Dispersion of niobate compound and method for producing the same

Abstract

The present application relates to a niobium compound dispersion liquid in which a niobium compound is dispersed in an organic solvent, and provides a novel niobium compound dispersion liquid in which a niobium compound is dispersed or dissolved in an organic solvent even if the organic solvent is substantially free of an organic compound having a volatilization temperature of 200°C or higher and a halogen element. A niobium compound dispersion liquid characterized by being a niobium compound dispersion liquid in which a part or all of a niobium compound is dispersed or dissolved in a mixed solvent in which a lower alcohol and water are used as main solvents and which contains a primary amine, a secondary amine, a tertiary amine, or a quaternary ammonium compound or two or more of them (which are also referred to as "amine compound solvent"), the niobium compound dispersion liquid containing 5.0% by mass or more of water, the content of the amine compound solvent with respect to the content of niobium (Nb) being 0.50 or more in terms of molar ratio, and the lower alcohol accounting for 70% by mass or more of a remaining portion (referred to as "remaining component") other than a component derived from the niobium compound, a component derived from the amine compound solvent, and a contained component other than water.

Description

TECHNICAL FIELD

[0001] The present application relates to a niobium acid compound dispersion liquid in which a niobium acid compound is dispersed or dissolved in an organic solvent, and a method for producing the same. BACKGROUND

[0002] As a niobium acid compound containing niobium (Nb) and oxygen (O), niobium oxide, niobium hydroxide, polyacid of niobium, and the like are known. They are used as, for example, a raw material or an additive for optics, electronics, and the like.

[0003] Further, since a niobium acid exhibits solid acidity, research as a catalyst has also been conducted. For example, in Non-Patent Literature 1, with respect to polyacids of Group 5 elements such as Nb in metal oxide clusters [MxOy]n- known as polyacids, an especially excellent base catalyst action is reported.

[0004] Further, since niobium oxide has a high refractive index and a high dielectric constant, in recent years, in optoelectronics materials and the like, a niobium acid compound dispersion liquid in which fine particles of a niobium acid compound are dispersed in a dispersion medium as a semiconductor material, a surface protective agent, an anti-reflective material, a refractive index adjusting agent, a catalyst, and the like has attracted attention and has been developed.

[0005] Such a niobium acid compound dispersion liquid, for example, by being applied to the surface of various members and being dried, can impart a desired function to the members. Among them, a niobium acid compound organic dispersion liquid in which a niobium acid compound is dispersed in an organic solvent can also be used for film formation of a resin and the like, and has excellent volatility, and thus has a characteristic of being high in film formation property.

[0006] With respect to such a niobium acid compound dispersion liquid, for example, in Patent Literature 1, as a method for producing a niobium acid sol which is high in compatibility with a hydrophilic solvent, a method for producing a niobium acid sol is disclosed, which is characterized by washing a niobium ammonium sol in which an inorganic acid is mixed to remove ammonia, and then heating in the presence of an amine compound to remove ammonia, and further adding an organic acid.

[0007] In Patent Literature 2, a niobium acid organic sol is disclosed, in which, in the case where fine particles containing a niobium acid as a main component and a stabilizing agent are contained, and ammonia is contained as an optional component, NH3 / Nb205 (molar ratio) < 1.0, and a method is disclosed as a method for producing the same, which includes the following steps: a step of preparing a mixed solution containing fine particles containing a niobium acid as a main component, a stabilizing agent such as an amine salt cationic surfactant or a quaternary ammonium compound salt cationic surfactant, and an amine compound, in the presence of water; and a step of performing solvent exchange on the mixed solution obtained in the above step to obtain the organic sol.

[0008] PRIOR ART DOCUMENTS

[0009] Non-patent literature

[0010] Non-Patent Literature 1: Seiji Yamazoe, “Application of Base Catalysts in Polyvalent Anionic Metal Oxide Clusters,” 2018, The Chemical Society of Japan

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-81220

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 2018-127392 Summary of the Invention

[0014] Problems to be solved by the invention

[0015] As mentioned above, most of the previously disclosed niobate compound dispersions contain low-volatility organic substances or halogens as stabilizers. Therefore, when the niobate compound dispersion is applied to the surface of various components and then dried at low temperature to form a film, there is a problem that these components remain in the surface film.

[0016] Furthermore, when the niobate oxide compound dispersion contains an organic acid as in Patent Document 1, there are also applications that are contraindicated with organic acids, and therefore the dispersion cannot be used in such applications.

[0017] Therefore, the present invention provides a novel niobate compound dispersion in which a niobate compound is dispersed in an organic solvent, wherein the niobate compound is dispersed or dissolved in the organic solvent even though the niobate compound does not substantially contain an organic substance having a volatilization temperature of 200°C or higher and a halogen element, and a method for producing the same.

[0018] Means for solving problems

[0019] The present invention provides a niobate compound dispersion, characterized in that the niobate compound is partially or completely dispersed or dissolved in a solvent containing a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium compound, or a mixed solvent of two or more thereof (hereinafter referred to as an "amine compound solvent"), comprising a lower alcohol and water as main solvents.

[0020] The niobium oxide compound dispersion contains 5.0% by mass or more of water, the content of the amine compound solvent is 0.50 or more relative to the content of niobium (Nb) in a molar ratio, and the lower alcohol accounts for 70% by mass or more of the components derived from the niobium oxide compound (referred to as "niobium oxide compound-derived components"), the components derived from the amine compound solvent (referred to as "amine compound solvent-derived components"), and the components other than water (referred to as "the remainder").

[0021] The present invention also provides a method for producing a niobate compound dispersion, characterized in that a compound containing niobium acid and ammonium ions, namely a niobate compound (called a "precursor"), a lower alcohol or even water, and the above-mentioned amine compound solvent are mixed.

[0022] Effects of the Invention

[0023] Niobate compounds are difficult to disperse or dissolve in solvents containing lower alcohols and water when used alone. However, if the solvent is used as the main solvent and the above-mentioned amine compound solvent is added thereto, the niobate compounds can be dispersed or dissolved.

[0024] Therefore, the niobate compound dispersion and its production method proposed in the present invention can provide a new niobate compound dispersion in which the niobate compound is dispersed or dissolved in an organic solvent even though the niobate compound does not substantially contain organic matter with a volatilization temperature of 200°C or above and halogen elements.

[0025] The niobate compound dispersion can be effectively used in various fields as a semiconductor material, a surface protective agent, an antireflection material, a refractive index adjuster, a catalyst, etc. In addition, it can also be used as a raw material for various materials. DETAILED DESCRIPTION

[0026] Next, the present invention will be described based on examples of embodiments. However, the present invention is not limited to the embodiments described below.

[0027] <<Niobic Acid Compound Dispersion>>

[0028] A niobate compound dispersion ("the present niobate compound dispersion"), which is an example of an embodiment of the present invention, is a dispersion or solution in which a portion or all of a niobate compound (referred to as "the present niobate compound") is dispersed or dissolved in a mixed solvent (referred to as "the present mixed solvent") having a lower alcohol and water as the main solvent and containing a primary amine, a secondary amine, a tertiary amine, or a quaternary ammonium compound, or two or more thereof, i.e., an amine compound solvent.

[0029] In the present invention, “the niobic acid compound is dispersed in the present mixed solvent” means a state in which particles of the niobic acid compound are uniformly dispersed without settling.

[0030] On the other hand, the phrase "the niobic acid compound is dissolved in the present mixed solvent" means that the niobic acid compound is dissolved in the present mixed solvent and is in a transparent state.

[0031] Furthermore, from the viewpoint of the dispersibility and light transmittance of the niobium compound particles in the present niobate compound dispersion, the light transmittance at a wavelength of 400 nm is preferably 65% ​​or greater, more preferably 80% or greater, more preferably 90% or greater, further preferably 95% or greater, and particularly preferably 99% or greater.

