EP0824505A2

EP0824505A2 - Method for depositing a reflective layer on glass, and resulting products

Info

Publication number: EP0824505A2
Application number: EP97915507A
Authority: EP
Inventors: Philippe Boire; Laurent Joret
Original assignee: Saint Gobain Vitrage SA
Current assignee: Saint Gobain Glass France SAS
Priority date: 1996-03-07
Filing date: 1997-03-06
Publication date: 1998-02-25
Also published as: CZ352497A3; JPH11504615A; TR199701320T1; BR9702119A; WO1997032823A3; WO1997032823A2; KR19990008413A

Abstract

A method for depositing and particularly continuously depositing a reflective layer (3) on a float line glass strip (10), wherein the layer contains a metal with a melting point no higher than the temperature at which the glass strip acquires dimensional stability. Deposition is performed in a controlled inert or reducing atmosphere once the glass strip (10) is dimensionally stable by contacting the strip surface with the powdered or molten metal (22) while the strip is at a temperature selected in such a way that the powder melts and coalesces or the molten metal forms a film on the strip surface, to give a continuous solid layer when the strip is at a temperature no higher than the melting point of the metal.

Description

METHOD FOR DEPOSITING ON GLASS A REFLECTIVE LAYER AND PRODUCTS OBTAINED

The invention relates to the method of depositing on glass a reflective layer, especially a metallic layer.

Depending on its thickness, a metal layer can in fact confer on a glass substrate intended to become a glazing different properties: at relatively small thickness, it plays the role of a protective coating against solar and / or low-emissivity radiation. With a greater thickness, it allows to obtain a real mirror with very strong light reflection. The most common example is silver: we know how to deposit it in a thin layer, in particular of interference thickness, by vacuum techniques of the sputtering type, or in a thicker layer for making mirrors, for example by the technique wet classic with a silver line. However, silver is a material of limited durability in a thin layer when it is exposed to a chemically aggressive medium, and the deposit techniques mentioned above are only carried out on, and discontinuously on, glass trays once cut from the glass ribbon from a float production line.

It was therefore interesting to look at other metals, with properties similar to silver but which we could manage to deposit at a lower cost continuously, directly on the glass ribbon of a float line, and having a superior durability, for example aluminum. From patent FR-2 01 1 563, it is thus known to deposit a layer of aluminum on a ribbon of glass, when it is in the very enclosure of the float bath, from a mass of molten metal emitting aluminum vapor towards the glass, vapor condensing on the surface of the glass ribbon to leave a continuous coating. However, this type of technique has drawbacks: its implementation is delicate, it is not easy to ensure a deposit of regular thickness, and, above all, the speed of deposition is low, the limiting factor being the pressure partial very low metallic aluminum vapor. From patent GB-A-2 248 853, it is also known to deposit layers of aluminum on a ribbon of float glass, at a temperature of at least 1,00 ° C. Here, it is a pyrolysis technique in the liquid phase, where organometallic compounds in a solvent are sprayed towards the glass and decompose there on contact with elementary metal. This type of pyrolysis is not without disadvantages either: it requires in particular the removal and treatment of large quantities of solvents.

The object of the invention is therefore to develop a new continuous manufacturing process on a ribbon of float glass with a metallic reflective layer which overcomes the aforementioned drawbacks, and which in particular allows obtaining layers of high quality compatible with the requirements of industrial glazing production.

The subject of the invention is a method of depositing, in particular continuously, on a glass ribbon of a float line, a reflective layer based on metal, the melting temperature of which is less than or equal to the temperature where the ribbon of glass acquires dimensional stability. It consists in depositing in a controlled, inert or reducing atmosphere, when the glass ribbon has already acquired this dimensional stability, by bringing the surface of the ribbon into contact with the metal in question in powder or molten form, the temperature of the ribbon when brought into contact being chosen so that the powder melts and coalesces, or the molten metal coats, on the surface of the ribbon, leaving a solid continuous layer when the temperature of the ribbon decreases during the process of forming flat glass up to a temperature less than or equal to the melting temperature of the metal. In the context of the invention, “metal” is understood to mean a material with electrical behavior essentially of the conductive type. It is an essentially metallic material, either based on at least two metals, for example in the form of an intermetallic compound, an alloy, or even a eutectic compound.

Advantageously, the “metal” according to the invention is based on at least one of the materials belonging to the group comprising aluminum, zinc, tin, cadmium. It can also optionally include silicon or another metal (in particular in a concentration of less than 15 atomic%). As preferred, non-limiting embodiments of this material, there may be mentioned aluminum, aluminum-tin alloys, aluminum-zinc, aluminum-silicon compounds, and in particular the aluminum-silicon eutectic compound comprising 12 atomic% of silicon and having a melting temperature of about 575 ° C. The term “continuous” layer also includes a layer which can be deposited on the glass ribbon so as to cover most, if not all, of its surface. But this also includes the layers which are deposited for example in the form of parallel strips, and therefore which only partially, but in a desired and controlled manner, cover the surface of the glass, for example for decorative purposes.

This also includes layers which appear macroscopically continuous, but which may, on a microscopic scale, cover only part of the glass ribbon.

Still in the context of the invention, the term "ribbon surface" includes not only the surface of the bare glass, but also the surface of the glass which may have been previously treated / covered with at least one given coating.

The invention preferably applies to a glass ribbon of a float line. It goes without saying, however, that it is not limited thereto and that it can also apply to a glass ribbon which is not from a float line or to a non-continuous glass substrate such as a glass tray.

The advantages of the process according to the invention are numerous: on the one hand, in the invention, the metal is only used in the solid or liquid phase, and not in the gas phase, as in the aforementioned patent FR-2 01 1 563. In fact, the implementation of the process is greatly facilitated, because it is easier to control the distribution of powder or liquid than vapor on the surface of the glass. In addition, we are freed from the limiting factor constituted by the vapor pressure of the metal, and therefore significantly higher deposition rates can be achieved. However, this is a primary advantage for making it possible to manufacture layers of relatively large thicknesses, in particular of sufficient thicknesses to transform the glass into a mirror. Indeed, in deposits on the float line within the enclosure of the float bath, the space where the deposition can be carried out, knowing that the glass must also have already stabilized dimensionally, is quite small, and it is therefore not necessarily possible to "compensate" for low deposition speed values by longer deposition times, longer metal / glass contact times

Furthermore, the method according to the invention involves either a fusion of a metal powder, or a "coating" of a metal previously melted on the surface of the glass. It is therefore not a pyrolysis in the usual sense of the term, whether in the solid, liquid or gas phase (then also called under the term CVD or Chemical Vapor Deposition). Pyrolysis in fact involves, on the contrary, a chemical reaction step of decomposition of precursors of the organometallic derivative type in contact with hot glass.

