Process for coating a substrate and for manufacturing a window

0001The invention relates to a method for depositing coatings preferably constituted by stacks of thin layers on a transparent substrate, particularly glass, intended to confer specific properties, including a very low light reflection, of the order of 1 at 2% or even lower, or solar control properties such as a strong reflection of thermal infrared (so-called low emissivity properties) or solar control (limitation of the energy flow through the substrate), or properties of hydrophobicity / hydrophilicity, without this list being however exhaustive and restrictive.

0002Such substrates are intended to constitute or be incorporated in a glazing unit having at least one of the previously described functionalities.

0003For example, and without this being restrictive, an antireflection coating is usually constituted by a stack of thin interferential layers, in general an alternation of layers based on high and low refractive index dielectric material, each layer having a thickness less than 1 micrometer and most often between a few nanometers and a few tens of nanometers. Embedded in a transparent support, usually glass, such a coating has the main function of reducing the light reflection and increase the light transmission. A substrate thus coated thus sees its transmitted light ratio / reflected light increase, which improves the visibility of the objects placed behind it. For maximum antireflection effect,

0004There are many applications to this type of product: it can be used for or incorporated into a glazing unit in the building, or used as glazing in sales furniture, for example as a store display cabinet and architectural domed glass, to better distinguish what is in the showcase, even when indoor lighting is low compared to outdoor lighting. It can also be used as countertop glass. Examples of such glazings are in particular marketed by the applicant company under the reference Vision-lite®. According to one application, it is also possible to use such substrates in the field of automotive glazing. This makes it possible to avoid certain parasitic reflections deemed unsightly. In addition, these reflections can disturb the driver, especially when night driving, especially if the vehicle is illuminated from the inside. Another possible application is glazing for a glass door of a refrigerator or freezer used especially in food stores.

0005According to another example of application requiring the obtaining of glass substrate coated on its two sides with different types of stacks, we now market double glazing in the field of energy insulation of buildings that incorporate as an inner sheet a such a substrate: it is provided with a first stack of layers on its face facing the double glazing gas blade, including at least one layer of precious metal, in particular silver, allowing this face to confer on the structure of low emissivity properties. On the other side (turned towards the interior of the building) is deposited a solar control stack comprising a conductive O x of the SnO type.₂ : F or ITO, allowing better control of the incoming solar flux by this double glazing face, in addition to the low emissivity function described above.

0006Of course, the present invention is not limited to the two previous examples of application but is generally intended for any method or product for which it is necessary to deposit a functional stack on each side of at least one substrate which constitutes or is incorporated in a glazing.

0007In order to obtain glazings incorporating a substrate provided with a stack of layers on a single face, a conventional obtaining method comprises depositing on a first face of the glass substrate, laid flat on conveyor means, with a first stack of layers. This deposit is conventionally carried out in devices called magnetron or "magnetron sputtering", in which the successive layers, within specific compartments, are deposited on the substrate held in motion on conveying rollers. According to currently well known and mastered techniques, the deposition of the material constituting a layer of the stack is obtained by sputtering a target of said material or a precursor of said material (constituting the cathode) under the effect of the positive particles created in a plasma of a so-called sputtering gas. Sputtering sources are usually magnetrons that use strong electric and magnetic fields.

0008The deposition of a stack on the other side of the substrate comprises the steps of reversal thereof and deposition in another device of a stack. In the particular case of identical stacks on both sides (in the case of antireflection coatings), it is advantageous to use, for example, the same device for depositing the two layers.

0009When the substrate is disposed horizontally in the deposition device (often referred to in the art as "horizontal coater"), however, depositing stacks on both sides of the same substrate has proved problematic. If, after cleaning, no trace of marks, especially in the form of scratches or other visible alteration of the first stack is detected on the glazing at the output of the deposit device, defects in the form of straight marks have yet appeared on the final glazing, that is to say after it has undergone a heat treatment, especially in the form of tempering or bending.

0010Due to the absence of these same traces on the stacks deposited at the output of the magnetron deposition device before the heat treatment, as well as any trace of deterioration of the stack such as cracks, it was first thought that a problem directly related to the heat treatment undergone by the layers. However, even by varying the conditions of the heat treatment in the direction of decreasing the temperature and / or the duration of the treatment, it has not been possible to suppress the appearance of these marks.

