JP7360294B2 - Particles containing silica and having a cavity inside an outer shell, a method for producing the same, a coating liquid containing the particles, and a substrate with a transparent coating containing the particles - Google Patents

Description

The present invention relates to particles containing silica and having a cavity inside the outer shell, and a method for producing the particles. The present invention also relates to a coating liquid for forming a transparent film containing the particles and a substrate with a transparent film containing the particles.

BACKGROUND ART Conventionally, in order to prevent reflection on the surface of a base material such as a sheet or lens made of glass, plastic, etc., an antireflection film has been formed on the surface thereof. For example, a coating of a low refractive index substance such as a fluororesin or magnesium fluoride is formed on the surface of a glass or plastic substrate by a coating method, a vapor deposition method, a CVD method, or the like. However, these methods are expensive. On the other hand, a coating liquid containing composite oxide colloidal particles made of silica and an inorganic oxide other than silica and having a refractive index of 1.36 to 1.44 is applied to the surface of the substrate to form an antireflection coating. There is a known method for forming (see, for example, Patent Document 1).

Furthermore, a method for producing porous hollow particles is known (see, for example, Patent Document 2). The hollow particles obtained by this method have a low refractive index, and the transparent coating formed using the hollow particles has a low refractive index and excellent antireflection performance.

Furthermore, it is known that when a transparent film containing hollow particles is provided on the front surface of a display device, it has excellent antireflection performance and improves display performance (see, for example, Patent Document 3).

Japanese Patent Application Publication No. 7-133105 Japanese Patent Application Publication No. 2001-233611 JP2002-079616A

However, when silica-based particles having internal cavities are used in an antireflection film, there is a risk that the hardness and strength (scratch resistance) of the resulting film may be reduced. In addition, if the particles are hollowed out excessively in order to lower their refractive index, the particles themselves become brittle, and the hardness and strength (scratch resistance) of the transparent coating using these particles will also be insufficient. .

As described above, if the hardness and strength of the particles are insufficient, there is a problem that at least one of the refractive index, hardness, and strength of the transparent film is insufficient.

In order to solve these problems, we decided to use the following particles having a shell containing silica and a cavity inside the shell in a coating liquid for forming a transparent film. The average particle diameter (D) of these particles is 20 to 250 nm, the diameter of the cavity is 0.5 to 0.9 times the particle diameter, the pore volume by N ₂ adsorption method is less than 1.0 cm ³ /g, and the following formula ( The refractive index (n _S ) of the outer shell determined in 1) is 1.38 or more, the refractive index (n _a ) is 1.08 to 1.34, and the carbon content is 3.0% by mass or less.

These particles have sufficient hardness and strength and a low refractive index because they have a cavity inside a dense outer shell containing silica. According to a coating liquid containing such particles, a substrate with a transparent film having high hardness (pencil hardness) and high strength (scratch resistance) can be obtained.

According to the particles of the present invention, a coating liquid can be obtained that can produce a transparent film that has low reflectance, excellent adhesion to a substrate, and high hardness and strength.

FIG. 2 is a cross-sectional view of particles of the present invention.

The particles according to the present invention are particles having an outer shell containing silica and a cavity inside the outer shell. (Hereinafter, the particles according to the present invention may be simply referred to as particles.) A cross section of this particle is schematically shown in FIG.

The average particle diameter D of the particles is 20 to 250 nm. When the average particle diameter is within this range, the particles can exist stably. In addition, it has good dispersibility in the coating liquid and in the film, and provides a film with high transparency, hardness, and strength. The average particle diameter is preferably 30 to 150 nm, more preferably 30 to 120 nm.

The diameter of the cavity inside the outer shell is 0.5 to 0.9 times the diameter (outer diameter) of the particle. When the diameter of the cavity is within this range, the structure of the outer shell can be maintained stably, so that the particle can exist stably. Moreover, high transparency, hardness, and strength of the coating can be obtained. Here, if it is less than 0.5 times, the thickness of the outer shell is too thick, and there is a possibility that sufficient transparency of the film cannot be obtained. If it is larger than 0.9 times, the outer shell may be too thin to maintain the particle structure. The diameter of the cavity is preferably 0.55 to 0.9 times the diameter of the particle, more preferably 0.6 to 0.85 times.

The pore volume of the particles by N ₂ adsorption is less than 1.0 cm ³ /g. When the pore volume is within this range, the structure of the outer shell is dense. If it is larger than 1.0 cm ³ /g, the structure of the outer shell is sparse (porous) and the hardness and strength of the outer shell are weak, so there is a risk that the structure of the outer shell cannot be maintained or that the hardness of the coating is insufficient. Otherwise, the strength may not be obtained. The pore volume is preferably less than 0.8 cm ³ /g, more preferably less than 0.5 cm ³ /g, and most preferably 0.0 cm ³ /g.

The refractive index n _a of the particles is between 1.08 and 1.34. When the refractive index is within this range, a transparent coating can be obtained. The refractive index is preferably 1.08 to 1.32, more preferably 1.08 to 1.30.

The refractive index n _S of the outer shell is 1.38 or more. When the refractive index n _S is 1.38 or more, the outer shell is dense. The upper limit of the refractive index _nS is not particularly set, but is, for example, 1.47. As shown in formula (1), the refractive index n _S is the average value D of the particle diameter, the average value D _O of the diameter of the cavity inside the outer shell, the refractive index n _a of the particle, and the refractive index n of the cavity. It is determined from _P. The refractive index n _P of the cavity varies depending on the conditions inside the cavity. For example, if the inside of the cavity is gas, the refractive index is 1.00. Further, if the inside of the cavity is a liquid, the refractive index is that of the liquid.

When the refractive index n _S is within this range, a transparent coating having sufficient hardness and strength can be obtained. If the refractive index n _S is smaller than 1.38, the hardness of the coating may be insufficient. The refractive index n _S is preferably 1.40 or more, more preferably 1.42 or more.

The carbon content of the particles is 3.0% by mass or less. The carbon contained in the particles originates from organic compounds such as organosilicon compounds, metal salts, reducing agents, pH adjusters, cleaning liquids, and solvents. This includes not only those intentionally added for the production of particles, but also those that are unavoidably present in raw materials, etc. If organic compounds are contained, the hardness and strength of the outer shell will be low, so when made into a film, transparency and dispersibility will decrease, making it impossible to obtain a transparent film with sufficient hardness and strength. There is a risk. The carbon content derived from such organic substances can be determined by analyzing the amount of C (carbon) as described later. The carbon content is preferably 1.0% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less.

In the ²⁹ Si-NMR spectroscopy of particles, the area Q ₁ of the peak that appears in the chemical shift range of -78 to -88 ppm, the area Q _{2 of the peak that appears in the chemical shift range of -88 to -98 ppm, and the area Q 2} of the peak that appears in the chemical shift range of -98 to -108 ppm. In the area Q ₃ of the peak and the area Q ₄ of the peak appearing at a chemical shift of -108 to -117 ppm, the ratio (Q ₁ /ΣQ) is essentially 0, the ratio (Q ₂ /ΣQ) is essentially 0, and the ratio (Q ₃ /ΣQ) is essentially 0. Q ₄ ) is preferably 0.01 to 0.7. Here, ΣQ=Q ₁ +Q ₂ +Q ₃ +Q ₄ .

The peak assigned to Q ₁ is the combination of one (-OSi) group and three (-OH) groups to the Si atom, and the peak assigned to Q ₂ is the combination of two (-OSi) groups and two The peak attributed to Q ₃ is the combination of three (-OSi) groups and one (-OH) group to the Si atom, and the peak attributed to Q ₂ is the Si atom. has four (-OSi) groups bonded to it.

Here, when the ratio (Q ₁ /ΣQ) and the ratio (Q ₂ /ΣQ) are essentially 0, it means that there may be peaks that are unavoidably detected due to the detection limit in measurement, noise, etc., but even if these are taken into consideration, This means that the value is also judged as "0". Specifically, both ratios determined by the above formula are 0.0001 or less. When the ratio (Q ₁ /ΣQ) and the ratio (Q ₂ /ΣQ) are substantially 0 and the ratio (Q ₃ /Q ₄ ) is 0.01 to 0.7, the particles are dense and have sufficient hardness and strength. A transparent film is obtained. If the ratio (Q ₁ /ΣQ) or (Q ₂ /ΣQ) is larger than 0.0001, the ratio of Si--O--Si bonds is small, so the hardness and strength of the coating may be insufficient.

It is difficult to obtain a ratio (Q ₃ /Q ₄ ) smaller than 0.01. When the ratio (Q ₃ /Q ₄ ) is larger than 0.7, the ratio of Si--O--Si bonds is low, so the hardness of the coating may be insufficient. The ratio (Q ₃ /Q ₄ ) is more preferably 0.02 to 0.5, and even more preferably 0.03 to 0.2.

The content of each element belonging to the alkali metal, which is an impurity in the particles, is preferably 1 ppm or less based on SiO ₂ when the element is expressed as an oxide. When the content is within this range, coalescence of the particles is reduced, so that the particles are uniformly dispersed in the coating liquid and the coating, and a transparent coating can be obtained, which is preferable. In addition, the stability of the coating liquid is improved, and the film hardness and transparency are increased, which are preferable. Here, if the content is more than 1 ppm, coalescence of particles increases, and there is a possibility that sufficient hardness of the film may not be obtained or transparency may become insufficient. The content is more preferably 0.1 ppm or less. Here, the alkali metal represents Li, Na, K, Rb, Cs, and Fr.

