Particle having outer shell containing silicon and cavity inside thereof, and method for producing the same

Abstract

To provide a particle that has a dense outer shell, a controlled particle surface of hydrophilic site, and also has a small moisture-absorption property and a low refractive index.SOLUTION: The particle has an outer shell containing silicon, a cavity inside thereof. The average particle diameter of the particle by image analysis is 15 to 150 nm. Further, the refractive index of the particle is 1.08 to 1.38. Furthermore, a ratio (A1 / A2) between a specific surface area (A1) calculated by BET method using steam gas and a specific surface area (A2) calculated by BET method using nitrogen gas is 1.0 or less. Additionally, a mass increase when the particle is dried at 200°C for 3 hours, and then leaving under the atmosphere of relative humidity 90% at 25°C to stand for 24 hours is 4.0 pts.mass or less for 100 pts.mass of the particle.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to particles having a silicon-containing shell and a cavity inside the shell, and a method for producing the same. [Background technology]

[0002] Conventionally, an anti-reflection film has been formed on the surface of a substrate such as glass, plastic sheet, or plastic lens to prevent reflection from the surface. For example, a coating film made of a low refractive index material such as fluororesin or magnesium fluoride has been formed on the surface of the glass or plastic substrate by coating, vapor deposition, or CVD. However, these methods are expensive. Therefore, a method of forming an anti-reflection film by applying a coating liquid containing low refractive index particles such as silica to the surface of the substrate is known (see, for example, Patent Document 1).

[0003] Also, methods for producing particles having a silicon-containing shell and a cavity inside are known (see, for example, Patent Documents 2 and 3). These particles have a low refractive index, and a transparent coating formed using these particles has a low refractive index and excellent anti-reflection performance.

[0004] Furthermore, it is known that a transparent coating having a hard coating function is formed on the surface of a substrate, a display device, or the like in order to improve the pencil hardness (hardness) and scratch resistance (strength) of the substrate, the display device, or the like. Specifically, a transparent organic resin film or inorganic film is formed on the surface of glass, plastic, the display device, or the like. In this case, it is known that blending particles such as silica into the coating improves adhesion to the substrate, strength, and the like. When using such particles, it is known that surface treatment with an organosilicon compound is performed to improve dispersibility in the matrix component (see, for example, Patent Document 4).

[0005] Furthermore, it is known that fluorinated organic compounds (PFAS) are added to the coating solution to improve the water resistance of the coating (see, for example, Patent Document 5). In recent years, concerns have arisen about the effects of PFAS on the human body and the environment, and international guidelines have been established to prohibit their use under the Stockholm Convention on Persistent Organic Pollutants (POPs Convention). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-133105 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-233611 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-226539 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-224436 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-108262 Summary of the Invention [Problem to be solved by the invention]

[0007] Hollow particles have a lower refractive index than solid particles but are weaker in strength. Therefore, when used in anti-reflective coatings, although the anti-reflective properties are improved, the resulting film may have a lower hardness and strength. Therefore, particles must not only have a low refractive index, but also sufficient hardness and strength. Furthermore, when anti-reflective coatings containing hollow particles are used in display devices, uniform reflectivity across the film surface is required. However, when moisture or water droplets adhere to low-refractive-index anti-reflective coatings, they can be seen as color unevenness. This is because the refractive index of water differs from that of anti-reflective coatings and hollow particles, resulting in a refractive index difference between areas with and without water. Traditionally, PFASs have been incorporated into coating solutions, and the presence of PFASs on the coating surface provides a water-repellent effect that prevents moisture and water droplets from adhering. However, with the recent trend toward PFAS-free coatings, hollow particles are required to be less susceptible to moisture absorption. Therefore, it is necessary to densify the particles (outer shell), control the hydrophilic sites on the surface, reduce moisture absorption (increase water resistance), and achieve particles with a low refractive index and sufficient hardness and strength. [Means for solving the problem]

[0008] To solve these problems, the following particles were discovered. These particles have a silicon-containing outer shell and a cavity inside. The average particle diameter of these particles measured by image analysis is 15 to 150 nm. The refractive index of these particles is 1.08 to 1.38. Furthermore, the ratio (A1 / A2) of the specific surface area (A1) calculated by the BET method using water vapor gas to the specific surface area (A2) calculated by the BET method using nitrogen gas is 1.0 or less. In addition, when these particles are dried at 200°C for 3 hours and then left in an atmosphere at 25°C and a relative humidity of 90% for 24 hours, the mass increase is 4.0 parts by mass or less per 100 parts by mass of particles.

[0009] Hereinafter, this "particle having a silicon-containing shell and a cavity inside" may be simply referred to as "particle" or "particle of the present invention."

[0010] These particles have a low refractive index, a dense outer shell, and controlled hydrophilic sites on the particle surface, resulting in high water resistance. A coating solution containing such particles can produce a coated substrate with excellent antireflection performance, reduced color unevenness, and high hardness and strength.

[0011] To obtain these particles, the following manufacturing method was discovered.

[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 of an inorganic element other than silicon are simultaneously added to this alkaline aqueous solution to prepare a dispersion of composite oxide particles a (second step). In this second step, the solutions added are adjusted so that the molar ratio (MOx / SiO2) is 0.01 to 2.0, where SiO2 represents the oxide of silicon and MOx represents the oxide of the inorganic element.

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

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

[0015] Next, the dispersion of silica particles obtained in the fourth step is heated to 150 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 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 this sixth step are similar to those of the particles described above. [Effects of the Invention]

[0018] The particles of the present invention provide a coated substrate having excellent anti-reflection properties, high water resistance, and high hardness and strength. DETAILED DESCRIPTION OF THE INVENTION

[0019] [particle] The particles according to the present invention will now be described.

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

[0021] The average particle diameter determined by particle image analysis is 15 to 150 nm. This is the average value of the equivalent circle diameter calculated from the area of ​​300 particles randomly selected from a transmission electron microscope (TEM) photograph taken at a predetermined magnification, which is then processed to determine the particle area. When the average particle diameter is within this range, the particles can exist in the dispersion without agglomeration or sedimentation. Furthermore, the particles have good dispersibility in the coating solution and in the film, resulting in a coated substrate with high transparency, anti-reflection performance, hardness, and strength.

[0022] Here, particles with an average particle size of less than 15 nm have a small proportion of voids in the particle (porosity), and the refractive index is not sufficiently low, resulting in insufficient anti-reflection performance. Conversely, particles with a size exceeding 150 nm are prone to light scattering and have low dispersibility in the coating solution, which may prevent the formation of a transparent coating film. The average particle size is preferably 30 to 120 nm, more preferably 40 to 100 nm, and even more preferably 40 to 80 nm.

[0023] The refractive index of the particles is 1.08 to 1.38. Within this range, a transparent coated substrate with high anti-reflection performance can be obtained. However, it is difficult to obtain particles with a refractive index of less than 1.08. Conversely, if the refractive index exceeds 1.38, the anti-reflection performance may be insufficient, depending on the refractive index of the substrate or the underlayer film. This 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) of the particles calculated by the BET method using water vapor gas to the specific surface area (A2) calculated by the BET method using nitrogen gas is 1.0 or less. When the ratio is in this range, the particle outer shell is dense, the particle surface has few hydrophilic sites, and a coated substrate having high water resistance, hardness, and strength and being transparent and having high anti-reflection performance can be obtained.

[0025] If the ratio (A1 / A2) exceeds 1.0, the particle surface will have many hydrophilic sites, resulting in reduced water resistance. Therefore, a coated substrate using such particles may not have sufficient water resistance, resulting in color unevenness. While there is no particular lower limit for the ratio (A1 / A2), it is, for example, 0.2. The ratio (A1 / A2) is preferably 0.8 or less, more preferably 0.6 or less.

[0026] When the particles are dried at 200°C for 3 hours and then left to stand for 24 hours in an atmosphere at 25°C and a relative humidity of 90%, the particle mass increases by 4.0 parts by mass or less per 100 parts by mass of particles. Within this range, the moisture absorption of the particles is suppressed (i.e., the particles have high water resistance), so when these particles are used, the occurrence of color unevenness is suppressed and a transparent coated substrate with high anti-reflection performance can be obtained.

[0027] Here, if the mass increase of the particles exceeds 4.0 parts by mass, the water resistance of the particles will be reduced. Therefore, a coated substrate using these particles may not have sufficient water resistance and may have color unevenness. There is no particular lower limit for the mass increase of these particles, but it may be, for example, 0.0 parts by mass. The mass increase of the particles is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, and particularly preferably 1.0 parts by mass or less.

[0028] The ratio (A2 / A3) of the specific surface area (A2) of the particles calculated by the BET method using nitrogen gas to the specific surface area (A3) calculated from the average particle diameter is preferably 1.00 to 1.30. When the ratio is within this range, the particle surface area is small, which reduces adhesion of moisture and water droplets, resulting in a coated substrate with high water resistance.

[0029] Here, it is difficult to obtain particles with a ratio (A2 / A3) of less than 1.00. Conversely, if it exceeds 1.30, the particle surface is large, so moisture or water droplets are likely to adhere, which may result in a decrease in 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 measurement method is 0.1 to 1.5 / nm 2 When the particle size is within this range, the particles have high water resistance, and a transparent coated substrate with high anti-reflection performance and little color unevenness can be obtained.

[0031] Here, the number density of silanol groups is 0.1 / nm 2It is difficult to obtain particles with a particle size of less than 1.5 particles / nm. 2 If the number density of silanol groups exceeds 0.2 to 1.0 groups / nm, the surface has a high affinity for moisture and water droplets, which may result in a decrease in water resistance. 2 , and more preferably 0.2 to 0.5 particles / nm 2 is.

[0032] The number density of silanol groups on particles is calculated from the Sears number and the specific surface area. The Sears number is measured by titration with sodium hydroxide according to the method described by Sears in Analytical Chemistry 28 (1956), 12, 1981-1983. Specifically, 30 g of sodium chloride is added to 150 g of silica particles diluted with pure water to a concentration of 1% by mass. The pH is adjusted to 4.0 with hydrochloric acid, and then 0.1 N aqueous sodium hydroxide solution is titrated at 0.1 ml / sec. The Sears number is expressed as the amount (Q) of aqueous sodium hydroxide solution required to reach a pH of 9.0. The Sears number (A) is the amount of 0.1 N NaOH solution required to titrate 1.5 g of particles, and is expressed by the following equation (1):

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

[0034] The number density (ρ) of silanol groups is expressed by the following formula (2).

[0035] ρ=(B×N A ) / (10 18 ×M×S BET ) ···(2) (where B is the amount of sodium hydroxide (mol) required to change the pH from 4.0 to 9.0 per 1.5 g of particles calculated from the Sears number (A), N A is Avogadro's number (particles / mol), M is the particle mass (1.5g), and S BETis the specific surface area (m 2 / g).

[0036] The ratio (A4 / A3) of the specific surface area (A4) calculated from pulse NMR measurement of a methanol dispersion of the particles to the specific surface area (A3) calculated from the average particle size is preferably 0.65 or less. When the ratio is in this range, the particles have high water resistance, and a transparent coated substrate with high anti-reflection performance and little color unevenness can be obtained.

[0037] Pulsed NMR is a measurement method that excites magnetization in a thermal equilibrium state in a static magnetic field by irradiating it with pulsed radio waves of several tens of megahertz, and observes the phenomenon in which the excited magnetization returns to its original thermal equilibrium state over time. Liquid molecules that are in contact with or adsorbed to particle surfaces respond differently to changes in the magnetic field than liquid molecules that are free and not in contact with the particle surfaces.

[0038] In general, the movement of liquid molecules adsorbed to particle surfaces is restricted, while liquid molecules not adsorbed to particle surfaces can move freely. As a result, the relaxation time of liquid molecules adsorbed to particle surfaces is shorter than that of other liquid molecules. The relaxation time observed in a liquid containing dispersed particles is the average of two relaxation times reflecting the liquid volume concentration on the particle surfaces and the liquid volume concentration in the free state.

