JP5747551B2 - Hydrophilic thin film and method for producing the same - Google Patents

Description

  The present invention relates to a hydrophilic thin film and a method for producing the same, and more particularly to a hydrophilic thin film exhibiting good hydrophilicity and excellent in durability and a method for producing the same.

  In the case of automobiles, trains and residential window glass, automobiles and residential mirrors such as bathrooms and washrooms, glasses, telescopes, binoculars, etc., it may become cloudy or dewed by rainwater, steam, moisture, etc. It is required to impart hydrophilicity to these glass surfaces.

  As a technique for imparting hydrophilicity to the surface of a member such as glass, a mirror, and a lens, a method for expressing hydrophilicity by applying a surfactant to the surface of the member is known. However, in this method, the applied surfactant is easily washed away by water and the hydrophilicity is not maintained.

  For example, Patent Document 1 discloses a method for expressing hydrophilicity by applying a water-soluble polymer to the surface of a member. Similar to the surfactant, it is difficult to hold the water-soluble polymer on the surface of the member, and the durability is poor.

  A method for forming a silica and / or alumina thin film on the surface of a member is described in Patent Document 2, for example. However, since the contact angle of water is not reduced only by the silica and / or alumina thin film, another means for reducing the contact angle is necessary. For this reason, this method complicates the manufacturing process.

  For example, Patent Literature 3 and Patent Literature 4 describe a technique for imparting hydrophilicity to the surface of a member by applying the hydrophilicity imparted to the titania when irradiated with light. However, the hydrophilic effect of titania is manifested only at the time of light irradiation, and when the light is not irradiated, the hydrophilic effect is not manifested, so that the use environment is limited.

  Japanese Patent Application Laid-Open No. H10-228688 describes a technique for combining phosphates such as phosphoric acid and aluminum phosphate with ceramics such as silica and alumina. However, there is no description that the thin film described in the literature has hydrophilicity. Moreover, when using phosphoric acid and a phosphate as a surface modifier as it is, hydrophilicity will fall under boiling water or high temperature, and it will be inferior to durability.

JP-A-7-102189 Japanese Patent Laid-Open No. 3-174986 Japanese Patent No. 3384284 Japanese Patent No. 3620619 JP 2005-53554 A

  It is an object of the present invention to provide a hydrophilic thin film that exhibits good hydrophilicity and excellent durability, and to provide a method for producing a hydrophilic thin film that produces the hydrophilic thin film by a simple method. To do.

As means for solving the above-mentioned problems,
(1) An alumina thin film provided on the surface of a substrate using a fibrous alumina sol is placed in an aqueous solution of nitrilotris (methylenephosphonic acid) at a temperature of 150 ° C. to 200 ° C. for 10 minutes to 60 hours. This is a method for producing a hydrophilic thin film that is hydrothermally synthesized .

As a second means for solving the problems of the present invention,
(2) When the XPS spectrum of the thin film surface is measured by X-ray photoelectron spectroscopy, which is manufactured by the manufacturing method described in (1) above, the P2p spectrum present in the range of 133.0 eV to 135.0 eV Ten points of the surface measured using a scanning probe microscope having Al—O—P bonds due to the peak and the peak of the spectrum of Al 2p existing in the range of 74.0 eV or more and 76.0 eV or less It is a hydrophilic thin film whose average roughness (Rz) is less than 20 nm .

  According to this invention, it is possible to provide a hydrophilic thin film that exhibits good hydrophilicity and excellent durability. Moreover, the manufacturing method of the hydrophilic thin film which can manufacture the said hydrophilic thin film with a simple method can be provided.

  The hydrophilic thin film of this invention has an Al—O—P bond, and the ten-point average roughness (Rz) of the surface measured using a scanning probe microscope is less than 20 nm.

  This hydrophilic thin film has good hydrophilicity even if the surface is smooth due to the presence of Al-OP bonds on the surface. Moreover, even after this hydrophilic thin film is immersed in boiling water or placed at a high temperature, the hydrophilicity is maintained and the durability is excellent.

