JP6582414B2 - Porous optical thin film coating liquid and method for producing the same - Google Patents

Description

The present invention relates to an optical thin-film coating liquid of suitable porous manufacture of a porous membrane as an ultra low refractive optical thin film to be applied to various optical elements and an image display device or the like and a method of manufacturing the same.

  Optical base materials such as digital cameras, broadcast cameras, in-vehicle cameras, optical pickup devices and semiconductor devices such as objective lenses, spectacle lenses, optical reflectors, and low-pass filters are used for the purpose of improving light transmittance. A protective film is applied. Conventionally, the antireflection film has been formed by a physical method such as vacuum deposition, sputtering, or ion plating. However, these film-forming methods have the disadvantage that they are expensive because they require vacuum equipment.

The single-layer antireflection film is designed to have a refractive index smaller than that of the base material and larger than that of an incident medium such as air. It is said that a refractive index of 1.2 to 1.25 is ideal for an antireflection film of a lens made of glass having a refractive index of about 1.5. However, since there is no substance having such an ideal refractive index in an antireflection film that can be formed by a physical method, MgF ₂ having a refractive index of 1.38 is widely used as an antireflection film material.

  However, in recent years, optical devices using light beams in a wide wavelength range have been manufactured, and an antireflection film having excellent optical characteristics in a wide wavelength range has been desired. Moreover, since an optical element is often composed of a plurality of lens groups, a multilayer antireflection film is generally provided in order to prevent a loss of transmitted light amount due to reflection on each lens surface. The multilayer antireflection film is designed so that the reflected light generated at each interface and the light incident on each layer cancel each other out by interference. The antireflection film having a multilayer structure has a disadvantage that the cost is higher.

  Therefore, a method for forming an antireflection film by a wet method using a sol-gel method using dehydration polycondensation (dip coating method, roll coating method, spin coating method, flow coating method, spray coating method, etc.) is proposed. Has been.

  For example, Japanese Patent Laid-Open No. 2006-215542 (Patent Document 1) includes a dense layer and a silica airgel porous layer that are sequentially formed on the surface of a base material, and the refractive index decreases in order from the base material to the silica airgel porous layer. Proposed anti-reflection coating. This silica airgel porous layer comprises (i) a sol or gel silicon oxide reacted with an organic modifier to form an organic modified sol or an organic modified gel, and (ii) the organic modified sol or the organic modified gel as a sol The resulting organically modified silica gel layer is subjected to a springback phenomenon to form an organically modified silica airgel layer, and (iii) the resulting organically modified silica airgel layer is heat treated to form an organically modified silica airgel layer. It is formed by removing the modifying group.

  The silica airgel porous layer has a refractive index as small as about 1.20, and the antireflection film having it has excellent antireflection characteristics in a wide wavelength range. And since it can produce by the sol-gel method, it is excellent also in cost performance. However, the mechanical strength was weak, the adhesion to the substrate was weak, and the scratch resistance was not sufficient.

  JP-A-2009-258711 (Patent Document 2) discloses a low refractive index having excellent mechanical strength and scratch resistance by applying a porous film made of silica aerogel to a substrate surface and drying it, followed by alkali treatment. A film is produced. However, the formation of the porous film and the hardening process of the film need to be performed in two stages of film formation and alkali treatment, and there are problems in cost performance and film formation stability in multiple stages.

JP 2006-215542 A JP 2009-258711 A

Accordingly, the present invention purposes, by adding a reagent for alkali treatment to the dispersion, excellent film formation and and storage stability alkali treatment can be performed at the same time a porous optical thin film to provide a suitable porous optical thin film coating liquid of the electrolyte and a manufacturing method thereof in the manufacture.

As a result of intense research in view of the above object, the present inventors, in the coating solution used for producing the porous optical thin film, a ketone organic modified silica particles are dispersed in a dispersion medium, and an alkali metal alkoxide By adding, it is possible to simultaneously perform film formation and alkali treatment in the formation of the porous film and the hardening process of the film, and it has excellent storage stability and handling properties, leveling properties and uniform formation during film formation. The inventors have found that a coating solution having excellent film properties can be obtained, and have arrived at the present invention.

