Colloidal particles of co-doped oxide, sol thereof, and production methods therefor

Abstract

Provided are: colloidal particles of a Ti-containing oxide and a sol thereof which retain a high refractive index and have excellent light resistance; and methods for producing the particles and the sol.　The colloidal particles of a Ti-containing oxide have an equivalent-circle diameter, determined by analyzing a transmission electron photomicrographic image, of 5-50 nm. Throughout the whole colloidal oxide particles, Zn and / or Fe is distributed and Nb and / or Ta is distributed.

Description

Co-doped oxide colloidal particles, sols thereof and method for producing the same

[0001] The present invention relates to oxide colloidal particles containing Ti, in which Zn and / or Fe, and Nb and / or Ta are distributed throughout the particles, a sol thereof, and a method for producing the same.

[0002] Titanium oxide particles and its sol (dispersion liquid) can be applied to a variety of optical components, and are used in applications such as eyeglass lenses, window glass, film-like coating agents, resin additives, displays, etc. Titanium oxide is also useful as an anti-reflective material and as a component of high refractive index materials, and has applications that make use of its characteristics as a high refractive index material.

[0003] On the other hand, titanium dioxide has a photocatalytic effect, and when irradiated with ultraviolet light, it generates reactive oxygen species, which accelerates the oxidative decomposition of organic materials such as resins, so the use of titanium dioxide can be problematic in terms of light resistance (weather resistance).Several methods are being considered to improve this light resistance.

[0004] For example, Patent Document 1 discloses composite rutile microparticles obtained by adding titanium chloride to a dispersion of zinc-added titanium oxide nanoparticles and reacting them, and discloses that the catalytic activity on the surface is low, and that even when the composite resin composition is prepared by mixing the composite resin with the nanoparticles, deterioration of the resin can be suppressed (see paragraphs

[0038] and

[0011] of Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2008-308386

[0006] However, simply doping titanium oxide with zinc (Zn) does not adequately suppress the photocatalytic activity of titanium oxide, which leads to the oxidative decomposition of resins. Furthermore, because there is concern about a decrease in the refractive index due to zinc doping, it is difficult to dramatically improve light resistance (weather resistance) while maintaining the refractive index using zinc doping alone, as in conventional techniques. In view of the limitations of the above-mentioned conventional techniques, the present invention aims to provide Ti-containing oxide colloidal particles and sols thereof that maintain a high refractive index and have excellent light resistance, as well as a method for producing the same.

[0007] The present inventors have conducted extensive research to solve the above problems and have found that when titanium oxide particles are irradiated with ultraviolet light, electrons released from the titanium oxide react with oxygen in the air to produce superoxide anion radicals (.O ２ － In light of the fact that reactive oxygen species accelerate the oxidative decomposition of resins, the inventors conceived and verified the concept of co-doping titanium oxide with at least one donor element and one acceptor element, with the aim of capturing both the electrons and holes that cause the generation of these two reactive oxygen species, while at the same time taking into consideration the maintenance of the high refractive index of titanium oxide.

[0008] That is, the gist of the present invention is as follows: [1] Oxide colloidal particles containing Ti, which have a circle-equivalent diameter of 5 to 50 nm as determined by transmission electron microscope image analysis, and in which Zn and / or Fe, and Nb and / or Ta are distributed throughout the oxide colloidal particles. [2] The oxide colloidal particles further contain Sn, and the ratio of Sn to Ti is SnO ２ / TiO ２ [3] The oxide colloid particles according to [1], wherein the ZnO content measured by XRF is 0.2 to 10 mass %. [4] The oxide colloid particles according to [1], wherein the Nb content measured by XRF is 0.2 to 10 mass %. ２ O ５ [5] The oxide colloid particles according to [1], wherein the content of Ta is 1 to 30 mass %. ２ O ５ [6] The oxide colloid particles according to [1], wherein the content of Fe by ICP measurement is 0.1 to 30 mass %. ２ O ３[7] The oxide colloid particles according to [1], wherein the content of is 0.001 mass % or more and less than 0.2 mass %. [7] The oxide colloid particles according to [1], wherein the standard deviation of the equivalent circle diameters as determined by transmission electron microscope image analysis is 0.1 to 3.0 nm, and the ratio of the standard deviation to the equivalent circle diameters (standard deviation / equivalent circle diameter) is 0.01 to 0.26. [8] The oxide colloid particles according to [1], wherein the dry density is 3.30 g / cm ３ ~4.00g / cm ３ and the ratio of dry density to theoretical density (dry density / theoretical density) is 0.71 to 1.0. [9] The oxide colloid particles according to [1], having a particle refractive index of 2.24 to 2.50.

[10] A sol of oxide colloid particles in which the oxide colloid particles according to [1] are dispersed as a dispersoid in a liquid medium, the sol having a Z-average particle diameter measured by a dynamic light scattering method of 5 to 500 nm.

[11] A dispersion is prepared by diluting the sol with a dispersion liquid of water:methanol = 1:1 (mass ratio) so that the solid content concentration of the sol becomes 0.05 mass %, and the dispersion is mixed with a 0.02 mass % glycerin solution of a sunset yellow dye in a mass ratio of 1:3, and the mixture is irradiated with light of a wavelength of 365 nm at an irradiation intensity of 0.4 mW / cm. ２

[12] A method for producing an aqueous sol of oxide colloidal particles, comprising the following steps (a) to (c): step (a): mixing a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and an iron- and / or zinc-containing compound with pure water, and heating the mixture at 110 to 200°C for 0.1 to 20 hours to obtain aqueous sol (a), step (b): ultrafiltrating aqueous sol (a), and then subjecting the mixture to ion exchange treatment to obtain aqueous sol (b), and step (c): mixing an Nb- and / or Ta-containing compound with aqueous sol (b), and then heating the mixture at 150 to 300°C for 0.1 to 20 hours to obtain aqueous sol (c).

[0009] According to the present invention, it is possible to realize Ti-containing oxide colloidal particles and a sol (dispersion liquid) thereof, which maintain the high refractive index of titanium oxide and have excellent light resistance (weather resistance), as well as a method for producing the same. In the Ti-containing oxide colloidal particles and sol thereof of the present invention, at least one type of donor element and one type of acceptor element are co-doped into titanium oxide, so that the particles and sol can maintain a high refractive index while suppressing the reaction of two active oxygen species (superoxide anion radicals (.O)) generated by ultraviolet irradiation. ２ － The Ti-containing oxide colloidal particles and the sol thereof of the present invention can capture both electrons and holes that cause the generation of cations (C, C, D, E ...

[0010] Preferred embodiments of the present invention will be described below. However, the following embodiments are merely examples for explaining the present invention, and the present invention is not limited to the following embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. Note that in this specification, the above-mentioned multiple numerical ranges shown as stepwise preferred ranges can also be understood as independently preferred upper or lower limits, focusing only on each upper or lower limit.

