Titanium dioxide particles for blue light blocking, titanium dioxide particle dispersion, paint composition, and coated substrate.

Abstract

To provide titanium dioxide particles with excellent blue light filtering capabilities. [Solution] Iron-containing titanium dioxide particles for blue light blocking.

Description

[Technical Field]

[0001] The present invention relates to titanium dioxide particles useful for blue light cutting applications, such as absorbing blue light emitted from digital displays, and to a dispersion, paint composition, and coated substrate containing the titanium dioxide particles. [Background technology]

[0002] It is known that blue light with wavelengths of 380-500nm, which has high energy within the visible light spectrum, emitted from digital displays such as personal computers, televisions, and smartphones, can strain the eyes when it enters them.

[0003] In recent years, one known method for blocking blue light entering the eyes is to use eyeglass lenses containing a blue light-blocking substance. As an example of a blue light-blocking substance, Patent Document 1 discloses that metal oxide hollow particles can shield (block) blue light. Furthermore, it is disclosed that rutile-type titanium oxide hollow particles are preferred as a preferred example of metal oxide hollow particles. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-072647 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, conventional titanium dioxide particles did not have sufficient performance to block blue light.

[0006] Therefore, the object of the present invention is to provide titanium dioxide particles that have excellent blue light-cutting properties. [Means for solving the problem]

[0007] The inventors have discovered that by including iron in titanium dioxide particles, the particles exhibit superior blue light filtering capabilities. [Effects of the Invention]

[0008] According to one aspect of the present invention, titanium dioxide particles with excellent blue light filtering capabilities can be provided. [Modes for carrying out the invention]

[0009] This invention relates to titanium dioxide particles for blue light filtering. The following describes in detail the titanium dioxide particles for blue light filtering according to embodiments of this invention.

[0010] [Titanium dioxide particles for blue light blocking] The titanium dioxide particles for blue light blocking according to this embodiment (hereinafter sometimes referred to as "titanium dioxide particles") contain iron. The crystal structure of the titanium dioxide particles may be any of the known rutile, anatase, or brookite types, or a mixture of these may be present. Among these crystal structures, the rutile crystal structure of the titanium dioxide particles is preferred, and a single rutile phase is more preferred. Rutile titanium dioxide tends to have a higher refractive index and lower photocatalytic activity compared to anatase and brookite titanium dioxide. Furthermore, the state of the iron contained in the titanium dioxide particles is not particularly limited. For example, (i) the iron may be solid-dissolved in the crystal structure of the titanium dioxide, or (ii) it may exist on the surface of the titanium dioxide particles or as an iron compound such as iron oxide.

[0011] It is preferable that titanium dioxide particles have iron dissolved in their crystal structure. Titanium dioxide particles with dissolved iron exhibit reduced transmittance of blue light (wavelength: 380-500 nm). This is thought to be because the solid solution of iron in the titanium dioxide crystal structure forms a band gap corresponding to the wavelength region that absorbs blue light. Furthermore, an unexpected secondary effect of reduced photocatalytic activity was also observed. Additionally, coating films containing such titanium dioxide particles exhibit a higher refractive index. Generally, solid solution refers to a state in which two or more elements (which may be metals or nonmetals) dissolve together, forming a uniform solid phase. Solid solutions obtained through solid solution are classified into substitutional solid solutions and interstitial solid solutions. When a specific element is dissolved in a crystal structure in this way, the interplanar spacing changes. In this embodiment, if the interplanar spacing changes and no X-ray diffraction peaks originating from iron or iron compounds are detected, it was determined that iron is dissolved in the crystal structure of titanium oxide. The change in interplanar spacing was judged based on the (110) plane of titanium oxide that does not contain a specific element in solid solution. For example, in the case of a rutile crystal structure, the interplanar spacing of the (110) plane of the reference titanium oxide was 0.3248 nm, so if it was 0.3250 nm or more, it was determined that the interplanar spacing had changed.

[0012] When the titanium dioxide particles are of the rutile type, the interplanar spacing of the (110) planes is preferably 0.3270 nm or more, more preferably 0.3274 nm or more, and particularly preferably 0.3278 nm or more. Titanium dioxide particles with such interplanar spacing have lower blue light transmittance. The upper limit of the interplanar spacing of the (110) planes obtained by X-ray diffraction measurement is not particularly limited, but may be 0.3500 nm or less, 0.3400 nm or less, or 0.3300 nm or less.

[0013] The iron content in titanium dioxide particles is preferably 3 mol% or more, more preferably 6 mol% or more, and particularly preferably 10 mol% or more, relative to titanium. Such titanium dioxide particles have a lower blue light transmittance. Their photocatalytic activity is also reduced. Furthermore, coating films containing such titanium dioxide particles have a higher refractive index. The iron content is preferably 30 mol% or less, more preferably 25 mol% or less, and particularly preferably 20 mol% or less. Such titanium dioxide particles tend to have a higher overall visible light transmittance.

