Near-infrared absorbing fiber, textile product, and method for producing near-infrared absorbing fiber

Abstract

To provide a near-infrared absorption fiber which contains near-infrared absorption particles containing a composite tungsten oxide, and can be set to a more neutral color tone.SOLUTION: A near-infrared absorption fiber contains a fiber, and near-infrared absorption particles arranged in one or more places selected from the surface and the inside of the fiber, wherein the near-infrared absorption particles contain a cesium tungstate, the cesium tungstate has a pseudo hexagonal crystal structure modulated to one or more kinds selected from orthorhombic, rhombohedral and cubic crystals, the cesium tungstate is represented by general formula: CsxWyOz, in a ternary composition diagram with Cs, W and O as each apex, and it has a composition in an area surrounded by four straight lines of x=0.6y, z=2.5y, y=5x and Cs2O:WO3=m:n (m and n are integers).SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a near-infrared absorbing fiber, a fiber product, and a method for producing a near-infrared absorbing fiber. [Background technology]

[0002] Various cold weather clothing, interior goods, and leisure items with enhanced thermal insulation have been devised and put into practical use. There are two main methods for increasing thermal insulation.

[0003] The first method is to physically increase the air space in the cold weather clothing, for example by controlling the woven or knitted structure of the clothing or by making the fibers used hollow or porous, thereby reducing the dissipation of heat generated by the human body and maintaining heat retention.

[0004] The second method is to improve the thermal insulation of cold weather clothing by actively storing heat, for example by applying chemical or physical processing to the entire garment or to the fibers that make up the garment, so that the heat generated by the human body is radiated back towards the human body or some of the sunlight received by the garment is converted into heat.

[0005] The first method mentioned above has been to increase the number of air spaces in the clothing, thicken the fabric, make the weave finer, or darken the color. Examples of this include winter clothing such as sweaters. Furthermore, for example, clothing commonly used for winter sports involves placing padding between the outer and inner layers, and the thickness of the air space created by the padding maintains warmth. However, padding makes clothing heavy and bulky, which is problematic for sportswear that require ease of movement. To address these problems, the second method mentioned above, which actively and effectively utilizes heat generated internally or from the outside, has begun to be adopted in recent years.

[0006] One known method for implementing the second method is to vapor-deposit metals such as aluminum or titanium onto the lining of clothing, and actively prevent heat dissipation by reflecting the radiant heat emitted from the body onto the metal-deposited surface. However, these methods not only require considerable costs for vapor-depositing metal onto clothing, but also result in poor yields due to uneven deposition, which ultimately leads to an increase in the price of the product itself.

[0007] Another method proposed for implementing the second method involves kneading ceramic particles such as alumina, zirconia, and magnesia into the fibers themselves, and utilizing the far-infrared radiation effect and light-to-heat conversion effect of these inorganic particles, i.e., actively incorporating external energy.

[0008] For example, Patent Document 1 states that the thermal conductivity is 0.3 kcal / m 2 The present invention discloses a heat-emitting fiber containing one or more inorganic fine particles such as silica or barium sulfate, which have heat-emitting properties and contain at least one metal or metal ion having a temperature of 1.0 s·sec·°C or higher.

[0009] Patent Document 2 discloses a heat-retaining composite fiber comprising a thermoplastic polymer A having a melting point of 110°C or higher and a thermoplastic polymer B having a melting point of 15 to 50°C, a cooling crystallization temperature of 40°C or lower, and a heat of crystallization of 10 mJ / mg or higher, wherein the composite fiber contains ceramic microparticles having far-infrared radiation capability in an amount of 0.1 to 20% by weight relative to the fiber weight, and the surface of the fiber is covered with polymer A.

[0010] Patent Document 3 proposes an infrared-absorbing processed textile product in which an infrared absorber consisting of a specified amino compound, an ultraviolet absorber used as needed, and a binder resin containing various stabilizers are dispersed and fixed.

[0011] Patent Document 4 proposes a near-infrared absorption processing method for a cellulosic fiber structure in which a dye selected from direct dyes, reactive dyes, naphthol dyes, and vat dyes, which has greater absorption in the near-infrared region than black dyes, is dyed in combination with another dye, thereby achieving a spectral reflectance of the fabric of 65% or less in the near-infrared absorption range of 750 to 1500 nm.

[0012] In Patent Documents 5 to 7, the present inventors propose fibers containing tungsten oxide microparticles or composite tungsten oxide microparticles on the surface and / or inside thereof, and textile products obtained by processing such fibers. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 11-279830 [Patent Document 2] Japanese Patent Application Publication No. 5-239716 [Patent Document 3] Japanese Patent Application Publication No. 8-3870 [Patent Document 4] Japanese Patent Application Publication No. 9-291463 [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-132042 [Patent Document 6] International Publication No. 2018 / 235839 [Patent Document 7] International Publication No. 2019 / 054476 [Non-patent literature]

[0014] [Non-Patent Document 1] K. Machida, M. Okada, and K. Adachi, "Excitations of free and localized electrons at nearby energies in reduced cesium tungsten bronze nanocrystals," Journal of Applied Physics, Vol. 125, 103103 (2019) [Non-patent document 2] S. Yoshio and K. Adachi, "Polarons in reduced cesium tungsten bronzes studied using the DFT+U method," Materials Research Express, Vol. 6, 026548 (2019) [Non-patent document 3] SF Solodovnikov, NV Ivannikova, ZA Solodovnikova, ES Zolotova, "Synthesis and X-ray diffraction study of potassium, rubidium, and cesium polytungstates with defect pyrochlore and hexagonal tungsten bronze structures," Inorganic Materials, Vol. 34, 845-853 (1998) [Non-patent document 4] S. Nakakura, AF Arif, K. Machida, K. Adachi, T. Ogi, Cationic defect engineering for controlling the infrared absorption of hexagonal cesium tungsten bronze nanoparticles, Inorg. Chem., 58, 9101-9107 (2019) Summary of the Invention [Problem to be solved by the invention]

[0015] In the heat-emitting fiber disclosed in Patent Document 1, which contains inorganic fine particles such as silica containing metals and having heat-emitting properties, the amount of inorganic fine particles added to the fiber is large, which increases the specific gravity of the fiber, making clothing heavy and making it extremely difficult to disperse the inorganic fine particles uniformly during melt spinning.

[0016] As mentioned above, there is also a known technique of attaching metals such as aluminum and titanium to fibers by adhesion or vapor deposition to impart a radiation reflecting effect and improve heat retention. However, the adhesion or vapor deposition process significantly changes the color of the fibers, which may limit their applications. Furthermore, there are various problems associated with the vapor deposition process, such as increased costs, the occurrence of vapor deposition spots due to handling of the fabric in the preparation process before the vapor deposition process, and a decrease in heat retention due to the removal of the vapor-deposited metal due to friction during washing or wearing.

[0017] According to the applicant's investigations, the tungsten oxide microparticles or composite tungsten oxide microparticles disclosed in, for example, Patent Documents 5 to 7, are materials that have high transmittance and low absorbance for visible light, but low transmittance and high absorbance for light in the near-infrared region. For this reason, fibers containing composite tungsten oxide microparticles are particularly promising for applications such as cold weather clothing. However, because they preferentially absorb long-wavelength visible light, i.e., red light, they are colored blue, and the degree of blueness increases with increasing amounts of microparticles added. As a result, fibers containing the microparticles as a near-infrared absorbing component and textile products obtained by processing such fibers are colored blue, making it difficult to color them in yellow or other pale colors other than blue, which are complementary colors of blue, by adding other pigments. Therefore, there has been a demand for fibers containing composite tungsten oxide with excellent near-infrared absorption properties and capable of producing more neutral colors that can be colored in complementary or pale colors.

[0018] Therefore, one aspect of the present invention aims to provide a near-infrared absorbing fiber that contains near-infrared absorbing particles containing a composite tungsten oxide and can have a more neutral color tone. [Means for solving the problem]

[0019] In one aspect of the invention, a fiber; and near-infrared absorbing particles disposed at one or more locations selected from the surface and the interior of the fiber, the near-infrared absorbing particles contain cesium tungstate, The cesium tungstate has a pseudo-hexagonal crystal structure that is modulated into one or more crystal structures selected from orthorhombic, rhombohedral, and cubic crystal structures; O, OH, OH 2 , O.H. 3 Contains one or more added ingredients selected from The cesium tungstate has the general formula Cs x W y O z In a ternary composition diagram represented by the formula (1), with Cs, W, and O at the vertices, the composition is within the region surrounded by the four straight lines x=0.6y, z=2.5y, y=5x, and CsO:WO=m:n (m and n are integers). [Effects of the Invention]

[0020] In one aspect of the present invention, it is possible to provide a near-infrared absorbing fiber that includes near-infrared absorbing particles containing a composite tungsten oxide and that can have a more neutral color tone. [Brief explanation of the drawings]

[0021] [Figure 1A] Figure 1A is a Cs-WO composition diagram with Cs, W, and O at the vertices. [Figure 1B] Figure 1B is an enlarged view of a portion of the Cs-WO composition diagram with Cs, W, and O at the vertices. [Figure 2]FIG. 2 shows powder XRD diffraction patterns of the near infrared absorbing particles produced in Examples 1 to 6 and Comparative Examples 1 and 2. [Figure 3] FIG. 3 shows powder XRD diffraction patterns of the near infrared absorbing particles produced in Examples 9 to 14. [Figure 4] FIG. 4 shows a transmission electron microscope bright-field image, a selected area electron diffraction image, and a high angle electron dark-field (HAADF) image of the near-infrared absorbing particles produced in Example 1. [Figure 5] FIG. 5 is an explanatory diagram of a near-infrared absorbing particle having a coating. [Figure 6] FIG. 6 is an explanatory diagram of the structure of the near-infrared absorbing fiber. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention. [Near-infrared absorbing fiber] The near-infrared absorbing fiber and textile product according to the present embodiment will be described in the following order: [1] near-infrared absorbing particles, [2] a method for producing near-infrared absorbing particles, [3] a near-infrared absorbing particle dispersion, [4] near-infrared absorbing fiber, [5] a method for producing near-infrared absorbing fiber, and [6] a textile product. [1] Near-infrared absorbing particles As will be described later, the near-infrared absorbing fiber of this embodiment contains near-infrared absorbing particles. Therefore, the near-infrared absorbing particles will be described first.

[0023] The near-infrared absorbing particles contain cesium tungstate, which is a composite tungsten oxide. The near-infrared absorbing particles of this embodiment may also be composed of cesium tungstate. However, even in this case, the inclusion of inevitable impurities is not excluded. (1) Cesium tungstate Cesium tungstate (cesium polytungstate) can have a pseudo-hexagonal crystal structure modified to one or more of orthorhombic, rhombohedral, and cubic crystals, specifically, a modified pseudo-hexagonal structure that is a partial modification of the hexagonal alkali tungsten bronze structure, selected from orthorhombic, rhombohedral, and cubic crystals.

[0024] The transmission color and optical absorption of cesium-doped hexagonal tungsten bronze particles, which have been conventionally used as near-infrared absorbing particles, are determined by their imaginary part of the dielectric function (ε2) and band structure.

[0025] In the visible light energy range (1.6 eV to 3.3 eV), cesium-doped hexagonal tungsten bronze (hereinafter also referred to as Cs-HTB) has a sufficiently large band gap that light absorption in the visible light range is essentially suppressed. Additionally, tungsten dd-orbital transitions and oxygen pp-orbital transitions are forbidden by the Fermi golden rule, reducing the probability of electronic transitions. These two factors result in small values ​​of ε2 at wavelengths in the visible light range. Since ε2 represents the absorption of photons by electrons, a small ε2 at wavelengths in the visible light range results in visible light transmittance. However, it has recently been revealed that absorption due to band-edge transitions exists near the shortest wavelengths in the visible light range (blue), and that localized surface plasmon resonance (LSPR) absorption and polaronic electronic transition absorption exist near the longest wavelengths in the visible light range (Non-Patent Document 1). These factors limit light transmittance in each case.

[0026] As mentioned above, the band gap of Cs-HTB is large enough that the band edge transition exceeds the energy of blue wavelength light, resulting in blue transmittance. Conversely, at red wavelengths, Cs-HTB has a large number of conduction electrons, resulting in strong LSPR absorption and polaronic absorption, and the base of this absorption extends into the red wavelengths, resulting in low red transmittance. Therefore, the transmitted color of a Cs-HTB nanoparticle-dispersed film appears blue due to the balance between these two.

