Near-infrared absorbing particles, manufacturing method of near-infrared absorbing particles, near-infrared absorbing particle dispersion, near-infrared absorbing laminate, near-infrared absorbing transparent substrate

Abstract

A near-infrared absorbing particle comprising cesium tungstate is provided, wherein the cesium tungstate has a quasi-hexagonal crystal structure modulated into one or more of orthorhombic, rhombohedral, and cubic crystals, and the cesium tungstate is formed by the general formula Cs xW yO z represents the ternary graph with Cs, W, and O as vertices, where x = 0.6y, z = 2.5y, y = 5x, and Cs... 2O:WO The composition of the region enclosed by four straight lines of 3 = m:n (where m and n are integers).

Description

[Technical Field]

[0001] This invention relates to near-infrared absorbing particles, a method for manufacturing near-infrared absorbing particles, a near-infrared absorbing particle dispersion, a near-infrared absorbing laminate, and a near-infrared absorbing transparent substrate. [Previous Technology]

[0002] According to the 5th edition of the Dictionary of Physics and Chemistry, "light is defined as electromagnetic waves with wavelengths in the range of approximately 1 nm to 1 mm." This wavelength range includes the visible light region and the infrared region.

[0003] Near-infrared rays contained in sunlight penetrate window materials and enter the room, causing the surface temperature of the walls and floors to rise, and the indoor temperature to rise as well. In order to make the indoor warm and hot environment comfortable, it has been carried out to block near-infrared rays entering through windows by using shading components in window materials, thereby preventing the indoor temperature from rising.

[0004] As a light-shielding component used in window materials, etc., Patent Document 1 proposes a light-shielding film containing black micro powder including inorganic pigments such as carbon black and titanium black, and organic pigments such as aniline black.

[0005] Furthermore, Patent Document 2 discloses a heat-insulating sheet made by using a strip-shaped film with infrared reflectivity and a strip-shaped film with infrared absorption as warp or weft yarns, respectively, to make a woven fabric. Moreover, as a strip-shaped film with infrared reflectivity, it also describes a product in which an aluminum vapor deposition process is performed on a synthetic resin film to further deposit a synthetic resin film.

[0006] In Patent Document 3, the applicant proposed an infrared shielding material microparticle dispersion, which is an infrared shielding material microparticle dispersion in a medium, wherein the infrared material microparticles contain tungsten oxide microparticles and / or composite tungsten oxide microparticles, and the particle diameter of the infrared material microparticles is more than 1 nm and less than 800 nm. (Prior Art Documents, Patent Documents)

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-029314; Patent Document 2: Japanese Patent Application Publication No. Hei 9-107815; Patent Document 3: International Publication No. 2005 / 037932; Non-Patent Document

[0008] Non-patent document 1: K. Machida, M. Okada, and K. Adachi, “Excitations of free and localized electrons at nearby energies in reduced cesium tungsten bronze nanocrystals,” Journal of Applied Physics, Vol. 125, 103103 (2019) Non-patent document 2: S. Yoshio and K. Adachi, “Polarons in reduced cesium tungsten bronzes studied using the DFT+U method,” Materials Research Express, Vol. 6, 026548 (2019) Non-patent literature 3: SF Solodovnikov, NV Ivannikova, ZA Solodovnikova, ES Zolotova, “Synthesis and X-ray diffraction study of potassium, rubidium, and cesium polytungstates with defect pyrochlore and hexagonal tungsten bronze structures,” Inorganic Materials, Vol. 34, 845-853 (1998) Non-patent literature 4: S. Nakakura, AF Arif, K. Machida, K. Adachi, T. Ogi, Cationic defect engineering for controlling the infrared absorption of hexagonal cesium tungsten bronze nanoparticles, Inorg. Chem., 58, 9101-9107 (2019) [Summary of the Invention]

[0009] [The problem the invention aims to solve]

[0010] In the aforementioned Patent Document 3, tungsten oxide particles and / or composite tungsten oxide particles are disclosed as infrared shielding material particles. The penetrating film in which these tungsten oxides are dispersed is colored blue, and the intensity of the blue color increases with increasing amount of these particles.

[0011] However, in recent years, applications such as automotive glass and photothermal conversion materials have required increased near-infrared absorption rate, that is, reduced solar transmittance, while the transmitted color is not colored with blue or other colors, and is a neutral color.

[0012] If a blue material such as a translucent film containing the aforementioned tungsten oxide is used as a base, the hue obtained when coloring glass using various pigments and dyes is limited. In particular, translucent colors of the yellow family, which are used as secondary colors, are difficult to obtain.

[0013] Furthermore, in photothermal conversion materials, specifically in applications such as bonding transparent resin components using photothermal conversion, a pure white color is required, but in the aforementioned tungsten oxide and other materials, a pure white color is difficult to achieve.

[0014] In contrast, for example, for a transmissive film in which a composite tungsten oxide is dispersed, its applications can be expanded if the transmissive color is neutralized, i.e., a transparent hue. However, in the case of a dispersion, there have been no reports to date of composite tungsten oxides that can achieve a neutral color while reducing solar transmittance.

[0015] Furthermore, various detectors are used in automobiles, which are an important industrial application. Examples of detectors include rain detectors that detect rainy days, light detectors that detect the setting sun, and Orbis detectors that are used as record detection detectors in traffic networks. Therefore, for automotive windows, based on the requirements for detector information transmission, the penetrability of near-infrared light in a specific wavelength band is required.

[0016] The infrared sensing light used by the above detector is near-infrared light with a wavelength close to red, around 800nm ​​to 900nm. For car windows, the requirement is for penetration that is opposite to the sun-blocking function of near-infrared light with wavelengths adjacent to them.

[0017] However, in the noble metal particles and compound particles such as LaB6 that have been known for use as shielding films, the wavelengths absorbed are visible light, so the penetration of the infrared light sensed by the detectors mentioned above is very low. In addition, in near-infrared absorbing particles such as ATO and ITO, the absorption wavelength of near-infrared light is too long, so even if the penetration of the detector wavelength is met, there is a problem that the sunlight shielding function becomes too low.

[0018] Therefore, in one aspect of the present invention, the object is to provide new near-infrared absorbing particles that suppress solar transmittance while possessing a more neutral hue in the transmitted color and ensuring transmittance at the detector wavelength. [Technical Means for Solving the Problem]

[0019] In one aspect of the present invention, a near-infrared absorbing particle is provided, which is a near-infrared absorbing particle containing cesium tungstate. The cesium tungstate has a crystal structure modulated into one or more quasi-hexagonal crystals selected from orthorhombic, rhombohedral, and cubic crystals. The cesium tungstate is represented by the general formula CsxWyOz. In a ternary composition diagram with Cs, W, and O as each vertex, it has a composition within the region enclosed by four straight lines: x = 0.6y, z = 2.5y, y = 5x, and Cs2O:WO3 = m:n (m and n are integers). <Effects of the Invention>

[0020] In one aspect of the present invention, new near-infrared absorbing particles are provided that can suppress solar transmittance while having a more neutral hue in the transmittance color and can ensure the transmittance of the detector wavelength.

Implementation Method

[0022] Hereinafter, this specific embodiment will be described with reference to the accompanying drawings. The present invention is not limited to the following embodiments, and various modifications and substitutions can be applied to the following embodiments without departing from the scope of the present invention. [Near-infrared absorbing particles] The near-infrared absorbing particles of this embodiment are near-infrared absorbing particles containing cesium tungstate. In addition, the near-infrared absorbing particles of this embodiment may also be near-infrared absorbing particles formed of cesium tungstate. However, even in this case, the presence of unavoidable impurities is not excluded. (1) Regarding cesium tungstate The cesium tungstate (cesium polytungstate) contained in the near-infrared absorbing particles of this embodiment can have a quasi-hexagonal crystal structure modulated into one or more of orthorhombic, rhombohedral, and cubic crystals. Specifically, such cesium tungstate can have a quasi-hexagonal crystal structure modified by partially deforming the hexagonal alkali tungsten bronze structure, and can have one or more of the following crystal structures selected from orthorhombic, rhombohedral, and cubic crystals.

[0023] Traditionally, the transmission color and light absorption of cesium-doped hexagonal tungsten bronze particles used as near-infrared absorbing particles have been defined by the imaginary part of their dielectric function (ε2) and their band structure. In the visible light energy region (1.6 eV to 3.3 eV), the band gap of cesium-doped hexagonal tungsten bronze (hereinafter also referred to as Cs-HTB) is sufficiently large, and light absorption in the visible light region is essentially suppressed. Furthermore, electron migration between tungsten's dd orbitals and between oxygen's pp orbitals is restricted by the Fermi golden rule, thus reducing the probability of electron migration. Due to the combined effect of these two factors, ε2 takes a small value in the visible light wavelength region. ε2 represents the absorption of photons brought about by electrons; therefore, if ε2 is small in the visible light wavelength region, visible light penetration occurs. However, it has recently been clarified that absorption due to bandgap migration exists near the blue wavelength, the shortest wavelength in the visible light region, and that local surface plasma resonance (LSPR) absorption and polarized electron migration absorption exist near the red wavelength, the longest wavelength (Non-Patent Document 1). Therefore, these absorptions are limited by light transmittance.

[0024] As described above, for Cs-HTB, the band gap is sufficiently large, so the energy of light shifting to blue wavelengths at the spectral ends is above that of blue wavelengths, resulting in blue transmittance. Conversely, on the red wavelength side, Cs-HTB has more conduction electrons, thus enhancing LSPR absorption and polarization absorption. The edges of this absorption extend throughout the red wavelength, thereby reducing red transmittance. Therefore, the transmittance color of the Cs-HTB nanoparticle dispersion film is blue due to the balance between the two.

[0025] In order to neutralize the blue-based transmission color of Cs-HTB, it is only necessary to enhance the absorption on the blue side and enhance the transmission on the red side.

[0026] To enhance the absorption on the blue side of Cs-HTB, this can be achieved by shifting, for example, the absorption position at the band end to a lower energy side. Shifting the absorption position at the band end to a lower energy side corresponds to narrowing the band gap of Cs-HTB. Therefore, this can be achieved by selecting a material with a slightly smaller band gap.

[0027] The so-called reduction of the red side absorption of Cs-HTB can be achieved by reducing the concentration of surface plasma resonant electrons and the concentration of polar bound electrons.

[0028] Based on the above investigation, the inventors of the present invention conducted various studies on cesium tungsten oxide, which is an oxide containing cesium (Cs) and tungsten (W), and improved the material while calculating the band structure using first-principles calculations. As a result, when the conventional hexagonal crystal structure is modulated into a quasi-hexagonal crystal structure such as orthorhombic, rhombohedral, or cubic crystal by changes in the microstructure, it was found that the band structure changes, and the amount of free electrons and bound electrons changes, resulting in a change in color.

[0029] Here, the term "modulated into one or more quasi-hexagonal crystal structures selected from orthorhombic, rhombohedral, and cubic crystals" refers to a quasi-hexagonal crystal structure modulated by the regular or irregular insertion of Cs-rich faces into the prismatic or basal surfaces of the hexagonal crystal. Furthermore, the term "Cs-rich face" has the same meaning as "faces lacking W or O". In addition, as described later, O, OH, OH2, and OH3 ions can substitute at Cs sites, and the introduction of these ions into the prismatic and basal surfaces can promote the modulation into a quasi-hexagonal crystal structure in the same way as Cs.

[0030] The crystal structures of orthorhombic, rhombohedral, and cubic crystals can be identified, for example, by electron diffraction. For example, when the c-axis is the direction of electron beam incident, the diffraction sites can be distinguished by observing the symmetry of the diffraction sites when electron beams are incident from the (0001) direction.

[0031] In a hexagonal crystal, the diffraction sites of the three prismatic planes (10-10), (01-10), and (1-100) appear at the same distance from the incident site within the reciprocal lattice plane. That is, in a hexagonal crystal, there are intervals between the same crystal planes. Furthermore, the aforementioned same distance includes cases considered as the same distance within the error range of electron diffraction site distance measurement. Therefore, in a hexagonal crystal, an electron diffraction pattern that is hexagonally symmetric, i.e., invariant with rotation relative to 60°, is formed.

[0032] In orthorhombic crystals, one type of prismatic surface site appears near the incident site compared to the other two types of prismatic surface sites. That is, in orthorhombic crystals, only one type of prismatic surface has long crystal plane intervals.

[0033] In a rhombohedral crystal, the three types of prismatic sites have different crystal plane spacings.

[0034] In cubic crystals, the same hexagonal symmetry pattern as that of hexagonal crystals can be easily identified as cubic symmetry by observation from the axis of other crystal zones.

[0035] In XRD powder patterns, quasi-hexagonal crystals are often regarded as a mixture of orthorhombic and hexagonal crystals, rhombohedral and hexagonal crystals, or cubic and hexagonal crystals. However, in order to insert the above-mentioned planar lattice defects, the position and intensity of the diffraction peaks are slightly changed.

[0036] As one method for obtaining a quasi-hexagonal crystal structure modulated into one or more of the orthorhombic, rhombohedral, and cubic crystals already described, one method is to add one or more additives selected from O, OH, OH2, and OH3. Therefore, the near-infrared absorbing particles of this embodiment preferably contain one or more additives selected from O, OH, OH2, and OH3.

[0037] One or more additives selected from the above-mentioned O, OH, OH2, OH3 are preferably present in one or more of the following locations in the crystallization of cesium tungstate: a hexagonal window, a hexagonal cavity, and a triangular cavity formed by three aggregates of the WO6 octahedron that constitutes the hexagonal crystalline alkaline tungsten bronze structure.

[0038] The hexagonal channel has two voids: a large hexagonal cavity and a hexagonal window. However, in the hexagonal crystal, the hexagonal cavity is the second largest void, surrounded by six oxygen atoms constituting the WO6 octahedron. The c-axis of the hexagonal window is adjacent to the Cs ions disposed in the hexagonal cavity. The trigonal cavity is a large void adjacent to the hexagonal window and extends along the c-axis of the hexagonal crystal. One or more of O, OH, OH2, and OH3 can also replace Cs and enter the hexagonal cavity. In the presence of a sufficient amount of Cs and in the presence of a large amount of intrusion water, it can invade the hexagonal window. Depending on the situation, it can invade the trigonal cavity on the bottom surface and the cavity on the prismatic surface in parallel with the hexagonal window void, and also replace Cs. By including the aforementioned additives, defective surfaces are created on the bottom and prismatic surfaces. However, at this point, the crystal structure transforms from hexagonal to orthorhombic, rhombohedral, and further cubic, resulting in a narrowing of the band gap and a reduction in the electron concentration in the conduction band. Therefore, compared to Cs-HTB, cesium tungstates with a quasi-hexagonal crystal structure can enhance absorption on the blue side and enhance transmission on the red side, thus neutralizing the blue-based transmission colors.

[0039] In this case, the orthorhombic, rhombohedral, and cubic crystals have an atomic arrangement similar to that of tungsten bronze hexagonal crystals, but can also be considered as quasi-hexagonal crystals with different symmetries than hexagonal crystals. If we avoid strictness and describe it roughly, inserting the W and O-deficient faces regularly or irregularly into one of the three types of prismatic faces of a hexagonal crystal results in an orthorhombic crystal, which breaks down the hexagonal symmetry. Therefore, in orthorhombic crystals, only one prismatic face has a long interplanar spacing. Using this, the modulation of the orthorhombic crystal can be easily identified by, for example, an (0001) electron diffraction pattern.

[0040] A rhombohedral crystal is a crystal in which the hexagonal symmetry is broken by regularly shifting the stacking along the c-axis of the bottom surface of the inserted hexagonal crystal, while the bottom surface of the hexagonal crystal receives the remaining Cs plane, i.e., the planes with missing W and O. In this case, the remaining Cs planes shift on the surface, while also involving expansion in the direction perpendicular to the plane, thus accompanied by changes in the prismatic plane spacing and the c-axis lattice constant. Therefore, the rhombohedral crystal has different plane spacings for all three prismatic planes. Using this case, a rhombohedral crystal can be easily identified, for example, by using (0001) electron diffraction patterns.

[0041] Furthermore, when the three axes of the rhombohedron intersect at 90 degrees, it becomes a cubic crystal. In addition, such a cubic crystal has a pyrochlore structure, and CsW2O6 is a typical example of its composition.

[0042] Therefore, the voids corresponding to the above-mentioned hexagonal windows, hexagonal cavities, and trigonal cavities also alternate in orthorhombic, rhombohedral, and cubic crystals. Therefore, the hexagonal windows, hexagonal cavities, and trigonal cavities in the cesium tungstate contained in the near-infrared absorbing particles of this embodiment also include the corresponding voids in orthorhombic, rhombohedral, and cubic crystals (pyrochlore phase).

[0043] Hereinafter, the configuration example of the near-infrared absorbing particle manufacturing method of this embodiment will be described, taking the case of a hexagonal window as an example, as a site or gap that can be replaced or invaded by O, OH, OH2, and OH3.

