AU2012324662A1

AU2012324662A1 - Insulating glazing having a high light-transmission coefficient

Info

Publication number: AU2012324662A1
Application number: AU2012324662A
Authority: AU
Inventors: Agustin PALACIOS-LALOY; Etienne Sandre-Chardonnal
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS
Priority date: 2011-10-20
Filing date: 2012-10-17
Publication date: 2014-06-05
Anticipated expiration: 2032-10-17
Also published as: KR20140088521A; FR2981645B1; ES2776134T3; MX360954B; PL2768783T3; CN103946174A; KR102042587B1; WO2013057424A1; EP2768783B1; AU2012324662B2; HUE048100T2; CN103946174B; EP2768783A1; IN2014CN03421A; MX2014004554A; FR2981645A1

Abstract

The invention relates to transparent single glazing formed by a sheet of glass provided with a coating consisting of a stack of thin layers acting on solar radiation, such that the glazing has a light transmission coefficient greater than or equal to 48% and a heat transmission coefficient (U) less than or equal to 5 W/m

Description

-I INSULATING GLAZING HAVING A HIGH LIGHT-TRANSMISSION COEFFICIENT The invention relates to glazings known as solar 5 control glazings, equipped with stacks of thin layers, at least one of which is functional, that is to say that it acts on solar radiation. The present invention relates more particularly to multilayer glazings, especially those intended mainly for the thermal 10 insulation of buildings. The term "functional" or else "active" layer is understood within the context of the present application to mean the layer or layers of the stack 15 which give the stack most of its thermal properties. Usually, the stacks of thin layers equipping the glazing give it substantially improved solar-control properties essentially through the intrinsic properties of this active layer. Said layer acts on the flux of 20 solar radiation passing through said glazing, as opposed to the other layers, which are generally made of a dielectric material and have the function of chemically or mechanically protecting said functional layer. 25 Such glazings equipped with stacks of thin layers act on the incident solar radiation either essentially via absorption of the incident radiation by the functional layer, or essentially via reflection by this same 30 layer. They are grouped together under the name of solar control glazing. They are sold and used essentially - either for essentially ensuring solar-radiation 35 protection of the dwelling and preventing an overheating thereof, such glazings being described in the solar-protection field, or essentially for ensuring thermal insulation of the dwelling and preventing heat losses, these glazings being described as insulating glazings. The expression "solar-protection" is thus understood within the context of the present invention to mean the 5 ability of the glazing to limit energy flux, in particular solar infrared radiation (SIR) passing through it from the outside to the inside of the dwelling or passenger compartment. 10 The expression "thermally insulating" is understood to mean a glazing equipped with at least one functional layer that gives it an energy loss, measured by the heat transmission coefficient U, of less than 5 W/m 2 /K. 15 Generally, all the light and energy characteristics presented in the present description are obtained according to the principles and methods described in the international standards ISO 9050 (2003) and ISO 10292 (1994) or European standards EN 410 (1998) 20 and EN 673 (1998) relating to the determination of the light, solar and energy characteristics of glazings used in glass for construction. Combined with the glass substrate, these coatings must 25 also be aesthetically pleasing, that is to say that the glazing equipped with its stack must have a colorimetry, in transmission and in external reflection, that is sufficiently neutral so as not to inconvenience the users or alternatively a slightly 30 blue or green shade in particular in the building field. The expressions "neutral colour" or "blue-green shade" are understood within the context of the present invention, in the CIE LAB (L*, a*, b*) colorimetry system, to mean absolute values a* and b* of less than 35 or equal to 10, or even of less than or equal to 5, said values a* and b* preferably being negative. From the interior side of the building (that is to say from the side of the glazing where the layer is - 3 present), the possible values of the colorimetry are not as restrictive as for the external face and deeper and more orangey-yellow colours may be accepted. 5 On the other hand, irrespective of the face of the glazing, this shade must be durable and uniform over the entire surface of the glazing, even if the stack of layers is subjected to premature wear conditions such as abrasion resulting from the cleaning of the panes of 10 glass or else a prolonged exposure to outside humidity and to successive washing operations. The solution to such a problem of durable retaining of the same colorimetry over the entire surface of the glass is particularly pressing when the stack of layers is 15 deposited on a single glazing, in particular on its face 2, that is to say the face intended to be turned towards the inside of the building. Ideally, these glazings equipped with stacks must also 20 be capable of undergoing a heat treatment of the toughening type without loss of their optical and/or energy properties. In particular, the glazings equipped with layers according to the invention must retain, after the heat treatment, in particular in transmission 25 or in external reflection, the substantially neutral colour or else the blue-green shade described previously. These coatings are conventionally deposited by 30 sputtering deposition techniques under vacuum and enhanced by a magnetic field from a cathode of the material or of a precursor of the material to be deposited, often referred to as a magnetron sputtering technique in the field. Such a technique is today 35 conventionally used especially when the coating to be deposited consists of a more complex stack of successive layers having thicknesses of a few nanometres or a few tens of nanometres.

