Complex tungsten oxide particles, near-infrared ray absorbing particle dispersion liquid, and near-infrared ray absorbing particle dispersion

Abstract

Complex tungsten oxide particles according to the present invention contain a complex tungsten oxide. The complex tungsten oxide is represented by the general formula MxWyOz (0.20 ≤ x / y ≤ 0.37, 2.2 ≤ z / y ≤ 3.3), and the crystal system is a hexagonal crystal. In a molar absorption coefficient curve in a range of 0.5-2.0 eV of a dispersion liquid in which the complex tungsten oxide particles are dispersed in a liquid medium or a dispersion in which the complex tungsten oxide particles are dispersed in a solid medium, the complex tungsten oxide particles have a lower peak value of an absorption curve of polaron absorption than a peak value of an absorption curve of localized surface plasmon absorption in a direction parallel to the c-axis of a complex tungsten oxide crystal contained in the complex tungsten oxide particle.

Description

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

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

[0002] Various near-infrared shielding technologies have been proposed to date that have good visible light transmittance and reduce solar radiation transmittance while maintaining transparency. Among these, near-infrared shielding technologies that use inorganic conductive fine particles have the advantages of superior near-infrared shielding properties compared to other technologies, low cost, radio wave transmittance, and high weather resistance.

[0003] For example, in Patent Document 1, a compound represented by the general formula M ｘ W ｙ O ｚ (wherein M is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; O is oxygen; and 0.001≦x / y≦1, 2.2≦z / y≦3.0) is dispersed as infrared-shielding material microparticles in a medium such as a resin; and techniques related to a method for producing the infrared-shielding material microparticles are also disclosed. Patent Document 1 also discloses an example of producing an infrared shielding film that is a thin-film dispersion of fine particles of an infrared shielding material.

[0004] According to Patent Document 1, it is possible to prepare a dispersion of infrared-shielding material particles that has excellent optical properties, such as more efficient shielding of sunlight, particularly light in the near-infrared region, while at the same time maintaining transmittance in the visible light region, etc. Therefore, application of the infrared-shielding particle dispersion disclosed in Patent Document 1 to various applications such as window glass has been studied.

[0005] Meanwhile, various studies have been conducted on methods for producing composite tungsten oxide particles that are useful as near-infrared shielding materials.

[0006] For example, the inventor of Patent Document 1 has reported in Non-Patent Document 1 that Cs ０．３２ WO ３ However, the synthesis method disclosed in Non-Patent Document 1 requires a pulverization process to produce nanoparticles because the particle diameter is large. This may increase the number of process steps.

[0007] Patent Document 2 proposes synthesizing potassium-cesium-tungsten bronze solid solution particles using a plasma torch in a reducing atmosphere.

[0008] Non-patent document 2 describes Cs by hydrothermal synthesis. ｘ WO ３ However, the hydrothermal synthesis method requires a synthesis time of several tens of hours or more. In addition, the hydrothermal synthesis method has a problem in that it requires a large number of steps, such as post-treatment steps.

[0009] Non-Patent Document 3 discloses a synthesis method based on inductively coupled thermal plasma technology. However, this synthesis method requires the introduction of an inductively coupled thermal plasma device, which increases the introduction and running costs.

[0010] Non-Patent Document 4 discloses a method for synthesizing a composite tungsten oxide by a water-solvent flame spray pyrolysis method. However, the amount of Cs was small, and therefore the infrared absorption characteristics were poor.

[0011] Non-Patent Document 5 discloses a method for synthesizing a composite tungsten oxide by aqueous solvent spray pyrolysis, which results in a composite tungsten oxide with little Cs desorption from the particle surface. However, the infrared absorption properties were poor.

[0012] Patent Documents 3 and 4 disclose methods for producing composite tungsten microparticles by flame spraying.

[0013] International Publication No. 2005 / 037932 Japanese Patent Publication No. 2012-532822 International Publication No. 2017 / 129516 US Patent Application Publication No. 2010 / 0102700

[0014] 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.4059-4061Guo 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.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.Hirano Tomoyuki, et al. "Synthesis of highly crystalline hexagonal cesium tungsten bronze nanoparticles by flame-assisted spray pyrolysis." Advanced Powder Technology, 2018, Vol.29, Issue 10, P.2512-2520.Nakakura Shuhei, et al. "Improved photochromic stability in less deficient cesium tungsten bronze nanoparticles." Advanced Powder Technology, 2020, Vol.31, Issue 2, P.702-707.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, Vol.125, Issue 10, P.103103.

[0015] As described above, composite tungsten oxide particles are useful as near-infrared shielding materials. However, there is a demand for materials that have better visible light transmittance and improved near-infrared shielding performance than conventionally known composite tungsten oxide particles.

[0016] Therefore, one aspect of the present invention aims to provide composite tungsten oxide particles that are excellent in visible light transmission performance and near-infrared shielding performance.

[0017] In one aspect of the present invention, there is provided a composite tungsten oxide particle comprising a composite tungsten oxide, the composite tungsten oxide being represented by the general formula M ｘ W ｙ O ｚ (wherein M element is one or more elements selected from alkali metal elements, alkaline earth metal elements, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; O is oxygen; and 0.20≦x / y≦0.37, 2.2≦z / y≦3.3), the crystal system is hexagonal, The present invention provides composite tungsten oxide particles, in which, in a molar absorption coefficient curve in the range of 0.5 eV to 2.0 eV of a dispersion obtained by dispersing the composite tungsten oxide particles in a liquid medium or a dispersion obtained by dispersing the composite tungsten oxide particles in a solid medium, the peak value of the absorption curve for polaron absorption is lower than the peak value of the absorption curve for localized surface plasmon absorption in an orientation parallel to the c-axis of the composite tungsten oxide crystal contained in the composite tungsten oxide particles.

[0018] According to one aspect of the present invention, composite tungsten oxide particles having excellent visible light transmission properties and near-infrared shielding properties can be provided.

[0019] FIG. 1 is a schematic diagram of a composite material production apparatus that can be suitably used in the method for producing composite tungsten oxide particles of this embodiment. FIG. 2 is an explanatory diagram of a reduction treatment apparatus used in the reduction treatment step. FIG. 3 is a schematic diagram of a near-infrared absorbing particle dispersion. FIG. 4 is a schematic diagram of a near-infrared absorbing particle dispersion. FIG. 5 is a schematic diagram of a near-infrared absorbing laminate. FIG. 6 is a schematic diagram of a near-infrared absorbing transparent substrate. FIG. 7A is a TEM image of composite tungsten oxide particles after a heat treatment step in Example 1. FIG. 7B is a particle size distribution of composite tungsten oxide particles after a heat treatment step in Example 1. FIG. 7C is a TEM image of composite tungsten oxide particles after a reduction treatment step in Example 1. FIG. 7D is a particle size distribution of composite tungsten oxide particles after a reduction treatment step in Example 1. FIG. 8 is an XRD pattern of the composite tungsten oxide particles obtained in Example 1. FIG. 9A is a transmitted light profile of the near-infrared absorbing particle dispersion obtained in Example 1. Fig. 9B is a transmitted light profile of the near-infrared absorbing particle dispersion obtained in Comparative Example 1. Fig. 10A shows the molar absorption coefficient curve obtained in Example 1, a diagram in which the molar absorption coefficient curve is separated into absorption curves of three absorption components, and a combined value. Fig. 10B shows the molar absorption coefficient curve obtained in Comparative Example 1, a diagram in which the molar absorption coefficient curve is separated into absorption curves of three absorption components, and a combined value. Fig. 11 is an optical profile of the transmittance of dispersions containing composite tungsten oxide particles of Example 1 and Comparative Example 1.

[0020] Specific examples of composite tungsten oxide particles, near-infrared absorbing particle dispersions, and near-infrared absorbing particle dispersions according to one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described below with reference to the drawings. The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Composite Tungsten Oxide Particles] The composite tungsten oxide particles of this embodiment contain composite tungsten oxide. The composite tungsten oxide particles may be composed of composite tungsten oxide, but this does not exclude the inclusion of inevitable impurities in this case.

[0021] The composite tungsten oxide is represented by the general formula M ｘ W ｙ O ｚ It is expressed as:

[0022] However, the M element in the above general formula is an alkali metal element, an alkaline earth metal element, a rare earth element, Mg (magnesium), Zr (zirconium), Cr (chromium), Mn (manganese), Fe (iron), Ru (ruthenium), Co (cobalt), Rh (rhodium), Ir (iridium), Ni (nickel), Pd (palladium), Pt (platinum), Cu (copper), Ag (silver), Au (gold), Zn (zinc), Cd (cadmium), Al (aluminum), Ga (gallium), In (indium), Tl (thallium), The element may be one or more elements selected from the group consisting of tungsten (W), silicon (Si), germanium (Ge), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), boron (B), fluorine (F), phosphorus (P), sulfur (S), selenium (Se), bromine (Br), tellurium (Te), titanium (Ti), niobium (Nb), vanadium (V), molybdenum (Molybdenum), tantalum (Ta), rhenium (Re), beryllium (Be), hafnium (Hf), osmium (Os), bismuth (Bi), and iodine (I). W represents tungsten, O represents oxygen, and x, y, and z preferably satisfy the relationships 0.20≦x / y≦0.37 and 2.2≦z / y≦3.3, respectively.

[0023] Examples of alkali metal elements include Li (lithium), Na (sodium), K (potassium), Rb (rubidium), Cs (cesium), and Fr (francium). Examples of alkaline earth metal elements include Ca (calcium), Sr (strontium), Ba (barium), and Ra (radium). Examples of rare earth elements include Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).

[0024] The crystalline system of the composite tungsten oxide is hexagonal.

[0025] Furthermore, in a molar absorption coefficient curve in the range of 0.5 eV to 2.0 eV of a dispersion in which the composite tungsten oxide particles are dispersed in a liquid medium or a dispersion in which the composite tungsten oxide particles are dispersed in a solid medium, the peak value of the polaron absorption curve is lower than the peak value of the absorption curve of localized surface plasmon absorption in an orientation parallel to the c-axis of the composite tungsten oxide crystal contained in the composite tungsten oxide particles.

[0026] The composite tungsten oxide particles of this embodiment will be described below. (1) Composition The composite tungsten oxide contained in the composite tungsten oxide particles has the general formula M ｘ W ｙ O ｚ The M element, W, O, x, y, and z in the formula have already been described, and therefore will not be described here.

[0027] The composite tungsten oxide can have one or more tungsten bronze-type crystal structures selected from, for example, a tetragonal crystal, a cubic crystal, and a hexagonal crystal structure. The composite tungsten oxide contained in the composite tungsten oxide particles of this embodiment is a hexagonal crystal structure.

[0028] When the composite tungsten oxide has a hexagonal crystal structure, the particles have improved light transmittance in the visible light region and improved light absorption in the near-infrared region.

[0029] Composite tungsten oxides function as near-infrared shielding materials even when they have a tetragonal or cubic tungsten bronze-type crystal structure. However, the absorption position of light in the near-infrared region tends to change depending on the crystal structure of the composite tungsten oxide. The absorption position of light in the near-infrared region tends to shift toward longer wavelengths in the tetragonal crystal compared to the cubic crystal, and further shift toward longer wavelengths in the hexagonal crystal compared to the tetragonal crystal. In addition, accompanying this shift in absorption position, hexagonal crystals absorb the least light in the visible region, followed by tetragonal crystals, and of these, cubic crystals absorb the most light in the visible region. Therefore, for applications that require more light in the visible region to be transmitted and more light in the near-infrared region to be shielded, it is preferable to use a composite tungsten oxide having a hexagonal tungsten bronze-type crystal structure.

[0030] As described above, when the composite tungsten oxide has a hexagonal crystal structure, the transmittance of the composite tungsten oxide particles in the visible light region and the absorption of the light in the near-infrared region 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.And, when one or more elements selected from Cs, Rb, K, Tl, Ba, and In are used as the M element, it is easy to form 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.

[0031] Here, the arrangement of the M element when the composite tungsten oxide has a hexagonal crystal structure will be described.

[0032] An octahedron formed by a unit of a W (tungsten) atom and six O (oxygen) atoms, i.e., an octahedron with O atoms at the vertices and a W atom in the center, is assembled into six units to form a hexagonal void (tunnel) composed of O atoms. An M element is then placed in the void to form one unit, and many of these units are assembled to form a hexagonal crystal structure.

[0033] When a composite tungsten oxide having a hexagonal crystal structure has a uniform crystal structure, the ratio of the amount of substance of the M element to W is 0.20≦x / y≦0.37, preferably 0.25≦x / y≦0.37, and more preferably 0.30≦x / y≦0.36. Theoretically, when z / y=3, the value of x / y becomes 0.33, and it is considered that the M element is arranged in all of the hexagonal voids. Note that the above x, y, and z are the same as those in the general formula M described above. ｘ W ｙ O ｚ In the above equation, x, y, and z are used, and so on.

[0034] The composite tungsten oxide is tungsten trioxide (WO ３ ) and an M element added. Since tungsten trioxide does not contain effective free electrons, the near-infrared absorbing effect cannot be achieved unless the ratio of oxygen to 1 mole of tungsten is less than 3. However, in composite tungsten oxide, free electrons are generated by adding an M element, and the near-infrared absorbing effect can be achieved. Therefore, the ratio of oxygen to 1 mole of tungsten can be 3 or less. Furthermore, the ratio of oxygen to 1 mole of tungsten may exceed 3. However, WO ２ The crystalline phase of WO may cause absorption or scattering of light in the visible light region, and may reduce absorption of light in the near-infrared region. ２ From the viewpoint of suppressing the formation of , the ratio of oxygen to 1 mole of tungsten is preferably set to be greater than 2.

[0035] Therefore, z / y, which is the ratio of oxygen to 1 mole of tungsten, preferably satisfies 2.2≦z / y≦3.3 as described above. (2) Regarding the average particle size When the composite tungsten oxide particles of this embodiment are used for applications requiring transparency, for example, the composite tungsten oxide particles preferably have an average particle size of 800 nm or less. This is because particles with an average particle size of 800 nm or less do not completely block light due to scattering, and can maintain high visibility of light in the visible light range while simultaneously efficiently maintaining transparency. In particular, when transparency of light in the visible light range is important, it is preferable to further consider the scattering of light in the visible light range by the particles.

[0036] When emphasis is placed on reducing scattering of light in the visible light range by such particles, the average particle size is more preferably 200 nm or less, and even more preferably 100 nm or less.