In addition, the content of each of Fe, Ti, Zn, Pd, Ag, Mn, Co, Mo, Sn, Al, and Zr, which are impurities in the particles, is less than 0.1 ppm, and the content of each of Cu, Ni, and Cr is less than 0.1 ppm. is preferably less than 1 ppb, and the content of each of U and Th is preferably less than 0.3 ppb. If the content of these impurities is within this range, a transparent film can be obtained, which is preferable. If the content of these impurities increases, the dispersion liquid becomes colored, and there is a possibility that a transparent film may not be obtained. In addition, when used in highly integrated logic and memory semiconductor circuits that require high purity, optical sensors, etc., metal elements may cause circuit insulation failure, short circuits, or decrease in light transmittance. do. This may cause 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, and the like. In particular, U and Th generate radioactivity, so if they are present in even a trace amount, they are undesirable because they cause semiconductor malfunctions due to the radioactivity.

In order to obtain particles with a low content of such impurities, it is preferable that the material of the apparatus used for preparing the particles be one that does not contain these elements and has high chemical resistance. Specifically, plastics such as Teflon (registered trademark), FRP, carbon fiber, alkali-free glass, etc. are preferable. Further, it is preferable that the raw materials used be purified by distillation, ion exchange, or filter removal.

As described above, methods for obtaining highly pure particles include preparing raw materials with low impurities in advance and suppressing contamination from particle preparation equipment. In addition to this, it is possible to reduce impurities from particles prepared without sufficient such measures.

The shape of the particles and the shape of the cavities are not particularly limited. Examples include a spherical shape, an ellipsoid (rugby ball) shape, a cocoon shape, a confetti shape, a chain shape, and a dice shape. Here, the particle shape is preferably spherical because it can be uniformly dispersed in the transparent film. The shape of the cavity preferably follows the shape of the particle. Although it depends on the thickness of the outer shell, when stress is applied to the particles, if the outer shell has a uniform thickness, sufficient hardness and strength can be obtained. Furthermore, it is preferable that the cavity also has a spherical shape similar to the shape of the spherical particle.

Moreover, in order to lower the refractive index and obtain a transparent coating, it is preferable that the cavity be substantially one. Here, "substantially one cavity" may include "particles in which multiple cavities exist inside the outer shell" due to coalescence of particles, etc., but " This means that the percentage of particles with one cavity inside the outer shell is 90% or more. The "number ratio of particles having 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%.

The particles preferably contain 90% by mass or more of silicon as silica. If it falls within this range, the compatibility with the matrix-forming component will improve. Therefore, the particles are highly dispersed in the transparent coating, and the strength and hardness of the coating are improved. The silicon content is more preferably 95% by mass or more as silica, still more preferably 98% by mass or more, and particularly preferably 100% by mass.

[Method for producing particles]
In the production method according to the present invention, a solution of a compound containing _silicon and an aqueous solution of an alkali-soluble compound of an inorganic element other than silicon are used. A first step of preparing a dispersion of composite oxide particles a by simultaneously adding them to an alkaline aqueous solution so that the molar ratio (MOx/SiO ₂ ) is 0.01 to 2 when expressed as MOx; 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 at a molar ratio (MOx/SiO ₂ ) smaller than the molar ratio in the above step to form composite oxide particles b. a second step of preparing a dispersion of composite oxide particles b, and adding an acid to the dispersion of composite oxide particles b to remove at least a part of the elements other than silicon constituting the composite oxide particles b; In the third step of preparing a dispersion liquid, the dispersion liquid of silica-based particles is heated at a heating rate of 0.3 to 3.0°C/min. After heating to 200-800°C at 0.04-2.0°C/min. and a fourth step of lowering the temperature to 100° C. or less. The silica particles may be washed if necessary.

Each step will be explained in detail below.

[First step]
In the first step, a dispersion of composite oxide particles a having an average particle diameter of 10 to 225 nm is prepared. The silicon-containing compound is at least one selected from silicates, acidic silicic acid solutions, and organic silicon compounds.

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 (water glass) and potassium silicate. Examples of the organic base include quaternary ammonium salts such as tetraethylammonium salt, and amines such as monoethanolamine, diethanolamine, and triethanolamine. Ammonium silicates or organic base silicates include alkaline solutions prepared by adding ammonia, quaternary ammonium hydroxide, amine compounds, etc. to a silicic acid solution.

As the acidic silicic acid solution, a silicic acid solution obtained by removing alkali by treating an alkaline silicate aqueous solution with a cation exchange resin can be used, and in particular, a silicic acid solution with a SiO ₂ concentration of about 7% by mass at pH 2 to pH 4 can be used. The following acidic silicic acid solutions are preferred.

As the organosilicon compound, an organosilicon compound represented by the following formula (2) is preferable.

R _n -SiX _4-n ...(2)
However, in the formula, R is an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, and may be the same or different. Examples of the substituent include an epoxy group, an alkoxy group, a (meth)acryloyloxy group, a mercapto group, a halogen atom, an amino group, and a phenylamino group. X is an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, a halogen atom, or a hydrogen atom, and n is an integer of 0 to 3.

By the way, in the organosilicon compound of formula (2), the compound where n is 1 to 3 has poor hydrophilicity, so it is preferable to hydrolyze it in advance so that it can be mixed uniformly into the reaction system. Well-known methods can be employed for hydrolysis. When a basic catalyst such as an alkali metal hydroxide, aqueous ammonia, or amine is used as a hydrolysis catalyst, these basic catalysts can be removed after hydrolysis and an acidic solution can be used. Further, when a hydrolyzate is prepared using an acidic catalyst such as an organic acid or an inorganic acid, it is preferable to remove the acidic catalyst by ion exchange or the like after hydrolysis. Note that the obtained hydrolyzate of the organosilicon compound is preferably used in the form of an aqueous solution. Here, the term "aqueous solution" refers to a state in which the hydrolyzate is not cloudy as a gel but is transparent.

Specific examples of organic silicon compounds include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, and dimethyldiethoxysilane. , phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(βmethoxyethoxy)silane, 3,3,3-trifluoropropyltrimethoxysilane, methyl-3 , 3,3-trifluoropropyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxytripropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, Sidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, N-β (aminoethyl ) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-amino Propyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, trimethylsilanol, methyltrichlorosilane, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane , vinyltrichlorosilane, trimethylbromosilane, diethylsilane and the like.

Oxides of inorganic elements other than silicon (MOx) include Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO 2 , SnO ₂ , CeO _{2 ,} P ₂ O ₅ , Sb ₂ O ₃ , MoO ₃ , ZnO ₂ , WO _3, etc., or two or more thereof may be used. Furthermore, examples of composite oxides of inorganic elements other than silicon include TiO ₂ --Al ₂ O ₃ and TiO ₂ --ZrO ₂ .

As a raw material for such an inorganic oxide, an alkali-soluble inorganic compound is preferable. Examples include alkali metal salts or alkaline earth metal salts, ammonium salts, and quaternary ammonium salts of metal or nonmetal oxoacids constituting oxides of inorganic elements other than silicon. Specifically, sodium aluminate, sodium tetraborate, zirconyl ammonium carbonate, potassium antimonate, potassium stannate, sodium aluminosilicate, sodium molybdate, cerium ammonium nitrate, sodium phosphate, etc. are suitable.

In order to prepare a dispersion of composite oxide particles a, in advance, an alkaline aqueous solution of a compound of an inorganic element other than silicon is prepared individually, or a mixed aqueous solution is prepared, and this aqueous solution is used for the purpose. The silicon oxide (SiO ₂ ) and the oxide of an inorganic element other than silicon (MOx) are gradually added to the aqueous alkaline solution while stirring, depending on the composite ratio. The pH of this aqueous alkaline solution is preferably adjusted to 10 or higher. The addition may be continuous or intermittent, but it is preferable to add both at the same time.

The molar ratio (MOx/SiO ₂ ) of the compound containing silicon and the compound of an inorganic element other than silicon is set to be 0.01 to 2 in the alkaline aqueous solution. If the molar ratio is within this range, the structure of the composite oxide particles will mainly be a structure in which silicon and elements other than silicon are alternately bonded with oxygen interposed. That is, many structures are generated in which an oxygen atom is bonded to the four bonds of a silicon atom, and an element M other than silicon is bonded to this oxygen atom. As a result, when the element M other than silicon is removed in the third step described below, the silicon atoms can also be removed as silicic acid monomers or oligomers along with the element M 2 without destroying the shape of the composite oxide particles. Here, if the molar ratio is less than 0.01, the cavity volume of the final particles will not be large enough. If the molar ratio is greater than 2, the composite oxide particles will be destroyed when elements other than silicon are removed in the third step, and particles having cavities inside the outer shell will not be obtained. The molar ratio is preferably 0.1 to 1.5. Further, the molar ratio can be gradually decreased while being added. The average particle diameter (Da) of the composite oxide particles after addition is preferably adjusted to approximately 10 to 225 nm (hereinafter, the composite oxide particles at this time may be referred to as primary particles).