[0044] One method for obtaining orthorhombic, rhombohedral, or cubic crystals selected from O, OH, OH2, and OH3 in a hexagonal window is to crystallize it in saturated water vapor during the crystallization process of synthesizing cesium tungstate. Generally, in the Cs-HTB structure, the ionic radius of Cs is slightly larger than that of the hexagonal cavity, making it difficult for Cs to move. Therefore, if it is necessary to temporarily crystallize it into a hexagonal crystal, it becomes difficult to diffuse and insert oxygen atoms or the like into the hexagonal window using subsequent heat treatment or the like. Therefore, a method was investigated in which the environment is filled with saturated water vapor before the crystallization of cesium tungstate, and water molecules and O, OH, and OH3 ions derived from water molecules are inserted into the hexagonal window during the crystallization of cesium tungstate. Therefore, as will be described later, the method for manufacturing near-infrared absorbing particles in this embodiment preferably includes a step of introducing water vapor at a heating temperature near the crystallization temperature of cesium tungstate and crystallizing it in an environment containing water vapor. If a dispersion film is made using near-infrared absorbing particles synthesized through the above process, and further heat-treated in a reducing environment as needed, to form a near-infrared absorbing particle dispersion, it is possible to maintain high visible light transmittance and sufficient near-infrared shielding effect while reducing blue tint in the color tone. In other words, it is possible to neutralize the blue-based transmittance color.

[0045] On the other hand, even after temporarily crystallizing hexagonal cesium tungstate, heating the cesium tungstate in a steam environment, or maintaining and heating it in a high-temperature and high-humidity environment, does not achieve the effect of neutralizing the aforementioned penetrating color. This is because, since it hinders the diffusion of elements with large ionic radii such as Cs through the hexagonal channels, if it is temporarily crystallized into a hexagonal crystal, a considerable number of oxygen atoms cannot diffuse through the hexagonal windows in the pores during subsequent heat treatment. Therefore, the aforementioned heating treatment in steam needs to be carried out during the initial crystallization during synthesis.

[0046] When crystallization is performed in an environment containing water vapor, it is also possible to simultaneously mix in a reducing gas such as hydrogen to crystallize the crystal in a reducing gas environment. Furthermore, if the crystal is temporarily crystallized in a water vapor environment, it can be further heated at a high temperature of 500°C to 950°C in an environment containing a reducing gas such as hydrogen, or an inactive gas. In either case, near-infrared absorbing particles with neutral transmission color and large near-infrared absorption effect can be obtained. By setting the temperature to 500°C or higher, the alignment of orthorhombic crystal structures with defects at equilibrium atomic positions is sufficiently achieved, improving the near-infrared absorption effect. Furthermore, by setting the temperature to 950°C or lower, the rate of crystal structure change can be appropriately maintained, and the appropriate crystallization state and electronic state can be easily controlled. However, if the heating temperature is higher than 950°C, for example, excessive reduction may occur, sometimes generating low-level oxides such as W metal and WO2, which is not preferable from this perspective.

[0047] By absorbing O, OH, OH2, and OH3 during initial heating and crystallization, one or more crystals selected from orthorhombic, rhombohedral, and cubic (pyrochlore phase) are formed, which are microscopically modified from hexagonal crystals. By heating these crystals in environments with varying degrees of reduction, various crystal structures selected from orthorhombic, rhombohedral, and cubic crystals with different amounts and distributions of lattice defects are generated.

[0048] The cesium tungstate contained in the near-infrared absorbing particles of this embodiment can have lattice defects of Cs, W, and O. The reasons for introducing lattice defects of Cs, W, and O into the cesium tungstate will be explained below.

[0049] In the composition near hexagonal Cs0.33WO3, crystal stability is determined by the balance between the stability of the structure with high crystal symmetry and the overall charge neutrality resulting from charge transfer and acceptance between elements. For example, the charge-neutral 2Cs2O・11WO3=Cs4W11O35 is considered a thermodynamically stable phase, but if heated in a reducing environment, it easily transforms into a highly symmetrical hexagonal Cs0.32WO3-y (Non-Patent Document 2). Cs0.32WO3-y is a quasi-stable structure with high crystal symmetry, while Cs4W11O35 is a charge-balanced stable composition. However, Cs4W11O35 exhibits poor symmetry in its atomic arrangement within the crystal. For example, in the model of Solodovnikov (Non-Patent Document 3), within the hexagonal arrangement of WO6 octahedra similar to hexagonal tungsten bronze, W and O defects are inserted at the (1,1,-2,0) planes (= orthorhombic (010) planes) with a spacing of b / 8 between orthorhombic unit cells, forming an orthorhombic crystal as a whole. That is, the defects of Cs, W, and O are a structure necessarily introduced to locally satisfy both crystal structure and charge balance, which has actually been observed recently using TEM and XRD (Non-Patent Document 4).

[0050] In the near-infrared absorbing particles of this embodiment, O, OH, OH2, and OH3 are absorbed into orthorhombic, rhombohedral, and cubic crystals with hexagonal windows, hexagonal cavities, and trigonal cavities, disrupting the local charge balance and thus further modifying the fine crystal structure. That is, during the introduction of water-derived components, H+ and H3O+ are introduced into the crystal, and these ions compete with Cs+ and W6+ in the crystal, thus achieving local charge neutrality through the defects of Cs and W. As a result, lattice defects containing Cs and W defects are introduced. O, OH, OH2, and OH3 not only invade the hexagonal windows but can also invade the trigonal cavities. Furthermore, OH2 and OH3 can be replaced by alkali elements (Cs) in the hexagonal cavities. In addition, in the case of charge-neutral OH2 substitution, the electrons generated by the originally present alkali ions (Cs+) disappear, thus reducing the electrons in the conduction band of the crystal.

[0051] Among cesium tungstates having a quasi-hexagonal crystal structure selected from orthorhombic, rhombohedral, and cubic crystals as described above, cesium tungstates satisfying excellent near-infrared absorption and visible light transmittance have a specified composition.

[0052] Here, Figure 1A shows a ternary composition diagram 10 with Cs, W, and O as the three vertices. Figure 1B is an enlarged representation of region 11 in the ternary composition diagram 10 of Figure 1A, with CsWO3, W2O3, and WO4 as vertices. It should be noted that this diagram does not represent the thermodynamic equilibrium phase, but rather a composition diagram for the convenience of representing the width of the system's composition. Therefore, CsWO3, W2O3, WO4, etc., are compositions for convenience and do not necessarily represent the actual compounds obtained.

[0053] The cesium tungstate contained in the near-infrared absorbing particles of this embodiment is preferably represented by the general formula CsxWyOz. In a ternary composition diagram with Cs, W, and O as vertices, it has a composition within the region enclosed by four straight lines: x = 0.6y, z = 2.5y, y = 5x, and Cs₂O:WO₃ = m:n (m and n are integers). Specifically, it is preferable to have a composition within the region 16 enclosed by the straight line 12 satisfying x = 0.6y, the straight line 13 satisfying z = 2.5y, the straight line 14 satisfying y = 5x, and the straight line 15 satisfying Cs₂O:WO₃ = m:n (m and n are integers) in the ternary composition diagrams shown in Figures 1A and 1B. In addition, region 16 also includes points on the aforementioned straight lines 12 to 15. Furthermore, the straight line 15 that satisfies Cs2O:WO3=m:n (m and n are integers) is shown in Figure 1A. In the ternary composition Figure 10, it is the straight line connecting Cs2O and WO3.

[0054] In the above ternary composition diagram, when x > 0.6y, cesium tungstate has a predominantly tetragonal crystal structure, and its near-infrared absorption effect disappears. Furthermore, when z < 2.5y, in the hexagonal-based structure of cesium tungstate, lower oxides of W are mixed in, significantly impairing both near-infrared absorption and visible light transmittance. When y > 5x, cesium tungstate becomes an internally grown crystal structure, known as WO3 mixed in the lower hexagonal structure, and its near-infrared absorption effect disappears. Furthermore, if compared to the straight line 15 where the Cs₂O:WO₃ ratio is an integer, entering the O-rich side on the right, no near-infrared absorption effect is obtained at all. Therefore, cesium tungstate preferably satisfies the range already described.

[0055] In the near-infrared absorbing particles of this embodiment, the cesium tungstate contained therein may have defects in each of the elements cesium, tungsten, and oxygen, but the atomic ratio (x / y) of cesium relative to tungsten may be any one of the ranges from 0.2 to 0.6. That is, the near-infrared absorbing particles of this embodiment preferably have defects in a portion of one or more elements selected from Cs and W constituting the crystal of cesium tungstate, and the x and y in the general formula CsxWyOz have a relationship of 0.2 ≤ x / y ≤ 0.6.

[0056] Since cesium and tungsten provide electrons for crystallization, the near-infrared absorption function can be improved by making x / y ≥ 0.2. Furthermore, by making x / y ≥ 0.2, a hexagonal crystal structure can be formed, which is a modulated hexagonal crystal structure. In Cs ions, if x / y exceeds 0.33 and becomes large, hexagonal cavities are entered and trigonal cavities also begin to occupy them, causing anomalies in the prismatic and basal planes. Therefore, locally, orthorhombic, rhombohedral, or cubic pyrochlore gradually transforms into a layered structure. Further, if x / y exceeds 0.6, it transforms into a tetragonal Cs₂W₃O₁₀ crystal structure, significantly impairing visible light transmittance and reducing its usefulness.

[0057] The near-infrared absorbing particles of this embodiment can take the hexagonal cesium tungsten bronze structure Cs0.33WO3 as a reference, and have defects in at least a portion of the W of the WO6 octahedron constituting the crystal. These W defects are mainly introduced as planar defects on the hexagonal prismatic surface and the bottom surface. Due to the ion repulsion of the atomic rows on both sides of the defective surface, the interplanar spacing increases, and the crystal symmetry changes from hexagonal to orthorhombic, rhombohedral, or cubic.

[0058] The near-infrared absorbing particles of this embodiment can use the hexagonal crystalline tungsten bronze structure CsW3O9 as a reference, and at least a portion of the O in the WO6 octahedron constituting the cesium tungstate crystal has defects. These O defects are randomly introduced, and due to the defects, locally present electrons are supplied to the system, thereby improving the near-infrared absorption function. In the known hexagonal crystalline tungsten bronze Cs0.32WO3-y, it is known that a maximum of 15% of all lattice points of O constituting the octahedron are distributed throughout y = 0.46 or y = 2.5 (Non-Patent Document 3). If the defect amount is higher than 0.5, the crystal becomes unstable, generating an heterogeneous phase and decomposing. The cesium tungstate CsxWyOz contained in the near-infrared absorbing particles of this embodiment can contain an amount of O defects equivalent to a maximum z / y = 2.5. However, it should be noted that when residual O, OH, OH2, OH3 are introduced into the voids such as hexagonal windows, the identification value of O obtained by chemical analysis includes these residual components.

[0059] The cesium tungstate contained in the near-infrared absorbing particles of this embodiment can replace a portion of Cs with an added element. In this case, the added element is preferably one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0060] The above-mentioned added elements have electron-donating properties and are located at Cs sites to assist in the electron supply to the conduction band of the WO octahedral framework. (2) Regarding the damp heat resistance of near-infrared absorbing particles, the near-infrared absorbing particles of this embodiment show improved damp heat resistance compared to those with added cesium hexagonal tungsten bronze. If it is assumed that a portion of the near-infrared absorbing particles of this embodiment contains one or more of orthorhombic, rhombohedral, and cubic (pyrochlore phase) crystals modulated by the intrusion and substitution of O, OH, OH2, and OH3, then this effect is a reasonable result. That is, the humidity degradation and moisture degradation of added cesium hexagonal tungsten bronze are essentially substitution reactions of Cs and water molecules, but when the cavity and window of the hexagonal channel, which is the main diffusion pathway for oxygen diffusion, are also buried by Cs, O, OH, OH2, and OH3, the substitution reaction is significantly slowed down. Therefore, the near-infrared absorbing particles of this embodiment not only suppress the loss of near-infrared absorption function under high humidity conditions, but also improve the resistance to damp heat by slowing down the deterioration reaction caused by moisture in the atmosphere, even in high-temperature heat resistance tests under normal humidity conditions. (3) Regarding the average particle size of the near-infrared absorbing particles, the average particle size of the near-infrared absorbing particles of this embodiment is not particularly limited, but is preferably 0.1 nm or more and 200 nm or less. This is because by making the average particle size of the near-infrared absorbing particles 200 nm or less, local surface plasma resonance is more significantly manifested, and thus the near-infrared absorption characteristics can be improved, that is, the solar transmittance can be suppressed in particular. In addition, this is because by making the average particle size of the near-infrared absorbing particles 0.1 nm or more, it can be easily manufactured industrially. Furthermore, the particle size is closely related to the color of the dispersion penetration film, that is, the near-infrared absorbing particle dispersion. Within the particle size range where Mie scattering is controlled, the smaller the particle size, the less short-wavelength scattering in the visible light region. Therefore, increasing the particle size has the effect of suppressing blue hues. If it exceeds 100 nm, the haze of the film, which is accompanied by light scattering, becomes unavoidable. If it exceeds 200 nm, in addition to the increase in film haze, the occurrence of surface plasma is also suppressed and LSPR absorption becomes excessively small.

[0061] Here, the average particle size of the near-infrared absorbing particles is known from the median particle size of multiple near-infrared absorbing particles measured by transmission electron microscopy images and the dispersed particle size measured by a particle size measuring device based on dynamic light scattering of dispersion.

[0062] Furthermore, in applications such as automotive windshields, particularly where transparency in the visible light region is important, it is preferable to further consider the reduction in scattering caused by near-infrared absorbing particles. When this reduction in scattering is important, the average particle size of the near-infrared absorbing particles is particularly preferably 30 nm or less.

[0063] The term "average particle size" refers to the particle size at which the cumulative value in the particle size distribution reaches 50%. In this specification, the term "average particle size" has the same meaning even in other parts. As a method for determining the particle size distribution used to calculate the average particle size, for example, a transmission electron microscope can be used to directly measure the particle size of each particle. In addition, the average particle size can also be measured by a particle size measuring device based on the dynamic light scattering method of the dispersion, as described above. (4) Regarding any configuration of near-infrared absorbing particles, near-infrared absorbing particles can be surface-treated for purposes such as surface protection, improved durability, oxidation prevention, and improved water resistance. The specific content of the surface treatment is not particularly limited. For example, the near-infrared absorbing particles of this embodiment can be coated with a compound containing one or more atoms selected from Si, Ti, Zr, and Al. That is, the near-infrared absorbing particles can have a coating made of the above-mentioned compound. As a compound containing one or more atoms selected from Si, Ti, Zr, and Al, examples include one or more atoms selected from oxides, nitrides, and carbides. Specifically, as schematically shown in FIG10, the near-infrared absorbing particle 90 may also have the aforementioned coating 91 on its surface 90A. FIG10 is a cross-sectional view through the center of the near-infrared absorbing particle 90 having the coating 91. FIG10 shows an example in which the coating 91 is uniformly disposed on the surface 90A of the near-infrared absorbing particle 90, but it is not limited to this form. The coating 91 may be disposed in a way that covers a part of the surface of the near-infrared absorbing particle 90, for example, it may be dotted. Furthermore, it is not limited to a form in which the thickness of the coating 91 is also uniform, and it may vary depending on the position. [Method for Manufacturing Near-Infrared Absorbing Particles] Next, an example of a method for manufacturing near-infrared absorbing particles according to this embodiment will be described. According to the method for manufacturing near-infrared absorbing particles according to this embodiment, the near-infrared absorbing particles already described can be manufactured, so the description is omitted.

[0064] There is no particular limitation on the manufacturing method of near-infrared absorbing particles. Any method that can manufacture near-infrared absorbing particles that satisfy the characteristics already described can be used without particular limitation. Here, an example of a manufacturing method for near-infrared absorbing particles will be described. (1) First heat treatment step The manufacturing method for near-infrared absorbing particles in this embodiment can have, for example, the following steps.

[0065] In the first heat treatment step, the compound raw material containing Cs and W is heated at a temperature of 400°C to 650°C in an environment containing water vapor or in an environment containing water vapor and reducing gas.

[0066] In the first heat treatment process, cesium tungstate is crystallized by heating at a temperature of 400°C to 650°C.

[0067] However, in order to make cesium tungstate a quasi-hexagonal crystal, it is preferable that the environment contains sufficient water vapor during the crystallization of cesium tungstate, i.e., when the WO6 unit and Cs form a hexagonal crystal together. During this crystallization process, Cs is mainly taken up into the hexagonal cavity, and water molecules or OH3+, OH- and O2- as its decomposition products are mainly taken up into the hexagonal window. When the composition contains a relatively large amount of Cs or water molecules, Cs or water molecules are also taken up into the trigonal cavity.

[0068] As a compound raw material containing Cs and W, a mixture of a compound raw material containing Cs and a compound raw material containing W can be used. As a compound raw material containing Cs and W, any material containing Cs and W is sufficient, for example, a mixture of Cs2CO3 and WO3 can be used.

[0069] However, the purpose of the crystallization process in the first heat treatment step described above is to incorporate water molecules, OH, O, etc., into the crystals during crystallization. Therefore, as a compound raw material containing Cs and W, it is preferable not to use cesium tungsten oxides that have already formed a hexagonal crystal structure, such as crystalline powders of nCs2O·mWO3 (n and m are integers, 3.6 ≤ m / n ≤ 9.0). As a compound raw material containing Cs and W, it is preferable not to use non-equilibrium cesium tungstates obtained by other methods such as sol-gel method, fusible polymerization method, gas phase synthesis, etc., as well as powders obtained by thermal plasma method, powders obtained by electron beam dissolution, etc. This is because in raw materials that have already formed a hexagonal crystal framework structure, Cs hinders the diffusion of oxygen atoms, etc., so water molecules, etc., are difficult to be incorporated into the crystals. That is, cesium tungstates with a hexagonal crystal structure are preferably not used as compound raw materials derived from Cs and W.

