JP2007112861A - Method for producing inorganic coating composition, hydrophilic coating film and article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an inorganic coating composition able to form a hydrophilic coating film excellent in hydrophilicity and transparency and having no existence of a cloud point, the hydrophilic coating film and products. <P>SOLUTION: The inorganic coating composition containing 0.1-2.0 mass% solid content is prepared by mixing an alumina sol in which boehmite particles are dispersed in a dispersion medium, a silica-alumina composite sol in which silica-alumina composite particles are dispersed in the dispersion medium, an organic solvent having ≤100°C boiling point at 0.1MPa and miscible with water, a surfactant and water. In preparing the inorganic coating composition, an alumina sol having 20-100nm average particle size of coagulation particles, 1-5nm average pore radius of xerogel and 0.10-0.30ml/g whole pore volume of the xerogel having 1-100nm pore radius is used as the alumina sol and a silica alumina composite sol having 30-100nm average particle size of the coagulation particles and 0.001-0.1 Al/Si atom ratio is used as the silica alumina composite sol. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an inorganic coating composition, a hydrophilic coating film, and an article having the coating film.

  Organic substrates such as plastics are excellent in transparency, and are therefore used in various applications such as various lamp covers, spectacle lenses, goggles, various instrument covers, agricultural films, and the like. However, organic substrates usually have a disadvantage that they are liable to cause condensation and cloudiness because they are not highly hydrophilic. For example, in the case of an instrument cover that is always exposed to the outside air, there may be a problem that the display becomes invisible because condensation occurs on the inner surface of the cover and fogging occurs. For these reasons, it is desired to impart hydrophilicity to the surface of the organic base material for the purpose of improving antifogging properties.

As a method for imparting hydrophilicity to the substrate surface, a method of forming an inorganic layer on the substrate is known. The following methods are known as the method.
(1) A method in which an inorganic paint containing alumina sol and silica sol is applied to a substrate and dried to form a coating film (Patent Document 1).
(2) A method of forming a coating film by applying an inorganic paint containing an alumina sol and a positively charged silica sol to a substrate and drying (Patent Document 2).

However, in the method (1), since the alumina particles are usually charged positively and the silica particles are negatively charged, the particles are aggregated when the alumina sol and silica sol are mixed. There is a problem of insufficient transparency. In addition, since the obtained coating film is porous, when the water adhering to the coating film evaporates and dries, the phenomenon becomes instantly whitish, but the transparency becomes poor and cloudy. There is a problem. (Hereafter, such a moment is called a cloud point.)
Although the method (2) does not cause aggregation of the alumina particles and the silica particles, there is a problem in that there is a cloud point because the obtained coating film is porous.
JP 60-69181 A Japanese Patent Publication No. 64-5078

  The present invention is a method for producing an inorganic coating composition capable of forming a hydrophilic coating film having excellent hydrophilicity and transparency, no cloud point, and excellent antifogging property, excellent hydrophilicity and transparency, and having a cloud point. An object of the present invention is to provide a hydrophilic coating film and an article excellent in antifogging property.

  The method for producing an inorganic coating composition of the present invention is a method for producing an inorganic coating composition capable of forming a hydrophilic coating film on an organic substrate, and an alumina sol in which boehmite particles are dispersed in a dispersion medium, A silica-alumina composite sol in which silica-alumina composite particles are dispersed in a dispersion medium, an organic solvent miscible with water having a boiling point at 0.1 MPa of 100 ° C. or less, a surfactant, and water are mixed, When obtaining an inorganic coating composition having a solid content concentration of 0.1 to 2.0% by mass, as an alumina sol, (a) the average particle size of aggregated particles of boehmite particles in the dispersion medium is 20 to 100 nm, (B) The average pore radius of the xerogel obtained by removing the dispersion medium from the alumina sol is 1 to 5 nm, and (c) the total pore volume of the pore radius of 1 to 100 nm in the xerogel is 0.10 to 0.10. (X) The average particle diameter of the aggregated particles of silica alumina composite particles in the dispersion medium is 30 to 100 nm, and (y) Al in silica alumina composite particles. A silica-alumina composite sol having an Si / Si atomic ratio of 0.001 to 0.1 is used, and boehmite particles are 60 to 90 parts by mass of 100 parts by mass of the total solid content of the inorganic coating composition. The amount of the organic solvent miscible with water having a particle of 10 to 40 parts by mass and a boiling point at 0.1 MPa of 100 ° C. or less is 10 to 69.9 parts by mass of 100 parts by mass of the inorganic coating composition. It is characterized by being.

As the alumina sol, it is preferable to use an alumina sol having a crystal thickness of 4 to 8 nm in the direction perpendicular to the (010) plane of (d) boehmite particles.
As the silica-alumina composite sol, it is preferable to use (z) silica-alumina composite sol which is a particle having a positive charge on the surface obtained by reacting silica-alumina composite particles with silica sol and polyaluminum chloride.
It is preferable to further add a hydrophilic polymer.

The hydrophilic coating film of the present invention is characterized by being formed by applying an inorganic coating composition obtained by the method for producing an inorganic coating composition of the present invention to an organic substrate.
The haze value of the hydrophilic coating film is preferably 1.5% or less.

The water contact angle of the hydrophilic coating film is preferably 10 ° or less.
The organic substrate is preferably an acrylic resin or polycarbonate.
The article of the present invention is characterized by having the hydrophilic coating film of the present invention on the surface of an organic substrate.

According to the method for producing an inorganic coating composition of the present invention, it is possible to obtain an inorganic coating composition that can form a hydrophilic coating film that is excellent in hydrophilicity and transparency, and has excellent antifogging properties without cloud points.
The hydrophilic coating film of the present invention is excellent in hydrophilicity and transparency, has no cloud point, and is excellent in antifogging property.
The article of the present invention is excellent in hydrophilicity and transparency, has no cloud point, and has excellent antifogging properties.

