Transparent substrate with at least one thin silicon nitride or oxynitride based layer and process for obtaining the same

The present invention relates to a transparent substrate which is provides with at least a thin layer. The main application of the invention is the manufacture of self-glazing Functional used either in buildings or in vehicles, or as a screen plasma television. Another possible application is surface treatment of containers of standard glass bottles.

In the context of the invention should be understood by a functional glazing glazing with at least one of the constituent transparent substrates is covered with a stack of thin layers, to impart particular properties, especially thermal, optical, electrical or mechanical, such as a scratch-resistant property.

There are so thin layers called low-emissivity, especially composed a doped metal oxide, eg tin oxide doped with fluorine (SnO₂: F) or oxide indium doped with tin (ITO), and can be deposited on glass by techniques pyrolysis. Once coated with a low-emissive layer, the substrate mounted glazing especially in a building reduces the emission in the far infrared to outside the room or passenger compartment through said glazing. Thereby reducing losses Energy due in part to this radiation leakage, it greatly improves comfort heat, especially in winter.

And the coated substrate may be double glazed, low-emissive layer being turned towards the gas gap spacing the two substrates, e.g. disposed on face 3 (the faces of a multiple glazing are conventionally numbered starting from the outermost face relative to the room or passenger compartment). Double glazing thus formed then has a reinforced thermal insulation, with a coefficient K heat exchange while maintaining low profit contributions of solar energy, with a solar factor (ie the ratio between the total energy entering the room and the incident solar energy) high. The reader is referred in this connection, including Patent Application EP 0544 577, FR-2704 543 and EP 0500 445.

The low-emissivity layers are also good electrical conductors, which allows to equip automotive glazing to make glazings heating / defrosting by providing the suitable current leads, described application for example in EP-0353 140.

There are also filter thin layers called selective or antisun which, deposited on substrates mounted glazing, reduce the heat input solar radiation through the glass in the room or the cabin through absorption / reflection. It can be, for example, nitride layers (or oxynitride) of titanium nitride TiN, such as those obtained by a technique of chemical vapor deposition and described in EP-patent applications 0 638 527 and EP-0 650 938. It may also be an aluminum reflective layer of small thickness (less than or equal to 30 nm). obtained in particular by metal vapor deposition, CVD or by the technique deposit described in international patent application PCT / FR-96/00362 filed on 07 March 1996 not to Saint-Gobain Vitrage.

The invention is also interested in techniques for depositing these various layers, and more particularly to those using a pyrolysis reaction. These last involves launching "precursors"; for example organo-metallic nature, either gaseous form or in powder form or liquid by themselves or in solution in a liquid, to the substrate surface at high temperature. said precursors, in contact therewith, there decompose leaving for example a metal layer, oxide, oxynitride, or nitride. The advantage of pyrolysis lies in the fact that allows for the deposition of the layers directly on a line glass ribbon flat glass manufacturing float, continuous, and also in the fact that the layers pyrolyzed have (in general) a strong adhesion to the substrate.

The low-emissivity layers or filter mentioned above are frequently part of a stack of layers, and are at least on one of their faces, in contact with another layer, typically a dielectric material with an optical role and / or protective.

Thus, in the abovementioned patent applications EP-0544 577 and FR 2704 543, the low-emissive layer. for example SnO₂: F, is surrounded by two dielectric layers SiO kind₂, SiOC or metallic oxide. layers of refractive index and thickness selected to adjust the optical appearance of the substrate, especially in reflection, by eg color.

In application EP-0500 445 patent also supra, the low-emissive layer ITO is surmounted by an aluminum oxide layer to protect it from oxidation, and also, under certain conditions, to eliminate the need to make him suffer a reducing annealing and / or allow the bending or tempering of the substrate once coated without deteriorating its properties.

The TiO layer₂ or the double layer TiO₂/ SiOC which overcomes the filter layer TiN in the aforementioned EP-0650 938 also acts to protect the TiN from oxidation and improve sustainability in general.

