Electromagnetic wave absorbing particles, electromagnetic wave absorbing particle dispersion liquid, electromagnetic wave absorbing particle dispersion, electromagnetic wave absorbing laminate

Abstract

To provide novel electromagnetic wave absorbing particles.SOLUTION: Provided are electromagnetic wave absorbing particles containing a composite oxide, wherein: the composite oxide contains element A, which is one or more elements selected from H, alkali metals, Mg, and alkali earth metals, and element B, which is one or more elements selected from Cr and Mo; and when the mole number of the element A and the mole number of the element B contained in the composite oxide are denoted by x and y, respectively, the following relation is satisfied: 0.001≤x / y≤1.5.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to electromagnetic wave absorbing particles, an electromagnetic wave absorbing particle dispersion liquid, an electromagnetic wave absorbing particle dispersion, and an electromagnetic wave absorbing laminate.

Background Art

[0002] According to the 5th edition of the Physical and Chemical Dictionary, it is defined that "electromagnetic waves with wavelengths in the range of about 1 nm to 1 mm are called light." This wavelength range includes the visible light region and the infrared region.

[0003] Near-infrared rays contained in sunlight penetrate through window materials and enter the room, causing the surface temperature of the walls and floors in the room to rise, and also increasing the room temperature. In order to make the indoor thermal environment comfortable, it has been conventionally done to prevent the indoor temperature from rising by using a light-shielding member on the window material or the like to block the near-infrared rays entering from the window.

[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] Further, Patent Document 2 discloses a heat-insulating sheet formed as a woven fabric with a strip-shaped film having infrared reflectivity and a strip-shaped film having infrared absorptivity as warp or weft, respectively. And it is also described that a synthetic resin film subjected to aluminum vapor deposition processing and further laminated with a synthetic resin film is used as the strip-shaped film having infrared reflectivity.

[0006] The applicant of the present application proposed in Patent Document 3 infrared absorption fine particles of antimony-containing tin oxide (ATO), an infrared absorption fine particle dispersion liquid using the infrared absorption fine particles, an infrared absorption fine particle dispersion, an infrared absorption combined transparent base material, an infrared absorption film, an infrared absorption glass, and a manufacturing method thereof. The above-mentioned infrared absorption fine particles of ATO and the like had excellent solar radiation shielding properties, that is, visible light transparency and infrared shielding properties.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] By the way, in recent years, electromagnetic wave absorbing particles capable of absorbing electromagnetic waves such as infrared rays have been used in various applications, and new electromagnetic wave absorbing particles are required so that an optimal material can be selected according to the application.

[0009] Therefore, one aspect of the present invention aims to provide novel electromagnetic wave absorbing particles.

Means for Solving the Problems

[0010] One aspect of the present invention provides electromagnetic wave absorbing particles containing a composite oxide, wherein the composite oxide is an A element which is at least one element selected from H, an alkali metal, Mg, and an alkaline earth metal, and a B element which is at least one element selected from Cr and Mo, and comprising oxygen and, when the amount of substance of the A element contained in the composite oxide is x and the amount of substance of the B element is y, the relationship of 0.001 ≦ x / y ≦ 1.5 is satisfied and having a volume-based cumulative 50% particle diameter of 1 nm or more and 50 nm or less and a cumulative 95% particle diameter of 5 nm or more and 100 nm or less as measured by a particle size distribution measuring device, and absorbing near-infrared light to provide electromagnetic wave absorbing particles.

Effects of the Invention

[0011] One aspect of the present invention can provide novel electromagnetic wave absorbing particles. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, [1] electromagnetic wave absorbing particles, [2] method for manufacturing electromagnetic wave absorbing particles, [3] electromagnetic wave absorbing particle dispersion liquid, [4] electromagnetic wave absorbing particle dispersion, and [5] electromagnetic wave absorbing laminate will be described in detail in this order.

[0013] [1] Electromagnetic Wave Absorbing Particles The inventor of the present invention has studied novel electromagnetic wave absorbing particles. The type of electromagnetic wave absorbed by the electromagnetic wave absorbing particles is not particularly limited, but as described above, electromagnetic wave absorbing particles that particularly absorb infrared rays or near-infrared rays are required. Therefore, the electromagnetic wave absorbing particles of the present embodiment are preferably infrared absorbing particles that absorb infrared rays, and more preferably near-infrared absorbing particles that absorb near-infrared rays.

[0014] When the inventor of the present invention studied new electromagnetic wave absorbing particles, attention was paid to the oxides of group 6 elements. However, since there are no effective free electrons or holes in the pentoxides (CrO3, MoO3) of group 6 elements, the absorption and reflection characteristics in the infrared region are few, and they are not effective as infrared absorbing materials. However, when a composite oxide obtained by adding a positive element to the above oxide is used, free electrons or holes are generated in the composite oxide, and thus absorption characteristics derived from free electrons or holes appear in the infrared region. For this reason, it has been found that new electromagnetic wave absorbing particles can be obtained.

[0015] Furthermore, the inventors of the present invention have found that there is a particularly effective range as electromagnetic wave absorbing particles in a specific part of the composition range of the composite oxide. Specifically, by setting the composition range of the composite oxide within a predetermined range, it has been found that it is transparent in the visible light region and has absorption in the infrared region, and the present invention has been completed. (Regarding the Composition of the Composite Oxide) The electromagnetic wave absorbing particles of this embodiment can contain a composite oxide. The composite oxide can contain an element A which is one or more elements selected from H, an alkali metal, Mg, and an alkaline earth metal, and an element B which is one or more elements selected from Cr (chromium) and Mo (molybdenum).

[0016] When the amount of substance of element A contained in the composite oxide is x and the amount of substance of element B contained in the composite oxide is y, it is preferable to satisfy the relationship of 0.001 ≦ x / y ≦ 1.5.

[0017] Note that the electromagnetic wave absorbing particles of this embodiment may be composed only of the above composite oxide. However, even in this case, it does not exclude the case where the electromagnetic wave absorbing particles of this embodiment contain unavoidable impurities mixed in during the manufacturing process or the like.

[0018] As described above, by adding element A, which is a positive element, to the oxide containing element B to form the above composite oxide, electromagnetic wave absorption characteristics can be exhibited. Element A is preferably one or more elements selected from H, an alkali metal, Mg, and an alkaline earth metal as described above. Particularly from the viewpoint of improving the stability in the above composite oxide, element A is preferably one or more elements selected from alkaline earth metals, that is, Ca, Sr, Ba, and Ra, and more preferably one or more elements selected from Ca, Sr, and Ba.

[0019] Also, element B can be one or more elements selected from Cr and Mo as described above, and is preferably Mo.

[0020] Regarding the value of x / y indicating the content ratio of element A to element B in the composite oxide, if it is 0.001 or more as described above, a sufficient amount of free electrons or holes is generated in the composite oxide, and the desired electromagnetic wave absorption effect can be obtained. And the higher the content of element A, the more the supply amount of free electrons increases, and the electromagnetic wave absorption efficiency also increases. However, the effect also saturates when the value of x / y is about 1.5. Also, if the value of x / y is 1.5 or less, generation of an impurity phase in the electromagnetic wave absorbing particles can be avoided. For this reason, as described above, it is preferable that 0.001 ≤ x / y ≤ 1.5, more preferably 0.5 ≤ x / y ≤ 1.2, still more preferably 0.8 ≤ x / y ≤ 1.1, and most preferably x / y = 1.0.

[0021] Incidentally, the above composite oxide can be represented, for example, by the general formula A x B y O z In this general formula, A represents element A, B represents element B, and O represents oxygen. As shown by the above general formula, the above composite oxide is preferably composed of, for example, element A, element B, and oxygen.

[0022] As described above, by adding element A to the oxide containing element B, free electrons or holes are supplied to the composite oxide, and the electromagnetic wave absorption characteristics can be exhibited. Therefore, the amount of oxygen contained in the composite oxide is not particularly limited. However, by setting the amount of oxygen within a predetermined range, the amount of free electrons or holes in the composite oxide can be set within a particularly suitable range from the viewpoint of enhancing the electromagnetic wave absorption characteristics. Thus, for z / y corresponding to the content ratio of oxygen to element B in the composite oxide, it is preferably 1.0 < z / y ≤ 5.0, more preferably 2.0 < z / y ≤ 4.0, and still more preferably 2.0 < z / y ≤ 3.0.

[0023] z / y corresponds to the content ratio of oxygen to B element in terms of the amount of substance in the composite oxide as described above, and is a value that affects the oxygen deficiency amount or oxygen excess amount of the composite oxide. As described above, the amount of free electrons or holes in the composite oxide can also be controlled by the amount of oxygen. Therefore, it is preferable to control the value of z / y according to the required electromagnetic wave absorption characteristics and the like. The value of z / y can be easily controlled by the synthesis conditions of the electromagnetic wave absorbing particles and the like.

[0024] The general formula A above x B y O z In x, y, and z, it is preferable to satisfy 0 ≦ (2x + 6y - 2z) / y ≦ 6, more preferably to satisfy 1 ≦ (2x + 6y - 2z) / y ≦ 4.5, and even more preferably to satisfy 1.5 ≦ (2x + 6y - 2z) / y ≦ 3.5. The above (2x + 6y - 2z) / y indicates a measure of the excess or deficiency of electrons per B element. When the above range is satisfied, a particularly high electromagnetic wave absorption effect can be exhibited. (Regarding the crystal structure of the composite oxide) According to the study by the inventor of the present invention, when the composite oxide has any crystal structure selected from cubic, tetragonal, and orthorhombic crystal structures, the transmission of light in the visible light region is particularly improved, and the absorption of light in the infrared region is improved. However, in order to obtain the effect of improving the transmission of light in the visible light region and improving the absorption of light in the infrared region, it is sufficient that the unit structure of the cubic, tetragonal, or orthorhombic crystal structure is included in the composite oxide, and the composite oxide may partially contain an amorphous or other structure.

