Hafnium compound-containing sol-gel solution, method for producing a hafnium compound-containing sol-gel solution, and method for producing a hafnium-containing film

Abstract

To provide a sol-gel liquid containing a hafnium compound, which can be coated uniformly even on a hydrophilic substrate surface.SOLUTION: Provided is a sol-gel liquid comprising: a lower alcohol with a carbon number of 5 or less as a solvent; a hafnium compound as a hafnium source; and a polyalcohol having either or both of an ether group and an N atom in the molecule as a wettability improving agent. Preferably, the sol-gel liquid further comprises a stabilizing agent. It is also preferable that a content of the hafnium compound is set in a range of 0.05 mass% to 10 mass%, and a content of the polyalcohol is set in a range of 0.05 mass% to 20 mass%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a hafnium compound-containing sol-gel liquid used for forming a hafnia-containing film containing hafnia (also known as hafnium(IV) oxide, chemical formula: HfO₂) on the surface of a substrate, a method for producing the hafnium compound-containing sol-gel liquid, and a method for producing a hafnia-containing film using the hafnium compound-containing sol-gel liquid.

Background Art

[0002] Conventionally, the above-described hafnia-containing film has been formed on the surfaces of various substrates as a high-hardness hard coat film or an etching mask. Here, as a method for forming the above-described hafnia-containing film, as disclosed in, for example, Patent Documents 1 and 2, a method using a hafnium compound-containing sol-gel liquid containing a hafnium compound serving as a hafnia source has been proposed. In Patent Documents 1 and 2, a hafnia-containing film is formed by applying a hafnium compound-containing sol-gel liquid to the surface of a substrate and curing the applied film of the hafnium compound-containing sol-gel liquid.

[0003] By the way, as disclosed in Patent Document 1, the hafnium compound-containing sol-gel liquid has low wettability to metal surfaces, so it has been difficult to form a coating film of the hafnium compound-containing sol-gel liquid with a uniform thickness on the surface of a metal substrate. Therefore, in Patent Document 1, after performing degreasing treatment or electrolytic treatment on the surface of a metal substrate, the hafnium compound-containing sol-gel liquid is applied to achieve uniformity of the coating film of the hafnium compound-containing sol-gel liquid.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Patent Document 2

[0005] However, the method described in Patent Document 1 requires degreasing and electrolytic treatment of the metal substrate surface, which complicates the process and may increase manufacturing costs. Furthermore, depending on the surface condition after degreasing and electrolytic treatment, it may not be possible to uniformly apply the hafnium compound-containing sol-gel solution. In particular, with substrates made of easily oxidized metals such as aluminum, an oxide film may form on the substrate surface, making it hydrophilic, which could prevent the uniform application of the hafnium compound-containing sol-gel solution.

[0006] This invention has been made in view of the circumstances described above, and aims to provide a hafnium compound-containing sol-gel solution that can be uniformly applied even to hydrophilic substrate surfaces, a method for producing this hafnium compound-containing sol-gel solution, and a method for producing a hafnium-containing film using this hafnium compound-containing sol-gel solution. [Means for solving the problem]

[0007] To solve the above problems, the hafnium compound-containing sol-gel solution of embodiment 1 of the present invention has a number of carbon atoms that serve as the solvent. 3 or more It is characterized by containing a lower alcohol of 5 or less, a hafnium compound that serves as a hafnia source, and a polyalcohol having either an ether group and / or an N atom in its molecule as a wettability improver.

