Particles having a silicon-containing casing and cavity inside same,

Abstract

Provided is a particle which contains a silicon-containing shell and a cavity inside the shell, and which has an average particle diameter of 15-150 nm, a refractive index of 1.08-1.38, and a ratio (A1 / A2) of 1.0 or less, the average particle diameter being obtained by image analysis, the ratio (A1 / A2) being the ratio (A1 / A2) of the specific surface area (A1) to the specific surface area (A2), and the refractive index being 1.08-1.38. The particle has a specific surface area (A1) calculated according to a BET method using a water vapor gas and a specific surface area (A2) calculated according to a BET method using a nitrogen gas, and when the particle is dried at 200 DEG C for 3 hours and then left to stand in an atmosphere having a relative humidity of 90% at 25 DEG C for 24 hours, the mass increase of the particle is 4.0 parts by mass or less with respect to 100 parts by mass of the dried particle.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based on Japanese Patent Application No. 2024-053928 filed with the Japan Patent Office on March 28, 2024, and Japanese Patent Application No. 2025-012737 filed with the Japan Patent Office on January 29, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0001] The present disclosure relates to particles having an outer shell containing silicon and a cavity inside the outer shell, and a method for producing the same. Background Art

[0002] In the past, in order to suppress the surperficial reflection of base materials such as glass, plastic sheet or plastic lens, reflection-inhibiting film was formed on its surface. For example, by coating method, vapor deposition method or CVD method etc., the coating of low-refractive-index materials such as fluororesin or magnesium fluoride was formed on the surface of the base material such as glass or plastic. However, the cost of these methods is expensive. Therefore, the method for forming reflection-inhibiting film by the coating fluid being coated on the surface of the base material is known, wherein the coating fluid contains the low-refractive-index particles (for example, with reference to Japanese Patent Laid-Open No. 7-133105 bulletin) made of silicon dioxide etc.

[0003] In addition, methods for producing particles having a silicon-containing shell and a cavity therein are known (for example, see Japanese Patent Application Publication Nos. 2001-233611 and 2013-226539). These particles have a low refractive index. Therefore, a transparent coating formed using these particles has a low refractive index and excellent reflection suppression performance.

[0004] Furthermore, it is known that a transparent coating having a hard coating function is formed on the surface of a substrate or a display device, thereby improving the pencil hardness (hardness) and scratch resistance (strength) of the substrate or the display device. Specifically, an organic resin film or an inorganic film having transparency is formed on the surface of glass, plastic or a display device. At this time, particles such as silicon dioxide are incorporated into the coating. Thus, it is known that the adhesion between the coating and the substrate or the strength of the substrate with the coating is improved. It is known that when using such particles, in order to improve the dispersibility to the matrix component, a surface treatment is performed by an organosilicon compound (for example, with reference to Japanese Patent Application Publication No. 2013-224436).

[0005] Furthermore, it is known that an organic fluorine compound (PFAS) is added to a coating liquid to improve the water resistance of a coating film (for example, see Japanese Patent Application Laid-Open No. 2009-108262).

[0006] In recent years, concerns have been raised about the impact of PFAS on humans and the environment. Internationally, the Stockholm Convention on Persistent Organic Pollutants (POPs Convention) has also established a policy to ban the use of PFAS. Summary of the Invention The particles of this embodiment are particles containing a silicon-containing shell and a cavity inside the shell, and the particles have an average particle size of 15 nm to 150 nm, a refractive index of 1.08 to 1.38, and a ratio A1 / A2 of 1.0 or less, wherein the average particle size is an average particle size obtained by image analysis, the ratio A1 / A2 is the ratio A1 / A2 of specific surface area A1 to specific surface area A2, the specific surface area A1 is calculated according to the BET method using water vapor gas, and the specific surface area A2 is calculated according to the BET method using nitrogen gas, and after the particles are dried at 200°C for 3 hours and then placed at 25°C in an atmosphere with a relative humidity of 90% for 24 hours, the mass increase of the particles is 4.0 parts by mass or less relative to 100 parts by mass of the particles after the drying. DETAILED DESCRIPTION In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, it may be apparent that one or more embodiments may be practiced without these specific details.

[0007] Compared with solid particles, particles with a cavity inside have a low refractive index but low strength. Therefore, when used for a reflection-suppressing film, although the reflection suppression ability is improved, the hardness or strength of the film is reduced. Therefore, for particles, not only a low refractive index is required, but also sufficient hardness and strength are required. In addition, when a reflection-suppressing film containing particles with a cavity inside is used for a display element, the uniformity of the reflectivity of the film surface is required. In addition, moisture or water droplets in the air attached to the reflection-suppressing film with a low refractive index are visually recognized as color unevenness (color mura). Here, the refractive index of water is different from the refractive index of the reflection-suppressing film or the particles with a cavity inside. Therefore, the refractive index difference between the part with water attached and the part without water attached is visually recognized as color unevenness. Usually, the attachment of moisture droplets is suppressed by the waterproof effect produced by making the PFAS in the coating liquid present on the surface of the film. However, in the recent trend of PFAS-free, particles with cavities inside are required to be less hygroscopic. Therefore, it is necessary to reduce hygroscopicity (improve water resistance) by densifying the particles (shell) and controlling the hydrophilic sites on the surface. This allows the particles to have a low refractive index and sufficient hardness and strength.

[0008] In order to solve such a problem, the following particles are provided. The particles have a shell containing silicon and a cavity inside the shell. The average particle size of the particles obtained by image analysis is 15nm to 150nm. In addition, the refractive index of the particles is 1.08 to 1.38. Furthermore, the ratio (A1 / A2) of the specific surface area (A1) to the specific surface area (A2) is 1.0 or less, wherein the specific surface area (A1) is the specific surface area (A1) calculated according to the BET method using water vapor gas, and the specific surface area (A2) is the specific surface area (A2) calculated according to the BET method using nitrogen gas. In addition, after the particles are dried at 200°C for 3 hours, the mass increase of the particles when placed at 25°C in an atmosphere of 90% relative humidity for 24 hours is 4.0 parts by mass or less relative to 100 parts by mass of the particles after drying.

[0009] Hereinafter, the “particles having an outer shell containing silicon and a cavity therein” may be simply referred to as “particles” or “particles according to the present embodiment”.

[0010] The particles have a low refractive index. In addition, the shell of the particles is dense. Furthermore, the hydrophilic portion of the particle surface is controlled, so the particles have high water resistance. According to the coating liquid containing such particles, a substrate with a film having excellent reflection suppression performance and high hardness and high strength can be obtained. Furthermore, the substrate with the film is not easy to produce color unevenness.

[0011] In order to obtain the particles, the following production method is provided.

[0012] First, an alkaline aqueous solution is prepared (first step). Next, a solution of a silicon-containing compound and an aqueous solution of an alkali-soluble compound containing an inorganic element other than silicon are simultaneously added to the alkaline aqueous solution. This produces a dispersion of composite oxide particles a (second step). In this second step, these added solutions are added so that the molar ratio (MOx / SiO2) is 0.01 to 2.0, where silicon oxide is represented by SiO2 and the inorganic element oxide is represented by MOx.

[0013] Next, a solution of a silicon-containing compound and an aqueous solution of an alkali-soluble compound containing an inorganic element other than silicon are simultaneously added to the dispersion of composite oxide particles a obtained in the second step. Thus, a dispersion of composite oxide particles b is prepared (third step). In this third step, when silicon oxide is represented as SiO2 and the oxide of the inorganic element is represented as MOx, the molar ratio (MOx / SiO2) of these added solutions is set to be smaller than the molar ratio in the second step. Furthermore, the average particle size of composite oxide particles b is 15 nm to 150 nm. The value obtained by subtracting the average particle size of composite oxide particles a from the average particle size of composite oxide particles b and then dividing by 2 is 3 nm to 14 nm.

[0014] Next, an acid is added to the dispersion of the composite oxide particles b obtained in the third step to remove at least a portion of elements other than silicon constituting the composite oxide particles b. Thus, a dispersion of silica particles is prepared (fourth step).

[0015] Next, the dispersion of silica particles obtained in the fourth step is heated to 150° C. to 300° C. at a pH of 9.0 to 11.0 (fifth step).

[0016] Next, the dispersion of silica particles obtained in the fifth step is heated to 150° C. to 400° C. at a pH of 5.0 to 8.0 (sixth step).

[0017] The properties of the particles in the dispersion obtained in the sixth step are based on the properties of the particles described above.

[0018] According to the particles of this embodiment, a coated substrate having excellent reflection suppression performance, high water resistance, and high hardness and strength can be obtained.

[0019] particle The particles of this embodiment will be described.

[0020] The particles have a silicon-containing shell and a cavity inside the shell. The average particle size of the particles obtained by image analysis is 15 nm to 150 nm. In addition, the refractive index of the particles is 1.08 to 1.38. Furthermore, the ratio (A1 / A2) of the specific surface area (A1) to the specific surface area (A2) is 1.0 or less, wherein the specific surface area (A1) is the specific surface area (A1) calculated according to the BET method using water vapor gas, and the specific surface area (A2) is the specific surface area (A2) calculated according to the BET method using nitrogen gas. In addition, after the particles are dried at 200°C for 3 hours, the mass increase of the particles when placed at 25°C in an atmosphere of 90% relative humidity for 24 hours is 4.0 parts by mass or less relative to 100 parts by mass of the particles after drying.

[0021] The average particle size of the particles obtained by image analysis is 15nm to 150nm. A transmission electron microscope (TEM) is used to take a photograph of the particles (TEM photograph) at a specified magnification. By image processing, the area of ​​the particles is obtained from the images of 300 randomly selected particles. The average value of the circle equivalent diameter (circular equivalent diameter) calculated from the area is defined as the above-mentioned average particle size. If the average particle size is within this range, the particles neither condense nor settle in the dispersion and can stably exist in the dispersion. In addition, the particles also show good dispersibility in the coating solution or the coating. Therefore, a substrate with a coating having high transparency, reflection suppression performance, hardness and strength can be obtained.

[0022] Here, the proportion of voids (void ratio) in particles with an average particle size of less than 15 nm is small. Therefore, the refractive index will not be sufficiently reduced. Therefore, the reflection suppression performance is insufficient. On the contrary, if it is greater than 150 nm, light scattering is likely to occur. As a result, the dispersibility of the particles in the coating solution is reduced. Therefore, there is a situation where a transparent coating cannot be obtained. The average particle size is preferably 30 nm to 120 nm, more preferably 40 nm to 100 nm, and even more preferably 40 nm to 80 nm.

[0023] The refractive index of the particles is 1.08 to 1.38. If the refractive index is within this range, a transparent coated substrate with high reflection suppression performance can be obtained. However, it is difficult to obtain particles with a refractive index less than 1.08. Conversely, if the refractive index exceeds 1.38, sufficient reflection suppression performance may not be achieved, depending on the refractive index of the substrate or underlying film. The refractive index is preferably 1.08 to 1.34, more preferably 1.08 to 1.30, and even more preferably 1.08 to 1.26.

[0024] The ratio (A1 / A2) of the specific surface area (A1) and specific surface area (A2) of the particles is 1.0 or less, wherein the specific surface area (A1) is the specific surface area (A1) calculated according to the BET method using water vapor gas, and the specific surface area (A2) is the specific surface area (A2) calculated according to the BET method using nitrogen gas. If the ratio (A1 / A2) is within this range, the shell of the particles is dense. As a result, there are few hydrophilic parts on the particle surface. Therefore, a substrate with a transparent coating having high water resistance, hardness, strength and reflection suppression performance can be obtained.

[0025] Here, if the ratio (A1 / A2) is greater than 1.0, there are many hydrophilic sites on the particle surface. As a result, the water resistance of the particle is reduced. Therefore, it is impossible to obtain sufficient water resistance from the substrate with a film using the particle, so there is a situation where uneven color is produced. The lower limit of the ratio (A1 / A2) is not particularly limited. This lower limit is, for example, 0.2. The ratio (A1 / A2) is preferably less than 0.8, more preferably less than 0.6.

[0026] After the particles are dried at 200°C for 3 hours and then placed at 25°C in an atmosphere of 90% relative humidity for 24 hours, the mass increase of the particles is 4.0 parts by mass or less relative to 100 parts by mass of the particles after drying. If the mass increase is within this range, the hygroscopicity of the particles is suppressed (i.e., the particles have high water resistance). Therefore, if these particles are used, the occurrence of color unevenness is suppressed. At the same time, a substrate with a transparent coating having high reflection suppression performance can be obtained.

[0027] Here, if the mass increase of the particles is greater than 4.0 mass parts, the water resistance of the particles is reduced. Therefore, it is impossible to obtain sufficient water resistance from the base material with the film using the particles, so there is a situation where uneven color is produced. The lower limit of the mass increase of the particles is not particularly set. This lower limit is, for example, 0.0 mass parts. The mass increase of the particles is preferably less than 3.0 mass parts, more preferably less than 2.0 mass parts, and particularly preferably less than 1.0 mass parts.

[0028] particle The ratio (A2 / A3) of the specific surface area (A2) to the specific surface area (A3) of the particles is preferably 1.00 to 1.30, wherein the specific surface area (A2) is the specific surface area (A2) calculated by the BET method using nitrogen gas, and the specific surface area (A3) is the specific surface area (A3) calculated based on the average particle size. If the ratio (A2 / A3) is within this range, the surface area of ​​the particles is small. Therefore, the amount of moisture or water droplets attached to the particle surface is reduced. As a result, a highly water-resistant coated substrate can be obtained.

[0029] It is inherently difficult to obtain particles with a ratio (A2 / A3) of less than 1.00. Conversely, if the ratio (A2 / A3) exceeds 1.30, the surface area of ​​the particles increases. Therefore, water or water droplets tend to adhere to the surface of the particles. This results in decreased water resistance. The ratio (A2 / A3) is more preferably 1.00 to 1.20, and even more preferably 1.00 to 1.10.

[0030] The number density of silanol groups on the particle surface calculated by the Sears method is preferably 0.1 silanol groups / nm. 2 ~1.5 / nm 2When the number density of the silanol groups is within this range, the particles have high water resistance, and a substrate with a coating having high reflection suppression performance and being transparent and less prone to color unevenness can be obtained.

[0031] Here, the number density of silanol groups is less than 0.1 / nm 2 On the contrary, if the number density of silanol groups is greater than 1.5 / nm 2 , the particles have a high affinity with water and water droplets. Therefore, there is a case where water resistance is reduced. The number density of silanol groups is more preferably 0.2 / nm 2 ~1.0 / nm 2 , more preferably 0.2 per nm 2 ~0.5 / nm 2 .

[0032] Here, the number density of silanol groups of the particles is calculated based on the Sears number and the specific surface area. The Sears number is measured by titration using sodium hydroxide according to the description of Sears in Analytical Chemistry 28 (1956), 12, 1981-1983. Specifically, 30 g of sodium chloride is added to 150 g of a dispersion of silica particles diluted with pure water so that the concentration of the silica particles is 1% by mass. Furthermore, the pH of the resulting dispersion is adjusted to 4.0 with hydrochloric acid. Thereafter, a 0.1 N aqueous sodium hydroxide solution is added dropwise to the dispersion at 0.1 ml / sec. At this time, "Q" is used to represent the amount of sodium hydroxide solution required to reach a pH of 9.0. That is, the Sears number (A) is the titration amount of the 0.1 N NaOH aqueous solution required for 1.5 g of particles. More specifically, the Sears number (A) is represented by the following formula (1).