- 4 The best performing stacks currently sold incorporate at least one metallic layer of silver type functioning essentially on the mode of the reflection of a major portion of the incident IR (infrared) radiation. These 5 stacks are thus mainly used as low-emissivity (or low e) glazings for the thermal insulation of buildings. These layers are however very sensitive to humidity and are therefore exclusively used in double glazings, on face 2 or 3 thereof in order to be protected from 10 humidity. It is thus not possible to deposit such layers on single glazings (also referred to as monolithic glazings). The stacks according to the invention do not comprise such layers of silver type, or else of gold or platinum type or else in very 15 negligible amounts, in particular in the form of inevitable impurities. Other metallic layers having a solar-protection function have also been reported in the field, 20 comprising functional layers of metallic or nitrided Nb type, as described for example in application WO 01/21540 or else in application WO 2009/112759. Within such layers, the solar radiation is this time predominantly absorbed non-selectively by the 25 functional layer comprising niobium, the IR radiation (that is to say the radiation for which the wavelength is between around 780 nm and 2500 nm) and the visible radiation (the wavelength of which is between around 380 and 780 nm) being absorbed indiscriminately by the 30 active layer. In the least expensive solar-control single glazings, a single functional layer of niobium is deposited on a single glass substrate. As is generally acknowledged, 35 the values of the thermal insulation coefficient U imposed by the standards in force in many countries can however in principle only be easily obtained in such single glazings if the functional layer of niobium is relatively thick, for example of the order of at least - 5 10 nanometres, or even more. Due to the non-selective absorption of this same layer with respect to the incident radiation, the light transmission coefficients of such glazings, within the meaning written in the 5 standard ISO 9050, are in principle very low, generally less than 30%6, and usually less than 20%, as can be seen in the examples reported in the aforementioned applications. 10 Ultimately, in view of such characteristics, it appears very difficult to obtain, from such stacks, solar control glazings that combine acceptable heat transfer coefficients U, in particular of less than 5 W/m 2 /K, while retaining a high enough light transmission, that 15 is to say of greater than 48% and preferably of greater than 50%, in order to ensure good illumination of the dwelling. As indicated previously, another constraint is also 20 imposed during the production of the glazing: when the latter consists of a single glass substrate, it must usually undergo one or more heat treatments which may be a bending if it is desired to give it a curve (shop window) but which is usually a toughening, in 25 particular in the building sector where it is desired that it be stronger and less dangerous in the event of impacts. The fact that layers are deposited on the glass before its heat treatment frequently leads to their deterioration and to a substantial modification 30 of their properties, especially their optical properties. A contrario, depositing the layers after the heat treatment of the glass proves complex and expensive. As described previously, it is therefore imperative that such glazings equipped with such layers 35 can undergo such heat treatments without significant variation of their initial colorimetric properties. Furthermore, when the stack comprising the functional layer is deposited on a single glazing, for example on - 6 face 2, that is to say on the internal face of the glazing with respect to the building or passenger compartment that it equips, it must have sufficient chemical and mechanical resistance especially to 5 exposure to the ambient atmosphere, in particular such that the colorimetry of the glazing, especially in transmission, remains, in the same way as before, substantially unchanged over the entire surface of the glazing. 10 The object of the present invention is to propose a single glazing (also referred to as monolithic glazing) simultaneously having sufficient thermal insulation properties, with in particular a heat transmission 15 factor U of less than 5 W/m 2 /K, a high light transmission, that is to say a light transmission factor TL of greater than 48%, preferably of greater than 50%, and which has no or virtually no colorimetric variation during heat treatments, especially of 20 toughening type, or else when it is subjected to chemical or mechanical attack such as an abrasion. According to the invention, by an appropriate selection of the various constituents of the stack of layers 25 deposited on the initial glass substrate as stated in the claims hereinbelow, a thermally insulating single glazing has thus been able to be obtained that has, in particular: - a light transmission of greater than 48% and 30 preferably of greater than 50%, - a heat transfer coefficient U of less than 5 W/m 2 /K, equivalent to a normal emissivity cn of less than 0.60 (60%), of the single glazing equipped with the solar-control stack, and 35 preferably a normal emissivity En of less than 0.58, - a good durability especially with regard to tests of chemical/mechanical ageing with retention of the initial colorimetry.

