JP2013001840A - Coating material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material composition, capable of forming a coating film having low refractive index, low reflectance and high strength, a method for producing the same, and a coating film or antireflection film formed using the coating material composition.SOLUTION: The coating material composition includes a matrix forming material and mesoporous silica particles, each of the mesoporous silica particles including a shell region having a mesopore structure including silica and a hollow region surrounded by the shell region. The average primary particle size of the mesoporous silica particles is 10-200 nm. The defect rate of the mesoporous silica particles is 20% or less, the defect rate being calculated by the following equation based on an image picked up by a scanning electron microscope. Defect rate=(the number of mesoporous silica particles with defects in the shell region of mesoporous silica particles subjected to defect confirmation)/(the number of mesoporous silica particles subjected to defect confirmation)×100.

Description

  The present invention relates to a coating composition, a coating film, an antireflection film, and a method for producing them.

  Antireflection films are widely used for flat panel displays, optical lenses, optical filters, automotive glass and the like. In order to exhibit excellent antireflection performance, it is important to lower the refractive index of the film. In order to reduce the refractive index of the film, a method is known in which air, which is a substance having the lowest refractive index, is contained inside the film, that is, the porosity of the film is increased.

  As a method for increasing the porosity of the membrane and reducing the refractive index, a method of incorporating porous silica particles into the membrane is known. For example, Patent Document 1 discloses a coating composition and a coating film containing hollow silica particles as porous silica particles.

JP 2009-203285 A

  However, in the prior art disclosed in Patent Document 1, there is a limit to increasing the porosity of the hollow silica particles, that is, reducing the refractive index of the coating film, from the viewpoint of maintaining the strength of the hollow silica particles, that is, the strength of the coating film. . Therefore, the refractive index and reflectance of the coating film formed using the coating composition containing the hollow silica particles disclosed in Patent Document 1 are not sufficiently low.

  The present invention relates to a coating composition which can form a coating film having a low refractive index, a low reflectance, and a high strength, a method for producing the same, and a coating film or an antireflection film formed using the coating composition. provide.

The coating composition of the present invention includes a matrix-forming material and mesoporous silica particles, and the mesoporous silica particles include an outer shell portion having a mesoporous structure containing silica and a hollow portion surrounded by the outer shell portion. In addition, the average primary particle diameter is 10 to 200 nm, and the defect rate of mesoporous silica particles calculated by the following (formula 1) based on an image obtained by photographing with a scanning electron microscope is 20% or less.
(Formula 1)
Defect rate = (number of mesoporous silica particles having defects in the outer shell portion among mesoporous silica particles confirmed to have defects) / (number of mesoporous silica particles confirmed to have defects) × 100

In addition, the coating composition of the present invention,
A matrix forming material;
A silica source is added to an emulsion containing emulsion droplets containing the hydrophobic organic compound obtained by pressurizing a mixed solution containing a hydrophobic organic compound, a surfactant and an aqueous solvent by a high-pressure emulsification method. And after forming a composite silica particle comprising an outer shell having a mesoporous structure containing silica and the hydrophobic organic compound present in a hollow portion surrounded by the outer shell, from the composite silica particle, A mesoporous silica particle obtained by removing the surfactant and the hydrophobic organic compound,
The addition amount of the silica source to said emulsion, relative to the hydrophobic organic compound 100 parts by mass, or 80 to 1000 parts by weight of SiO ₂ mass conversion.

The method for producing the coating composition of the present invention comprises:
A liquid mixture containing a hydrophobic organic compound, a surfactant, and an aqueous solvent is pressurized by a high-pressure emulsification method to form an emulsion containing emulsion droplets containing the hydrophobic organic compound, and then the emulsion is added to the emulsion. Adding a silica source to form composite silica particles including an outer shell portion containing silica and having a mesoporous structure and the hydrophobic organic compound existing in a hollow portion surrounded by the outer shell portion (I )When,
Removing the surfactant and the hydrophobic organic compound from the composite silica particles to obtain mesoporous silica particles (II);
Mixing the mesoporous silica particles and the matrix-forming material,
In the step (I), the amount of silica source added to the emulsion is 80 to 1000 parts by mass in terms of SiO _{2 with} respect to 100 parts by mass of the hydrophobic organic compound.

  The coating film of this invention is produced using the coating composition of this invention.

  The antireflection film of the present invention includes the coating film of the present invention.

  The present invention can provide a coating composition capable of forming a coating film having a low refractive index, a low reflectance, and a high strength, and a coating film or an antireflection film formed using the coating composition.

FIG. 1 is a transmission electron microscope image (TEM photograph) of hollow mesoporous silica particles obtained in <Production Example 1>. FIG. 2 is a scanning electron microscope image (SEM photograph) of the hollow mesoporous silica particles obtained in <Production Example 1>. FIG. 3 is a TEM photograph of the hollow mesoporous silica particles obtained in <Production Example 4>. FIG. 4 is an SEM photograph of hollow mesoporous silica particles obtained in <Production Example 4>.

  In the present application, the “mesopore structure” is a structure having a pore diameter of 1 to 10 nm and having a plurality of regularly arranged pores. The pore penetrates the outer shell portion so that the outside of the particle communicates with the hollow portion. The mesoporous structure is formed by the self-organization of silica, which occurs, for example, by mixing a cationic surfactant and a silica source.

  In the present application, “mesoporous silica particles” are particles including an outer shell portion of a mesoporous structure and a hollow portion existing inside the outer shell portion, and “hollow mesoporous silica particles” are mesoporous particles. It is a particle that includes an outer shell portion having a structure and a hollow portion existing inside the outer shell portion, and a gas such as air is filled in the hollow portion and pores.

  In the present application, the “defect rate” is a value calculated by the above (formula 1) based on an image obtained by photographing with a scanning electron microscope, and is a defect among arbitrary mesoporous silica particles in the coating composition. Is the number ratio of mesoporous silica particles observed. The mesoporous silica particles in which the outside of the particle communicates with the hollow part at a place other than the pores by the defect of the outer shell part reaching the hollow part is counted as “mesoporous silica particle having a defect in the outer shell part”. Examples of the defect form include cracks, holes, partial defects in other outer shell portions, or combinations thereof. The diameter of the pore is larger than the diameter of the pore diameter constituting the mesopore structure, for example, exceeding 10 nm.

  If the mesoporous silica particles are defective, the matrix forming material penetrates into the hollow portion, so that the volume of the hollow portion is reduced. That is, the porosity in the hollow part of the mesoporous silica particles in the coating composition is smaller than the porosity obtained by the measurement method described in the examples. Therefore, the defect of the mesoporous silica particles hinders the reduction of the refractive index and the reflectance. In addition, since the matrix forming material that has entered the hollow portion does not contribute to the bonding of the hollow mesoporous silica particles, the defect of the mesoporous silica particles also causes a decrease in the strength of the coating film. Further, since the mesoporous silica particles have a mesoporous structure in the outer shell portion, even if the outer shell portion is thicker than the hollow silica particles disclosed in Patent Document 1, an equivalent porosity is obtained. Can have. Therefore, the mesoporous silica particles are easier to maintain strength in increasing the porosity than the hollow silica particles disclosed in Patent Document 1.

  Therefore, the present inventors replaced the hollow silica particles disclosed in Patent Document 1 with a coating composition, the outer shell portion has a mesoporous structure, and the average primary particle diameter is 10 to 200 nm. By including mesoporous silica particles having a defect rate of 20% or less, the outer shell portion has a mesoporous structure, thereby improving the strength of the particles, increasing the porosity of the outer shell portion, and entering the hollow portion. A coating film such as an antireflection film having a low refractive index, a low reflectance, and a high strength is combined with a decrease in the amount of penetration of the matrix forming material and a suppression of a decrease in porosity in the hollow portion due to the decrease in the amount of penetration. It was found that can be formed.

  Furthermore, the present inventors have made the silica density of the outer shell portion high by setting the blending ratio of the silica source and the hydrophobic organic compound to a value within a predetermined range in the production process of the coating composition containing mesoporous silica particles. Thus, it has been found that the defect rate of mesoporous silica particles is significantly reduced. Further, since the amount of the matrix-forming material entering into the hollow portion is reduced due to a decrease in the defect rate of the mesoporous silica particles, consumption of the matrix-forming material that does not contribute to the joining of the hollow mesoporous silica particles is suppressed, and the strength of the coating film is increased. It has been found that the refractive index and the reflectance of the coating film can be lowered as well as the improvement.

  The coating composition of the present invention includes a matrix forming material and mesoporous silica particles.

[Mesoporous silica particles]
The mesoporous silica particles contained in the coating composition of the present invention include an outer shell portion having a mesoporous structure containing silica. The hollow portion and pores surrounded by the outer shell of the mesoporous silica particles are filled with an organic solvent described later, but the surfactant and / or hydrophobic organic used in the preparation of the coating composition. The compound may not be completely removed and may remain in a small amount.

  The average primary particle size of the mesoporous silica particles contained in the coating composition of the present invention is 10 to 200 nm from the viewpoint of ensuring the storage stability of the coating composition, reducing the reflectance of the coating film, and ensuring high transparency. Although it is necessary, from the same viewpoint, 30 to 100 nm is preferable, 40 to 80 nm is more preferable, and 50 to 70 nm is still more preferable. The details of the measurement conditions of the “average primary particle diameter” of the mesoporous silica particles are as shown in the Examples, and the hollow mesoporous silica having the same configuration except that air exists in the hollow portion and pores inside the outer shell portion. Equal to the value measured from the particles.