[0014] The titanium dioxide particles preferably contain at least one element selected from the group consisting of tin, silicon, zirconium, sodium, and potassium. Tin has the effect of suppressing the formation of crystalline structures other than rutile, such as anatase. As a result, the photocatalytic activity of titanium dioxide particles is lower, and the refractive index tends to be higher. The tin content is preferably 1 mol% or more, more preferably 4 mol% or more, and particularly preferably 7 mol% or more, relative to titanium. There is no particular upper limit to the tin content, but it may be 20 mol% or less, 15 mol% or less, or 10 mol% or less, relative to titanium. Silicon has the effect of lowering the photocatalytic activity of titanium dioxide particles. It also has the effect of improving the dispersibility of titanium dioxide particles in water. The silicon content is preferably 1 mol% or more, more preferably 5 mol% or more, and particularly preferably 10 mol% or more, relative to titanium. There is no particular upper limit to the silicon content, but it may be 30 mol% or less, 25 mol% or less, or 20 mol% or less, relative to titanium. Zirconium has the effect of lowering the photocatalytic activity of titanium oxide particles. The zirconium content is preferably 1 mol% or more, more preferably 3 mol% or more, and particularly preferably 5 mol% or more, relative to titanium. There is no particular upper limit to the zirconium content, but it may be 20 mol% or less, 15 mol% or less, or 10 mol% or less, relative to titanium. Alkali metals such as sodium and potassium enhance the dispersibility of titanium oxide particles in water, with potassium being preferred. The potassium content is preferably 0.1 mol% or more, 0.5 mol% or more, and particularly preferably 1 mol% or more, relative to titanium. There is no particular upper limit to the potassium content, but it may be 10 mol% or less, 5 mol% or less, or 3 mol% or less, relative to titanium.

[0015] The titanium content in the titanium oxide particles is preferably 40% by mass or more, more preferably 50% by mass or more, and particularly preferably 60% by mass or more, based on TiO2 equivalent, relative to the total amount of titanium oxide particles. A coating film containing such titanium oxide particles has a high refractive index. The upper limit of the titanium content is preferably 99% by mass or less, more preferably 80% by mass or less, and particularly preferably 75% by mass or less. Such titanium oxide particles can contain a large amount of iron and the aforementioned elements.

[0016] The average particle diameter of titanium oxide particles is preferably 5 nm or more, more preferably 8 nm or more, and particularly preferably 10 nm or more. The upper limit of the average particle diameter is preferably 50 nm or less, more preferably 40 nm or less, and particularly preferably 30 nm or less. When the average particle diameter falls within the above range, a dense and transparent coating film is easily formed when forming a coating film containing titanium oxide particles, which is preferable. In the present invention, the value of the average particle diameter is obtained by measuring the major axis and minor axis of primary particles using an electron microscope, taking (major axis + minor axis) / 2 as the particle diameter of each primary particle, and then calculating the average thereof (hereinafter also referred to as "average particle diameter (SEM)").

[0017] The titanium oxide particles may have a coating layer on their surfaces. For example, titanium oxide particles having a coating layer containing at least one element selected from the group consisting of Zr, Si, Al and the like tend to have low photocatalytic activity. Titanium oxide particles having a coating layer containing one or both of Si and Zr tend to have even lower photocatalytic activity. In addition, their dispersibility in water also tends to be good. Furthermore, they are easily surface-treated with a surface treatment agent such as an organosilicon compound.

[0018] The surface of the titanium oxide particles may be surface-treated with a surface treatment agent. The surface of the titanium oxide particles is hydrophobized by the surface treatment agent. This improves the dispersibility in resin components or organic solvent components contained in the liquid when preparing a dispersion or coating composition as described later. Further, in the case of titanium oxide particles having a coating layer, the surface of the coating layer may be surface-treated with a surface treatment agent. Examples of the surface treatment agent include organic amine compounds, polycarboxylic acid compounds, alkoxide compounds, and silane coupling agents. Examples of the alkoxide compound include tetraethoxysilane and the like.

[0019] As the organic amine compound, ammonia; alkylamines such as ethylamine, triethylamine, isopropylamine, diisopropylamine, and n-propylamine; Aralkylamines such as benzylamine; Alicyclic amines such as piperidine; Alkanolamines such as monoethanolamine and triethanolamine; and; Quaternary ammonium salts or quaternary ammonium hydroxides such as tetramethylammonium salts and tetramethylammonium hydroxide. Among these, alkylamines, quaternary ammonium hydroxides, and the like are preferably used. Further, one of these organic amine compounds may be used alone, or two or more thereof may be used.

[0020] The polycarboxylic acid compound is preferably a polycarboxylic acid or a polycarboxylic acid anhydride. Specific examples thereof include polycarboxylic acids such as adipic acid, itaconic acid, malic acid, and benzenetetracarboxylic acid; and polycarboxylic acid anhydrides such as trimellitic anhydride, pyromellitic anhydride, and hexahydrophthalic anhydride. Among these, benzenetetracarboxylic acid, trimellitic anhydride, pyromellitic anhydride, itaconic acid, and the like are preferably used from the viewpoint of excellent scratch resistance.

[0021] As a method for treating and modifying the surface of titanium oxide particles, conventionally known methods can be employed. For example, when an alkylamine is used as the organic amine compound, it is added to an aqueous dispersion of the titanium oxide particles, then heated to a temperature of about 40°C to 90°C and stirred for about 1 hour to 20 hours. Thereby, the alkylamine can be bonded to the surface of the titanium oxide particles to modify the surface. In this case, it is preferable that, at the stage where the operation of the surface modification (that is, a type of surface treatment) is completed, all of the amine groups of the organic amine compound are bonded to OH groups present on the surface of the coating layer of the titanium oxide particles. However, a part thereof may remain in an unreacted state.

[0022] [Dispersion containing titanium oxide particles] Titanium dioxide particles may be in powder form or in dispersion form in a solvent. In the case of a dispersion, it may be an aqueous dispersion, a dispersion of water and an organic solvent, or an organic solvent dispersion. In a dispersion containing an organic solvent as the dispersion medium, some or all of the water in the dispersion can be replaced with the organic solvent by, for example, a rotary evaporator, an ultrafiltration membrane, or other known method.

[0023] Organic solvents that can be used in dispersions containing titanium dioxide particles include: Alcohols such as methanol, ethanol, ethylene glycol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and octanol; Esters such as ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone; Ethers such as diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, and cyclohexanone; Aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; Cyclohexane and other cyclic hydrocarbons; and; Examples include dimethylformamide, N,N-dimethylacetamide, and amides such as N-methylpyrrolidone. These organic solvents may be used individually or in combination of two or more.

