Substrate with photocatalytic coating

The present invention is mainly composed of coated glass, ceramics, or vitreous ceramics having photocatalytic properties for producing utility glass or glass for various purposes such as transportation and building glass. Especially with respect to glass substrates, especially transparent glass substrates.

Studies have been conducted to make glass functional by depositing a thin layer on the surface of glass in order to give it special properties according to the intended use. For example, there are layers with optical function, such as so-called anti-glare layers, which consist of alternating layers of layers with high and low refractive indexes. Regarding the antistatic function and the antifreezing type heating function, for example, a conductive thin layer containing a metal or a doped metal oxide as a main component can be provided. Regarding the thermal function of awning or low radiation, for example, a thin layer containing a silver type metal or metal oxide or metal nitride as a main component can be used. In order to obtain a "rain repellent" effect, it is possible to provide a hydrophobic layer containing, for example, fluorinated organic silane as a main component.

Here, there is still a need called "dirt-repellent" for the base material, especially glass, that is, the goal is that the appearance and surface properties do not change over time. , For example, finger marks, floating organic substances present in the atmosphere, coagulating stains, and other stains that gradually accumulate on the surface of the substrate are sequentially removed as soon as they occur to reduce the frequency of cleaning and / or visibility. There is a need to improve.

As a matter of fact, it is known that there are specific semiconductor materials containing metal oxides as a main component, which can initiate a radical reaction that causes oxidation of organic substances when irradiated with an appropriate wavelength. Is commonly referred to as a "photocatalytic" or "photoreactive" material.

<p> An object of the present invention is to provide a photocatalytic coating on a substrate that exhibits a remarkable "antifouling" effect on the substrate and is industrially feasible.</p>

<p> The present invention provides the following inventions in order to solve the above problems. Anatase-type titanium oxide, which is glass, ceramic, or vitreous ceramic, with a coating having photocatalytic properties applied to at least a portion of at least one surface, and (1) at least partially crystalline, anatase-type titanium oxide. And (2) a mixture of amorphous or partially crystalline oxides selected from silicon oxide, titanium oxide, tin oxide, zirconium oxide and aluminum oxide, or inorganic substances in the form of mixed oxides, and said components (1). Is a coated substrate obtained by thermal decomposition of a titanium precursor selected from organic metal precursors and metal halide precursors; (2) Crystalline titanium oxide is in the form of crystals with an average size of 0.5-60 nm. The coated substrate according to (1); (3) The inorganic substance is a mixture of silicon oxide and titanium oxide; The coated substrate according to (1); (4) The inorganic substance is zirconium oxide (1). The coated substrate according to (1); (5) The coated substrate according to (1) where the inorganic substance is a mixture of zirconium oxide and silicon oxide; (6) The coating has a thickness of 5 to 100 nm (1). The coated substrate according to); and (7) at least one layer thereof, the multilayer glass which is the coated substrate according to (1).</p>

<p> According to the present invention, it is possible to provide a photocatalytic coating on a substrate which exhibits a remarkable antifouling effect on the substrate and can be manufactured industrially.</p>

The object of the present invention is a base material containing glass, ceramic, or vitreous ceramic as a main component, particularly transparent glass, and at least a part of crystalline titanium oxide is applied to at least a part of the surface thereof. A photocatalytic coating, including the above, is applied. Titanium oxide is preferably crystallized "in-situ" when forming a coating on the substrate.

Titanium oxide is, in fact, a type of semiconductor that decomposes organic matter deposited on its surface under the action of visible light or ultraviolet light. For this reason titanium oxide has been particularly selected for the production of "stain-proof" glass, mainly because this oxide has good mechanical properties for long-term effectiveness. This is because it exhibits strength and chemical resistance. Of course, it is important that the coating retains its integrity, even when the coating is directly exposed to many attacks, especially when the glass is attached to a building site (building, etc.) or production line (automobile, etc.). Is. These attacks include repetitive handling performed by mechanical or pneumatic gripping means, and when the glass is placed in place, wear (window wipers, wearable cloth) and aggressive chemistry. Material (SiO)₂Exposure to atmospheric pollutants, cleaning agents, etc.).

Also, crystalline titanium oxide has been selected, at least in part, as it has been demonstrated to have significantly better photocatalytic properties than amorphous titanium oxide. Preferably, it is anatase-type, rutile-type, or a mixed form of anatase and rutile, having a crystallinity of at least 25%, particularly about 30-80%, and is present near the surface (this property). Is mainly a surface property). (Crystallinity is TiO in the coating₂Crystal TiO for the total weight of₂It should be understood to mean the weight of. ) Also, especially in the case of anatase-type crystals, TiO that grows on the substrate.₂The crystal orientation affects the catalytic behavior of titanium oxide and there is a suitable orientation (1,1,0) that significantly promotes the photocatalyst.

