Niobic acid compound sol, sol-coated film and film-supporting substrate

Abstract

[Problem] To provide a niobic acid compound sol that can provide a film in which generation of interference fringes is suppressed. [Solution] This sol contains a niobic acid compound and at least one compound selected from the group consisting of oxides of metals selected from zirconium, tin, zinc, and cerium and fluorides of metals selected from magnesium and calcium.

Description

[Technical field]

[0001] The present invention relates to a niobate compound sol, and more particularly to a niobate compound sol, a sol-coated film, and a film-supporting substrate that can provide a film in which the occurrence of interference fringes is suppressed. [Background technology]

[0002] Niobate compounds have attracted attention as functional thin film materials due to their high refractive index and high optical transparency, and their application to optoelectronic materials, surface protection materials, anti-reflection materials, and refractive index adjustment materials is being considered. Methods for producing thin films made of niobate compounds can be broadly divided into two types: dry methods and wet methods. Dry methods include sputtering, ion plating, atomic layer deposition (ALD), and chemical vapor deposition (CVD). Wet methods include the sol-gel method and metalorganic deposition (MOD) method.

[0003] While the dry method generally requires large-scale equipment such as a vacuum device, the wet method has the advantage that it does not require such equipment and can form thin films at low cost. In addition, it is generally said that the wet method is superior to the dry method for forming thin films over a large area.

[0004] When forming a niobium compound thin film by a wet method, niobium alkoxide or niobium sol is generally used, but niobium alkoxide is very easily decomposed and difficult to handle. Therefore, various niobium sols have been proposed. As examples, peroxyniobic acid sol using hydrogen peroxide (Patent Document 1, etc.), niobium sol stabilized with oxalic acid or citric acid (Patent Document 2, etc.), sol produced by electrolysis of niobic acid compound (Patent Document 3, etc.), ammonium niobate sol obtained by reacting an aqueous solution of a niobium compound dissolved in hydrofluoric acid or the like with an aqueous ammonia solution (Patent Document 4, etc.), etc. have been proposed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP2008-81378A [Patent Document 2] JP 2005-200235 A [Patent Document 3] Japanese Patent Application Publication No. 5-222562 [Patent Document 4] JP 2011-190115 A Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned thin film from the sol is usually obtained by applying the sol to the surface of a substrate such as glass and heating and drying the applied film. However, the obtained thin film may have interference fringes, and there is a problem in the film quality such as aesthetics.

[0007] Therefore, the object of the present invention is to provide a niobic acid compound-based sol that can obtain a film with suppressed generation of interference fringes. Another object of the present invention is to provide a coating film of the above niobic acid compound-based sol and a film-supporting substrate using the same. [Means for solving the problem]

[0008] The present inventors have now found that by using a sol in which a specific oxide or fluoride is added to a niobic acid compound, the occurrence of interference fringes in the resulting film can be suppressed. The present invention is based on this finding.

[0009] The sol according to the present invention comprises A niobate compound; At least one compound selected from the group consisting of oxides of metals selected from zirconium, tin, zinc, and cerium, and fluorides of metals selected from magnesium and calcium; It includes.

[0010] According to another embodiment of the present invention, there is also provided a membrane containing the above sol.

[0011] Furthermore, according to another embodiment of the present invention, there is also provided a membrane-supporting substrate having the above-mentioned membrane on a surface of the substrate. Effect of the Invention

[0012] According to the present invention, by preparing a sol containing a niobic acid compound and a specific oxide or fluoride, it is possible to suppress the occurrence of interference fringes in a film obtained from the sol. The film can be applied to transparent conductive films, high dielectric constant films, insulating films, anti-reflection films, hard coat layers, photocatalytic members, etc. in semiconductor devices and optical devices. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <Niobic acid compound sol> The sol of the present invention will be described. The sol of the present invention contains a niobic acid compound and at least one specific oxide or fluoride. As the niobic acid compound sol, a known niobic acid compound sol can be used. In the present invention, the term "sol" refers to a particle dispersed in a dispersion medium, but when a film is formed using the sol, the term is defined as a concept that includes a film that is a gel containing a dispersion medium or a xerogel that does not contain a dispersion medium. In addition, the term "niobic acid compound" includes niobium oxide (Nb2O5), niobium hydroxide, and niobium polyacid.