[0033] A=(Q×f×100×1.5) / (W×C)···(1) (wherein, f represents the titer of the 0.1N sodium hydroxide aqueous solution used, C represents the particle concentration (mass %) in the dispersion, and W represents the collected amount of the dispersion (g))

[0034] In addition, the number density (ρ) of the silanol groups is represented by the following formula (2).

[0035] ρ=(B×N A ) / (10 18 ×M×S BET )···(2) (Where B represents the amount of sodium hydroxide (mol) required to increase the pH from 4.0 to 9.0 per 1.5 g of particles, calculated based on the Sears number (A), and N Arepresents Avogadro's constant (units / mol), M represents the particle mass (1.5 g), and S BET The specific surface area (m2) was measured using the BET method using nitrogen adsorption. 2 / g))

[0036] The ratio (A4 / A3) of the specific surface area (A4) of the particles to the specific surface area (A3) is preferably 0.65 or less, wherein the specific surface area (A4) is the specific surface area (A4) calculated by pulsed NMR measurement of a methanol dispersion, and the specific surface area (A3) is the specific surface area (A3) calculated by the average particle size. If the ratio (A4 / A3) is within this range, the particles have high water resistance. Therefore, a substrate with a transparent coating having high reflection suppression performance can be obtained. Moreover, the substrate is less likely to produce color unevenness.

[0037] In this pulsed NMR measurement method, pulsed radio waves of tens of MHz are irradiated to excite magnetization in thermal equilibrium within a static magnetic field. The phenomenon of the excited magnetization returning to its original thermal equilibrium state over time is observed. Liquid molecules in contact with or adsorbed on the particle surface respond differently to changes in the magnetic field than free liquid molecules not in contact with the particle surface.

[0038] Typically, the motion of liquid molecules adsorbed on the particle surface is restricted. On the other hand, liquid molecules not adsorbed on the particle surface can move freely. As a result, the relaxation time of the liquid molecules adsorbed on the particle surface is shorter than the relaxation time of other liquid molecules. The relaxation time observed in the liquid dispersed with particles is the average value of the relaxation time reflecting the liquid volume concentration on the particle surface and the relaxation time reflecting the liquid volume concentration in the free state.

[0039] In addition, the specific surface area (A4) of the particles calculated by pulse NMR measurement of the methanol dispersion refers to the specific surface area of ​​the portion of the particles wetted by the dispersion medium. Particles with fewer hydrophilic parts on the particle surface are in a state where there are fewer silanol groups on the particle surface. For the surface of such particles, there are fewer parts that are easily wetted by the hydrophilic dispersion medium. Therefore, the value of the specific surface area (A4) of the particles is smaller than the value of the "specific surface area (A3) calculated by the average particle size". Therefore, it is believed that the value of the specific surface area (A4) will vary depending on the degree of water resistance of the particles. In addition, the specific surface area (A4) value will also vary depending on the type of dispersion medium used during the measurement.

[0040] Here, if the ratio (A4 / A3) is greater than 0.65, there are many hydrophilic sites on the particle surface. Therefore, there is a case where water resistance is reduced. Alternatively, there is a case where the functional groups from the organosilicon compound cannot be fully introduced into the particle surface. As a result, there is a case where the hardness or strength of the substrate with the coating is reduced. There is no particular setting for the lower limit of the ratio (A4 / A3). The lower limit of the ratio (A4 / A3) is, for example, 0.10. The ratio (A4 / A3) is more preferably less than 0.60, and further preferably less than 0.50.

[0041] The specific surface area (A4) of the particles is obtained by equation (4) using the volume concentration (Ψp) of the particles obtained by equation (3) below.

[0042] Ψp=(Sc / Sd) / [(1-Sc) / Td]···Formula (3) (where Sc represents the solid content concentration of the particles in the dispersion (mass %), and Sd represents the density of the particles (g / cm 3 ), and Td represents the density of the dispersion medium at 25°C (g / cm 3 ))

[0043] Here, solid content concentration refers to the concentration obtained by converting the particles as solid components in the dispersion (the same applies below). Sd is the sum of the following two values: the value obtained by multiplying the density of the constituent components of the particle by their volume ratio, and the value obtained by multiplying the density of the constituent components inside the particle by their volume ratio. For example, in the case where the constituent components of the particles are silicon dioxide, an Sd value of 2.2 (unit: g / cm 3 ). In the case of aluminum oxide, an Sd value of 3.9 is used, in the case of tin oxide, an Sd value of 6.9 is used, in the case of antimony (V) oxide, an Sd value of 5.2 is used, in the case of titanium dioxide (anatase), an Sd value of 3.9 is used, in the case of titanium dioxide (rutile), an Sd value of 4.3 is used, in the case of zirconium oxide, an Sd value of 6.0 is used, in the case of zinc oxide, an Sd value of 5.6 is used, in the case of copper (II) oxide, an Sd value of 6.3 is used, in the case of iron (III) oxide, an Sd value of 5.2 is used, and in the case of indium oxide, an Sd value of 7.2 is used. In addition, when the particles are, for example, composite oxide particles, particles mixed with oxides, or a mixture of oxide particles, Sd can be calculated based on the proportion of the oxides. In addition, when the constituent component inside the particle is air, the Sd value is 0.0 g / cm 3. In the case of other gases or liquids, the corresponding density can also be used. For example, in the case of particles having a silicon-containing shell and a hollow inside thereof in the present embodiment, the porosity can be used as the volume ratio of the hollow portion. The porosity of the particle is defined as the ratio of the hollow portion in the particle to the particle. Specifically, first, a TEM photograph of the particle is taken. At this time, the density of the hollow portion of the particle is low, so the contrast of its hollow portion becomes low. On the contrary, the density of the shell portion is high, so the contrast of its shell portion becomes high. The hollow portion and the shell portion of the particle can be confirmed based on the difference in contrast. More specifically, the images of 300 randomly selected particles in the TEM photograph are image processed. Thus, the area of ​​the hollow portion is calculated. The equivalent circle diameter is calculated based on its area. The calculated equivalent circle diameter is defined as the average diameter of the hollow portion. Assuming that the shape of the particle at this time is a true sphere, the average volume of the primary particle and the average volume of the hollow portion can be calculated. The porosity is expressed as the ratio of the average volume of the hollow portion to the average volume of the primary particle. In addition, as Td, for example, when the dispersion medium is methanol, 0.79 g / cm 3 If another type of dispersion medium or a mixture of dispersion media is used, the corresponding density is used.

[0044] A4={[(Ra / Rb)-1]×Rb} / (Ka×Ψp) ···Formula (4) (Where A4 represents the specific surface area of ​​the particles (m 2 / g), Ra represents the reciprocal of the relaxation time of pulsed NMR in the measurement of the dispersion liquid, and Rb represents the reciprocal of the relaxation time of pulsed NMR in the measurement of the dispersion medium, and Ka represents a coefficient related to the dispersion medium and particles used)

[0045] The coefficient Ka is set so that the specific surface area (A3) obtained by averaging the primary particle diameters of the particles is equal to the specific surface area (A4) obtained by pulsed NMR measurement of a methanol dispersion of the particles. The methanol dispersion of the particles can be obtained by replacing the dispersion medium of the aqueous dispersion of the particles obtained in the fifth step with methanol.

[0046] The specific surface area (A3) of the particles can be determined using the average primary particle size (D) of the particles according to the following formula (5).

[0047] A3=6000 / Sd / D ···Formula (5) (Where Sd represents the density of the particles (g / cm 3 ))

[0048] The specific surface area (A4) of the particles in the aqueous dispersion obtained in the fifth step is obtained by equation (6) using the volume concentration (Ψp) of the particles obtained by equation (3).

[0049] A4={[(Rc / Rd)-1]×Rd} / (Ka×Ψp) ···Formula (6) (Where A4 represents the specific surface area of ​​the particles (m 2 / g), Rc represents the reciprocal of the relaxation time of pulsed NMR in the measurement of the dispersion of the particles, and Rd represents the reciprocal of the relaxation time of pulsed NMR in the measurement of the dispersion medium, and Ka represents a coefficient related to the dispersion medium and the particles used)

[0050] Here, the coefficient Ka is set so that the specific surface area (A3) and the specific surface area (A4) have the same value. Therefore, the coefficient Ka can be calculated from the equations (5) and (6). Ka={[(Rc / Rd)-1]×Rd} / (Ψp×A3)···Equation (7)

[0051] In the particles 29 In the Si-NMR analysis, a signal peak representing the Q1 to Q4 structures of silicon atoms appeared in the chemical shift range of -78ppm to -120ppm. Among the Q1 to Q4 structures, the signal peak representing the Q4 structure appeared in the chemical shift range of -108ppm to -120ppm. In the present embodiment, the ratio of the peak area of ​​the Q4 structure to the total area (peak area) of the peaks representing the individual Q1 to Q4 structures is preferably 82% or more. If the ratio of the peak area is within this range, the particles are dense. Therefore, a substrate with a coating having sufficient hardness and strength can be obtained.

[0052] In addition, 29 In Si-NMR spectroscopy, the peak of the Q1 structure appears in the chemical shift range of -78 ppm to -88 ppm, the peak of the Q2 structure appears in the chemical shift range of -88 ppm to -98 ppm, and the peak of the Q3 structure appears in the chemical shift range of -98 ppm to -108 ppm.

[0053] The peak attributed to the Q1 structure indicates that one (-OSi) group and three (-OH) groups are bonded to the Si atom. The peak attributed to the Q2 structure indicates that two (-OSi) groups and two (-OH) groups are bonded to the Si atom. The peak attributed to the Q3 structure indicates that three (-OSi) groups and one (-OH) group are bonded to the Si atom. The peak attributed to the Q4 structure indicates that four (-OSi) groups are bonded to the Si atom.

[0054] Here, if the ratio of the peak area of ​​the Q4 structure is less than 82%, the hardness or strength of the coated substrate may become insufficient. There is no particular upper limit for the ratio of the peak area of ​​the Q4 structure. The upper limit is, for example, 98%. The ratio of the peak area of ​​the Q4 structure is more preferably 86% or greater, and even more preferably 90% or greater.

[0055] The thickness of the outer shell of the particles is preferably 3.0 nm to 12.0 nm. When the outer shell thickness is within this range, a coated substrate having high transparency, reflection suppression performance, hardness, and strength can be obtained.

[0056] Here, if the shell thickness is less than 3.0 nm, it may be difficult to obtain sufficient strength to maintain the particle shape. Conversely, if the shell thickness is greater than 12.0 nm, the particles have a high refractive index. Therefore, it may be difficult to obtain a coated substrate with a low refractive index. The shell thickness is more preferably 3.0 nm to 10.0 nm, more preferably 3.0 nm to 8.0 nm, and particularly preferably 3.0 nm to 6.0 nm.

[0057] The particles preferably contain functional groups. In particular, if the particle shell contains functional groups, the particles have high dispersibility, which is the dispersibility in the dispersion medium, the coating liquid for film formation, or the matrix of the film. Therefore, for the substrate with the film using the particles, the aggregation of the particles is suppressed. Moreover, the substrate with the film has sufficient hardness and strength. In addition, the particle shell contains silicon, so it is possible to obtain particles with a low refractive index. At the same time, the presence of the surface OH group from silicon makes it easy to introduce the above-mentioned functional groups.

[0058] Examples of functional groups contained in the particle shell include at least one functional group selected from alkyl, acryloyl, (meth)acryloyl, vinyl, alkoxy, mercapto, epoxy, glycidyloxy, amino, phenyl, and phenylamino groups. Among these, alkyl, acryloyl, (meth)acryloyl, vinyl, mercapto, and epoxy groups are preferred due to their high polymerization ability. These functional groups can be determined by analyzing the dry powder of the particles using a Fourier transform infrared spectrometer (FT-IR).

[0059] These functional groups are preferably functional groups from the organosilicon compound shown in formula (8). The organosilicon compound can be used as, for example, a raw material for making particles before surface treatment, a surface treatment agent for the surface treatment of particles, or both. Here, as examples of raw materials for making particles before surface treatment, alkoxysilanes including tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) and phenyltrimethoxysilane can be cited. In addition, the shell surface of the particles treated with such a surface treatment agent has a majority of functional groups. Therefore, the particles have high dispersibility in the coating solution or the film. Therefore, the substrate with the film has sufficient hardness and strength.

[0060] R n -SiX 4-n (8) (wherein, R represents an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, X represents an alkoxy group, a hydroxyl group, or a hydrogen atom having 1 to 4 carbon atoms, and n represents an integer from 0 to 3)

[0061] The amount of the organosilicon compound containing these functional groups is preferably expressed as a solid content (R n -SiO (4-n) / 2 ) is calculated as 1.0 mass parts to 30 mass parts. If such particles are used for a substrate with a film, high adhesion between the substrate and the film can be obtained. In addition, the substrate with the film has high hardness and strength.

[0062] If the amount of the functional group-containing organosilicon compound is less than 1.0 parts by mass, sufficient dispersibility or stability may not be achieved. Therefore, when the particles are used for coating, a coated substrate with sufficient hardness and strength may not be obtained. Conversely, if the amount of the functional group-containing organosilicon compound exceeds 30 parts by mass, sufficient reflection suppression performance may not be achieved. The amount of the organosilicon compound is more preferably 2.0 to 25 parts by mass, and even more preferably 3.0 to 20 parts by mass.

[0063] In addition, as described above, the specific surface area (A4) obtained by pulse NMR measurement of a methanol dispersion of particles represents the specific surface area of ​​the portion of the particles wetted by the dispersion medium. Here, for the surface of the particles surface-treated with an organosilicon compound, the reaction between the organosilicon compound and the OH groups on the particle surface results in fewer OH groups than in the particles before the surface treatment. Therefore, the value of the specific surface area of ​​the portion of the particles wetted by the hydrophilic dispersion medium is small. Thus, the value of the specific surface area (A4) also varies with the amount of organosilicon compound chemically bonded to the particles by surface treatment. The particles of this embodiment have high water resistance. Therefore, even without surface treatment with an organosilicon compound, the value of the specific surface area (A4) is smaller than the "specific surface area (A3) calculated by the average particle size". By surface treating the particles, the specific surface area (A4) tends to become further smaller.

[0064] For the content (SiO2 content) of the silicon in the particle, the total amount of the metal elements other than the carbon constituting the particle is regarded as 100 parts by mass with an oxide benchmark, as the SiO2 in the particle when the silicon in the particle is converted to silicon dioxide (SiO2), the content (SiO2 content) of the silicon in the particle is calculated. SiO2 content is preferably more than 98 parts by mass. If SiO2 content is more than 98 parts by mass, it is possible to easily obtain a coating with low reflectivity, high hardness and high strength. This SiO2 content is more preferably more than 99 parts by mass, further preferably more than 99.5 parts by mass, and particularly preferably 100 parts by mass.