[0008] In the hafnium compound-containing sol-gel solution of Embodiment 1 of the present invention, a polyalcohol having either an ether group and / or a nitrogen atom in its molecule is contained as a wettability improving agent. This polyalcohol has a high affinity for hydrophilic surfaces because it contains multiple hydroxyl groups (-OH groups) in its molecule, and also has a high affinity for the hafnium compound-containing sol-gel solution because it has either an ether group (-O-) and / or a nitrogen atom in its molecule. Therefore, it is possible to uniformly apply the hafnium compound-containing sol-gel solution containing this polyalcohol to the surface of a hydrophilic substrate. Furthermore, since it contains a hafnium compound as a hafnium source, a hafnium-containing film can be formed by drying and calcining this hafnium compound-containing sol-gel solution. Furthermore, since a lower alcohol with 5 or fewer carbon atoms is used as the solvent, the solvent can be evaporated relatively easily, making it possible to stably form a hafnia-containing film.

[0009] Aspect 2 of the present invention is characterized in that the hafnium compound-containing sol-gel solution of Aspect 1 further contains a stabilizer. According to the hafnium compound-containing sol-gel solution of embodiment 2 of the present invention, since it contains a stabilizer, the deterioration of the hafnium compound-containing sol-gel solution can be suppressed, and handling becomes easier.

[0010] Aspect 3 of the present invention is characterized in that, in the hafnium compound-containing sol-gel solution of Aspect 1 or Aspect 2, the content of the hafnium compound is in the range of 0.05 mass% to 10 mass%, and the content of the polyalcohol is in the range of 0.05 mass% to 20 mass%. According to the hafnium compound-containing sol-gel solution of embodiment 3 of the present invention, since the content of the hafnium compound is within the above-mentioned range, a hafnium-containing film can be reliably formed by drying and calcining this hafnium compound-containing sol-gel solution. Furthermore, since the polyalcohol content is within the above-mentioned range, the hafnium compound-containing sol-gel solution can be applied more uniformly to the hydrophilic substrate surface.

[0011] The method for producing a hafnium compound-containing sol-gel solution according to aspect 4 of the present invention is a method for producing a hafnium compound-containing sol-gel solution according to aspects 1 to 3 of the present invention, wherein the number of carbon atoms in the solvent 3 or more The invention is characterized by comprising a hafnium compound addition step of adding the hafnium compound to a lower alcohol of 5 or less; a reflux step of refluxing the solvent to which the hafnium compound has been added; and a polyalcohol addition step of adding and mixing the polyalcohol after cooling to room temperature.

[0012] According to the method for producing a hafnium compound-containing sol-gel solution of embodiment 4 of the present invention, as described above, a hafnium compound, which serves as a hafnium source, is added to a lower alcohol, which serves as a solvent, and refluxed. After cooling to room temperature, a polyalcohol is added. This allows for a uniform dispersion of the hafnium compound and the polyalcohol in the solvent, enabling the stable production of a hafnium compound-containing sol-gel solution.

[0013] A method for producing a hafnia-containing film according to aspect 5 of the present invention is a method for producing a hafnia-containing film on the surface of a substrate, characterized by comprising: a hafnium compound-containing sol-gel liquid coating step of coating the surface of the substrate with a hafnium compound-containing sol-gel liquid according to aspects 1 to 3 of the present invention; a drying step of drying the coated hafnium compound-containing sol-gel liquid to form a hafnium compound-containing gel film; and a firing step of firing the hafnium compound-containing gel film to form a hafnia-containing film.

[0014] According to the method for producing a hafnia-containing film of aspect 5 of the present invention, since the hafnium compound-containing sol-gel solution described above is used, the solution can be uniformly applied even to the surface of a hydrophilic base material. Since the uniformly applied hafnium compound-containing sol-gel solution is dried and fired, a hafnia-containing film having a uniform thickness can be stably produced. [Effects of the Invention]

[0015] According to the present invention, there can be provided a hafnium compound-containing sol-gel solution that can be uniformly applied even to the surface of a hydrophilic base material, a method for producing the hafnium compound-containing sol-gel solution, and a method for producing a hafnia-containing film using the hafnium compound-containing sol-gel solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [Figure 1] It is a flow diagram illustrating a method for producing a hafnium compound-containing sol-gel solution according to an embodiment of the present invention. [Figure 2] It is a flow diagram illustrating a method for producing a hafnia-containing film according to an embodiment of the present invention. MODES FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, a hafnium compound-containing sol-gel solution, a method for producing a hafnium compound-containing sol-gel solution, and a method for producing a hafnia-containing film, which are embodiments of the present invention, will be described with reference to the drawings.