[0032] The "the niobate compound is dissolved in the mixed solvent (transparent)" means that the light transmittance at a wavelength of 400 nm is 100% in theory, but in practice, it can be regarded as transparent as long as it is 99.5% or more.

[0033] The "part or all of the niobate compound is dispersed or dissolved in the mixed solvent" can be determined by composition analysis of the niobate compound dispersion liquid, visual observation, and light transmittance measurement.

[0034] The present niobate compound dispersion liquid can be any one of a liquid, a suspension (sol), and a paste.

[0035] <The niobate compound>

[0036] The present niobate compound can be any compound containing niobate. For example, a compound containing Nb, O, and H, or a compound containing Nb, O, H, and N can be exemplified. Among them, from the viewpoint of excellent dispersibility and solubility in the mixed solvent, for example, ammonium niobate or a salt thereof is preferable. However, it is not limited to the above.

[0037] Among them, from the viewpoint of excellent dispersibility and solubility in the mixed solvent, the present niobate compound is preferably a compound having a polyacid structure.

[0038] Among them, from the viewpoint of excellent dispersibility and solubility in the mixed solvent, a compound of polyacid of niobium and ammonium ion is preferable. For example, a compound having a structure represented by the formula: [Nb x O y ] n- a hydrous compound having a structure represented by the formula: [Nb6O 19 ] 6- a hydrous compound having a structure represented by the formula: [Nb6O

[0039] In the case where the present niobate compound is a compound having niobate and ammonium ion, from the viewpoint of further improving the dispersibility and solubility of the present niobate compound, the molar ratio of the content of ammonium ion to the content of niobium (Nb) (NH4 + / Nb) is preferably 0.50 or more.

[0040] From the viewpoint, the molar ratio is more preferably 0.55 or more, and among them, particularly preferably 0.58 or more, and more particularly preferably 0.60 or more. On the other hand, from the viewpoint of not hindering the effect of the amine compound solvent, the upper limit value of the molar ratio (NH4 + / Nb) is 20 or less.

[0041] Note that the above-mentioned niobium (Nb) content and the above-mentioned content of ammonium ions (NH 4+ ) can be obtained from the niobate compound dispersion liquid.

[0042] The above-mentioned niobium (Nb) content can be obtained by the following gravimetric method: by drying a portion of the niobate compound dispersion liquid at 110°C for 24 hours, then firing at 1000°C for 4 hours to produce Nb2O5, calculating the concentration of Nb2O5 contained in the niobate compound dispersion liquid from the mass thereof, and calculating the Nb content from the Nb2O5 concentration. That is, by dividing the calculated Nb2O5 concentration (mass concentration) by 1 / 2 of the molecular weight of Nb2O5, i.e., 132.9, it can be converted to the molar concentration of Nb.

[0043] Further, the above-mentioned content of ammonium ions (NH + ) can be calculated, for example, by the following method: by the Kjeldahl method, the total content of ammonia nitrogen, primary to tertiary amine nitrogen, and quaternary ammonium nitrogen in the niobate compound dispersion liquid is obtained, on the other hand, the content of primary to tertiary amine nitrogen and quaternary ammonium nitrogen in the niobate compound dispersion liquid is obtained, for example, by the method described later, the value of the former content is subtracted from the latter content, and in the case of calculation in molar concentration, this value is used directly, and in the case of calculation in mass concentration, it is divided by the atomic weight of nitrogen, i.e., 14.01, and converted to the molar concentration of nitrogen (N) = molar concentration of NH 4+ .

[0044] The present niobate compound exists in the form of colloidal particles of the niobate compound in the present mixed solvent, or a part or all thereof is dissolved and exists in the form of ions.

[0045] For example, in the case where the present niobate compound is a compound having niobate and ammonium ions, in the present mixed solvent, it becomes to exist in the form of colloidal particles of the niobate compound, or in the form of ions of the niobate and the ammonium ions.

[0046] <the mixed solvent>

[0047] The present mixed solvent is a solvent in which a lower alcohol and water are used as the main solvent.

[0048] This "main solvent" means that the lower alcohol and water account for 50% by mass or more of the present mixed solvent, and the following cases are envisaged: the lower alcohol and water further account for 60% by mass or more thereof, further account for 70% by mass or more thereof, further account for 80% by mass or more thereof, further account for 90% by mass or more thereof, further account for 95% by mass or more thereof (including 100% by mass).

[0049] From the viewpoint of improving the dispersibility or even solubility of the niobium compound in the mixed solvent, the niobium compound dispersion liquid preferably contains 5.0% by mass or more of water, and further preferably 8.0% by mass or more thereof, 9.0% by mass or more thereof, 10% by mass or more thereof.

[0050] However, if the amount of water is too large, the film-forming properties can deteriorate, and thus the upper limit is preferably 95% by mass or less, and further preferably 90% by mass or less thereof, 85% by mass or less thereof.

[0051] Note that the water described above is usually contained in the case where the niobium compound-containing substance obtained by removing fluorine as described later is dried, and in the case where the amine compound solvent is used, and thus water is contained even if water is not added.

[0052] The "lower alcohol" in the mixed solvent refers to an alcohol having 5 or fewer carbon atoms, and also includes a polyhydric alcohol. Examples include methanol, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol, glycerol, and the like. However, the present application is not limited to these.

[0053] The mixed solvent is a solvent in which a lower alcohol and water are used as the main solvent, and a primary amine, a secondary amine, a tertiary amine, or a quaternary ammonium compound, or a mixture of two or more of these, i.e., an amine compound solvent, is contained.

[0054] Here, as the amine described above, a primary amine, a secondary amine, a tertiary amine, or a quaternary ammonium compound, or a mixture of two or more of these, can be used. From the viewpoint of solubility, a primary amine, a secondary amine, or a quaternary ammonium compound, or a mixture of two or more of these, is preferred, and a primary amine or a quaternary ammonium compound, or a mixture of these two, is more preferred.

[0055] As preferred specific examples, the following alkylamines (including quaternary alkylammonium compounds), choline [(CH3)3NCH2CH2OH] + ), hydroxycholine [(CH3)3NCH2CH2OH] + OH - ), and the like can be given.

[0056] As the alkylamine (including quaternary alkylammonium compound) described above, an alkylamine having 1 to 4 alkyl groups can be used. Of these, an alkylamine in which the number of alkyl groups is 1, 2, or 4 is preferred, and an alkylamine in which the number of alkyl groups is 1 or 4 is further preferred.

[0057] In the case where there are 2 to 4 alkyl groups, the 2 to 4 alkyl groups can all be the same, and in addition, different alkyl groups can be contained.

[0058] As the alkyl group of the alkylamine, from the viewpoint of solubility, an alkyl group having 1 to 6 carbon atoms is preferred, more preferably 4 or less, 3 or less, and further preferably 2 or less.

[0059] Specific examples of the above-mentioned alkylamines include methylamine, dimethylamine, trimethylamine, tetramethylammonium hydroxide (TMAH), ethylamine, methylethylamine, diethylamine, triethylamine, methyldiethylamine, dimethylethylamine, tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), n-propylamine, di-n-propylamine, tri-n-propylamine, isopropylamine, diisopropylamine, triisopropylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, isobutylamine, diisobutylamine, triisobutylamine, tert-butylamine, n-pentylamine, and n-hexylamine.

[0060] Among them, from the perspective of solubility, methylamine, dimethylamine, tetramethylammonium hydroxide (TMAH), ethylamine, methylethylamine, diethylamine, and tetraethylammonium hydroxide (TEAH) are preferred, with methylamine, ethylamine, tetramethylammonium hydroxide (TMAH), and tetraethylammonium hydroxide (TEAH) being more preferred. Tetramethylammonium hydroxide (TMAH) is most preferred.

[0061] Furthermore, the above-mentioned alkylamines may be used alone or in combination of two or more.