This coating is a single in which the crystalline titanium oxide contained in this coating, at least close to its surface, has an average size of 0.5-100 nm, preferably 1-50 nm, more preferably 10-40 nm, even more preferably 20-30 nm. It is advantageous to be produced in the form of "crystallites" as crystals. In fact, in this size range, titanium oxide was observed to have optimal photocatalytic activity, probably because crystals of this size form highly active surface regions.

As will be described in more detail below, coatings containing titanium oxide as the main component can be obtained by various methods, for example: 1. Decomposition of titanium precursor 1) Liquid thermal decomposition, powder thermal decomposition, chemistry of thermal decomposition method. Thermal decomposition in the gas phase known as vapor deposition (CVD), etc. 2) Immersion of sol-gel technology, cell coating, etc. 2. Vacuum technology Reactive or non-reactive cathode sputtering, etc. can be mentioned.

Also, in addition to crystalline titanium oxide, the coating also includes at least one other type of inorganic material, in particular, for example silicon oxide (or a mixture of oxides), titanium oxide, in the form of amorphous or partially crystalline oxides. It can contain tin oxide, zirconium oxide, aluminum oxide. This inorganic substance can participate in the photocatalytic action of crystalline titanium oxide by exhibiting a certain degree of photocatalytic action by itself, but as in the case of tin oxide and amorphous titanium oxide, crystalline TiO₂It may have a much weaker effect than.

Such a layer of "composite" oxide in which at least partially crystalline titanium oxide is mixed with at least one other oxide may be advantageous from an optical point of view, especially TiO.₂This is the case if one or more oxides with a lower index of refraction are selected, which can change the light reflection of the substrate provided on the coating by lowering the overall index of refraction of the coating. It can, and in particular, this reflection can be suppressed. This is, for example, TiO according to the production method described in Japanese Patent EP-0465309.₂/ Al₂O₃Layer consisting of, or TiO₂/ SiO₂This is true if a layer consisting of is selected. Here, of course, sufficient TiO to retain sufficient photocatalytic activity.₂It is necessary for the coating to have a content rate. That is, at least 40% by weight of the coating, especially at least 50% by weight of TiO, based on the total weight of the oxide in the coating.₂It is considered preferable to include. It is also possible to choose to overlay the coating with a grafted oleophobic and / or hydrophobic layer that is stable or resistant to the photocatalyst, eg, US Pat. No. 5,368,892 or US Pat. No. Described in patent application FR-94 / 08734 (corresponding to patent number FR-2722493, European patent EP-0692463) filed on July 13, 1994, which is mainly composed of organosilane fluoride described in 5389427. Perfluoroalkylsilane, especially the following formula: CF₃-(CF₂)_n-(CH₂)_m-SiX₃(In the formula, n is 0 to 12, m is 2 to 5, and X is a hydrolyzing group).

In order to increase the photocatalytic action of titanium oxide in the coating according to the present invention, it is necessary to mix other particles, particularly metal particles and particles mainly composed of cadmium, tin, tungsten, zinc, cerium and zirconium, in the coating. In the first place, it is possible to expand the absorption band of the coating.

The number of charge carriers can also be increased by doping by inserting metal elements of niobium, tantalum, iron, bismuth, cobalt, nickel, copper, ruthenium, cerium, or molybdenum into the crystal lattice of titanium oxide.

This doping can also be done solely by surface doping of titanium oxide or composite coatings, surface doping is done by covering at least part of the coating with metal oxides or salts, and the metals are iron, copper, etc. It is selected from ruthenium, cerium, molybdenum, vanadium, and bismuth.

Finally, the photocatalytic phenomenon involves covering at least a portion of the metal oxide or coating containing it with a noble metal in the form of a thin layer of platinum, rhodium, silver or palladium, thereby yielding and / or the reaction rate of the photocatalyst. It can also be enhanced by increasing.

Such catalysts, such as those deposited by vacuum technology, can in fact improve the number and / or lifetime of radicals generated by titanium oxide, promote chain reactions and result in decomposition of organic matter.

Quite surprisingly, this coating exhibits more than one property rather than just one, and immediately upon exposure to appropriate irradiation of visible and / or ultraviolet light such as sunlight. The presence of titanium oxide in the photocatalyst gradually eliminates the accumulation of organic contaminants, as described above, and this decomposition is caused by the radical oxidation process. Inorganic stains themselves are not decomposed by this process and therefore remain on the surface, but the photocatalyst decomposes the binding organics so that they no longer cause them to adhere to the surface and are easily removed. Will be.