[0018] The hafnium compound-containing sol-gel solution according to the present embodiment contains a lower alcohol having 5 or less carbon atoms that serves as a solvent, and further contains a hafnium compound that serves as a hafnia source, and a polyalcohol having one or both of an ether group and an N atom in a molecule as a wettability improver. In addition to these components, the solution may further contain a stabilizer.

[0019] Furthermore, in the hafnium compound-containing sol-gel liquid according to the present embodiment, it is preferable that the content of the hafnium compound serving as a hafnia source is in the range of 0.05 mass% or more and 10 mass% or less, and the content of the polyalcohol is in the range of 0.05 mass% or more and 20 mass% or less. That is, in the composition of the hafnium compound-containing sol-gel liquid according to the present embodiment, it is preferable that the content of the hafnium compound is in the range of 0.05 mass% or more and 10 mass% or less, the content of the polyalcohol is in the range of 0.05 mass% or more and 20 mass% or less, the content of the stabilizer is in the range of 0 mass% or more and 20 mass% or less, and the remainder is a solvent (lower alcohol having 5 or less carbon atoms). Here, the lower alcohol is an alcohol having 5 or less carbon atoms in the molecule and 2 or less hydroxyl groups (-OH groups).

[0020] Here, examples of the lower alcohol serving as the solvent include monohydric alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutyl alcohol, tert-butyl alcohol, n-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-pentyl alcohol, 3-methyl-2-butanol, and neopentyl alcohol, and dihydric alcohols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, and 1,4-butanediol. In the present embodiment, it is preferable to use propanol or butanol as the lower alcohol.

[0021] Examples of the hafnium compound serving as the hafnia source include hafnium compounds selected from the group consisting of hafnium halides, hafnium hypohalites, hafnium hyposulfite, hafnium halogenates, hafnium perhalogenates, hafnium inorganic acid salts, hafnium organic acid salts, hafnium alkoxides, and hafnium complexes.

[0022] In this embodiment, it is preferable to use a hafnium alkoxide with 5 or fewer carbon atoms as the hafnium compound that serves as the hafnium source. Specifically, it is preferable to use hafnium(IV) methoxide, hafnium(IV) ethoxide, hafnium(IV) propoxide, hafnium(IV) n-butoxide, hafnium(IV) t-butoxide, hafnium(IV) pentoxide, hafnium(IV) isopropoxide monoisopropylate, etc. By drying and calcining the hafnium compound-containing sol-gel solution, which contains these hafnium compounds that serve as the source of hafnia, hafnia (HfO2) is formed, and a hafnia-containing film is created.

[0023] Here, by setting the hafnium compound content in the hafnium compound-containing sol-gel solution to within the range of 0.05 mass% to 10 mass%, sufficient hafnia is formed by drying and calcining the hafnium compound-containing sol-gel solution, making it possible to reliably form a hafnia-containing film. Furthermore, the lower limit of the hafnium compound content is more preferably 0.1 mass% or more, and more preferably 0.2 mass% or more. On the other hand, the upper limit of the hafnium compound content is more preferably 8 mass% or less, and more preferably 5 mass% or less.

[0024] As polyalcohols having either an ether group and / or an N atom in the molecule that serve as a wettability improver, it is preferable to use, for example, diethylene glycol, triethylene glycol, tetraethylene glycol, diglycerol, dipentaerythritol, triethanolamine, diethanolamine, ethanolamine, heptanolamine, methanolamine, dimethyldiethanolamine, dimethylethanolamine, N-methylethanolamine, etc. Polyalcohols containing either an ether group or a nitrogen atom, or both, have a high affinity for hydrophilic surfaces due to the presence of multiple hydroxyl groups (-OH groups) within the molecule, and also have a high affinity for hafnium compound-containing sol-gel solutions due to the presence of either an ether group (-O-) or a nitrogen atom, or both. Therefore, hafnium compound-containing sol-gel solutions containing this polyalcohol can be uniformly applied to hydrophilic substrate surfaces.

