Window pane having a bendable emissivity-reducing coating

Abstract

The invention relates to a window pane which has an emissivity-reducing coating and comprises at least: - a glass pane (2) and - an emissivity-reducing coating (10) on a surface of the glass pane (2). The emissivity-reducing coating (10) comprises, in the specified order starting from the surface of the glass pane (2): - a dielectric blocking layer (11) against alkali diffusion, having a refractive index of at least 1.9, - an electrically conductive layer (13) based on a transparent conductive oxide, - a metal-based barrier layer (14) with a thickness of 12 nm to 30 nm, said barrier layer optionally being completely or partially oxidized, and - an upper dielectric anti-reflection layer (15) with a refractive index of maximally 1.6, said barrier layer (14) being based on titanium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten and / or chromium, preferably titanium.

Description

[0001] Window pane with a flexible emissivity-reducing coating

[0002] The invention relates to a window pane with an emissivity-reducing coating and its use.

[0003] It is known that window panes can be equipped with emissivity-reducing coatings to improve thermal comfort in the interior space defined by the window pane. Such coatings are also known as heat-reflecting coatings, low-emissivity coatings, or low-E coatings and are commonly used, for example, in vehicle roof windows. The emissivity-reducing coating is applied primarily to the interior-facing surface of the window pane. It exhibits reflective properties, particularly in the mid-infrared spectral range, and therefore has a reflective effect on thermal radiation. At low outside temperatures, the coating reduces heat radiation from the interior and thus prevents the interior from cooling down.At high outside temperatures, the coating partially absorbs the infrared radiation components of the sun's rays, particularly reducing the heat radiation from the heated window pane into the interior. The IR-reflecting properties are typically provided by a corrosion-resistant, electrically conductive layer, for example, based on a transparent conductive oxide (TCO) such as indium tin oxide (ITO). Dielectric layers are also usually present, which serve to improve the optical properties and / or protect the conductive layer.

[0004] Emissivity-reducing coatings of this type have been described in numerous publications. Reference is made to WO2018206236A1, WO2023237839A1, US2015017355A1, and US2015291471A1, for example.

[0005] WO2021105959A1 discloses an emissivity-reducing coating with a very thin metallic layer above the TCO layer with a thickness of 3 nm to 10 nm.

[0006] Window panes are often subjected to heat treatment, for example, to thermally toughen them. Window panes in the automotive sector, in particular, are also often bent, which also occurs at elevated temperatures. Since the coating is typically applied to the flat pane before the heat treatment or bending process, this places high demands on the coating. The coating must withstand the heat treatment, and especially the bending process, without cracks or other damage developing. Such cracks are primarily due to excessive oxidation of the TCO layer during the heat treatment.

[0007] WO2013131667A1 discloses a flexible emissivity-reducing coating, wherein the flexibility is ensured by a dielectric barrier layer for regulating oxygen diffusion above the TCO layer with a thickness of 10 nm to 40 nm. In a preferred embodiment, this barrier layer is based on silicon nitride, while all other layers are oxide in nature. This complicates the manufacturing process using magnetron sputtering because the coating application requires several separate chambers with different process gases (oxygen or nitrogen). Furthermore, the immediate successive application of oxide and nitride layers carries the risk of forming oxide-nitride mixed phases, which exhibit undefined optical properties.

[0008] From EP3296275B1 a vehicle window with an emissivity-reducing coating is known, which in example 7 (“sample 7”) has, starting from the window surface, a layer of TiO2 doped with SiO2 (10 nm), a layer of SiO2 (35 nm), a layer of ITO (150 nm), a layer of ZrBO (30 nm) and a layer of SiO2 (30 nm).

[0009] From W02008065962A1 a window pane with an IR-reflecting coating is known which, in Figure 4, starting from the pane surface, has a TiO2 layer (9 nm), a SiO2 layer (33 nm), a TiO2 layer (104 nm), a SiO2 layer (159 nm), a TiO2 layer (95 nm), a SiO2 layer (18 nm), a TiO2 layer (36 nm), an Ag layer (12 nm), an ITO layer (73 nm), an Ag layer (16 nm), a TiO2 layer (23 nm), a SiO2 layer (108 nm) and a TiO2 layer (92 nm).

[0010] There is a need for window panes with emissivity-reducing coatings that are temperable, particularly bendable, and easy to manufacture. The present invention is based on the object of providing such improved window panes. The object of the present invention is achieved according to the invention by a window pane according to claim 1. Preferred embodiments are set out in the subclaims.

[0011] The window pane according to the invention with an emissivity-reducing coating comprises at least:

[0012] - a glass pane and

[0013] - an emissivity-reducing coating on a surface of the glass pane.

[0014] The emissivity-reducing coating comprises, starting from the surface of the glass pane, in the following order:

[0015] - a dielectric blocking layer against alkali diffusion with a refractive index of at least 1.9,

[0016] - an electrically conductive layer based on a transparent conductive oxide,

[0017] - a metal-based barrier layer with a thickness of 12 nm to 30 nm, which is optionally fully or partially oxidized,

[0018] - a dielectric upper anti-reflective layer with a refractive index of not more than 1.6.