[0014] The above-mentioned known niobic acid compound sol may cause interference fringes in the film obtained when the sol is used to form a film. It is believed that the interference fringes are due to the high refractive index of the niobic acid compound. In the present invention, the occurrence of interference fringes in the film obtained from the sol can be suppressed by adding a specific oxide or fluoride to the niobic acid compound sol while maintaining this high refractive index. The reason for this is not clear, but it is known that the niobic acid compound has a negative charge as a surface charge, and it is believed that the electric potential of the sol changes by adding a specific oxide or fluoride, which has some effect on the film characteristics.

[0015] The niobic acid compound sol used in the sol of the present invention is a dispersion medium in which fine particles mainly composed of niobic acid are dispersed. The main component in the niobic acid fine particles is niobic acid, and preferably includes amorphous niobium oxide, niobium hydroxide, niobium polyacid, etc.

[0016] It is known that ammonia is strongly bound or adsorbed to the surface of niobic acid fine particles. The sol of the present invention may contain ammonia as an optional component. The term "containing ammonia" refers to the presence or absence of ammonia (NH3) in the sol, or the presence or absence of ammonia in the sol, i.e., the presence or absence of ammonia in the sol. 4+ Preferred examples of the ammonium salt include (NH4)3Nb(O2)4 and (NH4)3Nb(O2)3F2. These compounds may be used alone or in combination of two or more.

[0017] The above-mentioned niobium acid compound sol can be produced by a conventionally known method. For example, an aqueous solution in which a niobium compound is dissolved in hydrofluoric acid or a mixed acid of hydrofluoric acid and sulfuric acid is mixed and reacted with an aqueous ammonia solution while maintaining a pH of 8 or more to obtain a dispersion containing niobium acid microparticles, and then solid-liquid separation and washing as necessary are performed to isolate the precipitate, which is the solid content, and the obtained niobium acid compound is dispersed in a dispersion medium to obtain a niobium acid compound sol.

[0018] In the present invention, the oxide added to the niobic acid compound sol is at least one metal oxide selected from zirconium, tin, zinc, and cerium. By adding at least one of zirconium oxide, tin oxide, zinc oxide, and cerium oxide to the niobic acid compound sol, interference fringes of the film obtained from the sol can be suppressed. In addition, examples of the fluoride added to the niobic acid compound sol include magnesium fluoride and calcium fluoride. These oxides and fluorides may be used in combination of two or more.

[0019] Furthermore, in the present invention, it is preferable that one or more compounds selected from the above-mentioned specific oxides or fluorides and silicon oxide are included.By simply adding silicon oxide to niobic acid compound sol, the interference fringes of the film obtained from the sol are not improved, but it was unexpected that by including silicon oxide in combination with the above-mentioned specific oxides or fluorides, a film without interference fringes can be obtained.

[0020] The amount of oxide or fluoride added to the niobic acid compound sol is preferably 0.1 parts by mass or more and 40 parts by mass or less, more preferably 1 part by mass or more and 20 parts by mass or less, and even more preferably 3 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the total amount (solid content equivalent) of the niobic acid compound and the oxide or fluoride. If the amount of oxide or fluoride is too small, the suppression of interference fringes in the film obtained from the sol may be insufficient. On the other hand, if the amount of oxide or fluoride is too large, the properties (e.g., high refractive index, etc.) unique to the film made of the niobic acid compound may be impaired. The oxide, fluoride, and silicon oxide may be added to the niobic acid compound sol in the form of a sol. In this case, the amount is the amount of solid content in the sol.

