Transparent substrate coated with at least one thin layer based on silico nitride or oxynitride and method of obtaining same

Description of the invention

The present invention relates to a transparent substrate of the type of glass substrate coated with at least one thin layer based on silicon nitride or oxynitride, a method of making a transparent substrate of the type of glass substrate coated with at least one thin layer based on silicon nitride or oxynitride, and the use of the substrate.

The main application of the invention is the production of so-called functional window units for use in buildings or vehicles, or as a plasma TV screen. Another application is the surface treatment of containers such as glass bottles.

In the context of the present invention, the term functional window units should be understood to denote a window unit in which at least one of the constituent transparent substrates is covered with a stack of thin layers in order to give it specific properties, especially thermal, optical, electrical or mechanical properties such as resistance. for scratching.

There are so-called low-emissivity thin films, in particular composed of doped metal oxides, for example fluorine doped tin oxide (F: SnO2) or tin doped indium oxide (ITO), which can be deposited on the glass using a pyrolysis technique. A substrate mounted in a window unit, in particular in a building, once it has been coated with the low-emissivity layer makes it possible to reduce the far infrared emission outside the room or from inside the vehicle by the window unit. Thus, by reducing the energy loss caused in part by this radiation leakage, the thermal comfort in particular in winter is significantly improved.

A substrate coated in this way can be incorporated into a double-glazed window unit with the low-emissivity layer facing the gas-filled space separating the two substrates, for example positioned as a third surface (surfaces in multiple glazing units are arbitrarily numbered starting with the outermost plane in relation to interior of a room or vehicle). Therefore, the double-glazed window unit thus formed has improved thermal insulation with a low heat transfer coefficient K, while maintaining the benefits of solar energy input with high solar factor (i.e. the ratio of total energy entering the room to incident solar energy). This subject is particularly concerned with the patent applications EP-0 544 577, FR-2 704 543 and EP-0 500 445.

Low emissivity layers are usually made of good electrical conductors. This makes it possible to equip motor vehicles with window units which have been made heating / anti-icing window units by providing them with suitable power lines, the use of which is described, for example, in EP-0 353 140.

There are also thin filter layers, called selective or solar control layers, which, when deposited on substrates embedded in the window units, allow the solar radiation heat to be reduced through the window unit to the interior of the room or vehicle by absorption / reflection. They can, for example, be titanium nitride TiN (or titanium oxynitride) layers, such as those obtained by the gas phase pyrolysis technique and described in European patent applications EP-0 638 527 and EP-0 650 938. It may also be a thin (less than or equal to 30 nanometers) reflective aluminum layer, especially obtained by the condensation of metal vapors using chemical vapor deposition (CVD) or the deposition technique described in the international patent application WO 9732822.

The invention also relates to techniques for depositing these various layers, and more particularly to techniques involving a pyrolysis reaction. These techniques involve spraying "precursors", for example organometallic, which are either gaseous or powdered, or themselves liquids or as a liquid solution, onto the surface of a substrate which is heated to a high temperature. Upon contact with the substrate, the precursors decompose thereon leaving, for example, a layer of metal, oxide, oxynitride or nitride. The advantage of pyrolysis is that it allows the layers to be deposited directly on the glass ribbon in a continuous manner in a flat float glass production line, as well as that the pyrolysed layers have (in general) very good adhesion to the substrate.

The low emissivity or filter layers mentioned above often form part of the layer stack and are, at least on one of their sides, in contact with another layer, typically a dielectric material with an optical and / or protective function.

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Thus, in the aforementioned patent applications EP-0 544 577 and FR-2 704 543 a layer of low emissivity, for example made of F: SnO2, is surrounded by two dielectric layers of SiO2, SiOC or of the metal oxide type, which layers have the refractive index and the thickness selected so as to modify the optical appearance of the substrate, for example its color, especially when light is reflected.

In patent application EP-0 500 445, also mentioned previously, a low emissivity layer with ITO lies under the alumina layer in order to protect it from oxidation and also to avoid under certain conditions the need to undergo a reduction stress relief operation and / or to allow bending or hardening the already coated substrate without adversely affecting its properties.

The TiO2 layer or TiO2 / SiOC double layer that covers the TiN filter layer according to the aforementioned patent application EP-0 650 938 also has the function of preventing TiN from oxidation and usually improving its durability.

