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

Abstract

To provide near-infrared absorbing fiber which comprises near-infrared absorbing particles containing composite tungsten oxide and can have a more neutral color tone.SOLUTION: The near-infrared absorbing fiber comprises fiber and near-infrared absorbing particles, where the near-infrared absorbing particles contain cesium tungsten oxide having an orthorhombic or hexagonal crystal structure and represented by general formula CsxW1-yO3-z (0.2≤x≤0.4, 0<y≤0.4, 0<z≤0.46).SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Various cold-proof clothing, interiors, and leisure goods with enhanced heat retention effects have been devised and put into practical use. There are roughly two methods for enhancing the heat retention effect.

[0003] The first method is, for example, in cold-proof clothing, controlling the knitting structure, making the fibers used hollow or porous, etc., to physically increase the air layer in the cold-proof clothing, reducing the heat dissipation from the human body, and maintaining the heat retention.

[0004] The second method is, for example, in cold-proof clothing, subjecting the entire clothing or the fibers constituting the cold-proof clothing to chemical and physical processing to radiate the heat generated from the human body back to the human body again, or actively converting part of the sunlight received by the cold-proof clothing into heat, etc., to store heat and improve the heat retention.

[0005] As the first method described above, methods such as increasing the air layer in the clothing, thickening the fabric, making the weave finer, or darkening the color have been adopted. For example, clothing used in winter such as sweaters falls into the category of clothing using the first method. Also, for example, in clothing often used for winter sports clothing, batting is placed between the outer fabric and the inner fabric, and the heat retention is maintained by the thickness of the air layer of the batting. However, when batting is added, the clothing becomes heavy and bulky, causing problems in sports that require ease of movement. To solve these problems, in recent years, methods of actively and effectively using the heat generated inside or the heat from the outside, which is the second method described above, have begun to be adopted.

[0006] As one of the methods for implementing the second method, there is known a method of vapor-depositing a metal such as aluminum or titanium on the lining of clothing or the like, and reflecting the radiant heat emitted from the body by the metal vapor-deposited surface to actively prevent heat dissipation. However, these methods not only incur a considerable cost for vapor-depositing the metal on the clothing, but also result in a poor yield due to uneven vapor deposition and the like, ultimately leading to an increase in the price of the product itself.

[0007] Also, as another method for implementing the second method, there has been proposed a method of kneading ceramic particles such as alumina-based, zirconia-based, and magnesia-based into the fiber itself and utilizing the far-infrared radiation effect and the effect of converting light into heat that these ceramic particles possess, that is, a method of actively taking in external energy.

[0008] For example, Patent Document 1 describes a heat-ray radioactive fiber characterized by containing one or more kinds of inorganic fine particles having heat-ray radiation characteristics containing at least one kind of metal and metal ion having a thermal conductivity of 0.3 Kcal / m 2 ·sec·°C or more. Examples of the inorganic fine particles having heat-ray radiation characteristics include silica or barium sulfate.

[0009] Patent Document 2 describes a composite fiber composed of 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 crystallization temperature upon cooling of 40°C or lower, and a heat of crystallization of 10 mJ / mg or more, containing 0.1 to 20% by weight of ceramic fine particles having far-infrared radiation ability with respect to the fiber weight, and characterized in that the polymer A covers the fiber surface.

[0010] Patent Document 3 describes an infrared absorption processed fiber product obtained by dispersing and fixing a binder resin containing an infrared absorber composed of at least one kind of amino compound represented by a predetermined general formula on a fiber product.

[0011] Patent Document 4 describes a method for near-infrared absorption processing of a cellulose fiber structure in which a dye selected from direct dyes, reactive dyes, naphthol dyes, and vat dyes and having the property that its absorption in the near-infrared region is greater than that of black dyes is combined with another dye for dyeing, such that the spectral reflectance of the fabric within the range of 750 to 1500 nm is 65% or less as the degree of near-infrared absorption.

[0012] In Patent Documents 5 to 7, the applicant of the present application selected tungsten oxide fine particles and / or composite tungsten oxide fine particles as materials that have a high visible light transmittance and a low absorption rate, yet have a low transmittance and a high absorption rate for light in the near-infrared region, and proposed fibers containing these fine particles as near-infrared absorption components, and fiber products formed by processing such fibers. Despite being light in color, the above-mentioned fibers and fiber products absorb near-infrared rays of sunlight and convert them into heat, have moisture retention properties, and are highly designable such that they can be colored into various colors by adding other pigments.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Non-Patent Documents

[0014]

Non-Patent Document 1

Non-Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0015] Among them, the tungsten oxide fine particles or composite tungsten oxide fine particles disclosed in Patent Documents 5 to 7 are materials with a high transmittance and a low absorption rate of visible light, but a low transmittance and a high absorption rate of light in the near-infrared region. Therefore, fibers containing composite tungsten oxide fine particles and the like are particularly promising fibers for applications such as cold-proof clothing.

[0016] However, since the above composite tungsten oxide fine particles etc. preferentially absorb light with a long wavelength among visible light, that is, red light, they are accompanied by blue coloring, and the degree of blue becomes stronger as the addition amount of the fine particles increases. As a result, fibers containing composite tungsten oxide fine particles etc. as a near-infrared absorption component, and fiber products obtained by processing such fibers, are accompanied by blue coloring, and it has been difficult in some cases to color them with yellow-based or light colors other than blue, which are complementary colors of blue, by adding other pigments. Therefore, there has been a demand for fibers that contain a composite tungsten oxide excellent in near-infrared absorption characteristics and can have a more neutral color tone that can be colored with complementary colors or light colors.

[0017] Therefore, in one aspect of the present invention, an object is to provide a near-infrared absorption fiber that contains near-infrared absorption particles containing a composite tungsten oxide and can have a more neutral color tone.

Means for Solving the Problems

[0018] In one aspect of the present invention, there are provided a fiber and near-infrared absorption particles, and the near-infrared absorption particles contain cesium tungsten oxide represented by the general formula Cs x W 1-y O 3-z (0.2 ≦ x ≦ 0.4, 0 < y ≦ 0.4, 0 < z ≦ 0.46) and having an orthorhombic or hexagonal crystal structure. and the cesium tungsten oxide has linear or planar defects on one or more surfaces selected from the orthorhombic (010) plane, the {100} plane which is the prism plane of the hexagonal crystal, and the (001) plane which is the bottom plane of the hexagonal crystal A near-infrared absorption fiber is provided.

Effects of the Invention

[0019] In one aspect of the present invention, it is possible to provide a near-infrared absorption fiber that contains near-infrared absorption particles containing a composite tungsten oxide and can have a more neutral color tone.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0001] HEX zone axis of the pseudo-hexagonal crystal particles of powder A obtained in Experimental Example 1-1.

Figure 6

[0221] zone axis of the pseudo-hexagonal crystal particles of powder A obtained in Experimental Example 1-1.

Figure 7

[0001] HEX zone axis of the pseudo-hexagonal crystal particles of powder B obtained in Experimental Example 1-2.

Figure 8

[0001] HEX zone axis of the pseudo-hexagonal crystal particles of powder C obtained in Experimental Example 1-3. [Embodiments for Carrying Out the Invention]

[0021] 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] Regarding the near-infrared absorbing fiber of the present embodiment, [1] near-infrared absorbing particles and a method for producing near-infrared absorbing particles, [2] a near-infrared absorbing particle dispersion liquid, [3] a near-infrared absorbing fiber, and [4] a method for producing a near-infrared absorbing fiber will be described in this order. [1] Near-Infrared Absorbing Particles and a Method for Producing Near-Infrared Absorbing Particles (Near-Infrared Absorbing Particles) Conventionally, the transmitted color of cesium-added hexagonal tungsten bronze particles used as near-infrared absorbing particles is defined by the imaginary part of its dielectric function (ε2) (the ε2 obtained in the experiment is published in Non-Patent Document 1) and the band structure (Non-Patent Document 2).

[0022] In the energy region of visible light (1.6 eV to 3.3 eV), cesium-added hexagonal tungsten bronze (hereinafter abbreviated as Cs-HTB) has a sufficiently large band gap. In addition, since electron transitions between the d-d orbitals of tungsten are prohibited by Fermi's golden rule, the probability of electron transition becomes small, and ε2 takes a small value. Since ε2 represents the absorption of photons by electrons, visible light permeability occurs if ε2 is small at visible wavelengths. However, in the vicinity of the blue wavelength, which has the shortest wavelength in the visible light region, there is absorption due to interband transitions, and in the vicinity of the red wavelength, which has the longest wavelength, there are localized surface plasmon resonance (LSPR) absorption and polaronic electron transition absorption (Non-Patent Document 3). Therefore, each is subject to restrictions on light permeability.

[0023] As described above, in Cs-HTB, the band gap is sufficiently large, so interband transitions are above the energy of blue-wavelength light, and the blue permeability increases. Conversely, on the red-wavelength side, Cs-HTB has many conduction electrons, so LSPR absorption and polaronic absorption become stronger, and at the same time, since the absorption wavelength approaches the red-wavelength side, the permeability decreases. Therefore, the transmitted color of a Cs-HTB particle dispersion film or the like appears blue.

[0024] That is, in order to neutralize the blue transmitted color of Cs-HTB, it is sufficient to enhance the absorption on the blue side and the transmission on the red side. For this purpose, it is preferable to shift the absorption position of interband transitions to lower energy and weaken the LSPR absorption and polaronic absorption and shift them to the lower energy side.

[0025] In order to weaken the LSPR absorption and polaronic absorption, it is effective to reduce the amount of free electrons and bound electrons contained in the material.

[0026] The above-described increase in blue-side absorption is achieved by using materials with different energy band structures having a low-energy bandgap. Further, the red-side transmittance can be controlled by adjusting the amounts of cesium ions (Cs + ) and oxygen vacancies (V O ) which are sources of free electrons and bound electrons.

[0027] Based on the above considerations, the inventors of the present invention have conducted various studies on cesium tungstate, which is an oxide containing cesium (Cs) and tungsten (W). As a result, when near-infrared absorbing particles containing cesium tungstate obtained by reducing the crystal powder of a cesium tungstate precursor nCs2O·mWO3 (n and m are integers, 3.6 ≦ m / n ≦ 9.0) containing Cs and W are used, it has been found that the color tone of a near-infrared absorbing particle dispersion such as a dispersed transmission film or a near-infrared absorbing particle dispersion liquid decreases in blue and becomes neutralized. Further, it has been found that near-infrared absorbing fibers containing such near-infrared absorbing particles can also have a more neutral color tone.

[0028] The above near-infrared absorbing particles start from a compound having a bandgap narrower than that of hexagonal Cs-HTB and lower blue permeability, and by reducing this, V O is gradually increased, and the LSPR absorption and the polarronic absorption are gradually increased within an allowable range to optimize the red transmittance, thereby neutralizing the color tone.

