JP4507066B2 - Tungsten oxide-containing titanium oxide sol, production method thereof, coating agent and optical functional body - Google Patents

Description

  The present invention relates to a titanium oxide sol containing tungsten oxide, a method for producing the same, a coating agent containing them, and an optical functional body formed by applying the coating agent.

  Titanium oxide is known to have a photocatalytic effect that exhibits redox action by irradiating ultraviolet rays, decomposes harmful substances, exhibits antibacterial properties, and superhydrophilic phenomena. Product development is actively underway. Since the photocatalytic effect uses about several percent of ultraviolet energy contained in sunlight, the photocatalytic reaction is a very slow reaction, and the reaction occurs only during UV irradiation, so it is a common chemistry. The taste is greatly different from the catalytic reaction used in the synthesis. Therefore, the present photocatalyst is strongly desired to improve the function of effectively using the energy of visible light, and many improved techniques have been proposed.

  For example, nitrogen-doped titanium oxide that has been doped with nitrogen to shift the absorption wavelength to the longer wavelength side has been proposed, but this titanium oxide has a much worse quantum efficiency due to ultraviolet excitation than conventional titanium oxide, and is visible. In the case of a light source including light and ultraviolet light, the absolute performance is not necessarily improved. On the other hand, apart from the response of visible light, many studies have been made to enhance the function of the photocatalyst. As an example, tungsten oxide has been reported to enhance various photocatalytic effects. For example, it has been reported that a photocatalyst having a solid acid such as tungsten supported on its surface can be easily hydrophilized and can maintain its hydrophilicity for a long period of time (see, for example, Patent Document 1).

  Furthermore, there has been a report in which amorphous tungsten oxide coexists with photocatalytic titanium oxide to expect the same effect (for example, see Patent Document 2). In this report, as an example of amorphous tungsten oxide, a sol in which amorphous tungsten oxide particles are suspended is cited. This is because the amorphous tungsten oxide fine particles are made into a sol form such as silica sol, alumina sol or the like. Although it is presumed to be suspended in the substance, the coating agent composed of a mixture of such a suspended sol and a titanium oxide sol is not transparent per se and is uniform and transparent as in the present invention described later. A thin film cannot be manufactured.

In addition, as a method of forming a photocatalytic hydrophilic member having a high degree of hydrophilicity, after applying organic titanate to the substrate surface, hydrolyzing and dehydrating condensation polymerization of organic titanate, and then removing residual organic groups. Then, a method of generating crystalline titanium oxide and TiO ₂ / WO ₃ composite oxide by applying a tungstic acid-containing aqueous solution and baking at 400 ° C. or higher has been reported (for example, see Patent Document 3). .

  However, in these techniques, after forming a thin film of titanium oxide, tungsten is attached again to the surface and heat-treated to form tungsten oxide. Therefore, the process is complicated and a high-temperature heat treatment process is required. It was a big problem. In addition, recently, a technique has been disclosed in which a photocatalyst is imparted with visible light responsiveness by impregnating an ammonium tungstate solution on a titanium oxide powder and then firing to support tungsten oxide (for example, (See Patent Document 4).

The impregnation supporting method disclosed in Patent Document 4 is a general method for producing a heterogeneous catalyst, and tungsten oxide can be easily supported on titanium oxide. However, since a water-soluble salt of tungsten is used as a raw material, it is necessary to oxidize tungsten by baking at a high temperature of 300 ° C. or higher. As a result, the composite obtained after firing becomes particles of several microns or more, and its use is limited for applications requiring high transparency and design such as glass and plastic film.
In addition, as a photocatalyst exhibiting high activity with visible light, a photocatalyst including an acidic metal oxide (for example, tungsten) along with iron oxide on the surface of titanium oxide has been developed. However, this photocatalyst requires high-temperature firing. It is estimated that it is difficult to manufacture a thin film by a body (for example, see Patent Document 5).

