Particles with rutile crystal structure, methods for manufacturing the same, and methods for manufacturing particle dispersions, coating solutions, and film-coated substrates.

Abstract

This invention relates to particles with a rutile crystal structure. The particles have a grain diameter of 7 nm or more and contain at least 90% by weight of titanium oxide (equivalent to TiO₂) and 0.2% to 10% by weight of tin oxide (equivalent to SnO₂). Such particles are easily dispersed in solvents and have a high refractive index.

Description

[Technical Field]

[0001] This invention relates to particles having a rutile crystal structure and methods for manufacturing the same. [Previous Technology]

[0002] Conventionally, a coating liquid containing oxide particles with high refractive index is used to form a film with high refractive index on a substrate. Such films are used in, for example, eyeglasses, lenses, and touch panels for smartphones.

[0003] To form a film with a high refractive index, it is preferable that the particles have a high refractive index. For example, titanium oxide is known to have a high refractive index. In particular, titanium oxide with a rutile crystal structure has a high refractive index (see, for example, Japanese Patent Application Publication No. 2010-42947). Titanium oxide containing tin oxide readily forms a rutile crystal structure.

[0004] In addition, it is known that titanium oxide particles containing inorganic oxides such as silicon dioxide are easily dispersed (see, for example, International Publication No. 2018 / 181241). [Summary of the Invention]

[0005] In Patent Documents 1 and 2, because rutile composite particles containing titanium oxide and silicon dioxide are used, the titanium oxide content of the particles is reduced. Therefore, the refractive index of the film is reduced.

[0006] Therefore, the object of the present invention is to provide a particle that is easily dispersed in a solvent and has a high refractive index.

[0007] Therefore, the present invention relates to particles having a rutile crystal structure with a grain diameter (crystal diameter) of 7 nm or more. Such particles are easily dispersed in solvents. Here, the particles contain at least 90 wt% titanium oxide (equivalent to TiO2) and 0.2 wt% to 10 wt% tin oxide (equivalent to SnO2). Such particles have a high refractive index.

[0008] In addition, it is preferable that tin cannot be detected from the particle surface.

[0009] In addition, the particle size when the particles are dispersed in the solvent is preferably 100 nm or less.

[0010] Furthermore, the method for manufacturing particles with a rutile crystal structure includes: a step of preparing a dispersion of a titanium-containing compound; a step of preparing a dispersion of core particles (koa particles) with a rutile crystal structure; a step of preparing a mixed solution by mixing the dispersion of the titanium-containing compound and the dispersion of the core particles; and a step of growing core particle crystals by raising the mixed solution to 80°C or higher. The core particles contain titanium oxide and tin oxide.

Implementation Method

[0012] This invention relates to particles having a rutile crystal structure (hereinafter referred to as particles) with a grain diameter of 7 nm or more. Therefore, even if the particles contain 90% by weight or more titanium oxide (equivalent to TiO2) and 0.2% to 10% by weight tin oxide (equivalent to SnO2), they are easily dispersed in a solvent. In particular, even if the particle concentration is 20% by weight or more, such particles are easily and stably dispersed in water. Therefore, they are easy to handle industrially.

[0013] The larger the grain diameter of the particles, the smaller the specific surface area of ​​the particles. Therefore, the particles become easier to disperse in the solvent. In addition, the larger the grain diameter of the particles, the smaller the specific surface area, and therefore the higher the particle density. Therefore, the refractive index of the particles (hereinafter referred to as the particle refractive index) becomes higher. The refractive index of the film containing such particles (hereinafter referred to as the film refractive index) becomes higher. The grain diameter of the particles is preferably 9 nm or more, more preferably 12 nm or more.

[0014] The higher the titanium oxide content of the particles, the higher the refractive index of the particles. Therefore, this content is 90% by weight or more when converted to TiO2. Preferably, this content is 92% by weight or more when converted to TiO2, more preferably 95% by weight or more. Furthermore, if the particles contain tin oxide, the crystal structure of the particles tends to be rutile. However, from the viewpoint of particle refractive index, a lower tin oxide content is preferable. Therefore, this tin oxide content is 10% by weight or less when converted to SnO2. More preferably, this tin oxide content is 5% by weight or less when converted to SnO2.

[0015] Furthermore, if tin is not detectable from the particle surface, i.e., tin oxide is absent from the particle surface, the proportion of titanium oxide on the particle surface side (hereinafter referred to as the shell) is high. Therefore, the titanium oxide content of the particle as a whole tends to be high. On the other hand, if the particle's central side (hereinafter referred to as the core) contains tin oxide, the particle tends to form a rutile crystal structure. That is, when the core contains a sufficient amount of tin oxide to make the particle's crystal structure rutile, the shell may not contain tin oxide. The lower the proportion of tin in the core, the higher the titanium oxide content of the particle can be. Therefore, the proportion of tin in the core is preferably 6.5 atomic% (at%) or less. Here, the proportion of tin in the core is the number of tin atoms relative to the total number of titanium and tin atoms.

[0016] Furthermore, if the ratio of the average value of the minor diameter of the particles to the grain diameter (average value of minor diameter / grain diameter) is close to 1, the grain diameter becomes close to the minor diameter of the particles. As a result, the particle density becomes higher. Therefore, this ratio is preferably 0.8 to 3.0, more preferably 0.8 to 2.0, and even more preferably 0.8 to 1.5.

[0017] Furthermore, the smaller the average aspect ratio of the particles (hereinafter referred to as aspect ratio), the easier it is for the particles to disperse in the solvent or binder. Therefore, the haze of the film tends to be lower. In addition, the smaller the aspect ratio, the smaller the specific surface area of ​​the particles becomes. Therefore, the aspect ratio is preferably 1.0 to 2.3. In particular, if the grain diameter is 7 nm or more and the aspect ratio is 2.3 or less, the particles become easier to disperse in the solvent. The aspect ratio is preferably 1 to 2.1, more preferably 1 to 1.9, and even more preferably 1 to 1.6. It is even more preferably 1 to 1.5. In particular, when the grain diameter is 10 nm or more, the aspect ratio is preferably 1 to 1.9; when the grain diameter is 12.5 nm or more, the aspect ratio is preferably 1 to 1.8; and when the grain diameter is 17 nm or more, the aspect ratio is preferably 1 to 1.5. The aspect ratio is the ratio of the average value of the minor axis to the average value of the major axis of the particles.

[0018] When the particles are dispersed in a solvent, the average particle size (hereinafter referred to as the dispersion particle size) is preferably 100 nm or less. If a film is formed using particles of this size, the film transparency increases. In addition, the particles become less likely to settle. The dispersion particle size is more preferably 80 nm or less. On the other hand, if the dispersion particle size is 20 nm or more, the particles are easily dispersed in the solvent or binder. In particular, it is preferable to have a grain diameter of 7 nm or more and a dispersion particle size of 20 nm or more.

