Titania coatings

The present invention relates to a substrate having a titania coating on at least one surface, and a treatment for depositing a titania coating on the surface of the substrate. In a preferred example, the substrate is flat glass.

The titania coating is known to have photocatalytic self-cleaning properties. The substrate coated with titania and the manufacturing method thereof are described in, for example, European Patent Application Publication No. 901991, and International Publication Nos. WO 97/07069, WO 97/10186, WO 98/41480 and the same. It is disclosed in the pamphlet of WO 00/75087. Such titania coatings can be deposited by a variety of techniques including sol-gel treatment, spray pyrolysis treatment, magnetron sputtering vacuum deposition treatment (MSVD) and chemical vapor deposition treatment.

The inventor has developed a novel chemical vapor deposition treatment (hereinafter referred to as CVD treatment for convenience of explanation) for producing a titania-coated substrate having improved properties. In a preferred example, these CVD treatments can be used in conjunction with the production of float glass to economically produce novel titania coated glass sheets. These treatments include contacting the heated glass ribbon with steam containing a titanium precursor at a temperature sufficient to form the desired titania coating.

Various titanium precursors have been proposed for use in CVD treatment for titania deposition. Examples include inorganic titanium compounds such as titanium tetrachloride and organic titanium compounds such as titanium tetraisopropoxide and titanium tetraethoxydo. Oxygen-free precursors as part of the molecular structure are usually used in the presence of oxygen or oxygen-containing compounds. The pamphlet of WO 00/75087 discloses a CVD treatment using titanium tetrachloride with ethyl acetate. Precursors that contain oxygen as part of their molecular structure can be used with or without additional oxygen sources. The pamphlet of WO 00/75087 discloses a CVD treatment that uses titanium tetraethoxydo without any additional oxygen source. European Patent Application Publication No. 901991 discloses a CVD treatment using titanium tetraisopropoxide and titanium tetraethoxydo with oxygen gas.

There is still a need for a process to economically deposit the desired quality titania coating.

The inventor has produced a titania coating with improved properties in which the CVD treatment for depositing the titanium oxide coating using vapors containing organic titanium compounds and oxygen-containing organic compounds is more efficient than known treatments. I confirmed that it would be. According to this treatment, the coating film can be made smoother and more durable, and the catalyst can be less likely to be deactivated even when deposited directly on the glass surface.

Therefore, according to the first aspect of the present invention, a photocatalytically active coating containing titanium oxide is deposited on the surface of the substrate, and a fluid mixture containing an organic titanium compound and an oxygen-containing organic compound is applied to the titanium oxide coating. A process is provided that includes a step of contacting the surface of the substrate at a temperature high enough to form.

The organic titanium compound is preferably a compound having oxygen as a part of the molecular structure, and more preferably a compound in which at least one oxygen atom is bonded to the titanium atom. Examples of preferred titanium compounds are titanium alkoxides such as titanium tetraisopropoxide and titanium tetraethoxydo.

The oxygen-containing organic compound is preferably an ester, more preferably a carboxylic acid ester. Suitable esters are compounds of the following formula, RC (O) -OC (XX).¹)-C (YY¹)-R¹In the formula, R and R¹Represents an alkyl group or a hydrogen atom having 1 to 10 carbon atoms, and these R and R¹Can be different or the same, and X, X¹Y and Y¹Represents an alkyl group or a hydrogen atom having 1 to 4 carbon atoms, and these Y and Y¹At least one of these is a hydrogen atom, and these X and X¹Y and Y¹Are compounds that may be different or the same. R and R¹Is preferably an alkyl group or a hydrogen atom having 1 to 4 carbon atoms.

Examples of preferred esters for use in the treatment of the present invention are ethyl formate, ethyl acetate, ethyl propionate, ethyl butyrate, n-propylformate, n-propylacetate, n-propylpropionate, n-propyl. There are butylate, isopropylformate, isopropylacetate, isopropylpropionate, isopropylbutyrate, n-butylformate, n-butylacetate, sec-butylacetate and t-butylacetate.

Preferred esters for use in the present invention are ethyl formate, ethyl propionate, and particularly preferably ethyl acetate.