Here, the permanent self-cleaning coating preferably exhibits a pronounced hydrophilic and / or lipophilic outer surface, which has three very beneficial effects:

1. Hydrophilicity allows complete wetting of water that can deposit on the coating. When the phenomenon of water condensation occurs, there is a continuous thin film of completely clear water formed on the surface of the coating without depositing cloudy water droplets that obstruct the view. This "anti-condensation" effect is particularly pronounced when the contact angle with water below 5 ° is measured when exposed to light.

2. When water (especially rainwater) runs on a surface that has not been treated with a photocatalytic layer, a large number of rainwater droplets adhere to the surface and remain, and when it evaporates, unsightly stain marks mainly derived from inorganic substances Remains. In practice, the surrounding air-exposed surface is immediately covered with a layer of dirt, limiting it from getting wet with water. These stains are affected by the atmosphere in which the glass is present, in addition to other stains (particularly inorganic traces such as crystallization marks). In the case of the photocatalyst surface, these inorganic stains are not directly decomposed by the photocatalyst. In practice, most are removed due to the hydrophilicity provided by photocatalytic activity. This hydrophilicity, in fact, gives rise to the complete spread of raindrops. Therefore, there are no traces of evaporation anymore. Also, the presence of other inorganic stains on the surface is washed by the water film or redissolved in the case of crystals, thus removing most of them. In particular, it has the effect of "preventing inorganic stains" attracted by rain.

3. Coupled with water, the coating can be lipophilic, which, like water, allows organic matter deposited on the coating in the form of a continuous film that is less visible than a very local "stain". Dirt can be "wet". The "anti-fouling of organic matter" effect is obtained by two ways of action, i.e., when deposited on the coating, it quickly becomes obscured and further disappears by photocatalytically initiated radical decomposition.

The coating can be selected to have a rather smooth surface. In practice, some roughness may be beneficial for the following reasons: 1. Higher photocatalytic surface area can be formed and therefore higher photocatalytic activity can be induced. 2. Has a direct effect on wetting. Roughness actually enhances wettability. Smooth hydrophilic surfaces can become even more hydrophilic when roughened. In this case, "roughness" should be understood to mean both the surface roughness and the roughness caused by the porosity of the layer at least in part of the thickness of the layer.

All of the above effects are more pronounced if the coating is porous and coarse, with a rough photoreactive surface providing a pronounced hydrophilic effect. However, if it is too excessive, the roughness can be detrimental by providing a coating or accumulation of dirt and / or an optically unacceptable level of obscure appearance.

That is, TiO₂It has been demonstrated that the deposition method having a roughness of about 2 to 20 nm, preferably a roughness of 5 to 15 nm is advantageous for the coating containing the main component, and this roughness is measured by an atomic force microscope. Is evaluated by finding the root mean square (RMS) value for a surface area of 1 square μm. At such roughness, the coating exhibits hydrophilicity that is reflected in the contact angle with water, which contact angle can be less than 1 °. It has also been found to be beneficial to increase the porosity of the entire thickness of the coating. That is, the coating is TiO₂If consisting only, it preferably exhibits a porosity on the order of 65-99%, especially 70-90%, which in this case is about 3.8 TiO.₂Is indirectly defined as a percentage of the theoretical density of. One means of increasing such porosity is, for example, the deposition of coatings by sol-gel type techniques, including the deposition of organic metal type materials, where polyethylene glycol (PEG) type organic polymers are the organic metal precursors. After being added into the solution and the layer cured by heating, the PEG is burned to increase the porosity over the entire thickness of the layer.

The thickness of the coating according to the invention can vary, preferably from 5 nm to 1 μm, especially from 5 to 100 nm, especially from 10 to 80 nm, especially from 20 to 50 nm. In practice, the choice of thickness depends on various parameters, the intended use of the substrate glass, the TiO in the coating.₂It depends on the size of the crystallite and the presence of a high proportion of alkali metal in the substrate.

In the present invention, one or more separate thin layers having a function different from or assisting the function of the coating may be arranged between the base material and the coating. Specifically, antistatic function, thermal or optical function, anatase or rutile-type TiO₂It is a function of promoting crystal growth of the above, or a function as a layer forming a barrier against the movement of a specific element generated from the base material. Regarding the latter, especially when the base material is made of glass. The function as a barrier against sodium ions can be mentioned.

It is also possible to provide a laminate of "anti-glare" layers consisting of alternating thin layers of high index and low index, and according to the present invention, this coating constitutes the final layer of the laminate. In this case, the coating preferably has a relatively low index of refraction, such as a composite oxide of titanium and silicon.