0011The inventors have however established a link between the marks observed on the final glazing and the weight of the glass substrate. In particular, it appeared that the marks appeared after the heat treatment were all the more pronounced that the glass used had a large thickness. In particular, the marks have appeared systematically on tempered products for glass thicknesses greater than 3 mm, in particular of the order of 6 to 20 mm.

0012Although the two faces of the glazing after the deposition of the two stacks appear visually substantially identical, the inventors have connected the phenomenon of appearance of the marks after the heat treatment in contact between the rollers of the conveying means and the substrates already coated on a first time. face of the first stack. In particular, without this being considered as a definitive interpretation, a possible explanation for the appearance of the marks could be the weight of the substrate which presses on the layer deposited on the first face, and which is found in contact with the rollers the scrolling of the substrate in the device, for the purposes of depositing the second stack. Such an explanation, however, seems surprising in the light of

0013Art is known, for example from the patent application <patcit id="pcit0001" dnum="WO03065081A"><text>WO03 / 065081</text></patcit>, protective layers of stacks on transparent substrates, of depositing a temporary carbon layer on said stack. This protective layer is intended to prevent scratching or chemical degradation (including oxidation) of certain layers of the stack, including silver metal layers. The technical problem addressed in this application is very different from that solved by the present invention. In the publication<patcit id="pcit0002" dnum="WO03065081A"><text>WO03 / 065081</text></patcit>it is a question of protecting a simple stack of layers against the scratch during its handling and its transport and not to avoid the appearance of marks on a face of the substrate when it must be covered on both sides with stacks, in a device of the type "horizontal coater". In addition, as explained above, no trace of scratches appearing visually on the substrate at the output of the deposit device, the teaching of this application appears at first sight of no use in solving the problem according to the invention of in the appearance of marks after a heat treatment.<patcit id="pcit0003" dnum="US2003118860A"><text>US-2003118860</text></patcit> discloses a method of depositing two-sided thin layers on a glass substrate explicitly giving up a carbon layer. The present invention relates to a method for depositing coatings, preferably consisting of a stack of thin layers, on both sides of a glass substrate, comprising the following steps:<ul><li>in a first deposition device, depositing on a first face of the substrate a first coating,</li><li>depositing on said first coating a temporary protective layer, within said first device,</li><li>reversal of said substrate, so that the coated surface of the coating and the protective layer are found in contact with conveying means to a second deposition device,</li><li>in the second deposition device in which the substrate moves on said conveying means, deposition on the second face of a second coating, identical or different from the first coating,</li><li>optionally depositing on said second coating a temporary protective layer, preferably within said second device,</li></ul>wherein the first and second devices are magnetron sputtering devices and wherein the temporary protection layer is a layer comprising carbon. According to preferred embodiments of the deposition method according to the invention, which can be combined with each other if appropriate:<ul><li>The first and / or second coatings are stacks of thin layers less than 1 micrometer thick.</li><li>The temporary protective layer is a layer of carbon, in particular amorphous, with a thickness of between 1 and 50 nm, preferably with a thickness of between 1 and 10 nm. The temporary protective layer may advantageously be deposited by spraying a carbon target in an inert atmosphere, in particular Argon, preferably in said first device.</li><li>Said coatings are stacks comprising oxide, nitride or oxynitride layers, in particular at least one element selected from zinc, niobium, bismuth, tin, silicon, aluminum, titanium, zirconium, optionally comprising one or more metal layers.</li><li>At least one of said coatings (preferably both coatings) are stacks with antireflection properties on the surface of each side of the substrate.</li><li>The substrate is a glass sheet with a thickness of between 3 and 20 mm, preferably a thickness of between 6 and 20 mm, and very preferably a thickness of between 8 and 20 mm.</li></ul>The present invention also relates to a method for producing a glazing unit comprising a substrate coated on both sides with a coating preferably constituted by a stack of layers, in which:<ul><li>a deposition method according to the deposition method described above is used to obtain a glazing unit comprising at least one substrate comprising on each of its faces a coating, said substrate further comprising on at least one of its faces a temporary protective layer, over a coating,</li><li>the glazing thus obtained is subjected to an elimination treatment of the temporary layer.</li></ul>

0014Preferably, the elimination of the temporary layer is obtained by heating, by a surface treatment including in particular the implementation of a laser radiation, a plasma, an ion beam or under the effect of chemical agents. In particular, said elimination treatment may advantageously be carried out by the heat treatment consisting in quenching or bending said glazing. Glazing can be obtained by a deposition method as described above, comprising at least one substrate comprising on each of its faces a stack of thin layers, characterized in that said substrate further comprises on at least one of its faces, at above the stack present on said face, a temporary protective layer.

