Composite tungsten oxide particles, near-infrared absorbing particle dispersion, and near-infrared absorbing particle dispersion

Abstract

Composite tungsten oxide particles containing composite tungsten oxide, wherein: the composite tungsten oxide is represented by general formula MxWyOz (where the M element is one or more selected from alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, re, Be, Hf, Os, Bi, and I, 0.20≤x / y≤0.37, and 2.2≤z / y≤3.3); the crystal system is hexagonal; and when the composite tungsten oxide particles are observed from the (010) plane, the occupancy rate of the length of the side formed by a plane parallel to the c axis, among the sides surrounding the (010) plane, is 60% or greater.

Description

[Technical Field]

[0001] The present invention relates to composite tungsten oxide particles, near-infrared absorbing particle dispersions, and near-infrared absorbing particle dispersions. [Background technology]

[0002] Various technologies have been proposed to reduce solar radiation transmittance while maintaining transparency and having good visible light transmittance as near-infrared shielding technology. Among these, near-infrared shielding technology using inorganic conductive nanoparticles has advantages such as superior near-infrared shielding characteristics, low cost, radio wave transmittance, and high weather resistance compared to other technologies.

[0003] For example, in Patent Document 1, General formula M x W y O z The invention discloses infrared shielding material nanoparticle dispersions in which composite tungsten oxide nanoparticles, expressed as (where M is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, I, W is tungsten, O is oxygen, 0.001≦x / y≦1, 2.2≦z / y≦3.0) are dispersed in a medium such as a resin, as well as technologies related to methods for manufacturing said infrared shielding particles. Patent Document 1 also discloses examples of manufacturing infrared shielding films, which are thin-film infrared shielding material nanoparticle dispersions.

[0004] According to Patent Document 1, it is possible to produce an infrared shielding material particle dispersion that has excellent optical properties, such as more efficiently shielding sunlight, especially light in the near-infrared region, while simultaneously maintaining transmittance in the visible light region. For this reason, the application of the infrared shielding particle dispersion disclosed in Patent Document 1 to various applications such as window glass is being considered.

[0005] By the way, according to Non-Patent Document 2, Cs 0.32 WO3 particles, known as one of the photochromic materials, have the property that the bluish color intensifies by strong UV (ultraviolet) irradiation (hereinafter referred to as the UV coloring phenomenon). According to Non-Patent Document 2, it has also been reported that after the UV coloring phenomenon, when stored in a dark place, it gradually returns to the original light blue color. The above UV coloring phenomenon has emerged as an issue for the spread of composite tungsten oxide particles. From such a situation, research has been conducted to reduce the UV coloring phenomenon.

[0006] Non-Patent Document 3 discloses that a composite material of SiO2, UVA, and CWO was synthesized by adding tetraethyl orthosilicate and a UV absorber (ultraviolet-absorbing agent; UVA) to Cs 0.32 WO3 particles.

[0007] Also, Non-Patent Document 4 discloses that by using the melt blending process, Cs 0.32 WO3 particles are kneaded into an inert polymer to suppress the generation of protons present near the surface of Cs 0.32 WO3 particles.

[0008] The methods disclosed in the above Non-Patent Document 3, 4, etc. are intended to reduce the UV coloring phenomenon by compounding composite tungsten oxide particles with a UV absorber or the like, and for Cs 0.32 WO3 particles themselves, the properties have not been improved.

[0009] On the other hand, various studies have been made on the manufacturing method of composite tungsten oxide particles useful as a near infrared shielding material.

[0010] For example, the inventors of Patent Document 1, in Non-Patent Document 1, prepared Cs by the solid phase method 0.32A method for synthesizing WO3 nanoparticles has been proposed. However, in the synthesis method disclosed in Non-Patent Document 1, the particle size was large, and a grinding process was required to form nanoparticles. Therefore, the number of process steps might increase.

[0011] In Patent Document 2, it has been proposed to synthesize potassium cesium tungsten bronze solid solution particles using a plasma torch under a reducing atmosphere.

[0012] In Non-Patent Document 5, a synthesis method of Cs x WO3 by a hydrothermal synthesis method is disclosed. However, the hydrothermal synthesis method requires a synthesis time of several tens of hours or more. In addition, the hydrothermal synthesis method also has a problem of a large number of process steps such as post-treatment steps.

[0013] In Non-Patent Document 6, a synthesis method based on inductively coupled thermal plasma technology is disclosed. However, such a synthesis method requires the introduction of an inductively coupled thermal plasma device, resulting in high costs.

[0014] In Non-Patent Document 7, a synthesis method of composite tungsten oxide by an aqueous solvent flame spray pyrolysis method is disclosed. However, due to the small amount of Cs, the infrared absorption characteristics were low.

[0015] In Non-Patent Document​​​​​​​​​​​​​​​​​​[License 2] Japanese National Special Announcement No. 2012-532822 [License 3] International Publication No. 2017 / 129516 [License 4] U.S. Patent and Trademark Office Publication No. 2010 / 0102700 [Non-licensed literature]

[0018] [Non-licensed Document 1] Takeda Hiromitsu, and Kenji Adachi, "Near infrared absorption of tungsten oxide nanoparticle dispersions." Journal of the American Ceramic Society,2007, Vol.90, Issue 12, P.4059-4061 [Non-licensed Document 2] Adachi K., Ota Y., Tanaka H., Okada M., Oshimura N., & Tofuku A. (2013). Chromatic instabilities in cesium-doped tungsten bronze nanoparticles. Journal of Applied Physics, 114(19), 194304. [Non-licensed Document 3] Zeng Xianzhe, et al. "The preparation of a high performancenear-infrared shielding CsxWO3 / SiO2 composite resin coating and research on its optical stability under ultraviolet illumination." Journal of Materials Chemistry C 3.31 (2015): 8050-8060. [Non-licensed Document 4] Zhou Yijie, et al. "CsxWO3 nanoparticle-based organic polymer transparent foils: low haze, high near infrared-shielding ability and excellent photochromic stability." Journal of Materials Chemistry C 5.25 (2017): 6251-6258. [Non-patent Document 5] Guo Chongshen, et al., "Novel synthesis of homogenous CsxWO3 nanorods with excellent NIR shielding properties by a water controlled-release solvothermal process." Journal of Materials Chemistry,2010, Vol.20, Issue38, P.8227-8229. [Non-patent Document 6] Mamak Marc, et al., "Thermal plasma synthesis of tungsten bronze nanoparticles for near infra-red absorption applications." Journal of Materials Chemistry, 2010, Vol.20, Issue44, P.9855-9857. [Non-patent Document 7] Hirano Tomoyuki, et al. "Synthesis of highly crystalline hexagonal cesium tungsten bronze nanoparticles by flame-assisted spray pyrolysis." Advanced Powder Technology 29.10 (2018): 2512-2520. [Non-patent Document 8] Nakakura Shuhei, et al. "Improved photochromic stability in less deficient cesium tungsten bronze nanoparticles." Advanced Powder Technology 31.2 (2020): 702-707. [Non-Patent Document 9] Machida K.; Okada M; Adachi K. Excitations of free and localized electrons at nearby energies in reduced cesium tungsten bronze nanocrystals. J. Appl. Phys, 2019, 125(10), 103103. [Overview of the Initiative] [Problems that the invention aims to solve]

[0019] As previously mentioned, composite tungsten oxide particles are useful as near-infrared shielding materials. However, composite tungsten oxides may discolor when exposed to ultraviolet light.

[0020] Therefore, one aspect of the present invention aims to provide composite tungsten oxide particles that can suppress discoloration when exposed to ultraviolet light. [Means for solving the problem]

[0021] In one aspect of the present invention, composite tungsten oxide particles comprising a composite tungsten oxide, The aforementioned composite tungsten oxide is General formula M x W y O z (However, element M is one or more elements selected from Rb and Cs, W is tungsten, O is oxygen, 0.20 ≤ x / y ≤ 0.37, 2.2 ≤ z / y ≤ 3.3) The crystal system is hexagonal. When the composite tungsten oxide particles are observed from the (010) plane, among the edges surrounding the (010) plane, the edges parallel to the c-axis (100) The present invention provides composite tungsten oxide particles in which the occupancy rate of the length of the sides formed by the faces is 60% or more. [Effects of the Invention]

[0022] One aspect of the present invention is the provision of composite tungsten oxide particles that can suppress discoloration when exposed to ultraviolet light. [Brief explanation of the drawing]

[0023] [Figure 1] Figure 1 is a schematic diagram of a composite material manufacturing apparatus that can be suitably used in the method for producing composite tungsten oxide particles according to this embodiment. [Figure 2] Figure 2 is an explanatory diagram of the reduction apparatus used in the reduction process. [Figure 3] Figure 3 is a schematic diagram of a near-infrared absorbing particle dispersion. [Figure 4] Figure 4 is a schematic diagram of a near-infrared absorbing particle dispersion. [Figure 5] Figure 5 is a schematic diagram of a near-infrared absorbing laminate. [Figure 6] Figure 6 is a schematic diagram of a near-infrared absorbing transparent substrate. [Figure 7A] Figure 7A shows the XRD diffraction pattern of the composite tungsten oxide particles obtained in Example 1. [Figure 7B] Figure 7B shows the XRD diffraction pattern of the composite tungsten oxide particles obtained in Example 2. [Figure 7C] Figure 7C shows the lattice constants of the composite tungsten oxide particles obtained in Example 2. [Figure 8A] Figure 8A is a TEM image of the composite tungsten oxide particles obtained in Example 1. [Figure 8B] Figure 8B is a HAADF-STEM image of the composite tungsten oxide particles obtained in Example 1. [Figure 8C] Figure 8C is a HAADF-STEM image of the composite tungsten oxide particles obtained in Example 1. [Figure 9A] Figure 9A is a TEM image of the composite tungsten oxide particles obtained in Example 2. [Figure 9B] Figure 9B shows a HAADF-STEM image of the composite tungsten oxide particles obtained in Example 2. [Figure 9C] Figure 9C shows a HAADF-STEM image of the composite tungsten oxide particles obtained in Example 2. [Figure 10A] Figure 10A shows the change in the permeation profile of the ink obtained in Example 3 with respect to the grinding and dispersion processing time. [Figure 10B] Figure 10B shows the evaluation results of the particle size distribution of composite tungsten oxide particles contained in the ink obtained in Example 3 after a grinding and dispersion treatment time of 5 hours. [Figure 10C] Figure 10C is a TEM image of the composite tungsten oxide particles contained in the ink obtained in Example 3 after a grinding and dispersion treatment time of 5 hours. [Figure 11A] Figure 11A shows the measurement results of the molar absorption coefficient of composite tungsten oxide particles in the ink obtained in Example 3 and Comparative Example 2. [Figure 11B] Figure 11B shows the measurement results of the solar radiation transmittance of composite tungsten oxide particles in the ink obtained in Example 3 and Comparative Example 2. [Figure 12A] Figure 12A is an explanatory diagram showing the change in the absorbance curve when the near-infrared absorbing particle dispersion obtained in Example 3 is irradiated with UV light. [Figure 12B] Figure 12B is an explanatory diagram showing the change in the absorbance curve when the near-infrared absorbing particle dispersion obtained in Comparative Example 2 is irradiated with UV light. [Figure 13] Figure 13 is an explanatory diagram of ΔR with respect to ultraviolet irradiation dose when the near-infrared absorbing particle dispersions obtained in Example 3 and Comparative Example 2 are irradiated with UV light. [Figure 14]Figure 14 is an explanatory diagram showing the relationship between the amount of ultraviolet irradiation and ΔE when the near-infrared absorbing particle dispersions obtained in Example 3 and Comparative Example 2 are irradiated with UV light. [Figure 15A] Figure 15A shows the crystal structure of composite tungsten oxide particles, which are near-infrared absorbing particles. [Figure 15B] Figure 15B shows the HAADF-STEM image of the near-infrared absorbing particles obtained in Example 3. [Figure 15C] Figure 15C shows a HAADF-STEM image of the near-infrared absorbing particles obtained in Example 3. [Figure 15D] Figure 15D is a HAADF-STEM image of the near-infrared absorbing particles obtained in Example 3. [Figure 15E] Figure 15E shows the HAADF-STEM image of the near-infrared absorbing particles obtained in Comparative Example 2. [Figure 15F] Figure 15F shows the HAADF-STEM image of the near-infrared absorbing particles obtained in Comparative Example 2. [Figure 15G] Figure 15G shows the HAADF-STEM image of the near-infrared absorbing particles obtained in Comparative Example 2. [Figure 16A] Figure 16A shows the change in the permeation profile of the ink obtained in Comparative Example 2 due to the grinding and dispersion processing time. [Figure 16B] Figure 16B shows the evaluation results of the particle size distribution of composite tungsten oxide particles contained in the ink obtained in Comparative Example 2, after a grinding and dispersion treatment time of 7 hours. [Figure 16C] Figure 16C is a TEM image of the composite tungsten oxide particles contained in the ink obtained in Comparative Example 2, after a grinding and dispersion treatment time of 7 hours. [Modes for carrying out the invention]

[0024] Specific examples of composite tungsten oxide particles, near-infrared absorbing particle dispersions, and near-infrared absorbing particle dispersions according to one embodiment of this disclosure (hereinafter referred to as "this embodiment") will be described below with reference to the drawings. However, the present invention is not limited to these examples and is intended to be shown in the claims, with all modifications within the meaning and scope of equivalence to the claims being included. [Composite tungsten oxide particles] The composite tungsten oxide particles of this embodiment are composite tungsten oxide particles containing composite tungsten oxide. The composite tungsten oxide particles may also be composed solely of composite tungsten oxide, but this does not exclude the presence of unavoidable impurities.