  The hydrophilic thin film has an Al—O—P bond when the XPS spectrum of the thin film surface is measured by X-ray photoelectron spectroscopy using an X-ray photoelectron spectroscopy (ESCA or XPS) apparatus. It can be confirmed that the peak top of the binding energy is in the range of 133.0 eV to 135.0 eV and the peak top of the binding energy of the Al2p spectrum is in the range of 74.0 eV to 76.0 eV. it can.

  The peak of the P2p spectrum indicates the presence of phosphate ions on the thin film surface. The hydrophilic thin film according to the present invention expresses good hydrophilicity despite its smooth surface because a hydrogen bond is formed between O of this phosphate ion and H of water. This is because the affinity for water increases.

  The hydrophilic thin film of the present invention has a ten-point average roughness (Rz) measured with a scanning probe microscope (SPM) on the thin film surface of less than 20 nm, and is usually 0.1 nm or more. In general, on the hydrophilic surface, the uneven surface has a lower contact angle with water than the flat surface, and the hydrophilicity becomes better. However, the uneven surface is inferior in wear resistance. That is, when the uneven surface is worn, the convex portion is destroyed and the contact angle with water increases. However, since the hydrophilic thin film of the present invention is a flat surface having a relatively high hardness, the shape and structure of the surface is stable and does not change even when subjected to friction. As a result, the hydrophilic thin film of the present invention does not have a large contact angle with water due to a change in the shape of the surface, and retains hydrophilicity for a long period.

  The ten-point average roughness (Rz) is determined from the roughness curve at an arbitrary line segment of 500 nm on the surface of the thin film using a scanning probe microscope (SPM), from the highest peak to the fifth peak from the average line. It is calculated as the sum of the average value of the absolute values of the altitude and the average value of the absolute values of the altitudes of the lowest valley bottom to the fifth. For example, the ten-point average roughness can be measured for any five line segments on the thin film surface, and the arithmetic average of the measured values obtained can be set as the ten-point average roughness (Rz).

  In the hydrophilic thin film of the present invention, the contact angle with respect to water on the surface of the thin film is 10 ° or less. Generally, when the contact angle with respect to water on the surface of the thin film is 20 ° or less, the surface of the thin film can be evaluated as having hydrophilicity. In particular, when the contact angle with respect to water on the surface of the thin film is 10 ° or less, the surface of the thin film is It can be evaluated that it has super hydrophilicity. The hydrophilic thin film of the present invention has super hydrophilicity because the contact angle with water on the surface of the thin film is 10 ° or less. Further, the surface of the hydrophilic thin film having hydrophilicity usually has antifogging properties and antifouling properties.

  The contact angle is determined by dropping 2 μL of water droplets onto the surface of a hydrophilic thin film placed on a horizontal sample stage at room temperature, and tangent to the curved surface of the water droplets from the point of contact with the air and the hydrophilic film in the water droplets. The angle between the tangent when drawn and the surface of the hydrophilic film can be determined by measuring using a contact angle meter.

The hydrophilic thin film of the present invention is substantially free of silica (SiO ₂ ). Conventionally, when forming a hydrophilic thin film, silica (SiO ₂ ) is sometimes used. However, the hydrophilic thin film of the present invention has good hydrophilicity even when silica (SiO ₂ ) is not contained, and is excellent in durability.

  The hydrophilic thin film of this invention can be manufactured by the simple method demonstrated below, for example.

  In the method for producing a hydrophilic thin film of the present invention, an alumina sol is applied to the surface of a substrate, and then the resulting alumina thin film is cured by hydrothermal treatment in an aqueous solution of a phosphate group-containing compound. It is characterized by combining.

  The alumina hydrate particles and / or alumina particles dispersed in the alumina sol can take various forms such as a spherical shape, a needle shape, a fiber shape, a column shape, and a plate shape, and an alumina water having various shapes. Japanese particles and / or alumina particles may be contained.

  The alumina sol in the present invention can be prepared, for example, by hydrolyzing an aluminum compound, and is peptized under acidic or alkaline conditions as necessary. This hydrolysis can be performed by dissolving the aluminum compound in a solvent and treating the resulting solution under certain conditions.

  The form of the alumina hydrate particles or the alumina particles can be adjusted by appropriately selecting the type of the aluminum compound and the conditions for hydrolysis and peptization.