Layers with antistatic and / or thermal functions (eg, heating by providing power leads, low radiation, awnings, etc.) can be selected with a metal-type conductive material as the main component. For example, silver, metal-doped oxide types such as tin-doped indium oxide ITO, and fluorine-type halogen-doped tin oxide SnO.₂: F, SnO including antimony₂: Sb, indium-doped zinc oxide ZnO: In, fluorine-containing Zn: F, aluminum-containing ZnO: Al, and tin-containing ZnO: Sn. Also, SnO, a specific metal oxide that is stoichiometrically deficient in oxygen._2-xAnd ZnO_2-x(x &lt;2) can be mentioned.

The layer having an antistatic function preferably has a surface resistance value of 20 to 1000 Ω. To polarize this, a power lead can be provided (eg, an applied voltage of 5-100V). This controlled polarization can suppress the deposition of dust on the order of mm that can deposit on the coating, and in particular, dry dust adhering solely by the action of static electricity suddenly reverses the polarization of the layer. By doing so, this dust is eliminated.

A thin layer with optical function can be selected to reduce the reflection of light and / or to make the reflected color of the substrate more colorless. In this case, it is preferable to have a refractive index intermediate between the refractive index of the coating and the refractive index of the substrate and an appropriate optical thickness, and aluminum oxide Al.₂O₃, Tin oxide SnO₂, Indium oxide In₂O₃It can consist of an oxide or composite oxide of, or silicon carbonate or silicon nitride. For maximum suppression of reflected color, this thin layer is preferably close to the square root of the product of the two materials surrounding it, the index of refraction of the substrate and the coating of the invention. Similarly, it is advantageous to choose an optical thickness close to λ / 4 (ie, the product of the geometric thickness and the index of refraction), where λ is approximately the average wavelength of visible light, from about 500 to. It is 550 nm.

The thin layer having a barrier function against alkali metals is particularly silicon oxide, nitride, oxynitride, carbonitride, or fluorine-containing aluminum oxide Al.₂O₃: F or aluminum nitride can be selected as the main component. In practice, it has proven useful when the substrate is made of glass, because the transfer of sodium ions into the coating according to the invention adversely affects its photocatalytic properties.

The properties of the substrate or sublayer have the additional advantage of promoting crystallization of the deposited layer, especially in the case of CVD deposition.

That is, TiO by CVD₂Crystalline SnO during deposition₂The lower layer of: F promotes almost rutile-like growth, especially at deposition temperatures on the order of 400-500 ° C, whereas the surface of the lower layers of soda-lime glass and silicon carbide acid is especially 400- Induces anatase growth at deposition temperatures on the order of 600 ° C.

Any of these optional thin layers can be deposited in a known manner by vacuum cathodic sputtering techniques or other techniques such as solid phase, liquid phase or gas phase pyrolysis. Each of the above layers can have a plurality of functions, but each of them can also add a function.

Another object of the present invention is "anti-staining" (organic and / or inorganic stains) and / or "anti-condensation" glass, which incorporates the above-mentioned coating substrate. It can be a multi-unit of type, double glazing or laminated.

As such, the present invention is directed to the production of glass, ceramic, or vitreous ceramic products, in particular the production of "self-cleaning" glass. This latter is beneficial for building glass such as double glazing (then the coating can be placed "inside" and / or "outside", i.e. on surfaces 1 and / or surface 4. .). This has been found to be particularly beneficial for glass that is very difficult to clean and / or glass that needs to be cleaned very often, such as roof glass and airport glass. It is also related to transportation windows, where maintaining visibility is an essential safety standard. This coating can be applied to the front, side and rear windows of a car, especially on the window side facing the seat. This coating can prevent fogging and also remove dirty finger marks, nicotine and other organic stains, which are volatile released from the plastic interior of the car, especially the dashboard. There are retrograde agents (sometimes known as "fogging"). Other modes of transportation, such as aircraft and trains, can also find useful uses for windows with the coatings of the present invention.

There are many other potential applications, especially aquarium glass, store windows, green houses, balconies, interior furniture, street equipment, and even mirrors, TV screens, spectacle fields, or cosmetic materials. Surface materials, clad materials, exterior material tiles, etc.

As described above, the present invention can make these known products functional by imparting ultraviolet resistance, antifouling property, sterilization property, antireflection property, antistatic property, antibacterial property and the like. ..