  The defect rate of the mesoporous silica particles contained in the coating composition of the present invention is required to be 20% or less from the viewpoint of lowering the refractive index, lowering the reflectance, and improving the strength of the coating film. The lower the value, the better. For example, it is preferably 10% or less, more preferably 5% or less, and still more preferably 0%. The details of the measurement conditions of the “defect rate” of the mesoporous silica particles are as shown in the Examples, and the hollow mesoporous silica having the same configuration except that air exists in the hollow portion and pores inside the outer shell portion. Equal to the value measured from the particles.

  The average pore diameter of the mesoporous silica particles contained in the coating composition of the present invention is preferably 1.0 to 2.0 nm, and preferably 1.5 to 1.9 nm from the viewpoint of reducing the refractive index and reflectance of the coating film. More preferred. If the average pore diameter is 1.0 nm or more, preferably 1.5 nm or more, high porosity mesoporous silica particles can be obtained, and the refractive index and reflectance of the coating film can be further reduced. If the average pore diameter is 2.0 nm or less, preferably 1.9 nm or less, the matrix-forming material in the coating composition is difficult to enter the mesopores of the mesoporous silica particles, and the refractive index and reflection of the coating film are reduced. The rate can be further reduced, and the strength of the mesoporous silica particles can be increased. The details of the measurement conditions of the “average pore diameter” of the mesoporous silica particles are as shown in the Examples, and values measured from the hollow mesoporous silica particles having the same configuration except that air exists in the hollow portions and pores. equal.

  The average inner diameter (average hollow part diameter) of the outer shell portion of the mesoporous silica particles contained in the coating composition of the present invention is preferably 5 to 150 nm, and preferably 10 to 100 nm from the viewpoint of reducing the refractive index and reflectance of the coating film. Is more preferable, 30-60 nm is still more preferable, and 40-60 nm is still more preferable. The details of the measurement conditions of the “average inner diameter (average hollow part diameter) of the outer shell part” of the mesoporous silica particles are as shown in the examples, and the same configuration except that air exists in the hollow part and pores. Equal to the value measured from mesoporous silica particles.

  The average outer shell thickness of the mesoporous silica particles contained in the coating composition of the present invention is preferably 3 to 50 nm from the viewpoint of coexistence of reduction in the refractive index and reflectance of the coating film and improvement in the strength of the coating film, It is more preferably 5 to 20 nm, still more preferably 5 to 15 nm, still more preferably 7 to 12 nm, and even more preferably 8.2 to 10 nm. The details of the measurement conditions of the “average outer shell thickness” of the mesoporous silica particles are as shown in the Examples, and are measured from the hollow mesoporous silica particles having the same configuration except that air exists in the hollow portions and pores. Equal to value.

  The total porosity of the hollow mesoporous silica particles obtained by removing the organic solvent filled inside from the pores and outer shells of the mesoporous silica particles contained in the coating composition of the present invention is the refractive index of the coating film. From the viewpoint of coexistence of reduction in the rate and reflectance and improvement in the strength of the coating film, it is preferably 30 to 80%, more preferably 40 to 70%, still more preferably 45 to 60%, and 55 to 60 % Is even more preferable. The total porosity of the hollow mesoporous silica particles can be calculated from the porosity in the outer shell portion and the porosity in the hollow portion. From the viewpoint of reducing both the refractive index and reflectance of the coating film and improving the strength of the coating film, the porosity in the outer shell portion is preferably 10 to 60%, more preferably 15 to 50%, and the void in the hollow portion. The porosity is preferably 20 to 80%, more preferably 30 to 70%.

The content of mesoporous silica particles in the coating composition of the present invention is 0.2 in terms of SiO ₂ mass conversion concentration from the viewpoint of improving the storage stability of the coating composition and reducing the refractive index and reflectance of the coating film. -40 mass% is preferable, 0.2-10 mass% is more preferable, 0.2-1 mass% is further more preferable. Here, the SiO ₂ mass equivalent concentration refers to the mass ratio of SiO ₂ contained in the mesoporous silica particles in the coating composition.

[Matrix forming material]
As the matrix forming material contained in the coating composition of the present invention, for example, a material having transparency to visible light such as a silane compound and a fluorine group-containing resin can be used.

  Examples of the silane compound include polyfunctional alkoxysilanes such as tetraalkoxysilanes, trialkoxysilanes, dialkoxysilanes and the like. A silane compound can be used individually by 1 type or in mixture of 2 or more types. Moreover, methyl silicate oligomer, ethyl silicate oligomer, etc. which are these partial condensates are also mentioned.

  Examples of tetraalkoxysilanes include tetramethoxysilane and tetraethoxysilane.

  Examples of trialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxysilane. I-propyltrimethoxysilane, i-propyltriethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane (3,4-epoxycyclohexyl) methyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3,3 , 3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, and the like.

  Dialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3, 3, Examples include 3-trifluoropropylmethyldimethoxysilane and 3,3,3-trifluoropropylmethyldiethoxysilane.

  As the fluorine group-containing resin, a fluorine group-containing polymer containing a long-chain fluoroalkyl group can be used. As monomers for forming this fluorine group-containing polymer, for example, fluoroolefins, alkyl perfluoro vinyl ethers, alkoxyalkyl perfluoro vinyl ethers, perfluoro (alkyl vinyl ethers), perfluoro (alkoxy alkyl vinyl ethers) and the like are used. be able to. Examples of fluoroolefins include tetrafluoroethylene, hexafluoropropylene, and 3,3,3-trifluoropropylene. Examples of perfluoro (alkyl vinyl ether) include perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether), perfluoro (butyl vinyl ether), and perfluoro (isobutyl vinyl ether). Examples of perfluoro (alkoxyalkyl vinyl ether) include perfluoro (propoxypropyl vinyl ether). These monomers can be used alone or in combination of two or more, and can also be copolymerized with other monomers.

  Among these matrix forming materials, a silane compound is preferable from the viewpoints of reducing the refractive index and reflectance of the coating film and improving the strength of the coating film, and further from the viewpoint of cost reduction and improvement in manufacturability, and a methyl silicate oligomer or Ethyl silicate oligomers are more preferred, and methyl silicate oligomers are particularly preferred.

  The concentration of the matrix forming material contained in the coating composition of the present invention is the solid content concentration of the matrix forming material from the viewpoint of improving the storage stability of the coating composition and reducing the refractive index and reflectance of the coating film. The amount is preferably 0.1 to 60% by mass, more preferably 0.2 to 10% by mass, and further preferably 0.3 to 1% by mass. Here, the solid content concentration of the matrix-forming material means a non-volatile content when completely hydrolyzed and dried in the case of a silane compound, and in the case of a fluorine group-containing resin, the solvent is completely volatilized. It shows the non-volatile content after having been made.

The solid content concentration of the matrix forming material when the total of the solid content mass of the matrix forming material and the SiO ₂ mass of the mesoporous silica particles is 100% by mass is 20 to 20 from the viewpoint of reducing the refractive index and reflectance of the coating film. It is preferably 90% by mass, and more preferably 50-80% by mass. That is, the mass ratio (SiO ₂ mass of mesoporous silica particles / solid mass of the matrix forming material) is preferably 80/20 to 10/90, and more preferably 50/50 to 20/80.

[acid]
In the case where the matrix forming material is a silane compound, from the viewpoint of promoting hydrolysis and condensation reaction of functional groups such as alkoxy groups and exhibiting excellent performance of the coating composition and the coating film, an acid is contained in the coating composition. Also good. The acid may be an inorganic acid such as nitric acid, hydrochloric acid, and sulfuric acid, and may be an organic acid such as formic acid, acetic acid, and citric acid, but an inorganic acid is preferable from the viewpoint of the performance of the coating composition and the coating film, hydrochloric acid, Nitric acid is more preferred, and nitric acid is even more preferred. The amount of acid in the coating composition may be appropriately adjusted so that the silane compound has a desired structure. For example, methyl silicate oligomer (trade name: MS-51, manufactured by Tama Chemicals), acid as a matrix forming material When the 0.1N nitric acid aqueous solution is used, the amount of the 0.1N nitric acid aqueous solution is preferably 10 to 1000 parts by mass, more preferably 50 to 500 parts by mass, and 100 to 200 parts by mass with respect to 100 parts by mass of the methyl silicate oligomer. Part is more preferred. Further, the mixed solution of the silane compound and the acid is preferably 0 to 100 ° C., more preferably 10 to 50 ° C., further preferably 15 to 30 ° C., preferably 0.1 to 100 hours, more preferably 1 to 1 hour. The stirring may be performed for 48 hours, more preferably for 20 to 30 hours. By mixing the structure-controlled silane compound and mesoporous silica particles, a coating composition and a coating film exhibiting excellent performance can be obtained.

[Organic solvent]
The coating composition of the present invention contains an organic solvent as a solvent. The organic solvent is not particularly limited as long as it can be easily volatilized by heating. For example, alcohols, ketones, aromatic hydrocarbons, glycols, glycol ethers and the like can be used. Examples of alcohols include 1-propanol, methanol, ethanol, isopropanol and the like. Examples of ketones include acetone and methyl ethyl ketone, and examples of aromatic hydrocarbons include benzene and toluene. Examples of glycols include ethylene glycol and propylene glycol. Examples of glycol ethers include ethyl cellosolve, butyl cellosolve, ethyl carbitol, and butyl carbitol. These solvents can be used alone or in admixture of two or more. From the viewpoints of storage stability, cost reduction, ease of production of coating compositions, and improvement of coating film refractive index and reflectance, and coating film strength, alcohols are preferred as organic solvents, and isopropanol is more preferred. .

