Pane with emissivity-reducing coating

Abstract

The invention relates to a pane (10) comprising a substrate (1) and an emissivity-reducing coating (2) on a first surface (IV) of the substrate (1), which coating has, in the specified order starting from the substrate (1), at least: • a functional layer (2.1) based on a transparent conductive oxide; • a first optically low-refractive layer (2.2) having a refractive index of less than or equal to 1.6; • a top layer (2.3) having a thickness of 1 nm to 20 nm; wherein the top layer (2.3) is formed on the basis of silicon and wherein the first optically low-refractive layer (2.2) is arranged directly adjacent to the functional layer (2.1).

Description

[0001] Disc with emissivity-reducing coating

[0002] The invention relates to a pane with an emissivity-reducing coating, a heat-treated pane, a composite pane, a method for producing the pane or the heat-treated pane and a use of the pane or the heat-treated pane.

[0003] Glass panes with transparent, electrically conductive coatings are well known. This allows the glass panes to be given a function without significantly impairing visibility through the pane. Such coatings are used, for example, as heatable coatings or heat-reflecting coatings (so-called emissivity-reducing coatings or low-E coatings) on window panes for vehicles or buildings.

[0004] The interior of a vehicle or building can heat up considerably in summer when ambient temperatures are high and exposed to intense direct sunlight. However, if the outside temperature is lower than the interior temperature, which is particularly common in winter, a cold window acts as a heat sink, which is perceived as unpleasant. The interior must also be heated to prevent cooling through the window panes.

[0005] Emissivity-reducing coatings reflect a significant portion of solar radiation, particularly in the infrared range, which reduces interior heating in summer. The coating also reduces the emission of long-wave thermal radiation from a heated window into the interior. It also reduces the radiation of interior heat to the outside environment during low outdoor temperatures in winter.

[0006] To be effective, the emissivity-reducing coating must be applied to the interior surface of the pane, i.e., between the interior and the pane. There, the coating is exposed to the atmosphere, which precludes the use of corrosion-prone coatings, such as those based on silver. Coatings based on transparent conductive oxides (TCO), such as indium tin oxide (ITO), have proven effective as electrically conductive coatings on exposed surfaces due to their corrosion resistance and good conductivity. Such coatings are known, for example, from EP 2 141 135 A1, WO 2010 / 115558 A1, and WO 2011 / 105991 A1.

[0007] WO 2018 / 206236A1 discloses a composite pane with an electrically conductive layer having reflective properties with respect to thermal radiation, wherein fingerprints on the electrically conductive layer are less visible due to a special layer structure.

[0008] WO 2013 / 132176 A2 shows a glazing unit for the building sector with an electrically conductive layer based on ITO, wherein the coating serves in particular to reduce the condensation of moisture on the glazing unit.

[0009] WO 2015 / 055944 A1 relates to a method for producing a material comprising a glass or glass-ceramic film. The glass or ceramic film is at least partially coated on at least one of its surfaces with a thin film stack that does not contain a silver film and that contains at least one electrically conductive transparent oxide thin film and a thin homogenizing film. The homogenizing film consists of metal, a metal carbide, or a metal nitride other than aluminum nitride.

[0010] FR 2 963 343 A1 discloses a glazing comprising a glass substrate provided on one of its sides with a layer consisting of a thin-film stack comprising, starting from the substrate, a layer of a transparent, electrically conductive oxide, an intermediate layer having a refractive index in the range from 1.40 to 1.55 and a photocatalytic layer based on titanium oxide.

[0011] WO 2016 / 198901 A1 discloses glazing for minimizing or preventing bird collisions with windows or other glazing, wherein the glazing comprises at least one substrate having a UV-reflective coating deposited over the substrate in a patterned arrangement, and the UV-reflective coating comprises a plurality of stripes, each of the plurality of stripes having a thickness that varies by 10 nm or less over every 1 mm in width. The UV-reflective coating comprises titanium dioxide, and an anti-reflective coating may be disposed between the substrate and the UV-reflective coating. The anti-reflective coating may comprise a first layer comprising tin oxide, a second layer comprising silicon oxide, a third layer comprising fluorine-doped tin oxide, and a fourth layer comprising a silicon oxide.EP 1 518 838 A1 discloses a glass article comprising a transparent, heat-resistant glass sheet and a visible light shielding layer on the surface thereof, wherein an average transmittance of the glass article for visible light at a wavelength of 380-780 nm is 0.03-15% and an average infrared reflectance of the glass article at a wavelength of 1000-2500 nm is at least 50%.

[0012] FR 2 973 023 A1 discloses a multiple glazing unit with thermally insulating properties, obtained by combining a plurality of glass substrates separated by gas fins, the front side of the first substrate forming the outer wall of the glazing unit and the back side of the last substrate defining the inner wall of the glazing unit, the multiple glazing unit comprising: a first stack of layers with a low emissivity property comprising at least one metallic functional layer, a second stack of layers with a low emissivity property comprising at least one functional layer of a transparent conductive oxide and a layer consisting essentially of silicon oxide and arranged over the functional layer of the transparent conductive oxide.

