyvinyl acetal resin, acrylonitrile-styrene copolymer resin, or ethylene-vinyl acetate copolymer resin, or a thermosetting resin such as phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, thermosetting polyurethane resin, polyimide resin, or silicone resin.

[0093] As described above, the infrared-shielding fibers according to the present invention can shield infrared rays by containing a small amount of tungsten oxide fine particles and/or composite tungsten oxide fine particles as heat ray-shielding components on and/or inside the fiber surface.

[0094] The infrared-shielding fibers are processed into long fibers or short fibers depending on the application, and then spun and processed into woven fabrics or knitted fabrics by a known method to become an infrared-shielding fiber structure. Further, the infrared-shielding fibers are processed by a known method to become a non-woven fabric and an infrared-shielding fiber structure. Of course, the yarn (spun yarn) obtained by spinning the infrared-shielding fibers may be colorless or dyed. Further, the infrared-shielding fiber structure, such as a woven fabric, knitted fabric, or non-woven fabric, may be partially or entirely dyed.

[0095] The infrared-shielding fiber structure according to the present invention has good weather resistance and is colorless, and because the amount of infrared-shielding fine particles added is small, there is a high degree of freedom in coloring, such as dyeing, for the fiber structure and the resulting clothing, so designability is not impaired, and impairment of basic physical properties of the fibers, such as strength and elongation, can also be avoided. As a result, because the infrared-shielding fiber structure according to the present invention can prevent voyeuristic photography using infrared rays (penetration imaging with a CCD camera) without impairing the basic physical properties of textile products, it can be used for clothing such as innerwear, sportswear, and stockings.

(8) Method for Producing Infrared-Shielding Fine Particles

[0096] Next, the method for producing the infrared-shielding fine particles according to the present invention will be described by taking, as examples, the method for producing tungsten oxide fine particles represented by the general formula WO.sub.X and the method for producing composite tungsten oxide fine particles represented by the general formula M.sub.YWO.sub.Z.

[0097] The tungsten oxide fine particles and/or composite tungsten oxide fine particles can be obtained by weighing and mixing a predetermined amount of a tungsten compound, which is a starting material for the oxide fine particles, and then heat-treating the mixture in an inert gas atmosphere or a reducing gas atmosphere.

[0098] The tungsten compound as a starting material is preferably one or more selected from tungsten trioxide powder, tungsten dioxide powder, a hydrate of tungsten oxide, tungsten hexachloride powder, ammonium tungstate powder, a hydrate of tungsten oxide powder obtained by dissolving tungsten hexachloride in alcohol and then drying it, a hydrate of tungsten oxide powder obtained by dissolving tungsten hexachloride in alcohol, adding water to precipitate it, and drying it, a tungsten compound powder obtained by drying an aqueous ammonium tungstate solution, and metallic tungsten powder.

[0099] From the viewpoint of ease of the production process, it is more preferable to use a hydrate of tungsten oxide powder, tungsten trioxide, or a tungsten compound powder obtained by drying an aqueous ammonium tungstate solution when producing tungsten oxide fine particles, and from the viewpoint that each element can be easily and uniformly mixed when the starting material is a solution when producing composite tungsten oxide fine particles, it is more preferable to use an aqueous ammonium tungstate solution or a tungsten hexachloride solution. Using these raw materials and heat-treating them in an inert gas atmosphere or a reducing gas atmosphere, the tungsten oxide fine particles and/or composite tungsten oxide fine particles having the infrared-shielding function described above can be obtained.

[0100] The starting material of the composite tungsten oxide fine particles having the infrared-shielding function is the same tungsten compound as the starting material of the fine particles having the infrared-shielding function containing the tungsten oxide fine particles described above, but the starting material is further a tungsten compound containing the element M in the form of a simple substance or a compound. Here, in order to produce a tungsten compound as a starting material in which each component is uniformly mixed at the molecular level, it is preferable to mix each raw material in a solution, and it is preferable that the tungsten compound containing the element M is soluble in a solvent such as water or an organic solvent. Examples thereof include tungstate, chloride salt, nitrate, sulfate, oxalate, oxide, carbonate, and hydroxide of the element M, but the compound is not limited thereto, and any compound that can be in a solution state is preferable.