A mixture of two or more oxygen-containing organic compounds can be used. It is also possible to reduce the proportion of gaseous oxygen contained in the fluid mixture. It is not very desirable to introduce a large proportion of oxygen into the fluid mixture, which can result in the deposition of poorly characterized coatings. In addition, the fluid mixture usually contains an Inactive Carrier Gas with an Active Ingredient. The most common transport gases are nitrogen and helium. Oxygen-containing organic compounds and organic titanium compounds generally make up 0.1-1.0% by volume of the fluid mixture. The molar ratio of the oxygen-containing organic compound to the organic titanium compound is preferably in the range of 0.5: 1.0 to 1.2: 1.0, and more preferably in the range of 0.8: 1.0 to 1.0: 1.0.

The substrate is preferably a glass substrate. The glass is preferably flat glass, and in particular can be a continuous form of glass ribbon produced by float glass treatment. In a preferred example, the deposition process is performed online during the float glass manufacturing process.

It is necessary to bring the fluid mixture into contact with the heated substrate. Substrates should generally be heated to temperatures in the range 400-800 ° C. The temperature of the glass ribbon in the float glass manufacturing process is in the range of about 1100 ° C (high temperature side end of the float tank) to 600 ° C (low temperature side end of the float tank) in the float tank, and about 580 ° in the annealing slow cooling furnace. The range is C to 200 ° C. The treatment of the present invention can be carried out at an appropriate position in the float tank, in the gap between the float tank and the annealing slow cooling furnace, or at the high temperature side end of the annealing slow cooling furnace. The process of the present invention contacts the fluid mixture with the substrate when the substrate is in the temperature range of 610 ° C to 720 ° C, preferably 625 ° C to 700 ° C, more preferably 625 ° C to 650 ° C. It is preferable to carry out by letting. When these suitable treatments are carried out as part of the float glass manufacturing treatment, these treatments will be carried out at a certain position in the float tank.

The flow rate of the fluid mixture should be adjusted to obtain the desired coating. The optimum flow velocity is affected by various factors including the characteristics and temperature of the substrate, the surface area of the substrate, the line speed of the glass ribbon in the float glass manufacturing process, and the removal rate of exhaust gas from the coating treatment apparatus.

When a glass substrate is used, the titania coating may be deposited on the surface of the glass itself, or one or more undercoat coatings may be deposited on the glass prior to the deposition of the titania coating. In a preferred example of the present invention, a titania coating is deposited directly on the surface of the glass ribbon during the process of manufacturing the float glass. Placing the titania coating directly on the glass surface can improve the growth of titania as compared to depositing it on the primer coating.

The multilayer coating can be conveniently applied by providing two or more coating treatment devices in sequence along the glass ribbon. A particular type of undercoat that has been found to be advantageous is an alkali metal shielding layer. It is known that the photocatalytic activity may be reduced by the movement of sodium ions from the uncoated glass substrate into the photocatalytic titania layer deposited on the substrate. The use of a sodium ion shielding layer is disclosed, for example, in the pamphlets of WO 98/41480 and WO 00/75087. As another type of undercoat film, an alkali metal shielding layer is provided on a metal oxide film such as tin oxide in order to impart a color suppressing effect.

The alkali metal shielding undercoat layer may contain a metal oxide, but is preferably a layer of silicon oxide. Silicon oxide is silica, that is, stoichiometrically SiO₂It can contain other elements such as carbon (such layers are commonly referred to as silicon oxycarbides and are deposited as described in UK Patent Publication No. 2199848. ), Or can be impregnated with other elements such as nitrogen (such layers are commonly referred to as silicon oxynitrides).

The alkali metal shielding undercoat layer should be thick enough to reduce the movement of alkali metal ions into the titania layer to a desired degree and shield it. Also, the shielding layer preferably does not significantly affect the optical properties of the glass. The thinner the undercoat layer, the less impact it has on the optical properties, so the layer thickness can be chosen to provide a compromise between the above two preferred objectives. The typical thickness of the undercoat layer (if present) is 30-70 nm, preferably 40-60 nm.

Since the titania coating produced by the treatment of the present invention has a dense titanium dioxide layer, a decrease in photocatalytic activity due to the movement of sodium ions is prevented. The thickness of the coating required to prevent the reduction of the photocatalytic activity of the coating due to the movement of sodium ions from the glass to the coating surface can be reduced and preferably eliminated. If a sodium ion shielding undercoat layer is present, the thickness of this shielding layer can also be thinner than that used for the underlayer of the titania coating deposited by other CVD treatments. When the titania coating is deposited directly on the surface of the glass, the thickness of the titania coating is preferably in the range of 100 Å to 400 Å, more preferably 150 Å to 350 Å, most preferably 100 Å to 200 Å. When the titania coating is deposited on the alkali metal shielding undercoat layer, the thickness of the titania coating is preferably in the range of 100 Å to 200 Å.