[0024] [Paint composition containing titanium dioxide particles] A matrix-forming component may be added to a dispersion liquid containing titanium oxide particles to obtain a coating composition. As the matrix-forming component, matrix-forming components used in ordinary coating compositions can be used. For example, as a coating composition for forming a hard coat coating film, a coating composition containing at least one of an organosilicon compound and a hydrolyzate of an organosilicon compound as a matrix-forming component, and further containing the matrix-forming component and titanium oxide particles can be used.

[0025] Examples of the organosilicon compound include an alkoxysilane compound represented by the following general formula (I) or a hydrolyzate thereof (including partial hydrolyzates). R 1 a R 2 b Si(OR 3 ) 4-(a+b) (I) In the formula, R 1 is an alkyl group having 1 to 6 carbon atoms, an organic group having 8 or less carbon atoms containing a vinyl group, an organic group having 8 or less carbon atoms containing an epoxy group, an organic group having 8 or less carbon atoms containing a methacryloxy group, an organic group having 1 to 5 carbon atoms containing a mercapto group, or an organic group having 1 to 5 carbon atoms containing an amino group. R 2 is an alkyl group having 1 to 3 carbon atoms, an alkylene group, a cycloalkyl group, a halogenated alkyl group, or an allyl group. R 3 is an alkyl group having 1 to 3 carbon atoms, an alkylene group, or a cycloalkyl group. Further, a is an integer of 0 or 1, and b is an integer of 0, 1 or 2.

[0026] Examples of the organosilicon compounds include tetraethoxysilane, methyltrimethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, trimethylchlorosilane, α-glucidoxymethyltrimethoxysilane, α-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)-ethyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane. Among these, it is preferable to use tetraethoxysilane, methyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, or β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane. Furthermore, not just one of these silane compounds, but two or more may be used.

[0027] [Coating films and coated substrates containing titanium oxide particles] A coating composition containing titanium dioxide particles can be used to form a coating film on various substrates such as glass or plastic, creating a coated substrate. Such a coating film has a low transmittance of blue light. This coating film also includes a hard coat coating, and this coated substrate can be used as an optical substrate for eyeglass lenses, sunglass lenses, various optical lenses such as cameras, front panels for optical displays, display cases, window glass, contact glass for photocopiers, automotive light covers, and various ultraviolet shielding filters. The thickness of the coating film is not particularly limited. To increase the strength of the coating film, the thickness of the coating film is preferably 0.5 μm or more, and more preferably 1 μm or more. The upper limit of the thickness of the coating film is not particularly limited, but it may be 100 μm or less, 50 μm or less, or 30 μm or less.

[0028] [Method for producing titanium dioxide particles] Titanium dioxide particles can be prepared, for example, by a manufacturing method comprising the following steps (1) to (3). However, the manufacturing method for titanium dioxide particles is not limited to the method described below. (1) Gel preparation process (2) Hydrothermal treatment precursor preparation process (3) Hydrothermal treatment process The following is a detailed description of one example of the manufacturing method.

[0029] (1) Gel preparation process This process involves neutralizing an aqueous solution containing titanium to prepare a gel. Adding iron to the titanium-containing aqueous solution at this stage makes it easier for the iron to dissolve into the final titanium oxide particles.

[0030] The aqueous solution can be prepared by dissolving a titanium raw material in water, or by dissolving an iron raw material in water. Conventionally known raw materials such as titanium tetrachloride, titanium sulfate, and titanium alkoxide can be used as the titanium raw material. Conventionally known raw materials such as chlorides, carbonates, and nitrates can be used as the iron raw material. In addition, if the aqueous solution further contains elements other than titanium and iron, conventionally known raw materials such as chlorides, carbonates, and nitrates containing these elements can be used. These raw materials are preferably water-soluble, and if they are not water-soluble, they are preferably finely granulated to disperse uniformly in water. The pH of the aqueous solution is preferably 3 or less.

[0031] In this process, an alkaline aqueous solution with a pH of 10 or higher can be used to neutralize the aqueous solution. For example, an alkaline aqueous solution in which sodium hydroxide, potassium hydroxide, or ammonia is dissolved in water can be used. The gel is formed by mixing the aqueous solution and the alkaline aqueous solution so that the pH becomes 4 or higher. The gel can be recovered by filtration and may be washed with water or the like if necessary.

[0032] (2) Hydrothermal treatment precursor preparation process This step involves redispersing (disintegrating) the gel obtained in the previous step in water to prepare a hydrothermal treatment precursor. In this step, elements other than titanium (such as iron) can also be added after the gel has been disintegrated. The elements other than titanium can be conventionally known raw materials such as chlorides, carbonates, and nitrates containing this element.

[0033] Conventional methods can be used to disintegrate the gel. For example, a method of dispersing the gel in water and sonicating it, or a method of dispersing it in water using an acid or alkali can be used. Alternatively, hydrogen peroxide solution may be used to disintegrate it. In this case, it is preferable to adjust the amount of water so that the concentration of solids in the final hydrothermal treatment precursor is 10% by mass or less.

[0034] The average particle size of the solids contained in the hydrothermal treatment precursor obtained in this process is preferably 1000 nm or less, more preferably 800 nm or less, and particularly preferably 700 nm or less. If this average particle size is too large, the gel will not be sufficiently disintegrated, and elements such as iron will not be easily dissolved. This average particle size may be 5 nm or more, 50 nm or more, or 100 nm or more. The average particle size of the solids contained in the hydrothermal treatment precursor is calculated using cumulant analysis from particle size distribution data obtained using dynamic light scattering (DLS) (hereinafter also referred to as "average particle size (DLS)").