[0019] The refractive index of the particles varies depending on factors such as particle composition, density, crystal structure, and grain diameter. This refractive index is preferably 1.95 or higher, more preferably 2.05 or higher, and even more preferably 2.10 or higher. Obtaining particles with a refractive index of 2.8 or higher is relatively difficult.

[0020] Hereinafter, the particle dispersion will be described. The particle dispersion contains the aforementioned particles and a solvent. When the solvent is water, 20% by weight or more of the particles can be stably dispersed in water. On the other hand, in order to disperse the aforementioned particles in an organic solvent, the particle surface must be treated with a surface treatment agent. A portion of this surface treatment agent can be dispersed in the organic solvent without binding to the particles. Furthermore, when the solvent is an organic solvent (in the case of an organic solvent dispersion), two or more surface treatment agents may be contained. Examples of surface treatment agents include silicon compounds, titanium compounds, zirconium compounds, aluminum compounds, etc. Among them, silicon compounds are easy to process industrially.

[0021] If the organic solvent dispersion contains a surface treatment agent with alkoxy groups, the alkoxy groups will hydrolyze. In the dispersion, the hydrolyzed alkoxy groups undergo a dehydration condensation reaction with the OH groups on the particle surface (hereinafter referred to as chemical bonding). Therefore, the particles become easier to disperse in the organic solvent. Furthermore, by containing a catalyst or water in the organic solvent dispersion, the hydrolysis reaction of the alkoxy groups is promoted. At the same time, chemical bonding is promoted.

[0022] An alkyl group is bonded to the oxygen atom of the alkoxy group. The smaller the molecular weight of the alkyl group, the faster the hydrolysis reaction of the alkoxy group becomes. Therefore, the alkyl group is preferably methyl or ethyl.

[0023] As a surface treatment agent, molecules with the general formula (RO)nM(X)4-n can be cited. n is an integer from 1 to 4. M represents any one of Si, Ti, and Zr. If M is Si, it is easy to process industrially. If there is only one M in the molecule, it is easy to process industrially because the reaction rate of the molecule is easy to control. X is a hydrocarbon group. For example, it represents Me, Et, Pr, -(CH2)3OC(=O)C(CH3)(=CH2), -(CH2)3OC(=O)CH(=CH2), and -CH=CH2. R is a hydrocarbon group. When M is Si, by making R Me or Et, the reaction rate of the molecule is easy to control. Therefore, it is easy to process industrially.

[0024] The more alkoxy groups a surface treatment agent has, the easier it is for the surface treatment agent to chemically bond with the particle surface. Furthermore, if a surface treatment agent with more alkoxy groups bonds with the particle surface, the number of alkoxy groups on the particle surface increases. Therefore, the particles become easier to disperse in the alcohol. The surface treatment agent preferably has 3 to 4 alkoxy groups. When the solvent is an alcohol, the surface treatment agent preferably has 4 alkoxy groups. Hereinafter, a surface treatment agent having 4 alkoxy groups will be referred to as a first surface treatment agent.

[0025] If the dispersion contains 20 to 85 parts by mass of a first surface treatment agent (equivalent to 3 to 30 parts by mass in oxide form (or SiO2 if the surface treatment agent is a silicon compound)) relative to 100 parts by mass of particles, the particles are easily dispersed in the alcohol. Furthermore, the larger the grain diameter of the particles, the less surface treatment agent is required.

[0026] If the particles are treated with a surface treatment agent having a hydrocarbon group (hereinafter referred to as the second surface treatment agent), the particles are easily dispersed in organic solvents (hereinafter referred to as hydrophobic solvents) that are more hydrophobic than alcohols. In this case, by giving the second surface treatment agent three alkoxy groups and one hydrocarbon group, the particles become even more easily dispersed in the hydrophobic solvent. The second surface treatment agent differs from the first surface treatment agent. The first surface treatment agent does not have a hydrocarbon group. The hydrocarbon group is not an alkyl group bonded to the oxygen atom of an alkoxy group.

[0027] Examples of hydrophobic solvents include organic solvents having at least one of ester bonds, ether bonds, and ketone groups. Organic solvents having such bonds or functional groups readily dissolve UV-curable adhesives. Among such organic solvents, propylene glycol monomethyl ether acetate (PGMEA) is preferred.

[0028] If the particle surface is treated with the first surface treatment agent and the second surface treatment agent, the particles become easier to disperse in hydrophobic solvents or UV-curable adhesives.

[0029] Furthermore, if a surface treatment agent having a (meth)acrylate group is combined with particles, the particles can be bonded to a UV-curable adhesive by UV irradiation. As a result, the film becomes denser and the film refractive index increases. Therefore, preferably, the hydrocarbon group of the second surface treatment agent has a (meth)acrylate group, or the hydrocarbon group of the second surface treatment agent is a (meth)acrylate group.

[0030] When the solvent is water, treating the particle surface with silicon dioxide forms a denser layer on the particle surface than when using a surface treatment agent. Even with a small amount of surface treatment agent, such particles are easily dispersed in organic solvents (especially alcohols). That is, with such particles, it is easy to replace the solvent of the dispersion with an organic solvent. The isoelectric point of the aqueous dispersion of these particles is 3 or less (however, this is the isoelectric point when the solid content concentration is 0.5% by mass). On the other hand, without treating the particle surface with silicon dioxide, the isoelectric point of the aqueous dispersion of these particles is in the range of 4 to 6. Furthermore, if the particle surface is treated with silicon dioxide or a surface treatment agent, it is possible to observe crystal structures other than rutile.

[0031] When the solvent is water, it is preferable to treat the particle surface with silicon dioxide, which is equivalent to 2 or more parts by mass of SiO2 relative to 100 parts by mass of the particles. That is, it is preferable that the silicon dioxide content of the particles is 2 or more parts by mass relative to 100 parts by mass of the particles, and the isoelectric point of the aqueous dispersion is 3 or less. Even if the amount of surface treatment agent is small, such particles are easily dispersed in organic solvents (especially alcohols). It is more preferable that the silicon dioxide content is 4 or more parts by mass. On the other hand, if the silicon dioxide content is too high, the refractive index of the particles becomes low. Therefore, it is preferable that the silicon dioxide content is 20 or less parts by mass relative to 100 parts by mass of the particles. When treating the particle surface with silicon dioxide at a rate of 2 parts by mass or more relative to 100 parts by mass of particles, it is preferable to treat the particle surface with a first surface treatment agent at a rate of 10 to 30 parts by mass relative to 100 parts by mass of particles [3 to 10 parts by mass in oxide form (or SiO2 if the surface treatment agent is a silicon compound)].

[0032] The coating liquid will be described below. The coating liquid contains particles, a surface treatment agent, a binder, and an organic solvent. By forming a film using a coating liquid containing the aforementioned particles, the film refractive index increases. If a coating liquid containing a binder is used, a film can be formed. If a portion of the surface treatment agent acts as a binder, the binder may not be included. Examples of binders include monomers before polymerization, oligomers, and polymers formed after polymerization of these substances. Among these, monomers or oligomers are preferred. When the film is cured, the film becomes denser more easily when using a coating liquid containing monomers or oligomers compared to a coating liquid containing polymers. Since the adamantane backbone has a high refractive index, if an adamantane derivative is used as a monomer or oligomer, the film refractive index increases. The organic solvent can be appropriately selected depending on the type of binder added when preparing the coating liquid.