[0101] The raw materials for producing the tungsten oxide fine particles and composite tungsten oxide fine particles described above will be described in detail again below.

[0102] The tungsten compound, which is the starting material for obtaining tungsten oxide fine particles represented by the general formula WO.sub.X, may be one or more selected from tungsten trioxide powder, tungsten dioxide powder, a hydrate of tungsten oxide, tungsten hexachloride powder, ammonium tungstate powder, a hydrate of tungsten oxide powder obtained by dissolving tungsten hexachloride in alcohol and then drying it, a hydrate of tungsten oxide powder obtained by dissolving tungsten hexachloride in alcohol, adding water to precipitate it, and drying it, a tungsten compound powder obtained by drying an aqueous ammonium tungstate solution, and metallic tungsten powder; from the viewpoint of ease of the production process, it is more preferable to use a hydrate of tungsten oxide powder, tungsten trioxide powder, or a tungsten compound powder obtained by drying an aqueous ammonium tungstate solution.

[0103] The starting material for obtaining composite tungsten oxide fine particles represented by the general formula M.sub.YWO.sub.Z containing the element M may be a powder obtained by mixing one or more powders selected from tungsten trioxide powder, tungsten dioxide powder, a hydrate of tungsten oxide, tungsten hexachloride powder, ammonium tungstate powder, a hydrate of tungsten oxide powder obtained by dissolving tungsten hexachloride in alcohol and then drying it, a hydrate of tungsten oxide powder obtained by dissolving tungsten hexachloride in alcohol, adding water to precipitate it, and drying it, a tungsten compound powder obtained by drying an aqueous ammonium tungstate solution, and metallic tungsten powder, and a powder of a simple substance or compound containing the element M.

[0104] Further, when the tungsten compound as the starting material for obtaining the composite tungsten oxide fine particles is a solution or dispersion liquid, each element can be easily and uniformly mixed.

[0105] From this viewpoint, it is more preferable that the starting material of the composite tungsten oxide fine particles is a powder obtained by mixing an alcohol solution of tungsten hexachloride or an aqueous ammonium tungstate solution and a solution of a compound containing the element M, and then drying the mixture.

[0106] Similarly, it is also preferable that the starting material of the composite tungsten oxide fine particles is a powder obtained by dissolving tungsten hexachloride in alcohol, adding water to form a precipitate to obtain a dispersion liquid, mixing this with a powder of a simple substance or compound containing the element M, or a solution of a compound containing the element M, and then drying the mixture.

[0107] Examples of the compound containing the element M include tungstate, chloride, nitrate, sulfate, oxalate, oxide, carbonate, and hydroxide of the element M, but the compound is not limited thereto, and any compound that can be in a solution state may be used. Further, when industrially producing the composite tungsten oxide fine particles, it is preferable to use a hydrate of tungsten oxide powder or tungsten trioxide and carbonate or hydroxide of the element M because no harmful gas or the like is generated in steps such as heat treatment.

[0108] Here, as the heat treatment conditions in an inert atmosphere for the tungsten oxide fine particles and composite tungsten oxide fine particles, a temperature of 650 C. or higher is preferable. The starting material heat-treated at 650 C. or higher has a sufficient infrared-shielding function and is efficient as fine particles having an infrared-shielding function. It is preferable to use an inert gas such as Ar or N.sub.2 as the inert gas. Further, as the heat treatment conditions in a reducing atmosphere, it is preferable to first heat-treat the starting material in a reducing gas atmosphere at 100 C. or higher and 850 C. or lower, and then heat-treat it in an inert gas atmosphere at a temperature of 650 C. or higher and 1200 C. or lower. The reducing gas at this time is not particularly limited, but H.sub.2 is preferable. Further, when H.sub.2 is used as the reducing gas, the composition of the reducing atmosphere is preferably such that H.sub.2 is 0.1% or more by volume ratio, and more preferably 2% or more. If H.sub.2 is 0.1% or more by volume ratio, reduction can be efficiently promoted.

EXAMPLES

[0109] Hereinafter, examples of the present invention will be specifically described, together with comparative examples.