[0027] That is, to neutralize the blue transmission color of Cs-HTB, it is necessary to increase the absorption on the blue side and increase the transmission on the red side.

[0028] Strengthening the blue absorption of Cs-HTB can be achieved, for example, by shifting the absorption position of the band edge transition to lower energy. Shifting the absorption position of the band edge transition to lower energy corresponds to narrowing the band gap of Cs-HTB. Therefore, this can be achieved by selecting a material with a slightly smaller band gap.

[0029] The red absorption of Cs-HTB can be weakened by decreasing the concentration of surface plasmon resonance electrons or polaron-bound electrons.

[0030] Based on the above considerations, the inventors of the present invention have investigated various cesium tungsten oxides, which are oxides containing cesium (Cs) and tungsten (W), and have improved the material by using band structure calculations based on first-principles calculations. As a result, they have found that when the conventional hexagonal crystal structure is modified to an orthorhombic, rhombohedral, or cubic pseudo-hexagonal structure by changing the microstructure, the band structure changes and the amount of free and bound electrons changes, resulting in a change in color.

[0031] Here, a pseudo-hexagonal structure modulated to one or more of the orthorhombic, rhombohedral, and cubic crystals refers to a pseudo-hexagonal crystal in which Cs-rich planes are inserted regularly or randomly into the prism or basal planes of the hexagonal crystal. A Cs-rich plane is synonymous with a plane lacking W or O. Furthermore, as described below, O, OH, OH2, and OH3 ions can substitute for the Cs site, and the introduction of these ions into the prism or basal planes can promote the modulation of the pseudo-hexagonal crystal structure, just like Cs.

[0032] Orthorhombic, rhombohedral, and cubic crystal structures can be identified, for example, by electron diffraction, by noting the symmetry of the diffraction spots when the electron beam is incident along the c-axis, i.e., from the (0001) direction.

[0033] In a hexagonal crystal, the diffraction spots of the three types of prism planes, (10-10), (01-10), and (1-100), appear at the same distance from the incident spot within the reciprocal lattice plane. In other words, the hexagonal crystal has the same crystal plane spacing. Note that the above-mentioned "same distance" includes distances that can be considered to be the same within the error range of the electron diffraction spot distance measurement. For this reason, the hexagonal crystal produces an electron diffraction pattern that is hexagonally symmetric, i.e., invariant to a 60° rotation.

[0034] In the orthorhombic crystal, one type of prism surface spot appears closer to the incident spot than the other two types of prism surface spots, i.e., in the orthorhombic crystal, only one type of prism surface has a long crystal plane spacing.

[0035] In a rhombohedral crystal, the three types of prism surface spots have different crystal plane spacings.

[0036] Cubic crystals have the same hexagonal symmetry as hexagonal crystals, but the cubic symmetry can be easily identified by observing from other crystal zone axis directions.

[0037] In XRD powder patterns, pseudohexagonal crystals are often considered to be a mixed pattern of orthorhombic and hexagonal crystals, or a mixed pattern of rhombohedral and hexagonal crystals, or a mixed pattern of cubic and hexagonal crystals. However, due to the insertion of the planar lattice defects mentioned above, the positions and intensities of the diffraction peaks change slightly.

[0038] One method for obtaining a pseudo-hexagonal crystal structure modulated to one or more types selected from the above-mentioned orthorhombic, rhombohedral, and cubic crystals is to add one or more types of additive components selected from O, OH, OH2, and OH3. Therefore, in the near infrared absorbing particles of the present embodiment, it is preferable that the cesium tungstate contains one or more types of additive components selected from O, OH, OH2, and OH3.

[0039] The one or more additive components selected from O, OH, OH2, and OH3 are preferably present at one or more positions selected from hexagonal windows and hexagonal cavities present in hexagonal tunnels that penetrate the c-axis direction of a hexagon formed by six WO6 octahedra that constitute the hexagonal alkali tungsten bronze structure of a cesium tungstate crystal, and triangular cavities formed by three WO6 octahedra.

[0040] The hexagonal tunnel has two voids: the large hexagonal cavity and the hexagonal window. The hexagonal window is the second largest void in the hexagonal crystal after the hexagonal cavity and is surrounded by six oxygen atoms that make up the WO6 octahedron. The hexagonal window is adjacent to the Cs ions located in the hexagonal cavity above and below it in the c-axis direction. The trigonal cavity is the next largest void after the hexagonal window and penetrates the hexagonal crystal along the c-axis direction. One or more of O, OH, OH2, and OH3 can enter the hexagonal cavity by substituting for Cs, but they also invade the hexagonal window when there is a sufficient amount of Cs or when there is a large amount of invaded water. In some cases, they invade the trigonal cavity at the bottom or the cavities on the prism surface in parallel with the hexagonal window void, replacing Cs. The addition of the above-mentioned additives creates defects on the base and prism surfaces, which shifts the crystal structure from hexagonal to orthorhombic, rhombohedral, and then cubic, narrowing the band gap and reducing the conduction band electron density. As a result, cesium tungstate, which has a pseudo-hexagonal crystal structure, can enhance absorption on the blue side and transmission on the red side compared to Cs-HTB, neutralizing blue transmission colors.

[0041] In this case, the orthorhombic, rhombohedral, and cubic crystals can be considered pseudo-hexagonal crystals, which have atomic arrangements similar to those of hexagonal tungsten bronze, but have a different symmetry from hexagonal crystals. Roughly speaking, without being too strict, the orthorhombic crystals in this case are crystals in which hexagonal symmetry is broken by inserting, regularly or randomly, planes lacking W and O atoms into one of the three prism faces of a hexagonal crystal. Therefore, in an orthorhombic crystal, only one prism face has a longer interplanar spacing. Using this, modulation to an orthorhombic crystal can be easily identified, for example, by the (0001) electron diffraction pattern.

[0042] In this case, a rhombohedron is formed by inserting a plane that accepts excess Cs into the basal surface of a hexagonal crystal, i.e., a plane lacking W and O, and by systematically displacing the stacking of the basal surface in the c-axis direction, breaking the hexagonal symmetry. In this case, the excess Cs plane includes not only displacement on the plane but also expansion in the direction perpendicular to the plane, resulting in a change in the prism plane spacing and a change in the c-axis lattice constant. Therefore, in a rhombohedron, all three prism planes have different spacings. Utilizing this, modulation to a rhombohedron can be easily identified, for example, by the (0001) electron diffraction pattern.

[0043] Furthermore, when the three axes of the rhombohedron intersect at 90 degrees, it becomes a cubic crystal. This cubic crystal has a pyrochlore structure, and a typical composition is CsW2O6.

[0044] Therefore, voids corresponding to the above-mentioned hexagonal windows, hexagonal cavities, and trigonal cavities are also inherited by orthorhombic crystals, rhombohedral crystals, and cubic crystals. Therefore, the hexagonal windows, hexagonal cavities, and trigonal cavities in the cesium tungstate contained in the near infrared absorbing particles of the present embodiment also refer to the corresponding voids in the orthorhombic crystals, rhombohedral crystals, and cubic crystals (pyrochlore phase).

[0045] Hereinafter, a structural example of the method for producing near infrared absorbing particles of this embodiment will be described, mainly taking as an example the case of a hexagonal window as a site or gap where O, OH, OH2, and OH3 can be substituted or penetrated.

[0046] One method for obtaining orthorhombic, rhombohedral, or cubic crystals in which one or more species selected from O, OH, OH2, and OH3 are present in the hexagonal window is to crystallize the cesium tungstate in saturated water vapor during crystallization during synthesis. Generally, in a Cs-HTB structure, the ionic radius of Cs is slightly larger than the hexagonal cavity, making it difficult for Cs to move. Therefore, once crystallized into a hexagonal crystal, it becomes difficult to diffuse and insert oxygen atoms or the like into the hexagonal window through subsequent heat treatment or the like. Therefore, we devised a method in which the atmosphere is filled with saturated water vapor before the cesium tungstate crystallizes, and water molecules and O, OH, and OH3 ions derived from the water molecules are inserted into the hexagonal window simultaneously with the crystallization of the cesium tungstate. Therefore, as described below, the method for producing near-infrared absorbing particles of this embodiment preferably includes a step of introducing water vapor at a heating temperature close to the crystallization temperature of the cesium tungstate and crystallizing the cesium tungstate in an atmosphere containing water vapor. When near-infrared absorbing fibers are produced using the near-infrared absorbing particles synthesized through the above steps, or near-infrared absorbing particles that have been further heat-treated in a reducing atmosphere as necessary, the blueness of the color tone can be reduced while the near-infrared absorbing effect is sufficiently maintained, i.e., a neutral color tone can be achieved.

[0047] On the other hand, once hexagonal cesium tungstate crystals are produced, heating the cesium tungstate in a water vapor atmosphere or maintaining and heating it in a high-temperature, high-humidity environment does not neutralize the transmitted color. This is because elements with a large ionic radius, such as Cs, inhibit the diffusion of oxygen atoms and other atoms through hexagonal tunnels, so once the crystals are crystallized into hexagonal crystals, subsequent heat treatments make it difficult for oxygen atoms and other atoms to diffuse into the hexagonal windows of the voids. Therefore, the heat treatment in water vapor must be performed during the initial crystallization process.

[0048] When heating in an atmosphere containing water vapor during crystallization, it is also possible to simultaneously mix in a reducing gas such as hydrogen gas and crystallize in a reducing gas atmosphere. Furthermore, if the crystals are once crystallized in a water vapor atmosphere, they can be further heated at a high temperature of 500°C to 950°C in an atmosphere containing a reducing gas such as hydrogen gas, or in an inert gas atmosphere. In either case, near-infrared absorbing particles with a neutralized transmitted color and a high near-infrared absorption effect can be obtained. By heating at 500°C or higher, the arrangement of equilibrium atomic positions, such as an orthorhombic crystal structure containing defects, is sufficiently promoted, thereby enhancing the near-infrared absorption effect. Furthermore, by heating at 950°C or lower, the speed of crystal structure change can be maintained at an appropriate level, allowing for easy control of the appropriate crystalline state and electronic state. Note that heating at temperatures higher than 950°C, for example, excessive reduction, may result in the production of lower oxides such as W metal and WO2, which is undesirable from this perspective.

[0049] During the initial crystallization by heating with water vapor, the incorporation of O, OH, OH2, and OH3 results in the formation of one or more crystal types selected from orthorhombic, rhombohedral, and cubic (pyrochlore phase) crystals, which are microscopically modified from hexagonal crystals. By heating these in atmospheres with different degrees of reduction, one or more crystal structures selected from various orthorhombic, rhombohedral, and cubic crystals with different amounts and distributions of lattice defects are generated.

[0050] The cesium tungstate contained in the near infrared absorbing particles of the present embodiment may have lattice defects of Cs, W, or O. The reason why lattice defects of Cs, W, or O are introduced into the cesium tungstate will be described below.

[0051] Hexagonal Cs 0.33 At compositions around WO3, crystal stability is determined by the balance between structural stability due to high crystal symmetry and charge balance stability, where charge transfer between elements produces overall charge neutrality. For example, the charge-neutral 2Cs2O·11WO3=Cs4W 11 O 35is considered to be a thermodynamically stable phase, but when heated in a reducing atmosphere, it easily transforms into a hexagonal Cs with high crystal symmetry. 0.32 WO 3-y (Non-Patent Document 2) 0.32 WO 3-y is a metastable structure with high crystal symmetry, while Cs4W 11 O 35 is a stable composition in terms of charge balance. 11 O 35 has poor symmetry in the atomic arrangement within the crystal. For example, in the model by Solodovnikov (Non-Patent Document 3), in the hexagonal arrangement of WO6 octahedra, the same as in hexagonal tungsten bronze, planes with missing W and O atoms are inserted at a b / 8 pitch in the hexagonal (1,1,-2,0) plane (= orthorhombic (010) plane) of the orthorhombic unit cell, resulting in an orthorhombic crystal as a whole. In other words, the Cs, W, and O defects were inevitably introduced to locally satisfy both the crystal structure and charge balance, and have actually been observed recently using TEM and XRD (Non-Patent Document 4).

