WO2023217992A1

WO2023217992A1 - Reflective glazing comprising a chromium layer

Info

Publication number: WO2023217992A1
Application number: PCT/EP2023/062668
Authority: WO
Inventors: Sacha ABADIE; Paula GONZALEZ DIAZ; Pedro ENRIQUEZ FERNANDEZ
Original assignee: Saint-Gobain Glass France
Priority date: 2022-05-13
Filing date: 2023-05-11
Publication date: 2023-11-16
Also published as: FR3135456A1; FR3135456B1

Abstract

The invention relates to a reflective glazing capable of withstanding heat treatment, in particular annealing, bending and/or tempering, the glazing comprising a glass substrate and a stack of layers including a layer comprising silicon oxide having a thickness of between 15 and 35 nm, a metal layer based on chromium Cr having a thickness of between 45 and 65 nm, a layer comprising silicon nitride having a thickness of more than 20 nm and less than 30 nm and a layer consisting essentially of a metal chosen from titanium, zirconium, silicon or mixtures thereof, which metal has a thickness of more than 1 nm and less than 3 nm.

Description

Description Title: REFLECTIVE GLASS INCLUDING A CHROME LAYER. The present invention relates to glazing comprising a stack of layers of metallic appearance reflecting visible light and capable of withstanding thermal treatments of the annealing, bending, thermal quenching type. Such glazing comprises on a glass substrate a coating 10 comprising an essentially metallic layer reflecting a major part of the visible light, most often in silver or alternatively in another metal such as chrome. Most often this reflective layer is encapsulated in the stack by dielectric materials to protect it from corrosion. Glazing coated with such a stack of layers having this fundamental structure are known in different embodiments. In other cases of use, for example for covering walls or facades, for aesthetic reasons, the emphasis here is placed more on the reflective properties of the stack of layers. In many cases, a metallic appearance reflection is desired, but we often prefer an attenuated reflection with very reduced light transmission. Glazing having a high metallic reflection and a relatively low light transmission are thus very decorative. In architecture, they are often used for cladding walls, facades (as glazing or facade paving) as mirror elements, as semi-transparent mirrors or as decorative glass plates. They can also be provided with an additional decorative impression and are most often used in tempered and/or curved (curved) form. If they are used as monolithic glass panes, the surface layer is exposed without any protection to the atmosphere, so that it must have a particularly high resistance capacity against the atmospheric influences but also sufficient resistance to scratches, essential in particular for cleaning operations. For safety reasons and/or with a view to increasing their resistance to bending and impacts, the 5 coated glass substrates intended for these applications are conventionally prestressed by thermal tempering, i.e. say heated to a temperature above 500°C, 550°C or even 600°C and then very quickly cooled. The stack of thin reflective layers described above must be able to overcome this thermal stress without damage. In particular its aesthetic, optical or even thermal or energetic properties, coated glass glazing must not be disturbed as a result. In particular, it is important that these glazings retain relatively neutral colors after such tempering, on the side of the uncoated glass face (called the glass side face) but also on the side of the stack of layers (called the glass side). stacking side), that the chemical and physical resistance is sufficient to resist external attacks. Above all, it is also essential that the quenching operations 20 do not lead to the appearance of corrosion points (often called pinholes in the field.) It has already been described by the applicant company, in the publication EP 0 962 429 A1, a semi-transparent glazing with a light transmission of between 2 and 4% having high thermal resistance. In the case of this known stack of layers, the dielectric base layer consists of a material based on SiO2, Al ₂ O _3, SiON, Si ₃ N ₄ or AlN or a mixture of at least two of these materials. Among all these materials, it is indicated in paragraph [0028] that the use of a base layer of silicon nitride is to be preferred because it protects the chromium layer better than another layer such as oxide. silicon. The upper layer according to this publication can be based on silicon, silicon nitride or aluminum nitride. It is indicated in this publication that the thickness of this layer is between 2 and 20 nm, so as to limit the color in reflection of the glazing, particularly on the coating side. New glazing is now being sought with a light transmission significantly lower than that covered by EP 0962 429, and in particular less than 1%, or even less than 0.5%. To obtain such glazing, the applicant company thickened the chrome layer, based on the