By the way, the application of tungsten oxide-containing titanium oxide has been studied in addition to these, and for example, the application to stainless steel rust prevention, antibacterial properties in the dark, and light control glass is considered (see Non-Patent Document 1). .
The above-mentioned uses such as decomposition of harmful substances, hydrophilicity, rust prevention, antibacterial, and light control are all due to the combined effect of tungsten oxide and titanium oxide, but the thin film coating material formed on the substrate has photocatalytic activity. From this viewpoint, it is desired that the particle diameter is small and the transparency is high. On the other hand, regarding the construction, there is a strong demand for a method capable of forming a transparent thin film coating containing titanium oxide and tungsten oxide on a base material in one step at a low temperature. In order to satisfy these requirements, either a titanium oxide sol containing tungsten oxide or a mixture of a tungsten oxide sol and a titanium oxide sol that are compatible with each other can be considered. Although many types are commercially available, there has never been a sol containing tungsten oxide alone or both tungsten oxide and titanium oxide. To obtain a thin film containing both, tungsten oxide is laminated in different steps as described above. The heat treatment must be carried out at a high temperature or by mixing and applying an aqueous solution containing tungsten to the titanium oxide sol. In order to solve such problems, development of a tungsten oxide sol or a titanium oxide sol containing tungsten oxide has been strongly desired.

WO97 / 23572 WO01 / 068786 Japanese Patent Laid-Open No. 10-095635 JP 2002-126517 A JP 2003-190811 A "Newsletter Photocatalyst" Photofunctional Materials Study Group, 2003, vol. 11, p.

  In view of the above-mentioned problems, the present invention provides a new tungsten oxide-containing titanium oxide sol for producing a tungsten oxide-containing titanium oxide transparent film in a single step at a low temperature, a method for producing the same, and a transparent coating agent using the same. It is to provide.

As a result of intensive studies on a method for producing a titanium oxide sol containing tungsten oxide that is effective in improving the performance of the photocatalyst and imparting functions, the inventors have developed a highly transparent tungsten oxide-containing titanium oxide sol. The invention has been completed.
That is, in the present invention, b2−b1 <0 , where b1 is the color quality index b value of the reflected color before ultraviolet irradiation, and b2 is the color quality index b value of the reflected color after ultraviolet irradiation , and oxide content tungsten regarding WO ₃ / TiO ₂ (molar ratio) = 0.0003 to 0.070 and a tungsten oxide-containing titanium oxide sol to titanium oxide (TiO ₂₎ as WO _3. In addition, the present invention provides a titanic acid gel obtained by decomposition of a water-soluble titanium salt, ammonia having NH ₃ / TiO ₂ (molar ratio) = 0.05 to 0.5, and WO ₃ / TiO ₂ (molar ratio) = 0.0003 to 0.070. The present invention relates to a method for producing a tungsten oxide-containing titanium oxide sol obtained by heat-treating a solution containing a tungsten compound at 100 to 160 ° C. Furthermore, this invention relates to the coating agent which consists of a tungsten oxide containing titanium oxide sol of this invention, and the optical function body formed by apply | coating it.

  The sol of the present invention comprises a titanium oxide sol containing tungsten oxide in the form of a sol having a small particle diameter, and after applying this sol to a substrate, it is simply dried and baked at a high temperature and has excellent photocatalytic activity. Can be easily formed.

Hereinafter, the present invention will be described in detail.
The sol of the present invention has b2−b1 <0 , where b1 is the color quality index b value of the reflected color before ultraviolet irradiation, and b2 is the color quality index b value of the reflected color after ultraviolet irradiation , and oxide content tungsten regarding WO ₃ / TiO ₂ (molar ratio) = 0.0003 to 0.070 and a tungsten oxide-containing titanium oxide sol to titanium oxide (TiO ₂₎ as WO _3.