[0052] In the near-infrared absorbing particles of this embodiment, in the orthorhombic, rhombohedral, or cubic crystals in which O, OH, OH2, or OH3 is incorporated into the hexagonal windows, hexagonal cavities, or trigonal cavities, the local charge balance is disturbed, and the crystal microstructure is further modified. + and H3O + are introduced into the crystal, but these ions are Cs + and W 6+ In order to compete with the OH atoms, local charge neutrality is achieved by the vacancies of Cs and W. As a result, lattice defects including vacancies of Cs and W are introduced. O, OH, OH2, and OH3 may invade not only the hexagonal windows but also the trigonal cavities. Furthermore, OH2 and OH3 may substitute for the alkali element (Cs) in the hexagonal cavity, and when the charge-neutral OH2 is substituted, the alkali ion (Cs) that was originally present may be vacant. + ) no longer emits electrons, so the conduction band electrons in the crystal decrease.

[0053] Among the cesium tungstates having a pseudo-hexagonal crystal structure modulated to one or more types selected from orthorhombic, rhombohedral, and cubic crystals, those that satisfy excellent near-infrared absorption effects and visible light transmittance have a predetermined composition.

[0054] Figure 1A shows a ternary composition diagram 10 with Cs-WO as the three vertices. Figure 1B shows an enlarged view of the region 11 in the ternary composition diagram 10 of Figure 1A, with CsWO3, W2O3, and WO4 as the vertices. It should be noted that this diagram is not a phase diagram showing the thermodynamic equilibrium phases, but rather a convenient composition diagram showing the range of compositions in this system. Therefore, CsWO3, W2O3, WO4, etc. are compositions shown for convenience, and it does not refer to whether these are actually obtained compounds.

[0055] The cesium tungstate contained in the near infrared absorbing particles of the present embodiment is represented by the general formula Cs x W y O z In a ternary composition diagram represented by the formula (1), with Cs, W, and O at the vertices, it is preferable that the composition be within the region surrounded by the four lines x=0.6y, z=2.5y, y=5x, and Cs2O:WO3=m:n (m and n are integers). Specifically, in the ternary composition diagram shown in Figures 1A and 1B, it is preferable that the composition be within region 16 surrounded by line 12 satisfying x=0.6y, line 13 satisfying z=2.5y, line 14 satisfying y=5x, and line 15 satisfying Cs2O:WO3=m:n (m and n are integers). Note that region 16 also includes points on lines 12 to 15. Moreover, a line 15 that satisfies Cs2O:WO3=m:n (m and n are integers) is a line that connects Cs2O and WO3 in the ternary composition diagram 10, as shown in FIG. 1A.

[0056] In the above ternary composition diagram, when x > 0.6y, cesium tungstate has a predominantly tetragonal crystal structure, resulting in the loss of near-infrared absorption. Furthermore, when z < 2.5y, cesium tungstate has a hexagonal structure with lower W oxides mixed in, significantly impairing its near-infrared absorption and visible light transmittance. When y > 5x, cesium tungstate has a crystal structure called intergrowth, in which WO3 is mixed into the hexagonal substructure, resulting in the loss of near-infrared absorption. Furthermore, if the Cs2O:WO3 ratio falls to the O-rich side (to the right of line 15, where the Cs2O:WO3 ratio is an integer), no near-infrared absorption effect is obtained. Therefore, it is preferable for cesium tungstate to satisfy the aforementioned range.

[0057] The cesium tungstate contained in the near-infrared absorbing particles of this embodiment may have defects in each of the elements cesium, tungsten, and oxygen, but the atomic ratio (x / y) of cesium to tungsten may be in the range of 0.2 or more and 0.6 or less. That is, the near-infrared absorbing particles of this embodiment have defects in part of one or more elements selected from Cs and W that constitute the crystal of the cesium tungstate, and are represented by the general formula Cs x W y O z It is preferable that x and y satisfy the relationship 0.2≦x / y≦0.6.

[0058] Cesium and tungsten supply electrons to the crystal, so by setting x / y to 0.2 or more, near-infrared absorption function can be improved. Furthermore, by setting x / y to 0.2 or more, it is possible to create a hexagonal crystal structure or a crystal structure in which the hexagonal crystal is modulated. When x / y exceeds 0.33, Cs ions cannot fit into the hexagonal cavity and begin to occupy the trigonal cavity as well, causing modulations on the prism faces and bases, gradually changing locally into a layered structure of orthorhombic, rhombohedral, or cubic pyrochlore. Furthermore, when x / y exceeds 0.6, the tetragonal Cs2W3O 10 The crystal structure changes to the above, which significantly impairs the visible light transmittance and reduces the usefulness.

[0059] The near-infrared absorbing particles of this embodiment have a hexagonal cesium tungsten bronze structure Cs 0.33 Using WO3 as a base, the WO6 octahedra that make up the crystal can have defects in at least some of the W. These W defects are introduced as planar defects mainly on the hexagonal prism faces or bases, but because the ionic repulsion of the atomic rows on both sides of the defect plane increases the interplanar spacing, the crystal symmetry changes from hexagonal to orthorhombic, rhombohedral, or cubic.

[0060] The near-infrared absorbing particles of this embodiment can have vacancies in at least some of the O atoms in the WO octahedra that make up the cesium tungstate crystal, based on the hexagonal alkali tungsten bronze structure CsW3O9. These O vacancies are introduced randomly, and the vacancies can supply localized electrons to the system, enhancing the near-infrared absorbing function. The known hexagonal tungsten bronze Cs 0.32 WO 3-y In the near-infrared absorbing particles of this embodiment, it is known that the vacancy rate is y=0.46 or up to 15% of all the lattice points of O constituting the octahedron (Non-Patent Document 3). When the vacancy rate exceeds 0.5, the crystal becomes unstable, a different phase is generated, and decomposition occurs. The cesium tungstate Cs contained in the near-infrared absorbing particles of this embodiment x W y O z In this case, it is possible to include an O vacancy amount equivalent to a maximum z / y = 2.5. However, when excess O, OH, OH2, or OH3 is introduced into voids such as hexagonal windows, it is important to note that the identified O value obtained by chemical analysis includes these excess amounts.

[0061] In the cesium tungstate contained in the near infrared absorbing particle of the present embodiment, a part of Cs may be substituted with an additional element. In this case, the additional element is preferably one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0062] These added elements have electron donating properties and assist in donating electrons to the conduction band of the WO octahedral framework at the Cs site. (2) Moisture and heat resistance of near-infrared absorbing particles The near-infrared absorbing particles of this embodiment exhibit improved moist heat resistance compared to cesium-doped hexagonal tungsten bronze. This effect is reasonable considering that a portion of the near-infrared absorbing particles of this embodiment contains one or more types of crystals selected from orthorhombic, rhombohedral, and cubic (pyrochlore) phases modulated by interstitial substitution with O, OH, OH2, and OH3. In other words, humidity and moisture degradation of cesium-doped hexagonal tungsten bronze is essentially a substitution reaction between Cs and water molecules. However, when the cavities and windows of the hexagonal tunnels, which are the main oxygen diffusion pathways, are filled with Cs, O, OH, OH2, and OH3, this substitution reaction is significantly slowed down. Therefore, the near-infrared absorbing particles of this embodiment not only suppress the loss of near-infrared absorbing function in high-humidity environments, but also slow down atmospheric moisture-mediated degradation reactions in high-temperature heat resistance tests at normal humidity, thereby improving moist heat resistance. (3) Average particle size of near-infrared absorbing particles The average particle size of the near-infrared absorbing particles of this embodiment is not particularly limited, but is preferably 0.1 nm or more and 200 nm or less. This is because, by setting the average particle size of the near-infrared absorbing particles to 200 nm or less, localized surface plasmon resonance is more pronounced, thereby particularly enhancing the near-infrared absorption characteristics, i.e., particularly suppressing the solar transmittance. Furthermore, by setting the average particle size of the near-infrared absorbing particles to 0.1 nm or more, the near-infrared absorbing particles can be easily produced industrially. Furthermore, the particle size is closely related to the color of the near-infrared absorbing fiber. In the particle size range where Mie scattering is dominant, the smaller the particle size, the less scattering of short wavelengths in the visible light region. Therefore, while increasing the particle size has the effect of suppressing the blue hue, an average particle size exceeding 200 nm suppresses the generation of surface plasmons and reduces LSPR absorption. Therefore, by setting the average particle size of the near-infrared absorbing particles to 200 nm or less, the color of the near-infrared absorbing fiber can be made particularly neutral while maintaining a certain level of LSPR absorption.

[0063] Furthermore, if the average particle size of the near-infrared absorbing particles is 200 nm or less, it is possible to prevent clogging of the filter, thread breakage, etc. during the spinning, drawing, and other processes in producing the near-infrared absorbing fiber. Furthermore, by setting the average particle size of the near-infrared absorbing particles to 200 nm or less, it becomes easier to uniformly mix and disperse the near-infrared absorbing particles in the spinning raw material of the near-infrared absorbing fiber.

[0064] Here, the average particle size of the near-infrared absorbing particles can be known from the median size of a plurality of near-infrared absorbing particles measured from a transmission electron microscope image, or the dispersed particle size measured with a particle size measuring device based on a dynamic light scattering method of a dispersion liquid.

[0065] In particular, when the film is applied to an application in which transparency in the visible light region is important, it is preferable to further consider reducing scattering by near-infrared absorbing particles. When the reduction in scattering is important, it is particularly preferable that the average particle size of the near-infrared absorbing particles is 30 nm or less.

[0066] The average particle size refers to the particle size at 50% of the cumulative value in the particle size distribution, and the same meaning applies to the average particle size in other parts of this specification. A method for measuring particle size distribution to calculate the average particle size can be, for example, direct measurement of the particle size of each particle using a transmission electron microscope. The average particle size can also be measured using a particle size measuring device based on the dynamic light scattering method of the dispersion liquid, as described above. (4) Optional configuration of near-infrared absorbing particles The near-infrared absorbing particles may be subjected to a surface treatment for purposes such as surface protection, improved durability, oxidation prevention, and improved water resistance. The specific content of the surface treatment is not particularly limited. For example, as shown in FIG. 5 , the near-infrared absorbing particles of this embodiment may have a coating 51 on a surface 50A of a near-infrared absorbing particle 50. Specifically, the surface of the near-infrared absorbing particle 50 may be coated with a coating 51 of a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn. That is, the near-infrared absorbing particles may have a coating of the above-mentioned compound. In this case, examples of the compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn include one or more selected from oxides, nitrides, carbides, and the like.

[0067] 5 merely schematically illustrates the shape of the near-infrared absorbing particle, and is not limited to such a shape. For example, the near-infrared absorbing particle 50 may be irregularly shaped instead of spherical. The coating 51 does not need to completely cover the surface 50A of the near-infrared absorbing particle 50, and may be disposed so as to cover only a portion of the surface 50A. Furthermore, the thickness of the coating 51 may vary depending on the location on the surface 50A of the near-infrared absorbing particle 50. [2] Manufacturing method for near-infrared absorbing particles Next, a structural example of the method for producing near-infrared absorbing particles according to this embodiment will be described. Since the method for producing near-infrared absorbing particles according to this embodiment can produce the near-infrared absorbing particles described above, a part of the description will be omitted.

[0068] The method for producing near-infrared absorbing particles is not particularly limited, and any method can be used as long as it can produce near-infrared absorbing particles that satisfy the above-mentioned properties. Here, one configuration example of the method for producing near-infrared absorbing particles will be described. (1) First heat treatment process The method for producing near-infrared absorbing particles of the present embodiment can include, for example, the following steps.

[0069] A first heat treatment step in which a compound raw material containing Cs and W is heated at 400°C or higher and 650°C or lower in an atmosphere containing water vapor or an atmosphere containing water vapor and a reducing gas.

[0070] In the first heat treatment step, the cesium tungstate can be crystallized by heating at 400° C. or higher and 650° C. or lower.

[0071] However, in order to make cesium tungstate a pseudo-hexagonal crystal, it is preferable to have sufficient water vapor in the atmosphere when the cesium tungstate crystallizes, i.e., when the WO6 units form hexagonal crystals with Cs. During this crystallization process, Cs is mainly taken up into the hexagonal cavities, and water molecules or its decomposition product, OH3 + , O.H. - and O 2- is mainly taken up in the hexagonal windows. When the composition contains a relatively large amount of Cs or water molecules, Cs or water molecules are also taken up in the three-sided cavities.

[0072] The compound raw material containing Cs and W can be a mixture of a compound raw material containing Cs and a compound raw material containing W. The compound raw material containing Cs and W can be any material containing Cs and W, and for example, a mixture of Cs2CO3 and WO3 can be used.

