WO2024071033A1

WO2024071033A1 - Organic solvent sol of amine-containing hollow silica particles, and method for producing same

Info

Publication number: WO2024071033A1
Application number: PCT/JP2023/034712
Authority: WO
Inventors: 透西村; 修平山田; 将大飛田
Original assignee: 日産化学株式会社
Priority date: 2022-09-30
Filing date: 2023-09-25
Publication date: 2024-04-04
Also published as: TW202428515A

Abstract

[Problem] To provide: an organic solvent sol of hollow silica particles, in which the sol contains an amine, the hollow silica particles have a specific surface charge, exhibit high dispersibility in a resin, and have a space inside an outer shell; a method for producing same; and a film-forming composition. [Solution] Provided is an organic solvent sol of hollow silica particles, in which the sol contains an amine and the hollow silica particles have a space inside an outer shell. The amine is at least one type of amine selected from among a primary amine, secondary amine and tertiary amine having a total of 1-10 carbon atoms. The water solubility of the amine is 80 g/L or more. The content of the amine is 0.001-10 mass% relative to SiO2 in the hollow silica particles. The average particle diameter of the hollow silica particles, as measured using a dynamic light-scattering method, is 20-150 nm. The surface charge amount is 5-250 μeq/g, as calculated per 1 g of SiO2 in the hollow silica particles. The organic solvent is an alcohol, ketone, ether or ester having 1-10 carbon atoms. Also provided is a film-forming composition that contains the organic solvent sol of hollow silica particles and an organic resin.

Description

Organic solvent sol of amine-containing hollow silica particles and method for producing same

The present invention relates to a sol containing an amine and having hollow silica particles dispersed in an organic solvent, a method for producing the sol, and a film-forming composition containing the sol.

Hollow silica particles have a silica outer shell and a space inside the shell, and due to their characteristics, they have properties such as a low refractive index, low thermal conductivity (thermal insulation), and electrical insulation.
Hollow silica particles consist of a core which corresponds to the hollow portion and a shell which forms the outside of the core. An aqueous dispersion of hollow silica particles can be obtained by forming a silica layer on the outside of the core in an aqueous medium and then removing the core.
For example, a composition for forming a transparent coating film containing hollow silica particles having a surface charge amount of 5 to 20 μeq/g-SiO ₂ and a binder component has been disclosed (see Patent Document 1).
In addition, hollow silica particles whose surfaces are coated with a silane compound and whose thermal weight loss at 200° C. to 500° C. is 1% by mass or more have been disclosed (see Patent Document 2).

International Publication No. 2007-060884 JP 2013-014506 A

The present invention provides an organic solvent sol of hollow silica particles that contain an amine in the sol and have a space inside the outer shell, a method for producing the sol, and a coating-forming composition that contains the sol.

As a first aspect, the present invention provides an organic solvent sol of hollow silica particles containing an amine in the sol and having a space inside an outer shell;
As a second aspect, the sol according to the first aspect, in which the amine is at least one amine selected from the group consisting of primary amines, secondary amines, and tertiary amines having 1 to 10 carbon atoms;
As a third aspect, the sol according to the first or second aspect, wherein the amine is a water-soluble amine having a water solubility of 80 g/L or more.
As a fourth aspect, the sol according to any one of the first to third aspects, in which the content of the amine is 0.001 to 10 mass% relative to the _SiO2 of the hollow silica particles;
As a fifth aspect, the sol according to any one of the first to fourth aspects, in which the hollow silica particles have an average particle size of 20 to 150 nm as measured by a dynamic light scattering method.
As a sixth aspect, the sol according to any one of the first to fifth aspects, in which the hollow silica particles have a surface charge amount calculated per gram of _SiO2 of 5 to 250 μeq/g;
As a seventh aspect, the sol according to any one of the first to sixth aspects, in which the organic solvent is an alcohol, a ketone, an ether, or an ester having 1 to 10 carbon atoms;
As an eighth aspect, the hollow silica particles may further be represented by formula (1), formula (2), or formula (3):
(In formula (1), R ¹ represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, or a cyano group, and is bonded to a silicon atom via a Si-C bond; R ² represents an alkoxy group, an acyloxy group, or a halogen group; a represents an integer of 1 to 3;
In formula (2) and formula (3), ^R3 and ^R5 each represent an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms and bonded to a silicon atom via a Si-C bond, ^R4 and ^R6 each represent an alkoxy group, an acyloxy group, or a halogen group, Y represents an alkylene group, an NH group, or an oxygen atom, b is an integer of 1 to 3, c is an integer of 0 or 1, and d is an integer of 1 to 3.
The sol according to any one of the first to seventh aspects, which is coated with at least one silane compound selected from the group consisting of silane compounds represented by the following formula:
As a ninth aspect, a coating-forming composition comprising the sol according to any one of the first to eighth aspects and an organic resin;
According to a tenth aspect, there is provided a film obtained from the film-forming composition according to the ninth aspect, the film having a visible light transmittance of 80% or more.
As an eleventh aspect, the present invention relates to the following steps (A) to (C):
Step (A): preparing a hollow silica aqueous sol;
Step (B): adding at least one amine selected from the group consisting of primary amines, secondary amines, and tertiary amines having a water solubility of 80 g/L or more and having 1 to 10 carbon atoms to the hollow silica aqueous sol of step (A) in an amount of 0.001 to 10% by mass based on the _SiO2 of the hollow silica particles;
A process (C) for replacing the aqueous medium of the aqueous sol of hollow silica particles obtained in the process (B) with an alcohol, a ketone, an ether, or an ester having 1 to 10 carbon atoms;
As a twelfth aspect, a method for producing a sol according to the eleventh aspect, the method including, after completion of the step (C), a step (D) of further adding at least one silane compound selected from the group consisting of silane compounds represented by the formula (1), the formula (2), and the formula (3), and heating;
As a thirteenth aspect, the method for producing a sol according to the eleventh or twelfth aspect, in which the step (C) is a step of performing solvent replacement of the aqueous medium with an alcohol having 1 to 10 carbon atoms, and then performing solvent replacement with a ketone, ether, or ester having 1 to 10 carbon atoms;
As a fourteenth aspect, there is provided the method for producing a sol according to the twelfth aspect, in which the step (C) is a step of performing solvent substitution of the aqueous medium with an alcohol having 1 to 10 carbon atoms, and the step (D) is a step of adding at least one silane compound selected from the group consisting of silane compounds represented by the above formulas (1), (2), and (3), heating, and then performing solvent substitution of the alcohol solvent with a ketone, ether, or ester having 1 to 10 carbon atoms; and as a fifteenth aspect, there is provided a method for adjusting a surface charge of hollow silica particles, using the production method according to any one of the eleventh to fourteenth aspects.

The present invention relates to an organic solvent sol of hollow silica particles containing amines in the sol and having a space inside the outer shell. It is known that hollow silica particles dispersed in an organic solvent have a charge on the surface. The organic solvent sol of hollow silica particles itself, or the amount of surface charge of the hollow silica particles when the organic solvent sol of hollow silica particles is mixed with an organic resin binder, can greatly affect the stability and dispersibility. For example, when hollow silica particles are dispersed in a highly polar solvent or resin binder, stable dispersibility can be obtained if the amount of surface charge of the hollow silica particles is within a specific range. The reason for the need to obtain stable dispersibility is that when a coating is formed, it is advantageous for the hollow silica particles to be uniformly present in the cured coating and not localized in order to exert their function. This is because the hollow silica particles are delocalized in the cured coating, so that the entire film has the same effect. When the effect is an optical anti-reflection function, it is preferable in that the entire film maintains uniform performance.

The surface charge amount of hollow silica particles in a dispersion medium is due to the silanol groups on the surface of the silica particles, but it has been found that the surface charge amount can be adjusted to any specific range by adding an amine.
The present invention relates to an organic solvent sol of hollow silica particles containing an amine in the sol and having spaces inside the outer shell, a method for producing the organic solvent sol, and a coating-forming composition using the organic solvent sol.

The present invention is an organic solvent sol of hollow silica particles that contain an amine in the sol and have a space inside the outer shell (hereinafter, also referred to as hollow silica organic solvent sol).

Hollow silica particles have a silica shell and a space inside the shell. Hollow silica particles are obtained by forming a shell mainly composed of silica on the surface of the part corresponding to the core, which is called the template in a dispersion medium, and removing the part corresponding to the core. The aqueous hollow silica sol (hollow silica aqueous sol) obtained in this way can be solvent-substituted with an alcohol solvent, which is an organic solvent, after adding an amine. The above-mentioned alcohol solvent is preferably an alcohol having 1 to 5 carbon atoms that may have an ether bond, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. Thereafter, if desired, the hollow silica particles can be coated with a silane compound, and the solvent can then be further solvent-substituted with another organic solvent.

In the present invention, examples of organic solvents include alcohols, ketones, ethers, and esters having 1 to 10 carbon atoms.

The alcohol having 1 to 10 carbon atoms is an aliphatic alcohol, and examples of such alcohol include primary alcohols, secondary alcohols, and tertiary alcohols. Furthermore, it is also possible to use polyhydric alcohols, such as dihydric alcohols and trihydric alcohols.
Examples of the monohydric primary alcohol include methanol, ethanol, 1-propanol, 1-butanol, and 1-hexanol.
Examples of the monohydric secondary alcohol include 2-propanol, 2-butanol, cyclohexanol, propylene glycol monomethyl ether, and propylene glycol monoethyl ether.
An example of the monohydric tertiary alcohol is tert-butyl alcohol.
Examples of the dihydric alcohol include methanediol, ethylene glycol, and propylene glycol.
An example of the trihydric alcohol is glycerin.

As the ketone having 1 to 10 carbon atoms, an aliphatic ketone can be preferably used. Examples include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, methyl cyclopentanone, etc.

As the ether having 1 to 10 carbon atoms, an aliphatic ether can be preferably used. Examples include dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, 1,4-dioxane, etc.

As the ester having 1 to 10 carbon atoms, an aliphatic ester can be preferably used. Examples include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, dimethyl maleate, diethyl maleate, dipropyl maleate, dimethyl adipate, diethyl adipate, dipropyl adipate, etc.

In the hollow silica aqueous sol and hollow silica organic solvent sol, which are the raw materials, the hollow silica particles can have an average particle size measured by dynamic light scattering (DLS) in the range of 20 to 150 nm, or 30 to 150 nm, or 40 to 150 nm, or 50 to 150 nm, or 60 to 150 nm, or 60 to 120 nm. The concentration of _SiO2 particles can be 1 to 50 mass% or 5 to 40 mass%, typically 10 to 30 mass%.

The sol has an alkaline pH, for example, 7.5 to 12 or 7.5 to 11, but can typically be used in the range of 7.5 to 10. The above pH is the pH when the organic solvent sol and the same mass of pure water are mixed at a ratio of 1:1. It is possible to measure the pH when an organic solvent that can be mixed with water is used as the organic solvent, but when the solvent is subsequently replaced with a hydrophobic organic solvent, it is preferable to measure the pH in advance at the stage of the methanol solvent sol.
For example, for a sol whose dispersion medium is a hydrophilic organic solvent, such as methanol sol or propylene glycol monomethyl ether sol, the pH can be measured using a solution in which pure water and the sol are mixed in a mass ratio of 1: 1. For a sol whose dispersion medium is a hydrophobic organic solvent, such as methyl ethyl ketone sol, the pH can be measured using a solution in which pure water, methanol, and methyl ethyl ketone sol are mixed in a mass ratio of 1: 1: 1.

