Near-infrared absorbing particles, method for producing near-infrared absorbing particles, near-infrared absorbing particle dispersion, near-infrared absorbing laminate, and near-infrared absorbing transparent substrate

Abstract

Provided are near-infrared absorbing particles containing cesium tungstate, wherein: the cesium tungstate has the crystal structure of a pseudohexagonal crystal converted to at least one selected from an orthorhombic crystal, a rhombohedral crystal, and a cubic crystal; and the cesium tungstate is represented by general formula CsxWyOz and has a composition within the region surrounded by the four straight lines of x=0.6y, z=2.5y, y=5x, and Cs2O:WO3=m:n (where m and n are integers) in a three-dimensional composition diagram with Cs, W, and O as vertices.

Description

[Technical Field]

[0001] The present invention relates to near-infrared absorbing particles, a method for producing near-infrared absorbing particles, a near-infrared absorbing particle dispersion, a near-infrared absorbing laminate, and a near-infrared absorbing transparent substrate. [Background technology]

[0002] According to the 5th edition of the Physics and Chemistry Dictionary, "Electromagnetic waves with wavelengths in the range of approximately 1 nm to 1 mm are called light." This wavelength range includes the visible light and infrared regions.

[0003] Near-infrared rays contained in sunlight penetrate window materials and enter indoor spaces, raising the surface temperatures of the walls and floors, and thus the indoor air temperature. To maintain a comfortable indoor thermal environment, conventional methods have been to use shading materials in window materials and the like to block the near-infrared rays that enter through windows, thereby preventing the indoor air temperature from rising.

[0004] Patent Document 1 proposes a light-shielding film containing black fine powder including inorganic pigments such as carbon black and titanium black, and organic pigments such as aniline black, as a light-shielding material used in window materials and the like.

[0005] Patent Document 2 discloses a thermal insulation sheet made of a woven fabric in which a strip-shaped film having infrared reflectivity and a strip-shaped film having infrared absorbency are used as warp and weft, respectively. It also describes that the strip-shaped film having infrared reflectivity is made by depositing aluminum on a synthetic resin film and laminating another synthetic resin film on top of it.

[0006] The present applicant has proposed in Patent Document 3 an infrared-shielding material microparticle dispersion in which infrared material microparticles are dispersed in a medium, the infrared material microparticles containing tungsten oxide microparticles and / or composite tungsten oxide microparticles, and the infrared material microparticles having a particle diameter of 1 nm or more and 800 nm or less. [Prior art documents] [Chartered documents]

[0007]

Patent Document 1

Patent document 2

Patent document 3

Non-licensed literature

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

[0009] The above-mentioned Patent Document 3 discloses tungsten oxide particles and / or composite tungsten oxide particles as infrared-shielding material particles. A transparent film in which these tungsten oxides are dispersed is colored blue, and the blue color becomes stronger as the amount added increases.

[0010] However, in recent years, for applications such as automotive glass and photothermal conversion materials, there has been a demand for a neutral color that does not have blue or other coloring in the transmitted light while increasing the near-infrared absorptance, i.e., decreasing the solar transmittance.

[0011] If a blue material such as the tungsten oxide-dispersed transparent film is used as the base material, the hues that can be obtained when adjusting the color of the glass with various pigments or dyes are limited, and it is particularly difficult to achieve a complementary yellow color.

[0012] Furthermore, in applications such as photothermal conversion materials, specifically in applications such as adhesion of transparent resin members by photothermal conversion, pure white color development is required, but it is difficult to achieve pure white color development with materials such as the above-mentioned tungsten oxides.

[0013] On the other hand, for example, if a transmission film in which a composite tungsten oxide is dispersed can have a neutral transmission color, i.e., a transparent color tone, its applications can be expanded. However, no composite tungsten oxide that can achieve a neutral color while reducing solar transmittance when used as a dispersion has been reported.

[0014] Additionally, various sensors are being used in automobiles, which are an important industrial application. These include rain sensors that detect rain, light sensors that detect sunset, and speed cameras that detect traffic records in traffic networks. For this reason, automobile windows are required to be transparent to near-infrared light in a specific wavelength range in order to transmit sensor information.

[0015] The infrared rays detected by the above sensors are near-infrared rays with wavelengths close to red, around 800nm ​​to 900nm. For automobile windows, transparency is required, which contradicts the solar radiation blocking function of blocking near-infrared rays with wavelengths adjacent to these.

[0016] However, conventionally known shielding films made of precious metal particles and compound particles such as LaB6 have very low transmittance for the infrared light they detect, because their absorption wavelengths fall within the visible light range. Furthermore, near-infrared absorbing particles such as ATO and ITO have a problem in that even if they satisfy the transmittance of the sensor wavelength, their solar radiation shielding function is too low because their near-infrared absorption wavelengths are too long.

[0017] Therefore, one aspect of the present invention aims to provide novel near-infrared absorbing particles that have a more neutral color tone of transmitted light while suppressing solar radiation transmittance and that can also ensure transmittance at the sensor wavelength. [Means for solving the problem]

[0018] In one aspect of the present invention, there is provided a near-infrared absorbing particle comprising cesium tungstate, The cesium tungstate has a pseudo-hexagonal crystal structure that is modulated into one or more crystal structures selected from orthorhombic, rhombohedral, and cubic crystal structures; The cesium tungstate has the general formula Cs x W y O z In a ternary composition diagram represented by the formula (1), with Cs, W, and O at the vertices, the near-infrared absorbing particles have a composition within the region surrounded by the four straight lines x=0.6y, z=2.5y, y=5x, and CsO:WO=m:n (m and n are integers). [Effects of the Invention]

[0019] In one aspect of the present invention, it is possible to provide novel near-infrared absorbing particles that have a more neutral color tone of transmitted light while suppressing solar radiation transmittance and that can also ensure transmittance at sensor wavelengths. [Brief explanation of the drawings]

[0020] [Figure 1A] Figure 1A is a Cs-WO composition diagram with Cs, W, and O at the vertices. [Figure 1B] Figure 1B is an enlarged view of a portion of the Cs-WO composition diagram with Cs, W, and O at the vertices. [Figure 2] FIG. 2 shows powder XRD diffraction patterns of the near infrared absorbing particles produced in Examples 1 to 7 and Comparative Examples 1 and 3. [Figure 3] FIG. 3 shows powder XRD diffraction patterns of the near infrared absorbing particles produced in Examples 10 to 15. [Figure 4]FIG. 4 shows a transmission electron microscope bright-field image, a selected area electron diffraction image, and a high angle electron dark-field (HAADF) image of the near-infrared absorbing particles produced in Example 1. [Figure 5] FIG. 5 shows the spectral transmittance profiles of the near-infrared absorbing films produced in Examples 1 to 4 and Comparative Examples 1 to 3. [Figure 6] FIG. 6 shows the spectral transmittance profiles of the near-infrared absorbing films produced in Examples 5 to 7, 11, 13, and 14 and Comparative Examples 1 to 3. [Figure 7] FIG. 7 is a plot of the Hunter color index b* value versus the a* value for the near-infrared absorbing particle dispersions prepared in Examples 1 to 15 and Comparative Examples 1 to 8. [Figure 8] FIG. 8 is a plot of the transmittance at a wavelength of 900 nm (T900) versus the solar transmittance (ST21) of the near infrared absorbing particle dispersions produced in Examples 1 to 11, 13, and 14 and Comparative Examples 2 to 5. [Figure 9A] FIG. 9A is a graph showing the moist heat resistance of the near infrared absorbing film produced in Example 7. [Figure 9B] FIG. 9B is a diagram showing the moist heat resistance of the near infrared absorbing film produced in Comparative Example 3. [Figure 10] FIG. 10 is a schematic diagram of a near-infrared absorbing particle when it has a coating. [Figure 11] FIG. 11 is a schematic diagram of a near-infrared absorbing particle dispersion liquid. [Figure 12] FIG. 12 is a schematic diagram of a near-infrared absorbing particle dispersion. [Figure 13] FIG. 13 is a schematic diagram of a near-infrared absorbing laminate. [Figure 14] FIG. 14 is a schematic diagram of a near-infrared absorbing transparent substrate. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention. [Near-infrared absorbing particles] The near-infrared absorbing particles of the present embodiment are near-infrared absorbing particles containing cesium tungstate. Note that the near-infrared absorbing particles of the present embodiment may also be near-infrared absorbing particles made of cesium tungstate. However, even in this case, the inclusion of inevitable impurities is not excluded. (1) Cesium tungstate The cesium tungstate (cesium polytungstate) contained in the near-infrared absorbing particles of this embodiment may have a pseudo-hexagonal crystal structure modified to one or more types selected from orthorhombic, rhombohedral, and cubic crystals. Specifically, the cesium tungstate may have one or more types of crystal structure selected from orthorhombic, rhombohedral, and cubic crystals modified from a pseudo-hexagonal structure that is a partial modification of a hexagonal alkali tungsten bronze structure.

[0022] The transmission color and optical absorption of cesium-doped hexagonal tungsten bronze particles, which have been used as near-infrared absorbing particles, are determined by the imaginary part of the dielectric function (ε2) and the band structure. In the visible light energy range (1.6 eV to 3.3 eV), cesium-doped hexagonal tungsten bronze (hereinafter also referred to as Cs-HTB) has a sufficiently large band gap that light absorption in the visible light range is essentially suppressed. Additionally, tungsten dd-orbital transitions and oxygen pp-orbital transitions are forbidden by the Fermi golden rule, reducing the probability of electronic transitions. These two factors result in small values ​​of ε2 at wavelengths in the visible light range. Since ε2 represents the absorption of photons by electrons, a small ε2 at wavelengths in the visible light range results in visible light transmittance. However, it has recently been revealed that absorption due to band-edge transitions exists near the shortest wavelengths in the visible light range (blue), and that localized surface plasmon resonance (LSPR) absorption and polaronic electronic transition absorption exist near the longest wavelengths in the visible light range (Non-Patent Document 1). These factors limit light transmittance in each case.

[0023] As mentioned above, the band gap of Cs-HTB is large enough that the band edge transition exceeds the energy of blue wavelength light, resulting in blue transmittance. Conversely, at red wavelengths, Cs-HTB has a large number of conduction electrons, resulting in strong LSPR absorption and polaronic absorption, and the base of this absorption extends into the red wavelengths, resulting in low red transmittance. Therefore, the transmitted color of a Cs-HTB nanoparticle-dispersed film appears blue due to the balance between these two.

[0024] That is, to neutralize the blue transmission color of Cs-HTB, it is necessary to increase the absorption on the blue side and increase the transmission on the red side.

[0025] Strengthening the blue absorption of Cs-HTB can be achieved, for example, by shifting the absorption position of the band edge transition to lower energy. Shifting the absorption position of the band edge transition to lower energy corresponds to narrowing the band gap of Cs-HTB. Therefore, this can be achieved by selecting a material with a slightly smaller band gap.

[0026] The red absorption of Cs-HTB can be weakened by decreasing the concentration of surface plasmon resonance electrons or polaron-bound electrons.

[0027] Based on the above considerations, the inventors of the present invention have investigated various cesium tungsten oxides, which are oxides containing cesium (Cs) and tungsten (W), and have improved the material by using band structure calculations based on first-principles calculations. As a result, they have found that when the conventional hexagonal crystal structure is modified to an orthorhombic, rhombohedral, or cubic pseudo-hexagonal structure by changing the microstructure, the band structure changes and the amount of free and bound electrons changes, resulting in a change in color.

[0028] Here, a pseudo-hexagonal structure modulated to one or more of the orthorhombic, rhombohedral, and cubic crystals refers to a pseudo-hexagonal crystal in which Cs-rich planes are inserted regularly or randomly into the prism or basal planes of the hexagonal crystal. A Cs-rich plane is synonymous with a plane lacking W or O. Furthermore, as described below, O, OH, OH2, and OH3 ions can substitute for the Cs site, and the introduction of these ions into the prism or basal planes can promote the modulation of the pseudo-hexagonal crystal structure, just like Cs.

[0029] Orthorhombic, rhombohedral, and cubic crystal structures can be identified, for example, by electron diffraction, by noting the symmetry of the diffraction spots when the electron beam is incident along the c-axis, i.e., from the (0001) direction.

[0030] In a hexagonal crystal, the diffraction spots of the three types of prism planes, (10-10), (01-10), and (1-100), appear at the same distance from the incident spot within the reciprocal lattice plane. In other words, the hexagonal crystal has the same crystal plane spacing. Note that the above-mentioned "same distance" includes distances that can be considered to be the same within the error range of the electron diffraction spot distance measurement. For this reason, the hexagonal crystal produces an electron diffraction pattern that is hexagonally symmetric, i.e., invariant to a 60° rotation.

[0031] In the orthorhombic crystal, one type of prism surface spot appears closer to the incident spot than the other two types of prism surface spots, i.e., in the orthorhombic crystal, only one type of prism surface has a long crystal plane spacing.

[0032] In a rhombohedral crystal, the three types of prism surface spots have different crystal plane spacings.

[0033] Cubic crystals have the same hexagonal symmetry as hexagonal crystals, but the cubic symmetry can be easily identified by observing from other crystal zone axis directions.

[0034] In XRD powder patterns, pseudohexagonal crystals are often considered to be a mixed pattern of orthorhombic and hexagonal crystals, or a mixed pattern of rhombohedral and hexagonal crystals, or a mixed pattern of cubic and hexagonal crystals. However, due to the insertion of the planar lattice defects mentioned above, the positions and intensities of the diffraction peaks change slightly.

[0035] One method for obtaining a pseudo-hexagonal crystal structure modulated to one or more types selected from the above-mentioned orthorhombic, rhombohedral, and cubic crystals is to add one or more types of additive components selected from O, OH, OH2, and OH3. Therefore, the near infrared absorbing particles of the present embodiment preferably contain one or more types of additive components selected from O, OH, OH2, and OH3.