[0021] In the above-mentioned sol in which a specific oxide or fluoride is added to the niobic acid compound sol, the particle diameter of the dispersed particles (colloidal particles) dispersed in the dispersion medium is not particularly limited, but typically, the particle diameter (D 90) is 1000 nm or less, preferably 500 nm or less. If the particle size of the dispersed particles is large, the smoothness of the obtained film decreases, and the transparency of the film may be impaired due to light scattering. In addition, the particle size (D 90 The particle diameter (D) of the colloidal particles is preferably 20 nm or more. 90 If the particle diameter (D) is less than 20 nm, the stability of the sol decreases, and the adhesion and strength of the film formed from the sol to the substrate decreases. 90 ) is the volume cumulative particle size (D) at 90% cumulative volume measured by dynamic light scattering. 90 )

[0022] In addition, in the sol obtained by adding a specific oxide or fluoride to the niobic acid compound sol, the content of the dispersed particles is preferably 70% by mass or less, more preferably 50% by mass or less, as the upper limit, based on the entire sol, and is preferably 0.1% by mass or more, more preferably 1% by mass or more, as the lower limit, based on the entire sol.

[0023] The niobic acid compound sol of the present invention can use either water or an organic solvent as a dispersion medium, but from the viewpoint of the stability of the dispersed particles in the sol, water, a hydrophilic solvent, or a mixture of water and a hydrophilic solvent can be preferably used. The dispersion medium may also contain a known additive that is soluble in the dispersion medium. Examples of hydrophilic solvents include alcohols, esters, ethers, and ketones. Examples of alcohols include methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butanol, isobutyl alcohol, 2-butanol, hexanol, butyl carbitol, 1-methoxy-2-propanol, ethylene glycol, propylene glycol, glycerol, pentaerythritol, sorbitol, 2-ethoxyethanol, and 2-butoxyethanol.

[0024] Examples of the esters include formates such as methyl formate, ethyl formate, propyl formate, and isopropyl formate; acetates such as methyl acetate, ethyl acetate, propyl acetate, and isopropyl acetate; and cyclic esters such as γ-butyrolactone.

[0025] Examples of ethers include diethyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, 1,3-propanediol dimethyl ether, 1,2-butanediol dimethyl ether, 1,3-butanediol dimethyl ether, 1,4-butanediol dimethyl ether, 2,3-butanediol dimethyl ether, 1,4-dioxane, 1,3-dioxane, tetrahydrofuran, 2-methoxyethyl acetate, and 3-methoxypropyl acetate.

[0026] Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, isopropyl methyl ketone, tert-butyl methyl ketone, acetylacetone, diacetyl, and cyclohexanone.

[0027] In addition, the niobium acid compound sol of the present invention may contain known additives used as film-forming materials, and leveling agents, defoamers, thickeners, rheology adjusters, etc. can be added as necessary.

[0028] Examples of the leveling agent include fluorine-based surfactants, silicones, organically modified polysiloxanes, acrylic resins, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, allyl acrylate, allyl methacrylate, benzyl acrylate, benzyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, and the like. These may be used alone or in combination of two or more.

[0029] Examples of the defoaming agent include silicones, surfactants, polyethers, higher alcohols, glycerin higher fatty acid esters, glycerin higher fatty acid esters of acetate, glycerin higher fatty acid esters of lactate, glycerin higher fatty acid esters of citric acid, glycerin higher fatty acid esters of succinic acid, glycerin higher fatty acid esters of diacetyltartaric acid, glycerin acetate, polyglycerin higher fatty acid esters, and polyglycerin condensed ricinoleic acid esters. These may be used alone or in combination of two or more.

[0030] Examples of thickeners include polyvinyl alcohol, acrylic resins, polyethylene glycol, polyurethane, hydrated castor oil, aluminum stearate, zinc stearate, aluminum octylate, fatty acid amides, oxidized polyethylene, dextrin fatty acid esters, dibenzylidene sorbitol, vegetable oil-based polymerized oils, surface-treated calcium carbonate, organic bentonite, silica, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, sodium alginate, casein, sodium caseinate, xanthan gum, polyether urethane modified products, poly(acrylic acid-acrylic acid esters), montmorillonite, and the like. These may be used alone or in combination of two or more.

