WO2025067766A1 - Illuminated glazing element with emissivity-reducing coating - Google Patents

Abstract

The present invention relates to an illuminated glazing element, comprising a glass pane (2) with a first surface (III) and a second surface (IV), the glazing element being - equipped with at least one light source (5) that is suitable for incoupling light into the glass pane (2) such that the light propagates in the glass pane (2), in particular by way of total-internal reflection at the first surface (III) and the second surface (IV), - provided with at least one light-scattering structure (6) that is suitable for outcoupling said light from the glass pane (2) via the first surface (III) and/or via the second surface (IV), - provided with at least one emissivity-reducing coating (4) on the second surface (IV) of the glass pane (2), wherein, starting from the glass pane (2) and in the specified order, the emissivity-reducing coating (4) comprises • exactly one functional layer (4.1) based on a transparent conductive oxide with a layer thickness of between 130 nm and 500 nm, • exactly one high-index layer (4.2) with a refractive index of at least 1.9, and • exactly one low-index layer (4.3) with a refractive index of no more than 1.7, and wherein the functional layer (4.1) is arranged immediately adjacently to the glass pane (2).

Description

Illuminated glazing element with emissivity-reducing coating

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

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-scattering structures can be used to couple the light back out of the glass pane, thereby creating the illumination. The shape of the light-scattering 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 W02014/060409A1, WO2014/167291A1 or WO2023/144282A1. 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.

In the automotive sector, such illuminated glass panes are particularly interesting as roof panes. 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.

Likewise, glass panes are known which are equipped with emissivity-reducing coatings (so-called low-E coatings), which improve the thermal comfort in the interior of the vehicle by reflecting thermal radiation. Transparent emissivity-reducing coatings can, for example, contain a functional layer based on indium tin oxide (ITO). For example, reference is made to WO2013/131667A1 and WO2018/206236A1. The emissivity-reducing coatings are typically applied to the interior-side surface of the glass pane (or the entire glazing element if it comprises more than one single They are arranged (at least in the glass pane) and have reflective properties in the mid-IR range. In summer, they reduce the radiation of heat 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.

WO2022/063505A1 discloses a composite pane with electrically controllable optical properties, which in a preferred embodiment has an emissivity-reducing coating containing a layer of an electrically conductive oxide arranged between two dielectric layers.

WO2022/136107A1 discloses a glazing comprising at least one pane and at least one light source arranged on the pane for coupling light into the pane, wherein the pane has at least one light coupling-out region for coupling out light totally reflected in the pane from the pane, and wherein the glazing and preferably the pane has at least one metal-based functional layer and/or at least one electro-optical functional element for electrically switching optical properties.

If such an emissivity-reducing coating is applied to the surface of an illuminated glass pane of the type mentioned above, undesirable effects may occur. The coating influences the reflection behavior of the said surface, which also results in 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.

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.

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 in the glazing element, and, on the other hand, is provided with an emissivity-reducing coating, hereinafter also referred to as a low-E coating. The coating should not lead to a significant loss of intensity of the coupled light. The reflectivity of the coupled light should therefore be as high as possible at the boundary surface of the coating in order to achieve the highest possible intensity. of light. The reflectivity of light at the coating interface can be described by the reflectance R _LiG of the reflected light for reflection at the coating interface at a reflection angle of 80°. The glazing element should also have low emissivity. Furthermore, the coating should be efficient and cost-effective to produce.

These and other objects are achieved according to the invention by an illuminated glazing element according to the independent patent claim. Advantageous embodiments of the invention emerge from the subclaims. A method for producing an illuminated glazing element and the use of the illuminated glazing element according to the invention emerge from the independent patent claims.

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 insulating glazing, the glass pane is connected to another pane via a circumferential spacer in the edge region, thereby forming a typically inert gas-filled or evacuated space between the panes. The glazing element can be used as a window pane, for example as a window pane in vehicles, buildings, or interiors. However, the glazing element can also be used as a component of furniture or electrical devices, for example as a door pane of a cupboard or shelf, or as a pane of an oven door. The glazing element can also be used as a furnishing item, for example as a display board in bars or discos.

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. 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.

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.

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 coated surface is preferably an exposed surface of the glazing element, and the adjacent optically less dense medium is air. The other interface is preferably the first surface of the glass pane - in this case, the light propagates only within 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.