[0065] Thus, the particles preferably contain silicon (Si) as a main constituent element. Here, the constituent elements of the particles may be any of the following (a) to (c). These elements are derived from materials suitable for use in preparing the particles.

[0066] (a)SiO2 (b) An oxide containing Si and at least one element selected from the group consisting of Al, Sn, Sb, Ti, Zr, Zn, Cu, Fe, and In. The oxide containing these elements may be a mixture or a composite oxide. (c) A mixture of the above (a) and the above (b)

[0067] In addition, when the total amount of the metal elements other than the carbon constituting the particles is regarded as 100 parts by mass on an oxide basis, the content of the elements other than Si in the above-mentioned item (b) in the particles is preferably less than 2 parts by mass on an oxide basis. Here, if this content is more than 2 parts by mass, the refractive index of the particles increases, and therefore there is a situation where the reflectivity of the coating becomes higher. Alternatively, there is a situation where a transparent coating cannot be obtained due to coloring, etc. This content is more preferably less than 1 part by mass, further preferably less than 0.5 parts by mass, and particularly preferably 0 parts by mass.

[0068] In addition, as long as it does not deviate from the refractive index range of the above-mentioned particles, "particles having a shell and a hollow inside thereof" or so-called "solid particles" having no hollow inside the particles may also exist in addition to the particles listed in (a) to (c) above. The ratio of these other particles that are not particles of the present embodiment also varies according to the type and composition ratio of the elements constituting the particles. For example, in the case of "solid particles" having an SiO2 content of more than 98 parts by mass and the same average particle size as the particles of the present embodiment, the ratio of the number of solid particles to the total number of particles is preferably less than 10%. This ratio can be obtained by, for example, counting the number of particles of the present embodiment and the number of solid particles in a specified field of view of a TEM photograph. If the ratio is 10% or more, the refractive index is higher than the desired range. Therefore, there is a situation where the desired reflection suppression performance cannot be obtained during coating. The number ratio of such solid particles is more preferably less than 5%, further preferably less than 2%, particularly preferably less than 1%, and most preferably 0%. If particles containing different elemental species are present, mapping is performed on the particles in a predetermined field of view using energy dispersive X-ray analysis (EDS), for example. The number of particles according to this embodiment and the number of particles containing different elemental species are then counted. This allows the ratio of particles according to this embodiment to particles containing different elemental species to be determined.

[0069] Particles may contain alkali metal or alkaline earth metal elements as impurities. When these elements are considered to originate from oxides, the content of these impurity elements relative to the particles is preferably 500 ppm or less. Low content of these elements suppresses aggregation of the particles with the elements. Consequently, dispersions and coatings containing the particles exhibit high stability. Furthermore, the particles are uniformly dispersed in the coating or coating. Consequently, a coating with high hardness and strength can be obtained.

[0070] If the content exceeds 500 ppm, the proportion of agglomerated particles increases. Consequently, sufficient dispersion and coating stability may not be achieved. Alternatively, sufficient hardness and strength of the coating may not be achieved. The content is more preferably 100 ppm or less. Furthermore, alkali metals include Li, Na, K, Rb, Cs, and Fr. Alkaline earth metals include Be, Mg, Ca, Sr, Ba, and Ra.

[0071] In addition, there are cases where the particles contain Ag, Cr, Cu, Mn, Mo, Ni, or Pd as impurity elements. The content of these impurity elements is preferably less than 100 ppm. In addition, the content of U and the content of Th are preferably less than 0.3 ppb. If the content of these elements increases, there is a case where the dispersion is colored. Alternatively, there is a case where a coating with the desired refractive index cannot be obtained. Furthermore, when the particles are used for semiconductor circuits or optical sensors that require high purity and high integration, the elements Ag, Cr, Cu, Mn, Mo, Ni, and Pd are not to be mentioned. For the above-mentioned elements Al, As, B, Bi, Cd, Co, Fe, Ga, Ge, In, Pb, Sb, Sn, Ti, V, Zn, and Zr, the content of each is preferably less than 0.1 ppm. If the content of any of these elements is 0.1 ppm or more, the metal element may cause poor insulation of the circuit, short circuit the circuit, and reduce the light transmittance. This can lead to, for example, a decrease in the dielectric constant of the insulating film, an increase in the impedance of the metal wiring, a delay in response speed, or an increase in power consumption. In particular, when the metal element is U or Th, radioactivity (radioactivity) is generated. Therefore, even in trace amounts, these metal elements can cause malfunction of the semiconductor due to radioactivity. Therefore, the presence of these metal elements is not preferred.

[0072] In order to obtain particles with low content of such elements, the material of the device used to manufacture the particles is preferably free of these elements and has high chemical resistance. Specifically, examples of preferred materials include plastics containing FRP and carbon fiber, and alkali-free glass. In addition, the raw materials used are preferably refined by distillation, ion exchange, or filter removal.

[0073] As an example of a method for obtaining high-purity particles, as mentioned above, one can pre-prepare raw materials with low contents of these elements. Alternatively, methods can be used to suppress the incorporation of these elements from the equipment used to produce the particles. Furthermore, it is also possible to reduce the presence of these elements in particles produced without fully implementing such measures.

[0074] The shape of particle and the shape of cavity are not particularly limited.As the example of these shapes, sphere, ellipsoid (rugby ball) shape, cocoon shape, can enumerate confit shape, chain and dice shape.Wherein, spherical particles have high dispersibility, can be evenly dispersed in coating, therefore preferably.In addition, the shape of the cavity in the shell is preferably along the shape of particle outer shape.This is because, although also relevant with the thickness of shell, when particle is stressed, shell has uniform thickness so that sufficient hardness and intensity can be obtained.And the shape of cavity is also preferably spherical similar to the shape of spherical particles.

[0075] To lower the refractive index and achieve a transparent coating, the void is preferably substantially a single void. Here, "substantially a single void" means that while particles may contain multiple voids within their shells due to aggregation, the proportion of particles containing a single void within their shells is 90% or greater. The proportion of particles containing a single void within their shells is preferably 95% or greater, more preferably 98% or greater, even more preferably 99% or greater, and most preferably 100%.

[0076] The porosity of the particles is preferably 5% to 80%. However, the porosity of the particles is not particularly limited as long as the above-mentioned refractive index is met. If the porosity of the particles is less than 5%, the refractive index will not be sufficiently low. Consequently, the reflection suppression performance will be insufficient. Conversely, if the porosity of the particles exceeds 80%, the hardness and strength may be reduced. The proportion of voids in the particles is more preferably 15% to 70%, and even more preferably 25% to 60%.

[0077] The dispersion medium and concentration of the dispersion liquid are not particularly limited as long as the particles are stably dispersed in the liquid without aggregation or precipitation.

[0078] Examples of dispersion media include water, alcohols, esters, glycols, ethers, ketones, and aprotic polar solvents. These dispersion media may be used alone, or two or more dispersion media may be mixed and used.

[0079] The solid content concentration of the particles is preferably 1% to 40% by mass. If the solid content concentration is less than 1% by mass, processing may take time when producing the coating solution. Conversely, if the solid content concentration is greater than 40% by mass, the stability of the dispersion may decrease. The concentration of the dispersion is more preferably 5% to 35% by mass, and even more preferably 10% to 30% by mass.

[0080] Method for producing particle dispersion The method for producing particles of the present embodiment includes the following first to sixth steps in sequence. In the first step, an alkaline aqueous solution is prepared. In the second step, each solution of the "solution of a silicon-containing compound" and the "aqueous solution of an alkali-soluble compound of an inorganic element other than silicon" is added simultaneously to the alkaline aqueous solution in a molar ratio (MOx / SiO2) of 0.01 to 2.0. Here, SiO2 represents "silicon oxide". MOx represents "alkali-soluble oxide of an inorganic element other than silicon". Thus, a dispersion of composite oxide particles a is prepared. In the third step, each solution of the "solution of a silicon-containing compound" and the "aqueous solution of an alkali-soluble compound of an inorganic element other than silicon" is added in a molar ratio smaller than the molar ratio (MOx / SiO2) in the second step. Thus, a dispersion of composite oxide particles b is prepared. Here, composite oxide particles b have an average particle size of 15 nm to 150 nm. Furthermore, the average particle size of composite oxide particles a obtained in the second step is subtracted from the average particle size, and the value obtained by dividing by 2 is 3 nm to 14 nm. In the fourth step, an acid is added to the dispersion of the composite oxide particles b, and then at least a portion of the elements other than silicon that constitute the composite oxide particles b is removed. In this manner, a dispersion of silica particles is prepared. In the fifth step, the dispersion of silica particles obtained in the fourth step is heated to 150°C to 300°C at a pH of 9.0 to 11.0. In the sixth step, the dispersion of silica particles obtained in the fifth step is heated to 150°C to 400°C at a pH of 5.0 to 8.0. In this manner, the particles of this embodiment are obtained.

[0081] The particles produced in this manner have a low refractive index. Furthermore, the particle shell is dense. Furthermore, the hydrophilic portion of the particle surface is controlled, resulting in the particles having high water resistance. When the particles are used for coating, the coating exhibits excellent reflection suppression performance, is less prone to color unevenness, and has high hardness and strength. Each of the above steps will be described in detail below.

[0082] First process First, prepare an alkaline aqueous solution. Here, the alkaline aqueous solution preferably contains an element that forms an amphoteric oxide. The element that forms an amphoteric oxide means that the oxide containing the element is soluble in an acid with a pH of less than 3 and is soluble in an alkali with a pH of more than 10. More specifically, the alkaline aqueous solution contains at least one element selected from Al, As, B, Bi, Cd, Co, Fe, Ga, Ge, In, Pb, Sb, Si, Sn, Ti, V, Zn and Zr. Among them, Al is preferred from the viewpoint of reacting with silicon-containing compounds and easily forming composite oxide particles. In addition, similarly, Si (silicon) is preferred from the viewpoint of easily reacting with silicon-containing compounds. Examples of alkaline aqueous solutions containing these suitable elements include sodium aluminate aqueous solution, aluminum hydroxide aqueous solution and sodium silicate aqueous solution.

[0083] The alkaline aqueous solution is not particularly limited as long as it has a pH greater than 7. When an amphoteric element is dissolved and present, the pH is preferably 10 or higher. The pH is more preferably 10.5 or higher, even more preferably 11 or higher, and particularly preferably 11 to 13. Furthermore, the alkaline aqueous solution may contain particles containing the aforementioned "element that forms an amphoteric oxide." The particles containing the "element that forms an amphoteric oxide" in the alkaline aqueous solution preferably have an average particle size of 5 to 25 nm.

[0084] Here, if the average particle size of the particles is less than 5 nm, it is difficult to obtain the particles themselves. Conversely, if the average particle size is greater than 25 nm, the refractive index of the particles of this embodiment may not be sufficiently low. Alternatively, it may be difficult to obtain the desired resist film. The average particle size is more preferably 5 nm to 20 nm, and even more preferably 5 nm to 15 nm.

[0085] The oxide conversion concentration of the element that becomes amphoteric oxide in the alkaline aqueous solution is preferably less than 5.0 mass %. If it is in the concentration of this range, it is possible to suppress the aggregation of the particles obtained in the second step. The lower limit of this concentration is not particularly set. For example, from the viewpoint of being able to stably obtain particles with a uniform particle size, i.e., high true sphericity (true sphericity), the lower limit of this concentration is 0.1 mass %. This concentration is more preferably less than 4.0 mass %, and further preferably less than 3.5 mass %.

[0086] Second process In this step, the "silicon-containing compound solution" and the "aqueous solution of an alkali-soluble compound of an inorganic element other than silicon" are simultaneously added to the "alkaline aqueous solution" prepared in the first step. This creates a dispersion of composite oxide particles a. This solution is added to the "alkaline aqueous solution" at a molar ratio (MOx / SiO2) of 0.01 to 2.0. Here, SiO2 represents "silicon oxide" and MOx represents "inorganic element oxide other than silicon."

[0087] Here, examples of the “silicon-containing compound” include at least one selected from silicates, acidic silicic acid solutions, and organic silicon compounds.

[0088] Preferred examples of silicates include one or more silicates selected from alkali metal silicates, ammonium silicates, and organic base silicates. Examples of alkali metal silicates include sodium silicate and potassium silicate. Examples of organic bases include quaternary ammonium salts such as tetraethylammonium salt, and amines such as monoethanolamine, diethanolamine, and triethanolamine. Ammonium silicates and organic base silicates also include alkaline solutions obtained by adding ammonia, quaternary ammonium hydroxides, or amine compounds to a silicic acid solution.

[0089] As the acidic silicic acid solution, for example, a silicic acid solution obtained by treating an alkaline silicic acid aqueous solution with a cation exchange resin to remove the alkali can be used. In particular, an acidic silicic acid solution having a pH of 2 to 4 is preferred.

[0090] The organosilicon compound used in the second step is preferably an organosilicon compound represented by the above formula (8) wherein n is 0 to 3.

[0091] In addition, among the organosilicon compounds represented by formula (8), compounds in which n is 1 to 3 lack hydrophilicity. Therefore, such compounds are preferably treated in advance by hydrolysis so that they can be uniformly mixed in the reaction system. Hydrolysis can be carried out by a known method. When a basic catalyst such as an alkali metal hydroxide, ammonia water or amine is used as a hydrolysis catalyst, these basic catalysts can also be removed after hydrolysis to prepare an acidic solution for use. In addition, when an acidic catalyst such as an organic acid or an inorganic acid is used to prepare a hydrolyzate, it is preferred to remove the acidic catalyst by ion exchange or the like after hydrolysis. In addition, the hydrolyzate of the obtained organosilicon compound is preferably used in the form of an aqueous solution. Here, the aqueous solution means that the solution is not turbid as a gel of the hydrolyzate and has transparency.

[0092] Examples of the organosilicon compound include the organosilicon compounds described in Table 1 below, wherein n is 0 to 3. Examples of preferred organosilicon compounds include TMOS, TEOS, 3-methacryloxypropyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, and 8-methacryloxyoctyltrimethoxysilane.

[0093] Examples of "alkali-soluble compounds of inorganic elements other than silicon" include alkali metal salts and alkaline earth metal salts, ammonium salts, and quaternary ammonium salts of metal and non-metal oxyacids that constitute oxides of inorganic elements other than silicon. Specific examples include sodium aluminate, sodium tetraborate, ammonium zirconyl carbonate, potassium antimonate, potassium stannate, sodium aluminosilicate, sodium molybdate, cerium ammonium nitrate, and sodium phosphate.

[0094] These "silicon-containing compounds" and "compounds of inorganic elements other than silicon" have high solubility in alkaline environments. However, when these compounds are mixed in this high-solubility pH range, the solubility of oxyacid ions such as silicate and aluminate decreases. As a result, these complexes precipitate and form colloidal particles.

[0095] The concentrations of the solution of the "silicon-containing compound" and the aqueous solution of the "alkali-soluble compound of an inorganic element other than silicon" are preferably 0.05% by mass to 10.0% by mass as SiO2 and MOx, respectively. Within these concentration ranges, aggregation between particles is suppressed, resulting in particles with high sphericity.