[0011] [Oxide Colloid Particles] In the present invention, "oxide colloid particles" refers to colloidal-sized metal oxide fine particles that can exist in a colloidal state in a liquid medium. This is consistent with "a sol of oxide colloid particles in which oxide colloid particles are dispersed as a dispersoid in a liquid medium," which is one embodiment of the present invention. The oxide colloid particles of the present invention refer to titanium oxide-based colloidal particles that contain Ti and are doped with Zn and / or Fe, and Nb and / or Ta. In one embodiment of the present invention, the Ti-containing oxide colloidal particles have a circle-equivalent diameter of 5 to 50 nm as determined by transmission electron microscope image analysis, and Zn and / or Fe, and Nb and / or Ta are distributed throughout the oxide colloidal particles. Zn and / or Fe doped into the Ti-containing oxide colloidal particles are capable of reacting with superoxide anion radicals (.O), one of two active oxygen species generated by ultraviolet irradiation of titanium oxide. ２ －Nb and / or Ta doped into the Ti-containing oxide colloidal particles can serve as donors for capturing holes that cause the generation of hydroxyl radicals (.OH), one of two active oxygen species generated by ultraviolet irradiation of titanium oxide. Any element that exhibits such a function can be suitably used. However, from the viewpoint of suppressing a decrease in refractive index due to doping, it is preferable to use Zn and / or Fe. From the viewpoint of suppressing coloration, it is particularly preferable to use Zn or a very small amount of Fe, and it is even more preferable to use Zn and a very small amount of Fe. Nb and / or Ta doped into the Ti-containing oxide colloidal particles can serve as donors for capturing holes that cause the generation of hydroxyl radicals (.OH), one of two active oxygen species generated by ultraviolet irradiation of titanium oxide. Any element that exhibits such a function can be suitably used. However, from the viewpoint of suppressing a decrease in refractive index due to doping, it is preferable to use Nb and / or Ta, and it is particularly preferable to use Nb. The oxide colloidal particles of the present invention are particles containing Ti, and further containing Zn and / or Fe, and Nb and / or Ta, and among these, particles containing Zn and Nb are preferred. In the oxide colloidal particles of the present invention, the statement that Zn and / or Fe, and Nb and / or Ta are "distributed throughout the oxide colloidal particles" does not mean that Zn and / or Fe, and Nb and / or Ta are uniformly distributed throughout the oxide colloidal particles. That is, Zn and / or Fe, and Nb and / or Ta may be partially distributed on the surface and / or inside the oxide colloidal particles. As long as the effects of the present invention are not impaired, Zn and / or Fe, and Nb and / or Ta may be distributed primarily on either the surface or inside of the colloidal particles, for example. The state and degree of distribution of metal elements in the oxide colloidal particles can be determined by mapping or line scanning from an electron microscope image. The state and degree of distribution of each metal element in the oxide colloidal particles of the present invention can also be determined by these methods and used as a criterion for evaluating each particle or as an index for comparing particles.

[0012] In one embodiment of the present invention, the equivalent circle diameter of the oxide colloidal particles determined by transmission electron microscope (TEM) image analysis is the average value of the equivalent circle diameters determined by analyzing 500 particles observed in a TEM image using an automatic image processing analyzer, as will be described later. Taking into consideration transparency when applied to optical components, etc., the equivalent circle diameter is preferably 5 to 50 nm, more preferably 5 to 30 nm, even more preferably 5 to 20 nm, and particularly preferably 7 to 20 nm.

[0013] The content of Ti in the oxide colloid particles is not particularly limited, but from the viewpoint of forming uniform titanium oxide, which is the object of the present invention, it is preferable that Ti is the main component, and Ti oxide (TiO ２ ) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

[0014] In one embodiment of the present invention, the oxide colloid particles may further contain Sn. There is no particular limitation on the Sn content in the oxide colloid particles. However, in consideration of the effects of the present invention, the ratio of Sn to Ti is preferably the ratio in terms of their oxides (SnO ２ / TiO ２ ), and the ratio is preferably 0.01 to 0.1, more preferably 0.01 to 0.08, further preferably 0.02 to 0.08, and particularly preferably 0.03 to 0.07. ２ / TiO ２ ) can be calculated using the molar ratio.

[0015] The contents of Ti, Zn and / or Fe, Nb and / or Ta, and Sn in the oxide colloidal particles can be measured by a conventionally known method, for example, by X-ray fluorescence (XRF) analysis. More specifically, they can be measured by the method described in the Examples below. Furthermore, the contents of Ti, Zn and / or Fe, Nb and / or Ta, and Sn in the oxide colloidal particles of the present invention can be appropriately controlled by the type and amount of compounds, etc. that serve as supply sources of each element, as well as the production conditions of the oxide colloidal particles and their sol.

[0016] In one embodiment of the present invention, there is no particular limitation on the content of Zn and / or Fe in the oxide colloid particles. However, in consideration of the effects of the present invention, as described above, it is preferable to use Zn or a very small amount of Fe from the viewpoint of suppressing coloration, and it is more preferable to use Zn and a very small amount of Fe. Specifically, it is preferable to use Zn oxide (ZnO) and / or Fe oxide (FeO) by XRF measurement. ２ O ３ ) is preferably 0.2 to 10 mass%, more preferably 0.2 to 8 mass%, even more preferably 0.2 to 5 mass%, and particularly preferably 0.5 to 3 mass%. By setting the upper limit at such a value, it is possible to suppress a decrease in the refractive index of the oxide colloidal particles, and also to prevent an excessive amount of doping element that is not effectively doped from behaving as an unnecessary impurity. Furthermore, in one embodiment of the present invention, in view of suppressing coloration as an effect achieved by the present invention, it is possible to prevent the Fe ２ O ３ The upper limit of the content of is preferably less than 0.20% by mass, more preferably 0.15% by mass or less, even more preferably 0.10% by mass or less, and particularly preferably 0.05% by mass or less. In addition, in one embodiment of the present invention, in consideration of the effect of the present invention of improving light resistance, it is preferable that the content of Fe be less than 0.20% by mass by ICP measurement. ２ O ３ The lower limit of the content of is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and particularly preferably 0.02% by mass or more. In one embodiment of the present invention, in consideration of the effect of the present invention of suppressing coloration, it is preferable that the content of (Fe ２ O ３ Content (mass%) / (TiO ２ +Fe ２ O ３The upper limit of the total content (mass%) of (Fe) is preferably less than 0.0010, more preferably 0.0008 or less, and particularly preferably 0.0005 or less. In one embodiment of the present invention, in consideration of the effect of the present invention of improving light resistance, it is preferable that the total content (mass%) of (Fe) ２ O ３ Content (mass%) / (TiO ２ +Fe ２ O ３ The lower limit of the total content (mass%) of the above is preferably 0.00001 or more, more preferably 0.0001 or more, and particularly preferably 0.0002 or more.

[0017] In one embodiment of the present invention, there is no particular limitation on the content of Nb and / or Ta in the oxide colloid particles. However, in consideration of the effects of the present invention, it is preferable that the content of Nb oxide (Nb ２ O ５ ) and / or Ta oxide (Ta ２ O ５ ) is preferably 0.1 to 30 mass%, more preferably 0.6 to 30 mass%, more preferably 0.6 to 20 mass%, more preferably 1 to 30 mass%, more preferably 2 to 25 mass%, even more preferably 3 to 20 mass%, and particularly preferably 4 to 18 mass%. By setting the upper limit at such a value, it is possible to suppress a decrease in the refractive index of the oxide colloidal particles, and to prevent an excess amount of the doping element that is not effectively doped from behaving as an unnecessary impurity.