<Method for producing inorganic coating composition>
The method for producing an inorganic coating composition of the present invention is a method for producing an inorganic coating composition capable of forming a hydrophilic coating film on an organic substrate, and an alumina sol in which boehmite particles are dispersed in a dispersion medium, A method of mixing silica-alumina composite sol in which silica-alumina composite particles are dispersed in a dispersion medium, an organic solvent miscible with water having a boiling point of 100 MPa or less at 0.1 MPa, a surfactant, and water. is there.

(Alumina sol)
In the present invention, an alumina sol in which boehmite particles are dispersed in a dispersion medium is used as the alumina sol. By including boehmite particles in the inorganic coating composition, a highly hydrophilic coating film can be formed.
Boehmite particles are alumina hydrate having a boehmite structure represented by a composition formula AlOOH.xH ₂ O (0 ≦ x <2).

  As the alumina sol, (a) an alumina sol having an average particle diameter of aggregated boehmite particles in the dispersion medium of 20 to 100 nm is used. If the average particle size of the aggregated particles is less than 20 nm, the resulting hydrophilic coating film is likely to crack and become cloudy, which may cause the film to become cloudy. If the average particle diameter of the aggregated particles exceeds 100 nm, the transparency of the obtained hydrophilic coating film is impaired, and the resulting hydrophilic coating film tends to be porous with a large pore radius and pore volume, and is antifogging. May get worse. The average particle diameter of the aggregated particles is more preferably 30 to 80 nm. The average particle size of the aggregated particles in the alumina sol is measured using a dynamic light scattering particle size analyzer.

  As the alumina sol, (b) the average pore radius of the xerogel (alumina hydrate powder) obtained by removing the dispersion medium from the alumina sol is 1 to 5 nm, and (c) the pore radius of the xerogel is 1 to 100 nm. An alumina sol having a total pore volume of 0.10 to 0.30 ml / g is used.

When the average pore radius of the xerogel is less than 1 nm, the hydrophilicity of the obtained hydrophilic coating film is deteriorated. When the average pore radius of the xerogel exceeds 5 nm, the transparency of the resulting hydrophilic coating film is deteriorated.
When the total pore volume of the xerogel having a pore radius of 1 to 100 nm is less than 0.10 ml / g, the hydrophilicity of the obtained hydrophilic coating film is deteriorated. When the total pore volume of the xerogel having a pore radius of 1 to 100 nm exceeds 0.30 ml / g, the resulting hydrophilic coating film becomes porous, a cloud point is generated, and the antifogging property is lowered.
The average pore radius of the xerogel is preferably 1 to 3 nm. The total pore volume of the xerogel having a pore radius of 1 to 100 nm is preferably 0.10 to 0.25 ml / g.

The average pore radius of the xerogel and the total pore volume of the pore radius of 1 to 100 nm were determined by depressurizing the xerogel obtained by drying alumina sol at 140 ° C. to a constant weight at 120 ° C. for 2 hours at 1 × 10 ⁻² Torr. After gassing, it is measured using a nitrogen adsorption / desorption device. The total pore volume with a pore radius of 1 to 100 nm is the pore volume distribution in a pore volume distribution in which the vertical axis is the pore volume and the horizontal axis is the pore radius. It is an integrated value.

  As the alumina sol, it is preferable to use (d) an alumina sol having a crystal thickness (hereinafter referred to as crystal size) in the direction perpendicular to the (010) plane of boehmite particles of 4 to 8 nm. By setting the crystal size to 4 nm or more, boehmite particles are hardly aggregated, and an alumina sol having an average particle size of aggregated particles of 100 nm or less is obtained. By setting the crystal size to 8 nm or less, a highly transparent hydrophilic coating film is obtained, and the average pore radius of the xerogel is 5 nm or less, and the total pore volume of the pore radius of 1 to 100 nm is 0.30 ml / g or less. The crystal size is more preferably 4 to 6 nm.

  The crystal size was determined by performing X-ray diffraction analysis on the xerogel obtained by drying the alumina sol at 140 ° C. to a constant weight. From the diffraction angle 2θ (°) of the peak on the (020) plane and the half-value width B (rad), It is determined using Scherrer's equation (t = 0.9λ / Bcos θ). In the formula, t is a crystal size, and λ is an X-ray wavelength.

As the dispersion medium for the alumina sol, water containing an acid is preferable. The acid acts as a peptizer to stabilize the alumina sol.
Examples of the acid include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and amidosulfuric acid; and organic acids such as acetic acid. As the acid, acetic acid or amidosulfuric acid is particularly preferable.

The alumina sol is produced, for example, by preparing a slurry containing alumina hydrate, aging this, and then adding an acid.
The production method of the alumina sol is as follows: (1) A method of ripening an alumina gel obtained by hydrolyzing an aluminum alkoxide such as aluminum isopropoxide, aluminum dodexide, etc., and then adding an acid, ) After aging the hydrated gel of alumina obtained by adding alkali metal hydroxide to alkali metal aluminate and mixing with acid or acidic aluminum salt such as aluminum chloride, aluminum sulfate, aluminum nitrate etc. (3) Alumina hydrate obtained by ion exchange of alkali metal aluminate or acidic aluminum salt with ion exchange resin is aged, and then acid is added to the slurry. And how to solve the problem.

  The alumina hydrate in the resulting slurry is amorphous or boehmite particles having a very small crystal size, and the subsequent aging causes crystal growth of the boehmite particles, increasing the crystal size and the average of xerogel. The pore volume and the total pore volume with a pore radius of 1 to 100 nm are increased. The crystal growth rate can be controlled by the pH, temperature, and time of the slurry containing the alumina hydrate.

The pH of the slurry containing alumina hydrate is preferably 3.5 to 10.0. The higher the pH, the faster the crystal growth rate. When the pH is less than 3.5, alumina hydrate does not precipitate. When pH exceeds 10.0, it does not become boehmite particles, but bayerite particles are generated.
The aging temperature of the slurry containing alumina hydrate is preferably 40 to 105 ° C. Higher temperatures tend to increase the crystal growth rate. If the temperature is lower than 40 ° C., the crystal growth rate is too slow. When the temperature exceeds 105 ° C., a pressure vessel or the like is required for aging, and a large facility is required.