stacks described in this publication. Such thickening leads to a drop in light transmission but together with an increase in the visibility of defects such as corrosion points as described subsequently in the 10 examples. The invention thus aims to develop glazing having a light reflection RL of the glass greater than 45% and preferably greater than 50% and a light transmission TL less than 1%, and preferably less than 0.5%, and comprising a stack of 15 reflective layers with a metallic appearance, having high resistance to scratching and corrosion and high thermal stability, such that it can withstand heat treatment at a temperature above 500°C, in particular quenching, a bending or other, without the appearance of corrosion points (pinholes) and whose coloring is substantially neutral in reflection on the glass side (a* and b* less than 5 in absolute value and if possible negative in the Lab system) and very little color on the stacking side (in particular a value of b* less than or equal to 6 to avoid too marked yellow coloring), after said heat treatment. 25 More particularly, the present invention relates to reflective glazing capable of withstanding heat treatment, in particular of the annealing, bending and/or quenching type, said glazing comprising a glass substrate and a stack of layers deposited on one of the faces 30 of said substrate glassmaker, said stack successively comprising, from the surface of said substrate: - a layer comprising silicon oxide with a thickness of between 15 and 35 nm, - a metallic layer based on chromium Cr, with a thickness of between 45 and 65 nm, - a layer comprising silicon nitride, of thickness greater than 20 nm and less than 30 nm, - a layer consisting essentially of a metal chosen from titanium, zirconium, silicon or mixtures thereof, with a thickness greater than 1 nm and less than 3 nm. 5 According to preferred but non-limiting embodiments of the present invention, which can of course if necessary be combined with each other: - The metal layer comprises more than 80% by weight of chromium, and preferably more than 90% by weight of chromium. 10 - The metallic layer consists essentially of chromium. - The metal layer consists of an alloy of chromium with at least one other metallic element, in which chromium represents more than 50% by weight of said alloy, said at least one element being preferably chosen from Al and/or Si. - The metal layer consists of a CrAl alloy preferably comprising 20-25% by weight of Al, a CrSi alloy comprising 15 to 49% by weight of Si, or a CrAlSi alloy comprising 70-80% in weight of Cr. - The layer comprising silicon oxide has a thickness of between 21 and 29 nm. - The chromium-based metal layer has a thickness of between 50 and 60 nm. - The layer comprising silicon nitride has a thickness of between 21 and 28 nanometers, preferably between 21 and 25 nm. - The stack includes only one layer based on chrome. - Stacking does not include silver or gold layers. - The stack does not include any metallic layers other than that based on chrome. 30 - The layer comprising silicon oxide is directly in contact with the surface of the glass substrate and directly in contact with the chromium-based layer. - The chromium-based layer is directly in contact with the layer comprising silicon nitride. 35 - The layer consisting essentially of titanium, zirconium or silicon is directly in contact with the layer comprising silicon nitride. - The layer consisting essentially of titanium, zirconium or silicon is the last layer of the stack. - said stack only comprises the layer comprising silicon oxide, the layer based on chromium, the layer comprising silicon nitride and the layer consisting essentially of a metal chosen from titanium, zirconium, silicon or their mixtures. - The light transmission of said coated glazing is less than 10 to 1%, preferably less than 0.5%. - The light reflection on the uncoated side of the stack is greater than 45%, preferably greater than 50%. - The stack of layers is in the form of a discontinuous coating, of the decoration or weft type. 15 - A layer of opaque color, in particular of the paint or enamel type, covers the areas of the glazing free from stacking. - Said glazing is annealed, curved and/or tempered. -said glazing is monolithic. The layer comprising silicon nitride mainly comprises silicon and nitrogen as main constituents. In particular, silicon and nitrogen together represent more than 50%, more than 60% or even more than 70% or even more than 80% of the atoms present in a layer, or even more than 90% of the atoms present in a layer. . Preferably, said layers comprising silicon nitride are essentially made up of silicon and nitrogen and optionally of at least one element chosen from aluminum, boron or zirconium, preferably aluminum, apart from inevitable impurities. Said layers comprising silicon nitride are in principle free of oxygen except for unavoidable impurities, for example they comprise less than 5 mole% of elemental oxygen, in particular less than 1 mole% of elemental oxygen. Preferably, said layer has an N/Si ratio greater than 1.25 and are stoichiometric or substantially stoichiometric layers, preferably substantially stoichiometric. By “stoichiometric”, we mean that the N/Si ratio is equal to 1.33 for these nitride layers based on silicon, corresponding to the compound Si3N4. By “substantially stoichiometric”, we mean for example that the value measured for this Si3N4 compound differs by less than 5% from this theoretical value. 