As the tungsten oxide, hexavalent tungsten trioxide (WO ₃ ) is the most stable and is generally a yellow powder, but when it is exposed to light in water, it is reduced and turns blue. This discoloration phenomenon is caused by the formation of a lower oxide, also called W ₄ O ₁₁ or W ₁₀ O _29, and is a reaction unique to tungsten oxide (WO ₃ ). And this photoreaction is considered to be the cause of the optical function expression of tungsten oxide. On the other hand, tungstic acid (H ₂ WO ₄ ) and ammonium tungstate, which are precursors of tungsten oxide, do not cause such a change. Therefore, as described above, it is necessary to perform high-temperature firing to form tungsten oxide. By the way, the tungsten oxide-containing titanium oxide sol of the present invention has b1 as the color quality index b value of the reflected color before ultraviolet irradiation, and b1 as the reflected color color after irradiation. When b2, b2−b1 <0. This condition corresponds to the photoreduction reaction of tungsten oxide, and by satisfying the above condition, the sol shows a blue color derived from a lower oxide. The conditions for ultraviolet irradiation are not particularly limited, but for example, energy sufficient to irradiate black light having an ultraviolet intensity of about ² mW / cm ^{2 at} 360 nm for 1 hour is sufficient. The state of the sample at the time of color difference measurement may be a sol solution or a powder obtained by drying it at about 100 ° C. In either case, it is possible to confirm the change in b value of the reflected color due to discoloration accompanying reduction. In the present invention, it is based on the following “measurement of color quality index b value before and after ultraviolet irradiation”.

The sol of the present invention is characterized in that the tungsten oxide content is WO ₃ / WO ₃ / TiO ₂ (molar ratio) = 0.0003 to 0.070 with respect to titanium oxide (TiO ₂ ), preferably in the range of 0.001 to 0.050. is there. If the content of tungsten oxide is less than this, the function derived from tungsten oxide cannot be expressed, and if the amount is higher than this, not only can the stable sol not be produced because the sol tends to cause thickening, gelation, etc. It tends to inhibit the production of titanium oxide sol particles. Regarding the particle size of the sol of the present invention, the average particle size measured by the dynamic scattering method described later is 5 to 100 nm, preferably 10 to 50 nm, more preferably 15 to 30 nm. The sol of the present invention exhibits a Tyndall phenomenon, and the form thereof is not limited to a mixture of titanium oxide sol and tungsten oxide sol, or a composite sol of both oxides, but the entire system is within the above particle diameter range. Furthermore, the sol of the present invention is capable of providing a transparent thin film, and is characterized in that the haze ratio when the solid content concentration of titanium oxide is 1% by mass is 50% or less, preferably 30% or less. The haze ratio is measured by putting the sol of the present invention in a transparent cell having an optical path length of 1 cm using a commercially available transmissive color difference meter. The haze rate is an index representing turbidity, and if this value is 50% or more, it is not preferable because a film becomes turbid when it is formed using this sol, and in order to obtain a film with excellent transparency The haze ratio is preferably 50% or less.

Next, regarding the method for producing a tungsten oxide-containing titanium oxide sol of the present invention, titanic acid gel obtained by decomposition of a water-soluble titanium salt, NH ₃ / TiO ₂ (molar ratio) = 0.05 to 0.5 ammonia, WO ₃ / TiO ₂ (molar ratio) = 0.0003 to 0.070 A solution containing a tungsten compound is heat-treated at 100 to 160 ° C., but the production method of the sol of the present invention will be described in detail below. .