[0025] The above composite tungsten oxide has the general formula M x W y O z It is represented as follows.

[0026] In the above general formula, element M can be one or more elements selected from alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I. Furthermore, W represents tungsten and O represents oxygen, and it is preferable that x, y, and z satisfy 0.20 ≤ x / y ≤ 0.37 and 2.2 ≤ z / y ≤ 3.3, respectively.

[0027] Furthermore, the crystal system of the composite tungsten oxide is hexagonal.

[0028] Furthermore, when the composite tungsten oxide particles are observed from the (010) plane, the occupancy rate of the length of the edges formed by the planes parallel to the c-axis among the edges surrounding the (010) plane is 60% or more. (1) About the composition The composite tungsten oxide contained in the composite tungsten oxide particles is, as mentioned above, formulated with the general formula Mx W y O z It is expressed as follows. The elements M, W, O, and x, y, and z in the formula have already been explained, so we will omit their explanation here.

[0029] The composite tungsten oxide can have one or more tungsten bronze-type crystal structures selected from, for example, tetragonal, cubic, and hexagonal crystal structures. In this embodiment, the composite tungsten oxide contained in the composite tungsten oxide particles is hexagonal.

[0030] When the composite tungsten oxide has a hexagonal crystal structure, the transmission of light in the visible light region and the absorption of light in the near-infrared region of the particles are improved.

[0031] Composite tungsten oxides also function as infrared shielding materials when they take on the tetragonal or cubic tungsten bronze structure. However, the absorption position of near-infrared light tends to change depending on the crystal structure of the composite tungsten oxide. This absorption position in the near-infrared region shifts to longer wavelengths when it is tetragonal compared to cubic, and further to longer wavelengths when it is hexagonal. In addition, along with this variation in absorption position, the absorption of visible light is least in the hexagonal structure, followed by the tetragonal structure, and among these, the absorption of visible light is greatest in the cubic structure. Therefore, for applications where more visible light is transmitted and more infrared light is shielded, it is preferable to use hexagonal tungsten bronze.

[0032] As described above, when the composite tungsten oxide has a hexagonal crystal structure, the transmittance of light in the visible light region and the absorption of light in the near-infrared region of the composite tungsten oxide particles are particularly improved. For this reason, it is preferable that the composite tungsten oxide particles contain a composite tungsten oxide with a hexagonal crystal structure. Furthermore, using one or more elements selected from Cs, Rb, K, Tl, Ba, and In as the M element facilitates the formation of a hexagonal crystal. For this reason, it is preferable that the M element contains one or more elements selected from Cs, Rb, K, Tl, Ba, and In, and it is more preferable that the M element contains one or more elements selected from Rb and Cs.

[0033] Here, we will explain the arrangement of element M when the composite tungsten oxide has a hexagonal crystal structure.

[0034] An octahedron is formed using a tungsten (W) atom and six oxygen (O) atoms as units. This octahedron, with an O atom at its vertex and a W atom in its center, is formed by the aggregation of six such octahedra, creating a hexagonal void (tunnel) composed of O atoms. An M element is then placed within this void to form a single unit, and numerous such units aggregate to form a hexagonal crystal structure.

[0035] When a composite tungsten oxide having a hexagonal crystal structure has a uniform crystal structure, the molar ratio of element M to W is 0.20 ≤ x / y ≤ 0.37, and preferably 0.30 ≤ x / y ≤ 0.36. Theoretically, when z / y = 3, the value of x / y becomes 0.33, which suggests that element M is distributed in all hexagonal voids. Note that the above x, y, and z are as described in the general formula M x W y O z These represent x, y, and z in the given context, and so on.

[0036] Similarly, when z / y=3, both cubic and tetragonal composite tungsten oxides have an upper limit on the amount of M element (amount added) due to their structure. The maximum amount of M element per mole of tungsten is 1 mole for cubic tungsten and approximately 0.5 moles for tetragonal tungsten. Note that the maximum amount of M element per mole of tungsten in the tetragonal case varies depending on the type of M element, but as mentioned above, approximately 0.5 moles is the amount that is easily manufactured industrially.

[0037] Composite tungsten oxides have a composition in which element M is added to tungsten trioxide (WO3). Since tungsten trioxide does not contain effective free electrons, it cannot exhibit an infrared absorption effect unless the ratio of oxygen to 1 mole of tungsten is less than 3. However, in composite tungsten oxides, free electrons are generated by adding element M, and an infrared absorption effect can be obtained. For this reason, the ratio of oxygen to 1 mole of tungsten can be 3 or less. Also, the ratio of oxygen to 1 mole of tungsten may exceed 3. However, the crystalline phase of WO2 may cause absorption and scattering of light in the visible light region, potentially reducing the absorption of light in the near-infrared region. For this reason, from the viewpoint of suppressing the formation of WO2, it is preferable to have a ratio of oxygen to 1 mole of tungsten greater than 2.

[0038] Therefore, it is preferable that the ratio of oxygen to 1 mole of tungsten, z / y, satisfies 2.2 ≤ z / y ≤ 3.3, as described above. (2) Regarding particle size When the composite tungsten oxide particles of this embodiment are used in applications where transparency is required, for example, it is preferable that the composite tungsten oxide particles have a particle diameter of 800 nm or less. This is because particles with a particle diameter of 800 nm or less do not completely block light due to scattering, thus maintaining high visibility in the visible light region and efficiently maintaining transparency at the same time. When transparency in the visible light region is particularly important, it is preferable to further consider scattering by the particles.

[0039] When prioritizing the reduction of scattering by such particles, the particle size is more preferably 200 nm or less, and even more preferably 100 nm or less.

[0040] This is because, with smaller particle sizes, the scattering of light in the visible light region (wavelengths 400nm to 780nm) due to geometric scattering or Mie scattering is reduced. As a result, infrared shielding films such as near-infrared absorbing particle dispersions become cloudy, preventing the loss of clear transparency. Furthermore, when the particle size is 200nm or less, the above-mentioned geometric scattering or Mie scattering is reduced, and the Rayleigh scattering region is established. In the Rayleigh scattering region, scattered light is reduced in proportion to the sixth power of the particle size, so as the particle size decreases, scattering is reduced and transparency improves. Moreover, when the particle size is 100nm or less, scattered light becomes very small, which is desirable. From the viewpoint of avoiding light scattering, smaller particle sizes are preferable.

[0041] Therefore, when it is required to maintain high visibility in the visible light region, as described above, the composite tungsten oxide particles of this embodiment preferably have a particle diameter of 800 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less. The lower limit of the particle diameter of the composite tungsten oxide particles of this embodiment is not particularly limited, but it is preferably 1 nm or more, and more preferably 10 nm or more.

[0042] The particle size of the composite tungsten oxide particles in this embodiment can be determined by observing the particles, for example, with a SEM or TEM, and drawing the smallest circumscribed circle that circumscribes the particles. (3) Regarding discoloration caused by ultraviolet irradiation The phenomenon of coloration that occurs when composite tungsten oxide particles are irradiated with ultraviolet light is due to the absence of M element in the composite tungsten oxide particles.

[0043] Furthermore, considering the relationship between the crystal structure of hexagonal composite tungsten oxide particles and the M element vacancies, it can be seen that the M element does not detach from the particles from planes parallel to the c-axis, such as the (100) plane of the hexagonal prismatic faces.

[0044] As previously described, composite tungsten oxide is formed from octahedra, which are octahedra with O atoms at their vertices and W atoms in the center. Six of these octahedra combine to form hexagonal voids (tunnels) composed of O atoms, into which M elements are placed, forming one unit. Many of these units combine to form a hexagonal crystal structure. The hexagonal voids are parallel to the (001) plane. The (001) plane is perpendicular to the c-axis. The hexagonal voids (tunnels) open in the direction of the c-axis. On the other hand, the (100) plane, which is one of the planes parallel to the c-axis, is perpendicular to the (001) plane, and M elements cannot escape from the (100) plane because they are blocked by O and W atoms. Therefore, M elements cannot escape from the (100) plane and other prismatic faces of the hexagonal crystal that are parallel to the c-axis.

[0045] In this embodiment, when observed from the (010) plane, the composite tungsten oxide particles have a ratio of 60% or more of the length of the edges formed by planes parallel to the c-axis among the edges surrounding the (010) plane. That is, in the observed (010) plane of the particle, the ratio of the length of the edges formed by planes parallel to the c-axis to the total length of the edges forming the outer periphery (outer shape) is 60% or more.

[0046] Although particles are three-dimensional, the planes constituting a particle can be determined by knowing the orientation of the planes that make up the edges forming the outer perimeter of a plane observed from a certain direction. Therefore, in this embodiment, by knowing the orientation of the planes that make up the edges forming the outer perimeter of the (010) plane of a composite tungsten oxide particle when observed from the (010) plane from which the M element cannot be desorbed, it is possible to determine whether the particle is likely to desorb the M element. The orientation of the particle planes can be investigated using a TEM (transmission electron microscope).

[0047] The image shows a hexagonal composite tungsten oxide particle observed from the (010) plane. If there are many planes parallel to the c-axis among the edges surrounding the (010) plane, the detachment of element M can be prevented. On the other hand, planes with components oriented in the direction of the c-axis, such as the (001) plane and the (102) plane, have the aforementioned hexagonal voids (tunnels) opening outwards from the particle, making it easier for element M to detach.

[0048] In the composite tungsten oxide particles of this embodiment, by making the occupancy rate of the edges formed by the edges parallel to the c-axis among the edges surrounding the (010) surface when observed from the (010) surface 60% or more, the number of edges with components oriented in the c-axis direction, such as the (001) surface and the (102) surface, can be reduced. As a result, the desorption of element M can be suppressed in the composite tungsten oxide particles of this embodiment.

[0049] The desorption of element M from composite tungsten oxide particles occurs during heat treatment processes such as heat treatment and reduction treatment during the synthesis of composite tungsten oxide particles, as well as during the process of dispersing composite tungsten oxide particles in a solvent to prepare a dispersion.

[0050] During the heat treatment process, the M element detaches from the composite tungsten oxide particles due to the heat. In the process of preparing the dispersion, the composite tungsten oxide particles collide with ceramic beads or other stirring media, breaking down agglomeration and dispersing in the solvent. In addition, collisions with the ceramic beads cause the particles to break, creating new surfaces. If the new surfaces created by the collisions are parallel to the c-axis of the composite tungsten oxide, the detachment of the M element can be prevented. However, if the surfaces created by the breakage are oriented in the direction of the c-axis, for example, (001), the M element will dissolve into the solvent during the dispersion process. Furthermore, when the composite tungsten oxide particles are stirred in the solvent, the M element detaches from the surfaces oriented in the direction of the c-axis.

[0051] In order to suppress the desorption of element M during processes such as heat treatment and dispersion preparation, it is preferable that the composite tungsten oxide particles of this embodiment have an occupancy rate of 60% or more, which is the ratio of the length of the edges formed by the edges parallel to the c-axis among the edges surrounding the observed (010) surface.

[0052] Even after heat treatment and dispersion treatment, by maintaining the above-mentioned occupancy rate of 60% or more in the composite tungsten oxide particles, the deficiencies of element M during heat treatment and dispersion treatment are suppressed, resulting in composite tungsten oxide particles that can suppress discoloration during ultraviolet irradiation.

[0053] Furthermore, by ensuring that the composite tungsten oxide particles after heat treatment or dispersion treatment have a occupancy rate of 60% or more, the composite tungsten oxide particles before heat treatment or dispersion treatment also have a occupancy rate of 60% or more. (4) Regarding the decrease in element M when distributed processing is performed As described above, the phenomenon of coloration when composite tungsten oxide particles are irradiated with ultraviolet light is due to the absence of M element in the composite tungsten oxide particles, and such absences occur when the composite tungsten oxide particles are subjected to dispersion treatment, etc.

[0054] Therefore, when the composite tungsten oxide particles of this embodiment are dispersed in a dispersion medium, it is preferable that the decrease in the ratio of the amount of substance of element M (M) to tungsten (W), which is M / W, after the dispersion treatment compared to before the dispersion treatment is 0.1 or less.

[0055] The above reduction is determined by calculating the difference in M / W before and after the dispersion treatment. By keeping the above reduction in M / W to 0.1 or less, it means that the deficiency of the M element during the dispersion treatment is suppressed, resulting in composite tungsten oxide particles with fewer M element deficiencies. Therefore, with such composite tungsten oxide particles, discoloration can be suppressed even when irradiated with ultraviolet light.

[0056] The above dispersion treatment can be carried out for 0.5 hours or more using 0.3 mmφ ZrO2 beads with 1% by mass of the composite tungsten oxide particles to be evaluated, 1% by mass of an amine-based acrylic copolymer dispersant, and the remainder being methyl isobutyl ketone as a dispersion medium. [Method for producing composite tungsten oxide particles] The outline of the method for producing the composite tungsten oxide particles of this embodiment will be described.

[0057] The method for producing composite tungsten oxide particles according to this embodiment can produce the composite tungsten oxide particles described above, so the matters already explained will be omitted from this explanation. It should be noted that this merely shows an example configuration for the method for producing composite tungsten oxide particles, and the method for producing composite tungsten oxide particles described above is not limited to the following example configuration.

[0058] In this embodiment, a method for producing composite tungsten oxide particles that can directly synthesize composite tungsten oxide particles with a particle diameter of 1 μm or less is desirable. If composite tungsten oxide particles with a particle diameter of 1 μm or less can be synthesized directly, fine particles with less damage from grinding and dispersion, such as composite tungsten oxide particles with a particle diameter of 800 nm or less, can be obtained. If the damage from grinding of the composite tungsten oxide particles is minimized, the generation of surfaces with components oriented in the c-axis direction due to grinding can be suppressed.