[0096] Here, if the concentration of the "silicon-containing compound" solution and the concentration of the "alkali-soluble compound of an inorganic element other than silicon" aqueous solution are less than 0.05% by mass (SiO2 and MOx, respectively), the particle growth rate slows. Consequently, production efficiency may decrease until the desired average particle size of the composite oxide particles a is achieved. Conversely, if the concentration exceeds 10.0% by mass, particles may aggregate. This results in particle shape distortion and aggregation.

[0097] For the addition of the solution in this step, the pH of the reaction system is preferably 10 or higher. The preferred reaction temperature is 50°C to 98°C. When the pH and temperature are within these ranges, the addition of the "silicon-containing compound solution" and the "aqueous solution of an alkali-soluble inorganic element compound other than silicon" allows for efficient particle growth of the composite oxide particles a. The pH is more preferably 10.5 or higher, and even more preferably 10.5 to 13. Furthermore, the temperature is more preferably 65°C to 98°C, and even more preferably 80°C to 98°C.

[0098] Next, the molar ratio (MOx / SiO2) will be described.

[0099] If the aforementioned "alkali-soluble compound of an inorganic element other than silicon" is represented as an "oxide," suitable examples of the oxide include one or more oxides of Al2O3, As2O3, B2O3, Bi2O3, CdO, CoO, Fe2O3, Ga2O3, GeO2, In2O3, PbO, Sb2O3, SnO2, TiO2, VO, ZnO2, and ZrO2. Furthermore, examples of these "complex oxides of inorganic elements other than silicon" include zinc oxide / aluminum oxide and indium tin oxide. These oxides are referred to as MOx, and their molar number is used in the calculation of the molar ratio. If multiple types of these oxides are present in the reaction system, the total molar number of each oxide is used. Furthermore, the molar number when the aforementioned "silicon-containing compound" is represented as SiO2 is used in the calculation of the molar ratio.

[0100] The calculation of the molar ratio in the second step does not include the "elements that form amphoteric oxides" used in the first step. Furthermore, alkali metals and alkaline earth metals are not "elements that constitute particles" but rather are treated as impurities. Therefore, these alkali metals and alkaline earth metals are not included as MOx.

[0101] These alkali metals and alkaline earth metals are also treated in the same manner in the third step described later.

[0102] The addition of the "solution of the silicon-containing compound" and the "aqueous solution of the compound of an alkali-soluble inorganic element other than silicon" in the second step is performed simultaneously so that the molar ratio (MOx / SiO2) of these added solutions is 0.01 to 2.0. If the molar ratio (MOx / SiO2) in the second step is within this range, the structure of the composite oxide particles is mainly a structure in which silicon and elements other than silicon are alternately bonded via oxygen. That is, in most structures of the composite oxide particles, oxygen atoms are bonded to silicon atoms through four bonds. In addition, the element M other than silicon is bonded to these oxygen atoms. Therefore, when the element M other than silicon is removed in the fourth step described later, the shape of the composite oxide particles will not be destroyed, and the silicon atoms can also be removed as silicic acid monomers or oligomers along with the element M.

[0103] If the molar ratio is less than 0.01, the proportion of "elements other than silicon" removed in the fourth step described later is small. Consequently, the porosity of the resulting particles may be insufficient. Conversely, if the molar ratio exceeds 2.0, particle growth is inhibited. Consequently, production efficiency until the desired average particle size of the composite oxide particles a is achieved may be reduced. This molar ratio is preferably 0.1 to 2.0, and more preferably 0.2 to 2.0.

[0104] In this manner, in the fourth step described later, the composite oxide particles a obtained in the second step are removed by acid treatment. This creates a cavity inside the outer shell of the resulting particles. Therefore, the composite oxide particles a preferably have a morphology that is easily removed by acid treatment.

[0105] The composite oxide particles a are preferably produced so as to have an average particle diameter (Da) of approximately 10 nm to 145 nm.

[0106] Here, if the average particle size (Da) is less than 10nm, the shell of the particles finally obtained becomes thicker. Therefore, there is a case where the porosity of the particles is not large enough. On the contrary, if it is greater than 145nm, there is a case where the removal of elements M other than silicon is not sufficient in the fourth step described later. As a result, the porosity of the particles is not large enough, so it is difficult to obtain particles with a low refractive index. Furthermore, there is a case where the light scattering of the particles becomes larger. In this case, there is a case where the transparency and haze of the coating become insufficient. The average particle size (Da) is more preferably 25nm to 115nm, more preferably 35nm to 95nm, and particularly preferably 35nm to 75nm.

[0107] The third process In the third step, the "silicon-containing compound solution" and the "aqueous solution of an alkali-soluble inorganic element compound other than silicon" are added to the dispersion of composite oxide particles a so that the molar ratio (MOx / SiO2) is smaller than the molar ratio (MOx / SiO2) of the solution added in the second step. This allows composite oxide particles a to grow, thereby producing a dispersion of composite oxide particles b.

[0108] If the molar ratio (MOx / SiO2) in the second step is set to A and the molar ratio (MOx / SiO2) in the third step is set to B, then the ratio (B / A) is preferably less than 1.0. If the ratio (B / A) is less than 1.0, the silica component of the surface layer of the composite oxide particles becomes more, and the formation of the shell becomes easier. As a result, even if elements other than silicon are removed in the fourth step described later, the shape of the composite oxide particles will not be destroyed. As a result, hollow silica particles can be stably obtained. If the ratio (B / A) is more than 1.0, it is difficult to form a shell with many silica components. Therefore, when elements other than silicon are removed in the fourth step, there is a situation where the composite oxide particles are destroyed. In this case, it becomes difficult to maintain the particle shape. Therefore, there is a situation where it is difficult to obtain hollow silica particles. The ratio (B / A) is more preferably less than 0.8, and further preferably less than 0.6.

[0109] The composite oxide particles b have an average particle size (Db) of 15 nm to 150 nm. Furthermore, the composite oxide particles b are prepared so that a value (Dc) is 3 nm to 14 nm, where the value (Dc) is obtained by subtracting the average particle size (Da) of the composite oxide particles a from the average particle size (Db) of the composite oxide particles b and dividing the result by 2.

[0110] Here, if the average particle size (Db) is less than 15nm, the porosity of the particles becomes smaller. Therefore, there is a case where it is difficult to obtain a low refractive index film. On the contrary, if it is greater than 150nm, the light scattering of the particles becomes larger. Therefore, there is a case where the transparency and haze of the coating become insufficient. The average particle size (Db) is preferably 30nm to 120nm, more preferably 40nm to 100nm, and further preferably 40nm to 80nm. In addition, here, if the value (Dc) is less than 3nm, the shell finally obtained becomes too thin, wherein the value (Dc) is the value obtained by subtracting the average particle size of the composite oxide particles a from the average particle size of the composite oxide particles b and divided by 2 (Dc). Therefore, there is a case where it is difficult to maintain the shape of the particles. On the contrary, the refractive index of the particles having a value (Dc) greater than 14nm will not be low enough. Therefore, there is a case where it is difficult to obtain the desired reflection suppression performance. The value (Dc) is more preferably 3nm to 10nm, further preferably 3nm to 8nm, and particularly preferably 3nm to 6nm.

[0111] The composite oxide particles b form a layer around the composite oxide particles a having a lower molar ratio (MOx / SiO2) than that of the composite oxide particles a. This layer is less susceptible to acid corrosion than the composite oxide particles a, thus forming the outer shell of the resulting particles.

[0112] The "silicon-containing compound" and "alkali-soluble compound of an inorganic element other than silicon" used in the third step are selected from the compounds exemplified in the second step. These compounds may be the same as those used in the second step. Alternatively, compounds different from the compounds exemplified in the second step may be used.

[0113] The pH of the dispersion of the composite oxide particles a used in the third step is preferably 10 or higher.

[0114] The concentrations of the solution of the "silicon-containing compound" and the aqueous solution of the "alkali-soluble compound of an inorganic element other than silicon" are preferably 0.05% by mass to 3.0% by mass as SiO2 and MOx, respectively. When the concentrations of the compounds in these solutions fall within these ranges, aggregation of the composite oxide particles a obtained in the second step is suppressed. As a result, monodispersed particles can be obtained.

[0115] During the addition of the solution in the third step, the pH of the reaction system is preferably 10 or higher. The preferred reaction temperature is 50°C to 98°C. Within these pH and temperature ranges, the addition of the "silicon-containing compound solution" and the "aqueous solution of an alkali-soluble inorganic element compound other than silicon" allows for efficient growth of the composite oxide particles b. The pH of the reaction system is more preferably 10.5 or higher, and even more preferably 10.5 to 13. Furthermore, the reaction temperature is more preferably 65°C to 98°C, and even more preferably 80°C to 98°C.

[0116] The fourth process In the fourth step, an acid is added to the dispersion of the composite oxide particles b to remove at least a portion of the elements other than silicon that constitute the composite oxide particles b. Thus, a dispersion of silica particles is prepared. These elements can be dissolved and removed using, for example, an inorganic acid or an organic acid. Alternatively, these elements can be removed by ion exchange by contacting the dispersion of silica particles with a cation exchange resin. Alternatively, these elements can be removed by a combination of these methods.

[0117] The concentration of the dispersion of the composite oxide particles b also varies depending on the treatment temperature, but is preferably 0.1% by mass to 30% by mass based on the composite oxide particles b in terms of oxide.

[0118] Here, if the concentration is less than 0.1% by mass, the amount of silicon dioxide dissolved increases. Therefore, it may be difficult to maintain the shape of the composite oxide particles. Furthermore, due to the low concentration, the processing efficiency is reduced. Conversely, if the concentration exceeds 30% by mass, the dispersibility of the particles may become insufficient. Furthermore, for composite oxide particles containing a high content of elements other than silicon, it may be difficult to uniformly or effectively remove the elements other than silicon. The concentration of the dispersion of composite oxide particles b is more preferably 0.5% to 25% by mass.

[0119] The removal of the above elements is preferably performed until the molar ratio (MOx / SiO2) of the obtained particles becomes 0.03 or less.

[0120] Here, if the molar ratio (MOx / SiO2) exceeds 0.03, it may be difficult to obtain the desired refractive index of the final particles or the strength required to maintain the shape of the particles. The molar ratio (MOx / SiO2) is more preferably 0.01 or less.

[0121] After at least a portion of the elements other than silicon are removed, the silica particle dispersion can be cleaned as needed using a known cleaning method such as ultrafiltration. Cleaning removes at least a portion of the dissolved elements other than silicon. In this case, for example, by pre-removing a portion of the alkali metal ions in the dispersion and then performing ultrafiltration, a silica particle dispersion with high dispersion stability can be obtained.

[0122] Alternatively, the dispersion after "at least a portion of the elements other than silicon have been removed" may be contacted with at least one of a cation exchange resin and an anion exchange resin. This also allows for the removal of a portion of dissolved elements other than silicon, alkali metal ions, and the like. Efficient cleaning can be achieved by heating the dispersion during cleaning.

[0123] By performing washing in this manner, the content of alkali metals and the like as impurities in the finally obtained particles can be effectively reduced.

[0124] Fifth process In this step, the silica particle dispersion obtained in the fourth step is heated to 150°C to 300°C at a pH of 9.0 to 11.0. This densifies the particles, resulting in a coated substrate having high hardness and strength.

[0125] Here, if the pH is less than 9.0, the densification of the particles is insufficient. Therefore, there is a case where the hardness or strength of the coated substrate becomes insufficient. Conversely, if the pH is greater than 11.0, the particles will dissolve excessively. As a result, there is a case where particles with cavities inside cannot be obtained. The pH is preferably 9.5 to 11.0, and more preferably 10.0 to 10.8.

[0126] Furthermore, if the heating temperature is less than 150°C, the particles may not be fully densified. This may result in insufficient hardness and strength of the coated substrate. Conversely, if the temperature exceeds 300°C, the particles may dissolve excessively. Consequently, particles with internal cavities may not be obtained. The temperature is preferably 160°C to 280°C, more preferably 180°C to 280°C.

[0127] The concentration of the silica particle dispersion in this step is preferably 0.1% by mass to 30% by mass in terms of silica.

[0128] Here, if the concentration is less than 0.1% by mass, the particles will dissolve excessively. Therefore, there may be cases where particles with cavities inside cannot be obtained. In addition, due to the low concentration, the processing efficiency becomes low. On the other hand, if the concentration is higher than 30% by mass, there may be cases where the particles aggregate. Alternatively, there may be cases where the densification of the particles becomes insufficient. In these cases, there may be cases where the hardness or strength of the substrate with the coating becomes insufficient. The concentration of the dispersion of the composite oxide particles b is more preferably 0.5% to 25% by mass.

[0129] Sixth process In the sixth step, the silica particle dispersion obtained in the fifth step is heated to 150°C to 400°C at a pH of 5.0 to 8.0. This improves the water resistance of the particles. Consequently, a coated substrate with excellent anti-reflection properties that is less prone to color unevenness can be obtained.

[0130] Here, if the pH is less than 5.0, the solubility of the particles is high. Therefore, hydrophilic sites are easily formed on the particle surface. As a result, the water resistance of the film-coated substrate may become insufficient. Conversely, if the pH is greater than 8.0, the water resistance of the film-coated substrate may also become insufficient. The pH is preferably 5.5 to 7.5, and more preferably 6.0 to 7.0.

[0131] Furthermore, if the heating temperature is less than 150°C, the particles may not dissolve. In this case, the reduction of the hydrophilic portion of the particle surface may be insufficient. As a result, the water resistance of the coated substrate may become insufficient. Conversely, if the temperature exceeds 400°C, the particles may dissolve excessively. As a result, particles with cavities inside may not be obtained. The temperature is preferably 160°C to 300°C, and more preferably 180°C to 250°C.

[0132] The concentration of the silica particle dispersion in the sixth step is preferably 0.1% by mass to 30% by mass in terms of silica.

[0133] Here, if the concentration is less than 0.1% by mass, the particles will dissolve excessively. As a result, particles with internal cavities may not be obtained. In addition, due to the low concentration, the processing efficiency becomes low. On the other hand, if the concentration exceeds 30% by mass, the particles may aggregate. In this case, the water resistance of the particles becomes insufficient, and the reflection suppression performance of the coated substrate may become insufficient. In addition, color unevenness may occur. Alternatively, the transparency may be reduced. The concentration of the dispersion of the composite oxide particles b is more preferably 0.5% to 25% by mass.

[0134] The particles obtained in the sixth step can also be surface-treated by adding an organosilicon compound to the particles. As the organosilicon compound used, it is preferred to use an organosilicon compound represented by the above formula (8) in which n is 0 to 3. Here, when using an organosilicon compound in which n is 0, it is preferred to use a partial hydrolyzate of the organosilicon compound. By introducing a functional group, the dispersibility in the coating liquid or the coating is improved. As a result, the substrate with the coating has sufficient hardness and strength. As the organosilicon compound, a single compound can be used. Alternatively, two or more compounds can be used in combination.

[0135] As a method for surface treatment of particles, first, a dispersion of particles is prepared. As a dispersion medium, alcohols such as methanol or ethanol are preferably used. The organosilicon compound represented by formula (8) is added to the dispersion in a specified amount. Next, the organosilicon compound is hydrolyzed. For the hydrolysis, water may be added as needed. The ratio (Mw / Mo) of the number of moles of water used (Mw) to the number of moles of the organosilicon compound (Mo) is preferably 1 or more.

