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 is a near-infrared absorbing particle containing cesium tungstate, wherein the cesium tungstate has a pseudo-hexagonal crystal structure selected from one or more of orthorhombic, rhombohedral, and cubic crystals, and the cesium tungstate is represented by the general formula Cs x W y O z It indicates the composition within the area surrounded by four straight lines of x=0.6y, z=2.5y, y=5x and Cs2O:WO3=m:n (m, n are integers) in a ternary 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 Art

[0002] The fifth edition of the Physical and Chemical Dictionary defines light as “electromagnetic waves with a wavelength of approximately 1 nm to 1 mm.” This wavelength range includes the visible light region and the infrared region.

[0003] Near-infrared radiation contained in sunlight penetrates through window materials and other materials, entering indoor spaces. This heats up the walls and floors, raising the indoor temperature. To maintain a comfortable indoor thermal environment, window materials and other materials have traditionally been used to block near-infrared radiation from entering through windows, thereby preventing indoor temperatures from rising.

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

[0005] Patent Document 2 also discloses a thermal insulation sheet woven with an infrared-reflective tape film and an infrared-absorbing tape film as the warp or weft, respectively. Furthermore, Patent Document 2 discloses a tape film having infrared reflectivity, wherein aluminum is vapor-deposited onto a synthetic resin film and then laminated with a further synthetic resin film.

[0006] In patent document 3, the applicant proposed an infrared shielding material particle dispersion, which is an infrared shielding material particle dispersion in which infrared material particles are dispersed in a medium. The infrared material particles contain tungsten oxide particles and / or composite tungsten oxide particles, and the particle diameter of the infrared material particles is greater than 1 nm and less than 800 nm.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-029314

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 9-107815

[0011] Patent Document 3: International Publication No. 2005 / 037932

[0012] Non-patent literature

[0013] Non-patent document 1: K.Machida, M.Okada, and K.Adachi, "Excitations of free and localized electrons at nearby energies in reduced cesium tungsten bronzenanocrystals," Journal of Applied Physics, Vol.125,103103(2019)

[0014] Non-patent document 2: S. Yoshio and K. Adachi, "Polarons in reduced cesiumtungsten bronzes studied using the DFT+U method," Materials Research Express, Vol. 6, 026548 (2019)

[0015] Non-patent document 3: SFSolodovnikov, NVIvannikova, ZASolodovnikova, ESZolotova, "Synthesis and X-ray diffraction study of potassium, rubidium, andcesium polytungstates with defect pyrochlore and hexagonal tungsten bronzestructures," Inorganic Materials, Vol. 34, 845-853 (1998)

[0016] Non-patent literature 4: S. Nakakura, AF Arif, K. Machida, K. Adachi, T. Ogi, Cationicdefect engineering for controlling the infrared absorption of hexagonalcesium tungsten bronze nanoparticles, Inorg. Chem., 58, 9101-9107 (2019) Summary of the Invention

[0017] Problems to be solved by the invention

[0018] Patent Document 3 discloses tungsten oxide particles and / or composite tungsten oxide particles as infrared shielding material particles. A permeable film in which these tungsten oxides are dispersed is colored blue, and the degree of blue color increases as the amount added increases.

[0019] However, in recent years, applications such as automotive glass and photothermal conversion materials have required improvements in near-infrared absorptivity, that is, reductions in solar transmittance, while also requiring a neutral transmitted color without bluish or other coloration.

[0020] When using a blue material such as the above-mentioned tungsten oxide-dispersed transparent film as a base, the hue obtainable when coloring the glass using various pigments and dyes is limited. In particular, it is difficult to obtain a yellow-based transparent color as a secondary color.

[0021] Furthermore, in applications such as photothermal conversion materials, specifically, bonding of transparent resin members utilizing photothermal conversion, pure white coloring is required. However, pure white coloring is difficult with materials such as the aforementioned tungsten oxide.

[0022] In contrast, for example, if the transmitted color of a transparent membrane containing a dispersed composite tungsten oxide were neutralized, that is, transparent, its applications could be expanded. However, there have been no reports to date of composite tungsten oxides that can achieve a neutral color while reducing solar transmittance when dispersed.

[0023] Furthermore, various sensors are used in automobiles, a crucial industrial application. Examples include rainfall sensors that detect rain, light sensors that detect sundown, and Orbis sensors used for recording and detecting traffic patterns in transportation networks. Therefore, automotive windows require near-infrared light transmittance within a specific wavelength range to facilitate information transmission from these sensors.

[0024] The infrared rays detected by the above detectors are near infrared rays with wavelengths close to red around 800nm ​​to 900nm. Car windows are required to have transmittance that is opposite to the sunlight shielding function of shielding near infrared rays with wavelengths adjacent to these.

[0025] However, the absorption wavelengths of noble metal particles and compound particles such as LaB6, which have been known for use as shielding films, extend beyond visible light, resulting in extremely low transmittance for infrared light used by these detectors. Furthermore, near-infrared absorbing particles such as ATO and ITO absorb near-infrared light at wavelengths that are too long. Therefore, even if transmittance meets the detector wavelength, the sunlight shielding function is still too low.

[0026] Therefore, one aspect of the present invention aims to provide novel near-infrared absorbing particles that suppress solar transmittance, have a more neutral color tone for transmission, and can ensure transmittance at a detector wavelength.

[0027] Methods for solving problems

[0028] One aspect of the present invention provides near-infrared absorbing particles comprising cesium tungstate.

[0029] The cesium tungstate has a pseudo-hexagonal crystal structure selected from orthorhombic, rhombohedral, and cubic.

[0030] The above cesium tungstate is represented by the general formula Cs x W y O z It indicates that, in a ternary composition diagram with Cs, W, and O as vertices, the composition is within the area surrounded by four straight lines: x=0.6y, z=2.5y, y=5x, and Cs2O:WO3=m:n (m and n are integers).

[0031] Effects of the Invention

[0032] According to one aspect of the present invention, novel near-infrared absorbing particles can be provided that suppress solar transmittance, have a more neutral color tone for transmission, and ensure transmittance at a detector wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1A A graph composed of Cs, W, and O with Cs, W, and O as vertices.

[0034] Figure 1B This is an enlarged view of a portion of the Cs, W, and O component graph with Cs, W, and O as each vertex.

[0035] Figure 2 These are the powder XRD diffraction patterns of the near-infrared absorbing particles prepared in Examples 1 to 7 and Comparative Examples 1 and 3.

[0036] Figure 3 These are the powder XRD diffraction patterns of the near-infrared absorbing particles produced in Examples 10 to 15.

[0037] Figure 4 The images are a transmission electron microscope bright-field image, a restricted-field electron diffraction image, and a high-angle diffusion dark-field (HAADF) image of the near-infrared absorbing particles produced in Example 1.

[0038] Figure 5 These are spectral transmittance graphs of the near-infrared absorbing films produced in Examples 1 to 4 and Comparative Examples 1 to 3.

[0039] Figure 6 These are spectral transmittance graphs of the near-infrared absorbing films produced in Examples 5 to 7, 11, 13, and 14, and Comparative Examples 1 to 3.

[0040] Figure 7 The Hunter color index b of the near infrared absorbing particle dispersions prepared in Examples 1 to 15 and Comparative Examples 1 to 8 is ＊ Value relative to a ＊ Value graph.

[0041] Figure 8 This is a graph showing the transmittance (T900) at a wavelength of 900 nm of the near-infrared absorbing particle dispersions prepared in Examples 1 to 11, 13, and 14 and Comparative Examples 2 to 5 relative to the solar transmittance (ST21).

[0042] Figure 9A This is a graph showing the moist heat resistance characteristics of the near infrared ray absorbing film produced in Example 7.

[0043] Figure 9B This is a graph showing the moist heat resistance characteristics of the near infrared ray absorbing film produced in Comparative Example 3.

[0044] Figure 10 Schematic diagram of near-infrared absorbing particles with a coating.

[0045] Figure 11 Schematic diagram of a near-infrared absorbing particle dispersion.

[0046] Figure 12 Schematic diagram of the near-infrared absorbing particle dispersion.

[0047] Figure 13 Schematic diagram of a near-infrared absorbing laminate.

[0048] Figure 14 Schematic diagram of a near-infrared absorbing transparent substrate. DETAILED DESCRIPTION

[0049] Hereinafter, the present specific embodiment will be described with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and substitutions can be made to the following embodiment without departing from the scope of the present invention.

[0050] [Near-infrared absorbing particles]

[0051] The near-infrared absorbing particles of this embodiment are near-infrared absorbing particles containing cesium tungstate. Alternatively, the near-infrared absorbing particles of this embodiment can be formed solely of cesium tungstate. However, even in this case, the inclusion of unavoidable impurities is not excluded.

[0052] (1) About cesium tungstate

[0053] The cesium tungstate (cesium polytungstate) contained in the near-infrared absorbing particles of this embodiment can have a pseudo-hexagonal crystal structure selected from orthorhombic, rhombohedral, and cubic. Specifically, such cesium tungstate can have a pseudo-hexagonal structure selected from orthorhombic, rhombohedral, and cubic. Specifically, such cesium tungstate can have a pseudo-hexagonal structure modified from a partially deformed hexagonal alkali tungsten bronze structure.

[0054] Conventionally, the transmission color and light absorption of cesium-doped hexagonal tungsten bronze particles used as near-infrared absorbing particles are determined by the imaginary part (ε2) of their dielectric function and the band structure.

[0055] In the energy region of visible light (1.6eV~3.3eV), the band gap of cesium hexagonal tungsten bronze (hereinafter also recorded as Cs-HTB) is sufficiently large, and the absorption of light in the visible light region is basically suppressed. In addition, the electron migration between the dd orbits of tungsten and the electron migration between the pp orbits of oxygen are limited by Fermi's golden law, so the probability of electron migration becomes smaller. Through the action of these two, ε2 takes a small value in the wavelength of the visible light region. ε2 represents the absorption of photons brought by electrons, so if ε2 is small in the wavelength of the visible light region, visible light transmittance is generated. However, it has recently been clarified that near the shortest blue wavelength in the visible light region, absorption caused by band end migration exists, and near the longest red wavelength, local surface plasmon resonance (LSPR) absorption and polarized electron migration absorption exist (non-patent document 1). Therefore, they are respectively subject to light transmittance restrictions.

[0056] As mentioned above, Cs-HTB has a sufficiently large band gap, resulting in a shift in the band edge to above the energy of blue wavelengths, resulting in blue transmittance. Conversely, Cs-HTB has more conduction electrons on the red wavelength side, resulting in enhanced LSPR absorption and polarization absorption. This absorption edge extends across the red wavelength, reducing red transmittance. Therefore, the transmission color of Cs-HTB nanoparticle-dispersed films appears blue due to the balance between the two.

[0057] That is, in order to neutralize the blue-based transmission color of Cs-HTB, it is only necessary to enhance the absorption on the blue side and enhance the transmission on the red side.

[0058] To enhance the blue-side absorption of Cs-HTB, for example, the absorption position of the band edge shift can be shifted to the lower energy side. Shifting the absorption position of the band edge shift to the lower energy side corresponds to narrowing the band gap of Cs-HTB. Therefore, this can be achieved by selecting a material with a slightly smaller band gap.

[0059] The reduction of the red absorption of Cs-HTB can be achieved by reducing the concentration of surface plasmon resonance electrons and the concentration of polaron-bound electrons.

[0060] Based on the above findings, the inventors of the present invention conducted various studies on cesium tungsten oxide, an oxide composed of cesium (Cs) and tungsten (W), and conducted material improvements while utilizing band structure calculations based on first-principles calculations. Their findings revealed that when the conventional hexagonal crystal structure is modified to have a pseudo-hexagonal structure, such as orthorhombic, rhombohedral, or cubic, through microstructural changes, the band structure changes, and the amount of free and bound electrons changes, resulting in a change in color.

[0061] Here, the term "modulation into a pseudohexagonal structure selected from one or more of orthorhombic, rhombohedral, and cubic" refers to a pseudohexagonal structure in which Cs-rich surfaces are regularly or irregularly inserted into the prism faces or base of the hexagonal crystal. Furthermore, the term "Cs-rich surface" has the same meaning as a surface deficient in W or O. Furthermore, as described later, O, OH, OH2, and OH3 ions can substitute at Cs sites. The introduction of these ions into the prism faces and base can promote the modulation into a pseudohexagonal structure, similar to Cs.

[0062] The crystal structures of orthorhombic, rhombohedral, and cubic crystals can be identified, for example, by electron diffraction. For example, when the c-axis is the direction of electron beam incidence, the difference can be distinguished by noting the symmetry of the diffraction sites when observing from the (0001) direction.

[0063] In a hexagonal crystal, the diffraction sites of the three prism planes (10-10), (01-10), and (1-100) appear at the same distance from the incident site within the reciprocal lattice plane. That is, in a hexagonal crystal, the crystal planes have the same spacing. Furthermore, the aforementioned same distance includes situations where the distance is considered the same within the error range of the electron diffraction site distance measurement. Therefore, in a hexagonal crystal, the electron diffraction pattern is hexagonally symmetrical, that is, rotationally invariant with respect to 60°.

[0064] In orthorhombic crystals, one type of prism plane site appears closer to the incident point than the other two types of prism plane sites. In other words, in orthorhombic crystals, only one type of prism plane has a long interplanar spacing.

[0065] In rhombohedral crystals, the three prism face sites have different crystal plane spacings.

[0066] In a cubic crystal, the same hexagonal symmetric pattern as that of a hexagonal crystal is formed, and the cubic symmetry can be easily identified by observing from the axial direction of other crystal bands.

[0067] Pseudo-hexagonal crystals are often seen as mixed patterns of orthorhombic and hexagonal crystals, rhombohedral and hexagonal crystals, or cubic and hexagonal crystals in XRD powder patterns. However, the position and intensity of the diffraction peaks slightly change due to the insertion of the above-mentioned planar lattice defects.

[0068] One method for obtaining a pseudohexagonal crystal structure selected from the aforementioned orthorhombic, rhombohedral, and cubic crystals is to add one or more additives selected from O, OH, OH₂, and OH₃. Therefore, the near-infrared-absorbing particles of this embodiment preferably contain one or more additives selected from O, OH, OH₂, and OH₃.

[0069] One or more additive components selected from the above-mentioned O, OH, OH2, and OH3 are preferably present in the crystal of cesium tungstate, at one or more positions selected from the group consisting of a hexagonal window, a hexagonal cavity, and a triangular cavity formed by three WO6 octahedra aggregated together, which are formed in a hexagonal channel extending in the c-axis direction and formed by six WO6 octahedra aggregated together to constitute a hexagonal alkali tungsten bronze structure.

[0070] In the hexagonal channel, there are two gaps of large hexagonal cavity and hexagonal window, but the hexagonal window is the second largest in the hexagonal crystal, which is surrounded by 6 oxygens constituting the WO6 octahedron. The c-axis of the hexagonal window is adjacent to the Cs ions configured in the hexagonal cavity. The trigonal cavity is a large gap next to the hexagonal window, which penetrates the c-axis of the hexagonal crystal. One or more selected from O, OH, OH2, and OH3 can also replace Cs and enter the hexagonal cavity. In the presence of a sufficient amount of Cs, in the case of a large amount of intrusion water, it invades the hexagonal window. Depending on the situation, it invades the trigonal cavity and the cavity of the prism surface of the bottom surface in parallel with the hexagonal window gap, and in addition replaces Cs. By containing the above-mentioned additives, the bottom surface and the prism surface generate defective surfaces, but at this time, the crystal structure changes from hexagonal crystal to orthorhombic crystal, rhombohedral crystal, and further cubic crystal, resulting in the narrowing of the band gap and the reduction of the conduction band electron concentration. Therefore, cesium tungstate having a pseudohexagonal crystal structure can enhance absorption on the blue side and enhance transmission on the red side compared to Cs-HTB, thereby neutralizing the blue transmission color.

[0071] In this case, the orthorhombic, rhombohedral, and cubic crystals have atomic arrangements similar to those of tungsten bronze hexagonal crystals, but can also be considered pseudo-hexagonal crystals, which have different symmetry from hexagonal crystals. If we avoid rigor and describe it roughly, the product of the collapse of hexagonal symmetry is the orthorhombic crystal, which is the result of regularly or irregularly inserting W and O-deficient faces into one of the three types of prism faces of hexagonal crystals. Therefore, in orthorhombic crystals, only one prism face has a long interplanar spacing. Utilizing this situation, the modulation of orthorhombic crystals can be easily identified by, for example, the (0001) electron diffraction pattern.