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.

The glazing element is further provided with at least one light-diffusing structure suitable for coupling said light out of the glass pane via its first surface and/or via its second surface. The light-diffusing structure is arranged on a the totally reflecting surfaces or formed therein or arranged or formed between the totally reflecting surfaces. The light-scattering structure is preferably arranged on the first or the second surface of the glass pane or formed therein. In a further advantageous embodiment, the light-scattering structure is applied to a separate carrier film, in particular to a film made of polyethylene terephthalate (PET), which is arranged on one of the totally reflecting surfaces or between the totally reflecting surfaces. If 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.

According to the invention, the second surface of the glass pane is provided with an emissivity-reducing coating which, starting from the glass pane, comprises, in the specified order, precisely one layer referred to as a functional layer based on a transparent conductive oxide (also referred to as TCO or transparent conductive oxide), precisely one high-refractive-index layer with a refractive index of at least 1.9, and precisely one low-refractive-index layer with a refractive index of at most 1.7. According to the invention, the functional layer is arranged directly adjacent to the glass pane.

The inventors have determined that such a layer sequence is an emissivity-reducing coating with advantageous properties, suitable for use in illuminated glazing elements. This layer sequence is characterized by its special emissivity-reducing effect. Emissivities of less than or equal to 35% can be achieved, and in the best case even less than or equal to 25%. Furthermore, the coating is well suited for use in illuminated glazing elements, which is particularly evident in the high reflectivity of the coupled light at the coating interface.

The functional layer has a thickness of 130 nm to 500 nm. In this range, the low-E coating achieves a good emissivity-reducing effect while simultaneously achieving sufficiently low absorption. Furthermore, this layer thickness range leads to high reflectivity of the coupled light at the coating interface. The inventors have found that a coating according to the invention comprising a functional layer, a high-refractive layer with a refractive index of at least 1.9 and a low-refractive layer with a refractive index of at most 1.7 leads to a particularly high reflectivity of the coupled-in light at the interface of the coating.

The functional layer is preferably based on aluminum-doped zinc oxide (AZO, ZnO:Al), fluorine-doped tin oxide (FTO, SnO2:F) or antimony-doped tin oxide (ATO, SnO2:Sb).

If a layer (thin layer) 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 functional layer based on a transparent conductive oxide is therefore predominantly formed from this material. The functional layer based on a transparent conductive oxide preferably comprises at least 90 wt.% of a transparent conductive oxide, particularly preferably at least 95 wt.% of a transparent conductive oxide.

Preferably, the high-index layer is formed on the basis of silicon nitride (SisN^), aluminum-doped silicon nitride (SisN^Al), titanium-doped silicon nitride (SisN^Ti), zirconium-doped silicon nitride (SisN^Zr) and/or boron-doped silicon nitride (SisN^B). These materials have the required refractive index of at least 1.9.

In an advantageous embodiment, the high-index layer has a thickness between 10 nm and 200 nm, in a particularly advantageous embodiment between 20 nm and 150 nm.

The low-refractive-index layer is preferably formed from silicon oxide (SiO2), aluminum-doped silicon oxide (SiO2:Al), titanium-doped silicon oxide (SiO2:Ti), zirconium-doped silicon oxide (SiO2:Zr), and/or boron-doped silicon oxide (SiO2:B). These materials have the required refractive index of at most 1.7.

In an advantageous embodiment, the low-refractive-index layer has a thickness between 50 nm and 200 nm. The inventors have found in optical simulations that the above-mentioned materials are particularly well suited for optimizing the reflectivity of the coupled light at the interface of the coating and reducing emissivity.

In addition, they found that the above-mentioned ranges for the layer thicknesses of the high-refractive-index and low-refractive-index layers are suitable for achieving an emissivity-reducing effect of the functional layer and, at the same time, for optimizing the reflectivity of the coupled light at the interface of the coating.

As described above, the functional layer is arranged directly adjacent to the glass pane, i.e. there are no further layers between the functional layer and the glass pane, which simplifies the manufacturing process and reduces costs. There is therefore no dielectric layer between the functional layer and the glass pane and consequently no barrier layer either. A barrier layer usually reduces or prevents the diffusion of alkali ions from the glass pane _into a layer system. A barrier layer can be based, for example, on tin oxide (SnO2), _silicon oxynitride ( _SixOyNz ) or silicon nitride (SiaN^).