[0029] In the above cesium tungstate precursor nCs2O·mWO3 containing Cs, the charges of Cs and W, which are positive elements, are neutralized by O and it is a non-conductor. In compounds lined up on the WO3-Cs2O line such as Cs2W7O 22 , Cs6W 20 O 63 , Cs2W6O 19 , Cs4W 11 O 35 , Cs6W 11 O 36 , Cs2W3O 10 , since the valences are balanced, the Fermi energy EF It exists between the valence band and the conduction band and is a non-conductor. When the Cs / W ratio (molar ratio) is 0.2 or more, in order to incorporate Cs with a large ionic radius, the basic framework formed by W-O octahedra has a hexagonal symmetry structure with large hexagonal voids, or a planar defect containing W deficiency (tungsten deficiency) enters the atomic arrangement of hexagonal or cubic crystals (pyrochlore structure) with large hexagonal voids, resulting in a crystal structure with reduced symmetry to orthorhombic or monoclinic.

[0030] For example, in 2Cs2O·11WO3, in the model of Solodovnikov1998 (Non-Patent Document 4), a plane with W and O deficiencies at a pitch of b / 8 of the orthorhombic unit cell is inserted into the hexagonal arrangement of W-O octahedra similar to hexagonal tungsten bronzes on the hexagonal (110) plane (= orthorhombic (010) plane), and the overall structure is orthorhombic. In these cesium tungsten oxide precursors nCs2O·mWO3 (n and m are integers, 3.6 ≦ m / n ≦ 9.0), the band gap is narrower than that of Cs-HTB, and therefore the blue transmittance is low. However, when this is heated and reduced, the whole gradually changes to the hexagonal crystal structure of tungsten bronzes. During this process, the band structure changes, the band gap widens, and the absorption of blue becomes weaker, so it was found that the blue transmittance increases. In addition, at this time, as the reduction progresses, electrons are gradually injected into the conduction band to become a conductor, and the band gap gradually widens due to the Burstein-Moss effect, so the blue transmittance becomes even stronger.

[0031] When the orthorhombic crystal becomes hexagonal by heating and reduction, the planar defect containing W deficiency in the orthorhombic crystal gradually disappears, and the hexagonal crystal framework of W-O octahedra is formed. The planar defect containing W deficiency exists on the (010) ORTH plane, and this plane is inherited by the hexagonal prism plane {100} HEX , that is, [(100) HEX ,(010) HEX ,(110) HEX , so it gradually becomes a hexagonal crystal with defects on the {100} HEX plane with heating and reduction. The hexagonal crystal at this time is {100} HEXIt deviates from perfect hexagonal symmetry due to defects on the surface and can be said to be in a pseudo-hexagonal crystal state. Along with such heat reduction, the crystal structure changes from orthorhombic to pseudo-hexagonal and further to hexagonal. At this time, it contains W defects included in the orthorhombic (010) ORTH The surface defects of the plane are inherited by the surface defects of the {100} HEX plane and gradually decrease, and are finally considered to disappear.

[0032] Along with the change in the crystal structure during heat reduction, the electronic structure also changes. The disappearance of W defects brings a large amount of electron injection into the material. In the orthorhombic crystal, the outer shell electrons of Cs are consumed for the neutralization of O and the overall charge is neutral. However, when the W defects decrease and it becomes pseudo-hexagonal, six outer shell electrons per W atom are consumed for the neutralization of O, so the outer shell electrons of Cs enter the W-5d orbit at the lower part of the conduction band and become free electrons. These free electrons bring about the absorption of near-infrared light due to LSPR absorption. On the other hand, heat reduction simultaneously has the effect of generating V O . The generation of V O proceeds at random sites. When V O occurs, the two adjacent W atoms become charge-excessive, and localized electrons bound to W 5+ are generated (Non-Patent Document 2). These localized electrons transition to the vacancies at the upper part of the conduction band and bring about polarronic absorption, but a part of them is excited to the free electron orbit and brings about LSPR absorption (Non-Patent Document 3). Since the absorption by these free electrons and bound electrons both has a peak wavelength in the near-infrared range, the tail of the absorption extends to the red wavelength, thus reducing the red transmittance. The greater the amount of free electrons and bound electrons, that is, the greater the degree of reduction, the higher the wavelength shift of the LSPR absorption and polarronic absorption wavelengths, and the greater the absorption amount, so the red transmittance decreases.

[0033] Therefore, by reducing the crystal powder of cesium tungstate precursor nCs2O·mWO3 (n, m are integers, 3.6 ≦ m / n ≦ 9.0) and adjusting the degree of reduction at that time, the blue transmission color can be neutralized.

[0034] The near-infrared absorbing particles of the present embodiment described above can be produced by heating a crystal powder of a cesium tungstate precursor nCs2O·mWO3 containing Cs and W in a reducing atmosphere at 650°C or higher and 950°C or lower. In the formula of the cesium tungstate, n and m are integers, and it is preferable to satisfy 3.6 ≦ m / n ≦ 9.0.

[0035] That is, as the near-infrared absorbing particles, crystal powder of a cesium tungstate precursor nCs2O·mWO3 (n, m are integers, 3.6 ≦ m / n ≦ 9.0) containing cesium and tungsten can be used, which are obtained by heating and reducing in an atmosphere of a reducing gas at 650°C or higher and 950°C or lower.

[0036] In order for all or part of them to become hexagonal tungsten bronze by heating and reduction, the value of m / n needs to be in the range of 3.6 ≦ m / n ≦ 9.0 as described above. If it is less than 3.6, a cubic pyrochlore phase will be formed after heating and reduction, with strong coloring and no near-infrared absorption. If it is greater than 9.0, phase separation into hexagonal tungsten bronze and tungsten trioxide will occur after heating and reduction, and the near-infrared absorption effect will be significantly reduced. The cesium tungstate precursor is more preferably Cs4W 11 O 35 That is, as the near-infrared absorbing particles, it is more preferable to use particles obtained by heating and reducing a cesium tungstate precursor containing a Cs4W 11 O 35 phase as the main phase in an atmosphere of a reducing gas at 650°C or higher and 950°C or lower. By using near-infrared absorbing particles obtained by high-temperature reduction of Cs4W 11 O 35 , when the near-infrared absorbing particles are dispersed, a large near-infrared absorption effect can be obtained while having a transmitted color with suppressed blueness. Here, the main phase means the phase containing the most in terms of mass ratio.

[0037] When reducing cesium tungstate oxide as described above, the heating temperature is preferably 650°C or higher and 950°C or lower. By setting the temperature to 650°C or higher, the structural change from orthorhombic to hexagonal can proceed sufficiently, enhancing the near-infrared absorption effect. Also, by setting the temperature to 950°C or lower, the speed of the crystal structure change can be appropriately maintained, and it can be easily controlled to an appropriate crystal state and electronic state. Note that if the heating temperature is higher than 950°C and the reduction proceeds too far, lower oxides such as W metal and WO2 may be generated, which is also not preferable from this perspective.

[0038] And the near-infrared absorbing particles of this embodiment are represented by the general formula Cs x W 1-y O 3-z (0.2 ≤ x ≤ 0.4, 0 < y ≤ 0.4, 0 < z ≤ 0.46) and can contain cesium tungstate oxide having an orthorhombic or hexagonal crystal structure. Note that the near-infrared absorbing particles can also contain cesium tungstate oxide having an orthorhombic crystal structure and cesium tungstate oxide having a hexagonal crystal structure simultaneously.

[0039] When the cesium tungstate oxide contained in the near-infrared absorbing particles satisfies the above general formula, the degree of W deficiency and oxygen vacancies V o is in an appropriate range. When dispersed to form a near-infrared absorbing particle dispersion, near-infrared absorbing fiber, etc., while suppressing the solar transmittance, the transmitted color can be made a more neutral color tone.

[0040] Note that the near-infrared absorbing particles can also be composed of the above complex tungstate oxide. However, even in this case, it does not exclude containing unavoidable impurities mixed in during the manufacturing process and the like.

[0041] Conventionally known tungsten bronzes for near-infrared absorption have a hexagonal crystal structure. On the other hand, the complex tungstate oxide possessed by the near-infrared absorbing particles of this embodiment can have an orthorhombic or hexagonal crystal structure. Here, the hexagonal crystal includes pseudo-hexagonal crystals.

[0042] Cesium tungstate, which is a composite tungstate containing near-infrared absorbing particles, preferably has linear or planar defects on one or more surfaces selected from the orthorhombic (010) plane, the {100} plane which is the prism plane of the hexagonal crystal, and the (001) plane which is the bottom plane of the hexagonal crystal. The above-mentioned defects include stacking irregularities based on the displacement between planes, and disorders in the arrangement and atomic positions of Cs atoms and W atoms within the plane. Therefore, the electron diffraction spots often have streaks. The {100} plane which is the prism plane of the above-mentioned hexagonal crystal means the (100) plane, the (010) plane, and the (110) plane. Such defects in the composite tungstate, that is, lattice defects, are accompanied by at least W deficiency, specifically, partial deficiency of W. This W deficiency causes the lack of electrons in the crystal, and as described above, this is one of the essential causes and acts on the neutralization of the blue tone.

[0043] Cesium tungstate has defects, and such defects can include tungsten deficiency as described above.

[0044] In addition, some of the O in the W-O octahedron, that is, the WO6 octahedron, which constitutes the orthorhombic or hexagonal crystal that is the basic structure of cesium tungstate, can also have further deficiencies. Such defects can be random defects. The vacancy V of this octahedral oxygen O can be randomly introduced as described above, and in the known hexagonal tungsten bronze Cs 0.32 WO 3―y it is known that y = 0.46 or up to 15% of the total O lattice points (Non-Patent Document 5). The general formula Cs x W 1―y O 3―z representing cesium tungstate containing near-infrared absorbing particles in this embodiment can contain V O in an amount of up to z = 0.46. That is, z can be 0.46 or less.

[0045] The lattice constant of cesium tungsten oxide corresponds to the amount of defects, composition, and crystallinity in the crystal lattice. Although variations in the value of the a-axis are observed with respect to these variables, the value of the c-axis corresponds relatively well to the amount of lattice defects or optical properties. As a result, it is preferable that the cesium tungsten oxide contained in the near-infrared absorbing particles of the present embodiment has a c-axis length in hexagonal conversion of 7.560 Å or more and 7.750 Å or less. By setting the c-axis length in hexagonal conversion of cesium tungsten oxide within the above range, the near-infrared absorption effect can be sufficiently enhanced, and the visible light transmittance can be particularly enhanced. Note that when cesium tungsten oxide is hexagonal, conversion is not necessary, and the c-axis length in the hexagonal crystal becomes the c-axis length in the above hexagonal conversion.

