Bronze solar control glazing

Abstract

The present invention relates to heat treatable solar control glazing having high mechanical durability. The solar control glazing of the invention has a substantially pure silicon reflective layer sandwiched between two dielectric layers. The solar control glazing of the invention has a low visible light transmittance and a high reflectance on both sides. As an advantage of the invention, the coated glass has a bronze coloration in transmission.

Description

Bronze solar control glazingTechnical Field

[0001] The present invention relates to heat treatable solar control glazing having high mechanical durability. More particularly the invention discloses a coated glass substrate, the coating comprising one reflective functional layer sandwiched between two dielectric layers. The coated glass of the invention has a low visible light transmittance and a high reflectance on both glass sides. As an advantage of the invention, the coated glass has a bronze colouration in transmission. The coated glass of the invention may be used in building or vehicles for single glass pane window, multiple glazing or laminated glazing and any suitable home appliances.Prior Art

[0002] The most important function of solar control glazing is to prevent overheating by solar radiation into the interior of a building, thereby improving comfort and also reducing the cost of air conditioning systems, especially in warm weather climate. One main request of the architects is that windows incorporating such glazing should moreover fulfil certain aesthetic specifications, namely in terms of colour of transmitted and / or reflected light and in terms of levels of light reflectance. One other important request is that such a glazing must be able to face high temperature heat treatment. Such high temperature treatment may be necessary to toughen the glazing or to bend it. Finaly, the glazing must be chemically and mechanically resistant to ensure a good durability and of course the glazing must also fulfil safety requirements. This last point means that the glazing must be tempered or installed in a laminated form.

[0003] For solar control, a stack with a nickel chrome based functional layer sandwiched between two dielectric layers is well known for a long time. This stack is known to be heat treatable but can also show some weaknesses namely in terms of chemical and mechanical durability. For exampleW02005024085A2 points a lack of corrosion resistance to alkaline solution or humidity and mechanical performance.

[0004] W02014130506A1 disclose a mirror based on a reflective metallic or substantially metallic silicon aluminium layer, sandwiched between two dielectric layers. The aluminium ratio increases the reflectance of the layer but too much Aluminium harms the stability of the silicon layer. All layers are deposited by PVD and the resulting stack is presented as being heat treatable and durable. Nevertheless a protective layer may be requested for improving overall durability (PVD top coat, paint, polymer film).

[0005] WO2018189488A1 discloses a silicon nitride layer with a quite huge nitrogen deficiency allowing a quite high light reflection. This layer is sandwiched between 2 dielectric layers. Such a stack is claimed to be chemically resistant and present also some mechanical durability. No information is given concerning reflection on the glass side and still the durability may be improved.

[0006] There is still possibilities to propose new and improved solar control glazing that meet all the requirements mentioned above.Object of the invention

[0007] The object of the invention is to propose a solar control glazing with a quite simple at least 3 layers stack having a low light transmittance with a beautiful bronze colour and a high external reflection. The glazing of the invention is at least qualified as a class B coated article and may even fulfil requirements of class A on certain aspects. The glazing must also be heat treatable and have a good durability for both chemical and mechanical aspects.Summary of invention

[0008] It is known (see above) that a reflecting silicon-aluminium layer gives a high light reflection and a low light transmission. If aluminium helps for the reflection, it appears nevertheless that aluminium can be responsible for some degradation, mainly during the heat treatment of the glass coated with a SiAl reflecting layer. In a first attempt to improve the mechanical durability, tests have been made with a SiAl reflecting layer containing only 0.1 weight % ofaluminium (table 1 ). The tests summarized in the table show that transmittance decreases when the SiAl layer thickness increases, while both reflectance increase. This shows that even with a very low amount of aluminium, the SiAl layer remains a reflecting layer. Nevertheless, all samples fail to pass the abrasion test.

[0009] Table 1

[0010] Looking for a solution to mechanical weakness of the SiAl layer containing 0.1 % of Al, the inventor has investigated the impact of increasing the thickness of the second dielectric (SiN2 in the examples). The examples are listed in the table 2, the thicknesses of the different layers are given in nm. The result of the abrasion test has been assessed on each sample before (BB) and after (AB) heat treatment and a real improvement is observed when the thickness of the second dielectric layer (SiN2) increases. Nevertheless, this higher thickness results in a lower b* value in transmission which is not acceptable if we want a bronze colour in transmission.

