JP2011157506A - Coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition forming a coating film having a low refractive index and a low reflectance, to provide a method for producing the same, and to provide the coating film or an antireflection film formed by using the coating composition. <P>SOLUTION: The coating composition includes a matrix-forming material; and mesoporous silica particles containing a shell part having a mesoporous structure containing silica, and having an average primary particle diameter of 10-200 nm. The coating film formed by using the coating composition includes the matrix; and the hollow mesoporous silica particles containing the shell part having the mesoporous structure containing the silica and a hollow part present on the inside of the shell part, and having an average primary particle diameter of 10-200 nm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coating composition, a coating film, an antireflection film, and methods 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 the strength of the hollow silica particles, that is, the coating film strength. Therefore, the refractive index and the 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 provides a coating composition capable of forming a coating film having a low refractive index and a low reflectance, a method for producing the same, and a coating film or an antireflection film formed using the coating composition.

  The coating composition of the present invention includes a matrix forming material and mesoporous silica particles having an outer shell portion having a mesoporous structure containing silica and having an average primary particle diameter of 10 to 200 nm.

  The coating film of the present invention is a coating film prepared from the coating composition of the present invention.

  The coating film of the present invention comprises a hollow mesoporous silica having an average primary particle diameter of 10 to 200 nm, comprising a matrix, an outer shell portion having a mesoporous structure containing silica, and a hollow portion existing inside the outer shell portion. Particles.

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

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. A step (I) of adding a silica source to form a composite silica particle containing silica and a mesoporous structure having a mesopore structure and the emulsified droplets inside the outer shell,
Removing the surfactant and the emulsified droplets from the composite silica particles (II);
including.

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

  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 having a mesoporous structure outer shell and a hollow structure, and “hollow mesoporous silica particles” are outer shells having a mesoporous structure and It is a particle that includes a hollow portion that exists inside the outer shell portion, and in which air exists in the hollow portion and pores.

  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 inside of the hollow part and the pores of the outer shell part of the mesoporous silica particles are filled with an organic solvent to be described later, but the surfactant and / or hydrophobic organic compound used in preparing the coating composition May be present in small amounts.

  The average primary particle diameter of the mesoporous silica particles contained in the coating composition of the present invention is required to be 10 to 200 nm from the viewpoints of storage stability of the coating composition, reduction of the reflectance of the coating film, and high transparency. However, from the same viewpoint, it is preferably 30 to 100 nm, and more preferably 40 to 80 nm. 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 the 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 2.5 nm from the viewpoint of reducing the refractive index and reflectance of the coating film, and is preferably 1.0 to 2. It is more preferable that it is 3 nm, and it is further more preferable that it is 1.0-2.2 nm. If the average pore diameter is 1.0 nm or more, high porosity mesoporous silica particles can be obtained, and the refractive index and reflectance of the coating film can be reduced. Moreover, if the average pore diameter is 2.5 nm or less, the matrix forming material in the coating composition is less likely to enter the mesopores of the mesoporous silica particles, and the refractive index and reflectance of the coating film can be reduced. 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 part of the mesoporous silica particles contained in the coating composition of the present invention is preferably 5 to 150 nm from the viewpoint of reducing the refractive index and reflectance of the coating film. More preferably, it is -100nm, and it is further more preferable that it is 30-60nm. The details of the measurement conditions of the “average inner diameter of the outer shell (average hollow diameter)” of the mesoporous silica particles are as shown in the Examples, and the same configuration except that air exists in the hollow and the 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, and further preferably 5 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 of the rate and reflectance and improvement of the strength of the coating film, it is preferably 50 to 80%, more preferably 60 to 80%, and further preferably 65 to 80%. The total porosity of the hollow mesoporous silica particles can be calculated from the porosity of the outer shell portion and the porosity of 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 of the outer shell is preferably 10 to 60%, more preferably 15 to 50%, and the void in the hollow part. The porosity is preferably 20 to 80%, more preferably 40 to 70%.