[0013] If both oxide and nitride layers are used in a coating, this requires a special separation of the gases used for the oxide layer application and those used for the nitride layer application during the coating application process. This increases manufacturing complexity and costs. Furthermore, the immediate successive application of oxide and nitride layers carries the risk of forming mixed oxide-nitride phases, which exhibit undefined optical properties.

[0014] After applying an emissivity-reducing coating, panes are often subjected to heat treatment and mechanical transformation. Automotive panes, such as windshields, side windows, roof windows, or rear windows, are typically bent and often subjected to prestressing or partial prestressing.

[0015] The present invention is based on the object of providing a pane with an emissivity-reducing coating that is characterized by its thermal radiation-insulating effect. Furthermore, the pane should be manufactured with minimal manufacturing effort and at low cost. The object of the present invention is achieved according to the invention by a pane according to claim 1. Preferred embodiments are set out in the subclaims.

[0016] The invention relates to a pane comprising a substrate and an emissivity-reducing coating on a first surface of the substrate. The emissivity-reducing coating comprises, in the specified order, starting from the substrate, at least

[0017] • a functional layer based on a transparent conductive oxide,

[0018] • a first optically low-refractive layer with a refractive index of less than or equal to 1.6 and

[0019] • a cover layer with a thickness of 1 nm to 20 nm.

[0020] According to the invention, the first optically low-refractive-index layer is arranged directly adjacent to the functional layer. This means that no further layer is applied between the functional layer and the first optically low-refractive-index layer. According to the invention, the cover layer is formed from silicon.

[0021] As described above, the pane according to the invention comprises a substrate and an emissivity-reducing coating on a first surface of the substrate. Thus, the pane according to the invention is a coated pane.

[0022] The emissivity-reducing coating is a coating that reflects heat radiation. This type of emissivity-reducing coating is often also referred to as a low-E coating or low-emissivity coating. Its function is to prevent heat radiation from entering the interior (IR components of solar radiation) and also to prevent heat radiation from leaving the interior. In principle, the emissivity-reducing coating can also serve other functions, for example, as a heatable coating when electrically contacted, so that it is heated by the flow of an electric current.

[0023] The pane according to the invention is preferably a window pane and is intended to separate the interior from the exterior environment in an opening, for example in a vehicle or a building. The first surface of the substrate on which the emissivity-reducing coating is arranged is preferably the interior-side surface of the pane or substrate. For the purposes of the invention, the interior-side surface is understood to be the surface that is intended to face the interior when the pane is in the installed position. This is particularly advantageous with regard to thermal comfort in the interior. At high outside temperatures and in the presence of solar radiation, the emissivity-reducing coating can particularly effectively reflect, at least in part, the thermal radiation radiated by the entire pane towards the interior.At low outside temperatures, the emissivity-reducing coating can effectively reflect the heat radiation emitted from the interior, thus reducing the cold pane's effect as a heat sink. Alternatively, the emissivity-reducing coating can also be applied to the exterior surface of the substrate. This can be particularly useful in the architectural field, for example, as an anti-condensation coating on a window pane.

[0024] Since the first optically low-refractive-index layer is arranged directly adjacent to the functional layer, the emissivity-reducing coating does not require an additional nitride-based layer between the functional layer and the first optically low-refractive-index layer. Since no nitride materials are used in the application of the functional layer, the first optically low-refractive-index layer, and the cover layer, gas separation for the application of oxide and nitride layers is not required. Therefore, the pane according to the invention is characterized by the fact that it can be produced particularly easily, reliably, and cost-effectively compared to conventional panes with emissivity-reducing coatings.

[0025] The functional layer can contain, for example, indium tin oxide (ITO), aluminum-zinc mixed oxide (AZO), indium-zinc mixed oxide (IZO), gallium-doped tin oxide (GZO), fluorine-doped tin oxide (SnO2:F), antimony-doped tin oxide (SnO2:Sb), or niobium-doped titanium oxide (TiO2:Nb). In a particularly advantageous embodiment, the functional layer is based on indium tin oxide. Particularly good results are achieved with this material, especially since it is characterized by low resistivity and low scatter in sheet resistance.

[0026] In a preferred embodiment, the functional layer has a thickness of 30 nm to 200 nm, particularly preferably 50 nm to 130 nm. In this layer thickness range, particularly good thermal properties of the pane are achieved.

[0027] In a particularly advantageous embodiment, the first optically low-refractive-index layer is based on silicon oxide, which can be doped or undoped. Doped silicon oxide is particularly preferably used, in particular aluminum-doped silicon oxide, titanium-doped silicon oxide, zirconium-doped silicon oxide, or boron-doped silicon oxide. Particularly good results are achieved with these materials. These materials are cost-effective and easy to apply.

[0028] The first optically low-refractive-index layer preferably has a thickness of 30 nm to 200 nm, particularly preferably 50 nm to 200 nm. This layer thickness range is particularly suitable for achieving low absorption and high transmittance of visible light through the pane. Furthermore, by varying the thickness of the first optically low-refractive-index layer, the reflectance of visible light at the pane can be particularly well adjusted. This makes it possible, for example, to set a particularly low reflectance of visible light at the pane, which is particularly desirable when the pane is used as a roof pane in a motor vehicle.