However, it is important to be able to ensure the consistency of the thin layer stack. Thus, it is essential that the layers exhibit:

- resistance to chemical agents.

This is needed because it is often the case that an already layered transparent substrate is stored for quite a long time before being incorporated into the window unit. If the substrate is not carefully packaged, which is costly, the layers it covers may be exposed directly to a polluted atmosphere or may be cleaned with detergents that are not well suited to removing dust, even if the substrates are subsequently bonded together. together in double glazing units or in laminated window units with embedded thin layers as the second or third surface, and thus protected. Moreover, in addition to these storage problems, stacks prone to chemical corrosion do not provide incentives to use the substrates as "monolithic window units or to lay down layers such that, in the case of multiple glazing units, they represent the first or fourth surface, i.e., configuration in the layers of which are exposed to the ambient atmosphere all year round;

- resistance to mechanical damage.

For example, an already layered transparent substrate may be used in a configuration in which it is easily exposed to scratch-type damage. As a result, firstly, the substrate no longer has the "correct" aesthetic appearance because it is partially scratched and, secondly, the durability of both the stack and the substrate is greatly limited due to the possible introduction of mechanically weakened spots, as the case may be.

Therefore, there is a constant search for a stack of layers with increased chemical and / or mechanical durability. However, these may not be improvements to the detriment of the optical properties of the assembly formed by the substrate and the thin layer stack.

As previously mentioned, there are already superimposed layers of dielectric material which provide a certain degree of protection to the layers beneath them in the stack. In order to preserve the integrity of those exposed to severe or prolonged corrosion and / or to completely protect possibly "weaker" lower layers, European Patent Application EP-0 712 815 describes a thin layer based on an oxide containing silicon and a third element, for example in the form of a fluorine F halogen. which facilitates the formation of a mixed silicon / aluminum structure.

This layer is particularly suitable for use as the last layer in a stack where the functional layer in the window unit is a filtering or low emissivity layer as it can fulfill an optical function, in particular an optimal appearance function under light reflection, and can guarantee a certain degree of consistency in appearance. window assemblies over time.

However, it is not necessarily able to withstand mechanical damage such as scratching as it does not have extremely high hardness.

It is known that one type of hard thin layer, especially designed to be durable and stable to mechanical abrasion and / or chemical action, is a silicon nitride based thin layer which may, depending on the circumstances, contain a certain amount of impurities such as oxygen. and coal.

Thus, there is known one type of silicon nitride-based thin film deposited on a substrate by gas-phase pyrolysis using two precursors, including a silicon-containing precursor,

The precursor is either inorganic, such as ammonia, or organic, such as hydrazine, in particular methyl-substituted hydrazine, as a silane-containing precursor.

When the deposition is carried out using a nitrogen-containing ammonia-type precursor, the temperatures are too high (greater than 700 ° C) to be suitable for, for example, the continuous deposition of a soda-lime silicate glass ribbon in a float chamber, for example. because at these temperatures these standard glasses have not yet achieved constant dimensions.

As for the nitrogen-containing hydrazine-type precursors, they have a degree of toxicity that makes their industrial use problematic.

It is also known to deposit a thin layer based on silicon nitride by the same technique as mentioned above, in particular using not two precursors but only one containing both silicon and nitrogen in the Si (NMe2) 4-nHn type. The deposition rates that can be achieved are too low to allow this deposition process to be used on an industrial scale. Moreover, the synthesis of this product is relatively complex and therefore expensive, and the respective proportions of the silicon-containing and nitrogen-containing precursor or precursors can no longer be changed.

Additionally, the known silicon nitride thin films have some disadvantages:

on the one hand, they are not necessary, sufficiently hard and less durable, in particular when they are vacuum deposited in order to impart a scratch resistance function to a substrate provided with such a single layer or a stack of thin layers containing this layer; and

on the other hand, especially when deposited by pyrolysis, they absorb wavelengths in the visible light range, which is detrimental to the optics.

The object of the present invention is therefore to avoid the aforementioned disadvantages, and thus to develop a new thin layer based on silicon nitride or oxynitride, having a higher hardness, at the same time being much less absorbing, and able to form part of a thin layer stack, in particular so as to fulfill the function of securing the stack of thin layers. the layers in which it is incorporated against chemical action.