[0037] If the average particle size of the composite tungsten oxide particles is small, scattering of light in the visible light region due to geometric scattering or Mie scattering is reduced. As a result, particularly clear transparency can be obtained for near-infrared shielding films such as near-infrared absorbing particle dispersions. When the average particle size is 200 nm or less, the geometric scattering or Mie scattering is reduced, and the Rayleigh scattering region is reached. In the Rayleigh scattering region, scattered light decreases in proportion to the sixth power of the average particle size, so as the average particle size decreases, scattering of light in the visible light region is reduced and transparency is improved. Furthermore, when the average particle size is 100 nm or less, scattered light is very little, which is preferable. From the viewpoint of avoiding scattering of light in the visible light region, a smaller average particle size is preferable.

[0038] Therefore, when the composite tungsten oxide particles of this embodiment are required to maintain high visibility in the visible light region as described above, the average particle size is preferably 800 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less. The lower limit of the average particle size of the composite tungsten oxide particles of this embodiment is not particularly limited, but is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more.

[0039] Therefore, the average particle size of the composite tungsten oxide particles of this embodiment is preferably, for example, 1 nm or more and 800 nm or less, more preferably 5 nm or more and 200 nm or less, even more preferably 10 nm or more and 200 nm or less, and even more preferably 10 nm or more and 100 nm or less.

[0040] The average particle size of composite tungsten oxide particles is calculated by measuring the particle size of each composite tungsten oxide particle from a transmission electron microscope image. Specifically, three fields of view are selected at a magnification that includes 200 or more composite tungsten oxide particles in one field of view, and the image of the composite tungsten oxide particles in each field of view is binarized, and the average particle size is calculated by image analysis. The upper limit of the number of composite tungsten oxide particles in one field of view is not particularly limited, and for example, the magnification may be selected so that one field of view includes 500 or less composite tungsten oxide particles. All composite tungsten oxide particles in the three fields of view may be evaluated, but for example, a total of 500 to 800 particles may be selected, or a total of 600 to 700 particles may be selected in the three fields of view.

[0041] Specifically, the equivalent circle diameter is calculated from the area of ​​each composite tungsten oxide particle, and this is used as the particle diameter of the composite tungsten oxide particle. The average particle diameter can then be calculated by adding up the particle diameters of all the composite tungsten oxide particles evaluated and dividing by the number of particles evaluated. That is, the arithmetic mean value of the particle diameters of the composite tungsten oxide particles evaluated can be used as the average particle diameter. (3) Peak Separation and Integrated Intensity of Localized Surface Plasmon Absorption and Polaron Absorption of Composite Tungsten Oxide Particles The composite tungsten oxide particles of this embodiment can be prepared as a near-infrared absorbing particle dispersion by being placed in a liquid medium. Furthermore, the composite tungsten oxide particles of this embodiment can be prepared as a near-infrared absorbing particle dispersion by being placed in a solid medium.

[0042] The composite tungsten oxide particles of this embodiment contained in the near-infrared absorbing particle dispersion liquid or near-infrared absorbing particle dispersion can have a particle size of nanometer order and absorb infrared rays, particularly near-infrared rays.

[0043] As will be described later, the composite tungsten oxide particles of this embodiment are preferably produced by a production method that can directly synthesize composite tungsten oxide particles having a small particle size, for example, a particle size of 1 μm or less.

[0044] By using composite tungsten oxide particles produced by a production method that can directly synthesize composite tungsten oxide particles with small particle sizes, it is possible to suppress damage to the composite tungsten oxide particles when they are pulverized and dispersed during the preparation of a dispersion, etc. Specifically, compared to when composite tungsten oxide particles with a particle size of more than 1 μm are synthesized by a conventionally known solid-phase method or the like and then a dispersion, etc. is prepared, the occurrence of lattice defects, etc. (damage) during the pulverization and dispersion of the composite tungsten oxide particles can be suppressed.

[0045] In the process of crushing and dispersing the composite tungsten oxide particles, if the constituent elements are detached or the crystal lattice is displaced, the electronic structure of the composite tungsten oxide particles also changes, which affects the plasma frequency that constitutes the localized surface plasmon resonance of the particles. In the composite tungsten oxide particles of this embodiment, the plasma frequency that constitutes the localized surface plasmon resonance that is expressed has predetermined characteristics.

[0046] Therefore, the composite tungsten oxide particles of this embodiment can be near-infrared absorbing particles that are excellent in visible light transmission performance and near-infrared shielding performance.

[0047] The composite tungsten oxide particles of this embodiment can be dispersed in a liquid medium or dispersed in a solid medium. These dispersions and dispersions have excellent infrared shielding effects, achieving a peak transmittance of 75% or more in the wavelength range of 500 nm to 600 nm and a bottom transmittance of 5% or less in the near-infrared region. Furthermore, dispersions and dispersions using the composite tungsten oxide particles of this embodiment can transmit red light with a wavelength of around 800 nm, compared to, for example, the dispersion of composite tungsten oxide particles shown in Comparative Example 1. This can also contribute to improving the color tone of dispersions and dispersions using composite tungsten oxide particles. Specifically, for example, a transmittance of 50% or more can be achieved at a wavelength of 700 nm and a transmittance of 30% or more at a wavelength of 800 nm. Meanwhile, the dispersions and dispersions also exhibit a rapid absorption of infrared light at wavelengths around 1000 nm. For this reason, by using the composite tungsten oxide particles of this embodiment, it is possible to obtain a dispersion liquid or dispersion that has a more neutral transmitted color tone while suppressing the solar radiation transmittance and that can also ensure transmittance of the sensor wavelength.

[0048] Below, we will consider the molar absorption coefficient curve obtained from the absorption curve measured by a spectrophotometer for a dispersion in which the composite tungsten oxide particles of this embodiment are dispersed in a liquid medium or a dispersion in which the composite tungsten oxide particles are dispersed in a solid medium.

[0049] The absorption in the absorption curve is caused by the localized surface plasmon absorption and polaron absorption of the composite tungsten oxide crystals contained in the composite tungsten oxide particles, and the absorption curve is formed as a result of the combination of these absorptions.

[0050] In the case of composite tungsten oxide particles, the localized surface plasmon absorption exhibits anisotropy with respect to the c-axis of the composite tungsten oxide crystal. Specifically, in the case of composite tungsten oxide particles, the localized surface plasmon absorption includes localized surface plasmon resonance absorption in a direction perpendicular to the c-axis (LSPR⊥) and localized surface plasmon resonance absorption in a direction parallel to the c-axis (LSPR / / ).

[0051] That is, in composite tungsten oxide particles, there are three absorption components: absorption due to localized surface plasmon resonance in a direction perpendicular to the c-axis (vertical direction) (LSPR⊥), absorption due to localized surface plasmon resonance in a direction parallel to the c-axis (parallel direction) (LSPR / / ), and polaron absorption. Therefore, the molar absorption coefficient curve of the composite tungsten oxide particles can be separated into three absorption curves.

[0052] Specifically, the wavelength on the horizontal axis of the molar absorption coefficient curve is converted to energy (eV), and the molar absorption coefficient curve is fitted with a Gaussian distribution and a Lorentzian distribution based on Mie scattering theory, and then the absorption curve is separated into an absorption curve due to localized surface plasmon resonance in a direction perpendicular to the c-axis (LSPR⊥), an absorption curve due to localized surface plasmon resonance in a direction parallel to the c-axis (LSPR / / ), and an absorption curve due to polaron absorption.

[0053] In addition, a calculation is also performed to verify that the curve obtained by adding together the three separated absorption curves matches the actually measured molar absorption coefficient curve.

[0054] When separating into three absorption curves, if the molar absorption curve for the wavelength energy is nearly symmetrical, a Gaussian distribution is applied, and if it is asymmetrical, a Lorentzian distribution is applied. By finding the three absorption curves in this separation process, the average value (peak energy (wavelength)) of the Gaussian or Lorentzian distribution can be determined.

[0055] In Non-Patent Document 6, the molar extinction coefficient curve is separated into three absorption components: absorption due to localized surface plasmon resonance in an orientation perpendicular to the c-axis (LSPR⊥), absorption due to localized surface plasmon resonance in an orientation parallel to the c-axis (LSPR / / ), and polaron absorption. Furthermore, Non-Patent Document 6 also describes that the composite tungsten oxide particles exhibit absorption with peaks in the following order from the low-energy side: localized surface plasmon resonance in an orientation perpendicular to the c-axis, localized surface plasmon absorption in an orientation parallel to the c-axis, and polaron absorption. That is, absorption due to polarons appears in the high-energy region (the short-wavelength side of the near-infrared region).

[0056] According to Non-Patent Document 6, the absorption curve peak of absorption due to localized surface plasmon resonance in a direction perpendicular to the c-axis (LSPR⊥) appears at an energy of approximately 0.7 eV to 0.9 eV, and the absorption curve peak of absorption due to localized surface plasmon resonance in a direction parallel to the c-axis (LSPR / / ) appears at an energy of approximately 0.9 eV to 1.0 eV. Also, according to Non-Patent Document 6, the absorption curve peak of polaron absorption appears at an energy of approximately 1.3 eV to 1.5 eV. Specific absorption curve fitting is attempted by assuming that each absorption peak exists in a range expanded by ±0.2 eV from the above energy range in which each absorption peak appears.

[0057] Each Gaussian distribution is expressed by equation (1).

[0058] In formula (1), A represents the peak intensity, b represents the average value, E represents the energy, and c represents the standard deviation.

[0059] The Lorentz distribution is expressed by the following equation (2).

[0060] In equation (2), E is the energy, b is the average value, and d is a constant.

[0061] The absorption curves in the range of 0.5 eV to 2.0 eV (wavelengths of 620 nm to 2500 nm) were separated using these functions and the results are shown in Figures 10A and 10B. The near-infrared region (wavelengths of 780 nm to 2500 nm) is 0.5 eV to 1.59 eV.

[0062] Fig. 10A shows the molar absorption coefficient curve of the composite tungsten oxide particles according to Example 1, which is an example of the composite tungsten oxide particles of this embodiment. Fig. 10B shows the molar absorption coefficient curve of the composite tungsten oxide particles according to Comparative Example 1, which is an example of the composite tungsten oxide particles synthesized by a conventional solid-phase method and then pulverized.

[0063] 10A and 10B are merely examples, and the absorption curves in each figure are illustrative and not limited to these absorption curves, but the composite tungsten oxide particles of the present embodiment exhibit a tendency similar to the molar absorption coefficient curve shown in FIG. 10A.

[0064] The absorption peak in the localized surface plasmon resonance (LSPR⊥) absorption curve in the direction perpendicular to the c-axis of the composite tungsten oxide particle according to Example 1 shown in FIG. 10A is 0.86 eV (wavelength 1435 nm), and the integrated intensity of the absorption curve is 96015.38 [L eV / (mol cm)].

[0065] In the molar extinction coefficient curve shown in FIG. 10A , the absorption peak in the absorption curve of localized surface plasmon resonance (LSPR / / ) in the direction parallel to the c-axis is 1.20 eV (wavelength 1030 nm), and the integrated intensity of the absorption curve is 33042.00 [L eV / (mol cm)].

[0066] In the molar absorption coefficient curve shown in FIG. 10A, the absorption peak in the polaron absorption curve is 1.26 eV (wavelength 985 nm), and the integrated intensity of the absorption curve is 12265.60 [L·eV / (mol·cm)].

[0067] 10A , the proportion of the integrated intensity of the polaron absorption curve is 8.7% of the integrated intensity of the three absorption curves. The composite tungsten oxide particles of Example 1 were synthesized by a flame method, and the integrated intensity of the polaron absorption was reduced compared to composite tungsten oxide particles synthesized by a conventional solid-phase method.

[0068] 10B shows the molar absorption coefficient curve of the composite tungsten oxide particles according to Comparative Example 1, which were synthesized by a conventional solid-phase method and then pulverized. In the molar absorption coefficient curve shown in FIG. 10B, the absorption peak in the localized surface plasmon resonance (LSPR⊥) absorption curve perpendicular to the c-axis is 0.80 eV (wavelength 1550 nm), and the integrated intensity of the absorption curve is 78843.30 [L eV / (mol cm)].

[0069] In the molar extinction coefficient curve shown in FIG. 10B , the absorption peak in the absorption curve of localized surface plasmon resonance (LSPR / / ) in the direction parallel to the c-axis is 1.00 eV (wavelength 1240 nm), and the integrated intensity of the absorption curve is 20209.67 [L eV / (mol cm)].

[0070] In the molar absorption coefficient curve shown in FIG. 10B, the absorption peak in the polaron absorption curve is 1.40 eV (wavelength 885 nm), and the integrated intensity of the absorption curve is 31174.01 [L·eV / (mol·cm)].

[0071] Of the integrated intensities of the three absorption curves in the molar absorption coefficient curve shown in FIG. 10B, the proportion of the integrated intensity of the absorption curve of polaron absorption is 23.9%.

[0072] As is clear from the comparison of the proportions of integrated intensities of the polaron absorption curves above, the composite tungsten oxide particles of Example 1 have weaker polaron absorption than the composite tungsten oxide particles of Comparative Example 1. This is also shown by the fact that the peak value of the polaron absorption curve appearing at 1.26 eV (wavelength 985 nm) of the composite tungsten oxide particles of Example 1 is weaker than the peak value of the polaron absorption appearing at 1.40 eV (wavelength 885 nm) of the composite tungsten oxide synthesized by the solid-phase method.

[0073] Furthermore, the composite tungsten oxide particles of Example 1 have a higher ratio of integrated intensity of the absorption curves of LSPR⊥ and LSPR / / , which are absorptions due to localized surface plasmon resonance. In particular, the ratio of integrated intensity of the absorption curve of LSPR / / in the composite tungsten oxide particles of Example 1 is higher than the ratio of integrated intensity of the absorption curve of LSPR / / in the composite tungsten oxide particles of Comparative Example 1, which were synthesized by a solid-phase method and pulverized. These differences in absorption state are reflected in optical properties.

[0074] Here, the integrated intensity of each of the three absorption curves is the integrated intensity at 0.5 eV or more and 2.0 eV or less (wavelength 620 nm or more and 2500 nm or less). By comparing the integrated intensities of the three absorption components, i.e., localized surface plasmon resonance (LSPR⊥) in an orientation perpendicular to the c-axis, localized surface plasmon resonance (LSPR / / ) in an orientation parallel to the c-axis, and polaron absorption, within the above range, the contributions of the three absorption components in the near-infrared region (wavelength 780 nm or more and 2500 nm or less) can be determined.