[0073] However, the purpose of the crystallization process in the first heat treatment step is to incorporate water molecules, OH, O, etc. into the crystals during crystallization. Therefore, as a compound raw material containing Cs and W, it is preferable not to use cesium tungsten oxide that already forms a hexagonal crystal structure, such as crystal powder of nCs2O·mWO3 (n and m are integers, 3.6≦m / n≦9.0). As a compound raw material containing Cs and W, it is also preferable not to use cesium tungstates obtained by other methods, such as the sol-gel method or complex polymerization method, non-equilibrium cesium tungstates obtained by gas-phase synthesis, powders obtained by thermal plasma methods, or powders obtained by electron beam melting. In raw materials that already form a hexagonal crystal structure, Cs inhibits the diffusion of oxygen atoms, making it difficult for water molecules to be incorporated into the crystals. In other words, it is preferable not to use cesium tungstates with a hexagonal crystal structure as a compound raw material containing Cs and W.

[0074] The supply of water vapor during the crystallization process of the first heat treatment step is preferably achieved by, for example, supplying superheated water vapor into a heating furnace. Superheated water vapor is high-enthalpy water vapor obtained by further heating saturated water vapor vaporized at 100°C to a temperature above 100°C, and may be supplied together with a carrier gas. When the carrier gas is an inert gas, an atmosphere nearly free of oxygen is formed. Superheated water vapor may be supplied at 400°C or above, at which point crystallization becomes active, but it is preferable to supply it from a temperature sufficiently low before crystallization. A mixture of superheated water vapor and an inert gas, or a mixture of superheated water vapor, an inert gas, and a reducing gas such as hydrogen, may also be supplied. When a reducing gas is mixed, the rate of hexagonal crystal arrangement tends to increase, and even if the same orthorhombic, rhombohedral, or cubic crystal is used, different microscopic defect structures may be obtained.

[0075] In the first heat treatment step, heating may be performed in an atmosphere not containing water vapor, such as an inert atmosphere, before or after crystallization of the cesium tungstate.

[0076] The method for producing near infrared ray absorbing particles of the present embodiment may further include any optional steps. (2) Second heat treatment process The method for producing near infrared absorbing particles of this embodiment may also include, after the first heat treatment step, a second heat treatment step of heating at a temperature of 500° C. or more and 950° C. or less in an atmosphere containing a reducing gas.

[0077] The second heat treatment process involves heating and reducing the material powder that has undergone the first heat treatment process at a temperature between 500°C and 950°C. This process stabilizes the orthorhombic, rhombohedral, and cubic crystals, which have defect structures, by annealing. The high-temperature reduction process also serves to remove some of the oxygen in the WO6 octahedra. The reduction and removal of the octahedral oxygen generates bound electrons on adjacent W atoms, resulting in a structural treatment that enhances near-infrared absorption properties.

[0078] When performing the thermal reduction treatment, it is preferable to perform it under a stream of a reducing gas. As the reducing gas, a mixed gas containing a reducing gas such as hydrogen and one or more inert gases selected from nitrogen, argon, etc. can be used. Alternatively, heating in a water vapor atmosphere or a vacuum atmosphere or other mild heating and reduction conditions may be used in combination.

[0079] The second heat treatment step may be composed of a plurality of steps, and after the heating in the reducing gas atmosphere, heating in an inert gas atmosphere may be further carried out.

[0080] Furthermore, in the second heat treatment step, if partial removal of oxygen from the WO octahedra is not intended, heating can be performed in an inert gas atmosphere instead of the reducing gas atmosphere within the above temperature range. That is, the second heat treatment step can be performed in an inert gas atmosphere or a reducing gas atmosphere at a temperature of 500°C to 950°C.

[0081] As described above, the method for producing the near-infrared absorbing particles of the present embodiment is not particularly limited. As the method for producing the near-infrared absorbing particles, various methods that can form a predetermined structure including a defect microstructure can be used.

[0082] The near-infrared absorbing particles may be produced by synthesizing a tungstate by a solid phase method, a liquid phase method, or a gas phase method in an atmosphere in which water molecules coexist. (3) Crushing process As described above, the near-infrared absorbing particles are preferably pulverized into fine particles, and therefore the method for producing near-infrared absorbing particles may also include a pulverization step of pulverizing the powder obtained in the first heat treatment step and the second heat treatment step.

[0083] The specific means for pulverizing and pulverizing is not particularly limited, and various means capable of mechanical pulverization can be used. As the mechanical pulverization method, a dry pulverization method using a jet mill or the like can be used. Furthermore, mechanical pulverization may be performed in a solvent in the process of obtaining a near-infrared absorbing particle dispersion liquid described below.

[0084] If necessary, further sieving or the like can be carried out. (4) Coating process As described above, the surface of the near infrared absorbing particle may be coated with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn. Therefore, the method for producing the near infrared absorbing particle may further include, for example, a coating step of coating the near infrared absorbing particle with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn.

[0085] In the coating step, the specific conditions for coating the surfaces of the near infrared absorbing particles are not particularly limited. For example, a coating step may be included in which an alkoxide containing one or more metals selected from the above metal group is added to the near infrared absorbing particles to be coated, and a film is formed on the surfaces of the near infrared absorbing particles. [3] Near-infrared absorbing particle dispersion Next, a configuration example of the near-infrared absorbing particle dispersion liquid of this embodiment will be described.

[0086] The near-infrared absorbing particle dispersion of the present embodiment can also be used, for example, when producing near-infrared absorbing fibers, which will be described later.

[0087] The near-infrared absorbing particle dispersion of the present embodiment can contain the above-described near-infrared absorbing particles and one or more liquid mediums selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers. The near-infrared absorbing particle dispersion preferably has a configuration in which near-infrared absorbing particles are dispersed in a liquid medium.

[0088] As described above, the liquid medium may be one or more selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers.

[0089] As the organic solvent, various types can be selected, such as alcohols, ketones, esters, hydrocarbons, and glycols. Specific examples of the solvent include one or more selected from the group consisting of alcohol solvents such as isopropyl alcohol, methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propanol; ketone solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester solvents such as 3-methyl-methoxy-propionate and butyl acetate; glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol methyl ether acetate, and propylene glycol ethyl ether acetate; amides such as formamide, N-methylformamide, dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; and halogenated hydrocarbons such as ethylene chloride and chlorobenzene.

[0090] However, among these, organic solvents with low polarity are preferred, and in particular, isopropyl alcohol, ethanol, 1-methoxy-2-propanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, n-butyl acetate, etc. These organic solvents can be used alone or in combination of two or more.

[0091] Examples of fats and oils that can be used include one or more selected from drying oils such as linseed oil, sunflower oil, and tung oil; semi-drying oils such as sesame oil, cottonseed oil, rapeseed oil, soybean oil, and rice bran oil; non-drying oils such as olive oil, coconut oil, palm oil, and dehydrated castor oil; fatty acid monoesters obtained by directly esterifying fatty acids of vegetable oils with monoalcohols; ethers; and petroleum solvents such as Isopar (registered trademark) E, Exxor (registered trademark) Hexane, Heptane, E, D30, D40, D60, D80, D95, D110, and D130 (all manufactured by ExxonMobil).

[0092] As the liquid resin, for example, one or more types selected from liquid acrylic resin, liquid epoxy resin, liquid polyester resin, liquid urethane resin, etc. can be used.

[0093] As the liquid plasticizer, for example, a liquid plasticizer for plastics can be used.

[0094] The components contained in the near-infrared absorbing particle dispersion are not limited to the near-infrared absorbing particles and the liquid medium described above. The near-infrared absorbing particle dispersion may further contain any optional components added thereto, as necessary.

[0095] For example, an acid or alkali may be added to the near-infrared absorbing particle dispersion liquid as needed to adjust the pH of the dispersion liquid.

[0096] In addition, in order to further improve the dispersion stability of the near infrared absorbing particles in the near infrared absorbing particle dispersion liquid described above and to prevent the dispersed particle size from becoming coarse due to re-aggregation, various surfactants, coupling agents, and the like may be added to the near infrared absorbing particle dispersion liquid as dispersants.

[0097] The dispersant, such as the surfactant or coupling agent, can be selected depending on the application, but it is preferable that the dispersant has one or more functional groups selected from an amine-containing group, a hydroxyl group, a carboxyl group, and an epoxy group. These functional groups adsorb to the surface of the near-infrared absorbing particles to prevent aggregation and have the effect of uniformly dispersing the near-infrared absorbing particles, for example, in an infrared shielding film formed using the near-infrared absorbing particles. It is more preferable that the dispersant is a polymeric dispersant having one or more functional groups selected from the above functional groups (functional groups) in the molecule.

[0098] Suitable commercially available dispersants include SOLSPERSE3000, SOLSPERSE9000, SOLSPERSE11200, SOLSPERSE13000, SOLSPERSE13240, SOLSPERSE13650, SOLSPERSE13940, SOLSPERSE16000, SOLSPERSE17000, SOLSPERSE18000, SOLSPERSE20000, SOLSPERSE21000, SOLSPERSE24000SC, SOLSPERSE24000GR, SOLSPERSE26000, SOLSPERSE27000, SOLSPERSE28000, and SOLSPERSE29000 manufactured by Lubrizol Japan Co., Ltd. PERSE31845, SOLSPERSE32000, SOLSPERSE32500, SOLSPERSE32550, SOLSPERSE32600, SOLSPERSE33000, SOLSPERSE33500, SOLSPERSE34750, SOLSPERSE35100, SOLSPERSE35200, SO LSPERSE36600, SOLSPERSE37500, SOLSPERSE38500, SOLSPERSE39000, SOLSPERSE41000, SOLSPERSE41090, SOLSPERSE53095, SOLSPERSE55000, SOLSPERSE56000, SOLSPERSE76500 etc; Disperbyk-101, Disperbyk-103, Disperbyk-107, Disperbyk-108, Disperbyk-109, Disperbyk-110, Disperbyk-111, Disperbyk-112, Disperbyk-116, Disperbyk-130, Disperbyk-140, Disperbyk-142, Disperbyk-145, Disperbyk-154, Disperbyk-161, Disperbyk-162, Disperbyk-163, Disperbyk-164, Disperbyk-165, Disperbyk-166, Disperbyk-167, Disperbyk-168, Disperbyk-170, Disperbyk-171, Disperbyk-172, Disperbyk-173, Disperbyk-174, Disperbyk-175, Disperbyk-176, Disperbyk-177, Disperbyk-178, Disperbyk-179, Disperbyk-180, Disperbyk-181, Disperbyk-182, Disperbyk-183, Disperbyk-184, Disperbyk-185, Disperbyk-186, Disperbyk-187, Disperbyk-188, Disperbyk-189, Disperbyk-200, Disperbyk-2010, Disperbyk-2011, Disperbyk-2012, Disperbyk-2013, Disperbyk-2014, Disperbyk-2015, Disperbyk-2016, Disperbyk-2017, Disperbyk-2018, Disperbyk-2019, Disperbyk-210, Disperbyk-2110, Disperbyk- sperbyk-171, Disperbyk-174, Disperbyk-180, Disperbyk-181, Disperbyk-182, Disperbyk-183, Disperbyk-184, Disperbyk-185, Disperbyk-190, Disperbyk-2000, Disperbyk-2001, Disperbyk-2020, D isperbyk-2025, Disperbyk-2050, Disperbyk-2070, Disperbyk-2095, Disperbyk-2150, Disperbyk-2 155, Anti-Terra-U, Anti-Terra-203, Anti-Terra-204, BYK-P104, BYK-P104S, BYK-220S, BYK-6919, etc.; BASF Japan Ltd. EFKA4008, EFKA4046, EFKA404 7, EFKA4015, EFKA4020, EFKA4050, EFKA4055, EFKA4060, EFKA4080, EFKA4300, EFKA4330, EFKA44 00, EFKA4401, EFKA4402, EFKA4403, EFKA4500, EFKA4510, EFKA4530, EFKA4550, EFKA4560, EFKA4585, EFKA4800, EFKA5220, EFKA6 230, JONCRYL67, JONCRYL678, JONCRYL586, JONCRYL611, JONCRYL680, JONCRYL682, JONCRYL690, JONCRYL819, JONCRYL-JDX5050, etc.; Examples include one or more selected from Ajisper PB-711, Ajisper PB-821, Ajisper PB-822, and the like, all of which are manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0099] The method for dispersing near-infrared absorbing particles in a liquid medium is not particularly limited as long as it can disperse the near-infrared absorbing particles in the liquid medium. In this case, it is preferable that the near-infrared absorbing particles be dispersed so that their average particle size is 200 nm or less, and more preferably so that they are dispersed so that their average particle size is 0.1 nm or more and 200 nm or less. This is because a small average particle size reduces the scattering of light in the visible light region with wavelengths of 400 nm or more and 780 nm or less due to geometric scattering or Mie scattering. As a result of this reduced light scattering, for example, a near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment, in which near-infrared absorbing particles are dispersed in a resin or the like, can be prevented from becoming like frosted glass, thereby preventing the loss of clear transparency. That is, when the average particle size is 200 nm or less, the light scattering mode weakens from the geometric scattering or Mie scattering mode and becomes the Rayleigh scattering mode. In the Rayleigh scattering region, scattered light is proportional to the sixth power of the dispersed particle size, so scattering decreases and transparency improves as the dispersed particle size decreases. When the average particle size is 100 nm or less, the scattered light is reduced to a minimum, which is preferable.