[0025] When x / y, which represents the content ratio of element A to element B in the composite oxide, is 1.0, and z / y, which represents the content ratio of oxygen to element B in the composite oxide, is 3.0, the crystal structure of the composite oxide becomes a cubic perovskite structure. Specifically, SrMoO3, BaMoO3, etc. become cubic perovskite structures. Taking this as the basic structure, when the value of x / y is less than 1.0, it may become a cubic perovskite structure with a deficiency of element A. Also, when the value of z / y is less than 4.0, it may become a cubic perovskite structure with oxygen deficiency. Furthermore, when the ABO3 block and the BO block are regularly stacked, it may also become a tetragonal or orthorhombic crystal structure. In addition, when the value of z / y is greater than 3.0 and less than 3.5, a planar lattice defect may be inserted into the cubic perovskite structure, resulting in a tetragonal or orthorhombic crystal structure.

[0026] As electromagnetic wave absorbing particles, materials with strong electromagnetic wave absorption in the infrared region and weak electromagnetic wave absorption in the visible light region are often required. However, since the required performance varies depending on the application and other factors, it is not possible to generally determine which of the above crystal structures is preferable.

[0027] The absorption wavelength of the electromagnetic wave absorbing particles of this embodiment often falls around 780 nm, which is the boundary between the visible light region and the infrared region. However, depending on the crystal structure of the composite oxide contained and the presence or absence of element deficiency, the absorption wavelength of the electromagnetic wave may shift to the short wavelength side, or the electromagnetic wave absorption may increase, resulting in a decrease in visible light transparency.

[0028] Thus, due to the composition of the composite oxide, the relationship between the crystal structure and the electromagnetic wave absorption characteristics also changes. Therefore, the crystal structure of the composite oxide contained in the electromagnetic wave absorbing particles of this embodiment is not particularly limited and can be selected according to the composition of the composite oxide and the required electromagnetic wave absorption characteristics, etc. (Regarding the particle characteristics of the electromagnetic wave absorbing particles) The particle characteristics such as the particle diameter of the electromagnetic wave absorbing particles of this embodiment are not particularly limited and can be arbitrarily selected according to the required electromagnetic wave absorption characteristics, etc.

[0029] The electromagnetic wave absorbing particles of the present embodiment preferably have a volume-based cumulative 50% particle diameter of 1 nm or more and 50 nm or less, and a cumulative 95% particle diameter of 5 nm or more and 100 nm or less, as measured by a particle size distribution measuring device.

[0030] Generally, it is known that a material containing free electrons or holes exhibits a reflection absorption response to electromagnetic waves around the region of sunlight with a wavelength of 200 nm or more and 2600 nm or less due to plasma oscillation. When powder particles of such a material are made into particles smaller than the wavelength of light, it is known that geometric scattering in the visible light region (wavelength of 380 nm or more and 780 nm or less) is reduced and transparency in the visible light region is obtained.

[0031] In this specification, "transparency" is used in the sense of "less scattering and high transmittance with respect to light in the visible light region."

[0032] Therefore, when the electromagnetic wave absorbing particles of the present embodiment are used in applications that require transparency in the visible light region, it is preferable that the volume-based cumulative 95% particle diameter measured by a particle size distribution measuring device is 100 nm or less. This is because particles with a cumulative 95% particle diameter of 100 nm or less do not completely shield light by scattering, can maintain visibility in the visible light region, and at the same time can efficiently maintain transparency. In particular, when emphasizing transparency in the visible light region, it is preferable to further consider scattering by particles.

[0033] When further reduction of scattering by the electromagnetic wave absorbing particles is required, the cumulative 95% particle diameter is more preferably 70 nm or less, and even more preferably 50 nm or less. If the particle diameter of the electromagnetic wave absorbing particles is small, scattering of light in the visible light region with a wavelength of 400 nm or more and 780 nm or less due to geometric scattering or Mie scattering is reduced. Therefore, by setting the cumulative 95% particle diameter of the electromagnetic wave absorbing particles within the above range, for example, it is possible to more reliably avoid the situation where an electromagnetic wave absorbing particle dispersion using the electromagnetic wave absorbing particles becomes cloudy like frosted glass and clear transparency cannot be obtained. When the cumulative 95% particle diameter becomes 70 nm or less, the above geometric scattering or Mie scattering is reduced, and it enters the Rayleigh scattering region. And in the Rayleigh scattering region, since the scattered light is proportional to the sixth power of the particle diameter, the scattering is reduced and the transparency is improved as the particle diameter decreases.

[0034] Furthermore, when the cumulative 95% particle diameter becomes 50 nm or less, the scattered light becomes very small, which is preferable. From the viewpoint of avoiding light scattering, since it is preferable that the cumulative 95% particle diameter is smaller, the lower limit value of the cumulative 95% particle diameter is not particularly limited, but the cumulative 95% particle diameter is preferably 5 nm or more. This is because industrial production is easy if the cumulative 95% particle diameter is 5 nm or more.

[0035] As described above, by setting the cumulative 95% particle diameter to 100 nm or less, for example, the haze value of an electromagnetic wave absorbing particle dispersion in which the electromagnetic wave absorbing particles of the present embodiment are dispersed in a solid medium can be set to 30% or less at a visible light transmittance of 85% or less. By setting the haze to 30% or less, particularly clear transparency can be obtained.

[0036] From the viewpoint of obtaining particularly excellent electromagnetic wave absorption characteristics, the cumulative 50% particle diameter of the volume-based electromagnetic wave absorbing particles measured by a particle size distribution measuring device is preferably 1 nm or more. However, from the viewpoint of enhancing the transparency in the visible light region, for the same reason as the cumulative 95% particle diameter, the cumulative 50% particle diameter is preferably 50 nm or less.

[0037] The cumulative 50% particle size and cumulative 95% particle size of the electromagnetic wave absorbing particles can be measured using a particle size distribution measuring apparatus (for example, UPA-150 manufactured by Nikkiso Co., Ltd.) based on the dynamic light scattering method analyzed by the frequency analysis method.

[0038] The particle size distribution data is expressed as the integrated % or frequency % with respect to the particle size scale, but conversely, it may also be expressed as the particle size with respect to the integrated % scale. The distribution curve expressed as the particle size with respect to the integrated % scale, for example, the particle size at the point where the horizontal axis of 10% intersects is the cumulative 10% particle size, the particle size at the point where the horizontal axis of 50% intersects is the cumulative 50% particle size, and the particle size at the point where the horizontal axis of 95% intersects is the cumulative 95% particle size. It is not particularly fixed at 10%, 50%, and 95%, and any integrated % can be used as needed. The 50% particle size is also called the median diameter and is very commonly used. When comparing the sizes of the particle size distributions of multiple samples, since it is necessary to represent the size of the measurement object by a single numerical value, this median diameter is often used. For this reason, the median diameter is often confused with the average particle diameter, but the definitions are different, and usually these two diameters do not match. These two diameters match only when the particle size distribution is symmetric about the center (50% diameter). [2] Method for manufacturing electromagnetic wave absorbing particles Next, the method for manufacturing the electromagnetic wave absorbing particles of the present embodiment will be described. Since the electromagnetic wave absorbing particles described above can be manufactured by the method for manufacturing the electromagnetic wave absorbing particles of the present embodiment, some explanations of the matters already described will be omitted.

[0039] The electromagnetic wave absorbing particles of the present embodiment can be manufactured by a solid-phase reaction method. When synthesizing by the solid-phase reaction method, an A element compound and a B element compound can be used as raw materials.

[0040] The method for manufacturing the electromagnetic wave absorbing particles of the present embodiment can have a mixed powder preparation step (first mixed powder preparation step) of preparing a mixed powder of an A element compound or an A element simple substance and a B element compound or a B element simple substance.

[0041] As the A element source, an A element compound or a simple substance of the A element can be used. As the A element compound used as a raw material, it is preferably at least one selected from oxides, hydroxides, carbonates, nitrates, sulfates, oxalates, organic compounds, sulfides, and chlorides of the A element.

[0042] Since the suitable A element has already been described, the description is omitted here.

[0043] As the B element compound or simple substance of the B element serving as the B element source, it is preferably at least one selected from trioxides (CrO3, MoO3), dioxides (MoO2), tri-dioxides (Cr2O3), simple metal (Cr, Mo), hydroxides, carbonates, nitrates, sulfates, acetates, oxalates, ammonium salts, organic compounds, sulfides, chlorides, and hydrates of oxides obtained by dissolving chlorides in a liquid such as alcohol, adding water for hydrolysis, and evaporating the solvent. Since the suitable B element has already been described, the description is omitted here.

[0044] In the mixed powder preparation process, the specific procedure for obtaining a mixed powder of the A element compound or simple substance of the A element and the B element compound or simple substance of the B element is not particularly limited. For example, a method of dry-mixing the above A element compound, etc. and B element compound, etc. in a powder state to obtain a mixed powder can be mentioned. Also, a mixed powder can be obtained by dissolving the A element compound, etc. in water, wet-mixing it with the B element compound, etc., and then drying.

[0045] In the mixed powder preparation step, it is preferable to mix the A element and the B element in the obtained mixed powder so that the molar ratio of the A element to the B element is the same as the ratio of the A element to the B element in the target composite oxide. That is, it is preferable to mix so as to satisfy A:B = x:y, which is the ratio of the molar amount (A) of the A element to the molar amount (B) of the B element in the composite oxide. As described above, it is preferable that x / y satisfies 0.001 ≦ x / y ≦ 1.5, more preferably 0.5 ≦ x / y ≦ 1.2, still more preferably 0.8 ≦ x / y ≦ 1.1, and most preferably x / y = 1.0. For this reason, it is preferable to mix the A element compound and the B element compound so as to be within the above preferable range.