5 Indeed, it should be noted that the layers comprising silicon nitride according to the invention are obtained by a magnetron-assisted cathode sputtering process from a metallic silicon target which may comprise a minor quantity of another element such as aluminum and/or zirconium, for example around 8 atomic% of aluminum, in a reactive atmosphere containing nitrogen. In such a case, the N/Si ratio can vary significantly from the theoretical value 1.33 (= 4/3) (corresponding to the defined compound Si3N4) taking into account the stoichiometries of the defined compounds AlN and Si3N4. As an example, for a layer of silicon nitride comprising a little aluminum, obtained with the target described above (8% aluminum), the N/Si ratio of the stoichiometric layer theoretically corresponds to a formulation: 92% (SiN1.33) / 8% (AlN) i.e. an N/Si ratio of 1.41 (based on a theoretical formula 0.92 SiN1.33 0.08 AlN, i.e. a ratio: N/Si 20 = [(0.92×1.33+0.08×1)/(0.92)] = 1.41). Likewise, the layer comprising silicon oxide mainly comprises silicon and oxygen as main constituents. In particular, silicon and oxygen together represent more than 50%, more than 60% or even more than 70% or even more than 80% of the atoms present in a layer, or even more than 90% of the atoms present in a layer. . Preferably, said layers comprising silicon oxide consist essentially of silicon and oxygen and optionally of at least one element chosen from aluminum, boron or zirconium, preferably aluminum, with 30 impurities inevitable near. The layers comprising silicon oxide according to the invention are obtained by a magnetron-assisted cathode sputtering process from a metallic silicon target which may comprise a minor quantity of another element such as aluminum and/or zirconium, for example around 8 atomic% of aluminum, in a reactive atmosphere containing oxygen. In particular the silicon target is the same as that used to obtain the silicon nitride layer described previously. The reflective functional layer is based on chrome. It preferably consists essentially of chromium, or even consists of chromium, apart from inevitable impurities. It can alternatively be based on an alloy comprising mainly chromium, in particular more than 50% chromium by weight, preferably more than 60% by weight, or even more than 70% by weight or even more than 80% by weight and in a very preferred more than 90% weight of chromium. 10 This concerns in particular a binary chromium-aluminum alloy CrAl, with a mass content of 10% to 40% aluminum, in particular 20 to 25% by weight of aluminum. It is also a chromium-silicon alloy, Cr-Si, with preferably at least 5 to 10% by weight of silicon, in particular between 5 and 49% by weight of silicon. It may also be a three-component alloy such as the Cr-Al-Si alloy, preferably comprising at least 60% by weight of chromium, in particular between 70 and 80% by weight of chromium. The upper layer of metal with a thickness greater than 1 nm and less than 3 nm consists essentially of a metal chosen from Ti, Zr, Si or their mixtures. Preferably the thickness of this layer is between 1.5 nm and 2.5 nm. For example, the atomic sum of these three elements can represent more than 90%, or even more than 95% of the atoms in the layer (except oxygen). Preferably the layer consists essentially of Ti. During a heating step such as quenching, bending or annealing, this layer is at least partially oxidized to the corresponding oxide. Thus, a layer of Ti is ultimately present in the stack in the form of TiOx, after quenching. The stacks of layers according to the invention make it possible to fulfill to a large extent all of the aforementioned requirements, the desired result being produced by the combined action of the different layers of the stack. The glazing according to the invention is constituted by a glass substrate on which the layers of the stack are deposited and are said to be "bombable", and/or "tempenable", that is to say that they can undergo such a heat treatment. without significant modification of their appearance (particularly in terms of corrosion and colorimetry). The stacks of layers according to the invention are advantageously deposited on the glass substrates following known reactive cathode sputtering processes assisted by a magnetic field in industrial continuous coating installations. The coated glazing can then be subjected to a usual tempering process, without the stack of layers significantly losing its desired optical and aesthetic properties, in particular its colors in reflection. 