  Examples of the aluminum compound as a raw material for preparing the alumina sol include a sol-forming aluminum compound capable of forming an aluminum oxide sol in a solvent such as water or an aqueous organic solvent.

  Examples of the sol-forming aluminum compound include aluminum halides, aluminum halides, aluminum hypohalites, aluminum halides, aluminum perhalogenates, aluminum inorganic acid salts, aluminum organic acid salts, and aluminum. Mention may be made of aluminum compounds selected from the group consisting of alkoxides and aluminum complexes.

  Specifically, examples of the aluminum halide include aluminum trifluoride, aluminum trichloride, aluminum tribromide, and aluminum triiodide. Examples of the aluminum hypohalite include hypochlorous acid. Examples thereof include aluminum oxide, aluminum hypobromite, and aluminum hypoiodite.

  Examples of the aluminum halide salt include aluminum chlorate, aluminum bromate, and aluminum iodate, and examples of the aluminum perhalogenate include aluminum perchlorate, aluminum perbromate, and aluminum periodate. Examples of the aluminum inorganic acid salt include aluminum nitrate and aluminum sulfate.

Examples of the aluminum organic acid salt include Al (OCHO) ₃ , Al (OCOR ³ ) ₃ (where R ³ is a linear alkyl group having 1 to 20 carbon atoms, a branched alkyl group, a cyclic alkyl group, or a carbon number) Monocarboxylate represented by 6 to 20 aromatic group), Al ₂ (OCOR ⁴ COO) ₃ (where R ⁴ is a linear alkylene group having 1 to 20 carbon atoms, branched alkylene group, cyclic) Dicarboxylate represented by an alkylene group or an aromatic group having 6 to 20 carbon atoms), Al (OH) ₂ (OCOR ⁵ ), Al ₂ O (OH) (OCOR ⁵ ) ₃ , Al ₄ O ₃ (OCOR ⁵ ) in ₆ any conventional aluminum carboxylate (or more chemical formula represented by the formula, R ⁵ represents a linear alkyl group having 1 to 20 carbon atoms, branched alkyl groups, cyclic alkyl group, an aralkyl group, Others can be cited showing.) An aromatic group having 6 to 20 carbon atoms.

  Examples of the monocarboxylate include aluminum formate, aluminum acetate, aluminum propionate, aluminum butyrate, aluminum valerate, aluminum caproate, aluminum heptanoate, aluminum octoate, aluminum nonanoate, aluminum decanoate, aluminum myristate, and palmitic acid. Examples of the dicarboxylate include aluminum oxalate and aluminum succinate.

As the alkoxide of aluminum, Al (OR ⁶ ) ₃ (where R ⁶ is a linear alkyl group having 1 to 20 carbon atoms, a branched alkyl group, a cycloalkyl group, an aralkyl group, or 6 to 20 carbon atoms). A compound represented by the following formula:

  Examples of the aluminum alkoxide may include aluminum isopropylate, mono-sec-butoxyaluminum diisopropylate, aluminum sec-butylate, and aluminum ethylate.

  Examples of the aluminum complex include diketone complexes, diketone complex halides, and diketone complex inorganic acid salts.

  Examples of the diketone complex include acetylacetonatoaluminum, aluminum acetoacetate, 1,3-propanedionate aluminum, 1,3-diphenyl-1,3-propanedionate aluminum, 1-phenylpropanedionate aluminum and Examples include polonato aluminum.

  Examples of the diketone complex halide include acetylacetonato aluminum chloride, aluminum acetoacetate chloride, 1,3-propanedionate aluminum chloride, 1,3-diphenyl-1,3-propanedionate aluminum chloride, 1 -Diketone complex chlorides such as phenylpropanedionato aluminum chloride, troponatoaluminum chloride, acetylacetonatoaluminum bromide, aluminum acetoacetate bromide, 1,3-propanedionato aluminum bromide, 1,3-diphenyl-1 , 3-propanedionate aluminum bromide, diphenyl complex bromide such as 1-phenylpropanedionato aluminum bromide, tropolonato aluminum bromide, acetylacetonato aluminum iodide, aluminum acetoacetate iodide, 1, Propane dionatoaluminum iodide, 1,3-diphenyl-1,3-propanedionato aluminum iodide, 1-phenylpropane dinatoaluminum iodide, tropolonatoaluminum iodide and the like diketone complex iodide, acetylacetonate Aluminum fluoride, aluminum acetoacetate fluoride, 1,3-propanedionato aluminum fluoride, 1,3-diphenyl-1,3-propanedionato aluminum fluoride, 1-phenylpropane dinato aluminum fluoride and tropolo A diketone complex fluoride such as natoaluminum fluoride can be used.