[0019] The metal-based barrier layer protects the electrically conductive layer based on the transparent conductive oxide (TCO) from excessive oxidation, particularly during thermal treatment of the coated glass pane, such as occurs during thermal tempering or a glass bending process. According to the invention, the thickness of this barrier layer is selected such that, on the one hand, it is sufficiently thick to effectively reduce the oxidation of the TCO layer, and, on the other hand, sufficiently thin so as not to critically reduce light transmission. Compared to nitride barrier layers known in the art (particularly those based on silicon nitride), the metallic barrier layer offers process-related advantages.This avoids the use of nitrogen as a process gas (at least for this layer), which would have to be laboriously separated from the oxygen process gas of the surrounding layers. Furthermore, many metals can be sputtered at significantly higher deposition rates than silicon nitride, resulting in lower energy consumption. These are major advantages of the present invention. The barrier layer is typically applied as a metallic layer. If the glass pane is subjected to a thermal treatment (e.g., by thermal tempering or glass bending), the barrier layer can be fully or partially oxidized, so that it is present in the final product partially (i.e., over part of its layer thickness) or completely (i.e., over its entire layer thickness) as a metal oxide layer.Part of the protective effect of the metallic barrier layer against the TCO layer is based on the oxidation, because it traps oxygen, which then cannot reach the TCO layer and oxidize it.

[0020] The window pane can be structurally formed by only the glass pane with the emissivity-reducing coating (single glazing). However, it is possible for the window pane to include another pane (or even several additional panes) bonded to the coated glass pane in the manner of an insulating glazing unit or a laminated unit.

[0021] The window pane is intended to separate an interior space from an exterior environment in a window opening (for example, in a building or vehicle). The glass pane (and any other panes of the window pane) has an exterior surface and an interior surface, and a circumferential side edge running between them. For the purposes of the invention, the "exterior surface" refers to the main surface intended to face the exterior environment in the installed position. For the purposes of the invention, the "interior surface" refers to the main surface intended to face the interior in the installed position.

[0022] In a preferred embodiment, the emissivity-reducing coating is applied to the interior-facing surface of the glass pane. This interior-facing surface of the glass pane is particularly preferably also the interior-facing surface of the entire window pane, exposed to the interior. The emissivity-reducing coating can then optimally exert its effect because it is positioned between the window pane and the interior space defined by it, and can act on all the thermal radiation emanating from the window pane.

[0023] Alternatively, the emissivity-reducing coating can also be applied to the outer surface of the glass pane, which is then preferably the outer surface of the entire window pane exposed to the external environment. This can be particularly useful in the architectural field, for example, as an anti-condensation coating.

[0024] The window pane according to the invention is preferably a vehicle pane, for example a windshield, side window, roof window, or rear window of a vehicle. The window pane is preferably designed either as a monolithic glass pane (structurally formed only from the coated glass pane, which is then preferably thermally tempered) or as a composite pane, wherein the glass pane is bonded to another pane via a thermoplastic layer. Since vehicle windows are typically curved, the bendable emissivity-reducing coating according to the invention is particularly advantageous. However, the window pane can in principle also be used in the architectural field, for example as a window or door pane of a building or an interior space, or as a glass facade.

[0025] The emissivity-reducing coating according to the invention is a thin-film stack, i.e., a sequence of thin individual layers. It is particularly transparent, so that the light transmission of the window pane is not excessively reduced and visibility through the window pane is still possible.

[0026] Emissivity-reducing coatings are also known as heat-reflecting coatings, low-emissivity coatings, or low-E coatings. Emissivity is the measure that indicates how much heat radiation the pane emits into an interior space in its installed position compared to an ideal heat radiator (a blackbody). Emissivity-reducing coatings prevent heat from entering the interior (IR components of solar radiation and, in particular, the thermal radiation from the pane itself) and also prevent heat from being emitted from the interior. They exhibit reflective properties against infrared radiation, particularly against thermal radiation in the spectral range of 5 pm - 50 pm (see also standard DIN EN 12898:2019-06). This effectively improves thermal comfort in the interior.At high outside temperatures and in sunlight, the emissivity-reducing coatings can at least partially reflect the thermal radiation radiated from the entire pane toward the interior. At low outside temperatures, they can reflect the thermal radiation radiated from the interior and thus reduce the effect of the cold pane as a heat sink. The interior-side emissivity of the window pane according to the invention is preferably less than or equal to 40%, more preferably less than or equal to 35%, and most preferably less than or equal to 30%. Interior-side emissivity is understood to mean the normal emissivity at 283 K according to the standard DIN EN 12898:2019-06.

[0027] The emissivity-reducing coating is typically applied over the entire surface of the glass pane. A peripheral edge region and / or other locally limited areas, which serve, for example, for data transmission, may be uncoated. The coated portion of the substrate surface is preferably at least 80%, particularly preferably at least 90%. However, a full-surface emissivity-reducing coating is preferred.

[0028] For the purposes of the present invention, refractive indices are generally specified relative to a wavelength of 550 nm. The refractive index is fundamentally independent of the measurement method. It can be determined, for example, using ellipsometry. Ellipsometers are commercially available, for example, from Sentech.

[0029] The optical thickness is the product of the geometric thickness and the refractive index (at 550 nm). The optical thickness of a layer sequence is calculated as the sum of the optical thicknesses of the individual layers.

[0030] Unless otherwise stated, the specification of layer thicknesses refers to the geometric thickness of a layer. If the optical thickness is meant instead, this is explicitly stated. The optical thickness, as defined by the invention, is the product of the geometric thickness and the refractive index at 550 nm.

[0031] The oxides, nitrides, and carbides mentioned in this description can be deposited stoichiometrically, substoichiometrically, or superstoichiometrically with respect to oxygen, nitrogen, or carbon content, respectively. This also applies if stoichiometric molecular formulas are given in the description of the materials for the sake of simplicity and better understanding.