[0072] When the bottom surface of the hexagonal crystal is inserted to accept the remaining Cs surface, that is, the surface where W and O are missing, the c-axial stacking of the bottom surface is regularly shifted, and the crystal in which the hexagonal symmetry collapses is a rhombohedral crystal in this case. In this case, while the remaining Cs surface is shifted on the surface, it includes expansion in the direction perpendicular to the surface, which is accompanied by changes in the prism surface spacing and the c-axis lattice constant. Therefore, in the rhombohedral crystal, the surface spacing of the three prism faces is different. Using this situation, modulation into a rhombohedral crystal can be easily identified, for example, by a (0001) electron diffraction pattern.

[0073] Furthermore, when the three axes of the rhombohedron intersect at 90 degrees, a cubic crystal is formed. In addition, such a cubic crystal is a pyrochlore structure, and CsW2O6 can be cited as a typical composition.

[0074] Therefore, the voids corresponding to the hexagonal windows, hexagonal cavities, and rhombohedral cavities described above also alternate in orthorhombic, rhombohedral, and cubic crystals. Therefore, the hexagonal windows, hexagonal cavities, and rhombohedral cavities in the cesium tungstate contained in the near-infrared absorbing particles of this embodiment also include the corresponding voids in orthorhombic, rhombohedral, and cubic crystals (pyrochlore phase).

[0075] Hereinafter, a configuration example of the method for producing near-infrared absorbing particles according to the present embodiment will be described, mainly taking the case of a hexagonal window as an example of sites or gaps where O, OH, OH 2 , and OH 3 can substitute or invade.

[0076] As one of the methods for obtaining orthorhombic, rhombohedral and cubic crystals selected from O, OH, OH2, OH3 in the hexagonal window, a method for crystallizing it in saturated water vapor during the crystallization of the synthesized cesium tungstate can be cited. Generally speaking, in the Cs-HTB structure, the ionic radius of Cs is slightly larger than that of the hexagonal cavity, so Cs is difficult to move. Therefore, if it is temporarily crystallized into a hexagonal crystal, it is difficult to diffuse oxygen atoms, etc. into the hexagonal window using subsequent heat treatment. Therefore, before the crystallization of cesium tungstate, the atmosphere is filled with saturated water vapor, and while the cesium tungstate is crystallized, water molecules, O, OH, OH3 ions derived from water molecules are inserted into the hexagonal window. Therefore, as described later, the method for manufacturing near-infrared absorbing particles of the present embodiment preferably has a process of introducing water vapor at a heating temperature near the crystallization of cesium tungstate and crystallizing it in an atmosphere containing water vapor. By using the near-infrared absorbing particles synthesized through the above process and, if necessary, further heat-treated in a reducing atmosphere to produce a dispersion film containing the near-infrared absorbing particles, it is possible to achieve high visible light transmittance, maintain a sufficient near-infrared shielding effect, and reduce the blue tint. In other words, it is possible to neutralize the blue-based transmitted color.

[0077] On the other hand, even if the cesium tungstate is temporarily crystallized into hexagonal crystals and then heated in a water vapor atmosphere, or even if it is held and heated in a high-temperature, high-humidity environment, the effect of neutralizing the above-mentioned transparent color is not achieved. This is because the diffusion of oxygen atoms and the like through the hexagonal channels of elements with large ionic radii, such as Cs, is hindered. Therefore, if the hexagonal crystals are temporarily crystallized, the subsequent heat treatment prevents the diffusion of oxygen atoms and the like into the interstitial hexagonal windows. Therefore, the heating treatment in water vapor must be performed during the initial crystallization during synthesis.

[0078] When heating in an atmosphere containing water vapor during crystallization, a reducing gas such as hydrogen can also be simultaneously mixed in to allow crystallization to proceed in a reducing gas atmosphere. Furthermore, if the crystals are temporarily crystallized in a water vapor atmosphere, they can be further heat-treated at a high temperature of 500°C to 950°C in an atmosphere containing a reducing gas such as hydrogen, an inert gas, or the like. In either case, near-infrared-absorbing particles with a neutral transmission color and a strong near-infrared absorption effect can be obtained. By setting the temperature above 500°C, the equilibrium atomic positions of the orthorhombic structure containing defects are fully aligned, enhancing the near-infrared absorption effect. Furthermore, by setting the temperature below 950°C, the rate of crystal structure change can be appropriately maintained, making it easier to control the appropriate crystal state and electronic state. Furthermore, if the heating temperature is set above 950°C, for example, excessive reduction may occur, which may result in the formation of lower oxides such as W metal and WO2, which is not preferred from this perspective.

[0079] During the initial crystallization by heating with water vapor, O, OH, OH2, and OH3 are absorbed, thereby forming one or more crystals selected from orthorhombic, rhombohedral, and cubic crystals (pyrochlore phase) that are microscopically modified from hexagonal crystals. By heating these crystals in atmospheres with varying degrees of reduction, various crystal structures selected from orthorhombic, rhombohedral, and cubic crystals with varying amounts and distributions of lattice defects are generated.

[0080] The cesium tungstate contained in the near-infrared absorbing particles of the present embodiment may have lattice defects of Cs, W, and O. The reason for introducing lattice defects of Cs, W, and O into the cesium tungstate is described below.

[0081] In hexagonal Cs 0.33 In the composition near WO3, the crystal stability is determined by the balance between the stability of the structure due to the high crystal symmetry and the stability of the charge balance between the charge transfer between the elements to produce the overall charge neutrality. For example, it is considered that the charge neutral 2Cs2O·11WO3=Cs4W 11 O 35 It is a thermodynamically stable phase, but if 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 It is a quasi-stable structure with high crystal symmetry. On the other hand, Cs4W 11 O 35 It is a stable composition in terms of charge balance. However, Cs4W 11 O 35The atomic arrangement within the crystal is poorly symmetric. For example, in Solodovnikov's model (Non-Patent Document 3), within the hexagonal arrangement of WO6 octahedra, which is similar to hexagonal tungsten bronze, W and O defects are inserted into the hexagonal (1,1,-2,0) plane (=orthorhombic (010) plane) at a spacing of b / 8 of the orthorhombic unit cell, resulting in an orthorhombic structure overall. This means that Cs, W, and O defects are inevitably introduced to locally satisfy both the crystal structure and charge balance. This has been recently observed using TEM and XRD (Non-Patent Document 4).

[0082] In the near-infrared absorbing particles of this embodiment, O, OH, OH2, and OH3 are absorbed into the orthorhombic, rhombohedral, and cubic crystals of the hexagonal window, hexagonal cavity, and rhombohedral cavity, and the local charge balance is disrupted, thereby further modifying the crystal microstructure. That is, during the introduction of the component derived from water, H + 、H3O + are introduced into the crystals, where these ions react with Cs + 、W 6+ Competition is carried out, so local charge neutrality is achieved through the absence of Cs and W. As a result, lattice defects including the absence of Cs and W are introduced. O, OH, OH2, and OH3 not only invade the hexagonal window, but also the trigonal cavity. Furthermore, OH2 and OH3 can be replaced by alkali elements (Cs) in the hexagonal cavity. In addition, when the charge-neutral OH2 is replaced, the originally existing alkali ions (Cs + ) disappears, so the conduction band electrons of the crystal are reduced.

[0083] Among the cesium tungstates having a pseudo-hexagonal structure prepared to have one or more selected from the group consisting of orthorhombic, rhombohedral, and cubic structures, the cesium tungstates satisfying excellent near-infrared absorption effect and visible light transmittance have a predetermined composition.

[0084] here, Figure 1A Indicates a 3-element structure with Cs, W, and O as the 3 vertices Figure 10 . Figure 1B For the general Figure 1A The three-component composition Figure 10 This diagram shows an enlarged view of region 11, with CsWO3, W2O3, and WO4 as vertices. It should be noted that this diagram does not represent a thermodynamic equilibrium phase state diagram; rather, it is a composition diagram designed to conveniently illustrate the compositional breadth of the system. Therefore, CsWO3, W2O3, WO4, etc. are simply compositions shown for convenience, and it is not possible to determine whether these represent the actual compounds obtained.

[0085] The cesium tungstate contained in the near infrared absorbing particles of this embodiment is preferably represented by the general formula Cs x Wy O z Indicates that, in a three-dimensional composition diagram with Cs, W, and O as vertices, the composition is within the region surrounded by four straight lines of x = 0.6y, z = 2.5y, y = 5x, and Cs2O:WO3 = m:n (m and n are integers). Specifically, it is preferred that Figure 1A 、 Figure 1B In the ternary composition diagram shown, the composition within the region 16 is surrounded by the straight line 12 satisfying x=0.6y, the straight line 13 satisfying z=2.5y, the straight line 14 satisfying y=5x, and the straight line 15 satisfying Cs2O:WO3=m:n (m, n are integers). In addition, the region 16 also includes the points on the straight lines 12 to 15. In addition, the straight line 15 satisfying Cs2O:WO3=m:n (m, n are integers) is as shown in FIG. Figure 1A As shown, in the 3-element composition Figure 10 In the figure, it is a straight line connecting Cs2O and WO3.

[0086] In the above ternary composition diagram, when x > 0.6y, cesium tungstate has a predominantly tetragonal crystal structure, and its near-infrared absorption effect disappears. Furthermore, when z < 2.5y, cesium tungstate has a hexagonal-based structure mixed with lower-order W oxides, significantly impairing its near-infrared absorption effect and visible light transmittance. When y > 5x, cesium tungstate has an intergrowth crystal structure, known as WO3, mixed within the underlying structure of the hexagonal crystals, and its near-infrared absorption effect disappears. Furthermore, if the structure moves to the O-rich side to the right of the straight line 15, where the Cs2O:WO3 ratio is an integer, no near-infrared absorption effect is achieved. Therefore, cesium tungstate preferably falls within the range described above.

[0087] 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 within a range of 0.2 to 0.6. That is, the near-infrared absorbing particles of this embodiment preferably have defects in a portion of one or more elements selected from Cs and W constituting the crystal of the cesium tungstate. The general formula Cs x W y O z The relationship between x and y is 0.2≤x / y≤0.6.

[0088] Since cesium and tungsten supply electrons to the crystal, by making x / y greater than 0.2, the near-infrared absorption function can be improved. In addition, by making x / y greater than 0.2, a hexagonal crystal or a crystal structure in which the hexagonal crystal is modulated can be formed. In the Cs ion, if x / y exceeds 0.33 and becomes larger, it enters the hexagonal cavity and the trigonal cavity also begins to occupy, and the prism surface and the bottom surface become abnormal. Therefore, locally, the orthorhombic, rhombohedral or cubic pyrochlore gradually changes into a stacked structure. Further, if x / y exceeds 0.6, it becomes tetragonal Cs2W3O 10 The crystal structure of the nanostructured carbon nanotubes is significantly impaired, and their usefulness is reduced.

[0089] The near infrared absorbing particles of this embodiment can convert the hexagonal cesium tungsten bronze structure Cs 0.33 Using WO3 as a reference, at least a portion of the W in the WO6 octahedron that constitutes the crystal has defects. These W defects are introduced primarily as planar defects on the hexagonal prism faces and bases. Due to ionic repulsion between the atomic columns on both sides of the defect face, the interplanar spacing increases, thus changing the crystal symmetry from hexagonal to orthorhombic, rhombohedral, and cubic.

[0090] The near-infrared absorbing particles of this embodiment can be based on the hexagonal alkali tungsten bronze structure CsW3O9. At least a portion of the O atoms in the WO6 octahedron constituting the crystal of cesium tungstate has defects. These O defects are introduced randomly, and due to the defects, localized electrons are supplied to the system, thereby improving the near-infrared absorption function. 0.32 WO 3-y It is known that the maximum 15% of all lattice points of y=0.46 or O constituting the octahedron is covered (Non-Patent Document 3). If the defect amount exceeds 0.5, the crystal becomes unstable, generates a heterogeneous phase, and decomposes. The cesium tungstate Cs contained in the near-infrared absorbing particles of this embodiment x W y O z In the embodiment, the maximum amount of O defects corresponding to z / y = 2.5 can be included. However, it should be noted that when excess O, OH, OH2, and OH3 are introduced into the voids such as the hexagonal window, the O identification value obtained by chemical analysis includes these excess components.

[0091] The cesium tungstate contained in the near-infrared absorbing particles of this embodiment may have a portion of the Cs replaced by an additional element. In this case, the additional element is preferably one or more selected from the group consisting of Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0092] These additional elements have electron donating properties and assist in the electron donation to the conduction band of the WO octahedral skeleton at the Cs site.

[0093] (2) Regarding the moisture and heat resistance of near-infrared absorbing particles

[0094] The near-infrared absorbing particles of this embodiment show improved resistance to moisture and heat compared to cesium hexagonal tungsten bronze. This effect is a reasonable result if it is considered that a portion of the near-infrared absorbing particles of this embodiment contains one or more selected from orthorhombic, rhombohedral, and cubic crystals (pyrochlore phase) modulated by intrusive substitution of O, OH, OH2, and OH3. That is, the humidity degradation and moisture degradation of cesium hexagonal tungsten bronze are essentially substitution reactions between Cs and water molecules. However, when the cavities and windows of the hexagonal channels, which are the main diffusion pathways for oxygen diffusion, are also embedded in Cs, O, OH, OH2, and OH3, the substitution reaction is greatly slowed down. Therefore, in the near-infrared absorbing particles of this embodiment, not only is the loss of near-infrared absorption function in a high-humidity environment suppressed, but even in a high-temperature heat resistance test under normal humidity, the degradation reaction by moisture in the atmosphere is slowed down, leading to improved resistance to moisture and heat.

[0095] (3) Average particle size of near-infrared absorbing particles

[0096] The average particle size of the near-infrared absorbing particles of the present embodiment is not particularly limited, and is preferably between 0.1 nm and 200 nm. This is because, by making the average particle size of the near-infrared absorbing particles less than 200 nm, the local surface plasmon resonance is more significantly expressed, and therefore, in particular, the near-infrared absorption characteristics can be improved, that is, in particular, the solar transmittance can be suppressed. In addition, this is because by making the average particle size of the near-infrared absorbing particles more than 0.1 nm, it is possible to easily manufacture industrially. In addition, the particle size is closely related to the dispersed permeable film, that is, the color of the near-infrared absorbing particle dispersion. Within the particle size range where Mie scattering is controlled, the smaller the particle size, the more the scattering of short wavelengths in the visible light region is reduced. Therefore, if the particle size is increased, it has the effect of suppressing the blue hue. If it exceeds 100 nm, it becomes impossible to ignore the size of the haze of the film accompanied by light scattering. If it exceeds 200 nm, in addition to the increase in the haze of the film, the generation of surface plasmons is also suppressed and the LSPR absorption becomes excessively smaller.

[0097] Here, the average particle size of the near-infrared absorbing particles can be determined from the median particle size of a plurality of near-infrared absorbing particles measured from a transmission electron microscope image or the dispersed particle size measured by a particle size analyzer using a dynamic light scattering method of the dispersion.

[0098] Furthermore, when using the near-infrared absorbing particles for applications where transparency in the visible light range is important, such as in automobile windshields, it is preferable to further consider the reduction in scattering caused by the near-infrared absorbing particles. When this reduction in scattering is important, the average particle size of the near-infrared absorbing particles is particularly preferably 30 nm or less.

[0099] The so-called average particle size refers to the particle size at the 50th percentile of the cumulative value in the particle size distribution. In this specification, the average particle size has the same meaning even in other parts. As a method for measuring the particle size distribution for calculating the average particle size, for example, direct measurement of the particle size of each particle using a transmission electron microscope can be used. In addition, the average particle size can also be measured using a particle size measuring device based on the dynamic light scattering method of the dispersion as described above.

[0100] (4) Regarding the arbitrary configuration of near-infrared absorbing particles

[0101] The near-infrared absorbing particles can be surface-treated for purposes such as surface protection, durability improvement, oxidation prevention, and improved water resistance. The specific content of the surface treatment is not particularly limited. For example, the near-infrared absorbing particles of this embodiment can be coated with a compound containing one or more atoms selected from Si, Ti, Zr, and Al. In other words, the near-infrared absorbing particles can be coated with the aforementioned compound. Examples of the compound containing one or more atoms selected from Si, Ti, Zr, and Al include one or more selected from oxides, nitrides, and carbides.

[0102] Specifically, for example Figure 10 As schematically shown, the near infrared absorbing particles 90 may further have the above-mentioned coating 91 on their surfaces 90A. Figure 10 This corresponds to a cross-sectional view of a plane passing through the center of the near-infrared absorbing particle 90 having the coating 91 . Figure 10 , an example is shown in which the coating 91 is uniformly disposed over the entire surface 90A of the near-infrared absorbing particle 90. However, the present invention is not limited to this configuration. The coating 91 may be disposed so as to cover a portion of the surface of the near-infrared absorbing particle 90, for example, as dots. Furthermore, the thickness of the coating 91 is not limited to a uniform configuration and may vary depending on the location.