Hollow silica organic solvent sol can be obtained by replacing the aqueous medium of the aqueous sol with an alcohol solvent having 1 to 5 carbon atoms, and if desired, further replacing the solvent with an organic solvent, and moisture may remain in the solvent during this process. At the stage of the alcohol sol of hollow silica particles, the sol may contain, for example, 0.1 to 3.0% by mass of residual moisture. And at the stage of the organic solvent sol of hollow silica particles, the sol may contain 0.01 to 0.5% by mass of residual moisture.

In addition, the viscosity of hollow silica organic solvent sol can be set in the range of 1.0 to 10.0 mPa·s.

An amine can be added to the hollow silica organic solvent sol of the present invention.
The amine used in the present invention may be a water-soluble amine having a water solubility of 80 g/L or more, or 100 g/L or more.

The raw material hollow silica aqueous sol and the hollow silica organic solvent sol obtained by solvent replacement may contain amine, or amine and ammonia. The amine may be added and contained in the range of 0.001 to 10 mass%, or 0.01 to 10 mass%, or 0.1 to 10 mass% relative to the SiO ₂ of the hollow silica particles. The base component, which is the amine or the amine and ammonia, may be expressed as the total nitrogen amount in the hollow silica particle organic solvent sol, and may be contained in the range of, for example, 10 to 100,000 ppm, or 100 to 10,000 ppm, or 100 to 3,000 ppm, or 100 to 2,000 ppm, typically 200 to 2,000 ppm.

The above amines include aliphatic amines and aromatic amines, with aliphatic amines being preferred. At least one amine selected from the group consisting of primary amines, secondary amines, and tertiary amines having 1 to 10 carbon atoms can be used as the amine. The amines are water-soluble and at least one amine selected from the group consisting of primary amines, secondary amines, and tertiary amines having 1 to 10 carbon atoms.

For example, primary amines include monomethylamine, monoethylamine, monopropylamine, monoisopropylamine, monobutylamine, monoisobutylamine, monosec-butylamine, mono-tert-butylamine, monomethanolamine, monoethanolamine, monopropanolamine, monoisopropanolamine, monobutanolamine, monoisobutanolamine, monosec-butanolamine, mono-tert-butanolamine, etc.

Secondary amines include dimethylamine, diethylamine, dipropylamine, diisopropylamine, N-methylethylamine, N-ethylisobutylamine, dimethanolamine, diethanolamine, dipropanolamine, diisopropanolamine, N-methanolethylamine, N-methylethanolamine, N-ethanolisobutylamine, and N-ethylisobutanolamine.

Tertiary amines include trimethylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, triisobutylamine, trisec-butylamine, tritert-butylamine, trimethanolamine, triethanolamine, tripropanolamine, triisopropanolamine, tributanolamine, triisobutanolamine, trisec-butanolamine, tritert-butanolamine, etc.

As the above amine, amines having a water solubility of 80 g/L or more, or 100 g/L or more can be preferably used. As these amines, primary amines and secondary amines are preferred, and secondary amines are preferably used due to their low volatility and high solubility, such as diisopropylamine and diethanolamine.

In the present invention, by including the above-mentioned amine in the sol, the surface charge amount of the hollow silica particles converted to 1 g of SiO ₂ can be set to 5 μeq/g or more, or 25 μeq/g or more. Typically, it can be set in the range of 5 to 250 μeq/g, or 25 to 250 μeq/g, or 25 to 100 μeq/g, or 25 to 80 μeq/g, or 25 to 50 μeq/g.
In the present invention, the surface charge amount of the hollow silica particles can be adjusted to any desired value by adjusting the type and amount of the amine added.

In the present invention, the surfaces of the hollow silica particles can be coated with a silane compound.
As the silane compound, a hydrolysate of at least one silane compound selected from the group consisting of silane compounds represented by formulas (1) to (3) can be used.
In the above formula (1), R ¹ represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, or a cyano group, and is bonded to a silicon atom via a Si-C bond; R ² represents an alkoxy group, an acyloxy group, or a halogen group; a represents an integer of 1 to 3;
In the above formulas (2) and (3), ^R3 and ^R5 each represent an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms and are bonded to a silicon atom via a Si-C bond; ^R4 and ^R6 each represent an alkoxy group, an acyloxy group, or a halogen group; Y represents an alkylene group, an NH group, or an oxygen atom; b is an integer of 1 to 3; c is an integer of 0 or 1; and d is an integer of 1 to 3.

The alkyl group may be an alkyl group having 1 to 18 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a cyclopropyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, a cyclobutyl group, a 1-methyl-cyclopropyl group, a 2-methyl-cyclopropyl group, an n-pentyl group, a 1-methyl-n-butyl group, a 2-methyl-n-butyl group, a 3-methyl-n-butyl group, a 1,1-dimethyl-n-propyl group, a 1,2-dimethyl-n-propyl group, a 2,2-dimethyl-n-propyl group, a 1-ethyl-n-propyl group, a cyclopentyl group, a 1-methyl-cyclobutyl group, a 2-methyl-cyclobutyl group, a 3- Methyl-cyclobutyl group, 1,2-dimethyl-cyclopropyl group, 2,3-dimethyl-cyclopropyl group, 1-ethyl-cyclopropyl group, 2-ethyl-cyclopropyl group, n-hexyl group, 1-methyl-n-pentyl group, 2-methyl-n-pentyl group, 3-methyl-n-pentyl group, 4-methyl-n-pentyl group, 1,1-dimethyl-n-butyl group, 1,2-dimethyl-n-butyl group, 1,3-dimethyl-n-butyl group, 2,2-dimethyl-n-butyl group, 2,3-dimethyl-n-butyl group, 3,3-dimethyl-n-butyl group, 1-ethyl-n-butyl group, 2-ethyl-n-butyl group, 1,1,2-trimethyl-n-propyl group, 1,2,2- trimethyl-n-propyl group, 1-ethyl-1-methyl-n-propyl group, 1-ethyl-2-methyl-n-propyl group, cyclohexyl group, 1-methyl-cyclopentyl group, 2-methyl-cyclopentyl group, 3-methyl-cyclopentyl group, 1-ethyl-cyclobutyl group, 2-ethyl-cyclobutyl group, 3-ethyl-cyclobutyl group, 1,2-dimethyl-cyclobutyl group, 1,3-dimethyl-cyclobutyl group, 2,2-dimethyl-cyclobutyl group, 2,3-dimethyl-cyclobutyl group, 2,4-dimethyl-cyclobutyl group, 3,3-dimethyl-cyclobutyl group, 1-n-propyl-cyclopropyl group, 2-n-propyl-cyclopropyl group, 1- Examples of the cyclopropyl group include, but are not limited to, i-propyl-cyclopropyl group, 2-i-propyl-cyclopropyl group, 1,2,2-trimethyl-cyclopropyl group, 1,2,3-trimethyl-cyclopropyl group, 2,2,3-trimethyl-cyclopropyl group, 1-ethyl-2-methyl-cyclopropyl group, 2-ethyl-1-methyl-cyclopropyl group, 2-ethyl-2-methyl-cyclopropyl group, and 2-ethyl-3-methyl-cyclopropyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, and octadecyl group.

Alkylene groups include those derived from the alkyl groups mentioned above.

The above aryl group includes aryl groups having 6 to 30 carbon atoms, such as, but not limited to, a phenyl group, a naphthyl group, an anthracene group, and a pyrene group.

The alkenyl group may be an alkenyl group having 2 to 10 carbon atoms, such as an ethenyl group, a 1-propenyl group, a 2-propenyl group, a 1-methyl-1-ethenyl group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-ethylethenyl group, a 1-methyl-1-propenyl group, a 1-methyl-2-propenyl group, a 1-pentenyl group, a 2-pentenyl group, a 3-pentenyl group, a 4-pentenyl group, a 1-n-propylethenyl group, a 1-methyl-1-butenyl group, a 1-methyl-2-butenyl group, a 1-methyl-3-butenyl group, a 2-ethyl-2-propenyl group, a 2-methyl-1-butenyl group, a 2-methyl-2-butenyl group, a 2-methyl-3-butenyl group, Examples of the aryl group include, but are not limited to, 3-methyl-1-butenyl group, 3-methyl-2-butenyl group, 3-methyl-3-butenyl group, 1,1-dimethyl-2-propenyl group, 1-i-propylethenyl group, 1,2-dimethyl-1-propenyl group, 1,2-dimethyl-2-propenyl group, 1-cyclopentenyl group, 2-cyclopentenyl group, 3-cyclopentenyl group, 1-hexenyl group, 2-hexenyl group, 3-hexenyl group, 4-hexenyl group, 5-hexenyl group, 1-methyl-1-pentenyl group, 1-methyl-2-pentenyl group, 1-methyl-3-pentenyl group, 1-methyl-4-pentenyl group, 1-n-butylethenyl group, 2-methyl-1-pentenyl group, and 2-methyl-2-pentenyl group.

The above alkoxy groups include alkoxy groups having 1 to 10 carbon atoms, such as, but not limited to, methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, n-pentyloxy, 1-methyl-n-butoxy, 2-methyl-n-butoxy, 3-methyl-n-butoxy, 1,1-dimethyl-n-propoxy, 1,2-dimethyl-n-propoxy, 2,2-dimethyl-n-propoxy, 1-ethyl-n-propoxy, and n-hexyloxy.

The above acyloxy group includes acyloxy groups having 2 to 10 carbon atoms, such as, but not limited to, methylcarbonyloxy group, ethylcarbonyloxy group, n-propylcarbonyloxy group, i-propylcarbonyloxy group, n-butylcarbonyloxy group, i-butylcarbonyloxy group, s-butylcarbonyloxy group, t-butylcarbonyloxy group, n-pentylcarbonyloxy group, 1-methyl-n-butylcarbonyloxy group, 2-methyl-n-butylcarbonyloxy group, 3-methyl-n-butylcarbonyloxy group, 1,1-dimethyl-n-propylcarbonyloxy group, 1,2-dimethyl-n-propylcarbonyloxy group, 2,2-dimethyl-n-propylcarbonyloxy group, 1-ethyl-n-propylcarbonyloxy group, n-hexylcarbonyloxy group, 1-methyl-n-pentylcarbonyloxy group, 2-methyl-n-pentylcarbonyloxy group, etc.

The above halogen groups include fluorine, chlorine, bromine, iodine, etc.

An example of an organic group having a polyether group is a polyetherpropyl group having an alkoxy group, such as (CH ₃ O) ₃ SiC ₃ H ₆ (OC ₂ H ₄ ) n OCH _3. n can be in the range of 1 to 100 or 1 to 10.

Examples of organic groups having an epoxy group include the 2-(3,4-epoxycyclohexyl)ethyl group and the 3-glycidoxypropyl group.

The above (meth)acryloyl group refers to both acryloyl and methacryloyl groups. Examples of organic groups having a (meth)acryloyl group include a 3-methacryloxypropyl group and a 3-acryloxypropyl group.

An example of an organic group having a mercapto group is the 3-mercaptopropyl group.

Examples of organic groups having an amino group include a 2-aminoethyl group, a 3-aminopropyl group, an N-2-(aminoethyl)-3-aminopropyl group, an N-(1,3-dimethyl-butylidene)aminopropyl group, an N-phenyl-3-aminopropyl group, and an N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl group.

An example of an organic group having a ureido group is the 3-ureidopropyl group.

An example of an organic group having a cyano group is the 3-cyanopropyl group.

The silane compounds represented by the above formulas (2) and (3) are preferably compounds capable of forming trimethylsilyl groups on the surface of silica particles.
Examples of such compounds include the following.
In the above formula, R ¹² represents an alkoxy group, for example, a methoxy group or an ethoxy group. As the silane compound, a silane compound manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

The hydroxyl groups on the surface of the silica particles, for example the silanol groups in the case of silica particles, react with the above-mentioned silane compound, and the surface of the silica particles can be coated with the above-mentioned silane compound through siloxane bonds. The reaction can be carried out at temperatures ranging from 20°C to the boiling point of the dispersion medium, for example, at temperatures ranging from 20°C to 100°C. The reaction can be carried out for about 0.1 to 6 hours.