The tungsten oxide-containing titanium oxide sol of the present invention uses a titanic acid gel obtained by decomposing a water-soluble salt of titanium as a precursor material for titanium oxide. Examples of the water-soluble salt of titanium include titanium chloride, titanium oxychloride, titanium sulfate, and titanium oxysulfate. Examples of the decomposition of the water-soluble salt of titanium include thermal decomposition and neutralization decomposition. For example, metatitanic acid by thermal decomposition, regular titanic acid by neutralization decomposition, and the like correspond to the titanate gel of the present invention. In particular, a normal titanate gel obtained by neutralization decomposition provides a titanate gel suitable for the highly transparent photocatalyst sol of the present invention. Now, an example of a method for producing the titanic acid gel is as follows. Titanium oxychloride diluted with water is made into a 0.1 to 10% by mass aqueous solution as titanium oxide (TiO ₂ ), and this is treated with ammonia water in the range of room temperature to 80 ° C. By mixing, a white precipitate is obtained. At this time, the concentration of ammonia water to be used is preferably 0.5 to 10% by mass, and the ammonia amount (NH ₃ ) with respect to the chlorine amount (Cl) contained in the titanium oxychloride aqueous solution is 1.0 to 2.0 in molar ratio. Good. The addition method is not particularly limited, and titanium oxychloride may be added to ammonia water, or ammonia water may be added to titanium oxychloride. By washing and removing ammonium salt from the obtained slurry, the titanic acid gel used in the present invention can be obtained. On the other hand, examples of the tungsten compound include tungsten oxide, tungstic acid, ammonium tungstate, and the like. As the ammonium tungstate, ammonium paratungstate, ammonium metatungstate, or the like can be used.

Next, the titanate gel and the tungsten compound, which are raw materials for the sol, are uniformly mixed in the presence of ammonia. The mixing method and mixing order of the three components are not particularly limited, but it is particularly important to uniformly mix all the components. For example, in a titanic acid gel slurry whose concentration is adjusted to 0.1 to 15% by mass as titanium oxide, first, ammonia having a molar ratio of NH ₃ / TiO ₂ = 0.05 to 0.5, more preferably 0.08 to 0.3, is contained. When the amount of ammonia is less than NH ₃ / TiO ₂ = 0.05, the slurry is not peptized even after heat treatment, and thus the desired sol cannot be obtained. On the other hand, when NH ₃ / TiO ₂ = 0.5 or more, it is not a condition for industrially stable production because it tends to thicken and gel, and the handleability may deteriorate. Ammonia is most easily added as an aqueous solution, and the concentration of addition is not particularly limited. A point to be particularly noted in the present invention is that the ammonia amount means the total ammonia amount present in the reaction system. That is, when the ammonia used in the neutralization decomposition remains in the slurry of the titanate gel or when ammonium tungstate is used as the tungsten raw material, the ammonia amount in the entire reaction system is added by adding the ammonia. Ammonia must be added so that it is within.

The amount of the tungsten compound is preferably in a molar ratio of 0.0003 to 0.070 as tungsten oxide (WO ₃ ) with respect to titanium oxide (TiO ₂ ) in the titanate gel, and preferably in the range of 0.001 to 0.05. If the amount of tungsten oxide is less than this, the effect of using tungsten is almost lost. On the other hand, adding more tungsten oxide than this to the titanium oxide is not preferable because an effect corresponding to the amount can no longer be expected and a stable sol cannot be obtained. The form of addition of the tungsten compound may be a solid or a solution, but in the case of a solid, it is necessary to sufficiently dissolve tungsten by stirring or the like. In particular, when tungsten oxide is used, it is difficult to dissolve it. Therefore, it is necessary to dissolve it with sufficient stirring, and it is preferable to use it after it is dissolved in an aqueous ammonia solution. In addition, when ammonium tungstate is used, the titanate gel slurry may temporarily increase in viscosity. Therefore, it may be diluted and mixed if necessary. What is important in the present invention is that the tungsten compound is completely dissolved in the slurry containing titanate gel and ammonia.

The sol of the present invention is obtained by adjusting the concentration of the titanate gel, ammonia and tungsten compound uniformly mixed in this way to 1 to 10% by mass (total amount as TiO ₂ , NH ₃ , WO ₃ ) and heat-treating. be able to. With regard to the heat treatment temperature, a sol having high functionality, transparency and stability can be obtained by hydrothermal treatment at 100 ° C. to 160 ° C., preferably 110 to 140 ° C. If the heat treatment temperature is lower than 100 ° C, it is not preferable because a sol reaction does not occur or a thick turbid and strongly sol can be formed. Conversely, if the heat treatment temperature is higher than 160 ° C, it is no longer suitable for the treatment temperature. In addition, the sol cannot be expected, and the sol thickens or particles precipitate, which is not preferable. Regarding the heat treatment time, sufficient time for the titanic acid gel to become a sol is required, but it is usually in the range of 2 to 12 hours. During this heat treatment, the titanate gel becomes anatase-type titanium oxide sol particles, and the tungsten compound becomes tungsten oxide. After the heat treatment, the whole becomes transparent and shows the Tyndall phenomenon which is a characteristic of the sol.