[0011] Table 2

[0012] Surprisingly, the inventor has now discovered that a silicon reflecting layer without aluminium, meaning a glass substrate coated with a substantially pure silicon layer, results in a glazing such that the transmittance is about 30% and the reflectance on both sides is greater than 40%, preferably greater than 45% and more preferably greater than 48%. The coated glass substrate has abeautiful bronze colour in transmission and a quite neutral colour in reflection. The inventor has also discovered that said coated glass substrate successfully passed the abrasion test.

[0013] By substantially pure silicon layer, it is here meant that the layer contains nearly no other element, more particularly nearly no other metallic nor semi metallic element. More particularly, the substantially pure silicon layer contains less than 0.02 weight % of aluminium. Advantageously, the substantially pure silicon layer contains less than 1 weight % of overall metallic and semi metallic impurities.

[0014] According to an advantageous embodiment of the invention, the substantially pure silicon layer has a thickness that is at least 8 nm, preferably at least 10 nm and more preferably at least 12 nm and that is at most 30 nm, preferably at most 25 nm and more preferably at most 20 nm.

[0015] According to this invention a substantially pure silicon layer is deposited on a glass substrate. The substrate may be any type of glass. The substantially pure silicon layer is deposited by the very well known magnetron sputtering technic from a substantially pure silicon target under a pure argon atmosphere. The substantially pure silicon target has a proportion of silicon of at least 99.0 weight %, preferably 99.5 weight % and more preferably 99.95 weight %. Also speaking of a pure argon atmosphere means that only traces of contaminant could be present like unavoidable traces of nitrogen and / or oxygen.

[0016] According to an advantageous embodiment of the invention, the substantially pure silicon layer is sandwiched between two dielectric layers. By dielectric layer, we mean any layer made of a material having a resistivity of at least 1010W.m. Advantageously, each of those two dielectric layers is based on one of an oxide, a nitride or an oxynitride of any element or mixture of any element chosen from silicon, titanium, zirconium, zinc, tin, aluminium.

[0017] The choice of one or both dielectric layers and the thickness of the layers is made to adjust the optical properties, and particularly, the desire colour in transmission and reflection and also to improve the robustness of the stack.

[0018] According to a particular embodiment of this invention, the first dielectric (diell ) is the closest to the glass substrate. Preferably, the first dielectric is contacting the glass substrate. The first dielectric layer has a thickness which is comprised between 5 and 50 nm.

[0019] According to the invention, the substantially pure silicon layer is deposited above the first dielectric layer and preferably, the substantially pure silicon layer is deposited in direct contact with said first dielectric layer.

[0020] According to the invention a second dielectric layer (diel2) is deposited above and contacting the substantially pure silicon layer of the invention. The second dielectric layer has a thickness which is comprised between 5 and 50 nm.

[0021] According to a particular embodiment of the invention, the second dielectric layer is the last layer of the stack of the invention.

[0022] According a particular embodiment of the invention, a protective top coat is deposited above the second dielectric layer. By protective top coat we mean a single or multiple layer system which is designed to improve the chemical and I or mechanical resistance of the entire coating.

[0023] According to a preferred embodiment of the invention, the second dielectric layer is thicker than the first dielectric layer.

[0024] According to a preferred embodiment of the invention, the first dielectric layer is a first silicon nitride inclusive layer. The first silicon nitride inclusive layer is deposited by PVD from a silicon target under an atmosphere comprising argon and nitrogen in a 50 / 50 proportion. More particularly, the silicon target may comprise a metal such as aluminium in an amount of up to 20 weight percent, preferably about 8 weight percent.

[0025] Advantageously this first silicon nitride layer has a thickness that is at least 8 nm, preferably at least 10 nm and more preferably at least 12 nm and that is at most 30 nm, preferably at most 25 nm and more preferably at most 20 nm. The first silicon nitride layer is deposited under the substantially pure silicon layer of the invention and preferably, the first silicon layer is deposited directly in contact with the glass substrate.

[0026] According to a preferred embodiment, the second dielectric layer is a silicon nitride inclusive layer (SiN2) and is deposited by PVD from a silicon targetunder an atmosphere comprising argon and nitrogen in a 50 / 50 proportion. More particularly, the silicon target may comprise a metal such as aluminium in an amount of up to 20 weight percent, preferably about 8 weight percent.