The surfaces of the hollow silica particles can be coated by adding a silane compound to the silica sol in an amount corresponding to a coating amount of 0.1 silicon atoms/nm ² to 6.0 silicon atoms/nm ² on the silica particle surfaces.

Water is necessary for the hydrolysis of the silane compound, and if the sol is an aqueous solvent, the aqueous solvent is used. When the aqueous medium is replaced with an organic solvent, the water remaining in the solvent can also be used. For example, water present in the organic solvent at 0.01 to 1% by mass can be used. The hydrolysis can be performed with or without a catalyst.
When the reaction is carried out without a catalyst, the surface of the silica particles is on the acidic side. When a catalyst is used, examples of the hydrolysis catalyst include metal chelate compounds, organic acids, inorganic acids, organic bases, and inorganic bases. Examples of the metal chelate compounds as the hydrolysis catalyst include triethoxy mono(acetylacetonato)titanium and triethoxy mono(acetylacetonato)zirconium. Examples of the organic acids as the hydrolysis catalyst include acetic acid and oxalic acid. Examples of the inorganic acids as the hydrolysis catalyst include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. Examples of the organic bases as the hydrolysis catalyst include pyridine, pyrrole, piperazine, and quaternary ammonium salts. Examples of the inorganic bases as the hydrolysis catalyst include ammonia, sodium hydroxide, and potassium hydroxide.

The organic acid may be at least one organic acid selected from the group consisting of divalent aliphatic carboxylic acids, aliphatic oxycarboxylic acids, amino acids, and chelating agents. Divalent aliphatic carboxylic acids include oxalic acid, malonic acid, and succinic acid. Aliphatic oxycarboxylic acids include glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid. Amino acids include glycine, alanine, valine, leucine, serine, and threonine. Chelating agents include ethylenediaminetetraacetic acid, L-aspartic acid-N,N-diacetic acid, and diethylenetriaminepentaacetic acid. Organic acid salts include alkali metal salts, ammonium salts, and amine salts of the above organic acids. Alkali metals include sodium and potassium.

In the present invention, a film-forming composition is obtained that contains the hollow silica organic solvent sol and an organic resin.

A film-forming composition is obtained by selecting and mixing a thermosetting or photocurable resin as the organic resin. A cured product can be obtained by adding a curing agent such as an amine-based curing agent, an acid anhydride-based curing agent, a radical generator-based curing agent (thermal radical generator, photoradical generator), or an acid generator-based curing agent (thermal acid generator, photoacid generator).

The film-forming composition of the present invention contains an organic resin and a curing agent, and the film-forming composition can be applied to or filled into a substrate and then heated, irradiated with light, or a combination thereof to form a cured product. Examples of organic resins (curable resins) include resins having functional groups such as epoxy groups or (meth)acryloyl groups, and isocyanate-based resins. For example, photocurable polyfunctional acrylates can be preferably used.

Examples of the polyfunctional acrylate include polyfunctional acrylates having difunctional, trifunctional, tetrafunctional or higher functional groups in the molecule, such as neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.
These polyfunctional acrylates may also be described below.

The film-forming composition of the present invention may contain a surfactant (leveling agent).
The surfactant (leveling agent) may be an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or a silicone surfactant. The surfactant (leveling agent) may be added in an amount of 0.01 to 5 phr or 0.01 to 1 phr relative to the organic resin.

Anionic surfactants that can be used in the present invention include sodium and potassium salts of fatty acids, alkylbenzene sulfonates, higher alcohol sulfates, polyoxyethylene alkyl ether sulfates, α-sulfofatty acid esters, α-olefin sulfonates, monoalkyl phosphates, and alkanesulfonates.

For example, alkylbenzenesulfonates include sodium salts, potassium salts and lithium salts, such as sodium C10-C16 alkylbenzenesulfonate, C10-C16 alkylbenzenesulfonic acid, and sodium alkylnaphthalenesulfonate.

Examples of higher alcohol sulfate ester salts include sodium dodecyl sulfate (sodium lauryl sulfate) with 12 carbon atoms, triethanolamine lauryl sulfate, and triethanolammonium lauryl sulfate.

Examples of polyoxyethylene alkyl ether sulfates include sodium polyoxyethylene styrenated phenyl ether sulfate, ammonium polyoxyethylene styrenated phenyl ether sulfate, sodium polyoxyethylene decyl ether sulfate, ammonium polyoxyethylene decyl ether sulfate, sodium polyoxyethylene lauryl ether sulfate, ammonium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene tridecyl ether sulfate, and sodium polyoxyethylene oleyl cetyl ether sulfate.

Examples of α-olefin sulfonates include sodium α-olefin sulfonate.

Examples of alkane sulfonates include sodium 2-ethylhexyl sulfate.

Cationic surfactants that can be used in the present invention include, for example, alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, and amine salt agents.

Alkyltrimethylammonium salts are quaternary ammonium salts that have chloride or bromide ions as counterions. Examples include dodecyltrimethylammonium chloride, cetyltrimethylammonium chloride, coconut alkyltrimethylammonium chloride, and alkyl (C16-18) trimethylammonium chloride.

Dialkyldimethylammonium salts have two lipophilic main chains and two methyl groups. Examples include bis(hydrogenated tallow)dimethylammonium chloride, such as didecyldimethylammonium chloride, dicoconucleic acid alkyldimethylammonium chloride, dihydrogenated tallow alkyldimethylammonium chloride, and dialkyl(C14-18)dimethylammonium chloride.

Alkyl dimethyl benzyl ammonium salts are quaternary ammonium salts that have one lipophilic main chain, two methyl groups, and one benzyl group, and examples of these include benzauconium chloride, such as alkyl (C8-18) dimethyl benzyl ammonium chloride.

Amine salt agents include those in which the hydrogen atom of ammonia is replaced with one or more hydrocarbon groups, such as N-methylbishydroxyethylamine fatty acid ester hydrochloride.

The amphoteric surfactants used in the present invention include N-alkyl-β-alanine type alkylamino fatty acid salts, alkylcarboxybetaine type alkylbetaines, and N,N-dimethyldodecylamine oxide type alkylamine oxides. Examples of these include lauryl betaine, stearyl betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, and lauryl dimethylamine oxide.

The nonionic surfactant used in the present invention is selected from polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, alkyl glucosides, polyoxyethylene fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and fatty acid alkanolamides.

For example, examples of polyoxyethylene alkyl ethers include polyoxyethylene dodecyl ether (polyoxyethylene lauryl ether), polyoxyalkylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyalkylene tridecyl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene behenyl ether, polyoxyethylene-2-ethylhexyl ether, and polyoxyethylene isodecyl ether.

Examples of polyoxyethylene alkylphenol ethers include polyoxyethylene styrenated phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene distyrenated phenyl ether, and polyoxyethylene tribenzyl phenyl ether.

Examples of alkyl glucosides include decyl glucoside and lauryl glucoside.

Examples of polyoxyethylene fatty acid esters include polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, polyethylene glycol distearate, polyethylene glycol dioleate, and polypropylene glycol dioleate.

Sorbitan fatty acid esters include sorbitan monocaprylate, sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan monosesquioleate, and ethylene oxide adducts thereof.

Examples of polyoxyethylene sorbitan fatty acid esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan triisostearate.

Fatty acid alkanolamides include coconut oil fatty acid diethanolamide, beef tallow fatty acid diethanolamide, lauric acid diethanolamide, and oleic acid diethanolamide.

Further examples include polyoxyalkyl ethers or polyoxyalkyl glycols such as polyoxyethylene polyoxypropylene glycol, polyoxyethylene fatty acid esters, polyoxyethylene hydrogenated castor oil ether, sorbitan fatty acid ester alkyl ethers, alkyl polyglucosides, sorbitan monooleate, and sucrose fatty acid esters.

The silicone surfactant used in the present invention is a compound having a repeating unit containing a siloxane bond in the main chain. Silicone surfactants having a weight average molecular weight in the range of 500 to 50,000 can be used. These may be modified silicone surfactants, and examples of such surfactants include those having an organic group introduced into the side chain and/or end of a polysiloxane. Examples of organic groups include amino groups, epoxy groups, alicyclic epoxy groups, carbinol groups, mercapto groups, carboxyl groups, aliphatic ester groups, aliphatic amide groups, and polyether groups. Examples of silicone surfactants include the following product names: Toray Silicone DC3PA, Toray Silicone SH7PA, Toray Silicone DC11PA, Toray Silicone SH21PA, Toray Silicone SH28PA, Toray Silicone SH29PA, Toray Silicone SH30PA, Toray Silicone SH8400 (all manufactured by Dow Corning Toray Co., Ltd.), Silwet l-77, L-7280, L-7001, L-7002, L-7200. , L-7210, L-7220, L-7230, L7500, L-7600, L-7602, L-7604, L-7605, L-7622, L-765 7, L-8500, L-8610 (all manufactured by Momentive Performance Materials), KP-341, KF-6001, KF-6002 (all manufactured by Shin-Etsu Silicones Co., Ltd.), BYK307, BYK323, BYK330 (all manufactured by BYK-Chemie), etc. For example, the product name L-7001 (manufactured by Dowsil Corporation) can be suitably used as a polyether modified silicone.

In the present invention, a film-forming composition containing the above organic solvent sol and an organic resin is obtained. The film-forming composition can be obtained by removing the organic solvent from the organic solvent sol to form a film-forming composition containing hollow silica particles and an organic resin.

When the film-forming composition is a thermosetting film-forming composition, the heat curing agent can be contained in the range of 0.01 to 50 phr, or 0.01 to 10 phr, relative to the resin containing a functional group such as an epoxy group or a (meth)acryloyl group. For example, the heat curing agent can be contained in a ratio of 0.5 to 1.5 equivalents, preferably 0.8 to 1.2 equivalents, relative to the functional group such as an epoxy group or a (meth)acryloyl group. The equivalent of the heat curing agent relative to the curable resin is indicated by the equivalent ratio of the heat curing agent to the functional group of the cured resin.

Examples of the heat curing agent include phenol resins, amine-based curing agents, polyamide resins, imidazoles, polymercaptans, acid anhydrides, heat radical generators, heat acid generators, etc. In particular, radical generator-based curing agents, acid anhydride-based curing agents, and amine-based curing agents are preferred.
Even if these thermosetting agents are solid, they can be used by dissolving them in a solvent. However, evaporation of the solvent causes a decrease in density of the cured product, and the formation of pores, resulting in a decrease in strength and a decrease in water resistance. Therefore, it is preferable that the curing agent itself is liquid at room temperature and normal pressure.

Examples of phenolic resins include phenol novolac resin and cresol novolac resin.

Examples of amine-based hardeners include piperidine, N,N-dimethylpiperazine, triethylenediamine, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, 2-(dimethylaminomethyl)phenol, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, N-aminoethylpiperazine, di(1-methyl-2-aminocyclohexyl)methane, menthenediamine, isophoronediamine, diaminodicyclohexylmethane, 1,3-diaminomethylcyclohexane, xylylenediamine, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, 3,3'-diethyl-4,4'-diaminodiphenylmethane, diethyltoluenediamine, etc. Among these, liquids such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, N-aminoethylpiperazine, di(1-methyl-2-aminocyclohexyl)methane, menthenediamine, isophoronediamine, diaminodicyclohexylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, and diethyltoluenediamine can be preferably used.

Polyamide resins include those produced by condensation of dimer acid and polyamine, such as polyamidoamines that have primary and secondary amines in the molecule.

Imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, and epoxy imidazole adduct.

