Particles having a rutile crystal structure, a method for producing the same, and a dispersion liquid, a coating liquid, and a method for producing a film substrate

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 wt% titanium oxide (equivalent to TiO2) and 0.2 wt% to 10 wt% 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 with a rutile crystal structure and methods for manufacturing them. Background Technology

[0002] Traditionally, coating solutions containing oxide particles with high refractive index are used to form high refractive index films on substrates. Such films are used in applications such as eyeglasses, lenses, and touch panels for smartphones.

[0003] To form a film with a high refractive index, it is preferable to have particles with 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] The technical problem that the invention aims to solve

[0006] In patent documents 1 and 2, due to the use of rutile composite particles containing titanium dioxide and silicon dioxide, the titanium dioxide content of the particles is reduced. Therefore, the refractive index of the film is reduced.

[0007] 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.

[0008] Technical means to solve technical problems

[0009] Therefore, this 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.

[0010] In addition, it is preferable that tin is not detectable from the particle surface.

[0011] In addition, the particle size when the particles are dispersed in the solvent is preferably less than 100 nm.

[0012] 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 the core particle crystals by raising the mixed solution to 80°C or higher. The core particles contain titanium oxide and tin oxide. Detailed Implementation

[0013] This invention relates to particles (hereinafter referred to as particles) having a rutile crystal structure 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 solvents. In particular, even with a particle concentration of 20% by weight or more, such particles are easily and stably dispersed in water. Therefore, they are easy to handle industrially.

[0014] The larger the grain diameter of the particles, the smaller their specific surface area. Therefore, the particles become easier to disperse in the solvent. Furthermore, the larger the grain diameter, the smaller the specific surface area, and thus the higher the particle density. Consequently, 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.

[0015] 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.

[0016] Furthermore, if tin is not detectable on 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 overall titanium oxide content of the particle tends to be high. On the other hand, if the central side of the particle (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.

[0017] Furthermore, if the ratio of the average minor diameter of the particles to the grain diameter (average 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 increases. 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.

[0018] 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. Additionally, the smaller the aspect ratio, the smaller the specific surface area of ​​the particles. 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 minor axis to the average major axis of the particles.

[0019] When 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's transparency increases. Furthermore, the particles become less prone to settling. A dispersion particle size of 80 nm or less is more preferable. 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, a grain diameter of 7 nm or more and a dispersion particle size of 20 nm or more are preferred.

[0020] The refractive index of the particles varies depending on factors such as particle composition, density, crystal structure, and grain diameter. Preferably, the refractive index is 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.

[0021] The particle dispersion will now 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, 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 disperse 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 included. Examples of surface treatment agents include silicon compounds, titanium compounds, zirconium compounds, and aluminum compounds. Silicon compounds are particularly easy to process industrially.

[0022] 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 also promoted.

[0023] 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. Therefore, the alkyl group is preferably methyl or ethyl.

[0024] As a surface treatment agent, the general formula (RO) can be cited as an example. n M(X) 4-n The molecule is a molecule. n is an integer from 1 to 4. M represents any one of Si, Ti, or Zr. If M is Si, it is easy to handle industrially. If there is only one M in the molecule, it is easy to handle 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, the reaction rate of the molecule is easy to control by making R Me or Et. Therefore, it is easy to handle industrially.

[0025] 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.

[0026] For 100 parts by mass of particles, if the dispersion contains 20 to 85 parts by mass [equivalent to 3 to 30 parts by mass in oxide form (or SiO2 if the surface treatment agent is a silicon compound)] of a first surface treatment agent, the particles are easily dispersed in the alcohol. Furthermore, the larger the particle grain diameter, the less surface treatment agent is required.

[0027] If particles are treated with a surface treatment agent containing 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.

[0028] 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.

[0029] If the particle surface is treated with a first surface treatment agent and a second surface treatment agent, the particles become easier to disperse in hydrophobic solvents or UV-curable adhesives.

[0030] Furthermore, if a surface treatment agent with 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 its 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.

