KR20050086064A - Method for preparing titanium oxide by tungsten oxide thin films for hydrophilicity - Google Patents

Abstract

The present invention relates to a method for manufacturing a titanium oxide hydrophilic thin film substituted with tungsten oxide, specifically, a tungsten-titanium precursor solution in a sol state by dissolving a mixture of tungsten halide and titanium alkoxide of 10 wt% or less in a chelating agent. Preparing (step 1), coating the sol solution on the surface of the substrate (step 2), heat treating the coated substrate at 350 to 500 ° C. to form an amorphous WO ₃ -TiO ₂ composite oxide ( It relates to a method for producing a hydrophilic thin film comprising the step 3).

In the manufacturing method of the present invention, a chelating agent is used to control the rate of hydrolysis, and to lower the heat treatment temperature to produce a uniform composite oxide thin film having a particle size of several tens of nanometers. It can be coated on a variety of substrate surface, such as can be manufactured at a low price. In addition, the thin film produced by the manufacturing method can maintain hydrophilicity for a long time after ultraviolet irradiation.

Description

Tungsten Oxide Substituted Titanium Oxide Hydrophilic Thin Film Production Method {METHOD FOR PREPARING TITANIUM OXIDE BY TUNGSTEN OXIDE THIN FILMS FOR HYDROPHILICITY}

The present invention relates to a method of manufacturing a hydrophilic thin film, and more particularly, to a method of manufacturing a titanium oxide hydrophilic thin film substituted with tungsten oxide.

When the humidity is high or the temperature difference is severe, water droplets are formed on the vehicle glass due to the temperature difference or due to rainfall, which obscures the driver's view. In addition, the driver has to pay attention to suppress the condensation phenomenon in addition to driving in order to solve this problem, resulting in traffic safety problems. In order to solve this problem, attempts have been made to prevent condensation on the vehicle glass.

In order to suppress the water droplet formation described above, a method of coating a hydrophilic polymer material or an inorganic hydrophilic film on a vehicle glass is known in the art.

In Japanese Patent Laid-Open No. 3-129357, a hydrophilic thin film was prepared by coating a polymer layer on a glass surface. However, the method exhibits a property that surface hydrophilicity decreases over time due to adhesion contaminants, and also causes a problem of wear resistance of the polymer layer.

In order to solve this problem, the inorganic hydrophilic thin film is mainly used. The inorganic hydrophilic thin film is a photoinductive hydrophilic thin film mainly composed of TiO ₂ having a photocatalyst function, and various manufacturing methods have been tried to improve the hydrophilicity of the thin film.

In Korean Patent Publication Nos. 2003-0048696 and 2002-0034713, attempts have been made to improve the photocatalytic TiO ₂ photofunctional hydrophilicity of a glass surface by treatment with a hydroxyl group (OH ⁻ ) or a sulfuric acid group (SO ₄ ^2- ).

In Japanese Patent Laid-Open No. 10-95635, a superhydrophilic thin film was prepared by coating SiO ₂ TiO ₂ sol. However, since the heat treatment temperature of the coating film is low, the hardness and strength of the coating film by the organic residue are low.

A similar method for preparing a porous TiO ₂ -WO ₃ coated hydrophilic thin film has been proposed. In Japanese Patent Laid-Open No. 10-114544, WO ₃ / TiO ₂ was coated stepwise to form a WO ₃ bilayer thin film on crystalline TiO ₂ to prepare a WO ₃ -TiO ₂ thin film only at the interface. However, there is a hassle to prepare a WO ₃ -TiO ₂ composite oxide thin film having superhydrophilic photocatalytic activity by a complicated step.

In Japanese Patent Laid-Open No. 10-114546, a TiO ₂ / ZrO ₂ composite oxide thin film was prepared by baking a photocatalytic TiO ₂ sol and a zirconium alkoxide mixture at 500 ° C. high temperature. However, the above method is limited in the type of substrate by the high firing temperature.

In addition, according to Korean Patent Application No. 1998-703128, a photoexcitation hydrophilic thin film and a composite of various single oxides (TiO ₂ , SiO ₂ , WO ₃ , and Fe ₂ O 3) by a sol-gel method and sputtering method A thin film production method for oxide (TiO ₂ -SiO ₂ and TiO ₂ -SnO ₂ ) systems has been proposed.