However, it is important to ensure the integrity of the multilayer stacks thin. Thus, they must:<ul><li>an ability to withstand chemical attack. Indeed, it happens frequently than the transparent substrate, once coated with layers or stored for quite a long period before being mounted glazing. If it is not carefully conditioning sealed manner, and therefore expensive; the layers of which it is coated may find directly exposed to a polluted atmosphere or subjected to cleaning by detergents not well suited for dusting, even if the substrates are later assembled in double-glazing or laminated glazing, with thin layers arranged front 2 or 3, thus protected. Moreover, besides the storage problem, stacks chemical corrosion are likely to curb the use of substrates as "Monolithic glazing" or an arrangement of layers facing 1 or 4 in the case of Glass pack, that is to say, configurations where the layers are year round exposed to the ambient atmosphere.</li><li>an ability to withstand mechanical damage, for example, the substrate transparent, once coated with layers may be used in configurations where it is easily exposed to damage from scratch kind. Therefore, firstly the substrate no longer offers a visually aesthetic ((correct "since partially striped and on the other hand, the durability of both the stack and the substrate is reduced, the mechanical weakening sources may, if necessary, be introduced.</li></ul>

We are therefore constantly looking for stacks of layers sustainability chemical and / or improved mechanical. However, these improvements should not make at the expense of the optical qualities of the assembly constituted by the substrate and the stack of thin layers.

As previously mentioned, there are already overcoat material dielectric exerting a certain protection of the underlying layers in the stack. To stay upright face intense chemical corrosion or long duration and / or fully protect the underlying layers possibly more "fragile", demand EP-patent 0 712 815 describes an oxide-based thin film comprising silicon and a third element, such as a halogen of the fluorine type F, which facilitates forming a composite structure of silicon and aluminum.

This layer is particularly suitable to serve as a last layer in stacks where the functional layer is the filter or low-emissivity type to glazing, because it can perform a particular optical function an optimization function the appearance in reflection and guarantee a certain constancy in time of the appearance of glazing.

However, it is not necessarily capable of resisting mechanical damage such as scratching, because it has a hardness which is not extremely high.

It is known that type of hard thin film particularly adapted for durable and stable to mechanical abrasion and / or chemical attack is a thin layer based on silicon nitride, which may, if desired, contain a certain proportion of impurities such as oxygen and carbon.

It is thus known a type of thin layer based on silicon nitride deposited on a substrate by a pyrolysis technique by gaseous phase from two precursors, silicon precursor being a silane, nitrogen-containing precursor being either inorganic ammonia type or organic type include hydrazine substituted by methyl.

When the deposit is made from the type nitrogen precursors ammonia, temperatures are too high (over 700 ° C) to be compatible eg with a continuous deposition on a silico-sodo-calcic glass ribbon in a chamber float bath since, at these temperatures, these standard glasses have not yet attteint their dimensional stability.

Nitrogen precursors of hydrazine type have meanwhile some toxicity which makes them difficult industrial application.

It is also known to deposit a thin layer based on silicon nitride by the same procedure as mentioned above, in particular using not two precursors, but one that is both silicon and nitrogen type Si (NMe₂)_4-nH_not. The deposition rates that can be achieved are too weak to operate the deposition process on an industrial scale. In addition, the synthesis of this product is relatively complex and therefore expensive, and it can no longer modulate the proportions respective of (the) precursor (s) nitrogen (s) and silicon (s).

Furthermore, thin films based on silicon nitride have known some disadvantages:<ul><li>on the one hand, they are not necessarily sufficiently hard and have a lesser sustainability, especially when deposited under vacuum to power through example, impart to a substrate with this single layer or a stack of layers thin layer comprising such an anti-scratch function.</li><li>on the other hand, particularly when deposited by pyrolysis, they are absorbent at the wavelengths of the visible range, which is detrimental from the point of optical sight.</li></ul>

The object of the invention is therefore to alleviate the above drawbacks and thus developing a new thin nitride or silicon oxynitride having a greater hardness while very little absorbent, and likely to part of a stack of thin layers, in particular to play a protective role vis-a-vis of etching the thin-film stack in which it is is incorporated.

Another object of the invention to provide a new method for depositing a thin layer based on silicon nitride or silicon oxynitride, in particular by a technique gaseous phase pyrolysis compatible with a continuous deposition on a glass ribbon in the chamber of a float bath and that achieves high deposition rates.