-7 The subject of the invention thus firstly consists of a single transparent insulating glazing, consisting of a sheet of glass equipped with a coating consisting of a 5 stack of thin layers that act on solar radiation, in such a way that the glazing has a light transmission coefficient of greater than or equal to 48% and preferably greater than 50% and a heat transmission coefficient U of less than or equal to 5 W/m 2 /K, said 10 glazing being characterized in that said coating comprises, from the surface of the substrate: - an underlayer consisting essentially of a nitride or of an oxynitride of aluminium and/or of silicon, having a physical thickness between 30 15 and 60 nm, - a functional layer of niobium Nb, having a physical thickness of between around 6 nm and around 7 nm, - an overlayer for protecting the functional layer 20 with respect to the outside environment, said overlayer consisting either of a single layer consisting essentially of a nitride or of an oxynitride of aluminium and/or of silicon or of an assembly comprising the superposition of a layer 25 essentially of a nitride or of an oxynitride of aluminium and/or of silicon and of a layer of an oxide chosen from silicon oxide and titanium oxide, the total optical thickness of said overlayer being between 80 and 110 nm. 30 The physical (or geometric) thickness of a layer is understood within the context of the present invention to mean the actual thickness of the layer, such as can be measured in particular by conventional electron 35 microscopy techniques. The optical thickness is understood conventionally within the context of the present invention to mean the preceding physical thickness multiplied by the -8 refractive index n of the material which constitutes it, measured at 550 nrm. According to preferred embodiments of the invention 5 which may, if necessary, be combined together: - Said coating additionally comprises at least one layer of a material chosen from the group consisting of Ti, Mo, Al or an alloy comprising at least one of these elements, preferably Ti, 10 positioned with respect to the glass substrate on top of the functional layer and directly in contact therewith, said layer having a physical thickness between around 0.2 nm and around 2 nm. - Said coating additionally comprises at least one 15 layer of a material chosen from the group consisting of Ti, Mo, Al or an alloy comprising at least one of these elements, preferably Ti, positioned with respect to the glass substrate underneath the functional layer and directly in 20 contact therewith, said layer having a physical thickness between around 0.2 nm and around 2 nm. - The overlayer consists of the succession of a layer consisting essentially of silicon nitride and of a layer of silicon oxide, the physical 25 thickness of the aluminium and/or silicon nitride or oxynitride layer being between 40 and 50 nm and the physical thickness of the silicon oxide layer being between 3 and 10 nm. - The overlayer consists of the succession of a 30 layer consisting essentially of silicon nitride and of a layer of titanium oxide, the physical thickness of the silicon nitride layer being between 30 and 45 nm and the physical thickness of the titanium oxide layer being between 5 and 35 15 nm. - The overlayer consists of a layer consisting essentially of silicon nitride, additionally optionally comprising aluminium. The underlayer essentially consists of silicon - 9 nitride, additionally optionally comprising aluminium. The total optical thickness of said overlayer is between 90 and 105 nm, in particular between 90 5 and 100 nm. The stack of thin layers is positioned on face 2 of the single glazing by numbering the faces of the substrate from the outside to the inside of the building or the passenger compartment that it 10 equips. Finally, the present invention also relates to a facade facing panel of spandrel glass type incorporating at least one glazing as described previously or to a side 15 window, a rear window or a roof for a motor vehicle or other vehicle constituted by or incorporating said glazing. The coatings according to the invention make it 20 possible to obtain a relatively high value of the light transmission of the substrate, while retaining a significant insulating effect, despite the very small thickness of the functional layer: the measurements carried out indeed show a good compromise between the 25 level of light transmission TL and the heat transfer coefficient U of the multilayer substrate. The terms "on top of" and. "underneath" refer in the present description to the respective position of said 30 layers with respect to the glass substrate supporting the stack of said layers. Without departing from the scope of the invention, it is possible according to the invention to dope the 35 preceding silicon nitride layers with elements of the following type: Al, Zr, B, etc., so as to modify the colour in transmission and/or in reflection of the glazing, according to techniques that are well known in the art.