[0070] The supply of water vapor during the crystallization process of the first heat treatment step is preferably achieved by supplying superheated steam, for example, in a heating furnace. Superheated steam is high-enthalpy water vapor that has been further heated to a high temperature of 100°C or higher from saturated water vapor that has vaporized at 100°C, and can be supplied together with a carrier gas. When the carrier gas is an inert gas, an environment close to an oxygen-free state is formed. The superheated steam can be supplied at temperatures above 400°C, where crystallization becomes more active, but is preferably supplied from a sufficiently low temperature before crystallization. It can be supplied as a mixture of superheated steam and an inert gas, or a mixture of superheated steam, an inert gas, and a reducing gas such as hydrogen. In the case of a mixed reducing gas, there is a tendency for an increased rate of hexagonal crystallization, and sometimes even with the same orthorhombic, rhombohedral, or cubic crystals, products with different microscopic defect structures are obtained.

[0071] In the first heat treatment process, heating can be carried out in an environment without water vapor, such as an inactive environment, before or after the crystallization of cesium tungstate.

[0072] The manufacturing method of near-infrared absorbing particles in this embodiment can further include any step. (2) Second heat treatment step The manufacturing method of near-infrared absorbing particles in this embodiment can further include a second heat treatment step after the first heat treatment step, in which the particles are heated in an environment containing a reducing gas at a temperature of 500°C or higher and 950°C or lower.

[0073] The second heat treatment step is, for example, a process of heating and reducing the material powder that has undergone the first heat treatment step at a temperature of 500°C to 950°C. This process involves annealing and stabilizing orthorhombic, rhombohedral, or cubic crystals with defective structures, while simultaneously removing the oxygen portion of the WO6 octahedrons through high-temperature reduction. By removing the octahedral oxygen, adjacent W atoms generate bound electrons, resulting in a structure that improves near-infrared absorption characteristics.

[0074] When performing a heating reduction process, it is preferable to carry it out under a stream of reducing gas. As the reducing gas, a mixture of reducing gas such as hydrogen and one or more inert gases selected from nitrogen, argon, etc. can be used. In addition, other mild heating and reduction conditions such as heating in a steam environment or a vacuum environment can be used.

[0075] The second heat treatment step can also be composed of multiple steps, and can be further heated in an inactive gas environment after heating in the above-mentioned reducing gas environment.

[0076] Furthermore, in the second heat treatment step, without intending to remove even a portion of the oxygen from the WO6 octahedron, it is possible to convert the environment into one containing a reducing gas or an environment containing an inert gas, and then heat the process within the aforementioned temperature range. That is, the second heat treatment step can be performed in an environment containing a reducing gas or an environment containing an inert gas, at a temperature of 500°C to 950°C.

[0077] As already described, the method for manufacturing near-infrared absorbing particles in this embodiment is not particularly limited. Various methods capable of forming a defined structure including fine defect structures can be used as the method for manufacturing near-infrared absorbing particles.

[0078] The method for manufacturing near-infrared absorbing particles can be used in an environment where water molecules coexist, and methods such as solid-phase method, liquid-phase method, and gas-phase method for synthesizing tungstates can be employed. (3) The pulverization process, as already described, preferably involves miniaturizing the near-infrared absorbing particles into microparticles. Therefore, the method for manufacturing near-infrared absorbing particles can also include a pulverization process that pulverizes the powder obtained by the first heat treatment process and the second heat treatment process.

[0079] The specific means of pulverization and micronization are not particularly limited, and various means capable of mechanical pulverization can be used. As a mechanical pulverization method, dry pulverization methods using jet mills or the like can be used. In addition, mechanical pulverization can be performed in a solvent during the process of obtaining the near-infrared absorbing particle dispersion described later.

[0080] Further sieving, etc., can be performed as needed. (4) Modification process: As already described, the surface of the near-infrared absorbing particles can be modified with a compound containing one or more atoms selected from Si, Ti, Zr, and Al. Therefore, the method for manufacturing near-infrared absorbing particles can further include, for example, a modification process in which the near-infrared absorbing particles are modified with a compound containing one or more atoms selected from Si, Ti, Zr, and Al.

[0081] In the modification process, the specific conditions for modifying the near-infrared absorbing particles are not particularly limited. For example, a modification process can also be included in which an alkoxide containing one or more metals selected from the above-mentioned metal group is added to the modified near-infrared absorbing particles to form a film on the surface of the near-infrared absorbing particles. [Near-infrared absorbing particle dispersion] Next, an example of a composition of the near-infrared absorbing particle dispersion of this embodiment will be described.

[0082] The near-infrared absorbing particle dispersion of this embodiment can contain the near-infrared absorbing particles described above, and one or more liquid media selected from water, organic solvents, oils, liquid resins, and liquid plasticizers. That is, as shown in FIG11 for example, the near-infrared absorbing particle dispersion 100 of this embodiment can contain the near-infrared absorbing particles 101 described above and the liquid medium 102. The near-infrared absorbing particle dispersion preferably has a configuration in which near-infrared absorbing particles are dispersed in the liquid medium. In addition, FIG11 is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to such a form. For example, in FIG11, the near-infrared absorbing particles 101 are shown as spherical particles, but the shape of the near-infrared absorbing particles 101 is not limited to such a form and can have any shape. As already described, the near-infrared absorbing particles 101 may also have a coating on their surface, for example. In addition to near-infrared absorbing particles 101 and liquid medium 102, near-infrared absorbing particle dispersion 100 may also contain other additives as needed.

[0083] As a liquid medium, as already described, one or more selected from water, organic solvent, oil, liquid resin, and liquid plasticizer can be used.

[0084] As an organic solvent, it can be selected from various organic solvents such as alcohols, ketones, hydrocarbons, glycols, and water. Specifically, examples include alcohol solvents such as isopropanol, methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propanol; ketone solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester solvents such as 3-methyl-methoxy-propionate and butyl acetate; diol 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; acetamides such as methylamine, N-methylmethylamine, dimethylmethylamine, dimethylacetamide, and N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; and halogenated hydrocarbons such as dichloroethane and chlorobenzene.

[0085] Among these, the most preferred are organic solvents with low polarity, and more preferably are isopropanol, ethanol, 1-methoxy-2-propanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, n-butyl acetate, etc. These organic solvents can be used in combination of one or more.

[0086] As an oil, for example, one or more of the following petroleum-based solvents can be used: 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 that directly esterify the fatty acids of vegetable oils with monohydric alcohols; ethers; Isoper (registered trademark) E; Exxsol (registered trademark) Hexane; Heptane; E; D30; D40; D60; D80; D95; D110; D130 (and above, manufactured by Exxon Mobil).

[0087] As a liquid resin, one or more of the following can be used: liquid acrylic resin, liquid epoxy resin, liquid polyester resin, liquid urethane resin, etc.

[0088] As a liquid plasticizer, liquid plasticizers for plastics, for example, can be used.

[0089] The components contained in the near-infrared absorbing particle dispersion are not limited to the aforementioned near-infrared absorbing particles and liquid medium. The near-infrared absorbing particle dispersion may also contain any additional components as needed.

[0090] For example, acid or alkali can be added to the near-infrared absorbing particle dispersion as needed to adjust the pH of the dispersion.

[0091] In addition, in order to further improve the dispersion stability of near-infrared absorbing particles in the above-mentioned near-infrared absorbing particle dispersion and avoid the coarsening of dispersed particle size caused by reagglomeration, various surfactants, coupling agents and the like can be added to the near-infrared absorbing particle dispersion as dispersants.

[0092] The surfactant, coupling agent, or other dispersant can be selected according to the application. Preferably, the dispersant has one or more functional groups selected from amine groups, hydroxyl groups, carboxyl groups, and epoxy groups. These functional groups have the effect of adsorbing onto the surface of near-infrared absorbing particles to prevent aggregation, and also uniformly dispersing the near-infrared absorbing particles in an infrared shielding film formed using near-infrared absorbing particles. It is further desirable to use a polymeric dispersant having one or more of the aforementioned functional groups (functional group groups).

[0093] Commercially available dispersants suitable for use include those selected from Solsperse (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, 250 (manufactured by Lubrizol Co., Ltd., Japan) and 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 (made by EFKA Additives), AJISTOR (registered trademark), PA111, PB821, PB822, PN411, FEIME KKUSU L-12 (made by Ajinomoto 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 (made by BYK Japan Co., Ltd.), Disparlon (registered trademark) One or more of the following: 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.), ARUFON (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toa Synthetic Co., Ltd.).

[0094] The method for dispersing near-infrared absorbing particles in a liquid medium is not particularly limited as long as it is a method that can disperse near-infrared absorbing particles in a liquid medium. In this case, it is preferable to disperse the particles in a manner that makes the average particle size of the near-infrared absorbing particles 200 nm or less, and more preferably disperse them in a manner that makes the average particle size 0.1 nm or more and 200 nm or less.

[0095] Examples of methods for dispersing near-infrared absorbing particles in a liquid medium include dispersion methods using devices such as bead mills, ball mills, sand mills, paint shakers, and ultrasonic homogenizers. Among these, using a media-stirred mill such as a bead mill, ball mill, sand mill, or paint shaker to pulverize and disperse the particles is preferred from the viewpoint of shortening the time required to achieve the desired average particle size. By using a media-stirred mill for pulverization-dispersion, near-infrared absorbing particles can be dispersed into the liquid medium while simultaneously undergoing microparticle atomization due to collisions between near-infrared absorbing particles and collisions of the media with the near-infrared absorbing particles, resulting in a more microparticle-sized dispersion of the near-infrared absorbing particles. In other words, it is a pulverization-dispersion process.

[0096] The average particle size of the near-infrared absorbing particles, as described above, is preferably 0.1 nm to 200 nm. This is because if the average particle size is small, the scattering of light in the visible light region with wavelengths of 400 nm to 780 nm is reduced due to geometric scattering or Mie scattering. As a result, the near-infrared absorbing particle dispersion dispersed in resin or the like becomes a cloudy glass, thus avoiding a lack of clear transparency. That is, if the average particle size is 200 nm or less, the aforementioned geometric scattering or Mie scattering in light scattering weakens, and it becomes a Reichscat scattering mode. This is because in the Reichscat scattering region, the scattered light is proportional to the sixth power of the dispersed particle size. Therefore, with the reduction of the dispersed particle size, scattering decreases, and transparency increases. Moreover, if the average particle size is 100 nm or less, the scattered light becomes very little, which is preferable.

[0097] However, the near-infrared absorbing particles in the near-infrared absorbing particle dispersion obtained by using the near-infrared absorbing particle dispersion of this embodiment, in which the near-infrared absorbing particles are dispersed in a solid medium such as a resin, are limited to the known method of adding the dispersion to the solid medium, and there is no aggregation compared to the average particle size of the near-infrared absorbing particles in the dispersion.

[0098] Furthermore, if the average particle size of the near-infrared absorbing particles is between 0.1 nm and 200 nm, it is possible to avoid the near-infrared absorbing particle dispersion and its molded body (plate, sheet, etc.) becoming a gray product with monotonously reduced transmittance.

[0099] The content of near-infrared absorbing particles in the near-infrared absorbing particle dispersion of this embodiment is not particularly limited, but is preferably 0.01% by mass or more and 80% by mass or less. This is because by making the content of near-infrared absorbing particles 0.01% by mass or more, sufficient solar transmittance can be achieved. Furthermore, this is because by making it 80% by mass or less, the near-infrared absorbing particles can be uniformly dispersed in the dispersion medium. [Near-infrared absorbing particle dispersion] Next, an example of the composition of the near-infrared absorbing particle dispersion of this embodiment will be described.

[0100] The near-infrared absorbing particle dispersion of this embodiment includes the near-infrared absorbing particles and a solid medium as described above. Specifically, for example, as schematically shown in FIG12, the near-infrared absorbing particle dispersion 110 may include the near-infrared absorbing particles 111 as described above and a solid medium 112, wherein the near-infrared absorbing particles 111 may be disposed in the solid medium 112. Moreover, in the near-infrared absorbing particle dispersion of this embodiment, the near-infrared absorbing particles are preferably dispersed in the solid medium. In addition, FIG12 is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to such a form. For example, FIG12 shows the near-infrared absorbing particles 111 as spherical particles, but the shape of the near-infrared absorbing particles 111 is not limited to such a form and can have any shape. The near-infrared absorbing particles 111 may also have a coating on their surface, for example. In addition to the near-infrared absorbing particles 111 and the solid medium 112, the near-infrared absorbing particle dispersion 110 may also include other additives as needed.

[0101] Hereinafter, the near-infrared absorbing particle dispersion according to this embodiment will be described in the following order: (1) characteristics of the solid medium and the near-infrared absorbing particle dispersion, (2) manufacturing method of the near-infrared absorbing particle dispersion, (3) additives, and (4) applicable examples. (1) Characteristics of the solid medium and the near-infrared absorbing particle dispersion As a solid medium, thermoplastic resins, thermosetting resins, and ultraviolet curing resins are examples of medium resins. That is, resins can be used as solid media.

[0102] The specific material of the resin used in the solid medium is not particularly limited, but preferably, for example, one resin selected from the group consisting of polyester resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene-vinyl acetate copolymer, polyvinyl acetal resin, and ultraviolet-curable resin, or a mixture of two or more resins selected from the above resin group. Furthermore, polyethylene terephthalate resin can be used as the polyester resin.

[0103] These media resins may also contain polymeric dispersants having one or more functional groups selected from amine groups, hydroxyl groups, carboxyl groups, and epoxy groups in their skeleton.

[0104] The solid medium is not limited to a medium resin; a binder using a metal alkoxide can also be used as a solid medium. Representative metal alkoxides include those of Si, Ti, Al, and Zr. By hydrolyzing and polycondensing the binder using these metal alkoxides through heating or similar means, the solid medium can also become a near-infrared absorbing particle dispersion containing oxides.

[0105] The proportion of near-infrared absorbing particles in the near-infrared absorbing particle dispersion involved in this embodiment is not particularly limited, but the near-infrared absorbing particle dispersion preferably contains 0.001% by mass or more and 80% by mass or less of near-infrared absorbing particles.

[0106] There is no particular limitation on the shape of the near-infrared absorbing particle dispersion of this embodiment, but the near-infrared absorbing particle dispersion of this embodiment preferably has a sheet shape, a plate shape, or a film shape. This is because by making the near-infrared absorbing particle dispersion into a sheet shape, a plate shape, or a film shape, it can be used for various applications.

[0107] The hue of the near-infrared absorbing particle dispersion of this embodiment varies depending on the concentration of the near-infrared absorbing particles it contains. If the Hunter color index of the near-infrared absorbing particle dispersion of this embodiment is evaluated using, for example, a concentration of L* = 88, that is, in the Hunter color index L* = 88 section, the near-infrared absorbing particle dispersion of this embodiment preferably has near-infrared shading characteristics with a solar transmittance of 67% or less, and exhibits hue neutrality satisfying b* ≥ 0 and b* ≥ 1.6 × a* + 8.0. When the color index b* is negative, the blue is too high and neutral colors are not visible. Even if b* is positive, a larger b* value is needed if the color index a* increases in order for the dispersion to be considered neutral. The criterion is b* ≥ 1.6 × a* + 8.0. Furthermore, the aforementioned solar transmittance is more preferably 50% or less.

[0108] The near-infrared absorbing particle dispersion of this embodiment exhibits high detector wavelength transmittance. Detector wavelength transmittance varies depending on the concentration of near-infrared absorbing particles contained in the near-infrared absorbing particle dispersion. If the concentration is low, the transmittance is naturally high, but at the same time, the solar transmittance also increases, and the solar shading effect decreases. The near-infrared absorbing particles described already have the effect of shifting the near-infrared absorption peak towards the longer wavelength side according to changes in their own electronic structure. Therefore, without reducing the particle concentration, and without changing the size of the near-infrared absorption peak, detector wavelength transmittance can be improved. When evaluating the indicators that simultaneously satisfy sunlight shading and detector wavelength transmittance, if the evaluation is carried out on the Hunter color index L*=88 section, the near-infrared absorbing particle dispersion of this embodiment preferably shows a T900 as the transmittance at a wavelength of 900nm of 10% or more, a ST21 (%) as the sunlight transmittance of 67% or less, and T900 (%) and ST21 (%) satisfy the detector wavelength transmittance of T900≧1.4×ST21-41.0.

[0109] The wavelengths of various detectors exist in the vicinity of 800nm ​​to 1000nm, and the required signal strength is also discrete depending on the type of detector. For a brightness of approximately L* = 88, a 10% reduction in transmittance for light with a wavelength of 900nm cannot sufficiently ensure the signal strength. If the dispersion is diluted to reduce the particle concentration, T900 will increase, but ST21 will also increase simultaneously. The increase gradient of T900 relative to the increase in ST21 is preferably higher than a reference, which is determined by ST21(%) ≤ 67 and T900(%) ≥ 1.4 × ST21(%) - 41.0.

[0110] By using the near-infrared absorbing particles already described, the near-infrared absorbing particle dispersion of this embodiment can satisfy the above-mentioned hue and detector wavelength penetration. (2) Method for manufacturing near-infrared absorbing particle dispersion The method for manufacturing near-infrared absorbing particle dispersion of this embodiment will be described below. In addition, this is only a configuration example of the method for manufacturing near-infrared absorbing particle dispersion, and the method for manufacturing near-infrared absorbing particle dispersion already described is not limited to the following configuration example.

[0111] The near-infrared absorbing particle dispersion of this embodiment can be manufactured, for example, using a masterbatch. In this case, the manufacturing method of the near-infrared absorbing particle dispersion of this embodiment may also include, for example, the following masterbatch preparation step.