[0075] In the composite tungsten oxide particle of this embodiment, the ratio of the integrated intensity of polaron absorption to the sum of the integrated intensity of localized surface plasmon resonance (LSPR⊥) absorption in a direction perpendicular to the c-axis, the integrated intensity of localized surface plasmon resonance (LSPR / / ) absorption in a direction parallel to the c-axis, and the integrated intensity of polaron absorption is preferably 20% or less, more preferably 15% or less, and more preferably 12% or less.

[0076] The sum of the integrated intensity of the localized surface plasmon resonance (LSPR⊥) absorption in a direction perpendicular to the c-axis, the integrated intensity of the localized surface plasmon resonance (LSPR / / ) absorption in a direction parallel to the c-axis, and the integrated intensity of the polaron absorption is equal to the integrated intensity of the molar absorption coefficient curve in the range of 0.5 eV to 2.0 eV. This means that the integrated intensity of the polaron absorption in the range of 0.5 eV to 2.0 eV is preferably 20% or less of the integrated intensity of the molar absorption coefficient curve in this range.

[0077] 10B , the polaron absorption peak appears near 1.40 eV (wavelength 885 nm) in the composite tungsten oxide particles of Comparative Example 1. Composite tungsten oxide particles with strong polaron absorption have an absorption peak near a wavelength of 885 nm, which reduces the transmission of red light in the visible light range, making it difficult for the transmitted color to become neutral.

[0078] On the other hand, the composite tungsten oxide particles of this embodiment preferably have an integrated polaron absorption intensity of the composite tungsten oxide crystals contained in the composite tungsten oxide particles of 20% or less relative to the integrated intensity of the molar absorption coefficient curve in the range of 0.5 eV to 2.0 eV of the dispersion or dispersion. By setting the ratio of the integrated polaron absorption intensity within the above range, it can be made smaller than the ratio of the integrated polaron absorption intensity to the integrated intensity of the molar absorption coefficient curve in composite tungsten oxide particles synthesized by the conventional solid-phase method. Therefore, the absorption around a wavelength of 885 nm is weakened, and as a result, the transmission of red light in the visible light range is not reduced, making it easy to achieve a neutral color tone. From the viewpoint of these characteristics, in the dispersion or dispersion of the composite tungsten oxide particles of this embodiment, the ratio of the integrated polaron absorption intensity to the integrated intensity of the molar absorption coefficient curve in the range of 0.5 eV to 2.0 eV is preferably 20% or less.

[0079] Furthermore, in the composite tungsten oxide particles of this embodiment, in a molar absorption coefficient curve of the dispersion liquid or dispersion in the range of 0.5 eV to 2.0 eV, the integrated intensity of the absorption curve of polaron absorption is preferably lower than the integrated intensity of the absorption curve of localized surface plasmon absorption in an orientation parallel to the c-axis of the composite tungsten oxide crystal contained in the composite tungsten oxide particles.

[0080] The relationship between the integrated intensity of the absorption curve of the localized surface plasmon absorption in the direction parallel to the c-axis and the integrated intensity of the polaron absorption also appears in the relationship with the peak values ​​of each absorption curve.

[0081] For this reason, the composite tungsten oxide particles of this embodiment preferably have a polaron absorption curve whose peak value is lower than the peak value of the localized surface plasmon absorption curve in an orientation parallel to the c-axis of the composite tungsten oxide crystals contained in the composite tungsten oxide particles, in a molar absorption coefficient curve of the dispersion liquid or dispersion in the range of 0.5 eV to 2.0 eV.

[0082] In the composite tungsten oxide particles of this embodiment, the integrated intensity or peak value of the absorption curve of the localized surface plasmon absorption in the direction parallel to the c-axis is higher than the integrated intensity or peak value of the polaron absorption, resulting in rapid absorption of infrared light at a wavelength of around 1000 nm. That is, the composite tungsten oxide particles of this embodiment have weak absorption of light at a wavelength of around 800 nm due to polaron absorption, but are effective in absorbing infrared light at a wavelength of around 1000 nm. In contrast, composite tungsten oxide particles synthesized by the conventional solid-phase method have a higher integrated intensity or peak value of polaron absorption than the integrated intensity or peak value of the localized surface plasmon absorption in the direction parallel to the c-axis, as shown in FIG. 10B . This difference is reflected in the color of the transmitted light, and the composite tungsten oxide particles of this embodiment can achieve a neutral color tone for the transmitted light when used as a dispersion or dispersion. Furthermore, the composite tungsten oxide particles of this embodiment can exhibit excellent properties in terms of visible light transmission and near-infrared shielding.

[0083] The reason why the polaron absorption of the composite tungsten oxide particles of this embodiment is weak is thought to be because composite tungsten oxide particles with a particle size of 1 μm or less are directly synthesized when the composite tungsten oxide particles of this embodiment are produced. That is, this is because damage to the composite tungsten oxide particles is small when the particle size is pulverized to, for example, 200 nm or less, and defects are unlikely to occur in the crystal lattice. In contrast, in the conventionally known solid-phase method, particles with a particle size exceeding 1 μm are pulverized to, for example, a particle size of 200 nm or less, which is likely to cause defects in the particle crystal lattice. The electrons that contribute to polaron absorption are electrons derived from defects. The composite tungsten oxide particles of this embodiment have few defects even in the production process, resulting in less polaron absorption and, in terms of characteristics, transmitting light with a neutral color tone.

[0084] According to the Drude-Lorentz analysis by Machida et al. in Non-Patent Document 6, Cs prepared by the solid phase method in the same manner as in Comparative Example 1 ０．３２ WO ３－ｙ In the particle, the Cs free electrons contribute to an absorption peak in the absorption curve of LSPR / / at 1.0 eV.

[0085] On the other hand, V Ｏ Electrons (electrons resulting from oxygen vacancies) contribute to the absorption peak (0.8 eV) in the LSPR⊥ absorption curve in the xy direction and the polaron absorption peak around 1.5 eV. The above three types of absorption overlap, resulting in a peak at 0.9 eV with a shoulder at 1.5 eV in the molar absorption coefficient curve of the composite tungsten oxide particles prepared by the solid-state method and milled.

[0086] From the above findings and the results shown in FIGS. 10A and 10B, it can be seen that the absorption peak of the composite tungsten oxide particles of this embodiment prepared by the flame spray method in Example 1 is V Ｏ The absorption peak due to the localized surface plasmon resonance (LSPR / / ) in the direction parallel to the c-axis caused by Cs free electrons is small, and the absorption peak due to the localized surface plasmon resonance (LSPR / / ) in the direction parallel to the c-axis caused by Cs free electrons is large.

[0087] In the composite tungsten oxide particles of this embodiment, the integrated intensity of the localized surface plasmon absorption in the direction parallel to the c-axis of the composite tungsten oxide crystal contained in the composite tungsten oxide particles is preferably 10% to 30%, more preferably 15% to 30%, and even more preferably 20% to 30%, relative to the integrated intensity of the molar absorption coefficient curve in the range of 0.5 eV to 2.0 eV of the dispersion or dispersion. As described above, the localized surface plasmon absorption in the direction parallel to the c-axis of the composite tungsten oxide particles of this embodiment contributes to the absorption of light with a wavelength of around 1000 nm. With respect to the integrated intensity of the molar absorption coefficient curve in the range of 0.5 eV to 2.0 eV, the integrated intensity of the localized surface plasmon absorption in the direction parallel to the c-axis satisfies the above range, and as a result, the composite tungsten oxide particles of this embodiment exhibit excellent near-infrared shielding performance.

[0088] Furthermore, the molar absorption coefficient of the powder constituting the composite tungsten oxide particles in the dispersion or dispersion liquid can be determined from the molar absorption coefficient curve. The molar absorption coefficient of the powder constituting the composite tungsten oxide particles of this embodiment is preferably 2600 L / (mol cm) or more, and more preferably 2800 L / (mol cm) or more.

[0089] By adjusting the manufacturing conditions of conventionally known composite tungsten oxide particles, the peak value of the absorption curve for polaron absorption can be made lower than the peak value of the absorption curve for localized surface plasmon absorption in the direction parallel to the c-axis.

[0090] However, when the peak value of the absorption curve of the polaron absorption is lower than the peak value of the absorption curve of the localized surface plasmon absorption in the direction parallel to the c-axis in a conventionally known composite tungsten oxide particle, the molar extinction coefficient becomes less than 2000 L / (mol cm). A high molar extinction coefficient is desirable for an infrared-shielding material, and a high molar extinction coefficient enables excellent infrared-shielding effect to be achieved even with a small amount of infrared-absorbing material.

[0091] FIG. 11 shows the results of the calculation using the composite tungsten oxide particles according to Example 1 at 0.5 g / m ２ and a dispersion liquid containing composite tungsten oxide particles according to Comparative Example 1, which is an example of conventionally known composite tungsten oxide particles, at a concentration of 0.5 g / m. ２ 11 is an optical profile of the transmittance of a dispersion when the composite tungsten oxide particles according to Example 1 contained 1000 L / (mol cm). The molar absorption coefficient of the composite tungsten oxide particles according to Example 1, obtained from the optical profile of transmittance shown in FIG. 11, is 3000 L / (mol cm). The molar absorption coefficient of the composite tungsten oxide particles according to Comparative Example 1 is 2500 L / (mol cm). As shown in FIG. 11, even when the amount of composite tungsten oxide particles per unit area is the same, the composite tungsten oxide particles according to Example 1, which is an example of the composite tungsten oxide particles of this embodiment, have low transmittance in the wavelength range from around 900 nm to around 1680 nm, i.e., they have a high effect of absorbing near-infrared rays.

[0092] Therefore, the composite tungsten oxide particles of this embodiment can achieve an excellent near-infrared shielding effect and a neutral color tone. [Method for producing composite tungsten oxide particles] An outline of the method for producing the composite tungsten oxide particles of this embodiment will be described.

[0093] According to the method for producing composite tungsten oxide particles of this embodiment, the above-mentioned composite tungsten oxide particles can be produced, so the description of the matters already explained will be omitted. Note that here, only a configuration example of the method for producing composite tungsten oxide particles is shown, and the above-mentioned method for producing composite tungsten oxide particles is not limited to the following configuration example.

[0094] The method for producing composite tungsten oxide particles of this embodiment is preferably a method that can directly synthesize composite tungsten oxide particles having a particle size of 1 μm or less. If composite tungsten oxide particles having a particle size of 1 μm or less can be directly synthesized, fine particles that are less affected by damage caused by pulverization or dispersion, for example, composite tungsten oxide particles having a particle size of 800 nm or less, can be obtained.

[0095] A preferred method for directly synthesizing composite tungsten oxide particles having a particle size of 1 μm or less is a production method in which a raw material aerosol containing an M element source and a tungsten element source is synthesized via a heat treatment step in which the raw material aerosol is supplied to an electric furnace, flame, or plasma.

[0096] The M element source is a raw material containing the M element, and the tungsten element source is a raw material containing tungsten.

[0097] Therefore, the method for producing composite tungsten oxide particles of the present embodiment can include the following raw material preparation step, aerosol formation step, heat treatment step, and reduction treatment step.

[0098] In the raw material preparation step, a raw material containing an M element source and a tungsten element source can be prepared.

[0099] In the aerosol forming step, the raw material prepared in the raw material preparing step can be aerosolized.

[0100] In the heat treatment process, the aerosolized raw material can be heat treated in a reaction field.

[0101] In the reduction treatment step, the particles obtained in the heat treatment step can be reduced in an atmosphere containing a reducing gas. (1) Regarding Each Step Hereinafter, each step of the method for producing composite tungsten oxide particles of this embodiment will be described. (1-1) Raw Material Preparation Step In the raw material preparation step, a raw material containing an M element source and a tungsten element source (hereinafter also referred to as a "W element source") can be prepared.

[0102] In the raw material preparation step, the raw materials can be blended and prepared so that the ratio of the amount of substance of the M element to the amount of substance of the W element contained in the raw materials corresponds to the composition of the target composite tungsten oxide particles.

[0103] The state of the raw material prepared in the raw material preparation step is not particularly limited, and may be liquid or solid, and it is preferable that an aerosol can be formed by spraying or the like. Note that the aerosol refers to a mixture of minute liquid or solid particles suspended in a gas and the surrounding gas. (When the raw material is a liquid) When the raw material is a liquid, the raw material can be prepared, for example, by preparing a solution containing an M element source and a W element source.

[0104] Alternatively, a solution containing an M element source and a solution containing a W element source may be prepared in advance, and the two solutions may be mixed in the raw material preparation step to form a raw material mixed solution.

[0105] The raw material may be supplied in the form of droplets to the heat treatment step described below. In this case, a raw material preparation step can be carried out by mixing a solution containing an M element source and a solution containing a W element source immediately before supplying the raw material to a droplet formation section (droplet formation means) that forms the droplets, or in the droplet formation section. Then, an aerosol formation step described below can be carried out in the droplet formation section.

[0106] For example, if premixing a solution containing an M element source with a solution containing a W element source poses problems such as gelation, it is preferable to prepare both solutions in advance as described above and mix them immediately before the aerosol formation step. When the raw material preparation step is performed immediately before the aerosol formation step, the ratio of the amounts of substance of the M element and the W element in the raw material can be adjusted to a desired range by adjusting the concentrations of both solutions and the speeds at which both solutions are sent to the droplet formation unit.

[0107] As described above, when the raw material preparation step is carried out immediately before the aerosol formation step, the aerosol formation step and the raw material preparation step do not need to be clearly separated, and both steps can be carried out continuously.

[0108] When the solution containing the M element source and the solution containing the W element source are mixed in the raw material preparation step as described above, the specific method for mixing is not particularly limited, and any method can be used.

[0109] The W element source is not particularly limited, and may be any raw material containing tungsten, such as simple tungsten or a tungsten compound. As the W element source, a tungsten salt or the like may be used, and for example, hexacarbonyl tungsten may be preferably used. Hexacarbonyl tungsten is, for example, W(CO) ６ As the solution containing the W element source, an organic solution containing the W element source can be preferably used because of ease of handling.