  Examples of the aluminum complex include ethyl acetoacetate aluminum isopropylate, aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum isopropylate, and the like.

  Among these, aluminum alkoxides are preferable because they have moderate hydrolyzability and easy removal of by-products, and those having a lower alkoxyl group having 2 to 5 carbon atoms are particularly preferable.

  Examples of the method for hydrolyzing the sol-forming aluminum compound include a method in which the sol-forming aluminum compound is added to an appropriate organic solvent and then the solution is brought into contact with water. In this case, water may be added to the solvent in advance. In the hydrolysis, an acid or a base may be present as a catalyst. In addition, a transparent sol solution can be prepared by suspending the sol-forming aluminum compound in water and adding an acid or a base as a catalyst.

  The reaction temperature at the time of hydrolysis can usually be room temperature to 100 ° C., but from the viewpoint of promoting the sol-forming reaction, the reaction temperature is in a range higher than room temperature, for example, 40 to 100 ° C. It is preferable to set the temperature within the range. The reaction time for the hydrolysis is usually 0.1 to 10 hours, preferably 0.5 to 5 hours, particularly preferably 0.5 to 4 hours.

  Examples of the aqueous organic solvent used for dissolving the sol-forming aluminum compound include an alcohol-based organic solvent that dissolves in water, a mixture of these alcohol-based organic solvents, and one or more alcohol-based organic solvents and water. A mixture etc. can be mentioned.

  Examples of the alcohol organic solvent include 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, neopentyl alcohol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 4 Monohydric alcohols such as methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol and cyclohexanol, as well as ethylene glycol, propylene glycol and trimethyle Glycol, 1,2-butanediol, 1,3-butanediol, it may be mentioned dihydric alcohols such as 1,4-butanediol.

  The concentration at which the sol-forming aluminum compound is dissolved in the solvent can be appropriately selected. Specifically, the concentration is adjusted such that the sol-forming aluminum compound is 0.1 to 50 parts by mass with respect to 100 parts by mass of the solvent, and preferably 1 to 30 parts by mass. Adjusted.

  Examples of the acid that can be used as a catalyst when the sol-forming aluminum compound is reacted with the solvent include inorganic acids and organic acids. Examples of the inorganic acid include hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, sulfuric acid and the like, and examples of the organic acid include lower monocarboxylic acid. Can include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, and the like.

  Examples of the base that can be used as a catalyst include caustic alkalis such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, amines such as primary amine, secondary amine, and tertiary amine, ethanolamine, and 3-amino-1 -Propanolamine, N, N-diethylethanolamine, N, N-dimethylethanolamine, aminoethylethanolamine, N-methyl-N, N-diethanolamine, N, N-dibutylethanolamine, N-methyl-N-ethanol Examples include alkanolamines such as amines.

  In the present invention, the substrate to which the alumina sol is applied is not particularly limited as long as it is a material that is required to impart hydrophilicity, and examples thereof include glass, metal, ceramics, and plastics. Among these materials, a glass having a high degree of demand for preventing or suppressing fogging or condensation due to rain water, steam, moisture, or the like is preferable.

  The glass is not limited, and examples thereof include quartz glass, 96% quartz glass, soda lime glass, aluminoborosilicate glass, borosilicate glass, aluminosilicate glass, and lead glass. Can include window glass for cars and trains, mirrors for cars, mirrors for houses such as bathrooms and washrooms, glasses, telescopes, binoculars, and the like.

  In this invention, an alumina thin film is formed by applying the alumina sol to the substrate surface and then curing the resulting coating film. Before applying the alumina sol to the substrate surface, the substrate surface Is preferably cleaned. This is because by cleaning the substrate surface, a uniform coating film can be formed without causing repelling.