[0018] In one embodiment of the present invention, the standard deviation of the equivalent circle diameters of oxide colloidal particles determined by transmission electron microscope (TEM) image analysis is the standard deviation of the equivalent circle diameters determined by analyzing 500 particles observed in TEM images using an automatic image processing analyzer, as described below. Taking into consideration transparency when applied to optical components, the standard deviation is preferably 0.1 to 3.0 nm, more preferably 0.1 to 2.7 nm, even more preferably 0.1 to 2.4 nm, and particularly preferably 0.1 to 2.0 nm. Furthermore, the ratio of the standard deviation of the equivalent circle diameters to the equivalent circle diameter (standard deviation / equivalent circle diameter) is preferably 0.01 to 0.26, preferably 0.01 to 0.22, more preferably 0.01 to 0.21, even more preferably 0.01 to 0.20, and particularly preferably 0.01 to 0.19.

[0019] The dry density and theoretical density of the oxide colloidal particles can be measured by the method described in the Examples below. In one embodiment of the present invention, the dry density of the oxide colloidal particles is 3.30 to 4.00 g / cm, taking into consideration the effects of the present invention and the hardness of the optical member when applied to the member. ３ is preferably 3.40 to 4.00 g / cm ３ More preferably, it is 3.50 to 4.00 g / cm ３ More preferably, it is 3.70 to 4.00 g / cm ３ It is particularly preferable that the ratio of the dry density to the theoretical density (dry density / theoretical density) is 0.71 to 1.0, more preferably 0.74 to 1.0, even more preferably 0.77 to 1.0, and particularly preferably 0.80 to 1.0.

[0020] The particle refractive index of the oxide colloidal particles can be measured by the method described in the Examples below. In one embodiment of the present invention, the particle refractive index of the oxide colloidal particles is preferably 2.24 to 2.50, more preferably 2.27 to 2.50, and particularly preferably 2.30 to 2.50, in view of the effect of the present invention that the oxide colloidal particles are titanium oxide-based colloidal particles and can maintain a high refractive index even when doped with other elements.

[0021] [Sol of Oxide Colloid Particles] The sol (dispersion) of oxide colloid particles of the present invention is a sol in which the oxide colloid particles of the present invention are dispersed as a dispersoid in a liquid medium. In one embodiment of the present invention, the particle refractive index of the oxide colloid particles can be measured by the method described in the Examples below. In consideration of the transparency and dispersibility when applied to optical components, the Z-average particle size measured by a dynamic light scattering (DLS) method is preferably 5 to 500 nm, more preferably 5 to 200 nm, even more preferably 5 to 100 nm, still more preferably 5 to 55 nm, even more preferably 5 to 35 nm, and particularly preferably 5 to 30 nm.

[0022] The dispersion medium constituting the sol of the oxide colloidal particles is not particularly limited, and a liquid medium containing water and / or an organic solvent can be used, but an organic solvent is preferred from the viewpoint of the film-forming properties of the coating composition, compatibility with the binder, etc. As the organic solvent, methanol, methyl ethyl ketone, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, etc. can be preferably used.

[0023] In addition to the oxide colloidal particles and the dispersion medium, the sol may contain an amine from the viewpoints of sol stabilization, pH adjustment, etc. As the amine, alkylamines such as ethylamine, diethylamine, n-propylamine, isopropylamine, diisopropylamine, dipropylamine, n-butylamine, isobutylamine, diisobutylamine, triethylamine, and benzylamine, and alkanolamines such as monoethanolamine and triethanolamine can be preferably used. Among these, diisopropylamine, diisobutylamine, and the like can be particularly preferably used. There are no particular restrictions on the amount of amine used, but from the viewpoint of refractive index, etc., the concentration in the sol is preferably 0.1 to 2.0% by mass, and particularly preferably 0.3 to 1.0% by mass.

[0024] [Method for Producing Aqueous Sol of Oxide Colloid Particles] In the present invention, the method for producing an aqueous sol of oxide colloid particles comprises the following steps (a) to (c), and can be carried out as illustrated in the examples described below: Step (a): mixing a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and an iron- and / or zinc-containing compound with pure water, and heating the mixture at 110 to 200°C for 0.1 to 20 hours to obtain aqueous sol (a), Step (b): ultrafiltrating aqueous sol (a) and then subjecting it to ion exchange treatment to obtain aqueous sol (b), Step (c): mixing an Nb- and / or Ta-containing compound with aqueous sol (b), and then heating the mixture at 150 to 300°C for 0.1 to 20 hours to obtain aqueous sol (c).

[0025] <Regarding Step (a)> In step (a), when the nitrogen-containing basic compound, the titanium-containing compound, the fatty acid, and the iron- and / or zinc-containing compound are mixed with pure water, a tin-containing compound or the like may be further added and mixed in. In this case, the tin-containing compound may be used as a rutilating agent.

[0026] Specific examples of the nitrogen-containing basic compound include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, octyltrimethylammonium hydroxide, tributylmethylammonium hydroxide, trioctylmethylammonium hydroxide, benzyltrimethylammonium hydroxide, benzyltriethylammonium hydroxide, benzyltripropylammonium hydroxide, benzyltributylammonium hydroxide, monomethyltriethanolammonium hydroxide, dimethyldiethanolammonium hydroxide, etc. These may be used alone or in combination of two or more.

[0027] Specific examples of titanium-containing compounds include titanium methoxide, titanium ethoxide, titanium tetra-n-propoxide, titanium tetraisopropoxide, etc. These may be used alone or in combination of two or more.

[0028] Specific examples of fatty acids include oxalic acid, malonic acid, succinic acid, phthalic acid, isophthalic acid, etc. These may be used alone or in combination of two or more.

[0029] Specific examples of the iron-containing compound include iron oxide, iron chloride, iron acetate, iron oxalate dihydrate, etc. These may be used alone or in combination of two or more.

[0030] Specific examples of zinc-containing compounds include zinc oxide, zinc chloride, zinc acetate, zinc oxalate dihydrate, etc. These may be used alone or in combination of two or more.

[0031] Specific examples of tin-containing compounds include metastannic acid, tin oxalate, sodium stannate, potassium stannate, etc. In the present invention, these may be used alone or in combination of two or more.

[0032] In step (a), the heating temperature is preferably 110°C to 200°C, more preferably 120°C to 180°C, and even more preferably 130°C to 170°C, from the viewpoint of promoting crystallization (nuclear particle generation) of the oxide colloidal particles and suppressing aggregation of the oxide colloidal particles. In step (c), the heating time is preferably 0.1 to 20 hours, more preferably 0.5 to 10 hours, and even more preferably 1 to 7 hours, from the viewpoint of reactivity. Stirring may be performed during heating.

[0033] In step (a), the heating can be carried out by filling the mixed solution into a pressure-resistant container (autoclave) and subjecting it to hydrothermal treatment. Alternatively, before the heating, the mixed solution may be heated and dissolved under stirring at a temperature lower than the heating temperature (e.g., 80°C), which may also be referred to as "aging," and then the IPA may be removed at a temperature of around 95°C.