[0046] In addition, the electromagnetic wave absorbing particles of the present embodiment can also be synthesized in multiple steps in order to obtain electromagnetic wave absorbing particles containing a composite oxide of the target composition. In this case, in the first mixed powder preparation step, the A element compound, the B element compound, etc. can be mixed so as to have the composition of the intermediate product.

[0047] And the manufacturing method of the electromagnetic wave absorbing particles of the present embodiment can have a firing step (first firing step) of firing the mixed powder obtained in the mixed powder preparation step.

[0048] The conditions of the firing step are not particularly limited. In the firing step, for example, the above mixed powder can be fired in any atmosphere selected from an inert gas alone atmosphere, a reducing gas alone atmosphere, a vacuum atmosphere, a mixed gas atmosphere of an inert gas and a reducing gas, and an oxidizing atmosphere containing oxygen.

[0049] For example, when introducing oxygen deficiency into a complex oxide and making z / y in the aforementioned general formula smaller than the stoichiometric ratio, the firing atmosphere is preferably a mixed gas atmosphere of an inert gas and a reducing gas. The reducing gas is not particularly limited, but for example, hydrogen gas is preferable. When hydrogen gas is used as the reducing gas, the volume ratio of hydrogen gas is preferably 1% or more, more preferably 3% or more. The upper limit of the volume ratio of hydrogen gas is not particularly limited, and since it can be a reducing gas alone, it can be up to 100%.

[0050] The inert gas is not particularly limited, but one or more selected from nitrogen gas, noble gases, etc. can be used.

[0051] The oxidizing atmosphere may be an atmosphere containing oxygen. For example, an atmosphere containing oxygen at a volume ratio of 18% or more and 100% or less can be used. For example, an air atmosphere can be used.

[0052] The conditions of the firing temperature in the firing process are not particularly limited, but the firing temperature is preferably equal to or higher than the temperature at which the generated complex oxide begins to crystallize and equal to or lower than the melting point of the complex oxide. Specifically, for example, the firing temperature is preferably 1000°C or more and 1700°C or less.

[0053] In order to make the electromagnetic wave absorbing particles of the present embodiment be electromagnetic wave absorbing particles containing a composite oxide of a target composition, the synthesis can also be carried out in multiple steps. When carrying out the synthesis in multiple steps, a B element compound or a simple substance of the B element can be further added and mixed to the intermediate product obtained in the above firing step (first firing step) (second mixed powder preparation step). The B element compound or the like used at this time is not particularly limited, but for example, the compounds described above in the first mixed powder preparation step can be used. In the second mixed powder preparation step, it is preferable to mix so that the molar ratio of the A element and the B element in the obtained mixed powder becomes the ratio of the A element and the B element in the target composite oxide. That is, it is preferable to mix so as to satisfy A:B = x:y, which is the ratio of the amount of substance (A) of the A element and the amount of substance (B) of the B element in the composite oxide. Since the mixing can be carried out in the same manner as in the case of the mixed powder preparation step, the description is omitted here.

[0054] Then, the obtained mixed powder is subjected to a firing step (second firing step) to prepare the electromagnetic wave absorbing particles of the present embodiment. The conditions of the second firing step are not particularly limited, but since the firing atmosphere and the firing temperature can be carried out in the same manner as described in the above firing step (first firing step), for example, the description is omitted here. Note that the first firing step and the second firing step may have the same firing conditions or different firing conditions.

[0055] By performing the steps described above, the electromagnetic wave absorbing particles of the present embodiment can be obtained. After the firing step is completed, if necessary, the obtained electromagnetic wave absorbing particles can be crushed, pulverized, sieved, etc. to obtain a desired particle size distribution. [3] Electromagnetic Wave Absorbing Particle Dispersion Next, the electromagnetic wave absorbing particle dispersion of the present embodiment will be described.

[0056] The electromagnetic wave absorbing particle dispersion of the present embodiment can contain a liquid medium and the above-described electromagnetic wave absorbing particles contained in the liquid medium. The electromagnetic wave absorbing particles are preferably dispersed in the liquid medium.

[0057] The electromagnetic wave absorbing particle dispersion liquid of this embodiment can be obtained by using the aforementioned electromagnetic wave absorbing particles, or in other words, by using the electromagnetic wave absorbing particles obtained by the manufacturing method of the aforementioned electromagnetic wave absorbing particles.

[0058] In addition to the above electromagnetic wave absorbing particles and liquid medium, the electromagnetic wave absorbing particle dispersion liquid can further contain a dispersant and other additives as desired. The electromagnetic wave absorbing particle dispersion liquid can be used as an intermediate product or a coating liquid of the electromagnetic wave absorbing particle dispersion.

[0059] The liquid medium means a medium that is liquid at the temperature of use, and it is particularly preferably a medium that is liquid at room temperature (27°C). The liquid medium is not particularly limited and can be arbitrarily selected according to the application and the like. However, as the liquid medium, one or more selected from water, organic solvents, liquid plasticizers, oils and fats, and compounds polymerized by curing can be preferably used.

[0060] Hereinafter, the electromagnetic wave absorbing particle dispersion liquid of this embodiment will be described in the order of (1) the materials contained, (2) the manufacturing method of the electromagnetic wave absorbing particle dispersion liquid, (3) the usage method of the electromagnetic wave absorbing particle dispersion liquid, and the articles using the same. (1) Regarding the materials contained (1-1) Electromagnetic wave absorbing particles The electromagnetic wave absorbing particle dispersion liquid of this embodiment can contain the aforementioned electromagnetic wave absorbing particles. Since the electromagnetic wave absorbing particles have already been described, the description will be omitted here. (1-2) Liquid medium (1-2-1) Organic solvent As the organic solvent used as the liquid medium, for example, one or more selected from alcohol-based, ketone-based, ester-based, glycol derivatives, amides, aromatic hydrocarbons, etc. can be used.

[0061] Specifically, alcohol-based materials such as methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzyl alcohol, and diacetone alcohol; Ketone-based materials such as acetone, methyl ethyl ketone, dimethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone; Ester-based materials such as 3-methyl-methoxy-propionate, n-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 monomethyl ether acetate, propylene glycol monoethyl ether acetate; Amides such as formamide, N-methylformamide, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone; Aromatic hydrocarbons such as toluene, xylene; It can be made from one or more selected from ethylene chloride, chlorobenzene, etc. as an organic solvent.

[0062] Among the above organic solvents, in particular, one or more selected from dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, n-butyl acetate, etc. can be more preferably used. (1-2-2) Oils and fats The oils and fats used as the liquid medium are not particularly limited, but vegetable oils or compounds derived from vegetable oils can be preferably used.

[0063] As the vegetable oil, one or more selected from drying oils such as linseed oil, sunflower oil, tung oil, perilla oil, semi-drying oils such as sesame oil, cottonseed oil, rapeseed oil, soybean oil, rice bran oil, peony oil, and non-drying oils such as olive oil, coconut oil, palm oil, dehydrated castor oil, etc. can be preferably used.

[0064] As the compounds derived from vegetable oils, one or more selected from fatty acid monoesters obtained by directly esterifying fatty acids of vegetable oils with monoalcohols, ethers, etc. can be preferably used.

[0065] Also, commercially available petroleum solvents can also be used as oils and fats.

[0066] As commercially available petroleum solvents, Isopar (registered trademark) E, Exxsol (registered trademark) (the same applies hereinafter) Hexane, Heptane, E, D30, D40, D60, D80, D95, D110, D130 (the above are manufactured by ExxonMobil), etc. can be used. (1-2-3) Liquid plasticizer As the liquid plasticizer used as the liquid medium, for example, plasticizers that are compounds of monohydric alcohols and organic acid esters, plasticizers that are ester-based such as polyhydric alcohol organic acid ester compounds, plasticizers that are phosphoric acid-based such as organic phosphoric acid-based plasticizers, etc. One or more selected from the above can be mentioned. In addition, those that are liquid at room temperature are preferably used.

[0067] Among them, plasticizers that are ester compounds synthesized from polyhydric alcohols and fatty acids can be preferably used. The ester compounds synthesized from the polyhydric alcohols and fatty acids are not particularly limited, but for example, glycol-based ester compounds obtained by the reaction of glycols and monobasic organic acids, etc. can be preferably used. As the above glycols, one or more selected from triethylene glycol, tetraethylene glycol, tripropylene glycol, etc. can be preferably used. Further, as the above monobasic organic acids, one or more selected from butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptylic acid, n-octylic acid, 2-ethylhexanoic acid, pelargonic acid (n-nonanoic acid), decanoic acid, etc. can be preferably used.

[0068] In addition, ester compounds of tetraethylene glycol, tripropylene glycol, and monobasic organic substances can also be preferably used. Among them, one or more selected from fatty acid esters of triethylene glycol such as triethylene glycol dihexanoate, triethylene glycol di-2-ethylbutyrate, triethylene glycol dioctanoate, triethylene glycol di-2-ethylhexanoate, etc. can be preferably used. Furthermore, fatty acid esters of triethylene glycol can also be preferably used. (1-2-4) Compounds polymerized by curing As the compound polymerized by curing used in the infrared absorption particle dispersion of the present embodiment, monomers and oligomers that form polymers by polymerization reactions caused by heat, light, water, etc. can be preferably used.

[0069] Specifically, for example, methyl methacrylate monomer, acrylate monomer, styrene resin monomer, etc. can be used as the compound polymerized by curing.