By the way, even if this molar ratio is within the above-mentioned range, if the average particle diameter of the primary particles is less than 10 nm, the outer shell of the finally obtained particles will be thick and the cavity volume of the particles will not be sufficiently large. Furthermore, if the average particle diameter of the primary particles exceeds 225 nm, the removal of elements M other than silicon will be insufficient in the third step described below, and the cavity volume of the particles will not be sufficiently large, making it difficult to obtain particles with a low refractive index. becomes difficult.

In the production method of the present invention, when preparing a dispersion of composite oxide particles a, it is also possible to use a dispersion containing seed particles as a starting material. In this case, the seed particles include one or more particles of SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , CeO ₂ and the like. In addition, examples of composite oxides include particles such as SiO ₂ -Al ₂ O ₃ , TiO ₂ -Al ₂ O ₃ , TiO ₂ -ZrO ₂ , SiO ₂ -TiO ₂ , SiO ₂ -TiO ₂ -Al ₂ O ₃ , etc. It will be done. These sols can usually be used as dispersions containing seed particles. Such seed particles can be prepared by known methods. For example, it can be obtained by adding an acid or an alkali to a metal salt, a mixture of metal salts, or a metal alkoxide corresponding to the above-mentioned inorganic oxide, hydrolyzing it, and aging it if necessary.

A solution of the above-mentioned silicon-containing compound and an aqueous solution of an alkali-soluble compound of an inorganic element other than silicon are added to this kind of particle-dispersed alkaline aqueous solution in the same manner as in the above-mentioned aqueous alkaline solution. do. At this time, the pH of the aqueous alkaline solution in which the seed particles are dispersed is preferably adjusted to 10 or more.

In this way, when composite oxide particles are grown using seed particles as seeds, the particle size of the grown particles can be easily controlled and particles with uniform particle size can be obtained. The addition ratio of the solution of the silicon-containing compound added to the seed particle dispersion and the aqueous solution of the alkali-soluble compound of the inorganic element other than silicon is in the same range as in the case of addition to the aqueous alkaline solution described above. However, the molar ratio (MOx/SiO ₂ ) of the additive liquid is calculated by subtracting the amount of seed particles.

Compounds containing silicon and compounds of inorganic elements other than silicon have high solubility on the alkali side. However, when they are mixed in this pH range where their solubility is high, the solubility of oxoacid ions such as silicate ions and aluminate ions decreases, and these composites precipitate and grow into colloidal particles, or they form on seed particles. It precipitates and grain growth occurs.

[Second process]
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 added at a molar ratio (MOx/SiO ₂ ) smaller than the molar ratio in the first step to form a composite. A dispersion of oxide particles b is prepared. As a result, composite oxide particles a (primary particles) are grown. The average particle diameter Db of the composite oxide particles b after addition is preferably adjusted to 20 to 250 nm.

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

When the molar ratio (MOx/SiO ₂ ) in the first step is A, and the molar ratio (MOx/SiO ₂ ) in the second step is B, it is preferable that the ratio B/A is less than 1. If the ratio B/A is less than 1, the surface layer of the composite oxide particles will be rich in silica, making it easy to form a shell. As a result, even if elements other than silicon are removed in the third step described below, the shape of the composite oxide particles is not destroyed, and particles having a cavity inside the outer shell containing silica can be stably obtained. I can do it. When the ratio B/A is 1 or more, a shell containing a large amount of silica cannot be generated, and therefore, when elements other than silicon are removed in the third step, the composite oxide particles are destroyed and the particle shape cannot be maintained. For this reason, there is a possibility that particles having a cavity inside the outer shell containing silica cannot be obtained. The ratio B/A is more preferably 0.8 or less, and even more preferably 0.7 or less.

The ratio (Da/Db) of the average particle diameter Da of composite oxide particles a (primary particles) to the average particle diameter Db of composite oxide particles b obtained by growing the same is in the range of 0.5 to 0.9. It is preferable. If the ratio (Da/Db) is less than 0.5, the removal of elements other than silicon in the third step will be insufficient, the cavity volume of the obtained particles will not be sufficiently large, and particles with a low refractive index will be obtained. It may become difficult to do so. In addition, if the ratio (Da/Db) is larger than 0.9, depending on the particle size (specifically, composite oxide particles with an average particle size (Db) of less than 20 nm), the inside of the outer shell containing silica may There is a possibility that particles having cavities may not be obtained. The ratio (Da/Db) is more preferably from 0.6 to 0.88, even more preferably from 0.7 to 0.85.

In the second step, an electrolyte salt may be added to the dispersion of composite oxide particles a having an average particle diameter Da of approximately 10 to 225 nm.

Here, specific examples of the electrolyte salt include water-soluble electrolyte salts such as sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, potassium sulfate, ammonium nitrate, ammonium sulfate, magnesium chloride, and magnesium nitrate.

By adding a charged salt, an outer shell is more likely to be formed when elements other than silicon are removed in the third step. Although the mechanism by which such an effect is obtained is not clear, there is a large amount of silica on the surface of the grown composite oxide particles, and the acid-insoluble silica acts as a protective film for the composite oxide particles. I think of it as something.

The amount of electrolyte salt to _be added is _determined by the _ratio (M _E / _MS ) is preferably 0.1 to 10. When the ratio (M _E /M _S ) is less than 0.1, the effect of adding the electrolyte salt cannot be sufficiently seen. Even if the ratio (M _E / M _S ) is larger than 10, the effect of adding electrolyte salt will not be improved, and perhaps because this acts as a buffer, particle growth in the second step will be impaired or It takes time to remove elements other than silicon in the three steps, which may reduce economic efficiency. The ratio (M _E /M _S ) is more preferably 0.2 to 8. The electrolyte salt may be added in its entirety at the start of the second step, or may be added in its entirety when adding the solution of a compound containing silicon and the aqueous solution of an alkali-soluble compound of an inorganic element other than silicon. , may be added continuously or intermittently.

[Third step]
In the third 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 constituting the composite oxide particles b, thereby preparing a dispersion of silica-based particles. The elements can be removed, for example, by dissolving them using mineral acids or organic acids, by ion exchange removal by bringing them into contact with a cation exchange resin, or by a combination of these methods.

The concentration of the dispersion of the composite oxide particles b varies depending on the treatment temperature, but is preferably 0.1 to 50% by mass of the composite oxide particles b in terms of oxide. Here, if the concentration is less than 0.1% by mass, the amount of dissolved silica will increase, so there is a possibility that the shape of the composite oxide particles cannot be maintained. Also, the processing efficiency is low due to the low concentration. If the concentration is higher than 50% by mass, the dispersibility of the particles will be insufficient, and in particular, in composite oxide particles with a high content of elements other than silicon, it will be difficult to remove elements other than silicon uniformly or efficiently. There is a possibility that it cannot be done. The concentration of the dispersion liquid of composite oxide particles b is more preferably 0.5 to 25% by mass.

It is preferable to remove the above elements until the molar ratio (MOx/SiO ₂ ) of the obtained silica-based particles becomes 0.2 or less. If the molar ratio (MOx/SiO ₂ ) is larger than 0.2, the refractive index of the finally obtained "particles having a cavity inside the outer shell containing silica" and the hardness and strength of the particles may be insufficient. There is a risk that this may occur. The molar ratio (MOx/SiO ₂ ) is more preferably 0.1 or less.

In this step, an electrolyte salt may be added as in the second step. The amount added is also preferably 0.1 to 10 as a ratio (M _E /M _S ), similarly to the second step. The electrolyte salt may be added in its entirety at the start of the third step, or may be added continuously or intermittently when removing at least a portion of the elements other than silicon. However, the amount added in the third step should be such that if electrolyte salt is added in the second step, the total amount of the second and third steps will be within the above range unless it is removed. . The ratio (M _E /M _S ) is more preferably 0.2 to 8.

[Fourth step]
In the fourth step, the silica particles are washed as necessary, and the temperature increase rate is set at 0.3 to 3.0°C/min. After heating to 200-800°C at 0.04-2.0°C/min. temperature at a rate of at least below 100°C.

The dispersion of silica-based particles from which at least a portion of elements other than silicon have 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 cleaning. In this case, if a portion of the alkali metal ions and the like in the dispersion are removed in advance and then subjected to ultrafiltration, a dispersion of silica-based particles with high dispersion stability can be obtained.

Further, by bringing the element-removed dispersion into contact with at least one of a cation exchange resin and an anion exchange resin, a portion of the dissolved elements other than silicon or alkali metal ions can be removed. Further, when cleaning, heating can be performed for effective cleaning.

By washing in this way, the content of impurities such as alkali metals in "particles containing silica and having a cavity inside the outer shell" obtained by heat-treating silica-based particles is effectively reduced. be able to. These contents conform to the impurity contents of the above-mentioned "particles containing silica and having a cavity inside the outer shell." For example, the elements belonging to alkali metals in the washed silica-based particles are each 500 ppm or less relative to SiO ₂ when expressed as an oxide.

If the content of each impurity in the silica-based particles is within the range of impurities in the particles described above, washing in this step is not particularly required.

In this way, a dispersion of silica-based particles containing a small amount of alkali metal etc. is heated at a heating rate of 0.3 to 3.0°C/min. Heat to 200-800℃. After heating, the temperature is 0.04 to 2.0°C/min. temperature at a rate of at least below 100°C.