That is, the porous optical thin film coating liquid of the present invention is a dispersion in which the organic modified silica particles are dispersed in a ketone dispersion medium, and characterized in that the alkali metal alkoxide is added To do.

The silica nanoparticles are represented by the following formula (1)
M _p SiCl _q ・ ・ ・ (1)
(Where p is an integer of 1 to 3, q is an integer of 1 to 3 that satisfies q = 4-p, M is hydrogen, an alkyl group, or an aryl group, and the alkyl group is substituted or unsubstituted. The aryl group is substituted or unsubstituted and has 6 to 18 carbon atoms), and is preferably organically modified with monohalosilane.

  The alkali metal alkoxide is preferably an alkali metal alkoxide having 1 to 3 carbon atoms.

The ketone solvent is preferably at least one selected from the group consisting of methyl ethyl ketone and 4-methyl-2-pentanone.

The silica solid content concentration of the dispersion is preferably 0.1 to 7.0% by mass, and the alkali metal alkoxide / silica nanoparticles are preferably 5.0 × 10 ^{−3 to} 2.0 by mass ratio. The median diameter of the silica nanoparticles is preferably 10 to 100 nm.

In the method of the present invention for producing the coating solution, a silica wet gel is produced by hydrolytic polymerization of alkoxysilane, and the silica wet gel is ultrasonically dispersed in the ketone dispersion medium to disperse silica nanoparticles. A liquid is produced, and the alkali metal alkoxide is added to the dispersion. An organic modified silica wet gel is prepared by reacting with an organic modifier before ultrasonically dispersing the silica wet gel, and the organic modified silica wet gel is ultrasonically dispersed in the dispersion medium. It is preferable to produce a dispersion of the prepared silica nanoparticles.

  The alkoxysilane is at least one selected from at least one first alkoxysilane selected from tetrafunctional alkoxysilanes and oligomers of dimer to pentamer and trifunctional second alkoxysilanes. Preferably there is.

  The second alkoxysilane preferably contains at least one functional group selected from a 3-methacryloxypropyl group, a 3-glycidoxypropyl group, and a vinyl group, and the first alkoxysilane and the second alkoxysilane The mixing ratio of alkoxysilane is preferably 1: 1 to 10: 1 in terms of molar ratio.

  Prior to organic modification of the silica nanoparticles, the solvent of the silica wet gel is preferably replaced with at least one selected from n-hexane and 4-methyl-2-pentanone.

  The ultrasonic dispersion is preferably performed under conditions of oscillation frequency: 10 to 30 kHz, rated output: 50 to 1200 W, and ultrasonic treatment time: 5 to 180 minutes.

The coating liquid of the present invention in which silica nanoparticles are dispersed in a ketone-based dispersion medium and an alkali metal alkoxide is added performs film formation and alkali treatment simultaneously in forming a porous film and hardening the film. it can be excellent in storage stability, and handling properties during film formation, excellent in leveling property and uniformity film formability.

3 is a photograph showing the coating liquids of Example 1 and Example 3.

[1] Method for Producing Coating Liquid A method for producing a coating liquid according to an embodiment of the present invention comprises producing a silica wet gel by hydrolytic polymerization of an alkoxysilane, and the silica wet gel in a ketone-based dispersion medium. A dispersion of organically modified silica nanoparticles is produced by ultrasonic dispersion, and an alkali metal alkoxide is added to the dispersion. An organic modified silica wet gel is prepared by reacting with an organic modifier before ultrasonically dispersing the silica wet gel, and the organic modified silica wet gel is ultrasonically dispersed in the dispersion medium. You may produce | generate the dispersion liquid of the made silica nanoparticle.

(1) Preparation of silica wet gel
(a) Raw material
(a-1) Alkoxysilane Alkoxysilane may be either a monomer or an oligomer, but at least one first alkoxysilane selected from a tetrafunctional alkoxysilane and a dimer to pentamer oligomer and a trifunctional first silane. It is preferably at least one selected from two alkoxysilanes. By using an alkoxysilane having three or more alkoxyl groups or a mixture thereof as a starting material, a silica airgel film having excellent uniformity can be obtained.