It is also an object of the present invention to provide a method for producing a transparent substrate coated with at least one thin layer based on silicon nitride or oxynitride, in particular using a vapor phase pyrolysis technique which is suitable for continuous deposition on a glass ribbon in a float bath chamber, and which allows for a faster deposition rate.

A transparent substrate of the glass substrate type, covered with at least one thin layer based on silicon nitride or oxynitride, is characterized according to the invention in that the thin layer deposited at a temperature between 550 ° C and 760 ° C, preferably between 660 ° C and 760 ° C has geometric thickness between 5 nanometers and 5 micrometers, in particular between 20 and 1000 nanometers, and contains the elements Si, O, N, C in the following amounts in atomic percentages:

- Si: 30 to 60%, in particular 40 to 50%,

- N: from 10 to 56%, in particular from 20 to 56%,

- O: from 1 to 40%, in particular from 5 to 30%,

- C: from 1 to 40%, in particular from 5 to 30%.

Preferably the thin layer contains at least one dopant, in particular in the form of halogen, preferably fluorine F and / or in the form of phosphorus P or boron B, preferably in an amount in atomic percentages between 0.1 and 5%.

Preferably the thin layer is homogeneous or has a composition gradient towards its thickness.

Preferably the thin layer has a light absorption coefficient of A_L. less than 2% at a geometric thickness of 100 nanometers.

Preferably the thin layer has a refractive index greater than 1.6, in particular between 1.8 and 2.0, preferably 1.85.

Preferably the thin layer forms part of a thin layer stack of which at least one layer is a functional layer having thermal properties, in particular filtering, sun protection or low emissivity, and / or photocatalytic properties, such as a mirror-function layer consisting of a doped metal oxide. , of a nitride / oxynitride of a metal or a metal such as aluminum or silicon, or part of a stack of anti-reflection layers.

Preferably the thin layer is below the functional layer, in particular as a barrier layer for the diffusion of ions, especially alkali metals and oxygen from a substrate, of the glass substrate type, or as a barrier layer for the migration of ions from the functional layer to the substrate, substrate type

PL 191 071 B1 glass, which is to be used for the production of a plasma screen, or as a seed layer or having an optical role.

Preferably, the thin layer is on the functional layer, in particular as a layer protecting the functional layer against high-temperature oxidation or against chemical corrosion, a mechanical protection layer such as a scratch-resistant layer, an optical layer, or a layer improving the adhesion of the upper layer.

Preferably, the functional layer is made of fluorine doped tin oxide F: SnO 2, tin doped indium oxide ITO, indium doped zinc oxide In: ZnO, fluorine doped zinc oxide F: ZnO, aluminum doped zinc oxide Al: ZnO or tin doped zinc oxide Sn: ZnO, mixed oxide Cd2SnO₄, titanium nitride TiN or titanium oxynitride, or zirconium nitride ZrN.

Preferably the thin layer is the only layer covering the substrate or is associated with the anti-burn layer as a scratch-resistant functional layer.

Preferably the thin layer has a geometric thickness of at least 250 nanometers.

Preferably, the thin layer forms part of a glass / TiN and / or ZrN-type stack / SiOC and / or SiO2 thin layer and provides a strong interface between TiN and / or ZrN and SiOC and / or SiO2, and an anti-oxidation layer after the deposited top layer is deposited. SiOC and / or SiO2 layers on and / or off the production line.

Preferably the TiN layer has a geometric thickness between 10 and 50 nanometers, the thin layer has a geometric thickness between 5 and 20 nanometers, the superimposed SiOC and / or SiO2 layer has a geometric thickness between 30 and 100 nanometers and the stack has a selectivity of at least 7%.

A method for producing a transparent substrate of the glass substrate type coated with at least one thin layer based on silicon nitride or oxynitride by a gas phase pyrolysis technique using at least two precursors, including at least one silicon precursor and at least one nitrogen precursor, is characterized by according to the invention in that at least one amine nitrogen precursor is used and the thin layer is deposited at a temperature between 550 ° C and 760 ° C, preferably between 660 ° C and 760 ° C.

Preferably, a silane such as silicon hydride and / or an alkyl silicon or a silazane is used as the silicon precursor.

Preferably, the amine used is a primary, secondary or tertiary amine, in particular one with alkyl radicals having from 1 to 6 carbon atoms each.