[0034] <Regarding Step (b)> In step (b), the aqueous sol (a) can be subjected to ultrafiltration to desalt and wash the colloidal particles or to concentrate the aqueous sol (a). Inclusion of such a step is preferable in terms of transparency, dispersibility, etc.

[0035] In the step (b), after ultrafiltration of the aqueous sol (a), it is preferable to subject the aqueous sol to an ion exchange treatment (a treatment of exchanging cations and / or anions) in terms of dispersibility, etc. The conditions for the ion exchange are not particularly limited, but a preferred example is Na ＋ , K. ＋ Ions such as H ＋ It can be exchanged for ions such as

[0036] <Regarding Step (c)> In the step (c), specific examples of the Nb-containing compound include niobic acid hydrate (Nb ２ O ５ / nH ２Examples of the Ta-containing compound include niobium pentoxide, niobate (V) ammonium oxalate hydrate, and niobium hydroxide. In the present invention, from the viewpoint of reactivity, niobic acid hydrate and niobium pentoxide are preferred, and niobic acid hydrate is more preferred. In the above step (c), specific examples of the Ta-containing compound include tantalic acid hydrate (Ta ２ O ５ / nH ２ Examples of suitable tantalum oxides include tantalum(V) pentoxide, tantalum(V) ammonium oxalate hydrate, and tantalum hydroxide. In the present invention, among these, tantalum acid hydrate and tantalum pentoxide are preferred, and tantalum acid hydrate is more preferred, from the viewpoint of reactivity.

[0037] In the above step (c), the heating temperature is preferably 150°C to 300°C, more preferably 160°C to 280°C, and even more preferably 170°C to 250°C, from the viewpoint of sufficiently dissolving the Nb and / or Ta-containing compound. In addition, in the above step (c), the heating time is preferably 0.1 to 20 hours, more preferably 1 to 15 hours, and even more preferably 5 to 10 hours, from the viewpoint of sufficiently distributing Nb and / or Ta throughout the oxide colloidal particles. Stirring may be performed during heating. In step (c), the heating can be performed by filling the aqueous sol (b) into a pressure-resistant container (autoclave) and subjecting it to hydrothermal treatment.

[0038] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to these examples in any way.

[0039] The physical properties of the dispersion (sol) were determined by the following measurement methods.

[0040] [Solid content concentration] The sol was weighed using a crucible, dried on a hot plate at 110°C to remove the solvent, and pre-dried. This was then fired in an electric furnace in an air atmosphere at 600°C for 30 minutes. The crucible was weighed, and the solid content concentration in the sol was calculated from the weight of the residue.

[0041] [Average particle size by dynamic light scattering (DLS) (dynamic light scattering particle size)] The sol was diluted with a dispersion solvent to a scattering intensity of 200 to 400 cps, and the dispersion was measured using the solvent parameters with a dynamic light scattering measurement device (manufactured by Malvern Instruments Ltd., trade name Zeta-sizer). The average secondary particle size was the Z-average particle size (DLS particle size) measured by dynamic light scattering.

[0042] [L Value] A sample prepared by dispersing a sol in a dispersion solvent (e.g., pure water) to a solids concentration of 3.0% by mass was placed in a quartz cell (manufactured by JUKI Electronics Co., Ltd., product name L500E0B1000 Glass Cell 10) having a length of 4 cm, a width of 1 cm, and a height of 5 cm, and the L value was measured using a spectrophotometer (manufactured by JUKI Electronics Co., Ltd., product name JUKI AY555). The transmission chamber (integrating sphere inlet) was shielded from light with a jig (manufactured by JUKI Electronics Co., Ltd., product name Zero Cap) for zero calibration, and then pure water was poured into the glass cell for white calibration. The cell filled with the sample was placed on the integrating sphere side of the transmission chamber, and the L value was measured by irradiating it with light having a wavelength of 555 nm with the transmission chamber closed.

[0043] [YI Value] The sol was weighed using a petri dish, dried on a hot plate at 110°C, and the solvent was removed to obtain a powder. For the measurement, a spectrophotometer (manufactured by JUKI Electronics Co., Ltd., product name AY555) was used. A black box (manufactured by JUKI Electronics Co., Ltd.) was placed on the sample stage to perform zero calibration, and then a barium plate for white calibration was placed on the sample stage to perform white calibration. A 30φ glass cell filled with 3 g of powder was placed on the sample stage, and light with a wavelength of 555 nm was irradiated while shielded by the black box to measure the YI value (YI Ｄ１９２５ ) was measured.

[0044] [XRD Measurement] The sol was dried on a hot plate at 110°C and pulverized using a mortar and pestle to obtain a dry powder, which was subjected to measurement of the powder X-ray diffraction pattern (also simply referred to as the X-ray diffraction (XRD) pattern) under the following conditions.

[0045] [XRD measurement conditions] Apparatus used: MiniFlex 600 (manufactured by Rigaku Corporation) Radiation source: CuKα Voltage: 40 kV Current: 15 mA Sample rotation: None Slit conditions: Variable + fixed slit system Divergence slit: 0.625 deg. Divergence vertical limiting slit: 10 mm Scattering slit: Open Receiving slit: Open Scanning mode: Continuous Scanning speed: 2° / min Counting unit: Counts Step width: 0.0100° Operating axis: 2θ / θ Scanning range: 5,000 to 80,000°

[0046] [X-ray Fluorescence Analysis] The sol was dried at 110°C on a hot plate and pulverized using a mortar and pestle to obtain a dry powder. 0.3 g of this dry powder was spread over an analytical polyethylene container (manufactured by Rigaku Corporation, trade name Roll Sheet, Cat. No. 3399G003) tightly covered with a polypropylene film, and the mass ratio of the metal oxide was measured using an X-ray fluorescence analyzer (also known as XRF, manufactured by Rigaku Corporation, trade name Supermini 200) under the following conditions. Metal oxides can take different forms depending on the valence of the metal. However, in the present application, when converting to metal oxide, they are treated as the most representative metal oxide, and the oxide of Ti is expressed as TiO. ２ , Sn oxide is SnO ２ , oxide of Fe is Fe ２ O ３ Zn oxide is ZnO, Nb oxide is Nb ２ O ５ , Ta oxide is Ta ２ O ５ was converted as

[0047] [X-ray fluorescence analysis conditions] Apparatus used: Supermini 200 (manufactured by Rigaku Corporation) X-ray tube: end window type (200 W single target) Target material: Pd Tube voltage: 50 kV Tube current: 4 mA Duty cycle: 100% Analyzing crystal: LiF (200) Detector: SC (scintillation counter) Scanning range: 10 to 118° Atmosphere: vacuum Form of component: oxide

[0048] [ICP Analysis] The sol was collected in a conical beaker, sulfuric acid was added, and the mixture was heated to melt. Hydrochloric acid was then added, followed by the addition of pure water for dilution. The amounts of Ti and Fe in the resulting solution were analyzed in terms of oxides (TiO ２ , Fe ２ O ３ ) and Fe ２ O ３ The content of (Fe ２ O ３ Content (mass%) / (TiO ２ +Fe ２ O ３ The total content (mass%) of

