Illuminated glazing element with emissivity-reducing coating

Abstract

The present invention relates to an illuminated glazing element, comprising a glass pane (2) having a first surface (III) and a second surface (IV), wherein the glazing element - is equipped with at least one light source (5), which is suitable for coupling light into the glass pane (2) in such a way that the light propagates in the glass pane (2), and - is provided with at least one light-diffusing structure (6), which is suitable for coupling said light out of the glass pane (2) via the first surface (III) and / or via the second surface (IV), wherein the second surface (IV) of the glass pane (2) is provided with an emissivity-reducing coating (4) comprising exactly one electrically conductive layer (4.1) based on a transparent conductive oxide and the electrically conductive layer (4.1) has an imaginary proportion k of the refractive index within the wavelength range from 380 nm to 780 nm, for which k < 0.035 applies.

Description

[0001] Illuminated glazing element with emissivity-reducing coating

[0002] The invention relates to an illuminated glazing element with at least one glass pane, a method for its production and its use.

[0003] Illuminated glass panes are known as such. For illumination, the glass pane is equipped with a light source, typically a light-emitting diode, whose light is coupled into the glass pane in such a way that it spreads through the glass pane like a light guide, in particular by total internal reflection at the surfaces of the glass pane. Light-diffusing structures can be used to couple the light back out of the glass pane, thereby creating the illumination. The shape of the light-diffusing structures can be freely selected, so that illuminated surfaces of any shape, for example as a pattern, can be created. Illuminated glass panes of this type are known, for example, from WO2014 / 060409A1, WO2014 / 167291 A1 or the subsequently published application WO2023 / 144282. The light can be coupled in via the side edge surface of the glass pane, via the edge surface of a recess in the glass pane, or via one of the main surfaces of the glass pane.In the latter case, the light is transmitted through the glass pane and reflected back into the glass pane by a light coupling device located opposite the light source in such a way that the condition of total internal reflection is met. The light coupling device has appropriately inclined reflective surfaces. For example, microprism films can be used as light coupling devices.

[0004] In the automotive sector, such illuminated glass panes are particularly interesting as roof windows. The illuminated glass pane typically represents the inner pane of a laminated pane. However, such illuminated glass panes can also be used for other vehicle windows, as well as for windows in buildings and architecture, or in furnishings.

[0005] Likewise, glass panes equipped with emissivity-reducing coatings (so-called LowE coatings) are known, which improve thermal comfort in the vehicle interior by reflecting thermal radiation. Transparent emissivity-reducing coatings can, for example, contain a functional layer based on indium tin oxide (ITO). Examples include WO2013131667A1, WO2018206236A1, DE202022100518U1, and DE202013006875U1. The emissivity-reducing coatings are typically applied to the interior-facing surface of the glass pane (or the entire glazing element if it comprises more than a single glass pane) and have reflective properties in the mid-IR range. In summer, they reduce the radiation of thermal energy from the heated glass pane into the interior.In winter, they reduce the radiation of heat from the interior through the glass pane into the outside environment.

[0006] From WO2022 / 136107A1 and WO 2007 / 077099A1, it is known in principle that such an emissivity-reducing coating can be applied to the surface of an illuminated glass pane of the type mentioned above. However, undesirable effects can occur. The coating influences the reflection behavior of said surface, which also occurs at the total internal reflection of the light from the light source coupled into the glass pane. Thus, the coating can lead to a loss of intensity of the coupled light and / or to a change in its color ("color cast").

[0007] There is therefore a need for emissivity-reducing coatings that can be used on illuminated glass panes of the type mentioned above without the coating having a negative impact on the lighting.

[0008] The present invention is based on the object of providing an illuminated glazing element with at least one glass pane, wherein the glass pane serves, on the one hand, to distribute the light from a light source within the glazing element and, on the other hand, is provided with an emissivity-reducing coating, also referred to below as a low-E coating. The coating should not lead to a significant loss of intensity of the coupled light, nor to a change in its color. The glazing element should also have low emissivity, a low interior-side reflectance, and a reflection color as neutral as possible on the interior side. Furthermore, the coating should be efficient and cost-effective to produce.

[0009] The object of the present invention is achieved by an illuminated glazing element according to claim 1. Preferred embodiments emerge from the subclaims.

[0010] The illuminated glazing element, within the meaning of the invention, is a pane- or plate-like object comprising at least one glass pane and, in particular, structurally formed from at least one glass pane. The glazing element can be a single glass pane and structurally consist only of said glass pane. The glass element can alternatively be a laminated pane or insulating glazing containing said glass pane. In a laminated pane, the glass pane is connected to another pane via a thermoplastic intermediate layer. In an insulating glazing unit, the glass pane is connected to another pane via a circumferential spacer in the edge region, thereby forming a space between the panes that is typically filled with an inert gas or evacuated. The glazing element can be used as a window pane, for example as a window pane in vehicles, buildings, or interiors.The glazing element can also be used as a component of furniture or electrical appliances, for example, as a door panel for a cupboard or shelf, or as a panel for an oven door. The glazing element can also be used as a furnishing item, for example, as a display panel in bars or nightclubs.

[0011] The illuminated glazing element according to the invention comprises at least one glass pane. The glass pane has a first surface (main surface) and a second surface (main surface), which are typically substantially parallel to each other, as well as a side edge surface extending between the first and second surfaces.

[0012] The glazing element or glass pane can be flat or curved in one or more directions of the room. In the latter case, one of the surfaces is typically concave and the other convex. The side edge surface can be flat. However, it is common practice to grind the side edge surface to minimize the risk of injury. The side edge surface is then curved or rounded, in particular convexly curved or rounded.

[0013] The glazing element, in particular the glass pane, is equipped with at least one light source which is suitable for coupling the light emitted by it into the glass pane in such a way that the light spreads (at least) in the glass pane.

[0014] The propagation of light in the glazing element occurs in particular through total internal reflection at two interfaces to an optically less dense medium (medium with a lower refractive index). One of these interfaces is the second surface of the glass pane, which is provided with the emissivity-reducing coating. This is preferably an exposed surface of the glazing element, and the adjacent optically less dense medium is preferably air. The other interface is preferably the first surface of the glass pane - in this case, the light propagates only in the glass pane. In particular, if the glazing element is designed as a composite pane, at least one further layer can be in contact with the first surface, which has essentially the same refractive index as the glass pane, so that the first surface does not represent a reflective interface.In this case, the other interface is the surface of said at least one further layer facing away from the glass pane, where there is a transition to an optically less dense medium.

[0015] In other words, the propagation of light in the glazing element occurs by total reflection at the second surface of the glass pane provided with the emissivity-reducing coating and a further interface, which is preferably the first surface of the glass pane, but in the case of a composite pane can also be formed by the surface of a layer facing away from the glass pane, which is in contact with the first surface and has the same refractive index as the glass pane.

[0016] The glazing element is further provided with at least one light-scattering structure suitable for coupling said light out of the glass pane via its first surface and / or via its second surface. The light-scattering structure is arranged on or formed in one of the totally reflecting surfaces or between the totally reflecting surfaces. Preferably, the light-scattering structure is arranged on or formed in the first or second surface of the glass pane. When the light propagating in the glazing element strikes the light-scattering structure, it is scattered, thereby preventing total reflection, so that the scattered light is coupled out of the glazing element (in particular the glass pane) and leaves the glazing element.