[0046] When the diffraction pattern of a sample of the cesium tungsten oxide contained in the near-infrared absorbing particles of the present embodiment is measured by the X-ray powder diffraction method, it is often identified as a mixed phase of orthorhombic and hexagonal crystals. For example, when reducing the raw material of Cs4W 11 O 35 , it is identified as a mixed phase of orthorhombic Cs4W 11 O 35 and hexagonal Cs 0.32 WO3. In this case, the lattice constants of each phase can be obtained by Rietveld analysis or the like, and these can be converted into values in hexagonal conversion. As already explained, orthorhombic crystals are hexagonal crystals with lattice defect planes, so the lattice constants of orthorhombic crystals can be converted into the lattice constants of hexagonal crystals using an appropriate lattice correspondence model. Assuming the correspondence of lattice changes between orthorhombic and hexagonal crystals to be the model of Solodovnikov 1998 (Non-Patent Document 4), from the geometric relationship with respect to this model, 4a orth 2 +b orth 2 =64a hex 2 = 64b hex 2 , c orth =c hex relationships are extracted, so all lattice constants in hexagonal conversion can be obtained using these equations. Note that a orth , b orth , c orthmeans the lengths of the a-axis, b-axis, and c-axis of the orthorhombic crystal. Also, a hex , b hex , c hex means the lengths of the a-axis, b-axis, and c-axis of the hexagonal crystal.

[0047] In the cesium tungstate contained in the near-infrared absorbing particles of this embodiment, part of Cs may be substituted with an additive element. In this case, it is preferable that the additive element is one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0048] The above additive element has electron-donating properties and assists in donating electrons to the conduction band of the W-O octahedral skeleton at the Cs site.

[0049] 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, the localized surface plasmon resonance is more significantly manifested, so the near-infrared absorption characteristics can be particularly enhanced, that is, the solar transmittance can be particularly suppressed. Also, by setting the average particle size of the near-infrared absorbing particles to 0.1 nm or more, it can be easily manufactured industrially. Also, the particle size is closely related to the color of a near-infrared absorbing particle dispersion or the like, which is a dispersion transmission film in which near-infrared absorbing particles are dispersed. In the particle size range where Mie scattering is dominant, the shorter the wavelength in the visible light region, the less the scattering as the particle size decreases. Therefore, increasing the particle size has the effect of particularly suppressing the blue color tone, but when it exceeds 100 nm, the haze of the film due to light scattering becomes too large to be ignored, and when it exceeds 200 nm, in addition to the increase in the haze of the film, the generation of surface plasmons is suppressed and the LSPR absorption may become excessively small.

[0050] Here, the average particle size of the near-infrared absorbing particles can be known from the average value of the particle sizes of a plurality of near-infrared absorbing particles measured from a transmission electron microscope image, or from the dispersed particle size measured by a particle size measuring device based on the dynamic light scattering method of the dispersion liquid.

[0051] In addition, when applying particularly to applications that emphasize transparency in the visible light region, for example, when it is required to particularly suppress the influence on the color tone of near-infrared absorbing fibers, etc., it is preferable to further consider reducing scattering by the near-infrared absorbing particles. When emphasizing such scattering reduction, the average particle size of the near-infrared absorbing particles is particularly preferably 30 nm or less.

[0052] Also, the near-infrared absorbing particles can be surface-treated for purposes such as surface protection, durability improvement, antioxidant property, and water resistance improvement. The specific content of the surface treatment is not particularly limited. For example, the near-infrared absorbing particles of this embodiment can have the surface of the near-infrared absorbing particles coated with a compound containing one or more kinds of atoms selected from Si, Ti, Zr, Al, and Zn. At this time, examples of the compound containing one or more kinds of atoms (elements) selected from Si, Ti, Zr, Al, and Zn include one or more selected from oxides, nitrides, carbides, etc.

[0053] Here, the band structures of cesium tungstate and the cesium tungstate precursor will be described.

[0054] As described above, it has been shown that when nCs2O·mWO3 (n and m are integers, 3.6 ≤ m / n ≤ 9.0) is reduced at a high temperature, a solar radiation shielding material with a transmission color closer to neutral can be obtained. During high-temperature reduction, hexagon crystallization including the disappearance of W deficiency and the generation of V O inject electrons into the conduction band, which is considered to be the source of near-infrared absorption manifestation. Such changes in the electronic structure are verified by first-principles calculations.

[0055] Figure 1(a) shows the crystal structure of Cs4W 11 O 35 Also, Figure 1(b) shows Cs 0.33 WO3, which is Cs4W 12 O 36shows the crystal structure. In FIGS. 1(a) and 1(b), cesium 11 and oxygen 12 are shown. Note that the same type of atoms are hatched the same. Since tungsten is arranged in the octahedron formed by oxygen 12, it is not shown in FIGS. 1(a) and 1(b). FIG. 1(b) is the structure of Cs 0.33 WO3 with the axes re-oriented in orthorhombic form for comparison with Cs4W in FIG. 1(a). 11 O 35

[0056] The structure of Cs4W in FIG. 1(a) 11 O 35 is a structure in which W and O are regularly missing in the crystal structure of Cs4W in FIG. 1(b). 12 O 36

[0057] The band structures of the cesium tungsten oxides with the crystal structures shown in FIGS. 1(a) and 1(b) are shown in FIGS. 2(a) and 2(b), respectively. Also, based on Cs4W in FIG. 1(b) 12 O 36 , the band structures of Cs4W 11 O 36 with one W missing, and Cs6W 17 O 54 with one W missing and the cell enlarged 1.5 times in the b-axis direction are shown in FIGS. 2(c) and 2(d), respectively.

[0058] The band structures of Cs4W shown in FIGS. 2(a) and 2(b) 11 O 35 , and Cs4W 12 O 36 are similar, but the position of the Fermi energy (E F ) is within the band gap in the former and at the lower part of the conduction band in the latter. Therefore, Cs4W 11 O 35 is an insulator, and Cs4W 12 O 36 is a conductor. In Cs4W 11 O 35 , Cs4W 12 O 36 ​​When viewed with reference to [something], there is a shortage of one each of W and O in the unit cell. When W and O are sufficient, Cs4W 12 O 36 forms a hexagonal WO3 network, and it is interpreted that Cs electrons are injected into its W-5d orbitals to become a conductor (Non-Patent Document 6).

[0059] Cs4W in Fig. 2(c) 11 O 36 is a structure in which one W is reduced from Cs4W in Fig. 2(b) 12 O 36 .

[0060] Cs6W in Fig. 2(d) 17 O 54 , that is, 3Cs2O·17WO3, is a structure in which one W is reduced while maintaining charge neutrality when viewed from Cs4W in Fig. 2(b) 12 O 36 , that is, Cs6W 18 O 54 .

[0061] The amount of W deficiency decreases in the order of Fig. 2(a), Fig. 2(d), and Fig. 2(b), but E F rises successively toward the bottom of the conduction band, which supports that W electrons are injected into the W-5d orbitals, increasing the conduction electrons and enhancing the near-infrared absorption Cs4W 12 O 36 When O is deficient from [Cs4W], detailed calculation examples have already been reported, and it has been found that localized orbitals are introduced at the bottom of the conduction band and both free electrons and localized electrons increase significantly (Non-Patent Document 2).

[0062] In the experimentally obtained pseudo-hexagonal crystal (an intermediate structure in the phase transition between orthorhombic and hexagonal crystals), an electronic state in which the above elements are mixed is considered. That is, upon reduction, with the disappearance of W deficiency and the formation of V O , electrons are gradually injected into the conduction band, and the Fermi energy E F rises from the band gap to the lower part of the conduction band.

[0063] Based on these band structures, the results of calculating the dielectric function including the Drude term are shown in Fig. 3. Focusing on the position of ε1 = 0 of the dielectric function ε1 shown in Fig. 3(b), the screened plasma frequency (Ω SP ) is found to increase in the order of Cs4W 11 O 35 , Cs6W 17 O 54 , Cs4W 12 O 36 , Cs4W 12 O 35 . It is expected that the near-infrared absorption will increase in this order, and this tendency is consistent with the observation results.

[0064] From the dielectric function ε2 plot shown in Fig. 3(a), it can be seen that ε2 in the visible region is generally small for cesium tungstate oxide. At 3.3 eV in the blue region indicated by the dotted line 31, the absorption of Cs4W 11 O 35 and Cs6W 17 O 54 with a narrow band gap is large due to interband transitions. On the other hand, at 1.6 eV in the red region indicated by the dotted line 32, the absorption of Cs4W 12 O 35 is large due to being affected by the tail of surface plasmon absorption. It is expected that the transmitted light in the red region will decrease in the order of decreasing Ω SP . Compared with the conventionally used cesium tungstate oxide, the reason for the decrease in blue in the cesium tungstate oxide contained in the near-infrared absorption particles suitable for use in the near-infrared absorption fibers of this embodiment is that Cs 0.33 W 1-y O 3―z phase containing W deficiency is formed by using nCs2O·mWO3 (3.6 ≤ m / n ≤ 9.0) with W and O deficiencies as a raw material, resulting in an increase in absorption on the high-energy side. By adjusting the high-temperature reduction of nCs2O·mWO3 (3.6 ≤ m / n ≤ 9.0), the band gap and the amount of conduction band injected electrons can be adjusted, and the bluish color tone can be adjusted. It was also confirmed that the near-infrared absorption effect at that time was maintained at a relatively high level. (Method for manufacturing near-infrared absorption particles) The production method of the near-infrared absorbing particles of the present embodiment is not particularly limited, and any method can be used as long as it can produce near-infrared absorbing particles that satisfy the above-described characteristics. Here, a configuration example of the production method of the near-infrared absorbing particles will be described.

[0065] The production method of the near-infrared absorbing particles of the present embodiment can include, for example, the following steps.

[0066] A cesium tungstate oxide precursor synthesis step of synthesizing a cesium tungstate oxide precursor which is a tungstate containing cesium. A heat reduction step of heating and reducing the cesium tungstate oxide precursor at 650°C or higher and 950°C or lower in an atmosphere of a reducing gas.

[0067] Hereinafter, each step will be described. (1) Cesium tungstate oxide precursor synthesis step In the cesium tungstate oxide precursor synthesis step, a tungstate containing cesium, that is, a cesium tungstate oxide precursor which is a cesium tungstate can be synthesized. When the cesium tungstate oxide precursor has already been synthesized, the production method of the near-infrared absorbing particles of the present embodiment can also start from the heat reduction step.

[0068] Note that the cesium tungstate oxide precursor which is a cesium tungstate is preferably a crystalline powder of nCs2O·mWO3 (n and m are integers, 3.6 ≤ m / n ≤ 9.0). As the cesium tungstate oxide precursor which is a cesium tungstate, a stable cesium tungstate is more preferable. As the stable cesium tungstate, Cs4W O 11 O 35 、Cs2W6O 19 、Cs6W 20 O 63 、Cs2W7O 22 、Cs6W 11 O 36One or more selected from the like. The cesium tungsten oxide precursor is particularly Cs4W as the main phase 11 O 35 It is more preferable that the cesium tungsten oxide precursor contains a phase.