  The longer the aging time of the slurry containing the alumina hydrate, the longer the crystal grows. The aging time may be appropriately set so that the average pore radius, the total pore volume with a pore radius of 1 to 100 nm, and the crystal size are in a desired range. If the time is too short, it is amorphous or the crystal size is not 4 nm or more. If the time is too long, an alumina sol in which the crystal size exceeds 8 nm and the average pore radius of the xerogel and the total pore volume of the pore radius of 1 to 100 nm are within a predetermined range cannot be obtained. The aging time is preferably 2 to 6 hours.

  After the aging slurry is washed with an ultrafiltration device or the like as necessary, an acid is added, and if necessary, concentration, ultrasonic treatment, or the like is performed to obtain an alumina sol containing boehmite particles. When the average particle size of the aggregated boehmite particles in the alumina sol does not become 100 nm or less simply by adding and concentrating the acid, the average particle size of the aggregated particles of the alumina sol can be reduced to 100 nm or less by performing ultrasonic treatment.

(Silica alumina composite sol)
The silica-alumina composite sol is a sol in which silica-alumina composite particles are dispersed in a dispersion medium. By including the silica-alumina composite particles in the inorganic coating composition, it is possible to form a hydrophilic coating film that is highly hydrophilic and hardly cracks. By making cracks difficult for the hydrophilic coating film, the hydrophilic coating film does not become cloudy and becomes less cloudy.

  Silica-alumina composite particles are particles obtained by combining silica and alumina. The compounded state of silica and alumina can be estimated by measuring the zeta potential. The surface of the silica particles is usually negatively charged and the zeta potential is negative in a wide pH range. However, when complexed with alumina, the surface charge becomes positive and the zeta potential becomes positive. The zeta potential of the silica-alumina composite particles in the dispersion medium is preferably +10 mV or more. Thereby, the silica alumina composite particles have an appropriate stability in the dispersion medium.

  As the silica-alumina composite sol, (x) a silica-alumina composite sol having an average particle diameter of aggregated particles of silica-alumina composite particles in a dispersion medium of 30 to 100 nm is used. When the average particle size of the aggregated particles is less than 30 nm, the resulting hydrophilic coating film is likely to crack, and the film becomes cloudy and cloudy. If the average particle diameter of the aggregated particles exceeds 100 nm, the transparency of the obtained hydrophilic coating film is impaired, and the resulting hydrophilic coating film becomes porous with a large pore radius and pore volume, thus preventing fogging. Sexuality gets worse. The average particle diameter of the aggregated particles is more preferably 40 to 80 nm. The average particle size of the aggregated particles in the silica-alumina composite sol is measured using a dynamic light scattering particle size analyzer.

  As the silica-alumina composite sol, (y) a silica-alumina composite sol having an Al / Si atomic ratio of 0.001 to 0.1 in the silica-alumina composite particles is used. If the Al / Si atomic ratio is within this range, the surface of the silica-alumina composite particles is positively charged, so that it does not easily aggregate with the positively charged boehmite particles, so that a hydrophilic coating film with excellent transparency is obtained. be able to. When the Al / Si atomic ratio is less than 0.001, the silica-alumina composite particles are not positively charged. When the Al / Si atomic ratio exceeds 0.1, the scratch resistance of the resulting hydrophilic coating film may be lowered. The Al / Si atomic ratio is particularly preferably 0.01 to 0.1.

As the silica-alumina composite sol, (z) a silica-alumina composite sol that is obtained by reacting silica-alumina composite particles with silica sol and polyaluminum chloride and having positive charges on the surface is preferable. Specifically, a silica-alumina composite sol obtained by a method of gradually adding polyaluminum chloride that exhibits acidity when dissolved in water to a silica sol containing silica particles is preferable.
Examples of the dispersion medium for the silica-alumina composite sol include water, methanol, ethanol, 1-propanol, 2-propanol, and the like, and water is particularly preferable from the viewpoint of sol stability.

  As the silica-alumina composite sol, (v) a silica-alumina composite sol in which the average pore radius of the xerogel obtained by removing the dispersion medium from the silica-alumina composite sol is 1 to 8 nm is preferable. When the average pore radius of the xerogel is less than 1 nm, the hydrophilicity of the obtained hydrophilic coating film is deteriorated. When the average pore radius of the xerogel exceeds 8 nm, the transparency of the obtained hydrophilic coating film is deteriorated. The average pore radius of the xerogel is preferably 2 to 7 nm.

  As the silica-alumina composite sol, (w) a silica-alumina composite sol having a total pore volume of 0.10 to 0.30 ml / g in a xerogel with a pore radius of 1 to 100 nm is preferable. When the total pore volume of the xerogel having a pore radius of 1 to 100 nm is less than 0.10 ml / g, the hydrophilicity of the obtained hydrophilic coating film is deteriorated. When the total pore volume of the xerogel having a pore radius of 1 to 100 nm exceeds 0.30 ml / g, the resulting hydrophilic coating film becomes porous, a cloud point is generated, and the antifogging property is lowered. The total pore volume of the xerogel having a pore radius of 1 to 100 nm is preferably 0.10 to 0.25 ml / g.

  The average pore radius of the xerogel of the silica-alumina composite sol and the total pore volume with a pore radius of 1 to 100 nm can be measured in the same manner as the alumina sol.

(Surfactant)
In producing the inorganic coating composition, a surfactant is added. By adding a surfactant, the wettability of the inorganic coating composition with respect to the organic substrate is improved, and a hydrophilic coating film having a uniform and good appearance can be obtained, and the hydrophilicity of the hydrophilic coating film is also improved. To do.
Examples of the surfactant include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

As the surfactant, —CH ₂ CH ₂ O—, —SO ₂ —, —NR— (R is a hydrogen atom or an organic group), —NH ₂ , —SO ₃ Y and —COOY (Y is hydrogen) A nonionic surfactant having one or more structural units selected from the group consisting of an atom, a sodium atom, a potassium atom or an ammonium group), which may impair the storage stability and hydrophilicity of the inorganic coating composition. Therefore, a nonionic surfactant having a structural unit of —CH ₂ CH ₂ O— is particularly preferable. Nonionic surfactants include, for example, alkyl polyoxyethylene ether, alkyl polyoxyethylene-polypropylene ether, fatty acid polyoxyethylene ester, fatty acid polyoxyethylene sorbitan ester, fatty acid polyoxyethylene sorbitol ester, alkyl polyoxyethylene amine , Alkyl polyoxyethylene amide, polyether-modified silicone surfactants, and the like.