  As the means for cleaning, for example, when the base material is glass, a cleaning means using a detergent, particularly a neutral detergent, can be used. When the base material is metal, a degreasing agent-containing liquid can be used. A means for dipping treatment can be mentioned.

  The degreasing agent in the degreasing agent-containing solution is preferably a degreasing agent containing a basic compound, and examples thereof include sodium hydroxide, sodium carbonate, sodium silicate, sodium phosphate, and sodium borate.

  Examples of the method of applying the alumina sol on the surface of the substrate include a dip method in which the substrate is immersed in the alumina sol and then gently lifted, or a casting method in which the alumina sol is cast on the fixed substrate surface by an appropriate method. A continuous method in which a substrate is immersed in alumina sol from one end of a tank in which the alumina sol is stored, and the substrate is taken out from the other end of the tank, and the centrifugal force acting on the substrate by dropping the alumina sol on the rotating substrate Examples thereof include a spinner method in which an alumina sol is cast on a substrate, and a spray method in which the alumina sol is sprayed on the surface of the substrate.

  The coating amount of the alumina-containing sol liquid is not uniform depending on the viscosity of the alumina-containing sol liquid and other conditions. If a thin film having a desired thickness cannot be obtained by a single application, the application can be repeated several times.

  The alumina sol coating film coated on the surface of the substrate by the various methods described above is dried as necessary and then subjected to a curing treatment to form an alumina thin film. As the curing treatment, heat treatment or light irradiation treatment can be mentioned, and as the light irradiation treatment, ultraviolet irradiation treatment is preferable.

  There is no particular limitation on the conditions of the heat treatment (hereinafter sometimes referred to as firing treatment) for forming the alumina thin film, but the temperature can be selected according to the heat-resistant temperature of the substrate. An appropriate temperature at 100 ° C. or higher is employed. When heating the substrate, it may be heated directly to the temperature, preheated at a relatively low temperature, and then heated to the temperature. The time is usually in the range of 1 minute to 10 hours, preferably in the range of 10 minutes to 5 hours.

  Although there is no special restriction | limiting in the conditions of the ultraviolet irradiation process for forming an alumina thin film, It is preferable to irradiate with ultraviolet rays under room temperature-150 degreeC. As the ultraviolet light source to be irradiated, a high pressure mercury lamp or a low pressure mercury lamp can be used. When these mercury lamps are used, ultraviolet light having an appropriate intensity can be irradiated at low cost.

  The thickness of the obtained alumina thin film can be appropriately determined according to the application, and is usually preferably in the range of 10 to 1000 nm.

  The method for producing a hydrophilic thin film of the present invention is characterized in that the alumina thin film formed as described above is hydrothermally synthesized in an aqueous solution of a phosphate group-containing compound.

  As the phosphate group-containing compound, the phosphoric acid group is dissociated from the phosphate group-containing compound by hydrothermal synthesis described later in an aqueous solution of the phosphate group-containing compound, so that the aluminum in the alumina thin film If it is a compound which couple | bonds with ion and forms an Al-OP bond, there will be no restriction | limiting in particular, A phosphoric acid group containing organic compound and a phosphoric acid group containing inorganic compound can be mentioned.

Examples of the phosphoric acid group-containing organic compound include a compound represented by any one of the following formulas (1) and (2) or a salt thereof.
R ₂ PO ₃ (CH ₂ ) _u SiX ₃ (1)
[R ₂ PO ₃ (CH ₂ ) _u ] _v NH _w (2)
[However, R represents a hydrogen atom, an alkyl group, an alkoxy group, an allyl group or an O-phenyl group, and two Rs may be the same or different. X represents halogen, —OH (hydroxyl group) or —OR ¹ (R ¹ represents an alkyl group or an allyl group). u represents an integer of 1 to 10. v and w represent integers, and the sum of v and w is 3. ]

  Examples of the alkyl group include a methyl group, an ethyl group, and an isopropyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, and an isopropoxy group. Examples of the halogen include chlorine, bromine and iodine.

  Specific examples of the preferable phosphoric acid group-containing organic compound include 3-trihydroxysilylpropylmethylphosphonate-sodium salt (hereinafter sometimes abbreviated as “HSiP”) and nitrilotris (methylenephosphonic acid) (hereinafter, “ NTP ”may be abbreviated as“ NTP ”).