Preferably, the amine used is ethylamine C2H5NH2, methylamine CH3NH2, dimethylamine (CH3) 2NH, butylamine C4H9NH2 or propylamine C3H7NH2.

Preferably, the ratio of the amount of nitrogen precursor or precursors to the amount of silicon precursor or precursors, expressed as mole numbers, is between 5 and 30, preferably 10.

Preferably a dopant precursor independent of silicon precursors and nitrogen precursors is used and is, in particular, a fluorinated gas of the CF4 type when doping with fluorine F, and an organic phosphate carrier gas such as PO (OCH3) 3, or a gas such as triethylphosphite, trimethylphosphite, trimethylborate, PCh or PF5, PBr3 or PCb when doping is phosphorus P or boron B.

Preferably, the thin film is deposited in a substantially inert or hydrogen-containing oxygen-free atmosphere continuously on the float glass ribbon in a float chamber and / or in an inert or reducing atmosphere control box.

The invention also relates to the use of a substrate as described above for the production of window units provided with thin films for sun protection of the filtering or low emissivity type, and / or scratch-resistant, and / or having a mirror or anti-glare function, and / or having a dirt-resistant function. , on the "front and rear" surfaces of flat panel type emission screens, such as plasma screens.

Preferably, the substrate is used to manufacture window units provided with curable / bendable and / or highly durable thin films.

Preferably, the substrate is used for monolithic, laminated or multi-pane window units in which the substrate or substrates are transparent or uniformly colored.

The invention also encompasses the use of a substrate as described above for treating the inner and / or outer surface of containers, such as glass bottles or flasks.

Surprisingly, this thin layer turned out to be both hard compared to other known silicon nitride thin layers and very transparent and therefore having low or no absorbance at wavelengths in the visible light range: high content

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Si and N show that it is a material composed mainly of silicon nitride. By changing the proportion between the minority components, type C and O, the layer properties can be fine-tuned. Thus, by varying the relative proportions of carbon and oxygen, it is possible to both, for example, "fine-tune" the density and refractive index of the thin layer to impart mechanical hardness and optical properties that are useful and desirable. A possible change in the aforementioned relative proportions can be realized, for example in terms of optics, by using a gentle CO2-type oxidizing agent. This is because carbon and nitrogen tend to increase the refractive index, and oxygen has the opposite effect.

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 may contain other elements in the form of impurities such as fluorine, phosphorus or boron, preferably in an amount in atomic percentages between 0.1 and 5%. The layer may also be homogeneous or have a composition gradient towards its thickness.

Preferably, the thin layer has a light absorption coefficient of A_L. less than 2% at a geometric thickness of 100 nanometers, and its optical quality has been particularly demonstrated when the layer in question is deposited using a gas-phase pyrolysis technique as explained below.

The thin layer is preferably part of a thin layer stack, at least one layer of which is a functional layer having thermal properties, in particular filtering, sun protection or low emissivity and / or electrical properties, and / or optical properties, and / or photocatalytic properties, such as like a layer having a mirror function, consisting of a doped metal oxide, metal nitride / oxynitride, or a metal such as aluminum or silicon. It can also form part of a stack of anti-reflective layers, acting as a high-index or "intermediate" index layer.

It is possible to choose as the doped metal oxide or nitride / metal oxynitride, fluorine doped tin oxide F: SnO2, tin doped indium oxide ITO, indium doped zinc oxide In: ZnO, fluorine doped zinc oxide F: ZnO, aluminum doped zinc oxide Al: ZnO, tin-doped zinc oxide Sn: ZnO, mixed oxide Cd2SnO₄, titanium nitride TiN or zirconium nitride ZrN.

Such a layer may be below the functional layer. It can then, in particular, act as a barrier layer for the diffusion of ions, in particular alkali metals and oxygen from a glass-type substrate, or else as a seed layer, and / or have an optical role (color modification, anti-opalescence effect, anti-reflection effect). In some applications such as a plasma screen, it may also act as a barrier layer for the migration of Ag + ions from the silver-based functional layers into a glass-type substrate.

According to another variant of the invention, the layer can be placed on the functional layer. It can therefore serve, in particular, as a protective layer for the functional layer against high-temperature oxidation or against chemical corrosion, as a mechanical protective layer in the form of a scratch-resistant layer, as an optical layer or as a layer improving the adhesion of the upper layer.