This difference plays a very positive role in the characteristics of the layers obtained. The layers according to the invention tend to be more adherent, denser, less "rough" than pyrolyzed layers, because they result from the fusion of elemental metal. They also tend to crystallize better, because in the invention, crystallization is carried out during the solidification of the layer at the speed corresponding to the cooling speed of the glass ribbon along its course on the float line. The crystallization, at least partially, of a pyrolyzed layer generally takes place in a much more “brutal” manner, during the decomposition of the precursors, and is often accompanied by mechanical stresses

The layers according to the invention also tend to be purer, since there is little risk of impurities being incorporated into the layers. layers in formation, which is not the case with pyrolyzed layers, which may contain, for example, a certain level of residual carbon originating from the decomposition of organic precursors in the glass

And all these improvements go in the direction of higher quality layers and greater durability ^{• the} more dense the layer and adherent to the glass, the more it is able to resist corrosion, in particular in humid environment, or oxidation , which is advantageous if the glass ribbon is then cut into substrates intended to undergo heat treatments such as bending and / or tempering. Low surface roughness also provides better corrosion resistance and minimizes any “haze” effect due to a certain amount of diffuse reflection. Finally, high purity, in particular a very low rate of absorbent particles of the carbon type, associated with a relatively high level of crystallization give the layers according to the invention a very high light reflection, which is sought above all for manufacturing mirrors.

The industrial feasibility of the process according to the invention therefore does not operate at the expense of the performance of the reflective layers thus produced, on the contrary.

It is important that the deposits are made in an inert or reducing atmosphere, in order to ensure that the metal powder does not oxidize before it comes into contact with the glass ribbon, nor the layer itself during its formation. deposit in the enclosure of the float bath, and thus benefit from its controlled atmosphere which is a mixture of nitrogen and hydrogen Alternatively, it is possible to deposit downstream of the enclosure of the float bath, in particular in an essentially sealed box possibly extending said enclosure. Such an "extension" is described in particular in patent FR-2,348,894.

Advantageously, the reflective layer is deposited when the glass ribbon is at a temperature greater than or equal to the melting temperature of the metal: this ensures the melting of the metal particles arriving on the glass, and / or good distribution of the molten metal on its surface The contacting of the metal in powder form with the surface of the glass can be carried out according to two different embodiments.

The first embodiment consists in spraying said metallic powder in suspension in an inert or reducing carrier gas, in order to avoid its oxidation, in particular using a dispensing nozzle. It may be a static nozzle, which is arranged above the glass and substantially transversely to its axis of travel, over all or part of the width of said strip. It can also be a movable nozzle, which is moved back and forth along an axis substantially transverse to the axis of travel of the glass ribbon. In the case of the deposition of a layer made of a single metal, for example Al, the powder is made only of grains of said metal. When the final layer is made of an alloy, the powder is preferably a mixture of powders of each of the components of the final coating, a mixture the proportions of which can be adjusted as required, or a powder directly produced from the alloy.

The particle size of the powder or mixture of powders (in fact the average diameter of the particles constituting it) is advantageously between 0.1 μm and 100 μm and in particular between 1.0 and 50 micrometers, for example between 5 and 1 0 micrometers. In such a range of particle sizes, the “grains” of powder will be able to melt and coalesce optimally on the glass.

The second embodiment consists in generating “in situ” the metal in pulverulent form above the glass ribbon, from at least one metallic derivative, in particular gaseous, which is caused to decompose into metal by thermal activation and / or bringing them into contact with derivatives capable of reacting together. This is another way of ensuring that the metal, formed in the inert or reducing atmosphere prevailing above the glass, is not oxidized. In addition, starting from raw materials in gaseous form, one can draw inspiration from the gas phase pyrolysis technology, CVD, without having all the aforementioned drawbacks, since in the context of the invention, if there is well decomposed, it takes place above the glass and not in contact with it. The powder thus formed preferably has the same particle size as that mentioned above.

Preferably, the formation of metal powder "in situ" is done from metal derivative (s) chosen from metal alkyls, metal hydrides, mixed hydride and metal alkyl compounds. complexed with ammonia or an amine, in particular alanes in the case of aluminum: either a single type of "precursor" is chosen, or different types of precursors, in particular when the layer to be obtained is made of an alloy.

Their metal decomposition temperature is generally between 50 ° C and 600 ° C, in particular between 1 00 ° C and 450 ° C. It can therefore be seen that such a range of temperatures does not coincide with the temperature that the glass ribbon has when depositing the layer: there is, unlike a gas phase pyrolysis, decorrelation between the decomposition temperature of the derivative metal chosen and the temperature of the glass at the time of deposition, and we therefore have much more freedom to optimize each of them independently of the other, and to select the appropriate metal derivative (s) ( s).

It is possible to associate, in the invention, with the metal derivative (s) at least one additive which promotes nucleation or of controlled growth of the metal grains. This additive helps to adjust the particle size of the powder formed above the glass.

The metal derivatives are therefore introduced above the glass ribbon in gaseous form, advantageously using a device whose walls define a guide channel for the powder generated. The walls of this cavity are preferably substantially vertical, possibly divergent or, on the contrary, convergent in the direction of the glass ribbon, and over at least part of its height, an appropriate "thermal gradient" is created. The term “thermal gradient” is understood to mean precise control of the temperature which, relatively gradually, is preferably chosen to increase in the direction of the glass. It is by this adjustment of this temperature gradient that we will control the moment and the area in the cavity, where the metal derivatives will decompose into metal grains, and on the other hand good growth of metallic grains to arrive at a particle size satisfactory, in particular from 5 to 10 micrometers as in the first embodiment according to the invention

In a preferred variant, the method consists in injecting the metallic derivatives into the upper part of the cavity of the device, and in extracting the effluents resulting from their decomposition by lateral evacuation means provided in the walls of the cavity, extraction carried out preferably at or near the level where the metallic powder is formed and where it reaches a sufficient particle size. We thus ensure their evacuation before they touch the glass or become incorporated by chemical reaction in the metal grains to form for example a carbide or a nitride of the metal concerned, the powder "falling" in turn by simple gravity on the glass. One can also provide for injecting at at least one point in the cavity an inert or reducing gas: it can help to avoid any risk of agglomeration of metal powder on the walls of the cavity. Furthermore, the cavity being at least partially in the inert and / or reducing atmosphere prevailing above the glass, it is designed so as to be itself filled with such an atmosphere. If the gaseous metal derivatives are introduced in suspension in a carrier gas, the latter will of course also be chosen preferably of an inert and / or reducing nature.

Whether the metal powder is sprayed directly or from metal derivatives, it should be understood in the invention that it liquefies or fuses either in contact with the glass, or near the glass but slightly above it, under the glass. effect of the heat emitted at a short distance from the glass ribbon. It can then arrive in a rain of droplets on the glass.