[0025] Here, by setting the content of polyalcohols having either an ether group and / or an N atom in the hafnium compound-containing sol-gel solution to within the range of 0.05 mass% to 20 mass%, the wettability can be sufficiently improved, making it possible to uniformly apply the hafnium compound-containing sol-gel solution to a hydrophilic substrate surface. Furthermore, the lower limit of the content of polyalcohols having either an ether group and / or a nitrogen atom in the molecule is more preferably 0.1 mass% or more, and more preferably 0.2 mass% or more. On the other hand, the upper limit of the content of polyalcohols having either an ether group and / or a nitrogen atom in the molecule is more preferably 10 mass% or less, and more preferably 5 mass% or less.

[0026] As a stabilizer, it is preferable to use, for example, acetylacetone, ethyl acetoacetate, acetoin, hydroxyacetone, malonic acid, acetic acid, acetic anhydride, lactic acid, oxalic acid, citric acid, tartaric acid, etc. Adding a stabilizer to a hafnium compound-containing sol-gel solution can suppress its degradation and improve its handling. Therefore, a stabilizer may be added as needed.

[0027] In this case, it is preferable that the content of the stabilizer in the hafnium compound-containing sol-gel solution be within the range of 0 mass% to 10 mass%. Furthermore, the lower limit of the stabilizer content is more preferably 0.05 mass% or more, and more preferably 0.1 mass% or more. On the other hand, the upper limit of the stabilizer content is more preferably 8 mass% or less, and more preferably 5 mass% or less.

[0028] Next, the method for producing the hafnium compound-containing sol-gel solution according to this embodiment will be explained with reference to the flow chart in Figure 1.

[0029] In this embodiment, the method for producing a hafnium compound-containing sol-gel solution includes, as shown in Figure 1, a hafnium compound addition step S01 in which a hafnium compound is added to a lower alcohol with 5 or fewer carbon atoms which serves as a solvent; a reflux step S02 in which the solvent to which the hafnium compound, which serves as the hafnium source, is refluxed; and a polyalcohol addition step S03 in which, after being cooled to room temperature, a polyalcohol having either an ether group and / or an N atom in its molecule is added and mixed. A solvent addition step S04 may be included to adjust the composition. Furthermore, if a stabilizer is added, a stabilizer addition step S05 will be included.

[0030] In the hafnium compound addition step S01, the hafnium compound is added to the lower alcohol, which serves as the solvent, while the lower alcohol is heated and stirred. Furthermore, it is preferable to use a non-oxidizing atmosphere when adding the substance, and in this embodiment, a nitrogen atmosphere is used. Furthermore, it is preferable that the temperature of the lower alcohol when adding the hafnium compound be within the range of 5°C to 40°C.

[0031] In reflux step S02, the solvent to which the hafnium compound has been added is heated and refluxed while being stirred. In this reflux step S02, the heating temperature is preferably within the range of 80°C to 200°C. Furthermore, the holding time at the heating temperature is preferably within the range of 0.5 hours to 5 hours. Furthermore, if a stabilizer is to be added, it is preferable to perform the stabilizer addition step S05 before the reflux step S02.

[0032] In the polyalcohol addition step S03, the solvent from which the reflux step S02 was performed is cooled to room temperature (for example, within the range of 20°C to 30°C), and then a polyalcohol having either an ether group or an N atom, or both, in its molecule is added and mixed by stirring.

[0033] In the solvent addition step S04, a lower alcohol is added as a solvent to adjust the composition of the hafnium compound-containing sol-gel solution.