[0049] [Theoretical Density] The theoretical density of the particles was calculated from the theoretical density of each metal oxide and the mass ratio of the metal oxide measured by XRF. The theoretical density value of each metal oxide was ２ : 4.26 g / cm ３ , SnO ２ : 6.95 g / cm ３ , Fe ２ O ３ : 5.24 g / cm ３ , ZnO: 5.47g / cm ３ , Nb ２ O ５ : 4.47 g / cm ３ , Ta ２ O ５ : 8.74 g / cm ３ The theoretical density (g / cm) was calculated using the following formula: ３ ) = (4.26 × TiO ２ Ratio (mass%) / 100+6.95×SnO ２ (mass%) / 100+5.24×Fe ２ O ３ (mass%) / 100+5.47×ZnO ratio (mass%) / 100+4.47×Nb ２ O ５ Ratio (mass%) / 100)+8.74×Ta ２ O ５ Ratio (mass%) / 100)

[0050] [Dry Density] The sol was dried on a hot plate at 110°C and pulverized using a mortar and pestle to obtain a dry powder, which was measured using a dry density meter (Shimadzu Corporation, trade name: AccuPycII 1340 TEC) at 25°C under a helium atmosphere.

[0051] [Evaluation of Light Fastness of Dispersion] A dispersion was prepared by diluting a sample sol with a water:methanol = 1:1 (mass ratio) dispersion so that the solid content concentration of the sample sol was 0.05 mass %, and the dispersion was mixed with a 0.02 mass % glycerin solution of a dye (Sunset Yellow) in a mass ratio of 1:3 to prepare a sample. This was placed in a quartz cell with a length of 1 mm, a width of 1 cm, and a height of 5 cm and sealed. After that, the sample was irradiated with an ultraviolet lamp (manufactured by AS ONE Corporation, product name: SLUV-6) with a wavelength range of I-rays (wavelength 365 nm) selected at an irradiation intensity of 0.4 mW / cm. ２ The film was irradiated with ultraviolet light (wavelength: 365 nm) for 10 minutes.

[0052] On the other hand, the absorbance (A) of the sample at a wavelength of 490 nm before and after ultraviolet irradiation was ０ and A １０ ) was measured using an ultraviolet-visible spectrophotometer (Shimadzu Corporation, trade name UV-3600), and the fading rate of the dye (change in absorbance at a wavelength of 490 nm) was calculated using the following formula: ０ ) indicates the absorbance at a wavelength of 490 nm before irradiation with I-rays (wavelength 365 nm), and (A １０ ) indicates the absorbance at a wavelength of 490 nm after irradiating with I-rays (wavelength 365 nm) for 10 minutes. １０ ) / (A ０ )) x 100

[0053] Furthermore, the photocatalytic activity of the particles was evaluated based on the following criteria. The lower the fading change rate of the particles, the more suppressed the photocatalytic activity. ◎: Fading change rate less than 1% ◯: Fading change rate 1% or more but less than 15% △: Fading change rate 15% or more but less than 45% ×: Fading change rate 45% or more Among these, a fading change rate of less than 15% is preferred, less than 9% is more preferred, and less than 1% is even more preferred.

[0054] [Particle Refractive Index] The refractive index of particles in the sol was measured by the following steps i) to iii). i) Preparation of Sol-Formulated Varnish 1.57 g of polyurethane dispersion (manufactured by Nicca Chemical Co., Ltd., trade name Evaphanol HA-170, solids concentration 37.0% by mass) was weighed into a plastic container, and to this was added a water-dispersed sol equivalent to 0.29 g of solids, 0.20 g of a methanol solution (10% by mass L-7604) of a leveling agent (DOWSIL trade name L-7604), and pure water so that the total blend amount was 20.0 g. The mixture was stirred at room temperature for 1 hour to prepare 20.0 g of sol-formulated varnish (solids concentration 4.4% by mass, particle blend amount: 50 phr). Next, 1.18 g of polyurethane dispersion (manufactured by Nicca Chemical Co., Ltd., trade name Evaphanol HA-170, solids concentration 37.0 mass%) was weighed into a plastic container, and to this was added a sol equivalent to 0.44 g of solids, 0.20 g of a methanol solution (10 mass% L-7604) of a leveling agent (DOWSIL trade name L-7604), and pure water so that the total blend amount was 20.0 g, and the mixture was stirred at room temperature for 1 hour to prepare 20.0 g of a sol-blended varnish (solids concentration 4.4 mass%, particle blend amount: 100 phr). Next, 2.36 g of polyurethane dispersion (manufactured by Nicca Chemical Co., Ltd., trade name Evaphanol HA-170, solids concentration 37.0% by mass) was weighed into a plastic container, and 0.20 g of a methanol solution (10% by mass L-7604) of a leveling agent (DOWSIL trade name L-7604) and 17.44 g of pure water were added thereto, and the mixture was stirred at room temperature for 1 hour to prepare 20.0 g of particle-free varnish (solids concentration 4.4% by mass, particle blending amount: none).

[0055] ii) Preparation of particle-containing film The sol-containing varnish obtained in i) was irradiated with UV- ３ Approximately 0.5 mL of the solution was dropped onto the treated Si substrate and coated using a spin coater (manufactured by Mikasa Co., Ltd., product name Opticoat MS-B100) so that the film thickness after coating would be 0.3 μm. The solution was then heated on a hot plate at 80°C for 5 minutes and heat-treated in an oven at 120°C for 1 hour to prepare particle-blended films (particle blending amounts: 50 phr, 100 phr, none).

[0056] iii) Measurement of refractive index of particle-blended film, calculation of refractive index of particles The refractive index of the particle-blended film obtained in ii) (particle blending amount: 50 phr, 100 phr, none) was measured using an ellipsometer (multi-angle incident spectroscopic ellipsometer, product name VASE, manufactured by J.A. Woollam Japan Co., Ltd.) In a two-component system of resin and particles, the refractive index of the film was plotted against the volume fraction of the particles, and the refractive index at 100 vol% of particles was calculated by extrapolation as the refractive index of the particles.

[0057] [TEM Observation] The sol was diluted with a dispersion solvent to a concentration that did not cause lamination during observation, and the diluted solution was dropped onto a TEM mesh (manufactured by Oken Shoji Co., Ltd., product name: Elastic Carbon ELS-C10 STEM Cu100P grid specification), and after air drying, the particles were observed with a transmission electron microscope (manufactured by JEOL Ltd., product name: JEM-F).

[0058] [Circle-equivalent diameter, standard deviation] 500 particles observed in a TEM image were analyzed using an automatic image processing analyzer (LUZEX AP, manufactured by Nireco Corporation) to determine the average value and standard deviation of the circle-equivalent diameter.