[0017] According to the invention, the second surface of the glass pane is provided with an emissivity-reducing coating which has precisely one electrically conductive layer based on a transparent conductive oxide (also referred to as TCO or transparent conductive oxide), and the electrically conductive layer has an imaginary component k of the refractive index within the wavelength range from 380 nm to 780 nm, for which k < 0.035 applies. This means that for each wavelength within the wavelength range from 380 nm to 780 nm, the electrically conductive layer has an imaginary component k of the refractive index for which k < 0.035 applies. In the entire wavelength range, no k value occurs that is not less than 0.035. Preferably, the electrically conductive layer has an imaginary component k of the refractive index within the wavelength range from 380 nm to 780 nm, for which k<0.030, particularly preferably k<0.025.Exactly one electrically conductive layer means that, beyond the electrically conductive layer based on a TCO, there is no further electrically conductive layer inside, below, or above the emissivity-reducing coating. If the low-E coating contains additional layers beyond the electrically conductive layer, these are dielectric layers.

[0018] The complex refractive index n is the sum of the real part of the refractive index n and the product of the imaginary part n; multiplied by the imaginary number i: n = n + i * ni

[0019] The imaginary part ni of the complex refractive index is also called the extinction coefficient k. The extinction coefficient describes the attenuation power of an optical medium, with k increasing the more strongly incident light is absorbed by the material. The value of the extinction coefficient k depends on the chemical and crystallographic structure of the material.

[0020] The inventors have found that a low-E coating comprising a single electrically conductive layer based on a TCO is particularly suitable for achieving high light intensity radiated into the glazing, provided that the imaginary component of the refractive index of the TCO layer in the wavelength range from 380 nm to 780 nm is less than k = 0.035. This wavelength range corresponds to that of visible light, in which the illuminated glazing element is also operated. If the extinction coefficient is selected to be so small, only a slight attenuation of the light coupled into the illuminated glazing element occurs due to absorption, and a high light intensity of the illuminated glazing element is maintained.

[0021] Preferably, within the wavelength range from 380 nm to 490 nm, the electrically conductive layer has an imaginary component k of the refractive index for which k < 0.020, particularly preferably k < 0.015. Within the wavelength range from 490 nm to 575 nm, the electrically conductive layer preferably has an imaginary component k of the refractive index for which k < 0.015, particularly preferably k < 0.010. Preferably, within the wavelength range from 600 nm to 700 nm, the electrically conductive layer has an imaginary component k of the refractive index for which k < 0.025, particularly preferably k < 0.020. This makes it possible to maintain a particularly high light intensity in these wavelength ranges. Here, too, this means that for each wavelength within the said wavelength range, the value for k is smaller than the respectively specified value.The wavelength ranges in question are particularly relevant because typical light sources in violet / blue, green and red colors have emission wavelengths in these ranges.

[0022] The refractive index is fundamentally independent of the measurement method; it can be determined, for example, using ellipsometry. Ellipsometry is a common optical method for determining layer thicknesses and optical constants, allowing both the real and imaginary parts of the refractive index to be determined. Ellipsometers are commercially available, for example, from Sentech.

[0023] The extinction coefficient of the electrically conductive layer is determined by measuring the imaginary part of the refractive index of the low-E coating within the wavelength range of 380 nm to 780 nm. Beyond the electrically conductive layer, the low-E coating comprises at most dielectric layers. Dielectrics do not contribute to absorption and can therefore be neglected, allowing direct conclusions to be drawn about the electrically conductive layer from the measurements of the low-E coating.

[0024] Unless otherwise stated, the refractive indices of additional layers of the low-E coating are generally based on a wavelength of 550 nm within the scope of the present invention. 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. Unless otherwise stated, the specified layer thicknesses are geometric layer thicknesses.

[0025] The electrically conductive layer is preferably based on indium tin oxide (ITO). Alternatively, the conductive layer can also be based on, for example, indium zinc mixed oxide (IZO), aluminum-doped zinc oxide (AZO, ZnO:Al), 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). Such layers are corrosion-resistant and can be used on exposed surfaces. The real part of the complex refractive index of the TCO layer is preferably between 1.5 and 2.3.

[0026] If a layer (thin film) of a coating is formed based on a material, the layer consists predominantly of this material, in particular essentially of this material alongside any impurities or dopants. The electrically conductive layer based on a TCO is therefore predominantly formed from this material. The electrically conductive layer based on a transparent conductive oxide preferably comprises at least 90 wt.% of a TCO, particularly preferably at least 95 wt.% of a TCO, and in particular consists of a transparent conductive oxide.

[0027] The electrically conductive layer is preferably deposited by means of physical vapor deposition. In principle, it is possible to influence the extinction coefficient k via the oxygen content in the process gas during physical vapor deposition, in particular during magnetic field-assisted cathode sputtering. In a preferred embodiment, an oxygen content of 1% by volume to 3% by volume is selected in the process gas. Such an oxygen content is particularly suitable for producing an electrically conductive TCO layer with an extinction coefficient k of less than 0.035 in the wavelength range from 380 nm to 780 nm. The electrically conductive layer is particularly preferably based on indium tin oxide (ITO) and deposited by means of physical vapor deposition with an oxygen content of 1% by volume to 3% by volume in the process gas.This achieves particularly good results in terms of absorption properties.

[0028] In a preferred embodiment, the emissivity-reducing coating has a specific sheet resistance of less than 250 pQ*cm, particularly preferably less than 200 pQ*cm.

[0029] The glazing arrangement preferably has an interior-side emissivity of less than or equal to 40%, more preferably less than or equal to 35%, most preferably less than or equal to 30%. Interior-side emissivity refers to the measure that indicates how much thermal radiation the pane emits into an interior, for example a building or vehicle, in the installed position compared to an ideal thermal radiator (a blackbody). For the purposes of the invention, emissivity is understood to mean the normal emissivity at 283 K according to standard EN 12898. The electrically conductive layer preferably has a thickness of 60 nm to 100 nm, more preferably 65 nm to 95 nm. In these ranges, a good emissivity-reducing effect of the low-E coating and, at the same time, a sufficiently low absorption of the electrically conductive layer is achieved.

[0030] The low-E coating preferably comprises one or more dielectric layers arranged above or below the one TCO layer. Typically, a dielectric layer or layer sequence is arranged below and / or above the TCO layer, improving the optical properties, in particular the transmission and reflectivity. The emissivity-reducing coating is then also a thin-film stack, i.e., a sequence of thin individual layers. Preferred embodiments of the emissivity-reducing coating, which achieve particularly good results, are described below.

[0031] If a first layer is arranged above a second layer, this means within the meaning of the invention that the first layer is arranged further away from the substrate to which the coating is applied 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 further away from the substrate than the first layer. The low-E coating is preferably designed as a thin-film sequence, wherein it comprises a plurality of thin films which are deposited one above the other on the second surface of the glass pane. If a first of these thin films is applied below a second thin film, the distance between the first thin film and the second surface of the glass pane is smaller than the distance between the second thin film and the latter.

[0032] Anti-reflective coatings, which have a lower refractive index than the TCO layer and are positioned above and below it, have a significant influence on the optical properties. These anti-reflective coatings can increase transmission through the pane and reduce reflectivity, particularly due to interference effects. The effect depends crucially on the refractive index and layer thickness.

[0033] In an advantageous embodiment, the emissivity-reducing coating comprises a dielectric lower anti-reflective coating arranged beneath the TCO layer. The refractive index of the lower anti-reflective coating is preferably at most 1.8, for example, from 1.3 to 1.8, particularly preferably at most 1.6, for example, from 1.3 to 1.6. The thickness of the lower anti-reflective coating is preferably from 5 nm to 25 nm, preferably from 5 nm to 20 nm.

[0034] In an advantageous embodiment, the emissivity-reducing coating comprises a dielectric upper anti-reflective coating arranged above the TCO layer. The refractive index of the upper anti-reflective coating is preferably at most 1.8, for example from 1.3 to 1.8, particularly preferably at most 1.6, for example from 1.3 to 1.6. The thickness of the upper anti-reflective coating is preferably from 45 nm to 100 nm, for example from 50 nm to 75 nm.