In a particularly advantageous embodiment, the emissivity-reducing coating consists of exactly one functional layer based on fluorine-doped tin oxide, antimony-doped tin oxide or aluminum-doped zinc oxide with a layer thickness between 130 nm and 500 nm, exactly one high-refractive-index layer with a refractive index of at least 1.9 and exactly one low-refractive-index layer with a refractive index of at most 1.7, in this case it does not contain any additional layers.

A scratch-resistant coating can be applied to the emissivity-reducing coating to protect against scratches. This coating is then positioned at a greater distance from the second surface of the glass pane than the emissivity-reducing coating and, depending on the application and installation situation of the glazing element, can also be exposed, i.e., accessible and touchable by people. The scratch-resistant coating is thus positioned at a greater distance from the second surface of the glass pane than the functional layer, the high-refractive-index layer, and the low-refractive-index layer.

The stated values for refractive indices are measured at a wavelength of 550 nm. Methods for determining refractive indices are known to those skilled in the art. The refractive indices stated within the scope of the invention are, for example, Ellipsometry can be determined using commercially available ellipsometers.

If the glazing element according to the invention is a window pane (for example of a vehicle, a building, an interior space, a piece of furniture, a refrigerator, or a piece of furnishing), it is intended to be inserted into a window opening and there to separate an interior space 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 space 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.

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.

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 may serve, for example, for data transmission or for coupling in light. The coated portion of the second surface of the glass pane is preferably at least 80%.

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. In this case, the totally reflecting interfaces are the first and second surfaces of the glass pane, which form exposed surfaces of the glazing element. 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, 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 that faces the interior in the installed position. The outer pane refers to the pane facing the outside environment. The interior-side 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 one another by the thermoplastic intermediate layer.

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. In principle, 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 next surface, at which a transition to an optically less dense medium occurs. This interface can lie within the intermediate layer, on the surface of the further pane facing the intermediate layer, or even on the surface of the further pane facing away from the intermediate layer.

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. 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.

The glazing element is provided with a light source suitable for coupling light into the glass pane. The light can be coupled in, 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 interfaces to an optically less dense medium (in particular the surfaces of the glass pane) described above. 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 a _T of total reflection can be determined as a _T = arcsin where n _± is the refractive index of the glass pane and n ₂ is the refractive index of the adjacent medium.

In certain embodiments of the invention, the medium adjacent to the first surface of the glass pane differs from the medium adjacent to the second surface. This is the case, for example, with laminated panes that, in addition to the glass pane used as the inner pane, include a thermoplastic intermediate layer and an outer pane that are bonded together by lamination. In this case, one of the surfaces of the glass pane borders the surrounding atmosphere and the other surface borders the thermoplastic intermediate layer of the laminated pane. Therefore, different critical angles of total internal reflection occur at the two surfaces. In this case, the portion of light that hits the surfaces at an angle of incidence that is greater than the greater critical angle of total internal reflection spreads out within the glass pane.

The refractive index and the critical angle of total reflection also depend on the wavelength of 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 is a _T = 41 °. If the interface is a surface of the glass pane that faces the intermediate layer of a laminated pane that is in the form of a PVB film (refractive index 1.48 at a light wavelength of 589 nm), the critical angle of total reflection is a _T = 77 °. As is usual 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 reflection is also determined in a similar way 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.

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.

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).

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.

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 spreads (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, as a structured plastic film, or as a plastic plate with a planar arrangement of microprisms. The light coupling means reflects the light back into the glass pane, but at a changed angle that deviates from 0° to the surface normal. The light is refracted at the surface of the glass pane and at least part of the resulting light in the glass pane hits the opposite surface at an angle of incidence that is greater than the critical angle of total internal reflection, whereby the light is coupled into the glass pane.

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.

In a second preferred embodiment, the light source is arranged in a recess of the glass pane. The glass pane therefore has a recess. This recess is preferably a hole, i.e. a passage, which extends between the first and the second surface of the glass pane. However, the recess can alternatively also be a depression in the manner of a blind bore (blind-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 passage. The blind bore preferably extends from a surface into the glass pane which forms an exposed surface of the glass element according to the invention. The light source can then be inserted subsequently and, in the event of a defect, can be easily replaced. In the case of a composite pane, that surface of the glass pane is the exposed surface which 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 over which the recess is introduced into the glass pane.