  The concentration of the aqueous solution of the phosphoric acid group-containing organic compound in the hydrothermal synthesis is not particularly limited, but is usually 0.01 to 50% by mass, preferably 0.1 to 30% by mass.

Examples of the phosphoric acid group-containing inorganic compound include MPO ₄ , M _{n + 2} P _n O _{3n + 1} , (M ^I PO ₃ ) _n , (M ^II (PO ₃ ) ₂ ) _n , and (M ^III (PO ₃ ) ₃ ) _n . Inorganic compounds and their ester compounds (where M is a hydrogen atom or any metal ion, M ^I is a hydrogen atom or a +1 valent metal ion, M ^II is a +2 valent metal ion, and M ^III is a +3 valent metal) Represents an ion, and n represents an integer of 2 or more.

  Specific examples of the phosphoric acid group-containing inorganic compound include phosphoric anhydride, metaphosphoric acid, pyrophosphoric acid, orthophosphoric acid, triphosphoric acid, tetraphosphoric acid, ammonium phosphate, ammonium hydrogen phosphate, sodium phosphate, sodium hydrogen phosphate , Potassium phosphate, potassium hydrogen phosphate, calcium phosphate, calcium hydrogen phosphate, sodium phosphate, sodium hydrogen phosphate, aluminum phosphate, aluminum hydrogen phosphate, zinc phosphate, zinc hydrogen phosphate, and the like.

  The concentration of the aqueous solution of the phosphoric acid group-containing inorganic compound in the hydrothermal synthesis is not particularly limited, but is usually 0.01 to 50% by mass, preferably 0.1 to 30% by mass.

  Examples of a method for hydrothermally synthesizing the alumina thin film in an aqueous solution of a phosphoric acid group-containing compound include, for example, a group in which an alumina thin film is formed on a surface of a heat-resistant container containing the aqueous solution of the phosphoric acid group-containing compound. The material is placed in an autoclave and the hydrothermal synthesis is performed in a temperature range of 150 ° C. to 180 ° C. for 10 minutes to 60 hours, preferably 30 minutes to 30 hours. Can be mentioned. At this time, an aqueous solution of a phosphoric acid group-containing compound to the extent that the alumina thin film is immersed may be contained in the container.

  Thus, a hydrophilic thin film is manufactured by hydrothermal synthesis. The base material on which the hydrophilic thin film taken out from the container is formed is appropriately washed with pure water.

  The hydrophilic thin film of the present invention can be applied to glass, metal, ceramics, plastics and the like. Since the hydrophilic thin film of the present invention exhibits good hydrophilicity and excellent durability, it is suitably used for the material that requires antifogging and antifouling properties over a long period of time. The hydrophilic thin film of the present invention is formed on the surface of window glass for houses, automobiles, trains, etc., mirrors such as bathrooms and toilets, military or consumer telescopes, binoculars and reflectors, etc. The antifogging and antifouling properties of the window glass and mirror can be maintained over a long period of time. Further, when the inner surface of the water supply pipe is coated with the hydrophilic thin film of the present invention, the inner surface of the pipe becomes hydrophilic, so that the water supply load is reduced and water supply power can be saved.

  Hereinafter, the present invention will be described in more detail with reference to examples. These examples do not limit the invention.

<Example 1>
(Preparation of hydrophilic thin film)
A hydrophilic thin film was formed on the surface of an alkali-free glass as a substrate according to the following procedure.
(1) Preparation of alumina thin film 18.0 g of pure water was added to 2.00 g of fibrous alumina sol A (produced by Kawaken Fine Chemical Co., Ltd., alumina content 5.0 mass%, fiber length 1400 nm, fiber diameter 4-5 nm), and room temperature The mixture was stirred for 10 minutes, and HCl having a concentration of 10% by mass was added until pH 1 was obtained, whereby an alumina sol coating liquid A was obtained.