  The tetrafunctional alkoxysilane includes, for example, an alkoxy group having 1 to 6 carbon atoms such as methoxy, ethoxy, normal propoxy, isopropoxy, normal butoxy, isobutoxy, secondary butoxy, tertiary butoxy, pentyloxy, hexyloxy and the like. Is preferred. Each alkoxy group may be the same or different. Specific examples of the tetrafunctional alkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. The alkoxysilane oligomer is obtained by hydrolysis and polycondensation of an alkoxysilane monomer.

  The trifunctional second alkoxysilane preferably contains at least one functional group selected from a 3-methacryloxypropyl group, a 3-glycidoxypropyl group, and a vinyl group. Examples of the alkoxy group include alkoxy groups having 1 to 6 carbon atoms such as methoxy, ethoxy, normal propoxy, isopropoxy, normal butoxy, isobutoxy, secondary butoxy, tertiary butoxy, pentyloxy, hexyloxy and the like. Each alkoxy group may be the same or different. Specific examples of the second alkoxysilane include vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- Examples thereof include glycidoxypropyltriethoxysilane.

  The mixing ratio of the first alkoxysilane and the second alkoxysilane is preferably 1: 1 to 10: 1 in molar ratio. Within this range, the hydrolysis polycondensation reaction of alkoxysilane proceeds uniformly, it is easy to form a silica skeleton, organically modified silica nanoparticles with excellent particle size and excellent dispersibility can be produced, and excellent film formation A silica airgel film having good properties and film thickness uniformity is obtained. The above range is more preferably 3: 1 to 6: 1.

(a-2) Reaction solvent for silica synthesis reaction solution The reaction solvent for the silica synthesis reaction solution is preferably composed of water and alcohol. As the alcohol, methanol, ethanol, n-propyl alcohol, and i-propyl alcohol are preferable, and ethanol is particularly preferable. The water / alcohol molar ratio of the solvent is preferably 0.01-2. If the water / alcohol molar ratio is more than 2, the hydrolysis reaction proceeds too quickly. When the water / alcohol molar ratio is less than 0.01, the alkoxysilane is not sufficiently hydrolyzed and the formation of the silica skeleton hardly occurs.

(a-3) Catalyst It is preferable to add an aqueous solution obtained by adding a catalyst for hydrolysis reaction to an alcohol solution of alkoxysilane. By adding an appropriate catalyst, the hydrolysis reaction of alkoxysilane can be promoted. The catalyst may be acidic or basic, but basic is preferred. Acidic catalysts include hydrochloric acid, nitric acid and acetic acid. Basic catalysts include ammonia, amines, NaOH and KOH. Preferred amines include alcohol amines and alkyl amines (for example, methylamine, dimethylamine, trimethylamine, n-butylamine and n-propylamine).

(b) Preparation of silica wet gel Mix and dissolve alkoxy silane, alcohol and water with added catalyst. The alcohol solvent / alkoxysilane molar ratio is preferably 3 to 200. If the molar ratio is less than 3, the alkoxysilane is too difficult to dissolve, and the degree of polymerization of the alkoxysilane becomes too high. When the molar ratio is more than 200, the degree of polymerization of alkoxysilane becomes too low and it becomes difficult to form a wet gel. The catalyst / alkoxysilane molar ratio is preferably 1 × 10 ⁻⁵ to 1 and more preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ . When the molar ratio is less than 1 × 10 ⁻⁵ , the alkoxysilane is not sufficiently hydrolyzed. Even if the molar ratio exceeds 1, the catalytic effect does not increase. The water / alkoxysilane molar ratio is preferably 0.5-20, and more preferably 5-15.

  The solution containing alkoxysilane is aged for 1 to 168 hours. Specifically, the solution is allowed to stand at 15 to 60 ° C. or slowly stirred. After adding alcohol to alkoxysilane and stirring at 15 to 30 ° C. for 5 to 30 minutes, water containing a basic catalyst is added and stirred at 15 to 30 ° C. for 5 to 30 minutes, and at 20 to 30 ° C. for 12 to 12 minutes. It is particularly preferable to stand for 72 hours. Gelation proceeds by aging, and a silica wet gel is formed. After conducting the silica synthesis reaction, it is preferable to wash the silica wet gel with an alcohol such as ethanol to remove unreacted substances and the like.