[0136] Here, when the ratio (Mw / Mo) is less than 1, hydrolysis may become insufficient. As a result, for example, the transparency and haze of the coating may become insufficient. There is no particular upper limit for this ratio. If the ratio exceeds 500, the hydrolysis reaction becomes intense. As a result, the organosilicon compounds may polymerize with each other. In this case, effective organosilicon compound treatment of the particle surface may be difficult. The ratio is more preferably 1 to 100.

[0137] In addition, during the hydrolysis, an acid or base may be used as a hydrolysis catalyst as needed. Ammonia is preferred. If ammonia is used, the catalyst remaining in the dispersion can be easily removed. As a result, the stability of the dispersion can be easily maintained. The number of moles of ammonia used (M N ) to the molar number (Mo) of the organosilicon compound (M N / Mo) is preferably in the range of 0.05 to 50.

[0138] Here, in the ratio (M NIf the ratio (Mo / Mo) is less than 0.05, hydrolysis may be insufficient. In this case, for example, the transparency and haze of the coating may be insufficient. If the ratio exceeds 50, the hydrolysis reaction becomes intense. As a result, the organosilicon compounds may polymerize with each other. As a result, effective organosilicon compound treatment of the particle surface may be difficult. The ratio is more preferably 0.1 to 10.

[0139] The surface treatment is preferably performed in a homogeneous system. In order to promote the reaction between the particles and the organosilicon compound, the dispersion containing the particles of the added organosilicon compound is preferably heated in the homogeneous system at a temperature below the boiling point of the dispersion medium (e.g., room temperature to 120°C) for 0.5 to 48 hours.

[0140] This surface treatment chemically bonds the organosilicon compound to the particle surface. When the surface-treated particles are used in a substrate with a reflection-reducing coating, the particles exhibit high dispersibility within the coating. Consequently, a substrate with a coating having excellent strength can be obtained.

[0141] Examples of organosilicon compounds include those listed in Table 1. A single organosilicon compound may be contained in the particles. Alternatively, multiple compounds may be contained in the particles. For surface treatment, the particles can be treated with a single organosilicon compound, or with a mixture of multiple compounds. Furthermore, the particles can be treated with a single compound followed by a mixture of multiple compounds. Alternatively, the particles can be treated in stages using multiple compounds separately.

[0142] Table 1

[0143] The amount of the organosilicon compound is preferably such that the solid content (R n -SiO (4-n) / 2 The particles are surface-treated so that the amount of the additive is 1.0 to 30 parts by mass.

[0144] The physical properties and preferred ranges of the particles finally obtained by the production method of this embodiment are the same as those of the above-described particles.

[0145] Coating liquid for film formation The particles of this embodiment can be used in a coating solution for film formation. The coating solution comprises particles, a matrix-forming component, and a dispersion medium. The dispersion medium comprises at least one of water and an organic dispersion medium. In addition, additives such as a polymerization initiator, a leveling agent, or a surfactant may also be included.

[0146] Relative to the total amount of solid components such as the particles and matrix forming components contained, the concentration of the particles in the coating solution is preferably 5% to 95% by mass in terms of solid components. Here, if the concentration of the particles is less than 5% by mass, there is a situation where the refractive index of the coating film cannot be fully reduced. On the contrary, if it is greater than 95% by mass, there is a situation where cracks occur in the coating film. In this case, there is a situation where the adhesion of the particles to the substrate becomes insufficient. As a result, there is a situation where hardness, strength, transparency and haze etc. become insufficient. The concentration of the particles is more preferably 10% to 85% by mass, and further preferably 20% to 70% by mass.

[0147] Examples of matrix-forming components include inorganic matrix-forming components and organic resin matrix-forming components. More specific examples of matrix-forming components include polycondensates of organosilicon compounds, ultraviolet curable resins, thermosetting resins, and thermoplastic resin matrices.

[0148] Examples of the ultraviolet curable resin include (meth)acrylic resins, γ-glycidyl ether oxide resins, urethane resins, and vinyl resins.

[0149] Examples of the thermosetting resin include urethane resin, melamine resin, silicone resin, butyral resin, reactive silicone resin, phenol resin, epoxy resin, unsaturated polyester resin, and thermosetting acrylic resin.

[0150] Examples of the thermoplastic resin include polyester resin, polycarbonate resin, polyamide resin, polyphenylene ether resin, thermoplastic acrylic resin, vinyl chloride resin, fluororesin, vinyl acetate resin, and silicone rubber.

[0151] These resins may also be copolymers or modified forms containing two or more resins. Alternatively, two or more resins may be used in combination. In addition, these resins may also be emulsion resins, water-soluble resins, or hydrophilic resins.

[0152] From the perspectives of particle dispersibility and ease of forming a film-coated substrate, the components forming these resins are preferably monomers or oligomers.

[0153] Relative to the total amount of solid components such as the particles and matrix-forming components contained, the concentration of the matrix-forming components in the coating solution is preferably 5% to 95% by mass in terms of solid components. Here, if the concentration of the matrix-forming components is less than 5% by mass, film formation is difficult. In addition, even if a film is obtained, there is a situation where cracks are generated in the film. In this case, there is a situation where the adhesion between the particles and the substrate becomes insufficient. As a result, there is a situation where hardness, strength, transparency and haze become insufficient. On the contrary, if it is greater than 95% by mass, the amount of the particles is small. Therefore, there is a situation where the refractive index will not be fully reduced. The concentration of the matrix-forming components is more preferably 15% to 90% by mass, and further preferably 30% to 80% by mass.

[0154] As an organic dispersion medium, a dispersion medium that can uniformly disperse particles and dissolve or disperse additives such as matrix-forming components and polymerization initiators can be used. Among them, hydrophilic dispersion media and polar dispersion media are preferred. As shown in Table 2, examples of hydrophilic dispersion media include alcohols, esters, glycols, and ethers. In addition, examples of polar dispersion media include esters, ketones, and aprotic dispersion media. These dispersion media can be used alone. Alternatively, two or more dispersion media can be used in combination.

[0155] Table 2

[0156] As the additive, any conventional additive that can be used for film formation can be appropriately used. For example, a polymerization initiator or a leveling agent can be used to promote polymerization of the matrix-forming component or enhance film-forming properties.

[0157] Examples of the polymerization initiator include the polymerization initiators shown in Table 3.

[0158] Examples of the leveling agent include acrylic leveling agents, silicone leveling agents, and acrylic silicone leveling agents. From the viewpoint of improving strength, it is preferable to use a fluorine-based leveling agent among these leveling agents.

[0159] To calculate the concentration of these additives in the coating solution, for convenience, the additives contained as solid components in the coating solution during film formation are counted as matrix-forming components. After film formation, these additives are counted as the matrix.

[0160] Table 3

[0161] The solid content concentration of the coating liquid (the ratio of the total solid content of the particles and the solid content of the matrix-forming component to the coating liquid) is preferably 0.1% by mass to 60% by mass.

[0162] If the solids concentration of the coating liquid is less than 0.1% by mass, processing time is required when producing the film-coated substrate, resulting in reduced productivity. Conversely, if it exceeds 60% by mass, the stability of the coating liquid may decrease. Furthermore, the viscosity of the coating liquid increases, resulting in reduced coating properties. The solids concentration of the coating liquid is more preferably between 1% and 50% by mass.

[0163] Substrate with coating The coating liquid described above can be used to form a coating film on a substrate. Such a substrate with a coating film is used, for example, in display devices requiring transparency.

[0164] Specifically, the coating liquid applied on the substrate is dried and irradiated with ultraviolet rays. Thus, a film is formed on the substrate. The coating method of the coating liquid is not particularly limited as long as it is a method that can form a film on the substrate. As examples of the coating method used, well-known methods including spraying, spin coating, roller coating, rod coating, slit coater printing, gravure printing and micro-gravure printing can be cited. During the drying, for example, the coating liquid is heated to about 50°C to 150°C. Thus, the dispersion medium is evaporated and removed. Thereafter, the dried coating liquid is irradiated with ultraviolet rays. Thus, the polymerization of the resin component is promoted. In this way, the hardening of the film can be achieved. The film is mainly formed by the matrix (resin) component and particles.

[0165] The ratio of the solid content of the coating film containing the particles and the matrix-forming components in the coating liquid is directly the ratio of the particle component to the matrix in the coating film. As mentioned above, the additives in the coating liquid that remain as solids are counted as the matrix.

[0166] The film thickness of the coating can be appropriately selected according to the intended use. For example, if it is a transparent coating, the preferred film thickness is 80 nm to 350 nm. Here, if the film thickness is thinner than 80 nm, the hardness or strength of the coating may be insufficient. In addition, there may be cases where the coating is too thin and sufficient reflection suppression performance cannot be obtained. On the contrary, if the film thickness is thicker than 350 nm, the coating is prone to cracking. Therefore, there may be cases where the strength of the coating becomes insufficient. In addition, due to the excessive thickness of the coating, there may be cases where the transparency and haze become insufficient. In this case, there may be cases where the reflection suppression performance is reduced. The film thickness is more preferably 85 nm to 220 nm, and even more preferably 90 nm to 110 nm.

[0167] The refractive index of the transparent coating is preferably 1.10 to 1.45. However, it is difficult to obtain a transparent coating with a refractive index less than 1.10. If the refractive index exceeds 1.45, reflection suppression performance may be insufficient depending on the refractive index of the substrate or other films formed as needed below the transparent coating. The refractive index of the transparent coating is more preferably 1.10 to 1.40, and even more preferably 1.10 to 1.35.

[0168] The light transmittance of the coated substrate is preferably 85.0% or higher. If the light transmittance is less than 85.0%, the image clarity of a display device may be insufficient. The light transmittance is more preferably 90.0% or higher.

[0169] Furthermore, the haze of the film-coated substrate is preferably 2.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

[0170] Furthermore, the reflectance of the coated substrate is preferably 2.0% or less, more preferably 1.5% or less, further preferably 1.0% or less, and particularly preferably 0.7% or less.

[0171] The hardness of the coating is preferably H or higher. If the hardness is lower than H, the hardness may be insufficient as a hard coating film. The hardness is more preferably 2H or higher, and even more preferably 3H or higher.

[0172] By specifying the load / cm 2 The strength of the film is evaluated by sliding #0000 steel wool 50 times under the specified load. Preferably, no streak-like scratches are observed on the film surface when the specified load is 200 g. More preferably, no scratches are observed when the specified load is 500 g. Even more preferably, no scratches are observed when the specified load is 1000 g.

[0173] The water resistance of the coating is evaluated by visually observing a drop mark, wherein the drop mark is a drop mark after distilled water added to the substrate with the coating is left for 30 minutes and then wiped. The drop mark preferably disappears within 30 minutes after wiping. Here, if the drop mark is observed for more than 30 minutes, there is a situation where the reflection in the display device becomes uneven. In this case, there is a situation where uneven color is visually recognized. The drop mark more preferably disappears within 5 minutes after wiping. More preferably, no drop mark is observed immediately after wiping.

[0174] The substrate can be any known substrate. Preferred examples of substrates include transparent resin substrates such as polycarbonate, acrylic resin, polyethylene terephthalate, triacetyl cellulose (TAC), polymethyl methacrylate resin, and cycloolefin polymer from the viewpoints of transparency, flexibility, and toughness. The thickness of the substrate is not particularly limited. Considering durability and operability, the thickness of the substrate is preferably 10 μm to 100 μm, more preferably 20 μm to 80 μm.

[0175] To evaluate the adhesion between the film and the substrate, first, apply cellophane tape to the surface of the film-coated substrate, which has been scratched in a grid pattern (a rising mesh pattern) with a knife. Then, peel off the cellophane tape. The greater the number of remaining grid patterns, the harder it is to peel the film from the substrate, indicating greater adhesion between the film and the substrate, which is preferred.

[0176] In addition to such a substrate, a substrate with a coating formed thereon with another coating may be used. Examples of the other coating include conventionally known hard coating films, primer films, high refractive index films, and conductive films.

[0177] Hereinafter, embodiments of the present disclosure will be described.

[0178] Example 1 Preparation of particle dispersion To 65.6 g of an aqueous dispersion of silica particles (Cataloid SI-30, manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle size 12 nm, solids concentration 30.5% by mass) was added 9934.4 g of pure water. Subsequently, 10.0 kg of an alkaline aqueous solution having a pH of 12.5 was prepared by adding a 1% by mass aqueous NaOH solution (first step).

[0179] Next, 67.0 kg of an aqueous sodium silicate solution having a SiO2 concentration of 1.5% by mass and 67.0 kg of an aqueous sodium aluminate solution having an Al2O3 concentration of 0.5% by mass were added to the alkaline aqueous solution heated to 80°C. This was then washed by centrifugal sedimentation to obtain a dispersion of composite oxide particles (a1). The composite oxide particles (a1) had an average particle size of 49 nm (second step).

[0180] Next, 162.0 kg of a sodium silicate aqueous solution having a SiO2 concentration of 1.5% by mass and 54.0 kg of a sodium aluminate aqueous solution having a Al2O3 concentration of 0.5% by mass were added to the dispersion of the composite oxide particles (a1) heated to 98°C. The dispersion was then washed using an ultrafiltration membrane to adjust the solid content concentration to 13% by mass. The dispersion with the adjusted solid content concentration was then filtered through a capsule filter having a pore size of 1 μm. Thus, a dispersion of composite oxide particles (b1) was obtained. The composite oxide particles (b1) had an average particle size of 60 nm (third step).

[0181] To 5000 g of the dispersion of composite oxide particles (b1) was added 11250 g of pure water. Furthermore, the pH was adjusted to 1.0 by dropwise addition of concentrated hydrochloric acid (35.5% by mass). While adding 10 L of a hydrochloric acid aqueous solution at pH 3 and 5 L of pure water, the dissolved aluminum salt was separated and washed using an ultrafiltration membrane. Thus, silica particles (c1) having a concentration of 10% by mass were obtained (step 4).

[0182] Next, aqueous ammonia was added to 500 g of the dispersion of silica particles (c1). The pH of the dispersion was adjusted to 10.6. The dispersion, transferred to a pressure vessel, was heated to 250°C and maintained at that temperature for 10 hours. The dispersion was then cooled to room temperature. Thus, silica particles (d1) were obtained (step 5).

[0183] Next, ion exchange treatment was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation). The pH of the dispersion was then adjusted to 6.5 by adding aqueous ammonia. The dispersion, transferred to a pressure-resistant container, was heated to 250° C. and maintained at that temperature for 10 hours. The dispersion was then cooled to room temperature. Thus, silica particles (e1) were obtained (step 6).

[0184] Thereafter, 800 g of a cation exchange resin (Diyaon SK1B manufactured by Mitsubishi Chemical Corporation) was used to perform an ion exchange treatment for 3 hours. Next, 400 g of an anion exchange resin (Diyaon SA20A manufactured by Mitsubishi Chemical Corporation) was used to perform an ion exchange treatment for 3 hours. Thereafter, further, 400 g of a cation exchange resin (Diyaon SK1B manufactured by Mitsubishi Chemical Corporation) was used to perform cleaning by ion exchange treatment at 80°C for 3 hours. Thus, an aqueous dispersion of "particles having a silicon-containing shell and a cavity inside the shell (primary particles)" (P1) was obtained.