[0036] The one or more additive components selected from O, OH, OH2, and OH3 are preferably present at one or more positions selected from hexagonal windows and cavities present in hexagonal tunnels that penetrate the c-axis direction of a hexagon formed by six WO6 octahedra that constitute the hexagonal alkali tungsten bronze structure of a cesium tungstate crystal, and triangular cavities formed by three WO6 octahedra.

[0037] The hexagonal tunnel has two voids: the large hexagonal cavity and the hexagonal window. The hexagonal window is the second largest void in the hexagonal crystal after the hexagonal cavity and is surrounded by six oxygen atoms that make up the WO6 octahedron. The hexagonal window is adjacent to the Cs ions located in the hexagonal cavity above and below it in the c-axis direction. The trigonal cavity is the next largest void after the hexagonal window and penetrates the hexagonal crystal along the c-axis direction. One or more of O, OH, OH2, and OH3 can enter the hexagonal cavity by substituting for Cs, but they also invade the hexagonal window when there is a sufficient amount of Cs or when there is a large amount of invaded water. In some cases, they invade the trigonal cavity at the bottom or the cavities on the prism surface in parallel with the hexagonal window void, replacing Cs. The addition of the above-mentioned additives creates defects on the base and prism surfaces, which shifts the crystal structure from hexagonal to orthorhombic, rhombohedral, and then cubic, narrowing the band gap and reducing the conduction band electron density. As a result, cesium tungstate, which has a pseudo-hexagonal crystal structure, can enhance absorption on the blue side and transmission on the red side compared to Cs-HTB, neutralizing blue transmission colors.

[0038] In this case, the orthorhombic, rhombohedral, and cubic crystals can be considered pseudo-hexagonal crystals, which have atomic arrangements similar to those of hexagonal tungsten bronze, but have a different symmetry from hexagonal crystals. Roughly speaking, without being too strict, the orthorhombic crystals in this case are crystals in which hexagonal symmetry is broken by inserting, regularly or randomly, planes lacking W and O atoms into one of the three prism faces of a hexagonal crystal. Therefore, in an orthorhombic crystal, only one prism face has a longer interplanar spacing. Using this, modulation to an orthorhombic crystal can be easily identified, for example, by the (0001) electron diffraction pattern.

[0039] In this case, a rhombohedron is formed by inserting a plane that accepts excess Cs into the basal surface of a hexagonal crystal, i.e., a plane lacking W and O, and by systematically displacing the stacking of the basal surface in the c-axis direction, breaking the hexagonal symmetry. In this case, the excess Cs plane includes not only displacement on the plane but also expansion in the direction perpendicular to the plane, resulting in a change in the prism plane spacing and a change in the c-axis lattice constant. Therefore, in a rhombohedron, all three prism planes have different spacings. Utilizing this, modulation to a rhombohedron can be easily identified, for example, by the (0001) electron diffraction pattern.

[0040] Furthermore, when the three axes of the rhombohedron intersect at 90 degrees, it becomes a cubic crystal. This cubic crystal has a pyrochlore structure, and a typical composition is CsW2O6.

[0041] Therefore, voids corresponding to the above-mentioned hexagonal windows, hexagonal cavities, and trigonal cavities are also inherited by orthorhombic crystals, rhombohedral crystals, and cubic crystals. Therefore, the hexagonal windows, hexagonal cavities, and trigonal cavities in the cesium tungstate contained in the near infrared absorbing particles of the present embodiment also refer to the corresponding voids in the orthorhombic crystals, rhombohedral crystals, and cubic crystals (pyrochlore phase).

[0042] Hereinafter, a structural example of the method for producing near-infrared absorbing particles of this embodiment will be described, mainly taking as an example the case of a hexagonal window as a site or gap where O, OH, OH2, and OH3 can be substituted or penetrated.

[0043] One method for obtaining orthorhombic, rhombohedral, or cubic crystals in which one or more species selected from O, OH, OH2, and OH3 are present in the hexagonal window is to crystallize the cesium tungstate in saturated water vapor during crystallization during synthesis. Generally, in a Cs-HTB structure, the ionic radius of Cs is slightly larger than the hexagonal cavity, making it difficult for Cs to move. Therefore, once crystallized into a hexagonal crystal, it becomes difficult to diffuse and insert oxygen atoms or the like into the hexagonal window through subsequent heat treatment or the like. Therefore, we devised a method in which the atmosphere is filled with saturated water vapor before the cesium tungstate crystallizes, and water molecules and O, OH, and OH3 ions derived from the water molecules are inserted into the hexagonal window simultaneously with the crystallization of the cesium tungstate. Therefore, as described below, the method for producing near-infrared absorbing particles of this embodiment preferably includes a step of introducing water vapor at a heating temperature close to the crystallization temperature of the cesium tungstate and crystallizing the cesium tungstate in an atmosphere containing water vapor. When a dispersion film, which is a near-infrared absorbing particle dispersion, is produced using the near-infrared absorbing particles synthesized through the above steps, or near-infrared absorbing particles that have been further heat-treated in a reducing atmosphere as necessary, the film has high visible light transmittance and can reduce the bluish color tone while sufficiently maintaining the near-infrared shielding effect, i.e., can neutralize the blue-based transmitted color.

[0044] On the other hand, once hexagonal cesium tungstate crystals are produced, heating the cesium tungstate in a water vapor atmosphere or maintaining and heating it in a high-temperature, high-humidity environment does not neutralize the transmitted color. This is because elements with a large ionic radius, such as Cs, inhibit the diffusion of oxygen atoms and other atoms through hexagonal tunnels, so once the crystals are crystallized into hexagonal crystals, subsequent heat treatments make it difficult for oxygen atoms and other atoms to diffuse into the hexagonal windows of the voids. Therefore, the heat treatment in water vapor must be performed during the initial crystallization process.

[0045] When heating in an atmosphere containing water vapor during crystallization, it is also possible to simultaneously mix in a reducing gas such as hydrogen gas and crystallize in a reducing gas atmosphere. Furthermore, if the crystals are once crystallized in a water vapor atmosphere, they can be further heated at a high temperature of 500°C to 950°C in an atmosphere containing a reducing gas such as hydrogen gas, or in an inert gas atmosphere. In either case, near-infrared absorbing particles with a neutralized transmitted color and a high near-infrared absorption effect can be obtained. By heating at 500°C or higher, the arrangement of equilibrium atomic positions, such as an orthorhombic crystal structure containing defects, is sufficiently promoted, thereby enhancing the near-infrared absorption effect. Furthermore, by heating at 950°C or lower, the speed of crystal structure change can be maintained at an appropriate level, allowing for easy control of the appropriate crystalline state and electronic state. Note that heating at temperatures higher than 950°C, for example, excessive reduction, may result in the production of lower oxides such as W metal and WO2, which is undesirable from this perspective.

[0046] During the initial crystallization by heating with water vapor, the incorporation of O, OH, OH2, and OH3 results in the formation of one or more crystal types selected from orthorhombic, rhombohedral, and cubic (pyrochlore phase) crystals, which are microscopically modified from hexagonal crystals. By heating these in atmospheres with different degrees of reduction, one or more crystal structures selected from various orthorhombic, rhombohedral, and cubic crystals with different amounts and distributions of lattice defects are generated.

[0047] The cesium tungstate contained in the near infrared absorbing particles of the present embodiment may have lattice defects of Cs, W, or O. The reason why lattice defects of Cs, W, or O are introduced into the cesium tungstate will be described below.

[0048] Hexagonal Cs 0.33 At compositions around WO3, crystal stability is determined by the balance between structural stability due to high crystal symmetry and charge balance stability, where charge transfer between elements produces overall charge neutrality. For example, the charge-neutral 2Cs2O·11WO3=Cs4W 11 O 35is considered to be a thermodynamically stable phase, but when heated in a reducing atmosphere, it easily transforms into a hexagonal Cs with high crystal symmetry. 0.32 WO 3-y (Non-Patent Document 2) 0.32 WO 3-y is a metastable structure with high crystal symmetry, while Cs4W 11 O 35 is a stable composition in terms of charge balance. 11 O 35 has poor symmetry in the atomic arrangement within the crystal. For example, in the model by Solodovnikov (Non-Patent Document 3), in the hexagonal arrangement of WO6 octahedra, the same as in hexagonal tungsten bronze, planes with missing W and O atoms are inserted at a b / 8 pitch in the hexagonal (1,1,-2,0) plane (= orthorhombic (010) plane) of the orthorhombic unit cell, resulting in an orthorhombic crystal as a whole. In other words, the Cs, W, and O defects were inevitably introduced to locally satisfy both the crystal structure and charge balance, and have actually been observed recently using TEM and XRD (Non-Patent Document 4).

[0049] In the near-infrared absorbing particles of this embodiment, in the orthorhombic, rhombohedral, or cubic crystals in which O, OH, OH2, or OH3 is incorporated into the hexagonal windows, hexagonal cavities, or trigonal cavities, the local charge balance is disturbed, and the crystal microstructure is further modified. + and H3O + are introduced into the crystal, but these ions are Cs + and W 6+ In order to compete with the OH atoms, local charge neutrality is achieved by the vacancies of Cs and W. As a result, lattice defects including vacancies of Cs and W are introduced. O, OH, OH2, and OH3 may invade not only the hexagonal windows but also the trigonal cavities. Furthermore, OH2 and OH3 may substitute for the alkali element (Cs) in the hexagonal cavity, and when the charge-neutral OH2 is substituted, the alkali ion (Cs) that was originally present may be vacant. + ) no longer emits electrons, so the conduction band electrons in the crystal decrease.

[0050] Among the cesium tungstates having a pseudo-hexagonal crystal structure modulated to one or more types selected from orthorhombic, rhombohedral, and cubic crystals, those that satisfy excellent near-infrared absorption effects and visible light transmittance have a predetermined composition.

[0051] Figure 1A shows a ternary composition diagram 10 with Cs-WO as the three vertices. Figure 1B shows an enlarged view of the region 11 in the ternary composition diagram 10 of Figure 1A, with CsWO3, W2O3, and WO4 as the vertices. It should be noted that this diagram is not a phase diagram showing the thermodynamic equilibrium phases, but rather a convenient composition diagram showing the range of compositions in this system. Therefore, CsWO3, W2O3, WO4, etc. are compositions shown for convenience, and it does not refer to whether these are actually obtained compounds.

[0052] The cesium tungstate contained in the near infrared absorbing particles of the present embodiment is represented by the general formula Cs x W y O z In a ternary composition diagram represented by the formula (1), with Cs, W, and O at the vertices, it is preferable that the composition be within the region surrounded by the four lines x=0.6y, z=2.5y, y=5x, and Cs2O:WO3=m:n (m and n are integers). Specifically, in the ternary composition diagram shown in Figures 1A and 1B, it is preferable that the composition be within region 16 surrounded by line 12 satisfying x=0.6y, line 13 satisfying z=2.5y, line 14 satisfying y=5x, and line 15 satisfying Cs2O:WO3=m:n (m and n are integers). Note that region 16 also includes points on lines 12 to 15. Moreover, a line 15 that satisfies Cs2O:WO3=m:n (m and n are integers) is a line that connects Cs2O and WO3 in the ternary composition diagram 10, as shown in FIG. 1A.

[0053] In the above ternary composition diagram, when x > 0.6y, cesium tungstate has a predominantly tetragonal crystal structure, resulting in the loss of near-infrared absorption. Furthermore, when z < 2.5y, cesium tungstate has a hexagonal structure with lower W oxides mixed in, significantly impairing its near-infrared absorption and visible light transmittance. When y > 5x, cesium tungstate has a crystal structure called intergrowth, in which WO3 is mixed into the hexagonal substructure, resulting in the loss of near-infrared absorption. Furthermore, if the Cs2O:WO3 ratio falls to the O-rich side (to the right of line 15, where the Cs2O:WO3 ratio is an integer), no near-infrared absorption effect is obtained. Therefore, it is preferable for cesium tungstate to satisfy the aforementioned range.

[0054] The cesium tungstate contained in the near-infrared absorbing particles of this embodiment may have defects in each of the elements cesium, tungsten, and oxygen, but the atomic ratio (x / y) of cesium to tungsten may be in the range of 0.2 or more and 0.6 or less. That is, the near-infrared absorbing particles of this embodiment have defects in part of one or more elements selected from Cs and W that constitute the crystal of the cesium tungstate, and are represented by the general formula Cs x W y O z It is preferable that x and y satisfy the relationship 0.2≦x / y≦0.6.

[0055] Cesium and tungsten supply electrons to the crystal, so by setting x / y to 0.2 or more, near-infrared absorption function can be improved. Furthermore, by setting x / y to 0.2 or more, it is possible to create a hexagonal crystal structure or a crystal structure in which the hexagonal crystal is modulated. When x / y exceeds 0.33, Cs ions cannot fit into the hexagonal cavity and begin to occupy the trigonal cavity as well, causing modulations on the prism faces and bases, gradually changing locally into a layered structure of orthorhombic, rhombohedral, or cubic pyrochlore. Furthermore, when x / y exceeds 0.6, the tetragonal Cs2W3O 10 The crystal structure changes to the above, which significantly impairs the visible light transmittance and reduces the usefulness.

[0056] The near-infrared absorbing particles of this embodiment have a hexagonal cesium tungsten bronze structure Cs 0.33 Using WO3 as a base, the WO6 octahedra that make up the crystal can have defects in at least some of the W. These W defects are introduced as planar defects mainly on the hexagonal prism faces or bases, but because the ionic repulsion of the atomic rows on both sides of the defect plane increases the interplanar spacing, the crystal symmetry changes from hexagonal to orthorhombic, rhombohedral, or cubic.