The polymercaptan is preferably liquid, for example, one in which a mercaptan group is present at the end of a polypropylene glycol chain or one in which a mercaptan group is present at the end of a polyethylene glycol chain.

As an acid anhydride hardener, an anhydride of a compound having multiple carboxyl groups in one molecule is preferred. Examples of these acid anhydride hardeners include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol bistrimellitate, glycerol tristrimellitate, maleic anhydride, tetrahydrophthalic anhydride, methyl tetrahydrophthalic anhydride, endomethylene tetrahydrophthalic anhydride, methyl endomethylene tetrahydrophthalic anhydride, methyl butenyl tetrahydrophthalic anhydride, dodecenyl succinic anhydride, hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, succinic anhydride, methylcyclohexene dicarboxylic anhydride, and chlorendic anhydride.

Examples of the thermal acid generator include sulfonium salts and phosphonium salts, with sulfonium salts being preferred. For example, the following compounds can be mentioned.
In formula (C-1), R represents an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 20 carbon atoms, and an alkyl group having 1 to 12 carbon atoms is particularly preferred.

Among these, the following are preferred, which are liquid at room temperature and pressure: methyltetrahydrophthalic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride (methylnadic anhydride, methylhimic anhydride), hydrogenated methylnadic anhydride, methylbutenyltetrahydrophthalic anhydride, dodecenylsuccinic anhydride, methylhexahydrophthalic anhydride, and a mixture of methylhexahydrophthalic anhydride and hexahydrophthalic anhydride. These liquid acid anhydrides have a viscosity of about 10 mPas to 1,000 mPas when measured at 25°C.

Examples of thermal radical generators include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-methylpropionate)dimethyl, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, tert-butyl hydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, and benzoyl peroxide. These can be obtained from Tokyo Chemical Industry Co., Ltd.

When obtaining the cured product, a curing aid may be used in combination as appropriate. Examples of the curing aid include organic phosphorus compounds such as triphenylphosphine and tributylphosphine, quaternary phosphonium salts such as ethyltriphenylphosphonium bromide and methyltriphenylphosphonium diethyl phosphate, and quaternary ammonium salts such as 1,8-diazabicyclo(5,4,0)undecane-7-ene, salts of 1,8-diazabicyclo(5,4,0)undecane-7-ene and octylic acid, zinc octylate, and tetrabutylammonium bromide. These curing aids can be included in a ratio of 0.001 to 0.1 parts by mass per part by mass of the curing agent.

The composition is obtained as a thermosetting varnish by mixing a resin, a curing agent, and optionally a curing aid. The mixing can be carried out in a reaction vessel using a stirring blade or kneader.

Mixing is done by a hot mixing method at a temperature of 60°C to 100°C for 0.5 to 1 hour.

The obtained curable film-forming composition is a thermosetting coating composition, and has an appropriate viscosity for use, for example, as a liquid sealant. The liquid thermosetting film-forming composition can be prepared to any viscosity and can be used as a transparent sealant for LEDs and the like by casting, potting, dispenser, printing, or other methods, allowing partial sealing at any desired location. The liquid thermosetting composition is directly mounted on an LED or the like while still in liquid form using the method described above, and then dried and cured to obtain a cured product.

Thermosetting film-forming composition (thermosetting coating composition) is applied to a substrate and heated at a temperature of 80 to 200°C to obtain a cured product.

When the film-forming composition is a photocurable resin composition, it can contain 0.01 to 50 phr or 0.01 to 10 phr of photocuring agent (photoradical generator, photoacid generator) relative to the resin containing functional groups such as epoxy groups or (meth)acryloyl groups. For example, it can contain 0.5 to 1.5 equivalents, preferably 0.8 to 1.2 equivalents of photocuring agent (photoradical generator, photoacid generator) relative to functional groups such as epoxy groups or (meth)acryloyl groups. The equivalent of photocuring agent relative to the curable resin is indicated by the equivalent ratio of photocuring agent to functional groups of the resin.

The photoradical generator is not particularly limited as long as it generates radicals directly or indirectly when irradiated with light.

Examples of photoradical polymerization initiators as photoradical generators include imidazole compounds, diazo compounds, bisimidazole compounds, N-arylglycine compounds, organic azide compounds, titanocene compounds, aluminate compounds, organic peroxides, N-alkoxypyridinium salt compounds, and thioxanthone compounds. Examples of azide compounds include p-azidobenzaldehyde, p-azidoacetophenone, p-azidobenzoic acid, p-azidobenzalacetophenone, 4,4'-diazidochalcone, 4,4'-diazidodiphenyl sulfide, and 2,6-bis(4'-azidobenzal)-4-methylcyclohexanone. Examples of the diazo compound include 1-diazo-2,5-diethoxy-4-p-tolylmercaptobenzene borofluoride, 1-diazo-4-N,N-dimethylaminobenzene chloride, and 1-diazo-4-N,N-diethylaminobenzene borofluoride. Examples of the bisimidazole compound include 2,2'-bis(o-chlorophenyl)-4,5,4',5'-tetrakis(3,4,5-trimethoxyphenyl)-1,2'-bisimidazole, and 2,2'-bis(o-chlorophenyl)-4,5,4',5'-tetraphenyl-1,2'-bisimidazole. Examples of titanocene compounds include dicyclopentadienyl-titanium-dichloride, dicyclopentadienyl-titanium-bisphenyl, dicyclopentadienyl-titanium-bis(2,3,4,5,6-pentafluorophenyl), dicyclopentadienyl-titanium-bis(2,3,5,6-tetrafluorophenyl), dicyclopentadienyl-titanium-bis(2,4,6-trifluorophenyl), dicyclopentadienyl-titanium-bis(2,6-difluorophenyl), and dicyclopentadienyl. -titanium-bis(2,4-difluorophenyl), bis(methylcyclopentadienyl)-titanium-bis(2,3,4,5,6-pentafluorophenyl), bis(methylcyclopentadienyl)-titanium-bis(2,3,5,6-tetrafluorophenyl), bis(methylcyclopentadienyl)-titanium-bis(2,6-difluorophenyl), and dicyclopentadienyl-titanium-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl).

Further examples of photoradical generators include 1,3-di(tert-butyldioxycarbonyl)benzophenone, 3,3',4,4'-tetrakis(tert-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone, 2-mercaptobenzimidazole, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone.

These photoradical polymerization agents are available, for example, under the trade name Irgacure TPO (component is 2,4,6-trimethylbenzoyldiphenylphosphine oxide) (c1-1-1) manufactured by BASF, under the trade name Omnirad 819 (component is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) (c1-1-2) manufactured by IGM RESINS, and under the trade name Irgacure 184 (component is 1-hydroxycyclohexyl phenyl ketone) (c1-1-3) manufactured by IGM RESINS.

The photoacid generator is not particularly limited as long as it generates acid directly or indirectly when irradiated with light.

Specific examples of photoacid generators include triazine compounds, acetophenone derivative compounds, disulfone compounds, diazomethane compounds, sulfonic acid derivative compounds, onium salts such as iodonium salts, sulfonium salts, phosphonium salts, and selenium salts, metallocene complexes, and iron arene complexes.

The onium salts used as the photoacid generators include iodonium salts such as diphenyliodonium chloride, diphenyliodonium trifluoromethanesulfonate, diphenyliodonium mesylate, diphenyliodonium tosylate, diphenyliodonium bromide, diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluoroantimonate, diphenyliodonium hexafluoroarsenate, bis(p-tert-butylphenyl)iodonium hexafluorophosphate, bis(p-tert-butylphenyl)iodonium mesylate, bis(p-tert-butylphenyl)iodonium tosylate, bis(p-tert-butylphenyl)iodonium trifluoromethanesulfonate, bis(p-tert-butylphenyl)iodonium Examples of iodonium salts include bis(alkylphenyl)iodonium salts such as iodonium tetrafluoroborate, bis(p-tert-butylphenyl)iodonium chloride, bis(p-chlorophenyl)iodonium chloride, bis(p-chlorophenyl)iodonium tetrafluoroborate, and bis(4-t-butylphenyl)iodonium hexafluorophosphate, alkoxycarbonylalkoxy-trialkylaryliodonium salts (e.g., 4-[(1-ethoxycarbonyl-ethoxy)phenyl]-(2,4,6-trimethylphenyl)-iodonium hexafluorophosphate, etc.), and bis(alkoxyaryl)iodonium salts (e.g., bis(alkoxyphenyl)iodonium salts such as (4-methoxyphenyl)phenyliodonium hexafluoroantimonate).

Examples of sulfonium salts include triphenylsulfonium chloride, triphenylsulfonium bromide, tri(p-methoxyphenyl)sulfonium tetrafluoroborate, tri(p-methoxyphenyl)sulfonium hexafluorophosphonate, tri(p-ethoxyphenyl)sulfonium tetrafluoroborate, triphenylsulfonium triflate, triphenylsulfonium hexafluoroantimonate, and triphenylsulfonium hexafluorophosphate; as well as sulfonium salts such as (4-phenylthiophenyl)diphenylsulfonium hexafluoroantimonate, (4-phenylthiophenyl)diphenylsulfonium hexafluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluorophosphate, and (4-methoxyphenyl)diphenylsulfonium hexafluoroantimonate.

Phosphonium salts include triphenylphosphonium chloride, triphenylphosphonium bromide, tri(p-methoxyphenyl)phosphonium tetrafluoroborate, tri(p-methoxyphenyl)phosphonium hexafluorophosphonate, tri(p-ethoxyphenyl)phosphonium tetrafluoroborate, 4-chlorobenzenediazonium hexafluorophosphate, and benzyltriphenylphosphonium hexafluoroantimonate.

Selenium salts such as triphenylselenium hexafluorophosphate, and metallocene complexes such as (η5 or η6-isopropylbenzene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate are examples.

In addition, the following compounds can also be used as the photoacid generator.

As the photoacid generator, _sulfonium salt compounds and iodonium salt compounds are preferred. _Examples of the anion species thereof include _CF3SO3- ^, _C4F9SO3- ^, _C8F17SO3- ^, _{camphorsulfonate} anion, tosylate anion, _BF4- _, ^PF6- ^, _AsF6- ^, and _SbF6- . In particular _, anion species such as hexafluorophosphate ion and _{hexafluoroantimonate} ion, which show strong acidity ^, are preferred.

The film-forming composition of the present invention may contain conventional additives as necessary. Examples of such additives include pigments, colorants, thickeners, sensitizers, defoamers, coatability improvers, lubricants, stabilizers (antioxidants, heat stabilizers, light resistance stabilizers, etc.), plasticizers, dissolution promoters, fillers, antistatic agents, etc. These additives may be used alone or in combination of two or more kinds.

Examples of methods for applying the film-forming composition of the present invention include flow coating, spin coating, spray coating, screen printing, casting, bar coating, curtain coating, roll coating, gravure coating, dipping, and slitting.

In the present invention, the photo-coating composition (film-forming composition) can be applied onto a substrate and cured by exposure to light. It can also be heated before or after exposure to light.

The thickness of the coating can be selected from the range of about 0.01 μm to 10 mm depending on the application of the cured product. For example, when used as a photoresist, it can be about 0.05 to 10 μm (particularly 0.1 to 5 μm), when used as a printed wiring board, it can be about 5 μm to 5 mm (particularly 100 μm to 1 mm), and when used as an optical thin film, it can be about 0.1 to 100 μm (particularly 0.3 to 50 μm).

When obtaining a transparent coating, the coating's visible light transmittance can be made 80% or more, or 90% or more, typically 90 to 96%.