In the present invention, by heating a dispersion of silica-based particles, thermally liberated silicon is precipitated in the silica-based particles, and by lowering the temperature, it is deposited and immobilized on the silica-based particles. ``Particles that have a cavity inside an outer shell containing silica'' are produced.

Since the outer shell containing such silica is dense, the interior is maintained in a gas phase or liquid phase with a low refractive index. Therefore, the particles themselves are dense and have a low refractive index.

Here, the temperature increase rate is 0.3°C/min. If it is less than that, it takes too much time to raise the temperature to the target temperature, resulting in poor production efficiency. The temperature increase rate is 3.0°C/min. If it is faster than this, the silicon content in the particles will rapidly dissolve, and there is a risk that the particles will not be densified. The temperature increase rate is 0.5 to 2.5°C/min. is preferably 0.8 to 2.2°C/min. is more preferable.

Next, if the heating temperature is less than 200° C., there is a risk that the silicon content in the particles will be insufficiently precipitated. Even if the temperature exceeds 800° C., no further improvement in precipitation in the particles can be obtained, and there is a risk that manufacturing costs will increase. After heating to the target temperature, the temperature may be lowered, but in order to produce stably, it is preferable to maintain that temperature for 30 minutes or more. The heating is preferably performed at 360 to 750°C, more preferably from 400 to 750°C.

Next, if the temperature decreasing rate is less than 0.04° C./min, manufacturing costs may increase. The temperature decreasing rate is 2.0°C/min. If the speed is faster than that, the silicon content will be deposited onto the silica-based particles, but the particles may not be densified. The temperature decreasing rate is 0.08 to 1.8°C/min. is preferably 0.12 to 1.5°C/min. is more preferable.

The lowered temperature may be less than 100°C. For ease of handling, the temperature may be lowered to room temperature. However, as will be described later, when the temperature is raised again, if the temperature is lowered too much, there is a risk that it will take time to lower or raise the temperature or that extra energy will be required. As long as the temperature is lower than 100° C., the temperature may be lowered by increasing the temperature lowering rate without being limited to the range of the temperature lowering rate described above.

It is preferable to repeat the temperature raising and temperature lowering operations described above multiple times. By repeating this operation, the dissolution and deposition of the silicon component is also repeated, so that "particles having a cavity inside the outer shell containing silica" which are denser and have a lower refractive index can be obtained. The conditions for repeating the operation may be the same each time, or the heating rate and temperature may be changed.

The film-forming paint obtained using the thus obtained "particles containing silica and having a cavity inside the shell" has improved stability, coating properties, and the like. Furthermore, when such particles are used in a coating or the like, substances with a high refractive index, such as matrix-forming components, cannot enter the inside of the outer shell of the particles. Therefore, a transparent film with a low refractive index can be obtained. Furthermore, this coating has excellent adhesion to the base material and has high hardness and strength.

In the present invention, after the third step, it is preferable to add a silica source such as a silica sol, a silicic acid solution, or an organic silicon compound having a low content of impurities to the silica-based particle dispersion. By performing this before the fourth step of hydrothermal treatment, the outer shell containing silica becomes more dense and has a low refractive index, high hardness and strength. "particles" are obtained.

The purpose of adding this silica source is to more actively dissolve and deposit silicon in the fourth step. For this reason, a fine silica source is preferable. For example, when using silica sol as a silica source, the average particle diameter thereof is preferably less than 30 nm, although it depends on the average particle diameter of the silica-based particles. Moreover, when the silica source used is an organic silicon compound, the organic silicon compound shown in formula (2) in the above-mentioned first step can be used. In formula (2), when using an organosilicon compound in which n is 0, it is preferable to use a partial hydrolyzate of the organosilicon compound. Silica sources may be used alone or in combination.

The amount of the silica source is preferably 1 to 200 parts by weight as SiO ₂ as a solid content, based on 100 parts by weight of the silica particles. Here, if the amount of silica source is less than 1 part by mass, the effect of its addition cannot be sufficiently obtained. Even if the amount of silica source is more than 200 parts by mass, the densification of the particles will not be further improved. Moreover, the refractive index of the particles increases, and there is a possibility that particles having a desired refractive index cannot be obtained. The amount of silica source is more preferably 5 to 100 parts by mass, and even more preferably 20 to 55 parts by mass.

Also when adding these silica sources, it is preferable to repeat the temperature raising and temperature lowering operations multiple times as described above. From the viewpoint of forming a coating layer and densifying the particles, this addition is preferably carried out before the temperature is raised.

These silica sources may be added only once before the temperature is raised, or may be added every time the temperature raising and lowering operations are repeated, or intermittently.

In the present invention, after the fourth step, it is preferable to add an organic silicon compound to surface-treat the particles.

As the organosilicon compound used, it is preferable to use an organosilicon compound in which n is 1 to 3 as shown in formula (2) in the above-mentioned first step. Here, when using an organosilicon compound in which n is 0, it is preferable to use a partial hydrolyzate of the organosilicon compound.

The surface treatment of the particles is carried out by preparing an alcohol dispersion of the particles, adding a predetermined amount of the organosilicon compound represented by formula (2) and water, and hydrolyzing the organosilicon compound. For this hydrolysis, an acid or alkali is used as a hydrolysis catalyst, if necessary.

The organosilicon compound is preferably present as a solid content in an amount of 0.1 to 100 parts by mass as R _n --SiO _(4-n)/2 based on 100 parts by mass of particles. If the particles are surface-treated with an organosilicon compound, their compatibility with the matrix-forming components will be improved.

Here, if the amount of the organosilicon compound is less than 0.1 part by mass, the effect of its addition cannot be sufficiently obtained. On the contrary, the dispersibility of the particles may become insufficient and haze may occur in the resulting transparent film. Even if the amount of the organosilicon compound is more than 100 parts by mass, the dispersibility of the particles will not be further improved. Moreover, since the number of sites that bond with the matrix increases, there is a risk that the adhesion to the base material will be insufficient. The amount of the organosilicon compound is more preferably approximately 2 to 80 parts by weight, and even more preferably 3 to 50 parts by weight.

[Coating liquid for forming transparent film]
The particles described above can be applied to a coating liquid for forming a transparent film. That is, the coating liquid contains particles, a matrix forming component, and an organic solvent. In addition to this, additives such as a polymerization initiator, a leveling agent, and a surfactant may be included. Next, the main components contained in this coating liquid will be explained.

The concentration of particles in the coating liquid is preferably 5 to 95% by mass as solid content, based on the total amount of solid content such as particles and matrix-forming components. If the amount of particles is less than 5% by mass, the refractive index of the coating may not be sufficiently reduced. On the other hand, if it is more than 95% by mass, there is a risk that cracks will occur in the film, that the adhesion to the base material will be insufficient, and that the hardness, strength, transparency, haze, etc. may deteriorate. The concentration of the particles is more preferably 10 to 85% by mass, and even more preferably 20 to 70% by mass.

As the matrix-forming component, an organic resin-based matrix-forming component is suitable. Examples include components forming a matrix such as ultraviolet curable resin, thermosetting resin, and thermoplastic resin.

Examples of ultraviolet curable resins include (meth)acrylic acid resins, γ-glycyloxy resins, urethane resins, and vinyl resins. Examples of thermosetting resins include urethane resins, melamine resins, silicone resins, butyral resins, reactive silicone resins, phenol resins, epoxy resins, unsaturated polyester resins, and thermosetting acrylic resins. Examples of the thermoplastic resin 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. These resins may be copolymers or modified products of two or more types, or may be used in combination. Moreover, these resins may be emulsion resins, water-soluble resins, or hydrophilic resins.

The components forming these resins are preferably monomers or oligomers from the viewpoint of particle dispersibility and ease of coating.

The concentration of the matrix-forming component in the coating liquid is preferably 5 to 95% by mass as a solid content, based on the total amount of solid content such as particles and matrix-forming components contained. When the matrix-forming component is less than 5% by mass, it is difficult to form a film. Furthermore, even if a film is obtained, there is a risk that cracks will occur in the film, that the adhesion to the base material will be insufficient, and that the hardness, strength, transparency, haze, etc. may deteriorate. On the other hand, if it is more than 95% by mass, the amount of particles is small, so there is a risk that the refractive index cannot be reduced sufficiently. The concentration of this matrix-forming component is more preferably 15 to 90% by mass, and even more preferably 30 to 80% by mass.

As the organic solvent, one that can uniformly disperse particles and dissolve or disperse additives such as matrix forming components and polymerization initiators is used. Among these, hydrophilic solvents and polar solvents are preferred. Examples of the hydrophilic solvent include alcohols, esters, glycols, and ethers. Examples of the polar solvent include esters and ketones.

Examples of alcohols include methanol, ethanol, propanol, 2-propanol, butanol, diacetone alcohol, furfuryl alcohol, and tetrahydrofurfuryl alcohol.

Examples of esters include methyl acetate, ethyl acetate, isopropyl acetate, propyl acetate, isobutyl acetate, butyl acetate, isopentyl acetate, pentyl acetate, 3-methoxybutyl acetate, 2-ethylbutyl acetate, cyclohexyl acetate, ethylene glycol monoacetate, etc. .

Examples of glycols include ethylene glycol and hexylene glycol.