[0035] In an advantageous embodiment, the emissivity-reducing coating has both a lower anti-reflective layer below the TCO layer and an upper anti-reflective layer above the TCO layer.

[0036] The anti-reflective coatings provide particularly advantageous optical properties of the pane. They increase the pane's transparency and promote a neutral color impression. The anti-reflective coatings are 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 may contain dopants and is preferably doped with aluminum (SiO2:Al), boron (SiO2:B), titanium (SiO2:Ti), hafnium (SiO2:Hf), or zirconium (SiO2:Zr).

[0037] Depending on the application of the illuminated glazing element, greater or lesser transparency may be desired or required. While a lower level of transparency is acceptable or even desirable for decorative glazing or vehicle roof glazing, for example, a transmission of at least 70% in the visible range of the light spectrum is legally required for vehicle windshields.

[0038] The upper anti-reflective coating can be the topmost layer of the coating. It is then located at the greatest distance from the substrate surface (the second surface of the glass pane) and is the final layer of the layer stack. Depending on the application and installation situation of the glazing element, this layer can also be exposed, i.e., 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 can, for example, serve to improve scratch protection and be based on zirconium oxide, titanium oxide, or hafnium oxide.

[0039] In an advantageous embodiment, the emissivity-reducing coating between the TCO layer and the upper anti-reflective coating comprises an upper dielectric barrier layer for regulating oxygen diffusion with a refractive index of at least 1.9. The barrier layer serves to adjust the oxygen supply to an optimal level. Particularly good results are achieved when the refractive index of the barrier layer is between 1.9 and 2.5.

[0040] The upper dielectric barrier layer for regulating oxygen diffusion is preferably based on a nitride or a carbide. The upper dielectric barrier layer can, for example, be based on a nitride or carbide of tungsten, niobium, tantalum, zirconium, hafnium, chromium, titanium, silicon, or aluminum. In a preferred embodiment, the upper dielectric barrier layer is based on silicon nitride or silicon carbide, in particular silicon nitride (SisN), which achieves particularly good results. The silicon nitride can be doped and, in a preferred development, is doped with aluminum (SisNAl), zirconium (SisNZr), hafnium (SisNHf), titanium (SisNTi), or boron (SisNB). During a heat treatment after the application of the coating according to the invention, the silicon nitride can be partially oxidized.A barrier layer deposited as SiN4 then contains Si after the temperature treatment. x N y O z , with the oxygen content typically ranging from 0 atomic% to 35 atomic%.

[0041] The thickness of the upper dielectric barrier layer is preferably from 5 nm to 40 nm, more preferably from 8 nm to 25 nm, and most preferably from 9 nm to 15 nm. This allows for particularly advantageous regulation of the oxygen content of the TCO layer. The thickness of the barrier layer is selected with regard to oxygen diffusion, rather than the optical properties of the pane. However, it has been shown that barrier layers with thicknesses within the specified range are compatible with the emissivity-reducing coating according to the invention and its optical requirements.

[0042] In an advantageous embodiment, the emissivity-reducing coating comprises a lower dielectric blocking layer against alkali diffusion beneath the TCO layer, and optionally beneath the lower anti-reflective coating. The blocking layer reduces or prevents the diffusion of alkali ions from the glass substrate into the layer system. Alkali ions can negatively influence the properties of the coating. The refractive index of the lower blocking layer is preferably at least 1.9. Particularly good results are achieved when the refractive index of the blocking layer is between 1.9 and 2.5. The blocking 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, Nb20s, Bi20s, TiO2, Ta2Os, Y2O3, ZrO2, HfO2, SnO2, or ZnSnOx, or nitrides such as AlN.The blocker layer is particularly preferably based on silicon nitride (SisN^), which achieves particularly good results. The silicon nitride can have doping and, in a preferred development, is doped with aluminum (SisN^Al), with titanium (SisN^Ti), with zirconium (SisN^Zr), with hafnium (SisN^Hf) or with boron (SisN^B). The thickness of the blocker layer is preferably from 10 nm to 50 nm, particularly preferably from 10 nm to 40 nm, for example from 15 nm to 35 nm. The blocker layer is preferably the bottom layer of the layer stack, thus having direct contact with the substrate surface, where it can optimally develop its effect.

[0043] In a particularly advantageous embodiment, the coating consists only of the described layers and contains no additional layers. The emissivity-reducing coating particularly preferably consists of the following layers in the specified order, starting from the substrate surface (second surface of the glass pane):

[0044] - lower blocking layer against alkali diffusion

[0045] - a lower anti-reflective layer

[0046] - electrically conductive layer based on a TCO

[0047] - upper barrier layer to regulate oxygen diffusion

[0048] - upper anti-reflective layer

[0049] If the glazing element according to the invention is a window pane (for example of a vehicle, a building, an interior, a piece of furniture, or a piece of furnishing), it is intended to be inserted into a window opening and there to separate an interior from an external environment. The glass pane then has an external surface and an internal surface. For the purposes of the invention, the term "external surface" refers to the main surface intended to face the external environment in the installed position. For the purposes of the invention, the term "internal surface" refers to the main surface intended to face the interior in the installed position. Instead of being used as a window pane in the narrower sense, the glazing element can equally be used as a door pane or facade glazing, with the above statements applying analogously.

[0050] The second surface provided with the emissivity-reducing coating is preferably the interior-facing surface of the glass pane, and particularly preferably the interior-facing surface of the entire glazing element exposed to the interior. This is advantageous with regard to thermal comfort in the interior, because, in particular, the heat radiation from the heated glazing element into the interior is optimally reduced. In principle, however, it is also conceivable for the second surface of the glass pane to form the exterior surface of the glass pane and / or even of the entire glazing element.

[0051] The emissivity-reducing coating is typically applied over the entire surface of the second surface, possibly with the exception of a peripheral edge region and / or other locally limited areas that can be used, for example, for data transmission or for coupling light. The coated portion of the substrate surface is preferably at least 80%.

[0052] In a first preferred embodiment, the glazing element according to the invention is a single glass pane and is structurally formed only from the glass pane, which serves as a light guide for the light from the light source. The totally reflecting interfaces in this case are the first and second surfaces of the glass pane, which form exposed surfaces of the glazing element.

[0053] In a second preferred embodiment, the glazing element according to the invention is a composite pane. In addition to the light-conducting glass pane with the emissivity-reducing coating and the light source, the composite pane comprises a further pane (in particular a glass pane) which is connected to the light-conducting glass pane via a thermoplastic intermediate layer. The further pane likewise has a first surface, a second surface and a circumferential side edge surface running therebetween. If the glass element is a window pane, one of the panes can be referred to as the outer pane and the other pane as the inner pane. For the purposes of the invention, the inner pane refers to the pane of the composite pane which, in the installed position, faces the interior. The outer pane refers to the pane facing the outside environment.The interior surface of the outer pane and the exterior surface of the inner pane face each other and the thermoplastic intermediate layer and are connected to each other by the thermoplastic intermediate layer.

[0054] In the case of the laminated pane, the totally reflecting interfaces are also preferably the first and second surfaces of the light-conducting glass pane. Typically, the glass pane has a refractive index that differs sufficiently from that of the intermediate layer to ensure total reflection. However, it is conceivable that a layer of the intermediate layer adjacent to the glass pane, or even the entire intermediate layer, has the same refractive index as the glass pane, so that no total reflection occurs on the surface of the glass pane facing the intermediate layer. In this case, the reflective interface is formed by the nearest surface, where a transition to an optically less dense medium occurs.This interface can be located within the intermediate layer, on the surface of the further disc facing the intermediate layer, or even on the surface of the further disc facing away from the intermediate layer.