[0112] Masterbatch preparation process for obtaining masterbatch in which near-infrared absorbing particles are dispersed in a solid medium.

[0113] In the masterbatch production process, it is possible to produce a masterbatch in which near-infrared absorbing particles are dispersed in a solid medium.

[0114] There is no particular limitation on the specific method of preparing the masterbatch. For example, the masterbatch can be prepared by dispersing near-infrared absorbing particles in a dispersion liquid or near-infrared absorbing particles in a solid medium and granulating the solid medium.

[0115] In addition, as near-infrared absorbing particles, near-infrared absorbing particle dispersion powder obtained by removing the liquid medium from the near-infrared absorbing particle dispersion can also be used.

[0116] For example, a near-infrared absorbing particle dispersion, near-infrared absorbing particles, near-infrared absorbing particle powder, and powder or granules of a solid medium are uniformly mixed with other additives as needed to prepare a mixture. Furthermore, the mixture can be processed into granules by kneading it using a vented single-shaft or twin-shaft extruder and cutting the molten extruded wire bundle, thereby producing a masterbatch. In this case, cylindrical or prismatic shapes can be examples of granule shapes. Additionally, a so-called thermal cutting method, in which the molten extrudate is directly cut, can be used when producing granules. In this case, the shape is usually close to spherical.

[0117] Furthermore, in the masterbatch production process, when using a near-infrared absorbing particle dispersion as a raw material, it is preferable to reduce or remove the liquid medium originating from the near-infrared absorbing particle dispersion. In this case, the degree to which the liquid medium contained in the near-infrared absorbing particle dispersion is removed is not particularly limited. For example, it is preferable to remove the liquid medium from the near-infrared absorbing particle dispersion until an allowable amount remains in the masterbatch. In addition, when a liquid plasticizer is used as the liquid medium, all of the liquid plasticizer may remain in the near-infrared absorbing particle dispersion.

[0118] There are no particular limitations on the method for reducing or removing the liquid medium contained in the near-infrared absorbing particle dispersion, or the mixture of the near-infrared absorbing particle dispersion and the solid medium. For example, it is preferable to perform vacuum drying on the near-infrared absorbing particle dispersion, etc. Specifically, the near-infrared absorbing particle dispersion, etc., is dried under reduced pressure while stirring, separating the composition containing near-infrared absorbing particles from the components of the liquid medium. As an apparatus used for this vacuum drying, a vacuum stirring type dryer can be used; any apparatus with the above-mentioned functions is acceptable and is not particularly limited. In addition, the pressure value during the depressurization process in the drying step is appropriately selected.

[0119] By using this vacuum drying method, the removal efficiency of liquid media such as near-infrared absorbing particle dispersions is improved. Furthermore, the near-infrared absorbing particle dispersion powder and the near-infrared absorbing particle dispersion liquid used as raw materials are not exposed to high temperatures for extended periods. Therefore, agglomeration of the near-infrared absorbing particles dispersed in the near-infrared absorbing particle dispersion powder and near-infrared absorbing particle dispersion liquid does not occur, which is preferable. Furthermore, the productivity of the near-infrared absorbing particle dispersion powder, etc., is improved, and the recovery of solvents such as evaporated liquid media is easier, making it preferable from an environmental perspective.

[0120] Preferably, solvent components with a boiling point below 120°C are thoroughly removed from the near-infrared absorbing particle dispersion obtained after this drying process. For example, the residual amount of such solvent components is preferably 2.5% by mass or less. This is because if the residual solvent component is 2.5% by mass or less, when the near-infrared absorbing particle dispersion is processed into, for example, a near-infrared absorbing particle dispersion, no bubbles are generated, and the appearance and optical properties are well maintained. Furthermore, this is because if the residual solvent component in the near-infrared absorbing particle dispersion is 2.5% by mass or less, when stored in the state of near-infrared absorbing particle dispersion for a long time, no agglomeration caused by the natural drying of the residual solvent components occurs, and long-term stability is maintained.

[0121] The obtained masterbatch can be adjusted to maintain the dispersion state of the near-infrared absorbing particles contained in the near-infrared absorbing particle dispersion by adding a solid medium and kneading.

[0122] Furthermore, the method for manufacturing near-infrared absorbing particle dispersion of this embodiment can, as needed, include a molding step of molding a near-infrared absorbing particle dispersion of a desired shape by adding a solid medium to the obtained masterbatch, as described above, and molding the product.

[0123] There is no particular limitation on the specific method for forming the near-infrared absorbing particle dispersion, and methods such as well-known extrusion molding and injection molding can be used.

[0124] In the molding process, for example, it is possible to manufacture near-infrared absorbing particle dispersions in the form of planar, curved sheet, plate, or film shapes. The method of molding into sheet, plate, or film shapes is not particularly limited, and various known methods can be used. For example, calendering, extrusion, casting, blow molding, etc., can be used.

[0125] The method for manufacturing near-infrared absorbing particle dispersion in this embodiment is not limited to the form having the above-described masterbatch preparation process.

[0126] For example, the method for manufacturing near-infrared absorbing particle dispersion of this embodiment can also be in the form of having the following steps.

[0127] A precursor liquid preparation process is performed by mixing monomers, oligomers and uncured liquid solid media precursors of solid media with near-infrared absorbing particles (near-infrared absorbing particle dispersion powder) and near-infrared absorbing particle dispersion liquid to prepare a precursor liquid for near-infrared absorbing particle dispersion.

[0128] The near-infrared absorbing particle dispersion manufacturing process involves solidifying the above-mentioned monomer or other solid medium precursors through chemical reactions such as condensation and polymerization to produce a near-infrared absorbing particle dispersion.

[0129] For example, when using an acrylic resin as a solid medium, it is possible to mix acrylic monomers, an acrylic UV-curable resin, and near-infrared absorbing particles to obtain a near-infrared absorbing particle dispersion precursor liquid.

[0130] Next, if the near-infrared absorbing particle dispersion precursor liquid is filled into a specified mold or the like and subjected to free radical polymerization, a near-infrared absorbing particle dispersion using an acrylic resin is obtained.

[0131] The case of using a resin that is cured by cross-linking as a solid medium is the same as the case of using the above-mentioned acrylic resin. By performing a cross-linking reaction on the near-infrared absorbing particle dispersion precursor liquid, a dispersion can be obtained.

[0132] (3) When resin is used as a solid medium, the near-infrared absorbing particle dispersion of this embodiment can generally also contain known additives such as plasticizers, flame retardants, colorants, and fillers added to these resins. However, as already described, the solid medium is not limited to resin, and binders using metal alkoxides can also be used.

[0133] The shape of the near-infrared absorbing particle dispersion involved in this embodiment is not particularly limited. As already described, it can take the form of a sheet, plate or film.

[0134] When used as an interlayer for a transparent substrate such as glass, together with a near-infrared absorbing particle dispersion in sheet, plate, or film shape, the solid medium contained in the near-infrared absorbing particle dispersion sometimes lacks sufficient flexibility and adhesion to the transparent substrate when used directly. In this case, the near-infrared absorbing particle dispersion preferably contains a plasticizer. Specifically, for example, the solid medium is polyvinyl acetal resin, and when used for the above-described applications, the near-infrared absorbing particle dispersion preferably further contains a plasticizer.

[0135] As the plasticizer described above, any substance used as a plasticizer in the solid medium of the near-infrared absorbing particle dispersion of this embodiment can be used. For example, as a plasticizer used in a near-infrared absorbing particle dispersion composed of polyvinyl acetal resin, examples include plasticizers of primary alcohol and organic acid ester compounds, ester-based plasticizers such as polyol organic acid ester compounds, and phosphoric acid-based plasticizers such as organophosphate plasticizers. Any plasticizer is preferably liquid at room temperature. Among these, plasticizers of ester compounds synthesized from polyols and fatty acids are preferred. (4) Application Examples The near-infrared absorbing particle dispersion of this embodiment can be used in various ways, and its use and application are not particularly limited. Hereinafter, examples of application of the near-infrared absorbing particle dispersion of this embodiment will be described for near-infrared absorbing transparent substrates, near-infrared absorbing intermediate films, and near-infrared absorbing laminates. (4-1) Near-infrared absorbing transparent substrate The near-infrared absorbing transparent substrate of this embodiment includes a transparent substrate and a near-infrared absorbing layer on at least one side of the transparent substrate, and the near-infrared absorbing layer can be a near-infrared absorbing particle dispersion as described above. Specifically, as shown in FIG14, which is a cross-sectional schematic diagram along the lamination direction of the transparent substrate and the near-infrared absorbing layer, the near-infrared absorbing transparent substrate 130 can have a transparent substrate 131 and a near-infrared absorbing layer 132. The near-infrared absorbing layer 132 can be disposed on at least one side 131A of the transparent substrate 131.

[0136] The near-infrared absorbing transparent substrate of this embodiment can have a transparent substrate as described above. As a transparent substrate, it is preferable to use one or more selected from, for example, transparent film substrates and transparent glass substrates.

[0137] The membrane substrate is not limited to a membrane shape; for example, it can be a plate shape or a sheet shape. As the material for this membrane substrate, one or more selected from polyester resin, acrylic resin, urethane resin, polycarbonate resin, polyethylene resin, ethylene-vinyl acetate copolymer, vinyl chloride resin, fluoropolymer resin, etc., can be used for various purposes. However, polyester resin is preferred as the material for the membrane substrate, and polyethylene terephthalate resin (PET resin) is particularly more preferred. That is, the membrane substrate is preferably a polyester resin film, and more preferably a polyethylene terephthalate resin film.

[0138] When the membrane substrate is used as a transparent substrate, the surface of the membrane substrate is preferably treated to facilitate adhesion to the near-infrared absorption layer.

[0139] Furthermore, in order to improve the adhesion between the glass substrate or film substrate and the near-infrared absorbing layer, it is also a preferred configuration to form an intermediate layer on the glass substrate or film substrate, and to form the near-infrared absorbing layer on the intermediate layer. The composition of the intermediate layer is not particularly limited, and it can be formed by polymer film, metal layer, inorganic layer (e.g., inorganic oxide layer of silicon dioxide, titanium dioxide, zirconium oxide, etc.), organic / inorganic composite layer, etc.

[0140] Since the near-infrared absorbing particle dispersion has already been described, the description is omitted here. In addition, the shape of the near-infrared absorbing particle dispersion is not particularly limited, but it is preferable to have a sheet shape, plate shape or film shape.

[0141] The manufacturing method of the near-infrared absorbing transparent substrate of this embodiment will be described.

[0142] The near-infrared absorbing transparent substrate of this embodiment can be manufactured, for example, by using the near-infrared absorbing particle dispersion already described, to form a near-infrared absorbing layer on the transparent substrate, which is a near-infrared absorbing particle dispersion in a solid medium.

[0143] Therefore, the manufacturing method of the near-infrared absorbing transparent substrate of this embodiment can have, for example, the following steps.

[0144] A coating process in which a coating liquid containing a dispersion of near-infrared absorbing particles, as described above, is applied to the surface of a transparent substrate. A near-infrared absorbing layer forming process in which the liquid medium in the coating liquid is evaporated.

[0145] The coating liquid used in the coating process can be prepared by mixing a solid medium such as a resin or a metal alkoxide, or a solid medium precursor, into a near-infrared absorbing particle dispersion that has already been described.

[0146] As already described, a solid medium precursor refers to one or more selected from monomers, oligomers and uncured solid media.

[0147] If a near-infrared absorbing layer is formed as a coating on a transparent substrate, the near-infrared absorbing layer becomes a state in which near-infrared absorbing particles are dispersed in a solid medium. Therefore, such a near-infrared absorbing layer becomes a near-infrared absorbing particle dispersion. In this way, by providing a near-infrared absorbing particle dispersion on the surface of a transparent substrate, a near-infrared absorbing transparent substrate can be manufactured.

[0148] The solid medium, solid medium precursor, (1) characteristics of the solid medium and near-infrared absorbing particle dispersion, and (2) manufacturing method of near-infrared absorbing particle dispersion have been described, so the description is omitted here.

[0149] In order to form a near-infrared absorbing layer on a transparent substrate, the method of applying the coating liquid to the transparent substrate is not particularly limited as long as it can uniformly coat the coating liquid onto the surface of the transparent substrate. Examples include rod coating, gravure coating, spray coating, dip coating, spin coating, screen printing, roller coating, and curtain coating.

[0150] Here, taking the case of using a UV-curable resin as a solid medium and applying it using a rod coating method to form a near-infrared absorption layer as an example, the steps for fabricating a near-infrared absorption layer on the surface of a transparent substrate will be explained.

[0151] A coating liquid with appropriately adjusted concentration and additives is applied to a transparent substrate using a bar numbered to achieve the desired thickness and near-infrared absorbing particle content for the near-infrared absorbing layer, in a manner that provides adequate leveling properties. Furthermore, by removing the solvent, such as the liquid medium contained in the coating liquid, through drying, and then curing it by irradiating it with ultraviolet light, a coating layer serving as a near-infrared absorbing layer can be formed on the transparent substrate.

[0152] The drying conditions for the coating film vary depending on the type and proportion of each component and solvent used. Generally, it is a temperature between 60°C and 140°C and a drying time between 20 seconds and 10 minutes. There are no particular restrictions on ultraviolet irradiation; for example, ultra-high pressure mercury lamps or other ultraviolet exposure machines can be used.

[0153] Furthermore, the adhesion between the substrate and the near-infrared absorption layer, the smoothness of the coating film during coating, and the drying properties of the organic solvent can be controlled by the pre- and post-processes (pre-process and post-process) before and after the formation of the near-infrared absorption layer. Examples of the aforementioned pre- and post-processes include, for example, a substrate surface treatment process, a pre-baking process (pre-heating of the substrate), and a post-baking process (post-heating of the substrate), which can be appropriately selected. Preferably, the heating temperature in the pre-baking process and / or the post-baking process is 80°C to 200°C, and the heating time is 30 seconds to 240 seconds.

[0154] The manufacturing method of the near-infrared absorbing transparent substrate of this embodiment is not limited to the method described above. Other configuration examples of the manufacturing method of the near-infrared absorbing transparent substrate of this embodiment may include a form having the following steps.

[0155] A near-infrared absorbing particle dispersion, as described above, is coated onto the surface of a transparent substrate and dried. An adhesive coating and curing process is then performed on the surface coated with the near-infrared absorbing particle dispersion, using a solid medium such as a resin, metal alkoxide, or a solid medium precursor.

[0156] In this case, a film in which near-infrared absorbing particles are dispersed on the surface of a transparent substrate is formed by coating and drying the near-infrared absorbing particle dispersion. Furthermore, the near-infrared absorbing particle dispersion can be coated using the same method as described in the coating process of the method for manufacturing a near-infrared absorbing transparent substrate.

[0157] Moreover, by applying an adhesive to a film in which the near-infrared absorbing particles are dispersed and then curing it, a cured adhesive can be disposed between the near-infrared absorbing particles to form a near-infrared absorbing layer.

[0158] The near-infrared absorbing transparent substrate can also have a coating on the surface of the near-infrared absorbing particle dispersion. That is, it can also have a multilayer film.

[0159] The coating may be, for example, a film containing one or more oxides selected from Si, Ti, Zr, and Al. In this case, the coating may be formed, for example, by coating a coating solution containing one or more alkoxides selected from Si, Ti, Zr, and Al, and a partially hydrolyzed condensate of the alkoxide, onto a near-infrared absorbing layer, followed by heating.

[0160] By forming a coating, the coated components fill the gaps in the accumulation of near-infrared absorbing particles in the first layer, thereby suppressing the refraction of visible light and further reducing the haze value of the film, thus improving the visible light transmittance. In addition, the adhesion of near-infrared absorbing particles to the substrate can be improved.

[0161] Here, from the viewpoint of ease of film formation operation and cost, a coating method is preferred as a method for forming a coating film made of any one or more alkoxides containing Si, Ti, Zr, and Al, or their partially hydrolyzed condensates, on a film containing near-infrared absorbing particle monomers or near-infrared absorbing particles.

[0162] The coating solution used in the above coating method can be a coating solution containing one or more alkoxides of any one of Si, Ti, Zr, and Al, or a partially hydrolyzed condensate of such alkoxide, which is suitable for use in solvents such as water and alcohol. The content of the alkoxides in the coating solution is not particularly limited, but is preferably 40% by mass or less, calculated based on the oxides obtained after heating. Furthermore, the pH can be adjusted by adding acids or bases as needed.

[0163] By applying the coating liquid as a second layer onto a film with near-infrared absorbing particles as the main component and heating it, it is possible to easily form an oxide film containing one or more oxides selected from Si, Ti, Zr, and Al as the coating layer. An organosilazane solution is preferably used as the binder component or component of the coating liquid according to this embodiment.

[0164] As an inorganic binder or coating, the heating temperature of the substrate after coating with a near-infrared absorbing particle dispersion containing any one or more metal alkoxides of Si, Ti, Zr, and Al, and their hydrolyzed polymers, is not particularly limited. For example, the substrate heating temperature is preferably 100°C or higher, and more preferably above the boiling point of the solvent in the coating liquid such as the near-infrared absorbing particle dispersion.

[0165] This is because if the substrate heating temperature is above 100°C, the polymerization reaction of the metal alkoxide or the hydrolyzed polymer of the metal alkoxide contained in the coating film can be terminated. Furthermore, this is because if the substrate heating temperature is above 100°C, water and organic solvents, which are solvents, are almost entirely absent from the film, and thus these solvents do not contribute to the reduction in visible light transmittance in the heated film.