From the economical viewpoint, the coating composition of the present invention is usually produced as a concentrated liquid and is often diluted at the time of use. The coating composition of the present invention may be used as it is, or in the case of a concentrated liquid, for example, it may be used after diluting with the organic solvent. When diluting the concentrate, the dilution factor is not particularly limited, and can be appropriately determined according to the concentration of each component (content of mesoporous silica particles, etc.) in the concentrate, the coating method, and the like. Both the content of mesoporous silica particles (concentration in terms of SiO ₂ mass) and the concentration of matrix forming material (solid content concentration) in the coating composition are concentrations at the time of use.

[Method for producing coating composition]
Next, an example of the manufacturing method of the coating composition of this invention is demonstrated.

[Step (I): Preparation of mixture]
In the method for producing a coating composition of the present invention, first, a mixed solution containing a hydrophobic organic compound, a surfactant, and an aqueous solvent is prepared.

  The liquid mixture can be adjusted, for example, by adding a hydrophobic organic compound and a surfactant to the aqueous solvent. The hydrophobic organic compound and the surfactant may be added to the aqueous solvent in this order, or may be added simultaneously. The aqueous solvent may be stirred during the addition of the hydrophobic organic compound and / or the surfactant, or may be stirred after the addition.

  The stirring time varies depending on the type of stirrer used and the like, but is preferably 1 minute or longer, more preferably 2 minutes or longer, and even more preferably 5 minutes or longer when the whole is uniformly mixed.

  There is no restriction | limiting in particular about the kind of stirrer used for the said stirring. Examples of the stirrer include a magnetic stirrer, a pencil mixer, a homomixer, a homogenizer, and an ultrasonic disperser. As a commercially available stirrer, for example, Disper (manufactured by PRIMIX), Clearmix (manufactured by M-Technique), Cavitron (manufactured by Taiheiyo Kiko) and the like can be used.

  The temperature of the mixed solution during stirring is preferably kept at 0 to 90 ° C. from the viewpoint of preventing evaporation of the aqueous solvent and suppressing fluctuations in the concentration of the hydrophobic organic compound and the surfactant in the mixed solution. It is more preferable to keep at -50 ° C.

(Hydrophobic organic compounds)
The hydrophobic organic compound means a compound having low solubility in water and forming a phase separation with water. The hydrophobic organic compound is preferably dispersible in an aqueous solvent in the presence of a surfactant, and is preferably dispersible in an aqueous solvent in the presence of a quaternary ammonium salt that is an example of a surfactant.

  When water is used as the aqueous solvent, the temperature range in which the hydrophobic organic compound is in a liquid state is preferably 0 to 100 ° C, and more preferably 20 to 90 ° C.

The hydrophobic organic compound preferably has LogP _OW of 1 or more, more preferably 2 to 25. Here, LogP _OW is a 1-octanol / water partition coefficient of a chemical substance and refers to a value obtained by calculation by the log K _OW method. Specifically, the chemical structure of a compound is decomposed into its constituents, and the hydrophobic fragment constants of each fragment are integrated (Meylan, WM and PH Howard. 1995. Atom / fragment contribution method for a reference octanol -water partition coefficients. See J. Pharm. Sci. 84: 83-92).

  As a hydrophobic organic compound, oil agents, such as a hydrocarbon compound, an ester compound, a C6-C22 fatty acid, and silicone oil, are mentioned, for example.

  Examples of the hydrocarbon compound include alkanes having 5 to 18 carbon atoms, cycloalkanes having 5 to 18 carbon atoms, liquid paraffin, liquid petroleum jelly, squalane, squalene, perhydrosqualene, trimethylbenzene, xylene and benzene. In these, a C5-C18 alkane and a C5-C18 cycloalkane are preferable.

  Examples of the ester compound include glycerin esters of fatty acids having 6 to 22 carbon atoms, specifically, mink oil, titol oil, soybean oil, sweet almond oil, beauty leaf oil, palm oil, grape seed oil, sesame seeds. Oil, corn oil, parrham oil, Arara oil, rapeseed oil, sunflower oil, cottonseed oil, apricot oil, castor oil, avocado oil, jojoba oil, olive oil, cereal germ oil, glycerin triisostearate and the like.

  In addition, as an ester compound, condensation of a fatty acid having 4 to 22 carbon atoms with an ester of a monohydric alcohol having 1 to 22 carbon atoms or a fatty acid having 4 to 22 carbon atoms and a polyhydric alcohol other than glycerol having 1 to 22 carbon atoms. Specifically, isopropyl myristate, isopropyl palmitate, butyl stearate, hexyl laurate, isononyl isononanoate, 2-ethylhexyl palmitate, 2-hexyldecyl laurate, 2-octyldecyl palmitate, Examples include 2-octyldodecyl myristate. Examples of other ester compounds include esters of polycarboxylic acid compounds and alcohols, specifically, diisopropyl adipate, 2-octyldodecyl lactic acid ester, di-2-ethylhexyl oxalate, diisostearyl malate. And diglycerin tetraisostearate.

  Examples of fatty acids having 6 to 22 carbon atoms include caproic acid, caprylic acid, capric acid, 2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, or Examples include isostearic acid.

  Examples of the silicone oil include polydimethylsiloxane (PDMS), fatty acid, aliphatic alcohol, polysiloxane modified with polyoxyalkylene, fluorosilicone, perfluorosilicone oil, and the like.

  Polydimethylsiloxane (PDMS) may be phenylated, for example, phenyltrimethicone, or optionally substituted with aliphatic and / or aromatic groups. In addition, they are hydrocarbon-based oils or silicone oils because of their high utilization, and optionally a cyclic silicone having a pendant silicone chain or an alkyl group or alkoxy group present at the end. A straight-chain silicone containing 2 to 7 silicon atoms is preferable, and octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexadecamethylcyclohexasiloxane, heptamethylhexyltrisiloxane, heptamethyloctyltrisiloxane and the like are particularly preferable. . The above utilization rate means the proportion of the amount of the hydrophobic organic compound included in the outer shell portion of the amount of the hydrophobic organic compound used for adjusting the mixed solution.

  These hydrophobic organic compounds may be used alone or in admixture of two or more at any ratio.

  Among these hydrophobic organic compounds, they are easily emulsified by one or more surfactants selected from quaternary ammonium salts represented by the following general formula (1) and general formula (2), and the utilization rate is high. Therefore, an alkane having 5 to 18 carbon atoms and a cycloalkane having 5 to 18 carbon atoms are preferable.

  The content of the hydrophobic organic compound in the mixed solution is preferably 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L from the viewpoint of improving the utilization rate of the hydrophobic organic compound, More preferably, it is 5-80 mmol / L, and 10-30 mmol / L is especially preferable.

(Aqueous solvent)
Examples of the aqueous solvent used in the method for producing a coating composition of the present invention include water or a mixed solvent composed of water and a water-soluble organic solvent. From the viewpoint of the stability of emulsified droplets, an aqueous solvent is used. The solvent is preferably made of water only. Examples of water include distilled water, ion exchange water, and ultrapure water. Examples of the water-soluble organic solvent include methanol, ethanol, acetone, 1-propanol, 2-propanol and the like. When the aqueous solvent contains a water-soluble organic solvent, the content of the water-soluble organic solvent in the aqueous solvent is preferably 0.1 to 50% by mass, more preferably 1 to 40%, from the viewpoint of the stability of the emulsion droplets. It is 1-30 mass%, More preferably, it is 1-30 mass%.

(Surfactant)
The surfactant used in the production method of the present invention is selected from quaternary ammonium salts represented by the following general formula (1) and general formula (2) from the viewpoint of improving the utilization rate of the hydrophobic organic compound. One or more surfactants are preferred.
[R ¹ (CH ₃ ) ₃ N] ⁺ X− (1)
[R ¹ R ² (CH ₃ ) ₂ N] ⁺ X− (2)
(In the formula, R ¹ and R ² each independently represents a linear or branched alkyl group having 4 to 22 carbon atoms, and X − represents a monovalent anion.)

R ¹ and R ² in the above general formula (1) and general formula (2) are each independently preferably from 6 to 18 carbon atoms, more preferably carbon from the viewpoint of improving the utilization rate of the hydrophobic organic compound. It is a linear or branched alkyl group of formula 8-16. Examples of the alkyl group having 4 to 22 carbon atoms include various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, various tetradecyl groups, and various hexadecyl groups. , Various octadecyl groups, various eicosyl groups, and the like. Here, “various” includes all isomers such as n-isomer, iso-isomer and tert-isomer.

  X- in the general formulas (1) and (2) is preferably selected from monovalent anions such as halogen ions, hydroxide ions, and nitrate ions from the viewpoint of forming highly regular mesopores. One or more types. X- is more preferably a halogen ion, still more preferably a chloride ion or a bromide ion, and still more preferably a chloride ion.

  Examples of the alkyltrimethylammonium salt represented by the general formula (1) include butyltrimethylammonium chloride, hexyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethyl Ammonium chloride, stearyltrimethylammonium chloride, butyltrimethylammonium bromide, hexyltrimethylammonium bromide, octyltrimethylammonium bromide, decyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide Bromide, stearyl trimethyl ammonium bromide, and the like.