[0057] The near-infrared absorbing particles of this embodiment can have vacancies in at least some of the O atoms in the WO octahedra that make up the cesium tungstate crystal, based on the hexagonal alkali tungsten bronze structure CsW3O9. These O vacancies are introduced randomly, and the vacancies can supply localized electrons to the system, enhancing the near-infrared absorbing function. The known hexagonal tungsten bronze Cs 0.32 WO 3-y In the near-infrared absorbing particles of this embodiment, it is known that the vacancy rate is y=0.46 or up to 15% of all the lattice points of O constituting the octahedron (Non-Patent Document 3). When the vacancy rate exceeds 0.5, the crystal becomes unstable, a different phase is generated, and decomposition occurs. The cesium tungstate Cs contained in the near-infrared absorbing particles of this embodiment x W y O z In this case, it is possible to include an O vacancy amount equivalent to a maximum z / y = 2.5. However, when excess O, OH, OH2, or OH3 is introduced into voids such as hexagonal windows, it is important to note that the identified O value obtained by chemical analysis includes these excess amounts.

[0058] In the cesium tungstate contained in the near infrared absorbing particle of the present embodiment, a part of Cs may be substituted with an additional element. In this case, the additional element is preferably one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0059] These added elements have electron donating properties and assist in donating electrons to the conduction band of the WO octahedral framework at the Cs site. (2) Moisture and heat resistance of near-infrared absorbing particles The near-infrared absorbing particles of this embodiment exhibit improved moist heat resistance compared to cesium-doped hexagonal tungsten bronze. This effect is reasonable considering that a portion of the near-infrared absorbing particles of this embodiment contains one or more types of crystals selected from orthorhombic, rhombohedral, and cubic (pyrochlore) phases modulated by interstitial substitution with O, OH, OH2, and OH3. In other words, humidity and moisture degradation of cesium-doped hexagonal tungsten bronze is essentially a substitution reaction between Cs and water molecules. However, when the cavities and windows of the hexagonal tunnels, which are the main oxygen diffusion pathways, are filled with Cs, O, OH, OH2, and OH3, this substitution reaction is significantly slowed down. Therefore, the near-infrared absorbing particles of this embodiment not only suppress the loss of near-infrared absorbing function in high-humidity environments, but also slow down atmospheric moisture-mediated degradation reactions in high-temperature heat resistance tests at normal humidity, thereby improving moist heat resistance. (3) Average particle size of near-infrared absorbing particles The average particle size of the near-infrared absorbing particles of this embodiment is not particularly limited, but is preferably 0.1 nm or more and 200 nm or less. This is because, by setting the average particle size of the near-infrared absorbing particles to 200 nm or less, localized surface plasmon resonance is more pronounced, thereby particularly enhancing the near-infrared absorption characteristics, i.e., particularly suppressing the solar transmittance. Furthermore, by setting the average particle size of the near-infrared absorbing particles to 0.1 nm or more, industrial production is easy. Furthermore, the particle size is closely related to the color of the dispersion transmission film, i.e., the near-infrared absorbing particle dispersion. In the particle size range where Mie scattering is dominant, the smaller the particle size, the less scattering of short wavelengths in the visible light region. Therefore, increasing the particle size has the effect of suppressing the blue hue, but if the particle size exceeds 100 nm, the film haze due to light scattering becomes significant, and if it exceeds 200 nm, in addition to increasing the film haze, the generation of surface plasmons is suppressed, resulting in excessively small LSPR absorption.

[0060] Here, the average particle size of the near-infrared absorbing particles can be known from the median size of a plurality of near-infrared absorbing particles measured from a transmission electron microscope image, or the dispersed particle size measured with a particle size measuring device based on a dynamic light scattering method of a dispersion liquid.

[0061] In addition, when the film is applied to an application where transparency in the visible light region is particularly important, such as an automobile windshield, it is preferable to further consider reducing scattering by near-infrared absorbing particles. When the reduction in scattering is important, it is particularly preferable that the average particle size of the near-infrared absorbing particles is 30 nm or less.

[0062] The average particle size refers to the particle size at 50% of the cumulative value in the particle size distribution, and the same meaning applies to the average particle size in other parts of this specification. A method for measuring particle size distribution to calculate the average particle size can be, for example, direct measurement of the particle size of each particle using a transmission electron microscope. The average particle size can also be measured using a particle size measuring device based on the dynamic light scattering method of the dispersion liquid, as described above. (4) Optional configuration of near-infrared absorbing particles The near-infrared absorbing particles may be subjected to a surface treatment for purposes such as surface protection, improved durability, oxidation prevention, and improved water resistance. The specific content of the surface treatment is not particularly limited, but for example, the surface of the near-infrared absorbing particles of this embodiment may be coated with a compound containing one or more atoms selected from Si, Ti, Zr, and Al. That is, the near-infrared absorbing particles may be coated with the above-mentioned compound. In this case, examples of the compound containing one or more atoms selected from Si, Ti, Zr, and Al include one or more selected from oxides, nitrides, carbides, and the like. Specifically, for example, as schematically shown in Fig. 10, a near-infrared absorbing particle 90 may have the coating 91 on its surface 90A. Note that Fig. 10 is a cross-sectional view taken along a plane passing through the center of a near-infrared absorbing particle 90 having the coating 91. Fig. 10 shows an example in which the coating 91 is uniformly disposed over the entire surface 90A of the near-infrared absorbing particle 90, but is not limited to this form, and the coating 91 may be disposed so as to cover part of the surface of the near-infrared absorbing particle 90, for example, may be scattered. Furthermore, the thickness of the coating 91 is not limited to being uniform, and may vary depending on the position. [Method of manufacturing near-infrared absorbing particles] Next, a configuration example of the method for producing near-infrared absorbing particles according to this embodiment will be described. Since the method for producing near-infrared absorbing particles according to this embodiment can produce the near-infrared absorbing particles described above, a part of the description will be omitted.

[0063] The method for producing near-infrared absorbing particles is not particularly limited, and any method can be used as long as it can produce near-infrared absorbing particles that satisfy the above-mentioned properties. Here, one configuration example of the method for producing near-infrared absorbing particles will be described. (1) First heat treatment process The method for producing near-infrared absorbing particles of the present embodiment can include, for example, the following steps.

[0064] A first heat treatment step in which a compound raw material containing Cs and W is heated at 400°C or higher and 650°C or lower in an atmosphere containing water vapor or an atmosphere containing water vapor and a reducing gas.

[0065] In the first heat treatment step, the cesium tungstate can be crystallized by heating at 400° C. or higher and 650° C. or lower.

[0066] However, in order to make cesium tungstate a pseudo-hexagonal crystal, it is preferable to have sufficient water vapor in the atmosphere when the cesium tungstate crystallizes, i.e., when the WO6 units form hexagonal crystals with Cs. During this crystallization process, Cs is mainly taken up into the hexagonal cavities, and water molecules or its decomposition product, OH3+ , O.H. - and O 2- is mainly taken up in the hexagonal windows. When the composition contains a relatively large amount of Cs or water molecules, Cs or water molecules are also taken up in the three-sided cavities.

[0067] The compound raw material containing Cs and W can be a mixture of a compound raw material containing Cs and a compound raw material containing W. The compound raw material containing Cs and W can be any material containing Cs and W, and for example, a mixture of Cs2CO3 and WO3 can be used.

[0068] However, the purpose of the crystallization process in the first heat treatment step is to incorporate water molecules, OH, O, etc. into the crystals during crystallization. Therefore, it is preferable not to use cesium tungsten oxides that already form a hexagonal crystal structure, such as crystal powders of nCs2O·mWO3 (n and m are integers, 3.6≦m / n≦9.0), as the compound raw material containing Cs and W. It is also preferable not to use cesium tungstates obtained by other methods, such as the sol-gel method or complex polymerization method, non-equilibrium cesium tungstates obtained by gas-phase synthesis, or powders obtained by thermal plasma or electron beam melting. In raw materials that already form a hexagonal crystal structure, Cs inhibits the diffusion of oxygen atoms, making it difficult for water molecules to be incorporated into the crystals. In other words, it is preferable not to use cesium tungstates with a hexagonal crystal structure as the compound raw material containing Cs and W.

[0069] The supply of water vapor during the crystallization process of the first heat treatment step is preferably achieved by, for example, supplying superheated water vapor into a heating furnace. Superheated water vapor is high-enthalpy water vapor obtained by further heating saturated water vapor vaporized at 100°C to a temperature above 100°C, and may be supplied together with a carrier gas. When the carrier gas is an inert gas, an atmosphere nearly free of oxygen is formed. Superheated water vapor may be supplied at 400°C or above, at which point crystallization becomes active, but it is preferable to supply it from a temperature sufficiently low before crystallization. A mixture of superheated water vapor and an inert gas, or a mixture of superheated water vapor, an inert gas, and a reducing gas such as hydrogen, may also be supplied. When a reducing gas is mixed, the rate of hexagonal crystal arrangement tends to increase, and even if the same orthorhombic, rhombohedral, or cubic crystal is used, different microscopic defect structures may be obtained.

[0070] In the first heat treatment step, heating may be performed in an atmosphere not containing water vapor, such as an inert atmosphere, before or after crystallization of the cesium tungstate.

[0071] The method for producing near infrared ray absorbing particles of the present embodiment may further include an optional step. (2) Second heat treatment process The method for producing near infrared absorbing particles of this embodiment may also include, after the first heat treatment step, a second heat treatment step of heating at a temperature of 500° C. or more and 950° C. or less in an atmosphere containing a reducing gas.

[0072] The second heat treatment process involves heating and reducing the material powder that has undergone the first heat treatment process at a temperature between 500°C and 950°C. This process stabilizes the orthorhombic, rhombohedral, and cubic crystals, which have defect structures, by annealing. The high-temperature reduction process also serves to remove some of the oxygen in the WO6 octahedra. The reduction and removal of the octahedral oxygen generates bound electrons on adjacent W atoms, resulting in a structural treatment that enhances near-infrared absorption properties.

[0073] When performing the thermal reduction treatment, it is preferable to perform it under a stream of a reducing gas. As the reducing gas, a mixed gas containing a reducing gas such as hydrogen and one or more inert gases selected from nitrogen, argon, etc. can be used. Alternatively, heating in a water vapor atmosphere or a vacuum atmosphere or other mild heating and reduction conditions may be used in combination.

[0074] The second heat treatment step may be composed of a plurality of steps, and after the heating in the reducing gas atmosphere, heating in an inert gas atmosphere may be further carried out.

[0075] Furthermore, in the second heat treatment step, if partial removal of oxygen from the WO octahedra is not intended, heating can be performed in an inert gas atmosphere instead of the reducing gas atmosphere within the above temperature range. That is, the second heat treatment step can be performed in an inert gas atmosphere or a reducing gas atmosphere at a temperature of 500°C to 950°C.

[0076] As described above, the method for producing the near-infrared absorbing particles of the present embodiment is not particularly limited. As the method for producing the near-infrared absorbing particles, various methods that can form a predetermined structure including a defect microstructure can be used.

[0077] The near-infrared absorbing particles may be produced by synthesizing a tungstate by a solid phase method, a liquid phase method, or a gas phase method in an atmosphere in which water molecules coexist. (3) Crushing process As described above, the near-infrared absorbing particles are preferably pulverized into fine particles, and therefore the method for producing near-infrared absorbing particles may include a pulverization step of pulverizing the powder obtained in the first heat treatment step and the second heat treatment step.

[0078] The specific means for pulverizing and pulverizing is not particularly limited, and various means capable of mechanical pulverization can be used. As the mechanical pulverization method, a dry pulverization method using a jet mill or the like can be used. Furthermore, mechanical pulverization may be performed in a solvent in the process of obtaining a near-infrared absorbing particle dispersion liquid described below.

[0079] If necessary, further sieving or the like can be carried out. (4) Modification process As described above, the surface of the near infrared absorbing particles may be modified with a compound containing one or more atoms selected from Si, Ti, Zr, and Al. Therefore, the method for producing near infrared absorbing particles may further include, for example, a modification step of modifying the near infrared absorbing particles with a compound containing one or more atoms selected from Si, Ti, Zr, and Al.

[0080] In the modification step, the specific conditions for modifying the near infrared absorbing particles are not particularly limited. For example, a modification step may be included in which an alkoxide containing one or more metals selected from the above metal group is added to the near infrared absorbing particles to be modified, thereby forming a coating on the surface of the near infrared absorbing particles. [Near-infrared absorbing particle dispersion] Next, a configuration example of the near-infrared absorbing particle dispersion liquid of this embodiment will be described.

[0081] The near-infrared absorbing particle dispersion of this embodiment can contain the near-infrared absorbing particles described above and one or more liquid media selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers. That is, as shown in Fig. 11, for example, a near-infrared absorbing particle dispersion 100 of this embodiment can contain the near-infrared absorbing particles 101 described above and a liquid medium 102. The near-infrared absorbing particle dispersion preferably has a configuration in which near-infrared absorbing particles are dispersed in a liquid medium. 11 is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to this form. For example, in FIG. 11, the near-infrared absorbing particles 101 are depicted as spherical particles, but the shape of the near-infrared absorbing particles 101 is not limited to this form and may have any shape. As described above, the near-infrared absorbing particles 101 may have, for example, a coating on their surfaces. The near-infrared absorbing particle dispersion 100 may contain other additives as needed in addition to the near-infrared absorbing particles 101 and the liquid medium 102.

[0082] As the liquid medium, as described above, one or more selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers can be used.

[0083] As the organic solvent, various solvents can be selected, such as alcohols, ketones, hydrocarbons, glycols, and water-based solvents. Specific examples include alcohol solvents such as isopropyl alcohol, methanol, ethanol, 1-propanol, isopropyl alcohol, butanol, pentanol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propanol; ketone solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester solvents such as 3-methyl-methoxypropionate and butyl acetate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethyl ketone. Examples of the alkyl ether include one or more selected from glycol derivatives such as propylene 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-propylidone; aromatic hydrocarbons such as toluene and xylene; and halogenated hydrocarbons such as ethylene chloride and chlorobenzene.