[0069] These cesium tungstates can be prepared, for example, by firing a raw material powder mixture containing cesium and tungsten at 700 ° C or higher and 1000 ° C or lower in the air. The production method of cesium tungstate is not limited to the above form, and other methods such as the sol-gel method and the complex polymerization method can also be used.

[0070] In addition, as the cesium tungstate used as the starting material, a non-equilibrium tungstate obtained by gas phase synthesis or the like may be used. Powders obtained by the thermal plasma method, powders obtained by electron beam melting, etc. are included in this. (2) Heating reduction step The cesium tungsten oxide precursor as the starting material described above, specifically, for example, a cesium tungstate having one or more crystal structures selected from orthorhombic, monoclinic, and pseudo-hexagonal crystals can be subjected to the heating reduction step.

[0071] In the heating reduction step, the above-mentioned cesium tungsten oxide precursor can be heated and reduced at 650 ° C or higher and 950 ° C or lower in an atmosphere of a reducing gas. By carrying out the heating reduction step, near-infrared absorbing particles containing cesium tungsten oxide having a desired composition can be obtained.

[0072] When performing the heating reduction treatment, it is preferably carried out under a gas flow 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. In addition, heating in a water vapor atmosphere or a vacuum atmosphere and other mild heating and reduction conditions may be used in combination.

[0073] Note that the method for manufacturing the near-infrared absorbing particles of the present embodiment is not particularly limited to the above form. As the method for manufacturing the near-infrared absorbing particles, various methods capable of forming a predetermined structure including a defective microstructure can be used. Examples of the method for manufacturing the near-infrared absorbing particles include a method of reducing tungstate obtained by a solid-phase method, a liquid-phase method, or a gas-phase method, and a method of reducing WO3 in molten alkali halide.

[0074] The method for manufacturing the near-infrared absorbing particles can further include an arbitrary step. (3) Grinding step As described above, it is preferable that the near-infrared absorbing particles are refined into particles. Therefore, in the method for manufacturing the near-infrared absorbing particles, a grinding step of grinding the powder obtained by the heat reduction step can be included.

[0075] The specific means for grinding and refining is not particularly limited, and various means capable of mechanically grinding can be used. As a mechanical grinding method, a dry grinding method using a jet mill or the like can be used. Also, in the process of obtaining the near-infrared absorbing particle dispersion liquid described later, mechanical grinding in a solvent may be performed. In this case, since the near-infrared absorbing particles are dispersed in the liquid medium in the grinding step, it can also be referred to as a grinding and dispersion step. (4) Coating step As described above, the surface of the near-infrared absorbing particles may be coated with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn. Therefore, the method for manufacturing the near-infrared absorbing particles can further include, for example, a coating step of coating the near-infrared absorbing particles with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn.

[0076] In the coating step, the specific conditions for coating the near-infrared absorbing particles are not particularly limited. For example, an alkoxide or the like containing one or more atoms selected from the above atomic group (metal group) can be added to the near-infrared absorbing particles to be modified to form a film on the surface of the near-infrared absorbing particles. [2] Near-infrared absorbing particle dispersion liquid Next, a configuration example of the near-infrared absorbing particle dispersion of the present embodiment will be described.

[0077] The near-infrared absorbing particle dispersion of the present embodiment can also be used, for example, when manufacturing the near-infrared absorbing fibers described later.

[0078] The near-infrared absorbing particle dispersion of the present embodiment can include the aforementioned near-infrared absorbing particles and one or more liquid media 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 the near-infrared absorbing particles are dispersed in the liquid medium.

[0079] As the liquid medium, as described above, one or more selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers can be used.

[0080] As the organic solvent, various types such as alcohol-based, ketone-based, hydrocarbon-based, and glycol-based can be selected. Specifically, alcohol-based solvents such as isopropyl alcohol, methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propanol; ketone-based solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester-based 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; formamide, N-methyl -lmonomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, etc.; formamide, N-methyl One or more selected from amides such as N,N-dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as ethylene chloride and chlorobenzene, etc. can be mentioned.

[0081] However, among these, organic solvents with low polarity are preferred. 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. are more preferred. These organic solvents can be used alone or in combination of two or more.

[0082] Examples of the oil and fat 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 subjecting fatty acids of vegetable oils and monoalcohols to an ester reaction; ethers; petroleum solvents such as Isopar (registered trademark) E, Exxsol (registered trademark) Hexane, Heptane, E, D30, D40, D60, D80, D95, D110, D130 (the above are manufactured by ExxonMobil), etc. can be used.

[0083] As the liquid resin, one or more selected from, for example, liquid acrylic resin, liquid epoxy resin, liquid polyester resin, liquid urethane resin, etc. can be used.

[0084] As the liquid plasticizer, for example, a liquid plasticizer for plastics can be used.

[0085] The components contained in the near-infrared absorbing particle dispersion are not limited to only the above-mentioned near-infrared absorbing particles and the liquid medium. The near-infrared absorbing particle dispersion can also contain, if necessary, further arbitrary components.

[0086] For example, an acid or an alkali may be added to the near-infrared absorbing particle dispersion as necessary to adjust the pH of the dispersion.

[0087] In addition, in the above-described near-infrared absorbing particle dispersion, in order to further improve the dispersion stability of the near-infrared absorbing particles and avoid coarsening of the dispersion particle size due to re-aggregation, various surfactants, coupling agents, etc. can be added as dispersants to the near-infrared absorbing particle dispersion.

[0088] The dispersants such as the surfactant and the coupling agent can be selected according to the application, but the dispersant preferably has one or more selected from a group containing an amine, a hydroxyl group, a carboxyl group, and an epoxy group as a functional group. These functional groups adsorb on the surface of the near-infrared absorbing particles to prevent aggregation, and have an effect of uniformly dispersing the near-infrared absorbing particles even in an infrared shielding film formed using the near-infrared absorbing particles, for example. A polymer dispersant having one or more selected from the above functional groups (functional group groups) in the molecule is more desirable.

[0089] Commercially available dispersants that can be preferably used include Solsperse (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, 250 (manufactured by Nippon Lubrizol Corporation) EFKA (registered trademark) 4008, 4009, 4010, 4015, 4046 , 4047, 4060, 4080, 7462, 4020, 4050, 4055, 4400, 4401, 4402, 4403, 4300, 4320, 4330, 4340, 6220, 6225, 6700, 6780, 6782, 8503 (manufactured by Efka Additives), Ajsper (registered trademark) PA111, PB821, PB822, PN411, Feimex L-12 (manufactured by Ajinomoto Fine-Techno Co., Ltd.), DisperBYK (registered trademark) 101, 102, 106, 108, 111, 116, 130, 140, 142, 145, 161, 162, 163, 164, 166, 167, 168, 170, 171, 174, 180, 182, 192, 193, 2000, 2001, 2020, 2025, 2050, 2070, 2155, 2164, 220S, 300, 306, 320, 322, 325, 330, 340, 350, 377, 378, 380N, 410, 425, 430 (manufactured by Pick-Chemie Japan Co., Ltd.), Disparon (registered trademark) 1751N, 1831, 1850, 1860, 1934, DA-400N, DA-703-50, DA-725, DA-705, DA-7301, DN-900, NS-5210, NVI-8514L (manufactured by Kusumoto Chemical Co., Ltd.), Alphon (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), etc. One or more selected from these can be mentioned.

[0090] 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. At this time, it is preferable that the average particle size of the near-infrared absorbing particles can be dispersed to be 200 nm or less, and more preferably 0.1 nm or more and 200 nm or less.

[0091] As a method for dispersing near-infrared absorbing particles in a liquid medium, for example, there are dispersion treatment methods using devices such as bead mills, ball mills, sand mills, paint shakers, ultrasonic homogenizers, etc. Among them, from the viewpoint of shortening the time required to obtain the desired average particle size by pulverizing and dispersing with a medium stirring mill such as a bead mill, ball mill, sand mill, paint shaker, etc. using a medium (beads, balls, Ottawa sand), it is preferable. By the pulverization-dispersion treatment using a medium stirring mill, at the same time as the dispersion of the near-infrared absorbing particles in the liquid medium, fine particle formation also proceeds due to collisions between the near-infrared absorbing particles and collisions of the medium with the near-infrared absorbing particles, and the near-infrared absorbing particles can be made finer and dispersed. That is, it is pulverized-dispersed.

[0092] The average particle size of the near-infrared absorbing particles is preferably 0.1 nm or more and 200 nm or less as described above. This is because if the average particle size is small, scattering of light in the visible light region with a wavelength of 400 nm or more and 780 nm or less due to geometric scattering or Mie scattering is reduced. As a result of such reduction of light scattering, for example, a near-infrared absorbing particle dispersion in which near-infrared absorbing particles are dispersed in a resin or the like obtained using the near-infrared absorbing particle dispersion liquid of the present embodiment does not become cloudy like frosted glass and clear transparency can be avoided. That is, when the average particle size becomes 200 nm or less, the mode of the above geometric scattering or Mie scattering of light scattering becomes weak and the Rayleigh scattering mode is obtained. In the Rayleigh scattering region, the scattered light is proportional to the sixth power of the dispersed particle size, so the scattering is reduced and the transparency is improved as the dispersed particle size decreases. And when the average particle size becomes 100 nm or less, the scattered light becomes very small, which is preferable.

[0093] By the way, as long as a known method of adding the dispersion liquid to the solid medium is performed, the dispersion state of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion in which the near-infrared absorbing particles are dispersed in a solid medium such as a resin obtained using the near-infrared absorbing particle dispersion liquid of the present embodiment does not aggregate more than the average particle size of the near-infrared absorbing particles in the dispersion liquid.

[0094] In addition, if the average particle diameter of the near-infrared absorbing particles is 0.1 nm or more and 200 nm or less, it is possible to avoid the near-infrared absorbing particle dispersion and its molded body (such as a plate or a sheet) produced from becoming a grayish one with a monotonously decreasing transmittance.

[0095] The content of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion liquid of the present 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 absorption rate can be exhibited by setting the content of the near-infrared absorbing particles to 0.01% by mass or more. Further, by setting it to 80% by mass or less, the near-infrared absorbing particles can be uniformly dispersed in the dispersion medium. [3] Near-infrared absorbing fiber The near-infrared absorbing fiber according to the present embodiment will be described.

[0096] The near-infrared absorbing fiber of the present embodiment can include a fiber and near-infrared absorbing particles. As the near-infrared absorbing particles, the above-described near-infrared absorbing particles can be used. Therefore, the near-infrared absorbing particles are, for example, the general formula Cs x W 1-y O 3-z (0.2 ≦ x ≦ 0.4, 0 < y ≦ 0.4, 0 < z ≦ 0.46) represented, and can contain cesium tungstate having an orthorhombic or hexagonal crystal structure.