[0031] When the solvent is water, treating the particle surface with silica creates a denser layer on the particle surface than when using a surface treatment agent. Even with a small amount of surface treatment agent, these particles are easily dispersed in organic solvents (especially alcohols). That is, with such particles, it is easy to displace the solvent of the dispersion from water to an organic solvent. The isoelectric point of the aqueous dispersion of these particles is 3 or less (however, this is the isoelectric point at a solid content concentration of 0.5% by mass). On the other hand, without silica treatment, 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 silica or a surface treatment agent, it is possible to observe crystal structures other than rutile.

[0032] When the solvent is water, it is preferable to treat the particle surface with silica, 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 silica 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 with a small amount of surface treatment agent, such particles are easily dispersed in organic solvents (especially alcohols). The silica content is more preferably 4 or more parts by mass. On the other hand, if the silica content is too high, the refractive index of the particles becomes low. Therefore, the silica content is preferably 20 or less parts by mass relative to 100 parts by mass of the particles. When treating the particle surface with silica, which is 2 or more parts by mass relative to 100 parts by mass of the particles, it is preferable to treat the particle surface with a first surface treatment agent, which is 10 to 30 parts by mass relative to 100 parts by mass of the particles [equivalent to 3 to 10 parts by mass of oxide (or SiO2 if the surface treatment agent is a silicon compound)].

[0033] The coating solution is described below. The coating solution contains particles, a surface treatment agent, a binder, and an organic solvent. By forming a film using a coating solution containing the aforementioned particles, the film's refractive index increases. If a coating solution 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. Monomers or oligomers are preferred. When curing the film, the film becomes denser more easily when using a coating solution containing monomers or oligomers compared to a coating solution containing a polymer. Since the adamantane backbone has a high refractive index, using an adamantane derivative as a monomer or oligomer results in a higher film refractive index. The organic solvent can be appropriately selected based on the type of binder added during the preparation of the coating solution.

[0034] A higher concentration of solids in the coating solution facilitates the formation of 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.

[0035] If the boiling point of the organic solvent is 80°C or higher, the coating solution can be dried slowly, resulting in a denser film. A boiling point of 100°C or higher is more preferable. On the other hand, if the boiling point is 200°C or lower, the organic solvent is less likely to remain, making the film more prone to shrinkage. Therefore, the film's hardness increases. A boiling point of 180°C or lower is more preferable.

[0036] The manufacturing method of the particles is described below. First, a dispersion of a titanium-containing compound and a dispersion of core particles (hereinafter referred to as core particles) with a rutile crystal structure are prepared <Preparation Step>. Next, the dispersion of the titanium-containing compound and the dispersion of the core particles are mixed to prepare a mixture <Mixture Step>. By raising the mixture to 80°C or higher, crystals are grown based on the core particles <Crystal Growth Step>. By growing crystals based on the core particles, the tin oxide content of the particles decreases. Therefore, the titanium oxide content of the particles increases relatively. Furthermore, the grain diameter increases. After the crystal growth step, the core particles become the core of the particles, and the titanium-containing compound becomes the shell of the particles. Each step is described in detail below.

[0037] <Preparation Process>

[0038] The nucleus particles used 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 removing tin oxide from the titanium-containing compound, the refractive index of the particles increases.

[0039] If the nuclei contain tin oxide, they readily form a rutile crystal structure. The tin oxide content of the nuclei is simply the amount that makes the crystal structure of the nuclei rutile. If the crystal structure of the nuclei is not rutile, the particles will become mixed crystals or crystals other than rutile. The grain diameter of the nuclei is simply the size that allows them to disperse in the solvent. If the solvent is water, the nuclei are easily dispersed.

[0040] Titanium-containing compounds can include titanium oxides or hydroxides. After obtaining a gel by neutralizing the titanium compound, a dispersion of the titanium compound is obtained by degelating the gel. There are no particular limitations on the titanium compound as long as it is water-soluble. Specific examples of titanium 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 film's refractive index or the dispersibility of particles. Therefore, washing the gel with water is preferable. When the gel is degelatinated with hydrogen peroxide, the nuclei readily grow crystals in a rutile state. Adding hydrogen peroxide to the gel and maintaining it at 50°C to 100°C facilitates gel degelatination.