  The amount of the surfactant added is preferably 10 to 2000 ppm in the inorganic coating composition, and more preferably 100 to 1000 ppm. There exists a possibility that the wettability of the inorganic coating composition with respect to an organic base material may fall that the quantity of surfactant is less than 10 ppm. When the amount of the surfactant exceeds 2000 ppm, the hydrophilicity of the hydrophilic coating film may be lowered.

(water)
Water is added when manufacturing the inorganic coating composition. Water serves as a dispersion medium for stably dispersing boehmite particles and silica-alumina composite particles in the inorganic coating composition.
The amount of water added is appropriately adjusted so as to have the following content when totaled with the amount of water contained in the alumina sol and silica-alumina composite sol.
The water content is preferably 30 to 89.9 parts by mass, more preferably 40 to 79.9 parts by mass, out of 100 parts by mass of the inorganic coating composition. By setting the water content to 30 parts by mass or more, the storage stability in long-term storage is improved. By setting the water content to 89.9 parts by mass or less, the solid content concentration of the inorganic coating composition does not become too low, and the required film thickness is easily obtained.

(Organic solvent)
When the inorganic coating composition is produced, an organic solvent miscible with water having a boiling point at 0.1 MPa of 100 ° C. or lower is added. An organic solvent having a boiling point of 100 ° C. or less and miscible with water improves the wettability of the inorganic coating composition with respect to the organic substrate, and further, drying after applying the inorganic coating composition to the organic substrate is performed at a low temperature. It can also be performed in a short time.

As the organic solvent miscible with water and having a boiling point at 0.1 MPa of 100 ° C. or lower, alcohol is preferable in that boehmite particles and silica-alumina composite particles in the inorganic coating composition are stably dispersed.
Examples of the alcohol include methanol (boiling point: 65 ° C), ethanol (boiling point: 78 ° C), 2-propanol (boiling point: 83 ° C), tert-butanol (boiling point: 83 ° C), 1-propanol (boiling point: 97 ° C). , 3-buten-2-ol (boiling point: 97 ° C.) and the like.

  The content of the organic solvent miscible with water having a boiling point at 0.1 MPa of 100 ° C. or less is 10 to 69.9 parts by mass, and 20 to 59.9 parts by mass, out of 100 parts by mass of the inorganic coating composition. Part is preferred. By setting the content of the organic solvent to 10 parts by mass or more, the wettability of the inorganic coating composition with respect to the organic base material is improved. By setting the content of the organic solvent to 69.9 parts by mass or less, the evaporation rate of the dispersion medium when the inorganic coating composition is applied becomes appropriate, and the occurrence of white turbidity unevenness can be suppressed. In addition, boehmite particles and silica-alumina composite particles are stably dispersed in the inorganic coating composition.

(Hydrophilic polymer)
When producing an inorganic coating composition, a hydrophilic polymer may be appropriately added. By adding a hydrophilic polymer, the strength of the obtained hydrophilic coating film can be improved.
Examples of the hydrophilic polymer include polyacrylic acid, polyvinyl alcohol, polybutyral, polyurethane, and cellulose.

  The amount of the hydrophilic polymer is preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, out of 100 parts by mass of the total solid content of the inorganic coating composition. By making the amount of the hydrophilic polymer 30 parts by mass or less, a decrease in hydrophilicity of the obtained hydrophilic coating film can be suppressed.

(Other additives)
When producing an inorganic coating composition, additives such as coloring dyes, pigments, ultraviolet absorbers and antioxidants may be added as appropriate.

(Inorganic coating composition)
The solid content concentration of the inorganic coating composition obtained as described above is 0.1 to 2.0% by mass, and preferably 0.2 to 1.0% by mass. By setting the solid content concentration to 0.1% by mass or more, the obtained hydrophilic coating film does not become too thin, and the hydrophilicity can be sufficiently exhibited. By setting the solid content concentration to 2.0% by mass or less, the obtained hydrophilic coating film is not too thick and the decrease in transparency is suppressed, and the pore volume per unit area of the hydrophilic coating film is large. It does not become too much and the antifogging property does not decrease.

  The ratio of boehmite particles to silica-alumina composite particles in the inorganic coating composition is such that boehmite particles are 60 to 90 parts by mass and 10 to 10 of silica-alumina composite particles in 100 parts by mass of the total solid content of the inorganic coating composition. -40 mass parts. It is particularly preferable that the boehmite particles are 70 to 80 parts by mass and the silica particles are 20 to 30 parts by mass. By setting the silica alumina composite particles to 10 to 40 parts by mass, the resulting hydrophilic coating film is hardly cracked, and thus the hydrophilic coating film does not become cloudy and hardly becomes cloudy.

<Hydrophilic coating film>
The hydrophilic coating film of the present invention is a coating film formed by applying an inorganic coating composition obtained by the production method of the present invention to an organic substrate. The hydrophilic coating film is excellent in hydrophilicity, transparency and antifogging property.
As the organic substrate, various materials can be used as necessary. Examples of the organic substrate include polyethylene terephthalate, acrylic resin, polycarbonate, polyethylene resin, polyvinyl chloride, and fluorine resin. As the substrate, acrylic resin or polycarbonate is particularly preferable because of its good transparency.
Examples of the shape of the substrate include a film, a plate, and a molded product. In the case of a plate, the plate is not limited to a flat plate, and may be a plate having a curved surface.

The substrate may be subjected to a surface treatment as necessary. By performing the surface treatment, the wettability of the substrate is improved, and the adhesion between the obtained hydrophilic coating film and the substrate is improved. The surface treatment method is not particularly limited, but known plasma treatment, discharge treatment such as corona discharge, UV treatment, and ozone treatment; chemical treatment using acid, alkali, etc .; physical treatment using an abrasive, etc. Can be mentioned.
Examples of the coating method include brush coating, roller coating, spin coating, dip coating, coating by various printing methods, curtain flow, die coating, flow coating, spray coating, and the like.