[0034] Through the above steps, the hafnium compound-containing sol-gel solution of this embodiment is produced.

[0035] Next, a method for producing a hafnia-containing film using the hafnium compound-containing sol-gel solution described above will be explained with reference to the flow chart in Figure 2.

[0036] In the method for manufacturing a hafnia-containing film according to this embodiment, as shown in Figure 2, the method comprises a hafnium compound-containing sol-gel liquid coating step S11 in which the hafnium compound-containing sol-gel liquid according to this embodiment is applied to the surface of a substrate, a drying step S12 in which the applied hafnium compound-containing sol-gel liquid is dried to form a hafnium compound-containing gel film, and a firing step S13 in which the hafnium compound-containing gel film is fired to form a hafnia-containing film.

[0037] In this embodiment, the substrate on which the hafnia-containing film is formed is a metal substrate, but it is not limited to metals. There are no particular restrictions as long as a hydrophilic film such as an oxide film is formed on the surface of the substrate. Furthermore, the surface of this substrate may have irregularities formed on it by processes such as blasting or etching. As substrates, single metals such as aluminum, titanium, iron, nickel, zinc, magnesium, and copper, as well as their alloys, oxides, elemental semiconductors such as silicon and gallium, and compound semiconductors such as silicon oxide, silicon nitride, silicon carbide, indium phosphide, gallium nitride, gallium arsenide, and gallium oxide can be used.

[0038] In the hafnium compound-containing sol-gel solution coating step S11, the hafnium compound-containing sol-gel solution according to this embodiment is applied to the surface of the substrate. At this time, there are no particular restrictions on the coating method, and methods such as spraying and dipping may be used, but in this embodiment, the hafnium compound-containing sol-gel solution is applied by spin coating. Herein, as described above, the hafnium compound-containing sol-gel solution of this embodiment contains a polyalcohol having either an ether group or an N atom, or both, in its molecule, making it possible to uniformly coat even hydrophilic substrate surfaces.

[0039] In this hafnium compound-containing sol-gel solution coating step S11, the hafnium compound-containing sol-gel solution of this embodiment (containing a polyalcohol having either an ether group and / or an N atom in its molecule as a wetting agent) is applied to the surface of the substrate for the first time, and then the hafnium compound-containing sol-gel solution for the second coat is applied. Here, the hafnium compound-containing sol-gel liquid for recoating may or may not contain the wetting agent described above. Furthermore, for the hafnium compound-containing sol-gel solution used for overcoating, it is preferable to use one with a higher hafnium compound content than the hafnium compound-containing sol-gel solution of this embodiment.

[0040] In drying step S12, a hafnium compound-containing gel film is formed by drying the hafnium compound-containing sol-gel solution applied to the substrate surface. In this embodiment, since the hafnium compound-containing sol-gel solution uses a lower alcohol with 5 or fewer carbon atoms as the solvent, the solvent can be evaporated relatively easily in drying step S12. In this drying process S12, the heating conditions are preferably an air or oxygen atmosphere, a heating temperature within the range of 100°C to 400°C, and a holding time at the heating temperature within the range of 0.5 minutes to 10 minutes. Alternatively, a hafnium compound-containing gel film of a predetermined thickness may be formed by repeatedly performing the hafnium compound-containing sol-gel coating step S11 and the drying step S12.

[0041] In the firing process S13, a hafnium compound-containing gel film is heated and fired to form a hafnium-containing film. In this firing process S13, the heating conditions are preferably an atmosphere of air or oxygen, a heating temperature within the range of 400°C to 1000°C, and a holding time at the heating temperature within the range of 0.5 minutes to 10 minutes. Furthermore, if the hafnium compound-containing sol-gel coating step S11 and the drying step S12 are repeated, the calcination step S13 may be performed after each drying step S12.

[0042] Through the above process, a hafnia-containing film is produced on the surface of the substrate.