0015The glazings described above can also meet the following achievements:<ul><li>The first and / or second coatings are stacks of thin layers less than 1 micrometer thick.</li><li>The substrate is a glass sheet with a thickness of between 3 and 20 mm, preferably a thickness of between 6 and 20 mm, and very preferably a thickness of between 8 and 20 mm.</li><li>Said coatings are stacks comprising oxide, nitride or oxynitride layers, in particular at least one element selected from zinc, niobium, bismuth, tin, silicon, aluminum, titanium, zirconium, optionally comprising one or more metal layers.</li><li>At least one of said coatings (preferably both coatings) are stacks with antireflection properties on the surface of each side of the substrate.</li></ul>

0016For the purposes of the present invention, the term "stacking" is normally understood to mean, in a conventional and general manner, a succession of at least two layers. Even if generally in current glazings, the desired functionality is ensured by the deposition of a plurality of thin layers in the form of a stack, the present invention does not exclude, however, the case where at least one of the coatings is constituted. than a single layer deposited on the surface of the substrate, especially in the form of an email or a paint.

0017Thin film is understood to mean a layer having a thickness of less than 1 micrometer and most often between a few nanometers and a few tens of nanometers, usually obtained by a vacuum deposition method, in particular of the magnetron sputtering type.

0018For the purposes of the present invention, a coating or a stack may only partially cover the surface of the glass substrate.

0019For the purposes of the present invention, the term "temporary protection layer" is intended to mean an additional layer deposited above the desired coating (of the stack) and which is temporary in time. Provisional means that this additional layer can be easily removed in a step subsequent to the manufacture of the stack and deposition of said layer, preferably under the effect of heat, or by a surface treatment of the "etching" type, in particular by the use of laser-type radiation, a plasma, an ion beam or under the effect of chemical agents. Preferably the elimination is obtained under the effect of heat, by a heat treatment.

0020This elimination step may according to the invention be dedicated to this operation or preferably be part of the overall process for implementing the final glazing. In particular, in the latter case, in a preferred manner, the removal step is performed during the tempering or bending of the coated glazing.

0021Ideally, however, the elimination does not affect the properties of the protected coating or in a limited way, and in any case in an easily corrigeable manner, in particular by modifying the initial parameters of the quenching or bending heat treatment or by minimal adaptations of the constitution of the initial coating (in particular of the stack of layers) to compensate for the small variations induced by the protective layer.

0022In order to further illustrate the present invention, an example of its implementation is given below, with the aid of the attached figure, without of course that it can be considered as limiting the scope of the invention. 'invention.

0023On the <figref idrefs="f0001">figure 1</figref>schematically there is shown a glass substrate 10 conveyed by conveying means 2 comprising a plurality of rollers 3 in a magnetron sputtering layer-type deposition device 4. The device consists of several compartments 5, 6, 7, 8, in which are deposited by magnetron sputtering the successive layers of the stack whose thickness varies from a few nanometers to a few tens of nanometers, according to techniques well known in the art. By way of illustration, there is shown diagrammatically on the<figref idrefs="f0001">figure 1</figref> a first target 13, from which the particles 14 of the material sprayed from the target are deposited on the glass substrate 10. On the<figref idrefs="f0001">figure 1</figref>only four compartments 5 to 8 have been shown, but it is understood that the device 4 comprises the number of compartments necessary for depositing the desired stack. For example, the stack may be a four-layer stack alternating the layers of higher and lower refractive indices. In an additional and terminal compartment 9, according to the invention, a carbon target 15 is disposed which is sprayed according to the well-known techniques described above, the carbon in the form of nanometric particles 16 being deposited on the stack 11 of layers formed in the previous compartments of the device. An intermediate glazing unit 20 is thus obtained at the outlet of the device comprising a substrate 10 coated on one side of the desired antireflection stack 11 and a temporary protective layer 12 of amorphous carbon. This carbon layer is very thin, for example of thickness between 1 and 10 nanometers. Its thickness is normally adjusted according to the thickness of the glass substrate.