The transparency of the hydrophilic coating film can be evaluated by the haze value. The haze value of the hydrophilic coating film is preferably 1.5% or less, and more preferably 1.0% or less. If the haze value is 1.5% or less, the hydrophilic coating film has sufficient transparency.
The hydrophilicity of the hydrophilic coating film can be evaluated by the contact angle of water. The water contact angle of the hydrophilic coating film is preferably 10 ° or less, and more preferably 5 ° or less. When the contact angle is 10 ° or less, the hydrophilic coating film has sufficient hydrophilicity and antifogging properties.

  The thickness of the hydrophilic coating film is preferably 0.1 to 1.0 μm, and more preferably 0.2 to 0.8 μm. By making the film thickness of the hydrophilic coating film 0.1 μm or more, a decrease in hydrophilicity can be suppressed. By making the film thickness of the hydrophilic coating film 1.0 μm or less, a decrease in the transparency of the hydrophilic coating film can be suppressed.

<Article>
The article of the present invention has the hydrophilic coating film of the present invention on the surface of an organic substrate. Examples of the article include polyethylene terephthalate, acrylic resin, polycarbonate, polyethylene resin, polyvinyl chloride, fluororesin and other plastic films, plates, molded articles, and the like.

Examples (Examples 1-4, Example 9, Example 16, Example 17) and comparative examples (Examples 5-8, Examples 10-15) are shown below.
In the examples, the average particle size of the aggregated particles was measured using a dynamic light scattering particle size analyzer (manufactured by Nikkiso Co., Ltd., model: Microtrac UPA).
The average pore radius of xerogel and the total pore volume of pore radius of 1 to 100 nm were measured with a nitrogen adsorption / desorption device (manufactured by Cantachrome, Autosorb 3B type).
The crystal size was obtained from the Scherrer equation by performing powder X-ray diffraction using an X-ray diffractometer (manufactured by Rigaku Corporation, model: miniflex).
The thickness of the hydrophilic coating film was measured by a stylus method after scraping the coating film on the sample with a cutter.

[Example 1]
(Synthesis of alumina sol A)
1343 g of ion-exchanged water was added to 308 g of an aluminum chloride aqueous solution (manufactured by Taki Chemical Co., Ltd., trade name: Takibine # 100, Al ₂ O ₃ concentration 11.5% by mass, Cl concentration 24.5% by mass, the same shall apply hereinafter) While stirring, 243 g of an aqueous sodium aluminate solution (manufactured by Asada Chemical Industry Co., Ltd., Model: # 2019, Al ₂ O ₃ concentration 20 mass%, Na ₂ O concentration 19 mass%, the same applies hereinafter) was added. Next, after the temperature of this liquid was raised to 95 ° C., 106 g of an aqueous sodium aluminate solution was added again while stirring, and then the liquid temperature was kept at 95 ° C. while stirring and aged for 4 hours to obtain a slurry. The pH of the liquid immediately after adding sodium aluminate at 95 ° C. was 9.2.

After washing the mature slurry using an ultrafiltration device, the temperature is raised to 95 ° C. again, and amide sulfuric acid is added in an amount of 3% by mass of the total solid content of the washed slurry, and the solid content concentration Was concentrated under reduced pressure until it reached 10.0%, and then ultrasonically dispersed until the average particle size of the aggregated particles became 100 nm or less, whereby alumina sol A was obtained.
The average particle diameter of the aggregated particles in the alumina sol A was 71 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the alumina sol A was 1.8 nm, and the total pore volume of the pore radius of 1 to 100 nm was 0.25 ml / g. . Moreover, as a result of measuring the obtained xerogel by powder X-ray diffraction, it was confirmed that it was boehmite, and the crystal size of the boehmite particles was 4.5 nm.

(Synthesis of silica-alumina composite sol a)
14.9 g of polyaluminum chloride aqueous solution (manufactured by Taki Chemical Co., Ltd., trade name: Takibaine # 1500, Al ₂ O ₃ concentration 23.5% by mass, Cl concentration 8.1% by mass, basicity 84%) and 889 g of water After mixing and heating to 40 ° C. with stirring, silica sol having an average particle size of 27 nm (manufactured by Catalyst Kasei Kogyo Co., Ltd., trade name: Cataloid SI-50, SiO ₂ concentration 48.4% by mass, Na ₂₎ 96.1 g of O concentration 0.5 mass%) was added. After completion of the addition, the mixture was aged by stirring for 1 hour while maintaining the temperature at 40 ° C., then cooled and sonicated to obtain a silica-alumina composite sol a (Al / Si atom) having a solid content concentration of 5.0 mass%. Ratio = 0.09). The average particle diameter of the aggregated particles in the silica-alumina composite sol a was 44 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the silica-alumina composite sol a is 3.1 nm, and the total pore volume of the pore radius of 1 to 100 nm is 0.20 ml / g. Met.

(Manufacture of inorganic coating composition)
Into a glass container, 5.25 g of alumina sol A and 46.25 g of ion-exchanged water were added. Then, while stirring, 3.5 g of silica-alumina composite sol a, 40.0 g of 2-propanol, and 1% by mass with ion-exchanged water. 5.0 g of diluted nonionic surfactant (Nihon Unicar Co., Ltd., trade name: L-77) was added and stirred at 20 ° C. for 1 hour, and an inorganic coating composition having a solid content concentration of 0.7 mass% Got. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 75 parts by mass, and silica-alumina composite particles were 25 parts by mass. The content of 2-propanol was 40 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

(Application of inorganic coating composition)
The inorganic coating composition was spray-coated on a 100 mm × 100 mm × 2.0 mm thick acrylic substrate (Mitsubishi Rayon, trade name: Acrylite) using a spray gun. After application, the sample was dried at 50 ° C. for 30 minutes to obtain a sample on which a hydrophilic coating film having a thickness of 0.4 μm was formed.
About the sample in which the hydrophilic coating film was formed, it evaluated by the method shown below. The evaluation results are shown in Table 1.