[0039] The specific surface area (A4) calculated from pulsed NMR measurements of a particle dispersion in methanol refers to the specific surface area of ​​the particle in the portion wetted by the dispersion medium. Particles with few hydrophilic sites on their surface have few silanol groups on their surface. Since the surface of such particles has few areas that are easily wetted by the hydrophilic dispersion medium, the specific surface area (A4) of the particle is smaller than the "specific surface area (A3) calculated from the average particle diameter." This means that the value of this specific surface area (A4) can be said to change depending on the degree of water resistance of the particle. The value of the specific surface area (A4) also changes depending on the type of dispersion medium used during measurement.

[0040] If the ratio (A4 / A3) exceeds 0.65, the number of hydrophilic sites on the particle surface increases, which may result in a decrease in water resistance, or the introduction of functional groups derived from the organosilicon compound onto the particle surface may be insufficient, which may result in a decrease in hardness and strength of the coated substrate. The lower limit of the ratio (A4 / A3) is not particularly set, but is, for example, 0.10. The ratio (A4 / A3) is more preferably 0.60 or less, and even more preferably 0.50 or less.

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

[0042] Ψp=(Sc / Sd) / [(1-Sc) / Td]...Equation (3) (where Sc is the solid concentration of particles in the dispersion (mass%), Sd is the particle density (g / cm 3 ), and Td is the density of the dispersion medium at 25°C (g / cm 3 ) indicates.

[0043] Here, the solid content concentration is the concentration of particles converted into solid content in the dispersion (the same applies hereinafter). Sd is the value obtained by multiplying the density of the constituent component of the particle by its volume fraction, and the value obtained by multiplying the density of the constituent component inside the particle by its volume fraction. For example, if the constituent component of the particle is silica, it is 2.2; if it is alumina, it is 3.9; if it is tin oxide, it is 6.9; if it is antimony (V) oxide, it is 5.2; if it is titania (anatase), it is 3.9; if it is titania (rutile), it is 4.3; if it is zirconia, it is 6.0; if it is zinc oxide, it is 5.6; if it is copper (II) oxide, it is 6.3; if it is iron (III) oxide, it is 5.2; and if it is indium oxide, it is 7.2 (unit: g / cm). 3 ) If the particles are composite oxide particles, particles containing a mixture of oxides, or a mixture of oxide particles, Sd can be calculated according to the proportion of the oxides. If the constituent component inside the particle is air, Sd is 0.0 g / cm 3For other gases or liquids, the corresponding density is used. For example, in the case of particles of the present invention having a silicon-containing outer shell and a cavity inside it, the porosity is used as the volume ratio of the cavity. The porosity of a particle is defined as the proportion of the cavity in the particle. Specifically, first, a TEM photograph of the particle is taken. At this time, the cavity portion of the particle has a low density, so the contrast of that portion is low. Conversely, the outer shell portion has a high density, so the contrast of that portion is high. The cavity portion and the outer shell portion of the particle can be identified by this difference in contrast. More specifically, image processing is performed on 300 randomly selected particles in the TEM photograph to determine the area of ​​the cavity portion, and the circle-equivalent diameter is calculated from that area, which is used as the average diameter of the cavity portion. The particle shape is assumed to be a perfect sphere, and the average volume of the primary particles and the average volume of the cavity portion are calculated. The porosity is expressed as the ratio of the average volume of the cavity portion to the average volume of the primary particles. Furthermore, when the dispersion medium is methanol, for example, Td is 0.79 g / cm. 3 If other types of dispersion media or mixtures of dispersion media are used, use the corresponding densities.

[0044] A4={[(Ra / Rb)-1]×Rb} / (Ka×Ψp)...Equation (4) (where A4 is the specific surface area of ​​the particle (m 2 / g), Ra is the reciprocal of the relaxation time of pulse NMR in the measurement of the dispersion liquid, Rb is the reciprocal of the relaxation time of pulse NMR in the measurement of the dispersion medium, and Ka is a coefficient depending on the dispersion medium and particles used.

[0045] The coefficient Ka is calculated assuming that the specific surface area (A3) obtained from the average primary particle diameter of the particles is the same as the specific surface area (A4) obtained by pulse NMR measurement of a methanol dispersion of the particles obtained by replacing the dispersion medium of the aqueous dispersion of the particles that has been subjected to the fifth step with methanol.

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

[0047] A3=6000 / Sd / D...Formula (5) (where Sd is the particle density (g / cm 3 ) indicates.

[0048] The specific surface area (A4) of the particles that have been subjected to the fifth step can be obtained by equation (6) using the volume concentration (Ψp) of the particles obtained by equation (3).

[0049] A4={[(Rc / Rd)-1]×Rd} / (Ka×Ψp)...Equation (6) (where A4 is the specific surface area of ​​the particle (m 2 / g), Rc is the reciprocal of the pulse NMR relaxation time in the measurement of the particle dispersion, Rd is the reciprocal of the pulse NMR relaxation time in the measurement of the dispersion medium, and Ka is a coefficient depending on the dispersion medium and 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, so from equations (5) and (6), Ka={[(Rc / Rd)-1]×Rd} / (Ψp×A3)...Equation (7) It can be calculated as:

[0051] Particle 29 In Si-NMR analysis, the ratio of the area of ​​the peak representing the Q4 structure of silicon atoms appearing at a chemical shift of -108 to -120 ppm to the total area of ​​the peaks representing the Q1 to Q4 structures of silicon atoms appearing at a chemical shift of -78 to -120 ppm is preferably 82% or more.Within this range, the particles are dense, and a coated substrate with sufficient hardness and strength can be obtained.

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

[0053] The peak assigned to Q1 is due to one (-OSi) group and three (-OH) groups bonded to the Si atom, the peak assigned to Q2 is due to two (-OSi) groups and two (-OH) groups bonded to the Si atom, the peak assigned to Q3 is due to three (-OSi) groups and one (-OH) group bonded to the Si atom, and the peak assigned to Q4 is due to four (-OSi) groups bonded to the Si atom.

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

[0055] The thickness of the particle outer shell is preferably 3.0 to 12.0 nm, which allows for the production of a coated substrate with high transparency, anti-reflection performance, hardness, and strength.

[0056] If the shell thickness is less than 3.0 nm, it may be difficult to obtain the strength necessary to maintain the particle shape. Conversely, if it exceeds 12.0 nm, the particle refractive index will be high, making it difficult to obtain a coated substrate with a low refractive index. The shell thickness is more preferably 3.0 to 10.0 nm, even more preferably 3.0 to 8.0 nm, and particularly preferably 3.0 to 6.0 nm.

[0057] The particles preferably contain functional groups. In particular, by containing functional groups in the particle shell, the particles have high dispersibility in the dispersion medium, the coating solution for forming the coating, or the matrix of the coating, and the coated substrate using these particles has sufficient hardness and strength because the particle aggregation is suppressed. In addition, by containing silicon in the particle shell, particles with a low refractive index can be obtained, and the presence of surface OH groups derived 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 selected from alkyl groups, acryloyl groups, (meth)acryloyl groups, vinyl groups, alkoxy groups, mercapto groups, epoxy groups, glycidoxy groups, amino groups, phenyl groups, and phenylamino groups. Among these, alkyl groups, acryloyl groups, (meth)acryloyl groups, vinyl groups, mercapto groups, and epoxy groups are preferred because they have high polymerization ability. These functional groups can be identified by measuring and analyzing dry powder of the particles using a Fourier transform infrared spectrometer (FT-IR).

[0059] These functional groups are preferably derived from an organosilicon compound represented by formula (8). This organosilicon compound can be used, for example, as a raw material used to prepare the aforementioned "original particles," as a surface treatment agent used to treat the surface of the particles, or both. Examples of raw materials for preparing the "original particles" include alkoxysilanes such as tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and phenyltrimethoxysilane. Particles treated with such surface treatment agents have many functional groups on the outer shell surface, which makes them highly dispersible in coating solutions and coatings, and provides sufficient hardness and strength on coated substrates.

[0060] 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.)

[0061] The amount of the organosilicon compound containing these functional groups is determined based on the solid content (R n -SiO (4-n) / 2 ) is preferably 1.0 to 30 parts by mass. When such particles are used in a coated substrate, the substrate has high adhesion to the coating, and has high hardness and strength.

[0062] If the amount of the organosilicon compound containing a functional group is less than 1.0 part by mass, sufficient dispersibility and stability may not be obtained, and when these particles are used in a coating, a coated substrate with sufficient hardness and strength may not be obtained. Conversely, if the amount is more than 30 parts by mass, sufficient anti-reflection performance may not be exhibited. 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] As mentioned above, the specific surface area (A4) determined by pulsed NMR measurement of a methanol dispersion of particles indicates the specific surface area of ​​the particle in the portion wetted with the dispersion medium. Here, particles surface-treated with an organosilicon compound have fewer OH groups on their particle surface than the original particles due to the reaction between the organosilicon compound and the OH groups on the particle surface, so the specific surface area of ​​the particle in the portion wetted with the hydrophilic dispersion medium is smaller. Therefore, the specific surface area (A4) also varies depending on the amount of surface treatment (chemical bonding) of the organosilicon compound on the particles. Because the particles of the present invention have high water resistance, the specific surface area (A4) is smaller than the "specific surface area (A3) calculated from the average particle diameter" even without surface treatment with an organosilicon compound. By surface-treating these particles, the specific surface area (A4) tends to be further reduced.

[0064] The silicon content in the particles is preferably 98 parts by mass or more as silica (SiO2) when the total amount of metal elements other than carbon constituting the particles is expressed as 100 parts by mass on an oxide basis. If the SiO2 content is 98 parts by mass or more, a coating having low reflectivity and high hardness and strength is easily obtained. The SiO2 content is more preferably 99 parts by mass or more, even more preferably 99.5 parts by mass or more, and particularly preferably 100 parts by mass.

[0065] As described above, the constituent components of the particles preferably contain silicon (Si) as a main element. Here, the constituent components of the particles may be any of the following (a) to (c). These elements are derived from materials that are preferably used in producing the particles.

[0066] (a) SiO2 (b) An oxide containing Si and at least one element selected from 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 (a) and (b) above

[0067] Incidentally, the content of elements other than Si in the particles in the above item (b) is preferably less than 2 parts by mass on an oxide basis when the total amount of metal elements other than carbon constituting the particles is expressed as 100 parts by mass on an oxide basis. Here, if this content is 2 parts by mass or more, the refractive index of the particles may increase, which may increase the reflectance of the coating, or a transparent coating may not be obtained due to coloring, etc. This content is more preferably less than 1 part by mass, even more preferably less than 0.5 parts by mass, and particularly preferably 0 parts by mass.

[0068] In addition to the particles listed in (a) to (c) above, "particles having an outer shell and a cavity therein" and so-called "solid particles" without a cavity inside the particle may also be present, provided that the refractive index does not deviate from the above-mentioned particle range. The proportion of these particles other than the particles of the present invention varies depending on the type and composition ratio of the elements constituting the particles. For example, in the case of "solid particles" containing 98 parts by mass or more of silicon as SiO2 and having a similar average particle size to the particles of the present invention, the proportion of solid particles to the total particles is preferably less than 10%. This proportion can be determined, for example, by counting the number of particles of the present invention and solid particles in a predetermined field of view of a TEM photograph. If this proportion is 10% or more, the refractive index will be higher than the desired range, and the desired anti-reflection performance may not be achieved when the particles are coated. In the case of such solid particles, the proportion is more preferably less than 5%, even more preferably less than 2%, particularly preferably less than 1%, and most preferably 0%. If particles of a different element type are present, the ratio of the particles of the present invention to other particles can be determined by, for example, mapping particles in a predetermined field of view by energy dispersive X-ray analysis (EDS) and counting the number of particles of the present invention and particles of a different element type.