10 After deposition of the stack of layers according to the invention, an additional layer can be applied, for example a layer of continuous color in particular opaque, on the coated side, possibly for aesthetic purposes or to manufacture opaque glazing of the type lightens. This layer can also be made of paint or enamel, obtained by baking an enamelling composition in a known manner. In this case, the cooking operation can advantageously be linked to the annealing, bending or quenching operation of the glass substrate carrying the stack. The two operations can thus be concomitant. 20 The invention and its advantages are illustrated by the following examples: ^ Reference example (according to EP0962429) 25 The reference example is example 4 of the previous publication EP0962429 A1, which describes the following glazing: Glass - 15 nm Si3N4 - 35 nm Cr - 3 nm Si3N4 - 3 nm Ti, where the Ti is, after quenching, at least partially oxidized to titanium oxide TiOx. Example 1 (comparative) In this example, glazing identical to the reference example is synthesized but in which the thickness of the chromium layer is increased to 55 nm. 35 The conditions for depositing the stack are as follows: On an industrial vacuum coating installation, 4 mm thick Planiclear ™ clear float glass substrates are coated using a conventional cathode sputtering process assisted by a magnetic field, to obtain the following stack of layers: Glass - 15 nm Si3N4 - 55 nm Cr - 3 nm Si3N4 - 3 nm Ti The SiO2 layer is sputtered in DMS mode (Dual-Magnetron-Sputter mode), with two cathodes and an alternating current under a reactive atmosphere from a Si target with a working gas composed of Ar/O2, and the Si3N4 layer under a reactive atmosphere from a Si target with a working gas composed of Ar/N2, according to well-known techniques in the domain. The Cr layer is obtained by sputtering a target made of Cr in an atmosphere made of argon. The upper layer of Ti is obtained by sputtering a target made of Ti in an atmosphere made of argon. Example 2 (comparative) In this example, we increased the thickness of the silicon nitride layer deposited above the chrome layer: We proceed in the same way as for example 1 to obtain the glazing following: Glass - 22 nm Si3N4 - 55 nm Cr - 23 nm Si3N4 – 2 nm of Ti Example 3 (according to the invention) In this example, we proceed in the same way as for example 1 to obtain the glazing following: Glass - 22 nm SiO2 - 55 nm Cr - 23 nm Si3N4 - 2 nm of Ti Example 4 (comparative) In this example, we proceed in the same way as for example 1 to obtain the following glazing: Glass - 22 nm SiO ₂ - 55 nm Cr - 23 nm Si ₃ N ₄ - 3 nm of Ti Example 5 (comparative) In this example, we proceed in the same way as for the example 1 to obtain the following glazing: Glass - 22 nm SiO2 - 55 nm Cr - 23 nm Si3N4 - 1 nm of Ti Example 6 (comparative) In this example, we proceed in the same way as for example 1 for the obtaining the following glazing: Glass - 22 nm SiO2 - 55 nm Cr - 30 nm Si3N4 - 2 nm of Ti Example 7 (comparative) In this example, we proceed in the same way as for example 1 to obtain the following glazing: Glass - 22 nm SiO2 - 55 nm Cr - 23 nm Si3N4 The glazing thus coated is thermally tempered in an industrial tempering installation, by heating to a temperature of approximately 650°C and rapid cooling by blowing cold air according to usual techniques. The glazing is then subjected to the following tests to determine their resistance to tempering and their potential use: - Optical quality: The measurement of the transmission of the layer system in the visible spectral zone TL, of the reflection in the spectral zone visible RL (according to illuminant D65) according to standard ISO9050 (2003). The coordinates a* and b* are determined in the CIELAB colorimeter system (L, a*, b*). - Mechanical resistance: the scratch resistance of the coatings was measured using a SCRATCH HARDNESS TESTER 413 device supplied by the company Erichsen according to the following protocol: The sample is mounted on a rotating table (number of revolutions in the standard version: 5 min ^-1 ). The test tool is attached to a load arm with an adjustable weight that allows the pressure of the tool to be adjusted to the sample (load range 0 to 10 N). The resistance of the sample to this effect is assessed visually using the scratch track. The sample is considered suitable for marketing if there is no no visible scratches with a load of 1 N and low visibility of scratches at 3 and 5N. - Quenching corrosion test: the number of corrosion points is observed visually after quenching. We define 3 levels 5 of occurrence: ++: very numerous points of corrosion (pinholes) +: a few visible points of corrosion 0: no visible points of corrosion 10 The results of the tests carried out to evaluate the properties of the layers are collected in the following Table I, in which the results of the tests on the coated glazing after the tempering treatment are reported.