[0059] For directly synthesizing composite tungsten oxide particles with a particle size of 1 μm or less, a manufacturing method is preferable in which raw materials containing an M element source and a tungsten element source are supplied to an electric furnace, flame, or plasma to synthesize the particles.

[0060] Therefore, the method for producing composite tungsten oxide particles according to this embodiment may include the following raw material preparation step, aerosol formation step, and heat treatment step.

[0061] In the raw material preparation process, raw materials containing an M element source and a tungsten element source can be prepared.

[0062] In the aerosol formation process, the raw materials prepared in the raw material preparation process can be aerosolized.

[0063] In the heat treatment process, the aerosolized raw materials can be heat-treated in the reaction field. (1) Regarding each process The following describes each step in the method for producing the composite tungsten oxide particles of this embodiment. (1-1) Raw material preparation process In the raw material preparation process, raw materials containing an M element source and a tungsten element source (hereinafter also referred to as "W element source") can be prepared.

[0064] In the raw material preparation process, the raw materials can be blended and prepared so that the ratio of the amount of M element to the amount of W element contained in the raw materials corresponds to the composition of the desired composite tungsten oxide particles.

[0065] The state of the raw materials prepared in the raw material preparation process is not particularly limited; they may be liquids or powders, and it is preferable that they can form aerosols by spraying or other means. An aerosol refers to a mixture of fine liquid or solid particles suspended in a gas and the surrounding gas.

[0066] If the raw material is a liquid, it can be prepared by, for example, preparing a solution containing an M element source and a W element source.

[0067] Alternatively, a solution containing the M element source and a solution containing the W element source can be prepared separately in advance, and both solutions can be mixed during the raw material preparation process to create the raw material mixture solution.

[0068] For the heat treatment process described later, the raw materials can also be supplied in the form of droplets, for example. In this case, the raw material preparation process can be carried out by mixing the solution containing the M element source and the solution containing the W element source immediately before supplying them to the droplet forming unit (droplet forming means) or within the droplet forming unit. Then, the aerosol formation process described later can be carried out in the droplet forming unit.

[0069] For example, if pre-mixing a solution containing the M element source and a solution containing the W element source causes problems such as gelation, it is preferable to prepare both solutions in advance as described above and mix them immediately before the aerosol formation process. When the raw material preparation process is carried out immediately before the aerosol formation process, the molar ratio of the M element to the W element in the raw material can be adjusted to a desired range by adjusting the concentrations of both solutions and the rate at which both solutions are supplied to the droplet formation section.

[0070] As mentioned above, when the raw material preparation process is carried out immediately before the aerosol formation process, the aerosol formation process and the raw material preparation process do not need to be clearly distinguished, and both processes can be carried out continuously.

[0071] As described above, when mixing a solution containing the M element source and a solution containing the W element source in the raw material preparation process, the specific method of mixing is not particularly limited, and any method can be used.

[0072] The W element source is not particularly limited, and tungsten salts can be used, for example, hexacarbonyltungsten is preferably used. Hexacarbonyltungsten can be represented as, for example, W(CO)6. Furthermore, as the solution containing the W element source, an organic solution containing the W element source can be preferably used due to its ease of handling, etc.

[0073] As a solution containing the M element source, for example, a solution of a salt containing the M element can be used. The type of salt of the M element that serves as the M element source is not particularly limited, but for example, one or more types selected from carbonates, acetates, nitrates, hydroxides, etc. of the M element can be used.

[0074] As a solution containing the M element source, an ethanol solution containing the M element source can be suitably used due to its ease of handling and other factors.

[0075] For example, even when element M is cesium, one or more salts selected from carbonates, acetates, nitrates, hydroxides, etc., can be used as the salt of the element M source, but acetates are particularly preferable. This is because cesium acetate dissolves particularly easily in ethanol.

[0076] Furthermore, the ratio of element M to 1 mole of tungsten in the resulting composite tungsten oxide, i.e., the doping amount, is determined by the ratio of element W source to element M source when forming the raw material mixed solution. Therefore, it can be controlled, for example, by adjusting the concentration of the solution containing element W source or the concentration of the solution containing element M source.

[0077] The concentration of the W element source in the solution containing the W element source, i.e., the concentration of the W element salt, is not particularly limited. For example, it is preferable that the tungsten concentration of the solution containing the W element source be between 0.001 mol / L and 10 mol / L, more preferably between 0.01 mol / L and 10 mol / L, and even more preferably between 0.01 mol / L and 1 mol / L. This is because setting the tungsten concentration of the solution containing the W element source to 0.001 mol / L or higher ensures a sufficient production amount of composite tungsten oxide particles per unit time, allowing for sufficient recovery by, for example, a filter, thereby increasing productivity. Furthermore, setting the tungsten concentration of the solution containing the W element source to 10 mol / L or lower suppresses the reprecipitation of the dissolved W element source, inhibits the aggregation of the generated particles, and prevents the inclusion of, for example, coarse composite tungsten oxide particles of 1 μm or larger. In addition, additives such as pH adjusting agents and surfactants can be added to the solution containing the W element source.

[0078] Furthermore, the concentration of the M element source in the solution containing the M element source is not particularly limited and can be selected according to the desired composition of the composite tungsten oxide particles to be manufactured, the concentration of the W element source in the solution containing the W element source, etc.

[0079] In addition to solutions containing the W element source and solutions containing the M element source, any other components can be added to the raw material mixture solution.

[0080] Up to this point, the explanation has been based on the example of a liquid raw material, but the raw material can also be a solid, for example, a powder. When the raw material is a powder, it can be prepared by mixing, for example, a powder of an M element compound and a powder of a tungsten compound. Alternatively, for example, a precursor powder can be used as a raw material by adding a tungsten compound powder to a solution containing an M element source, stirring, and removing the solvent by drying or other means.

[0081] When the raw material is solid, the W element source is not particularly limited, and tungsten salts can be used, for example, H2WO4 or ammonium paratungstate can be preferably used.

[0082] In H2WO4, the elements other than tungsten are H (hydrogen) and O (oxygen), and these elements are discharged from the system during the heat treatment process described later. Therefore, using H2WO4 as the W element source is preferable because it allows for the production of composite tungsten oxide particles with suppressed impurity contamination.

[0083] As a source of element M, for example, a powder of a salt containing element M can be used. The type of salt containing element M is not particularly limited, but for example, one or more types selected from carbonates, acetates, nitrates, hydroxides, etc. of element M can be used.

[0084] For example, even when element M is cesium, one or more of the following can be used: carbonate, acetate, nitrate, hydroxide, etc., but carbonate can be used particularly preferably. (1-2) Aerosol formation process In the method for producing composite tungsten oxide particles according to this embodiment, it is preferable to supply the raw materials prepared in the raw material preparation step to the heat treatment step in the form of an aerosol. Specifically, it is preferable to transport the aerosol using a carrier gas such as oxygen and subject it to the heat treatment step.

[0085] Therefore, the method for producing composite tungsten oxide particles of this embodiment may also include an aerosol formation step in which the raw materials are converted into an aerosol containing droplets or particles of the raw materials.

[0086] The means and methods for forming the aerosol in the aerosol formation process are not particularly limited and can be selected according to the state of the raw materials, etc.

[0087] When the raw material is a liquid, an aerosol can be formed by spraying the liquid onto a carrier gas using various atomizers such as centrifugal atomizers or two-fluid nozzles. Alternatively, droplets can be formed by applying ultrasonic irradiation to the liquid.

[0088] When the raw material is a powder, an aerosol can be formed by a device that disperses the powder and supplies the powder into an airflow. For example, an aerosol can be formed by an aerosol forming device that includes a stirring section such as a rotating brush or agitator, and a powder supply section including a piston or screw feeder that sends the raw material to the stirring section. The raw material powder supplied from the powder supply section is dispersed into particles in the stirring section, and an aerosol can be generated from the raw material powder by sending each particle into a carrier gas. The stirring section allows for the selection of the rotation speed of the brush or agitator to disperse the raw material powder into particles, and it is preferable to rotate it at high speed.

[0089] When forming droplets dispersed in a gas during the aerosol formation process, the size of the droplets to be formed is not particularly limited, but the diameter of the droplets is preferably 100 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. By setting the diameter of the droplets to 100 μm or less, it is possible to prevent the resulting composite tungsten oxide particles from becoming coarse, and to obtain composite tungsten oxide particles on the order of nanometers. The lower limit of the size of the droplets formed in the aerosol formation process is not particularly limited. However, it is difficult to form excessively small droplets, and productivity may decrease, so it is preferable that the size is, for example, 1 μm or more.

[0090] When forming solid particles dispersed in a gas during the aerosol formation process, the particle size is not particularly limited, but the particle diameter is preferably 100 μm or less, more preferably 10 μm or less, and even more preferably 3 μm or less. By setting the particle diameter to 100 μm or less, it becomes possible to more reliably perform heat treatment to the interior of the particles. The particle diameter can be measured in the same way as the particle diameter of the composite tungsten oxide particles described above. (1-3) Heat treatment process In the heat treatment process, the raw material can be processed into composite tungsten oxide particles by heat treatment. The heat treatment only needs to be performed at a temperature of 500°C or higher, and the configuration of the heat source is not particularly limited. Therefore, the heat treatment process can be carried out by introducing the raw material into a flame using a carrier gas, or by introducing it into a tubular electric furnace. In both cases, the heat treatment temperature can be set to 500°C or higher. By performing heat treatment at 500°C or higher, compounds contained in the raw material decompose, and tungsten reacts with M element to form composite tungsten oxide.

[0091] The heat treatment temperature should be at least 500°C, as long as it allows the reaction between tungsten and element M to proceed. However, it is preferable to be at least 550°C, and more preferably at least 1000°C. While there is no particular upper limit to the heat treatment temperature, it is preferable to be at least 1500°C from the viewpoint of suppressing energy consumption.

[0092] As mentioned above, a flame can be used in the heat treatment process, allowing the raw materials to be heat-treated using a flame. By using a flame in the heat treatment process, the particle size of the resulting composite tungsten oxide particles can be selected by adjusting the temperature of the flame reaction field.

[0093] When a liquid raw material is sprayed onto a carrier gas to form droplets, and these droplets are introduced into a flame to synthesize composite tungsten oxide particles, the raw material droplets are transported through the flame by a carrier gas such as oxygen. Once the raw material droplets are transported into the flame, the solvent, such as an organic solvent containing the W and M element sources of the raw material, burns, and the solvent is decomposed by the combustion reaction. The heat generated by the combustion reaction contributes to the decomposition reaction of the W and M element sources, and these precipitate during the cooling process at the tail of the flame.

[0094] For example, as previously mentioned, hexacarbonyltungsten can be used as a W element source, and cesium acetate can be used as an M element source if the M element is cesium. These salts decompose during the heat treatment process. At this time, W readily precipitates as WO6, while Cs does not readily form oxides as a monomer, and some of it passes through the filter and is discharged out of the system as nano-sized powder without precipitating.

[0095] In the above case, during the decomposition process of the solute portion, tungsten and element M react to form a composite tungsten oxide.

[0096] When a flame is used in the heat treatment process, the conditions for flame formation are not particularly limited, but the flame can be formed using, for example, a mixed gas containing oxygen and hydrocarbons. By forming a flame with a mixed gas containing oxygen and hydrocarbons, a flame with a stable temperature can be formed, and composite tungsten oxide particles with suppressed variations in particle size can be produced.

[0097] While there are no particular limitations on the method of adjusting the flame size or flame temperature, it is preferable to adjust the flow rates of both gases, for example, by adjusting the flow rate ratio of oxygen in the gas mixture supplied to the flame to that of a combustible gas such as hydrocarbons, while maintaining a flow rate ratio that allows for the combustion of the combustible gas. This is because it allows for adjustment of the flame intensity while ensuring the amount of oxygen necessary for combustion of the combustible gas.

[0098] For example, when a flame is formed using a gas mixture containing oxygen and propane, it is preferable that the ratio of propane to oxygen (burner) flow rates in the gas mixture be 5 to 8 parts oxygen to 1 part propane, and that the propane flow rate be in the range of 0.5 L / min to 2 L / min or more. This is because, when the propane flow rate is 1 part, the oxygen flow rate is 5 or more parts, which sufficiently promotes the combustion of propane, a flammable gas. However, to prevent an excessive supply of oxygen, it is preferable to supply 8 or less parts oxygen to 1 part propane.

[0099] The heat treatment temperature, such as that of the flame reaction field, also affects the particle size of the resulting composite tungsten oxide particles.

[0100] This is presumed to be because the thermal energy in the reaction field, such as a flame, is used for the sublimation of the generated composite tungsten oxide particles, causing the particles to burst during sublimation and yield particles with a very small particle size.

[0101] The composite tungsten oxide particles obtained by heat treatment can be recovered, for example, using a filter. (1-4) Reduction process Particles obtained through a heat treatment process, specifically composite tungsten oxide particles, may not exhibit infrared absorption properties. Therefore, the inventors of this invention conducted research and found that by further performing a reduction treatment process on the composite tungsten oxide particles obtained through the heat treatment process, the composite tungsten oxide particles can exhibit infrared absorption properties.

[0102] Therefore, the method for producing composite tungsten oxide particles according to this embodiment may also include a reduction treatment step in which the particles obtained in the heat treatment step are subjected to reduction treatment in an atmosphere containing a reducing gas. Specifically, for example, the method for producing composite tungsten oxide particles according to this embodiment may include a reduction treatment step after the heat treatment step in which the particles are subjected to reduction treatment in an atmosphere containing a reducing gas at a temperature in the range of higher than 400°C and lower than 700°C.