[0069] The content of each of the alkali metal and alkaline earth metal elements, which are impurities in the particles, expressed as oxides of the elements is preferably 500 ppm or less relative to the particles. A low content of these elements reduces particle coalescence, resulting in high stability of the dispersion and coating solution. Furthermore, the particles are uniformly dispersed in the coating solution and coating, resulting in a coating with high hardness and strength.

[0070] If the content is more than 500 ppm, the proportion of particles that adhere to each other increases, which may result in insufficient stability of the dispersion or coating solution, or insufficient hardness and strength of the coating. The content is more preferably 100 ppm or less. The alkali metals refer to Li, Na, K, Rb, Cs, and Fr, and the alkaline earth metals refer to Be, Mg, Ca, Sr, Ba, and Ra.

[0071] Furthermore, the content of each of the impurities Ag, Cr, Cu, Mn, Mo, Ni, and Pd in ​​the particles is preferably less than 100 ppm, and the content of each of U and Th is preferably less than 0.3 ppb. If the content of these elements is too high, the dispersion may become colored, or a coating with the desired refractive index may not be obtained. Furthermore, when the particles are used in semiconductor circuits such as highly integrated logic and memory, which require high purity, or in optical sensors, the content of each of the elements Ag, Cr, Cu, Mn, Mo, Ni, and Pd, as well as the aforementioned elements Al, As, B, Bi, Cd, Co, Fe, Ga, Ge, In, Pb, Sb, Sn, Ti, V, Zn, and Zr, is preferably less than 0.1 ppm. If the content of these elements is 0.1 ppm or more, the metal elements may cause circuit insulation failure, short-circuit the circuit, or reduce light transmittance. This may result in a decrease in the dielectric constant of the insulating film, an increase in the impedance of the metal wiring, a delay in response speed, an increase in power consumption, etc. U and Th are particularly undesirable because they generate radioactivity, and even the presence of trace amounts of these elements can cause semiconductors to malfunction due to the radioactivity.

[0072] To obtain particles with low content of such elements, it is preferable to use equipment for particle production that is free of these elements and highly chemical-resistant. Specifically, plastics such as FRP and carbon fiber, and alkali-free glass are preferred. Furthermore, it is preferable to purify the raw materials used by distillation, ion exchange, and filtration.

[0073] As described above, methods for obtaining high-purity particles include preparing raw materials with low levels of these elements in advance and suppressing contamination from the particle production equipment.In addition, it is possible to reduce the levels of these elements in particles produced without taking sufficient measures.

[0074] The shape of the particles and the shape of the cavities are not particularly limited. Examples include spherical, ellipsoidal (rugby ball), cocoon-like, confetti-like, chain-like, and dice-like shapes. Among these, spherical particles are preferred because they have high dispersibility and can be uniformly dispersed in the coating. Furthermore, the cavities inside the outer shell preferably have a shape that follows the particle outer shape. This depends on the thickness of the outer shell, but when stress is applied to the particles, a uniform shell thickness can provide sufficient hardness and strength. Furthermore, it is preferable that the cavities are spherical, similar to the shape of the spherical particles.

[0075] It is preferable that this cavity be substantially one cavity in order to reduce the refractive index and obtain a transparent coating. Here, "substantially one cavity" means that the "proportion of particles with one cavity inside the outer shell" is 90% or more, although some particles may have "particles with multiple cavities inside the outer shell" due to particle coalescence or the like. The "proportion of particles with one cavity inside the outer shell" is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and most preferably 100%.

[0076] The porosity of the particles is preferably 5 to 80%. However, there are no particular limitations as long as the above-mentioned refractive index is satisfied. Here, if it is less than 5%, the refractive index will not be sufficiently low, resulting in insufficient anti-reflection performance. Conversely, if it 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 the dispersion medium include water, alcohols, esters, glycols, ethers, ketones, and aprotic polar solvents, which may be used alone or in combination of two or more.

[0079] The concentration of the dispersion liquid is preferably 1 to 40% by mass in terms of the solid content of the particles. If the solid content is less than 1% by mass, the processing time required for producing the coating liquid may be long. Conversely, if the solid content exceeds 40% by mass, the stability of the dispersion liquid may decrease. The concentration of the dispersion liquid is more preferably 5 to 35% by mass, and even more preferably 10 to 30% by mass.

[0080] [Method for producing particle dispersion liquid] The method for producing particles according to the present invention comprises the following steps: a first step of preparing an alkaline aqueous solution; a second step of simultaneously adding to the alkaline aqueous solution solutions of "a solution of a silicon-containing compound" and "a solution of a compound of an alkali-soluble inorganic element other than silicon" so that the molar ratio (MOx / SiO2) is 0.01 to 2.0, where "oxide of silicon" is represented as SiO2 and "oxide of an alkali-soluble inorganic element other than silicon" is represented as MOx, to produce a dispersion of composite oxide particles a; and a third step of simultaneously adding to the alkaline aqueous solution solutions of "a solution of a silicon-containing compound" and "a solution of a compound of an alkali-soluble inorganic element other than silicon" so that the molar ratio (MOx / SiO2) is 0.01 to 2.0, where "oxide of silicon" is represented as SiO2 and "oxide of an alkali-soluble inorganic element other than silicon" is represented as MOx. The method includes, in order, a third step of adding the silicon dioxide particles and the silicon dioxide particles in a molar ratio of 15 to 150 nm to prepare a dispersion of composite oxide particles b having an average particle size of 15 to 150 nm, and a value obtained by subtracting the average particle size of the composite oxide particles a obtained in the second step from this average particle size and dividing the result by 2 to give a dispersion of silica particles of 3 to 14 nm, a fourth step of adding an acid to the dispersion of composite oxide particles b to remove at least a portion of the elements other than silicon that constitute composite oxide particles b to prepare a dispersion of silica particles, a fifth step of heating the dispersion of silica particles to 150 to 300°C at a pH of 9.0 to 11.0, and a sixth step of heating the dispersion of silica particles obtained in the fifth step to 150 to 400°C at a pH of 5.0 to 8.0. The particles of the present invention are thereby obtained.

[0081] The particles produced in this way have a low refractive index, a dense outer shell, and controlled hydrophilic sites on the particle surface, resulting in high water resistance. When these particles are used in coatings, they have excellent anti-reflection performance, are less likely to produce color unevenness, and have high hardness and strength. Each step is described below.

[0082] [First step] First, an alkaline aqueous solution is prepared. Here, the alkaline aqueous solution preferably contains an element that can form an amphoteric oxide. An element that can form an amphoteric oxide means that an oxide containing that element dissolves in an acid with a pH of 3 or less and in an alkali with a pH of 10 or more. 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 these, Al is preferred because it easily reacts with silicon-containing compounds to form composite oxide particles. Similarly, Si (silicon) is preferred because it easily reacts with silicon-containing compounds. Examples of alkaline aqueous solutions containing these suitable elements include aqueous solutions of sodium aluminate, aluminum hydroxide, and sodium silicate.

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

[0084] Here, if the average particle diameter of the particles is less than 5 nm, it is difficult to obtain the particles themselves. Conversely, if the average particle diameter exceeds 25 nm, the refractive index of the particles of the present invention finally obtained may not be sufficiently low, and it may be difficult to obtain the desired resist film. This average particle diameter is more preferably 5 to 20 nm, and even more preferably 5 to 15 nm.

[0085] The oxide-equivalent concentration of the element that becomes the amphoteric oxide in the alkaline aqueous solution is preferably less than 5.0% by mass. This concentration can suppress the aggregation of the particles obtained in the second step. There is no particular lower limit for this concentration, but from the viewpoint of stably obtaining particles with a uniform particle size and high sphericity, it is, for example, 0.1% by mass. This concentration is more preferably less than 4.0% by mass, and even more preferably less than 3.5% by mass.

[0086] [Second process] In this step, a dispersion of composite oxide particles a is prepared by simultaneously adding a solution of a silicon-containing compound and an aqueous solution of an alkali-soluble compound of an inorganic element other than silicon to the alkaline aqueous solution prepared in the first step. The solutions to be added are adjusted so that the molar ratio (MOx / SiO2) is 0.01 to 2.0, where SiO2 represents the oxide of silicon and MOx represents the oxide of an inorganic element other than silicon.

[0087] Here, the "compound containing silicon" may be, for example, at least one selected from silicates, acidic silicic acid solutions, and organic silicon compounds.

[0088] The silicate is preferably one or more silicates selected from alkali metal silicates, ammonium silicates, and silicates of organic bases. Examples of alkali metal silicates include sodium silicate and potassium silicate. Examples of organic bases include quaternary ammonium salts such as tetraethylammonium salts, and amines such as monoethanolamine, diethanolamine, and triethanolamine. Examples of ammonium silicates or silicates of organic bases include alkaline solutions in which ammonia, quaternary ammonium hydroxide, amine compounds, etc. are added to a silicic acid solution.

[0089] The acidic silicic acid solution can be obtained by removing the alkali by treating an aqueous alkali silicate solution with a cation exchange resin, and an acidic silicic acid solution having a pH of 2 to 4 is particularly preferred.

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

[0091] Incidentally, among the organosilicon compounds of formula (8), compounds where n is 1 to 3 have poor hydrophilicity, so it is preferable to hydrolyze them in advance so that they can be uniformly mixed in the reaction system. Well-known methods can be used for hydrolysis. When a basic catalyst such as an alkali metal hydroxide, aqueous ammonia, or an amine is used as a hydrolysis catalyst, the basic catalyst can be removed after hydrolysis, and the resulting solution can be used as an acidic solution. Furthermore, when an acidic catalyst such as an organic acid or inorganic acid is used to prepare a hydrolyzate, it is preferable to remove the acidic catalyst by ion exchange or the like after hydrolysis. The obtained hydrolyzate of the organosilicon compound is preferably used in the form of an aqueous solution. Here, "aqueous solution" means that the hydrolyzate is transparent and not in a cloudy, gel-like state.

[0092] Examples of the organosilicon compound include those shown in Table 1 below, where n is 0 to 3. For example, TMOS, TEOS, 3-methacryloxypropyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, and 8-methacryloxyoctyltrimethoxysilane are preferred.

[0093] Examples of "alkali-soluble compounds of inorganic elements other than silicon" include alkali metal salts or alkaline earth metal salts, ammonium salts, and quaternary ammonium salts of metal or nonmetal oxoacids that form 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, ammonium cerium nitrate, and sodium phosphate.

[0094] These "compounds containing silicon" and "compounds of inorganic elements other than silicon" have high solubility in alkaline solutions. However, when they are mixed in this high-solubility pH range, the solubility of oxo-acid ions such as silicate ions and aluminate ions decreases, and these compounds precipitate to form colloidal particles.

[0095] The concentration of the solution of the "silicon-containing compound" and the concentration of the aqueous solution of the "alkali-soluble compound of an inorganic element other than silicon" are preferably 0.05 to 10.0 mass% as SiO2 and MOx, respectively. When the concentrations are within this range, adhesion of particles to each other is suppressed, and particles with high sphericity can be obtained.

[0096] Here, if the concentration of the solution of the "silicon-containing compound" and the concentration of the aqueous solution of the "alkali-soluble compound of an inorganic element other than silicon" are less than 0.05 mass% as SiO2 and MOx, respectively, the particle growth rate will be slow, and the production efficiency until the desired average particle size of the composite oxide particles a is achieved may be low. Conversely, if the concentration exceeds 10.0 mass%, the particles may coalesce, resulting in irregular particle shapes or aggregation.

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

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

[0099] If the aforementioned "alkali-soluble compounds of inorganic elements other than silicon" are expressed as "oxides," suitable examples include one or more of Al2O3, As2O3, B2O3, Bi2O3, CdO, CoO, Fe2O3, Ga2O3, GeO2, In2O3, PbO, Sb2O3, SnO2, TiO2, VO, ZnO2, and ZrO2. Examples of these "complex oxides of inorganic elements other than silicon" include zinc alumina oxide and indium tin oxide. These oxides are referred to as MOx, and the number of moles is used to calculate the molar ratio. If multiple types of these oxides are present in the reaction system, the sum of the number of moles of each oxide is used. The number of moles of the aforementioned "silicon-containing compounds" expressed as SiO2 is used to calculate the molar ratio.