The recess, whether a feedthrough or a depression, is defined by a circumferential edge surface extending between the main surfaces of the glass pane. In the case of a feedthrough, this is the only boundary surface of the recess. In the case of a pocket-like depression, a further boundary surface is present, which faces the main surface of the glass pane to which the depression 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.

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. For example, it is conceivable for the light source to be located in a housing, with one part of the housing being inserted into the recess, while another part of the housing is outside the recess. The light source is positioned in the portion of the housing outside the recess, and the light is redirected by reflective surfaces or waveguides within 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.

In a third preferred embodiment, the light source is associated with the side edge surface of the glass pane and is suitable for directing light via the side edge surface into the glass pane. 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 be located in a housing or holder and fixed there, whereby the housing or holder is attached to the glass pane in such a way, for example, glued or clamped, 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. For example, it is conceivable for the light source to be located in a housing that contains reflective surfaces or waveguides through which the beam path of the light 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 be arranged, for example, in front of or behind the glass pane in the viewing direction. 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.

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

The glazing element (in particular the glass pane) is also provided with a light-scattering structure capable of 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.

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 strikes 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. 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.

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.

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 burned 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 manufacture of the composite pane, the film is inserted between the outer and inner panes to form the intermediate layer, with the printed surface facing the glass pane, in particular with 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. But opaque or semi-transparent light-scattering structures with pigments are also conceivable, for example white structures. Light-scattering structures can also be created by roughening the relevant surface of the glass pane or the interlayer. This roughening can be achieved mechanically (e.g., by grinding techniques) or by laser processing. Laser processing, particularly in the case of a laminated pane, has the advantage that the light-scattering structure can also be incorporated into the finished laminated pane, even if it is intended to be located inside the laminated pane, since the laser radiation can also be focused onto a plane inside the laminated pane, for example, through the transparent glass pane. Laser processing also makes it possible to create the light-scattering 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. However, the glass pane can in principle 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. Preference is given to panes with a thickness in the range of 0.5 mm to 10 mm, particularly preferably from 1 mm to 5 mm. In the case of a composite pane, the same applies to the other pane, whereby the material and thickness of the outer pane and the inner pane can be selected independently of one another.

The glass pane is preferably clear to allow light to spread effectively through the inner pane. In the case of a laminated pane, the other pane and the intermediate layer can be clear, tinted, or colored.

The thermoplastic intermediate layer comprises at least one layer of a thermoplastic bonding 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 area through which no vision is possible. This masking area is preferably arranged circumferentially in an edge region and surrounds a central transparent see-through area 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 composite pane) on the other pane. The masking print is typically formed from an enamel containing glass frits and a pigment, which is applied using a screen printing process and then fired.

In an advantageous embodiment, the functional layer is applied by means of chemical vapor deposition (CVD), in particular at the output of a float glass plant (float CVD).

In an advantageous embodiment, the functional layer has a thickness between 250 nm and 500 nm. The inventors have determined that particularly low emissivity can be achieved for these layer thicknesses. In this way, emissivity values of less than or equal to 35%, preferably even less than or equal to 25%, can be achieved.

The invention also includes a method for producing an illuminated glazing element according to the invention, wherein

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

(b) the second surface of the glass pane is provided with an emissivity-reducing coating which, starting from the glass pane, is applied in the specified order

• exactly one functional layer based on a transparent conductive oxide with a layer thickness between 130 nm and 500 nm,

• exactly one high-index layer with a refractive index of at least 1.9 and

• comprises exactly one low-refractive layer with a refractive index of at most 1.7, wherein the functional layer is arranged directly adjacent to the glass pane (2),

(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. 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).

The functional layer of the emissivity-reducing coating is placed directly adjacent to the glass pane. This immediate proximity offers process and cost advantages. No additional layer, such as a barrier layer, needs to be applied between the functional layer and the glass pane. This simplifies the manufacturing process and reduces costs.

The functional layer of the emissivity-reducing coating is preferably deposited by vapor deposition on the second surface of the glass pane, particularly preferably by chemical vapor deposition (CVD), in particular at the exit of a float glass plant (float CVD).