[0035] (3) Hydrothermal treatment process This step involves hydrothermally treating the hydrothermal treatment precursor obtained in the previous step to prepare iron-containing titanium oxide particles.

[0036] In this process, the hydrothermal treatment precursor can be hydrothermally treated using conventionally known equipment such as an autoclave. The hydrothermal treatment temperature is preferably in the range of 100°C to 250°C, more preferably in the range of 120°C to 220°C, and particularly preferably in the range of 130°C to 210°C. The holding time in the aforementioned temperature range is preferably in the range of 1 hour to 48 hours, more preferably in the range of 5 hours to 24 hours, and particularly preferably in the range of 10 hours to 20 hours.

[0037] The liquid after hydrothermal treatment contains titanium oxide particles, which may be separated and washed as needed. Furthermore, the separated titanium oxide particles can be calcined to enhance their crystallinity.

[0038] When forming a coating layer on the surface of titanium dioxide particles, for example, it can be formed by the method described in Japanese Patent Application Publication No. 2009-155496. Furthermore, when the titanium dioxide particles are dispersed in an organic solvent or a solution containing a dispersed resin, the surface of the particles or the surface of the coating layer can be hydrophobized (surface treated) using the method described in the same publication.

[0039] [Method for producing a dispersion containing titanium dioxide particles] Dispersions containing titanium dioxide particles can be prepared by dispersing the titanium dioxide particles in a solvent. Conventional methods can be used to disperse the titanium dioxide particles in a solvent. For example, if the titanium dioxide particles are in powder form, the dispersion can be prepared by adding them to water or an organic solvent and then performing a dispersion treatment such as bead milling or ultrasonic treatment. In this case, if the concentration of solids in the dispersion is 50% by mass or less, the titanium dioxide particles will disperse more easily in the solvent. In addition, the zeta potential of the titanium dioxide particles can be measured and the pH can be adjusted to a range suitable for dispersion.

[0040] When using an organic solvent as the solvent for a dispersion containing titanium dioxide particles, the organic solvents described above can be used.

[0041] [Method for manufacturing a paint composition containing titanium dioxide particles] A paint composition containing titanium dioxide particles can be prepared using titanium dioxide particles by conventionally known methods. For example, it can be prepared by adding a matrix-forming component to the aforementioned dispersion. This paint composition may be a thermosetting paint composition or a photocuring paint composition.

[0042] In the case of a thermosetting paint composition, it can be prepared by adding a matrix-forming component and, if necessary, a thermosetting curing catalyst or additives to a dispersion containing titanium dioxide particles.

[0043] Furthermore, in the case of a photocurable coating composition, it can be prepared by adding a matrix-forming component and, if necessary, a photocuring catalyst, additives, etc., to a dispersion containing titanium dioxide particles.

[0044] Examples of the matrix-forming components are those described above.

[0045] As a curing catalyst for thermosetting, Amines such as n-butylamine, triethylamine, guanidine, and biguanidide; Amino acids such as glycine; Metallic acetylacetonates such as aluminum acetylacetone, chromium acetylacetonate, titanyl acetylacetonate, and cobalt acetylacetonate; Metal salts of organic acids such as sodium acetate, zinc naphthenate, cobalt naphthenate, zinc octoate, and tin octoate; Perchloric acid, ammonium perchlorate, magnesium perchlorate, and other perchloric acid derivatives or their salts; Acids such as hydrochloric acid, phosphoric acid, nitric acid, and p-toluenesulfonic acid; Organic carboxylic acids such as adipic acid, itaconic acid, malic acid, trimellitic anhydride, pyromelitic anhydride, and hexahydrophthalic anhydride; and; Lewis acids such as tin chloride, aluminum chloride, iron chloride, titanium chloride, zinc chloride, and antimony chloride can be used. These may be used individually or in combination of two or more.

[0046] As photocuring catalysts, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2-hydroxymethyl-2-methylphenylpropane-1-ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl-ketone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one can be used. These may be used individually or in combination of two or more.

[0047] Additives that can be used include surfactants, leveling agents, UV absorbers, light stabilizers, diluent solvents, preservatives, antifouling agents, antibacterial agents, defoamers, UV degradation inhibitors, and dyes. These may be used individually or in combination of two or more.

[0048] [Method for manufacturing a substrate coated with titanium dioxide particles] A substrate coated with titanium dioxide particles can be prepared using a substrate and the aforementioned coating composition by a conventionally known method.

[0049] Examples of substrates include various substrates made of glass, plastic, etc. A specific example is a plastic substrate used as an optical lens. The thickness of the coating film formed on the substrate varies depending on the application of the coated substrate, but to obtain coating strength, it is preferable to have a thickness of 0.5 μm or more, and more preferably 1 μm or more. The upper limit of the coating film thickness is not particularly limited, but it may be 100 μm or less, 50 μm or less, or 30 μm or less. If there is no need to increase the coating strength, the coating film thickness may be less than 0.5 μm, less than 0.3 μm, or less than 0.1 μm.

[0050] When preparing a coated substrate containing titanium dioxide particles using the aforementioned thermosetting or photocurable coating compositions, the coated substrate can be prepared by applying these coating compositions to the substrate using conventionally known methods such as dipping, spraying, spinning, roll coating, or bar coating, drying, and curing by heat treatment or ultraviolet irradiation.