Example 1

[0110] 10 parts by weight of Cs.sub.0.33WO.sub.3 fine particles (specific surface area: 20 m.sup.2/g), 80 parts by weight of toluene, and 10 parts by weight of a dispersant for fine particle dispersion were mixed, and dispersion treatment was performed with a media stirring mill to prepare a Cs.sub.0.33WO.sub.3 fine particle dispersion liquid (liquid a) having an average dispersed particle diameter of 32 nm.

[0111] Next, toluene was removed from the Cs.sub.0.33WO.sub.3 fine particle dispersion liquid (liquid a) using a spray dryer to obtain Cs.sub.0.33WO.sub.3 fine particle dispersed powder (powder a).

[0112] The obtained CS.sub.0.33WO.sub.3 fine particle dispersed powder (powder a) was added to polyethylene terephthalate resin pellets, which are a thermoplastic resin, and uniformly mixed with a blender, and then the mixture was melt-kneaded and extruded with a twin-screw extruder, and the extruded strands were cut into pellets to obtain a masterbatch a containing 80 wt % of CS.sub.0.33WO.sub.3 fine particles, which are an infrared absorption component.

[0113] The obtained masterbatch a and a masterbatch b composed of polyethylene terephthalate containing no CS.sub.0.33WO.sub.3 fine particles prepared by the same method were mixed at a weight ratio of 1:1 to obtain a mixed masterbatch containing 40 wt % of CS.sub.0.33WO.sub.3 fine particles. The average particle size of the Cs.sub.0.33WO.sub.3 fine particles at the time of production of the mixed masterbatch was observed to be 25 nm from a dark-field image formed by a single diffraction ring using a TEM (transmission electron microscope).

[0114] Next, the mixed masterbatch containing 40 wt % of the Cs.sub.0.33WO.sub.3 fine particles was melt-spun, and then drawn to produce a polyester multifilament yarn a, and then the polyester multifilament yarn a was cut to produce a polyester staple a containing 40 wt % of CS.sub.0.33WO.sub.3 fine particles.

[0115] Further, the masterbatch b containing no Cs.sub.0.33WO.sub.3 fine particles was melt-spun and then drawn to produce a polyester multifilament yarn b, and then the polyester multifilament yarn b was cut in the same manner as described above to produce a polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles.

[0116] A spun yarn was produced using the polyester staple a containing 40 wt % of Cs.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles, and a knitted product (infrared-shielding fiber structure) was produced using this spun yarn, and the obtained knitted product was dyed brown with a cationic dye to produce a knitted product according to Example 1.

[0117] The reason why the knitted product according to Example 1 was obtained by dyeing is to avoid a situation in which the undyed white knitted product becomes see-through even with visible light.

(Average Reflectance of Knitted Product According to Example 1)

[0118] When producing the spun yarn, the mixing ratio of the polyester staple a containing 40 wt % of Cs.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles is appropriately set so that the content of Cs.sub.0.33WO.sub.3 fine particles per unit area of the knitted product according to Example 1 is 0.13 g/m.sup.2.

[0119] When the reflectance of the knitted product according to Example 1 at 5 nm intervals in the wavelength range of 800 nm to 1300 nm was measured using a spectrophotometer manufactured by Hitachi, Ltd., the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Example 1 at wavelengths of 800 nm to 1300 nm was 62%.

(Evaluation of Knitted Product According to Example 1)

[0120] Next, the knitted product according to Example 1 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) by the following test method according to Boken Standard BQE A 033 of the Japan Spinners Inspecting Foundation.

Test Method

[0121] (1) A test piece of the knitted product (infrared-shielding fiber structure) is placed on a transmission determination plate (visual acuity test chart) and placed on a test stand.

[0122] (2) Light is projected onto the surface of the test piece at an intensity of about 7 mW/cm.sup.2 using an infrared projector.

[0123] (3) The test piece is normally photographed with a digital camera.

[0124] (4) The test piece is photographed through with an infrared camera.

[0125] (5) The image taken through is checked, and the presence or absence of infrared transmission is determined.

Determination Result

[0126] No infrared transmission was observed for the knitted product according to Example 1.

[0127] This result is shown in Table 1 below.