Chemical vapor deposition at the end of a float glass plant (float CVD) is familiar to those skilled in the art. In chemical vapor deposition at the end of a float glass plant, the layer to be applied is deposited onto a glass substrate present in the form of a ribbon at the exit of the float glass plant. This means that reheating of the substrate for chemical vapor deposition is not required, or only required to a limited extent, since the substrate already has a sufficiently high temperature at the exit of the float glass plant. Direct deposition at the end of a float glass plant is therefore a cost-effective, simple process for depositing the functional layer. In particular, it is possible to apply fluorine-doped tin oxide (SnO2:F), antimony-doped tin oxide (SnO2:Sb), or aluminum-doped zinc oxide (ZnO:Al) using float CVD. In addition, emissivity-reducing coatings can be produced by applying float CVD, which result in particularly low emissivity and particularly high reflectivity of the coupled light at the interface of the coating.

Alternative deposition methods for the functional layer are plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD) or physical vapor deposition (PVD), for example vapor deposition, prefers cathode sputtering and, in particular, magnetic field-assisted cathode sputtering (“magnetron sputtering”).

The low-refractive-index layer and the high-refractive-index layer are preferably deposited by physical vapor deposition (PVD), preferably by magnetic field-assisted cathode sputtering ("magnetron sputtering"). Alternatively, the low-refractive-index layer and the high-refractive-index layer can also be deposited by chemical vapor deposition (CVD).

Silicon oxide (SiO2), aluminum-doped silicon oxide (SiO2:Al), titanium-doped silicon oxide (SiO2:Ti), zirconium-doped silicon oxide (SiO2:Zr) and boron-doped silicon oxide (SiO2:B) are particularly well suited for deposition by means of magnetic field-assisted cathode sputtering, which makes them particularly suitable materials for use as a low-refractive-index layer, as well as silicon nitride (Sis1^ ), aluminum-doped silicon nitride (SisN^Al), titanium-doped silicon nitride (SisN^Ti), zirconium-doped silicon nitride (SisN^Zr) and boron-doped silicon nitride (SisN^B), which makes them particularly suitable materials for use as a high-refractive-index layer.

Preferably, the emissivity-reducing coating is subjected to a thermal post-treatment after deposition. Such methods for thermally annealing coatings are known in principle to those skilled in the art.

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 the light-diffusing layer 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.

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 under the influence of heat, vacuum, and/or pressure. 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.

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.

They show:

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

Fig. 2 is an enlarged view of section Z from Fig. 1,

Fig. 3 shows a cross section through a further embodiment of the inventive

glazing element,

Fig. 4 shows a cross section through a further embodiment of the inventive

glazing element,

Fig. 5 is an enlarged view of a section of a cross section through an embodiment of a glazing element not according to the invention.

Fig. 1 and Fig. 2 each show a detail of a first embodiment of the glazing element according to the invention. The glazing 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. 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. Likewise, the glass pane 2 has two parallel main surfaces, namely a first surface III, which represents the outside surface, and a second surface IV, which represents the inside surface.

The glass pane 2 acts as the light-conducting layer of the illuminated glazing element. A light source 5 is attached to the second (interior-side) 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 with 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 Fig. 1. A portion of the light strikes surfaces III and IV of glass pane 2 at an angle of incidence 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 and IV due to the different adjacent medium). This portion of light propagates through repeated total internal reflection within glass pane 2.

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 inconspicuously arranged in this opaque edge region (masking region).

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. 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 it does not lead to a significant loss of intensity of the propagating light. The emissivity-reducing coating 4 is formed as a stack of thin layers. The individual layers can be seen in the enlarged view of Fig. 2.

In the embodiment shown in Fig. 2, the emissivity-reducing coating 4 consists of a functional layer 4.1 based on a transparent conductive oxide, a high-refractive-index layer 4.2, and a low-refractive-index layer 4.3. The functional layer 4.1 based on a transparent conductive oxide has a layer thickness between 130 nm and 500 nm; for example, it is a 300 nm thick layer based on fluorine-doped tin oxide (SnO2:F). The high-refractive-index layer 4.2 has a refractive index of at least 1.9 and is, for example, a 134 nm thick layer based on silicon nitride (SiSn). The low-refractive-index layer 4.3 has a refractive index of at most 1.7 and is, for example, based on silicon oxide (SiO2) with a layer thickness of 100 nm.