[0031] Examples of the rheology adjuster include oxidized polyolefin amites, fatty acid amides, oxidized polyolefins, urea-modified urethanes, methylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, ω,ω'-dipropyl ether diisocyanate, thiodipropyl diisocyanate, cyclohexyl-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,5-dimethyl-2,4-bis(isocyanatomethyl)benzene, 1,5-dimethyl-2,4-bis(ω-isocyanatoethyl)benzene, 1,3,5-trimethyl-2,4-bis(isocyanatomethyl)benzene, and 1,3,5-triethyl-2,4-bis(isocyanatomethyl)benzene. These may be used alone or in combination of two or more.

[0032] Even if the sol of the present invention contains the above-mentioned solvent or additive, it is preferable that the sol contains 0.1 mass% or more and 50 mass% or less of niobic acid compound, more preferably 1 mass% or more and 20 mass% or less of niobic acid compound. If the content of niobic acid compound is too small, it is difficult to form a niobic acid compound film even if it is formed. On the other hand, if the content of niobic acid compound in the sol is too large, the stability of colloidal particles may be impaired.

[0033] The sol of the present invention can be prepared by mixing niobic acid compound particles, at least one of the above-mentioned specific oxide or fluoride particles, and a dispersion medium. At that time, it may be prepared by mixing a sol of a niobic acid compound (i.e., a sol consisting of niobic acid compound particles and a dispersion medium) with a sol of a specific oxide or fluoride (i.e., a sol consisting of a specific oxide or fluoride particle and a dispersion medium), or it may be prepared by mixing niobic acid compound particles, specific oxide or fluoride particles, and a dispersion medium, and grinding the particles. It may also be prepared by adding specific oxide or fluoride particles and, if necessary, a dispersion medium to a sol of a niobic acid compound, mixing and grinding, or it may be prepared by adding niobic acid compound particles and, if necessary, a dispersion medium to a sol of a specific oxide or fluoride, mixing and grinding.

[0034] The grinding means used for grinding the particles includes a grinding device capable of finely grinding in a wet manner, for example, a media stirring mill such as a bead mill. The grinding media used in the grinding device may be made of glass, alumina, zircon, zirconia, steel, etc. Among these, zirconia is preferably used because of its relatively high density, high grinding power, and lack of iron contamination.

[0035] The shape of the grinding medium is not particularly limited, but from the viewpoint of uniform pulverization, approximately spherical grinding medium can be preferably used.The size of the grinding medium is also not particularly limited, but from the viewpoint of obtaining a stable sol, when the shape is spherical, the diameter is preferably 0.5 mm or less, more preferably 0.2 mm or less, and particularly preferably 0.1 mm or less.In addition, from the viewpoint of easy separation of the sol and the grinding medium, the lower limit of the size of the grinding medium is preferably 0.02 mm or more, more preferably 0.03 mm or more.

[0036] When preparing the sol, the content of the dispersed particles can be set within the above range by appropriately adjusting the blending amount of each component including the dispersion medium. The concentration of the sol can be adjusted by the blending amount of the dispersion medium. For example, a sol having a higher concentration than the desired concentration is prepared, and the desired concentration can be adjusted by adding and mixing the dispersion medium to the sol. In addition, when adjusting the concentration of the sol by the dispersion medium, the additional dispersion medium may be the same as or different from the dispersion medium in the sol.

[0037] <Membrane containing sol> The sol of the present invention described above can be applied to the surface of a substrate to form a film. The obtained film may be one that has changed from a sol state to a gel state containing a dispersion medium or a xerogel state that does not contain a dispersion medium. Examples of the film formation method include known methods in the film production process using a wet method. Specifically, spin coating, dip coating, spray coating, flow coating, roll coating, curtain coating, bar coating, screen printing, etc. can be mentioned, but from the viewpoint of forming a high-quality film, spin coating, dip coating, spray coating, and bar coating are preferred.