[0103] [Method for producing near-infrared absorbing particles]

[0104] Next, a configuration example of the method for producing near-infrared absorbing particles according to the present embodiment will be described. According to the method for producing near-infrared absorbing particles according to the present embodiment, the near-infrared absorbing particles already described can be produced, and therefore, a description thereof will be omitted.

[0105] The method for producing near-infrared absorbing particles is not particularly limited, and any method that can produce near-infrared absorbing particles satisfying the above-described characteristics can be used without particular limitation. Here, a configuration example of a method for producing near-infrared absorbing particles is described.

[0106] (1) First heat treatment step

[0107] The method for producing the near-infrared absorbing particles according to the present embodiment can include, for example, the following steps.

[0108] In the first heat treatment step, the 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.

[0109] In the first heat treatment step, cesium tungstate can be crystallized by heating at 400° C. or higher and 650° C. or lower.

[0110] However, in order to make cesium tungstate into pseudo-hexagonal crystal, it is preferable to fully contain water vapor in the atmosphere when cesium tungstate crystallizes, that is, when WO6 units form hexagonal crystals together with Cs. In this crystallization process, Cs is mainly absorbed into the hexagonal cavity, and water molecules or OH3 as its decomposition product + OH - and O 2- They are mainly absorbed into the hexagonal window. When there are relatively many Cs or water molecules in the composition, Cs or water molecules are also absorbed into the trigonal cavity.

[0111] As the compound raw material containing Cs and W, a mixture of a compound raw material containing Cs and a compound raw material containing W can be used. As the compound raw material containing Cs and W, any material containing Cs and W will suffice, and for example, a mixture of Cs2CO3 and WO3 can be used.

[0112] However, the purpose of the crystallization process in the first heat treatment step is to absorb water molecules, OH, O, etc. into the crystals during crystallization. Therefore, as a raw material for a compound containing Cs and W, it is preferable not to use cesium tungsten oxide that has already formed a hexagonal structure, such as a crystalline powder of nCs2O·mWO3 (n and m are integers, 3.6≤m / n≤9.0). As a raw material for a compound containing Cs and W, it is preferable to use cesium tungstates obtained by other methods such as sol-gel and staggered polymerization, or non-equilibrium cesium tungstates obtained by gas phase synthesis. Powders obtained by thermal plasma methods or powders obtained by electron beam dissolution are also not used as raw materials. This is because in raw materials that have already formed a hexagonal skeleton structure, Cs hinders the diffusion of oxygen atoms, making it difficult for water molecules, etc., to be absorbed into the crystals. In other words, cesium tungstates with a hexagonal structure are preferably not used as a raw material derived from a compound containing Cs and W.

[0113] The supply of water vapor in the crystallization process of the first heat treatment step is preferably achieved by supplying superheated water vapor in a heating furnace, for example. Superheated water vapor is a high-enthalpy water vapor that is obtained by further applying heat to saturated water vapor vaporized at 100°C to become a high-temperature water vapor of more than 100°C, and can be supplied together with a carrier gas. When the carrier gas is an inert gas, an atmosphere close to an oxygen-free state is formed. Superheated water vapor can be supplied at a temperature of more than 400°C where crystallization becomes active, and is preferably supplied at a sufficiently low temperature before crystallization. It can be supplied as a mixed gas of superheated water vapor and an inert gas, or as a mixed gas of superheated water vapor, an inert gas and a reducing gas such as hydrogen. When a reducing gas is mixed, there is a tendency for the speed of hexagonal crystal arrangement to increase, and sometimes even for the same orthorhombic, rhombohedral, or cubic crystals, products with different microscopic defect structures are obtained.

[0114] 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.

[0115] The method for producing near-infrared absorbing particles according to the present embodiment may further include an arbitrary step.

[0116] (2) Second heat treatment step

[0117] The method for producing near-infrared absorbing particles of the present embodiment may further include, after the first heat treatment step, a second heat treatment step of heating at a temperature of 500° C. to 950° C. in an atmosphere containing a reducing gas.

[0118] The second heat treatment step, for example, involves heating and reducing the material powder that has undergone the first heat treatment step at a temperature between 500°C and 950°C. This process stabilizes the orthorhombic, rhombohedral, and cubic crystals, which have defect structures, through annealing, while also partially removing oxygen from the WO6 octahedrons through high-temperature reduction. The reduction and removal of octahedral oxygen creates bound electrons on adjacent W atoms, resulting in a structural treatment that enhances near-infrared absorption properties.

[0119] When performing a heat reduction treatment, it is preferably performed under a stream of a reducing gas. The reducing gas may be a mixed gas containing a reducing gas such as hydrogen and one or more inert gases selected from nitrogen, argon, etc. Alternatively, other mild heating and reducing conditions such as heating in a steam atmosphere or vacuum atmosphere may be used.

[0120] The second heat treatment step may be constituted by a plurality of steps, and heating in an inert gas atmosphere may be further performed after the heating in the reducing gas atmosphere.

[0121] Furthermore, in the second heat treatment step, if there is no intention to completely remove a portion of the oxygen in the WO6 octahedron, the atmosphere may be changed to an atmosphere containing a reducing gas, and heating may be performed in an inert gas atmosphere within the above-mentioned temperature range. That is, the second heat treatment step may be performed in an atmosphere containing a reducing gas or an inert gas atmosphere at a temperature of 500°C to 950°C.

[0122] As described above, the method for producing the near-infrared absorbing particles of the present embodiment is not particularly limited. As a method for producing the near-infrared absorbing particles, various methods capable of forming a predetermined structure including a defective microstructure can be used.

[0123] The near-infrared absorbing particles can be produced by synthesizing tungstate by a solid phase method, a liquid phase method, or a gas phase method in an atmosphere where water molecules coexist.

[0124] (3) Crushing process

[0125] As described above, the near-infrared absorbing particles are preferably miniaturized to form fine particles. Therefore, the method for producing near-infrared absorbing particles may further include a pulverization step of pulverizing the powder obtained by the first and second heat treatment steps.

[0126] The specific means of pulverization and micronization are not particularly limited, and various means capable of mechanical pulverization can be used. As a mechanical pulverization method, a dry pulverization method using a jet mill or the like can be used. In addition, mechanical pulverization can be performed in a solvent during the process of obtaining the near-infrared absorbing particle dispersion described later.

[0127] Screening and the like can also be further performed as needed.

[0128] (4) Modification process

[0129] As already described, the near-infrared-absorbing particles can have their surfaces 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 can 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.

[0130] The specific conditions for modifying the near-infrared-absorbing particles in the modification step are not particularly limited. For example, a modification step may be performed by adding an alkoxide containing one or more metals selected from the above-mentioned metal group to the modified near-infrared-absorbing particles to form a coating on the surface of the near-infrared-absorbing particles.

[0131] [Near-infrared absorbing particle dispersion]

[0132] Next, a configuration example of the near-infrared absorbing particle dispersion according to the present embodiment will be described.

[0133] 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. Figure 11 As shown, the near infrared absorbing particle dispersion 100 of this embodiment can include the already described near infrared absorbing particles 101 and the liquid medium 102. The near infrared absorbing particle dispersion preferably has a structure in which the near infrared absorbing particles are dispersed in the liquid medium.

[0134] in addition, Figure 11 This is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to this form. Figure 11 Although the near-infrared-absorbing particles 101 are described as spherical particles, the shape of the near-infrared-absorbing particles 101 is not limited to this form and can have any shape. As already described, the near-infrared-absorbing particles 101 can also have a coating on their surface. The near-infrared-absorbing particle dispersion 100 can contain other additives as needed, in addition to the near-infrared-absorbing particles 101 and the liquid medium 102.

[0135] As the liquid medium, as already described, one or more selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers can be used.

[0136] As the organic solvent, various organic solvents such as alcohol-based, ketone-based, hydrocarbon-based, glycol-based, and water-based organic solvents can be selected. Specifically, examples include alcohol solvents such as isopropyl alcohol, methanol, ethanol, 1-propanol, isopropyl alcohol, butanol, amyl alcohol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propanol; ketone solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester solvents such as 3-methyl-methoxy-propionate and butyl acetate; glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol methyl ether acetate, and propylene glycol ethyl ether acetate; amides such as formamide, N-methylformamide, dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; and halogenated hydrocarbons such as dichloroethane and chlorobenzene.

[0137] Among these, low-polarity organic solvents are most preferred, and particularly 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.

[0138] As the oil and fat, for example, 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 direct ester reaction of fatty acids of vegetable oils with monohydric alcohols; ethers; and petroleum-based solvents such as Isoper (registered trademark) E, Exxsol (registered trademark) Hexane, Heptane, E, D30, D40, D60, D80, D95, D110, and D130 (all manufactured by ExxonMobil) can be used.

[0139] As the liquid resin, for example, one or more selected from liquid acrylic resins, liquid epoxy resins, liquid polyester resins, liquid urethane resins, and the like can be used.

[0140] As the liquid plasticizer, for example, liquid plasticizers for plastics can be used.

[0141] The components contained in the near-infrared absorbing particle dispersion are not limited to the aforementioned near-infrared absorbing particles and liquid medium, and the near-infrared absorbing particle dispersion may further contain arbitrary components as needed.

[0142] For example, an acid or a base may be added to the near-infrared absorbing particle dispersion as needed to adjust the pH of the dispersion.

[0143] Furthermore, in order to further improve the dispersion stability of the near-infrared absorbing particles and prevent the coarsening of the dispersed particle size due to reaggregation, various surfactants, coupling agents, etc. may be added as dispersants to the near-infrared absorbing particle dispersion.

[0144] Dispersants such as surfactants and coupling agents can be selected depending on the intended use. Preferably, the dispersant has one or more functional groups selected from amine-containing groups, hydroxyl groups, carboxyl groups, and epoxy groups. These functional groups adsorb to the surface of the near-infrared absorbing particles to prevent aggregation, and also uniformly disperse the near-infrared absorbing particles in an infrared shielding film formed using the near-infrared absorbing particles. Furthermore, polymeric dispersants containing one or more of the above functional groups (functional group groups) in the molecule are desirable.

[0145] Examples of commercially available dispersants that can be suitably used include Solsperse (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, 250 (manufactured by Japan Lubrizol Co., Ltd.), 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), AJISTOR (registered trademark), PA111, PB821, PB822, PN411, FEIME KKUSU 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 (byk Japan Co., Ltd.), Disparlon (registered trademark) 1751N, 1831, 1850, 1860, 1934, DA-400N, DA-703-50, DA-725, DA-705, DA-7301, DN-900, NS-5210, NVI-8514L (manufactured by Kusumoto Chemicals Co., Ltd.), ARUFON (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), etc., one or more

[0146] The method for dispersing the near-infrared absorbing particles in the liquid medium is not particularly limited, as long as the method can disperse the near-infrared absorbing particles in the liquid medium. In this case, the near-infrared absorbing particles are preferably dispersed so that the average particle size is 200 nm or less, and more preferably dispersed so that the average particle size is 0.1 nm or more and 200 nm or less.

[0147] Examples of methods for dispersing near-infrared absorbing particles in a liquid medium include those using devices such as bead mills, ball mills, sand mills, paint shakers, and ultrasonic homogenizers. Among these, pulverization and dispersion using a media agitation mill such as a bead mill, ball mill, sand mill, or paint shaker that uses media (beads, balls, or Ottawa sand) is preferred from the perspective of shortening the time required to achieve the desired average particle size. The pulverization-dispersion process using a media agitation mill allows the near-infrared absorbing particles to be dispersed in the liquid medium while simultaneously undergoing micronization caused by collisions between the near-infrared absorbing particles and collisions of the media with the near-infrared absorbing particles, resulting in a more micronized dispersion of the near-infrared absorbing particles. In other words, a pulverization-dispersion process is performed.

[0148] The average particle size of the near-infrared absorbing particles is as described above, preferably between 0.1nm and 200nm. This is because, if the average particle size is small, due to geometric scattering or Mie scattering, the scattering of light in the visible light region of wavelengths of 400nm and below 780nm is reduced, and as a result, the near-infrared absorbing particles dispersed in the near-infrared absorbing particle dispersion of resin etc. becomes cloudy glass, which can avoid not obtaining clear transparency. That is, if the average particle size is below 200nm, the geometric scattering or Mie scattering mode in the light scattering weakens and becomes a Rayleigh scattering mode. This is because in the Rayleigh scattering region, scattered light is proportional to the sixth power of the dispersed particle size, so as to reduce the dispersed particle size, scattering is reduced and transparency is improved. Moreover, if the average particle size is below 100nm, the scattered light becomes very small, which is preferred.

[0149] However, the dispersion state of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment, in which the near-infrared absorbing particles are dispersed in a solid medium such as a resin, is limited to the known method of adding the dispersion to the solid medium, and there is no agglomeration compared to the average particle size of the near-infrared absorbing particles in the dispersion.

[0150] Furthermore, when the average particle size of the near-infrared absorbing particles is 0.1 nm to 200 nm, it is possible to avoid the produced near-infrared absorbing particle dispersion and its molded product (plate, sheet, etc.) becoming a gray product with monotonically decreasing transmittance.

[0151] 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, from 0.01% to 80% by mass. This is because a near-infrared-absorbing particle content of 0.01% by mass or greater allows for sufficient solar transmittance. Furthermore, a content of 80% by mass or less allows for uniform dispersion of the near-infrared-absorbing particles within the dispersion medium.

[0152] [Near-infrared absorbing particle dispersion]

[0153] Next, a configuration example of the near-infrared absorbing particle dispersion according to this embodiment will be described.

[0154] The near-infrared absorbing particle dispersion of this embodiment comprises the near-infrared absorbing particles and a solid medium as described above. Specifically, for example, Figure 12 As schematically shown, the near-infrared absorbing particle dispersion 110 can include the near-infrared absorbing particles 111 and the solid medium 112 described above, and the near-infrared absorbing particles 111 can be arranged in the solid medium 112. Moreover, in the near-infrared absorbing particle dispersion of this embodiment, the near-infrared absorbing particles are preferably dispersed in the solid medium. Figure 12 This is a schematic diagram, and the near-infrared absorbing particle dispersion of this embodiment is not limited to this form. Figure 12 , the near-infrared absorbing particles 111 are described as spherical particles. However, the shape of the near-infrared absorbing particles 111 is not limited to this and can have any shape. For example, the near-infrared absorbing particles 111 can also have a coating on their surface. The near-infrared absorbing particle dispersion 110 can contain other additives as needed, in addition to the near-infrared absorbing particles 111 and the solid medium 112.

[0155] The near-infrared absorbing particle dispersion according to this embodiment will be described below in the order of (1) properties of the solid medium and the near-infrared absorbing particle dispersion, (2) method for producing the near-infrared absorbing particle dispersion, (3) additives, and (4) application examples.

[0156] (1) Characteristics of solid medium and near-infrared absorbing particle dispersion

[0157] Examples of the solid medium include dielectric resins such as thermoplastic resins, thermosetting resins, and ultraviolet curing resins. In other words, resins can be preferably used as the solid medium.

[0158] The specific material of the resin used in the solid medium is not particularly limited, but is preferably, for example, one resin selected from the group consisting of polyester resins, polycarbonate resins, acrylic resins, styrene resins, polyamide resins, polyethylene resins, vinyl chloride resins, olefin resins, epoxy resins, polyimide resins, fluororesins, ethylene-vinyl acetate copolymers, polyvinyl acetal resins, and ultraviolet curing resins, or a mixture of two or more resins selected from the above resin group. Furthermore, polyethylene terephthalate resin can be suitably used as the polyester resin.

[0159] These dielectric resins may further contain a polymeric dispersant having one or more functional groups selected from the group consisting of an amine group containing an amine in its main skeleton, a hydroxyl group, a carboxyl group, and an epoxy group.

[0160] The solid medium is not limited to dielectric resins. A binder using a metal alkoxide can also be used as the solid medium. Representative examples of such metal alkoxides include alkoxides of Si, Ti, Al, and Zr. By hydrolyzing and polycondensing the binder using these metal alkoxides through heating or the like, the solid medium can be converted into a dispersion of near-infrared absorbing particles containing an oxide.

[0161] The content ratio of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion according to the present embodiment is not particularly limited, but the near-infrared absorbing particle dispersion preferably contains 0.001% by mass to 80% by mass of the near-infrared absorbing particles.

[0162] 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, plate, or film shape. This is because the near-infrared-absorbing particle dispersion can be used in a variety of applications by having a sheet, plate, or film shape.