[0185] The solvent of the aqueous dispersion of the particles (P1) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of the particles (P1) having a solid content concentration of 20% by mass.

[0186] Surface treatment of particles using organosilicon compounds To 200 g of the methanol dispersion of the particles (P1), 0.4 g of aqueous ammonia having a concentration of 28% by mass and 4.0 g of pure water were added, and the dispersion was stirred at room temperature for 0.5 hours.

[0187] Next, 4.0 g of γ-methacryloxypropyltrimethoxysilane (KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.) as an organic silicon compound was added to the methanol dispersion (the solid content (R n -SiX 4-n ) is calculated as 10 parts by mass). Then, the dispersion was stirred at 50° C. for 24 hours. Thus, a dispersion of surface-treated particles (S1) was obtained.

[0188] The particles and their dispersions were measured by the following methods.

[0189] The characteristics of the particles in each production process are shown in Tables 4 and 5. In addition, the properties of the particles and the dispersion are shown in Tables 6 and 7 (the same applies to the following Examples and Comparative Examples).

[0190] (1) Average particle size A particle dispersion diluted to 0.01% by mass was dried on a collodion film of a copper mesh for electron microscopy. Next, a photograph of the dried dispersion was taken at a predetermined magnification using a field emission transmission electron microscope (HF5000, manufactured by Hitachi High-Technologies). Images of 300 randomly selected particles from the resulting TEM photograph were processed. Thus, the area of ​​the particles was determined. The equivalent circle diameter was determined from the area. The average value of the equivalent circle diameters was defined as the average particle size of the particles.

[0191] (2) Refractive index Collect the particle dispersion in an evaporator to evaporate the dispersion medium. Then, vacuum dry the resulting residue at 120°C for 24 hours. This will yield a particle powder. Add 2 or 3 drops of a standard refractive index liquid with a known refractive index to a glass plate. Next, mix the standard refractive index liquid and the powder. Perform this operation using various standard refractive index liquids. The refractive index of the standard refractive index liquid when the mixture becomes transparent is defined as the refractive index of the particles.

[0192] (3) Specific surface area (A1) obtained by the BET method using water vapor gas The particle dispersion was heated to 105°C, maintained at this temperature for 3 hours, and then dried. The resulting powder was vacuum degassed using a specific surface area measurement device (Belsorp mini II, manufactured by BEL Japan Co., Ltd.) while water vapor was adsorbed onto the powder. The specific surface area (A1) was calculated using the BET method based on the amount of adsorbed gas for each measurement gas.

[0193] (4) Specific surface area (A2) obtained by the BET method using nitrogen gas The powder was vacuum degassed using a specific surface area measuring device (Belsorp mini II, manufactured by BEL Japan Co., Ltd.) in the same manner as the particle specific surface area (A1) described above, while nitrogen gas was adsorbed onto the powder. The specific surface area (A2) was calculated using the BET method based on the amount of nitrogen adsorbed.

[0194] (5) Mass increase due to moisture absorption The particle dispersion was collected in an evaporator to evaporate the dispersion medium. The resulting residue was then heated to 200°C and maintained at this temperature for 3 hours before drying. The dried residue was then placed at 25°C in an atmosphere with a relative humidity of 90% for 24 hours. The resulting particle powder was then mass-measured, where the mass of the powder was measured before and after the 24-hour exposure at 25°C in an atmosphere with a relative humidity of 90%. The difference in mass between the particles before and after exposure was used to determine the increase in particle mass.

[0195] (6) Specific surface area (A3) calculated from the average particle size The specific surface area (A3) was determined by the following formula (5) using the average particle size of the particles.

[0196] A3=6000 / Sd / D ···Formula (5) (Where Sd represents the density of the particles (g / cm 3 ), D represents the average particle size of the particles (nm)

[0197] (7) Number density of silanol groups on the particle surface The number density of silanol groups in the particles is calculated based on the Sears number and the specific surface area. Specifically, the number density of silanol groups is determined based on the above-mentioned formula (1) and formula (2).

[0198] The Sears number is determined by titration with NaOH in accordance with the description of Sears in Analytical Chemistry 28 (1956), 12, 1981-1983. Specifically, an evaporator is used to replace the solvent of the methanol dispersion of the particles with water. Next, the aqueous dispersion of the particles is diluted with pure water in such a way that the concentration of the silica particles becomes 1% by mass. After adding 30 g of sodium chloride to 150 g of the diluted aqueous dispersion of the particles, the pH of the aqueous dispersion is adjusted to 4.0 with hydrochloric acid. A 0.1 N aqueous sodium hydroxide solution is added dropwise to the pH-adjusted aqueous dispersion at 0.1 ml / sec. The Sears number is expressed by the amount of NaOH aqueous solution required to achieve a pH of 9.0 in the aqueous dispersion. (That is, the Sears number is the titration amount of the 0.1 N NaOH aqueous solution relative to 1.5 g of particles). In addition, an automatic titrator is used for the titration using the 0.1 N NaOH aqueous solution. The titration rate is fixed at 0.1 mL / sec.

[0199] (8) Specific surface area (A4) based on pulsed NMR The relaxation time of the particle dispersion and the relaxation time of the dispersion medium were measured using pulsed NMR (Acorn Area manufactured by Xigo nanotools). The specific surface area (A4) was calculated using the formula (3) and formula (4). In addition, the measurement conditions were a magnetic field of 0.3 T and a measurement frequency of 13 MHz. The measurement kernel was 1 H. As the measurement method, the CPMG pulse sequence method was adopted. The sample amount was 1 mL. The Ka value was set to 0.000168. The measurement temperature was 25°C. Here, the following value is used as the Ka value: the value calculated by the above-mentioned formula (5) to formula (7) after performing pulse NMR measurement on a methanol dispersion of surface-treated particles (P1) with a solid content concentration of 20.0% by mass and 25°C, and a methanol dispersion medium.

[0200] (9) Particles based on 29 The ratio of the area of ​​the peak indicating the Q4 structure in Si-NMR analysis In the solid 6 mmφ sample tube probe of the NMR apparatus (VNMRS-600 manufactured by Agilent), the sample was not rotated and the dispersion of particles placed in a dedicated zirconium oxide sample tube was measured using the single pulse non-decoupling method. Polydimethylsiloxane was used as a secondary standard. The chemical shift of polydimethylsiloxane was set to -34.44 ppm. Based on the obtained spectrum, the analysis software Origin was used to calculate the area of ​​each peak by waveform separation processing. More specifically, in 29In Si-NMR spectroscopy, the value of (Q4 / ∑Q) × 100 is calculated based on the area of ​​the peak appearing at a chemical shift of -78 ppm to -88 ppm (Q1), the area of ​​the peak appearing at a chemical shift of -88 ppm to -98 ppm (Q2), the area of ​​the peak appearing at a chemical shift of -98 ppm to -108 ppm (Q3), and the area of ​​the peak appearing at a chemical shift of -108 ppm to -120 ppm (Q4). Here, ∑Q = Q1 + Q2 + Q3 + Q4.

[0201] (10) Particle shell thickness, porosity, and density The average particle size of the particle is the same as that of the particle, and the average volume of the particle is calculated according to the TEM photo. The average particle size of the particle is the same as that of the particle, and the average volume of the particle is calculated according to the TEM photo. The average particle size of the particle is the same as that of the particle, and the average volume of the particle is calculated according to the TEM photo. The area of ​​the cavity of the particle is calculated according to its area. The circle equivalent diameter is defined as the average of the cavity diameter. The average particle size of the particle and the average difference of the cavity diameter are divided by 2 and the value obtained is calculated as the thickness of the particle shell. In addition, the average volume of the particle and the average volume of the cavity when the shape of the particle and the cavity is assumed to be a true sphere is obtained. As the ratio of the average volume of the cavity relative to the average volume of the particle, the voidage is calculated. In addition, the density (Sd) of the particle is obtained by the voidage obtained, the ratio of the constituent components of the particle, its density.

[0202] (11) Functional groups contained in the particle shell The presence or absence of functional groups contained in the particle shell and the types thereof were determined by the following method.

[0203] First, the dispersion was dried by an evaporator and then dried at 150° C. A Fourier transform infrared spectrometer (FT-IR) (FT / IR-6100 manufactured by JASCO Corporation) was used to analyze the dispersion by diffuse reflection method in the wave number region of 700 cm -1 ~4000cm -1 , resolution 4.0cm -1 The dry powder was measured under the conditions of 50 cumulative measurements. A TGS detector was used. Functional groups were identified by referring to the SDBS database of organic compound spectra (https: / / sdbs.db.aist.go.jp (National Institute of Advanced Industrial Science and Technology, 2021.01)) based on the peaks detected in the resulting spectrum.

[0204] (12) Solid content of organosilicon compound having functional groups The dispersion was centrifuged for 30 minutes using a small ultracentrifuge (CS150GXL manufactured by Hitachi Koki Co., Ltd.) at a temperature of 10°C and a rotation speed of 1,370,000 rpm (1,000,000G). The precipitate recovered from the treated liquid was vacuum dried at 120°C for 24 hours to obtain a particle powder. The mass reduction of the powder before and after heating at 500°C was measured using a thermogravimetric differential thermal analyzer (TG / DTAEXSTAR6000 MSD manufactured by Hitachi High-Technologies Co., Ltd.). The silicon content from the organosilicon compound was calculated from the difference in the amount of particles before and after heating. Next, the calculated silicon content was converted into a solid component (R ) from the organosilicon compound corresponding to the structure of the organosilicon compound used for surface treatment. n -SiO (4-n) / 2 Thus, the solid content of the organosilicon compound having a functional group was determined.

[0205] (13) Particle shape and the ratio of solid particles The shape of the particles and the ratio of the number of solid particles to the total particle size were determined from the TEM images, similar to the average particle size of the particles described above.

[0206] (14) Content of metal elements and metal impurities in particles The content of the metallic elements (alkali metals, alkaline earth metals, Al, Ag, Co, Cr, Cu, Fe, In, Mn, Ni, Pd, Sb, Si, Sn, Th, Ti, U, Zn and Zr, etc.) in the particles is obtained by the following method. First, after dissolving the particles with hydrofluoric acid, the hydrofluoric acid is removed by heating. Afterwards, pure water is added as needed. An ICP inductively coupled plasma emission spectrometry mass spectrometer (ICPM-8500 manufactured by Shimadzu Corporation) is used to measure the resulting solution. In addition, the content of the metallic elements other than the above-mentioned impurity elements is calculated in such a way that the total amount of the metallic elements other than the carbon contained in the particles is calculated as 100 parts by mass based on an oxide benchmark.

[0207] Production of coating liquid for forming reflection-reducing film The dispersion medium of the methanol dispersion of the produced particles (S1) was replaced with methyl isobutyl ketone (MIBK) using an evaporator, thereby preparing an MIBK dispersion of particles (S1) having a solid content concentration of 20.5% by mass.

[0208] 8.05 g of an MIBK dispersion of the particles (S1), 1.07 g of a multifunctional acrylate resin (Lite Acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), 0.12 g of a bifunctional acrylate resin (SR-238F manufactured by Tomoe Industries Co., Ltd.), 0.05 g of a reactive silicone oil (KF-2012 manufactured by Shin-Etsu Chemical Co., Ltd.), 0.37 g of a silicone-modified polyurethane acrylate (Zhiguang UT-4314 manufactured by Mitsubishi Chemical Co., Ltd., solid content concentration 30% by mass), 0.09 g of a photopolymerization initiator (Omnirad TPO H manufactured by IGM RESINS BV), 64.65 g of isopropyl alcohol, and MIBK were added. 9.60 g of propylene glycol and 16.00 g of isopropylene glycol were mixed to prepare a coating liquid for forming a reflection-reducing film having a solid content concentration of 3.0% by mass.

[0209] Manufacturing of coated substrates A hard coating (ELCOM HP-1004 manufactured by JGC Catalysts & Chemicals Co., Ltd.) was applied to a TAC film (FT-PB40UL-M manufactured by Fujifilm Corporation, thickness 40 μm, refractive index 1.51) by a bar coating method (#18). The applied hard coating was dried at 80°C for 120 seconds. Thereafter, the film was heated to 300 mJ / cm 2 The hard coating was cured by irradiating the substrate with ultraviolet light. Thus, a substrate with a hard coating film was produced. The hard coating film had a thickness of 8 μm. This hard coating film was used in all examples and comparative examples.

[0210] Next, a coating liquid for forming a reflection-reducing film was applied to the hard coating film by a bar coating method (#4). The coating liquid was dried at 80°C for 120 seconds. Thereafter, a 600 mJ / cm 2 The coating liquid was irradiated with ultraviolet rays to cure it. Thus, a substrate with a transparent coating film for suppressing reflection was produced.

[0211] The following properties of the film-coated substrate were measured, and the results are shown in Tables 8 and 9 (the same applies to the following Examples and Comparative Examples).

[0212] (15) Film thickness of hard coating film The thickness of the hard coating film was measured at five randomly selected locations on the coating using a digital gauge (Ono Sokki Gauge ST-0230 and Digital Gauge DG-5100). The average of the obtained thicknesses was defined as the thickness of the hard coating film.

[0213] (16) Film thickness and reflectivity of the transparent coating for reflection suppression The film thickness and reflectance at a wavelength of 550 nm of the coating were measured using an ellipsometer (EMS-1 manufactured by ULVAC Co., Ltd.) The measured values ​​were classified according to the following criteria to evaluate the reflectance. Evaluation criteria: Below 0.7%: A More than 0.7% and less than 1.0%: B More than 1.0% and less than 1.5%: C More than 1.5% and less than 2.0%: D Greater than 2.0%: E

[0214] (17) Haze and total light transmittance The haze and total light transmittance of the film-coated substrate were measured using a haze meter (NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd.).