[0027] Advantageously the second silicon nitride layer has a thickness that is at least 9 nm, preferably at least 11 nm and more preferably at least 13 nm and that is at most 50 nm, preferably at most 45 nm and more preferably at most 40 nm.

[0028] According to a particular embodiment, the stack of the invention comprises a first silicon nitride layer (SiN1 ), a substantially pure silicon layer (Si) and a second silicon nitride layer (SiN2). To make such a stack through magnetron sputtering implies that first and the second silicon nitride layers are deposited in a very well known way from a silicon target under an atmosphere containing enough nitrogen to form a SisN4 layer. It is also possible that the target used both silicon nitride layers contains up to 20% weight of aluminium, preferably 8% weight of aluminium. The substantially pure silicon layer is deposited from a substantially pure silicon target, under a pure argon gas atmosphere. More particularly the substantially pure silicon target has a silicon purity of at least 99.0 weight %, preferably 99.5 weight % and more preferably 99.95 weight %. Nevertheless, the man skilled in the art knows that with the proximity of sputtering chambers, contamination of the substantially pure silicon layer with nitrogen is difficult to avoid.

[0029] In a particular embodiment, the stack of the invention consists of the 3 layers described above, which are from the glass substrate: a first silicon nitride layer (SiN1 ), a substantially pure silicon layer (Si) and a second silicon nitride layer (SiN2), meaning that no other layer is present.

[0030] According to another embodiment a top coat is deposited above the stack comprising the following succession from the glass substrate: first dielectric layer I substantially pure silicon layer I second dielectric layer I protective top coat.

[0031] According to any embodiment of this invention, the substrate is a float glass having a thickness between 2 and 12 mm. It may be any type of float glass, clear, extra clear or coloured glass. The difference between clear and extraclear resides in the iron content: when the glass composition comprises a total iron (expressed in terms of Fe2Os) content of less than or equal to 0.015 weight%, the glass is characterized as an extra clear glass. Preferably the glass sheet used for the coated glass of the invention is made of a soda-lime glass.

[0032] According to any embodiment, the glazing of the invention is a coated glass substrate characterized by a light transmittance that is at most 40%, preferably at most 35% and more preferably at most 32%.

[0033] According to any embodiment, the glazing of the invention is a coated glass substrate characterized by a light reflectance both on glass and coating side which is at least 40%, preferably at least 45% and more preferably at least 48%.

[0034] According to a preferred embodiment, the glazing of the invention has a “bronze colour” in transmission, corresponding to the b* colour parameter being greater than 10. The colour in reflection is quite neutral or may be slightly coloured.

[0035] According to other embodiment of the invention, other colours in transmission could be obtained by adjusting the dielectric layers of the stack.

[0036] According to any embodiment of this invention the coated glazing will be used for building or vehicle and may be installed as a monolithic glazing, a multiple glazing or a laminate glazing. Alternatively, the glazing may be used as furniture for any kind of house appliances.

[0037] According to any embodiment of the invention, when the coated glazing is used in a laminate, the laminated glass usually consists of at least two glass sheets assembled by a polymeric film, such as polyvinylbutyral (PVB), ethylenevinylacetate (EVA), thermoplastic polyurethanes (TPU) or ionoplast interlayer such as SentryGlas®.

[0038] For any application (monolithic, multiple glazing or laminated glazing), the coated side of the glazing of the invention may be in any position (any glass surface)

[0039] According to any embodiment of the invention, the coated glazing may be used in the form of a flat glazing or a bent glazing.

[0040] According to any embodiment, the glazing of the invention passes the chemical and mechanical durability tests comprising one abrasion test for the mechanical resistance, the climatic chamber to check the resistance to humidity and the corrosion resistance to alkaline solution. The tests have been performed before and after heat treatment. Those tests have been chosen as reference since it appears that they were the most sensitive and difficult to satisfy.

[0041] As another big advantage of the invention, the optical properties before and after heat treatment show a very good heat treatability of the coated glass of the invention.Brief description of drawings

[0042] This and other aspects of the present invention will now be described with reference to details discussed below. The following description and drawings are illustrative of the disclosure and are not to be construed as limiting the disclosure. The drawings are not to scale and should not be considered as a limitation of the invention.