(2) Solvent replacement of silica wet gel The solvent of the silica wet gel may be replaced with at least one organic solvent selected from n-hexane and 4-methyl-2-pentanone. The solvent incorporated in the gel can be replaced by repeating the operation of pouring the solvent to be replaced into the container containing the gel, shaking, and then decanting. By replacing the silica wet gel solvent with the organic solvent before the organic modification of the silica nanoparticles, the dispersibility of the organic modifier into the silica wet gel is improved and the organic modification reaction of the silica wet gel is sufficiently uniform. Can proceed to.

(3) Organic Modification of Silica Wet Gel In order to organically modify the silica nanoparticles, an organic modifier solution may be added to the silica wet gel. By adding a solution of an organic modifier to the silica wet gel so that the silica wet gel and the organic modifier solution are in sufficient contact with each other, hydrophilic groups such as hydroxyl groups at the ends of the silica nanoparticles constituting the silica wet gel are formed. Substitutes a hydrophobic organic group. It is preferable to add an organic modifier solution to a gel having a large surface area of the wet gel, such as by cutting to about 5 to 30 mm square. By increasing the surface area of the silica wet gel in advance, the reaction with the organic modifier can be efficiently advanced.

The organic modifier for modifying the surface of silica nanoparticles is represented by the following formula (1):
M _p SiCl _q・ ・ ・ (1)
(Where p is an integer of 1 to 3, q is an integer of 1 to 3 that satisfies q = 4-p, M is hydrogen, an alkyl group, or an aryl group, and the alkyl group is substituted or unsubstituted. The aryl group is substituted or unsubstituted and has 6 to 18 carbon atoms.), And a mixture thereof.

  Specific examples of organic modifiers include trimethylchlorosilane, trimethylbromosilane, triethylchlorosilane, (3, 3, 3, -trifluoropropyl) dimethylchlorosilane, ethyldimethylchlorosilane, vinyldimethylchlorosilane, vinyldimethylfluorosilane, allyldimethylchlorosilane, n -Propyldimethylchlorosilane, 3-chloropropyldimethylchlorosilane, 4-chlorobutyldimethylchlorosilane, chloromethyldimethylchlorosilane, 3-cyanopropyldimethylchlorosilane, cyclohexyldimethylchlorosilane, n-decyldimethylchlorosilane, di-t-butylchlorosilane, di- t-butylmethylchlorosilane, diisopropylchlorosilane, diphenylchlorosilane, diphenylmethylchlorosilane, triphenylchlorosilane, Enethyldimethylchlorosilane, 3-phenoxypropyldimethylchlorosilane, phenyldimethylchlorosilane, diphenyl (methyl) chlorosilane, diphenyl (methyl) bromosilane, phenylmethylchlorosilane, vinylphenylmethylchlorosilane, t-butyldiphenylchlorosilane, dimethyl (1-naphthyl) Examples include bromosilane. The organic modifier is preferably a monohalosilane, particularly preferably an alkylmonohalosilane. Specific examples include triethylchlorosilane and trimethylchlorosilane.

  Although depending on the type and concentration of the organic modifier, it is generally preferred that the organic modification reaction proceed at 10 to 40 ° C. If it is less than 10 ° C., the organic modifier is too difficult to react with the silica nanoparticles. If it exceeds 40 ° C, the organic modifier reacts easily with other than silica. During the reaction, it is preferable to stir the solution so that there is no distribution in the temperature and concentration of the solution. For example, when the organic modifier solution is a trimethylchlorosilane 4-methyl-2-pentanone solution, the silanol group is sufficiently silyl-modified when held at 10 to 40 ° C. for about 10 to 40 hours (for example, 30 hours). The modification rate is generally about 10 to 30%.

(4) Ultrasonic treatment By ultrasonic treatment, a silica wet gel is dispersed in a dispersion medium to form a dispersion. It is considered that the gel aggregated by an electric force or van der Waals force is dissociated by ultrasonic treatment, or the covalent bond between the metal and oxygen is broken to be in a dispersed state. The frequency of the ultrasonic wave to be irradiated is preferably 10 to 30 kHz. The output is preferably 50 to 1200 W.