[0029] The cover layer is formed on the basis of silicon as described above, in other words, it is based on silicon.

[0030] If a layer is formed on the basis of a material, it consists predominantly of this material, in particular essentially of this material in addition to any impurities or dopants.

[0031] The cover layer preferably consists of doped or undoped silicon. The cover layer particularly preferably consists of zirconium-doped silicon, titanium-doped silicon, hafnium-doped silicon, or aluminum-doped silicon. The cover layer most preferably consists of aluminum-doped silicon. Cover layers consisting of the aforementioned materials are particularly suitable for achieving low absorption and high transmittance of visible light through the pane. Furthermore, this ensures sufficient protection of the functional layer during heat treatment, thus, in particular, preventing overoxidation of the transparent conductive oxide of the functional layer.

[0032] The cover layer is preferably the uppermost layer of the emissivity-reducing coating, i.e., of all the layers of the emissivity-reducing coating, it is the layer that has the greatest distance from the substrate. The cover layer preferably has a thickness of 2 nm to 15 nm, particularly preferably 3 nm to 14 nm. This layer thickness range is particularly suitable for achieving low absorption and high transmittance of visible light through the pane. These layer thicknesses of the cover layer also ensure sufficient protection of the functional layer during heat treatment, thus, in particular, preventing overoxidation of the transparent conductive oxide of the functional layer.

[0033] In a particularly advantageous embodiment, the emissivity-reducing coating does not comprise any additional layers. This embodiment has the advantage that it simplifies the manufacturing process. In a particularly advantageous embodiment of the pane according to the invention, the pane thus comprises a substrate and an emissivity-reducing coating on a first surface of the substrate, which consists, in the specified order starting from the substrate, of a functional layer based on a transparent conductive oxide, a first optically low-refractive-index layer with a refractive index of less than or equal to 1.6, and a cover layer with a thickness of 1 nm to 20 nm, wherein the cover layer is based on silicon.

[0034] Alternatively, it is possible for the emissivity-reducing coating to comprise additional layers. In a particularly advantageous embodiment, the emissivity-reducing coating additionally comprises a highly optically refractive layer with a refractive index greater than or equal to 1.9. The highly optically refractive layer is positioned at a shorter distance from the substrate than the functional layer.

[0035] In this embodiment, the optically high-refractive-index layer serves as a dielectric barrier layer against alkali diffusion. If the substrate is a glass substrate, the optically high-refractive-index layer reduces or prevents the diffusion of alkali ions from the glass substrate into the emissivity-reducing coating. Alkali ions can negatively influence the properties of the coating. Furthermore, the optically high-refractive-index layer, in conjunction with the first optically low-refractive-index layer, advantageously contributes to adjusting the color and reflection of the overall layer structure. Particularly good results are achieved when the refractive index of the optically high-refractive-index layer is between 1.9 and 2.5.The optically highly refractive layer preferably contains 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, Nb20s, Bi2O3, TiO2, Ta2Os, ZrO2, HfO2, SnO2, or ZnSnO. x, or nitrides such as AlN, TiN, TaN, ZrN or NbN. The optically high-refractive index layer particularly preferably contains silicon nitride (SisN^), with which particularly good results are achieved. The silicon nitride can be doped and, in a preferred embodiment, is doped with aluminum (SisN^Al), with titanium (SisN^Ti), with zirconium (SisN^Zr) or with boron (SiA N^B). The optically high-refractive index layer is preferably the bottom layer of the emissivity-reducing coating and therefore has direct contact with the substrate surface, where it can optimally develop its effect. At the same time, the optically high-refractive index layer also serves as an adhesion layer for the other layers on the substrate. The optically high-refractive index layer preferably has a thickness of 10 nm to 50 nm, particularly preferably of 20 nm to 40 nm.

[0036] In a further preferred embodiment, the emissivity-reducing coating additionally comprises a second optically low-refractive-index layer with a refractive index of less than or equal to 1.6. The second optically low-refractive-index layer is spaced closer to the substrate than the functional layer. Particularly preferably, the emissivity-reducing coating comprises both the optically high-refractive-index layer and the second optically low-refractive-index layer. In this case, the second optically low-refractive-index layer is spaced further from the substrate than the optically high-refractive-index layer. In these embodiments, the second optically low-refractive-index layer serves as a dielectric anti-reflective layer. The second optically low-refractive-index layer reduces the reflection factor, thereby increasing the transparency of the pane and preferably ensuring a neutral color impression.The second low-refractive-index layer preferably contains an oxide or fluoride, particularly preferably silicon oxide, magnesium fluoride, or calcium fluoride. Silicon oxide is very particularly preferably used. This can contain dopants and is preferably doped with aluminum (SiO2:Al), boron (SiO2:B), titanium (SiO2:Ti), or zirconium (SiO2:Zr). The second low-refractive-index layer preferably has a thickness of 5 nm to 40 nm, particularly preferably 10 nm to 35 nm.

[0037] Particularly preferably, the emissivity-reducing coating does not comprise any further additional layers apart from the aforementioned optically high-refractive-index layer with a refractive index greater than or equal to 1.9 and the aforementioned second optically low-refractive-index layer with a refractive index less than or equal to 1.6. In particular, the emissivity-reducing coating does not have any additional functional layers based on a transparent conductive oxide.