  Examples of the dialkyldimethylammonium salt represented by the general formula (2) include dibutyldimethylammonium chloride, dihexyldimethylammonium chloride, dioctyldimethylammonium chloride, didodecyldimethylammonium chloride, ditetradecyldimethylammonium chloride, dibutyldimethylammonium bromide, dihexyl. Examples thereof include dimethylammonium bromide, dioctyldimethylammonium bromide, didodecyldimethylammonium bromide, and ditetradecyldimethylammonium bromide.

  Among these quaternary ammonium salts, the alkyltrimethylammonium salt represented by the general formula (1) is particularly preferable from the viewpoint of forming regular mesopores, and includes alkyltrimethylammonium bromide and alkyltrimethylammonium chloride. At least one surfactant selected from the group is more preferable, at least one surfactant selected from the group consisting of dodecyltrimethylammonium chloride and dodecyltrimethylammonium bromide is more preferable, and dodecyltrimethylammonium chloride is particularly preferable.

  These surfactants may be used alone or in admixture of two or more at any ratio. By selecting the type of surfactant, the average pore size of the mesoporous silica particles can be adjusted as appropriate.

  The content of the surfactant in the mixed solution may be appropriately adjusted according to the surface area of the emulsified droplets in the emulsion obtained by pressurizing the mixed solution by the high pressure emulsification method, but the yield of mesoporous silica particles and From the viewpoint of improving dispersibility and obtaining mesoporous silica particles having a narrow particle size distribution, it is preferably 0.1 to 100 mmol / L, more preferably 0.2 to 80 mmol / L, and more preferably 0.5 to 70 mmol / L is more preferable, and 40 to 60 mmol / L is particularly preferable.

[Step (I): Preparation of emulsion containing emulsion droplets]
In the method for producing a coating composition of the present invention, the mixed liquid prepared as described above is pressurized by a high-pressure emulsification method to form an emulsion containing emulsion droplets containing a hydrophobic organic compound.

  The average primary particle size of the emulsified droplets is preferably 5 to 150 nm, more preferably 10 to 100 nm, from the viewpoint of forming mesoporous silica particles having a small average primary particle size and a narrow primary particle size distribution. More preferably, it is 30-60 nm. If the average primary particle size of the emulsified droplets is within the above range, formation of mesoporous silica particles whose average primary particle size is shorter than the wavelength of visible light, for example, the average primary particle size is 10 to 200 nm, and the average pore size is 1 It is easy to form mesoporous silica particles having a thickness of 0.0 to 2.0 nm. Therefore, the coating composition manufactured by an example of the manufacturing method of the coating composition of this invention can be used suitably as a low refractive index material used for optical films, such as a low refractive index film | membrane, for example.

  The average primary particle size of the emulsified droplets can be estimated from the inner diameter of the outer shell portion of the mesoporous silica particles obtained by the method for producing a coating composition of the present invention. Specifically, the mesoporous silica particles contained in the coating composition of the present invention were dried to remove the organic solvent filled inside from the pores and outer shell portions, and observed with a transmission electron microscope. Measure the hollow part diameter (inner diameter of the outer shell part) of all the particles (100-150 particles) in 5 visual fields containing ~ 30 particles on the photograph, and calculate the number average value of the emulsified droplets. An average primary particle size is obtained.

  High-pressure emulsification of the mixed liquid is performed, for example, in a high-pressure dispersion unit of a high-pressure emulsification disperser. The high-pressure dispersion unit includes a thin channel. When the mixed solution is pushed into the high-pressure dispersion section at a predetermined pressure and passes through the flow path, a shearing force or the like is applied to the mixed solution, whereby the mixed solution becomes an emulsion containing emulsified droplets.

  The cross-sectional shape of the flow path is not particularly limited as long as the mixed liquid can be pressurized at a predetermined pressure. For example, in the case of a circular shape, the diameter is preferably 20 to 200 μm, and more preferably 50 to 50 μm. 100 μm.

  Although there is no restriction | limiting in particular about the high pressure emulsification disperser which can be used, From a viewpoint of the simplicity of handling operation, a microfluidizer (M-110EHi by a microfluidics company), a starburst (manufactured by Sugino machine company), a nanomizer (Yoshida machine industry) (Made by company) etc. are mentioned preferably.

  The form of the high-pressure dispersion unit may be any of a collision type, a penetration type, a ball collision type, and the like. The counter-collision type has, for example, a structure in which a flow path is branched into a plurality of parts in the middle, and fluid flowing through each branch path can be collided at a portion where the flow paths merge again. The through type has, for example, a structure in which a plurality of through holes having a uniform diameter are integrated. The ball collision type has a structure in which the material can be atomized by causing the material injected at an ultra-high pressure to collide with a ceramic ball.

  In emulsifying the mixed liquid under high pressure, the pressure applied to the mixed liquid is preferably 20 to 250 MPa, more preferably from the viewpoint of forming an emulsified droplet having a small average primary particle size and a narrow primary particle size distribution. It is 30-220 MPa, More preferably, it is 40-200 MPa. By adjusting the pressure applied to the mixed liquid, it is possible to form emulsified droplets having a desired average primary particle size and a narrow primary particle size distribution. The said pressure can be confirmed with the pressure display part with which a high-pressure emulsification disperser is equipped.

  The number of high-pressure emulsification treatments may be appropriately selected according to the above pressure and the desired average primary particle size of the emulsified droplets, but from the viewpoint of obtaining emulsified droplets with high uniformity, that is, a small particle size distribution. More than once, and more preferably three times or more. Moreover, 10 times or less are preferable from a viewpoint of productivity, 5 times or less are more preferable, and 3 times or less are especially preferable. That is, 2-10 times are preferable, 3-5 times are more preferable, and 3 times are especially preferable.

[Step (I): Formation of outer shell having mesoporous structure containing silica]
In the method for producing a coating composition of the present invention, a silica source is added to the emulsion prepared as described above, and an outer shell portion having a mesoporous structure containing silica is formed on the surface of the emulsified droplets. The composite silica particles containing the outer shell part and the hydrophobic organic compound (emulsified droplets) existing inside the outer shell part are precipitated to obtain a composite silica particle-containing dispersion.

  The silica source may be added to the emulsion as it is, but a silica source-containing liquid obtained by adding the silica source to a predetermined solvent may be added to the emulsion. The solvent is preferably a water-soluble organic solvent such as methanol, ethanol, acetone, propanol, or isopropanol from the viewpoint of improving the ease of reaction control of the silica source, but methanol is particularly preferable. These water-soluble organic solvents are preferably dehydrated.

(Silica source)
As a silica source, what produces | generates a silanol compound by a hydrolysis is preferable, and the compound shown by following General formula (3)-(7) is mentioned specifically ,.
SiY ₄ (3)
R ³ SiY ₃ (4)
R ³ ₂ SiY ₂ (5)
R ³ ₃ SiY (6)
Y ₃ Si—R ⁴ —SiY ₃ (7)
(In the formula, each R ³ independently represents an organic group in which a carbon atom is directly bonded to a silicon atom, R ⁴ represents a hydrocarbon group or a phenylene group having 1 to 4 carbon atoms, and Y represents A monovalent hydrolyzable group that becomes a hydroxy group by hydrolysis.)

In general formulas (3) to (7), more preferably, each R ³ is independently a hydrocarbon group having 1 to 22 carbon atoms in which a part of hydrogen atoms may be substituted with fluorine atoms. Specifically, it is an alkyl group having 1 to 22 carbon atoms, preferably 4 to 18 carbon atoms, more preferably 6 to 18 carbon atoms, and particularly preferably 8 to 16 carbon atoms, a phenyl group, or a benzyl group. ⁴ is an alkanediyl group having 1 to 4 carbon atoms (methylene group, ethylene group, trimethylene group, propane-1,2-diyl group, tetramethylene group, etc.) or a phenylene group, and Y is 1 to 22 carbon atoms, More preferably, it is a C1-C8, especially preferably C1-C4 alkoxy group, or a halogen group excluding fluorine.

Preferable examples of the silica source include the following compounds.
-The silane compound in which Y is a C1-C3 alkoxy group or a halogen group except a fluorine in General formula (3).
In general formula (4) or (5), R ³ is a phenyl group, a benzyl group, or a hydrogen atom in which part of the hydrogen atom is substituted with a fluorine atom, preferably 1 to 10 carbon atoms, Trialkoxysilane or dialkoxysilane which is preferably a hydrocarbon group having 1 to 5 carbon atoms.
A compound in which Y is a methoxy group and R ⁴ is a methylene group, an ethylene group or a phenylene group in the general formula (7).
Among these, tetramethoxysilane, tetraethoxysilane, phenyltriethoxysilane, and 1,1,1-trifluoropropyltriethoxysilane are preferable, and tetramethoxysilane is particularly preferable. These silica sources may be used alone or in admixture of two or more at any ratio.

The amount of the silica source added to the emulsion is required to be 80 to 1000 parts by mass in terms of SiO _{2 with} respect to 100 parts by mass of the hydrophobic organic compound from the viewpoint of suppressing damage to the outer shell part. From the viewpoint of 100 parts by mass of the hydrophobic organic compound, 100 to 700 parts by mass in terms of SiO ₂ is preferable, 150 to 600 parts by mass is more preferable, 200 to 500 parts by mass is further preferable, and 200 to 300 parts by mass. Part is even more preferable.