[0051] When manufacturing a coated substrate, the substrate surface may be pre-treated with an alkali, acid, or surfactant, polished with inorganic or organic fine particles, or subjected to primer treatment or plasma treatment in order to improve the adhesion between the substrate, such as a plastic substrate, and the coating. [Examples]

[0052] The following describes specific embodiments of the present invention. The present invention is not limited to these embodiments. [Measurement method or evaluation method] Various measurements or evaluations were performed as follows:

[0053] [1] Average particle size (SEM) The shape of the primary titanium oxide particles contained in the measurement samples obtained in each example was observed using a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation, S-5500). The observation samples were prepared as follows: The measurement sample was diluted with water to a solid content concentration of 0.05 mass%, then coated onto a collodion film-coated metal grid (Oken Shoji Co., Ltd.), and the solvent was evaporated by irradiating it with a 250W infrared lamp for 30 minutes to prepare the observation sample. This observation sample was observed at an accelerating voltage of 30kV and at a magnification that allowed the shape of the primary particles to be confirmed. From the images obtained from the observation, the shape of 100 primary particles was measured with calipers, and the minor and major axes were determined. (Minor axis + Major axis) / 2 was used as the particle diameter of the primary particle, and the average value of the particle diameters of the 100 primary particles was used as the average particle diameter.

[0054] [2] Solid content concentration The solvent contained in the sample was removed by infrared irradiation or other means to obtain a residue. This residue was calcined at 1000°C for 1 hour to obtain the ignition residue (solid content). The ratio of the mass of the solid content to the mass of the sample was defined as the solid content concentration.

[0055] [3] pH measurement A 50 mL sample of the substance to be measured was placed in a container. This container was then placed in a constant temperature bath maintained at 25°C. Next, the glass electrode of a pH meter (Horiba F22), calibrated with three standard solutions of pH 4, 7, and 9, was inserted into the container, and the pH value of the substance was measured. If the substance contained an organic solvent, it was diluted 10-fold with distilled water before measurement.

[0056] [4] Crystal structure analysis of particles The sample obtained in each example was placed in a porcelain crucible (Type B-2) and dried at 110°C for 12 hours. The crucible was then placed in a desiccator and cooled to room temperature to obtain a dried product. Next, this dried product was mixed with a small amount of strontium titanate (manufactured by Kojun Chemical Laboratory Co., Ltd.) and ground for 15 minutes. The powder X-ray diffraction pattern was then measured using a SmartLab X-ray diffractometer (manufactured by Rigaku Corporation). The obtained diffraction pattern was analyzed using PDXL2 Version 2.7.2.0 software to identify peak positions, and the peak (2θ) originating from the (110) plane of the mixed strontium titanate was corrected to 32.374 degrees. The measurement conditions and data analysis details are as follows. This measurement yielded the crystal structure of titanium oxide and the interplanar spacing of the (110) plane. Regarding the crystal structure of titanium oxide, if only a single crystal structure was obtained as a result of the data analysis, it was described as a single phase. • Measurement conditions Measurement device: Powder X-ray diffraction analyzer SmartLab (manufactured by Rigaku Corporation) X-ray generator: 9kW open tube (CuKα source (wavelength: 0.154058nm), voltage 45kV, current 200mA) Soller / PSC:5.0deg IS length: 10.0mm PSA: None Soller: 5.0deg IS:1 / 2 RS1: 13mm RS2: 20mm Scan step: 0.02deg Scan range: 5-70deg Scan speed: 5deg / min X-ray detector: High-speed one-dimensional X-ray detector (D / TeX Ultra 250) Measurement atmosphere: Under atmospheric pressure Sample stage: Al2O3 sample holder (bottomless) • Data analysis Analysis software: Integrated powder X-ray diffraction analysis software PDXL2 Version 2.7.2.0 (manufactured by Rigaku Corporation) Smoothing: Smoothing using B-Splne (X threshold 1.5) Background removal: Fitting method Kα2 removal: intensity ratio 0.497 Peak search: Second derivative method, σ-cut value = 3, σ-cut range 0.5~20.0 Profile fitting method: Fitting to measurement data Profile fitting peak shape: Split pseudo-Voigt function

[0057] [5] Method for measuring composition / elemental content (Titanium, iron, silicon, and tin) The sample obtained in each example was placed in a zirconia crucible, and the solvent was removed by infrared irradiation to obtain the solid content. Na2O2 and NaOH were added to the obtained solid content and heated to obtain a molten product. Sulfuric acid and hydrochloric acid were added to the obtained molten product, and then it was diluted with water to obtain a solution for measurement. The amounts of titanium, iron, silicon, and tin contained in the obtained solution for measurement were measured using an ICP instrument (Shimadzu Corporation, ICPS-8100). These were converted to oxides (TiO2, Fe2O3, SiO2, and SnO2) and their respective compositions were calculated as mass % relative to the total amount of solid content in the sample, and these were defined as the composition of titanium oxide particles. In addition, the number of moles of iron, silicon, and tin relative to the number of moles of titanium contained in the titanium oxide particles was calculated in mole percent.

[0058] (zirconium) The sample obtained in each example was placed in a platinum dish. Hydrofluoric acid and sulfuric acid were added to this platinum dish and heated, and then water was added to dissolve the solid components contained in the sample. Furthermore, this was diluted with water to obtain the measurement solution. The amount of zirconium contained in the obtained measurement solution was measured using an ICP instrument (Shimadzu Corporation, ICPS-8100). The amount of zirconium was converted to oxide equivalent (ZrO2), and the zirconium composition was calculated as a mass % relative to the total amount of solid components contained in the sample, and this was taken as the composition of titanium oxide particles. In addition, the number of moles of zirconium relative to the number of moles of titanium contained in the titanium oxide particles was calculated in mole percent.

[0059] (potassium) The sample obtained in each example was placed in a platinum dish. Hydrofluoric acid and sulfuric acid were added to the platinum dish and heated, and then water was added to dissolve the solid components contained in the sample. This was then diluted with water to obtain the measurement solution. The amount of potassium contained in the obtained measurement solution was measured using an atomic absorption spectrometer (Hitachi, Ltd., Z-5300). The amount of potassium was converted to oxide (K2O), and the potassium composition was calculated as a mass % relative to the total amount of solid components contained in the sample, and this was taken as the composition of the titanium oxide particles. In addition, the number of moles of potassium relative to the number of moles of titanium contained in the titanium oxide particles was calculated in mole %.