[0038] In a preferred embodiment, the first low-refractive-index layer is arranged directly adjacent to the cover layer. Unless otherwise stated, the specified layer thickness or thicknesses refer to the geometric thickness of a layer.

[0039] The interior emissivity of the pane according to the invention is preferably less than or equal to 45%, particularly preferably less than or equal to 35%, and most particularly preferably less than or equal to 30%. Interior emissivity refers to the measure that indicates how much thermal radiation the pane emits into an interior, for example, a building or vehicle, in its installed position compared to an ideal heat radiator (a black body). For the purposes of the invention, emissivity is understood to mean the normal emissivity at 283 K according to the EN 12898 standard.

[0040] The sheet resistance of the emissivity-reducing coating according to the invention is preferably from 10 ohms / square to 100 ohms / square, particularly preferably from 20 ohms / square to 60 ohms / square. The sheet resistance and the interior-side emissivity of the pane according to the invention are correlated, with a reduction in the sheet resistance of the emissivity-reducing coating leading to a reduction in the interior-side emissivity.

[0041] The substrate is made of an electrically insulating, particularly rigid material, preferably ceramic or glass. In a preferred embodiment, the substrate contains soda-lime glass, but can in principle also contain other types of glass, for example, borosilicate glass or quartz glass. The substrate can be largely transparent or tinted or colored. The substrate preferably has a thickness of 0.1 mm to 20 mm, typically 1.5 mm to 5 mm. The substrate can be flat or curved.

[0042] The refractive indices specified in the invention can be determined, for example, by means of ellipsometry, whereby commercially available ellipsometers can be used, e.g. from Sentech.

[0043] The pane according to the invention, comprising the substrate and the emissivity-reducing coating, is already characterized by good properties with regard to absorption and optics. However, these properties can be further improved by heat treatment. The pane according to the invention can thus also be regarded as an intermediate product in the production of a heat-treated pane. The invention therefore also relates to a heat-treated pane obtained by heat-treating a pane according to the invention at at least 400°C. The heat treatment preferably takes place at a temperature of at least 500°C, more preferably at a temperature of at least 600°C. The heat treatment preferably takes place over a period of at least 1 minute, more preferably at least 2 minutes, most preferably at least 5 minutes, for example 10 minutes.

[0044] The heat treatment can, in particular, reduce the surface resistance of the emissivity-reducing coating. The emissivity-reducing coating of the heat-treated pane according to the invention preferably has a surface resistance of 10 ohms / square to 100 ohms / square, particularly preferably of 20 ohms / square to 60 ohms / square. The interior-side emissivity of the heat-treated pane according to the invention is preferably less than or equal to 45%, particularly preferably less than or equal to 35%, and very particularly preferably less than or equal to 30%, wherein the interior-side emissivity for the heat-treated pane according to the invention is determined in the same way as for the pane according to the invention.

[0045] Furthermore, the optical properties of the heat-treated pane according to the invention are significantly improved compared to the optical properties of the pane according to the invention; in particular, the transmittance of visible light is increased. The heat treatment can be carried out in various ways, for example, by heating the pane using an oven or a radiant heater. Alternatively, the heat treatment can also be carried out by irradiation with light, for example, using a lamp or a laser as the light source.

[0046] In an advantageous embodiment, the heat treatment takes place as part of a thermal tempering process or as part of a bending process, particularly in the case of a glass substrate. During a thermal tempering process, the heated substrate is exposed to an air stream, which rapidly cools it. Compressive stresses develop on the pane surface and tensile stresses in the pane core. The characteristic stress distribution increases the fracture strength of the glass panes. Tempering can also be preceded by a bending process.

[0047] The heat treatment causes oxidation of the cover layer with the oxygen in the ambient air. If the cover layer is based on silicon (Si), for example, and the silicon is undoped, the heat treatment absorbs oxygen from the ambient air and oxidizes it at least partially to silicon oxide (SiO2). In the case of a doped cover layer, for example, made of aluminum-doped silicon (Si:Al), the heat treatment also causes oxidation, so that the cover layer contains Si after the heat treatment. x Al y O z contains.

[0048] The substrate can be transparent or semi-transparent, for example, tinted. "Transparent" in the context of the invention means a light transmission (according to ISO 9050:2003) of at least 50%, preferably at least 60%, and particularly preferably at least 70%. Semi-transparent (according to ISO 9050:2003) in the context of the invention means a light transmission of at most 50%, preferably at most 30%, and particularly preferably at most 10%.

[0049] In addition to being used as a single pane, the pane according to the invention or the heat-treated pane according to the invention can also be part of a composite pane. The invention therefore also relates to a composite pane. The composite pane comprises a pane according to the invention or a heat-treated pane according to the invention, as well as a thermoplastic intermediate layer and a second pane. The second pane is bonded to the pane or the heat-treated pane via the thermoplastic intermediate layer. The emissivity-reducing coating is arranged on the first surface of the substrate facing away from the second pane.