[0062] On the other hand, as the quaternary ammonium compound, in addition to the quaternary alkylammonium compounds described as the above-mentioned alkylamines, for example, quaternary ammonium compounds containing no halogen, such as benzyltrimethylammonium hydroxide and choline hydroxide, can also be preferably mentioned.

[0063] The present mixed solvent may further contain solvent components other than the above-mentioned main solvent and amine compound solvent (referred to as "other solvent components").

[0064] Examples of the other solvent components include ketones, ethers, and nitriles.

[0065] <Composition of the Niobate Compound Dispersion>

[0066] In the present niobate compound dispersion, from the viewpoint of improving the dispersibility and even solubility of the present niobate compound in the present mixed solvent, the content of the above-mentioned amine compound solvent relative to the content of niobium (Nb) is preferably 0.50 or more, more preferably 0.60 or more, 0.80 or more, or 1.0 or more, in terms of molar ratio.

[0067] However, from the viewpoint of easy drying during film formation, the molar ratio is preferably 30 or less, more preferably 20 or less, or 10 or less.

[0068] At this time, the "content of the amine compound solvent" includes the content derived from the amine compound solvent and the content derived from the present niobium compound, i.e., the precursor described later.

[0069] In the present niobium compound dispersion liquid, from the viewpoint of effective use of niobium, the content of niobium is preferably 0.1% by mass or more, further preferably 0.5% by mass or more, 1.0% by mass or more, of niobium, in terms of Nb2O5. On the other hand, from the viewpoint of dispersion and solubility, the content of niobium is preferably 40% by mass or less, further preferably 35% by mass or less, 30% by mass or less, in terms of Nb2O5.

[0070] Note that, in the present niobium compound dispersion liquid, niobium or niobic acid is not necessarily present in the state of Nb2O5. The content of niobium or niobic acid in terms of Nb2O5 is based on the convention when expressing the concentration of Nb.

[0071] The content of niobium in the present niobium compound dispersion liquid can be measured by the following gravimetric method: the mass of Nb2O5 obtained by evaporating and drying 20 mL of the dispersion liquid and firing at 1000°C for 4 hours is measured.

[0072] In the present niobium compound dispersion liquid, the content of the above-described amine compound solvent is preferably appropriately adjusted in accordance with the content of niobium. If a standard is cited, from the viewpoint of dispersibility, it is preferable to contain 2.0% by mass or more, further preferably 3.0% by mass or more, 5.0% by mass or more. On the other hand, it is further preferable to contain 30% by mass or less, 20% by mass or less.

[0073] As for the content of the above-described amine compound solvent in the present niobium compound dispersion liquid, as for primary to tertiary amines, it can be measured by hexane extraction and gas chromatography mass spectrometry (GC-MS), and as for quaternary ammonium compounds, it can be measured by direct MS.

[0074] As the apparatus of the above-described GC-MS, JMS-Q1500GC manufactured by JEOL Ltd. or the like can be used. Further, as the apparatus of the above-described direct MS, Q-Exactive manufactured by Thermo Fisher Scientific Inc. or the like can be used.

[0075] In the present niobate compound dispersion, the ratio of lower alcohol to water is preferably 5.5 parts by mass or greater, more preferably 6.0 parts by mass or greater, 8.0 parts by mass or greater, or 10 parts by mass or greater, per 100 parts by mass of the lower alcohol, from the perspective of dispersion and even dissolution. On the other hand, from the perspective of film-forming properties on resins, the water content is preferably 1000 parts by mass or less.

[0076] The lower alcohols and water can be measured by gas chromatography-mass spectrometry (GC-MS), and JMS-Q1500GC manufactured by JEOL Ltd. or the like can be used.

[0077] In the present niobic acid compound dispersion, the lower alcohol preferably accounts for 70% by mass or more of the components other than the niobic acid compound-derived component, the amine compound solvent-derived component, and water (referred to as "the remainder").

[0078] When the lower alcohol accounts for 70% by mass or more of the remainder, dispersibility or solubility or both can be improved.

[0079] From this viewpoint, it is more preferred that lower alcohols account for 80% by mass or more of the remainder, and even more preferably, it is more preferred that lower alcohols account for 90% by mass or more, and 95% by mass or more (including 100% by mass) of the remainder.

[0080] It should be noted that the "niobate compound-derived components" mentioned above refer to the present niobic acid compound and components obtained by dissolving the present niobic acid compound in the present mixed solvent, such as niobic acid ions, ammonium ions, and the like.

[0081] Furthermore, the "component derived from the amine compound solvent" refers to not only the present amine compound solvent but also a component transformed by the reaction of the present amine compound solvent with the present niobic acid compound or the like.

[0082] The remainder may contain various additives in addition to organic solvents other than lower alcohols (for example, acetone).

[0083] The content of "niobate compound-derived components" in the present niobate compound dispersion can be measured by the following method (gravimetric method): Nb2O5 is generated by evaporation and calcination at 1000°C for 4 hours, and the "niobate compound-derived components" contained in the dispersion are calculated from the mass of the generated Nb2O5.

[0084] On the other hand, the content of "components derived from the amine compound solvent" can be measured by hexane extraction and gas chromatography-mass spectrometry (GC-MS) for primary to tertiary amines, and by direct MS for quaternary ammonium compounds.

[0085] One of the characteristics of the present niobate compound dispersion liquid is that it can also be substantially free of a stabilizing agent or an organic acid or the like organic substance having a volatilization temperature of 200°C or higher and a halogen element.

[0086] Here, the "substantially free of an organic substance having a volatilization temperature of 200°C or higher and a halogen element" means that they are not intentionally contained, and means that they are not contained except for the case where they are unintentionally contained, that is, the case where they are inevitably contained as impurities.

[0087] The above "stabilizing agent" refers to an amine salt cationic surfactant, a quaternary ammonium compound salt cationic surfactant, or the like listed in Japanese Patent Application Publication No. 2018-127392. However, it is not limited to these.

[0088] As the above amine salt cationic surfactant, for example, octadecylamine, oxyethylene dodecylamine, polyoxyethylene dodecylamine, or the like can be listed.

[0089] As the above quaternary ammonium compound salt cationic surfactant, for example, dialkyldimethylammonium chloride, alkyltrimethylammonium chloride, alkyl dimethyl benzyl ammonium chloride, or the like can be listed.

[0090] The above "organic acid" can list moncarboxylic acid, dicarboxylic acid, hydroxycarboxylic acid, or the like described in Patent Document 1.

[0091] For example, as the above moncarboxylic acid, formic acid, acetic acid, propionic acid, n-butyric acid, valeric acid, or the like can be listed, as the above dicarboxylic acid, oxalic acid, succinic acid, maleic acid, malonic acid, fumaric acid, glutaric acid, or the like can be listed, and as the above hydroxycarboxylic acid, citric acid, glycolic acid, lactic acid, tartaric acid, malic acid, or the like can be listed.

[0092] However, the organic acid is not limited to these.

[0093] The matter that the organic substance having a volatilization temperature of 200°C or higher is not contained can be determined by ion chromatography, liquid chromatography, gas chromatography, or the like.

[0094] In addition, the matter that the halogen element is not contained can be determined by ICP emission spectrometry (high-frequency inductively coupled plasma emission spectrometry, ICP-OES / ICP-AES) and ion chromatography, or the like.

[0095] <Properties of the present niobate compound dispersion liquid>

[0096] The present niobate compound dispersion liquid can be in a state where colloidal particles formed of the present niobate compound are dispersed and suspended in the present mixed solvent, that is, a sol state, or can be in a state where the present niobate compound is dissolved in the present mixed solvent to be a transparent liquid.

[0097] Further, in a case where the colloidal particles formed of the present niobate compound are dispersed and suspended in the present mixed solvent, it is also possible that a part of the colloidal particles are dissolved in the present mixed solvent.