As described above, the inorganic hydrophilic film is often performed by the sol-gel coating method, and the hydrophilic oxide thin film prepared by the sol-gel coating method is coated with a TiO ₂ thin film on a glass substrate and then SnO ₂ , ZrO _2. In addition, WO ₃ is coated to prepare a composite oxide in a multi-step coating method, and is a useful method for preparing a composite oxide having high crystallinity due to high firing temperature.

However, the inorganic hydrophilic thin film has a problem that it is difficult to control the particle size of the inorganic oxide according to the sol-gel method, the manufacturing method itself is complicated, the firing temperature is high, the type of substrate.

An object of the present invention is to solve and improve the above problems, the manufacturing method is simple, it is possible to manufacture the amorphous composite oxide thin film having a low firing temperature, and also to provide a method for producing a hydrophilic thin film excellent in physical properties will be.

In order to achieve the above object, the present invention comprises the steps of dissolving a mixture of up to 10% by weight of tungsten halide and titanium alkoxide in a chelating agent to prepare a sol tungsten-titanium precursor solution (step 1),

Coating the sol solution onto the surface of the substrate (step 2), and

The coated substrate is heat-treated at 350 to 500 ° C. to provide an amorphous hydrophilic thin film comprising the step (step 3) of forming an amorphous WO ₃ -TiO ₂ composite oxide.

Hereinafter, the present invention will be described in detail.

Step 1 dissolves a mixture of tungsten halides and titanium alkoxides in a chelating agent to prepare a tungsten-titanium precursor solution in sol state.

The tungsten halide is a tungsten precursor dissolved in the chelating agent, preferably WCl ₃ , and is used in an amount of 10% by weight or less based on the mixture of tungsten halide and titanium alkoxide.

In addition, titanium alkoxide is used as a raw material of titanium oxide selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide and titanine butoxide to be dissolved in the chelating agent.

The chelating agent serves to control the hydrolysis rate of the tungsten and titanium, it is preferable to use acetylacetone (CH ₃ COCH ₂ COCH ₃ ) in the present invention.

The concentration of the tungsten-titanium precursor solution in the sol state obtained in the above step is preferably 0.5 × 10 ⁻⁴ to 0.01 M, most preferably 0.01 M. The concentration of the precursor solution in the above range is such that the particle size of the layer of the final composite oxide has a spherical shape of 10 to 50 nm, leading to the desired particle size for obtaining the most desirable physical properties. Thus, when the concentration of the solution is out of the range, there is a problem that the effect of the hydrophilicity is reduced by affecting the particle size and the surface roughness of the composite oxide layer.

In step 1, the sol solution further includes a surfactant to improve the hydrophilicity of the coated thin film. Preferred surfactants are C ₁₄ H ₃₃ (CH ₃ ) ₃ NBr). C _n H _{2n + 1} (OCH ₂ CH ₂ ) _x OH (= C _n EO _x ). N in the series is 12-23, and x is It is cetyltrimethylmonium bromide which is 0-100, and it is preferable to add at 10% weight part or less with respect to the said mixture.

In step 2 the sol solution is coated onto the surface of the substrate. The substrate may be glass, ceramic or metal, preferably glass. The coating method uses a conventional dip coating or spin coating method used in the art.

In step 3, the coated substrate is heat treated at 350 to 500 ° C. By heat treatment at the heat treatment temperature, it is possible to produce a uniform amorphous composite oxide having a particle size of several tens of nanometers, it is possible to obtain an excellent hydrophilic effect due to this feature. Therefore, when the heat treatment temperature is less than the above range, the desired hydrophilic property cannot be obtained, and when the heat treatment temperature is exceeded, a problem arises in that the usable substrate is limited.

The thin film thus prepared is in the form of amorphous WO ₃ -TiO ₂ , the particle size of the thin film is 10 to 50 nm spherical shape, the total thickness is preferably 10 to 500 nm.