Another possibility according to the invention is not to start from a metal powder or gaseous metal derivatives, but from the already molten metal, which can be distributed on the surface of the glass using a nozzle. static distribution arranged above the glass and transversely to its axis of travel, which delivers a "curtain" of molten metal on the glass. Alternatively, it is also possible to have recourse to a movable nozzle, driven in a transverse reciprocating movement above the glass, of the spray gun type. As mentioned above, the reflective layers according to the invention have two very advantageous characteristics:

3 on the one hand, they are dense, more than layers which would, for example, be obtained by pyrolysis or, a fortiori, by vacuum deposition techniques of the sputtering or evaporation type. This density, in particular for aluminum layers, of at least 80 and even at least 90 to 95% of the theoretical mass density of said material. And such a high density makes it possible to reach higher light reflection values, at a given thickness, (note that these density values can be measured, indirectly, from the electron density values measured by a reflectometer at X-rays),

G on the other hand, these layers contain little or no impurities, while carbon, oxygen or nitrogen type impurities tend to increase the absorption and / or transmission of the layer at the expense of its light reflection. This low level of impurities therefore combines with a high density to achieve a maximum mirror effect at a given thickness. The maximum impurity values vary slightly as a function of the process according to the invention chosen: if one “starts” with the materials constituting the layer, in pulverulent or molten form, without involving decomposition of precursors at least partially organic, the layer can be extremely pure. Thus, it generally does not contain more than 1 atomic% of impurities such as 0 or C, impurities possibly being incorporated into the layer during its formation, for example by atmospheric pollution or being present in the starting powder. Most often, the level of impurities is less than 1 atomic% and remains below the detectability threshold of the measuring devices, in this case a scanning electron microprobe. If, on the other hand, one starts from precursors in the form of metal derivatives at least partially organic, the reflective layers remain very pure, but possibly with a slightly higher level of impurities than in the previous case, in particular at most 2 to 3 atomic%. It may be carbon, oxygen or nitrogen, in particular when starting from compounds of the alane type. Whatever the way in which the metal is brought into contact with the glass, it may be advantageous to treat the surface of the glass before the deposition of the metal layer proper. There can be at least two reasons for carrying out such a pretreatment: on the one hand, it may aim to facilitate wetting / bonding of the layer on the glass. On the other hand, it can also aim to inhibit a parasitic reaction at the glass / metal interface which would tend to form, from the metal and the silicon oxide contained in the glass, the metal oxide corresponding to the metal and silicon.

It may only be a surface “sensitization”, consisting in bringing a gaseous product into contact with the glass without any real chemical reaction taking place, but with at least partial adsorption of the gas by the surface of the glass. The gas may, for example, be titanium tetrachloride TiCI ₄ .

However, the pretreatment can also include the deposition of at least one so-called “intermediate” layer before the deposition of the layer. The intermediate layer or layers can be advantageously chosen based on at least one of the materials belonging to the following group: silicon, oxides such as silicon oxide, oxycarbide or oxynitride, titanium oxide Ti0 ₂ , cerium oxide, aluminum oxide Al ₂ 0 ₃ , zirconium oxide Zr0 ₂ , zinc oxide ZnO, nitrides such as aluminum nitride AIN, silicon nitride Si ₃ N ₄ , titanium nitride TiN, zirconium nitride, boron oxide, yttπum oxide, magnesium oxide, mixed AI and Si oxide, fluorinated aluminum oxide , magnesium fluoride MgF ₂ . It can also be carbides. Their deposition is preferably carried out by gas phase pyrolysis (CVD). This intermediate layer preferably has a maximum refractive index of 1.8 and a light absorption at most equal to 3%. Its optical thickness may be between 40 and 120 nm and preferably between 70 and 100 nm. The chemical role of this intermediate layer is therefore the protection of the thin metallic reflective layer, either at the end of the production of the mirror, at the outlet of the enclosure of the float bath, or subsequently during a subsequent heat treatment of the mirror or even over time, during the lifetime of the mirror in normal use situation, in a bathroom for example. Once the reflective metallic layer has been deposited on the float glass ribbon, it is advisable to consider an after-treatment intended to protect it from oxidation. The most effective way to do this is to cover it with at least one so-called "additional" layer, especially when the tape is still in the inert or reducing atmosphere in which the reflective layer has been deposited.

The additional layer or layers may in particular be chosen based on nitride, such as aluminum nitride, silicon nitride or titanium nitride. However, they can also be based on oxide (s), in particular comprising at least one oxide belonging to the following group: titanium oxide Ti0 ₂ , tin Sn0 ₂ , zirconium Zr0 ₂ , zinc, niobium, tungsten , antimony, bismuth, tantalum, Ytπum, aluminum nitride or silcium, or fluorinated tin oxide or "diamond-like carbon" (DLC), aluminum oxide Al ₂ 0 ₃ , in oxide, oxycarbide and / or silicon oxynitride, vanadium oxide. In the latter case, to further limit any contact of the reflective metallic layer with an oxygen-containing compound, provision may be made to deposit between the metallic layer and the oxide layer or layers a "sacrificial" layer of silicon, sufficient to avoid metal / oxide contact, but thin enough not to penalize the stacking of layers in terms of light absorption (this remark also applies when choosing an "intermediate" layer of pure silicon: it is advantageous to also limit the thickness to a few nanometers). The deposits of additional layer (s) are preferably produced by gas phase pyrolysis.

The additional layer covering the reflective metallic layer can have a gradient in chemical composition and / or refractive index in its thickness. It can in particular be a gradient of increasing or decreasing index, in particular by deposition of a material with low refractive index (for example between 1, 45 and 1, 60), gradually increasing as and as the layer is formed from a material with a higher refractive index, in particular greater than 2 or vice versa. A chemical composition gradient very advantageously allows to give two properties to a single layer, and to optimize them in parallel without sacrificing one for the benefit of the other, in particular with regard to the adhesion of the layer to the layer (or layers) with which (which ) it is in contact as well as its mechanical / chemical durability ... This index gradient and / or this chemical composition gradient can be obtained by gas phase pyrolysis, using a distribution nozzle using two injection slots, one for each of the gaseous precursors necessary for obtaining the two materials with low and high index, and by configuring it so as to cause, along the glass, a partial and progressive mixture between the two gaseous veins coming from two slots of injection

As a “gradient additional layer” of preferred composition, a layer based on silicon oxide is used which is gradually enriched with titanium oxide: if a thin layer of “sacrificial” silicon is placed on the reflective layer , an excellent adhesion Si / Si0 ₂ or Sι / SiO _x C _v is thus obtained on the side of the reflective layer, and the stack is "completed" with titanium oxide which, if it is well crystallized , has very interesting anti-soiling and / or anti-fogging characteristics, due to its known photocatalytic properties.

It is also possible to choose to cover the metallic reflecting layer with at least one sequence of layers with low and high indices, for example a sequence Si0 ₂ / Ti0 ₂ .