[0032] If a first layer is arranged above a second layer, this means, within the meaning of the invention, that the first layer is arranged farther from the glass pane than the second layer. If a first layer is arranged below a second layer, this means, within the meaning of the invention, that the second layer is arranged farther from the glass pane than the first layer.

[0033] If a layer (thin film) of a coating is formed on the basis of a material, the layer consists predominantly of this material (more than 50 atomic%), in particular essentially of this material in addition to any impurities or dopants.

[0034] The materials may contain dopants, particularly aluminum, boron, antimony, zirconium, or titanium. These dopants can provide dielectric materials with a certain degree of electrical conductivity. However, those skilled in the art will identify them as dielectric layers in terms of their function, as is common in the field of thin films. The material of the dielectric layers preferably has an electrical conductivity (the inverse of the resistivity) of less than 10' 4 S / m. The material of the electrically conductive layers preferably has an electrical conductivity of greater than 10 4 S / m on.

[0035] The dielectric blocker layer reduces or prevents the diffusion of alkali ions from the glass pane into the layer system. Alkali ions can negatively influence the properties of the coating. Furthermore, the blocker layer advantageously contributes to adjusting the optical properties of the overall layer structure. According to the invention, the refractive index of the blocker layer is at least 1.9 (i.e., greater than or equal to 1.9), preferably from 1.9 to 2.5. The blocker layer is preferably the bottommost layer of the layer stack, thus having direct contact with the substrate surface, where it can optimally unfold its effect.

[0036] The blocker layer is preferably formed on the basis of an oxide, a nitride or a carbide, preferably of tungsten, chromium, niobium, tantalum, zirconium, hafnium, titanium, silicon or aluminum, for example oxides such as WO3, Nb2O5, Bi2O5, TiO2, Ta2O5, ZrO2, HfO2, SnO2 or ZnSnOx, or nitrides such as AlN or SiO2N. The blocker layer is particularly preferably formed on the basis of silicon nitride (SiO2N), with which particularly good results are achieved. The silicon nitride can contain dopants, for example aluminum (SiO2NAl), titanium (SiO2NTi), zirconium (SiO2NZr) or boron (SiO2NB).

[0037] During a heat treatment after application of the coating according to the invention, the silicon nitride can be partially oxidized. A blocking layer deposited as SiSn4 then contains Si after the heat treatment. x N y Oz, with the oxygen content typically ranging from 0 atomic% to 35 atomic%.

[0038] The thickness of the blocking layer is preferably from 10 nm to 50 nm, particularly preferably from 20 nm to 40 nm, for example from 25 nm to 35 nm. This is advantageous with regard to the blocking effect against alkali diffusion and the optical properties of the window pane. The optical thickness of the blocking layer is preferably from 20 nm to 100 nm, particularly preferably from 40 nm to 80 nm, for example from 50 nm to 70 nm.

[0039] The electrically conductive layer based on a transparent conductive oxide (TCO layer) provides the IR-reflecting properties of the emissivity-reducing coating. TCO layers are corrosion-resistant and can be used on exposed surfaces. The refractive index of the TCO layer is preferably between 1.7 and 2.3.

[0040] The electrically conductive layer is preferably based on indium tin oxide (ITO), which has proven particularly effective, particularly due to its low resistivity and low sheet resistance variation. Alternatively, the conductive layer can also be based on, for example, indium zinc mixed oxide (IZO), gallium-doped tin oxide (GZO), fluorine-doped tin oxide (FTO, SnO2:F), antimony-doped tin oxide (ATO, SnO2:Sb), or niobium-doped titanium oxide (TiO2:Nb).

[0041] The thickness of the TCO layer is preferably from 30 nm to 150 nm, particularly preferably from 50 nm to 130 nm, for example from 60 nm to 120 nm. This achieves particularly good results with regard to electrical conductivity while simultaneously maintaining sufficient optical transparency.

[0042] According to the invention, the barrier layer is formed from a metal. The barrier layer protects the TCO layer from excessive oxidation, particularly during heat treatment during the manufacturing process. It can be completely or partially oxidized, so that the final product can contain a completely or partially oxidized barrier layer instead of a purely metallic barrier layer.

[0043] The metal on which the barrier layer is based should be corrosion-resistant so that the emissivity-reducing coating can be applied to an exposed surface of the window pane. According to the invention, the metal is titanium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten, or chromium, or mixtures or alloys thereof. Titanium is preferred. The titanium can be doped or alloyed, for example, with silicon, aluminum, zirconium, niobium, or chromium. In a preferred embodiment, the barrier layer is in direct contact with the TCO layer, so that no additional layers are arranged between the barrier layer and the TCO layer. The protective effect of the barrier layer against the TCO layer is then particularly effective.

[0044] According to the invention, the thickness of the barrier layer is between 12 nm and 30 nm. Thinner barrier layers are insufficient to protect the TCO layer from oxidation, while thicker barrier layers exhibit excessive light absorption and excessively reduce the light transmission of the window pane. The thickness of the barrier layer is preferably between 12 nm and 25 nm, more preferably between 15 nm and 25 nm, and most preferably between 15 nm and 20 nm. This is particularly advantageous with regard to protecting the TCO layer from oxidation and ensuring high transparency.