0024On the <figref idrefs="f0002">figure 2</figref> the glazing 20 is shown at the input of the same device 4, after that has been returned by appropriate robotic means, so that the temporary protective layer 11 is in contact with the rollers 3. A second stack identical to the previous one is then deposited in the compartments 5 to 8 so as to obtain a glazing consisting of a substrate coated on both sides with an antireflection stack. According to a first embodiment (which does not correspond to that described on the<figref idrefs="f0002">figure 2</figref>), the magnetron compartment 9 comprising the carbon target is deactivated. In this mode and more generally according to the invention, a glazing unit comprising a single carbon layer is obtained on the first stack. According to another possible embodiment and as described in the<figref idrefs="f0002">figure 2</figref>the magnetron compartment 9 comprising the carbon target 15 is kept activated during the second pass. According to this mode and more generally according to the invention, a glazing unit 21 comprising a carbon layer on each face, above each stack, is obtained.

0025The glazing can then be stored, stored and transported and delivered to a place of transformation where it can in particular be tempered, curved or undergo another heat treatment step during which the temporary layer of carbon is removed.

0026In the above example, the elimination of the temporary carbon layer is obtained during a thermal process performed on the glazing for its proper implementation such as bending or quenching. Without departing from the scope of the present invention, it is nevertheless possible to envisage other modes of elimination specific to the layer such as laser treatment, elimination by laser radiation, plasma or ion beam or by chemical compounds, these However, the latter solutions are not preferred according to the invention.

0027The details and advantageous features of the invention are more particularly detailed below, in the examples which follow.

0028All of the following examples relate to four-layer antireflection stacks. The layers have all been deposited according to conventional and well-known cathodic sputtering techniques of a magnetic field-reactive target without the need to further describe this well-known technique as indicated above. The different layers were obtained continuously in the same installation in accordance with that schematically described on the<figref idrefs="f0001">figures 1</figref> and <figref idrefs="f0002">2</figref> and provided with compartments dedicated to the deposition of each of the layers constituting the stack.

0029More precisely, the deposition of SiO layers₂ was conventionally obtained in an oxidizing atmosphere made of an Ar / O mixture₂ and from the sputtering of metallic Si targets. The Si targets used contained metallic aluminum (8% by weight), in particular to make them more conductive.

0030The deposition of the mixed oxide layers of zinc and tin was obtained in an oxidizing atmosphere made of an Ar / O mixture₂ and sputtering metal targets comprising a mixture of zinc and tin in metallic form, the composition of the target mixture being adapted to obtain a weight ratio Sn / Zn equal to about 60/40 in the Sn layers_xZn_thereO finally obtained in the antireflection stack.

0031The composition of the layers and in particular the Sn / Zn ratio has been measured by conventional microprobe microprobe techniques (also known as Electron Probe Microanalyser or EPMA).

Example 1 (comparative):

0032On both sides of a glass substrate, is deposited according to conventional magnetron sputtering techniques and as indicated above the same antireflection stack with four interference layers.

0033The glass is a 4 mm thick silico-soda-lime glass, marketed under the name Planilux by Saint-Gobain Vitrage. The deposited stack is present on both sides of the glass support and is constituted by the following layers, from the surface of the glass:<ol><li>1: Sn_xZn_thereO_z 20 nm thick, (Sn / Zn mass ratio of about 60/40, as measured by microprobe)</li><li>2: SiO₂ 30 nm thick,</li><li>3: Sn_xZn_thereO_z 110 nm thick, (Sn / Zn mass ratio of about 60/40, as measured by microprobe)</li><li>4: SiO₂ 90 nm thick.</li></ol>

0034The first layer 1 is called high index. This first layer 1 is a mixed zinc and tin oxide of general formula Sn_xZn_thereO_zwherein the weight ratio Sn / Zn is of the order of 60/40. Its thickness is of the order of 20 nm. The refractive index of this layer is close to 2.0 at 550 nm. It is deposited in the first compartment 5 on the<figref idrefs="f0001">figure 1</figref>. In the following compartment 6 and on this first layer 1, a layer 2 of SiO₂ with a refractive index of about 1.48 is deposited, according to the method described above, then in the compartment 7 a third layer 3 of mixed oxide Sn_xZn_thereO_z, substantially identical in composition to the previous one, that is to say obtained from the same metal target, but with a thickness equal to 110 nm. A fourth layer of SiO₂ complete the stacking.