[Table 1] Test Example Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 ) s R eee O

*data EP0962429 NM: not measured The test results show that the stability of the stack, in particular its corrosion level and its colorimetry, is not affected by the thermal quenching treatment described previously only for example 3 according to the invention, that is to say in which the thicknesses and the materials used in the stack are selected according to the criteria defined previously, and as reported in the claims which follow. In detail, we can see in the table above that the use of a layer of silicon oxide below the layer of chromium is much more effective in preventing the appearance of corrosion points such as “pinholes”. . Without linking such an observation to any theory, it is possible that such defects were already present in example 4 of EP0962429 with a chromium thickness of 35 nm as described in the comparative example but were not visually detectable, due to a TL greater than 2%. Thus, comparative examples 1 and 2, which include an underlayer based on silicon nitride, exhibit such defects, unlike layers whose underlayer is based on silicon oxide. Comparative Example 1 shows in particular that the thickening of the chrome layer in the example according to EP 0962429 leads to the visual appearance of very numerous points of corrosion, making such a product unsaleable. 10 Comparative Example 2 further shows that a thicker underlayer based on silicon nitride leads to a marked and undesirable yellow appearance of the glazing in reflection on the stacking side (value of b* much greater than 6). Examples 3 to 7, by comparison with Examples 1 and 2, unexpectedly show that the combination of an underlayer comprising silicon oxide and an overlayer comprising silicon nitride with a thickness greater than 20 nm makes it possible to effectively prevent the formation of said corrosion points. Comparative Examples 4 and 5 show the importance of selecting the thickness of the layer between 1 and 3 nm: thus a thickness of 3 nm leads to an undesirable marked yellow appearance of the glazing in reflection on the stacking side whereas a layer of 1 nm does not provide sufficient mechanical strength of the stack. Comparison of comparative example 7 with example 3 according to the invention also shows that an additional metallic layer of Ti above the layer of silicon nitride in the stack only very slightly modifies the value b * in reflection on the stacking side, but only if its thickness does not reach 3 nanometers (comparative example 4). 30 Comparative Example 6 shows that too much thickness of the silicon nitride layer above the reflective chromium layer of chromium also leads to an undesirable marked yellow appearance of the glazing in reflection on the stacking side (b* much higher to 6). 35 The substrate provided with the stack of layers is preferably made of glass, and can be used as monolithic or incorporated glazing in a laminated glazing or multiple insulating glazing structure. It can remain transparent or be opaque, and be continuous or present patterns. 5

Claims

Claims 1. Reflective glazing capable of withstanding heat treatment, in particular of the annealing, bending and/or quenching type, said glazing comprising a glass substrate and a stack of layers deposited on one of the faces of said glass substrate, said stack comprising successively, from the surface of said substrate: - a layer comprising silicon oxide with a thickness between 15 and 35 nm, - a metallic layer based on chromium Cr, with a thickness between 45 and 65 nm, - a layer comprising silicon nitride, with a thickness greater than 20 nm and less than 30 nm, - a layer consisting essentially of a metal chosen from titanium, zirconium, silicon or their mixtures, with a thickness greater than 1 nm and less than 3nm.

2. Glazing according to claim 1, in which the metal layer consists essentially of chromium.

3. Glazing according to claim 1, in which the metal layer consists of an alloy of chromium with at least one other metallic element, in which the chromium represents more than 0% by weight of said alloy, said at least one element being chosen from reference among Al and/or Si.

4. Glazing according to claim 1, in which the metal layer consists of a CrAl alloy preferably comprising 0-25% by weight of Al, of a CrSi alloy comprising 15 to 49% by weight of Si, or d a CrAlSi alloy comprising 70-80% by weight of Cr.

5. Glazing according to one of the preceding claims, in which the layer comprising silicon oxide has a thickness of between 21 and 29 nm.

6. Glazing according to one of the preceding claims, in which the chromium-based metal layer has a thickness of between 50 and 60 nm.

7. Glazing according to one of the preceding claims in which the layer comprising silicon nitride has a thickness between 21 and 28 nanometers, preferably between 21 and 25 nm.

8. Glazing according to one of the preceding claims in which the stack comprises only a single layer based on chrome. 5

9. Glazing according to one of the preceding claims in which the layer comprising silicon oxide is directly in contact with the surface of the glass substrate and directly in contact with the chromium-based layer.

10. Glazing according to one of the preceding claims in which the chromium-based layer is directly in contact with the layer comprising silicon nitride.

11. Glazing according to one of the preceding claims in which the layer consisting essentially of titanium, zirconium or silicon is directly in contact with the layer comprising silicon nitride.

12. Glazing according to one of the preceding claims in which the layer consisting essentially of titanium, zirconium or silicon is the last layer of the stack.

13. Glazing according to one of the preceding claims in which said stack only comprises the layer comprising silicon oxide, the layer based on chromium, the layer comprising silicon nitride and the layer consisting essentially of a chosen metal among titanium, zirconium, silicon or their mixtures.

14. Glazing according to one of the preceding claims in which the light transmission is less than 1%, preferably less than 0.5%.

15. Glazing according to one of the preceding claims in which the light reflection on the uncoated side of the stack is greater than 45%, preferably greater than 50%.

16. Glazing according to one of the preceding claims, in which the stack of layers is in the form of an iscontinuous coating, of the decoration or frame type.

17. Glazing according to the preceding claim, in which a layer of opaque color covers the areas of the glazing free from stacking.

18. Glazing according to one of the preceding claims, characterized in that it is annealed, curved and/or tempered.

19. Glazing according to one of the preceding claims, characterized in that it is monolithic. 5