[0055] The light-conducting glass pane with the emissivity-reducing coating is preferably the inner pane of the laminated pane, and the other pane is the outer pane. The second surface of the glass pane provided with the emissivity-reducing coating is preferably the interior-facing surface of the glass pane (inner pane), which faces away from the intermediate layer and the outer pane and is exposed to the interior. This achieves particularly good emissivity-reducing properties and particularly advantageously improves thermal comfort in the interior.

[0056] Alternatively, it is also possible for the light-conducting glass pane with the emissivity-reducing coating to be the outer pane, and the other pane to be the inner pane. In this case, too, the second surface of the glass pane with the emissivity-reducing coating is the surface facing away from the intermediate layer, i.e., the outer surface exposed to the external environment.

[0057] The glazing element is provided with a light source suitable for coupling light into the glass pane. The light can be coupled in particular via the side edge surface of the glass pane, via the edge surface of a recess in the glass pane, or with the aid of a light coupling means via one of the surfaces (main surfaces) of the glass pane. The light is radiated into the glass pane and propagates (at least) within the glass pane, being totally reflected at the previously described interfaces to an optically less dense medium (in particular, the surfaces of the glass pane). More precisely, those portions of the light that strike said surfaces at an angle of incidence greater than the respective critical angle of total reflection are totally reflected. Since there is a transition from an optically denser to an optically less dense medium, a critical angle OCT of total reflection can be determined as a.T = arcsin(— ), where ni is the refractive index of the glass pane and n2 is the refractive index of the adjacent medium.

[0058] In certain embodiments of the invention, the medium adjacent to the first surface of the transparent layer differs from the medium adjacent to the second surface. This is the case, for example, with laminated panes consisting of two laminated glass panes, one of the glass panes being used as the transparent layer. In this case, one of the surfaces of said glass pane borders the surrounding atmosphere and the other surface borders the thermoplastic interlayer of the laminated pane. Therefore, different critical angles of total internal reflection occur at the two surfaces. In this case, the portion of light in the glass pane that hits the surfaces at an angle of incidence greater than the larger critical angle of total internal reflection spreads out.

[0059] The refractive index and the critical angle of total reflection also depend on the wavelength of the light from the light source. At a wavelength of 589 nm, the refractive index of a pane of glass made of soda-lime glass, for example, is 1.52. If the interface is an exposed surface of the glass pane and the adjacent medium is the surrounding atmosphere (in particular air: refractive index 1.00 at a light wavelength of 589 nm), the critical angle of total reflection OCT is 41°. If the interface is a surface of the glass pane that faces the intermediate layer of a laminated pane made of PVB film (refractive index 1.48 at a light wavelength of 589 nm), the critical angle of total reflection OCT is 77°. As is common in ray optics, the angle of incidence is the angle that the light beam incident on the surface makes to the surface normal at the point of impact.The critical angle of total internal reflection is also determined analogously to the surface normal. During operation, the light source emits visible light, i.e., electromagnetic radiation in the visible spectral range, specifically in the range from 380 nm to 780 nm. The light source can have one or more emission bands located in the visible spectral range and covering part of it. However, the light source can also have a broad emission band that covers the entire visible spectral range. The emission band(s)—and thus the color of the emitted light—can be freely selected according to the requirements of the specific application.

[0060] The glazing element can contain a single light source or multiple light sources whose light is coupled into the glass pane at different locations. The light from the light source can be coupled into the glass pane directly or via an optical element, such as a lens or a collimator.

[0061] The light source is preferably a light-emitting diode (LED). The electroluminescent material of the LED can be, for example, an inorganic semiconductor or an organic semiconductor. In the latter case, it is also referred to as an organic light-emitting diode (OLED).

[0062] The coupling of the light from the light source into the glass pane can be carried out in different ways, with three embodiments being particularly preferred.

[0063] In a first preferred embodiment, the light source is assigned to one of the two surfaces (main surfaces) of the glass pane. The light source is arranged on one of the surfaces and radiates light into the glass pane via this surface. The glazing element is equipped with a light coupling means opposite the light source, which is irradiated with light from the light source through the glass pane. The light coupling means is suitable for coupling the light into the glass pane via the surface facing away from the light source and facing the light coupling means, so that at least a portion of the light propagates (at least) through the glass pane by total internal reflection. For this purpose, the light coupling means typically has reflective surfaces that are suitably inclined relative to the surface of the glass pane.The light coupling means can be designed, for example, as a microprism film, a structured plastic foil, or a plastic plate with a planar arrangement of microprisms. The light coupling means reflects the light back into the glass pane, but at a modified angle that deviates from 0° to the surface normal. The light is refracted at the surface of the glass pane, and at least a portion of the resulting light in the glass pane strikes the opposite surface at an angle of incidence greater than the critical angle of total internal reflection, thereby coupling the light into the glass pane.

[0064] The light source is preferably arranged on an exposed surface of the glass pane or glazing element, so that it can be retrofitted and easily replaced in the event of a defect. Particularly preferred is the interior-side exposed surface of the glass pane or glazing element, which is preferably also provided with the emissivity-reducing coating (second surface of the glass pane). The light coupling means is preferably arranged on the first surface of the glass pane.

[0065] In a second preferred embodiment, the light source is assigned to a recess in the glass pane. The glass pane therefore has a recess. This recess is preferably a hole, i.e. a feedthrough, which extends between the first and the second surface of the glass pane. Alternatively, however, the recess can also be a depression in the manner of a blind bore (bag-like depression) which extends from the first surface or the second surface into the glass pane, but without reaching the opposite main surface, which would result in a feedthrough. The blind bore preferably extends from a surface which forms an exposed surface of the glass element according to the invention into the glass pane. The light source can then be retrofitted and easily replaced in the event of a defect.In the case of a laminated pane, the exposed surface of the glass pane is the surface facing away from the intermediate layer. The recess can be created in the glass pane, for example, by mechanical drilling or laser processing. The recess is preferably round, but can in principle have any desired shape, for example, even a polygonal shape. This refers to the base area of ​​the recess in the plane of the at least one surface of the glass pane, via which the recess is introduced into the glass pane.

[0066] The recess, whether a through-hole or a recess, is defined by a peripheral edge surface extending between the main surfaces of the glass pane. In the case of a through-hole, this is the only boundary surface of the recess. In the case of a pocket-like recess, a further boundary surface is present, facing the main surface of the glass pane to which the recess does not extend, and which, as it were, forms the bottom of the blind hole. If the glazing element comprises several light sources, a separate recess is preferably provided for each light source.

[0067] In this embodiment, the light source is assigned to the said edge surface of the recess and is suitable for coupling light into the glass pane via this edge surface. The light source itself can be arranged in the recess so that it is in the plane defined by the glass pane and the emitted light hits the edge surface directly. The light source can, for example, be clamped into the recess or glued to the edge surface. It is also conceivable for the light source to be located in a housing or holder and fixed there, with the housing or holder being inserted into the recess, preferably with a precise fit. Alternatively, however, it is also possible for the light source not to irradiate the edge surface directly, but rather for the radiation to be first deflected.It is conceivable that the light source is located in a housing, with one part of the housing being inserted into the recess, while another part of the housing is located outside the recess. The light source is positioned in the part of the housing outside the recess, and the light is redirected by reflective surfaces or waveguides in the housing such that it illuminates the edge surface of the recess. Said housing is preferably attached to an exposed surface of the glass pane and extends from there into the recess.