[0166] The thickness of the near-infrared absorbing layer on the transparent substrate of this embodiment is not particularly limited, but practically it is preferably 10 μm or less, and more preferably 6 μm or less. This is because if the thickness of the near-infrared absorbing layer is 10 μm or less, in addition to having sufficient pencil hardness and abrasion resistance, it can prevent process abnormalities such as warping of the substrate film during the evaporation of solvents and curing of adhesives in the near-infrared absorbing layer. (4-2) Near-infrared absorbing intermediate film, near-infrared absorbing laminate The near-infrared absorbing laminate of this embodiment can have a laminated structure including the near-infrared absorbing particle dispersion and the transparent substrate as described above. The near-infrared absorbing laminate of this embodiment can be formed by laminating the near-infrared absorbing particle dispersion and the transparent substrate as elements.

[0167] Examples of near-infrared absorbing laminates include, for example, a plurality of transparent substrates having two or more layers laminated, and near-infrared absorbing particle dispersions already described. In this case, the near-infrared absorbing particle dispersion can be disposed, for example, between transparent substrates, and used as an intermediate film for near-infrared absorption. Specifically, as shown in FIG13, which is a schematic cross-sectional view along the lamination direction of the transparent substrate and the near-infrared absorbing particle dispersion, the near-infrared absorbing laminate 120 can have a plurality of transparent substrates 1211, 1212 and a near-infrared absorbing particle dispersion 122. Moreover, the near-infrared absorbing particle dispersion 122 can be disposed between a plurality of transparent substrates 1211, 1212. FIG13 shows an example having two transparent substrates 1211, 1212, but is not limited to this configuration.

[0168] The above-mentioned intermediate film for near-infrared absorption preferably has any shape, such as sheet shape, plate shape or film shape.

[0169] The transparent substrate is suitable for use with one or more of the following: transparent plate glass, plate-shaped plastic, and film-shaped plastic in the visible light region.

[0170] When using plastic as a transparent substrate, the material of the plastic is not particularly limited and can be selected according to the application. For example, one or more of the following can be used: polycarbonate resin, acrylic resin, polyester resin, polyamide resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, ion-crosslinked polymer resin, fluoropolymer resin, etc. Furthermore, polyethylene terephthalate resin is suitable as the polyester resin.

[0171] The transparent substrate may contain particles with sunlight-shading function. As particles with sunlight-shading function, near-infrared absorbing particles with near-infrared shading properties can be used.

[0172] By having a near-infrared absorbing particle dispersion as described therein, a structure is obtained by suppressing solar transmittance, having a more neutral hue in the transmittance, and being able to match a type of solar shading as a near-infrared absorbing laminate that can ensure the transmittance of the detector wavelength.

[0173] In addition, by bonding and integrating multiple transparent substrates that hold near-infrared absorbing particle dispersions together using a known method, the above-mentioned near-infrared absorbing laminate can also be manufactured.

[0174] When using the described near-infrared absorbing particle dispersion as the intermediate film for near-infrared absorption, the solid medium described in the near-infrared absorbing particle dispersion can be used as the solid medium. However, from the viewpoint of improving the adhesion strength between the near-infrared absorbing intermediate film and the transparent substrate, the solid medium is preferably a polyvinyl acetal resin.

[0175] The near-infrared absorption intermediate film of this embodiment can be manufactured using the manufacturing method of the near-infrared absorbing particle dispersion already described. For example, it can be made into a near-infrared absorption intermediate film having any shape, such as a sheet shape, a plate shape, or a film shape.

[0176] Furthermore, if the intermediate film for near-infrared absorption does not possess sufficient flexibility and adhesion to a transparent substrate, it is preferable to add a liquid plasticizer for the medium resin. For example, if the medium resin used in the intermediate film for near-infrared absorption is a polyvinyl acetal resin, the addition of a liquid plasticizer for the polyvinyl acetal resin is beneficial for improving adhesion to the transparent substrate.

[0177] As a plasticizer, a substance that is used as a plasticizer relative to a solid medium can be used. For example, as a plasticizer used in an infrared shielding film made of polyvinyl acetal resin, examples include plasticizers of primary alcohols and organic acid esters, ester-based plasticizers such as polyol organic acid ester compounds, and phosphoric acid-based plasticizers such as organophosphate plasticizers. Any plasticizer is preferably liquid at room temperature. Among these, plasticizers of ester compounds synthesized from polyols and fatty acids are preferred.

[0178] Furthermore, at least one metal selected from the group consisting of silane coupling agents, metal salts of carboxylic acids, metal hydroxides, and metal carbonates can be added to the intermediate film for near-infrared absorption. The metal constituting the metal salt, metal hydroxide, or metal carbonate of the carboxylic acid is not particularly limited, but is preferably selected from at least one metal selected from sodium, potassium, magnesium, calcium, manganese, cesium, lithium, rubidium, and zinc. The content of at least one metal selected from the group consisting of metal salts of carboxylic acids, metal hydroxides, and metal carbonates in the intermediate film for near-infrared absorption is preferably 1% by mass or more and 100% by mass or less relative to the near-infrared absorbing particles.

[0179] Furthermore, the intermediate film for near-infrared absorption may, in addition to the near-infrared absorbing particles already described, contain at least one type of particle selected from the group consisting of oxide particles, composite oxide particles, or boride particles of two or more elements.

[0180] The near-infrared absorbing laminate may contain at least one layer of an interlayer film disposed between transparent substrates, which contains an ultraviolet absorber. Examples of ultraviolet absorbers include one or more compounds selected from compounds having a malonic acid ester structure, compounds having an oxaloaniline structure, compounds having a benzotriazole structure, compounds having a benzophenone structure, compounds having a triazine structure, compounds having a benzoic acid ester structure, and compounds having a hindered amine structure.

[0181] Furthermore, it is obviously preferable that the intermediate layer of the near-infrared absorbing laminate is composed only of the near-infrared absorbing intermediate film according to this embodiment.

[0182] The near-infrared absorption intermediate film described herein is a near-infrared absorbing particle dispersion. It is self-evident that the near-infrared absorbing particle dispersion according to this embodiment can be used without being held by two or more transparent substrates that transmit visible light. That is, the near-infrared absorbing particle dispersion according to this embodiment can be manufactured as a single near-infrared absorbing particle dispersion.

[0183] The near-infrared absorbing laminate according to this embodiment is not limited to the form described above, where a near-infrared absorbing particle dispersion is disposed between transparent substrates. Any configuration can be used if the laminate includes a near-infrared absorbing particle dispersion and a transparent substrate. [Example]

[0184] Hereinafter, the present invention will be specifically described with reference to the examples. However, the present invention is not limited to the following examples. (Evaluation Methods) Here, the evaluation methods in the following examples and comparative examples will be described first. (Chemical Analysis) Chemical analysis of the obtained near-infrared absorbing particles was performed by atomic absorption spectrometry (AAS) for Cs and by ICP emission spectroscopy (ICP-OES) for W (tungsten). For O, a light element analysis apparatus (ON-836) from LECO Corporation was used. (X-ray Diffraction Measurement) X-ray diffraction measurement was performed by powder XRD using Cu-Kα rays with an X'Pert-PRO / MPD apparatus from Spectris Corporation.

[0185] (Optical Properties of Near-Infrared Absorbing Transparent Substrates) The visible light transmittance (VLT) and solar transmittance (ST21) of the near-infrared absorbing transparent substrates were measured according to ISO 9050 and JIS R 3106 (2019). Specifically, the transmittance was measured using a Hitachi High-Tech U-4100 spectrophotometer and calculated by multiplying by the corresponding coefficient of the solar spectrum. For the transmittance measurement, measurements were taken at 5 nm intervals for wavelengths between 300 nm and 2100 nm. The L*a*b* color indices were calculated according to JIS Z 8701 (1999) for the tristimulus values ​​X, Y, and Z relative to a D65 standard light source at a light source angle of 10°, and the tristimulus values ​​were obtained according to JIS Z 8729 (2004). [Example 1] (Preparation and evaluation of near-infrared absorbing particles) A ​​total of 20 g of cesium carbonate (Cs₂CO₃) and tungsten trioxide (WO₃) were weighed, mixed, and kneaded. The resulting mixture was placed in a carbon boat and dried at 110°C for 12 hours in atmospheric conditions. This yielded a cesium tungsten oxide precursor powder, which serves as a raw material for a compound containing Cs and W.

[0186] The above-mentioned cesium tungsten oxide precursor powder was placed in an alumina boat and placed in a heated muffle furnace. While flowing a mixed gas of superheated steam and nitrogen gas at a volume ratio of 50:50, the temperature was raised to 550°C and held for 1 hour. The mixed gas is described in Table 1 as 50% N2-50% superheated H2O. Next, the supplied gas was changed to 100% nitrogen gas, and while flowing the nitrogen gas, the temperature was raised to 800°C and held for 1 hour after holding at 550°C for 0.5 hours. Afterwards, the temperature was lowered to room temperature, yielding a slightly greenish-white powder (first heat treatment step).

[0187] The X-ray powder diffraction pattern of the white powder was identified as Cs4W11O35 (ICDD 00-51-1891).

[0188] Next, the white powder was placed in a carbon boat and placed in a tubular furnace. It was heated in a 1% H₂-Ar gas stream (described as 1% H₂-Ar in Table 1) and held at 550°C for 1 hour for reduction. Then, the supplied gas was changed to 100% Ar gas, and the temperature was maintained at 550°C for 30 minutes while the Ar gas was flowing. The temperature was then increased to 800°C and heated for 1 hour, followed by cooling to room temperature to obtain a light water-colored powder A (second heat treatment process). The manufacturing conditions for the near-infrared absorbing particles are summarized in Table 1. Furthermore, the following evaluation results are shown in Table 2.

[0189] The XRD powder pattern of powder A obtained here is shown in Figure 2, exhibiting a wide two-phase mixed pattern with hexagonal Cs0.32WO3 as the main phase and orthorhombic Cs4W11O35 as the second phase. Chemical analysis of powder A yielded a Cs / W ratio of 0.33 in molar ratio. The composition ratios of other components are shown in Table 2. The XRD powder pattern in this case is a mixture of diffraction lines from both hexagonal Cs0.32WO3 and orthorhombic Cs4W11O35; however, the diffraction lines of Cs4W11O35 show a slight shift in position and intensity from the ideal value. No data matching this diffraction pattern was found in the ICDD database.

[0190] When the powder is observed using a transmission electron microscope (Hitachi High-Tech Co., Ltd. HF-2200), particles 40 as shown in Figure 4(A) are observed. The crystallization of each particle is as shown in the limited field electron diffraction pattern in Figure 4(B). It is not a mixed structure of two phases separated into hexagonal and orthorhombic crystals, but is observed as a single-phase structure. The electron diffraction pattern shown in Figure 4(B) is a pattern corresponding to the

[0001] zone of hexagonal crystal, and the diffraction sites show the plane indices when viewed as hexagonal crystals. If the plane spacing is determined from the closest diffraction sites in the three directions, it is found that only in the (01-10) plane spacing, 3.88 Å is significantly increased compared to the values ​​of 3.48 Å and 3.43 Å in the other two directions, indicating a shift from the correct hexagonal symmetry. In addition, in crystallography, a negative index is indicated by a horizontal line above the number, but for ease of description, a negative sign is added before the number in this specification.

[0191] On the other hand, Figure 4(C) shows an atomic image obtained using the STEM-HAADF method (high-angle scattering dark-field observation in scanning electron mode). In the HAADF method, the larger the atom number, the greater the density of atoms in the projection direction, resulting in brighter and stronger atomic sites. Therefore, if it matches the projection plane information of the

[0001] zone, the type of atoms on a specific image is determined. The strongest site in Figure 4(C) is the W atom, but it is arranged along the (01-10) plane. In the hexagonal crystal, the same arrangement was not observed along the equivalent (1-100) plane and (10-10) plane. A pattern was observed in the (01-10) site direction in Figure 4(C), indicating that a large number of planar defects (W and O defects) are inserted only in the (01-10) plane. This can be interpreted as an increase in the interplanar spacing of the (01-10) plane. If the original crystal was hexagonal, then the (01-10), (1-100), and (10-10) planes, which intersect at 60°, have almost no introduced defects. Only the (01-10) plane has a large number of planar defects inserted, indicating that the hexagonal symmetry has been lost and the crystal has been modulated into an orthorhombic crystal. By means of the regular position of arrow 41 in Figure 4(B), the W-defective plane is introduced with a period of approximately 3.88 Å. As described above, it can be known that the near-infrared absorbing particle is a single crystal particle of cesium tungstate with a quasi-hexagonal crystal structure modulated into an orthorhombic crystal.

[0192] Furthermore, if the obtained near-infrared absorbing particle powder is irradiated with 25W Al-Kα X-rays using X-ray photoelectron spectroscopy (ULVAC-PHI XPS-Versa Probe II) and the excited photoelectrons are observed, it can be seen that the O1s peak near 530.45 eV has a shoulder on the high-energy side. The composition near 532.80 eV is considered to be due to peak separation caused by H2O, and it is found to contain a large amount of OH2. In addition, by thermal desorption spectrophotometry, it can be confirmed that OH and OH2 are expelled from the crystal in the temperature range of 500°C to 700°C when heated. Based on these observations, it is speculated that OH and OH2 are contained in the cesium tungstate of powder A, and furthermore, if the voids in the quasi-hexagonal crystals that elongate along the uniaxial direction are considered, they invade the window voids of the hexagonal channels. It is believed that crystallization in superheated steam introduces water and its decomposition products into the crystals. However, it is also believed that the H+ and H3O+ ions generated at this time compete with the positive W ions, causing some of the W ions to detach. (Preparation and evaluation of near-infrared absorbing particle dispersion) Next, 20% by mass of powder A, 10% by mass of an acrylic polymeric dispersant with amine-containing functional groups (hereinafter referred to as "dispersant a"), and 70% by mass of methyl isobutyl ketone (MIBK) as a solvent were weighed. These materials were placed in a glass container with 0.3 mm diameter silica beads and dispersed and pulverized for 5 hours using a paint shaker to obtain dispersion A.

[0193] Here, the average particle size of the near-infrared absorbing particles in dispersion A (the dispersed particle size measured by the ELS-8000 manufactured by Otsuka Electronics Co., Ltd., a particle size measuring device based on dynamic light scattering method) was 31.4 nm.

[0194] 50 parts by weight of a UV-curable resin (Toa Synthetic Aronix UV-3701) for hard coating were mixed with 100 parts by weight of the dispersion A to prepare a near-infrared absorbing particle coating liquid A. Furthermore, the appropriately diluted near-infrared absorbing coating liquid was applied to a polyethylene terephthalate (PET) resin film (Teijin HPE-50, hereinafter also referred to as "PET film") serving as a transparent film substrate using a rod coater to form a coated film. In other embodiments, the same PET film was used as the transparent substrate.

[0195] A PET film with a coating is dried at 80°C for 5 minutes to evaporate the organic solvent, which is a liquid medium. Then, the hard coating is cured with ultraviolet curing resin using a high-pressure mercury lamp to produce a near-infrared absorbing film A with a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a near-infrared absorbing dispersion, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0196] The transmittance of the obtained near-infrared absorption film A was measured using a Hitachi High-Tech U-4100 spectrophotometer, and the spectrophotometric transmittance spectrum was obtained. The spectrum is shown in Figure 5.

[0197] Based on the spectrum shown in Figure 5, it can be confirmed that there is strong absorption in the near-infrared region with a wavelength of around 2100 nm as the bottom of the transmittance and high transmittance in the visible light region (above 380 nm and below 780 nm).

[0198] The visible light transmittance (VLT) and solar transmittance (ST21) were measured to be VLT = 72.31% and ST21 = 46.47%, respectively, indicating that it is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film A is L* = 87.91, a* = -2.72, b* = 9.33, and the blue color is very weak and close to neutral, that is, it shows a neutral hue. This is evident from the following: as shown in the comparison with the transmittance spectrum of the CWO dispersion film with blue shown in Comparative Example 3 of Figure 5, the transmittance is significantly reduced near the blue wavelength of 400 nm compared with the CWO dispersion film, while the transmittance is significantly increased near the red wavelength of 700 nm compared with the CWO dispersion film.

[0199] Furthermore, as shown in Figure 7, the values ​​of the color index are such that at the L* = 88 section, b* ≧ 0 and b* ≧ 1.6 × a* + 8.0 are fully satisfied. Additionally, in Figure 7, line 71 indicates b* = 0, and line 72 indicates b* = 1.6 × a* + 8.0.

[0200] Furthermore, as shown in Figure 8, it can be seen that the T900 in the L*=88 section is 39.84%, which fully satisfies T900≧10%. In addition, the solar shading characteristic ST21 satisfies ST21≦67%, further fully satisfying T900≧1.4×ST21-41.0, which has sufficient detector wavelength penetration. In addition, in Figure 8, line 81 refers to T900=10, line 82 refers to ST21=67, and line 83 refers to T900=1.4×ST21-41.0. [Comparative Example 1] (Preparation and evaluation of near-infrared absorbing particles) The cesium tungsten oxide precursor powder obtained in Example 1 was added to a carbon boat and heated to 850°C in an atmospheric tubular furnace and held for 20 hours. It was then temporarily cooled to room temperature and pulverized and mixed using a pulverizer. The powder was then heated again to 850°C in the atmosphere and held for 20 hours, followed by cooling to room temperature, yielding an extremely thin, greenish-white powder i. The X-ray powder diffraction pattern of powder i is shown in Figure 2, slightly mixed with Cs6W11O36, but roughly identified as a single phase of Cs4W11O35 (ICDD 0-51-1891). Chemical analysis of powder i showed a Cs / W ratio of 0.36. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersions) Using powder i, dispersion i was obtained by dispersing and pulverizing using the same steps as in Example 1. Dispersion i was grayish-white in color, and the average particle size of the near-infrared absorbing particles in dispersion i was 32.0 nm.