When a photoacid generator is used, the light to which the film-forming composition is irradiated or exposed may be, for example, gamma rays, X-rays, ultraviolet rays, visible light, etc., and is usually visible light or ultraviolet rays, particularly ultraviolet rays. The wavelength of the light is, for example, about 150 to 800 nm, preferably about 150 to 600 nm, more preferably about 200 to 400 nm, particularly about 300 to 400 nm. The amount of light to be irradiated varies depending on the thickness of the coating film, but can be, for example, about 2 to 20,000 mJ/cm ² , preferably about 5 to 5,000 mJ/cm ^2. The light source can be selected according to the type of light to be exposed. For example, in the case of ultraviolet rays, a low-pressure mercury lamp, a high-pressure mercury lamp, an extra-high-pressure mercury lamp, a deuterium lamp, a halogen lamp, a laser beam (helium-cadmium laser, excimer laser, etc.), etc. can be used. Such light irradiation causes the curing reaction of the composition to proceed.

Heating of the coating of the film-forming composition containing a thermal acid generator, or heating of the coating of the film-forming composition containing a photoacid generator, which is performed as necessary before or after light irradiation, is performed, for example, at about 60 to 250°C, preferably 100 to 200°C. The heating time can be selected from the range of 3 seconds or more (for example, about 3 seconds to 5 hours), for example, 5 seconds to 2 hours, preferably about 20 seconds to 30 minutes, and can usually be selected from the range of about 1 minute to 3 hours (for example, about 5 minutes to 2.5 hours).

Furthermore, when forming a pattern or image (e.g., when manufacturing a printed wiring board, etc.), the coating film formed on the substrate may be subjected to pattern exposure. This pattern exposure may be performed by scanning with laser light, or by irradiating light through a photomask. The non-irradiated areas (unexposed areas) generated by such pattern exposure may be developed (or dissolved) with a developer to form a pattern or image.

The developer may be an aqueous alkaline solution or an organic solvent.
Examples of the alkaline aqueous solution include aqueous solutions of alkali metal hydroxides such as potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate; aqueous solutions of quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline; and aqueous solutions of amines such as ethanolamine, propylamine, and ethylenediamine.

The alkaline developer is generally an aqueous solution having a concentration of 10% by mass or less, and preferably has a concentration of 0.1 to 3.0% by mass, etc. The developer may further contain alcohols or surfactants, and the amount of each of these added is preferably 0.05 to 10 parts by mass relative to 100 parts by mass of the developer.
Of these, an aqueous solution of 0.1 to 2.38% by weight of tetramethylammonium hydroxide can be used.

In addition, as the organic solvent for the developer, a general organic solvent can be used, such as acetone, acetonitrile, toluene, dimethylformamide, methanol, ethanol, isopropanol, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, propylene glycol butyl ether acetate, ethyl lactate, cyclohexanone, etc., and one or a mixture of two or more of these can be used. In particular, propylene glycol methyl ether, propylene glycol methyl ether acetate, ethyl lactate, etc. can be preferably used.

In the present invention, an adhesion promoter can be added for the purpose of improving the adhesion between the cured film and the substrate after development. Examples of such adhesion promoters include chlorosilanes such as trimethylchlorosilane, dimethylvinylchlorosilane, methyldiphenylchlorosilane, and chloromethyldimethylchlorosilane, alkoxysilanes such as trimethylmethoxysilane, dimethyldiethoxysilane, methyldimethoxysilane, dimethylvinylethoxysilane, diphenyldimethoxysilane, and phenyltriethoxysilane, silazanes such as hexamethyldisilazane, N,N'-bis(trimethylsilyl)urea, dimethyltrimethylsilylamine, and trimethylsilylimidazole, vinyltrichlorosilane, 3-chloropropyltrimethoxysilane, and the like. Examples of the adhesion promoter include silanes such as silane, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-(N-piperidinyl)propyltrimethoxysilane; heterocyclic compounds such as benzotriazole, benzimidazole, indazole, imidazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, urazole, thiouracil, mercaptoimidazole, and mercaptopyrimidine; and ureas such as 1,1-dimethylurea and 1,3-dimethylurea, or thiourea compounds. The adhesion promoters may be used alone or in combination of two or more. The amount of these adhesion promoters added is usually 18% by mass or less, preferably 0.0008 to 9% by mass, and more preferably 0.04 to 9% by mass, based on the solid content.
In this specification, the solid content refers to the components remaining after removing the solvent from the composition.

The composition of the present invention may contain a sensitizer. Examples of sensitizers that can be used include anthracene, phenothiazene, perylene, thioxanthone, and benzophenone thioxanthone. Examples of sensitizing dyes include thiopyrylium salt dyes, merocyanine dyes, quinoline dyes, styrylquinoline dyes, ketocoumarin dyes, thioxanthene dyes, xanthene dyes, oxonol dyes, cyanine dyes, rhodamine dyes, and pyrylium salt dyes. Anthracene sensitizers are particularly preferred, and when used in combination with a cationic curing catalyst (radiation-sensitive cationic polymerization initiator), they dramatically improve sensitivity and also have a radical polymerization initiation function. In the hybrid type in which the cationic curing system of the present invention and the radical curing system are used in combination, the catalyst species can be simplified. Specific examples of anthracene compounds that are effective include dibutoxyanthracene and dipropoxyanthraquinone. The amount of sensitizer added is 0.01 to 20% by mass, preferably 0.01 to 10% by mass, based on the solid content.

The composition of the present invention can be photocured or thermally cured using a photoradical generator, a thermal radical generator, a photoacid generator, or a thermal acid generator. When a photoacid generator or a thermal acid generator is used, for example, commonly used epoxy curing agents (e.g., amines or acid anhydrides) are not used, or even if they are used, the content of these agents is extremely small, which improves the storage stability of the composition.

The composition has been found to have photocationic polymerization properties. The composition of the present invention has a higher curing speed than conventional liquid epoxy compounds (e.g., alicyclic epoxy compounds having an epoxycyclohexyl ring). Because of the fast curing speed, it is possible to reduce the amount of acid generator added and to use weak acid generators. Since metals can corrode due to acid active species remaining after UV irradiation, reducing the amount of acid generator used is important in preventing metal corrosion. Because the composition of the present invention has a fast curing speed, thick film curing is possible.

Curing by UV irradiation can be applied to materials (equipment) that are sensitive to heat.
The thermosetting and photocuring materials using the film-forming composition of the present invention have characteristics such as fast curing, transparency, and small shrinkage on curing, and can be used for coating and bonding electronic parts, optical parts (anti-reflection coating), and precision mechanical parts. For example, they can be used for bonding mobile phone and camera lenses, optical elements such as light-emitting diodes (LEDs) and semiconductor lasers (LDs), liquid crystal panels, biochips, camera lenses and prisms, magnetic parts of hard disks of personal computers, pickups of CD and DVD players (parts that capture optical information reflected from the disk), speaker cones and coils, motor magnets, circuit boards, electronic parts, and parts inside the engine of automobiles.

The composition of the present invention can be used as a hard coat material for surface protection of automobile bodies, lamps, electrical appliances, building materials, plastics, etc., and can be applied to, for example, automobile and motorcycle bodies, headlight lenses and mirrors, plastic lenses for glasses, mobile phones, game consoles, optical films, ID cards, etc.

The composition of the present invention can be used as an ink material for printing on metals such as aluminum, plastics, etc., and can be used as printing ink for cards such as credit cards and membership cards, switches for electrical appliances and office equipment, keyboards, and ink for inkjet printers for CDs, DVDs, etc.

The composition of the present invention can be used in combination with 3D CAD to harden resins to create complex three-dimensional objects, in photolithography applications such as in the production of industrial product models, and in optical fiber coatings, adhesives, optical waveguides, thick-film resists, etc.

The film-forming composition of the present invention can also be suitably used as an insulating resin for electronic materials such as anti-reflective films, semiconductor sealing materials, adhesives for electronic materials, printed wiring board materials, interlayer insulating film materials, and sealing materials for power modules, as well as an insulating resin for high-voltage equipment such as generator coils, transformer coils, and gas-insulated switchgear.

The organic solvent sol of hollow silica particles of the present invention can be produced by a method including the following steps (A) to (C).
Step (A): preparing a hollow silica aqueous sol;
Step (B): adding at least one amine selected from the group consisting of primary amines, secondary amines, and tertiary amines having a water solubility of 80 g/L or more and having 1 to 10 carbon atoms to the hollow silica aqueous sol of step (A) in an amount of 0.001 to 10% by mass based on the SiO ₂ of the hollow silica;
Step (C): A step of replacing the aqueous medium of the aqueous sol of hollow silica particles obtained in step (B) with an alcohol, ketone, ether, or ester having 1 to 10 carbon atoms.

The hollow silica particles used in step (A) have a silica shell and a space inside the shell. Hollow silica is obtained by forming a shell mainly made of silica on the surface of the part that corresponds to the core, known as the template, in an aqueous dispersion medium, and then removing the part that corresponds to the core. The template can be made from organic matter (e.g., hydrophilic organic resin particles such as polyethylene glycol, polystyrene, polyester, etc.) or inorganic matter (e.g., hydrophilic inorganic compound particles such as calcium carbonate, sodium aluminate, etc.).

In step (B), an amine is added to the hollow silica aqueous sol of step (A). The amine has a water solubility of 80 g/L or more, or 100 g/L or more, and at least one amine selected from primary to tertiary amines having a total carbon atom number of 1 to 10 can be added in a ratio of 0.001 to 10 mass % based on the SiO ₂ of the hollow silica. The amines mentioned above can be used as these amines.

The step (C) is a step of subjecting the aqueous medium of the aqueous sol of hollow silica obtained in the step (B) to solvent replacement with an alcohol, ketone, ether or ester having 1 to 10 carbon atoms.
The aqueous medium of the aqueous sol of hollow silica can be replaced with an organic solvent, and the aqueous medium of the aqueous sol can be replaced with a hydrophilic organic solvent and then with a hydrophobic organic solvent.
That is, the above-mentioned step (C) is a step of solvent-substitution of the aqueous medium of the aqueous sol with an alcohol having 1 to 10 carbon atoms, and then further solvent-substitution of the alcohol solvent with a ketone, ether, or ester having 1 to 10 carbon atoms.

　During or after the completion of the above step (C), a step (D) can be added in which at least one silane compound selected from the group consisting of silane compounds represented by the above formulas (1), (2), and (3) is added and heated.

In other words, after the aqueous medium of the aqueous sol in step (C) is solvent-substituted with an alcohol having 1 to 10 carbon atoms, at least one silane compound selected from the group consisting of silane compounds represented by formulas (1), (2), and (3) is added and heated in step (D), and then the alcohol solvent in step (C) can be solvent-substituted with a ketone, ether, or ester having 1 to 10 carbon atoms.

The heating temperature after adding the silane compound is 40°C or higher, and preferably below the reflux temperature of the solvent used. The heating time can be in the range of 0.1 to 10 hours.

In the present invention, the surface charge of hollow silica particles can be adjusted as desired using the above-mentioned method for producing hollow silica organic solvent sol.