[0068] In a third preferred embodiment, the light source is assigned to the side edge surface of the glass pane and is suitable for coupling light into the glass pane via the side edge surface. The light emitted by the light source can hit the side edge surface directly. The light source can be located to the side of the glass pane in the plane defined by the glass pane. For this purpose, the light source can be attached directly to the side edge surface, for example, glued or clamped. Alternatively, the light source can also be located in a housing or holder and fixed there, wherein the housing or holder is attached to the glass pane, for example, glued or clamped, in such a way that the light source irradiates the side edge surface. However, it is also possible for the light source not to irradiate the side edge surface directly, but rather for the radiation to be first deflected.It is conceivable for the light source to be located in a housing containing reflective surfaces or waveguides through which the light beam path is shaped. This housing is attached to the glass pane in such a way that the beam path guides the light to the side edge surface of the glass pane. The light source itself then does not have to be located to the side of the glass pane in the plane defined by the glass pane, but can, for example, be arranged in front of or behind the glass pane in the viewing direction. The said housing is preferably attached to an exposed surface of the glass pane and extends from there to the side edge surface of the glass pane.

[0069] A combination of the embodiments described above is also conceivable, wherein several light sources are present whose light is coupled into the glass pane in different ways.

[0070] The glazing element (in particular the glass pane) is also provided with a light-scattering structure suitable for coupling the coupled light out of the glass pane via the first and / or second surface. The light-scattering structure is arranged on one of the two totally reflecting interfaces or between them.

[0071] The light-scattering structure preferably has direct contact with one of the surfaces of the glass pane, so that the light propagating through the glass pane hits it. The light-scattering properties of the light-scattering structure prevent total internal reflection. The light-scattering structure represents a scattering center, so to speak, where the light is scattered and therefore not totally reflected. Since scattering is fundamentally non-directional, at least some of the scattered light leaves the glass pane. This can be used to create illumination or to display information or aesthetic forms.

[0072] The surface of the glazing element covered by the light-diffusing structure appears to the observer as a luminous surface. This can be used, for example, for lighting (e.g., an interior) or for creating a display to present information or aesthetic forms. The luminous structure can be present in a single, contiguous area of ​​the glazing element or in several separate areas. The light-diffusing structure allows for the creation of any desired shape or pattern.

[0073] The light-diffusing structure can be applied directly to the first or second surface of the glass pane or formed there. Alternatively, the light-diffusing structure can be provided, for example, on a carrier film that is attached to the first or second surface, for example by gluing. If the glass element according to the invention is a laminated pane, the light-diffusing structure can be applied to the surface of the thermoplastic intermediate layer that is in contact with the glass pane. Alternatively, the light-diffusing structure (for example, applied to a carrier film) can be inserted between the glass pane and the intermediate layer.

[0074] In an advantageous embodiment, the light-scattering structure is formed as a print, in particular as a print on one of the surfaces of the glass pane or - in the case of a composite pane - on the surface of the intermediate layer facing the glass pane. A print on the glass pane is preferably formed as a light-scattering enamel. This enamel can be printed, for example, using a screen printing process. It preferably contains glass frits, which are fired into the surface of the glass pane, creating a roughened and therefore light-scattering surface. A print on the intermediate layer can be realized by printing a surface of a thermoplastic film with a light-scattering printing paste, for example using a screen printing process.During the production of the laminated pane, the film is inserted between the outer and inner panes to form the intermediate layer, with the printed surface facing the glass pane, particularly in direct contact with the glass pane. In an advantageous embodiment, the light-scattering structure is transparent, so that it does not significantly restrict visibility through the glass pane. The print (the enamel or printing paste) therefore preferably contains no pigment. However, opaque or semi-transparent light-scattering structures containing pigments are also conceivable, for example, white structures.

[0075] Light-diffusing structures can also be created by roughening the relevant surface of the glass pane or the intermediate layer. This roughening can be done mechanically (e.g. by grinding techniques) or by laser processing. Laser processing has the advantage, particularly in the case of a laminated pane, that the light-diffusing structure can also be incorporated into the finished laminated pane, even if it is to be located inside the laminated pane, since the laser radiation can also be focused on a plane inside the laminated pane, for example through the transparent glass pane. Laser processing also makes it possible to create the light-diffusing structure inside the glass pane rather than on a surface. The glass pane is preferably made of soda-lime glass, which is common for window panes.In principle, the glass pane can also be made of other types of glass (e.g., borosilicate glass, quartz glass, aluminosilicate glass). In a preferred embodiment, glass compositions with a transmission in the visible range of the light spectrum of greater than 90% are used. The thickness of the glass pane can vary widely. Preferably, panes with a thickness in the range of 0.5 mm to 10 mm are used, more preferably 1 mm to 5 mm. In the case of a composite pane, the same applies to the additional pane, whereby the material and thickness of the additional pane and the glass pane can be selected independently of each other.

[0076] The glass pane is preferably clear so that the light can spread advantageously within the glass pane. In the case of a laminated pane, the further pane and the intermediate layer can be clear or also tinted or colored. In particular, if the glazing element comprises the laminated pane and is used as a roof pane in a vehicle, the laminated pane can comprise a tinted intermediate layer and / or a tinted further pane. In particular, if the glass pane is the inner pane of the laminated pane facing the vehicle interior and the further pane is the outer pane facing the outside environment, this can enable both high light intensity and a color-neutral display, whereby the tinted intermediate layer or the tinted outer pane increase thermal comfort, especially in strong sunlight, and prevent the vehicle occupants from being dazzled.The tinted outer pane or the tinted intermediate layer preferably has a visible light transmittance of less than 50%, particularly preferably less than 20%.

[0077] The thermoplastic intermediate layer comprises at least one layer of a thermoplastic connecting material, which preferably contains 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. The thickness of the film is preferably from 0.3 mm to 2 mm, with standard thicknesses of 0.36 mm and 0.76 mm being particularly common. The 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. The glazing element preferably has an opaque masking region through which no vision is possible. This masking region is preferably arranged circumferentially in an edge region and surrounds a central transparent see-through region in a frame-like manner.This is particularly common for vehicle windows. The masking area is preferably formed by an opaque masking print on the glass pane and / or (in the case of a laminated pane) on the other pane. The masking print is typically made of an enamel containing glass frits and a pigment, preferably applied using a screen printing process and then fired. In an alternative embodiment, the masking print is applied using a digital printing process and then fired.

[0078] The invention also comprises a method for producing an illuminated glazing element according to the invention, wherein

[0079] (a) a glass sheet is provided having a first surface and a second surface,

[0080] (b) the second surface of the glass pane is provided with an emissivity-reducing coating which comprises exactly one electrically conductive layer based on a transparent conductive oxide, and the electrically conductive layer has an imaginary component k of the refractive index within the wavelength range from 380 nm to 780 nm, for which k < 0.035 applies,

[0081] (c) the glass pane is equipped with at least one light source which is suitable for coupling light into the glass pane in such a way that the light propagates in the glass pane, in particular by total reflection at the first surface and the second surface.

[0082] The glazing element is provided with at least one light-scattering structure suitable for coupling said light out of the glass pane via the first surface and / or via the second surface. This can be done between process steps (a) and (b), between process steps (b) and (c), or after process step (c).

[0083] The emissivity-reducing coating is preferably deposited on the substrate surface by vapor deposition, for example by chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), or atomic layer deposition (ALD). Physical vapor deposition (PVD), for example, vapor deposition, is particularly preferred, and cathodic sputtering and, in particular, magnetic-field-assisted cathodic sputtering are very particularly preferred. In a preferred embodiment of the method according to the invention, the emissivity-reducing coating is deposited by vapor deposition, in particular by magnetic-field-assisted cathodic sputtering.An electrically conductive layer according to the invention with an imaginary component k of the refractive index of less than 0.035 can be realized in particular by adding a proportion of 1% to 3% oxygen by volume to the process gas. The electrically conductive layer is preferably deposited by magnetic-field-assisted cathode sputtering in DC mode, with the glass pane preferably not being actively heated.