[0033] The higher the concentration of solids in the coating solution, the easier it is to form a thick film. Furthermore, the coating solution is easy to handle industrially. Therefore, this concentration is preferably 10% by weight or more, more preferably 20% by weight or more. On the other hand, if the concentration is 50% by weight or less, the viscosity of the coating solution is easily reduced. This concentration is preferably 30% by weight or less.

[0034] If the boiling point of the organic solvent is 80°C or higher, the coating solution can be dried slowly, thus making the film denser. This boiling point is more preferably 100°C or higher. On the other hand, if the boiling point is 200°C or lower, the organic solvent is less likely to remain, thus making the film more prone to shrinkage. Therefore, the film's hardness increases. This boiling point is more preferably 180°C or lower.

[0035] The manufacturing method of the particles will be described below. First, a dispersion of a titanium-containing compound and a dispersion of nuclei with a rutile crystal structure (hereinafter referred to as nuclei) are prepared <Preparation Step>. After this, the dispersion of the titanium-containing compound and the dispersion of the nuclei are mixed to prepare a mixture <Mixing Step>. By raising the mixture to 80°C or higher, crystals are grown based on the nuclei <Crystal Growth Step>. By growing crystals based on the nuclei, the tin oxide content of the particles decreases. Therefore, the titanium oxide content of the particles increases relatively. In addition, the grain diameter increases. After the crystal growth step, the nuclei become the core of the particles, and the titanium-containing compound becomes the shell of the particles. Each step will be described in detail below.

[0036] <Preparation Process>

[0037] The nucleus particles that serve as the starting point for crystal growth contain tin oxide and have a rutile crystal structure. Even if the titanium-containing compound does not contain tin oxide, by growing such nucleus particle crystals, the particles also become rutile crystal structures. Here, by making the titanium-containing compound free of tin oxide, the refractive index of the particles increases.

[0038] If the nucleus contains tin oxide, it will readily become rutile. The tin oxide content of the nucleus only needs to be the amount that makes the crystal structure of the nucleus rutile. If the crystal structure of the nucleus is not rutile, the particles will become mixed crystals or crystal structures other than rutile. The grain diameter of the nucleus only needs to be the size that it is dispersed in the solvent. If the solvent is water, the nucleus is easily dispersed.

[0039] The titanium-containing compound may include titanium oxides or hydroxides. After obtaining a gel by neutralizing the titanium-containing compound, a dispersion of the titanium-containing compound is obtained by degelating the gel. There are no particular limitations as long as the titanium-containing compound is water-soluble. Examples of titanium-containing compounds include titanium tetrachloride, titanium trichloride, titanium sulfate, titanium oxysulfate, and titanium hydride. The resulting gel contains titanium hydroxide. Salts in the gel can reduce the refractive index of the film or the dispersibility of the particles. Therefore, it is preferable to wash the gel with water. When the gel is degelatinated with hydrogen peroxide, the nuclei readily grow crystals in a rutile state. When hydrogen peroxide is added to the gel, if the gel is kept at a temperature of 50°C to 100°C, the gel readily degelats.

[0040] <Mixed Processes>

[0041] In this process, a mixture is prepared by mixing a dispersion of a titanium-containing compound and a dispersion of nuclei. By keeping the weight ratio of the titanium-containing compound to the nuclei (amount of titanium-containing compound / amount of nuclei) at 7 or less, it is difficult to form crystals other than rutile. Here, the weights of the solid components and nuclei are the weights after converting the amounts of Ti and Sn in the raw materials into TiO2 and SnO2, respectively. The titanium-containing compound is the solid component of the dispersion of the titanium-containing compound.

[0042] <Crystal Growth Process>

[0043] In this process, crystals are grown based on nuclei by raising the mixture to 80°C or higher. When the mixture temperature is below 80°C, the crystal growth rate is slow, resulting in smaller grain diameters. Furthermore, the reaction becomes incomplete under these conditions, leaving behind yellow titanium-containing compounds. When raising the mixture to 80°C or higher, hydrothermal synthesis (autoclave treatment) is preferable. The higher the hydrothermal synthesis temperature, the larger the grain diameter. Therefore, this temperature is preferably 100°C or higher, more preferably 130°C or higher. On the other hand, if the temperature is below 300°C, production efficiency is higher. This temperature is more preferably below 250°C. Additionally, the longer the hydrothermal synthesis time, the higher the density of the particles. Therefore, this time is preferably 1 hour or more, more preferably 5 hours or more, and more preferably 10 hours or more. On the other hand, if the time is below 50 hours, production efficiency is higher. This time is more preferably below 40 hours, and more preferably below 20 hours.

[0044] If crystal growth is repeated multiple times, the titanium oxide content of the particles increases. Furthermore, the grain diameter and particle size (particle size) increase. Additionally, the aspect ratio decreases. The preferred number of crystal growth cycles is 2 to 5. When the number of crystal growth cycles is 2 to 3, the haze of the particle film is low. Furthermore, in this case, the film refractive index is high. Compared to the case of 2 to 3 cycles, the particle refractive index is even higher when the number of crystal growth cycles is 4 to 5. On the other hand, compared to the case of 2 to 3 cycles, the film haze is even higher when the number of crystal growth cycles is 4 to 5. In the crystal growth after the second cycle, the crystal-grown particles are used as nuclei for the mixing and crystal growth processes.

[0045] Preferably, the particle surface is treated with silicon dioxide before being treated with a surface treatment agent. Specifically, silicon dioxide is added to an aqueous dispersion of the particles after crystal growth, and then the aqueous dispersion is subjected to hydrothermal synthesis. This results in a dense silicon dioxide layer forming on the particle surface. If the specific surface area of ​​silicon dioxide is 100 m² / g to 600 m² / g, it is less likely to produce microparticles and coarse particles. A more preferred specific surface area of ​​silicon dioxide is 200 m² / g to 550 m² / g, and even more preferably 300 m² / g to 550 m² / g. During hydrothermal synthesis, the lower the concentration of the solid component in the aqueous dispersion, the more densely a silicon dioxide layer will form on the particle surface. Therefore, during hydrothermal synthesis, the concentration of this solid component is preferably 5% by weight or less, more preferably 3% by weight or less, and even more preferably 1.5% by weight or less. In the case of hydrothermal synthesis, the higher the hydrothermal synthesis temperature, the more densely a silicon dioxide layer will form on the particle surface. Therefore, the temperature is preferably 100°C or higher, more preferably 150°C or higher. On the other hand, if the temperature is below 200°C, the production efficiency is higher. The temperature is more preferably below 180°C. In addition, the longer the hydrothermal synthesis time, the denser the silicon dioxide layer will form on the particle surface. Therefore, the time is preferably 1 hour or more, more preferably 15 hours or more. On the other hand, if the time is below 40 hours, the production efficiency is high. The time is more preferably below 20 hours.