[0084] Of these, organic solvents with low polarity are preferred, and more preferred are 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.

[0085] 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).

[0086] 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.

[0087] As the liquid plasticizer, for example, a liquid plasticizer for plastics can be used.

[0088] 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.

[0089] 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.

[0090] In addition, in order to further improve the dispersion stability of the near infrared absorbing particles in the near infrared absorbing particle dispersion liquid described above and to prevent the dispersed particle size from becoming coarse due to re-aggregation, various surfactants, coupling agents, and the like may be added to the near infrared absorbing particle dispersion liquid as dispersants.

[0091] 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. A polymeric dispersant having one or more functional groups selected from the above functional groups (functional groups) in its molecule is more preferable.

[0092] 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 Efka 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.), Dispalyn (registered trademark) Examples of the acrylic acid ester include one or more selected from 1751N, 1831, 1850, 1860, 1934, DA-400N, DA-703-50, DA-725, DA-705, DA-7301, DN-900, NS-5210, NVI-8514L (manufactured by Kusumoto Chemicals Co., Ltd.), Alphon (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), and the like.

[0093] The method for dispersing the near-infrared absorbing particles in a liquid medium is not particularly limited as long as it can disperse the near-infrared absorbing particles in the liquid medium. In this case, it is preferable that the near-infrared absorbing particles be dispersed so that their average particle size is 200 nm or less, and more preferably 0.1 nm or more and 200 nm or less.

[0094] Examples of methods for dispersing near-infrared absorbing particles in a liquid medium include dispersion methods using devices such as a bead mill, a pole mill, a sand mill, a paint shaker, and an ultrasonic homogenizer. Among these, pulverization and dispersion using a media agitation mill such as a bead mill, a pole mill, a sand mill, or a paint shaker that uses a medium media (beads, poles, or Ottawa sand) is preferred from the viewpoint of shortening the time required to achieve a desired average particle size. By the pulverization-dispersion treatment using a media agitation mill, not only is the near-infrared absorbing particles dispersed in the liquid medium, but also finer particle size is promoted due to collisions between the near-infrared absorbing particles and collisions between the medium and the near-infrared absorbing particles, allowing the near-infrared absorbing particles to be dispersed in a finer particle size. In other words, a pulverization-dispersion treatment is performed.

[0095] As described above, the average particle size of the near-infrared absorbing particles is preferably 0.1 nm or more and 200 nm or less. This is because a small average particle size reduces scattering of light in the visible light region with wavelengths of 400 nm or more and 780 nm or less due to geometric scattering or Mie scattering, which can prevent a near-infrared absorbing particle dispersion in which near-infrared absorbing particles are dispersed in a resin or the like from becoming like frosted glass and failing to achieve 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 Rayleigh scattering mode. In the Rayleigh scattering region, scattered light is proportional to the sixth power of the dispersed particle size, so scattering decreases as the dispersed particle size decreases, improving transparency. Furthermore, an average particle size of 100 nm or less is preferable because scattered light is significantly reduced.

[0096] Incidentally, the dispersion state of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion obtained by using the near-infrared absorbing particle dispersion of the present embodiment, in which the near-infrared absorbing particles are dispersed in a solid medium such as a resin, does not cause aggregation of particles having a particle size smaller than the average particle size of the near-infrared absorbing particles in the dispersion, as long as a known method for adding the dispersion to the solid medium is used.

[0097] Furthermore, when the average particle size of the near-infrared absorbing particles is 0.1 nm or more and 200 nm or less, it is possible to prevent the near-infrared absorbing particle dispersion and its molded product (plate, sheet, etc.) from being produced as grayish with monotonically decreasing transmittance.

[0098] The content of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion of this embodiment is not particularly limited, but is preferably, for example, 0.01% by mass or more and 80% by mass or less. This is because a sufficient solar radiation transmittance can be exhibited by setting the content of the near-infrared absorbing particles to 0.01% by mass or more. Also, by setting the content to 80% by mass or less, the near-infrared absorbing particles can be uniformly dispersed in the dispersion medium. [Near-infrared absorbing particle dispersion] Next, a configuration example of the near-infrared absorbing particle dispersion of this embodiment will be described.

[0099] The near-infrared absorbing particle dispersion of this embodiment includes the near-infrared absorbing particles described above and a solid medium. Specifically, for example, as schematically shown in FIG. 12 , the near-infrared absorbing particle dispersion 110 can include the near-infrared absorbing particles 111 described above and a solid medium 112, and the near-infrared absorbing particles 111 can be disposed in the solid medium 112. In the near-infrared absorbing particle dispersion of this embodiment, the near-infrared absorbing particles are preferably dispersed in the solid medium. Note that FIG. 12 is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to this form. For example, while the near-infrared absorbing particles 111 are depicted as spherical particles in FIG. 12 , the shape of the near-infrared absorbing particles 111 is not limited to this form and can have any shape. The near-infrared absorbing particles 111 can also have, for example, a coating on their surfaces. In addition to the near-infrared absorbing particles 111 and the solid medium 112, the near-infrared absorbing particle dispersion 110 can also include other additives as needed.

[0100] 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 solid media and near-infrared absorbing particle dispersions Examples of the solid medium include thermoplastic resins, thermosetting resins, ultraviolet curing resins, etc. That is, resins can be suitably used as the solid medium.

[0101] The 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-curable resin, or a mixture of two or more resins selected from the group. Polyethylene terephthalate resin is preferably used as the polyester resin.

[0102] These medium resins may also contain a polymeric dispersant having, in the main skeleton, one or more functional groups selected from an amine-containing group, a hydroxyl group, a carboxyl group, and an epoxy group.

[0103] The solid medium is not limited to a resin medium, and a binder using a metal alkoxide can also be used as the solid medium. Typical examples of such metal alkoxides include alkoxides of Si, Ti, Al, Zr, etc. By subjecting a binder using such a metal alkoxide to hydrolysis and condensation polymerization by heating, etc., it is also possible to obtain a near-infrared absorbing particle dispersion in which the solid medium contains an oxide.

[0104] The content of 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 near infrared absorbing particles in an amount of 0.001 mass % or more and 80 mass % or less.

[0105] 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.

[0106] The color tone of the near-infrared absorbing particle dispersion of this embodiment varies depending on the concentration of the near-infrared absorbing particles contained therein. The Hunter color index of the near-infrared absorbing particle dispersion of this embodiment can be calculated, for example, by L * = 88, that is, the Hunter color index L * In the cross section of b = 88, the near-infrared absorbing particle dispersion of the present embodiment has a near-infrared shielding property with a solar radiation transmittance of 67% or less, and * ≧0, b * ≧1.6×a * It is preferable that the color exhibits a color neutrality satisfying +8.0. * If the value is negative, the color is too blue and does not appear neutral. * Even if the color index a is a positive value, the dispersion must have a neutral color. * The larger the b * The value is required. * ≧1.6×a * It is judged as +8.0. It is more preferable that the solar radiation transmittance is 50% or less.

[0107] The near-infrared absorbing particle dispersion of this embodiment exhibits high sensor wavelength transmittance. The sensor wavelength transmittance varies depending on the concentration of near-infrared absorbing particles contained in the near-infrared absorbing particle dispersion. A low concentration naturally increases transmittance, but at the same time increases solar radiation transmittance, resulting in a decrease in solar radiation shielding properties. The near-infrared absorbing particles described above have the effect of shifting the near-infrared absorption peak to the longer wavelength side by changing their own electronic structure, so it is possible to improve the sensor wavelength transmittance without lowering the particle concentration or changing the magnitude of the near-infrared absorption peak. When evaluating an index that simultaneously satisfies solar radiation shielding properties and sensor wavelength transmittance, the L of the Hunter color index is used.* When evaluated at the 88 cross section, the near infrared absorbing particle dispersion of the present embodiment preferably exhibits sensor wavelength transmittance such that T900, which is the transmittance at a wavelength of 900 nm, is 10% or more, ST21 (%), which is the solar radiation transmittance, is 67% or less, and T900 (%) and ST21 (%) satisfy T900≧1.4×ST21-41.0.

[0108] The wavelengths of various sensors are around 800nm ​​to 1000nm, and the required signal strength varies depending on the sensor type, but generally, L * For a brightness of 88, a transmittance of less than 10% for 900 nm light will not ensure sufficient signal strength. Diluting the dispersion to lower the particle concentration naturally increases T900, but ST21 also increases at the same time. It is preferable for the gradient of increase in T900 relative to the increase in ST21 to be higher than a certain standard, which is determined by ST21 (%) ≦ 67 and T900 (%) ≧ 1.4 × ST21 (%) - 41.0.

[0109] By using the near-infrared absorbing particles described above, the near-infrared absorbing particle dispersion of this embodiment can satisfy the above-mentioned color tone and sensor wavelength transmittance. (2) Method for producing near-infrared absorbing particle dispersion The method for producing the near-infrared absorbing particle dispersion of this embodiment will be described below. Note that the following merely illustrates a configuration example of the method for producing the near-infrared absorbing particle dispersion, and the method for producing the near-infrared absorbing particle dispersion described above is not limited to the following configuration example.

[0110] 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.

[0111] A masterbatch preparation process in which a masterbatch in which near-infrared absorbing particles are dispersed in a solid medium is obtained.

[0112] In the masterbatch preparation step, a masterbatch in which near-infrared absorbing particles are dispersed in a solid medium can be prepared.

[0113] 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.

[0114] 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.

[0115] For example, a mixture is prepared by uniformly mixing a near-infrared absorbing particle dispersion, near-infrared absorbing particles, near-infrared absorbing particle dispersion powder, 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.

[0116] 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.

[0117] 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 a mixture of the near-infrared absorbing particle dispersion and a solid medium. For example, it is preferable to dry the near-infrared absorbing particle dispersion or the like under reduced pressure. Specifically, the near-infrared absorbing particle dispersion or the like is dried under reduced pressure while stirring, to separate the near-infrared absorbing particle-containing composition from the liquid medium components. Examples of devices used for the reduced pressure drying include vacuum agitation dryers, but any device having the above functions may be used, and are not particularly limited. Furthermore, the pressure value during the reduced pressure reduction in the drying step is appropriately selected.

[0118] The use of the reduced-pressure drying method improves the efficiency of removing the liquid medium and the like derived from the near-infrared absorbing particle dispersion, and also prevents the near-infrared absorbing particle dispersion powder obtained after reduced-pressure drying and the near-infrared absorbing particle dispersion liquid as a raw material from being exposed to high temperatures for a long period of 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.

[0119] 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. 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.

[0120] The dispersion concentration of the obtained master batch can be adjusted while maintaining the dispersed state of the near infrared absorbing particles contained in the near infrared absorbing particle dispersion by adding a solid medium and kneading the master batch.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] For example, the method for producing the near infrared absorbing particle dispersion of the present embodiment may have the following steps.

[0126] A precursor liquid preparation step of mixing a solid medium monomer, an oligomer, and an uncured liquid solid medium precursor with near-infrared absorbing particles (near-infrared absorbing particle dispersion powder) or a near-infrared absorbing particle dispersion liquid to prepare a near-infrared absorbing particle dispersion precursor liquid.

[0127] a near-infrared absorbing particle dispersion preparation step in which the solid medium precursor such as the monomer is cured by a chemical reaction such as condensation or polymerization to prepare a near-infrared absorbing particle dispersion;

[0128] 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.

[0129] 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.

[0130] 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.

[0131] (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, and a filler. However, as described above, the solid medium is not limited to a resin, and a binder using a metal alkoxide may also be used.

[0132] 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.

[0133] 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 purposes, it is preferable that the near-infrared absorbing particle dispersion further contains a plasticizer.

[0134] 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 used in the near-infrared absorbing particle dispersion made of a polyvinyl acetal resin include plasticizers that are compounds of monohydric alcohols and organic acid esters, ester-based plasticizers such as polyhydric alcohol-organic acid ester compounds, and phosphoric acid-based plasticizers such as 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. (4) Application examples The near-infrared absorbing particle dispersion of this embodiment can be used in various modes, and its use and application modes are not particularly limited. Hereinafter, a near-infrared absorbing transparent substrate, a near-infrared absorbing interlayer film, and a near-infrared absorbing laminate will be described as application examples of the near-infrared absorbing particle dispersion of this embodiment. (4-1) Near-infrared absorbing transparent substrate The near-infrared absorbing transparent substrate of this embodiment includes a transparent substrate and a near-infrared absorbing layer on at least one surface of the transparent substrate, and the near-infrared absorbing layer can be the near-infrared absorbing particle dispersion described above. 14, 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 130 can have a transparent substrate 131 and a near-infrared absorbing layer 132. The near-infrared absorbing layer 132 can be disposed on at least one surface 131A of the transparent substrate 131.

[0135] The near-infrared absorbing transparent substrate of this embodiment may have a transparent substrate as described above. The transparent substrate may preferably be, for example, one or more types selected from a transparent film substrate and a transparent glass substrate.

[0136] 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 types 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.

[0137] 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.

[0138] In order to improve the adhesion between the glass substrate or film substrate and the near-infrared absorbing layer, it is also preferable to form an intermediate layer on the glass substrate or film substrate and 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 composed of, for example, 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, etc.

[0139] 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.

[0140] A method for producing the near-infrared absorbing transparent substrate of this embodiment will be described.

[0141] 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.

[0142] Therefore, the method for producing the near-infrared absorbing transparent substrate of this embodiment can include, for example, the following steps.

[0143] A coating step of coating a coating liquid containing the near-infrared absorbing particle dispersion liquid described above onto the surface of a transparent substrate. A near-infrared absorbing layer forming step in which the liquid medium in the coating liquid is evaporated and then a near-infrared absorbing layer is formed.

