Insulating glass panel comprising a thin chromium-based layer

Abstract

A transparent glass article comprising at least one glass substrate, at least one of the faces of which is provided with a coating formed by a stack of thin layers, including at least one functional layer providing the article with solar control properties, said coating comprising the following series of layers, with reference to the surface of said substrate: - a first layer comprising silicon nitride; - a functional metal chromium-based layer with a physical thickness that is greater than or equal to 1 nm and less than or equal to 9 nm; - a second layer comprising silicon nitride, wherein said first and second layers comprising silicon nitride are directly in contact with the functional metal chromium-based layer.

Description

TITLE INSULATING GLASS PANEL COMPRISING A THIN CHROMIUM-BASED LAYER DESCRIPTION The invention relates to insulating glazings known as solar-control glazings, provided with stacks of thin layers, at least one of which is functional, that is to say that it acts on the solar and / or thermal radiation essentially by reflection and / or absorption of the near infrared (solar) or far infrared (thermal) radiation. The present invention relates more particularly to multilayer glazings, in particular those intended mainly for the thermal insulation of buildings. The expression "functional" or else "active" layer(s) is understood within the context of the present application to mean the layer(s) of the stack which give the stack most of its thermal properties. Usually, the stacks of thin layers equipping the glazing give it improved solar-control properties essentially through the intrinsic properties of this active layer. Said layer acts on the flux of solar radiation passing through said glazing, as opposed to the other layers, which are generally made of a dielectric material and essentially have the function of chemically or mechanically protecting said functional layer or of adjusting the color. Such glazings provided 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 layer. They are grouped together under the name of solar-control glazing. They are sold and used essentially: - either for essentially ensuring solar-radiation 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 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. In order to measure the energy insulation properties of the glazings, use is made in the field of the solar factor, denoted SF or g in the field. As is known, the solar factor g is equal to the ratio of the energy passing through the glazing (i.e. entering the space) to the incident solar energy. More particularly, it corresponds to the sum of the flux transmitted directly through the glazing and the flux absorbed by the glazing (including therein the stacks of layers optionally present on one of its surfaces) and then possibly re-emitted toward the interior (the space). Good thermal insulation properties thus first require a low resistivity of the functional layer. However, such a property also results in a higher light absorption, which tends to substantially reduce the light transmission within the glazing. The object of the present invention is firstly to provide a glazing equipped with a stack exhibiting a good compromise between its light transmission and its thermal insulation properties. Generally, all the light characteristics presented in the present description, in particular the light transmission TL and the light reflection Rc, and also the factor g, are obtained according to the principles and methods described in the standard NF EN 410 (2011) relating to the determination of the light and energy characteristics of glazings used in glass for the construction industry. Ideally, such glazings should have a substantially neutral color both in transmission and in reflection, whether on the face of the glazing on which the stack is deposited (interior side) or on opposite face (exterior side). The best-performing stacks currently sold incorporate at least one metallic layer of silver type operating essentially on the mode of reflecting a major portion of the incident IR (infrared) radiation. These stacks are thus used mainly as glazings of the low-emissivity (or low-e) type for the thermal insulation of buildings. However, these layers are very sensitive to moisture and are therefore exclusively used in double glazings, on face 2 or 3 thereof, in order to be protected from moisture. 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 based on silver, or else based on gold or platinum, or else in very negligible amounts, in particular in the form of unavoidable impurities. Likewise, the functional layers, indeed even the stacks, of the glass articles according to the invention are free from nickel or copper. The drawback of the layers based on silver is also their poor mechanical strength, which also explains their use almost exclusively in the construction field on the interior faces of a multiple glazing (for example faces 2 and 3 of a double glazing). Other metallic layers with a solar-protection function have also been reported in the field, comprising functional layers of the metallic Nb or nitrided Nb (NbN) 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 nonselectively by the functional layer comprising niobium, the IR radiation (i.e. the wavelength of which is between approximately 780 nm and 2500 nm) and the visible radiation (the wavelength of which is between approximately 380 and 780 nm) being absorbed without distinction by the active layer. In addition to the solar-protection properties, in the field of the construction industry, or even the motor vehicle industry, privacy glazing is sometimes desired, i.e. glazing that allows