[0098] (optical transmittance)

[0099] The present niobate compound dispersion liquid is one having an optical transmittance of more than 65% at a wavelength of 400 nm, and it is further preferable that it be more than 70%, and further more preferable that it be more than 80% thereof, more than 90% thereof (including 100%).

[0100] As described above, the present niobate compound dispersion liquid has an optical transmittance of more than 65% due to the dispersion and dissolution of the niobate compound in the present mixed solvent.

[0101] (HSP)

[0102] In the present niobate compound dispersion liquid, from the viewpoint of improving the solubility of the present niobate compound in the present mixed solvent, the HSP values of the niobate compound-derived component, the amine compound solvent-derived component, and the remaining components other than water, such as lower alcohols and other mixed solvent components, are preferably:

[0103] dD (dispersion term) ≤ 16.0, dP (polarity term) = 8.5 to 11.5, and dH (hydrogen bond term) ≥ 16.0.

[0104] From the viewpoint, dD (dispersion term) is further preferably 15.8 or less, and further more preferably 15.5 or less.

[0105] dP (polarity term) is further preferably 8.0 or more or 11.0 or less, and further more preferably 8.5 or more or 10.5 or less.

[0106] dH (hydrogen bond term) is further preferably 18.5 or more, and further more preferably 19.0 or more.

[0107] Note that the HSP value (Hansen Solubility Parameter) is an index indicating how much a certain substance is dissolved in another certain substance.

[0108] The HSP is a parameter in which the solubility parameter introduced by Hildebrand is divided into three components of a dispersion term δD, a polarity term δP, and a hydrogen bond term δH, and is expressed in a three-dimensional space. The dispersion term δD indicates the effect by dispersion forces, the polarity term δP indicates the effect by dipole-dipole forces, and the hydrogen bond term δH indicates the effect by hydrogen bond forces, and is written as:

[0109] dD (dispersion term) = δD: energy derived from intermolecular dispersion forces

[0110] dP (polar term) = δP: Energy derived from polar forces between molecules

[0111] dH (hydrogen bond term) = δH: Energy derived from the hydrogen bonding force between molecules.

[0112] (Here, the unit of each is MPa 0.5 . )

[0113] The dispersion term reflects the effect of van der Waals forces, the polar term reflects the effect of dipole moments, and the hydrogen bonding term reflects the effects of water, alcohol, etc. Furthermore, substances with similar vectors based on HSP can be judged to have high solubility. The degree of vector similarity can be determined by the distance between Hansen solubility parameters (HSP distance).

[0114] Furthermore, the Hansen solubility parameter is not only an indicator for judging solubility, but also an indicator for judging the extent to which a certain substance can easily exist in another substance, that is, the extent to which it can be dispersed.

[0115] In the present invention, HSPs [δD, δP, δH] can be easily estimated from the chemical structure using, for example, the computer software Hansen Solubility Parameters in Practice (HSPiP). Specifically, they are determined from the chemical structure using the Y-MB method implemented in HSPiP. Alternatively, if the chemical structure is unknown, they can be determined using the sphere method implemented in HSPiP from the results of solubility tests using various solvents.

[0116] The HSP of a mixed component of a lower alcohol and other mixed solvent components can be determined as follows from the mixing ratio (volume ratio).

[0117] [dDm, dPm, dHm]=[(a*dD1+b*dD2), (a*dP1+b*dP2), (a*dH1+b*dH2)] / (a+b)

[0118]

[0119] Mixing ratios are calculated by volume.

[0120] (From "HSP for Beginners" https: / / pirika.com / HSP / JP / Examples / Docs / 4Beginner.htm)" quoted.)

[0121] (Adhesion)

[0122] The present niobate compound dispersion can be a solution that is evaluated as "acceptable" in the adhesion evaluation described below when applied as a coating liquid as follows.

[0123] <Adhesion Evaluation>

[0124] A dispersion of a niobate compound was applied once to a soda glass substrate using a spin coater. The soda glass substrate with the coating was calcined at 200°C for 3 hours and then cooled to 25°C. A 24 mm x 15 m piece of cellophane tape as described in JIS Z 1522:2009, "Cellophane Tape," was attached to the surface of the coating. The surface of the tape was rubbed three times with the fingertips. Within one minute, the tape was peeled off by grasping the ends at an angle of 60°±10° for 0.5 to 1.0 seconds. A film having a smooth coating surface and no peeling was evaluated as acceptable.

[0125] <Method for producing the present niobate compound dispersion>

[0126] Next, a preferred method for producing the present niobate compound dispersion (referred to as "the present production method") will be described.

[0127] An example of the present production method includes a method in which a niobate compound (referred to as a "precursor"), a compound containing niobic acid and ammonium ions, a lower alcohol or even water, and the aforementioned amine compound solvent are mixed to obtain a niobate compound dispersion in which the precursor is dispersed or dissolved (referred to as a "dispersion step"). However, the present method for producing a niobate compound dispersion is not limited to this method.

[0128] As long as the present production method includes the above-mentioned steps, other steps or other treatments may be added as appropriate.

[0129] The niobate compound dispersion obtained by the present production method is ultimately a dispersion in which a part or all of the niobate compound is dispersed or dissolved in a mixed solvent containing a lower alcohol or even water and the above-mentioned amine compound solvent.

[0130] (Precursor)

[0131] From the viewpoint of high dispersibility and even solubility in the present mixed solvent, the above-mentioned precursor is preferably a compound having niobic acid and ammonium ions, and the molar ratio of the ammonium ion content to the niobium (Nb) content (NH4 + / Nb) is preferably 0.50 or more, more preferably 0.55 or more, 0.58 or more, or 0.60 or more. On the other hand, from the viewpoint of not inhibiting the effect of the amine compound solvent, it is preferably 20 or less, more preferably 10 or less.

[0132] It should be noted that the ammonium ions (NH4 +The content of the niobium oxide compound can be determined by the same method as in the case of the above-described niobium compound. However, in the case where it is known that the precursor does not contain primary to tertiary amines and quaternary ammonium compounds, it can be determined only by the Kjeldahl method.

[0133] (Method for producing precursor)

[0134] As the method for producing the precursor, a niobium fluoride aqueous solution can be added to an aqueous ammonia solution to obtain a niobium-containing precipitate (referred to as "reverse neutralization step"), and fluorine is removed from the niobium-containing precipitate to obtain a niobium oxide compound-containing substance, i.e., the above-described precursor. However, the method for producing the precursor is not limited to this method.

[0135] The method for producing the precursor can have other steps or other treatments added as appropriate as long as it has the above-described step.

[0136] [Reverse neutralization step]

[0137] In the reverse neutralization step, it is preferable to add a niobium fluoride aqueous solution to an aqueous ammonia solution of a prescribed concentration to obtain a niobium-containing precipitate. That is, it is preferable to perform reverse neutralization.

[0138] It is preferable to perform reverse neutralization in which a niobium fluoride aqueous solution is added to an aqueous ammonia solution to perform neutralization, rather than forward neutralization in which an aqueous ammonia solution is added to a niobium fluoride aqueous solution to perform neutralization.

[0139] It is presumed that by performing reverse neutralization, the structure of the niobium oxide becomes a structure that is easily soluble in water.

[0140] The niobium fluoride aqueous solution can be produced by reacting niobium or a niobium oxide with hydrofluoric acid (HF) to produce niobium fluoride (H2NbF7), which is dissolved in water.

[0141] Further, the niobium fluoride aqueous solution is preferably produced so as to contain niobium in an amount of 1 to 100 g / L in terms of Nb2O5in addition to water (e.g., pure water). At this time, if the niobium concentration is 1 g / L or more, the niobium oxide compound becomes easily soluble in water, and therefore the niobium concentration of the niobium fluoride aqueous solution is more preferably 1 g / L or more in terms of Nb2O5, and further preferably 10 g / L or more, 20 g / L or more thereof, in consideration of productivity. On the other hand, if the niobium concentration is 100 g / L or less, the niobium oxide compound becomes easily soluble in water, and therefore it is more preferable to be 90 g / L or less, and further preferable to be 80 g / L or less, 70 g / L or less thereof, in order to more reliably synthesize the niobium oxide compound that is easily soluble in water.

