Method for preparing a photocatalytic coating integrated into glazing heat treatment

PROCESS FOR THE PREPARATION OF A PHOTOCATALYTIC COATING INTEGRATED IN THE HEAT TREATMENT OF A GLAZING

The present invention relates to glazing units provided with a coating having photocatalytic properties, of the type comprising at least partially crystallized titanium oxide, in particular in anatase form. Several techniques are known for the preparation of such a coating, in particular on a glass sheet, in order to obtain a product with high optical quality. Are available for example a sol-gel process consisting of a deposit of titanium dioxide precursor in solution, then heating so as to form the crystallized dioxide in anatase form, a pyrolysis process in particular in the gas phase (Chemical Vapor Deposition - CVD - ), in which precursors of titanium dioxide in the gas phase are brought into contact with the hot substrate, optionally during cooling, in particular the atmosphere side of a glass leaving the float. Cathode sputtering, known from patent WO 97/10186, also turns out to be particularly advantageous from the industrialization point of view. It is a vacuum technique which allows, in particular, very fine adjustment of the thicknesses and the stoichiometry of the deposited layers. It is generally assisted by magnetic field for more efficiency. It can be reactive: we start from an essentially metallic target, here based on titanium (possibly alloyed with another metal or silicon), and the spraying is done in an oxidizing atmosphere, generally an Ar / O mixture.₂. It can also be non-reactive, starting from a so-called ceramic target which is already in the oxidized form of titanium (possibly alloyed). The titanium dioxide produced by sputtering is generally amorphous or poorly crystallized and it is necessary to heat it later so that it crystallizes in the photocatalytically active form. Application WO 02/24971 describes the deposition on glass of titanium dioxide coatings partially crystallized anatase, by sputtering at relatively high working pressure of at least 2 Pa; in a first variant, the substrate is at 220-250 ° C for example during the deposition, a conventional annealing at around 400 ° C is then carried out if necessary; in a second variant, the deposition is carried out on a substrate at room temperature, then the assembly is heated to 550 ° C. at most, for a few hours. In the current state of knowledge, if particular properties requiring an annealing, bending, quenching or other heat treatment at more than 600 ° C., or even up to 700 ° C. in certain cases, were sought for a glazing with TiO₂ photocatalytic, the specialist would inevitably deposit TiO₂ or its precursors after this heat treatment, then would activate it or cause the precursors to react by applying a more moderate temperature. In particular, it is estimated that temperatures above 600 ° C. favor the crystallization of TiO₂ rutile form, less photocatalytically active than the anatase form. However, the inventors have succeeded in obtaining high photocatalytic activity and optical quality by crystallizing titanium dioxide at the temperatures of conventional heat treatments of glass, which makes it possible to obtain this crystallization by quenching alone, or otherwise, and to avoid an additional subsequent heating operation at a more moderate temperature. To this end, the subject of the invention is a process for the preparation of a material with photocatalytic properties comprising titanium oxide at least partially crystallized, in particular in anatase form, characterized in that it employs temperatures exceeding 600 ° C. This therefore results in better integration of this preparation in various industrial processes, which are thereby simplified by the elimination of a specific crystallization operation at relatively low temperature. The duration of these procedures is shortened accordingly. The devices are reduced because heating means perform two functions simultaneously. Finally, the cost of these methods is reduced. According to preferred embodiments and / or having particularly motivated the invention: - the process implements temperatures exceeding 630 ° C; - It implements a tempering and / or bending treatment of a glazing (that is to say in particular temperatures up to 700 ° C.). In order to obtain excellent results in the exemplary embodiments below, the method of the invention comprises depositing a coating of titanium oxide on a first face of a first transparent or semi-transparent substrate of the type glass, glass-ceramic which, if necessary, has been provided beforehand with one or more stacks of functional layers and / or functional layers, the nature of which will be described in detail below. According to other advantageous characteristics of the process of the invention: it comprises the deposition, on the second face of said first transparent or semi-transparent substrate or on a second face belonging to a second transparent or semi-transparent substrate, of one or more stacks of functional layers and / or functional layers, the nature of which is also detailed below (thus the process of the invention makes it possible to obtain transparent or semi-transparent products with mechanical properties obtained by heat treatment at relatively high temperature, and likely to have the widest range combined functionality); - Said implementation of temperatures exceeding 600 ° C is subsequent to deposition on said first and second faces (however any other variant in which these temperatures are not applied after deposition on the second face is not excluded from the invention , as long as they are after the deposit on the first side; in other words, the deposition product on the second face may not be subjected to temperatures exceeding 600 ° C., for example by carrying out the deposition on the second face after implementation of these temperatures or, in the case where the second face belongs to a second substrate, this may not be associated with the first - in double glazing, laminated glazing ...