[0041] <Mixed Processes>

[0042] In this process, a mixture is prepared by mixing a dispersion of a titanium-containing compound and a dispersion of nuclear particles. By maintaining a weight ratio of the titanium-containing compound to the nuclear particles (amount of titanium-containing compound / amount of nuclear particles) of 7 or less, it is difficult to form crystals other than rutile. Here, the weights of the solid components and the nuclear particles 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.

[0043] <Crystal Growth Process>

[0044] 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, crystal growth is slow, resulting in smaller grain diameters. Furthermore, the reaction becomes incomplete, leaving behind yellow titanium-containing compounds. When raising the mixture to 80°C or higher, hydrothermal synthesis (autoclave treatment) is preferable. Higher hydrothermal synthesis temperatures result in larger grain diameters. Therefore, this temperature is preferably 100°C or higher, more preferably 130°C or higher. On the other hand, production efficiency is higher when the temperature is below 300°C. This temperature is more preferably 250°C. Additionally, longer hydrothermal synthesis times result in denser 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, production efficiency is higher when the time is below 50 hours. This time is more preferably 40 hours or less, and more preferably 20 hours or less.

[0045] If crystal growth is repeated multiple times, the titanium oxide content of the particles increases. Furthermore, the grain diameter and particle size increase. Additionally, the aspect ratio decreases. The preferred number of crystal growth cycles is 2 to 5. With 2 to 3 crystal growth cycles, the haze of the particle film is low. Furthermore, the film refractive index is high in this case. Compared to 2 to 3 cycles, the particle refractive index is even higher with 4 to 5 crystal growth cycles. On the other hand, compared to 2 to 3 cycles, the film haze is even higher with 4 to 5 crystal growth cycles. In the crystal growth processes after the second cycle, the grown particles are used as nuclei for mixing and crystal growth processes.

[0046] Preferably, the particle surface is treated with silica before being treated with a surface treatment agent. Specifically, silica is added to an aqueous dispersion of the crystal-grown particles, and then the dispersion is subjected to hydrothermal synthesis. This results in a dense silica layer forming on the particle surface. If the specific surface area of ​​the silica is 100 m²... 2 / g~600m 2 If the specific surface area is / g, then it is less likely to produce microparticles and coarse particles. A more preferable specific surface area for silica is 200m².2 / g~550m 2 / g, further preferably 300m 2 / g~550m 2 / g. During hydrothermal synthesis, the lower the concentration of the solid component in the aqueous dispersion, the more densely a silica 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 silica layer will form on the particle surface. Therefore, this temperature is preferably 100°C or higher, and even more preferably 150°C or higher. On the other hand, if the temperature is 200°C or lower, the production efficiency is higher. This temperature is more preferably 180°C or lower. In addition, the longer the hydrothermal synthesis time, the more densely silica will be treated on the particle surface. Therefore, this time is preferably 1 hour or more, and more preferably 15 hours or more. On the other hand, if the time is 40 hours or less, the production efficiency is high. This time is more preferably 20 hours or less.

[0047] The following describes a method for manufacturing an organic solvent dispersion of particles. A surface treatment agent is added to an aqueous dispersion of the particles after crystal growth, thereby treating the particle surface. Afterward, the solvent of the dispersion is replaced from water with an organic solvent. The surface treatment agent preferably has alkoxy groups. Since alkoxy-containing surface treatment agents can chemically bond with the particle surface, the particles become easily dispersed in the organic solvent.

[0048] After adding the surface treatment agent, the dispersion is kept at a temperature above 40°C for at least 1 hour to allow the surface treatment agent to rapidly treat the particles. The holding time is preferably less than 20 hours.

[0049] 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.