[0100] Examples of methods for dispersing near-infrared absorbing particles in a liquid medium include dispersion methods using devices such as a bead mill, a pole mill, a sand mill, a paint shaker, and an ultrasonic homogenizer. Among these, pulverization and dispersion using a media agitation mill such as a bead mill, a pole mill, a sand mill, or a paint shaker that uses a medium media (beads, poles, or Ottawa sand) is preferred from the viewpoint of shortening the time required to achieve a desired average particle size. By the pulverization-dispersion treatment using a media agitation mill, not only is the near-infrared absorbing particles dispersed in the liquid medium, but also finer particle size is promoted due to collisions between the near-infrared absorbing particles and collisions between the medium and the near-infrared absorbing particles, allowing the near-infrared absorbing particles to be dispersed in a finer particle size. In other words, a pulverization-dispersion treatment is performed.

[0101] Incidentally, the dispersion state of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion obtained by using the near-infrared absorbing particle dispersion of the present embodiment, in which the near-infrared absorbing particles are dispersed in a solid medium such as a resin, does not cause aggregation of particles having a particle size smaller than the average particle size of the near-infrared absorbing particles in the dispersion, as long as a known method for adding the dispersion to the solid medium is used.

[0102] When the average particle size of the near-infrared absorbing particles is 0.1 nm or more and 200 nm or less, it is possible to prevent the near-infrared absorbing particle dispersion and its molded body (plate, sheet, etc.) from being produced as grayish with monotonically decreasing transmittance.

[0103] The content of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion of this embodiment is not particularly limited, but is preferably, for example, 0.01% by mass or more and 80% by mass or less. This is because a sufficient solar radiation absorptivity can be exhibited by setting the content of the near-infrared absorbing particles to 0.01% by mass or more. Also, by setting the content to 80% by mass or less, the near-infrared absorbing particles can be uniformly dispersed in the dispersion medium. [4] Near-infrared absorbing fiber The near-infrared absorbing fiber according to this embodiment will be described.

[0104] FIG. 6 is a schematic diagram of a near-infrared absorbing fiber of this embodiment. FIG. 6 is a schematic cross-sectional view of a near-infrared absorbing fiber 60 taken along a plane passing through a central axis CA of a fiber 61. As shown in FIG. 6, the near-infrared absorbing fiber 60 of this embodiment contains fibers 61 and near-infrared absorbing particles 62 disposed at one or more locations selected from the surface 61A and the interior 61B of the fibers 61. Note that FIG. 6 is a schematic diagram showing an example in which the near-infrared absorbing particles 62 are disposed on both the surface 61A and the interior 61B of the fibers 61, but this configuration is not limited thereto. The near-infrared absorbing particles 62 may be disposed on only one of the surface 61A and the interior 61B of the fibers 61. Furthermore, although the near-infrared absorbing particles 62 are depicted as spherical particles in FIG. 6, the shape of the near-infrared absorbing particles 62 is not limited thereto and may have any shape. (1) Near-infrared absorbing particles The near-infrared absorbing fiber of this embodiment can contain the near-infrared absorbing particles described above. Since the near-infrared absorbing particles have already been described, further description will be omitted here.

[0105] The amount of near-infrared absorbing particles contained in the near-infrared absorbing fiber of this embodiment is not particularly limited, but since the near-infrared absorbing ability per unit weight of the near-infrared absorbing particles is very high, a usage amount of about 1 / 4 to 1 / 10 of that of ITO or ATO can achieve the same near-infrared absorbing effect. Specifically, the near-infrared absorbing fiber of this embodiment preferably contains the near-infrared absorbing particles in a proportion of, for example, 0.001% by mass or more and 80% by mass or less relative to the solid content of the fiber. Furthermore, from the viewpoint of the weight of the near-infrared absorbing fiber and raw material costs, the near-infrared absorbing fiber of this embodiment more preferably contains the near-infrared absorbing particles in a proportion of 0.005% by mass or more and 50% by mass or less relative to the solid content of the fiber.

[0106] By incorporating near-infrared absorbing particles at a ratio of 0.001% by mass or more relative to the solid content of the fiber, sufficient near-infrared absorbing effect can be obtained even with a thin fabric. Furthermore, by incorporating near-infrared absorbing particles at a ratio of 80% by mass or less relative to the solid content of the fiber, deterioration of spinnability due to clogging of the filter or thread breakage during spinning can be avoided, and 50% by mass or less is even more preferable. Furthermore, by incorporating near-infrared absorbing particles at a ratio of 80% by mass or less relative to the solid content of the fiber, the near-infrared absorbing particle content can be reduced, so the physical properties of the fiber are not impaired. (2) Fiber Various fibers can be selected depending on the application of the near-infrared absorbing fiber, and can contain one or more types selected from the fiber group consisting of synthetic fibers, semi-synthetic fibers, natural fibers, regenerated fibers, and inorganic fibers. The fiber can be any of a single type of fiber, a blend, a doubling, and a mixed yarn made by mixing fibers. Therefore, the fiber can be any fiber selected from the above fiber group, a blend containing one or more types of fibers selected from the above fiber group, a doubling containing one or more types of fibers selected from the above fiber group, or a mixed yarn made by mixing one or more types of fibers selected from the above fiber group.

[0107] In consideration of the ease with which the near-infrared absorbing particles can be incorporated into the fibers and the durability of heat retention, the fibers preferably contain synthetic fibers, and more preferably are made of synthetic fibers. (2-1) Fiber type (synthetic fiber) As the synthetic fiber, for example, one or more types selected from polyurethane fibers, polyamide fibers, acrylic fibers, polyester fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinylidene chloride fibers, polyvinyl chloride fibers, polyether ester fibers, etc. can be suitably used.

[0108] Examples of polyamide fibers include nylon, nylon 6, nylon 66, nylon 11, nylon 610, nylon 612, aromatic nylon, and aramid.

[0109] Examples of acrylic fibers include polyacrylonitrile, acrylonitrile-vinyl chloride copolymer, and modacrylic.

[0110] Examples of polyester fibers include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate.

[0111] Examples of polyolefin fibers include polyethylene, polypropylene, and polystyrene.

[0112] Examples of polyvinyl alcohol fibers include vinylon.

[0113] Examples of polyvinylidene chloride fibers include vinylidene.

[0114] Examples of polyvinyl chloride fibers include polyvinyl chloride.

[0115] Examples of polyetherester fibers include Rexe and Success. (semi-synthetic fiber) As the semi-synthetic fiber, for example, one or more types selected from cellulose-based fibers, protein-based fibers, chlorinated rubber, hydrochloric rubber, etc. can be suitably used.

[0116] Examples of cellulosic fibers include acetate, triacetate, and acetate oxide.

[0117] Examples of protein-based fibers include Promix. (natural fibers) As the natural fiber, for example, one or more types selected from plant fibers, animal fibers, mineral fibers, etc. can be suitably used.

[0118] Examples of plant fibers include cotton, kapok, flax, hemp, jute, Manila hemp, sisal, New Zealand hemp, ramie, palm, rush, and wheat straw.

[0119] Examples of animal fibers include wool such as sheep's wool, goat's hair, mohair, cashmere, alpaca, angora, camel, and vicuna, as well as silk, down, and feathers.

[0120] Examples of mineral fibers include asbestos. (recycled fiber) As the regenerated fiber, for example, one or more types selected from cellulose-based fibers, protein-based fibers, alginate fibers, rubber fibers, chitin fibers, and mannan fibers can be suitably used.

[0121] Examples of cellulosic fibers include rayon, viscose rayon, cupro, polynosic, and cuprammonium rayon.

[0122] Examples of protein fibers include casein fiber, peanut protein fiber, corn protein fiber, soy protein fiber, and regenerated silk. (inorganic fiber) As the inorganic fiber, for example, one or more types selected from metal fiber, carbon fiber, and silicate fiber can be suitably used.

[0123] Examples of the metal fibers include metal fibers, gold threads, silver threads, and heat-resistant alloy fibers.

[0124] Examples of silicate fibers include glass fibers, slag fibers, and rock fibers. (2-2) Fiber shape The cross-sectional shape of the fiber is not particularly limited, and examples thereof include one or more types selected from circular, triangular, hollow, flat, Y-shaped, star-shaped, and sheath-core shapes. The near-infrared absorbing particles can be incorporated into one or more locations selected from the surface and interior of the fiber in various forms. For example, in the case of a sheath-core shape, the near-infrared absorbing particles may be incorporated into the core or sheath of the fiber. The fiber may be in the form of a filament (long fiber) or a staple (short fiber). (3) Additives The near-infrared absorbing fiber of the present embodiment may contain additives such as antioxidants, flame retardants, deodorizers, insect repellents, antibacterial agents, and ultraviolet absorbers depending on the purpose, within the range that does not impair the performance of the fiber.

[0125] The near-infrared absorbing fiber of this embodiment may also contain particles of a far-infrared emitting substance capable of emitting far-infrared rays.

[0126] The particles of the far-infrared emitting material can be disposed at one or more locations selected from the surface and the interior of the fiber.

[0127] The far-infrared emitting material may be one or more selected from metal oxides such as ZrO2, SiO2, TiO2, Al2O3, MnO2, MgO, Fe2O3, and CuO; carbides such as ZrC, SiC, and TiC; and nitrides such as ZrN, Si3N4, and AlN.

[0128] The cesium tungstate contained in the near-infrared absorbing particles has the property of absorbing solar energy with wavelengths of 0.3 μm to 3 μm, and particularly selectively absorbs the near-infrared region around wavelengths of 0.9 μm to 2.2 μm, converting it to heat or re-radiating it. Meanwhile, the particles of the far-infrared emitting material have the ability to receive the energy absorbed by the cesium tungstate, a near-infrared absorbing material, convert that energy into thermal energy with wavelengths of mid- to far-infrared, and then radiate it. For example, ZrO2 particles convert the energy absorbed by the cesium tungstate into thermal energy with wavelengths of 2 μm to 20 μm, and then radiate it. Therefore, when the particles of the far-infrared emitting material capable of emitting far-infrared rays coexist with the aforementioned near-infrared absorbing particles inside or on the surface of the fiber, the solar energy absorbed by the near-infrared absorbing particles is efficiently consumed inside or on the surface of the fiber, resulting in more effective heat retention.

[0129] The content of the far-infrared emitting material particles is not particularly limited, but is preferably 0.001% by mass or more and 80% by mass or less relative to the solid content of the fiber. This is because a content of 0.001% by mass or more can achieve a sufficient thermal energy radiation effect even if the fabric is thin. Furthermore, by setting the content of the far-infrared emitting material to 80% by mass or less, it is possible to more reliably avoid a decrease in spinnability of the near-infrared absorbing fiber due to filter clogging, yarn breakage, etc. during spinning. [5] Manufacturing method for near-infrared absorbing fiber Next, a method for producing the near-infrared absorbing fiber of this embodiment will be described. Since the method for producing the near-infrared absorbing fiber of this embodiment can produce the near-infrared absorbing fiber described above, a description of the matters already described will be omitted.

[0130] The method for producing the near-infrared absorbing fiber of this embodiment is not particularly limited, and may include, for example, a step of arranging near-infrared absorbing particles at one or more locations selected from the surface and the interior of the fiber. As the near-infrared absorbing particles can be the near-infrared absorbing particles already described, further description will be omitted here.

[0131] In the above-mentioned disposing step, the method for disposing the near-infrared absorbing particles at one or more locations selected from the surface and the interior of the fiber is not particularly limited.

[0132] For example, the following methods (a) to (d) can be mentioned.

[0133] (a) A method in which near-infrared absorbing particles are directly mixed into the raw polymer of synthetic fibers and then spun.

[0134] (b) A method in which a master batch is prepared in advance by incorporating near-infrared absorbing particles into a part of the raw polymer at a high concentration, and this is diluted and adjusted to a predetermined concentration at the time of spinning before spinning.