[0059] Example 1 Preparation of titanium oxide-stannic oxide-zinc oxide-niobium oxide composite oxide colloidal particles (1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heating at 140°C for 5 hours. 219.3 g of a 35% by mass aqueous solution of tetraethylammonium hydroxide was dissolved in 197.3 g of pure water, and then 6.7 g of metastannic acid (SnO ２ 5.7g in terms of titanium tetraisopropoxide, 213.5g (TiO ２ 49.3 g of oxalic acid dihydrate (containing 60.0 g in terms of oxalic acid), 49.3 g of oxalic acid dihydrate (containing 35.1 g in terms of oxalic acid), and 3.3 g of zinc oxide were added under stirring to obtain a mixed solution (excluding the amount of ZnO, the amount of TiO ２ Conversion and SnO ２(Containing a total solids content of 65.7 g, calculated as a total of 65.7 g). After holding the mixed solution at 80°C for 2 hours, pure water was added to maintain a constant liquid level while holding at 95°C for 5 hours to prepare a mixed solution. The obtained mixed solution was diluted with 689.4 g of pure water, and the mixed solution was placed in a glass-lined autoclave vessel. The mixed solution was subjected to hydrothermal treatment at 140°C for 5 hours at a stirring speed of 100 rpm, and cooled to room temperature to obtain sol (a). (2) Preparation of sol (b) by ultrafiltration and ion exchange treatment of sol (a) The obtained sol (a) was desalted and washed by ultrafiltration, and after adding 1.7 g of 35% by mass tetraethylammonium hydroxide, the solution was passed through a column packed with 500 milliliters of ion exchange resin (Amberlite (trade name) IRA-410, manufactured by Organo Corporation) for the purpose of anion exchange treatment to obtain sol (b). The sol (b) is an alkaline aqueous dispersion sol of titanium oxide-stannic oxide-zinc oxide composite oxide colloidal particles, with a pH of 11.8 and a solids concentration (TiO ２ , SnO ２ , and ZnO) 3.5 mass %, and the primary particle size was 5 to 15 nm when observed with a transmission electron microscope. (3) Preparation of sol (c) by mixing an Nb-containing compound into sol (b) and subjecting it to hydrothermal treatment at 240°C. 150.0 g of the obtained sol (b) (TiO ２ Conversion, SnO ２ The total solid content was 5.25 g (based on the total of ZnO and ZnO equivalents) and 24.6 g of pure water, 1.14 g of niobic acid (niobium hydroxide) (Nb ２ O ５ The mixture was added with stirring, and then placed in an autoclave made of SUS, and subjected to hydrothermal treatment at 240°C for 5 hours to obtain sol (c). After the hydrothermal treatment at 240°C for 5 hours, sol (c) was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-zinc oxide-niobium oxide composite oxide colloidal particles, with a pH of 9.3 and a solids concentration (TiO ２ , SnO ２ , ZnO, and Nb ２ O ５) 3.5% by mass, and the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope. This sol was dried at 110°C and the powder was subjected to X-ray diffraction analysis, which confirmed that it was a rutile crystal. The experimental conditions and various measurement results are shown in Table 1. As is clear from Table 1, in the case of sol (c) of Example 1, the dispersion light resistance (fading rate of the dye) was extremely low at 0.4%, the photocatalytic activity of the particles was significantly suppressed, and it was rated as "Excellent", and it was also found that the particle refractive index maintained a high value of 2.32.

[0060] Example 2 Preparation of titanium oxide-stannic oxide-zinc oxide-niobium oxide composite oxide colloidal particles In the step of "(3) Preparation of sol (c) by mixing Nb-containing compound into sol (b) and hydrothermal treatment at 240°C" in Example 1, the weight of niobic acid (niobium hydroxide) added was changed to 1.14 g (Nb ２ O ５ (converted to 0.93g) to 0.23g (Nb ２ O ５ Sol (c) was prepared in the same manner as in Example 1, except that the amount of sol (c) was changed to 0.19 g in terms of the amount of sol (c). As a result, similar to Example 1, the sol (c) after hydrothermal treatment at 240°C for 5 hours was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-zinc oxide-niobium oxide composite oxide colloidal particles, and had a pH of 10.6 and a solids concentration (TiO ２ , SnO ２ , ZnO, and Nb ２ O ５ As in Example 1, except that the content of sol (c) in the dispersion was 3.1 mass %, the primary particle diameter was 5 to 15 nm as observed with a transmission electron microscope, and it was confirmed that the particles were rutile crystals. The experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (c) of Example 2, the light resistance of the dispersion (the rate of fading of the dye) was extremely low at 0.9%, the photocatalytic activity of the particles was significantly suppressed, and the sol was rated as "Excellent", and the particle refractive index maintained a high value of 2.34.

[0061] Example 3 Preparation of titanium oxide-stannic oxide-zinc oxide-niobium oxide composite oxide colloidal particles In "(3) Preparation of sol (c) by mixing Nb-containing compound into sol (b) and hydrothermal treatment at 240°C" in Example 1, the weight of niobic acid (niobium hydroxide) added was changed to 1.14 g (Nb ２ O ５ (converted to 0.93g) to 0.68g (Nb ２ O ５ Sol (c) was prepared in the same manner as in Example 1, except that the amount of sol (c) was changed to 0.56 g (calculated as 0.56 g). As a result, similar to Example 1, sol (c) after hydrothermal treatment at 240°C for 5 hours was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-zinc oxide-niobium oxide composite oxide colloidal particles, and had a pH of 10.0 and a solids concentration (TiO ２ , SnO ２ , ZnO, and Nb ２ O ５ As in Example 1, except that the content of sol (c) in the dispersion was 3.3 mass %, the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope, and it was confirmed that the sol was a rutile crystal. The experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (c) of Example 3, the light resistance of the dispersion (the rate of fading of the dye) was extremely low at 0.8%, the photocatalytic activity of the particles was significantly suppressed, and the sol was rated as "Excellent", and the particle refractive index maintained a high value of 2.33.

[0062] Example 4 Preparation of titanium oxide-stannic oxide-zinc oxide-niobium oxide composite oxide colloidal particles Sol (c) was prepared in the same manner as in Example 1, except that in "(1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heat-treating at 140°C for 5 hours," the weight of zinc oxide added was changed from 3.3 g to 1.7 g. As a result, as in Example 1, sol (c) after hydrothermal treatment at 240°C for 5 hours was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-zinc oxide-niobium oxide composite oxide colloidal particles, and had a pH of 9.3 and a solids concentration (TiO ２ , SnO ２ , ZnO, and Nb ２ O ５As in Example 1, except that the content of sol (c) in the dispersion was 3.5 mass %, the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope, and it was confirmed that the particles were rutile crystals. The experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (c) of Example 4, the light resistance of the dispersion (the rate of fading of the dye) was extremely low at 0.7%, the photocatalytic activity of the particles was significantly suppressed, and the sol was rated as "Excellent", and the particle refractive index maintained a high value of 2.33.

[0063] Example 5 Preparation of titanium oxide-stannic oxide-ferric oxide-niobium oxide composite oxide colloidal particles In the procedure of Example 1, "(1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heating at 140°C for 5 hours," 0.097 g of iron (II) oxalate dihydrate (Fe) was used instead of zinc oxide. ２ O ３ Sol (c) was prepared in the same manner as in Example 1, except that 0.043 g of stannic oxide was added to the sol (c). As a result, similar to Example 1, the sol (c) after hydrothermal treatment at 240°C for 5 hours was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-ferric oxide-niobium oxide composite oxide colloidal particles, and had a pH of 7.1 and a solids concentration (TiO ２ , SnO ２ , Fe ２ O ３ , and Nb ２ O ５ As in Example 1, except that the content of sol (c) in the dispersion was 3.5% by mass, the primary particle diameter was 5 to 15 nm as observed with a transmission electron microscope, and it was confirmed that the particles were rutile crystals. The experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (c) of Example 5, the light resistance of the dispersion (the rate of fading of the dye) was extremely low at 0.3%, the photocatalytic activity of the particles was significantly suppressed, and the sol was rated as "Excellent", and the particle refractive index maintained a high value of 2.34.