Each additional layer preferably has a geometric thickness of at least 10 nm, and in particular between 20 and 150 nm, in particular between 50 and 120 nm. More generally, as regards the nature of the materials constituting the additional “external” and additional “internal” intermediate layers, these are chosen so as to “interfere” optically as little as possible with the reflective layer.

Preferably, they are therefore chosen on the basis of material or mixture of transparent material (s) in the wavelengths belonging to the visible range.

They can thus be based on oxide (s), oxycarbide (s) or oxynιtride (s) of the elements of group 2a, 3b, 4b, 3a, 4a and lanthanides of the table of Mendeleief's periodic classification, in particular the oxides, oxycarbons or oxynitrides of magnesium Mg, calcium Ca, yttrium Y, titanium Ti, zirconium Zr, hafnium Hf, cerium Ce (Ce0 ₂ or Ce ₂ 0 ₃ ) , aluminum Al, silicon Si or tin Sn. As transparent oxides, it is also possible to use doped metal oxides such as fluorine-doped tin oxide.

Sn0 ₂ : F.

Among all these compounds, it is advantageous to choose the oxides which have a standard free enthalpy value of formation ΔG ° per mole of oxygen at high temperature, in particular around 500 to 600 ° C, which is less than or equal to that of metal of which the reflective layer is made, referring for example to the diagram mentioning the free enthalpies of oxide formation as a function of the temperature, also known as the Ellingham diagram. Thus, thermodynamically, the oxidation of the metal of the reflective layer is not favored, and this therefore limits to the maximum any risk of oxidation or deterioration of the reflective layer when it is deposited which, if it is carried out on the float glass ribbon, is actually carried out around 450 to 700 ° C.

Thus, when the reflective layer is chosen based on aluminum, it is advantageous to choose as external and / or internal complementary layers layers based on aluminum oxides, zirconium, magnesium or lanthanum. These oxide layers can in particular be deposited by pyrolysis techniques in solid, liquid or gaseous phase. If the deposit takes place in the enclosure of the float bath, it will rather be pyrolysis in the CVD gas phase. Outside the float enclosure, CVD techniques and solid or liquid pyrolysis techniques can be used. Thus, it is possible to deposit by CVD oxide layers such as silicon oxide or oxycarbide from gaseous precursors of the silane and ethylene type, as described in patent EP-0 51 8 755. The Ti0 layers ₂ can be deposited by CVD from an alcoholate such as titanium tetra-isopropylate, and tin oxide, still by CVD from tin monobutyltrichloride or tin dibutyldiacetate. Aluminum oxide layers can be deposited by liquid or gas pyrolysis from organometallic precursors such as acetylacetonate or aluminum hexafluoroacetonate.

The transparent complementary layers can also be chosen based on nitride or a mixture of nitrides of at least one of the elements of group 3a of the periodic table, such as aluminum nitride.

AIN, gallium GaN _x or boron BN _X. The layers of AIN can be deposited, for example by CVD, in a known manner, from alkyl or aluminum hydride precursors associated with nitrogenous precursors of ammonia and / or amine type. Silicon nitride Si ₃ N ₄ can also be used as transparent nitride. Silicon nitride Si ₃ N ₄ is indeed also a very effective material for protecting the reflective layer from oxidation. It can be deposited by CVD from silane and ammonia and / or amine.

At least one of the complementary layers, and more particularly the outer layer, can also be chosen based on a transparent material of the diamond or “Diamond-like Carbon” (DLC) type, this type of material having a high hardness and thus protecting very effectively stacking the underlying layers of mechanical abrasions if necessary (this is also true, to a lesser extent, for titanium oxide). At least one of the “internal” and “external” complementary layers can also be chosen not based on transparent materials in the visible, but on the contrary based on more or less absorbent material (s) in the visible , different from those which could also constitute the reflective layer. So that they do not interfere or almost not optically, as is the case with the pre-listed transparent materials, it is therefore preferable to confine this type of complementary layers to small thicknesses, in particular less than or equal to 1 0 nm, in particular of the order of 1 to 8 nm. They may be transition metal nitrides such as tungsten nitride W, zirconium Zr, hafnium Hf, niobium Nb, titanium Ti or even carbon nitride. It can also be semiconductor materials such as silicon.

The materials are then chosen according to their affinity with respect to the glass and / or the material of the reflective layer and their chemical inertness. vis-à-vis the latter. Thus, it may be advantageous to choose a thin internal Si layer when the reflective layer is made of metal, this material being an effective barrier to the diffusion of alkalis and oxygen from the glass, and, moreover, capable of playing the role of glass / metal adhesion promoter. Silicon can be deposited by CVD from SiH ₄ .

At least one of the complementary layers may also have a chemical composition gradient in its thickness, which very advantageously makes it possible to confer a double property on a single layer.

It may thus be an “internal” complementary layer based on Si0 ₂ or SiO _x C _γ progressively enriched in silicon, or based on Si0 ₂ or SiO _x C _y gradually enriched in metal oxide of the reflective layer such as Al ₂ 0 ₃ if the reflective layer is made of aluminum. This optimizes the role of adhesion promoter and mechanical stress reducer of the internal layer, with an improved affinity of the latter both at its interface with the glass and at its interface with the reflective layer.

The external complementary layer may also have a chemical composition gradient based on the oxide of the metal of the reflecting layer such as AI ₂ 0 ₃ or based on SiO _x C _y , gradually enriched with titanium oxide, the oxide of type Al ₂ 0 ₃ having good affinity and high chemical inertness with respect to aluminum when it is this type of material which constitutes the reflective layer, Ti0 ₂ in turn being able to improve mechanical durability of the stack and possibly give it interesting anti-fog / anti-fouling properties, as described in patent FR95 / 1 0839 filed on September 1, 1995.

These chemical composition gradients can be obtained by gas phase pyrolysis, using a distribution nozzle using two injection slots, one for each of the gas precursors necessary for obtaining the two materials, and by configuring it so as to cause , along the glass, a partial and progressive mixing between the two gas streams coming from two injection slots, as is for example described in application PCT / FR96 / 01 073 filed on July 10, 1 996. The internal and external complementary layers generally have geometric thicknesses between 1 and 200 nm, in particular between 30 and

1 60 nm if they are transparent and between 1 and 5 nm if they are absorbent. In fact, the thicknesses of the complementary layers are to be modulated as a function of many parameters, including the very nature of these layers, that of the reflective layer, and the type of attacks that the stacking of layers will have to undergo. Thus, it is preferable that the reflective layer is

Chemically "isolated", using both an internal complementary layer and an external complementary layer, to preserve its properties during its hot deposition. In addition, if the glass substrate must then undergo heat treatments of the annealing, bending or quenching type, these layers will again fulfill their protective role, and in the latter case, it may be advantageous to provide them thicker than in the case where the substrate does not have to undergo this type of post-deposition treatment.