  The ultrasonic treatment time is preferably 5 to 180 minutes. The longer the ultrasonic wave is irradiated, the finer the silica wet gel clusters are, and the less the aggregation is. For this reason, colloidal particles of organically modified silica are close to monodisperse in a silica wet gel obtained by ultrasonic treatment. When the ultrasonic treatment time is less than 5 minutes, the colloidal particles are not sufficiently dissociated. Even when the sonication time is longer than 120 minutes, the dissociation state of the organically modified silica colloidal particles hardly changes.

The dispersion medium is preferably an organic solvent that is excellent in handling property, leveling property, and uniform film forming property during film formation and can disperse organically modified silica nanoparticles. As specific examples, ketone solvents include methyl ethyl ketone and 4-methyl-2. - pentanone and the like. The dispersion medium may be the same type as the organic solvent used for the solvent replacement of the silica wet gel or a different type.

The ketone solvent has an excellent affinity for organically modified silica . In the ketone solvent, the organically modified silica is in a good dispersion state. The substituent that the ketone has may be an alkyl group or an aryl group. Preferred alkyl groups are those having about 1 to 5 carbon atoms.

  The ketone solvent preferably has a boiling point of 60 ° C. or higher. Ketones having a boiling point of less than 60 ° C. are too volatile during the ultrasonic irradiation process described below. For example, when acetone is used as a dispersion medium, a large amount of acetone volatilizes during ultrasonic irradiation, so that it is difficult to adjust the concentration of the dispersion. In addition, there is also a problem that sufficient film formation time cannot be obtained because the film is volatilized too quickly in the film formation process.

  Of the ketone solvents, preferred are asymmetric ketones having different substituents on both sides of the carbonyl group. Since the asymmetric ketone has a large polarity, it has a particularly excellent affinity for the organically modified silica.

(5) Addition of alkali metal alkoxide An alkali metal alkoxide is added to a dispersion in which organically modified silica nanoparticles are dispersed in a dispersion medium. The addition of the alkali metal alkoxide is preferably performed using a solution of the alkali metal alkoxide. Alkali metal alkoxide is used as an alkali used for alkali treatment. Since the alkali used for the alkali treatment is an alkali metal alkoxide having an alkoxyl group in the same manner as the alkoxysilane starting material of the silica nanoporous film, the conditions necessary for film formation and alkali treatment become relatively close. Sometimes it becomes possible to carry out the alkali treatment simultaneously. Further, it is easy to clean the residue after film formation and alkali treatment.

  The alkali metal alkoxide is preferably an alkali metal alkoxide having 1 to 3 carbon atoms. Specifically, lithium methoxide, lithium ethoxide, lithium isopropoxide, potassium methoxide, potassium ethoxide, potassium isopropoxide, sodium methoxide, sodium ethoxide, sodium isopropoxide and the like can be mentioned. Particularly preferred alkali metal alkoxides are sodium methoxide and sodium ethoxide. As the alkoxyl group of the alkali metal alkoxide, it is preferable to use the same type of alkoxysilane as the starting material of the silica nanoparticles. Thereby, the reactivity of the unreacted silanol group by the alkali treatment during film formation is improved.

[2] Coating Liquid The porous optical thin film coating liquid of the present invention is a dispersion liquid in which organically modified silica nanoparticles are dispersed in a ketone-based dispersion medium, and an alkali metal alkoxide is added thereto. Since the alkali metal alkoxide is added to the coating liquid of the present invention, the alkali treatment can be performed simultaneously with the film formation. Since the unreacted silanol groups are condensed by the alkali treatment and the Si—O—Si bond is increased, a silica airgel film having excellent scratch resistance and small change with time can be formed. When a ketone-based dispersion medium is used as the dispersion medium, excellent handling properties, leveling properties, and uniform film formation properties can be obtained during film formation.

  Silica nanoparticles of inorganic materials are organically modified to modify the surface, thereby improving dispersibility in a dispersion medium composed of an organic solvent, and reaction of silanol groups with an alkali treatment reagent of alkali metal alkoxide in the dispersion medium. Can be suppressed, and the coating liquid can be delayed in gelation. Therefore, a coating solution having excellent storage stability is obtained, and stable mass production of a silica airgel film using such a coating solution is possible.