  By the way, it is judged that tungsten in the sol of the present invention has a form of tungsten oxide because it exhibits the same photoreducibility as solid tungsten oxide as described above. For example, even if a tungsten compound is further added to the anatase-type titanium oxide sol obtained by the method of the present invention without adding a tungsten compound, and even if this mixture is heat-treated again under the conditions shown in the present invention, b2−b1 < Does not satisfy 0. Further, even if only an aqueous solution of tungstic acid or an ammonium tungstate salt is subjected to hydrothermal treatment under the conditions of the present invention, a tungsten oxide sol cannot be obtained. From the above, it is considered that the tungsten oxide-containing titanium oxide sol of the present invention is produced only when heat treatment is performed in the presence of titanate gel, ammonia and a tungsten compound. In general, colloidal particles are often handled by an ultrafiltration membrane, and particles of several nanometers or more cannot pass through the ultrafiltration membrane, but a solution in which tungstic acid is dissolved in aqueous ammonia or Even when the tungsten compound solution such as an aqueous solution of ammonium tungstate is treated as it is or under the heat treatment conditions of the present invention, it easily passes through an ultrafiltration membrane having a fractional molecular weight of 10,000. Moreover, even if the slurry in which ammonia and a tungsten compound are added to and mixed with the titanic acid gel slurry is filtered through the filter membrane, leakage of tungsten species is also observed. However, since the tungsten oxide-containing titanium oxide sol obtained according to the method of the present invention has no leakage of tungsten species in the filtrate, the tungsten oxide is bound to titanium oxide in some form or the tungsten oxide itself is colloidal. Presumed to be particles. Therefore, the tungsten oxide-containing titanium oxide sol of the present invention has completely different properties from those obtained by simply mixing a tungsten salt or the like with the titanium oxide sol, and can be obtained only by the production method of the present invention.

  The sol of the present invention obtained as described above is ammonia alkaline and has a pH of 9 to 10, but may be adjusted to a higher pH by adding ammonia or an amine. It can also be made acidic by the technique disclosed in JP-A-2001-206720 filed earlier. Regarding the sol concentration of the present invention, it may be diluted after production, or may be concentrated using an ultrafiltration membrane or the like. The sol of the present invention produces a tungsten oxide-containing titanium oxide sol according to the charged composition because, surprisingly, tungsten oxide and titanium oxide do not leak out of the system at all even when the concentration operation using the ultrafiltration membrane described above is performed. It has extremely excellent characteristics that it can be made.

  The tungsten oxide-containing titanium oxide sol of the present invention is thin-film coated and used for various applications. When forming a thin film, the sol may be directly applied to the substrate and baked, but generally a functional film can be formed at a lower temperature by mixing a binder component to form a coating agent. For example, an inorganic binder component such as silica sol or alkali silicate solution or an organic or organic-inorganic composite binder such as a resin emulsion can be added to the sol of the present invention to form a transparent thin film coating agent. Moreover, it can also be used as a coating agent using binders, such as silicon alkoxides, such as tetraethoxysilane and ethyl silicate 40, using alcohols, such as ethanol and propanol, as a solvent.

  The amount of binder used varies depending on the type of binder, composition of the sol of the present invention, application, desired film function, etc., but generally the amount of the binder component is about 10 to 50% by mass of the total solid content weight. To be mixed. The curing of the coating film depends on the properties of the binder, but may be dried or heat-treated so as to exhibit a desired hardness at room temperature to 300 ° C. The tungsten oxide-containing titanium oxide sol of the present invention exhibits excellent effects even when the heat treatment temperature is 300 ° C. or lower because tungsten is already an oxide.