Another important use of coatings according to the invention is with electrically controllable absorption variable glasses such as electrochromic glass, liquid crystal glass (including dichloro dyes if desired), glass containing systems of suspended particles, viologen glass, etc. It is an application to be combined. These glasses generally include a plurality of transparent substrates, between which "active" elements are placed, allowing the coating to be beneficially placed on at least one outer surface of these substrates.

Especially in the case of electrochromic glass, when the glass is in a colored state, its absorption can bring about some heating of the surface and promote photocatalytic decomposition of the carbonaceous material deposited on the coating of the present invention. Further details of the structure of electrochromic glass can be referred to in European patent application EP-A-0575207, which describes electrochromic laminated double glazing, and the coating of the invention can be placed on surface 1. it can.

Another object of the present invention is various processes for forming the coating of the present invention. Pyrolysis deposition techniques can be used, which is advantageous when a glass substrate is used, as the coating can be deposited directly and continuously on a strip of float glass.

Pyrolysis can be carried out in a solid phase from one or more powders of one or more precursors of the organometallic type.

Pyrolysis can also be carried out in a liquid phase from a solution containing a titanium chelate and / or an organometallic titanium precursor of titanium alcoholate. Such precursors are mixed with at least one other organometallic precursor. Further details on the properties and deposition conditions of titanium precursors can be referred to in patents FR-2310977, EP-0465309.

Pyrolysis is also TiCl by a technique known as CVD (Chemical Vapor Deposition).₄Halide species such as or titanium tetraisopropoxide species Ti (OiPr)₄It can also be done in the gas phase from at least one titanium precursor, such as titanium alcoholate. Further, the crystallization of the layer can be controlled by the type of the lower layer as described above.

In addition, coatings can be deposited by other techniques, especially in combination with "sol-gel". Various deposition methods are also possible, such as "dipping" (also known as "dip coating") and cell-based deposition known as "cell coating". Spray coating and laminar coating methods are also possible, the latter technique being described in detail in International Patent Application WO-94 / 01598. All of these deposition methods generally use a solution containing at least one organometallic precursor of titanium, especially of the alcoholate species, which is coated on one or both sides of the substrate and then pyrolyzed. ..

Also, in any deposition technique, it may be advantageous to coat in at least two sequential steps instead of just one step, which means that if a relatively thick coating is used, the coating It is observed to promote the crystallization of titanium oxide throughout the thickness.

Similarly, it is beneficial to subject the coating with photocatalytic properties to the annealing heat treatment after deposition. Heat treatment is fundamental to sol-gel or laminated coating techniques for pyrolyzing one or more organic metal precursors into oxides after the substrate has been coated and for improving wear resistance. However, this does not apply to thermal decomposition techniques that thermally decompose the precursor as soon as it comes into contact with the substrate. Here, in the former case and the latter case, TiO₂Post-deposition heat treatment after formation improves its crystallinity. Also, the heat treatment temperature of choice may allow adequate control of oxide crystallinity, anatase and / or rutile crystallinity.

Here, in the case of a base material made of soda-lime glass, a plurality of long-term annealings may cause a decrease in photocatalytic activity because the alkali metal is excessively transferred from the base material to the photocatalyst layer. Use a barrier layer between the substrate (if made of standard glass) and the coating, select a substrate made of glass of the appropriate composition, or use soda-lime glass with a surface from which alkali metals have been removed. Doing so can eliminate this risk.

Other useful details and features of the invention will be apparent by the following unrestricted examples with reference to the accompanying drawings. FIG. 1 is a cross section of a glass substrate with a coating according to the present invention. FIG. 2 is a diagram of a sol-gel deposition method by so-called dip coating. FIG. 3 is a diagram of the so-called "cell coating" deposition method. FIG. 4 is a diagram of the so-called "spray coating" deposition method. FIG. 5 is a diagram of the deposition technique by laminating coating.

As schematically shown in FIG. 1, all of the examples below relate to the deposition of a so-called "antifouling" coating 3 on a transparent substrate 1 that is essentially titanium oxide-based.

The base material 1 is made of transparent soda ash silica glass having a thickness of 4 mm, a length of 50 cm, and a width of 50 cm. It goes without saying that the present invention is not limited to this particular type of glass. Also, the glass may be curved rather than flat. There is an optional thin layer 2 between the coating 3 and the substrate 1, which is a silicon carbide (SiOC) acid (SiOC) intended to form a barrier to the diffusion of alkali metals and / or to reduce light reflection. ) Is the main component, or a layer intended for antistatic and / or low radiation layers (which does not have to have a significantly lower radiation effect) and / or particularly reduces the reflected color. Fluorine-doped tin oxide SnO intended to form a layer₂: F is the main component layer.