[0046] Hereinafter, a method for manufacturing an organic solvent dispersion of particles will be described. A surface treatment agent is added to an aqueous dispersion of particles after crystal growth, and the particle surface is treated with the surface treatment agent. Afterward, the solvent of the dispersion is replaced from water with an organic solvent. The surface treatment agent preferably has alkoxy groups. Since the alkoxy-containing surface treatment agent can chemically bond with the particle surface, the particles become easily dispersed in the organic solvent.

[0047] After adding the surface treatment agent, the particles are rapidly treated by keeping the dispersion at or above 40°C for at least 1 hour. The holding time is preferably 20 hours or less.

[0048] By treating the particle surface in the aqueous dispersion with a first surface treatment agent, the particles become less likely to aggregate in the alcohol. After this treatment, an alcohol dispersion can be prepared by replacing the solvent with alcohol. By adding a second surface treatment agent to this alcohol dispersion, the particle surface can be treated with the second surface treatment agent. After this, the solvent (alcohol) of the alcohol dispersion is replaced with a hydrophobic solvent. If the solvent is replaced in this way, the particles are less likely to aggregate. If the amount of the second surface treatment agent added is 10 parts by mass or more relative to 100 parts by mass of particles, the particles become easier to disperse in the hydrophobic solvent. This amount added is more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more. On the other hand, in order to increase the particle concentration in the film, this amount added is preferably 50 parts by mass or less relative to 100 parts by mass of particles, and more preferably 40 parts by mass or less. In addition, when the particle surface is treated with the second surface treatment agent, the hydrolysis reaction of the second surface treatment agent is promoted by adding water or a catalyst.

[0049] A coating liquid is obtained by adding a binder to an organic solvent dispersion of particles. The organic solvent dispersion can be used as a coating liquid when a portion of the surface treatment agent acts as a binder.

[0050] A film-coated substrate is produced by forming a film on a substrate using the above-described coating liquid. Specifically, after applying the coating liquid to the substrate, the coating liquid is dried to form a film. Examples of coating methods include spin coating, bar coating, gravure coating, and slot coating. Drying refers to the evaporation and removal of the solvent. If the drying temperature is 60°C or higher, the drying time is shortened. In addition, the solvent becomes less likely to remain in the film. Therefore, a dense film can be obtained. On the other hand, if the temperature is 120°C or lower, the substrate is less likely to deform. This temperature is more preferably 100°C or lower, and even more preferably 80°C or lower. In addition, to improve production efficiency, it is preferable to cure the film after the coating liquid has dried.

[0051] Example

[0052] Example 1

[0053] The preparation method of the particles will be described in detail below. The preparation conditions of the particles are shown in Table 1.

[0054] [Particle Preparation]

[0055] <Preparation Process>

[0056] First, a dispersion of the titanium compound and a dispersion of the nuclear particles were prepared as follows. 523 g of an aqueous solution of titanium tetrachloride (7.66% by mass, converted to TiO2) and 523 g of ammonia (7.66% by mass) were mixed. A white slurry (gel) with a pH of 9.2 was thus prepared. The slurry was filtered. 400.5 g of a cake with a solid content of 10% by mass was obtained by washing the gel with pure water. The cake was diluted to 1.5% by mass with pure water to obtain a slurry again. 457.7 g of an aqueous solution of hydrogen peroxide (peracidified hydrogen water) with a concentration of 35% by mass was added to the slurry. The dispersion was heated at 80°C for 1 hour. 877 g of pure water was added to the dispersion to obtain a dispersion of the titanium compound (titanium oxide concentration of 1.0% by weight, converted to TiO2). The pH of this dispersion was 7.8, and the laser particle size was 37 nm. For laser particle size, the dispersion was diluted with water to 0.01% by weight and determined by electrophoretic light scattering using an ELSZ-2000S manufactured by Otsuka Electronics Co., Ltd. In the following examples and comparative examples, all laser particle sizes were measured at this concentration.

[0057] A cation exchange resin (manufactured by Mitsubishi Kemical) was added to 4005g of a dispersion containing a titanium compound. 495g of a potassium stannate aqueous solution diluted to 1% by weight with pure water was added to the dispersion. The ion exchange resin was separated from the dispersion. A dispersion of nuclear particles was obtained by hydrothermal synthesis of the dispersion at 165°C for 18 hours in an autoclave.

[0058] <Mixed Processes>

[0059] Then, a mixture was prepared by mixing 4500g of a dispersion of titanium-containing compound and 4500g of a dispersion of nuclear particles. The laser particle size of the mixture was 37nm.

[0060] <Crystal Growth Process>

[0061] Nuclear particle crystals were grown by hydrothermal synthesis of the mixture in an autoclave. The hydrothermal synthesis conditions were set at 165°C for 18 hours. The laser particle size of the dispersion after the first crystal growth was 37 nm.

[0062] In this embodiment, the nuclear particle crystal was grown twice. In the second crystal growth, the particle crystal was grown in the same manner as in the first crystal growth, except that the dispersion from the first crystal growth was used as the dispersion for the nuclear particles. The laser particle size of the dispersion after the second crystal growth was 43 nm. The laser particle size (dispersion particle size) of the particle dispersions of other embodiments and comparative examples are also shown in Table 3. The dispersion was concentrated using an ultrafiltration membrane device to obtain 2250 g of an aqueous dispersion of particles (solid component concentration of 4% by mass).

[0063] [Preparation of organic solvent dispersion of particles]

[0064] The preparation of the organic solvent dispersion of the particles will be described in detail below. The preparation conditions of the dispersion are shown in Table 2.

[0065] First, an alcohol dispersion of the particles was prepared as follows. 2250 g of methanol and 56.3 g of tetraethyl orthosilicate (containing 28.8% by mass of silicon as SiO2) as the first surface treatment agent were added to 2250 g of an aqueous dispersion of the particles. The dispersion was heated and stirred at 50°C for 18 hours to obtain an aqueous / methanol dispersion of the particles. After cooling the dispersion to room temperature, the solvent in the dispersion was replaced with methanol using an ultrafiltration membrane. The dispersion was concentrated to obtain 531 g of an alcohol dispersion of the particles (solid content concentration of 20% by mass). The water content in this dispersion was 0.3% by mass.

[0066] 10.6 g of ammonia water (5% by mass) was added to 531 g of the alcohol dispersion of the particles. Additionally, 31.9 g of 3-methylacryloxypropyltrimethoxysilane (KBM-503 manufactured by Shin-Etsu Chemical Industry Co., Ltd., containing 24.2% by mass of silicon as SiO2) was added as a second surface treatment agent. The dispersion was heated and stirred at 50°C for 18 hours. The dispersion was then cooled to room temperature. The solvent of the dispersion was replaced with propylene glycol monomethyl ether acetate (PGMEA), which has a higher hydrophobicity than alcohol, using a rotary evaporator. Thus, 570 g of an organic solvent dispersion of the particles (solid content concentration 20% by mass) was obtained.