  The optical functional body of the present invention refers to a base material or member imparted with a photocatalytic function to which a coating agent using the sol of the present invention is applied. For example, building materials such as tiles, glass, wall materials, fluorescent lamps and the like Examples include lighting equipment such as covers, automobile materials, sanitary ware, and the like.

  As described above, the sol of the present invention is mainly described as a sol for photocatalysts. However, since the present sol has titanium oxide and tungsten oxide dispersed very stably and uniformly, the sol of the present invention has optical functions such as photochromism and high refractive index. Even if it is used as a catalyst raw material other than a photocatalyst such as a conductive film, an excellent effect is exhibited.

  Examples of the tungsten oxide-containing titanium oxide sol of the present invention will be specifically described below, but the present invention is not limited thereto. In addition, unless otherwise indicated,% shows the mass%.

The physical properties of the tungsten oxide-containing titanium oxide sol of the present invention are measured by the following method.
Measurement of color quality index b value before and after UV irradiation The color quality index of the sample was measured using a color difference meter Z-1001DP (manufactured by Nippon Denshoku Industries Co., Ltd.). 5mL of the sample before UV irradiation is put into a glass cell, and the color quality index b value (b1) of the reflected color is measured. Next, after irradiating the sample with black light having a wavelength of 360 nm and an ultraviolet intensity of ² mW / cm ² for 2 hours, the color quality index b value (b2) of the reflected color is measured, and the b2−b1 value is obtained from the obtained data.
Measurement of average particle diameter The average particle diameter was measured using a dynamic light scattering color particle size distribution analyzer LB-500 (manufactured by Horiba, Ltd.).
Measurement of haze ratio The haze ratio was measured using a color difference meter COH-300A (manufactured by Nippon Denshoku Industries Co., Ltd.). As a measurement condition, a sample diluted to a TiO ₂ concentration of 1% was put in a glass cell having an optical path length of 1 cm and measured.

[Example 1]
After adding 2,500 g of 3% aqueous ammonia with stirring to 20000 g of 0.5% TiO ₂ aqueous solution obtained by diluting TiO ₂ 27.7%, Cl 32.4% titanium oxychloride (manufactured by Sumitomo Titanium), a white gel was obtained. Washing was performed until chlorine in the filtrate was not detected, and a titanate gel slurry containing 4.2% TiO ₂ was obtained. The amount of ammonia in this slurry was 0.12 as NH ₃ / TiO ₂ (molar ratio). 0.046 g of tungstic acid (H ₂ WO ₄ ) (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 200 g of this slurry and stirred until the slurry became white. This was put in a sealed pressure vessel and heat-treated at 120 ° C. for 5 hours to obtain the sol of the present invention. The obtained sol was further concentrated using an ultrafiltration membrane to obtain a concentrated sol having a solid content of 9.92%. The WO ₃ concentration of the sol was 0.05%, the TiO ₂ concentration was 9.86%, and WO ₃ / TiO ₂ (molar ratio) = 0.0018. The color change of the obtained sol was changed to blue after UV irradiation, and the b2-b1 value was -2.90. The average particle size was 25 nm and the haze ratio was 8.19%.

[Example 2]
A sol was obtained in the same manner as in Example 1 except that the amount of tungstic acid added was 0.28 g.
The obtained sol was further concentrated using an ultrafiltration membrane to obtain a concentrated sol having a solid content of 8.34%. The WO ₃ concentration of the sol was WO ₃ 0.25%, TiO ₂ 8.09%, and WO ₃ / TiO ₂ (molar ratio) = 0.0107. The color change of the obtained sol was changed to blue after ultraviolet irradiation, and the b2-b1 value was -3.18. The average particle size was 23 nm and the haze ratio was 6.82%.