[0215] (18) Determination of scratch resistance (strength) Use #0000 steel wool to specify the load / cm 2 The coated substrate was slid 50 times. The surface of the coated film was visually observed for each load. The observation results were classified according to the following criteria to evaluate the scratch resistance. Evaluation criteria: 1000g / cm 2 Above: A 500g / cm 2 Above and less than 1000g / cm 2 :B 200g / cm 2 Above and less than 500g / cm 2 :C Less than 200g / cm 2 :D

[0216] (19) Pencil hardness Pencil hardness was measured using a pencil hardness tester in accordance with JIS K 5400. First, a pencil was placed at a 45-degree angle relative to the coating surface. Next, the pencil, under a specified load, was pulled at a constant speed. The coating surface was then observed for scratches. The results were classified according to the following criteria to evaluate pencil hardness. Evaluation criteria: 3 hours and above: A 2H:B H:C B or below: D

[0217] (20) Water resistance After distilled water was dripped onto the coated substrate, it was left for 30 minutes and then wiped off. The remaining drip marks on the coated substrate were then visually observed. The results were classified according to the following criteria to evaluate water resistance. Evaluation criteria: No trace of dripping was observed: A Although traces of addition were visible, they disappeared within 5 minutes: B The trace of dripping disappears in more than 5 minutes and within 30 minutes: C Dropping traces can still be observed for more than 30 minutes: D

[0218] (21) Adhesion Use a knife to create 11 parallel scratches on the surface of the film-coated substrate at 1 mm intervals vertically and horizontally, forming a grid of 100 squares. Then, apply cellophane tape to the surface of the film-coated substrate. Next, peel off the cellophane tape. Count the number of squares remaining where the film has not been peeled off from the substrate. The number of remaining squares is classified according to the following criteria to evaluate adhesion. Evaluation criteria: The number of remaining squares is 100: A The number of remaining squares is less than 99: B

[0219] Example 2 In the first step, a sodium aluminate aqueous solution having an Al2O3 concentration of 22% by mass is added to pure water, thereby preparing 30.0 kg of a sodium aluminate aqueous solution having an Al2O3 concentration of 1.0% by mass and a pH of 12.6. In the second step, 4.6 kg of a sodium silicate aqueous solution and 4.6 kg of a sodium aluminate aqueous solution are used. In the third step, 58.5 kg of a sodium silicate aqueous solution and 19.5 kg of a sodium aluminate aqueous solution are used. In the fifth step, the pH is set to 9.5. In addition, the heating temperature is set to 160°C. In the sixth step, the pH is set to 5.0. In addition, the heating temperature is set to 200°C. Furthermore, in the surface treatment of the particles, 10.0 g of γ-methacryloyloxypropyltrimethoxysilane is used as an organic silicon compound. The other means and conditions are the same as those in Example 1. Thus, a dispersion of particles is produced.

[0220] The dispersion medium of the methanol dispersion of the particles was replaced with MIBK, thereby obtaining a dispersion of particles having a solid content concentration of 20.5% by mass. 8.31 g of an MIBK dispersion of these particles, 1.02 g of a multifunctional acrylate resin (Light Acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), 0.11 g of a bifunctional acrylate resin (SR-238F manufactured by Tomoe Industry Co., Ltd.), 0.05 g of a reactive silicone oil (KF-2012 manufactured by Shin-Etsu Chemical Co., Ltd.), 0.37 g of a silicone-modified polyurethane acrylate (Zhiguang UT-4314 manufactured by Mitsubishi Chemical Corporation, solid content concentration 30% by mass), 0.08 g of a photopolymerization initiator (Omnirad TPO H manufactured by IGM RESINS BV), 64.66 g of isopropyl alcohol, 9.39 g of MIBK, and 16.00 g of isopropylene glycol were mixed. Thus, a coating liquid for forming a reflection-reducing film having a solid content concentration of 3.0% by mass was prepared. The other means and conditions were the same as those in Example 1. In this manner, a substrate with a coating was produced.

[0221] Example 3 In the first step, 9900.0 g of pure water is added to 100.0 g of an aqueous dispersion of silica particles (USBB-120 manufactured by JGC Catalysts & Chemicals Co., Ltd., with an average particle size of 25 nm and a solid content concentration of 20% by mass). Thereafter, an aqueous NaOH solution having a concentration of 1% by mass is added to prepare 10.0 kg of an alkaline aqueous solution having a pH of 12.5. In the second step, 110.0 kg of an aqueous sodium silicate solution and 110.0 kg of an aqueous sodium aluminate solution are used. In the third step, 249.0 kg of an aqueous sodium silicate solution and 83.0 kg of an aqueous sodium aluminate solution are used. In the fifth step, the pH is set to 11.0. In addition, the heating temperature is set to 300°C. In the sixth step, the heating temperature is set to 400°C. Other means and conditions are the same as in Example 1. In this way, a dispersion of particles, a coating liquid and a coated substrate are manufactured.

[0222] Example 4 In the first step, a sodium aluminate aqueous solution having an Al2O3 concentration of 22% by mass is added to pure water, thereby preparing 20.0 kg of a sodium aluminate aqueous solution having an Al2O3 concentration of 1.0% by mass and a pH of 12.6. In the second step, 6.0 kg of a sodium silicate aqueous solution and 3.2 kg of a sodium aluminate aqueous solution are used. In the third step, 156.0 kg of a sodium silicate aqueous solution and 52.0 kg of a sodium aluminate aqueous solution are used. In the fifth step, the pH is set to 10.0. In addition, the heating temperature is set to 180°C. Furthermore, in the surface treatment of the particles, 8.0 g of γ-methacryloyloxypropyltrimethoxysilane is used as an organosilicon compound. The other means and conditions are the same as those in Example 1. In this way, a dispersion of particles is manufactured.

[0223] The dispersion medium of the methanol dispersion of the particles was replaced with MIBK, thereby obtaining a dispersion of particles having a solid content concentration of 20.5% by mass. 9.00 g of an MIBK dispersion of the particles, 0.89 g of a multifunctional acrylate resin (Light Acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), 0.10 g of a bifunctional acrylate resin (SR-238F manufactured by Tomoe Industry Co., Ltd.), 0.05 g of a reactive silicone oil (KF-2012 manufactured by Shin-Etsu Chemical Co., Ltd.), 0.37 g of a silicone-modified polyurethane acrylate (Zhiguang UT-4314 manufactured by Mitsubishi Chemical Corporation, solid content concentration 30% by mass), 0.08 g of a photopolymerization initiator (Omnirad TPO H manufactured by IGM RESINS BV), 64.67 g of isopropyl alcohol, 8.84 g of MIBK, and 16.00 g of isopropylene glycol were mixed. In this manner, a reflection-reducing film-forming coating liquid having a solid content concentration of 3.0% by mass was prepared. Other means and conditions were the same as those in Example 1. In this manner, a substrate with a coating film was prepared.

[0224] Example 5 In the first step, 9975.3 g of pure water is added to 24.7 g of an aqueous dispersion of silica particles (Cataloid SI-40 manufactured by JGC Catalysts & Chemicals Co., Ltd., with an average particle size of 17 nm and a solid content of 40.5% by mass). Thereafter, an aqueous NaOH solution having a concentration of 1% by mass is added to prepare 10.0 kg of an alkaline aqueous solution having a pH of 12.5. In the second step, 90.0 kg of an aqueous sodium silicate solution and 90.0 kg of an aqueous sodium aluminate solution are used. In the third step, 201.0 kg of an aqueous sodium silicate solution and 67.0 kg of an aqueous sodium aluminate solution are used. In the fifth step, the pH is set to 10.9. In addition, the heating temperature is set to 290°C. In the sixth step, the pH is set to 8.0. In addition, the heating temperature is set to 300°C. The other means and conditions are the same as those in Example 1. In this way, a dispersion of particles, a coating liquid and a substrate with a coating are manufactured.

[0225] Example 6 In the first step, 9950.6 g of pure water was added to 49.4 g of an aqueous dispersion of silica particles (SI-40 manufactured by JGC Catalysts & Chemicals Co., Ltd.). Thereafter, an aqueous NaOH solution having a concentration of 1% by mass was added to prepare 10.0 kg of an alkaline aqueous solution having a pH of 12.5. In the second step, 88.5 kg of an aqueous sodium silicate solution and 88.5 kg of an aqueous sodium aluminate solution were used. In the third step, 180.0 kg of an aqueous sodium silicate solution and 60.0 kg of an aqueous sodium aluminate solution were used. In the fifth step, the pH was set to 10.8. In addition, the heating temperature was set to 200°C. In the sixth step, the pH was set to 7.5. The other means and conditions were the same as in Example 1. In this way, a dispersion of particles, a coating solution and a coated substrate were manufactured. The properties of the manufactured dispersion, coating solution and substrate were evaluated.

[0226] Example 7 In the first step, 9900.0 g of pure water is added to 100.0 g of an aqueous dispersion of silica particles (USBB-120 manufactured by JGC Catalysts & Chemicals Co., Ltd.). Thereafter, an aqueous NaOH solution having a concentration of 1% by mass is added to prepare 10.0 kg of an alkaline aqueous solution having a pH of 12.5. In the second step, 84.2 kg of an aqueous sodium silicate solution and 84.2 kg of an aqueous sodium aluminate solution are used. In the third step, 147.0 kg of an aqueous sodium silicate solution and 49.0 kg of an aqueous sodium aluminate solution are used. In the fifth step, the pH is set to 10.0. In addition, the heating temperature is set to 180°C. In the sixth step, the pH is set to 7.0. In addition, the heating temperature is set to 180°C. The other means and conditions are the same as those in Example 1. In this way, a dispersion of particles, a coating solution and a coated substrate are manufactured. The properties of the manufactured dispersion, coating solution and substrate are evaluated.

[0227] Example 8 In the fifth step, the pH was set to 9.8. In the sixth step, the pH was set to 7.5. Furthermore, the heating temperature was set to 160°C. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, coating solution, and film-coated substrate were produced. The properties of the produced dispersion, coating solution, and substrate were evaluated.

[0228] Example 9 In the second step, 22.0 kg of sodium silicate aqueous solution and 22.0 kg of sodium aluminate aqueous solution were used. In the third step, 84.0 kg of sodium silicate aqueous solution and 28.0 kg of sodium aluminate aqueous solution were used. In the fifth step, the pH was set to 10.2. In addition, the heating temperature was set to 280°C. In the sixth step, the pH was set to 7.0. In addition, the heating temperature was set to 220°C. The other means and conditions were the same as in Example 1. In this way, a dispersion liquid, a coating liquid and a substrate with a coating were manufactured. The characteristics of the manufactured dispersion liquid, coating liquid and substrate were evaluated.

[0229] Example 10 In the third step, 207.0 kg of sodium silicate aqueous solution and 69.0 kg of sodium aluminate aqueous solution were used. In the fifth step, the heating temperature was set to 300°C. In the sixth step, the heating temperature was set to 400°C. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, coating solution, and film-coated substrate were produced. The properties of the produced dispersion, coating solution, and substrate were evaluated.

[0230] Example 11 In the first step, a sodium aluminate aqueous solution having an Al2O3 concentration of 22% by mass was added to pure water, thereby preparing 10.0 kg of a sodium aluminate aqueous solution having an Al2O3 concentration of 1.0% by mass and a pH of 12.6. In the second step, 57.2 kg of a sodium silicate aqueous solution and 19.1 kg of a sodium aluminate aqueous solution were used. In the third step, 172.5 kg of a sodium silicate aqueous solution and 57.5 kg of a sodium aluminate aqueous solution were used. In the fifth step, the pH was set to 9.5. In addition, the heating temperature was set to 150°C. In the sixth step, the pH was set to 5.5. In addition, the heating temperature was set to 150°C. In addition, in the surface treatment of the particles, 2.0 g of γ-methacryloyloxypropyltrimethoxysilane was used as an organic silicon compound. The other means and conditions were the same as those in Example 1. In this way, a dispersion liquid of particles, a coating liquid and a substrate with a coating were manufactured.

[0231] Example 12 In the sixth step, the pH was set to 6.0. The heating temperature was set to 180° C. Other means and conditions were the same as those in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0232] Example 13 In the third step, 207.0 kg of sodium silicate aqueous solution and 69.0 kg of sodium aluminate aqueous solution were used. In the fifth step, the heating temperature was set to 300°C. In the sixth step, the heating temperature was set to 300°C. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a coated substrate were produced.

[0233] Example 14 In the second step, 42.0 kg of sodium silicate aqueous solution and 42.0 kg of sodium aluminate aqueous solution were used. In the third step, 106.5 kg of sodium silicate aqueous solution and 35.5 kg of sodium aluminate aqueous solution were used. In the fifth step, the pH was set to 9.0. In addition, the heating temperature was set to 150°C. In the sixth step, the heating temperature was set to 150°C. The other means and conditions were the same as in Example 1. In this way, a particle dispersion, a coating solution, and a coated substrate were produced.

[0234] Example 15 In the second step, 52.0 kg of sodium silicate aqueous solution and 52.0 kg of sodium aluminate aqueous solution were used. In the third step, 174.0 kg of sodium silicate aqueous solution and 58.0 kg of sodium aluminate aqueous solution were used. In the fifth step, the heating temperature was set to 300°C. In the sixth step, the heating temperature was set to 350°C. In addition, in the surface treatment of the particles, 12.0 g of γ-methacryloyloxypropyltrimethoxysilane was used as an organic silicon compound. The other means and conditions were the same as in Example 1. In this way, a particle dispersion, a coating liquid, and a substrate with a coating were produced.

[0235] Example 16 In the second step, 22.0 kg of sodium silicate aqueous solution and 22.0 kg of sodium aluminate aqueous solution were used. In the third step, 75.0 kg of sodium silicate aqueous solution and 25.0 kg of sodium aluminate aqueous solution were used. Furthermore, 0.6 g of γ-methacryloyloxypropyltrimethoxysilane was used as the organosilicon compound for the particle surface treatment. The same procedures were used as in Example 1 except for these. In this manner, a particle dispersion, coating solution, and coated substrate were produced.

[0236] Example 17 In the second step, 95.0 kg of sodium silicate aqueous solution and 95.0 kg of sodium aluminate aqueous solution were used. In the third step, 258.0 kg of sodium silicate aqueous solution and 86.0 kg of sodium aluminate aqueous solution were used. In the fifth step, the pH was set to 11.0. In addition, the heating temperature was set to 180°C. Furthermore, in the surface treatment of the particles, 8.0 g of γ-methacryloyloxypropyltrimethoxysilane was used as an organic silicon compound. The other means and conditions were the same as in Example 1. In this way, a dispersion liquid of particles, a coating liquid and a substrate with a coating were manufactured.

[0237] Example 18 In the second step, 13.1 kg of sodium silicate aqueous solution and 79.8 kg of sodium aluminate aqueous solution were used. In the third step, 54.9 kg of sodium silicate aqueous solution and 18.3 kg of sodium aluminate aqueous solution were used. In the fifth step, the heating temperature was set to 200°C. In the sixth step, the pH was set to 8.0. In addition, the heating temperature was set to 180°C. Furthermore, in the surface treatment of the particles, 1.1 g of γ-methacryloyloxypropyltrimethoxysilane was used as an organic silicon compound. The other means and conditions were the same as those in Example 1. In this way, a dispersion liquid, a coating liquid and a substrate with a coating were manufactured.

[0238] Example 19 In the surface treatment of the particles with an organosilicon compound, tetraethoxysilane (Tama Chemical Industry Co., Ltd., orthosilicic acid ETIL ES28) was used as the organosilicon compound. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were prepared.

[0239] Example 20 In the surface treatment of the particles with an organosilicon compound, γ-acryloxypropyltrimethoxysilane (KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the organosilicon compound. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were prepared.

[0240] Example 21 In the first step, a sodium aluminate aqueous solution having an Al2O3 concentration of 22% by mass is added to pure water, thereby preparing 30.0 kg of a sodium aluminate aqueous solution having an Al2O3 concentration of 4.5% by mass and a pH of 12.6. In the second step, 20.4 kg of a sodium silicate aqueous solution and 0.6 kg of a sodium aluminate aqueous solution are used. In the third step, 339.0 kg of a sodium silicate aqueous solution and 113.0 kg of a sodium aluminate aqueous solution are used. In the fifth step, the pH is set to 10.0. In addition, the heating temperature is set to 180°C. Furthermore, in the surface treatment of the particles, 8.0 g of γ-methacryloyloxypropyltrimethoxysilane is used as an organosilicon compound. The other means and conditions are the same as those in Example 1. In this way, a dispersion of particles is manufactured.

