Glazing provided with a stack of thin layers for solar protection and/or heat insulation

IS 2 298 192 T3

DESCRIPTION

Glazing provided with a stack of thin layers for sun protection and / or thermal insulation.

The invention relates to transparent substrates, in particular made of rigid mineral material, such as glass (or organic, such as a polymer substrate, rigid or flexible), said substrates being coated by a stack of thin layers comprising at least one performance layer. of a metallic type that can act on solar radiation and / or infrared radiation of great wavelength.

The invention relates more particularly to the use of such substrates for manufacturing thermal insulation and / or solar protection glazing. These glazings are intended both to equip buildings and vehicles, in particular with a view to reducing the effort of air conditioning and / or reducing excessive overheating caused by the ever increasing importance of glazed surfaces in rooms.

A type of layer stacking known to confer such properties on substrates is constituted by at least one metallic layer, such as a silver layer, which is arranged between two coatings of dielectric material of the metallic oxide type. This stacking is generally obtained by a succession of deposits made by a technique that uses vacuum, such as sputtering eventually assisted by magnetic field. Two very thin metallic layers can also be envisaged on both sides of the silver layer, the underlying layer as a fixation and nucleation layer, and the overlay as a protective or "sacrificial" layer in order to avoid alteration of the silver if the oxide layer on top is sputter-deposited in the presence of oxygen.

Thus, European patents EP-0 611213, EP-0 678 484 and EP-0 638 528 of stacks of this type, of one or two layers based on silver, are known.

It is also known from patent EP-0 847 965 a stack of two layers of silver conceived in such a way that it can undergo a heat treatment of the pumping or quenching type without significant optical evolution, thanks to the use of oxygen barrier layers of the nitride type. silicon and layers that stabilize the silver layers.

Finally, it is known from patent EP-0 844 219 a stacking of two layers of silver -of very different thicknesses, which allow obtaining glazing with a solar factor reduced to at least 32% (the solar factor FS is the ratio between the total energy that enters the premises through the glazing considered and the incident solar energy).

In general, but more particularly in the domain of double glazing for the habitat, it is interesting to be able to regulate the level of light transmission of the glazing in a certain interval without, however, having to completely reconfigure the stack of thin layers each time.

Solutions have already been proposed to meet this objective: patent FR-2 751 666 proposes to insert an absorbent layer based on iron oxide between the glass and the first dielectric layer. Patent FR-2 708 262 proposes to insert an absorbent layer of the titanium nitride type in contact with and on top of the silver layer. However, these solutions present a drawback both in one case and the other, in the case in which the stack of thin layers undergoes a heat treatment of the annealing, pumping or quenching type: the absorbent layer will largely evolve optically and / or optically evolve the layer stack as a whole.

Indeed, if it is in contact with glass, or with silver, under the effect of heat it will have a tendency to oxidize, deteriorate or deteriorate the adjacent layers in a more or less controllable manner. Thus, if the absorbent layer is in direct contact with the silver layer it tends to destabilize it by oxidizing it. If it is in contact with the glass, the layer will be modified by diffusion of the alkali ions from the glass.

The object of the invention is then to regulate the level of light transmission of glazings provided with stacks of thin layers described above, without the aforementioned drawback, namely, without creating a strong optical evolution of the stacks in the event of heat treatment.

Secondarily, the invention also aims to regulate the level of light transmission and / or the selectivity of the glazing, however without increasing the level of external light reflection too significantly, preferably by limiting this light reflection to a value lower than 20%.

Secondly, the object of the invention is also that this control of the light transmission level is obtained in a relatively simple way and is flexible to use on an industrial scale.

The invention first aims at a glazing that comprises at least one transparent substrate provided with a stack of thin layers comprising an alternation of n functional layer (s) with reflection properties in infrared and / or solar radiation and n + 1 coatings composed of one or more layers of dielectric material, so that each functional layer is arranged between two coatings. Furthermore, at least one absorbent layer in the visible is inserted between two layers of dielectric material of at least one of said coatings. In this configuration, the absorbent layer is neither in direct contact with the glass (which limits the problems of diffusion of oxygen and alkalis under the effect of heat) nor in direct contact with the silver (which limits the

ES 2 298 192 T3 problems of deterioration of the silver layer induced by oxidation of the absorbent layer on contact, also under the effect of heat).

According to a first variant, the stack comprises a single functional layer arranged between two coatings (case in which n = 1).