[0050] A coating solution is obtained by adding a binder to an organic solvent dispersion of particles. The organic solvent dispersion can serve as a coating solution when a portion of the surface treatment agent acts as a binder.

[0051] A film-coated substrate is produced by forming a film on a substrate using the aforementioned 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 below 120°C, the substrate is less likely to deform. This temperature is more preferably below 100°C, and even more preferably below 80°C. Furthermore, to improve production efficiency, it is preferable to cure the film after the coating liquid has dried.

[0052] Example

[0053] Example 1

[0054] The preparation method of the particles is described in detail below. The preparation conditions of the particles are shown in Table 1.

[0055] [Particle Preparation]

[0056] <Preparation Process>

[0057] 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 wt% TiO2 equivalent) and 523 g of ammonia (7.66 wt% ammonia) were mixed. This prepared a white slurry (gel) with a pH of 9.2. The slurry was filtered. The gel was washed with pure water to obtain 400.5 g of a cake with a solid content of 10 wt%. The cake was diluted to 1.5 wt% 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 wt% 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 wt% TiO2 equivalent). The pH of this dispersion was 7.8, and the laser particle size was 37 nm. The laser particle size was determined by diluting the dispersion with water to 0.01% by weight using an ELSZ-2000S electrophoretic light scattering method manufactured by Otsuka Electronics Co., Ltd. In the following examples and comparative examples, all laser particle sizes were measured at this concentration.

[0058] 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 then 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.

[0059] <Mixed Processes>

[0060] 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.

[0061] <Crystal Growth Process>

[0062] 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.

[0063] 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 from 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 content concentration of 4% by mass).

[0064] [Preparation of organic solvent dispersions of particles]

[0065] The preparation of the organic solvent dispersion of the particles is described in detail below. The preparation conditions of the dispersion are shown in Table 2.

[0066] 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% silicon by mass, converted from 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.

[0067] 10.6 g of ammonia (5% by mass) was added to 531 g of the alcohol dispersion of the particles. Additionally, 31.9 g of 3-methacryloyloxypropyltrimethoxysilane (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. This yielded 570 g of an organic solvent dispersion of the particles (20% by mass solids).

[0068] [Preparation of coating solution]

[0069] The preparation method of the coating solution is described below. The preparation conditions of the coating solutions 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.

[0070] The physical properties of the particles were determined using the following methods. Results from other examples and comparative examples are also shown in Table 3.

[0071] (1) Particle composition

[0072] The aqueous dispersion of the particles was diluted to a solids concentration of 1%. Powdered particles were 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 (SII SPS5520 or Shimadzu ICPS-8100). These contents were then converted to SnO2, TiO2, and SiO2 contents of the particles, respectively.

[0073] (2) Crystal structure / grain diameter

[0074] The aqueous dispersion of the particles was diluted to a solids concentration of 1%. A sample for analysis was prepared by drying 200 g of this aqueous dispersion at 110°C for 20 hours (48 hours at 60°C in 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 peaks using the Scherrer equation (D = K × λ / (β × cosθ)). The Miller index (110) for rutile was selected 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 width of the diffraction line (rad), and θ is the Bragg angle (rad).

[0075] (3) Average of minor axis / aspect ratio

[0076] 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. The film was dried at 50°C for 10 minutes. The particles were photographed using a Hitachi Hightech S-5500 scanning electron microscope (SEM). One hundred 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 and major axes was calculated. The ratio of the average minor axis to the average major axis (average minor axis / average major axis) was used as the aspect ratio.

[0077] (4) Whether tin was detected on the particle surface

[0078] 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-trimethylbenzoyl)-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 film is then dried using a high-pressure mercury lamp (GS Yuasa Co., Ltd., manufactured by EYEUVMETER) at 3000 mJ / cm². 2 The coating solution was dried under ultraviolet light under specific conditions to prepare a sample (film) for XPS measurement. The following XPS measurements confirmed that no tin oxide was detected on the particle surface.

[0079] Because a surface treatment agent is present on the outermost surface of the film, titanium may not be detected in some cases. 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).