[0103] The conditions for the reduction treatment are not particularly limited, but it is preferable to select the reduction treatment conditions such that, when the composite tungsten oxide particles after the reduction treatment are analyzed by X-ray diffraction, the crystal structure does not change before and after the reduction treatment process, and metallic tungsten or the like does not precipitate.

[0104] In the reduction process, the composite tungsten oxide particles obtained in the heat treatment process can be reduced by heating and cooling them in a reducing atmosphere containing a reducing gas, i.e., by heat treatment.

[0105] During the reduction process, the composite tungsten oxide particles may be stirred or left to stand. The handling of the composite tungsten oxide particles during the reduction process can be selected as appropriate, but it is preferable to select handling conditions that prevent the deposition of metallic tungsten.

[0106] The reduction treatment temperature is preferably higher than 400°C, more preferably 500°C or higher, and even more preferably 550°C or higher.

[0107] The upper limit of the temperature for the reduction treatment is not particularly limited, but it is preferably less than 700°C, more preferably 650°C or less, and even more preferably less than 650°C.

[0108] Furthermore, when the raw material is liquid, reducing the raw material concentration during the aerosol formation process results in smaller particle sizes. Since smaller particles are easier to reduce, the temperature during the reduction process can be lowered compared to conventional methods. In the reduction process, the temperature can be raised from room temperature to the reduction temperature, and then lowered back down to room temperature.

[0109] The reduction conditions can be determined from the optical properties of the resulting composite tungsten oxide particles.

[0110] By raising the reduction temperature above 400°C, the reduction treatment of the composite tungsten oxide particles can be advanced, allowing them to exhibit infrared absorption properties more reliably. Furthermore, by keeping the temperature below 700°C, the reduction of the composite tungsten oxide particles to metallic tungsten can be suppressed.

[0111] The reducing atmosphere is preferably a mixture of an inert gas such as argon and a reducing gas such as H2 gas (hydrogen gas), with H2 gas being the preferred reducing gas.

[0112] When using H2 gas as the reducing gas, the H2 gas content in the reducing atmosphere can be appropriately selected, but the H2 gas content is preferably in the range of 0.1% to 10% by volume, and more preferably in the range of 2% to 10%. Caution is required because reduction in an atmosphere consisting only of a reducing gas may cause the reduction reaction to proceed excessively, leading to the precipitation of metallic tungsten.

[0113] The reduction treatment process should preferably last at least 30 minutes, including the total time from heating to cooling. There is no particular upper limit to the reduction treatment process time; however, it is preferable to select a suitable time by conducting preliminary tests, for example, to prevent excessive reduction. The total time from heating to cooling refers to the time from when heating starts at room temperature, when the reduction treatment temperature is reached, and when it cools back down to room temperature. During this time, it is preferable that the composite tungsten oxide particles are placed in the reducing atmosphere described above.

[0114] By performing this reduction process, it is possible to convert the unintended phase of the composite tungsten oxide particles obtained after the heat treatment process into the desired composite tungsten oxide phase. (2) Apparatus that can be suitably used in the method for producing composite tungsten oxide particles (2-1) Composite material manufacturing equipment An example of the configuration of a composite material manufacturing apparatus that can be suitably used in the method for producing composite tungsten oxide particles of this embodiment is described below.

[0115] Figure 1 is a schematic diagram of the composite material manufacturing apparatus 10 of this embodiment.

[0116] The composite material manufacturing apparatus 10 includes a first storage section 11 containing a raw material solution containing M element and tungsten element, a two-fluid nozzle 12 that forms droplets of the raw material and simultaneously forms a flame, and a reaction tube 13 connected to a filter 14 for collecting the formed composite tungsten oxide particles.

[0117] A raw material solution and a carrier gas can be supplied to the two-fluid nozzle 12 to form an aerosol (aerosol formation step). For example, oxygen and hydrocarbons are supplied to the two-fluid nozzle 12, and together a flame reaction field is formed. The formed aerosol can be supplied into the flame and heat treated (heat treatment step). Cooling water pipes 131 are arranged around the reaction tube 13, and the cooling water circulates. The composite tungsten oxide particles introduced into the reaction tube 13 are recovered by a filter 14 such as a bag filter.

[0118] Additionally, an ejector 15 may be provided at the downstream end to adjust the amount of carrier gas supplied.

[0119] Here, we have shown an example of a composite material apparatus that forms droplets of raw materials and heat-treats them using a flame to form composite tungsten oxide particles. However, the apparatus is not limited to this configuration, and the raw materials may be powders, and the heat source used for heat treatment may be an electric furnace, etc. (2-2) Reduction treatment device The reduction treatment apparatus can carry out the reduction treatment process described above.

[0120] The reduction treatment apparatus is not particularly limited, as long as it is configured to carry out the reduction treatment process described above. For example, it may include a container for storing composite tungsten oxide particles, which are particles obtained in the composite material manufacturing apparatus described above, a gas pipe for supplying a mixed gas to form a reducing atmosphere into the container, and a heat source for heating the container.

[0121] Alternatively, a mixed gas that creates a reducing atmosphere can be introduced into the container and exhausted, and the composite tungsten oxide particles to be treated can be placed under the airflow of the mixed gas. In this case, gas piping can be provided, including a supply pipe for the mixed gas and an exhaust pipe, to form such an airflow.

[0122] Additionally, a stirring blade or similar device may be used to agitate the composite tungsten oxide particles inside the container.

[0123] Figure 2 is a schematic diagram showing one example of the configuration of a reduction apparatus, and shows a cross-sectional view of the reaction tube 21 of the reduction apparatus 20 through the central axis.

[0124] The reduction treatment apparatus 20 is a horizontal tubular furnace, and can be used by attaching a gas introduction pipe (not shown) to one opening 21A of the reaction tube 21 and a gas exhaust pipe (not shown) to the other opening 21B of the tubular furnace. By supplying a mixed gas that creates a reducing atmosphere from the opening 21A, a reducing atmosphere can be created inside the reaction tube 21.

[0125] A heater 22 can be provided around the reaction tube 21, and the composite tungsten oxide particles can be placed in a ceramic container 23, such as a boat, and positioned in the reaction tube 21 of the tubular furnace at a location corresponding to the heater 22.

[0126] By using the reduction treatment apparatus 20, the inside of the reaction tube 21 is made into a reducing atmosphere, and the heater 22 is used to heat it to a desired temperature, thereby performing a reduction treatment on the composite tungsten oxide particles 24 placed in the container 23. [Near-infrared absorbing particle dispersion] Next, an example of the configuration of the near-infrared absorbing particle dispersion of this embodiment will be described.

[0127] The near-infrared absorbing particle dispersion of this embodiment may include near-infrared absorbing particles and a liquid medium. The composite tungsten oxide particles described above can be used as the near-infrared absorbing particles.

[0128] As the liquid medium, one or more selected from, for example, water, organic solvents, oils and fats, liquid resins, and liquid plasticizers can be used. That is, as shown in Figure 3 for example, the near-infrared absorbing particle dispersion 30 of this embodiment may include near-infrared absorbing particles 31 and a liquid medium 32. It is preferable that the near-infrared absorbing particle dispersion has a configuration in which near-infrared absorbing particles are dispersed in a liquid medium.

[0129] Figure 3 is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to this form. For example, in Figure 3, the near-infrared absorbing particles 31 are represented by circles and described as spherical particles, but the shape of the near-infrared absorbing particles 31, which are the composite tungsten oxide particles described above, is not limited to this form and can have any shape. The near-infrared absorbing particles 31 may also have a coating on their surface, for example. In addition to the near-infrared absorbing particles 31 and the liquid medium 32, the near-infrared absorbing particle dispersion 30 may also contain other additives as needed.

[0130] As described above, one or more liquid media selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers can be used.

[0131] Various organic solvents can be selected, including alcohol-based, ketone-based, ester-based, hydrocarbon-based, and glycol-based solvents. Specifically, these include alcohol-based solvents such as isopropyl alcohol, methanol, ethanol, 1-propyl ketone, isopropyl ketone, butanol, pentanol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propyl ketone; ketone-based solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester-based solvents such as 3-methyl-methoxypropyl ketone and butyl acetate; and ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monoethyl ether. One or more of the following can be selected: glycol derivatives such as ethylene glycol isopropyl ether, propyl glycol monomethyl ether, propyl glycol monoethyl ether, propyl glycol methyl ether acetate, and propyl glycol ethyl ether acetate; amides such as formamide, N-methylformamide, dimethylformamide, dimethylacetamide, and N-methyl-2-pyridone; aromatic hydrocarbons such as toluene and xylene; and halogenated hydrocarbons such as ethylene glycol and chlorobenzene.

[0132] However, among these, organic solvents with low polarity are preferred, and in particular, isopropyl alcohol, ethanol, 1-methoxy-2-propylanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propyl glycol monomethyl ether acetate, and n-butyl acetate are more preferred. These organic solvents can be used individually or in combination of two or more.

[0133] As oils and fats, one or more selected from drying oils such as linseed oil, sunflower oil, and tung oil; semi-drying oils such as sesame oil, cottonseed oil, rapeseed oil, soybean oil, and rice bran oil; non-drying oils such as olive oil, coconut oil, palm oil, and dehydrated castor oil; fatty acid monoesters obtained by directly esterifying fatty acids of vegetable oils with monoalcohols; ethers; and petroleum-based solvents such as Isopar® E, Exsol® Hexane, Heptan, E, D30, D40, D60, D80, D95, D110, and D130 (all manufactured by ExxonMobil) can be used.

[0134] As the liquid resin, one or more types selected from, for example, liquid acrylic resin, liquid epoxy resin, liquid polyester resin, liquid urethane resin, etc., can be used.

[0135] As a liquid plasticizer, for example, a liquid plasticizer for plastics can be used.

[0136] The components contained in the near-infrared absorbing particle dispersion are not limited to the near-infrared absorbing particles and liquid medium described above. The near-infrared absorbing particle dispersion may also contain any additional components as needed.

[0137] For example, the pH of the near-infrared absorbing particle dispersion may be adjusted by adding an acid or alkali as needed.

[0138] Furthermore, in the near-infrared absorbing particle dispersion described above, various surfactants, coupling agents, etc., can be added to the near-infrared absorbing particle dispersion as dispersants to further improve the dispersion stability of the near-infrared absorbing particles and to avoid coarsening of the dispersed particle size due to re-aggregation.

[0139] The dispersant, such as the surfactant or coupling agent, can be selected according to the application, but it is preferable that the dispersant has one or more functional groups selected from amine-containing groups, hydroxyl groups, carboxyl groups, and epoxy groups. These functional groups adsorb to the surface of near-infrared absorbing particles to prevent aggregation and have the effect of uniformly dispersing the near-infrared absorbing particles in an infrared shielding film formed using the near-infrared absorbing particles. A polymeric dispersant having one or more of the above-mentioned functional groups (or functional group group) in its molecule is even more desirable.

[0140] Suitable commercially available dispersants include Solspers® 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, 250 (manufactured by Lubrizol Japan Co., Ltd.) and EFKA®. 4008, 4009, 4010, 4015, 4046, 4047, 4060, 4080, 7462, 4020, 4050, 4055, 4400, 4401, 4402, 4403, 4300, 4320, 4330, 4340, 6220, 6225, 6700, 6780, 6782, 8503 (manufactured by F-CA Additives), Azisper (registered trademark) PA111, PB821, PB822, PN411, Phemex L-12 (manufactured by Ajinomoto Fine Techno Co., Ltd.), DisperBYK (registered trademark) 101, 102, 106, 108, 111, 116, 130, 140, 142, 145, 161, 162, 163, 164, 166, 167, 168, 170, 171, 174, 180, 182, 192, 193, 2000, 2001, 2020, 2025, 2050, 2070, 2155, 2164, 220S, 300, 306, 320, 322, 325, 330, 340, 350, 377, 378, 380N, 410, 425, 430 (manufactured by Pick Chemistry Japan Co., Ltd.), Disparon (registered trademark) One or more types selected from 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 Kasei Co., Ltd.), Alphon (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), etc. are listed.

[0141] The method for dispersing near-infrared absorbing particles into a liquid medium is not particularly limited, as long as it is a method that can disperse the near-infrared absorbing particles into the liquid medium. In this case, it is preferable that the near-infrared absorbing particles are dispersed so that their average particle size is 200 nm or less, and more preferably so that they are dispersed so that they are between 0.1 nm and 200 nm.

[0142] Methods for dispersing near-infrared absorbing particles into a liquid medium include, for example, dispersion methods using devices such as bead mills, ball mills, sand mills, paint shakers, and ultrasonic homogenizers. Among these, grinding and dispersion using a media stirring mill such as a bead mill, ball mill, sand mill, or paint shaker that uses a media (beads, balls, Ottawa sand) is preferable from the viewpoint of shortening the time required to achieve the desired average particle size. Grinding and dispersion processing using a media stirring mill simultaneously disperses the near-infrared absorbing particles into the liquid medium and also promotes micronization through collisions between near-infrared absorbing particles and collisions of the media with the near-infrared absorbing particles, allowing the near-infrared absorbing particles to be dispersed into even finer particles. In other words, it is ground and dispersed.

[0143] The average particle size of the near-infrared absorbing particles is preferably 0.1 nm to 200 nm, as described above. This is because a smaller average particle size reduces the scattering of light in the visible light region with wavelengths between 400 nm and 780 nm due to geometric scattering or Mie scattering. As a result, it is possible to avoid the near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment, where the near-infrared absorbing particles are dispersed in a resin or the like, becoming cloudy and losing clear transparency. In other words, when the average particle size is 200 nm or less, the geometric scattering or Mie scattering mode of light scattering weakens, and the mode becomes Rayleigh scattering. In the Rayleigh scattering region, scattered light is proportional to the sixth power of the dispersed particle size, so scattering decreases and transparency improves as the dispersed particle size decreases. Furthermore, when the average particle size is 100 nm or less, the scattered light becomes very small, which is preferable. An average particle size of 30 nm or less is even more preferable.