To do this, the invention first relates to a transparent substrate type glass substrate coated with at least one thin layer based on nitride or oxynitride silicon. According to the invention, the thin layer comprises the elements Si, O, N, C in the following atomic percentages:<ul><li>Si: 30 to 60%, especially 40 to 50%,</li><li>N: from 10 to 56%, in particular 70 to 56%,</li><li>O: 1 to 40%, especially 5 to 30%,</li><li>C: from 1 to 40%, especially 5 to 30%.</li></ul>

Surprisingly, this thin layer has proved to be both very hard compared to other thin layers based on known silicon nitride, very transparent and therefore little or no absorbent at the wavelengths of the visible field: high levels of Si and N show that it is in the presence of a predominantly material silicon nitride. By modulating the proportion between minority constituents the type C, O, we manage to fine-tune the properties of the layer. So, playing on in relative proportions of carbon and oxygen, we can both such "fix" finely density and the refractive index of the thin layer so as to impart mechanical hardness and optical properties quite interesting and focused. For play on the above relative proportions, one can possibly do with a CO oxidizing type of light₂, For example for optical reasons. The carbon and nitrogen have a tendency to increase the refractive index, oxygen having more the effect reverse.

For example, the refractive index of the layer is greater than 1.6, in particular between 1.8 and 2.0, preferably 1.85.

The layer can include other elements as an additive such as fluorine, phosphorus or boron, preferably in an atomic percentage of between 0.1 and 5%. The layer may also be homogeneous or composition gradient in its thickness.

Advantageously, the thin layer has a light absorption coefficient AT_L less than 2% for 100 nanometers of geometric thickness, optical quality particularly highlighted when depositing said layer is effected by a pyrolysis technique in gas phase, as explained below.

The thin layer advantageously forms part of a stack of thin layers, of which at least one is a functional film having thermal properties, particularly filter, sun protection or low-emissivity and / or electrical properties and / or optical properties and / or photocatalytic properties, such as a functional layer mirror, doped metal oxide, nitride / metallic oxynitride or metal type aluminum or silicon. It can also be part of a stack of antireflection layers. playing the role of high-index layer index or "intermediate".

As doped metal oxide or nitride / metallic oxynitride, it can be selected doped tin oxide with fluorine SnO₂: F, indium oxide doped with tin ITO, zinc oxide doped with indium ZnO: In, with fluorine ZnO: F, with aluminum ZnO: Al, with tin ZnO: Sn, oxide mixed CD₂ SnO₄, Titanium nitride, TiN, ZrN zirconium nitride.

According to an additional feature, the layer may be in the layer functional. It can then fill such as a barrier layer to the diffusion ions include alkaline, oxygen from the glass substrate type, or yet the role of nucleation layer, and / or having an optical function (adjusting color, anti-iridescence effect, antireflection effect). In some applications of the plasma-screen type it may also fulfill the role of barrier layer to the migration of ions Ag⁺ at From the functional layers based on silver to the glass substrate type.

According to another feature, the layer may be disposed on the layer functional. It can then be used, in particular a protective layer of the layer functional vis-à-vis high-temperature oxidation or chemical corrosion, mechanical protection layer of anti-scratch type of optical function layer of couch e improving the adhesion of the top layer.

According to another characteristic, the thin layer is the only layer covering the substrate and advantageously fulfills a scratch-resistant function. The geometrical thickness of the layer can be adjusted freely in a very wide range of 5nm to 5 .mu.m, in particular between 20 and 1000 nanometers, a rather substantial thickness of at least 250 nm being preferred by example to accentuate the scratch-resistant effect of the substrate with at less said layer, a thin layer generally being sought for another functionality (nucleation, membership ...).

The invention also relates to the substrate process to obtain defined above, which process consists in depositing the thin layer based on nitride silicon by a pyrolysis technique by gaseous phase (also called "Chemical Vapor Deposition "in English or CVD) using at least two precursors, at least one silicon and at least one nitrogen. According to the method of the invention, at least one nitrogen precursor is an amine.

The choice of such a nitrogen precursor is particularly advantageous: it is a adequate reactivity to the extent that it allows to deposit at temperatures where the glass substrate of the standard soda-lime-type substrate has reached its perfect dimensional stability, particularly in the context of a glass production line fleet.

Moreover, the deposition rates achieved are sufficiently high to be able to deposit substantial thicknesses in the float chamber.