[0201] Following the same steps as in Example 1, UV-curable resin was added to and mixed in dispersion i to obtain coating liquid i, and then a near-infrared absorption film i was obtained. The transmittance spectrum of the near-infrared absorption film i is shown in Figures 5 and 6. As for the spectroscopic characteristics at this time, it can be seen that VLT = 73.33% and ST21 = 78.73%, indicating that the infrared absorption effect is almost non-existent.

[0202] It can be seen that the Hunter color index at the L*=88 section shows a*=0.70 and b*=8.53. As shown in Figure 7, these values ​​do not satisfy b*≧1.6×a*+8.0. The T900 at the L*=88 section is 96.20%, which has high penetrability and fully satisfies T900≧10%. However, in Figure 8, it is drawn on the right side outside the figure, and the sunlight shading characteristic does not satisfy ST21≦67% at all. [Comparative Example 2] A dispersion of In2O3:Sn (hereinafter referred to as "ITO"), which is known as a transparent conductive oxide with a colorless and transparent neutral hue, was prepared. It is known that ITO particles have a neutral hue, but depending on the reduction method and manufacturing method, there are various types of particles ranging from slightly bluish to brownish. Here, ITO powder (powder ii) manufactured by ENAM Corporation, which is close to pure transparent, was used.

[0203] Using this powder ii, and except for the same steps as in Example 1, dispersion ii was obtained by dispersion and pulverization. The color of dispersion ii is water-colored, and the average particle size of the particles in dispersion ii is 30.2 nm.

[0204] Following the same steps as in Example 1, UV-curable resin was added and mixed into dispersion ii to obtain coating liquid ii, and then a near-infrared absorption film ii was obtained. The transmittance spectrum of the near-infrared absorption film ii is shown in Figures 5 and 6, with a peak around 600 nm, showing a curve indicating high transmittance at the red wavelength. As the spectroscopic characteristics at this time, VLT = 72.33% and ST21 = 45.94%, confirming the infrared absorption effect. However, this infrared absorption characteristic is low in this example.

[0205] The Hunter color index at the L*=88 section shows values ​​of a*=-2.04 and b*=13.68. As shown in Figure 7, at the L*=88 section, these values ​​satisfy b*≧1.6×a*+8.0, confirming the neutrality of the hue.

[0206] The T900 in the L*=88 section is 46.39%, exhibiting high penetrability and fully satisfying T900≧10%. Furthermore, as shown in Figure 8, the solar shading characteristics satisfy ST21≦67%, and T900≧1.4×ST21-41.0 is also satisfied. However, it is evident that ST21 shows a higher value compared to the present invention, resulting in lower solar shading characteristics. Furthermore, it is known that approximately five times the amount of ITO particles are required to obtain the same solar shading characteristics as CPT particles, necessitating more ITO raw material. [Comparative Example 3] The cesium tungsten oxide precursor powder obtained in Example 1 was added to a carbon boat. Under a 1 volume% H2 gas flow with N2 as the charge carrier, the mixture was maintained at 550°C for 2 hours, then switched to a 100 volume% N2 gas flow and maintained for 1 hour. Afterward, the temperature was raised to 800°C and maintained for 1 hour, followed by slow cooling to room temperature to obtain powder iii. Powder iii is dark blue in color. The X-ray powder diffraction pattern of powder i is shown in Figure 2, and it was identified as a single phase of Cs0.32WO3 (ICDD 0-81-1244), a hexagonal cesium tungsten oxide. Chemical analysis of powder iii showed a Cs / W ratio of 0.34. The composition ratios of other components are shown in Table 2.

[0207] Using this powder iii, and except for the same steps as in Example 1, dispersion iii was obtained. The color of dispersion iii is blue, and the average particle size of the particles in dispersion iii is 24.6 nm.

[0208] Following the same steps as in Example 1, UV-curable resin was added to and mixed in dispersion iii to obtain coating liquid iii, and then a near-infrared absorption film iii was obtained. The transmittance spectrum of the near-infrared absorption film iii, as shown in Figures 5 and 6, is a curve with high transmittance at the blue wavelength. As a spectroscopic characteristic, VLT = 72.19% and ST21 = 32.88%, confirming a very excellent infrared absorption effect.

[0209] However, as shown in Figure 7, the Hunter color index at the L*=88 section displays values ​​of a*=-6.57 and b*=-1.25, with b* becoming negative, indicating that blue is a prominent hue. However, it satisfies b*≧1.6×a*+8.0.

[0210] As shown in Figure 8, the solar shading characteristics fully meet ST21≦67%, confirming excellent solar shading characteristics. However, T900≧1.4×ST21-41.0 is not met. Furthermore, T900 in the L*=88 section is as low as 4.85%, indicating low detector wavelength penetration.

[0211] Further, the near-infrared absorption film iii was placed in a constant temperature and humidity chamber and kept in an environment of 85°C and 90% relative humidity for 13 days. The transmittance spectrum was then measured and compared with the spectrum before maintenance (initial spectrum in the figure). The results are shown in Figure 9B. [Comparative Examples 4 to 8] By appropriately varying the MIBK dilution rate of the near-infrared absorption particle coating liquid iii prepared by Comparative Example 3, a series of near-infrared absorption films iv to viii with different particle concentrations were prepared. A series of optical property values ​​are summarized in Table 2. As observed in the a*-b* space of the L*=88 section shown in Figure 7, the hue of these films is b*<0, and the blue hue is not improved. That is, even if the blue-hued CWO dispersion is simply diluted, the blue hue remains, suggesting that the material's own physical properties need to be changed in order to improve the hue. As shown in Figure 8, the infrared absorption in Comparative Examples 4 and 5 was too weak, failing to satisfy T900 ≥ 1.4 × ST21 - 41.0. Except for Comparative Examples 4 and 5, T900 < 10, indicating an excessively low value.

[0212] Thus, by changing the concentration of near-infrared absorbing particles in the film, the hue (especially a*), T900, and ST21 can be changed. It is known that in order to satisfy all the requirements well in a balanced way, the physical properties and electronic structure of the material itself need to be changed. [Example 2] (Preparation and evaluation of near-infrared absorbing particles) The cesium tungsten oxide precursor powder prepared in Example 1 was loaded onto an alumina boat and placed in a heated muffle furnace. The temperature was raised to 150°C while flowing with 100% by volume nitrogen gas. The gas supplied here was changed to a mixture of superheated steam and hydrogen and nitrogen gas in a volume ratio of 50:1:49 (expressed in Table 1 as %H2-49%N2-50% superheated H2O). The temperature was raised to 550°C while flowing with this mixed gas and held for 1 hour. It was then cooled directly to room temperature to obtain water-colored powder B (first heat treatment step).

[0213] The X-ray powder diffraction pattern of this powder is shown in Figure 2, exhibiting broad diffraction lines. Hexagonal Cs0.32WO3 is the main phase, but the diffraction lines of orthorhombic Cs4W11O35 and pyrochlore (Cs2O)0.44W2O6 phases are mixed as heterogeneous phases. The diffraction lines of the pyrochlore phase are broad, and the reflection position is slightly offset. It is believed that O, OH, OH2, and OH3 from water are absorbed into the pyrochlore cavity. The (111) face of the cubic pyrochlore phase has a hexagonal symmetry similar to the bottom face of the hexagonal crystal, and the pyrochlore cavity is equivalent to the voids of the hexagonal and trigonal cavities in the hexagonal crystal. In other embodiments, the presence of a small amount of pyrochlore phase reflection in the XRD powder pattern is also frequently observed.

[0214] Furthermore, when a particle in the powder was observed with a transmission electron microscope from the (0001) direction, the position of the prismatic spot in the electron diffraction pattern was only one short one, accompanied by weak spots. Therefore, it can be concluded that the hexagonal crystal is an orthorhombic crystal modulated by prismatic defects.

[0215] Chemical analysis of powder B showed that Cs / W = 0.32. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Using the prepared powder B, dispersion B was obtained by operating in the same manner as in Example 1.

[0216] The average particle size of the near-infrared absorbing particles in dispersion B was determined to be 26.3 nm by dynamic light scattering method.

[0217] Using this dispersion B, except as otherwise described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film B having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0218] For the obtained near-infrared absorption film B, the spectrophotometric transmittance spectrum obtained by a Hitachi High-Tech U-4100 spectrophotometer is shown in Figure 5. Based on the spectrum shown in Figure 5, strong absorption in the near-infrared region with a transmittance base around 1405 nm and transmission in the visible light region from 380 nm to 780 nm can be confirmed. It was confirmed that the transmittance in the blue region is significantly reduced compared to the near-infrared absorption film iii of Comparative Example 3, and the near-infrared transmission around 900 nm is significantly reduced compared to the near-infrared absorption film ii using ITO in Comparative Example 2.

[0219] The visible light transmittance (VLT) and solar transmittance (ST21) were measured to be VLT = 72.20% and ST21 = 39.29%, respectively. It can be seen that it is transparent in visible light and has a strong near-infrared absorption effect.

[0220] The color index of the near-infrared absorbing film B is L* = 87.93, a* = -4.02, b* = 4.29. The blue color is weak and close to neutral, indicating a neutral hue. For a thinly dispersed near-infrared absorbing particle film with a VLT of 70-80% used for automotive window coverings, the blue color is practically imperceptible. As shown in Figure 7, at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0221] Furthermore, as shown in Figure 8, it can be seen that the T900 in the L*=88 section is 16.32%, which satisfies T900≧10%, thus possessing detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0, thus possessing sufficient detector wavelength penetration. [Example 3] (Manufacturing and evaluation of near-infrared absorbing particles) The water-colored powder B obtained in Example 2 was laid on a carbon boat and kept at 550°C for 2 hours in a gas flow of 1 volume% H2-Ar. Next, the supplied gas was changed to 100 volume% nitrogen gas, and the mixture was kept at 550°C for 0.5 hours while the nitrogen gas was flowing. Then, the temperature was increased and kept at 800°C for 1 hour. The mixture was cooled to room temperature to obtain water-colored powder C (second heat treatment step).

[0222] Chemical analysis of powder C yielded a Cs / W ratio of 0.31 by mass. The composition ratios of other components are shown in Table 2.

[0223] The X-ray powder diffraction pattern of powder C is shown in Figure 2. Compared with Examples 1 and 2, it has broad diffraction lines, showing a mixed pattern of diffraction lines from hexagonal Cs0.32WO3 and orthorhombic Cs4W11O35. However, the position and intensity of the diffraction lines of Cs4W11O35 are not completely consistent with the ICDD data.

[0224] One particle in the powder was observed using a transmission electron microscope in the (0001) direction. The results showed that the position of the prismatic site in the electron diffraction pattern was only one short one, accompanied by weak streaks. Therefore, it can be concluded that the hexagonal crystal is an orthorhombic crystal modulated by prismatic defects. (Preparation and evaluation of near-infrared absorbing particle dispersion) Powder C was used, and the same procedure as in Example 1 was followed to prepare dispersion C. The average particle size of the near-infrared absorbing particles in dispersion C was measured to be 29.6 nm by dynamic light scattering.

[0225] Using the dispersion C, except as described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film C having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0226] The spectrophotometric transmittance spectrum of the obtained near-infrared absorption film C is shown in Figure 5. Strong absorption in the near-infrared region around 1800 nm and transmission in the visible light region were confirmed. The transmittance in the blue and red regions decreased and increased, respectively, compared to the near-infrared absorption film iii of Comparative Example 3, and was improved to a neutral color. Furthermore, it was confirmed that the near-infrared transmission around 900 nm was significantly reduced compared to the near-infrared absorption film ii using ITO in Comparative Example 2, and that it exhibited a strong near-infrared absorption effect compared to the near-infrared absorption film ii using ITO.

[0227] The measured values ​​are VLT = 72.31% and ST21 = 43.45%, indicating transparency in visible light and strong near-infrared absorption. The color index of the near-infrared absorption film C is L* = 87.93, a* = -3.24, and b* = 8.19, indicating a weak blue color close to neutral, i.e., displaying a neutral hue. For a thinly dispersed film of this near-infrared absorbing particles with VLT = 70-80% used for automotive window coverings, it can be said that the blue color is almost imperceptible. As shown in Figure 7, at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0228] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 30.10%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 4] (Preparation and evaluation of near-infrared absorbing particles) The light-colored powder B obtained in Example 2 was laid on a carbon boat and heated in a gas stream of 100% volume Ar, held at 800°C for 1 hour. Afterwards, it was cooled to room temperature to obtain the light-colored powder D.

[0229] The X-ray powder diffraction pattern of powder D is shown in Figure 2, exhibiting broad diffraction lines and displaying a mixed pattern of diffraction lines from hexagonal Cs0.32WO3 and orthorhombic Cs4W11O35. The position and intensity of the diffraction lines of Cs4W11O35 are not entirely consistent with the ICDD data.

[0230] When a particle in the powder was observed from the (0001) direction using a transmission electron microscope, the position of the prismatic spot in the electron diffraction pattern was only one short one, accompanied by weak spots. Therefore, it can be concluded that the hexagonal crystal is an orthorhombic crystal modulated by prismatic defects.

[0231] Chemical analysis of powder D showed that Cs / W = 0.33. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Using the prepared powder D, the dispersion D was obtained by operating in the same manner as in Example 1.

[0232] The average particle size of the near-infrared absorbing particles in dispersion D was determined to be 32.1 nm by dynamic light scattering method.

[0233] Using the dispersion D, except as otherwise described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film D having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0234] The spectrophotometric transmittance spectrum of the obtained near-infrared absorption film D is shown in Figure 5. Strong absorption in the near-infrared region around 1950 nm and transmission in the visible light region were confirmed. The transmittance in the blue and red regions decreased and increased, respectively, compared to the near-infrared absorption film iii of Comparative Example 3, and was improved to a neutral color. Furthermore, it was confirmed that the near-infrared transmission around 900 nm was significantly reduced compared to the near-infrared absorption film ii using ITO in Comparative Example 2, and that it exhibited a strong near-infrared absorption effect compared to the near-infrared absorption film ii using ITO.

[0235] Measured as VLT = 72.20% and ST21 = 48.19%, it is known to be transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film D is L* = 87.85, a* = -2.11, b* = 8.75, indicating a weak blue color close to neutral, i.e., displaying a neutral hue. For a thin dispersion film of this near-infrared absorbing particles with VLT = 70-80% used in automotive window coverings, it can be said that the blue color is almost imperceptible. As shown in Figure 7, at the L* = 88 section, it can be seen that b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0236] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 42.56%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 5] (Preparation and evaluation of near-infrared absorbing particles) The light-colored powder B obtained in Example 2 was laid on a carbon boat and heated to 800°C in a gas stream of 100% volume Ar. Here, the supplied gas was changed to 1% volume H2-Ar, and the temperature was maintained at 800°C for 10 minutes in such a gas stream. Afterwards, it was cooled to room temperature, yielding the light-colored powder E.

[0237] The X-ray powder diffraction pattern of powder E is shown in Figure 2, exhibiting broad diffraction lines and displaying a mixed pattern of diffraction lines from hexagonal Cs0.32WO3 and orthorhombic Cs4W11O35. The position and intensity of the diffraction lines of Cs4W11O35 are not entirely consistent with the ICDD data.

[0238] When a particle in the powder was observed from the (0001) direction using a transmission electron microscope, the position of the prismatic spot in the electron diffraction pattern was only one short one, accompanied by weak spots. Therefore, it can be concluded that the hexagonal crystal is an orthorhombic crystal modulated by prismatic defects.

[0239] Chemical analysis of powder E showed that Cs / W = 0.32. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Using the prepared powder E, the dispersion E was obtained by operating in the same manner as in Example 1.

[0240] The average particle size of the near-infrared absorbing particles in dispersion E was determined to be 25.0 nm by dynamic light scattering.

[0241] Using the dispersion E, except as described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film E having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0242] The spectrophotometric transmittance spectrum of the obtained near-infrared absorption film E is shown in Figure 6. Strong absorption in the near-infrared region around 1600 nm and transmission in the visible light region were confirmed. The transmittance in the blue and red regions decreased and increased, respectively, compared to the near-infrared absorption film iii of Comparative Example 3, and was improved to a neutral color. Furthermore, it was confirmed that the near-infrared transmission around 900 nm was significantly reduced compared to the near-infrared absorption film ii using ITO in Comparative Example 2, and that it exhibited a strong near-infrared absorption effect compared to the near-infrared absorption film ii using ITO.

[0243] The measured values ​​are VLT = 72.38% and ST21 = 36.29%, indicating transparency in visible light and strong near-infrared absorption. The color index of the near-infrared absorption film E is L* = 88.12, a* = -5.17, and b* = 3.79, indicating a weak blue color close to neutral, i.e., displaying a neutral hue. For a thinly dispersed film of this near-infrared absorbing particles with VLT = 70-80% used for automotive window coverings, it can be said that the blue color is almost imperceptible. As shown in Figure 7, at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0244] In addition, as shown in Figure 8, the T900 in the L*=88 section is 11.80%, which satisfies T900≧10%, thus indicating that it has detector wavelength penetration. Furthermore, the solar shading characteristics satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. 〔Example 6〕 (Preparation and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) The water-colored powder E obtained in Example 5 was used, and the dispersion time was doubled. Otherwise, the operation was the same as in Example 1 to obtain dispersion F.