[0045] The upper anti-reflective coating has an anti-reflective effect, reducing reflections on the coated pane surface and increasing light transmission through the pane. It also promotes a neutral color impression. According to the invention, the refractive index of the upper anti-reflective coating is at most 1.6 (i.e., less than or equal to 1.6), preferably from 1.3 to 1.6.

[0046] The upper anti-reflective coating is preferably based on an oxide or fluoride, particularly preferably based on silicon oxide, magnesium fluoride, or calcium fluoride, in particular based on silicon oxide (SiO2). The silicon oxide can contain dopants, for example, aluminum (SiO2:Al), boron (SiO2:B), titanium (SiO2:Ti), or zirconium (SiO2:Zr).

[0047] The thickness of the upper anti-reflective coating is preferably from 30 nm to 200 nm, particularly preferably from 40 nm to 100 nm, for example from 50 nm to 70 nm. This achieves good anti-reflective properties and a neutral color. The optical thickness of the upper anti-reflective coating is preferably from 40 nm to 300 nm, particularly preferably from 60 nm to 150 nm.

[0048] In an advantageous development, a dielectric lower anti-reflective coating is arranged between the blocking layer and the electrically conductive layer. This further reduces reflections on the coated pane surface, further improves light transmission, and promotes a neutral color impression. The refractive index of the lower anti-reflective coating is preferably at most 1.6 (i.e., less than or equal to 1.6), particularly preferably from 1.3 to 1.6.

[0049] The emissivity-reducing coating then comprises, starting from the surface of the glass pane, in the following order:

[0050] - the dielectric blocking layer against alkali diffusion,

[0051] - the dielectric lower anti-reflective layer,

[0052] - the TCO layer,

[0053] - the barrier layer based on a metal,

[0054] - the dielectric upper anti-reflective layer.

[0055] The lower anti-reflective coating is preferably based on an oxide or fluoride, particularly preferably based on silicon oxide, magnesium fluoride, or calcium fluoride, in particular based on silicon oxide (SiO2). The silicon oxide can contain dopants, for example, aluminum (SiO2:Al), boron (SiO2:B), titanium (SiO2:Ti), or zirconium (SiO2:Zr).

[0056] The thickness of the lower anti-reflective layer is preferably from 5 nm to 50 nm, particularly preferably from 10 nm to 40 nm, for example from 20 nm to 40 nm. This achieves good anti-reflective properties and a neutral color. The optical thickness of the lower anti-reflective layer is preferably from 7 nm to 75 nm, particularly preferably from 15 nm to 60 nm.

[0057] The upper anti-reflective coating can be the topmost layer of the coating. It then has the greatest distance from the surface of the glass pane and is the final layer of the layer stack, which is exposed, accessible, and touchable by people. However, it is also possible for one or more additional individual layers to be arranged above the upper anti-reflective coating. Such an additional layer (cover layer) can, for example, serve to improve scratch protection and / or abrasion resistance and can be based on zirconium oxide, titanium oxide, titanium zirconium oxide, silicon zirconium oxide, or hafnium oxide and have a thickness of 1 nm to 10 nm, in particular 2 nm to 5 nm. A photocatalytic layer for self-cleaning can also be used as the top layer (cover layer) and can be based on titanium oxide.In a particularly preferred embodiment, the coating consists only of the described layers and contains no additional layers. The emissivity-reducing coating then consists of the following layers in the specified order, starting from the surface of the glass pane:

[0058] - the blocking layer against alkali diffusion,

[0059] - optionally (and preferably) the lower anti-reflective layer,

[0060] - the TCO layer,

[0061] - the barrier layer,

[0062] - the upper anti-reflective layer,

[0063] - optionally the top layer.

[0064] In a first embodiment, the window pane according to the invention is a monolithic glass pane (single pane of glass) and is structurally formed solely from the glass pane with the emissivity-reducing coating. The glass pane is preferably tempered, in particular thermally tempered, to improve stability and fracture resistance and to minimize the risk of injury in the event of glass breakage. Such a single pane of glass can be used, for example, as a window pane in vehicles (in particular as a side window or rear window, but also as a roof pane) or as a window pane in building-like structures, for example, garden sheds, agricultural facilities (such as barns), or hunting facilities (such as hunting hides).

[0065] The glass pane preferably has a thickness of 2 mm to 10 mm, in particular of 3 mm to 6 mm.

[0066] In a second embodiment, the window pane is designed as a laminated pane. The surface of the glass pane facing away from the emissivity-reducing coating is bonded to another glass pane via a thermoplastic intermediate layer. Such a laminated pane can be used in particular as a vehicle window (for example as a windshield or roof window, but also as a side window or rear window). Alternatively, the laminated pane can also be used on its own as a window pane in building-like structures, for example garden sheds, agricultural facilities (such as barns) or hunting facilities (such as hunting blinds), or as a component of insulating glazing as a window, door or facade pane of a building. The laminated pane can also be used, for example, as an oven door or refrigerator door or as a component thereof.

[0067] The glass pane with the coating according to the invention preferably forms the inner pane of the composite pane, while the other glass pane forms the outer pane. The window pane is intended to separate the interior (for example, of a building or vehicle) from the exterior environment in a window opening. For the purposes of the invention, the "inner pane" refers to the glass pane facing the interior. The "outer pane" refers to the glass pane facing the exterior environment.

[0068] The invention therefore also comprises a composite pane which comprises a further glass pane (in particular as an outer pane) and the glass pane according to the invention with the emissivity-reducing coating (in particular as an inner pane), which are connected to one another via a thermoplastic intermediate layer, wherein the emissivity-reducing coating is arranged on the surface of the glass pane facing away from the intermediate layer.