- 10 Although the application more particularly targeted by the invention is glazing for buildings, it is clear that other applications can be envisaged, especially in 5 the glazings of vehicles (apart from the windscreen where a very high light transmission is required), such as side windows, the sunroof, the rear window. The invention and its advantages are described in 10 greater detail hereinbelow by means of the non-limiting examples below, which are examples according to the invention and comparative examples. In all the examples and the description, the thicknesses given are physical thicknesses. 15 All the substrates are made of clear glass having a thickness of 6 mm of Planilux type sold by the company Saint-Gobain Glass France. 20 All the layers are deposited in a known manner by magnetron sputtering. The layers made of pure metal (Nb, Ti) are deposited from the sputtering of targets made of metal in a reduced and inert (100% argon) atmosphere. The layers made of silicon nitride 25 (subsequently denoted by Si 3

N

4 even if the layer deposited does not necessarily correspond to this assumed stoichiometry) are deposited from a target made of metallic silicon (doped with 8% by weight of aluminium) in a reactive atmosphere containing nitrogen 30 (40% Ar and 60% N 2 ) . The layers made of Si 3

N

4 therefore contain a small amount of aluminium. The layers made of silicon oxide (subsequently denoted by SiO 2 even if the layer deposited does not necessarily correspond to this assumed stoichiometry) are deposited from the metallic 35 target made of silicon in a reactive atmosphere that contains oxygen, according to well-known techniques. The layers made of titanium oxide (subsequently denoted by TiO 2 even if the layer deposited does not necessarily correspond to this assumed stoichiometry) are deposited - 11 from a metallic target made of titanium in a reactive atmosphere that contains oxygen, according to techniques that are also well known. The following refractive indices, as given in the 5 literature, are given: nSi3N4 of the order of 2, nT, 0 2 of the order of 2.3 and nsio2 of the order of 1.45. EXAMPLE I (according to WO 01/21540) 10 This example has a functional layer made of Nb and an underlayer and overlayer made of Si 3

N

4 according to the following sequence: 15 Glass/Si 3

N

4 (10 nm)/Nb (35 nm)/Si 3

N

4 (30 nm) After the deposition of the layers, the glazing undergoes the following heat treatment: heating at 620 0 C for 10 minutes followed by toughening. 20 MXAMPLE 2 (according to WO 200/112759) This example uses a sequence of layers deposited on the same substrate, a very fine layer of metallic titanium 25 also being deposited on top of and underneath the functional layer, according to the teaching of the publication WO 2009/112759. The stack thus comprises the following succession of layers: 30 Glass/Si 4 (40 mi)/Ti (1 nm)/Nb (10 nm) /Ti (1 nm)/Si 3