[0245] The average particle size of the near-infrared absorbing particles in the dispersion F was determined to be 23.7 nm by dynamic light scattering.

[0246] Using the dispersion F, except as otherwise described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film F having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0247] The spectroscopic transmittance spectrum of the obtained near-infrared absorption film F is shown in Figure 6. Strong absorption in the near-infrared region, with a bottom around 1600 nm, and transmission in the visible light region are confirmed. The spectrum is almost identical to that of the near-infrared absorption film E prepared in Example 5, except that the transmittance in the blue region is slightly increased. The average particle size decreases with increasing dispersion time, thus increasing the transmission of blue wavelengths due to Mie scattering. Compared to Example 5, the transmittance spectrum confirms a slight increase in the blue hue, but compared to the near-infrared absorption film of Comparative Example 3, the hue has been improved.

[0248] The measured values ​​were VLT = 72.28% and ST21 = 36.40%, indicating that it is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film F is L* = 88.15, a* = -5.00, and b* = 0.93. Compared with the near-infrared absorption film iii of Comparative Example 3, the blue color is weaker and closer to a neutral color, that is, it shows a neutral hue.

[0249] As shown in Figure 7, these values ​​indicate that at section L* = 88, b* ≧ 0 and b* ≧ 1.6 × a* + 8.0 are satisfied.

[0250] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 11.24%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 7] (Preparation and evaluation of near-infrared absorbing particles) The light-colored powder B obtained in Example 2 was laid on a carbon boat and held at 500°C for 30 minutes in a gas flow of 1 volume% H2-Ar. Next, the supplied gas was changed to 100 volume% nitrogen gas, and while flowing nitrogen gas, it was held at 550°C for 30 minutes, and then further heated to 800°C for 1 hour. Afterwards, it was cooled to room temperature to obtain the light-colored powder G.

[0251] The X-ray powder diffraction pattern of powder G is shown in Figure 2, exhibiting broad diffraction lines and displaying a mixed pattern of diffraction lines from hexagonal Cs0.32WO3 and orthorhombic Cs4W11O35. The position and intensity of the diffraction lines of Cs4W11O35 are not entirely consistent with the ICDD data.

[0252] When a particle in the powder was observed from the (0001) direction using a transmission electron microscope, the position of the prismatic spot in the electron diffraction pattern was only one short one, accompanied by weak spots. Therefore, it can be concluded that the hexagonal crystal is an orthorhombic crystal modulated by prismatic defects.

[0253] Chemical analysis of powder G showed that Cs / W = 0.31. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) The prepared powder G was used, except that the operation was the same as in Example 1, to obtain dispersion G.

[0254] The average particle size of the near-infrared absorbing particles in the dispersion G was determined to be 31.8 nm by dynamic light scattering.

[0255] Using the dispersion G, except as described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film G having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0256] The spectroscopic transmittance spectrum of the obtained near-infrared absorption film G is shown in Figure 6. Strong absorption in the near-infrared region around 1850 nm and transmission in the visible light region were confirmed. The transmittance in the blue and red regions decreased and increased, respectively, compared to the near-infrared absorption film iii of Comparative Example 3, and was improved to a neutral color. Furthermore, it was confirmed that the near-infrared transmission around 900 nm was significantly reduced compared to the near-infrared absorption film ii using ITO in Comparative Example 2, and that it exhibited a strong near-infrared absorption effect compared to the near-infrared absorption film ii using ITO.

[0257] The measured values ​​are VLT = 72.29% and ST21 = 41.88%, indicating transparency in visible light and strong near-infrared absorption. The color index of the near-infrared absorption film G is L* = 87.94, a* = -3.54, and b* = 7.59, indicating a weak blue color close to neutral, i.e., displaying a neutral hue. For a thinly dispersed film of this near-infrared absorbing particles with VLT = 70-80% used for automotive window coverings, it can be said that the blue color is almost imperceptible. As shown in Figure 7, at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0258] In addition, as shown in Figure 8, the T900 in the L*=88 section is 26.36%, which satisfies T900≧10%, so it can be seen that it has detector wavelength penetration. Furthermore, the solar shading characteristics satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0.

[0259] The near-infrared absorption film G was placed in a constant temperature and humidity chamber and kept in an environment with a temperature of 85°C and a relative humidity of 90% for 15 days. The transmittance spectrum was then measured and compared with the spectrum before the maintenance period. The results are shown in Figure 9A. As already described, the same test was performed on the near-infrared absorption film iii prepared by Comparative Example 3 (maintenance period of 13 days), and the spectrum was compared with the spectrum before the test. As shown in Figures 9A and 9B, in the near-infrared absorption film G of Example 7, the change in ST21 was 0.04%, which was almost no change. However, in the near-infrared absorption film iii of Comparative Example 3, a partial decrease in the intensity of near-infrared absorption was observed, while ST21 changed by 3.47%. [Example 8] A total of 20 g of cesium carbonate (Cs₂CO₃) and tungsten trioxide (WO₃) were weighed out, mixed, and kneaded. The resulting mixture was placed in a carbon boat and dried at 110°C for 12 h in atmospheric conditions. This yielded a cesium tungsten oxide precursor powder, which serves as a raw material for a compound containing Cs and W.

[0260] Moreover, the above-mentioned cesium tungsten oxide precursor powder was used, and the first heat treatment process was performed under the same conditions as in Example 2.

[0261] The powder obtained from the first heat treatment process was laid on a carbon boat and heated to 800°C in a gas stream of 100% Ar by volume. Then, the supplied gas was changed to a gas stream of 1% H2-Ar by volume, and the gas was kept at 800°C for 10 minutes while flowing such gas, and then cooled to room temperature to obtain a water-colored powder H.

[0262] The X-ray powder diffraction pattern of powder H has broad diffraction lines, showing a mixed pattern of diffraction lines from hexagonal Cs0.20WO3 (ICDD0-083-1333) and orthorhombic Cs4W11O35. The position and intensity of the diffraction lines of Cs4W11O35 are not entirely consistent with the ICDD data.

[0263] One particle in the powder was observed with a transmission electron microscope from the (0001) direction. The results showed that the position of the prismatic spot in the electron diffraction pattern was only one short one, accompanied by weak spots. Therefore, it was identified as a hexagonal crystal that was modulated by prismatic defects.

[0264] Chemical analysis of powder H showed that Cs / W = 0.20. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Powder H was prepared, and dispersion H was obtained by operating in the same manner as in Example 1.

[0265] The average particle size of the near-infrared absorbing particles in the dispersion H was determined to be 28.6 nm by dynamic light scattering.

[0266] Using the dispersion H, except as described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film H having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0267] The spectrophotometer of the near-infrared absorption film H shows VLT = 72.32% and ST21 = 46.98%, indicating transparency in visible light and strong near-infrared absorption. The color index of the near-infrared absorption film H is L* = 88.04, a* = -2.40, and b* = 8.51, indicating a weak blue color close to neutral, i.e., displaying a neutral hue. For a thinly dispersed near-infrared absorbing particle film with VLT = 70-80% used in automotive window coverings, it is practically a film with almost no blue tint. As shown in Figure 7, at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0268] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 38.30%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 9] A total of 20g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed in a molar ratio of Cs2CO3:WO3 = 3:10, mixed, and kneaded. The resulting mixture was placed in a carbon boat and dried at 110°C for 12h in the atmosphere. Thus, a cesium tungsten oxide precursor powder, serving as a raw material for a compound containing Cs and W, was obtained.

[0269] Moreover, the above-mentioned cesium tungsten oxide precursor powder was used, and the first heat treatment process was performed under the same conditions as in Example 2.

[0270] The powder obtained from the first heat treatment process was laid on a carbon boat and heated to 800°C in a gas stream of 100% Ar. Then, the supplied gas was changed to 1% H2-Ar, and the temperature was maintained at 800°C for 10 minutes while such gas was flowing, and then cooled to room temperature to obtain water-colored powder I.

[0271] The X-ray powder diffraction pattern of powder I has broad diffraction lines, with rhombohedral Cs6W11O36 and Cs8.5W15O48 as the main phases, showing a slightly mixed pattern of hexagonal Cs0.32WO3 and tetragonal Cs2W3O10 diffraction lines. However, the position and intensity of the diffraction lines of Cs6W11O36 and Cs8.5W15O48 are not completely consistent with the ICDD data.

[0272] One particle in the powder was observed from the (0001) direction using a transmission electron microscope. The results showed that the positions of the three prismatic sites in the electron diffraction pattern all exceeded the experimental error range. Therefore, it can be concluded that the hexagonal crystal is mainly composed of rhombohedral crystals modulated by the bottom surface defects.

[0273] Chemical analysis of powder I showed Cs / W = 0.59. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Using the prepared powder I, dispersion I was obtained by operating in the same manner as in Example 1.

[0274] The average particle size of the near-infrared absorbing particles in dispersion I was determined to be 30.4 nm by dynamic light scattering method.

[0275] Using this dispersion I, except as otherwise described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film I having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0276] The spectrophotometer of the obtained near-infrared absorption film I shows VLT = 72.27% and ST21 = 43.25%, indicating that it is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film I is L* = 87.97, a* = -3.70, b* = 6.61, indicating a weak blue color close to neutral, i.e., displaying a neutral hue. For a thinly dispersed near-infrared absorbing particle film with VLT = 70-80% used for automotive window coverings, it can be said that the blue color is almost imperceptible. As shown in Figure 7, at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0277] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 28.51%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 10] A total of 20g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed in a molar ratio of Cs2CO3:WO3=2:11, mixed, and kneaded. The resulting mixture was placed in a carbon boat and dried at 110°C for 12h in the atmosphere. Thus, a cesium tungsten oxide precursor powder, serving as a raw material for a compound containing Cs and W, was obtained.

[0278] Moreover, using the above-mentioned cesium tungsten oxide precursor powder, except that the first heat treatment process was performed under the same conditions as in Example 2, a light green powder J was obtained.

[0279] The X-ray powder diffraction pattern of powder J has broad diffraction lines, with the pyrochlore phase (Cs₂O)₀.₄W₂O₆ as the main phase, showing a slightly mixed pattern of diffraction lines from hexagonal Cs₀.₃₂WO₃ and orthorhombic Cs₄W₁₁O₃₅. However, the positions and intensities of the diffraction lines of (Cs₂O)₀.₄W₂O₆ and Cs₄W₁₁O₃₅ are not entirely consistent with the ICDD data.

[0280] The electron diffraction pattern of the cubic crystal was obtained during transmission electron microscopy observation of the powder.

[0281] Chemical analysis of powder J showed that Cs / W = 0.36. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Using the prepared powder J, the dispersion J was obtained by operating in the same manner as in Example 1.

[0282] The average particle size of the near-infrared absorbing particles in the dispersion J was determined to be 31.6 nm by dynamic light scattering.

[0283] Using the dispersion J, except as otherwise described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film J having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0284] The spectrophotometer of the obtained near-infrared absorption film J shows VLT = 72.37% and ST21 = 50.79%, indicating that it is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film J is L* = 87.87, a* = -1.44, and b* = 11.06, indicating that the blue color is extremely weak and close to neutral, showing a neutral hue. For a thinly dispersed near-infrared absorbing particle film with VLT = 70-80% used for automotive window coverings, it can be said that the blue color is almost imperceptible. As shown in Figure 7, at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0285] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 40.60%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 11] (Preparation and evaluation of near-infrared absorbing particles) Powder J prepared in Example 10 was laid on a carbon boat, and the temperature was raised to 800°C while flowing with 100% by volume Ar gas. Moreover, the supplied gas was changed to 1% by volume H2-Ar, and the temperature was maintained at 800°C for 10 minutes while flowing with such gas, and then cooled to room temperature to obtain a water-colored powder K.

[0286] The X-ray powder diffraction pattern of this powder is shown in Figure 3, displaying a mixed pattern of diffraction lines from hexagonal Cs0.32WO3, orthorhombic Cs4W11O35, rhombohedral Cs6W11O36, and Cs8.5W15O48. However, the positions and intensities of the diffraction lines of Cs4W11O35, Cs6W11O36, and Cs8.5W15O48 are not entirely consistent with the ICDD data.

[0287] One particle in the powder was observed from the (0001) direction using a transmission electron microscope. The results showed that the positions of the three prismatic sites in the electron diffraction pattern all exceeded the experimental error range. Therefore, it can be concluded that the hexagonal crystal is mainly composed of rhombohedral crystals modulated by the bottom surface defects.

[0288] Chemical analysis of powder K showed Cs / W = 0.36. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Using the prepared powder K, the dispersion K was obtained by operating in the same manner as in Example 1.

[0289] The average particle size of the near-infrared absorbing particles in the dispersion K was determined to be 27.5 nm by dynamic light scattering.

[0290] Using the dispersion K, except as described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film K having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0291] The spectrophotometer of the obtained near-infrared absorption film K, obtained using a Hitachi High-Tech U-4100 spectrophotometer, is shown in Figure 6. Based on the spectrum shown in Figure 6, strong absorption in the near-infrared region, with a transmittance around 1650 nm as the bottom, and transmission in the visible light region from 380 nm to 780 nm can be confirmed. The transmittance in the blue and red regions is decreased and increased, respectively, compared to the near-infrared absorption film iii of Comparative Example 3, and is improved to a neutral color. Furthermore, it is confirmed that the near-infrared transmission around 900 nm is significantly increased compared to the near-infrared absorption film iii of Comparative Example 3, indicating strong transmittance at the detector wavelength.

[0292] The visible light transmittance (VLT) and solar transmittance (ST21) were measured to be VLT = 72.36% and ST21 = 44.01%, respectively. It can be seen that it is transparent in visible light and has a strong near-infrared absorption effect.

[0293] The color index of the near-infrared absorbing film K is L* = 88.10, a* = -2.72, b* = 7.05. The blue color is extremely weak and close to a neutral color, that is, it displays a neutral hue. For the thin dispersion film of this near-infrared absorbing particles used for automotive window coverings with a VLT of 70-80%, it can be said that the blue color is almost imperceptible. As shown in Figure 7, these values ​​satisfy b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 at the L* = 88 section.

[0294] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 27.21%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0. [Example 12] (Preparation and evaluation of near-infrared absorbing particles) Powder J prepared in Example 10 was laid on a carbon boat and kept at 500°C for 30 minutes in a gas flow of 1 volume% H2-Ar. Moreover, the supplied gas was changed to 100 volume% nitrogen gas, and the mixture was kept at 800°C for 1 hour while flowing with such nitrogen gas, and then cooled to room temperature to obtain a water-colored powder L.

[0295] The X-ray powder diffraction pattern of this powder is shown in Figure 3, displaying a mixed pattern of diffraction lines from hexagonal Cs0.32WO3, orthorhombic Cs4W11O35, rhombohedral Cs6W11O36, and Cs8.5W15O48. However, the positions and intensities of the diffraction lines of Cs4W11O35, Cs6W11O36, and Cs8.5W15O48 are not entirely consistent with the ICDD data.

[0296] One particle in the powder was observed from the (0001) direction using a transmission electron microscope. The results showed that the positions of the three prismatic sites in the electron diffraction pattern all exceeded the experimental error range. Therefore, it can be concluded that the hexagonal crystal is mainly composed of rhombohedral crystals modulated by the bottom surface defects.

[0297] Chemical analysis of powder L showed Cs / W = 0.35. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Powder L was prepared, and dispersion L was obtained by operating in the same manner as in Example 1, except that.

[0298] The average particle size of the near-infrared absorbing particles in the dispersion L was determined to be 28.6 nm by dynamic light scattering.

[0299] Using the dispersion L, except as otherwise described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film L having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0300] The spectral transmittance of the obtained near-infrared absorption film L was measured, and the results were VLT = 72.35% and ST21 = 60.85%, indicating that it is transparent in visible light and has a strong near-infrared absorption effect.

[0301] The color index of the near-infrared absorption film L is L* = 87.89, a* = -0.44, b* = 9.26. The blue color is extremely weak and close to a neutral color, showing a neutral hue. As shown in Figure 7, these values ​​indicate that at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0302] Furthermore, the T900 in the L*=88 section is 64.02%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0. [Example 13] A total of 20g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed in a molar ratio of Cs2CO3:WO3=1:5, mixed, and kneaded. The resulting mixture was placed in a carbon boat and dried at 110°C for 12h in the atmosphere. Thus, a cesium tungsten oxide precursor powder, serving as a raw material for a compound containing Cs and W, was obtained.

[0303] Furthermore, the aforementioned precursor powder was placed in an alumina boat and positioned in a heated muffle furnace, where it was heated to 150°C while 100% by volume nitrogen gas was flowing through it. The gas supplied here was then changed to a mixture of superheated steam, hydrogen, and nitrogen gas in a volume ratio of 50:1:49, and the temperature was increased to 550°C while flowing through this mixed gas, and maintained for 1 hour. It was then directly cooled to room temperature to obtain a water-colored powder M (first heat treatment step).