[0110] The M element source is not particularly limited, and may be any raw material containing the M element, such as the M element alone or a compound containing the M element. The M element source may be a solution containing the M element source, and as the solution containing the M element source, for example, a solution of a salt containing the M element can be used. The type of salt containing the M element that is the M element source is not particularly limited, and for example, one or more types selected from carbonates, acetates, nitrates, hydroxides, etc. of the M element can be used.

[0111] As the solution containing the M element source, an ethanol solution containing the M element source can be preferably used because of ease of handling.

[0112] For example, even when the M element is cesium, one or more salts containing the M element may be selected from carbonates, acetates, nitrates, hydroxides, etc. containing cesium, but acetates are particularly preferred because cesium acetate is particularly easily dissolved in ethanol.

[0113] The ratio of the M element to 1 mole of tungsten element in the obtained composite tungsten oxide, i.e., the doping amount, is determined by the ratio of the W element source to the M element source when forming the raw material mixed solution. Therefore, the doping amount can be controlled by, for example, the concentration of the solution containing the W element source or the concentration of the solution containing the M element source.

[0114] There are no particular limitations on the concentration of the W element source contained in the solution containing the W element source, i.e., the concentration of a salt of W element, etc. For example, the tungsten concentration of the solution containing the W element source is preferably 0.001 mol / L or more and 10 mol / L or less, more preferably 0.01 mol / L or more and 10 mol / L or less, and even more preferably 0.01 mol / L or more and 1 mol / L or less.

[0115] By setting the tungsten concentration in the solution containing the W element source to 0.001 mol / L or more, a sufficient amount of composite tungsten oxide particles can be produced per unit time, and a sufficient amount can be recovered using, for example, a filter, thereby increasing productivity.

[0116] Furthermore, by setting the tungsten concentration of the solution containing the W element source to 10 mol / L or less, reprecipitation of the dissolved W element source is suppressed, aggregation of the generated particles is suppressed, and the inclusion of coarse composite tungsten oxide particles, for example, with a particle size greater than 1 μm, can be suppressed.

[0117] Furthermore, additives such as agents for adjusting pH and surfactants can be added to the solution containing the W element source.

[0118] Furthermore, the concentration of the M element source contained in the solution containing the M element source is not particularly limited, and can be selected depending on the desired composition of the composite tungsten oxide particles to be produced, the concentration of the W element source contained in the solution containing the W element source, and the like.

[0119] Any component can be added to the raw material mixed solution in addition to the solution containing the W element source and the solution containing the M element source. (When the raw material is solid) Up to this point, the raw material has been described as a liquid, but the raw material may be solid, for example, in the form of powder.

[0120] When the raw material is a powder, the raw material can be prepared, for example, by mixing a powder of an M element compound with a powder of a tungsten compound. Alternatively, for example, a precursor powder can be prepared by adding a tungsten compound powder to a solution containing an M element source, stirring the mixture, and then removing the solvent by drying or the like to obtain the raw material.

[0121] When the raw material is a solid, the W element source is not particularly limited, and tungsten salts or the like can be used. For example, H ２ WO ４ and ammonium paratungstate can be preferably used.

[0122] H ２ WO ４ The elements other than tungsten are H (hydrogen) and O (oxygen), and the elements other than tungsten are discharged to the outside of the system in the heat treatment process described later. ２ WO ４ can be preferably used because it is possible to obtain composite tungsten oxide particles in which the inclusion of impurities is suppressed.

[0123] The M element source can be, for example, a powder of a salt containing the M element. The type of salt containing the M element is not particularly limited, but one or more types selected from carbonates, acetates, nitrates, hydroxides, etc. of the M element can be used.

[0124] For example, even when the M element is cesium, the salt containing the M element can be one or more selected from cesium-containing carbonates, acetates, nitrates, hydroxides, etc., with carbonates being particularly preferred. (1-2) Aerosol Formation Step In the method for producing composite tungsten oxide particles of this embodiment, it is preferable to supply the raw material prepared in the raw material preparation step in the form of an aerosol to the heat treatment step. Specifically, it is preferable to transport the aerosol containing the raw material using a carrier gas such as oxygen and subject it to the heat treatment step.

[0125] Therefore, the method for producing composite tungsten oxide particles of the present embodiment can also include an aerosol formation step in which the raw material is converted into an aerosol containing droplets or particles of the raw material.

[0126] The means and method for forming the aerosol in the aerosol forming step are not particularly limited, and can be selected depending on the state of the raw material, etc.

[0127] When the raw material is a liquid, an aerosol can be formed by spraying the liquid toward a carrier gas using various atomizers such as a centrifugal atomizer or a two-fluid nozzle. Alternatively, droplets can be formed by irradiating the liquid with ultrasound.

[0128] When the raw material is a powder, an aerosol can be formed by a device that disperses the raw material powder and supplies the powder into an airflow. For example, the aerosol can be formed by an aerosol forming device that includes a stirring unit such as a rotating brush or stirring blade, and a powder supply unit that includes a piston or screw feeder that delivers the raw material to the stirring unit. The raw material powder supplied from the powder supply unit is dispersed into particles that make up the powder in the stirring unit, and an aerosol can be generated from the raw material powder by sending each particle into a carrier gas. The stirring unit allows the rotation speed of the brush or stirring blade to be selected so that the raw material powder can be dispersed into particles, and it is preferable to rotate it at high speed.

[0129] When forming droplets dispersed in a gas in the aerosol forming process, the size of the formed droplets 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 obtained composite tungsten oxide particles from becoming coarse, and it is possible to obtain composite tungsten oxide particles on the order of nanometers. Note that the lower limit of the size of the droplets formed in the aerosol forming process is not particularly limited. However, since it is difficult to form excessively small droplets and there is a risk of reduced productivity, it is preferable that the droplet size be, for example, 1 μm or more.

[0130] When forming solid particles dispersed in a gas in 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 is possible to more reliably perform heat treatment to the inside of the particles. The particle diameter can be measured in the same manner as the particle size of the composite tungsten oxide particles described above. (1-3) Heat Treatment Process In the heat treatment process, the raw material is heat-treated to process the raw material into composite tungsten oxide particles. 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 performed by using a carrier gas to introduce the raw material into a flame, a tubular electric furnace, or a plasma. Whether a flame, an electric furnace, or plasma is used, the heat treatment temperature can be 500°C or higher. By carrying out the heat treatment at 500° C. or higher, the compounds contained in the raw material are decomposed, and tungsten reacts with the M element to form a composite tungsten oxide.

[0131] The heat treatment temperature is sufficient as long as it can promote the reaction between tungsten and the element M, and therefore may be 500° C. or higher, preferably 550° C. or higher, and more preferably 1000° C. or higher. There is no particular upper limit to the heat treatment temperature, but from the viewpoint of suppressing energy consumption, it is preferably 4000° C. or lower.

[0132] In the heat treatment step, for example, a flame can be used as described above, and the raw material can be heat-treated using the flame. By using a flame in the heat treatment step and adjusting the temperature of the flame reaction field, the particle size of the resulting composite tungsten oxide particles can be selected.

[0133] When a liquid raw material is atomized into a carrier gas to form droplets, and the droplets are introduced into a flame to synthesize composite tungsten oxide particles, the droplets of the raw material are transported through the flame by a carrier gas such as oxygen gas. When the droplets of the raw material are transported into the flame, the organic solvent containing the raw material tungsten element source and M element source burns, and the organic solvent is decomposed by the combustion reaction. The heat generated by the combustion reaction contributes to the decomposition reaction of the W element source and the M element source, and the organic solvent precipitates during the cooling process in the tail flame of the flame field.

[0134] For example, as mentioned above, the W element source may be tungsten hexacarbonyl, and the M element source may be cesium acetate if the M element is cesium. These salts decompose in the heat treatment process. At this time, W is converted to WO ６ On the other hand, Cs does not easily form oxides as a monomer, and some of it passes through the filter and is discharged to the outside of the system without being able to precipitate as nano-sized powder.

[0135] In the above case, tungsten reacts with the M element during the decomposition process of the solute portion to form a composite tungsten oxide.

[0136] When a flame is used in the heat treatment process, the conditions for forming the flame are not particularly limited, but the flame can be formed using, for example, a mixed gas containing oxygen and a hydrocarbon. By forming a flame using a mixed gas containing oxygen and a hydrocarbon, a flame with a stable temperature can be formed, and composite tungsten oxide particles can be produced with reduced variation in particle size, etc.

[0137] The method for adjusting the flame size and temperature is not particularly limited, but it is preferable to adjust the flow rates of the oxygen and flammable gases such as hydrocarbons in the gas mixture supplied to the flame, while maintaining a flow rate ratio that allows the flammable gas to burn. This is because it is possible to adjust the heat power while ensuring the amount of oxygen necessary for the flammable gas to burn.

[0138] For example, when the flame is formed using a gas mixture containing oxygen and propane, the volume ratio of the flow rates of propane and oxygen in the gas mixture is preferably 1:1, and the ratio of oxygen to propane is preferably 5 to 8. In this case, the flow rate of propane is preferably in the range of 0.5 L / min to 2 L / min.

[0139] This is because, when the flow rate of propane is 1, the combustion of propane, which is a combustible gas, can be sufficiently promoted by setting the flow rate of oxygen to 5 or more. However, to avoid excessive oxygen supply, it is preferable to supply 8 or less parts of oxygen per 1 part of propane.

[0140] The heat treatment temperature in the flame reaction field, etc. also affects the particle size of the resulting composite tungsten oxide particles.

[0141] This is presumably because thermal energy in a reaction field such as a flame is used to sublimate the generated composite tungsten oxide particles, causing the particles to burst upon sublimation, resulting in particles with a fine particle size.

[0142] The composite tungsten oxide particles obtained by the heat treatment can be collected, for example, using a filter. (1-4) Reduction Treatment Step Particles obtained through the heat treatment step, specifically composite tungsten oxide particles, may not exhibit near-infrared absorption properties. Therefore, the inventors of the present invention conducted studies and found that by further performing a reduction treatment step in which the composite tungsten oxide particles obtained through the heat treatment step are subjected to a reduction treatment, the composite tungsten oxide particles can exhibit near-infrared absorption properties.

[0143] Therefore, the method for producing composite tungsten oxide particles of this embodiment can also have a reduction treatment step in which the particles obtained in the heat treatment step are reduced in an atmosphere containing a reducing gas. Specifically, for example, the method for producing composite tungsten oxide particles of this embodiment can have a reduction treatment step in which the particles obtained in the heat treatment step are reduced in an atmosphere containing a reducing gas at a temperature in the range of more than 400°C and less than 700°C after the heat treatment step.

[0144] The conditions for the reduction treatment are not particularly limited, but it is preferable to select the conditions for the reduction treatment so that when the composite tungsten oxide particles after the reduction treatment are analyzed by X-ray diffraction pattern, the crystal structure does not change before and after the reduction treatment step and metallic tungsten and the like do not precipitate.

[0145] In the reduction treatment step, the composite tungsten oxide particles obtained in the heat treatment step can be reduced by raising and lowering the temperature in a reducing atmosphere containing a reducing gas, that is, by performing heat treatment.

[0146] During the reduction treatment step, the composite tungsten oxide particles may be stirred or left to stand, and the handling of the composite tungsten oxide particles during the reduction treatment step can be selected appropriately, but it is preferable to select handling conditions so as not to cause precipitation of metallic tungsten.

[0147] The temperature of the reduction treatment (reduction treatment temperature) is preferably higher than 400°C, more preferably 450°C or higher, and even more preferably 500°C or higher.

[0148] The upper limit of the temperature of the reduction treatment is not particularly limited, but is preferably less than 700°C, more preferably 650°C or less, and even more preferably less than 650°C.

[0149] In addition, when the raw material is a liquid, the particle size obtained in the aerosol formation step decreases when the raw material concentration is reduced. Since the particles with a smaller diameter are easier to reduce, the temperature in the reduction treatment step can be lowered. In the reduction treatment step, the temperature can be raised from room temperature to the reduction treatment temperature and then lowered back to room temperature.

[0150] The reduction conditions can be determined based on the optical properties of the resulting composite tungsten oxide particles.

[0151] By setting the reduction temperature to above 400° C., the reduction process of the composite tungsten oxide particles can be advanced, and near-infrared absorption properties can be more reliably exhibited. Furthermore, by setting the temperature to below 700° C., reduction of the composite tungsten oxide particles to metallic tungsten can be suppressed.

[0152] The reducing atmosphere is a mixture of an inert gas such as argon and H ２ It is preferable to use a mixed gas atmosphere with a reducing gas such as H ２ Gas is preferred.

[0153] H as a reducing gas ２ When gas is used, H in a reducing atmosphere ２ The gas content can be appropriately selected. ２ The gas content is preferably in the range of 0.1% to 10% by volume, more preferably 2% to 10% by volume. Care must be taken when reduction is carried out in an atmosphere containing only a reducing gas, as this may cause the reduction reaction to proceed excessively, resulting in the precipitation of metallic tungsten.

[0154] The reduction treatment time is preferably 30 minutes or more, including the total time from temperature increase to temperature decrease. There is no particular upper limit to the reduction treatment time, and it is preferable to select it by conducting a preliminary test or the like so that the reduction does not proceed excessively. Here, the total time from temperature increase to temperature decrease means the time from starting temperature increase from room temperature, reaching the reduction treatment temperature, and cooling to room temperature. It is preferable that the composite tungsten oxide particles are placed in the reducing atmosphere described above during this time.

[0155] By carrying out the reduction treatment step in this manner, it is possible to convert the undesired heterogeneous phase into the desired composite tungsten oxide phase in the composite tungsten oxide particles obtained after the heat treatment step.

[0156] In the heat treatment step and the reduction treatment step, it is preferable to conduct a preliminary test or the like and select the heat treatment conditions, etc., so that when the obtained composite tungsten oxide particles are made into a dispersion or a dispersion, the above-mentioned absorption curves in the molar extinction coefficient curve have the desired relationship. (2) Apparatus that can be suitably used in the method for producing composite tungsten oxide particles (2-1) Composite material production apparatus An example of the configuration of a composite material production apparatus that can be suitably used in the method for producing composite tungsten oxide particles of this embodiment will be described below.

[0157] FIG. 1 is a diagram schematically illustrating a composite material manufacturing apparatus 10 according to the present embodiment.