The addition amount of the silica source with respect to the emulsion is preferably 20 to 200 parts by mass, and 30 to 150 parts by mass in terms of SiO _{2 with} respect to 100 parts by mass of the surfactant, from the viewpoint of suppressing damage to the outer shell. Preferably, 35-100 mass parts is more preferable, 35-80 mass parts is more preferable, and 35-50 mass parts is more preferable.

The content of the silica source in the mixed solution containing the emulsion and the silica source is 0.1 mass in terms of SiO ₂ mass in terms of improving the productivity of mesoporous silica particles and improving the dispersibility of the composite silica particles. % Or more, more preferably 0.3% by weight or more, still more preferably 0.5% by weight or more, and even more preferably 0.7% by weight or more. Further, from the viewpoint of suppressing aggregation of mesoporous silica particles and exhibiting excellent film properties, it is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less in terms of SiO ₂ mass. Even more preferred is less than or equal to mass%. That is, 0.1 to 10% by mass in terms of SiO ₂ mass is preferable, 0.1 to 5% by mass is preferable, 0.1 to 3% by mass is preferable, 0.1 to 1% by mass is preferable, and 0.3 -1 mass% is still more preferable, 0.5-1 mass% is still more preferable, and 0.7-1 mass% is still more preferable.

  The total amount of silica source added to the emulsion may be once but may be continuous or intermittent. In order to prevent agglomeration of the generated particles, it is preferable to continue stirring the emulsion until the reaction of the silica source is completed. After the addition of the silica source is completed, a predetermined time (e.g. (24 hours) It is preferable to continue stirring.

  The rate of addition of the silica source to the emulsion is preferably adjusted as appropriate in consideration of the capacity of the reaction system, the type of silica source, the rate of increase in the concentration of the silica source added to the emulsion, and the like.

  The temperature of the emulsion during the addition of the silica source is preferably 10 to 90 from the viewpoint of suppressing the fluctuation of the emulsion droplet stability and the concentration of the hydrophobic organic compound and the surfactant in the mixed solution. It is 10 degreeC, More preferably, it is 10-80 degreeC, More preferably, it is 10-50 degreeC.

  The pH of the emulsion during the addition of the silica source is preferably 8.5 to 12.0, more preferably 9.0 to 11 from the viewpoint of efficiently hydrolyzing and dehydrating and condensing the silica source. Is preferably adjusted to .5. For adjusting the pH of the emulsion, for example, sodium hydroxide, ammonia, or tetraalkylammonium hydroxide is preferably used. These pH adjusters are preferably added to a mixed solution when adjusting a mixed solution containing a surfactant, a hydrophobic organic compound, and an aqueous solvent. The pH of the mixed solution is preferably 8.5 to 12.0, more preferably 9.0 to 11.5, and further preferably 9.5 to 11.5. The pH can be measured using a pH meter (for example, HORIBA, Ltd., D-21), and is a value one minute after the electrode is immersed in the mixed solution.

[Step (II): Removal of surfactant]
In the method for producing a coating composition of the present invention, the composite silica particle-containing dispersion obtained as described above and the cation exchange resin are mixed, and the composite silica in the composite silica particle-containing dispersion is mixed with stirring. The surfactant is adsorbed on the cation exchange resin by bringing the particles into contact with the cation exchange resin. After completion of stirring, the cation exchange resin is removed by decantation to obtain an aqueous mesoporous silica particle dispersion. With the removal of the surfactant, it is presumed that the hydrophobic organic compound present in the hollow portion surrounded by the outer shell portion is also removed. With the removal of the hydrophobic organic compound, it is presumed that the aqueous solvent enters the hollow portion of the mesoporous silica particles through the pores. The removal of the hydrophobic organic compound can be confirmed, for example, by the disappearance of the endothermic peak derived from the hydrophobic organic compound in thermal mass spectrometry. Thermal mass spectrometry is performed on the dried hollow mesoporous silica particles.

  There is no restriction | limiting in particular as a cation exchange resin, A commercial item can be used. From the viewpoint of increasing the removal efficiency of the surfactant in the composite silica particle-containing dispersion, a strongly acidic cation exchange resin is preferable. For example, Amberlite IR120B (H + type) manufactured by Organo Corporation can be used.

The contact treatment between the composite silica particles and the cation exchange resin can be performed by a conventional method such as a batch method or a column method. The treatment temperature in the contact treatment system (the temperature of the mixture of the composite silica particle-containing dispersion and the cation exchange resin) and the treatment time (stirring time) are the mass ratio (organic content) of the organic content and SiO ₂ in the hollow mesoporous silica particles described later. (Mass of SiO ₂ / mass of SiO ₂ ) may be appropriately determined so as to be a desired value (0 to 0.5). From the viewpoint of improving the ease of production of the coating composition of the present invention, the treatment temperature is 10-80 degreeC is preferable and 20-40 degreeC is more preferable. From the same viewpoint, the treatment time is preferably 0.1 to 24 hours, more preferably 0.5 to 10 hours, and further preferably 2 to 6 hours.

The amount of the cation exchange resin used in the batch method can be appropriately determined so that the above-mentioned mass ratio (mass of organic content / mass of SiO ₂ ) (0 to 0.5) becomes a desired value. From the viewpoint of improving the ease of production of the coating composition, 1 to 20 equivalents are preferable with respect to 1 equivalent of an organic cation such as a surfactant in the composite silica particle-containing dispersion, and 5 to 15 equivalents are more preferable.

[Step (II): Dilution-concentration step]
Next, the composite silica particle-containing dispersion subjected to the contact treatment with the cation exchange resin is diluted with an organic solvent, and then concentrated. This dilution-concentration process is repeated several times. The dilution-concentration step is performed to replace the aqueous solvent or the like filled in the outer shell of the mesoporous silica particles or in the pores with the organic solvent. When the surfactant and / or hydrophobic organic compound remaining without being removed by the contact treatment with the cation exchange resin is present in the inner shell or in the pores of the mesoporous silica particles, the dilution-concentration step is performed. By passing, the amount of residual surfactant and / or the amount of residual hydrophobic organic compound can be reduced. If an organic solvent in which the hydrophobic organic compound is soluble is used, the residual hydrophobic organic compound can be removed more effectively.

  As the organic solvent, the above-mentioned [organic solvent] which is contained in the coating composition of the present invention and can be easily volatilized by heating can be used.

  The dilution factor is preferably 1.5 to 100 times, more preferably 2 to 50 times, and further preferably 2 to 10 times, from the viewpoint of improving ease of manufacture. From the viewpoint of storage stability of the mesoporous silica particle-containing dispersion, the concentration factor is preferably 1.5 to 100 times, more preferably 2 to 50 times, and further preferably 2 to 10 times. The number of repetitions of the dilution-concentration step is preferably 1 to 20 times, more preferably 3 to 10 times, and even more preferably 4 to 9 times, from the viewpoint of reducing the water content and improving the ease of production.

In the organic solvent dispersion containing the obtained mesoporous silica particles, the concentration in terms of SiO ₂ mass of the mesoporous silica particles is 1 to 20% by mass from the viewpoint of improving the ease of production of the coating composition and the storage stability of the dispersion. It is preferable that 2 to 15% by mass is more preferable, and 3 to 12% by mass is further preferable.

By drying the mesoporous silica particles in the dispersion, the organic solvent, etc. in the pores and inside the outer shell (in the hollow portion) is removed, and air exists in the pores and inside the outer shell (in the hollow portion). Hollow mesoporous silica particles are obtained. The mass ratio of the organic component and SiO ₂ in the hollow mesoporous silica particles (the mass of the organic component / the mass of SiO ₂ ) is preferably 0 to 0.5 from the viewpoint of reducing the refractive index and the reflectance of the coating film. From the viewpoint of coexistence of reduction in refractive index and reflectance of the coating film and improvement in dispersibility of mesoporous silica particles in the coating composition, and from the viewpoint of suppressing a decrease in film strength due to a large amount of organic components, 0 to 0.4 is preferable and (0 to 0.3 is more preferable) (mass of organic content / mass of SiO ₂ ).

  As described above, in step (II), the surfactant and the hydrophobic organic compound are removed from the composite silica particles by bringing the dispersion containing the composite silica particles obtained in step (I) into contact with the cation exchange resin. After the removal, the dispersion is diluted and concentrated with an organic solvent in this order to obtain an organic solvent dispersion containing mesoporous silica particles.

[Step (III)]
Next, the coating composition of the present invention can be obtained by mixing the obtained organic solvent dispersion containing mesoporous silica particles, a matrix-forming material, and, if necessary, an organic solvent.

  As described above, the coating composition of the present invention is a milk containing emulsion droplets containing the hydrophobic organic compound by pressurizing a mixed solution containing the hydrophobic organic compound, the surfactant, and the aqueous solvent by a high-pressure emulsification method. After forming a suspension, a silica source is added to the emulsion, and a composite silica containing a silica-containing outer shell portion having a mesoporous structure and a hydrophobic organic compound inside the outer shell portion Obtaining a dispersion containing particles, bringing the dispersion into contact with a cation exchange resin, and then diluting and concentrating the dispersion with an organic solvent in this order, the dispersion, the matrix-forming material, Is obtained by mixing.

  In the case where the matrix forming material is, for example, a silane compound, from the viewpoint of promoting hydrolysis and condensation reaction of functional groups such as alkoxy groups, and exhibiting excellent performance of the coating composition and the coating film, On the other hand, it is preferable to mix the [acid] together with the matrix forming material. As the solvent, the above-mentioned [organic solvent] that can be easily volatilized by heating can be used.