[0304] The X-ray powder diffraction pattern of powder M has broad diffraction lines, obtaining the same pattern as in Example 10. That is, the pyrochlore phase (Cs₂O)₀.₄W₂O₆ is the main phase, in which a slightly mixed pattern of diffraction lines of hexagonal Cs₀.₃₂WO₃ and orthorhombic Cs₄W₁₁O₃₅ is shown. However, the position and intensity of the diffraction lines of (Cs₂O)₀.₄W₂O₆ and Cs₄W₁₁O₃₅ are not completely consistent with the ICDD data.

[0305] The electron diffraction pattern of the cubic crystal was obtained during transmission electron microscopy observation of the powder.

[0306] Chemical analysis of powder M showed Cs / W = 0.40. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Using the prepared powder M, the dispersion M was obtained by operating in the same manner as in Example 1.

[0307] The average particle size of the near-infrared absorbing particles in the dispersion M was determined to be 32.3 nm by dynamic light scattering method.

[0308] Using the dispersion M, except as described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film M having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0309] The spectrophotometer obtained from the Hitachi High-Tech U-4100 spectrophotometer for the obtained near-infrared absorption film M is shown in Figure 6. Based on the spectrum shown in Figure 6, strong absorption in the near-infrared region with a transmittance around 1470 nm and transmission in the visible light region from 380 nm to 780 nm can be confirmed. The transmittance in the blue and red regions is decreased and increased, respectively, compared to the near-infrared absorption film iii of Comparative Example 3, and is improved to a neutral color. Furthermore, it is confirmed that the near-infrared transmission around 900 nm is significantly increased compared to the near-infrared absorption film iii of Comparative Example 3, indicating strong transmittance at the detector wavelength.

[0310] The visible light transmittance (VLT) and solar transmittance (ST21) were measured to be VLT = 72.38% and ST21 = 50.81%, respectively. It can be seen that it is transparent in visible light and has a strong near-infrared absorption effect.

[0311] The color index of the near-infrared absorbing film M is L* = 87.87, a* = -1.46, b* = 10.98, indicating an extremely weak blue color and a neutral hue. For a thinly dispersed near-infrared absorbing particle film with a VLT of 70-80% used for automotive window coverings, it is practically a film where the blue color is almost imperceptible. As shown in Figure 7, these values ​​satisfy b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 at the L* = 88 section.

[0312] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 40.43%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0. [Example 14] (Preparation and evaluation of near-infrared absorbing particles) Powder M prepared in Example 13 was laid on a carbon boat, and the temperature was raised to 800°C while flowing with 100% by volume Ar gas. Moreover, the supplied gas was changed to 1% by volume H2-Ar, and the temperature was maintained at 800°C for 10 minutes while flowing with such gas, and then cooled to room temperature to obtain a water-colored powder N.

[0313] The X-ray powder diffraction pattern of this powder is shown in Figure 3, displaying a mixed pattern of diffraction lines from hexagonal Cs0.32WO3, orthorhombic Cs4W11O35, rhombohedral Cs6W11O36, and Cs8.5W15O48. However, the positions and intensities of the diffraction lines of Cs4W11O35, Cs6W11O36, and Cs8.5W15O48 are not entirely consistent with the ICDD data.

[0314] One particle in the powder was observed from the (0001) direction using a transmission electron microscope. The results showed that the positions of the three prismatic points in the electron diffraction pattern all exceeded the experimental error range. Therefore, it can be concluded that the hexagonal crystal is mainly composed of rhombohedral crystals modulated by the bottom surface defects.

[0315] Chemical analysis of powder N showed Cs / W = 0.42. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) The prepared powder N was used, and the same procedure as in Example 1 was followed to obtain dispersion N.

[0316] The average particle size of the near-infrared absorbing particles in the dispersion N was determined to be 25.2 nm by dynamic light scattering.

[0317] Using the dispersion N, except as described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film N having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0318] The spectrophotometer of the obtained near-infrared absorption film N, obtained using a Hitachi High-Tech U-4100 spectrophotometer, is shown in Figure 6. Based on the spectrum shown in Figure 6, strong absorption in the near-infrared region, with a transmittance base around 1630 nm, and transmission in the visible light region from 380 nm to 780 nm can be confirmed. The transmittance in the blue and red regions is reduced and increased, respectively, compared to the near-infrared absorption film iii of Comparative Example 3, and is improved to a neutral color. Furthermore, it is confirmed that the near-infrared transmission around 900 nm is significantly increased compared to the near-infrared absorption film iii of Comparative Example 3, indicating strong detector wavelength penetration.

[0319] The visible light transmittance (VLT) and solar transmittance (ST21) were measured to be VLT = 72.32% and ST21 = 44.99%, respectively. It can be seen that it is transparent in visible light and has a strong near-infrared absorption effect.

[0320] The color index of the near-infrared absorbing film N is L* = 88.01, a* = -2.66, b* = 7.17, indicating an extremely weak blue color and a neutral hue. For a thinly dispersed near-infrared absorbing particle film with a VLT of 70-80% used in automotive window coverings, it is practically a film where the blue color is almost imperceptible. As shown in Figure 7, these values ​​satisfy b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 at the L* = 88 section.

[0321] Furthermore, as shown in Figure 8, the T900 in the L*=88 section is 27.74%, satisfying T900≧10%, thus indicating that it has detector wavelength penetration. In addition, the solar shading characteristics satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0. [Example 15] (Preparation and evaluation of near-infrared absorbing particles) Powder M prepared in Example 13 was laid on a carbon boat and held at 500°C for 30 minutes in a gas flow of 1 volume% H2-Ar. Moreover, the supplied gas was changed to 100 volume% Ar, and the gas was flowed while holding at 550°C for 30 minutes. Then, the temperature was further increased, and the temperature was held at 800°C for 1 hour. After cooling to room temperature, a water-colored powder O was obtained.

[0322] The X-ray powder diffraction pattern of this powder is shown in Figure 3, displaying a mixed pattern of diffraction lines from hexagonal Cs0.32WO3, orthorhombic Cs4W11O35, rhombohedral Cs6W11O36, and Cs8.5W15O48. However, the positions and intensities of the diffraction lines of Cs4W11O35, Cs6W11O36, and Cs8.5W15O48 are not entirely consistent with the ICDD data.

[0323] One particle in the powder was observed from the (0001) direction using a transmission electron microscope. The results showed that the positions of the three prismatic points in the electron diffraction pattern all exceeded the experimental error range. Therefore, it can be concluded that the hexagonal crystal is mainly composed of rhombohedral crystals modulated by the bottom surface defects.

[0324] Chemical analysis of powder O showed Cs / W = 0.42. The composition ratios of other components are shown in Table 2. (Preparation and evaluation of near-infrared absorbing particle dispersion) Using the prepared powder O, the dispersion O was obtained by operating in the same manner as in Example 1.

[0325] The average particle size of the near-infrared absorbing particles in the dispersion O was determined to be 29.9 nm by dynamic light scattering method.

[0326] Using this dispersion O, except as described in Example 1, a coating film was formed on a PET film, and the UV-curable resin was cured to produce a near-infrared absorbing film O having a coating layer containing near-infrared absorbing particles. Furthermore, the coating layer is a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film is a near-infrared absorbing transparent substrate.

[0327] The spectral transmittance of the obtained near-infrared absorption film O was measured, and the results showed that VLT = 72.35% and ST21 = 65.41%, indicating that it is transparent in visible light and has near-infrared absorption effect.

[0328] The color index of the near-infrared absorption film O is L* = 87.91, a* = -0.03, b* = 8.21. The blue color is extremely weak, showing a neutral hue close to that of ITO. As shown in Figure 7, these values ​​indicate that at the L* = 88 section, b* ≥ 0 and b* ≥ 1.6 × a* + 8.0 are satisfied.

[0329] In addition, the T900 in the L*=88 section is 70.15%, which satisfies T900≧10%, so it can be seen that it has detector wavelength penetration. Furthermore, the solar shading characteristics satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0.

[0330] [Table 1][Table 2] The XRD powder patterns of the powders prepared in Examples 1 to 8 all showed a mixed pattern of hexagonal Cs0.32WO3 and orthorhombic Cs4W11O35. However, the intensity ratio and position of the diffraction lines were observed to be out of phase with the ICDD data, which was thought to be due to the effect of irregular insertion of planar defects into the prismatic surface. It was confirmed that the (0001) electron diffraction pattern at the prismatic surface site was modulated towards the crystal structure of the orthorhombic crystal with an increase in the interplanar spacing. In addition, in the XRD powder patterns of the powders prepared in Examples 9 to 15, a mixture of hexagonal Cs0.32WO3 and rhombohedral Cs6W11O36, Cs8.5W15O48 or pyrochlore phase (Cs2O)0.44W2O6 was observed. The position and intensity distribution of the rhombohedral and pyrochlore phase diffraction lines were observed to be out of phase with the ICDD data. It was confirmed that the three types of prismatic sites in the (0001) electron diffraction pattern were accompanied by changes in the facet spacing, indicating modulation towards a rhombohedral crystal structure. Furthermore, in the powder with a pattern identified as a pyrochlore phase by XRD, a cubic electron diffraction pattern was confirmed. Thus, it can be confirmed that the cesium tungstate contained in the powders prepared in Examples 1-15 has a quasi-hexagonal crystal structure.

[0331] As shown in the transmittance spectra of Figures 5 and 6, in Examples 1 to 7, 11, 13, and 14, the bottom of the absorption occurs with large near-infrared absorption in the wavelength range of 1400 nm to 2000 nm. Furthermore, at visible wavelengths, the spectra of the near-infrared absorption film iii of Comparative Example 3 (which has strong blue) and the near-infrared absorption film ii of Comparative Example 2 (which is neutral) are located between these two spectra. Compared to the near-infrared absorption film iii, the spectrum is weak in blue and strong in red, indicating an improvement in hue towards neutrality.

[0332] In the a*-b* space of the L*=88 cross section in Figure 7, the near-infrared absorption films of Examples 1 to 15 are located between the near-infrared absorption film ii of Comparative Example 2 and the near-infrared absorption film iii of Comparative Example 3, confirming the neutralization of the hue.

[0333] Furthermore, regarding the degree of low solar transmittance and the degree of high detector wavelength transmittance, as shown in Figure 8 and Table 2, it was confirmed that the near-infrared absorption film ii of Comparative Example 2 and the near-infrared absorption films of Examples 1 to 15 were in the ideal range.

[0334] Based on the results in Figure 9A, it can be confirmed that even when the near-infrared absorption film G of Example 7 is added to a constant temperature and humidity chamber and kept in an environment with a temperature of 85°C and a relative humidity of 90% for 15 days, the optical spectrum does not change. In contrast, it can be confirmed that the near-infrared absorption film iii of Comparative Example 3 has changed.

[0335] The X-ray powder diffraction pattern of powder G involved in Example 7, as shown in Figure 2, has broad diffraction lines, showing a mixed pattern of diffraction lines of hexagonal Cs0.32WO3 and orthorhombic Cs4W11O35. Therefore, in a way that can suppress the substitution reaction between Cs and water molecules, which is the cause of humidity degradation and moisture degradation in hexagonal tungsten bronze, it is believed that the cavity and window of the hexagonal channel, which is the main diffusion pathway for oxygen diffusion, are embedded by Cs, O, OH, OH2, and OH3.

[0336] In contrast, the powder iii involved in Comparative Example 3, as shown in Figure 2, was identified as a single phase of Cs0.32WO3 (ICDD 0-81-1244), a hexagonal cesium tungsten oxide, which did not adequately encapsulate the cavity and window of the hexagonal channel. Therefore, it was considered that the substitution reaction between Cs and water molecules was not easily suppressed. This application claims priority based on Japanese Patent Application No. 2020-173574 filed with the Japanese Patent Office on October 14, 2020, and incorporates the entire contents of Japanese Patent Application No. 2020-173574 into this international application. [Simplified Explanation of the Diagram]

[0021] [Figure 1A] is a diagram showing the composition of Cs, W, and O with Cs, W, and O as each vertex. [Figure 1B] is a magnified diagram showing a portion of the composition of Cs, W, and O with Cs, W, and O as each vertex. [Figure 2] is a powder XRD diffraction pattern of near-infrared absorbing particles prepared in Examples 1-7 and Comparative Examples 1 and 3. [Figure 3] is a powder XRD diffraction pattern of near-infrared absorbing particles prepared in Examples 10-15. [Figure 4] is a transmission electron microscope bright-field image, confined-field electron diffraction image, and high-angle scattering dark-field (HAADF) image of near-infrared absorbing particles prepared in Example 1. [Figure 5] is a spectrophotometric transmittance spectrum of near-infrared absorbing films prepared in Examples 1-4 and Comparative Examples 1-3. [Figure 6] is a spectrophotometric transmittance spectrum of near-infrared absorbing films prepared in Examples 5-7, 11, 13, 14, and Comparative Examples 1-3. [Figure 7] is a graph showing the Hunter color index b* value relative to the a* value of the near-infrared absorbing particle dispersions prepared in Examples 1-15 and Comparative Examples 1-8. [Figure 8] is a graph showing the transmittance (T900) at a wavelength of 900 nm relative to the solar transmittance (ST21) of the near-infrared absorbing particle dispersions prepared in Examples 1-11, 13, 14 and Comparative Examples 2-5. [Figure 9A] is a graph showing the damp heat resistance characteristics of the near-infrared absorbing film prepared in Example 7. [Figure 9B] is a graph showing the damp heat resistance characteristics of the near-infrared absorbing film prepared in Comparative Example 3. [Figure 10] is a schematic diagram of near-infrared absorbing particles with a coating. [Figure 11] is a schematic diagram of a near-infrared absorbing particle dispersion. [Figure 12] is a schematic diagram of a near-infrared absorbing particle dispersion. [Figure 13] is a schematic diagram of a near-infrared absorbing laminate. [Figure 14] is a schematic diagram of a near-infrared absorbing transparent substrate.

Claims

1. A near-infrared absorbing particle comprising cesium tungstate, wherein the cesium tungstate has a crystal structure modulated into one or more quasi-hexagonal crystals selected from orthorhombic, rhombohedral, and cubic crystals, the cesium tungstate being represented by the general formula CsxWyOz, having a composition within the region enclosed by four straight lines x = 0.6y, z = 2.5y, y = 5x and Cs₂O:WO₃ = m:n in a ternary composition diagram with Cs, W, and O as vertices, wherein... m and n are integers.

2. The near-infrared absorbing particles of Request 1 contain one or more additives selected from O, OH, OH2, and OH3.

3. Near-infrared absorbing particles as in claim 2, wherein, The added component is present at one or more of the following positions: hexagonal windows, hexagonal cavities, and trigonal cavities formed by WO6 octahedra selected from the crystals of this cesium tungstate.

4. Near-infrared absorbing particles as described in any of claims 1 to 3, wherein, A portion of one or more elements selected from Cs and W that constitute the crystal of this cesium tungstate has a defect, and the x and y of the general formula CsxWyOz have a relationship of 0.2≦x / y≦0.

6.

5. Near-infrared absorbing particles as described in any of claims 1 to 3, wherein, A portion of the O atom in the WO6 octahedron that makes up the crystal of this cesium tungstate is defective.

6. Near-infrared absorbing particles as described in any of claims 1 to 3, wherein, A portion of the Cs in this cesium tungstate is replaced by an added element, which is selected from one or more of Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

7. The near-infrared absorbing particles of any of the requests 1 to 3 have an average particle size of 0.1 nm to 200 nm.

8. The near-infrared absorbing particles of any one of claims 1 to 3 are coated with a compound containing one or more atoms selected from Si, Ti, Zr, and Al.

9. A method for manufacturing near-infrared absorbing particles, which is the method for manufacturing near-infrared absorbing particles according to any one of claims 1 to 8, comprising a first heat treatment step: heating a compound raw material containing Cs and W in an environment containing water vapor, or in an environment containing water vapor and a reducing gas, at a temperature of 400°C to 650°C.

10. The method for manufacturing near-infrared absorbing particles as claimed in claim 9, wherein after the first heat treatment step, a second heat treatment step is performed: heating at a temperature of 500°C to 950°C in an environment containing a reducing gas.

11. A near-infrared absorbing particle dispersion comprising: near-infrared absorbing particles of any one of claims 1 to 8 and a solid medium.

12. The near-infrared absorbing particle dispersion as claimed in claim 11, wherein, The solid medium is resin.

13. The near-infrared absorbing particle dispersion as claimed in claim 12, wherein, The resin is a resin selected from one of the resin groups consisting of polyester resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene-vinyl acetate copolymer, polyvinyl acetal resin and ultraviolet-curable resin, or a mixture of two or more resins selected from the resin group.

14. The near-infrared absorbing particle dispersion of any one of claims 11 to 13 has a sheet shape, plate shape or film shape.

15. The near-infrared absorbing particle dispersion of any one of the claims 11 to 13 has a solar transmittance of less than 67% in the section with Hunter color index L* = 88, and satisfies b* ≧ 0 and b* ≧ 1.6 × a* + 8.

0.

16. The near-infrared absorbing particle dispersion of any one of claims 11 to 13, in the section with Hunter color index L* = 88, has a transmittance T900 at a wavelength of 900 nm of 10% or more, and a solar transmittance ST21 (%) of 67% or less, and the T900 and the ST21 satisfy T900 ≥ 1.4 × ST21 - 41.

0.

17. A near-infrared absorbing laminate comprising a near-infrared absorbing particle dispersion and a transparent substrate according to any one of claims 11 to 16.

18. A near-infrared absorbing transparent substrate comprising: a transparent substrate and a near-infrared absorbing layer on at least one side of the transparent substrate, wherein the near-infrared absorbing layer is a near-infrared absorbing particle dispersion of any one of claims 11 to 16.

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