[0158] The composite material manufacturing apparatus 10 has a storage section 11 containing a raw material solution, a two-fluid nozzle 12 that forms droplets of the raw material and also forms a flame, and a reaction tube 13 connected to a filter 14 that collects the formed composite tungsten oxide particles. As already explained, the raw material solution can be a solution containing an M element source and a W element source.

[0159] An aerosol can be formed by supplying a raw material solution and a carrier gas to the two-fluid nozzle 12 (aerosol formation step). For example, oxygen and a hydrocarbon can be supplied to the two-fluid nozzle 12, and together they form a flame reaction field. The formed aerosol can be supplied into the flame and subjected to heat treatment (heat treatment step).

[0160] Cooling water circulates through a cooling water pipe 131 disposed around the reaction tube 13. The composite tungsten oxide particles introduced into the reaction tube 13 are collected by a filter 14 such as a bag filter.

[0161] In addition, an ejector 15 may be provided at the most downstream side to adjust the supply amount of carrier gas.

[0162] Here, an example of the configuration of a composite material apparatus in which droplets of raw material are formed and heat-treated using a flame to form composite tungsten oxide particles is shown, but the present invention is not limited to this configuration, and the raw material may be a powder or the like, and the heat source used for the heat treatment may be an electric furnace, etc. (2-2) Reduction Treatment Apparatus The reduction treatment apparatus can carry out the reduction treatment step described above.

[0163] The reduction treatment device is not particularly limited as long as it is configured to be able to carry out the reduction treatment step described above. For example, it may include a container for storing the composite tungsten oxide particles obtained by the composite material production device described above, a gas pipe for supplying a mixed gas that forms a reducing atmosphere into the container, and a heat source for heating the container.

[0164] Alternatively, a mixed gas that forms a reducing atmosphere may be introduced into the container and then exhausted, and the composite tungsten oxide particles to be treated may be placed under a gas flow of the mixed gas. In this case, a gas supply pipe and an exhaust pipe may be provided as gas pipes so that such a gas flow can be formed.

[0165] Furthermore, a stirring blade or the like may be used in combination to stir the composite tungsten oxide particles in the container.

[0166] FIG. 2 is a diagram showing a schematic configuration example of a reduction treatment device, and shows a cross section taken along a plane passing through the central axis of a reaction tube 21 of a reduction treatment device 20.

[0167] The reduction treatment device 20 is a horizontal tubular furnace, and can be used by attaching a gas inlet pipe (not shown) to a first end 21A, which is an end along the length of the reaction tube 21, and by attaching a gas exhaust pipe (not shown) to a second end 21B, which is located opposite to the first end 21A of the reaction tube 21. Then, by supplying a mixed gas that forms a reducing atmosphere from the first end 21A, the inside of the reaction tube 21 can be made into a reducing atmosphere.

[0168] 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 placed at a position corresponding to the heater 22 inside the reaction tube 21 of the tubular furnace.

[0169] Using the reduction treatment device 20, the inside of the reaction tube 21 is made into a reducing atmosphere, and heating is performed to a desired temperature by the heater 22, thereby performing a reduction treatment on the composite tungsten oxide particles 24 placed in the container 23. [Near-infrared absorbing particle dispersion] Next, a configuration example of the near-infrared absorbing particle dispersion of the present embodiment will be described.

[0170] The near-infrared absorbing particle dispersion of the present embodiment can include near-infrared absorbing particles and a liquid medium. The near-infrared absorbing particles can be the composite tungsten oxide particles according to one aspect of the present disclosure.

[0171] 3, for example, a near-infrared absorbing particle dispersion 30 of the present embodiment can contain near-infrared absorbing particles 31 and a liquid medium 32. The near-infrared absorbing particle dispersion preferably has a configuration in which near-infrared absorbing particles are dispersed in a liquid medium.

[0172] 3 is a schematic diagram, and the near-infrared absorbing particle dispersion liquid of this embodiment is not limited to this form. For example, in FIG. 3, the near-infrared absorbing particles 31 are represented by circles and depicted as spherical particles, but the shape of the near-infrared absorbing particles 31, which are the above-described composite tungsten oxide particles, is not limited to this form and can have any shape. The near-infrared absorbing particles 31 may have, for example, a coating on their surfaces. The near-infrared absorbing particle dispersion liquid 30 may contain other additives as needed in addition to the near-infrared absorbing particles 31 and the liquid medium 32.

[0173] The liquid medium may be one or more selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers.

[0174] As the organic solvent, various types can be selected, such as alcohols, ketones, esters, hydrocarbons, and glycols. Specific examples of the solvent include one or more selected from alcohol-based solvents such as isopropyl alcohol, methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propanol; ketone-based solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester-based solvents such as 3-methyl-methoxy-propionate and butyl acetate; glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol methyl ether acetate, and propylene glycol ethyl ether acetate; amides such as formamide, N-methylformamide, dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; and halogenated hydrocarbons such as ethylene chloride and chlorobenzene.

[0175] However, among these, organic solvents with low polarity are preferred, and in particular, isopropyl alcohol, ethanol, 1-methoxy-2-propanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, n-butyl acetate, etc. These organic solvents can be used alone or in combination of two or more.

[0176] Examples of fats and oils that can be used include one or more selected from drying oils such as linseed oil, sunflower oil, and tung oil; semi-drying oils such as sesame oil, cottonseed oil, rapeseed oil, soybean oil, and rice bran oil; non-drying oils such as olive oil, coconut oil, palm oil, and dehydrated castor oil; fatty acid monoesters obtained by directly esterifying fatty acids of vegetable oils with monoalcohols; ethers; and petroleum solvents such as Isopar (registered trademark) E, Exxor (registered trademark) Hexane, Heptane, E, D30, D40, D60, D80, D95, D110, and D130 (all manufactured by ExxonMobil).

[0177] As the liquid resin, for example, one or more types selected from liquid acrylic resin, liquid epoxy resin, liquid polyester resin, liquid urethane resin, etc. can be used.

[0178] As the liquid plasticizer, for example, a liquid plasticizer for plastics can be used.

[0179] The components contained in the near-infrared absorbing particle dispersion are not limited to the near-infrared absorbing particles and the liquid medium described above. The near-infrared absorbing particle dispersion may further contain any optional components added thereto, as necessary.

[0180] For example, an acid or alkali may be added to the near-infrared absorbing particle dispersion liquid as needed to adjust the pH of the dispersion liquid.

[0181] In addition, in order to further improve the dispersion stability of the near infrared absorbing particles in the near infrared absorbing particle dispersion and to prevent the dispersed particle size from becoming coarse due to re-aggregation, various surfactants, coupling agents, and the like may be added to the near infrared absorbing particle dispersion as dispersants.

[0182] The dispersant, such as the surfactant or coupling agent, can be selected depending on the application, but it is preferable that the dispersant has one or more functional groups selected from an amine-containing group, a hydroxyl group, a carboxyl group, and an epoxy group. These functional groups adsorb to the surface of the near-infrared absorbing particles to prevent aggregation and have the effect of uniformly dispersing the near-infrared absorbing particles even in an infrared shielding film formed using the near-infrared absorbing particles. It is more preferable that the dispersant is a polymeric dispersant having one or more functional groups selected from the above functional groups (functional groups) in the molecule.

[0183] Suitable commercially available dispersants include Solsperse (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, and 250 (manufactured by Lubrizol Japan Co., Ltd.), and EFKA (registered trademark). 4008, 4009, 4010, 4015, 4046, 4047, 4060, 4080, 7462, 4020, 4050, 4055, 4400, 4401, 4402, 4403, 4300, 4320, 4330, 4340, 6220, 6225, 6700, 6780, 6782, 8503 (manufactured by Fuka Additives), Ajisper (registered trademark) PA111, PB821, PB822, PN411, Famex L-12 (manufactured by Ajinomoto Fine-Techno Co., Ltd.), DisperBYK (registered trademark) 101, 102, 106, 108, 111, 116, 130, 140, 142, 145, 161, 162, 163, 164, 166, 167, 168, 170, 171, 174, 180, 182, 192, 193, 2000, 2001, 2020, 2025, 2050, 2070, 2155, 2164, 220S, 300, 306, 320, 322, 325, 330, 340, 350, 377, 378, 380N, 410, 425, 430 (manufactured by Pick Chemie Japan Co., Ltd.), Disparlon (registered trademark) 1751N, 1831, 1850, 1860, 1934, DA-400N, DA-703-50, DA-725, DA-705, DA-7301, DN-900, NS-5210, NVI-8514L (manufactured by Kusumoto Chemicals Co., Ltd.), Arfon (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), and the like.

[0184] The method for dispersing the near-infrared absorbing particles in a liquid medium is not particularly limited as long as the method can disperse the near-infrared absorbing particles in the liquid medium. In this case, the near-infrared absorbing particles are preferably dispersed so that their average particle size is 800 nm or less, more preferably 1 nm or more and 800 nm or less.

[0185] Examples of methods for dispersing near-infrared absorbing particles in a liquid medium include dispersion methods using devices such as a bead mill, a ball mill, a sand mill, a paint shaker, and an ultrasonic homogenizer. Among these, pulverization and dispersion using a media agitation mill such as a bead mill, a ball mill, a sand mill, or a paint shaker that uses a medium media (beads, balls, Ottawa sand) is preferred from the viewpoint of shortening the time required to achieve a desired average particle size. By the pulverization-dispersion treatment using a media agitation mill, not only is the near-infrared absorbing particles dispersed in a liquid medium, but also finer particle size is promoted due to collisions between the near-infrared absorbing particles and collisions of the medium with the near-infrared absorbing particles, and the near-infrared absorbing particles can be dispersed in a finer particle size. In other words, the pulverization-dispersion treatment is performed.

[0186] As described above, the average particle size of the near-infrared absorbing particles is preferably 1 nm or more and 800 nm or less. This is because a small average particle size reduces scattering of light in the visible light region due to geometric scattering or Mie scattering. Furthermore, for example, a near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment, in which near-infrared absorbing particles are dispersed in a solid medium such as a resin, can achieve particularly clear transparency. That is, when the average particle size is 200 nm or less, the light scattering mode weakens from the geometric scattering or Mie scattering mode and shifts to the Rayleigh scattering mode. In the Rayleigh scattering region, scattered light is proportional to the sixth power of the dispersed particle size, so scattering decreases and transparency improves as the dispersed particle size decreases. Furthermore, an average particle size of 100 nm or less is preferable because scattered light is significantly reduced. An average particle size of 30 nm or less is even more preferable.

[0187] The dispersion state of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment can be made equivalent to the dispersion state of the near-infrared absorbing particles in the dispersion, as long as the dispersion is added to a solid medium by a known method. In other words, the near-infrared absorbing particles in the near-infrared absorbing particle dispersion are less likely to aggregate than the near-infrared absorbing particles in the near-infrared absorbing particle dispersion, and the average particle size can be made equivalent.

[0188] Furthermore, when the average particle size of the near infrared absorbing particles is 1 nm or more and 800 nm or less, the transparency of the produced near infrared absorbing particle dispersion and its molded body (plate, sheet, etc.) can be particularly improved.

[0189] The content of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion liquid of this embodiment is not particularly limited, but is preferably, for example, 0.01% by mass or more and 80% by mass or less. This is because a sufficient solar radiation shading rate can be exhibited, that is, the solar radiation transmittance can be sufficiently suppressed, by setting the content of the near-infrared absorbing particles to 0.01% by mass or more. Furthermore, this is because a content of the near-infrared absorbing particles to 80% by mass or less can uniformly disperse the near-infrared absorbing particles in the dispersion medium.

[0190] The near-infrared absorbing particle dispersion of this embodiment contains the composite tungsten oxide particles described above, and therefore can be a near-infrared absorbing particle dispersion with excellent visible light transmittance and near-infrared shielding performance. Furthermore, the near-infrared absorbing particle dispersion of this embodiment has an excellent near-infrared shielding effect, achieving a transmittance peak of 75% or more in the wavelength range of 500 nm to 600 nm, and a transmittance bottom of 5% or less in the near-infrared region. Furthermore, the near-infrared absorbing particle dispersion of this embodiment can achieve a transmittance of 50% or more at a wavelength of 700 nm and a transmittance of 30% or more at a wavelength of 800 nm. Therefore, the near-infrared absorbing particle dispersion of this embodiment can suppress solar transmittance, while providing a more neutral transmitted color and ensuring transmittance at sensor wavelengths. [Near-infrared absorbing particle dispersion] Next, an example of the configuration of the near-infrared absorbing particle dispersion of this embodiment will be described.

[0191] The near-infrared absorbing particle dispersion of this embodiment includes near-infrared absorbing particles and a solid medium. The near-infrared absorbing particles may be the above-described composite tungsten oxide particles.

[0192] Specifically, for example, as schematically shown in Fig. 4 , a near-infrared absorbing particle dispersion 40 can include near-infrared absorbing particles 41, which are the above-described composite tungsten oxide particles, and a solid medium 42, and the near-infrared absorbing particles 41 can be disposed in the solid medium 42. In the near-infrared absorbing particle dispersion of the present embodiment, the near-infrared absorbing particles are preferably dispersed in the solid medium.

[0193] 4 is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to this form. For example, in FIG. 4, the near-infrared absorbing particles 41 are represented by circles and depicted 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 can also have, for example, a coating on their surfaces. The near-infrared absorbing particle dispersion 40 can also contain other additives as needed, in addition to the near-infrared absorbing particles 41 and the solid medium 42.

[0194] The near-infrared absorbing particle dispersion according to this embodiment will be described below in the following order: (1) properties of the solid medium and the near-infrared absorbing particle dispersion, (2) a method for producing the near-infrared absorbing particle dispersion, (3) additives, and (4) application examples. (1) Properties of the solid medium and the near-infrared absorbing particle dispersion Examples of the solid medium include medium resins such as thermoplastic resins, thermosetting resins, and ultraviolet-curing resins. That is, resins can be suitably used as the solid medium.

[0195] The specific resin material used for the solid medium is not particularly limited, but is preferably one resin selected from the group consisting of polyester resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene-vinyl acetate copolymer, polyvinyl acetal resin, and ultraviolet curing resin, or a mixture of two or more resins selected from the group. Polyethylene terephthalate resin is preferably used as the polyester resin.

[0196] These medium resins may also contain a polymeric dispersant having, in the main skeleton, one or more functional groups selected from the group containing an amine, a hydroxyl group, a carboxyl group, and an epoxy group.