According to yet another variant, the thin layer is the only layer covering the substrate and preferably has a scratch resistance function. The geometric thickness of the layer can be modified very freely over a very wide range from 5 nanometers to 5 micrometers, in particular between 20 and 1000 nanometers. A fairly substantial thickness, for example at least 250 nanometers, is advantageous for accentuating the scratch-resistant effect of a substrate provided with at least one layer in question, and a layer having a lower thickness is generally desirable for other functions (nucleation, adhesion, etc.).

The present invention also relates to a method for the preparation of the above-defined substrate which consists in depositing a thin layer based on silicon nitride by a vapor phase pyrolysis (also called CVD) technique using at least two precursors, including at least one silicon precursor and at least one nitrogen precursor. In the process of the present invention, at least one nitrogen precursor is an amine.

The choice of such a nitrogen-containing precursor is particularly advantageous: it has a reactivity sufficient to permit the deposition to be carried out at temperatures at which the standard soda-lime silicate glass substrate has completely achieved its constant dimensions, in particular in the context of a glass production line of the type. float.

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In addition, the deposition rates achieved are sufficiently high to allow the deposition of substantial thicknesses in the float chamber.

The selected silicon containing precursor may preferably be a silane in the form of silicon hydride and / or alkyl silicon or a silazane.

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

Thus it could be C2H ethylamine₅NH2, methylamine CH3NH2, dimethylamine (CH3)₂NH, butylamine C4H9NH2 or propylamine C3H7NH2.

The selection of an appropriate amine to obtain a layer having a given geometric thickness and / or a given refractive index results from a tradeoff to be found among a number of parameters such as steric hindrance, reactivity, and the like.

Preferably, the ratio of the amount of nitrogen precursor to the amount of silicon containing precursor, expressed as mole numbers, is between 5 and 30, and is preferably 10.

In fact, it is important to control this ratio in order to avoid, on the one hand, an insufficient nitrogen content and, on the other hand, the risk of nucleation in the gas phase and as a result of the risk of powder formation. The risk of clogging of the device and reduced production efficiency is thus reduced.

When it is desired to incorporate an dopant, the dopant precursor is selected independently of the silicon-containing precursor and the amine precursor. This may be, for example, a fluorinated gas such as CF4 when the desired dopant is Fluorine F, or an organic phosphate carrier gas such as PO (OCH3) 3, or a gas such as triethylphosphite, trimethylphosphite, trimethylborate, PF5, PCh, PBr3 or PCl5 when the desired dopant is phosphorus P or boron B. Advantageously, these admixtures typically allow the deposition rate to be increased.

The deposition temperature is suitable for the choice of precursors, in particular amines. Preferably, it is between 550 and 760 ° C. It can advantageously be between 600 and 700 ° C., i.e. between the temperature at which the glass, in particular the silico-soda-lime glass, is dimensionally stabilized and the temperature at which it exits the float chamber.

Preferably, in a variant where the substrate glass blend is suitable for electronic applications, the temperature is between 660 and 760 ° C.

According to this variant, a preferred mixture may be that described in patent application WO 96/11887. This mixture, expressed as a percentage by weight, has the following composition:

<td>SiO2</td><td> 45</td><td> - 60%</td>

<td>Al2O3</td><td> 0</td><td> - 20%</td>

<td>ZrO2</td><td> 0</td><td> - 20%</td>

<td>B2O3</td><td> 0</td><td> - 20%</td>

<td>Na2O</td><td> 2</td><td> - 12%</td>

<td>K2O</td><td> 3,5</td><td> - 9%</td>

<td>CaO</td><td> 1</td><td> - 13%</td>

<td>MgO</td><td> 0</td><td> - 8%</td>

with conditions:

SiO₂ + Al₂O3 + ZrO₂ &lt;70% · Al2O3 + ZrO2&gt; 2% · Na2O + K2O&gt; 8% and option BaO and / Iub SrO in the following proportions:

11% &lt;MgO + CaO + BaO + SrO &lt;30% with annealing bottom temperature of at least 530 ° C and with factor α 80 to 95 x 10⁷ (° C).