[0144] Incidentally, the dispersion state of near-infrared absorbing particles in a near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment, in which near-infrared absorbing particles are dispersed in a solid medium such as a resin, will not aggregate more than the average particle size of the near-infrared absorbing particles in the dispersion, as long as the known method of adding the dispersion to the solid medium is used.

[0145] 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 products (plates, sheets, etc.) becoming monotonically gray in color with decreasing transmittance.

[0146] The content of near-infrared absorbing particles in the near-infrared absorbing particle dispersion of this embodiment is not particularly limited, but is preferably, for example, 0.01% by mass or more and 80% by mass or less. This is because a content of 0.01% by mass or more of near-infrared absorbing particles allows for sufficient solar transmittance, that is, sufficient suppression of solar transmittance. Furthermore, a content of 80% by mass or less allows for uniform dispersion of near-infrared absorbing particles within the dispersion medium. [Near-infrared absorbing particle dispersion] Next, an example of the configuration of the near-infrared absorbing particle dispersion of this embodiment will be described.

[0147] The near-infrared absorbing particle dispersion of this embodiment includes near-infrared absorbing particles and a solid medium. The composite tungsten oxide particles described above can be used as the near-infrared absorbing particles. Specifically, for example, as schematically shown in Figure 4, the near-infrared absorbing particle dispersion 40 can include near-infrared absorbing particles 41, which are the composite tungsten oxide particles described above, and a solid medium 42, with the near-infrared absorbing particles 41 being arranged in the solid medium 42. In this embodiment, it is preferable that the near-infrared absorbing particles are dispersed in the solid medium. Note that Figure 4 is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to this form. For example, in Figure 4, the near-infrared absorbing particles 41 are represented by circles and described as spherical particles, but the shape of the near-infrared absorbing particles 41 is not limited to this form and can have any shape. The near-infrared absorbing particles 41 may also have a coating on their surface, for example. The near-infrared absorbing particle dispersion 40 may also contain other additives as needed, in addition to the near-infrared absorbing particles 41 and the solid medium 42.

[0148] The near-infrared absorbing particle dispersion according to this embodiment will be described below in the following order: (1) characteristics of the solid medium and the near-infrared absorbing particle dispersion, (2) method for producing the near-infrared absorbing particle dispersion, (3) additives, and (4) application examples. (1) Properties of solid media and near-infrared absorbing particle dispersions Examples of solid media include thermoplastic resins, thermosetting resins, and UV-curing resins. In other words, resins can be suitably used as the solid medium.

[0149] The specific material of the resin used for the solid medium is not particularly limited, but it is preferably one resin selected from the group of resins 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 curing resin, or a mixture of two or more resins selected from the aforementioned group. Polyethylene terephthalate resin can be suitably used as the polyester resin.

[0150] These media resins may also contain polymeric dispersants having one or more functional groups selected from amine-containing groups, hydroxyl groups, carboxyl groups, and epoxy groups in their main skeleton.

[0151] The solid medium is not limited to resins; binders using metal alkoxides can also be used as solid media. Typical examples of such metal alkoxides include those of Si, Ti, Al, and Zr. By hydrolyzing and condensing binders using these metal alkoxides through heating or other means, it is possible to obtain a near-infrared absorbing particle dispersion in which the solid medium contains oxides.

[0152] The content ratio of near-infrared absorbing particles in the near-infrared absorbing particle dispersion according to this embodiment is not particularly limited, but it is preferable that the near-infrared absorbing particle dispersion contains 0.001% by mass or more and 80% by mass or less of near-infrared absorbing particles.

[0153] The shape of the near-infrared absorbing particle dispersion in this embodiment is not particularly limited, but it is preferable that the near-infrared absorbing particle dispersion in this embodiment be in the form of a sheet, a board, or a film. This is because the near-infrared absorbing particle dispersion can be applied to a variety of applications by being in the form of a sheet, a board, or a film. (2) Method for producing near-infrared absorbing particle dispersion The method for producing the near-infrared absorbing particle dispersion of this embodiment is described below. Note that this merely shows an example configuration for the method of producing the near-infrared absorbing particle dispersion, and the method for producing the near-infrared absorbing particle dispersion described above is not limited to the following example configuration.

[0154] The near-infrared absorbing particle dispersion of this embodiment can be manufactured, for example, using a masterbatch. In this case, the method for manufacturing the near-infrared absorbing particle dispersion of this embodiment may include, for example, the following masterbatch manufacturing step.

[0155] In the masterbatch preparation process, a masterbatch can be prepared in which near-infrared absorbing particles are dispersed in a solid medium.

[0156] The specific method for producing a masterbatch is not particularly limited. For example, a masterbatch can be produced by dispersing a near-infrared absorbing particle dispersion or near-infrared absorbing particles in a solid medium and then pelletizing the solid medium.

[0157] Furthermore, as near-infrared absorbing particles, a near-infrared absorbing particle dispersion powder obtained by removing the liquid medium from a near-infrared absorbing particle dispersion can also be used.

[0158] For example, a mixture can be prepared by uniformly mixing a near-infrared absorbing particle dispersion, near-infrared absorbing particles, or near-infrared absorbing particle dispersion powder with a solid medium in powder or pellet form, and other additives as needed. Then, a masterbatch can be manufactured by kneading this mixture in a vented single-screw or twin-screw extruder and processing the molten extruded strand into pellets by cutting. In this case, the pellets can be cylindrical or prismatic in shape. It is also possible to use the so-called hot-cut method, in which the molten extruded material is cut directly, when producing pellets. In this case, a shape close to a sphere is common.

[0159] Furthermore, when a near-infrared absorbing particle dispersion is used as a raw material in the masterbatch preparation process, it is preferable to reduce or remove the liquid medium derived from the near-infrared absorbing particle dispersion. In this case, there is no particular limit to the extent to which the liquid medium contained in the near-infrared absorbing particle dispersion is removed. For example, it is preferable to remove the liquid medium from the near-infrared absorbing particle dispersion to an amount that is acceptable to remain in the masterbatch. If a liquid plasticizer is used as the liquid medium, the entire amount of the liquid plasticizer may remain in the near-infrared absorbing particle dispersion.

[0160] The method for reducing and removing the liquid medium contained in the near-infrared absorbing particle dispersion or a mixture of the near-infrared absorbing particle dispersion and a solid medium is not particularly limited. For example, it is preferable to carry out a drying process in which the near-infrared absorbing particle dispersion is dried under reduced pressure. Specifically, the near-infrared absorbing particle dispersion is dried under reduced pressure while being stirred to separate the near-infrared absorbing particle-containing composition from the components of the liquid medium. An example of an apparatus used for this reduced-pressure drying is a vacuum-stirring type dryer, but any apparatus having the above function is acceptable and is not particularly limited. In addition, the pressure value during the reduced pressure in the drying process is selected as appropriate.

[0161] By using this vacuum drying method, the efficiency of removing liquid media and other substances derived from the near-infrared absorbing particle dispersion is improved. Furthermore, since the near-infrared absorbing particle dispersion powder obtained after vacuum drying and the raw material, the near-infrared absorbing particle dispersion liquid, are not exposed to high temperatures for extended periods, aggregation of the near-infrared absorbing particles dispersed in the near-infrared absorbing particle dispersion powder and the near-infrared absorbing particles dispersed in the dispersion liquid does not occur, which is preferable. In addition, the productivity of the near-infrared absorbing particle dispersion powder and other substances is increased, and the evaporated liquid media and other solvents can be easily recovered, which is also preferable from an environmental perspective.

[0162] In the near-infrared absorbing particle dispersion powder obtained after the drying process, it is preferable to thoroughly remove solvent components with a boiling point of 120°C or lower. For example, it is preferable that the residual amount of such solvent components be 2.5% by mass or less. If the residual solvent components are 2.5% by mass or less, bubbles will not be generated when the near-infrared absorbing particle dispersion powder is processed into, for example, a near-infrared absorbing particle dispersion, and the appearance and optical properties will be well maintained. Furthermore, if the residual solvent components in the near-infrared absorbing particle dispersion powder are 2.5% by mass or less, when the near-infrared absorbing particle dispersion powder is stored for a long period of time, aggregation due to natural drying of the residual solvent components will not occur, and long-term stability will be maintained.

[0163] The resulting masterbatch can be mixed with a solid medium to adjust the dispersion concentration of the near-infrared absorbing particles while maintaining their dispersion state.

[0164] Furthermore, the method for producing the near-infrared absorbing particle dispersion of this embodiment may optionally include a molding step in which the obtained masterbatch, or a masterbatch to which a solid medium has been added as described above, is molded to form a near-infrared absorbing particle dispersion of a desired shape.

[0165] The specific method for forming the near-infrared absorbing particle dispersion is not particularly limited, but known methods such as extrusion molding and injection molding can be used.

[0166] In the molding process, for example, near-infrared absorbing particle dispersions can be manufactured in the form of sheets, boards, or films, which are formed into planar or curved shapes. The method for forming the material into sheets, boards, or films is not particularly limited, and various known methods can be used. For example, calendering rolls, extrusion, casting, inflation, etc., can be used.

[0167] The method for producing the near-infrared absorbing particle dispersion according to this embodiment is not limited to the form having the masterbatch preparation step described above.

[0168] For example, the method for producing the near-infrared absorbing particle dispersion of this embodiment may also have the following steps.

[0169] A precursor preparation step involves mixing a solid medium precursor, such as a monomer, oligomer, or uncured liquid solid medium, with near-infrared absorbing particles, a near-infrared absorbing particle dispersion powder, or a near-infrared absorbing particle dispersion liquid to prepare a near-infrared absorbing particle precursor.

[0170] A near-infrared absorbing particle dispersion preparation process, which involves curing a solid media precursor such as the above-mentioned monomer by a chemical reaction such as condensation or polymerization to produce a near-infrared absorbing particle dispersion.

[0171] For example, when using acrylic resin as the solid medium, a precursor liquid for a near-infrared absorbing particle dispersion can be obtained by mixing acrylic monomer or an acrylic-based UV-curing resin with near-infrared absorbing particles.

[0172] Next, by filling the near-infrared absorbing particle dispersion precursor liquid into a predetermined mold or the like and performing radical polymerization, a near-infrared absorbing particle dispersion using acrylic resin can be obtained.

[0173] When using a resin that hardens by crosslinking as the solid medium, the dispersion can be obtained by crosslinking the near-infrared absorbing particle dispersion precursor liquid, similar to the case where acrylic resin is used as described above.

[0174] (3) Additives When resin is used as the solid medium, the near-infrared absorbing particle dispersion of this embodiment may also contain known additives such as plasticizers, flame retardants, color inhibitors, and fillers that are typically added to these resins. However, as mentioned above, the solid medium is not limited to resin, and binders using metal alkoxides can also be used.

[0175] The shape of the near-infrared absorbing particle dispersion according to this embodiment is not particularly limited, but as described above, it can take the form of, for example, a sheet, a board, or a film.

[0176] When a near-infrared absorbing particle dispersion in sheet, board, or film form is used as an intermediate layer for a transparent substrate such as laminated glass, the solid medium contained in the near-infrared absorbing particle dispersion may not have sufficient flexibility or adhesion to the transparent substrate as is. In this case, it is preferable that the near-infrared absorbing particle dispersion contains a plasticizer. Specifically, for example, if the solid medium is polyvinyl acetal resin and it is used for the above-mentioned applications, it is preferable that the near-infrared absorbing particle dispersion further contains a plasticizer.

[0177] As the plasticizer described above, substances used as plasticizers in the solid medium used in the near-infrared absorbing particle dispersion of this embodiment can be used. For example, plasticizers used in a near-infrared absorbing particle dispersion composed of polyvinyl acetal resin include plasticizers that are compounds of monohydric alcohols and organic acid esters, ester-based plasticizers such as polyhydric alcohol organic acid ester compounds, and phosphoric acid-based plasticizers such as organophosphate plasticizers. It is preferable that all of these plasticizers are liquid at room temperature. Among these, plasticizers that are ester compounds synthesized from polyhydric alcohols and fatty acids are preferred. (4) Examples of application The near-infrared absorbing particle dispersion of this embodiment can be used in various ways, and its use and application are not particularly limited. Below, examples of applications of the near-infrared absorbing particle dispersion of this embodiment will be described, including near-infrared absorbing interlayer films, near-infrared absorbing laminates, and near-infrared absorbing transparent substrates. (4-1) Near-infrared absorbing interlayer film, near-infrared absorbing laminate The near-infrared absorbing laminate of this embodiment may have a laminated structure including the near-infrared absorbing particle dispersion described above and a transparent substrate. The near-infrared absorbing laminate of this embodiment may have the near-infrared absorbing particle dispersion described above and a transparent substrate as elements, and may be a laminate formed by laminating these together.

[0178] An example of a near-infrared absorbing laminate is one in which two or more transparent substrates are laminated with the near-infrared absorbing particle dispersion described above. In this case, the near-infrared absorbing particle dispersion can be placed, for example, between the transparent substrates and used as an interlayer for near-infrared absorption.

[0179] In this case, specifically, as shown in Figure 5, 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 50 can have multiple transparent substrates 521, 522 and a near-infrared absorbing particle dispersion 51. The near-infrared absorbing particle dispersion 51 can be arranged between the multiple transparent substrates 521, 522. Although Figure 5 shows an example with two transparent substrates 521, 522, the configuration is not limited to this.