[0043] Fig.1 illustrates one embodiment of the invention.Description

[0044] Definitions- The wording “substantially pure silicon layer” means that very low amount of other components are present, more particularly metallic or semimetallic elements and that the main component, the silicon, is sufficient to fulfil the main function. Nevertheless we cannot exclude unavoidable contamination from the process (like nitrogen or oxygen incorporation).- In the meaning of the invention, while speaking of the glazing of the invention, we mean a monolithic glass substrate with one side coated with the stack of the invention.- As used herein, the term comprising or comprise, are to be construed as being inclusive and open ended, and not exclusive. Specifically, whenused in the specification and claims, the terms "comprises" and "comprising" and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.- For the sake of clarity, when using terms like “under”, "below", "above", "lower", "upper", "first" or "last" herein, it is always in the context of a sequence of layers starting from the glass below, going upward, further away from the glass. Such sequences may comprise additional intermediate layers, in between the defined layers, if nothing else is specified. The word “sandwiched” describes a layer deposited between two other layers.- Unless otherwise defined, all technical and scientific terms used herein are intended to have the same meaning as commonly understood to one of ordinary skill in the art- By glass side, we mean the main glass surface which is not coated and by coated side, we mean the other main glass surface which is bearing the coating stack

[0045] Symbol and acronyms meaning

[0046] When speaking about heat treatment, it consist in particular of heating the glass sheet to a temperature higher than 560° C in air, e.g., between 560°C and 700°C, and in particular around 640°C to 670°C, for a period of about 3, 4, 6, 8, 10, 12 or even 15 minutes, depending on the type of treatment and the thickness of the sheet. In the case of a bending treatment, the glass sheet may then be bent to the desired shape. The toughening treatment consists of abruptly cooling the surface of the flat or bent glass sheet by air jets or cooling fluid to obtain a mechanical reinforcement of the sheet..

[0047] The optical characteristics are measured in accordance with the norm EN410 (2011 ) and colour parameters are given in accordance with international colour system CIELAB.

[0048] The chemical durability is assessed in accordance with the norm 1096-2 (2012) through the resistance to condensation (annex B) disclosed here as the climatic chamber test (CC). Duration of the test is fixed to 21 days. A rating from 1 to 5 is given, 5 being the best.

[0049] Resistance to alkaline corrosion is assessed with the following procedure. Half of the surface of the glass samples to be tested is im merged in a 0.1 M sodium hydroxide solution at pH 13 during 48h at room temperature. Evaluation through visual inspection results in a rating from 1 to 5, the rating is the same as for the climatic chamber. A rating below 3 being KO and from 3 being OK.

[0050] The mechanical durability is assessed through abrasion test. A suspension of 160 g of silica (500 mesh) is prepared in 1 litre water. Glass samples (10 x 20 cm) are fixed with the coated side upward and a pad continuously fed with the abrasion suspension is allowed to run in a back and forth motion for 600 times during 30 minutes. The test is conducted at room temperature. The samples are then removed, rinsed with water and dried. The samples are evaluated on a scale from 0 to 8 (see below).0: the coating is completely removed1 : 70% of the coating is removed2: 50-70% of the coating is removed 3: 30-50% of the coating is removed 4: less than 30% of the coating is removed5: partial local coating removal6: several scratches are visible in transmission7: some scratches are visible in transmission8: some wear of the coating may be observed in reflexion on the coating sideDescription of embodiments / examples

[0051] The invention will be illustrated by some examples but one must understand that those examples are by no way limiting the scope of the invention. The PVD process is very well known by the skilled person and will not be detailed to avoid useless information.

[0052] The substrate is a soda-lime-silicate glass substrate with a thickness of about 4 mm.

[0053] The silicon target that is used for the deposition of the substantially pure silicon layer, has a great purity. Its specifications are given in the table 3.

[0054] Table 3

[0055] After preparation, the glass is installed to the conveyor to enter deposition installation. In the first zone, Si Al target (8% weight Al) is sputtered under an atmosphere of mixed argon I nitrogen (50 / 50) for the deposition of the first dielectric layer (SiN 1 ). In the second zone, the substantially pure silicon target (see table 3) is sputtered in a pure argon atmosphere. Finally in a third zone, a SiAl target (8% weight Al) is sputtered under an atmosphere of mixed argon I nitrogen (50 / 50) for the deposition of the second dielectric (SiN2). The different sputtering zones are separated by separation tunnel to avoid gas mixing as much as possible.

[0056] In the table 4, we illustrate 2 examples of the invention obtained by the process described above and 2 comparative examples. In all examples the silicon nitride layers are stoichiometric in nitrogen. We start the table with example 7 to avoid confusion with previous table 1 and 2.