[0070] As described above, two or more types of the liquid media described can also be used in combination. Furthermore, if necessary, an acid or an alkali may be added to these liquid media to adjust the pH. (1-3) Dispersant In the electromagnetic wave absorption particle dispersion of the present embodiment, in order to further improve the dispersion stability of the electromagnetic wave absorption particles and avoid coarsening of the particle size due to re-aggregation, the electromagnetic wave absorption particle dispersion of the present embodiment can also contain various dispersants, surfactants, coupling agents, etc.

[0071] The dispersant, coupling agent, and surfactant can be selected according to the application, but it is preferable that they are materials having one or more selected from a group containing an amine, a hydroxyl group, a carboxyl group, a phosphate group, and an epoxy group as functional groups. These functional groups have the effect of adsorbing on the surface of the electromagnetic wave absorption particles to prevent aggregation and uniformly disperse them. Polymer dispersants having one or more selected from these functional groups in the molecule can be more preferably used as the above dispersant.

[0072] Preferable specific examples of commercially available dispersants include SOLSPERSE (registered trademark, the same hereinafter) 3000, 5000, 9000, 11200, 12000, 13000, 13240, 13650, 13940, 16000, 17000, 18000, 20000, 21000, 24000SC, 24000GR, 26000, 27000, 28000, 31845, 32000, 32500, 32550, 32600, 33000, 33500, 34750, 35100, 35200, 36600, 37500, 38500, 39000, 41000, 41090, 53095, 55000, 56000, 71000, 76500, J180, J200, M387, etc. manufactured by Lubrizol Japan Ltd.; SOLPLUS (registered trademark, the same hereinafter) D510, D520, D530, D540, DP310, K500, L300, L400, R700, etc.; Disperbyk (registered trademark, the same hereinafter) -101, 102, 103, 106, 107, 108, 109, 110, 111, 112, 116, 130, 140, 142, 145, 154, 161, 162, 163, 164, 165, 166, 167, 168, 170, 171, 174, 180, 181, 182, 183, 184, 185, 190, 191, 192, 2000, 2001, 2009, 2020, 2025, 2050, 2070, 2095, 2096, 2150, 2151, 2152, 2155, 2163, 2164, Anti-Terra (registered trademark, the same hereinafter) -U, 203, 204, etc. manufactured by BYK Japan Co., Ltd.;BYK® (hereinafter the same) - P104, P104S, P105, P9050, P9051, P9060, P9065, P9080, 051, 052, 053, 054, 055, 057, 063, 065, 066N, 067A, 077, 088, 141, 220S, 300, 302, 306, 307, 310, 315, 320, 322, 323, 325, 330, 331, 333, 337, 340, 345, 346, 347, 348, 350, 354, 355, 358N, 361N, 370, 375, 377, 378, 380N, 381, 392, 410, 425, 430, 1752, 4510, 6919, 9076, 9077, W909, W935, W940, W961, W966, W969, W972, W980, W985, W995, W996, W9010, Dynwet800, Siclean3700, UV3500, UV3510, UV3570, etc.; EFKA® (hereinafter the same) 2020, 2025, 3030, 3031, 3236, 4008, 4009, 4010, 4015, 4020, 4046, 4047, 4050, 4055, 4060, 4080, 4300, 4310, 4320, 4330, 4340, 4400, 4401, 4402, 4403, 4500, 5066, 5220, 6220, 6225, 6230, 6700, 6780, 6782, 7462, 8503, etc. manufactured by Efka Additives; JONCRYL® (hereinafter the same) 67, 678, 586, 611, 680, 682, 690, 819, -JDX5050, etc. manufactured by BASF Japan; TERPLUS® (hereinafter the same) MD1000, D 1180, D 1130, etc. manufactured by Otsuka Chemical; AJISPER® (hereinafter the same) PB-711, PB-821, PB-822, etc. manufactured by Ajinomoto Fine-Techno; DISPARLON® (hereinafter the same) 1751N, 1831, 1850, 1860, 1934, DA-400N, DA-703-50, DA-325, DA-375, DA-550, DA-705, DA-725, DA-1401, DA-7301, DN-900, NS-5210, NVI-8514L, etc. manufactured by Kusumoto ChemicalAlphon (registered trademark) (the same shall apply hereinafter) UH-2170, UC-3000, UC-3910, UC-3920, UF-5022, UG-4010, UG-4035, UG-4040, UG-4070, Reseda (registered trademark) (the same shall apply hereinafter) GS-1015, GP-301, GP-301S, etc. manufactured by Toagosei Co., Ltd.; Dianal (registered trademark) (the same shall apply hereinafter) BR-50, BR-52, BR-60, BR-73, BR-77, BR80, BR-83, BR-85, BR-87, BR-88, BR-90, BR-96, BR-102, BR-113, BR-116, etc. manufactured by Mitsubishi Chemical Corporation.

[0073] In addition, a liquid dispersant having a glass transition temperature lower than room temperature can also be used instead of the liquid medium. That is, the electromagnetic wave absorbing particle dispersion liquid of the present embodiment can also contain an electromagnetic wave absorbing particle and a liquid dispersant, and can also be composed of an electromagnetic wave absorbing particle and a liquid dispersant. Preferred specific examples of commercially available liquid dispersants include SOLSPERSE (registered trademark) 20000 manufactured by Lubrizol Japan, Disparlon (registered trademark) (the same shall apply hereinafter) DA234, DA325, DA375, etc. manufactured by Kusumoto Chemicals, Ltd. (1-4) Other Additives The electromagnetic wave absorbing particle dispersion liquid of the present embodiment can also contain additives such as various surfactants and resin components for controlling coatability, leveling property, and drying property. When adding the additive, the electromagnetic wave absorbing particle dispersion liquid preferably contains the additive in a small amount in the range of 5% by mass or less of the dispersion liquid. Examples of the surfactant include anionic, cationic, nonionic, or amphoteric ones.

[0074] In addition, in order to impart flexibility to the electromagnetic wave absorbing particle dispersion obtained by using the electromagnetic wave absorbing particle dispersion liquid, the dispersion liquid can also contain one or more organic resins selected from silicone resins, acrylic resins, polyester resins, polyurethane resins, hydrophilic organic resins containing a polyoxyalkylene group, epoxy resins, etc. When adding the organic resin, the electromagnetic wave absorbing particle dispersion liquid preferably contains the organic resin in a small amount in the range of 5% by mass or less of the electromagnetic wave absorbing particle dispersion liquid.

[0075] In addition, in order to impart crack prevention properties to the electromagnetic wave absorbing particle dispersion prepared using the electromagnetic wave absorbing particle dispersion liquid, the electromagnetic wave absorbing particle dispersion liquid can also contain one or more resins selected from thermosetting resins, thermoplastic resins, ultraviolet curable resins, etc. When adding the resin, it is preferable that the electromagnetic wave absorbing particle dispersion liquid contains the resin in the range of 20% by mass or less of the dispersion liquid. More specifically, examples of the above resin include acrylic resins, epoxy resins, polyester resins, amino resins, urethane resins, furan resins, silicone resins, and modified products of these resins. (2) Method for producing electromagnetic wave absorbing particle dispersion liquid The method for producing the electromagnetic wave absorbing particle dispersion liquid of the present embodiment is not particularly limited. The electromagnetic wave absorbing particle dispersion liquid of the present embodiment can be prepared, for example, by adding the aforementioned electromagnetic wave absorbing particles and, if necessary, a dispersant and other additives into the aforementioned liquid medium and dispersing them. In addition, as described above, a liquid dispersant can also be used instead of the liquid medium.

[0076] The method for dispersing electromagnetic wave absorbing particles and the like in a liquid medium is not particularly limited. For example, a pulverization-dispersion treatment method using devices such as a bead mill, ball mill, sand mill, paint shaker, ultrasonic homogenizer, etc. can be mentioned. Among them, medium stirring mills such as bead mills, ball mills, sand mills, and paint shakers using medium media such as beads, balls, and Ottawa sand can be preferably used because the electromagnetic wave absorbing particles can be made into a desired particle size in a short time.

[0077] By the pulverization-dispersion treatment using a medium stirring mill, at the same time as the dispersion of the electromagnetic wave absorbing particles in the liquid medium, the pulverization into fine particles also proceeds due to the collision of the electromagnetic wave absorbing particles with each other and the collision of the medium media with the electromagnetic wave absorbing particles, etc., and the electromagnetic wave absorbing particles can be made into finer particles and dispersed. That is, it is pulverized and dispersed.

[0078] In the electromagnetic wave absorbing particle dispersion liquid, the dispersion concentration of the electromagnetic wave absorbing particles is preferably 0.01% by mass or more and 80% by mass or less. This is because sufficient electromagnetic wave absorption characteristics can be exhibited by setting the content of the electromagnetic wave absorbing particles to 0.01% by mass or more. Also, by setting it to 80% by mass or less, the electromagnetic wave absorbing particles can be uniformly dispersed in the liquid medium. The electromagnetic wave absorbing particle dispersion liquid of the present embodiment can select a combination of a liquid medium, a dispersant, a coupling agent, and a surfactant, so that, for example, even when placed in a constant temperature bath at 40°C, gelation of the dispersion liquid or sedimentation of the particles does not occur for 6 months or more, and an increase in the particle diameter can be suppressed. (3) Method of using the electromagnetic wave absorbing particle dispersion liquid and article using the electromagnetic wave absorbing particle dispersion liquid The uses and the like of the electromagnetic wave absorbing particle dispersion liquid of the present embodiment are not particularly limited, and it can be used for various applications.

[0079] The electromagnetic wave absorbing particle dispersion liquid of the present embodiment can be used as an electromagnetic wave absorbing base material by forming a dispersion film, for example, by appropriately coating the surface of a base material. The dispersion film is also a kind of electromagnetic wave absorbing particle dispersion and also a kind of dried solid of the electromagnetic wave absorbing particle dispersion liquid.