[Example 3]
A sol was obtained in the same manner as in Example 1 except that the amount of tungstic acid was 0.48 g.
The obtained sol was further concentrated using an ultrafiltration membrane to obtain a concentrated sol having a solid content of 7.07%. The WO ₃ concentration of the sol was WO ₃ 0.35%, TiO ₂ 6.72%, and WO ₃ / TiO ₂ (molar ratio) = 0.018. The color change of the obtained sol was changed to blue after irradiation with ultraviolet rays, and the b2-b1 value was −4.39. The average particle size was 28 nm, and the haze ratio was 14.31%.

[Example 4]
A sol was obtained in the same manner as in Example 1 except that the amount of tungstic acid was changed to 1.00 g.
The obtained sol was further concentrated using an ultrafiltration membrane to obtain a concentrated sol having a solid content of 6.83% by weight. The WO ₃ concentration of the sol was WO ₃ 0.70%, TiO ₂ 6.12%, and WO ₃ / TiO ₂ (molar ratio) = 0.039. The color change of the obtained sol was changed to blue after UV irradiation, and the b2-b1 value was -2.45. The average particle size was 29 nm, and the haze ratio was 18.21%.

[Example 5]
A sol was obtained in the same manner as in Example 1 except that the amount of tungstic acid was 0.48 g and 18 g of 3% aqueous ammonia solution was added. The WO ₃ concentration of the obtained sol was WO ₃ 0.19%, TiO ₂ 3.66%, and WO ₃ / TiO ₂ (molar ratio) = 0.018. The color change of the obtained sol was changed to blue after UV irradiation, and the b2-b1 value was -3.65. The average particle size was 28 nm, and the haze ratio was 18.12%.

[Example 6]
A sol was obtained in the same manner as in Example 1 except that 1.68 g of a 50% aqueous solution of ammonium metatungstate was added instead of tungstic acid. The WO ₃ concentration of the obtained sol was WO ₃ 0.40%, TiO ₂ 3.77%, and WO ₃ / TiO ₂ (molar ratio) = 0.036. The color change of the obtained sol was changed to blue after UV irradiation, and the b2-b1 value was -2.91. The average particle size was 32 nm, and the haze ratio was 38.49%.

[Example 7]
A sol was obtained in the same manner as in Example 1 except that 0.43 g of tungsten oxide and 18 g of 3% aqueous ammonia were added in place of the tungstic acid of Example 1. The WO ₃ concentration of the obtained sol was WO ₃ 0.19%, TiO ₂ 3.66%, and WO ₃ / TiO ₂ (molar ratio) = 0.018. The color change of the obtained sol was changed to blue after UV irradiation, and the b2-b1 value was -2.78. The average particle size was 25 nm, and the haze ratio was 25.07%.

[Example 8]
Coating agents were prepared using the sols of Examples 1 to 3, and the following tests were performed. That is, the concentration of each of the sols of Examples 1 to 3 was adjusted so that TiO ₂ = 5% by weight, and lithium silicate 35 (SiO ₂ = 20%) (manufactured by Nippon Chemical Industry Co., Ltd.) in a weight ratio of TiO ₂ / SiO ₂ = 8/2, and the resulting coating agent was spin-coated on a slide glass at 1000 rpm, and then irradiated with black light having a wavelength of 360 nm and an ultraviolet intensity of ² mW / cm ² for 24 hours to contact angle with water ≈ 0 And then left in a dark place to observe the change in contact angle over time. As a comparative example, a coating agent was prepared in the same manner using a titanium oxide sol prepared without using tungstic acid by the method of Example 1 instead of the sol of the present invention, and subjected to the test. The result is shown in FIG. As is clear from this result, it can be seen that the film using the sol of the present invention exhibits an excellent hydrophilic effect.