The silicon precursor selected may advantageously be a silane, hydride and / or alkyl silicon, silazane.

The amine may be selected from primary amines, secondary or tertiary, in particular alkyl radicals having 1 to 6 carbon atoms each.

Thus, it may be ethylamine C₂H₅NH₂, Methylamine CH₃NH₂, of the dimethylamine (CH₃)₂NH, butylamine C₄H₉NH₂, Propylamine C₃H₇NH₂.

The choice of the appropriate amine to a geometric layer thickness and / or of given refractive index is a compromise to be found between a number of parameters such as steric hindrance, reactivity ...

Preferably, the ratio by number of moles of the quantity of nitrogen precursor on the amount of silicon precursor lies between 5 and 30, preferably equal to 10.

It is indeed important to control such a report to avoid firstly a insufficient incorporation of nitrogen and secondly the risk of gas phase nucleation and thereby the risk of powder formation. This limits the risk of clogging device and production declines.

In a further feature, when it is desired to incorporate an additive, chooses a precursor of the additive independent of the silicon precursor and the amine. he can for example, be a fluorinated gas type CF₄ when the desired additive is fluorine F or a phosphate-containing organic gas such PO (OCH₃)₃ or a type of gas triethylphosphite, trimethylphosphite, triméthylborite, mp₅, PCl₃, PBr₃ PCl₅ when the desired additive is phosphorus P or boron B. These additives enable advantageously to generally increase the deposition rate.

The deposition temperature is in line with the choice of precursors. including the amine. Preferably, it is between 550 and 760 ° C. She may be preferably between 600 and 700 ° C: this is to say between the temperature where the glass in particular silico-sodo-calcic is dimensionally stable and the temperature it has to leaving the float chamber.

Advantageously, in the variant in which the glass composition of the substrate is adapted to an electronic application, it is between 660 ° C and 760 ° C.

According to this variant, an advantageous composition may be that described in WO-96/11887. Thereof, is expressed in percentages by weight of type:<tables><table><tgroup cols="2"><tbody><row><entry align="left">SiO₂</entry><entry align="right">45-68%</entry></row><row><entry align="left">al₂O₃</entry><entry align="right">0-20%</entry></row><row><entry align="left">ZrO₂</entry><entry align="right">0-20%</entry></row><row><entry align="left">B₂O₃</entry><entry align="right">0-20%</entry></row><row><entry align="left">N / A₂O</entry><entry align="right">2-12% </entry></row><row><entry align="left">K₂O</entry><entry align="right">3.5 to 9%</entry></row><row><entry align="left">CaO</entry><entry align="right">1-13%</entry></row><row><entry align="left">MgO</entry><entry align="right">0-8%</entry></row></tbody></tgroup></table></tables>with:<ul><li>SiO₂ Al +₂O₃ + ZrO₂ ≤ 70%</li><li>al₂O₃ + ZrO₂ ≥ 2%</li><li>N / A₂O + K₂O ≥ 8%</li></ul>and optionally BaO and / or SrO in following proportions:<st32:che xmlns:st32="http://www.matrixware.com/ns/st32/">11% ≤ MgO + CaO + BaO + SrO ≤ 30%</st32:che>with a strain point of at least 530 ° C and a coefficient α of 80 to 95.10^-7° C^-1.

Another advantageous composition, drawn from the application FR97 / 00498 is always in weight percent, of the type:<tables><table><tgroup cols="2"><tbody><row><entry align="left">SiO₂</entry><entry align="left">55-65%, preferably 55-60%</entry></row><row><entry align="left">al₂O₃</entry><entry align="left">0-5%</entry></row><row><entry align="left">ZrO₂</entry><entry align="left">5-10%</entry></row><row><entry align="left">B₂O₃</entry><entry align="left">0-3%</entry></row><row><entry align="left">N / A₂O</entry><entry align="left">2-6%</entry></row><row><entry align="left">K₂O</entry><entry align="left">5-9%</entry></row><row><entry align="left">MgO</entry><entry align="left">0-6%, preferably 1-6%</entry></row><row><entry align="left">CaO</entry><entry align="left">3-11%, preferably 7-11%</entry></row><row><entry align="left">SrO</entry><entry align="left">4-12%</entry></row><row><entry align="left">BaO</entry><entry align="left">0-2%</entry></row></tbody></tgroup></table></tables>with:<ul><li>N / A₂O + K₂O ≥ 10%</li><li>MgO + CaO + SrO + BaO&gt; 11%, preferably&gt; 15%</li></ul>and a strain point of at least 600 ° C. (Another alternative is, keeping proportions of the other components unchanged. to choose Al rate₂O₃ 5 10% and a level of ZrO₂ from 0 to 5%).