[0100] The molar ratio in the second step is calculated without including the "elements that become amphoteric oxides" used in the first step.Alkali metals and alkaline earth metals are not "elements that make up particles" but are treated as impurities, so they are not included in the above MOx.

[0101] These points will be similarly handled in the third step described below.

[0102] In the second step, the "solution of a silicon-containing compound" and the "aqueous solution of an alkali-soluble compound of an inorganic element other than silicon" are added simultaneously so that the molar ratio (MOx / SiO2) of these solutions is 0.01 to 2.0. When the molar ratio (MOx / SiO2) in the second step is within this range, the structure of the composite oxide particles is primarily one in which silicon and elements other than silicon are alternately bonded via oxygen. That is, many structures are formed in which oxygen atoms are bonded to the four bonds of a silicon atom, and an element other than silicon, M, is bonded to these oxygen atoms. This allows the silicon atoms to be removed as silicic acid monomers or oligomers along with the element M without destroying the shape of the composite oxide particles when the element other than silicon, M, is removed in the fourth step described below.

[0103] If the molar ratio is less than 0.01, the proportion of "elements other than silicon" removed in the fourth step described below will be small, and the porosity of the final particles may not be sufficiently large. Conversely, if the molar ratio exceeds 2.0, particle growth will be suppressed, and the production efficiency until the desired average particle diameter of composite oxide particles a is achieved may be reduced. This molar ratio is preferably 0.1 to 2.0, more preferably 0.2 to 2.0.

[0104] In this way, the composite oxide particles a obtained in the second step are removed by acid treatment in the fourth step described below, forming hollow spaces inside the outer shells of the finally obtained particles. Therefore, the composite oxide particles a are preferably in a form that can be easily removed by acid treatment.

[0105] The composite oxide particles a are preferably prepared so that the average particle diameter (Da) is approximately 10 to 145 nm.

[0106] If the average particle diameter (Da) is less than 10 nm, the shell of the resulting particles may be too thick, resulting in an insufficient particle porosity. Conversely, if it exceeds 145 nm, the removal of elements M other than silicon in the fourth step described below may be insufficient, resulting in an insufficient particle porosity, making it difficult to obtain particles with a low refractive index, or increasing particle light scattering, resulting in insufficient coating transparency and haze. The average particle diameter (Da) is more preferably 25 to 115 nm, even more preferably 35 to 95 nm, and particularly preferably 35 to 75 nm.

[0107] [Third step] In this step, a "solution of a silicon-containing compound" and an "aqueous solution of an alkali-soluble compound of an inorganic element 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 causes composite oxide particles a to grow, producing a dispersion of composite oxide particles b.

[0108] If the molar ratio (MOx / SiO2) in the second step is A and the molar ratio (MOx / SiO2) in the third step is B, it is preferable to set the ratio (B / A) to less than 1.0. If the ratio (B / A) is less than 1.0, the silica component in the surface layer of the composite oxide particles will be increased, facilitating the formation of an outer shell. As a result, even if elements other than silicon are removed in the fourth step described below, the shape of the composite oxide particles will not be destroyed, and hollow silica particles can be stably obtained. If the ratio (B / A) is 1.0 or more, it is difficult to form an outer shell rich in silica components, and therefore the composite oxide particles will be destroyed when elements other than silicon are removed in the fourth step, making it difficult to maintain the particle shape. This may make it difficult to obtain hollow silica particles. The ratio (B / A) is more preferably 0.8 or less, and even more preferably 0.6 or less.

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

[0110] If the average particle diameter (Db) is less than 15 nm, the porosity of the particles will be small, making it difficult to obtain a film with a low refractive index. Conversely, if it exceeds 150 nm, the particles will exhibit increased light scattering, potentially resulting in insufficient transparency and haze for the coating. The average particle diameter (Db) is preferably 30 to 120 nm, more preferably 40 to 100 nm, and even more preferably 40 to 80 nm. If the value (Dc) obtained by subtracting the average particle diameter of composite oxide particles a from the average particle diameter of composite oxide particles b and dividing the result by 2 is less than 3 nm, the resulting outer shell will be too thin, making it difficult to maintain the particle shape. Conversely, if the value (Dc) exceeds 14 nm, the refractive index will not be sufficiently low, making it difficult to obtain the desired antireflection performance. The value (Dc) is more preferably 3 to 10 nm, even more preferably 3 to 8 nm, and particularly preferably 3 to 6 nm.

[0111] In the composite oxide particles b, a layer having a lower molar ratio (MOx / SiO2) than that of the composite oxide particles a is formed around the composite oxide particles a. This layer is less susceptible to acid attack than the composite oxide particles a, and therefore forms the outer shell of the final particles.

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

[0113] The dispersion of composite oxide particles a used in this step preferably has a pH of 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 to 3.0 mass% in terms of SiO2 and MOx, respectively. When the concentrations are within these ranges, aggregation of the composite oxide particles a obtained in the second step is suppressed, and monodisperse particles can be obtained.

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

[0116] [Fourth step] In this step, an acid is added to the dispersion of composite oxide particles b to remove at least a portion of the elements other than silicon that constitute composite oxide particles b, thereby producing a dispersion of silica particles. The elements can be removed, for example, by dissolving them using a mineral acid or an organic acid, by contacting them with a cation exchange resin to remove them by ion exchange, or by a combination of these methods.

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

[0118] If the concentration is less than 0.1% by mass, the amount of dissolved silica will be large, which may make it difficult to maintain the shape of the composite oxide particles. Furthermore, the low concentration will result in low treatment efficiency. Conversely, if the concentration is higher than 30% by mass, the particles may not be sufficiently dispersible. Furthermore, if the composite oxide particles contain a large amount of elements other than silicon, it may be difficult to uniformly or efficiently 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 carried out until the molar ratio (MOx / SiO2) of the resulting particles becomes 0.03 or less.

[0120] If the molar ratio (MOx / SiO2) is greater than 0.03, it may be difficult to obtain the refractive index of the particles obtained in the end and the strength required to maintain the particle shape. The molar ratio (MOx / SiO2) is more preferably 0.01 or less.

[0121] The dispersion of silica particles from which at least a portion of the elements other than silicon has been removed can be washed by a known washing method such as ultrafiltration, if necessary. At least a portion of the dissolved elements other than silicon are removed by washing. In this case, if a portion of the alkali metal ions and the like in the dispersion is removed in advance and then ultrafiltration is performed, a dispersion of silica particles with high dispersion stability can be obtained.

[0122] Furthermore, this dispersion from which "at least a portion of the elements other than silicon have been removed" can also be contacted with at least one of a cation exchange resin and an anion exchange resin to remove a portion of the dissolved elements other than silicon, alkali metal ions, etc. When washing, heating the resin can ensure effective washing.

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

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

[0125] If the pH is less than 9.0, the particles may not be sufficiently densified, resulting in insufficient hardness and strength of the coated substrate. Conversely, if the pH is more than 11.0, the particles may be excessively dissolved, resulting in a risk of not obtaining particles with internal cavities. The pH is preferably 9.5 to 11.0, more preferably 10.0 to 10.8.

[0126] Furthermore, if the heating temperature is below 150°C, the particles may not be sufficiently densified, and the hardness and strength of the coated substrate may be insufficient. Conversely, if the temperature exceeds 300°C, the particles may be excessively melted, and particles with internal cavities may not be obtained. This temperature is preferably 160 to 280°C, more preferably 180 to 280°C.

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

[0128] If the concentration is less than 0.1% by mass, the particles may be excessively dissolved, and particles with internal cavities may not be obtained. Furthermore, the low concentration reduces the processing efficiency. Conversely, if the concentration is higher than 30% by mass, the particles may aggregate, or the particles may not be sufficiently densified, resulting in insufficient hardness and strength of the coated substrate. The concentration of the dispersion of composite oxide particles b is more preferably 0.5 to 25% by mass.

[0129] [Sixth step] In this step, the silica particle dispersion obtained in the fifth step is heated to 150 to 400° C. at a pH of 5.0 to 8.0, thereby increasing the water resistance of the particles and producing a coated substrate with excellent anti-reflection performance and less color unevenness.

[0130] If the pH is less than 5.0, the particles have high solubility, which tends to generate hydrophilic sites on the particle surface, potentially resulting in insufficient water resistance of the coated substrate. Conversely, if the pH is greater than 8.0, the coated substrate may also have insufficient water resistance. The pH is preferably 5.5 to 7.5, more preferably 6.0 to 7.0.

[0131] Furthermore, if the heating temperature is below 150°C, the particles will not dissolve, the hydrophilic sites on the particle surface will not be reduced sufficiently, and the water resistance of the coated substrate may be insufficient. Conversely, if the temperature exceeds 400°C, the particles will dissolve excessively, and particles with internal cavities may not be obtained. This temperature is preferably 160 to 300°C, more preferably 180 to 250°C.

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

[0133] If the concentration is less than 0.1% by mass, the particles may be excessively dissolved, possibly resulting in particles with internal cavities. Furthermore, the low concentration reduces the processing efficiency. Conversely, if the concentration is greater than 30% by mass, the particles may aggregate, the water resistance of the particles may be insufficient, the anti-reflection performance of the coated substrate may be insufficient, and color unevenness and transparency may be reduced. The concentration of the dispersion of composite oxide particles b is more preferably 0.5 to 25% by mass.

[0134] The particles obtained in the sixth step may be surface-treated by adding an organosilicon compound. The organosilicon compound used is preferably an organosilicon compound represented by the above-mentioned formula (8) in which n is 0 to 3. When an organosilicon compound in which n is 0 is used, it is preferable to use a partial hydrolyzate of the organosilicon compound. The introduction of a functional group improves dispersibility in the coating solution or coating, and is preferable because it provides sufficient hardness and strength to the coated substrate. These organosilicon compounds may be used alone or in combination.

[0135] The particle surface treatment method begins by preparing a particle dispersion. It is preferable to use an alcohol such as methanol or ethanol as the dispersion medium. A predetermined amount of an organosilicon compound represented by formula (8) is added to the dispersion, and the organosilicon compound is hydrolyzed. Water can be added to this hydrolysis as needed. The ratio (Mw / Mo) of the number of moles of water (Mw) to the number of moles of the organosilicon compound (Mo) is preferably 1 or greater.

[0136] If the ratio (Mw / Mo) is less than 1, hydrolysis may be insufficient, resulting in insufficient transparency and haze of the coating. There is no particular upper limit to this ratio, but if this ratio exceeds 500, the hydrolysis reaction may become intense, resulting in polymerization of the organosilicon compounds, making it difficult to efficiently treat the particle surfaces with the organosilicon compound. This ratio is more preferably 1 to 100.

[0137] In this hydrolysis, an acid or alkali may be used as a catalyst for hydrolysis, if necessary. Among these, ammonia is preferred. This is because if ammonia is used, it can be easily removed even if it remains in the dispersion, and the stability of the dispersion is easily maintained. The number of moles of ammonia used (M N ) and the mole number (Mo) of the organosilicon compound (M N / Mo) is preferably in the range of 0.05 to 50.

[0138] Here, the ratio (M NIf the ratio ( / Mo) is less than 0.05, hydrolysis may be insufficient, resulting in insufficient transparency and haze of the coating. If this ratio exceeds 50, the hydrolysis reaction may become so intense that the organosilicon compounds may polymerize with each other, making it difficult to efficiently treat the particle surfaces with the organosilicon compound. This ratio is more preferably 0.1 to 10.

[0139] The surface treatment is preferably carried out in a homogeneous system, and in order to promote the reaction between the particles and the organosilicon compound, it is preferable to heat the particles at a temperature below the boiling point of the dispersion medium (for example, room temperature to 120°C) for 0.5 to 48 hours.