Ethers include diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol isopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether , propylene glycol monomethyl ether acetate, etc.

Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, butyl methyl ketone, cyclohexanone, methyl cyclohexanone, dipropyl ketone, methyl pentyl ketone, diisobutyl ketone, and the like.

Other polar solvents include dimethyl carbonate, toluene, and the like.

These may be used alone or in combination of two or more.

As the additive, any additive that can be used conventionally for forming an antireflection film can be used. For example, a polymerization initiator, a leveling agent, etc. are used to promote polymerization of matrix-forming components and improve film-forming properties.

Examples of the polymerization initiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)2,4,4-trimethyl-pentylphosphine oxide, and 2-hydroxymethyl -2-methylphenyl-propane-1-ketone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl] -2-morpholinopropan-1-one and the like.

Examples of the leveling agent include acrylic leveling agents, silicone leveling agents, acrylic silicone leveling agents, and the like. These leveling agents preferably have a fluorine group.

Regarding the concentration of these additives in the coating solution, those contained as solids when formed into a film are counted as matrix-forming components for convenience, and after forming into a film, they are counted as the matrix.

The solid content concentration of the coating liquid (the ratio of the solid content of the total solid content of particles and matrix-forming components to the coating liquid) is preferably 0.1 to 60% by mass. If the solid content concentration of the coating liquid is less than 0.1% by mass, the concentration stability of the coating material will be low, making coating difficult and possibly making it difficult to obtain a uniform film. Further, due to haze or poor appearance, productivity, manufacturing reliability, etc. may be reduced. On the other hand, if it is higher than 60% by mass, the stability of the coating liquid may deteriorate. Furthermore, since the viscosity of the coating liquid increases, there is a risk that the coating properties will be reduced. Furthermore, the haze of the coating increases, the surface roughness increases, and the strength may become insufficient. The solid content concentration of the coating liquid is more preferably 1 to 50% by mass.

[Method for producing base material with transparent film]
A transparent film is formed on a base material using the above-mentioned coating liquid.

Specifically, after applying a coating liquid onto a base material, drying and ultraviolet ray irradiation are performed to form a transparent film on the base material. The method for applying the coating liquid is not particularly limited as long as it can form a transparent film on the substrate. For example, well-known methods such as a spray method, a spinner method, a roll coating method, a bar coating method, a slit coater printing method, a gravure printing method, a microgravure printing method, etc. can be employed. Drying is performed by heating, for example, to about 50 to 150° C. to evaporate and remove the solvent. Thereafter, ultraviolet rays are irradiated to promote polymerization of the resin component and harden the coating. The transparent film is mainly formed of a matrix (resin) component and particles.

In this way, a base material with a transparent film on which a transparent film is formed is produced. The transparent film includes particles and a matrix. In a transparent film, the ratio of the solid content of the particles in the coating liquid to the matrix-forming component directly becomes the ratio of the particle components to the matrix in the film. As mentioned above, among the additives in the coating liquid, those remaining as solid content are counted here as the matrix.

The thickness of the transparent film is preferably 80 to 350 nm. If the film thickness is less than 80 nm, the strength and scratch resistance of the film may be insufficient. Furthermore, the film may be too thin to provide sufficient antireflection performance. On the other hand, if the film thickness is thicker than 350 nm, the film may be prone to cracks and the strength of the film may be insufficient, or the film may be too thick and the antireflection performance may deteriorate. Furthermore, if the shrinkage is extremely large, cracks may occur. This film thickness is more preferably 85 to 220 nm, and even more preferably 90 to 110 nm.

Further, the refractive index of the transparent film is preferably 1.10 to 1.45.

It is difficult to obtain a transparent film with a refractive index of less than 1.10, and if the refractive index exceeds 1.45, it will be formed on the refractive index of the base material or the lower layer of the transparent film formed as necessary. Although it varies depending on the refractive index of other films, the antireflection performance may be insufficient.

The refractive index of the transparent coating of the present invention is measured using an ellipsometer (EMS-1 manufactured by ULVAC). The refractive index of the transparent film is more preferably 1.15 to 1.35.

The light transmittance of the transparent coated substrate is preferably 85.0% or more. When the light transmittance is lower than 85.0%, there is a risk that the image clarity in a display device or the like may be insufficient. This light transmittance is more preferably 90.0% or more.

Further, the haze of the transparent coated substrate is preferably 3% or less, more preferably 0.3% or less.

Further, the reflectance of the transparent coated substrate is preferably 2.0% or less, more preferably 1.2% or less.

The strength (scratch resistance) of the transparent film is evaluated by sliding it on #0000 steel wool at a load of 1 kg/cm ² . It is preferable that no streak-like scratches be observed on the membrane surface after at least 100 sliding cycles, more preferably no scratches should be observed after 500 sliding cycles, and no scratches should be observed after 1000 sliding cycles. It is even more preferable not to have any.

The pencil hardness of the transparent coating is preferably 2H or higher. If the hardness is less than 2H, the hardness is insufficient as an antireflection film. The pencil hardness is more preferably 3H or higher, and even more preferably 4H or higher.

Any known base material can be used. For example, transparent resin base materials such as polycarbonate, acrylic resin, polyethylene terephthalate (PET), triacetyl cellulose (TAC), polymethyl methacrylate resin (PMMA), and cycloolefin polymer (COP) are preferred. These base materials have excellent adhesion to the transparent film formed by the above-mentioned coating liquid, and can provide a transparent film-coated base material having excellent hardness, strength, and the like. Therefore, it is suitably used for thin base materials. The thickness of the base material is not particularly limited, but is preferably 10 to 100 μm, more preferably 20 to 80 μm.

Moreover, a coated base material in which another coat is formed on such a base material can also be used. Other coatings include, for example, conventionally known primer films, hard coat films, high refractive index films, conductive films, and the like.

Examples of the present invention will be described below. Here, particles surface-treated with an organic silicon compound are exemplified.

[Example 1]
<Production of particles (P1) having a cavity inside the outer shell containing silica>
Add 9950 g of pure water to 50 g of an aqueous dispersion of seed particles (USBB-120, manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 25 nm, solid content concentration 20 mass %, Al ₂ O ₃ content in solid content 27 mass %). After the addition, 1% by weight of sodium hydroxide was added to adjust the pH to 11.0. Thereafter, it was heated to 98° C., and 1.87 kg of a sodium silicate aqueous solution with a concentration of 1.5% by mass as SiO ₂ and 1.87 kg of a sodium aluminate aqueous solution with a concentration of 0.5% by mass as Al ₂ O ₃ were added. 87 kg were added. Thereafter, washing was performed by centrifugal sedimentation to obtain a dispersion of composite oxide particles (a-1). The average particle diameter of the composite oxide particles (a-1) was 44 nm.

The composite oxide particles (a-1) were heated to 98°C, and 6.31 kg of a sodium silicate aqueous solution having a concentration of 1.5% by mass as SiO ₂ and 0.5% as Al ₂ O ₃ were added. 2.10 kg of a sodium aluminate aqueous solution of % by mass was added. Thereafter, the mixture was washed with an ultrafiltration membrane to make the solid content concentration 13% by mass, and then filtered through a capsule filter with an opening of 1 μm to obtain a dispersion of composite oxide particles (b-1). The average particle diameter of the composite oxide particles (b-1) was 58 nm.

1125 g of pure water was added to 500 g of this dispersion of composite oxide particles (b-1), and concentrated hydrochloric acid (concentration 35.5% by mass) was further added dropwise to adjust the pH to 1.0. While adding 10 L of a pH 3 aqueous hydrochloric acid solution and 5 L of pure water, the dissolved aluminum salt was separated and washed using an ultrafiltration membrane to obtain silica-based particles (c-1) with a concentration of 5% by mass.

Next, 100 g of silica-based particles (c-1) were added with silica sol (Cataroid SI-550 manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 5 nm, solid content concentration 20% by mass, Na ₂ O concentration 0.8) as a silica source. % by mass) was added thereto and thoroughly stirred. Thereafter, aqueous ammonia was added to adjust the pH of the dispersion to 10.8. The temperature was raised from 25°C to 360°C over 335 minutes, held for 24 hours, and then cooled to 25°C over 420 minutes. Thereafter, the temperature was again raised from 25° C. to 360° C. over 335 minutes, held for 24 hours, and then cooled to 25° C. over 420 minutes, and the same operation was performed once again (3 times in total). Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning, and the particles (P1 ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of 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.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P1), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with methyl isobutyl ketone (MIBK) using an evaporator to obtain an MIBK dispersion of particles (P1) with a solid content concentration of 20% by mass.

Table 1 shows the manufacturing conditions for this particle (P1). Further, Table 2 shows the properties of the particles (P1) measured by the following methods (the same applies to the following Examples and Comparative Examples).

The physical properties of the particles (P1) were measured by an image analysis method. Specifically, first, the MIBK dispersion of particles (P1) was diluted with methanol to 0.01% by mass, and then dried on a collodion membrane of a copper cell for an electron microscope. Next, this was photographed using a field emission transmission electron microscope (HF5000, manufactured by Hitachi High-Technologies Corporation) at a magnification of 1,000,000 times. An arbitrary 1000 particles in the obtained photographic projection diagram (SEM image, TEM photograph) were measured by the following methods (1) to (5).