(Analysis Method)
[Measurement of _SiO2 concentration]
The hollow silica sol was placed in a crucible and dried by heating on a hot plate at a temperature about 10° C. higher than the boiling point of the dispersion medium to remove the dispersion medium. The resulting silica gel was then calcined at 1,000° C., and the calcination residue was weighed and calculated.
[Moisture measurement]
The value was determined by Karl Fischer titration.
[Measurement of Viscosity]
The viscosity was measured at 25° C. using a BL type viscometer.
[pH Measurement]
The pH was measured at 25° C. using a pH meter (manufactured by DKK Toa Corporation).
For the methanol sol and propylene glycol monomethyl ether sol, the measurement was performed using a solution in which pure water and the sol were mixed in a mass ratio of 1:1, and for the methyl ethyl ketone sol, the measurement was performed using a solution in which pure water, methanol, and methyl ethyl ketone sol were mixed in a mass ratio of 1:1:1.
[Measurement of total nitrogen content]
Measurements were performed under the following conditions using a total nitrogen trace analyzer (TN-2100V, manufactured by Mitsubishi Chemical Analytech Co., Ltd.).
・Pyrolysis furnace Inlet temperature: 800℃, Outlet temperature: 900℃
Ar (argon) flow rate: 100 mL/min, O ₂ (oxygen) flow rate: 500 mL/min
・Detector (chemiluminescence detector)
Low concentration mode _O3 (ozone) flow rate: 600 mL/min
The measurement sample was prepared by diluting the hollow silica sol to a predetermined volume with methyl ethyl ketone using a measuring flask so that the total nitrogen content was 1 to 10 ppm. 20 μL of the measurement sample was injected into the device to measure the area value, and the total nitrogen content of the measurement sample was calculated from a calibration curve created from the area values of standard samples with total nitrogen contents of 0 ppm, 1 ppm, and 10 ppm that were prepared in advance.
[Measurement of particle size by dynamic light scattering method]
Measurements were made using a dynamic light scattering particle size measuring device (Zetersizer Nano, manufactured by Spectris).
[Measurement of surface charge amount]
The silica was diluted with 10 mL of methanol so that the silica concentration was about 0.5% by mass to prepare a measurement sample. Using a particle charge meter (manufactured by Voith Turbo, product name PCD-06), a titration value was measured until the flow potential of the measurement sample reached zero using an N/1000 DADMAC solution (manufactured by Voith Turbo) as a standard cation titrant. The titration value obtained was divided by the mass of silica contained in the measurement sample to obtain the surface charge (μeq/g) converted per 1 g of SiO ₂ of the hollow silica particles.
[Measurement of specific surface area by BET (nitrogen gas adsorption method)]
The cationic components in the hollow silica sol were removed with an H-type cation exchange resin, and the dried product from which the solvent was removed by heat treatment was pulverized in a mortar and further treated for 2 hours at 250° C. The specific surface area of this dried and pulverized product was measured by a gas adsorption specific surface area measuring device (Monosorb™ MS-22 manufactured by Quantachrome Instruments, Inc.) using a mixed gas of 30% N ₂ (nitrogen) and 70% He (helium) as the carrier gas by the B.E.T. one-point method.
[Measurement of average primary particle size by TEM (transmission electron microscope)]
The particles in the hollow silica sol were photographed using a transmission electron microscope (JEM-F200, manufactured by JEOL Ltd.), and approximately 300 arbitrarily selected particles were binarized using an automatic image processing analyzer (LUZEX' AP, manufactured by Nireco Corporation), and the diameter of the projected area converted into a circle was measured as the average primary particle diameter (HEYWOOD diameter).
[Calculation of specific surface area ratio]
The specific surface area ratio was defined as the value obtained by dividing the BET specific surface area by the specific surface area calculated from the average primary particle diameter measured by TEM, assuming that the particles were truly spherical with a true density of 2.2 g/ ^cm 3 .

Example 1
(Preparation of hollow silica methanol sol (1))
100.22 g of a commercially available hollow silica aqueous sol (Ningbo Dilato Co., Ltd., HKT-D20-225-1, _SiO2 concentration is 20.7 mass%, pH 9.0, dynamic light scattering particle size 88 nm, specific surface area by BET method 107 ^m2 /g, average primary particle size by TEM 82 nm, specific surface area ratio 3.2) was charged into a 500 mL eggplant flask, and 0.04 g of diisopropylamine was added while stirring with a magnetic stirrer, and mixed for 2 hours. Then, 38.09 g of methanol was added while stirring, and mixed for 2 hours. Using a rotary evaporator, water was distilled off while feeding about 3000 mL of methanol under reduced pressure (pressure 150 Torr, bath temperature 80 ° C.) to obtain a hollow silica methanol sol (1).
The obtained hollow silica methanol sol had a _SiO2 concentration of 15.5 mass%, a moisture content of 1.7%, a viscosity of 1.8 mPa sec, a pH of 8.2, a particle size measured by a dynamic light scattering method of 99 nm, a total nitrogen content of 438 ppm, and a surface charge amount calculated per 1 g of _SiO2 of the hollow silica particles of 26 μeq/g.

(Preparation of membrane containing hollow silica methanol sol (1))
18.33 g of dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd., product name KAYARAD DPHA) as a UV curing resin was weighed into a brown bottle, and 5 phr of a UV curing agent (Omnirad 819) and 0.1 phr of a leveling agent (manufactured by Dowsil Corporation, product name L-7001) were added thereto, and the mixture was dissolved in 34.99 g of propylene glycol monomethyl ether to prepare a UV curing resin liquid (concentration: 35% by mass).
1.61g of hollow silica methanol sol (1) ( _SiO2 concentration 15.5 mass%) obtained in Example 1 was weighed into a brown bottle, and propylene glycol monomethyl ether and methanol were added so that the total amount was 5.00g, and the final solvent composition was propylene glycol monomethyl ether/methanol = 6/4 by weight ratio, and 0.71g of the UV curable resin liquid prepared above was added, and then mixed at room temperature for 1h to prepare a hollow silica methanol sol (1)/UV curable resin mixed varnish. The solid content concentration was 10 mass%, and the amount of hollow silica ( _SiO2 ) was 100 phr.
About 2 mL of the obtained hollow silica methanol sol (1) / UV curable resin mixed varnish was dropped onto a glass substrate, and a spin coater (Mikasa Co., Ltd., Opticoat MS-B100) was used to uniformly spread the mixture on the glass substrate under the conditions of 200 rpm x 5 sec, 3 sec increase to 1000 rpm, and 1000 rpm x 30 sec. Then, the mixture was baked on a hot plate at 100 ° C. x 3 min, and irradiated with UV light under the condition of an integrated light amount of 2000 mJ / cm ² to prepare a film formed from a varnish containing hollow silica methanol sol (1). The total light transmittance of the obtained mixture film was measured using a spectroscopic haze meter (Nippon Denshoku Kogyo Co., Ltd., SH7000), and the result was 91.6%. The total light transmittance of the glass substrate was 91.0%, which was a high value compared to the total light transmittance of a film prepared under the same conditions using only UV curable resin, which was 90.7%, and was a highly transparent mixture film.

Example 2
(Preparation of hollow silica methanol sol (2))
100.01 g of a commercially available hollow silica aqueous sol (Ningbo Dilat Co., Ltd., HKT-D20-225-1, _SiO2 concentration 20.7%, pH 9.0, dynamic light scattering particle size 88 nm, BET specific surface area 107 ^m2 /g, TEM average primary particle size 82 nm, specific surface area ratio 3.2) was charged into a 500 mL recovery flask, and hollow silica methanol sol (2) was obtained by the same procedure as in Example 1, except that the amount of diisopropylamine added was changed to 0.10 g and the amount of methanol was changed to 37.98 g.
The obtained hollow silica methanol sol (2) had a _SiO2 concentration of 15.1 mass%, a moisture content of 0.9%, a viscosity of 1.6 mPa sec, a pH of 8.7, a particle size measured by a dynamic light scattering method of 108 nm, a total nitrogen content of 409 ppm, and a surface charge amount calculated per 1 g of _SiO2 of the hollow silica particles of 25 μeq/g.

(Preparation of Hollow Silica Propylene Glycol Monomethyl Ether Sol (1))
42.66g of hollow silica methanol sol (2) ( _SiO2 concentration 18.2 mass%) before concentration adjustment obtained in Example 2 was charged into a 200mL eggplant flask, and 7.36g of propylene glycol monomethyl ether was added. Then, using a rotary evaporator, the bath temperature was 60°C, the pressure was gradually reduced from 150 Torr to 80 Torr, and while feeding 60g of propylene glycol monomethyl ether, methanol was distilled off to obtain hollow silica propylene glycol monomethyl ether sol.
The obtained hollow silica propylene glycol monomethyl ether sol (1) had a _SiO2 concentration of 13.4 mass%, a moisture content of 0.2%, a viscosity of 3.5 mPa·sec, a pH of 8.1, a particle size measured by dynamic light scattering of 103 nm, and a total nitrogen content of 330 ppm.

(Preparation of membrane containing hollow silica methanol sol (2))
A film formed from hollow silica methanol sol (2)/UV curable resin mixed varnish and varnish containing hollow _silica methanol sol (2) was prepared by the same operation as in Example 1, except that 1.66 g of hollow silica methanol sol (2) (SiO2 concentration 15.1 mass%) obtained in Example 2 was used. The total light transmittance of the obtained blended film was 92.8%, and it was a blended film with high transparency.

(Preparation of a film formed from a varnish containing hollow silica propylene glycol monomethyl ether sol (1))
A film formed from hollow silica propylene glycol monomethyl ether sol (1) / _UV curable resin mixed varnish and varnish containing hollow silica propylene glycol monomethyl ether sol (1) was prepared by the same operation as in Example 1, except that 1.86 g of hollow silica propylene glycol monomethyl ether sol (1) (SiO2 concentration 13.4 mass%) obtained in Example 2 was used. The total light transmittance of the obtained blended film was 92.2%, and it was a blended film with high transparency.

Example 3
(Preparation of hollow silica methanol sol (3))
100.15 g of a commercially available hollow silica aqueous sol (Ningbo Dilat Co., Ltd., HKT-D20-225-1, _SiO2 concentration 20.7%, pH 9.0, dynamic light scattering particle size 88 nm, BET specific surface area 107 ^m2 /g, TEM average primary particle size 82 nm, specific surface area ratio 3.2) was charged into a 500 mL recovery flask, and the same procedure as in Example 1 was repeated except that the amount of diisopropylamine added was changed to 0.21 g and the amount of methanol was changed to 38.02 g, to obtain hollow silica methanol sol (3).
The obtained hollow silica methanol sol (3) had a _SiO2 concentration of 15.5 mass%, a moisture content of 1.6%, a viscosity of 1.8 mPa sec, a pH of 8.6, a particle size measured by a dynamic light scattering method of 101 nm, a total nitrogen content of 410 ppm, and a surface charge amount calculated per 1 g of _SiO2 of the hollow silica particles of 25 μeq/g.

(Preparation of hollow silica methyl ethyl ketone sol (1))
50.02 g of the hollow silica methanol sol (3) ( _SiO2 concentration 15.5 mass%) obtained in Example 3 was charged into a 200 mL eggplant flask, and 0.35 g of 3-methacryloxypropyltrimethoxysilane was added as a surface treatment agent. The surface was treated by heating for 5 hours while refluxing under stirring. After that, using a rotary evaporator, the bath temperature was 75°C and the pressure was gradually reduced from 500 Torr to 400 Torr, and 150 mL of methyl ethyl ketone was fed to distill off the methanol, thereby obtaining a hollow silica methyl ethyl ketone sol (1).
The obtained hollow silica methyl ethyl ketone sol (1) had a _SiO2 concentration of 15.5 mass%, a moisture content of 0.1%, a viscosity of 3.1 mPa·sec, a pH of 7.8, a particle size measured by a dynamic light scattering method of 106 nm, and a total nitrogen content of 360 ppm.