[0043] In this embodiment, the hafnium compound-containing sol-gel liquid, configured as described above, contains a polyalcohol having either an ether group and / or an N atom in its molecule as a wettability improver. Therefore, it has a high affinity for hydrophilic surfaces, and in the hafnium compound-containing sol-gel liquid coating step S11, it is possible to uniformly coat the hydrophilic substrate surface.

[0044] Furthermore, since it contains a hafnium compound as a hafnium source, a hafnium-containing film can be formed by drying and calcining this hafnium compound-containing sol-gel solution. Furthermore, since a lower alcohol with 5 or fewer carbon atoms is used as the solvent, the solvent can be evaporated relatively easily in the drying step S12, making it possible to stably form a hafnia-containing film.

[0045] In this embodiment, if a stabilizer is further included in the hafnium compound-containing sol-gel solution, the deterioration of the hafnium compound-containing sol-gel solution can be suppressed, and the handling of the hafnium compound-containing sol-gel solution becomes easier.

[0046] Furthermore, in the hafnium compound-containing sol-gel liquid of this embodiment, if the hafnium compound content is in the range of 0.05 mass% to 10 mass% and the polyalcohol content is in the range of 0.05 mass% to 20 mass%, then by drying and calcining this hafnium compound-containing sol-gel liquid, a hafnium-containing film can be reliably formed, and the hafnium compound-containing sol-gel liquid can be applied more uniformly to the surface of a hydrophilic substrate.

[0047] As described above, the method for producing a hafnium compound-containing sol-gel solution according to this embodiment includes a hafnium compound addition step S01 in which a hafnium compound is added to a lower alcohol with 5 or fewer carbon atoms which serves as a solvent, a reflux step S02 in which the solvent to which the hafnium compound has been added is refluxed, and a polyalcohol addition step S03 in which a polyalcohol is added and mixed after being cooled to room temperature. Therefore, the hafnium compound and the polyalcohol can be uniformly dispersed in the solvent, and a hafnium compound-containing sol-gel solution can be stably produced. Furthermore, if the process includes a stabilizer addition step S05, the deterioration of the hafnium compound-containing sol-gel solution can be suppressed.

[0048] The method for manufacturing a hafnia-containing film according to this embodiment includes a hafnium compound-containing sol-gel liquid coating step S11 in which the hafnium compound-containing sol-gel liquid according to this embodiment is applied to the surface of a substrate, a drying step S12 in which the applied hafnium compound-containing sol-gel liquid is dried to form a hafnium compound-containing gel film, and a firing step S13 in which the hafnium compound-containing gel film is fired to form a hafnia-containing film. As a result, the hafnium compound-containing sol-gel liquid can be uniformly applied to the surface of a hydrophilic substrate, and a hafnia-containing film of uniform thickness can be stably manufactured.

[0049] Although embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. [Examples]

[0050] The results of the verification experiments conducted to confirm the effectiveness of the present invention are described below.

[0051] Under a nitrogen atmosphere, the solvents shown in Table 1 were heated to the temperatures shown in Table 2 and stirred while the hafnium compounds shown in Table 1 were added. Next, after adding the stabilizers shown in Table 1, reflux treatment was carried out under the conditions shown in Table 2. After cooling to room temperature, the wetting agents shown in Table 1 were added and stirred. Then, a lower alcohol, which serves as the solvent, was added to adjust the composition. This allowed us to produce the hafnium compound-containing sol-gel solutions of the present invention example and comparative example. Furthermore, in order to serve as a standard for the wettability evaluation described later, the hafnium compound-containing sol-gel solutions were produced under the same composition and conditions as the respective present invention example and comparative example, except that a wettability improving agent was not added.

[0052] The wettability of the hafnium compound-containing sol-gel solutions of the present invention and comparative examples on hydrophilic substrate surfaces was evaluated as follows.