N

4 (60 nm) The glazing according to this example is not in accordance with the present invention with respect to the thickness of the functional layer and the optical 35 thickness of the overlayer (120 nm), The substrate coated with the stack then undergoes the same heat treatment as described in Example 1. EXAMPLE 3 (comparative) - 12 This example uses a sequence of layers deposited on the same substrate, a very fine layer of metallic titanium also being deposited on top of and underneath the 5 functional layer, according to the teaching of the publication WO 2009/112759. The stack thus comprises the following succession of layers: Glass/Sib4 (40 m) /Ti (Kl m) /Nb (around 8-9 nm) /Ti (1 nm) /Si (60 nM) 10 The glazing according to this example is not in accordance with the present invention with respect to the thickness of the functional layer and the optical thickness of the overlayer (120 nm). 15 The substrate coated with the stack then undergoes the same heat treatment as described in Example 1. EXAMPLE 4 (according to the invention) 20 This example uses a sequence of layers in accordance with the invention, deposited on the same substrate. The stack thus comprises the following succession of layers: 25 Glass/Sia 4 (45 m) /Ti (:l nm)/Nb (6 nm)/Ti (-I n)/SiN 4 (38 rm)/TiO2 (9nm) The optical thickness of the overlayer, consisting of the layers of silicon nitride and of titanium oxide, is of the order of 98 nm. 30 The substrate coated with the stack then undergoes the same heat treatment as described in the preceding examples. EXAMPLE 5 (according to the invention) 35 This example uses the same sequence of layers as in the preceding example, deposited on the same substrate, with the exception of the overlayer. The stack thus comprises the following succession of layers: - 13 Glass/i 3

N

4 (45 m) /Ti (4l nm) /Nb (6 nm) /TI (l nm) /SiN 4 (46 nm) /Si (5 nm) The optical thickness of the overlayer, consisting of the layers of silicon nitride and of silicon oxide, is of the order of 100 nm. The substrate coated with the stack then undergoes the same heat treatment as described in the preceding examples. 10 EXAMPLE 6 (according to the invention) This example uses the same sequence of layers as in the preceding example, deposited on the same substrate, 15 with the exception of the overlayer. The stack thus comprises the following succession of layers: Glass/Si 3

N

4 (45 nrm)/Ti (~1 nm)/Nb (6 nm)t/Ti (-1 nm)/Si 3

N

4 (49 nm) 20 The optical thickness of the overlayer, consisting of the layers of silicon nitride, is of the order of 100 nm. The substrate coated with the stack then undergoes the same heat treatment as described in the preceding 25 examples. EXAMPLE 2b (com arative) This example uses the same sequence of layers as 30 Example 2 above, deposited on the same substrate, with the exception of the underlayer of silicon nitride, the thickness of which is optimized to increase the light transmission thereof. The stack thus comprises the following succession of layers: 35 Glass/Si 3

N

4 (60 nm)/Ti (>l nm)/Nb (10 nm);/Ti ( nm)/SiN 4 (60 nm) The optical thickness of the overlayer, consisting of the single layer of silicon nitride, is of the order of - 14 123 nm. The substrate coated with the stack then undergoes the same heat treatment as described in the preceding examples. EXAMPLE 3b (comparative) This example uses the same sequence of layers as Example 3 above, deposited on the same substrate, with 10 the exception of the two layers of silicon nitride, which are optimized in order to increase the light transmission thereof. The stack thus comprises the following succession of layers: 15 Glass/SiAN 4 (60 nrn)/Ti (;1 nr)/Nb (8-9 nm)/Ti (-1 nm)/Si 3

N

4 (60 nm) The optical thickness of the overlayer and of the underlayer, each consisting of the single layer of silicon nitride, is of the order of 120 nm. 20 The substrate coated with the stack then undergoes the same heat treatment as described in the preceding examples.