0035The method for depositing the stacks on both sides is that described above using the <figref idrefs="f0001">figures 1</figref> and <figref idrefs="f0002">2</figref>, but the compartment 9 is not activated according to this comparative example: a first passage of the glass substrate is implemented in the magnetron sputtering deposition device 4 for depositing the first stack on one of the faces according to the principles described above, then the substrate is returned and reintroduced into the same device 4 for depositing the second antireflection stack identical to the first on the second face. After cleaning the glazing thus obtained, constituted by the glass substrate coated on each of its main faces by the same stack, no additional major defect appears visually on one of the two faces, compared with respect to the other.

0036The glazing is tempered according to the standard techniques of the art. Quenching is performed by heating the substrate at about 685 ° C for 200 seconds and then quenching it.

0037After tempering, the glazing this time shows on one of its faces the visible presence of traces in the form of roughly rectilinear marks, without these being assimilated to scratches.

Example 2 (according to the invention):

0038This example is identical to the previous one, with the difference that this time the compartment 9 is activated, so that an amorphous carbon layer 12 is deposited on the first stack 11, in accordance with the present invention.

0039Complementary analyzes, in particular of X-ray diffraction, show that the temporary protective layer consists essentially of amorphous carbon.

0040The glazing is then quenched as indicated in the preceding example, this heat treatment having the effect of eliminating all of the carbon.

0041Unlike the glazing obtained according to Example 1, no defects (in particular in the form of the marks previously described) appear on the face on which the first stack had been deposited, after removal of the temporary carbon protection layer by the treatment. quenching.

0042The optical and colorimetric properties of the glazings obtained according to Examples 1 and 2, after quenching, were measured.

0043In general, all the luminous characteristics presented in the present description are obtained according to the principles and methods described in the European (and French) standard EN 410 relating to the determination of the luminous and solar characteristics of the glazings used in glass for construction. Conventionally, the refractive indices are measured at a wavelength of 550 nm. By R_The and T_Thefor the purposes of the present description, it is understood to mean the reflections on the layer and transmissions with normal incidence, under the illuminant D65 with a field of view of 2 °. By (L *, a *, b *) is meant in the sense of the present invention the coordinates of the color space under the illuminant D65 with a field of view of 2 ° in reflection layer side.

0044The experimental results are summarized in Table 1 which follows:<tables id="tabl0001" num="0001"><table frame="all"><title>Table 1</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="20mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><colspec colnum="3" colname="col3" colwidth="15mm" /><colspec colnum="4" colname="col4" colwidth="10mm" /><colspec colnum="5" colname="col5" colwidth="12mm" /><thead><row><entry align="center" valign="top" /><entry align="center" valign="top">T_The (%)</entry><entry align="center" valign="top">R_The (%)</entry><entry align="center" valign="top">at*</entry><entry align="center" valign="top">b *</entry></row></thead><tbody><row><entry align="center">Example 1</entry><entry align="center">97.2</entry><entry align="center">0.95</entry><entry align="center">3.6</entry><entry align="center">-11.0</entry></row><row><entry align="center">Example 2</entry><entry align="center">97.1</entry><entry align="center">0.93</entry><entry align="center">3.5</entry><entry align="center">-11.3</entry></row></tbody></tgroup></table></tables>

0045The results reported in the table above demonstrate the antireflection effect of the stack present on the surface of the glass support: whereas the bare glass has a reflection R_The greater than 8%, it is lowered to 0.93% when the stack is deposited on both sides.

0046It is also observed that the antireflection properties of the glazing are not affected by the deposition and then the elimination of the temporary carbon protection layer.