[0084] Preferably, the emissivity-reducing coating is subjected to a thermal post-treatment after deposition. Such methods for thermally annealing conductive coatings are known in principle to those skilled in the art. The inventors have found that thermal treatment of the emissivity-reducing coating facilitates the achievement of the refractive indices according to the invention.

[0085] If the glass element is a laminated pane, the glass pane is bonded to another pane via a thermoplastic interlayer. In this case, it is also possible for the light-diffusing structure and either the light-diffusing or diffractive layer or the opaque element to be applied not to the glass pane, but to the interlayer or to be inserted between the interlayer and the glass pane, as described above. The light source is preferably applied after the laminated pane.

[0086] Known lamination processes can be used, such as autoclave processes, vacuum bag processes, vacuum ring processes, calender processes, vacuum laminators, or combinations thereof. The bonding of the outer and inner panes is typically achieved using heat, vacuum, and / or pressure.

[0087] The invention further encompasses the use of a glazing element according to the invention as a window pane of a vehicle. A particularly preferred use is a vehicle roof pane. The vehicle can in principle be any land vehicle, watercraft, or aircraft, and is preferably a passenger car, truck, or rail vehicle. The glazing element can also be used in buildings, for example as a window pane, glass facade, or glass door, either outdoors or indoors, in particular as a window pane of a building or an interior. The glazing element can also be used as a component of furniture, electrical devices, as a component of furnishings, or as a furnishing.

[0088] 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.

[0089] They show:

[0090] Fig. 1 shows a cross section through a first embodiment of the glazing element according to the invention,

[0091] Fig. 2 is an enlarged view of section Z from Figure 1,

[0092] Fig. 3 shows a cross section through a further embodiment of the glazing element according to the invention,

[0093] Fig. 4 shows a cross section through a further embodiment of the glazing element according to the invention,

[0094] Fig. 5 Diagrams of the extinction coefficient k (imaginary part of the complex refractive index) for conventional and inventive ITO layers,

[0095] Fig. 6 is a diagram of the real part of the complex refractive index n for the conventional and the inventive ITO layers from Fig. 5

[0096] Figures 1 and 2 each show a detail of a first embodiment of the glazing element according to the invention. The glass element is designed as a composite pane comprising a glass pane 2 as the inner pane, which is connected to an outer pane 1 via a thermoplastic intermediate layer 3. The outer pane 1 and the glass pane 2 are made of soda-lime glass and each have 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. The glazing element is shown flat, but can also be cylindrically or spherically curved depending on the intended use. The glazing element is intended, for example, as a roof pane of a passenger car.

[0097] In the installed position, the outer pane 1 faces the outside environment, while the glass pane 2 faces the vehicle interior. The outer pane 1 has an outside surface I facing the outside environment and an inside surface II facing the vehicle interior. The glass pane 2 also has two parallel main surfaces, namely a first surface III representing the outside surface, and a second surface IV representing the inside surface. The glass pane 2 functions as the light-conducting layer of the illuminated glazing element. A light source 5 is attached to the second (inside) surface IV of the glass pane 2. Opposite the light source 5, a light coupling means 7 is attached to the first (outside) surface III of the glass pane 2. The light source 5 irradiates the light coupling means 7 through the glass pane 2. The light source 5 is designed as a light-emitting diode.The light coupling means 7 is designed as a microprism film with a plurality of reflection surfaces that are inclined relative to the surfaces III, IV. The reflected light then re-enters the glass pane 2 via the first surface III at a changed beam angle. The light is thus coupled into the glass pane 2 via the first surface III by means of the light coupling means 7. The light radiation is indicated by arrows in the figure. A portion of the light strikes the surfaces III, IV of the glass pane 2 at an angle of incidence that is greater than the critical angle of total internal reflection (or greater than the greatest critical angle of total internal reflection, since different critical angles of total internal reflection occur at the two surfaces III, IV due to the different adjacent medium). This portion of the light propagates through repeated total internal reflection in the glass pane 2.

[0098] In a peripheral edge region of the glazing element, an opaque masking print 9 is applied to the interior-facing surface II of the outer pane 1. The light source 5 and the light coupling means 7 are discreetly arranged in this opaque edge region (masking region).

[0099] The first surface III of the glass pane 2 is provided with a plurality of light-scattering structures 6, at which the light is scattered and total internal reflection is prevented. Thus, the light is coupled out of the glass pane 2, in particular via the second surface IV, so that the vehicle occupants perceive the surfaces with the light-scattering structures 6 as luminous surfaces.

[0100] The second (interior-side) surface IV of the glass pane 2 is provided with an emissivity-reducing coating 4, the optical properties of which are optimized such that, in particular, it does not lead to a significant loss of intensity of the propagating light and does not change its color. The emissivity-reducing coating 4 is formed as a stack of thin layers. The individual layers can be seen in the enlarged view of Figure 2. The emissivity-reducing coating 4 consists of a lower dielectric blocking layer 4.2, a lower dielectric anti-reflective layer 4.3a, an electrically conductive layer 4.1, an upper dielectric barrier layer 4.4, an upper dielectric anti-reflective layer 4.3b, and a scratch-protection layer 4.5. The lower dielectric blocking layer 4.2 has a refractive index of at least 1.9 and prevents the diffusion of alkali ions from the glass pane 2 into the layers above the blocker layer 4.2. The lower dielectric anti-reflection layer 4.3a has a refractive index of at most 1.6, the upper dielectric anti-reflection layer 4.3b has a refractive index of at most 1.8. The anti-reflection layers 4.3a, 4.3b increase the transmission through the pane and reduce the reflectivity. The upper dielectric barrier layer 4.4 regulates the oxygen diffusion into the layer stack and has a refractive index of at least 1.9. The electrically conductive layer 4.1 consists of ITO and has an imaginary component k of the refractive index within the wavelength range from 380 nm to 780 nm, for which k < 0.035 applies.

[0101] Figure 3 shows a further embodiment of the glazing element according to the invention. The glazing element is fundamentally constructed in the same way as the embodiment in Figure 1, but differs in the type of light coupling. The light source 5 is attached to the side edge surface e of the glass pane 2 and radiates the light via this side edge surface e into the glass pane 2. Here, too, a portion of the light strikes the surfaces III, IV of the glass pane 2 at an angle of incidence that is greater than the (largest) critical angle of total internal reflection and spreads through repeated total internal reflection in the glass pane 2.

[0102] The side edge surface e is shown flat for the sake of simplicity, but in reality is often convexly rounded due to edge grinding.

[0103] Figure 4 shows a further embodiment of the glazing element according to the invention. The glazing element is basically constructed in the same way as in the embodiment of the figures.

[0104] 1 and 3, but differs in the way the light is coupled. The glass pane

[0105] 2 is provided with a recess A, which extends as a feedthrough completely through the glass pane 2, i.e. from its first surface III to its second surface IV. This recess A has, for example, a circular base and is delimited by a circumferential edge surface i. The light source 5 is inserted into the recess A, for example glued to the edge surface i. The light is coupled into the glass pane 2 via the edge surface i. Here, too, a portion of the light strikes the surfaces III, IV of the glass pane 2 at an angle of incidence that is greater than the (largest) critical angle of total internal reflection and spreads through repeated total internal reflection in the glass pane 2.

[0106] 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. Thus, the dielectric layer sequences can also comprise more or fewer layers. The dielectric layer sequences do not have to be symmetrical. Exemplary materials and layer thicknesses can be found in the following examples. The emissivity-reducing coatings are applied to the second surface IV of the glass pane 2 and, when the glazing element is installed in a vehicle, are located adjacent to the vehicle interior.