Examples 1-3 Examples 1-3 relate to coating 3 deposited using the liquid phase pyrolysis method. This operation can be performed continuously using appropriate distribution nozzles located beside and above the float glass at the outlet of the float bath chamber. In this example, the operation is discontinuously performed using a movable nozzle that is placed relative to a substrate that has already been cut to a predetermined size, and this substrate sprays a suitable solution at a constant speed. Preheat in the oven to a temperature of 400-650 ° C before passing. Example 1 In this example, there is no voluntary layer. Coating 3 is a solution containing titanium diisopropoxide diacetylacetonate and titanium tetraoctylene glycolate, which are two kinds of organic metal titanium precursors, dissolved in a mixed solvent of two kinds of solvents, ethyl acetate and isopropanol. Used to deposit.

It should be recognized that it is possible to replace all precursors with different precursors of the same type, specifically titanium acetylacetonate, titanium (methylacetate acetate), titanium of different titanium chelate. (Ethylacetacetate), or the type of titanium triethanolamine or titanium diethanolaminate.

As soon as substrate 1 reached the desired temperature in the oven, i.e. about 500 ° C, the substrate was passed under a nozzle that sprayed the mixture at room temperature with compressed air.

TiO with a thickness of about 90 nm₂Although the layer was obtained, the thickness can be controlled by changing the passing speed of the base material 1 with respect to the nozzle and / or the temperature of the base material.

This layer exhibits excellent mechanical behavior. Its wear resistance test is comparable to that obtained for solid glass surfaces.

This can be bent and dip coated. It showed no bloom, i.e., the scattered light transmittance of the coated substrate was less than 0.6% (560 nm D).₆₅Measured by light source). Example 2 Following Example 1, however, SnO with a thickness of 73 nm between the base material 1 and the coating 3₂: F layer 2 was inserted. This layer was obtained by thermal decomposition of dibutyltin difloride DBTF powder. It can also be obtained by a known method by thermal decomposition in the liquid phase or the gas phase as described in patent application EP-A-0648196. In the gas phase, monobutyltin trichloride and fluoride precursor (optionally H₂Mixtures (combined with O-type "mild" oxidants) can also be used. The refractive index of the obtained layer was about 1.9. Its surface resistance was about 50Ω.

In Example 1 above, the coated substrate 1 mounted as double glazing has a coating on surface 1 (the other substrate 1'is uncoated but is based by a 12 mm air layer. It had the same properties and dimensions as Material 1), and exhibited a color saturation value at 26% reflection and a color saturation value at 6.8% transmission.

In this example 2, the color saturation (golden) in reflection was only 3.6% and the transmission was 1.1%.

That is, SnO₂The lower layer of: F can impart antistatic properties to the base material due to its conductivity, and also gives a favorable effect to the color tone of the base material by making the color tone significantly more neutral in both transmission and reflection. This color is caused by the presence of a titanium oxide coating that exhibits a relatively high index of refraction. Appropriate feeding can be applied to polarize it to prevent the accumulation of large size dust on the order of mm.

In addition, this lower layer is a photocatalyst TiO.₂Prevents alkali metals from diffusing into the layer. In this way, the photocatalytic activity is improved. Example 3 Following Example 2, however, in this example, a layer 2 containing silicon carbide as the main component, which has a refractive index of about 1.75 and a thickness of about 50 nm, is inserted between the base material 1 and the coating 3. , This layer is a nitrogen-diluted SiH as described in patent application EP-A-0518755.₄Obtained by CVD from a mixture of ethylene and ethylene. This layer is an alkali metal (Na) generated from the base material 1.⁺, K⁺) And alkaline earth metals (Ca⁺⁺) Is particularly effective in preventing the tendency of the coating to diffuse toward the coating 3, which significantly improves the photocatalytic activity. Also, SnO₂Like: F, it has an index of refraction between the base material (1.52) and coating 3 (about 2.30 to 2.35), so it is possible to reduce the color strength of the base material in both reflection and transmission. Light reflection value of material R_LCan be reduced as a whole.

Examples 4-7 below relate to deposition by CVD. Examples 4-7 Example 4 This example relates to depositing coating 3 directly on substrate 1 by CVD using a standard nozzle, as described in patent application EP-A-0518755 above. As a precursor, either an organometallic compound or a metal halide is used. In this example, titanium tetraisopropyrate was chosen as the organometallic compound, which is advantageous due to its high volatility and wide usable temperature of 300-650 ° C. In this example, sedimentation is performed at about 425 ° C and TiO₂The thickness of was 15 nm.