According to a second variant, the stack comprises two functional layers alternated with three coatings (case in which n = 2).

Conveniently, the functional layer (s) are based on silver or on a metallic alloy containing silver.

The absorbent layer (or absorbent layers, the invention not being limited to the insertion of a single absorbent layer) can be chosen from different materials: it can be a metal or a metallic alloy of the Ti, Nb, Zr or NiCr type. It can also be a metal oxide, such as chromium oxide, iron oxide or a sub-stoichiometric oxide of titanium or zinc. Finally, it can be a metal nitride, such as titanium, niobium, zirconium, chromium or NiCr nitride.

Preferably, the thickness of the absorbent layer in the visible according to the invention is limited to small values: its thickness is conveniently less than or equal to 7 nm, and even rather less than 5 or 3 nm. Normally a thickness between 1 and 3 nm is chosen: the first characteristic of the absorbent layer, mentioned above, is the absence of its direct contact with the glass or with the silver layer. Its second characteristic is its thinness: being very thin, it does not serve to greatly reduce the transmission, but rather to adjust it precisely in some percentage units.

According to a preferred embodiment of the invention, the absorbent layer in the visible is located between two layers of dielectrics of which at least one is based on a silicon nitride and / or aluminum.

In a first variant, it is found between two layers of one of these nitrides. This is, in effect, the optimal configuration to "encapsulate" in the best way the absorbent layer to isolate it from interactions with species that can oxidize or degrade it (oxygen from the air or glass, or from the adjacent oxide layer, species that diffuse from the silver layer under the effect of heat ...). Indeed, silicon and / or aluminum nitrides are known for their great chemical inertness, even at high temperatures. They not only play their usual role of dielectric with an optical function and with a protection function of the silver layers (with a refractive index of the order of 2), but they will also play the role of screen layers.

In this configuration, a heat treatment of the annealing, pumping or quenching type will not (or very little) affect the absorbent layer, making the nitride layers a barrier to oxygen and preventing it from oxidizing. Consequently, there will be no more noticeable variation in the light transmission of the stack as a whole than that observed for the stack in the absence of an absorbent layer (for example a modification of 3% at most).

In a second variant, the absorbent layer in the visible is arranged in the coating between a layer based on metal oxide (s) (or silicon oxide) and a layer of aluminum and / or silicon nitride. The preferred configuration is that the oxide layer is under the absorbent layer, and the nitride layer is on top. According to this variant, there is direct contact between the absorbent layer and the oxide layer. Consequently, in case of heat treatment the absorbent layer may undergo oxidation, but on the one hand it is limited (especially when a nitride covers it, the insulator of oxygen from the atmosphere), on the other hand this oxidation can be beneficial in the sense that the absorbent layer gets to "trap" oxygen and thus preserve the other layers of the stack from oxidation. A slightly higher variation in light transmission of the stack is then generally observed than in the case of the first variant, which can reach up to 4 to 5% for example.

At least one of the coatings of the stack according to the invention comprises at least one oxide layer chosen from at least one of the following oxides: zinc oxide, tin oxide, titanium oxide, silicon oxide, tantalum oxide, niobium oxide, zirconium oxide. As stated in the patent EP-0 847 965 cited above, it is indeed interesting that the coatings comprise both layers of metal oxide and layers of silicon or aluminum nitride.

Thus, under at least one of the functional layers it is convenient to have a layer based on zinc oxide, which tends to facilitate the adhesion and crystallization of the functional layer based on silver and thus increase its quality and stability at high temperature. .

It is also desirable that the or at least one of the functional layers is under a layer based on zinc oxide to increase adhesion.

To ensure that the stack can undergo heat treatments of the annealing, quenching or pumping type without too significant optical evolution, it is preferable that each of the coatings comprises at least one layer of silicon nitride and / or aluminum.

IS 2 298 192 T3

Optionally, a thin layer of sub-stoichiometric metal or metal oxide (possibly nitrided) can be inserted between each functional layer and the coating arranged above it and / or the coating arranged below it. These can be layers of titanium, niobium, nickel-chromium alloy, which eventually become partially oxidized during the deposition of the stack (when the following layer is deposited by reactive sputtering in the presence of oxygen). They are usually designated under the name of fixing layers (for the layer below) or sacrificial layer or layer "blocker" (blocking) (for the layer above).