[0038] The substrate on which the film is provided is not particularly limited, and examples of substrates that can be used include resin substrates and composite resin substrates such as polyimide resin, polyethylene terephthalate resin, polyethylene resin, polypropylene resin, polycarbonate resin, acrylic resin, polyester resin, ABS resin, AAS resin, polyvinyl chloride resin, and polyethylene naphthalate; and inorganic substrates such as ceramics such as glass, quartz, and pottery, silicon, various metals, various metal oxide films, and composite materials thereof.

[0039] The above-mentioned sol can be applied to the surface of the substrate and further heated to make the sol more stable. The heat treatment method may be heating at 100°C or less, or hydrothermal treatment at 100°C or more, and the treatment time can be any condition within 1 minute to 10 hours. The longer the heat treatment time, the more the crystallization of the niobic acid compound progresses, and the refractive index of the film obtained generally improves.

[0040] The film provided on the substrate surface can be not only a single layer but also a multilayer film of two or more layers. To produce a multilayer film, a sequential lamination method in which a layer is coated and heat-treated one by one is repeated, or a lamination method in which multiple layers are formed by repeated coating and then heat-treated all at once is possible.

[0041] The film formed on the surface of the substrate can be used as a film-supporting substrate for various applications, such as transparent conductive films, high dielectric constant films, insulating films, anti-reflection films, hard coat layers, photocatalytic members, etc. in semiconductor devices and optical devices. EXAMPLES

[0042] Next, the embodiment of the present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass".

[0043] <Preparation of Sol> The following materials were used as raw materials for preparing the sol. The volume cumulative particle diameter (D 90 ) was performed by measuring the particle size distribution using a particle size distribution analyzer (DelsaNano HC, manufactured by Beckman Coulter, Inc.). However, since the particle diameter of the niobic acid compound was large, the particle size distribution was measured using a laser diffraction particle size distribution analyzer, Microtrac MT3300EXII (manufactured by Microtrac BELL, Inc.). Niobate compound (Nb hydroxide, manufactured by Mitsui Mining & Smelting Co., Ltd., D 90 = 3.6 μm) Calcium fluoride (Mitsui Mining & Smelting Co., Ltd., D 90= 100 nm) Zirconium oxide (zirconia sol containing 40% by mass of zirconium oxide: Nanouse (registered trademark) ZR, manufactured by Nissan Chemical Industries, Ltd.) Cerium oxide (Mitsui Mining & Smelting Co., Ltd., D 90 =80nm) Silicon oxide (colloidal silica containing 30% by mass of silicon oxide: Snowtex (registered trademark), manufactured by Nissan Chemical Industries, Ltd.) Ammonia (25% by weight ammonia water) Silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0044] A sol was prepared by mixing the above-mentioned raw materials in a prescribed ratio according to the composition shown in Table 1 below. Specifically, a total of 99.9 g of each component, excluding silicone oil, was added to a 200 mL plastic bottle with a 100 mL measuring line, and zirconia beads with a diameter of 0.05 mm were added up to the 100 mL measuring line of the plastic bottle. Next, the lid of the plastic bottle was closed, and the mixture was placed in a paint shaker (manufactured by Asada Iron Works Co., Ltd.) and crushed for 5 hours. After crushing, the mixture was passed through a test sieve with 20 μm openings to separate and remove the zirconia beads, and 0.1 g of silicone oil was added and mixed to prepare a sol. For each sol prepared, the volume cumulative particle diameter (D 90 ) were measured. When measuring the volume cumulative particle diameter using a particle size distribution measuring device, the obtained sol was first poured as is into the measuring cell up to the marked line, and then the particle distribution measurement was performed after confirming that the device displayed that the sample concentration was measurable. The measurement results are shown in Table 1 below.