Embodiments of the stack of layers according to the invention can be the following:

AIN / AI / SiO _x C _v AI / SιO _x C _v

SiO _x C _y / AI / SιO _x C _v

Sι / AI / SιO _x C _v

AI ₂ 0 ₃ / AI / AI ₂ 0 ₃

The invention also provides for the application of a glass substrate as previously described and the outer layer of which is in Tι0 ₂ (or ends with Tι0 ₂ in the case of a composition gradient layer) for the production of a glazing or an anti-fouling and / or anti-fog mirror, as well as the application of this substrate, the external complementary layer of which is harder than the reflecting layer and in particular based on diamond or “diamond like carbon” , to the production of abrasion-resistant mirrors.

It is also planned to apply the glass substrate of the invention to the production of a heated glazing thanks to the passage of current in the reflective layer, of suitable thickness. The subject of the invention is also all the products obtained, in particular those obtained after cutting the float glass ribbon, preferably from the process defined above, or by any other process making it possible to obtain similar characteristics, in particular in terms of density. and low levels (or even zero or almost zero rates) of impurities at the level, in particular, of the reflective layers.

Two applications are particularly targeted: firstly, it is a question of using these products as glazing, both for the building and for the automobile, the reflective layer of metal, in particular aluminum, giving them a sun protection function. The thickness of the reflective layer is then usually limited to at most 30 nm, in order to keep a sufficient level of light transmission.

Second, they can be used as mirrors. In this case, it is necessary to achieve a very strong reflection of light and it is therefore preferable to use layers of metal at least 30 nm thick this time.

More generally, the coated glass substrate according to the invention has very diverse applications, and can be used in reflecting or semi-reflecting mirrors, including the bottom mirrors of photovoltaic cell, the bottom mirrors and the mirrors photocopier, solar protection glazing for buildings or any vehicle (of the low-emissivity or anti-solar type), electromagnetic radiation glazing (radar waves, or radio waves), mirrors, glass elements for furnishing, interior walls of the aquarium or swimming pool type, as interior partitions, decorative glass. The substrate according to the invention can also be used by using the reflective layer as a conductive electrode, for example in electrochemically active glazing such as electrochromic glazing, viologen, liquid crystal glazing or glass with optical valve.

The invention also relates to the process for manufacturing the stack of layers with which the glass substrate is coated, in particular by hot deposition of the reflective layer from molten powder metal according to the “DPM” process previously mentioned. The complementary layer (s) are preferably deposited by pyrolytic deposition in the gas, liquid or solid phase.

The preferred manufacturing method consists of depositing all of the layers hot, on the ribbon of a float glass, preferably depositing at least the first two layers in the enclosure of the float bath. Thus, the deposits are made in continuous with a gain in terms of time and significant production cost compared to deposition techniques of sputtering, sol-gel or immersion in a silver plating bath, with in addition solidity and adhesion to the substrate characteristics of the layers deposited at high temperature.

An exemplary embodiment of products according to the invention can also be a glass substrate, mirror or glazing, which contains the aluminum / aluminum nitride sequence, or alternatively aluminum / silicon / oxide, or alummium / aluminum nitride.

Other details and advantageous characteristics appear from the following description of nonlimiting exemplary embodiments with the aid of the following figures:

O Figure 1: a cross section of a coated glass substrate according to the invention,

O Figure 2: a cross section of the portion of the enclosure of the float bath where the metallic reflective layer according to the invention is deposited.

Note that both Figure 1 and Figure 2 are very schematic representations not scrupulously respecting the proportions, this in order to facilitate their reading.

The following examples were produced on a ribbon of float glass 4 mm thick, clear soda-lime-silica glass which, once cut, is marketed by the company SAINT-GOBAIN VITRAGE under the name of Planilux.

It could just as easily be extra-clear glass or mass-tinted glass, such as glass which, once cut, are sold by SAINT-GOBAIN VITRAGE, respectively under the name of Diamant and under the name of Parsol.

After cutting, we obtain, as shown in FIG. 1, glass substrates provided with a stack of layers in the following manner: the substrate 1 is coated with an optional first layer 2 known as silicon intermediate, itself covered by the reflective metal layer 3.

This is covered with an additional optional layer 4 again based on silicon, on which is placed a second additional layer.

5. In all the examples, the reflective layer 3 is made of aluminum, and is deposited on the glass ribbon by a process explained using FIG. 2.

The portion of glass ribbon 10 as shown in this figure is located in the enclosure of the float bath: the ribbon 1 0 floats on the surface of a bath of molten tin 1 1 inside an enclosure not shown containing the tin bath and filled with a controlled atmosphere composed of a mixture of nitrogen and hydrogen. The glass pours onto the tin bath 1 1 from a glass melting furnace, not shown, located to the left of FIG. 2, spreads there to form a ribbon, which is extracted from the bath at a constant speed in the direction of the arrow by extractor means mounted at the outlet of the bath, on the right side of the figure.

Above the strip 10, which is about 3.30 meters wide, in a zone of the float bath where the glass has acquired its dimensional stability, is mounted a device 12 arranged entirely inside the enclosure of the float bath. This is in the form of a gas distribution nozzle, above the glass ribbon 10, arranged transversely to its axis of travel and over its entire width. The device 1 2 defines a cavity 1 5 of approximately parallelepiped shape using internal lateral walls 1 4 and upper 14 ′, including walls 1 4 transverse to the axis of the glass which are substantially vertical or slightly convergent or divergent in direction of the glass. These walls end, in the lower part, very close to the surface of the glass, for example at a distance d of less than 20 millimeters from the surface of the glass. In these walls are made different openings: • openings in the upper wall 14 'and / or in the side walls 1 4 ensuring a passage of the gas mixture N ₂ + H ₂ from the enclosure of the float bath inside the cavity 1 5;

• a plurality of openings 1 6 formed in the upper wall 1 4 'or in the upper part of the walls 14, arranged in regular line over the entire width of the cavity 1 5, like injectors, into which open supply ducts 1 7 connected to means for supplying a gas mixture x not shown;

• a plurality of openings 1 8 formed in at least one of the transverse side walls 1 4, in particular at about a quarter or 3/4 of the height of said walls, into which open gas discharge conduits connected to means extraction not shown;

• a plurality of openings 1 9 formed in at least one of the side walls of the cavity 1 5, in particular in the first third of the height of the cavity, into which open gas supply conduits 20 connected to means d 'supply of a N ₂ + H ₂ mixture not shown, similar or identical mixture to that prevailing in the float enclosure.