[0142] From the viewpoint of completely dissolving niobium or a niobium oxide, the pH of the niobium fluoride aqueous solution is preferably 2 or less, and further preferably 1 or less thereof.

[0143] On the other hand, the ammonia concentration of the above-described aqueous ammonia solution is preferably 5.0 to 30 mass %.

[0144] By setting the ammonia concentration of the aqueous ammonia solution for reverse neutralization to 5.0 mass % or more, it is possible to eliminate the residual Nb dissolution and to completely dissolve niobium and niobates in water. On the other hand, if the ammonia concentration of the aqueous ammonia solution is 30 mass % or less, it is near the saturated aqueous ammonia solution of ammonia, and thus is preferable.

[0145] From the above viewpoint, the ammonia concentration of the aqueous ammonia solution is preferably 5.0 mass % or more, further preferably 10 mass % or more thereof, 15 mass % or more thereof, 20 mass % or more thereof, 25 mass % or more thereof. On the other hand, it is preferably 30 mass % or less, further preferably 29 mass % or less thereof, 28 mass % or less thereof.

[0146] In the reverse neutralization step, the addition amount of the aqueous niobium fluoride solution with respect to the aqueous ammonia solution (NH3 / Nb205molar ratio) is preferably set to 95 to 300, further preferably set to 100 or more or 200 or less thereof, 110 or more or 150 or less thereof.

[0147] Both the aqueous niobium fluoride solution and the aqueous ammonia solution are at normal temperature.

[0148] In the reverse neutralization step, when the above-described aqueous niobium fluoride solution is added to the above-described aqueous ammonia solution, it is preferable to perform the neutralization reaction within 1 minute. That is, it is preferable to perform the neutralization reaction by, for example, pouring all at once or the like within 1 minute, rather than slowly adding the above-described aqueous niobium fluoride solution over time.

[0149] At this time, the addition time of the above-described aqueous niobium fluoride solution is preferably set to within 1 minute, further preferably set to within 30 seconds thereof, within 10 seconds thereof.

[0150] [F washing step]

[0151] Since the solution obtained in the above-described neutralization reaction, that is, the niobium-containing precipitate contains fluorine compounds such as ammonium fluoride as impurities, it is preferable to remove them to obtain a niobate compound-containing substance.

[0152] The method for removing the fluorine compounds is arbitrary. For example, in addition to a method using a membrane such as reverse osmosis filtration, ultrafiltration, and precision filtration using aqueous ammonia or pure water, centrifugal separation and other publicly known methods can be used.

[0153] The F washing step can be performed at normal temperature, and does not particularly require individual temperature adjustment.

[0154] Next, the niobate compound-containing substance obtained by removing the fluorine in the above process can also be dried as necessary. The drying method at this time can be appropriately selected from known drying methods.

[0155] However, if the moisture is completely removed, there is a possibility that the structure and even the properties of the niobate compound change, and thus it is preferable to leave the moisture. In this sense, it is preferable not to perform drying after centrifugal separation.

[0156] (Dispersion process)

[0157] In the dispersion process, as described above, it is only necessary to mix the above niobate compound (precursor), a lower alcohol or water as a main solvent, and the above amine compound solvent to obtain a niobate compound dispersion liquid in which the niobate compound is dispersed or dissolved.

[0158] At this time, the order in which the above precursor, the above main solvent, and the above amine compound solvent are mixed is not particularly limited.

[0159] For example, the following operation can be performed: the above precursor is added to a solvent in which a lower alcohol or water is used as a main solvent to prepare a slurry, and the above amine compound solvent is added to and dispersed or dissolved in the slurry to obtain a niobate compound dispersion liquid.

[0160] Further, the following operation can be performed: the above precursor is added to and dispersed or dissolved in a mixed solvent in which a lower alcohol or water is used as a main solvent and to which the above amine compound solvent is added to obtain a niobate compound dispersion liquid.

[0161] Note that "a lower alcohol or water is used as a main solvent" means a case in which only a lower alcohol is used as a main solvent and a case in which a lower alcohol and water are used as main solvents.

[0162] However, the dispersion process is not limited to these methods.

[0163] Among them, it is preferable that a solvent be prepared only from a lower alcohol or a solvent be prepared by mixing water and a lower alcohol, the precursor be added to the solvent, a slurry be prepared by stirring as necessary, and the above amine compound solvent be added to the slurry to prepare a niobate compound dispersion liquid.

[0164] At this time, as described above, even in a case in which only a lower alcohol is used as a solvent, the moisture contained in the niobate compound becomes a main solvent containing water and an alcohol. Further, note that the amine compound solvent also often contains water.

[0165] The niobate compound dispersion liquid obtained by such an operation becomes a dispersion liquid in which part or all of the niobate compound is dispersed or dissolved in a mixed solvent in which a lower alcohol and water are used as main solvents and which contains the above amine compound solvent.

[0166] Furthermore, when the niobic acid compound-containing material and the amine compound solvent obtained by removing fluorine contain water, this water also corresponds to the water in the mixed solvent of the niobic acid compound dispersion.

[0167] As the amine of the amine compound solvent, as described above, a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium compound, or a mixture of two or more thereof can be used.

[0168] Among them, from the viewpoint of solubility, primary amines, secondary amines, quaternary ammonium compounds, or mixtures of two or more thereof are preferred, and primary amines, quaternary ammonium compounds, or mixtures of the two are also preferred.

[0169] Specifically, preferred examples include alkylamines (including quaternary alkylammonium compounds), choline ([(CH3)3NCH2CH2OH] + ), choline hydroxide ([(CH3)3NCH2CH2OH] + OH - )wait.

[0170] As the alkylamine (including quaternary alkylammonium compounds), alkylamines having 1 to 4 alkyl groups can be used. Among them, alkylamines having 1, 2, or 4 alkyl groups are preferred, and alkylamines having 1 or 4 alkyl groups are more preferred.

[0171] When the group has 2 to 4 alkyl groups, the 2 to 4 alkyl groups may all be the same, or may contain different alkyl groups.

[0172] As the alkyl group of the alkylamine, from the viewpoint of solubility, an alkyl group having 1 to 6 carbon atoms is preferred, more preferably 4 or less, 3 or less, and even more preferably 2 or less.

[0173] Specific examples of the above-mentioned alkylamines include methylamine, dimethylamine, trimethylamine, tetramethylammonium hydroxide (TMAH), ethylamine, methylethylamine, diethylamine, triethylamine, methyldiethylamine, dimethylethylamine, tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), n-propylamine, di-n-propylamine, tri-n-propylamine, isopropylamine, diisopropylamine, triisopropylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, isobutylamine, diisobutylamine, triisobutylamine, tert-butylamine, n-pentylamine, and n-hexylamine.

[0174] Among them, from the viewpoint of solubility, methylamine, dimethylamine, tetramethylammonium hydroxide (TMAH), ethylamine, methylethylamine, diethylamine, tetraethylammonium hydroxide (TEAH) are preferred, among which methylamine, ethylamine, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH) are further preferred. Tetramethylammonium hydroxide (TMAH) is particularly most preferred.

[0175] On the other hand, as the quaternary ammonium compound, in addition to the quaternary alkylammonium compounds described above as the alkylamines, for example, benzyltrimethylammonium hydroxide, choline hydroxide and the like, which do not contain halogen, can be preferably exemplified.

[0176] In the case where the main solvent is prepared by mixing water and a lower alcohol, with respect to the mixing ratio of the lower alcohol and water, from the viewpoint of dispersibility, it is preferred to mix so that the content of water is 5.5 parts by mass or more with respect to the content of the lower alcohol, 100 parts by mass, and it is further preferred to mix so that it is 6.0 parts by mass or more, 8.0 parts by mass or more, 10 parts by mass or more, among them. On the other hand, from the viewpoint of film formability to the resin, it is preferred to mix so that it is 1000 parts by mass or less.