- only after it has been subjected to these temperatures -association of a first substrate of tempered glass and a second of non-tempered glass-. In the opposite case, also in accordance with the invention, the products deposited on the first and second faces are heated simultaneously to more than 600 ° C., which can be advantageous and economical, the second substrate if it exists then being additionally also heat treated); - the deposits on said first and second faces are carried out by sputtering and advantageously, in this case, in line and simultaneously or almost simultaneously, in a substantially identical direction and in an opposite direction (is particularly intended the use of an installation cathode sputtering assisted by magnetic field from above and below, commonly known as “sputter up and down”, in which the first and second faces are horizontal and oriented respectively upwards and downwards, so that they are brought into contact by spray cones of vertical downward direction -down- for TiO₂, respectively ascending -up- for thermal control stacking). However, any other orientation of the first and second faces is not excluded from the invention: vertical, more or less inclined. The subject of the invention is also a glass sheet, at least one face of which carries a coating of a material comprising titanium oxide, characterized in that it is capable of being or has been subjected to a heat treatment at over 600 ° C, such as quenching and / or bending, while preserving the photocatalytic activity and the optical quality required for anti-fouling glazing. Firstly the heat treatment at more than 600 ° C. does not affect the product to such an extent that it makes it unsuitable for use as anti-fouling glazing; it has even been found, not without surprise, that the photocatalytic activity is comparable, or even better in certain cases, to that obtained after thermal treatments according to the teaching of the above-mentioned application WO 02/24971 (for example annealing at 500 ° C for 1 hour). The use of temperatures of more than 600 ° C. is also not incompatible with a high optical quality, by which reference is essentially made to the absence of defects visible to the eye: blurring, dots or pits, cracks . Advantageously from an industrial point of view, the average colorimetric variation in reflection on the photocatalytic coating side induced by this heat treatment, ΔE, is at most 2.8, preferably at most 2.3; this expresses the fact that the colorimetry in reflection of the final product is close to that of the deposit product before heat treatment. ΔE is calculated by the equation ΔE = (ΔL² + Δa^*2 + Δb^*2 )^1/2 in which Δ expresses the variation of a parameter induced by heating, L the clarity, a and b^* chromaticity coordinates (L colorimetry system, a^*, b^* : the positive values ​​of a^* go red, negative values ​​go green, positive values ​​of b^* go towards yellow and negative towards blue; the values ​​area of ​​a^* and B^* close to 0 is achromatic). Other objects of the invention consist of - monolithic, laminated, single or multiple glazing, comprising a glass sheet as described above; - Monolithic, laminated, single or multiple glazing, at least one first face of at least one first glass sheet constituting a coating of a material with photocatalytic properties, obtained in accordance with the process of the invention. According to other preferred characteristics of this glazing: - under said coating of a material with photocatalytic properties, said first face carries one or more stacks of functional layers and / or functional layers, comprising at least one layer which acts as a barrier to the migration of glass alkalines likely to result from the application of temperatures exceeding 600 ° C (for the latter we know SiO₂ , Yes₃NOT₄ , AIN by magnetron sputtering, SiOC by CVD ..., for other functionalities, the stacks and layers provided below can be used for said second face, excluding the hydrophilic and hydrophobic layers, intended to be in contact with the atmosphere); - The second face of said first glass sheet or a second face belonging to a second constitutive glass sheet carries one or more stacks of functional layers and / or functional layers chosen from a thermal control stack such as anti-solar, low -emissive, a stack or a layer with optical functionality such as anti-reflection, filtration of light radiation, coloring, diffusing, a layer of an anti-fouling photocatalytic material, in particular of the high activity type, a hydrophilic layer, a hydrophobic layer, a network of conductive wires or a conductive layer, in particular heating, of antenna or anti-static, alone or in combination. Another object of the invention is the application of this glazing as "self-cleaning" glazing, in particular anti-fog, anti-condensation and anti-fouling, in particular glazing for the building of the double-glazing type, glazing for vehicle of the windshield type, rear window, automobile side windows, rear view mirror, glazing for trains, planes, boats, utility glazing such as aquarium glass, display case, greenhouse, interior furnishings, urban furniture (bus shelters, advertising panel. ..), mirror, computer type display system screen, television, telephone, electrically controllable glazing such as electrochromic, liquid crystal, electroluminescent glazing, photovoltaic glazing. The invention is illustrated below by way of examples.