[0053] A 50mm square, 2mm thick aluminum alloy substrate (A5052) was prepared as the base material. The surface of this substrate was blast-treated using SiC to form an uneven surface with a surface roughness (arithmetic mean roughness) Ra of 2 μm. Furthermore, by blasting the substrate to create an uneven surface, reflected light from the substrate is suppressed, making it easier to evaluate the area ratio of wetting spread in terms of color difference. In addition, by creating a surface with a large surface area that does not wet easily, the differences in the effect of each sample become more pronounced.

[0054] 0.1 mL of hafnium compound-containing sol-gel solution was dropped onto the center of the blasted surface of the substrate after blasting, and allowed to stand. The dropped hafnium compound-containing sol-gel solution spread over the substrate due to surface tension. After standing for 5 minutes following dropwise application, the area wetted by the hafnium compound-containing sol-gel solution was measured using a microscope. The same evaluation was performed three times, and the average value was calculated.

[0055] An improvement was defined as "present" if the wetting spread area increased by 20% or more compared to a hafnium compound-containing sol-gel solution without the addition of a wetting improvement agent. Compared to a hafnium compound-containing sol-gel solution without the addition of a wetting agent, solutions with an increase in wetting area of ​​less than 20% were classified as having "no improvement effect." The evaluation results are shown in Table 2.

[0056] [Table 1]

[0057] [Table 2]

[0058] In Comparative Example 1, ethylene glycol without an ether group in its molecule was added as a wetting improver, but the wettability could not be improved. In Comparative Example 2, diethylene glycol monomethyl ether having one hydroxyl group in its molecule was added as a wetting improver, but the wettability could not be sufficiently improved. In Comparative Example 3, diethylene glycol methyl ether, which does not have a hydroxyl group in its molecule, was added as a wetting agent, but the wettability could not be sufficiently improved. In Comparative Example 4, glycerin without an ether group or N atom in its molecule was added as a wetting improver, but the wettability could not be sufficiently improved.

[0059] In contrast, in Example 1-11 of the present invention, a polyalcohol having either an ether group and / or an N atom in its molecule is added as a wetting improver, and it was confirmed that the wettability is sufficiently improved. Therefore, it has been confirmed that, according to the present invention, it is possible to provide a hafnium compound-containing sol-gel liquid that can be uniformly applied even to hydrophilic substrate surfaces.

Claims

1. A hafnium compound-containing sol-gel solution characterized by containing a lower alcohol having 3 to 5 carbon atoms as a solvent, a hafnium compound as a hafnia source, and a polyalcohol having either an ether group and / or an N atom in its molecule as a wettability improver.

2. The hafnium compound-containing sol-gel solution according to claim 1, further characterized by containing a stabilizer.

3. The hafnium compound content is within the range of 0.05 mass% to 10 mass%, The hafnium compound-containing sol-gel solution according to claim 1, characterized in that the content of the polyalcohol is in the range of 0.05 mass% to 20 mass%.

4. A method for producing a hafnium compound-containing sol-gel solution according to any one of claims 1 to 3, A hafnium compound addition step is performed by adding the hafnium compound to a lower alcohol having 3 to 5 carbon atoms, which serves as a solvent. A reflux step in which the solvent to which the hafnium compound is added is refluxed, After cooling to room temperature, the polyalcohol is added and mixed in a polyalcohol addition step, A method for producing a hafnium compound-containing sol-gel solution, characterized by comprising the following features.

5. A method for producing a hafnia-containing film, comprising forming a hafnia-containing film on the surface of a substrate, A hafnium compound-containing sol-gel solution coating step, wherein the hafnium compound-containing sol-gel solution described in any one of claims 1 to 3 is applied to the surface of the substrate, A drying step in which the applied hafnium compound-containing sol-gel solution is dried to form a hafnium compound-containing gel film, A firing step to form a hafnium-containing film by firing the aforementioned hafnium compound-containing gel film, A method for producing a hafnia-containing film, characterized by comprising the following features.

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