  The median diameter of the silica nanoparticles (when the silica nanoparticles are organically modified, the median diameter of the organically modified silica nanoparticles) is preferably 10 to 100 nm. Here, the median diameter is the particle diameter at which the cumulative value becomes 50% when the cumulative curve is obtained with the total volume of the aggregate of particles as 100%, and is obtained by the dynamic light scattering method. When the median diameter of the silica nanoparticles is within this range, a silica airgel film having a substantially smooth surface can be obtained. If the median diameter of silica nanoparticles is less than 10 nm, the particles tend to agglomerate with each other, resulting in poor dispersibility in the dispersion medium.

  The silica solid content concentration of the dispersion is preferably 0.1 to 7.0% by mass. If the silica solid content concentration is within this range, a thin layer having a uniform film thickness can be formed while maintaining the dispersibility of the silica nanoparticles. The silica solid content concentration of the dispersion is more preferably 2.0 to 5.0% by mass.

It is preferable that the alkali metal alkoxide / silica nanoparticles have a mass ratio of 5.0 × 10 ^{−3 to} 2.0. When the mass ratio is within this range, high reactivity of unreacted silanol groups by alkali treatment during film formation can be obtained. More preferably, the alkali metal alkoxide / silica nanoparticles have a mass ratio of 1.0 × 10 ^{−2 to} 5.0 × 10 ⁻¹ .

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
(1-1) Preparation of silica wet gel To a mixture of 5.90 g of methyl silicate 51 (average tetramer of tetramethoxysilane) manufactured by Fuso Chemical Co., Ltd. and 50.55 g of methanol (special grade) manufactured by Wako Pure Chemical Industries, Ltd. 3.20 g of 0.1N ammonia water prepared from 28% ammonia (special grade) manufactured by Wako Pure Chemical Industries, Ltd. was added and stirred for 10 minutes. Thereafter, the mixture was allowed to stand at room temperature for 3 days to accelerate the hydrolysis polycondensation reaction and age.

(1-2) Solvent replacement of silica wet gel The silica wet gel prepared in step (1-1) was cut into a size of about 2 cm square, and the resulting product was placed in a crystal dish and ethanol (special grade) manufactured by Wako Pure Chemical Industries, Ltd. ) And stirred slowly at 300 rpm for 1 day using a magnetic stirrer to replace the solvent in the silica wet gel with ethanol. By decantation after substitution, a silica wet gel substituted with ethanol solvent was obtained. Ethanol used for solvent replacement was added at a rate of 100 ml per 20 g of silica wet gel.

  4-methyl-2-pentanone (special grade) manufactured by Wako Pure Chemical Industries, Ltd. was added to the silica wet gel solvent-substituted with ethanol, and stirred gently at 300 rpm for 1 day using a magnetic stirrer. The solvent in it was replaced with 4-methyl-2-pentanone. By decantation after substitution, a silica wet gel substituted with solvent by 4-methyl-2-pentanone was obtained. 4-methyl-2-pentanone used for solvent substitution was added at a rate of 100 ml per 20 g of silica wet gel.

(1-3) Organic modification of silica wet gel 60 g of the silica wet gel prepared in step (1-2) was placed in a crystal dish, and trimethylchlorosilane manufactured by Tokyo Chemical Industry Co., Ltd. and 4-manufactured by Wako Pure Chemical Industries, Ltd. A liquid mixture consisting of methyl-2-pentanone (special grade) was added, and the mixture was gently stirred at 300 rpm for 1 day using a magnetic stirrer to organically modify the ends of the silica nanoparticles in the silica wet gel. Decantation after organic modification gave an organically modified silica wet gel. A mixed solution of trimethylchlorosilane and 4-methyl-2-pentanone was prepared by mixing at a volume ratio of 5 ml: 95 ml. For organic modification of the silica wet gel, a mixed solution of trimethylchlorosilane and 4-methyl-2-pentanone was added at a ratio of 100 ml to 20 g of the silica wet gel.