[0050] The second pane preferably comprises a second substrate or consists essentially of a second substrate. The second substrate, like the substrate, is made of an electrically insulating, in particular rigid material, preferably of glass or plastic. In a preferred embodiment, the second substrate contains soda-lime glass, but can in principle also contain other types of glass, for example borosilicate glass or quartz glass. In a further preferred embodiment, the second substrate contains polycarbonate (PC) or polymethyl methacrylate (PMMA). In a preferred embodiment, the second substrate is made of the same material as the first substrate. The second substrate can be largely transparent or also tinted or colored. The second substrate preferably has a thickness of 0.1 mm to 20 mm, typically 1.5 mm to 5 mm. The second substrate can be flat or curved.

[0051] In the automotive sector, the composite pane according to the invention can be used, in particular, as a roof pane. In this case, the pane or the heat-treated pane preferably forms the inner pane of the composite pane, thus facing the vehicle interior. The second pane in this case forms the outer pane of the composite pane, thus facing the outside environment. The emissivity-reducing coating is then applied to the first surface of the substrate facing the interior.

[0052] Alternatively, it is also possible for the pane or the heat-treated pane to form the outer pane of the composite pane, thus facing the outside environment. In this case, the second pane forms the inner pane of the composite pane, thus facing the interior. The emissivity-reducing coating is then applied to the first surface of the substrate facing the outside environment.

[0053] The thermoplastic intermediate layer is preferably formed as at least one thermoplastic composite film and is based on ethylene-vinyl acetate (EVA), polyvinyl butyral (PVB), or polyurethane (PU), or mixtures or copolymers or derivatives thereof, particularly preferably based on polyvinyl butyral (PVB), and additionally contains additives known to those skilled in the art, such as plasticizers. The thermoplastic composite film preferably contains at least one plasticizer. The thermoplastic intermediate layer preferably has a thickness of 0.3 mm to 2 mm, with a standard thickness of 0.76 mm being particularly common. The thermoplastic intermediate layer can also comprise multiple layers of thermoplastic material and, for example, be formed from multiple polymer films arranged flatly one above the other.

[0054] The above statements and preferred embodiments in connection with the pane, the heat-treated pane, and the composite pane apply equally to the method. The following statements and preferred embodiments in connection with the method according to the invention apply equally to the pane, the heat-treated pane, and the composite pane.

[0055] The invention also relates to a method for producing a pane according to the invention or a heat-treated pane according to the invention, wherein at least: a) a substrate is provided, b) in the specified order

[0056] • a functional layer based on a transparent conductive oxide,

[0057] • a first optically low-refractive layer with a refractive index of less than or equal to 1.6 and

[0058] • a cover layer with a thickness of 1 nm to 20 nm, which is based on silicon, is applied to a first surface of the substrate.

[0059] According to the invention, the first optically low-refractive-index layer is applied directly to the functional layer; thus, no other layers are applied to the functional layer prior to the first optically low-refractive-index layer. The inventive method for producing a pane according to the invention has the advantage that no additional gas separation is necessary during the application of the functional layer and the first optically low-refractive-index layer. Therefore, the pane according to the invention can be manufactured with minimal manufacturing effort and cost-effectively.

[0060] In a preferred embodiment, before step b), an optically high-refractive-index layer with a refractive index greater than or equal to 1.9 and / or a second optically low-refractive-index layer with a refractive index less than or equal to 1.6 is applied to the substrate in the specified order.

[0061] The individual layers of the emissivity-reducing coating can be applied by known methods, preferably by vapor deposition, particularly preferably physical vapor deposition, and most preferably by magnetic field-assisted cathode sputtering (magnetron sputtering). This is particularly advantageous with regard to simple, rapid, cost-effective, and uniform coating of the substrate. Cathode sputtering takes place in a protective gas atmosphere, for example, argon, or in a reactive gas atmosphere, for example, by adding oxygen or nitrogen. However, the layers can also be applied by other methods known to those skilled in the art, for example by vapor deposition or chemical vapor deposition (CVD), by atomic layer deposition (ALD), by plasma-enhanced vapor deposition (PECVD), or by wet-chemical processes.

[0062] In a particularly preferred embodiment, the pane according to the invention is subsequently subjected to a heat treatment to obtain a heat-treated pane according to the invention. For this purpose, the pane is heated to a temperature of at least 400°C. In a particularly advantageous embodiment, the pane is heated to at least 500°C, in particular to at least 600°C. The heat treatment preferably takes place as part of a thermal tempering process or a bending process. The pane according to the invention, the heat-treated pane according to the invention, or the composite pane according to the invention can be part of an illuminated glazing element.The illuminated glazing element comprises the pane according to the invention, the heat-treated pane according to the invention, or the composite pane according to the invention, as well as at least one light source suitable for coupling light into the substrate in such a way that the light propagates in the substrate, in particular by total reflection at the first surface of the substrate, and at least one light-scattering structure suitable for coupling the light out of the substrate via the first surface and the second surface. The pane according to the invention, the heat-treated pane according to the invention, or the composite pane according to the invention are particularly well suited as a component of an illuminated glazing element because the emissivity-reducing coating does not lead to a significant loss of intensity of the coupled-in light.