[0064] Example 6 Preparation of titanium oxide-stannic oxide-ferric oxide-zinc oxide-niobium oxide composite oxide colloidal particles In the "(1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heating at 140°C for 5 hours" procedure of Example 1, 0.097 g of iron (II) oxalate dihydrate was added after the addition of oxalic acid dihydrate. ２ O ３ Sol (c) was prepared in the same manner as in Example 1, except that 0.043 g of stannic oxide was added to the sol (c). As a result, similar to Example 1, the sol (c) after hydrothermal treatment at 240°C for 5 hours was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-ferric oxide-zinc oxide-niobium oxide composite oxide colloidal particles, and had a pH of 7.5 and a solids concentration (TiO ２ , SnO ２ , Fe ２ O ３ , ZnO, and Nb ２ O ５ As in Example 1, except that the content of sol (c) in the dispersion was 3.5 mass %, the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope, and it was confirmed that the particles were rutile crystals. The experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (c) of Example 6, the light resistance of the dispersion (the rate of fading of the dye) was extremely low at 0.2%, the photocatalytic activity of the particles was significantly suppressed, and the sol was rated as "Excellent", and the particle refractive index maintained a high value of 2.32.

[0065] Example 7 Preparation of titanium oxide-stannic oxide-ferric oxide-zinc oxide-tantalum oxide composite oxide colloidal particles In the "(1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heating at 140°C for 5 hours" procedure of Example 1, 0.097 g of iron (II) oxalate dihydrate was added after the addition of oxalic acid dihydrate. ２ O ３ In "(3) Preparation of sol (c) by mixing an Nb-containing compound into sol (b) and subjecting it to hydrothermal treatment at 240°C", 1.01 g of tantalic acid (tantalum hydroxide) was added instead of niobic acid (niobium hydroxide). ２ O ５Sol (c) was prepared in the same manner as in Example 1, except that 0.93 g of stannic oxide-iron oxide-zinc oxide-tantalum oxide composite oxide was added. As a result, similar to Example 1, sol (c) after hydrothermal treatment at 240°C for 5 hours was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-ferric oxide-zinc oxide-tantalum oxide composite oxide colloidal particles, and had a pH of 10.1 and a solids concentration (TiO ２ , SnO ２ , Fe ２ O ３ , ZnO, and Ta ２ O ５ As in Example 1, except that the content of sol (c) in the dispersion was 3.5 mass %, the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope, and it was confirmed that the particles were rutile crystals. The experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (c) of Example 7, the light resistance of the dispersion (the rate of fading of the dye) was extremely low at 0.1%, the photocatalytic activity of the particles was suppressed, and the sol was rated as "Excellent", and the particle refractive index maintained a high value of 2.27.

[0066] Example 8 Preparation of titanium oxide-stannic oxide-ferric oxide-zinc oxide-tantalum oxide composite oxide colloidal particles In the "(1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heating at 140°C for 5 hours" procedure of Example 1, 0.097 g of iron (II) oxalate dihydrate was added after the addition of oxalic acid dihydrate. ２ O ３ In "(3) Preparation of sol (c) by mixing an Nb-containing compound into sol (b) and subjecting it to hydrothermal treatment at 240°C", 0.93 g of tantalum pentoxide (Ta) was added instead of niobic acid (niobium hydroxide). ２ O ５ Sol (c) was prepared in the same manner as in Example 1, except that 0.93 g of stannic oxide-iron oxide-zinc oxide-tantalum oxide composite oxide was added. As a result, similar to Example 1, sol (c) after hydrothermal treatment at 240°C for 5 hours was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-ferric oxide-zinc oxide-tantalum oxide composite oxide colloidal particles, and had a pH of 10.6 and a solids concentration (TiO ２ , SnO ２ , Fe ２O ３ , ZnO, and Ta ２ O ５ As in Example 1, except that the content of sol (c) in the dispersion was 3.5 mass %, the primary particle diameter was 5 to 23 nm when observed with a transmission electron microscope, and it was confirmed that the particles were rutile crystals. The experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (c) of Example 8, the light resistance of the dispersion (the rate of fading of the dye) was low at 8.6%, the photocatalytic activity of the particles was suppressed, and the result was rated as "Good," and it was also found that the particle refractive index maintained a high value of 2.36.

[0067] Comparative Example 1 Preparation of Titanium Oxide-Stannic Oxide-Zinc Oxide Composite Oxide Colloidal Particles Sol (b) was prepared in the same manner as in Example 1, except that the step "(3) Mixing Sol (b) with an Nb-containing compound and Preparing Sol (c) by Hydrothermal Treatment at 240°C" in Example 1 was not carried out at all. In other words, sol (b) does not contain Nb element. As a result, sol (b) in Comparative Example 1 was the same as sol (b) in Example 1. In other words, the sol (b) obtained by passing the liquid through a column was an alkaline aqueous dispersion sol of titanium oxide-stannic oxide-zinc oxide composite oxide colloidal particles, with a pH of 11.8 and a solids concentration (TiO ２ , SnO ２ , and ZnO) 3.5% by mass, and the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope. The above experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (b) of Comparative Example 1, the light resistance of the dispersion (the rate of fading of the dye) was extremely high at 55.1%, and the photocatalytic activity of the particles was not suppressed, so it was rated as "X". Furthermore, the particle refractive index was 2.23, which was lower than that of the sol (c) of any of the Examples, and it was found that a high value could not be maintained.

[0068] Comparative Example 2 Preparation of titanium oxide-stannic oxide-iron oxide composite oxide colloidal particles In the procedure of Example 1, "(1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heating at 140°C for 5 hours," 0.097 g of iron (II) oxalate dihydrate (Fe) was used instead of zinc oxide. ２ O ３Sol (b) was prepared in the same manner as in Example 1, except that 0.043 g of Nb was added to sol (b) and the step "(3) Preparation of sol (c) by mixing an Nb-containing compound into sol (b) and hydrothermal treatment at 240°C" was not carried out at all. In other words, Zn and Nb elements were not added to sol (b). As a result, sol (b) of Comparative Example 2 was the same as sol (b) of Example 1, that is, the sol (b) obtained by passing the liquid through the column was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-ferric oxide composite oxide colloidal particles, with a pH of 11.7 and a solids concentration (TiO ２ , SnO ２ , and Fe ２ O ３ ) 3.9% by mass, and the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope. The above experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (b) of Comparative Example 2, the light resistance of the dispersion (the rate of fading of the dye) was extremely high at 62.6%, and the photocatalytic activity of the particles was not suppressed, so it was rated as "X." Furthermore, the particle refractive index was 2.25, which was lower than that of the sol (c) of any of the Examples, and it was found that a high value could not be maintained.