[0107] The layer sequences of an emissivity-reducing coating 4 on a glass pane 2 according to inventive examples B1 to B6, together with the materials and geometric layer thicknesses of the individual layers, are shown in Table 1. The dielectric layers can be doped independently of one another, for example with boron, titanium, zirconium, or aluminum. The electrically conductive layer 4.1, provided as an ITO layer, is deposited with an oxygen content in the process gas according to Table 1 by means of magnetic field-assisted sputtering. The magnetic field-assisted sputtering is carried out, for example, in an industrial plant in direct current (DC) mode without active heating of the glass pane 2 during deposition. The glass pane 2 has a thickness of 2.0 mm and is made of soda-lime glass. Examples B1 to B3 and B4 to B6 each show identical layer stacks, in the first case with a thin TiO x-Top layer as a scratch protection layer 4.5 and in the second case without such a scratch protection layer 4.5. Examples B1 to B3 and B4 to B6 differ from each other in the oxygen content during the deposition of the ITO layer.

[0108] Table 2 shows further examples B7 to B12 according to the invention. Examples B7 to B9 and B10 to B12 differ from one another in the oxygen content during the deposition of the ITO layer. Layer variants with thicker ITO are considered here. Table 3 shows non-inventive comparative examples C1 to C4, wherein an emissivity-reducing coating 4 according to the comparative examples has the identical basic structure as in the examples according to the invention, but differs in the layer thicknesses and the oxygen content of the process gas during the deposition of the electrically conductive layer 4.1 (ITO). The structure of the emissivity-reducing coating 4 in comparative example C1 corresponds to the layer structure of the emissivity-reducing coating 4 in examples B1, B2 and B3 with the difference that in C1 the oxygen content in the process gas is 0% during the deposition of the ITO layer.The layer structure also corresponds to the emissivity-reducing one.

[0109] Coating 4 in comparative example V2 corresponds to the layer structure of B4, B5 and B6, the layer structure in V3 corresponds to that of B7, B8 and B9 and the layer structure in V4 corresponds to that of B10, B11, B12, in each case with the difference that in comparative examples V2, V3 and V4 the oxygen content in the process gas during the deposition of the ITO layer is 0%.

[0110] Table 1

[0111] Table 2 Table 3

[0112] In Table 4 the maximum extinction coefficient k ma x of the electrically conductive layer 4.1 in the visible light wavelength range from 380 nm to 780 nm for different oxygen contents in the ITO process gas. In the inventive examples B1 to B12, the electrically conductive layer 4.1 has maximum extinction coefficients k in the visible light wavelength range. max of 0.021, 0.015 and 0.016, which are thus less than 0.035, which is a prerequisite for an example according to the invention. In addition, the maximum extinction coefficient k of the electrically conductive layer 4.1 is stated in each of the wavelength ranges from 380 nm to 490 nm, from 490 nm to 575 nm and from 600 nm to 700 nm. The examples according to the invention have maximum extinction coefficients k of less than 0.020 in the wavelength range from 380 nm to 490 nm, of less than 0.015 in the wavelength range from 490 nm to 575 nm and of less than 0.025 in the wavelength range from 600 nm to 700 nm. The comparative examples have an extinction coefficient k above these values ​​in each of the wavelength ranges mentioned.

[0113] In the comparative examples V1 to V4, the electrically conductive layer 4.1 has a maximum extinction coefficient k in the wavelength range of visible light from 380 nm to 780 nm max of 0.048, which is greater than 0.035, which is why the comparative examples are not in accordance with the invention. Table 4

[0114] Table 5 summarizes some characterizing parameters of the inventive examples B1 to B3 in comparison with Comparative Example C1. The reflectance R and the color values ​​a* and b* of the reflected light are each determined using the standard light source D65 with a 10° detector for a reflection below 8° at the emissivity-reducing coating as seen from the vehicle interior (referred to as Ri_(coating), a* CO atin g , b* CO ating) and for the reflection within the glass at the coating interface below 80° (denoted as Ri_(interface), a*j n interface, b*j nThe values ​​shown for the reflectance R and the color values ​​a* and b* were determined by simulations using the CODE software. The reflection angles mentioned are given in relation to the respective surface normal. RL is a measure of the reflectivity of light radiation and should be as low as possible for Ri_(coating) to avoid unwanted reflections inside the vehicle, whereas Ri_(interface) should be maximized with a view to optimizing the light intensity of the illuminated glazing element. The color values ​​in the L*a*b* color space are a measure of how color-neutral the light reflection is; the values ​​should be as close to zero as possible.

[0115] For Examples B1 to B3 and Comparative Example C1, the sheet resistance and emissivity after heat treatment were also determined, which are shown in Table 5. Low values ​​for sheet resistance and emissivity enable greater thermal comfort. Examples B1 and B2 are therefore preferred because they exhibit high light reflection in the glass and low emissivity. Table 5

[0116] Table 6 and Table 7 show the reflection properties of the coating both from the outside (coating) and from the inside (interface) for the inventive examples B4 to B12 and the comparative examples V2 to V4.

[0117] All examples according to the invention have an optimized light intensity of the illuminated glazing element, with RL(interface) being above 96% and color values ​​a*j ninterface and b*interface between -1.7 and 0.0. At the same time, the reflectivity Ri_(coating) of the coating, at less than or equal to 7% for a clear glass, is considered low. The reflection color a* CO atin g and b* CO atin g is within customer-acceptable ranges.

[0118] The color values ​​a*j n interface and b*j n The interfaces are significantly more neutral for the inventive examples. This is important for light transmission without color shift. Table 6

[0119] Table 7 It should be noted that the values ​​for reflectivity and color values ​​depend on the degree of tinting of the pane and can differ between a single pane and a composite pane. While an extra-clear single pane of glass was examined for Tables 5 to 7, a laminated composite pane is considered in Table 8. The composite pane comprises the glass pane 2 made of extra-clear glass with the emissivity-reducing coating 4 from each of the inventive examples B1, B2 and B3 and the comparative example C1, and an outer pane 1 likewise made of extra-clear glass, which is connected to the glass pane 2 via a thermoplastic intermediate layer 3, wherein the thermoplastic intermediate layer 3 is made of polyvinyl butyral (PVB) and is heavily tinted. By heavily tinted is meant that the transmittance of visible light through the composite pane is reduced to, for example, approx.6%, whereas with the individual pane a transmittance of visible light of, for example, around 92% is achieved, where the transmittance of visible light is the average transmittance in a wavelength range from 380 nm to 780 nm. This is particularly advantageous when a glazing element comprising the laminated pane is used as a roof pane in a vehicle. The use of a tinted laminated pane instead of a single pane has a major influence on the reflective properties of the layer viewed from the outside (“coating”), but does not influence the reflective properties within the glass (“interface”), which in turn determine the light conduction.

[0120] Table 8

[0121] Figure 5 shows the extinction coefficient k of several TCO layers as a function of wavelength. The TCO layers are designed as ITO layers deposited by means of magnetic field assisted cathode sputtering. In each case, no oxygen (0% O2) was added to the process gas, as in Comparative Examples V1, V2, V3 and V4, 1.5% oxygen was added, as in Inventive Examples B1, B4, B7 and B10, 3% oxygen was added, as in Inventive Examples B2, B5, B8 and B11, and 4% oxygen was added, as in Inventive Examples B3, B6, B9 and B12. The extinction coefficient k for 0% oxygen is shown as a solid line, for 1.5% oxygen as a broad dashed line, for 3% oxygen as a fine dashed line, and for 4% oxygen as a very fine dashed line.According to the example according to the invention, the ITO layer has an imaginary component k of the refractive index within the wavelength range from 380 nm to 780 nm, for which k < 0.035 applies. Figure 5b) shows the values ​​from Figure 5a) in a more detailed view in the visible wavelength range from 380 nm to 780 nm. It can be seen from Figure 5b) that the comparative examples with 0% oxygen content are not comparative examples according to the invention, since the extinction coefficient k is not less than 0.035 across the entire wavelength range. In the examples with 1.5%, 3% and 4% oxygen content, on the other hand, the extinction coefficient is less than 0.035 across the entire wavelength range from 380 nm to 780 nm. These are therefore examples according to the invention. It should be noted that these are only exemplary values ​​that show that it is possible to influence the extinction coefficient k based on the oxygen content in the process gas.