[0144] 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.

[0145] As described above, the solid medium precursor refers to one or more selected from the solid medium monomer, oligomer, and uncured solid medium.

[0146] 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.

[0147] 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.

[0148] The method for applying the coating liquid onto the transparent substrate to provide the 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.

[0149] 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 is applied by a bar coating method to form a near-infrared absorbing layer.

[0150] 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 the solvent, such as the liquid medium, contained in the coating solution is removed by drying, the coating solution is cured by irradiating it with ultraviolet light, thereby forming a coating layer that is a near-infrared absorbing layer on the transparent substrate.

[0151] Drying conditions for the coating film vary depending on the type and proportion of each component and solvent, but are typically about 20 seconds to 10 minutes at a temperature of 60° C. to 140° C. 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.

[0152] 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 controlled by the pre- and post-processes (pre-process and post-process) before and after the formation of the near-infrared absorbing layer. Examples of the pre- and post-processes include a surface treatment process for 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 as appropriate. The heating temperature in the pre-baking process and / or 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.

[0153] The method for producing the near-infrared absorbing transparent substrate of this embodiment is not limited to the above-described method. Another example of the method for producing the near-infrared absorbing transparent substrate of this embodiment includes the following steps.

[0154] A near-infrared absorbing particle dispersion coating and drying step in which the above-mentioned near-infrared absorbing particle dispersion is coated on the surface of a transparent substrate and dried. A binder application and curing step in which a binder using a solid medium such as a resin or 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 cured.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] The coating layer can be a coating film of an oxide containing one or more elements selected from, for example, Si, Ti, Zr, and Al. In this case, the coating layer can 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.

[0159] By providing a coating layer, the coating component fills the gaps between the accumulated near-infrared absorbing particles in the first layer, forming a film and suppressing the refraction of visible light, thereby further reducing the haze value of the film and improving the visible light transmittance. It also improves the adhesion of the near-infrared absorbing particles to the substrate.

[0160] 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.

[0161] The coating liquid used in the above coating method can be suitably 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.

[0162] By applying the coating liquid as a second layer onto a film containing near-infrared absorbing particles as a main component and heating the coating liquid, it is possible to easily form an oxide coating containing one or more elements selected from Si, Ti, Zr, and Al, which is a coating layer. It is also preferable to use an organosilazane solution as a binder component used in the coating liquid according to this embodiment or as a component of the coating liquid.

[0163] The heating temperature of the substrate after application of the near-infrared absorbing particle dispersion containing one or more metal alkoxides of Si, Ti, Zr, and Al and their hydrolysis polymers as the inorganic binder or coating film, or the coating liquid, is not particularly limited. For example, the heating temperature of the substrate is preferably 100°C or higher, more preferably higher than the boiling point of the solvent in the coating liquid, such as the near-infrared absorbing particle dispersion.

[0164] This is because the polymerization reaction of the metal alkoxide or 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, almost no water or organic solvents remain in the film, so these solvents do not cause a decrease in the visible light transmittance of the film after heating.

[0165] 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 and scratch resistance are exhibited, and in addition, process abnormalities such as warping of the substrate film can be avoided during evaporation of the solvent in the near-infrared absorbing layer and curing of the binder. (4-2) Near-infrared absorbing interlayer film, near-infrared absorbing laminate The near-infrared absorbing laminate of this embodiment can have a laminate structure including the near-infrared absorbing particle dispersion and a transparent substrate described above. The near-infrared absorbing laminate of this embodiment can be a laminate having the near-infrared absorbing particle dispersion and a transparent substrate as elements and stacking these together.

[0166] 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. In this case, specifically, as shown in Fig. 13 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 120 can have a plurality of transparent substrates 1211, 1212 and a near-infrared absorbing particle dispersion 122. The near-infrared absorbing particle dispersion 122 can be disposed between the plurality of transparent substrates 1211, 1212. Although Fig. 13 shows an example in which two transparent substrates 1211, 1212 are provided, the present invention is not limited to this embodiment.

[0167] The near-infrared absorbing interlayer film preferably has any one of a sheet shape, a board shape, and a film shape.

[0168] The transparent substrate may suitably be one or more selected from glass sheets, plastic sheets, and plastic films that are transparent in the visible light range.

[0169] When 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.

[0170] 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.

[0171] By interposing the near-infrared absorbing particle dispersion described above as a constituent member of an intermediate layer sandwiched between a plurality of transparent base materials, it is possible to obtain a solar-shading laminated structure, which is a type of near-infrared absorbing laminate, that has a more neutral color tone of transmitted color while suppressing solar radiation transmittance and is also capable of ensuring transmittance at the sensor wavelength.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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. 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.

[0176] As the plasticizer, a substance that is used as a plasticizer for a resin of a solid medium can be used. For example, plasticizers that can be used in an infrared shielding film made of a polyvinyl acetal resin include plasticizers that are compounds of monohydric alcohols and organic acid esters, ester-based plasticizers such as polyhydric alcohol-organic acid ester compounds, and phosphoric acid-based plasticizers such as 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.

[0177] 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.

[0178] Furthermore, the near-infrared absorbing interlayer film may contain, in addition to the near-infrared absorbing particles described above, at least one type of particle selected from the group consisting of oxide particles, composite oxide particles, and boride particles containing two or more elements selected from the group consisting of Sb, V, Nb, Ta, W, Zr, F, Zn, Al, Ti, Pb, Ga, Re, Ru, P, Ge, In, Sn, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Tb, Lu, Sr, and Ca. The near-infrared absorbing interlayer film may contain such particles in an amount of 5% to 95% by mass, with the total amount including the near-infrared absorbing particles being 100% by mass.

[0179] The near-infrared absorbing laminate may contain an ultraviolet absorber in at least one layer of the interlayer film disposed between the transparent substrates. Examples of the ultraviolet absorber include one or more compounds selected from the group consisting of 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.

[0180] 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.

[0181] 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.

[0182] The near-infrared absorbing laminate according to the present embodiment is not limited to the above-described configuration 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. [Example]

[0183] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the following examples. (Evaluation method) First, the evaluation methods used in the following examples and comparative examples will be described. (chemical analysis) The obtained near-infrared absorbing particles were chemically analyzed by atomic absorption spectrometry (AAS) for Cs and by inductively coupled plasma optical emission spectroscopy (ICP-OES) for W (tungsten). A LECO light element analyzer (ON-836) was used for O. (X-ray diffraction measurement) X-ray diffraction measurements were carried out by powder XRD measurement using Cu-Kα radiation with a Spectris X'Pert-PRO / MPD device.

[0184] (Optical properties of near-infrared absorbing transparent substrate) The visible light transmittance (VLT) and solar transmittance (ST21) of the near-infrared absorbing transparent substrate were measured in accordance with ISO 9050 and JIS R 3106 (2019). Specifically, the transmittance was measured using a spectrophotometer U-4100 manufactured by Hitachi High-Tech Corporation, and calculated by multiplying it by a coefficient corresponding to the solar spectrum. The transmittance was measured at 5 nm intervals in the wavelength range of 300 nm to 2100 nm. * a * b * The color index was calculated in accordance with JIS Z 8701 (1999) by calculating the tristimulus values ​​X, Y, and Z for a D65 standard light source and a light source angle of 10°, and then calculated from the tristimulus values ​​in accordance with JIS Z 8729 (2004). [Example 1] (Production and evaluation of near-infrared absorbing particles) A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:6. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0185] The cesium tungsten oxide precursor powder was placed on an alumina boat and placed in a heating muffle furnace. While flowing a mixed gas of superheated steam and nitrogen gas (volume ratio: 50:50), the temperature was raised to 550°C and held for 1 hour. In Table 1, the mixed gas is represented as 50% N2-50% superheated H2O. Next, the gas supplied was changed to 100% nitrogen gas by volume. While flowing nitrogen gas, the temperature was held at 550°C for 0.5 hours, then the temperature was raised to 800°C and held for 1 hour. The temperature was then lowered to room temperature, yielding a slightly greenish-white powder (first heat treatment step).

[0186] The X-ray powder diffraction pattern of this white powder is Cs4W 11 O 35 (ICDD 00-51-1891).

[0187] Next, this white powder was placed in a carbon boat and placed in a tubular furnace. The temperature was increased in a 1% by volume H-Ar gas flow (represented as 1% H-Ar in Table 1) and the temperature was held at 550°C for 1 hour for reduction. Next, the gas supply was changed to 100% by volume Ar gas, and the temperature was held at 550°C for 30 minutes while Ar gas was flowing. The temperature was then increased to 800°C and heated for 1 hour, after which the temperature was lowered to room temperature to obtain a pale blue powder A (second heat treatment step). The production conditions for the near-infrared absorbing particles are summarized in Table 1. The following evaluation results are shown in Table 2.

[0188] The XRD powder pattern of the obtained powder A shows that the main phase is hexagonal Cs as shown in Figure 2. 0.32 WO3, the second phase is orthorhombic Cs4W 11 O 35 A broad two-phase mixture pattern was observed. Chemical analysis of Powder A revealed that the molar ratio of Cs / W was 0.33. The composition ratios of the other components are shown in Table 2. The XRD powder pattern in this case showed hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction lines of both Cs4W were mixed. 11 O 35The diffraction lines of were observed to have slight deviations from the ideal positions and intensities. No data matching this diffraction pattern was found in the ICDD database.

[0189] When this powder was observed under a transmission electron microscope (Hitachi High-Tech Corporation HF-2200), fine particles 40 were observed, as shown in Figure 4(A). The crystals of each fine particle were observed as a single-phase structure, rather than a mixed structure consisting of two separate phases, hexagonal and orthorhombic, as shown in the selected-area electron diffraction pattern in Figure 4(B). The electron diffraction pattern shown in Figure 4(B) corresponds to the hexagonal

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

[0190] On the other hand, Figure 4(C) shows an atomic image taken using the STEM-HAADF method (high-angle-angle-diffusion dark-field observation in scanning electron mode). The higher the atomic number and the greater the atomic density in the projection direction, the brighter and more intense the atomic spot obtained. When combined with the projection plane information of the

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

[0191] Furthermore, the obtained near-infrared-absorbing particle powder was irradiated with 25 W Al-Kα X-rays using an X-ray photoelectron spectrometer (ULVAC-PHI XPS-Versa Probe II). Observation of excited photoelectrons revealed that the O1s peak near 530.45 eV had a shoulder on the high-energy side. The component near 532.80 eV was assumed to be due to H2O, and peak separation revealed that it contained a large amount of OH2. Furthermore, thermal desorption spectroscopy confirmed that OH and OH2 were expelled from the crystals during heating in the temperature range between 500°C and 700°C. These observations suggest that OH and OH2 are contained in the cesium tungstate of Powder A. Considering the voids in the uniaxially elongated pseudohexagonal crystals, they are presumed to have infiltrated the window voids of the hexagonal tunnel. It is believed that water and its decomposition products were introduced into the crystals during crystallization in superheated steam, and the H generated during this process was also a major source of hydrogen. + and H3O + It is thought that the ions competed with the positive W ions, leading to partial desorption of the W ions. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Next, 20% by mass of the prepared powder A, 10% by mass of an acrylic polymer dispersant having an amine-containing functional group (hereinafter referred to as "dispersant a"), and 70% by mass of methyl isobutyl ketone (MIBK) as a solvent were weighed out. These weighed materials were placed in a glass container together with 0.3 mm diameter silica beads, and dispersed and pulverized for 5 hours using a paint shaker to obtain dispersion A.

[0192] Here, the average particle size of the near-infrared absorbing particles in dispersion A (dispersed particle size measured with a particle size measuring device based on dynamic light scattering, ELS-8000 manufactured by Otsuka Electronics Co., Ltd.) was measured to be 31.4 nm.

[0193] 100 parts by mass of this dispersion A was mixed with 50 parts by mass of a UV-curable resin for hard coating (Akunix UV-3701 manufactured by Toa Gosei Co., Ltd.) to obtain a near-infrared absorbing particle coating solution A. Then, the near-infrared absorbing coating solution was appropriately diluted and applied to a transparent film substrate, a polyethylene terephthalate (PET) resin film (HPE-50 manufactured by Teijin Co., Ltd., hereinafter also referred to as "PET film"), using a bar coater to form a coating film. In addition, the same PET film was used as a transparent substrate in other examples as well.

[0194] The PET film provided with the coating film was dried at 80°C for 5 minutes to evaporate the organic solvent, which was the liquid medium, and then the UV-curable resin for hard coating was cured with a high-pressure mercury lamp to produce near-infrared absorbing film A, which was provided with a coating layer containing near-infrared absorbing particles. Note that the coating layer was a near-infrared absorbing dispersion, and the near-infrared absorbing film was a form of near-infrared absorbing transparent substrate.

[0195] The transmittance of the obtained near-infrared absorbing film A was measured using a U-4100 spectrophotometer manufactured by Hitachi High-Technologies Corporation, and the spectral transmittance profile was determined. The profile is shown in FIG.

[0196] The profile shown in Figure 5 confirms strong absorption in the near-infrared region, with the transmittance bottoming out around a wavelength of 2100 nm, and high transmittance in the visible light region (380 nm to 780 nm).

[0197] The visible light transmittance (VLT) and solar radiation transmittance (ST21) were measured to be VLT = 72.31% and ST21 = 46.47%, respectively, indicating that the film is transparent to visible light and has a strong near-infrared absorption effect. The color index of near-infrared absorbing film A is L * =87.91, a * =-2.72, b *= 9.33, which means that the blue color was very weak and close to a neutral color, i.e., a neutral color tone. This is evident from the comparison with the transmission profile of the bluish CWO dispersion film shown in Comparative Example 3 in Figure 5, where the transmittance is significantly lower than that of the CWO dispersion film at blue wavelengths around 400 nm, and significantly higher than that of the CWO dispersion film at red wavelengths around 700 nm.