The glass substrate is usually transparent soda lime float glass. The glass substrate can be tinted glass, i.e. glass to which a colorant such as iron oxide, cobalt oxide, nickel oxide, selenium oxide or titanium oxide has been added. Such tinted glass is readily available in various shades such as gray, bronze, blue and green.

The treatment of the present invention is advantageous in that titania is deposited more stably than the conventionally known treatment. The treatment of the present invention can be operated for a longer period of time without deteriorating any product quality, which improves the economic efficiency of the treatment. In addition, this coating exhibits a more neutral color as measured by the CIELAB color system (illumination C). Analysis has shown that this coating contains a smaller amount of carbon atoms than before, which is believed to give it a more neutral color. A coating containing less than 10% carbon provides the preferred features of the present invention.

The coated substrate of the present invention exhibits novel and useful properties. In particular, the titania coating can be composed of substantially or primarily crystalline titania, which has a smoothness comparable to that of an amorphous titania coating. Products provided with such a coating exhibit a high degree of photocatalytic activity obtained by crystalline titania, and the smoothness of the coating surface makes it difficult for mud and other contaminants to adhere to the surface, and any product that adheres to the surface. It has the advantage that mud can be easily washed off.

Suitable coated substrates of the present invention have a crystalline titania coating with a roughness value of less than 3.0 nm, more preferably less than 1.5 nm, and most preferably less than 1 nm on at least one surface. is there. Such a substrate is novel and has other features of the present invention.

The coating film of the present invention is further characterized in that the average particle size in a plane (which can be measured using a high resolution SEM) is smaller than 20 nm, preferably smaller than 15 nm, and most preferably smaller than 10 nm. And. Such small particle sizes are obtained from a columnar particle structure, and in the preferred coating of the present invention, the ratio of diameter to height of titania particles (which can be measured using XTEM) is greater than 0.6. Small, preferably less than 0.4. The coating film of the present invention has a relatively uniform particle size, which can be evaluated by visual inspection by SEM.

According to the present invention, it is possible to produce a thinner titania coating having a low reflectance, preferably 12% or less, while maintaining photocatalytic activity and durability. These improved properties are obtained by the dense and small particle structure of the coating.

For the purposes of this application, the photocatalytic activity is such that the strength on the substrate surface is 0.76 W / m.²It is evaluated by measuring the reduction rate of the integrated absorption peak corresponding to the CH expansion and contraction of the stearic acid thin film, which is generated by irradiating UV light from a UVA lamp having a peak wavelength of 340 nm for 30 minutes at / nm. The stearic acid thin film can be formed by spin casting a methanol solution of stearic acid onto the surface of the substrate.

Freshly prepared or washed glass has a hydrophilic surface (a hydrostatic contact angle of less than about 40 ° indicates a hydrophilic surface), with organic contaminants on this surface. It adheres rapidly and the contact angle increases. A particular advantage of the coated substrate of the present invention (particularly coated glass) is that the contact angle during production is small, but more importantly, organic contaminants adhere to the coated surface. In some cases, irradiating the coated surface with ultraviolet light of an appropriate wavelength will reduce or destroy these contaminants, thus reducing the contact angle of the surface. A further advantage is that water spreads over surfaces with low contact angles, reducing the dispersal of water droplets on the surface (eg due to rain) and any dirt or other contaminants that were not destroyed by the photocatalytic activity of the surface. To wash away. The static water contact angle is the angle determined by the meniscus of the water droplet on the glass surface, as known by measuring the diameter of a known volume of water droplet on the glass surface and calculating it using an iterative procedure. Can be measured.

The haze of the coated substrate is preferably 1% or less, more preferably 0.5% or less, still more preferably 0.2% or less, because of the visibility through the coated transparent substrate. This is because it becomes clearer and more advantageous.

In a preferred example, the coated surface of the substrate is more durable than that of existing titania coated self-cleaning glass. The coated surface preferably maintains photocatalytic activity after a 500-stroke European standard wear test, and more preferably maintains photocatalytic activity after a 1000-stroke European standard wear test.