[0063] The invention also relates to the use of a pane according to the invention, a heat-treated pane according to the invention or a composite pane according to the invention in buildings or in means of transport for traffic on land, in the air or on water, in particular in trains, ships and motor vehicles, for example as a windscreen, rear window, roof window and / or side window, particularly preferably as a roof window.

[0064] The invention is explained in more detail below with reference to drawings and exemplary embodiments. The drawings are schematic representations and not to scale. The drawings do not limit the invention in any way.

[0065] They show:

[0066] Fig. 1 shows a cross section through an embodiment of a disc according to the invention

[0067] Fig. 2 shows a cross section through a further embodiment of a disc according to the invention

[0068] Fig. 3 shows a cross section through an embodiment of a composite pane according to the invention

[0069] Fig. 4 is a flow chart illustrating a method according to the invention for producing a pane according to the invention

[0070] Fig. 5 is a flow chart illustrating a method according to the invention for producing a heat-treated pane according to the invention. Fig. 1 shows an embodiment of a pane 10 according to the invention. The pane 10 comprises a substrate 1 and an emissivity-reducing coating 2. The substrate 1 is made, for example, from soda-lime glass and has a thickness of 2.1 mm. The pane 10 is intended, for example, as a roof pane of a motor vehicle. The substrate 1 has a first surface IV and a second surface III, wherein the emissivity-reducing coating 2 is arranged on the first surface IV. The emissivity-reducing coating 2 comprises, starting from the substrate 1, a functional layer 2.1, a first optically low-refractive-index layer 2.2, and a cover layer 2.3. The functional layer 2.1 is formed on the basis of a transparent conductive oxide, for example, indium tin oxide (ITO), and has a thickness of 72 nm, for example. The first optically low-refractive-index layer 2.2 is formed, for example, on the basis of aluminum-doped silicon oxide (SiO2:Al) and has a thickness of 50 nm. The cover layer 2.3 consists, for example, of aluminum-doped silicon (Si:Al) and has a thickness of 5 nm.

[0071] Fig. 2 shows a further embodiment of a pane 10 according to the invention. The embodiment shown in Fig. 2 differs from the embodiment of Fig. 1 only in that an optically high-refractive-index layer 2.4 and a second optically low-refractive-index layer 2.5 are additionally arranged between the substrate 1 and the functional layer 2.1. The optically high-refractive-index layer 2.4 is arranged directly adjacent to the first surface IV of the substrate 1 and has a refractive index greater than or equal to 1.9. The optically high-refractive-index layer 2.4 is formed, for example, on the basis of aluminum-doped silicon nitride (SisN^Al) and has a thickness of 30 nm.

[0072] The second optically low-refractive-index layer 2.5 has a refractive index less than or equal to 1.6 and is arranged between the optically high-refractive-index layer 2.4 and the functional layer 2.1. The second optically low-refractive-index layer 2.5 is formed, for example, from aluminum-doped silicon oxide (SiO2:Al) and has a thickness of 20 nm.

[0073] Fig. 3 shows an embodiment of a composite pane according to the invention. The composite pane comprises the pane 10 from Fig. 1, a thermoplastic intermediate layer 11 and a second pane 12 which has a first surface I and a second surface II. The intermediate layer 11 is made, for example, from polyvinyl butyral (PVB) and is 0.76 mm thick. The second pane 12 is made as a second substrate made of glass, for example from soda-lime glass and is 2.1 mm thick. The composite pane is, for example, a roof pane in a motor vehicle. The thermoplastic intermediate layer 11 is connected to the second surface III of the substrate 1 and to the second surface II of the second pane 12. Typically, in this case, the pane 10 is the inner pane facing the vehicle interior and the second pane 12 is the outer pane of the composite pane facing the outside environment.In this case, the first surface IV of the substrate 1, to which the emissivity-reducing coating 2 is applied, faces the vehicle interior.

[0074] Fig. 4 shows a flow chart illustrating a method according to the invention for producing a pane 10 according to the invention. The first step S1 is the provision of a substrate 1.

[0075] In a second step S2, an emissivity-reducing coating 2 is then applied to a first surface IV of the substrate 1. First, a functional layer 2.1 based on a transparent conductive oxide is applied. Subsequently, a first optically low-refractive-index layer 2.2 with a refractive index of less than or equal to 1.6 is applied directly onto the functional layer 2.1. A cover layer 2.3 with a thickness of 1 nm to 20 nm is then applied, with the cover layer 2.3 being based on silicon.

[0076] Fig. 5 shows a flowchart illustrating a method according to the invention for producing a heat-treated pane according to the invention. The method of Fig. 5 differs from the method of Fig. 4 only in that, after the second step S2, the pane 10 is additionally subjected to a heat treatment at at least 400°C as a third step S3.