[0080] The X-ray photoelectron spectroscopy (XPS) analysis was performed using an ESCALAB220Xi manufactured by ServoSymtech. Spectroscopic measurements were conducted at 190 W X-rays, a pass energy of 100 eV (wide and narrow 20 eV), an analysis diameter of 250 × 1000 μm, and with the charge neutralizer on. An Ar gas cluster ion gun was used, with an accelerating voltage of 3 kV and an etching rate of 3.5 nm / min (silicon oxide film). Calibration of the 1s (CH) binding energy was performed at 284.8 eV. The energy intensity of the C1s peak was observed between 284 and 286 eV. O1s was observed at 532eV–534eV, Ti2p at 454eV–467eV, and Sn3d5 at 483eV–490eV.

[0081] (5) Particle refractive index Np'

[0082] The particle refractive index Np' was determined using the following method. The refractive index Np' was also determined in the following examples and comparative examples.

[0083] First, three coating solutions (a) to (c) were prepared and then applied onto a silicon wafer (manufactured by Matsuzaki Seisakusho: 6-inch debugging wafer (P-type), thickness: 625 μm) using spin coating. The coating solution was then dried at 80°C for 2 minutes. The coating was then tested using an EYEUVMETER at 3000 mJ / cm². 2 Under certain conditions, the coating solution was dried by ultraviolet irradiation to produce a film-coated substrate (silicon wafer). The refractive index Nav' of these film-coated substrates (silicon wafers) was measured using a spectroscopic ellipsometry (manufactured by Semilabo Corporation, Japan: SE-2000).

[0084] Three levels of coating solution (a) to coating solution (c) were prepared as follows.

[0085] (a) Preparation of coating solution with a weight ratio of [particles:ADDA = 6:4]

[0086] An organic solvent dispersion of particles with a mixed solid content of 20% by mass was prepared by adding 60.0 g of ADDA and 0.5 g of Omnirad TPO-H. Coating solution (a) was prepared by adding 60.0 g of PGMEA.

[0087] (b) Preparation of coating solution with a weight ratio of [particles:ADDA = 7:3]

[0088] A 70.0 g organic solvent dispersion of particles with a mixed solid content of 20% by mass, 6.0 g ADDA, and 0.4 g Omnirad TPO-H were prepared. A coating solution (b) was prepared by adding 70.0 g PGMEA to the dispersion.

[0089] (c) Preparation of coating solution with a weight ratio of [particles:ADDA = 8:2]

[0090] An organic solvent dispersion containing 80.0 g of particles with a mixed solid content of 20% by mass, 4.0 g of ADDA, and 0.3 g of Omnirad TPO-H was prepared. A coating solution (c) was prepared by adding 80.0 g of PGMEA to the dispersion.

[0091] 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).

[0092] [Formula 1]

[0093]

[0094] In Equation 1, f(m) is the volume fraction of particles relative to the total solids. m is the weight fraction of particles relative to the total solids, 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.

[0095] [Equation 2]

[0096]

[0097] In Equation 2, Nav is the film refractive index, Nm is the binder refractive index (here, the refractive index of ADDA is 1.7), and Np is the particle refractive index.

[0098] Substitute the particle weight fraction *m*, the specific gravity of the binder *dm*, and the specific gravity of the particles *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 all three levels has been obtained. Substitute 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 each of the three levels of *f(m). Calculate the deviation σ(Nav-Nav') between these calculated film refractive indices *Nav* and the measured film refractive index *Nav'*. Calculate the squared deviation σ from these deviations. 2 Sum of squared deviations Σσ 2 Sum of the squared deviations of these ∑σ 2 The minimum particle refractive index Np is defined as particle refractive index Np'. That is, particle refractive index Np' is determined by 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.).