(appearance)
The hydrophilic coating film on the surface of the sample was observed with the naked eye, and “O” indicates that coating unevenness and cracks are not generated, and “X” indicates that coating unevenness or cracks are generated.
(transparency)
Transparency was evaluated by measuring the haze value of the sample. The haze value was measured using a haze computer (manufactured by Suga Test Instruments Co., Ltd., model: HGM-3DP) according to JIS K7105. A haze value of 1.5% or less was rated as “◯”, and a haze value exceeding 1.5% as “x”.
(Hydrophilic)
The contact angle of water with respect to the hydrophilic coating film was measured to evaluate hydrophilicity. The contact angle of water was measured using a contact angle meter (CA-X type, manufactured by Kyowa Interface Science Co., Ltd.).

(Initial anti-fogging property)
When the surface of the hydrophilic coating is blown, no fogging occurs. The case where it became whitish and appeared cloudy (cloudy weather was present), or the case where it looked cloudy at the same time as breath was blown was marked as x.
(Anti-fog durability)
The sample was left in a room at a temperature of 25 ° C. and a humidity of 60% for 4 days, and then the antifogging property was evaluated by blowing on the surface of the hydrophilic coating film.

[Example 2]
(Synthesis of silica alumina composite sol b)
Polyaluminum chloride aqueous solution (manufactured by Taki Chemical Co., Ltd., trade name: Takibaine # 1500, Al ₂ O ₃ concentration 23.5 mass%, Cl concentration 8.1 mass%, basicity 84%) 7.7 g and water 872.4 g The mixture was heated to 40 ° C. with stirring, and then stirred with a silica sol having an average particle size of 45 nm (trade name: Cataloid SI-45P, Cataloid SI-45P, SiO ₂ concentration: 40.2% by mass, 119.9 g) (Na ₂ O concentration 0.4 mass%) was added. After completion of the addition, the mixture was aged by stirring for 1 hour while maintaining the temperature at 40 ° C., then cooled and sonicated to obtain a silica-alumina composite sol b (Al / Si atom) having a solid content concentration of 5.0 mass%. Ratio = 0.04). The average particle diameter of the aggregated particles in the silica-alumina composite sol b was 60 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the silica-alumina composite sol b is 5.2 nm, and the total pore volume of the pore radius of 1 to 100 nm is 0.22 ml / g. Met.

  An inorganic coating composition was obtained in the same manner as in Example 1 except that the silica alumina composite sol b was used instead of the silica alumina composite sol a. A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 3]
(Synthesis of silica-alumina composite sol c)
Aqueous polyaluminum chloride (manufactured by Taki Chemical Co., Ltd., trade name: Takibaine # 1500, Al ₂ O ₃ concentration 23.5% by mass, Cl concentration 8.1% by mass, basicity 84%) 7.7 g and water 795.6 g The mixture was heated to 40 ° C. with stirring, and then stirred with a silica sol having an average particle size of 60 nm (manufactured by Catalyst Kasei Kogyo Co., Ltd., SiO ₂ concentration 24.5 mass%, Na ₂ O concentration 0.1 mass). %) 196.7 g was added. After completion of the addition, the mixture was aged by stirring for 1 hour while maintaining the temperature at 40 ° C., then cooled and sonicated to obtain a silica-alumina composite sol c (Al / Si atom) having a solid content concentration of 5.0 mass%. Ratio = 0.04). The average particle diameter of the aggregated particles in the silica-alumina composite sol c was 77 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the silica-alumina composite sol c is 7.0 nm, and the total pore volume of the pore radius of 1 to 100 nm is 0.22 ml / g. Met.

  An inorganic coating composition was obtained in the same manner as in Example 1 except that the silica alumina composite sol c was used instead of the silica alumina composite sol a. A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 4]
Ion-exchanged water was added to commercially available alumina sol (manufactured by Nissan Chemical Industries, trade name: alumina sol 520, Al ₂ O ₃ concentration 20.5 mass%) to obtain alumina sol B having a solid content concentration of 10.0 mass%. The average particle size of the aggregated particles in the alumina sol B was 84 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the alumina sol B was 2.7 nm, and the total pore volume of the pore radius of 1 to 100 nm was 0.30 ml / g. . Moreover, as a result of measuring the obtained xerogel by powder X-ray diffraction, it was confirmed that it was boehmite, and the crystal size of the boehmite particles was 7.2 nm.

  An inorganic coating composition was obtained in the same manner as in Example 2 except that alumina sol B was used instead of alumina sol A. A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 5 (comparative example)]
Ion-exchanged water was added to commercially available alumina sol (manufactured by Nissan Chemical Industries, trade name: alumina sol 200, Al ₂ O ₃ concentration 10.9% by mass) to obtain alumina sol C having a solid content concentration of 10.0% by mass. The average particle size of the aggregated particles in the alumina sol C was 1800 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the alumina sol C was 1.1 nm, and the total pore volume of the pore radius of 1 to 100 nm was 0.11 ml / g. . Moreover, as a result of measuring the obtained xerogel by powder X-ray diffraction, it was amorphous.

  An inorganic coating composition was obtained in the same manner as in Example 1 except that alumina sol C was used instead of alumina sol A. A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. The haze value was 3.0, the transparency was poor, and it looked cloudy when breathed.

[Example 6 (comparative example)]
Ion-exchanged water is added to a commercially available alumina sol (catalyst AS-2, product name: Cataloid AS-2, Al ₂ O ₃ concentration 10.2% by mass) to obtain an alumina sol D having a solid content concentration of 10.0% by mass. It was. The average particle diameter of the aggregated particles in the alumina sol D was 156 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the alumina sol D was 2.9 nm, and the total pore volume of the pore radius of 1 to 100 nm was 0.37 ml / g. . Moreover, as a result of measuring the obtained xerogel by powder X-ray diffraction, it was confirmed that it was boehmite, and the crystal size of the boehmite particles was 8.0 nm.