[0057] Table 4

[0058] All samples have been heat treated following a known process (heated to 670°C for 3.5 min). The optical characteristics have been analysed before (BB) and after (AB) heat treatment, and the results are given in the table 5. The values of visible light transmittance (Tv), reflectance on the glass side (Rg) and reflectance on the coated side (Rc) are given in percent. The colour parameters (La*b*) given relates to the light transmittance or reflectance given above them. Chemical and mechanical resistances have been assessed and results are given as well in table 5. These 3 durability tests have been chosen because they were the more sensitive.

[0059] Table 5

[0060] As can be seen from the table above, both examples of the invention fulfil optical parameters requested and durability tests. Regarding the comparative examples, the stack of the invention was much more resistant, mainly for the resistance to alkaline corrosion and the mechanical abrasion resistance.

[0061] Optical parameters before and after heat treatment have been compared in order to evaluate the heat treatability of the stack. In the table 6, we have compared the examples 8 and the comparative example 9. To make comparison easier, we have summarized the performances of both coating in terms of DE* for light transmission and reflection on both sides. Those values are calculated from the table 5 thanks to the formula given in paragraph 45.

[0062] Table 6

[0063] As can be seen from the table above, the stack of the invention is very stable for the colour parameters before and after heat treatment. The stack of the invention has a very good heat treatability as can be seen in table 6.

Claims

ClaimsClaim 1. A glazing comprising a glass substrate and a substantially pure silicon layer wherein the substantially pure silicon layer containing less than 0.02% weight of aluminium is deposited by PVD from a pure silicon target and and wherein the substantially pure silicon layer is sandwiched between first and second dielectric layers, the first dielectric layer being closest to the glass substrate.Claim 2. The glazing of claim 1 wherein the substantially pure silicon layer contains less than 1 % of total metallic or semi metallic impurities, preferably less than 0.5% of total metallic or semi metallic impurities and more preferably less than 0,05% of total metallic or semi metallic impurities..Claim 3. The glazing of any previous claim wherein the substantially pure silicon layer has a thickness that is at least 8 nm, preferably at least 10 nm and more preferably at least 12 nm and wherein the substantially pure silicon layer has a thickness that is at most 30 nm, preferably at most 25 nm and more preferably at most 20 nm.Claim 4. The glazing of any previous claim wherein the first dielectric layer has a thickness which is comprised between 5 to 50 nm.Claim 5. The glazing of any previous claim wherein the first dielectric layer is deposited directly in contact with the glass substrate.Claim 6. The glazing of any previous claim wherein, the substantially pure silicon layer is deposited above and contacting the first dielectric layerClaim 7. The glazing of any previous claim wherein, the second dielectric layer is deposited above and contacting the substantially pure silicon layer.Claim 8. The glazing of any previous claim wherein the second dielectric layer has a thickness which is comprised between 5 to 50 nm.Claim 9. The glazing of any previous claim wherein, the second dielectric layer is the last layer of the stack of the invention.Claim 10. The glazing of any previous claim wherein a protective top coat is deposited above the second dielectric layer.Claim 11 . The glazing of any previous claim wherein the second dielectric layer is thicker than the first dielectric layerClaim 12. The glazing of any previous claim wherein the first dielectric layer is a first silicon nitride layer and wherein the first silicon nitride layer has a thickness that is at least 8 nm, preferably at least 10 nm and more preferably at least 12 nm and wherein the first silicon nitride layer has a thickness that is at most 30 nm, preferably at most 25 nm and more preferably at most 20 nm.Claim 13. The glazing of any previous claim wherein the second dielectric layer is a second silicon nitride layer and wherein the second silicon nitride layer has a thickness that is at least 9 nm, preferably at least 11 nm and more preferably at least 13 nm and wherein the second silicon nitride layer has a thickness that is at most 50 nm, preferably at most 45 nm and more preferably at most 40 nm.Claim 14. A method for the preparation of the glazing of any previous claim wherein the substantially pure silicon layer is deposited from a pure silicon target in a pure argon atmosphere.Claim 15. The method of the previous claim wherein the pure silicon target has a purity of at least 99.0 weight %, preferably 99.5 weight % and more preferably 99.95 weight %.Claim 16. The use of a glazing of any previous claim as a laminated glazing.Claim 17. The use of a glazing of any previous claim as a multiple glazing.Claim 18. The use of a glazing of any previous claim for a house appliance.

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