[0135] (c) A method in which near-infrared absorbing particles are uniformly dispersed in advance in a raw material monomer or oligomer solution, and the target raw material polymer is synthesized using this dispersion, and at the same time, the near-infrared absorbing particles are uniformly dispersed in the raw material polymer, and then the polymer is spun.

[0136] (d) A method in which near-infrared absorbing particles are attached to the surface of fibers obtained by spinning in advance using a binder or the like.

[0137] The methods for producing the master batches used in the above method (a) and method (b) will now be briefly described.

[0138] The method for producing the masterbatch is not particularly limited. For example, first, a near-infrared absorbing particle dispersion, powder or pellets of a thermoplastic resin, and other additives as necessary are uniformly melt-mixed using a mixer or kneader while removing a solvent such as a liquid medium. By such an operation, a mixture in which the near-infrared absorbing particles are uniformly dispersed in the thermoplastic resin can be prepared.

[0139] Examples of the mixer include a Riboblender, a tumbler, a Nauta mixer, a Henschel mixer, a super mixer, a planetary mixer, etc. Examples of the kneader include a Banbury mixer, a kneader, a roll, a kneader-ruder, a single-screw extruder, a twin-screw extruder, etc.

[0140] The method for producing a mixture of near-infrared absorbing particles and a resin is not limited to the above method. For example, after preparing a near-infrared absorbing particle dispersion, the solvent such as the liquid medium of the dispersion may be removed by a known method, and the obtained powder may be uniformly melt-mixed with powder or pellets of a thermoplastic resin and, if necessary, other additives to produce a mixture in which the near-infrared absorbing particles are uniformly dispersed in a thermoplastic resin. Alternatively, a method may be used in which the powder of near-infrared absorbing particles is directly added to a thermoplastic resin and then uniformly melt-mixed.

[0141] A mixture of the near-infrared absorbing particles obtained by the above-described method and a thermoplastic resin is kneaded in a vented single-screw or twin-screw extruder and processed into pellets, thereby obtaining a masterbatch containing near-infrared absorbing particles.

[0142] Here, the above methods (a) to (d) that can be applied to the placement step will be explained using specific examples.

[0143] Method (a): For example, a case where polyester fibers are used as the fibers will be described.

[0144] A near-infrared absorbing particle dispersion is added to polyethylene terephthalate resin pellets, which are a thermoplastic resin, and the mixture is uniformly mixed in a blender. The resulting mixture is then melt-kneaded in a twin-screw extruder to obtain a near-infrared absorbing particle-containing masterbatch. This near-infrared absorbing particle-containing masterbatch can be melt-mixed at a temperature close to the melting temperature of the resin and spun, for example, by various known methods. As mentioned above, the masterbatch can also be prepared by methods other than those described above.

[0145] Method (b): A near-infrared absorbing particle-containing masterbatch is prepared by the method described in Method (a), etc. Then, the masterbatch and a target amount of a masterbatch made of polyethylene terephthalate to which no near-infrared absorbing particles have been added are melt-mixed at a desired mixing ratio near the melting temperature of the resin, and spun according to a known method.

[0146] Method (c): For example, a case where urethane fibers are used as the fibers will be described.

[0147] A polymeric diol containing near-infrared absorbing particles is reacted with an organic diisocyanate in a twin-screw extruder to synthesize an isocyanate-terminated prepolymer, which is then reacted with a chain extender to produce a polyurethane solution (raw polymer).The polyurethane solution is then spun according to a known method.

[0148] Method (d): For example, the case where near-infrared absorbing particles are attached to the surface of natural fibers will be described.

[0149] First, a treatment liquid is prepared by mixing near-infrared absorbing particles, one or more binder resins selected from acrylic, epoxy, urethane, and polyester, and a solvent such as water.

[0150] Next, natural fibers are immersed in the prepared treatment solution, or the natural fibers are impregnated with the prepared treatment solution by padding, printing, spraying, or the like, and then dried. This allows the near-infrared absorbing particles to adhere to the natural fibers. Method (d) can be applied to semi-synthetic fibers, regenerated fibers, inorganic fibers, or blends, doubling, or mixed fibers thereof, in addition to the natural fibers described above.

[0151] When carrying out the methods (a) to (d), the dispersion method for dispersing the near-infrared absorbing particles in the dispersion medium is not particularly limited, and any method that can uniformly disperse the near-infrared absorbing particles in a liquid, i.e., the dispersion medium, may be used. For example, methods such as a medium stirring mill, a ball mill, a sand mill, and ultrasonic dispersion can be suitably applied. Note that the near-infrared absorbing particle dispersion liquid described above can be used as the near-infrared absorbing particles dispersed in the dispersion medium.

[0152] In dispersing the near-infrared absorbing particles, it is preferable to set the dispersion process conditions so as to ensure that the ratio of the XRD peak top intensity of the near-infrared absorbing particles to the XRD peak intensity of the (220) plane of a silicon powder standard sample (640c, manufactured by NIST) is 0.13 or more, when the value of the XRD peak intensity is 1. By doing so, the near-infrared absorbing fiber according to this embodiment can exhibit particularly excellent optical properties.

[0153] Furthermore, the dispersion medium for the near-infrared absorbing particles is not particularly limited and can be selected according to the fibers to be mixed. For example, one or more types selected from various common organic solvents such as alcohols, ethers, esters, ketones, and aromatic compounds, and water can be used.

[0154] Furthermore, when the near-infrared absorbing particles are attached to or mixed with fibers or the polymer that is the raw material thereof, the dispersion of the near-infrared absorbing particles may be directly mixed with the fibers or the polymer that is the raw material thereof. If necessary, the pH may be adjusted by adding an acid or alkali to the dispersion of the near-infrared absorbing particles, and various surfactants, coupling agents, etc. may also be added to further improve the dispersion stability of the near-infrared absorbing particles.

[0155] As described above, according to the near-infrared absorbing fiber of this embodiment, by disposing near-infrared absorbing particles inside or on the surface of the fiber, it is possible to provide a fiber that efficiently absorbs near-infrared rays from sunlight and the like and has excellent heat retention properties.

[0156] Furthermore, the near-infrared absorbing fiber of this embodiment has good weather resistance, excellent transparency, and is low-cost, and the near-infrared absorbing particles have a neutral color tone. Therefore, the design of textile products using the near-infrared absorbing fiber of this embodiment is not impaired, and the fiber can be colored in complementary or light colors, and basic physical properties of the fiber, such as strength and elongation, can be avoided from being impaired. As a result, the near-infrared absorbing fiber of this embodiment can be used for various applications, such as textile products that require heat retention, such as cold weather clothing, sports clothing, stockings, curtains, and other industrial textile products, and can be colored in complementary or light colors.

[0157] In the near-infrared absorbing fiber of this embodiment, the near-infrared absorbing particles are preferably contained uniformly inside and on the surface of the fiber. By containing the near-infrared absorbing particles uniformly inside and on the surface of the near-infrared absorbing fiber of this embodiment, even when the content of the near-infrared absorbing particles is small, the near-infrared rays contained in sunlight and the like can be efficiently absorbed, and a fiber with excellent heat retention can be provided.

[0158] In the near-infrared absorbing fiber of this embodiment, it is preferable that the near-infrared absorbing particles and the particles of the far-infrared emitting material described above are uniformly contained inside or on the surface of the fiber. By uniformly containing the near-infrared absorbing particles and the particles of the far-infrared emitting material described above inside or on the surface of the near-infrared absorbing fiber of this embodiment, even when the content of the near-infrared absorbing particles is small, it is possible to provide a fiber that efficiently absorbs and utilizes near-infrared rays contained in sunlight, etc., and is particularly excellent in heat retention.

[0159] Incidentally, "uniformly contained" means that the near-infrared absorbing particles and the like are contained inside or on the surface of the fiber in a state where they are not aggregated and formed into clumps. [6] Textile products The textile product of this embodiment can contain the near-infrared absorbing fiber described above. Specifically, the textile product of this embodiment can be obtained by processing the near-infrared absorbing fiber described above and can contain the near-infrared absorbing fiber described above. Note that the textile product of this embodiment can also be made of the near-infrared absorbing fiber described above.

[0160] The textile product of the present embodiment includes the near-infrared absorbing fiber described above, which has good weather resistance, excellent transparency, and low cost, and in which the near-infrared absorbing particles have a neutral color tone. Therefore, the textile product can be colored in a complementary color or a light color without impairing the design of the textile product, and the basic physical properties of the fiber, such as strength and elongation, can be avoided from being impaired. [Example]

[0161] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the following examples. (Evaluation method) First, the evaluation methods used in the following examples and comparative examples will be described. (chemical analysis) The obtained near-infrared absorbing particles were chemically analyzed by atomic absorption spectrometry (AAS) for Cs and by inductively coupled plasma optical emission spectroscopy (ICP-OES) for W (tungsten). A LECO light element analyzer (ON-836) was used for O. (X-ray diffraction measurement) X-ray diffraction measurements were carried out by powder XRD measurement using Cu-Kα radiation with a Spectris X'Pert-PRO / MPD instrument.

[0162] [Example 1] (Production and evaluation of near-infrared absorbing particles) A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:6. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0163] The cesium tungsten oxide precursor powder was placed on an alumina boat and placed in a heating muffle furnace. While flowing a mixed gas of superheated steam and nitrogen gas (volume ratio: 50:50), the temperature was raised to 550°C and held for 1 hour. In Table 1, the mixed gas is represented as 50% N2-50% superheated H2O. Next, the gas supplied was changed to 100% nitrogen gas by volume. While flowing nitrogen gas, the temperature was held at 550°C for 0.5 hours, then the temperature was raised to 800°C and held for 1 hour. The temperature was then lowered to room temperature, yielding a slightly greenish-white powder (first heat treatment step).

[0164] The X-ray powder diffraction pattern of this white powder is Cs4W 11 O 35 (ICDD 00-51-1891).

[0165] Next, this white powder was placed in a carbon boat and placed in a tubular furnace. The temperature was increased in a 1% by volume H-Ar gas flow (represented as 1% H-Ar in Table 1) and the temperature was held at 550°C for 1 hour for reduction. Next, the gas supply was changed to 100% by volume Ar gas, and the temperature was held at 550°C for 30 minutes while Ar gas was flowing. The temperature was then increased to 800°C and heated for 1 hour, after which the temperature was lowered to room temperature to obtain a pale blue powder A (second heat treatment step).

[0166] The XRD powder pattern of the obtained powder A shows that the main phase is hexagonal Cs as shown in Figure 2. 0.32 WO3, the second phase is orthorhombic Cs4W 11 O 35 A broad two-phase mixture pattern was observed. Chemical analysis of Powder A revealed that the molar ratio of Cs / W was 0.33. The composition ratios of the other components are shown in Table 2. The XRD powder pattern in this case showed hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction lines of both Cs4W were mixed. 11 O 35 The diffraction lines of were observed to have slight deviations from the ideal positions and intensities. No data matching this diffraction pattern was found in the ICDD database.

[0167] When this powder was observed under a transmission electron microscope (Hitachi High-Tech Corporation HF-2200), fine particles 40 were observed, as shown in Figure 4(A). The crystals of each fine particle were observed as a single-phase structure, rather than a mixed structure consisting of two separate phases, hexagonal and orthorhombic, as shown in the selected-area electron diffraction pattern in Figure 4(B). The electron diffraction pattern shown in Figure 4(B) corresponds to the hexagonal

[0001] crystal zone, and the diffraction spots indicate the plane indices when considered as hexagonal. When the corresponding interplanar spacings were calculated from the nearest diffraction spots in the three directions, only the (01-10) interplanar spacing was 3.88 Å, significantly larger than the values ​​for the other two directions, 3.48 Å and 3.43 Å, indicating deviation from precise hexagonal symmetry. Note that, although in crystallography, negative indices are usually indicated by a bar above the number, for convenience of description, a minus sign is used in front of the number in this specification.