  An inorganic coating composition was obtained in the same manner as in Example 1 except that alumina sol D was used instead of alumina sol A. A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. The haze value was 1.8, the transparency was poor, and it looked cloudy when breathed.

[Example 7 (comparative example)]
In the synthesis of the alumina sol A of Example 1, alumina sol E having a solid content concentration of 10.0% by mass was obtained in the same manner as in Example 1 except that it was aged for 24 hours instead of being kept at 95 ° C. for 4 hours. The average particle diameter of the aggregated particles in the alumina sol E was 80 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the alumina sol E was 8.0 nm, and the total pore volume of the pore radius of 1 to 100 nm was 0.80 ml / g. . Moreover, as a result of measuring the obtained xerogel by powder X-ray diffraction, it was confirmed that it was boehmite, and the crystal size of the boehmite particles was 8.2 nm.

  An inorganic coating composition was obtained in the same manner as in Example 1 except that alumina sol E was used instead of alumina sol A. A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. The haze value was 1.6, the transparency was poor, and it looked cloudy when breathed.

[Example 8 (comparative example)]
(Synthesis of silica alumina composite sol d)
Aqueous polyaluminum chloride (manufactured by Taki Chemical Co., Ltd., trade name: Takibaine # 1500, Al ₂ O ₃ concentration 23.5% by mass, Cl concentration 8.1% by mass, basicity 84%) 7.7 g and water 882.8 g The mixture was heated to 40 ° C. with stirring, and then stirred, and the silica sol having an average particle size of 80 nm (manufactured by Catalyst Kasei Kogyo Co., Ltd., trade name: Cataloid SI-80P, SiO ₂ concentration 40.4% by mass, 109.5 g of Na ₂ O concentration 0.4 mass%) was added. After completion of the addition, the mixture was aged by stirring for 1 hour while maintaining the temperature at 40 ° C., then cooled and sonicated to obtain a silica-alumina composite sol d (Al / Si atom) having a solid content concentration of 5.0 mass%. Ratio = 0.04). The average particle diameter of the aggregated particles in the silica-alumina composite sol d was 110 nm. The average pore radius of the xerogel obtained by removing the dispersion medium from the silica-alumina composite sol d is 11.0 nm, and the total pore volume of the pore radius of 1 to 100 nm is 0.22 ml / g. Met.

  An inorganic coating composition was obtained in the same manner as in Example 1 except that the silica alumina composite sol d was used instead of the silica alumina composite sol a. A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. The haze value was 1.6, the transparency was poor, and it looked cloudy when breathed.

[Example 9]
After adding 3.0 g of alumina sol A and 50.0 g of ion-exchanged water to a glass container, with stirring, the silica-alumina composite sol a 2.0 g, 2-propanol 40.0 g, and diluted to 1% by mass with ion-exchanged water 5.0 g of a nonionic surfactant (trade name: L-77, manufactured by Nihon Unicar Co., Ltd.) was added and stirred at 20 ° C. for 1 hour to obtain an inorganic coating composition having a solid content concentration of 0.4 mass%. Obtained. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 75 parts by mass, and silica-alumina composite particles were 25 parts by mass. The content of 2-propanol was 40 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

  A hydrophilic coating film having a thickness of 0.2 μm was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 10 (comparative example)]
After putting 0.38 g of alumina sol A and 54.37 g of ion-exchanged water in a glass container, while stirring, dilute to 1% by mass with 0.25 g of silica-alumina composite sol, 40.0 g of 2-propanol, and ion-exchanged water. 5.0 g of a nonionic surfactant (trade name: L-77, manufactured by Nihon Unicar Co., Ltd.) was added and stirred at 20 ° C. for 1 hour to obtain an inorganic coating composition having a solid content concentration of 0.05% by mass. Obtained. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 75 parts by mass, and silica-alumina composite particles were 25 parts by mass. The content of 2-propanol was 40 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

  A hydrophilic coating film having a thickness of 0.03 μm was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. The haze value was 0.1 and the transparency was very good, but the contact angle of water exceeded 10 ° and the hydrophilicity was poor, and it looked cloudy when breathed.

[Example 11 (comparative example)]
After putting 15.75 g of alumina sol A and 28.75 g of ion-exchanged water in a glass container, 10.5 g of silica-alumina composite sol a, 40.0 g of 2-propanol, and diluted to 1% by mass with ion-exchanged water while stirring. 5.0 g of a nonionic surfactant (trade name: L-77, manufactured by Nippon Unicar Co., Ltd.) was added and stirred at 20 ° C. for 1 hour to obtain an inorganic coating composition having a solid content concentration of 2.1% by mass. Obtained. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 75 parts by mass, and silica-alumina composite particles were 25 parts by mass. The content of 2-propanol was 40 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

  A hydrophilic coating film having a thickness of 1.2 μm was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. The haze value was 1.8, the transparency was poor, and it looked cloudy when breathed.

[Example 12 (comparative example)]
After putting 7.0 g of alumina sol A and 48.0 g of ion-exchanged water in a glass container, with stirring, the nonionic surfactant diluted to 1% by mass with 2-propanol 40.0 g and ion-exchanged water (Nippon Unicar) Manufactured, trade name: L-77) 5.0 g was added and stirred at 20 ° C. for 1 hour to obtain an inorganic coating composition having a solid content concentration of 0.7 mass%. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 100 parts by mass, and silica-alumina composite particles were 0 parts by mass. The content of 2-propanol was 40 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

  A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. The appearance was ◯, but when blown, fine cracks appeared and it looked cloudy.

[Example 13 (comparative example)]
After putting alumina sol A 3.5g and ion-exchanged water 44.5g in a glass container, while stirring, silica alumina composite sol a 7.0g, 2-propanol 40.0g, and ion-exchanged water to 1% by mass 5.0 g of diluted nonionic surfactant (Nihon Unicar Co., Ltd., trade name: L-77) was added and stirred at 20 ° C. for 1 hour, and an inorganic coating composition having a solid content concentration of 0.7 mass% Got. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 50 parts by mass, and silica-alumina composite particles were 50 parts by mass. The content of 2-propanol was 40 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

  A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. Many fine cracks were generated on the surface of the hydrophilic coating film.