[0180] The near-infrared absorbing particle dispersion that serves as the near-infrared absorbing interlayer preferably has one of the following shapes: sheet, board, or film.

[0181] The transparent substrate can preferably be one or more selected from transparent glass plates, plate-shaped plastics, or film-shaped plastics in the visible light region.

[0182] When using plastic as a transparent substrate, the type of plastic is not particularly limited and can be selected according to the application. For example, one or more types can be used selected from polycarbonate resin, acrylic resin, polyester resin, polyamide resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, ionomer resin, fluororesin, etc. Polyethylene terephthalate resin can be suitably used as the polyester resin.

[0183] The transparent substrate may contain particles that have a solar radiation shielding function. As particles that have a solar radiation shielding function, near-infrared absorbing particles having near-infrared shielding properties can be used.

[0184] By interposing the aforementioned near-infrared absorbing particle dispersion as a component of the intermediate layer sandwiched between multiple transparent substrates, a solar radiation shielding laminate structure, a type of near-infrared absorbing laminate, can be created that suppresses discoloration even when exposed to ultraviolet light. Furthermore, a solar radiation shielding laminate structure, a type of near-infrared absorbing laminate, can be created that suppresses solar radiation transmittance while maintaining a more neutral color tone for transmission and ensuring transmittance of sensor wavelengths.

[0185] Furthermore, the above-mentioned near-infrared absorbing laminate can also be formed by bonding and integrating multiple transparent substrates facing each other, with a near-infrared absorbing particle dispersion sandwiched between them, using a known method.

[0186] When using the near-infrared absorbing particle dispersion described above as a near-infrared absorbing interlayer, the solid medium can be the one described for the near-infrared absorbing particle dispersion. However, from the viewpoint of increasing the adhesion strength between the near-infrared absorbing interlayer and the transparent substrate, the solid medium is preferably polyvinyl acetal resin.

[0187] The near-infrared absorbing interlayer of this embodiment can be manufactured by the method for manufacturing near-infrared absorbing particle dispersions described above, and can be a near-infrared absorbing interlayer having any of the following shapes: sheet, board, or film.

[0188] Furthermore, if the near-infrared absorbing interlayer does not have sufficient flexibility or adhesion to the transparent substrate, it is preferable to add a liquid plasticizer for the media resin. For example, if the media resin used for the near-infrared absorbing interlayer is polyvinyl acetal resin, adding a liquid plasticizer for polyvinyl acetal resin is beneficial for improving adhesion to the transparent substrate.

[0189] As a plasticizer, substances used as plasticizers for solid resins can be used. For example, plasticizers applied to near-infrared absorbing particle dispersions using polyvinyl acetal resin as a solid medium include plasticizers that are compounds of monohydric alcohols and organic acid esters, ester-based plasticizers such as polyhydric alcohol organic acid ester compounds, and phosphoric acid-based plasticizers such as organophosphate plasticizers. It is preferable that all plasticizers are liquid at room temperature. Among these, plasticizers that are ester compounds synthesized from polyhydric alcohols and fatty acids are preferred.

[0190] Furthermore, at least one substance selected from the group consisting of silane coupling agents, metal salts of carboxylic acids, metal hydroxides, and metal carbonates may be added to the near-infrared absorbing interlayer. The metals constituting the metal salts of carboxylic acids, metal hydroxides, and metal carbonates are not particularly limited, but it is preferable that they be at least one substance selected from sodium, potassium, magnesium, calcium, manganese, cesium, lithium, rubidium, and zinc. In the near-infrared absorbing interlayer, it is preferable that the content of at least one substance selected from the group consisting of metal salts of carboxylic acids, metal hydroxides, and metal carbonates is 1% by mass or more and 100% by mass or less relative to the near-infrared absorbing particles.

[0191] Furthermore, the near-infrared absorbing interlayer may, if necessary, contain, in addition to the near-infrared absorbing particles, at least one of the following particles: oxide particles, composite oxide particles, or boride particles containing two or more elements selected from the group consisting of Sb, V, Nb, Ta, W, Zr, F, Zn, Al, Ti, Pb, Ga, Re, Ru, P, Ge, In, Sn, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Tb, Lu, Sr, and Ca. The near-infrared absorbing interlayer may contain such particles in a range of 5% to 95% by mass, when the total amount of these particles with the near-infrared absorbing particles is considered to be 100% by mass.

[0192] The near-infrared absorbing laminate may contain an ultraviolet absorber in at least one layer of the interlayer film placed between transparent substrates. Examples of ultraviolet absorbers include one or more compounds selected from compounds having a malonic acid ester structure, compounds having an oxalic acid anilide structure, compounds having a benzotriazole structure, compounds having a benzophenone structure, compounds having a triazine structure, compounds having a benzoate structure, and compounds having a hindered amine structure.

[0193] It goes without saying that the intermediate layer of the near-infrared absorbing laminate may be composed solely of the near-infrared absorbing interlayer according to this embodiment.

[0194] The near-infrared absorbing interlayer described herein is one embodiment of a near-infrared absorbing particle dispersion. The near-infrared absorbing particle dispersion according to this embodiment can, of course, be used without being sandwiched between two or more transparent substrates that transmit visible light. In other words, the near-infrared absorbing particle dispersion according to this embodiment can function as a near-infrared absorbing particle dispersion on its own.

[0195] The near-infrared absorbing laminate according to this embodiment is not limited to the form in which a near-infrared absorbing particle dispersion is arranged between transparent substrates as described above, but can take any configuration as long as it has a laminated structure including a near-infrared absorbing particle dispersion and a transparent substrate. (4-2) Near-infrared absorbing transparent substrate The near-infrared absorbing transparent substrate of this embodiment comprises a transparent substrate and a near-infrared absorbing layer disposed on at least one surface of the transparent substrate, and the near-infrared absorbing layer can be the near-infrared absorbing particle dispersion described above.

[0196] Specifically, as shown in Figure 6, a schematic cross-sectional view along the lamination direction of the transparent substrate and the near-infrared absorbing layer, the near-infrared absorbing transparent substrate 60 may have a transparent substrate 61 and a near-infrared absorbing layer 62. The near-infrared absorbing layer 62 can be arranged on at least one surface 61A of the transparent substrate 61.

[0197] The near-infrared absorbing transparent substrate of this embodiment may have a transparent substrate as described above. Preferably, one or more types of transparent substrates can be selected from, for example, a film substrate (transparent film substrate) and a glass substrate (transparent glass substrate).

[0198] The film substrate is not limited to a film shape; for example, it may be in the shape of a board or a sheet. The material of the film substrate can preferably be one or more selected from polyester resin, acrylic resin, urethane resin, polycarbonate resin, polyethylene resin, ethylene vinyl acetate copolymer, vinyl chloride resin, fluororesin, etc., and can be used for various purposes. However, the material of the film substrate is preferably polyester resin, and more preferably polyethylene terephthalate resin (PET resin). That is, the film substrate is preferably a polyester resin film, and more preferably a polyethylene terephthalate resin film.

[0199] When a film substrate is used as the transparent substrate, it is preferable that the surface of the film substrate be surface-treated to facilitate adhesion with the near-infrared absorbing layer.

[0200] Furthermore, in order to improve the adhesion between the glass substrate or film substrate and the near-infrared absorbing layer, it is also preferable to form an intermediate layer on the glass substrate or film substrate and form the near-infrared absorbing layer on the intermediate layer. The composition of the intermediate layer is not particularly limited and can be made of, for example, a polymer film, a metal layer, an inorganic layer (for example, an inorganic oxide layer such as silica, titania, or zirconia), or an organic / inorganic composite layer.

[0201] Since near-infrared absorbing particle dispersions have already been described, their explanation will be omitted here. The shape of the near-infrared absorbing particle dispersion is not particularly limited, but it is preferable to have, for example, a sheet shape, a board shape, or a film shape.

[0202] The method for manufacturing the near-infrared absorbing transparent substrate of this embodiment will be described.

[0203] The near-infrared absorbing transparent substrate of this embodiment can be manufactured, for example, by using the near-infrared absorbing particle dispersion described above to form a near-infrared absorbing layer on the transparent substrate, which is a near-infrared absorbing particle dispersion in which near-infrared absorbing particles are dispersed in a solid medium.

[0204] Therefore, the method for manufacturing the near-infrared absorbing transparent substrate of this embodiment may include, for example, the following coating step and near-infrared absorbing layer formation step.

[0205] The coating process involves applying a coating solution containing the aforementioned near-infrared absorbing particle dispersion to the surface of a transparent substrate.

[0206] The near-infrared absorbing layer formation process involves evaporating the liquid medium in the coating solution and then forming a near-infrared absorbing layer.

[0207] The coating solution used in the coating process can be prepared, for example, by adding and mixing a resin, a solid medium such as a metal alkoxide, or a solid medium precursor to the near-infrared absorbing particle dispersion described above.

[0208] As previously described, a solid media precursor means one or more selected from monomers, oligomers, and uncured, liquid solid media.

[0209] When a near-infrared absorbing layer, which is a coating film, is formed 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, the near-infrared absorbing layer becomes a near-infrared absorbing particle dispersion. In this way, a near-infrared absorbing transparent substrate can be manufactured by providing a near-infrared absorbing particle dispersion on the surface of a transparent substrate.

[0210] The solid medium and the solid medium precursors have already been described in (1) the characteristics of the solid medium and the near-infrared absorbing particle dispersion, and (2) the method for producing the near-infrared absorbing particle dispersion, so their explanation will be omitted here.

[0211] The method for applying a coating solution to a transparent substrate in order to provide a near-infrared absorbing layer on the transparent substrate is not particularly limited, as long as it is a method that can uniformly apply the coating solution to the surface of the transparent substrate. Examples include bar coating, gravure coating, spray coating, dip coating, spin coating, screen printing, roll coating, and flow coating.

[0212] This section describes the procedure for creating a near-infrared absorbing layer on the surface of a transparent substrate, using an example where an ultraviolet-curing resin is used as the solid medium and a coating solution is applied using the bar coating method to form a near-infrared absorbing layer.

[0213] A coating solution, whose concentration and additives have been appropriately adjusted to have adequate leveling properties, is applied onto a transparent substrate using a wire bar with a bar number that satisfies the desired thickness of the near-infrared absorbing layer and the content of near-infrared absorbing particles. After removing the solvent, such as the liquid medium, contained in the coating solution by drying, the solid medium is cured by irradiation with ultraviolet light, thereby forming a coating layer, which is a near-infrared absorbing layer, on the transparent substrate.

[0214] The drying conditions for the coating film vary depending on the type and proportion of each component and solvent used, but typically, it can be carried out at a temperature of 60°C to 140°C for 20 seconds to 10 minutes. There are no particular restrictions on ultraviolet irradiation, and ultraviolet exposure equipment such as ultra-high pressure mercury lamps can be suitably used.

[0215] In addition, the adhesion between the substrate and the near-infrared absorbing layer, the smoothness of the coating film during coating, and the drying properties of the organic solvent can be manipulated by pre- and post-processing steps (pre-processing and post-processing) before the formation of the near-infrared absorbing layer. Examples of such pre- and post-processing steps include a substrate surface treatment step, a pre-bake (pre-heating of the substrate) step, and a post-bake (post-heating of the substrate) step, which can be selected as appropriate. Preferably, the heating temperature in the pre-bake and post-bake steps is 80°C to 200°C, and the heating time is 30 seconds to 240 seconds.

[0216] The method for manufacturing the near-infrared absorbing transparent substrate of this embodiment is not limited to the method described above. Other examples of the method for manufacturing the near-infrared absorbing transparent substrate of this embodiment include the following configurations which include a near-infrared absorbing particle dispersion coating and drying process, or a binder coating and curing process.

[0217] The near-infrared absorbing particle dispersion coating and drying process involves coating the surface of a transparent substrate with the near-infrared absorbing particle dispersion described above and drying it.

[0218] The binder application and curing process involves applying a binder, such as a resin, a solid medium like a metal alkoxide, or a solid medium precursor, onto a surface coated with a near-infrared absorbing particle dispersion, and then curing it.

[0219] In this case, a film in which near-infrared absorbing particles are dispersed is formed on the surface of the transparent substrate by the coating and drying process of the near-infrared absorbing particle dispersion. The near-infrared absorbing particle dispersion can be applied by the same method as described in the coating process of the manufacturing method of the near-infrared absorbing transparent substrate described above.

[0220] Then, by applying a binder to a film on which the near-infrared absorbing particles are dispersed and curing it, the cured binder is arranged between the near-infrared absorbing particles, forming a near-infrared absorbing layer.

[0221] The near-infrared absorbing transparent substrate may also have a coating layer on the surface of the near-infrared absorbing particle dispersion; in other words, it may have a multilayer film.

[0222] The coating layer can be a coating film of an oxide containing, for example, one or more elements selected from Si, Ti, Zr, and Al. In this case, the coating layer can be formed, for example, by applying a coating solution containing one or more elements selected from alkoxides containing one or more elements from Si, Ti, Zr, and Al, and partially hydrolyzed condensed polymers of said alkoxides, onto a near-infrared absorption layer, and then heating.

[0223] By providing a coating layer, the coated components fill the gaps where the first layer of near-infrared absorbing particles is deposited, forming a film that suppresses the refraction of visible light. This reduces the film's haze value and improves visible light transmittance. Furthermore, it improves the adhesion of the near-infrared absorbing particles to the substrate.

[0224] Here, as a method for forming a coating film consisting of an alkoxide containing one or more of Si, Ti, Zr, and Al, or a partially hydrolyzed condensed polymer thereof, on near-infrared absorbing particles alone or on a film containing near-infrared absorbing particles, a coating method is preferred from the viewpoint of ease of film formation and cost.