[0163] The color tone of the near infrared absorbing particle dispersion of the present embodiment varies depending on the concentration of the near infrared absorbing particles contained. ＊ = 88, which is the Hunter color index L ＊ =88 section, the near infrared absorbing particle dispersion of this embodiment preferably has a near infrared shielding property with a solar transmittance of 67% or less and satisfies b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0 neutrality of color. ＊ In the case of negative values, the blue is too strong and the neutral color cannot be seen. ＊ For the dispersion to be considered neutral, if the color index a is positive, ＊ If it gets bigger, you need a bigger b ＊ Value. Its benchmark is b ＊ ≥1.6×a ＊ The solar transmittance is more preferably 50% or less.

[0164] The near-infrared absorbing particle dispersion of this embodiment shows high detector wavelength transmittance. The detector wavelength transmittance varies depending on the concentration of the near-infrared absorbing particles contained in the near-infrared absorbing particle dispersion. If the concentration is low, the transmittance is of course high, but at the same time the sunlight transmittance also becomes higher, and the sunlight shielding property is reduced. The near-infrared absorbing particles already described have the effect of shifting the near-infrared absorption peak to the long wavelength side according to the change of their own electronic structure, so the detector wavelength transmittance can be improved without reducing the particle concentration and without changing the size of the near-infrared absorption peak. When evaluating the index that satisfies both sunlight shielding and detector wavelength transmittance, if the L value of the Hunter color index is less than 0. ＊ =88 section, the near-infrared absorbing particle dispersion of this embodiment preferably shows that T900 as the transmittance at a wavelength of 900nm is greater than 10%, ST21(%) as the sunlight transmittance is less than 67%, and T900(%) and ST21(%) satisfy the detector wavelength transmittance of T900≥1.4×ST21-41.0.

[0165] The wavelengths of various detectors are around 800nm ​​to 1000nm, and the required signal strength varies depending on the type of detector. ＊ =88, and when the transmittance for light at a wavelength of 900 nm is reduced by 10%, sufficient signal strength cannot be achieved. Diluting the dispersion to reduce particle concentration naturally increases T900, but ST21 also increases simultaneously. The gradient of the T900 increase relative to the ST21 increase is preferably above a threshold, determined by ST21(%) ≤ 67 and T900(%) ≥ 1.4 × ST21(%) - 41.0.

[0166] By using the above-described near-infrared absorbing particles, the near-infrared absorbing particle dispersion of the present embodiment can satisfy the above-mentioned color tone and detector wavelength transmittance.

[0167] (2) Method for producing near-infrared absorbing particle dispersion

[0168] The following describes a method for producing a near-infrared absorbing particle dispersion according to this embodiment. Note that this merely illustrates a configuration example of a method for producing a near-infrared absorbing particle dispersion, and the method for producing a near-infrared absorbing particle dispersion described above is not limited to the following configuration example.

[0169] The near-infrared absorbing particle dispersion of the present embodiment can be produced using, for example, a masterbatch. In this case, the method for producing the near-infrared absorbing particle dispersion of the present embodiment can further include, for example, the following masterbatch preparation step.

[0170] A masterbatch production process for obtaining a masterbatch in which near-infrared absorbing particles are dispersed in a solid medium.

[0171] In the masterbatch preparation step, a masterbatch in which near-infrared absorbing particles are dispersed in a solid medium can be prepared.

[0172] The specific method for preparing the masterbatch is not particularly limited. For example, the masterbatch can be prepared by dispersing a near-infrared absorbing particle dispersion or near-infrared absorbing particles in a solid medium and granulating the solid medium.

[0173] Furthermore, as the near-infrared absorbing particles, near-infrared absorbing particle dispersion powder obtained by removing the liquid medium from the near-infrared absorbing particle dispersion can also be used.

[0174] For example, a near-infrared absorbing particle dispersion, near-infrared absorbing particles, near-infrared absorbing particle dispersion powder, and a powder or granule of a solid medium are uniformly mixed with other additives as needed to prepare a mixture. In addition, the mixture can be kneaded using a vented single-shaft or double-shaft extruder, and the melt-extruded strands are cut to form particles, thereby producing a masterbatch. In this case, the shape of the particles can be cylindrical or prismatic. In addition, when making the particles, a so-called hot cutting method can also be used in which the melt extrudate is directly cut. In this case, the shape is usually close to spherical.

[0175] Furthermore, during the masterbatch preparation process, when using a near-infrared absorbing particle dispersion as the raw material, it is preferable to reduce or remove the liquid medium derived from the near-infrared absorbing particle dispersion. In this case, the extent of removal of the liquid medium contained in the near-infrared absorbing particle dispersion is not particularly limited. For example, it is preferable to remove the liquid medium from the near-infrared absorbing particle dispersion until a permissible amount remains in the masterbatch. Furthermore, when using a liquid plasticizer as the liquid medium, the entire amount of the liquid plasticizer may remain in the near-infrared absorbing particle dispersion.

[0176] The method for reducing or removing the liquid medium contained in the near-infrared absorbing particle dispersion from the near-infrared absorbing particle dispersion or the mixture of the near-infrared absorbing particle dispersion and the solid medium is not particularly limited. For example, it is preferred to dry the near-infrared absorbing particle dispersion under reduced pressure. Specifically, the near-infrared absorbing particle dispersion is dried under reduced pressure while stirring to separate the composition containing the near-infrared absorbing particles from the components of the liquid medium. As an apparatus used for this reduced pressure drying, a vacuum stirring type dryer can be cited, and there is no particular limitation as long as it is an apparatus having the above-mentioned functions. In addition, the pressure value during the reduced pressure of the drying process is appropriately selected.

[0177] The use of this reduced-pressure drying method improves the efficiency of removing the liquid medium and other substances derived from the near-infrared-absorbing particle dispersion. Furthermore, the near-infrared-absorbing particle dispersion powder obtained after reduced-pressure drying and the near-infrared-absorbing particle dispersion serving as the raw material are not exposed to high temperatures for extended periods of time. This prevents aggregation of the near-infrared-absorbing particles dispersed in the near-infrared-absorbing particle dispersion powder and the near-infrared-absorbing particle dispersion, which is preferred. Furthermore, the productivity of the near-infrared-absorbing particle dispersion powder and other substances is improved, and the recovery of evaporated solvents such as the liquid medium is facilitated, which is also preferred from an environmental perspective.

[0178] It is preferable to fully remove solvent components with a boiling point of 120°C or less from the near-infrared absorbing particle dispersion powder obtained after the drying step. For example, the residual amount of such solvent components is preferably 2.5% by mass or less. This is because when the near-infrared absorbing particle dispersion powder is processed into, for example, a near-infrared absorbing particle dispersion, bubbles are prevented from forming, and the appearance and optical properties are well maintained. Furthermore, when the near-infrared absorbing particle dispersion powder contains a residual solvent component of 2.5% by mass or less, aggregation due to natural drying of the residual solvent component is avoided during long-term storage of the near-infrared absorbing particle dispersion powder, thereby maintaining long-term stability.

[0179] The obtained masterbatch can be kneaded by adding a solid medium, thereby adjusting the dispersion concentration of the near-infrared absorbing particles contained in the near-infrared absorbing particle dispersion while maintaining the dispersion state of the near-infrared absorbing particles.

[0180] Furthermore, the method for producing a near-infrared absorbing particle dispersion of the present embodiment may, if necessary, include a step of molding the obtained masterbatch or a product obtained by adding a solid medium to the masterbatch as described above to form a near-infrared absorbing particle dispersion of a desired shape.

[0181] The specific method for molding the near-infrared absorbing particle dispersion is not particularly limited, and for example, a known method such as extrusion molding and injection molding can be used.

[0182] In the molding step, for example, a near-infrared absorbing particle dispersion can be produced in the form of a flat or curved sheet, plate, or film. The method for molding into a sheet, plate, or film shape is not particularly limited, and various known methods can be used. For example, a calender roll method, an extrusion method, a casting method, an inflation method, etc. can be used.

[0183] The method for producing the near-infrared absorbing particle dispersion of the present embodiment is not limited to the embodiment having the above-mentioned masterbatch preparation step.

[0184] For example, the method for producing the near-infrared absorbing particle dispersion of the present embodiment may also have the following steps.

[0185] A precursor solution preparation step is to mix solid medium monomers, oligomers and an uncured liquid solid medium precursor with near infrared absorbing particles (near infrared absorbing particle dispersion powder) and a near infrared absorbing particle dispersion to prepare a near infrared absorbing particle dispersion precursor solution.

[0186] A near-infrared absorbing particle dispersion production step is to solidify the solid medium precursor such as the monomer through a chemical reaction such as condensation or polymerization to produce a near-infrared absorbing particle dispersion.

[0187] For example, when an acrylic resin is used as the solid medium, an acrylic monomer, an acrylic ultraviolet curable resin, and near-infrared absorbing particles are mixed to obtain a near-infrared absorbing particle dispersion precursor liquid.

[0188] Next, when the near-infrared absorbing particle dispersion precursor liquid is filled into a predetermined mold or the like and radical polymerization is performed, a near-infrared absorbing particle dispersion using an acrylic resin is obtained.

[0189] When a resin that cures by crosslinking is used as the solid medium, a dispersion can be obtained by subjecting the near-infrared absorbing particle dispersion precursor liquid to a crosslinking reaction, similarly to the case of using the acrylic resin.

[0190] (3) Additives

[0191] When a resin is used as the solid medium, the near-infrared absorbing particle dispersion of this embodiment may also contain known additives (additives) such as plasticizers, flame retardants, anti-coloring agents, and fillers added to these resins. However, as already described, the solid medium is not limited to resins, and binders using metal alkoxides may also be used.

[0192] The shape of the near-infrared absorbing particle dispersion according to the present embodiment is not particularly limited, and as already described, it can take the form of, for example, a sheet shape, a plate shape, or a film shape.

[0193] When used as an interlayer with a transparent substrate such as glass along with a sheet, plate, or film-shaped near-infrared-absorbing particle dispersion, the solid medium contained in the near-infrared-absorbing particle dispersion may not be sufficiently flexible or adhere well to the transparent substrate when used as is. In such cases, the near-infrared-absorbing particle dispersion preferably contains a plasticizer. Specifically, for example, if the solid medium is polyvinyl acetal resin, the near-infrared-absorbing particle dispersion preferably further contains a plasticizer when used for such applications.

[0194] As the plasticizer, any of the solid media used as plasticizers in the near-infrared absorbing particle dispersion of this embodiment can be used. For example, plasticizers used in near-infrared absorbing particle dispersions composed of polyvinyl acetal resin include plasticizers that are compounds of primary alcohols and organic acid esters, ester-based plasticizers such as polyol organic acid ester compounds, and phosphate-based plasticizers such as organophosphate-based plasticizers. Any of these plasticizers is preferably liquid at room temperature. Among these, plasticizers that are ester compounds synthesized from polyols and fatty acids are preferred.

[0195] (4) Application examples

[0196] The near-infrared-absorbing particle dispersion of this embodiment can be used in various ways, and its use and application are not particularly limited. Below, as examples of the application of the near-infrared-absorbing particle dispersion of this embodiment, a near-infrared-absorbing transparent substrate, a near-infrared-absorbing interlayer film, and a near-infrared-absorbing laminate are described.

[0197] (4-1) Near-infrared absorbing transparent substrate

[0198] 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. The near-infrared absorbing layer can be the near-infrared absorbing particle dispersion described above.

[0199] Specifically, as a schematic cross-sectional view along the stacking direction of the transparent substrate and the near-infrared absorbing layer, Figure 14 As shown, the near-infrared absorbing transparent substrate 130 can include 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.

[0200] The near-infrared absorbing transparent substrate of the present embodiment can include a transparent substrate as described above. As the transparent substrate, for example, one or more selected from a transparent film substrate and a transparent glass substrate can be preferably used.

[0201] Film substrate is not limited to film shape, for example, can be plate shape or sheet shape.As the material of this film substrate, can be suitable for using more than one selected from polyester resin, acrylic resin, urethane resin, polycarbonate resin, polyethylene resin, ethylene-vinyl acetate copolymer, vinyl chloride resin, fluororesin etc., can be used according to various purposes.However, as the material of film substrate, preferably polyester resin, particularly more preferably polyethylene terephthalate resin (PET resin).That is, film substrate is preferably polyester resin film, more preferably polyethylene terephthalate resin film.

[0202] 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 with the near-infrared absorbing layer.

[0203] Furthermore, to improve 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, or to form the near-infrared absorbing layer on the intermediate layer. The composition of the intermediate layer is not particularly limited and can be, for example, a polymer film, a metal layer, an inorganic layer (e.g., an inorganic oxide layer such as silicon dioxide, titanium dioxide, or zirconium oxide), or an organic / inorganic composite layer.

[0204] The near-infrared absorbing particle dispersion has already been described, so its description is omitted here. The shape of the near-infrared absorbing particle dispersion is not particularly limited, but is preferably in the form of a sheet, plate, or film.

[0205] A method for producing the near-infrared absorbing transparent substrate according to the present embodiment will be described.

[0206] The near infrared absorbing transparent substrate of this embodiment can be produced, for example, by forming a near infrared absorbing layer on a transparent substrate as a near infrared absorbing particle dispersion in which near infrared absorbing particles are dispersed in a solid medium using the near infrared absorbing particle dispersion liquid described above.

[0207] Therefore, the method for producing the near-infrared absorbing transparent substrate of the present embodiment can include, for example, the following steps.

[0208] A coating step is performed in which a coating liquid containing the above-described near-infrared absorbing particle dispersion is applied to the surface of the transparent substrate.

[0209] A near infrared absorbing layer forming step of forming a near infrared absorbing layer after evaporating the liquid medium in the coating liquid.

[0210] The coating liquid used in the coating step can be prepared by, for example, adding a solid medium such as a resin or a metal alkoxide, or a solid medium precursor to the above-described near-infrared absorbing particle dispersion and mixing the mixture.

[0211] As already described, the solid medium precursor refers to one or more types selected from the group consisting of monomers, oligomers, and uncured solid media.

[0212] When a near-infrared absorbing layer is formed as a coating on a transparent substrate, the near-infrared absorbing layer becomes a dispersion of near-infrared absorbing particles in a solid medium. Therefore, such a near-infrared absorbing layer becomes a dispersion of near-infrared absorbing particles. Thus, by disposing a dispersion of near-infrared absorbing particles on the surface of a transparent substrate, a near-infrared absorbing transparent substrate can be produced.

[0213] The solid medium, solid medium precursor, (1) properties of the solid medium and the near-infrared absorbing particle dispersion, and (2) method for producing the near-infrared absorbing particle dispersion have been described, and therefore their description is omitted here.

[0214] In order to form a near-infrared absorbing layer on a transparent substrate, the method for applying the coating liquid to the transparent substrate is not particularly limited, as long as it can be applied evenly to the surface of the transparent substrate. Examples include bar coating, gravure coating, spray coating, dip coating, spin coating, screen printing, roll coating, and curtain coating.

[0215] Here, the steps for forming a near-infrared absorbing layer on the surface of a transparent substrate will be described by taking as an example the case where a near-infrared absorbing layer is formed by coating with an ultraviolet curing resin as a solid medium using a bar coating method.

[0216] A coating liquid, with appropriately adjusted concentrations and additives, is applied to a transparent substrate to achieve appropriate leveling properties using a wire rod with a bar number that satisfies the desired thickness of the near-infrared absorbing layer and content of near-infrared absorbing particles. The coating liquid is then dried to remove the solvent, such as the liquid medium, and then cured by ultraviolet irradiation, thereby forming a coating layer serving as a near-infrared absorbing layer on the transparent substrate.

[0217] The drying conditions for the coating film vary depending on the types and proportions of the components and solvents used, but are generally between 60°C and 140°C for approximately 20 seconds and 10 minutes. There are no particular limitations on the UV exposure; for example, an ultraviolet exposure device such as an ultrahigh pressure mercury lamp can be used.

[0218] In addition, it is also possible to operate the adhesion between the substrate and the near-infrared absorbing layer, the smoothness of the coating film during coating, the dryness of the organic solvent, etc. by the front and back processes (front process, back process) of the formation of the near-infrared absorbing layer. As the above-mentioned front and back processes, for example, a surface treatment process of the substrate, a pre-baking (front heating of the substrate) process, a post-baking (post-heating of the substrate) process, etc. can be mentioned, and they can be appropriately selected. Preferably, the heating temperature in the pre-baking process and / or the post-baking process is 80°C or more and 200°C or less, and the heating time is 30 seconds or more and 240 seconds or less.

[0219] The method for producing the near-infrared absorbing transparent substrate of the present embodiment is not limited to the above method. As another configuration example of the method for producing the near-infrared absorbing transparent substrate of the present embodiment, a method having the following steps can also be mentioned.