[0069] The two glass panes preferably each have a thickness of 0.5 mm to 5 mm, in particular of 1 mm to 3 mm.

[0070] The thermoplastic intermediate layer contains at least one thermoplastic polymer, preferably ethylene-vinyl acetate (EVA), polyvinyl butyral (PVB), or polyurethane (PU), or mixtures or copolymers or derivatives thereof, particularly preferably PVB. The intermediate layer is typically formed from at least one thermoplastic film (connecting film), in particular based on PVB, EVA, or PU. This means that the film consists predominantly of the said polymer (proportion greater than 50 wt%). In addition to the polymer, the film may contain further additives, in particular plasticizers. The thickness of the intermediate layer is preferably from 0.2 mm to 2 mm, particularly preferably from 0.3 mm to 1 mm.

[0071] In an advantageous further development, the surface of the other glass pane facing the intermediate layer (especially the outer pane) is provided with a solar control coating. A solar control coating reflects infrared components of solar radiation and can thus reduce the heating of the window pane (and thus its emissivity) as well as the heating of the interior due to direct sunlight.

[0072] The sun protection coating preferably contains at least one IR-reflecting layer based on a metal, in particular based on silver. The IR-reflecting layer preferably contains at least 90 wt.% silver, more preferably at least 99 wt.% silver, most preferably at least 99.9 wt.% silver. The silver layer may contain dopants, for example, palladium, gold, copper, or aluminum. The thickness of the silver layer is typically between 5 nm and 20 nm.

[0073] In addition to the metallic layer, dielectric layers or layer sequences are typically present. Dielectric layers or layer sequences are also referred to below as dielectric layer modules. The solar protection coating comprises n metallic layers and (n+1) dielectric layer modules, with the dielectric layer modules and the metallic layers arranged alternately, so that each metallic layer is located between two dielectric layer modules, and one layer module is located between adjacent metallic layers. The number n is a natural number greater than or equal to 1 (n > 1).

[0074] In a preferred embodiment, the sun protection coating comprises at least two metallic layers (n > 2), for example, exactly two metallic layers (n = 2), or even at least three metallic layers (n > 3), for example, exactly three metallic layers (n = 3). A plurality of metallic layers can improve the IR-reflecting effect without excessively reducing light transmission, because the individual metallic layers can be made thinner. On the other hand, the number of metallic layers should not be too large to keep production costs low.

[0075] The layer modules can be formed independently of one another, as individual dielectric layers or as dielectric layer sequences (i.e., a plurality of consecutive dielectric layers). Common dielectric layers of such a thin-film stack include, for example:

[0076] Anti-reflective coatings which reduce the reflection of visible light and thus increase the transparency of the coated pane, for example based on silicon nitride (Sisl^U), silicon-metal mixed nitrides such as silicon zirconium nitride (SiZrN), titanium oxide (TiCh), aluminium nitride (AIN) or tin oxide (ZnO), with layer thicknesses of, for example, 10 nm to 100 nm;

[0077] - Adaptation layers which improve the crystallinity of the electrically conductive layer, for example based on zinc oxide (ZnO), with layer thicknesses of, for example, 3 nm to 20 nm;

[0078] Smoothing layers which improve the surface structure for the overlying layers, for example based on a non-crystalline oxide of tin, silicon, titanium, zirconium, hafnium, zinc, gallium and / or indium, in particular based on tin-zinc mixed oxide (ZnSnO), with layer thicknesses of, for example, 3 nm to 20 nm.

[0079] The sun protection coating can optionally include blocking layers that protect the metallic layers from degradation. Blocking layers are typically very thin metal-containing layers based on niobium, titanium, nickel, chromium, zirconium, or alloys thereof, with layer thicknesses of, for example, 0.1 nm to 0.5 nm.

[0080] The solar control coating is preferably applied over the entire surface of the pane, with the exception of a peripheral edge area and, optionally, a local area that serves as communication, sensor, or camera windows to ensure the transmission of electromagnetic radiation through the pane and is therefore not coated with the solar control coating. The peripheral uncoated edge area, for example, has a width of up to 20 cm. It prevents direct contact of the solar control coating with the surrounding atmosphere, thus protecting the solar control coating inside the laminated pane from corrosion and damage. Preferably, at least 80% of the pane surface is coated with the solar control coating.

[0081] The solar control coating can also be embedded in the thermoplastic intermediate layer instead of being applied to the surface of the outer pane, for example applied to a carrier film (preferably based on PET) which is inserted between two thermoplastic connecting films.

[0082] In a third embodiment, the window pane is designed as an insulating glass pane. The glass pane according to the invention with the emissivity-reducing coating is connected to another glass pane in the edge region via a frame-like spacer, so that a cavity is formed between the two panes. The cavity is typically filled with an inert gas. The emissivity-reducing coating is preferably arranged on the surface of the glass pane facing away from the spacer. The glass pane with the emissivity-reducing coating preferably forms the inner pane of the insulating glass pane, while the other glass pane forms the outer pane. In this case, it is possible for the other glass pane to be equipped with a sun protection coating of the type described above, preferably on its surface facing the spacer.Such insulating glass panes can be used, for example, as window, door, or facade panes (glass facade) of a building. The insulating glass pane can also be used, for example, as an oven or refrigerator door.

[0083] The two glass panes preferably each have a thickness of 1 mm to 10 mm, in particular of 3 mm to 8 mm.