This means that in the self-cleaning coated substrate of the present invention, the coated surface is exposed to the outside where the coating is easily damaged by abrasion (for example, glass coated with the outside of the window as the coating surface is used). It is advantageous because there are many.

The European standard wear test refers to the wear test described in Part 2 (1999) of the European standard BS EN 1096, which reciprocates the felt pad at a given speed and pressure on the sample surface. ..

In the present invention, even after the European standard wear test, if the static water contact angle is reduced to less than 15 ° by irradiating with UV light (for example, the peak wavelength is 351 nm), the coated substrate becomes a photocatalyst. Maintain activity. To obtain this contact angle after the coated substrate is worn, the strength on the surface of the coated substrate is typically about 0.76 W / m.²Irradiation is performed at / nm and it takes less than 48 hours.

The haze of the coated substrate after the European standard abrasion test is preferably 2% or less.

The durable coated substrate according to the present invention is also durable against humidity cycles (those intended to have the same effect as weathering). Therefore, in a preferred example of the present invention, the coated surface of the substrate has durability to a humidity cycle such that the coated surface maintains the photocatalytic activity even after performing a humidity cycle test of 200 cycles. Here, the humidity cycle test is a test in which the coating film is exposed to a temperature cycle of 35 ° C to 75 ° C to 35 ° C for 6 hours at a relative humidity of almost 100%. The coated substrate maintains its photocatalytic activity even after the humidity cycle test if it is irradiated with UV light to reduce the static water contact angle to less than 15 °.

The durability of the coating can also be evaluated by an etching test of sodium hydroxide. The coated glass sample is immersed in a 1 M sodium hydroxide solution maintained at a temperature of 75 ° C. The etching test ends when the coating can be removed from the surface of the glass or when the optical properties of the glass are significantly impaired. The glass coated by the treatment of the present invention is not affected even if it is immersed for 6 hours, and according to a preferred example, it is not affected even if it is immersed for 10 hours.

The coatings of the present invention also have improved scratch resistance. The photocatalytically active coating will necessarily be present on the exposed surface of the glass, but remains on the aesthetically unacceptable glass when scratched during treatment or after mounting. Abrasion resistance is measured using a pin-on-disk test that utilizes a variable load on the pin. Scratch resistance is measured as the minimum load that causes continuous scratches on the surface. The coating film of the present invention does not cause scratches under a load of 3 Nm, the coating film of a suitable example does not cause scratches even at a load of 5 Nm, and in a more preferable example, scratches do not occur even at a load of 10 Nm. The coated substrate according to the present invention is used in many applications, for example, as window glazing including a multiple glazing unit in which the first glazing pane of the coated substrate is separated and opposed to the second glazing pane, or the coated substrate is coated. If it is glass, it is used as a laminated glass including a first glass ply made of coated glass, a polymer intermediate layer (for example, polyvinyl butyral), and a second glass ply.

The coated substrate of the present invention can be advantageously used not only for a self-cleaning substrate (particularly self-cleaning glass for windows) but also for reducing the concentration of air pollutants. For example, coated glass is exposed to UV wavelength light (including UV wavelengths present in sunlight) and has air pollutants, such as nitrogen oxides, ozone and organic contaminants, adhering to the coated surface of the glass. Can be destroyed. Such usage can result in relatively high concentrations of organic contaminants (especially in strong sunlight), but the usable surface area of glass is also relatively large outdoors in densely built buildings (eg in urban areas). It is especially advantageous on the road). Alternatively, coated glass can be used (with the coated surface inside) to reduce the concentration of air pollutants in buildings, especially office buildings, where the concentration of air pollutants is relatively high.

The present invention will be described below with reference to the drawings, but this is not a limitation of the present invention. The coating layer can be adhered onto the glass substrate on the production line using chemical vapor deposition during the glass production process. FIG. 1 shows an apparatus advantageous for producing the coated glass product of the present invention on a production line (the whole is represented by reference numeral 10), and this apparatus includes a float section 11 and a slow cooling section 12. , Has a cooling section 13. The float section 11 has a bottom portion 14 provided with a molten tin tank 15, a roof 16, a side wall portion (not shown), and an end wall portion 17, which together form a sealing portion. A closed area 18 is formed by forming the above, and a non-oxidizing atmosphere is maintained in the closed area 18 to prevent oxidation of the tin tank 15. During the operation of this device 10, the molten glass 19 is injected into the hearth 20 and flows from there through the underside of the metering wall 21 onto the surface of the lower tin tank 15 and the float glass ribbon 37. The float glass ribbon 37 is taken out by the lift-out roll 22 and conveyed through the slow cooling section 12 and then passed through the cooling section 13.