[0067] [Preparation of coating solution]

[0068] Hereinafter, the preparation method of the coating liquid will be described. The preparation conditions of the coating liquids of other examples and comparative examples are also shown in Table 2. 100.0 g of an organic solvent dispersion of the particles was added and mixed, 6.0 g of ADDA (manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a binder, and 0.4 g of Omnirad TPO-H as a photopolymerization initiator.

[0069] The physical properties of the particles were determined by the following method. Results of other embodiments and comparative examples are also shown in Table 3.

[0070] (1) Particle composition

[0071] The aqueous dispersion of the particles was diluted to a solid content concentration of 1%. Powder of the particles was obtained by drying 100g of the aqueous dispersion at 100°C for 10 minutes. The powder was then ashed using a burner. The powder was melted by adding sodium peroxide and sodium hydroxide. Furthermore, the powder was dissolved by adding sulfuric acid and hydrochloric acid. The Sn, Ti, and Si contents of the solution were determined using ICP-OES (SPS5520 manufactured by SII Corporation or ICPS-8100 manufactured by Shimadzu Corporation). These contents were then converted into SnO2, TiO2, and SiO2 contents of the particles, respectively.

[0072] (2)Crystal structure / grain diameter

[0073] The aqueous dispersion of the particles was diluted to a solids concentration of 1%. A sample for analysis was prepared by drying 200g of this aqueous dispersion at 110°C for 20 hours (48 hours at 60°C for Example 7 only). X-ray structural analysis of the sample was performed using a RINT 1400 (registered trademark) manufactured by Rigaku Co., Ltd. The diffraction peak pattern was analyzed using PDXL to confirm that the particle crystal structure was rutile. The grain diameter of the particles was calculated from the half-width at half-maximum (FWHM) of the diffraction peak using the Scherrer equation (D = K × λ / (β × cosθ)). The Miller index (110) for rutile was chosen as the diffraction peak. D is the grain size (nm), K is the Scherrer constant, λ is the wavelength of the X-ray (nm), β is the diffraction width (rad), and θ is the Bragg angle (rad).

[0074] (3) Average of minor diameter / aspect ratio

[0075] The aqueous dispersion of the particles was diluted to a solids concentration of 0.002%. One drop of the diluted dispersion was added to a collodion film. It was dried at 50°C for 10 minutes. The particles were photographed using a Hitachi High-Tech Noroge S-5500 scanning electron microscope (SEM). 100 particles were randomly selected from the images projected onto the SEM film, and their minor and major axes were measured. The average of the minor axes and the average of the major axes were calculated. The ratio of the average minor axis to the average major axis (average minor axis / average major axis) was taken as the aspect ratio.

[0076] (4) Whether tin was detected on the particle surface

[0077] For cases where tin oxide is not detectable on the particle surface but the core contains tin oxide, X-ray photoelectron spectroscopy (XPS) can be used for determination. However, since it is difficult to perform the determination using only particles, a film is prepared as the test sample as follows. First, a dispersion (coating solution) is prepared by adding 1.1 g of diphenyl(2,4,6-trimethylbenzyl)-phenylphosphine oxide (IGMResins B.V., manufactured by Omnirad (registered trademark) TPO-H) as a photopolymerization initiator to 300 g of an organic solvent dispersion of particles. This dispersion is coated onto a silicon wafer substrate and dried at 80°C for 2 minutes. The dried coating solution is irradiated with ultraviolet light at 3000 mJ / cm2 using a high-pressure mercury lamp (GS Yuasa Co., Ltd., manufactured by EYEUVMETER) to prepare a sample (film) for XPS determination. The following XPS determination confirms that tin oxide is not detectable on the particle surface.

[0078] Due to the presence of a surface treatment agent on the outermost surface of the film, titanium may not be detected. Therefore, the proportion of tin on the particle surface is determined by etching to a depth at which titanium is detected. For example, in this embodiment, etching is performed to a depth of 1.2 nm to detect titanium. At this depth, Ar etching is performed for 20 seconds. That is, Ar etching is performed at a rate of 0.06 nm / second. Detection of titanium is defined as a titanium proportion of 1.0 at% or higher. This proportion is the number of titanium atoms relative to the total number of atoms of carbon, oxygen, titanium, and tin. Since the detection limit of XPS is generally 0.1 at%, tin is not present on the particle surface below this value. Therefore, when the proportion of tin at the depth at which titanium is detected is less than 0.1 at% (i.e., tin is not detected), it is considered that tin oxide is not present on the particle surface. In this embodiment, since this proportion is less than 0.1 at%, tin is not detected from the particle surface. In the case where tin is present in the core, tin is detected by further etching (the proportion of tin is 0.1 at% or higher).

[0079] The X-ray photoelectron spectroscopy analysis apparatus used was an ESCALAB220Xi manufactured by Surface Geometry Co., Ltd. Spectroscopic measurements were performed under the following conditions: X-ray 190W, pass energy 100eV and narrow 20eV, analytical diameter 250×1000μm, and charge neutralizer on. An Ar Gass Cluster Ion was used for the measurements, with an accelerating voltage of 3kV and an etching rate of 3.5nm / min (silicon oxide film). Calibration of the 1s (CH) binding energy was performed at 284.8eV. The energy intensity of the C1s peak was observed between 284eV and 286eV. O1s was observed at 532eV~534eV, Ti2p at 454eV~467eV, and Sn3d5 at 483eV~490eV.

[0080] (5) Particle refractive index Np'

[0081] The particle refractive index Np' was determined by the following method. The refractive index Np' was also determined in the following examples and comparative examples.

[0082] First, three coating solutions (a) to (c) were prepared and then coated onto a silicon wafer (manufactured by Matsuzaki Manufacturing Co., Ltd.: 6-inch debugging wafer (P-type), thickness: 625 μm) by spin coating. The coating solution was dried at 80°C for 2 minutes. The dried coating solution was irradiated with ultraviolet light at 3000 mJ / cm2 using an EYEUVMETER to fabricate a film-coated substrate (silicon wafer). The refractive index Nav' of these film-coated substrates (silicon wafers) was measured using a spectroellipsometer (manufactured by Semilabo Co., Ltd., Japan: SE-2000).

[0083] Three levels of coating solution (a) to coating solution (c) were prepared as follows.

[0084] (a) Preparation of coating solution with a weight ratio of [particles:ADDA=6:4]

[0085] A 60.0 g organic solvent dispersion of particles with a mixed solid component concentration of 20% by mass, 8.0 g ADDA and 0.5 g Omnirad TPO-H were prepared. A coating solution (a) was prepared by adding 60.0 g PGMEA to the dispersion.

[0086] (b) Preparation of coating solution with a weight ratio of [particles:ADDA=7:3]

[0087] 70.0 g of an organic solvent dispersion of particles with a mixed solid component concentration of 20% by mass, 6.0 g of ADDA, and 0.4 g of Omnirad TPO-H were prepared. Coating solution (b) was prepared by adding 70.0 g of PGMEA to it.