daytime vision easily from the inside toward the outside for the occupants of a space, a building or a vehicle, but that presents a mirror appearance from the outside toward the inside that prevents vision in this direction. However, in nighttime vision, i.e. when the exterior brightness is greater than the internal brightness, such a glazing may present the drawback of exhibiting this same mirror effect, this time from the outside toward the inside if the interior reflection is too great. To resolve such a problem, it is necessary to propose glass articles, the luminous characteristics of which are suitable. In particulier, the problem described above was able to be resolved according to the invention by means of the development of glass articles of which: the light transmission is greater than or equal to 20%, the light reflection on the glass side (exterior face) Riext is greater than or equal to 25%, indeed even greater than or equal to 30%, the light reflection on the stack side (interior face) Ruint is less than or equal to 20%, indeed even less than or equal to 15%, the difference between the two light reflections Riext - RLint (denoted also ARL in the remainder of the description) is greater than 15% or even greater than 18%, indeed even greater than 20%. The term stack side is understood to mean the face of the glazing on which the stack is deposited. The term glass side is understood to mean the face of the glazing opposite the one on which the stack is deposited, which in principle is not covered. Within the meaning of the present invention, the terms “exterior face” (or “external face”) and “interior face” (or “internal face”) refer to the position of the glazing when this equips the building or the vehicle that it equips. Equally, the glass articles and glazings according to the invention have energy insulation properties in accordance with those required in the field, in particular a solar factor g close to and preferably less than 50%, indeed even less than 45% or even less than 40% in certain configurations. The object of the present invention is to propose a glass article that makes it possible to solve the technical problems described above. More precisely, the present invention relates to a transparent glass article, comprising at least one glass substrate provided on at least one of the faces thereof with a coating consisting of a stack of thin layers, including at least one functional layer imparting solar-control properties to said article, said coating comprising the sequence of following layers, with reference to the surface of said substrate: a first layer comprising silicon nitride, a functional layer based on chromium metal, having a physical thickness greater than or equal to 1 nm and less than or equal to 9 nm, preferably greater than or equal to 2 nm and less than or equal to 8 nm, a second layer comprising silicon nitride, wherein said first and second layers comprising silicon nitride are directly in contact with the functional layer based on chromium metal. According to particular and preferred embodiments of the present invention, which may be, if need be, combined together: - The first layer comprising silicon nitride has a thickness between 1 and 100 nm, preferably between 10 and 80 nm. - The second layer comprising silicon nitride has a thickness between 1 and 100 nm, preferably between 1 and 50 nm, more preferably between 2 and 25 nm. - The first layer comprising silicon nitride is thicker than the second layer comprising silicon nitride. - The stack does not comprise any layers based on Ag, Au, Pt, Cu, Ni or stainless steel. - The stack comprises a single functional layer based on chromium metal, the thickness of the layer being between 2 and 9 nm, in particular between 3 and 8 nm. - The stack consists of the sequence of the following layers: SiNx / Cr / SiNx wherein SiNx denotes said layer comprising silicon nitride and Cr denotes said layer based on chromium metal. - The stack comprises two functional layers based on chromium, a third layer comprising silicon nitride being inserted in the stack between the two functional layers based on chromium. The third layer of chromium is directly in contact with the layers based on chromium, according to the sequence of following layers: SiN / Cr / SiNx / Cr / SiNx wherein SiNx denotes said layers comprising silicon nitride and Cr denotes said layers based on chromium metal. In particular the value of x may deviate from the conventional value corresponding to the defined compound SisN4 (x=1.33), in the direction of a superstoichiometry of nitrogen or preferentially of a substoichiometry of nitrogen, even if in principle it does not differ by more than 20% from this theoretical value. The functional layer(s) based on chromium comprise more than 80 at% of chromium. - The functional layer(s) consist essentially of chromium and preferably consist of chromium, apart from the unavoidable impurities. - The first layer comprising silicon nitride is deposited directly on the glass substrate and is in contact therewith. - At least one layer comprising a metal oxide is present between the surface of the glass substrate and the first layer comprising silicon nitride, the metal oxide preferably being chosen from an oxide of an element chosen from silicon, titanium, tin, zinc, aluminum, zirconium or a mixture of at least two of these elements, in particular silicon oxide, titanium oxide or a zinc tin oxide. - At least one layer comprising a metal oxide is present on top of said sequence of layers, the metal oxide preferably being chosen from an oxide of an element chosen from silicon, titanium, tin, zinc, aluminum or a mixture of at least two of these elements, in particular silicon oxide, titanium