[Example 14 (comparative example)]
After putting 5.25 g of alumina sol A and 81.25 g of ion-exchanged water in a glass container, while stirring, dilute to 1% by mass with silica-alumina composite sol 3.5 g, 2-propanol 5.0 g, and ion-exchanged water. 5.0 g of a nonionic surfactant (trade name: L-77, manufactured by Nihon Unicar Company) was added and stirred at 20 ° C. for 1 hour to obtain an inorganic coating composition having a solid content concentration of 0.7% by mass. Obtained. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 75 parts by mass, and silica-alumina composite particles were 25 parts by mass. The content of 2-propanol was 5 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

  An attempt was made to form a hydrophilic coating film in the same manner as in Example 1 except that the inorganic coating composition was used. As a result, the inorganic coating composition was repelled on the acrylic substrate, and uneven coating was observed after drying. .

[Example 15 (comparative example)]
After putting 5.25 g of alumina sol A and 6.25 g of ion-exchanged water into a glass container, while stirring, dilute to 1% by mass with silica-alumina composite sol a 3.5 g, 2-propanol 80.0 g and ion-exchanged water. 5.0 g of a nonionic surfactant (trade name: L-77, manufactured by Nihon Unicar Company) was added and stirred at 20 ° C. for 1 hour to obtain an inorganic coating composition having a solid content concentration of 0.7% by mass. Obtained. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 75 parts by mass, and silica-alumina composite particles were 25 parts by mass. The content of 2-propanol was 80 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

  An attempt was made to form a hydrophilic coating film in the same manner as in Example 1 except that the inorganic coating composition was used. As a result, the evaporation rate of the dispersion medium was too high and uneven coating was observed after drying.

[Example 16]
Water was added to polyvinyl alcohol (trade name: POVAL 124, manufactured by Kuraray Co., Ltd.) and dissolved by heating to obtain a polyvinyl alcohol aqueous solution having a solid content concentration of 5.0% by mass.
A glass container was charged with 4.46 g of alumina sol A and 46.16 g of ion-exchanged water, and while stirring, 2.98 g of silica-alumina composite sol a, 1.4 g of an aqueous polyvinyl alcohol solution, 40.0 g of 2-propanol, ions 5.0 g of a nonionic surfactant (trade name: L-77, manufactured by Nihon Unicar Co., Ltd.) diluted to 1% by mass with exchange water was added and stirred at 20 ° C. for 1 hour to obtain a solid content concentration of 0.7. A mass% inorganic coating composition was obtained. Of 100 parts by mass of the total solid content in the inorganic coating composition, boehmite particles were 67 parts by mass, silica-alumina composite particles were 22 parts by mass, and polyvinyl alcohol was 11 parts by mass. The content of 2-propanol was 40 parts by mass out of 100 parts by mass of the inorganic coating composition. The content of the surfactant in the inorganic coating composition was 500 ppm.

  A hydrophilic coating film was formed in the same manner as in Example 1 except that the inorganic coating composition was used. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 17]
A hydrophilic coating film was formed in the same manner as in Example 1 except that a polycarbonate substrate (100 mm × 100 mm × 2.0 mm thickness) was used instead of the acrylic substrate. The sample on which the hydrophilic coating film was formed was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

According to the production method of the present invention, an inorganic coating composition that can form a hydrophilic coating film that is excellent in hydrophilicity and transparency and has no cloud point on an organic substrate can be obtained.

Claims (9)

A method for producing an inorganic coating composition capable of forming a hydrophilic coating film on an organic substrate,
An alumina sol in which boehmite particles are dispersed in a dispersion medium, a silica-alumina composite sol in which silica-alumina composite particles are dispersed in a dispersion medium, a surfactant, water, and water having a boiling point of 100 ° C. or less at 0.1 MPa. When an inorganic coating composition having a solid content concentration of 0.1 to 2.0% by mass is mixed with a miscible organic solvent,
As the alumina sol, (a) the average particle diameter of the aggregated boehmite particles in the dispersion medium is 20 to 100 nm, and (b) the average pore radius of the xerogel obtained by removing the dispersion medium from the alumina sol is 1 to 5 nm. (C) using an alumina sol having a total pore volume of 0.10 to 0.30 ml / g with a pore radius of 1 to 100 nm in the xerogel,
As the silica-alumina composite sol, (x) the average particle diameter of the aggregated particles of the silica-alumina composite particles in the dispersion medium is 30 to 100 nm, and (y) the Al / Si atomic ratio in the silica-alumina composite particles is 0.001 to 0. .1 using silica-alumina composite sol,
Among 100 parts by mass of the total solid content of the inorganic coating composition, boehmite particles are 60 to 90 parts by mass, and silica alumina composite particles are 10 to 40 parts by mass,
The manufacturing method of the inorganic coating composition whose amount of the organic solvent miscible with water whose boiling point in 0.1 MPa is 100 degrees C or less is 10-69.9 mass parts out of 100 mass parts of inorganic coating compositions. .   The manufacturing method of the inorganic coating composition of Claim 1 using the alumina sol whose thickness of the crystal | crystallization of the direction perpendicular | vertical to the (010) plane of (d) boehmite particle | grains is 4-8 nm as an alumina sol.   The silica-alumina composite sol (z) is used, wherein the silica-alumina composite sol (z) is obtained by reacting silica sol with polyaluminum chloride and is a particle having a positive charge on the surface. The manufacturing method of the inorganic coating composition as described.   The manufacturing method of the inorganic coating composition in any one of Claims 1-3 which add a hydrophilic polymer further.   The hydrophilic coating film formed by apply | coating to the organic base material the inorganic coating composition obtained by the manufacturing method in any one of Claims 1-4.   The hydrophilic coating film of Claim 5 whose haze value is 1.5% or less.   The hydrophilic coating film of Claim 5 or 6 whose contact angle of water is 10 degrees or less.   The hydrophilic coating film in any one of Claims 5-7 whose organic base material is an acrylic resin or a polycarbonate. An article having the hydrophilic coating film according to any one of claims 5 to 8 on the surface of an organic substrate.