[0084] The window pane can be flat, as is common in architecture, for example, or as occurs with vehicle windows for buses, trains, or tractors. In an advantageous embodiment, however, the window pane is curved, as is common for motor vehicle windows. Typical radii of curvature are in the range of approximately 10 cm to approximately 40 m. A particular advantage of the invention is that the emissivity-reducing coating can be subjected to a bending process. During the associated temperature treatment, the TCO layer is protected by the barrier layer from excessive oxidation, which would otherwise manifest itself, for example, in the form of cracks in the coating. The barrier layer is oxidized in the process. In a curved window pane, the barrier layer is therefore typically completely or partially oxidized.

[0085] The glass pane is preferably made of glass, in particular soda-lime glass, which is common for window panes. However, the glass pane can also be made of other types of glass (e.g., borosilicate glass, quartz glass, aluminosilicate glass) or transparent plastics ("organic glasses," such as polymethyl methacrylate or polycarbonate). The same applies to any additional glass pane as part of the window pane according to the invention.

[0086] The window pane according to the invention is preferably transparent, so that at least a certain degree of visibility through the window pane is possible. However, the degree of this visibility depends very much on the specific intended use of the window pane. For example, for window panes in the architectural field and for certain vehicle windows (particularly windshields and front side windows), a high level of light transmission is common or even required by law. In these cases, the light transmission of the window pane is preferably greater than 70%. For other vehicle windows (particularly roof windows, rear windows and rear side windows), a strong tint is sometimes common. In these cases, the light transmission of the window pane is preferably greater than 2% and, for example, less than 30% or even less than 10%. The term light transmission (total transmission) refers to the light transmission defined by ECE-R 43, Annex 3, Section 9.1 specifies the procedure for testing the light transmittance of motor vehicle windows. Tinting can be achieved by tinting or coloring the glass pane with the emissivity-reducing coating – in the case of laminated windows, alternatively or additionally by tinting or coloring the other glass pane and / or the interlayer.

[0087] The window pane according to the invention is manufactured by preparing the glass pane and applying the emissivity-reducing coating. Cutting the glass pane to its final dimensions can be done before or after the coating.

[0088] The method comprises the following steps in the given order: a) Providing a glass pane, b) Applying an emissivity-reducing coating to a surface of the glass pane, wherein b.1. a dielectric blocking layer against alkali diffusion with a

[0089] refractive index of at least 1.9, b.2. optionally a dielectric lower anti-reflective coating with a

[0090] refractive index of not more than 1.6, b.3. an electrically conductive layer based on a transparent conductive oxide, b.4. a barrier layer based on titanium, zirconium, hafnium, vanadium, niobium,

[0091] Tantalum, tungsten and / or chromium with a thickness of 12 nm to 30 nm and b.5. a dielectric upper anti-reflective layer with a refractive index of not more than 1.6, b.6. optionally a dielectric cover layer deposited in the specified order,

[0092] The glass pane with the emissivity-reducing coating is then optionally subjected to a thermal transformation process (in particular a thermal tempering process or a bending process), whereby the barrier layer is partially or completely oxidized.

[0093] In a preferred process, no further layers are deposited on the surface of the glass pane apart from the specified layers.

[0094] The optional thermal transformation process involves a heat treatment, typically at temperatures above 500 °C. Such a transformation process is preferably carried out, particularly as a glass bending process. If the process is carried out without such a transformation process, the barrier layer in the final product remains a metal-based layer, without oxidation.

[0095] The emissivity-reducing coating is preferably applied to the respective pane surface by physical vapor deposition (PVD), particularly preferably by cathode sputtering, and most preferably by magnetic field-assisted cathode sputtering. In principle, however, the coatings can also be applied, for example, by chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PECVD), by vapor deposition, or by atomic layer deposition (ALD). The same applies to any solar control coating on another pane of glass that is part of the window pane.

[0096] If the window pane is to be curved, the glass pane undergoes a bending process (before or after coating, preferably after coating). If the window pane is a composite pane, the outer and inner panes are preferably bent congruently together (i.e., simultaneously and using the same tool), as this ensures the shape of the panes is optimally matched for subsequent lamination. Typical temperatures for glass bending processes range from 500°C to 700°C.

[0097] If the window pane is a composite pane, the glass pane is joined to the other glass pane via the intermediate layer. Known processes are used for this, for example, autoclave processes, vacuum bag processes, vacuum ring processes, calendering processes, vacuum laminators, or combinations thereof. The joining of glass panes is usually carried out under the influence of heat, vacuum, and / or pressure. Laminating preferably takes place after any glass bending process. The invention further encompasses the use of a window pane according to the invention in buildings or in means of transport on land, water, or in the air. Preference is given to use as a vehicle window, for example as a windshield, side window, roof window, or rear window, in particular as a vehicle roof window.The vehicle is, for example, an aircraft or helicopter, a ship, a rail vehicle or a motor vehicle, for example a passenger car, a truck, a bus or an agricultural or construction vehicle, with motor vehicles being preferred.

[0098] The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way.

[0099] They show:

[0100] Fig. 1 shows a cross section through an embodiment of the window pane according to the invention with the emissivity-reducing coating,

[0101] Fig. 2 is an enlarged view of section Z from Figure 1,

[0102] Fig. 3 shows a cross section through a further embodiment of the window pane according to the invention with the emissivity-reducing coating.