[0197] The solid medium is not limited to a medium resin, and a binder using a metal alkoxide can also be used as the solid medium. Typical examples of the metal alkoxide include alkoxides of Si, Ti, Al, Zr, etc. By subjecting a binder using such a metal alkoxide to hydrolysis and condensation polymerization by heating or the like, it is also possible to obtain a near-infrared absorbing particle dispersion in which the solid medium contains an oxide.

[0198] The content ratio of the near infrared absorbing particles in the near infrared absorbing particle dispersion according to this embodiment is not particularly limited, but the near infrared absorbing particle dispersion preferably contains the near infrared absorbing particles in an amount of 0.001 mass % or more and 80 mass % or less.

[0199] The shape of the near infrared absorbing particle dispersion of this embodiment is not particularly limited, but the near infrared absorbing particle dispersion of this embodiment preferably has a sheet shape, a board shape, or a film shape, because forming the near infrared absorbing particle dispersion into a sheet shape, a board shape, or a film shape allows it to be applied to various uses.

[0200] The near-infrared absorbing particle dispersion of this embodiment contains the composite tungsten oxide particles described above, and therefore can be a near-infrared absorbing particle dispersion with excellent visible light transmittance and near-infrared shielding performance. Furthermore, the near-infrared absorbing particle dispersion of this embodiment has an excellent near-infrared shielding effect, in that even if the peak transmittance in the wavelength range of 500 nm to 600 nm is 75% or more, the bottom transmittance in the near-infrared region can be 5% or less. Furthermore, the near-infrared absorbing particle dispersion of this embodiment can achieve a transmittance of 50% or more at a wavelength of 700 nm and a transmittance of 30% or more at a wavelength of 800 nm. Therefore, the near-infrared absorbing particle dispersion of this embodiment can suppress solar transmittance, while providing a more neutral transmitted color and ensuring transmittance at sensor wavelengths. (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 the following merely illustrates a configuration example of the method for producing a near-infrared absorbing particle dispersion, and the method for producing a near-infrared absorbing particle dispersion according to one embodiment of the present disclosure is not limited to the following configuration example.

[0201] The near infrared absorbing particle dispersion of this embodiment can be produced, for example, by using a masterbatch. In this case, the production method of the near infrared absorbing particle dispersion of this embodiment can also include, for example, the following masterbatch production step.

[0202] In the masterbatch preparation step, a masterbatch in which near-infrared absorbing particles are dispersed in a solid medium can be prepared.

[0203] The specific method for producing the masterbatch is not particularly limited. For example, the masterbatch can be produced by dispersing a near-infrared absorbing particle dispersion or near-infrared absorbing particles in a solid medium and pelletizing the solid medium.

[0204] As the near-infrared absorbing particles, a near-infrared absorbing particle dispersion powder obtained by removing the liquid medium from a near-infrared absorbing particle dispersion liquid can also be used.

[0205] For example, a mixture is 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 powder or pellets, and, if necessary, other additives. The mixture is then kneaded in a vented single-screw or twin-screw extruder, and processed into pellets by cutting melt-extruded strands, thereby producing a masterbatch. In this case, the pellets may have a cylindrical or prismatic shape. Alternatively, a so-called hot-cut method can be used to produce pellets, in which the melt-extruded material is directly cut. In this case, pellets typically have a shape close to spherical.

[0206] In addition, when a near-infrared absorbing particle dispersion is used as a raw material in the masterbatch preparation step, it is preferable to reduce or remove the liquid medium derived from the near-infrared absorbing particle dispersion. In this case, the degree to which the liquid medium contained in the near-infrared absorbing particle dispersion is removed is not particularly limited. For example, it is preferable to remove the liquid medium from the near-infrared absorbing particle dispersion or the like to an amount that is allowable to remain in the masterbatch. In addition, when 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.

[0207] There are no particular limitations on the method for reducing or removing the liquid medium contained in the near infrared absorbing particle dispersion from the near infrared absorbing particle dispersion or the mixture of the near infrared absorbing particle dispersion and the solid medium.

[0208] For example, it is preferable to carry out a drying step in which the near-infrared absorbing particle dispersion or the like is dried under reduced pressure. Specifically, the near-infrared absorbing particle dispersion or the like is dried under reduced pressure while being stirred, and the near-infrared absorbing particle-containing composition and the liquid medium components are separated. An example of an apparatus used for the reduced pressure drying is a vacuum stirring type dryer, but any apparatus having the above functions may be used, and is not particularly limited. Furthermore, the pressure value during the reduced pressure in the drying step is appropriately selected.

[0209] The use of a vacuum drying method improves the efficiency of removing the liquid medium and the like derived from the near-infrared absorbing particle dispersion. Furthermore, the near-infrared absorbing particle dispersion powder obtained after vacuum drying and the near-infrared absorbing particle dispersion liquid as a raw material are not exposed to high temperatures for a long time, which is preferable because aggregation of the near-infrared absorbing particle dispersion powder and the near-infrared absorbing particles dispersed in the near-infrared absorbing particle dispersion liquid does not occur. Furthermore, the productivity of the near-infrared absorbing particle dispersion powder and the like is increased, and the evaporated solvent such as the liquid medium can be easily recovered, which is also preferable from an environmental perspective.

[0210] It is preferable to thoroughly remove solvent components having a boiling point of 120°C or less from the near-infrared absorbing particle dispersion powder or the like obtained after the drying step. For example, it is preferable that the remaining amount of such solvent components is 2.5% by mass or less. This is because, if the remaining solvent components are 2.5% by mass or less, when the near-infrared absorbing particle dispersion powder or the like is processed into, for example, a near-infrared absorbing particle dispersion, no bubbles are generated, and good appearance and optical properties are maintained. Furthermore, if the remaining solvent components in the near-infrared absorbing particle dispersion powder are 2.5% by mass or less, aggregation due to natural drying of the remaining solvent components does not occur when the near-infrared absorbing particle dispersion powder is stored for a long period of time, and long-term stability is maintained.

[0211] The obtained master batch can be kneaded with the addition of a solid medium, thereby adjusting the dispersion concentration while maintaining the dispersed state of the near-infrared absorbing particles contained in the master batch, which is a near-infrared absorbing particle dispersion.

[0212] Furthermore, the method for producing the near infrared absorbing particle dispersion of the present embodiment may include, as necessary, a molding step of molding the obtained master batch or the master batch to which a solid medium has been added as described above, to form a near infrared absorbing particle dispersion having a desired shape.

[0213] The specific method for molding the near-infrared absorbing particle dispersion is not particularly limited, but for example, known methods such as extrusion molding and injection molding can be used.

[0214] In the molding step, for example, a near-infrared absorbing particle dispersion can be produced in the shape of a sheet, a board, or a film, which is molded into a flat or curved shape. The method for molding into a sheet, a board, or a film is not particularly limited, and various known methods can be used. For example, a calendar roll method, an extrusion method, a casting method, an inflation method, etc. can be used.

[0215] The method for producing the near-infrared absorbing particle dispersion of the present embodiment is not limited to the embodiment having the masterbatch production step.

[0216] For example, the method for producing a near-infrared absorbing particle dispersion of the present embodiment may have the following precursor liquid preparation step and near-infrared absorbing particle dispersion production step.

[0217] In the precursor liquid preparation step, a solid medium precursor, which is one or more types selected from a monomer or oligomer of a solid medium and an uncured liquid solid medium, is mixed with near-infrared absorbing particles, near-infrared absorbing particle dispersion powder, or near-infrared absorbing particle dispersion liquid to prepare a near-infrared absorbing particle dispersion precursor liquid.

[0218] In the near-infrared absorbing particle dispersion preparation step, the solid medium precursor such as the above-mentioned monomer is cured by a chemical reaction such as condensation or polymerization, thereby preparing the near-infrared absorbing particle dispersion.

[0219] For example, when an acrylic resin is used as the solid medium, a near-infrared absorbing particle dispersion precursor liquid can be obtained by mixing an acrylic monomer or an acrylic ultraviolet curable resin with near-infrared absorbing particles.

[0220] Next, the near-infrared absorbing particle dispersion precursor liquid is filled into a predetermined mold or the like and subjected to radical polymerization, thereby obtaining a near-infrared absorbing particle dispersion using an acrylic resin.

[0221] When a resin that hardens by crosslinking is used as the solid medium, a dispersion can be obtained by subjecting a near-infrared absorbing particle dispersion precursor liquid to a crosslinking reaction, as in the case of using the acrylic resin described above.

[0222] (3) Additives When a resin is used as the solid medium, the near infrared absorbing particle dispersion of the present embodiment may also contain known additives (additives) that are usually added to such resins, such as a plasticizer, a flame retardant, a coloring inhibitor, a filler, etc. However, as described above, the solid medium is not limited to a resin, and a binder using a metal alkoxide may also be used.

[0223] The shape of the near infrared absorbing particle dispersion according to this embodiment is not particularly limited, but as described above, it can be in the form of, for example, a sheet, a board, or a film.

[0224] When a near-infrared absorbing particle dispersion in the form of a sheet, board, or film is used as an intermediate layer of 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 it is.In this case, it is preferable that the near-infrared absorbing particle dispersion contains a plasticizer.Specifically, for example, when the solid medium is a polyvinyl acetal resin and the near-infrared absorbing particle dispersion is used for the above-mentioned intermediate layer of a transparent substrate, it is preferable that the near-infrared absorbing particle dispersion further contains a plasticizer.

[0225] The plasticizer may be a substance used as a plasticizer in the solid medium used in the near-infrared absorbing particle dispersion of this embodiment. For example, plasticizers applicable to near-infrared absorbing particle dispersions using a polyvinyl acetal resin as the 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 phosphate-based plasticizers such as organic phosphate-based plasticizers. It is preferable that any of these plasticizers be liquid at room temperature. Among these, plasticizers that are ester compounds synthesized from polyhydric alcohols and fatty acids are preferred. (4) Application Examples The near-infrared absorbing particle dispersion of this embodiment can be used in various embodiments, and its use and application are not particularly limited. Below, application examples of the near-infrared absorbing particle dispersion of this embodiment are described, including a near-infrared absorbing interlayer film, a near-infrared absorbing laminate, and a near-infrared absorbing transparent substrate. (4-1) Near-infrared absorbing interlayer film and near-infrared absorbing laminate The near-infrared absorbing laminate of this embodiment can have a laminate structure including the near-infrared absorbing particle dispersion described above and a transparent substrate. The near-infrared absorbing laminate of this embodiment has the above-described near-infrared absorbing particle dispersion and a transparent substrate as elements, and can be a laminate obtained by laminating these elements.

[0226] The near-infrared absorbing laminate may be, for example, a laminate of two or more transparent substrates and the above-described near-infrared absorbing particle dispersion. In this case, the near-infrared absorbing particle dispersion is disposed between the transparent substrates, and can be used as a near-infrared absorbing interlayer film.

[0227] In this case, specifically, as shown in Fig. 5 which is a cross-sectional schematic view along the lamination direction of the transparent substrate and the near-infrared absorbing particle dispersion, the near-infrared absorbing laminate 50 can have a plurality of transparent substrates 521, 522 and a near-infrared absorbing particle dispersion 51. The near-infrared absorbing particle dispersion 51 can be disposed between the plurality of transparent substrates 521, 522. Although Fig. 5 shows an example in which two transparent substrates 521, 522 are provided, the present invention is not limited to this embodiment.

[0228] The near-infrared absorbing particle dispersion that becomes the near-infrared absorbing interlayer film preferably has any one of a sheet shape, a board shape, and a film shape.

[0229] The transparent substrate may be one or more selected from the group consisting of glass sheets, plastic sheets, and plastic films that are transparent in the visible light range.

[0230] When a plastic is used as the transparent substrate, the plastic material is not particularly limited and can be selected depending on the application, and can be, for example, one or more types selected from polycarbonate resin, acrylic resin, polyester resin, polyamide resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, ionomer resin, fluororesin, etc. As the polyester resin, polyethylene terephthalate resin can be preferably used.

[0231] The transparent substrate may contain particles having a solar radiation shielding function. As the particles having a solar radiation shielding function, near-infrared absorbing particles having near-infrared shielding properties can be used.

[0232] By interposing the near-infrared absorbing particle dispersion described above as a constituent member of an intermediate layer sandwiched between a plurality of transparent substrates, a solar radiation-shielding laminated structure, which is a type of near-infrared absorbing laminate, having excellent visible light transmission performance and near-infrared shielding performance can be obtained. Furthermore, with the near-infrared absorbing particle dispersion described above, even if the peak transmittance in the wavelength region of 500 nm to 600 nm is 75% or more, a transmittance of 50% or more at a wavelength of 700 nm and a transmittance of 30% or more at a wavelength of 800 nm can be achieved. Therefore, a solar radiation-shielding laminated structure, which is a type of near-infrared absorbing laminate, can be obtained that has a more neutral transmitted color tone while suppressing solar radiation transmittance and is also capable of ensuring transmittance at sensor wavelengths.

[0233] The near-infrared absorbing laminate can also be obtained by bonding and integrating a plurality of transparent substrates facing each other with the near-infrared absorbing particle dispersion sandwiched therebetween by a known method.

[0234] When the near-infrared absorbing particle dispersion described above is used as a near-infrared absorbing interlayer film, the solid medium may be any of those described for the near-infrared absorbing particle dispersion. However, from the viewpoint of increasing the adhesive strength between the near-infrared absorbing interlayer film and the transparent substrate, the solid medium is preferably a polyvinyl acetal resin.

[0235] The near-infrared absorbing interlayer film of this embodiment can be produced by the above-described method for producing a near-infrared absorbing particle dispersion, and can be in the form of, for example, a sheet, a board, or a film.

[0236] If the near-infrared absorbing interlayer film does not have sufficient flexibility or adhesion to the transparent substrate, it is preferable to add a liquid plasticizer for the medium resin, which is a solid medium. For example, if the medium resin used in the near-infrared absorbing interlayer film is a polyvinyl acetal resin, adding a liquid plasticizer for the polyvinyl acetal resin is beneficial for improving adhesion to the transparent substrate.

[0237] As the plasticizer, a substance that is used as a plasticizer for a resin as a solid medium can be used. For example, examples of plasticizers that can be applied to a near-infrared absorbing particle dispersion using a 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 organic phosphoric acid-based plasticizers. It is preferable that any of these plasticizers be liquid at room temperature. Among these, plasticizers that are ester compounds synthesized from polyhydric alcohols and fatty acids are preferred.