[0177] <Use of the niobate dispersion liquid>

[0178] The niobate dispersion liquid can be utilized, for example, as a coating liquid on a building material, a vehicle member, an electronic device frame, a semiconductor material, a film, a pigment, a catalyst, and the like, which are made of glass, resin, metal plate, oxide, carbide, nitride, sulfide, and the like. However, the use of the niobate dispersion liquid is not limited to the coating liquid.

[0179] <Explanation of the sentence>

[0180] When expressed as "X to Y" (X, Y are arbitrary numbers) in the present specification, unless otherwise specified, the meaning of "X or more and Y or less" is included, and the meaning of "preferably greater than X" or "preferably less than Y" is also included.

[0181] Further, in the case where it is expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), the intention of the gist of "preferably greater than X" or "preferably less than Y" is also included.

[0182] Examples

[0183] For the present application, further explanation is made by the following examples. However, the following examples do not limit the present application.

[0184] (Example 1)

[0185] An aqueous niobium fluoride solution containing 50 g / L of niobium (Nb2O5= 4.69 mass%) was prepared by dissolving 100 g of niobium pentoxide in 200 g of a 55 mass% aqueous hydrofluoric acid solution, and adding 1830 mL of ion exchange water.

[0186] The aqueous niobium fluoride solution 400 mL was added to 1 L of aqueous ammonia (NH3 concentration: 25 mass%) in less than 1 minute to obtain a reaction liquid (pH 11). The reaction liquid was a slurry of niobate compound hydrate, in other words, a slurry of niobium-containing precipitate.

[0187] Next, the reaction liquid was decanted using a centrifugal separator, and washed until the free fluorine amount of the supernatant became 100 mg / L or less to obtain a niobate compound-containing substance (precursor-containing substance) from which fluorine was removed.

[0188] The water content of the niobate compound-containing substance (precursor-containing substance) was 35.3 mass%.

[0189] In the niobate compound-containing substance (precursor-containing substance), the molar ratio (NH4 + / Nb) of the ammonium ion content to the niobium (Nb) content was 0.8.

[0190] At this time, as for the Nb content, Nb2O5 was produced by drying a part of the niobate compound-containing substance at 110°C for 24 hours and firing at 1000°C for 4 hours, the Nb2O5 concentration in the niobate compound was calculated from the mass, and the Nb content was calculated from the Nb2O5 concentration.

[0191] Further, as for the ammonium ion content, it was measured by the Kjeldahl method.

[0192] To 13.2 g of the niobate compound-containing substance (precursor-containing substance) from which fluorine was removed, 48.4 g of ethanol (water content: 0.5 mass%) was added and stirred, and then 8.4 g of tetramethylammonium hydroxide 5 hydrate (amine compound solvent: TMAH concentration: 50 mass%, water content: 50 mass%, Table 1: “amine compound solvent-containing substance”) was added so as to have a tetramethylammonium hydroxide concentration of 6.0 mass% and stirred to prepare a slurry containing 10 mass% of niobium in terms of Nb2O5. The slurry was stirred for 24 hours to obtain a niobate compound dispersion liquid (sample). The water content in the niobate compound dispersion liquid (sample) was 13.0 mass%.

[0193] Since the tetramethylammonium hydroxide 5 hydrate and the niobium acid compound-containing substance described above contain water, the niobium acid compound dispersion liquid (sample) obtained in Example 1 is a niobium acid compound dispersion liquid in which a part or all of the niobium acid compound is dispersed or dissolved in a mixed solvent in which a lower alcohol and water are used as main solvents and which contains tetramethylammonium hydroxide as an amine compound solvent.

[0194] (Example 2)

[0195] In Example 1, instead of adding ethanol (water content: 0.5 mass%) to the niobium acid compound-containing substance (precursor-containing substance), a solvent containing ethanol (water content: 0.5 mass%) and pure water at a mass ratio of 11.3:13.1 was added to the niobium acid compound-containing substance (precursor-containing substance) and stirred, and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, water content: 50 mass%) was added so as to make the concentration of tetramethylammonium hydroxide 4.0 mass% and stirred, and a slurry containing 10 mass% of niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium acid compound dispersion liquid (sample). The content of water in the niobium acid compound dispersion liquid (sample) was 50.1 mass%.

[0196] (Example 3)

[0197] In Example 1, instead of adding ethanol (water content: 0.5 mass%) to the niobium acid compound-containing substance (precursor-containing substance), a solvent containing ethanol (water content: 0.5 mass%) and pure water at a mass ratio of 26.3:29.1 was added to the niobium acid compound-containing substance (precursor-containing substance) and stirred, and then an aqueous methylamine solution (methylamine concentration: 40 mass%, water content: 60 mass%) was added so as to make the concentration of methylamine 10.0 mass% and stirred, and a slurry containing 10 mass% of niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium acid compound dispersion liquid (sample). The content of water in the niobium acid compound dispersion liquid (sample) was 51.6 mass%.

[0198] (Example 4)

[0199] In Example 1, instead of adding ethanol (water content: 0.5 mass%) 48.4 g and stirring in the niobium compound-containing material (precursor-containing material), ethanol (water content: 0.5 mass%) 40.8 g was added and stirred in the niobium compound-containing material (precursor-containing material), and then tetraethylammonium hydroxide 5 hydrate (TEAH concentration: 35 mass%, water content: 65 mass%) was added and stirred in such a manner that the concentration of tetraethylammonium hydroxide became 8.0 mass%, to prepare a slurry containing 10 mass% niobium in terms of Nb2O5, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound dispersion liquid (sample). The content of water in the niobium compound dispersion liquid (sample) was 21.8 mass%.

[0200] (Example 5)

[0201] In Example 1, instead of adding ethanol (water content: 0.5 mass%) in the niobium compound-containing material (precursor-containing material), a solvent containing isobutyl alcohol (water content: 1.0 mass%) and methanol (water content: 0.2 mass%) at a mass ratio of 42.4:24.7 was added and stirred in the niobium compound-containing material (precursor-containing material), and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, water content: 50 mass%) was added and stirred in such a manner that the concentration of tetramethylammonium hydroxide became 7.0 mass%, to prepare a slurry containing 10 mass% niobium in terms of Nb2O5, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound dispersion liquid (sample). The content of water in the niobium compound dispersion liquid (sample) was 14.1 mass%.

[0202] As in Example 1, since water is contained in the above-mentioned tetramethylammonium hydroxide 5 hydrate and the niobium compound-containing material, the niobium compound dispersion liquid (sample) obtained in Example 5 is a niobium compound dispersion liquid in which part or all of the niobium compound is dispersed or dissolved in a mixed solvent in which a lower alcohol and water are used as main solvents, and tetramethylammonium hydroxide as an amine compound solvent is contained.

[0203] (Example 6)

[0204] In Example 1, instead of adding ethanol in the niobium compound-containing material (precursor-containing material), a solvent containing isobutyl alcohol (water content: 1.0 mass%), ethylene glycol (water content: 0.5 mass%), and methanol (water content: 0.2 mass%) in a mass ratio of 34.6:5.6:29.0 was added in the niobium compound-containing material (precursor-containing material) and stirred, and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, water content: 50 mass%) was added in a manner such that the concentration of tetramethylammonium hydroxide became 5.0 mass% and stirred, and a slurry containing 10 mass% niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound dispersion liquid (sample). The content of water in the niobium compound dispersion liquid (sample) was 12.1 mass%.

[0205] As in Example 1, since water is contained in the above-mentioned tetramethylammonium hydroxide 5 hydrate and niobium compound-containing material, the niobium compound dispersion liquid (sample) obtained in Example 6 is a niobium compound dispersion liquid in which a part or all of the niobium compound is dispersed or dissolved in a mixed solvent in which a lower alcohol and water are used as main solvents and which contains tetramethylammonium hydroxide as an amine compound solvent.