(1) Average particle diameter (D)
The area of the particle (P1) was determined from image processing of the SEM image, and the equivalent circle diameter was determined from the area. The average value of the equivalent circle diameter was defined as the average particle diameter of the particles.

(2) Cavity diameter The area of the cavity inside the outer shell of the particle (P1) was determined from the TEM photograph, and the equivalent circle diameter was determined from the area, and this was defined as the cavity diameter. Moreover, the average value of this cavity diameter was defined as D _O.

(3) Particle shape The ratio of the short axis and long axis of the particle (P1) was determined from the SEM image. Here, if the average value of the ratio of major axis/minor axis was less than 1.2, it was considered to be spherical.

(4) Cavity shape and proportion of particles with one cavity The ratio of the short axis and long axis of the cavity inside the outer shell of the particle (P1) was determined from the TEM photograph. Here, if the average value of the ratio of major axis/minor axis was less than 1.2, it was considered to be spherical. Additionally, the number of cavities within the particles was measured and the proportion thereof was determined.

(5) Pore volume by N ₂ adsorption method The MIBK dispersion of particles (P1) was dried in an evaporator and dried at 105°C. One gram of the powder was placed in a cell, nitrogen was adsorbed using a nitrogen adsorption device (BELSORP-mini II (manufactured by Microtrac Bell Co., Ltd.)), and the pore volume was measured.

(6) Refractive index of particles (n _a )
The MIBK dispersion of particles (P1) was taken into an evaporator to evaporate the dispersion medium. Next, this was dried at 120°C to form a powder. Two or three drops of a standard refractive liquid with a known refractive index were dropped onto a glass plate, and the above powder was mixed therein. This operation was performed using various standard refractive liquids, and the refractive index of the standard refractive liquid when the mixed liquid became transparent was taken as the refractive index of the silica-based hollow particles.

(7) Particle outer shell refractive index ( _ns )
Using the average particle diameter (D) of the particles, the average value of the cavity diameter inside the outer shell (D _O ), and the refractive index ( _na ) of the particles, determined by the method described above, the outer shell of the particle can be calculated using the following formula. The refractive index ( _ns ) was determined.

(8) Carbon content The carbon content in the particles (P1) was determined by drying the MIBK dispersion of the particles (P1) at 120°C and calcining it at 400°C using a carbon sulfur analyzer (EMIA-320V manufactured by HORIBA). ).

(9) ²⁹ Q ₁ , Q ₂ , Q ₃ , Q ₄ and their ratios by Si-NMR A MIBK dispersion of particles (P1) was placed in a dedicated glass cell, and 5% by mass of tetramethylsilane was added as a reference substance. Measurement was performed using an NMR device (JNM-EX270 model manufactured by JEOL Ltd., analysis software Excalibur manufactured by JEOL Ltd.). More specifically, in the single pulse non-decoupling method, the area (Q ₁ ) of the peak appearing at the chemical shift of -78 to -88 ppm in ²⁹ Si-NMR spectroscopy and the peak appearing at the chemical shift of -88 to -98 ppm (Q ₂ ), the area of the peak appearing at the chemical shift of -98 to -108 ppm (Q ₃ ), and the area of the peak appearing at the chemical shift of -108 to -117 ppm (Q ₄ ), the ratio (Q ₁ /ΣQ ), the ratio (Q ₂ /ΣQ) and the ratio (Q ₃ /Q ₄ ) were determined.

(10) Content of alkali metals and other elements Content of alkali metals in particles (P1), content of Fe, Ti, Zn, Pd, Ag, Mn, Co, Mo, Sn, Al, Zr, Cu, Regarding the content of Ni and Cr, and the content of U and Th, the particles are dissolved in hydrofluoric acid, heated to remove the hydrofluoric acid, and then pure water is added as necessary, and the resulting solution is determined. Measurement was performed using an ICP inductively coupled plasma emission spectrometer mass spectrometer (for example, ICPM-8500 manufactured by Shimadzu Corporation).

(11) Silica content The MIBK dispersion of particles (P1) was dried at 120°C for 12 hours. The content of silica (SiO ₂ ) was determined using a fluorescent X-ray analyzer (EA600VX, manufactured by Hitachi High-Tech Science Co., Ltd.).

<Production of coating liquid (1) for forming an antireflection transparent film>
The MIBK dispersion of particles (P1) was diluted to a solid content concentration of 5% by mass. 50 g of this diluted dispersion, 1.67 g of acrylic resin (Hitalloid 1007 manufactured by Hitachi Chemical Co., Ltd.) and 52.6 g of a mixed solvent of isopropanol and n-butanol (1/1 (mass ratio)) were thoroughly mixed to create a transparent A film-forming coating liquid (1) was produced. The coating liquid for forming a transparent film is shown in Table 3 (the same applies to the following Examples and Comparative Examples).

<Production of base material with anti-reflection transparent coating (1)>
Hard coat paint (ELCOM HP-1004 manufactured by JGC Catalysts Kasei Co., Ltd.) was applied to TAC film (FT-PB80UL-M manufactured by Panac Corporation, thickness 80 μm, refractive index 1.51) using a bar coater method (#18). and dried at 80° C. for 120 seconds. Thereafter, a hard coat film was prepared by irradiating and curing ultraviolet rays at 300 mJ/cm ² . The thickness of the hard coat film was 8 μm.

Next, the coating liquid (1) for forming an antireflection transparent film was applied using a bar coater method (#4), dried at 80°C for 120 seconds, and then irradiated with ultraviolet rays of 600 mJ/cm ² in an N ₂ atmosphere. It was cured to produce an antireflection transparent coated substrate (1).

The antireflection transparent coated substrate (1) was measured for the following items. The results are shown in Table 3 (the same applies to the following Examples and Comparative Examples).

(12) Film thickness, refractive index, reflectance Using an ellipsometer (manufactured by ULVAC, EMS-1), the film thickness, film refractive index, and light beam with a wavelength of 550 nm of the base material with antireflection transparent coating (1) were measured. The reflectance was measured.

(13) Total light transmittance and haze Using a haze meter (manufactured by Suga Test Instruments Co., Ltd.), the total light transmittance and haze of the antireflection transparent coated substrate (1) were measured.

(14) Adhesion On the surface of the anti-reflection transparent coated base material (1), use a knife to make 11 parallel scratches at 1 mm intervals vertically and horizontally to create 100 squares, adhere cellophane tape to these, and then Adhesion was evaluated by classifying the number of squares that remained without the film peeling off when the cellophane tape was peeled off into the following three levels.
Number of remaining squares: 90 or more: ◎
Number of remaining squares: 85-89:○
Number of remaining squares: 84 or less: △

(15) Measurement of scratch resistance Using #0000 steel wool, sliding was performed 100 times at a load of 1,500 g/cm ² , the surface of the film was visually observed, and evaluated using the following criteria.
Evaluation criteria;
No streaky scars are observed: ◎
Slight streak-like scratches are observed: ○
Many streak-like scratches are observed: △
The entire surface is scraped: ×

(16) Pencil hardness Pencil hardness was measured using a pencil hardness tester according to JIS K 5400. That is, a pencil was set at an angle of 45 degrees with respect to the surface of the transparent coating, and the pencil was pulled at a constant speed under a predetermined load, and the presence or absence of scratches was observed.

[Example 2]
<Production of particles (P2) having a cavity inside the outer shell containing silica>
Add 29,250 g of pure water to 750 g of an aqueous dispersion of seed particles (USBB-120, manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 25 nm, solid content concentration 20 mass %, Al ₂ O ₃ content in solid content 27 mass %). After the addition, 1% by weight of sodium hydroxide was added to adjust the pH to 11.0. Thereafter, it was heated to 98°C, and 5.83 kg of a sodium silicate aqueous solution with a concentration of 1.5% by mass as SiO ₂ and 5.83 kg of a sodium aluminate aqueous solution with a concentration of 0.5% by mass as Al ₂ O ₃ were added. was added. Thereafter, washing was performed by centrifugal sedimentation to obtain a dispersion of composite oxide particles (a-2). At this time, the average particle diameter of the composite oxide particles (a-2) was 225 nm.

The composite oxide particles (a-2) were heated to 98°C, and 2.21 kg of a sodium silicate aqueous solution having a concentration of 1.5% by mass as SiO ₂ and 0.5% as Al ₂ O ₃ were added. 0.74 kg of a sodium aluminate aqueous solution of % by mass was added. Thereafter, the mixture was washed with an ultrafiltration membrane to make the solid content concentration 13% by mass, and then filtered through a capsule filter with an opening of 1 μm to obtain a dispersion of composite oxide particles (b-2). The average particle diameter of the composite oxide particles (b-2) was 240 nm.

1125 g of pure water was added to 500 g of this dispersion of composite oxide particles (b-2), and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0. While adding 10 L of aqueous hydrochloric acid solution at pH 3 and 5 L of pure water, the dissolved aluminum salt was separated and washed using an ultrafiltration membrane to obtain silica-based particles (c-2) with a concentration of 5% by mass.