Fig. 3 shows a further embodiment of the glazing element according to the invention. The glazing element is basically constructed in the same way as the embodiment in Fig. 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.

The side edge surface e is shown flat for the sake of simplicity, but in reality it is often convexly rounded as a result of edge grinding.

Fig. 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.

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

2 is provided with a recess A, which extends as a lead-through 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 area and is bounded 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 propagates through repeated total internal reflection in the glass pane 2.

Fig. 5 shows a detailed cross-sectional view of a glazing element not according to the invention. The non-inventive embodiment shown in Fig. 5 differs from that shown in Fig. 2 in that a barrier layer 4.4 is arranged between the glass pane 2 and the functional layer 4.1. The barrier layer 4.4 is characterized by a refractive index of at least 1.7, it is formed, for example, on the basis of tin oxide (SnO2) or silicon nitride (SiO2N) and has a thickness of, for example, 50 nm. The functional layer 4.1 based on a transparent conductive oxide has a layer thickness between 130 nm and 500 nm and is, for example, a 300 nm thick layer based on fluorine-doped tin oxide (SnO2:F). The high-index layer 4.2 has a refractive index of at least 1.9 and is, for example, a 134 nm thick layer based on silicon nitride (SiO2N). The low-index layer 4.3 has a refractive index of at most 1.7 and is, for example, based on silicon oxide (SiO2) with a layer thickness of 100 nm.

The structure of illuminated glazing elements with emissivity-reducing coatings is explained below using examples according to the invention and comparative examples. 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.

The reflectance R _LiG of the reflected light for reflection within the glass pane at the coating interface at a reflection angle of 80° is compared between the examples and the comparative examples. The values of the reflectance R _LiG shown were determined by optical simulations. The reflection angle is given relative to the surface normal. R _LiG (80°) should be maximized to optimize the light intensity of the illuminated glazing element. The values for R _LiG (80°) given in the following tables are averaged over a reflection angle of 80° in the visible spectrum.

In addition, the emissivity of the inventive examples and the comparative examples is compared using simulation values to determine whether the emissivity-reducing effect is impaired in the inventive examples compared to the comparative examples. For good suitability as an emissivity-reducing coating, the emissivity should be less than or equal to 35%; for particularly good suitability, it should be less than or equal to 25%.

Table 1

Comparative Example V1.1 from Table 1 is an embodiment not according to the invention, wherein an emissivity-reducing coating 4 consisting of a 300 nm thick functional layer 4.1 of fluorine-doped tin oxide (SnO2:F) without additional high-index and low-index layers is applied to the glass pane. Example B1 is an embodiment according to the invention, wherein the emissivity-reducing coating 4, starting from the glass pane 2, consists of a 300 nm thick layer of fluorine-doped tin oxide (SnO2:F) as functional layer 4.1, a 134 nm thick SiA1N layer as high-index layer 4.2, and a 100 nm thick SiO2 layer. as a low-refractive-index layer 4.3. Comparative Example V1.2 is a non-inventive embodiment which differs from Example B1 in that a 50 nm thick SiA/N layer is arranged as a barrier layer 4.4 between the glass pane 2 and the functional layer 4.1. The layer sequence in Comparative Example V1.2 is thus as shown in Fig. 5. In Comparative Examples V1.1 and V1.2 and in Example B1, the emissivity is 25% in each case. The reflectance R _LiG (80°) increases from 79.1% in Comparative Example V1.1 to 88.5% in Example B1 according to the invention. The presence of the high-refractive-index layer 4.2 and the low-refractive-index layer 4.3 thus increases the reflectance R _LiG (80°), while meeting the target specification for particularly good suitability as an emissivity-reducing coating, namely an emissivity of less than or equal to 25%. The reflectance R _LiG (80°) increases from 83.7% in the comparative example C1.2 to 88.5% in the inventive example B1. The arrangement of the functional layer 4.1 directly adjacent to the glass pane 2 thus increases the reflectance R _LiG (80°), while meeting the target specification for particularly good suitability as an emissivity-reducing coating, namely an emissivity of less than or equal to 25%.