The concentration of the mesoporous silica particles contained in the coating composition of the present invention is 0.2 in terms of SiO ₂ weight conversion from the viewpoint of improving the storage stability of the coating composition and reducing the refractive index and reflectance of the coating film. It is preferably -40% by weight, more preferably 0.2-10% by weight, and further preferably 0.2-1% by weight. Here, the SiO ₂ weight equivalent concentration refers to the proportion by weight 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, 3,3,3-trifluoropropylmethyldiethoxysilane, and the like.

  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, silane compounds are preferred 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 ease of production, and methyl silicate oligomers and 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. It is preferably 0.1 to 60% by weight, more preferably 0.2 to 10% by weight, and further preferably 0.3 to 1% by weight.

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

[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 2-propanol, methanol, ethanol 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 of coating compositions, cost reduction, ease of production, reduction of refractive index and reflectance of coating film, and improvement of coating strength, alcohols are preferred as organic solvents, and 2-propanol is preferred. 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.

[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 an 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 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 liquid during stirring is preferably maintained 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 liquid. ~ 50 ° C is more preferred.

(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 the presence of a surfactant, and is preferably dispersible in the presence of a quaternary ammonium salt which 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 fats and oils such as 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. And oil, sesame seed oil, corn oil, parrham oil, arara oil, rapeseed oil, sunflower oil, cottonseed oil, apricot oil, castor oil, avocado oil, jojoba oil, olive oil, or grain germ oil.

  Examples of ester compounds include condensates of fatty acids having 4 to 22 carbon atoms and monohydric or polyhydric alcohols other than glycerin, such as isopropyl myristate and isopropyl palmitate. Butyl stearate, hexyl laurate, isononyl isononanoate, 2-ethylhexyl palmitate, 2-hexyldecyl laurate, 2-octyldecyl palmitate, 2-octyldecyl myristate, and the like. Other ester compounds include esters of polyvalent carboxylic acid compounds and alcohols, specifically, diisopropyl adipate, lactic acid 2-octyldodecyl ester, 2-diethylhexyl oxalate, diisostearyl malate, Examples thereof include glyceryl triisostearate and diglyceryl triisostearate.

  Examples of the fatty acid having 6 to 22 carbon atoms include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, and 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. They are also hydrocarbon-based oils or silicone oils because of their high utilization and optionally contain alkyl groups or alkoxy groups that are pendant to the silicone chain or present at the ends. A linear or cyclic silicone containing 2 to 7 silicon atoms is preferred, and in particular, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexadecamethylcyclohexasiloxane, heptamethylhexyltrisiloxane, heptamethyloctyltrisiloxane and the like. 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.

(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 water-based solvent contains a water-soluble organic solvent, the content of the water-soluble organic solvent in the water-based solvent is preferably 0.1 to 50% by weight, more preferably 1 to 40%, from the viewpoint of the stability of the emulsion droplets. % By weight, more preferably 1 to 30% by weight.

(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.

  X in general formula (1) and general formula (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. 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, dihexyldimethylammonium bromide, dioctyldimethylammonium bromide, didodecyldimethylammonium bromide, ditetradecyl. Examples thereof include dimethylammonium bromide.

  Among these quaternary ammonium salts, from the viewpoint of forming regular mesopores, the alkyltrimethylammonium salt represented by the general formula (1) is particularly preferable, and alkyltrimethylammonium bromide or alkyltrimethylammonium chloride is more preferable. 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 emulsion 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 More preferably, it is 70 mmol / L.

[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 possible to easily form mesoporous silica particles of 0.0 to 2.5 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.

  The 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 and a penetration type. 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.

  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 pressure and the desired average primary particle size of the emulsified droplets, but is preferably 1 to 10 times, more preferably 1 to 5 times.

[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. Then, composite silica particles containing an outer shell part and a hydrophobic organic compound (emulsified droplet) existing inside the outer shell part are precipitated.