Example 2

[0128] A spun yarn was produced using the polyester staple a and polyester staple b, a knitted product (infrared-shielding fiber structure) was produced using this spun yarn, and the obtained knitted product was dyed in the same manner as in Example 1 to produce a knitted product according to Example 2.

[0129] The same procedure as in Example 1 was performed, except that when producing the spun yarn, the mixing ratio of the polyester staple a containing 40 wt % of Cs.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles was appropriately set so that the content of Cs.sub.0.33WO.sub.3 fine particles per unit area of the knitted product according to Example 2 was 0.17 g/m.sup.2; the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Example 2 at wavelengths of 800 nm to 1300 nm was 58%.

(Evaluation of Knitted Product According to Example 2)

[0130] When the knitted product according to Example 2 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) in the same manner as in Example 1, no infrared transmission was observed for the knitted product according to Example 2.

[0131] This result is also shown in Table 1 below.

Example 3

[0132] A spun yarn was produced using the polyester staple a and polyester staple b, a knitted product (infrared-shielding fiber structure) was produced using this spun yarn, and the obtained knitted product was dyed in the same manner as in Example 1 to produce a knitted product according to Example 3.

[0133] The same procedure as in Example 1 was performed, except that when producing the spun yarn, the mixing ratio of the polyester staple a containing 40 wt % of CS.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles was appropriately set so that the content of Cs.sub.0.33WO.sub.3 fine particles per unit area of the knitted product according to Example 3 was 0.26 g/m.sup.2; the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Example 3 at wavelengths of 800 nm to 1300 nm was 50%.

(Evaluation of Knitted Product According to Example 3)

[0134] When the knitted product according to Example 3 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) in the same manner as in Example 1, no infrared transmission was observed for the knitted product according to Example 3.

[0135] This result is also shown in Table 1 below.

Example 4

[0136] A spun yarn was produced using the polyester staple a and polyester staple b, a knitted product (infrared-shielding fiber structure) was produced using this spun yarn, and the obtained knitted product was dyed in the same manner as in Example 1 to produce a knitted product according to Example 4.

[0137] The same procedure as in Example 1 was performed, except that when producing the spun yarn, the mixing ratio of the polyester staple a containing 40 wt % of CS.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles was appropriately set so that the content of Cs.sub.0.33WO.sub.3 fine particles per unit area of the knitted product according to Example 4 was 0.87 g/m.sup.2; the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Example 4 at wavelengths of 800 nm to 1300 nm was 18%.

(Evaluation of Knitted Product According to Example 4)

[0138] When the knitted product according to Example 4 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) in the same manner as in Example 1, no infrared transmission was observed for the knitted product according to Example 4.

[0139] This result is also shown in Table 1 below.

Example 5

[0140] A spun yarn was produced using the polyester staple a and polyester staple b, a knitted product (infrared-shielding fiber structure) was produced using this spun yarn, and the obtained knitted product was dyed in the same manner as in Example 1 to produce a knitted product according to Example 5.

[0141] The same procedure as in Example 1 was performed, except that when producing the spun yarn, the mixing ratio of the polyester staple a containing 40 wt % of CS.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles was appropriately set so that the content of Cs.sub.0.33WO.sub.3 fine particles per unit area of the knitted product according to Example 5 was 1.73 g/m.sup.2; the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Example 5 at wavelengths of 800 nm to 1300 nm was 4%.

(Evaluation of Knitted Product According to Example 5)

[0142] When the knitted product according to Example 5 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) in the same manner as in Example 1, no infrared transmission was observed for the knitted product according to Example 5.

[0143] This result is also shown in Table 1 below.

Example 6

[0144] A spun yarn was produced using the polyester staple a and polyester staple b, a knitted product (infrared-shielding fiber structure) was produced using this spun yarn, and the obtained knitted product was dyed in the same manner as in Example 1 to produce a knitted product according to Example 6.

[0145] The same procedure as in Example 1 was performed, except that when producing the spun yarn, the mixing ratio of the polyester staple a containing 40 wt % of CS.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles was appropriately set so that the content of Cs.sub.0.33WO.sub.3 fine particles per unit area of the knitted product according to Example 6 was 2.60 g/m.sup.2; the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Example 6 at wavelengths of 800 nm to 1300 nm was 1%.