EXAMPLE 1

In this example we compare the transformation of TiO₂ amorphous obtained by magnetron sputtering in its active form by industrial quenching on the one hand, annealing at 500 ° C for 1 hour on the other hand. The photocatalytic activity is evaluated at the end of the two treatments by means of the stearic acid photodegradation test followed by infrared transmission, described in application WO 00/75087. A 60 nm thick layer of SiOC by gas phase pyrolysis (CVD) is deposited on three samples of clear silica-soda-lime glass 4 mm thick, as on WO 01/32578, and on three others a layer of SiO₂ 100 nm thick by magnetron sputtering. TiO coatings are formed on the six samples₂ of variable thicknesses by magnetron sputtering at a working pressure of 26.10^"3 mbar, then the photocatalytic activity is evaluated as indicated above after the two aforementioned heat treatments. The results are reported in Table I below.

Table I

<img file="WO2005009914A2_D0001.tif" />

Contrary to what was expected, not only does industrial quenching not drastically reduce photocatalytic activity, but it is at least comparable to that resulting from TiO activation treatments₂ known from the state of the art as shown in particular by WO 02/24971 already cited. In fact, the activity is weaker after quenching than in test No. 4. Consequently, the TiO₂ prepared here can be quenched from the point of view of photocatalytic activity, even by using barrier sublayers to the diffusion of glass alkalines of usual thickness.

EXAMPLE 2 Tests 1, 3 and 5 above, as well as tests No. 7 and 8 characterized by respective thicknesses of photocatalytic coating obtained of 27 and 19 nm (same barrier sublayer of SiO₂, same TiO preparation conditions₂ than in tests 1, 3 and 5), a measurement of the average colorimetric variation in reflection on the coating side induced by industrial quenching, ΔE, is measured. The meaning of the different parameters in the L, a colorimetry system^*, b^* and the equation allowing to calculate ΔE from ΔL, <img file="WO2005009914A2_D0002.tif" /> Δb^* are as described above. The results are reported in Table II below.

Board

<img file="WO2005009914A2_D0003.tif" />

The relatively low average colorimetric variation values, or in some cases ideally less than 2, express a slight variation in color on reflection on the photocatalytic coating side after industrial quenching of all the coatings, which excludes the unwanted production of quenched colorimetric products in reflection too modified during quenching. It becomes easier to predict the final color before quenching. EXAMPLE 3

This example relates to double glazing consisting of two sheets of glass 4 mm thick between which is inserted an air gap 15 mm thick. In this example and the following, the side 2 of the double glazing, that is to say the side in contact with the air gap of the glass sheet intended to be installed closest to the outside atmosphere (and not that intended for the interior side of a building), is coated with a stack of thermal control layers, produced by magnetron sputtering. This process is particularly practical for depositing the widest range of natures of layers, by varying them and precisely controlling the thicknesses, on an industrial scale. Here this stack is low-emissive, that is to say reflecting thermal infrared radiation (wavelengths of the order of 10 μm) and capable of retaining heat inside a building for example . The association of the thermal control stack on face 2 and a stack obtained by magnetron sputtering and comprising TiO is studied from an optical point of view.₂ photocatalytic and SiO undercoat₂ barrier to the diffusion of alkalis on face 1, intended to be in contact with the external atmosphere. In the following, X and Y respectively denote the low-emissive stacks which differ from that of Example 2 of Application EP 0 718 250 A2 only by modifying the thickness of the layer (2) in 25 nm, layers (2) in 19 nm and (3) in 29 nm respectively. The following four glazing compositions are tested, defined below only by the glass sheet on the outside: 3a: 4 mm glass / 36 nm Si₃NOT-_t/ X 3b: 18 nm TiO₂/ 150 nm SiO₂/ 4 mm glass / X 3c: 18 nm TiO₂/ 75 nm SiO₂/ 9 nm If₃N4 63 nm SiO₂/ 4 mm glass / X 3d: (same photocatalytic stack as 3b) ... 14 mm glass / Y In this example as well as in examples 4-7 below, all the stacks have been subjected to industrial quenching. The optical characteristics of the glazing in transmission are evaluated, reflection on the "inside" side of the building (that is to say face 4 of the double glazing, of which only the faces 1 and 2 are functionalized as indicated above), reflection on the "outside" side. of the building (side 1: glass or TiO₂) (light transmission and reflection TL and RL in%, chromaticity coordinates a^* and B^* in transmission and reflection on both sides of the glazing, as mentioned above). The results are reported in the following tables.