[Example 9]
After adding citric acid having a molar ratio of 0.4 to titanium oxide to the tungsten oxide-containing titanium oxide sol obtained in Example 3, the mixture was placed in a sealed pressure vessel and heat-treated at 120 ° C. for 3 hours, and then the filtrate was electrolyzed using an ultrafiltration membrane. The sol was washed until the conductivity became 0.1 mS / cm or less to obtain a sol having a total solid content of 10% and a pH of 3.2. The composition of the obtained sol was TiO ₂ 12.8% and WO ₃ 0.66%. To 37.1 g of this sol, 58.5 g of ethanol and 4.4 g of tetraethoxysilane were added and stirred for 24 hours to obtain a coating agent. The coating agent was spin-coated on a glass substrate at 1000 rpm and then dried and cured at 100 ° C. to obtain a tungsten oxide-containing titanium oxide film. This coated glass was colorless and transparent. When this glass was inserted into the glass cell and the haze ratio was measured using a color difference meter COH-300A (manufactured by Nippon Denshoku Industries Co., Ltd.), it was 1% or less.

[Comparative Example 1]
The titanic acid gel slurry obtained in Example 1 is put in a sealed pressure vessel and heat-treated at 120 ° C. for 5 hours to obtain a sol made of only titanium oxide, and then 0.54 g of tungstic acid is added and dissolved to contain tungstic acid. A sol was obtained. When the color change was examined by the same method as in Example 1, no color change was observed before and after the ultraviolet irradiation, and b2−b1 = 0. That is, using this sol, a coating agent was prepared in the same manner as in Example 8 and subjected to the test. As a result, it showed hydrophilicity similar to that of the titanium oxide sol prepared without using tungstic acid by the method of Example 1. .

[Comparative Example 2]
The sol obtained in Comparative Example 1 was further treated at 120 ° C. for 5 hours to obtain a sol containing a tungsten compound. When the color change was examined by the same method as in Example 1, no color change was observed before and after the ultraviolet irradiation, and b2−b1 = 0. That is, using this sol, a coating agent was prepared in the same manner as in Example 8 and subjected to the test. As a result, it showed hydrophilicity similar to that of the titanium oxide sol prepared without using tungstic acid by the method of Example 1. .

  Titanium oxide, which is often used as a photocatalyst, is known to improve hydrophilicity and degradation performance of pollutants due to the combined effect with tungsten oxide. This heat treatment process is necessary, and this effect could not be used for the low heat resistant base material. However, the use of the tungsten oxide-containing titanium oxide sol of the present invention makes the construction easy and one-step woody agent. In addition, it can be effectively used for low heat resistant substrates such as plastic and paper, and in addition, it can easily form a highly transparent thin film at low temperature, and its industrial significance is extremely large. It is.

It is a figure which shows the time-dependent change of the contact angle of the material surface by the coating agent using the sol and titanium oxide sol of this invention.

Claims (7)

When b1 is the color quality index b value of the reflected color before ultraviolet irradiation and b2 is the color quality index b value of the reflected color after ultraviolet irradiation, b2−b1 <0 and the tungsten oxide content is WO ₃ is a tungsten oxide-containing titanium oxide sol in which WO ₃ / TiO ₂ (molar ratio) = 0.0003 to 0.070 with respect to titanium oxide (TiO ₂ ) . Average tungsten oxide containing titanium oxide sol according to claim 1, wherein the particle size of 5 to 100 nm. 3. The tungsten oxide-containing titanium oxide sol according to claim 1, wherein the solid content concentration of titanium oxide is 50% or less at a haze ratio of 1% by mass as TiO ₂ . A coating agent comprising the tungsten oxide-containing titanium oxide sol according to any one of claims 1 to 3 . 5. An optical functional body obtained by applying the coating agent according to claim 4 . A titanic acid gel obtained by decomposition of a water-soluble titanium salt, ammonia with NH ₃ / TiO ₂ (molar ratio) = 0.05 to 0.5, and a tungsten compound with WO ₃ / TiO ₂ (molar ratio) = 0.0003 to 0.070 The method for producing a tungsten oxide-containing titanium oxide sol according to claim 1 , wherein the solution containing the mixture is heat-treated at 100 to 160 ° C. The method for producing a tungsten oxide-containing titanium oxide sol according to claim 6 , wherein the tungsten compound is one or more tungsten compounds selected from tungsten oxide, tungstic acid or ammonium tungstate.

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