According to a preferred variant, the stack comprises two silver-based functional layers with three coatings, and the absorbent layer in the visible is inserted in the so-called "intermediate" coating, that is, the one arranged between the two functional layers. It has been shown that it is in this configuration that the absorbent layer appears the most stabilized / insulated, and that the external reflection appearance of the glazing is the best. An example of stacking according to the invention is as follows:

Transparent substrate / Yes₃N₄/ ZnO / Ag / ZnO / Si₃N₄/ TiN or NbN / Si₃N₄/ ZnO / Ag / ZnO / Si₃N₄ possibly with thin layers of metal (possibly partially oxidized) of the titanium type on one of the faces at least of the silver layers.

The invention relates to all glazing provided with these stacks; the laminar glazing (where the stack is deposited on one of the rigid substrates or on a flexible substrate of the polyethylene terephthalate type, PET, which is led to be assembled with the two rigid substrates by thermoplastic sheets), the glazing laminar so-called asymmetric, multiple glazing of the double-glazing type preferably with stacking on face 2 or face 3 of the glazing (numbering the faces of the substrates, conventionally, from the outermost face to the inner face of the glazing once mounted in a room). The invention relates more particularly to double glazing which has:

Σ luminous transmissions T_L 75% at the most, in particular 70% or 65% at the most, particularly at least 40%, or between 55 and 65% or between 45 and 55%, particularly in the vicinity of 50% and 60%, me

Σ an external light reflection R_L less than or equal to 20%, particularly 17% at the most, and / or

Σ values ​​of a * and b * in external light reflection less than or equal to 1, preferably negative (even after having undergone heat treatments of the quenching type), more particularly in the case of stacks of two silver layers.

The key point of the invention is therefore that the absorbent layer in the visible inserted in a particular way in conventional stacks makes it possible to regulate their light transmission without optically evolving in case of heat treatment and / or without disturbing the reflection aspect of the substrate .

Conveniently the absorbent layer (s) according to the invention have an intrinsic light absorption of at least 3%, in particular between 4 and 15% or between 6 and 12% (each one or the set of said absorbent layers if the invention uses several of them).

The invention will be described in more detail with the aid of the following examples.

In all of the examples, the stacks are deposited on a 6 mm silico-sodium-calcium clear glass substrate. The substrate is then mounted in double glazing with a second identical glass substrate, so that the stack is on face 2 and that the gas sheet interposed between the 2 glasses is argon and 12 mm thick. These glazings are primarily intended for the home, such as thermal insulation / solar control glazing).

In all the examples, a first double-glazing assembly is made with the glass provided with non-tempered layers, then a second assembly in which the glass, once provided with the stacking of layers, has undergone a tempering under the usual conditions in the field (which includes heating the glass at 640 ° C for several minutes).

All layers of the stacks are deposited by magnetic field-assisted sputtering: (oxide layers by reactive sputtering in the presence of oxygen of metallic targets or possibly sub-stoichiometric ceramic targets, nitride layers by reactive sputtering in the presence of nitrogen).

IS 2 298 192 T3

Comparative Example 1

Layer stacking is as follows: (the table below indicates the layer thicknesses in nanometers)

<img file="ES2298192T3_D0001.tif" />

It is comparative, since it does not have an absorbent layer in the visible between two layers of dielectric. The two layers of titanium on top of the silver layers are very thin and become oxidized (at least partially) during the deposition of the next ZnO layer (as in the examples below).

Examples 2 and 3 according to the invention

The examples reflect the stacking of the example 1 adding a layer of titanium nitride "in the middle" of the Si layer.₃N₄ of the dielectric coating between the two layers of silver. This is the first variant of the invention, in which the absorbent layer is protected from oxidation by the two layers that surround it.

The table below regroups the thicknesses in nm of each of the layers.

<td></td><td>Example 2</td><td>Example 3</td>

<td>Glass</td><td> -</td><td> -</td>

<td>Yes₃N &lt;</td><td> 31</td><td> 31</td>

<td>ZnO</td><td> 10</td><td> 10</td>

<td>Ag</td><td> 9.5</td><td> 9,5</td>

<td>You</td><td> 0,8</td><td> 0,8</td>

<td>ZnO</td><td> 10</td><td> 10</td>

<td>SijN »</td><td> 32</td><td> 32</td>

<td>TiN</td><td> 0,7</td><td> 1,4</td>

<td>Yes₃N₄</td><td> 32</td><td> 32</td>

IS 2 298 192 T3

<img file="ES2298192T3_D0002.tif" />

The table below summarizes the following data for each of Examples 1 to 3:

transmission T_L in% according to Illuminant D65;

the dominant wavelength T_D transmission, in nm;

the Rlext exterior light reflection value in%;

the value of a * and b * in light reflection according to the colorimetry system (L, a *, b *);

the solar factor FS, according to a DIN standard.