[0140] When the particles whose surfaces are chemically bonded to the organosilicon compound by this surface treatment are used in an anti-reflection coated substrate, the particles have high dispersibility in the coating, and a coated substrate with excellent strength can be obtained.

[0141] Examples of organosilicon compounds include those shown in Table 1. These organosilicon compounds may be contained in the particles alone or in combination. In the surface treatment, these organosilicon compounds may be used alone or in combination, or may be used in stages with the same type, a mixture of multiple types, or multiple types separately.

[0142] [Table 1]

[0143] The amount of the organosilicon compound is 100 parts by mass of the particles before surface treatment. n -SiO (4-n) / 2 ) is preferably 1.0 to 30 parts by mass.

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

[0145] [Coating liquid for film formation] The particles of the present invention can be used in a coating solution for forming a film. This coating solution contains particles, a matrix-forming component, and a dispersion medium. The dispersion medium contains at least one of water and an organic dispersion medium. In addition to these, the coating solution may contain additives such as a polymerization initiator, a leveling agent, and a surfactant.

[0146] The particle concentration in the coating solution is preferably 5 to 95% by mass in terms of solid content relative to the total amount of solid content, such as the particles and matrix-forming components, contained therein. If the particle concentration is less than 5% by mass, the refractive index of the coating film may not be sufficiently reduced. Conversely, if it is more than 95% by mass, cracks may occur in the coating film, adhesion to the substrate may be insufficient, and hardness, strength, transparency, haze, etc. may be insufficient. The particle concentration is more preferably 10 to 85% by mass, and even more preferably 20 to 70% by mass.

[0147] The matrix-forming component may be an inorganic matrix-forming component or an organic resin matrix-forming component, such as a polycondensate of an organosilicon compound, an ultraviolet-curable resin, a thermosetting resin, or a thermoplastic resin.

[0148] Examples of ultraviolet curable resins include (meth)acrylic resins, γ-glycyloxy resins, urethane resins, and vinyl resins.

[0149] Examples of thermosetting resins include urethane resins, melamine resins, silicon resins, butyral resins, reactive silicone resins, phenolic resins, epoxy resins, unsaturated polyester resins, and thermosetting acrylic resins.

[0150] Thermoplastic resins include polyester resin, polycarbonate resin, polyamide resin, polyphenylene oxide resin, thermoplastic acrylic resin, vinyl chloride resin, fluororesin, vinyl acetate resin, silicone rubber, and the like.

[0151] These resins may be copolymers or modified products of two or more kinds, or may be used in combination. Furthermore, these resins may be emulsion resins, water-soluble resins, or hydrophilic resins.

[0152] The components forming these resins are preferably monomers or oligomers in view of particle dispersibility and ease of forming a substrate with a coating.

[0153] The concentration of the matrix-forming component in the coating solution is preferably 5 to 95% by mass in terms of solid content, based on the total amount of solid content, such as the particles and matrix-forming component, contained therein. If the concentration of the matrix-forming component is less than 5% by mass, it is difficult to form a film. Even if a film is obtained, there is a risk that the film may crack, its adhesion to the substrate may be insufficient, and its hardness, strength, transparency, haze, etc. may be insufficient. Conversely, if it is more than 95% by mass, the amount of particles may be so small that the refractive index may not be sufficiently reduced. The concentration of this matrix-forming component is more preferably 15 to 90% by mass, and even more preferably 30 to 80% by mass.

[0154] As the organic dispersion medium, one that can uniformly disperse particles and dissolve or disperse additives such as matrix-forming components and polymerization initiators is used. Among these, 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. Examples of polar dispersion media include esters, ketones, and aprotic dispersion media. These may be used alone or in combination of two or more.

[0155] [Table 2]

[0156] Any additives that can be conventionally used for film formation can be used, such as a polymerization initiator and a leveling agent, which can be used to promote polymerization of the matrix-forming components and improve film-forming properties.

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

[0158] Examples of the leveling agent include acrylic leveling agents, silicone leveling agents, acrylic silicone leveling agents, etc. Among these leveling agents, those having a fluorine group are preferably used from the viewpoint of improving strength.

[0159] Regarding the concentration of these additives in the coating solution, those contained as solids when the coating is formed are counted as matrix-forming components for convenience, and are counted as the matrix after the coating is formed.

[0160] [Table 3]

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

[0162] Here, if the solids concentration of the coating solution is less than 0.1% by mass, it may take a long time to process the coated substrate, which may result in a decrease in productivity. Conversely, if it is more than 60% by mass, the stability of the coating solution may decrease. Furthermore, the viscosity of the coating solution may increase, which may result in a decrease in coatability. The solids concentration of the coating solution is more preferably 1 to 50% by mass.

[0163] [Substrate with coating] The coating liquid is used to form a coating on a substrate. Such a coated substrate is used, for example, in display devices that require transparency.

[0164] Specifically, the coating liquid is applied to a substrate, followed by drying and ultraviolet irradiation to form a coating on the substrate. The method for applying the coating liquid is not particularly limited as long as it can form a coating on the substrate. Well-known methods such as spraying, spinning, roll coating, bar coating, slit coater printing, gravure printing, and microgravure printing can be used. Drying involves heating to, for example, about 50 to 150°C to evaporate and remove the dispersion medium. Then, ultraviolet irradiation is performed to promote polymerization of the resin component, thereby increasing the hardness of the coating. The coating is mainly formed from a matrix (resin) component and particles.

[0165] In the coating, the ratio of the solid content of the particles and matrix-forming components in the coating solution is the same as the ratio of the particle components and matrix in the coating. As mentioned above, the additives remaining as solids in the coating solution are counted as the matrix.

[0166] The film thickness of the coating can be appropriately selected depending on the application. For example, a transparent coating preferably has a thickness of 80 to 350 nm. If the film thickness is thinner than 80 nm, the hardness and strength of the coating may be insufficient. Furthermore, if the film is too thin, sufficient anti-reflection performance may not be obtained. Conversely, if the film thickness is thicker than 350 nm, the film may be prone to cracking, resulting in insufficient strength. Furthermore, if the film is too thick, the transparency and haze may be insufficient, and the anti-reflection performance may be reduced. This film thickness is more preferably 85 to 220 nm, and even more preferably 90 to 110 nm.

[0167] The refractive index of the transparent coating is preferably 1.10 to 1.45. It is difficult to obtain a transparent coating with a refractive index of less than 1.10, and if the refractive index exceeds 1.45, the anti-reflection performance may be insufficient, although this depends on the refractive index of the substrate or the refractive index of other films formed below the transparent coating, if necessary. 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 more. If the light transmittance is less than 85.0%, the clarity of images may be insufficient on display devices, etc. The light transmittance is more preferably 90.0% or more.

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

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

[0171] The hardness of the coating is preferably H or more. If it is less than H, the hardness is insufficient as a hard coat film. The hardness is more preferably 2H or more, and even more preferably 3H or more.

[0172] The strength of the coating was measured using #0000 steel wool at a specified load / cm 2 The film is evaluated by sliding 50 times under the above conditions. It is preferable that no streaky scratches are observed on the film surface when the specified load is 200 g. This strength is more preferably such that no scratches are observed at 500 g, and even more preferably such that no scratches are observed at 1000 g.

[0173] The water resistance of the coating is evaluated by dropping distilled water onto the coated substrate, leaving it for 30 minutes, wiping it off, and visually observing the drop marks. This water resistance is preferably such that the drop marks disappear within 30 minutes after wiping. If the drop marks remain visible for more than 30 minutes, the reflection in the display device may become non-uniform, which may be visually recognized as color unevenness. This water resistance is more preferably such that the drop marks disappear within 5 minutes, and even more preferably such that the drop marks are not visible immediately after wiping.

[0174] Any known substrate can be used, but from the viewpoints of transparency, flexibility, toughness, etc., transparent resin substrates such as polycarbonate, acrylic resin, polyethylene terephthalate, triacetyl cellulose (TAC), polymethyl methacrylate resin, cycloolefin polymer, etc. are preferred. There are no particular restrictions on the thickness of the substrate, but in consideration of durability and handleability, it is preferably 10 to 100 μm, more preferably 20 to 80 μm.

[0175] The adhesion between the coating and the substrate is preferably achieved by scratching the surface of the coated substrate with a knife in a grid pattern, adhering cellophane tape to the scratched surface, and then peeling off the cellophane tape. The more grid patterns that remain, the more likely the coating will not peel off and the higher the adhesion to the substrate.

[0176] Furthermore, a coated substrate having another coating formed on the substrate can also be used. Examples of the other coating include a conventionally known hard coat film, a primer film, a high refractive index film, and a conductive film.

[0177] Examples of the present invention will be described below.

[0178] [Example 1] <Production of particle dispersion> 9934.4 g of pure water was added to 65.6 g of an aqueous dispersion of silica particles (Cataloid SI-30, manufactured by JGC Catalysts and Chemicals Co., Ltd., average particle size 12 nm, solid content 30.5% by mass), and then a 1% by mass aqueous NaOH solution was added to prepare 10.0 kg of an aqueous solution with a pH of 12.5 (first step).

[0179] Next, this was heated to 80°C, and 67.0 kg of a sodium silicate aqueous solution with a SiO2 concentration of 1.5 mass% and 67.0 kg of a sodium aluminate aqueous solution with an Al2O3 concentration of 0.5 mass% were added. After that, washing was carried out by centrifugal sedimentation to obtain a dispersion of composite oxide particles (a1). The average particle diameter of these composite oxide particles (a1) was 49 nm (second step).

[0180] This dispersion of composite oxide particles (a1) was heated to 98°C, and 162.0 kg of a sodium silicate aqueous solution with a SiO2 concentration of 1.5 mass% and 54.0 kg of a sodium aluminate aqueous solution with an Al2O3 concentration of 0.5 mass% were added. The mixture was then washed using an ultrafiltration membrane, and the solids concentration was adjusted to 13 mass%. The mixture was then filtered through a capsule filter with 1 μm openings to obtain a dispersion of composite oxide particles (b1). The average particle diameter of the composite oxide particles (b1) was 60 nm (third step).

[0181] 11,250 g of pure water was added to 5,000 g of this dispersion of composite oxide particles (b1), and concentrated hydrochloric acid (concentration: 35.5% by mass) was added dropwise to adjust the pH to 1.0. 10 L of a hydrochloric acid solution at pH 3 and 5 L of pure water were added to the dispersion, and the dissolved aluminum salt was separated and washed using an ultrafiltration membrane to obtain silica particles (c1) with a concentration of 10% by mass (fourth step).

[0182] Next, ammonia water was added to 500 g of the dispersion of silica particles (c1) to adjust the pH of the dispersion to 10.6, and the dispersion was transferred to a pressure-resistant container, heated to 250°C and maintained for 10 hours, and then cooled to room temperature to obtain silica particles (d1) (fifth step).

[0183] Next, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), and then ammonia water was added to adjust the pH of the dispersion to 6.5, and the dispersion was transferred to a pressure-resistant container. Next, the dispersion was heated to 250°C and maintained for 10 hours, and then cooled to room temperature to obtain silica particles (e1) (sixth step).

[0184] Thereafter, ion exchange was performed for 3 hours using 800 g of a cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), followed by ion exchange for 3 hours using 400 g of an anion exchange resin (Diaion SA20A manufactured by Mitsubishi Chemical Corporation). Thereafter, ion exchange was further performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation) at 80°C, followed by washing, to obtain an aqueous dispersion of "particles (original particles) having a silicon-containing outer shell and a cavity inside" (P1).

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

[0186] <Surface treatment of particles with organosilicon compounds> To 200 g of the methanol dispersion of the particles (P1), 0.4 g of ammonia water with a concentration of 28% by mass and 4.0 g of pure water were added, and the mixture 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 (solid content (R n -SiX 4-n ) was added, and the mixture was stirred at 50°C for 24 hours to obtain a dispersion of surface-treated particles (S1).