Next, 100 g of silica particles (c-2) were added with silica sol (Cataroid SI-50 manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 25 nm, solid content concentration 48% by mass, Na ₂ O concentration 0.5 mass) as a silica source. %) was added and thoroughly stirred. Thereafter, aqueous ammonia was added to adjust the pH of the dispersion to 10.5. The temperature was raised from 25°C to 360°C over 335 minutes, held for 24 hours, and then cooled to 25°C over 420 minutes. Thereafter, the temperature was again raised from 25° C. to 360° C. over 335 minutes, held for 24 hours, and then cooled to 25° C. over 420 minutes, and the same operation was performed once again (3 times in total). Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning, and particles (P2 ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (P2) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (P2) with a solid content concentration of 20% by mass.

Next, 2 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P2), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (P2) with a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (2) and the coated substrate (2)>
The coating liquid for forming an antireflection transparent film (2) and the antireflection coating solution were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (P2) was used instead of the MIBK dispersion of particles (P1). A substrate with a transparent film (2) was produced and its properties were evaluated.

[Example 3]
<Production of particles (P3) having a cavity inside the outer shell containing silica>
After adding 17,000 g of pure water to 3,000 g of an aqueous dispersion of seed particles (Cataroid SI-550 manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 5 nm, SiO ₂ concentration 20 mass %), 1 mass % of sodium hydroxide was added. The pH was adjusted to 10.0. Thereafter, the mixture was heated to 80° C., and 1369 g of a sodium silicate aqueous solution having a concentration of 1.5% by mass as SiO ₂ and 1369 g of a sodium aluminate aqueous solution having a concentration of 0.5% by mass as Al ₂ O ₃ were added. . Thereafter, washing was performed by centrifugal sedimentation to obtain a dispersion of composite oxide particles (a-3). At this time, the average particle diameter of the composite oxide particles (a-3) was 19 nm.
The composite oxide particles (a-3) were heated to 85°C, and 2820 g of a sodium silicate aqueous solution with a concentration of 1.5% by mass as SiO ₂ and 0.5% by mass as Al ₂ O ₃ were added. 940 g of a sodium aluminate aqueous solution was added. Thereafter, the mixture was washed with an ultrafiltration membrane to make the solid content concentration 13% by mass, and then filtered through a capsule filter with an opening of 1 μm to obtain a dispersion of composite oxide particles (b-3). The average particle diameter of the composite oxide particles (b-3) was 22 nm.

1125 g of pure water was added to 500 g of this dispersion of composite oxide particles (b-3), and concentrated hydrochloric acid (concentration 35.5% by mass) was further added dropwise to adjust the pH to 1.0. While adding 10 L of a pH 3 aqueous hydrochloric acid solution and 5 L of pure water, the dissolved aluminum salt was separated and washed using an ultrafiltration membrane to obtain silica-based particles (c-3) with a concentration of 5% by mass.

Next, 52.5 g of a silicic acid solution (4.0% by mass as SiO ₂ , Na ₂ O concentration 12 ppm) as a silica source was added to 100 g of silica-based particles (c-3), and the mixture was thoroughly stirred. Thereafter, aqueous ammonia was added to adjust the pH of the dispersion to 9.5. The temperature was raised from 25°C to 360°C over 335 minutes, held for 24 hours, and then cooled to 25°C over 420 minutes. Thereafter, the temperature was again raised from 25° C. to 360° C. over 335 minutes, held for 24 hours, and then cooled to 25° C. over 420 minutes, and the same operation was performed once again (3 times in total). Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning, and particles (P3) having a cavity inside the outer shell containing silica were washed. ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (P3) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (P3) with a solid content concentration of 20% by mass.

Next, 10 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P3), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (P3) with a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (3) and base material with the film (3)>
Instead of the MIBK dispersion of particles (P1), use the MIBK dispersion of particles (P3), add 1.07 g of acrylic resin (Hitalloid 1007, manufactured by Hitachi Chemical Co., Ltd.), and mix 1/2 of isopropanol and n-butanol. 1 (mass ratio) A coating liquid for forming an antireflection transparent film (3) and a substrate with an antireflection transparent film (3) were produced in the same manner as in Example 1, except that 85.7g of the mixed solvent was used. and evaluated each characteristic.

[Example 4]
<Production of particles (P4) having a cavity inside the outer shell containing silica>
Silica sol (Cataroid SI-550 manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 5 nm, solid content concentration 20 mass %, Na ₂ O concentration 0.8 mass %) was added to 1000 g of silica particles (c-1) as a silica source. 128g of was added and thoroughly stirred. Next, this was ion-exchanged for 1 hour using 200 g of a cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation).

Next, aqueous ammonia was added to adjust the pH of the dispersion to 10.0, and the dispersion was dried at 110° C. for 6 hours to obtain powder. This was heated from 25°C to 750°C over 258 minutes, held for 5 hours, and then cooled to 50°C over 375 minutes.

Thereafter, 500 g of water was added to 50 g of powder, and then a 1% aqueous NaOH solution was added so that the pH was 10.2. Thereafter, dispersion treatment was performed using a bead mill using a 0.02 mm ZrO ₂ media.

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning, and particles (P4) having a cavity inside the outer shell containing silica were washed. ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (P4) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (P4) with a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P4), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (P4) with a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (4) and base material with the film (4)>
The coating liquid for forming an antireflection transparent film (4) and the antireflection transparent coating were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (P4) was used instead of the MIBK dispersion of particles (P1). A transparent coated substrate (4) was produced and its properties were evaluated.

[Example 5]
<Production of particles (P5) having a cavity inside the outer shell containing silica>
Silica sol (Cataroid SI-550 manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 5 nm, solid content concentration 20 mass %, Na ₂ O concentration 0.8 mass %) was added to 1000 g of silica particles (c-1) as a silica source. 62.5g of was added and thoroughly stirred.

Next, aqueous ammonia was added to adjust the pH of the dispersion to 10.5, and the temperature was raised from 25°C to 200°C over 583 minutes, held for 24 hours, and then cooled to 25°C over 4400 minutes. . This operation was repeated twice.

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of a cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning, and particles (P5) having a cavity inside the outer shell containing silica were washed. ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (P5) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (P5) with a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P5), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (P5) with a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (5) and base material with the film (5)>
The coating liquid for forming an antireflection transparent film (5) and the antireflection coating solution were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (P5) was used instead of the MIBK dispersion of particles (P1). A transparent coated base material (5) was produced and its properties were evaluated.

[Example 6]
<Production of particles (P6) having a cavity inside the outer shell containing silica>
After adding 1000 g of ethanol and 50 g of aqueous ammonia to 1000 g of silica particles (c-1), the liquid temperature was adjusted to 35°C. To this was added 88.5 g of tetraethoxysilane as a silica source, and the mixture was thoroughly stirred. Thereafter, the solvent was replaced with water using an ultrafiltration membrane.

Next, aqueous ammonia was added to adjust the pH of the dispersion to 10.5, and the temperature was raised from 25°C to 360°C over 335 minutes, held for 24 hours, and then cooled to 25°C over 419 minutes. . This operation was repeated three times.

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning, and particles (P6 ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (P6) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (P6) with a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P6), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (P6) with a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (6) and base material with the film (6)>
The coating liquid for forming an antireflection transparent film (6) and the antireflection transparent coating were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (P6) was used instead of the MIBK dispersion of particles (P1). A substrate with a transparent film (6) was manufactured and its properties were evaluated.

[Example 7]
<Production of particles (P7) having a cavity inside the outer shell containing silica>
Aqueous ammonia was added to 1000 g of silica particles (c-1) to adjust the pH of the dispersion to 10.5, and then dried at 110° C. for 6 hours to obtain a powder. The temperature was raised from 25°C to 360°C over 335 minutes, held for 24 hours, and then cooled to 25°C over 420 minutes. This operation was repeated three times.

Thereafter, 500 g of water was added to 50 g of powder, and then a 1% aqueous NaOH solution was added so that the pH was 10.2. Thereafter, dispersion treatment was performed using a bead mill using a 0.02 mm ZrO ₂ media.

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning, and particles (P7) having a cavity inside the outer shell containing silica were washed. ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (P7) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (P7) with a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P7), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (P7) with a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (7) and base material with the film (7)>
The coating liquid for forming an antireflection transparent film (7) and the antireflection transparent coating were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (P7) was used instead of the MIBK dispersion of particles (P1). A transparent film-coated base material (7) was formed and its properties were evaluated.

[Example 8]
<Production of particles (P8) having a cavity inside the outer shell containing silica>
Add 128 g of high-purity silica sol (manufactured by JGC Catalysts & Chemicals Co., Ltd. LNA-2000, average particle diameter 23 nm, solid content concentration 12.6% by mass) as a silica source to 1000 g of silica-based particles (c-1), and stir thoroughly. did.

Next, aqueous ammonia was added to adjust the pH of the dispersion to 10.8, and the dispersion was dried at 110° C. for 6 hours to obtain powder. The temperature was raised from 25°C to 360°C over 335 minutes, held for 24 hours, and then cooled to 25°C over 420 minutes. This operation was repeated three times.

Thereafter, 500 g of water was added to 50 g of powder, and then a 1% aqueous NaOH solution was added so that the pH was 10.2. Thereafter, dispersion treatment was performed using a bead mill using a 0.02 mm ZrO ₂ media.

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of a cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning. ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (P8) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (P8) having a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P8), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (P8) with a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (8) and base material with the film (8)>
The coating liquid for forming an antireflection transparent film (8) and the antireflection transparent coating were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (P8) was used instead of the MIBK dispersion of particles (P1). A transparent film-coated base material (8) was formed and its properties were evaluated.