[0238] The near-infrared absorbing interlayer film may also contain at least one selected from the group consisting of a silane coupling agent, a metal salt of carboxylic acid, a metal hydroxide, and a metal carbonate. The metal constituting the metal salt of carboxylic acid, the metal hydroxide, and the metal carbonate is not particularly limited, but is preferably at least one selected from sodium, potassium, magnesium, calcium, manganese, cesium, lithium, rubidium, and zinc. In the near-infrared absorbing interlayer film, the content of the at least one selected from the group consisting of a metal salt of carboxylic acid, a metal hydroxide, and a metal carbonate is preferably 1% by mass or more and 100% by mass or less relative to the near-infrared absorbing particles.

[0239] Furthermore, the near-infrared absorbing interlayer film may contain, in addition to the near-infrared absorbing particles, at least one type of particles 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, Yb, Lu, Sr, and Ca. The near-infrared absorbing interlayer film may contain such particles in an amount of 5% by mass to 95% by mass, where the total amount of the near-infrared absorbing particles and the near-infrared absorbing particles is 100% by mass.

[0240] In the near-infrared absorbing laminate, at least one layer of the interlayer film disposed between the transparent substrates may contain an ultraviolet absorber. Examples of the ultraviolet absorber include one or more 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.

[0241] It goes without saying that the intermediate layer of the near-infrared absorbing laminate may be composed solely of the near-infrared absorbing intermediate film according to this embodiment.

[0242] The near-infrared absorbing interlayer film described here is one embodiment of the near-infrared absorbing particle dispersion. Of course, the near-infrared absorbing particle dispersion according to this embodiment can 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 alone as a near-infrared absorbing particle dispersion.

[0243] The near-infrared absorbing laminate according to this embodiment is not limited to the above-described form in which a near-infrared absorbing particle dispersion is disposed between transparent substrates, and any configuration can be adopted as long as it has a layered 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 according to this embodiment includes 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.

[0244] 6 , which is a cross-sectional schematic view taken along the lamination direction of the transparent substrate and the near-infrared absorbing layer, the near-infrared absorbing transparent substrate 60 can have a transparent substrate 61 and a near-infrared absorbing layer 62. The near-infrared absorbing layer 62 can be disposed on at least one surface 61A of the transparent substrate 61.

[0245] The near-infrared absorbing transparent substrate of this embodiment may have a transparent substrate as described above. As the transparent substrate, for example, one or more types selected from a transparent film substrate and a transparent glass substrate can be preferably used.

[0246] The film substrate is not limited to a film shape and may be, for example, a board shape or a sheet shape. As the material of the film substrate, one or more selected from polyester resin, acrylic resin, urethane resin, polycarbonate resin, polyethylene resin, ethylene vinyl acetate copolymer, vinyl chloride resin, fluororesin, etc. can be suitably used, and can be used according to various purposes. However, as the material of the film substrate, polyester resin is preferred, and polyethylene terephthalate resin (PET resin) is more preferred. That is, the film substrate is preferably a polyester resin film, and more preferably a polyethylene terephthalate resin film.

[0247] When a film substrate is used as the transparent substrate, the surface of the film substrate is preferably subjected to a surface treatment in order to facilitate adhesion to the near-infrared absorbing layer.

[0248] In order to improve the adhesion between the glass substrate or the film substrate and the near-infrared absorbing layer, it is also preferable to form an intermediate layer on the glass substrate or the film substrate and then form the near-infrared absorbing layer on the intermediate layer. The configuration of the intermediate layer is not particularly limited, and it can be formed, for example, by a polymer film, a metal layer, an inorganic layer (e.g., an inorganic oxide layer such as silica, titania, or zirconia), an organic / inorganic composite layer, or the like.

[0249] The near-infrared absorbing particle dispersion has been described above, and therefore will not be described here. The shape of the near-infrared absorbing particle dispersion is not particularly limited, but it is preferably in the shape of a sheet, a board, or a film, for example.

[0250] A method for producing the near-infrared absorbing transparent substrate of this embodiment will be described.

[0251] The near-infrared absorbing transparent substrate of the present embodiment can be produced by, for example, using the above-described near-infrared absorbing particle dispersion liquid to form, on a transparent substrate, a near-infrared absorbing layer that is a near-infrared absorbing particle dispersion in which near-infrared absorbing particles are dispersed in a solid medium.

[0252] Therefore, the method for producing the near-infrared absorbing transparent substrate of this embodiment can include, for example, the following coating step and near-infrared absorbing layer forming step.

[0253] In the coating step, a coating liquid containing the near-infrared absorbing particle dispersion liquid described above is applied to the surface of a transparent substrate.

[0254] In the near-infrared absorbing layer forming step, the liquid medium in the coating liquid is evaporated, and then the near-infrared absorbing layer is formed.

[0255] The coating liquid used in the coating step can be prepared by, for example, 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 liquid described above.

[0256] As described above, the solid medium precursor refers to one or more selected from a monomer, an oligomer, and an uncured liquid solid medium.

[0257] When a near-infrared absorbing layer, which is a coating film, is formed on a transparent substrate, the near-infrared absorbing layer is in a state in which near-infrared absorbing particles are dispersed in a solid medium. Therefore, such a near-infrared absorbing layer becomes a near-infrared absorbing particle dispersion. In this way, by providing the near-infrared absorbing particle dispersion on the surface of the transparent substrate, a near-infrared absorbing transparent substrate can be produced.

[0258] The solid medium and the solid medium precursor have been described in (1) Properties of the solid medium and the near infrared absorbing particle dispersion and (2) Method for producing the near infrared absorbing particle dispersion, and therefore description thereof will be omitted here.

[0259] The method for applying the coating liquid onto the transparent substrate to provide a near-infrared absorbing layer on the transparent substrate is not particularly limited as long as it can uniformly apply the coating liquid to the surface of the transparent substrate, and examples thereof include bar coating, gravure coating, spray coating, dip coating, spin coating, screen printing, roll coating, and flow coating.

[0260] Here, the procedure for producing a near-infrared absorbing layer on the surface of a transparent substrate will be described using as an example a case where an ultraviolet curable resin is used as a solid medium and a coating liquid is applied by a bar coating method to form a near-infrared absorbing layer.

[0261] The coating solution, the concentration and additives of which have been appropriately adjusted to provide adequate leveling properties, is applied to a transparent substrate using a wire bar with a bar number that satisfies the thickness of the near-infrared absorbing layer and the content of the near-infrared absorbing particles required. After removing the solvent, such as the liquid medium, contained in the coating solution by drying, ultraviolet light is irradiated to cure the solid medium, thereby forming a coating layer that is a near-infrared absorbing layer on the transparent substrate.

[0262] The drying conditions for the coating film vary depending on the type and proportion of each component and solvent, but typically can be carried out at a temperature of 60° C. to 140° C. for 20 seconds to 10 minutes. There are no particular limitations on the type of ultraviolet light irradiation, and an ultraviolet exposure device such as an ultra-high pressure mercury lamp can be suitably used.

[0263] In addition, the adhesion between the substrate and the near-infrared absorbing layer, the smoothness of the coating film during coating, the drying property of the organic solvent, etc. can be manipulated by the pre-processing and post-processing before and after the formation of the near-infrared absorbing layer. Examples of the pre-processing and post-processing include a surface treatment process of the substrate, a pre-baking process (pre-heating of the substrate), and a post-baking process (post-heating of the substrate), and these can be selected appropriately. The heating temperature in the pre-baking process and the post-baking process is preferably 80° C. or higher and 200° C. or lower, and the heating time is preferably 30 seconds or higher and 240 seconds or lower.

[0264] The method for producing the near-infrared absorbing transparent substrate of the present embodiment is not limited to the above-described method. Other examples of the method for producing the near-infrared absorbing transparent substrate of the present embodiment include a method including the following steps of applying a near-infrared absorbing particle dispersion and drying, or applying a binder and curing.

[0265] In the near-infrared absorbing particle dispersion coating and drying step, the near-infrared absorbing particle dispersion described above is coated on the surface of the transparent substrate and dried.

[0266] In the binder application and curing step, a binder using a resin, a solid medium such as a metal alkoxide, or a solid medium precursor is applied to the surface on which the near-infrared absorbing particle dispersion liquid has been applied, and then cured.

[0267] In this case, a film having near-infrared absorbing particles dispersed therein is formed on the surface of the transparent substrate by the near-infrared absorbing particle dispersion coating and drying steps. The near-infrared absorbing particle dispersion can be coated by the same method as that described for the coating step in the above-mentioned method for producing a near-infrared absorbing transparent substrate.

[0268] Then, a binder is applied onto the film in which the near-infrared absorbing particles are dispersed, and then cured, so that the cured binder is disposed between the near-infrared absorbing particles, thereby forming a near-infrared absorbing layer.

[0269] The near-infrared absorbing transparent substrate may further have a coating layer on the surface of the near-infrared absorbing particle dispersion, i.e., may have a multilayer film.

[0270] The coating layer may be a coating film of an oxide containing one or more elements selected from Si, Ti, Zr, and Al, for example. In this case, the coating layer may be formed, for example, by applying a coating liquid containing one or more elements selected from alkoxides containing one or more elements of Si, Ti, Zr, and Al, and partial hydrolysis polycondensates of the alkoxides, onto the near-infrared absorbing layer, followed by heating.

[0271] By providing the coating layer, the coated component fills the gaps between the deposited near-infrared absorbing particles of the first layer to form a film, suppressing the refraction of visible light, thereby further reducing the haze value of the film and improving the visible light transmittance. Also, the adhesion of the near-infrared absorbing particles to the substrate can be improved.

[0272] Here, as a method for forming a coating film made of an alkoxide containing one or more of Si, Ti, Zr, and Al or a partially hydrolyzed condensation polymer thereof on the near infrared absorbing particles alone or on a film containing the near infrared absorbing particles, a coating method is preferred from the viewpoints of ease of film formation operation and cost.

[0273] The coating liquid used in the coating method can be preferably one containing one or more alkoxides of Si, Ti, Zr, and Al in a solvent such as water or alcohol, or one or more partial hydrolysis polycondensates of the alkoxides. The content of the alkoxides in the coating liquid is not particularly limited, but is preferably 40 mass% or less in terms of oxides in the coating obtained after heating. Furthermore, the pH can be adjusted by adding an acid or alkali as needed.

[0274] The coating liquid is applied as a second layer onto a film containing near-infrared absorbing particles as a main component, and then heated, whereby an oxide coating containing one or more elements selected from Si, Ti, Zr, and Al can be easily formed as a coating layer. It is also preferable to use an organosilazane solution as a binder component used in the coating liquid or as a component of the coating liquid.

[0275] The heating temperature of the substrate after application of the near-infrared absorbing particle dispersion liquid containing one or more metal alkoxides of Si, Ti, Zr, and Al and their hydrolysis polymers, or the coating liquid, is not particularly limited. For example, the heating temperature of the substrate 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.

[0276] This is because the polymerization reaction of the metal alkoxide or the hydrolysis polymer of the metal alkoxide contained in the coating film can be completed when the substrate heating temperature is 100° C. or higher. Also, when the substrate heating temperature is 100° C. or higher, the solvent water or organic solvent hardly remains in the film, and therefore these solvents do not cause a decrease in the visible light transmittance of the film after heating.

[0277] In the near-infrared absorbing transparent substrate of the present embodiment, the thickness of the near-infrared absorbing layer on the transparent substrate is not particularly limited, but is preferably 10 μm or less in practical use, and more preferably 6 μm or less. This is because, if the thickness of the near-infrared absorbing layer is 10 μm or less, sufficient pencil hardness is exhibited to provide scratch resistance, and in addition, process abnormalities such as warping of the substrate film can be avoided during volatilization of the solvent in the near-infrared absorbing layer and curing of the binder.

[0278] Specific examples will be described below, but the present invention is not limited to these examples. (1) Evaluation Method (1-1) Powder X-ray Diffraction Pattern The powder X-ray diffraction pattern (XRD pattern) of the composite tungsten oxide particles was measured using a powder X-ray diffractometer (BRUKER D2 PHASER). The powder X-ray diffraction pattern was measured using CuKα radiation as the radiation source, with a tube voltage of 45 kV and a tube current of 40 mA. (1-2) Transmitted Light Profile The optical properties of the near-infrared absorbing particle dispersion were measured using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.) to measure the transmitted light profile at 5 nm intervals in the wavelength range of 200 nm to 2600 nm. (1-3) Composition Analysis The proportions of each component contained in the composite tungsten oxide particles were evaluated by the following method.

[0279] The mass proportion of Cs was determined as an average value of three measurements for each sample using a polarized Zeeman atomic absorption spectroscopy (AAS, model: ZA3300, manufactured by Hitachi High-Tech Corporation).

[0280] The mass ratio of W was determined as the average value of three analyses of each sample performed using inductively-coupled plasma optical emission spectroscopy (ICP-OES, model: ICPE-9800, manufactured by Shimadzu Corporation).

[0281] The mass percentage of O was determined as the average value of three analyses per sample performed using an infrared detector for oxygen detection (infrared absorption spectroscopy (IRS)) with an oxygen / nitrogen / hydrogen analyzer (ON-836, LECO Japan Corp.). Example 1 Composite tungsten oxide particles were produced and evaluated using the composite material production apparatus 10 shown in FIG. 1 and the reduction treatment apparatus 20 shown in FIG. 2. Specific conditions are described below.

[0282] The composite material manufacturing apparatus 10 has a storage section 11 containing a solution containing a W element source and an M element source, which are raw material solutions; a two-fluid nozzle 12 that forms droplets of the raw materials and also forms a flame; and a reaction tube 13 connected to a filter 14 that collects the formed composite tungsten oxide particles.

[0283] The supply rate of the raw material solution to the two-fluid nozzle 12 was set to 3 g / min. The flow rate of oxygen, which was a carrier gas, was set to 15 L / min, controlled by the ejector 15. The air flow rate in the ejector 15 was controlled to be within the range of 160 L / min to 180 L / min.

[0284] Propane gas and oxygen gas were used to form the flame by the two-fluid nozzle 12, with the flow rate of the propane gas being 1.2 L / min and the flow rate of the oxygen gas being 6.0 L / min.

[0285] The raw material is W(CO) ６ in tetrahydrofuran (THF) (a solution containing a W element source) and a solution in which cesium acetate, an M element source, is dissolved in ethanol (a solution containing an M element source) were used and stored in the storage unit 11. The mixed solution, which was the raw material, was prepared so that the ratio of the amount of substance of Cs (Cs) as the M element contained therein to the amount of substance of tungsten (W), Cs / W, was 0.37.