(1-4) Washing of organically modified silica wet gel Take 60 g of the silica wet gel prepared in step (1-3) in a crystal dish and add 4-methyl-2-pentanone (special grade) manufactured by Wako Pure Chemical Industries, Ltd. The organically modified silica wet gel was washed by adding and stirring gently at 300 rpm for 1 day using a magnetic stirrer. Then, the organic modifier silica wet gel from which the organic modifier and by-products were removed was obtained by decantation. 4-Methyl-2-pentanone used for washing was added at a ratio of 100 ml to 20 g of silica wet gel.

(1-5) Preparation of Ultrasonic Dispersion of Organic Modified Silica Wet Gel Take organic modified silica wet gel prepared in step (1-4) in a 100 ml disposable beaker and add 4-methyl- Add 2-pentanone (special grade), and stir at 700 rpm using a magnetic stirrer for 2 hours with an ultrasonic dispersion device (rated output 600 W, oscillation frequency 19.5 KHz ± 1 KHz) from Nippon Seiki Seisakusho Co., Ltd. did. The concentration of the dispersion was adjusted to 3.5% by mass as the silica solid content concentration. The silica solid content concentration of the dispersion was prepared from the solid content calculated from the mass before and after drying when the organically modified silica wet gel was dried in a 120 ° C. blast constant temperature thermostat (inert oven) for 2 hours.

(1-6) Addition of alkali metal alkoxide to organic-modified silica nanoparticle dispersion 3 ml of ultrasonic dispersion (organic-modified silica nanoparticle dispersion) of organic-modified silica wet gel prepared in step (1-5) and Wako Pure 0.9 ml of a 0.35 mass% sodium methoxide methanol solution prepared from 28 mass% sodium methoxide methanol solution manufactured by Yakuhin Co., Ltd. was mixed to prepare a one-component silica airgel membrane production coating solution.

Example 2
(2-1) Preparation of silica wet gel Methyl silicate 51 (average tetramer of tetramethoxysilane) 5.90 g manufactured by Fuso Chemical Industry Co., Ltd. Silaace S710 (3-methacryloxypropyltrimethoxysilane) 1.00 manufactured by Chisso Corporation and a mixture of 50.55 g of methanol (special grade) manufactured by Wako Pure Chemical Industries, Ltd. and 3.20 g of 0.15 N aqueous ammonia prepared from 28% ammonia (special grade) manufactured by Wako Pure Chemical Industries, Ltd. were added and stirred for 10 minutes. . Thereafter, the mixture was allowed to stand at room temperature for 3 days to accelerate the hydrolysis polycondensation reaction and age.

  Perform steps (2-2) to (2-6) in the same manner as steps (1-2) to (1-6) in Example 1 except that the silica wet gel prepared in step (2-1) was used. A one-part coating solution for producing a silica airgel film was prepared.

Example 3
Steps (3-1) and (3-2) were performed in the same manner as steps (1-1) and (1-2) in Example 1. Except for using the silica wet gel prepared in step (3-2) in steps (3-5) and (3-6) without performing organic modification step (1-3) and step (1-4). It carried out similarly to the process (1-5) and (1-6) of Example 1, and produced the coating liquid for manufacture of a one-component silica airgel film.

Example 4
Step (4-1) was performed in the same manner as Step (2-1) in Example 2, and Steps (4-2), (4-5), and (4-6) were produced in Step (4-1). Except that the silica wet gel was used, the same procedure as in steps (3-2), (3-5) and (3-6) of Example 3 was carried out to prepare a one-component silica airgel film production coating solution. .

Storage stability test of coating solution Leave each of Examples 1 to 4 at a temperature of 25 ± 5 ° C and a relative humidity of 40 ± 20%, and the amount of time until fluidity is lost. Confirmed by tilting. The coating liquid that did not lose fluidity kept the liquid level horizontal, but the coating liquid that gelled due to loss of fluidity did not move even when the container was tilted. The obtained results are shown in Table 1.

  As can be seen from Table 1, the coating liquids of Examples 1 and 2 were able to maintain the viscosity for 2 days, and Examples 3 and 4 were able to maintain the viscosity for about 1 hour. The coating liquids of Examples 1 and 2 were superior in storage stability compared to Examples 3 and 4. Moreover, the coating liquid of Example 1 and Example 3 which was left to stand on the said conditions for 1 day is shown in FIG. As shown in FIG. 1, the coating liquid of Example 1 maintained fluidity, but it can be seen that the coating liquid of Example 3 lost fluidity.