[0069] Comparative Example 3 Preparation of titanium oxide-stannic oxide-iron oxide composite oxide colloidal particles In the procedure of Example 1, "(1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heating at 140°C for 5 hours," 0.391 g of iron (II) oxalate dihydrate (Fe) was used instead of zinc oxide. ２ O ３ Sol (b) was prepared in the same manner as in Example 1, except that 0.173 g of Nb was added to sol (b) and the step "(3) Preparation of sol (c) by mixing an Nb-containing compound into sol (b) and hydrothermal treatment at 240°C" was not carried out at all. In other words, sol (b) does not contain Zn and Nb elements. As a result, sol (b) of Comparative Example 3 was the same as sol (b) of Example 1, that is, the sol (b) obtained by passing the liquid through the column was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-ferric oxide composite oxide colloidal particles, with a pH of 11.7 and a solids concentration (TiO ２ , SnO２ , and Fe ２ O ３ ) 4.1% by mass, and the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope. The above experimental conditions and various measurement results are shown in Table 1. As is clear from Table 1, for sol (b) of Comparative Example 3, the dispersion light resistance (dye fading change rate) was somewhat high at 18.7%, and the photocatalytic activity of the particles was not sufficiently suppressed, resulting in a rating of "△." The particle refractive index was 2.25, lower than that of sol (c) of any of the Examples, and it was found that a high value could not be maintained. In addition, the YI value of the powder was 22, higher than that of any of the Examples, indicating that coloration derived from Fe was not suppressed.

[0070] Comparative Example 4 Preparation of titanium oxide-stannic oxide-ferric oxide-zinc oxide composite oxide colloidal particles In the "(1) Preparation of sol (a) by mixing water, a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and a zinc-containing compound and heating at 140°C for 5 hours" procedure of Example 1, 0.097 g of iron (II) oxalate dihydrate was added after the addition of oxalic acid dihydrate. ２ O ３ Sol (b) was prepared in the same manner as in Example 1, except that 0.043 g of Nb-containing compound was added to sol (b) and the step of "(3) Mixing sol (b) with Nb-containing compound and preparing sol (c) by hydrothermal treatment at 240°C" was not carried out at all. In other words, sol (b) does not contain Nb element. As a result, sol (b) of Comparative Example 4 was the same as sol (b) of Example 1, that is, the sol (b) obtained by passing the liquid through the column was an aqueous dispersion sol of alkaline titanium oxide-stannic oxide-ferric oxide composite oxide colloidal particles, with a pH of 11.7 and a solids concentration (TiO ２ , SnO ２ , and Fe ２ O ３) 3.9% by mass, and the primary particle diameter was 5 to 15 nm when observed with a transmission electron microscope. The above experimental conditions and the results of various measurements are shown in Table 1. As is clear from Table 1, in the sol (b) of Comparative Example 4, the dispersion light resistance (fading rate of the dye) was high at 47.0%, and the photocatalytic activity of the particles was not suppressed, so it was rated as "X." The particle refractive index was 2.25, which was lower than that of the sol (c) of any of the Examples, and it was found that a high value could not be maintained.

[0071]

[0072]

[0073]

[0074] In the present invention, titanium oxide is co-doped with Nb and Zn, and holes and electrons generated by the photocatalytic activity of titanium oxide are trapped by Nb and Zn, respectively, thereby making it possible to suppress the generation of reactive oxygen species. The results of the dispersion light resistance evaluation showed that the sols containing titanium oxide co-doped with Nb and Zn in Examples 1 to 4 had significantly improved light resistance compared to the sol containing titanium oxide doped with Zn only in Comparative Example 1, and it was confirmed that all of the titanium oxides co-doped with Nb and Zn in Examples 1 to 4 had extremely high light resistance and maintained a high refractive index.

[0075] The oxide colloidal particles of the present invention, a sol containing the oxide colloidal particles, and a method for producing the oxide colloidal particles can simultaneously achieve high levels of various properties that are highly valuable in practice, such as high light resistance, a high refractive index, and a fine particle size, exceeding the limits of conventional technology. Therefore, the particles are useful for various applications such as optical materials, including high refractive index sols for eyeglasses and optical applications, and are highly applicable in various fields of industries such as optical equipment, medical equipment, electrical and electronic equipment, communications, and medicine.

Claims

1. Oxide colloid particles containing Ti, which have a circle equivalent diameter of 5 to 50 nm as determined by transmission electron microscope image analysis, and in which Zn and / or Fe, and Nb and / or Ta are distributed throughout the oxide colloid particles.

2. The oxide colloid particles further contain Sn, and the ratio of Sn to Ti is SnO ２ / TiO ２ 2. The oxide colloid particles according to claim 1, wherein the .gamma.-to-.alpha..gamma.

3. The oxide colloid particles according to claim 1, wherein the ZnO content determined by XRF measurement is 0.2 to 10 mass %.

4. Nb by XRF measurement ２ O ５ The oxide colloid particles according to claim 1, wherein the content of 5. Ta by XRF measurement ２ O ５ The oxide colloid particles according to claim 1, wherein the content of 6. Fe by ICP measurement ２ O ３ The oxide colloid particles according to claim 1, wherein the content of is 0.001% by mass or more and less than 0.2% by mass.

7. The oxide colloid particles according to claim 1, wherein the standard deviation of the equivalent circle diameters as determined by transmission electron microscope image analysis is 0.1 to 3.0 nm, and the ratio of the standard deviation to the equivalent circle diameters (standard deviation / equivalent circle diameter) is 0.01 to 0.

26.

8. Dry density is 3.30 g / cm ３ ~4.00g / cm ３ 2. The oxide colloid particles according to claim 1, wherein the ratio of dry density to theoretical density (dry density / theoretical density) is 0.71 to 1.

0.

9. The oxide colloid particles according to claim 1, wherein the particle refractive index is 2.24 to 2.

50.

10. A sol of oxide colloid particles in which the oxide colloid particles according to claim 1 are dispersed as dispersoid in a liquid medium, the sol having a Z-average particle size of 5 to 500 nm as measured by dynamic light scattering.

11. The sol was diluted with a dispersion liquid containing water and methanol in a ratio of 1:1 (by mass) to prepare a dispersion liquid having a solids concentration of 0.05% by mass. The dispersion liquid was mixed with a 0.02% by mass glycerin solution of sunset yellow dye in a mass ratio of 1:3, and the mixture was irradiated with light having a wavelength of 365 nm at an intensity of 0.4 mW / cm. ２ 11. The sol according to claim 10, wherein when irradiated with 490 nm light for 10 minutes, the change in absorbance of the mixture at a wavelength of 490 nm before and after irradiation is less than 15%.

12. A method for producing an aqueous sol of oxide colloidal particles, comprising the following steps (a) to (c): step (a): mixing a nitrogen-containing basic compound, a titanium-containing compound, a fatty acid, and an iron- and / or zinc-containing compound with pure water, and heating the mixture at 110 to 200°C for 0.1 to 20 hours to obtain aqueous sol (a); step (b): ultrafiltrating aqueous sol (a), and then subjecting the mixture to ion exchange treatment to obtain aqueous sol (b); step (c): mixing an Nb- and / or Ta-containing compound with aqueous sol (b), and then heating the mixture at 150 to 300°C for 0.1 to 20 hours to obtain aqueous sol (c).

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