In the manufacturing method of the present invention, a metal oxide precursor may be controlled using a chelating agent to control a hydrolysis rate, and a heat treatment temperature may be lowered to obtain a uniform amorphous composite oxide thin film having a particle size of several tens of nanometers. In addition, the thin film thus obtained has a photoinduced superhydrophilicity, which can be significantly lowered to a contact angle of 2 ° in the case of a thin film manufactured by the present invention than a contact angle (20 °) when using only titanium alkoxide (FIG. 1 (c) and ( d)). This increases the site where the formation of WO ₃ can constrain the charge, which increases oxygen vacancies, making it superhydrophilic.

Hereinafter, the present invention will be described by the following examples, but the present invention is not limited thereto.

Example 1 Preparation of Hydrophilic Thin Film According to Concentration

(1) Into 30 g of ethanol solution 8.484 ml of titanium isopropoxide (Ti ( ⁱ OPr) ₄ ), (95 wt%) and 0.594 g (5 wt%) of tungsten chloride (WCl ₆ ), 5.859 ml of acetylacetone ( CH ₃ COCH ₂ COCH ₃ ) was added and mixed to prepare a precursor solution at a concentration of 0.01 M.

(2) 0.339 ml of titanium isopropoxide (Ti ( ⁱ OPr) ₄ ), (95 wt%) and 0.0237 g (5 wt%) of tungsten chloride (WCl ₆ ), 0.234 ml of acetylacetone (30 g of ethanol solution) CH ₃ COCH ₂ COCH ₃ ) was added and mixed to prepare a precursor solution to a concentration of 0.4 × 10 ^-3 M.

(3) 0.0424 ml of titanium isopropoxide (Ti ( ⁱ OPr) ₄ ), (95 wt.%) And tungsten chloride (WCl ₆ ) 0.00297 g (5 wt.%), 0.029 ml of acetylacetone (30 g of ethanol solution) CH ₃ COCH ₂ COCH ₃ ) was added and mixed to prepare a concentration precursor solution of 0.5 × 10 ⁻⁴ M.

Thin films coated with a composite oxide precursor by dip coating a glass substrate treated with a washing solution (H ₂ SO ₄ / H ₂ O ₂ = 3: 1, v / v) to the solutions prepared in (1) to (3), respectively. Was prepared.

The prepared thin film was dried at 110 ° C. and then calcined at 450 ° C. for 2 hours to prepare a WO ₃ -TiO ₂ thin film.

After leaving the prepared composite oxide thin film in the dark room for 5 days, the change of contact angle before and after UV irradiation of 40 nmW / cm <2> of 365 nm was measured. The results are shown in Fig.

As shown in FIG. 1 , the contact angle after UV irradiation of the WO ₃ -TiO ₂ thin film prepared as the solution of 0.01M concentration showed a superhydrophilicity of 2 ° or less.

In addition, as a result of measuring using the SEM of the obtained thin film, as shown in Figure 2 , it can be seen that the particles having a spherical shape, in particular, the thin film prepared in a 0.01 M concentration solution of the particles 10 to 50 nm It can be seen that it has a spherical form of. It can be seen that the thin film prepared from the solution of 0.01M concentration in relation to FIG. 1 has a spherical shape with an appropriate particle size and shows superhydrophilicity of a contact angle of 2 ° or less after UV irradiation.

Example 2 Preparation of Hydrophilic Thin Film According to Temperature

In Example 1 (using a solution of 0.01M concentration), the coated thin film was calcined at (a) 300 ° C, (b) 400 ° C, (c) 450 ° C, and (d) 500 ° C, respectively. The results of the change in contact angle before and after UV irradiation of the prepared thin film are shown in FIG. 3. As shown in FIG. 3, the thin films prepared at the heat treatment temperatures of 400 ° C., 450 ° C., and 500 ° C. exhibit high contact angle changes, but the degree decreases with decreasing temperature, and the change in contact angle is the smallest at 300 ° C. Could.

Example 3 Preparation of Hydrophilic Thin Film Added Surfactant

In order to control the roughness of the surface, a thin film was prepared in the same manner except that 5 wt% of F127, a surfactant, was added to the 0.01 M precursor solution of Example 1.

Comparative Example 1

A thin film was prepared in the same manner as in Example 1 except that a thin film coated with only (Ti ( ⁱ OPr) ₄ ) except for WCl ₆ was prepared.