[0088] (c) Preparation of coating solution with a weight ratio of [particles:ADDA=8:2]

[0089] An organic solvent dispersion of particles with a mixed solid component concentration of 20% by mass, 80.0 g of ADDA, 4.0 g of Omnirad TPO-H, and 0.3 g of PGMEA were prepared. A coating solution (c) was prepared by adding 80.0 g of PGMEA to the dispersion.

[0090] Then, the film refractive index Nav (calculated value) is calculated using Equation 1 (conversion formula for volume fraction / weight fraction) and Equation 2 (Maxwell-Garnett formula).

[0091] [Equation 1]

[0092] In Equation 1, f(m) is the volume fraction of particles relative to the total solid composition. m is the weight fraction of particles relative to the total solid composition, dm is the specific gravity of the binder (here, the specific gravity of ADDA is 1.1 g / ml), and dp is the specific gravity of the particles. Here, the specific gravity dp is the sum of the products of the content of each component contained in the particles and their specific gravity. The specific gravity dp of the components TiO2, SiO2, and SnO2 contained in these particles are 4.3 g / ml (only Comparative Example 4 is anatase type, so it is 3.8 g / ml), 2.2 g / ml, and 7.0 g / ml, respectively. The content of each component is the value obtained by dividing the content (mass%) obtained from the composition of the particles in (1) by 100.

[0093] [Equation 2]

[0094] In Equation 2, Nav is the film refractive index, Nm is the adhesive refractive index (here, the refractive index of ADDA is 1.7), and Np is the particle refractive index.

[0095] Substitute the particle weight fraction m, adhesive specific gravity dm, and particle specific gravity dp in coating solutions (a) to (c) into Equation 1. Since the weight fraction m is for three levels (a) to (c), f(m) for the three levels has already been obtained. Substitute the values ​​in increments of 0.01 into the particle refractive index Np in Equation 2 within the range of 1.70 to 2.70 to calculate the film refractive index Nav. Calculate the film refractive indices Nav for the three levels of f(m). Calculate the deviation σ(Nav-Nav') between these film refractive indices Nav (calculated values) and film refractive index Nav' (measured values). Calculate the squared deviation σ2 and the sum of squared deviations Σσ2 from these deviations. Set the particle refractive index Np with the minimum sum of squared deviations Σσ2 as the particle refractive index Np'. That is, determine the particle refractive index Np' using the least squares method. The particle refractive index Np' determined by this method includes factors such as the particle's affinity for the binder in the film, particle size, particle shape, and the properties of the particle surface (amount of surface treatment agent or composition / structure of the particle surface, etc.).

[0096] [Fabrication of film-coated substrates]

[0097] Films were formed on a glass substrate and a silicon wafer respectively using a coating solution to produce a film-coated substrate (glass substrate) and a film-coated substrate (silicon wafer). The total light transmittance and haze of the film-coated substrate (glass substrate) were measured using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd.: NDH-5000). In addition, the refractive index and film thickness of the film-coated substrate (silicon wafer) were evaluated using a spectroscopic ellipsometry (manufactured by Nippon Semilabo Co., Ltd.: SE-2000). The measurement / evaluation results of other examples and comparative examples are also shown in Table 3.

[0098] (Fabrication of film-coated substrate (glass substrate))

[0099] The coating liquid was applied to a glass substrate (manufactured by Hama Shinsha: FL glass (glass), thickness: 3 mm, refractive index: 1.51) by spin coating. After drying at 80°C for 2 minutes, the film was irradiated with ultraviolet light at 3000 mJ / cm² using a high-pressure mercury lamp (manufactured by GS Yuasa Co., Ltd.: EYEUVMETER) to produce a film-coated substrate (glass substrate). Furthermore, the uncoated glass substrate had a total light transmittance of 99.0% and a haze of 0.1%.

[0100] (Fabrication of film-coated substrate (silicon wafer))

[0101] The coating solution was applied to a silicon wafer (manufactured by Matsuzaki Seisakusho: 6-inch test wafer (P-type), thickness: 625 μm) by spin coating. After drying at 80°C for 2 minutes, the film was irradiated with ultraviolet light at 3000 mJ / cm2 using an EYEUVMETER to produce a film-coated substrate (silicon wafer).

[0102] [Example 2]

[0103] The dispersion after the first crystal growth in Example 1 was concentrated using an ultrafiltration membrane device to obtain 2250 g of an aqueous dispersion of particles (solid content concentration of 4% by mass). In the preparation of the organic solvent dispersion of particles, except that 2250 g of methanol and 75 g of tetraethyl orthosilicate were added to the 2250 g of the aqueous dispersion of particles, an alcohol dispersion of particles (solid content concentration of 20% by mass) was obtained in the same manner as in Example 1. 11.2 g of ammonia water (5% by mass) was added to the alcohol dispersion. In addition, 33.5 g of KBM-503 as a second surface treatment agent was added to the alcohol dispersion. After adding KBM-503, an organic solvent dispersion of particles (solid content concentration of 20% by mass) was obtained in the same manner as in Example 1. In the preparation of the coating solution, except that the organic solvent dispersion was used, the coating solution was prepared in the same manner as in Example 1.

[0104] [Example 3]

[0105] In the crystal growth process, the crystal was grown in the same manner as in Example 1, except that the number of crystal growths was set to 5. In the (n+1)th crystal growth, the dispersion after the nth crystal growth was used as the dispersion of the nuclei. Otherwise, the crystal growth was performed in the same manner as the first time (however, n was 1 to 4). The dispersion after the 5th crystal growth was concentrated by using an ultrafiltration membrane device to obtain 2250 g of an aqueous dispersion of particles (solid content concentration of 4% by mass). In the preparation of the organic solvent dispersion of particles, except that 2250 g of methanol and 37.5 g of tetraethyl orthosilicate were added to the 2250 g of the aqueous dispersion of particles, an alcohol dispersion of particles (solid content concentration of 20% by mass) was obtained in the same manner as in Example 1. 10.1 g of ammonia water (5% by mass) was added to the alcohol dispersion. In addition, 30.2 g of KBM-503 as a second surface treatment agent was added to the alcohol dispersion. After adding KBM-503, an organic solvent dispersion of the particles (solid content concentration 20% by mass) was obtained in the same manner as in Example 1. In the preparation of the coating solution, the coating solution was prepared in the same manner as in Example 1, except that the organic solvent dispersion was used.

[0106] [Example 4]

[0107] In the mixing process, except that the amount of the titanium compound dispersion was changed to 7716 g and the amount of the nuclear particle dispersion was changed to 1286 g, the nuclear particle crystals were grown in the same manner as in Example 1. The number of crystal growth cycles was set to 1. The dispersion was concentrated using an ultrafiltration membrane device to obtain 2250 g of an aqueous dispersion of particles (solid content concentration of 4% by mass). In the preparation of the organic solvent dispersion of particles, except that the aqueous dispersion was used, the coating solution was prepared in the same manner as in Example 1.