Claims (15)

Organically modified silica nanoparticles a dispersion dispersed in a ketone dispersion medium, a porous optical thin film coating liquid, wherein the alkali metal alkoxide is added. 2. The coating solution for optical thin film according to claim 1, wherein the silica nanoparticles are represented by the following formula (1):
M _p SiCl _q ... (1)
(Where p is an integer of 1 to 3, q is an integer of 1 to 3 that satisfies q = 4-p, M is hydrogen, an alkyl group, or an aryl group, and the alkyl group is substituted or unsubstituted. And an aryl group is substituted or unsubstituted and has 6 to 18 carbon atoms), and is organically modified. The optical thin film coating liquid according to claim 1 or 2, wherein the silica nanoparticles coating liquid for an optical thin film characterized in that it is an organic modified by monohalosilane. The optical thin film coating liquid according to claim 1, wherein the alkali metal alkoxide coating solution for optical thin film characterized in that an alkali metal alkoxide having 1 to 3 carbon atoms. The optical thin film coating liquid according to any one of claims 1-4, wherein the ketone-based dispersion medium, and wherein the at least one selected from the group consisting of methyl ethyl ketone and 4-methyl-2-pentanone Coating solution for optical thin film . The optical thin film coating liquid according to any one of claims 1 to 5 coating solution for optical thin film silica solid concentration of the dispersion is characterized in that it is a 0.1 to 7.0 mass%. The optical thin film coating liquid according to any one of claims 1 to 6 coating for optical thin film, wherein the alkali metal alkoxide / the silica particles is 5.0 × 10 ^-3 to 2.0 in mass ratio liquid. The optical thin film coating liquid according to any one of claims 1 to 7 coating liquid for an optical film, wherein the median diameter of the silica particles is 10 to 100 nm. It is a method of manufacturing the coating liquid for optical thin films in any one of Claims 1-8 , Comprising: A silica wet gel is produced | generated by hydrolyzing an alkoxysilane, The said silica wet gel is made into the said ketone-type dispersion | distribution. A method for producing a coating solution for an optical thin film , which comprises ultrasonically dispersing in a medium to produce a dispersion of silica nanoparticles, and adding the alkali metal alkoxide to the dispersion. The method for producing a coating liquid for an optical thin film according to claim 9 , wherein an organic modified silica wet gel is produced by reacting the silica wet gel with an organic modifier before ultrasonically dispersing the silica wet gel. A method for producing a coating liquid for an optical thin film , wherein a dispersion of organically modified silica nanoparticles is produced by ultrasonically dispersing a wet gel in the ketone dispersion medium. The method for producing a coating liquid for an optical thin film according to claim 9 or 10 , wherein the alkoxysilane is at least one first alkoxy selected from tetrafunctional alkoxysilanes and oligomers of dimers to pentamers thereof. A method for producing a coating solution for an optical thin film, which is at least one selected from silane and a trifunctional second alkoxysilane. 12. The method for producing an optical thin film coating solution according to claim 11 , wherein the second alkoxysilane is at least one functional group selected from a 3-methacryloxypropyl group, a 3-glycidoxypropyl group, and a vinyl group. The manufacturing method of the coating liquid for optical thin films characterized by including. 13. The method for producing an optical thin film coating liquid according to claim 11 or 12 , wherein a mixing ratio of the first alkoxysilane and the second alkoxysilane is 1: 1 to 10: 1 in terms of a molar ratio. A method for producing a coating liquid for an optical thin film . In the method for manufacturing an optical thin film coating liquid according to claim 10-13, prior to organic modification of the silica particles are selected solvent of the wet silica gel from n- hexane and 4-methyl-2-pentanone A method for producing a coating liquid for an optical thin film , characterized by substituting at least one kind. In the method for manufacturing an optical thin film coating liquid according to claim 9-14, wherein the ultrasonic dispersing oscillation frequency: 10 to 30 kHz, rated output: 50 to 1200 W and sonication Time: 5 to 180 minutes The manufacturing method of the coating liquid for optical thin films characterized by performing on conditions.