(Evaluation of Knitted Product According to Example 6)

[0146] When the knitted product according to Example 6 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) in the same manner as in Example 1, no infrared transmission was observed for the knitted product according to Example 6.

[0147] This result is also shown in Table 1 below.

Example 7

[0148] A spun yarn was produced using the polyester staple a and polyester staple b, a knitted product (infrared-shielding fiber structure) was produced using this spun yarn, and the obtained knitted product was dyed in the same manner as in Example 1 to produce a knitted product according to Example 7.

[0149] The same procedure as in Example 1 was performed, except that when producing the spun yarn, the mixing ratio of the polyester staple a containing 40 wt % of CS.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles was appropriately set so that the content of Cs.sub.0.33WO.sub.3 fine particles per unit area of the knitted product according to Example 7 was 4.33 g/m.sup.2; the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Example 7 at wavelengths of 800 nm to 1300 nm was 0.07%.

(Evaluation of Knitted Product According to Example 7)

[0150] When the knitted product according to Example 7 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) in the same manner as in Example 1, no infrared transmission was observed for the knitted product according to Example 7.

[0151] This result is also shown in Table 1 below.

Comparative Example 1

[0152] A spun yarn was produced using only the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles, a knitted product was produced using this spun yarn, and the obtained knitted product was dyed in the same manner as in Example 1 to obtain a knitted product according to Comparative Example 1.

[0153] When the reflectance of the knitted product according to Comparative Example 1 at 5 nm intervals in the wavelength range of 800 nm to 1300 nm was measured using a spectrophotometer manufactured by Hitachi, Ltd., the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Comparative Example 1 at wavelengths of 800 nm to 1300 nm was 77%.

(Evaluation of Knitted Product According to Comparative Example 1)

[0154] When the knitted product according to Comparative Example 1 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) in the same manner as in Example 1, infrared transmission was observed for the knitted product according to Comparative Example 1.

[0155] This result is also shown in Table 1 below.

Comparative Example 2

[0156] A spun yarn was produced using the polyester staple a and polyester staple b, a knitted product (infrared-shielding fiber structure) was produced using this spun yarn, and the obtained knitted product was dyed in the same manner as in Example 1 to obtain a knitted product according to Comparative Example 2.

[0157] The same procedure as in Example 1 was performed, except that when producing the spun yarn, the mixing ratio of the polyester staple a containing 40 wt % of CS.sub.0.33WO.sub.3 fine particles and the polyester staple b containing no Cs.sub.0.33WO.sub.3 fine particles was appropriately set so that the content of Cs.sub.0.33WO.sub.3 fine particles per unit area of the knitted product according to Comparative Example 2 was 0.09 g/m.sup.2; the spectral characteristics shown in FIG. 1 were obtained, and from these spectral characteristics, the average reflectance of the knitted product according to Comparative Example 2 at wavelengths of 800 nm to 1300 nm was 67%.

(Evaluation of Knitted Product According to Comparative Example 2)

[0158] When the knitted product according to Comparative Example 2 was evaluated for prevention of voyeuristic photography using infrared rays (penetration imaging with a CCD camera) in the same manner as in Example 1, infrared transmission was observed for the knitted product according to Comparative Example 2.

[0159] This result is also shown in Table 1 below.

TABLE-US-00001 TABLE 1 Amount of Average Cs.sub.0.33WO.sub.3 Fine Reflectance in Japan Spinning Particles Added 800 nm to 1300 Inspection (g/m.sup.2) nm (%) Foundation Test Example 1 0.13 62 Transmittance not observed Example 2 0.17 58 Transmittance not observed Example 3 0.26 50 Transmittance not observed Example 4 0.87 18 Transmittance not observed Example 5 1.73 4 Transmittance not observed Example 6 2.60 1 Transmittance not observed Example 7 4.33 0.07 Transmittance not observed Comparative 0.00 77 Transmittance Example 1 observed Comparative 0.09 67 Transmittance Example 2 observed

POSSIBILITY OF INDUSTRIAL APPLICATION

[0160] According to the infrared-shielding fiber structure of the present invention, because the function of preventing voyeuristic photography using infrared rays can be maintained for a long period of time, it has industrial applicability to innerwear, sportswear, etc., which are easily subject to voyeuristic photography.