Table III.1: transmission

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Table III.2: internal side reflection

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Table III.3: reflection on the outside

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The comparison of glazing 3a and 3b indicates how the addition of the photocatalytic coating is likely to disturb the optical characteristics of the glazing: there is thus a reduction in TL, a substantial increase in RL on both sides, and an increase in chromaticity in reflection on both sides of the glazing towards blue-green (negative values ​​of a and b^*). By the glazing 3c, compared with the glazing 3b, a part of the TL lost is recovered, one advantageously approaches the two RLs of the glazing 3a again, and its colorimetric values ​​in reflection.

EXAMPLE 4

The methodology of example 3 is repeated for the following glazing units (the stacks facing 2 reflect the solar radiation, corresponding to average wavelengths of the order of 1 μm). In this example, X and Y respectively denote the anti-solar stack sold by the company Saint-Gobain Glass France under the registered trademark SGG Coollite ST®108, respectively the stack obtained by multiplying the thicknesses of the extreme layers of this last by 3.7 - proximal side of the glass substrate - and 2/3 - distal side -: 4a: 6 mm glass / X 4b: 18 nm TiO₂/ 150nm SiO₂/ 6 mm glass / X 4c: 18 nm TiO₂/ 50 nm SiO₂/ 12 nm If₃NOT₄/ 71 nm SiO₂/ 6 mm glass / X 4d: same photocatalytic stack as 4b / 6 mm glass / Y In this example and in the following the glazings are composed of two sheets of glass 6 mm thick between which an air space is inserted 12 mm thick. The results are reported in the three tables below.

Table IV.1: transmission

<img file="WO2005009914A2_D0007.tif" /> Table IV.2: internal side reflection

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Table IV.3: reflection on the outside

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Here, the TL is little affected by the addition of TiO₂ which also provides a slight decrease in yellow color in reflection on the TiO exterior side₂ (4b) / glass (4a). The modification of the anti-solar stack (4d) brings a gain in TL, a substantial decrease in RL on the interior side, accompanied by a slight increase in yellow color in reflection.

EXAMPLE 5

Example 4 is reproduced, X and Y designating respectively the anti-solar stack marketed by the company Saint-Gobain Glass France under the registered trademark SGG Coollite ST® 120, and the stack differing from the latter only in multiplying by 2 the thickness of the proximal layer of the glass substrate: 5a: 6 mm glass / X 5b: 18 nm TiO₂/ 150 nm Si0₂/ 6 mm glass / X 5c: 18 nm TiO₂/ 68 nm SiO₂/ 10 nm ShNJ 69 nm SiO₂/ 6 mm glass / X 5d: same as 5b / 6 mm glass / Y Table V.1: transmission

<img file="WO2005009914A2_D0010.tif" />

Table V.2: internal side reflection

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Table V.3: reflection on the outside

<img file="WO2005009914A2_D0012.tif" />

5c with respect to 5b presents with respect to 5a a partial recovery of the lost TL as well as of the two RLs and, notably, a total recovery of color in reflection on both sides, even with a slightly increased neutrality of coloring. With 5d, the recovered TL is increased, the reflection on the inside is slightly higher (less good) while the reflection on the outside (TiO₂) is reduced to an even lower level (better) than the RL of 5a on the outside (glass). EXAMPLE 6

The preceding example is reproduced for the following glazings, in which X and Y respectively denote the anti-solar stack sold by the company Saint-Gobain Glass France under the registered trademark SGG Coollite ST®136, and the stack not differing from the latter only by multiplying the thickness of the proximal and distal layers of the glass substrate by 1.7 and 0.774: 6a: 6 mm glass / X 6b: 18 nm TiO₂/ 150 nm SiO₂/ 6 mm glass / X 6c: 18 nm TiO₂/ 66 nm SiO₂/ 10 nm S.₃NOT₄/ 57 nm SiO₂/ 6 mm glass / X 6d: same photocatalytic stack as 6b / 6 mm glass / Y

Table VI.1: transmission

<img file="WO2005009914A2_D0013.tif" />

Table VI.2: internal side reflection

<img file="WO2005009914A2_D0014.tif" /> Table VI.3: reflection on the outside

<img file="WO2005009914A2_D0015.tif" />

The comparison of 6a and 6b is characterized by an increase in RL on the exterior side of the glazing and, to a lesser extent, by an increase in chromaticity of the second compared to the first. By optimizing the photocatalytic stack 6c, part of the lost TL is recovered, the RL on the outside is reduced substantially while recovering the color in reflection on the same face (even with a more neutral colorimetry than 6a). By modifying the 6d anti-solar stack, the RL on the outside (TiO₂) is lowered to a level even lower than that of 6a on the glass side, and the yellow color component in reflection on the interior side of the glazing is weakened compared to that of the other three glazings.