[0198] The color index values ​​are calculated as follows: * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found that this fully satisfies +8.0. In addition, in Figure 7, the line 71 is * =0, and line 72 is b * =1.6×a * It means +8.0.

[0199] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 39.84%, which fully satisfied T900≧10%, and the solar shading characteristic ST21 satisfied ST21≦67%.Furthermore, it was found that T900≧1.4×ST21-41.0 was fully satisfied, providing sufficient sensor wavelength transmittance.In Figure 8, line 81 represents T900=10, line 82 represents ST21=67, and line 83 represents T900=1.4×ST21-41.0. [Comparative Example 1] (Production and evaluation of near-infrared absorbing particles) The cesium tungsten oxide precursor powder obtained in Example 1 was placed in a carbon boat, heated to 850°C in a tubular furnace in the atmosphere, and held for 20 hours. The temperature was then lowered to room temperature, and the powder was crushed and mixed in a grinder. The powder was then heated again to 850°C in the atmosphere, held for 20 hours, and then lowered to room temperature, yielding a very slightly greenish white powder i. The X-ray powder diffraction pattern of this powder i, as shown in Figure 2, showed a slight CsW 11 O 36 There are some mixed in, but it's mostly Cs4W 11 O 35It was identified as a single phase (ICDD 0-51-1891). Chemical analysis of powder i showed a Cs / W ratio of 0.36. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion and pulverization treatment was performed in the same manner as in Example 1, except that Powder i was used, to obtain Dispersion i. Dispersion i was grayish white, and the average particle size of the near-infrared absorbing particles in Dispersion i was 32.0 nm.

[0200] In the same manner as in Example 1, an ultraviolet-curable resin was added to and mixed with dispersion liquid i to obtain coating liquid i, and then a near-infrared absorbing film i was obtained. The transmission profiles of near-infrared absorbing film i are shown in Figures 5 and 6. The spectral characteristics obtained at this time were VLT = 73.33% and ST21 = 78.73%, indicating that there was almost no infrared absorbing effect.

[0201] Hunter color index is L * At the cross section =88, a * =0.70, b * These values ​​correspond to the values ​​of b * ≧1.6×a * It was found that +8.0 was not satisfied. * The T900 at the =88 cross section was 96.20%, which was a high transmittance, and T900≧10% was fully satisfied, but in Figure 8 it is plotted on the right side outside the figure, and the solar shading properties did not at all satisfy ST21≦67%. Comparative Example 2 We prepared a dispersion of In2O3:Sn (hereinafter referred to as "ITO"), a colorless, transparent, neutral-colored oxide known as a transparent conductive oxide. ITO fine particles are known to have a neutral color, but there are various types, ranging from slightly blue to brown, depending on the reduction method and production method. Here, we used ITO powder (Powder II) manufactured by ENAM, which is close to pure transparency.

[0202] Except for using this powder ii, dispersion and pulverization treatment was performed in the same manner as in Example 1 to obtain dispersion liquid ii. The color of dispersion liquid ii was light blue, and the average particle size of the particles in dispersion liquid ii was 30.2 nm.

[0203] In the same manner as in Example 1, a UV-curable resin was added to and mixed with the dispersion liquid II to obtain a coating liquid II, followed by a near-infrared absorbing film II. As shown in Figures 5 and 6, the transmission profile of the near-infrared absorbing film II exhibited a curve with a peak near 600 nm and a high transmittance for red wavelengths. The spectral characteristics obtained at this time were VLT = 72.33% and ST21 = 45.94%, confirming the infrared absorption effect. However, these infrared absorption characteristics were low compared to the other examples.

[0204] Hunter color index is L * At the cross section =88, a * =-2.04, b * These values ​​are shown in Figure 7. * At the cross section =88, b * ≧1.6×a * The color meets the +8.0 standard, confirming neutrality of color tone.

[0205] L * The T900 at the =88 cross section was 46.39%, a high transmittance, fully satisfying T900 ≥ 10%. Furthermore, as shown in Figure 8, the solar shading properties satisfied ST21 ≤ 67% and T900 ≥ 1.4 × ST21 - 41.0. However, compared to the product of the present invention, the ST21 value was higher, indicating that the solar shading properties were lower than those of the product of the present invention. Furthermore, the amount of ITO fine particles required to achieve the same solar shading properties was about five times that of CPT particles, indicating that a larger amount of ITO raw material was required. Comparative Example 3 The cesium tungsten oxide precursor powder obtained in Example 1 was placed in a carbon boat and held at 550°C for 2 hours under a 1% by volume H gas flow with N gas as a carrier. The flow was then changed to 100% by volume N gas and held for 1 hour. The temperature was then increased to 800°C and held for 1 hour, and the powder was slowly cooled to room temperature to obtain powder III. Powder III was dark blue in color. The X-ray powder diffraction pattern of this powder I, as shown in Figure 2, showed Cs 0.32 It was identified as a single phase WO3 (ICDD 0-81-1244), a hexagonal cesium tungsten oxide. Chemical analysis of powder iii showed a Cs / W ratio of 0.34. The composition ratios of other components are shown in Table 2.

[0206] Except for using this powder iii, dispersion and pulverization treatment was carried out in the same manner as in Example 1, to obtain dispersion liquid iii. Dispersion liquid iii was blue in color, and the average particle size of the particles in dispersion liquid iii was 24.6 nm.

[0207] A coating solution iii was obtained by adding an ultraviolet-curable resin to the dispersion solution iii and mixing them in the same manner as in Example 1, and then a near-infrared absorbing film iii was obtained. As shown in Figures 5 and 6, the transmission profile of the near-infrared absorbing film iii showed a curve with high transmittance for blue wavelengths, and the obtained spectral characteristics were VLT = 72.19% and ST21 = 32.88%, confirming an extremely excellent infrared absorption effect.

[0208] However, the Hunter color index is L, as shown in Figure 7. * At the cross section =88, a * =-6.57, b * = -1.25, and b * The value was negative, and the color was predominantly blue. * ≧1.6×a * +8.0 was satisfactory.

[0209] As shown in Figure 8, the solar shading property fully satisfied ST21≦67%, confirming excellent solar shading property, but did not satisfy T900≧1.4×ST21-41.0, and L *The T900 at the =88 cross section was only 4.85%, and the sensor wavelength transmittance was low.

[0210] Furthermore, the near-infrared absorbing film iii was placed in a thermo-hygrostat and kept at a temperature of 85°C and a relative humidity of 90% for 13 days, and then the transmittance profile was measured and compared with the profile before the keeping (initial in the figure). The results are shown in Figure 9B. [Comparative Examples 4 to 8] A series of near-infrared absorbing films iv to viii with different particle concentrations were prepared by appropriately changing the MIBK dilution ratio of the near-infrared absorbing particle coating solution iii prepared in Comparative Example 3. The optical property values ​​of the series are summarized in Table 2. The color tones of these films were measured using the L shown in Figure 7. * =88 cross section a * -b * In space, both are b * <0, meaning the bluish color tone was not improved. In other words, simply diluting a blue-colored CWO dispersion leaves the blue color tone, suggesting that the physical properties of the material itself must be changed to improve the color tone. As shown in Figure 8, Comparative Examples 4 and 5 had too weak infrared absorption and did not satisfy the condition T900 ≥ 1.4 × ST21-4 1.0. All but Comparative Examples 4 and 5 showed T900 < 10, which was too low.

[0211] In this way, by changing the concentration of near-infrared absorbing particles in the film, the color tone (especially a * ), T900, and ST21 can be changed, but it turns out that in order to achieve a good balance and satisfaction, it is necessary to change the physical properties and electronic structure of the material itself. [Example 2] (Production and evaluation of near-infrared absorbing particles) The cesium tungsten oxide precursor powder prepared in Example 1 was placed on an alumina boat and placed in a heating muffle furnace. The temperature was raised to 150°C while flowing 100% by volume of nitrogen gas. The gas supplied here was changed to a gas containing superheated steam, hydrogen gas, and nitrogen gas in a volume ratio of 50:1:49 (represented in Table 1 as 1% H2-49% N2-50% superheated H2O). The temperature was raised to 550°C while flowing this mixed gas and maintained at that temperature for 1 hour. The temperature was then lowered to room temperature, yielding light blue powder B (first heat treatment step).

[0212] The X-ray powder diffraction pattern of this powder has broad diffraction lines, as shown in Figure 2, and is consistent with hexagonal Cs 0.32 The main phase is WO3, but the orthorhombic Cs4W 11 O 35 and pyrochlore phase (CsO) 0.44 The diffraction lines of the W2O6 phase showed a pattern mixed with a different phase. The diffraction lines of this pyrochlore phase were broad and the reflection positions were slightly shifted. It is thought that O, OH, OH2, and OH3 derived from water were incorporated into the pyrochlore cavities. The (111) plane of the cubic pyrochlore phase is a plane with hexagonal symmetry similar to the basal plane of a hexagonal crystal, and the pyrochlore cavities correspond to the voids between the hexagonal and trigonal cavities in a hexagonal crystal. In other examples, small amounts of reflections from the pyrochlore phase were often observed mixed in the XRD powder patterns.

[0213] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction image was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0214] Chemical analysis of Powder B showed that Cs / W=0.32. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion B was obtained in the same manner as in Example 1, except that the prepared powder B was used.

[0215] The average particle size of the near-infrared absorbing particles in Dispersion B was measured to be 26.3 nm by dynamic light scattering.

[0216] Except for using this dispersion B, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film B provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0217] The spectral transmittance profile of the obtained near-infrared absorbing film B, measured using a Hitachi High-Tech U-4100 spectrophotometer, is shown in Fig. 5. The profile shown in Fig. 5 confirmed strong absorption in the near-infrared region, with the transmittance bottoming out around 1405 nm, and transmittance in the visible light region from 380 nm to 780 nm. It was confirmed that the transmittance in the blue region was significantly reduced compared to that of the near-infrared absorbing film iii of Comparative Example 3, and that the transmittance of near-infrared light in the vicinity of 900 nm was significantly reduced compared to that of the near-infrared absorbing film ii of Comparative Example 2 using ITO.

[0218] The visible light transmittance (VLT) and solar radiation transmittance (ST21) were measured to be VLT = 72.20% and ST21 = 39.29%, respectively, indicating that the film is transparent to visible light and has a strong near-infrared absorption effect.

[0219] The color index of near-infrared absorbing film B is L * =87.93, a * =-4.02, b * = 4.29, which indicates a weak blue color and a neutral color, i.e., a neutral color tone. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80%, which is used for automobile windshields, is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0220] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 16.32%, which satisfies T900≧10%, so it has sensor wavelength transmittance.In addition, the solar radiation shading properties satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0, so it was found to have sufficient sensor wavelength transmittance. [Example 3] (Production and evaluation of near-infrared absorbing particles) The light blue powder B obtained in Example 2 was spread on a carbon boat and held at 550°C for 2 hours in a 1% by volume H-Ar gas flow. Next, the gas supplied was changed to 100% by volume nitrogen gas, and the boat was held at 550°C for 0.5 hours while flowing nitrogen gas, then heated and held at 800°C for 1 hour. The boat was cooled to room temperature, and light blue powder C was obtained (second heat treatment step).

[0221] Chemical analysis of Powder C revealed that the Cs / W ratio was 0.31. The composition ratios of other components are shown in Table 2.

[0222] As shown in Figure 2, the X-ray powder diffraction pattern of Powder C has broader diffraction lines than those of Examples 1 and 2, and is a hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed with Cs4W. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0223] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion C was prepared in the same manner as in Example 1, except that Powder C was used. The average particle size of the near-infrared absorbing particles in Dispersion C was measured by dynamic light scattering to be 29.6 nm.

[0224] Except for using this dispersion C, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film C provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0225] The spectral transmittance profile of the obtained near-infrared absorbing film C is shown in Figure 5. Strong absorption in the near-infrared region, bottoming out around 1800 nm, and transmittance in the visible light region were confirmed. The transmittances in the blue and red regions were decreased and increased, respectively, compared to the near-infrared absorbing film iii of Comparative Example 3, indicating an improvement in color tone to a neutral color. Furthermore, the transmittance of near-infrared light in the vicinity of 900 nm was significantly decreased compared to the near-infrared absorbing film ii using ITO of Comparative Example 2, confirming that the film has a stronger near-infrared absorption effect than the near-infrared absorbing film ii using ITO.

[0226] The measured values ​​were VLT=72.31% and ST21=43.45%, which showed that the film was transparent to visible light and had a strong near-infrared absorbing effect. The color index of near-infrared absorbing film C was L * =87.93, a * =-3.24, b * = 8.19, which indicates a weak blue color and a neutral color, i.e., a neutral color tone. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80%, which is used for automobile windshields, is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0227] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 30.10%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 4] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat, heated in a 100% by volume Ar gas flow, and held at 800° C. for 1 hour. The temperature was then lowered to room temperature, and a pale blue powder D was obtained.

[0228] The X-ray powder diffraction pattern of Powder D has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0229] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0230] Chemical analysis of Powder D showed that Cs / W=0.33. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion D was obtained in the same manner as in Example 1, except that the prepared powder D was used.

[0231] The average particle size of the near-infrared absorbing particles in Dispersion D was measured to be 32.1 nm by dynamic light scattering.

[0232] Except for using this dispersion D, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film D provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0233] The spectral transmittance profile of the obtained near-infrared absorbing film D is shown in Figure 5. Strong absorption in the near-infrared region, bottoming out around 1950 nm, and transmittance in the visible light region were confirmed. The transmittances in the blue and red regions were decreased and increased, respectively, compared to the near-infrared absorbing film iii of Comparative Example 3, indicating an improvement in color tone to a neutral color. Furthermore, the transmittance of near-infrared light in the vicinity of 900 nm was significantly decreased compared to the near-infrared absorbing film ii using ITO of Comparative Example 2, confirming that the film has a stronger near-infrared absorption effect than the near-infrared absorbing film ii using ITO.