[0225] As the coating solution used in the above coating method, a solvent such as water or alcohol containing one or more alkoxides containing Si, Ti, Zr, or Al, or one or more partially hydrolyzed condensed polymers of said alkoxides, can be suitably used. The content of the alkoxides etc. in the above coating solution is not particularly limited, but for example, it is preferable to have 40% by mass or less in terms of oxides in the coating obtained after heating. In addition, the pH can be adjusted by adding acids or alkalis as needed.

[0226] By applying the coating liquid as the second layer onto a film mainly composed of near-infrared absorbing particles and heating it, an oxide film containing one or more selected from Si, Ti, Zr, and Al, which is a coating layer, can be easily formed. It is also preferable to use an organosilazane solution as a binder component used in the coating liquid or a component of the coating liquid.

[0227] The heating temperature of the base material after coating a near-infrared absorbing particle dispersion liquid containing one or more selected from metal alkoxides of any one or more of Si, Ti, Zr, and Al and their partial hydrolysis polycondensates, or a coating liquid (coating solution) is not particularly limited. For example, the heating temperature of the base material is preferably 100 °C or higher, and more preferably higher than the boiling point of the solvent in the coating liquid such as the near-infrared absorbing particle dispersion liquid.

[0228] This is because when the heating temperature of the base material is 100 °C or higher, the polymerization reaction of the metal alkoxide contained in the coating film or the hydrolysis polymer of the metal alkoxide can be completed. Also, when the heating temperature of the base material is 100 °C or higher, water or an organic solvent as the solvent hardly remains in the film, so in the film after heating, these solvents do not cause a reduction in visible light transmittance.

[0229] The thickness of the near-infrared absorbing layer on the transparent base material of the present embodiment is not particularly limited, but in practical use, 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 exhibiting sufficient pencil hardness and having scratch resistance, when the solvent in the near-infrared absorbing layer volatilizes and the binder cures, process abnormalities such as warping of the base material film can be avoided.

Example

[0230] Specific examples will be given and described below, but the present invention is not limited to these examples. (1) Evaluation method (1-1) Powder X-ray diffraction Powder X-ray diffraction patterns (XRD patterns) were measured for composite tungsten oxide particles using a powder X-ray diffractometer (X'Pert PRO MPD (Malvern Panalytical)). CuKα radiation was used as the radiation source, and the measurements were performed with a tube voltage of 45kV and a tube current of 40mA. (1-2) Observation of TEM images and HAADF images The obtained composite tungsten oxide particles were observed using a transmission electron microscope. High-angle angular dark-field (HAADF) images were also observed using a JEOL STEM (model: JEM-ARM200F). The particle contrast in HAADF images is proportional to the number of atoms in the particle and the number of atoms. Since the contrast is brighter as more heavier atoms are stacked, the brightest and second brightest contrasts are thought to be tungsten oxide (W), the third brightest contrast is thought to be cinnabar (Cs), and oxygen (O) cannot be observed. (1-3)Visible Light Transmittance, Solar Transmittance The optical properties of the ink were measured using a spectrophotometer (Hitachi, Ltd. U-4100), and the visible light transmittance and solar transmittance were calculated according to JIS R 3106 (2019). (1-4) Composition analysis The proportion of each component contained in the composite tungsten oxide particles was evaluated using the following method.

[0231] The mass percentage of Cs was calculated as the average of three measurements taken for each sample using a polarized Zeeman atomic absorption spectroscopy (AAS, model: ZA3300, manufactured by Hitachi High-Tech Corporation).

[0232] The mass percentage of W was calculated as the average value obtained by analyzing each sample three times using inductively-coupled plasma optical emission spectroscopy (ICP-OES, model: ICPE-9800, manufactured by Shimadzu Corporation).

[0233] The mass percentage of oxygen was calculated using an oxygen, nitrogen, and hydrogen analyzer (ON-836, LECO Japan Corp.) with an infrared absorption spectroscopy (IRS) detector for oxygen detection, and the average value was obtained from three analyses performed on each sample. (1-5)ΔR, ΔE To compare the absorbance and color changes of the near-infrared absorbing particle dispersions prepared in Example 3 and Comparative Example 2 after UV irradiation, ΔR (the ratio of the maximum absorbance after irradiation to the maximum absorbance before UV irradiation) and ΔE (the amount of color change) were used to eliminate the influence of the coating film concentration.

[0234] As described above, ΔR is the value obtained by dividing the maximum absorbance after UV irradiation (ABS_after UV) by the maximum absorbance before UV irradiation (ABS_initial). That is, ΔR = ABS_after UV / ABS_initial.

[0235] ΔE can be calculated using the following equation (1), where ΔL * Δa * Δb * This was determined from the measurement results using a spectrophotometer, in accordance with ISO 11664-4:2008, and is CIE 1976 L * a * b * Color value L in the color space * a * , b * This represents the change in the value before and after UV irradiation.

[0236]

number

[0237] The composite material manufacturing apparatus 10 includes a first storage section 11 containing a solution containing a W element source and an M element source, which are the raw material solutions; a two-fluid nozzle 12 that forms droplets of the raw material and simultaneously forms a flame; and a reaction tube 13 connected to a filter 14 for collecting the formed composite tungsten oxide particles.

[0238] The supply rate of the raw material solution to the two-fluid nozzle 12 was set to 3 g / min. The flow rate of the carrier gas, oxygen, was controlled by the ejector 15 to 9 L / min. The air flow rate in the ejector 15 was controlled to be within the range of 160 L / min to 180 L / min.

[0239] For flame formation using the two-fluid nozzle 12, propane gas and oxygen gas were used, with a propane gas flow rate of 1.0 L / min and an oxygen gas flow rate of 5.0 L / min.

[0240] As raw materials, a mixed solution was used, consisting of a solution in which W(CO)6, a W element source, was dissolved in THF (tetrahydroflon) (solution containing the W element source), and a solution in which cesium acetate, a M element source, was dissolved in ethanol (solution containing the M element source). This mixed solution was then stored in the first storage section 11. The mixed raw material was prepared so that the Cs / W ratio, which is the ratio of the amount of substance of the M element Cs (Cs) to the amount of substance of the tungsten element (W), was 0.38.

[0241] From the first storage unit 11, the above-mentioned raw material solution and oxygen, which is a carrier gas, were supplied to the two-fluid nozzle 12 to form an aerosol (aerosol formation step).

[0242] As described above, propane gas and oxygen gas were supplied to the two-fluid nozzle 12 to form a flame reaction field, and the formed aerosol was supplied into the flame for heat treatment (heat treatment step).

[0243] The composite tungsten oxide particles obtained in the heat treatment step were introduced into the reaction tube 13. A cooling water pipe 131 was arranged around the reaction tube 13, and the cooling water was circulating. The composite tungsten oxide particles introduced into the reaction tube 13 were collected by a filter 14 which is a bag filter.

[0244] The obtained composite tungsten oxide particles were evaluated as described above.

[0245] The XRD pattern of the obtained composite tungsten oxide particles is shown in Fig. 7A. In the obtained XRD pattern, the diffraction peak of hexagonal Cs 0.33 WO3 and the diffraction peak of (Cs2O) 0.44 W2O6 ICDD:00-047-0566 were partly confirmed. In Figs. 7A and 7B, the position of the diffraction peak of Cs 0.33 WO3 is also shown together.

[0246] Also, the TEM image and HAADF image of the obtained composite tungsten oxide particles are shown in Figs. 8A to 8C. From the TEM image shown in Fig. 8A, the particle size was about 50 nm to 200 nm. That is, the particle size was within the range of 10 nm or more and 200 nm or less. Also, it was confirmed that the particles have facets (flat surfaces). From the HAADF-STEM images shown in Figs. 8B and 8C, since the W-deficient columns generated in the W / Cs columns were confirmed at the reaching positions, these particles were classified as cesium polytungstate.

[0247] When the Cs / W ratio of these particles was analyzed by ICP or the like, it was confirmed that the Cs / W ratio decreased from 0.38 which is the charged composition to 0.37. The O / W ratio was 3.13. [Example 2] The composite tungsten oxide particles obtained in Example 1 were subjected to a reduction treatment using the reduction treatment apparatus 20 shown in Fig. 2.

[0248] As shown in Figure 2, under an airflow of 3 vol.% H2 / 97 vol.% Ar, heaters 22 were placed around the reaction tube 21, and the temperature was raised from room temperature to 500°C. After the part where the container 23 containing the composite tungsten oxide particles 24 was placed reached the reduction treatment temperature, it was held for 2 hours, and then cooled to room temperature to perform the reduction treatment (reduction treatment step).

[0249] The XRD patterns of the obtained composite tungsten oxide particles are shown in Figure 7B. The obtained XRD patterns are hexagonal Cs 0.33 We confirmed that it contained only the diffraction peak of WO3.

[0250] Furthermore, TEM and HAADF images of the obtained composite tungsten oxide particles are shown in Figures 9A to 9C. From the TEM image shown in Figure 9A, it was confirmed that the particle size was approximately 50 nm to 200 nm. That is, the particle diameter was within the range of 10 nm to 200 nm. The particles also had facets. From the HAADF-STEM images shown in Figures 9B and 9C, it was confirmed that the W and Cs deficiencies had completely disappeared.

[0251] Analysis of the Cs / W ratio of these particles using ICP and other methods showed that the Cs / W ratio decreased further from 0.37 to 0.34 compared to Example 1. However, the value of 0.34 is 0.01 higher than the theoretical composition ratio of 0.33, and since it is single-phase on the above XRD pattern, it is considered that there are virtually no Cs defects. The O / W ratio was 2.83.

[0252] Upon examining the lattice constants shown in Figure 7C, we find that Cs 0.33 It is located approximately 0.003 Å to the upper left and above WO3 in terms of both the a-axis and c-axis lengths, suggesting that a composite tungsten oxide doped with Cs up to a theoretical ratio of 0.33 was successfully synthesized in nanoparticle form.

[0253] Table 1 shows the semi-quantitative results obtained by XPS measurement of the composite tungsten oxide particles. A VersaProbe II from ULVAC-FI was used for XPS. A monochromatic Al-Kα X-ray source was used, with a beam diameter of 100 μmφ, an X-ray output of 25 W, and a target vacuum of 5.7 × 10⁻⁶. -7 The implementation was carried out at a level below Pa.

[0254] It is known that alkali elements can dopage tungsten to a maximum of 1 / 3 of its molar mass in a hexagonal crystal structure. However, in this example, ratios greater than 0.372 and 0.33 were observed. This suggests that alkali elements may be present in greater quantities on the surface of the particles.

[0255] [Table 1] [Example 3] An ink dispersion was prepared using 1% by mass of the composite tungsten oxide particles obtained in Example 2, 1% by mass of an amine-based acrylic copolymer dispersant, and the remainder as methyl isobutyl ketone (hereinafter also referred to as MIBK) as a dispersion medium. The ink was prepared by dispersing and grinding the composite tungsten oxide particles and dispersion medium using 0.3 mmφ ZrO2 beads with a paint shaker.

[0256] In Example 3, the optical properties of the dispersion were measured by varying the dispersion and grinding time to 0.5 hours, 1 hour, 2 hours, 4 hours, and 5 hours. This allows us to understand the changes that occur during the dispersion and grinding process of the composite tungsten oxide particles from Example 2.

[0257] The obtained dispersion, which is the ink, was diluted with MIBK to a concentration of 0.02% by mass of composite tungsten oxide particles, and the molar absorption coefficient and transmission profile were measured using a quartz cell with a UV-Vis-NIR spectrophotometer (model: U-4100, manufactured by Hitachi High-Tech Corporation). The spectral characteristics of the dispersion, which is the ink, were measured using the same procedure in the following examples and comparative examples.

[0258] Figure 10A shows the changes in the measured transmission profiles of inks prepared by varying the grinding time of composite tungsten oxide particles. It was confirmed that the absorption characteristics in the infrared region did not change even when the grinding time was about 2 hours, and that the scattering of light in the visible light region decreased after 2 hours of grinding.

[0259] Figures 10B and 10C show the particle size distribution measured from TEM images of the composite tungsten oxide powder in the ink obtained after a 5-hour dispersion and grinding treatment, as well as the TEM images themselves. The average particle size was 14.3 nm, and the standard deviation was 2.7 nm. No coarse particles larger than 70 nm were observed. The average particle size and standard deviation are the average and standard deviation values ​​for the particle size measured from the TEM images mentioned above.

[0260] Table 1 shows the semi-quantitative results of XPS measurement of the composite tungsten oxide powder in the ink obtained after a 5-hour dispersion and grinding treatment. Although the grinding treatment reduced the Cs / W ratio to 0.307 compared to Example 2, it was confirmed that it was still higher than the Cs / W ratio shown in Comparative Example 2.

[0261] Figure 11A compares the molar absorption coefficients of the composite tungsten oxide particles dispersed and ground for 5 hours in Example 3 and the composite tungsten oxide particles dispersed and ground for 7 hours in Comparative Example 2.

[0262] In Comparative Example 2, absorption peaks were observed at 0.8 and 1.4 eV, while in Example 3, an absorption peak appeared at 0.95 eV.

[0263] According to the Drude-Lorentz analysis by Machida et al. in Non-Patent Document 9, Cs prepared by the solid-phase method 0.32 WO 3-y In powder form, Cs free electrons contribute to 1.0 eV LSPR / / , while V OElectrons contribute to the LSPR⊥ (0.8eV) in the xy direction and to the polaron around 1.4eV. The three types of absorption described above overlap, resulting in a 0.8eV peak with a shoulder at 1.4eV. Based on the above findings and the results shown in Figure 11A, the absorption peak of the composite tungsten oxide particles of this example prepared by the flame spray method is V compared to the absorption peak of the composite tungsten oxide particles of Comparative Example 2, described later, prepared by the solid-phase method. O The absorption peaks originating from this substance are thought to be few.