It is recalled that the so-called lower annealing temperature ( "Strain Point") is the temperature that has a glass when it reaches a viscosity η equal to 10^14.5 poises.

It is thus preferable to deposit the atmosphere layer essentially inert or reducing, for example in admixture N₂/ H₂ without or almost without oxygen on a continuous float glass ribbon in the float chamber and / or in a box control of the inert atmosphere, without oxygen, in order to deposit further downstream of the line float, optionally at temperatures somewhat lower.

The invention thus allows the manufacture of filtering solar control glazing with stacks of the type:<ul><li>glass / TiN and / or ZrN / layer of the invention / SiOC and / or SiO₂, said layer of the invention to have a much stronger interface between the TiN layer and / or the ZrN layer on the one hand, and the SiOC layer and / or the SiO layer₂, on the other hand. It also allows for effective protection of the TiN and / or ZrN against the possible risk of surface oxidation is on industrial line after deposition the layer of SiOC and / or SiO₂Or off an industrial line for example when the substrate provided with the stack of layers, once cut, undergoes treatment thermal type bending / toughening or annealing. Advantageously, the layer has a geometrical thickness of between 10 and 50 nanometers, the thin layer according the invention has a geometric thickness of between 5 and 20 nanometers, and overlayer of SiOC and / or SiO₂ a geometrical thickness between 30 and 100 nanometers.</li><li>or type:    glass / Al / thin layer according to the invention,</li></ul>the aluminum reflective layer being either of small thickness (less than or equal to 30 nm) is thicker when mirroring is desired, such as that described in the aforementioned international patent application PCT / FR-96/00362, the layer thin according to the invention having both a protective agent role vis-à-vis the oxidation and an anti-ravure function.

The invention also allows for windows whose functionality essential is to be scratch-proof, that is to say glazing such as floor tiles, the glass furniture where the glass substrate is only coated with the thin layer based on Yes₃NOT₄ according to the invention optionally combined with an anti-iridescence layer.

and it protects advantageously glass of all dégradation.La thin layer according to the invention may also be associated low-emissive layers with stacks of the type:    glass / SiOC / SnO₂: F or ITO / thin layer according to the invention.

In these stacks, the SiOC sublayer may obviously be replaced by other metal oxides such as those described in patent application EP-0677 493.

The thin layer of the invention allows even manufacture any type of functional glazing provided with a stack of thin layers which are of great durability and are capable of being hardened and / or curled when the substrate used is a glass substrate.

The invention further allows for glazing where an antifouling function is sought, with stacks of the type:    Glass / thin layer of the invention / TiO₂

In these stacks, the thin layer according to the invention is essentially to role of serving as the barrier layer glass migrant alkali to the base layer titanium oxide TiO₂; the photocatalytic effect of the latter is thus increased. Furthermore, if the thickness of the layer according to the invention is adapted so that it is in interferential interaction, it also has the role of being an anti-iridescence layer.

The titanium oxide TiO₂ may be in the form of particles predominantly crystalline anatase type, as described in the patent application WO 97/10188.

But it may also be in the form of a film at least partly crystalline, as described in the patent application WO 97/10186.

Finally, the invention allows the manufacture of emissive screen type screens such dishes that plasma screens. The thin layer of the invention can then play roles different depending on the nature of the chemical composition of the substrate on which it is deposited and / or destination (front or rear) of the same substrate in the screen and therefore, the nature of the functional layers which surmount, such as electrodes, phosphors (lanterns), essential elements for the operation of the screen.

Thus, if the glass substrate is of the "alkali-blocked", that is to say, composition substantially devoid of diffusing species of the alkaline type, layer thin the invention meets very effectively the essential role of barrier layer migration of diffusing species of topcoats to the substrate, in particular of the silver-based electrode.

Similarly, in the case where the composition of the glass substrate contains alkali, it also acts as a barrier layer to migration.