[0241] The dispersion medium of the methanol dispersion of the particles was replaced with MIBK, thereby obtaining a dispersion of particles having a solid content concentration of 20.5% by mass. 8.31 g of an MIBK dispersion of the particles, 1.02 g of a multifunctional acrylate resin (Light Acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), 0.11 g of a bifunctional acrylate resin (SR-238F manufactured by Tomoe Industry Co., Ltd.), 0.05 g of a reactive silicone oil (KF-2012 manufactured by Shin-Etsu Chemical Co., Ltd.), 0.37 g of a silicone-modified polyurethane acrylate (Zhiguang UT-4314 manufactured by Mitsubishi Chemical Corporation, solid content concentration 30% by mass), 0.08 g of a photopolymerization initiator (Omnirad TPO H manufactured by IGM RESINS BV), 64.66 g of isopropyl alcohol, 9.39 g of MIBK, and 16.00 g of isopropylene glycol were mixed. In this manner, a reflection-reducing film-forming coating liquid having a solid content concentration of 3.0% by mass was prepared. Other means and conditions were the same as those in Example 1. In this manner, a substrate with a coating film was prepared.

[0242] Example 22 In the fifth step, the heating temperature was set to 300°C. In the sixth step, the heating temperature was set to 350°C. Furthermore, the surface treatment of the particles with an organosilicon compound was not performed. Other methods and conditions were the same as in Example 1. In this manner, a dispersion of particles was produced.

[0243] The dispersion medium of the methanol dispersion of the particles was replaced with propylene glycol monomethyl ether (PGME), thereby obtaining a dispersion of particles having a solid content concentration of 20.5% by mass. 3.46 g of the PGME dispersion of the particles, 1.92 g of a multifunctional acrylate resin (Light Acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), 0.21 g of a bifunctional acrylate resin (SR-238F manufactured by Tomoe Industry Co., Ltd.), 0.05 g of a reactive silicone oil (KF-2012 manufactured by Shin-Etsu Chemical Co., Ltd.), 0.37 g of a silicone-modified polyurethane acrylate (Zhiguang UT-4314 manufactured by Mitsubishi Chemical Co., Ltd., solid content concentration 30% by mass), 0.15 g of a photopolymerization initiator (Omnirad TPO H manufactured by IGM RESINS BV), 64.60 g of isopropyl alcohol, 13.25 g of PGME, and 16.00 g of isopropylene glycol were mixed. In this manner, a coating liquid for forming a reflection-reducing film having a solid content concentration of 3.0% by mass was prepared. The other means and conditions were the same as those in Example 1. In this manner, a substrate with a coating was produced.

[0244] Comparative Example 1 In the first step, a sodium aluminate aqueous solution with an Al2O3 concentration of 22% by mass was added to pure water to prepare 50.0 kg of a sodium aluminate aqueous solution with an Al2O3 concentration of 1.0% by mass and a pH of 12.6. In the second step, 1.2 kg of a sodium silicate aqueous solution and 1.2 kg of a sodium aluminate aqueous solution were used. In the third step, 174.0 kg of a sodium silicate aqueous solution and 58.0 kg of a sodium aluminate aqueous solution were used. Other methods and conditions were the same as in Example 1. In this manner, a dispersion of particles was produced.

[0245] The dispersion medium of the methanol dispersion of the particles was replaced with MIBK to obtain a dispersion of particles having a solid content concentration of 20.5% by mass. 8.31 g of an MIBK dispersion of the particles, 1.02 g of a multifunctional acrylate resin (Light Acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), 0.11 g of a bifunctional acrylate resin (SR-238F manufactured by Tomoe Industry Co., Ltd.), 0.05 g of a reactive silicone oil (KF-2012 manufactured by Shin-Etsu Chemical Co., Ltd.), 0.37 g of a silicone-modified polyurethane acrylate (Zhiguang UT-4314 manufactured by Mitsubishi Chemical Corporation, solid content concentration 30% by mass), 0.08 g of a photopolymerization initiator (Omnirad TPO H manufactured by IGM RESINS BV), 64.66 g of isopropyl alcohol, 9.39 g of MIBK, and 16.00 g of isopropylene glycol were mixed. In this manner, a reflection-reducing film-forming coating liquid having a solid content concentration of 3.0% by mass was prepared. Other means and conditions were the same as those in Example 1. In this manner, a substrate with a coating film was prepared.

[0246] Comparative Example 2 In the first step, 9950.0 g of pure water was added to 50.0 g of an aqueous dispersion of silica particles (USBB-120 manufactured by JGC Catalysts & Chemicals Co., Ltd.). Subsequently, an aqueous NaOH solution having a concentration of 1% by mass was added to prepare 10.0 kg of an alkaline aqueous solution having a pH of 12.5. In the second step, 60.0 kg of an aqueous sodium silicate solution having a concentration of 4.0% by mass of SiO2 and 20.0 kg of an aqueous sodium aluminate solution having a concentration of 4.0% by mass of Al2O3 were used. In the third step, 276.0 kg of an aqueous sodium silicate solution and 92.0 kg of an aqueous sodium aluminate solution were used. The other means and conditions were the same as those in Example 1. In this way, a dispersion of particles, a coating solution, and a coated substrate were prepared.

[0247] Comparative Example 3 In the first step, a sodium aluminate aqueous solution with an Al2O3 concentration of 22% by mass was added to pure water to prepare 10.0 kg of a sodium aluminate aqueous solution with an Al2O3 concentration of 1.0% by mass and a pH of 12.6. In the second step, 6.2 kg of a sodium silicate aqueous solution and 6.2 kg of a sodium aluminate aqueous solution were used. In the third step, 222.0 kg of a sodium silicate aqueous solution and 74.0 kg of a sodium aluminate aqueous solution were used. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0248] Comparative Example 4 A particle dispersion, a coating liquid, and a film-coated substrate were prepared in the same manner as in Example 1, except that the pH in the sixth step was set to 9.0 and the heating temperature was set to 300°C.

[0249] Comparative Example 5 A particle dispersion, a coating liquid, and a film-coated substrate were prepared in the same manner as in Example 1, except that the heating temperature in the fifth step was set to 200° C., the sixth step was not performed, 1.1 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound in the surface treatment of the particles, and stirring was performed at 50° C. for 6 hours.

[0250] Comparative Example 6 In the sixth step, the heating temperature was set to 120°C. Furthermore, 0.2 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound for the particle surface treatment. Furthermore, the stirring temperature was 50°C, and the stirring time was 6 hours. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0251] Comparative Example 7 In the first step, a sodium aluminate aqueous solution with an Al2O3 concentration of 22% by mass was added to pure water to prepare 10.0 kg of a sodium aluminate aqueous solution with an Al2O3 concentration of 1.0% by mass and a pH of 12.6. In the second step, 167.1 kg of a sodium silicate aqueous solution and 0.5 kg of a sodium aluminate aqueous solution were used. In the third step, 144.0 kg of a sodium silicate aqueous solution and 48.0 kg of a sodium aluminate aqueous solution were used. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0252] Comparative Example 8 In the first step, 9902.4 g of pure water is added to 97.6 g of an aqueous dispersion of silica particles (Cataloid SI-550 manufactured by JGC Catalysts & Chemicals Co., Ltd., with an average particle size of 5 nm and a solid content concentration of 20.5% by mass). Thereafter, an aqueous NaOH solution having a concentration of 1% by mass is added to prepare 10.0 kg of an aqueous solution having a pH of 12.5. In the second step, 63.0 kg of an aqueous sodium silicate solution and 63.0 kg of an aqueous sodium aluminate solution are used. In the third step, 159.0 kg of an aqueous sodium silicate solution and 53.0 kg of an aqueous sodium aluminate solution are used. In the fifth step, the pH is set to 9.5. In addition, the heating temperature is set to 160°C. In the sixth step, the pH is set to 5.0. In addition, the heating temperature is set to 200°C. Furthermore, in the surface treatment of the particles, 8.0 g of γ-methacryloyloxypropyltrimethoxysilane is used as an organic silicon compound. Other means and conditions are the same as those in Example 1. In this manner, a dispersion of particles was prepared.

[0253] The dispersion medium of the methanol dispersion of the particles was replaced with MIBK to obtain a dispersion of particles having a solid content concentration of 20.5% by mass. 8.31 g of an MIBK dispersion of the particles, 1.02 g of a multifunctional acrylate resin (Light Acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), 0.11 g of a bifunctional acrylate resin (SR-238F manufactured by Tomoe Industry Co., Ltd.), 0.05 g of a reactive silicone oil (KF-2012 manufactured by Shin-Etsu Chemical Co., Ltd.), 0.37 g of a silicone-modified polyurethane acrylate (Zhiguang UT-4314 manufactured by Mitsubishi Chemical Corporation, solid content concentration 30% by mass), 0.08 g of a photopolymerization initiator (Omnirad TPO H manufactured by IGM RESINS BV), 64.66 g of isopropyl alcohol, 9.39 g of MIBK, and 16.00 g of isopropylene glycol were mixed. In this manner, a reflection-reducing film-forming coating liquid having a solid content concentration of 3.0% by mass was prepared. Other means and conditions were the same as those in Example 1. In this manner, a substrate with a coating film was prepared.

[0254] Comparative Example 9 In the fifth step, the pH was set to 8.0. Furthermore, the heating temperature was set to 180°C. The heating temperature in the sixth step was also set to 180°C. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0255] Comparative Example 10 In the fifth step, the pH was set to 11.6. The heating temperature was set to 300° C. Other means and conditions were the same as those in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0256] Comparative Example 11 In the fifth step, the pH was set to 9.2. Furthermore, the heating temperature was set to 120°C. The heating temperature in the sixth step was set to 180°C. Other methods and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0257] Comparative Example 12 In the fifth step, the pH was set to 10.8. The heating temperature was set to 350° C. Other means and conditions were the same as those in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0258] Comparative Example 13 In the sixth step, the pH was set to 4.0. The heating temperature was set to 350° C. Other means and conditions were the same as those in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0259] Comparative Example 14 In the sixth step, the heating temperature was set to 120° C. Other means and conditions were the same as those in Example 1. In this manner, a particle dispersion, a coating liquid, and a film-coated substrate were produced.

[0260] Comparative Example 15 In the fifth step, the pH was set to 9.0. Furthermore, the heating temperature was set to 150°C. In the sixth step, the pH was set to 7.0. Furthermore, the heating temperature was set to 450°C. Other means and conditions were the same as in Example 1. In this manner, a particle dispersion, a coating solution, and a film-coated substrate were produced.

[0261] [Table 4]

[0262] [Table 5]

[0263] [Table 6]

[0264] [Table 7]

[0265] [Table 8]

[0266] [Table 9] The foregoing detailed description has been presented for purposes of illustration and description. Many modifications and variations are possible in light of the foregoing teachings. It is not intended to be exhaustive or to limit the subject matter described herein to the precise forms disclosed. Although the subject matter has been described using language specific to structural features and / or methodological functions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or functions described above. Rather, the specific features and functions described above are disclosed as example forms of implementing the claims appended hereto.

Claims

1. A particle, wherein The particle comprises a shell containing silicon and a cavity inside the shell, The particles have an average particle size of 15 nm to 150 nm, a refractive index of 1.08 to 1.38, and a ratio A1 / A2 of 1.0 or less, wherein the average particle size is an average particle size obtained by image analysis, and the ratio A1 / A2 is a ratio A1 / A2 of a specific surface area A1 to a specific surface area A2. The specific surface area A1 is calculated according to the BET method using water vapor gas. The specific surface area A2 is calculated according to the BET method using nitrogen gas, After the particles are dried at 200° C. for 3 hours and then left at 25° C. in an atmosphere with a relative humidity of 90% for 24 hours, the mass increase of the particles is 4.0 parts by mass or less per 100 parts by mass of the particles after drying.

2. The particle according to claim 1, wherein A ratio A2 / A3 of the specific surface area A2 of the particles to a specific surface area A3 calculated based on the average particle size is 1.00 to 1.

30.

3. The particle according to claim 1, wherein The number density of silanol groups on the surface of the particles calculated by the Sears method was 0.1 per nm. 2 ~1.5 / nm 2 .

4. The particle according to claim 1, wherein The ratio A4 / A3 of the specific surface area A4 calculated by pulse NMR measurement of a methanol dispersion of the particles to the specific surface area A3 is 0.65 or less.

5. The particle according to claim 1, wherein The particles 29 In Si-NMR analysis, relative to the total area of ​​the peaks representing the Q1 to Q4 structures of silicon atoms appearing in the chemical shift range of -78ppm to -120ppm, the proportion of the area of ​​the peak representing the Q4 structure of the silicon atom appearing in the chemical shift range of -108ppm to -120ppm is more than 82%.

6. The particle according to claim 1, wherein The thickness of the shell is 3.0 nm to 12.0 nm.

7. The particle according to claim 1, wherein The particles include at least one functional group selected from an alkyl group, an acryloyl group, a (meth)acryloyl group, a vinyl group, a mercapto group, and an epoxy group.

8. A method for producing particles, wherein: The manufacturing method includes a first step, a second step, a third step, a fourth step, a fifth step, and a sixth step in sequence. In the first step, an alkaline aqueous solution is prepared; In the second step, a solution of a silicon-containing compound and an aqueous solution of an alkali-soluble compound containing an inorganic element other than silicon are simultaneously added to the alkaline aqueous solution in such a manner that the molar ratio MOx / SiO2 is 0.01 to 2.0, thereby preparing a dispersion of composite oxide particles a. Said SiO2 represents said silicon oxide, The MOx represents an oxide of the inorganic element; In the third step, the solution of the silicon-containing compound and the aqueous solution of the alkali-soluble compound of the inorganic element other than silicon are added so that the molar ratio MOx / SiO2 is smaller than the molar ratio MOx / SiO2 in the second step, thereby preparing a dispersion of the composite oxide particles b. The composite oxide particles b have an average particle size of 15 nm to 150 nm. The average particle size of the composite oxide particles a is subtracted from the average particle size of the composite oxide particles b, and the resultant value is divided by 2, and is 3 nm to 14 nm; In the fourth step, an acid is added to the dispersion of the composite oxide particles b to remove at least a portion of elements other than silicon constituting the composite oxide particles b, thereby preparing a dispersion of silica particles. In the fifth step, the dispersion of the silica particles is heated to 150° C. to 300° C. at a pH of 9.0 to 11.0; and In the sixth step, the dispersion of the silica particles is heated to 150° C. to 400° C. at a pH of 5.0 to 8.

0.

9. The method for producing particles according to claim 8, wherein The manufacturing method comprises: After the sixth step, at least one of the organosilicon compound represented by the following formula (8) and its partial hydrolyzate is added. R n -SiX 4-n (8) In the formula, R is an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, X is an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a hydrogen atom, and n is an integer of 0 to 3.

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