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

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

[0190] (1) Average particle size The particle dispersion was diluted to 0.01% by mass and then dried on a collodion film of a copper cell for an electron microscope. It was then photographed at a predetermined magnification using a field emission transmission electron microscope (HF5000, manufactured by Hitachi High-Technologies Corporation). The particle area of ​​300 randomly selected particles in the obtained TEM photograph was calculated by image processing, and the equivalent circle diameter was calculated from the area. The average of the equivalent circle diameters was used as the average particle diameter of the particles.

[0191] (2) Refractive index The particle dispersion was placed in an evaporator and the dispersion medium was evaporated. It was then vacuum dried at 120°C for 24 hours to obtain a particle powder. A few drops of a standard refractive index liquid with a known refractive index were placed on a glass plate, and the powder was mixed with this. This procedure was repeated with various standard refractive index liquids, and the refractive index of the standard refractive index liquid when the mixed liquid became transparent was taken as the refractive index of the particles.

[0192] (3) Specific surface area by BET method using water vapor gas (A1) The particle dispersion was heated to 105°C and held at this temperature for 3 hours to dry. Using a specific surface area measuring device (Belsorp mini II manufactured by Japan Bell Co., Ltd.), the obtained powder was vacuum degassed while water vapor was adsorbed, and the specific surface area (A1) was calculated from the amount of adsorption of each gas using the BET method.

[0193] (4) Specific surface area by BET method using nitrogen gas (A2) In the same manner as in the measurement of the specific surface area (A1) of the particles described above, the obtained powder was vacuum degassed using a specific surface area measuring device (Belsorp mini II manufactured by Bell Japan Co., Ltd.) while nitrogen gas was adsorbed, and the specific surface area (A2) was calculated from the amount of adsorbed nitrogen using the BET method.

[0194] (5) Mass increase due to moisture absorption The particle dispersion was placed in an evaporator to evaporate the dispersion medium. The mixture was then heated to 200°C and held for 3 hours to dry. The mixture was then left for 24 hours in an atmosphere at 25°C and a relative humidity of 90%. The particle powder thus obtained was measured before and after being left for 24 hours in an atmosphere at 25°C and a relative humidity of 90%, and the particle mass increase was calculated from the difference between the particle mass before and after being left.

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

[0196] A3=6000 / Sd / D...Formula (5) (where Sd is the particle density (g / cm 3) and D indicates the average particle size (nm).

[0197] (7) Number density of silanol groups on the particle surface The number density of silanol groups of particles is calculated from the Sears number and the specific surface area, specifically, by the above-mentioned formulas (1) and (2).

[0198] The Sears number was measured by NaOH titration according to the method described by Sears in Analytical Chemistry 28 (1956), 12, 1981-1983. Specifically, a methanol dispersion of particles was solvent-exchanged with water using an evaporator, and this aqueous dispersion of particles was diluted with pure water to a silica particle concentration of 1% by mass. 150 g of the diluted solution was added with 30 g of sodium chloride and adjusted to pH 4.0 with hydrochloric acid. The solution was then titrated with 0.1 N NaOH at a rate of 0.1 ml / s, and the Sears number was expressed as the amount of NaOH required to reach a pH of 9.0. (In other words, the Sears number is the amount of 0.1 N NaOH titrated to 1.5 g of particles.) The titration with 0.1 N NaOH was performed using an automatic titrator at a fixed titration rate of 0.1 ml / s.

[0199] (8) Specific surface area by pulsed NMR (A4) For the particle dispersion, the relaxation times of the dispersion and the dispersion medium were measured using a pulse NMR (Acorn Area manufactured by Xigo nanotools), and the specific surface area (A4) was calculated using the above-mentioned formulas (3) and (4). The measurement conditions were a magnetic field of 0.3 T, a measurement frequency of 13 MHz, and a measurement nucleus of 1 The H NMR measurement was performed by the CPMG pulse sequence method with a sample volume of 1 ml, a Ka value of 0.000168, and a temperature of 25° C. Here, the Ka value was calculated from pulse NMR measurements of a methanol dispersion of the surface-treated particles (P1) and the methanol dispersion medium at a solid content of 20.0 mass % and 25° C. using the above-mentioned formulas (5) to (7).

[0200] (9) Particle 29The area ratio of the peak representing the Q4 structure in Si-NMR analysis The particle dispersion is placed in a dedicated zirconia sample tube and measured using a 6 mm diameter sample tube probe for solids on an NMR device (Agilent VNMRS-600) using the single pulse non-decoupling method without sample rotation. Polydimethylsiloxane is used as the secondary standard, and the chemical shift is set to -34.44 ppm. The spectrum obtained is subjected to waveform separation using the analysis software Origin, and the area of ​​each peak is calculated. More specifically, 29 In Si-NMR spectroscopy, the area of ​​the peak appearing at chemical shifts of -78 to -88 ppm (Q1), the area of ​​the peak appearing at chemical shifts of -88 to -98 ppm (Q2), the area of ​​the peak appearing at chemical shifts of -98 to -108 ppm (Q3), and the area of ​​the peak appearing at chemical shifts of -108 to -120 ppm (Q4) were calculated as (Q4 / ΣQ) × 100, where ΣQ = Q1 + Q2 + Q3 + Q4.

[0201] (10) Particle shell thickness, porosity, and density As with the average particle diameter described above, the area of ​​the cavity portion of the particle was determined from the TEM photograph, and the circle-equivalent diameter was calculated from that area. The average value of these circle-equivalent diameters was taken as the average cavity diameter. The difference between the average particle diameter of the particles and the average cavity diameter was divided by 2 to calculate the thickness of the particle's outer shell. Furthermore, assuming the shape of the particles and cavities to be perfect spheres, the average volume of the particles and the average volume of the cavities were determined, and the porosity was calculated as the ratio of the average volume of the cavities to the average volume of the particles. Furthermore, the particle density (Sd) was calculated from the obtained porosity, the proportion of the particle's constituent components, and its density.

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

[0203] First, the dispersion liquid was dried in an evaporator and then dried at 150° C. The dried powder was analyzed by a diffuse reflectance method using a Fourier transform infrared spectrometer (FT-IR) (FT / IR-6100 manufactured by JASCO Corporation) in the wavenumber range of 700 cm-1 ~4000cm -1 , detector: TGS, resolution: 4.0 cm -1 Measurements were performed with 50 accumulations, peaks were detected, and functional groups were identified by referring to the organic compound spectrum database SDBS (https: / / sdbs.db.aist.go.jp (National Institute of Advanced Industrial Science and Technology, 2021.01)).

[0204] (12) Solid content of organosilicon compound having functional groups The dispersion was centrifuged for 30 minutes using a small ultracentrifuge (Hitachi Koki Co., Ltd., CS150GXL) at a temperature of 10°C and a rotation speed of 1,370,000 rpm (1,000,000 G). The precipitate from the treatment solution was collected and vacuum dried at 120°C for 24 hours to obtain a particle powder. The mass loss of this powder before and after heating at 500°C was measured using a thermogravimetric differential thermal analyzer (Hitachi High-Tech Science Co., Ltd., TG / DTA EXSTAR6000 MSD). The amount of silicon derived from the organosilicon compound was calculated from the difference with the original particle mass. Next, the solid content (R) derived from the organosilicon compound was determined from the structure of the organosilicon compound used in the surface treatment. n -SiO (4-n) / 2 The solid content of the organosilicon compound having a functional group was calculated by converting the amount of the solid content into the amount of the organosilicon compound having a functional group.

[0205] (13) Particle shape and solid particle number ratio In the same manner as in the case of the average particle diameter of the particles described above, the particle shape and the ratio of the number of solid particles to the total number of particles were determined from the TEM photographs. The shape of the particles produced this time was spherical in both the Examples and Comparative Examples.

[0206] (14) Content of metal elements and metal impurities in particles The content of metal elements (alkali metals, alkaline earth metals, Al, Ag, Co, Cr, Cu, Fe, In, Mn, Ni, Pd, Sb, Si, Sn, Th, Ti, U, Zn, Zr, etc.) in the particles was measured by dissolving the particles in hydrofluoric acid, heating to remove the hydrofluoric acid, adding pure water as needed, and measuring the resulting solution using an ICP inductively coupled plasma optical emission spectrometer mass spectrometer (ICP-8500, manufactured by Shimadzu Corporation). Note that for metal elements other than the above-mentioned impurity elements, the total amount of metal elements other than carbon contained in the particles was calculated so that it was 100 parts by mass on an oxide basis.

[0207] <Production of Coating Solution for Forming Anti-Reflection Film> The dispersion medium of the produced methanol dispersion of particles (S1) was replaced with methyl isobutyl ketone (MIBK) using an evaporator to prepare an MIBK dispersion of particles (S1) with a solid content concentration of 20.5 mass %.

[0208] 8.05 g of the MIBK dispersion of particles (S1), 1.07 g of a multifunctional acrylate resin (Light Acrylate DPE-6A manufactured by Kyoeisha Chemical Co., Ltd.), 0.12 g of a bifunctional acrylate resin (SR-238F manufactured by Tomoe Engineering Co., Ltd.), 0.05 g of reactive silicone oil (KF-2012 manufactured by Shin-Etsu Chemical Co., Ltd.), 0.37 g of silicone-modified polyurethane acrylate (Shikoh UT-4314 manufactured by Mitsubishi Chemical Corporation, solids 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, 9.60 g of MIBK, and 16.00 g of isopropyl glycol were mixed to produce a coating solution for forming an anti-reflective coating having a solids concentration of 3.0% by mass.

[0209] <Production of coated substrate> A hard coat paint (ELCOM HP-1004 manufactured by JGC Catalysts and Chemicals Co., Ltd.) was applied to a TAC film (FT-PB40UL-M manufactured by Fujifilm Corporation, thickness 40 μm, refractive index 1.51) using a bar coater (#18), dried at 80°C for 120 seconds, and then applied with 300 mJ / cm 2The hard coat film was cured by irradiation with ultraviolet light of 1000 kJ / cm 2 , thereby producing a substrate with a hard coat film. The hard coat film had a thickness of 8 μm. This hard coat film was used in common in all examples and comparative examples.

[0210] Next, a coating solution for forming an anti-reflective coating was applied onto the hard coat film by a bar coater method (#4), dried at 80°C for 120 seconds, and then subjected to 600 mJ / cm 2 in a nitrogen atmosphere. 2 The coating was cured by irradiation with ultraviolet light of 1000 kJ / cm 2 , to produce a substrate with a transparent anti-reflection coating.

[0211] The coated substrate was measured for the following items, and the results are shown in Tables 8 and 9 (the same applies to the following Examples and Comparative Examples).

[0212] (15) Thickness of hard coat film The thickness of the hard coat film was determined as the average value of measurements taken at any five points on the film using a digital gauge (gauge stand ST-0230 and digital gauge counter DG-5100, manufactured by Ono Sokki Co., Ltd.).