[0080] Further, the electromagnetic wave absorbing particle dispersion liquid of the present embodiment can be dried and, if necessary, pulverized to obtain a powdery electromagnetic wave absorbing particle dispersion (which may be described as "dispersion powder" in this specification). That is, the dispersion powder is also a kind of electromagnetic wave absorbing particle dispersion and also a kind of dried solid of the electromagnetic wave absorbing particle dispersion liquid. The dispersion powder is a powdery dispersion in which the electromagnetic wave absorbing particles are dispersed in a solid medium such as a dispersant. Since the dispersion powder contains a dispersant, it is possible to easily redisperse the electromagnetic wave absorbing particles into the medium by mixing with an appropriate medium.

[0081] The above-mentioned dispersion powder can also be used as a raw material for adding electromagnetic wave absorbing particles to electromagnetic wave absorbing products in a dispersed state. That is, the dispersion powder in which the electromagnetic wave absorbing particles of the present embodiment are dispersed in a solid medium can be dispersed again in a liquid medium and used as a dispersion liquid for infrared absorbing products, or as described later, the dispersion powder can be kneaded into a resin and used as an electromagnetic wave absorbing particle dispersion.

[0082] The electromagnetic wave absorbing particle dispersion liquid of the present embodiment can be used in various applications that utilize photothermal conversion.

[0083] For example, by adding the electromagnetic wave absorbing particle dispersion liquid to an uncured thermosetting resin or adding an uncured thermosetting resin to the electromagnetic wave absorbing particle dispersion liquid, a curable ink composition can be obtained. The above-mentioned curable ink composition contains the aforementioned electromagnetic wave absorbing particles, and the electromagnetic wave absorbing particles function as an auxiliary agent for increasing the calorific value generated by irradiation with electromagnetic waves such as infrared rays. Since the curable ink composition contains a thermosetting resin, by irradiating the curable ink composition with electromagnetic waves such as infrared rays, the electromagnetic wave absorbing particles function as an auxiliary agent for increasing the calorific value as described above, and the thermosetting resin can be cured. By providing the curable ink composition on a substrate, for example, when irradiating with electromagnetic waves such as infrared rays, the adhesion between the cured product of the curable ink composition and the substrate can also be enhanced.

[0084] Therefore, in addition to the uses as a conventional ink, the curable ink composition can be suitably used, for example, in applications of a stereolithography method in which coating and curing by irradiation with electromagnetic waves such as infrared rays are repeatedly performed and stacked to form a three-dimensional object.

[0085] In addition, by adding the electromagnetic wave absorbing particles of the present embodiment to a heat-melted thermoplastic resin or adding a thermoplastic resin with high solubility in a solvent after dispersing the electromagnetic wave absorbing particles of the present embodiment in an appropriate solvent, a thermoplastic resin-containing ink composition can be obtained.

[0086] A thermoplastic resin-containing ink composition is provided, for example, on a substrate and irradiated with electromagnetic waves such as infrared rays, whereby a cured product of the thermoplastic resin-containing ink composition can be adhered to the substrate through solvent removal and heat fusion of the resin. At this time, also in such a thermoplastic resin-containing ink composition, similarly to the case of the above-described curable ink composition, the electromagnetic wave absorbing particles function as an auxiliary agent for increasing the amount of heat generated by irradiation with electromagnetic waves such as infrared rays.

[0087] Therefore, in addition to the use as a conventional ink, the thermoplastic resin-containing ink composition can be suitably used, for example, for applications of stereolithography in which coating, solvent removal by irradiation with electromagnetic waves such as infrared rays, and heat fusion of the resin are repeatedly performed and stacked to form a three-dimensional object.

[0088] The above-described curable ink composition and thermoplastic resin-containing ink composition explained so far are also examples of the electromagnetic wave absorbing particle dispersion liquid of the present embodiment. [4] Electromagnetic wave absorbing particle dispersion Next, the electromagnetic wave absorbing particle dispersion of the present embodiment will be explained.

[0089] The electromagnetic wave absorbing particle dispersion of the present embodiment can contain a solid medium and the above-described electromagnetic wave absorbing particles contained in the solid medium. The electromagnetic wave absorbing particles are preferably dispersed in the solid medium.

[0090] The solid medium means a medium that is solid at the temperature of use, and is particularly preferably a medium that is solid at room temperature (27°C). As the solid medium, resin, glass, etc. can be used.

[0091] As the solid medium, resin can be particularly preferably used from the viewpoint of ease of handling, etc.

[0092] When using a resin as the solid medium, the type of resin is not particularly limited. However, the resin can be, for example, one type of resin selected from the resin group consisting of polyester resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene-vinyl acetate copolymer, polyvinyl acetal resin, and ultraviolet curable resin, or a mixture of two or more types of resins selected from the above resin group.

[0093] The content ratio of the electromagnetic wave absorbing particles in the electromagnetic wave absorbing particle dispersion is not particularly limited. However, the electromagnetic wave absorbing particle dispersion preferably contains the electromagnetic wave absorbing particles at a ratio of 0.001 mass% or more and 80 mass% or less. This is because by containing the electromagnetic wave absorbing particles at 0.001 mass% or more, a sufficient infrared shielding function can be exhibited. Also, by setting the content ratio of the electromagnetic wave absorbing particles to 80 mass% or less, granulation of the electromagnetic wave absorbing particles with each other in the solid medium can be suppressed, so that particularly good transparency can be maintained. Also, the amount of the electromagnetic wave absorbing particles used can be suppressed, which is advantageous in terms of cost. Furthermore, by setting the content ratio of the electromagnetic wave absorbing particles to 80 mass% or less, the ratio of the solid medium contained in the electromagnetic wave absorbing particle dispersion can be increased, and the strength of the dispersion can be enhanced.

[0094] The shape etc. of the electromagnetic wave absorbing particle dispersion of this embodiment is not particularly limited and can be arbitrarily selected according to the application etc. For example, the electromagnetic wave absorbing particle dispersion of this embodiment is preferably in any one of a sheet shape, a board shape, and a film shape.

[0095] Regarding the electromagnetic wave absorbing particle dispersion of this embodiment, it will be described in the order of (1) the manufacturing method of the electromagnetic wave absorbing particle dispersion, (2) the electromagnetic wave absorbing base material, (3) the usage method of the electromagnetic wave absorbing particle dispersion and the article using the same. (1) The manufacturing method of the electromagnetic wave absorbing particle dispersion The manufacturing method of the electromagnetic wave absorbing particle dispersion is not particularly limited. The electromagnetic wave absorbing particle dispersion can be manufactured, for example, by kneading the aforementioned electromagnetic wave absorbing particles into a solid medium such as a resin and molding it into a desired shape such as a film or a board.

[0096] The electromagnetic wave absorbing particle dispersion can also be produced by mixing the aforementioned electromagnetic wave absorbing particle dispersion liquid with a solid medium such as resin. Also, a powdery dispersion in which the electromagnetic wave absorbing particles are dispersed in a solid medium, that is, by adding the aforementioned dispersion powder to a liquid medium and mixing it with a solid medium such as resin, it is also possible to produce an electromagnetic wave absorbing particle dispersion.

[0097] The shape of the electromagnetic wave absorbing particle dispersion of the present embodiment is not particularly limited. For example, when using resin as the solid medium, for example, it can be in the form of a sheet with a thickness of 0.1 μm or more and 50 mm or less, a board shape, or a film shape.

[0098] As described above, when kneading the aforementioned electromagnetic wave absorbing particles into a solid medium such as resin to prepare an electromagnetic wave absorbing particle dispersion, at a temperature near the melting point of the resin, which is the solid medium (for example, about 200°C or more and 300°C or less), the electromagnetic wave absorbing particles and the solid medium are heated and mixed and kneaded.

[0099] In addition, the material obtained by kneading the electromagnetic wave absorbing particles into a solid medium can be formed into a desired shape, but it can also be pelletized once, and the pellets can be formed into a desired shape such as a film or a board by various methods.

[0100] The forming method is not particularly limited, and for example, an extrusion molding method, an inflation molding method, a solution casting method, a casting method, etc. can be used.

[0101] As described above, when the electromagnetic wave absorbing particle dispersion is in the form of a sheet, a board, or a film, its thickness is not particularly limited and can be selected according to the application, etc.

[0102] Also, the filler amount with respect to the solid medium in the electromagnetic wave absorbing particle dispersion, that is, the blending amount of the electromagnetic wave absorbing particles, can be arbitrarily selected according to the thickness of the electromagnetic wave absorbing particle dispersion, the optical properties, mechanical properties, etc. required for the electromagnetic wave absorbing particle dispersion. For example, generally 80% by mass or less with respect to the resin is preferable.

[0103] If the filler amount with respect to the solid medium is 80% by mass or less, granulation of electromagnetic wave absorbing particles in the solid medium can be suppressed, so that particularly good transparency can be maintained. In addition, the amount of electromagnetic wave absorbing particles used can also be suppressed, which is advantageous in terms of cost.

[0104] The lower limit of the filler amount with respect to the solid medium is not particularly limited. However, from the viewpoint of the electromagnetic wave absorbing particle dispersion exhibiting a sufficient infrared shielding function, it is preferably, for example, 0.001% by mass or more.

[0105] The electromagnetic wave absorbing particle dispersion can also be used in a state where the electromagnetic wave absorbing particle dispersion in which electromagnetic wave absorbing particles are dispersed in a solid medium is further pulverized into a powder. When adopting this configuration, in the powdery electromagnetic wave absorbing particle dispersion, the electromagnetic wave absorbing particles are sufficiently dispersed in the solid medium. Therefore, by dissolving the powdery electromagnetic wave absorbing particle dispersion in an appropriate liquid medium or kneading it with resin pellets, etc. as a so-called masterbatch, a liquid or solid electromagnetic wave absorbing particle dispersion can be easily produced.