[0234] The measured values ​​were VLT=72.20% and ST21=48.19%, which showed that the film was transparent to visible light and had a strong near-infrared absorbing effect. The color index of the near-infrared absorbing film D was L * =87.85, a * =-2.11, b * = 8.75, which means that the blue is weak and close to a neutral color, i.e., a neutral color tone. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80%, which is used for automobile windshields, is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0235] Also, as shown in Figure 8, L *The T900 at the =88 cross section was 42.56%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 5] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas supplied was changed to 1% by volume H-Ar, and the temperature was maintained at 800°C for 10 minutes in the gas flow. The temperature was then lowered to room temperature, and a pale blue powder E was obtained.

[0236] The X-ray powder diffraction pattern of Powder E has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0237] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0238] Chemical analysis of Powder E showed that Cs / W=0.32. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion E was obtained in the same manner as in Example 1, except that the prepared powder E was used.

[0239] The average particle size of the near-infrared absorbing particles in Dispersion E was measured to be 25.0 nm by dynamic light scattering.

[0240] Except for using this dispersion E, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film E provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0241] The spectral transmittance profile of the obtained near-infrared absorbing film E is shown in Figure 6. Strong absorption in the near-infrared region, bottoming out around 1600 nm, and transmittance in the visible light region were confirmed. The transmittances in the blue and red regions were decreased and increased, respectively, compared to the near-infrared absorbing film iii of Comparative Example 3, indicating an improvement in color tone to a neutral color. Furthermore, the transmittance of near-infrared light in the vicinity of 900 nm was significantly decreased compared to the near-infrared absorbing film ii using ITO of Comparative Example 2, confirming that the film has a stronger near-infrared absorption effect than the near-infrared absorbing film ii using ITO.

[0242] The measured values ​​were VLT=72.38% and ST21=36.29%, which showed that the film was transparent to visible light and had a strong near-infrared absorbing effect. The color index of the near-infrared absorbing film E was L * =88.12, a * =-5.17, b * = 3.79, which indicates a weak blue color and a neutral color tone. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80%, which is used for automobile windshields, is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0243] Also, as shown in Figure 8, L *The T900 at the =88 cross section was 11.80%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 6] (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion F was obtained in the same manner as in Example 1, except that the light blue powder E obtained in Example 5 was used and the dispersion time was doubled.

[0244] The average particle size of the near-infrared absorbing particles in Dispersion F was measured to be 23.7 nm by dynamic light scattering.

[0245] Except for using this dispersion F, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film F provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0246] The spectral transmittance profile of the obtained near-infrared absorbing film F is shown in Figure 6. Strong absorption in the near-infrared region, bottoming out around 1600 nm, and transmission in the visible light region were confirmed. The profile was almost the same as that of the near-infrared absorbing film E produced in Example 5, except for a slight increase in transmittance in the blue region. Increasing the dispersion time reduced the average particle size, and therefore, the transmission of blue wavelengths increased due to the effect of Mie scattering. Although the color tone was slightly bluer than in Example 5, the transmission profile confirmed that the color tone had been improved compared to the near-infrared absorbing film iii of Comparative Example 3.

[0247] The measured values ​​were VLT=72.28% and ST21=36.40%, which showed that the film was transparent to visible light and had a strong near-infrared absorbing effect. The color index of the near-infrared absorbing film F was L * =88.15, a * =-5.00, b *=0.93, which showed a weaker blue color and closer to a neutral color, that is, a neutral color tone, as compared with the near infrared absorbing film iii of Comparative Example 3.

[0248] These values ​​are calculated as shown in Figure 7. * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0249] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 11.24%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 7] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat and held at 500°C for 30 minutes in a 1% by volume H-Ar gas flow. Next, the gas supplied was changed to 100% by volume nitrogen gas, and the boat was held at 550°C for 30 minutes while flowing nitrogen gas. After that, the temperature was further increased to 800°C and held for 1 hour. The temperature was then lowered to room temperature, and pale blue powder G was obtained.

[0250] The X-ray powder diffraction pattern of Powder G has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0251] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0252] Chemical analysis of Powder G showed that Cs / W=0.31. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion G was obtained in the same manner as in Example 1, except that the prepared powder G was used.

[0253] The average particle size of the near-infrared absorbing particles in Dispersion G was measured to be 31.8 nm by dynamic light scattering.

[0254] Except for using this dispersion G, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film G provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0255] The spectral transmittance profile of the obtained near-infrared absorbing film G is shown in Figure 6. Strong absorption in the near-infrared region, bottoming out around 1850 nm, and transmittance in the visible light region were confirmed. The transmittance in the blue and red regions was decreased and increased, respectively, compared to the near-infrared absorbing film iii of Comparative Example 3, indicating an improvement in color tone to a neutral color. Furthermore, the transmittance of near-infrared light in the vicinity of 900 nm was significantly decreased compared to the near-infrared absorbing film ii using ITO of Comparative Example 2, confirming that the film has a stronger near-infrared absorption effect than the near-infrared absorbing film ii using ITO.

[0256] The measured values ​​were VLT=72.29% and ST21=41.88%, which showed that the film was transparent to visible light and had a strong near-infrared absorbing effect. The color index of the near-infrared absorbing film G was L * =87.94, a * =-3.54, b * = 7.59, which indicates a weak blue color and a neutral color, i.e., a neutral color tone. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80%, which is used for automobile windshields, is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L* At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0257] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 26.36%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0.

[0258] This near-infrared absorbing film G was placed in a thermo-hygrostat and kept in an environment of 85°C and 90% relative humidity for 15 days, after which its transmittance profile was measured and compared with the profile before keeping. The results are shown in Figure 9A. As described above, a similar test was performed on the near-infrared absorbing film iii produced in Comparative Example 3 (keeping period: 13 days), and the profile before the test was compared. As a result, as shown in Figures 9A and 9B, the near-infrared absorbing film G of Example 7 showed almost no change in ST21, at 0.04%, whereas the near-infrared absorbing film iii of Comparative Example 3 showed a slight decrease in near-infrared absorption intensity, with a change in ST21 of 3.47%. [Example 8] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:10. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0259] The first heat treatment step was carried out under the same conditions as in Example 2, except that the cesium tungsten oxide precursor powder was used.

[0260] The powder obtained in the first heat treatment step was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas being supplied was changed to a 1% by volume H-Ar gas flow, and the temperature was maintained at 800°C for 10 minutes while the gas was being supplied. Then, the temperature was lowered to room temperature, and light blue powder H was obtained.

[0261] The X-ray powder diffraction pattern of powder H has broad diffraction lines, indicating that it is hexagonal Cs 0.20 WO3 (ICDD0-083-1333) and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0262] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism spot appearing in the electron diffraction pattern was short and accompanied by a weak streak, and the powder was identified as an orthorhombic crystal with the hexagonal crystals modulated by prismatic defects.

[0263] Chemical analysis of Powder H showed that Cs / W=0.20. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion H was obtained in the same manner as in Example 1, except that the prepared powder H was used.

[0264] The average particle size of the near-infrared absorbing particles in Dispersion H was measured to be 28.6 nm by dynamic light scattering.

[0265] Except for using this dispersion H, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film H provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0266] From the spectral transmittance profile of the obtained near-infrared absorbing film H, VLT = 72.32% and ST21 = 46.98% were measured, and it was found that the film was transparent to visible light and had a strong near-infrared absorbing effect. The color index of the near-infrared absorbing film H was L * =88.04, a * =-2.40, b * = 8.51, which indicates a weak blue color and a neutral color, i.e., a neutral color tone. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80%, which is used for automobile windshields, is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0267] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 38.30%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 9] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 3:10. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0268] The first heat treatment step was carried out under the same conditions as in Example 2, except that the cesium tungsten oxide precursor powder was used.

[0269] The powder obtained in the first heat treatment step was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas supplied was changed to 1% by volume H-Ar, and the temperature was maintained at 800°C for 10 minutes while the gas was flowing, and then the temperature was lowered to room temperature to obtain light blue powder I.

[0270] The X-ray powder diffraction pattern of Powder I has broad diffraction lines, indicating that it is a rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 is the main phase, and hexagonal Cs 0.32 WO3 and tetragonal Cs2W3O 10 The diffraction patterns showed a slight mixture of Cs6W. 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0271] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0272] Chemical analysis of Powder I showed that Cs / W=0.59. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion I was obtained in the same manner as in Example 1, except that the prepared powder I was used.

[0273] The average particle size of the near-infrared absorbing particles in Dispersion I was measured to be 30.4 nm by dynamic light scattering.

[0274] Except for using this dispersion liquid I, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film I provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0275] From the spectral transmittance profile of the obtained near-infrared absorbing film I, VLT = 72.27% and ST21 = 43.25% were measured, and it was found that the film was transparent to visible light and had a strong near-infrared absorbing effect. The color index of the near-infrared absorbing film I was L * =87.97, a * =-3.70, b * = 6.61, which means that the blue color is weak and close to a neutral color, i.e., a neutral color tone. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80%, which is used for automobile windshields, is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0276] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 28.51%, which satisfied T900≧10%, so it had sensor wavelength transparency, and the solar radiation shading properties satisfied ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 10] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 2:11. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0277] Then, the first heat treatment step was carried out under the same conditions as in Example 2, except that the above cesium tungsten oxide precursor powder was used, and a pale green powder J was obtained.

[0278] The X-ray powder diffraction pattern of Powder J has broad diffraction lines, indicating the pyrochlore phase (CsO). 0.44 The main phase is W2O6, and the hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O35 The diffraction patterns showed a slight mixture of the (Cs2O) 0.44 W2O6 and Cs4W 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0279] Transmission electron microscopy of this powder revealed a cubic electron diffraction pattern.

[0280] Chemical analysis of Powder J showed that Cs / W=0.36. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion J was obtained in the same manner as in Example 1, except that the prepared powder J was used.

[0281] The average particle size of the near-infrared absorbing particles in Dispersion J was measured to be 31.6 nm by dynamic light scattering.

[0282] Except for using this dispersion J, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to produce a near-infrared absorbing film J provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0283] From the spectral transmittance profile of the obtained near-infrared absorbing film J, VLT = 72.37% and ST21 = 50.79% were measured, and it was found that the film was transparent to visible light and had a strong near-infrared absorbing effect. The color index of the near-infrared absorbing film J was L * =87.87, a * =-1.44, b * = 11.06, which means that the blue color is extremely weak and close to a neutral color, i.e., a neutral color tone is displayed. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80% used in automobile windshields is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L * At the cross section =88, b* ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0284] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 40.60%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar shading properties satisfy ST21≦67% while also satisfying T900≧1.4×ST21-41.0. [Example 11] (Production and evaluation of near-infrared absorbing particles) Powder J prepared in Example 10 was spread on a carbon boat and heated to 800°C while flowing 100% by volume of Ar gas. Then, the gas being supplied was changed to 1% by volume of H-Ar, and the boat was kept at 800°C for 10 minutes while flowing this gas, and then cooled to room temperature to obtain light blue powder K.

[0285] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0286] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0287] Chemical analysis of the powdered K showed that Cs / W=0.36. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion liquid K was obtained in the same manner as in Example 1, except that the prepared powder K was used.

[0288] The average particle size of the near-infrared absorbing particles in Dispersion K was measured to be 27.5 nm by dynamic light scattering.

[0289] Except for using this dispersion liquid K, a coating film was formed on a PET film and the ultraviolet curable resin was cured to produce a near-infrared absorbing film K provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0290] The spectral transmittance profile of the obtained near-infrared absorbing film K, measured using a Hitachi High-Tech U-4100 spectrophotometer, is shown in Figure 6. The profile shown in Figure 6 confirmed strong absorption in the near-infrared region, with the transmittance bottoming out around 1650 nm, and transmittance in the visible light region from 380 nm to 780 nm. The transmittance in the blue and red regions decreased and increased, respectively, compared with that of the near-infrared absorbing film iii of Comparative Example 3, demonstrating an improvement in color tone toward a neutral color. Furthermore, the transmittance of near-infrared light near 900 nm was significantly increased compared with that of the near-infrared absorbing film iii of Comparative Example 3, confirming strong sensor wavelength transmittance.

[0291] The visible light transmittance (VLT) and solar radiation transmittance (ST21) were measured to be VLT = 72.36% and ST21 = 44.01%, respectively, indicating that the film is transparent to visible light and has a strong near-infrared absorption effect.

[0292] The color index of near-infrared absorbing film K is L * =88.10, a * =-2.72, b *= 7.05, which means that the blue color is extremely weak and close to a neutral color, i.e., a neutral color tone is displayed. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80% used in automobile windshields is a film that gives off almost no blue tint. These values ​​are obtained by comparing the L * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0293] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 27.21%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0. [Example 12] (Production and evaluation of near-infrared absorbing particles) The powder J prepared in Example 10 was spread on a carbon boat and held in a 1% by volume H-Ar gas flow at 500°C for 30 minutes. Then, the gas supplied was changed to 100% by volume nitrogen gas, and the boat was held at 800°C for 1 hour while the nitrogen gas was flowing, and then cooled to room temperature to obtain a light blue powder L.

[0294] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0295] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0296] Chemical analysis of Powder L showed that Cs / W=0.35. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion liquid L was obtained in the same manner as in Example 1, except that the prepared powder L was used.

[0297] The average particle size of the near-infrared absorbing particles in the dispersion L was measured to be 28.6 nm by dynamic light scattering.