[0099] [Fabrication of film-coated substrates]

[0100] Films were formed on glass substrates and silicon wafers respectively using a coating solution to create film-coated substrates (glass substrates) and film-coated substrates (silicon wafers). The total light transmittance and haze of the film-coated substrates (glass substrates) were measured using a haze meter (manufactured by Denshoku Kogyo Co., Ltd., NDH-5000). The refractive index and film thickness of the film-coated substrates (silicon wafers) were evaluated using a spectroscopic ellipsometry (manufactured by Semilabo Co., Ltd., SE-2000). The measurement / evaluation results of other examples and comparative examples are also shown in Table 3.

[0101] (Fabrication of film-coated substrates (glass substrates))

[0102] The coating solution was applied to a glass substrate (Hamashinsha Manufacturing: FL Glass (Glass), thickness: 3mm, refractive index: 1.51) using a spin coating method. After drying at 80°C for 2 minutes, it was then heated using a high-pressure mercury lamp (GS Yuasa Manufacturing: EYEUVMETER) at 3000mJ / cm². 2 Under certain conditions, the film is irradiated with ultraviolet light to create a film-coated substrate (glass substrate). Furthermore, the uncoated glass substrate has a total light transmittance of 99.0% and a haze of 0.1%.

[0103] (Fabrication of film-coated substrates (silicon wafers))

[0104] The coating solution was applied to a silicon wafer (manufactured by Matsuzaki Seisakusho: 6-inch debugging wafer (P-type), thickness: 625 μm) using spin coating. After drying at 80°C for 2 minutes, the solution was tested using an EYEUVMETER at 3000 mJ / cm². 2 Under certain conditions, the film is irradiated with ultraviolet light to produce a film-coated substrate (silicon wafer).

[0105] [Example 2]

[0106] The dispersion following 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 the particles, except that 2250 g of methanol and 75 g of tetraethyl orthosilicate were added to the 2250 g aqueous dispersion, an alcohol dispersion of the 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 this alcohol dispersion. Furthermore, 33.5 g of KBM-503 as a second surface treatment agent was added to this alcohol dispersion. After adding KBM-503, an organic solvent dispersion of the 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.

[0107] [Example 3]

[0108] 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 the particles (solid content concentration of 4% by mass). In the preparation of the organic solvent dispersion of the 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 the particles, an alcohol 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 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.

[0109] [Example 4]

[0110] 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.

[0111] [Example 5]

[0112] In the preparation of the organic solvent dispersion of the particles, the amount of tetraethyl 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.

[0113] [Example 6]

[0114] The aqueous dispersion of the particles from Example 1 was diluted to a solids concentration of 1% by mass. Silica sol (manufactured by Nichikai Catalyst Chemical Co., Ltd.: Cataloy (registered trademark) SN-350, with a specific surface area of ​​375 m² / g) was added to 9000g of this aqueous dispersion. 2 36 g of the dispersion (containing 15% by weight of silica) was hydrothermally synthesized in an autoclave at 165°C for 18 hours. The dispersion was then cooled to room temperature. The dispersion was concentrated using an ultrafiltration membrane device to obtain 2385 g of an aqueous dispersion of particles (solid content concentration of 4% by weight). That is, the particles were surface-treated with silica. In the preparation of the organic solvent dispersion of the particles, except that 2250 g of methanol and 19.9 g of tetraethyl orthosilicate were added to 2250 g of the aqueous dispersion of the particles, an alcohol dispersion of the particles (solid content concentration of 20% by weight) was obtained in the same manner as in Example 1. 10.1 g of ammonia water (5% by weight) was added to the alcohol dispersion. Furthermore, 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 (solid content concentration of 20% by weight) 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 prepared before surface treatment with silica. That is, the same XPS test sample as in Example 1 was used.

[0115] The isoelectric point of the aqueous dispersion of 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 pH increments. The pH at which the zeta potential ±0 mV is drawn along a straight line was defined as the isoelectric point. At this point, 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 apparatus (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.

[0116] [Example 7]

[0117] 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.

[0118] [Comparative Example 1]

[0119] 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 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.