  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. Examples of the solvent include water-soluble organic solvents such as methanol, ethanol, acetone, propanol, isopropanol, and preferably methanol. 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 the 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, a phenyl group, or a benzyl 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, and R 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 phenylene group, and Y is more preferably 1 to 22 carbon atoms. Is a C1-C8, particularly 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 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 (for example, 0.01 to 10 ° C. at 0.01 to 80 ° C.). (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 stability of the emulsified droplets 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.

  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.

By controlling the addition amount of the silica source, the thickness of the outer shell portion of the mesoporous silica particles can be controlled. From the viewpoint of improving production efficiency and dispersibility of the resulting composite silica particles, the addition amount of the silica source is 0.1% in terms of SiO ₂ weight equivalent in the dispersion obtained by adding the silica source to the emulsion. Is preferably 10 to 10% by weight, and more preferably 0.1 to 2% by weight.

[Step (II): Removal of surfactant]
In the method for producing a coating composition of the present invention, the composite silica particles in the composite silica particle-containing dispersion obtained as described above and the cation exchange resin are brought into contact with stirring, thereby bringing the cation exchange resin into a surface activity. Adsorb the agent. After completion of stirring, the cation exchange resin is removed by decantation to obtain an aqueous mesoporous silica particle dispersion. It is inferred that the emulsified droplets (hydrophobic organic compound) inside the outer shell are also removed along with the removal of the surfactant. With the removal of the emulsified droplets, it is presumed that the aqueous solvent enters through the pores inside the outer shell of the mesoporous silica particles. 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 thermogravimetric analysis. Thermogravimetric analysis is performed on the dried 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 and treatment time (stirring time) in the contact treatment system are set so that the weight ratio of organic component to SiO ₂ (weight of organic component / weight of SiO ₂ ) in the hollow mesoporous silica particles described later is a desired value. What is necessary is just to determine suitably, but from a viewpoint of the ease of manufacture of the coating composition of this invention, 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 weight ratio (weight of organic component / weight of SiO ₂ ) is a desired value, but it is easy to produce the coating composition of the present invention. From the viewpoint of properties, 1 to 20 equivalents are preferable and 5 to 15 equivalents are more preferable with respect to 1 equivalent of an organic cation such as a surfactant in the composite silica particle-containing dispersion.

  The dispersion containing composite silica particles may be processed by directly contacting the cation exchange resin. However, from the viewpoint of suppressing adverse effects due to the removal of the surfactant, that is, aggregation, precipitation, gelation, and the like of the composite silica particles in the composite silica particle-containing dispersion, and stably dispersing the composite silica particles, Before contacting, it is preferable to mix the dispersion containing the composite silica particles and the organic silane to bond organic groups to the surface of the composite silica particles.

  The organic silane can be mixed with the composite silica particle-containing dispersion by, for example, mixing an organic silane-containing acidic liquid with the composite silica particle-containing dispersion. The organic silane-containing acidic liquid contains, for example, an aqueous solvent and a pH adjuster in addition to the organic silane.

  As the organic silane, for example, a hydrolyzable organic silane having an organic group such as alkoxysilane, disiloxane, or chlorosilane is preferable, and disiloxane is more preferable. These organosilanes can be used alone or in admixture of two or more.

The disiloxane is preferably a compound represented by the following general formula (8).
R ⁵ ₃ SiOSiR ⁶ ₃ (8)
(In the formula, R ⁵ and R ⁶ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an allyl group, an aryl group, or an alkoxy group, and the plurality of R ⁵ and R ⁶ are the same or different. May be.)

Among the compounds represented by the general formula (8), hexaalkyldisiloxane having an alkyl group having 1 to 3 carbon atoms is preferable, and in particular, hexamethyldisiloxane [(CH ₃ ) ₃ SiOSi (CH ₃ ) ₃ ]. Is preferred.