[0108] [Example 5]

[0109] In the preparation of the organic solvent dispersion of the particles, the amount of ethyl orthosilicate added was set to 43.8 g, the amount of ammonia added was set to 10.3 g, and the amount of KBM-503 added was set to 30.8 g. Otherwise, the coating solution was prepared in the same manner as in Example 1.

[0110] [Example 6]

[0111] The aqueous dispersion of the particles from Example 1 was diluted to a solid content concentration of 1% by mass. 36g of silica sol (manufactured by Nichih Chemical Co., Ltd.: Catalog (registered trademark) SN-350, with a specific surface area of ​​375 m² / g and containing 15% by mass of silica) was added to 9000g of this aqueous dispersion. The dispersion was hydrothermally synthesized at 165°C for 18 hours using an autoclave. The dispersion was cooled to room temperature. The dispersion was concentrated using an ultrafiltration membrane device to obtain 2385g of an aqueous dispersion of the particles (solid content concentration of 4% by mass). That is, the particles were surface-treated with silica. In the preparation of the organic solvent dispersion of the particles, except that 2250g of methanol and 19.9g of ethyl orthosilicate were added to 2250g of the aqueous dispersion of the particles, an alcoholic dispersion of the particles (solid content concentration of 20% by mass) was obtained in the same manner as in Example 1. 10.1 g of ammonia (5% by mass) was added to the alcohol dispersion. Additionally, 30.1 g of KBM-503 as a second surface treatment agent was added to the alcohol dispersion. After adding KBM-503, an organic solvent dispersion of the particles (solids concentration 20% by mass) was obtained in the same manner as in Example 1. In the preparation of the coating solution, the coating solution was prepared in the same manner as in Example 1, except that the organic solvent dispersion was used. Furthermore, the XPS test sample was prepared using particles before surface treatment with silicon dioxide. That is, the same XPS test sample as in Example 1 was used.

[0112] The isoelectric point of the aqueous dispersion of the particles obtained in this embodiment was determined as follows. Using a zeta potential meter (manufactured by Malvern, "ZETASIZER Nano-ZS"), the zeta potential was measured at each pH level while adjusting the pH at intervals within 1. The pH at which the zeta potential ±0 mV is drawn along a straight line was defined as the isoelectric point. At this time, the concentration of the measured particles was set to 0.25% by mass, and diluted with pure water. Furthermore, pH adjustment was performed using an automatic titration device (manufactured by Malvern, "MPT-2"). A 0.1 M sodium hydroxide aqueous solution was used to increase the pH, and a 0.1 M hydrochloric acid solution was used to decrease the pH. The isoelectric point was 2.3.

[0113] [Example 7]

[0114] In the crystal growth process, instead of hydrothermal synthesis, the nucleus crystals were grown by reflux and heating with stirring at 90°C for 40 hours. Otherwise, the coating solution was prepared in the same manner as in Example 1.

[0115] [Comparative Example 1]

[0116] The dispersion of the nuclear particles from Example 1 was concentrated using an ultrafiltration membrane device to obtain 1125 g of an aqueous dispersion of the particles (solid content concentration of 4% by mass). 1125 g of methanol and 28.2 g of tetraethyl orthosilicate (manufactured by Tama Chemical Co., Ltd., containing 28.8% by mass of silicon as SiO2) were added to this aqueous dispersion. When the aqueous dispersion was heated to 50°C, the viscosity of the dispersion increased, and the dispersion became turbid.

[0117] [Comparative Example 2]

[0118] The mixture from Example 1 was stirred at 60°C for 40 hours to obtain an aqueous dispersion of the particles. The aqueous dispersion was pale yellow. The particles in the aqueous dispersion were a mixture of rutile and anatase crystals.

[0119] [Comparative Example 3]

[0120] 2250 g of an aqueous solution of titanium tetrachloride (equivalent to 2 wt% TiO2) and 880 g of ammonia (equivalent to 15 wt%) were mixed. A white slurry (gel) with pH 8.6 was thus prepared. After filtering the slurry, the gel was washed with pure water. 900 g of a cake with a solid content concentration of 5 wt% was thus obtained. 514 g of an aqueous solution of hydrogen peroxide (equivalent to 35 wt%) and 2100 g of pure water were added to the 900 g of cake. It was heated at 80°C for 1 hour. In addition, 986 g of pure water was added to it. 48.8 g of Catalog SN-350 and 683.8 g of pure water were added to 4500 g of this dispersion. The dispersion was hydrothermally synthesized in an autoclave at 165°C for 18 hours to obtain a dispersion of 5232.6 g of nuclear particles. 4500 g of the dispersion of the titanium-containing compound of Example 1 was added to this 4500 g of dispersion. The dispersion was hydrothermally synthesized in an autoclave at 165°C for 18 hours. The resulting dispersion had a laser particle size of 400 nm and was turbid.

[0121] [Comparative Example 4]

[0122] The dispersion of the nuclear particles obtained in Comparative Example 3 was concentrated using an ultrafiltration membrane device to obtain an aqueous dispersion of the particles (solid content concentration of 10% by weight). Dealkalization was performed by adding a cation exchange resin to the aqueous dispersion. The ion exchange resin was separated from the aqueous dispersion. In the preparation of the organic solvent dispersion of the particles, except that 2250g of methanol and 65.5g of ethyl orthosilicate were added to 2250g of the aqueous dispersion, an alcohol dispersion of the particles (solid content concentration of 20% by weight) was obtained in the same manner as in Example 1. 12.4g of ammonia water (5% by weight) was added to the alcohol dispersion. Furthermore, 77.3g of KBM-503 as a second surface treatment agent was added to the alcohol dispersion. After adding KBM-503, an organic solvent dispersion of the particles (solid content concentration of 20% by weight) was obtained in the same manner as in Example 1. In the preparation of the coating solution, except that the organic solvent dispersion was used, the coating solution was prepared in the same manner as in Example 1.

[0123] [Comparative Example 5]

[0124] 2000g of an aqueous solution of titanium tetrachloride (equivalent to 7.5% by weight of TiO2) and 2000g of ammonia (equivalent to 7.5% by weight) were mixed. A white slurry (gel) with pH 9.2 was thus prepared. After filtering the slurry, the gel was washed with pure water. 1500g of a cake with a solid content of 10% by weight was thus obtained. The 1500g of cake was diluted to 1.5% by weight with pure water. 1714g of an aqueous solution of hydrogen peroxide (equivalent to 35% by weight) was added to it. It was heated at 80°C for 1 hour. A dispersion of titanium-containing compounds was obtained by adding 3286g of pure water. The pH of this aqueous solution was 7.8. The dispersion was de-alkali-treated by adding cation exchange resin to 15000g of the dispersion. 1901g of an aqueous solution of potassium stannate (equivalent to 1% by weight) was added to the dispersion. The ion exchange resin was separated from the dispersion. 634g of Catalog SN-350 and 3591g of pure water were added to the dispersion. The dispersion was hydrothermally synthesized at 165°C for 18 hours using an autoclave. The dispersion was concentrated using an ultrafiltration membrane device. Dealkalization was performed by adding cation exchange resin to 2641 g of the dispersion. An aqueous dispersion of particles was prepared by separating the ion exchange resin from the dispersion. The laser particle size of this aqueous dispersion was 15 nm. In the preparation of the organic solvent dispersion of the particles, except that 2250 g of methanol and 165.1 g of ethyl orthosilicate were added to 2250 g of the aqueous dispersion, an alcohol dispersion of the particles (solids concentration 20% by mass) was obtained in the same manner as in Example 1. 31.2 g of ammonia water (5% by mass) was added to the alcohol dispersion. Furthermore, 93.9 g of KBM-503 as a second surface treatment agent was added to the alcohol dispersion. After adding KBM-503, an organic solvent dispersion of the particles (solids concentration 20% by mass) was obtained in the same manner as in Example 1. In the preparation of the coating solution, the coating solution was prepared in the same manner as in Example 1, except that the organic solvent dispersion was used.