Also, Tetra ethoxy Titanium Ti (OE)_t)₄Is also appropriate and TiCl as a halide₄Can be mentioned. Example 5 Perform in the same manner as in Example 4, except that in this example, 15 nm TiO₂The layer was not deposited directly on the glass, but on a 50 nm SiOC underlayer that was deposited in the same manner as in Example 3. Example 6 Perform in the same way as in Example 4, but in this example, TiO₂The layer thickness was 65 nm. Example 7 Do the same as in Example 5, but in this example TiO₂The layer thickness was 60 nm.

From these Examples 4-7, the substrates coated in this way exhibited good mechanical behavior for wear testing. In particular, TiO₂No layer peeling was observed. Example 8 In this example, a technique using a sol-gel combination technique using a deposition method by "dip" (also known as "dip coating") was used. This principle is shown in FIG. 2, in which the substrate 1 is immersed in a liquid solution 4 containing one or more suitable precursors of the coating 3 and the substrate 1 is immersed at a controlled speed using a motor device 5. Was pulled up. The choice of pull-up rate can adjust the thickness of the solution remaining on the surfaces on the two sides of the substrate, thus evaporating the solvent and then decomposing the precursor into oxides of the coating after heat treatment. The thickness can be adjusted.

Titanium tetrabutoxide Ti (O-Bu) in a 1: 1 molar ratio in an ethanol solution containing 0.2 mol tetrabutoxide per liter of ethanol to deposit coating 3.₄Solution 4 containing and stabilizing diethanolamine DEA, or a mixture of the precursor and solvent described in Example 1 was used (other precursors such as titanium (diethanolamineate) dibutoxide could also be used).

The base material 1 can include a SiOC lower layer. After pulling from each solution 4, substrate 1 was heated at 100 ° C for 1 hour, then gradually increased in temperature and heated at 550 ° C for about 3 hours.

Coating 3 is obtained on each surface, which in both cases is a highly crystalline TiO in the form of anatase.₂Met. Example 9 This example uses a technique known as "cell coating" and the principle is shown in Figure 3. This involves forming a narrow cavity defined by two substantially parallel faces 6 and 7 and two seals 8 and 9, with at least one of these faces 6 and 7 being treated. It consists of the surface of the base material 1. The cavity is then filled with solution 4 of one or more precursors of the coating, and then solution 4 is withdrawn in a controlled manner to form a wet meniscus, eg, using a peristaltic pump 10. When the solution is withdrawn, a film of the solution remains on the surface of the substrate 1.

Cavity 5 is then retained for at least the time required for drying. The film is cured by heat treatment. The advantage of this technique over "dip coating" is that it can treat only one of the two surfaces of substrate 1, in particular, and it does not need to be systematic unless a masking system is adopted.

The base material 1 provided a thin layer 2 containing silicon carbide SiOC as a main component.

In Example 6, the solution 4 described in Example 8 was used, respectively. Then TiO₂The same heat treatment was performed to obtain coating 3.

Coating 3 showed good mechanical durability.

In SEM (scanning electron micrograph), the field effect showed the morphology of single crystal grains with a diameter of about 30 nm. The roughness of this coating results in higher wettability compared to non-coarse coatings.

These same solutions 4 can also be used to deposit the coating by "spray coating" as shown in FIG. 4, where solution 4 is sprayed into a mist on the static substrate 1. Alternatively, it can be done by a layered coating as shown in FIG. In the latter case, a substrate 1 supported by vacuum suction on a support 11 made of stainless steel and Teflon passes over a tank 12 containing the solution, and the solution partially passes through the grooved cylinder 14. The integrated tank 12 and cylinder 14 move over the entire length of the substrate 1, and the mask 13 prevents the solvent from evaporating from solution 4 to temperature. For more information on this technique, see International Patent Application WO-94 / 01598 described above.

The substrates obtained in the above example were tested to characterize with a deposited coating and to evaluate "anti-condensation" and "dirt-repellent".

-Test 1-This is a test for cloudiness. This consists of observing changes in the photocatalyst and coating structure (hydroxyl groups, porosity, roughness levels) after wetting. When the surface is photocatalytic, the carbon-containing microfouling substance adhering to the coating is decomposed over time, and the surface is hydrophilic, and thus is anti-fog. Also, suddenly reheat the previously coated substrate, place it cold or simply blow on the substrate, observe if cloudiness appears, measure the time if it does, and then measure the cloudiness. Measure the time it takes for the disappearance.

-Test 2-This is about assessing the hydrophilicity and lipophilicity of the surface of Coating 3 compared to a solid glass surface, leaving the substrate in an external atmosphere for a week in natural light, darkness, and then UV light. By measuring water droplets and DOP (dioftyl phthalate) droplets on the surface after exposure to 20 minutes.