In addition, values for the reflectance at an angle of 80° for light of wavelengths 450 nm, 530 nm and 630 nm are listed for the comparative examples V1.1 and V1.2 and example B1 in order to compare the reflectance for different colors of visible light.

Table 2

Comparative example V2.1 from Table 2 is a non-inventive embodiment with an emissivity-reducing coating 4 consisting of a 150 nm thick functional layer of fluorine-doped tin oxide (SnO2:F). Example B2 is an inventive embodiment, wherein the emissivity-reducing coating 4, starting from the glass pane 2, consists of a 150 nm thick SnO2:F layer as functional layer 4.1, a 26 nm thick SiO2N layer as high-refractive-index layer 4.2, and a 100 nm thick SiO2 layer as low-refractive-index layer 4.3. Comparative example V2.2 is a non-inventive embodiment which differs from example B2 in that a 50 nm thick SiO2N layer is arranged as barrier layer 4.4 between the glass pane 2 and the functional layer 4.1. The layer sequence in Comparative Example V2.2 is thus as shown in Fig. 5. In Comparative Examples V2.1 and V2.2 and in Example B2, the emissivity is 35%. The reflectance R _LiG (80°) increases from 88.1% in Comparative Example V2.1 to 96.0% in Example B2 according to the invention. The presence of the high-refractive-index layer 4.2 and the low-refractive-index layer 4.3 thus increases the reflectance R _LiG (80°), while maintaining the target emissivity of less than or equal to 35%. The coating is therefore suitable as an emissivity-reducing coating. The reflectance R _LiG (80°) increases from 92.8% in Comparative Example V2.2 to 96.0% in Example B2 according to the invention. Due to the arrangement of the functional layer 4.1 directly Adjacent to the glass pane 2, the reflectance R _LiG (80°) is thus increased, while the target of an emissivity of less than or equal to 35% is met, the coating is therefore suitable as an emissivity-reducing coating.

In addition, values for the reflectance at an angle of 80° for light of wavelengths 450 nm, 530 nm and 630 nm are listed for the comparative examples V2.1 and V2.2 and example B2 in order to compare the reflectance for different colors of visible light.

Table 3

Comparative Example V3 from Table 3 is a non-inventive embodiment with an emissivity-reducing coating consisting of a 300 nm thick functional layer of aluminum-doped zinc oxide (ZnO:Al). Example B3 is an inventive embodiment, wherein the emissivity-reducing coating, starting from the glass pane, consists of a 300 nm thick ZnO:Al layer as functional layer 4.1, a 101 nm thick SiA/N layer as high-refractive-index layer 4.2, and a 109 nm thick SiO2 layer as low-refractive-index layer 4.3. In Comparative Example V3 and Example B3, the emissivity is 25%, the reflectance R _LiG (80°) increases from 71.9% in Comparative Example V3 to 88.1% in Example B3 according to the invention. The presence of the high-refractive-index layer 4.2 and the low-refractive-index layer 4.3 thus increases the reflectance R _LiG (80°), while meeting the target specification for particularly good suitability as an emissivity-reducing coating, namely an emissivity of less than or equal to 25%.

As can be seen from Table 1 , Table 2 and Table 3, the reflectance R _LiG (80°) shows increases between 3.2 % points and 16.2 % points in the examples for the Inventive embodiments compared to the comparative examples. Thus, the inventive embodiments show an increase in the intensity of reflected light within the glass pane compared to the comparative examples. This is evident for both fluorine-doped tin oxide (SnO2:F) and aluminum-doped zinc oxide (ZnO:Al).

The presence of the high-refractive-index layer 4.2 and the low-refractive-index layer 4.3 thus increases the reflectance R _LiG (80°) in all three examples according to the invention, while maintaining the target specification for good suitability as an emissivity-reducing coating, namely an emissivity of less than or equal to 35%. Likewise, the arrangement of the functional layer 4.1 directly adjacent to the glass pane 2 increases the reflectance R _LiG (80°), while maintaining the target specification for good suitability as an emissivity-reducing coating, namely an emissivity of less than or equal to 35%.