[0168] On the other hand, Figure 4(C) shows an atomic image taken using the STEM-HAADF method (high-angle-angle-diffusion dark-field observation in scanning electron mode). The higher the atomic number and the greater the atomic density in the projection direction, the brighter and more intense the atomic spot obtained. When combined with the projection plane information of the

[0001] crystal zone, the atomic species in the image can be identified. The most intense spot in Figure 4(C) is a W atom, but it is aligned along the (01-10) plane. A similar arrangement is not observed along the equivalent (1-100) or (10-10) planes in a hexagonal crystal. The streaks observed in the (01-10) spot direction in Figure 4(C) indicate that many planar defects (W and O vacancies) have been inserted only in the (01-10) plane, which is interpreted as increasing the interplanar spacing of the (01-10) plane. In a hexagonal crystal, almost no defects are introduced into the (01-10), (1-100), and (10-10) planes, which intersect at 60°. However, many planar defects have been inserted only into the (01-10) plane, causing it to lose its hexagonal symmetry and become orthorhombic. The regular spots indicated by arrow 41 in Figure 4(B) show that the W vacancy planes have been introduced with a periodicity of approximately 3.88 Å. As described above, it was determined that these near-infrared absorbing particles are single-crystal particles of cesium tungstate with a pseudo-hexagonal crystal structure that has been modulated into an orthorhombic crystal.

[0169] Furthermore, the obtained near-infrared-absorbing particle powder was irradiated with 25 W Al-Kα X-rays using an X-ray photoelectron spectrometer (ULVAC-PHI XPS-Versa Probe II). Observation of excited photoelectrons revealed that the O1s peak near 530.45 eV had a shoulder on the high-energy side. The component near 532.80 eV was assumed to be due to H2O, and peak separation revealed that it contained a large amount of OH2. Furthermore, thermal desorption spectroscopy confirmed that OH and OH2 were expelled from the crystals during heating in the temperature range between 500°C and 700°C. These observations suggest that OH and OH2 are contained in the cesium tungstate of Powder A. Considering the voids in the uniaxially elongated pseudohexagonal crystals, they are presumed to have infiltrated the window voids of the hexagonal tunnel. It is believed that water and its decomposition products were introduced into the crystals during crystallization in superheated steam, and the H generated during this process was also a major source of hydrogen. + and H3O + It is thought that the ions competed with the positive W ions, leading to partial desorption of the W ions. (Near-infrared absorbing fibers, production and evaluation of textile products)

[0170] 10% by mass of the prepared powder A, 10% by mass of an acrylic polymer dispersant having an amine-containing functional group (hereinafter referred to as "dispersant A"), and 80% by mass of toluene as a solvent were weighed out. These weighed materials were placed in a glass container together with 0.3 mm diameter silica beads and dispersed and pulverized for 1 hour using a paint shaker to obtain dispersion A.

[0171] Toluene was removed from dispersion A using a spray dryer, thereby obtaining a near-infrared absorbing particle dispersion powder according to Example 1. The obtained near-infrared absorbing particle dispersion powder was added to polyethylene terephthalate resin pellets, which is a thermoplastic resin, and mixed uniformly in a blender. After that, the mixture was melt-kneaded and extruded in a twin-screw extruder, and the extruded strands were cut into pellets, thereby obtaining a masterbatch containing 40 mass % of near-infrared absorbing particles, which are a near-infrared absorbing component.

[0172] The masterbatch was melt-spun and then drawn to produce a polyester multifilament yarn, which is the near-infrared absorbing fiber according to Example 1. The obtained near-infrared absorbing fiber contained 40% by mass of near-infrared absorbing particles, the same as the masterbatch. The obtained near-infrared absorbing fiber had a structure in which polyethylene terephthalate fibers were combined with near-infrared absorbing particles disposed on the surface and inside of the fibers. The polyester multifilament yarns produced in the following other examples also had the same structure.

[0173] The average particle size of near-infrared absorbing particles contained in the polyester multifilament yarn, which is a near-infrared absorbing fiber, was calculated to be 30 nm using an image processing device based on a transmission electron microscope image. The particle size of each particle is the diameter of the circumscribed circle of the particle, and the average particle size is calculated as the median diameter in the particle size distribution of particle sizes measured for 100 particles.

[0174] The obtained polyester multifilament yarn was cut to prepare polyester staples, which were then used to produce spun yarn. This spun yarn was then used to obtain a knitted product, which is a textile product according to Example 1 having heat-retaining properties. The solar reflectance of the produced knitted product sample was adjusted to 8%. Adjustment of the solar reflectance of the knitted product sample to 8% was performed in all of the examples and comparative examples described below.

[0175] The spectral characteristics of the knitted product were measured using a Hitachi spectrophotometer to measure the transmittance and reflectance of light with wavelengths of 200 to 2100 nm, and the solar absorptance was calculated according to JIS A 5759 (2019). The solar absorptance was calculated from the formula: solar absorptance (%) = 100% - solar transmittance (%) - solar reflectance (%). The calculated solar absorptance was 51.1%. Furthermore, the color index of the knitted product was calculated from the reflectance, and it was found to be L * =88, a * =-2, b * = 9, which confirmed that the blue color was very weak and the color tone was neutral.

[0176] The results are shown in Table 3. Table 3 also shows the results obtained in Examples 2 to 14 and Comparative Examples 1 and 2, which will be described later.

[0177] Next, the temperature-raising effect on the backside of the fabric of the produced knitted product was measured as follows: In an environment of 20°C and 60% RH, a lamp with a spectrum similar to sunlight (solar simulator XL-03E50 modified by Seric Co., Ltd.) was irradiated from a distance of 30 cm from the fabric of the knitted product, and the temperature of the backside of the fabric was measured at regular intervals (0 seconds, 30 seconds, 60 seconds, 180 seconds, 360 seconds, and 600 seconds) using a radiation thermometer (HT-11 manufactured by Minolta Co., Ltd.).

[0178] The results are shown in Table 4. Table 4 also shows the results obtained in Examples 2 to 14 and Comparative Examples 1 and 2, which will be described later. [Example 2] (Production and evaluation of near-infrared absorbing particles) The cesium tungsten oxide precursor powder prepared in Example 1 was placed on an alumina boat and placed in a heating muffle furnace. The temperature was raised to 150°C while flowing 100% by volume of nitrogen gas. The gas supplied here was changed to a gas containing superheated steam, hydrogen gas, and nitrogen gas in a volume ratio of 50:1:49 (represented in Table 1 as 1% H2-49% N2-50% superheated H2O). The temperature was raised to 550°C while flowing this mixed gas and maintained at that temperature for 1 hour. The temperature was then lowered to room temperature, yielding light blue powder B (first heat treatment step).

[0179] The X-ray powder diffraction pattern of this powder has broad diffraction lines, as shown in Figure 2, and is consistent with hexagonal Cs 0.32 The main phase is WO3, but the orthorhombic Cs4W 11 O 35 and pyrochlore phase (CsO) 0.44The diffraction lines of the W2O6 phase showed a pattern mixed with a different phase. The diffraction lines of this pyrochlore phase were broad and the reflection positions were slightly shifted. It is thought that O, OH, OH2, and OH3 derived from water were incorporated into the pyrochlore cavities. The (111) plane of the cubic pyrochlore phase is a plane with hexagonal symmetry similar to the basal plane of a hexagonal crystal, and the pyrochlore cavities correspond to the voids between the hexagonal and trigonal cavities in a hexagonal crystal. In other examples, small amounts of reflections from the pyrochlore phase were often observed mixed in the XRD powder patterns.

[0180] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction image was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0181] Chemical analysis of Powder B showed that Cs / W=0.32. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder B was used. The evaluation results are shown in Tables 3 and 4. [Example 3] (Production and evaluation of near-infrared absorbing particles) The light blue powder B obtained in Example 2 was spread on a carbon boat and held at 550°C for 2 hours in a 1% by volume H-Ar gas flow. Next, the gas supplied was changed to 100% by volume nitrogen gas, and the boat was held at 550°C for 0.5 hours while flowing nitrogen gas, then heated and held at 800°C for 1 hour. The boat was cooled to room temperature, and light blue powder C was obtained (second heat treatment step).

[0182] Chemical analysis of Powder C revealed that the Cs / W ratio was 0.31. The composition ratios of other components are shown in Table 2.

[0183] As shown in Figure 2, the X-ray powder diffraction pattern of Powder C has broader diffraction lines than those of Examples 1 and 2, and is a hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed with Cs4W. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0184] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder C was used. The evaluation results are shown in Tables 3 and 4. [Example 4] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat, heated in a 100% by volume Ar gas flow, and held at 800° C. for 1 hour. The temperature was then lowered to room temperature, and a pale blue powder D was obtained.

[0185] The X-ray powder diffraction pattern of Powder D has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0186] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0187] Chemical analysis of Powder D showed that Cs / W=0.33. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder D was used. The evaluation results are shown in Tables 3 and 4. [Example 5] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas supplied was changed to 1% by volume H-Ar, and the temperature was maintained at 800°C for 10 minutes in the gas flow. The temperature was then lowered to room temperature, and a pale blue powder E was obtained.

[0188] The X-ray powder diffraction pattern of Powder E has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0189] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0190] Chemical analysis of Powder E showed that Cs / W=0.32. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder E was used. The evaluation results are shown in Tables 3 and 4. [Example 6] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat and held at 500°C for 30 minutes in a 1% by volume H-Ar gas flow. Next, the gas supplied was changed to 100% by volume nitrogen gas, and the boat was held at 550°C for 30 minutes while flowing nitrogen gas. After that, the temperature was further increased to 800°C and held for 1 hour. The temperature was then lowered to room temperature, and pale blue powder F was obtained.

[0191] The X-ray powder diffraction pattern of Powder F has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0192] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0193] Chemical analysis of Powder F showed that Cs / W=0.31. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder F was used. The evaluation results are shown in Tables 3 and 4. [Example 7] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:10. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0194] The first heat treatment step was carried out under the same conditions as in Example 2, except that the cesium tungsten oxide precursor powder was used.

[0195] The powder obtained in the first heat treatment step was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas being supplied was changed to a 1% by volume H-Ar gas flow, and the temperature was maintained at 800°C for 10 minutes while the gas was being supplied. Then, the temperature was lowered to room temperature, and light blue powder G was obtained.

[0196] The X-ray powder diffraction pattern of powder G has broad diffraction lines, indicating that it is hexagonal Cs 0.20 WO3 (ICDD0-083-1333) and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0197] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism spot appearing in the electron diffraction pattern was short and accompanied by a weak streak, and the powder was identified as an orthorhombic crystal with the hexagonal crystals modulated by prismatic defects.

[0198] Chemical analysis of Powder G showed that Cs / W=0.20. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder G was used. The evaluation results are shown in Tables 3 and 4. [Example 8] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 3:10. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0199] The first heat treatment step was carried out under the same conditions as in Example 2, except that the cesium tungsten oxide precursor powder was used.

[0200] The powder obtained in the first heat treatment step was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas supplied was changed to 1% by volume H-Ar, and the temperature was maintained at 800°C for 10 minutes while the gas was flowing, and then the temperature was lowered to room temperature to obtain light blue powder H.

[0201] The X-ray powder diffraction pattern of Powder H has broad diffraction lines, indicating that it is a rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 is the main phase, and hexagonal Cs 0.32 WO3 and tetragonal Cs2W3O 10 The diffraction patterns showed a slight mixture of Cs6W. 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0202] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0203] Chemical analysis of Powder H showed that Cs / W=0.59. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder H was used. The evaluation results are shown in Tables 3 and 4. [Example 9] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 2:11. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0204] Then, the first heat treatment step was carried out under the same conditions as in Example 2, except that the above cesium tungsten oxide precursor powder was used, and a pale green powder I was obtained.

[0205] The X-ray powder diffraction pattern of Powder I has broad diffraction lines as shown in Figure 3, indicating the pyrochlore phase (CsO). 0.44 The main phase is W2O6, and the hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns showed a slight mixture of the (Cs2O) 0.44 W2O6 and Cs4W 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0206] Transmission electron microscopy of this powder revealed a cubic electron diffraction pattern.

[0207] Chemical analysis of Powder I showed that Cs / W=0.36. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except for using Powder I. The evaluation results are shown in Tables 3 and 4. [Example 10] (Production and evaluation of near-infrared absorbing particles) The powder I produced in Example 9 was spread on a carbon boat and heated to 800°C while flowing 100% by volume of Ar gas. Then, the gas being supplied was changed to 1% by volume of H-Ar, and the boat was kept at 800°C for 10 minutes while flowing this gas, and then cooled to room temperature to obtain a light blue powder J.

[0208] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0209] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0210] Chemical analysis of Powder J showed that Cs / W=0.36. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder J was used. The evaluation results are shown in Tables 3 and 4. [Example 11] (Production and evaluation of near-infrared absorbing particles) The powder I prepared in Example 9 was spread on a carbon boat and held in a 1% by volume H-Ar gas flow at 500°C for 30 minutes. Then, the gas being supplied was changed to 100% by volume nitrogen gas, and the boat was held at 800°C for 1 hour while the nitrogen gas was flowing, and then cooled to room temperature to obtain a light blue powder K.