[0077] The structure of the emissivity-reducing coating is explained below using examples according to the invention and comparative examples. The layer structures shown are merely examples. Exemplary materials and layer thicknesses can be found in the following examples. Table 1

[0078] Table 1 shows comparative examples C1, C2, and C3 for panes not according to the invention and examples B1, B2, B3, B4, and B5 for panes according to the invention. In all comparative examples and in all examples according to the invention, the respective pane comprises a substrate 1 made of soda-lime glass and having a thickness of 2.1 mm. An emissivity-reducing coating is applied to the substrate 1, the design of which differs between the examples according to the invention and the comparative examples. In the inventive examples B1, B2, B3, B4, and B5, the emissivity-reducing coating 2 comprises, starting from the substrate 1, an optically high-refractive-index layer 2.4, a second optically low-refractive-index layer 2.5, a functional layer 2.1, a first optically low-refractive-index layer 2.2, and a cover layer 2.3. The inventive examples B1, B2, and B3 differ only in the thickness of the cover layer 2.3, which has a thickness of 2 nm in B1, a thickness of 5 nm in B2 and a thickness of 10 nm in B3. The inventive examples B4 and B5 have the same layer sequence as examples B1, B2 and B3, but differ in their layer thicknesses. The comparative example V1 differs from the inventive examples B1, B2 and B3 only in that the cover layer 2.3 is not present in comparative example V1; instead, an additional layer is arranged between the functional layer 2.1 and the first optically low-refractive-index layer 2.2, which is based on aluminum-doped silicon nitride (Si3N4:Al) and has a thickness of 9 nm. The comparative example V2 differs from the inventive examples B1, B2 and B3 only in that the cover layer 2.3 is not present.Comparative example V3 differs from inventive examples B4 and B5 only in that the cover layer 2.3 is not present; instead, an additional layer is arranged between the functional layer 2.1 and the first optically low-refractive-index layer 2.2, which is formed on the basis of aluminum-doped silicon nitride (SisN^Al) and has a thickness of 9 nm.

[0079] Table 2

[0080] Table 2 shows the reflectance RL in % for visible light, the transmittance TL in % for visible light, and the absorbance of visible light in % for Comparative Examples V1, V2, V3, V1*, M2*, and V3* and for Inventive Examples B1, B2, B3, B4, B5, B1*, B2*, B3*, B4*, and B5*. V1*, M2*, and V3* denote the panes from Comparative Examples V1, M2, and V3 in the state after heat treatment at 640°C for a period of 10 minutes; analogously, B1*, B2*, B3*, B4*, and B5* denote heat-treated panes according to the invention, which were obtained from the panes according to Examples B1, B2, B3, B4, and B5 by heat treatment at 640°C for a period of 10 minutes. The reflection coefficient RL refers to the proportion of light that hits the disc from the direction corresponding to the first

[0081] Surface IV, which faces the emissivity-reducing coating, is reflected by the emissivity-reducing coating at an angle of 8° to the surface normal, while the transmittance TL describes the proportion of visible light that is transmitted through the pane at an angle of 0° to the surface normal, and the absorbance describes the proportion of visible light that is absorbed by the emissivity-reducing coating. A standard light source of illuminant A with a 10° detector is used here. Reflectance RL and transmittance TL are each determined using a TEC5 spectrometer. The specified values ​​for reflectance RL, transmittance TL, and absorbance are determined by averaging over the spectrum of visible light in the wavelength range from 380 nm to 780 nm.

[0082] As described above, the heat treatment leads to at least partial oxidation of the cover layer with the oxygen from the ambient air, whereby the heat-treated cover layer in examples B1*, B2*, B3*, B4* and B5* Si x Al y O z Table 2 shows that the optical properties of the heat-treated panes according to the invention are improved compared to the optical properties of the panes according to the invention in the state before heat treatment, as can be seen in particular in a lower sheet resistance, an increased transmittance and a lower absorptivity.

[0083] The inventive examples B1, B2, B3, B4 and B5 show similar values ​​with regard to the transmission, reflection and absorption properties as the comparative examples V1, V2 and V3, likewise the inventive examples for heat-treated panes B1*, B2*, B3*, B4* and B5* show similar values ​​with regard to the transmission, reflection and absorption properties.

[0084] The panes according to the invention according to Examples B1, B2, B3, B4 and B5 and the heat-treated panes according to the invention according to Examples B1*, B2*, B3*, B4* and B5* all have a transmittance of greater than or equal to 77%, with the heat-treated panes according to the invention according to Examples B1* to B5* even having a transmittance of greater than or equal to 84%.

[0085] The inventive examples B1* and B2* for heat-treated panes show particularly low absorption values ​​of 1.4% and 1.2%.

[0086] The examples of panes B1, B2, B3, B4, and B5 according to the invention have a sheet resistance of less than 80 Ω / sq, while the examples of heat-treated panes B1*, B2*, and B3* according to the invention have a sheet resistance of 30 Ω / sq to 40 Ω / sq. The reduced sheet resistance in the post-heat treatment state particularly demonstrates the improvement in the emissivity-reducing properties due to the heat treatment, since a reduction in sheet resistance indicates a reduction in the interior emissivity.

[0087] For the comparative examples and the examples for the heat-treated panes V1*, V3*, B1*, B2*, B3*, B4*, and B5*, the interior-side emissivity is also given. For all examples according to the invention for heat-treated panes B1*, B2*, B3*, B4*, and B5*, the emissivity is less than 45%, and for examples B3* and B4*, it is even less than 30%.