[0045] <Preparation of membrane-supported substrate> A glass substrate (76×26 mm) was used as the substrate, and the surface of the glass substrate was washed with detergent, followed by ultrasonic cleaning in alcohol for 10 minutes, and then UV cleaning was performed by irradiating the glass substrate surface with ultraviolet light (wavelength 325 nm) for 30 seconds just before coating with the sol. The glass substrate was then placed on a spin coater, and each sol obtained as described above was collected with a micropipette, and 0.7 mL of the sol was dropped onto the glass substrate to form a film (conditions: 1000 rpm×20 seconds). Next, the glass substrate on which the film was formed was dried at 100° C. for 10 minutes to produce a film-supported substrate.

[0046] <Visual evaluation of film> The film formed on the glass substrate was visually observed to evaluate whether interference fringes were observed or not, according to the following criteria: A: Almost no interference fringes are visible (good) B: Some interference fringes are visible, but still usable (acceptable) C: Interference fringes are clearly visible (not acceptable) The evaluation results are shown in Table 1 below.

[0047] <Semi-quantitative evaluation of membrane> The prepared film-supported substrate was placed on black paper, a white board was set up in front of the photographing direction, and the film surface was photographed with a digital camera from 30 degrees above. Each digital image was imported into image processing software (PhotoShop, registered trademark), and a portion (12 mm x 12 mm) with few foreign matter on the film surface was selected, and the selected portion was divided into nine 4 mm square areas, and the color code of the center area of ​​each area (4 mm x 4 mm) was determined. The obtained color code (hexadecimal) of each area was converted to a decimal number, and the standard deviation of the nine areas was calculated from the converted numerical value. A smaller standard deviation indicates that there is no color difference and interference fringes are suppressed. The standard deviations calculated as above were as shown in Table 1 below.

[0048] [Table 1]

[0049] As is clear from the evaluation results in Table 1, in the evaluation of the interference fringes of the formed film, the standard deviation value calculated from the color code taken with a digital camera is in good agreement with the results of the visual evaluation. When the niobate compound sol does not contain a specific oxide or fluoride (Example 1), interference fringes are clearly observed, whereas in the niobate compound sols containing a specific oxide or fluoride (Examples 2, 3, and Examples 5 to 11), the occurrence of interference fringes is suppressed. Furthermore, when only silicon oxide is added to a niobate compound sol, no improvement in the interference fringes is observed (Example 4), but it can be seen that the interference fringes are improved by further adding a specific oxide or fluoride (Examples 7, 9, and 11).

Claims

1. A niobate compound, At least one compound selected from the group consisting of an oxide of a metal selected from zirconium and cerium, and a fluoride of a metal selected from magnesium and calcium; A sol comprising: The niobate compound is contained in an amount of 1 mass% or more and 20 mass% or less, The compound selected from the group consisting of an oxide of a metal selected from zirconium and cerium, and a fluoride of a metal selected from magnesium and calcium is contained in an amount of 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the total amount (converted into solid content) of the niobate compound.

2. A niobate compound, Silicon oxide, At least one compound selected from the group consisting of an oxide of a metal selected from zirconium and cerium, and a fluoride of a metal selected from magnesium and calcium; Including, sol.

3. A sol described in claim 1 or 2 for forming a thin film.

4. The sol according to any one of claims 1 to 3, comprising two or more compounds selected from the group consisting of an oxide of at least one metal selected from zirconium, tin, zinc, silicon, and cerium, and a fluoride of at least one metal selected from magnesium and calcium.

5. The particle diameter (D) of the colloidal particles dispersed in the sol at 90% of the cumulative volume measured by dynamic light scattering. ９０ The sol according to any one of claims 1 to 4, wherein the average particle diameter is 20 nm or more.

6. The sol according to claim 1 or 3, wherein the niobate compound is contained in an amount of 0.1 mass % or more and 50 mass % or less.

7. The sol according to any one of claims 1 to 6, further comprising ammonia.

8. A membrane comprising the sol according to any one of claims 1 to 7.

9. A membrane-supporting substrate comprising the membrane according to claim 8 on a surface of the substrate.

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