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Another preferred blend taken from patent application FR 97/00498 is a blend with the composition, still in percent by weight:

<td>SiO2</td><td> 55</td><td>- 60%, preferably 55 - 60%</td>

<td>Al2O3</td><td> 0</td><td> - 5%</td>

<td>ZrO2</td><td> 5</td><td> - 10%</td>

<td>B2O3</td><td> 0</td><td> - 3%</td>

<td>Na2O</td><td> 2</td><td> - 6%</td>

<td>K2O</td><td> 5</td><td> - 9%</td>

<td>MgO</td><td> 0</td><td>- 6%, preferably 1 - 6%</td>

<td>CaO</td><td> 3</td><td>- 11%, preferably 7 - 11%</td>

<td>SrO</td><td> 4</td><td> - 12%</td>

<td>BaO</td><td> 0</td><td> - 2%</td>

with conditions:

· Na2O + K2O&gt; 10% · MgO + CaO + SrO + BaO&gt; 11%, preferably&gt; 15%, and with an annealing lower temperature of at least 600 ° C. (Another variant is to choose the A ^ O3 content from 5 to 10% and the ZrO2 content from 0 to 5%, keeping the proportions of the other components unchanged).

It should be recalled that the so-called lower annealing temperature (stress decay temperature) is the temperature at which the glass reaches a viscosity η equal to 10 Pa · s.

Thus, it is preferable to deposit the layer in an essentially inert or reducing atmosphere, for example an N2 / H2 mixture with no or almost no oxygen, continuously on a float glass ribbon in a float chamber and / or in a neutral holding box, free from oxygen. oxygen in the atmosphere to deposit the layer downstream of the float glass production line, possibly at slightly lower temperatures.

The invention therefore allows the production of filtering, solar energy controlling window units with stacks of the type:

- glass / TiN and / or ZrN / layer according to the present invention / SiOC and / or SiO2, the thin layer according to the present invention enabling a much stronger phase interface between, on the one hand, the TiN layer and / or the ZrN layer and , on the other hand, a layer of SiOC and / or a layer of SiO2. The layer also makes it possible to provide any effective protection of TiN and / or ZrN against the risk of surface oxidation, either on the production line after the SiOC and / or SiO2 layer has been deposited, or off-line, e.g. when the substrate provided with the stack of layers has already been cut and processed thermal, such as flexing / hardening or stress relief. Preferably, the layer has a geometric thickness between 5 and 20 nanometers, and the applied SiOC and / or SiO2 layer has a geometric thickness between 30 and 100 nanometers;

and more types:

- glass / Al / a thin layer according to the present invention, the reflective aluminum layer either having a low thickness (less than or equal to 30 nanometers) or a greater thickness when a mirror function is desired, such as that described in the aforementioned international patent application WO 9732822, and the thin layer according to the present invention serves as both an anti-oxidation agent and a function of imparting scratch resistance.

The invention also makes it possible to produce window units whose primary function is to provide scratch resistance, i.e. window units used as floor panels and glass furniture, in which the glass substrate is only coated with the Si3N4-based thin layer of the present invention, optionally in combination with a layer. anti-opalescence.

Preferably, the glass is thus protected against any wear. The thin substrate layer of the present invention can also be combined with the low emissivity layers using stacks of the type:

- glass / SiOC / F: SnO2 or ITO / thin layer according to the present invention.

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In these stacks, the underlying SiOC layer can of course be replaced by another metal oxide, such as that described in patent application EP-0 677 493.

In accordance with the present invention, it is possible to manufacture any type of functional thin-film stacked window unit that has high durability and is capable of curing and / or bending when the substrate is a glass substrate.

The invention further enables the production of window units for which a dirt-resistant function is desired by the use of stacks of the type:

- glass / thin layer according to the present invention / TiO2.

In these stacks the thin layer according to the present invention is essentially intended to act as a barrier against alkali metals migrating from the glass into the titanium oxide based layer TiO2, thereby enhancing the photocatalytic effect of the latter. Additionally, if the thickness of the layer according to the present invention is sufficient to cause inertial interactions, it also functions as an anti-palescence layer.

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

However, it can also be in the form of an at least partially crystallized film, such as that described in WO 97/10186.

Finally, the invention allows the production of flat screen type emission screens, such as plasma screens. The thin layer may then perform various functions, depending on the nature of the chemical composition of the substrate on which it is deposited and / or on the location (front or back surface) on the same substrate in the screen, and therefore on the nature of the functional layers applied thereon. such as electrodes and phosphors (photophores), essential components for the operation of the screen.