  The alkali-free glass was washed with a neutral detergent, rinsed with pure water, water droplets were removed with an air gun and dried to obtain a coating glass substrate. Next, the alumina sol coating liquid A was applied on a washed alkali-free glass substrate by a spinner method for 5 seconds at a rotational speed of 500 rpm, and then applied for 20 seconds at a rotational speed of 2000 rpm, thereby producing an alumina gel film A. The obtained alumina gel film A was irradiated with ultraviolet rays for 10 minutes using a high-pressure mercury lamp (H1000L, manufactured by Toshiba Lighting & Technology Corp.) to obtain an alumina thin film A.

(2) Hydrothermal synthesis of alumina thin film Alumina thin film A was hydrothermally synthesized using a 1 mass% nitrilotris (methylenephosphonic acid) (NTP) aqueous solution by the following process. That is, the alumina thin film A was immersed in a Teflon (registered trademark) inner cylinder containing a 1 mass% nitrilotris (methylenephosphonic acid) (NTP) aqueous solution. This inner cylinder was placed in an autoclave and heat-treated at 180 ° C. for 4 or 6 hours to obtain hydrothermal synthesis samples A-1 or A-2, respectively. After heating, the sample was taken out from the autoclave and washed with pure water to obtain a transparent sample.

(Durability test)
The hydrothermal synthesis samples A-1 and A-2 obtained in Example 1 are subjected to the following (1) boiling water durability test and (2) heat resistance test, and then measuring the contact angle of each sample with water. The durability was evaluated. The contact angle of the sample with respect to water was measured using an automatic contact angle meter DM-501 (manufactured by Kyowa Interface Science Co., Ltd.). The contact angle was measured using 2 μL water droplets.

  The contact angle of the hydrothermal synthesis sample, the sample after the boiling water durability test, and the sample after the heat resistance test with respect to water was measured immediately after the test, and further measured after 2 days and 7 days. The results are shown in Table 2.

(1) Boiling water durability test 150 mL of pure water was placed in a 200 mL capacity beaker and heated until boiling. Next, hydrothermal synthesis samples A-1 and A-2 were immersed in the boiling water for 1 hour. Thereafter, hydrothermal synthesis samples A-1 and A-2 were taken out from boiling water and dried.

(2) Heat resistance test Hydrothermal synthesis samples A-1 and A-2 were placed in an electric furnace at 100 ° C, heated for 2 hours, and then allowed to cool naturally.

<Example 2>
Except for replacing the fibrous alumina sol A in Example 1 with fibrous alumina sol B (Alumina content 5.0 mass%, fiber length 2000 nm, fiber diameter 4-5 nm, manufactured by Kawaken Fine Chemical Co., Ltd.) Alumina thin film B was prepared, and hydrothermal synthesis was performed on alumina thin film B in the same manner as in Example 1. Alumina hydrothermal synthesis samples B-1 (180 ° C./4 hours hydrothermal synthesis) and B-2 ( 180 ° C./6 hours hydrothermal synthesis). These samples were subjected to a durability test in the same manner as in Example 1.

<Example 3>
Except for replacing the fibrous alumina sol A in Example 1 with a plate-like alumina sol C (Alumina content 5.5% by mass, long side 20-50 nm, short side 10-50 nm, thickness 5-20 nm, manufactured by Kawaken Fine Chemical Co., Ltd.) In the same manner as in Example 1, an alumina thin film C was produced, and the alumina thin film C was hydrothermally synthesized in the same manner as in Example 1. ) And C-2 (hydrothermal synthesis at 180 ° C./6 hours). These samples were subjected to a durability test in the same manner as in Example 1.

<Examples 4, 5, and 6>
The boiling water durability test in Examples 1, 2, and 3 was performed in the same manner as in Example 1 except that the boiling water durability test was changed from 1 hour to 2 hours.

<Examples 7, 8, and 9>
The heat resistance test in Examples 1, 2, and 3 was performed in the same manner as in Example 1 except that the heat test was changed from 2 hours to 4 hours.

<Comparative Example 1>
A durability test was conducted in the same manner as in Example 1 using the alumina thin film A produced in Example 1 as a sample.

<Comparative Example 2>
Using the alumina thin film B produced in Example 2 as a sample, a durability test was conducted in the same manner as in Example 1.

<Comparative Example 3>
A durability test was conducted in the same manner as in Example 1, using the alumina thin film C produced in Example 3 as a sample.