[0286] The raw material solution and oxygen as a carrier gas were supplied from the storage section 11 to the two-fluid nozzle 12 to form an aerosol (aerosol forming step).

[0287] 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 and subjected to heat treatment (heat treatment process).

[0288] In the heat treatment step, when the composite tungsten oxide particles obtained after the heat treatment step are subjected to a reduction treatment step, Cs ０．３３ WO ３The heat treatment conditions were selected so that composite tungsten oxide particles with a confirmed phase were produced and so that the respective absorption curves in the molar absorption coefficient curve of the dispersion or the like had the desired relationship. Specifically, the heat treatment conditions were selected based on the results of tests conducted in advance. In the heat treatment step, the raw material was heat-treated at a temperature of 550°C or higher.

[0289] The composite tungsten oxide particles obtained in the heat treatment step were introduced into reaction tube 13. Cooling water piping 131 was arranged around reaction tube 13, and cooling water was circulated through it. The composite tungsten oxide particles introduced into reaction tube 13 were collected by filter 14, which was a bag filter.

[0290] The composite tungsten oxide particles obtained after the heat treatment step were evaluated for their XRD patterns.

[0291] Figure 8 shows the XRD pattern of the obtained composite tungsten oxide particles. In Figure 8, the XRD pattern (A) shown as "As produced" is the XRD pattern of the composite tungsten oxide particles after the heat treatment step. Hexagonal Cs ０．３３ WO ３ (ICDD: 81-1245) or orthorhombic Cs ４ W １１ O ３５ (ICDD: 51-1891) and a small amount of cubic pyrochlore (Cs ２ O) ０．４４ W ２ O ６ (ICDD: 47-0566) phase. The minor crystalline phase was identified using Rietveld analysis.

[0292] Further, reduction treatment was carried out using the reduction treatment device 20 shown in FIG.

[0293] As shown in FIG. ２ In a gas flow of 97% by volume of Ar, a heater 22 was provided around the reaction tube 21, and the temperature was raised from room temperature to 500°C. After the part where the container 23 was placed reached the reduction treatment temperature, the part was maintained at that temperature for 2 hours, and then cooled to room temperature to perform reduction treatment (reduction treatment step). In this way, reduced particles, which are composite tungsten oxide particles according to Example 1, were obtained.

[0294] FIG. 7A shows a TEM image of the composite tungsten oxide particles after the heat treatment step, and FIG. 7B shows the particle size distribution.

[0295] FIG. 7C shows a TEM image of the composite tungsten oxide particles after the reduction treatment step, and FIG. 7D shows the particle size distribution.

[0296] The particle size distribution of the composite tungsten oxide particles was calculated by observing them in three fields of view using a transmission electron microscope. Specifically, images of a total of 600 to 700 composite tungsten oxide particles were observed in the three fields of view, and the area of ​​each particle was calculated from the binarized data, and the equivalent circle diameter of each particle was calculated.

[0297] Figure 8 shows the XRD pattern of the obtained composite tungsten oxide particles. In Figure 8, the XRD pattern (B) shown as "Heat treated" is the XRD pattern of the composite tungsten oxide particles after the reduction treatment step. The obtained XRD pattern shows that Cs ０．３３ WO ３ The diffraction peaks included only the peaks of , , and it was confirmed that the crystal system was hexagonal.

[0298] The composite tungsten oxide particles after the reduction treatment step according to Example 1 were subjected to the composition analysis described above, and the Cs / W ratio, which is the ratio of the amounts of cesium and tungsten, was determined. As a result, it was confirmed that the Cs / W ratio decreased from 0.37 in the starting composition to 0.34. However, the value of 0.34 is 0.01 higher than the theoretical composition ratio of 0.33, and since the XRD pattern shows a single phase, it is believed that there is almost no Cs deficiency.

[0299] Furthermore, when the composition of the composite tungsten oxide particles was analyzed, it was confirmed that the O / W ratio, which is the ratio of the amounts of oxygen and tungsten, was 2.841. In the following description, the composite tungsten oxide particles were evaluated using XRD patterns and Cs ０．３３ WO ３ It is written as follows.

[0300] 23% by mass of the composite tungsten oxide particles after the reduction treatment step according to Example 1, 8% by mass of an acrylic polymer dispersant (amine value 48 mg KOH / g) having an amine-containing functional group (hereinafter referred to as "dispersant a"), and 69% by mass of butyl acetate were weighed out. The weighed materials were placed in a paint shaker together with zirconia beads having a diameter of 0.05 mm, and a dispersion treatment was carried out for 100 minutes using the paint shaker to obtain the near-infrared absorbing particle dispersion liquid according to Example 1, Cs ０．３３ WO ３ A particle dispersion was obtained.

[0301] The average particle size of the composite tungsten oxide particles in the dispersion liquid of Example 1 obtained was measured (measured by a transmission electron microscope) and was found to be 27.2 nm.

[0302] The average particle size of the composite tungsten oxide particles was calculated by observing them in three fields of view using a transmission electron microscope.Specifically, the images of a total of 600 to 700 composite tungsten oxide particles were observed in three fields of view, and the area of ​​each particle was calculated from the binarized data, and the equivalent circle diameter of each particle was calculated.Then, the particle sizes of all the composite tungsten oxide particles evaluated, that is, the arithmetic mean value of the equivalent circle diameters, was taken as the average particle size.

[0303] Cs according to Example 1 ０．３３ WO ３ The particle dispersion liquid was separated, and the solvent was removed to obtain Cs ０．３３ WO ３ particles were obtained.

[0304] The transmitted light profile was measured under the above-mentioned conditions as the optical properties of the near-infrared absorbing particle dispersion liquid according to Example 1. The results of the transmitted light profile are shown in FIG.

[0305] A molar absorption coefficient curve was obtained from the absorption curve obtained when measuring the transmitted light profile of the near-infrared absorbing particle dispersion liquid according to Example 1. Then, as described above, the molar absorption coefficient curve was separated into absorption curves of three absorption components: an absorption curve of localized surface plasmon resonance (LSPR⊥) in a direction perpendicular to the c-axis, an absorption curve of localized surface plasmon resonance (LSPR / / ) in a direction parallel to the c-axis, and an absorption curve of polaron absorption. The results are shown in FIG. 10A. In FIG. 10A, "exp." is the actual measured value, and "calc" is the sum of the absorption curves of the three absorption components.

[0306] In FIG. 10A, "σ LSPR⊥c" means the absorption curve of localized surface plasmon resonance (LSPR⊥) in the direction perpendicular to the c-axis. In FIG. 10A, "σ LSPR / / c" means the absorption curve of localized surface plasmon resonance (LSPR⊥) in the direction parallel to the c-axis. In FIG. 10A, "σ polaron" means the absorption curve of polaron absorption. The same notation is used in FIG. 10B, which shows the evaluation results of Comparative Example 1. [Comparative Example 1] Cs was added to 0.330 kg of water. ２ CO ３ 0.216 kg was dissolved in H ２ WO ４ The mixture was added to 1.000 kg of the mixture, thoroughly stirred, and then dried to obtain a dried product.

[0307] Next, N ２ 5% H by volume with gas as carrier ２ The dried product was placed in an electric furnace and heated while gas was being supplied, and calcined at a temperature of 800°C for 1 hour. After that, the supply gas was changed to N ２ The gas was switched to only the gas, and the temperature was lowered to room temperature, whereby a coarse composite tungsten oxide powder according to Comparative Example 1 was obtained.

[0308] The obtained coarse composite tungsten oxide powder (23 mass%), dispersant a (8 mass%), and butyl acetate (69 mass%) were weighed out. The weighed materials were placed in a paint shaker together with zirconia beads having a diameter of 0.3 mm, and a dispersion treatment was carried out using the paint shaker for 15 hours to obtain a near-infrared absorbing particle dispersion liquid according to Comparative Example 1.

[0309] The average particle size of the composite tungsten oxide particles in the dispersion liquid according to Comparative Example 1 obtained (measured by a transmission electron microscope) was 25.1 nm. The average particle size was measured and calculated using the same procedures and conditions as in Example 1. The dispersion liquid according to Comparative Example 1 was also sampled, and the solvent was removed to obtain the composite tungsten oxide particles according to Comparative Example 1, Cs ０．３３ WO ３ particles were obtained.

[0310] The transmitted light profile was measured under the above-mentioned conditions as the optical properties of the near-infrared absorbing particle dispersion liquid according to Comparative Example 1. The results of the transmitted light profile are shown in FIG.

[0311] A molar absorption coefficient curve was obtained from the absorption curve obtained when measuring the transmitted light profile of the near-infrared absorbing particle dispersion liquid according to Comparative Example 1. Then, as described above, the molar absorption coefficient curve was separated into absorption curves of three absorption components: an absorption curve of localized surface plasmon resonance (LSPR⊥) in an orientation perpendicular to the c-axis, an absorption curve of localized surface plasmon resonance (LSPR / / ) in an orientation parallel to the c-axis, and an absorption curve of polaron absorption. The results are shown in FIG. 10B .

[0312] In the near infrared absorbing particle dispersion liquid of Example 1 shown in FIG. 9A , it was confirmed that even if the peak of the transmittance in the wavelength region of 500 nm to 600 nm was set to 75% or more, the bottom of the transmittance in the near infrared region could be set to 5% or less.

[0313] In contrast, in the near-infrared absorbing particle dispersion liquid of Comparative Example 1 shown in FIG. 9B , when the peak of the transmittance in the wavelength region of 500 nm to 600 nm was set to 75% or more, the bottom of the transmittance in the near-infrared region could not be set to 5% or less, and it was confirmed that the near-infrared shielding effect was inferior.

[0314] Furthermore, it was confirmed from Table 1 that the transmittance at a wavelength of 700 nm of the near-infrared absorbing particle dispersion of Example 1 was higher than the transmittance of the near-infrared absorbing particle dispersion composed of conventional composite tungsten oxide particles of Comparative Example 1. In other words, the near-infrared absorbing particle dispersion of Example 1 also transmits light on the long wavelength side of the visible light region (wavelengths of 380 nm or more and 780 nm or less). This shows that the composite tungsten oxide of Example 1 also transmits red light with a wavelength of around 800 nm, and therefore also contributes to improving the color tone of the composite tungsten oxide particles.

[0315] Table 2 shows the peak positions, peak intensities, and integrated intensities of the absorption curves of the three absorbing elements according to Example 1 and Comparative Example 1. Furthermore, Table 3 shows the ratios of the integrated intensities of the absorption curves of the three absorbing elements to the integrated intensity of the molar extinction coefficient curve.

[0316]

[0317] As shown in FIG. 10A and Table 2, it can be confirmed that the intensity of the absorption peak in the absorption curve of polaron absorption is lower than the intensity (peak value) of the absorption peak in the absorption curve of localized surface plasmon resonance (LSPR / / ) in the direction parallel to the c-axis of the composite tungsten oxide particle according to Example 1.

[0318] Furthermore, as shown in Table 3, the integrated intensity of the absorption curve of polaron absorption relative to the integrated intensity of the molar absorption coefficient curve of the composite tungsten oxide particle according to Example 1 was 8.7%, and the integrated intensity of the absorption curve of localized surface plasmon resonance (LSPR / / ) in the direction parallel to the c-axis was 23.4%. Such light absorption characteristics are reflected in the optical profile in FIG. 9A and the transmittance in Table 1.

[0319] This application claims priority based on Japanese Patent Application No. 2023-170833, filed with the Japan Patent Office on September 29, 2023, the entire contents of which are incorporated herein by reference.

[0320] DESCRIPTION OF SYMBOLS 10 Composite material manufacturing apparatus 11 Storage section 12 Two-fluid nozzle 13 Reaction tube 131 Piping 14 Filter 15 Ejector 20 Reduction treatment device 21 Reaction tube 21A First end 21B Second end 22 Heater 23 Container 24 Composite tungsten oxide particles 30 Near-infrared absorbing particle dispersion 31 Near-infrared absorbing particles 32 Liquid medium 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 Transparent substrate 522 Transparent substrate 60 Near-infrared absorbing transparent substrate 61 Transparent substrate 61A One surface 62 Near-infrared absorbing layer

Claims

1. Composite tungsten oxide particles containing a composite tungsten oxide, the composite tungsten oxide being represented by the general formula M ｘ W ｙ O ｚ (wherein M element is one or more elements selected from alkali metal elements, alkaline earth metal elements, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; O is oxygen; 0.20≦x / y≦0.37, 2.2≦z / y≦3.3), the crystal system is hexagonal, Composite tungsten oxide particles, in which, in a molar absorption coefficient curve in the range of 0.5 eV to 2.0 eV of a dispersion obtained by dispersing the composite tungsten oxide particles in a liquid medium or a dispersion obtained by dispersing the composite tungsten oxide particles in a solid medium, the peak value of the absorption curve of polaron absorption is lower than the peak value of the absorption curve of localized surface plasmon absorption in an orientation parallel to the c-axis of the composite tungsten oxide crystal contained in the composite tungsten oxide particles.

2. The composite tungsten oxide particles according to claim 1, wherein the integrated intensity of the polaron absorption of the composite tungsten oxide crystal contained in the composite tungsten oxide particles is 20% or less relative to the integrated intensity of the molar absorption coefficient curve.

3. The composite tungsten oxide particle according to claim 1, wherein the integrated intensity of localized surface plasmon absorption in an orientation parallel to the c-axis of the composite tungsten oxide crystal contained in the composite tungsten oxide particle is 10% or more and 30% or less of the integrated intensity of the molar absorption coefficient curve.

4. Composite tungsten oxide particles according to any one of claims 1 to 3, wherein the M element includes one or more elements selected from the group consisting of Rb and Cs.

5. Composite tungsten oxide particles according to any one of claims 1 to 3, having an average particle size of 10 nm or more and 200 nm or less.

6. A near-infrared absorbing particle dispersion liquid comprising near-infrared absorbing particles and a liquid medium, wherein the near-infrared absorbing particles are the composite tungsten oxide particles according to any one of claims 1 to 3.

7. A near infrared absorbing particle dispersion comprising near infrared absorbing particles and a solid medium, wherein the near infrared absorbing particles are the composite tungsten oxide particles according to any one of claims 1 to 3.

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