  According to an example of the method for producing a coating composition of the present invention, mesoporous silica and its precursor (composite silica particles) are not taken out from the liquid during the production of the coating composition. A coating composition having good particle dispersibility can be provided.

  Next, another example of the method for producing the coating composition of the present invention will be described.

  From [Step (I): Preparation of liquid mixture] to [Step (I): Formation of outer shell having a mesoporous structure containing silica] and an example of the method for producing the coating composition of the present invention, In the other example of the method for producing the coating composition of the present invention, the removal of the surfactant and the hydrophobic organic compound inside the outer shell (inside the hollow part) (step (II)) is as follows. Do.

  After separating the composite silica particles in the dispersion containing the composite silica particles from the dispersion medium, the composite silica particles are dried and then baked using an electric furnace or the like, and the surfactant and the hydrophobic organic in the composite silica particles Remove the compound. Further, if necessary, the composite silica particles separated from the dispersion medium may be subjected to at least one treatment selected from the group consisting of contact with an acidic liquid, washing with water, and drying before firing. When the composite silica particles are brought into contact with the acidic liquid, a surfactant such as a quaternary ammonium salt in the pores of the composite silica particles can be efficiently removed.

  The firing temperature is preferably 350 to 800 ° C., more preferably 450 to 700 ° C. from the viewpoint of reliably removing the surfactant and the hydrophobic organic compound and improving the strength of the mesopore structure, and the firing time is , Preferably 1 to 10 hours.

  Examples of the method for separating the composite silica particles include a filtration method and a centrifugal separation method. In the drying treatment performed after separating the composite silica particles by these methods and before firing, the temperature in the dryer is preferably 50 to 150 ° C. from the viewpoint of suppressing carbonization of organic substances attached to the composite silica particles. More preferably, it is 80-120 degreeC.

  Examples of the acidic liquid include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid; organic acids such as acetic acid and citric acid; liquids obtained by adding a cation exchange resin or the like to water or ethanol, and hydrochloric acid is particularly preferable. The pH of the acidic liquid is preferably 1.5 to 5.0.

  Next, when the obtained hollow mesoporous silica particles, the matrix forming material, and the organic solvent are mixed, the coating composition of the present invention can be obtained. For example, when the matrix forming material is a silane compound, the [acid] is preferably mixed.

In another example of the method for producing the coating composition of the present invention, since the composite silica particles are fired, the strength of the mesoporous silica particles is high and the organic component is also removed by firing, so that the refractive index is lower. In addition, a coating film having high strength can be formed.
[Formation method of coating film]

  The support to which the coating composition of the present invention is applied is not particularly limited, and examples thereof include polycarbonate, polyphenylene sulfide, polysulfone, polypropylene, polymethyl methacrylate, polyvinyl alcohol, polyethylene terephthalate, polyethylene naphthalate, and polyamide. Conventionally known translucent films such as polyaramid, polyimide, cellulose triacetate, and cycloolefin polymer are used. Moreover, transparent inorganic substrates, such as glass, quartz, ITO, etc. are used.

  Although the thickness of a support body does not have a restriction | limiting in particular and changes with uses, Usually, it is preferable in it being 50-5000 micrometers.

  The surface of the support to which the coating composition is applied may be subjected to a surface treatment such as corona or plasma treatment.

  Examples of the coating method for applying the coating composition include spin coating, roll coating, curtain coating, a slide auto method, a die coating method, a blade coating method, a bar coating method, a flow coating method, and a spray coating method.

  The coating speed may be appropriately selected according to the coating composition coating method, the viscosity of the coating composition, and the like.

The coating layer formed by applying the coating composition to the support becomes a coating film by being dried for a predetermined time at a predetermined drying temperature. The organic solvent filled in the pores of the mesoporous silica particles in the coating layer and the inside of the outer shell (inside the hollow portion) is removed by volatilization, the mesoporous silica particles become hollow mesoporous silica particles, and the matrix forming material becomes a matrix. When the matrix forming material is, for example, a methyl silicate oligomer, the matrix is made of silica (SiO ₂ ). The drying temperature is preferably 50 to 200 ° C, more preferably 100 to 150 ° C. The drying time is preferably 1 to 600 minutes, more preferably 2 to 10 minutes. When the hydrophobic organic compound remains in the mesoporous silica particles in the coating composition, it is assumed that the hydrophobic organic compound is evaporated and removed during the drying process of the coating layer.

  Next, the coating film of the present invention will be described.

  The coating film of the present invention includes a matrix and hollow mesoporous silica particles dispersed in the matrix. The hollow mesoporous silica particles include an outer shell portion having a mesoporous structure containing silica and a hollow portion existing inside the outer shell portion. The average primary particle diameter of the hollow mesoporous silica particles is 10 to 200 nm.

  Since the coating film of the present invention is formed using the coating composition of the present invention containing mesoporous silica particles having an average primary particle diameter of 10 to 200 nm, the film thickness thereof is preferably 10 to 300 nm, more preferably 50 to The thickness may be 200 nm, more preferably 70 to 150 nm, even more preferably 70 to 130 nm, and particularly preferably 80 to 120 nm. Therefore, the coating film of the present invention is suitable as an antireflection film.

  The coating film of the present invention contains, for example, hollow mesoporous silica particles having an average pore diameter of 1.0 to 2.0 nm, an average primary particle diameter of 10 to 200 nm, and a total porosity of 40 to 80%. Therefore, by selecting the content of hollow mesoporous silica particles in the coating film and the type of matrix forming material, the coating film of the present invention has the following refractive index, minimum reflectance, total light transmittance, and haze value. Can be presented.

  The refractive index of the coating film of the present invention is preferably 1.10 to 1.40, more preferably 1.20 to 1.36, and still more preferably 1.22 from the viewpoint of improving the antireflection performance of the coating film. 1.33. Details of the measurement conditions of “refractive index” are as shown in the examples.

  The minimum reflectance of the coating film of the present invention is preferably 0 to 2%, more preferably 0 to 1.5%, and still more preferably 0 to 1.0% from the viewpoint of improving the antireflection performance of the coating film. is there. Details of the measurement conditions of “minimum reflectance” are as shown in the examples.

  The total light transmittance of the coating film of the present invention is preferably 90 to 100%, more preferably 93 to 100%, and still more preferably 95 to 100%, from the viewpoint of improving the antireflection performance of the coating film. Details of the measurement conditions of “total light transmittance” are as shown in the examples.

  The haze value of the coating film of the present invention is preferably 0 to 10%, more preferably 0 to 3%, further preferably 0 to 1%, and still more preferably 0, from the viewpoint of improving the antireflection performance of the coating film. ~ 0.5%. Details of the measurement conditions of “haze value” are as shown in the examples.

  Hereinafter, the present invention will be described by way of examples. In Examples and Comparative Examples described later, various dimensions of the hollow mesoporous silica particles were measured and evaluated by the following methods. The hollow mesoporous silica particles were obtained by drying the mesoporous silica particles at 100 ° C. for 1 day in order to remove the organic solvent. Therefore, the powder X-ray diffraction (XRD) pattern of the hollow mesoporous silica particles, the average primary The particle diameter, average hollow part diameter, average outer shell part thickness, average pore diameter, porosity, and defect rate can be regarded as the same as those of mesoporous silica particles.

(1) Measurement of powder X-ray diffraction (XRD) pattern Powder X-ray diffraction measurement was performed using a powder X-ray diffractometer (manufactured by Rigaku Corporation, trade name: RINT2500VPC). A continuous scanning method with a scanning range of diffraction angle (2θ) of 1 to 20 ° and a scanning speed of 4.0 ° / min was used.
X-ray source: Cu-kα
Tube voltage: 40 mA
Tube current: 40 kV
Sampling width: 0.02 °
Divergent slit: 1/2 °
Divergence slit length: 1.2mm
Scattering slit: 1/2 °
Receiving slit: 0.15mm

(2) Measurement of average primary particle diameter, average hollow part diameter (average inner diameter of outer shell part) and average outer shell part thickness Transmission electron microscope (TEM) (trade name: JEM-2100, manufactured by JEOL Ltd.) The hollow mesoporous silica particles were observed at an acceleration voltage of 160 kV. The diameter, the hollow part diameter, and the outer shell part thickness of all particles in five fields of view containing 20 to 30 hollow mesoporous silica particles were measured on a photograph, and the number average primary particle diameter, the number average hollow part diameter, and The number average outer shell thickness was determined. The hollow mesoporous silica particles were observed using a sample obtained by attaching a sample to a Cu mesh (200-A mesh, manufactured by Oken Shoji Co., Ltd.) with a carbon support film for high resolution and removing the excess sample by blowing. It was.

(3) Measurement of BET specific surface area and average pore diameter Hollow mesoporous silica by a multipoint method using liquid nitrogen using a specific surface area / pore distribution measuring device (manufactured by Shimadzu Corporation, trade name: ASAP2020) The BET specific surface area of the particles was measured, and a value was derived within a range where parameter C was positive. The BJH method was adopted for deriving the BET specific surface area, and the peak top was defined as the average pore diameter. The porosity in the outer shell was calculated by the t-plot method. The sample was pretreated by heating at 120 ° C. for 2 hours.