[0103] Figures 1 and 2 each show a detail of a window pane according to the invention. This is a monolithic glass pane (single pane of glass), which is structurally formed from a single glass pane 2. The glass pane 2 is made of soda-lime glass and has a thickness of, for example, 3.5 mm. The glass pane 2 is provided with an emissivity-reducing coating 10.

[0104] The window pane is provided, for example, as a side window of a motor vehicle. It is typically curved, even though it is shown flat in the figure for simplicity. The coating 10 is applied to the interior-facing surface of the glass pane 2, which, in the installed position, faces the vehicle interior. This interior-facing surface is typically concavely curved, while the opposite exterior surface is convexly curved.

[0105] The emissivity-reducing coating 10 is suitable and intended to reflect the thermal radiation emanating from the heated glass pane 2 at high outside temperatures, thereby reducing the heating of the vehicle interior. At low outside temperatures, it reduces the radiation of heat from the vehicle interior. The coating 10 thus improves thermal comfort in the vehicle interior.

[0106] The emissivity-reducing coating 10 consists, starting from the surface of the glass pane 2, in the specified order:

[0107] - a dielectric blocking layer 11 against alkali diffusion,

[0108] - a dielectric lower anti-reflective layer 12, - an electrically conductive layer 13 based on a TCO,

[0109] - a barrier layer 14 based on a metal and

[0110] - a dielectric upper anti-reflective layer 15.

[0111] The blocker layer 11 is made of aluminum-doped silicon nitride (SiSnAl) and has a thickness of, for example, 30 nm. Its refractive index is 2.0. The lower anti-reflective layer 12 is made of aluminum-doped silicon oxide (SiO2:Al) and has a thickness of, for example, 17 nm. Its refractive index is 1.45. The electrically conductive layer 13 is made of indium tin oxide (ITO) and has a thickness of, for example, 72 nm. The barrier layer 14 is based on titanium (Ti) and has a thickness of, for example, 20 nm. The upper anti-reflective layer 15 is made of aluminum-doped silicon oxide (SiO2:Al) and has a thickness of, for example, 57 nm. Its refractive index is 1.45.

[0112] During the bending process, the glass pane 2 is exposed to elevated temperatures and then rapidly cooled to impart thermal prestress. This inherently carries the risk of excessive oxidation of the electrically conductive layer 13, which is evident, for example, in cracks in the coating 10 after bending. The barrier layer 14 according to the invention effectively prevents this oxidation and imparts its flexibility to the coating 10. This is the major advantage of the barrier layer 14 according to the invention.

[0113] The blocking layer 11 prevents the diffusion of alkali ions from the glass pane 2 into the coating 10. The electrically conductive layer 13 provides the IR-reflecting properties, allowing the coating 10 to reflect thermal radiation. The upper anti-reflective layer 15 leads to reduced reflection and increased light transmission, so that the coating 10 is transparent overall and can be applied to window panes without concern. The lower anti-reflective layer 12 is not absolutely necessary for the use of the coating 10 as an emissivity-reducing coating. However, it is preferred because it can contribute to further anti-reflective properties and thus to higher light transmission and a more neutral color.

[0114] During the thermal treatment, the barrier layer 14 is typically fully or partially oxidized. The barrier layer 14 is deposited as a pure or doped titanium layer (Ti layer) on the glass pane 2. However, in the bent final product, it can be present as a titanium oxide layer (TiO2 layer) (complete oxidation), or part of the total layer thickness can be present as a Ti layer and another part as a TiO2 layer (partial oxidation).

[0115] For the sake of clarity, stoichiometric molecular formulas have been given here for the oxides and nitrides used. This does not imply that the layers must necessarily be stoichiometric. They can be stoichiometric, substoichiometric, or hyperstoichiometric in terms of oxygen or nitrogen content.

[0116] Figure 3 shows a further embodiment of the window pane according to the invention. The window pane is designed as a composite pane consisting of a glass pane with the coating 10 according to the invention, which functions as the inner pane, and an outer pane 1, which are bonded together via a thermoplastic intermediate layer 3.

[0117] The glass pane 2 is made of soda-lime glass and has a thickness of, for example, 1.6 mm. The outer pane 1 is also made of soda-lime glass and has a thickness of, for example, 2.1 mm. The intermediate layer 3 is formed, for example, from a PVB film with a thickness of 0.76 mm.

[0118] The window pane is intended as a roof pane of a vehicle. It is typically curved, although it is shown flat in the figure for simplicity. The coating 10 is applied to the interior-facing surface of the glass pane 2, which, in the installed position, faces the vehicle interior. This interior-facing surface is typically concavely curved.

[0119] The outer pane 1 is provided with a sun protection coating 20, which is applied to its surface facing the intermediate layer 3. A peripheral edge region is uncoated, so that the sun protection coating 20 has no contact with the surrounding atmosphere. The sun protection coating is formed, for example, from three silver layers and four dielectric layer sequences arranged alternately. The sun protection coating reflects infrared components of the sun's radiation, thus reducing the heating of the window pane and the vehicle interior. Examples

[0120] Test panes were produced with a glass pane 2 made of soda-lime glass and an emissivity-reducing coating 10 deposited on the glass pane 2 by magnetron sputtering. The layer thicknesses and materials of the examples according to the invention

[0121] 1 and 2 as well as comparative examples 1-4 can be found in Tables 1 and 2.

[0122] Table 1

[0123] Table 2 The panes were then subjected to a bending process. Table 3 summarizes observations on the panes after the bending process: the number of cracks that occurred in the coating 10, as well as the light transmission TL, the light reflection R, and the light absorption AL.