[0120] [Comparative Example 2]

[0121] The mixture from Example 1 was stirred at 60°C for 40 hours to obtain an aqueous dispersion of the particles. This aqueous dispersion was pale yellow. The particles in the aqueous dispersion were a mixture of rutile and anatase crystals.

[0122] [Comparative Example 3]

[0123] 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 to prepare a white slurry (gel) with pH 8.6. The slurry was filtered, and the gel was washed with pure water. 900 g of a cake with a solid content of 5 wt% was 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. The mixture was heated at 80°C for 1 hour. 986 g of pure water was then added. 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 a dispersion of the titanium-containing compound from Example 1 was then 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.

[0124] [Comparative Example 4]

[0125] 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 this aqueous dispersion. The ion exchange resin was then separated from the aqueous dispersion. In the preparation of the organic solvent dispersion of the particles, an alcohol dispersion of the particles (solid content concentration of 20% by weight) was obtained in the same manner as in Example 1, except that 2250g of methanol and 65.5g of tetraethyl orthosilicate were added to 2250g of the aqueous dispersion. 12.4g of ammonia water (5% by weight) was added to this alcohol dispersion. Furthermore, 77.3g of KBM-503 as a second surface treatment agent was added to this 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, the coating solution was prepared in the same manner as in Example 1, except that the organic solvent dispersion was used.

[0126] [Comparative Example 5]

[0127] 2000g of an aqueous solution of titanium tetrachloride (equivalent to 7.5 wt% TiO2) and 2000g of ammonia (equivalent to 7.5 wt% ammonia) were mixed to prepare a white slurry (gel) with a pH of 9.2. The slurry was filtered, and the gel was washed with pure water. 1500g of a cake with a solid content of 10 wt% was obtained. This cake was diluted to 1.5 wt% with pure water. 1714g of an aqueous solution of hydrogen peroxide (equivalent to 35 wt%) was added. The mixture was heated at 80°C for 1 hour. A dispersion of the titanium compound 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 a cation exchange resin to 15000g of the dispersion. 1901g of an aqueous solution of potassium stannate (equivalent to 1 wt%) 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, an alcohol dispersion of the particles (solids concentration of 20% by mass) was obtained in the same manner as in Example 1, except that 2250 g of methanol and 165.1 g of tetraethyl orthosilicate were added to 2250 g of the aqueous dispersion. 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 of 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.

[0128]

[0129]

[0130]

Claims

1. A particle having a rutile crystal structure, wherein, The particle comprises: a core containing tin and titanium; and a shell containing titanium. The grain diameter is 7 nm or more. The particles contain more than 90% by weight of titanium oxide, which is equivalent to TiO2. The particles contain tin oxide, which is converted to SnO2 at a rate of 0.2% to 10% by weight. The tin content of the core is 0.1 at% to 6.5 at%. The tin content of the shell is less than 0.1 at%.

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

3. The dispersion as described in claim 2, characterized in that, The solvent is water. Relative to 100 parts by mass of the particles, the particles contain at least 2 parts by mass of silicon dioxide, equivalent to SiO2. The isoelectric point of the dispersion is below 3.

4. A method for manufacturing particles, characterized in that, The manufacturing method comprises: The process for preparing a dispersion containing titanium compounds; The process for preparing a dispersion of nuclei with a rutile crystal structure; The mixing process for preparing the mixture by mixing the dispersion of the titanium-containing compound and the dispersion of the nuclear particles; and A crystal growth process for preparing particles is achieved by raising the mixture to above 80°C and growing crystals based on the nuclear particles. The nuclear particles contain titanium oxide and tin oxide. In the mixing process, the dispersion of the titanium-containing compound and the dispersion of the core particles are mixed such that the particles contain at least 95% by weight of titanium oxide (equivalent to TiO2) and 0.2% to 5% by weight of tin oxide (equivalent to SnO2).

5. The method for manufacturing particles as described in claim 4, characterized in that, The manufacturing method comprises, in sequence: The process of adding silica to the dispersion after the crystal growth process; and The process of hydrothermal synthesis of the dispersion after adding the silica.

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

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

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