The non-oxidizing atmosphere within the float section 11 is maintained by introducing a suitable gas containing, for example, nitrogen and 2% by volume hydrogen into the closed area 18 via a conduit 23 operably connected to the manifold 24. .. This non-oxidizing gas compensates for gas loss (because part of the non-oxidizing atmosphere flows out of the closed area 18 through the underside of the end wall 17) and is slightly higher than the ambient pressure. Introduce from conduit 23 into the closed area 18 at a flow rate sufficient to maintain. The tin tank 15 and the closed area 18 are heated by radiant heat downward from the heater 25. The heated closed area 18 is generally maintained at a temperature of approximately 1330 ° F to 1400 ° F (721 ° C to 760 ° C). The atmosphere in the slow cooling section 12 is typically air, and the cooling section 13 is not closed. Here, the fan 26 blows the ambient air onto the glass.

The device 10 is also provided with a series of coaters 27, 28, 29 and 30 arranged above the float glass ribbon 37 in the float section 11. Each of these coaters is supplied with a precursor gas mixture for forming individual coating layers, which directs these precursor gas mixtures to the heated surface of the float glass ribbon 37. The temperature of the float glass ribbon 37 is highest at the position of the coater 27 closest to the hearth 20 and lowest at the position of the coater 30 closest to the slow cooling section 12.

The present invention will be further described with reference to the following examples. In these examples, the coating film was deposited on a float glass ribbon moving in a float tank by laminar chemical vapor deposition during a glass manufacturing process. In this example, the glass ribbon was coated with one or two coating layers.

All gas volumes are measured at standard temperature and pressure unless otherwise stated. The coating layer thickness values were measured using an optical model of the reflection and transmission spectra of the coated glass and a high resolution scanning electron microscope. The thickness of the coating was measured with an uncertainty of about 5%. The transmission characteristics and reflection characteristics of the coated glass were measured using a spectrophotometer U-4000 manufactured by Hitachi, Ltd. Visible light reflectance and visible light transmittance of the coated glass were measured using a D65 illuminant and a CIE standard 2 ° observer based on ISO standard 9050 (Parry Moon air mass = 2). The haze of the coated glass was measured using a haze meter with the product name of WYK-Gardner, Hazeguard +. Due to this specification, the photocatalytic activity increases the intensity of light on the substrate surface to about 0.76 W / m.²It is determined by measuring the reduction rate of the integrated absorption peak corresponding to the CH expansion and contraction of the stearic acid thin film, which is caused by irradiating with UV light from a UVA lamp having a peak wavelength of / nm of 340 nm for 30 minutes. This stearic acid thin film can be formed by spin casting a methanol solution of stearic acid onto the surface of a substrate.

The stearic acid thin film is a 20 microliter methanol solution of stearic acid (8.8x10) on the coated surface of the glass of the sample.^-3mol · dm^-3) Was spin-cast at 2000 rpm for 1 minute to form a size of 7-8 square centimeters. The transmitted infrared spectrum was measured. At this time, on the glass-coated side, the light intensity on the glass-coated surface is approximately 0.76 W / m.²It was irradiated with a UVA-351 lamp (manufactured by Q-Panel, Cleveland, Ohio, USA) with a peak wavelength of 351 nm.

The static contact angle of the coated glass was placed on the surface of the coated glass after irradiating the coated glass with a UVA351 lamp for about 2 hours (or otherwise specified time) (about 1-5). Evaluated by measuring the diameter of the water droplets (in the volume of microliters). In a preferred example of the present invention, the contact angle will be less than 10 °, and in a more preferred example, the contact angle will be less than 5 °.