oxide, zirconium oxide or a mixture of these oxides. - The article is thermally toughened and / or curved. The functional layer(s) based on chromium comprise at least 50 at% of chromium. Preferably, the functional layer(s) of the stack have at least 70 at%, indeed even at least 80 at% of chromium, or even preferentially more than 90 at% of chromium. According to one very preferred embodiment, the functional layer(s) consist essentially of chromium and more preferably consist of chromium, apart from the unavoidable impurities. Without departing from the invention however, the functional layer(s) may comprise one or more other atoms, for example chosen from Al, Si, Mo, W, Zn, Ti, Mg, Co, Ni. The content of chromium and that of the other elements optionally present may be measured according to any known technique. By way of example, mention may be made of XPS (X-ray photoelectron spectrometry). The functional layer(s) according to the invention may comprise a minimal portion of nitrogen and / or oxygen, but less than 15 at%, or even less than 10 at%, indeed even less than 5 at%. Preferably however, the functional layer(s) according to the invention do not in principle comprise nitrogen or oxygen or else in the form of unavoidable impurities, resulting for example from a heat treatment of the glazing such as a toughening or a curving. Likewise, the functional layer(s) according to the invention do not in principle comprise carbon or hydrogen or else in the form of unavoidable impurities. In the layers according to the invention comprising silicon nitride, the silicon nitride preferably represents at least 50 wt% of silicon nitride, on the basis of a SisN4 formulation, and preferably more than 80% of silicon nitride or even more than 90% of silicon nitride, on the basis of the SisN4 formulation. Said layers preferably consist essentially of silicon nitride, but may also comprise an element other than silicon, in particular aluminum. Aluminum is in particular commonly used, in proportions that may range up to 15 at%, in the silicon targets used for magnetic field-enhanced (magnetron) sputtering deposition of the stacks of thin layers on solar-control glazings, and in particular the layers based on silicon nitride. Thus, without departing from the scope of the invention, the silicon of said layers may be substituted by elements of the type Al, Zr, B, etc., in particular so as to modify the color in transmission and / or in reflection of the glazing, according to techniques well known in the art and in proportions that may range up to 15 at%. The coatings according to the invention are conventionally deposited by 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 the magnetron sputtering technique in the field. Such a technique is conventionally used today, in particular when the coating to be deposited consists of a more complex stack of successive layers, having thicknesses of several nanometers or several tens of nanometers. The present invention also relates to a facade cladding panel of spandrel type incorporating at least one glazing as previously described or to a side window, a rear window or a roof for a motor vehicle or other vehicle consisting of or incorporating said glazing. According to the invention, the functional layers according to the invention make it possible to obtain a value of the light transmission of the substrate that is relatively high, while retaining a significant insulating effect, despite the very thin thickness of the functional layer, after a heat treatment. The terms “underlayer” and “overlayer” refer in the present description to the respective position of said layers with respect to the functional layer(s) in the stack, said stack being supported by the glass substrate taken as reference. In particular, the underlayer is generally the layer in contact with the glass substrate and the overlayer is the outermost layer of the stack, facing away from the substrate. While the application more particularly targeted by the invention is the glazing for the construction industry, it is clear that other applications can be envisaged, in particular in the glazings of vehicles (apart from the windshield, where a very high light transmission is required), such as the side glass panes, sunroof, rear window. The invention and its advantages are described in more detail below, by means of the nonlimiting examples below, which are according to the invention and comparative. In all the examples and the description, the thicknesses given are physical thicknesses. All the substrates are made of 6-mm thick clear glass of Planilux® type sold by Saint-Gobain Glass France. All the layers are deposited in a known manner by magnetic field-enhanced sputtering (often referred to as magnetron sputtering). In a well-known manner, the various successive layers are deposited in the successive compartments of the sputtering device, each compartment being provided with a specific metal target made of Si, or Cr, under conditions selected for the deposition of a specific layer of the stack. For example, the layers made of silicon nitride are deposited in a first compartment of the device from a target of silicon metal (doped with 8 wt% of aluminum), in a reactive atmosphere containing nitrogen (40% Ar and 60% Nz). The layers made of silicon nitride, denoted SisN4, therefore contain a small amount of aluminum. These layers are denoted subsequently according to the conventional general formulation SisN4, even if the layer deposited does not necessarily correspond to this assumed stoichiometry. The layers made of chromium metal are deposited from the sputtering of a target of Cr metal under an inert atmosphere (i.e. by means of a plasma obtained from the gas argon alone) or under a plasma