(4) Porosity From the number average primary particle diameter and the number average hollow part diameter determined in (2) above, assuming that the hollow mesoporous silica particles and the hollow part are spheres, the volume average primary particle diameter and the volume average Calculate the hollow part diameter, calculate the porosity derived from the hollow part of the hollow mesoporous silica particles from the volume average primary particle diameter and the volume average hollow part diameter, and calculate the porosity in the outer shell part and the porosity in the hollow part. From these, the total porosity of the hollow mesoporous silica particles was calculated.

(5) Determination of organic content The organic content contained in the hollow mesoporous silica particles was measured using a differential type differential thermal balance (TG-DTA) (trade name: Thermo Plus TG8120, manufactured by Rigaku Corporation). Under air flow (300 mL / min), the temperature was increased from 25 to 700 ° C. at a rate of 10 ° C./min, and the remaining mass measured at 700 ° C. was the weight of SiO ₂ , and the weight loss during heating to 200 to 700 ° C. was organic The mass ratio (mass of organic component / weight of SiO ₂ ) was determined.

(6) Defect rate calculation Hollow mesoporous silica particles are observed using a field emission type high resolution scanning electron microscope (FE-SEM, Hitachi S-4800, magnification 50,000 to 100,000 times). The defect rate of the mesoporous silica particles was calculated from the above (Equation 1) using the number of hollow mesoporous silica particles having a defect such as a crack reaching the hollow portion in the outer shell portion among the 200 counted. As described above, since the hollow mesoporous silica particles are obtained by drying the mesoporous silica particles at 100 ° C. for 1 day in order to remove the organic solvent, the defect rate of the hollow mesoporous silica particles is mesoporous silica particles. Can be equated with that of Therefore, in (Formula 1) (the number of mesoporous silica particles having defects in the outer shell portion of the mesoporous silica particles whose presence or absence of defects has been confirmed), the outer shell portion of 200 hollow mesoporous silica particles has a defect. For the number of hollow mesoporous silica particles in (Formula 1), the number of hollow mesoporous silica particles confirmed for the presence of defects, ie, 200, is substituted for (number of mesoporous silica particles confirmed for the presence of defects) in (Equation 1). To do.

<Production Example 1>
Add 2 g of dodecane (manufactured by Kanto Chemical) to an aqueous solution in which 10.4 g of dodecyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry) and 1.66 g of 25% tetramethylammonium hydroxide aqueous solution (manufactured by Kanto Chemical) are dissolved in 800 g of water. And stirred to obtain a mixed solution (pH 11.0). A pencil mixer was used as the stirrer, and the stirring time was 5 minutes. The concentration of dodecyltrimethylammonium chloride in the mixed solution is 48 mmol / L, the concentration of dodecane is 14 mmol / L, and the temperature of the mixed solution during stirring is 20 ° C.

  Supply the resulting mixture to a high-pressure emulsifier (trade name: Microfluidizer M-110EHi, manufactured by Microfluidics) equipped with a Y-type chamber (manufactured by Microfluidics) with a channel diameter of 75 μm and mix By applying a pressure of 150 MPa to the liquid, a high-pressure emulsification treatment was performed on the mixed liquid. This high-pressure emulsification treatment was performed three times.

  After adding 8.4 g of tetramethoxysilane (manufactured by Tokyo Chemical Industry) as a silica source to 400 g of the obtained emulsion, these were stirred with a magnetic stirrer for 24 hours to obtain a composite silica particle aqueous dispersion.

  40 g of a strongly acidic cation exchange resin (Amberlite 120B (H), manufactured by Organo) was added to the total amount of the composite silica particle aqueous dispersion, and these were stirred at 20 ° C. for 5 hours. After the stirring was stopped, the cation exchange resin was removed by decantation to obtain an aqueous mesoporous silica particle dispersion.

The mesoporous silica particle aqueous dispersion was diluted 2-fold with isopropanol (IPA), and then concentrated 2-fold with evaporation (50 ° C.). By repeating this IPA dilution-concentration step 9 times, a mesoporous silica particle IPA dispersion (Karl Fischer moisture 0.5 wt% or less) was obtained. This mesoporous silica particle IPA dispersion was further concentrated by evaporation to obtain a mesoporous silica particle IPA dispersion having a SiO ₂ mass conversion concentration of 10.7%.

As a result of XRD measurement of hollow mesoporous silica particles obtained by drying the above mesoporous silica particle IPA dispersion at 100 ° C. for 1 day, an XRD peak (plane spacing d = 4.4 nm) derived from the mesopore structure was found. confirmed. The BET specific surface area was 490 m ² / g. As a result of TG-DTA analysis, the mass ratio (mass of organic content / mass of SiO ₂ ) in the hollow mesoporous silica particles was 0.13. The porosity of the hollow portion of the hollow mesoporous silica particles was 41%, and the porosity of the outer shell portion was 19%. Table 1 shows the average primary particle diameter, average hollow part diameter, average outer shell thickness, average pore diameter, total porosity, and defect rate.

<Production Example 2>
A mesoporous silica particle IPA dispersion having a SiO ₂ mass equivalent concentration of 6.1% was obtained in the same manner as in Production Example 1 except that the amount of tetramethoxysilane (manufactured by Tokyo Chemical Industry) was changed to 11.2 g.

As a result of performing XRD measurement on the hollow mesoporous silica particles in the same manner as in <Production Example 1>, an XRD peak (plane spacing d = 4.5 nm) derived from the mesopore structure was confirmed. The BET specific surface area was 440 m ² / g. As a result of TG-DTA analysis, the mass ratio (mass of organic content / mass of SiO ₂ ) in the hollow mesoporous silica particles was 0.14. The porosity of the hollow portion of the hollow mesoporous silica particles was 33%, and the porosity of the outer shell portion was 17%. Table 1 shows the average primary particle diameter, average hollow part diameter, average outer shell thickness, average pore diameter, total porosity, and defect rate.

<Production Example 3>
A mesoporous silica particle IPA dispersion having a SiO ₂ mass conversion concentration of 4.4% was obtained in the same manner as in Production Example 1, except that the amount of tetramethoxysilane (manufactured by Tokyo Chemical Industry) was 5.6 g.

As a result of performing XRD measurement on the hollow mesoporous silica particles in the same manner as in <Production Example 1>, an XRD peak derived from the mesopore structure (plane spacing d = 4.2 nm) was confirmed. The BET specific surface area was 720 m ² / g. As a result of TG-DTA analysis, the mass ratio (mass of organic content / mass of SiO ₂ ) in the hollow mesoporous silica particles was 0.10. The porosity of the hollow part of the hollow mesoporous silica particles was 45%, and the porosity of the outer shell part was 27%. Table 1 shows the average primary particle diameter, average hollow part diameter, average outer shell thickness, average pore diameter, total porosity, and defect rate.

<Production Example 4>
1 g of dodecane (manufactured by Kanto Chemical) is added to an aqueous solution in which 4 g of dodecyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry) and 0.83 g of 25% tetramethylammonium hydroxide aqueous solution (manufactured by Kanto Chemical) are dissolved in 400 g of water and stirred. As a result, a mixed solution (pH 11.5) was obtained. A pencil mixer was used as the stirrer, and the stirring time was 5 minutes. The concentration of dodecyltrimethylammonium chloride in the mixed solution is 38 mmol / L, the concentration of dodecane is 15 mmol / L, and the temperature of the mixed solution during stirring is 20 ° C.

  Supply the resulting mixture to a high-pressure emulsifier (trade name: Microfluidizer M-110EHi, manufactured by Microfluidics) equipped with a Y-type chamber (manufactured by Microfluidics) with a channel diameter of 75 μm and mix By applying a pressure of 150 MPa to the liquid, a high-pressure emulsification treatment was performed on the mixed liquid. The high-pressure emulsification treatment was performed only once.

  After adding 1 g of tetramethoxysilane (manufactured by Tokyo Chemical Industry) as a silica source to 250 g of the obtained emulsion, these were stirred with a magnetic stirrer for 5 hours to obtain a composite silica particle aqueous dispersion.

  20 g of strongly acidic cation exchange resin (Amberlite 120B (H), manufactured by Organo) was added to the total amount of the composite silica aqueous dispersion, and these were stirred at 20 ° C. for 5 hours. After the stirring was stopped, the cation exchange resin was removed by decantation to obtain an aqueous mesoporous silica particle dispersion.

The mesoporous silica particle aqueous dispersion was diluted 2-fold with isopropanol (IPA), and then concentrated 2-fold with evaporation (50 ° C.). By repeating this IPA dilution-concentration step seven times, a mesoporous silica particle IPA dispersion (Karl Fischer moisture 0.16 wt%) was obtained. This mesoporous silica particle IPA dispersion was further concentrated by evaporation to obtain a mesoporous silica particle IPA dispersion having a SiO ₂ mass conversion concentration of 10%.

As a result of XRD measurement of the hollow mesoporous silica particles in the same manner as in <Production Example 1>, an XRD peak (plane spacing d = 4.4 nm) derived from the mesopore structure was confirmed. As a result of TG-DTA analysis, the mass ratio (mass of organic content / mass of SiO ₂ ) in the hollow mesoporous silica particles was 0.20. The porosity of the hollow part of the hollow mesoporous silica particles was 49%, and the porosity of the outer shell part was 27%. Table 1 shows the average primary particle diameter, average hollow part diameter, average outer shell thickness, average pore diameter, and total porosity.