[0122] Figure 6 shows a graph of the real part of the refractive index n as a function of wavelength for the ITO layers of the inventive examples and the non-inventive comparative examples from Figure 5. The refractive indices were each determined using ellipsometry. List of reference symbols:

[0123] (1) Outer pane

[0124] (2) Glass pane / inner pane

[0125] (3) thermoplastic intermediate layer

[0126] (4) emissivity-reducing coating

[0127] (4.1) electrically conductive layer

[0128] (4.2) lower dielectric blocking layer

[0129] (4.3) Anti-reflective coatings

[0130] (4.3a) lower dielectric anti-reflection layer

[0131] (4.3b) upper dielectric anti-reflection layer

[0132] (4.4) upper dielectric barrier layer

[0133] (4.5) Scratch protection layer

[0134] (5) Light source

[0135] (6) light-scattering structure

[0136] (7) Light coupling means

[0137] (9) Cover printing

[0138] (I) outside surface of the outer pane 1

[0139] (II) interior surface of the outer pane 1

[0140] (III) first surface of the glass pane 2

[0141] (IV) second surface of the glass pane 2

[0142] (A) Recess in the glass pane 2

[0143] (e) Side edge surface of the glass pane 2

[0144] (i) Edge surface of the recess A

[0145] Z enlarged section

Claims

Patent claims 1. Illuminated glazing element comprising a glass pane (2) with a first surface (III) and a second surface (IV), wherein the glazing element - is equipped with at least one light source (5) which is suitable for coupling light into the glass pane (2) in such a way that the light propagates in the glass pane (2), in particular by total reflection at the first surface (III) and the second surface (IV), - is provided with at least one light-scattering structure (6) which is suitable for coupling said light out of the glass pane (2) via the first surface (III) and / or via the second surface (IV), - is provided with at least one emissivity-reducing coating (4) on the second surface (IV) of the glass pane (2), wherein the emissivity-reducing coating (4) comprises exactly one electrically conductive layer (4.1) based on a transparent conductive oxide and the electrically conductive layer (4.1) has an imaginary component k of the refractive index within the wavelength range from 380 nm to 780 nm, for which k < 0.035 applies.

2. Illuminated glazing element according to claim 1, wherein the electrically conductive layer (4.1) is based on indium tin oxide (ITO), indium zinc mixed oxide (IZO), fluorine-doped tin oxide (FTO, SnO2:F), aluminum-doped zinc oxide (AZO, ZnO:Al), gallium-doped zinc oxide (GZO, ZnO:Ga), antimony-doped tin oxide (ATO, SnO2:Sb) and / or niobium-doped titanium oxide (TiO2:Nb), preferably indium tin oxide.

3. Illuminated glazing element according to claim 1 or 2, wherein the emissivity-reducing coating (4) has a specific sheet resistance of less than 250 |Ω*cm, preferably less than 200 Ω*cm.

4. Illuminated glazing element according to one of claims 1 to 3, wherein the electrically conductive layer (4.1) has an imaginary component k of the refractive index within the wavelength range from 600 nm to 700 nm, for which k < 0.025, preferably k < 0.

020.

5. Illuminated glazing element according to one of claims 1 to 4, wherein the electrically conductive layer (4.1) has a thickness of 60 nm to 100 nm, preferably of 65 nm to 95 nm.

6. Illuminated glazing element according to one of claims 1 to 5, wherein the emissivity-reducing coating (4) extending from the glass pane (2) comprises at least - a lower dielectric blocking layer (4.2) against ion diffusion with a refractive index of at least 1.9, - a lower dielectric anti-reflection layer (4.3a) with a refractive index of not more than 1.6, - the electrically conductive layer (4.1), - an upper dielectric barrier layer (4.4) for regulating oxygen diffusion with a refractive index of at least 1.9 and - an upper dielectric anti-reflection layer (4.3b) with a refractive index of at most 1.

8.

7. Illuminated glazing element according to claim 6, wherein the lower dielectric blocking layer (4.2) is formed on the basis of silicon nitride and preferably has a thickness of 10 nm to 40 nm, particularly preferably of 15 nm to 35 nm.

8. Illuminated glazing element according to claim 6 or 7, wherein the lower dielectric anti-reflection layer (4.3a) is formed on the basis of SiC>2 and preferably has a thickness of 5 nm to 25 nm, particularly preferably 5 nm to 20 nm.

9. Illuminated glazing element according to one of claims 6 to 8, wherein the upper dielectric barrier layer (4.4) is formed on the basis of silicon nitride and preferably has a thickness of 5 nm to 40 nm, particularly preferably of 8 nm to 25 nm, most particularly preferably of 9 nm to 15 nm.

10. Illuminated glazing element according to one of claims 6 to 9, wherein the upper dielectric anti-reflection layer (4.3b) is formed on the basis of SiC>2 and preferably has a thickness of 45 nm to 100 nm, particularly preferably 50 nm to 75 nm.

11. Illuminated glazing element according to one of claims 1 to 10, wherein the glass pane (2) is the inner pane of a composite pane and is connected to an outer pane (1) via a thermoplastic intermediate layer (3) and wherein the second surface (IV) of the glass pane (2) faces away from the intermediate layer (3).

12. Illuminated glazing element according to one of claims 1 to 11, wherein the light source (5) is arranged on one of the surfaces (III, IV), in particular the second surface (IV), and the glazing element is equipped with a light coupling means (7) opposite the light source (5), in particular on the first surface (III), which is suitable for coupling the light striking the light coupling means (7) through the glass pane (2) into the glass pane (2).

13. Illuminated glazing element according to one of claims 1 to 11, wherein the glass pane (2) has a recess (A) which is delimited by a circumferential edge surface (i), and wherein the light source (5) is arranged in or on the recess (A) in such a way that it is suitable for coupling light into the glass pane (2) via the edge surface (i).

14. Illuminated glazing element according to one of claims 1 to 11, wherein the at least one light source (5) is arranged on a side edge surface (e) of the glass pane (2) extending between the first surface (III) and the second surface (IV) in such a way that it is suitable for coupling light into the glass pane (2) via the side edge surface (e).

15. A method for producing an illuminated glazing element, wherein (a) a glass pane (2) is provided having a first surface (III) and a second surface (IV), (b) the second surface (IV) of the glass pane (2) is provided with an emissivity-reducing coating (4) which has exactly one electrically conductive layer (4.1) based on a transparent conductive oxide, and the electrically conductive layer (4.1) has an imaginary component k of the refractive index within the wavelength range from 380 nm to 780 nm, for which k < 0.035 applies, (c) the glass pane (2) is provided with at least one light source (5) which is suitable for coupling light into the glass pane (2) in such a way that the light propagates in the glass pane (2), in particular by total reflection at the first surface (III) and the second surface (IV), wherein the glazing element is provided with at least one light-scattering structure (6) which is suitable for coupling said light out of the glass pane (2) via the first surface (III) and / or via the second surface (IV).

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