[Example 9]
<Production of particles (P9) having a cavity inside the outer shell containing silica>
Silica sol (Cataroid SI-550 manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 5 nm, solid content concentration 20 mass %, Na ₂ O concentration 0.8 mass %) was added to 1000 g of silica particles (c-1) as a silica source. 128g of was added and thoroughly stirred. Next, this was ion-exchanged for 1 hour using 200 g of a cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation).

Thereafter, aqueous ammonia was added to adjust the pH of the dispersion to 10.8, followed by drying at 110° C. for 6 hours to obtain powder. This was heated from 25°C to 600°C over 575 minutes, held for 5 hours, and then cooled to 50°C over 550 minutes. This operation was repeated three times.

Thereafter, 500 g of water was added to 50 g of powder, and then 1% NaOH aqueous solution was added so that the pH was 10.0. Thereafter, dispersion treatment was performed using a bead mill using a 0.02 mm ZrO ₂ media.

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, using 200 g of cation exchange resin (Diaion SK1B manufactured by Mitsubishi Chemical Corporation), ion exchange was performed at 80°C for 3 hours for cleaning, and particles (P9) having a cavity inside the outer shell containing silica were washed. ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (P9) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (P9) with a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (P9), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (P9) with a solid content concentration of 20% by mass.
<Production of coating liquid for forming an antireflection transparent film (9) and base material with the film (9)>
The coating liquid for forming an antireflection transparent film (9) and the antireflection coating solution were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (P9) was used instead of the MIBK dispersion of particles (P1). A transparent film-coated base material (9) was formed and its properties were evaluated.

[Comparative example 1]
<Production of particles (R1) having a cavity inside the outer shell containing silica>
Silica sol (Cataroid SI-550 manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 5 nm, solid content concentration 20 mass %, Na ₂ O concentration 0.8 mass %) was added to 1000 g of silica particles (c-1) as a silica source. 62.5g of was added and thoroughly stirred.

Next, aqueous ammonia was added to adjust the pH of the dispersion to 10.5, and the temperature was raised from 25°C to 150°C over 25 minutes, held for 24 hours, and then cooled to 25°C over 42 minutes. .

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, the particles (R1 ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (R1) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (R1) with a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (R1), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (R1) with a solid content concentration of 20% by mass.

<Production of the coating liquid for forming an antireflection transparent film (R1) and the coated substrate (R1)>
The coating for forming an antireflection transparent film (R1) and the antireflection transparent coating were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (R1) was used instead of the MIBK dispersion of particles (P1). A coated base material (R1) was produced and its properties were evaluated.

[Comparative example 2]
<Production of particles (R2) having a cavity inside the outer shell containing silica>
After adding 1000 g of ethanol and 50 g of aqueous ammonia to 1000 g of silica particles (c-1), the liquid temperature was adjusted to 35°C. To this, 57.9 g of methyltrimethoxysilane was added as a silica source and thoroughly stirred. Thereafter, the solvent was replaced with water using an ultrafiltration membrane.

Next, after adding ammonia water to adjust the pH of the dispersion to 10.5, the temperature was raised from 25°C to 360°C over 335 minutes, held for 24 hours, and then cooled to 25°C over 419 minutes. did. This operation was repeated three times.

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, the particles (R2 ) was obtained. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (R2) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (R2) with a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (R2), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion of particles (R2) with a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (R2) and base material with the film (R2)>
The coating liquid for forming an antireflection transparent film (R2) and the antireflection coating solution were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (R2) was used instead of the MIBK dispersion of particles (P1). A substrate with a transparent film (R2) was manufactured and its properties were evaluated.

[Comparative example 3]
<Production of particles (R3) having a cavity inside the outer shell containing silica>
Silica particles (Cataroid SI-550 manufactured by JGC Catalysts & Chemicals Co., Ltd., average particle diameter 5 nm, solid content concentration 20 mass %, Na ₂ O concentration 0.8 mass %) were added to 1000 g of silica particles (c-1) as a silica source. ) was added thereto and thoroughly stirred.

Next, 10.6 g of 10% NaOH aqueous solution was added to adjust the pH of the dispersion to 10.5. After that, the temperature was raised from 25°C to 360°C over 335 minutes and held for 24 hours, and then the temperature was increased to 419°C. It was cooled to 25° C. over several minutes. This operation was repeated three times.

Thereafter, ion exchange was performed for 3 hours using 400 g of a cation exchange resin (Diaion SK1B, manufactured by Mitsubishi Chemical Corporation), and then for 3 hours using 200 g of an anion exchange resin (Diaion SA20A, manufactured by Mitsubishi Chemical Corporation). Ion exchanged. Thereafter, the particles (R2 ) was obtained. However, this particle had a hole in its outer shell, and the cavity inside the outer shell was not closed by the outer shell. The solid content concentration of this dispersion was 20% by mass.

The solvent of this aqueous dispersion of particles (R3) was replaced with methanol using an ultrafiltration membrane to prepare a methanol dispersion of particles (R3) with a solid content concentration of 20% by mass.

Next, 6 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 g of a methanol dispersion of the particles (R3), and heat treatment was performed at 50° C. for 6 hours. Thereafter, the solvent was replaced with MIBK using an evaporator to obtain an MIBK dispersion with particles (R3) having a solid content concentration of 20% by mass.

<Production of coating liquid for forming an antireflection transparent film (R3) and base material with the film (R3)>
The coating liquid for forming an antireflection transparent film (R3) and the antireflection transparent coating were prepared in the same manner as in Example 1, except that the MIBK dispersion of particles (R3) was used instead of the MIBK dispersion of particles (P1). A substrate with a transparent film (R3) was manufactured and its properties were evaluated.

Claims (9)

A particle having a cavity inside an outer shell containing silica,
The average particle diameter (D) of the particles is 20 to 250 nm,
The diameter of the cavity is 0.6 to 0.85 times the diameter of the particle,
The pore volume of the particles measured by N ₂ adsorption method is less than 1.0 cm ³ /g;
The refractive index (n _a ) of the particles is 1.08 to 1.34,
The carbon content of the particles is 3.0% by mass or less,
The refractive index (n _S ) of the outer shell determined by the following formula is 1.38 to 1.47,
The area ( ^Q ₁ ) of the peak appearing at chemical shift -78 to -88 ppm , the area (Q ₂ ) of the peak appearing at chemical shift -88 to -98 ppm, and the chemical shift -98 in 29 Si-NMR spectroscopy of the particles. The ratio (Q 1 _/ (Q ₁ +Q _{2 +} Q _{3 +} Q ₄ )) is essentially 0, the ratio (Q ₂ /(Q ₁ +Q ₂ +Q ₃ +Q ₄ )) is substantially 0, and the ratio (Q ₃ /Q ₄ ) is 0.01 to 0.7 .

The particles according to claim 1, wherein the particles have a carbon content of 0.02 to 3.0% by mass. The particles according to claim 1, wherein the content of each element belonging to an alkali metal in the particles is 1 ppm or less based on SiO ₂ when the elements are expressed as oxides. The content of each of Fe, Ti, Zn, Pd, Ag, Mn, Co, Mo, Sn, Al, and Zr in the particles is less than 0.1 ppm, the content of each of Cu, Ni, and Cr is less than 1 ppb, and U , Th is less than 0.3 ppb. A coating liquid for forming a transparent film, comprising the particles according to claim 1, a matrix-forming component, and an organic solvent. A base material with a transparent film, wherein a transparent film containing the particles according to claim 1 and a matrix is formed on the base material. When a solution of a compound containing silicon and an aqueous solution of an alkali-soluble compound of an inorganic element other than silicon are expressed, the oxide of silicon is expressed as SiO ₂ and the oxide of the inorganic element is expressed as MOx. A first step of preparing a dispersion of composite oxide particles a by simultaneously adding them to an alkaline aqueous solution so that the ratio (MOx/SiO ₂ ) is 0.01 to 2;
Next, a solution of a compound containing silicon and an aqueous solution of an alkali-soluble compound of an inorganic element other than silicon are added at a molar ratio (MOx/SiO ₂ ) smaller than the molar ratio in the first step. , a second step of preparing a dispersion of composite oxide particles b;
Next, a third step is to prepare a dispersion of silica-based particles by adding an acid to the dispersion of the composite oxide particles b to remove at least a part of the elements other than silicon constituting the composite oxide particles b. process and
The dispersion liquid of the silica-based particles was heated at a heating rate of 0.3 to 3.0°C/min. After heating to 200-800°C at 0.04-2.0°C/min. A fourth step of lowering the temperature to below 100°C at a rate of
A method for producing particles having a cavity inside an outer shell containing silica. 8. The method for producing particles according to claim 7, wherein the heating and temperature lowering processes are repeated multiple times. Between the third step and the fourth step, a step of adding at least one of an organosilicon compound represented by the following formula (2) and a partial hydrolyzate thereof to the dispersion of silica-based particles. The method for producing particles according to claim 7, characterized in that:
R _n -SiX _4-n (2)
(In the formula, R is an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different from each other. Substituents include an epoxy group, an alkoxy group, a (meth)acryloyloxy group, Examples include mercapto group, halogen atom, amino group, and phenylamino group.