  The aqueous solvent contained in the organic silane-containing acidic liquid is preferably a mixed solvent of water and a water-soluble organic solvent, more preferably an aqueous alcohol solution, from the viewpoint of improving the reactivity between the organic silane and the composite silica particles, and methanol. An aqueous solution, an aqueous ethanol solution, and an aqueous 2-propanol solution are more preferable.

  As the pH adjuster contained in the organic silane-containing acidic liquid, strong acids are preferable and inorganic acids are more preferable from the viewpoint of improving the reactivity between the organic silane and the composite silica particles and reducing the refractive index and reflectance of the coating film. Of these, hydrochloric acid and nitric acid are more preferable.

  The pH of the composite silica particle dispersion mixed with the organic silane-containing acidic liquid is preferably 1.0 to 7.0 from the viewpoint of improving the reactivity between the organic silane and the composite silica particles, and is preferably 1.5 to 4.0. More preferably, it is more preferably 1.7-3.0.

[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 still more preferably 2 to 10 times, from the viewpoint of improving manufacturability. The concentration 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 storage stability of the mesoporous silica particle-containing dispersion. 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 8 times, from the viewpoint of reducing the amount of water and ease of production.

In the organic solvent dispersion containing the obtained mesoporous silica particles, the concentration in terms of SiO ₂ weight of the mesoporous silica particles is 1 to 20% by weight from the viewpoint of ease of production of the coating composition and storage stability of the dispersion. 2 to 15% by weight is more preferable, and 5 to 12% by weight is more preferable.

By drying the mesoporous silica particles in the dispersion, the organic solvent and the like in the pores and inside the outer shell are removed, and hollow mesoporous silica particles in which air exists in the pores and inside the outer shell are obtained. The weight ratio of organic component to SiO ₂ (weight of organic component / weight of SiO ₂ ) in the hollow mesoporous silica particles is preferably 0 to 0.5 from the viewpoint of reducing the refractive index and reflectance of the coating film. From the viewpoint of coexistence of the reduction in the refractive index and reflectance of the coating film and the dispersibility of the mesoporous silica particles in the coating composition, and from the viewpoint of suppressing the decrease in film strength due to the high organic content, the weight ratio (organic The weight of min / weight of SiO ₂ is more preferably 0.1 to 0.4, and further preferably 0.2 to 0.3.

  As described above, in 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 the cation exchange resin, The dispersion is diluted with an organic solvent and concentrated 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, the 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 particle including a silica-containing outer shell portion having a mesopore structure and the emulsified droplets inside the outer shell portion The dispersion is brought into contact with the cation exchange resin, and then the dispersion is diluted and concentrated with an organic solvent in this order, and then the dispersion and the matrix-forming material are combined. It is obtained by mixing.

  According to one 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.

  The steps from [Preparation of liquid mixture] to [Formation of outer shell portion having mesopore structure containing silica] are the same as the above-described method for producing the coating composition of the present invention. In another example of the production method, removal of the surfactant and emulsified droplets (hydrophobic organic compound) inside the outer shell (step (II)) is performed as follows.

  After separating the composite silica particles from the dispersion medium, the composite silica particles are dried and then baked using an electric furnace or the like to remove the surfactant and the hydrophobic organic compound in the composite silica particles. 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 solution, 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 separation method 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.

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 inside the pores and the outer shell of the mesoporous silica particles in the coating layer 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. Therefore, the coating film of the present invention is suitable as an antireflection film.

  The coating film of the present invention includes, for example, hollow mesoporous silica particles having an average pore diameter of 1.0 to 2.5 nm, an average primary particle diameter of 10 to 200 nm, and a total porosity of 50 to 80%. Therefore, by selecting the content of the 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. 1.30. Details of the measurement conditions of “refractive index” are as shown in the examples.

  From the viewpoint of improving the antireflection performance of the coating film, the minimum reflectance of the coating film of the present invention is preferably 0 to 2%, more preferably 0 to 1%, and still more preferably 0 to 0.8%. 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. The details of the measurement conditions of “total light transmission” are as shown in the examples.