[0220] The near-infrared absorbing particle dispersion described above is applied to the surface of a transparent substrate and then dried.

[0221] An adhesive coating and curing step is a step of coating and curing an adhesive using a solid medium such as a resin, a metal alkoxide, or a solid medium precursor on a surface coated with the near-infrared absorbing particle dispersion.

[0222] In this case, a film in which near-infrared absorbing particles are dispersed is formed on the surface of the transparent substrate through the steps of applying the near-infrared absorbing particle dispersion and drying. The near-infrared absorbing particle dispersion can be applied using the same method as described in the coating step of the method for producing the near-infrared absorbing transparent substrate.

[0223] Then, by applying a binder on the film in which the near-infrared absorbing particles are dispersed and curing the binder, the cured binder is arranged between the near-infrared absorbing particles, thereby forming a near-infrared absorbing layer.

[0224] The near-infrared absorbing transparent substrate may further have a coating layer on the surface of the near-infrared absorbing particle dispersion, that is, may also include a multilayer film.

[0225] The coating layer can be, for example, a coating film containing one or more oxides selected from Si, Ti, Zr, and Al. In this case, the coating layer can be formed by applying a coating liquid containing one or more alkoxides selected from Si, Ti, Zr, and Al, and partially hydrolyzed condensates of the alkoxides, onto the near-infrared absorbing layer, followed by heating.

[0226] By providing a coating layer, the coated component fills the gaps between the deposited near-infrared absorbing particles forming the first layer, thereby forming a film. This suppresses the refraction of visible light, thereby further reducing the haze value of the film and improving the visible light transmittance. Furthermore, the adhesion of the near-infrared absorbing particles to the substrate can be improved.

[0227] Here, as a method for forming a coating film composed of an alkoxide containing one or more of Si, Ti, Zr, and Al, or a partially hydrolyzed polycondensate thereof, on a film containing near-infrared absorbing particles alone or containing near-infrared absorbing particles, a coating method is preferred from the viewpoint of ease of film formation operation and cost.

[0228] The coating liquid used in the above-mentioned coating method can be suitably a coating liquid containing one or more alkoxides containing any one of Si, Ti, Zr, and Al, or partially hydrolyzed polycondensates of the alkoxides, in a solvent such as water or alcohol. The content of the alkoxides in the coating liquid is not particularly limited; for example, it is preferably 40% by mass or less, calculated as the oxide in the coating obtained after heating. Furthermore, an acid or base can be added as needed to adjust the pH.

[0229] By applying this coating liquid as a second layer onto a film containing near-infrared absorbing particles as a main component and heating it, an oxide film containing one or more selected from Si, Ti, Zr, and Al can be easily formed as a coating layer. An organosilazane solution is also preferably used as a binder component or a component of the coating liquid used in the coating liquid according to this embodiment.

[0230] The substrate heating temperature after application of the inorganic binder, coating film, near-infrared absorbing particle dispersion containing one or more metal alkoxides of Si, Ti, Zr, and Al, and their hydrolyzed polymers, and coating solution is not particularly limited. For example, the substrate heating temperature is preferably 100°C or higher, and more preferably at or above the boiling point of the solvent in the coating solution, such as the near-infrared absorbing particle dispersion.

[0231] This is because, if the substrate heating temperature is 100°C or higher, the polymerization reaction of the metal alkoxide or the hydrolyzed polymer of the metal alkoxide contained in the coating film is completed. Furthermore, if the substrate heating temperature is 100°C or higher, almost no water or organic solvent as a solvent remains in the film, and thus, these solvents do not cause a decrease in visible light transmittance in the heated film.

[0232] The thickness of the near-infrared-absorbing layer on the near-infrared-absorbing transparent substrate of this embodiment is not particularly limited, but is preferably 10 μm or less, and more preferably 6 μm or less. This is because a near-infrared-absorbing layer with a thickness of 10 μm or less not only exhibits sufficient pencil hardness and abrasion resistance but also avoids process abnormalities such as warping of the substrate film caused by volatilization of the solvent in the near-infrared-absorbing layer and curing of the adhesive.

[0233] (4-2) Near-infrared absorbing interlayer film and near-infrared absorbing laminate

[0234] The near-infrared absorbing laminate of this embodiment can have a laminated structure including the near-infrared absorbing particle dispersion and the transparent substrate described above. The near-infrared absorbing laminate of this embodiment can have the near-infrared absorbing particle dispersion and the transparent substrate described above as elements, and can be made into a laminated structure including these.

[0235] Examples of near-infrared absorbing laminates include a laminate comprising two or more transparent substrates and the aforementioned near-infrared absorbing particle dispersion. In this case, the near-infrared absorbing particle dispersion can be disposed between the transparent substrates to serve as a near-infrared absorbing interlayer.

[0236] In this case, specifically, as shown in the schematic cross-sectional view along the stacking direction of the transparent substrate and the near-infrared absorbing particle dispersion, Figure 13 As shown, the near-infrared absorbing laminate 120 can include a plurality of transparent substrates 1211 and 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 and 1212. Figure 13 , an example having two transparent substrates 1211 and 1212 is shown, but the present invention is not limited to this form.

[0237] The near-infrared absorbing interlayer film preferably has any shape of a sheet, a plate, or a film.

[0238] As the transparent substrate, one or more materials selected from plate glass, plate-shaped plastics, and film-shaped plastics that are transparent in the visible light region can be preferably used.

[0239] When plastic is used as the transparent substrate, the material of the plastic is not particularly limited and can be selected according to the intended use. For example, one or more resins selected from polycarbonate resins, acrylic resins, polyester resins, polyamide resins, vinyl chloride resins, olefin resins, epoxy resins, polyimide resins, ionomer resins, fluororesins, etc. can be used. In addition, polyethylene terephthalate resin can be preferably used as the polyester resin.

[0240] The transparent substrate may contain particles having a sunlight shielding function. As the particles having a sunlight shielding function, near-infrared absorbing particles having near-infrared shielding properties can be used.

[0241] By interposing the already described near-infrared absorbing particle dispersion as a constituent member of an intermediate layer sandwiched between multiple transparent substrates, a structure is obtained that suppresses the solar transmittance while having a more neutral hue of the transmitted color and can match the solar shielding of a near-infrared absorbing stack that can ensure transmittance at the detector wavelength.

[0242] Furthermore, the near-infrared absorbing laminate can be produced by bonding and integrating a plurality of transparent substrates facing each other with the near-infrared absorbing particle dispersion interposed therebetween using a known method.

[0243] When the near-infrared-absorbing particle dispersion described above is used as the near-infrared-absorbing interlayer film, the solid medium described in the near-infrared-absorbing particle dispersion can be used. However, from the perspective of improving the adhesion strength between the near-infrared-absorbing interlayer film and the transparent substrate, the solid medium is preferably a polyvinyl acetal resin.

[0244] The near-infrared absorbing interlayer film of this embodiment can be produced by the method for producing the near-infrared absorbing particle dispersion described above, and can be formed into any shape, for example, a sheet, plate, or film.

[0245] Furthermore, if the near-infrared absorbing interlayer film lacks sufficient flexibility and adhesion to the transparent substrate, it is preferable to add a liquid plasticizer for the dielectric resin. For example, if the dielectric resin used in the near-infrared absorbing interlayer film is polyvinyl acetal resin, the addition of a liquid plasticizer for the polyvinyl acetal resin is beneficial for improving adhesion to the transparent substrate.

[0246] As plasticizers, substances that are used as plasticizers for solid resins can be used. For example, plasticizers used in infrared shielding films made of polyvinyl acetal resin include plasticizers that are compounds of primary alcohols and organic acid esters, ester-based plasticizers such as polyol organic acid ester compounds, and phosphate-based plasticizers such as organic phosphoric acid-based plasticizers. Any of these plasticizers is preferably liquid at room temperature. Among these, plasticizers that are ester compounds synthesized from polyols and fatty acids are preferred.

[0247] 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 a carboxylic acid, a metal hydroxide, and a metal carbonate. The metal constituting the metal salt of a carboxylic acid, metal hydroxide, or metal carbonate is not particularly limited, but is preferably at least one selected from the group consisting of sodium, potassium, magnesium, calcium, manganese, cesium, lithium, rubidium, and zinc. The content of the at least one selected from the group consisting of a metal salt of a carboxylic acid, metal hydroxide, and metal carbonate in the near-infrared absorbing interlayer film is preferably from 1% to 100% by mass relative to the near-infrared absorbing particles.

[0248] Furthermore, the near-infrared absorbing interlayer film may, as needed, contain, in addition to the near-infrared absorbing particles already described, at least one type of particle selected from oxide particles, composite oxide particles, or boride particles containing two or more elements selected from the group consisting of Sb, V, Nb, Ta, W, Zr, F, Zn, Al, Ti, Pb, Ga, Re, Ru, P, Ge, In, Sn, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Tb, Lu, Sr, and Ca. The near-infrared absorbing interlayer film may contain such particles in an amount ranging from 5% to 95% by mass, with the total amount of the particles and the near-infrared absorbing particles being 100% by mass.

[0249] The near-infrared absorbing laminate may contain a UV absorber in at least one layer of the interlayer film disposed between the transparent substrates. Examples of the UV absorber include one or more compounds selected from the group consisting of compounds having a malonate 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.

[0250] It is a matter of course that the intermediate layer of the near-infrared absorbing laminate is preferably constituted only by the near-infrared absorbing intermediate film according to this embodiment.

[0251] The near-infrared-absorbing interlayer film described here is one embodiment of a near-infrared-absorbing particle dispersion. The near-infrared-absorbing particle dispersion according to this embodiment can naturally 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 be implemented as a standalone near-infrared-absorbing particle dispersion.

[0252] The near infrared absorbing laminate according to the present embodiment is not limited to the above-mentioned configuration in which the near infrared absorbing particle dispersion is arranged between transparent substrates, and any configuration may be employed as long as it has a laminated structure including the near infrared absorbing particle dispersion and transparent substrates.

[0253] [Example]

[0254] Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the following Examples.

[0255] (Evaluation method)

[0256] First, the evaluation methods in the following Examples and Comparative Examples will be described.

[0257] (Chemical Analysis)

[0258] Chemical analysis of the obtained near-infrared absorbing particles was performed by atomic absorption analysis (AAS) for Cs, by ICP optical emission spectrometry (ICP-OES) for W (tungsten), and by light element analysis (ON-836) from LECO Corporation for O.

[0259] (X-ray diffraction measurement)

[0260] X-ray diffraction measurement was performed by powder XRD measurement using Cu-Kα radiation using an X'Pert-PRO / MPD apparatus manufactured by Spectris Corporation.

[0261] (Optical properties of near-infrared absorbing transparent substrates)

[0262] The visible light transmittance (VLT) and sunlight transmittance (ST21) of the near-infrared absorbing transparent substrate are measured in accordance with ISO 9050 and JIS R 3106 (2019). Specifically, the transmittance is measured using a spectrophotometer U-4100 manufactured by Hitachi High-Tech (Co., Ltd.) and calculated by multiplying it by a coefficient corresponding to the spectrum of sunlight. When measuring the transmittance, the wavelength is measured at 5nm intervals for a range of 300nm to 2100nm. ＊ a ＊ b ＊ The color index was calculated according to JIS Z 8701 (1999) by using the tristimulus values ​​X, Y, and Z at a light source angle of 10° relative to a D65 standard light source, and was then determined from the tristimulus values ​​according to JIS Z 8729 (2004).

[0263] [Example 1]

[0264] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0265] A total of 20g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded so that the molar ratio of Cs2CO3:WO3 was 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, which serves as a raw material for a compound containing Cs and W.

[0266] The cesium tungsten oxide precursor powder was placed on an alumina boat and placed in a heated muffle furnace. While flowing a 50:50 by volume mixture of superheated steam and nitrogen, the temperature was raised to 550°C and held for 1 hour. The gas mixture is represented in Table 1 as 50% N₂ - 50% superheated H₂O. The gas supply was then changed to 100% by volume nitrogen. While flowing nitrogen, the temperature was maintained at 550°C for 0.5 hours, then raised to 800°C for 1 hour. The temperature was then lowered to room temperature, yielding a slightly greenish white powder (first heat treatment step).

[0267] The X-ray powder diffraction pattern of the white powder was identified as Cs4W 11 O 35 (ICDD 00-51-1891).

[0268] Next, the white powder was placed in a carbon boat in a tubular furnace. The temperature was raised in a 1% by volume H₂-Ar flow (represented as 1% H₂-Ar in Table 1) and maintained at 550°C for 1 hour for reduction. The supplied gas was then changed to 100% by volume Ar gas, and the temperature was maintained at 550°C for 30 minutes while Ar gas flowed. The temperature was then raised to 800°C for 1 hour, and then cooled to room temperature, yielding a light aqua-colored powder A (second heat treatment step).

[0269] The production conditions of the near-infrared absorbing particles are summarized in Table 1. Table 2 also shows the following evaluation results.

[0270] The XRD powder pattern of powder A obtained here is as follows Figure 2 As shown, the main phase is hexagonal Cs 0.32 WO3, and the second phase becomes orthorhombic Cs4W 11 O 35 The wide two-phase mixed pattern was obtained by chemical analysis of powder A. The Cs / W ratio was 0.33 in terms of molar ratio. The composition ratios of other components are shown in Table 2. The XRD powder pattern in this case was hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction lines of the two are mixed, but Cs4W 11 O 35 The diffraction lines of the α-ray diffraction pattern were observed to be slightly offset from the ideal positions and intensities. No data matching this diffraction pattern was found in the ICDD database.

[0271] When the powder was observed using a transmission electron microscope (HF-2200, manufactured by Hitachi High-Tech Co., Ltd.), Figure 4(A) shows the particles 40. The crystal structure of each particle is as follows Figure 4 As shown in the restricted field electron diffraction pattern (B), a single-phase structure was observed instead of a mixed structure in which two phases of hexagonal and orthorhombic crystals were separated. Figure 4 The electron diffraction image shown in (B) is a pattern corresponding to the

[0001] crystal band of a hexagonal crystal. The diffraction sites show the plane indices when viewed as a hexagonal crystal. If the corresponding plane spacing is calculated from the closest diffraction sites in the three directions, only the (01-10) plane spacing is With the values ​​of the other 2 directions, and In crystallography, negative indices are represented by a dash before the number, but for ease of description, a minus sign is placed before the number in this specification.

[0272] on the other hand, Figure 4 (C) shows an atomic image captured using the STEM-HAADF method (scanning electron high-angle dark field observation). In the HAADF method, larger atomic numbers and greater atomic density in the projection direction result in brighter and more intense atomic sites. Therefore, if the projection plane information matches the

[0001] crystal band, the atomic species in the image are identified. Figure 4 The strongest sites in (C) are W atoms, but they are arranged along the (01-10) plane. In the hexagonal crystal, the same arrangement is not observed along the equivalent (1-100) plane and (10-10) plane. Figure 4 Spots are observed in the (01-10) site direction of (C), so it can be seen that a large number of planar defects (W, O defects) are inserted only in the (01-10) plane, which is interpreted as an increase in the plane spacing of the (01-10) plane. If it is originally a hexagonal crystal, there are almost no defects introduced into the (01-10) plane, (1-100) plane, and (10-10) plane that intersect at 60°. Only a large number of planar defects are inserted in the (01-10) plane, which shows that the hexagonal symmetry is lost and modulated into an orthorhombic crystal. Figure 4 The regular position of the arrow 41 in (B) is roughly As described above, it is known that the near-infrared absorbing particles are single crystal particles of cesium tungstate having a pseudo-hexagonal crystal structure adjusted to an orthorhombic structure.

[0273] Furthermore, if the powder of the obtained near-infrared absorbing particles is irradiated with 25W Al-Kα X-rays by X-ray photoelectron spectroscopy (XPS-Versa Probe II manufactured by ULVAC-PHI) and the excited photoelectrons are observed, it can be seen that the O1s peak near 530.45eV has a shoulder on the high energy side. The component near 532.80eV is considered to have undergone peak separation due to H2O, and as a result, it is known that a large amount of OH2 is contained. In addition, by thermal desorption spectroscopy, it can be confirmed that OH and OH2 are discharged from the crystals in the temperature range of 500°C to 700°C during heating. Based on these observations, it is speculated that OH and OH2 are contained in the cesium tungstate of powder A, and if the voids in the pseudo-hexagonal crystals elongated along a single axis are considered, they invade the window voids of the hexagonal channels. It is believed that water and its decomposition products are introduced into the crystals by crystallization in superheated water vapor, but it is believed that the H generated at this time + 、H3O + ions compete with the positive W ions, causing some of the W ions to be released.