[0213] (16) Thickness and reflectance of anti-reflection transparent coating 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.) and the reflectance was evaluated according to the following classification. Evaluation criteria: 0.7% or less: ◎◎ Over 0.7% and 1.0% or less: ◎ Over 1.0% and 1.5% or less: ○ Over 1.5% and 2.0% or less: △ Over 2.0%: ×

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

[0215] (18) Measurement of scratch resistance Use #0000 steel wool and apply a specified load / cm 2The coating was slid 50 times under each load. The surface of the coating was visually inspected at each load. The results were classified into the following categories to evaluate the strength. Evaluation criteria: 1000g / cm 2 That's all:◎ 500g / cm 2 More than 1000g / cm 2 Less than:○ 200g / cm 2 More than 500g / cm 2 Less than:△ 200g / cm 2 Less than: ×

[0216] (19) Pencil hardness The pencil hardness was measured using a pencil hardness tester in accordance with JIS K 5400. That is, a pencil was set at a 45-degree angle to the coating surface, and a predetermined load was applied and pulled at a constant speed to observe whether scratches were present. The hardness was evaluated according to the following classification. Evaluation criteria: 3H or more:◎ 2H:○ H:△ B or less: ×

[0217] (20)Water resistance Distilled water was dropped onto the coated substrate, left for 30 minutes, and then wiped off, and the remaining traces were visually observed. Water resistance was evaluated by classifying them as follows: Evaluation criteria: No drip marks observed: ◎ Drip marks are visible but disappear within 5 minutes: ○ Droplet marks disappear within 5 minutes or less than 30 minutes: △ Drip marks are visible for more than 30 minutes: ×

[0218] (21) Adhesion The surface of the coated substrate was scratched with a knife in 11 parallel lines spaced 1 mm apart to create 100 squares, to which cellophane tape was adhered. The cellophane tape was then peeled off and the number of squares where the coating remained was counted. The results were classified as follows to evaluate adhesion. Evaluation criteria: Number of remaining squares: 100 Number of remaining squares: 99 or less: ×

[0219] [Example 2] In the first step, a sodium aluminate aqueous solution having an Al2O3 concentration of 22% by mass was added to pure water to prepare 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 were prepared; in the third step, 58.5 kg of a sodium silicate aqueous solution and 19.5 kg of a sodium aluminate aqueous solution were prepared; in the fifth step, the pH was set to 9.5 and the heating temperature to 160°C; in the sixth step, the pH was set to 5.0 and the heating temperature to 200°C; and in the surface treatment of the particles, 10.0 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound. A particle dispersion was produced in the same manner as in Example 1, except for this.

[0220] The dispersion medium of the methanol dispersion of these particles was replaced with MIBK to obtain a particle dispersion with a solid content of 20.5% by mass. 8.31 g of the MIBK dispersion of these particles, 1.02 g of a multifunctional acrylate resin (Kyoeisha Chemical Co., Ltd. Light Acrylate DPE-6A), 0.11 g of a bifunctional acrylate resin (Tomoe Engineering Co., Ltd. SR-238F), 0.05 g of reactive silicone oil (Shin-Etsu Chemical Co., Ltd. KF-2012), 0.37 g of silicone-modified polyurethane acrylate (Mitsubishi Chemical Co., Ltd. Shikoh UT-4314, solids concentration 30% by mass), 0.08 g of a photopolymerization initiator (IGM Resins BV Omnirad TPO H), 64.66 g of isopropyl alcohol, 9.39 g of MIBK, and 16.00 g of isopropyl glycol were mixed to produce an anti-reflective coating coating solution with a solids concentration of 3.0% by mass. A coated substrate was produced in the same manner as in Example 1.

[0221] [Example 3] In the first step, 9900.0 g of pure water was added to 100.0 g of an aqueous dispersion of silica-based particles (USBB-120 manufactured by JGC Catalysts and Chemicals Co., Ltd., average particle size 25 nm, solid content concentration 20% by mass), and then a 1% by mass NaOH aqueous solution was added to prepare 10.0 kg of an aqueous solution with 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 were added. In the third step, 249.0 kg of an aqueous sodium silicate solution and 83.0 kg of an aqueous sodium aluminate solution were added. In the fifth step, the pH was 11.0, the heating temperature was 300 ° C., and in the sixth step, the heating temperature was 400 ° C. Except for this, the particle dispersion, coating liquid, and coated substrate were produced in the same manner as in Example 1.

[0222] [Example 4] A particle dispersion was produced in the same manner as in Example 1, except that in the first step, a sodium aluminate aqueous solution having an Al2O3 concentration of 22 mass% was added to pure water to prepare 20.0 kg of a sodium aluminate aqueous solution having an Al2O3 concentration of 1.0 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 were used; in the third step, 156.0 kg of a sodium silicate aqueous solution and 52.0 kg of a sodium aluminate aqueous solution were used; in the fifth step, the pH was set to 10.0, the heating temperature was set to 180°C, and 8.0 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound in the particle surface treatment.

[0223] The dispersion medium of the methanol dispersion of these particles was replaced with MIBK to obtain a particle dispersion with a solid content of 20.5% by mass. 9.00 g of the MIBK dispersion of these particles, 0.89 g of a multifunctional acrylate resin (Kyoeisha Chemical Co., Ltd. Light Acrylate DPE-6A), 0.10 g of a bifunctional acrylate resin (Tomoe Engineering Co., Ltd. SR-238F), 0.05 g of reactive silicone oil (Shin-Etsu Chemical Co., Ltd. KF-2012), 0.37 g of silicone-modified polyurethane acrylate (Mitsubishi Chemical Co., Ltd. Shikoh UT-4314, solids concentration 30% by mass), 0.08 g of a photopolymerization initiator (IGM Resins BV Omnirad TPO H), 64.67 g of isopropyl alcohol, 8.84 g of MIBK, and 16.00 g of isopropyl glycol were mixed to produce an anti-reflective coating coating solution with a solids concentration of 3.0% by mass. A coated substrate was produced in the same manner as in Example 1.

[0224] [Example 5] In the first step, 9975.3 g of pure water was added to 24.7 g of an aqueous dispersion of silica particles (JGC Catalysts and Chemicals Co., Ltd., Cataloid SI-40, average particle size 17 nm, solid content 40.5% by mass), and then a 1% by mass NaOH aqueous solution was added to prepare 10.0 kg of an aqueous solution with 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 were added. In the third step, 201.0 kg of an aqueous sodium silicate solution and 67.0 kg of an aqueous sodium aluminate solution were added. In the fifth step, the pH was 10.9, the heating temperature was 290 ° C., and in the sixth step, the pH was 8.0, the heating temperature was 300 ° C. Except for these, the particle dispersion, coating liquid, and coated substrate were produced in the same manner as in Example 1.

[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 and Chemicals Co., Ltd.), and then a 1% by mass NaOH aqueous solution was added to prepare 10.0 kg of an aqueous solution with 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 added. In the third step, 180.0 kg of an aqueous sodium silicate solution and 60.0 kg of an aqueous sodium aluminate solution were added. In the fifth step, the pH was set to 10.8, the heating temperature was set to 200°C, and in the sixth step, the pH was set to 7.5. Except for this, a particle dispersion, a coating solution, and a coated substrate were produced in the same manner as in Example 1, and their properties were evaluated.

[0226] [Example 7] In the first step, 9900.0 g of pure water was added to 100.0 g of an aqueous dispersion of silica-based particles (USBB-120, manufactured by JGC Catalysts and Chemicals Co., Ltd.), and then a 1% by mass NaOH aqueous solution was added to prepare 10.0 kg of an aqueous solution with 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 were added. In the third step, 147.0 kg of an aqueous sodium silicate solution and 49.0 kg of an aqueous sodium aluminate solution were added. In the fifth step, the pH was set to 10.0 and the heating temperature was set to 180°C. In the sixth step, the pH was set to 7.0 and the heating temperature was set to 180°C. Except for these, a particle dispersion, a coating solution, and a coated substrate were produced in the same manner as in Example 1, and their properties were evaluated.

[0227] [Example 8] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the pH in the fifth step was set to 9.8, the pH in the sixth step was set to 7.5, and the heating temperature was set to 160°C, and each property was evaluated.

[0228] [Example 9] A particle dispersion, a coating liquid, and a coated substrate were produced and their properties were evaluated in the same manner as in Example 1, except that in the second step, 22.0 kg of the sodium silicate aqueous solution and 22.0 kg of the sodium aluminate aqueous solution were used, in the third step, 84.0 kg of the sodium silicate aqueous solution and 28.0 kg of the sodium aluminate aqueous solution were used, in the fifth step, the pH was 10.2 and the heating temperature was 280°C, and in the sixth step, the pH was 7.0 and the heating temperature was 220°C.

[0229] [Example 10] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the amount of sodium silicate aqueous solution in the third step was 207.0 kg, the amount of sodium aluminate aqueous solution was 69.0 kg, the heating temperature in the fifth step was 300°C, and the heating temperature in the sixth step was 400°C, and the properties of each 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 to prepare 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 prepared; in the third step, 172.5 kg of a sodium silicate aqueous solution and 57.5 kg of a sodium aluminate aqueous solution were prepared; in the fifth step, the pH was set to 9.5 and the heating temperature to 150°C; in the sixth step, the pH was set to 5.5 and the heating temperature to 150°C; and in the particle surface treatment, 2.0 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound. Except for this, particle dispersions, coating solutions, and coated substrates were prepared in the same manner as in Example 1.

[0231] [Example 12] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the pH in the sixth step was 6.0 and the heating temperature was 180°C.

[0232] [Example 13] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the amount of sodium silicate aqueous solution in the third step was 207.0 kg, the amount of sodium aluminate aqueous solution was 69.0 kg, the heating temperature in the fifth step was 300°C, and the heating temperature in the sixth step was 300°C.

[0233] [Example 14] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that in the second step, the amount of the sodium silicate aqueous solution was 42.0 kg and the amount of the sodium aluminate aqueous solution was 42.0 kg, in the third step, the amount of the sodium silicate aqueous solution was 106.5 kg and the amount of the sodium aluminate aqueous solution was 35.5 kg, in the fifth step, the pH was 9.0, the heating temperature was 150°C, and in the sixth step, the heating temperature was 150°C.

[0234] [Example 15] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the amount of sodium silicate aqueous solution in the second step was 52.0 kg and the amount of sodium aluminate aqueous solution was 52.0 kg, the amount of sodium silicate aqueous solution in the third step was 174.0 kg and the amount of sodium aluminate aqueous solution was 58.0 kg, the heating temperature in the fifth step was 300°C, the heating temperature in the sixth step was 350°C, and 12.0 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound in the particle surface treatment.

[0235] [Example 16] A particle dispersion, a coating solution, and a coated substrate were produced in the same manner as in Example 1, except that the amounts of the sodium silicate aqueous solution and the sodium aluminate aqueous solution in the second step were 22.0 kg and 22.0 kg, respectively, and that the amounts of the sodium silicate aqueous solution and the sodium aluminate aqueous solution in the third step were 75.0 kg and 25.0 kg, respectively, and that 0.6 g of γ-methacryloxypropyltrimethoxysilane was used as the organic silicon compound in the surface treatment of the particles.

[0236] [Example 17] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that in the second step, 95.0 kg of the sodium silicate aqueous solution and 95.0 kg of the sodium aluminate aqueous solution were used, in the third step, 258.0 kg of the sodium silicate aqueous solution and 86.0 kg of the sodium aluminate aqueous solution were used, in the fifth step, the pH was 11.0, the heating temperature was 180°C, and 8.0 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound in the particle surface treatment.

[0237] [Example 18] A particle dispersion, a coating solution, and a coated substrate were produced in the same manner as in Example 1, except that in the second step, 13.1 kg of the sodium silicate aqueous solution and 79.8 kg of the sodium aluminate aqueous solution were used, in the third step, 54.9 kg of the sodium silicate aqueous solution and 18.3 kg of the sodium aluminate aqueous solution were used, in the fifth step, the heating temperature was 200°C, in the sixth step, the pH was 8.0 and the heating temperature was 180°C, and in the particle surface treatment, 1.1 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound.

[0238] [Example 19] A particle dispersion, a coating solution, and a coated substrate were produced in the same manner as in Example 1, except that tetraethoxysilane (Tama Chemicals Co., Ltd., ethyl orthosilicate ES28) was used as the organosilicon compound in the surface treatment of the particles with an organosilicon compound.

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

[0240] [Example 21] A particle dispersion was produced in the same manner as in Example 1, except that in the first step, a sodium aluminate aqueous solution having an Al2O3 concentration of 22 mass% was added to pure water to prepare 30.0 kg of a sodium aluminate aqueous solution having an Al2O3 concentration of 4.5 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 were used; in the third step, 339.0 kg of a sodium silicate aqueous solution and 113.0 kg of a sodium aluminate aqueous solution were used; in the fifth step, the pH was set to 10.0, the heating temperature was set to 180°C, and 8.0 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound in the particle surface treatment.