  From the viewpoint of improving the antireflection performance of the coating film, the haze value of the coating film of the present invention is preferably 0 to 10%, more preferably 0 to 3%, and still more preferably 0 to 1%. 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 measurements and evaluations of hollow mesoporous silica particles were performed by the following methods.

(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 of 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 of the outer shell part and the porosity of 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 airflow (300 mL / min), the temperature was increased from 25 to 700 ° C. at a rate of 10 ° C./min, and the remaining weight measured at 700 ° C. was the weight of SiO ₂ , and the weight loss during heating to 200 to 700 ° C. was organic Measured as the weight of minutes, the weight ratio of these (weight of organic content / weight of SiO ₂ ) was determined.

<Production Example 1>
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, and the concentration of dodecane is 15 mmol / L.

  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 The liquid mixture was emulsified by applying a pressure of 150 MPa to the liquid.

  250 g of the obtained emulsion was brought to 20 ° C., 1 g of tetramethoxysilane (manufactured by Tokyo Chemical Industry) was added as a silica source to the emulsion, and then these were stirred with a magnetic stirrer for 5 hours to obtain an aqueous dispersion of composite silica particles. Got.

  0.32 g of water, 0.46 g of concentrated hydrochloric acid (manufactured by Wako Pure Chemical Industries), 0.60 g of 2-propanol (hereinafter IPA, manufactured by Wako Pure Chemical Industries), 0.40 g of hexamethyldisiloxane (manufactured by Wako Pure Chemical Industries), 20 ° C. The hexamethyldisiloxane-containing liquid obtained by stirring for 1 hour and 200 g of the above composite silica particle aqueous dispersion were stirred and mixed at 20 ° C. for 24 hours (pH 2.0 after stirring and mixing).

  20 g of a strongly acidic cation exchange resin (Amberlite 120B (H), manufactured by Organo) was added to 202 g of a mixed liquid obtained by mixing the hexamethyldisiloxane-containing liquid and the composite silica aqueous dispersion, Stir at 5 ° 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 above mesoporous silica particle aqueous dispersion was diluted 2-fold with 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 weight conversion concentration of 8.7%.

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 = 4.3 nm) derived from the mesopore structure was found. confirmed. From TEM observation, it was confirmed that the average primary particle diameter was 63 nm, the average hollow part diameter was 47 nm, the average outer shell thickness was 8 nm, and the outer shell part had mesopores. The BET specific surface area was 870 m ² / g, and the average pore diameter was 2.2 nm. As a result of TG-DTA analysis, the weight ratio of the hollow mesoporous silica particles (weight of organic component / weight of SiO ₂ ) was 0.30. The hollow portion of the hollow mesoporous silica particles had a porosity of 62%, the outer shell portion had a porosity of 21%, and the total porosity was 70%.

<Production Example 2>
In Production Example 1, a mesoporous silica particle IPA dispersion having a SiO ₂ weight conversion concentration of 10% was prepared in the same manner as in Production Example 1 except that the reaction between the hexamethyldisiloxane-containing liquid and the composite silica aqueous dispersion was not performed. Obtained.

As a result of XRD measurement on hollow mesoporous silica particles obtained by drying the 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 confirmed. It was done. From TEM observation, it was confirmed that the average primary particle diameter was 50 nm, the average hollow part diameter was 37 nm, the average outer shell thickness was 6 nm, and the outer shell part had mesopores. The BET specific surface area was 850 m ² / g and the average pore diameter was 2.1 nm. As a result of TG-DTA analysis, the weight ratio (weight of organic component / weight of SiO ₂ ) in the hollow mesoporous silica particles was 0.20. The hollow portion of the hollow mesoporous silica particles had a porosity of 49%, the outer shell portion had a porosity of 27%, and the total porosity was 63%.