[0106] The solid media that form the matrix of the above-mentioned sheets, boards, and films are not particularly limited and can be selected according to the application. As described above, resins can be preferably used from the perspective of handleability. When using a resin as the solid medium, one type of resin selected from the resin group consisting of polyester resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene-vinyl acetate copolymer, polyvinyl acetal resin, and ultraviolet curable resin, or a mixture of two or more types of resins selected from the above resin group can be preferably used. In particular, as a resin with low cost, high transparency, and wide versatility, one or more types of resins selected from polyethylene terephthalate resin, acrylic resin, polyamide resin, vinyl chloride resin, polycarbonate resin, olefin resin, epoxy resin, polyimide resin, etc. can be preferably used. Also, fluororesin can be used considering weather resistance. (2) Electromagnetic wave absorbing substrate The electromagnetic wave absorbing particle dispersion of this embodiment also includes an electromagnetic wave absorbing substrate having a substrate and a dispersion film containing the above-mentioned electromagnetic wave absorbing particles disposed on the surface of the substrate.

[0107] Such an electromagnetic wave absorbing substrate can be manufactured, for example, by the following procedure.

[0108] Prepare an electromagnetic wave absorbing particle dispersion liquid by mixing the above-mentioned electromagnetic wave absorbing particles, a liquid medium such as an organic solvent like alcohol or water, a resin binder, and optionally a dispersant (dispersion liquid preparation step).

[0109] Next, apply the above-mentioned electromagnetic wave absorbing particle dispersion liquid onto the surface of an appropriate substrate (coating step).

[0110] Remove the liquid medium or cure it to obtain an electromagnetic wave absorbing particle dispersion (dispersion preparation step).

[0111] Through the above steps, an electromagnetic wave absorbing substrate with an electromagnetic wave absorbing particle dispersion directly laminated on the substrate surface is obtained.

[0112] The above resin binder component can be selected according to the application, and examples thereof include ultraviolet curable resins, thermosetting resins, room temperature curable resins, thermoplastic resins, and the like.

[0113] On the other hand, an electromagnetic wave absorbing particle dispersion liquid containing no resin binder component may be applied, and an electromagnetic wave absorbing particle dispersion may be laminated on the surface of the base material. Further, after applying the electromagnetic wave absorbing particle dispersion liquid containing no resin binder component, a liquid medium containing a binder component may be applied on the layer of the electromagnetic wave absorbing particle dispersion.

[0114] Specifically, for example, a liquid electromagnetic wave absorbing particle dispersion liquid in which electromagnetic wave absorbing particles are dispersed in one or more liquid media selected from organic solvents, organic solvents in which resins are dissolved, organic solvents in which resins are dispersed, and water is applied to the surface of the base material. Then, the obtained coating film can be solidified by an appropriate method to obtain an electromagnetic wave absorbing base material.

[0115] Further, a liquid electromagnetic wave absorbing particle dispersion liquid containing a resin binder component is applied to the surface of the base material, and the obtained coating film can be solidified by an appropriate method to obtain an electromagnetic wave absorbing base material.

[0116] Furthermore, a liquid electromagnetic wave absorbing particle dispersion liquid obtained by mixing an electromagnetic wave absorbing particle dispersion in which electromagnetic wave absorbing particles are dispersed in a solid medium in powder form with a predetermined medium is applied to the surface of the base material, and the obtained coating film can be solidified by an appropriate method to obtain an electromagnetic wave absorbing base material.

[0117] Of course, among the above liquid electromagnetic wave absorbing particle dispersion liquids, an electromagnetic wave absorbing particle dispersion liquid obtained by mixing two or more types can be applied to the surface of the base material, and the obtained coating film can be solidified by an appropriate method to obtain an electromagnetic wave absorbing base material.

[0118] The material of the substrate used for the electromagnetic wave absorbing substrate is not particularly limited as long as it is a transparent body, but one or more selected from glass, resin sheets, resin boards, resin films, etc. are preferably used. Note that the transparent body is a material that transmits light in the visible light region, and the degree of light transmission in the visible light region can be arbitrarily selected according to the use of the electromagnetic wave absorbing substrate and the like.

[0119] The resin used for the resin sheet, resin board, and resin film is not particularly limited and can be selected according to the required characteristics such as the surface state and durability of the sheet, board, and film. Examples of the above resin include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymers, acrylic polymers such as polymethyl methacrylate, styrene polymers such as polystyrene and acrylonitrile-styrene copolymer, polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, olefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as aromatic polyamide, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, allylate polymers, polyoxymethylene polymers, epoxy polymers, and one or more selected from transparent polymers such as binary and ternary copolymers, graft copolymers, and blends thereof. In particular, biaxially oriented polyester films such as polyethylene terephthalate, polybutylene terephthalate, or polyethylene-2,6-naphthalate are more suitable in terms of mechanical properties, optical properties, heat resistance, and economy. The biaxially oriented polyester film may be a copolymerized polyester type. (3) Method of using the electromagnetic wave absorbing particle dispersion and articles using the same The electromagnetic wave absorbing particle dispersion and the electromagnetic wave absorbing base material of the present embodiment described so far can transmit light in the visible light region and shield light in the infrared region. Therefore, for example, in various buildings and vehicles, it can be used for window materials and the like for the purpose of shielding light in the infrared region while sufficiently taking in visible light and suppressing the temperature rise indoors while maintaining brightness. It can also be suitably used for filters and the like that shield infrared rays radiated forward from a PDP (Plasma Display Panel).

[0120] In addition, since the electromagnetic wave absorbing particles of the present embodiment have absorption in the infrared region, when an infrared laser is irradiated onto the printing surface containing the electromagnetic wave absorbing particles, infrared rays having a specific wavelength are absorbed. Therefore, a forgery prevention printed matter obtained by printing a forgery prevention ink containing the electromagnetic wave absorbing particles on one or both sides of a substrate to be printed can be irradiated with infrared rays having a specific wavelength, and by reading the reflection or transmission thereof, the authenticity of the printed matter can be determined from the difference in the amount of reflection or transmission. The forgery prevention printed matter is an example of the electromagnetic wave absorbing particle dispersion of the present embodiment.

[0121] In addition, an ink obtained by mixing the above-described electromagnetic wave absorbing particle dispersion liquid and a binder component is applied onto a substrate, and after drying the applied ink, the dried ink is cured to form a photothermal conversion layer. The photothermal conversion layer generates heat at a location irradiated with an electromagnetic wave laser such as infrared rays and can heat an adjacent material. Therefore, the photothermal conversion layer can generate heat only at a desired location with high positional accuracy by irradiation with an electromagnetic wave laser such as infrared rays. For this reason, the photothermal conversion layer can be applied as a local heating medium in a wide range of fields such as electronics, medicine, agriculture, and machinery. For example, it can be suitably used as a donor sheet used when forming an organic electroluminescence element by a laser transfer method, a thermal paper for a thermal printer, or an ink ribbon for a thermal transfer printer. The photothermal conversion layer is an example of the electromagnetic wave absorbing particle dispersion of the present embodiment.

[0122] Further, by dispersing the aforementioned electromagnetic wave absorbing particles in an appropriate medium and incorporating the dispersion in one or more selected locations from the surface and the interior of the fiber, an infrared absorbing fiber can be obtained. Since the infrared absorbing fiber contains electromagnetic wave absorbing particles, it can efficiently absorb near-infrared rays and the like from sunlight, etc., and becomes an infrared absorbing fiber with excellent heat retention properties. Since the infrared absorbing fiber transmits light in the visible light region, it becomes an infrared absorbing fiber with excellent design properties.

[0123] As a result, it can be used in various applications such as cold-proof clothing, sports clothing, stockings, curtains and other textile products that require heat retention, and other industrial textile products. The infrared absorbing fiber is an example of the electromagnetic wave absorbing particle dispersion of the present embodiment.

[0124] Also, the electromagnetic wave absorbing particle dispersion of the present embodiment can be applied to materials such as the roofs and outer wall materials of agricultural and horticultural houses. Since the electromagnetic wave absorbing particle dispersion of the present embodiment transmits visible light, it can ensure the light necessary for the photosynthesis of plants in the agricultural and horticultural house. And since the electromagnetic wave absorbing particles of the present embodiment can efficiently absorb light such as near-infrared light contained in sunlight other than visible light, it can be used as a heat insulating material for agricultural and horticultural facilities with heat insulating properties. The heat insulating material for agricultural and horticultural facilities is an example of the electromagnetic wave absorbing particle dispersion of the present embodiment. [5] Electromagnetic wave absorbing laminate The electromagnetic wave absorbing laminate of the present embodiment can have a laminated structure including the aforementioned electromagnetic wave absorbing particle dispersion and a transparent base material. Examples of the electromagnetic wave absorbing laminate include a case where two or more transparent base materials and the above-mentioned electromagnetic wave absorbing particle dispersion are laminated. In this case, the electromagnetic wave absorbing particle dispersion can be disposed between the transparent base materials, for example, and used as an intermediate film for electromagnetic wave absorption.

[0125] In this case, the intermediate film for electromagnetic wave absorption preferably has any one of a sheet shape, a board shape, and a film shape.

[0126] As the transparent substrate, one or more selected from plate glass, plate-shaped plastics, film-shaped plastics, etc., which are transparent in the visible light region, can be preferably used. Note that the transparent substrate being transparent in the visible light region means that it is a substrate that transmits light in the visible light region. The degree of light transmission of the transparent substrate in the visible light region can be arbitrarily selected according to the use of the electromagnetic wave absorption laminate, etc.

[0127] When using plastic as the transparent substrate, the material of the plastic is not particularly limited and can be selected according to the use. For example, one or more selected from polycarbonate resin, acrylic resin, polyester resin, polyamide resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, ionomer resin, fluororesin, etc. can be used. Note that as the polyester resin, polyethylene terephthalate resin can be preferably used.