[0264] Furthermore, to demonstrate the appropriateness of comparing the composite tungsten oxide particles subjected to 5-hour dispersion and grinding treatment in Example 3 with those subjected to 7-hour dispersion and grinding treatment in Comparative Example 2, Figure 11B shows the relationship between VLT (Visible Light Transmittance) and Solar Transmittance. As shown in Figure 11B, both exhibit almost identical visible light transmittance and solar transmittance.

[0265] In other words, while the properties of powders synthesized by gas-phase methods to date have been similar to those of liquid-fed spray pyrolysis (LFSP) or solid-fed spray pyrolysis (SFSP), it was confirmed that the composite tungsten oxide particles obtained in this example asymptotically approached those of the powder synthesized by the solid-phase method in Comparative Example 2.

[0266] Figure 12A shows the evaluation results of the lightfastness of the composite tungsten oxide particles synthesized in this example. A coating solution was prepared by mixing a dispersion of the composite tungsten oxide particles synthesized in this example with UV-curable resin UV-3701 (Toagosei Co., Ltd.) in a mass ratio of 1:1. Next, the coating solution was applied onto a soda glass substrate (3 mm thick × 10 mm × 10 mm thick) using a wire bar (#6), and heated at 100°C for 1 minute to dry and remove the organic solvent contained in the coating solution. Furthermore, a cured film, which is a near-infrared absorbing particle dispersion, was prepared on a transparent glass substrate by polymerizing and curing the UV-curable resin in the coating solution using a UV conveyor device (model: ECS-401GX, manufactured by I-Graphics Co., Ltd.).

[0267] The UV source in the UV conveyor system is a mercury lamp (model: H04-L41, manufactured by iGraphics Co., Ltd.) with a dominant wavelength of 365 nm, and the lamp power of the UV conveyor was set to 2.0 kW. With this system, the intensity was 134.8 mW / cm². 2 UV irradiation was performed, and the cumulative intensity was 815.9 mJ / cm². 2 , 1631.8 mJ / cm² 2 3263.6 mJ / cm² 2 4895.4 mJ / cm² 2 The transmission profiles of near-infrared absorbing particle dispersions were measured for each sample at different cumulative intensities. Three measurements were taken for each sample, and the average value was used.

[0268] Figure 12A shows the change in absorbance before and after UV irradiation of the near-infrared absorbing particle dispersion of this embodiment shown in Figure 12A. In Figure 12A, absorbance curve 121 is before UV irradiation, and the absorbance curves along the direction indicated by the arrow labeled "UV Irradiation" in the figure show the absorbance curves with the highest cumulative UV irradiation intensity. Therefore, absorbance curve 122 represents the evaluation result for the sample with the highest cumulative UV irradiation intensity.

[0269] As shown in Figure 12A, the absorbance curve 121 of the near-infrared absorbing particle dispersion before UV irradiation confirmed that the absorbance at a wavelength of 1350 nm reached a maximum value of 0.71356. The integrated intensity was 4895.4 mJ / cm². 2 In the absorbance curve 122 of the near-infrared absorbing particle dispersion irradiated with UV light, the peak position shifted to a wavelength of 1325 nm, and its maximum value changed to 0.826.

[0270] Figure 12B shows the change in absorbance before and after UV irradiation of the near-infrared absorbing particle dispersion of Comparative Example 2, which will be described later. In Figure 12B, absorbance curve 121 is before UV irradiation, and the absorbance curve with a large cumulative intensity of UV irradiation is shown along the direction indicated by the arrow labeled "UV Irradiation" in the figure. Therefore, absorbance curve 122 represents the evaluation result for the sample with the largest cumulative intensity of UV irradiation.

[0271] As shown in Figure 12B, the absorbance curve 121 of the near-infrared absorbing particle dispersion before UV irradiation confirmed that the absorbance at a wavelength of 1420 nm reached a maximum value of 0.537. The integrated intensity was 4895.4 mJ / cm². 2 In the absorbance curve 122 of the near-infrared absorbing particle dispersion irradiated with UV light, the peak position shifted to a wavelength of 1400 nm, and its maximum value changed to 0.714.

[0272] Figure 13 shows the results of evaluating the change in absorbance due to UV irradiation as ΔR, after removing the difference in initial absorbance. In this example, even at the maximum UV irradiation dose, the sample synthesized had a ΔR of 0.179, confirming that the change was almost suppressed. On the other hand, the sample shown as Comparative Example 2 had an integrated UV irradiation intensity of 4895.4 mJ / cm². 2 Even after irradiation until it reached that point, it continued to change.

[0273] Figure 14 shows the results of evaluating the amount of color change due to UV irradiation as ΔE. It can be confirmed that the near-infrared absorbing particle dispersion of this embodiment suppresses the amount of color change before and after UV irradiation compared to the near-infrared absorbing particle dispersion of Comparative Example 2.

[0274] To investigate the factors that reduced the amount of absorbance change and color change during UV irradiation compared to Comparative Example 2, HAADF-STEM images of near-infrared absorbing particles and schematic diagrams of their crystal structure are shown in Figures 15A to 15D. Figure 15A shows the crystal structure of the composite tungsten oxide particles as viewed from the observation direction of the composite tungsten oxide particles shown in Figures 15B to 15D.

[0275] The Cs atoms in the hexagonal crystal structure exist in one-dimensional channels called hexagonal tunnels, and are surrounded by WO6 octahedra. Therefore, it is inferred that the desorption direction of Cs is parallel to the c-axis, i.e., the direction of direction index

[0001] . Figures 15B to 15D show HAADF-STEM images of the powder observed with {010} incidence. As shown in Figure 15B, when the composite tungsten oxide particles of this embodiment are observed from the (010) plane, the only edges surrounding the (010) plane that are formed by planes not parallel to the c-axis, i.e., the edges formed by the (001) plane in the case of Figure 15B, are edges 151 and 152.

[0276] The edges formed by other exposed surfaces, i.e., edges formed by surfaces parallel to the c-axis, are the edges formed by the (100) surface in the case of Figure 15B, and correspond to edges 153 and 154.

[0277] The combined length of sides 151 and 152 is 34.7 nm. On the other hand, the combined length of sides 153 and 154, which are formed by planes parallel to the c-axis, is 71.9 nm. Therefore, when the composite tungsten oxide particles are observed from the (010) plane, it was confirmed that the proportion of the lengths of the sides formed by planes parallel to the c-axis among the sides surrounding the (010) plane is 71.9 ÷ (34.7 + 71.9) × 100 = 67.4%.

[0278] While the evaluation results for a single particle are shown here, when other similar composite tungsten oxide particles were evaluated, the occupancy rate was always 60% or higher.

[0279] Furthermore, when the composite tungsten oxide particles prepared in Example 1 and Example 2 were similarly evaluated, the occupancy rate was 60% or higher. [Comparative Example 1] As comparative example 1, Cs 0.33 WO3 powder was synthesized.

[0280] Tungstic acid was added to an aqueous solution of cesium carbonate, stirred, and then the water was dried off by holding the mixture at 100°C for 12 hours to prepare the precursor.

[0281] The precursor has a molar ratio of cesium atoms (Cs) to tungsten atoms (W) of Cs / W = 0.33.

[0282] The obtained precursor was packed into a calcination vessel and calcined at 800°C for 1 hour in a reducing atmosphere with a volume ratio of H2 / N2 = 3 / 97. 0.32 WO3 consisted of coarse particles, even the finest ones being over 100 μm in size. The obtained coarse Cs 0.33 XRD results for WO3 powder: Cs 0.33 The diffraction peak was confirmed to be solely that of WO3. Furthermore, the Cs / W ratio determined by ICP analysis was 0.33.

[0283] Table 1 shows the semi-quantitative results obtained by XPS measurement of the composite tungsten oxide powder. The Cs / W ratio was 0.400. [Comparative Example 2] An ink dispersion was prepared using 1% by mass of the composite tungsten oxide particles obtained in Comparative Example 1, 1% by mass of an amine-based acrylic copolymer dispersant, and the remainder as methyl isobutyl ketone as a dispersion medium. The ink was prepared by dispersing and grinding the composite tungsten oxide particles, dispersant, and dispersion medium using 0.3 mmφ ZrO2 beads with a paint shaker.

[0284] In Comparative Example 2, the optical properties of the dispersion were measured by varying the dispersion and grinding time to 0.5 hours, 1 hour, 2 hours, 4 hours, 5 hours, and 7 hours. This allows us to understand the changes that occur during the dispersion and grinding process of the composite tungsten oxide particles in Comparative Example 1.

[0285] Figure 16A shows the changes in the measured transmission profiles of inks prepared by varying the grinding time of composite tungsten oxide particles. At a grinding time of 0.5 hours, the transmittance in the infrared region was low, around 20%, but by increasing the grinding time to 2 hours or more, the transmittance in the infrared region decreased to around 5%. Further extension of the grinding time reduced the effect of Rayleigh scattering, improving visible transparency. Finally, a practical dispersion was obtained with a grinding time of 7 hours.

[0286] The particle size distribution measured from TEM images of the composite tungsten oxide powder in the ink obtained after a 7-hour dispersion and grinding treatment is shown in Figures 16B and 16C, respectively. The average particle size (average particle diameter) was 24.6 nm, and the standard deviation was 30 nm.

[0287] Table 1 shows the semi-quantitative results of XPS measurement of the composite tungsten oxide powder in the ink obtained after a 7-hour dispersion and grinding treatment. The Cs / W ratio was 0.283, which is lower than in Example 3, and is presumed to be due to the desorption of Cs from the surface during the long grinding treatment.

[0288] As previously described in the explanation of Example 3, using Figures 12A, 12B, 13, and 14, the near-infrared absorbing particle dispersion of Comparative Example 2 showed a greater change in color before and after UV irradiation compared to the near-infrared absorbing particle dispersion of Example 3.

[0289] Here, as in Example 3, Figures 15E to 15G show HAADF-STEM images of the powder observed with {010} incidence. As shown in Figure 15E, when the composite tungsten oxide particles of this comparative example are observed from the (010) plane, the edges surrounding the (010) plane that are formed by planes not parallel to the c-axis, i.e., in the case of Figure 15E, the edges formed by the (001) plane and the (102) plane, are edges 161 to 164.

[0290] The edges formed by other exposed surfaces, i.e., edges formed by surfaces parallel to the c-axis, are the edges formed by the (100) surface in the case of Figure 15E, and correspond to edges 165 and 166.

[0291] Therefore, when the composite tungsten oxide particles were observed from the (010) plane, it was confirmed that the occupancy rate of the edges formed by the planes parallel to the c-axis among the edges surrounding the (010) plane was 31.7%.

[0292] From the above results, it is inferred that when the composite tungsten oxide particles are observed from the (010) plane, the ratio of the lengths of the edges formed by the planes parallel to the c-axis among the edges surrounding the (010) plane contributed to the difference in the coloring properties when irradiated with ultraviolet light, i.e., the difference in photochromic properties.

[0293] This application claims priority based on Japanese Patent Application No. 2022-061250, filed with the Japan Patent Office on March 31, 2022, and the entire contents of Japanese Patent Application No. 2022-061250 are incorporated herein by reference. [Explanation of symbols]

[0294] 10 Composite material manufacturing equipment 11. First storage unit 12 Two-fluid nozzle 13 reaction tube 131 Piping 14 filters 15 Ejectors 20 Reduction treatment device 21 reaction tube 21A One side 21B The other mouth 22 Heater 23 Container 24. Composite tungsten oxide particles 30 Near-infrared absorbing particle dispersion 31 Near-infrared absorbing particles 32 Liquid media 40 Near-infrared absorbing particle dispersion 41 Near-infrared absorbing particles 42 Solid medium 50 Near-infrared absorbing laminate 51 Near-infrared absorbing particle dispersion 521, 522 Transparent base material 60 Near-infrared absorbing transparent substrate 61 Transparent base material 61A One side 62 Near-infrared absorption layer 151-154 sides 161-166 sides

Claims

1. Composite tungsten oxide particles containing composite tungsten oxide, The aforementioned composite tungsten oxide is General formula M ｘ W ｙ O ｚ (However, element M is one or more elements selected from Rb and Cs, W is tungsten, O is oxygen, 0.20 ≤ x / y ≤ 0.37, 2.2 ≤ z / y ≤ 3.3) The crystal system is hexagonal. The composite tungsten oxide particles, when observed from the (010) plane, have a ratio of 60% or more of the length of the edges formed by the (100) plane parallel to the c-axis among the edges surrounding the (010) plane.

2. The composite tungsten oxide particles according to claim 1, wherein the particle diameter is 10 nm or more and 200 nm or less.

3. When a dispersion process is performed in which the material is dispersed in a dispersion medium, the difference between the state before the dispersion process and the state after the dispersion process is as follows: The composite tungsten oxide particles according to claim 1 or claim 2, wherein the decrease in the amount of substance ratio M / W, which is the ratio of the amount of substance of element M (M) to tungsten (W), is 0.1 or less.

4. It comprises near-infrared absorbing particles and a liquid medium. A dispersion of near-infrared absorbing particles, wherein the near-infrared absorbing particles are the composite tungsten oxide particles described in claim 1 or claim 2.

5. It comprises near-infrared absorbing particles and a solid medium. A near-infrared absorbing particle dispersion wherein the near-infrared absorbing particles are the composite tungsten oxide particles described in claim 1 or claim 2.

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