[0206] (Example 7)

[0207] In Example 1, instead of adding ethanol (water content: 0.5 mass%) in the niobium compound-containing material (precursor-containing material), a solvent containing ethanol (water content: 0.5 mass%) and pure water in a mass ratio of 21.4:39.7 was added in the niobium compound-containing material (precursor-containing material) and stirred, and then dimethylamine aqueous solution (dimethylamine concentration: 50 mass%, water content: 50 mass%) was added in a manner such that the concentration of dimethylamine became 10.0 mass% and stirred, and a slurry containing 10 mass% niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound dispersion liquid (sample). The content of water in the niobium compound dispersion liquid (sample) was 56.5 mass%.

[0208] (Example 8)

[0209] In Example 1, instead of adding ethanol (moisture content: 0.5 mass%) in the niobium compound-containing material (precursor-containing material), a solvent containing ethanol (moisture content: 0.5 mass%) and pure water at a mass ratio of 5.7:7.7 was added in the niobium compound-containing material (precursor-containing material) and stirred, and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, moisture content: 50 mass%) was added in such a manner that the concentration of tetramethylammonium hydroxide became 15.0 mass% and stirred, and a slurry containing 30 mass% niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound dispersion liquid (sample). The content of water in the niobium compound dispersion liquid (sample) was 42.7 mass%.

[0210] (Example 9)

[0211] In Example 1, instead of adding ethanol (moisture content: 0.5 mass%) in the niobium compound-containing material (precursor-containing material), a solvent containing ethanol (moisture content: 0.5 mass%), acetone (moisture content: 0.5 mass%), and pure water at a mass ratio of 49.0:4.7:14.0 was added in the niobium compound-containing material (precursor-containing material) and stirred, and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, moisture content: 50 mass%) was added in such a manner that the concentration of tetramethylammonium hydroxide became 0.7 mass% and stirred, and a slurry containing 1.0 mass% niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound dispersion liquid (sample). The content of water in the niobium compound dispersion liquid (sample) was 8.5 mass%.

[0212] (Comparative Example 1)

[0213] In Example 1, instead of adding ethanol (moisture content: 0.5 mass%) in the niobium compound-containing material (precursor-containing material), a solvent containing ethanol (moisture content: 0.5 mass%), acetone (moisture content: 0.5 mass%), and pure water at a mass ratio of 49.0:4.7:14.0 was added in the niobium compound-containing material (precursor-containing material) and stirred, and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, moisture content: 50 mass%) was added in such a manner that the concentration of tetramethylammonium hydroxide became 0.7 mass% and stirred, and a slurry containing 1.0 mass% niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound dispersion liquid (sample). The content of water in the niobium compound dispersion liquid (sample) was 8.5 mass%.

[0214] (Comparative Example 2)

[0215] In Example 1, instead of adding ethanol (water content: 0.5 mass%) to the niobium compound-containing material (precursor-containing material), a solvent containing ethanol (water content: 0.5 mass%), acetone (water content: 0.5 mass%), and pure water in a mass ratio of 48.0: 1.7: 18.0 was added to the niobium compound-containing material (precursor-containing material) and stirred, and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, water content: 50 mass%) was added so as to make the concentration of tetramethylammonium hydroxide 0.7 mass% and stirred, and a slurry containing 1.0 mass% of niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound-containing liquid (sample). The content of water in the niobium compound-containing liquid (sample) was 4.3 mass%.

[0216] (Comparative Example 3)

[0217] In Example 1, 52.6 g of ethanol (water content: 0.5 mass%) was added to the niobium compound-containing material (precursor-containing material) and stirred, and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, water content: 50 mass%) was added so as to make the concentration of tetramethylammonium hydroxide 3.0 mass% and stirred, and a slurry containing 10 mass% of niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound-containing liquid (sample). The content of water in the niobium compound-containing liquid (sample) was 10.0 mass%.

[0218] (Comparative Example 4)

[0219] In Example 1, instead of adding ethanol (water content: 0.5 mass%) to the niobium compound-containing material (precursor-containing material), a solvent containing ethanol (water content: 0.5 mass%), acetone (water content: 0.5 mass%), and pure water in a mass ratio of 48.0: 1.7: 18.0 was added to the niobium compound-containing material (precursor-containing material) and stirred, and then tetramethylammonium hydroxide 5 hydrate (TMAH concentration: 50 mass%, water content: 50 mass%) was added so as to make the concentration of tetramethylammonium hydroxide 0.7 mass% and stirred, and a slurry containing 1.0 mass% of niobium in terms of Nb2O5was prepared, and otherwise, the same operation as in Example 1 was performed to obtain a niobium compound-containing liquid (sample). The content of water in the niobium compound-containing liquid (sample) was 4.3 mass%.

[0220] (Comparative Example 5)

[0221] In Example 1, instead of adding ethanol (water content: 0.5 mass %) to the niobium oxide compound-containing material (precursor-containing material), a solvent containing ethanol (water content: 0.5 mass %), acetone (water content: 0.5 mass %), and pure water at a mass ratio of 32.0:4.7:31.0 was added to the niobium oxide compound-containing material (precursor-containing material) and stirred. Subsequently, tetramethylammonium hydroxide pentahydrate (TMAH concentration: 50 mass %, water content: 50 mass %) was added to the niobium oxide compound-containing material (precursor-containing material) to achieve a tetramethylammonium hydroxide concentration of 0.7 mass %, and stirred. A slurry containing 1.0 mass % niobium in terms of Nb2O5 was prepared in the same manner as in Example 1, except that the above procedures were followed. The water content in this niobium oxide compound dispersion (sample) was 8.5 mass %.

[0222] Table 1 shows the usage amounts, purity, water content, etc. of the precursors, lower alcohols, pure water, and amine compound solvents used in Examples and Comparative Examples, as well as the water content of the resulting niobate compound dispersions ("Nb acid aqueous solutions").

[0223] Furthermore, the water content, the molar ratio of the amine compound solvent to Nb, and the proportion of the remaining lower alcohol were calculated for the niobate compound-containing solutions (samples) obtained in Examples and Comparative Examples.

[0224] It should be noted that the niobate compounds in the niobate compound-containing solutions (samples) obtained in Examples 1 to 9 and Comparative Examples 1 to 5 are similar to the niobate compound-containing substances (precursor-containing substances) in that the molar ratio of the ammonium ion content to the niobium (Nb) content (NH4 + / Nb) are both 0.8.

[0225] [Table 1]

[0226]

[0227] *1 IBA: Isobutyl alcohol (also known as 2-methyl-1-propanol)

[0228] *2 EG: Ethylene glycol (also known as ethane-1,2-diol)

[0229] *3 (MEK): Methyl ethyl ketone (also known as 2-butanone) <not a lower alcohol>

[0230] *4 (Acetone): Also known as 2-propanone <not a lower alcohol>

[0231] *5 Pure water: Applicable to pure water additives (excluding water in precursors, lower alcohols, and amine compound solvents)

[0232] Note that the IBA *1 : isobutyl alcohol (alias 2-methyl-1-propanol), EG *2 : ethylene glycol (alias 1.2-ethanediol), (MEK) *3 : methyl ethyl ketone (alias 2-butanone) <not a lower alcohol>, (acetone) *4 : alias 2-propanone <not a lower alcohol>, pure water *5 : target of the pure water additive (excluding moisture in the precursor content, lower alcohol, etc., amine compound solvent content).

[0233] <Transmittance measurement>

[0234] A spectrophotometer was used to measure the transmittance of the niobium acid compound dispersion liquid (sample) obtained in Examples 1 to 9 or the niobium acid compound-containing liquid (sample) obtained in Comparative Examples 1 to 5.