[0298] Except for using this dispersion liquid L, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to prepare a near-infrared absorbing film L provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0299] The spectral transmittance of the obtained near-infrared absorbing film L was measured to be VLT=72.35% and ST21=60.85%, and it was found that the film was transparent to visible light and had a strong near-infrared absorbing effect.

[0300] The color index of near-infrared absorbing film L is L * =87.89, a * =-0.44, b * = 9.26, which means that the blue color is very weak and the color is close to a neutral color. These values ​​are shown in Figure 7. * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0301] Also, L* The T900 at the =88 cross section was 64.02%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0. [Example 13] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:5. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0302] The precursor powder was then placed on an alumina boat in a heating muffle furnace and heated to 150°C while flowing 100% by volume of nitrogen gas. The gas supplied here was changed to a gas containing superheated steam, hydrogen gas, and nitrogen gas in a volume ratio of 50:1:49, and the temperature was raised to 550°C while flowing this mixed gas and maintained at that temperature for 1 hour. The temperature was then lowered to room temperature, yielding a light blue powder M (first heat treatment step).

[0303] The X-ray powder diffraction pattern of Powder M had broad diffraction lines, and the same pattern as that of Example 10 was obtained. That is, the pyrochlore phase (CsO) 0.44 The main phase is W2O6, and the hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns showed a slight mixture of the (Cs2O) 0.44 W2O6 and Cs4W 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0304] Transmission electron microscopy of this powder revealed a cubic electron diffraction pattern.

[0305] Chemical analysis of Powder M showed that Cs / W=0.40. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion liquid M was obtained in the same manner as in Example 1, except that the prepared powder M was used.

[0306] The average particle size of the near-infrared absorbing particles in Dispersion M was measured to be 32.3 nm by dynamic light scattering.

[0307] Except for using this dispersion M, a coating film was formed on a PET film and the ultraviolet curable resin was cured to produce a near-infrared absorbing film M provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0308] The spectral transmittance profile of the obtained near-infrared absorbing film M was measured using a Hitachi High-Tech U-4100 spectrophotometer, and is shown in Figure 6. The profile shown in Figure 6 confirmed strong absorption in the near-infrared region, with the transmittance bottoming out around 1470 nm, and transmittance in the visible light region from 380 nm to 780 nm. The transmittance in the blue and red regions decreased and increased, respectively, compared with that of the near-infrared absorbing film iii of Comparative Example 3, demonstrating an improvement in color tone toward a neutral color. Furthermore, the transmittance of near-infrared light in the vicinity of 900 nm was significantly increased compared with that of the near-infrared absorbing film iii of Comparative Example 3, confirming strong sensor wavelength transmittance.

[0309] The visible light transmittance (VLT) and solar radiation transmittance (ST21) were measured to be VLT = 72.38% and ST21 = 50.81%, respectively, indicating that the film is transparent to visible light and has a strong near-infrared absorption effect.

[0310] The color index of near-infrared absorbing film M is L * =87.87, a * =-1.46, b *= 10.98, which means that the blue color is extremely weak and the color tone is neutral. It can be said that a thin dispersion film of the present near-infrared absorbing particles at VLT = 70 to 80%, which is used for automobile windshields, is a film that gives off almost no blue color. These values ​​are shown in Figure 7, * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0311] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 40.43%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0. [Example 14] (Production and evaluation of near-infrared absorbing particles) The powder M prepared in Example 13 was spread on a carbon boat and heated to 800°C while flowing 100% by volume of Ar gas. Then, the gas supplied was changed to 1% by volume of H-Ar, and the boat was kept at 800°C for 10 minutes while flowing this gas, and then cooled to room temperature to obtain light blue powder N.

[0312] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0313] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0314] Chemical analysis of the powder N showed that Cs / W=0.42. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion N was obtained in the same manner as in Example 1, except that the prepared powder N was used.

[0315] The average particle size of the near-infrared absorbing particles in Dispersion N was measured to be 25.2 nm by dynamic light scattering.

[0316] Except for using this dispersion liquid N, a coating film was formed on a PET film and the ultraviolet curable resin was cured to produce a near-infrared absorbing film N provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0317] The spectral transmittance profile of the obtained near-infrared absorbing film N, measured using a Hitachi High-Tech U-4100 spectrophotometer, is shown in Figure 6. The profile shown in Figure 6 confirmed strong absorption in the near-infrared region, with the transmittance bottoming out around 1630 nm, and transmittance in the visible light region from 380 nm to 780 nm. The transmittance in the blue and red regions decreased and increased, respectively, compared with that of the near-infrared absorbing film iii of Comparative Example 3, demonstrating an improvement in color tone toward a neutral color. Furthermore, the transmittance of near-infrared light near 900 nm was significantly increased compared with that of the near-infrared absorbing film iii of Comparative Example 3, confirming strong sensor wavelength transmittance.

[0318] The visible light transmittance (VLT) and solar radiation transmittance (ST21) were measured to be VLT = 72.32% and ST21 = 44.99%, respectively, indicating that the film is transparent to visible light and has a strong near-infrared absorption effect.

[0319] The color index of near-infrared absorbing film N is L * =88.01, a * =-2.66, b * = 7.17, which means that the blue color is extremely weak and the color tone is neutral. It can be said that the film with the dilute dispersion of the near-infrared absorbing particles used in automobile windshields at VLT = 70 to 80% is a film that gives off almost no blue color. These values ​​are shown in Figure 7, * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0320] Also, as shown in Figure 8, L * The T900 at the =88 cross section was 27.74%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar shading properties satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0. [Example 15] (Production and evaluation of near-infrared absorbing particles) The powder M prepared in Example 13 was spread on a carbon boat and held in a 1% by volume H-Ar gas flow at 500°C for 30 minutes. Then, the gas being supplied was changed to 100% by volume Ar, and the boat was held at 550°C for 30 minutes while the gas was being flowed. The temperature was then further increased to 800°C and held for 1 hour, and the temperature was then lowered to room temperature to obtain a light blue powder O.

[0321] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0322] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0323] Chemical analysis of the powder O showed that Cs / W=0.42. The composition ratios of other components are shown in Table 2. (Production and evaluation of near-infrared absorbing particle dispersion and near-infrared absorbing particle dispersion) Dispersion liquid O was obtained in the same manner as in Example 1, except that the prepared powder O was used.

[0324] The average particle size of the near-infrared absorbing particles in the dispersion O was measured to be 29.9 nm by dynamic light scattering.

[0325] Except for using this dispersion O, a coating film was formed on a PET film and the ultraviolet-curable resin was cured to produce a near-infrared absorbing film O provided with a coating layer containing near-infrared absorbing particles in the same manner as in Example 1. The coating layer was a near-infrared absorbing particle dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0326] The spectral transmittance of the obtained near-infrared absorbing film O was measured, and the results were VLT=72.35% and ST21=65.41%, which indicated that the film was transparent to visible light and had a near-infrared absorbing effect.

[0327] The color index of the near-infrared absorbing film O is L * =87.91, a * =-0.03, b* = 8.21, which means that the blue color is extremely weak and the color tone is neutral, similar to that of ITO. These values ​​are shown in Figure 7. * At the cross section =88, b * ≧0, b * ≧1.6×a * It was found to satisfy +8.0.

[0328] Also, L * The T900 at the =88 cross section was 70.15%, which satisfies T900≧10%, so it has sensor wavelength transparency, and the solar radiation shading properties satisfy ST21≦67% while fully satisfying T900≧1.4×ST21-41.0.

[0329] [Table 1] [Table 2] The XRD powder patterns of the powders prepared in Examples 1 to 8 all showed hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 However, the intensity ratio and position of the diffraction lines were observed to deviate from the ICDD data, which is thought to be due to the influence of irregular planar defects inserted on the prism surface. The (0001) electron diffraction pattern showed an increase in the interplanar spacing of one of the prism surface spots, confirming the modulation of the crystal structure to orthorhombic. In addition, the XRD powder patterns of the powders prepared in Examples 9 to 15 all showed hexagonal Cs 0.32 WO3 and rhombohedral Cs6W 11 O 36 , Cs 8.5 W 15 O 48 or pyrochlore phase (CsO) 0.44Although the presence of W2O6 was observed, the diffraction line positions and intensity distributions of the rhombohedral and pyrochlore phases deviated from the ICDD data. The (0001) electron diffraction patterns showed changes in the interplanar spacing of all three prism surface spots, confirming the modulation of the crystal structure to rhombohedral. Furthermore, the powders identified as having a pyrochlore phase pattern by XRD also showed cubic electron diffraction patterns. This confirms that the cesium tungstates contained in the powders prepared in Examples 1 to 15 have a pseudohexagonal crystal structure.

[0330] As shown in the transmission profiles in Figures 5 and 6, significant near-infrared absorption occurs with the absorption bottom at wavelengths of 1400 nm to 2000 nm in Examples 1 to 7, 11, 13, and 14. In addition, at visible wavelengths, the profiles are positioned between the blue-intense profile of near-infrared absorbing film iii of Comparative Example 3 and the neutral profile of near-infrared absorbing film ii of Comparative Example 2, and the blue is weaker and the red is stronger than that of near-infrared absorbing film iii, indicating an improvement in the neutral color tone.

[0331] L in Figure 7 * =88 a at cross section * -b * In space, the near infrared absorbing films of Examples 1 to 15 are located between the plots of the near infrared absorbing film ii of Comparative Example 2 and the near infrared absorbing film iii of Comparative Example 3, confirming the neutralization of color tone.

[0332] Furthermore, in terms of low solar radiation transmittance and high sensor wavelength transmittance, as shown in FIG. 8 and Table 2, it was confirmed that the near-infrared absorbing films of Examples 1 to 15, including the near-infrared absorbing film ii of Comparative Example 2, were in a desirable range.

[0333] 9A , it was confirmed that the optical profile of the near-infrared absorbing film G according to Example 7 did not change even when it was placed in a thermo-hygrostat and kept in an environment of a temperature of 85° C. and a relative humidity of 90% for 15 days. In contrast, it was confirmed that the optical profile of the near-infrared absorbing film iii according to Comparative Example 3 changed.

[0334] As shown in FIG. 2, the X-ray powder diffraction pattern of Powder G according to Example 7 has broad diffraction lines, and is a hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 This suggests that the cavities and windows of the hexagonal tunnels, which are the main oxygen diffusion pathways, are filled with Cs, O, OH, OH2, and OH3, so as to suppress the substitution reaction between Cs and water molecules, which is the cause of humidity and moisture degradation in hexagonal tungsten bronze.

[0335] In contrast, the powder iii according to Comparative Example 3 had a Cs 0.32 It was identified as a single phase WO3 (ICDD 0-81-1244), a hexagonal cesium tungsten oxide, and the cavities of the hexagonal tunnel and the windows were not sufficiently filled. As a result, it is thought that it was difficult to suppress the substitution reaction between Cs and water molecules. This application claims priority based on Japanese Patent Application No. 2020-173574, filed with the Japan Patent Office on October 14, 2020, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0336] 91 Covering 100 Near-infrared absorbing particle dispersion 90, 101, 111 Near-infrared absorbing particles 102 Liquid Media 110 Near-infrared absorbing particle dispersion 112 Solid media 120 Near-infrared absorbing laminate 1211, 1212 Transparent base material 122 Near-infrared absorbing particle dispersion 130 Near-infrared absorbing transparent substrate 131 Transparent base material 131A One side 132 Near-infrared absorbing layer

Claims

1. Near-infrared absorbing particles containing cesium tungstate, The cesium tungstate has a pseudo-hexagonal crystal structure that is modulated into one or more crystal structures selected from orthorhombic, rhombohedral, and cubic crystal structures; The cesium tungstate has the general formula Cs ｘ W ｙ O ｚ In the ternary composition diagram with Cs, W, and O at the vertices, x = 0.6y, z = 2.5y, y = 5x, and Cs ２ O:W.O. ３ = m:n (m and n are integers) are near-infrared absorbing particles having a composition within the region surrounded by four straight lines.

2. O, OH, OH ２ , O.H. ３ 2. The near infrared absorbing particle according to claim 1, further comprising one or more additive components selected from the group consisting of:

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

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

6.

5. WO constituting the cesium tungstate crystal ６ The near infrared absorbing particle according to any one of claims 1 to 4, wherein a part of O in the octahedron is missing.

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

7. The near infrared absorbing particles according to any one of claims 1 to 6, having an average particle size of 0.1 nm or more and 200 nm or less.

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

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

10. The method for producing near-infrared absorbing particles according to claim 9 , further comprising a second heat treatment step of heating the particles at a temperature of 500° C. or higher and 950° C. or lower in an atmosphere containing a reducing gas after the first heat treatment step.

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

12. The near infrared absorbing particle dispersion according to claim 11, wherein the solid medium is a resin.

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

14. The near infrared absorbing particle dispersion according to claim 11 , which has a sheet shape, a board shape, or a film shape.

15. Hunter color index L ＊ In the cross section of 88, the solar transmittance is 67% or less, and b ＊ ≧0, b ＊ ≧1.6×a ＊ The near infrared absorbing particle dispersion according to claim 11 , wherein the near infrared absorbing particle dispersion satisfies +8.

0.

16. Hunter color index L ＊ = 88 cross section, T900, which is the transmittance at a wavelength of 900 nm, is 10% or more, 16. The near infrared absorbing particle dispersion according to claim 11, wherein ST21 (%) representing solar radiation transmittance is 67% or less, and the T900 and the ST21 satisfy T900≧1.4×ST21−41.

0.

17. A near-infrared absorbing laminate having a laminate structure comprising the near-infrared absorbing particle dispersion according to claim 11 and a transparent substrate.

18. A transparent substrate; a near-infrared absorbing layer is provided on at least one surface of the transparent substrate; The near-infrared absorbing transparent substrate, wherein the near-infrared absorbing layer is the near-infrared absorbing particle dispersion according to any one of claims 11 to 16.

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