[0097] The near-infrared absorbing fiber of the present embodiment only needs to contain a fiber and near-infrared absorbing particles as described above, and the arrangement of the near-infrared absorbing particles is not particularly limited, but the near-infrared absorbing particles are preferably arranged in one or more portions selected from the surface and the inside of the fiber.

[0098] The near-infrared absorbing fiber of the present embodiment can be prepared by dispersing the near-infrared absorbing particles obtained by the above-described synthesis method in an appropriate medium and containing the dispersion in one or more portions selected from, for example, the surface and the inside of the fiber.

[0099] Hereinafter, the members contained in the near-infrared absorbing fiber of the present embodiment will be described. (1) Fiber (1-1) Regarding the type of fiber

[0100] The fibers contained in the near-infrared absorbing fibers of this embodiment can be variously selected according to the application and are not particularly limited. Examples of the fibers include a group of fibers composed of synthetic fibers, semi-synthetic fibers, natural fibers, regenerated fibers, inorganic fibers, and one or more selected from mixed yarns obtained by blending, combining, or mixing two or more types of fibers selected from the above fiber group. That is, fibers selected from the above fiber group can be used, and fibers selected from the above mixed yarns can also be used.

[0101] Among them, considering the ease of containing near-infrared absorbing particles inside the fibers, etc., and the heat retention durability, it is preferable that the fibers contain synthetic fibers, and it is more preferable that they are composed of synthetic fibers. (1-1-1) Synthetic fibers The synthetic fibers are not particularly limited. For example, one or more selected from polyurethane fibers, polyamide-based fibers, acrylic-based fibers, polyester-based fibers, polyolefin-based fibers, polyvinyl alcohol-based fibers, polyvinylidene chloride-based fibers, polyvinyl chloride-based fibers, polyether ester-based fibers, etc. can be preferably used.

[0102] Examples of polyamide-based fibers include nylon, nylon 6, nylon 66, nylon 11, nylon 610, nylon 612, aromatic nylon, aramid, etc.

[0103] Examples of acrylic-based fibers include polyacrylonitrile, acrylonitrile-vinyl chloride copolymer, modacrylic, etc.

[0104] Examples of polyester-based fibers include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, etc.

[0105] Examples of polyolefin fibers include polyethylene, polypropylene, polystyrene, etc.

[0106] Examples of polyvinyl alcohol fibers include vinylon, etc.

[0107] Examples of polyvinylidene chloride fibers include vinylidene, etc.

[0108] Examples of polyvinyl chloride fibers include polyvinyl chloride, etc.

[0109] Examples of polyether ester fibers include Lexe, Success, etc. (1-1-2) Semi-synthetic fibers As semi-synthetic fibers, for example, one or more selected from cellulose-based fibers, protein-based fibers, chlorinated rubber, hydrochloric acid rubber, etc. can be used.

[0110] Examples of cellulose-based fibers include acetate, triacetate, oxidized acetate, etc.

[0111] Examples of protein-based fibers include Promix, etc. (1-1-3) Natural fibers As natural fibers, for example, one or more selected from plant fibers, animal fibers, mineral fibers, etc. can be used.

[0112] Examples of plant fibers include cotton, kapok, flax, hemp, jute, manila hemp, sisal hemp, New Zealand hemp, ramie, palm, rush, wheat straw, etc.

[0113] Examples of animal fibers include wool such as wool, mohair, cashmere, alpaca, angora, camel, vicuña, silk, down, feathers, etc.

[0114] Examples of mineral fibers include asbestos, etc. (1-1-4) Regenerated fibers As the regenerated fiber, for example, one or more selected from cellulose fibers, protein fibers, algin fibers, rubber fibers, chitin fibers, mannan fibers, etc. can be used.

[0115] Examples of the cellulose fibers include rayon, viscose rayon, cupra, polynosic, cuprammonium rayon, etc.

[0116] Examples of the protein fibers include casein fiber, peanut protein fiber, corn protein fiber, soybean protein fiber, regenerated silk thread, etc. (1-1-5) Inorganic fibers As the inorganic fibers, for example, one or more selected from metal fibers, carbon fibers, silicate fibers, etc. can be used.

[0117] Examples of the metal fibers include metal fiber, gold thread, silver thread, heat-resistant alloy fiber, etc.

[0118] Examples of the silicate fibers include glass fiber, mineral wool fiber, rock fiber, etc. (1-2) Shape of the fiber The cross-sectional shape of the fiber is not particularly limited, and examples thereof include one or more selected from circular, triangular, hollow, flat, Y-shaped, star-shaped, core-sheath type, etc.

[0119] The content and arrangement form of the near-infrared absorbing particles in the fiber are not particularly limited. For example, when the cross-sectional shape of the fiber is core-sheath type, the near-infrared absorbing particles may be contained in the core part or the sheath part of the fiber. Further, the shape of the fiber is not particularly limited, and it may be a filament (long fiber) or a staple (short fiber). (2) Near-infrared absorbing particles As the near-infrared absorbing particles, the above-described near-infrared absorbing particles can be used. Since the near-infrared absorbing particles have already been described, the description thereof is omitted here.

[0120] In the near-infrared absorbing fiber of the present embodiment, the content of the near-infrared absorbing particles is not particularly limited and can be selected according to the properties required for the near-infrared absorbing fiber and the like.

[0121] However, since the near-infrared absorption ability per unit mass of the above-mentioned near-infrared absorbing particles is very high, compared with ITO and ATO, an equivalent near-infrared absorption effect can be exhibited with about one-fourth to one-tenth of the usage amount.

[0122] The ratio of the near-infrared absorbing particles contained in the near-infrared absorbing fiber of the present embodiment is not particularly limited and can be arbitrarily selected according to the performance required for the near-infrared absorbing fiber and the like. The near-infrared absorbing fiber of the present embodiment preferably contains, for example, near-infrared absorbing particles in a proportion of 0.001% by mass or more and 80% by mass or less based on the solid content of the fiber, and more preferably contains them in a proportion of 0.005% by mass or more and 50% by mass or less.

[0123] By containing the near-infrared absorbing particles in a proportion of 0.001% by mass or more based on the solid content of the fiber, a sufficient near-infrared absorption effect can be obtained even when the fabric containing the near-infrared absorbing fiber is thin. Further, by containing the near-infrared absorbing particles in a proportion of 80% by mass or less based on the solid content of the fiber, it is possible to more reliably avoid a decrease in spinnability due to clogging of the filter or yarn breakage when spinning the near-infrared absorbing fiber. Further, by setting the above content of the near-infrared absorbing particles to 80% by mass or less, it is possible to more reliably avoid impairing the physical properties of the fiber. (3) Far-infrared radiation substance, additive The near-infrared absorbing fiber of the present embodiment can be composed only of the above fiber and near-infrared absorbing particles, but can also contain an arbitrary component, for example, a far-infrared radiation substance described below according to the purpose, or an additive. Note that even when the near-infrared absorbing fiber is composed only of the fiber and near-infrared absorbing particles as described above, it does not exclude containing unavoidable components and the like mixed in the manufacturing process. (3-1) Far-infrared radiation substance Far-infrared radiation materials are materials having the ability to emit far-infrared rays, and are preferably in particulate form. That is, as far-infrared radiation materials, far-infrared radiation material particles can be preferably used.

[0124] The far-infrared radiation material can be disposed at one or more locations selected from the surface and the interior of the fiber.

[0125] Examples of far-infrared radiation materials include one or more selected from metal oxides such as ZrO2, SiO2, TiO2, Al2O3, MnO2, MgO, Fe2O3, CuO, carbides such as ZrC, SiC, TiC, and nitrides such as ZrN, Si3N4, AlN.

[0126] The cesium tungstate oxide contained in the near-infrared absorbing particles has the property of absorbing solar energy with a wavelength of 0.3 μm or more and 3 μm or less, and particularly selectively absorbs the near-infrared region in the vicinity of the region with a wavelength of 0.9 μm or more and 2.2 μm or less, and converts it into heat or re-radiates it.

[0127] On the other hand, the particles of the far-infrared radiation material have the ability to receive the energy absorbed by the cesium tungstate oxide, which is a near-infrared absorbing material, and convert and radiate the energy into thermal energy with a mid- and far-infrared wavelength. For example, ZrO2 particles convert and radiate this energy into thermal energy with a wavelength of 2 μm or more and 20 μm or less. Therefore, when the far-infrared radiation material having the ability to emit the far-infrared rays and the above-described near-infrared absorbing particles coexist inside or on the surface of the fiber, the solar energy absorbed by the near-infrared absorbing particles is efficiently consumed inside and on the surface of the fiber, and more effective heat retention is achieved.

[0128] In addition, the content of the far-infrared radiation substance is not particularly limited and can be selected according to the performance required for the near-infrared absorbing fiber, etc. The near-infrared absorbing fiber of the present embodiment preferably contains a far-infrared radiation substance at a ratio of 0.001% by mass or more and 80% by mass or less, for example, based on the solid content of the fiber. This is because by setting the content ratio of the far-infrared radiation substance to 0.001% by mass or more, a sufficient thermal energy radiation effect can be obtained even if the fabric containing the near-infrared absorbing fiber is thin. Also, by setting the content ratio of the far-infrared radiation substance to 80% by mass or less, it is possible to more reliably avoid a decrease in spinnability due to clogging of the filter or yarn breakage, etc. during spinning for the near-infrared absorbing fiber. (3-2) Additive Examples of the additive include an antioxidant, a flame retardant, a deodorant, an insect repellent, an antibacterial agent, an ultraviolet absorber, etc. The additive can be used by being contained, for example, within a range that does not impair the performance of the near-infrared absorbing fiber. [4] Method for manufacturing near-infrared absorbing fiber The method for manufacturing the near-infrared absorbing fiber of the present embodiment will be described. According to the method for manufacturing the near-infrared absorbing fiber of the present embodiment, since the above-described near-infrared absorbing fiber can be manufactured, the description of the matters already explained will be omitted.

[0129] The method for manufacturing the near-infrared absorbing fiber of the present embodiment can have a near-infrared absorbing fiber manufacturing step of preparing a near-infrared absorbing fiber containing a fiber and a near-infrared absorbing fiber.

[0130] Since the near-infrared absorbing particles and the fiber have already been described, the description will be omitted here. The near-infrared absorbing particles are, for example, as described above, represented by the general formula Cs x W 1-y O 3-z (0.2 ≦ x ≦ 0.4, 0 < y ≦ 0.4, 0 < z ≦ 0.46) and can contain cesium tungstate having an orthorhombic or hexagonal crystal structure.

[0131] In the near-infrared absorbing fiber manufacturing step, specifically, for example, the near-infrared absorbing particles can be arranged at one or more locations selected from the surface and the inside of the fiber.

[0132] The method of disposing the near-infrared absorbing particles at one or more locations selected from the surface and inside of the fiber is not particularly limited. For example, any of the following methods (a) to (d) can be used.