<Example 1>
A mixed solution comprising 33.5 parts by weight of a methyl silicate oligomer (trade name: MS-51, manufactured by Tama Chemical), 430 parts by weight of IPA, and 50 parts by weight of a 0.1N nitric acid aqueous solution as a matrix forming material was stirred at 20 ° C. for 24 hours. After 128 parts by weight of the mesoporous silica particle IPA dispersion (SiO ₂ weight conversion concentration 8.7%) of Production Example 1 was mixed with this mixed liquid, it was further diluted with IPA, so that the total solid content concentration was 1% by weight and the weight ratio. (Mesoporous silica particle SiO ₂ weight / matrix forming material solid content weight (SiO ₂ weight)) is 40/60, mesoporous silica particle SiO ₂ weight equivalent concentration is 0.4% by weight, matrix forming material solid content A coating composition having a concentration of 0.6% by weight was obtained.

  The above coating composition was spin-coated with a spin coater (manufactured by Able) on a glass slide substrate (trade name: S-1111, refractive index 1.52, manufactured by Matsunami) and silicon substrate (manufactured by Niraco) washed with acetone. (1000 rpm, 30 seconds), and then dried at 120 ° C. for 5 minutes to prepare a coating film in which hollow mesoporous silica particles are 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>
The mesoporous silica particle IPA dispersion of Production Example 2 was used instead of the mesoporous silica particle IPA dispersion of Production Example 1, and the weight ratio (SiO ₂ weight of mesoporous silica particles / solid content weight of matrix forming material (SiO ₂ weight)). Resin composition in the same manner as in Example 1, except that the mesoporous silica particles have a SiO ₂ weight equivalent concentration of 0.3 wt% and the solid content concentration of the matrix forming material is 0.7 wt%. And a coating film was prepared.

<Example 4>
The mesoporous silica particle IPA dispersion of Production Example 2 was used instead of the mesoporous silica particle IPA dispersion of Production Example 1, and the weight ratio (SiO ₂ weight of mesoporous silica particles / solid content weight of matrix forming material (SiO ₂ weight)). 20/80, the resin composition in the same manner as in Example 1 except that the mesoporous silica particles had a SiO ₂ weight equivalent concentration of 0.2 wt% and the matrix forming material had a solid content concentration of 0.8 wt%. A coating film was prepared.

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

From the TEM observation, it was confirmed that the silica powder obtained by drying the commercially available silica at 100 ° C. for 1 day was spherical particles having an average primary particle diameter of 20 nm. The silica powder had a BET specific surface area of 250 m ² / g, an average pore size of 4.4 nm, and had a broad pore size distribution. The total porosity of the silica powder was 25%.

<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.

  As shown in Table 1 above, the coating films of Examples 1 to 4 containing the mesoporous silica particles of Production Example 1 or 2 have a lower refractive index and reflectance than the coating film of Comparative Example 1 or 2.

  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 having an outer shell portion having a mesoporous structure containing silica and having an average primary particle diameter of 10 to 200 nm.   The coating composition according to claim 1, wherein the mesoporous silica particles have an average pore diameter of 1.0 to 2.5 nm in the outer shell portion.   The coating film produced using the coating composition of Claim 1 or 2.   A coating film comprising a matrix, a hollow mesoporous silica particle having an average primary particle diameter of 10 to 200 nm including an outer shell portion having a mesoporous structure containing silica and a hollow portion existing inside the outer shell portion. .   The coating film of Claim 3 or 4 whose film thickness is 10-300 nm.   The antireflection film containing the coating film in any one of Claims 3-5. It is a manufacturing method of the coating composition of Claim 1 or 2, Comprising:
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. A step (I) of adding a silica source to form a composite silica particle containing silica and a mesoporous structure having a mesopore structure and the emulsified droplets inside the outer shell,
Removing the surfactant and the emulsified droplets from the composite silica particles (II);
A method for producing a coating composition, comprising: 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 7, wherein the organic solvent dispersion containing mesoporous silica particles is obtained by performing the concentration and the concentration in this order.