The present invention will be described with reference to the following experimental examples. A series of deposition treatments were carried out using the equipment shown in Fig. 1.<u style="single">Experimental Examples 1 to 6</u> The first set of deposits was performed 6 times. The temperature of the glass at the point where the titanium precursor came into contact with the glass was 630 ° C. The line speed was 350 m / h. The processing parameters are shown in Table 1.<tables num="1"><img file="JP2006521470A_D0001.tif" /></tables>S / C = Silica coated float glass TIPO = Titanium tetraisopropoxide F / G = Uncoated soda lime float glass TET = Titanium tetraethoxydo

<u style="single">Experimental Examples 7-12</u> The second set of 6 deposits was performed. The temperature of the glass at the point where the titanium precursor came into contact with the glass was 625 ° C. The line speed was 550 m / h. In these plurality of experimental examples, an oxygen gas stream was introduced and mixed with the titanium precursor just before the deposition treatment on the glass. The processing parameters are shown in Table 2.<tables num="2"><img file="JP2006521470A_D0002.tif" /></tables>

The characteristics of the coated glass produced in Experimental Examples 1 to 12 were measured. The results are shown in Table 3.<tables num="3"><img file="JP2006521470A_D0003.tif" /></tables>

<u style="single">Experimental Examples 13-18</u> The third set of deposition treatments was performed on a 5.7 mm thick float glass ribbon using titanium tetraisopropoxide and ethyl acetate. The line speed was 361 m / h. The deposition process was performed on one of the two coating positions in the float tank. The temperature of the glass at this position is shown in Table 4 below.<tables num="4"><img file="JP2006521470A_D0004.tif" /></tables>

The predetermined characteristics of the coated glass produced in Experimental Examples 17 and 18 were measured, and the results are shown in Table 5 below.<tables num="5"><img file="JP2006521470A_D0005.tif" /></tables> Experimental Example 18 is a comparative example in which the deposition treatment was carried out without ethyl acetate. Experimental Example 17 is an example in which the deposition treatment was carried out using ethyl acetate according to the present invention. The product of Experimental Example 17 was found to be smoother and had a more neutral color.

<u style="single">Experimental Examples 19 ~ 26</u> The fourth set of deposition treatments was performed on a 5.0 mm thick float glass ribbon using titanium tetraethoxydo and ethyl acetate. The line speed was 434m / h. The deposition treatment was performed on one of the two coating positions in the float tank used in Experimental Examples 13 to 18 above. The processing parameters are shown in Table 6.<tables num="6"><img file="JP2006521470A_D0006.tif" /></tables>

<u style="single">Experimental Examples 27 ~ 30</u> The fifth set of deposition treatments was performed on a 3.2 mm thick float glass ribbon using titanium tetraethoxydo and ethyl acetate. The line speed was 558m / h. The deposition process was carried out at a position where the temperature of the glass was 625 ° C. The processing parameters are shown in Table 7.<tables num="7"><img file="JP2006521470A_D0007.tif" /></tables>

<u style="single">Experimental Examples 31 ~ 38</u> In this set of examples, sedimentation was performed using a bidirectional experimental coater. In this coater, the flat glass is heated on a conveyor furnace in order to simulate the conditions assumed in the float glass manufacturing process. The glass was then moved to the reactor. A mixed gas containing helium, a titanium precursor and ethyl acetate was brought into contact with the upper surface of the glass. This mixed gas was formed by mixing the preheating gas streams shown in Table 7. Titanium oxide deposition began due to the high temperature of the glass. The coated glass was taken out and cooled in air. The reflectance and durability of the coated glass were measured, and the results are shown in Table 8.<tables num="8"><img file="JP2006521470A_D0008.tif" /></tables> These results show a pair of experiments performed on the same day. The experimental device generates a gas stream from a heated bubbler containing a reactant, and the transfer rate of chemical substances is susceptible to temperature changes of this bubbler. The transfer rate is comparable because the temperature setting of the bubbler has not changed on any day. From each pair of experiments, it can be seen that the introduction of ethyl acetate produces a film with low reflectance without adversely affecting the durability of the film.

<u style="single">Experimental Examples 39 ~ 42</u> Yet another set of deposition treatments was carried out in the float tanks of Experimental Examples 1-30 described above. The results are shown in Table 9.<tables num="9"><img file="JP2006521470A_D0009.tif" /></tables> Experimental Examples 40 and 41 are those in which oxygen is introduced into the treatment of Experimental Example 13 (shown here as Experimental Example 39). From the results of Experimental Examples 40 and 41, it can be seen that the introduction of oxygen may adversely affect the coating film. Experimental Example 42 is an example of a thinner coating. The contact angle of this coating was 8.9 °. In addition, this coating was unaffected for up to 7 hours in a durability test with sodium hydroxide, and its photocatalytic activity was 90%.

<figref num="1">FIG. 1 is a diagram showing an apparatus for performing online chemical vapor deposition according to the present invention.</figref>