[0088] List of reference symbols:

[0089] (10) Disc

[0090] (1) Substrat

[0091] (2) emissivity-reducing coating

[0092] (2.1) Functional layer

[0093] (2.2) first optically low-refractive layer

[0094] (2.3) Top layer

[0095] (2.4) optically highly refractive layer

[0096] (2.5) second optically low-refractive layer

[0097] (11) Intermediate layer

[0098] (12) second disc

[0099] (I) first surface of the second disc 12

[0100] (II) second surface of the second disc 12

[0101] (III) second surface of the substrate 1

[0102] (IV) first surface of the substrate 1

Claims

Patent claims 1. A pane (10) comprising a substrate (1) and an emissivity-reducing coating (2) on a first surface (IV) of the substrate (1), which in the specified order starting from the substrate (1) comprises at least • a functional layer (2.1) based on a transparent conductive oxide, • a first optically low-refractive layer (2.2) with a refractive index of less than or equal to 1.6, • comprises a cover layer (2.3) with a thickness of 1 nm to 20 nm, wherein the cover layer (2.3) is formed on the basis of silicon and wherein the first optically low-refractive layer (2.2) is arranged directly adjacent to the functional layer (2.1).

2. Disc (10) according to claim 1, wherein the functional layer (2.1) is formed on the basis of indium tin oxide.

3. Pane (10) according to claim 1 or 2, wherein the functional layer (2.1) has a thickness of 30 nm to 200 nm, preferably of 50 nm to 130 nm.

4. Disc (10) according to one of claims 1 to 3, wherein the first optically low-refractive-index layer (2.2) has a thickness of 30 nm to 200 nm and / or is formed on the basis of doped or undoped silicon oxide.

5. Disc (10) according to one of claims 1 to 4, wherein the cover layer (2.3) has a thickness of 2 nm to 15 nm, preferably of 3 nm to 14 nm.

6. Disc (10) according to one of claims 1 to 5, wherein the cover layer (2.3) consists of doped or undoped silicon, preferably zirconium-doped silicon, titanium-doped silicon, hafnium-doped silicon or aluminum-doped silicon, very particularly preferably aluminum-doped silicon.

7. Pane (10) according to one of claims 1 to 6, wherein the first optically low-refractive-index layer (2.2) is arranged immediately adjacent to the cover layer (2.3).

8. Pane (10) according to one of claims 1 to 7, wherein the emissivity-reducing coating (2) in the specified order starting from the substrate (1) additionally • an optically highly refractive layer (2.4) with a refractive index greater than or equal to 1.9 and / or • a second optically low-refractive-index layer (2.5) with a refractive index less than or equal to 1.6, wherein the optically high-refractive-index layer (2.4) and the second optically low-refractive-index layer (2.5) have a smaller distance from the substrate (1) than the functional layer (2.1).

9. A pane (10) according to claim 8, wherein the optically high-refractive-index layer (2.4) is formed on the basis of silicon nitride, aluminum-doped silicon nitride, titanium-doped silicon nitride, zirconium-doped silicon nitride or boron-doped silicon nitride and / or the second optically low-refractive-index layer (2.5) is formed on the basis of silicon oxide, aluminum-doped silicon oxide, titanium-doped silicon oxide, zirconium-doped silicon oxide or boron-doped silicon oxide.

10. Heat-treated disc obtained by heat-treating a disc (10) according to one of claims 1 to 9 at at least 400 °C.

11. Composite pane, comprising a pane (10) according to one of claims 1 to 9 or a heat-treated pane according to claim 10 and a thermoplastic intermediate layer (11) and a second pane (12), wherein the second pane (12) is connected to the pane (10) or the heat-treated pane via the thermoplastic intermediate layer (11) and wherein the emissivity-reducing coating (2) is arranged on the first surface (IV) of the substrate (1) facing away from the second pane (12).

12. A method for producing a coated disc (10) according to any one of claims 1 to 9 or a heat-treated disc according to claim 10, wherein at least: a) a substrate (1) is provided, b) in the specified order • a functional layer (2.1) based on a transparent conductive oxide, • a first optically low-refractive layer (2.2) with a refractive index of less than or equal to 1.6, • a cover layer (2.3) with a thickness of 1 nm to 20 nm, which is based on silicon, are applied to a first surface (IV) of the substrate (1), wherein the first optically low-refractive-index layer (2.2) is applied directly to the functional layer (2.1).

13. The method according to claim 12, wherein before step b) in the specified order an optically high-refractive-index layer (2.4) with a refractive index greater than or equal to 1.9 and / or a second optically low-refractive-index layer (2.5) with a refractive index less than or equal to 1.6 are applied to the first surface (IV) of the substrate (1).

14. The method according to claim 12 or 13 for producing a heat-treated pane according to claim 10, wherein the pane (10) is heated to at least 400°C, preferably at least 500°C, particularly preferably at least 600°C after step b).

15. Use of the pane (10) according to one of claims 1 to 9, a heat-treated pane according to claim 10 or a composite pane according to claim 11 in buildings or in means of transport for traffic on land, in the air or on water, in particular in trains, ships and motor vehicles, for example as a windscreen, rear window, side window and / or roof window.

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