- 15 Table 1 Optical and energy properties Heat XAMPLE treatment

T

1 Emissivity Example 1 Before 11 14 (WO 01/21540) After 18 is Example 2 Before 42 32 WO 09/112759) After 40 37 Example 3 Before 48 39 Compp) After 47 45 Example 4 Before 53 50 (inv) After 51 56 Example 5 Before 52 50 (inv) After 50 56 Example 6 Before 52 50 (inv) After 5-1 56 Example 2b Before 47 32 Compp. After 46 37 Example 3b Before 51 39 Compp.) After 50 45 The data listed in Table I show that Examples 1, 2 and 5 3 according to the prior art do not make it possible to obtain the desired criteria, namely a light transmission greater than or equal to 48% and preferably greater than or equal to 50% and a coefficient U of less than 5 W/m 2 /K (corresponding to a 10 normal emissivity of less than 58%). It can be seen that such objectives may nevertheless be achieved by a person skilled in the art starting from the stack of Example 3b by optimizing the optical 15 thickness of the overlayer and the underlayer, so as to increase the light transmission. Examples 4, 5 and 6 according to the invention also make it possible to directly obtain such criteria owing to the very small - 16 thickness of the functional layer. On the other hand, a glazing equipped with a niobium layer having a thickness greater than or equal to 10 nm cannot have a light transmission of greater than 48% as shown by 5 Example 2b, for which the respective thicknesses of the various layers have however been optimized in order to maximize the light transmission of the glazing. The chemical resistance properties of the glazings 10 according to Examples 6 (according to the invention) and 3b (comparative) were measured by an HH test, the experimental conditions of which are given below: The glazings are placed in a chamber maintained at atmospheric pressure, under a temperature of 500C in an 15 atmosphere comprising 95% relative humidity. The test is carried out on a portion of the glazing on two samples according to the same protocol for a same duration of 14 days, the rest of the glazing being 20 protected from the humidity. The objective is to characterize the possible variations of colour in transmission, internal reflection and external reflection which would degrade the aesthetics of the glazings with respect to their original appearance, 25 particularly if the chemical attacks are localized and give rise to marks of a visibly different colour. The quantity chosen for characterizing this change is, in the CIE (L*, a*, b*) colorimetric system, the quantity AE* conventionally defined by the equation: 30 AE *= (Aa*)2 + (Ab*) 2 + (AL*) 2 Table 2 below gives, for each of the two samples, the colorimetric differences, in transmission and in internal and external reflection, between the region of 35 the glazing that has not undergone the chemical treatment and the treated region of the glazing.

- 17 Table 2 Example 6 Example 3b Region of the HH test Outside HH test Outside glazing of test of test L t~ - - - - - - - - - --- -----7 678-80- 8 L*T 76 7880 80 -------- -- ------- a*T -1.2 2.1 -4.1 4.2 _b*T 4.9 3.3 3.5 7.4 kAET 3 4 --------- -------- -- -- - -- Rext 46 48 44 46 a*RLext -1.4 -1 6 2.5 1.7 e 0.1 1 3 -10.3 8.2 AEaext 2 3 L*Rint 40 33 24 19 -a*RLint 57.3 22.3 30 ............ -- _- --- -- _ _ _ __ _ b*RLint 29 28 .8 -3.5 -32

AER

1 'nt 9 30 5 It is observed that the quantities measured LET and AERLext between a region subjected to the HH test and a region that has not been treated is small for the two glazings according to Examples 6 and 3b, which indicates a substantially constant colorimetry of the 10 glazings subjected to environment attacks, when they are observed from the outside. On the contrary, examination of the colorimetry between a region subjected to the HH test and a region that has 15 not been treated on the inner face of the glazing (that is to say the face turned towards the inside of the building) as measured by the quantity AERLint, shows very large colorimetric variations of the glazing according to comparative Example 3b. On the contrary, the glazing 20 from Example 6 according to the invention is characterized by a much smaller colorimetric variation.

- 18 Ultimately, only the glazing coated with a stack according to the invention can therefore undergo the accelerated ageing test without its colorimetric properties, and also the desired optical and energy 5 properties, being substantially modified thereby. The same HH tests were also carried out on glazings according to Example 5 according to the invention. The results obtained are given in Table 3 below: 10 Table 3 Example 5 Region of HH test Outside the glazinq of test L*t_ 75.9 75.8 a*T _ -2.2 -2.2 --------------- - - b -5.2 -5.1 LET 01Z L*R 495 4 9. -1.3 -1.3 - b*Rt 7 -_-_ - 1.7 -1- -i35 3938 a*p nt 3.5 3.3 _b*R_ 30.2 30 3 tEL 0.4 Here too, it can be seen that between a region 15 subjected to the HH test and a region that has not been treated, the glazings of Example 5 according to the invention are characterized by a very small colorimetric variation, as measured by the quantity 20 In conclusion, the solar-protection glazings according to the invention appear highly advantageous and not very expensive in particular for equipping buildings, - 19 without however excluding applications in motor vehicles and all vehicles: side windows, rear windows, sunroof , which may furthermore have enamelled coatings. 5 The stacks of layers according to the invention make it possible to obtain solar-control glazings having the desired TL and thermal insulation values and the colorimetry of which remains substantially constant, under the effect of the various treatments and chemical 10 attacks to which they may be subjected during their manufacture and their use. By application of the present invention, it is thus possible to manufacture solar-control glazings that 15 allow improved vision and that also have a very good chemical durability, without significant variation of their colorimetry over time. Without departing from the scope of the invention, it 20 is also possible to make spandrel glass containing enamelled layers, rather than lacquered layers, which is industrially very advantageous, since the enamelling is carried out during the toughening process, whereas lacquering requires an additional manufacturing step. 25