These values ​​are given for double glazing without toughening of layered glass ("untempered") and for double glazing with tempered layered glass ("with temper").

<td>Examples</td><td>T_L</td><td>Ad</td><td>Rlext</td><td>to*</td><td>b *</td><td>FS</td>

<td>Comparative Example 1</td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>without temper</td><td> 63,4</td><td> 516</td><td> 17,1</td><td> -4,4</td><td> -3,5</td><td> 34</td>

<td>with temper</td><td> 65,3</td><td> 508</td><td> 21.1</td><td> -3.8</td><td> -4.7</td><td> 34</td>

<td>Example 2</td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>without temper</td><td> 60,2</td><td> 496</td><td> 16,4</td><td> -3,9</td><td> 0.7</td><td> 33</td>

<td>with temper</td><td> 62,3</td><td> 493</td><td> 17,4</td><td> -0,6</td><td> -2,5</td><td> 33</td>

<td>Example 3</td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>without temper</td><td> 57,6</td><td> 501</td><td> 13,4</td><td> -4,6</td><td> -5,0</td><td> 31</td>

<td>with temper</td><td> 59,5</td><td> 497</td><td> 14,5</td><td> -2,7</td><td> -7.8</td><td> 31</td>

From these data the following conclusions can be drawn:

With the additional TiN layer according to the invention, the T_L by 2 to 7 or 8% adjusting its thickness accordingly, although a moderate external reflection level is preserved, clearly less than 20% (the same decrease in TL could be obtained by thickening the silver layers, but to the detriment of external light reflection which then increases significantly).

This adjustment can be made with a very thin layer: less than 2 nm of TIN, therefore without significantly increasing the production cycle time of the stack, without significantly increasing the cost or complexity of it.

The addition of this absorbent layer also has as a direct consequence a gain of at least 1 to 3 points of FS.

Even without quenching, the absorbent layer according to the invention has a beneficial effect on external reflection by reducing it by at least 1 to 4% (at comparable TL levels), and allows to preserve negative a * and b * values ​​(that is, a residual color in reflection in the blue-green, which is the most investigated tint at the moment).

IS 2 298 192 T3

All these advantages are preserved even when the stack undergoes a temper: there are certainly slight variations in T_L or from R_L, but the light reflection remains well below 20% (contrary to the comparative example where it increases by about 4% and exceeds the 20% threshold). It is proof that the TiN layer is stable, it has not (little) evolved optically thanks to its "encapsulation" between two nitrides.

It should also be noted that it may be preferable that the two nitride layers that surround the TiN layer are not of the same thickness, the one farthest from the substrate being able to be thicker by, for example, a third (around 20, 30 or 40%) with respect to the other (or reciprocally).

It should also be noted that the TiN layer can be replaced by a NbN layer or by a metal layer of the Ti, Nb or Zr type.

Finally, note the strong dissymmetry in the thicknesses of the two silver layers, which particularly follows the teaching of patent EP-0 844 219 cited above.

Examples 4, 5 and 5 bis

Those examples are similar to example 3, with layers of TiN (example 4) and NbN (example 5) as absorbent layers. They are always in accordance with the first variant of the invention.

The table below regroups the thicknesses in nm of each of the layers of the stack:

<td></td><td>Example 4</td><td>Example 5</td><td>Example 5a</td>

<td>Glass</td><td> -</td><td> -</td><td> -</td>

<td>Yes₃N₄</td><td> 31</td><td> 31</td><td> 29</td>

<td>ZnO</td><td> 10</td><td> 10</td><td> 10</td>

<td>Ag</td><td> 8, 5</td><td> 8, 5</td><td> 8,5</td>

<td>You</td><td> 0.8</td><td> 0,8</td><td> 0,8</td>

<td>ZnO</td><td> 10</td><td> 10</td><td> 10</td>

<td>Yes₃N₄</td><td> 31</td><td> 31</td><td> 30</td>

<td>Absorbent layer</td><td>NbN: 1.4</td><td>TiN: 1.4</td><td>TiN: 2</td>

<td>Yes₃N₄</td><td> 31</td><td> 31</td><td> 30</td>

<td>ZnO</td><td> 10</td><td> 10</td><td> 10</td>

<td>Ag</td><td> 17,0</td><td> 17,0</td><td> 20,2</td>

<td>You</td><td> 0,8</td><td> 0,8</td><td> 0.8</td>

<td>ZnO</td><td> 10</td><td> 10</td><td> 10</td>

<td>Yes₃N₄</td><td> 23</td><td> 23</td><td> 20</td>

It should be noted that examples 2 to 5 bis according to the invention show good optical quality after hardening, without the appearance of corrosion pits or anchoring defects in particular.