  FIG. 1 shows a TEM photograph (magnification: 20000 times) of the hollow mesoporous silica particles obtained in <Production Example 1>, and FIG. 2 shows an SEM photograph (magnification: 100000) of the hollow mesoporous silica particles obtained in <Production Example 1>. 3), a TEM photograph (magnification: 40000 times) of the hollow mesoporous silica particles obtained in <Production Example 4>, and a SEM photograph of the hollow mesoporous silica particles obtained in <Production Example 4> in FIG. (Magnification: 50000 times).

  As shown in FIGS. 1 and 3, in <Production Example 1> and <Production Example 4>, hollow particles are formed, and solid particles are not formed. As shown in FIGS. 2 and 4, the hollow mesoporous silica particles obtained in <Production Example 1> are more uniform in particle diameter than the hollow mesoporous silica particles obtained in <Production Example 4>. In addition, defects are observed for the hollow mesoporous silica particles obtained in <Production Example 4>, but no defects are observed for the hollow mesoporous silica particles obtained in <Production Example 1>.

  Table 2 summarizes the component ratios and the emulsification conditions in the emulsions prepared in Production Examples 1 to 4 to which the silica source was added.

<Example 1>
A mixed solution comprising 33.5 parts by mass of a methyl silicate oligomer (trade name: MS-51, manufactured by Tama Chemical), 430 parts by mass of IPA, and 50 parts by mass of a 0.1N nitric acid aqueous solution as a matrix forming material was stirred at 20 ° C. for 24 hours. 104 parts by mass of the mesoporous silica particle IPA dispersion of Production Example 1 (SiO ₂ mass conversion concentration 10.7%) was mixed with this mixture, and further diluted with IPA, so that the total solid content concentration was 1% by mass and the mass ratio. (Mesoporous silica particle SiO ₂ mass / matrix forming material solid content mass (SiO ₂ mass)) is 40/60, mesoporous silica particle SiO ₂ mass equivalent concentration is 0.4 mass%, matrix forming material solid content A coating composition having a concentration of 0.6% by mass was obtained.

  Spin coater (Kyowa Riken Co., Ltd. K-359SD-1) was applied to a slide glass substrate (trade name: S-1111, refractive index 1.52, manufactured by Matsunami) and silicon substrate (manufactured by Niraco) washed with acetone. ) Was spin-coated (1000 rpm, 30 seconds) and then dried at 120 ° C. for 5 minutes to prepare a coating film in which hollow mesoporous silica particles were dispersed in a silica matrix.

<Example 2>
A coating composition and a coating film were prepared in the same manner as in Example 1 except that the mesoporous silica particle IPA dispersion of Production Example 2 was used instead of the mesoporous silica particle IPA dispersion of Production Example 1.

<Example 3>
A coating composition and a coating film were prepared in the same manner as in Example 1 except that the mesoporous silica particle IPA dispersion liquid of Production Example 3 was used instead of the mesoporous silica particle IPA dispersion liquid of Production Example 1.

<Reference Example 1>
A coating composition and a coating film were prepared in the same manner as in Example 1 except that the mesoporous silica particle IPA dispersion of Production Example 4 was used instead of the mesoporous silica particle IPA dispersion of Production Example 1.

<Comparative Example 1>
A coating composition and a coating film were prepared in the same manner as in Example 1 except that commercially available silica (IPA silica sol, IPA-ST manufactured by Nissan Chemical Industries) was used instead of the mesoporous silica particle IPA dispersion of Production Example 1.

From the TEM observation, it was confirmed that the silica powder obtained by drying the commercially available silica at 120 ° C. for 1 day was a spherical particle having an average primary particle diameter of 20 nm. The silica powder had a BET specific surface area of 210 m ² / g, an average pore size of 5.2 nm, and had a broad pore size distribution. The total porosity of the silica powder was 0%.

<Comparative example 2>
A resin composition and a coating film were prepared in the same manner as in Example 1 except that the mesoporous silica particle IPA dispersion was not blended.

<Evaluation method of coating film>
(Total light transmittance, haze value)
The total light transmittance and haze value were measured using an integrating sphere light transmittance measuring device (trade name: HR-150, manufactured by Murakami Color Research Laboratory) defined in JIS K-7105.

(Minimum reflectance)
Using a spectrophotometer (trade name: U-3300, manufactured by Hitachi, Ltd.), a reflection spectrum in a wavelength region of 380 to 780 nm was measured at an incident angle of 8 ° with a black cloth applied to the back surface of the slide glass. The minimum reflectance of the coating film was obtained by correcting the slide glass without a coating film with a black cloth as a blank.

(Refractive index, film thickness)
Using an automatic ellipsometer (trade name: DHA-XA / S6, manufactured by Mizoji Optics Co., Ltd.), using a He-Ne laser (wavelength 632.8 nm) as a light source, the refractive index and film thickness of the coating film at an incident angle of 70 ° It was measured. The refractive index and film thickness of the coating film were calculated as the refractive index of silicon substrate 3.8750, the absorption coefficient 0.023, the refractive index 1 of the incident medium (air), the absorption coefficient 0, and the absorption coefficient 0 of the coating film.

(Abrasion resistance test (film strength test))
The scratch resistance test was performed using a surface property tester HEIDON-14DR (manufactured by Shinto Kagaku Co.). Specifically, steel wool # 0000 (Japan) was applied to a coating film formed on a slide glass substrate (trade name: S-1111, manufactured by Matsunami, width 26 × length 76 mm) while applying a load of 250 g. 1 cm width was rubbed in the longitudinal direction. Steel wool # 0000 was reciprocated 10 times, and the sliding speed of steel wool # 0000 was 1 reciprocation / second. In Table 1, “B” is indicated when the entire surface of the rubbed surface is scratched and it is determined that the utility value as a coating film is lost, and “A” is indicated otherwise.

  As shown in Table 1 above, the coating films of Examples 1 to 3 containing hollow mesoporous silica particles derived from the mesoporous silica particles of Production Examples 1 to 3 have a refractive index higher than that of Comparative Example 1 or 2. And reflectivity is low. In Production Examples 1 to 3, the amount of silica source added to the emulsion containing emulsion droplets containing the hydrophobic organic compound is a value within the range of 80 to 1000 parts by mass with respect to 100 parts by mass of the hydrophobic organic compound. On the other hand, in Reference Example 1, the amount is 64 parts by mass with respect to 100 parts by mass of the hydrophobic organic compound. The defect rate of the mesoporous silica particles of Production Examples 1 to 3 was lower than that of the mesoporous silica particles of Production Example 4 and was 20% or less. As a result of the scratch resistance test, scratches were observed in the coating film of Reference Example 1, but no scratches were observed in the coating films of Examples 1 to 3.

  As described above, the present invention is useful as a coating composition and a coating film for an antireflection film.

Claims (8)

A coating composition comprising a matrix forming material and mesoporous silica particles,
The mesoporous silica particles include an outer shell portion having a mesoporous structure containing silica and a hollow portion surrounded by the outer shell portion, and an average primary particle diameter thereof is 10 to 200 nm.
A coating composition having a defect rate of 20% or less of mesoporous silica particles calculated by the following (formula 1) based on an image obtained by photographing with a scanning electron microscope.
(Formula 1)
Defect rate = (number of mesoporous silica particles having defects in the outer shell portion among mesoporous silica particles confirmed to have defects) / (number of mesoporous silica particles confirmed to have defects) × 100 A matrix forming material;
A silica source is added to an emulsion containing emulsion droplets containing the hydrophobic organic compound obtained by pressurizing a mixed solution containing a hydrophobic organic compound, a surfactant and an aqueous solvent by a high-pressure emulsification method. And after forming a composite silica particle comprising an outer shell having a mesoporous structure containing silica and the hydrophobic organic compound present in a hollow portion surrounded by the outer shell, from the composite silica particle, A mesoporous silica particle obtained by removing the surfactant and the hydrophobic organic compound,
The addition amount of the silica source to said emulsion, relative to the hydrophobic organic compound 100 parts by mass, or 80 to 1000 parts by weight of SiO ₂ mass conversion coating composition.   The coating composition of Claim 1 or 2 whose average pore diameter in the said outer shell part of the said mesoporous silica particle is 1.0-2.0 nm. A method for producing the coating composition according to any one of claims 1 to 3,
A liquid mixture containing a hydrophobic organic compound, a surfactant, and an aqueous solvent is pressurized by a high-pressure emulsification method to form an emulsion containing emulsion droplets containing the hydrophobic organic compound, and then the emulsion is added to the emulsion. Adding a silica source to form composite silica particles including an outer shell portion containing silica and having a mesoporous structure and the hydrophobic organic compound existing in a hollow portion surrounded by the outer shell portion (I )When,
Removing the surfactant and the hydrophobic organic compound from the composite silica particles to obtain mesoporous silica particles (II);
Mixing the mesoporous silica particles and the matrix-forming material,
In the step (I), the amount of the silica source added to the emulsion is 80 to 1000 parts by mass in terms of SiO _{2 with} respect to 100 parts by mass of the hydrophobic organic compound. . In the step (II),
After removing the surfactant from the composite silica particles by bringing the dispersion containing the composite silica particles obtained in step (I) into contact with a cation exchange resin, the dispersion is diluted with an organic solvent. The method for producing a coating composition according to claim 4, wherein the organic solvent dispersion containing the mesoporous silica particles is obtained by performing the concentration in this order.   The coating film produced using the coating composition in any one of Claims 1-3.   The coating film of Claim 6 whose film thickness is 10-300 nm.   An antireflection film comprising the coating film according to claim 6.