Claims

1. Single transparent glazing, consisting of a sheet of glass equipped with a coating consisting of a 5 stack of thin layers that act on solar radiation, in such a way that the glazing has a light transmission coefficient of greater than or equal to 48% and a heat transmission coefficient U of less than or equal to 5 W/m

2 /K, said glazing being 10 characterized in that said coating comprises, from the surface of the substrate: - an underlayer consisting essentially of a nitride or of an oxynitride of aluminium and/or of silicon, having a physical thickness between 15 30 and 60 nm, - a functional layer of niobium Nb, the physical thickness of which is between around 6 nm and around 7 nm, - an overlayer for protecting the functional layer 20 with respect to the outside environment, said overlayer consisting either of a single layer consisting essentially of a nitride or of an oxynitride of aluminium and/or of silicon or of an assembly comprising the superposition of a 25 layer essentially of a nitride or of an oxynitride of aluminium and/or of silicon and of a layer of an oxide chosen from silicon oxide and titanium oxide, the total optical thickness of said overlayer being between 80 and 110 nm. 30 2, Glazing according to Claim 1, in which said coating additionally comprises at least one layer of a material chosen from the group consisting of Ti, Mo, Al or an alloy comprising at least one of 35 these elements, positioned with respect to the glass substrate on top of the functional layer and in contact therewith, said layer having a physical thickness between around 0.2 nm and around 2 nm. - 21

3. Glazing according to either of Claims 1 and 2, in which said coating additionally comprises at least one layer of a material chosen from the group consisting of Ti, Mo, Al or an alloy comprising at 5 least one of these elements, positioned with respect to the glass substrate on top of and underneath the functional layer and in contact therewith, said layer having a physical thickness between around 0.2 nm and around 2 nm. 10

4. Glazing according to either of Claims 2 and 3, in which said material is Ti.

5. Glazing according to one of the preceding claims, 15 in which the overlayer consists of the succession of a layer consisting essentially of silicon nitride and of a layer of silicon oxide, the physical thickness of the aluminium and/or silicon nitride or oxynitride layer being between 40 and 20 50 nm and the physical thickness of the silicon oxide layer being between 3 and 10 nm.

6. Glazing according to one of Claims 1 to 4, in which the overlayer consists of the succession of 25 a layer consisting essentially of silicon nitride and of a layer of titanium oxide, the physical thickness of the silicon nitride layer being between 30 and 45 nm and the physical thickness of the titanium oxide layer being between 5 and 30 15 nm.

7. Glazing according to one of Claims 1 to 4, in which the overlayer consists of or comprises a layer consisting essentially of silicon nitride, 35 additionally optionally comprising aluminium.

8. Glazing according to one of the preceding claims, in which the underlayer essentially consists of - 22 silicon nitride, additionally optionally comprising aluminium.

9. Glazing according to one of the preceding claims, 5 in which the total optical thickness of said overlayer is between 90 and 105 nm, in particular between 90 and 100 nm.

10. Single glazing incorporating the substrate 10 according to one of the preceding claims, the stack of thin layers being positioned on face 2 of the single glazing by numbering the faces of the substrate from the outside to the inside of the building or the passenger compartment that it 15 equips.

11. Facade facing panel of spandrel glass type incorporating at least one glazing according to one of Claims 1 to 10.