(Preparation of membrane containing hollow silica methanol sol (3))
A film formed from hollow silica methanol sol (3)/UV curable resin mixed varnish and varnish containing hollow _silica methanol sol (3) was prepared by the same operation as in Example 1, except that 1.61 g of hollow silica methanol sol (3) (SiO2 concentration 15.5 mass%) obtained in Example 3 was used. The total light transmittance of the obtained blended film was 92.1%, and it was a blended film with high transparency.
(Preparation of membrane containing hollow silica methyl ethyl ketone sol (1))
1.61 g of hollow silica methyl ethyl ketone sol (1) ( _SiO2 concentration 15.5 mass%) obtained in Example 3 was weighed into a brown bottle, and propylene glycol monomethyl ether and methyl ethyl ketone were added so that the total amount was 5.00 g and the final solvent composition was propylene glycol monomethyl ether/methyl ethyl ketone = 6/4 by weight ratio, and 0.71 g of the UV curable resin liquid prepared in Example 1 was added, and the mixture was mixed at room temperature for 1 hour to prepare a hollow silica methyl ethyl ketone sol (1)/UV curable resin mixed varnish. The solid content concentration was 10 mass%, and the amount of hollow silica ( _SiO2 ) was 100 phr.
About 2 mL of the obtained hollow silica methyl ethyl ketone sol (1) / UV curable resin mixed varnish was dropped onto a glass substrate, and a spin coater (Mikasa Co., Ltd., Opticoat MS-B100) was used to uniformly spread the mixture on the glass substrate under the conditions of 200 rpm x 5 sec, 3 sec increase to 1000 rpm, and 1000 rpm x 30 sec. Thereafter, the mixture was baked on a hot plate at 100 ° C. x 3 min, and irradiated with UV light under the condition of an accumulated light amount of 2000 mJ / cm ² to prepare a film formed from a varnish containing hollow silica methyl ethyl ketone sol (1). The total light transmittance of the obtained mixture film was measured using a spectroscopic haze meter (Nippon Denshoku Kogyo Co., Ltd., SH7000), and was 92.8%. The total light transmittance of the glass substrate was 91.0%, which was higher than the total light transmittance of 90.7% of a film prepared under the same conditions using only a UV-curable resin, making this a highly transparent blend film.

Example 4
(Preparation of hollow silica methanol sol (4))
100.05 g of a commercially available hollow silica aqueous sol (Ningbo Dilat Co., Ltd., HKT-D20-225-1, _SiO2 concentration 20.7%, pH 9.0, dynamic light scattering particle size 88 nm, BET specific surface area 107 ^m2 /g, TEM average primary particle size 82 nm, specific surface area ratio 3.2) was charged into a 500 mL recovery flask, and hollow silica methanol sol (4) was obtained by the same procedure as in Example 1, except that the amount of diisopropylamine added was changed to 0.50 g and the amount of methanol was changed to 38.06 g.
The obtained hollow silica methanol sol (4) had a _SiO2 concentration of 15.5 mass%, a moisture content of 1.2%, a viscosity of 1.7 mPa sec, a pH of 8.9, a particle size measured by a dynamic light scattering method of 99 nm, a total nitrogen content of 458 ppm, and a surface charge amount calculated per 1 g of _SiO2 of the hollow silica particles of 30 μeq/g.

(Preparation of hollow silica methyl ethyl ketone sol (2))
50.03 g of the hollow silica methanol sol (4) ( _SiO2 concentration 15.5%) obtained in Example 4 was charged into a 200 mL eggplant flask, and the amount of 3-methacryloxypropyltrimethoxysilane added as a surface treatment agent was changed to 0.35 g. Except for this, the same operation as in Example 3 was performed to obtain a hollow silica methyl ethyl ketone sol (2).
The obtained hollow silica methyl ethyl ketone sol (2) had a _SiO2 concentration of 15.6 mass%, a moisture content of 0.2%, a viscosity of 3.3 mPa·sec, a pH of 8.3, a particle size measured by dynamic light scattering of 102 nm, and a total nitrogen content of 387 ppm.

(Preparation of membrane containing hollow silica methanol sol (4))
A film formed from hollow silica methanol sol (4)/UV curable resin mixed varnish and varnish containing hollow _silica methanol sol (4) was prepared by the same operation as in Example 1, except that 1.61 g of hollow silica methanol sol (4) (SiO2 concentration 15.5 mass%) obtained in Example 4 was used. The total light transmittance of the obtained blended film was 92.4%, and it was a blended film with high transparency.
(Preparation of membrane containing hollow silica methyl ethyl ketone sol (2))
A film formed from a hollow silica methyl ethyl ketone sol (2)/UV curable resin mixed varnish _and a varnish containing hollow silica methyl ethyl ketone sol (2) was prepared by the same operation as in Example 3, except that 1.61 g of hollow silica methyl ethyl ketone sol (2) (SiO2 concentration 15.6 mass%) obtained in Example 4 was used. The total light transmittance of the obtained blended film was 92.3%, and it was a blended film with high transparency.

Example 5
(Preparation of hollow silica methanol sol (5))
100.15 g of a commercially available hollow silica aqueous sol (Ningbo Dilato Co., Ltd., HKT-D20-225-1, _SiO2 concentration 20.7% by mass, pH 9.0, dynamic light scattering particle size 88 nm, BET specific surface area 107 ^m2 /g, TEM average primary particle size 82 nm, specific surface area ratio 3.2) was charged into a 500 mL recovery flask, and the same procedure as in Example 1 was repeated except that the amount of diisopropylamine added was changed to 1.00 g and the amount of methanol was changed to 38.07 g, to obtain hollow silica methanol sol (5).
The obtained hollow silica methanol sol (5) had a _SiO2 concentration of 15.5 mass%, a moisture content of 0.8%, a viscosity of 1.6 mPa sec, a pH of 8.5, a particle size measured by a dynamic light scattering method of 98 nm, a total nitrogen content of 414 ppm, and a surface charge amount calculated per 1 g of _SiO2 of the hollow silica particles of 27 μeq/g.

(Preparation of hollow silica methyl ethyl ketone sol (3))
50.05 g of the hollow silica methanol sol (5) ( _SiO2 concentration 15.5 mass%) obtained in Example 5 was charged into a 200 mL eggplant flask, and the amount of 3-methacryloxypropyltrimethoxysilane added as a surface treatment agent was changed to 0.35 g. Except for this, the same operation as in Example 3 was performed to obtain a hollow silica methyl ethyl ketone sol (3).
The obtained hollow silica methyl ethyl ketone sol (3) had a _SiO2 concentration of 15.5 mass%, a moisture content of 0.0%, a viscosity of 2.7 mPa·sec, a pH of 7.9, a particle size measured by a dynamic light scattering method of 103 nm, and a total nitrogen content of 359 ppm.

(Preparation of membrane containing hollow silica methanol sol (5))
A film formed from hollow silica methanol sol (5)/UV curable resin mixed varnish and varnish containing hollow _silica methanol sol (5) was prepared by the same operation as in Example 1, except that 1.61 g of hollow silica methanol sol (5) (SiO2 concentration 15.5 mass%) obtained in Example 5 was used. The total light transmittance of the obtained blended film was 92.7%, and it was a blended film with high transparency.

(Preparation of membrane containing hollow silica methyl ethyl ketone sol (3))
A film formed from a hollow silica methyl ethyl ketone sol (3)/UV curable resin mixed varnish _and a varnish containing hollow silica methyl ethyl ketone sol (3) was prepared by the same operation as in Example 3, except that 1.61 g of hollow silica methyl ethyl ketone sol (3) (SiO2 concentration 15.5 mass%) obtained in Example 5 was used. The total light transmittance of the obtained blended film was 92.8%, and it was a blended film with high transparency.

Example 6
(Preparation of hollow silica methanol sol (6))
Commercially available hollow silica aqueous sol (Ningbo Dilat Co., Ltd., HKT-D20-225-1, _SiO2 concentration 20.7%, pH 9.0, dynamic light scattering particle size 88 nm, specific surface area 107 ^m2 /g by BET method, average primary particle size 82 nm by TEM, specific surface area ratio 3.2) 100.06 g was charged into a 500 mL eggplant flask, and 1.41 g of 28% ammonia water was added while stirring the sol with a magnetic stirrer sol, and mixed for 2 hours. Then, 0.04 g of diisopropylamine was added while stirring, and mixed for 2 hours, and 38.01 g of methanol was added while stirring, and mixed for 2 hours. Using a rotary evaporator, water was distilled off while feeding about 3000 mL of methanol under reduced pressure (pressure 150 Torr, bath temperature 80 ° C.) to obtain a hollow silica methanol sol (6).
The obtained hollow silica methanol sol (6) had a _SiO2 concentration of 15.7 mass%, a moisture content of 1.1%, a viscosity of 1.7 mPa sec, a pH of 9.0, a particle size measured by a dynamic light scattering method of 99 nm, a total nitrogen content of 553 ppm, and a surface charge amount calculated per 1 g of _SiO2 of the hollow silica particles of 30 μeq/g.

(Preparation of hollow silica methyl ethyl ketone sol (4))
50.00 g of the hollow silica methanol sol (6) ( _SiO2 concentration 15.7 mass%) obtained in Example 6 was charged into a 200 mL eggplant flask, and the amount of 3-methacryloxypropyltrimethoxysilane added as a surface treatment agent was changed to 0.35 g. Except for this, the same operation as in Example 3 was performed to obtain a hollow silica methyl ethyl ketone sol (4).
The obtained hollow silica methyl ethyl ketone sol (4) had a _SiO2 concentration of 15.6 mass%, a moisture content of 0.3%, a viscosity of 4.2 mPa·sec, a pH of 8.5, a particle size measured by a dynamic light scattering method of 103 nm, and a total nitrogen content of 436 ppm.

(Preparation of membrane containing hollow silica methanol sol (6))
A film formed from hollow silica methanol sol (6)/UV curable resin mixed varnish and varnish containing hollow _silica methanol sol (6) was prepared by the same operation as in Example 1, except that 1.59 g of hollow silica methanol sol (6) (SiO2 concentration 15.7 mass%) obtained in Example 6 was used. The total light transmittance of the obtained blended film was 92.7%, and it was a blended film with high transparency.
(Preparation of membrane containing hollow silica methyl ethyl ketone sol (4))
A film formed from a hollow silica methyl ethyl ketone sol (4)/UV curable resin mixed varnish _and a varnish containing hollow silica methyl ethyl ketone sol (4) was prepared by the same operation as in Example 3, except that 1.61 g of hollow silica methyl ethyl ketone sol (4) (SiO2 concentration 15.6 mass%) obtained in Example 6 was used. The total light transmittance of the obtained blended film was 92.1%, and it was a blended film with high transparency.

(Example 7)
(Preparation of hollow silica methanol sol (7))
105.47 g of a commercially available hollow silica aqueous sol (Ningbo Dilat Co., Ltd., HKT-D20-225-1, _SiO2 concentration 20.7% by mass, pH 9.0, dynamic light scattering particle size 88 nm, BET specific surface area 107 ^m2 /g, TEM average primary particle size 82 nm, specific surface area ratio 3.2) was charged into a 500 mL eggplant flask, and hollow silica methanol sol (7) was obtained by the same procedure as in Example 1, except that the amount of 28% ammonia water added was changed to 3.77 g, the amount of diisopropylamine to 0.05 g, and the amount of methanol to 40.07 g.
The obtained hollow silica methanol sol (7) had a _SiO2 concentration of 15.5 mass%, a moisture content of 1.1%, a viscosity of 1.4 mPa sec, a pH of 9.3, a particle size measured by a dynamic light scattering method of 101 nm, a total nitrogen content of 1346 ppm, and a surface charge amount calculated per 1 g of _SiO2 of the hollow silica particles of 36 μeq/g.

(Preparation of hollow silica methyl ethyl ketone sol (5))
50.02 g of the hollow silica methanol sol (7) ( _SiO2 concentration 15.5 mass%) obtained in Example 7 was charged into a 200 mL eggplant flask, and the amount of 3-methacryloxypropyltrimethoxysilane added as a surface treatment agent was changed to 0.35 g. Except for this, the same operation as in Example 3 was performed to obtain a hollow silica methyl ethyl ketone sol (5).
The obtained hollow silica methyl ethyl ketone sol (5) had a _SiO2 concentration of 15.5 mass%, a moisture content of 0.1%, a viscosity of 2.8 mPa·sec, a pH of 8.4, a particle size measured by dynamic light scattering of 102 nm, and a total nitrogen content of 1043 ppm.