-Test 3-This consists of depositing a layer of organosilanes on a substrate to be evaluated, irradiating it with ultraviolet light (UVA), and photocatalytically decomposing it. Since organosilanes improve wettability, the contact angle between the base material and water during irradiation indicates the state of decomposition of the adherent layer. The rate of disappearance of this layer is related to the photocatalytic activity of the substrate.

The attached organosilane is the trifluorosilane octadecyltrichlorosilane (OTS). Adhesion is done by immersion.

The test equipment will include a 1-6 rotating turntable with a low pressure UV lamp. Place the test piece to be evaluated on the turntable and face the surface to be evaluated toward the UV irradiation side. Depending on their position and the number of lamps lit, each test piece is 0.5 W / cm²~ 50W / m²Receive UV irradiation. For Examples 1,2,3,8,9, the irradiation power is 1.8W / m²And for Examples 4-7, 0.6W / m²And said.

The time of each measurement of the contact angle was changed from 20 minutes to 3 hours depending on the photocatalytic activity of the test piece under cloudy weather. The measurement was performed using a goniometer. Prior to irradiation, the glass exhibited a contact angle of approximately 100 °. If this angle is less than 20 ° after irradiation, it is considered that the layer has broken down.

Each specimen tested is characterized by an average rate of disappearance of the layer, determined as nm / h, i.e., which allows the thickness of the deposited organosilane layer to reach a final steady-state value of less than 20 °. It is a value divided by the irradiation time (time for extinguishing the organosilane).

All of the above examples passed Test 1, that is, they remained completely transparent when breathed on the coated substrate, whereas on the uncoated substrate it was very A cloudy layer visible to the eyes adhered to.

Samples of each example were subjected to Test 2, and the coated substrate showed a contact angle of 5 ° or less with water and dioctyl phthalate after irradiation with ultraviolet rays. In contrast, solid glass showed a contact angle of 40 ° with water and a contact angle of 20 ° with diofthylphthalate under the same conditions.

The results of Test 3 of the coated substrate in the above example are summarized in the table below.

<tables num="1"><img file="JP2005205411A_D0001.tif" /></tables>

<tables num="2"><img file="JP2005205411A_D0002.tif" /></tables>

Regarding the above table, especially in the presence of a lower layer of SiOC, TiO due to the barrier effect on alkali metals and alkaline earth metals that can move from the glass.₂It can be seen that it enhances the photocatalytic activity of coatings containing (comparison of Examples 4 and 5 or Examples 6 and 7).

Also, TiO₂The thickness of the coating containing is found to play a role (comparison of Examples 1 and 3), i.e. TiO with a thickness greater than the average size of the single crystal or "crystallite".₂It can be seen that the coating provides a better photocatalytic effect.

In fact, the TiO obtained by CVD₂The coating exhibits highly developed crystallization with crystal sizes on the order of 20-30 nm. Example 6 (65 nm TiO₂) Photocatalytic activity is shown in Example 4 (15 nm TiO).₂It turns out that it is significantly higher than that of (only). Therefore, TiO is at least twice the average diameter of the crystals contained.₂It is advantageous to apply a coating. Alternatively, as in Example 5, a thin thickness of TiO₂Keep the coating, but select the underlayer with the right properties and the right thickness, and start with the first layer of crystallites as much as possible.₂Can also be crystal-grown.

TiO₂Crystallization was observed to be slightly inferior to coatings deposited by methods other than CVD. However, as mentioned above, all factors such as slightly inferior crystallization are subject to optimization, and the relatively low catalytic activity is in harmony with the advantages of being able to use a relatively inexpensive and less complex deposition process. is there. Also, if necessary, the appropriate lower layer is TiO₂Doping can also be used to enhance the performance of catalytic activity. Moreover, from the comparison between Examples 2 and 3, it has been confirmed that the properties of the lower layer affect the crystal morphology and, in fact, the photocatalytic activity of the coating.

The present invention may provide a photocatalytic coating on a substrate that exhibits a significant "antifouling" effect on the substrate and is industrially feasible.

<figref num="1">It is a cross section of a glass base material provided with the coating according to the present invention.</figref><figref num="2">It is a figure of the sol-gel deposition method by so-called "dip coating".</figref><figref num="3">It is a figure of the so-called "cell coating" deposition method.</figref><figref num="4">It is a figure of a so-called "spray coating" deposition method.</figref><figref num="5">It is a figure of the deposition technique by the laminated coating.</figref>

Code description

1 Base material 2 Thin layer 3 Coating 4 Solution 5 Cavity 11 Support 12 Tank 13 Mask 14 Grooved cylinder