generated from the gas argon. Examples 1 to 5: In all the examples 1 to 5 which follow, the glass substrate was thus covered successively by a stack of layers comprising a functional layer made of chromium flanked by a first layer (underlayer) made of SisN4 and by a second layer (overlayer) of SisNa. In these examples, the stack therefore consists of a chromium layer encapsulated by two silicon nitride layers according to the following sequence: Glass / SizN4 (15 layer) / Cr / SisN4 (2M layer) Various stacks are synthesized to adjust the solar factor and the light transmission to various possible configurations desired in the field of the construction industry. Thus, in example 1, the thicknesses of the various layers are configured so as to obtain a glazing having a low solar factor whereas, for example 5, it is sought on the other hand to maximize the light transmission through the glazing. The glass articles thus synthesized according to the conventional techniques are then heated and toughened according to conventional techniques in the field (heating at 620°C for 10 minutes followed by toughening). Table 1 below brings together information regarding the composition of the solar- protection stacks according to examples 1 to 5 according to the invention: [Table 1] Thickness (nm) Thickness (nm) Thickness (nm) SisNa 1%t layer Cr layer SisN4 2M layer Example 1 62 16 Example 2 62 5 14 Example 3 15 4 2 Example 3 15 4 2 Example 4 45 3 3 The values of light transmission TL and of external light reflection Rext and internal light reflection Rint are measured in the range 380 nm to 780 nm according to the methods described in the standard NF EN 410 (2011). The solar factor g is also measured according to this standard, in the range 300 nm to 2500 nm. The results obtained are brought together in table 2 which follows: [Table 2] TL Rex Rint ARL g Example 1 22 47 11 36 32 Example 2 28 42 8 34 38 Example 3 32 30 11 19 42 Example 4 40 34 27 48 Example 5 46 30 10 20 52 It is seen that the glass articles according to examples 1 to 5 fulfilling the conditions set out above for obtaining a privacy solar-protection glazing, it being possible for the values of TL and of g to be adjusted according to the thickness of the chromium layer. It is further observed that ARL (Rex - Ruin) is in all cases close to 20, indeed even substantially greater than 20, which makes it possible to guarantee the “privacy” properties of such glazings, within the meaning previously described. The colorimetrc values in transmission, in internal reflection and in external reflection according to the standard L, a*, b* are reported in table 3 which follows: [Table 3] a*TL b*tL a*RLext b*RLext a*RrLint b*RrLint Example 1 0.6 -2.3 -14 53 4.4 -0.5 Example 2 0.6 -2.7 -1.5 4.8 5.8 27 Example 3 1.5 -1.8 -14 141 -1.8 5.8 Example4 | 0.6 -1.3 -1.1 -2.2 3.7 43 Example 5 0.4 -3.5 -1.3 3 17 7.4 It can be seen that the values of the coefficients a* and b* are relatively low and in all cases less than or equal to 8, which conveys a relative neutrality of the color perceived both in reflection and in transmission. Comparative examples: Itis possible to compare the properties of the stacks of the application WO 01 / 21540 cited above with those of the stacks according to the invention and described above. Example 4 of application WO 01 / 21540 describes a stack comprising the following sequence of layers: Glass / SisNa (10 nm) / Nb (12 nm) / SisN4 (17 nm) In the table on page 18 of this publication, it is indicated that the light transmission is 32%. It can be calculated that the solar factor g is around 36%. The values of Riext and of Ruint reported in the publication are respectively equal to 14% and 25%. While the values of TL and g of this example according to the prior art are comparable to examples 2 or 3 reported in table 2 above, it can be seen that the values of the exterior and interior reflections do not make it possible to obtain the privacy glazing, within the meaning described above, the AR. being even negative in this configuration. Similarly, example 6 of application WO 01 / 21540 describes a sequence of layers in the stack: Glass / SizNa4 (10 nm) / NbN (10 nm) / SiaN4 (15 nm) In the table on page 18 of this publication, it is indicated that the light transmission is 31%. It can be calculated that the solar factor g is around 48%. The values of Riext and of Ruint reported in the publication are respectively equal to 18% and 28%. While the values of TL and g of this example according to the prior art are comparable to example 4 reported in table 2 above, it can be seen that the values of the exterior and interior reflections do not make it possible to obtain the privacy glazing, within the meaning described above, the AR. being even negative in this configuration. Example 6: In this example, a stack comprising two chromium layers and corresponding to the following sequence of layers was deposited: Glass / SisN4 / Cr / SiasNa / Cr / SisNa The exact compositions of the stacks are given in table 4 which follows starting from the surface of the glass: [Table 4] Thickness Thickness Thickness Thickness SisNa Thickness SiaNs 2M | SiaN 12 layer | Cri layer | intermediate | Crz layer layer layer 28 15 44 3 2 Example 6 28 The optical and energy characteristics of the glass substrate are given in table 5 which follows: [Table 5] Tu Riext Ruint ARL g Example 6 28 31 8 23 39 The colorimetric characteristics of the glass substrates are given in table 6 which follows: [Table 6] aL b*1L a“RLext b*Reext a“RLint b*RLint Example 6 2.3 -1 -0.2 2.8 3.6 1.1 The data reported in the preceding tables 4 to 6 show that the stacks according to the invention comprising two layers based on chromium have moreover a very great colorimetric neutrality.