The table below summarizes for these three examples the same photometric data as for the previous examples 1 to 3, with the same conventions, and also:

the purity in transmission pe in percentage, the value of AE in reflection, without unit, which, in the colorimetry system (L, a *, b *) is calculated according to the formula [(a * f - a * i)² + (b * f - b * i)² + (L * f - L * i) 2]^1/2 with a * i, b * i and L * i the values ​​before hardening, and a * f, b * f and L * f the values ​​after hardening.

IS 2 298 192 T3

<td>Examples</td><td>Tl</td><td>Ad</td><td>Pe</td><td>Rl. «T</td><td>to*</td><td>b *</td><td>ΔΕ</td><td>FS</td>

<td>Example 4</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>before tempering</td><td> 58,5</td><td> 537</td><td> 3,4</td><td> 14,2</td><td> -1,0</td><td> -7,8</td><td> -</td><td> 32</td>

<td>after tempering</td><td> 59,6</td><td> 521</td><td> 2,2</td><td> 15,7</td><td> -2,7</td><td> -9,0</td><td> 2,9</td><td> 33</td>

<td>Example 5</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>before tempering</td><td> 58,6</td><td> 542</td><td> 4,6</td><td> 14,4</td><td> -0,7</td><td> -9,0</td><td> -</td><td> 32</td>

<td>after tempering</td><td> 60,4</td><td> 531</td><td> 2,8</td><td> 16,0</td><td> -2,1</td><td> -10,1</td><td> 2,7</td><td> 33</td>

<td>Example 5a</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>before tempering</td><td> 49,4</td><td> 500</td><td> 6,4</td><td> 16,2</td><td> -1,9</td><td> -5,3-</td><td></td><td> 26</td>

<td>after tempering</td><td> 50,6</td><td> 494</td><td> 2.8</td><td> 17.9</td><td> -1,6</td><td> -6,2-</td><td></td><td> 26</td>

It is noted that the increase in light transmission after hardening is very limited: around 1.5% with the NbN layer, around 2 or 1.2% with a TiN layer depending on its thickness. Even so, the color in external reflection evolves shortly after hardening: the values ​​of a * and b * remain negative, with a decrease in the value of a * by about -2 and a variation in the value of b * of ± 1. Example 5a is particularly good on this point, with a value of a * that does not evolve more than +0.3 and a value of b * that does not evolve more than -0.9.

Example 6

This example is in accordance with the second variant of the invention: the absorbent layer is located in the upper dielectric coating (on top of the second silver layer), between an oxide layer and a nitride layer.

The table below regroups the thicknesses in nm of each of the layers of the stack:

<img file="ES2298192T3_D0003.tif" />

The glass has been mounted as before in double glazing, without tempering and after tempering. The optical evolution after quenching is as follows:

Σ AT_l = T_L after quenching - T_L before hardening = + 2.4%,

IS 2 298 192 T3

Σ Ab * in external reflection = b * after quenching - b * before quenching = 2,

Σ R_lext after hardening = 16.5%,

Σ T ratio_L/ FS = around 62-63 / 33.

There is no pitting of corrosion, even if the tank parameters are not perfectly adjusted, and the unlocking defects are very small and very few.

Various configurations in which the absorbent layer lies between an oxide layer and a nitride layer have been tested, evaluating the optical quality of the stacks after quenching. They are the variants of example 6 detailed below (the thicknesses of all the layers except for the absorbent layer are the same as those of example 6):

Example 6.1

Substrate / Yes₃N₄/ ZnO / Ag / Ti / ZnO / TiN (1 to 3 nm) / Si₃N₄/ ZnO / Ag / Ti / ZnO / Si₃N₄

Example 6.2

Substrate / Si3N4 / ZnO / Ag / Ti / ZnO / Si3N4 / TiN (1 to 3 nm) / ZnO / Ag / Ti / ZnO / Si3N4

Example 6.3

Substrate / Si3N4 / ZnO / Ag / Ti / ZnO / Si3N4 / ZnO / Ag / Ti / ZnO / TiN (1 to 3 nm) / Si3N4

Example 6.4

Substrate / Yes₃N₄/ ZnO / Ag / Ti / ZnO / TiN (1 to 2 nm) / Si₃N₄/ ZnO / Ag / Ti / ZnO / TiN (1 to 2 nm) / Si₃N₄

This example therefore uses two absorbent layers.