EXAMPLE 7

The preceding example is reproduced with the following glazings, in which X and Y respectively denote the anti-solar stack sold by the company Saint-Gobain Glass France under the registered trademark SGG Coollite ST®150, and the stack not differing from by removing the proximal layer from the glass substrate and multiplying the thickness of the intermediate layer by 1.5, and the thickness of the distal layer by 0.68: 7a: 6mm glass / X 7b: 18 nm TiO₂/ 150 nm SiO₂/ 6 mm glass / X 7c: 18 nm TiO₂/ 64 nm SiO₂/ 13 nm SN 50 nm SiO₂/ 6 mm glass / X 7d: same photocatalytic stack as 7b / 6 mm glass / Y Table VII.1: transmission

<img file="WO2005009914A2_D0016.tif" />

Table VII.2: internal side reflection

<img file="WO2005009914A2_D0017.tif" />

Table VII.3: reflection on the outside

<img file="WO2005009914A2_D0018.tif" /> We notice in particular the quasi-recovery of color in reflection on the outside side of 7c compared to 7a.

EXAMPLE 8 This example relates to a so-called “four season” stack, both sunscreen and low-emissivity, sold by the company Saint-Gobain Glass France under the registered brand Planistar®. Unlike the thermal control stacks of the previous examples, but like those of the following examples, this is not subjected to industrial quenching, which is therefore carried out, if necessary, before its deposition, on the glass sheet possibly provided with its TiO coating₂ and the barrier sublayer. We test the glazing 8a: 6 mm glass / Planistar® 8b: 18 nm TiO₂/ 150 nm Si0₂/ 6 mm glass / Planistar® 8c: 18 nm TiO₂/ 68 nm SiO₂/ 8nm Si₃NOT₄/ 58 nm SiO₂/ 6 mm glass / Planistar®

Table VIII.1: transmission

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Table VI II .2: internal side reflection

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Table VIII.3: exterior side reflection

<img file="WO2005009914A2_D0021.tif" />

The glazing 8c, compared with 8b, restores the coloring in reflection on the inside side of 8a, as well as on the outside side where the decrease in RL compared to 8b is on the other hand a little more significant. EXAMPLE 9

The thermal control stack is an anti-solar stack sold by the company Saint-Gobain Glass France under the registered brand SKN® 154. The glazings 9a: 6 mm glass / SKN® 154 9b: 18 nm TiO are tested.₂/ 150 nm SiO₂/ 6 mm glass / ... same as 9a 9c: 18 nm TiO₂/ 68 nm SiO₂/ 8 nm If₃NOT₄/ 58 nm SiO₂/ 6 mm glass / same as 9a

Table IX.1: transmission

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Table IX.2: internal side reflection

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Table IX.3: exterior side reflection

<img file="WO2005009914A2_D0024.tif" />

Here is particularly obvious, on the outside, obtaining with 9c an RL intermediate between that of the other two glazings, and a blue component of the coloring in reflection almost at the same level as in the absence of TiO₂ (9a). EXAMPLE 10

We tested the SKN® 165B stack also sold by the applicant company, and more particularly the glazing 10a: 6 mm glass / SKN® 165B 10b: 18 nm TiO₂/ 150 nm SiO₂/ 6 mm glass / ... same as 10a 10c: 18 nm TiO₂/ 69 nm SiO₂/ 9 nm If₃NOT₄/ 49 nm SiO₂/ 6 mm glass / ... same as 10a

Table X.1: transmission

<img file="WO2005009914A2_D0025.tif" />

Table X.2: internal side reflection

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Table X.3: reflection on the outside

<img file="WO2005009914A2_D0027.tif" /> EXAMPLE 11

A SiOC layer barrier to the migration of alkali metals, 50 nm thick, covered with a 15 nm layer of TiO is formed on a glass sheet.₂ photocatalytic by a CVD process by reproducing Example 5 of patent EP 0 850 204 B1. The photocatalytic activity evaluated by photodegradation of stearic acid followed by infrared transmission as previously is 9.10^"3cm^"1min^"1, and 7.10^"3cm^"1min^"1 after industrial quenching, which corresponds to maintaining functionality in a large and satisfactory proportion. Thus, the invention makes available the possibility of preparing glazings with photocatalytic anti-fouling coatings which are quenchable and of high activity, under the best industrial conditions, with light transmission and reflection levels and colorimetric characteristics in transmission and in reflection easily adjustable to the values ​​sought by the user.