The invention also applies to containers of surface treatment type glass bottle or vials, the hard layer according to the invention reinforcing said containers for example vis-à-vis actions that can deteriorate and this regardless or inhomogeneity relative thickness of the recorded layer. Depositing the layer lasts according to the invention can thus be carried out on the external wall of the containers in the mechanically strengthening especially against impacts but also on the inner wall of containers in order, for example, to prevent the release element from the substrate.

Other details and advantageous features hereinafter apparent from the description Examples of non-limiting embodiments with Figure 1 and 2 attached. For the sake of clarity, these figures do not respect the proportions on the relative thicknesses of different materials.

In all the following examples, the deposition of all thin films is carried out in the float chamber.

<u>EXAMPLE 1</u>

1 shows a glass substrate 1 clear silica-soda-lime 3 millimeters thick, for example that sold under the brand PLANILUX by Saint-Gobain Vitrage, covered with the thin layer based on nitride 2 silicon developed by the invention.

The thin layer based on silicon nitride 2 is obtained by a technique of chemical vapor deposition from silane SiH₄ that is the silicon precursor, and ethylamine C₂H₅NH₂, Which is the nitrogen-containing precursor.

The precursor flow rates are chosen such that the volume ratio of the quantity ethylamine on the amount of silane is about 10. This setting is advantageous in that it maximizes the contribution of each component of the layer. Indeed, it has been observed that it should not be:<ul><li>too high otherwise there may be a risk of gas phase nucleation and therefore a risk of powder formation.</li><li>if too low there may be insufficient incorporation of nitrogen in the layer.</li></ul>

A range of ratios from 5 to 30 proves perfectly adequate, when you want depositing a layer of 50 to 300 nm thick from a silane and ethylamine.

The deposit was made on the substrate 1 heated to a temperature between 600 and 650 ° C, at atmospheric pressure.

Under these conditions, Layer 2 growth rate according to the invention reached 60 nm per minute.

The layer 2 obtained as shown in Figure 1 has a thickness of about 350 nanometers and a refractive index of about 1.85.

A microprobe analysis indicates that the layer 2 comprises, as percentages atomic, 32.7% silicon, 30.6% nitrogen, 21.1% carbon and 15.6% oxygen.

The deposition technique of the invention allows to modulate the quantities of different elements incorporated, including that of carbon by playing different parameters such as the temperature at which the deposition is performed, the use of another amine as ethylamine or a mixture of amines or ammonia added to ethylamine as a precursor of nitrogen.

The various amines which have an appropriate reactivity are as follows: the methylamine CH₃NH₂, Dimethylamine (CH₃)₂NH, butylamine C₄H₉NH₂ and propylamine C₃H₇NH₂. Satisfactory temperatures depositing the layer 2 according the invention are within a range of 550 to 700 ° C.

The spectrophotometric characteristics of such a layer are grouped in the table below, in which T_L, R_L, AT_L respectively represent the values ​​of the light transmission of the light reflection and light absorption percentage:<tables><table><tgroup cols="4"><tbody><row><entry align="center" /><entry align="center">T_L</entry><entry align="center">R_L</entry><entry align="center">AT_L</entry></row><row><entry align="center">layer 2</entry><entry align="center">84</entry><entry align="center">13</entry><entry align="center">3</entry></row></tbody></tgroup></table></tables>these values ​​being measured from the illuminant D₆₅., At near-normal incidence.

It is found that the layer according to the invention has a very light absorption low and it is free of blur. (Recall that the blur is the report of the diffuse transmission to the light transmission at a wavelength equal to 550 nm).

On the substrate 1 covered with the single layer 2 of the invention was carried out a test that evaluates the strength of said layer. This test is performed to with wheels made of abrasive powder embedded in an elastomer. The machine is manufactured by the company TABER INSTRUMENT CORPORATION This is the model 174 "Standard Abrasion Tester". the wheels are type CSIOF loaded with 500 grams. Subjecting the substrate 1 covered locally to 50 rotations and then carried out using a optical microscope counting the stripes on four square side equal to 1 inch or 2.54 cm. After realizing this count, the average R is calculated from the number of scratches per square. Finally, calculate the "Taber score" T_S following formula:<st32:che xmlns:st32="http://www.matrixware.com/ns/st32/">T_S R = -0.18 + 10</st32:che> To a layer 2 according to the invention is 300 nanometers of geometric thickness, "Score" is equal to 9.3. This value indicates a minor deterioration and thus reveals very good resistance of the layer according to the invention to scratching.