[0211] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0212] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0213] Chemical analysis of the powdered K showed that Cs / W=0.35. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder K was used. The evaluation results are shown in Tables 3 and 4. [Example 12] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:5. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0214] The precursor powder was then placed on an alumina boat in a heating muffle furnace and heated to 150°C while flowing 100% by volume of nitrogen gas. The gas supplied here was changed to a gas containing superheated steam, hydrogen gas, and nitrogen gas in a volume ratio of 50:1:49, and the temperature was raised to 550°C while flowing this mixed gas and maintained at that temperature for 1 hour. The temperature was then lowered to room temperature, yielding a light blue powder L (first heat treatment step).

[0215] The X-ray powder diffraction pattern of Powder L has broad diffraction lines as shown in Figure 3, indicating the pyrochlore phase (CsO). 0.44 The main phase is W2O6, and the hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns showed a slight mixture of the (Cs2O) 0.44 W2O6 and Cs4W 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0216] Transmission electron microscopy of this powder revealed a cubic electron diffraction pattern.

[0217] Chemical analysis of Powder L showed that Cs / W=0.40. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing fibers) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder L was used. The evaluation results are shown in Tables 3 and 4. [Example 13] (Production and evaluation of near-infrared absorbing particles) The powder L prepared in Example 12 was spread on a carbon boat and heated to 800°C while flowing 100% by volume of Ar gas. Then, the gas being supplied was changed to 1% by volume of H-Ar, and the boat was kept at 800°C for 10 minutes while flowing this gas, and then cooled to room temperature to obtain a light blue powder M.

[0218] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0219] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0220] Chemical analysis of Powder M showed that Cs / W=0.42. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder M was used. The evaluation results are shown in Tables 3 and 4. [Example 14] The powder L prepared in Example 12 was spread on a carbon boat and held in a 1% by volume H-Ar gas flow at 500°C for 30 minutes. Then, the gas being supplied was changed to 100% by volume Ar, and the boat was held at 550°C for 30 minutes while the gas was being flowed. The temperature was then further increased to 800°C and held for 1 hour, and the temperature was then lowered to room temperature to obtain light blue powder N.

[0221] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0222] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0223] Chemical analysis of the powder N showed that Cs / W=0.42. The composition ratios of other components are shown in Table 2. (Near-infrared absorbing fibers, production and evaluation of textile products) A near-infrared absorbing particle dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product were obtained and evaluated in the same manner as in Example 1, except that Powder N was used. The evaluation results are shown in Tables 3 and 4. [Comparative Example 1] (Production and evaluation of near-infrared absorbing particles) The cesium tungsten oxide precursor powder obtained in Example 1 was placed in a carbon boat, heated to 850°C in a tubular furnace in the atmosphere, and held for 20 hours. The temperature was then lowered to room temperature, and the powder was crushed and mixed in a grinder. The powder was then heated again to 850°C in the atmosphere, held for 20 hours, and then lowered to room temperature, yielding a very slightly greenish white powder i. The X-ray powder diffraction pattern of this powder i, as shown in Figure 2, showed a slight CsW 11 O 36 There are some mixed in, but it's mostly Cs4W 11 O 35 It was identified as a single phase (ICDD 0-51-1891). Chemical analysis of powder i showed a Cs / W ratio of 0.36. The composition ratios of other components are shown in Table 2.

[0224] (Production and evaluation of near-infrared absorbing fibers) A near-infrared absorbing particle-dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product according to Comparative Example 1 were obtained and evaluated in the same manner as in Example 1, except that the white powder i obtained in Comparative Example 1 was used instead of the powder A according to Example 1. The evaluation results are shown in Tables 3 and 4. Comparative Example 2 The cesium tungsten oxide precursor powder obtained in Example 1 was placed in a carbon boat and held at 550°C for 2 hours under a 1% by volume H gas flow with N gas as a carrier. The flow was then changed to 100% by volume N gas and held for 1 hour. The temperature was then increased to 800°C and held for 1 hour, and the powder was slowly cooled to room temperature to obtain powder II. Powder II was dark blue in color. The X-ray powder diffraction pattern of this powder II, as shown in Figure 2, showed Cs 0.32 It was identified as a single phase WO3 (ICDD 0-81-1244), a hexagonal cesium tungsten oxide. Chemical analysis of powder II showed a Cs / W ratio of 0.34. The composition ratios of other components are shown in Table 2.

[0225] (Production and evaluation of near-infrared absorbing fibers) A near-infrared absorbing particle-dispersed powder, a masterbatch, a polyester multifilament yarn, and a knit product according to Comparative Example 2 were obtained and evaluated in the same manner as in Example 1, except that Powder ii obtained in Comparative Example 2 was used instead of Powder A according to Example 1. The evaluation results are shown in Tables 3 and 4.

[0226] [Table 1]

[0227] [Table 2]

[0228] [Table 3]

[0229] [Table 4] The XRD powder patterns of the powders prepared in Examples 1 to 7 all showed hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 However, the intensity ratio and position of the diffraction lines were observed to deviate from the ICDD data, which is thought to be due to the influence of irregular planar defects inserted on the prism surface. The (0001) electron diffraction pattern showed an increase in the interplanar spacing of one of the prism surface spots, confirming the modulation of the crystal structure to orthorhombic. In addition, the XRD powder patterns of the powders prepared in Examples 8 to 14 all showed hexagonal Cs 0.32 WO3 and rhombohedral Cs6W 11 O 36 , Cs 8.5 W 15 O 48 or pyrochlore phase (CsO) 0.44 Although the presence of W2O6 was observed, the diffraction line positions and intensity distributions of the rhombohedral and pyrochlore phases deviated from the ICDD data. The (0001) electron diffraction patterns showed changes in the interplanar spacing of all three prism surface spots, confirming the modulation of the crystal structure to rhombohedral. Furthermore, the powders identified as having a pyrochlore phase pattern by XRD also showed cubic electron diffraction patterns. This confirms that the cesium tungstates contained in the powders prepared in Examples 1 to 14 have a pseudohexagonal crystal structure.

[0230] The textile products using the near-infrared absorbing fibers produced in Examples 1 to 14, which contain near-infrared absorbing particles containing cesium tungstate that satisfy the predetermined composition, all have a color tone of b * Ga b * ≧0, and it was confirmed that the blue color was very weak and the color tone was neutral.

[0231] In contrast to this, the near-infrared absorbing particles contained in the near-infrared absorbing fibers of Comparative Examples 1 and 2 do not contain cesium tungsten oxide that satisfies the predetermined composition.

[0232] The textile product using the near-infrared absorbing fiber produced in Comparative Example 1 exhibited a neutral color tone, but had a low solar absorptance of 12.4%. It was also confirmed that the temperature rise on the back surface of the textile product of Comparative Example 1 when irradiated with light from a solar-like spectrum lamp shown in Table 4 was lower than in Examples 1 to 14. This is thought to be because the near-infrared absorbing particles contained in the near-infrared absorbing fiber used in Comparative Example 1 had a low solar absorptance.

[0233] In addition, the textile product using the near-infrared absorbing fiber produced in Comparative Example 2 had a color tone of b * Ga b * <0, and it can be seen that the blue tinge is clearly recognized. In other words, it was confirmed that the color does not become neutral. [Explanation of symbols]

[0234] 10 Ternary Composition Diagram 11, 16 areas 12~15 straight line 40 Fine particles 41 Arrow 50, 62 Near-infrared absorbing particles 50A surface 51 Covering 60 Near-infrared absorbing fiber 61 Fiber 61A surface 61B Internal CA center axis

Claims

1. Fiber and and near-infrared absorbing particles disposed at one or more locations selected from the surface and the interior of the fiber, the near-infrared absorbing particles contain cesium tungstate, The cesium tungstate has a pseudo-hexagonal crystal structure that is modulated to one or more types selected from orthorhombic, rhombohedral, and cubic crystals, and contains one or more types of additive components selected from O, OH, OH 2 , and OH 3 ; The cesium tungstate has the general formula Cs ｘ W ｙ O ｚ In the ternary composition diagram with Cs, W, and O at the vertices, x = 0.6y, z = 2.5y, y = 5x, and Cs ２ O:W.O. ３ = m:n (m and n are integers) are near-infrared absorbing fibers having a composition within the region surrounded by four straight lines.

2. The additive component is WO of the cesium tungstate crystal. ６ 2. The near-infrared absorbing fiber according to claim 1, wherein the octahedron is present at one or more positions selected from a hexagonal window, a hexagonal cavity, and a trigonal cavity.

3. The cesium tungstate crystal has a partial deficiency in one or more elements selected from Cs and W, The general formula Cs ｘ W ｙ O ｚ 3. The near-infrared absorbing fiber according to claim 1, wherein x and y satisfy the relationship 0.2≦x / y≦0.

6.

4. WO constituting the cesium tungstate crystal ６ The near-infrared absorbing fiber according to claim 1 , wherein a part of the O in the octahedron is deficient.

5. 5. The near-infrared absorbing fiber according to claim 1, wherein a portion of Cs in the cesium tungstate is substituted with an additional element, and the additional element is one or more elements selected from the group consisting of Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

6. 6. The near-infrared absorbing fiber according to claim 1, wherein the near-infrared absorbing particles have an average particle size of 0.1 nm or more and 200 nm or less.

7. 7. The near-infrared absorbing fiber according to claim 1, wherein the surface of the near-infrared absorbing particle is coated with a compound containing one or more types of atoms selected from Si, Ti, Zr, Al, and Zn.

8. 8. The near-infrared absorbing fiber according to claim 1, wherein the content of the near-infrared absorbing particles is 0.001% by mass or more and 80% by mass or less with respect to the solid content of the fiber.

9. It also contains particles of far-infrared emitting material, the particles of the far-infrared emitting material are disposed at one or more locations selected from the surface and the interior of the fiber; 9. The near-infrared absorbing fiber according to claim 1, wherein the content of the particles of the far-infrared emitting substance is 0.001% by mass or more and 80% by mass or less based on the solid content of the fiber.

10. 10. The near-infrared absorbing fiber according to any one of claims 1 to 9, wherein the fiber is any fiber selected from a fiber group consisting of synthetic fibers, semi-synthetic fibers, natural fibers, regenerated fibers, and inorganic fibers; a blended yarn containing one or more types of fibers selected from the fiber group; a doubled yarn containing one or more types of fibers selected from the fiber group; or a mixed yarn containing one or more types of fibers selected from the fiber group.

11. 11. The near-infrared absorbing fiber according to claim 10, wherein the synthetic fiber is at least one type selected from the group consisting of polyurethane fibers, polyamide fibers, acrylic fibers, polyester fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinylidene chloride fibers, polyvinyl chloride fibers, and polyether ester fibers.

12. 12. The near-infrared absorbing fiber according to claim 10, wherein the semi-synthetic fiber is at least one selected from the group consisting of cellulose-based fiber, protein-based fiber, chlorinated rubber, and hydrochloric rubber.

13. 13. The near-infrared absorbing fiber according to claim 10, wherein the natural fiber is at least one type selected from the group consisting of plant fiber, animal fiber, and mineral fiber.

14. 14. The near-infrared absorbing fiber according to claim 10, wherein the regenerated fiber is one or more fibers selected from the group consisting of cellulose-based fibers, protein-based fibers, alginate fibers, rubber fibers, chitin fibers, and mannan fibers.

15. 15. The near-infrared absorbing fiber according to claim 10, wherein the inorganic fiber is at least one type selected from the group consisting of metal fiber, carbon fiber, and silicate fiber.

16. A textile product comprising the near-infrared absorbing fiber according to any one of claims 1 to 15.

17. a disposing step of disposing near-infrared absorbing particles at one or more locations selected from the surface and the interior of the fiber, the near-infrared absorbing particles contain cesium tungstate, The cesium tungstate has a pseudo-hexagonal crystal structure that is modulated to one or more types selected from orthorhombic, rhombohedral, and cubic crystals, and contains one or more types of additive components selected from O, OH, OH 2 , and OH 3 ; The cesium tungstate has the general formula Cs ｘ W ｙ O ｚ In the ternary composition diagram with Cs, W, and O at the vertices, x = 0.6y, z = 2.5y, y = 5x, and Cs ２ O:W.O. ３ A method for producing a near-infrared absorbing fiber having a composition within a region surrounded by four straight lines of m:n (m and n are integers).

Images