[0124] Table 3

[0125] In Comparative Examples 1-3, a titanium-based barrier layer 14 was used, albeit with a thinner thickness than required by the invention. It is clearly evident that such thin barrier layers are not suitable for protecting the TCO layer from oxidation. 100 cracks, or even significantly more, appeared on the analyzed surface. The coating 10 did not survive the bending process unscathed.

[0126] In Examples 1 and 2 according to the invention, the number of cracks is significantly reduced. If cracks were observed at all, they occurred so rarely that the coating 10 can be characterized as flexible. At the same time, however, the barrier layers are sufficiently thin so that light reflection and light absorption are not excessively increased, and a comparatively high light transmission is achieved.

[0127] Comparative Example 4 did not have a metal-based barrier layer 14, but rather a silicon nitride-based barrier layer 14', as proposed in WO2013131667A1. Good bendability is also observed here—the coating 10 exhibits only a few cracks after bending. However, the metallic barrier layer 14 according to the invention has, in particular, process-related advantages. Metallic barrier layers 14 can be sputtered at higher deposition rates. Furthermore, the deposition process does not require nitrogen process gas, which would otherwise have to be laboriously separated from the oxygen process gas of the surrounding layers.

[0128] List of reference symbols:

[0129] (1) Outer pane

[0130] (2) Glass pane

[0131] (3) thermoplastic intermediate layer

[0132] (10) emissivity-reducing coating

[0133] (11) Blocking layer against alkali diffusion

[0134] (12) lower anti-reflective layer

[0135] (13) electrically conductive layer based on a TCO (TCO layer)

[0136] (14) Barrier layer based on a metal

[0137] (14') Barrier layer based on silicon nitride

[0138] (15) upper anti-reflective layer

[0139] (20) Sun protection coating

[0140] (Z) enlarged section

Claims

Patent claims 1 . Window pane with an emissivity-reducing coating, comprising at least - a glass pane (2) and - an emissivity-reducing coating (10) on a surface of the glass pane (2), wherein the emissivity-reducing coating (10) is applied starting from the surface of the glass pane (2) in the specified order - a dielectric blocking layer (11) against alkali diffusion with a refractive index of at least 1.9, - an electrically conductive layer (13) based on a transparent conductive oxide, - a barrier layer (14) based on a metal with a thickness of 12 nm to 30 nm, which is optionally completely or partially oxidized, - a dielectric upper anti-reflection layer (15) with a refractive index of at most 1.6, wherein the barrier layer (14) is based on titanium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten and / or chromium, preferably based on titanium.

2. Window pane according to claim 1, wherein the barrier layer (14) is in direct contact with the electrically conductive layer (13).

3. Window pane according to claim 1 or 2, wherein the thickness of the barrier layer (14) is from 15 nm to 25 nm, preferably from 15 nm to 20 nm.

4. Window pane according to one of claims 1 to 3, wherein the transparent conductive oxide is indium tin oxide (ITO).

5. Window pane according to one of claims 1 to 4, wherein the electrically conductive layer (13) has a thickness of 30 nm to 150 nm, preferably of 50 nm to 130 nm.

6. Window pane according to one of claims 1 to 5, wherein the blocking layer (11) is formed on the basis of silicon nitride, which is optionally partially oxidized.

7. Window pane according to one of claims 1 to 6, wherein the blocking layer (11) has a thickness of 10 nm to 50 nm, preferably of 20 nm to 40 nm.

8. Window pane according to one of claims 1 to 7, wherein the upper Anti-reflective layer (15) is formed on the basis of silicon oxide.

9. Window pane according to one of claims 1 to 8, wherein the upper Anti-reflective layer (15) has a thickness of 30 nm to 200 nm, preferably 40 nm to 100 nm.

10. Window pane according to one of claims 1 to 9, wherein a dielectric lower anti-reflection layer (12) with a refractive index of at most 1.6 is arranged between the blocking layer (11) and the electrically conductive layer (13), which is preferably based on silicon oxide and has a thickness of 5 nm to 50 nm, particularly preferably of 10 nm to 40 nm.

11. Window pane according to one of claims 1 to 10, which is designed as a composite pane, wherein the surface of the glass pane (2) facing away from the emissivity-reducing coating (10) is connected to an outer pane (1) via a thermoplastic intermediate layer (3).

12. Window pane according to claim 11, wherein the surface of the outer pane (1) facing the intermediate layer (3) is provided with a sun protection coating (20) which contains at least one silver-based layer.

13. Window pane according to one of claims 1 to 12, which is curved, wherein the barrier layer (14) is completely or partially oxidized.

14. A process for producing a window pane with an emissivity-reducing coating, comprising at least the following process steps in the specified order: (1) Providing a glass pane (2), (2) applying an emissivity-reducing coating (10) to a surface of the glass pane (2), wherein a. a dielectric blocking layer (11) against alkali diffusion with a refractive index of at least 1.9, b. an electrically conductive layer (13) based on a transparent conductive oxide, c. a barrier layer (14) based on titanium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten and / or chromium with a thickness of 12 nm to 30 nm, d. a dielectric upper anti-reflection layer (15) with a refractive index of at most 1.6, are deposited on the surface in the specified order, (3) optionally carrying out a thermal transformation process, in particular a thermal tempering process or bending process, wherein the Barrier layer (14) is partially or completely oxidized.

15. Use of a window pane according to one of claims 1 to 13 as a vehicle window, in particular as a vehicle roof window.

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