[0133] (a) A method of mixing near-infrared absorbing particles into a raw material polymer of a synthetic fiber and spinning.

[0134] (b) A method of producing a masterbatch in which a part of the raw material polymer contains near-infrared absorbing particles at a high concentration in advance, diluting and adjusting the masterbatch to a predetermined concentration during spinning, and then spinning.

[0135] (c) A dispersion solution in which near-infrared absorbing particles are dispersed in a raw material monomer or oligomer solution is prepared in advance. Then, while synthesizing the target raw material polymer using the dispersion solution, the near-infrared absorbing particles are dispersed in the raw material polymer, and then spun.

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

[0137] Here, the methods (a) to (d) will be further described with specific examples.

[0138] (a) method: The case of using polyester fiber as the fiber will be described as an example.

[0139] First, a near-infrared absorbing particle dispersion liquid is added to polyethylene terephthalate resin pellets, which are thermoplastic resins, uniformly mixed with a blender, and then the solvent is removed. By melt-kneading the mixture from which the solvent has been removed with a twin-screw extruder, a masterbatch containing near-infrared absorbing particles is obtained. The obtained masterbatch is melt-mixed near the melting temperature of the resin and spun by, for example, various known methods to produce near-infrared absorbing fibers.

[0140] The manufacturing method of the above masterbatch is not particularly limited. For example, first, a near-infrared absorbing particle dispersion, powder or pellets of a thermoplastic resin, and, if necessary, other additives are melt-mixed using a kneader while removing the solvent, whereby a mixture in which near-infrared absorbing particles are dispersed in the thermoplastic resin can be prepared.

[0141] The kneader is not particularly limited. For example, one or more selected from mixers such as a ribbon blender, tumbler, Nauta mixer, Henschel mixer, super mixer, planetary mixer, etc., and Banbury mixers, kneaders, rolls, kneader extruders, single-screw extruders, twin-screw extruders, etc. can be used.

[0142] The method for preparing a mixture in which near-infrared absorbing particles are dispersed in the resin is not limited to the above form.

[0143] For example, after preparing a near-infrared absorbing particle dispersion, first, the dispersion medium of the dispersion is removed by a known method. Then, the powder obtained by removing the dispersion medium, powder or pellets of a thermoplastic resin, and, if necessary, other additives are uniformly melt-mixed to produce a mixture in which near-infrared absorbing particles are dispersed in the thermoplastic resin. In addition, for the production of a mixture in which near-infrared absorbing particles are dispersed in a thermoplastic resin, a method of directly adding near-infrared absorbing particles to the thermoplastic resin and melt-mixing them can also be used.

[0144] The mixture of near-infrared absorbing particles and thermoplastic resin obtained by the above method is kneaded with a vented single-screw or twin-screw extruder and processed into pellets, whereby a masterbatch containing near-infrared absorbing particles can be obtained.

[0145] (b) Method: Using the same method as in (a) or others, a masterbatch containing near-infrared absorbing particles is prepared. Then, the masterbatch and a masterbatch made of polyethylene terephthalate without near-infrared absorbing particles are melt-mixed near the melting temperature of the resin at a desired mixing ratio and spun according to a known method, whereby near-infrared absorbing fibers can be produced.

[0146] Method of (c): For example, the case of using urethane fibers as the fibers will be described as an example.

[0147] A high molecular weight diol containing near-infrared absorbing particles and an organic diisocyanate are reacted in a twin-screw extruder to synthesize an isocyanate group-terminated prepolymer, and then a chain extender is reacted thereto to produce a polyurethane solution (raw material polymer). By spinning the polyurethane solution according to various known methods, near-infrared absorbing particles can be produced.

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

[0149] Next, the prepared natural fibers are immersed in the prepared treatment liquid, or the prepared treatment liquid is impregnated into the natural fibers by padding, printing, spraying, etc., and then dried. Thereby, near-infrared absorbing particles can be attached to the natural fibers. And the method of (d) can be applied to any of the above-mentioned natural fibers, semi-synthetic fibers, regenerated fibers, inorganic fibers, or their blends, ply yarns, and mixed fibers.

[0150] In addition, the method for preparing the dispersion liquid of near-infrared absorbing particles that can be used when implementing the above methods (a) to (d) is not particularly limited. For example, it can be prepared by the method described above with a near-infrared absorbing particle dispersion liquid.

[0151] In the dispersion of the near-infrared absorbing particles, when the value of the XRD peak intensity of the (220) plane of the silicon powder standard sample (manufactured by NIST, 640c) is set to 1, it is preferable to set the conditions of the dispersion step so that the value of the ratio of the XRD peak top intensity of the near-infrared absorbing particles, specifically the cesium tungstate contained therein, is 0.13 or more. By performing the dispersion treatment so as to satisfy the above conditions and preparing the near-infrared absorbing fiber using the obtained dispersion liquid, the optical characteristics of the near-infrared absorbing fiber can be particularly enhanced.

[0152] In addition, the dispersion medium of the near-infrared absorbing particle dispersion liquid is not particularly limited and can be selected according to the fiber to be mixed. For example, various general organic solvents such as alcohol, ether, ester, ketone, and aromatic compounds, and water can be preferably used.

[0153] When attaching and mixing the near-infrared absorbing particles to fibers or polymers serving as raw materials thereof, the dispersion liquid of the near-infrared absorbing particles can be directly mixed with the fibers or polymers serving as raw materials thereof. Further, if necessary, an acid or an alkali may be added to the near-infrared absorbing particle dispersion liquid to adjust the pH, or various surfactants, coupling agents, etc. may be added to further improve the dispersion stability of the near-infrared absorbing particles.

[0154] As described above, the near-infrared absorbing fiber of the present embodiment contains a fiber and near-infrared absorbing particles, and the near-infrared absorbing particles have a neutral color tone. Therefore, it is possible to obtain a neutral color tone also for the near-infrared absorbing fiber. Further, since the near-infrared absorbing particles contain cesium tungstate, the near-infrared absorbing fiber of the present embodiment can be a fiber having excellent heat retention properties. As a result, the designability of the fiber product using the near-infrared absorbing fiber is not impaired, and it can be colored with complementary colors or light colors.

[0155] And the near-infrared absorbing fiber of the present embodiment can be used in various applications such as fiber products such as cold-proof clothing, sports clothing, stockings, curtains, etc. that require heat retention properties, and other industrial fiber products. Fiber product The fiber product of the present embodiment is obtained by processing the aforementioned near-infrared absorbing fiber and can contain the aforementioned near-infrared absorbing fiber. In addition, the fiber product of the present embodiment can also be composed of the aforementioned near-infrared absorbing fiber.

Example

[0156] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

[0157] First, the evaluation method of the near-infrared absorbing particles in the following experimental examples will be described. (Chemical analysis) The chemical analysis of the obtained near-infrared absorbing particles was performed by atomic absorption spectrometry (AAS) for Cs and by inductively coupled plasma optical emission spectrometry (ICP-OES) for W (tungsten). For O, a light element analyzer (manufactured by LECO, model ON-836) was used, and the sample was melted in He gas and reacted with carbon in the crucible, and the CO gas thus generated was analyzed by IR absorption spectrometry for quantification. In the following Experimental Examples 1-1 to 1-13, powders of near-infrared absorbing particles containing cesium tungsten composite oxides having W deficiency were obtained. Therefore, for Powders A to M, which are near-infrared absorbing particles obtained in Experimental Examples 1-1 to 1-13, the composition ratios obtained by multiplying the composition ratios when W is set to 1 by the values corresponding to the W deficiency determined by TEM observation and the like all satisfy the general formula Cs x W 1-y O 3-z (0.2 ≦ x ≦ 0.4, 0 < y ≦ 0.4, 0 < z ≦ 0.46). (X-ray diffraction measurement) The X-ray diffraction measurement was carried out by powder XRD measurement using Cu-Kα rays with a Spectris X'Pert-PRO / MPD device.

[0158] Measurements were performed after calibrating the diffraction angle using a standard sample (NIST640e). Then, Rietveld analysis was performed on the obtained XRD diffraction pattern to determine the lattice constants of the crystal phases. In Table 1, the identified crystal phases are indicated in the "Pattern" column of the "XRD" column. In the case of "Orthorhombic + Hexagonal", it means that both orthorhombic and hexagonal crystals are included. Also, in the case of "Orthorhombic", it means that orthorhombic crystals are included, and in the case of "Hexagonal", it means that hexagonal crystals are included.

[0159] In the case of a mixed phase of orthorhombic and hexagonal crystals, the lattice constants for each phase were determined. Then, the lattice constant of the orthorhombic crystal was converted to the lattice constant of the hexagonal crystal using the following lattice correspondence model. The correspondence of the lattice change between the orthorhombic and hexagonal crystals was extracted from the model of Solodovnikov 1998 (Non-Patent Document 4), Equation 4a orth 2 +b orth 2 =64a hex 2 = 64b hex 2 、c orth =c hex Using this, the lattice constants in terms of hexagonal crystal were determined. In the above equation, a orth 、b orth 、c orth represent the lengths of the a-axis, b-axis, and c-axis of the orthorhombic crystal. Also, a hex 、b hex 、c hex represent the lengths of the a-axis, b-axis, and c-axis of the hexagonal crystal. [Experimental Example 1] Near-infrared absorbing particles used in Experimental Example 2 described later were manufactured and evaluated. [Experimental Example 1-1] Cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded in a molar ratio of Cs2CO3:WO3 = 2:11. The kneaded product thus obtained was placed in a carbon boat and heated twice at 850 °C for 20 hours each in a tubular furnace in the atmosphere to obtain a powdery A´ which was a very pale greenish white powder. When heating, after heating at 850 °C for 20 hours, it was taken out once, pulverized and mixed, and then reheated under the same conditions.

[0160] The obtained white powder, powder A´, was evaluated as follows.

[0161] The X-ray powder diffraction pattern slightly contained Cs6W 11 O 36 but was almost identified as a single phase of Cs4W 11 O 35 (ICDD 00-51-1891).

[0162] The lattice constants were measured as a = 14.6733 Å, b = 52.3841 Å, and c = 7.7424 Å. These values were extremely close to those of Solodovnikov (Non-Patent Document 4), a = 14.6686 Å, b = 52.3971 Å, and c = 7.7356 Å. The chemical analysis result of this white powder was Cs 0.36 WO 3.18 which was almost consistent with the weighed composition.

[0163] Next, TEM observation of the obtained white powder, powder A´, was performed. When a restricted-field electron beam diffraction pattern was taken, an orthorhombic spot pattern was obtained. Fig. 4 shows the spot pattern taken from the c-axis direction of the orthorhombic crystal. Periodicity of b / 8 cycle appeared in the b-axis direction, and the presence of the W- and O-deficient planes was confirmed. Also, from the streak running in the b-axis direction, it was found that there were some plane defects on the b-plane. This spot pattern of the c-axis zone axis is close to six-fold symmetry, but the angle between the (480) and (4-80) spots is 52.2°, deviating from 60° in the case of six-fold symmetry, and it is considered that this deviation from six-fold symmetry is due to the W- and O-deficient planes incorporated in the b / 8 cycle.