[0128] The transparent substrate may contain particles having an electromagnetic wave absorption function. As the particles having an electromagnetic wave absorption function, for example, the above-described electromagnetic wave absorption particles can be used.

[0129] By using the above-described electromagnetic wave absorption particle dispersion as a constituent member of the intermediate layer sandwiched between a plurality of transparent substrates, a solar radiation shielding composite structure, which is a type of electromagnetic wave absorption laminate that transmits visible light and has an electromagnetic wave absorption function, can be obtained.

[0130] Note that the above-described electromagnetic wave absorption laminate can also be obtained by bonding and integrating a plurality of transparent substrates facing each other with the electromagnetic wave absorption particle dispersion interposed therebetween by a known method.

[0131] When using the above-described electromagnetic wave absorption particle dispersion as an intermediate film for electromagnetic wave absorption, as the solid medium, those described for the electromagnetic wave absorption particle dispersion can be used. However, from the viewpoint of enhancing the adhesion strength between the intermediate film for electromagnetic wave absorption and the transparent substrate, the solid medium is preferably a polyvinyl acetal resin.

[0132] The above intermediate film for electromagnetic wave absorption can be manufactured by the method for manufacturing the electromagnetic wave absorption particle dispersion described above, and can be, for example, an intermediate film for electromagnetic wave absorption having any one of a sheet shape, a board shape, or a film shape.

[0133] In addition, when the intermediate film for electromagnetic wave absorption does not sufficiently have flexibility and adhesiveness to the transparent base material, it is preferable to add a liquid plasticizer for the medium resin. For example, when the medium resin used for the intermediate film for electromagnetic wave absorption is a polyvinyl acetal resin, the addition of a liquid plasticizer for the polyacetal resin is beneficial for improving the adhesiveness to the transparent base material.

[0134] As the plasticizer, a substance used as a plasticizer for the medium resin can be used. For example, as the plasticizer used for an infrared ray shielding film composed of a polyvinyl acetal resin, plasticizers such as compounds of monohydric alcohols and organic acid esters, ester-based plasticizers such as polyhydric alcohol organic acid ester compounds, and phosphoric acid-based plasticizers such as organic phosphoric acid-based plasticizers can be mentioned. It is preferable that any plasticizer is liquid at room temperature. Among them, a plasticizer which is an ester compound synthesized from a polyhydric alcohol and a fatty acid is preferable.

[0135] In addition, 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 can also be added to the intermediate film for electromagnetic wave absorption. The metal constituting the metal salt of the carboxylic acid, the metal hydroxide, and the metal carbonate is not particularly limited, but it is preferably at least one selected from sodium, potassium, magnesium, calcium, manganese, cesium, lithium, rubidium, and zinc. In the intermediate film for near-infrared ray absorption, it is preferable that the content of at least one selected from the group consisting of a metal salt of a carboxylic acid, a metal hydroxide, and a metal carbonate is 1% by mass or more and 100% by mass or less with respect to the electromagnetic wave absorption particles.

[0136] Furthermore, the intermediate film for electromagnetic wave absorption can also contain, if necessary, in addition to the aforementioned electromagnetic wave absorption particles, at least one type of particle selected from oxide particles, composite oxide particles, and boride particles containing two or more elements selected from the group consisting of Sb, V, Nb, Ta, W, Zr, F, Zn, Al, Ti, Pb, Ga, Re, Ru, P, Ge, In, Sn, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Tb, Lu, Sr, and Ca. The intermediate film for electromagnetic wave absorption can contain such particles in the range of 5% by mass or more and 95% by mass or less when the total of such particles and the electromagnetic wave absorption particles is 100% by mass.

[0137] The electromagnetic wave absorption laminate may contain an ultraviolet absorber in at least one of the intermediate films disposed between the transparent substrates. Examples of the ultraviolet absorber include one or more selected from compounds having a malonic ester structure, compounds having an oxalic anilide structure, compounds having a benzotriazole structure, compounds having a benzophenone structure, compounds having a triazine structure, compounds having a benzoate structure, compounds having a hindered amine structure, and the like.

[0138] Of course, the intermediate layer of the electromagnetic wave absorption laminate may be composed only of the intermediate film for electromagnetic wave absorption.

[0139] The intermediate film for electromagnetic wave absorption described here is also an example of an electromagnetic wave absorption particle dispersion. Further, the electromagnetic wave absorption laminate of the present embodiment is not limited to the form in which the electromagnetic wave absorption particle dispersion is disposed between the transparent substrates as described above, and any configuration can be adopted as long as it has a laminated structure including the electromagnetic wave absorption particle dispersion and the transparent substrate.

Examples

[0140] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. (Evaluation method) First, the evaluation methods in the following examples and reference examples will be described. (Cumulative 50% particle size, cumulative 95% particle size) The particle size distribution of the electromagnetic wave absorbing particles in the examples and reference examples was measured by a particle size distribution measuring apparatus (UPA-150 manufactured by Nikkiso Co., Ltd.) based on the dynamic light scattering method for analyzing by the frequency analysis method. As the measurement conditions, the particle refractive index was set to 1.81, and a non-spherical particle shape was used. Also, the background was measured with methyl isobutyl ketone, and the solvent refractive index was set to 1.40. Then, the cumulative 50% particle diameter and the cumulative 95% particle diameter were determined from the obtained particle size distribution. (Crystal Structure) Using the electromagnetic wave absorbing particles obtained by removing the solvent from the electromagnetic wave absorbing particle dispersion, the crystal structure of the composite oxide contained in the electromagnetic wave absorbing particles was measured.

[0141] The measurement was carried out by the powder X-ray diffraction method (θ-2θ method) using a powder X-ray diffractometer (X'Pert-PRO / MPD manufactured by PANalytical B.V.) for the X-ray diffraction pattern of the electromagnetic wave absorbing particles. The crystal structure contained in the particles was specified from the obtained X-ray diffraction pattern.

[0142] (Optical Properties of the Dispersion) The optical properties of the electromagnetic wave absorbing particle dispersions in the examples and reference examples were measured as follows. First, the electromagnetic wave absorbing particle dispersion was diluted with methyl isobutyl ketone as the solvent in a glass cell for measurement of a spectrophotometer. At this time, the dilution ratio was set so that the visible light transmittance after dilution became 70%. Next, a transmittance profile was measured at intervals of 5 nm in the range of 200 nm or more and 2600 nm or less in wavelength by a spectrophotometer (UH4150 manufactured by Hitachi High-Tech Science Corporation), and the visible light transmittance and the solar radiation transmittance were calculated in the range of 300 nm or more and 2100 nm or less based on JIS R 3106 (2019). At this time, in the measurement, the incident direction of the light of the spectrophotometer was set to a direction perpendicular to the glass cell for measurement. Also, a blank solution containing only methyl isobutyl ketone as the solvent in the glass cell for measurement was used as the baseline of the light transmittance. (Optical Properties of the Electromagnetic Wave Absorbing Substrate) The optical properties of the electromagnetic wave absorbing base materials in the examples and reference examples were measured using a spectrophotometer (UH4150 manufactured by Hitachi High-Tech Science Corporation). The transmission light profile was measured at 5 nm intervals in the wavelength range of 200 nm or more and 2600 nm or less, and the visible light transmittance and solar radiation transmittance were calculated based on JIS R 3106 (2019) in the wavelength range of 300 nm or more and 2100 nm or less. (Haze) The haze value of the electromagnetic wave absorbing base material was measured using a haze meter (HM-150N manufactured by Murakami Color Technology Laboratory Co., Ltd.) and calculated based on JIS K 7136 (2000). [Example 1] (Electromagnetic wave absorbing particles) 8.65 g of strontium oxide (SrO, manufactured by Fujifilm Wako Pure Chemical Corporation, purity 96.8%) and 11.58 g of molybdenum oxide (MoO3, manufactured by Kanto Chemical Co., Inc., purity 100.0%) were thoroughly mixed to be uniform. The obtained mixed powder was placed in an alumina boat and fired at a temperature of 1300 °C for 2 hours in an air atmosphere to obtain strontium molybdate with the composition formula SrMoO4 as an intermediate product.

[0143] 6.05 g of the obtained SrMoO4, 1.31 g of SrO, and 1.18 g of molybdenum powder (Mo, manufactured by Fujifilm Wako Pure Chemical Corporation, purity 99.3%) were thoroughly mixed to be uniform. At this time, the Sr:Mo molar ratio after mixing was 1:1. 4 g of the obtained mixed powder was taken and placed in an alumina crucible, and fired at a temperature of 1300 °C for 3 hours under a 3% by volume H2 gas stream using Ar gas as a carrier to obtain strontium molybdate with the composition formula SrMoO z (2.0 < z ≤ 3.0).

[0144] (Electromagnetic wave absorbing particle dispersion liquid) 6% by mass of strontium molybdate according to Example 1 and 6% by mass of an acrylic polymer dispersant (acrylic dispersant with an amine value of 48 mgKOH / g and a decomposition temperature of 250 °C) having a group containing an amine as a functional group were mixed with 88% by mass of methyl isobutyl ketone to obtain a mixed solution (slurry). The obtained mixed solution was put into a glass bottle together with φ0.3 mm ZrO2 beads, loaded into a paint shaker, and subjected to grinding and dispersion treatment for 5 hours to obtain an electromagnetic wave absorbing particle dispersion liquid according to Example 1. At this time, strontium molybdate particles become electromagnetic wave absorbing particles.

[0145] When the particle size distribution of the electromagnetic wave absorbing particle dispersion liquid according to Example 1 was measured, the cumulative 50% particle diameter was 34 nm and the cumulative 95% particle diameter was 48 nm.