The optical quality after hardening of these glasses has been evaluated by the density of the defects of less than 2 microns and by the density of the defects of at least 2 microns. The most favorable configurations are those of Example 6.3 and those of Example 6.4:

Σ For Example 6.3, with 2 nm and 3 nm of absorbent layer, there is no defect of more or less than 2 microns.

Σ For Example 6.4, there are few defects when the two absorbent layers are each 1 nm thick, and no defects if the first from the substrate has a thickness of 1 nm and the second a thickness of 2 nm. (The configuration according to example 6.3 can be considered as better than that of example 6.4 since any defect with 2 nm in one case, and 2 + 1 nm at least in the other case is avoided).

for example 6.2 the optimal configuration is observed with 3 nm of absorbent layer (few defects) for example 6.1 the optimal configuration is observed with 3 nm of absorbent layer as well (no defect of less than 2 microns, few defects of at least 2 micrometers) for comparison, if example 6.1 is reproduced omitting the absorbent layer, after quenching there is a high density of both defects of less than 2 microns and defects of at least 2 microns, prohibitive density for a commercial product.

It is therefore seen that two parameters have to be taken into account to ensure good optical quality after hardening of the stacks according to the invention: the place of the absorbent layer (s) in the stack (preferably "in" the outermost dielectric or in the intermediate dielectric of the stacks of two silver layers), and its thickness (s) (variable according to the configurations, but preferably from at least 1.5 or 2 nm, and even rather around 3 nm when the absorbent layer is "in" the intermediate dielectric).

It is also seen that the presence of the absorbent layer improves the heat treatment performance of the stack as a whole.

IS 2 298 192 T3

Comparative Example 7

This example is given as a comparison, insofar as this time the absorbent layer is in direct contact with the glass:

<td></td>

<td>Glass</td>

<td>TiN</td>

<td>Yes₃N₄</td>

<td>ZnO</td>

<td>Ag</td>

<td>You</td>

<td>ZnO</td>

<td>Yes₃N₄</td>

<td>ZnO</td>

<td>Ag</td>

<td>You</td>

<td>ZnO</td>

<td>Yes₃N₄</td>

<td>Comparative Example 7</td>

<td>nm</td>

<td> 1,4</td>

<td> 31</td>

<td> 10</td>

<td> 8,5</td>

<td> 0,8</td>

<td> 10</td>

<td> 62</td>

<td> 10</td>

<td> 17,8</td>

<td> 0,8</td>

<td> 10</td>

<td> 23</td>

Double-glazed glass is always mounted in the same way, without tempering and after tempering: AT_L = + 4%, Ab * in external reflection = -2 to -3, very poor optical quality: many corrosion pits.

This example demonstrates that placing the layer directly in contact with the glass has a disastrous impact on the optical quality of the glass after tempering, with a significant increase in TL.

In conclusion, the insertion of an absorbent layer in the visible (and beyond) between dielectrics of the nitride and / or oxide type allows a fine control of the light transmission, a gain of FS, without the optical disturbances that one could have feared, very particularly in external reflection and very particularly when the layers undergo a heat treatment: global optical evolution of the stacking limited in case of hardening (less than +/- 3% or even + / 2% in TL), maintenance of a moderate external reflection level and satisfactory colorimetry in external reflection, optical quality after hardening satisfactory.

Glazings comprising a substrate provided with the stack according to the invention can also comprise one or more other functionalities: they can comprise, for example, a TiO-based anti-fouling coating₂ photocatalytic, a hydrophobic coating based on fluoropolymer, a hydrophilic coating based on SiO₂ o SiOC, one or more anti-reflection coatings. These coatings are preferably arranged on at least one of the outer faces of the glazing (the faces turned towards the outside, as opposed to the faces turned towards the inner thermoplastic sheet in the case of a laminate or the faces turned towards the sheet of air. , gas or vacuum in the case of insulating glazing).

The stack according to the invention can also be heated, with electrical power and the appropriate connections.