[0164] The obtained white powder, Cs4W 11 O 35The powder was thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800 °C in an Ar gas stream. While maintaining the temperature at 800 °C, the gas stream was switched to a mixed gas stream of 1 vol% H2 gas using Ar gas as a carrier (hereinafter, vol% is simply denoted as %), and after reduction for 5 minutes, the H2 gas was stopped, and it was gradually cooled to 100 °C only with the Ar gas stream, and then the Ar gas stream was stopped and gradually cooled to room temperature, and powder A was taken out. The color tone of the taken-out powder A was light blue.

[0165] The XRD pattern of powder A showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. When the lattice constants of each phase were determined by the Rietveld method, for the orthorhombic crystal, a = 14.6609 Å, b = 52.4040 Å, c = 7.7419 Å (the hexagonal crystal conversion values are a = 7.5062 Å, c = 7.7419 Å), and for the hexagonal crystal, a = 7.4170 Å, c = 7.5752 Å. It was confirmed that the value of the c-axis was in the range of 7.560 Å ≤ c ≤ 7.750 Å.

[0166] Next, when powder A was observed by TEM, orthorhombic crystal particles and pseudo-hexagonal crystal particles were observed.

[0167] Here, the electron diffraction image of the pseudo-hexagonal crystal particles is shown in Fig. 5. The pseudo-hexagonal crystal particles showed a diffraction pattern close to that of a hexagonal crystal, as shown by the electron diffraction image of the

[0001] HEX zone axis in Fig. 5. Here, the interplanar angle between (200) HEX and (110) HEX was measured to be 59.2°, which was a value close to that of a hexagonal crystal.

[0168] Next, powder A was observed in the STEM-HAADF mode (STEM: scanning transmission electron microscopy, HAADF: High-angle annular dark field).

[0169] The HAADF image of the pseudo-hexagonal crystal particles observed from the

[0221] zone axis is shown in Fig. 6. In the HAADF mode, atomic grains are observed with brightness proportional to the atomic number and the probability of atomic existence in the projection direction. Therefore, the linear region along the (110) HEX identified as a W defect with the largest atomic number. Traces of such W defect regions were confirmed to spread planar along the (110) HEX by observation from another direction. Also, a part of the trace with weak contrast is considered to shrink linearly.

[0170] In this experimental example, the heat reduction treatment was set for 5 minutes, which is shorter than other experimental examples described later. At the initial stage of reduction at high temperature, the orthorhombic (010) ORTH W defects contracted and a structural transition occurred to pseudo-hexagonal crystals. In the pseudo-hexagonal crystals, many W defect regions in the process of contraction were observed on the {100} HEX plane. [Experimental Example 1-2] Powder A´ obtained in Experimental Example 1-1, Cs4W 11 O 35 powder was thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800 °C in an Ar gas stream. While maintaining the temperature at 800 °C, the gas stream was switched to a mixed gas stream of 1% H2 gas with Ar gas as the carrier, and after reducing for 15 minutes, the H2 gas was stopped, and it was slowly cooled to 100 °C only with the Ar gas stream, and then the Ar gas stream was stopped and slowly cooled to room temperature, and powder B was taken out. The color tone of the taken-out powder B was blue.

[0171] The XRD pattern of powder B showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. When the lattice constants of each phase were determined by the Rietveld method, for the orthorhombic crystal, a = 14.6576 Å, b = 52.4315 Å, c = 7.7412 Å (the hexagonal crystal conversion values are a = 7.5088 Å, c = 7.7412 Å), and for the hexagonal crystal, a = 7.4122 Å, c = 7.5940 Å were obtained. It was confirmed that the value of the c-axis was in the range of 7 .560 Å ≤ c ≤ 7.750 Å.

[0172] Next, TEM observation of powder B was carried out. As in the case of powder A obtained in Experimental Example 1-1, orthorhombic particles and pseudo-hexagonal particles were observed. The pseudo-hexagonal particles showed a diffraction pattern close to that of hexagonal crystals, as shown by the electron diffraction image with the

[0001] zone axis in Fig. 7. Here, the interplanar angle between (200) HEX and (110) HEX was measured to be 59.5°, which was a value close to that of hexagonal crystals. HEX [Experimental Example 1-3] The powder A' obtained in Experimental Example 1-1, Cs4W 11 O 35 powder was thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800 °C in an Ar gas stream. While maintaining the temperature at 800 °C, the gas stream was switched to a stream mixed with 1% H2 gas using Ar gas as a carrier, and after reduction for 30 minutes, the H2 gas was stopped, and it was gradually cooled to 100 °C only with the Ar gas stream, and then the Ar gas stream was stopped and gradually cooled to room temperature to take out powder C. The color tone of the taken-out powder C was dark blue.

[0173] The XRD pattern of powder C showed a two-phase mixture pattern of orthorhombic and hexagonal crystals. When the lattice constants of each phase were determined by the Rietveld method, for the orthorhombic phase, a = 14.6649 Å, b = 52.4010 Å, c = 7.7451 Å (the hexagonal crystal conversion values are a = 7.5064 Å, c = 7.7451 Å), and for the hexagonal phase, a = 7.4076 Å, c = 7.6107 Å were obtained. It was confirmed that the value of the c-axis was in the range of 7.560 Å ≤ c ≤ 7.750 Å for both.

[0174] Next, TEM observation of powder C was carried out. As in the case of powder A obtained in Experimental Example 1-1, orthorhombic particles and pseudo-hexagonal particles were observed. The pseudo-hexagonal particles showed a diffraction pattern of hexagonal crystals, as shown by the electron diffraction image with the

[0001] zone axis in Fig. 8. Here, the interplanar angle between (200) HEX and (110) HEX was measured to be 60.0°, which was the value of hexagonal crystals. [Experimental Examples 1-4 to Experimental Examples 1-7] The powder A' obtained in Experimental Example 1-1, Cs4W 11 O 35 ​The reduction time during the reduction treatment of the powder was changed to 35 to 90 minutes as shown in Table 1 to prepare Powder D, Powder E, Powder F, and Powder G. The powder color tones of Powder D to Powder G were all dark blue, and the XRD lattice constants were as shown in the table.

[0175] As shown in Table 1, in Experimental Examples 1-4, an orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystal was 7.7440 Å (Experimental Examples 1-4). [Experimental Examples 1-8 to Experimental Examples 1-11] Cs4W which is Powder A´ obtained in Experimental Example 1-1 11 O 35 The heating temperature and reduction time during the heat reduction treatment of the powder were changed as shown in Table 1. Specifically, in Experimental Example 1-8, it was 650 °C for 120 minutes, in Experimental Example 1-9, it was 700 °C for 60 minutes, in Experimental Example 1-10, it was 900 °C for 10 minutes, and in Experimental Example 1-11, it was 950 °C for 20 minutes. Except for the above points, in the same manner as when preparing Powder A in Experimental Example 1-1, Powder H, Powder I, Powder J, and Powder K were prepared. Light blue, blue, dark blue, and dark blue powders were obtained respectively. The lattice constants determined from the XRD patterns of the obtained powders were as shown in Table 1.

[0176] As shown in Table 1, in Experimental Examples 1-8 and Experimental Example 1-9, an orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystal was 7.7428 Å (Experimental Example 1-8) and 7.7471 Å (Experimental Example 1-9). [Experimental Example 1-12] Cesium carbonate and tungsten trioxide were mixed at a molar ratio of Cs2CO3:WO3 = 3:11, thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated at 850 °C for 5 hours to obtain a very thin white powder with a greenish tint. The main phase of this white powder was Cs6W 11 O 36 which was identified as (ICDD1-70-632), but it was a mixed phase with Cs4W 11 O 35

[0177] The obtained white powder was heat-treated at 800 °C for 30 minutes in a 1% H2-N2 gas stream to obtain a dark blue Powder L.​

[0178] The XRD pattern of powder L showed a two-phase mixture pattern of orthorhombic and hexagonal crystals. The lattice constants determined from the obtained XRD pattern of powder L are as shown in Table 1. In addition, as described above, the orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystal was 7.7449 Å. [Experimental Example 1-13] Cesium carbonate and tungsten trioxide were mixed at a molar ratio of Cs2CO3:WO3 = 1:6, thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated at 850 °C for 5 hours to obtain a very thin greenish white powder. The main phase of this white powder was identified as Cs4W 11 O 35 However, it was a mixed phase with Cs2W6O 19 (ICDD00-045-0522).

[0179] The obtained white powder was heat-treated at 800 °C for 30 minutes in a 1% H2-N2 gas stream to obtain a dark blue powder M.

[0180] The XRD pattern of powder M showed a two-phase mixture pattern of orthorhombic and hexagonal crystals. The lattice constants determined from the obtained XRD pattern of powder M are as shown in Table 1. In addition, the orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystal was 7.7466 Å.

[0181]

Table 1

[0182] As shown in the above Experimental Example 1-1 to Experimental Example 1-13, when the white Cs4W 11 O 35 or Cs6W 11 O 36 and Cs2W6O 19 containing Cs4W 11 O 35 powder is reduced at high temperature, the color of the powder gradually changes from light blue to blue and then to dark blue.

[0183] Also, Cs4W 11 O35 In the phase, lattice defects including W defects exist and it is orthorhombic. However, when it is reduced at high temperature, it was confirmed that the lattice defects including W defects are reduced and disappear, and the orthorhombic crystal changes to a hexagonal crystal.

[0184] It should be noted that it has been confirmed that all of the cesium tungstate oxides contained in powders A to M obtained in Experimental Examples 1-1 to 1-13 have W defects and O defects. [Experimental Example 2] Near-infrared absorbing fibers were produced and evaluated using the near-infrared absorbing particles produced in Experimental Example 1.

[0185] Experimental Examples 2-1 to 2-13 are examples, and Experimental Examples 2-14 and 2-15 are comparative examples. [Experimental Example 2-1] 10% by mass of powder A prepared in Experimental Example 1-1, 10% by mass of an acrylic polymer dispersant having a group containing an amine as a functional group (hereinafter abbreviated as "dispersant a"), and 80% by mass of toluene as a solvent were weighed. These weighed materials were put into 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 liquid A which is a near-infrared absorbing particle dispersion liquid.

[0186] Here, when measuring the average particle diameter of the near-infrared absorbing particles in dispersion liquid A (the dispersed particle diameter measured by ELS-8000 manufactured by Otsuka Electronics Co., Ltd., which is a particle diameter measuring device based on the dynamic light scattering method), it was 28.2 nm.