In the thickness of the internal walls 14, 14 'and external 21 of the device 1 2, there are arranged means capable of controlling and regulating the temperature of the cavity 1 5 along its height h, in particular associated heat / heat means cooling means, the operation of which is dependent on temperature measurements inside the cavity carried out regularly by suitable sensors: this is created either by manual adjustments to said heat insulation / cooling means, or by automatic regulation electronics / computing, a temperature profile along the height h of the cavity, so as to have an increasing temperature gradient towards the glass ribbon 1 0, which starts at around 30 to 100 ° C in the upper part nearby openings 1 6 up to more than 600 ° C near the glass. The device 1 2 operates in the following manner: one injects permanently through the openings 1 6 of the aluminum derivative vapor in suspension in an inert gas such as nitrogen; it is the mixture x mentioned above. This derivative can be in particular AI (CH ₃ ) ₃ , AI (C ₂ H ₅ ) ₃ , AIH ₃ (NH ₃ ) or AIH ₃ (amino). Here, it is more precisely dimethylmonoethylamine alane, hydride stabilized by an amine decomposing into metallic aluminum at approximately 1 80 to 200 ° C, and whose formula is AIH ₃ (N (C ₂ H ₅ ) (CH ₃ ) ₂ )

In the injection zone of the cavity, the temperature is around 40 ° C., the mixture x is projected into the cavity substantially perpendicular to the plane defined by the glass ribbon 1 0. The temperature in the cavity increases as and as we get closer to the glass, the alane decomposes to form powdered aluminum 22 in an area h _! of the cavity 1 5 where its decomposition temperature is reached, an area located approximately in the upper half of the cavity: the aluminum grains are then entrained by simple gravity in contact with the glass, while the effluents from the decomposition of the alane, are extracted through the openings 1 8, in this hi area of powder formation. The parameters of the decomposition reaction of the alane are adjusted, in particular to obtain a powder of grains of sufficiently large diameter so that the effluent can be extracted without entraining the powder 22 formed in the extraction conduits and also to prevent the effluents from reacting at higher temperatures with the aluminum grains according to an undesired chemical mechanism.

The powder "arrives" on the glass ribbon when the latter is at a temperature of 660 to 700 ° C., in particular of approximately 680 ° C., that is to say at a temperature which is situated between the temperature maximum at which the glass is dimensionally stable (700-750 ° C) and the melting temperature of aluminum (approximately 650-660 ° C). The aluminum grains, in contact with the glass, instantly melt and the droplets coalesce to leave a continuous molten aluminum film, which will gradually solidify as the temperature of the glass decreases to drop below the aluminum melting temperature.

The final thickness of the aluminum layer thus deposited can be modulated as required by adjusting different deposition parameters, in particular the concentration of alane in the gaseous mixture x, the flow rate of said mixture, etc.

Furthermore, the injection through the openings 1 9 of H ₂ / N ₂ gas mixture is carried out so that the mixture is projected upwards from the cavity 1 5, in particular approximately tangential to the side walls

1 4: this avoids the accumulation of aluminum powder along these walls, so it slows down the fouling of the cavity 1 5 and prevents any risk of sudden fall of grains agglomerated at a point of the tape which can harm the quality of the coating.

Using the diagram in FIG. 1, the layer 3 of aluminum is therefore deposited using the device 1 2 which has just been described. Prior to this deposition, a thin layer 2 of pure silicon from silane is deposited by CVD, in a known manner, for example as described in French patent FR-2 382 51 1, using a nozzle disposed just upstream of the device 1 2, when the glass ribbon has already acquired its dimensional stability, that is to say when it is at about 700 ° C.

Before the glass ribbon provided with the intermediate layer 2 of silicon and the reflective layer 3 of aluminum leaves the enclosure of the float bath, one or more additional layers are deposited, the sequences of which will be given in detail in the following examples . These are layers of aluminum nitride, which are deposited by CVD in a known manner from alkyl precursors or aluminum hydride with ammonia or amine, and / or layers of oxide such as oxide. or silicon oxycarbide, which is deposited in a known manner by CVD from silane and ethylene, as described in patent EP-0 518 755, or also from tin oxide deposited by CVD in known manner from gaseous precursors such as tin monobutyltrichoride or tin dibutyldiacetate, or titanium oxide deposited by CVD in known manner from gaseous precursors such as a titanium alcoholate of the titanium tretopropylate type.

It can be noted that instead of or in combination with the oxide layer of Sn0 ₂ or of Ti0 ₂ , it is equally possible to use silicon oxide layers deposited by CVD from gaseous precursors such as tetraethoxysilane . It could also be layers of aluminum oxide, deposited by CVD from gaseous precursors such as acetylacetonate or aluminum hexafluoroacetonate. It is also possible to choose a layer of vanadium oxide, which can be deposited by CVD from gaseous precursors of vanadium alcoholate type such as vanadium tetraethylate, or halide type such as VCI ₅ or oxychloride type such as VOCI ₃ .

Instead of or in combination with the layer of aluminum nitride, it is also possible to use a layer of silicon nitride, which can be obtained by CVD from a gaseous mixture of silane and ammonia and / or amine.

In the case where it is planned to deposit a layer 5 of oxide and not of nitride on top of the aluminum layer 3, a thin layer 3 of silicon is interposed, deposited by CVD like the layer 1 previously mentioned.

All the deposits are therefore, in the following examples, produced in the float enclosure, that is to say in a strictly non-oxidizing atmosphere and when the glass is at a temperature ranging between approximately

750-700 ° C for the deposition of the first layer of silicon and at least

580-590 ° for the deposition of the last layer of the stack, the glass ribbon usually “leaving” the enclosure of the float bath at a temperature of around 580 ° C.

EXAMPLE 1

Using the previously detailed techniques, the following layer sequence is deposited on the surface of the glass ribbon 10 (the geometric thicknesses are specified under each of the layers, expressed in nanometers): glass' ¹¹ / Al ^{, 31} / AIN ^{( 5} > 50 nm 1 30 nm EXAMPLE 2

The sequence is as follows: glass ^<1) / Al ⁽³⁾ / (AIN / Ti0 ₂ ) ⁽⁵⁾

50 nm 60 nm 50 nm EXAMPLE 3 glass' ¹¹ / Si ^'21 / Al' ³¹ / Si ^{, 4)} / (SiO _x C _v / Ti0 ₂ ) ^(5> 2nm 50 nm 4 nm 70 nm 60 nm The index of the SiO _x C _y layer is HERE set to approximately 1.55.

EXAMPLE 4

The sequence is this time as follows: glass ^m / Al ^<3) / (AIN / Ti0 ₂ ) ^15> 50 nm 60 nm 50 nm The index of aluminum nitride is approximately 1.85. EXAMPLE 5

The sequence is as follows glass ⁿ "/ AI ¹³¹ / Si ^'41 / Sn0 ₂ ^<5> 50 nm 4 nm 1 20nm EXAMPLE 6

The sequence is as follows glass ⁽¹⁾ / Al ⁽³ > / / SS.i ' ⁽⁴⁴⁾⁾ / (gradient layer Sι0 ₂ / Ti0 ₂ )' ^5I 60 nm 5 nm 1 20nm

The Si0 ₂ / Ti0 ₂ gradient layer is a layer obtained by CVD, it has a composition containing at least 80% by weight of Si0 ₂ at the interface with the underlying silicon layer (4) up to at least 80% by weight of Ti0 ₂ at the interface with air. It is obtained according to the technique set out in patent application FR-95/08421 of July 1, 1,995, in particular in example 9, from precursors of silicon oxide and titanium oxide pre-mentioned. .