List of reference symbols:

(1) Outer pane

(2) Glass pane / inner pane

(3) thermoplastic intermediate layer

(4) emissivity-reducing coating

(4.1) Functional layer

(4.2) high-index layer

(4.3) low-refractive layer

(4.4) Barrier layer

(5) Light source

(6) light-scattering structure

(7) Light coupling means

(9) opaque cover print

(I) outside surface of the outer pane 1

(II) interior surface of the outer pane 1

(III) first surface of the glass pane 2

(IV) second surface of the glass pane 2

(A) Recess in the glass pane 2

(e) Side edge surface of the glass pane 2

(i) Edge surface of the recess A

(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) is applied starting from the glass pane (2) in the specified order • exactly one functional layer (4.1) based on a transparent conductive oxide with a layer thickness between 130 nm and 500 nm, • exactly one high-index layer (4.2) with a refractive index of at least 1.9, and • comprises exactly one low-refractive-index layer (4.3) with a refractive index of at most 1.7 and wherein the functional layer (4.1) is arranged directly adjacent to the glass pane (2). 2. Illuminated glazing element according to claim 1, wherein the functional layer (4.1) is formed on the basis of fluorine-doped tin oxide, antimony-doped tin oxide or aluminum-doped zinc oxide. 3. Illuminated glazing element according to claim 1 or 2, wherein the functional layer (4.1) is applied by means of chemical vapor deposition (CVD), in particular at the output of a float glass plant. 4. Illuminated glazing element according to one of claims 1 to 3, wherein the functional layer (4.1) has a thickness between 250 nm and 500 nm. 5. Illuminated glazing element according to one of claims 1 to 4, wherein the high-refractive-index layer (4.2) is formed on the basis of silicon nitride, aluminum-doped silicon nitride, titanium-doped silicon nitride, zirconium-doped silicon nitride and/or boron-doped silicon nitride. 6. Illuminated glazing element according to one of claims 1 to 5, wherein the low-refractive-index layer (4.3) is formed on the basis of silicon oxide, aluminum-doped silicon oxide, titanium-doped silicon oxide, zirconium-doped silicon oxide and/or boron-doped silicon oxide. 7. Illuminated glazing element according to one of claims 1 to 6, wherein the high-refractive-index layer (4.2) has a thickness of 10 nm to 200 nm, preferably of 20 nm to 150 nm. 8. Illuminated glazing element according to one of claims 1 to 7, wherein the low-refractive-index layer (4.3) has a thickness of 50 nm to 200 nm. 9. Illuminated glazing element according to one of claims 1 to 8, wherein the emissivity-reducing coating (4) consists of • exactly one functional layer (4.1) based on fluorine-doped tin oxide, antimony-doped tin oxide or aluminum-doped zinc oxide with a layer thickness between 130 nm and 500 nm • exactly one high-index layer (4.2) with a refractive index of at least 1.9, and • exactly one low-refractive layer (4.3) with a refractive index of at most 1.7. 10. Illuminated glazing element according to one of claims 1 to 9, which is designed as a composite pane and comprises an outer pane (1) and an inner pane which are connected to one another via at least one thermoplastic intermediate layer (3), the inner pane being the glass pane (2). 11. Illuminated glazing element according to one of claims 1 to 10, 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) and/or wherein at least one light source (5) is arranged in such a way is arranged on a side edge surface (e) of the glass pane (2) extending between the first surface (III) and the second surface (IV), such that it is suitable for coupling light into the glass pane via the side edge surface (e). 12. A method for producing an illuminated glazing element according to any one of claims 1 to 11, wherein at least (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 at least one emissivity-reducing coating (4), wherein the emissivity-reducing coating (4) is applied starting from the glass pane (2) in the specified order • exactly one functional layer (4.1) based on a transparent conductive oxide with a layer thickness between 130 nm and 500 nm, • exactly one high-index layer (4.2) with a refractive index of at least 1.9 and • comprises exactly one low-refractive layer (4.3) with a refractive index of at most 1.7, and wherein the functional layer (4.1) is arranged directly adjacent to the glass pane (2), (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). 13. The method according to claim 12, wherein the functional layer (4.1) of the emissivity-reducing coating (4) is applied by means of chemical vapor deposition (CVD), in particular at the output of a float glass plant. 14. Use of a glazing element according to one of claims 1 to 11 as a window pane of a vehicle, in particular as a vehicle roof pane, or in buildings, for example as a window pane, glass facade or glass door in the exterior or Indoors, or as part of furniture, electrical appliances, Furnishings or as a furnishing item.