(Preparation of membrane containing hollow silica methanol sol (7))
A film formed from hollow silica methanol sol (7)/UV curable resin mixed varnish and varnish containing hollow _silica methanol sol (7) was prepared by the same operation as in Example 1, except that 1.61 g of hollow silica methanol sol (7) (SiO2 concentration 15.5 mass%) obtained in Example 7 was used. The total light transmittance of the obtained blended film was 92.7%, and it was a blended film with high transparency.

(Preparation of membrane containing hollow silica methyl ethyl ketone sol (5))
A film formed from a hollow silica methyl ethyl ketone sol (5)/UV curable resin mixed varnish and a varnish containing hollow silica methyl ethyl ketone sol (5) was prepared by the same operation as in Example 3, except that _1.61 g of hollow silica methyl ethyl ketone sol (5) (SiO2 concentration 15.5 mass%) obtained in Example 7 was used. The total light transmittance of the obtained blended film was 92.4%, and it was a blended film with high transparency.

(Example 8)
(Preparation of hollow silica methanol sol (8))
Commercially available hollow silica aqueous sol (Ningbo Dilato, HKT-A20-40D, _SiO2 concentration 20.0%, pH 9.3, dynamic light scattering particle size 55 nm, specific surface area 116 ^m2 /g by BET method, average primary particle size 43 nm by TEM, specific surface area ratio 1.8) 551.10 g was charged into a 2000 mL eggplant flask, and 0.55 g of diethanolamine was added while stirring with a magnetic stirrer, and mixed for 2 h. Then, 139.76 g of methanol was added while stirring, and mixed for 2 h. Using a rotary evaporator, water was distilled off while feeding about 12,000 mL of methanol under reduced pressure (pressure 580 Torr, bath temperature 120 ° C.) to obtain a hollow silica methanol sol (8).
The obtained hollow silica methanol sol (8) had a _SiO2 concentration of 23.5%, a moisture content of 0.6%, a viscosity of 2.8 mPa sec, a pH of 9.0, a particle size measured by a dynamic light scattering method of 63 nm, a total nitrogen content of 641 ppm, and a surface charge amount calculated per 1 g of _SiO2 of the hollow silica particles of 34 μeq/g.

(Preparation of hollow silica methyl ethyl ketone sol (6))
25.00 g of the raw material methanol sol obtained in Example 8, in which the SiO ₂ concentration of the hollow silica methanol sol (8) was adjusted to 20.5% by mass, was charged into a 300 mL eggplant flask, 8.20 g of methanol and 0.26 g of pure water were added, and the mixture was stirred with a magnetic stirrer. 0.25 g of γ-methacryloxypropyltrimethoxysilane was added as a surface treatment agent, and the mixture was heated under reflux for 5 hours to perform surface treatment. After that, using a rotary evaporator, the pressure was gradually reduced from 500 Torr to 400 Torr at a bath temperature of 75° C., and about 80 mL of methyl ethyl ketone was fed while distilling off the methanol to obtain a hollow silica methyl ethyl ketone sol (6).
The obtained hollow silica methyl ethyl ketone sol (6) had a _SiO2 concentration of 22.4%, a moisture content of 0.4%, a pH of 9.3, and a particle size measured by a dynamic light scattering method of 66 nm.

(Comparative Example 1) Preparation of amine-free hollow silica methanol sol Commercially available hollow silica aqueous sol (Ningbo Dilat Co., Ltd., HKT-D20-225-1, _SiO2 concentration 20.7%, pH 9.0, dynamic light scattering particle size 88 nm) 100.04 g was charged into a 500 mL eggplant flask, and 38.02 g of methanol was further added. Using a rotary evaporator, an attempt was made to prepare a hollow silica methanol sol by distilling off water while feeding about 3000 mL of methanol under reduced pressure (pressure 150 Torr, bath temperature 80 ° C.), but thickening and gelation occurred during the replacement with methanol, and the desired hollow silica methanol sol was not obtained.

In Tables 1 and 2, (hollow silica methanol sol) indicates a sol in which hollow silica particles are dispersed in methanol. MeOH in the (dispersion medium) column indicates methanol. (pH) indicates the pH when hollow silica methanol sol and the same mass of pure water are mixed at 1:1. (Amine amount) indicates the addition ratio (mass%) of hollow silica particles to SiO ₂ , and was contained in the hollow silica methanol sol according to the addition ratio. (DLS) indicates the average particle size (nm) of hollow silica particles by dynamic light scattering method. (Total nitrogen amount) indicates the total nitrogen amount (ppm) in the hollow silica particle sol of the base component consisting of amine or amine and ammonia. (Surface charge amount) indicates the surface charge amount (μeq/g) converted per 1 g of SiO ₂ of the hollow silica particles. Note that gelation indicates that the hollow silica sol has gelled and the physical property value cannot be measured.

In Table 3 above, (hollow silica organic solvent sol) indicates a sol in which hollow silica particles are dispersed in an organic solvent. In the (dispersion medium) column, PGME indicates propylene glycol monomethyl ether, and MEK indicates methyl ethyl ketone. (pH) indicates the pH value measured in a solution in which pure water and the sol were mixed at a mass ratio of 1:1 for the propylene glycol monomethyl ether sol, and the pH value measured in a solution in which pure water, methanol, and methyl ethyl ketone sol were mixed at a mass ratio of 1:1:1 for the methyl ethyl ketone sol. In the (surface treatment) column, "none" indicates that the surface of the silica particles was not treated with a silane coupling agent, and MPS indicates that the surface of the silica particles was treated with 3-methacryloxypropyltrimethoxysilane. (DLS) indicates the average particle size (nm) of the hollow silica particles measured by dynamic light scattering. (Total nitrogen content) indicates the total nitrogen content (ppm) of the base component consisting of amine or amine and ammonia in the hollow silica particle sol.

In Tables 4 and 5, (film containing hollow silica methanol sol) indicates a film formed by coating a substrate with a resin composition in which a sol of hollow silica particles dispersed in methanol is blended with a UV-curable resin and then photocuring the film. The (UV-curable resin) column indicates the polyfunctional acrylate used, with DPHA indicating KAYARAD DPHA (polyfunctional acrylate: component dipentaerythritol hexaacrylate), manufactured by Nippon Kayaku Co., Ltd. (blended amount) indicates the blended amount (phr) of hollow silica particles relative to the UV-curable resin. (Total light transmittance) indicates the total light transmittance (%) of the resulting coating.

In Tables 6 and 7, (film containing hollow silica organic solvent sol) shows a film formed by coating a substrate with a resin composition in which a sol of hollow silica particles dispersed in an organic solvent is blended with a UV-curable resin, and then photocuring the film. The (UV-curable resin) column shows the polyfunctional acrylate used, with DPHA being Nippon Kayaku Co., Ltd.'s product name KAYARAD DPHA (polyfunctional acrylate: component dipentaerythritol hexaacrylate). (Amount blended) shows the amount (phr) of hollow silica particles blended with the UV-curable resin. (Total light transmittance) shows the total light transmittance (%) of the resulting coating.

The above evaluation results show that when the aqueous medium was replaced with methanol without adding a water-soluble amine to the hollow silica aqueous sol, thickening and gelation occurred during the solvent replacement process, and the desired hollow silica methanol sol could not be obtained. In contrast, when a predetermined amount of diisopropylamine was added as a water-soluble amine to the hollow silica aqueous sol to replace the solvent, thickening and gelation were avoided, and it was confirmed that it was possible to obtain the desired hollow silica methanol sol and control the sol to a sol of hollow silica particles with a surface charge amount of a certain value or more. In addition, it was confirmed that the blended film prepared by blending the obtained hollow silica methanol sol with resin had excellent dispersion uniformity of the hollow silica particles in the resin, and therefore had high transparency (total light transmittance). Furthermore, it was confirmed that the solvent replacement with other organic solvents such as propylene glycol monomethyl ether and methyl ethyl ketone is possible by using the obtained hollow silica methanol sol as a raw material.

The present invention provides hollow silica particles that have a specific surface charge and are highly dispersible in resins, and provides an organic solvent sol of hollow silica particles that contain an amine in the sol and have a space inside the outer shell, a method for producing the same, and a coating-forming composition.

Claims

An organic solvent sol of hollow silica particles with spaces inside the shell, containing amine in the sol.
The sol according to claim 1, wherein the amine is at least one amine selected from the group consisting of primary amines, secondary amines, and tertiary amines having 1 to 10 carbon atoms.
The sol according to claim 1 or 2, wherein the amine is a water-soluble amine having a water solubility of 80 g/L or more.
The sol according to any one of claims 1 to 3, wherein the content of the amine is 0.001 to 10 mass% relative to the SiO2 of the hollow silica particles.
The sol according to any one of claims 1 to 4, wherein the average particle size of the hollow silica particles measured by dynamic light scattering is 20 to 150 nm.
The sol according to any one of claims 1 to 5, wherein the surface charge amount of the hollow silica particles calculated per 1 g of SiO2 is 5 to 250 μeq/g.
The sol according to any one of claims 1 to 6, wherein the organic solvent is an alcohol, ketone, ether, or ester having 1 to 10 carbon atoms.
The hollow silica particles may further comprise a compound represented by formula (1), formula (2), or formula (3):
(In formula (1), R 1 represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, or a cyano group, and is bonded to a silicon atom via a Si-C bond; R 2 represents an alkoxy group, an acyloxy group, or a halogen group; a represents an integer of 1 to 3;
In formula (2) and formula (3), R3 and R5 each represent an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms and bonded to a silicon atom via a Si-C bond, R4 and R6 each represent an alkoxy group, an acyloxy group, or a halogen group, Y represents an alkylene group, an NH group, or an oxygen atom, b is an integer of 1 to 3, c is an integer of 0 or 1, and d is an integer of 1 to 3.
The sol according to any one of claims 1 to 7, which is coated with at least one silane compound selected from the group consisting of silane compounds represented by the following formula:
A film-forming composition comprising the sol according to any one of claims 1 to 8 and an organic resin.
A film obtained from the film-forming composition according to claim 9, which has a visible light transmittance of 80% or more.
The following steps (A) to (C):
Step (A): preparing a hollow silica aqueous sol;
Step (B): adding at least one amine selected from the group consisting of primary amines, secondary amines, and tertiary amines having a water solubility of 80 g/L or more and having 1 to 10 carbon atoms to the hollow silica aqueous sol of step (A) in an amount of 0.001 to 10% by mass based on the SiO2 of the hollow silica particles;
9. The method for producing a sol according to any one of claims 1 to 8, further comprising: step (C): a step of subjecting the aqueous medium of the aqueous sol of hollow silica particles obtained in step (B) to solvent replacement with an alcohol, a ketone, an ether, or an ester having 1 to 10 carbon atoms.
The method for producing a sol according to claim 11 further comprises a step (D) of adding at least one silane compound selected from the group consisting of formulas (1), (2), and (3) and heating after completion of the step (C).
The method for producing a sol according to claim 11 or 12, wherein the step (C) is a step of replacing the solvent in the aqueous medium with an alcohol having 1 to 10 carbon atoms, and then replacing the solvent with a ketone, ether, or ester having 1 to 10 carbon atoms.
The method for producing a sol according to claim 12, wherein the step (C) is a step of replacing the aqueous medium with an alcohol having 1 to 10 carbon atoms, and the step (D) is a step of adding at least one silane compound selected from the group consisting of silane compounds represented by the above formulas (1), (2), and (3), heating, and then replacing the alcohol solvent with a ketone, ether, or ester having 1 to 10 carbon atoms.
A method for adjusting the surface charge of hollow silica particles, which comprises using the method for producing hollow silica particles according to any one of claims 11 to 14.