<Comparative Example 4>
The alumina thin film A produced in Example 1 was immersed in a 1% by mass nitrilotris (methylenephosphonic acid) (NTP) aqueous solution at room temperature for 1 minute. Then, it heated for 30 minutes at 250 degreeC using the electric furnace, and the alumina thin film sample D was obtained. A durability test was performed in the same manner as in Example 1 using the alumina thin film sample D as a sample.

[Measurement of XPS spectrum]
About each sample mentioned above, the XPS spectrum was measured with the composite electron spectrometer ESCA-5800 (made by ULVAC-PHI) by X-ray photoelectron spectroscopy. The obtained binding energy data was subjected to charge correction with the peak top of the Cs1 spectrum set to 284.6 eV. P and Al chemical species were evaluated by the binding energy values (eV) of the P2p and Al2p spectra. The results are shown in Table 1.
The measurement conditions are as follows.
X-ray source: Monochromated-Al-Kα ray Light extraction angle: 15 to 45 °
Measurement depth: about 2nm
Measurement area: 2 x 0.8mm ²
The measurement sample was set to the apparatus as it was by appropriately folding the sample.

[Measurement of average roughness]
About each sample mentioned above, the roughness of the sample surface was measured using the scanning probe microscope (made by NanoScope 3a Digital Instruments), and the 10-point average roughness (Rz) in the length of 500 nm was evaluated.
The measurement conditions are as follows.
Measurement mode: Atomic force microscope (AFM)
Scan size: 500nm
Scan rate: 1Hz
Number of samples: 256
Cantilever: NCH-10V
The results are shown in Table 1.

  As shown in Table 1, in Samples A-1 to C-2, the peak top of the P2p spectrum is 133.0 eV or more and 135.0 eV or less, and the peak top of the Al2p spectrum is 74.0 eV or more and 76.0 eV or less. did. From these results, it was confirmed that Al-OP bonds exist on the surfaces of these samples.

  On the other hand, since no peak of the P2p spectrum was present in samples A to C, it was confirmed that phosphate ions were not present on the surface of the sample. In Sample D, the peak top of the P2p spectrum was present at 132.7 eV, and the peak top of the Al2p spectrum was present at 73.6 eV. From these results, it was confirmed that there was no Al—OP bond on the surface of Sample D.

  Furthermore, as shown in Table 1, all of Samples A-1 to C-2 and A to D had a 10-point average roughness of the surface of 20 nm or less, and were extremely flat surfaces.

  As shown in Table 2, all the samples within the scope of the present invention exhibited a super-hydrophilic property because the water contact angle of the sample after hydrothermal synthesis was 10 ° or less. The water contact angles of the samples measured after the boiling water durability test and after the heat resistance test were both 20 ° or less and were hydrophilic. From these results, it was shown that the samples within the scope of the present invention are excellent in durability. Further, since a thin film having a surface with a contact angle with water of 20 ° or less usually has antifogging properties and antifouling properties, samples within the scope of the present invention have antifogging properties and antifouling properties. .

  Samples A, B, C, and D outside the scope of the present invention had a contact angle with water of 20 ° or less immediately after sample preparation, but the sample water measured after the boiling water durability test and after the heat resistance test was measured. The contact angle with respect to was significantly greater than 20 ° and showed no hydrophilicity. From these results, it was shown that samples A, B, C, and D were inferior in durability.

Claims (2)

The alumina thin film provided on the substrate surface using a fibrous alumina sol is hydrothermally heated in an aqueous solution of nitrilotris (methylenephosphonic acid) at 150 ° C. or higher and 200 ° C. or lower for 10 minutes or longer and 60 hours or shorter. A method for producing a hydrophilic thin film to be synthesized . The claimed manufactured by the manufacturing method according to claim 1, when measured with XPS spectrum of a thin film surface by X-ray photoelectron spectroscopy, the peak and 74 of P2p spectrum present in the 135.0eV following range of 133.0eV 10-point average roughness of a surface having an Al—O—P bond due to the peak of the spectrum of Al 2p existing in the range of not less than 0.0 eV and not more than 76.0 eV and measured using a scanning probe microscope A hydrophilic thin film having (Rz) of less than 20 nm .