[0060] [6] Evaluation of photocatalytic activity of titanium dioxide particles A dispersion was obtained by adding an appropriate solvent to the measurement sample obtained in the example so that the Ti concentration (in TiO2 equivalent) was 0.335% by mass and the water / methanol ratio was 1 / 1 (by mass). Next, the obtained dispersion was mixed with a glycerin solution containing 0.02% by mass of Sunset Yellow FCF dye in a mass ratio (mass of dispersion / mass of glycerin solution) of 1 / 3 to prepare a sample for evaluation. This evaluation sample was placed in a quartz cell with a depth of 1 mm, a width of 1 cm, and a height of 5 cm to create a Sunset Yellow-containing test specimen. A UV lamp (manufactured by AS ONE Corporation, LUV-6) was used to irradiate a 1 cm wide x 5 cm high surface of the sunset yellow-containing test specimen with ultraviolet light for 5 hours. The wavelength of the UV lamp was set to the I-line (wavelength 365 nm). The UV intensity on the irradiated surface of the sunset yellow-containing test specimen was 0.4 mW / cm². 2 The distance between the ultraviolet lamp and the irradiation surface of the sunset yellow-containing test specimen was adjusted so that the wavelength was equivalent to 365 nm. The absorbance at a wavelength of 490 nm was measured for the evaluation sample and the sample after UV irradiation using a UV-Vis spectrophotometer (JASCO Corporation, V-750). The absorbance of the evaluation sample was designated as A0, and the absorbance of the sample after UV irradiation as A5. The sunset yellow (SY) fading rate was calculated using the following formula. SY fading rate (%)=((A5 / A0)-1)×100 This was used as an indicator of photocatalytic activity. This indicator shows that the closer the SY fading rate is to 0, the lower the photocatalytic activity, and the closer the SY fading rate is to -100, the higher the photocatalytic activity.

[0061] [7] Blue light blocking performance (dispersion) The sample obtained in each example was diluted with water to adjust the solid content concentration to 0.1% by mass. This sample was placed in a quartz cell measuring 1 mm in depth, 1 cm in width, and 5 cm in height, and the transmittance at wavelengths of 380 to 500 nm was measured using a UV-Vis spectrophotometer V-750 (manufactured by JASCO Corporation). Of these, the transmittance from 380 to 500 nm was measured at 1 nm intervals, and the average value and the transmittance at 440 nm were recorded.

[0062] [8] Refractive index of the coating film The reflectance of the coating on the coated substrate obtained in each example was measured using a reflectance measuring instrument (Olympus Corporation, USPM-RUIII). Using the obtained reflectance, the refractive index of the coating on the coated substrate was calculated from the following equation 1.

[0063]

number

[0064] [9] Blue light blocking performance (on coated substrates) Using a UV-Vis spectrophotometer V-750 (manufactured by JASCO Corporation), the transmittance of the coated substrates obtained in each example was measured at wavelengths of 380 to 500 nm. Of these, the transmittance from 380 to 500 nm was measured at 1 nm intervals, and the average value and the transmittance at 440 nm were calculated.

[0065] [Preparation of titanium oxide particles, paint compositions, and coated substrates] Titanium dioxide particles were prepared using the following raw materials. Titanium tetrachloride aqueous solution: Ti concentration (TiO2 equivalent) 7.75% by mass Ferric chloride aqueous solution: Fe concentration (as Fe2O3 equivalent) 7.75% by mass Ammonia solution: NH3 concentration 15% by mass Hydrogen peroxide solution: H2O2 concentration 35% by mass Potassium stannate aqueous solution: K2SnO3 concentration 1% by mass Potassium zirconium carbonate aqueous solution: Zr concentration (converted to ZrO2) 1% by mass Silica sol: Si concentration (SiO2 equivalent) 15% by mass (Average particle size (DLS) 16nm) Zirconium oxychloride aqueous solution: ZrO2 equivalent concentration 36.5% by mass Potassium hydroxide: 85% purity Sodium silicate: SiO2 equivalent concentration 4.5% by mass

[0066] [Example 1] (1) Gel preparation process 2877 g of titanium tetrachloride aqueous solution, 159.7 g of ferric chloride aqueous solution, and ammonia water were mixed and the pH was adjusted to 9.5 to obtain a white slurry. Next, this slurry was filtered, and the filtrate was washed with water to obtain 1850 g of a gel containing Ti and Fe with a solid content of 10% by mass.

[0067] (2) Hydrothermal treatment precursor preparation process 181 g of the gel obtained in the aforementioned process was weighed, and 384 g of hydrogen peroxide solution and 1314 g of water were added to it. The mixture was then stirred at 80°C for 1 hour. After stirring, 363 g of water was added to obtain 2242 g of lysis solution. This lysis solution was brownish and translucent, with a pH of 7.6, and the average particle size (DLS) of the solids in the lysis solution was 606 nm (calculated using cumulant analysis from particle size distribution data obtained using dynamic light scattering (ELS-Z, manufactured by Otsuka Electronics Co., Ltd.)). After mixing the cation exchange resin with this lysis solution, 265 g of potassium stannate aqueous solution and 193 g of potassium zirconium carbonate aqueous solution were gradually added under stirring. Subsequently, the cation exchange resin was separated, and 18 g of silica sol and 282 g of water were added to obtain 3000 g of hydrothermal treatment precursor.