[0146] Also, when the solvent (dispersion medium) was removed from the electromagnetic wave absorbing particle dispersion liquid and the powder X-ray diffraction pattern of strontium molybdate according to Example 1 was measured, diffraction peaks attributable to the crystal phase of SrMoO3 with a cubic perovskite structure were confirmed.

[0147] When the electromagnetic wave absorbing particle dispersion liquid according to Example 1 was diluted with methyl isobutyl ketone as the solvent and the optical properties were measured, the visible light transmittance was 70% and the solar radiation transmittance was 43%. (Electromagnetic wave absorbing particle dispersion) The electromagnetic wave absorbing particle dispersion liquid according to Example 1 and a UV curable resin (Aronix UV-3701 manufactured by Toagosei Co., Ltd.) were weighed so that the mass ratio was 1:1, mixed and stirred to prepare a dispersion liquid for forming an electromagnetic wave absorbing base material. Then, using a bar coater with bar No. 10, the dispersion liquid for forming an electromagnetic wave absorbing base material was applied onto clear glass with a thickness of 3 mm, dried under the conditions of 70 °C for 1 minute, and irradiated with a high-pressure mercury lamp to obtain an electromagnetic wave absorbing base material according to Example 1. The electromagnetic wave absorbing base material is an example of an electromagnetic wave absorbing fine particle dispersion.

[0148] When the optical properties of the obtained electromagnetic wave absorbing base material according to Example 1 were measured, the visible light transmittance was 68% and the solar radiation transmittance was 44%. Also, when the haze was measured, it was 0.3%.

[0149] The manufacturing conditions according to Example 1 are shown in Table 1, and the results are shown in Tables 1 and 2. [Example 2] An intermediate product represented by the composition formula BaMoO4 was obtained using barium carbonate (BaCO3, manufactured by Fujifilm Wako Pure Chemical Corporation, purity 99.9%) instead of strontium oxide. Then, using BaMoO4 instead of SrMoO4, the molar ratio of Ba to Mo, which is the molar ratio of Ba and Mo after mixing BaMoO4, BaCO3, and molybdenum powder, was set to 1:1. Electromagnetic wave absorbing particles were prepared in the same manner as in Example 1 except for the above points.

[0150] By the above procedure, barium molybdate represented by the composition formula BaMoO z (2.0 < z ≤ 3.0) was prepared.

[0151] Also, an electromagnetic wave absorbing particle dispersion and an electromagnetic wave absorbing base material were prepared in the same manner as in Example 1 except for using the electromagnetic wave absorbing particles, and the same evaluation as in Example 1 was carried out. The evaluation results are shown in Tables 1 and 2. [Example 3] An intermediate product represented by the composition formula SrCrO4 was obtained using chromium oxide (CrO3, manufactured by Fujifilm Wako Pure Chemical Corporation, purity 98%) instead of molybdenum oxide. Then, using SrCrO4 instead of SrMoO4, the molar ratio of Sr to Cr, which is the molar ratio of Sr and Cr after mixing SrCrO4, SrO, and chromium powder (Cr, manufactured by Fujifilm Wako Pure Chemical Corporation, purity 99.5%), was set to 1:1. Electromagnetic wave absorbing particles were prepared in the same manner as in Example 1 except for the above points.

[0152] By the above procedure, strontium chromate represented by the composition formula SrCrO z (2.0 < z ≤ 3.0) was prepared.

[0153] Except for using the electromagnetic wave absorbing particles, an electromagnetic wave absorbing particle dispersion liquid and an electromagnetic wave absorbing base material were prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was carried out. The evaluation results are shown in Tables 1 and 2. [Reference Example 1] 54.9 g of SnCl4·5H2O (Wako Pure Chemical Industries, Ltd., Wako Special Grade, purity 98% or more) was dissolved in 340 g of water at 25°C to obtain a tin compound solution. To the tin compound solution, 12.7 ml of a methanol solution (Yoneyama Pharmaceutical Co., Ltd., reagent special grade, purity 99.8% or more) in which 4.2 g of SbCl3 (Wako Pure Chemical Industries, Ltd., JIS special grade, purity 98% or more), which is an antimony compound, was dissolved, and an NH4OH aqueous solution (Wako Pure Chemical Industries, Ltd., reagent special grade, concentration 30%), which is an alkaline solution diluted to a concentration of 16%, were added dropwise in parallel. Then, by the parallel dropping, a hydroxide containing tin and antimony, which is a precursor of antimony-doped tin oxide (hereinafter abbreviated as ATO) electromagnetic wave absorbing particles, was formed and precipitated.

[0154] The addition amount of the antimony compound to the tin compound solution was 9.5 parts by mass in terms of antimony element with respect to 100 parts by mass of tin(IV) oxide from the viewpoint of desired optical properties. By setting the addition amount as such, ATO electromagnetic wave absorbing particles in which the Sn element is about 68% by mass and the Sb element is about 8% by mass can be produced.

[0155] As described above, ammonia water was used as the alkaline solution used as the precipitating agent, and the alkaline concentration was set to 16%, which is 1.6 times the chemical equivalent required for the tin compound and the antimony compound to form a hydroxide.

[0156] The parallel dropping time of the methanol solution and the alkaline solution was 25 minutes, and parallel dropping was carried out until the pH of the solution obtained by dropping reached 7.5. After the dropping was completed, stirring of the solution was continued for 10 minutes to achieve homogenization in the system. The temperature of the solution at that time was the same as the temperature during parallel dropping, and was set to 65°C.

[0157] Next, decantation was repeatedly performed on the precipitate for washing. Washing was sufficiently carried out until the conductivity of the supernatant of the washing liquid in the decantation became 1 mS / cm or less, followed by filtration.

[0158] Next, the washed precipitate was wet-treated with an anhydrous ethyl alcohol solution (reagent special grade, purity 99.5% or more, manufactured by Wako Pure Chemical Industries, Ltd.). During the wet-treatment, the mass ratio of [filtered precipitate: anhydrous ethyl alcohol solution] was set to a ratio of 1:4 (the alcohol ratio corresponding to 80%), and the filtered precipitate and the anhydrous ethyl alcohol solution were stirred at room temperature for 1 hour for wet-treatment to obtain a precursor. After completion of the wet-treatment, the precursor was dried at 90 °C for 10 hours to obtain a dried product.

[0159] Then, the ATO electromagnetic wave absorption particle precursor that had undergone the wet-treatment was heated to 700 °C in an air atmosphere and fired for 2 hours to produce the ATO electromagnetic wave absorption particles according to Reference Example 1.

[0160] As the electromagnetic wave absorption particles, SrMoO z Except that the ATO electromagnetic wave absorption particles according to Reference Example 1 were used instead of the particles, an electromagnetic wave absorption particle dispersion liquid and an electromagnetic wave absorption base material according to Reference Example 1 were prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was carried out. The evaluation results in Reference Example 1 are shown in Tables 1 and 2.

[0161]

Table 1

[0162]

Table 2

[0163] Moreover, it was confirmed that such visible light transmittance and solar radiation transmittance are the same as or superior to those of ATO, which has been conventionally used as electromagnetic wave absorbing particles. Therefore, it was confirmed that the electromagnetic wave absorbing particles obtained in Examples 1 to 3 are novel electromagnetic wave absorbing particles that can be put to practical use.

Claims

1. Electromagnetic wave absorbing particles containing a composite oxide, wherein the composite oxide consists of an element A which is one or more elements selected from H, an alkali metal, Mg, and an alkaline earth metal, an element B which is one or more elements selected from Cr and Mo, and oxygen, when the amount of substance of the element A contained in the composite oxide is x and the amount of substance of the element B is y, the relationship 0.001 ≦ x / y ≦ 1.5 is satisfied, the electromagnetic wave absorbing particles having a volume-based cumulative 50% particle diameter of 1 nm or more and 50 nm or less and a cumulative 95% particle diameter of 5 nm or more and 100 nm or less as measured by a particle size distribution measuring device and absorbing near-infrared rays.

2. The electromagnetic wave absorbing particles according to Claim 1, wherein the element A is one or more elements selected from Ca, Sr, Ba, and Ra.

3. The element A is one or more elements selected from Ca, Sr, and Ba, the element B is Mo, and the electromagnetic wave absorbing particles according to Claim 1 or Claim 2 satisfying 0.5 ≦ x / y ≦ 1.

2.

4. A liquid medium, and the electromagnetic wave absorbing particles according to any one of Claims 1 to 3 contained in the liquid medium, an electromagnetic wave absorbing particle dispersion.

5. The electromagnetic wave absorbing particle dispersion according to Claim 4, wherein the liquid medium contains one or more selected from water, an organic solvent, a liquid plasticizer, an oil or fat, and a compound polymerized by curing.

6. A solid medium, and the electromagnetic wave absorbing particles according to any one of Claims 1 to 3 contained in the solid medium, an electromagnetic wave absorbing particle dispersion.

7. The electromagnetic wave absorbing particle dispersion according to Claim 6, wherein the solid medium is a resin.

8. The resin is one resin selected from the resin group consisting of a polyester resin, a polycarbonate resin, an acrylic resin, a styrene resin, a polyamide resin, a polyethylene resin, a vinyl chloride resin, an olefin resin, an epoxy resin, a polyimide resin, a fluororesin, an ethylene-vinyl acetate copolymer, a polyvinyl acetal resin, and an ultraviolet curable resin, or a mixture of two or more resins selected from the resin group, the electromagnetic wave absorbing particle dispersion according to Claim 7.

9. The electromagnetic wave absorbing particle dispersion according to any one of Claims 6 to 8 having a sheet shape, a board shape, or a film shape.

10. The electromagnetic wave absorbing particle dispersion according to any one of Claims 6 to 9, and An electromagnetic wave absorbing laminate having a laminate structure including a transparent substrate and...

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