[0274] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0275] Next, 20% by mass of the prepared powder A, 10% by mass of an acrylic polymer dispersant having an amine-containing group as a functional group (hereinafter referred to as "dispersant a"), and 70% by mass of methyl isobutyl ketone (MIBK) as a solvent were weighed. These weighed materials were placed in a glass container along with 0.3 mm diameter silica beads and dispersed and pulverized for 5 hours using a paint shaker to obtain a dispersion A.

[0276] Here, the average particle size of the near-infrared absorbing particles in the dispersion A was measured (dispersed particle size measured by ELS-8000 manufactured by Otsuka Electronics Co., Ltd., which is a particle size measuring apparatus based on a dynamic light scattering method) and was found to be 31.4 nm.

[0277] 50 parts by mass of a UV-curable resin for a hard coat layer (Aronix UV-3701 manufactured by Toagosei) was mixed with 100 parts by mass of this dispersion A to prepare a near-infrared absorbing particle coating solution A. This near-infrared absorbing coating solution, which had been appropriately diluted, was then applied to a polyethylene terephthalate (PET) resin film (HPE-50 manufactured by Teijin, hereinafter referred to as "PET film") serving as a transparent film substrate using a bar coater to form a coating film. In other examples, the same PET film was used as the transparent substrate.

[0278] The PET film with the coating was dried at 80°C for 5 minutes to evaporate the organic solvent serving as the liquid medium. The hard coat layer was then cured with an ultraviolet curable resin using a high-pressure mercury lamp to produce a near-infrared absorbing film A having a coating layer containing near-infrared absorbing particles. The coating layer was a near-infrared absorbing dispersion, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0279] The transmittance of the obtained near infrared absorbing film A was measured using a U-4100 spectrophotometer manufactured by Hitachi High-Tech Co., Ltd., and a spectral transmittance spectrum was obtained. Figure 5 .

[0280] according to Figure 5 The graph shown shows strong absorption in the near-infrared region with the bottom of the transmittance around a wavelength of 2100 nm, and high transmittance in the visible light region (380 nm to 780 nm).

[0281] The visible light transmittance (VLT) and the solar transmittance (ST21) were measured to be VLT = 72.31% and ST21 = 46.47%, respectively, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect.

[0282] The color index of near infrared absorbing film A is L ＊ =87.91, a ＊ =-2.72, b ＊ =9.33, the blue is very weak and close to neutral color, that is, it shows a neutral tone. This is clear from the following situation: Figure 5 As shown in the comparison of the transmission spectra of the blue CWO dispersion film shown in Comparative Example 3, the transmittance is significantly lower than that of the CWO dispersion film near the blue wavelength of 400 nm, and the transmittance is significantly higher than that of the CWO dispersion film near the red wavelength of 700 nm.

[0283] The color index value is as follows Figure 7 As shown, it can be seen that in L ＊ =88 sections, fully satisfying b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0. In addition, Figure 7 In the figure, line 71 refers to b ＊ =0, straight line 72 refers to b ＊ =1.6×a ＊ +8.0.

[0284] In addition, Figure 8 As shown, we can see that L ＊= T900 in the 88 section is 39.84%, which fully satisfies T900 ≥ 10%. In addition, the solar shielding characteristic ST21 satisfies ST21 ≤ 67%, and further satisfies T900 ≥ 1.4 × ST21 - 41.0, indicating sufficient transmittance at the detector wavelength. Figure 8 In the figure, straight line 81 indicates T900=10, straight line 82 indicates ST21=67, and straight line 83 indicates T900=1.4×ST21-41.0.

[0285] [Comparative Example 1]

[0286] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0287] The cesium tungsten oxide precursor powder obtained in Example 1 was placed in a carbon boat and heated in the atmosphere using a tubular furnace to 850°C for 20 hours. The mixture was then cooled to room temperature and crushed and mixed using a pestle. The mixture was then heated again in the atmosphere to 850°C for 20 hours and cooled to room temperature to obtain an extremely thin, greenish white powder i. The X-ray powder diffraction pattern of the powder i is shown below. Figure 2 As shown, slightly mixed with Cs6W 11 O 36 , but roughly identified as Cs4W 11 O 35 Single phase (ICDD0-51-1891). Chemical analysis of powder i showed Cs / W = 0.36. The composition ratios of other components are shown in Table 2.

[0288] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0289] Dispersion liquid i was obtained by dispersing and pulverizing in the same manner as in Example 1 except that powder i was used. Dispersion liquid i was off-white in color, and the average particle size of the near-infrared absorbing particles in dispersion liquid i was 32.0 nm.

[0290] In the same manner as in Example 1, an ultraviolet curable resin was added to and mixed with the dispersion i to obtain a coating liquid i, and then a near infrared ray absorbing film i was obtained. The transmittance spectrum of the near infrared ray absorbing film i is shown in FIG. Figure 5 and Figure 6 The spectral characteristics at this time showed that VLT = 73.33% and ST21 = 78.73%, indicating that there was almost no infrared absorption effect.

[0291] It can be seen that the Hunter color index is ＊ =88 section, showing a ＊ =0.70, b ＊ =8.53. These values ​​are as follows Figure 7As shown, b is not satisfied ＊ ≥1.6×a ＊ +8.0. L ＊ = T900 in the 88 section is 96.20%, which has a large permeability and fully meets T900 ≥ 10%, but Figure 8 In the figure, it is plotted on the right side outside the figure, and the solar shielding characteristics do not meet ST21≤67% at all.

[0292] [Comparative Example 2]

[0293] A dispersion of In2O3:Sn (hereinafter referred to as "ITO"), a colorless, transparent, neutral-toned transparent conductive oxide, was prepared. ITO particles are known to have a neutral hue, but depending on the reduction method and production method, they can vary from slightly bluish to brown. Here, ITO powder (powder ii) manufactured by ENAM, which has a nearly pure, transparent color, was used.

[0294] Dispersion liquid ii was obtained by dispersing and pulverizing in the same manner as in Example 1 except that this powder ii was used. The color of dispersion liquid ii was aqua color, and the average particle size of the particles in dispersion liquid ii was 30.2 nm.

[0295] The same steps as those in Example 1 were followed by adding and mixing the ultraviolet curing resin into the dispersion ii to obtain the coating solution ii, and then obtaining the near infrared ray absorbing film ii. The transmission spectrum of the near infrared ray absorbing film ii is shown in FIG. Figure 5 、 Figure 6 As shown, a curve with a peak near 600 nm shows high red wavelength transmittance. The spectral characteristics at this point show VLT = 72.33% and ST21 = 45.94%, confirming infrared absorption. However, these infrared absorption characteristics are low in the examples.

[0296] Hunter color index in L ＊ =88 section, showing a ＊ =-2.04, b ＊ =13.68. These values ​​are as follows Figure 7 As shown, in L ＊ =88 sections, meeting b ＊ ≥1.6×a ＊ +8.0, confirming the neutrality of the tones.

[0297] L ＊ = T900 in the 88 section is 46.39%, which has a large transmittance and fully meets T900 ≥ 10%. In addition, the sunlight shielding characteristics are as follows Figure 8As shown, it is found that ST21 ≤ 67% and T900 ≥ 1.4 × ST21 - 41.0 are also satisfied. However, ST21 is higher than that of the product of the present invention, and the solar shielding properties are lower than those of the product of the present invention. Furthermore, it is found that the amount of ITO fine particles required to achieve the same solar shielding properties is approximately five times that of CPT particles, requiring more ITO raw material.

[0298] [Comparative Example 3]

[0299] The cesium tungsten oxide precursor powder obtained in Example 1 was added to a carbon boat and maintained at 550°C for 2 hours under a 1% by volume H2 gas flow with N2 gas as a carrier. The flow was then changed to 100% by volume N2 gas flow, maintained for 1 hour, then raised to 800°C, maintained for 1 hour, and slowly cooled to room temperature to obtain powder iii. The color of powder iii was dark blue. The X-ray powder diffraction pattern of powder i is shown in FIG. Figure 2 As shown, it was identified as Cs 0.32 WO3 single phase (ICDD 0-81-1244) is a hexagonal cesium tungsten oxide. Chemical analysis of powder iii showed Cs / W = 0.34. The composition ratios of other components are shown in Table 2.

[0300] Dispersion liquid iii was obtained by dispersing and pulverizing in the same manner as in Example 1 except that this powder iii was used. The color of dispersion liquid iii was blue, and the average particle size of the particles in dispersion liquid iii was 24.6 nm.

[0301] The same steps as those in Example 1 were followed by adding and mixing the ultraviolet curing resin into the dispersion iii to obtain the coating solution iii, and then obtaining the near infrared ray absorbing film iii. The transmittance spectrum of the near infrared ray absorbing film iii is shown in FIG. Figure 5 、 Figure 6 As shown, a curve with high transmittance at blue wavelengths was obtained, and as spectral characteristics, VLT = 72.19% and ST21 = 32.88% were obtained, confirming a very excellent infrared absorption effect.

[0302] However, the Hunter color index is Figure 7 As shown, in L ＊ =88 section, showing a ＊ =-6.57, b ＊ = -1.25, b ＊ The value becomes negative, showing blue as a striking hue. However, if b ＊ ≥1.6×a ＊ +8.0.

[0303] like Figure 8As shown, the solar shielding property fully satisfies ST21≤67%, confirming the excellent solar shielding property, but does not satisfy T900≥1.4×ST21-41.0. In addition, L ＊ = T900 in the 88 section is as small as 4.85%, and the detector wavelength transmittance is low.

[0304] Furthermore, the near infrared absorbing film iii was placed in a constant temperature and humidity chamber and kept at a temperature of 85°C and a relative humidity of 90% for 13 days. The transmission spectrum was measured and compared with the spectrum before maintenance (initial in the figure). The results are shown in Figure 9B .

[0305] [Comparative Examples 4 to 8]

[0306] By appropriately changing the MIBK dilution rate of the near infrared absorbing particle coating solution iii prepared in Comparative Example 3, a series of near infrared absorbing films iv to viii with different particle concentrations were prepared. The values ​​of the optical properties of the series are summarized in Table 2. The color tones of these films are shown in Figure 7 L shown ＊ = a of section 88 ＊ -b ＊ Observe in space, then it is b ＊ <0, the blue hue is not improved. That is, even if the blue CWO dispersion is simply diluted, the blue color remains, suggesting that in order to improve the hue, the physical properties of the material itself need to be changed. Figure 8 As shown, the infrared absorption was too weak in Comparative Examples 4 and 5, and T900≧1.4×ST21-41.0 was not satisfied. Except for Comparative Examples 4 and 5, T900<10, indicating an excessively low value.

[0307] By changing the concentration of the near infrared absorbing particles in the film, the color tone (especially a ＊ ), T900, and ST21 change, it can be seen that in order to satisfy all the requirements in a good balance, the physical properties and electronic structure of the material itself need to be changed.

[0308] [Example 2]

[0309] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0310] The cesium tungsten oxide precursor powder produced in Example 1 was placed on an alumina boat in a heated muffle furnace and heated to 150°C while flowing 100% by volume nitrogen gas. The supplied gas was changed to a mixture of superheated steam, hydrogen, and nitrogen at a volume ratio of 50:1:49 (expressed in Table 1 as % H2-49% N2-50% superheated H2O). While flowing this mixed gas, the temperature was raised to 550°C and held for 1 hour. The mixture was then cooled directly to room temperature to obtain a water-colored powder B (first heat treatment step).

[0311] The X-ray powder diffraction pattern of the powder is as follows Figure 2 As shown, it shows a broad diffraction line, hexagonal Cs 0.32 WO3 is the main phase, but orthorhombic Cs4W 11 O 35 With pyrochlore phase (Cs2O) 0.44 The diffraction lines of the W2O6 phase are a pattern of heterogeneous mixing. The diffraction lines of the pyrochlore phase are broad, and the reflection positions are slightly offset. It is believed that O, OH, OH2, and OH3 derived from water are absorbed into the pyrochlore cavity. The (111) plane of the cubic pyrochlore phase has a hexagonal symmetry similar to the bottom plane of the hexagonal crystal, and the pyrochlore cavity is equivalent to the gap between the hexagonal cavity and the trigonal cavity in the hexagonal crystal. In other examples, the presence of a small amount of mixed reflections of the pyrochlore phase in the XRD powder pattern is often observed.

[0312] Furthermore, when one particle in this powder was observed from the (0001) direction using a transmission electron microscope, the electron diffraction image showed a single short prism site with weak speckling, indicating that the hexagonal crystal is an orthorhombic crystal modulated by prism defects.

[0313] Chemical analysis of powder B showed Cs / W = 0.32. The composition ratios of other components are shown in Table 2.

[0314] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0315] A dispersion B was obtained in the same manner as in Example 1 except that the prepared powder B was used.

[0316] The average particle size of the near-infrared absorbing particles in the dispersion B was measured by a dynamic light scattering method and was found to be 26.3 nm.

[0317] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion B was used. This produced a near-infrared absorbing film B having a coating layer containing near-infrared absorbing particles. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0318] The spectral transmittance spectrum of the obtained near infrared absorbing film B obtained by using the U-4100 spectrophotometer of Hitachi High-Tech Co., Ltd. is shown in FIG. Figure 5 .according to Figure 5 The spectrum shown confirms strong absorption in the near-infrared region, with the transmittance bottom near 1405 nm, and transmission in the visible region between 380 nm and 780 nm. Transmittance in the blue region is significantly reduced compared to the near-infrared absorbing film iii of Comparative Example 3. Furthermore, near-infrared transmission near 900 nm is significantly reduced compared to the near-infrared absorbing film ii using ITO of Comparative Example 2.

[0319] The visible light transmittance (VLT) and the solar transmittance (ST21) were measured to be VLT = 72.20% and ST21 = 39.29%, respectively, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect.

[0320] The color index of the near infrared absorbing film B is L ＊ =87.93, a ＊ =-4.02, b ＊ = 4.29, the blue is weak and close to neutral, that is, it shows a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shading when VLT = 70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0321] In addition, Figure 8 As shown, we can see that L ＊ = T900 in the 88 section is 16.32%, which satisfies T900≥10%, and therefore has detector wavelength transmittance. In addition, while the sunlight shielding characteristics satisfy ST21≤67%, it fully satisfies T900≥1.4×ST21-41.0 and has sufficient detector wavelength transmittance.

[0322] [Example 3]

[0323] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0324] The water-colored powder B obtained in Example 2 was placed on a carbon boat and held at 550°C for 2 hours in a 1% by volume H2-Ar gas flow. The gas supply was then changed to 100% by volume nitrogen gas, and the mixture was held at 550°C for 0.5 hours while nitrogen flowed. The temperature was then raised and held at 800°C for 1 hour. The mixture was cooled to room temperature to obtain water-colored powder C (second heat treatment step).

[0325] Chemical analysis of powder C revealed a Cs / W ratio of 0.31 in terms of molar mass. Table 2 shows the composition ratios of other components.

[0326] The X-ray powder diffraction pattern of powder C is as follows Figure 2 As shown in the figure, compared with Examples 1 and 2, the diffraction lines are broad, showing hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction line mixing pattern of Cs4W 11 O 35 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0327] Observation of one particle in this powder from the (0001) direction using a transmission electron microscope revealed that the electron diffraction image showed only a single short prism site with weak speckling, indicating that the hexagonal crystal is an orthorhombic crystal modulated by prism defects.

[0328] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0329] A 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 the dispersion C was measured by a dynamic light scattering method and was found to be 29.6 nm.

[0330] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion C was used. A near-infrared absorbing film C having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0331] The spectral transmittance spectrum of the obtained near infrared absorbing film C is shown in Figure 5Strong absorption of the near-infrared region with a base around 1800nm ​​and transmission in the visible light region were confirmed. The transmittance in the blue and red regions decreased and increased, respectively, compared to the near-infrared absorbing film iii of Comparative Example 3, and the hue was improved to a neutral color. Furthermore, it was confirmed that the transmission of near-infrared light around 900nm was significantly reduced compared to the near-infrared absorbing film ii using ITO of Comparative Example 2, demonstrating a strong near-infrared absorption effect compared to the near-infrared absorbing film ii using ITO.

[0332] The results were VLT = 72.31% and ST21 = 43.45%, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film C is L ＊ =87.93, a ＊ =-3.24, b ＊ = 8.19, the blue is weak and close to neutral, that is, it shows a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shading when VLT = 70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0333] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 30.10%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and T900≥1.4×ST21-41.0.

[0334] [Example 4]

[0335] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0336] The light aqua powder B obtained in Example 2 was placed on a carbon boat, heated in a 100% by volume Ar gas flow, and maintained at 800° C. for 1 hour. The temperature was then lowered to room temperature to obtain a light aqua powder D.