The glass ribbon is then, in each of these 6 examples, cut and then the light reflection value R _L in percentage according to Illuminant D ₆₅ is measured on each of the 6 glass plates. The following results are obtained:

In conclusion, each of these 6 trays can be advantageously used as so-called “face 1” mirrors, that is to say mirrors where the observer looks at the glass substrate from the side where it is provided with the layer reflective 3. It goes without saying that by suitably adapting the sequence of the so-called intermediate 2 and / or additional layers 4, 5, the invention also makes it possible to manufacture so-called “face 2” mirrors, that is to say mirrors. where the observer looks at the substrate on the side opposite to that provided with the reflective layer.

Furthermore, the substrates provided with aluminum layers 3 thus produced, but a little thinner, for example of the order of 10 to 20 nm, can be used as sun protection glazing very satisfactorily. It can be seen that it is however important to protect the aluminum layer as well as possible from the risks of oxidation, both on the line, as soon as it leaves the float bath enclosure, and to preserve it during oxidative heat treatments of the bending or quenching type. The additional layers 5 according to the invention do this effectively. The intermediate silicon layer 2 is optional, it facilitates the adhesion of aluminum to glass, inhibits the reaction tending to manufacture at the glass / aluminum interface of alumina. It can however be eliminated or replaced by a gaseous treatment, for example by passing TiCI ₄ through the glass surface just before the deposition of the aluminum layer. The silicon layer 4 above the aluminum is also optional, it ensures that the aluminum layer does not oxidize during the deposition of the next oxide layer.

For optical reasons, in particular to amplify the light reflection, it is also possible to deposit additional layers, in particular of oxide, on the other face of the glass ribbon, for example in recovery.

The invention has therefore perfected the manufacture of mirrors or glazing for sun protection continuously, on the float line, a very advantageous yield and cost. The aluminum layer thus deposited is of high quality, it is in particular very dense, very pure and particularly adherent to glass (or to the layer which is underlying it).

Claims

1. Method for depositing, in particular continuously, on a glass ribbon (10) a float line of a reflective layer (3) based on metal whose melting temperature is less than or equal to the temperature where the glass ribbon acquires dimensional stability, characterized in that the deposition is carried out in an inert or reducing controlled atmosphere, when the glass ribbon (1 0) has already acquired its dimensional stability, by bringing the surface of said ribbon into contact with the metal (22 ) in powder form or in molten form, the temperature of the ribbon when brought into contact is chosen so that the powder melts and coalesces, or the molten metal coats, on the surface of the ribbon, leaving a continuous solid layer when the temperature tape is at a temperature less than or equal to the melting temperature of the metal.

2. Method according to claim 1, characterized in that the "metal" is based on a single metal, or based on an intermetallic compound, a metal alloy or a eutectic compound.

3. Method according to claim 1 or claim 2, characterized in that the "metal" is based on at least one of the metals belonging to the group comprising aluminum, zinc, tin, cadmium and optionally comprises silicon.

4. Method according to one of the preceding claims, characterized in that the deposition is carried out in the enclosure of the float bath.

5. Method according to claim 1 or claim 2 or 3, characterized in that the deposition is carried out downstream of the enclosure of the float bath, in particular in an essentially sealed box possibly extending said enclosure.

6. Method according to one of the preceding claims, characterized in that the deposition is carried out when the glass is at a temperature greater than or equal to the melting temperature of the metal.

7. Method according to claim 6, characterized in that the contacting of the metal in pulverulent form with the surface of the glass is carried out by spraying a powder in suspension in an inert or reducing carrier gas, in particular using a dispensing nozzle arranged above glass ribbon and transversely to its axis of travel, and able to distribute the powder over the entire width of the ribbon.

8. Method according to claim 7, characterized in that one chooses a particle size of powder comprised between 0, 1 and 1 00 μm, in particular between 1, 0 and 50 μm.

9. Method according to claim 4, characterized in that the metal is generated in powder form (22) above the glass ribbon, from metal derivatives, in particular gaseous, which is caused to decompose into metal by thermal activation and / or putting them in contact.

10. Method according to claim 9, characterized in that the derivatives are chosen from metal alkyls, metal hydrides, mixed hydride and metal alkyl compounds complexed with ammonia or with a primary, secondary or tertiary amine .

1 1. Process according to Claim 9 or 1 0, characterized in that the derivatives decompose into metal at a temperature between 50 ° C and

600 ° C, especially between 100 ° C and 450 ° C.

1 2. Method according to one of claims 9 to 1 1, characterized in that associated with (x) derivative (s) metal (s) at least one additive promoting nucleation or growth of metal grains.

1 3. Method according to one of claims 9 to 1 2, characterized in that the (s) derivative (s) metal (s) are introduced above the glass ribbon (10) in gaseous form using of a device (1 2) comprising a cavity (1 5) whose walls (14, 14 ') define a guide channel for the powder (22) generated by said derivatives in the direction of the glass ribbon (10).

14. Method according to claim 1 3, characterized in that the walls

(1 4) of the cavity (1 5) are substantially vertical, possibly converging or diverging towards the glass ribbon (1 0), and in that a thermal gradient is created over at least part of the height (h ) of said cavity.

1 5. Method according to one of claims 1 3 or 1 4, characterized in that the metal derivative (s) are injected into the upper part (1 6) of the cavity

(1 5) and in that the effluents from the decomposition of the derivatives are extracted by lateral evacuation means (23) formed in the walls (1 4) of said cavity (1 5), preferably at or near the level where the metal powder is formed and where it reaches a sufficient particle size.

1 6. Method according to one of claims 1 3 to 1 5, characterized in that one injects at at least one point (1 9) of the cavity (1 5) an inert or reducing gas.

1 7. Method according to one of claims 7 to 1 6, characterized in that the metal powder liquefies on the glass ribbon (1 0) or near it.

1 8. Method according to one of claims 1 to 6, characterized in that the molten metal is projected towards the glass ribbon, in particular using a static distribution nozzle delivering a curtain of molten metal to the - Above the ribbon and transversely to its axis of travel, or using a movable nozzle driven back and forth transversely to the axis of travel of the ribbon.