[0187] Toluene was removed from dispersion liquid A using a spray dryer to obtain near-infrared absorbing particle-dispersed powder according to Experimental Example 2-1. The obtained near-infrared absorbing particle-dispersed powder was added to polyethylene terephthalate resin pellets which are thermoplastic resins, uniformly mixed with a blender, and then the mixture was melt-kneaded and extruded with a twin-screw extruder, and the extruded strand was cut into pellets to obtain a masterbatch containing 40% by weight of near-infrared absorbing particles which are near-infrared absorbing components.

[0188] The masterbatch according to Experimental Example 2-1 was melt-spun together with a polyester masterbatch using the raw material polymer, and then drawn to produce the polyester multifilament yarn according to Experimental Example 2-1. At this time, the cesium tungstate oxide particles, which are near-infrared absorbing particles, were melt-spun with the raw material polymer so as to be 10% by mass based on the solid content of the fiber. When the average particle diameter of the cesium tungstate oxide particles at that time was calculated by an image processing apparatus using a transmission electron microscope image, it was 27 nm. The particle diameter of each particle is the diameter of the circumscribed circle of the particle, and the above average particle diameter is calculated as the average value of the particle diameters measured for 100 particles. Note that polyethylene terephthalate resin is used as the polyester resin of the polyester masterbatch.

[0189] The obtained polyester multifilament yarn was cut to produce polyester staple fibers, and spun yarns were produced using these. Then, a knitted product according to Experimental Example 2-1 having heat retention was obtained using these spun yarns.

[0190] Note that the solar reflectance of the produced knitted product sample was adjusted to 8%. The adjustment of the solar reflectance of the knitted product sample to 8% was performed in all of Experimental Examples 2-2 to 2-15 described later.

[0191] The spectral characteristics of the produced knitted product were measured for the transmittance and reflectance of light with wavelengths of 200 nm or more and 2100 nm or less using a spectrophotometer manufactured by Hitachi, Ltd., and the solar absorptance was calculated according to JIS A 5759 (2016). The solar absorptance was calculated by solar absorptance (%) = 100% - solar transmittance (%) - solar reflectance (%). The calculated solar absorptance was 51.1%. Further, when the color index of the knitted product was calculated from the reflectance, L * = 88, a * = -1, b * = 8, and it was confirmed that the blue color was very weak and the color tone was neutral.

[0192] The results are shown in Table 2. Table 2 also includes the results obtained in Experimental Examples 2-2 to 2-15 described below.

[0193] Next, the temperature rise effect on the back surface of the fabric of the knitted product produced was measured as follows.

[0194] Under an environment of 20°C and 60% RH, a solar ray approximation spectral lamp (Solar Simulator XL-03E50 modified, manufactured by Celic Co., Ltd.) was irradiated from a distance of 30 cm from the fabric of the knitted product, and the temperature of the back surface of the fabric was measured with a radiation thermometer (HT-11, manufactured by Minolta Co., Ltd.) at regular intervals (0 seconds, 30 seconds, 60 seconds, 180 seconds, 360 seconds, 600 seconds).

[0195] The results are shown in Table 3. Table 3 also includes the results obtained in Experimental Examples 2-2 to 2-15 described below. [Experimental Examples 2-2 to 2-13] Near-infrared absorbing particle dispersion powders, masterbatches, polyester multifilament yarns which are near-infrared absorbing fibers, and knitted products which are textile products according to Experimental Examples 2-2 to 2-13 were obtained and evaluated in the same manner as Experimental Example 2-1, except that powders B to M according to Experimental Examples 1-2 to 1-13 were used instead of the powder A according to Experimental Example 1-1. The evaluation results are shown in Table 2 and Table 3. [Experimental Example 2-14] Near-infrared absorbing particle dispersion powders, masterbatches, polyester multifilament yarns, and knitted products according to Experimental Example 2-14 were obtained and evaluated in the same manner as Experimental Example 2-1, except that the powder A' (Cs4W 11 O 35 powder) obtained in Experimental Example 1-1 was used instead of the powder A according to Experimental Example 1-1. The evaluation results are shown in Table 2 and Table 3. [Experimental Example 2-15] An aqueous solution of cesium carbonate (Cs2CO3), tungstic acid (H2WO4), and tungsten dioxide powder (WO2) were weighed, mixed, and kneaded to prepare a raw material mixture so as to have a composition of Cs2O·5WO3·4WO2. After sufficient mixing, the raw material mixture was thinly and evenly spread on a carbon boat and held at 550 °C for 60 minutes under a 1% H2 gas stream with N2 gas as the carrier, then changed to a 100% N2 gas stream, held for 1 hour, heated to 800 °C, held for 1 hour, and slowly cooled to room temperature to obtain powder O. The color of powder O was dark blue. As a result of chemical analysis, the composition Cs 0.33 WO 2.74 was obtained.

[0196] The XRD pattern of powder O showed a hexagonal single phase. Lattice constants a = 7.4088 Å and c = 7.6033 Å were obtained by Rietveld analysis. The value of the c-axis of the lattice constant was within the preferred range.

[0197] Next, when TEM observation was carried out, no particularly noticeable lattice defects were found. No noticeable lattice defects were observed in the STEM atomic image observation either, and no W deficiency was found.

[0198] Instead of powder A according to Experimental Example 1-1, near-infrared absorbing particle dispersion powder, masterbatch, polyester multifilament yarn, and knit product according to Experimental Example 2-15 were obtained and evaluated in the same manner as Experimental Example 2-1 except that the above Cs 0.33 WO 2.74 powder was used. The evaluation results are shown in Tables 2 and 3.

[0199]

Table 2

[0200]

Table 3

[0201] On the other hand, the near-infrared absorbing particles contained in the near-infrared absorbing fibers of Experimental Example 2-14 and Experimental Example 2-15 do not contain cesium tungstate oxide that satisfies the above general formula.

[0202] And the near-infrared absorbing fiber of Experimental Example 2-15 has a negative b * value, and it can be seen that the bluish color is clearly recognized. That is, it was confirmed that the near-infrared absorbing fiber of Experimental Example 2-15 cannot have a neutral color tone.

[0203] Although the near-infrared absorbing fiber of Experimental Example 2-14 could have a neutral color tone, as is clear from the results in Tables 2 and 3, it was confirmed that it was inferior in solar radiation absorption rate and the temperature rise effect of the fiber product was not sufficient. Therefore, it was confirmed that the near-infrared absorbing fiber of Experimental Example 2-14 does not have sufficient characteristics as a near-infrared absorbing fiber.

Claims

1. A fiber and near-infrared absorbing particles, wherein The near-infrared absorbing particles are represented by the general formula Cs ｘ W １－ｙ O ３－ｚ (0.2 ≤ x ≤ 0.4, 0 < y ≤ 0.4, 0 < z ≤ 0.46) and contain cesium tungstate having an orthorhombic or hexagonal crystal structure. the cesium tungstate has linear or planar defects on one or more planes selected from the orthorhombic (010) plane, the {100} plane which is the prism plane of the hexagonal crystal, and the (001) plane which is the bottom plane of the hexagonal crystal, and the near-infrared absorbing fiber.

2. The near-infrared absorbing fiber according to claim 1, wherein the cesium tungstate has defects, and the defects include tungsten deficiency.

3. The near-infrared absorbing fiber according to claim 1 or claim 2, wherein the cesium tungstate has a c-axis length in terms of hexagonal crystal of 7.560 Å or more and 7.750 Å or less.

4. WO that constitutes the crystal of the cesium tungsten oxide ６ The near-infrared absorbing fiber according to any one of claims 1 to 3, wherein a part of O in the octahedron has a defect.

5. A part of Cs in the cesium tungstate is substituted by an additive element, and the additive element is one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, Ga. The near-infrared absorbing fiber according to any one of claims 1 to 4.

6. The near-infrared absorbing fiber according to any one of claims 1 to 5, wherein the average particle size of the near-infrared absorbing particles is 0.1 nm or more and 200 nm or less.

7. The near-infrared absorbing fiber according to any one of claims 1 to 6, wherein the surface of the near-infrared absorbing particles is coated with a compound containing one or more atoms selected from Si, Ti, Zr, Al, Zn.

8. The near-infrared absorbing fiber according to any one of claims 1 to 7, wherein the near-infrared absorbing particles are contained in a proportion of 0.001% by mass or more and 80% by mass or less based on the solid content of the fiber.

9. The near-infrared absorbing fiber further includes a far-infrared emitting substance disposed at one or more locations selected from the surface and the inside of the fiber, and the far-infrared emitting substance is contained in a proportion of 0.001% by mass or more and 80% by mass or less based on the solid content of the fiber. The near-infrared absorbing fiber according to any one of claims 1 to 8.

10. The near-infrared absorbing fiber according to any one of claims 1 to 9, wherein the fiber is one or more selected from a fiber group composed of synthetic fibers, semi-synthetic fibers, natural fibers, regenerated fibers, inorganic fibers, and a mixed yarn obtained by blending, combining, or mixing two or more fibers selected from the fiber group.

11. The near-infrared absorbing fiber according to claim 10, wherein the synthetic fiber is one or more selected from polyurethane fiber, polyamide-based fiber, acrylic-based fiber, polyester-based fiber, polyolefin-based fiber, polyvinyl alcohol-based fiber, polyvinylidene chloride-based fiber, polyvinyl chloride-based fiber, and polyether ester-based fiber.

12. The near-infrared absorbing fiber according to claim 10 or claim 11, wherein the semi-synthetic fiber is one or more selected from cellulose-based fiber, protein-based fiber, chlorinated rubber, and hydrochloric acid rubber.

13. The near-infrared absorbing fiber according to any one of claims 10 to 12, wherein the natural fiber is one or more selected from plant fiber, animal fiber, and mineral fiber.

14. The near-infrared absorbing fiber according to any one of claims 10 to 13, wherein the regenerated fiber is one or more selected from cellulose-based fiber, protein-based fiber, algin fiber, rubber fiber, chitin fiber, and mannan fiber.

15. The near-infrared absorbing fiber according to any one of claims 10 to 14, wherein the inorganic fiber is one or more selected from metal fiber, carbon fiber, and silicate fiber.

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

17. A method for producing a near-infrared absorbing fiber, comprising a step of producing a near-infrared absorbing fiber containing a fiber and near-infrared absorbing particles, The near-infrared absorbing particles are represented by the general formula Cs ｘ W １－ｙ O ３－ｚ (0.2 ≤ x ≤ 0.4, 0 < y ≤ 0.4, 0 < z ≤ 0.46), and contain cesium tungstate having an orthorhombic or hexagonal crystal structure. The method for producing a near-infrared absorbing fiber, wherein the cesium tungstate oxide has linear or planar defects on one or more planes selected from the orthorhombic (010) plane, the {100} plane which is the prism plane of the hexagonal crystal, and the (001) plane which is the bottom plane of the hexagonal crystal.

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