[0235] = Transmittance measurement conditions =

[0236] • Apparatus: UH4150-type spectrophotometer

[0237] • Measurement mode: wavelength scan

[0238] • Data mode: %T (transmission)

[0239] • Measurement wavelength range: 200 to 2600 nm

[0240] • Scan speed: 600 nm / minute

[0241] • Sampling interval: 2 nm

[0242] The light transmittance at a wavelength of 400 nm was calculated from the measured transmittance, and is shown in Table 2.

[0243] <HSP value (Hansen Solubility Parameter)>

[0244] The HSP value of the solvent contained in the niobium acid compound dispersion liquid (sample) obtained in Examples 1 to 9 or the niobium acid compound-containing liquid (sample) obtained in Comparative Examples 1 to 5 was calculated by the Y-MB method using computer software Hansen Solubility Parameters in Practice (HSPiP), and is shown in Table 2.

[0245] <Adhesion evaluation>

[0246] The niobate compound dispersions (samples) obtained in Examples 1 to 9 or the niobate compound-containing solutions (samples) obtained in Comparative Examples 1 to 5 were applied once onto a soda glass substrate using a spin coater. The soda glass substrate with the coating film was calcined in air at 200°C for 3 hours and then cooled to 25°C. A 24 mm x 15 m cellophane tape (manufactured by Nichiban Co., Ltd., product name CT-24, thickness 0.053 mm) described in JIS Z 1522: 2009 was attached to the surface of the coating film. To ensure proper contact between the tape and the coating film, the surface of the tape was rubbed firmly three times with the fingertips. Within 1 minute, the tape was peeled off by grasping the end of the tape at an angle of 60°±10° for 0.5 to 1.0 seconds.

[0247] The samples with smooth coating film surfaces and no peeling were evaluated as “acceptable (○)”, while the samples with partial peeling or uneven film were evaluated as “unacceptable (×)”. The results are shown in Table 2.

[0248] In addition, samples that could not be slurried or dissolved and could not be evaluated were marked as "not evaluable" (-).

[0249] [Table 2]

[0250]

[0251] *1: Since the niobate compound-containing liquid separates into two phases, the transmittance at 400 nm cannot be measured.

[0252] *2: Unable to disperse and slurry

[0253] Note that, regarding the samples of Comparative Examples 1 and 2, since the niobate compound-containing liquid separated into two phases, the light transmittance at a wavelength of 400 nm could not be measured.

[0254] Regarding Comparative Example 5, since the dispersibility was poor and slurry could not be formed, the light transmittance at a wavelength of 400 nm could not be measured.

[0255] (Inspection)

[0256] The niobate compound dispersions (samples) obtained in Examples 1 to 9 do not substantially contain organic substances having a volatilization temperature of 200° C. or higher and halogen elements due to the raw materials and the production method.

[0257] From the results of the above examples and comparative examples and the results of the experiments conducted by the inventors of the present application to date, it is known that by using a low alcohol and water as the main solvent, and adding a primary amine, a secondary amine, a tertiary amine, or a quaternary ammonium compound or a mixture of two or more of these, i.e., the above-mentioned amine compound solvent, it is possible to improve the dispersibility or even solubility of the niobate compound, and it is possible to obtain a niobate compound dispersion liquid in which part or all of the niobate compound is dispersed or dissolved.

[0258] Further, with respect to the content of water in the niobate compound dispersion liquid, the following results were confirmed: if the content of water in the examples is 8.5% by mass or more, the dispersibility or even solubility is preferably compared with Comparative Example 4 in which the content of water is 4.3% by mass. Thus, it is known that from the viewpoint of improving the dispersibility or even solubility of the niobate compound, it is preferable to adjust the amount of water in such a manner that the content of water in the niobate compound dispersion liquid is 5.0% by mass or more.

[0259] Further, with respect to the content of the above-mentioned amine compound solvent, the following results were confirmed: if the ratio of the content of the above-mentioned amine compound solvent to the content of niobium (Nb) in the examples is 0.73 or more, the dispersibility or even solubility of the niobate compound is preferably compared with Comparative Example 3 in which the ratio is 0.44. Thus, it is also known that from the viewpoint of improving the dispersibility or even solubility of the niobate compound, it is preferable to adjust the content of the above-mentioned amine compound solvent to the content of niobium (Nb) in such a manner that the molar ratio is 0.50 or more.

[0260] Further, with respect to the proportion of the low alcohol, the following results were confirmed: if the proportion of the low alcohol in the examples is 77.8% by mass, the dispersibility or even solubility of the niobate compound is preferably compared with Comparative Example 5 in which the proportion is 50.8% by mass. Thus, it is also known that from the viewpoint of improving the dispersibility or even solubility of the niobate compound, it is preferable to adjust the proportion of the low alcohol in such a manner that the low alcohol accounts for 70% by mass or more of the above-mentioned niobate compound-derived component, the above-mentioned amine compound solvent-derived component, and the water-excluding contained components.

Claims

1. A niobate compound dispersion, characterized in that: The present invention relates to a niobate compound dispersion in which a part or all of a niobate compound is dispersed or dissolved in a solvent containing a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium compound, or a mixed solvent of two or more thereof, and a lower alcohol and water as main solvents. The primary amine, secondary amine, tertiary amine, quaternary ammonium compound, or two or more thereof are also referred to as "amine compound solvents". The lower alcohol is an alcohol having a carbon number of 5 or less, The niobate compound dispersion does not contain organic matter with a volatilization temperature of more than 200° C. and halogen elements. The niobate compound dispersion contains 5.0% by mass or more of water, The content of the amine compound solvent relative to the content of niobium Nb is 0.80 or more in terms of molar ratio. The lower alcohol accounts for 70% by mass or more of the components other than the components derived from the niobic acid compound, the components derived from the amine compound solvent, and water, which is referred to as the "remainder." The niobate compound is a compound containing niobate and ammonium ions, and the molar ratio of the ammonium ion content to the niobium Nb content (NH4 + / Nb) is more than 0.60 and 20 or less.

2. The niobate compound dispersion according to claim 1, wherein The light transmittance at a wavelength of 400 nm is 99.5% or more.

3. A method for producing a niobate compound dispersion, characterized in that: A compound containing niobic acid and ammonium ions, i.e., a niobic acid compound, a lower alcohol or even water, and a primary amine, a secondary amine, a tertiary amine or a quaternary ammonium compound, or two or more thereof, are mixed. The niobic acid compound is referred to as a "precursor," and the primary amine, a secondary amine, a tertiary amine or a quaternary ammonium compound, or two or more thereof, is also referred to as an "amine compound solvent." The lower alcohol is an alcohol having a carbon number of 5 or less, The produced niobium oxide compound dispersion does not contain organic matter with a volatilization temperature of 200° C. or higher and halogen elements, contains 5.0% by mass or higher of water, the content of the amine compound solvent is 0.80 or higher in terms of molar ratio relative to the content of niobium (Nb), and the lower alcohol accounts for 70% by mass or higher of the components other than the components derived from the niobium oxide compound, the components derived from the amine compound solvent, and water, which is referred to as the "remainder." In the precursor, the molar ratio of ammonium ion content to Nb content (NH4 + / Nb) is more than 0.60 and 20 or less.

4. The niobate compound dispersion according to claim 1 or 2, which is evaluated as acceptable in the following adhesion evaluation. <Adhesion Evaluation> A dispersion of a niobate compound was applied once to a soda glass substrate using a spin coater. The soda glass substrate with the coating was calcined at 200°C for 3 hours and then cooled to 25°C. A 24 mm x 15 m cellophane tape was attached to the surface of the coating in accordance with JIS Z 1522:2009. The surface of the tape was rubbed three times with the fingertips. Within 1 minute, the tape was peeled off by grasping the ends at an angle of 60°±10° for 0.5 to 1.0 seconds. A test result was evaluated as "passing" if the coating surface was smooth and no peeling occurred.

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