[0241] The dispersion medium of the methanol dispersion of these particles was replaced with MIBK to obtain a particle dispersion with a solid content of 20.5% by mass. 8.31 g of the MIBK dispersion of these particles, 1.02 g of a multifunctional acrylate resin (Kyoeisha Chemical Co., Ltd. Light Acrylate DPE-6A), 0.11 g of a bifunctional acrylate resin (Tomoe Engineering Co., Ltd. SR-238F), 0.05 g of reactive silicone oil (Shin-Etsu Chemical Co., Ltd. KF-2012), 0.37 g of silicone-modified polyurethane acrylate (Mitsubishi Chemical Co., Ltd. Shikoh UT-4314, solids concentration 30% by mass), 0.08 g of a photopolymerization initiator (IGM Resins BV Omnirad TPO H), 64.66 g of isopropyl alcohol, 9.39 g of MIBK, and 16.00 g of isopropyl glycol were mixed to produce an anti-reflective coating coating solution with a solids concentration of 3.0% by mass. A coated substrate was produced in the same manner as in Example 1.

[0242] [Example 22] A particle dispersion was produced in the same manner as in Example 1, except that the heating temperature in the fifth step was 300°C, the heating temperature in the sixth step was 350°C, and the surface treatment of the particles with an organosilicon compound was not performed.

[0243] The dispersion medium of the methanol dispersion of these particles was replaced with propylene glycol monomethyl ether (PGME) to obtain a particle dispersion with a solid content of 20.5% by mass. 3.46 g of the PGME dispersion of these particles, 1.92 g of a multifunctional acrylate resin (Kyoeisha Chemical Co., Ltd. Light Acrylate DPE-6A), 0.21 g of a bifunctional acrylate resin (Tomoe Engineering Co., Ltd. SR-238F), 0.05 g of reactive silicone oil (Shin-Etsu Chemical Co., Ltd. KF-2012), 0.37 g of silicone-modified polyurethane acrylate (Mitsubishi Chemical Co., Ltd. Shikoh UT-4314, solids concentration 30% by mass), 0.15 g of a photopolymerization initiator (IGM Resins BV Omnirad TPO H), 64.60 g of isopropyl alcohol, 13.25 g of PGME, and 16.00 g of isopropyl glycol were mixed to produce an anti-reflective coating coating solution with a solids concentration of 3.0% by mass. A coated substrate was produced in the same manner as in Example 1.

[0244] [Comparative Example 1] A particle dispersion was produced in the same manner as in Example 1, except that in the first step, a sodium aluminate aqueous solution having an Al2O3 concentration of 22 mass% was added to pure water to prepare 50.0 kg of a sodium aluminate aqueous solution having an Al2O3 concentration of 1.0 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, and 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.

[0245] The dispersion medium of the methanol dispersion of these particles was replaced with MIBK to obtain a particle dispersion with a solid content of 20.5% by mass. 8.31 g of the MIBK dispersion of these particles, 1.02 g of a multifunctional acrylate resin (Kyoeisha Chemical Co., Ltd. Light Acrylate DPE-6A), 0.11 g of a bifunctional acrylate resin (Tomoe Engineering Co., Ltd. SR-238F), 0.05 g of reactive silicone oil (Shin-Etsu Chemical Co., Ltd. KF-2012), 0.37 g of silicone-modified polyurethane acrylate (Mitsubishi Chemical Co., Ltd. Shikoh UT-4314, solids concentration 30% by mass), 0.08 g of a photopolymerization initiator (IGM Resins BV Omnirad TPO H), 64.66 g of isopropyl alcohol, 9.39 g of MIBK, and 16.00 g of isopropyl glycol were mixed to produce an anti-reflective coating coating solution with a solids concentration of 3.0% by mass. A coated substrate was produced in the same manner as in Example 1.

[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-based particles (USBB-120, manufactured by JGC Catalysts and Chemicals Co., Ltd.), and then a 1% by mass NaOH aqueous solution was added to prepare 10.0 kg of an aqueous solution with a pH of 12.5. In the second step, 60.0 kg of an aqueous sodium silicate solution with a 4.0% by mass SiO concentration and 20.0 kg of an aqueous sodium aluminate solution with a 4.0% by mass AlO concentration were used. In the third step, 276.0 kg of the aqueous sodium silicate solution and 92.0 kg of the aqueous sodium aluminate solution were used. Except for this, the particle dispersion, coating solution, and coated substrate were produced in the same manner as in Example 1.

[0247] Comparative Example 3 A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that in the first step, a sodium aluminate aqueous solution having an AlO concentration of 22 mass% was added to pure water to prepare 10.0 kg of a sodium aluminate aqueous solution having an AlO concentration of 1.0 mass% and a pH of 12.6, in the second step, 6.2 kg of the sodium silicate aqueous solution and 6.2 kg of the sodium aluminate aqueous solution were used, and in the third step, 222.0 kg of the sodium silicate aqueous solution and 74.0 kg of the sodium aluminate aqueous solution were used.

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

[0249] Comparative Example 5 A particle dispersion, a coating solution, and a coated substrate were produced 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 particle surface treatment, and stirring was performed at 50°C for 6 hours.

[0250] Comparative Example 6 A particle dispersion, a coating solution, and a coated substrate were produced in the same manner as in Example 1, except that the heating temperature in the sixth step was set to 120°C, 0.2 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound in the surface treatment of the particles with an organosilicon compound, and stirring was carried out at 50°C for 6 hours.

[0251] Comparative Example 7 A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that in the first step, a sodium aluminate aqueous solution having an AlO concentration of 22 mass% was added to pure water to prepare 10.0 kg of a sodium aluminate aqueous solution having an AlO concentration of 1.0 mass% and a pH of 12.6, in the second step, 167.1 kg of the sodium silicate aqueous solution and 0.5 kg of the sodium aluminate aqueous solution were used, and in the third step, 144.0 kg of the sodium silicate aqueous solution and 48.0 kg of the sodium aluminate aqueous solution were used.

[0252] [Comparative Example 8] In the first step, 97.6 g of an aqueous dispersion of silica particles (JGC Catalysts and Chemicals Co., Ltd., Cataloid SI-550, average particle size 5 nm, solid content 20.5% by mass) was added to 9902.4 g of pure water, and then a 1% by mass NaOH aqueous solution was added to prepare 10.0 kg of an aqueous solution with 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 were used. In the third step, 159.0 kg of an aqueous sodium silicate solution and 53.0 kg of an aqueous sodium aluminate solution were used. In the fifth step, the pH was 9.5, the heating temperature was 160 ° C., and in the sixth step, the pH was 5.0, the heating temperature was 200 ° C., and in the surface treatment of the particles, 8.0 g of γ-methacryloxypropyltrimethoxysilane was used as the organosilicon compound. The particle dispersion was produced in the same manner as in Example 1.

[0253] The dispersion medium of the methanol dispersion of these particles was replaced with MIBK to obtain a particle dispersion with a solid content of 20.5% by mass. 8.31 g of the MIBK dispersion of these particles, 1.02 g of a multifunctional acrylate resin (Kyoeisha Chemical Co., Ltd. Light Acrylate DPE-6A), 0.11 g of a bifunctional acrylate resin (Tomoe Engineering Co., Ltd. SR-238F), 0.05 g of reactive silicone oil (Shin-Etsu Chemical Co., Ltd. KF-2012), 0.37 g of silicone-modified polyurethane acrylate (Mitsubishi Chemical Co., Ltd. Shikoh UT-4314, solids concentration 30% by mass), 0.08 g of a photopolymerization initiator (IGM Resins BV Omnirad TPO H), 64.66 g of isopropyl alcohol, 9.39 g of MIBK, and 16.00 g of isopropyl glycol were mixed to produce an anti-reflective coating coating solution with a solids concentration of 3.0% by mass. A coated substrate was produced in the same manner as in Example 1.

[0254] Comparative Example 9 A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the pH in the fifth step was 8.0 and the heating temperature was 180°C, and the heating temperature in the sixth step was 180°C.

[0255] [Comparative Example 10] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the pH in the fifth step was 11.6 and the heating temperature was 300°C.

[0256] [Comparative Example 11] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the pH in the fifth step was 9.2, the heating temperature was 120°C, and the heating temperature in the sixth step was 180°C.

[0257] [Comparative Example 12] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the pH in the fifth step was 10.8 and the heating temperature was 350°C.

[0258] [Comparative Example 13] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the pH in the sixth step was 4.0 and the heating temperature was 350°C.

[0259] [Comparative Example 14] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that the heating temperature in the sixth step was 120°C.

[0260] [Comparative Example 15] A particle dispersion, a coating liquid, and a coated substrate were produced in the same manner as in Example 1, except that in the fifth step, the pH was set to 9.0 and the heating temperature was set to 150°C, and in the sixth step, the pH was set to 7.0 and the heating temperature was set to 450°C.

[0261] [Table 4]

[0262] [Table 5]

[0263] [Table 6]

[0264] [Table 7]

[0265] [Table 8]

[0266] [Table 9]

Claims

1. A particle having an outer shell containing silicon and a cavity therein, the particles have an average particle size of 15 to 150 nm as determined by image analysis, a refractive index of 1.08 to 1.38, and a ratio (A1 / A2) of a specific surface area (A1) calculated by a BET method using water vapor gas to a specific surface area (A2) calculated by a BET method using nitrogen gas of 1.0 or less; Particles characterized in that the mass increase when the particles are dried at 200°C for 3 hours and then left to stand in an atmosphere at 25°C and a relative humidity of 90% for 24 hours is 4.0 parts by mass or less per 100 parts by mass of the particles.

2. 2. The particles according to claim 1, wherein the ratio (A2 / A3) of the specific surface area (A2) of the particles to the specific surface area (A3) calculated from the average particle diameter is 1.00 to 1.

30.

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

4. 2. The particle according to claim 1, characterized in that the ratio (A4 / A3) of the specific surface area (A4) calculated from pulse NMR measurement of a methanol dispersion of the particle to the specific surface area (A3) is 0.65 or less.

5. The particles ２９ In Si-NMR analysis, the chemical shift of silicon atom appears in the range of -78 to -120 ppm. １ ~Q ４ The sum of the areas of the peaks representing the structure is the Q of the silicon atom whose chemical shift appears at -108 to -120 ppm. ４ 2. The particle according to claim 1, wherein the area ratio of the peak representing the structure is 82% or more.

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

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

8. a first step of preparing an alkaline aqueous solution; A solution of a silicon-containing compound and an aqueous solution of an alkali-soluble compound of an inorganic element other than silicon are each mixed together to form an oxide of silicon, SiO ２ When the oxide of the inorganic element is expressed as MOx, the molar ratio (MOx / SiO ２ a second step of simultaneously adding the above-mentioned aqueous alkaline solution to the above-mentioned aqueous alkaline solution so that the ratio of the total weight of the composite oxide particles a to the total weight of the composite oxide particles a is 0.01 to 2.0, The solution of the silicon-containing compound and the aqueous solution of the alkali-soluble compound of the inorganic element other than silicon are each mixed in the molar ratio (MOx / SiO ２ a third step of adding the composite oxide particles b to the dispersion liquid so that the molar ratio is smaller than that of the composite oxide particles a, thereby preparing a dispersion liquid of composite oxide particles b having an average particle size of 15 to 150 nm, and a value obtained by subtracting the average particle size of the composite oxide particles a from the average particle size and dividing the result by 2 being 3 to 14 nm; a fourth step of adding an acid to the dispersion of the composite oxide particles b to remove at least a portion of the elements other than silicon constituting the composite oxide particles b, thereby preparing a dispersion of silica particles; a fifth step of heating the dispersion of silica particles at a pH of 9.0 to 11.0 to 150 to 300°C; a sixth step of heating the dispersion of silica particles obtained in the fifth step at a pH of 5.0 to 8.0 and a temperature of 150 to 400°C; A method for producing particles comprising, in order:

9. 9. The method for producing particles according to claim 8, wherein after the sixth step, at least one of an organosilicon compound represented by the following formula (8) and a partial hydrolyzate thereof 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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