[0337] The X-ray powder diffraction pattern of powder D is as follows: Figure 2 As shown, it has broad diffraction lines, showing hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The pattern of the diffraction line mixture. Cs4W 11 O 35The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0338] Observation of one particle in this powder from the (0001) direction using a transmission electron microscope revealed that the electron diffraction image showed only a single short prism site with weak speckling, indicating that the hexagonal crystal is an orthorhombic crystal modulated by prism defects.

[0339] Chemical analysis of powder D showed Cs / W = 0.33. The composition ratios of other components are shown in Table 2.

[0340] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0341] A dispersion D was obtained in the same manner as in Example 1 except that the prepared powder D was used.

[0342] The average particle size of the near-infrared absorbing particles in the dispersion D was measured by a dynamic light scattering method and was found to be 32.1 nm.

[0343] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion D was used. A near-infrared absorbing film D having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0344] The spectral transmittance spectrum of the obtained near infrared absorbing film D is shown in Figure 5 Strong absorption of the near-infrared region with a base around 1950nm and transmission in the visible light region were confirmed. The transmittance in the blue and red regions decreased and increased, respectively, compared to the near-infrared absorbing film iii of Comparative Example 3, and the hue was improved to a neutral color. In addition, it was confirmed that the transmission of near-infrared light around 900nm was significantly reduced compared to the near-infrared absorbing film ii using ITO of Comparative Example 2, and that it had a strong near-infrared absorption effect compared to the near-infrared absorbing film ii using ITO.

[0345] The results were VLT = 72.20%, ST21 = 48.19%, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film D is L ＊ =87.85, a ＊ =-2.11, b ＊ = 8.75, the blue is weak and close to neutral, that is, it shows a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shading when VLT = 70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0346] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 42.56%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and T900≥1.4×ST21-41.0.

[0347] [Example 5]

[0348] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0349] The light aqua powder B obtained in Example 2 was placed on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. The supplied gas was changed to 1% by volume H₂-Ar, and the temperature was maintained at 800°C for 10 minutes in this gas flow. The temperature was then lowered to room temperature, yielding a light aqua powder E.

[0350] The X-ray powder diffraction pattern of powder E is as follows Figure 2 As shown, it has broad diffraction lines, showing hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The pattern of the diffraction line mixture. Cs4W 11 O 35 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0351] Observation of one particle in this powder from the (0001) direction using a transmission electron microscope revealed that the electron diffraction image showed only a single short prism site with weak speckling, indicating that the hexagonal crystal is an orthorhombic crystal modulated by prism defects.

[0352] Chemical analysis of powder E showed Cs / W = 0.32. The composition ratios of other components are shown in Table 2.

[0353] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0354] A dispersion E was obtained in the same manner as in Example 1 except that the prepared powder E was used.

[0355] The average particle size of the near-infrared absorbing particles in the dispersion E was measured by a dynamic light scattering method and was found to be 25.0 nm.

[0356] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion E was used. A near-infrared absorbing film E having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0357] The spectral transmittance spectrum of the obtained near infrared absorbing film E is shown in Figure 6 Strong absorption of the near-infrared region with a base around 1600nm and transmission in the visible region were confirmed. The transmittance in the blue and red regions decreased and increased, respectively, compared to the near-infrared absorbing film iii of Comparative Example 3, and the hue was improved to a neutral color. Furthermore, it was confirmed that the transmission of near-infrared light around 900nm was significantly reduced compared to the near-infrared absorbing film ii using ITO of Comparative Example 2, demonstrating a strong near-infrared absorption effect compared to the near-infrared absorbing film ii using ITO.

[0358] The results are VLT = 72.38%, ST21 = 36.29%, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film E is L ＊ =88.12, a ＊ =-5.17, b ＊ = 3.79, the blue is weak and close to neutral, that is, it shows a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shading when VLT = 70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0359] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 11.80%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and T900≥1.4×ST21-41.0.

[0360] [Example 6]

[0361] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0362] Dispersion F was obtained in the same manner as in Example 1 except that the water-colored powder E obtained in Example 5 was used and the dispersion time was doubled.

[0363] The average particle size of the near-infrared absorbing particles in the dispersion liquid F was measured by a dynamic light scattering method and was found to be 23.7 nm.

[0364] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion F was used. A near-infrared absorbing film F having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0365] The spectral transmittance spectrum of the obtained near infrared absorbing film F is shown in Figure 6 . Strong absorption in the near-infrared region with a base near 1600 nm and transmittance in the visible region can be confirmed. The spectrum is almost the same as that of the near-infrared absorbing film E produced in Example 5, but the difference is that the transmittance in the blue region has increased slightly. As the average particle size decreases with increasing dispersion time, the transmittance of blue wavelengths increases due to the effect of Mie scattering. Compared with Example 5, the transmittance spectrum confirms that the hue has slightly increased in blue, but the hue has been improved compared to the near-infrared absorbing film of Comparative Example 3.

[0366] The results were VLT = 72.28%, ST21 = 36.40%, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film F is L ＊ =88.15, a ＊ =-5.00, b ＊ =0.93, and compared with the near-infrared absorbing film iii of Comparative Example 3, the blue color is weaker and closer to neutral color, that is, it shows a neutral color tone.

[0367] These values ​​are Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0368] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 11.24%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and T900≥1.4×ST21-41.0.

[0369] [Example 7]

[0370] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0371] The light aqua powder B obtained in Example 2 was placed on a carbon boat and held at 500°C for 30 minutes in a 1 vol% H2-Ar gas flow. Next, the gas supply was changed to 100 vol% nitrogen gas and held at 550°C for 30 minutes while nitrogen flowed. The temperature was then raised further and held at 800°C for 1 hour. The temperature was then lowered to room temperature, yielding a light aqua powder G.

[0372] The X-ray powder diffraction pattern of powder G is as follows Figure 2 As shown, it has broad diffraction lines, showing hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The pattern of the diffraction line mixture. Cs4W 11 O 35 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0373] Observation of one particle in this powder from the (0001) direction using a transmission electron microscope revealed that the electron diffraction image showed only a single short prism site with weak speckling, indicating that the hexagonal crystal is an orthorhombic crystal modulated by prism defects.

[0374] Chemical analysis of powder G showed Cs / W = 0.31. The composition ratios of other components are shown in Table 2.

[0375] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0376] A dispersion G was obtained in the same manner as in Example 1 except that the prepared powder G was used.

[0377] The average particle size of the near-infrared absorbing particles in the dispersion liquid G was measured by a dynamic light scattering method and was found to be 31.8 nm.

[0378] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion G was used. A near-infrared absorbing film G having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0379] The spectral transmittance spectrum of the obtained near infrared absorbing film G is shown in Figure 6. It was possible to confirm strong absorption in the near-infrared region with a base near 1850nm and transmission in the visible light region. The transmittance in the blue region and the red region decreased and increased, respectively, compared to the near-infrared absorbing film iii of Comparative Example 3, and the hue was improved to a neutral color. In addition, it was confirmed that the transmission of near-infrared light near 900nm was significantly reduced compared to the near-infrared absorbing film ii using ITO of Comparative Example 2, and that it had a strong near-infrared absorption effect compared to the near-infrared absorbing film ii using ITO.

[0380] The results were VLT = 72.29%, ST21 = 41.88%, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect. The color index of the near-infrared absorption film G is L ＊ =87.94, a ＊ =-3.54, b ＊ =7.59, the blue is weak and close to neutral, that is, it shows a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shading when VLT=70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0381] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 26.36%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and T900≥1.4×ST21-41.0.

[0382] The near infrared absorbing film G was placed in a constant temperature and humidity chamber and kept at a temperature of 85°C and a relative humidity of 90% for 15 days. The transmission spectrum was measured and compared with the spectrum before the maintenance. Figure 9A As described above, the same test was conducted on the near infrared absorbing film iii prepared in Comparative Example 3 (maintained for 13 days) and the spectrum was compared with that before the test. Figure 9A 、 Figure 9B As shown, in the near infrared absorbing film G of Example 7, the change in ST21 was 0.04%, which was almost unchanged. However, in the near infrared absorbing film iii of Comparative Example 3, a partial decrease in the near infrared absorption intensity was observed, and ST21 changed by 3.47%.

[0383] [Example 8]

[0384] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded so that the molar ratio of Cs2CO3:WO3 was 1:10. The resulting kneaded mixture was placed in a carbon boat and dried at 110°C in air for 12 hours. This yielded a cesium tungsten oxide precursor powder, which serves as a raw material for a compound containing Cs and W.

[0385] Furthermore, the first heat treatment step was performed under the same conditions as in Example 2 except that the above-mentioned cesium tungsten oxide precursor powder was used.

[0386] The powder obtained in the first heat treatment step was placed on a carbon boat and heated to 800°C in a 100% by volume Ar flow. The supplied gas was then changed to a 1% by volume H2-Ar flow, and the temperature was maintained at 800°C for 10 minutes while this gas flowed. The temperature was then lowered to room temperature, yielding a water-colored powder H.

[0387] The X-ray powder diffraction pattern of powder H has broad diffraction lines, showing hexagonal Cs 0.20 WO3(ICDD0-083-1333) and orthorhombic Cs4W 11 O 35 The pattern of the diffraction line mixture. Cs4W 11 O 35 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0388] Observation of one particle in the powder from the (0001) direction using a transmission electron microscope revealed that the electron diffraction image showed only a single short prism site with weak speckling, indicating that the hexagonal crystals were orthorhombic crystals modulated by prism defects.

[0389] Chemical analysis of powder H showed Cs / W = 0.20. The composition ratios of other components are shown in Table 2.

[0390] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0391] A dispersion H was obtained in the same manner as in Example 1 except that the prepared powder H was used.

[0392] The average particle size of the near-infrared absorbing particles in the dispersion H was measured by a dynamic light scattering method and was found to be 28.6 nm.

[0393] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion H was used. A near-infrared absorbing film H having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0394] The spectral transmittance of the obtained near infrared absorbing film H was measured to be VLT = 72.32% and ST21 = 46.98%, indicating that it is transparent in visible light and has a strong near infrared absorbing effect. The color index of the near infrared absorbing film H is L ＊ =88.04, a ＊ =-2.40, b ＊ = 8.51, the blue is weak and close to neutral, that is, it shows a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shading when VLT = 70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0395] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 38.30%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and T900≥1.4×ST21-41.0.

[0396] [Example 9]

[0397] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded so that the molar ratio of Cs2CO3:WO3 was 3:10. The resulting kneaded 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, which serves as a raw material for a compound containing Cs and W.

[0398] Furthermore, the first heat treatment step was performed under the same conditions as in Example 2 except that the above-mentioned cesium tungsten oxide precursor powder was used.

[0399] The powder obtained in the first heat treatment step was placed on a carbon boat and heated to 800° C. in a 100% by volume Ar gas flow. The supplied gas was then changed to 1% by volume H 2 -Ar, and the temperature was maintained at 800° C. for 10 minutes while this gas flowed. The temperature was then lowered to room temperature, yielding a water-colored powder I.

[0400] The X-ray powder diffraction pattern of powder I has broad diffraction lines, rhombohedral Cs6W 11 O 36 、Cs 8.5 W 15 O 48 The main phase shows hexagonal Cs 0.32 WO3, tetragonal Cs2W3O 10 The diffraction lines of Cs6W are slightly mixed. 11 O 36 、Cs 8.5 W 15 O 48 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0401] Observation of one particle of this powder using a transmission electron microscope from the (0001) direction revealed that the positions of the three prism facets in the electron diffraction image differed beyond the experimental error range. This suggests that the hexagonal crystals are primarily rhombohedral crystals modulated by basal defects.

[0402] Chemical analysis of powder I showed Cs / W = 0.59. The composition ratios of other components are shown in Table 2.

[0403] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0404] A dispersion liquid I was obtained in the same manner as in Example 1 except that the prepared powder I was used.

[0405] The average particle size of the near-infrared absorbing particles in the dispersion liquid I was measured by a dynamic light scattering method and was found to be 30.4 nm.

[0406] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion I was used. A near-infrared absorbing film I having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0407] The spectral transmittance of the obtained near infrared absorbing film I was measured to be VLT = 72.27% and ST21 = 43.25%, indicating that it is transparent in visible light and has a strong near infrared absorbing effect. The color index of the near infrared absorbing film I is L ＊ =87.97, a ＊ =-3.70, b ＊ = 6.61, the blue is weak and close to neutral, that is, it shows a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shading when VLT = 70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0408] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 28.51%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and T900≥1.4×ST21-41.0.

[0409] [Example 10]

[0410] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed and mixed at a molar ratio of Cs2CO3:WO3 = 2:11. The mixture was then placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, which serves as a raw material for a compound containing Cs and W.

[0411] Furthermore, the first heat treatment step was performed under the same conditions as in Example 2 except that the above-mentioned cesium tungsten oxide precursor powder was used, thereby obtaining a light green powder J.

[0412] The X-ray powder diffraction pattern of powder J has broad diffraction lines, indicating a pyrochlore phase (Cs2O) 0.44 W2O6 is the main phase, in which hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 The diffraction lines of (Cs2O) are slightly mixed. 0.44 W2O6 and Cs4W 11 O 35 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0413] Transmission electron microscopic observation of the powder revealed an electron diffraction pattern of a cubic crystal.

[0414] Chemical analysis of powder J showed Cs / W = 0.36. The composition ratios of other components are shown in Table 2.

[0415] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0416] A dispersion J was obtained in the same manner as in Example 1 except that the prepared powder J was used.

[0417] The average particle size of the near-infrared absorbing particles in the dispersion J was measured by a dynamic light scattering method and was found to be 31.6 nm.

[0418] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion J was used. A near-infrared absorbing film J having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0419] The spectral transmittance of the obtained near infrared absorbing film J was measured to be VLT = 72.37% and ST21 = 50.79%, indicating that it is transparent in visible light and has a strong near infrared absorbing effect. The color index of the near infrared absorbing film J is L ＊ =87.87, a ＊ =-1.44, b ＊ = 11.06, the blue is extremely weak and close to neutral, that is, it shows a neutral tone. For the thin dispersion film of the present near-infrared absorbing particles used for automobile window shading when VLT = 70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0420] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 40.60%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and T900≥1.4×ST21-41.0.

[0421] [Example 11]

[0422] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0423] Powder J prepared in Example 10 was placed on a carbon boat and heated to 800° C. while flowing 100% by volume Ar gas. The supplied gas was then changed to 1% by volume H 2 -Ar, and the temperature was maintained at 800° C. for 10 minutes while flowing this gas. The temperature was then lowered to room temperature to obtain a water-colored powder K.

[0424] The X-ray powder diffraction pattern of the powder is as follows Figure 3 As shown, hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 The diffraction line mixing pattern of Cs4W 11 O 35 、Cs6W 11 O 36 、Cs 8.5 W 15 O 48 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0425] Observation of one particle of this powder using a transmission electron microscope from the (0001) direction revealed that the positions of the three prism facets in the electron diffraction image differed beyond the experimental error range. This suggests that the hexagonal crystals are primarily rhombohedral crystals modulated by basal defects.

[0426] Chemical analysis of powder K showed Cs / W = 0.36. The composition ratios of other components are shown in Table 2.

[0427] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0428] A dispersion K was obtained in the same manner as in Example 1 except that the prepared powder K was used.

[0429] The average particle size of the near-infrared absorbing particles in the dispersion K was measured by a dynamic light scattering method and was found to be 27.5 nm.

[0430] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion K was used. A near-infrared absorbing film K having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0431] The spectral transmittance spectrum of the obtained near-infrared absorbing film K obtained by using the U-4100 spectrophotometer of Hitachi High-Tech Co., Ltd. is shown in FIG. Figure 6 .according to Figure 6 The spectrum shown confirms strong absorption in the near-infrared region, with the transmittance bottom near 1650 nm, and transmission in the visible region between 380 nm and 780 nm. Transmittance in the blue and red regions decreases and increases, respectively, compared to the near-infrared absorbing film III of Comparative Example 3, resulting in an improvement in color tone to a neutral color. Furthermore, transmission of near-infrared light near 900 nm is significantly increased compared to the near-infrared absorbing film III of Comparative Example 3, demonstrating strong transmittance at the detector wavelength.

[0432] The visible light transmittance (VLT) and the solar transmittance (ST21) were measured to be VLT = 72.36% and ST21 = 44.01%, respectively, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect.

[0433] The color index of the near infrared absorbing film K is L ＊ =88.10,a ＊ =-2.72, b ＊ =7.05, the blue color is extremely weak and close to neutral color, that is, it shows a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shading when VLT=70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0434] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 27.21%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and fully satisfy T900≥1.4×ST21-41.0.