[0068] (3) Hydrothermal treatment process The hydrothermal treatment precursor obtained in the aforementioned process was divided into portions and placed in a high-pressure reaction decomposition vessel (San-ai Kagaku Co., Ltd., HU-100), and heated at 165°C for 18 hours. This was cooled to room temperature to obtain 3000 g of titanium dioxide particle dispersion. This titanium dioxide particle dispersion was concentrated using an ultrafiltration membrane to obtain a titanium dioxide particle dispersion with a solid content of 10% and a pH of 8.1. This was used as the measurement sample, and measurements [1] to [7] described in the aforementioned measurement or evaluation methods were performed. The results are shown in Table 1.

[0069] (4) Preparation of paint composition 18.8 g of epoxy-functionalized silane SILQUEST A-187J (manufactured by MOMENTIVE) and 2.8 g of methyl alcohol were mixed. 5.5 g of 0.01 N aqueous hydrochloric acid solution was added dropwise while stirring. After addition, the mixture was stirred at room temperature overnight to obtain the hydrolysis product of the epoxy-functionalized silane. To this hydrolysis product of the epoxy-functionalized silane, 192.4 g of the measurement sample obtained in the aforementioned hydrothermal treatment step, 32.9 g of 1-methoxy-2-propanol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.4 g of acetylacetone aluminum (manufactured by Kishida Chemical Co., Ltd.), and the silicone-based surfactant DOWSIL L-7604 (manufactured by Dow-Toray Industries, Inc.) were added as a leveling agent. 0.1 g was added. This was stirred at room temperature overnight to prepare the paint composition. The weight fraction of titanium dioxide particles was 50% by weight relative to the total weight of solids contained in this paint composition.

[0070] (5) Preparation of coated substrate A glass substrate was placed in a spin coater (Mikasa Corporation, MS-A200). The rotation speed was then adjusted so that the coating thickness was 1 μm, and the aforementioned coating composition was dropped onto the substrate. The substrate with the coating composition attached was dried at 120°C for 2 hours to prepare a coated substrate. The measurements described in [8] and [9] above were performed on this coated substrate. The results are shown in Table 1.

[0071] [Example 2] (1) Gel preparation process 2670 g of titanium tetrachloride aqueous solution, 298.8 g of ferric chloride aqueous solution, and ammonia water were mixed, and the pH was adjusted to 9.5 to obtain a white slurry. Next, this slurry was filtered, and the filtrate was washed with water to obtain 1790 g of a gel containing Ti and Fe with a solid content of 10% by mass.

[0072] (2) Hydrothermal treatment precursor preparation process 234 g of the gel obtained in the aforementioned process was weighed, and 1547 g of hydrogen peroxide solution and 1771 g of water were added to it. The mixture was then stirred at 80°C for 1 hour. After stirring, 2463 g of water was added to obtain 6015 g of lysis solution. This lysis solution was brownish and translucent, with a pH of 7.9, and the average particle size of the solids in the solution was 172 nm (calculated using cumulant analysis from particle size distribution data obtained using dynamic scattering method (ELS-Z, manufactured by Otsuka Electronics Co., Ltd.)). After mixing the cation exchange resin with this lysis solution, 668 g of potassium stannate aqueous solution and 517 g of potassium zirconium carbonate aqueous solution were gradually added under stirring. Subsequently, the cation exchange resin was separated, and 24 g of silica sol and 776 g of water were added to obtain 8000 g of hydrothermal treatment precursor.

[0073] (3) Hydrothermal treatment process A measurement sample was obtained in the same manner as in Example 1 (3), except that the hydrothermal treatment precursor obtained in the aforementioned process was used. The measurements described in [1] to [7] above were performed on this measurement sample. The results are shown in Table 1.

[0074] The subsequent steps involved preparing the paint composition and the coated substrate in the same manner as in (4) and (5) of Example 1. Using this coated substrate, the measurements described in [8] and [9] above were performed. The results are shown in Table 1.

[0075] [Example 3] (1) Gel preparation process 2336 g of titanium tetrachloride aqueous solution, 412.1 g of ferric chloride aqueous solution, and ammonia water were mixed, and the pH was adjusted to 9.5 to obtain a white slurry. Next, this slurry was filtered, and the filtrate was washed with water to obtain 1510 g of a gel containing Ti and Fe with a solid content of 10% by mass.

[0076] (2) Hydrothermal treatment precursor preparation process 160 g of the gel obtained in the aforementioned process was weighed, and 389 g of hydrogen peroxide solution and 1353 g of water were added to it. The mixture was then stirred at 80°C for 1 hour. After stirring, 2636 g of water was added to obtain 4538 g of lysis solution. This lysis solution was brown and translucent, with a pH of 7.9, and the average particle size (DLS) of the solids in the lysis solution was 164 nm. After mixing the cation exchange resin with this lysis solution, 236 g of potassium stannate aqueous solution and 195 g of potassium zirconium carbonate aqueous solution were gradually added under stirring. The cation exchange resin was then separated, and 9 g of silica sol and 291 g of water were added to obtain 5269 g of hydrothermal treatment precursor.

[0077] (3) Hydrothermal treatment process A measurement sample was obtained in the same manner as in Example 1 (3), except that the hydrothermal treatment precursor obtained in the aforementioned process was used. The measurements described in [1] to [7] above were performed on this measurement sample. The results are shown in Table 1.

[0078] The subsequent steps involved preparing the paint composition and the coated substrate in the same manner as in (4) and (5) of Example 1. Using this coated substrate, the measurements described in [8] and [9] above were performed. The results are shown in Table 1.

[0079] [Example 4] (1) Gel preparation process The gel was obtained in the same manner as in Example 3 (1).

[0080] (2) Hydrothermal treatment precursor preparation process A hydrothermal treatment precursor was obtained in the same manner as in Example 3 (2), except that an aqueous solution of potassium zirconium carbonate was not added.