Experimental Example 1 Measurement of Change of Contact Angle after XRD Pattern and UV Irradiation of the Prepared Hydrophilic Thin Film

For the structural analysis of the prepared hydrophilic thin film, Phillips 1730 X-ray diffractometer was used, and the contact angle measurement was performed at room temperature before and after 10 hours irradiation of Hg-Xe lamp with intensity of 365 nm and 40 mW / ㎠ (CA-X). , Kyowa Interface Science, Saitama, Japan).

The results of the XRD pattern and the change of contact angle before and after UV irradiation of the hydrophilic thin films prepared in Example 1 and Comparative Example 1 are shown in FIGS. 4 and 5, respectively.

As shown in FIG. 4, it can be seen that WO ₃ -TiO ₂ appears in the XRD pattern of (3), which shows that amorphous WO ₃ -TiO ₂ is produced at the firing temperature.

In addition, as shown in FIG. 5, tungsten was well substituted in the TiO ₂ structure. The amorphous WO ₃ -TiO ₂ prepared above shows that the contact angle before and after UV irradiation shows a significantly lower superhydrophilicity than that of WO ₃ or TiO ₂ . This is because water droplets in the air are adsorbed on the surface without a contact angle, transparency can be maintained, and light transmission or reflectivity can be maintained for a long time, thereby preventing a safety accident of a vehicle due to securing a view.

As described above, the production method of the present invention was able to produce a uniform composite oxide thin film having a particle size of several tens of nanometers by controlling the rate of hydrolysis by using a chelating agent, lowering the heat treatment temperature, even at a low temperature It can be sintered to coat various substrate surfaces such as glass or ceramics, as well as to be manufactured at low cost. In addition, the thin film prepared by the above method shows that the contact angle after ultraviolet irradiation shows a significantly lower superhydrophilicity than WO ₃ or TiO ₂ . This is because water droplets in the air are adsorbed on the surface without a contact angle, transparency can be maintained, and light transmission or reflectivity can be maintained for a long time, thereby preventing a safety accident of a vehicle due to securing a view.

1 shows contact angle changes and optical micrographs before and after UV irradiation of a WO ₃ -TiO ₂ thin film according to Example 1 of the present invention, (a) and (c) are contact angle changes and optical micrographs before UV irradiation, respectively (B) and (d) show contact angle changes and optical micrographs after UV irradiation,

2 is a SEM photograph according to the concentration of the WO ₃ -TiO ₂ thin film according to Example 1 of the present invention, ((a) is 0.01M, (b) is 0.4x10 ^-3 M, and (c) is 0.5x10 ^-4 M.)

3 is a graph showing changes in contact angles before (a) and after (b) according to the firing temperature of the WO ₃ -TiO ₂ thin film according to Example 2 of the present invention,

4 is a graph showing XRD patterns of WO _3, TiO _2, and WO ₃ -TiO ₂ thin films according to Example 1 and Comparative Example 1 of the present invention, ((a) WO ₃ (b) TiO ₂ (c) WO ₃ -TiO ₂ )

5 is a graph showing changes in contact angles before (a) and after (b) UV irradiation of WO _3, TiO _2, and WO ₃ -TiO ₂ thin films according to Example 1 and Comparative Example 1 of the present invention.

Claims (8)

Dissolving a mixture of up to 10% by weight of tungsten halide and titanium alkoxide in a chelating agent to prepare a sol tungsten-titanium precursor solution (step 1), Coating the sol solution onto the surface of a substrate (step 2), Heat-treating the coated substrate at 350 to 500 ° C. to form an amorphous WO ₃ -TiO ₂ composite oxide (step 3). The method of manufacturing a hydrophilic thin film according to claim 1, further comprising dissolving a surfactant in the sol solution. The method of claim 1, wherein the tungsten halide is WCl ₃ . The method of claim 1, wherein the titanium alkoxide is selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide and titanium butoxide. The method according to claim 1, wherein the chelating agent is acetylacetone. The method for producing a hydrophilic thin film according to claim 1, wherein the concentration of the sol solution is 0.5x10 ^{-4 to} 0.01 M. The method of manufacturing a hydrophilic thin film according to claim 1, wherein the substrate is glass, ceramic or metal. The method of claim 1, wherein the coating is performed by dip or spin coating.