[0435] [Example 12]

[0436] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0437] Powder J prepared in Example 10 was placed on a carbon boat and maintained at 500°C for 30 minutes in a 1 vol% H2-Ar gas flow. The supplied gas was then changed to 100 vol% nitrogen gas, and the mixture was maintained at 800°C for 1 hour while flowing this nitrogen gas. The mixture was then cooled to room temperature to obtain a water-colored powder L.

[0438] The X-ray powder diffraction pattern of the powder is as follows Figure 3 As shown, hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 The diffraction line mixing pattern of Cs4W 11 O 35 、Cs6W 11 O 36 、Cs 8.5 W 15 O 48 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0439] Observation of one particle of this powder using a transmission electron microscope from the (0001) direction revealed that the positions of the three prism facets in the electron diffraction image differed beyond the experimental error range. This suggests that the hexagonal crystals are primarily rhombohedral crystals modulated by basal defects.

[0440] Chemical analysis of powder L showed Cs / W = 0.35. The composition ratios of other components are shown in Table 2.

[0441] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0442] Dispersion liquid L was obtained in the same manner as in Example 1 except that the prepared powder L was used.

[0443] The average particle size of the near-infrared absorbing particles in the dispersion L was measured by a dynamic light scattering method and was found to be 28.6 nm.

[0444] A coating film was formed on a PET film, and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion L was used. A near-infrared absorbing film L having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0445] The spectral transmittance of the obtained near-infrared absorbing film L was measured to find that it was VLT = 72.35% and ST21 = 60.85%, indicating that it was transparent to visible light and had a strong near-infrared absorbing effect.

[0446] The color index of the near infrared absorbing film L is L ＊ =87.89, a ＊ =-0.44, b ＊ = 9.26, the blue is extremely weak and close to neutral color, showing a neutral tone. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0447] In addition, L ＊ = T900 in the 88 section is 64.02%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and fully satisfy T900≥1.4×ST21-41.0.

[0448] [Example 13]

[0449] A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed and mixed so that the molar ratio of Cs2CO3:WO3 was 1:5. The mixture was then placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, which serves as a raw material for a compound containing Cs and W.

[0450] The precursor powder was placed on an alumina boat and placed in a heated muffle furnace. The temperature was raised to 150°C while flowing 100% by volume nitrogen gas. The supplied gas was changed to a mixture of superheated steam, hydrogen, and nitrogen at a volume ratio of 50:1:49. The temperature was raised to 550°C while flowing this mixed gas and maintained for 1 hour. The temperature was then directly lowered to room temperature to obtain a water-colored powder M (first heat treatment step).

[0451] The X-ray powder diffraction pattern of powder M has broad diffraction lines, and the same pattern as that of Example 10 is obtained. That is, the pyrochlore phase (Cs2O) 0.44 W2O6 is the main phase, in which hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 The diffraction lines of (Cs2O) are slightly mixed. 0.44 W2O6 and Cs4W 11O 35 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0452] Transmission electron microscopic observation of the powder revealed an electron diffraction pattern of a cubic crystal.

[0453] Chemical analysis of powder M showed Cs / W = 0.40. The composition ratios of other components are shown in Table 2.

[0454] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0455] A dispersion M was obtained in the same manner as in Example 1 except that the prepared powder M was used.

[0456] The average particle size of the near-infrared absorbing particles in the dispersion liquid M was measured by a dynamic light scattering method and was found to be 32.3 nm.

[0457] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion M was used. A near-infrared absorbing film M having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0458] The spectral transmittance spectrum of the obtained near-infrared absorbing film M obtained by using the U-4100 spectrophotometer of Hitachi High-Tech Co., Ltd. is shown in FIG. Figure 6 .according to Figure 6 The spectrum shown confirms strong absorption in the near-infrared region, with the transmittance bottom near 1470 nm, and transmission in the visible region between 380 nm and 780 nm. Transmittance in the blue and red regions decreases and increases, respectively, compared to the near-infrared absorbing film III of Comparative Example 3, resulting in an improvement in color tone to a neutral color. Furthermore, transmission of near-infrared light near 900 nm is significantly increased compared to the near-infrared absorbing film III of Comparative Example 3, demonstrating strong transmittance at the detector wavelength.

[0459] The visible light transmittance (VLT) and the solar transmittance (ST21) were measured to be VLT = 72.38% and ST21 = 50.81%, respectively, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect.

[0460] The color index of the near infrared absorbing film M is L ＊ =87.87, a ＊ =-1.46, b ＊= 10.98, the blue color is extremely weak, showing a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shielding when VLT = 70 to 80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0461] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 40.43%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and fully satisfy T900≥1.4×ST21-41.0.

[0462] [Example 14]

[0463] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0464] Powder M prepared in Example 13 was placed on a carbon boat and heated to 800° C. while flowing 100% by volume Ar gas. The supplied gas was then changed to 1% by volume H 2 -Ar, and the temperature was maintained at 800° C. for 10 minutes while flowing this gas. The temperature was then lowered to room temperature to obtain a water-colored powder N.

[0465] The X-ray powder diffraction pattern of the powder is as follows Figure 3 As shown, hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 The diffraction line mixing pattern of Cs4W 11 O 35 、Cs6W 11 O 36 、Cs 8.5 W 15 O 48 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0466] Observation of one particle of this powder using a transmission electron microscope from the (0001) direction revealed that the positions of the three prism facets in the electron diffraction image differed beyond the experimental error range. This suggests that the hexagonal crystals are primarily rhombohedral crystals modulated by basal defects.

[0467] Chemical analysis of powder N showed Cs / W = 0.42. The composition ratios of other components are shown in Table 2.

[0468] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0469] Dispersion liquid N was obtained in the same manner as in Example 1 except that the prepared powder N was used.

[0470] The average particle size of the near-infrared absorbing particles in the dispersion liquid N was measured by a dynamic light scattering method and was found to be 25.2 nm.

[0471] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion N was used. A near-infrared absorbing film N having a coating layer containing near-infrared absorbing particles was produced. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0472] The spectral transmittance spectrum of the obtained near-infrared absorbing film N obtained by using the U-4100 spectrophotometer of Hitachi High-Tech Co., Ltd. is shown in FIG. Figure 6 .according to Figure 6 The spectrum shown confirms strong absorption in the near-infrared region, with the transmittance bottom near 1630 nm, and transmission in the visible region between 380 nm and 780 nm. Transmittance in the blue and red regions decreases and increases, respectively, compared to the near-infrared absorbing film III of Comparative Example 3, resulting in an improvement in color tone to a neutral color. Furthermore, transmission of near-infrared light near 900 nm is significantly increased compared to the near-infrared absorbing film III of Comparative Example 3, demonstrating strong transmittance at the detector wavelength.

[0473] The visible light transmittance (VLT) and the solar transmittance (ST21) were measured to be VLT = 72.32% and ST21 = 44.99%, respectively, indicating that the film is transparent in visible light and has a strong near-infrared absorption effect.

[0474] The color index of the near infrared absorbing film N is L ＊ =88.01,a ＊ =-2.66, b ＊ =7.17, the blue color is extremely weak, showing a neutral tone. For the thin dispersion film of the present near infrared absorbing particles used for automobile window shielding when VLT=70-80%, it can be said that the blue color is almost not perceived. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b＊ ≥1.6×a ＊ +8.0.

[0475] In addition, Figure 8 As shown, L ＊ = T900 in the 88 section is 27.74%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and fully satisfy T900≥1.4×ST21-41.0.

[0476] [Example 15]

[0477] (Production and Evaluation of Near-Infrared Absorbing Particles)

[0478] Powder M prepared in Example 13 was placed on a carbon boat and maintained at 500°C for 30 minutes in a 1 vol% H2-Ar gas flow. The supplied gas was then changed to 100 vol% Ar and maintained at 550°C for 30 minutes while this gas flowed. The temperature was then further increased to 800°C for 1 hour and then cooled to room temperature to obtain a water-colored powder O.

[0479] The X-ray powder diffraction pattern of the powder is as follows Figure 3 As shown, hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 The diffraction line mixing pattern of Cs4W 11 O 35 、Cs6W 11 O 36 、Cs 8.5 W 15 O 48 The diffraction line positions and intensities are not completely consistent with the ICDD data.

[0480] Observation of one particle of this powder using a transmission electron microscope from the (0001) direction revealed that the positions of the three prism facets in the electron diffraction image differed beyond the experimental error range. This suggests that the hexagonal crystals are primarily rhombohedral crystals modulated by basal defects.

[0481] Chemical analysis of powder O showed Cs / W = 0.42. Composition ratios of other components are shown in Table 2.

[0482] (Production and Evaluation of Near-Infrared Absorbing Particle Dispersion Liquid and Near-Infrared Absorbing Particle Dispersion)

[0483] A dispersion O was obtained in the same manner as in Example 1 except that the prepared powder O was used.

[0484] The average particle size of the near-infrared absorbing particles in the dispersion O was measured by a dynamic light scattering method and was found to be 29.9 nm.

[0485] A coating film was formed on a PET film and the ultraviolet curable resin was cured in the same manner as in Example 1, except that this dispersion O was used. This produced a near-infrared absorbing film O having a coating layer containing near-infrared absorbing particles. The coating layer was a dispersion of near-infrared absorbing particles, and the near-infrared absorbing film was one form of a near-infrared absorbing transparent substrate.

[0486] 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 showed that the film was transparent in visible light and had a near-infrared absorbing effect.

[0487] The color index of the near infrared absorbing film O is L ＊ =87.91, a ＊ =-0.03, b ＊ =8.21, the blue color is extremely weak, showing a neutral tone close to ITO. Figure 7 As shown, it can be seen that in L ＊ =88 sections, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.0.

[0488] In addition, L ＊ = T900 in the 88 section is 70.15%, which satisfies T900≥10%, so it can be seen that it has detector wavelength transmittance. In addition, the sunlight shielding characteristics satisfy ST21≤67% and fully satisfy T900≥1.4×ST21-41.0.

[0489] [Table 1]

[0490]

[0491] [Table 2]

[0492]

[0493] 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 35The mixed phase pattern was observed, but the intensity ratio and position of the diffraction lines were offset from the ICDD data, which is believed to be caused by the irregular insertion of planar defects into the prism surface. It was confirmed that the (0001) electron diffraction pattern at the prism surface site was modulated to the orthorhombic crystal structure with the increase of the interplanar spacing. In addition, hexagonal Cs was observed in the XRD powder patterns of the powders prepared by Examples 9 to 15. 0.32 WO3 and rhombohedral Cs6W 11 O 36 、Cs 8.5 W 15 O 48 or pyrochlore phase (Cs2O) 0.44 The mixed presence of W2O6 resulted in the observed shift in the diffraction line positions and intensity distributions of the rhombohedral and pyrochlore phases compared to the ICDD data. It was confirmed that all three prism plane sites in the (0001) electron diffraction pattern exhibited a modulation of the crystal structure toward rhombohedral crystals accompanied by changes in interplanar spacing. Furthermore, a cubic electron diffraction pattern was observed in the powder identified as a pyrochlore phase by XRD. This confirms that the cesium tungstate contained in the powders produced in Examples 1 to 15 possesses a pseudohexagonal crystal structure.

[0494] like Figure 5 、 Figure 6 As shown in the transmission spectrum, the absorption bottom of Examples 1 to 7, 11, 13, and 14 occurs at a wavelength of 1400 nm to 2000 nm, with a large near-infrared absorption. Furthermore, at visible wavelengths, the spectrum is located between the spectra of the near-infrared absorbing film iii of Comparative Example 3, which has a strong blue hue, and the near-infrared absorbing film ii of Comparative Example 2, which has a neutral hue. Compared to the near-infrared absorbing film iii, the spectrum has a weaker blue hue and a stronger red hue, indicating an improvement in hue toward neutrality.

[0495] Figure 7 L ＊ = a in section 88 ＊ -b ＊ In the space, the near infrared absorbing films of Examples 1 to 15 were located between the near infrared absorbing film ii of Comparative Example 2 and the near infrared absorbing film iii of Comparative Example 3, and neutralization of the color tone was confirmed.

[0496] Furthermore, for the low degree of solar transmittance and the high degree of detector wavelength transmittance, as Figure 8 As shown in 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 an ideal region.

[0497] according to Figure 9AThe results showed that even after the near-infrared absorbing film G of Example 7 was placed in a constant temperature and humidity chamber at 85°C and 90% relative humidity for 15 days, the optical spectrum remained unchanged. In contrast, changes were observed in the near-infrared absorbing film iii of Comparative Example 3.

[0498] The X-ray powder diffraction pattern of the powder G involved in Example 7 is as follows: Figure 2 As shown, it has broad diffraction lines, showing hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 Therefore, it is believed that the cavity and window of the hexagonal channel, which is the main diffusion path for oxygen diffusion, are buried with Cs, O, OH, OH2, and OH3 in order to suppress the substitution reaction between Cs and water molecules, which is the cause of humidity and water degradation of hexagonal tungsten bronze.

[0499] In contrast, the powder iii involved in Comparative Example 3 is as follows Figure 2 As shown, it was identified as Cs 0.32 The WO3 single phase (ICDD0-81-1244) is a hexagonal cesium tungsten oxide that does not fully embed the cavities and windows of the hexagonal channels. As a result, it is believed that it is difficult to suppress the substitution reaction between Cs and water molecules.

[0500] This application claims priority based on Japanese Patent Application No. 2020-173574 filed with the Japan Patent Office on October 14, 2020, and the entire contents of Japanese Patent Application No. 2020-173574 are incorporated herein by reference.

[0501] Explanation of symbols

[0502] 91 covered

[0503] 100 Near-infrared absorbing particle dispersion

[0504] 90, 101, 111 near-infrared absorbing particles

[0505] 102 liquid medium

[0506] 110 Near-infrared absorbing particle dispersion

[0507] 112 solid media

[0508] 120 Near infrared ray absorbing laminate

[0509] 1211, 1212 transparent substrate

[0510] 122 Near-infrared absorbing particle dispersion

[0511] 130 Near infrared absorbing transparent substrate

[0512] 131 transparent substrate

[0513] 131A

[0514] 132 Near-infrared absorption layer.

Claims

1. A near-infrared absorbing particle comprising cesium tungstate, The cesium tungstate has a crystal structure in which a Cs-rich face is regularly or irregularly inserted into a prism face or a bottom face of the hexagonal crystal to adjust the hexagonal crystal into one or more pseudo-hexagonal crystals selected from orthorhombic, rhombohedral, and cubic crystals. The cesium tungstate is represented by the general formula Cs x W y O z Indicates that, in a three-dimensional composition diagram with Cs, W, and O as vertices, there is a composition within the region enclosed by four straight lines: x = 0.6y, z = 2.5y, y = 5x, and Cs2O:WO3 = m:n, where m and n are integers.

2. The near-infrared absorbing particles according to claim 1, comprising one or more additional components selected from the group consisting of O, OH, OH2, and OH3.

3. The near-infrared absorbing particles according to claim 2, The additive component is present at one or more positions selected from the group consisting of a hexagonal window, a hexagonal cavity, and a trigonal cavity formed by WO6 octahedrons in the crystal of the cesium tungstate.

4. The near-infrared absorbing particles according to any one of claims 1 to 3, A portion of one or more elements selected from Cs and W constituting the cesium tungstate crystal has defects, The general formula Cs x W y O z The relationship between x and y is 0.2≤x / y≤0.

6.

5. The near-infrared absorbing particles according to any one of claims 1 to 3, A portion of the O atoms in the WO 6 octahedron constituting the cesium tungstate crystal is defective.

6. The near-infrared absorbing particles according to any one of claims 1 to 3, A portion of Cs in the cesium tungstate is substituted by 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 3, The average particle size is 0.1 nm or more and 200 nm or less.

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

9. A method for producing near-infrared absorbing particles, the method according to any one of claims 1 to 8, comprising a first heat treatment step: 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.

10. The method for producing near-infrared absorbing particles according to claim 9, After the first heat treatment step, a second heat treatment step is provided: heating is performed at a temperature of 500° C. to 950° C. in an atmosphere containing a reducing gas.

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

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

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

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

15. The near-infrared absorbing particle dispersion according to any one of claims 11 to 13, In the Hunter color index L ＊ =88 section, the solar transmittance is below 67%, meeting b ＊ ≥0, b ＊ ≥1.6×a ＊ +8.

0.

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

0. 17 . A near-infrared absorbing laminate comprising a laminate structure comprising the near-infrared absorbing particle dispersion according to claim 11 and a transparent substrate.

18. A near-infrared absorbing transparent substrate comprising: Transparent substrate, and A near infrared absorbing layer on at least one side of the transparent substrate, 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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