[0081] (3) Hydrothermal treatment process A measurement sample was obtained in the same manner as in Example 1 (3), except that the hydrothermal treatment precursor obtained in the aforementioned process was used. The measurements described in [1] to [7] above were performed on this measurement sample. The results are shown in Table 1.

[0082] The subsequent steps involved preparing the paint composition and the coated substrate in the same manner as in (4) and (5) of Example 1. Using this coated substrate, the measurements described in [8] and [9] above were performed. The results are shown in Table 1.

[0083] [Example 5] A mixture of 256 g of zirconium oxychloride aqueous solution and 4462 g of water was mixed with 212 g of aqueous ammonia to obtain a white slurry. This slurry was then filtered, and the filtrate was washed with water to obtain 1000 g of zirconium gel with a ZrO2 equivalent concentration of 10% by mass. 30 g of zirconium gel was mixed with 250 g of water, and then 6 g of potassium hydroxide was added to obtain an alkaline slurry. 56 g of hydrogen peroxide solution was added to this slurry, and the mixture was heated to 50°C to dissolve the zirconium gel. 218 g of water was then added to obtain 560 g of an aqueous solution of zirconic acid peroxide with a ZrO2 equivalent concentration of 0.5% by mass. 206 g of sodium silicate was diluted with 794 g of water, and then dealkalized using a cation exchange resin to obtain 1000 g of a silicate aqueous solution with an SiO2 equivalent concentration of 4.5% by mass.

[0084] 818 g of the titanium dioxide particle dispersion from Example 1 was diluted with 3271 g of water to prepare 4089 g of a dispersion with a solid content of 2% by mass. 279 g of the zirconic acid peroxide aqueous solution and 216 g of the silicate aqueous solution obtained in the previous step were gradually added to this dispersion. After adding the entire amount of these, the mixture was aged for 1 hour under stirring at a temperature of 90°C. This mixture was then divided into portions and charged into a high-pressure reaction decomposition vessel (San-ai Kagaku Co., Ltd., HU-100), and heated at 165°C for 18 hours. This mixture was cooled to room temperature to obtain a dispersion of titanium dioxide particles coated with a composite oxide of zirconium and silicon. This dispersion was concentrated using an ultrafiltration membrane (Asahi Kasei Corporation, SIP-1013) to obtain a dispersion of titanium dioxide particles coated with a composite oxide of zirconium and silicon with a solid content of 10% and a pH of 8.5. This was used as a measurement sample, and measurements [1] to [7] described in the measurement or evaluation method above were performed. The results are shown in Table 1.

[0085] The subsequent steps involved preparing the paint composition and the coated substrate in the same manner as in (4) and (5) of Example 1. Using this coated substrate, the measurements described in [8] and [9] above were performed. The results are shown in Table 1.

[0086] [Comparative Example 1] (1) Gel preparation process 1031 g of an aqueous titanium tetrachloride solution was mixed with ammonia water, and the pH was adjusted to 9.1 to obtain a white slurry. Next, the slurry was filtered, and the filtrate was washed with water to obtain 525 g of a Ti-containing gel with a solid content of 10% by mass.

[0087] (2) Hydrothermal treatment precursor preparation process 91 g of the gel obtained in the aforementioned process was weighed, and 108 g of hydrogen peroxide solution and 541 g of water were added to it. The mixture was then stirred at 80°C for 1 hour. After stirring, 208 g of water was added to obtain 948 g of lysis solution. This lysis solution was brownish and translucent, with a pH of 7.9, and the average particle size of the solids in the solution was 33 nm (calculated using cumulant analysis from particle size distribution data obtained using dynamic scattering method (ELS-Z, manufactured by Otsuka Electronics Co., Ltd.)). After mixing the cation exchange resin with this lysis solution, 119 g of potassium stannate aqueous solution was gradually added under stirring. Subsequently, the cation exchange resin was separated, and 14 g of silica sol and 220 g of water were added to obtain 1301 g of hydrothermal treatment precursor.

[0088] (3) Hydrothermal treatment process A measurement sample was obtained in the same manner as in Example 1 (3), except that the hydrothermal treatment precursor obtained in the aforementioned process was used. The measurements described in [1] to [7] above were performed on this measurement sample. The results are shown in Table 1.

[0089] The subsequent steps involved preparing the paint composition and the coated substrate in the same manner as in (4) and (5) of Example 1. Using this coated substrate, the measurements described in [8] and [9] above were performed. The results are shown in Table 1.

[0090] [Comparative Example 2] A dispersion of titanium oxide particles coated with a zirconium-silicon composite oxide was obtained in the same manner as in Example 5, except that the titanium oxide particle dispersion of Example 1 was replaced with the titanium oxide particle dispersion of Comparative Example 1. This was used as a measurement sample, and measurements [1] to [7] described in the measurement or evaluation method above were performed. The results are shown in Table 1.

[0091] The subsequent steps involved preparing the paint composition and the coated substrate in the same manner as in (4) and (5) of Example 1. Using this coated substrate, the measurements described in [8] and [9] above were performed. The results are shown in Table 1.

[0092] [Table 1]

Claims

1. Titanium dioxide particles containing iron, for blocking blue light.

2. Titanium oxide particles for blue light blocking according to claim 1, wherein the iron content is 6 mol% or more in molar percentage relative to titanium.

3. Titanium oxide particles for blue light blocking according to claim 1, having a coating layer on its surface.

4. A titanium dioxide particle dispersion comprising the blue light-cutting titanium dioxide particles described in claim 1.

5. A paint composition comprising the blue light-cutting titanium oxide particles and matrix-forming component described in claim 1.

6. A coated substrate containing titanium oxide particles for blue light blocking as described in claim 1.

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