Thus, in the case where the glass substrate is of the "blocked alkali" type, i.e. largely free of diffusible elements of the alkali type, the thin layer according to the present invention very effectively fulfills the essential role of a barrier layer for the migration of the elements diffusing from the top coating towards the substrate, in particular a silver-based electrode.

Likewise, in the case where the composition of the glass substrate includes alkali metals, it also acts as a barrier layer to the migration of these metals.

The invention is also applicable to the surface treatment of containers, such as glass bottles or flasks, the hard layer according to the present invention reinforcing said containers, for example when handled when damage is most likely to occur , regardless of the observed heterogeneity in the relative thickness of the discussed material. layers. The deposition of the hard layer according to the present invention can thus be carried out on the outer wall of the containers with mechanical reinforcement, in particular impact protection, but also on the inner wall of the containers, so as to prevent ingredients from escaping from the substrate, for example.

The subject matter of the invention is explained in more detail in the embodiment in which Fig. 1 shows a transparent silicon-soda-lime glass substrate coated with a thin layer based on silicon nitride, and Fig. 2 shows a window unit with a stack of thin films containing a thin layer based on silicon nitride. silicon nitride. For the sake of clarity, this drawing is out of proportion with the relative thicknesses of the different materials.

In all of the following examples, the deposition of all thin layers is performed in a float chamber.

Example I.

FIG. 1 shows, in accordance with the present invention, a transparent silicon-soda-lime glass substrate 1 with a thickness of 3 millimeters, for example that sold under the trademark PLANILUX by Saint-Gobain Vitrage, coated with a silicon nitride thin film 2.

Thin layer 2, based on silicon nitride, is obtained by a gas-phase pyrolysis technique using SiH4, which is a silane-containing precursor, and C2H ethylamine₅NH2, which is a nitrogen-containing precursor.

The flow rates of the precursors are chosen such that the volume ratio of the amount of ethylamine to the amount of silane is approximately 10. This parameter is advantageous in that it optimizes the deposition of each of the layer components. This is because it has been observed that this ratio must not be:

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- too high; otherwise there may be a risk of nucleation in the gas phase and thus the risk of formation of a powder; or

- too short; otherwise, insufficient nitrogen incorporation into the layer may occur.

The ratio range of 5 to 30 turns out to be quite satisfactory when it is desired to deposit a layer 50 to 300 nanometers thick using silane and ethylamine.

The deposition was carried out on the substrate 1 heated to a temperature between 600 and 650 ° C under atmospheric pressure.

Under these conditions, the growth rate of layer 2 according to the invention reached 60 nanometers per minute.

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

Microanalysis shows that layer 2 contains, at atomic percentages, 32.7% silicon, 30.6% nitrogen, 21.1% carbon and 15.6% oxygen.

The process of the present invention makes it possible to modify the amounts of the various components incorporated, in particular such as carbon, by changing various parameters such as the temperature at which the deposition is carried out, the use of an amine other than ethylamine as nitrogen precursor or a mixture of amines, or ammonia added to ethylamine. .

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

The spectrophotometric characteristics of such a layer are given in the table below, where Tl, Rl and Al are the values ​​of light transmission, light reflection and light absorption, respectively:

Tl R_l AND_llayer 2 84 13 3 these values ​​were measured using a D65 illuminator in almost perpendicular incident light.

It is observed that the layer according to the present invention has a very low light absorption and is free from any haze. (Note that turbidity is the ratio of the scattered light transmission to the light transmission at a wavelength of 550 nanometers.)

The test was carried out on the substrate 1 according to the present invention covered with a single layer 2, which made it possible to determine the mechanical strength of this layer. This test is performed with abrasive wheels made of abrasive powder embedded in the elastomer. The machine is manufactured by Taber Instrument Corporation. This is the standard Model 174 Abrasion Tester and the grinding wheels are CSIOF type with a weight of 500 g. Coated substrate 1 is rotated locally 50 and then the number of scratches is counted using an optical microscope in four squares of 1 inch, i.e., 2.54 cm, square. After the scratches are counted, the average scratch number R in a square is calculated. Finally, the Taber number Ts is calculated from the formula:

Ts = - 0.18R + 10.