[0125] [Table 1] Particle preparation conditions nuclear particles Crystal structure Composition of nuclear particles weight ratio ※ (Titanium-containing compounds / nuclear particles) Crystal growth Temperature (°C) Crystal growth frequency TiO2 content (quality%) SnO2 content (quality%) SiO2 content (quality%) Example 1 Rutile 89 11 0 1 165 2 Example 2 Rutile 89 11 0 1 165 1 Example 3 Rutile 89 11 0 1 165 5 Example 4 Rutile 89 11 0 6 165 1 Example 5 Rutile 89 11 0 1 165 2 Example 6 Rutile 89 11 0 1 165 2 Example 7 Rutile 89 11 0 1 90 2 Comparative Example 1 Rutile - - - - - 0 Comparative Example 2 Rutile 89 11 0 1 60 1 Comparative Example 3 Anatase 86 0 14 1 165 1 Comparative Example 4 Anatase - - - - - 0 Comparative Example 5 Rutile - - - - - 0 ※ Weight ratio per crystal growth cycle

[0126] [Table 2] Preparation conditions of organic solvent dispersions Coating solution preparation conditions Silicon dioxide First surface treatment agent Second surface treatment agent Adhesive SN-350 TEOS KBM-503 ADDA Amount added [parts by mass (relative to 100 parts by mass of particles)] Example 1 — 62.5 35.5 38.0 Example 2 — 83.3 37.1 39.9 Example 3 — 41.7 33.5 36.0 Example 4 — 62.5 35.5 38.0 Example 5 — 48.6 34.3 36.7 Example 6 6 22.2 33.5 36.2 Example 7 — 62.5 35.5 38.0 Comparative Example 1 — 62.5 — — Comparative Example 2 — — — — Comparative Example 3 — — — — Comparative Example 4 — 62.5 35.5 38.0 Comparative Example 5 — 62.5 35.5 38.0 SN-350: Catalog SN-350 (silicone sol) manufactured by Nichii Catalyst Chemical Co., Ltd. TEOS: Ethyl silicate manufactured by Tama Chemical Co., Ltd. KBM-503: KBM-503 (3-methylpropenyloxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Industry Co., Ltd. ADDA: Daiyapulest ADDA manufactured by Mitsubishi Gas Chemical Co., Ltd.

[0127] [Table 3] Particle properties Evaluation results of film-coated substrates crystal structure Grain diameter (nm) composition Was tin detected (on the particle surface)? Compare: Average short diameter / grain diameter Aspect Ratio Dispersed particle size (nm) Refractive index Haze (%) Total light transmittance (%) Refractive index @ 550nm Thickness (nm) TiO2 content (mass%) SnO2 content (mass%) SiO2 content (mass%) Example 1 Rutile 13 97 3 0 none 1.4 1.7 43 2.2 0.4 89.2 1.90 220 Example 2 Rutile 9 94 6 0 none 1.7 2.0 37 2.1 0.4 87.5 1.86 230 Example 3 Rutile twenty three 99.7 0.3 0 none 1.3 1.2 70 2.3 0.9 83.4 1.95 238 Example 4 Rutile 12 98 2 0 none 1.4 1.9 42 2.2 0.5 88.2 1.89 222 Example 5 Rutile 13 97 3 0 none 1.4 1.7 43 2.2 0.8 84.7 1.93 222 Example 6 Rutile 13 97 3 0 none 1.4 1.7 43 2.3 0.5 88.5 1.95 240 Example 7 Rutile 9 97 3 0 none 1.4 2.0 37 2.2 0.4 89.0 1.89 220 Comparative Example 1 Rutile 6 89 11 0 have - - - - — — — — Comparative Example 2 mixed crystal - - - - - - - - - — — — — Comparative Example 3 Anatase - - - - - - - - - — — — — Comparative Example 4 Anatase 6 86 0 14 - 1.7 1.4 14 2.0 0.4 86.8 1.79 220 Comparative Example 5 Rutile 6 71 9 20 have 1.5 2.2 15 1.9 0.4 86.3 1.74 222 [Simplified Explanation of the Diagram]

[0011] None.

Claims

1. A particle having a rutile crystal structure, wherein, The particles contain a core of tin and titanium and a shell of titanium oxide, with a grain diameter of 7 nm or more. The particles contain more than 90% by weight of titanium oxide (equivalent to TiO2) and 0.2% to 10% by weight of tin oxide (equivalent to SnO2). The ratio of tin atoms in the core to the total number of titanium and tin atoms is 0.1 to 6.5 at. Tin is not detectable when the surface of the shell is measured by XPS.

2. A dispersion, said dispersion being a particle dispersion containing particles as described in claim 1 and a solvent, wherein, The average particle size is below 100 nm.

3. The dispersion as described in claim 2, wherein, The solvent is water, and the particles contain at least 2 parts by mass of silicon dioxide (equivalent to SiO2) per 100 parts by mass of the particles, and the isoelectric point of the dispersion is 3 or less.

4. A method for manufacturing particles, characterized in that the manufacturing method comprises: a step of preparing a dispersion of a titanium-containing compound; a step of preparing a dispersion of nuclei having a rutile crystal structure; a mixing step of preparing a mixed solution by mixing the dispersion of the titanium-containing compound and the dispersion of the nuclei; and a crystal growth step of preparing particles by growing crystals based on the nuclei by raising the mixed solution to 80°C or higher, wherein the nuclei contain titanium oxide and tin oxide, and in the mixing step, the dispersion of the titanium-containing compound and the dispersion of the nuclei are mixed until the particles contain at least 94% by weight of titanium oxide (equivalent to TiO2) and 0.2-6% by weight of tin oxide (equivalent to SnO2).

5. A method for manufacturing particles as described in claim 4, wherein, The manufacturing method comprises, in sequence, a step of adding silicon dioxide to a dispersion after the crystal growth step; and a step of hydrothermal synthesis of the dispersion after adding the silicon dioxide.

6. A coating liquid, characterized in that it contains particles as described in claim 1.

7. A method for manufacturing a film-coated substrate, characterized in that a film is formed on the substrate using a coating liquid as described in claim 6.