As a comparative example, one can note that a layer of tin oxide doped fluorine SnO₂F 340 nanometers of geometric thickness, known as the layer "Hardest" deposited by a pyrolysis technique by gaseous phase present, following the test a "Taber score" T_S equal to 9,1.

It is therefore clear that based on silicon nitride layer according to the invention is a layer which inherently has very good resistance to mechanical abrasion and is from an optical point of view very satisfactory since very transparent and very few absorbent at the wavelengths of the visible range.

<u>EXAMPLE 2</u>

Figure 2 shows a type of sunscreen glazing comprising a thin-film stack in which was incorporated the layer according to the invention.

The glass substrate 1 clear silica-soda-lime 6 millimeters thick is coated with three successive layers:<ul><li>a first layer 3 of TiN thickness of 23 nm obtained by pyrolysis phase gas from a titanium tetrachloride TiCl₄ and methylamine CH₃NH₂ such as described in patent application EP-0 638 527.</li><li>a second layer according to the invention thickness of approximately equal to 10 manometers and refractive index equal to 1.85, deposited under the same conditions as Example 1.</li><li>a third layer 4 of silicon oxycarbide SiOC thickness 65 nm, refractive index equal to 1.65, also obtained by pyrolysis in the gas phase from silane and ethylene as described in patent application EP-0518 755, the layer essentially form silicon-oxidizing to the exit from the float, and particularly in the lehr.</li></ul>

It was therefore a type of stack:    glass / TiN / Si₃NOT₄ / SiOC.

<u>EXAMPLE 3</u>

this comparative example using a stack was performed:    glass / TiN / SiOC where the two layers of TiN and SiOC have the same characteristics as those defined previously and are obtained under the same deposition conditions.

It is found that the layer 2 of the invention, even a thin, creates a very strong interface between the first layer 3 of TiN and the overlayer 4 of SiOC.

In addition, the layer 2 according to the invention effectively protects the TiN of the possible risk of surface oxidation on the industrial line after deposition of the overlayer 4 SiOC. Where appropriate, it isolates the TiN when the substrate when cut, undergoes subsequent heat treatments of the bending / toughening or annealing.

Similarly after measuring the spectrophotometric values, including light transmission T_L for each of the two stacks of Examples 2 and 3 and the solar factor F_S, it is found that the selectivity for the difference T_L-F_Sis much better in the case of the "tri-layer" of Example 2 with the layer 2 according to the invention sandwiched between two layers of TiN and SiOC since its value is 10%. In the case of "bi-layer" of Example 3 is less than 7%.

Note finally that if in the two previous configurations, the layer based silicon nitride according to the invention is homogeneous in its thickness, it is also well provide some inhoniogénéité composition in its thickness, including to modulate the refractive index and permit optical compatibility and / or optimal chemical with the layer above and / or below such as for example a enriched layer of Si₃NOT₄ the side of the TiN and enriched layer SiON side SiOC in a sun protection glazing using the same layers as in example 2. This layer "gradient" can be obtained from the same deposition technique gas phase pyrolysis but using a nozzle capable of creating chemical gradients as described in patent application FR-2736632.

In conclusion, the invention has developed a new layer based on nitride silicon, particularly able to withstand mechanical abrasion and very satisfactory from a optically since very little absorbent, which is not the case of layers based Si₃NOT₄ known.

Very advantageously, the layer according to the invention can be deposited by chemical gas phase at high deposition rates using a nitrogen-containing precursor which may be industrial use without prohibitive cost.

The nitrogen-containing precursor used is also an adequate response because it allows to reach deposition temperatures from which it is possible without difficulty Major produce tri-layer stacks in line on the ribbon of float glass by example to achieve an anti-solar glazing with the functional layer and the TiN last layer of SiOC, the layer according to the invention being advantageously incorporated into stacking "bi-layer" classic to give a more solid interface and isolate the functional layer from oxidation after the deposition of the overcoat layer of SiOC and this, without disrupt production on an industrial line, or during heat treatments off industrial line substrate.