Claims

CLAIMS 1. A transparent glass article, comprising at least one glass substrate provided on at least one of the faces thereof with a coating consisting of a stack of thin layers, including at least one functional layer imparting solar-control properties to said article, said coating comprising the sequence of following layers, with reference to the surface of said substrate: a first layer comprising silicon nitride, a functional layer based on chromium metal, having a physical thickness greater than or equal to 1 nm and less than or equal to 9 nm, a second layer comprising silicon nitride, wherein said first and second layers comprising silicon nitride are directly in contact with the functional layer based on chromium metal.

2. The article as claimed in claim 1, wherein the first layer comprising silicon nitride has a thickness between 1 and 100 nm, preferably between 10 and 80 nm.

3. The article as claimed in either of the preceding claims, wherein the second layer comprising silicon nitride has a thickness between 1 and 100 nm, preferably between 1 and 50 nm, more preferably between 2 and 25 nm.

4. The article as claimed in one of the preceding claims, wherein the first layer comprising silicon nitride is thicker than the second layer comprising silicon nitride.

5. The article as claimed in one of the preceding claims, wherein the stack does not comprise any layers based on Ag, Au, Pt, Cu, Ni or stainless steel.

6. The article as claimed in one of the preceding claims, comprising a single functional layer based on chromium metal. / . The article as claimed in the preceding claim, wherein the stack consists of the sequence of the following layers: SiNx / Cr / SiNx wherein SiNx denotes said layer comprising silicon nitride and Cr denotes said layer based on chromium metal.

8. The article as claimed in one of claims 1 to 5, characterized in that the stack comprises two functional layers based on chromium, a third layer comprising silicon nitride being inserted in the stack between the two functional layers based on chromium.

9. The article as claimed in the preceding claim, in the third layer of chromium is directly in contact with the layers based on chromium, according to the sequence of following layers: SiN / Cr / SiNx / Cr / SiNx wherein SiNx denotes said layers comprising silicon nitride and Cr denotes said layers based on chromium metal.

10. The article as claimed in one of the preceding claims, wherein the functional layer(s) based on chromium comprise more than 70 at% of chromium.

11. The article as claimed in one of the preceding claims, wherein the functional layer(s) consist essentially of chromium and preferably consist of chromium, apart from the unavoidable impurities.

12. The article as claimed in one of the preceding claims, wherein the first layer comprising silicon nitride is deposited directly on the glass substrate and is in contact therewith.

13. The article as claimed in one of claims 1 to 11, wherein at least one layer comprising a metal oxide is present between the surface of the glass substrate and the first layer comprising silicon nitride, the metal oxide preferably being chosen from an oxide of an element chosen from silicon, titanium, tin, zinc, aluminum, zirconium or a mixture of at least two of these elements, in particular silicon oxide, titanium oxide or a zinc tin oxide.

14. The article as claimed in one of the preceding claims, wherein at least one layer comprising a metal oxide is present on top of said sequence of layers, the metal oxide preferably being chosen from an oxide of an element chosen from silicon, titanium, tin, zinc, aluminum or a mixture of at least two of these elements, in particular silicon oxide, titanium oxide, zirconium oxide or a mixture of these oxides.

15. The article as claimed in one of the preceding claims, characterized in that it is thermally toughened and / or curved.

16. A facade cladding panel of spandrel type incorporating at least one article as claimed in one of the preceding claims.