1 9. Method according to one of the preceding claims, characterized in that the surface of the glass ribbon is treated before depositing the reflective layer (3) based on metal, in particular by bringing into contact / adsorption of vapors of the type TiCI ₄ , or by depositing at least one intermediate layer, in particular of silicon Si, of oxide such as aluminum oxide Al ₂ 0 ₃ , silicon oxide, oxynitride or oxycarbide Si0 ₂ , SiON or SiOC, zirconium oxide Zr0 ₂ , cerium oxide, titanium oxide Ti0 ₂ , zinc oxide ZnO, or boron oxide, of ytt

πum, of magnesium, or mixed oxide of AI and Si, of fluorinated aluminum oxide in mangesium fluoride, or in nitride such as aluminum nitride AIN, silicon nitride Si ₃ N ₄ , nitride of titanium, zirconium nitride, or carbide, layer for example deposited by gas phase pyrolysis.

20. Method according to one of the preceding claims, characterized in that the reflective layer (3) based on metal is covered with at least one additional layer (5) intended to protect it from oxidation, in particular when the glass ribbon is still in the inert and / or reducing controlled atmosphere where said reflective layer has been deposited

21. Method according to claim 1 9, characterized in that one chooses the

(the) additional layer (s) based on nitride such as aluminum nitride, silicon nitride or titanium nitride

22. Method according to claim 1 9 or 20, characterized in that the additional layer (s) is chosen, optionally deposited on a thin "sacrificial" layer of silicon (4), based on oxide (s) comprising at least one oxide of the following group: titanium oxide Tι0 ₂ , tin oxide Sn0 ₂ , zirconium oxide Zr0 ₂ , oxide, oxycarbide and / or silicon oxynitride Sι0 ₂ , SiOC or SiON, aluminum oxide Al ₂ 0 ₃ , vanadium oxide, zinc oxide, niobium, tungsten, antimony, bismuth, tantalum, ytrium, aluminum or silicon nitride, oxide of fluorinated tin, in “Carbon-Like-Diamond”.

23. The method of claim 1 9 or 20, characterized in that the reflective layer (3) is covered with an additional layer (5) having a composition gradient or refractive index in its thickness, in particular by deposition of a material such as silicon oxide gradually enriched with a material such as titanium oxide.

24. The method of claim 19 to 21, characterized in that the reflective layer (3) is covered with at least one sequence of low index and high index layers, for example a sequence Si0 ₂ / Tι0 ₂ .

25. Method according to one of the preceding claims, characterized in that the glass ribbon of a float line is substituted either a glass ribbon not originating from a float line or a non-continuous glass substrate such as a tray of glass.

26. Glazing (1) obtained by cutting the glass ribbon (1 0) float covered according to the method according to one of the preceding claims, characterized in that ^r \\ is provided with a reflective layer (3) of aluminum with a thickness less than or equal to 30 nm with sun protection function.

27. Mirror (1) obtained by cutting the float ribbon (1 0) covered according to the method according to one of the preceding claims, characterized in that this is provided with a reflective layer (3) of thick aluminum greater than or equal to 30 nm.

28. Glazing (1) according to claim 26 or mirror according to claim

26, characterized in that W is provided with the sequence aluminum / SiOC or aluminum / AIN or aluminum / TiN or aluminum / Si / oxide.

29. Glass substrate provided with at least one reflecting layer (3) based on a metal of the intermetallic compound, alloy or eutectic compound type, in particular based on at least one of the metals belonging to the group comprising aluminum, zinc, tin, cadmium and also optionally comprising silicon, characterized in that the substrate (1) is also provided with an “external” complementary layer (4) and / or an internal complementary layer (2) with respect to to said reflecting layer (3) and intended (s) to ensure its chemical and / or mechanical durability.

30. Glass substrate (1) according to claim 29, characterized in that the “internal” complementary layer (2) and / or the “external” complementary layer (4) are based on transparent material (s) in the wavelengths belonging to the visible range and of the oxide type (s) chosen from at least one of the compounds comprising the oxides, oxycarbons or oxynitrides of the elements of group 2a, 3b, 4b, 3a, 4a and lanthanides from the periodic table, such as the oxides of Mg, Ca, Y, Ti, Zr, Hf, Ce, Al, Si, Sn, or also based on transparent doped metal oxides such as Sn0 ₂ : F.

31. Glass substrate (1) according to one of claims 29 or 30, characterized in that the "internal" additional layer (2) and / or the "external" additional layer (4) are based on transparent material (x) ( s) in the wavelengths belonging to the visible range and of the nitride type (s), in particular based on nitride of at least one of the elements of group 3a of the periodic table, such as AI nitride, of Ga or boron, or also based on silicon nitride.

32. Glass substrate (1) according to claim 28, characterized in that the “internal” complementary layer (2) and / or the “external” complementary layer layer (4) are based on transparent material (s) in wavelengths belonging to the visible range of the “Carbon-Like-Diamond” type.

33. Glass substrate (1) according to claim 29, characterized in that the “internal” complementary layer (2) and / or the complementary layer "External" (4) are based on material (s) absorbing (s) in wavelengths belonging to the visible range and different from those constituting the reflecting layer (3), of the transition metal nitride type such as nitride of W, Zr, Hf, Nb, Ti or carbon nitride, or also of silicon Si, preferably confined to geometric thicknesses less than or equal to 10 nm, in particular of the order of 1 to 8 nm.

34. Glass substrate (1) according to claim 29, characterized in that the “internal” complementary layer (2) and / or the “external” complementary layer (4) has a chemical composition gradient in its thickness, in particular a layer "internal" (2) complementary based on Si0 ₂ or SiO _x C _y gradually enriched in silicon or based on Si0 ₂ or SiO _x C _y gradually enriched in Al ₂ 0 ₃ , and / or a complementary layer "External" (4) based on AI ₂ 0 ₃ or SiO _x C _y or Si0 ₂ gradually enriched in Ti0 ₂ , or based on Si gradually enriched in SiO _x C _y or in Si0 ₂ .

35. Glass substrate (1) according to one of claims 29 to 34. Characterized in that the geometric thickness of the "internal" (2) and "external" (4) complementary layers is between 1 and 200 nm, in particular between 30 and 1 60 nm.

36. Glass substrate (1) according to one of claims 29 to 35, characterized in that the reflective layer (3) is located between an “internal” complementary layer (2) and an “external” complementary layer (4) of natures and thicknesses chosen in order to preserve the properties of the reflective layer (3) during its hot deposition, and possibly subsequently in the case where the glass substrate (1) is intended to undergo after thermal deposition of the layers of the annealing, bending or quenching type.

37. Glass substrate according to one of claims 29 to 36, characterized in that the reflective layer (3) has a density of at least 80, and in particular of at least 90 or 95% of its theoretical mass density.

38. Glass substrate according to one of claims 29 to 37, characterized in that the reflecting layer (3) has a content of impurities, in particular C, N, O, of at most 3 atomic%, in particular of plus 1 atomic%.