For layer 2 according to the present invention having a geometric thickness of 300 nanometers this number is 9.3. This value indicates very little damage and is therefore indicative of a very good scratch resistance of the substrate layer of the present invention.

From the comparative example, it can be seen that the 340 nanometer fluorine doped tin oxide F: SnO2 layer, known as the "hardest" layer deposited by gas phase pyrolysis, yielded a Taber number of 9.1 on the test.

From this it is clearly seen that the silicon nitride-based substrate layer of the present invention is a layer that inherently has very good mechanical abrasion resistance and, from an optically standpoint, is very satisfactory because it is very transparent and has very low absorbance at wavelengths from visible range.

Example II.

Figure 2 shows a sun protection window unit having a stack of thin layers into which a layer 2 according to the present invention is incorporated.

A transparent silico-soda-lime glass substrate 1 with a thickness of 6 millimeters is covered with three successive layers:

a first TiN layer 3 with a thickness of 23 nanometers, obtained by gas-phase pyrolysis with titanium tetrachloride TiClU and methylamine CH3NH2, as described in the patent application EP-0 638 527;

PL 191 071 B1

- a second layer 2 according to the invention with a thickness of approximately 10 nanometers and a refractive index of 1.85, deposited under the same conditions as in Example 1; and

a third layer 4 of SiOC silicon oxocarbide with a thickness of 65 nanometers and a refractive index of 1.65, also obtained by gas phase pyrolysis with silane and ethylene as described in the patent application EP-0 518 755, layer substantially containing silicon is oxidized on leaving the buoyancy chamber, and more specifically in the lehr.

The stack is therefore of the type:

- glass / TiN / SiaNL / SiOC.

Example III.

This comparative example was produced using a stack consisting of:

- glass / TiN / SiOC, in which the two layers, TiN and SiOC, have the same characteristics as defined above and are obtained under the same deposition conditions.

It is observed that the layer 2 according to the invention, even at a low thickness, forms a very strong interface between the first TiN layer 3 and the superimposed SiOC layer 4.

In addition, the layer 2 according to the present invention, after the application of the upper SiOC layer 4, provides effective protection of the TiN against the risk of surface oxidation in the production line. Where appropriate, it insulates the TiN as the already cut substrate undergoes successive heat treatment steps such as flexure / hardening or stress relief.

Likewise, after measuring the spectrophotometric values, in particular the light transmission T1 as well as the solar factor Fs, for each of the two stacks of Examples 2 and 3, it is observed that the selectivity corresponding to the difference T1 - Fs is much better for the stack with three layers z of example 2, with the layer 2 according to the present invention sandwiched between two layers of TiN and SiOC, because the selectivity value is 10%. In the case of the two-layer stack of Example 3, this value is less than 7%.

Finally, it should be noted that if in the above two configurations the silicon nitride layer is homogeneous throughout its thickness, it is also obviously possible to provide some compositional heterogeneity in the direction of its thickness, in particular so as to vary the refractive index and take into account optimal optical and / or chemical compatibility with the layer above and / or below it, such as, for example, the SiaN4 enriched layer on the TiN side and SiON enriched layer on the SiOC side in a solar control window unit using the same layers as in Example 2. This "gradient" layer can be obtained by the same vapor-phase pyrolysis deposition technique, but with a nozzle capable of producing chemical gradients, such as that described in patent application FR-2 736 632.

In conclusion, the invention provides a silicon nitride-based layer which has a particular ability to withstand mechanical abrasion and is highly satisfactory from an optical point of view since it has a very low absorbance, which is not the case with the known SiaN4-based layers.

Very advantageously, the layer according to the invention can be deposited by gas-phase pyrolysis at high deposition rates, using a nitrogen-containing precursor that can be used on an industrial scale without incurring excessive costs.

The nitrogen-containing precursor used furthermore has a suitable reactivity as it allows to reach deposition temperatures at which it is possible without great difficulty to produce a three-layer stack on a float glass strip in sequence, for example to produce a solar control window assembly with a functional layer of TiN and a final layer of SiOC. , the layer according to the present invention preferably being incorporated into a conventional two-layer stack, to create a stronger interface and protect the functional layer from oxidation after deposition of the upper SiOC layer, without interrupting production on the production line, or also during off-line heat treatment of the substrate.

Patent claims